ANATOMY, DESCRIPTIVE AND SURGICAL. BY HENRY GRAY, F.R.S., Fellow of the Royal College of Surgeons; Lecturer on Anatomy at St. George's Hospital Medical School. THE DRAWINGS BY H. V. CARTER, M.D., Late Demonstrator of Anatomy at St. George's Hospital. WITH ADDITIONAL DRAWINGS IN LATER EDITIONS. A NEW AMERICAN FROM THE THIRTEENTH ENGLISH EDITION. EDITED BY T. PICKERING PICK, Surgeon to, and Lecturer on Surgery at, St. George's Hospital; Senior Surgeon, Victoria Hospital for Children; Member of the Court of Examiners, Royal College of Surgeons of England. PHILADELPHIA: LEA BROTHERS & CO. 1893. Entered according to Act of Congress, in the year 1893, by LEA BROTHERS & CO., in the office of the Librarian of Congress at Washington. All rights reserved. Westcott & Thomson, Stereotypers and Electrotypers, Philada. William J. Doknan, Printer, Philada. TO SIR BENJAMIN COLLINS BRODIE, BART., F.R.S., D.C.L., SERJEANT-SURGEON TO THE QUEEN, CORRESPONDING MEMBER OF THE INSTITUTE OF FRANCE, Ubis Work is Bebicateb IN ADMIRATION OF HIS GREAT TALENTS AND IN REMEMBRANCE OF MANY ACTS OF KINDNESS SHOWN TO THE AUTHOR FROM AN EARLY PERIOD OF HIS PROFESSIONAL CAREER. PUBLISHER'S NOTICE. A book which since 1857 has been the recognized text-book used by the great majority of English-speaking students of medicine requires no introduc- tion to the profession except to say that the successive issues of thirteen editions have been utilized to perfect the work by subjecting it to the scrutiny of the fore- most anatomists of a generation. In this way a degree of accuracy and com- pleteness has been attained which it would be impossible to secure otherwise in a science consisting, like anatomy, in a multitude of minute details. These details have been steadily multiplying with the advance of knowledge, and even more marked have been their practical applications in the domains of medicine and surgery. The consideration given to these applications has always been a prominent feature of the present work, and this distinctive characteristic has received the especial care of the editors. In fact, in no previous edition have the changes and improvements in every portion been so great. The text has been most thoroughly revised; the splendid series of illustrations has been re-engraved wherever additional clearness could be attained, and has been rein- forced with new engravings wherever completeness has seemed to demand it. These illustrations have long been known as the most effective and intelligible anatomical drawings accessible to the student, and in their present improved shape this supremacy, it is hoped, will be fully maintained. The present edition is therefore offered to the profession in the full assurance that it will more than ever be found worthy of the favor heretofore accorded to it as the standard text-book of Anatomy. 5 PREFACE TO THE THIRTEENTH EDITION. When Henry Gray published this work in 1858, he entitled it Anatomy, Descriptive and Surgical, and he introduced under each subdivision such observations on practical points of Surgery as show the necessity of an accurate acquaintance with the anatomy of the part under examination. This was the first time that such an endeavor had been made by an English Anatomist. In preparing this edition the Editor has endeavored to follow in the lines originally laid down by the Author, and has tried to keep before himself the fact that the work is intended for Students of Surgery rather than for the Scien- tific Anatomist. Not that the Editor would wish to disparage, for an instant, the study of Philosophical or Scientific Anatomy, but that he thought it right, con- sidering the class of students for whom the work is primarily intended, that he should be practical rather than abstract and theoretical. Accordingly, he has not altered in any way the original plan of the work, but has endeavored to render it more practical, and of more use to the student, who will hereafter have to apply his knowledge of Anatomy to his practice of Surgery, by intro- ducing a considerably increased amount of Surgical Anatomy, and by pointing out the bearings of Anatomy on the practice of Surgery. In addition to this, the whole work has undergone a careful revision, and in some minor details a rearrangement has been made. The Editor is deeply indebted to his friend Mr. Ross for much kind assist- ance in the preparation of this edition, and also for the help that he has rendered him in passing these pages through the press. To Dr. Leonard Remfry he is also much indebted for his kindness in revis- ing the section on the anatomy of the Female Organs of Generation. Several newr illustrations have been added, principally from dissections in the Hunterian Museum of the Royal College of Surgeons. The Editor takes this opportunity of thanking Prosector Pearson for the kind interest he has dis- played and assistance he has rendered in the preparation of these drawings, w'hich were taken from dissections made by this master in the art of dissecting. 7 CONTENTS. PAGE The Blood 33 The Lymph and Chyle 37 The Animal Cell 38 Epithelium 41 Connective Tissue 45 Pigment 50 Cartilage 51 White Fibro-cartilage 52 Yellow or Reticular, Elastic Cartilage ... 53 Bone 54 Development of Bone 59 Muscular Tissue 64 Unstriped Muscle 68 Nervous Tissue 69 The Brain 73 The Nerves 73 The Sympathetic Nerve 75 GENERAL ANATOMY. PAGE Origin and Termination of Nerves .... 75 The Ganglia . 79 The Vascular System 80 The Arteries 80 The Capillaries 82 The Veins 84 The Lymphatics 85 The Lymphatic Glands 87 The Skin and its Appendages 89 The Nails 92 The Hair 93 The Sebaceous Glands 94 The Sudoriferous Glands 95 Serous Membranes 96 Synovial Membranes 96 Mucous Membranes . 97 Secreting Glands 98 DEVELOPMENT. Growth and Development of the Body ... 100 The Ovum 100 Fecundation of 101 Segmentation of 102 Division of Blastodermic Membrane 104 First Rudiments of the Embryo 107 The Amnion Ill The Chorion 112 The Allantois 113 The Decidua 114 The Placenta 114 Development of the Embryo Proper 115 The Spine 115 The Ribs and Sternum 117 The Cranium and Face 117 The Nervous Centres 120 The Nerves 122 The Eye 122 The Ear 124 The Nose 125 The Skin, Glands, and Soft Parts .... 125 The Limbs 126 The Muscles 126 The Blood-vascular System 126 Vitelline Circulation 126 Placental Circulation 128 The Alimentary Canal and its Appendages . . 133 The Respiratory Organs 135 The Urinary Organs 135 The Generative Organs 137 Male Organs 138 Female Organs 138 External Organs 139 Chronological Tables of the Development of the Feetus 143 DESCRIPTIVE AND SURGICAL ANATOMY. OSTEOLOGY.-THE SKELETON. The Skeleton 145 Number of the Bones 145 Form of Bones 145 The Spine. General Characters of a Vertebra 146 Characters of the Cervical Vertebrae 147 Atlas 148 Axis 149 Vertebra Prominens 151 Characters of the Dorsal Vertebrae 151 Peculiar Dorsal Vertebrae 153 Characters of the Lumbar Vertebrae 153 Structure of the Vertebrae 154 Development of the Vertebrae 154 " " Atlas 155 " Axis 156 *' Seventh Cervical .... 156 " Lumbar Vertebrae . . . 156 Progress of Ossification in the Spine 156 Sacrum 157 Coccyx 161 Of the Spine in general 162 Surface Form of Spine 164 Surgical Anatomy of Spine 164 The Skull. Bones of the Cranium 165 Occipital Bone 166 Parietal Bones 170 Frontal Bone 172 Temporal Bones , 175 Sphenoid Bone 182 Ethmoid Bone 187 Development of the Cranium 189 The Fontanelles 190 Wormian Bones 190 Congenital Fissures and Gaps 190 Bones of the Face: Nasal Bones 191 Superior Maxillary Bones 191 Changes produced in Upper Jaw by Age . 197 Lachrymal Bones 197 Malar Bones 198 9 10 CONTENTS. PAGE Palate Bones 199 Inferior Turbinated Bones 202 Vomer 203 Lower Jaw 203 Changes produced in the Lower Jaw by Age 206 Sutures of the Skull 207 Vertex of the Skull 210 Base of the Skull, Internal Surface 210 Anterior Fossa 210 Middle Fossa 212 Posterior Fossa 213 Base of Skull, External Surface 213 Lateral Region of the Skull 216 Temporal Fossa 217 Mastoid Portion 218 Zygomatic Fossa 218 Spheno-maxillary Fossa 218 Anterior Region of the Skull 219 Orbits 219 Nasal Fossae 221 Surface Form of Skull 224 Surgical Anatomy of Skull 226 Os Hyoides 229 The Thorax. The Sternum 230 The Ribs 234 Peculiar Ribs 236 Costal Cartilages 238 Surface Form of Chest . 238 Surgical Anatomy of Chest 239 The Upper Extremity. The Shoulder and Pelvic Girdles 240 The Clavicle 240 Surface Form 243 Surgical Anatomy 243 The Scapula 244 Surface Form 249 Surgical Anatomy 249 The Humerus 249 Surface Form 255 ' Surgical Anatomy 255 The Forearm 256 The Ulna 256 Surface Form 261 I The Radius 261 Surface Form 263 Surgical Anatomy of Bones of Forearm . 263 | PAGE The Hand ... 254 The Carpus 264 Bones of the Upper Row 264 Bones of the Lower Row 268 The Metacarpus 269 Peculiar Characters of the Metacarpal Bones . 270 Phalanges 272 Surface Form of Bones of Hand 272 Surgical Anatomy of Bones of Hand . . 273 Development of the Bones of the Hand . . . 273 The Lower Extremity. The Hip 274 Os Innominatum 274 Ilium 274 Ischium 277 Os Pubis 279 Development of the Os Innominatum .... 280 The Pelvis 281 Differences between the Male and Female Pelvis 284 Surface Form of Bones of Pelvis 285 Surgical Anatomy of Bones of Pelvis . . 285 The Femur or Thigh-Bone 286 Surface Form 292 Surgical Anatomy 292 The Leg 293 Patella 293 Surface Form 294 Surgical Anatomy 294 Tibia 295 Surface Form 298 Fibula 299 Surface Form 301 Surgical Anatomy of Bones of Leg . - . 301 The Foot 301 Tarsus 301 Os Calcis 301 Astragalus 305 Cuboid '..... 305 Navicular 306 Cuneiform 307 Metatarsal Bones 308 Phalanges 310 Development of the Bones of the Foot . . . 310 Construction of the Foot as a whole ... 311 Surface Form of Foot 312 Surgical Anatomy of Foot 313 Sesamoid Bones 314 THE ARTICULATIONS Structures composing the Joints 315 Articular Lamella of Bone 315 Ligaments 315 Synovial Membrane 315 Bursae 316 Synovia 316 Forms of Articulation: Synarthrosis 316 Amphiarthrosis 317 Diarthrosis 317 Movements of Joints 318 Articulations of the Trunk. Articulations of the Vertebral Column .... 321 " " Atlas with the Axis . . . 325 " " Spine with the Cranium . 327 " " Atlas with the Occipital Bone 327 Articulation of the Axis with the Occipital Bone 328 Surgical Anatomy of Articulations of the Spine. 329 Temporo-maxillary Articulation 329 Surface Form .. . 332 Surgical Anatomy , . . 332 Articulations of the Ribs with the Vertebrae: Costo-vertebral 332 Costo-transverse 333 Articulations of the Cartilages of the Ribs with the Sternum and Ensiform Cartilage .... 336 Interchondral Articulations 336 Ligaments of the Sternum 338 Articulation of the Pelvis with the Spine . . . 338 Articulations of the Pelvis : Articulation of the Sacrum and Ilium . , 338 Ligament between the Sacrum and Ischium 339 Articulation of the Sacrum and Coccyx . 341 Articulation of the Pubes 341 Articulations of the Upper Extremity. Sterno-clavicular 342 Surface Form 344 Surgical Anatomy 344 Acromio-clavicular 344 Surface Form 346 Surgical Anatomy 346 Proper Ligaments of the Scapula 346 Shoulder-joint 347 Surface Form 350 Surgical Anatomy 350 Elbow-joint 351 Surface Form 354 Surgical Anatomy 354 Radio-ulnar Articulations 355 Surface Form 358 Wrist-joint .... - 358 Surface Form 359 Surgical Anatomy 359 CONTENTS. 11 PAGE Articulations of the Carpus 359 of the first row of Carpal Bones. 359 of the second row of Carpal Bones 360 " of the two rows of Carpal Bones. 360 Carpo-metacarpal Articulations 361 of the Metacarpal Bone of Thumb and Trapezium 361 of the four inner Metacarpal Bones and Carpus 362 Articulations of the Metacarpal Bones .... 363 Metacarpo-phalangeal Articulations 363 Surface Form 364 Articulations of the Phalanges 364 Articulations of the Lower Extremity. Hip-joint 364 Surface form 368 Surgical Anatomy 368 Knee-joint 370 Surface Form 376 Surgical Anatomy 376 Articulations between the Tibia and Fibula . 378 PAGE Ankle-joint 379 Surface Form 381 Surgical Anatomy 381 Articulations of the Tarsus 382 of the Os Calcis and Astragalus. 382 of the Os Calcis and Cuboid . . 383 of the Os Calcis and Navicular . 384 Surgical Anatomy 384 of the Astragalus and Navicular. 384 of the Navicular and Cuneiform. 385 of the Navicular and Cuboid . . 385 of the Cuneiform with each other 385 of the External Cuneiform and Cuboid 386 Torso-metatarsal Articulations 386 Articulations of the Metatarsal Bones .... 387 Synovial Membranes in Tarsal and Metatarsal Joints .... 387 Metatarso-phalangeal Articulations 388 Articulations of the Phalanges 389 Surface Form 389 MUSCLES AND FASCLE. General Description of Muscle 390 " . Tendons 391 Aponeuroses .... 391 " " Fascia 391 Muscles and Fasciae of the Cranium and Face. Subdivision into Groups 392 Cranial Region. Dissection 393 Occipito-frontalis 394 Auricular Region. Dissection 395 Attrahens Aurem 395 Attollens Aurem 396 Retrahens Aurem 396 Actions 396 Palpebral Region. Dissection 396 Orbicularis Palpebrarum 396 Corru gator Supercilii 397 Tensor Tarsi 397 Actions 397 Orbital Region. Dissection 398 Levator Palpebrje • . . . . 398 Rectus Superior, Inferior, Internal, and Ex- ternal Recti 399 Superior Oblique 399 Inferior Oblique 399 Actions 400 Surgical Anatomy 400 Nasal Region. Pyramidalis Nasi 401 Levator Labii Superioris Alaeque Nasi .... 401 Dilatator Naris, Anterior and Posterior . . . 401 Compressor Nasi 401 Compressor Narium Minor 401 Depressor Alee Nasi 401 Actions 401 Superior Maxillary Region. Levator Labii Superioris (Proprius) ..... 402 Levator Anguli Oris 402 Zygomatici 402 Actions 402 Inferior Maxillary Region. Dissection 402 Levator Labii Inferioris 402 Depressor Labii Inferioris 403 Depressor Anguli Oris 403 Intermaxillary Region. Dissection 403 Orbicularis Oris 403 Buccinator 404 Risorius 404 Actions 404 Temporo-Maxillary Region. Masseteric Fascia 405 Masseter 405 Temporal Fascia 405 Dissection 405 Temporal 405 Pterygo-Maxillary Region. Dissection 406 External Pterygoid 406 Internal Pterygoid 407 Actions 407 Surface Form of Muscles of Head and Face . 408 Muscles and Fascia: of the Neck. Subdivision into Groups 408 Superficial Region. Dissection 409 Superficial Cervical Fascia 409 Platysma Myoides 409 Deep Cervical Fascia 409 Sterno-mastoid 411 Boundaries of the Triangles of the Neck . . . 411 Actions 412 Surgical Anatomy 413 Infra-hyoid Region. Dissection 413 Sterno-hyoid 413 Sterno-thyroid 413 Thyro-hyoid 413 Omo-hyoid 414 Actions 415 Supra-hyoid Region. Dissection 415 Digastric 415 Stylo-hyoid 415 Stylo-hyoid Ligament 416 Mylo-hyoid 416 Genio-hyoid 416 Actions 416 Lingual Region. Dissection 417 Genio-hyo-glossus 418 Hyo-glossus 418 Chrondro-glossus . ' . . 418 12 CONTENTS. PAGE Stylo-glossus 418 Palato-glossus 418 Muscular Substance of Tongue 418 Superior Lingualis . 419 Transverse Lingualis 420 Vertical Lingualis 420 Inferior Lingualis 420 | Actions 420 Pharyngeal Region. Dissection 421 Inferior Constrictor 421 Middle Constrictor 422 Superior Constrictor 422 Stylo-pharyngeus 422 Actions 423 Palatal Region. Dissection 423 Levator Palati 423 Tensor Palati 424 Azygos Uvulae 424 I Palato-glossus 424 j Palato-pharyngeus 424 Salpingo-pharyngeus 425 Actions 425 Surgical Anatomy 425 Vertebral Region (Anterior). Eectus Capitis Anticus Major 426 Eectus Capitis Anticus Minor 426 Eectus Lateralis 427 Longus Colli 427 Vertebral Region (Lateral). Scalenus Anticus 427 Scalenus Medius 427 Scalenus Posticus 428 Actions . . i 428 Surface Form of Muscles of Neck 429 Muscles and Fasciae of the Trunk. Subdivision into Groups 429 The Back. Subdivision into Layers 429 First Layer. Dissection 430 Superficial and Deep Fasciae 430 Trapezius 430 Ligamentum Nuchae 432 Latissimus Dorsi 432 Second Layer. Dissection 433 Levator Anguli Scapulae 433 Ebomboideus Minor 433 Ehomboideus Major 434 Actions 434 Third Layer. Dissection 434 Serratus Posticus Superior 434 Serratus Posticus Inferior . 434 Vertebral Aponeurosis 435 Lumbar Fascia 435 Splenius 435 Actions 436 Fourth Layer. Dissection 436 Erector Spinae 436 Uio-costalis 436 Musculus Accessorius ad Ilio-costalem .... 438 Cervicalis Ascendens 438 Longissimus Dorsi 438 Transversalis Colli 438 Trachelo-mastoid 438 ■Spinalis Dorsi 438 Spinalis Colli 438 Complexus 439 Biventer Cervicis 439 Fifth Layer. PAGE Dissection 439 Semispinalis Dorsi et Colli 439 Multitidus Spin® 440 Rotatores Spin® 440 Supraspinales 440 Interspinales 440 Extensor Coccygis 440 Intertransversales 440 Rectus Capitis Posticus Major 441 Rectus Capitis Posticus Minor 441 Obliquus Capitis Inferior 441 Obliquus Capitis Superior 441 Suboccipital Triangle 441 Actions 442 Surface Form of Muscles of Back 442 The Thorax. Intercostal Fasciae 443 External and Internal Intercostals 444 Infracostales (subcostales) 444 Triangularis Sterni 444 Levatores Costarum 444 Actions 445 Muscles of Inspiration and Expiration .... 446 Diaphragmatic Region. Diaphragm 446 Actions ... . 448 The Abdomen. Dissection 449 Obliquus Externus 450 External Abdominal Ring 451 The Intercolumnar Fibres 452 The Intercolumnar Fascia 452 Poupart's Ligament 452 Gimbernat's Ligament 453 Triangular Ligament . 453 Obliquus Internus 453 Cremaster 454 Transversalis 454 Rectus 455 Pyramidalis 457 Linea Alba 458 Line® Semilunares, Line® Transvers® . . . 458 Actions 458 Fascia Transversalis 458 Internal Abdominal Ring 458 Inguinal Canal 459 Surface Form of Muscles of Abdomen .... 459 Deep Muscles of the Abdomen. Quadratus Lumborum 460 Muscles of the Pelvic Outlet and Perhueum. Corrugator Cutis Ani 460 External Sphincter Ani 460 Internal Sphincter Ani 461 Levator Ani 461 Coccygeus 462 Superficial Perineal Fascia 462 Trans versus Perin®i 463 Accelerator Urin® 463 Erector Penis 464 Triangular Ligament 465 Compressor Urethr® 467 Muscles of the Perinseum in the Female. Transversus Perin®i 466 Sphincter Vagin® 466 Erector Clitoridis 467 Triangular Ligament 467 Compressor Urethr® 467 Muscles and Fasci.e of the Upper Extremity. Subdivision into Groups 467 Dissection of Pectoral Region and Axilla . . 468 Fasci® of the Thorax 468 CONTENTS. 13 The Shoulder. Anterior Thoracic Region. PAGE Pectoralis Major 469 Costo-coracoid Membrane 470 Pectoralis Minor 471 Subclavius 471 Actions 472 Lateral Thoracic Region. Serratus Magnus 472 Actions 473 Acromial Region. Deltoid 473 Actions 474 Anterior Scapular Region. Subscapular Fascia 474 Subscapularis 474 Actions 475 Posterior Scapular Region. Dissection 475 Supraspinous Fascia 475 Supraspinatus 475 Infraspinous Fascia 47q Infraspinatus 475 Teres Minor 476 Teres Major 476 Actions 477 The Arm. Anterior Humeral Region. Deep Fascia of Arm 477 Coraco-brachialis 478 Biceps 478 Brachialis Anticus 479 Actions 479 Posterior Humeral Region. Triceps 479 Subanconeus 480 Actions 480 The Forearm. Deep Fascia of Forearm 480 Anterior Brachial Region, Superficial Layer. Pronator Radii Teres 481 Flexor Carpi Radialis 481 Palmaris Longus 482 Flexor Carpi Ulnaris 482 Flexor Digitorum Sublimis 482 Deep Layer. Flexor Profundus Digitorum 483 Flexor Longus Pollicis 484 Pronator Quadratus 485 Actions 485 Radial Region. Dissection 485 Supinator Longus 485 Extensor Carpi Radialis Longior 486 Extensor Carpi Radialis Brevior 486 Posterior Brachial Region, Superficial Layer. Extensor Communis Digitorum 487 Extensor Minimi Digiti 487 Extensor Carpi Ulnaris 488 Anconeus 488 Deep Layer. Supinator Brevis 488 Extensor Ossis Metacarpi Pollicis 488 Extensor Longus Pollicis 490 Extensor Indicis 490 Actions 490 The Hand. Dissection 491 Anterior Annular Ligament 491 Synovial Membranes of the Flexor Tendons at the Wrist 491 Posterior Annular Ligament 492 Deep Palmar Fascia 492 Superficial Transverse Ligament of the Fingers 494 Radial Group 494 Abductor Pollicis 494 Opponens Pollicis 494 Flexor Brevis Pollicis 494 Adductor Obliquus Pollicis 495 Adductor Transversus Pollicis 495 Actions 496 Ulnar Group 496 Palmaris Brevis 496 Abductor Minimi Digiti 496 Flexor Brevis Minimi Digiti 497 Opponens Minimi Digiti 497 Actions 498 Middle Palmar Group 498 Lu rubricates 498 Interossei Dorsales 498 Interossei Palmares 498 Actions 499 Surface form of Muscles of LTpper Extremity . 499 Surgical Anatomy of the Muscles of the Upper Extremity. Fractures of the Clavicle 501 " Acromion Process 501 " Coracoid Process 502 " Humerus 502 " Olecranon 503 " " Radius 503 " Ulna 504 " Radius and Ulna 504 " Lower end of Radius .... 504 Muscles and Fascia: of the Lower Extremity. Subdivision into Groups 504 Iliac Region. Dissection 505 Iliac Fascia 505 Psoas Magnus 506 Psoas Parvus 506 Iliacus 506 Actions 507 Surgical Anatomy 507 The Thigh. Anterior Femoral Region. Dissection 507 Superficial Fascia 508 Deep Fascia (Fascia Lata) 508 Saphenous Opening 509 Iliac and Pubic portions of Fascia Lata . . . 510 Tensor Vagina' Femoris 510 Sartorius 510 Quadriceps Extensor 511 Rectus Femoris 511 Vastus Externus 511 Vastus Internus and Crureus 512 Subcrureus 512 Actions 512 Surgical Anatomy 513 Internal Femoral Region. Dissection 513 Gracilis 513 Pectineus 513 Adductor Longus 514 Adductor Brevis 514 Adductor Magnus 515 Actions 515 Surgical Anatomy 516 The Hip. Gluteal Region. Dissection 516 Gluteus Maximus 516 14 CONTENTS. PAGE Gluteus Medius 517 Gluteus Minimus 518 Pyriformis 518 Obturator Membrane 518 Obturator Internus 518 Gemelli 519 Quadratus Femoris 519 Obturator Exteruus . 520 Actions 520 Posterior Femoral Region. Dissection 520 Biceps 520 Semitendinosus 521 Semimembranosus 521 Actions 521 Surgical Anatomy of Hamstring Tendons . . 522 The Leg. Dissection of Front of Leg 522 Deep Fascia of the Leg . . . • 522 Anterior Tibiofibular Region. Tibialis Anticus 523 Extensor Proprius Hallucis 523 Extensor Longus Digitorum 525 Peroneus Tertius 524 Actions 524 Posterior Tibiofibular Region, Superficial Layer. Dissection 524 Gastrocnemius 524 Soleus 525 Tendo Achillis 525 Plantaris 526 Actions 526 Deep Layer. Deep Transverse Fascia of Leg 526 Popliteus 526 Flexor Longus Hallucis 527 Flexor Longus Digitorum 527 Tibialis Posticus 528 Actions 528 Fibular Region. PAGE Peroneus Longus 529 Peroneus Brevis 529 Actions 529 Surgical Anatomy of Tendons around Ankle 530 The Foot. Anterior Annular Ligament 530 Internal Annular Ligament 530 External Annular Ligament 531 Plantar Fascia 531 Dorsal Region. Extensor Brevis Digitorum 532 Plantar Region. Subdivision into Groups 532 Subdivision into Layers 532 First Layer 532 Abductor hallucis 532 Flexor brevis digitorum 532 Fibrous Sheaths of Flexor Tendons . . . 533 Abductor Minimi Digiti 533 Second Layer 534 Flexor Accessorius 534 Lumbricales 534 Third Layer 534 Flexor Brevis Hallucis 534 Adductor Obliquus Hallucis 535 Flexor Brevis Minimi Digiti 535 Adductor Transversus Hallucis 535 Fourth Layer 536 Interossei 536 Surface Form of Muscles of Lower Extremity 537 Surgical Anatomy of the Muscles of the Lower Extremity. Fracture of the Neck of the Femur 539 " the Femur below Trochanter Minor 539 " the Femur above the Condyles . 540 " the Patella 540 " the Tibia 540 " the Fibula, with Dislocation of the Foot outward 540 THE ARTERIES. General Anatomy. Subdivision into Pulmonary and Systemic . . 541 Distribution of-Where found 541 Mode of Division-Anastomoses - ■ 541 Pulmonary Artery 542 THE AORTA. Divisions 543 Ascending Aorta 543 Coronary Arteries 544 Arch of Aorta 545 Peculiarities 545 Surgical Anatomy 546 Branches 547 Peculiarities of Branches 547 Arteria Innominata. Relations 547 Peculiarities 548 Surgical Anatomy 548 Common Carotid Arteries. Course and Relations 549 Peculiarities 551 Surface Marking 551 Surgical Anatomy 551 External Carotid Artery. Course and Relations 553 Surface Marking 553 Surgical Anatomy 553 Branches 554 Superior Thyroid Artery. Course and Relations 554 Branches 554 Surgical Anatomy 554 Lingual Artery. Course and Relations 555 Branches 555 Surgical Anatomy 555 Facial Artery. Course and Relations 556 Branches 556 Peculiarities 558 Surgical Anatomy 558 Occipital Artery. Course and Relations 558 Branches 559 Posterior Auricular Artery. Course and Relations 559 Branches 559 Ascending Pharyngeal Artery. Course and Relations 560 Branches 560 Surgical Anatomy 561 Temporal Artery. Course and Relations 561 Branches 561 Surgical Anatomy 501 CONTENTS. 15 Internal Maxillary Artery. PAGE Course and Relations 561 Peculiarities 561 Branches from First Portion 562 " " Second Portion 563 " " Third Portion 564 Surgical Anatomy of the Triangles of the Neck. Anterior Triangular Space. Inferior Carotid Triangle 565 Superior Carotid Triangle 566 Submaxillary Triangle 566 Posterior Triangular Space. Occipital Triangle 567 Subclavian Triangle 567 Internal Carotid Artery. Cervical Portion 568 Petrous Portion 568 Cavernous Portion 568 Cerebral Portion 568 Peculiarities 569 Surgical Anatomy 570 Branches 570 Ophthalmic Artery 570 Cerebral Branches of Internal Carotid . . . 572 The Blood-vessels of the Brain 575 Arteries of Upper Extremity. Subclavian Arteries. First Part of Right Subclavian Artery .... 579 First Part of Left Subclavian Artery .... 579 Second Part of Subclavian Artery 580 Third Part of Subclavian Artery 580 Peculiarities 581 Surface Marking 581 Surgical Anatomy 581 Branches 583 Vertebral Artery 583 Basilar Artery . 585 Circle of Willis 586 Thyroid Axis 586 Inferior Thyroid 586 Suprascapular Artery 587 Transversalis Colli 587 Internal Mammary 588 Superior Intercostal 589 The Axilla 589 Surgical Anatomy of the Axilla 591 Axillary Artery. First Portion 591 Second Portion 592 Third Portion 592 Peculiarities 592 Surface Marking 593 Surgical Anatomy 593 Branches 594 Brachial Artery. Relations 595 Bend of the Elbow 595 Peculiarities of Brachial Artery 596 Surface Form 597 Surgical Anatomy 597 Branches 598 Radial Artery. Relations 599 Deep Palmar Arch 600 Peculiarities 600 Surface Marking 600 Surgical Anatomy 600 Branches 601 Ulnar Artery. Relations 603 Peculiarities of Ulnar Artery 603 Surface Marking 604 PAGE Surgical Anatomy 604 Branches 604 Superficial Palmar Arch 606 Arteries of the Trunk. Descending Aorta . 607 Thoracic Aorta. Course and Relations .• 607 Surgical Anatomy 607 Branches 608 Abdominal Aorta. Course and Relations 610 Surface Marking 611 Surgical Anatomy 611 Branches 611 Cceliac Axis 612 Gastric Artery 613 Hepatic Artery 613 Splenic Artery 613 Superior Mesenteric Artery 614 Inferior Mesenteric Artery 616 Suprarenal Arteries 617 Renal Arteries 618 Spermatic Arteries 618 Ovarian Arteries 618 Phrenic Arteries 618 Lumbar Arteries 619 Middle Sacral Artery 619 Luschka's Gland 619 Common Iliac Arteries. Course and Relations . 620 Branches 620 Peculiarities 620 Surface Marking 621 Surgical Anatomy 621 Internal Iliac Artery. Course and Relations 623 Peculiarities 623 Surgical Anatomy 623 Branches 624 Vesical Arteries 624 Hsemorrhoidal Arteries 624 Uterine Arteries 624 Vaginal Arteries 624 Obturator Artery 624 Peculiarities 625 Internal Pudic Artery 625 In the Male 625 Peculiarities 626 Surgical Anatomy 626 Branches 626 In the Female 627 Sciatic Artery 628 Ilio-lumbar Artery 628 Lateral Sacral Artery 629 Gluteal Artery 629 Surface Marking of Branches of Internal Iliac . 629 Surgical Anatomy of Branches of Internal Iliac 630 External Iliac Artery. Course and Relations 630 Surgical Anatomy 630 Deep Epigastric Artery 631 Deep Circumflex Iliac Artery 632 Arteries of the Lower Extremity. Femoral Artery. Course and Relations 632 Scarpa's Triangle . 632 Hunter's Canal 632 Common Femoral 633 Superficial Femoral 634 Peculiarities 635 Surface Marking ' 635 Surgical Anatomy 635 Branches 637 16 CONTENTS. PAGE Deep Femoral 637 Branches 638 Popliteal Space 639 Popliteal Artery. Course and Relations 640 Peculiarities 640 Surface Marking 640 Surgical Anatomy 640 Branches 641 Anterior Tibial Artery. Course and Relations 643 Peculiarities 644 Surface Marking 644 Surgical Anatomy 644 Branches 644 Dorsalis Pedis Artery. PAGE Course and Relations 645 Peculiarities 645 Surface Marking 645 Surgical Anatomy 645 Branches 645 Posterior Tibial Artery. Course and Relations 646 Peculiarities 647 Surface Marking 647 Surgical Anatomy 647 Branches 648 Peroneal Artery. Course and Relations 648 Peculiarities 648 Plantar Arteries 649 Surface Marking 650 Surgical Anatomy 650 THE VEINS. General Anatomy. Subdivision into Pulmonary, Systemic, and Portal 651 Anastomoses of Veins 651 Superficial Veins 651 Deep Veins, Verne Comites 652 Sinuses 652 Pulmonary Veins 652 Systemic Veins 652 Veins of the Head and Neck. Frontal Vein 653 Facial Vein 654 Surgical Anatomy 654 Temporal Vein 654 Internal Maxillary Vein 654 Temporo-maxillary Vein 655 Posterior Auricular Vein 655 Occipital Vein 665 Veins of the Neck. External Jugular Vein 655 Surgical Anatomy 655 Posterior External Jugular Vein 656 Anterior Jugular Vein 656 Internal Jugular Vein 656 Surgical Anatomy 656 Lingual Vein ... 656 Pharyngeal Vein 656 Thyroid Veins 656 Vertebral Veins . . .... 657 Veins of the Diploe 657 Cerebral Veins. Superficial Cerebral Veins 658 Deep Cerebral Veins 659 Cerebellar Veins 659 Sinuses of the Dura Mater. Superior Longitudinal Sinus 659 Inferior Longitudinal, Straight Sinuses . . . 660 Lateral Sinus . 660 Occipital Sinuses 661 Cavernous Sinuses 661 Surgical Anatomy 661 Circular Sinus 662 Superior Petrosal Sinus 662 Inferior Petrosal Sinus 662 Transverse Sinuses 663 Emissary Veins . 663 Veins of the Upper Extremity and Thorax. Superficial Veins 664 Deep Veins 664 Axillary Vein 666 Surgical Anatomy 667 Subclavian Vein 667 Innominate Veins 667 Peculiarities of 667 Internal Mammary Veins 668 Inferior Thyroid Veins 668 Superior Intercostal Veins 668 Superior Vena Cava 669 Azygos Veins 669 Bronchial Veins 670 Spinal Veins 670 Veins of the Lower Extremity-Abdomen and Pelvis. Internal Saphenous Vein 672 External Saphenous Vein 672 Popliteal Vein 673 Femoral Vein 674 External Iliac Vein 674 Internal Iliac Vein 674 Common Iliac Veins . 675 Inferior Vena Cava 675 Peculiarities 676 Lumbar Veins 676 Spermatic Veins 676 Surgical Anatomy 676 Ovarian Veins 676 Renal and Suprarenal Veins 677 Phrenic Veins 677 Hepatic Veins 677 Portal System of Veins. Superior Mesenteric Vein 677 Splenic Vein 677 Inferior Mesenteric Vein 677 Gastric Veins . 678 Portal Vein 679 Cardiac Veins 679 Coronary Sinus 679 THE LYMPHATICS. General Anatomy. Subdivision into Deep and Superficial .... 681 Lymphatic or Conglobate Glands 681 Thoracic Duct 682 Right Lymphatic Duct 682 Lymphatics of Head, Face, and Neck. Lymphatic Glands of Head 683 Lymphatics of the Head 683 Superficial Lymphatics of the Face 684 Deep Lymphatics of the Face 684 CONTENTS. 17 PAGE Lymphatics of the Cranium 684 Superficial Cervical Glands 685 Deep Cervical Glands 685 Superficial and Deep Cervical Lymphatics . . 686 Lymphatics of the Upper Extremity. Superficial Lymphatic Glands 686 Deep Lymphatic Glands 686 Axillary Glands 686 Superficial Lymphatics of Upper Extremity . 687 Deep Lymphatics of Upper Extremity .... 688 Lymphatics of the Lower Extremity. Superficial Inguinal Glands 688 Deep Lymphatic Glands 688 Anterior Tibial Gland 688 Deep Popliteal Glands 688 Deep Inguinal Glands 688 Gluteal and Ischiatic Glands 688 Superficial Lymphatics of Lower Extremity . 688 Internal Group 688 External Group 689 Deep Lymphatics of Lower Extremity .... 689 Lymphatics of Pelvis and Abdomen. Lymphatic Glands of Pelvis 689 External Iliac Glands 689 Internal Iliac Glands 690 Sacral Glands 690 Lumbar Glands 690 Superficial Lymphatics of Wall of Abdomen . 691 " " of Gluteal Eegion . . 691 " " of Scrotum and Peri- naeum 691 " " of Penis 691 " " of Labia,Nymphae,and Clitoris 691 PAGE Deep Lymphatics of Pelvis and Abdomen . . 691 Lymphatics of Bladder 691 " of Rectum 691 " of Uterus 691 " of Testicle : . . . . 692 of Kidney 692 of Liver 692 Lymphatic Glands of Stomach 692 Lymphatics of Stomach 692 Lymphatic Glands of Spleen 692 Lymphatics of Spleen . 692 Lymphatic System of the Intestine. Lymphatic Glands of Small Intestines (Mesen- teric Glands) 693 Lymphatic Glands of Large Intestine ... 693 Lymphatics of Small Intestines (Lacteals) . . 693 of Large Intestine 693 Lymphatics of Thorax. Deep Lymphatic Glands of Thorax . . . 693 Intercostal Glands 693 Internal Mammary Glands 693 Anterior Mediastinal Glands 693 Posterior Mediastinal Glands 693 Superior Lymphatics on Front of Thorax . 693 Deep Lymphatics of Thorax 693 Intercostal Lymphatics 694 Internal Mammary Lymphatics*. . . . 694 Lymphatics of Diaphragm . 694 Bronchial Glands ... 694 Lymphatics of Lung 694 Cardiac Lymphatics 694 Thymic Lymphatics 694 Thyroid Lymphatics 694 Lymphatics of (Esophagus 694 NERVOUS SYSTEM. General Anatomy. Subdivision into Cerebro-spinal Axis, Ganglia, and Nerves 695 The Spinal Cord and its Membranes. Dissection 695 Membranes of the Cord 695 Dura Mater 695 Arachnoid 696 Pia Mater 696 Ligamentum Denticulatum 697 Spinal Cord 697 Fissures of Cord 698 Columns of Cord 698 Structure of the Cord 698 Commissure of the Cord 699 Minute Anatomy of the Cord 700 Neuroglia 700 White Substance 700 Gray Substance 702 The Brain and its Membranes. Membranes of the Brain 704 Dura Mater. Structure 704 Arteries, Veins 704 Nerves 705 Glandulfie'Pacchioni 705 Processes of the Dura Mater 705 Falx Cerebri 705 Tentorium Cerebelli 705 Falx Cerebelli• . 706 The Arachnoid Membrane. Subarachnoid Space 706 Cerebro-Spinal Fluid 706 The Pia Mater 706 The Brain. Subdivision into Cerebrum, Cerebellum, Pons Varolii, Medulla Oblongata 707 Weight of Brain 707 Medulla Oblongata. Pyramids 709 Lateral Tract, and Olivary Body 709 Funiculus of Rolando 709 Funiculus Cuneatus 709 Restiform Bodies 710 Funiculus Gracilis 710 Posterior Surface of Medulla Oblongata . . . 710 Structure of Medulla Oblongata 711 " of Pyramid 711 " of Olivary Body ... 711 " of Lateral Tract 711 '' of Funiculus of Rolando 711 " of Funiculus Cuneatus 711 " of Funiculus Gracilis 711 " of Restiform Body 711 Arciform Fibres of Medulla 712 Raphe 712 Formatio Reticularis 712 Gray Matter of Medulla 713 The Pons Varolii. Structure 714 Microscopic Anatomy of Pons 715 Septum 716 Cerebrum. Upper Surface of Cerebrum 717 Convolutions 717 Structure of the Convolutions 717 Lobes and Fissures of the Brain 717 Fissure of Sylvius 717 Fissure of Rolando 717 Parieto-occipital Fissure 718 Frontal Lobe ... 718 Parietal Lobe 720 Occipital Lobe 721 Temporo-sphenoidal Lobe 721 18 CONTENTS. PAGE Central Lobe 721 Calloso-marginal Fissure 722 Parieto-occipital Fissure ....... 722 Calcarine Fissure 722 Collateral Fissure 722 Dentate Fissure 722 Gyrus Fornicatus 723 Marginal Convolution 723 Quadrate Lobe 723 Cuneate Lobe ...... .... 723 Uncinate Gyrus or Internal Occipito-tem- poral Convolution 723 External Occipito-temporal Convolution . 724 Cerebral Localization and Topography . 724 Base of the Brain 727 General Arrangement of the Parts composing the Cerebrum 730 Interior of the Cerebrum 730 Corpus Callosum 731 Lateral Ventricle 732 Corpus Striatum 733 Tsenia Semicircularis 734 Choroid Plexus 735 Corpus Fimbriatum 735 Hippocampus Major 735 Transverse Fissure 736 Septum Lucidum 736 Fifth Ventricle 737 Fornix 737 Velum Interpositum 738 Thalamus Opticus 738 Third Ventricle 738 Commissures of Third Ventricle . . . 740 Foramen of Monro 740 Pineal Gland 740 Corpora Quadrigemina 741 Corpora Geniculata 742 Structure of Cerebrum 742 White Matter of the Cerebrum 742 Diverging Fibres 743 Commissural Fibres . 743 Gray Matter of the Cortex 744 Gray Matter of the Basal Ganglia 746 Central Gray Matter of the Cerebrum .... 747 Cerebellum. Its Position and Size 747 Its Weight, etc 748 Lobes of the Cerebellum 748 Cerebellum, Upper Surface 748 " Under Surface 748 Inferior Vermiform Process 749 Internal Structure of the Cerebellum .... 749 White Matter of Cerebellum 750 Peduncles of Cerebellum 750 Valve of Vieussens 750 Gray Matter of Cerebellum 751 Microscopical Appearance of Cortex 751 Fourth Ventricle 752 Lining Membrane 753 Choroid Plexus 753 Gray Matter, Origin of Cranial Nerves from . 753 The Cranial Nerves. Enumeration 754 Olfactory Nerve 754 Surgical Anatomy 755 Optic Nerve 755 Tracts 755 Commissure 756 Surgical Anatomy 756 Motor Oculi Nerve 757 Surgical Anatomy .... 758 Pathetic Nerve 758 Surgical Anatomy 759 Trifacial Nerve 759 Gasserian Ganglion 759 Ophthalmic Nerve 759 Lachrymal and Frontal Branches .... 760 Nasal Branches 761 Ophthalmic Ganglion 761 PAGE Superior Maxillary Nerve 763 Spheno-palatine Ganglion 765 Inferior Maxillary Nerve 767 Auriculo-temporal Branch 768 Lingual Branch 769 Inferior Dental Branch 769 Otic Ganglion 770 Submaxillary Ganglion 771 Surgical Anatomy of Fifth Nerve ..... 771 Abducens Nerve 772 Belations of the Orbital Nerves in the Cavern- ous Sinus 772 Belations, etc. in the Sphenoidal Fissure . . . 772 " in the Orbit 773 Surgical Anatomy 773 Facial Nerve 773 Branches of Facial Nerve 774 Surgical Anatomy 777 Auditory Nerve 778 Surgical Anatomy 778 Glosso-pharyngeal Nerve 778 Pneumogastric (Vagus) Nerve 781 Surgical Anatomy 784 Spinal Accessory Nerve 785 Surgical Anatomy 785 Hypoglossal Nerve 786 Surgical Anatomy 788 The Spinal Nerves. Roots of the Spinal Nerves 788 Origin of Anterior Roots 788 " of Posterior Roots 789 Ganglia of the Spinal Nerves 789 Posterior Divisions of the Spinal Nerves . . . 789 Anterior Divisions of the Spinal Nerves . . . 789 Cervical Nerves. Roots of the Cervical Nerves 790 Posterior Divisions of the Cervical Nerves . . 790 Anterior Divisions of the Cervical Nerves . . 792 The Cervical Plexus. Superficial Branches of the Cervical Plexus . 793 Deep Branches of the Cervical Plexus .... 795 The Brachial Plexus. Branches above the Clavicle. Posterior Thoracic 798 Suprascapular 800 Branches beloiv the Clavicle. Anterior Thoracic 800 Subscapular Nerves 800 Circumflex Nerve 801 Musculo-cutaneous Nerve 801 Internal Cutaneous Nerve 802 Lesser Internal Cutaneous Nerve 802 Median Nerve 802 Ulnar Nerve 804 Musculo-spiral Nerve 805 Radial Nerve 806 Posterior Interosseous Nerve 807 Surgical Anatomy of Brachial Plexus .... 807 Dorsal Nerves. Roots of the Dorsal Nerves 808 Posterior Divisions of the Dorsal Nerves . . . 808 Anterior Divisions of the Dorsal Nerves . . . 808 First Dorsal Nerve 808 Upper Dorsal Nerves 810 Lower Dorsal Nerves 810 Last Dorsal Nerve 811 The Lumbar Nerves. Root of Lumbar Nerves 812 Posterior Division of Lumbar Nerves .... 812 Anterior Divisions of Lumbar Nerves .... 812 The Lumbar Plexus. Branches of Lumbar Plexus 813 Ilio-hypogastric Nerve 813 CONTENTS. 19 PAGE Ilio-inguinal Nerve 813 Genito-crural Nerve 814 External Cutaneous Nerve 816 Obturator Nerve 816 Accessory Obturator Nerve 816 Anterior Crural Nerve 817 Branches of Anterior Crural . 817 Middle Cutaneous 817 Internal Cutaneous 817 Long Saphenous 818 Muscular and Articular Branches .... 818 The Sacral and Coccygeal Nerves. Roots of, origin of 819 Posterior Divisions of Sacral Nerves 819 Coccygeal Nerve 820 Anterior Divisions of Sacral Nerves 820 The Sacral Plexus. Superior Gluteal Nerve 823 Inferior Gluteal Nerve 823 Pudic Nerve 823 Small Sciatic Nerve 824 Great Sciatic Nerve 824 Internal Popliteal Nerve 824 Short Saphenous Nerve 825 Posterior Tibial Nerve .... 825 Plantar Nerves 825 External Popliteal or Peroneal Nerve .... 826 Anterior Tibial Nerve 827 Musculo-cutaneous Nerve 827 Surgical Anatomy of Lumbar and Sacral Plexus 827 The Sympathetic Nerve. Subdivision of, into Parts 829 PAGE Branches of the Ganglia, General Description of 829 Cervical Portion of the Gangliated Cord 831 Superior Cervical Ganglion 831 Carotid Plexus 831 Cavernous Plexus 831 Middle Cervical Ganglion 834 Inferior Cervical Ganglion 834 Thoracic Part of the Gangliated Cord . 834 Great Splanchnic Nerve 835 Lesser Splanchnic Nerve 835 Smallest Splanchnic Nerve 835 Lumbar Portion of the Gangliated Cord. 835 Pelvic Portion of the Gangliated Cord . 836 The Great Plexuses of the Sympathetic. Cardiac Plexuses 836 Great Cardiac Plexus 836 Superficial Cardiac Plexus 836 Coronary Plexuses 837 Solar Plexus 837 Phrenic Plexus 837 Suprarenal Plexus 837 Renal Plexus 837 Spermatic Plexus 837 Coeliac Plexus 838 Superior Mesenteric Plexus . 839 Aortic Plexus 839 Inferior Mesenteric Plexus 839 Hypogastric Plexus 839 Pelvic Plexus 840 Inferior Hsemorrhoidal Plexus 840 Vesical Plexus 840 Prostatic Plexus 840 Vaginal Plexus 840 Uterine Plexus 840 ORGANS OF SENSE. Tongue. Structure of 842 Papillae of 842 Glands of 844 Fibrous Septum of 845 Arteries and Nerves of 845 Muscles of 845 Nerves of 846 Surgical Anatomy of 846 Nose. Cartilages of 848 Muscles of 849 Skin 849 Mucous Membrane 849 Arteries, Veins, and Nerves 849 Nasal Fossse. Mucous Membrane of 850 Superior, Middle, and Inferior Meatuses . . . 850 Arteries, Veins, and Nerves of Nasal Fossae . . 851 Surgical Anatomy of Nose and Nasal Fossae . . 851 Eye. Situation, Form of 852 Capsule of Tenon 853 Tunics of, sclerotic . . • 853 Cornea 854 Choroid 856 Ciliary Processes 857 Iris 858 Membrana Pupillaris 860 Ciliary Muscle 860 Retina '..... 860 Structure of Retina 860 Structure of Retina at Yellow Spot . . . . 864 Arteria Centralis Retinae 864 Humors of the Eye. Aqueous Humor 865 Anterior Chamber 865 Posterior Chamber 865 Vitreous Body 865 Crystalline Lens and its Capsule 866 Changes Produced in the Lens by Age .... 866 Suspensory Ligament of Lens 867 Canal of Petit . 867 Vessels of the Globe of the Eye 867 Nerves of Eyeball 867 Surgical Anatomy of Eye 867 Appendages of the Eye. Eyebrows 869 Eyelids 869 Eyelashes 869 Structure of the Eyelids 869 Tarsal Plates 870 Meibomian Glands 870 Conjunctiva . 870 Carunculae Lachrymales 871 Lachrymal Apparatus. Lachrymal Gland 871 " Canals 872 " Sac 872 Nasal Duct 873 Front of Eye 873 Surgical Anatomy 873 Ear. External Ear. Pinna, or Auricle 874 Structure of Auricle 874 Ligaments of the Pinna 875 Muscles of the Pinna 875 Arteries, Veins, and Nerves of the Pinna . . . 876 Auditory Canal 876 Surface Form 877 Middle Ear, or Tympanum. Cavity of Tympanum 878 Eustachian Tube 880 20 CONTENTS. PAGE Membrani Tympani ... 880 Structure of 880 Ossicles of the Tympanum 880 Ligaments of the Ossicula 881 Muscles of the Tympanum 882 Mucous Membrane of Tympanum 882 Arteries of Tympanum 882 Veins and Nerves of Tympanum 882 Internal Ear, or Labyrinth. Vestibule 883 Semicircular Canals: Superior Semicircular Canal 884 Posterior Semicircular Canal 884 External Semicircular Canal 884 PAGE Cochlea : Central Axis of, or Modiolus 885 Spiral Canal of 885 Scala Tympani, Scala Vestibuli, and Scala Media 886 The Organ of Corti 886 Perilymph 888 Membranous Labyrinth 888 Utricle and Saccule - . 888 Membranous Semicircular Canals 889 Endolymph 889 Otoliths 889 Vessels of the Labyrinth 889 Auditory Nerve, Vestibular Nerve 890 Cochlear Nerve 890 Surgical Anatomy 890 THE ORGANS OF DIGESTION. Subdivisions of the Alimentary Canal .... 892 The Mouth 892 The Lips 892 The Cheeks 893 The Gums 894 The Teeth. General Characters of 894 Permanent Teeth 894 Incisors and Canine 894 Bicuspids 895 Molars 895 Temporary or Milk Teeth 896 Structure of the Teeth 896 Ivory or Dentine 897 Enamel 898 Cortical Substance 898 z Development of the Teeth 899 " of the Permanent Teeth .... 901 Eruption of the Teeth 902 The Palate. Hard Palate 903 Soft Palate 903 Uvula, Pillars of the Soft Palate 903 Mucous Membrane, Aponeurosis, and Muscles of Soft Palate 904 The Tonsils. Arteries 904 Veins and Nerves of Tonsils ....... 904 The Salivary Glands. Parotid Gland. Situation and Relations 904 Stenson's Duct 905 Vessels and Nerves of Parotid Gland .... 906 The Submaxillary Gland. Situation and Relations 906 Wharton's Duct 906 Vessels and Nerves of Submaxillary Gland . 907 The Sublingual Gland. Situation and Relations 907 Vessels and Nerves of 907 Structure of Salivary Glands 907 Surface Form of Mouth 909 The Pharynx and (Esophagus. Situation and Relations 910 Structure of Pharynx 910 Surgical Anatomy 911 Relations of (Esophagus 912 Structure 912 Vessels and Nerves of 913 Surgical Anatomy 913 The Abdomen. Boundaries 914 Apertures of 914 Regions 914 The Peritoneum. Reflections traced 917 Foramen of Winslow 918 Lesser Omentum 923 Great Omentum 923 Gastro-splenic Omentum 923 Mesentery 923 Meso-csecum 924 Meso-colon, Meso-rectum, Appendices Epiploicre 925 The Stomach. Situation 925 Splenic End, Pyloric End 925 Cardiac and Pyloric Orifices 926 Greater and Lesser Curvatures 926 Surfaces 926 Ligaments of 926 Alterations in Position . . . 926 Pylorus 926 Structure of Stomach 926 Serous and Muscular Coats 927 Mucous 927 Gastric Follicles 928 Vessels and Nerves of Stomach 929 Surface Marking 930 Surgical Anatomy 930 Small Intestines. Duodenum 931 Ascending Portion 931 Descending Portion 931 Transverse Portion 931 Vessels and Nerves of Duodenum 932 Jejunum 932 Ileum 933 Meckel's Diverticulum 933 Structure of Small Intestines 933 Serous and Muscular Coats . 933 Mucous Membrane and Epithelium 933 Valvulffi Conniventes 933 Villi, their Structure 934 Simple Follicles 936 Duodenal Glands 936 Solitary Glands 936 Peyer's Glands 937 Large Intestine. Ceecum 939 Appendix Cseci Vermiformis 939 Fossae in neighborhood of Caecum .... 940 Ileo-caecal Valve 940 Colon 941 Ascending 941 Transverse 941 Descending 941 Sigmoid Flexure 941 Rectum 944 Upper Portion 944 Middle Portion 944 Lower Portion 944 Structure of Large Intestine 944 CONTENTS. 21 PAGE Serous Coat 944 Muscular Coat 944 Areolar and Mucous Coats 945 Simple Follicles 945 Solitary Glands 945 Surface Form 946 Surgical Anatomy 946 Livee. Size, Weight, Position of 948 Its Surfaces and Borders 949 Longitudinal 949 Lateral 950 Coronary, Round Ligament 950 Fissures. Longitudinal 950 Fissure of Ductus Venosus 951 Portal Fissure 951 Fissures for Gall-bladder and Vena Cava . . . 951 Lobes. Right 952 Left 952 Quadratus Spigelii 952 Caudatus 952 Vessels of Liver 952 Nerves of Liver 953 Structure of Liver 953 Serous (.'oat 953 Fibrous Coat 953 Lobules 953 Hepatic Cells 954 Hepatic Artery 954 Portal Vein 954 PAGE Hepatic Veins 954 Biliary Ducts .... 955 The Gall-bladdee. Relations 956 Structure 956 Biliary Ducts 956 Hepatic Duct 956 Cystic Duct 956 Common Choledic Duct 957 Structure of Biliary Ducts . 957 Surface Marking of Liver 957 Surgical Anatomy 958 The Panceeas. Dissection 958 Relations 958 Duct 960 Structure 960 Vessels and Nerves 961 Surface Marking 961 Surgical Anatomy 961 The Spleen. Relations 961 Size and Weight 962 Structure of Serous and Fibrous Coats .... 962 Proper Substance 963 Splenic Artery, Distribution 963 Malpighian Bodies 964 Capillaries of Spleen 964 Veins of Spleen 965 Lymphatics and Nerves 965 Surface Marking of Spleen 965 Surgical Anatomy . 966 THE THORAX. Cavity of • 967 Upper Opening 967 Lower Opening 967 The Pericardium. Structure 968 Fibrous Layer 968 Serous Layer 969 The Heart. Position 970 Size 971 Subdivision into Four Cavities 971 Circulation of Blood in Adult 971 Auriculo-ventricular and Ventricular Grooves. 971 The Right Auricle. Sinus 972 Appendix 972 Openings 972 Valves 973 Relics of Foetal Structure 973 Musculi Pectinati 973 The Right Ventricle. Infundibulum 973 Openings 974 Tricuspid Valve 974 Semilunar 974 Chords® Tendineae and Columnse Carneae . . . 975 The Left Auricle. Sinus 975 Appendix 975 Openings 975 Musculi Pectinati 976 The Left Ventricle. Openings 976 Mitral and Semilunar Valves 977 Endocardium 978 Structure of Heart. Fibrous Rings 978 Muscular Structure 978 Muscular Structure of Auricles 978 Muscular Structure of Ventricles 978 Vessels and Nerves of Heart 979 Surface Marking of Heart 980 Peculiarities in Vascular System of Foetus . . 980 Foramen Ovale, Eustachian Valve 980 Umbilical or Hypogastric Arteries 981 Ductus Arteriosus 981 Foetal Circulation 981 Changes in Vascular System at Birth .... 981 ORGANS OF VOICE AND RESPIRATION. The Larynx. Cartilages of the Larynx 984 Thyroid Cartilage 984 Cricoid Cartilage 985 Arytenoid Cartilages, Cartilages of Santo- rini and Wrisberg 986 Epiglottis 986 Ligaments of the Larynx 986 Ligaments connecting the Thyroid Cartilage with the Os Hyoides 987 Ligaments connecting the Thyroid Cartilage with the Cricoid 987 Ligaments connecting the Arytenoid Cartilages to the Cricoid 987 Ligaments of the Epiglottis 987 Superior Aperture of the Larynx 987 Cavity of the Larynx 988 Rima Glottidis a 988 False Vocal Cords . . . . F 988 True Vocal Cords 988 Ventricle of Larynx, Sacculus Laryngis . . . 988 Muscles of Larynx 989 Crico-thyroid 989 Crico-arytenoideus posticus 989 22 CONTENTS. PAGE Crico-arytenoideus lateralis 990 Arytenoideus 990 Thyro-arytenoideus 990 Arytenoideus rectus . ... f 991 Muscles of the Epiglottis 991 Thyro-epiglottideus 991 Aryteno-epiglottideus, superior 991 " inferior 991 Actions of Muscles of Larynx 991 Mucous Membrane of Larynx 992 Glands, Vessels, and Nerves of Larynx . . . 992 The Trachea. Relations 992 Bronchi 993 Structure of Trachea . 994 Surface Form 995 Surgical Anatomy of Laryngo-tracheal Region. 995 The Pleura. Reflections 997 Vessels and Nerves 998 Surgical Anatomy 998 The Mediastina. Superior Mediastinum 1000 Anterior Mediastinum 1000 Middle Mediastinum 1000 Posterior Mediastinum 1000 The Lungs. ' PAGE Surfaces 1001 Borders and Lobes 1002 Root of Lung 1002 Weight, Color, and Properties of Substance of Lung 1002 Structure of Lung 1002 Serous Coat and Subserous Areolar Tissue . 1002 Parenchyma and Lobules of Lung 1003 Bronchi, Arrangement of, in Substance of Lung 1003 Structure of smaller Bronchial Tubes .... 1003 The Air-cells 1003 Pulmonary Artery 1003 Pulmonary Capillaries and Veins ... . 1004 Bronchial Arteries and Veins 1004 Lymphatics and Nerves of Lung 1004 Surface Form of Lungs 1004 Surface Anatomy 1006 The Thyroid Gland. Surface and Relations 1007 Structure 1007 Vessels and Nerves 1008 Surgical Anatomy 1008 The Thymus Gland. Relations 1009 Structure 1009 Vessels and Nerves 1010 THE URINARY ORGANS. The Kidneys. Relations 1011 Dimensions, Weight 1011 General Structure 1012 Cortical Substance 1013 Medullary Substance 1013 Minute Structure 1013 Malpighian Bodies 1013 " Tufts '. . . 1013 " Capsule 1013 Tubuli Uriniferi, Course 1014 " " Structure 1016 Renal Blood-vessels 1017 Renal Veins 1018 Verne Recta 1018 Nerves 1018 Lymphatics 1019 Surface Form 1019 Surgical Anatomy 1019 The Ureters. Situation 1020 Calices 1020 Course 1020 Relations 1020 Structure 1020 The Suprarenal Capsules. Gelations 1021 Structure 1022 Vessels and Nerves 1023 The Pelvis. Boundaries 1023 Contents 1023 The Bladder. Shape, Position, Relations 1023 Subdivisions 1024 Urachus 1024 Ligaments 1026 Structure 1027 Interior of Bladder 1027 Vessels and Nerves 1028 Surface Form 1028 Surgical Anatomy 1029 Male Urethra. Divisions 1030 Structure 1030 Surgical Anatomy 1031 MALE GENERATIVE ORGANS. Prostate Gland 1032 Structure 1033 Vessels and Nerves 1033 Surgical Anatomy 1033 Cowper's Glands 1034 The Penis. Root : 1034 Glans Penis 1034 Body 1034 Corpora Cavernosa - 1035 Erectile Tissue 1035 Arteries of the Penis 1036 Corpus Spongiosum 1036 The Bulb 1036 Structure of Corpus Spongiosum 1037 Lymphatics of the Penis 1037 Nerves of the Penis 1037 Surgical Anatomy 1037 The Testes and their Coverings. Scrotum 1037 Coverings of the Testis1038 Vessels and Nerves of the Coverings of the Testis1039 The Spermatic Cord. Its Composition1039 Relations of, in Inguinal Canal1039 Arteries of the Cord1039 Veins of the Cord1039 Lymphatics and Nerves of the Cord1039 Surgical Anatomy1039 The Testes. Form and Situation 1040 Size and Weight•1040 Coverings1040 CONTENTS. 23 PAGE Tunica Vaginalis1040 Tunica Albuginea1041 Mediastinum Testis1041 Tunica Vasculosa1041 Structure of the Testis1041 Lobulus of the Testis1042 Tubuli Seminiferi1042 Arrangement in Lobuli1042 in Mediastinum Testis1042 in Epididymis1042 Vas Deferens, Course, Relations1043 Structure1043 PAGE Vas Aberrans1043 Surgical Anatomy1043 Vesiculte Seminales1044 Form and Size1044 Relations . . .'1044 Structure1044 Ducts1044 Descent of the Testes. Gubernaculum Testisv . 1045 Canal of Nuck1046 Mons Veneris, Labia Maj ora1047 " Labia Minora1048 Clitoris, Meatus Urinarius1048 Hymen, Glands of Bartholin1049 Female Urethra1049 Female Rectum1050 Vagina. Relations1050 Structure1050 Uterus. Situation, Form, Dimensions1051 Fundus, Body, and Cervix1051 Ligaments1052 Cavity of the Uterus1053 Cavity of the Cervix1053 Structure1053 Vessels and Nerves 1055 Its Form, Size, and Situation in the Foetus . . 1055 at Puberty1055 FEMALE ORGANS OF GENERATION. Its Form, Size, etc. during Menstruation . . . 1055 " during Pregnancy 1055 after Parturition1055 in Old Age1056 Appendages of the Uterus. Fallopian Tubes1056 Structure1056 Ovaries1057 Structure1057 Graafian Vesicles1058 Discharge of the Ovum1059 Ligament of the Ovary 1059 Round Ligaments1059 Vessels and Nerves of Appendages1060 Mammary Glands. Situation and Size1060 Nipple 1061 Structure of Mamma 1061 Vessels and Nerves1061 SURGICAL ANATOMY OF HERNIA. INGUINAL HERNIA. Coverings of Inguinal Hernia. Dissection . . 1062 Superficial Fascia1062 Superficial Vessels and Nerves1062 Deep Layer of Superficial Fascia1063 Aponeurosis of External Oblique1063 External Abdominal Ring1064 Pillars of the Ring1064 Intercolumnar Fibres1064 Fascia1064 Poupart's Ligament1065 Gimbernat's Ligament1065 Triangular Ligament1065 Internal Oblique Muscle1066 Cremaster1066 Transversalis Muscle1066 Spermatic Canal1067 Fascia Transversalis1067 Internal Abdominal Ring1068 Subserous Areolar Tissue1068 Deep Epigastric Artery1068 Peritoneum1068 Oblique Inguinal Hernia. Course and Coverings of Oblique Heruia . . . 1069 Seat of Stricture1070 Scrotal Hernia1071 Bubonocele1071 Congenital Hernia1071 Infantile and Encysted Hernia1071 Hernia into the Funicular Process1071 Direct Inguinal Hernia. Course and Coverings of the Hernia .... 1072 Seat of Stricture1072 Incomplete Direct Hernia1072 Comparative Frequency of Oblique and Direct Hernia1072 Division of Stricture in Inguinal Hernia . . 1072 SURGICAL ANATOMY OF FEMORAL HERNIA. Dissection1072 Superficial Fascia1072 Cutaneous Vessels1072 Internal Saphenous Vein1072 Superficial Inguinal Glands1075 Cutaneous Nerves1075 Deep Layer of Superficial Fascia1075 Cribriform Fascia1075 Fascia Lata1075 Iliac Portion1075 Pubic Portion1076 Saphenous Opening1076 Crural Arch1077 Gimbernat's Ligament1078 Crural Sheath•1078 Deep Crural Arch1079 Crural Canal1079 Femoral or Crural Ring 1080 Position of Parts around the Ring 1080 Septum Crurale1080 Descent of Femoral Hernia1081 Coverings of Femoral Hernia1081 Varieties of Femoral Hernia1081 Seat of Stricture;1082 24 CONTENTS. SURGICAL ANATOMY OF PERINEUM AND ISCHIO-RECTAL REGION. Ischio-Rectal Region. PAGE Dissection of 1083 Boundaries of1083 Superficial Fascia1083 Ischio-rectal Fossa1084 Position of Parts contained in 1084 Male Perineeum. Boundaries and Extent1084 Deep Layer of Superficial Fascia1085 Course taken by the Urine in Rupture of the Urethra 1085 Muscles of the Perinseum (Male) 1085 Deep Perineal Fascia 1086 Superficial Layer1086 Deep Layer . . .1087 Parts between the two Layers 1087 Compressor Urethra*.1087 PAGE Cowper's Glands1087 Pudic Vessels and Nerves1087 Artery of the Bulb 1087 Position of the Viscera at Outlet of Pelvis . . 1088 Prostate Gland1088 Surgical Anatomy of Lithotomy1089 Parts divided in the Operation1089 Parts to be avoided in the Operation . . . .1089 Abnormal Course of Arteries in the Perinseum 1089 Female Perineeum. Superficial Fascia1089 Deep Fascia1090 Compressor Urethrse1090 Perineal Body 1090 Pelvic Fascia1091 Obturator Fascia 1091 Recto-vesical Fascia1092 INDEX 109.3 Page 25-32 missing GENERAL ANATOMY. THE fluids of the body, which are intended for its nutrition, are the lymph, the chyle, and the blood. There are other fluids also which partially subserve the same purpose, as the saliva, the gastric juice, the bile, the intestinal secretion; and others which are purely excrementitious, as the urine. But there is no need to describe the rest in this place, since they are the secretions of special organs, and are described, as far as is judged necessary for the purposes of this work, in subsequent pages. We shall here speak first of the blood, and next of the lymph and chyle. THE BLOOD. The blood is a thickish, opaque fluid, of a bright-red or scarlet color when it flows from the arteries, of a dark-red or purple color when it flows from the veins. It is viscid, and has a somewhat clammy feeling; it is salt to the taste, and has a peculiar faint odor. It has an alkaline reaction. Its specific gravity at 60° F. is about 1.055, and its temperature is generally about 100° F., though varying slightly in different parts of the body. General Composition of the Blood.-When blood is drawn from the body and allowed to stand, it solidifies in the course of a very few minutes into a jelly-like mass, which has the same appearance and volume as the fluid blood, and, like it, looks quite uniform. Soon, however, drops of a transparent yellowish fluid begin to ooze out from the surface of this mass and to collect around it. Coincidently with this the clot begins to contract, so that, in the course of about twenty-four hours, the original mass of coagulated blood has become separated into two parts -a "clot" or "coagulum," considerably smaller and firmer than the first-formed jelly-like mass, and a large quantity of yellowish fluid, the serum, in which the clot floats. The clot thus formed consists of a solid, colorless material, called fibrin, and a large number of minute cells or corpuscles, called blood-corpuscles, which are entangled and enclosed in the fibrin. The fibrin is formed during the act of solidi- fication. In the fluid blood in the living body there are two substances, named fibrinogen and paraglobulin or serum globulin, which may be termed fibrin-factors. These two materials, when withdrawn from the body, become acted upon by a third material, also contained in the blood, and named a fibrin-ferment, and unite together, forming a solid substance, fibrin. This latter in its process of solidifica- tion encloses and entangles the blood-corpuscles, and thus the clot is formed. It must be stated, however, that recent observations have shown that, in the act of clotting outside the body, solutions of fibrinogen, on addition of fibrin- ferment, clot firmly, provided that the solution has a trace of a calcium salt. Consequently paraglobulin would not appear to be necessary for this process. The act of clotting outside the body, which is evidence of the death of the blood, is a process dissimilar to that which occurs inside the body. In the former case a body, fibrinogen, is acted upon by the fibrin-ferment, which appears only after the death of the white corpuscles. In the latter, intravascular clotting can be produced in two ways: (1) by directly stimulating living blood, as by the trans- fixion of an artery by a needle; or (2) by injection of proteid bodies, which con- tain lecithin, and which, when injected into the blood, kill in a few minutes by 33 34 GENERAL ANA TOAIY. producing intravascular clotting. Further, injection of fibrin-ferment into the blood has negative results; and again, addition of proteid and lecithin to blood, removed from the body, does not in any way affect the ordinary coagulation process. We may now consider the constituents of the blood in another way. If a drop of blood is placed in a thin layer on a glass slide and examined under the microscope, it will be seen to consist of a number of minute bodies or corpuscles floating in a clear fluid; and, on more minute examination, it will be found that these corpuscles are of two kinds. The one, greatly preponderating over the other in point of numbers, is termed the colored corpuscle; the other, fewer in number and less conspicuous, is termed the colorless corpuscle. From this we learn that blood is a fluid holding a large number of corpuscles of two varieties in suspension. The fluid is named liquor sanguinis or plasma, and must not be con- fused with the serum spoken of above in connection with the coagulation of the blood. It is serum and something more, for it contains one at least of the elements or factors from which fibrin is formed. The relation of these various constituents of blood to each other will be easily understood by a reference to the subjoined plan: Corpuscles Colored Colorless Clot Blood ' Fibrin Liquor Sanguinis Serum The blood-corpuscles, blood-disks, blood-globules are, as before stated, of two kinds: the red or colored, and the white or colorless corpuscles. The relative proportion of the one to the other has been variously estimated and no doubt varies under different circumstances. Thus venesection, by withdrawing a large proportion of the red globules, and by favoring the absorption of lymphatic fluid into the blood, greatly increases the relative proportion of the white corpuscles. Klein states that in healthy human blood there appears to be one white corpuscle for 600-1200 red ones. The proportion of corpuscles, colored and colorless com- bined, to liquor sanguinis is in one hundred volumes of blood about thirty-six volumes of the former to sixty-four of the latter. Colored corpuscles when examined under the microscope are seen to be circular disks, biconcave in profile, having a slight central depression, with a raised bor- der (Fig. 1. 6). When viewed with a moderate magnifying power, this central depression looks darker than the edge. When exam- ined singly by transmitted light, their color appears to be of a faint reddish-yellow when derived from arterial blood, and greenish-yellow in venous blood. It is to their aggregation that blood owes its red hue. Their size varies slightly even in the same drop of blood, but it may be stated that their average diameter is about s 0 of an inch, their thickness about yyyyy, or nearly one-quarter of their diameter. Besides these, especially in some anaemic and diseased conditions, certain cor- puscles are found of a much smaller size, about one- third or half the size of the ordinary one. These, however, are very scarce in normal blood. The number of red corpuscles in the blood is enormous; between 4,000,000 and 5,000,000 are contained in a cubic millimetre. Power states that the red corpuscles of an adult would present an aggregate surface of about 3000 square yards. Human blood-disks present no trace of a nucleus. They consist of two parts: a colorless envelope, or investing membrane, which is composed largely of fatty material, lecithin and cholesterine ; and a colored fluid contents, which is a solution of a substance named hcemoglobin. Hoemoglobin is a proteid compound of a very complex constitution (C600, H96o, Fig. 1.-Human blood-globules. a. Seen from the surface, b. Seen from the side. c. United in rou- leaux. d. Rendered spherical by water, e. Decolorized by the same. f. Blood-globules shrunk by evaporation. THE BLOOD. 35 N1m, FeS3, O179). It has a great affinity for oxygen, and when removed from the body crystallizes readily under certain circumstances. It is readily soluble in water, and the addition of this fluid to a drop of blood speedily dissolves out haemoglobin from the corpuscle. If the web of a frog's foot is spread out and examined under the microscope, the blood is seen to flow in a continuous stream through the vessels, and the corpuscles show no tendency to adhere to each other or to the wall of the vessel. Doubtless the same is the case in the human body ; but when drawn and examined on a slide without reagents, the blood-globules often collect into heaps like rouleaux of coins (Fig. 1, c). During life the red corpuscles may be seen to change their shape under pres- sure so as to adapt themselves to some extent to the size of the vessel. They are also highly elastic, for they speedily recover their shape when the pressure is removed. They are soon influenced by the medium in which they are placed, and by the specific gravity of the medium. In water they swell up, lose their shape, and become globular; subsequently the haemoglobin becomes dissolved out, and the envelope can be barely distinguished as a faint, circular outline. Solu- tions of salt or sugar, denser than the serum, give them a stellate or crenated appearance; and the usual shape may be restored by diluting the solution to the proper point. The same crenated outline may be produced as the first effect of the passage of an electric shock; subsequently, if sufficiently strong, the shock ruptures the envelope. A solution of salt or sugar of the same specific gravity as serum merely separates the blood-globules mechanically without changing their shape. The white corpuscles (Fig. 2) are rather larger than the red in human blood, measuring from about to tAtt °f an diameter. They consist of a transparent granular-looking protoplasm containing one, two, or more nuclei, and presenting bright granules, usually of a fatty nature, but which sometimes are of a reddish color, and are then supposed by some observers to be in a transition stage between the white and red cor- puscles. When absolutely at rest they are rounded or spheroidal, but under ordinary circumstances their form is very various, and they have the re- markable property of undergoing ''amoeboid" changes (Fig. 3). That is to say, they have the power of send- ing out finger-shaped or filamentous processes of their own substance, by which they move and take up granules from the surrounding substance. In locomotion the corpuscle pushes out a process of its substance-a pseudopodium, as it is called-and then shifts the rest of the body into it. In the same way, when any granule or particle comes in its way it wraps a pseudopodium round it, Fig. 2.-a. White corpuscles of human blood, d. Red corpuscles. High power. Fig. 3.-Human colorless blood-corpuscle, showing its successive changes of outline within ten minutes when kept moist on a warm stage. (Schofield.) and then, withdrawing it, lodges the particle in its own substance. By means of these amoeboid properties they have the power of wandering or emigrating from the blood-vessels by penetrating their coats, and thus finding their way into the perivascular spaces. The white corpuscle may be taken as the type of a true animal cell. It has no limiting membrane, but consists of a mass of transparent albuminous substance, called protoplasm, containing one or more nuclei. These nuclei become more 36 GENERAL ANATOMY. perceptible on the addition of acetic acid. The protoplasm contains bright granules, generally of a fatty nature. The white corpuscles are very similar to, if not identical with, the corpuscles of lymph and chyle, and they also bear a strong resemblance to the cells found in pus. From the fact that cells exactly like the colorless corpuscles are being constantly furnished to the blood by the lymphatic vessels, the chyle-ducts (and even the liver in the foetus), and also from their varying proportions in different parts of the circulation and in different pathological conditions, the colorless corpuscles are often regarded-with at any rate some probability-as an earlier stage of the colored blood-disks, but the evidence in favor of this cannot be regarded as conclusive. There can be no doubt that during embryonic life the red corpuscles are developed from mesoblastic cells in the vascular area of the blastoderm. They are at first nucleated and resemble white corpuscles, except in their color, and, like them, are possessed of amoeboid movements. They are succeeded by smaller, non-nucleated corpuscles, having all the characters of adult colored corpuscles, probably formed by a conversion of the former into the latter. So that at birth the nucleated red corpuscles have disappeared. In after life an important source of the red corpuscles is the red marrow of bones, in which certain cells found in the marrow are converted into colored blood-corpuscles by the loss of their nuclei, and by their protoplasm becoming tinged with yellow. It is probable, also, that the spleen may be a place for the formation of red corpuscles. This theory, which was formerly universally believed, and was then discarded for the hypothesis that the spleen was concerned in the destruction of the red corpuscles, has lately been revived by Bizzozero. The question must still be regarded as sub judice. The proportion of white corpuscles appears to vary considerably in different parts of the circulation, being much larger in the blood of the splenic vein and hepatic vein than in other parts of the body, while in the splenic artery they are very scanty. In addition to these corpuscles, a third variety is found in mammalian blood, and has been specially studied and described by Hayem, Bizzozero, and Osler. They are pale circular or oval disks, about one-quarter or one-third the size of the red blood-corpuscles, and apparently contain no nucleus. They have been named blood-plates or blood-plaques, and are supposed by Bizzozero to originate the fibrin- ferment, and to be especially concerned in the coagulation of the blood. The liquor sanguinis or plasma is the fluid part of the blood, and is composed of a permanently fluid portion, the serum, and of fibrin-factors, which unite spon- taneously when out of the body, and by their union form a solid substance, fibrin. These two fibrin-factors are named fibrinogen and paraglobulin or serum globulin. Paraglobulin is probably contained partly in solution in the plasma, and partly in the colorless corpuscles, and can be obtained by diluting the liquor sanguinis with ten times its volume of ice-cold water, and then transmitting through it a stream of carbon-dioxide. Fibrinogen may be obtained in the same way as para- globulin, but the liquor sanguinis must be still further diluted and the current of carbon-dioxide must pass for a much longer time. When these two fibrin factors are withdrawn from the body, their union to form fibrin is probably brought about by the agency of a third body, called a fibrin-ferment. Fibrin may be obtained by whipping the blood, after it has been withdrawn from the body, with a bundle of twigs, to which the fibrin, as it coagulates, adheres. Fibrin may also be obtained by filtering the freshly-drawn blood of an animal whose corpuscles are large, care being taken to retard coagulation as long as possible. Under these circumstances the corpuscles are retained on the filter, and the liquor sanguinis, passing through, coagulates and separates into fibrin, free from corpuscles, and serum. Fibrin, thus obtained, is a white or buff-colored substance, presenting a stringy appearance, and under the microscope exhibiting fibrillation. When exposed to the air for some time, it becomes hard, dry, brown, and brittle. It is LYMPH AND CHYLE. 37 a proteid compound, insoluble in hot or cold water, alcohol or ether. Under the influence of dilute hydrochloric acid it swells up, but does not dissolve; but when thus swollen it is easily dissolved by a solution of pepsin. If heated for a considerable time in a solution of dilute hydrochloric acid, it gradually dissolves. Serum is the fluid liquor sanguinis after the fibrin-factors have been separated from it. It is a straw-colored fluid having a specific gravity of 1.027, with an alkaline reaction. Upon boiling it becomes solid, on account of the albumen which it contains. It contains also salts, fatty matters, sugar, and gases. Gases of the Blood.-When blood is exposed to the vacuum of an air-pump, about half its volume is given off in the form of gases. These are carbonic acid, oxygen, and nitrogen. The relative quantities in 100 volumes of arterial and venous blood, at 0° C. and 1 m. pressure of mercury are shown in the accompanying table: Oxygen. Carbonic acid. Nitrogen. Arterial blood, ] 6 vols. 30 vols. 1 to 2 vols. Venous blood, 6 to 10 vols. 35 vols. 1 to 2 vols. Roughly stated, they are as follows: Carbonic acid about two-thirds of the whole quantity of gas, oxygen rather less than one-third, nitrogen below one- tenth (Huxley). The greater quantity of the oxygen is in loose chemical com- bination with the haemoglobin of the blood-corpuscles, but some part is simply absorbed, just as it would be by water. The carbonic acid is in a state of chemical combination with the salts of the serum, especially the sodium, with which it is combined partly as a carbonate and partly as a bicarbonate. The nitrogen is unimportant. It (or at least the greater part of it) is merely absorbed from the atmosphere under the pressure to which the blood is exposed, and can therefore be mechanically removed. Blood-crystals.-Haemoglobin, as stated above, when separated from the blood- corpuscles, readily undergoes crystallization. These crystals, named hcemoglobin crystals, all belong, with the exception of those obtained from the squirrel, to the rhombic system. In human blood they are elongated prisms (Fig. 4, a). In the Fig. 4.-Blood-crystals, a. Haemoglobin crystals from human blood, b. Haemin crystals from blood treated with acetic acid. c. Haematoidin crystals from an old apoplectic clot. squirrel they are hexagonal plates. Other crystals may be obtained by mixing dried blood with an equal quantity of common salt, and boiling it with a few drops of glacial acetic acid. A drop of the mixture placed on the slide will show the crystals on cooling. These are named hcemin crystals, and consist of small acic- ular prisms (Fig- 4, b). Occasionally in old blood-clots a third form of crystal is found, the haematoidin crystal (Fig. 4, c). LYMPH AND CHYLE. Lymph is a transparent, colorless, or slightly yellow fluid, which is conveyed by a system of vessels, named lymphatics, into the blood. These vessels take their rise in nearly all parts of the body, and take up from the worn-out tissues that portion which is still available for purposes of nutrition, and return it into the 38 GENERAL ANA TOMY. veins close to the heart, there to be mixed with the mass of the blood. The greater number of these lymphatics empty themselves into one main duct, the thoracic duct, which passes along the front of the spine and opens into one of the large veins at the root of the neck. The remainder empty themselves into a smaller duct, which terminates in the corresponding vein on the opposite side of the neck. Chyle is an opaque, milky-white fluid, absorbed by the villi of the small intestines from the food, and carried by a set of vessels similar to the lymphatics, named lacteals, to the commencement of the thoracic duct, where it is intermingled with the lymph and poured into the circulation through the same channels. It must be borne in mind that these two sets of vessels, lymphatics and lacteals, though differing in name, are identical in structure, and that the character of the fluid they convey is different only while digestion is going on. At other times the lacteals convey a transparent, nearly colorless fluid not to be distinguished from lymph. Both these sets of vessels, in their passage to the central duct, pass through certain small glandular bodies, termed lymphatic glands, where their contents undergo elaboration. Lymph, as its name implies, is a watery fluid. It closely resembles the liquor sanguinis, and contains about 5 per cent, of albumen and 1 per cent, of salts. When examined under the microscope, it is found to consist of a clear colorless fluid, in which are floating a number of corpuscles, lymph-corpuscles. These bodies are identical in structure, and not to be distinguished from the white blood- corpuscles previously described. They vary in number in different parts of the lymphatic vessels, and indeed are said by Kolliker to be absent in the smaller ones. They are always increased in number after the passage of the lymph through a lymphatic gland, and are said to be increased in size as the fluid ascends higher in the course of the circulation. Chyle is a milk-white fluid, which exactly resembles lymph in its physical and chemical properties, except that it has, in addition to the other constituents of lymph, an enormous amount of fatty granules, " the molecular basis of chyle,'' and it is to the presence of these molecules that chyle owes its milky color. Under the microscope it presents a number of corpuscles, named "chyle-corpuscles,'' which are indistinguishable from lymph-corpuscles or white blood-cells, and the molecular basis, consisting principally of fatty granules of extreme minuteness (Fig. 5, «), but also of a few small oil-globules. Lymph and chyle after their pas- sage through their respective glands, if withdrawn from the body and allowed to stand, separate more or less completely into a clear liquid, which is identical with the serum of the blood, and a thin jelly-like clot, consisting of a flbrillated matrix in which lymph-corpuscles or chyle-corpuscles and fatty molecules, as the case may be, are entangled. If the contents of the thoracic duct are exam- ined, especially after a meal, there may be found in it corpuscles with a reddish tinge. These are regarded as immature red corpuscles, or lymph- and chyle-corpuscles in process of transformation into blood-globules. They frequently give to the surface of clotted chyle and lymph a pinkish hue. They must not be mistaken for mature blood-glob- ules, which are sometimes found in lymph and chyle, and which are regarded by most observers as accidental-i. e. produced by the manipulations of the dissector. Fig. 5.-Chyle from the THE ANIMAL CELL. All the tissues and organs of which the body is composed were originally developed from a microscopic body (the ovum), consisting of a soft gelatinous THE ANIMAL CELL. 39 granular material enclosed in a membrane, and containing a vesicle, or small spherical body, inside which are one or more solid spots (see Fig. 73). This may be regarded as a perfect cell. Moreover, all the solid tissues can be shown to con- sist largely of similar bodies, differing, it is true, in external form, but essentially similar to an ovum. These are also cells. In the higher organisms all such cells may be defined as " nucleated masses of protoplasm of microscopic size." The two essentials, therefore, of an animal cell in the higher organisms are, the presence of a soft gelatinous granular material, similar to that found in the ovum, and which is usually styled protoplasm; and a small spherical body imbedded in it, and termed a nucleus;' the remaining con- stituents of the ovum-viz. its limiting membrane and the solid spot contained in the nucleus, called the nucleolus-are not considered essential to the cell, and in fact many cells exist without them. Protoplasm (sarcode, blastema, germinal matter, or bioplasm) is a proteid com- pound, consisting largely of muco-globulin. It also contains certain inorganic substances, as phosphorus and calcium, which latter appears to be essential to its life and function. It is of a semi-fluid, viscid consistence, and appears, sometimes, either as a hyaline substance, homogeneous and clear, or as a granular substance, consisting of minute molecules imbedded in a transparent matrix. These mole- cules are regarded by some as adventitious material taken in from without, and often probably of a fatty nature, since they are frequently soluble in ether. In most cells, however, protoplasm shows a more definite structure, consisting of minute striae or fibrils arranged in a clear transparent matrix, or a honeycombed reticulum containing in its interstices a homogeneous substance. Protoplasm is insoluble in water, coagulates at 130° F., and has a great affinity for certain staining reagents, as logwood or carmine. The most striking characteristics of protoplasm are its vital properties of motion and nutrition. By motion is meant the power which protoplasm has of changing its shape and position by some internal power in itself, which enables it to thrust out from its main body an irregular process, into which the whole of the protoplasmic substance is gradually drawn, so that the mass comes to occupy a new position. This, on account of its resemblance to the movements observed in the Amoeba or Proteus animalcule, has been termed " amoeboid movement." Ciliary movement, or the vibration of hair-like processes from the surface of any structure, may also be regarded as a variety of the motion with which protoplasm is endowed. Nutrition is the power which protoplasm has of attracting to itself the materials of growth from surrounding matter. When any foreign particle comes in contact with the protoplasmic substance, it becomes incorporated in it by being enwrapped by one or more processes projected from the parent mass and enclosed by them. When thus taken up, it may remain in the substance of the protoplasm for some time without change, and finally may be extruded again. The Nucleus is a minute body, imbedded in the protoplasm, and usually of a spherical or oval form, its size having little relation to the size of the cell. It is usually surrounded by a well-defined wall, the nuclear membrane, and is regarded as a portion of the protoplasmic substance, set apart for the purposes of repro- duction. The nuclear contents, known as the nuclear substance, is composed of a stroma or network and an interstitial substance, the relative amount of the two varying in different nuclei. In the adult nuclei, and especially in those about to divide, the network is exceedingly well developed, whilst in the young nuclei it is but ill-formed, and is represented only by short bands or fibrils connecting irreg- ular masses. In adult and in resting nuclei the fibres of the nuclear network stain very readily with certain dyes; they are therefore named Chromatin; while the interstitial substance does not stain readily, and is hence called Achromatin. The nuclear substance differs chemically from ordinary protoplasm in containing 1 In certain lower forms of life masses of protoplasm without any nucleus have been described by Huxley and others as cells. 40 GENERAL ANATOMY. nuclein, in its power of resisting the action of acids and alkalies, in its imbibing more intensely the stain of carmine, haematoxylin, etc., and in its remaining unstained by some reagents which color ordinary protoplasm; as, for example, nitrate of silver. The process of reproduction of cells commences in the nucleus, and is usually described as being brought about by indirect or by direct division. Indirect division, SIDE OR EQUATORIAL VIEW. END OR POLAR VIEW. SIDE OR EQUATORIAL VIEW. Fig. 6.-Karyokinesis, or indirect cell-division. Diagram explaining the formation of the chromatic and achromatic karyokinetic figures in epithelial cells and the way in which the prickles of prickle cells are formed. The radiating arrangement of protoplasmic granules is also indicated, although it is in the ova of the lower animals that this appearance has been more specially studied. All the figures are simplified for diagrammatic purposes, but represent stages which can easily be recognized in specimens properly stained. The longitudinal splitting of the filaments has not been represented, as it is probably of secondary importance. The polar ends of the loops often, if not always, break across like the equatorial end : this is purposely not represented in the diagram, a. Resting nucleus, the nuclear network deeply stained, b. Glomerulus, convolu- tion or skein, c. Rosette or wreath, n. Aster or monaster. E. Diaster or daughter star. F. Daughter rosettes. g. Daughter glomeruli or skeins, h. Daughter nuclei. (By Dr. S. or karyokinesis (karyomitosis'), has been observed in all the tissues-generative cells, epithelial tissue, connective tissue, muscular tissue, and nerve tissue-and it may THE ANIMAL CELL. 41 be that it will hereafter be shown that the division of cells always takes place in this way, and that the process of reproduction of cells by direct division is, as is believed by some observers, merely a sort of imperfect or abnormal karyokinesis. The process of reproduction by indirect division commences in the nucleus, the stroma of which undergoes complex changes, leading to the division of this body previous to the cleavage of the protoplasm of the cell. The changes consist briefly of the following: (1) At the commencement of the process the nuclear network is well developed, but shows only slight indications of activity. (2) The chromatic fibrils forming the nuclear network, after rearranging themselves, become thicker, and probably combined in one long filament, which forms a loose convolution. This is called the glomerulus or skein (Fig. 6, b). At the same time a number of protoplasmic granules arrange themselves at two points in the cell- protoplasm opposite each other; these points are called the poles, and the line midway between them, and bisecting at right angles a line connecting the two, is called the equator. (3) The filament becomes arranged in more or less distinct loops converging toward the two poles, resembling somewhat in appearance a rosette or wreath (Fig. 6, c). From the poles to the loops, fine threads, not stain- ing like the other (achromatic), are seen bridging across the space left between the filament and the cell-protoplasm. These are known as the nuclear spindle. (4) The loops now become flattened so as to form a festooned ring or star at the equator of the nucleus. This is known as the single star, aster, monaster. The loops begin to break transversely at the equator (Fig. 6, D*), having sometimes previously broken at their polar ends. The nuclear spindle or achromatin is very distinct, as well as a radiating arrangement of protoplasmic granules toward the poles. It is at this stage, or sometimes after, that a longitudinal splitting of the filaments occurs, so that they become more numerous and more slender. (5) After breaking across at the equator, the chromatic filaments move toward the poles as if they were guided by the achromatic threads. These threads bridge across between the two receding stars, which are known as diaster or daughter stars. The pro- toplasm, with its radiating granules, begins to group itself around the two poles (Fig. 6, e). (6) The daughter stars have now reached the poles ; the broken ends become united, so that each daughter chromatic filament becomes a single festooned filament, forming a rosette or wreath, the daughter rosettes or wreaths. There is now distinct evidence of cleavage in the protoplasm (Fig. 6, f). (7) By further irregular contraction the regular arrangement of the loops becomes lost, and the filament presents a convoluted appearance, constituting the daughter glomeruli or skeins (Fig. 6, g). The cleavage of the protoplasm is now complete except where the achromatic threads are found. (8) By further convolution and contraction the loops of the filament become fused together, and form again a network. The protoplasm is now again in contact with the nuclear network, which serves to form a wall around the nuclei, and two cZau/jZiter cells with nuclei are formed (Fig. 6, h). The remains of the achromatic threads bridge across the intercellular substance, constituting the prickles of prickle cells. In the reproduction of cells by direct division the process is brought about either by segmentation or by gemmation. In reproduction by segmentation or fission the nucleus first splits by becoming constricted in its centre, and thus assuming an hour-glass shape. This leads to a cleavage or division of the whole protoplasmic mass of the cell; and thus we find that two new cells have been formed, consisting of the same substance as the original one, and each containing a nucleus. These daughter cells are of course at first smaller than the original mother cell; but they grow, and the process may be repeated in them, so that multiplication may rapidly take place. In reproduction by gemmation a budding- off or separation of a portion of the nucleus and parent-cell takes place, and, becoming separated, forms a new organism. The cell-wall, which is not an essential constituent, and in fact is often absent, consists of a flexible, transparent, structureless or finely striated membrane, which is permeable to fluids. As far as is known, every animal cell is derived from a 42 GENERAL ANATOMY. pre-existing cell. The death of cells is accomplished either by their mechanical detachment from the surface, preceded possibly by their bursting and discharg- ing their contents, or by various forms of degeneration-fatty, pigmentary, or calcareous. All the surfaces of the body-the external surface of the skin, the internal surface of the digestive, respiratory, and genito-urinary tracts, the closed serous cavities, the inner coat of the vessels, and the ducts of all secreting and excreting glands-are covered by one or more layers of simple cells, called epithelium or epithelial cells. These cells are also present in the sensory and terminal parts of the organs of special sense, and in some other organs, as the pituitary and thyroid bodies. They serve various purposes, forming in some cases a protective layer, in others acting as an agent in secretion and excretion, and again in others being concerned in the elaboration of the organs of special sense. Thus, in the skin, the main purpose served by the epithelium (here called the epidermis) is that of protection. As the surface is worn away by the agency of friction or change of temperature new cells are supplied, and thus the surface of the true skin and the vessels and nerves which it contains are defended from damage. In the gastro- intestinal mucous membrane and in the glands the epithelial cells appear to be the principal agents in separating the secretion from the blood or from the aliment- ary fluids. In other situations (as the nose, fauces, and respiratory passages) the chief office of the epithelial cells appears to be to maintain an equable tempera- ture by the moisture with which they keep the surface always slightly lubricated. In the serous cavities they also keep the opposed layers moist, and thus facilitate their movements on each other. Finally, in all internal parts they ensure a perfectly smooth surface. Of late years there has been a tendency on the part of many histologists to divide these several epithelial linings into two classes: into (1) epithelial tissue proper, consisting of nucleated protoplasmic cells, which form continuous masses on the skin and mucous surfaces and the linings of the ducts and alveoli of secreting and excreting glands ; and (2) endothelium, which is composed of a single layer of flattened transparent squamous cells, joined edge to edge in such a man- ner as to form a membrane of cells. This is found on the free surfaces of the serous membranes, as the lining membrane of the heart, blood-vessels, and lym- phatics ; on the surface of the brain and spinal cord, and in the anterior chamber of the eye. And, though the separation must be an artificial one, since every gradation of transition between tbe two classes may be observed, it would seem advisable for the purpose of description to employ it. 1. True epithelial tissue consists of one or more layers of cells, united together EPITHELIUM. Fig. 7.-Epithelial cells from the oral cavity of man. Magnified 350 times, a. Large, b. Middle-sized, c. The same with two nuclei. by an interstitial cement-substance, supported on a basement-membrane, and is naturally grouped into two classes, according as there is a single layer of cells (simple EPITHELIUM. 43 epithelium) or more than one (stratified epithelium). The various kinds of epithelium, whether arranged in a single layer or in more than one layer, are usually spoken of as squamous or pavement, columnar, spheroidal or glandular, and ciliated. The pavement epithelium (Fig. 7) is composed of flat nucleated scales of vari- ous shapes, usually polygonal, and varying in size. These cells fit together by their edges, like the tiles of a mosaic pavement. The nucleus is generally flat- tened, but may be spheroidal. The flattening depends upon the thinness of the cell. The protoplasm of the cell presents a fine reticulum or honeycombed net- work, which gives to the cell the appearance of granulation. This kind of epi- thelium is found on the surface of the skin (epidermis) and on mucous surfaces which are subjected to friction. The nails, the hairs, and (in animals) the horns are a variety of this kind of epithelium. A variety of squamous epithelium which is found in the deeper layers of stratified pavement-epithelium has been termed prickle cells. These cells possess short fine fibrils which pass from their margins to those of neighboring cells, serv- ing to connect them together. They were first probably noticed by Max Schultze and Virchow, and it was believed that by them the cells were dovetailed together. Subsequently this was shown not to be so by Dr. Martyn, who pointed out that the prickles were attached to each other by their apices; and recently Dr. Dele- pine has stated that he believes the prickles of prickle cells are parts of fibrils forming internuclear bundles between the nuclei of the cells of an epithelium in a state of active growth (see page 41, and Fig. 6). The columnar or cylindrical epithelium (Fig. 8) is formed of cylindrical or rod-shaped cells, each containing a nucleus, and set together so as to form a com- Fig. 8.-Epithelium of the intestinal villi of the rabbit. Magnified 300 times, a. Base- ment-membrane. Fig. 9.-Simple columnar epithelium, from the mucous membrane of the intestine, with goblet-cells pouring out their contents. (Klein and Noble Smith.) plete membrane. The cells have a prismatic figure, more or less flattened from mutual pressure, and are set upright on the surface on which they are supported. Their protoplasm is always more or less longitudinally striated, and they contain a nucleus which is oval in shape and contains an intranuclear network. This form of epithelium covers the mucous membrane of nearly the whole gastro-intestinal tract and the glands of that part, the greater part of the urethra, the vas deferens, the prostate, Cowper's glands, Bartholini's glands, and a portion of the uterine mucous membrane. (roblet,- or chalice-coWs are a modification of the columnar cell. They appear to be formed by an alteration in shape of the columnar epithelium (ciliated or otherwise) consequent on the secretion into the interior of the cell of mwcm, the chief organic constituent of mucus, which distends the upper part of the cell, while the nucleus is pressed down toward its deep part, until the cell bursts and the mucus is discharged on to the surface of the mucous membrane, as shown in Fig. 9. The spheroidal or glandular epithelium (Fig. 10) is composed of circular or polyhedral cells. Like other forms of epithelial cells, the protoplasm is a fine reticulum, which gives to the cell the appearance of granulation. They are found in the terminal recesses of secreting glands, and the protoplasm of the cells usually contains the materials which the cells secrete. Ciliated epithelium (Fig. 11) may be of any of the preceding forms, but usually 44 GENERAL ANATOMY. inclines to the columnar shape. It is distinguished by the presence of minute processes, which are direct prolongations of the cell-protoplasm, like hairs or eye- lashes (cilia) standing up from the free surface. If the cells are examined during life or immediately on removal from the living body (for which in the human sub- Fig. 11-Ciliated epithelium from the human trachea. Magnified 350 times, a. Innermost layers of the elastic longitudinal fibres, b. Homogeneous innermost layers of the mucous membrane, c. Deepest round cells, d. Middle elongated cells, e. Superficial cells, bearing cilia. Fig. 10.-Spheroidal epithelium. Magnified 250 times. ject the removal of a nasal polypus offers a convenient opportunity) in tepid water, the cilia will be seen in lashing motion; and if the cells are separate, they will often be seen to be moved about in the field by that motion. The situations in which ciliated epithelium is found in the human body are: the respiratory tract from the nose downward, the tympanum and Eustachian tube, the Fallopian tube and upper portion of the uterus, the vasa efferentia, coni vas- culosi, and first part of the excretory duct of the testicle, and the ventricles of the brain and central canal of the spinal cord. Stratified epithelium consists of several layers of cells superimposed one on the top of the other and varying greatly in shape. The cells of the deepest layer are for the most part columnar in form, and as a rule form a sin- gle layer, placed vertically on the supporting membrane; above these are several layers of sphe- roidal cells, which as they ap- proach the surface become more and more compressed, until the superficial layers are found to consist of flattened scales, the margins of which overlap one another, so as to present an im- bricated appearance. Another form of stratified epithelium is found in what has been termed transitional epithelium, such as exists in the ureters and urinary bladder. Here the cells of the most superficial layer are cubical, with depressions on their under surfaces, which fit on to the rounded ends of the cells of the second layer, which are pear- shaped, the apices touching the basement-membrane. Between their tapering points is a third variety of cells, filling in the intervals between them, and of smaller size than those of the other two layers. Fig. 12.-Part of peritoneal surface of the central tendon of diaphragm of rabbit, prepared with nitrate of silver, s. Stomata. I. Lymph-channels, t. Tendon-bundles. The stomata are sur- rounded by germinating endothelial cells. (From Hand-book for the Physiological Laboratory, Klein.) CONNECTIVE TISSUES. 45 2. Endothelium.-As before stated, endothelial cells are flattened, transparent, squamous cells, attached by their margins by a semi-fluid homogeneous cement- substance, so as to form a continuous endothelial membrane. Though for the most part these cells are squamous, in some places cells may be found, either isolated or occurring in patches, which are polyhedral or even columnar. These latter cells are frequently to be found lining the stomata of serous membranes, and are supposed to be endothelial cells in an active state of division (Fig. 12). As a rule, the endothelial cells are polygonal in outline, with sinuous or jagged margins, and are in close apposition, the amount of cohesive matter uniting them being so slight as not to be apparent. Their protoplasmic substance appears to be gran- ular, but consists of fibrillie arranged in a network in which the nucleus is con- tained, limited by a membrane and having a well-developed reticulum. CONNECTIVE TISSUES. By the term connective tissue we mean a number of tissues which possess this feature in common-viz. that they serve the general purpose in the animal economy of supporting and connecting the tissues of the frame. These tissues may differ considerably from each other in external appearance, but they present neverthe- less many points of relationship with each other, and are moreover developed from the same embryonal elements. They are divided into three great groups: (1) the fibrous connective tissues, (2) cartilage, and (3) bone. The Fibrous Connective Tissues.-Three principal forms or varieties of fibrous connective tissue are recognized: (1) White fibrous tissue; (2) Yellow elastic tissue; (3) Areolar tissue. They are all composed of a matrix in which cells are imbedded, and between the cells are fibres of two kinds, the white and yellow or elastic. The difference between the three forms of tissue depends on the relative proportion of the two kinds of fibre, in the first variety enumerated theWzzA fibre preponderating; in the second variety the yellow elastic fibres being greatly in excess of the white; and the third form, areolar tissue, the two being blended in much more equal proportions. The white fibrous tissue (Fig. 13) is a true connecting structure, and serves three purposes in the animal economy. It serves to bind bones together in the form of ligaments, it serves to connect muscles to bones or other structures in the form of tendons, and it forms an invest- ing or protecting structure to various organs in the form of membranes. Examples of where it serves this latter office are to be found in the muscular fasciae or sheaths, the perios- teum, and perichondrium; the investments of the various glands, (such as the tunica albuginea testis, the capsule of the kidney, etc.), the investing sheath of the nerves (epineurium), and of various organs, as the penis and the eye (sheath of the corpora cavernosa and corpus spongiosum, and of the sclerotic). But in all these parts the student must bear in mind that the elastic tissue enters in greater or less proportion. It presents to the naked eye the appearance of silvery-white glistening fibres, covered over with a quantity of loose, flocculent tissue which binds the fibres together and carries the blood-vessels. It is not possessed of any elasticity, and only the very slightest extensibility; it is exceedingly strong, so that upon the application of any external violence the bone with which it is connected will fracture before the fibrous tissue will give way. When examined under the microscope it is found to Fig. 13.-White fibrous tissue. High power. 46 GENERAL ANATOMY. consist of waving bands or bundles of minute, transparent, homogeneous filaments or fibrillae, held together by an albuminous semi-fluid cement-substance (Fig. 14). In ligaments and tendons these bundles run parallel with each other; in mem- branes they intersect one another in different places. The bundles have a tendency to split up longitudinally or send off slips to join other bundles and receive others in return. The cells occurring in white fibrous tissue are often Fig. 14-Connective tissue. (Klein and Noble Smith.) a. The white fibrous element- a layer of more or less sharply-outlined, paral- lel, wavy bundles of connective-tissue fibrils. On the surface of this layer is 6, a network of fine elastic fibres. Fig. 15.-Tendon of mouse's tail, stained with logwood, showing chains of cells between the tendon-bundles. (From Qaain's Anatomy. E. A. Schafer.) called "tendon cells." They are situated on the surface of groups of bundles and are quadrangular in shape, arranged in rows in single file, each cell being separated from its neighbors by a narrow line of cement-substance. The nucleus is generally situated at one end of the cell, the nucleus of the adjoining cell being in close proximity to it (Fig. 15). Upon the addition of acetic acid to white fibrous tissue it swells up into a glassy-looking, indistinguishable mass. When boiled in water it is converted almost completely into gelatin. Yellow Elastic Tissue.-In certain parts of the body a tissue is found which when viewed in mass is of a yellowish color, and is possessed of great elasticity, so that it is capable of considerable extension, and when the extending force is with- drawn returns at once to its original condition. This is yellow elastic tissue, in which the elastic fibres greatly preponderate, to the almost complete exclusion of the white fibrous element. It is found in this condition in the ligamenta subflava, in the vocal cords, in the longitudinal coat of the trachea and bronchi, in the inner coats of the blood-vessels, especially the larger arteries, and to a very con- siderable extent in the thyro-hyoid, crico-thyroid, and stylo-hyoid ligaments. It is also found in the ligamentum nuchae of the lower animals. When viewed under the microscope (Fig. 16) it is seen to consist of an aggregation of curling fibres, with a well-defined outline. They are considerably larger in size than the fibrillae of the white fibrous element, and vary much, being from the to the 4 of an inch in diameter. The fibres form bold and wide curves, branch and freely anastomose with each other. They are homogeneous in appearance, and have a tendency to curl up, especially at their broken ends. In some parts, where the fibres are broad and large and the network close, the tissue presents the appearance of a membrane, with gaps or perforations corresponding to the inter- vening space. This is to be found in the inner coat of the arteries, and to it the name of fenestrated membrane has been given by Henle. The yellow elastic fibres remain unaltered by acetic acid. CONNECTIVE TISSUES. 47 Areolar tissue is so called because its meshes are easily distended, and thus separated into areolae or spaces, which all open freely into each other, and are consequently easily blown up with air, or permeated by fluid when injected into any part of the tissue. Such spaces, however, do not exist in the natural condition of the body, but the whole tissue forms one unbroken mem- brane composed of a number of inter- lacing fibres, variously superimposed. Hence the terra " the cellular mem- brane " is in many parts of the body more appropriate than its more modern equivalent. The chief use of the are- olar tissue is to bind parts together, while by the laxity of its fibres and the permeability of its areolae it allows them to move on each other, and affords a ready exit for inflammatory and other effused fluids. It is one of the most extensively distributed of all the tissues in the body. It is found beneath the skin in a continuous layer all over the body, connecting it to the subjacent parts. In the same way it is situated beneath the mucous and serous membranes. It is also found between muscles, vessels, and nerves, forming investing sheaths for them, and connecting them with surrounding structures. In addition to this, it is found in the interior of organs, binding together the various lobes and lobules of the compound glands, the various coats of the hollow viscera, and the fibres of muscles, etc., and thus forms one of the most important connecting media of the various structures or organs of which the body is made up. In many parts the areolae or interspaces of areolar tissue are occupied by fat-cells, constituting adi- pose tissue, which will presently be described. Areolar tissue presents to the naked eye a flocculent appearance, somewhat like spun silk. When stretched out, it is seen to consist of delicate soft elastic threads interlacing with each other in every direction and forming a network of extreme delicacy. When examined under the microscope it is found to be composed of white fibres and elastic fibres intercrossing in all directions, and united together by a homogeneous cement or ground-substance, and filled by cellular elements, which contain the protoplasm out of which the whole is developed and regenerated. These cell-spaces may be brought into view by treating the tissue with nitrate of silver, and exposing it to the light. This will color the fibres and ground-substance, leaving the cell-spaces unstained. The cells of areolar tissue (Fig. 17) are of two kinds: 1, flattened transparent Fig. 16.-Yellow elastic tissue. High power. Fig. 17.-Connective-tissue corpuscles. (Klein and Noble Smith.) m. Migratory connective-tissue cell. The other two are the ordinary branched cells, each with an oblong nucleus. 48 GENERA L A ATA TOMY. cells, with an oblong nucleus and more or less branched, and often united together by thin-branched processes; and 2, granular cells, some of which are of the size of white blood-corpuscles, and like them possessed of amoeboid movements; others are of larger size, and do not exhibit amoeboid movements to any appreciable extent. They lie imbedded in the ground-substance, and in some situations, where the areolar tissue is loose and the spaces large, so as to contain several cells, they form a sort of lining for it. In other situations where the tissue forms a membranous layer, the flattened cells, here unbranched, form an epithelial-like covering to its surface. Vessels and Nerves of Connective Tissue.-The blood-vessels of connective tissue are very few-that is to say, there are few actually destined for the tissue itself, although many vessels may permeate one of its forms, the areolar tissue, carrying blood to other structures. In white fibrous tissue the blood-vessels usually run parallel to the longitudinal bundles and between them, sending transverse com- municating branches across, and in some forms, as the periosteum and dura mater, being fairly numerous. In the yellow elastic tissue the blood-vessels also run between the fibres, and do not penetrate them. Lymphatic vessels are very numer- ous in most forms of connective tissue, especially in the areolar tissue beneath the skin and the mucous and the serous surfaces. They are also found in abundance in the sheaths of tendons, as well as in the tendons themselves. Nerves are to be found in the white fibrous tissue, where they terminate in a special manner; but it is doubtful whether any nerves terminate in areolar tissue; at all events, they have not yet been demonstrated, and the tissue is possessed of very little sensibility. Development of Connective Tissue.-Fibrous connective tissue is developed from embryonic connective-tissue cells derived from the mesoblast. At an early period of development it consists of nucleated cells and a muco-albuminous fluid, which subsequently becomes a pellucid jelly and forms the ground-substance. In this ground-substance the two varieties of fibres become developed. As to the manner in which they do so there are two theories, some believing that they are developed from the protoplasm of the cells, others that they are formed by a deposit in the ground-substance. In the former case the protoplasm of the cells is converted wholly into elementary fibres, the nucleus disappearing; or else the peripheral part of the protoplasm produces the fibrous tissue, the original cell growing again to its original size, and then throwing off a fresh portion to form a new cell, and itself persisting in contact with the fibres it has formed as a permanent connective- tissue corpuscle. Yellow elastic fibres are said by some to be formed by the processes of stellate embryonal cells, which, joining with processes of other cells, form the elastic fibres. Three special forms of connective tissue must be described: the mucoid, the lymphoid or retiform, and basement-membranes. 1. The mucoid or gelatinous connective tissue exists chiefly in the "jelly of Wharton," which forms the bulk of the umbilical cord, but is also found in some other situations in the foetus, as in the pulp of young teeth, and in certain stages of the development of connective tissue in various regions. In the adidt the vit- reous humor of the eye is formed of the same material. This tissue consists of nucleated cells, which branch and become connected so as to form trabecuhe, in which is contained a jelly-like substance, containing the chemical principle of mucus, or mucin, and in smaller quantities albumen, but no gelatin. Sometimes, as in the vitreous humor of the eye, the cells disappear and the jelly only remains. 2. Retiform connective tissue (Fig. 18) is found extensively in many parts of the body, forming the framework of some organs and entering into the construc- tion of many mucous membranes. It is formed of an interlacement or network of very fine fibres, which closely resemble white fibrous tissue, and in certain sit- uations may be demonstrated to be continuous with it. In many places flattened cells may be seen connected with the fibres and partially concealing them, pre- CONNECTIVE TISSUES. 49 senting an appearance as if the tissue were formed of a network of branching and anastomosing cells. This, however, is not so, as the cells can be removed or brushed away, leaving the fibres intact. In many situations the interstices of the fibres are filled with rounded granular corpuscles, and the tissue is then termed lymphoid or adenoid tissue. The neuroglia, or fine gelatinous connective tissue which supports the nervous elements in the cerebro-spinal axis and in the retina, is regarded as a modified form of the reti- form connective tissue. 3. Basement-membranes, formerly de- scribed as homogeneous membranes, are really a form of connective tissue. They constitute the supporting membrane, or membrana propria, supporting the epithe- lium of mucous membranes or secreting glands, and in other situations. By means of staining with nitrate of silver they may be shown to consist of flattened cells in close apposition, and form therefore an example of an epithelioid arrangement of connective-tissue cells. In some situations the cells, instead of adhering by their edges, give off branching processes, which join with similar processes of other cells, and so form a network rather than a continuous membrane. Adipose Tissue.-In almost all parts of the body the ordinary areolar tissue contains a variable quantity of adipose or fatty tissue. The principal situations where it is not found are the subcutaneous tissue of the eyelids, the penis and scrotum, the nymphte, within the cavity of the cranium, and in the lungs, except near the roots. Nevertheless, its distribution is not uniform, in some parts being collected in great abundance, as in the subcutaneous tissue, especially of the abdomen; around the kidneys; on the surface of the heart between the furrows; and in some other situations. Lastly, fat enters largely into the formation of the Fig. 18.-Retiform connective tissue, from a lymphatic gland: most of the lymph-corpuscles are removed. (From Klein's Elements of Histology.) a. The reticulum, c. A capillary blood-vessel. Fig. 19.-Adipose tissue. High power, a. Starlike appearance, from crystallization of fatty acids. marrow of bones. A distinction must, however, be made between fat and adipose tissue; the latter being a distinct tissue, the former an oily matter, which in addition to forming adipose tissue is also widely present in the body, as in the fat of the brain and liver, and in the blood and chyle, etc. 50 GENERAL ANATOMY. Fat-cells (Fig. 19) consist of a number of vesicles, varying in size, but of about the average diameter of of an inch. They are formed of an exceedingly delicate protoplasmic membrane, filled with fatty matter, which is liquid during life, but becomes solidified after death. They are round or spherical where they have not been subjected to pressure; otherwise they assume a more or less angular outline. A nucleus is always present, and can be easily demonstrat- ed by staining with logwood ; in the natural condition it is so compressed by the contained oily matter as to be scarcely recognizable. These fat-cells are contained in clusters in the areohe of fine connective tissue, and are held together mainly by a network of capillary blood-vessels, which are dis- tributed to them. Fat is an inorganized substance, consisting of a liquid material (gly- cerin) in combination with certain fatty acids, stearic, palmitic, and oleic. Sometimes the acids separate spontaneously before the fat is exam- ined, and are seen under the micro- scope in a crystalline form, as in Fig. 19, a. By boiling the tissue in ether or strong alcohol the fat may be extracted from the vesicle, which is then seen empty and shrunken. Fat is said to be first detected in the human embryo about the fourteenth week. According to Klein, the fat-cells are formed by the transformation of the protoplasmic connective-tissue corpuscles, into which small globules of fat find their way, and increase until they distend the corpuscle into the thin mantle of protoplasm which forms the cell-wall, and in which its nucleus is still to be seen (Fig. 20). Others of the connective-tissue corpuscles are transformed into the vessels and the lymphatic tissue which accompanies the vessels. Fig. 20.-Development of fat. (Klein and Noble Smith.) a. Minute artery, v. Minute vein. c. Capillary blood- vessels in the course of formation; they are not yet com- pletely hollowed out, there being still left in them proto- plasmic septa. d. The ground-substance, containing numerous nucleated cells, some of which are more dis- tinctly branched and flattened than others, and appear therefore more spindle-shaped. PIGMENT. In various parts of the body pigment is found; most frequently in epithelial cells and in the cells of connective tissue. Pigmented epithelial cells are found forming the external layer of the retina (Fig. 21) and on the posterior surface of the iris. Pigment is also found in the epithelial cells of the deeper layers of the cuticle in some parts of the body-such as the areola of the nipple and in colored patches of skin, and especially in the skin of the colored races, and also in hair. It is also found in the epithelial cells of the olfactory region and of the membranous labyrinth of the ear. In the connective-tissue cells pigment is frequently met with in the lower vertebrates. In man it is found in the choroid coat of the eye, and in the iris of all but the light-blue eyes and the albino. It is also occasionally met with in the cells of retiform tissue and in the pia mater of the upper part of the spinal cord. These cells are characterized by their larger size and branched processes, which, as well as the body of the cells, are filled with granules. The pigment consists of dark-brown or black granules of very small size, closely packed together within the cells, but not invading the nucleus. Occasionally the pigment is yellow, and when occurring in the cells of the cuticle constitutes "freckles." Fig. 21.-Pigment- cells of retina. CARTILAGE. 51 Cartilage is a non-vascular structure which is found in various parts of the body-in adult life chiefly in the joints, in the parietes of the thorax, and in various tubes, such as the air-passages, nostrils, and ears, which are to be kept permanently open. In the foetus at an early period the greater part of the skele- ton is cartilaginous. As this cartilage is afterward replaced by bone, it is called temporary, in contradistinction to that which remains unossified during the whole of life, and which is called permanent. Cartilage is divided, according to its minute structure, into true or hyaline cartilage, fibrous or fibro-cartilage, and yellow' or elastic or reticular cartilage. Besides these varieties met with in the adult human subject, there is a variety called cellular cartilage, which consists entirely, or almost entirely, of cells, united in some cases by a network of very fine fibres, in other cases apparently destitute of any intercellular substance. This is found in the external ear of rats, mice, and some other animals, and is present in the chorda dorsalis of the human embryo, but is not found in any other human structure. The various cartilages in the body are also classified, according to their function and position, into articular, interarticular, costal, and membraniform. Hyaline cartilage, which may be taken as the type of this tissue, consists of a gristly mass of a firm consistence, but of considerable elasticity and of a pearly- bluish color. Except where it coats the articular ends of bones, it is enveloped in a fibrous membrane, the perichondrium, from the vessels of which it imbibes its nutritive fluids, being itself destitute of blood-vessels; nor have any nerves been traced into it. Its intimate structure is very simple. If a thin slice is examined under the micro- scope, it will be found to consist of cells of a rounded or bluntly angular form, lying in groups of two or more in a granular or almost homogeneous matrix (Fig. 22). The cells, when arranged in groups of two or more, have generally a straight outline where they are in contact with each other, and in the rest of their cir- cumference are rounded. The cell-contents consist of clear translucent proto- plasm containing minute granules, and imbedded in this are one or two nuclei, having usually a granular appearance, but occasionally being clear and occupied by one or more nucleoli. The cells are imbedded in cavities in the matrix, called cartilage lacuna*, which are lined by a distinct transparent membrane called the capsule. Each lacuna is generally occupied by a single cell, but during the division of the cells it may contain two, four, or eight cartilage-cells. By boiling the cartilage for some hours and treating it with concentrated mineral acid, the capsule may be freed from the matrix, and can then be demonstrated as a distinct vesicle containing the cells. By exposure to the action of an electric shock the cell assumes a jagged outline and shrinks away from the interior of the capsule. The matrix is transparent and apparently without structure, or else presents a dimly granular appearance, like ground glass. Some observers have shown that the matrix of hyaline cartilage, and especially the articular variety, after prolonged maceration, can be broken up into fine fibrils. These fibrils are prob- ably of the same nature, chemically, as the white fibres of connective tissue. It is believed by some histologists that the matrix is permeated by a number of fine channels, which connect the lacunae with each other, and that these canals communicate with the lymphatics of the perichondrium, and thus the structure is permeated with a current of nutritious fluid. CARTILAGE. t iG. 22.-Human cartilage-cells, from the cricoid carti- lage. Magnified 350 times. 52 GENERAL ANATOMY. The articular cartilages, the temporary cartilages, and the costal cartilages are all of the hyaline variety. They present minute differences in the size and shape of their cells and in the arrangement of their matrix. In the articular cartilages, which show no tendency to ossification, the matrix is finely granular under a high power; the cells and nuclei are small and are disposed parallel to the surface in the superficial part, while nearer to the bone they become vertical. Articular cartilages have a tendency to split in a vertical direction, probably from some peculiarity in the intimate structure or arrangement of the component parts of the matrix. In disease this tendency to a fibrous splitting becomes very manifest. Articular cartilage is not covered by perichondrium, at least on its free surface, where it is exposed to friction, though a layer of connective tissue can be traced in the adult over a small part of its circumference continuous with that of the synovial membrane, and here the cartilage-cells are more or less branched and pass insensibly into the branched connective-tissue corpuscles of the synovial membrane. Articular cartilage forms a thin incrustation upon the joint-surfaces of the bones, and its elasticity enables it to break the force of any concussion, whilst its smoothness affords ease and freedom of movement. It varies in thickness accord- ing to the shape of the bone on which it lies ; where this is convex the cartilage is thickest at the centre, where the greatest pressure is received; and the reverse is the case on the concave surfaces of the bones. Articular cartilage appears to imbibe its nutriment partly from the vessels of the neighboring synovial mem- brane, partly from those of the bone upon which it is implanted. Mr. Toynbee has shown that the minute vessels of the cancellous tissue as they approach the articular lamella dilate and form arches, and then return into the substance of the bone. In the costal cartilages the cells and nuclei are large, and the matrix has a tendency to fibrous striation, especially in old age (Fig. 23). These cartilages are also very prone to ossify. In the thickest parts of the costal cartilages a few large vascular channels may be detected. This appears at first sight an exception to the statement that cartilage is a non-vascular tissue, but is not so really, for the vessels give no branches to the cartilage-substance itself, and the channels may rather be looked upon as involutions of the perichondrium. The ensiform cartilage may be regarded as one of the costal cartilages, and the cartilages of the nose and of the larynx and trachea resemble them in microscop- ical characters, except the epiglottis and cornicular laryngis, which are of the reticular variety. The hyaline cartilages, especially in adult and advanced life, are prone to calcify-that is to say, to have their matrix permeated by the salts of lime without any appearance of true bone. The process of calcification occurs also and still more frequently, according to Rollett, in such cartilages as those of the trachea, which are prone afterward to conversion into true bone. White fibro-cartilage consists of a mixture of white fibrous tissue and cartilag- inous tissue in various proportions; it is to the first of these two constituents that its flexibility and toughness are chiefly owing, and to the latter its elasticity. When examined under the microscope it is found to be made up of fibrous con- nective tissue arranged in bundles, with cartilage-cells between the bundles; these Fig. 23.-Costal cartilage from a man seventy-six years of age, showing the development of fibrous structure in the matrix, in several portions of the specimen two or three generations of cells are seen enclosed in a parent cell-wall. High power. CARTILAGE. 53 to a certain extent resemble tendon-cells, but may be distinguished from them by being surrounded by an investing capsule and by their being less flattened (Fig. 24). The fibro-cartilages admit of arrangement into four groups -interarticular, connecting, circumferential, and strati- form. The interarticular fibro-car- tilages (menisci') are flattened fibro-cartilaginous plates, of a round, oval, triangular, or sickle-like form, interposed between the articular carti- lages of certain joints. They are free on both surfaces, thin- ner toward their centre than at their circumference, and held in position by their mar- gins and extremities being con- nected to the surrounding ligaments. The synovial membrane of the joint is prolonged over them a short distance from their attached margins. They are found in the temporo-maxillary, sterno-clavicular, acromio-clavicular, wrist and knee-joints. These cartilages are usually found in those joints which are most exposed to violent concussion and subject to frequent movement. Their use is -to maintain the apposition of the opposed surfaces in their various motions; to increase the depth of the articular surfaces and give ease to the gliding movement; to moderate the effects of great pressure and deaden the intensity of the shocks to which the parts may be subjected. Humphry has pointed out that these inter- articular fibro-cartilages serve an important purpose in increasing the variety of movements in a joint. Thus, in the knee-joint there are two kinds of motion, -viz. angular movement and rotation, although it is a hinge joint, in which, as a rule, only one variety of motion is permitted; the former movement taking place between the condyles of the femur and the interarticular cartilage, the latter between the cartilage and the head of the tibia. So, also, in the temporo-maxil- lary joint, the upward and downward movement of opening and shutting the mouth takes place between the cartilage and the jaw-bone, the grinding movement between the glenoid cavity and the cartilage, the latter moving with the jaw-bone. The connecting fibro-cartilages are interposed between the bony surfaces of those joints which admit of only slight mobility, as between the bodies of the ver- tebrae and between the pubic bones. They form disks, which adhere closely to both of the opposed bones, and are composed of concentric rings of fibrous tissue, with cartilaginous laminae interposed, the former tissue predominating toward the circumference, the latter toward the centre. The circumferential fibro-cartilages consist of a rim of fibro-cartilage, which surrounds the margin of some of the articular cavities, as the cotyloid cavity of the hip and the glenoid cavity of the shoulder; they serve to deepen the articular surface and to protect the edges of the bone. The stratiform fibro-cartilages are those which form a thin coating to osseous grooves through which the'tendons of certain muscles glide. Small masses of fibro-cartilages are also developed in the tendons of some muscles, where they glide over bones, as in the tendons of the peroneus longus and the tibialis posticus. Yellow, or reticular, elastic cartilage is found in the human body in the auricle of the external ear, the Eustachian tubes, the cornicula laryngis, and the epiglottis. It consists of cartilage-cells and a matrix, the latter being pervaded in every direction, except immediately around each cell, by a network of yellow elastic fibres, branching and anastomosing in all directions (Fig. 25). The fibres resemble those of yellow elastic tissue, both in appearance and in being unaffected Fig. 24.-White fibro-cartilage from the semilunar disk of the patella joint of an ox. Magnified 100 times. 54 GENERAL ANATOMY. by acetic acid; and according to Rollett their continuity with the elastic fibres of the neighboring tissue admits of being demonstrated. The distinguishing feature of cartilage as to its chemical composition is that it yields on boiling a substance called chondrin, very similar to gelatin, but differing from it in not being precipitated by tannin. According to Kiihne there is a small amount of gelatin in hyaline cartilage. Virchow believes that the semilunar disks in the knee- joint are wrongly denomi- nated cartilages, since they yield no chondrin on boil- ing ; and he appears to re- gard them as a modification of a tendinous structure, which, however, agrees with the cartilages in the important particular of being non-vascular. Temporary cartilage and the process of its ossification will be described with Bone. Fig. 25.-Yellow cartilage, ear of horse. High power. BONE. Structure and Physical Properties of Bone.-Bone is one of the hardest struc- tures of the animal body ; it possesses also a certain degree of toughness and elasticity. Its color, in a fresh state, is of a pinkish white externally, and deep red within. On examining a section of any bone, it is seen to be composed of two kinds of tissue, one of which is dense and compact in texture, like ivory; the other consists of slender fibres and lamellae, which join to form a reticular struc- ture ; this, from its resemblance to lattice-work, is called cancellous. The com- pact tissue is always placed on the exterior of the bone; the cancellous is always internal. The relative quantity of these two kinds of tissue varies in different bones, and in different parts of the same bone, as strength or lightness is requisite. Close examination of the compact tissue shows it to be extremely porous, so that the difference in structure between it and the cancellous tissue depends merely upon the different amount of solid matter, and the size and number of spaces in each; the cavities being small in the compact tissue and the solid matter between them abundant, whilst in the cancellous tissue the spaces are large and the solid matter in smaller quantity. Bone during life is permeated by vessels and is enclosed in a fibrous membrane, the periosteum, by means of which many of these vessels reach the hard tissue. If the periosteum is stripped from the surface of the living bone, small bleeding points are seen, which mark the entrance of the periosteal vessels; and on section during life every part of the bone will be seen to exude blood from the minute vessels which ramify in it. The interior of the bones of the limbs presents a cylindrical cavity filled with marrow and lined by a highly vascular areolar structure, called the medullary membrane or internal periosteum, which, how- ever, is rather the areolar envelope of the cells of the marrow than a definite membrane. The periosteum adheres to the surface of the bones in nearly every part, excepting at their cartilaginous extremities. Where strong tendons or ligaments are attached to the bone, the periosteum is incorporated with them. It consists of two layers closely united together, the outer one formed chiefly of connective tissue, containing occasionally a few fat-cells; the inner one, of elastic fibres of the finer kind, forming dense membranous networks, which can be again separated BONE. 55 into several layers. In young bones the periosteum is thick, and very vascular, and is intimately connected at either end of the bone with the epiphysial cartilage, but less closely with the shaft, from which it is separated by a layer of soft blas- tema, containing a number of granular corpuscles or " osteoblasts," in which ossification proceeds on the exterior of the young bone. Later in life the peri- osteum is thinner, less vascular, and the osteoblasts have become converted into an epithelial layer, which is separated from the rest of the periosteum in many places by cleft-like spaces, which are supposed to serve for the transmission of lymph. The periosteum serves as a nidus for the ramification of the vessels previous to their distribution in the bone; hence the liability of bone to exfolia- tion or necrosis, when denuded of this membrane by injury or disease. Fine nerves and lymphatics, which generally accompany the arteries, may also be demonstrated in the periosteum. The marrow not only fills up the cylindrical cavity in the shafts of the long bones, but also occupies the spaces of the cancellous tissue and extends into the larger bony canals (Haversian canals) which contain the blood-vessels. It differs in composition in different bones. In the shafts of adult long bones the marrow is of a yellow color, and contains, in 100 parts, 96 of fat, 1 of areolar tissue and vessels, and 3 of fluid, with extractive matter, and consists of a matrix of fibrous tissue, supporting numerous blood-vessels and cells, most of which are fat-cells, but some few are "marrow-cells." In the flat and short bones, in the articular ends of the long bones, in the bodies of the vertebrae, in the cranial diploe, and in the sternum and ribs, it is of a red color, and contains, in 100 parts, 75 of water and 25 of solid matter, consisting of albumen, fibrin, extractive matter, salts, and a mere trace of fat. The red marrow consists of a small quantity of areolar tissue, blood-vessels, and numerous cells, some few of which are fat-cells, but the great majority roundish nucleated cells, the true " marrow-cells " of Kblliker. These marrow-cells resemble in appearance the white corpuscles of the blood, though they are larger and have a relatively larger nucleus and a clearer protoplasm, but, like them, possess amoeboid movements. Amongst them may be seen smaller cells, which possess a slightly pinkish hue; and it has been stated by Neumann that they are then in a transitional stage between marrow-cells and red blood- corpuscles, and that one of the sources of blood-globules is the marrow of the spongy bones. Griant-cells (myelo-plaques, osteoclasts}, large, multinucleated, protoplasmic masses, are also to be found in both sorts of adult marrow, but more particularly in red marrow. They were believed by Kblliker to be concerned in the absorption of bone matrix, and hence the name which he gave to them-osteoclasts. They excavate small shallow pits or cavities, which are named Howship's lacunae, in which they are found lying. Vessels of Bone.-The blood-vessels of bone are very numerous. Those of the compact tissue are derived from a close and dense network of vessels ramifying in the periosteum. From this membrane vessels pass into the minute orifices in the compact tissue, running through the canals which traverse its substance. The cancellous tissue is supplied in a similar way, but by a less numerous set of larger vessels, which, perforating the outer compact tissue, are distributed to the cavities of the spongy portion of the bone. In the long bones numerous apertures may be seen at the ends near the articular surfaces, some of which give passage to the arteries of the larger set of vessels referred to ; but the most numerous and largest apertures are for the veins of the cancellous tissue, which run separately from the arteries. The medullary canal in the shafts of the long bones is supplied by one large artery (or sometimes more), which enters the bone at the nutrient foramen (situated in most cases near the centre of the shaft), and perforates obliquely the compact structure. The medullary or nutrient artery, usually accompanied by one or two veins, sends branches upward and downward to supply the medullary membrane, which lines the central cavity and the adjoining canals. The ramifica- tions of this vessel anastomose with the arteries both of the cancellous and com- 56 GENERAL ANATOMY. pact tissues.1 In most of the flat, and in many of the short spongy bones, one or more large apertures are observed, which transmit, to the central parts of the bone, vessels corresponding to the medullary arteries and veins. The veins emerge from the long bones in three places (Kolliker): (1) by one or two large veins, which accompany the artery; (2) by numerous large and small veins at the artic- ular extremities; (3) by many small veins which arise in the compact substance. In the flat cranial bones the veins are large, very numerous, and run in tortuous canals in the diploic tissue, the sides of the canals being formed by a thin lamella of bone, perforated here and there for the passage of branches from the adjacent cancelli. The same condition is also found in all cancellous tissue, the veins being enclosed and supported by osseous structure and having exceedingly thin coats. When the bony structure is divided, the vessels remain patulous, and do not con- tract in the canals in which they are contained. Hence the constant occurrence of purulent absorption after amputation in those cases where the stump becomes inflamed and the cancellous tissue is infiltrated and bathed in pus. Lymphatic vessels, in addition to those found in the periosteum, have been traced by Cruikshank, into the substance of bone, and Klein describes them as running in the Haversian canals. Nerves are distributed freely to the periosteum, and accompany the nutrient arteries into the interior of the bone. They are said by Kolliker to be most numerous in the articular extremities of the long bones, in the vertebrae and the larger flat bones. Minute Anatomy.-The intimate structure of bone, which in all essential particulars is identical in the compact and cancellous tissue, is most easily studied in a transverse section from the compact wall of one of the long bones after maceration, such as is shown in Fig. 26. If this is examined with a rather low power the bone will be seen to be mapped out into a number of circular districts, each one of which consists of a central hole, surrounded by a number of concentric rings. These districts are termed Haversian systems; the central hole is an Haversian canal, and the rings around are layers of bone-tissue arranged concentrically around the cen- tral canal, and termed lamelice. More- over, on closer examination, it will be found that between these lamellae, and therefore also arranged concentrically around the central canal, are a number of little dark specks, the lacunce, and that these lacunae are connected with each other and with the central Haversian canal bv a number of fine dark lines, which radiate like the spokes of a wheel and are called canaliculi. All these structures -the concentric lamellae, the lacunae, and the canaliculi-may be seen in any single Haversian system, forming a circular district round a central, Haversian, canal. Between these circular systems, filling in the irregular intervals which are left between them, are other lamellae, with their lacunae and canaliculi, running in Fig. 26.-From a transverse section of the diaphysis of the humerus. Magnified 350 times, a. Haversian canals, b. Lacunae, with their eanaliculi in the lamellae of these canals, c. Lacunae of the interstitial lamellae. d. Others at the surface of the Haversian systems, with eanaliculi given off from one side. 1 This view is not, however, entertained by all anatomists. Mr. Charles Stewart believes that, in many cases at all events, the vessels of the periosteum supply only the circumferential lamellae on the surface of the shaft of the bone, which are formed from this membrane, and that the whole of the rest of its structure is supplied by the vessels of the medullary membrane, and that only very exceptionally does any anastomosis take place between the two sets of vessels. Certainly, in one microscopic section, which I had an opportunity of examining through the kindness of Mr. Stewart, this appeared to be the case. BONE. 57 various directions, but more or less curved (Fig. 27). These are termed interstitial lamellae. Again, other lamellae, for the most part found on the surface of the bone, are arranged concentrically to the circumference of bone, constituting, as it were, a single Haversian system of the whole bone, of which the medullary cavity would represent the Haversian canal. These latter lamellae are termed circumferential, or bv some authors primary or fundamental lamellae, to distinguish them from those laid down around the axis of the Haversian canals, which are then termed secondary or special lamellae. The Haversian canals, seen as round holes in a transverse section of bone at or about the centre of each Haversian system, may be demonstrated to be true canals if a longitudinal section is made, as in Fig. 29. It will then be seen that these round holes are tubes cut across, which run parallel with the longitudinal Fig. 27.-Transverse section of compact tissue of bone. Magnified about 150 diameters. (Sharpey.) axis of the bone for a short distance, and then branch and communicate. They vary considerably in size, some being as large as of an inch in diameter; the average size being, however, about of an inch. Near the medullary cavity the canals are larger than those near the surface of the bone. Each canal, as a rule, contains two blood-vessels, a small artery and vein; the larger ones also con- tain a small quantity of delicate connective tissue, with branched cells, the pro- cesses of which communicate with the branched processes of certain bone-cells in the substance of the bone. Those canals near the surface of the bone open upon it by minute orifices, and those near the medullary cavity open in the same way into this space, so that the whole of the bone is permeated by a system of blood-vessels running through the bony canals in the centre of the Haversian systems. The lamellae are thin plates of bone-tissue encircling the central canal, and might be compared, for the sake of illustration, to a number of sheets of paper pasted one over another around a central hollow cylinder. After macerating a piece of bone in dilute mineral acid, these lamellae may be stripped oft' in a longi- tudinal direction as thin films. If one of these is examined with a high power under the microscope it will be found to be composed of a finely reticular struc- ture, presenting the appearance of lattice-work made up of very slender, trans- parent fibres, decussating obliquely, and coalescing at the points of intersection so as to form an exceedingly delicate network. In many places the various lamellae may be seen to be held together by tapering fibres, which run obliquely through them, pinning or bolting them together. These fibres were first described by Sharpey, and were named by him perforating fibres. 58 GENERA L A NA TO MY. The lacunae are situated between the lamellae, and consist of a number of oblong spaces. In an ordinary microscopic section, viewed by transmitted light, they appear as dark, oblong, opaque spots, and were formerly believed to be solid cells. Subsequently, when it was seen that the Haversian canals were channels which lodge the vessels of the part, and the canaliculi minute tubes by which the plasma of the blood circulates through the tissue, it was taught that the lacunae were hollow spaces filled during life with the same fluid, and only lined (if lined at all) by a delicate membrane. But this view appears also to be delusive. Examination of the structure of bone, when recent, led Virchow to believe that the lacunae are occupied during life with a nucleated cell, the processes from which pass down the canal- iculi-a view which is now universally received (Fig. 28). It is by means of these cells that the fluids necessary for nutrition are brought into contact with the ultimate tissue of bone. The canaliculi are exceedingly minute channels, which pass across the lamellae and connect the lacunae with neighboring lacunae and also with the Haversian canal. From this central canal a number of the canaliculi are given off, which radiate from it, and open into the first set of lacunae, arranged around the Haversian canal, between the first and second lamellae. From these lacunae a second set of canaliculi are given off, which pass outward to the next series of lacunae, and so on until they reach the periphery of the Haver- sian system; here the canaliculi given off from the last series of lacunae do not communicate with the lacunae of neighboring Haversian systems, but after passing outward for a short distance form loops and return to their own lacuna. Thus every part of an Haversian system is supplied with nutrient fluids derived from the vessels in the Haversian canals and traversing the canaliculi and lacunae. The bone-cells are contained in the lacunae, which, however, they do not com- pletely fill. They are flattened nucleated cells, which Virchow has shown are homologous with those of connective tissue. The cells are branched, and the branches, especially in young bones, pass into the canaliculi from the lacunae. If a longitudinal section is examined, as in Fig. 29, the structure is seen to be the same. The appearance of concentric rings is replaced by that of lamellae or rows of lacunae, parallel to the course of the Haversian canals, and these canals appear like half-tubes instead of circular spaces. The tubes are seen to branch and communicate, so that each separate Haversian canal runs only a short distance. In other respects the structure has much the same appearance as in transverse sections. In sections of thin plates of bone (as in the walls of the cells which form the cancellous tissue) the Haversian canals are absent, and the canaliculi open into the spaces of the cancellous tissue (medullary spaces), which thus have the same func- tion as the Haversian canals in the more compact bone. Chemical Composition.-Bone consists of an animal and an earthy part inti- mately combined together. The animal part may be obtained by immersing the bone for a considerable time in dilute mineral acid, after which process the bone comes out exactly the same shape as before, but perfectly flexible, so that a long bone (one of the ribs, for example) can easily be tied in a knot. If now a transverse section is made (Fig. 30), the same general arrangement of the Haversian canals, lamellae, lacunae, and canaliculi is seen, though not so plainly, as in the ordinary section. Fig. 28.-Nucleated bone-cells and their processes, contained in the bone-laeunse and their canaliculi respectively. From a section through the vertebra of an adult mouse. (Klein and Noble Smith.) BONE. 59 The earthy part may be obtained separate by calcination, by which the animal matter is completely burned out. The bone will still retain its original form, but it will be white and brittle, will have lost about one-third of its original •weight, and will crumble down with the slightest force. The earthy matter confers on bone its hardness and rigidity, and the animal matter its tenacity. Fig. 30.-Section of bone after the removal of the earthy mat- ter by the action of acids. The animal base is often called cartilage, but differs from it in structure, in the fact that it is softer and more flexible, and that when boiled with a high pressure it is almost entirely resolved into gelatin. The organic constituent of bone forms about one-third, or 33.3 per cent.; the inorganic matter, two-thirds, or 66.7 per cent.; as is seen in the subjoined analysis of Ber- zelius : Fig. 29.-Section parallel to the surface from the shaft of the femur. Magnified 100 times, a. Haversian canals, b. Lacunae seen from the side. c. Others seen from the sur- face in lamellae which are cut horizontally. Organic matter . . . Gelatin and blood-vessels . . . 33.30 Phosphate of lime51.04 Carbonate of lime11.30 Fluoride of calcium .... 2.00 Phosphate of magnesia . . . 1.16 Soda and chloride of sodium . . 1.20 Inorganic or Earthy matter . . . Some chemists add to this about 1 per cent, of fat. Some difference exists in the proportion between the two constituents of bone at different periods of life. In the child the animal matter predominates, whereas in aged people the bones contain a larger proportion of earthy matter, and the animal matter is deficient in quantity and quality. Hence in children it is not uncommon to find, after an injury to the bones, that they become bent or only partially broken, whereas in old people the bones are more brittle and fracture takes place more readily. Some of the diseases, also, to which bones are liable mainly depend on the disproportion between the two constituents of bone. Thus in the disease called rickets, so common in the children of the poor, the bones become bent and curved, either from the superincumbent weight of the body, or under the action of certain muscles. This depends upon some defect of nutrition by which bone becomes deprived of its normal proportion of earthy matter, whilst the animal matter is of unhealthy quality. In the vertebrae of a rickety subject Dr. Bostock found in 100 parts 79.75 animal and 20.25 earthy matter. Development of Bone.-In the foetal skeleton some bones, such as the long bones of the limbs, are cartilaginous; others, as the cranial bones, are membran- ous. Hence two kinds of ossification are described: the intracartilaginous and the intramembranous; and to these a third is sometimes added, the subperiosteal; this, however, is the same as the second, only taking place under different cir- cumstances. 100.00 60 GENERAL ANATOMY. Intracartilaginous Ossification.-Just before ossification begins the bone is entirely cartilaginous, and in a long bone, which may be taken as an example, the process commences in the centre and proceeds toward the extremities, which for some time remain cartilaginous. Subsequently a similar process commences in one or more places in those extremities and gradually extends through it. The extremity does not, however, become joined to the shaft of the bone until growth has ceased, but remains separated by a layer of cartilaginous tissue termed epiphysial carti- lage. The first step in the ossifica- tion of the cartilage is that the cartilage-cells, at the point where ossification is commen- cing and which is termed a cen- tre of ossification, enlarge and arrange themselves in rows (Fig. 31). The matrix in which they are imbedded increases in quan- tity, so that the cells become further separated from each other. A deposit of calcareous material now takes place in this matrix, between the rows of cells, so that they become sepa- rated from each other by longi- tudinal columns of calcified matrix, presenting a granular and opaque appearance. Here and there the matrix between two cells of the same row also becomes calcified, and thus we have transverse bars of calcified substance stretching across from one calcareous column to another. Thus we have lon- gitudinal groups of the cartilage- cells enclosed in oblong cavities, the walls of which are formed of calcified matrix. These cavities are called the primary areolce (Sharpey). At the same time that this process is going on in the centre of the cartilage of which the foetal bone consists, certain changes are taking place on its surface. This is covered by a very vascular membrane, the periosteum, on the inner surface of which-that is to say, on the surface in contact with the cartilage-are a number of cells called osteoblasts. By the agency of these cells a thin layer of bony tissue is being formed between the periosteum and the cartilage, by the intramem- branous mode of ossification presently to be described. We have then, in this first stage of ossification, two processes going on simultaneously: in the centre of the cartilage the formation of a number of oblong spaces, formed of calcified matrix and containing the cartilage-cells enlarged and arranged in groups, and on the surface of the cartilage the formation of a layer of true membrane-bone. The second stage consists in the prolongation into the cartilage of processes of the deeper or osteogenetic layer of the periosteum (Fig. 32, zr). The processes consist of blood-vessels and cells (osteoblasts). They excavate passages through the new- formed bony layer by absorption, and pass through it into the calcified matrix (Fig. 32). Wherever these processes come in contact with the calcified walls of the Fig. 3L-Longitudinal section through the ossifying portion of a long bone in the human embryo, a. Cartilaginous region, b. Region of calcified matrix. BONE. 61 primary areolae they absorb it, and thus cause a fusion of the original cavities and the formation of larger spaces, which are termed the secondary areolce (Sharpey) Fig. 33.-Part of a longitudinal section of the developing femur of a rabbit, a. Flat- tened cartilage-cells, b. Enlarged cartilage- cells. c. (I. Newly-formed bone. e. Osteo- blasts. /. Giant-cells or osteoclasts, g. h. Shrunken cartilage-cells. (From Atlas of His- tology, Klein and Noble Smith.) Fig. 32.-Section of foetal bone of cat. ir. Irruption of the subperiosteal tissue, p. Fibrous layer of the perios- teum. o. Layer of osteoblasts, im. Subperiosteal bony deposit. (From Quain's Anatomy, E. A. Schafer.) or medullary spaces (Muller). In these secondary spaces the original cartilage- cells disappear, and their cavities become filled with embryonic marrow, consisting of osteoblasts and vessels, and derived, at all events in part, in the manner described above, from the osteogenetic layer of the periosteum (Fig. 33). What becomes of the cartilage-cells is not finally determined. By most histologists they are believed to be converted, after division, into osteoblasts, and so assist in form- ing the embryonic marrow. Others, on the other hand, believe that they are simply absorbed and take no part in the formation of bone. Thus far, then, we have got enlarged spaces (secondary areolae), the walls of which are still formed by calcified cartilage-matrix, containing an embryonic marrow, derived from the processes sent in from the osteogenetic layer of the peri- osteum, and consisting of blood-vessels and round cells, osteoblasts (Fig. 33), some of which probably are derived from the division of the original cartilage-cells, which have disappeared. The walls of these secondary areolae are at this time of only inconsiderable thickness, but they now become thickened by the deposition of lay- ers of new bone on their interior. This process takes place in the following manner: Some of the osteoblasts of the embryonic marrow, after undergoing rapid division, arrange themselves as an epithelioid layer on the surface of the 62 G ENERA L A NA TO MY. wall of the space (Fig. 34). This layer of osteoblasts forms a bony stratum, and thus the wall of the space becomes gradually covered with a layer of true osseous substance. On this a second layer of osteoblasts arrange them- selves, and in their turn form an os- seous layer. By the repetition of this process the original cavity becomes very much reduced in size, and at last only remains as a small circular hole in the centre, containing the remains of the embryonic marrow-that is, a blood-vessel and a few osteoblasts. This small cavity constitutes the Ha- Fig. 35.-Vertical section from the edge of the ossifying portion of the diaphysis of a metatar- sal bone from a foetal calf. (After Muller.) a. Ground-mass of the cartilage, b. Of the bone. c. Newly-formed bone-cells in profile, more or less imbedded in intercellular substance, d. Medul- lary canal in process of formation, with vessels ana medullary cells, e. f. Bone-cells on their broad aspect, g. Cartilage-capsules arranged in rows, and partly with shrunken cell-bodies. Fig. 34.-Transverse section from the femur of a human embryo about eleven weeks old. a. A med- ullary sinus cut transversely; and b, another, long- itudinally. c. Osteoblasts. <1. Newly-formed osseous substance of a lighter color, e. That of greater age. f. Lacunae with their cells, g. A cell still united to an osteoblast. versian canal of the perfectly ossified bone. The successive layers of osseous matter which have been laid down and which encircle this central canal, consti- tute the lamellae of which, as we have seen, each Haversian system is made up. As the successive layers of osteoblasts form osseous tissue, certain of the osteo- blastic cells remain included between the various bony layers. These continue persistent, and remain as the corpuscles of the future bone, the spaces enclosing them forming the lacunae (Fig. 34). The mode of the formation of the canaliculi is not known. Such are the changes which may be observed at one particular point, the centre of ossification. While they have been going on here a similar process has been proceeding in the same manner toward the end of the shaft, so that in the ossify- ing bone all the changes described above may be seen in different parts, from the true bone in the centre of the shaft to the hyaline cartilage at the extremities. The bone thus formed differs from the bone of the adult in being more spongy and less regularly lamellated. Thus far, then, we have followed the steps of a process by which a solid bony mass is produced, having vessels running into it from the periosteum, Haversian BONE. 63 canals in which those vessels run, medullary spaces filled with foetal marrow, lacunae with their contained bone-cells, and canaliculi growing out of these lacunae. This process of ossification, however, is not the origin of the whole of the skeleton, for even in those bones in which the ossification proceeds in a great measure from a single centre, situated in the cartilaginous shaft of a long bone, a considerable part of the original bone is formed by intramembranous ossification beneath the perichondrium or periosteum ; so that the girth of the bone is increased by bony deposit from the deeper layer of this membrane. The shaft of the bone is at first solid, but a tube is hollowed out in it by absorption around the vessels passing into it, which becomes the medullary canal. This absorption is supposed to be brought about by large " giant-cells," which have long been recognized as a constituent of foetal marrow, and which are believed by Kolliker to have the power of absorbing or dissolving bone, and he has therefore named them " osteoclasts " (Fig. 33, /). They vary in shape and size, and are known by containing a large number of clear nuclei, sometimes as many as twenty. The occurrence of similar cells in some tumors of bones has led to such tumors being denominated " myeloid." As more and more bone is removed by this process of absorption from the interior of the bone to form the medullary canal, so more and more bone is deposited on the exterior from the periosteum, until at length the bone has attained the shape and size which it is destined to retain during adult life. As the ossifi- cation of the cartilaginous shaft extends toward the articular ends it carries with it, as it were, a layer of cartilage, or the cartilage grows as it ossifies, and thus the bone is increased in length. During this period of growth the articular end, or epiphysis, remains for some time entirely cartilaginous; then a bony centre appears in it, and it commences the same process of intracartilaginous ossification; but this process never extends to any great distance. The epiphyses remain separated from the shaft by a narrow cartilaginous layer for a definite time. This layer ultimately ossifies, the distinction between shaft and epiphysis is obliterated, and the bone assumes its completed form and shape. The same remarks also apply to the processes of bone which are separately ossified, such as the trochanters of the femur. The bones, having been formed, continue to grow until the body has acquired its full stature. They increase in length by ossification continuing to extend in the epiphysial cartilage, which goes on growing in advance of the ossi- fying process. They increase in circumference by deposition of new bone, from the deeper layer of the periosteum, on their external surface, and at the same time an absorption takes place from within, by which the medullary cavity is increased. The medullary spaces which characterize the cancellous tissue are produced by the absorption of the original foetal bone in the same way as the original medul- lary canal is formed. The distinction between the cancellous and compact tissue appears to depend essentially upon the extent to which this process of absorption has been carried; and we may perhaps remind the reader that in morbid states of the bone inflammatory absorption produces exactly the same change, and converts portions of bone naturally compact into cancellous tissue. Intramembranous Ossification.-The intramembranous ossification is that by which the bones of the vertex of the skull are entirely formed. In the bones which are so developed no cartilaginous mould precedes the appearance of the bone-tissue. In the membrane which occupies the place of the future bone, a little network of bony spiculae is first noticed, radiating from the point of ossification. When these rays of growing bone are examined by the microscope, they are found to consist of a network of fine clear fibres and granular corpuscles, with a ground- substance between. The fibres are termed osteogenic fibres, and soon become dark and granular from calcification, and as they calcify they are found to enclose the granular corpuscles or " osteoblasts " (Fig. 36). The calcification not only involves the osteogenic fibres, but also the ground-substance of the tissue in which they are 64 GENERAL ANATOMY. contained. The corpuscles at first lie upon the osteogenic fibres, so that they can be removed by brushing the specimen with a hair-pencil, in order to render the fibres clear; but they grad- ually become involved in the ossifying matrix, and form the corpuscles of the future bone, the spaces in which they are enclosed constituting the la- cunae. As the tissue increases in thickness, vessels shoot into it, grooving for themselves spaces or channels, which be- come the Haversian canals. Thus, the intramembranous and intracartilaginous processes of ossification are similar in their more essential features. The number of ossific cen- tres is different in different bones. In most of the short bones ossification commences by a single point in the centre, and proceeds toward the cir- cumference. In the long bones there is a central point of ossification for the shaft or diaphysis; and one or more for each extremity, the epiphysis. That for the shaft is the first to appear. The union of the epiphyses with the shaft takes place in the reverse order to that in which their ossification began, and appears to be regulated by the direction of the nutrient artery of the bone. Thus, the nutrient arteries of the bones of the arm and fore-arm are directed toward the elbow, and the epiphyses of the bones forming this joint become united to the shaft before those at the opposite extremity. In the lower limb, on the other hand, the nutrient arteries pass in a direction from the knee: that is, upward in the femur, downward in the tibia and fibula; and in them it is observed that the upper epiphysis of the femur, and the lower epiphysis of the tibia and fibula, become first united to the shaft. Where there is only one epiphysis, the medullary artery is directed toward that end of the bone where there is no additional centre, as toward the acromial end of the clavicle, toward the distal end of the metacarpal bone of the thumb and great toe, and toward the proximal end of the other metacarpal and meta- tarsal bones. Besides these epiphyses for the articular ends, there are others for projecting parts or processes, which are formed separately from the bulk of the bone. For an account of these the reader must be referred to the description of the individual bones in the sequel. A knowledge of the exact periods when the epiphyses become joined to the shaft is often of great importance in medico-legal inquiries. It also aids the sur- geon in the diagnosis of many of the injuries to which the joints are liable; for it not infrequently happens that, on the application of severe force to a joint, the epiphysis becomes separated from the shaft, and such injuries may be mistaken for fracture or dislocation. Fig. 36.-Osteoblasts from the parietal bone of a human em- bryo thirteen weeks old. (After Gegenbauer.) a. Bony septa with the cells of the lacunse. b. Layers of osteoblasts, c. The latter in transition to bone-corpuscles. The muscles are formed of bundles of reddish fibres, endowed with the property of contractility. Two kinds of muscular tissue are found in the animal body-viz. that of voluntary or animal life, and that of involuntary or organic life. The muscles of animal life (striped muscles) are capable of being put in action and controlled by the will. They are composed of bundles of fibres enclosed in a MUSCULAR TISSUE. MUSCULAR TISSUE. 65 delicate web called the "internal perimysium," in contradistinction to the sheath of areolar tissue which invests the entire muscle, the "external perimysium." The bundles are termed " fasciculi; " they are prismatic in shape, of different sizes in different muscles, and for the most part placed parallel to one another, though they have a tendency to converge toward their tendinous attachments. Each fasciculus is made up of a bundle of fibres, which also run parallel with each other, and which are separated from one another by a delicate connective tissue derived from the peri- mysium, and termed endomysium (Fig. 37). A muscular fibre may be said to consist of a soft contractile substance enclosed in a tubular sheath, named by Bowman the sarcolemma. The fibres are cylindrical or prismatic in shape, and are of no great length, not extending, it is said, further than an inch ami a half. They end either by blending with the tendon or aponeurosis, or else by becoming drawn out into a tapering extremity which is connected to the neighboring fibre by means of the sarcolemma. Their breadth varies in man from to -gyro °f an inch, the average of the majority being about As a rule, the fibres do not divide or anastomose; but occasionally, especially in the tongue and facial muscles, the fibres may be seen to divide into several branches. The precise mode in which the muscular fibre joins the tendon has been variously described by different observers. It may, perhaps, be sufficient to say that the sarcolemma, or membranous investment of the muscular fibre, appears to become blended with the tissue of the tendon, and prolonged more or less into the tendon, so that the latter forms a kind of sheath around the fibre for a longer or shorter distance. When muscular fibres are attached to the skin or mucous membranes, their fibres are described by Hyde Salter as*becoming continuous with those of the areolar tissue. The sarcolemma, or tubular sheath of the fibre, is a transparent, elastic, and apparently homogeneous membrane of considerable toughness, so that it will some- times remain entire when the included substance is ruptured (see Fig. 38). On the internal surface of the sarcolemma in mammalia, and also in the substance of the fibre in the lower animals, elongated nuclei are seen (Fig. 55), and in connec- tion with these a row of granules, apparently fatty, is sometimes observed. Upon examination of a muscular fibre by transmitted light under a sufficiently high power, it is found to be apparently marked by alternate light and dark bands or striae, which pass transversely, or somewhat obliquely, round the fibre (Fig. 38). The dark and light bands are of nearly equal breadth, and alternate with great regularity. They vary in breadth from about the yyyy to the of an inch. Other striae pass longitudinally over the fibres, though they are less distinct than the former. This longitudinal striation gives the fibre the appearance of being made up of a bundle of fibrillae. The muscular fibre can be broken up either in a longitudinal or transverse direction (Fig. 39). If hardened in alcohol, it can be broken up longitudinally, and forms the so-called fibrillae of which some suppose the fibre to be made up. Each fibril is marked by transverse striae, and appears to consist of a single row of minute quadrangular particles, named " sarcous elements " by Bowman. A still further division, however, is capable of being made, and each of these fibrillae may be divided into minute threads (Fig. 40, b, d). consisting of an alternate dark and light spot. After exposure to the action of dilute hydrochloric acid, the muscular fibre can be broken transversely (Fig. 39, b). It then forms disks or plates, consisting of the same quadrangular particles, attached by their lateral surfaces. Upon closer examination with a very high power the appearances become more complicated and are susceptible of various interpretations. The transverse Fig. 37.-Transverse section from the sterno-mastoid in man. Magni- fied 50 times, a. External perimys- ium. b. Fasciculus, c. Internal perimysium, d. Fibre. 66 GENERAL ANATOMY. striation, which in Figs. 38 and 39 appears as a mere alternation of dark and light bands, is resolved into the appearance shown in Fig. 40, which shows a series"of broad daik bands, sepaiated by a light band, which is itself divided into two bva dark streak. This streak is termed Krause's membrane; it is continuous at each end with the sarcolemma investing the muscular fibre. Thus it may be said that the fibre is divided into a number of transverse compartments bv this membrane, each compartment containing in the centre a dark plate with' a bright border abo\e and below; that is to say, between the dark central part and the membrane of Krause. A muscular fibre presents, then, the appearance of the following layers in regular alternation: a dark layer, the transverse disk; a bright trans" paient layer, the lateral disk ; a dark line, the intermediate disk or membrane of Krause ; then another lateral disk, a transverse disk, and so on (Figs. 40 and 41). This appearance, following the observations of Rollett, is due to the mode of for- Fig. .39.-Fragments of striped elementary fibres, showing a cleavage in opposite directions. Magnified 300 diameters, a. Longitudinal cleavage. The longi- tudinal and transverse lines are both seen. Some lon- gitudinal lines are darker and wider than the rest, and are not continuous from end to end. This results from partial separation of thefibrillse. c. Fibrillae separated from one another by violence at the broken end of the fibre, and marked by transverse lines equal in width to those on the fibre, c', c" represent two appearances com- monly presented by the separated single fibrillae (more highly magnified). At c' the borders and transverse lines are all perfectly rectilinear, and the included spaces per- fectly rectangular. At c" the borders are scalloped and the spaces bead-like. When most distinct and definite the fibrilla presents the former of these appearances. b. Transverse cleavage. The longitudinal lines are scarcely visible, a. Incomplete fracture following the opposite surfaces of a disk, which stretches across the interval, and retains the two fragments in connection. The edge and surfaces of this disk are seen to be minutely granuTar, the granules corresponding in size to the thickness of the disk and to the distance bet ween the faint longitudinal lines, b. Another disk nearly detached, b'. Detached disk, more highly magnified, showing the sarcous elements. Fig. 38.-Two human muscular fibres. Magnified 350 times. In the one, the bundle of fibrillae (&) is torn, and the sarcolemma (a) is seen as an empty tube. m'ation of a muscular fibre, which is made up of two principal parts : 1, fibrillae ; and 2, a hyaline or faintly granular substance, resembling protoplasm, and called sarcoplasm. The fibrillae are arranged in bundles called muscular columns or sar- costyles, and these again in larger groups, which, collected together, form the fibre. The fibrillae are surrounded by the sarcoplasm, which surrounds also the columns and groups of columns, being in these latter situations greater in amount than between the fibrillae. So that on transverse section a muscular fibre is seen to be divided into a number of areas, called the areas of Cohnheim, more or less polyhedral in shape, and consisting of the columns of fibrillae surrounded by trans- parent series of sarcoplasm. And these areas are collected into larger or smaller groups, which in the same manner are surrounded by transparent sarcoplasm. Each area of Cohnheim presents a granular appearance due to the cross-section of its constituent fibrillae, surrounded by a small amount of the hyaline sarcoplasm. The fibrillae extend throughout the whole length of, and are parallel to, the long axis of the muscular fibre. They present the following appearances in regular alternation : (1) a dim prismatic or rod-shaped element, the sarcous element of Bowman ; (2) a thin bridge, which joins the sarcous element to (3) a dark granule. Then again TISSUE. 67 another thin bridge joining the same granule to the next sarcous element, and so on. When these fibrillte are collected together into columns, and the columns into muscular fibres, the appearance mentioned above is produced. The sarcous ele- ments, when arranged side by side and almost touching each other, with very little sarcoplasm between them, represent the transverse disk. The bridges, being much thinner than the sarcous element or the dark granules, have between each other a much larger amount of sarcoplasm, and this gives to this part the trans- parent appearance of the lateral disk. And, lastly, the granules joined edge to edge in a row present the appearance of a membrane, which represents the inter- mediate disk. On the muscular fibre, immediately beneath the sarcolemma, the sarcoplasm Fig. 41.-Part of a striped muscular fibre of the water-beetle, prepared with absolute alcohol. Magnified 300 diameters. (Klein and Noble Smith.) a. Sarcolemma. b. Membrane of Krause; owing to contrac- tion during hardening, the sarcolemma shows regular bulgings. At the side of Krause's membrane is the transparent lat- eral disk. Several nuclei of muscle-cor- puscles are shown, and in them a minute network. Fig. 40.-Portion of a medium-sized human muscular fibre. Magnified nearly 800 diameters, b. Separated bun- dles of fibrils, equally magnified, a. a. Larger, and b. b, smaller collections, c. Still smaller, d. d. The smallest which could be detached. becomes here and there collected into small, plate-like masses. They contain oval nuclei, and are termed "muscle-corpuscles." Finally, in the centre of each sarcous element a transparent lighter band can sometimes be discerned; this is known as the median disk of Hensen, and is due to the substance of the sarcous elements being here thinner. This form of muscular fibre composes the whole of the voluntary muscles, all the muscles of the ear, those of the larnyx, pharynx, tongue, the upper half of the oesophagus, the heart, and the walls of the large veins at the point where they open into it. The fibres of the heart, however, differ very remarkably from those of other striped muscles. They are smaller by one-third, and their transverse striae are by no means so distinct. The fibres are made up of distinct quadran- gular cells joined end to end (Fig. 42). Each cell contains a clear oval nucleus, situated near the centre of the cell. The extremities of the cells have a tendency to branch or divide, the subdivisions uniting with offsets from other cells, and thus producing an anastomosis of the fibres (Fig. 42). The connective tissue between the bundles of fibres is much less than in ordinary striped muscle, and no sarcolemma has been proved to exist. The capillaries of striped muscle are very abundant, and form a sort of rect- angular network, the branches of which run longitudinally in the edomysium between the muscular fibres, and are joined at short intervals by transverse anastomosing branches. The larger vascular channels, arteries and veins, are 68 GENERAL ANATOMY. found only in the perimysium, between the muscular fasciculi. The smaller ves- sels present peculiar saccular dilatations, which are supposed to act as receptacles for the blood during the contraction of the muscular fibres, when it is pressed out from some of the capil- laries. Nerves are profusely distributed to striped muscle. The mode of their termination will be described on a subsequent page. The existence of lymphatic vessels in striped muscle has not been ascertained, though they have been found in tendons and in the sheath of the muscle. The unstriped muscle, or muscle of organic life, is found in the walls of the hollow viscera - viz. the lower half of the oesophagus and the whole of the remainder of the gastro-intestinal tube ; in the trachea and bronchi, and the alveoli and infundibula of the lungs; in the gall-bladder and ductus communis choledochus; in the large ducts of the salivary and pancreatic glands; in the pelvis and calices of the kidney, the ureter, bladder, and urethra; in the female sexual organs-viz. the ovary, the Fallopian tubes, the uterus (enormously developed in preg- nancy), the vagina, the broad ligaments, and the erectile tissue of the clitoris; in the male sexual organs-viz. the dartos scroti, the vas deferens and epididymis, the vesiculae seminales, the prostate gland, and the corpora cavernosa and corpus spongiosum; in the ducts of certain glands, as in Wharton's duct; in the capsule and trabeculae of the spleen; in the mucous membranes, forming the muscularis mucosae; in the skin, forming the arrectores pilorum, and also in the sweat- glands ; in the arteries, veins, and lymphatics; in the iris and the ciliary muscle. Plain or unstriped muscular fibre is made up of spindle-shaped cells, called contractile fibre-cells, collected into bundles and held together by a cement-sub- stance, in which are contained some connective-tissue corpuscles (Fig. 43). These bundles are further aggregated into larger bundles or flattened bands, and bound together by ordinary connective tissue. The contractile fibre-cells (Fig. 44) are elongated, spindle-shaped, nucleated cells of various lengths, averaging from to of an inch in length, and t° tthto an inch in breadth. On transverse section they are more or less polv- hedral in shape, from mutual pressure. They present a faintly longitudinal stri- ated appearance, and consist of an elastic cell-wall containing a central bundle of fibrillae, representing the contractile substance, and an oval or rod-like nucleus, which includes, within a membrane, a fine network communicating at the poles of the nucleus with the contractile fibres (Klein). The adhesive interstitial sub- stance, which connects the fibre-cells together, represents the endomysium, or del- icate connective tissue which binds the fibres of striped muscular tissue into fas- ciculi ; while the tissue connecting the individual bundles together represents the perimysium. The unstriped muscle, as a rule, is not under the control of the will, nor is the contraction rapid and involving the whole muscle, as is the case with the muscles of animal life. The membranes which are composed of the unstriped muscle slowly contract in a part of their extent, generally under the influence of a mechanical stimulus, as that of distension or of cold; and then the contracted part slowly relaxes while another portion of the membrane takes up the contrac- tion. This peculiarity of action is most strongly marked in the intestines, con- stituting their vermicular motion. Chemical Composition of Muscle.-In chemical composition the muscular fibres of both forms consist mainly of a proteid substance-myosin-which Dr. M. Foster speaks of as intermediate between fibrin and globulin. It is readily converted by Fig. 42-Anastomosing muscular fibres of the heart seen in a longitu- dinal section. On the right the lim- its of the separate cells with their nuclei are exhibited somewhat dia- grammatically. NERVOUS TISSUE. 69 the action of dilute acids into syntonin or acid-albumen, and by the action of dilute alkalies into alkali-albumen. Muscle, which is neutral or slightly alkaline Fig. 44.-Muscular fibre-cells from human arteries. 1. From the popliteal artery, a. without; b. with acetic acid. 2. From a branch of the anterior tibial, a. Nuclei of the fibres. Magnified 350 times. Fig. 43.-Non-striated elementary fibres from the human colon, a. Treated with acetic acid, showing the corpuscles, b. Fragment of a detached fibre, not touched with acid. in reaction when at rest, is rendered acid by contraction, from the development probably of sarcolactic acid. After death muscle also exhibits an acid reaction, but this appears to be due to post-mortem change. NERVOUS TISSUE. The nervous tissues of the body are comprised in two great systems-the cerebrospinal and the sympathetic; and each of these systems consist of a central organ, or series of central organs, and of nerves. The cerebrospinal system comprises the brain (including the medulla oblongata), the spinal cord, the cranial nerves, the spinal nerves, and the ganglia connected with both these classes of nerves. The sympathetic system consists of a double chain of ganglia, with the nerves which go to and come from them. It is not directly connected with the brain or spinal cord, though it is so indirectly by means of its numerous communications with the cranial and spinal nerves. All these nervous tissues are composed chiefly of two different structures-the gray or vesicular, and the white or fibrous. It is in the former, as is generally supposed, that nervous impressions and impulses originate, and by the latter that they are conducted. Hence the gray matter forms the essential constituent of all the ganglionic centres, both those in the isolated ganglia and those aggregated in the cerebro-spinal axis ; while the white matter is found in all the commissural portions of the nerve-centres and in all the cerebro-spinal nerves. The nerves of the sympathetic system are chiefly composed of a somewhat different material in structure, which is named gray or gelatinous nerve-fibre. This form of nerve-fibre is also found in some of the cerebro-spinal nerves. The gray or vesicular nervous substance is distinguished by its dark reddish- gray color and soft consistence. It is found in the brain, spinal cord, and various ganglia, intermingled with the fibrous nervous substance, and also in some of the nerves of special sense, and in gangliform enlargements which are found here and there in the course of certain cerebro-spinal nerves. It is composed, as its name implies, of vesicles, or corpuscles, commonly called nerve-cells or ganglion-corpuscles, containing nuclei and nucleoli; the vesicles, together with the blood-vessels, in the 70 GENERAL ANATOMY. vesicular nerve-substance, and the nerve-fibres and vessels in the white nerve- substance, are imbedded in a peculiar ground-substance, which was regarded by Kblliker as a modified form of retiform connective tissue. It was named by Virchow neuroglia, and consists of large branched cells, the branches passing in every direction among the nerve-tissue, thus holding it and binding it together. It is developed from the epiblast, and contains neither the characteristic fibres nor cells of connective tissue, and therefore cannot be regarded as belonging to the true connective tissues. Each nerve-cell consists of a finely granular protoplasmic mate- rial, of a reddish or yellowish-brown color, which occasionally presents patches of a deeper tint, caused by the aggregation of pigment-granules (Fig. 45). No dis- Fig. 45.-Nerve-vesicles from the Gasserian ganglion of the human subject, a. A globular one with defined border, b. Its nucleus, c. Its nucleolus, d. Caudate vesicle, e. Elongated vesicle with two groups of pigment-particles, f. Vesicle surrounded by its sheath or capsule of nucleated particles. <7. The same, the sheath only being 111 focus. Magnified 300 diameters. Fig. 46.-Nerve-vesicles from the inner part of the gray matter of the convolutions of the human brain. Magnified 350 times. Nerve-cells: a. Larger, b. Smaller c Nerve- fibre with axis-cylinder. tinct limiting membrane or cell-wall has been ascertained to exist. The nucleus is, as a rule, a large, well-defined, round, vesicular body, often presenting an intra- nuclear network, and containing a nucleolus which is peculiarly clear and brilliant. The nerve-corpuscles vary in shape and size; some are small, spherical or ovoid, with generally an even outline, such as those frequently found in the spinal ganglia ; others are more or less angular, as in the ganglia of the sympathetic; others, again, are caudate or stellate in shape, and are characterized by their large size and by their having one or more tail-like processes issuing from them, which occa- sionally divide and subdivide into numerous branches (Fig. 46). These are found in greatest number in the gray matter of the spinal cord. Still others are flask- shaped, as in the cortex of the cerebellum; or conical, as in the cerebral convolu- tions. For the most part nerve-cells have one or more processes, and they are distinguished by the number of these processes, as unipolar, bipolar, or mul- tipolar cells. These processes are very delicate, apparently tubular, and contain a similar granular material to that found within the corpuscle. Some of the pro- cesses terminate in fine, transparent fibres, which become lost among the other elements of the nervous tissue; others may be traced until, after losing their granular appearance, they become continuous with an ordinary nerve-fibre. The white or fibrous nerve-substance or nerve-fibre is found universally in the nervous cords, and also constitutes a great part of the brain and spinal cord. The fibres of which it consists are of two kinds, the medullated or white fibres, and the non-medullated or gray fibres. The medullated fibres form the white part of the brain and spinal cord, and also the greater part of the cerebro-spinal nerves, and give to these structures ArER VO US TISSUE. 71 their opaque, white aspect. When perfectly fresh they appear to be homo- geneous ; but soon after removal from the body they present, when exam- ined by transmitted light, a double outline or con- tour, as if consisting of two parts. The central portion is named the axis-cylinder of Purkinje; around this is a sort of sheath of fatty material, named the white substance of Schwann, which gives to the fibre its double contour, and the whole is en- closed in a delicate membrane, the neurilemma,1 primitive sheath, or nucleated sheath of Schwann (Fig. 47). The axis-cylinder is the essential part of the nerve-fibre, and is always present; the other parts, the medullary sheath and the neurilemma, being occasionally absent, especially at the origin and termination of the nerve-fibre. It undergoes no interruption from its origin in the nerve-centre to its peripheral termination, and must be regarded as a direct prolongation of a nerve-cell. It con- stitutes about one-half or one-third of the nerve- tube, the white substance being greater in propor- tion in the nerves than in the central organs. It is perfectly transparent, and is therefore indistin- guishable in a perfectly fresh and natural state of the nerve. It is described by Kolliker as being distinguished from the white substance by the fact that, though soft and flexible, it is not fluid and viscid, but firm and elastic, somewhat like coagulated albumen, with which it appears for the most part also to agree in its chemical characters. When examined under a high power it presents the appearance of longitudinal striation, as if composed of very fine, homogeneous fibrillae, held together in a faintly granular interstitial material. Occasionally at its termination the axis-cylinder of a fibre may be seen to break up into exceedingly fine fibrillae, confirming the view of its fibrillar structure. These fibrillae have been termed the primitive fibrillce of Schultze. The axis-cylinder is said to be enveloped in a very delicate, hyaline sheath, which separates it from the white matter of Schwann. The medullary sheath or white matter of Schwann is regarded as being a fatty matter in a fluid state, which insulates and protects the essential part of the nerve-the axis-cylinder. The white matter varies in thickness to a very considerable extent, in some forming a layer of extreme thinness, so as to be scarcely distinguishable, in others forming about one-half the nerve-tube. The size of the nerve-fibres, which varies from 1 fr to an inch, depends mainly upon the amount of the white substance, though the axis-cylinder also varies in size within certain limits. The white matter of Schwann does not always form a continuous sheath to the axis-cylinder, but undergoes interruptions in its continuity at regular intervals, giving to the fibre the appearance of constriction at these points. These were first described by Ran- vier, and are known as the nodes of Ranvier (Fig. 48). The por- tion of nerve-fibre between two nodes is called an internodal seg- ment. The neurilemma or prim- itive sheath is not interrupted at the nodes, but passes over them as a continuous membrane. Each internodal segment contains an one of which is varicose, one of mid- dling thickness, and with a simple con- tour; and three thick, two of which are and °ne with gru' Fig. 48.-A node of Ranvier of a medullated nerve-fibre, viewed from above, magnified about 750 diameters. The medul- lary sheath is discontinuous at the node, whereas the axis-cyl- inder passes from one segment into the other. At the node the sheath of Schwann appears thickened. (Klein and Noble Smith.) 1 In older histological works the term " neurilemma " is used to designate the fibrous envelope of the whole nerve, now called " perineurium." 72 GENERAL ANATOMY. oval nucleus imbedded in the medullary sheath, and occasionally more than one nucleus may be seen in the same internode. Medullated nerve-fibres, when examined frequently present a beaded or varicose appearance: this is due to manipulation and pressure causing the oily matter to collect into drops, and in consequence of the extreme delicacy of the primitive sheath, even slight pressure will cause the transudation of the fatty matter, which collects as drops of oil outside the membrane. This is, of course, promoted by the action of ether (Fig. 49). The neurilemma or primitive sheath (sometimes called the tubular membrane or sheath of Schwann) presents the appearance of a delicate, structureless membrane. Here and there beneath it, and situated in depressions in the white matter of Schwann, are nuclei surrounded by a small amount of protoplasm. The nuclei are oval and somewhat flattened, and bear a definite rela- tion to the nodes of Ranvier; one nucleus generally lying in the centre of each node, though in some few instances two nuclei may be found in the same node. Non-medullated Fibres.-Most of the nerves of the sympathetic system, and some of the cerebro- spinal (see especially the descrip- tion of the olfactory nerve), con- sist of another variety of nervous fibres, which are called the gray or gelatinous nerve-fibres-fibres of Remak (Fig. 50). These con- sist of a bundle of finely striated fibrillm enclosed in a sheath. Nuclei may be detected at inter- vals in each fibre, situated be- tween the axis-cylinder and the neurilemma. In external appear- ance the gelatinous nerves are semi-transparent and gray or yellowish-gray. The individual fibres vary in size, generally averaging about half the size of the medullated fibres; but, on the one hand, the primitive fibrillae formed by the breaking up of the cerebro-spinal fibres, as above mentioned, are of hardly appreciable thickness; while, on the other hand, some of the gelatinous fibres (especially those on the olfactory bulb) are said to be three or four times as thick as those of the cerebro-spinal nerves. Chemical Composition.-The different portions of the nervous system are com- posed of the two above-described kinds of nervous structure, the chemical composi- tion of which is shown by the following analysis, by Lassaigne, which represents the relative proportion of the different constituents composing the grav and white matter of the brain. Fig. 49.-Magnified 300 diam- eters. a. Nerve-tube of the com- mon eel in water. The delicate line on its exterior indicates the tubular membrane. The dark double-edged inner one is the white matter of Schwann, slightly wrinkled, b. The same in ether. Several oil-globules have coalesced in the interior, and others have accumulated around the exterior of the tube. The white matter has in part disappeared. Fig. 50.-A small ner- vous branch from the sym- pathetic of a mammal, a. Two dark-bordered nerve- tubes among a number of Remak's fibres, b. Gray. White. Water 85.2 73.0 Albuminous matter 7.5 9.9 Colorless fat 1.0 13.9 Red fat 3.7 0.9 Osmazome and lactates 1.4 1.0 Phosphates 1.2 1.3 It appears from this analysis that the cerebral substance consists of albumen dissolved in water, combined with fatty matter and salts. The fattv matters consist of cerebrin, neurin, and lecithin. The two latter were first described by NER VO US TISSUE. 73 Liebreich as a crystalline phosphuretted fat, which he termed protagon. It seems probable, however, that it is simply a mixture of neurin and lecithin. Choles- terine is also described as one of the chemical constituents of the nervous tissues, being found in conjunction with lecithin. The salts are the phosphates of potash, soda, lime, magnesia, and iron, sulphate of potash, and chloride of sodium, with traces of silica. According to Vauquelin, the cord contains a larger proportion of fat than the brain; and according to L'Heritier, the nerves contain more albu- men and more soft fat than the brain. The nervous structures are divided, as before mentioned, into two great systems -viz. the cerebrospinal, comprising the brain and spinal cord, the nerves con- nected with these structures, and the ganglia situated on them; and the sympa- thetic, consisting of a double chain of ganglia and the nerves connected with them. All these structures require separate consideration; they are composed of the two kinds of nervous tissue above described, intermingled in various proportions and having, in some parts, a very intricate arrangement. The brain or encephalon is that part of the cerebro-spinal system which is contained in the cavity of the skull. It is divided into several parts, named the medulla oblongata, pons Varolii, cerebellum, and cerebrum. In these parts the gray or vesicular nervous matter is found partly on the surface of the brain, form- ing the convolutions of the cerebrum, and partly in the 1 ami me of the cerebellum. Again, gray matter is found in the interior of the brain, collected into large and distinct masses or ganglionic bodies, such as the corpus striatum, optic thalamus, and corpora quadrigemina. Finally, gray matter is found intermingled intimately with the white, but without definite arrangement, as in the corpora dentata of the medulla and cerebellum, or the gray matter in the pons Varolii and the floor of the fourth ventricle. The white matter of the brain is divisible into three distinct classes of fibres. These are, in the first place, the nerves which arise in the gray matter and pass out through the cranial foramina. Next, the fibres which connect the brain with the spinal cord; that is to say, those which are usually traced upward from the columns of the spinal cord, through the medulla oblongata into the encephalon, chiefly by means of the anterior pyramids, fasciculi teretes, and restiform bodies, passing through the pons Varolii and crura cerebri to expand into the corpora striata, optic thalamus, and convolutions (corona radiata), and by means of the restiform bodies into the cerebellum. The other class of white fibres in the brain are commissural, some of the commissures serving to connect different parts of the same hemisphere together (as the fornix, processus e cerebello ad testes, etc.), or even different parts of the same section or organ, as the arciform fibres of the medulla. Most of these commissures are longitudinal; while others, as the corpus callosum and the transverse fibres of the pons Varolii, are transverse, serving to connect opposite hemispheres together, and thus probably securing the single action of a double organ. The manner in which the gray and white matter are intermingled in the brain and spinal cord is very intricate, and can only be fully understood by a careful study of the details of its descriptive anatomy in the sequel. The further consid- eration of this subject will therefore be deferred until after the description of the various divisions of which the cerebro-spinal system is made up. The nerves are round or flattened cords, formed of the nerve-fibres already described. They are connected at one end with the cerebro-spinal centre or with the ganglia, and are distributed at the other end to the various textures of the body; they are subdivided into two great classes-the cerebrospinal, which pro- ceed from the cerebro-spinal axis, and the sympathetic or ganglionic nerves, which proceed from the ganglia of the sympathetic. The cerebro-spinal nerves consist of numerous nerve-fibres collected together and enclosed in a membranous sheath (Fig. 51). A small bundle of primitive fibres, enclosed in a tubular sheath, is called a funiculus; if the nerve is of small size, it may consist only of a single funiculus; but if large, the funiculi are collected together into larger bundles or 74 GENERAL ANATOMY. fasciculi, which are bound together in a common membranous investment, and constitute the nerve. In structure the common mem- branous investment, or sheath of the whole nerve, which is called the epi- neurium, as well as the septa given off from it, and which separate the fas- ciculi, consists of connective tissue, composed of white and yellow elastic fibres, the latter existing in great abundance. The tubular sheath of the funiculi, called the perineurium, consists of a fine, smooth, transparent membrane, which may be easily sepa- rated, in the form of a tube, from the fibres it encloses; in structure it con- sists of connective tissue, which has a distinctly lamellar arrangement, con- sisting of several lamellae, separated from each other by spaces containing lymph. The nerve-fibres are held to- gether and supported within the funic- uculus by delicate connective tissue, called the endoneurium. It is con- tinuous with septa which pass inward from the innermost layer of the peri- neurium, and consists of a ground-sub- stance in which are imbedded fine bun- dles of fibrous connective tissue which run for the most part longitudinally. It serves to support the capillary vessels, which are arranged so as to form a network with the elongated meshes. The cerebro-spinal nerves consist almost exclusively of the medullated nerve-fibres, the non-medullated existing in very small proportions. The blood-vessels supplying a nerve terminate in a minute capillary plexus, the vessels composing which pierce the perineurium and run, for the most part, parallel with the fibres; they are connected together by short, transverse vessels, forming narrow, oblong meshes, similar to the capillary system of muscle. Fine non-medullated nerve-fibres accompany these capillary vessels, vaso-motor fibres, and break up into elementary fibrils, which form a network around the vessel. Horsley has also recently demonstrated certain medullated fibres as running in the epineurium and terminating in tactile corpuscles or end-bulbs of Krause, or in small, but perfect, Pacinian corpuscles. These nerve-fibres, which Professor Marshall believes to be sensory, and which he has termed nervi nervorum, are considered by him to have an important bearing upon certain neuralgic pains. The nerve-fibres, as far as is at present knowm, do not coalesce, but pursue an uninterrupted course from the centre to the periphery. In separating a nerve, however, into its component funiculi, it may be seen that they do not pursue a perfectly insulated course, but occasionally join at a very acute angle with other funiculi proceeding in the same direction; from this, branches are given off, to join again in like manner with other funiculi. It must be remembered, however, that in these communications the nerve-fibres do not coalesce, but merely pass into the sheath of the adjacent nerve, become intermixed with its nerve-fibres, and again pass on, to become blended with the nerve-fibres in some adjoining funiculus. Nerves, in their course, subdivide into branches, and these frequently com- municate with branches of a neighboring nerve. In the subdivision of a nerve Fig. 51.-Transverse section through a microscopic nerve, representing a compound nerve-bundle, sur- rounded by perineurium. Magnified 120 diameters. The medullated fibres are seen as circles with a cen- tral dot-viz. medullary sheath and axis-cylinder-in transverse section. They are imbedded in endoneur- ium, containing numerous nuclei, which belong to the connective-tissue cells of the latter. (Klein and Noble Smith.) p. Perineurium, consistingof laminae of fibrous connective tissues, alternating with flattened nucleated connective-tissue cells. I. Lymph-space between peri- neurium and surface of nerve-bunule. AM VOCES' TISSUE. 75 the filaments of which it is composed are continued from the trunk into the branches, and at their junction with the branches of neighboring nerves the filaments pass to become intermixed with those of the other nerves in their further progress; in no instance, however, have the separate nerve-fibres been shown to inosculate. The communications which take place between two or more nerves form what is called a plexus. Sometimes a plexus is formed by the primary branches of the trunks of the nerves-as the cervical, brachial, lumbar, and sacral plexuses-and occasionally by the terminal funiculi, as in the plexuses formed at the periphery of the body. In the formation of a plexus the component nerves divide, then join, and again subdivide in such a complex manner that the individual funiculi become interlaced most intricately; so that each branch leaving a plexus may contain filaments from each of the primary nervous trunks which form it. In the formation also of smaller plexuses at the periphery of the body there is a free interchange of the funiculi and primitive fibres. In each case, however, the individual filaments remain separate and distinct, and do not inosculate with one another. It is probable that through this interchange of fibres the different branches passing off from a plexus have a more extensive connection with the spinal cord than if they each had proceeded to be distributed without such connection with other nerves. Consequently the parts supplied by these nerves have more extended relations with the nervous centres; by this means, also, groups of muscles may be associated for combined action. The sympathetic nerves are constructed in the same manner as the cerebro- spinal nerves, but consist mainly of non-medullated fibres, collected into funiculi, and enclosed in a sheath of connective tissue. There is, however, in these nerves a certain admixture of medullated fibres, and the amount varies in different nerves, and may be known by its color. Those branches of the sympathetic which present a well-marked gray color are composed more especially of gelatinous nerve-fibres, intermixed with a fewr medullated fibres; whilst those of a white color contain more of the latter fibres, and a few of the former. Occasionally, the gray and white cords run together in a single nerve, without any intermixture, as in the branches of communication between the sympathetic ganglia and the spinal nerves, or in the communicating cords between the ganglia. The nerve-fibres, both of the cerebro-spinal and sympathetic system, convey impressions of a twofold kind. The sensory nerves, called also centripetal or afferent nerves, transmit to the nervous centres impressions made upon the peripheral extremities of the nerves, and in this way the mind, through the medium of the brain, becomes conscious of external objects. The motor nerves, called also centrifugal or efferent nerves, transmit impressions from the nervous centres to the parts to which the nerves are distributed, these impressions either exciting muscular contraction, or influencing the processes of nutrition, growth, and secretion. Origin and Termination of Nerves.-By the expression " the termination of nerve-fibres " is signified their connection with the nerve-centres, and with the parts they supply. The former are sometimes called their origin, or central termination ; the latter their peripheral termination. The origin in some cases is single-that is to say, the whole nerve emerges from the nervous centre by a single root; in other instances the nerve arises by two or more roots, which come off from different parts of the nerve-centre, sometimes widely apart from each other, and it often happens, when a nerve arises in this way by two roots, that the functions of these two roots are different; as, for example, in the spinal nerves, each of which arises by two roots, the anterior of which is motor and the posterior sensory. The point where the nerve root or roots emerge from the nervous centre is named the superficial or apparent origin, but the fibres of which the nerve consists can be traced for a certain distance into the nervous centre to some por- tion of the gray substance, which constitutes the deep or real origin of the nerve. 76 GENERAL ANATOMY. The exact manner in which the fibres of which the nerve-root is made up arise at their deep origin is, to a certain extent, uncertain. But it would appear prob- able that there are two modes in which they originate and are connected with the nerve-cells. If the multipolar nerve-cells are examined, it will be found that one at least of their processes does not branch ; this process is named the axial-cylinder process, and at first has all the characters of an axis-cylinder. Soon, however, it acquires a medullary sheath, and has been traced to be directly continuous with a nerve-fibre. Other processes of a multipolar cell divide and subdivide as they pass away from the cell, until at last they form branches of extreme tenuity, and form an excessively minute network. These processes apparently consist of cell- protoplasm, and are named protoplasm processes. From the network which they form minute medullated nerve-fibres arise. So that it would appear that nerve- fibres arise: first, directly through the passage of the non-branched axis-cylinder process into a fibre; and, secondly, through the minute network formed by the branched protoplasm processes. Peripheral Terminations of Nerves.-The manner in which nerve-fibres ter- minate peripherally are several, and may be conveniently studied in the sensory and motor nerves respectively. Sensory nerves would appear to terminate either in minute primitive fibrillae or networks of these; or else in special terminal organs, which have been termed peripheral end-organs, and of which there are three principal varieties-viz. the end-bulbs of Krause, the tactile corpuscles of Wagner, and the Pacinian corpuscles. Termination in Fibrillse.-When a medullated nerve-fibre approaches its termi- nation, the white matter of Schwann suddenly disappears, leaving only the axis- cylinder surrounded by the neurilemma, and we have now a non-medullated fibre. This undergoes repeated division, and after a time loses its neurilemma, and consists only of an axis-cylinder, which can be seen, in preparations stained with chloride of gold, to be made up of fine varicose fibrils. Finally, the axis- cylinder breaks up into its constituent primitive nerve-fibrillae, which anastomose with one another, thus forming a network, and often present regular varicosities. This network passes between the elements of the tissue to which the nerves are distributed, which is always epithelial, the nerve-fibrils lying in the interstitial substance between the epithelial cells, and, as is believed by some, actually termi- nating within the cells as minute swellings close to the nucleus. In this way nerve-fibres have been found to terminate in the epithelium of the skin and mucous membranes, and in the anterior epithelium of the cornea. The end-bulbs of Krause (Fig. 52) are minute oblong or cylindrical corpuscles, into the interior of which the axis-cylinder of the nerve-fibre passes, and termi- nates in a coiled, plexiform mass or in a bulbous extremity. The corpuscle consists of a simple nucleated capsule, containing a soft, homogeneous core, in which the termination of the axis-cylinder is contained. The white matter of Schwann ceases abruptly as the axis-cylinder enters the corpuscle, but the perineurium is continued inward with the axis-cylinder, and forms an investment of the core, lining the interior of the capsule. The end-bulbs have been described as occurring in the conjunctiva (where, in man, they are spheroidal in shape), in the mucous membrane of the mouth, and in the cutis and mucous membrane of the penis, clitoris, and vagina, where they are termed genital corpuscles. The latter have a mulberry-like appearance, from being constricted by connective-tissue septa into from two to six knob-like masses. In the synovial membrane of certain joints (e. g. those of the fingers) rounded or oval end-bulbs have been found; these are designated articular end-bulbs. The tactile corpuscles (Fig 53), described by Wagner and Meissner, are oval- shaped bodies, made up of connective tissue, and consisting of a capsule, and imperfect membranous septa, derived from it, which penetrate its interior. The axis-cylinders, entering the capsule, pursue a convoluted course, supported by the septa, and terminate in small globular oi' pyriform enlargements, near the inner surface of the capsule. These tactile corpuscles have been described as occurring NERVOUS TISSUE. 77 in the papillae of the corium of the hand and foot, the front of the fore-arm, the skin of the lips, and the mucous membrane of the tip of the tongue, the palpebral Fig. 52.-End-bulb of Krause, a. Medul- lated nerve-fibre, b. Capsule of corpuscle. (From Klein's Elements of Histology.) Fig. 53-Papilla of the hand treated with acetic acid. Magnified 350 times. A. Side view of a papilla of the hand. a. Cortical layer, b. Tactile corpuscle, with transverse nuclei, c. Small nerve of the papilla, with neurilemma, d. Its two nervous fibres running with spiral coils around the tactile corpuscle, e. Apparent termination of one of these fibres, b. A tactile papilla seen from above, so as to show its transverse section, a. Cortical layer, b. Nerve-fibre, c. Outer layer of the tactile body, with nuclei, d. Clear interior substance. conjunctiva, and the skin of the nipple. They are not found in all the papillae; but from their existence in those parts in which the skin is highly sensitive, it is probable that they are specially concerned in the sense of touch, though their absence from the papillae of other tactile parts shows that they are not essential to this sense. The Pacinian corpuscles1 (Fig. 54) are found in the human subject chiefly on the nerves of the palm of the hand and sole of the foot and in the genital organs of both sexes, lying in the subcutaneous tissue; but they have also been described as connected with the nerves of the joints, and in some other* situations, as the mesentery of the cat and along the tibia of the rabbit. Each of these corpuscles is attached to and encloses the termination of a single nerve-fibre. The corpuscle, which is perfectly visible to the naked eye (and which can be most easily demon- strated in the mesentery of a cat), consists of a number of lamellae or capsules, arranged more or less concentrically around a central clear space, in which the nerve-fibre is contained. Each lamella is composed of bundles of fine connective- tissue fibres, and is lined on its inner surface by a single layer of nucleated endo- thelial cells. The central clear space, which is elongated or cylindrical in shape, is filled with a transparent material, in the middle of which is the single medullated fibre, which traverses the space to near its distal extremity. Here it terminates in a rounded knob or end, sometimes bifurcating previously, in which case each branch has a similar arrangement. Todd and Bowman have described minute arteries as entering by the sides of the nerves and forming capillary loops in the intercapsular spaces, and even penetrating into the central space. Other authors describe the artery as entering the corpuscle at the pole opposite to the nerve- fibre. Herbst has described a somewhat similar " nerve-ending " to the Pacinian cor- puscle, as being found in the mucous membrane of the tongue of the duck and irksome other situations. It differs, however, from the Pacinian corpuscles, in being smaller, its capsules thinner and more closely approximated, and especially in the fact that the axis-cylinder in the central clear space is coated with a con- tinuous row of nuclei. These bodies are known as the corpuscles of Herbst. Tactile corpuscles have been described by Grandry as occurring in the papillae of the beak and tongue of birds, and by Merkel as occurring in the papillae and 1 Often called in German anatomical works "corpuscles of Vater." 78 GENERAL ANATOMY. epithelium of the skin of man and animals, especially in those parts of the skin devoid of hair. They consist of a capsule composed of a very delicate, nucleated membrane, and contain two or more granular, somewhat flattened cells, between which the med- ullated nerve-fibre, which enters the capsule by piercing its investing membrane, is supposed to terminate. In the organs of special sense the nerves ter- minate in cells, which are modified epithelial cells, and have received the name of sensory or nerve- epithelium cells. The axis-cylinder, after divid- ing into fibrils, ends in epithelial cells, variously modified, and to the peripheral extremity of which are often connected peculiar styliform processes. These cells will be more particularly described in the sequel, in connection with the description of the organs of special sense. Motor nerves are to be traced either into un- striped or striped muscular fibres. In the un- striped or involuntary muscles the nerves are derived from the sympathetic, and are composed mainly of the non-medullated fibres. Near their termination they divide into a number of branches, which communicate and form an intimate plexus. At the junction of the branches small triangular nuclear bodies are situated. From these plexuses minute branches are given off, which divide and break up into the ultimate fibrillae of which the nerve is composed. These fibrillae course between the involuntary muscle-cells, and, according to Elischer, terminate on the surface of the cell, opposite the nucleus, in a minute swelling. Ar- nold and Frankenhauser believed that these ulti- mate fibrillae penetrated the muscular cell and ended in the nucleus. More recent observation has, however, tended to disprove this. In the striped or voluntary muscle, the nerves supplying the muscular fibres are derived from the cerebro-spinal nerves, and are composed mainly of medullated fibres. The nerve, after entering the sheath of the muscle, breaks up into fibres, or bundles of fibres, which form plexuses, and gradually divide until, as a rule, a single nerve-fibre enters a single muscular fibre. Sometimes, however, if the muscular fibre is loner, more than one nerve-fibre enters it. Within the muscular fibre the nerve terminates in a special expansion, called by Kiihne, who first accurately described them, motorial end-plates (Fig. 55).1 The nerve-fibre, on approaching the muscular fibre, suddenly loses its white matter of Schwann, which abruptly terminates ; the neurilemma becomes continuous with the sarco- lemina of the muscle, and only the axis-cylinder enters the muscular fibre, where it immediately spreads out, ramifying like the roots of a tree, immediately beneath the sarcolemma, and is imbedded in a layer of granular matter, containing a number of clear, oblong nuclei, the whole constituting an end-plate from which the contractile wave of the muscular fibre is said to start. The nerves supplying tendons have peculiar nerve-endings, and are especially numerous near the point where the tendon becomes muscular. In this situation spindle-shaped bodies are found, and are known as the organs of Golgi. They are apparently composed of several tendinous bundles fused into one, into which one Fig. 54.-Pacinian corpuscle, with its system of capsules and central cavity. a. Arterial twig, ending in capillaries, which form loops in some of the inter- capsular spaces, and one penetrates to the central capsule, b. The fibrous tissue of the stalk prolonged from the perineu- rium. n. Nerve-tube advancing to the central capsule, there losing its white matter, and stretching along the axis to the opposite end, where it is fixed by a tubercular enlargement. 1 They had, however, previously been noticed, though not accurately described, by Doyere, who named them " nerve-hillocks." NERVOUS TISSUE. 79 or more nerve-fibres pass, and, dividing, spread out between the tendon-bundles Fig. 55.-Muscular fibres of Lacerta viridis with the terminations of nerves, a. Seen in profile, p.p. The nerve end-plates, s.s. The base of the plate, consisting of a granular mass with nuclei, b. The same as seen in look- ing at a perfectly fresh fibre, the nervous ends being probably still excitable. (The forms of the variously- divided plate can hardly be represented in a woodcut by sufficiently delicate and pale contours to reproduce correctly what is seen in nature.) c. The same as seen two hours after death from poisoning by curare. Nerve-fibres occasionally terminate in tendons as end-bulbs or as small Pacinian corpuscles. The Ganglia may be regarded as separate and independent nervous centres, of smaller size and less complex structure than the brain, connected with each other, with the cerebro-spinal axis, and with the nerves in various situations. They are found on the posterior root of each of the spinal nerves; on the posterior or sen- sory root of the fifth cranial nerve; on the facial and auditory nerves; on the glosso-pharyngeal and pneumogastric nerves; and on the branches of certain spinal nerves. They are also found in a connected series along each side of the vertebral column, forming the trunk of the sympathetic; and on the branches of that nerve, generally in the plexuses or at the point of junction of two or more nerves with each other or with branches of the cerebro-spinal system. On section they are seen to consist of a reddish-gray substance, traversed by numerous white nerve-fibres; they vary considerably in form and size; the largest are found in the cavity of the abdomen; the smallest, not visible to the naked eye, exist in considerable numbers upon the nerves distributed to the different viscera. The ganglia are invested by a smooth and firm, closely-adhering, membranous envelope, consisting of dense areolar tissue; this sheath is continuous with the peri- neurium of the nerves, and sends nu- m<rous processes into the interior of the ganglion, which support the blood- vessels supplying its substance. In structure all ganglia are essen- tially similar (Fig. 56), consisting of the same structural elements as the other nervous centres-viz. a collection of vesicular nervous matter traversed by tubular and gelatinous nerve-fibred. The vesicular Fig. 56.-Section through a microscopic ganglion. Magnified 300 diameters. (Klein and Noble Smith.) c. Capsule of the ganglion, n. Nerve-fibres passing out of the ganglion. The nerve-fibres which entered the ganglion are not represented. The nerve-fibres are ordinary medullatea fibres, but the details of their structure are not shown, owing to the low magnifying power. The ganglion-cells are invested by a special capsule, lined by a few nuclei, which are here repre- sented as if contained in the capsule. 80 GENERA L A AL4 TOAfY. nervous matter consists of nerve- or ganglion-cells, most of which appear to be free and of a round or oval form; these are more especially seated near the sur- face of the ganglion; others are unipolar, bipolar, or multipolar, and their caudate processes give origin to nerve-fibres. In the ganglion the nerve-cells are usually enclosed in a transparent capsule with nuclei on its inner surface. The nerve- fibres on entering the ganglion lay aside their perineurium, which becomes con- tinuous with the capsule. Some of the fibres run through the ganglion without being connected with the cells ; others arise from the caudate processes of the cells. A remarkable modification of the bipolar nerve-cell is found in the sympa- thetic ganglia, especially in the frog, but also in some few instances in the mam- mal. The cells are pear-shaped, and from the narrow end two processes arise: one, a straight axis-cylinder process, into which the substance of the ganglion is prolonged; the other, a thin fibre, winds spirally round the straight fibre, and then passes away from the cell in the opposite direction, and becomes invested with a medullary sheath and neurilemma of its own, and constitutes a medullated fibre, while the straight axis-cylinder process forms a non-medullated fibre. THE VASCULAR SYSTEM. The Vascular System, exclusive of its central organ, the heart, is divided into four classes of vessels: the arteries, capillaries, veins, and lymphatics; the minute structure of which we will now proceed briefly to describe, referring the reader to the body of the work for all that is necessary in the details of their ordinary anatomy. Structure of Arteries (Fig. 57).-The arteries are composed of three coats: inter- nal or endothelial coat (tunica intima of Kblliker); middle muscular coat (tunica media); and external cellular coat (tunica adventitia). The two inner coats together are very easily separated from the external, as by the ordinary operation of tying a ligature on an artery. If a fine string be tied for- cibly upon an artery and then taken off. the external coat will be found undivided, but the internal coats are divided in the track of the ligature and can easily be fur- ther dissected from the outer coat. The inner coat can be separated from the middle by a little maceration, or it may be stripped off in small pieces; but, on account of its friability, it cannot be separated as a com- plete membrane. It is a fine, transparent, colorless structure which is highly elastic, and is commonly corrugated into longitudi- nal wrinkles. The inner coat consists of- 1. A layer of pavement-epithelium, the cells of which are polygonal, oval, or fusiform, and have very distinct round or oval nuclei. This endothelium, as it is now' generally called, is brought into view most distinctly by staining with nitrate of silver. 2. A subepithelial layer, consisting of delicate connective tissue with branched cells lying in the interspaces of the tissue. 3. An elastic or fenestrated layer, which con- sists of an elastic membrane containing a network of elastic fibres, having prin- Fig. 57.-Transverse section through a small artery and vein of the mucous membrane of the epiglottis of a child. Magnified about 350 diame- ters. (Klein and Noble Smith.) a. Arterv, show- ing the nucleated endothelium, e, which lines it: the vessel being contracted, the endothelial cells appear very thick. Underneath the endothelium is the wavy elastic intima. The chief part of the wall of the vessel is occupied by the circular mus- cle-coat m: the staff-shaped nuclei of the muscle- cells are well seen. Outside this is a, part of the adventitia. This is composed of bundles of con- nective-tissue fibres, shown in section, with the nuclei of the connective-tissue corpuscles. The adventitia gradually merges into the sur- rounding connective tissue, v. Vein showing a thin endothelial membrane, e, raised acciden- tally from the intima, which on account of its delicacy is seen as a mere line on the media m. This latter is composed of a few circular un- striped muscle-cells, a. The adventitia, simi- lar in structure to that of an artery. THE VASCULAR SYSTEM. 81 cipally a longitudinal direction and in which, under the microscope, small, elon- gated apertures or perforations may be seen, giving it a fenestrated appearance. It was therefore called by Henle the fenestrated membrane. This membrane forms the chief thickness of the inner coat, and can be separated into several layers, some of which present the appearance of a network of longitudinal elastic fibres, and others present a more membranous character, marked by pale lines having a longitudinal direction. In arteries of less than a line in diameter the subepithelial layer consists of a single layer of stellate cells, and the connective tissue is only largely developed in the large-sized vessels. The fenestrated mem- brane in microscopic arteries is a very thin layer, but in the larger arteries, and especially in the aorta, it has a very considerable thickness. The middle coat (tumca media) is distinguished from the inner by its color and by the transverse arrangement of its fibres, in contradistinction to the longi- tudinal direction of those of the inner coat. It consists of two varieties of struc- ture, yellow elastic tissue and muscular tissue, which are present in varying quan- tities in different vessels, according to their size, the former tissue preponderating in the larger vessels and the latter in the smaller ones. In the largest arteries this coat is of great thickness, of a yellow color, and highly elastic; it diminishes in thickness and becomes redder in color as the arteries become smaller, and finally becomes very thin and disappears. In small arteries this coat is purely muscular, consisting of muscle fibre-cells (Fig- 44) united to form lamellae which vary in number according to the size of the artery; the very small arteries having only a single layer, and those not larger than one-tenth of a line in diameter three or four layers. In arteries of medium size (Fig. 58) this coat becomes thicker in proportion to the size of the vessel; its layers of muscular tissue are more numerous and inter- mixed with numerous fine elastic fibres which unite to form broad-meshed networks. In the larger vessels, as the femoral, superior mesenteric, coeliac axis, external iliac, brachial and popliteal arte- ries, the elastic fibres unite to form lamellae, which alter- nate with the layers of mus- cular fibre. In the largest arteries the muscular tissue is only slightly developed and forms about one-third or one- fourth of the whole substance of the middle coat; this is especially the case in the aorta and trunk of the pul- monary artery, in which the individual cells of the mus- cular layer are imperfectly formed, while in the carotid, axillary, iliac, and sub- clavian arteries the muscular layer of the middle coat is more developed. The lamellae are well marked, may amount to fifty or sixty in number, and alternate regularly with the layers of muscular tissue. They are most distinct and arranged with greatest regularity in the abdominal aorta, innominate artery, and common carotid. In the larger arteries bundles of white connective-tissue fibres have also been found in small quantity in the middle coat. The external coat (tunica adventitia) consists mainly of fine and closely felted bundles of white connective tissue, but also contains elastic fibres in all but the o Fig. 58.-An artery from the mesentery of a child, .062"', and b, vein .067'" in diameter, treated with acetic acid and magnified 350 times, a. Tunica adventitia, with elongated nuclei, p. Nuclei of the contractile fibre-cells of the tunica media, seen partly from the surface, partly apparent in transverse section, y. Nuclei of the en- dothelial cells. 6. Elastic longitudinal fibrous coat. 82 GENERAL ANATOMY. smallest arteries. The elastic tissue is much more abundant next the tunica media, and it is sometimes described as forming here, between the adventitia and media, a special layer, the tunica elastica externa of Henle. This layer is most marked in arteries of medium size. In the largest vessels the external coat is relatively thin; but in small arteries it is as thick or thicker than the middle coat. In the smaller arteries it consists of a single layer of white connective tissue and elastic fibres; while in the smallest arteries, just above the capillaries, the elastic fibres are wanting, and the connective tissue, of which the coat is composed, becomes more homogeneous the nearer it approaches the capillaries, and is gradually reduced to a thin membranous envelope which finally disappears. Some arteries have extremely thin coats in proportion to their size; this is especially the case in those situated in the cavity of the cranium and spinal canal, the difference depending on the greater thinness of the external and middle coats. The arteries, in their distribution throughout the body, are included in a thin fibro-areolar investment, which forms what is called their sheath. In the limbs this is usually formed by a prolongation of the deep fascia; in the upper part of the thigh it consists of a continuation downward of the transversalis and iliac fasciae of the abdomen ; in the neck, of a prolongation of the deep cervical fascia. The included vessel is loosely connected with its sheath by a delicate areolar tissue; and the sheath usually encloses the accompanying veins, and sometimes a nerve. Some arteries, as those in the cranium, are not included in sheaths. All the larger arteries are supplied with blood-vessels like the other organs of the body; they are called the vasa vasorum. These nutrient vessels arise from a branch of the artery or from a neighboring vessel, at some considerable distance from the point at which they are distributed; they ramify in the loose areolar tissue connecting the artery with its sheath, and are distributed to the external coat, but do not, in man, penetrate the other coats; though in some of the larger mammals some few vessels have been traced into the middle coat. Minute veins serve to return the blood from these vessels; they empty themselves into the venae comites in connection with the artery. Lymphatic vessels and lymphatic spaces are also present in the outer coat. Arteries are also supplied with nerves, which are derived chiefly from the sym- pathetic, but partly from the cerebro-spinal system. They form intricate plexuses upon the surfaces of the larger trunks, and run along the smaller branches as single filaments or bundles of filaments, which twist around the vessel and unite with each other in a plexiform manner. The branches derived from these plexuses penetrate the external coat, and are principally distributed to the muscular tissue of the middle coat, and thus regulate, by causing the contraction and relaxation of this tissue, the amount of blood sent to any part. The Capillaries.-The smaller arterial branches (excepting those of the cavern- ous structure of the sexual organs, of the spleen, and in the uterine placenta) terminate in a network of vessels which pervade nearly every tissue of the body. These vessels, from their minute size, are termed capillaries (papillus, a hair). They are interposed between the smallest branches of the arteries and the com- mencing veins, constituting a network, the branches of which maintain the same diameter throughout; the meshes of the network being more uniform in shape and size than those formed by the anastomoses of the small arteries and veins. The diameter of the capillaries varies in the different tissues of the body, their usual size being about of an inch. The smallest are those of the brain and the mucous membranes of the intestines; and the largest those of the skin and the marrow of bone, where they are stated to be as large as yjTo of an inch. The form of the capillary net varies in the different tissues, the meshes being generally rounded or elongated. The rounded form of mesh is most common, and prevails where there is a dense network, as in the lungs, in most glands and mucous membranes, and in the cutis; here the meshes are more or less angular, sometimes nearly quadrangular or polygonal; more frequently irregular. Elongated meshes are observed in the bundles of fibres and tubes composing THE VASCULAR SYSTEM. 83 muscles and nerves, the meshes being usually of a parallelogram form, the long axis of the mesh running parallel with the long axis of the nerve and fibre. Some- times the capillaries have a looped arrangement; a single vessel projecting from the common network and returning after forming one or more loops, as in the papillae of the tongue and skin. The number of the capillaries, and the size of the meshes, determine the degree of vascularity of a part. The closest network and the smallest interspaces are found in the lungs and in the choroid coat of the eye. In these situations the interspaces are smaller than the capillary vessels them- selves. In the kidney, in the conjunctiva, and in the cutis the interspaces are from three to four times as large as the capillaries which form them; and in the brain from eight to ten times as large as the capillaries in their long diameter, and from four to six times as large in their transverse diameter. In the adventitia of arteries the width of the meshes is ten times that of the capillary vessels. As a general rule, the more active the function of the organ, the closer is its capillary net and the larger its supply of blood ; the network being very narrow in all growing parts, in the glands, and in the mucous membranes; wider in bones and ligaments, which are comparatively inactive; and nearly altogether absent in tendons, in which very little organic change occurs after their formation. Structure.-The walls of the capillaries consist of a fine, transparent, endothelial layer, composed of cells joined edge to edge by an interstitial cement-substance, and continuous with the endothelial cells which line the arteries and veins. When stained with nitrate of silver the edges which bound the endothelial cells are brought into view (Fig. 59). These cells are of large size and of an irregular polyg- onal or lanceolate shape, each containing an oval nucleus which may be brought into view by carmine or logwood. Between their edges, at various points of their meeting, roundish dark spots are sometimes seen, which have been described as Fig. 59.-Capillaries from the mesentery of a guinea-pig after treat- ment with solution of nitrate of sil- ver. a. Cells, b. Their nuclei. Fig. 60.-Finest vessels on the arterial side. From the human brain. Magnified 300 times. 1. Smallest artery. 2. Transition vessel. 3. Coarser capillaries. 4. Finer capillaries, a. Structure- less membrane still with some nuclei, representative of the tunica adventitia, b. Nuclei of the muscular fibre-cells, c. nuclei within the small artery, perhaps appertaining to an endothelium, d. Nuclei in the transition vessels. stomata, though they are closed by intercellular substance. They have been believed to be the situation through which the white corpuscles of the blood, when 84 GENERAL ANATOMY. migrating through the blood-vessels, emerge; but this view, though probable, is not universally accepted. In many situations a delicate sheath or envelope of branched nucleated connec- tive-tissue cells is found around the simple capillary tube, particularly in the larger ones; and in other places, especially in the glands, the capillaries are invested with retiform lymphatic tissue; and again, in other situations, as the pia mater of the brain and cord, and in the retina, the capillaries are invested with a sheath composed of a delicate endothelial membrane. In the largest capillaries (which ought, perhaps, to be described rather as the smallest arteries) there is, outside the endothelial layer, a muscular layer, consisting of contractile fibre-cells, arranged transversely, as in the tunica media of the larger arteries (Fig. 60). The veins, like the arteries, are composed of three coats-internal, middle, and external; and these coats are, with the necessary modifications, analogous to the coats of the arteries; the internal being the endothelial, the middle the muscular, and the external the connective or areolar. The main difference between the veins and the arteries is the comparative weakness of the middle coat of the former, and to this it is due that the veins do not stand open when divided, as the arteries do, and that they are passive rather than active organs of the circulation. In the veins immediately above the capillaries the three coats are hardly to be distinguished. The endothelium is supported on an outer membrane separable into two layers, the outer of which is the thicker, and consists of a delicate, nucleated membrane (adventitia), while the inner is composed of a network of longitudinal elastic fibres (media). In the veins next above these in size (one-fifth of a line, according to Kblliker) a muscular layer and a layer of circular fibres can be traced, forming the middle coat, while the elastic and connective elements of the outer coat become more distinctly perceptible. In the middle-sized veins the typical structure of these vessels becomes clear. The endothelium is of the same character as in the arteries, but its cells are more oval, less fusiform. It is supported by a connective-tissue layer, consisting of a delicate network of branched cells, and external to this is a layer of longitudinal elastic fibres, but seldom any appearance of a fenestrated membrane. This constitutes the internal coat. The middle coat is composed of a thick layer of connective tissue with elastic fibres, intermixed, in some veins, with a transverse layer of muscular fibres. The white fibrous element is in considerable excess, and the elastic fibres are in much smaller proportion in the veins than in the arteries. The outer coat consists of areolar tissue, as in the arteries, with longitudinal elastic fibres, Tji the largest veins the outer coat is from two to five times thicker than the middle coat, and contains a large number of longitudinal muscular fibres. This is most distinct in the inferior vena cava, and at the termination of this vein in the heart, in the trunks of the hepatic veins, in all the large trunks of the vena portae, in the splenic, superior mesenteric, external iliac, renal, and azygos veins. In the renal and portal veins it extends through the whole thickness of the outer coat, but in the other veins mentioned a layer of connective and elastic tissue is found external to the muscular fibres. All the large veins which open into the heart are covered for a short distance with a layer of striped muscular tissue continued on to them from the heart. Muscular tissue is wanting in the veins-(1) of the maternal part of the placenta; (2) in the venous sinuses of the dura mater and the veins of the pia mater of the brain and spinal cord; (3) in the veins of the retina; (4) in the veins of the cancellous tissue of bones ; (5) in the venous spaces of the corpora cavernosa. The veins of the above- mentioned parts consist of an internal endothelial lining supported on one or more layers of areolar tissue. The internal and external jugular veins and the subclavian vein are said to contain either no muscular fibres at all, or at all events only a slight amount in their middle coat. Most veins are provided with valves, which serve to prevent the reflux of the blood. They are formed by a reduplication of the inner coat, strengthened by THE VASCULAR SYSTEM. 85 connective tissue and elastic fibres, and are covered on both surfaces with endo- thelium, the arrangement of which differs on the two surfaces. On the surface of the valve next the wall of the vein the cells are arranged transversely; whilst on the other surface, over which the current of blood flows, the cells are arranged vertically in the direction of the current. Their form is semilunar. They are attached by their convex edge to the wall of the vein; the concave margin is free, directed in the course of the venous current, and lies in close apposition with the wall of the vein as long as the current of blood takes its natural course; if, how- ever, any regurgitation takes place, the valves become distended, their opposed edges are brought into contact, and the current is intercepted. Most commonly two such valves are found placed opposite one another, more especially in the smaller veins or in the larger trunks at the point where they are joined by smaller branches; occasionally there are three and sometimes only one. The wall of the vein on the cardiac side of the point of attachment of each segment of the valve is expanded into a pouch or sinus, which gives to the vessel, when injected or dis- tended with blood, a knotted appearance. The valves are very numerous in the veins of the extremities, especially of the lower extremities, these vessels having to conduct the blood against the force of gravity. They are absent in the very small veins-i. e. those less than of an inch in diameter; also in the venae cavae, the hepatic veins, portal vein and its branches, the renal, uterine, and ovarian veins. A few valves are found in the spermatic veins, and one also at their point of junction with the renal vein and inferior vena cava in both sexes. The cerebral and spinal veins, the veins of the cancellated tissue of bone, the pulmonary veins, and the umbilical vein and its branches, are also destitute of valves. They are occasionally found, few in number, in the venae azvgos and intercostal veins. The veins are supplied with nutrient vessels, vasa vasorum, like the arteries. Nerves also are distrib- uted to them in the same manner as to the arteries, but in much less abundance. The lymphatic vessels, including in this term the lacteal vessels, which are identical in structure with them, are composed of three coats. The internal is an endothelial and elastic coat. It is thin, trans- parent, slightly elastic, and ruptures sooner than the other coats. It is composed of a layer of elongated epithelial cells with serrated margins, by which the adjacent cells are dovetailed into one another. These are supported on a single layer of longitudinal elastic fibres. The middle coat is composed of smooth mus- cular and fine elastic fibres, disposed in a transverse direction. The external, or fibro-areolar, coat con- sists of filaments of connective tissue, intermixed with Fig. 62.-1. Endothelium from the under surface of the centrum tendineum of the rabbit, a. Stomata. 2. Endo- thelium of the mediastinum of the dog. a. Stomata. 3. Section through the pleura of the same animal, b. Free orifices of short lateral passages of the lymph-canals. (Copied from Ludwig, Schweigger-Seyael, and Dyb- kowsky.) Fig. 61.-Transverse section through the coats of the thoracic duct of man. Magnified 30 times, a. Endothelium, striated lamellse, and inner elastic coat. b. Longitudinal connective tissue of the middle coat. c. Transverse muscles of the same. d. Tunica adven- titia, with e, the longitudinal muscular fibres. smooth muscular fibres, longitudinally or obliquely disposed. It forms a protective covering to the other coats, and serves to connect the vessel with the neighboring structures. The above description applies only to the larges lymphatics; in the 86 GENERAL ANATOMY. smaller vessels there is no muscular or elastic coat, and their structure consists only of a connective-tissue coat, lined by endothelium. The thoracic duct (Fig. 61) is a somewhat more complex structure than the other lymphatics; it presents a distinct subepithelial layer of branched corpuscles, similar to that found in the arteries, and in the middle coat is a layer of connective tissue with its fibres arranged longitudinally. The lymphatics are supplied by nutrient vessels, which are distributed to their outer and middle coats; but no nerves have at present been traced into them. The lymphatics are very generally provided with valves, which assist mate- rially in effecting the circulation of the fluid they contain. These valves are formed of a thin layer of fibrous tissue, lined on both surfaces by endothelium. Their form is semilunar; they are attached by their convex edge to the sides of the vessel, the concave edge being free and directed along the course of the con- tained current. Usually two such valves, of equal size, are found opposite one another; but occasionally exceptions occur, especially at or near the anastomoses of lymphatic vessels. Thus, one valve may be of very rudimentary size and the other increased in proportion. The valves in the lymphatic vessels are placed at much shorter intervals than in the veins. They are most numerous near the lymphatic glands, and they are found more frequently in the lymphatics of the neck and upper extremity than in the lower. The wall of the lymphatics immediately above the point of attach- ment of each segment of a valve is expanded into a pouch or sinus, which gives to these vessels, when distended, the knotted or beaded appearance which they present. Valves are wanting in the vessels composing the plexiform network in which the lymphatics usually originate on the surface of the body. Origin of Lymphatics.-The finest visible lymphatic vessels (lymphatic capil- laries) form a plexiform network in the tissues and organs, and they consist of a single layer of endothelial plates, with more or less sinuous margins. These ves- sels commence in an intercommunicating system of clefts or spaces in the connec- tive tissue of the different organs, which have no complete endothelial lining. They have been named the rootlets of the lymphatics, and are identical with the spaces in which the connective-tissue corpuscles are contained. This then is properly regarded as one method of their commencement, when the lymphatic vessels are apparently continuous with spaces in the connective tissue, and Klein has described and figured a direct communication between these spaces and the lymphatic vessel.1 But the lymphatics have also other modes of origin, for the intestinal lacteals commence by closed extremities, though some observers believe that the closed extremity is continuous with a minute network contained in the substance of the villus, through which the lacteal is connected with the epithelial cells covering it. Again, it seems now to be conclusively proved that the serous membranes present stomata or openings between the epithelial cells (Fig. 62) by which there is an open communication with the lymphatic system, and through which the lymph is thought to be pumped by the ultimate dilatation and contraction of the serous surface, due to the movements of respiration and circulation,2 so that the serous and synovial sacs may be regarded, in a certain sense, as large lymph-cavities or sinuses. Von Recklinghausen was the first to observe the passage of milk and other colored fluids through these stomata on the peritoneal surface of the central tendon of the diaphragm. Again, in most glandular structures the lymphatic capillaries have a lacunar origin. Here they begin in irregular clefts or spaces in the tissue of the part; occupying the penetrating connective tissue and surrounding the lacunae or tubules of the gland, and in many places separating the capillary network from the alveolus or tubule, so that the interchange between the blood and the secreting cells of the part must be carried on through this lymph- 1 Atlas of Histology, pl. viii. fig. xiv. 2 The resemblance between lymph and serum led Hewson long ago to regard the serous cavities as sacs into which the lymphatics open. Recent microscopic discoveries confirm this opinion in a very interesting manner. THE VASCULAR SYSTEM. 87 space or lacuna. Closely allied to this is the mode of origin of lymphatics in perivascular and perineural spaces. Sometimes a minute artery may be seen to be ensheathed for a certain distance by a lymphatic capillary vessel, which is often many times wider than a blood-capillary. These are known as perivascular lymphatics. Terminations of Lymphatics.-The lymphatics, including the lacteals, discharge their contents into the veins at two points ; namely, at the angles of junction of the subclavian and internal jugular veins: on the left side by means of the thoracic duct, and on the right side by the right lymphatic duct. (See description of lymphatics on a subsequent page.) Lymphatic glands {conglobate glands} are small oval or bean-shaped bodies, situated in the course of lymphatic and lacteal vessels, so that the lymph and chyle pass through them on their way to the blood. They generally present on one side a slight depression-the Az'Zu/n-through which the blood-vessels enter and leave the interior. The efferent lymphatic vessel also emerges from the gland at this spot, while the afferent vessels enter the organ at different parts of the periphery. On section (Fig. 63), a lymphatic gland displays two different struc- tures: an external, of lighter color-the cortical; and an internal, darker-the medullary. The cortical structure does not form a complete investment, but is deficient at the hilum, where the medullary portion reaches the surface of the gland; so that the efferent vessel is derived directly from the medullary structure, while the afferent vessels empty themselves into the cortical substance. Lymphatic glands consist of (1) a fibrous envelope, or capsule, from which a framework of processes {trabeculcv} proceed inward, dividing the gland into open spaces {alveoli} freely communicating with each other; (2) a quantity of adenoid tissue occupying these spaces without completely filling them; (3) a free supply of blood-vessels, which are supported on the trabeculae; and (4) the afferent and efferent vessels. Little is known of the nerves, though Kblliker describes some fine nervous filaments passing into the hilum. The capsule is composed of a layer of connective tissue, and from its internal surface are given off a number of membranous septa or lamellae, consisting, in man, of connective tissue, with a small admixture of muscular fibre-cells; but in many of the lower animals composed almost entirely of involuntary muscular fibre. They pass inward, radiating toward the centre of the gland, for a certain distance; that is to say, for about one-third or one-fourth of the space between the circum- ference and the centre of the gland. They thus divide the outer part of its interior into a number of oval compart- ments or alveoli (Fig. 63). This is the cortical portion of the gland. After having penetrated into the gland for some distance, these septa break up into a number of smaller trabeculae, which form flattened bands or cords, interlacing with each other in all directions, forming in the central part of the organ a num- ber of intercommunicating spaces, also called alveoli. This is the medullary portion of the gland, and the spaces or alveoli in it not only freely communicate with each other, but also with the alveoli of the cortical portion. In these alveoli or spaces (Fig. 64) is contained the proper gland-substance or lymphoid tissue. The gland-pulp does not, how- ever, completely fill the alveolar spaces, but leaves, between its outer margin and the trabeculae forming the alveoli a channel or space of uniform width through- Fig. 63.-Section of small lymphatic gland, half- diagrammatically given, with the course of the lymph, a. The envelope, b. Septa between the fol- licles or alveoli of thd cortical part. c. System of septa of the medullary portion, down to the hilum, d. The follicles, e. Lymph-tubes of the medullary mass. f. Different lymphatic streams which sur- round the follicles, arid now through the interstices of the medullary portion, g. Confluence of these passing through the efferent vessel, h, at the hilum. 88 GENERAL ANATOMY. out. This is termed the lymph-path or lymph-sinus (Fig. 66). Running across it are a number of trabeculae of retiform connective tissue, the fibres of which are, Fig. 65.-From the medullary substance of an inguinal gland of the ox. (After'His.) a. Lymph- tube, with its complicated system of vessels, b. Retinacula stretched between the tube and the septa, c. Portion of another lymph-tube. d. Septa. Fig. 64.-Follicle from a lymphatic gland of the dog, in vertical section, a. Reticular sustentacular substance of the more external portion, b, of the more internal, and c, of the most external and most finely webbed part on the surface of the follicle, d. Origin of a large lymph-tube. e. Of a smaller one. /. Capsule, g. Septa, a. Vas afferens. i. Investing space of the follicle, with its retinacula, k. One of the divisions of the septa. 1,1. Attachment of the lymph-tubes to the septa. for the most part, covered by ramified cells. This tissue appears to serve the purpose of maintaining the gland-pulp in the centre of the space in its proper position. On account of the peculiar arrangement of the framework of the organ, the gland-pulp in the cortical portion is disposed in the form of nodules, and in the medullary part in the form of rounded cords. It consists of ordinary lymphoid tissue, be- ing made up of a delicate re- ticulum of retiform tissue, which is continuous with that in the lymph-paths, but mark- ed off from it by a closer retic- ulation ; in its meshes are closely packed lymph-corpus- cles, traversed by a dense plexus of capillary blood-ves- sels. The afferent vessels, as above stated, enter at all parts of the periphery of the gland, and after branching and form- ing a dense plexus in the sub- stance of the capsule, open into the lymph-sinuses of the cortical part. In doing this they lose all their coats except their endothelial lining, which is continuous with a layer of similar cells lining the lymph-paths. In like manner the efferent vessel commences from the lymph-sinuses of the medullary portion. The stream of lymph carried to the gland by the afferent vessel thus passes through the plexus in the capsule Fig. 66.-Section of lymphatic gland tissue, a. Trabeculae, b. Small artery in substance of same. c. Lymph-paths, d. Lymph- corpuscles. e. Capillary plexus. THE SKIN AND ITS APPENDAGES. 89 to the lymph-paths of the cortical portion, where it is exposed to the action of the gland-pulp; flowing through these, it enters the paths or sinuses of the medullary portion, and finally emerges from the hilum by means of the efferent vessel. The stream of lymph in its passage through the lymph-sinuses is much retarded by the presence of the reticulum. Hence morphological elements, either normal or morbid, are easily arrested and deposited in the sinuses. This is a matter of con- siderable importance in connection with the subject of poisoned wounds and the absorption of the poison by the lymphatic system, since by this means septic organisms carried along the lymphatic vessels may be arrested in the lymph-sinuses of the gland tissue, and thus be prevented from entering the general circulation. The arteries of the gland enter at the hilum, and either pass at once to the gland- pulp, to break up into a capillary plexus, or else run along the trabeculae, partly to supply them and partly running across the lymph-paths to assist in forming the capillary plexus of the gland-pulp. This plexus traverses the lymphoid tissue, but does not pass into the lymph-sinuses. From it the veins commence, and emerge from the organ at the same place as that at which the artery enters. THE SKIN AND ITS APPENDAGES. The skin (Fig. 67) is the principal seat of the sense of touch, and may be regarded as a covering for the protection of the deeper tissues; it is also an im- portant excretory and absorbing organ. It consists principally of a layer of vascular tissue, named the derma, corium, or cutis vera, and an external covering of epithelium, termed the epidermis or cuticle. On the surface of the former layer Superficial layers Rete Mucosum f Papilla - ( Corium . Epidermis or Cuticle Derma > or Cutis Fat-Cells. i Sub- .cutaneous > Cellular tissue Fibrous tissue - Sebaceous | Glands " ■ Sweat-Glands Nutrient Artery Fig. 67.-A sectional view of the skin (magnified). are the sensitive papillce ; and within, or imbedded beneath it, are certain organs with special functions-namely, the sweat-glands, hair-follicle8,axu\. sebaceous glands. The epidermis or cuticle (scarf-skin, Fig. 68) is an epithelial structure belong- 90 GENERAL ANATOMY. ing to the class of stratified epithelium. It is accurately moulded on the papillary layer of the derma. It forms a defensive covering to the surface of the true skin, Fig. 68.-Microscopic section of skin, showing the epidermis and derma; a hair in its follicle ; the erector pili muscle: sebaceous and sudoriferous glands. and limits the evaporation of watery vapor from its free surface. It varies in thickness in different parts. In some situations, as in the palms of the hands and soles of the feet, it is thick, hard, and horny in texture. This may be partly due to the fact that these parts are exposed to intermittent pressure, but that this is not the only cause is proved by the fact that the condition exists to a very consid- erable extent at birth. The more superficial layer of cells, called the horny layer (stratum corneum), may be separated by maceration from the deeper layers, which are called the rete mucosum, and which consist of several layers of differently shaped cells. The free surface of the epidermis is marked by a network of linear furrows of variable size, marking out the surface into a number of spaces of polyg- onal or lozenge-shaped form. Some of these furrows are large, as opposite the flexures of the joints, and correspond to the folds in the derma produced by their movements. In other situations, as upon the back of the hand, they are exceed- ingly fine, and intersect one another at various angles; upon the palmar surface of the hand and fingers and upon the sole of the foot these lines are very distinct and are disposed in curves. They depend upon the large size and peculiar arrange- ment of the papillae upon which the epidermis is placed. The deep surface of the epidermis is accurately moulded upon the papillary layer of the derma, each papilla being invested by its epidermic sheath ; so that when this layer is removed by maceration, it presents on its under surface a number of pits or depressions corre- sponding to the elevations in the papillae, as well as the ridges left in the intervals between them. Fine tubular prolongations are continued from this layer into the ducts of the sudoriferous and sebaceous glands. In structure, the epidermis consists of several layers of epithelial cells agglu- tinated together and having a laminated arrangement. These several layers may be described as composed of four different strata from within outward: (1) The rete Malpighii, composed of several layers of epithelial cells, of which the deepest layer is elongated in figure and placed perpendicularly on the surface of the corium, their lower ends being denticulate, to fit into corresponding denticula- tions of the true skin; while the succeeding lamime consist of cells of a more rounded or polyhedral form, the contents of which are soft, opaque, granular, and soluble in acetic acid. They are often marked on their surfaces with ridges and furrows, and are covered with numerous fibrils, which connect the surfaces of the cells : these are known as prickle cells (see page 43). (2) Immediately superficial to these is a single layer of flattened, spindle-shaped cells, the granular layer, which contain granules that become deeply stained in haematoxylin. They are THE SKIN AND ITS APPENDAGES. 91 supposed to be cells in a transitional stage between the protoplasmic cells of the rete Malpighii and the horny cells of the superficial layers. (3) Above this layer the cells become indistinct, and appear, in sections, to form a homogeneous or dimly striated membrane, composed of closely packed scales, in which traces of a flattened nucleus may be found. It is called the .stratum lucidum. (4) As these cells successively approach the surface by the development of fresh layers from beneath, they assume a flattened form from the evaporation of their fluid contents, and consist of many layers of horny epithelial scales in which no nucleus is discernible, forming the stratum corneum. These cells apparently become changed in their chemical composition, as they are now unaffected by acetic acid. The deepest layer of the rete Malpighii is separated from the papillae by an apparently homogeneous basement membrane, which is most distinctly brought into view in specimens prepared with chloride of gold. This, according to Klein, is merely the deepest portion of the epithelium, and is " made up of the basis of the individual cells, which have undergone a chemical and morphological altera- tion." The black color of the skin in the negro and the tawny color among some of the white races is due to the presence of pigment in the cells of the cuticle. This pigment is more especially distinct in the cells of the deeper layer or rete mucosum, and is similar to that found in the cells of the pigmentary layer of the retina. As the cells approach the surface and desiccate, the color becomes partially lost. The derma, corium, or cutis vera, is tough, flexible, and highly elastic, in order to defend the parts beneath from violence. It varies in thickness, from a quarter of a line to a line and a half, in differ- ent parts of the body. Thus it is very thick in the palms of the hands and soles of the feet; thicker on the posterior aspect of the body than the front, and on the outer than the inner side of the limbs. In the eyelids, scrotum, and penis it is exceedingly thin and delicate. The skin generally is thicker in the male than in the female, and in the adult than in the child. The corium consists of fibrous connective tissue, with a large admixture of elastic fibres and numerous blood-vessels, lymphatics, and nerves. The fibro- areolar tissue forms the framework of the cutis, and is differently arranged in different parts, so that it is usual to describe it as consisting of two layers: the deeper or reticular layer, and the superficial or papillary layer. Unstriped muscular fibres are found in the superficial layers of the corium, wherever hairs are found; and in the subcutaneous areolar tissue of the scrotum, penis, labia majora of the female, and the nipples. In the latter situation the fibres are arranged in bands, closely reticulated and disposed in superimposed laminae. The reticular layer consists of strong interlacing fibrous bands, composed chiefly of the white variety of fibrous tissue, but containing, also, some fibres of the yellow elastic tissue, which vary in amount in different parts, and connective- tissue corpuscles, which are often to be found flattened against the white fibrous tissue-bundles. Toward the attached surface the fasciculi are large and coarse, and the areolae which are left by their interlacement are large, and occupied by adipose tissue and sweat-glands. Below' this the elements of the skin become gradually blended with the subcutaneous areolar tissue, which, except in a few situations, contains fat. Toward the free surface the fasciculi are much finer, and their mode of interlacing close and intricate. The papillary layer is situated upon the free surface of the reticular layer ; it consists of numerous small, highly sensitive, and vascular eminences, the papillce, which rise perpendicularly from its surface, and form the essential element of the organ of touch. The papillae are conical-shaped eminences, having a round or blunted extremity, occasionally divided into two or more parts and connected by a thin base with the free surface of the corium. Their average length is about yi-jj of an inch, and they measure at their base yly of an inch in diameter. On the general surface of the body, more especially in those parts which are endowed with slight sensibility, they are few in number, minute, and 92 GENERAL ANATOMY. irregularly scattered over the surface; but in some situations, as upon the palmar surface of the hands and fingers, upon the plantar surface of the feet and toes, and around the nipple, they are long, of large size, closely aggregated together, and arranged in parallel curved lines, forming the elevated ridges seen on the free surface of the epidermis. In these ridges the larger papillae are arranged in a double row, with smaller papillae between them; and these rows are subdivided into small square-shaped spaces by short transverse furrows, regularly disposed; in the centre of each of these transverse furrows is the minute orifice of the duct of a sweat-gland. No papillae exist in the grooves between the ridges. In structure the papillae consist of very small and closely interlacing bundles of finely fibrillated tissue, with a. few elastic fibres. The arteries supplying the skin form a network in the subcutaneous tissue, from which branches are given off to supply the sweat-glands, the hair-follicles, and the fat. Other branches are given off which form a plexus immediately beneath the corium; from this fine capillary vessels pass into the papillae, forming, in the smaller papillae, a single capillary loop, but in the larger a more or less convoluted vessel. There are numerous lymphatics supplied to the skin which form two networks, superficial and deep, communicating with each other and with those of the subcutaneous tissue by oblique branches. They originate in the cell- spaces of the tissue. The nerves of the skin terminate partly in the epidermis and partly in the cutis vera. The former form a dense plexus in the superficial layer of the corium, which extends horizontally and gives off numerous fibrils; these are prolonged into the epidermis, and terminate between the cells, either in bulbous extremities or in a network ; or, according to more recent observations, in the deep epithelial cells themselves. The latter terminate in end-bulbs, touch-corpuscles, or Pacinian bodies in the manner already described; and, in addition to these, a considerable number of fibrils are distributed to the hair-follicles, which are said to entwine the follicle in a circular manner. Other nerve-fibres are supplied to the plain muscular tissues of the hair-muscles (arrectores pili) and to the muscular coat of the blood-vessels. These are probably non-medullated fibres. The appendages of the skin are the nails, the hairs, the sudoriferous and sebaceous glands, and their ducts. The nails and hairs are peculiar modifications of the epidermis, consisting essentially of the same cellular structure as that tissue. The nails are flattened, elastic structures of a horny texture, placed upon the dorsal surface of the terminal phalanges of the fingers and toes. Each nail is convex on its outer surface, concave within, and is implanted by a portion, called the root, into a groove in the skin; the exposed portion is called the body, and the anterior extremity the free edge. The nail has a very firm adhesion to the cutis, being accurately moulded upon its surface, as the epidermis is in other parts. The part of the cutis beneath the body and root of the nail is called the matrix, because it is the part from which the nail is produced. Corresponding to the body of the nail, the matrix is thick, and covered with large, highly vascular papillae, arranged in longitudinal rows, the color of which is seen through the transparent tissue. Behind this, near the root of the nail, the papillae are small, less vascular, and have no regular arrangement, and here the tissue of the nail is somewhat more opaque; hence this portion is of a whiter color, and is called the lunula on account of its shape. The cuticle, as it passes forward on the dorsal surface of the finger or toe, is attached to the surface of the nail, a little in advance of its root; at the extremity of the finger it is connected with the under surface of the nail a little behind its free edge. The cuticle and horny substance of the nail (both epidermic structures) are thus directly continuous with each other. The nails, in structure, consist of cells having a laminated arrangement, and these are essentially similar to those composing the epidermis. The deepest layer of cells, which lie in contact with the papillae of the matrix, are of elongated form, arranged perpendicularly to the THE SKIN AND ITS APPENDAGES. 93 surface and provided with nuclei; those which succeed them are of a rounded or polygonal form, the more superficial ones becoming broad, thin, and flattened, and so closely compacted as to make the limits of each cell very indistinct. It is by the successive growth of new cells at the root and under surface of the body of the nail that it advances forward and maintains a due thickness, whilst, at the same time, the growth of the nail in the proper direction is secured. As these cells in their turn become displaced by the growth of new cells, they assume a flattened form, lose their nuclei, and finally become closely compacted together into a firm, dense, horny texture. In chemical composition the nails resemble epidermis. According to Mulder, they contain a somewhat larger proportion of carbon and sulphur. The hairs are peculiar modifications of the epidermis, and consist essentially of the same structure as that membrane. They are found on nearly every part of the surface of the body, excepting the palms of the hands, soles of the feet, and the penis. They vary much in length, thickness, and color in different parts of the body and in different races of mankind. In some parts, as in the skin of the eyelids, they are so short as not to project beyond the follicles containing them ; in other parts, as upon the scalp, they are of considerable length : again, in other parts, as the eyelashes, the hairs of the pubic region, and the male whiskers and beard, they are remarkable for their thickness. The hairs generally present a cylindrical or more or less flattened form and a reniform outline upon transverse section. A hair consists of a root, the part implanted in the skin ; the shaft or stem, the portion projecting from its surface; and the point. The root of the hair presents at its extremity a bulbous enlargement, which is whiter in color and softer in texture than the shaft, and is lodged in a follicular involution of the epidermis called the hair-follicle. When the hair is of consider- able length the follicle extends into the subcutaneous cellular tissue. The hair- follicle commences on the surface of the skin with a funnel-shaped opening, and passes inward in an oblique direction to become dilated at its deep extremity, to correspond with the bulbous condition of the hair which it contains. It has opening into it, near its free ex- tremity, the orifices of the ducts of one or more seba- ceous glands (Fig. 68). At the bottom of each hair- follicle is a small conical vascular, eminence or papilla, similar in every respect to those found upon the sur- face of the skin ; it is continuous with the dermic layer of the follicle, is highly vascular and probably supplied with nervous fibrils; this is the part through which material is supplied for the production and constant growth of the hair. In structure the hair-follicle con- sists of two coats-an outer or dermic, and an inner or epidermic. The outer or dermic coat is formed mainly of fibrous tissue; it is continuous with the corium, is highly vascular, and supplied by numerous minute nervous filaments. It consists of three layers (Fig. 69). The most internal, next the cuticular lining of the follicle, consists of a hyaline basement-membrane, having a glassy, transparent appearance, which is well marked in the larger hair-follicles, but is not very distinct in the follicles of minute hairs. It is continuous with the basement-membrane of the surface of the corium. External to this is a layer of spindle-shaped cells, arranged in a circular manner around the follicle, but reaching only as high as the entrance of the ducts of the sebaceous glands. This is usually regarded as a muscular layer, the cells resembling unstriped muscle- Fig. 69.-Transverse section of hair-follicle. 1. Dermic coat of follicle. 2. Epidermic coat or root-sheath, a. Du ter layer of dermic coat, with blood-vessels. b,b. Vessels cut across, c. Middle layer, d. Inner or hyaline layer. e. Outer root-sheath, f, g. Inner root-sheath, h. Cuticle of root- sheath. i. Hair. (From Quain's Anatomy, Biesiadecki.) 94 GENERAL ANATOMY. cells. Externally is a thick layer of connective tissue, arranged in longitudinal bundles, in which are contained the blood-vessels and nerves. The inner or epidermic layer is closely adherent to the root of the hair, so that when the hair is plucked from its follicle this layer most commonly adheres to it and forms what is called the root-sheath. It consists of two strata, named respectively the outer and inner root-sheath ; the former of these corresponds with the Malpighian layer of the epidermis, and resembles it in the rounded form and soft character of its cells ; at the bottom of the hair-follicle these cells become con- tinuous with those of the root of the hair. The inner root-sheath consists of a delicate cuticle next the hair; then of one or two layers of horny, flattened, nucleated cells, known as Huxley's layer; and finally of a single layer of non- nucleated, horny, cubical cells, called Henle's layer. The hair-follicle contains the root of the hair, which terminates in a bulbous extremity, and is excavated so as to exactly fit the papilla from which it grows. The bulb is composed of polyhedral epithelial cells, which as they pass upward into the root of the hair become elongated and spindle-shaped, except some in the centre which remain polyhedral. Some of these latter cells contain pigment- granules, which give rise to the color of the hair. It occasionally happens that these pigment-granules completely fill the cells in the centre of the bulb, which gives rise to the dark tract of pigment often found, of greater or less length, in the axis of the hair. The shaft of the hair consists of a central pith or medulla, the fibrous part of the hair, and the cortex externally. The medulla occupies the centre of the shaft and ceases toward the point of the hair. It is usually wanting in the fine hairs covering the surface of the body, and commonly in those of the head. It is more opaque and deeper colored when viewed by transmitted light than the fibrous part; but when viewed by reflected light it is white. It is composed of rows of poly- hedral cells, which contain air-bubbles. The fibrous portion of the hair consti- tutes the chief part of the shaft; its cells are elongated and unite to form flattened fusiform fibres. Between the fibres are found minute spaces which contain either pigment-granules in dark hair or minute air-bubbles in white hair. In addition to this there is also a diffused pigment contained in the fibres. The cells which form the cortex of the hair consist of a single layer which surrounds those of the fibrous part; they are converted into thin, flat scales, having an imbricated arrangement. Connected with the hair-follicles are minute bundles of involuntary muscular fibres, termed arrectores pili. They arise from the superficial layer of the corium, and are inserted into the outer surface of the hair-follicle, below the entrance of the duct of the sebaceous gland. They are placed on the side toward which the hair slopes, and by their action elevate the hair (Fig. 68). The sebaceous glands are small, sacculated, glandular organs, lodged in the substance of the corium. They are found in most parts of the skin, but are most abundant in the scalp and face: they are also very numerous around the apertures of the anus, nose, mouth, and external ear; but are wanting in the palms of the hands and soles of the feet. Each gland consists of a single duct, more or less capacious, which terminates in a cluster of small secreting pouches or saccules. The sacculi connected with each duct vary, as a rule, in numbers from two to five, but, in some instances, may be as many as twenty. They are composed of a transparent, colorless membrane, enclosing a number of cells. Of these the outer layer or marginal cells are small, polyhedral, epithelial cells, continuous with the lining cells of the duct. The remainder of the sac is filled with larger cells, con- taining fat, except in the centre, where the cells have become broken up, leaving a cavity containing the debris of cells and a mass of fatty matter, which consti- tutes the sebaceous secretion. The orifices of the ducts open most frequently into the hair-follicles, but occasionally upon the general surface. On the nose and face the glands are of large size, distinctly lobulated, and often become much enlarged THE SKIN AND ITS APPENDAGES. 95 from the accumulation of pent-up secretion. The largest sebaceous glands are those found in the eyelids-the Meibomian glands. The sudoriferous or sweat glands are the organs by which a large portion of the aqueous and gaseous materials are excreted by the skin. They are found in almost every part of this structure, and are situated in small pits in the deep parts of the corium, or, more frequently, in the subcutaneous areolar tissue, surrounded by a quantity of adipose tissue. They are small, lobular, reddish bodies, consist- ing of a single convoluted tube, from which the afferent duct proceeds upward through the corium and cuticle, becomes somewhat dilated at its extremity, and opens on the surface of the cuticle by an oblique valve-like aperture. The efferent duct, as it passes through the epidermis, presents a spiral arrangement, being twisted like a corkscrew, in those parts where the epidermis is thick ; where, how- ever, it is thin, the spiral arrangement does not exist. In the superficial layers of the corium the duct is straight, but in the deeper layers it is convoluted or even twisted. The spiral course of these ducts is especially distinct in the thick cuticle of the palm of the hand and sole of the foot. The size of the glands varies. They are especially large in those regions where the amount of perspiration is great, as in the axillae, where they form a thin, mammillated layer of a reddish color, which corresponds exactly to the situation of the hair in this region; they are large also in the groin. Their number varies. They are most numerous on the palm of the hand, presenting, according to Krause, 2800 orifices on a square inch of the integument, and are rather less numerous on the sole of the foot. In both of these situations the orifices of the ducts are exceedingly regular, and cor- respond to the small transverse grooves which intersect the ridges of the papillae. In other situations they are more irregularly scattered, but in nearly equal num- bers, over parts including the same extent of surface. In the neck and back they are least numerous, their number amounting to 417 on the square inch (Krause). Their total number is estimated by the same writer at 2,381.248, and, supposing the aperture of each gland to represent a surface of Jg- of a line in diameter, he calculates that the whole of these glands would present an evaporating surface of about eight square inches. Each gland consists of a single tube intricately con- voluted, terminating at one end by a blind extremity, and opening at the other end upon the surface of the skin. In the larger glands this single duct usually divides and subdivides dichotomously ; the smaller ducts ultimately terminating in short csecal pouches, rarely anastomosing. The wall of the duct is thick, the width of the canal rarely exceeding one-third of its diameter. The tube, both in the gland and where it forms the excre- tory duct, consists of two layers-an outer, formed by fine areolar tissue, and an inner layer of epithelium. The external or fibro-cellular coat is thin, continuous with the superficial layer of the corium, and extends only as high as the surface of the true skin. The epithelial lining in the distal part of the coiled tube of the gland proper consists of a single layer of cubical epithelium, supported on a basement membrane, and beneath it, between the epithelium and the fibro-cellular coat, a layer of plain muscular fibres, arranged longitudinally. In the duct and the proximal part of the coiled tube of the gland proper there are two or more layers of polyhedral cells, lined on their internal surface-i. e. next the lumen of the tube-by a delicate membrane or cuticle, and on their outer sur- face by a limiting membrana propria, but there are do muscular fibres. The Fig. 70.-Coiled tube of a sweat-gland cut in vari- ous directions. a. Longitudinal section of the proxi- mal part of the coiled tube. b. Transverse section of the same. c. Longitudinal section of the distal part of the coiled tube. d. Transverse section of the same. (From Klein and Noble Smith's Atlas of Histology.) 96 GENERAL ANATOMY. epithelium is continuous with the epidermis and with the delicate internal cuticle which is all that is present in the epidermic portion of the tube. When the cuticle is carefully removed from the surface of the cutis, these convoluted tubes of epithelium may be drawn out and form short, thread-like processes on its under surface. The contents of the smaller sweat-glands are quite fluid; but in the larger glands the contents are semi-fluid and opaque, and contain a number of colored granules and cells which appear analogous to epithelial cells. The serous membranes form shut sacs and may he regarded as lymph-sacs, from which lymphatic vessels arise by stomata or openings between the epithelial cells (see page 86). The sac consists of one portion which is applied to the walls of the cavity which it lines-the parietal portion ; and another reflected over the surface of the organ or organs contained in the cavity-the visceral portion. Sometimes the sac is arranged quite simply, as the tunica vaginalis testis ; at others with numerous involutions or recesses, as the peritoneum, in which, nevertheless, the membrane can always be traced continuously around the whole circumference. The sac is completely closed, so that no communication exists between the serous cavity and the parts in its neighborhood. An apparent exception exists in the peritoneum of the female; for the Fallopian tube opens freely into the peritoneal cavity in the dead subject, so that a bristle can be passed from the one into the other. But this communication is closed during life, except at the moment of the passage of the ovum out of the ovary into the tube, as is proved by the fact that no inter- change of fluids ever takes place between the two cavities in dropsy of the perito- neum or in accumulation of fluid in the Fallopian tubes.1 The serous membrane is often supported by a firm, fibrous layer, as is the case with the pericardium, and such membranes are sometimes spoken of as " fibro-serous." The various serous membranes are the peritoneum, lining the cavity of the abdomen; the two pleurae and the pericardium, lining the lungs and heart respec- tively ; and the tunicae vaginales, surrounding each testicle in the scrotum.2 Serous membranes are thin, transparent, glistening structures, lined on their inner surface by a single layer of polygonal or pavement endothelial cells, supported on a matrix of fibrous connective tissue, with networks of fine elastic fibres, in which is contained numerous capillaries and lymphatics. On the surface of the endothelium between the cells numerous apertures or interruptions are to be seen. Some of these are stomata, surrounded by a ring of cubical epithelium (see Fig. 12), and communicate with a lymphatic capillary (see p. 86); others (pseudosto- matd) are mere interruptions in the epithelial layer, and are occupied by pro- cesses of the branched connective-tissue corpuscle of the subjacent tissue or by accumulations of the intercellular cement-substance. The secretion of these membranes is, in most cases, only sufficient in quantity to moisten the surface, but not to furnish any appreciable quantity of fluid. When a small quantity can be collected, it appears to resemble in many respects the lymph, and like that fluid coagulates spontaneously ; but when secreted in large quantities, as in dropsy, it is a watery fluid, which gives a precipitate of albumen on boiling. SEROUS MEMBRANES. SYNOVIAL MEMBRANES. Synovial membranes, like serous membranes, are connective-tissue membranes placed between two movable tissues, so as to diminish friction, as between the two articular ends of the bones forming a movable joint; between a tendon and a 1 The communication between the uterine cavity and the peritoneal sac is not only apparent in the dead subject, but is an anatomical fact, which is established by the continuity of its epithelium with that covering the uterus, Fallopian tubes, and fimbriae. 2 The arachnoid membrane, lining the brain and spinal cord was formerly regarded as a serous membrane, but is now no longer classed with them, as it differs from them in structure, and does not form a shut sac as do the other serous membranes. MUCO US JfEMB RA NE. 97 bone, where the former glides over the latter; and between the skin and various subcutaneous bony prominences. The synovial membranes are composed essentially of connective tissue, with the cells and fibres of that structure, containing numerous vessels and nerves. It was formerly supposed that these membranes were analogous in structure to the serous membranes, and consisted of a layer of flattened cells on a basement-mem- brane. No such cells, however, exist, and the only ones found on the surface are irregularly branched connective-tissue corpuscles, similar to those found through- out the tissue. Here and there these cells are collected in patches and present the appearance of epithelium, but do not possess the true characters of an endo- thelial layer. They are surrounded and held together by an albuminous ground- substance. A further description of the synovial membranes will be found in the descriptive anatomy of the joints. MUCOUS MEMBRANE. Mucous membranes line all those passages by which the internal parts com- municate with the exterior, and are continuous with the skin at the various orifices of the surface of the body. They are soft and velvety, and very vascular, and their surface is coated over by their secretion, mucus, which is of a tenacious con- sistence, and serves to protect them from the foreign substances introduced into the body with which they are brought in contact. They are described as lining the two tracts-the gastro-pulmonary and the genito-urinary; and all, or almost all, mucous membranes may be classed as belonging to and continuous with the one or the other of these tracts. The external surfaces of these membranes are attached to the parts which they line by means of connective tissue, which is sometimes very abundant, forming a loose and lax bed, so as to allow considerable movement of the opposed surfaces on each other. It is then termed the submucous tissue. At other times it is exceedingly scanty, and the membrane is closely connected to the tissue beneath; sometimes, for example, to muscle, as in the tongue; sometimes to cartilage, as in the larynx; and sometimes to bone, as in the nasal fossae and sinuses of the skull. In structure a mucous membrane is composed of corium and epithelium. The epithelium is of various forms, including the squamous, columnar, and ciliated, and is often arranged in several layers (see Fig. 11). This epithelial layer is supported by the corium, which is analogous to the derma of the skin, and con- sists of connective tissue, either simply areolar or containing a greater or less quantity of lymphoid tissue. This tissue is usually covered on its external surface by a transparent structureless basement-membrane, and internally merges into the submucous areolar tissue. It is only in some situations that the basement-mem- brane can be demonstrated. The corium is an exceedingly vascular membrane, containing a dense network of capillaries, which lie immediately beneath the epithelium, and are derived from small arteries in the submucous tissue. The fibro-vascular layer of the corium contains, besides the areolar tissue and vessels, unstriped muscle-cells, which form in many situations a definite layer, called the muscularis mucosce. These are situated in the deepest part of the mem- brane, and are plentifully supplied with nerves. Other nerves pass to the epi- thelium and terminate between the cells. Lymphatic vessels are found in great abundance, commencing either by caecal extremities or in networks, and com- municating with plexuses in the submucous tissue. Imbedded in the mucous membrane are found numerous glands, and project- ing from it are processes (villi and papillae) analogous to the papillae of the skin. These glands and processes, however, exist only at certain parts, and it will be more convenient to defer their description to the sequel, where the parts are described as they occur. 98 GENERAL ANATOMY. The secreting glands are organs in which the blood, circulating in capillary vessels, is brought into contact with epithelial cells, whereby certain elements are separated ("secreted") out of the blood. The essential parts therefore of a secreting gland are cells, which have the power of extracting from the blood cer- tain matters, and in some cases converting them into new chemical compounds; and blood-vessels, by which the blood is brought into close relationship with these cells. The general arrangement in all secreting structures-that is to say, not only in secreting glands, but also in secreting membranes-is that the cells are arranged on one surface of an extravascular basement-membrane, which supports them, and a minute plexus of capillary vessels ramifies on the other surface of the membrane. The cells then extract from the blood certain constituents which pass through the membrane into the cells, where they are prepared and elaborated. The basement-membrane does not, however, always exist, and any free surface would appear to answer the same purpose in some cases. By the various modifications of this secreting surface the different glands are formed. This is generally effected by an involution of the membrane in different ways, the object being to increase the extent of secreting surface within a given bulk. i In the simplest form a single involution takes place, constituting a simple gland; this may be either in the form of an open tube (Fig. 71, a), or the walls SECRETING GLANDS. Fig. 71.-Diagrammatic plan of varieties of secreting glands, a. Simple gland, b. Sacculated simple gland. C. Simple convoluted tubular gland, d, e. Racemose gland, f. Compound tubular gland. of the tube may be dilated so as to form a saccule (Fig. 71, b). These are named the simple tubular or saccular glands. Or, instead of a short tube, the involution may be lengthened to a considerable extent, and then coiled up to occupy less space. This constitutes the simple convoluted tubular gland, an example of which may be seen in the sweat-glands of the skin (Fig. 71, c). If, instead of a single involution, secondary involutions take place from the SECRETING GLANDS. 99 primary one, as in Fig. 71, d and E, the gland is then termed a compound one. These secondary involutions may assume either a saccular or tubular form, and so constitute the two subdivisions-the compound saccular or racemose gland, and the compound tubular. The racemose gland in its simplest form consists of a primary involution which forms a sort of duct, upon the extremity of which are found a number of secondary involutions, called saccules or alveoli, as in Brunner's glands (Fig. 71, d). But, again, in other instances, the duct, instead of being simple, may divide into branches, and these again into other branches, and so on ; each ultimate ramification terminating in a dilated cluster of saccules, and thus we may have the secreting surface almost indefinitely extended, as in the salivary glands (Fig. 71, e). In the compound tubular glands the division of the primary duct takes place in the same way as in the racemose glands, but the branches retain their tubular form, and do not terminate in saccular recesses, but become greatly length- ened out (Fig. 71, f). The best examples of this form of gland are to be found in the kidney and testicle. All these varieties of glands are produced by a more or less complicated involution of a secreting membrane, and they are all identical in structure; that is to say, the saccules or tubes, as the case may be, are lined with cells, generally spheroidal or columnar in figure, and on their outer surface is an intimate plexus of capillary vessels. The secretion, whatever it may be, is elimi- nated by the cells from the blood, and is poured into the saccule or tube, and so finds it way out through the primary involution on to the free surface of the secreting membrane. In addition, however, to these glands, which are formed by an involution of the secreting membrane, there are some few others which are formed by a protrusion of the same structure, as in the vascular fringes of synovial mem- branes. This form of secreting structure is not nearly so frequently met with. ORIGIN AND DEVELOPMENT OF THE BODY. The whole body is developed out of the ovum (Fig. 72) when fertilized by the spermatozoa. The ovum is merely a simple nucleated cell, or collection of protoplasm, and the spermatozoa disappear when they have accomplished their mysterious function. All the complicated changes by which the various intricate organs of the whole body are formed from one simple cell may be reduced to two general processes-viz. the segmentation or cleavage of cells, and their differentia- tion. The former process consists in the splitting of the nucleus and its investing cell-wall, whereby the original cell is represented by two. Thp differentiation of cells is a term used to describe that unknown power or tendency impressed on cells which, to all methods of examination now known, seem absolutely identical, whereby they grow into different forms; so that (to take the first instance which occurs in the growth of the embryo) the indifferent cells of the vascular area are differentiated, some of them into blood-globules, others into the solid tissue which forms the blood-vessels. The extreme complexity of the process of develop- Fig. 72.-Ovum of the sow. Fig. 73.-Human ovum from a mid- dle-sized follicle. Magnified 350 times. a. Vitelline membrane or zona pellucida. b. External border of the yolk and internal border of the vitelline mem- brane. c. Germinal vesicle and germi- nal spot. ment renders it at all times difficult to describe it intelligibly, and still more so in a work like this, where adequate space and illustration can hardly be afforded, having respect to the main purpose of the work. I can only hope to render the leading features of the pro- cess tolerably plain, and must refer the reader who wishes to follow the various changes more minutely to the special works on the subject, and especially the work of Fostei' and Balfour. Many of the statements which are accepted in human embryology are made only on the strength of experiments on the lower animals, direct observation on the human subject being impossible. The ovum is a small spheroidal body situated in immature Graafian vesicles near their centre, but in the mature ones in contact with the membrana granulosa 1 at that part of the vesicle which projects from the surface of the ovary. The cells of the membrana granulosa are accumulated round the ovum in greater number than at any other part of the vesicle, forming a kind of granular zone, the discus proligerus. The human ovum (Fig. 73) is extremely minute, measuring from toTT<y °f an inch in diameter. It is a cell consisting externally of a transparent envelope, the zona pellucida or vitelline membrane. Within this, and in close contact with it, is the yolk or vitellus; imbedded in the substance of the yolk is a small 100 1 See the description of the ovary at a future page. FERTILIZATION OF OVUM. 101 vesicular body, the germinal vesicle (vesicle of Purkinje), the nucleus of the cell; and this contains as its nucleolus a small spot, the macula germinativa, or germinal spot of Wagner. The zona pellucida, or vitelline membrane, is a thick, colorless, transparent membrane, which appears under the microscope as a radially striated membrane, bounded externally and internally by a dark outline. The striae are believed to be minute pores, and are regarded as the channels by -which nutritive particles are admitted into the interior of the ovum, and possibly the way by which the spermatozoa gain access into the interior of the ovum, after the rupture of the Graafian follicle. The presence of these striae has given to the zona pellucida the name of zona radiata, or striated membrane of the ovum. The zona pellucida corresponds to the chorium of the impregnated ovum. The yolk consists of granular protoplasm-i. e. granules or globules of various sizes, imbedded in a finely reticulated matrix. The smaller granules resemble pigment; the larger granules, which are in the greatest number at the periphery of the yolk, resemble fat-globules. In the human ovum the number of granules is comparatively small. Before and immediately after fertilization it shows dis- tinct movements of contraction and expansion. The germinal vesicle consists of a fine, transparent, structureless membrane containing a clear matrix, in which are occasionally found a few granules. It is about of an inch in diameter, and in immature ova lies nearly in the centre of the yolk; but as the ovum becomes developed it approaches the surface, and enlarges much less rapidly than the yolk. The germinal spot occupies that part of the periphery of the germinal vesicle which is nearest to the periphery of the yolk. It is opaque, of a yellow color, and finely granular in structure, measuring from to of an inch. The phenomena attending the discharge of the ova from the Graafian vesicles, since they belong as much or more to the ordinary function of the ovary than to the general subject of the growth of the body, are described with the anatomy of the ovaries on a subsequent page. Either before its escape from the Graafian follicle or immediately after, the ovum undergoes a peculiar change, which results in the formation of one or more peculiar bodies, the polar globules of Robin, the origin of which has not hitherto been known; and also with the formation of another body, which appears to take a remarkable part in fecundation, and is named the "female pronucleus." The manner in which these bodies are developed from the germinal vesicle is briefly as follows: Usually before the rupture of the Graafian follicle, but after the ovum has become mature or ripe, a portion of the germinal vesicle is protruded outside the yolk, but still remains within the vitelline membrane; this forms a small globular mass and constitutes the first polar globule. After a time, generally not till the ovum has entered the tube, a second protrusion of a portion of the germinal vesicle takes place, and forms a second polar globule. We have thus about two-thirds of the germinal vesicle extruded from the yolk and about one-third remaining behind, and at the ejection of each of these bodies a visible shrinking of the yolk takes place. The portion of the germinal vesicle which remains behind recedes from the surface toward the centre of the yolk and assumes a spherical form, and is now termed the "female pronucleus." All these changes, it must be understood, occur at each expulsion of an ovum, and are quite independent of fecundation. The first changes in the ovum which take place at the time of conception appear to be as follows: One or more spermatozoa penetrate the ovum, and come into contact with the yolk and with the portion of the germinal vesicle remaining in the yolk. It seems as if this normally occurs in the Fallopian tube,1 but it is possible that it sometimes occurs before the ovum has entered the tube, or after it 1 Many physiologists, as Bischoff and Dr. M. Barry, taught that the ovum is fecundated in the ovary, but the reasoning of Dr. Allen Thomson appears very cogent in proving that the usual spot at which the spermatozoa meet the ovum is in the tube, down which it slowly travels to the uterus, in its course becoming surrounded by an albuminous envelope derived from the walls of the tube. 102 DE VEL OEM ENT. has passed through the tube and reached the cavity of the uterus ; abnormally it may even take place in the peritoneal cavity. One spermatozoon, more advanced than the rest, becomes buried in the yolk, the tail disappears, and the head, a sort of nuclear body, constitutes the "male pronucleus." This gradually approaches the female pronucleus, which by this time is situated in the centre of the yolk. As soon as they come into contact they fuse into one, and thus fecundation is effected (Fig. 74). It is believed by some physiologists that one spermatozoon is sufficient for fecundation; but in all probability several spermatozoa, as a rule, Fig. 74.-Fertilization of the ovum of an echinoderm, s. Spermatozoon, m. pr. Male pronucleus, f. pr. Fe- male pronucleus. 1. Accession of a spermatozoon to the periphery of the vitellus. 2. Its penetration. 3. Trans- formation of the head of the spermatozoon into the male pronucleus. 4, 5. Blending of the male and female pronuclei. (From Quain's Anatomy, Selenka.) penetrate the yolk and undergo the same process of conversion into male pronuclei, reach the female pronucleus, and fuse with it.1 The first result of the fertilization of the ovum is a cleavage or multiplication of the yolk, which is first cleft into two masses, the germinal vesicle having pre- viously split up into two nuclei; so that it now consists of two separate masses of protoplasm, each containing a nucleus, situated within the original vitelline membrane, which takes no part in this process of division. Then, each of these two daughter elements divides in like manner, and thus four nucleated elements are formed, and so on, until at length a mulberry-like agglomeration of nucleated masses of protoplasm results (Fig. 75). These masses are sometimes termed vitel- line spheres. The manner in which segmentation occurs is somewhat peculiar. The two spheres resulting from the first cleavage are of unequal size. One, which for the sake of distinction we will call the upper or epiblastic cell, is larger than the other, the lotver or hypoblastic cell. And after they have divided three or four times the rate of cleavage in the spheres derived from the upper or epiblastic segment becomes more rapid than in those derived from the lower or hypo- blastic segment. In addition to this, the spheres derived from the upper segment have a tendency to spread over and enclose those from the lower segment; so that by about the ninth or tenth division there is an external layer of spheres derived from the primary upper or epiblastic segment surrounding and almost enclosing a mass of spheres, which in consequence of their diminished rate of cleavage are fewer in number and larger in size, derived from the primary lower or hypoblastic segment (Fig. 76, a). Fluid collects between the two sets of spheres, except at one part, where they remain in contact, ami the ovum is converted into a sac, formed by a layer of spheres derived from the upper primary segment, and containing at one part another mass of spheres derived from the lower primary segment (Fig. 76, b). The inner cells are rather more granular than the outer, 1 If the student refers to the development of the generative organs, he will find that the ovum of the female and the spermatozoon of the male are derived from fundamentally the same structures, and therefore their fusion is the union of two elements of very similar morphological value. SEGMENTATION OF OVUM. 103 beneath which they gradually spread, becoming applied over a part of their inner surface in a single layer; so that the cavity is afterward enclosed more or less completely in a double layer of cells. Fig. 75.-First stages of segmentation of a mammalian ovum; semi-diagrammatic. (From a drawing by Allen Thomson.) z.p. Zona pellucida. p. gl. Polar globules, ect. Epiblastic cell. ent. Hypoblastic cell. a. Division into two spheres, b. Stage of four spheres, c. Eight spheres, the epiblastic cells partially enclosing the hypo- blastic cells, d, e. Succeeding stages of segmentation, showing the more rapid division of the epiblastic cells and the enclosure of the hypoblastic cells by them. The ultimate destination of the outermost complete layer of spheres is, at present, doubtful. By some they are believed to be transitory and to gradually Fig. 76.-Ovum of the rabbit at the end of the process of segmentation, ep. epiblast, hy. Primitive hypo- blast. bp. Place where the epiblast has not yet grown over the hypoblast. (From Balfour, after Ed. van Beneden.) disappear in the course of the formation of the various layers of the blastodermic membrane; by others it is thought that they form the outer layer (epiblast) of this membrane. Adopting the latter and more general view, the ovum would consist of a cavity surrounded by (1) a layer of cells completely lining the inte- rior of the vitelline membrane, and (2) by a second layer internal to these and partially lining the interior of the outer layer, both sets of cells derived from the segmentation of the yolk. The double layer of cells is called the " blastodermic membrane," the outer laver being termed the " epiblast," and the innen the " hvpo- blast." At first the area of the blastodermic membrane, which consists of both the 104 D EI rEL OPMENT. inner and outer layers of cells, is a small disk, in which the first traces of the embryo are seen ; hence it is called the germinal disk or area germinativa (Fig. 77). The first trace of the embryo appears as a faint streak at the posterior end of the area germinativa, called the primitive trace. After the formation of the primitive trace, but previous to the appearance of the next parts of the embryo, presently to be described-viz. the laminae dorsales and the noto- chord-the blastodermic membrane consists of only two layers, the epiblast and hypoblast, but after the formation of these structures a third layer makes its appearance. This is the meso- blast, and is situated between the other two (Fig. 78). As to the precise origin of this third layer considerable difference of opinion exists. Accord- ing to some embryologists, it is formed entirely by proliferation of cells belonging to the epiblastic layer; according to others, it is formed by a splitting of the hypoblast, or, at all events, a differentiation of it into a central layer of mesoblastic cells and a lower Fig. 77.-Ovum with the germinal area, seen in profile to show the division of the blastodermic membrane. 1. Vitelline membrane. 2. Blastoderm. 3. Germinal area. 4. Place where the blastoderm is just divided into its two layers. Fig. 78.-Section across the anterior part of the medullary groove of an early embryo of the guinea pig. (By Schafer. From Quain's Anatomy, 1890.) ep. Folds of epiblast rising up on either side of the middle line, and thus bounding the medullary groove, m.y. Middle of medullary groove, hy. Hypoblast, which is in contact with the medullary epiblast at the middle of the groove, but is elsewhere separated from it by mesoblast, m, which has burrowed forward between the two primary layers. A cleft is seen in the mesoblast on either side; this is the commencement of the anterior part of the body-cavity, layer of hypoblastic cells. Or, what seems most probable, it is derived mainly from the epiblast, the hypoblast taking a smaller and more subordinate share in its formation. But in whichever way this third stratum may be formed, the blasto- dermic membrane eventually consists of three layers: The external, which used to be called the serous layer, but is now more commonly termed the epiblast, or ectoderm; the internal, the mucous layer, the hypoblast, or entoderm ; and the middle, which is now usually called the mesoblast or mesoderm, but which was for- merly named the "vascular layer." The epiblast is mainly concerned in the formation of the external cuticle and the whole of the nervous system. It consists of cells of an epithelial character; that is to say, cells of an irregular columnar shape, forming, for the most part, a single stratum, but becoming more numerous and flattened at the germinal disk. The epidermis of the body and all the involutions of the epidermis in the ducts of superficial glands, as the mammae, as well as the brain, the spinal cord, the nerves, and the portions of the nose, eye, and ear, which are directly formed from the brain, are developed from it. The external layer of the amnion is also formed from the epiblast, and probably also a portion of the chorion. The hypoblast is mainly concerned in forming the internal epithelium-viz. that of the whole alimentary passages except the mouth and a small portion of the rectum near the anus (which are formed by involutions of the epiblast); that of the respiratory tract, which is originally an offset from the alimentary canal ; and the epithelium of all the glandular organs which open into the intestinal tract. The hypoblast forms also the deeper layer of the umbilical vesicle and allantois. THE BLASTODERM. 105 Its cells are epithelial, and are at first flattened, but subsequently become columnar and larger than those of the epiblast. Fig. 79.*-Diagrams to show the development of the three layers of the blastodermic membrane on transverse section. A. Portion of the ovum with the zona pellucida and the germinal area. BCDEF G. Different stages of development, o. Umbilical vesicle, a. Amnion, i. Intestine, p. Peritoneal cavity, bounded by the splanchno-pleural and somato-pleural layers of mesoblast. 1. Vitelline membrane. 2. External blastodermic layer. 3. Middle layer. 4. Internal layer. 5. Medullary lamime and groove. 5'. Medullary canal. 6. Epi- dermic laminae. 7. Lateral flexures of the amnion. 7'. The same almost in contact. 8. Internal epithelial layer of the amnion. 9. Epidermis of the embryo. 10. Chorda dorsalis. 11. Vertebral lamime. 12. Protover- tebrae proper. 13. Muscular lamina1. 14. Lateral laminae. 15. Fibro-intestinal laminae. 16. Cutaneous laminae. 17. Internal fibrous layer of the umbilical vesicle. 18. Muscular laminae extending to meet the cutaneous. 19. External layer of the cutaneous lamina. 20. Internal layer of the same. 21. Mesentery. 22. Fibrous layer of the intestine. *The dotted lines indicate the parts belonging to the internal blastodermic layer; the plain lines, those belonging to the middle; the interrupted lines, those belonging to the external. The embryo has been repre- sented, in this and the following diagram, lying on its back. The natural position is generally assumed to be the reverse. All the rest of the embryo is formed from the mesoblast-viz. all the vascular 106 DE VEL OPMENT. and locomotive system, the cutis, all the connective tissues, and the genito-urinary organs-with the exception of the epithelium of the bladder and urethra, which is Fig. 80.*-Diagrams to show the development of the three blastodermic layers on antero-posterior section. A. Portion of ovum with the vitelline membrane and germinal area. BCD E F. Various stages of development. G. Ovum in the uterus and formation of decidua. 1. Vitelline membrane. 2. External blastodermic layer. 2'. Vesicula serosa. 3. Middle blastodermic layer. 4. Internal layer. 5. Vestige of the future embryo. 6. Ceph- alic flexure of the amnion. 7. Caudal flexure. 8. Spot where the amnion and vesicula serosa are continuous. 8'. Posterior umbilicus. 9. Cardiac cavity. 10. External fibrous layer of the umbilical vesicle. 11. External fibrous layer of the amnion. 12. Internal layer of the blastoderm forming the intestine. 13, 14. External laver of the allantois, extending to the inner surface of the vesicula serosa. 15. The same, now completely applied to the inner surface of the vesicula serosa. 16. Umbilical cord. 17. Umbilical vessels. 18. Amnion. 19. Chorion. 20. Foetal placenta. 21. Mucous membrane of uterus. 22. Maternal placenta. 23. Decidua reflexa. 24. Mus- cular wall of uterus. *The same note applies to this as to the preceding diagram. developed from the hypoblast. The vascular system of the foetus extends to the yolk and the maternal parts along the umbilical vesicle and allantois, so that the FIRST RUDIMENTS OF THE EMBRYO. 107 greater part of these bodies and the outer layer of the amnion are also formed out of the mesoblast. The foetal portion of the placenta, being essentially a vascular structure, is also developed from the mesoblast. Its cells are irregular and branched and surrounded by a considerable amount of intercellular fluid. It may therefore be regarded as resembling more closely embryonic connective tissue. First Rudiments of the Embryo (Figs. 79 and 80).-The primitive trace alluded to above as appearing in the area germinativa is a very transitory structure, which marks the direction of the embryonic axis, and is gradually lost in consequence of its place becoming occupied by the rudimentary spinal column. The first real approach toward a definite form in the embryo is made (1) by the development of the rudimentary spinal column; (2) by the cleavage of the middle layer of the blastodermic membrane from which a part of that column is derived; and (3) by the incurvation of the column at its cephalic end to form the brain and brain-case. First, a folding up of the cells of the epiblast or outer layer takes place. This commences in the anterior part of the area germinativa, and extends in the same direction as the primitive trace, gradually occupying its position until this latter is lost at the caudal extremity of the embryo (Fig. 81). This folding up of the epiblast gives rise to a longitudinal groove down its centre, in consequence of the manner in which the cells of the epiblast are heaped up into two longitudinal ridges, with a furrow between them, so that the sides and base of the groove are formed of epiblastic cells (Fig. 82, a). The mesoblast, lying between the epiblast and hypoblast, fills up the space thus caused between these two layers, so that the sides of the groove are occupied by a longitudinal thickening of mesoblast; the two masses being separated at the bottom of the groove by the junction of the epiblast and hypoblast at the situation of the primitive trace. The groove becomes deeper and deeper in consequence of the further growing up of the cells to form the ridge on either side. In this way the ridges eventually become two plates, the lamince dorsales or medullary plates, which finally coalesce and thus form a closed tube, the neural canal, lined by epiblast and having a covering of the same mem- brane (Fig. 82). These membranes are at first in contact with one another, but eventually become separated, mesoblastic structures growing up between them, and the line of coalescence becomes obliterated. The coalescence first takes place in the middle of the embryo, then toward the cephalic end, and lastly at the caudal extremity. The lining of this tube is developed into the nervous centres, the covering into the epidermis of the back and head. The cephalic extremity of the neural canal is soon seen to be more dilated than the rest, and to present constrictions dividing it imperfectly into three chambers: the brain is developed from this dilated portion; the spinal cord takes its origin from the remainder of the tube. Below the neural canal the hypoblast and epiblast are in contact, separating the two longitudinal thickenings of mesoblast on either side of the canal. Here a thickening of the hypoblast, commencing from the anterior end of the primitive trace, takes place, and gradually separates itself off from the hypo- blast, lying between this membrane and the epiblast, at the bottom of the neural canal. This is known as the notochord or chorda dorsalis. This when fully developed, forms a continuous rod-shaped body lying below the primitive groove and composed of clear epithelium-like cells. It is essentially an embryonic struc- ture, though traces of it remain in the centre of the intervertebral disks through- out life. The collection of mesoblastic cells, which forms a thick longitudinal column on either side of the neural canal, becomes separated from the rest of the mesoblastic layer. It undergoes a series of transverse segmentations and becomes converted into a row of well-defined, dark, square segments or masses, separated by clear, transverse intervals, called the protovertebrce or mesoblastic somites. They first make their appearance in the region which afterward becomes the neck, then further forward toward the head, and afterward extend along the body. These bodies, as will be explained hereafter, are not the same as the permanent verte- brae, but they are differentiated, partly into the vertebrae and partly into the 108 DE VEL OEM ENT. muscles and true skin. On either side of the protovertebrm the mesoblast splits into twTo layers, the upper, or that covered by epiblast, is called somatopleure, and the low'er, lined by hypoblast, the splanchnopleure (Fig. 82, b, 5-5')- From the Fig. 82.-Transverse sections through the embryo-chick before and some time after the closure of the medullary canal, to show the upward and downward inflections of the blastoderm. (After Remak.) a. At the end of the first day. 1. Notochord. 2. Primitive groove in the medullary canal. 3. Edge of the dorsal lamina. 4. Corneous layer or epiblast. Mesoblast divided in its inner part. f>. Hypoblast or epithe- lial laver. 7. Section of protoverte- bral plate, b. On the third day in the lumbar region. 1. Notochord in its sheath. 2. Medullary canal now closed in. 3. Section of the medul- lary substance of the spinal cord. 4. Corneous layer. 5. Somatopleure of the mesoblast. 5'. Splanchnopleure (one figure is placed in the pleuro- peritoneal cavity). 6. Layers of hy- poblast in the intestines spreading also over the yolk. 4X5. Part of the fold of the amnion formed by epi- blast and somatopleure. Fig. 81.-Embryonic area of the ovum of a rabbit at the seventh day. a<p Embryonic area, o, o. Region of the blastodermic vesicle immediately surrounding the embry- onic area. pr. Primitive streak, r/. Medullary groove. (From Kolliker.) former the skeleton muscles and true skin of the external parts of the body are derived, from the lat- ter, the muscular and other mesoblastic portions of the vis- cera. The space between them is the common pleuro-peritoneal cavity. Whilst the parietes of the body are still unclosed, this common pleuro-peritoneal cav- ity is continuous with the space between the amnion and cho- rion, as seen in Fig. 79, F. The embryo, which at first seems to be a mere streak, extends longi- tudinally and laterally. As it grows forward the cephalic end becomes remarkably curved on itself (cephalic flexure), and a smaller but distinct flexure takes place at its hinder end (caudal flexure). At the same time the sides of the embryo jrow and curve toward each other; so that the embryo is aptly compared to a canoe turned over (Fig. 83). In consequence of this incurv- Fig. 83.-Diagrammatic section through the ovum of a mam- mal in the long axis of the embryo, e. The cranio-vertebral axis. I, i. The cephalic and caudal portions of the primitive alimentary canal, a. The amnion, a'. The point of reflection into the false amnion, r. Yolk-sac, communicating with the middle part of the intestine by v i, the vitello-intestinal duct. u. The allantois. The ovum is surrounded externally by the villous chorion. THE EMBRYO. 109 ing of the embryo, both in an antero-posterior and a lateral direction, the original yolk, with the three layers derived from the cleavage of the blastodermic mem- brane which cover it, is converted into a sort of hour-glass shape with two unequal globes. The smaller globe is formed by the part of the blastodermic membrane (area germinativa) which has already undergone certain changes in the formation of the embryo, and constitutes the part which has been compared to a canoe. The larger globe is called the yolk-sac or imfo'ZzeaZ vesicle, and is formed by the rest of the blastodermic membrane-i. e. that part which is not concerned in the formation of the area germinativa. The two freely communicate through the constriction which is the site of the future umbilicus, and through this constriction the internal layer of the blastodermic membrane (the hypoblast) and the innermost of the two layers into which, as has been already stated, the mesoblast divides-viz. the splanch- nopleure, pass out; the incurving having only involved the somato-pleural layer of the mesoblast and the epiblast (Fig. 84). The umbilical vesicle is, therefore, at -Hypoblast -Splanchnopleure Epiblast Yolk-Sac Body of Embryo -Splanchnopleure jSomatopleure -Pleuro-peritoneal cavity Notochords Neural canal'' Fig. 84.-Diagrammatic section of embryo, showing the formation of the umbilical vesicle. first a mere part of the general cavity of the yolk, partly enclosed by the embryo; but as the latter grows round on all sides toward the umbilical aperture, the yolk becomes distinguished into two portions. One lies inside the embryo, and eventually forms a part of the intestinal cavity (out of which also, as will here- after be seen, the bladder is developed). The other lies external to the embryo ami remains therefore for a time a part of what is, in a more restricted sense, the ovum. The two parts are almost separated from each other by the meeting of the abdominal walls of the embryo at the umbilicus, through which they still communicate by a passage, the omphalo-mesenteric duct, the destination of which will be pointed out presently- The extra-embryonic portion is of small importance and very temporary duration in the human subject. It is for the purpose of supplying nutrition to the embryo during the very earliest period, before it can obtain it from the uterine sinuses of the mother. In the oviparous animals, however, where no supply of nutrition can be obtained from the mother, since the egg is entirely separated from her, the yolk-sac is large and of great importance, as it supplies nutrition to the chick during the whole of foetation. Vessels developed in the middle blastodermic layer soon cover the umbilical vesicle, forming the vascular area, the chief vessels of which are 4he omphalo-mesenteric, two in number (Fig. 85). The vessels of this area appear to absorb the fluid of the umbilical vesicle, which as the fluid is absorbed dries up and has no further function. The activity of the umbilical vesicle ceases about the fifth or sixth week, at the same time that the allantois, which is the great bond 110 DE VEL OPMEN T. of vascular connection between the embryo and the uterine tissues, is formed. In fact, the umbilical vesicle provides for the nutrition of the foetus from the ovum Fig. 85.-Magnified view of the human embryo of four weeks, with the membranes opened. (From Leish- mann after Coste.) y. The umbilical vesicle with the omphalo-mesenteric vessels, v, and its long tubular attachment to the intestine, c. The villi of the chorion, m. The amnion opened, u. Cul-de-sac of the allan- tois, and on each side of this the umbilical vessels passing out to the chorion. In the embryo: a. The eye. e. The ear-vesicle, h. The heart. I. The liver, o. The upper; n, the lower limb. w. Wolftian body, in front of which are the mesentery and fold of intestine. The Wolffian auct and tubes are not represented. itself, while the allantois is the channel whereby it is nourished from the uterine tissues. The umbilical vesicle, containing fluid, remains visible, however, up to the fourth or fifth month, with its pedicle and the omphalo-mesenteric vessels. The latter vessels become atrophied as the functional activity of the body with which they are connected ceases. So far we have traced-(1) the segmentation or cleavage of the yolk into a number of nucleated cells-" vitelline spheres." (2) The accumulation of fluid within the ovum, and the arrangement of the vitelline spheres around the fluid on the internal surface of the vitelline membrane, forming a second membrane, the " blastodermic membrane." (3) The separation of the blastodermic membrane into three layers, named, from within outward, the " hypoblast," the " mesoblast," and the "epiblast." (4) The formation of an elongated, oval-shaped disk, called the " area germinativa." (5) The appearance in the centre of the area germinativa of a delicate line of furrow, running longitudinally, and called the " primitive trace." (6) The formation of a distinct groove in the situation of this primitive trace, caused by the growing-up of the cells on either side of it, so as to form two longitu- dinal ridges, called the "laminae dorsales." (7) The increase and incurvation of these laminae dorsales, until they meet behind, enclosing a canal lined by epiblast. The canal is the neural canal, and from the epiblast which lines it the nervous centres are developed. (8) The formation, in the hypoblast immediately under this canal, of a continuous rod-shaped body, the "chorda dorsalis," or "notochord." (9) The formation from the mesoblast, on either side of the notochord, of a longi- THE AMNION. 111 tudinal column, divided into a number of square segments, the "protovertebrae." (10) The splitting of the mesoblast, external to the protovertebrae, into two layers- the outer, called the " somatopleure," lined externally by the epiblast; the inner, called the " splanchnopleure," lined internally by the hypoblast, a space being left between the two which forms the " pleuro-peritoneal cavity." (11) The curving of the embryo on itself, both longitudinally and laterally, so as to be comparable to a canoe; the Avails being formed of all three layers of the blastodermic membrane and the well of the canoe-that is the body-cavity of the embryo, opening into the cavity of the yolk-sac. (12) A portion of the yolk-sac lying in the body- cavity of the embryo, and a portion outside it; the two communicating by a duct, the " omphalo-mesenteric " duct. The portion of the yolk-sac external to the body- cavity is termed the umbilical vesicle, and provides nutrition to the embryo until such time as the allantois is formed; vessels, developed from the middle blasto- dermic layer, ramifying over it, and gradually absorbing its contents.1 The next step toward a clear understanding of the development of the embryo is to have a proper conception of the manner in which the membranes developing the foetus are formed. The membranes investing the foetus are the amnion, the chorion, and the decidua. The two former are developed from foetal structures, and are proper to the foetus; the latter is formed in the uterus, and is derived from the maternal structures. The Amnion.-The amnion is the membrane which immediately surrounds the embryo. It is of small size at first, but increases considerably toward the middle False amnion or chorion. Post, root gangl. P Amnion. Neural s' canal. Notochord! Primitive aorta" Mid-gut. - _ Muscle plate. - -Card. vein. Wolffian body and duct. ~ Coelom. Yolk- sac. Fig. 86.-Diagram of a transverse section of a mammalian embryo, showing the mode of formation of the amnion. The amniotic folds have nearly united in the middle line. (From Quain's Anatomy, vol. i. pt. 1, 1890.) Epiblast, blue; mesoblast, red: hypoblast and notochord, black. of pregnancy, as the foetus acquires the power of independent movement. It exists only in reptiles, birds, and mammals, which are hence called "Amniota," but is absent in amphibia and fishes. It is formed thus: At or near the extremities of the incurved foetus-that is to say, at the point of constriction of the blastodermic membrane, where the portion which has undergone changes to form the body of the embryo joins the part devoted to the formation of the umbilical vesicle-an inflection of the epiblast and outer layer of the mesoblast, which have become separated from the inner layer of the mesoblast and hypoblast by the formation bf the pleuro-peritoneal cavity, takes place (Fig. 79, d 7). These inflections or back- 1 According to Professor John A. Ryder, it is "very doubtful if any considerable amount of nutriment is supplied to the embryo from the yolk-sac at any time." 112 I) E VEL OPMENT. ward folds commence first at the cephalic extremity, and subsequently at the caudal end and sides, and deepen more and more, in consequence of the sinking of the embryo into the blastodermic vesicle, until, gradually approaching, they meet one another (Fig. 79, e 7). After they come in contact they fuse together, and the septum between them disappears; so that the inner layer of the cephalic fold becomes continuous with the inner layer of the caudal fold, and the outer with the outer (Fig. 79, f 7'). Thus we have two membranes, one formed by the inner layer of the fold-the true amnion-which encloses a space over the back of the embryo-the amniotic cavity (Fig. 79, F and G, a)-containing a clear fluid, the liquor amnii.1 The other, the outer layer of the fold-the/flZsc amnion-lines the internal surface of the original vitelline membrane. Between the two is an interval, which of course communicates with the pleuro-peritoneal cavity. This it continues to do until the body-walls of the embryo have grown up and coalesced at the umbilicus. Then the amniotic fold is carried downward, and encloses the umbilical cord, by which the foetus is attached to the placenta. The true amnion-or, as it is usually called, the amnion-is formed of two layers, derived respectively from the epiblast and from the parietal layer of the mesoblast. The one from the epiblast consists of nucleated cells; the other, from the mesoblast, has a fibrous, and, according to some embryologists, a muscular structure; at all events, it possesses the power of rhythmic contraction during life. In some animals this layer is vascular. The amnion is at first in close contact with the surface of the body of the embryo, but about the fourth or fifth week fluid begins to accumulate, and thus separates the two. The quantity steadily increases up to about the sixth month of pregnancy, after which it diminishes somewhat. The use of the liquor amnii is believed to be chiefly to allow of the movements of the foetus in the later stages of pregnancy, though it no doubt serves other purposes also. It contains about 1 per cent, of solid matter, chiefly albumen, with traces of urea, the latter probably derived from the urinary secretion of the foetus. The Chorion.-The chorion is rather a complex membrane made up essentially of two parts: first, of the membranes of the ovum external to the pleuro- peritoneal cavity-that is to say, of the vitelline membrane and false amnion ; and, secondly, of a diverticulum of those layers of the original blastodermic mem- brane which are internal to the pleuro-peritoneal cavity. This diverticulum is called the allantois. 1. The portion of the chorion which is formed from the membranes of the ovum external to the pleuro-peritoneal cavity.-We have seen that in the formation of the amnion we had two layers formed out of a reduplication of the epiblast and outer layer of the mesoblast: one-the true amnion-which surrounds the embryo and encloses a cavity between it and the embryo-the amniotic cavity; and secondly, the/hZse amnion, which lies in apposition with the internal surface of the vitelline membrane, and is continuous at its periphery with that part of the original epiblast and somatopleural layer of the mesoblast which did not enter into the formation of the area germinativa; and that between these two layers there is a space (which must not be confounded with the amniotic cavity) which com- municates with the pleuro-peritoneal space, and, according to Dalton, contains a semifluid, gelatinous material. The external part of the chorion is formed out of the vitelline membrane with the false amnion and its peripheral continuation with the external layers of the blastoderm; but the exact share which the three layers take in its formation is at present uncertain. By some embryologists it is believed that the vitelline membrane during the rapid growth of the ovum becomes attenu- ated, and finally lost; by others it is thought that it combines with the other layers 1 The student should be careful not to confound this cavity with that formed between the true and false amnion, which communicates with the pleuro-peritoneal cavity of the embryo. This latter space ought with more propriety to be called the " amniotic cavity," since it is contained between the layers of the amnion ; whereas the so-called amniotic cavity is not really between the layers of the amnion at all, but between the inner layer of the amnion and the body of the embryo. THE ALLANTOIS. 113 to form the chorion. But, whichever is true, at a very early period of gestation cellular processes or fringes grow outward from the external surface of the vitelline membrane, or, if this has disappeared, from the outer layer of the blastoderm, which has been likened by Dalton to tufts of seaweed. They are at first destitute of vessels, and are of simple cellular structure. These fringes, or villi, as they subsequently become, cover at first the whole surface of the chorion ; but as devel- opment progresses and the placenta, by which the extent of the attachment of the ovum to the uterine walls is to be limited, is about to be formed, the villi are not further developed over the rest of the chorion, but are confined to that part only which is to form the foetal portion of the placenta. They may, however, be recognized all over the chorion, as abortive processes, during the whole of foetal gestation. 2. The Allantois.-This structure is derived from the layers of the blastodermic membrane which are internal to the pleuro-peritoneal space, being formed by the projection of a hollow bud of that part of the hypoblast and splanchnopleure which is contained in the body-cavity of the embryo, and which, as we have before stated, is intended for the for- mation of the intestinal canal (Fig. 83, w). It extends into and through the pleuro-peritoneal space, into the cavity between the true and false am- nion, until it meets the latter, over the internal surface of which it spreads. In this diverticulum two arteries and two veins, the allantoic vessels, are developed. The arteries are in the first instance branches of the two primary divisions of the abdominal aorta, but subsequently, when the two aortas coalesce, they become branches of the hypogastric arteries. The veins join the veins of the yolk- sac, and form the umbilical veins.** When the allantois meets the chorion, branches from these allantoic vessels permeate the cellular tufts or fringes which have been described as grow- ing from the outer surface of the false amnion and convert them into villi, and these eventually form the foetal portion of the placenta1 (Fig. 85, e). The allantois is the chief agent of the early circulation, for it is the duct or tract along which the vessels extend which convey the blood of the embryo to the foetal chorion, where it is ex- posed to the influence of the mater- nal blood circulating in the decidua or uterine portion of the placenta, from which it imbibes the materials of nutrition, and to which it gives up effete materials, the removal of which is necessary for its purification. In some animals the allantois is a hollow' projection and is usually styled the allantoic vesicle; but in most mammals, and especially in man, the external or mesoblastic element Fig. 87.-Sectional plan of the gravid uterus in the third and fourth month. (From Wagner.) a. Plug of mucus in the neck of the uterus, b. Fallopian tube. c. The decidua vera. c2. The decidua vera passing into the right Fallopian tube : the cavity of the uterus is almost completely occupied by the ovum, e, e. Points of reflec- tion of the decidua reflexa (in nature the united decidua do not stop here, but pass over the whole uterine surface of the placenta), g. Supposed allantois, h. Umbilical vesicle, i. Amnion, k. Chorion, covered with the decidua reflexa. d. Cavity of the decidua, f. Decidua serotina, or placental decidua. 1 In some animals some of the vessels of the villi of the chorion are derived from the yolk-sac- that is from the omphalo-mesenteric vessels. 114 DE VEL OPMENT. undergoes great development, while the internal or hypoblastic element undergoes little increase beyond the body of the embryo, so that it is very doubtful whether any cavity exists in the allantois beyond the limits of the umbilicus, or whether it does not rather consist of a solid mass of material derived from the mesoblastic tissue.1 A portion of the allantoic vesicle within the body-cavity is eventually destined to form the bladder, while the remainder forms an impervious cord, the urachus, stretching from the summit of the bladder to the umbilicus. The part external to the foetus forms the umbilical cord, by which the foetus is connected with the villi of the chorion, and which eventually form the foetal portion of the placenta. The Decidua.-The growth of the chorion and placenta can only be understood by tracing the formation of the decidua. The decidua (Figs. 80 g, 87) is formed from the mucous membrane of the uterus. Even before the arrival of the fecundated ovum in the uterus the mucous membrane of the latter is vascular and tumid, and when the ovum has reached the uterus it becomes imbedded in the folds of the mucous mem- brane, which grow up around it and finally completely encircle it, so as to cover it in entirely and exclude it from the uterine cavity. Thus two portions of the uterine mucous membrane (decidua) are formed-viz. that which coats the muscular wall of the uterus, decidua vera, and that which is in contact with the ovum, decidua reflexa. The decidua vera at the os internum and at the open- ings of the Fallopian tubes is continuous with the lining membrane of these canals, the thickening of the original mucous membrane of the uterus which con- verts it into decidua abruptly ceasing at these points. The neck of the uterus after conception is closed by a plug of mucus. The decidua vera is perforated by the openings formed by the enlarged uterine glands, which become much hypertro- phied and developed into tortuous tubes. It contains at a later period numerous arteries and venous channels, continuous with the uterine and it is from it that the uterine part of the placenta is developed. The portion of the decidua vera which takes part in the formation of the placenta is called the decidua serotina (Fig. 87, f). The decidua reflexa is shaggy on its outer aspect, but smooth within. The vessels which it contains at first disappear after about the third month. About the fifth or sixth month the space between the two layers of the decidua disap- pears, and toward the end of pregnancy the decidua reflexa is transformed into a thin yellowish membrane, which constitutes the external envelope of the ovum. Much additional interest has been given to the physiology of the decidua by the fact, which seems to be now established by the researches of Dr. John Williams, that every discharge of an ovum, whether impregnated or not, is, as a rule, accompanied by the formation of a decidua, and that the essence of men- struation consists in the separation of a decidual layer of the mucous membrane from the uterus; while in the case of pregnancy there is no exfoliation of the membrane, but, on the contrary, it undergoes further development in the manner described above. The Placenta is the organ by which the connection between the foetus and mother is maintained. It therefore subserves the purposes both of circulation and respiration. It is formed of two parts, as already shown-viz. the maternal portion, which is developed out of the decidua vera (serotina), and the fetal portion formed out of the villi of the chorion. Its shape in the human subject is that of a disk, one side of which adheres to the uterine wall, while the other is covered by the amnion. The villi of the chorion gradually enlarge, forming large projections-"cotyledons"-which each contain the ramifications of vessels 1 Indeed, it would appear, from the researches of His, that in the human embryo not only is the allantois formed unusually early, as is admitted by all, but in an altogether exceptional manner, not consisting of an outgrowth from the portion of the splanchnopleure engaged in the formation of the alimentary canal, but being present from the very earliest period as a stalk connecting the posterior extremity of the embryo with the chorion. DEVELOPMENT OF THE EMBRYO PROPER. 115 communicating with the umbilical (allantoic) arteries and veins of the foetus. These vascular tufts are covered with epithelium, and project into corresponding depressions in the mucous membrane (decidua vera) of the uterine wall. The maternal portion of the placenta consists of a large number of sinuses formed by an enlargement of the vessels of the uterine wall. These bring the uterine blood into close proximity with the villi of the foetal placenta, which dip into the sinuses. The interchange of fluids necessary for the growth of the foetus and for the depuration of the blood takes place through the walls of the villi, but there is no direct continuity between the maternal and foetal vessels. The foetal ves- sels form tufts of capillaries, the blood from which is returned by small veins, which end in tributaries of the umbilical vein. The maternal arteries open into spaces somewhat after the manner of the arteries of the erectile tissues. These spaces communicate with a plexus of veins which anastomose freely with one another, and give rise, at the edge of the placenta, to a venous channel which runs around its whole circumference-the placental sinus. The umbilical cord appears about the end of the fifth week after conception. It consists of the coils of two arteries {umbilical, originally allantoic) and a single vein, united together by a gelatinous tissue {jelly of Wharton). There are origin- ally two umbilical veins, but one of these vessels becomes obliterated, as do also the two omphalo-mesenteric arteries and veins and the duct of the umbilical vesicle, all of which are originally contained in the rudimentary cord. The per- manent structures of the cord are, therefore, furnished by the allantois. In this manner the human embryo eventually becomes surrounded by three membranes : (1) the amnion, derived from the outer layer of the mesoblast and the epiblast; (2) the chorion, formed most probably by three layers-the allantois (which is derived from the inner layer of the mesoblast and hypoblast), the false amnion, and perhaps the vitelline membrane; and (3) the decidua, derived from the mucous membrane of the uterus. Development of the Embryo proper.-The further development of the embryo will, perhaps, be better understood if we follow as briefly as possible the principal facts relating to the chief parts of which the body consists-viz. the spine, the cranium, the pharyngeal cavity, mouth, etc., the nervous centres, the organs of the senses, the circulatory system, the alimentary canal and its appendages, the organs of respiration, and the genito-urinary organs.1 The reader is also referred to the chronological table of the development of the foetus at the end of this section. Development of the Spine.-We have already traced the first steps in the formation of the spine: (1) The looping up of two longitudinal folds from the cells of the epiblast on either side of the primitive streak, so as to form a groove, and the gradual growing together of these ridges {lamince dorsales) so as to con- vert the groove into a canal, which is lined by epiblast, and out of which the spinal cord is developed. (2) The formation in front of this groove of a con- tinuous cellular cord enclosed in a structureless sheath, the notochord or chorda dorsalis (Fig. 88). The notochord extends from the cephalic to the caudal extremity of the embryo, and lies in the place which is afterward occupied by the bodies of the vertebrae. (3) On either side of the neural canal a portion of the mesoblastic layer is divided longitudinally from the rest of the mesoblast, so as to form a thick column, which extends from the cephalic to the caudal extremity of the embryo on either side of the spinal canal and notochord (Fig. 82, a 7); this is the protovertebral column. From the greater part of it is derived tbe vertebral column, a small portion at the upper and outer part being differentiated from it and eventually forming the muscles of the back. (4) This column under- goes a process of transverse segmentation and becomes converted into a number 1 The scope of this work only permits the briefest possible reference to these subjects. Those who wish to study the subject of embryology in more detail are referred to Kolliker's Entwickelungs- geschichte ; to vol. i. pt. 1, of the tenth edition of Quain's Anatomy ; or to the works of Professor Dalton and of Foster and Balfour. 116 DE VEL OPMENT. of quadrilateral blocks, the protovertebral somites (Fig. 89). The process of seg- mentation commences in the cervical region and proceeds successively through Fig. 89.-Cervical part of the primi- tive vertebral column and adjacent parts of an embryo of the sixth, day, showing the division of the primitive vertebral segments. (From Kblliker, after Remak.) 1,1'. Chorda dorsalis in its sheath, point- ed at its upper end. 2, points by three lines to the original intervals 'of the primitive vertebrae. 3, in a similar man- ner, indicates the places of new divis- ion into permanent bodies of vertebrae, c indicates the body of the first cervical vertebra; in this and the next the primi- tive division has disappeared, as also in the two lowest represented-viz. d and the one above; in those intermediate the line of division is shown. 4, points in three places to the vertebral arches: and 5, similarly, to three commencing ganglia of the spinal nerves; the dotted segments outside these parts are the muscular plates. Fig. 88.-Transverse section through the dorsal region of an embryo chick, end of third day. (From Foster and Balfour.) Am. Amnion, mp. Muscle-plate, cv. Cardinal vein. Ao. Dorsal aorta at the point where its two roots begin to join. Ch. Noto- chord. Wd. Wolffian duct. Wb. Commencement of formation of Wolffian body. ep. Epiblast, so. Somatopleure. hy. Hypo- blast. The section passes through the place where the aliment- ary canal (hy) communicates with the yolk-sac. the other regions of the spine until a number of segments are formed, which correspond very closely to the number of the permanent vertebrae. (5) These protovertebral somites extend laterally; they grow forward and inward until they meet in front of the notochord in the middle line, which they thus enclose, and backward and inward around the spinal canal, which they also enclose. The notochord and the spinal canal are thus surrounded by a cellular mass derived from the mesoblastic layer, which constitutes the membranous matrix of the vertebrae. This structure is covered on its internal surface by hypoblast, and on its outer by epiblast, and presents the transverse segmentation already described (page 107). (6) The next step is the conversion of this primitive membranous matrix into cartilage. This takes place probably about the fourth or fifth week in the human embryo (Kblliker). The part of the protovertebral somites which has extended backward to enclose the spinal foramen, and which eventually forms the arches of the vertebrae, simply undergoes a process of chondrification, so that the permanent arches correspond to the primary segment of the protover- tebral somites, spaces being left between them for the spinal nerves and ganglia to grow out from the spinal cord. But a somewhat more complex change goes on in the portion of the protovertebral somites which encloses the notochord, and which is destined to form the bodies of the vertebrae. Here each one of the pro- tovertebral segments undergoes a second transverse division through its centre, and in the interval which is left between these secondary segmentations the fibrous structure of the intervertebral disks is formed. The half-segment of the original protovertebral somites on either side of this secondary segmentation joins with the segment above and below, and undergoes chondrification, and thus forms the basis of the body of a future vertebra. Each cartilaginous body of a vertebra THE CRANIUM. 117 is formed therefore out of half an original protovertebral plate joined to the half of another plate above or below it, as the case may be. (7) The notochord con- tained in the centre of this chondrifying mass does not continue to grow, but becomes in the human subject relatively smaller, so as, at last, to form a mere slender thread, except opposite the secondary segmentations; that is to say, cor- responding to the intervals between the bodies of the permanent vertebrae. Here it presents thickenings and forms an irregular network, the remains of which are to be found at all periods of life in the central pulp of the intervertebral disks. Development of the Ribs and Sternum.-The ribs are formed by extensions of the blastema of the vertebrae in the mesoblastic layer of the blastodermic mem- brane. These speedily undergo chondrification, and appear as cartilaginous bars, and become separated from the vertebrae at their posterior extremities. At their anterior ends the costal bars, which are to form the nine upper ribs, turn upward and fuse together so as to form a cartilaginous strip bounding a central median fissure. The strips on either side then join in the middle line from before back- ward, and so give rise to a longitudinal piece of cartilage, which represents the manubrium and gladiolus of the sternum. In the process of development the sternal attachment of the eighth rib disappears, while that of the ninth sub- divides, one portion remaining attached to the inferior extremity of the cartilag- inous sternum and becoming developed into the ensiform cartilage; the other por- tion receding from the sternum and becoming attached to the rib above. The further development of the vertebrae, ribs, and sternum, and the ossifica- tion of their cartilaginous structure, are described in the body of the work. Development of the Cranium in general, and the Face.-We have seen that the first trace of the embryo consists in the formation of a longitudinal fold of the epiblast on either side of a median groove, and that these folds or ridges grow backward and meet in the median line, thus forming a canal. This canal, at the cephalic extremity of the embryo, is dilated and forms a bulbous enlargement. The bulbous enlargement soon expands into three vesicular dilatations, which are known as the three primary cerebral vesicles, from which all the different parts of the encephalon are presently to be developed. The most anterior of the three forms the optic thalamus, whilst a hollow projection from it forms the corpus striatum and the cerebral hemispheres; the middle one forms the tubercula quad- rigemina; the posterior the medulla oblongata. The primary cerebral vesicles are at this time, of course, hollow, and their cavities freely communicate with each other at the points of constriction. As the embryo grows, the cerebral vesicles become twice bent forward on their own axis (Figs. 90, 91, a and b). The upper or posterior curvature is called the cerebral; the lower or anterior, the frontal protuberance. Thus, we have a triple cavity (see Fig. 91, A, where the three cavities are marked c, me, and mo) lined by epiblast and covered by the same structure. Between these two layers of epiblast, a layer of meso- blast, derived from the protovertebral plates of the trunk, is prolonged and spreads over the whole sur- face of the cerebral vesicles. From these structures the cranium and its contents are developed. The ex- ternal layer of the epiblast forms the superficial epi- thelium of the scalp. The mesoblastic layer forms the true skin, the blood-vessels, muscles, connective tissue, bones of the skull, and membranes of the brain. The layer of epiblast lining the cavity forms the nervous substance of the en- cephalon, while the cavity itself constitutes the ventricles. The upper end of the notochord terminates at its cephalic end in a pointed extremity which extends as far forward as the situation of the body of the future Fig. 90.-Longitudinal section of the head of an embryo four weeks old, seen from the' inside. 1. Ocular vesicle. 2. Optic nerve flattened out. 3. Fore brain. 4. Intermediary brain. 5. Middle brain. 6. Hinder brain. 7. After brain. 8. Anterior portion of the tentorium cerebelli. 9. Its lateral portion intervening between Nos. 4 and 5. 10. The pharyngeal curve, bent into a cul-de-sac. 11. The auditory vesicle. 118 DE VEL O PM ENT. sphenoid bone, and is there imbedded in a mass of tissue, the " investinggmass of Rathke." This mass, derived from mesoblastic tissue, becomes cartilaginous, and GJ 7 Fig. 91-Vertical section of the head in early embryos of the rabbit. Magnified. (From Mihalkovics). a. From an embryo of five millimetres long. b. From an embryo of six millimetres long. c. Vertical section of the anterior end of the notochord and pituitary body, etc. from an embryo sixteen millimetres long. In a, the fau- cial opening is still closed. In b, it is formed, c. Anterior cerebral vesicle, me. Mesocerebrum, mo. Medulla oblongata, co. Corneous layer, m. Medullary layer, if. Infundibulum, am. Amnion, spe. Spheno-ethmoidal. be. Central (dorsum sellee), and spo, spheno-occipital parts of the basis cranii. h. Heart, f. Anterior extremity of primitive alimentary canal and opening (later) of the fauces, i. Cephalic portion of primitive intestine, tha. Thalamus, p'. Closed opening or the involuted part of the pituitary body (py). ch. Notochord, ph. Pharynx. from it is developed the basi-occipital and basi-sphenoid bones; and by lateral expansions from it the occipitals, the greater wings of the sphenoid, and the periotic mass of cartilage surrounding the primary auditory vesicles. From the front of the investing mass of Rathke, which corresponds in position to the future dorsum selhn, two lateral bars are directed forward, enclosing a space which forms the pituitary fossa, in which the pituitary body is eventually developed. These bars are named the trabeculce cranii, and extend as far forward as the anterior extremity of the head, where they coalesce with each other. From them the pre- sphenoid and lateral masses of the ethmoid are developed; and from their coalescence a process is prolonged downward to form a portion of the framework of the face hereafter to be described. From the pre-sphenoids, which are developed from these trabeculae, a lateral expansion takes place, which forms the orbito- sphenoid or lesser wings of the sphenoid, enclosing the optic foramen. The portions of the base of the skull above enumerated are formed from car- tilage ; the remaining parts, comprising the vault of the skull, are of membran- ous formation. The head at first consists simply of a cranial cavity, the face being subse- quently developed in the manner now to be described by a series of arches with clefts between them (Fig. 92). It is usual in our text-books to describe the arches as a series of processes which jut out and grow downward, inclining toward each other until they meet in the middle line and thus form a series of inverted arches, whilst the clefts are the spaces left between each pair of processes. This, however, is scarcely the true description, and leads rather to the false impression that the arches are formed by processes budding out from the embryo, much in the same way as the extremities do, and that they are free on every side. What would appear rather to be the case is that the clefts are first formed, and that the arches consist of a thickening of the tissue on either side of the cleft. The arches thus formed may be divided into two sets, according as they are placed in front or behind the buccal cavity or mouth, the former being known as the pre-oral, and the latter as the post-oral or visceral arches. Four clefts on each side appear laterally in the undifferentiated somato-splanchno-pleural wall of the fore-gut, and between them thickenings occur which ultimately meet and fuse in the middle line, and above are connected with the investing mass. These are the so-called post-oral visceral THE FACE. 119 arches. Differentiation of tissue occurs from above downward, and cartilage is formed in them in connection with the investing mass. The first post-oral arch has no cleft in front of it, but forms a rim in front of the fore-gut. The pre-oral arches are formed in much the same way by local thickening, in which differentiation of tissue and formation of cartilage proceeds in a di- rection forward and downward from the in- vesting mass. The pre-oral or maxillary arch unites with the fronto-nasal process. The latter consists of three plates, a central single one and two lateral ones. The central is called the " mid-frontal" process. It is prolonged downward and forward from the middle of the base of the skull, from the point of coal- escence of the two trabeculae cranii, and from it the septum of the nose is developed. It is free in front and belowr, but behind it is united with the coalesced portion of the trabeculae, which therefore probably assists in the formation of the septum nasi, and, in addition, of the prominent part of the future nose. The lateral plates of the fronto-nasal process are4 separated from the central one by a depression or furrow on either side; these furrows form the primary nasal pits or fossae. The lateral plates project downward parallel to the mid-process for a certain distance, and then, curving inward, unite with it, thus shutting off the nasal fossae from the rest of the face. The lateral masses of the ethmoid and lachrymal bones are developed in the lateral plates, and by their union with the mid-frontal process form the intermaxillary bone and the lunula, or central part of the upper lip. The maxillary processes spring from the base of the skull farther back than the fronto-nasal process, and at their origin are closely connected with the first post-oral or visceral arch. They descend for a short distance, forming the outer wall of the orbit, in which the malar bone is developed; they then incline inward, and, meeting the lateral plate of the fronto-nasal process, form the door of the orbit, and shut it off from the rest of the face; then, continuing their course downward and inward, they join the mid-frontal process, and with it complete the alveolar arch and the superior maxillary bone. Finally, palatal processes are formed by an extension of the inner sides of this arch ; these coalesce with each other in the median line, thus separating the cavity of the mouth from the nasal fossae, and completing the palate. In front, however, the palatal processes do not join with the mid-frontal process, but a cleft is left which constitutes the naso- palatine canal. The post-oral arches are five in number in the Amniota, and of these the first only is concerned in the formation of the face proper, for the lower jaw or man- dible is developed from it, and hence it is called the mandibular arch. The second is named the hyoid arch : from it is formed the styloid process, the stylo-hyoid ligament, and the lesser cornu of the hyoid bone. The third, or thyro-hyoid arch, gives origin to the great cornu of the hyoid bone, while the body of this bone is formed between the second and third arches. This third arch, together with the fourth and fifth, corresponds to the arches which, in fishes and amphibia, form the gill-plates, but which, in the Amniota, never do so. They are appropriately named branchial, a name which was primarily given to the whole series by Rathke, who first described them. Fig. 92-Face of an embryo of 25 to 28 days. Magnified 15 times. 1. Frontal prominence. 2,3. Right and left olfactory fossa:. 4. Inferior max- illary tubercles, united in the middle line. 5. Superior maxillary tubercles. 6. Mouth of fau- ces. 7. Second pharyngeal arch. 8. Third. 9. Fourth. 10. Primitive ocular vesicle. 11. Prim- itive auditory vesicle. 120 DE VEL OPMENT. The deeper part of the first or mandibular arch contains a transitory cartilag- inous rod, which has long been known as the " cartilage of Meckel," the proximal end of which is at first attached to the basis cranii, and afterward to the periotic capsule. It is, during some part of foetal life, directly continuous with the mal- leus, which by some is believed to be developed from it. The median end of the lower jaw-bone is developed from this cartilage, the greater part of the rest of the bone being developed from membrane. Between the mandibular arch and the pre-oral arch the buccal cavity or mouth is formed; this therefore owes its origin to the formation of the pre-oral and post-oral arches, and consists of mesoblastic tissue lined by epiblast. As has been already stated (page 108), the cephalic end of the embryo becomes remarkably curved on itself, the fore- and mid-brain bending downward over the anterior portion of the original blastodermic membrane, which remains within the body of the embryo and from which the fore-gut is to be developed. This fore-gut terminates as a blind extremity beneath the head (Fig. 91, A, /). Another prominence forms on the ventral surface of the fore-gut, which represents the rudimentary heart (Fig. 91, a, A). Between these two prominences, caused by the projection of the fore-brain and the heart, an involution of the epiblast takes place, gradually deepening until it comes in contact with the upper part of the alimentary canal. This is the stomodceum or mouth, which becomes bounded by prominences, constituting the pre-oral and mandibular arches. It is at first quite distinct from the upper part of the alimentary canal, which, as we shall hereafter see, is formed by the inner or splanchno-pleural layer of the mesoblast and the hypoblast, the two cavities being separated by all the layers of the blastodermic membrane. A communication between the two is, however, gradually effected by the absorption of these layers at the anterior extremity of the primitive alimentary cavity and the hinder portion of the epiblastic involution from which the mouth is formed. Between each of these visceral arches are clefts, four in number, which run through the tissues of the neck to the cavity of the pharynx; the first persists, though only in a portion of its extent, forming the Eustachian tube, the meatus auditorius, and the tympanic cavity. The other fissures are wholly closed by the sixth week. Development of the Nervous Centres and the Nerves.-The medullary groove above described (page 107) presents, about the third week, three dilatations at its upper end, separated by two constrictions, and at its posterior part another dila- tation, called the rhomboidal sinus. Soon afterward the groove becomes a closed canal (medullary canal), and a soft blastema lines it, exhibiting corresponding dilatations. This is the rudiment of the cerebro-spinal axis. As the embryo grows, its cephalic part becomes more curved, and the three dilatations at the anterior end of the primitive cerebro-spinal axis become vesicles distinctly separate from each other (Fig. 90). These are the cerebral vesicles-anterior, middle, and pos- terior. The anterior cerebral vesicle (situated, at this period, quite below the middle vesicle) is the rudiment of the third ventricle, and of the parts surrounding it- viz. the optic thalami and all the parts which form the floor of the third ventricle. The middle vesicle repre- sents the aqueduct of Sylvius, with the corpora quadrigem- ina. The posterior vesicle is developed into the fourth ventricle, and its walls form the pons Varolii, medulla oblongata, and parts in the floor of the fourth ventricle. At an early period in the development of this primi- tive brain a protrusion takes place from the anterior vesicle, which is at first simple, but soon becomes divided into two parts by an antero-posterior fissure. These expand laterally, Fig. 93.-Section of the me- dulla in the cervical region, at six weeks. Magnified 50 diam- eters. 1. Central canal. 2. Its epithelium. 3. Anterior gray matter. 4. Posterior gray matter. 5. Anterior commissure. 6. Pos- terior portion of the canal, closed by the epithelium only. 7. An- terior column. 8. Lateral column. 9. Posterior column. 10. An- terior roots. 11. Posterior roots. THE NERVOUS CENTRES. 121 and the cerebral hemispheres and corpora striata are developed from them. From the fore-part of the posterior cerebral vesicle a similar protrusion takes place, forming the rudiment of the cerebellum. In consequence of these protrusions or outgrowths taking place, the three primary cerebral vesicles are now converted into six permanent rudiments of the brain and medulla oblon- gata. The anterior part of the original anterior cerebral vesicle (fore-brain, prosencephalon), now divided into two, constitutes the cerebral hemispheres, corpus callosum, corpora striata, fornix, lateral ventricles, and olfactory bulbs. These parts lie at first quite covered and concealed by those formed from the middle primary vesicle and by the optic thalami, which, with the optic nerves, the third ventricle and the parts in its floor, are furnished by the posterior portion of the anterior vesicle (inter-brain, thalamencephalon). By the third month, how- ever, the hemispheres have risen above the optic thalami, and by the sixth month above the cerebellum. Fissures are seen on the surface of the hemispheres at the third month, but all except one disappear. This one persists, and forms the fissure of Sylvius. The permanent fissures for the convolutions do not form till about the seventh or eighth month. The middle cerebral vesicle (mid-brain, mesen- cephalon) is at first situated at the summit of the angle shown on Fig. 90. Its smooth surface is soon divided, by a median and transverse groove, into four tubercles (tubercula quadrigemina), which are gradually covered in by the growth of the cerebral hemispheres. Its cavity diminishes as its walls thicken, and con- tracts to form the aqueduct of Sylvius. The crura cerebri are also formed from this vesicle. The third primary cerebral vesicle at an early period (between the ninth and twelfth week) consists of the hind-brain or epencephalon, forming the cerebellum, pons Varolii, and anterior part of the fourth ventricle, and of the after-brain or metencephalon, which forms the medulla oblongata with the rest of the fourth ventricle. The development of the pituitary body has of late received much attention. It is mainly formed by a diverticulum from the buccal involution of epiblast. At its upper and front part this involution, from which the mouth or stomodaeum is developed, forms a hollow saccular protrusion, which extends into the angle formed by the bend of the fore-with the mid-brain. Here it comes in contact with a median hollow protrusion, which passes downward and backward from the posterior portion of the anterior cerebral vesicle (Fig. 91, c, if). They become intimately connected, and together form the pituitary body or hypophysis. When the medullary groove is first closed, the foetal spinal marrow occupies its whole length, ami presents a large central canal, which gradually contracts in consequence of the thickening and rapid growth of the epiblast around it. This increase in thickness takes place principally at the sides, so that eventually the central canal acquires on section the appearance of a slit. According to some investigators, the two sides of this slit eventually join in the middle, and the original canal is divided into two: an anterior, which becomes the central perma- nent canal, which in after life is no longer perceptible to the eye, though it is still visible on microscopic section ; and a posterior, which becomes filled about the ninth week with a septum of connective tissue from the pia mater, and forms the posterior fissure of the cord. According to other observers, the posterior fissure is formed independently of the central canal as a cleft formed by the enlarging lateral halves of the cord, into which an ingrowth of connective tissue from the pia mater takes place. The anterior fissure is apparently formed in this latter manner, simply as a cleft left between the lateral halves of the cord. After the fourth month the spinal column begins to grow in length more rapidly than the medulla spinalis, so that the latter no longer occupies the whole canal. The cord is composed at first entirely of uniform-looking cells, which soon separate into two layers, the inner of which forms the epithelium of the central canal, while the outer forms the central gray substance of the cord. The white columns are formed later; their rudiments can be detected about the fourth week, and some embryologists believe that they are developed from the mesoblast. 122 DE VEL OPMENT. The cerebral and spinal membranes are, according to Kolliker, a production from the protovertebral disks, and are recognizable about the sixth week. As the fissures separating the segments of the cerebro-spinal axis appear, the membranes extend through them and the pia mater passes into the cerebral ventricles. Bischoff, however, describes the pia mater and arachnoid as developed from the cerebral vesicles, so that they are, according to him, formed in the position which they permanently occupy. The Nerves.-The nerves are developed, like the rest of the nervous system, from epiblast. The spinal nerves are developed as follows: Close to the point of involution of the epiblast in the median line-that is to say, in the angle of junction of the neural and general epiblast-a cellular swelling constituting the neural crest appears, and forms a continuous ridge on the dorsal aspect of the neural canal. On this crest enlargements occur, corresponding with the middle of each protovertebral segment. These grow downward between the neural canal and the mesoblastic tissue forming the protovertebrae, and occupy a position on the lateral wall of the canal. These enlargements are the rudiments of the ganglion of the posterior root; they are at first attached to the neural crest from which they spring, but subsequently this attachment becomes lost, and they then form isolated masses on either side of the neural canal, which now contains the rudimentary cord. They consist of oval cells, from either end of which a process eventually springs; one, passing centrally, grows into the embryonic cord and constitutes the posterior root of the nerve; the other, growing peripherally, joins the fibres of the anterior root to form the spinal nerve. The anterior root is, according to the recent researches of His, a direct out- growth of certain cells which are found in the rudimentary cord, and which are named neuroblasts. These cells, like those mentioned above, are oval, and have a prolongation directed outward toward the surface of the cord. These processes pass out of the cord in bundles and penetrate the mesoblast and join with fibres of the posterior root, and from the point of union the nerve grows toward its peripheral termination. Most of the cranial nerves are developed in the same manner as the posterior roots of the spinal nerves. That is to say, the neural crest, developed from the epiblast, is continued onward, along the dorsal surface of the cephalic portion of the neural tube, as far as the mid-brain. From this a series of swellings at irregular intervals form the rudimentary ganglia, from the polar cells of which the nerve is formed and its connection with the brain established. This appears to be the case with the third, fifth, the facial, the auditory, the glosso-pharyngeal, and the pneumogastric and probably the fourth. With regard to the mode of origin of the sixth, the spinal accessory, and the hypoglossal, our knowledge is not so exact, but they would appear to arise, like the anterior roots of the spinal nerves, from groups of oval cells (neuroblasts) in the basal laminae. The olfactory tract and bulb is a protrusion of the antero-ventral part of each cerebral hemisphere. This protrusion comes in contact with the thickened epiblast of the olfactory area (see page 125), from which neuroblastic cells, which are formed within the area, pass out and form a ganglion between the area and the olfactory bulb. From this ganglion cell-processes grow centripetally to form the nerve-roots, and centrifugally to form the olfactory nerves which ramify on the Schneiderian membrane. The optic nerve arises in a manner entirely different from any of the other cranial nerves, as a hollow outgrowth of the brain, which subsequently becomes solid. It will be considered in connection with the development of the eye. The sympathetic nerves are developed as outgrowths from the gangliated roots of the spinal and cranial nerves. Development of the Eye.-The nervous elements and non-vascular parts of the eye are formed from the epiblast, and the vascular portions from the meso- blast; but the method of development is somewhat complicated. The essential portion of the eye-i. e. the retina and the parts immediately connected with it THE EYE. 123 -is an outgrowth from the rudimentary brain (primitive ocular vesicle), and this outgrowth is met by an ingrowth from the common epidermic or corneous layer of the epiblast, out of which the lens and the conjunctival and corneal epithelium are developed. The first appearance of the eye consists in the protrusion or evolution from the medullary wall of the thalamencephalon, or inter-brain, of a vesicle, called the primitive ocular vesicle. This is at first an open cavity communicating by a hollow stalk with the general cavity of the cerebral vesicle. As development advances the hollow stalk becomes solid, and thus the optic nerve is formed, receiving, how- ever, in a way presently to be explained, mesoblastic elements for the formation of its central artery and connective tissue. As the primitive ocular vesicle is pro- longed forward, it meets the epidermic layer of the epiblast, which at the point of contact becomes thickened, and then forms a depression which gradually encroaches on the most prominent part of the primitive ocular vesicle, which in its turn appears to recede before it, so as to become at first depressed and then inverted in the manner indicated by the annexed figure (Fig. 94, a), so that the cavity is finally almost obliterated by the folding back of its anterior half, and the original sac converted into a cup-shaped cavity, the ocular cup, in which the involuted epiblastic layer, the rudiment of the lens, is received (Fig. 94, b). This cup- shaped cavity consists therefore of two layers: one, the outer, originally the posterior half of the primitive ocular vesicle, is thin, and eventually forms the pigmental layer of the retina;1 the other layer, the inner, originally the anterior or more prominent half, which has become folded back, and is much thicker, is converted into the nervous layers of the retina. Between the two are the remains of the cavity of the original primary vesicle, which finally becomes obliterated by the union of its two layers. As development proceeds the cup- shaped cavity or ocular cup increases in size, and thus a space is formed between it and the rudimentary lens which it contains ; this is the secondary ocular vesicle, and in it the vitreous humor is developed (Fig. 94, c). The folding in of the primary optic vesicle to produce the optic cup proceeds from above downward, and grad- ually surrounds the lens, but leaves an aperture or fissure below, the choroidal fissure or ocular cleft, through which vascular elements, within the vesicle and derived from the mesoblast, retain their con- nection with the rest of the mesoblast. This gap or cleft is continued for some distance Fig. 94.-Diagram of development of the lens a b c. Different stages of development. 1. Epidermic laver. 2. Thickening of this layer. 3. Crystalline depression. 4. Primitive ocular vesicle, its anterior part pushed back by the crystalline depression. 5. Posterior part of the primi- tive ocular vesicle, forming the external layer of the sec- ondary ocular vesicle. 6. Point of separation between the lens and the epidermic layer. 7. Cavity of the secondary ocular vesicle, occupied by the vitreous. Fig. 95.-Diagrammatic sketch of a vertical longitudinal section through the eyeball of a human foetus of four weeks. (After Kolliker). Magnified 100 diameters. The section is a little to the side, so as to avoid passing through the ocular cleft, c. The cuticle, where it becomes later the cornea. I. The lens. op. Optic nerve formed by the pedicle of the primary optic vesicle, vp. Pri- mary medullary cavity of the optic vesicle, p. The pigment-layer of the outer wall. r. The inner wall forming the retina, vs. Secondary optic vesicle containing the rudiment of the vitreous humor. into the stalk of the optic vesicle, and thus allows a process of the mesoblast to extend down the stalk to form the arteria centralis retinae and its accompanying 1 This layer forms functionally part of the choroid, and was formerly described as belonging to this membrane; it is now described as part of the retina, on account of its method of development. 124 DE VEL OPMENT. vein. The lens is at first a thickening of the epiblast; then a depression or involu- tion takes place, thus forming an open follicle, the margins of which gradually approach each other and coalesce, forming an enclosed cavity of epiblastic cells (Fig. 94). At the point of involution the external layer of epiblast separates from the ball of the lens and passes freely over the surface, so that the lens becomes dis- connected from the epiblastic layer from which it was developed, and recedes into the ocular cup, while the cuticular layer covering it is developed into the corneal epithelium. The cells forming the posterior or inner wall of the cavity, which is to form the lens, rapidly increase in size, becoming elongated and developed into fibres, and, filling up the cavity, convert it into a solid body. The cells on the anterior wall undergo no change and retain their cellular character. The secondary ocular vesicle, or space between the lens and the hollow of the ocular cup (Fig. 94, c 7. and 95), contains a quantity of mesoblastic tissue continuous through the ocular cleft with the rest of the mesoblast, and into this blood-vessels project themselves through the ocular cleft. The iris and ciliary processes are formed from this vas- cular tissue, and the choroid is developed in the mesoblast surrounding the ocular vesicle. A portion of this tissue also becomes converted into the vitreous humor, and surrounds the lens with a vascular membrane-the vascular capsule of the lens, which is connected with the termination of the temporary artery (hyaloid) that forms the continuation of the central artery of the retina through the vitreous chamber. This vascular capsule of the crystalline lens forms the membrana pupillaris (described on a subsequent page), and also attaches the borders of the iris to the capsule of the lens. It disappears about the seventh month. The eyelids are formed at the end of the third month as small cutaneous folds, which come together and unite in front of the globe and cornea. This union is broken up and the eyelids separate before the end of foetal life. The lachrymal canal appears to result from the non-closure of a fissure which exists between the lateral plates of the fronto-nasal and maxillary processes., Born, however, considers that it is formed by a thickening of the deeper layer of the epidermis which sinks into the corium and subsequently becomes hollowed out into a tube. Development of the Ear.-The first rudiment of the ear appears shortly after that of the eye, in the form of a thickening of the epiblast, on the outside of that part of the third primary cerebral vesicle which eventually forms the medulla oblongata, opposite the dorsal end of the second pharyngeal arch. The thicken- ing is then followed by an involution of the epiblast, which becomes deeper and deeper, sinking toward the base of the skull, and a flask-shaped cavity is formed; by the narrowing uf the external aperture the neck of the flask constitutes the recessus labyrinthi. The mouth of the flask then becomes closed, and thus a shut sac is formed, the primitive auditory or otic vesicle, which by its sinking inward comes to be placed between the ali-sphenoid and basi-occipital matrices. From it the internal ear is formed. The middle ear and the Eustachian tube are developed from the remains of the first branchial cleft, while the pinna and external meatus are developed from the soft parts overhanging the posterior mar- gin of the same cleft. The primary otic vesicle becomes imbedded in a mass of mesoblastic tissue, which rapidly undergoes chondrification and ossification. It, as before stated, is at first flask- or pear-shaped, the neck of the flask, or recessus labyrinthi, prolonged backward, forms the aquaeductus vestibuli. From it are given off certain prolongations or diverticula, from which the various parts of the labyrinth are formed. One from the anterior end gradually elongates, and, form- ing a tube bends on itself from left to right and becomes the cochlea. Three others, which appear on the surface of the vesicle, form the semicircular canals. Of these, the one which is to constitute the external semicircular canal does not appear at such an early date as the other two. Subsequently, a constriction takes place in the original vesicle, which, gradually increasing, divides it into two, and from these are formed the utricle and saccule. Finally, the auditory nerve, which has been developed from the "neural crest '' in the manner above described (page THE NOSE. 125 122), pierces the auditory capsule in two main divisions-one for the vestibule, the other for the cochlea. The middle ear and Eustachian tube are the remains of the first pharyngeal or branchial cleft (hyo-mandibular), and are, from an early period, closed by the formation of the membrana tympani, which consists of a layer of epiblast externally, a layer of hypoblast internally, and between the two of mesoblastic tissue constituting its fibrous and vascular layer. With regard to the exact mode of development of the ossicles of the middle ear there is consider- able difference of opinion. By some the malleus is believed to be developed from the proximal end of the mandibular (Meckel's) cartilage, and the incus from the proximal end of the hyoidean cartilage. Others, again, believe that they are both developed from the mandibular cartilage. A third group of observers believe that they are developed from a hyo-mandibular cartilage, similar to that which in some of the lower animals forms a suspensory apparatus for both mandibular and hyoidean arches. The stapes is believed by some to be formed by a deposit of cartilaginous cells around the fenestra ovalis; by others it is supposed to be developed from the proximal end of the hyoidean arch. The external auditory meatus is developed, like the pinna, from the soft parts on the posterior margin of the first visceral cleft by an outgrowth of the tissues in this situation. Development of the Nose.-The olfactory fossae, like the primary auditory vesicles, are formed in the first instance by a thickening and involution of the epiblast, which takes place at a point below and in front of the ocular vesicle (Fig. 92, 2, 3). The thickening appears at a very early period, about the fourth week. The borders of the involuted portion very soon become prominent, in con- sequence of the development of the mid-frontal and lateral naso-frontal plates above spoken of (page 119), which are formed on either side of the rudimentary fossse. As these processes increase the fossae deepen and become converted into a deep channel, which eventually forms the upper part of the nasal fossae-that is, the two superior meatuses, the part to which the olfactory nerves are dis- tributed. At this time they are continuous with the buccal cavity, a portion of which forms the lower part, or inferior meatus of the nasal fossae. For as the palatine septum is formed the buccal cavity is divided into two parts, the upper of which forms the lower part of the nasal fossae, while the remainder forms the permanent mouth. The soft parts of the nose are formed from the coverings of the frontal pro- jections and of the olfactory fossae. The nose is perceptible about the end of the second month. The nostrils are at first closed by epithelium, but this disappears about the fifth month. The olfactory nerve, as above pointed out, is formed from the anterior cerebral vesicle as a secondary vesicle on its under surface, and it lies upon the involuted epiblast, which subsequently forms the nasal fossae. Development of the Skin, Glands, and Soft Parts.-The epidermis is produced from the external, the true skin from the middle, blastodermic layer (Fig. 79, 19, 20). About the fifth week the epidermis presents two layers, the deeper one cor- responding to the rete mucosum. The subcutaneous fat forms about the fourth month, and the papillae of the true skin about the sixth. A considerable desqua- mation of epidermis takes place during foetal life, and this desquamated epidermis, mixed with a sebaceous secretion, constitutes the vernix caseosa, with which the skin is smeared during the last three months of foetal life. The nails are formed at the third month, and begin to project from the epidermis about the sixth. The hairs appear between the third and fourth months in the form of depressions of the deeper layer of the epithelium, which then become inverted by a projection from the papillary layer of the skin. The papillae grow into the interior of the epithelial layer; and finally, about the fifth month, the foetal hairs (lanugo) appeal- first on the head and then on the other parts. These hairs drop off after birth, and give place to the permanent hairs. The cellular structure of the sudorifer- ous and sebaceous glands is formed from the epithelial layer, while the connective 126 DE VEL OPMENT. tissue and blood-vessels are derived from the mesoblast about the fifth or sixth month. The mammary gland is also formed: partly from mesoblast-its blood- vessels and connective tissue; and partly from epiblast-its cellular elements. Its first rudiment is seen about the third month, in the form of a small projection inward of epithelial elements, which invade the mesoblast; from this similar tracts of cellular elements radiate; these subsequently give rise to the glandular follicles and ducts. The development of the former, however, remains imperfect, except in the adult female, and especially after pregnancy. Development of the Limbs.-The upper and lower limbs begin to project, as buds, from the anterior and posterior part of the embryo about the fourth week. These buds are formed by a projection of the somatopleure (z. e. the outer layer of the mesoblast and the epiblast), from the point where the mesoblast splits into its parietal and visceral layers, just external to the vertebral somites, of which they may be regarded as lateral extensions. The division of the terminal portion of the bud into fingers and toes is early indicated, and soon a notch or constric- tion marks the future separation of the hand or foot from the forearm or leg. Next, a similar groove appears at the site of the elbow or knee. The indifferent tissue or blastema, of which the whole projection is at first composed, is differen- tiated into muscle and cartilage before the appearance of any internal cleft for the joints between the chief bones. The muscles become visible about the seventh or eighth week. The source of their development is not completely determined for the muscles of the limbs. The vertebral muscles appear to be developed from the " muscle-plates " of the primi- tive vertebral disks (page 105, see Fig. 79, c, 13), and the muscles of the neck and jaws, as well as those which enclose the cavities of the thorax and abdomen, are also formed from the same source. They do not meet in the middle line of the body till about the fourth month. The cutaneous muscles are developed from the cutaneous portion of the middle blastodermic layer. Development of the Blood-vascular System.-There are three distinct stages in the development of the circulatory system before it arrives at its complete or adult condition, in accordance with the manner in which nourishment is provided for at different periods of the existence of the individual. In the first stage there is the vitelline circulation, during which nutriment is extracted from the yolk or contents of the vitelline membrane. In the second stage there is the placental circulation, which commences after the formation of the placenta, and during which nutrition is obtained by means of this organ from the blood of the mother. In the third stage there is the complete circulation of the adult, commencing at birth, and during which nutrition is provided for by the organs of the individual itself. 1. The vitelline circulation is carried on partly within the body of the embryo and partly external to it in the vascular area of the yolk. It consists of a median tubular heart, from which two vessels (arteries) project anteriorly. These carry the blood to a plexus of capillaries spread over the area vasculosa, and also, though to a less extent, in the body of the embryo. From this plexus the blood is returned by two vessels (veins) which enter the heart posteriorly, and thus a complete cir- culation is formed. In these vessels and the heart a fluid (blood') is contained, in which rudimentary corpuscles are found. The mode of formation of these elementary parts will have first to be considered. In mammalia the heart is formed by a hollowing out or vacuolation of a longi- tudinal group of mesoblastic cells on either side of the median line in front of the anterior extremity of the rudimentary pharynx, at about the level of the posterior primary cerebral vesicle. This vacuolation takes place in the visceral layer of the mesoblast, and round the cavity thus formed the layer becomes folded or redupli- cated, and presents two distinct strata of cells ; the inner and thinner layer forms the endocardium, the outer and thicker the muscular wall of the heart. In its very earliest and primitive condition the heart consists therefore of a pair of THE BLOOD-VASCULAR SYSTEM. 127 tubes, one on either side of the body. These, however, soon coalesce in the median line, and, fusing together, form a single central tube.1 Each of the two primary tubes receives posteriorly a large vessel (a vein), and is prolonged ante- riorly into a second vessel (an artery). So that after fusion of the heart-tubes has taken place, there is, in the primitive vitelline circulation, as above mentioned, a single tubular heart, with two arteries proceeding from it and two veins emptying themselves into it. The earliest vessels are also formed in the visceral layer of the mesoblast. They are developed from that part of the mesoblast which sur- rounds the portion of blastoderm which is occupied by the developing body of the embryo, and which is known as the "vascular area." So that the first blood- vessels are developed outside the body of the embryo. The indifferent cells of which this layei' is composed become "vacuolated;" that is, they become enlarged, and spaces are formed within them. The nuclei of these enlarged cells multiply; some few of the proliferated nuclei remain imbedded in the walls of the cell, but the greater number of them are free and are converted into blood-corpuscles. The vacuolated cells fuse together, forming cavities, and also give off processes which unite with processes of other cells : these in their turn become also vacuolated, and, communicating with the cavities in the original cells, a network of tubes is produced (Fig. 96). The tubes or primary vessels consist in the first instance of the original protoplasm of the cell, with here and there nuclei derived from the original divided nucleus imbedded in it. Then differentiation of the protoplasm into flattened cells around these nuclei takes place, and constitutes the wall of the capillary or the lining membrane of the larger vessel. In these latter other cells, derived from the mesoblast, apply them- selves externally and form the other coats of the vessel at a later period. The blood-disks are formed from the original divided nucleus of the vacuolated mesoblastic cells. They are free, and accumulate, each one around itself, a small quantity of the protoplasm of the cell, which rapidly acquires a tinge of color. The earliest blood-corpuscles are therefore at first nucleated, and in this and other re- spects resemble the white corpuscles. As soon, however, as the liver is formed, true white corpuscles make their appearance, and it seems that the chief source from which they are derived is the embryonic liver, though later on the spleen and lymphatic glands take up this function and continue it after birth. The nucleated condition of the red globules ceases before birth. The precise mode in which the nucleated white corpuscle is converted into the non-nucleated red blood-globule, whether by a change in the whole cell or by the disappearance of the cell and persistence of its nucleus, is not yet ascertained. The vitelline circulation commences about the fifteenth day and lasts till the fifth week. When fully established it is carried on as follows: Proceeding from the tubular heart are two arteries, the first aortic arteries (Fig. 97), which unite at some distance from the heart into a single artery. This runs down in front of the primitive vertebrae and in the walls of the intestinal cavity, and again divides into two primitive aortce or vertebral arteries, and these give off five or six omphalo-mesenteric arteries, which ramify in that part of the blastoderm which surrounds the developing body of the embryo, and which is known as the vascular area. They terminate peripherally in a circular vessel-the terminal Fig. 96.-Various forms of mother-cells under- going development into blood-vessels, from the middle layer of the chick's blastoderm. (Klein.) a. Large mother-cell vacuolated, forming the rudi- mentary vessel, b. The wall of this cell formed of protoplasm, with nuclei imbedded, and in some cases more or less detached and projecting, c. Processes connected with neighboring cells, formed of the common cellular substance of the germinal area. d. Blood-corpuscles, f. Small mother-cells -vacuolation commencing. B. Mother-cell in which only obscure granular matter is found. 1 In most fishes and in amphibia the heart originates as a single median tube. 128 DE VEL OPMENT. sinus. This vessel surrounds the vascular portion of the germinal area, but does not extend up to the anterior end of the embryo. It terminates on either side in a vein called the omphalo-mesenteric. The two omphalo-mesenteric veins open into the opposite extremity of the heart to that from which the arteries proceeded. 2. The Placental Circulation.-As the umbilical vesicle diminishes, the allantois, which is formed by a protrusion from the lower part of the intestine, enlarges and becomes converted into a vascular chorion, a part of which forms the placenta. When the umbilical vesicle disappears this be- comes the only source of nutrition for the embryo. The allantois carries with it two arteries, derived- from branches of the primitive aorta, and two veins; these vessels become much enlarged as the placental circulation is established, but subse- quently one of the veins disappears, and in the later stages of uterine life the circulation is car- ried on between the foetus and the placenta by two arteries and one vein (umbilical). During the occurrence of these changes great alterations take place in the prim- itive heart and blood-vessels, above alluded to, which will now require description. Further Development of the Heart.-The simple median tube, formed by the coalescence of the pair of tubes of which the primitive heart consists, becomes elongated and bent on itself, so as to form a S-shaped tube, the anterior part of the tube bending over to the right, and the posterior to the left. At the same time the middle portion is protruded forward and arches transversally from right to left and at the same time becomes twisted on itself, so that the extremity from which the arteries are prolonged is situated in front and to the right, and that into which the veins enter is behind and to the left. The bent tube then becomes divided by two transverse constrictions into three parts. One, the posterior, becomes the auricles, the middle one forms the two ventricular cavities, while the anterior forms the aortic bulb, from which the commencement of the aorta and pulmonary artery is developed. A division of each of these cavities now takes place, so as to convert them into right and left ventricle, right and left auricle, and aorta and pulmonary artery respectively. This division first takes place in the middle portion of the tubular heart, the rudimentary ventricular cavities (Fig. 97, a, 5). A partition rises up from the lower part of the right wall of this cavity, and gradually grows up until it reaches the constrictions which separate it from the other two, and thus the interventricular septum is completed. At the same time a cleft appears on the outside, a little to the right of the most prominent point, which ultimately becomes the apex of the heart. The cleft becomes less marked as development progresses, but remains to some extent persistent throughout life as the interventricular groove. The first appearance of a division in the posterior or auricular portion of the tubular heart makes its appearance, at a very early period of development, in the shape of two projecting pouches, one on either side; these are the rudiments of the auricular appendages, but the actual division of the cavity by a septum does not occur until some time after the appearance of the ventricular septum. This is formed by the growth of a partition from the anterior wall of the auricular cavity, which grows backward, and partially separates the cavity into two. The partition, however, is not completed until after birth, a part remaining unde- veloped, and thus permitting of a communication (foramen ovale) between the two auricles during the whole of foetal life. In a like manner the aortic bulb is divided into two by the growth of a septum downward, from the distal end of the bulb, which divides the cavity into the permanent aorta and the pulmonary artery. Fig. 97.-Heart at the fifth week. a. Opened from the abdominal aspect. 1. Arterial sinus. 2. Aortic arches uniting behind to form the descending aorta. 3. Auricle. 4. Auriculo-ven- tricular orifice. 5. Commencing septum ventriculorum. 6. Ventricle. 7. In- ferior vena cava. b. Posterior view of the same. 1. Trachea. 2. Lungs. 3. Ventricles. 4,5. Auricles. 6. Diaphragm. 7. Descending aorta. 8, 9,10. Pneumo- gastric nerves and their branches. THE ARTERIES. 129 Very soon a superficial furrow appears on the external surface of this portion of the heart corresponding to the septum internally, and, becoming deeper, the two vessels are gradually separated from each other through the septum, in the imme- diate neighborhood of the ventricular portion of the heart, whilst beyond this they still remain joined together, and give origin to the fourth and fifth aortic arches, presently to be described. Further Development of the Arteries.-In the vitelline circulation two arteries were described as coming oft' from the primitive heart, and running down in front of the developing vertebrae. The first change consists in the fusion of these arteries into one at some distance from the heart, thus forming the descending thoracic and abdominal aorta. In consequence of the heart falling backward to the lower part of the neck and then into the thorax as the head is developed, the two original arteries, proceeding from the heart to the point of fusion in the com- mon descending aorta become elongated, and assume an arched form, curving backward on each side, from the front of the body toward the vertebral column (Fig. 98, a). These are the first or primitive aortic arches. As the heart recedes into the thorax, and these arches, which correspond in position to the first pharyn- geal or mandibular arch, become elongated, four pairs of arches are formed behind Fig. 98.-Diagram of the formation of the aortic arches and the large arteries, i.n. in. iv. v. First,second, third, fourth, and fifth aortic arches, a. Common trunk from which the first pair spring; the place where the succeed- ing pairs are formed is indicated by dotted lines, b. Common trunk, with four arches and a trace of the fifth, c. Common trunk, with the three last pairs, the first two having been obliterated, d. The persistent arteries, those which have disappeared being indicated by dotted lines. 1. Common arterial trunk. 2. Thoracic aorta. 3. Right branch of the common trunk which is only temporary. 4. Left branch, permanent. 5. Axillary artery. 6. Vertebral. 7, 8. Subclavian. 9. Common carotid. 10. External; and 11, Internal carotid. 12. Aorta. 13. Pulmonary artery. 14,15. Right and left pulmonary arteries. them around the pharynx (Fig. 98). The arches, five in number, remain per- manent in fishes, giving off from their convex borders the branchial arteries to supply the gills. In many animals the five pairs do not exist together, for the first two have disappeared before the others are formed; but this is not so in man. where all five arches are present and pervious during a certain period of embryonic existence. Only some of the arches in mammalia remain as permanent structures; other arches, or portions of them, become obliterated or disappear. The first two arches entirely disappear. The third remains as a part of the internal carotid artery, the remainder being formed by the upper part of the posterior aortic root- i. e. the descending part of the original vessel which proceeded from the rudiment- ary tubular heart. The common and external carotid are formed from the ante- rior aortic root; that is, the ascending portion of the same primitive vessel. The fourth arch on the left side becomes developed into the permanent arch of the aorta in mammals; but in birds it is the fourth arch on the right side which forms the aortic arch ; while in reptiles the fourth arch on both sides persists, as there is a permanent double aortic arch. The fourth arch on the right side forms the subclavian artery, and by the junction of its commencement with the anterior aortic root, from which the common carotid is developed, it forms the innominate artery.1 The fifth arch on the left side forms the pulmonary artery and the duc- tus arteriosus; that on the right side becomes atrophied and disappears. The first part of the fifth left arch remains connected with that part of the bulbous aorta 1 This is interesting in connection with the position of the recurrent laryngeal nerve, which is thus seen to hook round the same primitive foetal structure, which becomes on the right side the sub- clavian artery, on the left the arch of the aorta. 130 DE VEL 0 PMENT. which is separated as the pulmonary stem, and with it forms the common pul- monary artery. From about the middle of this arch two branches are given off', which form the right and left pulmonary arteries respectively, and the remaining portion-i. e. the part beyond the origin of the branches, communicating with the left fourth arch, that is, the descending part of the arch of the aorta-constitutes vagus nerve. external '' carotid. internal carotid. common carotid.' recurrent, laryngqX nervS .vertebral, arch of aorta. right / subclavian. '.left subclavian. - arteriosus. innominate / artery. pulmonary ' ' trunk. ascending, aorta. descending aorta. Fig. 99.-Diagram to show the destination of the arterial arches in man and mammals. (Modified from Rathke. From Quain's Anatomy, vol i. pt. 1,1890.) The truncus arteriosus and the five arterial arches springing from it are represented in outline only ; the permanent vessels in colors-those belonging to the aortic system red, to the pulmonary system blue. the ductus arteriosus. This duct remains pervious during the whole of foetal life, and after birth becomes obliterated. The development of the arteries in the lower part of the body is going on dur- ing the same time. We have seen that originally there were two primitive arteries coming off' from the primary tubular heart, and that these two vessels, at some distance from the heart, became fused together to form a single median artery, which coursed down in front of the vertebrae to the bottom of the spinal column, forming the permanent descending aorta. From the extremity of this the two vitelline arteries, which were originally parts of the primitive main trunks, pass to the area vasculosa. As the umbilical vesicle dwindles and the allantois grows, two large branches are formed as lateral offshoots of the median aorta. These are the two umbilical or hypogastric arteries, and are concerned in the placental circu- lation. The portion of the median aorta beyond this point becomes much dimin- ished in size, and eventually forms the sacra media artery, and thus the two umbilical branches become in appearance bifurcating branches of the main aorta. The common and internal iliac arteries are developed from the proximal end of these umbilical arteries; the middle portion of the vessel, after birth, becomes partially atrophied, but in part remains pervious as the superior vesical artery ; the distal portion becomes obliterated, constituting part of the superior ligament of the bladder. The external iliac and femoral arteries are developed from a small branch given oft' from the umbilical arteries near their origin, and are at first of comparatively small size. Development of the Veins.-The formation of the great veins of the embryo may be best considered under two groups, visceral and parietal. THE VEINS. 131 The visceral are derived from the vitelline and umbilical veins. In the earliest period of the circulation of the embryo, we have seen that there were two veins (vitelline or omphalo-mesenteric) returning the blood from the vitelline membrane. These unite together to form a single channel, the venosus, which opens into the auricular extremity of the heart. As soon as the placenta begins to be formed two umbilical veins appear and open into the sinus venosus, close to the vitelline veins. The two vitelline veins enter the abdomen and run upward on either side of the intestinal canal; at the upper part of the abdomen, in the site of the future liver, which now begins to form around them, transverse communications are formed, which encircle the duodenum and enclose it in two vascular rings. The portion of veins above these vascular rings loses its connection with the sinus, while the portion between them breaks up into a capillary plexus, which ramifies in the now partially developed liver together with capillary vessels from the upper venous ring. Of these latter, some pass toward the heart and join the sinus. They have received the name of the vence hepaticce revehentes, and eventually become the hepatic veins; others ramify in the liver, under the name of vence hepaticce advehentes, and become the branches of the portal vein. The lower vascular ring receives veins from the stomach and intestines, and becomes the commencement of the portal vein. The umbilical veins at first open into the sinus venosus near to the vitelline veins. Subsequently this communication becomes interrupted by the develop- Fig. 100.-Diagrams illustrating the development of the great veins. The first figure shows the vertebral veins emptying into the heart by two lateral trunks, "the ducts of Cuvier." The second figure shows the form- ation of the iliac and subclavian veins, a. Inferior vena cava. b. Left innominate vein. The third figure shows the vertebral veins much diminished in size and the duct of Cuvier, on the left side, gradually dis- appearing. c. Vena azygos minor. The fourth figure shows the adult condition of the venous system. 1. Right auricle of heart. 2. Vena cava superior. 3. Jugular veins. 4. Subclavian veins. 5. Vena cava inferior. 6. Iliac veins. 7. Lumbar veins. 8. Vena azygos major. 9. Vena azygos minor. 10. Superior intercostal vein. (After Dalton.) merit of a vascular network; the vein on the right side atrophies and disappears, while that on the left side greatly enlarges, as the placental circulation becomes established, and communicates with the upper venous circle of the vitelline cir- culation. Finally a branch is formed between the upper venous circle and the right hepatic veins, which becomes the ductus venosus, and by it most of the blood from the umbilical vein is carried direct to the heart. The Parietal Veins.-The first appearance of a parietal system consists in the appearance of two short transverse veins (the ducts of Cuvier), which open on either side of the auricular portion of the heart. Each of these ducts is formed by an ascending and descending vein. The ascending veins return the blood from the parietes of the trunk and the Wolffian bodies, and are called cardinal veins. 132 DE VEL OPMENT. The two descending ones return the blood (Fig- 100) from the head, and are called primitive jugular veins. As the kidneys are developed, the veins conveying the blood from them unite together to form a single trunk which passes up the abdomen behind the intestines, and, jqining the common trunk of the vitelline and umbilical veins above the point of entrance of the venae revehentes, constitutes the inferior vena cava. Two small veins receiving branches from the lower extremity unite to form the lower part of the inferior vena cava, below the point of entrance of the veins from the kidneys. These are the primitive iliac veins, and in their course upward they cross the cardinal veins and communicate with them. The part of the iliac vein between this point of communication and their junction with one another constitutes the common iliac vein ; while the distal portion forms the external iliac vein. The internal iliac vein is formed from that part of the cardinal vein which lies below the point of communication. The greater part of the remainder of the car- dinal vein-that is to say, of that portion above the iliac veins-becomes obliter- ated ; a small part, however, at the upper extremity remains persistent, and becomes continuous with two new veins, which are formed one on either side of the vertebral column. These veins receive the intercostal and lumbar veins, and eventually form the azygos veins. They become joined by an oblique communicat- ing branch, which crosses the middle line, and constitutes the junction of the vena azygos minor with the vena azygos major. These veins are termed the posterior vertebral veins of Rathke. The upper part of the left one, with its continuation, the car- dinal vein, forms the superior intercostal of the left side. The veins first formed in the upper part of the trunk are, as above stated, the prim- itive jugular veins. In the greater part of their extent they become the external jug- ular vein. Shortly, two small branches may be noticed opening into them near their termination; these form the subcla- vian and internal jugular veins. From the point of junction of these veins on the left side, a communicating branch makes its appearance, running obliquely across the neck downward and to the right, to open into the primitive jugular vein of the right side below the point of entrance of the subclavian vein. At the same time, in consequence of the alteration in the position of the heart, and its descent into the thorax, the direction of the ducts of Cuvier becomes altered, and they assume an almost vertical position. From the portion of the primitive jugular veins, above the branch of communication, the internal jugulars are formed, except that part of the right one which lies between the point of entrance of the subclavian of this side and the termination of the communicat- ing branch, which becomes the right innomi- nate vein. The communicating branch be- comes the left innominate Vein. The primi- tive jugular of the right side, below the com- municating vein and the right duct of Cuvier, become the vena cava superior, into which the right cardinal (vena azygos major) enters. The lower part of the left primitive jugular, and the left duct of Cuvier becomes almost entirely obliterated, except the lower end, which remains as a Fig. 101.-Diagram of the forma tion of the main systemic veins, a. Heart and venous system at the period when there are two venae c'avae superiores, posterior view. 1. Left superior cava. 2. Right superior cava. 3. Inferior cava. 4. Left inferior cardinal. 5. Right inferior cardinal. 6. Right jugular. 7. Anastomosing branch between the jugulars (left innominate). 8. Subclavian. 9. Internal jugular. 10. External jugular. 11. Middle obliterated portion of the posterior cardinal veins. 12. Newly-formed posterior vertebral veins. 13. Anastomosis between the two ver- tebrals-trunk of small azygos. 14. Iliac veins, proceeding from anastomosis between the inferior cava and posterior cardinals. 15. Crural. 16. Hypogastric-originally the distal ends of the cardinals, b. Heart and perma- nent veins, posterior view. 1. Obliterated left superior cava. 6. Right innominate. 7. Left innominate. 8. Subclavian. 10. Jugular. 13. Trunk of the small azygos. 17. Coronary sinus receiving the coronary vein. 18. Superior in- tercostal. 19. Superior small azygos. 20. Inferior small azygos. THE ALIMENTARY CANAL. 133 fibrous band, or sometimes a small vein, and runs obliquely over the posterior sur- face of the left auricle. The termination of the left duct of Cuvier remains per- sistent, and forms the coronary sinus (Fig. 101). The foetal circulation is described at a future page. Development of the Alimentary Canal.-The development of the intestinal cavity is, as shown above (page 109), one of the earliest phenomena of embryonic life. The original intestine consists of an inflection of the hypoblast extending from one end of the embryo to the other, and is situated just below the primitive vertebral column. At either extremity it forms a closed tube, in consequence of the cephalic and caudal flexures (page 109), and this manifestly divides it into three parts; a front part, enclosed in the cephalic fold, called the fore-gut; a posterior part, enclosed in the caudal fold, the hind-gut; and a central part or mid-gut, Fig. 102.-Diagrammatic outline of a longitudinal vertical section of the chick on the fourtli day. ep. Epiblast, sm. Somatic mesoblast, hy. Hypoblast, vm. Visceral mesoblast, af. Cephalic fold. pf. Caudal fold am. Cavity of true amnion, ys. Yolk-sac." i. Intestine, s. Stomach and pharynx, a. Future anus, still closed. m. The mouth, me. The mesentery, al. The allantoic vesicle, pp. Space between inner and outer folds of amnion. (From Quain's Anatomy, Allen Thomson.) which at this time freely communicates with the umbilical vesicle (Fig. 102). The ends of the fore- and hind-gut do not communicate with the surface of the body, the buccal and anal orifices being subsequently formed by involutions of the epiblast, which later on form communications with the gut. From the fore-gut are developed the pharynx, oesophagus, stomach, and duodenum ; from the hind- gut, a part of the rectum; and from the middle division, the rest of the intestinal tube (Fig. 103). The changes which take place in the fore-gut are as follows: The middle portion becomes dilated to form the stomach, and undergoes a vertical rotation to the right, so that the posterior border, by which it is attached to the vertebral column by a mesentery, is now directed to the left, and the anterior border to the right. At this time it is straight, but it soon undergoes a lateral curve or bend to the right at its upper end. It thus assumes an oblique direction, and the left border (originally the posterior or attached border) becomes inferior, and forms the great cur- vature. The mesentery by which it was attached forms the great omentum. The portion of the fore-gut above this dilatation remains straight, forming the pharynx and oesophagus, and in consequence of the mes- oblast being here undivided, there is no serous investmerft to <his part of the tube. Below this, division of the mesoblast has taken place, and the splanchnopleure Fig. 103.-Early form of the alimentary canal. (From Kolliker, after Bischoff.) In a a front view, and in b an antero-posterior section are represented, a. Four pharyngeal or visceral plates, b. The pharynx, c, c. The commencing lungs, d. The stomach. /, f. The diverticula connected with the formation of the liver. <7. The yolk-sac into which the middle intestinal groove opens, h. The posterior part of the intestine. 134 I) E VEL OPMENT. alone forms the walls of the remainder of the intestinal canal, the space between this layer and the somatopleure constituting the pleuro-peritoneal cavity. The part of the fore-gut below the dilated stomach forms the duodenum, and in connection with this the liver and pancreas are developed. The hind-gut is also a closed tube, and from it the middle third of the rectum is developed, as well as the allantois (page 113), which will be again referred to in connection with the development of the bladder. The mid-gut is at first an open cavity freely communicating with the umbilical vesicle. As the body-walls grow, this communication contracts very materially, though it still exists to a certain extent, and the open cavity becomes converted into a straight tube, still open where it communicates with the umbilical vesicle. This tube grows rapidly in length, and presents a primitive curve or loop down- ward and forward, and, in consequence of its growth exceeding that of the walls of the body-cavity, a portion of the loop protrudes into the stalk of the umbilical vesicle. At a subsequent period, however, the walls of the abdomen grow more rapidly than the intestine, which again recedes into the body-cavity. At a short distance below the most prominent point of this loop a diverticulum arises, which marks the separation between the large and small intestine. The lower part of this diverticulum forms the vermiform appendix ; the proximal part, by its continued growth, constitutes the caecum. After this the anterior or upper part of the gut, corresponding to the small intestine, rapidly increases in length, and about the eighth week becomes convoluted. The lower or posterior part, corresponding to the large intestine, is at first less in calibre than the upper part, and lies wholly to the left side of the convolutions of the small intestine; but later on the curve of the large intestine begins to form, and the first part (ascending colon) slowly crosses over to the right side, first lying in the middle line, just below the liver. It is not until the sixth month that the caecum descends into the right iliac fossa, and so drags the ascending colon into its normal position in the right Hank. The peritoneal cavity is the space left between the visceral and parietal layers of the mesoblast, and the serous membrane is developed from these structures. The mesenteries are formed from mesoblastic tissue extending between the notochord and the gut which develops the vascular and connective-tissue elements of these parts. The buccal cavity is formed by an involution of the external layers of the blastodermic membrane, which passes inward and meets the pharynx, or upper part of the fore-gut. The two cavities are, however, at first completely separated from each other by all the layers of the blastoderm; but at an early period of development a vertical slit appears between them; this gradually widens and becomes the opening by which the common cavity of the nose and mouth commu- nicates with the pharynx. The common cavity is afterward divided into nose and mouth by the development of the palate, in the manner spoken of above. The tongue appears about the fifth week as a small elevation behind the inferior maxillary arch, to which another projection from the second pharyngeal arch is united. The epithelial layer is furnished by the epiblast. The tonsils appear about the fourth month. The anus is also formed by an inflection of the epiblast, which extends inward to a slight extent, and approaches the termination of the hind-gut, and finally com- municates with it by a solution of continuity in the septum between the two. The persistence of the foetal septum at either the buccal or anal orifices constitutes a well-known deformity-imperforate oesophagus or imperforate rectum, as the case may be. The liver appears after the Wolffian bodies, about the third week, in the form of a bifid mass of cells, connected with the epithelial and mesoblastic layers of the splanchnopleure. It projects from the intestine at that part which afterward forms the duodenum. This mass of cells becomes hollowed out into a cavity, lined by hypoblast, the rudiment of the main duct of the liver, the cells on either side being developed into the right and left lobes. These grow very rapidly around the vitelline and, later, the umbilical veins, which break up into a capillary plexus THE RESPIRATORY AND URINARY ORGANS. 135 and ramify in its substance. About the third month the liver almost fills the abdominal cavity. From this period the relative development of the liver is less active, more especially that of the left lobe, which now becomes smaller than the right; but the liver remains up to the end of foetal life relatively larger than in the adult. The gall-bladder appears about the second month, as an extension of the cavity from which the main duct of the liver is developed; and bile is detected in the intestines by the third month. The pancreas is also an early formation, being far advanced in the second month. It, as well as the .salivary glands, which appear about the same period, originates in a projection from the epithelial layer, which afterwTard forms a cavity, and the lobules of the gland are developed from the ramifications of this cavity. It is generally admitted that the epithelial lining of the ducts is furnished by the hypoblast, in the development of both the pancreas and the liver, and that the vessels owe their origin to the mesoblast. But authorities differ as to the mode of formation of the parenchyma, as to whether this is entirely of mesoblastic origin, or whether the hypoblast shares in its development. The spleen, on the other hand, is apparently entirely of mesoblastic origin, for there is never any connection between the intestinal cavity and the substance of this organ. It originates from the mesenteric fold which connects the stomach to the vertebral column (mesogastrium). Development of the Respiratory Organs.-The lungs appear somewhat later than the liver. They are developed from a small median cul-de-sac or diverticu- lum from the upper part of the fore-gut, immediately behind the fourth visceral cleft, as a projection from the epithelial and fibrous laminae of the intestines. During the fourth week a pouch is formed on either side of the central diver- ticulum, and opens freely through it into the fore-gut (pharynx). From these, other (secondary) pouches are given off, so that by the eighth week the form of the lobes of the lungs may be made out. The two primary pouches have thus a common pedicle of communication with the pharynx. This is developed into the trachea (Fig. 97, b), the cartilaginous rings of which are perceptible about the seventh week. The parts which afterward form the larynx are recognized as early as the sixth week-viz. a projection on either side of the pharyngeal open- ing, which is the rudiment of the arytenoid cartilage and a transverse elevation from the third pharyngeal arch, which afterward becomes the epiglottis; the vocal cords and ventricles of the larynx are seen about the fourth month. Traces of the diaphragm appear in the form of a fine membrane, separating the lungs from the Wolffian bodies, the stomach, and the liver, whilst the heart is still near the head. As the diaphragm extends forward from the vertebral column it separates the common pleuro-peritoneal cavity into two parts, a thoracic and abdominal. Development of the Urinary Organs.-The urinary organs appear to be entirely of mesoblastic origin, and are intimately connected with an embryonic glandular organ first discovered by Wolff, and hence called the Wolffian body. Recent researches have shown that the Wolffian bodies form a part of a set of glands which are found in all vertebrate and some invertebrate animals. These glands have been termed the segmental organs, and consist, in vertebrates, of branching tubes opening at one extremity into the body-cavity, and at the other by one or more main ducts into the cloaca or hind-gut.1 The segmental organ of vertebrates is divided into three parts, each of which possesses an excretory duct. The anterior of the three, situated in the region of the rudimentary heart, is termed the head- kidney or pronephros (Lankester), and its duct is the Mullerian duct. The central part is the Wolffian body, the mesonephros (Lankester), and its duct is the Wolffian duct. The posterior segment is the rudiment of the permanent kidney, and is formed later than the other two. It is named the metanephros (Lankester), and its duct is the ureter. 1 In invertebrates the external openings are on the sides of the body. 136 /) E VEL OPMENT. The segmental organ is perceptible about the third week, forming an elongated ridge of cells situated on either side of the primitive vertebrae and extending from the heart to the lower end of the embryo. It makes its appearance below the heart and behind the common pleuro-peritoneal cavity, from the mesoblast at the point of separation of its two layers into somatopleure and splanchnopleure. As this ridge is situated in front of the epiblast (reflected from the medullary cavity) at the side of the protovertebrae and behind the common pleuro-peritoneal cavity, it has been named "the intermediate cell-mass." It is at first solid, but soon a tube is hollowed out in it, by the formation of a lumen in its most prominent part; this is the segmental duct, the greater part of which forms the Wolffian duct. As the duct is formed it sinks downward and projects into the bodv- cavity. The remainder of the segmental organ-i. e. that part which is not con- cerned in the formation of the duct-becomes converted into tubes, which com- mence as branches from the duct and spread out at right angles with it. They are at first caecal, but soon acquire openings at their inner extremities into the body-cavity, the lower end of the segmental duct at the same time forming an opening into the urogenital sinus. Thus a communication is established through these tubes and duct between the pleuro-peritoneal cavity and the cloaca or hinder part of the alimentary canal. The next step is the formation of a second duct in the neighborhood of the original duct, with which some of the tubules of the anterior part of the segmental body (pronephros) are connected. This is the Mullerian duct. The ureter, which is formed later, is an offshoot from the hinder part of the Wolffian duct. The structure of the Wolffian body is in many respects analogous to that of the permanent kidney (Fig. 104). It is composed partly of an excretory canal or duct, into which open numerous " con- duits," rectilinear at first, but afterward tortuous, and partly of a cellular or glandular structure, in which Malpig- hian tufts are found. It is fixed to the diaphragm by a superior ligament, and to the spinal column by an inferior or lumbar ligament. Its office is the same as that of the kidneys-viz. to secrete fluid containing urea, which accumulates in the bladder. When the permanent kidneys are formed, the greater part of the Wolffian body disappears. The rest takes part in the formation of the organs of generation. The functional activity of the Wolf- fian bodies is very transitory; they attain their highest development by the sixth week, after which time they begin to decrease in size and have nearly disappeared by the end of the third month. The upper part of the segmental body, the prone- phros, also undergoes atrophy and disappears. In the male, the Wolffian duct persists, and becomes converted into the vas deferens, the Miillerian duct under- going atrophy; a vestige of it, however, remaining as the sinus prostaticus; whereas, on the other hand, in the female, the Miillerian duct remains and becomes converted into the whole length of the genital passages, while the Wolf- fian duct almost entirely disappears and remains only as a vestige. Prior to this, however, the Wolffian and Miillerian ducts (together with the ureter when formed) open into the common urogenital sinus or cloaca, which is the termination of the intestinal cavity, into which the allantois also opens in front (Fig. 105). As the allantois expands into the urinary bladder this common cavity is divided into two by a septum, to form the bladder in front and the rectum behind. The Wolffian and Mullerian ducts are soon connected by cellular substance into a single mass-the genital cord-in which the Wolffian ducts lay side by side in Fig. 104.-Enlarged view from the front of the left Wolffian body before the establishment of the distinction of sex.' (From Farre, after Kobelt.) a, a, l>, d. Tubular structure of the Wolffian body. e. Wolffian duct. f. Its upper extremity, <7. Its termi- nation in x, the urogenital sinus, h. The duct of Midler, i. Its upper, still closed, extremity, k. Its lower end, terminating in the urogenital sinus. I. The mass of blastema for the reproductive organ, ovary or testicle. THE URINARY AND GENERATIVE ORGANS. 137 front, and the ducts of Muller behind, at first separate, but later on uniting with each other. It has been stated that the kidney is developed from the lower part (meta- nephros) of the segmental organ. With this the ureter becomes connected in the following manner: It commences as a tubular diverticulum from the lower part of the segmental duct, close to the cloaca. It extends upward, and becomes divided into a number of caecal tubules, which represent the commencement of the several divisions of the pelvis of the kidney. These tubules are prolonged into the solid blastema of which the kidney at that time consists. The tubules then become convoluted, and masses of cells accumulate on their exterior, so as to give to the organ an appearance of lobulation. Between these cells vessels are developed, and the vascular glomeruli are gradually formed. The kidneys at first, therefore, consist of cortical substance only, but later on the proximal ends of the tubes become straight and arranged in bundles, and thus the pyramidal structure is developed. The lobulation of the kidney is perceptible for some time after birth. The urinary bladder, as before stated, is formed by a dilatation of the lower part of the stalk of the allantois. At the end of the second month this forms a spindle-shaped cavity, the bladder, which communicates with the lower part of the primitive intestine by a short canal, the first part of the urethra. The upper part of the stalk of the allantois, which is not dilated, forms the urachus; this extends up into the umbilical cord, and at an early period of embryonic existence forms a tube of com- munication with the allantois. It is obliter- ated before the termination of foetal life, but the cord formed by its obliteration is percep- tible throughout life, passing from the upper part of the bladder to the umbilicus, and it occasionally remains patent in the adult, constituting a well-known malformation. The suprarenal bodies are developed from two different sources. The medullary part of the organ is of epiblastic origin, and is derived from the tissues forming the sympa- thetic ganglia of the abdomen, while the cor- tical portion is of mesoblastic origin, and originates in the mesoblast just above the kidneys. The two parts are at first quite distinct, but become combined in the process of development. The suprarenal capsules are at first larger than the kidney, but become equal in size about the tenth week, and from that time decrease relatively to the kidney, though they remain, throughout foetal life, much larger in proportion than in the adult. Development of the Generative Organs.- The first appearance of the reproductive organs is essentially the same in the two sexes, and consists in a thickening at one spot of the epithelial layer which lines the peritoneal or body cavity, with a slight increase of the connective tissue beneath it, forming a low ridge. This is termed the genital ridge, and is situated on the mesial side of each Wolffian body, and from it the testicle in the one sex, and the ovary in the other, are developed. The ridge, as the embryo grows, gradually becomes pinched off from the Wolffian body, with which it is at first Fig. 105.-Diagram of the primitive uro- genital organs in the embryo previous to sex- ual distinction. The parts' are shown chiefly in profile, but the Mullerian and Wolffian ducts are seen from the front. 3. Ureter. 4. Urinary bladder. 5. Urachus, ot. The mass of blas- tema from which ovary or testicle is after- ward formed. W. Left Wolffian body. x. Part at the apex from which the coni vascu- losi are afterward developed. u\ w. Right and left Wolffian ducts, m, m. Right and left Mullerian ducts uniting together and with the Wolffian duets in pc, the genital cord. tiff. Sinus urogenitalis. i. Lower part of the intes- tine. cl. Common opening of the intestine and urogenital sinus, cp. Elevation which be- comes clitoris or penis. Is. Ridge from which the labia majora or scrotum are formed. 138 DE VEL OPMENT. continuous, though it still remains connected to the remnant of this body by a fold of peritoneum, the mesorchium or mesovarium. About the seventh week the distinction of sex begins to be perceptible. The epithelium on the genital ridge, which is called "germ-epithelium," in the female becomes distinctly columnar, multiplies rapidly, and begins to form primitive ova, in a manner presently to be described; whereas in the male, though the germ-epithelium has a tendency to become columnar, the cells are, on the whole, flatter and smaller than in the female. Development of Male Organs.-The tubuli seminiferi of the testicle appear at an early period. It is believed that they are formed by the extension of epithelial cells on the surface of the genital ridge, into its blastema; rows of cells are thus developed which become the lining cells of the seminal ducts. In some animals (e.g. reptiles) the segmental tubes of the Wolffian body have been found to extend into the body of the testis, and to form the tubes of this organ, which become lined with cells derived from the germ-epithelium, and it is probable that a similar process takes place in birds and mammals. The Mullerian ducts disappear in the male sex, with the exception of their lower ends. These unite in the middle line, and open by a common orifice into the urogenital sinus. This constitutes the utriculus hominis or sinus prostaticus. Occasionally, however, the upper end of the duct of Muller remains visible in the male, constituting the little pedunculated body, called the hydatid of Morgagni, sometimes found in the neighborhood of the epididymis,1 between the testes and globus major. The head of the epididymis, its canal, the vas deferens, and ejaculatory duct are formed from the canals and duct of the Wolffian body. One or more of the tubes of the Wolffian body form the vas aberrans and a structure described by Giraldes, and called, after him, "the organ of Giraldes," which bears a good deal of resemblance to the organ of Rosenmuller in the other sex. It consists of a number of convoluted tubules lying in the cellular tissue in front of the cord, and close to the head of the epididymis. The descent of the testis and the formation of the gubernaculum are described in the body of the work. Development of Female Organs.-The ovary, as above stated, is formed from the genital ridge, which becomes pinched off from the remains of the Wolffian body, but is still attached by a mesovarium. It consists of a central part of con- nective tissue covered by a layer of germ-epithelium, from which the ova are developed. This epithelium undergoes repeated division, so that it rapidly increases in thickness and forms several layers. Next certain of the cells become enlarged and spherical, and form what are called the primitive ova. Around these, other epithelial cells have a tendency to arrange themselves, so as to enclose the ovum in a follicle. The permanent ova, enclosed in their Graafian follicles, are thus formed. The Fallopian tube is developed from that portion of the duct of Muller which lies above the lumbar ligament of the Wolffian body. This duct is at first com- pletely' closed at its upper extremity, and its closed extremity remains permanent, forming a small cystic body attached to the fimbriated end of the Fallopian tube, and called the " hydatid of Morgagni." Below this a cleft forms in the duct, and is developed into the fimbriated opening of the Fallopian tube. Below this the duct of Muller and the ducts of the Wolffian bodies are united together in a structure called " the genital cord," in which the two Mullerian ducts approach each other, lying side by side, and finally coalesce to form the cavity of the vagina and uterus. This coalescence commences in the middle of the genital cord, and corresponds to the body of the uterus. The upper parts of the Mullerian ducts in the genital cord constitute the cornua of the uterus, little developed in the human species. The only remains of the Wolffian body in the 1 Mr. Osborn, in the St. Thomas's Hospital Reports, 1875, has written an interesting paper point- ing out the probable connection between this fcetal structure and one form of hydrocele. THE ORGANS OF GENERATION. 139 complete condition of the female organs are two rudimentary or vestigial struc- tures, which can be found, on careful search, in the broad ligament near the ovary ; the parovarium or organ of Rosenmuller and the epoophoron (Fig- 106). The organ of Rosenmuller consists of a number of tubes which converge to a transverse portion, the epoophoron, and this is sometimes prolonged into a distinct duct, running transversely, the duct of Gartner, which is much more conspicuous and extends far- ther in some of the lower animals. This is the remains of the Wolffian duct. About the fifth, month an annular constriction marks the posi- tion of the neck of the uterus, and after the sixth month the walls of the uterus begin to thicken. The round liga- ment is derived from the lumbar ligament of the Wolf- fian body, the peritoneum constitutes the broad ligament ; the superior ligament of the Wolffian body dis- appears with that structure (Fig. 107). The external organs of generation, like the internal, pass through a stage in Fig. 106.-Adult ovary, parovarium, and Fallopian tube. (From Farre, after Kobelt). a, a. Epoophoron formed from the upper part of the Wolffian body. b. Remains of the uppermost tubes, sometimes forming hydatids, c. Middle set of tubes, d. Some lower atrophied tubes, e. Atrophied remains of the Wolffian duet. /. The terminal bulb or hydatid, h. The Fallopian tube, originally the duct of Muller. i. Hydatid attached to the extremity. I. The ovary. Fig. 107.-Female genital organs of the embryo, with the remains of the Wolffian bodies. (After J. Muller.) a. From a foetal sheep, a. The kidneys, b. The ureters, c. The ovaries, d. Remains of Wolffian bodies, e. Fallopian tubes. /. Their abdominal openings, b. More advanced, from a foetal deer : a. Body of the uterus, b. Cornua, c. Tubes, d. Ovaries, e. Remains of Wolffian bodies, c. Still more advanced, from the human foetus of three months : a. The body of the uterus, b. The round ligament, c. The Fallopian tubes, d. The ovaries. e. Remains of the Wolffian bodies. which there is no distinction of sex (Fig. 108, II, in). We must therefore describe this stage, and then follow the development of the female and male organs respect- ively. As stated above, the anal depression at an early period is formed by an invo- lution of the external epithelium, and the intestine is still closed at its lower end. When the septum between the two opens, which is about the fourth week, the urachus in front and the intestine behind both communicate with the anal depres- sion. This, which is now called the cloaca, is afterward divided by a transverse 140 DE VEL DEMENT. septum, the perineum, which appears about the second month. Two tubes are thus formed; the posterior becomes the lower part of the rectum, the anterior is Fig. 108.-Development of the external genital organs. Indifferent type, I. II. in, Female. A and b. At the middle of the fifth month, c. At the beginning of the sixth. Male. a'. At the beginning of the fourth month. b'. At the middle of the fourth month, c'. At the end of the fourth month. 1. Cloaca. 2. Genital tubercle. 3. Glans penis or clitoridis. 4. Genital furrow. 5. External genital folds (labia majora or scrotum). 6. Umbilical cord. *. Anus. 8. Caudal extremity and coccygeal tubercle. 9. Labia minora. 10. Urogenital sinus. 11. Fraenum clitoridis. 12. Preputium penis or clitoridis. 13. Opening of the urethra. 14. Opening of the vagina. 15. Hymen. 16. Scrotal raphe. the urogenital sinus. In the sixth week a tubercle, the genital tubercle, is formed in front of the cloaca, and this is soon surrounded by two folds of skin, the genital folds. Toward the end of the second month the tubercle presents, on its lower aspect, a groove, the genital furrow, turned toward the cloaca. All these parts are well developed by the second month, yet no distinction of sex is possible. Female Organs (Fig. 108, a, b, c).-The female organs are developed by an easy transition from the above. The urogenital sinus persists as the vestibule of the vagina, and forms a single tube with the upper part of the vagina, which, as we have already seen, is developed from the united Mullerian ducts. The genital tubercle forms the clitoris, the genital folds the labia majora, and the lips of the genital furrow the labia minora, which remain open. Male Organs (Fig. 108, a', b', c')--In the male the changes are greater. The THE ORGANS OF GENERATION. 141 genital tubercle is developed into the penis, the glans appearing in the third month, the prepuce and corpora cavernosa in the fourth. The genital furrow closes and thus forms a canal, the spongy portion of the urethra. The urogenital sinus becomes elongated and forms the prostatic and membranous urethra. The genital folds unite in the middle line to form the scrotum, at about the same time as the genital furrow closes-viz. between the third and fourth months. The following table is translated from the work of Beaunis and Bouchard, with some alterations, especially in the earlier weeks. It will serve to present a resume of the above facts in an easily accessible form.1 1 It will be noticed that the time assigned in this table for the appearance of the first rudiment of some of the bones varies in some cases from that assigned in the description of the various bones in the sequel. This is a point on which anatomists differ, and which probably varies in different cases. CHRONOLOGICAL TABLE OF THE DEVELOPMENT OF THE FCETUS. (From Beaunis and Bouchard.) First Week.-During this period the ovum is in the Fallopian tube. Having been fertilized in the upper part of the tube, it slowly passes down, undergoing segmentation, and reaches the uterus probably about the end of the first week. During this time it does not undergo much increase in size. Second Week.-The ovum rapidly increases in size and becomes imbedded in the decidua, so that it is completely enclosed in the decidua reflexa by the end of this period. An ovum believed to be of the thirteenth day after conception is described by Reichert. There was no appearance of any embryonic structure. The equatorial margins of the ovum were beset with villi, but the surface in contact with the uterine wall and the one opposite to it were bare. In another ovum, described by His, believed to be of about the fourteenth day, there was a distinct indication of an embryo. There was a medullary groove bounded by folds. In front of this a slightly prominent ridge, the rudimentary heart. The amnion was formed and the embryo was attached by a stalk, the allantois, to the inner surface of the chorion. It may be said, therefore, that these parts, the amnion and the allantois, and the first rudiments of the embryo, the medullary groove, and the heart, are formed at the end of the second week. Third Week.-By the end of the third week the flexures of the embryo have taken place, so that it is strongly curved. The protovertebral disks, which begin to be formed early in the third week, present their full complement. In the nervous system the primary divisions of the brain are visible, and the primitive ocular and auditory vesicles are already formed. The primary circulation is established. The alimentary canal presents a straight tube com- municating with the yolk-sac. The pharyngeal arches are formed. The limbs have appeared as short buds. The Wolffian bodies are visible. Fourth Week.- The umbilical vesicle has attained its full development. The caudal extremity projects. The upper and the lower limbs and the cloacal aperture appear. The heart sep- arates into a right and left heart. The special ganglia and anterior roots of the spinal nerves, the olfactory fossae, the lungs and the pancreas can be made out. Fifth Week.-The allantois is vascular in its whole extent. The first traces of the hands and feet can be seen. The primitive aorta divides into aorta and pulmonary artery. The duct of Muller and genital gland are visible. The ossification of the clavicle and the lower jaw commences. The cartilage of Meckel occupies the first post-oral arch. Sixth Week.-The activity of the umbilical vesicle ceases. The pharyngeal clefts disappear. The vertebral column, primitive cranium, and ribs assume the cartilaginous condition. The posterior roots of the nerves, the membranes of the nervous centres, the bladder, kidney, tongue, larynx, thyroid body, the germs of teeth, and the genital tubercle and folds are apparent. Seventh Week.-The muscles begin to be perceptible. The points of ossification of the ribs, scapula, shaft of humerus, femur, tibia, palate, and upper jaw appear. Eighth Week.-The distinction of arm and forearm, and of thigh and leg, is apparent, as well as the interdigital clefts. The capsule of the lens and pupillary membrane, the interventricu- lar and commencement of the interauricular septum, the salivary glands, the spleen, and suprarenal capsules are distinguishable. The larynx begins to become cartilaginous. All the vertebral bodies are cartilaginous. The points of ossification for the ulna, radius, fibula, and ilium make their appearance. The two halves of the hard palate unite. The sympathetic nerves are now for the first time to be discerned. Ninth Week.-The corpus striatum and the pericardium are first apparent. The ovary and testicle can be distinguished from each other. The genital furrow appears. The osseous nuclei of the bodies and arches of the vertebrae, of the frontal, vomer, and malar bones of the shafts of the metacarpal and metatarsal bones, and of the phalanges appear. The union of the hard palate is completed. The gall-bladder is seen. Third Month.-The formation of the foetal placenta advances rapidly. The projection of the caudal extremity disappears. It is possible to distinguish the male and female organs from each other. The cloacal aperture in divided into two parts. The cartilaginous arches on the dorsal region of the spine close. The points of ossification for the occipital, sphenoid, lachrymal, nasal, squamous portion of temporal and ischium appear, as well as the orbital 142 THE FCETUS. 143 centre of the superior maxillary. The pons Varolii and fissure of Sylvius can be made out. The eyelids, the hair, and the nails begin to form. The mammary gland, the epiglottis, and prostate are beginning to develop. The union of the testicle with the canals of the Wolffian body takes place. Fourth Month.-The closure of the cartilaginous arches of the spine is complete. Osseous points for the first sacral vertebra and os pubis appear. The ossification of the malleus and incus takes place. The corpus callosum, the membrana lamina spiralis, the cartilage of the Eustachian tube, and the tympanic ring are seen. Fat is first developed in the sub- cutaneous cellular tissue. The tonsils are seen, and the closure of the genital furrow and the formation of the scrotum and prepuce take place. Fifth Month.-The two layers of the decidua begin to coalesce. Osseous nuclei of the axis and odontoid process, of the lateral points of the first sacral vertebra, of the median points of the second, and of the lateral masses of the ethmoid make their appearance. Ossification of the stapes and the petrous bone and ossification of the germs of the teeth take place. The germs of the permanent teeth and the organ of Corti appear. The eruption of hair on the head commences. The sudoriferous glands, Brunner's glands, the follicles of the tonsil and base of the tongue, and the lymphatic glands appear at this period. The differentiation between the uterus and vagina becomes apparent. Sixth Month.-The points of ossification for the anterior root of the transverse process of the seventh cervical vertebra, the lateral points of the second sacral vertebra, the median points of the third, the manubrium sterni and the os calcis appear. The sacro-vertebral angle forms. The cerebral hemispheres cover the cerebellum. The papillae of the skin, the sebaceous glands, and Peyer's patches make their appearance. The free border of the nail projects from the corium of the dermis. The walls of the uterus thicken. Seventh Month.-The additional points of the first sacral vertebra, the lateral points of the third, the median point of the fourth, the first osseous point of the body of the sternum, and the osseous point for the astragalus appear. Meckel's cartilage disappears. The cerebral convolutions, the island of Reil, and the tubercula quadrigemina are apparent. The pupillary membrane atrophies. The testicle passes into the vaginal process of the peritoneum. Eighth Month.-Additional points for the second sacral vertebra, lateral points for the fourth and median points for the fifth sacral vertebrae, can be seen. Ninth Month.-Additional points for the third sacral vertebra, lateral points for the fifth, osseous points for the middle turbinated bone, for the body and great cornu of the hyoid, for the second and third pieces of the body of the sternum, and for the lower end of the femur appear. Ossification of the bony lamina spiralis and axis of the cochlea takes place. The eyelids open, and the testicles are in the scrotum. DESCRIPTIVE AND SURGICAL ANATOMY. OSTEOLOGY-THE SKELETON. T|1HE entire skeleton in the adult consists of 200 distinct bones. These are- The spine or vertebral column (sacrum and coccyx included) 26 Cranium 8 Face 14 Os hyoides, sternum, and ribs 26 Upper extremities 64 Lower extremities 62 200 In this enumeration the patellae are included as separate bones, but the smaller sesamoid bones and the ossicula auditus are not reckoned. The teeth belong to the tegumentary system. These bones are divisible into four classes: Long, Short, Flat, and Irregular. The Long Bones are found in the limbs, where they form a system of levers, which have to sustain the weight of the trunk and to confer the power of locomo- tion. A long bone consists of a shaft and two extremities. The shaft is a hollow cylinder, contracted and narrowed to afford greater space for the bellies of the muscles; the walls consist of dense, compact tissue of great thickness in the middle, but becoming thinner toward the extremities; the spongy tissue is scanty, and the bone is hollowed out in its interior to form the medullary canal. The extremities are generally somewhat expanded for greater convenience of mutual connection, for the purposes of articulation, and to afford a broad surface for muscular attachment. Here the bone is made up of spongy tissue with only a thin coating of compact substance. The long bones are not straight, but curved, the curve generally taking place in two directions, thus affording greater strength to the bone. The bones belonging to this class are the clavicle, humerus, radius, ulna, femur, tibia, fibula, metacarpal and metatarsal bones, and the phalanges. Short Bones.-Where a part of the skeleton is intended for strength and com- pactness, and its motion is at the same time slight and limited, it is divided into a number of small pieces united together by ligaments, and the separate bones are short and compressed, such as the bones of the carpus and tarsus. These bones, in their structure, are spongy throughout, excepting at their surface, where there is a thin crust of compact substance. The patelloe also, together with the other sesamoid bones, are by some regarded as short bones. Flat Bones.-Where the principal requirement is either extensive protection or the provision of broad surfaces for muscular attachment, we find the osseous structure expanded into broad, flat plates, as is seen in the bones of the skull and the shoulder-blade. These bones are composed of two thin layers of compact tissue enclosing between them a variable quantity of cancellous tissue. In the cranial bones these layers of compact tissue are familiarly known as the tables of the 145 146 THE SKELETON. skull; the outer one is thick and tough; the inner one thinner, denser, and more brittle, and hence termed the vitreous table. The intervening cancellous tissue is called the diploe. The flat bones are: the occipital, parietal, frontal, nasal, lachrymal, vomer, scapula, os innominatum, sternum, ribs, and patella. The Irregular or Mixed Bones are such as, from their peculiar form, cannot be grouped under either of the preceding heads. Their structure is similar to that of other bones, consisting of a layer of compact tissue externally, and of spongy cancellous tissue within. The irregular bones are: the vertebrae, sacrum, coccyx, temporal, sphenoid, ethmoid, malar, superior maxillary, inferior maxillary, palate, inferior turbinated, and hyoid. Surfaces of Bones.-If the surface of any bone is examined, certain eminences and depressions are seen to which descriptive anatomists have given the following names. These eminences and depressions are of two kinds : articular and non-articular. Well-marked examples of articular eminences are found in the heads of the humerus and femur and of articular depressions in the glenoid cavity of the scapula and the acetabulum. Non-articular eminences are designated according to their form. Thus, a broad, rough, uneven elevation is called a tuberosity; a small, rough prominence, a tubercle; a sharp, slender, pointed eminence, a spine; a narrow, rough elevation, running some way along the surface, a ridge or line. The non-articular depressions are also of very variable form, and are described as fossce, grooves, furrows, fissures, notches, etc. These non-articular eminences and depressions serve to increase the extent of surface for the attachment of liga- ments and muscles, and are usually well marked in proportion to the muscularity of the subject. A prominent process projecting from the surface of a bone, which it has never been separate from or movable upon is termed an apophysis (from an excrescence); but if such process is developed as a separate piece from the rest of the bone, to which it is afterward joined, it is termed an epiphysis (from an accretion). THE SPINE. The Spine is a flexuous and flexible column formed of a series of bones called vertebrce (from vertere, to turn). The Vertebrae are thirty-three in number, exclusive of those which form the skull, and have received the names cervical, dorsal, lumbar, sacral, and coccygeal, according to the position which they occupy; seven being found in the cervical region, twelve in the dorsal, five in the lumbar, five in the sacral, and four in the coccygeal. This number is sometimes increased by an additional vertebra in one region, or the number may be diminished in one region, the deficiency being supplied by an additional vertebra in another. These observations do not apply to the cervical portion of the spine, the number of bones forming which is seldom increased or diminished. The vertebrae in the upper three regions of the spine are separate throughout the whole of life; but those found in the sacral and coccygeal regions are in the adult firmly united, so as to form two bones-five entering into the formation of the upper bone or sacrum, and four into the terminal bone of the spine or coccyx. General Characters of a Vertebra. Each vertebra consists of two essential parts-an anterior solid segment or body, and a posterior segment or arch. The arch is formed of two pedicles and two lamince, supporting seven processes-viz. four articular, two transverse, and one spinous. The bodies of the vertebrae are piled one upon the other, forming a strong pillar for the support of the cranium and trunk ; the arches forming a hollow cylinder behind the bodies for the protection of the spinal cord. The different CER VIC A L VER TER ICE. 147 vertebrae are connected together by means of the articular processes and the inter- vertebral cartilages; while the transverse and spinous processes serve as levers for the attachment of muscles which move the different parts of the spine. Lastly, between each pair of vertebrae apertures exist through which the spinal nerves pass from the cord. Each of these constituent parts must now be separately examined. The Body or Centrum is the largest and most solid part of a vertebra. Above and below it is flattened; its upper and lower surfaces are rough for the attach- ment of the intervertebral fibro-cartilages, and present a rim around their cir- cumference. In front, it is convex from side to side, concave from above down- ward. Behind, it is flat from above downward and slightly concave from side to side. Its anterior surface is perforated by a few small apertures, for the passage of nutrient vessels; whilst on the posterior surface is a single large, irregular aperture, or occasionally more than one, for the exit of veins from the body of the vertebra-the venae basis vertebra?. The Pedicles project backward, one on each side, from the upper part of the body of the vertebra, at the line of junction of its posterior and lateral surfaces. The concavities above and below the pedicles are the intervertebral notches; they are four in number, two on each side, the inferior ones being generally the deeper. When the vertebrae are articulated the notches of each contiguous pair of bones form the intervertebral foramina, which communicate with the spinal canal and transmit the spinal nerves and blood-vessels. The Laminae are two broad plates of bone which complete the vertebral arch behind, enclosing a foramen, the spinal foramen, which serves for the protection of the spinal cord; they are connected to the body by means of the pedicles. Their upper and lower borders are rough, for the attachment of the ligamenta subflava. The Spinous Process projects backward from the junction of the two laminae, and serves for the attachment of muscles. The Articular Processes, four in number, two on each side, spring from the junction of the pedicles with the laminae. The two superior project upward, their articular surfaces being directed more or less backward; the two inferior project downward, their articular surfaces looking more or less forward.1 The Transverse Processes, two in number, project one at each side from the point where the articular processes join the pedicle. They also serve for the attachment of muscles. Character of the Cervical Vertebrae (Fig. 109). The Cervical Vertebrae are smaller than those in any other region of the spine, and may readily be distinguished by the foramen in the transverse process, which does not exist in the transverse process of either the dorsal or lumbar vertebrae. The Body is small, comparatively dense, and broader from side to side than from before backward. The anterior and posterior surfaces are flattened and of equal depth; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and fore part of the vertebrae below. Its upper surface is concave transversely, and presents a pro- jecting lip on each side; its lower surface is convex from side to side, concave from before backward, and presents laterally a shallow concavity which receives the corresponding projecting lip of the adjacent vertebra. The pedicles are directed obliquely outward, and the superior intervertebral notches are deeper, but narrower, than the inferior. The lamince are narrow, long, thinner above than below, and overlap each other, enclosing the spinal foramen, which is very large, and of a triangular form. The spinous processes are short, and bifid at the extremity to afford greater extent of surface for the attachment of muscles, the two divisions being often of unequal size. They increase in length from the 1 It may, perhaps, be as well to remind the reader that the direction of a surface is determined by that of a line drawn at right angles to it. 148 THE SKELETON. fourth to the seventh. The articular processes are oblique: the superior are of an oval form, flattened, and directed backward and upward; the inferior forward and downward. The transverse processes are short, directed downward, outward, and forward, bifid at their extremity, and marked by a groove along their upper surface, which runs downward and outward from the superior intervertebral notch, and serves for the transmission of one of the cervical nerves. They are situated in front of the articular processes and on the outer side of the pedicles. The transverse processes are pierced at their base by a foramen, for the transmis- sion of the vertebral artery, vein, and plexus of nerves. Each process is formed by two roots: the anterior root, sometimes called the costal process, arises from the side of the body, and is the homologue of the rib in the dorsal region of the spine; the posterior root springs from the junction of the pedicle with the lamina, and corresponds with the transverse process in the dorsal region. It is by the Anterior tubercle of verse process. Foramen for vertebral artery. //,■ Transverse process. Posterior tubercle of transverse process. Spinal Foramen ■Superior articular process. ■Inferior articular process Spinous process. Fig. 109.-Cervical vertebra. junction of the two that the foramen for the vertebral vessels is formed. The extremity of each of these roots forms the anterior and posterior tubercles of the transverse processes.1 The peculiar vertebrae in the cervical region are the first, or Atlas; the second, or Axis ; and the seventh, or Vertebra prominens. The great modifications in the form of the atlas and axis are designed to admit of the nodding and rotatory movements of the head. The Atlas (Fig. 110) is so named from supporting the globe of the head. The chief peculiarities of this bone are that it lias neither body nor spinous process. The body is detached from the rest of the bone, and forms the odontoid process of the second vertebra ; while the parts corresponding to the pedicles join in front to form the anterior arch. The atlas consists of an anterior arch, a posterior arch, and two lateral masses. The anterior arch forms about one-fifth of the bone: its anterior surface is convex, and presents about its centre a tubercle, for the attach- ment of the Longus colli muscle; posteriorly it is concave, and marked by a smooth, oval or circular facet, for articulation with the odontoid process of the axis. The upper and lower borders give attachment to the anterior occipito- atlantal and the anterior atlanto-axial ligaments, which connect it with the occipital bone above and the axis below. The posterior arch forms about two-fifths of the circumference of the bone; it terminates behind in a tubercle, which is the rudi- ment of a spinous process, and gives origin to the Rectus capitis posticus minor. The diminutive size of this process prevents any interference in the movements between it and the cranium. The posterior part of the arch presents above and behind a rounded edge for the attachment of the posterior occipito-atlantal liga- 1 The anterior tubercle of the transverse process of the sixth cervical vertebra is of large size, and is sometimes known as "Chassaignac's" or the "carotid tubercle." It is in close relation with the carotid artery, which lies in front and a little external to it; so that, as was first pointed out by Chassaignac, the vessel can with ease be compressed against it. CER VIC A L VER TEBRIE. 149 ment, while in front, immediately behind each superior articular process, is a groove, sometimes converted into a foramen by a delicate bony spiculum which arches backward from the posterior extremity of the superior articular process. These grooves represent the superior intervertebral notches, and are peculiar from being situated behind the articular processes, instead of in front of them, as in the other vertebrie. They serve for the transmission of the vertebral artery, which, ascending through the foramen in the transverse process, winds round the lateral mass in a direction backward and inward. They also transmit the suboc- cipital nerve. On the under surface of the posterior arch, in the same situation, are two other grooves, placed behind the lateral masses, and representing the infe- rior intervertebral notches of other vertebrie. They are much less marked than the superior. The lower border also gives attachment to the posterior atlanto- axial ligament, which connects it with the axis. The lateral masses are the most bulky and solid parts of the atlas, in order to support the weight of the head; they present two articulating processes above, and two below. The two superior Diagram of section of odontoid process. Diagram of section of transverse ligament. Transverse process.' Foramen for 'vertebral artery. Groove for vertebral artery and 1st cervical nerve. Rudimentary spinous process Fig. 110.-First cervical vertebra, or atlas. are of large size, oval, concave, and approach each other in front, but diverge behind; they are directed upward, inward, and a little backward, forming a kind of cup for the condyles of the occipital bone, and are admirably adapted to the nodding movements of the head. Not unfrequently they are partially subdivided by a more or less deep indentation which encroaches upon each lateral margin. The inferior articular processes are circular in form, flattened or slightly concave, and directed downward and inward, articulating with the axis, and permitting the rotatory movements. Just below the inner margin of each superior articular surface is a small tubercle, for the attachment of the transverse ligament, which, stretching across the ring of the atlas, divides it into two unequal parts; the anterior or smaller segment receiving the odontoid process of the axis, the posterior allowing the transmission of the spinal cord and its membranes. This part of the spinal canal is of considerable size, to afford space for the spinal cord; and hence lateral displacement of the atlas may occur without compression of this structure. The transverse processes are of large size, project directly outward from the lateral masses, and serve for the attachment of special muscles which assist in rotating the head. They are long, not bifid, and perforated at their base by a canal for the vertebral artery, which is directed from below, upward and backward. The Axis (Fig. Ill) is so named from forming the pivot upon which the first vertebra, carrying the head, rotates. The most distinctive character of this bone is the strong, prominent process, tooth-like in form (hence the name odontoid), which rises perpendicularly from the upper surflice of the body. The body is of a triangular form, deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper and fore part of the adjacent vertebra. It presents in front a median longitudinal ridge, separating two lateral depressions for the attach- 150 THE SKELETON. ment of the Longus colli muscle of either side. The odontoid process presents two articulating surfaces: one in front, of an oval form, for articulation with the Odontoid process. Bough surface for check ligaments. Articular surface for atlas. Articular surface for transverse ligament. Body. Spinous process. I Transverse process. Inferior articular process. Fig. 111.-Second cervical vertebra, or axis. atlas; another behind, for the transverse ligament-the latter frequently encroach- ing on the sides of the process. The apex is pointed, and gives attachment to one fasciculus of the odontoid ligament (ligamentum suspensorium). Below the apex the process is somewhat enlarged, and presents on either side a rough impression for the attachment of the lateral fasciculi of the odontoid or check ligaments, which connect it to the occipital bone ; the base of the process, where it is attached to the body, is constricted, so as to prevent displacement from the transverse ligament, which binds it in this situation to the anterior arch of the atlas. Sometimes, however, this process does become dis- placed, especially in children, in whom the ligaments are more relaxed: instant death is the result of this accident. The pedicles are broad and strong, especially their anterior extrem- ities, which coalesce with the sides of the body and the root of the odontoid process. The lam- ince are thick and strong, and the spinal foramen large, but smaller than that of the atlas. The trans- verse processes are very small, not bifid, and perforated by the vertebral foramen, or foramen for the vertebral artery, which is directed obliquely upward and outward. The superior articular surfaces are round, slightly convex, directed upward and outward, and are peculiar in being supported on the body, pedicles, and transverse processes. The inferior articular surfaces have the same direction as those of the other cervical vertebrae. The superior intervertebral notches are very shallow, and lie behind the articular processes; the inferior in front of them, as in the other cervical vertebrae. The spinous process is of large size, very strong, deeply channelled on its under surface, and presents a bifid, tubercular extremity for the attachment of muscles which serve to rotate the head upon the spine. Seventh Cervical (Fig. 112).-The most distinctive character of this vertebra is Fig. 112.-Seventh cervical vertebra, or vertebra prominens. Spinous process. DORSAL VERTEBRAE. 151 the existence of a very long and prominent spinous process; hence the name "vertebra prominens." This process is thick, nearly horizontal in direction, not bifurcated, and has attached to it the ligamentum nuchae. The transverse process is usually of large size, especially its posterior root; its upper surface has usually a shallow groove, and it seldom presents more than a trace of bifurcation at its extremity. The vertebral foramen is sometimes as large as in the other cervical vertebrae, but is usually smaller on one or both sides, and sometimes wanting. On the left side it occasionally gives passage to the vertebral artery; more frequently the vertebral vein traverses it on both sides; but the usual arrangement is for both artery and vein to pass in front of the transverse process, and not through the foramen Characters of the Dorsal Vertebrae. The Dorsal Vertebrae are intermediate in size between those in the cervical and those in the lumbar region, and increase in size from above downward, the upper Superior articular process. Demi-facet for head of rib. Facet for tubercle of rib. Demi-facet for head of rib. Inferior articular process. Fig. 113.-A dorsal vertebra. vertebrae in this segment of the spine being much smaller than those in the lower part of the region. The dorsal vertebrae may be at once recognized by the pres- ence on the sides of the body of one or more facets or half-facets for the heads of the ribs. The bodies of the dorsal vertebrae resemble those in the cervical and lumbar regions at the respective ends of this portion of the spine; but in the middle of the dorsal region their form is very characteristic, being heart-shaped, and as broad in the antero-posterior as in the lateral direction. They are thicker behind than in front, flat above and below, convex and prominent in front, deeply concave behind, slightly constricted in front and at the sides, and marked on each side, near the root of the pedicle, by two demi-facets, one above, the other below. These are covered with cartilage in the recent state, and, when articulated with the adjoin- ing vertebrae, form, with the intervening fibro-cartilage, oval surfaces for the reception of the heads of the corresponding ribs. The pedicles are directed back- ward, and the inferior intervertebral notches are of large size, and deeper than in any other region of the spine. The lamince are broad, thick, and imbricated- that is to say, overlapping one another like tiles on a roof. The spinal foramen is small, and of a circular form. The spinous processes are long, triangular in form (bayonet-shaped), directed obliquely downward, and terminate in a tubercular extremity. They overlap one another from the fifth to the eighth, but are less 152 THE SKELETON. oblique in direction above and below. The articular processes are flat, nearly vertical in direction, and project from the upper and lower part of the pedicles; An entire facet above a demi-facet below. A demi-facet above. One entire facet. An entire facet. No facet on transverse process, which is ru- dimentary. Ah entire facet. No facet on trans- verse process. Inferior articular process, convex and turned out- ward. Fig. 114.-Peculiar dorsal vertebra. the superior being directed backward and a little outward and upward, the inferior forward and a little inward and downward. The transverse processes arise from the same parts of the arch as the posterior roots of the transverse processes in the neck, and are situated behind the articular processes and pedicles; they are thick, strong, and of great length, directed obliquely backward and outward, presenting a clubbed extremity, which is tipped on its anterior part by a small concave surface, for articulation with the tubercle of a rib. Besides the articular facet for the rib, three indistinct tubercles may be seen rising from the transverse processes, one at the upper border, one at the lower border, and one externally. In man they are comparatively of small size, and serve only for the attachment of muscles. But in some animals they attain considerable magnitude, either for LUMBAR VERTEBRAE. 153 the purpose of more closely connecting the segments of this portion of the spine or for muscular and ligamentous attachment. The peculiar dorsal vertebrae are the first, ninth, tenth, eleventh, and twelfth (Fig. 114). The First Dorsal Vertebra presents, on each side of the body, a single entire articular facet for the head of the first rib and a half facet for the upper half of the second. The upper surface of the body is like that of a cervical vertebra, being broad transversely, concave, and lipped on each side. The articular sur- faces are oblique, and the spinous process thick, long, and almost horizontal. The Ninth Dorsal has no demi-facet below. In some subjects, however, the ninth has two demi-facets on each side, then the tenth has a demi-facet at the upper part; none below. The Tenth Dorsal has (except in the cases just mentioned) an entire articular facet on each side above, which is partly placed on the outer surface of the pedicle. It has no demi-facet below. In the Eleventh Dorsal the body approaches in its form and size to the lumbar. The articular facets for the heads of the ribs, one on each side, are of large size, and placed chiefly on the pedicles, which are thicker and stronger in this and the next vertebra than in any other part of the dorsal region. The spinous process is short, nearly horizontal in direction, and presents a slight tendency to bifurcation at its extremity. The transverse processes are very short, tubercular at their extremities, and have no articular facets for the tubercles of the ribs. The Twelfth Dorsal has the same general characters as the eleventh, but may be distinguished from it by the inferior articular processes being convex and turned outward, like those of the lumbar vertebrae; by the general form of the body, laminae, and spinous process, approaching to that of the lumbar vertebrae; and by the transverse processes being shorter, and marked by three elevations, the superior, inferior, and external tubercles, which correspond to the mammillary, accessory, and transverse processes of the lumbar vertebrae. Traces of similar elevations are usually to be found upon the other dorsal vertebrae (vide ut supra}. Characters of the Lumbar Vertebrae. The Lumbar Vertebrae (Fig. 115) are the largest segments of the vertebral column, and can at once be distinguished by the absence of the foramen in the Superior articular process. Fig. 115.-Lumbar vertebra. transverse process, the characteristic point of the cervical vertebrae, and by the absence of any articulating facet on the side of the body, the distinguishing mark of the dorsal vertebrae. The body is large, and has a greater diameter from side to side than from before backward, slightly thicker in front than behind, flattened or slightly concave above and below, concave behind, and deeply constricted in front and at the sides, 154 77ZA SKELETON. presenting prominent margins, which afford a broad basis for the support of the superincumbent weight. The pedicles are very strong, directed backward from the upper part of the bodies; consequently, the inferior intervertebral notches are of considerable depth. The laminae are broad, short, and strong, and the spinal foramen triangular, larger than in the dorsal, smaller than in the cervical, region. The spinous processes are thick and broad, somewhat quadrilateral, horizontal in direction, thicker below than above, and terminating by a rough, uneven border. The superior articular processes are concave, and look backward and inward; the inferior, convex, look forward and outward; the former are separated by a much wider interval than the latter, embracing the lower articulating processes of the vertebra above. The transverse processes are long, slender, directed trans- versely outward in the upper three lumbar vertebrae, slanting a little upward in the lower two. They are situated in front of the articular processes, instead of behind them as in the dorsal vertebrae, and are homologous with the ribs. Of the three tubercles noticed in connection with the transverse processes of the twelfth dorsal vertebra, the superior ones become connected in this region with the back part of the superior articular processes, and have received the name of mammillary processes; the inferior are represented by a small process pointing downward, situated at the back part of the base of the transverse process, and called the accessory processes: these are the true transverse processes, which are rudimental in this region of the spine ; the external ones are the so-called transverse processes, the homologue of the rib, and hence sometimes called costal processes. Although in man these are comparatively small, in some animals they attain considerable size, and serve to lock the vertebrae more closely together. The Fifth Lumbar vertebra is characterized by having the body much thicker in front than behind, which accords with the prominence of the sacro-vertebral articulation; by the smaller size of its spinous process; by the wide interval between the inferior articulating processes; and by the greater size and thickness of its transverse processes. Structure of the Vertebrae.-The structure of a vertebra differs in different parts. The body is composed of light, spongy, cancellous tissue, having a thin coating of compact tissue on its external surface perforated by numerous orifices, some of large size, for the passage of vessels; its interior is traversed by one or two large canals, for the reception of veins, which converge toward a single large, irregular aperture or several small apertures at the posterior part of the body of each bone. The arch and processes projecting from it have, on the contrary, an exceedingly thick covering of compact tissue. Development.-Each vertebra is formed of four primary cartilaginous portions (Fig. 116), one for each lamina and its processes, and two for the body. Ossifica- tion commences in the laminae about the sixth week of foetal life, in the situation where the transverse processes afterward project, the ossific granules shooting backward to the spine, forward into the pedicles, and outward into the transverse and articular processes. Ossification in the body commences in the middle of the cartilage about the eighth week by two closely approximated centres, which speedily coalesce to form one central ossific point. According to some authors, ossifica- tion commences in the laminae only in the upper vertebrae-i. e. in the cervical and upper dorsal. The first ossific points in the lower vertebrae are those which are to form the body, the osseous centres for the laminae appearing at a subsequent period. At birth these three pieces are perfectly separate. During the first year the laminae become united behind by a portion of cartilage in which the spinous process is ultimately formed, and thus the arch is completed. About the third year the body is joined to the arch on each side, in such a manner that the body is formed frqjn the three original centres of ossification, the amount contributed by the ped- icles increasing in extent from below upward. Thus the bodies of the sacral vertebrae are formed almost entirely from the central nuclei; the bodies of the lumbar are formed laterally and behind by the pedicles; in the dorsal region the pedicles advance as far forward as the articular depressions for the head of the L UMBAR VER TER REE. 155 ribs, forming these cavities of reception; and in the neck the lateral portions of the bodies are formed entirely by the advance of the pedicles. Before puberty By If primary centres. 2 for body (8th week). By If secondary centres. i '-' I Ifor each lamina {6th week). Fig. 116.-Development of a vertebra. 1 for each trans- verse process, 16 years. By 2 additional plates. ■1 for upper surface of body, 21 years. Fig. 117. ,1 for under surface of body, 2 (sometimes 1) for spinous process (16 years). Fig. 118. no other changes occur, excepting a gradual increase in the growth of these primary centres; the upper and under surfaces of the bodies and the ends of the transverse and spinous processes being tipped with cartilage, in which ossific granules are not as yet deposited. At sixteen years (Fig. 118), four secondary centres appear, one for the tip of each transverse process, and two (sometimes united into one) for the end of the spinous process. At twenty-one years (Fig. 117), a thin circular epiphysial plate of bone is formed in the layer of cartilage situated on the upper and under sur- faces of the body, the former being the thicker of the two. All these become joined, and the bone is com- pletely formed between the twenty- fifth and thirtieth year of life. Exceptions to this mode of de- velopment occur in the first, second, and seventh cervical, and in the vertebrae of the lumbar region. The Atlas (Fig. 119).-The num- ber of centres of ossification of the atlas is very variable. It may be developed from two, three, four, or five centres. The most frequent ar- rangement is by three centres. Two of these are destined for the two lateral or neural masses, the ossifica- tion of which commences about the seventh week near the articular pro- cesses, and extend backward; these portions of bone are separated from one another behind, at birth, by a narrow interval filled in with carti- lage. Between the second and third years they unite either directly or through the medium of a separate centre developed in the cartilage in the middle line. The anterior arch, at birth, is altogether cartilaginous, and in this a sepa- rate nucleus appears about the end of the first year after birth, and, extending laterally, joins the neural processes in front of the pedicles. Sometimes there are two nuclei developed in the cartilage, one on either side of the median line, which join to form a single mass. And occasionally there is no separate centre, but the By 3 centres. 1 for anterior arch (1st year), not constant. 1 for each lateral mass before birth. Fig. 119.-Atlas. By 6 centres. for odontoid process (6th month). Exceptional cases. 1 for each lateral mass. 1 for body {6th month). 2 additional centres. Fig. 120.-Axis. for tubercles on superior articular process. Fig. 121.-Lumbar vertebra. 156 THE SKELETON. anterior arch is formed by the gradual extension forward and ultimate junction of the two neural processes. The Axis (Fig. 120) is developed by six centres. The body and arch of this bone are formed in the same manner as the corresponding parts in the other ver- tebrae : one centre (or two, which speedily coalesce) for the lower part of the body, and one for each lamina. The odontoid process consists originally of an extension upward of the cartilaginous mass in which the lower part of the body is formed. At about the sixth month of foetal life two osseous nuclei make their appearance in the base of this process: they are placed laterally, and join before birth to form a conical bilobed mass deeply cleft above; the interval between the cleft and the summit of the process is formed by a wedge-shaped piece of cartilage, the base of the process being separated from the body by a cartilaginous interval, which gradually becomes ossified at its circumference, but remains cartilaginous in its centre until advanced age.1 Finally, as Humphry has demonstrated, the apex of the odontoid process has a separate nucleus, which appears in the second year and joins about the twelfth year. In addition to these there is a secondary centre for a thin epiphysial plate on the under surface of the body of the bone. The Seventh Cervical.-The anterior or costal part of the transverse process of the seventh cervical is developed from a separate osseous centre at about the sixth month of foetal life, and joins the body and posterior division of the trans- verse process between the fifth and sixth years. Sometimes this process continues as a separate piece, and, becoming lengthened outward, constitutes what is known as a cervical rib. The Lumbar Vertebrae (Fig. 121) have two additional centres (besides those peculiar to the vertebrae generally) for the mammillary tubercles, which project from the back part of the superior articular processes. The transverse process of the first lumbar is sometimes developed as a separate piece, which may remain permanently unconnected with the remaining portion of the bone, thus forming a lumbar rib-a peculiarity which is rarely met with. Progress of Ossification in the Spine generally.-Ossification of the laminae of the vertebrae commences at the upper part of the spine, and proceeds gradually downward. Ossification of the bodies, on the other hand, commences a little below the centre of the spinal column (about the ninth or tenth dorsal vertebra), and extends both upward and downward. Although, however, the ossific nuclei make their first appearance in the lower dorsal vertebrae, the lumbar and first sacral are those in which these nuclei are largest at birth. Attachment of Muscles.-To the Atlas are attached nine pairs: the Longus colli, Rectus capitis anticus minor, Rectus lateralis, Obliquus capitis superior and inferior, Splenius colli, Levator anguli scapulae, First Intertransverse, and Rectus capitis posticus minor. To the Axis are attached eleven pairs: the Longus colli, Levator anguli scapulae, Splenius colli, Scalenus medius, Transversalis colli, Intertransversales, Obliquus capitis inferior, Rectus capitis posticus major, Semispinalis colli, Mul- tifidus spinae, Interspinales. To the remaining vertebrae, generally, are attached thirty-five pairs and a sin- gle muscle: anteriorly, the Rectus capitis anticus major, Longus colli, Scalenus anticus medius and posticus, Psoas magnus and parvus, Quadratus lumbo- rum. Diaphragm, Obliquus abdominis internus, and Transversalis abdominis- posteriorly, the Trapezius, Latissimus dorsi, Levator anguli scapulae, Rhomboideus major and minor, Serratus posticus superior and inferior, Splenius, Erector spinae, Ilio-costalis, Longissimus dorsi, Spinalis dorsi, Cervicalis ascendens, Transversalis colli, Trachelo-mastoid, Complexus, Biventer cervicis, Semispinalis dorsi and colli, Multifidus spinae, Rotatores spinae, Interspinales, Supraspinales, Intertransversales, Levatores costarum. 1 See Cunningham, Journ. Anat., vol. xx, p. 238. SACRAL AND COCCYGEAL VERTEBRAE. 157 Sacral and Coccygeal Vertebrae. The Sacral and Coccygeal Vertebrae consist, at an early period of life, of nine separate pieces, which are united in the adult so as to form two bones, five enter- ing into the formation of the sacrum, four into that of the coccyx. Occasionally, the coccyx consists of five bones.1 The Sacrum (sacer, sacred) is a large, triangular bone (Fig. 122), situated at the lower part of the vertebral column, and at the upper and back part of the pelvic Fig. 122.-Sacrum, anterior surface. cavity, where it is inserted like a wedge between the two innominate bones; its upper part or base articulating with the last lumbar vertebrae, its apex with the coccyx. The sacrum is curved upon itself, and placed very obliquely, its upper extremity projecting forward, and forming, with the last lumbar vertebra, a very prominent angle, called the promontory or sacro-vertebral angle ; whilst its central part is directed backward, so as to give increased capacity to the pelvic cavity. It presents for examination an anterior and posterior surface, two lateral surfaces, a base, an apex, and a central canal. The Anterior Surface is concave from above downward, and slightly so from side to side. In the middle are seen four transverse ridges, indicating the original division of the bone into five separate pieces. The portions of bone intervening between the ridges correspond to the bodies of the vertebrae. The body of the first segment is of large size, and in form resembles that of a lumbar vertebra ; the succeeding ones diminish in size from above downward, are flattened from before backward, and curved so as to accommodate themselves to the form of the sacrum, being concave in front, convex behind. At each end of the ridges above mentioned are seen the anterior sacral foramina, analogous to the intervertebral foramina. 1 Sir George Humphry describes this as the usual composition of the coccyx.-On the, Skeleton. p. 456. 158 THE SKELETON. four in number on each side, somewhat rounded in form, diminishing in size from above downward, and directed out- ward and forward; they transmit the anterior branches of the sacral nerves. External to these foramina is the lateral mass, consisting at an early period of life of separate segments; these become blended, in the adult, with the bodies, with each other, and with the posterior transverse processes. Each lateral mass is traversed by four broad, shallow grooves, which lodge the anterior sacral nerves as they pass outward, the grooves being separated by prominent ridges of bone, which give attachment to the slips of the Pyriformis muscle. If a vertical section is made through the centre of the bone (Fig. 123), the bodies are seen to be united at their cir- cumference by bone, a wide interval being left centrally, which, in the recent state, is filled by intervertebral substance. In some bones this union is more complete between the lower segments than between the upper ones. The Posterior Surface (Fig. 124) is convex and much narrower than the anterior. In the middle line are three or four tubercles, which represent the rudimentary spinous processes of the sac- ral vertebrae. Of these tubercles, the first is usually prominent, and perfectly distinct from the rest; the second and third are either separate or united into a tubercular ridge, which diminishes in size from above downward ; the fourth usually, and the fifth always, remaining un- developed. External to the spinous processes on each side are the lamin oe, broad and well marked in the first three pieces; sometimes the fourth, and generally the fifth, being undeveloped: in this situation the lower end of the sacral canal is exposed, and is liable to be opened in the sloughing of bed-sores. External to the laminae is a linear series of indistinct tubercles representing the articular processes ; the upper pair are large, well developed, and correspond in shape and direction to the superior articulating processes of a lumbar vertebra; the second and third are small; the fourth and fifth (usually blended together) are situated on each side of the sacral canal: they are called the sacral cornua, and articulate with the cornua of the coccyx. External to the articular processes are the four posterior sacral foramina ; they are smaller in size and less regular in form than the anterior, and transmit the posterior branches of the sacral nerves. On the outer side of the posterior sacral foramina is a series of tubercles, the rudiment- ary transverse processes of the sacral vertebrae. The first pair of transverse tubercles are of large size, very distinct, and correspond with each superior angle of the bone; the second, small in size, enter into the formation of the sacro-iliac articulation; the third give attachment to the oblique fasciculi of the posterior sacro-iliac ligaments ; and the fourth and fifth to the great sacro-sciatic ligaments. The interspace between the spinous and transverse processes on the back of the sacrum presents a wide, shallow concavity, called the sacral groove: it is continuous above with the vertebral groove, and lodges the origin of the Erector spinae. Fig. 123.-Vertical section of the sacrum. SACRAL AND COCCYGEAL VERTEBRAE. 159 The Lateral Surface, broad above, becomes narrowed into a thin edge below. Its upper half presents in front a broad, ear-shaped surface for articulation with .Upper half of fifth posterior sacral foramen. Fig. 124.-Sacrum, posterior surface. the ilium. This is called the auricular surface, atjd in the fresh state is coated with fibro-cartilage. It is bounded posteriorly by deep and uneven impressions, for the attachment of the posterior sacro-iliac ligaments. The lower half is thin and sharp, and gives attachment to the greater and lesser sacro-sciatic ligaments, and to some fibres of the Gluteus maximus; below, it presents a deep notch, which is converted into a foramen by articulation with the transverse process of the upper piece of the coccyx, and transmits the anterior division of the fifth sacral nerve. The Base of the sacrum, which is broad and expanded, is directed upward and forward. In the middle is seen a large oval articular surface, which is connected with the under surface of the body of the last lumbar vertebra by a fibre-carti- laginous disk. It is bounded behind by the large, triangular orifice of the sacral canal. The orifice is formed behind by the laminae and spinous process of the first sacral vertebra: the superior articular processes project from it on each side; they are oval, concave, directed backward and inward, like the superior articular processes of a lumbar vertebra ;• and in front of each articular process is an inter- vertebral notch, which forms the lower half of the last intervertebral foramen. Lastly, on each side of the large oval articular surface is a broad and flat triangular surface of bone, which extends outward, supports the Psoas magnus muscle and lumbo-sacral cord, and is continuous on each side with the iliac fossa. This is called the ala of the sacrum, and gives attachment to a few of the fibres of the Iliacus muscle. The Apex, directed downward and forward, presents a small, oval, concave surface for articulation with the coccyx. The Spinal Canal runs throughout the greater part of the bone; it is large 160 THE SKELETON. and triangular in form above, small and flattened, from before backward, below. In this situation its posterior wall is incomplete, from the non-development of the lamime and spinous processes. It lodges the sacral nerves, and is perforated by the anterior and posterior sacral foramina, through which these pass out. Structure.-It consists of much loose, spongy tissue within, invested externally by a thin layer of compact tissue. Differences in the Sacrum of the Male and Female.-The sacrum in the female is usually wider than in the male ; the lower half forms a greater angle with the upper, the upper half of the bone being nearly straight, the lower half pre- senting the greatest amount of curvature. The bone is also directed more obliquely backward, which increases the size of the pelvic cavity; but the sacro-vertebral angle projects less. In the male the curvature is more evenly distributed over the whole length of the bone, and is altogether greater than in the female. Peculiarities of the Sacrum.-This bone, in some cases, consists of six pieces; occasionally, the number is reduced to four. Sometimes the bodies of the first and second segments are not joined or the laminae and spinous processes have not coalesced. Occasionally the upper pair of transverse tubercles are not joined to the rest of the bone on one or both sides ; and, lastly, the sacral canal may be open for nearly the lower half of the bone, in consequence of the imperfect development of the laminae and spinous processes. The sacrum, also, varies considerably with respect to its degree of curvature. From the examination of a large number of skeletons it would appear that in one set of cases the anterior surface of this bone was nearly straight, the curvature, which was very slight, affecting only its lower end. In another set of cases the bone was curved throughout its whole length, but especially toward its middle. In a third set the degree of curvature was less marked, and affected especially the lower third of the bone. Development (Fig. 125).-The sacrum, formed by the union of five vertebrae, has thirty-five centres of ossification. The bodies of the sacral vertebrae have each three ossific centres: one for the central part, and one for the epiphysial plates on its upper and under surface. Occasionally the primary centres for the bodies of the first and second piece of the sacrum are double. The arch of each sacral vertebra is developed by two centres, one for each lamina. These unite with each other behind, and subsequently join the body. The lateral masses have six additional centres, two for each of the first three vertebrae. These centres make their appearance above and to the outer side of the anterior sacral foramina (Fig. 125), and are developed into separate segments Two epiphysial laminae for each lateral surface.* Additional centres for the first three pieces.* At birth. At 25th year. At 44 years. Fig. 125.-Development of the sacrum Fig. 126. Fig. 127. (Fig. 126); they are subsequently blended with each other, and with the bodies and transverse processes to form the lateral mass. Lastly, each lateral surface of the sacrum is developed by two epiphysial plates (Fig. 127): one for the auricular surface, and one for the remaining part of the thin lateral edge of the bone. THE COCCYX. 161 Period of Development.-At about the eighth or ninth week of foetal life ossi- fication of the central part of the bodies of the first three vertebrae commences, and at a somewhat later period that of the last two. Between the sixth and eighth months ossification of the laminae takes place; and at about the same period the characteristic osseous tubercles for the first three sacral vertebrae make their appearance. The period at which the arch becomes completed by the junction of the laminae with the bodies in front and with each other behind varies in different segments. The junction between the laminae and the bodies takes place first in the lower vertebrae as early as the second year, but is not effected in the upper- most until the fifth or sixth year. About the sixteenth year the epiphyses for the upper and under surfaces of the bodies are formed, and between the eighteenth and twentieth years those for each lateral surface of the sacrum make their appearance. The bodies of the sacral vertebrae are, during early life, separated from each other by intervertebral disks. But about the eighteenth year the two lowest segments become joined together by ossification extending through the disk. This process gradually extends upward until all the segments become united, and the bone is completely formed from the twenty-fifth to the thirtieth year of life. Articulations.-With four bones: the last lumbar vertebra, coccyx, and the two ossa innominata. Attachment of Muscles.-To eight pairs: in front, the Pyriformis and Coccyg- eus, and a portion of the Iliacus to the base of the bone; behind, the Gluteus maximus, Latissimus dorsi, Multifidus spinae, and Erector spinae, and sometimes the Extensor coccygis. The Coccyx. The Coccyx (xoxxuf, cuckoo), so called from having been compared to a cuc- koo's beak (Fig. 128), is usually formed of four small segments of bone, the most rudimentary parts of the vertebral column. In each of the first three segments may be traced a rudi- mentary body, articular and transverse processes; the last piece (sometimes the third) is a mere nodule of bone, without distinct processes. All the segments are destitute of pedicles, laminae, and spinous processes, and, consequently, of intervertebral foramina and spinal canal. The first segment is the largest: it resembles the lowermost sacral vertebra, and often exists as a separate piece; the last three, diminishing in size from above downward, are usually blended together so as to form a single bone. The gradual diminution in the size of the pieces gives this bone a triangular form, the base of the triangle joining the end of the sacrum. It presents for examination an anterior and posterior sur- face, two borders, a base, and an apex. The anterior surface is slightly concave, and marked with three transverse grooves, indicating the points of junction of the different pieces. It has attached to it the anterior sacro-coccygeal ligament and Levator ani muscle, and supports the lower end of the rectum. The posterior surface is convex, marked by transverse grooves similar to those on the anterior surface ; and presents on each side a lineal row of tubercles, the rudimentary articular processes of the coccygeal vertebrae. Of these, the supe- rior pair are large, and are called the cornua of the coccyx; they project upward, and articulate with the cornua of the sacrum, the junction between these two bones completing the fifth posterior sacral foramen for the transmission of the pos- terior division of the fifth sacral nerve. The lateral borders are thin, and present a Posterior surface. Fig. 128.-Coceyx. 162 THE SKELETON. series of small eminences, which represent the transverse processes of the coccygeal vertebrae. Of these, the first on each side is the largest, flattened from before backward, and often ascends to join the lower part of the thin lateral edge of the sacrum, thus completing the fifth anterior sacral foramen for the transmission of the anterior division of the fifth sacral nerve; the others diminish in size from above downward, and are often wanting. The borders of the coccyx are narrow, and give attachment on each side to the sacro-sciatic ligaments, to the Coccygeus muscle in front of the ligaments, and to the Gluteus maximus behind them. The base presents an oval surface for articulation with the sacrum. The apex is rounded, and has attached to it the tendon of the external Sphincter muscle. It is occasionally bifid, and sometimes deflected to one or other side. Development.-The coccyx is developed by four centres, one for each piece. Occa- sionally one of the first three pieces of this bone is developed by two centres, placed side by side. The ossific nuclei make their ap- pearance in the following order: in the first segment, at birth; in the second piece, at from five to ten years; in the third, from ten to fifteen years; in the fourth, from fif- teen to twenty years. As age advances these various segments become united in the fol- lowing order: the first two pieces join; then the third and fourth ; and, lastly, the bone is completed by the union of the second and third. At a late period of life, especially in females, the coccyx often becomes joined to the end of the sacrum. Articulation.-With the sacrum. Attachment of Muscles.-To four pairs and one single muscle: on either side, the Coccygeus; behind, the Gluteus maximus and Extensor coccygis, when present; at the apex, the Sphincter ani; and in front, the Levator ani. 1st cervical or Atlas. 2nd cervical or Axis. 1st dorsal. 1st lumbar. The Spine in General. The Spinal Column, formed by the junc- tion of the vertebrae, is situated in the median line, at the posterior part of the trunk ; its average length is about two feet two or three inches, measuring along the curved anterior surface of the column. Of this length the cervical part measures about five, the dorsal about eleven, the lumbar about seven inches, and the sacrum and coccyx the remainder. The female spine is about one inch less than the male. Fig, 129.-Lateral view of the spine. THE SPINE IN GENERAL. 163 Viewed in front, it presents two pyramids joined together at their bases, the upper one being formed by all the vertebrae from the second cervical to the last lumbar, the lower one by the sacrum and coccyx. When examined more closely, the upper pyramid is seen to be formed of three smaller pyramids. The upper- most of these consists of the six lower cervical vertebrae, its apex being formed by the axis or second cervical, its base by the first dorsal. The second pyramid, which is inverted, is formed by the four upper dorsal vertebrae, the base being at the first dorsal, the smaller end at the fourth. The third pyramid commences at the fourth dorsal, and gradually increases in size to the fifth lumbar. Viewed laterally (Fig. 129), the spinal column presents several curves, which correspond to the different regions of the column, and are called cervical, dorsal, lumbar, and pelvic. The cervical curve commences at the apex of the odontoid process, and terminates at the middle of the second dorsal vertebra; it is convex in front, and is the least marked of all the curves. The dorsal curve, which is concave forward, commences at the middle of the second, and terminates at the middle of the twelfth dorsal. Its most prominent point behind corresponds to the spine of the seventh dorsal vertebra. The lumbar curve commences at the middle of the last dorsal vertebra, and terminates at the sacro-vertebral angle. It is convex anteriorly; the convexity of the lower three vertebrae being much greater than that of the upper ones. The pelvic curve commences at the sacro- vertebral articulation and terminates at the point of the coccyx. It is concave anteriorly. The dorsal and pelvic curves are the primary curves, and begin to be formed at an early period of foetal life, and are due to the shape of the bodies of the vertebrae. The cervical and lumbar curves are compensatory or secondary, and are developed after birth in order to maintain the erect position. They are due mainly to the shape of the intervertebral disks. The spine has also a slight lateral curvature, the convexity of which is directed toward the right side. This is most probably produced, as Bichat first explained, chiefly by muscular action, most persons using the right arm in prefer- ence to the left, especially in making long-continued efforts, when the body is curved to the right side. In support of this explanation it has been found by Beclard that in one or two individuals who were left-handed the lateral curvature was directed to the left side. The spinal column presents for examination an anterior, a posterior, and two lateral surfaces; a base, summit, and spinal canal. The anterior surface presents the bodies of the vertebrae separated in the recent state by the intervertebral disks. The bodies are broad in the cervical region, narrow in the upper part of the dorsal, and broadest in the lumbar region. The whole of this surface is convex transversely, concave from above downward in the dorsal region, and convex in the same direction in the cervical and lumbar regions. The posterior surface presents in the median line the spinous processes. These are short, horizontal, with bifid extremities, in the cervical region. In the dorsal region they are directed obliquely above, assume almost a vertical direction in the middle, and are horizontal below', as are also the spines of the lumbar vertebrae. They are separated by considerable intervals in the loins, by narrower intervals in the neck, and are closely approximated in the middle of the dorsal region. Occasionally one of these processes deviates a little from the median line-a fact to be remembered in practice, as irregularities of this sort are attendant also on fractures or displacements of the spine. On either side of the spinous processes, extending the whole length of the column, is the vertebral groove formed by the laminae in the cervical and lumbar regions, where it is shallow, and by the laminae and transverse processes in the dorsal region, where it is deep and broad. In the recent state these grooves lodge the deep muscles of the back. External to the vertebral grooves are the articular processes, and still more externally the transverse process. In the dorsal region the latter processes stand backward, on 164 THE SKELETON. a plane considerably posterior to the same processes in the cervical and lumbar regions. In the cervical region the transverse processes are placed in front of the articular processes, and on the outer side of the pedicles, between the interver- tebral foramina. In the dorsal region they are posterior to the pedicles, interver- tebral foramina, and articular processes. In the lumbar they are placed also in front of the articular processes, but behind the intervertebral foramina. The lateral surfaces are separated from the posterior by the articular processes in the cervical and lumbar regions, and by the transverse processes in the dorsal. These surfaces present in front the sides of the bodies of the vertebrae, marked in the dorsal region by the facets for articulation with the heads of the ribs. More posteriorly are the intervertebral foramina, formed by the juxtaposition of the intervertebral notches, oval in shape, smallest in the cervical and upper part of the dorsal regions, and gradually increasing in size to the last lumbar. They are situated between the transverse processes in the neck, and in front of them in the back and loins, and transmit the spinal nerves. The base of that portion of the vertebral column formed by the twenty-four movable vertebrae is formed by the under surface of the body of the fifth lumbar vertebra; and the summit by the upper surface of the atlas. The vertebral or spinal canal follows the different curves of the spine; it is largest in those regions in which the spine enjoys the greatest freedom of move- ment, as in the neck and loins, where it is wide and triangular; and narrow and rounded in the back, where motion is more limited. Surface Form.-The only part of the vertebral column which lies closely under the skin, and so directly influences surface form, is the apices of the spinous processes. These are always distinguishable at the bottom of a median furrow, which, more or less evident, runs down the mesial line of the back from the external occipital protuberance above to the middle of the sacrum below. In the neck the furrow is broad, and terminates below in a conspicuous projec- tion. which is caused by the spinous process of the seventh cervical vertebra (vertebra promi- nens). Above this the spinous process of the sixth cervical vertebra may sometimes be seen; the other cervical spines are sunken, and are not visible, though the spine of the axis can be felt, and generally also the spines of the third, fourth, and fifth cervical vertebra?. In the dorsal region the furrow is shallow, and during stooping disappears, and then the spinous pro- cesses become more or less visible. The markings produced by these spines are small and close together. In the lumbar region the furrow is deep, and the situation of the lumbar spines is frequently indicated by little pits or depressions, especially if the muscles in the loins are well developed and the spine incurved. They are much larger and farther apart than in the dorsal region. In the sacral region the furrow is shallower, presenting a flattened area which terminates below at the most prominent part of the posterior surface of the sacrum, formed by the spinous process of the third sacral vertebra. At the bottom of the furrow may be felt the irregular posterior surface of the bone. Below this, in the deep groove leading to the anus, the coccyx may be felt. The only other portions of the vertebral column which can be felt from the surface are the transverse processes of three of the cervical vertebrae-viz. the first, the sixth, and the seventh. The transverse process of the atlas can be felt as a rounded nodule of bone just below and in front of the apex of the mastoid process, along the anterior border of the sterno-mastoid. The transverse process of the sixth cervical vertebra is of surgical importance. If deep pressure be made in the neck in the course of the carotid artery, opposite the cricoid cartilage, the prominent anterior tubercle of the transverse process of the sixth cervical vertebra can be felt. This has been named Chassaignac s tubercle, and against it the carotid artery may be most conveniently compressed by the finger. The transverse process of the seventh cervical vertebra can also often be felt. Occasionally the anterior root, or costal process, is large and segmented off, forming a cervical rib. Surgical Anatomy.-Occasionally the coalescence of the laminae is not completed, and con- sequently a cleft is left in the arches of the vertebrae, through which a protrusion of the spinal membranes (dura mater and arachnoid), and sometimes of the spinal cord itself, takes place, constituting the disease known asspour bifida. This disease is most common in the lumbo sacral region, on account of the fact, previously stated, that the closure of the arches takes place gradually from above downward ; but it may occur in the dorsal or cervical region, or the arches throughout the whole length of the canal may remain unapproximated. In some rare cases, in consequence of the non-coalescence of the two primary centres from which the body is formed, a similar condition may occur in front of the canal, the bodies of the vertebrae being found cleft and the tumor projecting into the thorax, abdomen, or pelvis, between the lateral halves of the bodies affected. The construction of the spinal column of a number of pieces, securely connected together and enjoying only a slight degree of movement between any two individual pieces, though per- THE SKULL. 165 mitting of a very considerable range of movement as a whole, allows a sufficient degree of mobility without any material diminution of strength. The many joints of which the spine is composed, together with the very varied movements to which it is subjected, render it liable to sprains; but so closely are the individual vertebrae articulated that these sprains are rarely or ever severe, and any amount of violence sufficiently great to produce tearing of the ligaments would tend rather to cause a dislocation or fracture. The further safety of the column and its less liability to injury is provided for by its disposition in curves, instead of in one straight line. For it is an elastic column, and must first bend before it breaks: under these circumstances, being made up of three curves, it represents three columns, and greater force is required to pro- duce bending of a short column than of a longer one that is equal to it in breadth and material. Again, the safety of the column is provided for by the interposition of the intervertebral disk between the bodies of the vertebrae, which act as admirable buffers in counteracting the effects of violent jars or shocks. Fracture-dislocation of the spine may be caused by direct or indirect violence, or by a combination of the two, as when a person, falling from a height, strikes against some prominence and is doubled over it. The fractures from indirect violence are the more com- mon, and here the bodies of the vertebrae are compressed, whilst the arches are torn asunder ; whilst in fractures from direct violence the arches are compressed and the bodies of the vertebrae separated from each other. It will therefore be seen that in both classes of injury the spinal marrow is the part least likely to be injured, and may escape damage even where there has been considerable lesion of the bony framework. For, as Mr. Jacobson states, "being lodged in the centre of the column, it occupies neutral ground in respect to forces which might cause fracture. For it is a law in mechanics that when a beam, as of timber, is exposed to breakage and the force does not exceed the limits of the strength of the material, one division resists compression, another laceration of the particles, while the third, between the two, is in a negative condition."1 Applying this principle to the spine, it will be seen that, whether the fracture-dislocation be pro- duced by direct violence or indirect, one segment, either the anterior or posterior, will be exposed to compression, the other to laceration, and the intermediate part, where the cord is situated, will be in a neutral state. When a fracture-dislocation is produced by indirect violence the dis- placement is almost always the same, the upper segment being driven forward on the lower, so that the cord is compressed between the body of the vertebra below and the arch of the vertebra above. The parts of the spine most liable to be injured are (1) the dorsi-lumbar region, for this part is near the middle of the column, and there is therefore a greater amount of leverage, and more- over the portion above is comparatively fixed, and the vertebrae which form it, though much smaller, have nevertheless to bear almost as great a weight as those below; (2) the cervico-dorsal region, because here the flexible cervical portion of the spine joins the more fixed dorsal region ; and (3) the alto-axoid region, because it enjoys an extensive range of movement, and, being near the skull, is influenced by violence applied to the head. In fracture-dislocation it has been proposed to trephine the spine and remove portions of the laminae and spinous processes. The operation can only be of use when the paralysis is due to the pressure of bone or the effusion of blood, and not to cases, which are by far the most common, where the cord is crushed to a pulp. And even in those cases where the cord is compressed by bone the portion of displaced bone which presses on the cord is generally the body of the vertebra below, and is therefore inaccess- ible to operation. The operative proceeding is one of great severity, involving an extensive and deep wound and great risk of septic meningitis, and, as the advantages to be derived from it are exceedingly problematical and confined to a very few cases, it is not often resorted to. Trephin- ing has also been resorted to in some cases of paraplegia due to Pott's disease of the spine. Here the paralysis is due to the pressure of inflammatory products, and w7here this is new scar- tissue, formed by the organization of granulation tissue, its removal has been attended with a very considerable amount of success. THE SKULL. The Skull, or superior expansion of the vertebral column, has been described as if composed of four vertebrae, the elementary parts of which are specially modified in form and size, and almost immovably connected, for the reception of the brain and special organs of the senses. These vertebrae are the occipital, parietal, frontal, and nasal. Descriptive anatomists, however, divide the skull into two parts, the Cranium and the Face. The Cranium a helmet) is composed of eight bones-viz. the occipital, two parietal, frontal, two temporal, sphenoid, and ethmoid. The Face is composed of fourteen bones-viz. the two nasal, two superior maxillary, two lachrymal, two malar, two palate, two inferior turbinated, vomer, and inferior maxillary. The ossiculi auditus, the teeth, and Wormian bones are not included in this enumeration. 1 Holmes's System of Surgery, vol. i. p. 529, 1883. 166 THE SKELETON. Occipital. Two Parietal. Frontal. Two Temporal. Sphenoid. Ethmoid. Cranium, 8 bones . Skull, 22 bones Two Nasal. Two Superior Maxillary. Two Lachrymal. Two Malar. Two Palate. Two Inferior Turbinated. Vomer. Inferior Maxillary. 77 -i . i Lace, 14 bones . THE CRANIUM. The Occipital Bone. The Occipital Bone (pb, caput, against the head) is situated at the back part SUPERIOR CONSTRICTOR -of Pharynx. Fig. 130.-Occipital bone. Outer surface. and base of the cranium, is trapezoid in form (Fig. 130), curved upon itself, and presents for examination two surfaces, four borders, and four angles. The external surface is convex. Midway between the summit of the bone and the posterior margin of the foramen magnum is a prominent tubercle, the external occipital protuberance, for the attachment of the Ligamentum nuchae; and, descending from it as far as the foramen, a vertical- ridge, the external occipital crest. This tubercle and crest vary in prominence in different skulls. Passing outward from the occipital protuberance is a semicircular ridge on each side, the THE CRANIUM. 167 superior curved line. Above this line there is often a second less distinctly marked ridge, called the highest curved line (linea suprema); to it the epicranial aponeurosis is attached. The bone between these two lines is smoother and denser than the rest of the surface. Running parallel with these from the middle of the crest is another semicircular ridge on each side, the inferior curved lines. The surface of the bone above the superior curved lines is rough and porous, and in the recent state is covered by the Occipito-frontalis muscle, while the ridges, as well as the surface of the bone between them, serve for the attachment of numerous muscles. The superior curved line gives attachment internally to the Trapezius, externally to the muscular origin of the Occipito-frontalis, and to the Sterno-cleido-mastoid to the extent shown in Fig. 130; the depressions between the curved lines to the Complexus internally, the Splenius capitis and Obliquus capitis superior exter- nally. The inferior curved line and the depressions below it afford insertion to the Rectus capitis posticus, major and minor. The foramen magnum is a large, oval aperture, its long diameter extending from before backward. It transmits the medulla oblongata and its membranes, the spinal accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries, and the occipito-axial ligaments. Its back part is wide for the transmis- sion of the medulla, and the corresponding margin rough for the attachment of the dura mater enclosing it; the fore part is narrower, being encroached upon by the condyles; it has projecting toward it, from below, the odontoid process, and its margins are smooth and bevelled internally to support the medulla oblongata. On each side of the foramen magnum are the condyles, for articulation with the atlas; they are convex, oblong, or reniform in shape, and directed downward and out- ward ; they converge in front, and encroach slightly upon the anterior segment of the foramen. On the inner border of each condyle is a rough tubercle for the attachment of the ligaments (check) which connect this bone with the odontoid process of the axis; whilst external to them is a rough tubercular prominence, the transverse or jugular process (the representative of the transverse process of a vertebra), channelled in front by a deep notch, which forms part of the jugular foramen or foramen lacerum posterius. The under surface of this process presents an eminence which represents the paramastoid process of some mammals. The eminence is occasionally large, and extends as low as the transverse process of the atlas. This surface affords attachment to the Rectus capitis lateralis muscle and to the lateral occipito-atlantal ligament; its upper or cerebral surface presents a deep groove which lodges part of the lateral sinus, whilst its external surface is marked by a quadrilateral rough facet, covered with cartilage in the fresh state, and articulating with a similar surface on the petrous portion of the temporal bone. On the outer side of each condyle, near its fore part, is a foramen, the anterior con- dyloid; it is directed downward, outward, and forward, and transmits the hypo- glossal nerve, and occasionally a meningeal branch of the ascending pharyngeal artery. This foramen is sometimes double. Behind each condyle is a fossa,1 some- times perforated at the bottom by a foramen, the posterior condyloid, for the trans- mission of a vein to the lateral sinus. In front of the foramen magnum is a strong quadrilateral plate of bone, the basilar process, wider behind than in front; its under surface, which is rough, presenting in the median line a tubercular ridge, the pharyngeal spine, for the attachment of the tendinous raphe and Superior constrictor of the pharynx; and on each side of it rough depressions for the attachment of the Rectus capitis anticus, major and minor. The Internal or Cerebral Surface (Fig. 131) is deeply concave. The posterior or occipital part is divided by a crucial ridge into four fossae. The two superior fossae receive the occipital lobes of the cerebrum, and present slight eminences and depressions corresponding to their convolutions. The two inferior, which receive the hemispheres of the cerebellum, are larger than the former, and com- 1 This fossa presents many variations in size. It is usually shallow, and the foramen small; occa- sionally wanting on one or both sides. Sometimes both fossa and foramen are large, but confined to one side only; more rarely, the fossa and foramen are very large on both sides. 168 THE SKELETON. paratively smooth ; both are marked by slight grooves for the lodgment of arteries. At the point of meeting of the four divisions of the crucial ridge is an eminence, the internal occipital protuberance. It nearly corresponds to that on the outer surface, and is perforated by one or more large vascular foramina. From this eminence the superior division of the crucial ridge runs upward to the superior angle of the bone ; it presents a deep groove for the superior longitudinal sinus, the margins of which give attachment to the falx cerebri. The inferior division, the internal occipital crest, runs to the posterior margin of the foramen magnum, Superior angle. Inferior angle. Fig. 131.-Occipital bone. Inner surface on the edge of which it becomes gradually lost; this ridge, which is bifurcated below, serves for the attachment of the falx cerebelli. It is usually marked by a single groove, which commences at the back part of the foramen magnum and lodges the occipital sinus. Occasionally the groove is double where two sinuses exist. The transverse grooves pass outward to the lateral angles; they are deeply channelled, for the lodgment of the lateral sinuses, their prominent margins afford- ing attachment to the tentorium cerebelli.1 At the point of meeting of these grooves is a depression, the torcular 11 er ophili.2 placed a little to one or the other side of the internal occipital protuberance. More anteriorly is the foramen mag- num, and on each side of it, but nearer its anterior than its posterior part, the 1 Usually one of the transverse grooves is deeper and broader than the other; occasionally, both grooves are of equal depth and breadth, or both equally indistinct. The broader of the two transverse grooves is nearly always continuous with the vertical groove for the superior longitudinal sinus. 1 The columns of blood coming in different directions were supposed to be pressed together at this point (torcular, a wine-press). THE CRANIUM. 169 internal openings of the anterior condyloid foramina ; the internal openings of the posterior condyloid foramina are a little external and posterior to them, protected by a small arch of bone. At this part of the internal surface there is a very deep groove in which the posterior condyloid foramen, when it exists, has its termina- tion. This groove is continuous, in the complete skull, with the transverse groove on the posterior part of the bone, and lodges the end of the same sinus, the lateral. In front of the foramen magnum is the basilar process, presenting a shallow depression, the basilar groove, which slopes from behind, upward and forward, and supports the medulla oblongata and part of the pons Aaroli i, and on each side of the basilar process is a narrow channel, which, when united with a similar channel on the petrous portion of the temporal bone, forms a groove which lodges the inferior petrosal sinus. Angles.-The superior angle is received into the interval between the posterior superior angles of the twTo parietal bones : it corresponds with that part of the skull in the foetus which is called the posterior fontanelle. The inferior angle is represented by the square-shaped surface of the basilar process. At an early period of life a layer of cartilage separates this part of the bone from the sphenoid, but in the adult the union between them is osseous. The lateral angles corre- spond to the outer ends of the transverse grooves, and are received into the interval between the posterior inferior angles of the parietal and the mastoid portion of the temporal. Borders.-The superior border extends on each side from the superior to the lateral angle, is deeply serrated for articulation with the parietal bone, and forms, by this union, the lambdoid suture. The inferior border extends from the lateral to the inferior angle; its upper half is rough, and articulates with the mastoid por- tion of the temporal, forming the masto-occipital suture ; the inferior half articu- lates with the petrous portion of the temporal, forming the petro-occipital suture; these two portions are separated from one another by the jugular process. In front of this process is a deep notch, which, with a similar one on the petrous por- tion of the temporal, forms the foramen laceruni posterius or jugular foramen. This notch is occasionally subdivided into two parts by a small process of bone, and it generally presents an aperture at its upper part, the internal opening of the posterior condyloid foramen. Structure.-The occipital bone consists of two compact laminae, called the outer and inner tables, having between them the diploic tissue; this bone is espe- cially thick at the ridges, protuberances, condyles, and internal part of the basilar process ; whilst at the bottom of the fossae, especially the inferior, it is thin, semi- transparent, and destitute of diploe. Development. (Fig. 132).-At birth the bone consists of four distinct parts : a tabular or expanded portion, which lies behind the foramen magnum ; two con- dylar parts, which form the sides of the foramen; and a basilar part, which lies in front of the foramen. The number of nuclei for the tabular part vary. As a rule, there are four, but there may be only one (Blandin) or as many as eight (Meckel). They ap- pear about the eighth week of foetal life, and soon unite to form a single piece, which is, however, fissured in the direction indicated in the plate. The basilar and two condyloid por- tions are each developed from a single nucleus, which appears a lit- tle later. The upper portion of the tabular surface-that is to say, the portion above the transverse fissure -is developed from membrane; the rest of the bone is developed from cartilage. *4 for occipital portion. Join about 4 yr. Join 5-6yr At birth the 4 pieces separate. -1 for each condyloid portion. Fig. 132.-Development of occipital bone. By seven centres. ~ 1 for basilar portion. 170 THE SKELETON. At about the fourth year the tabular and the two condyloid pieces join, and about the sixth year the bone consists of a single piece. At a later period, between the eighteenth and twenty-fifth years, the occipital and sphenoid become united, form- ing a single bone. Articulations.-With six bones: two parietal, two temporal, sphenoid, and atlas. Attachment of Muscles.-To twelve pairs : to the superior curved line are attached the Occipito-frontalis, Trapezius, and Sterno-cleido-mastoid. To the space between the curved lines, the Complexus,1 Splenius capitis, and Obliquus capitis superior; to the inferior curved line, and the space between it and the foramen magnum, the Rectus capitis posticus, major and minor; to the transverse process, the Rectus capitis lateralis ; and to the basilar process, the Rectus capitis anticus, major and minor, and Superior constrictor of the pharynx. The Parietal Bones. The Parietal Bones (paries, a wall) form, by their union, the sides and roof of the skull. Each bone is of an irregular quadrilateral form, and presents for examination two surfaces, four borders, and four angles. Surfaces.-The external surface (Fig. 133) is convex, smooth, and marked about its centre by an eminence called the parietal eminence, which indicates the point Articulates with Frontal Bone. /Articulates / with i Occipital bone. portion of temporal bone. Fig. 133.-Left parietal bone. External surface. where ossification commenced. Crossing the middle of the bone in an arched direction are two well-marked curved lines or ridges, of which the lower is the more distinct and is termed the temporal ridge; it marks the upper attachment of the temporal muscle and follows a semicircular course across the bone. The upper ridge is less marked, and pursues a similar course across the bone, but about two- 1 To these the Biventer cervicis should be added, if it is regarded as a separate muscle. THE PARIETAL BONES. 171 fifths of an inch above the temporal ridge ; it marks the attachment of the temporal fascia. Above these ridges the surface of the bone is rough and porous, and covered bv the aponeurosis of the Occipito-frontalis; between them the bone is smoother and more polished than the rest; below them the bone forms part of the temporal fossa, and affords attachment to the temporal muscle. At the back part of the superior border, close to the sagittal suture, is a small foramen, the parietal foramen, which transmits a vein to the superior longitudinal sinus, and sometimes a small branch of the occipital artery. Its existence is not constant, and its size varies considerably. The internal surface (Fig. 134), concave, presents eminences and depressions for lodging the convolutions of the cerebrum and numerous furrows for the rami- fications of the meningeal arteries; the latter run upward and backward from the Posterior superior angle. .Anterior superior angle. Posterior £ inferior angle. Anterior inferior angle. Fig. 134.-Left parietal bone. Internal surface. anterior inferior angle and from the central and posterior part of the lower border of the bone. Along the upper margin is part of a shallow groove, which, when joined to the opposite parietal, forms a channel for the superior longitudinal sinus, the elevated edges of which afford attachment to the falx cerebri. Near the groove are seen several depressions, especially in the skulls of old persons; they lodge the Pacchionian bodies. The internal opening of the parietal foramen is also seen when that aperture exists. Borders.-The superior, the longest and thickest, is dentated to articulate with its fellow of the opposite side, forming the sagittal suture. The inferior is divided into three parts : of these, the anterior is thin and pointed, bevelled at the expense of the outer surface, and overlapped by the tip of the great wing of the sphenoid; the middle portion is arched, bevelled at the expense of the outer surface, and overlapped by the squamous portion of the temporal; the posterior portion is thick and serrated for articulation with the mastoid portion of the temporal. The anterior border, deeply serrated, is bevelled at the expense of the outer surface above and of the inner below; it articulates with the frontal bone, forming the 172 THE SKELETON. coronal suture. The posterior border, deeply denticulated, articulates with the occipital, forming the lambdoid suture. Angles.-The anterior superior angle, thin and pointed, corresponds with that portion of the skull which in the foetus is membranous and is called the anterior fontanelle. The anterior inferior angle is thin and lengthened, being received in the interval between the great wing of the sphenoid and the frontal. Its inner surface is marked by a deep groove, sometimes a canal, for the anterior branch of the middle meningeal artery. The posterior superior angle corresponds with the junction of the sagittal and lambdoid sutures. In the foetus this part of the skull is membranous, and is called the posterior fontanelle. The posterior inferior angle articulates with the mastoid portion of the temporal bone, and generally presents on its inner surface a broad, shallow groove for lodging part of the lateral sinus. Development.-The parietal bone is formed in membrane, being developed by one centre, which corresponds with the parietal eminence, and makes its first appearance about the seventh or eighth week of foetal life. Ossification gradually extends from the centre to the circumference of the bone: the angles are conse- quently the parts last formed, and it is in their situation that the fontanelles exist previous to the completion of the growth of the bone. Articulations.-With five bones: the opposite parietal, the occipital, frontal, temporal, and sphenoid. Attachment of Muscles.-One only, the Temporal. The Frontal Bone. The Frontal Bone Efrons, the forehead) resembles a cockle-shell in form, and consists of two portions-a vertical or frontal portion situated at the anterior part PALPEBRARUM. Internal angular process. External angular process. Fig. 135.-Frontal bone. Outer surface. of the cranium, forming the forehead; and a horizontal or orbito-nasal portion which enters into the formation of the roof of the orbits and nasal fossae. THE FRONTAL BONE. 173 Vertical Portion.-External Surface (Fig. 135).-In the median line, traversing the bone from the upper to the lower part, is occasionally seen a slightly-elevated ridge, and in young subjects a suture, which represents the line of union of the two lateral halves of which the bone consists at an early period of life; in the adult this suture is usually obliterated and the bone forms one piece; traces of the obliterated suture are, however, generally perceptible at the lower part. On either side of this ridge, a little below the centre of the bone, is a rounded eminence, the frontal eminence. These eminences vary in size in different individuals, and are occasionally unsymmetrical in the same subject. They are especially prominent in cases of well-marked cerebral development. The whole surface of the bone above this part is smooth, ami covered by the aponeurosis of the Occipito-frontalis muscle. Below the frontal eminence, and separated from it by a slight groove, is the superciliary ridge, broad internally, where it is continuous with the nasal eminence, but less distinct as it arches outward. These ridges are caused by the projection outward of the frontal sinuses,1 and give attachment to the Orbicularis palpebrarum and Corrugator supercilii. Between the two superciliary ridges is a smooth surface, the glabella or nasal eminence. Beneath the superciliary ridge is the supraorbital arch, a curved and prominent margin, which forms the upper boundary of the orbit, and separates the vertical from the horizontal portion of the bone. The outer part of the arch is sharp and prominent, affording to the eye, in that situation, considerable protection from injury; the inner part is less promi- nent. At the junction of the internal and middle third of this arch is a notch, sometimes converted into foramen by a bony process, and called the supraorbital notch or foramen. It transmits the supraorbital artery, vein, and nerve. A small aperture is seen in the upper part of the notch, which transmits a vein from the diploe to join the supraorbital vein. The supraorbital arch terminates externally in the external angular process and internally in the internal angular process. The external angular process is strong, prominent, and articulates with the malar bone; running upward and backward from it are two well-marked lines, which, commencing together from the external angular process, soon diverge from each other and run in a curved direction across the bone. The lower one, the temporal ridge, gives attachment to the Temporal muscle, the upper one to the temporal fascia. Beneath them is a slight concavity that forms the anterior part of the temporal fossa and gives origin to the Temporal muscle. The internal angular processes are less marked than the external, and articulate with the lachrymal bones. Between the internal angular processes is a rough, uneven interval, the nasal notch, which articulates in the middle line with the nasal bone, and on either side with the nasal process of the superior maxillary bone. From the concavity of this notch projects a process, the nasal process, w hich extends beneath the nasal bones and nasal processes of the superior maxillary bones and supports the bridge of the nose. On the under surface of this is a long pointed process, the nasal spine, and on either side a small grooved surface enters into the formation of the roof of the nasal fossa. The nasal spine forms part of the septum of the nose, articulating in front with the nasal bones and behind the perpendicular plate of the ethmoid. Internal Surface (Fig. 136).-Along the middle line is a vertical groove, the edges of which unite below to form a ridge, the frontal crest; the groove lodges the superior longitudinal sinus, whilst its margins afford attachment to the falx cerebri. The crest terminates below at a small notch which is converted into a foramen by articulation with the ethmoid. It is called the foramen caecum, and varies in size in different subjects: it is sometimes partially or completely impervious, lodges a process of the falx cerebri, and when open transmits a vein 1 Some confusion is occasioned to . students commencing the study of anatomy by the name "sinuses" having been given to two perfectly different kinds of spaces connected with the skull. It may be as well, therefore, to state here, at the outset, that the "sinuses" in the interior of the cranium which produce the grooves on the inner surface of the bones are venous channels along which the blood runs in its passage back from the brain, while the "sinuses" external to the cranial cavity (the frontal, sphenoidal, ethmoidal, and maxillary) are hollow spaces in the bones themselves which communicate with the nostrils, and contain air. 174 THE SKELETON. from the lining membrane of the nose to the superior longitudinal sinus. On either side of the groove the bone is deeply concave, presenting eminences and depressions for the convolutions of the brain, and numerous small furrows for lodging the ramifications of the anterior meningeal arteries. Several small, irregular fossae are also seen on either side of the groove for the reception of the Pacchionian bodies. Horizontal Portion.-External Surface.-This portion of the bone consists of two thin plates, which form the vault of the orbit, separated from one another by the ethmoidal notch. Each orbital vault consists of a smooth, concave, triangular plate of bone, marked at its anterior and external part (immediately beneath the With superior maxillary. With nasal. Frontal sinus. With perpendicular plate of ethmoid. \ Under surface of nasal process, forming part of roof of nose. Fig. 136.-Frontal bone. Inner surface. external angular process) by a shallow depression, the lachrymal fossa, for lodging the lachrymal gland; and at its anterior and internal part by a depression (some- times a small tubercle) for the attachment of the cartilaginous pulley of the Superior oblique muscle of the eye. The ethmoidal notch separates the two orbital plates; it is quadrilateral, and filled up, when the bones are united, by the cribriform plate of the ethmoid. The margins of this notch present several half- cells, which, when united with corresponding half-cells on the upper surface of the ethmoid, complete the ethmoidal cells; two grooves are also seen crossing these edges transversely ; they are converted into canals by articulation with the ethmoid, and are called the anterior and posterior ethmoidal canals : they open on the inner wall of the orbit. The anterior one transmits the nasal nerve and anterior ethmoidal vessels, the posterior one the posterior ethmoidal vessels. In front of the ethmoidal notch, on either side of the nasal spine, are the openings of the frontal sinuses. These are two irregular cavities, which extend upward and outward, a variable distance, between the two tables of the skull, and are separated from one another by a thin, bony septum. They give rise to the THE TEMPORAL BONES. 175 prominences above the supraorbital arches called the superciliary ridges. In the child they are generally absent, and they become gradually developed as age advances. These cavities vary in size in different persons, are larger in men than in women, and are frequently of unequal size on the two sides, the right being commonly the larger. They are subdivided by a bony lamina, which is often dis- placed to one side. They are lined by mucous membrane, and communicate with the nose by the infundibulum, and occasionally with each other by apertures in their septum. The internal surface of the horizontal portion presents the convex upper surfaces of the orbital plates, separated from each other in the middle line by the ethmoidal notch, and marked by eminences and depressions for the convolutions of the frontal lobes of the brain. Borders.-The border of the vertical portion is thick, strongly serrated, bevelled at the expense of the internal table above, where it rests upon the parietal bones, and at the expense of the external table at each side, where it receives the lateral pressure of those bones; this border is continued below into a triangular rough surface which articulates with the great wing of the sphenoid. The border of the horizontal portion is thin, serrated, and articulates with the lesser wing of the sphenoid. Structure.-The vertical portion and external angular processes are very thick, consisting of diploic tissue contained between two compact laminae. The hori- zontal portion is thin, translucent, and composed entirely of compact tissue; hence the facility with which instruments can penetrate the cranium through this part of the orbit. Development (Fig. 137).-The frontal bone is formed in membrane, being devel- oped by two centres, one for each lateral half, which make their appearance about the seventh or eighth week, above the orbital arches. From this point ossification extends, in a radiating manner, upward into the forehead and backward over the orbit. At birth the bone consists of two pieces, which afterward become united, along the middle line, by a suture which runs from the vertex to the root of the nose. This suture usually becomes obliterated within a few years after birth ; but it occasionally remains throughout life. Occasionally secondary centres of ossifica- tion appeal* for the nasal spine-one on either side at the internal angular process where it articulates with the lachrymal bone; and sometimes there is one on either side at the lower end of the coronal suture. This latter centre sometimes remains ununited, and is known as the pterion ossicle, or it may join with the parietal, sphenoid, or temporal bone. Articulations.-With twelve bones: two parietal, the sphenoid, the ethmoid, two nasal, two superior maxillary, two lachrymal, and two malar. Attachment of Muscles.-To three pairs: the Corrugatorsupercilii, Orbicu- laris palpebrarum, and Temporal, on each side. Fig. 137.-Frontal bone at birth. Developed by two lateral halves. The Temporal Bones The Temporal Bones (tempus, time) are situated at the sides and base of the skull, and present for examination a squamous, mastoid, and petrous portion. The squamous portion (squama, a scale), the anterior and upper part of the bone, is scale-like in form, and thin and translucent in texture (Fig. 138), Its outer surface is smooth, convex, and grooved at its back part for the deep temporal arteries; it affords attachment to the Temporal muscle and forms part of the temporal fossa. At its back part may be seen a curved ridge-part of the temporal 176 THE SKELETON. ridge ; it serves for the attachment of the temporal fascia, limits the origin of the Temporal muscle, and marks the boundary between the squamous and mastoid Eminentia articularis. Glenoid fossa. - * Mastoid foramen. DIGASTRIC. STYLO- GLOSSUS 'stylo- hyoid. Auditory' process. Fig. 138.-Left temporal bone. Outer surface. portions of the bone. Projecting from the lower part of the squamous portion is a long, arched process of bone, the zygoma or zygomatic process. This process is at first directed outward, its two surfaces looking upward and downward; it then appears as if twisted upon itself, and runs forward, its surfaces now looking in- ward and outward. The superior border of the process is long, thin, and sharp, and serves for the attachment of the temporal fascia. The inferior, short, thick, and arched, has attached to it some fibres of the Masseter muscle. Its outer surface is convex and subcutaneous ; its inner is concave, and also affords attachment to the Masseter. The extremity, broad and deeply serrated, articulates with the malar bone. The zygomatic process is connected to the temporal bone by three divisions, called its roots-an anterior, middle, and posterior. The anterior, which is short, but broad and strong, is directed inward, to terminate in a rounded eminence, the eminentia articularis. This eminence forms the front boundary of the glenoid fossa, and in the recent state is covered with cartilage. The middle root forms the outer margin of the glenoid fossa; running obliquely inward, it terminates at the commencement of a well-marked fissure, the Glaserian fissure ; while the posterior root, which is strongly marked, runs from the upper border of the zygoma, in an arched direction, upward and backward, forming the posterior part of the temporal ridge. At the junction of the anterior root with the zygoma is a projection, called the tubercle, for the attachment of the external lateral ligament of the lower jaw; and between the anterior and middle roots is an oval depression, forming part of the glenoid fossa a socket), for the reception of the condyle of the lower jaw. This fossa is bounded, in front, by the eminentia articularis ; behind, by the tympanic plate; and, externally, by the auditory process and middle root of the zygoma; and is divided into two parts by a narrow slit, the Glaserian fissure. The anterior part, formed by the squamous portion of the bone, is smooth, covered in the recent state with cartilage, and articulates with the condyle of the lower jaw. This part of the glenoid fossa is separated from the auditory process by a THE TEMPORAL BONES. 177 small tubercle, the post-glenoid process, the representative of a prominent tubercle which, in some of the mammalia, descends behind the condyle of the jaw, and prevents it being displaced backward during mastication (Humphry). The poste- rior part of the glenoid fossa, which lodges a portion of the parotid gland, is formed chiefly by the tympanic plate, a lamina of bone, which forms the anterior wall of the tympanum and external auditory meatus. This plate of bone termi- nates externally in the auditory process, above in the Glaserian fissure, and below forms a sharp edge, the vaginal process, which gives origin to some of the fibres of the Tensor palati muscle. The Glaserian fissure, which leads into the tympanum, lodges the processus gracilis of the malleus, and transmits the tympanic branch of the internal maxillary artery. The chorda tympani nerve passes through a sepa- rate canal, parallel to the Glaserian fissure (canal of Huguier), on the outer side of the Eustachian tube, in the retiring angle between the squamous and petrous por- tions of the temporal bone.1 The internal surface of the squamous portion (Fig. 139) is concave, presents Aquxductus vestibuli! Depression for dura mater. Meatus auditorius internus. Eminence for superior semicircular canal. Hiatus Fallopii. Opening for smaller petrosal nerve. Depression for Gasserian ganglion. Bristle passed through carotid canal. numerous eminences and depressions for the convolutions of the cerebrum, and two well-marked grooves for the branches of the middle meningeal artery. Borders.-The superior border is thin, bevelled at the expense of the internal surface, so as to overlap the lower border of the parietal bone, forming the squam- ous suture. The anterior inferior border is thick, serrated, and bevelled, alter- nately at the expense of the inner and outer surfaces, for articulation with the great wing of the sphenoid. The Mastoid Portion (p.aaro~, a nipple or teat) is situated at the posterior part of the bone; its outer surface is rough, and gives attachment to the Occipito-frontalis and Retrahens aurem muscles. It is perforated by numerous foramina; one of these, of large size, situated at the posterior border of the bone, is termed the mastoid foramen; it transmits a vein to the lateral sinus and a small artery from the occipital to supply the dura mater. The position and size of this foramen Fig. 139.-Left temporal bone. Inner surface. 1 This small fissure must not be confounded with the large canal which lies above the Eustachian tube and transmits the Tensor tympani muscle. 178 THE SKELETON. are very variable. It is not always present; sometimes it is situated in the occipital bone or in the suture between the temporal and the occipital. The mastoid portion is continued below into a conical projection, the mastoid process, the size and form of which vary somewhat. This process serves for the attachment of the Sterno-mastoid, Splenius capitis, and Trachelo-mastoid muscles. On the inner side of the mastoid process is a deep groove, the digastric fossa, for the attachment of the Digastric muscle; and, running parallel with it, but more in- ternal, the occipital groove, which lodges the occipital artery. The internal surface of the mastoid portion presents a deep, curved groove, the/osaa sigmoidea, which lodges part of the lateral sinus; and into it may be seen opening the mastoid fora- men. A section of the mastoid process shows it to be hollowed out into a number of cellular spaces, communicating with each other, called the mastoid cells ; they open by a single or double orifice into the back of the tympanum, are lined by a prolongation of its lining membrane, and probably form some secondary part of the organ of hearing. The spaces at the upper and front part of the bone near the opening into the tympanum are large and irregular, and contain air. They diminish in size toward the lower part of the bone, those situated at the apex of the mastoid process being quite small and usually containing marrow (Fig. 140). Opening into mastoid cells. Mastoid cells- Aquxductus Fallopii.. Stapes. Promontory. Eustachian tube. Canal,for tensor tympani.. Processus cochleariformis. -Maliens. . Incus. TENSOR TYMPANI. ~Proc. cochleariformis. "Eustachian tube. Carotid canal. Carotid canal. / Fenestra rotunda. / Pyramid. K 'Styloid process. 'Aquseductus Fallopii. ''Marrow cells. Fig. 140.-Section through the petrous and mastoid portions of the temporal bone, showing the communi- cation of the cavity of the tympanum with the mastoid cells. The mastoid cells, like the other sinuses of the cranium, are not developed until after puberty; hence the prominence of this process in the adult. In consequence of the communication which exists between the tympanum and mastoid ctells. inflammation of the lining membrane of the former cavity may easily travel backward to that of the mastoid cells, leading to caries and necrosis of their walls and the risk of transfer- ence of the inflammation to the lateral sinus or encephalon. Borders.-The superior border of the mastoid portion is broad and rough, its serrated edge sloping outward, for articulation with the posterior inferior angle of the parietal bone. The posterior border, also uneven and serrated, articulates with the inferior border of the occipital bone between its lateral angle and jugular process. The Petrous Portion (nirpoQ, a stone), so named from its extreme density and hardness, is a pyramidal process of bone wedged in at the base of the skull between the sphenoid and occipital bones. Its direction from without is inward, THE TEMPORAL BONES. 179 forward, and a little downward. It presents for examination a base, an apex, three surfaces, and three borders, and contains, in its interior, the essential parts of the organ of hearing. The base is applied against the internal surface of the squamous and mastoid portions, its upper half being concealed; but its lower half is exposed by the divergence of those two portions of the bone, which brings into view the oval expanded orifice of a canal leading into the tympanum, the meatus auditorius ezternus. This canal is situated in front of the mastoid pro- cess, and between the posterior and middle roots of the zygoma; its upper mar- gin is smooth and rounded, but the greater part of its circumference is surrounded by a curved plate of bone, the auditory process, the free margin of which is thick and rough, for the attachment of the cartilage of the external ear. The apex of the petrous portion, rough and uneven, is received into the angular interval between the posterior border of the greater wing of the sphenoid and the basilar process of the occipital; it presents the anterior or internal orifice of the carotid canal, and forms the posterior and external boundary of the foramen lacerum medium. The anterior surface of the petrous portion (Fig. 139) forms the posterior part of the middle fossa of the skull. This surface is continuous with the squamous portion, to which it is united by a suture, the temporal or petro-squamous suture, the remains of which are distinct even at a late period of life; it presents six points for examination: 1, an eminence near the centre, which indicates the sit- uation of the superior semicircular canal; 2, on the outer side of this eminence a depression indicating the position of the tympanum; here the layer of bone which separates the tympanum from the cranial cavity is extremely thin, and is known as the tegmen tympani; 3, a shallow groove, sometimes double, leading outward and backward to an oblique opening, the hiatus Fallopii, for the passage of the petrosal branch of the Vidian nerve and the petrosal branch of the middle meningeal artery; 4, a smaller opening, occasionally seen external to the latter, for the passage of the smaller petrosal nerve; 5, near the apex of the bone, the termination of the carotid canal, the wall of which in this situation is deficient in front; 6, above this canal a shallow depression for the reception of the Gasserian ganglion. The posterior surface forms the front part of the posterior fossa of the skull, and is continuous with the inner surface of the mastoid portion of the bone. It presents three points for examination : 1. About its centre, a large orifice, the meatus auditorius internus, whose size varies considerably; its margins are smooth and rounded, and it leads into a short canal, about four lines in length, which runs directly outward and is closed by a vertical plate, the lamina cribrosa, which is divided by a horizontal crest, the crista falciformis, into two unequal portions; the lower presenting three foramina or sets of foramina; one, just below the posterior part of the crest, consisting of a number of small openings for the nerves to the saccule; a second, below and posterior to this, for the nerve to the posterior semicircular canal; and a third, in front and below the first, con- sisting of a number of small openings which terminate in the canalis centralis cochleae and transmit the nerve to the cochlea; the upper portion, that above the crista, presents behind a series of small openings for the passage of filaments to the vestibule and superior and external semicircular canal, and, in front, one large opening, the commencement of the aquaeductus Fallopii, for the passage of the facial nerve. 2. Behind the meatus auditorius, a small slit, almost hidden by a thin plate of bone, leading to a canal, the aquoeductus vestibuli, which transmits a small artery and vein and lodges a process of the dura mater. 3. In the inter- val between these two openings, but above them, an angular depression which lodges a process of the dura mater, and transmits a small vein into the cancellous tissue of the bone. The inferior or basilar surface (Fig. 141) is rough and irregular, and forms part of the base of the skull. Passing from the apex to the base, this surface presents eleven points for examination: 1, a rough surface, quadrilateral in form, which 180 THE SKELETON. serves partly for the attachment of the Levator palati and Tensor tympani muscles; 2, the large, circular aperture of the carotid canal, w hich ascends at first vertically, and then, making a bend, runs horizontally forward and inward; it transmits the internal carotid artery and the carotid plexus; 3, the aquoeductus cochleae, a small, triangular opening, lying on the inner side of the latter, close to the posterior border of the petrous portion; it transmits a vein from the cochlea which joins the internal jugular; 4, behind these openings a deep depression, the jugular fossa, which varies in depth and size in different skulls; it lodges the lateral sinus, and, with a similar depression on the margin of the jugular process of the occipital bone, forms the foramen lacerum posterius or jugular foramen; 5, a small foramen for the passage of Jacobson's nerve (the tympanic branch of the glosso-pharyngeal): this foramen is seen in front of the bony ridge dividing Canals for Eustachian tube and TENSOR TYMPANI MUSCLE. ' LEVATOR PALATI. tensor! ITYMPANI. Rough quadrilateral surface. Opening of carotid canal. Canal for Jacobson's nerve. Aquxductus cochlex. Canal for Arnold's nerve. Jugular fossa. Vaginal process. Styloid process. STYLO-PHARVNQSUS Stylo-mastoid foramen.'' Jugular surface.' Auricular Fig. 141.-Petrous portion. Inferior surface. the carotid canal from the jugular fossa; 6, a small foramen on the outer wall of the jugular fossa, for the entrance of the auricular branch of the pneumogastric (Arnold's) nerve; 7, behind the jugular fossa a smooth, square-shaped facet, the jugular surface; it is covered with cartilage in the recent state, and articulates with the jugular process of the occipital bone; 8, the vaginal process, a very broad, sheath-like plate of bone, which extends backward from the carotid canal and gives attachment to part of the Tensor palati muscle: this plate divides behind into two laminse, the outer of which is continuous with the auditory pro- cess, the inner with the jugular process: between these laminae is the ninth point for examination, the styloid process, a long, sharp spine, about an inch in length: it is directed downward, forward, and inward, varies in size and shape, and some- times consists of several pieces, united by cartilage ; it affords attachment to three muscles, the Stylo-pharyngeus, Stylo-hyoideus, and Stylo-glossus, and two liga- ments, the stylo-hyoid and stylo-maxillary ; 10, the stylo-mastoid foramen, a rather large orifice, placed between the styloid and mastoid processes : it is the termina- THE TEMPORAL BONES. 181 tion of the aquaeductus Fallopii, and transmits the facial nerve and stylo-mastoid artery; 11, the auricular fissure, situated between the auditory and mastoid pro- cesses, for the exit of the auricular branch of the pneumogastric nerve. Borders.-The superior, the longest, is grooved for the superior petrosal sinus, and has attached to it the tentorium cerebelli; at its inner extremity is a semilunar notch, upon which the fifth nerve lies. The posterior border is intermediate in length between the superior and the anterior. Its inner half is marked by a groove, which, when completed by its articulation with the occipital, forms the channel for the inferior petrosal sinus. Its outer half presents a deep excavation-the jugular fossa-which, with a similar notch on the occipital, forms the foramen lacerum posterius. A projecting eminence of bone occasionally stands out from the centre of the notch, and divides the foramen into two parts. The anterior border is divided into two parts-an outer joined to the squamous portion by a suture, the remains of which are distinct; an inner, free, articulating with the spinous process of the sphenoid. At the angle of junction of the petrous and squamous portions are seen two canals, separated from one another by a thin plate of bone, the processus cochleariformis; they both lead into the tympanum, the upper one transmitting the Tensor tympani muscle, the lower one the Eustachian tube. Structure.-The squamous portion is like that of the other cranial bones; the mastoid portion, cellular; and the petrous portion, dense and hard. Development (Fig. 142).-The temporal bone is developed by ten centres, exclusive of those for the internal ear and the ossicula-viz. one for the squamous portion including the zygoma, one for the tympanic plate, six for the petrous and mastoid parts, and two for the styloid process. Just before the close of foetal life the temporal bone consists of four parts: 1. The squamo-zygomatic, which is ossi- fied in membrane from a single nucleus, which appears at its lower part about the second month. 2. The tympanic plate, an imperfect ring, which encloses the tym- panic membrane. This is also ossified from a single centre, which appears rather later than that for the squamous portion. 3. Thepetro-mastoid, which is developed from six centres, which appear about the fifth or sixth month. Four of these are for the petrous portion, and are placed around the labyrinth, and two for the mas- toid (Vrolik). According to Huxley, the centres are more numerous, and are dis- posed so as to form three portions : (1) including most of the labyrinth, with a part of the petrous and mastoid, he has named prootic; (2) the rest of the petrous, the opisthotic; and (3) the remainder of the mastoid, the epiotic. The petro-mastoid is ossified in carti- lage. 4. The styloid process is also ossified in cartilage from two centres: one for the base, which appears before birth, and is termed the tympano-hyal; the other, comprising the rest of the process, is named the stylo-hyal, and does not appear tmtil after birth. Shortly before birth the tympanic plate joins with the squamous. The petrous and mastoid join with the squamous during the first year, and the tympano-hyal portion of the sty- loid process about the same time. The stylo-hyal does not join the rest of the bone until after puberty, and in some skulls never becomes united. The subsequent changes in this bone are, that the tympanic plate extends outward, so as to form the meatus auditorius; 1 for squamous portion, including' zygoma : 2d month. 1 for tympanic plate. 6 for petrous and mastoid portions. Fig. 142.-Development of the temporal bone. By ten centres. 2 for styloid process. 182 THE SKELETON. the glenoid fossa becomes deeper; and the mastoid part, which at an early period of life is quite flat, enlarges from the development of the cellular cavities in its interior. Articulations.-With five bones-occipital, parietal, sphenoid, inferior maxil- lary, and malar. Attachment of Muscles.-To fifteen: to the squamous portion, the Temporal; to the zygoma, the Masseter; to the mastoid portion, the Occipito-frontalis, Sterno- mastoid, Splenius capitis, Trachelo-mastoid, Digastricus, and Retrahens aurem ; to the styloid process, the Stylo-pharyngeus, Stylo-hyoideus, and Stylo-glossus; and to the petrous portion, the Levator palati, Tensor tympani, Tensor palati, and Stapedius. The Sphenoid Bone. The Sphenoid Bone a wedge) is situated at the anterior part of the base of the skull, articulating with all the other cranial bones, which it binds firmly and solidly together. In its form it somewhat resembles a bat with its wings extended ; and is divided into a central portion or body, two greater and two lesser wings extending outward on each side of the body, and two processes-the pterygoid processes-which project from it below. The body is of large size, cuboid in form, and hollowed out in its interior so as to form a mere shell of bone. It presents for examination four surfaces-a superior, an inferior, an anterior, and a posterior. The Superior Surface (Fig- 143).-In front is seen a prominent spine, the ethmoidal spine, for articulation with the cribriform plate of the ethmoid; behind Middle clinoid process. _ Posterior clinoid process. \ .Groove for \ olfactory \ trad. Ethmoidal spine. Foramen opticum Foramen lacerum ante- rius or Sphenoidal' fissure. Foramen rotundum. Foramen Vesalii.'' Foramen ovale.' Foramen spinosum. - I For 6th nerve. Petrosal process. Fig. 143.-Sphenoid bone. Superior surface. this a smooth surface presenting, in the median line, a slight longitudinal eminence, with a depression on each side for lodging the olfactory tracts. This surface is bounded behind by a ridge, which forms the anterior border of a narrow, trans- verse groove, the optic groove ; it lodges the optic commissure, and terminates on either side in the optic foramen, for the passage of the optic nerve and oph- thalmic artery. Behind the optic groove is a small eminence, olive-like in shape, the olivary process; and still more posteriorly, a deep depression, the pituitary fosse, or sella turcica, which lodges the pituitary body. This fossa is perforated by numerous foramina, for the transmission of nutrient vessels into the substance of the bone. It is bounded in front by two small eminences, one on either side, called the middle clinoid processes (xfiiw], a bed), which are sometimes connected by a spiculum of bone to the anterior clinoid processes, and behind by a square- THE SPHENOID BONE. 183 shaped plate of bone, the dorsum ephippii or dorsum selloe, terminating at each superior angle in a tubercle, the posterior clinoid processes, the size and form of which vary considerably in different individuals. These processes deepen the pituitary fossa, and serve for the attachment of prolongations from the tentorium cerebelli. The sides of the dorsum ephippii are notched for the passage of the sixth pair of nerves, and below present a sharp process, the petrosal process, which is joined to the apex of the petrous portion of the temporal bone, forming the inner boundary of the middle lacerated foramen. Behind this plate the bone presents a shallow depression, which slopes obliquely backward, and is continuous with the basilar groove of the occipital bone; it is called the clivus, and supports the upper part of the pons Varolii. On either side of the body is a broad groove, curved something like the italic letter f; it lodges the internal carotid artery and the cavernous sinus, and is called the carotid or cavernous groove. Along the outer margin of this groove, at its posterior part, is a ridge of bone in the angle between the body and greater wing, called the lingula. The posterior surface, quadrilateral Articulates with perpendicular Ethmoidal crest. plate of ethmoid. S'- Orbital .surface of greater icing. Pterygoid ridge. CPterygo- I palatine canal. ' j Groove for ala] of vomer. 1 RotirumS \ Artic. with I vomer. Internal pterygoid plate. Hamidar process. Fig. 144.-Sphenoid bone. Anterior surface.1 in form, is joined to the basilar process of the occipital bone. During childhood these bones are separated by a layer of cartilage; but in after-life (between the eighteenth and twenty-fifth years) this becomes ossified, ossification commencing above and extending downward; and the two bones then form one piece. The anterior surface (Fig. 144) presents, in the middle line, a vertical ridge of bone, the ethmoidal crest, which articulates in front with the perpendicular plate of the ethmoid, forming part of the septum of the nose. On either side of it are irregular openings leading into the sphenoidal cells or sinuses. These are two large irregular cavities hollowed out of the interior of the body of the sphenoid bone, and separated from one another by a more or less complete perpendicular bony septum. Their form and size vary considerably; they are seldom symmetrical, and are often partially subdivided by irregular osseous laminae. Occasionally, they extend into the basilar process of the occipital nearly as far as the foramen magnum. The septum is seldom quite vertical, being commonly bent to one or the other side. These sinuses do not exist in children, but they increase in size as age advances. They are partially closed, in front and below, by two thin, curved plates of bone, the sphenoidal turbinated bones, leaving a round opening at their upper parts, bv which they communicate with the upper and back part of the nose, and occasionally 1 In this figure, both the anterior and inferior surfaces of the body of the sphenoid bone are shown, the bone being held with the pterygoid processes almost horizontal. 184 THE SKELETON. with the posterior ethmoidal cells or sinuses. The lateral margins of this surface present a serrated edge, which articulates with the os planum of the ethmoid, completing the posterior ethmoidal cells; the lower margin, also rough and serrated, articulates with the orbital process of the palate bone, and the upper margin with the orbital plate of the frontal bone. The inferior surface presents, in the middle line, a triangular spine, the rostrum, which is continuous with the ethmoidal crest on the anterior surface, and is received into a deep fissure between the alae of the vomer. On each side may be seen a projecting lamina of bone, which runs horizontally inward from near the base of the pterygoid process : these plates, termed the vaginal processes, articulate with the edges of the vomer. Close to the root of the pterygoid process is a groove, formed into a complete canal when articulated with the sphenoidal process of the palate bone; it is called the pterygo-palatine canal, and transmits the pterygo-palatine vessels and pharyngeal nerve. The Greater Wings are two strong processes of bone which arise from the sides of the body, and are curved in a direction upward, outward, and backward, being prolonged behind into a sharp-pointed extremity, the spinous process of the sphenoid. Each wing presents three surfaces and a circumference. The superior or cerebral surface (Fig. 143) forms part of the middle fossa of the skull; it is deeply concave, and presents eminences and depressions for the convolutions of the brain. At its anterior and internal part is seen a circular aperture, the foramen rotunduni, for the transmission of the second division of the fifth nerve. Behind and external to this is a large oval foramen, the foramen ovale, for the trans- mission of the third division of the fifth nerve, the small meningeal artery, and sometimes the small petrosal nerve.1 At the inner side of the foramen ovale a small aperture may occasionally be seen opposite the root of the pterygoid process ; it is the foramen Vesalii, transmitting a small vein. Lastly, in the posterior angle, near to the spine of the sphenoid, is a short canal, sometimes double, the foramen spinosum; it transmits the middle meningeal artery. The external surface (Fig. 144) is convex, and divided by a transverse ridge, the pterygoid ridge,2 into two portions. The superior or larger, convex from above downward, concave from before backward, enters into the formation of the temporal fossa, and gives attachment to part of the Temporal muscle. The inferior portion, smaller in size and concave, enters into the formation of the zygomatic fossa, and affords attach- ment to the External pterygoid muscle. It presents, at its posterior part, a sharp-pointed eminence of bone, the spinous process, to which are connected the internal lateral ligament of the lower jaw and the Tensor palati muscle. The pterygoid ridge, dividing the temporal and zygomatic portions, gives attachment to part of the External pterygoid muscle. At its inner and anterior extremity is a triangular spine of bone which serves to increase the extent of origin of this muscle. The anterior or orbital surface, smooth and quadrilateral in form, assists in forming the outer wall of the orbit. It is bounded above by a serrated edge, for articulation with the frontal bone; below, by a rounded border which enters into the formation of the spheno-maxillary fissure. Internally, it presents a sharp border, which forms the lower boundary of the sphenoidal fissure, and has pro- jecting from about its centre a little tubercle of bone, which gives origin to one head of the External rectus muscle of the eye; and at its upper part is a notch for the transmission of a branch of the lachrymal artery; externally it presents a serrated margin for articulation with the malar bone. One or two small foramina may occasionally be seen for the passage of branches of the deep temporal arteries; they are called the external orbital foramina. Circumference of the great icing (Fig. 143): commencing from behind, from the body of the sphenoid to the spine, the outer half of this margin is serrated, for articulation with the petrous portion of the temporal bone, whilst the inner half forms the anterior 1 The small petrosal nerve sometimes passes through a special foramen between the foramen ovale and foramen spinosum. 2 Sometimes called infratemporal crest. THE SPHENOID BONE. 185 boundary of the foramen lacerum medium, and presents the posterior aperture of the Vidian canal for the passage of the Vidian nerve and artery. In front of the spine the circumference of the great wing presents a serrated edge, bevelled at the expense of the inner table below and of the external above, which articulates with the squamous portion of the temporal bone. At the tip of the great wing a triangular portion is seen, bevelled at the expense of the internal surface, for articulation with the anterior inferior angle of the parietal bone. Internal to this is a broad, serrated surface, for articulation with the frontal bone: this surface is continuous internally with the sharp inner edge of the orbital plate, which assists in the formation of the sphenoidal fissure, and externally with the serrated margin for articulation with the malar bone. The Lesser Wings (processes of Ingrassias) are two thin, triangular plates of bone which arise from the upper and lateral parts of the body of the sphenoid, and, projecting transversely outward, terminate in a sharp point (Fig. 143). The superior surface of each is smooth, flat, broader internally than externally, and supports part of the frontal lobe of the brain. The inferior surface forms the back part of the roof of the orbit and the upper boundary of the sphenoidal fissure or foramen lacerum anterius. This fissure is of a triangular form, and leads from the cavity of the cranium into the orbit; it is bounded internally by the body of the sphenoid-above, by the lesser wing; below, by the internal margin of the orbital surface of the great wing-and is converted into a foramen bv the articu- lation of this bone with the frontal. It transmits the third, the fourth, the three branches of the ophthalmic division of the fifth, the sixth nerve, some filaments from the cavernous plexus of the sympathetic, the orbital branch of the middle meningeal artery, a recurrent branch from the lachrymal artery to the dura mater, and the ophthalmic vein. The anterior border of the lesser wing is ser- rated for articulation with the frontal bone; the posterior, smooth and rounded, is received into the fissure of Sylvius of the brain. The inner extremity of this border forms the anterior clinoid process. The lesser wing is connected to the side of the body by two roots, the upper thin and flat, the lower thicker, obliquely directed, and presenting on its outer side, near its junction with the body, a small tubercle, for the attachment of the common tendon of three of the muscles of the eye. Between the two roots is the optic foramen, for the transmission of the optic nerve and ophthalmic artery. The Pterygoid Processes a wing; Ct do', likeness), one on each side, descend perpendicularly from the point where the body and greater wing unite (Fig. 145). Each process consists of an external and an internal plate, separated behind bv an intervening notch-the pterygoid fossa ; but joined partially in front. The external pterygoid plate is broad and thin, turned a little outward, and forms part of the inner wall of the zygomatic fossa. It gives attachment, bv its outer sur- face, to the External pterv- goid ; its inner surface forms part of the pterygoid fossa, and gives attachment to the Internal pterygoid. The in- ternal pterygoid plate is much narrower and longer, curving outward, at its extremity, into a hook-like process of bone, the hamular process, around which turns .the tendon of the Tensor palati muscle. On the posterior surface of the base of this plate is a small, oval, shallow depression, the scaphoid fossa, from which arises Fig. 145.-Sphenoid bone. Posterior surface. 186 THE SKELETON. the Tensor palati, and above which is seen the posterior orifice of the Vidian canal. Below and to the inner side of the Vidian canal, on the posterior surface of the base of this plate, is a little prominence, which is known by the name of the pterygoid tubercle. The outer surface of this plate forms part of the pterygoid fossa, the inner surface forming the outer boundary of the posterior aperture of the nares. The Superior constrictor of the pharynx is attached to its posterior edge. The two pterygoid plates are separated below by an angular interval, in which the pterygoid process, or tuberosity, of the palate bone is received. The anterior surface of the pterygoid process is very broad at its base, and forms the posterior wall of the spheno-maxillary fossa. It supports Meckel's ganglion. It presents, above, the anterior orifice of the Vidian canal; and below, a rough margin, which articulates with the perpendicular plate of the palate bone. The Sphenoidal Spongy Bones are two thin, curved plates of bones, which exist as separate pieces until puberty, and occasionally are not joined to the sphenoid in the adult. They are situated at the anterior and inferior part of the body of the sphenoid, an aperture of variable size being left in their anterior wall, through which the sphenoidal sinuses open into the nasal fossae. They are irregular in form and taper to a point behind, being broader and thinner in front. Their upper surface, which looks toward the cavity of the sinus, is concave; their under surface convex. Each bone articulates in front with the ethmoid, externally with the palate; its pointed posterior extremity is placed above the vomer, and is received between the root of the pterygoid process on the outer side and the rostrum of the sphenoid on the inner.1 Development.-Up to about the eighth month of foetal life the sphenoid bone consists of two distinct parts: posterior or post-sphenoid part, which comprises the pituitary fossa, the greater wings, and the pterygoid processes; and an anterior or pre-sphenoid part, to which the anterior part of the body and lesser wings belong. It is developed by fourteen centres: eight for the posterior sphenoid division, and six for the anterior sphenoid. The eight centres for the posterior sphenoid are-one for each greater wing and external pterygoid plate, one for each internal pterygoid plate, two for the posterior part of the body, and one on each side for the lingula. The six for the anterior sphenoid are one for each lesser wing, two for the anterior part of the body, and one for each sphenoidal turbinated bone. Post-sphenoid Division.-The first nuclei to appear are those for the greater wings. They make their appearance between the foramen rotundum and fora- men ovale about the eighth week, and from them the external pterygoid plates are also formed. Soon after, the nuclei for the posterior part of the body appear, one on either side of the sella turcica, and become blended together about the middle of foetal life. About the fourth month the remaining four centres appear, those for the internal pterygoid plates being ossified in membrane and becoming joined to the external pterygoid plate about the sixth month. The centres for the lingulae speedily become joined to the rest of the bone. Pre-sphenoid Division.-The first nuclei to appear are those for the lesser wings. They make their appearance about the ninth week, at the outer borders of the optic foramina. A second pair of nuclei appear on the inner side of the one for- (ee/i iesser- iirintf lit'O -for- /in/tricr part of body cnc for* car/v internal ptert/ipoicl plate one for' \ each yreoit iiriny eenrf /^,ry" \</oM\ptate one Ar ea.cA. h'nyizia cne eacn turvintifccc octu. Fig. 146.-Plan of the development of sphenoid. By fourteen centres. 1 A small portion of the sphenoidal turbinated bone sometimes enters into the formation of the inner wall of the orbit, between the os planum of the ethmoid in front, the orbital plate of the palate below, and the frontal above.-Cleland, Roy. Soc. Trans., 1862. THE ETHMOID BONE. 187 foramina shortly after, and, becoming united, form the front part of the body of the bone. The remaining two centres for the sphenoidal turbinated bones do not make their appearance until the end of the third year. The pre-sphenoid is united to the body of the post-sphenoid about the eighth month, so that at birth the bone consists of three pieces-viz. the body in the centre, and on each side the great wings with the pterygoid processes. The lesser wings become joined to the body at about the time of birth. At the first year after birth the greater wings and body are united. From the tenth to the twelfth year the spongy bones are partially united to the sphenoid, their junction being complete by the twentieth year. Lastly, the sphenoid joins the occipital from the eighteenth to the twenty-fifth year. Articulations.-The sphenoid articulates with all the bones of the cranium, and five of the face-the two malar, two palate, and vomer: the exact extent of articulation with each bone is shown in the accompanying figures.1 Attachment of Muscles.-To eleven pairs : the Temporal, External pterygoid, Internal pterygoid, Superior constrictor, Tensor palati, Levator palpebrae, Ob- liquus oculi superior, Superior rectus, Internal rectus, Inferior rectus, External rectus. The Ethmoid Bone. The Ethmoid (y6[j.b', a sieve) is an exceedingly light, spongy bone, of a cubical form, situated at the anterior part of the base of the cranium, between the twm orbits, at the root of the nose, and contributing to form each of these cavities. It consists of three parts: a horizontal plate, which forms part of the base of the cranium; a perpendicular plate, which forms part of the septum nasi; and two lateral masses of cells. The Horizontal or Cribriform Plate (Fig. 147) forms part of the anterior fossa of the base of the skull, and is received into the ethmoid notch of the frontal bone between the two orbital plates. Projecting upward from the middle line of this plate is a thick, smooth, tri- angular process of bone, the crista galli, so called from its resemblance to a cock's comb. Its base joins the cribriform plate. Its posterior border, long, thin,and slightly curved, serves for the attachment of the falx cerebri. Its anterior border, short and thick, articu- lates with the frontal bone, * and presents two small project- ing aim, which are received into corresponding depressions in the frontal, completing the foramen caecum behind. Its sides are smooth and some- times bulging; in which case it is found to enclose a small sinus.2 On each side of the crista galli the cribriform plate is narrow and deeply grooved, to support the bulb of the olfactory tract, and perforated by foramina for the passage of the olfactory nerves. These foramina are arranged in three rows: the innermost, which are the largest and least numerous, are lost in grooves on the upper part of the septum; the foramina of the outer row are continued on to the surface of With inferior turbinated bone. Fig. 147.-Ethmoid bone. Outer surface of right lateral mass (enlarged). 1 It also sometimes articulates with the tuberosity of the superior maxilla (see p. 192). 2 Sir George Humphry states that the crista galli is commonly inclined to one side, usually the opposite to that toward which the lower part of the perpendicular plate is bent.-{The Human Skele- ton, 1858, p. 277.) 188 THE SKELETON. the uppei' spongy bone. The foramina of the middle row are the smallest; they perforate the bone and transmit nerves to the roof of the nose. At the front part of the cribriform plate, on each side of the crista galli, is a small fissure, which transmits the nasal branch of the ophthalmic nerve; and at its posterior part a a triangular notch, which receives the ethmoidal spine of the sphenoid. The Perpendicular Plate (Fig. 148) is a thin, flattened lamella of bone, which descends from the under surface of the cribriform plate, and assists in forming the septum of the nose. It is much thinner in the middle than at the circum- ference, and is generally deflected a little to one side. Its anterior border articu- lates with the nasal spine of the frontal bone and crest of the nasal bones. Its posterior border, divided into two parts, articulates by its upper half with the eth- moidal crest of the sphenoid, by its lower half with the vomer. The inferior border serves for the attachment of the triangular cartilage of the nose. On each side of the perpendicular plate numerous grooves and canals are seen, leading from foramina on the cribriform plate ; they lodge filaments of the olfactory nerves. The Lateral Masses of the ethmoid consist of a number of thin-walled cellular cavities, the ethmoidal cells, interposed between two vertical plates of bone, the outer one of which forms part of the orbit, and the inner one part of the nasal fossa of the corresponding side. In the disarticulated bone many of these cells appear to be broken; but when the bones are articulated they are closed in at every part. The upper surface of each lateral mass presents a number of apparently half- broken cellular spaces; these are closed in when articulated by the edges of the ethmoidal notch of the frontal bone. Crossing this surface are two grooves on each side, converted into canals by articulation with the frontal; they are the anterior and posterior ethmoidal foramina, and open on the inner wall of the orbit. The posterior surface also presents large, irregular cellular cavities, which are closed in by articula- tion with the sphenoidal turbinated bones and orbi- tal process of the palate. The cells at the anterior surface are completed by the lachrymal bone and nasal process of the supe- rior maxillary, and those below also by the superior maxillary. The outer sur- face of each lateral mass is formed of a thin, smooth, square plate of bone, called the os planum; it forms part of the inner wall of the orbit, and articulates, above, with the orbital plate of the frontal; below, with the superior maxil- lary ; in front, with the lachrymal; and behind, with the sphenoid and orbital process of the palate. From the inferior part of each lateral mass, immediately beneath the os planum, there projects downward and backward an irregular lamina of bone, called the unciform process, from its hook-like form : it serves to close in the upper part of the orifice of the antrum, and articulates with the ethmoidal process of the inferior turbinated bone. It is often broken in disarticulating the bones. The inner surface of each lateral mass forms part of the outer wall of the nasal fossa of the corresponding side. It is formed of a thin lamella of bone, which descends from the under surface of the cribriform plate, and terminates below in a free, convoluted margin, the middle turbinated bone. The whole of this sur- Fig. 148.-Perpendicular plate of ethmoid (enlarged), shown by removing the right lateral mass. THE ETHMOID BONE. 189 face is rough and marked above by numerous grooves, which run nearly verti- cally downward from the cribriform plate; they lodge branches of the olfactory nerve, which are distributed on the mucous membrane covering the bone. The back part of this surface is subdivided by a narrow oblique fissure, the superior meatus of the nose, bounded above by a thin, curved plate of bone, the superior turbinated bone. By means of an orifice at the upper part of this fissure the posterior ethmoidal cells open into the nose. Below, and in front of the superior meatus, is seen the convex surface of the middle turbinated bone. It extends along the whole length of the inner surface of each lateral mass; its lower mar- gin is free and thick, and its concavity, directed outward, assists in forming the middle meatus. It is by a large orifice at the upper and front part of the middle meatus that the anterior ethmoidal cells, and through them the frontal sinuses, communicate with the nose by means of a funnel-shaped canal, the infundibulum. The cellular cavities of each lateral mass, thus walled in by the os planum on the outer side and by the other bones already mentioned, are divided by a thin trans- verse bony partition into two sets, which do not communicate with each other; they are termed the anterior and posterior ethmoidal cells or sinuses. The former, more numerous, communicate with the frontal sinuses above and the middle meatus below* by means of a long, flexuous canal, the infundibulum ; the posterior, less numerous, open into the superior meatus, and communicate (occasionally) with the sphenoidal sinuses. Development.-By three centres: one for the perpendicular lamella, and one for each lateral mass. The lateral masses are first developed, ossific granules making their appearance in the os planum between the fourth and fifth months of foetal life, and extending into the spongy bones. At birth the bone consists of the two lateral masses, which are small and ill-developed. During the first year after birth the perpen- dicular and horizontal plates begin to ossify, from a single nucleus, and become joined to the lateral masses about the beginning of the second year. The forma- tion of the ethmoidal cells, which completes the bone, does not commence until about the fourth or fifth year. Articulations.-With fifteen bones: the sphenoid, two sphenoidal turbinated, the frontal, and eleven of the face-the two nasal, two superior maxillary, two lachrymal, two palate, two inferior turbinated, and the vomer. No muscles are attached to this bone. Fig. 149.-Ethmoid bone. Inner surface of right lateral mass (enlarged). DEVELOPMENT OF THE CRANIUM. The early stages of the development of the cranium have already been described (see page 117). We have seen that it is formed from a layer of mesoblast, derived from the protovertebral plates of the trunk, which is spread over the whole surface of the rudimentary brain. That portion of this layer from which the bones of the skull are to be developed consists of a thin, membranous capsule. Ossification commences in the roof, and is preceded by the deposition of a membranous blastema upon the surface of the cerebral capsule, in which the ossifying process extends, the primitive membranous capsule becoming the internal periosteum, and being ultimately blended with the dura mater. Although the bones of the vertex of the skull appear before those at the base, and make considerable progress in their growth, at birth ossification is more advanced in the base, this portion of the skull forming a solid, immovable groundwork. 190 THE SKELETON. Before birth the bones at the vertex and side of the skull are separated from each other by membranous intervals in which bone is deficient. These intervals are principally found at the four angles of the parietal bones. Hence there are six fontanelles. Their formation is due to The Fontanelles. Fig. 150.-Skull at birth, showing the anterior and posterior fontanelles. Fig. 151.-The lateral fontanelles. the wave of ossification being circular and the bones quadrilateral; the ossific matter first meets at the margins of the bones, at the points nearest to their centres of ossification, and vacuities or spaces are left at the angles, which are called fontanelles, so named from the pulsations of the brain, which are perceptible at the anterior fontanelle, and were likened to the rising of water in a fountain. The anterior fontanelle is the largest, and corresponds to the junction of the sagittal and coronal sutures; the posterior fontanelle, of smaller size, is situated at the junction of the sagittal and lambdoid sutures; the remaining ones are situated at the inferior angles of each parietal bone. The latter are closed soon after birth ; the two at the two superior angles remain open longer; the posterior being closed in a few months after birth; the anterior remain- ing open until the first or second year. These spaces are gradually filled in by an extension of the ossifying process or by the development of a Wormian bone. Sometimes the anterior fontanelle remains open beyond two years, and is occasionally persistent throughout life. Supernumerary or Wormian1 Bones. In addition to the constant centres of ossification of the skull, additional ones are occasion- ally found in the course of the sutures. These form irregular, isolated bones, interposed between the cranial bones, and have been termed Wormian bones or ossa triquetra. They are most frequently found in the course of the lambdoid suture, but occasionally also occupy the situation of the fontanelles, especially the posterior and, more rarely, the anterior. Frequently one is found between the anterior inferior angle of the parietal bone and the greater wing of the sphenoid, the pterion ossicle (Fig. 151). They have a great tendency to be symmetrical on the two sides of the skull, and they vary much in size, being in some cases not larger than a pin's head, and confined to the outer table; in other cases so large that one pair of these bones may form the whole of the occipital bone above the superior curved lines, as described by Bedard and Ward. Their number is generally limited to two or three, but more than a hundred have been found in the skull of an adult hydrocephalic skeleton. In their development, structure, and mode of articulation they resemble the other cranial bones. An arrest in the ossifying process may give rise to deficiencies or gaps; or to fissures, which are of importance in a medico-legal point of view, as they are liable to be mistaken for fractures. The fissures generally extend from the margins toward the centre of the bone, but the gaps may be found in the middle as well as at the edges. In course of time they may become covered with a thin lamina of bone. Congenital Fissures and Gaps. The Facial Bones are fourteen in number-viz. the BONES OF THE FACE. Two Nasal. Two Superior Maxillary. Two Lachrymal. Tw'o Malar. Two Palate. Two Inferior Turbinated. Vomer. Inferior Maxillary. 1 Wormius, a physician in Copenhagen, is said to have given the first detailed description of these bones. 777A NASAL AND SUPERIOR MAXILLARY BONES. 191 " Of these, the upper and lower jaws are the fundamental bones for mastication, and the others are accessories; for the chief function of the facial bones is to provide an apparatus for mastication, while subsidiary functions are to provide for the sense-organs (eye, nose, tongue) and a vestibule to the respiratory and vocal organs. Hence the variations in the shape of the face in man and the lower animals depend chiefly on the question of the character of their food and their mode of obtaining it." 1 The Nasal Bone. The Nasal (nasus, the nose) are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, forming, by their junction, " the bridge " of the nose. Each bone presents for examination two surfaces and four borders. The outer surface is concave from above downward, convex from side to side; it is covered by the Pyramidalis and Compressor nasi muscles, and give attachment at its upper part to a few fibres of the Occipito-frontalis muscle (Theile). It is marked by numerous small arterial furrows, and perforated about its centre by a foramen, sometimes double, for the transmission of a small vein. Sometimes this foramen is absent on one or both sides, and occasionally the foramen caecum opens on this surface. The inner surface is concave from side to side, convex from above downward; in which direction it is traversed by a longitudinal groove (sometimes a canal), for the passage of a branch of the nasal nerve. The superior border is narrow, thick, and serrated, for articulation with the nasal notch of the frontal bone. The inferior border is broad, thin, sharp, inclined obliquely downward, outward, and back- ward, and serves for the attachment of the lateral cartilage of the nose. This border presents, about its middle, a notch, through which passes the branch of the nasal nerve above referred to, and is prolonged at its inner extremity into a sharp spine, which, when articulated with the opposite bone, forms the nasal angle. The external border is serrated, bevelled at the expense of the internal sur- face above and of the external below, to articulate with the nasal process of the superior maxillary. The internal bor- der, thicker above than below, articulates with its fellow of the opposite side, and is pro- longed behind into a vertical crest which forms part of the septum of the nose ; this crest articulates with the nasal spine of the frontal above, and the perpendicular plate of the ethmoid below. Development.-By one centre for each bone, which appears about the same period as in the vertebrae. Articulations.-With four bones: two of the cranium, the frontal and ethmoid, and tw'o of the face, the opposite nasal and the superior maxillary. Attachment of Muscles.-A few fibres of the Occipito-frontalis muscle. With frontal bone. With frontal spine. Crest. With •perpendicular plate of ethmoid. With ■opposite bone. Groove for nasal nerve. Outer Surface. Fig. 152.-Right nasal bone. Inner Surface. Fig. 153.-Left nasal bone. The Superior Maxillary Bones. The Superior Maxillary {maxilla, the jaw-bone) is one of the most important bones of the face from a surgical point of view, on account of the number of diseases to which some of its parts are liable. Its careful examination becomes, therefore, a matter of considerable interest. It is the largest bone of the face, excepting the lower jaw, and forms, by its union with its fellow of the opposite side, the whole 1 W. W. Keen, American edition, p. 185, 192 THE SKELETON. of the upper jaw. Each bone assists in the formation of three cavities, the roof of the mouth, the floor and outer wall of the nasal fossae, and the floor of the orbit, and also enters into the formation of two fossae, the zygomatic and spheno- maxillary, and two fissures, the spheno-maxillary and pterygo-maxillary. The bone presents for examination a body and four processes-malar, nasal, alveolar, and palate. The body is somewhat cuboid, and is hollowed out in its interior to form a large cavity, the antrum of Highmore. Its surfaces are four-an external or facial, a posterior or zygomatic, a superior or orbital, and an internal. The external or facial surface (Fig. 154) is directed forward and outward. Just above the incisor teeth is a depression, the incisive or myrtiform fossa, which gives origin to the Depressor alae nasi; and beloiv it to the alveolar border is attached a slip of the Orbicularis oris. Above and a little external to it the Compressor nasi arises. More external is another depression, the canine fossa, Outer Surface. Lachrymal tubercle. TENOO OCULI - - Posterior dental canals. Incisive fossa.- Maxillary tuberosity. Fig. 154.-Left superior maxillary bone. Outer surface. larger and deeper than the incisive fossa, from which it is separated by a vertical ridge, the canine eminence, corresponding to the socket of the canine tooth. The canine fossa gives origin to the Levator anguli oris. Above the canine fossa is the infraorbital foramen, the termination of the infraorbital canal; it transmits the infraorbital vessels and nerve. Above the infraorbital foramen is the margin of the orbit, which affords partial attachment to the Levator labii superioris proprius. To the sharp margin of bone which bounds this surface in front and separates it from the internal surface is attached the Dilator naris posterior. The posterior or zygomatic surface is convex, directed backward and outward, and forms part of the zygomatic fossa. It presents about its centre several aper- tures leading to canals in the substance of the bone; they are termed the posterior dental canals, and transmit the posterior dental vessels and nerves. At the lower part of this surface is a rounded eminence, the maxillary tuberosity, especially prominent after the growth of the wisdom-tooth, rough on its inner side for artic- ulation with the tuberosity of the palate bone, and sometimes with the external pterygoid plate. It gives attachment to a few fibres of origin of the Internal THE SUPERIOR MAXILLARY BONES. 193 pterygoid muscle. Immediately above the rough surface is a groove which, run- ning obliquely down on the inner surface of the bone, is converted into a canal by articulation with the palate-bone forming the posterior palatine canal. The superior or orbital surface is thin, smooth, triangular, and forms part of the floor of the orbit. It is bounded internally by an irregular margin which in front presents a notch, the lachrymal notch, which receives the lachrymal bone; in the middle articulates with the os planum of the ethmoid, and behind with the orbital process of the palate bone; bounded externally by a smooth, rounded edge which enters into the formation of the spheno-maxillary fissure, and which some- times articulates at its anterior extremity with the orbital plate of the sphenoid; bounded in front by part of the circumference of the orbit, which is continuous on the inner side with the nasal, on the outer side with the malar, process. Along the middle line of the orbital surface is a deep groove, the infraorbital, for the passage of the infraorbital vessels and nerve. The groove commences at the mid- dle of the outer border of this surface, and, passing forward, terminates in a canal, which subdivides into twm branches. One of the canals, the infraorbital, opens just below the margin of the orbit; the other, which is smaller, runs in the sub- stance of the anterior wall of the antrum; it is called the anterior dental canal, and transmits the anterior dental vessels and nerve to the front teeth of the upper jaw. From the back part of the infraorbital canal a second small canal is some- times given off, which runs in the substance of the bone, and conveys the middle dental nerve to the bicuspid teeth. Occasionally, this canal is derived from the anterior dental. At the inner and fore part of the orbital surface, just external to the lachrymal groove for the nasal duct, is a depression which gives origin to the Inferior oblique muscle of the eye. The internal surface (Fig. 155) is unequally divided into two parts by a hori- zontal projection of bone, the palate process : the portion above the palate process Bones partially closing orifice of antrum marked in outline. Ethmoid. Inferior turbinated. Palate.-. • Anterior nasal spine. Bristle passed •-through anterior \ palatine canal. forms part of the outer wall of the nasal fossae; that below it forms part of the cavity of the mouth. The superior division of this surface presents a large, irreg- ular opening leading into the antrum of Highmore. At the upper border of this aperture are numerous broken cellular cavities, which in the articulated skull are closed in by the ethmoid and lachrymal bones. Below the aperture is a smooth Fig. 155.-Left superior maxillary bone. Inner surface. 194 THE SKELETON. concavity which forms part of the inferior meatus of the nasal fossae, and behind it is a rough surface which articulates writh the perpendicular plate of the palate bone, traversed by a groove which, commencing near the middle of the posterior border, runs obliquely downward and forward, and forms, when completed by its articulation with the palate bone, the posterior palatine canal. In front of the opening of the antrum is a deep groove, converted into a canal by the lachrymal and inferior turbinated bones. It is called the lachrymal groove, and lodges the nasal duct. More anteriorly is a well-marked rough ridge, the inferior turbinated crest, for articulation with the inferior turbinated bone. The concavity above this ridge forms part of the middle meatus of the nose, whilst that below it forms part of the inferior meatus. The portion of this surface below the palate process is concave, rough and uneven, and perforated by numerous small foramina for the passage of nutrient vessels. It enters into the formation of the roof of the mouth. The Antrum of Highmore, or Maxillary Sinus, is a large, pyramidal cavity hollowed out of the body of the maxillary bone : its apex, directed outward, is formed by the malar process ; its base, by the outer wall of the nose. Its walls are everywhere exceedingly thin, and correspond to the orbital, facial, and zygo- matic surfaces of the body of the bone. Its inner wall, or base, presents, in the disarticulated bone, a large, irregular aperture, which communicates with the nasal fossa. The margins of this aperture are thin and ragged, and the aperture itself is much contracted by its articulation -with the ethmoid above, the inferior turbinated below, and the palate bone behind.1 In the articulated skull this cavity communicates with the middle meatus of the nasal fossae, generally by two small apertures left between the above-mentioned bones. In the recent state usually only one small opening exists, near the upper part of the cavity, sufficiently large to admit the end of a probe, the other being closed by the lining membrane of the sinus. Crossing the cavity of the antrum are often seen several projecting laminae of bone, similar to those seen in the sinuses of the cranium ; and on its posterior wall are the posterior dental canals, transmitting the posterior dental vessels and nerves to the teeth. Projecting into the floor are several conical processes, corresponding to the roots of the first and second molar teeth ;2 in some cases the floor is perfo- rated by the teeth in this situation. It is from the extreme thinness of the walls of this cavity that we are enabled to explain how a tumor growing from the antrum encroaches upon the adjacent parts, pushing up the floor of the orbit, and displacing the eyeball, projecting inward into the nose, protruding forward on to the cheek, and making its way backward into the zygomatic fossa and downward into the mouth. The Malar Process is a rough, triangular eminence, situated at the angle of separation of the facial from the zygomatic surface. In front it is concave, form- ing part of the facial surface; behind it is also concave, and forms part of the zygomatic fossa; above it is rough and serrated for articulation with the malar bone; whilst below a prominent ridge marks the division between the facial and zygomatic surfaces. A small part of the Masseter muscle arises from this process. The Nasal Process is a thick, triangular plate of bone, which projects upward, inward, and backward by the side of the nose, forming part of its lateral boundary. Its external surface is concave, smooth, perforated by numerous foramina, and gives attachment to the Levator labii superioris alaeque nasi, the Orbicularis palpebrarum, and Tendo oculi. Its internal surface forms part of the outer wall of the nose: at its upper part it presents a rough, uneven surface, wThich articulates with the ethmoid bone, closing in the anterior ethmoidal cells ; below this is a transverse ridge, the superior turbinated crest, for articulation with the 1 In some cases, at any rate, the lachrymal bone encroaches slightly on the anterior superior por- tion of the opening, and assists in forming the inner wall of the antrum. 2 The number of teeth whose fangs are in relation with the floor of the antrum is variable. The antrum " may extend so as to be in relation to all the teeth of the true maxilla, from the canine to the dens sapientice." (See Mr. Salter on Abscess of the Antrum, in a System of Surgery, edited by T. Holmes, 2d ed. vol. iv. p. 356.) THE SUPERIOR MAXILLARY BONES. 195 middle turbinated bone of the ethmoid, bounded below by a smooth concavity which forms part of the middle meatus; below this again is the inferior turbinated crest (already described), where the process joins the body of the bone. Its upper border articulates with the frontal bone. The anterior border of the nasal process is thin, directed obliquely downward and forward, and presents a serrated edge for articulation with the nasal bone ; its posterior border is thick, and hollowed into a groove, the lachrymal groove, for the nasal duct: of the two margins of this groove, the inner one articulates with the lachrymal bone, the outer one forms part of the circumference of the orbit. Just where the latter joins the orbital surface is a small tubercle, the lachrymal tubercle ; this serves as a guide to the position of the lachrymal sac in the operation for fistula lachrymalis. The lachrymal groove in the articulated skull is converted into a canal by the lachrymal bone and lachrymal process of the inferior turbinated; it is directed downward, and a little backward and outward, is about the diameter of a goose-quill, slightly palatine canal. Foramen of Stenson. Foramen of Scarpa. Posterior palatine canal. Accessory palatine foramen. Fig. 156.-The palate and alveolar arch. narrower in the middle than at either extremity, and terminates below in the inferior meatus. It lodges the nasal duct. The Alveolar Process is the thickest and most spongy part of the bone, broader behind than in front, and excavated into deep cavities for the reception of the teeth. These cavities are eight in number, and vary in size and depth according to the teeth they contain. That for the canine tooth is the deepest; those for the molars are the widest, and subdivided into minor cavities ; those for the incisors are single, but deep and narrow. The Buccinator muscle arises from the outer surface of this process, as far forward as the first molar tooth. The Palate Process, thick and strong, projects horizontally inward from the inner surface of the bone. It is much thicker in front than behind, and forms a considerable part of the floor of the nostril and the roof of the mouth. Its inferior surface (Fig. 156) is concave, rough and uneven, and forms part of the roof of the mouth. This surface is perforated by numerous foramina for the passage of the nutrient vessels, channelled at the back part of its alveolar border by a longitudinal groove, sometimes a canal, for the transmission of the posterior palatine vessels, and the anterior and external palatine nerves from Meckel's gan- 196 THE SKELETON. glion, and presents little depressions for the lodgment of the palatine glands. When the two superior maxillary bones are articulated together, a large orifice may be seen in the middle line, immediately behind the incisor teeth. This is the anterior palatine canal or fossa. This canal, as it passes through the thickness of the palate process, is divided into four compartments; that is to say, two canals branch off laterally to the right and left nasal fossae, and two canals, one in front and one behind, lie in the middle line. The former pair of these canals is named the foramina of Stenson, and through them passes the anterior or terminal branch of the descending or posterior palatine arteries, which ascend from the mouth to the nasal fossae. The remaining pair of canals is termed the foramina of Scarpa, and transmit the naso-palatine nerves, the left passing through the anterior, and the right through the posterior, canal. On the palatal surface of the process a delicate linear suture may sometimes be seen extending from the anterior palatine fossa to the interval between the lateral incisor and the canine tooth. This marks out the intermaxillary or incisive bone which in some animals exists permanently as a separate piece. It includes the whole thickness of the alveolus, the corresponding part of the floor of the nose, and the anterior nasal spine, and contains the sockets of the incisor teeth. One or two small foramina in the alveolar margin behind the incisor teeth are occasionally seen in the adult, almost constantly in the young subject. They are called the incisive foramina, and transmit vessels and nerves to the incisor teeth. The upper surface is concave from side to side, smooth, and forms part of the floor of the nose. It presents the upper orifices of the foramina of Stenson and Scarpa, the former being on each side of the middle line, the latter being situated in the intermaxil- lary suture, and therefore not visible unless the two bones are placed in apposition. The outer border of the palate process is incorporated with the rest of the bone. The inner border is thicker in front than behind, and is raised above into a ridge, the nasal crest, which, with the corresponding ridge in the opposite bone, forms a groove for the reception of the vomer. In front this crest rises to a considerable height, and this portion is named the incisor crest. _ The anterior margin is bounded by the thin, concave border of the opening of the nose, prolonged forward internally into a sharp process, forming, with a similar process of the opposite bone, the anterior nasal spine. The posterior border is serrated for articulation with the horizontal plate of the palate bone. Development.-This bone commences to ossify at a very early period, and ossification proceeds in it with great rapidity, so that it is difficult to ascertain with certainty its precise number of centres. It appears, however, probable that it is ossified by five primary and two secondary centres. The primary centres appear about the seventh or eighth week ; first, one each for the facial surface, the posterior part of the alveolus, and the orbital plate, and a few days later one for the palate process, and one for the front part of the alveolus, which carries the incisor teeth, and which corresponds to the pre-maxillary bone of the lower animals. All these, except the last, speedily fuse, and the two secondary centres, one for the nasal process and the other for the malar process, appear and join the rest of the bone. By the tenth week the bone consists of two portions-the greater part of the bone formed of six out of the seven centres and the pre-maxillary portion. The suture between these two portions on the palate persists till middle life, but is not to be seen on the facial surface. This is believed by Callender to be due to the fact that the front wall of the sockets of the incisive teeth is not formed by the pre-maxillary bone, but by an outgrowth from the facial part of the Anterior Surface. Inferior Surface. Fig. 157.-Development of superior maxillary bone. At birth. THE LACHRYMAL BONES. 197 superior maxilla. The antrum appears as a shallow groove on the inner surface of the bone at an earlier period than any of the other nasal sinuses, its develop- ment commencing about the fourth month of foetal life. The sockets for the teeth are formed by the growing downward of two plates from the dental groove, which subsequently becomes divided by partitions jutting across from the one to the other. Articulations.-With nine bones: two of the cranium, the frontal and ethmoid, and seven of the face-viz. the nasal, malar, lachrymal, inferior turbinated, palate, vomer, and its fellow of the opposite side. Sometimes it articulates with the orbital plate of the sphenoid, and sometimes -with its external pterygoid plate. Attachment of Muscles.-To twelve: the Orbicularis palpebrarum, Obliquus oculi inferior, Levator labii superioris alaeque nasi, Levator labii superioris proprius, Levator anguli oris, Compressor nasi, Depressor alas nasi, Dilatator naris posterior, Masseter, Buccinator, Internal pterygoid, and Orbicularis oris. CHANGES PRODUCED IN THE UPPER JAW BY AGE. At birth and during infancy the diameter of the bone is greater in an antero-posterior than in a vertical direction. Its nasal process is long, its orbital surface large, and its tuberosity well marked. In the adult the vertical diameter is the greater, owing to the development of the alveolar process and the increase in size of the antrum. In old age the bone approaches again in character to the infantile condition : its height is diminished, and after the loss of the teeth the alveolar process is absorbed, and the lower part of the bone contracted and diminished in thickness. The Lachrymal Bones. The Lachrymal (lachryma, a tear) are the smallest and most fragile bones of the face. They are situated at the front part of the inner wall of the orbit, and resemble somewhat in form, thinness, and size, a finger-nail; hence they are termed the ossa unguis. Each bone presents for examination two surfaces and four borders. The external or orbital surface (Fig. 158) is divided by a vertical ridge, the lachrymal crest, into two parts. The portion of bone in front of this ridge presents a smooth, concave, longitudinal groove, the free margin of which unites with the nasal process of the superior maxillary bone, completing the lachrymal groove. The upper part of this groove lodges the lachrymal sac; the lower part lodges the nasal duct. The portion of bone behind the ridge is smooth, slightly concave, and forms part of the inner wall of the orbit. The ridge, with a part of the orbital surface immediately behind it, affords attachment to the Tensor tarsi: the ridge terminates below in a small, hook-like projection, the hamular process, which articulates with the lachrymal tubercle of the superior maxillary bone, and completes the upper orifice of the lach- rymal groove. It sometimes exists as a separate piece, which is then called the lesser lachrymal bone. The internal or nasal surface presents a depressed furrow, corresponding to the ridge on its outer surface. The surface of bone in front of this forms part of the middle meatus, and that behind it articulates with the ethmoid bone, filling in the anterior ethmoidal cells. Of the four borders, the anterior is the longest, and articulates with the nasal process of the superior maxillary bone. The posterior, thin and uneven, articulates with the os planum of the ethmoid. The superior, the shortest and thickest, articulates with the internal angular process of the frontal bone. The inferior is divided by the lower edge of the vertical crest into two parts; the posterior part articulates with the orbital plate of the superior maxillary bone; the anterior portion is prolonged downward into a pointed pro- cess, which articulates with the lachrymal process of the inferior turbinated bone and assists in the formation of the lachrymal groove. With frontal. Fig. 158.-Left lach- rymal bone. External surface. (Slightly en- larged.) 198 THE SKELETON. Development.-By a single centre, which makes its appearance soon after ossification of the vertebrae has commenced. Articulations.-With four bones : two of the cranium, the frontal and ethmoid, and two of the face, the superior maxillary and the inferior turbinated. Attachment of Muscles.-To one muscle, the Tensor tarsi. The Malar Bones. The Malar (mala, the cheek) are two small, quadrangular bones, situated at the upper and outer part of the face : they form the prominence of the cheek, part of the outer wall and floor of the orbit, and part of the temporal and zygomatic fossae. Each bone presents for examination an external and an internal surface; four processes, the frontal, orbital, maxillary, and zygomatic; and four borders. The external surface (Fig. 159) is smooth, convex, perforated near its centre by one or two small apertures, the malar foramina, for the passage of nerves and vessels, covered by the Orbicularis palpebrarum muscle, and affords attachment to the Zygomaticus major and minor muscles. The internal surface (Fig. 160), directed backward and inward, is concave, presenting internally a rough, triangular surface, for articulation with the supe- With frontal. Bristles passed through temporo- malar canals. Fig. 159.-Left malar bone. Outer surface. Fig. 160.-Left malar bone. Inner surface. rior maxillary bone; and externally, a smooth, concave surface, which above forms the anterior boundary of the temporal fossa, and below, where it is wider, forms part of the zygomatic fossa. This surface presents, a little above its centre, the aperture of one or two malar canals, and affords attachment to part of two muscles, the Temporal above and the Masseter below. Of the four processes, the frontal is thick and serrated, and articulates with the external angular process of the frontal bone. The orbital process is a thick and strong plate, which projects backward from the orbital margin of the bone. Its supero-internal surface, smooth and concave, forms, by its junction with the orbital surface of the superior maxillary bone and with the great wing of the sphenoid, part of the floor arid outer wall of the orbit. Its infer o-erternal surface, smooth and convex, forms part of the zygomatic and temporal fossae. Its anterior margin is smooth and rounded, forming part of the circumference of the orbit. Its superior margin, rough and directed horizontally, articulates with the frontal bone behind the external angular process. Its posterior margin is rough, and serrated for articu- lation with the sphenoid ; internally it is also serrated for articulation with the orbital surface of the superior maxillary. At the angle of junction of the sphe- noidal and maxillary portions a short, rounded, non-articular margin is generally seen; this forms the anterior boundary of the spheno-maxillary fissure: occasion- ally, no such non-articular margin exists, the fissure being completed by the direct junction of the maxillary and sphenoid bones or by the interposition of a small THE PALATE BONES. 199 Wormian bone in the angular interval between them. On the upper surface of the orbital process are seen the orifices of one or two temporo-malar canals; one of these usually opens on the posterior surface, the other (occasionally two) on the facial surface : they transmit filaments (temporo-malar) of the orbital branch of the superior maxillary nerve. The maxillary process is a rough, triangular surface which articulates with the superior maxillary bone. The zygomatic pro- cess, long, narrow, and serrated, articulates with the zygomatic process of the temporal bone. Of the four borders, the antero-superior or orbital is smooth, arched, and forms a considerable part of the circumference of the orbit. The antero-inferior or maxillary border is rough, and bevelled at the expense of its inner table, to articulate with the superior maxillary bone; affording attachment by its margin to the Levator labii superioris proprius, just at its point of junction with the superior maxillary. The postero-superior or temporal border, curved like an italic letter/, is continuous above with the commencement of the temporal ridge; below, with the upper border of the zygomatic arch: it affords attachment to the temporal fascia. The postero-inferior or zygomatic border is continuous with the lower border of the zygomatic arch, affording attachment by its rough edge to the Masseter muscle. Development.-The malar bone ossifies generally from two, but occasionally from three, centres. One, which forms the chief part of the bone, appears about the seventh week, near the orbital margin. The second appears somewhat later, along the lower margin. The third, when it exists, is found in the hinder border. The bone is sometimes, after birth, seen to be divided by a horizontal suture into an upper and larger division and a lower and smaller. This divided condition is probably due to the persistent separation of the two centres of ossification. In some quadrumana the malar bone consists of two parts, an orbital and a malar, which are ossified by separate centres. Articulations.-With four bones : three of the cranium, frontal, sphenoid, and temporal; and one of the face, the superior maxillary. Attachment of Muscles.-To five: The Levator labii superioris proprius, Zygomaticus major and minor, Masseter, and Temporal. The Palate Bones. The Palate Bones (joalatum, the palate) are situated at the back part of the nasal fossae: they are wedged in between the superior maxillary bones and the pterygoid processes of the sphenoid. Each bone assists in the formation of three cavities: the floor and outer wall of the nose, the roof of the mouth, and the floor of the orbit, and enters into the formation of two fossae, the spheno-maxillary and pterygoid; and one fissure, the spheno-maxillary. In form the palate bone some- what resembles the letter L, and may be divided into an inferior or horizontal plate and a superior or vertical plate. The Horizontal Plate is thick, of a quadrilateral form, and presents two sur- faces and four borders. The superior surface, concave from side to side, forms the back part of the floor of the nostril. The inferior surface, slightly concave and rough, forms the back part of the hard palate. At its posterior part may be seen a transverse ridge, more or less marked, for the attachment of part of the aponeurosis of the Tensor palati muscle. At the outer extremity of this ridge is a deep groove converted into a canal by its articulation with the tuberosity of the superior maxillary bone, and forming the posterior palatine canal. Near this groove the orifices of one or two small canals, accessory posterior palatine, may be seen. The anterior border is serrated, bevelled at the expense of its inferior sur- face, and articulates with the palate process of the superior maxillary bone. The posterior border is concave, free, and serves for the attachment of the soft palate. Its inner extremity is sharp and pointed, and, when united with the opposite bone, forms a projecting process, the posterior nasal spine, for the attachment of the Azygos uvulae. The external border is united with the lower part of the perpen- 200 THE SKELETON. dicular plate almost at right angles. The internal border, the thickest, is serrated for articulation with its fellow of the opposite side ; its superior edge is raised into a ridge, which, united with the opposite bone, forms a crest in which the vomer is received. The Vertical Plate (Fig. 161) is thin, of an oblong form, and directed upward and a little inward. It presents two surfaces, an external and an internal, and four borders. The internal surface presents at its lower part a broad, shallow depression, which forms part of the inferior meatus of the nose. Immediately above this is a well-marked horizontal ridge, the inferior turbinated crest, for articulation with the inferior turbinated bone; above this, a second broad, shallow depression, which forms part of the middle mea- tus, surmounted above by a horizontal ridge less promi- nent than the inferior, the superior turbinated crest, for articulation with the middle turbinated bone. Above the superior turbinated crest is a narrow, horizontal groove, which forms part of the su- perior meatus. The external surface is rough and irregular through- out the greater part of its extent, for articulation with the inner surface of the su- perior maxillary bone, its upper and back part being smooth where it enters into the formation of the spheno-maxillary fossa; it is also smooth in front, where it covers the orifice of the antrum. Toward the back part of this surface is a deep groove, converted into a canal, the posterior palatine, by its articulation with the supe- rior maxillary bone. It transmits the pos- terior or descending palatine vessels and one of the descending palatine branches from Meckel's ganglion. The anterior border is thin, irregular, and presents, opposite the inferior turbi- nated crest, a pointed, projecting lamina, the maxillary process, which is directed forward, and closes in the lower and back part of the opening of the antrum. The posterior border (Fig. 162) presents a deep groove, the edges of which are serrated for articulation with the pterygoid process of the sphenoid. At the lower part of this border is seen a pyramidal process of bone, the pterygoid process or tuberosity of the palate, which is received into the angular interval between the two pterygoid plates of the sphenoid at their inferior extremity. This process presents at its back part a median groove and two lateral surfaces. The groove is smooth, and forms part Orbital process. Orbital surface. Maxillary surface. Superior meatus. Spheno-palatine foramen. Vertical Plate. Maxillary ' process. Horizontal Plate. Fig. 161.-Left palate bone. Internal view. (Enlarged.) Orbital process. ■Sphenoidal palatine foramen. Vertical Plate. x Sphenoidal process. -Articular portion. Mon-articular portion. Posterior palatine \ canal. External Surface. Posterior nasal spine. AZYGOS UVUL/E.r Horizontal Plate. Fig. 162.-Left palate bone. Posterior view. (Enlarged.) 77//-/ PALATE BONES. 201 of the pterygoid fossa, affording attachment to the Internal pterygoid muscle; whilst the lateral surfaces are rough and uneven, for articulation with the anterior border of each pterygoid plate. A few fibres'of the Superior constrictor arise from the tuberosity of the palate bone. The base of this process, continuous with the horizontal portion of the bone, presents the apertures of the accessory descending palatine canals, through which pass the two smaller descending branches of Meckel's ganglion ; whilst its outer surface is rough for articulation with the inner surface of the body of the superior maxillary bone. The superior border of the vertical plate presents two well-marked processes separated by an intervening notch or foramen. The anterior, or larger, is called the orbital process ; the posterior, the sphenoidal. The Orbital Process, directed upward and outward, is placed on a higher level than the sphenoidal. It presents five surfaces, which enclose a hollow cellular cavity, and is connected to the perpendicular plate by a narrow, constricted neck. Of these five surfaces, three are articular, two non-articular or free surfaces. The three articular are the anterior or maxillary surface, which is directed forward, outward, and downward, is of an oblong form, and rough for articulation with the superior maxillary bone. The posterior or sphenoidal surface is directed backward, upward, and inward. It ordinarily presents a small, open cell, which communicates ■with the sphenoidal cells, and the margins of which are serrated for articulation with the vertical part of the sphenoidal turbinated bone. The internal or ethmoidal surface is directed inward, upward, and forward, and articulates with the lateral mass of the ethmoid bone. In some cases the cellular cavity above mentioned opens on this surface of the bone; it then communicates with the posterior ethmoidal cells. More rarely it opens on both surfaces, and then communicates both with the posterior ethmoidal and the sphenoidal cells. The non-articular or free surfaces are the superior or orbital, directed upward and outward, of triangular form, concave, smooth, and forming the back part of the floor of the orbit; and the external or zygomatic surface, directed outward, backward, and downward, of an oblong form, smooth, lying in the spheno-maxil- lary fossa, and looking into the zygomatic fossa. The latter surface is separated from the orbital by a smooth, rounded border, which enters into the formation of the spheno-maxillary fissure. The Sphenoidal Process of the palate bone is a thin, compressed plate, much smaller than the orbital, and directed upward and inward. It presents three surfaces and two borders. The superior surface, the smallest of the three, articulates with the under surface of the sphenoidal turbinated bone; it presents a groove, which contributes to the formation of the pterygo-palatine canal. The internal surface is concave, and forms part of the outer wall of the nasal fossa. The external surface is divided into'an articular and a non-articular portion: the former is rough, for articulation with the inner surface of the pterygoid process of the sphenoid; the latter is smooth, and forms part of the spheno-maxillary fossa. The anterior border forms the posterior boundary of the spheno-palatine foramen. The posterior border, serrated at the expense of the outer table, articulates with the inner surface of the pterygoid process. The orbital and sphenoidal processes are separated from one another by a deep notch, which is converted into a foramen, the spheno-palatine, by articulation with the sphenoidal turbinated bone. Sometimes the two processes are united above, and form between them a complete foramen, or the notch is crossed by one or more spiculse of bone, so as to form two or more foramina. In the articulated skull this foramen opens into the back part of the outer wall of the superior meatus, and transmits the spheno-palatine vessels and the superior nasal and naso-palatine nerves. Development.-From a single centre, which makes its appearance about the second month at the angle of junction of the two plates of the bone. From this point ossification spreads inward to the horizontal plate, downward into the tuberosity, and upward into the vertical plate. In the foetus the horizontal plate 202 THE SKELETON. is much longer than the vertical, and even -after it is fully ossified the whole bone is at first remarkable for its shortness. Articulations.-With six bones: the sphenoid, ethmoid, superior maxillary, inferior turbinated, vomer, and opposite palate. Attachment of Muscles.-To four: the Tensor palati, Azygos uvulae, Internal pterygoid, and Superior constrictor of the pharynx. The Inferior Turbinated Bones. The Inferior Turbinated Bones (turbo, a whirl) are situated one on each side of the outer wall of the nasal fossae. Each consists of a layer of thin, spongy bone, curled upon itself like a scroll-hence its name "turbinated "-and extends hori- zontally along the outer wall of the nasal fossa, immediately below the orifice of the antrum. Each bone presents two surfaces, two borders, and two extremities. The internal surface (Fig. 163) is convex, perforated by numerous apertures, and traversed by longitudinal grooves and canals for the lodgment of arteries and Fig. 163.-Right inferior turbinated bone. Internal surface. Fig. 164.-Right inferior turbinated bone. External surface. veins. In the recent state it is covered by the lining membrane of the nose. The external surface is concave (Fig. 164), and forms part of the inferior meatus. Its upper border is thin, irregular, and connected to various bones along the outer wall of the nose. It may be divided into three portions : of these, the anterior articulates with the inferior turbinated crest of the superior maxillary bone; the posterior with the inferior turbinated crest of the palate bone ; the middle portion of the superior border presents three well-marked processes, which vary much in their size and form. Of these, the anterior and smallest is situated at the junction of the anterior fourth with the posterior three-fourths of the bone : it is small and pointed, and is called the lachrymal process ; it articulates by its apex with the anterior inferior angle of the lachrymal bone, and by its margins with the groove on the back of the nasal process of the superior maxillary, and thus assists in forming the canal for the nasal duct. At the junction of the two middle fourths of the bone, but encroaching on its posterior fourth, a broad, thin plate, the ethmoidal process, ascends to join the unciform process of the ethmoid ; from the lower border of this process a thin lamina of bone curves downward and outward, hooking over the lower edge of the orifice of the antrum, which it narrows below: it is called the maxillary process, and fixes the bone firmly on to the outer wall of the nasal fossa. The inferior border is free, thick, and cellular in structure, more especially in the middle of the bone. Both extremities are more or less narrow and pointed,' the posterior being the more tapering. If the bone is held so that its outer con- cave surface is directed backward (z. e. toward the holder), and its superior border, from which the lachrymal and ethmoidal processes project, upward, the lachrymal process will be directed to the side to which the bone belongs.1 Development.-By a single centre, which makes its appearance about the middle of foetal life. Articulations.-With four bones: one of the cranium, the ethmoid, and three of the face, the superior maxillary, lachrymal, and palate. No muscles are attached to this bone. 1 If the lachrymal process is broken off, as is often the case, the side to which the bone belongs may be known by recollecting that the maxillary process is nearer the back than the front of the bone. THE VOMER, THE INFERIOR MAXILLARY BONE. 203 The Vomer. The Vomer (vomer, a ploughshare) is a single bone, situated vertically at the back part of the nasal fossae, forming part of the septum of the nose. It is thin, somewhat like a ploughshare in form; but it varies in different individuals, being frequently bent to one or the other side; it presents for examination two surfaces and four borders. The lateral surfaces are smooth, marked by small furrows for the lodgment of blood-vessels, and by a groove on each side, sometimes a canal, the naso-palatine, which runs obliquely downward and forward to the intermaxillary suture; it transmits the naso-palatine nerve. The superior border, the thickest, presents a deep groove, bounded on each side by a hori- zontal projecting ala of bone ; the groove receives the rostrum of the sphenoid, whilst the alae are overlapped and retained by laminae (the vaginal processes) which project from the under surface of the body of the sphe- noid at the base of the pterygoid processes. At the front of the groove a fissure is left for the transmission of blood-vessels to the substance of the bone. The inferior border, the longest, is broad and uneven in front, where it articulates with the two superior maxillary bones; thin and sharp behind, where it joins with the palate bones. The upper half of the anterior border usually consists of two laminae of bone, between which is received the perpendic- ular plate of the ethmoid ; the lower half, also separated into two laminae, receives between them the lower margin of the triangular cartilage of the nose. The posterior border is free, concave, and separates the nasal fossae behind. It is thick and bifid above, thin below. The surfaces of the vomer are covered by mucous membrane, which is intimately connected with the periosteum, with the intervention of very little, if any, sub- mucous connective tissue. Hence polypi are rarely found growing from this sur- face, though they frequently grow from the outer wall of the nasal fossae, where the submucous tissue is abundant. Development.-The vomer at an early period consists of two laminae, separated by a very considerable interval, and'enclosing between them a plate of cartilage, which is prolonged forward to form the remainder of the septum. Ossification commences in it by a single centre about the eighth week. From this nucleus the two laminae are formed. They begin to coalesce at the low er part, but their union is not complete until after puberty. Articulations.-With six bones : two of the cranium, the sphenoid and ethmoid ; and four of the face, the two superior maxillary and the two palate bones; and with the cartilage of the septum. The vomer has no muscles attached to it. With sup. maxill. bones and palate. Fig. 165.-The vomer. The Inferior Maxillary Bone. The Inferior Maxillary Bone (the Mandible), the largest and strongest bone of the face, serves for the reception of the lower teeth. It consists of a curved, horizontal portion, the body, and two perpendicular portions, the rami, which join the back part of the body nearly at right angles. The Horizontal Portion or Body (Fig. 166), is convex in its general outline, and curved somewhat like a horseshoe. It presents for examination two surfaces and two borders. The external surface is convex from side to side, concave from 204 THE SKELETON. above downward. In the median line is a vertical ridge, the symphysis, which extends from the upper to the lower border of the bone, and indicates the point of junction of the two pieces of which the bone is composed at an early period of life. The lower part of the ridge terminates in a prominent triangular eminence, the mental process. This eminence is rounded below, and often presents a median depression separating two processes, the mental tubercles. It forms the chin, a feature peculiar to the human skull. On either side of the symphysis, just below the cavities for the incisor teeth, is a depression, the incisive fossa, for the attachment of the Levator menti (or Levator labii inferioris); more externally is attached a portion of the Orbicularis oris (Accessorii Orbicularis inferioris}, and, still more externally, a foramen, the mental foramen, for the passage of the mental vessels and nerve. This foramen is placed just below the interval between the two bicuspid teeth. Running outward from the base of the mental process on each side is a ridge, the External oblique line. The ridge is at first nearly horizontal, but afterward inclines upward and backward, and is continuous with the anterior border of the ramus: it affords attachment to the Depressor Coronoid process. Condyle. Ramus. Mental process. Groove for facial artery. -Angle. Fig. 166.-Inferior maxillary bone. Outer surface. Side view. labii inferioris and Depressor anguli oris; below it the platysma myoides is attached. The internal surface (Fig. 167) is concave from side to side, convex from above downward. In the middle line is an indistinct linear depression, corresponding to the symphysis externally; on either side of this depression, just below its centre, are four prominent tubercles, placed in pairs, two above and two below; they are called the genial tubercles, and afford attachment, the upper pair to the Genio- hyo-glossi muscles, the lower pair to the Genio-hyoidei muscles. Sometimes the tubercles on each side are blended into one ; at others they all unite into an irregular eminence ; or, again, nothing but an irregularity may be seen on the surface of the bone at this part. On either side of the genial tubercles is an oval depression, the sublingual fossa, for lodging the sublingual gland; and beneath the fossa a rough depression on each side which gives attachment to the anterior belly of the Digastric muscle. At the back part of the sublingual fossa the internal oblique line (mylo-hyoideari) commences; it is at first faintly marked, but becomes more distinct as it passes upward and outward, and is especially prominent opposite the last two molar teeth ; it affords attachment throughout its whole extent to the Mylo-hyoid muscle; the Superior constrictor of the pharynx with the pterygo- maxillary ligament being attached above its posterior extremity, near the alveolar margin. The portion of the bone above this ridge is smooth, and covered by the THE INFERIOR MAXILLARY BONE. 205 mucous membrane of the mouth ; the portion below presents an oblong depression, the submaxillary fossa, wider behind than in front, for the lodgment of the sub- -GENIO-HYO-GLOSSUS. - GEN IO-HYOIDEUS. Mylo-hyoid ridge. Body. Fig. 167.-Inferior maxillary bone. Inner surface. Side view. maxillary gland. The external oblique line and the internal or mylo-hyoidean line divide the body of the bone into a superior or alveolar and an inferior or basilar portion. The superior or alveolar border is wider, and its margins thicker, behind than in front. It is hollowed into numerous cavities, for the reception of the teeth ; these cavities are sixteen in number, and vary in depth and size according to the teeth which they contain. To its outer side, the Buccinator muscle is attached as far forward as the first molar tooth. The inferior border is rounded, longer than the superior, and thicker in front than behind; it presents a shallow groove, just where the body joins the ramus, over which the facial artery turns. The Perpendicular Portions, or Rami, are of a quadrilateral form. Each presents for examination two surfaces, four borders, and two processes. The external surface is flat, marked with ridges, and gives attachment throughout nearly the whole of its extent to the Masseter muscle. The internal surface presents about its centre the oblique aperture' of the inferior dental canal, for the passage of the inferior dental vessels and nerve. The margin of this opening is irregular; it presents in front a prominent ridge, surmounted by a sharp spine, the lingula, which gives attachment to the internal lateral ligament of the lower jaw, and at its lower and back part a notch leading to a groove, the mylo-hyoidean, which runs obliquely downward to the back part of the submaxillary fossa, and lodges the mylo-hyoid vessels and nerve. Behind the groove is a rough surface, for the insertion of the Internal pterygoid muscle. The inferior dental canal runs obliquely downward and forward in the substance of the ramus, and then horizontally forward in the body; it is here placed under the alveoli, with which it communi- cates by small openings. On arriving at the incisor teeth, it turns back to communicate with the mental foramen, giving off' two small canals, which run forward, to be lost in the cancellous tissue of the bone beneath the incisor teeth. This canal, in the posterior two-thirds of the bone, is situated nearer the internal surface of the jaw; and in the anterior third, nearer its external surface. Its walls are composed of compact tissue at either extremity, and of cancellous in the centre. It contains the inferior dental vessels and nerve, from which branches are distributed to the teeth through small apertures at the bases of the alveoli. The 206 THE SKELETON. lower border of the ramus is thick, straight, and continuous with the body of the bone. At its junction with the posterior border is the angle of the jaw, which is either inverted or everted, and marked by rough, oblique ridges on each side, for the attachment of the Masseter externally, and the Internal pterygoid internally; the stylo-maxillary ligament is attached to the bone between these muscles. The anterior border is thin above, thicker below, and continuous with the external oblique line. The posterior border is thick, smooth, rounded, and covered by the parotid gland. The upper border of the ramus is thin, and presents two processes, separated by a deep concavity, the sigmoid notch. Of these processes, the anterior is the coronoid, the posterior the condyloid. The Coronoid Process is a thin, flattened, triangular eminence of bone, which varies in shape and size in different subjects, and serves chiefly for the attachment of the Temporal muscle. Its external surface is smooth, and affords attachment to the Temporal muscle. Itg internal surface gives attachment to the Temporal muscle, and presents the commencement of a longitudinal ridge, which is continued to the posterior part of the alveolar process. On the outer side of this ridge is a deep groove, continued below on the outer side of the alveolar process ; this ridge and part of the groove afford attachment, above, to the Temporal; below, to the Buccinator muscle. The Condyloid Process, shorter but thicker than the coronoid, consists of two portions: the condyle, and the constricted portion which supports the condyle, the neck. The condyle is of an oblong form, its long axis being transverse, and set obliquely on the neck in such a manner that its outer end is a little more forward and a little higher than its inner. It is convex from before backward and from side to side, the articular surface extending farther on the posterior than on the anterior aspect. The neck of the condyle is flattened from before backward, and strengthened by ridges which descend from the fore part and sides of the condyle. Its lateral margins are narrow, and present externally a tubercle for the external lateral ligament. Its posterior surface is convex ; its anterior is hollowed out on its inner side by a depression (the pterygoid fossa}, for the attachment of the External pterygoid. The Sigmoid Notch, separating the two processes, is a deep semilunar depres- sion, crossed by the masseteric vessels and nerve. Development.-The lower jaw is developed principally from membrane, but partly from cartilage. The process of ossification commences early-before, indeed, any bone except the clavicle. Between the fifth and sixth week a centre of ossi- fication appears in the membrane on the outer surface of Meckel's cartilage (see page 120), from which the greater part of the bone is found. A second centre appears in the membrane on the inner surface of the tooth-sockets, from which the inner wall of the sockets of the teeth is formed ; this terminates above in the lingula. The anterior extremity of Meckel's cartilage becomes ossified, forming the body of the bone on each side of the symphysis. And, finally, two supplemental patches of cartilage appear at the condyle and at the angle, in which centres of ossification fdr these parts appear. At birth the bone consists of two halves, united by a fibrous symphysis, in which ossification takes place during the first year. Articulation.-With the glenoid fossae of the two temporal bones. Attachment of Muscles.-To fifteen pairs : to its external surface, commencing at the symphysis, and proceeding backward: Levator menti, Depressor labii infe- rioris, Depressor anguli oris, Platysma myoides, Buccinator, Masseter; a portion of the Orbicularis oris (Accessorii orbicularis inferioris) is also attached to this surface. To its internal surface, commencing at the same point: Genio-hyo- glossus, Genio-hyoideus, Mylo-hyoideus, Digastric, Superior constrictor, Temporal, Internal pterygoid, External pterygoid. The changes which the lower jaw undergoes after birth relate (1) to the alterations effected in the body of the bone by the first and second dentitions, the loss of the teeth in the aged, and CHANGES PRODUCED IN THE LOWER JAW RY AGE. THE INFERIOR MAXILLARY BONE. 207 Side View of the Lower Jaw at Different Periods of Life. Fig. 168.-At birth. Fig. 169.-At puberty. Fig. 170.-In the adult. Fig. 171.-In old age. 208 THE SKELETON. the subsequent absorption of the alveoli; (2) to the size and situation of the dental canal; and (3) to the angle at which the ramus joins with the body. At birth (Fig. J 68) the bone consists of lateral halves, united by fibrous tissue. The body is a mere shell of bone, containing the sockets of the two incisor, the canine, and the two tem- porary molar teeth, imperfectly partitioned from one another. The dental canal is of large size, and runs near the lower border of the bone, the mental foramen opening beneath the socket of the first molar. The angle is obtuse (175°), and the condyloid portion nearly in the same hori- zontal line with the body ; the neck of the condyle is short, and bent backward. The coronoid process is of comparatively large size, and situated at right angles with the rest of the bone. After birth (Fig. 169) the two segments of the bone become joined at the symphysis, from below upward, in the first year ; but a trace of separation may be visible in the beginning of the second year near the alveolar margin. The body becomes elongated in its whole length, but more especially behind the mental foramen, to provide space for the three additional teeth developed in this part. The depth of the body becomes greater, owing to increased growth of the alveolar part, to afford room for the fangs of the teeth, and by thickening of the subdental portion, which enables the jaw to withstand the powerful action of the masticatory muscles; but the alveolar portion is the deeper of the two, and. consequently, the chief part of the body lies above the oblique line. The dental canal after the second dentition is situated just above the level of tlie mylo-hyoid ridge, and the mental foramen occupies the position usual to it in the adult. The angle becomes less obtuse, owing to the separation of the jaws by the teeth. (About the fourth year it is 140°.) In the adult (Fig. 170) the alveolar and basilar portions of the body are usually of equal depth. The mental foramen opens midway between the upper and lower border of the bone, and the dental canal runs nearly parallel with the mylo-hyoid line. The ramus is almost vertical in direction, and joins the body nearly at right angles. In old age (Fig. 171) the bone becomes greatly reduced in size; for with the loss of the teeth the alveolar process is absorbed, and the basilar part of the bone alone remains; conse- quently, the chief part of the bone is below the oblique line. The dental canal, with the mental foramen opening from it, is close to the alveolar border. The rami are oblique in direction, the angle obtuse, and the neck of the condyle more or less bent backward. The Sutures. The bones of the cranium and face are connected to each other by means of Sutures. That is, the articulating surfaces or edges of the bones are more or less roughened or uneven, and are closely adapted to each other, a small amount of intervening fibrous tissue fastening them together. The Cranial Sutures may be divided into three sets : 1. Those at the vertex of the skull. 2. Those at the side of the skull. 3. Those at the base. The sutures at the vertex of the skull are three: the sagittal, coronal, and lambdoid. The Sagittal Suture (interparietal} is formed by the junction of the two parietal bones, and extends from the middle of the frontal bone backward to the superior angle of the occipital. In childhood, and occasionally in the adult, when the two halves of the frontal bone are not united, it is continued forward to the root of the nose. This suture is sometimes perforated, near its posterior extremity, by the parietal foramen; and in front, where it joins the coronal suture, a space is occasionally left which encloses a large Wormian bone. The Coronal Suture (fronto-parietal} extends transversely across the vertex of the skull, and connects the frontal with the parietal bones. It commences at the extremity of the greater wing of the sphenoid on one side, and terminates at the same point on the opposite side. The dentations of the suture are more marked at the sides than at the summit, and are so constructed that the frontal rests on the parietal above, whilst laterally the frontal supports the parietal. The Lambdoid Suture (occipito-parietal}, so called from its resemblance to the Greek letter A, connects the occipital with ftie parietal bones. It commences on each side at the mastoid portion of the temporal bone, and inclines upward to the end of the sagittal suture. The dentations of this suture are very deep and dis- tinct, and are often interrupted by several small Wormian bones. The sutures at the side of the skull extend from the external angular process of the frontal bone to the lower end of the lambdoid suture behind. The anterior portion is formed between the lateral part of the frontal bone above and the malar and great wing of the sphenoid below, forming the fronto-malar and fronto- THE SUTURES. 209 sphenoidal sutures. These sutures can also be seen in the orbit, and form part of the so-called transverse facial suture. The posterior portion is formed between the parietal bone above and the great wing of the sphenoid, the squamous and mastoid portions of the temporal bone, forming the spheno-parietal, squamo-parietal, and masto-parietal sutures. The Spheno-parietal is very short; it is formed by the tip of the great wing of the sphenoid, which overlaps the anterior inferior angle of the parietal bone. The Squamo-parietal, or Squamous Suture, is arched. It is formed by the squamous portion of the temporal bone overlapping the middle division of the lower border of the parietal. The Masto-parietal is a short suture, deeply dentated, formed by the posterior inferior angle of the parietal and the superior border of the mastoid portion of the temporal. The sutures at the base of the skull are the basilar in the centre, and on each side the petro-occipital, the masto-occipital, the petrosphenoidal, and the squamo- sphenoidal. The Basilar Suture is formed by the junction of the basilar surface of the occipital bone with the posterior surface of the body of the sphenoid. At an early period of life a thin plate of cartilage exists between these bones, but in the adult they become fused into one. Between the outer extremity of the basilar suture and the termination of the lambdoid an irregular suture exists, which is subdivided into two portions. The inner portion, formed by the union of the petrous part of the temporal with the occipital bone, is termed the petro-occipital. The outer portion, formed by the junction of the mastoid part of the temporal with the occipital, is called the masto-occipital. Between the bones forming the petro- occipital suture a thin plate of cartilage exists; in the masto-occipital is occa- sionally found the opening of the mastoid foramen. Between the outer extremity of the basilar suture and the spheno-parietal an irregular suture may be seen, formed by the union of the sphenoid with the temporal bone. The inner and smaller portion of this suture is termed the petro-sphenoidal; it is formed between the petrous portion of the temporal and the great wing of the sphenoid: the outer portion, of greater length and arched, is formed between the squamous portion of the temporal and the great wing of the sphenoid; it is called the squamo- sphenoidal. The cranial bones are connected with those of the face, and the facial bones with each other, by numerous sutures, which, though distinctly marked, have received no special names. The only remaining suture deserving especial con- sideration is the transverse. This extends across the upper part of the face, and is formed by the junction of the frontal with the facial bones : it extends from the external angular process of one side to the same point on the opposite side, and connects the frontal with the malar, the sphenoid, the ethmoid, the lachrymal, the superior maxillary, and the nasal bones on each side. The sutures remain separate for a considerable period after the complete for- mation of the skull. It is probable that they serve the purpose of permitting the growth of the bones at their margins, while their peculiar formation, together with the interposition of sutural ligament between the bones forming them, prevents the dispersion of blows or jars received upon the skull. Humphry remarks, " that, as a general rule, the sutures are first obliterated at the parts in which the ossification of the skull was last completed-viz. in the neighborhood of the fontanelles ; and the cranial bones seem in this respect to observe a similar law to that which regulates the union of the epiphyses to the shafts of the long bones." The same author remarks that the time of their disappearance is extremely variable: they are sometimes found well marked in skulls edentulous with age, while in others which have only just reached maturity they can hardly be traced. 210 THE SKELETON. The Skull, formed by the union of the several cranial and facial bones already described, when considered as a whole is divisible into five regions: a superior region or vertex, an inferior region or base, two lateral regions, and an interior region, the face. THE SKULL AS A WHOLE. The Vertex of the Skull. The Superior Region, or Vertex, presents two surfaces, an external and an internal. The external surface is bounded, in front, by the glabella and supraorbital ridges; behind, by the occipital protuberance and superior curved lines of the occipital bone; laterally, by an imaginary line extending from the outer end of the superior curved line, along the temporal ridge, to the external angular process of the frontal. This surface includes the vertical portion of the frontal, the greater part of the parietal, and the superior third of the occipital bone; it is smooth, convex, of an elongated oval form, crossed transversely by the coronal suture, and from before backward, by the sagittal, which terminates behind in the lambdoid. The point of junction of the coronal and sagittal sutures is named the bregma, and is represented by a line drawn vertically upward from the exter- nal auditory meatus, the head being in its normal position. The point of junc- tion of the sagittal and lambdoid sutures is called the lambda, and is about 2J inches above the external occipital protuberance. From before backward may be seen the frontal eminences and remains of the suture connecting the two lateral halves of the frontal bone; on each side of the sagittal suture are the parietal foramen and parietal eminence, and still more posteriorly the convex surface of the occipital bone. In the neighborhood of the parietal foramen the skull is often flattened, and to this region the name of obelion is sometimes given. The internal surface is concave, presents eminences and depressions for the convolutions of the cerebrum, and numerous furrows for the lodgment of branches of the meningeal arteries. Along the middle line of this surface is a longitudinal groove, narrow in front, where it commences at the frontal crest, but broader behind, where it lodges the superior longitudinal sinus, and by its margin affords attachment to the falx cerebri. On either side of it are several depressions for the Pacchionian bodies, and at its back part the internal openings of the parietal foramina. This surface is crossed, in front, by the coronal suture; from before backward by the sagittal; behind, by the lambdoid. The Base of the Skull The Inferior Region, or Base of the Skull, presents two surfaces-an internal or cerebral, and an external or basilar. The internal or cerebral surface (Fig. 172) presents three fossae, called the anterior, middle, and posterior fossae of the cranium. The Anterior Fossa is formed by the orbital plates of the frontal, the cribri- form plate of the ethmoid, the anterior third of the superior surface of the body, and the upper surface of the lesser wings of the sphenoid. It is the most elevated of the three fossae, convex externally where it corresponds to the roof of the orbit, concave in the median line in the situation of the cribriform plate of the ethmoid. It is traversed by three sutures, the etlimo-front al, ethmo-sphenoidal, and fronto- sphenoidal, and lodges the frontal lobe of the cerebrum. It presents, in the median line, from before backward, the commencement of the groove for the superior longitudinal sinus and the frontal crest for the attachment of the falx cerebri; foramen ccecum, an aperture formed between the frontal bone and the crista galli of the ethmoid, which, if pervious, transmits a small vein from the nose to the superior longitudinal sinus; behind the foramen caecum, the crista galli, the posterior margin of which affords attachment to the falx cerebri; on either side of the crista galli, the olfactory groove, which supports the bulb of the olfactory THE BASE OF THE SKULL. 211 tract, and presents three rows of foramina for its filaments, and in front a slit-like opening for the nasal branch of the ophthalmic division of the fifth nerve. On Groove for superior longitudinal sinus.- Grooves for anterior meningeal artery.. Foramen caecum.. Crista galli.. Slit for nasal nerve.. Groove for nasal nerve.- Anterior ethmoidal foramen. Orifices for olfactory nerves. Posterior ethmoidal foramen: Ethmoidal spine. Olfactory grooves. Optic foramen.. Optic groove. Olivary process. Anterior clinoid process.. Middle clinoid process.. Posterior clinoid process.- Groove for 6th nerve.. Foramen lacerum medium.. Orifice of carotid canal.- Depression for Gasserian ganglion. Meatus auditorius internus.. Slit for dura mater.- Superior petrosal groove.- Foramen lacerum posterius.- A nterior condyloid foramen.- Aquxductus vestibuli.- Posterior condyloid foramen.. Foramen magnum. Mastoid foramen.- Posterior meningeal grooves Fig. 172.-Base of the skull. Inner or cerebral surface. the outer side of each olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina ; the former, situated about the middle of the outer margin of the olfactory groove, transmits the anterior ethmoidal vessels and the nasal nerve, which latter runs in a depression along the surface of the ethmoid to 212 THE SKELETON. the slit-like opening above mentioned; whilst the posterior ethmoidal foramen opens at the back part of this margin under cover of the projecting lamina of the sphenoid, and transmits the posterior ethmoidal vessels. Farther back in the middle line is the ethmoidal spine, bounded behind by an elevated ridge, sepa- rating two longitudinal grooves which support the olfactory tracts. Behind this is a transverse sharp ridge, running outward on either side to the anterior margin of the optic foramen, and separating the anterior from the middle fossa of the base of the skull. The anterior fossa presents, laterally, eminences and depressions for the convolutions of the brain and grooves for the lodgment of the anterior meningeal arteries. The Middle Fossa, somewhat deeper than the preceding, is narrow in the middle line, but becomes wider at the side of the skull. It is bounded in front by the posterior margin of the lesser wing of the sphenoid, the anterior clinoid process, and the ridge forming the anterior margin of the optic groove ; behind, by the superior border of the petrdus portion of the temporal and the dorsum ephippi; externally by the squamous portion of the temporal, anterior inferior angle of the parietal bone, and greater wing of the sphenoid. It is traversed by four sutures, the squamo-parietal, spheno-parietal, squamo-sphenoidal, and petro-sphenoidal. In the middle line, from before backward, is the optic groove, which supports the optic commissure, and terminates on each side in the optic foramen, for the passage of the optic nerve and ophthalmic artery; behind the optic groove is the olivary process, and laterally the anterior clinoid processes, to which are attached processes of the tentorium cerebelli. Farther back is the sella turcica, a deep depression which lodges the pituitary gland, bounded in front by a small eminence on either side, the middle clinoid process, and behind by a broad square plate of bone, the dorsum ephippi, surmounted at each superior angle by a tubercle, the posterior clinoid process ; beneath the latter process is a notch, for the sixth nerve. On each side of the sella turcica is the cavernous groove: it is broad, shallow, and curved somewhat like the italic letter f; it •commences behind at the foramen lacerum medium, and terminates on the inner side of the anterior clinoid process, and presents along its outer margin a ridge of bone. This groove lodges the cavernous sinus, the internal carotid artery, and the nerves of the orbit. The sides of the middle fossa are of considerable depth; they present eminences and depressions for the convolutions of the brain and grooves for the branches of the middle meningeal artery ; the latter commence on the outer side of the foramen spinosum, and consist of two large branches, an anterior and a posterior; the former passing upward and forward to the anterior inferior angle of the parietal bone, the latter passing upward and backward. The following foramina may also be seen from before backward: Most anteriorly is the foramen lacerum anterius, or sphenoidal fissure, formed above by the lesser wing of the sphenoid; below, by the greater wing ; internally, by the body of the sphenoid ; and sometimes completed externally by the orbital plate of the frontal bone. It transmits the third, the fourth, the three branches of the ophthalmic division of the fifth, the sixth nerve, some filaments from the cavernous plexus of the sympathetic, the orbital branch of the middle meningeal artery, a recurrent branch from the lachrymal artery to the dura mater, and the ophthalmic vein. Behind the inner extremity of the sphenoidal fissure is the foramen rotundum, for the passage of the second division of the fifth or superior maxillary nerve; still more posteriorly is seen a small orifice, the foramen Vesalii, an opening situated between the foramen rotundum and ovale, a little internal to both : it varies in size in different individuals, and is often absent; when present, it transmits a small vein. It opens below into the pterygoid fossa, just at the outer side of the scaphoid depression. Behind and external to the latter opening is the foramen ovale, which transmits the third division of the fifth or inferior maxillary nerve, the small meningeal artery, and the small petrosal nerve.1 On the outer side of the foramen ovale is the foramen spinosum, for the passage of the middle meningeal artery ; and 1 See footnote, p. 184. THE BASE OF THE SKULL. 213 on the inner side of the foramen ovale, the foramen lacerum medium. The lower part of this aperture is filled up with cartilage in the recent state. The Vidian nerve and a meningeal branch from the ascending pharnygeal artery pierce this cartilage. On the anterior surface of the petrous portion of the temporal bone is seen, from without inward, the eminence caused by the projection of the superior semicircular canal; outside this a depression corresponding to the roof of the tympanum; the groove leading to the hiatus Fallopii, for the transmission of the petrosal branch of the Vidian nerve and the petrosal branch of the middle meningeal artery; beneath it, the smaller groove, for the passage of the lesser petrosal nerve; and, near the apex of the bone, the depression for the Gasserian ganglion ; and the orifice of the carotid canal, for the passage of the internal carotid artery and carotid plexus of nerves. The Posterior Fossa, deeply concave, is the largest of the three, and situated on a lower level than either of the preceding. It is formed by the posterior third of the superior surface of the body of the sphenoid, by the occipital, the petrous and mastoid portions of the temporal, and the posterior inferior angle of the parietal bone ; it is crossed by four sutures, the petro-occipital, the masto-occipital. the masto-parietal, and the basilar; and lodges the cerebellum, pons Varolii, and medulla oblongata. It is separated from the middle fossa in the median line by the dorsum ephippii, and on each side by the superior border of the petrous portion of the temporal bone. This border serves for the attachment of the tentorium cerebelli, is grooved for the superior petrosal sinus, and at its inner extremity presents a notch, upon which rests the fifth nerve. The circumference of the fossa is bounded posteriorly by the grooves for the lateral sinuses. In the centre of this fossa is the foramen magnum, bounded on either side by a rough tubercle, which gives attachment to the odontoid or check ligaments; and a little above these are seen the internal openings of the anterior condyloid foramina, through which pass the hypoglossal nerve and a meningeal branch from the ascending pharyngeal artery. In front of the foramen magnum is a grooved surface, formed by the basilar process of the occipital bone and by the posterior third of the superior surface of the body of the sphenoid, which supports the medulla oblongata and pons Varolii, and articulates on each side with the petrous portion of the temporal bone, forming the petro-occipital suture, the anterior half of which is grooved for the inferior petrosal sinus, the posterior half being encroached upon by the foramen lacerum posterius, or jugular foramen. This foramen presents three compartments: through the anterior passes the inferior petrosal sinus ; through the posterior, the lateral sinus and some meningeal branches from the occipital and ascending pharyngeal arteries; and through the middle, the glosso-pharyngeal, pneumo- gastric, and spinal accessory nerves. Above the jugular foramen is the internal auditory meatus, for the facial and auditory nerves and auditory artery; behind and external to this is the slit-like opening leading into the aqumductus vestibuli; whilst between the two latter, and near the superior border of the petrous portion, is a small, triangular depression which lodges a process of the dura mater and occasionally transmits a small vein into the substance of the bone. Behind the foramen magnum are the inferior occipital fossce, which lodge the hemispheres of the cerebellum, separated from one another by the internal occipital crest, which serves for the attachment of the falx cerebelli and lodges the occipital sinus. The posterior fossae are surmounted, above, by the deep transverse grooves for the lodgment of the lateral sinuses. These channels, in their passage outward, groove the occipital bone, the posterior inferior angle of the parietal, the mastoid portion of the temporal, and the jugular process of the occipital, and terminate at the back part of the jugular foramen. Where this sinus grooves the mastoid portion of the temporal bone the orifice of the mastoid foramen may be seen, and just previous to its termination it has opening into it the posterior condyloid foramen. Neither foramen is constant. The External Surface of the Base of the Skull (Fig. 173) is extremely irregular. It is bounded in front by the incisor teeth in the upper jaws; behind by the 214 THE SKELETON. Anterior palatine fossa. ■Transmits left naso-palatine nerve. -Transmits anterior palatine vessel. Transmits right naso-palatine nerve. Accessory palatine foramina. 'Posterior nasal spine. AZYGOS UVUL/E. Hamular process. -Sphenoid process of palate. ■Pterygo-palatine canal. -TENSOR TYMPANI. -Pharyngeal spine for SUPERIOR CONSTRICTOR .Situation of Eustachian tube and canal for tensor tympani. •TENSOR PALATI 'Canal for Jacobson's nerve. -Aquseductus cochlese. 'Foramen lacerum posterius. -Canal for Arnold's nerve. -Auricular fissure. Foramen magnum. Fig. 173.-Base of the skull. External surface. superior curved lines of the occipital bone; and laterally by the alveolar arch, the lower border of the malar bone, the zygoma, and an imaginary line extending from the zygoma to the mastoid process and extremity of the superior curved line THE BASE OF THE SKULL. 215 of the occiput. It is formed by the palate processes of the superior maxillary and palate bones, the vomer, the pterygoid processes, under surface of the great wing, spinous processes and part of the body of the sphenoid, the under surface of the squamous, mastoid, and petrous portions of the temporal, and the under surface of the occipital bone. The anterior part of the base of the skull is raised above the level of the rest of this surface (when the skull is turned over for the purpose of examination), surrounded by the alveolar process, which is thicker behind than in front, and excavated by sixteen depressions for lodging the teeth of the upper jaw, the cavities varying in depth and size according to the teeth they contain. Immediately behind the incisor teeth is the anterior palatine fossa. At the bottom of this fossa may usually be seen four apertures: two placed laterally, the foramina of Stenson, which open above, one in the floor of each nostril, and transmit the anterior branch of the posterior palatine vessels, and two in the median line in the intermaxillary suture, the foramina of Scarpa, one in front of the other, the anterior transmitting the left, and the posterior (the larger) the right, naso-palatine nerve. These two latter canals are sometimes wanting, or they may join to form a single one, or one of them may open into one of the lateral canals above referred to. The palatine vault is concave, uneven, perforated by numerous foramina, marked by depressions for the palatine glands, and crossed by a crucial suture, formed by the junction of the four bones of which it is composed. At the front part of this surface a delicate linear suture may frequently be seen, marking off the pre-maxillary portion of the bone. One or two small foramina in the alveolar margin behind the incisor teeth, occasionally seen in the adult, almost constantly in young subjects, are called the incisive foramina ; they transmit nervesand vessels to the incisor teeth. At each posterior angle of the hard palate is the posterior palatine foramen, for the transmission of the posterior palatine vessels and large descending palatine nerve; and running forward and inward from it a groove, for the same vessels and nerve. Behind the posterior palatine foramen is the tuberosity of the palate bone, perforated by one or more accessory posterior palatine canals, and marked by the commencement of a ridge, which runs transversely inward, and serves for the attachment of the tendinous expansion of the Tensor palati muscle. Projecting backward from the centre of the posterior border of the hard palate is the posterior nasal spine, for the attachment of the Azygos uvulae. Behind and above the hard palate is the posterior aperture of the nares, divided into two parts by the vomer, bounded above by the body of the sphenoid, below by the horizontal plate of the palate bone, and laterally by the pterygoid processes of the sphenoid. Each aperture measures about an inch and a quarter in the vertical and about half an inch in the transverse direction. At the base of the vomer may be seen the expanded alm of this bone, receiving between them the rostrum of the sphenoid. Near the lateral margins of the vomer, at the root of the pterygoid processes, are the pterygo-palatine canals. The pterygoid process, which bounds the posterior nares on each side, presents near its base the pterygoid or Vidian canal, for the A idian nerve and artery. Each process consists of two plates, which bifurcate at the extremity to receive the tuberosity of the palate bone, and are separated behind by the pterygoid fossa, which lodges the Internal pterygoid muscle. The internal plate is long and narrow, presenting on the outer side of its base the scaphoid fossa, for the origin of the Tensor palati muscle, and at its extremity the hamular process, around which the tendon of this muscle turns. The external pterygoid plate is broad, forms the inner boundary of the zygomatic fossa, and affords attachment by its outer surface to the External pterygoid muscle. Behind the nasal fossae in the middle line is the basilar surface of the occipital bone, presenting in its centre the pharyngeal spine, for the attachment of the Superior constrictor muscle of the pharynx, with depressions on each side for the insertion of the Rectus capitis anticus major and minor. At the base of the external pterygoid plate is the foramen ovale ; behind this, the foramen spinosum and the prominent spinous process of the sphenoid, which gives attachment to the internal lateral ligament of the lower jaw and the Tensor palati muscle. External 216 THE SKELETON. to the spinous process is the glenoid fossa, divided into two parts by the Glaserian fissure (page 176), the anterior portion concave, smooth, bounded in front by the eminentia articularis, and serving for the articulation of the condyle of the lower jaw; the posterior portion rough, bounded behind by the tympanic plate, and serving for the reception of part of the parotid gland. Emerging from between the laminae of the vaginal process of the tympanic plate is the styloid process, and at the base of this process is the stylo-mastoid foramen, for the exit of the facial nerve and entrance of the stylo-mastoid artery. External to the stylo-mastoid foramen is the auricular fissure, for the auricular branch of the pneumogastric, bounded behind by the mastoid process. Upon the inner side of the mastoid process is a deep groove, the digastric fossa ; and a little more internally the omjtnW groove, for the occipital artery. At the base of the internal pterygoid plate is a large and somewhat triangular aperture, the foramen lacerum medium, bounded in front by the great wing of the sphenoid, behind by the apex of the petrous portion of the temporal bone, and internally by the body of the sphenoid and basilar process of the occipital bone : it presents in front the posterior orifice of the Vidian canal; behind, the aperture of the carotid canal. The basilar surface of this opening is filled up in the recent state by a fibro-cartilaginous substance; across its upper or cerebral aspect pass the internal carotid artery and Vidian nerve. External to this aperture the petrosphenoidal suture is observed, at the outer termination of which is seen the orifice of the canal for the Eustachian tube and that for the Tensor tympani muscle. Behind this suture is seen the under surface of the petrous portion of the temporal bone, presenting, from within outward the quadrilateral, rough surface, part of which affords attachment to the Levator palati and Tensor tympani muscles; external to this surface the orifices of the carotid canal and the aquae- ductus cochleae, the former transmitting the internal carotid artery and the ascend- ing branches of the superior cervical ganglion of the sympathetic, the latter serving for the passage of a small artery and vein to the cochlea. Behind the carotid canal is a large aperture, the jugular fossa, formed in front by the petrous portion of the temporal, and behind by the occipital; it is generally larger on the right than on the left side, and is divided into three compartments by processes of dura mater. The anterior is for the passage of the inferior petrosal sinus ; the posterior, for the lateral sinus and some meningeal branches from the occipital and ascending pharyngeal arteries; the central one, for the glosso-pharyngeal, pneumogastric, and spinal accessory nerves. On the ridge of bone dividing the carotid canal from the jugular fossa is the small foramen for the transmission of Jacobson's nerve; and on the outer wall of the jugular foramen, near the root of the styloid process, is the small aperture for the transmission of Arnold's nerve. Behind the basilar surface* of the occipital bone is the foramen magnum, bounded on each side by the condyles, rough internally for the attachment of the cheek or odontoid ligaments, and presenting externally a rough surface, the jugular process, which serves for the attachment of the Rectus capitis lateralis muscle and the lateral occipito-atloid ligament. On either side of each condyle anteriorly is the anterior condyloid fossa, perforated by the anterior condyloid foramen, for the passage of the hypoglossal nerve and a meningeal artery. Behind each condyle is the posterior condyloid fossa, perforated on one or both sides by the posterior condyloid foramina, for the transmission of a vein to the lateral sinus. Behind the foramen magnum is the external occipital crest, terminating above at the external occipital protuberance, whilst on each side are seen the superior and inferior curved lines ; these, as well as the surfaces of bone between them, are rough for the attachment of the muscles, which are enumerated on page 170. The Lateral Region of the Skull. The Lateral Region of the Skull is of a somewhat triangular form, the base of the triangle being formed by a line extending from the external angular process of the frontal bone along the temporal ridge backward to the outer extremity of THE TEMPORAL FOSSA. 217 the superior curved line of the occiput: and the sides by twm lines, the one drawn downward and backward from the external angular process of the frontal bone to the angle of the lower jaw, the other from the angle of the jaw upw ard and S Parietal. ■X \ Frontal. Occipital. Fig. 174.-Side view of the skull. backward to the outer extremity of the superior curved line. This region is divisible into three portions-temporal fossa, mastoid portion, and zygomatic fossa. The Temporal Fossa. The Temporal Fossa is bounded above and behind by the temporal ridge, which extends from the external angular process of the frontal upward and backward across the frontal and parietal bones, curving downward behind to terminate in the posterior root of the zygomatic process. This ridge is generally double-at all events in front, where it is most marked. In front it is bounded by the frontal, malar, and great wing of the sphenoid: externally by the zygomatic arch, formed conjointly by the malar and temporal bones; below it is separated from the zygomatic fossa by the pterygoid ridge, seen on the outer surface of the great wing of the sphenoid. This fossa is formed by five bones, part of the frontal, great wing of the sphenoid, parietal, squamous portion of the temporal, and malar bones, and is traversed by six sutures, part of the transverse facial, spheno- malar, coronal, spheno-parietal, squamo-parietal, and squamo-sphenoidal. The point where the coronal suture crosses the temporal ridge is sometimes named the stephanion ; and the region where the four bones, the parietal, the frontal, the squamous, and the greater wing of the sphenoid, meet, at the anterior inferior angle of the parietal bone, is named the pterion. This point is about on a level with the 218 77AE? SKELETON. external angular process of the frontal bone ajid about one and a half inches behind it. This fossa is deeply concave in front, convex behind, traversed by grooves which lodge branches of the deep temporal arteries, and filled by the Temporal muscles. The Mastoid Portion of the side of the skull is bounded in front by the tubercle of the zygoma; above, by a line which runs from the posterior root of the zygoma to the end of the masto-parietal suture; behind and below by the masto-occipital suture. It is formed by the mastoid and part of the squamous and petrous por- tions of the temporal bone ; its surface is convex and rough for the attachment of muscles, and presents, from behind forward, the mastoid foramen, the mastoid process, the external auditory meatus surrounded by the auditory process, and, most anteriorly, the temporo-maxillary articulation. The Mastoid Portion. The Zygomatic Fossa. The Zygomatic Fossa is an irregularly shaped cavity, situated below and on the inner side of the zygoma; bounded, in front, by the tuberosity of the superior maxillary bone and the ridge which descends from its malar process; behind, by the posterior border of the pterygoid process and the eminentia articularis ; above, by the pterygoid ridge on the outer surface of the great wing of the sphenoid and the under part of the squamous portion of the temporal; below, by the alveolar border of the superior maxilla; internally, by the external pterygoid plate; and externally, by the zygomatic arch and ramus of the lower jaw. It contains the lower part of the Temporal, the External and Internal pterygoid muscles, the internal maxillary artery, and inferior maxillary nerve and their branches. At its upper and inner part may be observed two fissures, the spheno-maxillary and pterygo-maxillary. The Spheno-maxillary Fissure, horizontal in direction, opens into the outer and back part of the orbit. It is formed above by the lower border of the orbital surface of the great wing of the sphenoid; below, by the external border of the orbital surface of the superior maxilla and a small part of the palate bone ; externally, by a small part of the malar bone:1 internally, it joins at right angles with the pterygo-maxillary fissure. This fissure opens a communication from the orbit into three fossae-the temporal, zygomatic, and spheno-maxillary; it transmits the superior maxillary nerve and its orbital branch, the infraorbital vessels, and ascending branches from the spheno-palatine or Meckel's ganglion. The Pterygo-maxillary Fissure is vertical, and descends at right angles from the inner extremity of the preceding; it is a V-shaped interval, formed by the divergence of the superior maxillary bone from the pterygoid process of the sphenoid. It serves to connect the spheno-maxillary fossa with the zygomatic fossa, and transmits branches of the internal maxillary artery. It forms the entrance from the zygomatic fossa to the spheno-maxillary fossa. The Spheno-maxillary Fossa. The Spheno-maxillary Fossa is a small, triangular space situated at the angle of junction of the spheno-maxillary and pterygo-maxillary fissures, and placed beneath the apex of the orbit. It is formed above by the under surface of the body of the sphenoid and by the orbital process of the palate bone; in front, by the superior maxillary bone; behind, by the anterior surface of the base of the pterygoid process and lower part of the anterior surface of the great wing of the sphenoid; internally, by the vertical plate of the palate. This fossa has three fissures terminating in it-the sphenoidal, spheno-maxillary, and pterygo-maxillary; it communicates with three fossae, the orbital, nasal, and zygomatic, and with the cavity of the cranium, and has opening into it five foramina. Of these, there are 1 Occasionally the superior maxillary bone and the sphenoid articulate with each other at the anterior extremity of this fissure; the malar is then excluded from entering into its formation. 77//< ANTERIOR REGION OF THE SKULL. 219 three on the posterior wall: the foramen rotundum above; below and internal to this, the Vidian ; and still more inferiorly and internally, the pterygo-palatine. On the inner wall is the spheno-palatine foramen, by which the spheno-maxillary communicates with the nasal fossa; and below is the superior orifice of the posterior palatine canal, besides occasionally the orifices of the accessory posterior palatine canals. The fossa contains the superior maxillary nerve and Meckel's ganglion, and the termination of the internal maxillary artery. The Anterior Region of the Skull. The Anterior Region of the Skull, which forms the face, is of an oval form, presents an irregular surface, and is excavated for the reception of two of the organs of sense, the eye and the nose. It is bounded above by the glabella and margins of the orbit; below, by the prominence of the chin; on each side by the malar bone and anterior margin of the ramus of the jaw. In the median line are seen from above downward the glabella, and diverging from it are the superciliary ridges, which indicate the situation of the frontal sinuses and support the eyebrows. Beneath the glabella is the fronto-nasal suture, the mid-point of which is termed the nasion, and below this is the arch of the nose, formed by the nasal bones, and the nasal processes of the superior maxillary. The nasal arch is convex from side to side, concave from above downward, presenting in the median line the inter- nasal suture formed between the nasal bones, laterally the naso-maxillary suture formed between the nasal bone and the nasal process of the superior maxillary bone. Below the nose is seen the opening of the anterior nares, which is heart- shaped, with the narrow end upward, and presents laterally the thin, sharp margins serving for the attachment of the lateral cartilages of the nose, and in the middle line below a prominent process, the anterior nasal spine, bounded by two deep notches. Below this is the intermaxillary suture, and on each side of it the incisive fossa. Beneath this fossa are the alveolar processes of the upper and lower jaws, containing the incisor teeth, and at the lower part of the median line the symphysis of the chin, the mental process, with its two mental tubercles, separated by a median groove, and the incisive fossa of the lower jaw. On each side, proceeding from above downward, is the supraorbital ridge, terminating externally in the external angular process at its junction with the malar, and internally in the internal angular process; toward the inner third of this ridge is the supraorbital notch or foramen, for the passage of the supraorbital vessels and nerve, and at its inner side a slight depression, for the attachment of the pulley of the Superior oblique muscle. Beneath the supraorbital ridge is the opening of the orbit, bounded externally by the orbital ridge of the malar bone; below, by the orbital ridge formed by the malar, superior maxillary, and lachrymal bones; internally, by the nasal process of the superior maxillary and the internal angular process of the frontal bone. On the outer side of the orbit is the quadri- lateral anterior surface of the malar bone, perforated by one or two small malar foramina. Below the inferior margin of the orbit is the infraorbital foramen, the termination of the infraorbital canal, and beneath this the canine fossa, which gives attachment to the Levator anguli oris; bounded below by the alveolar processes, containing the teeth of the upper and lower jaws. Beneath the alveolar arch of the lower jaw is the mental foramen, for the passage of the mental vessels and nerve, the external oblique line, and at the lower border of the bone, at the point of junction of the body with the ramus, a shallow groove for the passage of the facial artery. The Orbits. The Orbits (Fig. 175) are two quadrilateral pyramidal cavities, situated at the upper and anterior part of the face, their bases being directed forward and outward, and their apices backward and inward, so that the axes of the two, if continued backward, would meet over the body of the sphenoid bone. Each orbit is formed of seven bones, the frontal, sphenoid, ethmoid, superior maxillary, malar, 220 THE SKELETON. lachrymal, and palate; but three of these, the frontal, ethmoid, and sphenoid, enter into the formation of both orbits, so that the two cavities are formed of eleven bones only. Each cavity presents for examination a roof, a floor, an inner and an outer wall, four angles, a circumference or base, and an apex. The roof is concave, directed downward and forward, and formed in front by the orbital plate of the frontal; behind by the lesser wing of the sphenoid. This surface presents internally the depression for the cartilaginous pulley of the Superior oblique muscle; externally, the depression for the lachrymal gland; and posteriorly, the suture connecting the frontal and lesser wing of the sphenoid. TENDO OCULI.- Anterior nares. Anterior nasal spine. Incisive fossa Groove for facial artery. Fig. 175.-Anterior region of the skull. The floor is nearly flat, and of less extent than the roof; it is formed chiefly by the orbital process of the superior maxillary; in front, to a small extent, by the orbital process of the malar, and behind, by the superior surface of the orbital process of the palate. This surface presents at its anterior and internal part, just external to the lachrymal groove, a depression for the attachment of the Inferior oblique muscle; externally, the suture between the malar and superior maxillary bones ; near its middle, the infraorbital groove ; and posteriorly, the suture between the maxillary and palate bones. The inner wall is flattened, and formed from before backward by the nasal process of the superior maxillary, the lachrymal, os planum of the ethmoid, and a small part of the body of the sphenoid. This surface presents the lachrymal groove and crest of the lachrymal bone, and the sutures connecting the lachrymal THE ANTERIOR REGION OF THE SKULL. 221 with the superior maxillary, the ethmoid with the lachrymal in front, and the ethmoid with the sphenoid behind. The outer wall is formed in front by the orbital process of the malar bone; behind, by the orbital surface of the sphenoid. On it are seen the orifices of one or two malar canals, and the suture connecting the sphenoid and malar bones. Angles.-The superior external angle is formed by the junction of the upper and outer walls; it presents, from before backward, the suture connecting the frontal with the malar in front and with the great wing of the sphenoid behind; quite posteriorly is the foramen lacerum anterius, or sphenoidal fissure, which transmits the third, the fourth, the three branches of the ophthalmic division of the fifth, the sixth nerve, some filaments from the cavernous plexus of the sym- pathetic, the orbital branch of the middle meningeal artery, a recurrent branch from the lachrymal artery to the dura mater, and the ophthalmic vein. The superior internal angle is formed by the junction of the upper and inner wall, and presents the suture connecting the frontal bone with the lachrymal in front and with the ethmoid behind. The point of junction of these three sutures has been named the dacryon. This angle presents two foramina, the anterior and posterior ethmoidal, the former transmitting the anterior ethmoidal vessels and nasal nerve, the latter the posterior ethmoidal vessels. The inferior external angle, formed by the junction of the outer wall and floor, presents the spheno-maxillary fissure, which transmits the superior maxillary nerve and its orbital branches, the infra- orbital vessels, and the ascending branches from the spheno-palatine or Meckel's ganglion. The inferior internal angle is formed by the union of the lachrymal and os planum of the ethmoid with the superior maxillary and palate bones. The circumference, or base, of the orbit, quadrilateral in form, is bounded above by the supraorbital ridge; below, by the anterior border of the orbital plate of the malar, superior maxillary, and lachrymal bones; externally, by the external angular process of the frontal and the malar bones; internally, by the internal angular process of the frontal and the nasal process of the superior maxillary. The circumference is marked by three sutures, the fronto-maxillary internally, the fronto-malar externally, and the malo-maxillary below; it contributes to the formation of the lachrymal groove, and presents, above, the supraorbital notch (or foramen), for the passage of the supraorbital vessels and nerve. The situated at the back of the orbit, corresponds to the optic foramen, a short, circular canal, which transmits the optic nerve and ophthalmic artery. It will thus be seen that there are nine openings communicating with each orbit-viz. the optic foramen, foramen lacerum anterius, spheno-maxillary fissure, supraorbital foramen, infraorbital canal, anterior and posterior ethmoidal foramina, malar foramina, and canal for the nasal duct. The Nasal Fossae. The Nasal Fossae are two large, irregular cavities situated on either side of the middle line of the face, extending from the base of the cranium to the roof of the mouth, and separated from each other by a thin vertical septum. They communi- cate by two large apertures, the anterior nares, with the front of the face, and by the two posterior nares with the pharynx behind. These fossae are much narrower above than below, and in the middle than at the anterior or posterior openings; their depth, which is considerable, is much greater in the middle than at either extremity. Each nasal fossa communicates with four sinuses, the frontal above, the sphenoidal behind, and the maxillary and ethmoidal on the outer wall. Each fossa also communicates with four cavities: with the orbit by the lachrymal groove, with the mouth by the anterior palatine canal, with the cranium by the olfactory foramina, and with the spheno-maxillary fossa by the spheno-palatine foramen ; and they occasionally communicate with each other by an aperture in the septum. The bones entering into their formation are fourteen in number: three of the cranium, the frontal, sphenoid, and ethmoid, and all the bones of the 222 THE SKELETON. face, excepting the malar and lower jaw-. Each cavity is bounded by a roof, a floor, an inner and an outer wall. The upper wall, or roof (Fig. 176), is long, narrow, and concave from before backward; it is formed in front by the nasal bones and nasal spine of the frontal, which are directed downward and forward; in the middle, by the cribriform plate of the ethmoid, w'hich is horizontal; and behind, by the under surface of the body of the sphenoid, and sphenoidal turbinated bones, which are directed downward and backward. This surface presents, from before backward, the internal aspect of the nasal bones; on their outer side, the suture formed between the nasal bone and the nasal process of the superior maxillary; on their inner side, the elevated crest which receives the nasal spine of the frontal and the perpendicular plate of the ethmoid, and articulates with its fellow of the opposite side; whilst the surface Roof. Nasal bone. Nasal spine of frontal bone. Horizontal plate of ethmoid. \ \ Sphenoid. \ .Probe passed through naso-lachrymal canal. ■ Bristle passed through infundibulum. Outer Wall. Nasal proc, of sup. max. -Lachrymal. -Ethmoid. - Unciform process of ethmoid. -'Inferior turbinated. .- Palate. ■Superior meatus. -Middle meatus. -Inferior meatus. Floor. Anterior nasal spine. Palate proc, of sup. max. Palate process of palate. Posterior nasal spine. Anterior palatine canal. Fig. 176.-Roof, floor, and outer wall of left nasal fossa. of the bones is perforated by a few small vascular apertures, and presents the longitudinal groove for the nasal nerve; farther back is the transverse suture, connecting the frontal with the nasal in front, and the ethmoid behind, the olfactory foramina and nasal slit on the under surface of the cribriform plate, and the suture between it and the sphenoid behind: quite posteriorly are seen the sphenoidal turbinated bones, the orifices of the sphenoidal sinuses, and the articulation of the alae of the vomer with the under surface of the body of the sphenoid. The floor is flattened from before backward, concave from side to side, and wider in the middle ftian at either extremity. It is formed in front by the palate process of the superior maxillary ; behind, by the palate process of the palate bone. This surface presents, from before backward, the anterior nasal spine; behind this, the upper orifices of the anterior palatine canal; internally, the elevated crest which articulates with the vomer; and behind, the suture between the palate and superior maxillary bones, and the posterior nasal spine. The inner wall, or septum (Fig. 177), is a thin vertical partition which sepa- rates the nasal fossae from one another; it is occasionally perforated, so that the THE ANTERIOR REGION OF THE SKULL. 223 fossae communicate, and it is frequently deflected considerably to one side.1 It is formed, in front, by the crest of the nasal bones and nasal spine of the frontal; in the middle, by the perpendicular plate of the ethmoid; behind, by the vomer and rostrum of the sphenoid; below, by the crest of the superior maxillary and palate bones. It presents, in front, a large, triangular notch, which receives the tri- angular cartilage of the nose; and behind, the guttural edge of the vomer. Its surface is marked by numerous vascular and nervous canals and the groove for Rostrum of sphenoid. Crest of nasal bone. Nasal spine of frontal bone. Perpendicular plate of ethmoid. Space for cartilage of septum .Crest of palate bone. .Crest of superior maxillary bone. Fig. 177.-Inner wall of nasal fossee, or septum of nose. the naso-palatine nerve, and is traversed by sutures connecting the bones of which it is formed. The outer wall (Fig. 176) is formed, in front, by the nasal process of the superior maxillary and lachrymal bones ; in the middle, by the ethmoid and inner surface of the superior maxillary and inferior turbinated bones; behind, by the vertical plate of the palate bone and the internal pterygoid plate of the sphenoid. This surface presents three irregular longitudinal passages, or meatuses, formed between three horizontal plates of bone that spring from it; they are termed the superior, middle, and inferior meatuses of the nose. The superior meatus, the smallest of the three, is situated at the upper and back part of each nasal fossa, occupying the posterior third of the outer wall. It is situated between the superior and middle turbinated bones, and has opening into it two foramina, the spheno- palatine at the back of its outer wall, and the posterior ethmoidal cells at the front part of the outer wall. The opening of the sphenoidal sinuses is usually at the upper and back part of the nasal fossae immediately behind the superior turbinated bone. The middle meatus is situated between the middle and inferior turbinated bones, and occupies the posterior two-thirds of the outer wall of the nasal fossa. It presents two apertures. In front is the orifice of the infundibulum, by which the middle meatus communicates with the anterior ethmoidal cells, and through these with the frontal sinuses. At the centre of the outer wall is the orifice of the antrum, which varies somewhat as to its exact position in different skulls. The inferior meatus, the largest of the three, is the space between the inferior turbinated 1 See footnote, p. 187. 224 THE SKELETON. bone and the floor of the nasal fossa. It'extends along the entire length of the outer wall of the nose, is broader in front than behind, and presents anteriorly the lower orifice of the canal for the nasal duct. The anterior nares present a heart-shaped or pyriform opening whose long axis is vertical and narrow extremity upward. This opening in the recent state is much contracted by the cartilages of the nose. It is bounded above by the inferior border of the nasal bone; laterally by the thin, sharp margin which separates the facial from the nasal surface of the superior maxillary bone; and below by the same border, where it slopes inward to join its fellow of the opposite side at the anterior nasal spine. The posterior nares are the two posterior oval openings of the nasal fossae, by which they communicate with the upper part of the pharynx. They are situated immediately in front of the basilar process, and are bounded above by the under surface of the body of the sphenoid ; below by the posterior border of the horizontal plate of the palate bone; externally, by the internal surface of the internal pterygoid plate; and internally, in the middle line, they are separated from each other by the guttural border of the vomer. Surface Form.-The various bony prominences or landmarks which are to be easily felt and recognized in the head and face, and which afford the means of mapping out the important structures comprised in this region, are as follows: 1. Supraorbital arch. 2. Internal angular process. 3. External angular process. 4. Zygomatic arch. 5. Mastoid process. 6. External occipital protuberance. 7. Superior curved line of occipital bone. 8. Parietal eminences. 9. Temporal ridge. 10. Frontal eminences. 11. Superciliary ridges. 12. Nasal bones. 13. Lower margin of orbit. 14. Lower jaw. 1. The supraorbital arches are to be felt throughout their entire extent, covered by the eye- brows. They form the upper boundary of the circumference or base of the orbit, and separate the face from the forehead. They are strong and arched, and terminate internally on each side of the root of the nose in the internal angular process, which articulates with the lachrymal bone. Externally they terminate in the external angular process, which articulates with the malar bone. This arched ridge is sharper and more defined in its outer than in its inner half, and forms an overhanging process which protects and shields the lachrymal gland. It thus pro- tects the eye in its most exposed situation and in the direction from which blows are most likely to descend. Tho supraorbital arch varies in prominence in different individuals. It is more marked in the male than in the female, and in some races of mankind than others. In the less civilized races, as the forehead recedes backward, the supraorbital arch becomes more prominent, and approaches more to the characters of the monkey tribe, in which the supraorbital arches are very largely developed, and acquire additional prominence from the oblique direction of the frontal bone. 2. The internal angular process is scarcely to be felt. Its position is indicated by the angle formed by the suprao ital arch with the nasal process of the superior maxillary bone and the lachrymal bone at the inner side of the orbit. Between the internal angular pro- cesses of the two sides is a broad surface which assists in forming the root of the nose, and immediately above this a broad, smooth, somewhat triangular surface, the glabella, situated between the superciliary ridges. 3. The external angular process is much more strongly marked than the internal, and is plainly to be felt. It is formed by the junction or confluence of the supra- orbital and temporal ridges, and, articulating with the malar bone, it serves to a very consider- able extent to support the bones of the face? In carnivorous animals the external angular pro- cess does not articulate with the malar, and therefore this lateral support to the bones of the face is not present. 4. The zygomatic arch is plainly to be felt throughout its entire length, being situated almost immediately under the skin. It is formed by the malar bone and the zygomatic process of the temporal bone. At its anterior extremity, where it is formed by the malar bone, it is broad and forms the prominence of the cheek; the posterior part is narrower, and termi- nates just in front and a little above the tragus of the external ear. The lower border is more plainly to be felt than the upper, in consequence of the dense temporal fascia being attached to the upper border, which somewhat obscures its outline. Its shape differs very much in individ- uals and in different races of mankind. In the most degraded type of skull-as, for instance, in the skull of the negro of the Guinea Coast-the malar bones project forward and not outward, and the zygoma at its posterior extremity extends farther outward before it is twisted on itself to be prolonged forward. This makes the zygomatic arch stand out in bold relief, and affords greater space for the Temporal muscle. In skulls which have a more pyramidal shape, as in the Esquimaux or Greenlander, the malar bones do not project forward and downward under the eyes, as in the preceding form, but take a direction outward, forming with the zygoma a large, rounded sweep or segment of a circle. Thus it happens that if two lines are drawn from the SURFACE FORM OF THE SKULL.. 225 zygomatic arches, touching the temporal ridges, they meet over the top of the head, instead of being parallel, or nearly so, as in the European skull, in which the zygomatic arches are not nearly so prominent. This gives to the face a more or less oval type. 5. Behind the ear is the mastoid portion of the temporal bone, plainly to be felt, and terminating below in a nipple- shaped process. Its anterior border can be traced immediately behind the concha, and its apex is on about a level with the lobule of the ear. It is rudimentary in infancy, but gradually develops in childhood, and is more marked in the negro than in the European. 6. The external occipital protuberance is always plainly to be felt just at the level where the skin of the neck joins that of the head. At this point the skull is thick for the purposes of safety, while radiating from it are numerous curved arches or buttresses of bone which give to this portion of the skull further security. 7. Running outward on either side from the external occipital protu- berance is an arched ridge of bone, which can be more or less plainly perceived. This is the superior curved line of the occipital bone, and gives attachment to some of the muscles which keep the head erect on the spine; accordingly, we find it more developed in the negro tribes, in whom the jaws are much more massive, and therefore require stronger muscles to prevent their extra weight carrying the head forward. Below this line the surface of bone at the back of the head is obscured by the overlying muscles. Above it, the vault of the cranium is thinly covered with soft structures, so that the form of this part of the head is almost exactly that of the upper portion of the occipital, the parietal, and the frontal bones themselves; and in bald persons even the lines of junction of the bones, especially the junction of the occipital and parietal at the lambdoid suture, may be defined as a slight depression, caused by the thickening of the borders of the bones in this situation. 8. In the line of the greatest transverse diameter of the head, on each side of the middle line, are generally to be found the parietal eminences, though sometimes these eminences are not situated at the point of the greatest transverse diameter, which is at some other prominent part of the parietal region. They denote the point where ossification of the bone began. They are much more prominent and well-marked in early life, in consequence of the sharper curve of the bone at this period, so that it describes the segment of a smaller circle. Later in life, as the bone grows, the curve spreads out and forms the segment of a larger circle, so that the eminence becomes less distinguishable. In consequence of this sharp curve of the bone in early life, the whole of the vault of the skull has a squarer shape than it has in later life, and this appearance may persist in some rickety skulls. The eminence is more apparent in the negro's skull than in that of the European. This is due to greater flat- tening of the temporal fossa in the former skull to accommodate the larger Temporal muscle which exists in these races. The parietal eminence is particularly exposed to injury from blows or falls on the head, but fracture is to a certain extent prevented by the shape of the bone, which forms an arch, so that the force of the blow is diffused over the bone in every direction. 9. At the side of the head may be felt the temporal ridge. Commencing at the external angular process, it may be felt as a curved ridge, passing upward and then curving backward, on the frontal bone, separating the forehead from the temporal fossa. It may then be traced, pass - ing backward in a curved direction, over the parietal bone, and, though less marked, still gen- erally to be recognized. Finally, the ridge curves downward, and terminates in the posterior root of the zygoma, which separates the squamous from the subcutaneous mastoid portion of the temporal bone. Mr. Victor Horsley has recently shown, in an article on the "Topography of the Cerebral Cortex. ' that the second temporal ridge (see page 170) can be made out on the living body. 10. The frontal eminences vary a good deal in different individuals, being con- siderably more prominent in some than in others, and they are often not symmetrical on the two sides of the body, the one being much more pronounced than the other. This is often especially noticeable in the skull of the young child or infant, and becomes less marked as age advances. I he prominence of the frontal eminences depends more upon the general shape of the whole bone than upon the size of the protuberances themselves. As the skull is more highly developed in consequence of increased intellectual capacity, so the frontal bone becomes more upright and the frontal eminences stand out in bolder relief. Thus they may be considered as affording, to a certain extent, an indication of the development of the hemispheres of the brain beneath, and of the mental powers of the individual. They are not so much exposed to injury as the parietal eminences. In falls forward the upper extremities are involuntarily thrown out, and break the force of the fall, and thus shield the frontal bone from injury. 11. Below the frontal eminences on the forehead are the superciliary ridges, which denote the position of the frontal sinuses, and vary according to the size of the sinuses in different individuals, being, as a rule, small in the female, absent in children, and sometimes unusually prominent in the male, when the frontal sinuses are largely developed. They commence on either side of the glabella, and at first present a rounded form, which gradually fades away at their outer ends. 12. The nasal bones form the prominence of the nose. They vary much in size and shape, and to them is due the varieties in the contour of this organ and much of the character of the face. Thus, m the Mongolian or Ethiopian they are flat, broad and thick at their base, giving to these tribes the flattened nose by which they are characterized, and differing very decidedly from the Caucasian, in whom the nose, owing to the shape of the nasal bones, is narrow, elevated at the bridge, and elongated downward. Below, the nasal bones are thin and connected with the car- tilages of the nose, and the angle or arch formed by their union serves to throw out the bridge of the nose, and is much more marked in some individuals than others. 13. The lower margin °-f f ie rbit, formed by the superior maxillary bone and the malar bone, is plainly to be felt throughout its entire length. It is continuous internally with the nasal process of the superior 226 THE SKELETON. maxillary bone, which forms the inner boundary of the orbit. At the point of junction of the lower margin of the orbit with the nasal process is to be felt a little tubercle of bone, which can be plainly perceived by running the finger along the bone in this situation. This tubercle serves as a guide to the position of the lachrymal sac, which is situated above and behind it. 14. The outline of the lower jaw is to be felt throughout its entire length. Just in front of the tragus of the external ear, and below the zygomatic arch, the condyle can be made out. When the mouth is opened this prominence of bone can be perceived advancing out of the glenoid fossa on to the eminentia articularis, and receding again when the mouth is closed. From the condyle the pos- terior border of the ramus can be felt extending down to the angle. A line drawn from the con- dyle to the angle would indicate the exact position of this border. From the angle to the symphysis of the chin the lower, rounded border of the body of the bone is plainly to be felt. At the point of junction of the two halves of the bone is a well-marked triangular eminence, the mental process, which forms the prominence of the chin. Surgical Anatomy.-An arrest in the ossifying process may give rise to deficiencies or gaps; or to fissures, which are of importance in a medico-legal point of view, as they are liable to he mistaken for fractures. The fissures generally extend from the margin toward the centre of the bone, but gaps may be found in the middle as well as at the edges. In course of time they may become covered with a thin lamina of bone. Occasionally a protrusion of the brain or its membranes may take place through one of these gaps in an imperfectly developed skull. When the protrusion consists of membranes only, and is filled with cerebro-spinal fluid, it is called a meningocele; when the protrusion consists of brain as well as membranes, it is termed an encephalocele ; and when the protruded brain is a prolonga- tion from one of the ventricles, and is distended by a collection of fluid from an accumulation in the ventricle, it is termed an hydrencephalocele. This latter condition is frequently found at the root of the nose, where a protrusion of the anterior horn of the lateral ventricle takes place through a deficiency of the fronto-nasal suture. These malformations are usually found in the middle line, and most frequently at the back of the head, the protrusion taking place through the fissures which separate the four centres of ossification from which the tabular portion is originally developed (see page 169). They most frequently occur through the upper part of the vertical fissure, which is the last to ossify, but not uncommonly through the lower part, when the foramen magnum may be incomplete, More rarely these protrusions have been met with in other situations than those two above mentioned, both through normal fissures, as the sagittal, lambdoid, and other sutures, and also through abnormal gaps and deficiencies at the sides, and even at the base of the skull. Fractures of the skull may be divided into those of the vault and those of the base. Frac- tures of the vault are usually produced by direct violence. This portion of the skull varies in thickness and strength in different individuals, but, as a rule, is sufficiently strong to resist a very considerable amount of violence without being fractured. This is due to several causes: the rounded shape of the head and its construction of a number of secondary elastic arches, each made up of a single bone; the fact that it consists of a number of bones, united, at all events in early life, by a sutural ligament, which acts as a sort of buffer and interrupts the continuity of any violence applied to the skull; the presence of arches or ridges, both on the inside and outside of the skull, which materially strengthen it; and the mobility of the head upon the spine which further enables it to withstand violence. The elasticity of the bones of the head is especially marked in the skull of the child, and this fact, together with the wide separation of the indi- vidual bones from each other, and the interposition between them of other softer structures renders fracture of the bones of the head a very uncommon event in infants and quite young children; as age advances and the bones become joined, fracture is more common, though still less liable to occur than in the adult. Fractures of the vault may, and generally do, involve the whole thickness of the bone ; but sometimes one table may be fractured without any correspond- ing injury to the other. Thus, the outer table of the skull may be splintered and driven into the diploe, or in the frontal or mastoid regions into the frontal or mastoid cells, without any injury to the internal table. And on the other hand, the internal table has been fractured, and por- tions of it depressed and driven inward, without any fracture of the outer table. As a rule, in fractures of the skull the inner table is more splintered and comminuted than the outer, and this is due to several causes. It is thinner and more brittle; the force of the violence as it passes inward becomes broken up, and is more diffused by the time it reaches the inner table; the bone, being in the form of an arch, bends as a whole and spreads out, and thus presses the particles together on the convex surface of the arch-i. e. the outer table-and forces them asunder on the concave surface or inner table; and, lastly, there is nothing firm under the inner table to support it and oppose the force. Fractures of the vault may be simple fissures or starred and comminuted fractures, and these may be depressed or elevated. These latter cases of fracture with elevation of the fractured portion are uncommon, and can only be produced by direct wound. In comminuted fracture a portion of the skull is broken into several pieces, the lines of fracture radiating from a centre where the chief impact of the blow was felt; if depressed, a fissure circumscribes the radiating line, enclosing a portion of skull. If this area is circular, it is termed a "pond" fracture, and would in all probability have been caused by a round instrument, as a life-preserver or hammer; if elliptical in shape, it is termed a " gutter fracture," and would owe its shape to the instrument which had produced it, as a poker. Fractures of the base are most frequently produced by the extension of a fissure from the SURGICAL ANATOMY OF THE BONES OF THE FACE. 227 vault, as in falls on the head, where the fissure starts from the part of the vault which first struck the ground. Sometimes, however, they are caused by direct violence, when foreign bodies have been forced through the thin roof of the orbit, through the cribriform plate of the ethmoid from being thrust up the nose, or through the roof of the pharynx. Other cases of fracture of the base occur from indirect violence, as in fracture of the occipital bone from impac- tion of the spinal column against its condyles in falls on the buttocks, knees, or feet, or in cases where the glenoid cavity has been fractured by the violent impact of the condyle of the lower jaw against it from blows on the chin. The most common place for fracture of the base to occur is through the middle fossa, and here the fissure usually takes a fairly definite course. Starting from the point struck, which is generally somewhere in the neighborhood of the parietal eminence, it runs downward through the parietal and squamous portion of the temporal bone and across the petrous portion of this bone, frequently traversing and implicating the internal auditory meatus, to the middle lacerated foramen. From this it may pass across the body of the sphenoid, through the pituitary fossa to the middle lacerated foramen of the other side, and may indeed travel round the whole cranium, so as to completely separate the anterior from the posterior part. The course of the fracture should be borne in mind, as it explains the symptoms to which fracture in this region may give rise; thus, if the fissure pass across the internal auditory meatus, injury to the facial and auditory nerves may result, with consequent facial paralysis and deafness; or the tubular pro- longation of the arachnoid around these nerves in the meatus may be torn, and thus permit of the escape of the cere bro-spinal fluid should there be a communication between the internal ear and the tympanum and the membrana tympani be ruptured, as is frequently the case; again, if the fissure passes across the pituitary fossa and the muco-periosteum covering the under surface of the body of the sphenoid is torn, blood will find its way into the pharynx and be swallowed, and after a time vomiting of blood will result. Fractures of the anterior fossa, involving the bones forming the roof of the orbit and nasal fossa, are generally the results of blows on the fore- head ; but fracture of the cribriform plate of the ethmoid may be a complication of fracture of the nasal bone. When the fracture implicates the roof of the orbit, the blood finds its way into this cavity, and, travelling forward, appears as a subconjunctival ecchymosis. If the roof of the nasal fossa be fractured, the blood escapes from the nose. In rare cases there may be also escape of cere bro-spinal fluid from the nose where the dura mater and arachnoid have been torn. In fractures of the posterior fossa extravasation of blood may appear at the nape of the neck. I'lie bones of the skull, being subcutaneous, are frequently the seat of nodes, and not un- commonly necrosis results from this cause, as well as from injury. Necrosis may involve the en- tire thickness of the skull, but is usually confined to the external table. Necrosis of the internal table alone is rarely met with. The bones of the skull are also frequently the seat of sarcoma- tous tumor. The skull in rickets is peculiar: the forehead is high, square, and projecting, and the antero-posterior diameter of the skull is long in relation to the transverse diameter. The bones of the face are small and ill-developed, and this gives the appearance of a larger head than actually exists. The bones of the head are often thick, especially in the neighborhood of the sutures, and the anterior fontanelle is late in closing, sometimes remaining unclosed till the fourth year. The condition of craniotabes has by some been also believed to be the result of rickets, by others is believed to be due to inherited syphilis. In these cases the bone undergoes atrophic changes in patches, so that it becomes greatly thinned in places, generally where there is pressure, as from the pillow or nurse's arm. It is, therefore, usually met with in the parietal bone and vertical plate of the occipital bone. In congenital syphilis deposits of porous bone are often found at the angles of the parietal bones and two halves of the frontal bone which bound the anterior fontanelle. 'These deposits are separated by the coronal and sagittal sutures, and give to the skull an appearance like a " hot cross bun.' They are known as Parrot's nodes, and such a skull has received the name of nati- form. from its fancied resemblance to the buttocks. In connection with the bones of the face a common malformation is cleft palate, owing to the non-union of the palatal processes of the maxillary or pre-oral arch (see page 120). This cleft may involve the whole or only a portion of the hard palate, and usually involves the soft palate also. 'The cleft is in the middle line, except it involves the alveolus in front, when it fol- lows the suture between the main portion of the bone and the pre-maxillary bone. Sometimes the cleft runs on either side of the pre-maxillary bone, so that this bone is quite isolated from the maxillary bones and hangs from the end of the vomer. The malformation is usually asso- ciated with hare-lip, which, when single, is almost always on one side, corresponding to the posi- tion of the suture between the lateral incisor and canine tooth. Some few cases of median hare- lip have been described. In double hare-lip there is a cleft on each side of the middle line. The bones of the face are sometimes fractured as the result of direct violence. The two most commonly broken are the nasal bone and the inferior maxilla, and of these the latter is by far the most frequently fractured of all the bones of the face. Fracture of the nasal bone is for the most part transverse, and takes place about half an inch from the free margin. The broken portion may be displaced backward or more generally to one side by the force which produced the lesion, as there are no muscles here which can cause displacement. The malar bone is probably never broken alone; that is to say, unconnected with a fracture of the other bones of the face. The zygomatic arch is occasionally fractured, and when this occurs from 228 THE SKELETON. direct violence, as is usually the case, the fragments may be displaced inward. This lesion is often attended with great difficulty or even inability to open and shut the mouth, and this has been stated to be due to the depressed fragments perforating the temporal muscle, but would appear rather to be caused by the injury done to the bony origin of the Masseter muscle. Fractures of the superior maxilla may vary much in degree, from the chipping off of a portion of the alveolar arch, a frequent accident when the "old key" instrument was used for the extraction of teeth, to an extensive comminution of the whole bone from severe violence, as the kick of a horse. The most common situation for a fracture of the inferior maxillary bone is in the neighborhood of the canine tooth, as at this spot the jaw is weakened by the deep socket for the fang of this tooth ; it is next most frequently fractured at the angle ; then at the symphysis, and finally the neck of the condyle or the coronoid process may be broken. Occasionally a double fracture may occur, one in either half of the bone. The fractures are usually compound, from laceration of the mucous membrane covering the gums. The displacement is mainly the result of the same violence as produced the injury, but may be further increased by the action of the muscles passing from the neighborhood of the symphysis to the hyoid bone. The superior and inferior maxillary bones are both of them frequently the seat of necrosis, though the disease affects the lower much more frequently than the upper jaw, probably on account of the greater supply of blood to the latter. It may be the result of periostitis, from tooth irritation, injury, or the action of some specific poison, as syphilis, or from salivation by mercury; it not unfrequently occurs in children after attacks of the exanthematous fevers, and a special form occurs from the action of the fumes of phosphorus in persons engaged in match- making. Tumors attack the jaw-bones not infrequently, and these may be either innocent or malig- nant: in the upper jaw cysts may occur in the antrum, constituting the so-called dropsy of the antrum ; or, again, cysts may form in either jaw in connection with the teeth : either cysts con- nected with the roots of fully-developed teeth, the "dental cyst;" or cysts connected with imperfectly developed teeth, the ' ' dentigerous cyst. ' ' Solid innocent tumors include the fibroma, the chondroma, and the osteoma. Of malignant tumors there are two classes, the sarcomata and the epithelioma. The sarcoma are of various kinds, the spindle-celled and round-celled, of a very malignant character, and the myeloid sarcoma, principally affecting the alveolar margin of the bone. Of the epitheliomata we find the squamous variety spreading to the bone from the palate or gum, and the cylindrical epithelioma originating in the antrum or nasal fossae. Both superior and inferior maxillary bones occasionally require removal for tumors and in some other conditions. The upper jaw is removed by an incision from the inner canthus of the eye, along the side of the nose, round the ala, and down the middle line of the upper lip. A second incision is carried outward from the inner canthus of the eye along the lower margin of the orbit as far as the prominence of the malar bone. The flap thus formed is reflected outward and the surface of the bone exposed. The connections of the bone to the other bones of the face are then divided with a narrow saw. They are (1) the junction with the malar bone, pass- ing into the spheno-maxillary fissure; (2) the nasal process; a small portion of its upper extremity, connected with the nasal bone in front, the lachrymal bone behind, and the frontal bone above, being left; (3) the connection with the bone on the opposite side and the palate in the roof of the mouth. The bone is now firmly grasped with lion-forceps, and by means of a rocking movement upward and downward the remaining attachments of the orbital plate with the ethmoid, and the back of the bone with the palate, broken through. The soft palate is first separated from the hard with a scalpel, and is not removed. Occasionally in removing the upper jaw it will be found that the orbital plate can be spared, and this should always be done if possi- ble. A horizontal saw-cut is to be made just below the infraorbital foramen and the bone cut through with a chisel and mallet. Removal of one-half of the lower jaw is sometimes required. If possible, the section of the bone should be made to one side of the symphysis, so as to save the genial tubercles and the origin of the genio-hyo-glossus muscle, as otherwise the tongue tends to fall backward and may produce suffocation. Having extracted the central or preferably the lateral incisor tooth, a vertical incision is made down to the bone, commencing at the free margin of the lip, and carried to the lower border of the bone; it is then carried along its lower border to the angle and up the posterior margin of the ramus to a level with the lobule of the ear. The flap thus formed is raised by separating all the structures attached to the outer surface of the bone. The jaw is now sawn through at the point where the tooth has been extracted, and the knife passed along the inner side of the jaw, separating the structures attached to this sur- face. The jaw is now grasped by the surgeon and strongly depressed, so as to bring down the coronoid process and enable the operator to sever the tendon of the temporal muscle. The jaw can be now further depressed, care being taken not to evert it or rotate it outward, which would endanger the internal maxillary artery, and the external pterygoid torn through or divided. The capsular ligament is now opened in front and the lateral ligaments divided, and the jaw removed with a few final touches of the knife. The antrum occasionally requires tapping for suppuration. This may be done through the socket of a tooth, preferably the first molar, the fangs of which are most intimately connected with the antrum, or through the facial aspect of the bone above the alveolar process. This latter method does not perhaps afford such efficient drainage, but there is less chance of food finding its way into the cavity. The operation may be performed by incising the mucous membrane above the second molar tooth, and driving a trocar or any sharp-pointed instrument into the cavity. 7777? HYOID BONE. 229 THE HYOID BONE. The Hyoid bone is named from its resemblance to the Greek upsilon; it is also called the lingual bone, because it supports the tongue and gives attachment to its numerous muscles. It is a bony arch, shaped like a horseshoe, and consisting of five segments, a body, two greater cornua, and two lesser cornua. It is sus- pended from the tip of the sty- loid processes of the temporal bone by ligamentous bands, the stylo-hyoid ligaments. The Body (basi-hyal) forms the central part of the bone, and is of a quadrilateral form; its anterior surface (Fig. 178), con- vex, directed forward and upward, is divided into two parts by a vertical ridge which descends along the median line, and is crossed at right angles by a hori- zontal ridge, so that this surface is divided into four spaces or depressions. At the point of meeting of these two lines is a prominent elevation, the tubercle. The portion above the horizontal ridge is directed upward, and is sometimes described as the superior border. The anterior surface gives attachment to the Genio-hyoid in the greater part of its extent; above, to the Genio-hyo-glossus; below, to the Mylo-hyoid, Stylo-hyoid, and aponeurosis of the Digastric (suprahyoid aponeurosis); and between these to part of the Hyo-glossus. The posterior surface is smooth, concave, directed backward and downward, and separated from the epiglottis by the thyro-hyoid membrane and by a quantity of loose areolar tissue. The superior border is rounded, and gives attachment to the thyro-hyoid membrane, part of the Genio-hyo-glossi and Chondro-glossi muscles. The inferior border gives attachment, in front, to the Sterno-hyoid; behind, to the Omo-hyoid and to part of the Thyro-hyoid at its junction with the great cornu. It also gives attachment to the Levator glanduhe thyroideae when this muscle is present. The lateral surfaces are small, oval, con- vex facets, covered with cartilage for articulation with the greater cornua. The Greater Cornua (thyro-hyat) project backward from the lateral surfaces of the body; they are flattened from above downward, diminish in size from before backward, and terminate posteriorly in a tubercle for the attachment of the lat- eral thyro-hyoid ligament. The outer surface gives attachment to the Hyo-glos- sus, their upper border to the Middle constrictor of the pharynx, their lower bor- der to part of the Thyro-hyoid muscle. In youth the great cornua are connected to the body by cartilaginous surfaces and held together by ligaments; in middle life they usually become joined. The Lesser Cornua (cerato-hyals} are two small, conical-shaped eminences attached by their bases to the angles of junction between the body and greater cornua, and giving attachment by their apices to the stylo-hyoid ligaments.1 The smaller cornua are connected to the body of the bone by a distinct diarthrodial joint, which usually persists throughout life, but occasionally becomes ankylosed. Development.-By five centres: one for the body, and one for each cornu. Ossification commences in the body about the eighth month, and in the greater cornua toward the end of foetal life. Ossification of the lesser cornua commences some months after birth. Attachment of Muscles.-Sterno-hyoid, Thyro-hyoid, Omo-hyoid, aponeurosis Greater Cornu. MIDDLE CONSTRICTOR Of PhflVynX. HYO-GLOSSUS. Lesser Cornu. GEN lO-HYO-QLOSSUS- CHONDRO- GLOSSUS. THYRO-MYOID. 'STYLO-HYOIO. . OMO-HYOID. Body," MYLO-HYOID. GENIO-HYOID. STERNO-HYOID. Fig. 178.-Hyoid bone. Anterior surface. (Enlarged). 1 These ligaments in many animals are distinct bones, and in man are occasionally ossified to a certain extent. 230 777/■/ SKELETON. of the Digastric, Stylo-hyoid, Mylo-hyoid, Genio-hyoid, Genio-hyo-glossus, Chon- dro-glossus, Hyo-glossus, Middle constrictor of the pharynx, and occasionally a few fibres of the Lingualis. It also gives attachment to the thyro-hyoidean membrane and the stylo-hyoid, thyro-hyoid, and hyo-epiglottic ligaments. Surface Form.-The hyoid bone can be felt in the receding angle below the chin, and the finger can be carried along the whole length of the bone to the greater cornu, which is situated just below the angle of the jaw. This process of bone is best perceived by making pressure on one cornu, and so pushing the bone over to the opposite side, when the cornu of this side will be distinctly felt immediately beneath the skin. This process of bone is an important landmark in ligature of the lingual artery. Surgical Anatomy.-The hyoid bone is occasionally fractured, generally from direct vio- lence, as in the act of garrotting or throttling. The great cornu is the part of the bone most fre- quently broken, but sometimes the fracture takes place through the body of the bone. In con- sequence of the muscles of the tongue having important connections with this bone, there is great pain upon any attempt being made to move the tongue, as in speaking or swallowing. THE THORAX. The Thorax, or Chest, is an osseo-cartilaginous cage containing and protecting the principal organs of respiration and circulation. It is conical in shape, being narrow above and broad below, flattened from before backward, and longer behind than in front. It is somewhat cordiform on transverse section. Boundaries.-The posterior surface is formed by the twelve dorsal vertebrae and the posterior part of the ribs. It is convex from above downward, and pre- sents on each side of the middle line a deep groove in consequence of the direction backward and outward which the ribs take from their vertebral extremities to their angles. The anterior surface is flattened or slightly convex, and inclined forward from above downward. It is formed by the sternum and costal cartilages. The lateral surfaces are convex; they are formed by the ribs, separated from each other by spaces, the intercostal spaces. These are eleven in number, and are occupied by the intercostal muscles. The upper opening of the thorax is reniform in shape, being broader from side to side than from before backward. It is formed by the first dorsal vertebra behind, the upper margin of the sternum in front, and the first rib on each side. It slopes downward and forward, so that the anterior part of the ring is on a lower level than the posterior. The antero-posterior diameter is about two inches. The lower opening is formed by the twelfth dorsal vertebra behind, by the twelfth rib at the sides, and in front by the cartilages of the eleventh, tenth, ninth, eighth, and seventh ribs, which ascend on either side and form an angle, the subcostal angle, from the centre of which the ensiform cartilage projects. It is wider trans- versely than from before backward. It slopes obliquely downward and backward, so that the cavity of the thorax is much deeper behind than in front. The Dia- phragm closes in the opening forming the floor of the thorax. In the female the thorax differs as follows from the male: 1. Its general capacity is less. 2. The sternum is shorter. 3. The upper margin of the sternum is on a level with the lower part of the body of the third dorsal vertebra, whereas in the male it is on a level with the lower part of the body of the second dorsal vertebra. 4. The upper ribs are more movable, and so allow a greater enlargement of the upper part of the thorax than in the male. The Sternum (arepvov., the chest) (Figs. 179, 180) is a flat, narrow bone, sit- uated in the median line of the front of the chest, and consisting, in the adult, of three portions. It has been likened to an ancient sword; the upper piece, repre- senting the handle, is termed the manubrium ; the middle and largest piece, which represents the chief part of the blade, is termed the gladiolus ; and the inferior piece, which is likened to the point of the sword, is termed the ensiform or xiphoid appendix. In its natural position its inclination is oblique from above downward and forward. It is flattened in front, concave behind, broad above, becoming The Sternum. THE STERNUM. 231 narrowed at the point where the first and second pieces are connected, after which it again widens a little, and is pointed at its extremity. Its average length in the adult is six inches, being rather longer in the male than in the female. The First Piece of the sternum, or Manubrium (pre-sternumf is of a somewhat triangular form, broad and thick above, narrow below at its junction with the middle piece. Its anterior surface, convex from side to side, concave from above downward, is smooth, and affords attachment on each side to the Pectoralis major and sternal origin of the Sterno-cleido-mastoid muscle. In well-marked bones the ridges limiting the attachment of these muscles are very distinct. Its posterior surface, concave and smooth, affords attachment on each side to the Sterno-hyoid and Sterno-thyroid muscles. The superior border, the thickest, presents at its centre the pre-sternal notch; and on each side an oval articular surface, directed upward, backward, and outward, for articulation with the sternal end of the clavicle. The inferior border presents an oval, rough surface, covered in the recent state with a thin layer of cartilage, for articulation with the second portion of the bone. The lateral borders are marked above by a depression for the first costal cartilage, and below by a small facet, which with a similar facet on the upper angle of the middle portion of the bone, forms a notch for the reception of the costal cartilage of the second rib. These articular surfaces are separated by a narrow, curved edge, which slopes from above downward and inward. The Second Piece of the sternum, or Gladiolus (mesosternum), considerably longer, narrower, and thinner than the first piece, is broader below than above. Its anterior surface is nearly flat, directed upward and forward, and marked by three transverse lines which cross the bone opposite the third, fourth, and fifth articular depressions. These lines are produced by the union of the four separate pieces of which this part of the bone consists at an early period of life. At the junction of the third and fourth pieces is occasionally seen an orifice, the sternal foramen; it varies in size and form in different individuals, and pierces the bone from before backward. This surface affords attachment on each side to the sternal origin of the Pectoralis major. The posterior surface, slightly concave, is also marked by three transverse lines, but they are less distinct than those in front: this surface affords attachment below, on each side, to the Triangularis sterni muscle, and occasionally presents the posterior opening of the sternal foramen. The superior border presents an oval surface for articulation with the manubrium. The inferior border is narrow, and articulates with the ensiform appendix. Each lateral border presents, at each superior angle, a small facet, which, with a similar facet on the manubrium, forms a cavity for the cartilage of the second rib; the four succeeding angular depressions receive the cartilages of the third, fourth, fifth, and sixth ribs; whilst each inferior angle presents a small facet, which, with a corresponding one on the ensiform appendix, forms a notch for the cartilage of the seventh rib. These articular depressions are separated by a series of curved interarticular intervals, which diminish in length from above downward, and correspond to the intercostal spaces. Most of the cartilages belonging to the true ribs, as will be seen from the foregoing description, articulate with the sternum at the line of junction of two of its primitive component seg- ments. This is well seen in many of the lower animals, where the separate parts of the bone remain ununited longer than in man. In this respect a striking analogy exists betw'een the mode of connection of the ribs with the vertebral column and the connection of their cartilages with the sternal column. The Third Piece of the sternum, the Ensiform or Xiphoid Appendix (meta- sternum), is the smallest of the three; it is thin and elongated in form, cartilagi- nous in structure in youth, but more or less ossified at its upper part in the adult. Its anterior surface affords attachment to the chondro-xiphoid ligament; its posterior surface, to some of the fibres of the Diaphragm and Triangularis sterni muscles; its lateral borders, to the aponeurosis of the abdominal muscles. Above it articulates with the lower end of the gladiolus, and at each superior angle presents a facet for the lower half of the cartilage of the seventh rib; below, by 232 THE SKELETON. Fig. 179.-Sternum and costal cartilages. Fig. 180.-Posterior surface of sternum. THE STERNUM. 233 its pointed extremity it gives attachment to the linea alba. This portion of the sternum is very various in appearance, being sometimes pointed, broad, and thin, sometimes bifid or perforated by a round hole, occasionally curved or deflected considerably to one or the other side. Structure.-The bone is composed of delicate cancellous structure, covered by a thin layer of compact tissue, which is thickest in the manubrium between the articular facets for the clavicles. Development.-The sternum, including the ensiform appendix, is developed by six centres: one for the first piece or manubrium, four for the second piece or for first piece, two or more centres. Arrest of development of lateral pieces, producing for second piece, usually one. for third for fourth for fifth placed laterally. ■Sternal fissure, and .Sternal foramen. Fig. .181.-Development of the sternum by six centres. Time of appearance. Fig. 182.-Time of union of sternum. gladiolus, and one for the ensiform appendix. Up to the middle of foetal life the sternum is entirely cartilaginous, and when ossification takes place the ossific Rarely unite, except in old age. 1 for 1st piece 1 or manubrium J 5-6th month foetal. s\ Between puberty ' and the 25th year. 4 for 2nd piece or gladiolus 6-7th month. r i 4 9th month. Soon after puberty. 5 1st year after birth. Partly cartilaginous to advanced life. 1 for ensiform cartilage 2nd to 18th year. Fig. 183.-Peculiarities in number of centres of sternum. Fig. 184.-Peculiarities in mode of union of sternum. granules are deposited in the middle of the intervals between the articular depres- sions for the costal cartilages, in the following order (Fig. 181): In the first piece, between the fifth and sixth months; in the second and third, between the sixth and seventh months; in the fourth piece, at the ninth month; in the fifth, within the first year or between the first and second years after birth; and in the ensiform appendix, between the second and the seventeenth or eighteenth years, by a single centre which makes its appearance at the upper part and proceeds gradually downward. To these may be added the occasional existence, as described by Breschet, of two small episternal centres, which make their appearance one on each side of the interclavicular notch. They are probably vestiges of the episternal bone of the monotremata and lizards. It occasionally happens that some of the segments are formed from more than one centre, the number and position of which vary (Fig. 183). Thus, the first piece may have two, three, or even six centres. hen 234 THE SKELETON. two are present, they are generally situated one above the other, the upper one being the larger;1 the second piece has seldom more than one; the third, fourth, and fifth pieces are often formed from two centres placed laterally, the irregular union of which will serve to explain the occasional occurrence of the sternal foramen (Fig. 184), or of the vertical fissure which occasionally intersects this part of the bone, and which is further ex- plained by the manner in which the cartilaginous matrix, in which ossification takes place, is formed (see page 117). Union of the various centres of the gladiolus commences about puberty, from below, and proceeds upward, so that by the age of twenty- five they are all united, and this portion of bone consists of one piece (Fig. 182). The ensiform car- tilage becomes joined to the gladiolus about forty. The manubrium is occasionally, but not invariably, joined to the gladiolus in advanced life by bone. When this union takes place, however, it is gen- rally only superficial, a portion of the centre of the sutural cartilage remaining unossified. Articulations.-With the clavicles and seven costal cartilages on each side. Attachment of Muscles.-To nine pairs and one single muscle: the Pectoralis major, Sterno- cleido-mastoid, Sterno-hyoid, Sterno-thyroid, Tri- angularis sterni, aponeuroses of the Obliquus ex- ternus, Obliquus internus, Transversalis, Rectus muscles, and Diaphragm. The Ribs. The Ribs are elastic arches of bone, which form the chief part of the thoracic walls. They are twelve in number on each side; but this number may be increased by the development of a cervical or lumbar rib, or may be dimin- ished to eleven. The first seven are connected behind with the spine and in front with the sternum, through the intervention of the costal cartilages; they are called true ribs. The remaining five are false ribs; of these, the first three have their cartilages attached to the cartilage of the rib above: the last two are free at their anterior extremities; they are termed floating ribs. The ribs vary in their direction, the upper ones being less oblique than those lower down and occupying the middle of the series. The extent of obliquity reaches its maximum at the ninth rib, and gradually de- creases from that rib to the twelfth. The ribs are situated one below the other in such a manner that spaces are left between them, which are called intercostal spaces. The length of these spaces corresponds to the length of the ribs; their breadth is more considerable in front than behind, and between the upper than Fig. 185.-A central rib of right side. Inner surface. 1 Sir George Humphry states that this is " probably the more complete condition." THE RTBS. 235 between the lower ribs. The ribs increase in length from the first to the seventh, when they again diminish to the twelfth. In breadth they decrease from above downward; in the upper ten the greatest breadth is at the sternal extremity. Common Characters of the Ribs (Fig. 185).-A rib from the middle of the series should be taken in order to study the common characters of the ribs. Each rib presents two extremities, a posterior or vertebral, an anterior or ster- nal, and an intervening portion-the body or shaft. The posterior or vertebral extremity presents for examination a head, neck, and tuberosity. The head (Fig. 186) is marked by a kidney-shaped articular sur- face, divided by a horizontal ridge into two facets for articulation with the costal cavity formed by the junction of the bodies of two contiguous dorsal vertebrae; the upper facet is small, the inferior one of larger size; the ridge separating them serves for the attachment of the interarticular ligament. The neck is that flat- tened portion of the rib which extends outward from the head; it is about an inch long, and is placed in front of the transverse process of the lower of the two vertebrae with which the head articulates. Its anterior surface is flat and smooth, its posterior rough for the attachment of the middle costo-transverse ligament, and perforated by numerous foramina, the direction of which is less constant than those found on the inner surface of the shaft. Of its two borders the superior presents a rough crest for the attachment of the anterior costo-transverse ligament; its inferior border is rounded. On the posterior surface of the neck, just where it Facet for body of upper dorsal vertebra.. Ridge for interarticular ligament. For anterior costo-transverse ligament. For posterior costo-transverse ligament. Facet for body of lower dorsal vertebra." For transverse process of lower dorsal vertebra. Fig. 186.-Vertebral extremity of a rib. External surface. joins the shaft, and nearer the lower than the upper border, is an eminence-the tuberosity, or tubercle; it consists of an articular and a non-articular portion. The articular portion, the more internal and inferior of the two, presents a small, oval surface for articulation with the extremity of the transverse process of the lower of the two vertebrae to which the head is connected. The non-articular portion is a rough elevation, which affords attachment to the posterior costo- transverse ligament. The tubercle is much more prominent in the upper than in the lower ribs. The shaft is thin and flat, so as to present two surfaces, an external and an internal, and two borders, a superior and an inferior. The external surface is convex, smooth and marked at its back part, a little in front of the tuberosity, by a prominent line, directed obliquely from above downward and outward; this gives attachment to a tendon of the Ilio-costalis muscle or of one of its accessory portions, and is called the angle. At this point the rib is bent in two directions. If the rib is laid upon its lower border, it will be seen that the portion of the shaft in front of the angle rests upon this border, while the portion of the shaft behind the angle is bent inward and at the same time tilted upward. The interval between the angle and the tuberosity increases gradually from the second to the tenth rib. The portion of bone between these two parts is rounded, rough, and irregular, and serves for the attachment of the Longissimus dorsi muscle. The portion of bone between the tubercle and sternal extremity is also slightly twisted upon its own axis, the external surface looking downward behind the angle, a little upward in front of it. This surface presents, toward its sternal extremity, an oblique line, the anterior angle. The internal surface is concave, smooth, directed a little upward behind the angle, a little downward in front of it. This surface is marked by a ridge which commences at the lower extremity of the head; it is 236 THE SKELETON. strongly marked as far as the inner side of the angle, and gradually becomes lost at the junction of the anterior with the middle third of the bone. The interval between it and the inferior border is deeply grooved, to lodge the intercostal vessels and nerve. At the back part of the bone this groove belongs to the inferior border, but just in front of the angle, where it is deepest and broadest, it corresponds to the internal surface. The superior edge of the groove is rounded ; it serves for the attachment of the Internal intercostal muscle. The inferior edge corresponds to the lower margin of the rib and gives attachment to the External intercostal. Within the groove are seen the orifices of numerous small foramina which traverse the wall of the shaft obliquely from before backward. The superior border, thick and rounded, is marked by an external and an internal lip. more distinct behind than in front; they serve for the attachment of the External and Internal intercostal muscles. The inferior border, thin and sharp, has attached to it the External intercostal muscle. The anterior or sternal extremity is flat- tened, and presents a porous, oval, concave depression, into which the costal cartilage is received. Peculiar Ribs. The ribs which require especial consideration are five in number-viz. the first, second, tenth, eleventh and twelfth. The first rib (Fig. 187) is one of the shortest and the most curved of all the ribs ; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward. The head is of small size, rounded, and presents only a single articular facet for articulation with the body of the first dorsal vertebra. The neck is narrow and rounded. The tuberosity, thick and prominent, rests on the outer border. There is no angle, but in this situation the rib is slightly bent, with the convexity of the bend upward, so that the head of the bone is directed downward. The upper surface of the shaft is marked by two shallow depressions, separated from one another by a small rough surface for the attachment of the Scalenus anticus muscle-the groove in front of it transmitting the subclavian vein, that behind it the subclavian artery. Between the groove for the subclavian artery and the tuberosity is a rough surface, for the attachment of the Scalenus medius muscle. The under surface is smooth, and destitute of the groove observed on the other ribs. The outer border is convex, thick, and rounded, and at its posterior part gives attachment to the first serration of the Serratus magnus; the inner is concave, thin, and sharp, and marked about its centre by the commence- ment of the rough surface for the Scalenus anticus. The anterior extremity is larger and thicker than any of the other ribs. The second rib (Fig. 188) is much longer than the first, but bears a very con- siderable resemblance to it in the direction of its curvature. The non-articular portion of the tuberosity is occasionally only slightly marked. The angle is slight and situated close to the tuberosity, and the shaft is not twisted, so that both ends touch any plane surface upon which it may be laid; but there is a similar though slighter bend, with its convexity Upward, to that found in the first rib. The shaft is not horizontal, like that of the first rib, its outer surface, which is convex, look- ing upward and a little outward. It presents, near the middle, a rough eminence for the attachment of the second and third digitations of the Serratus magnus; behind and above which is attached the Scalenus posticus. The inner surface, smooth and concave, is directed downward and a little inward; it presents a short groove toward its posterior part. The tenth rib (Fig. 189) has only a single articular facet on its head. The eleventh and twelfth ribs (Figs. 190 and 191) have each a single articular facet on the head, which is of rather large size ; they have no neck or tuberosity, and are pointed at the extremity. The eleventh has a slight angle and a shallow groove on the lower border. The twelfth has neither, and is much shorter than the eleventh, and the head has a slight inclination downward. Structure.-The ribs consist of cancellous tissue enclosed in a thin, compact layer. PECULIAR RIBS. 237 Development.-Each rib, with the exception of the last two, is developed by three centres : one for the shaft, one for the head, and one for the tubercle. The last two have only two centres, that for the tubercle being wanting. Ossification commences in the shaft of the ribs at a very early period, before its appearance in the vertebrae. The epiphysis of the head, which is of slightly angular shape, and that for the tubercle, of a lenticular form, make their appearance between the six- Fig. 187. Fig. 188. Angle slightly marked and close to tuberosity. First serration of Serratus magnus. Fig. 189. Single articular facet. Fig. 190. Single articular facet. Fig. 191. Single, articular facet. Figs. 187-191.-Peculiar ribs. teenth and twentieth years, and are not united to the rest of the bone until about the twenty-fifth year. Attachment of Muscles.-To nineteen : the Internal and External intercostals, Scalenus anticus, Scalenus medius, Scalenus posticus, Pectoralis minor, Serratus magnus, Obliquus externus, Quadratus lumborum, Diaphragm, Latissimus dorsi, Serratus posticus superior, Serratus posticus inferior, Ilio-costalis, Musculus accessorius ad ilio-costalem, Longissimus dorsi, Cervicalis ascendens, Levatores costarum, and Infracostales. 238 THE SKELETON. The Costal Cartilages. The Costal Cartilages (Fig. 179, p. 232)' are white, elastic structures, which serve to prolong the ribs forward to the front of the chest, and contribute very materially to the elasticity of its walls. The first seven are connected with the sternum, the next three with the lower border of the cartilage of the preceding rib. The car- tilages of the last two ribs, which have pointed extremities, float freely in the walls of the abdomen. Like the ribs, the costal cartilages vary in their length, breadth, and direction. They increase in length from the first to the seventh, then gradually diminish to the last. They diminish in breadth, as well as the intervals between them, from the first to the last. They are broad at their attachment to the ribs, and taper toward their sternal extremities, excepting the first two, which are of the same breadth throughout, and the sixth, seventh and eighth, which are enlarged where their margins are in contact. In direction they also vary : the first descends a little, the second is horizontal, the third ascends slightly, whilst all the rest follow the course of the ribs for a short extent, and then ascend to the sternum or preceding cartilage. Each costal cartilage presents two surfaces, two borders, and two extremities. The anterior surface is convex, and looks forward and upward : that of the first gives attachment to the costo-clavicular ligament and the Subclavius muscle ; that of the second, third, fourth, fifth, and sixth, at their sternal ends, to the Pectoralis major.1 The others are covered by, and give partial attach- ment to, some of the great flat muscles of the abdomen. The posterior surface is concave, and directed backward and downward, the first giving attachment to the Sterno-thyroid, and the six or seven inferior ones affording attachment to the Transversalis muscle and the Diaphragm. Of the two borders, the superior is concave, the inferior convex: they afford attachment to the Intercostal muscles, the upper border of the sixth giving attachment to the Pectoralis major muscle. The contiguous borders of the sixth, seventh, and eighth, and sometimes the ninth and tenth, costal cartilages present small, smooth, oblong-shaped facets at the points where they articulate. Of the two extremities, the outer one is continuous with the osseous tissue of the rib to which it belongs. The inner extremity of the first is continuous with the sternum; the six succeeding ones have rounded extremities, which are received into shallow concavities on the lateral margins of the sternum. The inner extremities of the eighth, ninth, and tenth costal cartilages are pointed, and are connected with the cartilage above. Those of the eleventh and twelfth are free and pointed. The costal cartilages are most elastic in youth, those of the false ribs being more so than the true. In old age they become of a deep yellow color, and are prone to calcify. Attachment of Muscles.-To nine: the Subclavius, Sterno-thyroid, Pectoralis major, Internal oblique, Transversalis, Rectus, Diaphragm, Triangularis sterni, and Internal intercostals. Surface Form.-The bones of the chest are to a very considerable extent covered by muscles, so that in the strongly-developed muscular subject they are for the most part con- cealed. In the emaciated subject, on the other hand, the ribs, especially in the lower and lateral region, stand out as prominent ridges with the sunken, intercostal spaces between them. In the middle line, in front, the superficial surface of the sternum is to be felt throughout its entire length, at the bottom of a deep median furrow situated between the two great pectoral muscles and called the sternal furrow. These muscles overlap the anterior surface somewhat, so that the whole of the sternum in its entire width is not subcutaneous ; and this overlapping is greater opposite the centre of the bone than above and below, so that the furrow is wider at its upper and lower parts, but narrower in the middle. The centre of the upper border of the ster- num is visible, constituting the pre-sternal notch, but the lateral parts of this border are obscured by the tendinous origins of the Sterno-mastoid muscles, which present themselves as oblique tendinous cords, which narrow and deepen the notch. Lower down on the subcutaneous surface a well-defined transverse ridge is always to be felt. This denotes the line of junction of the manubrium and body of the bone, and is a useful guide to the second costal cartilage, and thus to the identity of any given rib. The second rib being found through its costal cartilage, 1 The first and seventh also, occasionally, give origin to the same muscle. THE COSTAL CARTILAGES. 239 it is easy to count downward and find any other. Below this point the furrow spreads out, and, exposing more of the surface of the body of the sternum, terminates below in a sudden depression, the infrasternal depression or pit of the stomach (scrobiculus cordis), which corre- sponds to the ensiform cartilage. This depression lies between the cartilages of the seventh rib, and in it the ensiform cartilage may be felt. The sternum in its vertical diameter presents a general convexity forward, the most prominent point of which is at the joint between the manu- brium and gladiolus. On each side of the sternum the costal cartilages and ribs on the front of the chest are par- tially obscured by the great pectoral muscle; through which, however, they are to be felt as ridges, with depressed intervals between them, corresponding to the intercostal spaces. Of these spaces, the one between the second and third ribs is the widest, the next two somewhat nar- rower. and the remainder, with the exception of the last two, comparatively narrow. The lower border of the Pectoralis major muscle corresponds to the fifth rib, and below this, on the front of the chest, the broad, fiat outline of the ribs, as they begin to ascend, and the more rounded outline of the costal cartilages, are often visible. The lower boundary of the front of the thorax, the abdomino-thoracic arch, which is most plainly seen by arching the body backward, is formed by the ensiform cartilage and the cartilages of the seventh, eighth, ninth, and tenth ribs, and the extremities of the eleventh and twelfth ribs or their cartilages. On each side of the chest, from the axilla downward, the flattened external surfaces of the ribs may be defined in the form of oblique ridges, separated by depressions corresponding to the intercostal spaces. They are, however, covered by muscles, which obscure their outline to a certain extent in the strongly developed. Nevertheless, the ribs, with the exception of the first, can generally be followed over the front and sides of the chest without difficulty. The first rib, being almost completely covered by the clavicle and scapula, can only be distinguished in a small portion of its extent. At the back the angles of the ribs form a slightly-marked oblique line on each side of and some distance from the vertebral spines. This line diverges somewhat as it descends, and external to it is a broad, convex surface caused by the projection of the ribs beyond their angles. Over this surface, except where covered by the scapula, the individual ribs can be distinguished. Surgical Anatomy.-Malformations of the sternum present nothing of surgical importance beyond the fact that abscesses of the mediastinum may sometimes escape through the sternal foramen. Fractures of the sternum are by no means common, owing, no doubt, to the elasticity of the ribs and their cartilages, which support it like so many springs. It is frequently asso- ciated with fracture of the spine, and may be caused by forcibly bending the body either back- ward or forward until the chin becomes impacted against the top of the sternum. It may also be fractured by direct violence or by muscular action. The fracture usually occurs in the upper half of the body of the bone. Dislocation of the gladiolus from the manubrium also takes place, and is sometimes described as a fracture. The bone, being subcutaneous, is frequently the seat of gummatous tumors, and not uncom- monly is affected with caries. Occasionally the bone, and especially its ensiform appendix, becomes altered in shape and driven inward by the pressure, in workmen, of tools against their chest. The ribs are frequently broken, though from their connections and shape they are able to withstand great force, yielding under the injury and recovering themselves like a spring. The middle of the series are the ones most liable to fracture. The first, and to a less extent the second, being protected by the clavicle, are rarely fractured ; and the eleventh and twelfth, on account of their loose and floating condition, enjoy a like immunity. The fracture generally occurs from indirect violence, from forcible compression of the chest-wall, and the bone then gives way at its weakest part-i. e. just in front of the angle. But the ribs may also be broken by direct violence, when the bone gives way and is driven inward at the point struck, or by mus- cular action. It seems probable, however, that in these latter cases the bone has undergone some atrophic changes. Fracture of the ribs is frequently complicated with some injury to the viscera contained within the thorax or upper part of the abdominal cavity, and this is most likely to occur in fractures from direct violence. Fracture of the costal cartilages may also take place, though it is a comparatively rare injury. The thorax is frequently found to be altered in shape in certain diseases. The rickety thorax is caused chiefly by atmospheric pressure. The balance between the air on the inside of the chest and the outside during some stage of respiration is not equal, the pre- ponderance being in favor of the air outside; and this, acting on the softened ribs, causes them ' to be forced in at the junction of the cartilages with the bones, which is the weakest part. In consequence of this the sternum projects forward, with a deep depression on either side caused by the sinking in of the softened ribs. The depression is less on the left side, on account of the ribs being supported by the heart. The condition is known as "pigeon-breast." The lower ribs, however, are not involved in this deformity, as they are prevented from falling in by the presence of the stomach, liver, and spleen. And when the liver and spleen are enlarged, as they sometimes are in rickets, the lower ribs may be pushed outward: this causes a trans- verse constriction just above the costal arch. The anterior extremities of the ribs are usually enlarged in rickets, giving rise to what has been termed the "rickety rosary." The phthisical chest is often long and narrow, flattened from before backward, and with great obliquity of the ribs and projection of the scapulae. In pulmonary emphysema the chest is enlarged in all its diameters, and presents on section an almost circular outline. It has received the name of the 240 THE SKELETON. " barrel-shaped chest. " In severe cases of lateral curvature of the spine the thorax becomes much distorted. In consequence of the rotation of the bodies of the vertebrae which takes place in this disease the ribs opposite the convexity of the dorsal curve become extremely con- vex behind, being thrown out and bulging, and at the same time flattened in front, so that the two ends of the same rib are almost parallel. Coincident with this, the ribs on the opposite side, on the concavity of the curve, are sunk and depressed behind and bulging and convex in front. In addition to this the ribs become occasionally w'elded together by bony material. The ribs are frequently the seat of necrosis leading to abscesses and sinuses, which may burrow to a considerable extent over the wall of the chest. The only special anatomical point in connection with these is that care must be taken in dealing with them that the intercostal space is not punctured and the pleural cavity opened or the intercostal vessels wounded. In cases of empyema the chest requires opening to evacuate the pus. There is consider- able difference of opinion as to the best position to do this. Probably the best place in most cases will be found to be between the fifth and sixth ribs, in or a little in front of the mid- axillary line. This is the last part of the cavity to be closed by the expansion of the lung; it is not thickly covered by soft parts; the space between the two ribs is sufficiently great to allow of the introduction of a fair-sized drainage-tube, and the opening is in a dependent position, when the patient is confined to bed, as he usually inclines toward the affected side, so as to allow the sound lung the freest possible play, and so permits of efficient drainage. The extremities, or limbs, are those long, jointed appendages of the body which are connected to the trunk by one end and free in the rest of their extent. They are four in number: an upper or thoracic pair, connected with the thorax through the intervention of the shoulder, and subservient mainly to prehension; and a lower pair, connected with the pelvis, intended for support and locomotion. Both pairs of limbs are constructed after one common type, so that they present numerous analogies, while at the same time certain differences are observed in each, dependent on the peculiar offices they have to perform. The bones by which the upper and lower limbs are attached to the trunk are named respectively the shoulder and pelvic girdles, and they are constructed on the same general type, though presenting certain modifications relating to the different uses to which the upper and lower limbs are respectively applied. The shoulder girdle is formed by the scapula and clavicle, and is imperfect in front and behind. In front, however, the girdle is completed by the upper end of the sternum, with which the inner extremities of the clavicle articulate. Behind, the girdle is widely imperfect and the scapula is connected to the trunk by muscles only. The pelvic girdle is formed by the innominate bones, and is completed in front through the symphysis pubis, at which the two innominate bones articulate with each other. It is imperfect behind, but the intervening gap is filled in by the upper part of the sacrum. The pelvic girdle, therefore, presents, with the sacrum, a complete ring, comparatively fixed, and presenting an arched form which confers upon it a solidity manifestly intended for the support of the trunk, and in marked contrast to the lightness and mobility of the shoulder girdle. With regard to the morphology of these girdles, the blade of the scapula is generally believed to correspond to the ilium ; but with regard to the clavicles there is some difference of opinion: formerly it was believed that they corre- sponded to the ossa pubis, meeting at the symphysis, but it is now generally taught that the clavicle has no homologue in the pelvic girdle, and that the os pubis and ischium are represented by the small coracoid process in man and most mammals. OF THE EXTREMITIES. THE UPPER EXTREMITY. The bones of the upper extremity consist of those of the shoulder girdle, of the arm, the forearm, and the hand. The shoulder girdle consists of two bones, the clavicle and the scapula. THE SHOULDER. The Clavicle. The Clavicle (clavis, a key), or collar-bone, forms the anterior portion of the shoulder girdle. It is a long bone, curved somewhat like the italic letter /, and THE CLAVICLE. 241 placed nearly horizontally at the upper and anterior part of the thorax, immediately above the first rib. It articulates by its inner extremity with the upper border of the sternum, and by its outer extremity with the acromion process of the scapula, serving to sustain the upper extremity in the various positions which it assumes, whilst at the same time it allows of great latitude of motion in the arm.1 It presents a double curvature when looked at in front, the convexity being forward at the sternal end and the concavity at the scapular end. Its outer third is flat- tened from above downward, and extends, in the natural position of the bone, from a point opposite the coracoid process to the acromion. Its inner two-thirds are of a cylindrical form, and extend from the sternum to a point opposite the coracoid process of the scapula. External or Flattened Portion.-The outer third is flattened from above down- ward, so as to present two surfaces, an upper and a lower; and two borders, an anterior and a posterior. The upper surface is flattened, rough, marked by impressions for the attachment of the Deltoid in front and the Trapezius behind; between these two impressions, externally, a small portion of the bone is sub- cutaneous. The under surface is flattened. At its posterior border, a little external to the point where the prismatic joins with the flattened portion, is a rough eminence, the conoid tubercle ; this, in the natural position of the bone, surmounts the coracoid process of the scapula and gives attachment to the conoid ligament. From this tubercle an oblique line, occasionally a depression, passes forward and outward to near the outer end of the anterior border; it is called the oblique line, and affords attachment to the trapezoid ligament. The anterior border is concave, thin, and rough, and gives attachment to the Deltoid; it occasionally presents, at its inner end, at the commencement of the deltoid impression, a tubercle, the deltoid tubercle, which is sometimes to be felt in the living subject. posterior border is convex, rough, broader than the anterior, and gives attachment to the Trapezius. Internal or Cylindrical Portion.-The cylindrical portion forms the inner two- thirds of the bone. It is curved so as to be convex in front, concave behind, and is marked by three borders, separating three surfaces. The anterior border is continuous with the anterior margin of the flat portion. At its commencement it is smooth, and corresponds to the interval between the attachment of the Pectoralis major and Deltoid muscles; at the inner half of the clavicle it forms the lower boundary of an elliptical space for the attachment of the clavicular portion of the Pectoralis major, and approaches the posterior border of the bone. The superior border is continuous with the posterior margin of the flat portion, and separates the anterior from the posterior surface. At its commencement it is smooth and rounded, becomes rough toward the inner third for the attachment of the Sterno- mastoid muscle, and terminates at the upper angle of the sternal extremity. The posterior or subclavian border separates the posterior from the inferior surface, and extends from the conoid tubercle to the rhomboid impression. It forms the pos- terior boundary of the groove for the Subclavius muscle, and gives attachment to a layer of cervical fascia covering the Omo-hyoid muscle. The anterior surface is included between the superior and anterior borders. It is directed forward and a little upward at the sternal end, outward and still more upward at the acromial extremity, where it becomes continuous with the upper surface of the flat portion. Externally, it is smooth, convex, nearly subcutaneous, being covered only by the Platysma; but, corresponding to the inner half of the bone, it is divided by a more or less prominent line into two parts: a lower portion, elliptical in form, rough, and slightly convex, for the attachment of the Pectoralis major; and an upper part, which is rough, for the attachment of the Sterno-cleido-mastoid. Between 1 The clavicle acts especially as a fulcrum to enable the muscles to give lateral motion to the arm. It is accordingly absent in those animals whose fore limbs are used only for progression, but is present for the most part in those animals whose anterior extremities are clawed and used for prehension, though in some of them-as, for instance, in a large number of the carnivora-it is merely a rudi- mentary bone suspended among the muscles, and not articulating either with the scapula or sternum. 242 THE SKELETON. the two muscular is a small subcutaneous interval. The posterior or cervical surface is smooth, flat, and looks backward toward the root of the neck. It is limited, above, by the superior border; below, by the subclavian border; internally, by the margin of the sternal extremity; externally, it is continuous with the posterior border of the flat portion. It is concave from within outward, and is in relation, by its lower part, with the suprascapular vessels. This surface, at about the junction of the inner and outer curves, is also in close relation with the brachial plexus and subclavian vessels. It gives attachment, near the sternal extremity, to part of the Sterno-hyoid muscle; and presents, at or near the middle, a foramen, directed obliquely outward, which transmits the chief nutrient artery of the bone. Sometimes there are twTo foramina on the posterior surface, or one on the posterior, the other on the inferior surface. The inferior or subclavian Acromial extremity. Sternal extremity. surface is bounded, in front, by the anterior border; behind, by the subclavian border. It is narrow internally, but gradually increases in width externally, and Fig. 192.-Left clavicle. Superior surface. Fig. 193.-Left clavicle. Inferior surface. is continuous with the under surface of the flat portion. Commencing at the sternal extremity may be seen a small facet for articulation with the cartilage of the first rib. This is continuous with the articular surface at the sternal end of the bone. External to this is a broad, rough impression, the rhomboid, rather more than an inch in length, for the attachment of the costo-clavicular (rhomboid) ligament. The remaining part of this surface is occupied by a longitudinal groove, the subclavian groove, broad and smooth externally, narrow and more uneven internally; it gives attachment to the Subclavius muscle, and by its anterior margin to the costo-coracoid membrane. Not unfrequently this groove is sub- divided into two parts by a longitudinal line,which gives attachment to the inter- muscular septum of the Subclavius muscle. The internal or sternal extremity of the clavicle is triangular in form, directed inward and a little downward and forward; and presents an articular facet, concave from before backward, convex from above downward, which articulates with the sternum through the intervention of an interarticular fibro-cartilage; the circumference of the articular surface is rough, for the attachment of numerous THE CL A VICLE. 243 ligaments. The posterior border of this surface is prolonged backward, so as to increase the size of the articular facet; the upper border gives attachment to the interarticular fibro-cartilage, and the lower border is continuous with the costal facet on the inner end of the inferior or subclavian surface, which articulates with the cartilage of the first rib. The outer or acromial extremity, directed outward and forward, presents a small, flattened, oval facet, which looks obliquely downward, for articulation with the acromion process of the scapula. The circumference of the articular facet is rough, especially above, for the attachment of the acromio-clavicular ligaments. Peculiarities of the Bone in the Sexes and in Individuals.-In the female the clavicle is generally shorter, thinner, less curved, and smoother than in the male. In those persons who perform considerable manual labor, which brings into con- stant action the muscles connected with this bone, it becomes thicker and more curved, its ridges for muscular attachment become prominently marked, and its sternal end of a prismatic form. The right clavicle is generally longer, thicker, and rougher than the left. Structure.-The shaft, as well as the extremities, consists of cancellous tissue, invested in a compact layer much thicker in the middle than at either end-. The clavicle is highly elastic, by reason of its curves. From the experiments of Mr. Ward it has been shown that it possesses sufficient longitudinal elastic force to project its own weight nearly two feet on a level surface when a smart blow is struck on it; and sufficient transverse elastic force, opposite the centre of its anterior convexity, to throw its own weight about a foot. This extent of elastic power must serve to moderate very considerably the effect of concussions received upon the point of the shoulder. Development.-By two centres: one for the shaft and one for the sternal extremity. The centre for the shaft appears very early, before any other bone- according to Bedard, as early as the thirtieth day. The centre for the sternal end makes its appearance about the eighteenth or twentieth year, and unites with the rest of the bone about the twenty-fifth year. Articulations.-With the sternum, scapula, and cartilage of the first rib. Attachment of Muscles.-To six : the Sterno-cleido-mastoid, Trapezius, Pecto- ralis major, Deltoid, Subclavius, and Sterno-hyoid. Surface Form.-The clavicle can be felt throughout its entire length, even in persons who are very fat. Commencing at the inner end, the enlarged sternal extremity, where the bone projects above the upper margin of the sternum, can be felt, forming with the sternum and the rounded tendon of the Sterno-mastoid a V-shaped notch, the pre-sternal notch. Passing out- ward, the shaft of the bone can be felt immediately under the skin, with its convexity forward in the inner two-thirds, the surface partially obscured above and below by the attachments of the Sterno-mastoid and Pectoralis major muscles. In the outer third it forms a gentle curve backward, and terminates at the outer end in a somewhat enlarged extremity which articulates with the acromial process of the scapula. The direction of the clavicle is almost, if not quite, horizontal when the arm is lying quietly by the side, though in well-developed subjects it may incline a little upward at its outer end. Its direction is, however, very changeable with the varying movements of the shoulder-joint. Surgical Anatomy.-The clavicle is the most frequently broken of any single bone in the body. This is dpe to the fact that it is much exposed to violence, and is the only bony connec- tion between the upper limb and the trunk. The bone, moreover, is slender, and is very super- ficial. The bone may be broken by direct or indirect violence or by muscular action. The most common cause is, however, from indirect violence, and the bone then gives way at the junction of the outer with the inner two-thirds of the bone ; that is to say at the junction of the two curves, for this is the weakest part of the bone. The fracture is generally oblique, and the dis- placement of the fragments is inward, away from the surface of the body; hence compound frac- ture of the clavicle is of rare occurrence. Beneath the bone the main vessels of the upper limb and the great nerve-cords of the brachial plexus lie on the first rib, and are liable to be wounded in fracture, especially in fracture from direct violence, when the force of the blow drives the broken ends inward. Fortunately, the Subclavius muscle is interposed between these structures and the clavicle, and this often protects them from injury. The clavicle is not uncommonly the seat of sarcomatous tumors, rendering the operation of excision of the entire bone necessary. This is an operation of considerable difficulty and danger. It is best performed by exposing the bone freely, disarticulating at the acromial end. and turning it inward. The removal of the outer part is comparatively easy, but resection of 244 THE SKELETON. the inner part is fraught with difficulty, the main danger being the risk of wounding the great veins which are in relation with its under surface. The Scapula. The Scapula (<7xa7Tdwy, a spade) forms the back part of the shoulder girdle. It is a large, fiat bone, triangular in shape, situated at the posterior aspect and side of Fig. 194.-Left scapular anterior surface, or venter. the thorax, between the second and seventh, or sometimes the eighth, ribs, its poste- rior border or base being about an inch from, and nearly, but not quite parallel with the spinous processes of the vertebrae, so that it is rather closer to them above than beloiv. It presents for examination two surfaces, three borders, ami three angles. The anterior surface, or venter (Fig. 194), presents a broad concavity, the sub- scapular fossa. It is marked, in the posterior two-thirds, by several oblique ridges, which pass from behind obliquely outward and upward; the anterior third is smooth. The oblique ridges give attachment to the tendinous intersections, and the surfaces between them to the fleshy fibres, of the Subscapularis muscle. The THE SCAPULA. 245 anterior third of the fossa, which is smooth, is covered by, but does not afford attachment to, the fibres of this muscle. The venter is separated from the posterior border by a smooth, triangular margin at the superior and inferior angles, and in the interval between these by a narrow edge which is often deficient. This marginal surface affords attachment throughout its entire extent to the Serratus magnus muscle. The subscapular fossa presents a transverse depression at its upper part, where the bone appears to be bent on itself, forming a consider- able angle, called the subscapular angle, thus giving greater strength to the body of the bone from its arched form, while the summit of the arch serves to support the spine and acromion process. It is in this situation that the fossa is deepest, so that the thickest part of the Subscapularis muscle lies in a line perpendicular Groove for Dorsalis Scapulx Artery. Fig. 195.-Left scapula. Posterior surface, or dorsum. to the plane of the glenoid cavity, and must consequently operate most effectively on the head of the humerus, which is contained in that cavity. The posterior surface, or dorsum (Fig. 195), is arched from above downward, alternately concave and convex from side to side. It is subdivided unequallv into 246 77//-; SKELETON. two parts by the spine: the portion above the spine is called the supraspinous fossa, and that below it the infraspinous fossa. The supraspinous fossa, the smaller of the two, is concave, smooth, and broader at the vertebral than at the humeral extremity. It affords attachment by its inner two-thirds to the Supraspinatus muscle. The infraspinous fossa is much larger than the preceding; toward its vertebral margin a shallow concavity is seen at its upper part; its centre presents a promi- nent convexity, whilst toward the axillary border is a deep groove which runs from the upper toward the lower part. The inner two-thirds of this surface affords attachment to the Infraspinatus muscle; the outer third is only covered by it, without giving origin to its fibres. This surface is separated from the axillary border by an elevated ridge, which runs from the lower part of the glenoid cavity downward and backward to the posterior border, about an inch above the inferior angle. The ridge serves for the attachment of a strong aponeurosis which sepa- rates the Infraspinatus from the two Teres muscles. The surface of bone between this line and the axillary border is narrow in the upper two-thirds of its extent, and traversed near its centre by a groove for the passage of the dorsalis scapulae vessels; it affords attachment to the Teres minor. Its lower third presents a broader, somewhat triangular surface, which gives origin to the Teres major, and over which the Latissimus dorsi glides ; sometimes the latter muscle takes origin by a few fibres from this part. The broad and narrow portions of bone above alluded to are separated by an oblique line which runs from the axillary border, downward and backward, to meet the elevated ridge: to it is attached the aponeurosis separating the two Teres muscles from each other. The Spine is a prominent plate of bone which crosses obliquely the inner four-fifths of the dorsum of the scapula at its upper part, and separates the supra- from the infraspinous fossa: it commences at the vertebral border by a smooth, triangular surface, over which the Trapezius glides, separated from the bone by a bursa, and, gradually becoming more elevated as it passes forward, terminates in the acromion process, which overhangs the shoulder-joint. The spine is triangular and flattened from above downward, its apex corresponding to the posterior border, its base (which is directed outward) to the neck of the scapula. It presents two surfaces and three borders. Its superior surface is concave, assists in forming the supraspinous fossa, and affords attachment to part of the Supra- spinatus muscle. Its inferior surface forms part of the infraspinous fossa, gives origin to part of the Infraspinatus muscle, and presents near its centre the orifice of a nutrient canal. Of the three borders, the anterior is attached to the dorsum of the bone; the posterior, or crest of the spine, is broad, and presents two lips and an intervening rough interval. To the superior lip is attached the Trapezius to the extent shown in the figure. A rough tubercle is generally seen occupying that portion of the spine which receives the insertion of the middle and inferior fibres of this muscle. To the inferior lip, throughout its whole length, is attached the Deltoid. The interval between the lips is also partly covered by the fibres of these muscles. The external border, or base, the shortest of the three, is slightly concave, its edge thick and round, continuous above with the under surface of the acromion process, below with the neck of the scapula. The narrow portion of bone external to this border, and separating it from the glenoid cavity, is called the great scapular notch, and serves to connect the supra- and infraspinous fossae. The Acromion Process, so called from forming the summit of the shoulder (fkxpov, a summit; d)poz, the shoulder), is a large and somewhat triangular process, flattened from behind forward, directed at first a little outward, and then curving forward and upward, so as to overhang the glenoid cavity. Its upper surface, directed upward, backward, and outward, is convex, rough, and gives attachment to some fibres of the Deltoid, and in the rest of its extent it is subcutaneous. Its under surface is smooth and concave. Its outer border is thick and irregular, and presents three or four tubercles for the tendinous origins of the Deltoid muscle. Its inner margin, shorter than the outer, is concave, gives attachment to a portion THE SCAPULA. 247 of the Trapezius muscle, and presents about its centre a small oval surface for articulation with the acromial end of the clavicle. Its apex, which corresponds to the point of meeting of these two borders in front, is thin, and has attached to it the coraco-acromial ligament. Of the three borders or costse of the scapula, the superior is the shortest and thinnest; it is concave, terminating at its inner extremity at the superior angle, at its outer extremity at the coracoid process. At its outer part is a deep, semicircular notch, the suprascapular, formed partly by the base of the coracoid process. This notch is converted into a foramen by the transverse ligament, and serves for the passage of the suprascapular nerve. The adjacent margin of the superior border affords attachment to the Omo-hyoid muscle. The external, or axillary, border is the thickest of the three. It commences above at the lower margin of the glenoid cavity, and inclines obliquely downward and backward to the inferior angle. Immediately below the glenoid cavity is a rough impression (the infraglenoid tubercle'), about an inch in length, which affords attachment to the long head of the Triceps muscle; to this succeeds a longitudinal groove, which extends as far as its lower third and affords origin to part of the Subscapularis muscle. The inferior third of this border, which is thin and sharp, serves for the attachment of a few fibres of the Teres major behind and of the Subscapularis in front. The internal, or vertebral, border, also named the base, is the longest of the three, and extends from the superior to the inferior angle of the bone. It is arched, intermediate in thickness between the superior and the external borders, and the portion of it above the spine is bent considerably outward, so as to form an obtuse angle with the lower part. The vertebral border presents an anterior lip, a posterior lip, and an intermediate space. The anterior lip affords attachment to the Serratus magnus; the posterior lip, to the Supraspinatus above the spine, the Infraspinatus below; the interval between the two lips, to the Levator anguli scapulae above the triangular surface at the commencement of the spine, the Rhomboideus minor to the edge of that surface; the Rhomboideus major being attached by means of a fibrous arch connected above to the lower part of the triangular surface at the base of the spine, and below to the lower part of the posterior border. Of the three angles, the superior, formed by the junction of the superior and internal borders, is thin, smooth, rounded, somewhat inclined outward, and gives attachment to a few fibres of the Levator anguli scapulae muscle. The inferior angle, thick and rough, is formed by the union of the vertebral and axillary borders, its outer surface affording attachment to the Teres major and occasionally a few fibres of the Latissimus dorsi. The anterior angle is the thickest part of the bone, and forms what is called the head of the scapula. The head presents a shallow, pyriform, articular surface, the glenoid cavity (ykfrq, a socket), whose longest diameter is from above downward, and its direction outward and forward. It is broader below than above; at its apex is a slight impression (supraglenoid tubercle) to which is attached the long tendon of the Biceps muscle. It is covered with cartilage in the recent state; and its margins, slightly raised, give attachment to a fibro-cartilaginous structure, the glenoid ligament, by which its cavity is deepened. The neck of the scapula is the slightly depressed surface which sur- rounds the head; it is more distinct on the posterior than on the anterior surface, and below than above. In the latter situation it has arising from it a thick prom- inence, the coracoid process. The Coracoid Process, so called from its fancied resemblance to a crow's beak (xo(oa£, a crow), is a thick, curved process of bone which arises by a broad base from the upper part of the neck of the scapula; it is directed at first upward and inward, then, becoming smaller, it changes its direction and passes forward and outward. The ascending portion, flattened from before backward, presents in front a smooth, concave surface over which passes the Subscapularis muscle. The horizontal portion is flattened from above downward, its upper surface is convex and irregular, and gives attachment to the Pectoralis minor; its under surface is 248 THE SKELETON. smooth; its inner border is rough, and gives attachment to the Pectoralis minor; its outer border is also rough for the coraco-acromial ligament, while the apex is embraced by the conjoined tendon of origin of the short head of the Biceps and of the Coraco-brachialis. At the inner side of the root of the coracoid process is a rough impression for the attachment of the conoid ligament; and running from it obliquely forward and outward on the upper surface of the horizontal portion, an elevated ridge for the attachment of the trapezoid ligament. Structure.-In the head, processes, and all the thickened parts of the bone the scapula is composed of cancellous tissue, while in the rest of its extent it is composed of a thin layer of dense, compact tissue. The centre and upper part of the dorsum, but especially the former, are usually so thin as to be semitransparent; 1 for Body 8 week Fig. 196.-Plan of the development of the scapula. By seven centres. The epiphyses (except one for the coracoid process) appear from fifteen to seventeen years, and unite between twenty-two and twenty-five years of age. occasionally the bone is found wanting in this situation, and the adjacent muscles come into contact. Development (Fig. 196).-By seven centres: one for the body, two for the coracoid process, two for the acromion, one for the vertebral border, and one for the inferior angle. Ossification of the body of the scapula commences about the second month of foetal life by the formation of an irregular quadrilateral plate of bone immediately behind the glenoid cavity. This plate extends itself so as to form the chief part of the bone, the spine growing up from its posterior surface about the third month. At birth the chief part of the scapula is osseous, only the coracoid and acromion processes, the posterior border, and inferior angle being cartilaginous. About the first year after birth ossification takes place in the middle of the coracoid process, which usually becomes joined with the rest of the bone at the time when the other centres make their appearance. Between the fifteenth and seventeenth years ossification of the remaining centres takes place in quick succession, and THE SCAPULA. 249 in the following order: first, near the base of the acromion and in the root of the coracoid process, the latter appearing in the form of a broad scale; secondly, in the inferior angle and contiguous part of the posterior border ; thirdly, near the extremity of the acromion; fourthly, in the posterior border. The acromion process, besides being formed of two separate nuclei, has its base formed by an extension into it of the centre of ossification which belongs to the spine, the extent of which varies in different cases. The two separate nuclei unite, and then join with the extension carried in from the spine. These various epiphyses become joined to the bone between the ages of twenty-two and twenty-five years. Sometimes failure of union between the acromion process and spine occurs, the junction being effected by fibrous tissue or by an imperfect articulation ; in some cases of supposed fracture of the acromion with ligamentous union it is probable that the detached segment was never united to the rest of the bone. Very often, in addition to these, a minute epiphysis appears at the margin of the glenoid cavity. Articulations.-With the humerus and clavicle. Attachment of Muscles.-To seventeen: to the anterior surface, the Subscapu- laris; posterior surface, Supraspinatus, Infraspinatus; spine, Trapezius, Deltoid; superior border, Omo-hyoid; vertebral border, Serratus magnus, Levator anguli scapulae, Rhomboideus minor and major; axillary border, Triceps, Teres minor, Teres major; glenoid cavity, long head of the Biceps; coracoid process, short head of the Biceps, Coraco-brachialis, Pectoralis minor; and to the inferior angle occasionally a few fibres of the Latissimus dorsi. Surface Form.-The only parts of the scapula which are truly subcutaneous are the spine and acromion process, but, in addition to these, the coracoid process, the internal or vertebral border and inferior angle, and. to a less extent, the axillary border, may be defined. The acro- mion process and spine of the scapula are easily felt throughout their entire length, forming, with the clavicle, the arch of the shoulder. 'The acromion can be ascertained to be connected to the clavicle at the acromio-clavicular joint by running the finger along it, its position being often indicated by an irregularity or bony outgrowth from the clavicle close to the joint. The acromion can be felt forming the point of the shoulder, and from this can be traced backward to join the spine of the scapula. The place of junction is usually denoted by a prominence, which is sometimes called the angle. From here the spine can be felt as a prominent ridge of bone, marked on the surface as an oblique depression, which becomes less and less distinct, and terminates a little external to the spinous processes of the vertebrae. Its termination is usually indicated by a slight dimple in the skin on a level with the interval between the third and fourth dorsal spines. Below this point the vertebral border of the scapula may be traced, running downward and outward, and thus diverging from the vertebral spines, to the inferior angle of the bone, which can be recognized, although covered by the Latissimus dorsi muscle. From this angle the axillary border can usually be traced through this thick muscular covering, form- ing, with the muscles, the posterior fold of the axilla. The coracoid process may be felt about an inch below the junction of the middle and outer third of the clavicle. Its position is indi- cated on the surface of the body by a slight depression which corresponds to the interval between the Pectoralis major and Deltoid muscles. When the arms are hanging by the side, the upper angle of the scapula corresponds to the upper border of the second rib or the interval between the first and second dorsal spines, the inferior angle to the upper border of the eighth rib or the interval between the seventh and eighth dorsal spines. Surgical Anatomy.-Fractures of the body of the scapula are rare, owing to the mobility of the bone, the thick layer of muscles by which it is encased on both surfaces, and the elas- ticity of the ribs on which it rests. Fracture of the neck of the bone is also uncommon. The most frequent course of the fracture is from the suprascapular notch to the infraglenoid tubercle, and it derives its principal interest from its simulation to a subglenoid dislocation of the humerus. The diagnosis can be made by noting the alteration in the position of the coracoid process. A fracture of the neck external to, and not including, the coracoid process is said to occur, but it is exceedingly doubtful whether such an accident ever takes place. The acromion process is more frequently broken than any other part of the bone, and there is some- times, in young subjects, a separation of the epiphysis. It is believed that many of the cases of supposed fracture of the acromion, with fibrous union, which have been found on post-mor- tem examination are really cases of imperfectly united epiphysis. Sir Astley Cooper believed that most fractures of this bone united by fibrous tissue, and the cause of this mode of union was the difficulty there was in keeping the fractured ends in constant apposition. The coracoid process is occasionally broken off, either from direct violence or perhaps, rarely, from muscular action. Tumors of various kinds grow from the scapula. Of the innocent form of tumors prob- ably the osteomata are the most common. When it grows from the venter of the scapula, as it 250 THE SKELETON. sometimes does, it is of the compact variety, such as usually grows from membrane-formed bones, as the bones of the skull. This would appear to afford evidence that this portion of the bone is formed from membrane, and not, like the rest of the bone, from cartilage. Sarcomatous tumors sometimes grow7 from the scapula, and may necessitate removal of the bone, with or without amputation of the upper limb. The bone may be excised by a T incision, and, the flaps being reflected, the removal is commenced from the posterior or vertebral border, so that the subscapular vessels which lie along the axillary border are among the last structures divided, and can be at once secured. THE ARM. The Humerus. The Humerus is the longest and largest bone of the upper extremity; it pre- sents for examination a shaft and two extremities. The Upper Extremity is the largest part of the bone; it presents a rounded head, joined to the shaft by a constricted portion, called the neck, and two other eminences, the greater and lesser tuberosities (Fig. 197). The head, nearly hemispherical in form,1 is directed upward, inward, and a little backward, and articulates with the glenoid cavity of the scapula; its surface is smooth and coated with cartilage in the recent state. The circumference of its articular surface is slightly constricted, and is termed the anatomical neck, in con- tradistinction to the constriction which exists below the tuberosities. The latter is called the surgical neck, from its often being the seat of fracture. It should be remembered, however, that fracture of the anatomical neck does sometimes, though rarely, occur. The anatomical neck is obliquely directed, forming an obtuse angle with the shaft. It is more distinctly marked in the lower half of its circumference than in the upper half, where it presents a narrow groove, separating the head from the tuberosities. Its circumference affords attachment to the capsular ligament and is perforated by numerous vascular foramina. The greater tuberosity is situated on the outer side of the head and lesser tuberosity. Its upper surface is rounded and marked by three flat facets, sep- arated by two slight ridges: the anterior facet gives attachment to the tendon of the Supraspinatus; the middle one, to the Infraspinatus; the posterior facet and the shaft of the bone below it, to the Teres minor. The outer surface of the great tuberosity is convex, rough, and continuous with the outer side of the shaft. The lesser tuberosity is more prominent, although smaller than the greater: it is situated in front of the head, and is directed inward and forward. Its summit presents a prominent facet for the insertion of the tendon of the Subscapularis muscle. The tuberosities are separated from one another by a deep groove, the bicipital groove, so called from its lodging the long tendon of the Biceps muscle, with which runs a branch of the anterior circumflex artery. It commences above between the two tuberosities, passes obliquely downward and a little inward, and terminates at the junction of the upper with the middle third of the bone. It is deep and narrow at the commencement, and becomes shallow and a little broader as it descends. Its borders are called, respectively, the anterior and posterior bicipital ridges, and form the upper part of the anterior and inter- nal borders of the shaft of the bone. In the recent state it is covered with a thin layer of cartilage, lined by a prolongation of the synovial membrane of the shoulder-joint, and receives the tendon of insertion of the Latissimus dorsi muscle. The Shaft of the humerus is almost cylindrical in the upper half of its extent, prismatic and flattened below, and presents three borders and three surfaces for examination. The anterior border runs from the front of the great tuberosity above to the 1 Though the head is nearly hemispherical in form, its margin, as Sir G. Humphry has shown, is by no means a true circle. Its greatest measurement is from the top of the bicipital groove in a direction downward, inward, and backward. Hence it follows that the greatest elevation of the arm can be obtained by rolling the articular surface in this direction-that is to say, obliquely upward, outward, and forward. THE HUMERUS. 251 Surgical neck.- >SUPINATOR RADII LONGUS. CARPI RADlALlS LONGlOR. Common origin of FLEXOR CARPI RAOIALIS. PALMARIS LONQUS. FLEXOR SUBLIMIS DIGlTORUM. FLEXOR CARPI ULNARlS. -Common origin of EXTENSOR CARPI RADIALIS BREVIS, " COMMUNIS DIQITORUM. " MINIMI DIGITI. CARPI ULNARlS. SUPINATOR BREVIS. coronoid depression below, separating the internal from the external surface. Its Fig. 197.-Left humerus. Anterior view. 252 THE SKELETON. upper part is very prominent and rough, and forms the outer lip of the bicipital groove. It is sometimes called the anterior bicipital ridge, and serves for the attachment of the tendon of the Pectoralis major. About its centre it forms the anterior boundary of the rough deltoid impression ; below, it is smooth and rounded, affording attachment to the Brachialis anticus. The external border runs from the back part of the greater tuberosity to the external condyle, and separates the external from the posterior surface. It is rounded and indistinctly marked in its upper half, serving for the attachment of the lower part of the insertion of the Teres minor, and below this of the external head of the Triceps muscle ; its centre is traversed by a broad but shallow, oblique depression, the musculo-spiral groove ; its lower part is marked by a prominent, rough margin, a little curved from behind forward, the external condyloid ridge, which presents an anterior lip for the attachment of the Supinator longus above and Extensor carpi radialis longior below, a posterior lip for the Triceps, and an interstice for the attachment of the external intermuscular septum. The internal border extends from the lesser tuberosity to the internal condyle. Its upper third is marked by a prominent ridge, forming the posterior lip of the bicipital groove, and gives attachment to the tendon of the Teres major. About its centre is a rough ridge for the attachment of the Coraco-brachialis, and just below this is seen the entrance of the nutrient canal, directed downward. Some- times there is a second canal higher up, which takes a similar direction. The inferior third of this border is raised into a slight ridge, the internal condyloid ridge, which becomes very prominent below; it presents an anterior lip for the attachment of the Brachialis anticus, a posterior lip for the internal head of the Triceps, and an intermediate space for the internal intermuscular septum. The external surface is directed outward above, where it is smooth, rounded, and covered by the Deltoid muscle ; forward and outward below, where it is slightly concave from above downward, and gives origin to part of the Brachialis anticus muscle. About the middle of this surface is seen a rough, triangular impression for the insertion of the Deltoid muscle ; and below it the musculo-spiral groove, directed obliquely from behind, forward and downward, and transmitting the musculo-spiral nerve and superior profunda artery. The internal surface, less extensive than the external, is directed inward above, forward and inward below ; at its upper part it is narrow and forms the floor of the bicipital groove : to it is attached the Latissimus dorsi. The middle part of this surface is slightly rough for the attachment of some of the fibres of the tendon of insertion of the Coraco-brachialis ; its lower part is smooth, concave, and gives attachment to the Brachialis anticus muscle.1 The posterior surface (Fig. 198) appears somewhat twisted, so that its upper part is directed a little inward, its lower part backward and a little outward. Nearly the whole of this surface is covered by the external and internal heads of the Triceps, the former of which is attached to its upper and outer part, the latter to its inner and back part, the two being separated by the musculo-spiral groove. The Lower Extremity is flattened from before backward,' and curved slightly forward ; it terminates below in a broad, articular surface which is divided into two parts by a slight ridge. Projecting on either side are the external and inter- 1 A small, hook-shaped process of bone, varying from to | of an inch in length, is not unfre- quently found projecting from the inner surface of the shaft of the humerus two inches above the internal condyle. Lt is curved downward, forward, and inward, and its pointed extremity is connected to the internal border, just above the inner condyle, by a ligament or fibrous band, completing an arch through which the median nerve and brachial artery pass when these structures deviate from their usual course. Sometimes the nerve alone is transmitted through it, or the nerve may be accompanied by the ulnar artery in cases of high division of the brachial. A well-marked groove is usually found behind the process in which the nerve and artery are lodged. This space is analogous to the supracondyloid foramen in many animals, and probably serves in them to protect the nerve and artery from compression during the contraction of the muscles in this region. A detailed account of this process is given by Dr. Struthers, in his Anatomical and Physiological Observations, p. 202. An accessory portion of the Coraco- brachialis muscle is frequently connected with this process, according to Mr. J. Wood, {Journal of Anat. and Phys., No. 1, Nov., 1866, p. 47). THE HUMERUS. 253 nal condyles. The articular surface extends a little lower than the condyles, and is curved slightly forward, so as to occupy the more ante- rior part of the bone; its greatest breadth is in the transverse diameter, and it is obliquely di- rected, so that its inner extremity occupies a lower level than the outer. The outer portion of the articular surface presents a smooth, rounded eminence, which has received the name of the capitellum, or radial head of the humerus; it articulates with the cup-shaped depression on the head of the radius, and is limited to the front and lower part of the bone, not extending as far back as the other portion of the articular surface. On the inner side of this eminence is a shallow groove, in which is received the inner margin of the head of the radius. Above the front part of the capitellum is seen a slight de- pression which receives the anterior border of the head of the radius when the forearm is flexed. The inner portion of the articular surface, the trochlear, presents a deep depression between two well-marked borders. This surface is con- vex from before backward, concave from side to side, and occupies the anterior, lower, and pos- terior parts of the bone. The external border, less prominent than the internal, corresponds to the interval between the radius and the ulna. The internal border is thicker, more prominent, and consequently of greater length, than the external. The grooved portion of the articular surface fits accurately within the greater sigmoid cavity of the ulna: it is broader and deeper on the posterior than on the anterior aspect of the bone, and is inclined obliquely from behind for- ward and from without inward. Above the front part of the - trochlear surface is seen a smaller depression, the coronoid fossa, which receives the coronoid process of the ulna during flexion of the forearm. Above the back part of the trochlear surface is a deep, triangular depression, the olec- ranon fossa, in which is received the summit of the olecranon process in extension of the forearm. These fossae are separated from one another by a thin, transparent lamina of bone, which is some- times perforated, forming the supratrochlear for- amen ; their upper margins afford attachment to the anterior and posterior ligaments of the elbow- joint, and they are lined, in the recent state, by the synovial membrane of this articulation. The articular surfaces, in the recent state, are covered with a thin layer of cartilage. The external con- dyle is a small, tubercular eminence, less promi- nent than the internal, curved a little forward, and giving attachment to the external lateral lig- ament of the elbow-joint, and to a tendon common to the origin of some of the extensor and supi- Fig. 198.-Left humerus. Posterior surface 254 THE SKELETON. nator muscles. The internal condyle, larger and more prominent than the exter- nal, is directed a little backward: it gives attachment to the internal lateral liga- ment, to the Pronator radii teres, and to a tendon common to the origin of some of the tfexor muscles of the forearm. The ulnar nerve runs in a groove at the back of the internal condyle, or between it and the olecranon process. These eminences are directly continuous above with the external and internal borders-i. e. the external and internal condyloid ridges. The great prominence of the inner one renders it more liable to fracture. Structure.-The extremities consist of cancellous tissue, covered with a thin, com- pact layer; the shaft is composed of a cylinder of compact tissue, thicker at the centre than at the extremities, and hollowed out by a large medullary canal, which ex- tends along its whole length. Development.-By seven, or occasionally eight, centres (Fig. 199), one for the shaft, one for the head, one for the tuberosities, one for the radial head, one for the troch- lear portion of the articular surface, and one for each condyle. The nucleus for the shaft appears near the centre of the bone in the eighth week, and soon extends toward the extremities. At birth the humerus is ossified nearly in its whole length, the ex- tremities remaining cartilaginous. At the beginning of the second year ossification commences in the head of the bone, and during the third year the centre for the tuberosities makes its appearance, usually by a single ossific point, but sometimes, according to Beclard, by one for each tuberosity, that for the lesser being small and not appearing until the fifth year. By the sixth year the centres for the head and tuberosities have enlarged and become joined, so as to form a single large epiphysis. The lower end of the humerus is developed in the following manner: At the end of the second year ossification commences in the radial portion of the articular surface, and from this point extends inward, so as to form the chief part of the articular end of the bone, the centre for the inner part of the articular surface not appearing until about the age of twelve. Ossification commences in the internal condyle about the fifth year, and in the external one not until about the thirteenth or fourteenth year. About sixteen or seventeen years the outer condyle and both portions of the articulating surface (having already joined) unite with the shaft; at eighteen years the inner condyle becomes joined; whilst the upper epiphysis, although the first formed, is not united until about the twentieth year. Articulations.-With the glenoid cavity of the scapula and with the ulna and radius. Attachment of Muscles.-To twenty-four: to the greater tuberosity, the Supraspinatus, Infraspinatus, and Teres minor; to the lesser tuberosity, the Subscapularis ; to the anterior bicipital ridge, the Pectoralis major; to the posterior bicipital ridge, the Teres major; to the bicipital groove, the Latissimus dorsi; to the shaft, the Deltoid, Coraco-brachialis, Brachialis anticus, external and internal heads of the Triceps ; to the internal condyle, the Pronator radii teres, and common tendon of the Flexor carpi radialis, Palmaris longus, Flexor sublimis digitorum, Epiphyses of head and tuberosities blend at 5th year, and unite with shaft at 20th year. Unites with shaft at 18th year. Fig. 199.-Plan of the development of the humerus. By seven centres. THE HUMERUS. 255 and Flexor carpi ulnaris; to the external condyloid ridge, the Supinator longus and Extensor carpi radialis longior; to the external condyle, the common tendon of the Extensor carpi radialis brevior, Extensor communis digitorum, Extensor minimi digiti, Extensor carpi ulnaris, and Supinator brevis; to the back of the external condyle, the Anconeus. Surface Form.-The humerus is almost entirely clothed by the muscles which surround it, and the only parts of this bone which are strictly subcutaneous are small portions of the internal and external condyles. In addition to these, the tuberosities and a part of the head of the bone can be felt under the skin and muscles by which they are covered. Of these the greater tuberosity forms the most prominent bony point of the shoulder, extending beyond the acromion process and covered by the Deltoid muscle. It influences materially the surface form of the shoulder. It is best felt while the arm is lying loosely by the side ; if the arm be raised, it recedes from under the finger. The lesser tuberosity, directed forward and inward, is to be felt to the inner side of the greater tuberosity, just below the acromio-clavicular joint. Between the two tuberosities lies the bicipital groove. This can be defined by placing the finger and making firm pressure just internal to the greater tuberosity ; then, by rotating the humerus, the groove will be felt to pass under the finger as the bone is rotated. With the arm abducted from the side, by pressing deeply in the axilla the lower part of the head of the bone is to be felt. On each side of the elbow-joint, and just above it, the internal and external condyles of the bone are to be felt. Of these the internal is the more prominent, but the ridge passing upward from it, the internal condyloid ridge, is much less marked than the external, and, as a rule, is not to be felt. Occasionally, however, we find along this border the hook-shaped process men- tioned above. The external condyle is most plainly to be seen during semiflexion of the fore- arm, and its position is indicated by a depression between the attachment of the adjacent muscles. From it is to be felt a strong bony ridge running up the outer border of the shaft of the bone. This is the external condyloid ridge; it is concave forward, and corresponds with the curved direction of the lower extremity of the humerus. Surgical Anatomy.-There are several points of surgical interest connected with the humerus. First, as regards its development. The upper end, though the first to ossify, is the last to join the shaft, and the length of the bone is mainly due to growth from this upper epiphysis. Hence, in cases of amputation of the arm in young subjects the humerus continues to grow considerably, and the end of the bone which immediately after the operation was cov- ered with a thick cushion of soft tissue, begins to project, thinning the soft parts and rendering the stump conical. This may necessitate the removal of a couple of inches or so of the bone, and even after this operation a recurrence of the conical stump may take place. There are several points of surgical interest in connection with fractures. First, as regard their causation : the bone may be broken by direct or indirect violence like the other long bones, but, in addition to this, it is probably more frequently fractured by muscular action than any other of this class of bone in the body. It is usually the shaft, just below the insertion of the Deltoid, which is thus broken. I have seen the accident happen from throwing a stone, and in an apparently healthy adult from cutting a piece of hard "cake tobacco '' on a table. In this latter case there was no disease of the bone that could be discovered. Fractures of the upper end may take place through the anatomical neck, through the surgical neck, or separation of the greater tuberosity may occur. Fracture of the anatomical neck is a very rare accident; in fact, it is doubted by some whether it ever occurs. These fractures are usually considered to be intracapsular. but they are probably partly within and partly without the capsule, as the lower part of the capsule is inserted some little distance below the anatomical neck, while the upper part is attached to it. They may be impacted or non-impacted. In most cases there is little or no displacement on account of the capsule, in whole or in part, remaining attached to the lower fragment. But occasionally a very remarkable alteration in position takes place; the upper fragment turns on its own axis, so that the cartilaginous surface of the head rests against the upper end of the lower fragment. When the fractured end is entirely separated from all its surroundings, its vascular supply must be entirely cut off. and one would expect it, theoretically, to necrose. But this must be exceedingly rare, for Gurlt was unable to find a single authenti- cated case recorded. Separation of the upper epiphysis of the humerus sometimes occurs in the young subject, ami is marked by a characteristic deformity by which the lesion may be at once recognized. This consists in the presence of an abrupt projection at the front of the joint some short distance below the coracoid process, caused by the upper end of the lower fragment. In fractures of the shaft of the humerus the lesion may take place at any point, but appears to be more common in the lower than in the upper part of the bone. The points of interest in con- nection with these fractures are-(1) that the musculo-spiral nerve may be injured as it lies in the groove on the bone, or may become involved in the callus which is subsequently thrown out; and (2) the frequency of non-union. This is believed to be more common in the humerus than in any other bone, and various causes have been assigned for it. It would seem most probably to be due to the difficulty that there is in fixing the shoulder-joint and the upper fragment, and possibly also the elbow-joint and lower fragment also. Other causes which have been assigned for the non-union are: (1) that in attempting passive motion of the elbow-joint to overcome any rigidity which may exist, the movement does not take place at the articulation, but at the seat of fracture ; or that the patient, in consequence of the rigidity of the elbow, in attempting 256 THE SKELETON. to flex or extend the forearm moves the fragment and not the joint. (2) The presence of small portions of muscular tissue between the broken ends. (3) Want of support to the elbow, so that the weight of the arm tends to drag the lower fragment away from the upper. An import- ant distinction to make in fractures of the lower end of the humerus is between those that involve the joint and those which do not; the former always serious, as they may lead to impairment of the utility of the limb. They include the T-shaped fracture and oblique frac- tures which involve the articular surface. The fractures which do not involve the joint are the transverse above the condyles and detachment of one or other condyle. Under the head of separation of the epiphysis two separate injuries have been described. One where the whole of the four ossific centres which form the lower extremity of the bone are separated from the shaft; and secondly, where the articular portion is alone separated, the two condyles remaining attached to the shaft of the bone. The epiphysial line between the shaft and lower end runs across the bone just above the tips of the condyles, a point to be borne in mind in performing the operation of excision. Tumors originating from the humerus are of frequent occurrence. A not uncommon place for a chondroma to grow from is the shaft of the bone somewhere in the neighborhood of the insertion of the deltoid. Sarcomata frequently grow from this bone. The Forearm is that portion of the upper extremity which is situated between the elbow7 and the w rist. It is composed of two bones, the ulna and radius. THE FOREARM. The Ulna. The Ulna (Figs. 200, 201), so called from its forming the elbow is a long bone, prismatic in form, placed at the inner side of the forearm, parallel with the radius. It is the larger and longer of the two bones. Its upper extremity, of great thickness and strength, forms a large part of the articulation of the elbow- joint ; it diminishes in size from above downward, its lower extremity being very small, and excluded from the wrist-joint by the interposition of an interarticular fibro-cartilage. It is divisible into a shaft and two extremities. The Upper Extremity, the strongest part of the bone, presents for examination two large, curved processes, the Olecranon process and the Coronoid process; and two concave, articular cavities, the greater and lesser sigmoid cavities. The Olecranon Process (wAsvjj), elbow; xpavcov, head) is a large, thick, curved eminence situated at the upper and back part of the ulna. It is curved forward at the summit so as to present a prominent tip, its base being contracted where it joins the shaft. This is the narrowest part of the upper end of the ulna, and, consequently, the most usual seat of fracture. The posterior surface of the olecranon, directed backward, is triangular, smooth, subcutaneous, and covered by a bursa. Its upper surface, directed upward, is of a quadrilateral form, marked behind by a rough impression for the attachment of the Triceps muscle; and in front, near the margin, by a slight transverse groove for the attachment of part of the posterior ligament of the elbow-joint. Its anterior surface is smooth, concave, covered with cartilage in the recent state, and forms the upper and back part of the great sigmoid cavity. The lateral borders present a continuation of the same groove that was seen on the margin of the superior surface; they serve for the attachment of ligaments; viz. the back part of the internal lateral ligament internally, the posterior ligament externally. To the inner border is also attached a part of the Flexor carpi ulnaris, while to the outer border is attached the Anconeus. The Coronoid Process (xojowwy, anything hooked like a crow's beak) is a rough, triangular eminence of bone which projects horizontally forward from the upper and front part of the ulna, forming the lower part of the great sigmoid cavity. Its base is continuous with the shaft, and of considerable strength; so much so that fracture of it is an accident of rare occurrence. Its apex is pointed, slightly curved upward, and received into the coronoid depression of the humerus in flexion of the forearm. Its upper surface is smooth, concave, and forms the lower part of the greater sigmoid cavity. The under surface is concave, and marked internally by a rough impression for the insertion of the Brachialis anticus. At the junction of this surface with the shaft is a rough eminence, the tubercle of THE ULNA. 257 Ulna. Radius. FLEXOR SUBLIMIS DIGITORUM. PRONATOR RADII TERES. Occasional origin of FLEXOR LONGUS POLLICIS. Radial origin of flexor 1 SUBLIMIS DIGITORUM. SUPINATOR LONGUS. Groove for extensor ossis METACARPI POLLICIS. Groove for extensor BREVIS POLLICIS. Styloid process. Styloid process. Fig. 200.-Bones of the left forearm. Anterior surface. 258 THE SKELETON. the ulna, for the attachment of the oblique ligament. Its outer surface presents a narrow, oblong, articular depression, thp lesser sigmoid cavity. The inner surface, by its prominent, free margin, serves for the attachment of part of the internal lateral ligament. At the front part of this surface is a small, rounded eminence for the attachment of one head of the Flexor sublimis digitorum; behind the eminence, a depression for part of the origin of the Flexor profundus digitorum; and, descending from the eminence, a ridge which gives attachment to one head of the Pronator radii teres. Generally, the Flexor longus pollicis arises from the lower part of the coronoid process by a rounded bundle of muscular fibres. The Greater Sigmoid Cavity, so called from its resemblance to the old shape of the Greek letter A, is a semilunar depression of large size, formed by the olecranon and coronoid processes, and serving for articulation with the trochlear surface of the humerus. About the middle of either lateral border of this cavity is a notch which contracts it somewhat, and serves to indicate the junction of the two processes of which it is formed. The cavity is concave from above downward, and divided into two lateral parts by a smooth, elevated ridge which runs from the summit of the olecranon to the tip of the coronoid process. Of these two portions, the internal is the larger, and is slightly concave transversely; the external por- tion is convex above, slightly concave below. The articular surface, in the recent state, is covered with a thin layer of cartilage. The Lesser Sigmoid Cavity is a narrow, oblong, articular depression, placed on the outer side of the coronoid process, and serving for articulation with the head of the radius. It is concave from before backward, and its extremities, which are prominent, serve for the attachment of the orbicular ligament. In the recent state it is covered with a thin layer of cartilage. The Shaft, at its upper part, is prismatic in form, and curved from behind forward and from without inward, so as to be convex behind and externally; its central part is quite straight; its lower part rounded, smooth, and bent a little outward; it tapers gradually from above downward, and presents for examination three borders and three surfaces. The anterior border commences above at the prominent inner angle of the coro- noid process, and terminates below in front of the styloid process. It is well marked above, smooth and rounded in the middle of its extent, and affords attachment to the Flexor profundus digitorum: its lower fourth, marked off from the rest of the border by the commencement of an oblique ridge on the anterior surface, serves for the attachment of the Pronator quadratus. It separates the anterior from the internal surface. The posterior border commences above at the apex of the triangular subcuta- neous surface at the back part of the olecranon, and terminates below at the back part of the styloid process; it is well marked in the upper three-fourths, and gives attachment to an aponeurosis common to the Flexor carpi ulnaris, the Extensor carpi ulnaris, and the Flexor profundus digitorum muscles ; its lower fourth is smooth and rounded. This border separates the internal from the posterior surface. The external or interosseous border commences above by two lines, which con- verge one from each extremity of the lesser sigmoid cavity, enclosing between them a triangular space for the attachment of part of the Supinator brevis, and terminates below at the middle of the head of the ulna. Its two middle fourths are very pro- minent, its lower fourth is smooth and rounded. This border gives attachment to the interosseous membrane, except along its upper fourth, and separates the anterior from the posterior surface. The anterior surface, much broader above than below, is concave in the uppei- three-fourths of its extent, and affords attachment to the Flexor profundus digi- torum ; its lower fourth, also concave, to the Pronator quadratus. The lower fourth is separated from the remaining portion of the bone by a prominent ridge, directed obliquely from above downward and inward; this ridge (the oblique or Pronator ridge) marks the extent of attachment of the Pronator quadratus above. THE ULNA. 259 Ulna. Radius. •FLEXOR SUBLIMIS OIGITORUM. Posterior border of ulna: giving attachment to an aponeurosis common to< EXTENSOR CARPI ULNARlS. FLEXOR CARPI ULNARlS. FLEXOR PROFUNDUS DlGlTORUM. For EXTENSOR CARPI ULNARlS. POT EXTENSOR MINIMI DlQITl. For EXT. CARPI RAD. LONGIOR. I EXTENSOR CARPI RAOIALIS BREVIOR EXTENSOR LONGUS POLLICIS For< EXTENSOR INDICIS EXTENSOR COMMUNIS DlGlTORUM. Fig. 201.-Bones of the left forearm. Posterior surface. 260 THE SKELETON. At the junction of the upper with the middle third of the bone is the nutrient canal directed obliquely upward and. inward. The posterior surface, directed backward and outward, is broad and concave above, somewhat narrower and convex in the middle of its course, narrow, smooth, and rounded below. It presents, above, an oblique ridge, which runs from the posterior extremity of the lesser sigmoid cavity, downward to the posterior border ; the triangular surface above this ridge receives the insertion of the Anconeus muscle, whilst the ridge itself affords attachment to the Supinator brevis. The surface of bone below this is subdivided by a longitudinal ridge, sometimes called the perpendicular line, into two parts: the internal part is smooth, concave, and gives origin to (occasionally is merely covered by) the Extensor carpi ulnaris; the external portion, wider and rougher, gives attachment from above downward to part of the Supinator brevis, the Extensor ossis metacarpi pollicis, the Extensor longus pollicis, and the Extensor indicis muscles. The internal surface is broad and concave above, narrow and convex below. It gives attachment by its upper three-fourths to the Flexor profundus digitorum muscle : its lower fourth is subcutaneous. The Lower Extremity of the ulna is of small size, and excluded from the artic- ulation of the wrist-joint. It presents for examination two eminences, the outer and larger of which is a rounded, articular eminence, termed the head of the ulna, the inner, narrower and more projecting, is a non-articular eminence, the styloid process. The head presents an articular facet, part of which, of an oval form, is directed downward, and articulates with the upper surface of the interarticular fibro-cartilage which separates it from the wrist-joint; the remaining portion, directed outward, is narrow, convex, and received into the sigmoid cavity of the radius. The styloid process projects from the inner and back part of the bone, and descends a little lower than the head, terminating in a rounded summit, which affords attachment to the internal lateral ligament of the wrist. The head is separated from the styloid process, by a depression for the attachment of the triangular interarticular fibro-cartilage ; and behind, by a shallow groove for the passage of the tendon of the Extensor carpi ulnaris. Structure.-Similar to that of the other long bones. Development.-By three centres : one for the shaft, one for the inferior extremity, and one for the olec- ranon (Fig. 202). Ossification commences near the middle of the shaft about the eighth week, and soon extends through the greater part of the bone. At birth the ends are cartilaginous. About the fourth year a separate osseous nucleus appears in the middle of the head, which soon extends into the styloid pro- cess. About the tenth year ossific matter appears in the olecranon near its extremity, the chief part of this process being formed from an extension of the shaft of the bone into it. At about the sixteenth year the upper epiphysis becomes joined, and at about the twentieth year the lower one. Articulations.-With the humerus and radius. Attachment of Muscles.-To sixteen: to the olecranon, the Triceps, Anconeus, and one head of the Flexor carpi ulnaris. To the coronoid process, the Brachialis anticus, Pronator radii teres, Flexor sublimis digitorum, and Flexor profundus digitorum ; generally also the Flexor longus pollicis. To the shaft, the Flexor profundus digitorum, Pronator quad- ratus, Flexor carpi ulnaris, Extensor carpi ulnaris, Anconeus, Supinator brevis, Extensor ossis metacarpi pollicis, Extensor longus pollicis, and Extensor indicis. Olecranon. Appears at~ 10th year. .Joins shaft at 16 th year. Appears at 4th year. 'J<20thye^rat Inferior extremity. men?ofth0eu7naanByVhhrLdc.C THE RADIUS. 261 Surface Form.-The most prominent part of the ulna on the surface of the body is the olecranon process, which can always be felt at the back of the elbow-joint. When the fore- arm is Hexed the upper triangular surface can be felt, directed backward; during extension it recedes into the olecranon fossa, and the contracting fibres of the triceps prevent its being perceived. At the back of the olecranon is the smooth, triangular, subcutaneous surface, which below is continuous with the posterior border of the shaft of the bone; this is to be felt in every position of the joint. During extension the upper border of the olecranon is slightly above the level of the internal condyle, and the process itself is nearer to this condyle than the outer one. Running down the back of the forearm, from the apex of the triangular surface which forms the posterior surface of the olecranon, is a prominent ridge of bone, the posterior border of the ulna. This is to be felt throughout the entire length of the shaft of the bone, from the olecranon above to the styloid process below. As it passes down the forearm it pursues a sinuous course and inclines to the inner side, so that, though it is situated in the middle of the back of the limb above, it is on the inner side of the wrist at its termination. It becomes rounded off in its lower third, and may be traced below to the small, subcutaneous sur- face of the styloid process. Internal to this border the lower fourth of the internal surface is to be felt. The styloid process is to be felt as a prominent tubercle of bone, continuous above with the posterior subcutaneous border of the ulna, and terminating below in a blunt apex, which lies a little internal and behind, but on a level with, the wrist-joint. The styloid process is best felt when the hand is in the same line as the bones of the forearm, and in a position midway between supination and pronation. If the forearm is pronated while the finger is placed on the process, it will be felt to recede, and another prominence of bone will appear just external and above it. This is the head of the ulna, which articulates with the lower end of the radius and the triangular interarticular fibro-cartilage, and now projects between the tendons of the Extensor carpi ulnaris and the Extensor minimi digiti muscles. The Radius (radius, a ray, or spoke of a wheel) is situated on the outer side of the forearm, lying side by side with the ulna, which exceeds it in length and size. Its upper end is small, and forms only a small part of the elbow-joint; but its lower end is large, and forms the chief part of the wrist. It is one of the long bones, prismatic in form, slightly curved longitudinally, and, like other long bones, has a shaft and two extremities. The Upper Extremity presents a head, neck, and tuberosity. The head is of a cylindrical form, depressed on its upper surface into a shallow cup which articulates with the capitellum or radial head of the humerus. In the recent state it is covered with a layer of cartilage which is thinnest at its centre. Around the circumference of the head is a smooth, articular surface, broad internally where it articulates with the lesser sigmoid cavity of the ulna ; narrow in the rest of its circumference, w here it rotates within the orbicular ligament. It is coated w ith cartilage in the recent state. The head is supported on a round, smooth, and constricted portion of bone, called the neck, which presents, behind, a slight ridge, for the attachment of part of the Supinator brevis. Beneath the neck, at the inner and front aspect of the bone, is a rough eminence, the bicipital tuberosity. Its surface is divided into two parts by a vertical line-a posterior, rough portion, for the insertion of the tendon of the Biceps muscle; and an anterior, smooth portion, on which a bursa is interposed between the tendon and the bone. The Shaft of the bone is prismoid in form, narrower above than below, and slightly curved, so as to be convex outward. It presents three surfaces, separated by three borders. The anterior border extends from the lower part of the tuberosity above to the anterior part of the base of the styloid process below. It separates the anterior from the external surface. Its upper third is very prominent; and from its oblique direction, downward and outward, has received the name of the oblique line of the radius. It gives attachment externally to the Supinator brevis, internally to the Flexor longus pollicis, and between these to the Flexor sublimis digitorum. The middle third of the anterior border is indistinct and rounded. Its lower fourth is sharp, prominent, affords attachment to the Pronator quadratus, and terminates in a small tubercle, into which is inserted the tendon of the Supinator longus. The posterior border commences above at the back part of the neck of the The Radius. 262 THE SKELETON. radius, and terminates below at the posterior part of the base of the styloid process ; it separates the posterior from the external surface. It is indistinct above and below, but well marked in the middle third of the bone. The internal or interosseous border commences above at the back part of the tuberosity, where it is rounded and indistinct, becomes sharp and prominent as it descends, and at its lower part divides into two ridges, which descend to the anterior and posterior margins of the sigmoid cavity. This border separates the anterior from the posterior surface, and has the interosseous membrane attached to it throughout the greater part of its extent. The anterior surface is narrow and concave for its upper three-fourths, and gives attachment to the Flexor longus pollicis muscle; it is broad and flat for its lower fourth, and gives attachment to the Pronator quadratus. A prominent ridge limits the attachment of the Pronator quadratus below, and between this and the inferior border is a triangular rough surface for the attachment of the anterior ligament of the wrist-joint. At the junction of the upper and middle third of this surface is the nutrient foramen, which is directed obliquely upward. The posterior surface is rounded, convex, and smooth in the upper third of its extent, and covered by the Supinator brevis muscle. Its middle third is broad, slightly concave, and gives attachment to the Extensor ossis metacarpi pollicis above, the Extensor brevis pollicis below. Its lower third is broad, convex, and covered by the tendons of the muscles, which subsequently run in the grooves on the lower end of the bone. The external surface is rounded and convex throughout its entire extent. Its upper third gives attachment to the Supinator brevis muscle. About its centre is seen a rough ridge, for the insertion of the Pronator radii teres muscle. Its lower part is narrow, and covered by the tendons of the Extensor ossis metacarpi pollicis and Extensor brevis pollicis muscles. The Lower Extremity of the radius is large, of quadrilateral form, and provided with two articular surfaces--one at the extremity, for articulation with the carpus, and one at the inner side of the bone, for articulation with the ulna. The carpal articular surface is of triangular form, concave, smooth, and divided by a slight antero-posterior ridge into two parts. Of these, the external is large, of a triangular form, and articulates with the scaphoid bone; the inner, smaller and quadrilateral, articulates with the semilunar. The articular surface for the ulna is called the sigmoid cavity of the radius; it is narrow, concave, smooth, and articulates with the head of the ulna. The circumference of this end of the bone presents three surfaces-an anterior, external, and posterior. The anterior surface, rough and irregular, affords attachment to the anterior ligament of the wrist-joint. The external surface is prolonged obliquely downward into a strong, conical projection, the styloid process, which gives attachment by its base to the tendon of the Supinator longus, and by its apex to the external lateral ligament of the wrist- joint. The outer surface of this process is marked by a flat groove, which runs obliquely downward and forward, and gives passage to the tendons of the Extensor ossis metacarpi pollicis and the Extensor brevis pollicis. The posterior surface is convex, affords attachment to the posterior ligament of the wrist, and is marked by three grooves. Proceeding from without inward, the first groove is broad but shallow, and subdivided into two by a slightly elevated ridge: the outer of these two transmits the tendon of the Extensor carpi radialis longior, the inner the tendon of the Extensor carpi radialis brevior. The second, which is near the centre of the bone, is a deep but narrow groove, bounded on its outer side by a sharply-defined ridge; it is directed obliquely from above, downward and outward, and transmits the tendon of the Extensor longus pollicis. The third, lying most internally, is a broad groove, for the passage of the tendons of the Extensor indicis and Extensor communis digitorum. Structure.-Similar to that of the other long bones. Development (Fig. 203).-By three centres: one for the shaft and one for each extremity. That for the shaft makes its appearance near the centre of the bone THE RADIUS. 263 soon after the development of the humerus commences. At birth the shaft is ossified, but the ends of the bone are cartilaginous. About the end of the second year ossification commences in the lower epiph- ysis, and about the fifth year in the upper one. At the age of seventeenoreighteen the upper epiph- ysis becomes joined to the shaft, the lower epiph- ysis becoming united about the twentieth year. Articulation.-With four bones: the humerus, ulna, scaphoid, and semilunar. Attachment of Muscles.-To nine: to the tuberosity, the Biceps ; to the oblique ridge, the Supinator brevis, Flexor sublimis digitorum, and Flexor longus pollicis; to the shaft (its anterior surface), the Flexor longus pollicis and Pronator quadratus; (its posterior surface), the Extensor ossis metacarpi pollicis and Extensor brevis pollicis; (its outer surface), the Pronator radii teres; and to the styloid process, the Supinator longus. Surface Form.-Just below and a little in front of the posterior surface of the external condyle a part of the head of the radius may be felt, covered by the orbic- ular and external lateral ligaments. There is in this situ- ation a little dimple in the skin, which is most visible when the arm is extended, and which marks the posi- tion of the head of the bone. If the finger is placed on this dimple and the forearm pronated and supinated, the head of the bone will be distinctly perceived rotating in the lesser sigmoid cavity. The upper half of the shaft of the radius cannot be felt, as it is surrounded by the fleshy bellies of the muscles arising from the external condyle. The lower half of the shaft can be readily examined, though covered by tendons and muscles and not strictly subcutaneous. If traced downward, the shaft will be felt to terminate in a lozenge-shaped, convex surface on the outer side of the base of the styloid process. This is the only subcutaneous part of the bone, and from its lower extremity the apex of the styloid process will be felt bending inward toward the wrist. About the middle of the posterior aspect of the lower extremity of the bone is a well-marked ridge, best perceived when the hand is slightly flexed on the wrist. It bounds the oblique groove on the posterior surface of the bone, through which the tendon of the Extensor longus pollicis runs, and serves to keep that tendon in its place. Surgical Anatomy.-The two bones of the forearm are more often broken together than is either the radius or ulna separately. It is therefore convenient to consider the fractures of these two bones together in the first instance, and subsequently to mention the principal fractures which take place in each bone individually. These fractures may be produced by either direct or indirect violence, though more commonly by direct violence. When indirect force is applied to the forearm the radius generally alone gives way, though both bones may suffer. The fracture from indirect force generally takes place somewhere about the middle of the bones; fracture from direct violence may occur at any part, more often, however, in the lower half of the bone. The fracture is usually transverse, but may be more or less oblique. A point of interest in connection with these fractures is the tendency that there is for the two bones to unite across the interosseous membrane; the limb should therefore be put up in a position midway between supination and pronation, which is not only the most comfortable position, but also sep- arates the bones most widely from each other, and therefore diminishes the risk of the bones becoming united across the interosseous membrane. The splints, anterior and posterior, which are applied in these cases should be rather wider than the limb, so as to prevent any lateral pressure on the bones. For in these cases there is a greater liability to gangrene from the pressure of the splints than in other parts of the body. This is no doubt due principally to two causes: (1) the flexion of the forearm compressing to a certain extent the brachial artery and retarding the flow of blood to the limb; and (2) the superficial position of the two main arteries of the forearm in a part of their course, and their liability to be compressed by the splints. The special fractures of the ulna are-(1) Fracture of the olecranon. This may be caused by direct violence, falls on the elbow with the forearm flexed, or by muscular action by the sudden contraction of the triceps. The most common place for the fracture to occur is at the constricted portion where the olecranon joins the shaft of the bone, and the fracture may be either transverse or oblique; but any part may be broken, even a thin shell may be torn off. Fractures from direct violence are occasionally comminuted. The displacement is sometimes very slight, owing to the fibrous structures around the process not being torn. (2) Fracture of the coronoid process some- Appears atr 5th year. Unites with shaft about puberty. Appears at 2d year. Unites with shaft about 20th year. Lower extremity. Fig. 203.-Plan of the development of the radius. By three centres. 264 THE SKELETON. times occurs as a complication of dislocation backward of the bones of the forearm, but it is doubtful if it ever occurs as an uncomplicated injury. (3) Fractures of the shaft of the ulna may occur at any part, but usually take place at the middle of the bone or a little below it. They are almost always the result of direct violence. (4) The styloid process may be knocked off by direct violence. Fractures of the radius consist of- (1) Fracture of the head of the bone; this generally occurs in conjunction with some other lesion, but may occur as an uncomplicated injury. (2) Fracture of the neck may also take place, but is generally complicated with other injury. (3) Fractures of the shaft of the radius are very common, and may take place at any part of the bone. They may take place from either direct or indirect violence. (4) The most important fracture of the radius is that of the lower end (Colles's fracture). The fracture is transverse, and generally takes place about an inch from the lower extremity. It is caused by falls on the palm of the hand, and is an injury of advanced life, occurring more frequently in the female than the male. In consequence of the manner in which the fracture is caused, the upper fragment becomes driven into the lower, and impaction is the result; or else the lower fragment becomes split up into two or more pieces, so that no fixation occurs. Separation of the lower epiphysis of the radius may take place in the young. This injury and Colles's fracture may be distinguished from other injuries in this neighborhood-especially dislocation, with which it is liable to be confounded-by observing the relative positions of the styloid processes of the ulna and radius. Tn the natural condition of parts, with the arm hanging by the side, the styloid pro- cess of the radius is on a lower level than that of the ulna; that is to say, nearer the ground. After fracture or separation of the epiphysis this process is on the same or higher level than that of the ulna, whereas it would be unaltered in position in dislocation. THE HAND. The skeleton of the Hand is subdivided into three segments-the Carpus or wrist-bones ; the Metacarpus or bones of the palm ; and the Phalanges or bones of the fingers. The Carpus. The bones of the Carpus (xapnbs, the wrist), eight in number, are arranged in two rows. Those of the upper row, enumerated from the radial to the ulnar side, are the scaphoid, semilunar, cuneiform, and pisiform ; those of the lower row, enumerated in the same order, are the trapezium, trapezoid, os magnum, and unciform. Common Characters of the Carpal Bones. Each bone (excepting the pisiform) presents six surfaces. Of these the anterior or palmar and the posterior or dorsal are rough for ligamentous attachment, the dorsal surface being the broader, except in the scaphoid and semilunar. The superior or proximal and inferior or distal are articular, the superior generally convex, the inferior concave ; and the internal and external are also articular when in contact with contiguous bones, otherwise rough and tubercular. The structure in all is similar, consisting of cancellous tissue enclosed in a layer of compact bone. Each bone is also developed from a single centre of ossification. Bones of the Upper Row (Figs. 204, 205). The Scaphoid (axdtpp a boat; sc do', like) is the largest bone of the first row. It has received its name from its fancied resemblance to a boat, being broad at one end, and narrowed like a prow at the opposite. It is situated at the upper and outer part of the carpus, its long axis being from above downward, outward and forward. The superior surface is convex, smooth, of triangular shape, and articulates with the lower end of the radius. The inferior surface, directed downward, outward, and backward, is smooth, convex, also triangular, and divided by a slight ridge into two parts, the external of which articulates with the trapezium, the inner with the trapezoid, The posterior or dorsal surface presents a narrow, rough groove, which runs the entire breadth of the bone and serves for the attachment of ligaments. The anterior or palmar surface is concave above, and elevated at its lower and outer part into a prominent, rounded tubercle, which projects forward from the front of the carpus and gives attachment to the anterior annular ligament of the wrist. The external surface is rough and narrow, and gives attachment to the external lateral ligament of the wrist. The THE CARPUS. 265 internal surface presents two articular facets: of these, the superior or smaller one is flattened, of semilunar form, and articulates with the semilunar; the Carpus. EXTENSOR RADIALIS LONGIOR. EXTENSOR CARPI < ULNARIS. EXTENSOR CARPI RADIALIS BREVIOR. Metacarpus. EXTENSOR BREVIS1 POLLICIS. extensor longusJ POLLICIS. "W Phalanges. . 1st Row. EXTENSOR DIGITORUM COMMUNIS and \ EXTENSOR MINIMI DlGlTI. 2nd Row. EXTENSOR DIGITORUM communis and ( EXTENSOR INDICIS. fl 3 rd Row. EXTENSOR DIGITORUM/ COMMUNIS. EXTENSOR . digitorum/ COMMUNIS.\ Fig. 204.-Bones of the left hand. Dorsal surface. inferior or larger is concave, forming, with the semilunar bone, a concavity for the head of the os magnum. 266 THE SKELETON. To ascertain to which side the bone belongs, hold it with the superior or radial convex, articular, surface upward, and the posterior surface-i. e. the narrow, non-articular, grooved surface-toward you. The tubercle on the outer surface points to the side to which the bone belongs.1 Articulations.-With five bones: the radius above, trapezium and trapezoid below, os magnum and semilunar internally. The Semilunar (semi, half; luna, moon) bone may be distinguished by its deep concavity and crescentic outline. It is situated in the centre of the upper row of the carpus, between the scaphoid and cuneiform. The superior surface, convex, smooth, and bounded by four edges, articulates with the radius. The inferior surface is deeply concave, and of greater extent from before backward than trans- versely : it articulates with the head of the os magnum and by a long, narrow facet (separated by a ridge from the general surface) with the unciform bone. The anterior or palmar and posterior or dorsal surfaces are rough, for the attach- ment of ligaments, the former being the broader and of somewhat rounded form. The external surface presents a narrow, flattened, semilunar facet for articulation with the scaphoid. The internal surface is marked by a smooth, quadrilateral facet, for articulation with the cuneiform. Hold it with the convex articular surface for the radius upward, and the narrowest non-articular surface toward you. The semilunar facet for the scaphoid will be on the side to which the bone belongs. Articulations.-With five bones : the radius above, os magnum and unciform below, scaphoid and cuneiform on either side. The Cuneiform (cuneus, a wedge; forma, likeness) may be distinguished by its pyramidal shape (os pyramidal), and by its having an oval, isolated facet for articulation with the pisiform bone. It is situated at the upper and inner side of the carpus. The superior surface presents an internal, rough, non-articular por- tion, and an external or articular portion, which is convex, smooth, and articulates with the triangular interarticular fibro-cartilage of the wrist. The inferior sur- face, directed outward, is concave, sinuously curved, and smooth for articu- lation with the unciform. rV\\e posterior or dorsal surface is rough, for the attach- ment of ligaments. The anterior or palmar surface presents, at its inner side, an oval facet, for articulation with the pisiform ; and is rough externally, for liga- mentous attachment. The external surface, the base of the pyramid, is marked by a flat, quadrilateral, smooth facet, for articulation with the semilunar. The internal surface, the summit of the pyramid, is pointed and roughened, for the attachment of the internal lateral ligament of the wrist. Hold the bone with the surface supporting the pisiform facet away from you, and the concavo-convex surface for the unciform downward. The base of the wedge (i. e. the broad end of the bone) will be on the side to which it belongs. Articulations.-With three bones: the semilunar externally, the pisiform in front, the unciform below; and with the triangular, interarticular fibro-cartilage which separates it from the lower end of the ulna. The Pisiform (pisum, a pea ; forma, likeness) may be known by its small size and by its presenting a single articular facet. It is situated at the anterior and inner side of the carpus, is nearly circular in form, and presents on its posterior surface a smooth, oval facet, for articulation with the cuneiform. This facet approaches the superior, but not the inferior, border of the bone. The anterior or palmar surface is rounded and rough, and gives attachment to the anterior annular ligament and to the Flexor carpi ulnaris and Abductor minimi digiti muscles. The outer and inner surfaces are also rough, the former being convex, the latter usually concave. Hold the bone with the posterior surface-that which presents the articular 1 In these directions each bone is supposed to be placed in its natural position-that is, such a position as it would occupy when the arm is hanging by the side, the forearm in a position of supi- nation, the thumb being directed outward, and the palm of the hand looking forward. 77/Z-; CARPUS. 267 facet-toward you, in such a manner that the faceted portion of the surface is uppermost. The outer, convex surface will point to the side to which it belongs. Articulations.-With one bone, the cuneiform. Carpus. FLEXOR CARPI ULNARIS.* FLEXOR BREVIS MINIMI DIGITI.- Groove for tendon of < FLEXOR CARPI RADIALIS. FLEXOR OSSIS. CMETACARPI POLLICIS. EXTENSOR OSSIS. X"METACARPI POLLICIS. FLEXOR OSSIS METACARPI - MINIMI DIGITI. Metacarpris. Sesamoid ) bones. J ABDUCTOR POLLICIS. ABDUCTOR I I TRANSVERSUS. \ POLLICIS. FLEXOR BREVIS'' and ABDUCTOR MINIMI DIGITI.j flexor!/ \ BREVIS POLLICIS. ■ FLEXOR LONGUS POLLICIS. FLEXOR SUBLIMIS. FLEXOR < DIGITORUM PROFUNDUS. FLEXOR DIGITORUM SUBLIMIS. FLEXOR DIGITORUM PROFUNDUS. Fig. 205.-Bones of the left hand. Palmar surface. Attachment of Muscles.-To two: the Flexor carpi ulnaris and Abductor minimi digiti; and to the anterior annular ligament. 268 THE SKELETON. Bones of the Lower Row (Figs. 204, 205). The Trapezium a table) is of very irregular form. It may be distin- guished by a deep groove, for the tendon of the Flexor carpi radialis muscle. It is situated at the external and inferior part of the carpus, between the scaphoid and first metacarpal bone. The superior surface, concave and smooth, is directed upward and inward, and articulates with the scaphoid. The inferior surface, directed downward and inward, is oval, concave from side to side, convex from before backward, so as to form a saddle-shaped surface, for articulation with the base of the first metacarpal bone. The anterior or palmar surface is narrow and rough. At its upper part is a deep groove running from above obliquely down- ward and inward; it transmits the tendon of the Flexor carpi radialis, and is bounded externally by a prominent ridge, the oblique ridge of the trapezium. This surface gives attachment to the Abductor pollicis, Flexor ossis metacarpi pollicis, and Flexor brevis pollicis muscles, and the anterior annular ligament. The posterior or dorsal surface is rough. The external surface is also broad and rough, for the attachment of ligaments. The internal surface presents two articular facets: the upper one, large and concave, articulates with the trapezoid; the lower one, narrow and flattened, with the base of the second metacarpal bone. Hold the bone with the saddle-shaped surface downward and the grooved surface away from you. The prominent, rough, non-articular surface points to the side to which the bone belongs. Articulations.-With four bones : the scaphoid above, the trapezoid and second metacarpal bones internally, the first metacarpal below. Attachment of Muscles.-Abductor pollicis, Flexor ossis metacarpi pollicis, and part of the Flexor brevis pollicis. The Trapezoid is the smallest bone in the second row. It may be known by its wedge-shaped form, the broad end of the wedge forming the dorsal, the narrow end the palmar, surface, and by its having four articular surfaces touching each other and separated by sharp edges. The superior surface, quadrilateral in form, smooth, and slightly concave, articulates with the scaphoid. The inferior surface articulates with the upper end of the second metacarpal bone; it is convex from side to side, concave from before backward, and subdivided by an elevated ridge into two unequal lateral facets. The posterior or dorsal and anterior or palmar surfaces are rough, for the attachment of ligaments, the former being the larger of the two. The external surface, convex and smooth, articulates with the trapezium. The internal surface is concave and smooth in front, for articulation with the os magnum ; rough behind, for the attachment of an interosseous ligament. Hold the bone with the larger, non-articular surface toward you, and the smooth, quadrilateral articular surface upward. The convex, articular surface will point to the side to which the bone belongs.1 Articulations.-With four bones : the scaphoid above, second metacarpal bone below', trapezium externally, os magnum internally. The Os Magnum is the largest bone of the carpus, and occupies the centre of the wrist. It presents, above, a rounded portion or head, which is received into the concavity formed by the scaphoid and semilunar bones ; a constricted portion or neck; and, below, the body. The superior surface is rounded, smooth, and articulates with the semilunar. The inferior surface is divided by two ridges into three facets, for articulation with the second, third, and fourth metacarpal bones, that for the third (the middle facet) being the largest of the three. The posterior or dorsal surface is broad and rough; the anterior or palmar, narrow', rounded, and also rough, for the attachment of ligaments. The external surface articulates 1 Occasionally in a badly marked bone there is some difficulty in ascertaining to which side the bone belongs; the following method will sometimes be found useful: Hold the bone with its broader, non-articular surface upward, so that its sloping border is directed toward you. The border will slope to the side to which the bone belongs. THE METACARPUS. 269 with the trapezoid by a small facet at its anterior inferior angle, behind which is a rough depression for the attachment of an interosseous ligament. Above this is a deep and rough groove, which forms part of the neck and serves for the attachment of ligaments, bounded superiorly by a smooth, convex surface, for articulation with the scaphoid. The internal surface articulates with the unciform by a smooth, concave, oblong facet which occupies its posterior and superior parts, and is rough in front, for the attachment of an interosseous ligament. Hold the bone with the broader, non-articular surface toward you, and the head upward. The small, articular facet at the anterior inferior angle of the external surface will point to the side to which the bone belongs. Articulations.-With seven bones: the scaphoid and semilunar above; the second, third, and fourth metacarpal below; the trapezoid on the radial side; and the unciform on the ulnar side. Attachment of Muscles.-Part of the Adductor obliquus pollicis. The Unciform (uncus, a hook ; forma, likeness) may be readily distinguished by its wedge-shaped form and the hook-like process that projects from its palmar surface. It is situated at the inner and lower angle of the carpus, with its base downward, resting on the two inner metacarpal bones, and its apex directed upward and outward. The superior surface, the apex of the wedge, is narrow, convex, smooth, and articulates with the semilunar. The inferior surface articu- lates with the fourth and fifth metacarpal bones, the concave surface for each being separated by a ridge which runs from before backward. The posterior or dorsal surface is triangular and rough, for ligamentous attachment. The anterior or palmar surface presents, at its lower and inner side, a curved, hook-like pro- cess of bone, the unciform process, directed from the palmar surface forward and outward. It gives attachment by its apex to the annular ligament; by its inner surface to the Flexor brevis minimi digiti and the Flexor ossis metacarpi minimi digiti; and is grooved on its outer side, for the passage of the Flexor tendons into the palm of the hand. This is one of the four eminences on the front of the carpus to which the anterior annular ligament is attached, the others being the pisiform internally, the oblique ridge of the trapezium and the tuberosity of the scaphoid externally. The internal surface articulates with the cuneiform by an oblong facet cut obliquely from above, downward and inward. The external sur- face articulates with the os magnum by its upper and posterior part, the remaining portion being rough, for the attachment of ligaments. Hold the bone with the hooked process away from you, and the articular sur- face, divided into two parts, for the metacarpal bones, downward. The concavity of the process will be on the side to which the bone belongs. Articulations.-With five bones: the semilunar above, the fourth and fifth metacarpal below, the cuneiform internally, the os magnum externally. Attachment of Muscles.-To three : the Flexor brevis minimi digiti, the Flexor ossis metacarpi minimi digiti, the Flexor carpi ulnaris ; and to the anterior annular ligament. The Metacarpus. The Metacarpal Bones are five in number: they are long, cylindrical bones, presenting for examination a shaft and two extremities. Common Characters of the Metacarpal Bones. The Shaft is prismoid in form and curved longitudinally, so as to be convex in the longitudinal direction behind, concave in front. It presents three surfaces: two lateral and one posterior. The lateral surfaces are concave, for the attach- ment of the Interossei muscles, and separated from one another by a prominent line. The posterior or dorsal surface presents in its distal half a smooth, triangular, flattened area which is covered, in the recent state, by the tendons of the Extensor muscles. This triangular surface is bounded by two lines, which commence in small tubercles situated on the dorsal aspect of either side of the 270 THE SKELETON. digital extremity, and, running backward, converge to meet together a little behind the centre of the bone and form a ridge which runs along the rest of the dorsal surface to the carpal extremity. This ridge separates two lateral, sloping surfaces for the attachment of the Dorsal interossei muscles.1 To the tubercles on the digital extremities are attached the lateral ligaments of the metacarpo- phalangeal joints. The carpal extremity, or base, is of a cuboidal form, and broader behind than in front; it articulates above with the carpus, and on each side with the adjoining metacarpal bones ; its dorsal and palmar surfaces are rough, for the attachment of tendons and ligaments. The digital extremity, or head, presents an oblong surface, flattened at each side; it articulates with the proximal phalanx ; it is broader and extends farther forward in front than behind, and is longer in the antero-posterior than in the transverse diameter. On either side of the head is a tubercle for the attachment of the lateral ligament of the metacarpo-phalangeal joint. The posterior surface, broad and flat, supports the Extensor tendons; the anterior surface is grooved in the middle line for the passage of the Flexor tendons, and marked on each side by an articular eminence continuous with the terminal articular surface. The metacarpal bone of the thumb is shorter and wider than the rest, diverges to a greater degree from the carpus, and its palmar surface is directed inward toward the palm. The shaft is flattened and broad on its dorsal aspect, and does not present the ridge which is found on the other metacarpal bones; it is concave from before backward on its palmar surface. The carpal extremity, or base, presents a concavo-convex surface, for articulation with the trapezium; it has no lateral facets. The digital extremity is less convex than that of the other metacarpal bones, broader from side to side than from before backward, and terminates anteriorly in a small articular, eminence on each side, over which play two sesamoid bones. The side to which this bone belongs may be known by observing the little prominence which is situated on the outer or radial side of its posterior surface just above the base, for the tendon of the Extensor ossis metacarpi pollicis. If the bone is held with the palmar surface upward and the base toward the student, the prominence will point to the side to which the bone belongs. Another means by which the side to which the bone belongs may be ascertained is by holding it in the position it occupies in the hand, with the carpal extremity upward and the dorsal surface backward ; the narrower, radial border will point to the side to which it belongs. The metacarpal bone of the index finger is the longest and its base the largest of the other four. Its carpal extremity is prolonged upward and inward, forming a prominent ridge. The dorsal and palmar surfaces of this extremity are rough, for the attachment of tendons and ligaments. It presents four articular facets: three on the upper aspect of the base: the middle one of the three is the largest, concave from side to side, convex from before backward, for articulation with the trapezoid ; the external one is a small, flat, quadrilateral facet, for articulation with the trapezium; the internal one on the summit of the ridge is long and narrow, for articulation with the os magnum. The fourth facet is on the inner or ulnar side of the extremity of the bone, and is for articulation with the third metacarpal bone. The side to which this bone belongs is indicated by the absence of the lateral facet on the outer (radial) side of its base, so that if the bone is placed with its base toward the student and the palmar surface upward, the side on which there is no lateral facet will be that to which it belongs. Peculiar Characters of the Metacarpal Bones. 1 By these sloping surfaces the metacarpal bones of the hand may be at once differentiated from those of the foot. the metacarpus. 271 The metacarpal bone of the middle finger is a little smaller than the preceding: it presents a pyramidal eminence (the styloid process) on the radial side of its base (dorsal aspect) which extends upward behind the os magnum. The carpal, articular facet is concave behind, flat in front, and articulates with the os magnum. On the radial side is a smooth, concave facet, for articulation with the second metacarpal bone, and on the ulnar side two small, oval facets, for articulation with the fourth metacarpal. The side to which this bone belongs is easily recognized by the styloid pro- cess on the radial side of its base. With the palmar surface uppermost and the base toward the student, this process points toward the side to which the bone belongs. The metacarpal bone of the ring finger is shorter and smaller than the preced- ing, and its base small and quadrilateral; the carpal surface of the base present- ing two facets, for articulation with the unciform and os magnum. On the radial side are two oval facets, for articulation with the third metacarpal bone ; and on the ulnar side a single concave facet, for the fifth metacarpal. If this bone is placed with the base toward the student and the palmar surface upward, the radial side of the base, which has two facets for articulation with the third metacarpal bone, will be on the side to which it belongs. If, as sometimes happens in badly-marked bones, one of these facets is indistinguishable, the side may be known by selecting the surface on which the larger articular facet is present. This facet is for the fifth metacarpal bone, and would therefore be situated on the ulnar side ; that is, the one to which the bone does not belong. The metacarpal bone of the little finger presents on its base one facet, which is concavo-convex, and which articulates with the unciform bone, and one lateral, articular facet, which articulates with the fourth metacarpal bone. On its ulnar side is a prominent tubercle, for the insertion of the tendon of the Extensor carpi ulnaris. The dorsal surface of the shaft is marked by an oblique ridge which extends from near the ulnar side of the upper extremity to the radial side of the lower. The outer division of this surface serves for the attachment of the Fourth dorsal interosseous muscle; the inner division is smooth and covered by the Extensor tendons of the little finger. If this bone is placed with its base toward the student and its palmar surface upward, the side of the head which has a lateral facet will be that to which the bone belongs. Articulations.-Besides the phalangeal articulations, the first metacarpal bone articulates with the trapezium; the second with the trapezium, trapezoid, os magnum, and third metacarpal bones ; the third with the os magnum and second and fourth metacarpal bones; the fourth with the os magnum, unciform, and third and fifth metacarpal bones; and the fifth with the unciform and fourth metacarpal. The first has no lateral facets on its carpal extremity; the second has no lateral facet on its radial side, but one on its ulnar side; the third has one on its radial and two on its ulnar side; the fourth has two on its radial and one on its ulnar side; and the fifth has only one on its radial side. Attachment of Muscles.-To the metacarpal bone of the thumb, four: the Flexor ossis metacarpi pollicis, Flexor brevis pollicis, Extensor ossis metacarpi pollicis, and First dorsal interosseous. To the second metacarpal bone, seven: the Flexor carpi radialis, Extensor carpi radialis longior, Adductor transversus pollicis, Adductor obliquus pollicis, First and Second dorsal interosseous, and First palmar interosseous. To the third, six : the Extensor carpi radialis brevior, Flexor carpi radialis, Adductor transversus pollicis, Adductor obliquus pollicis, and Second and Third dorsal interosseous. To the fourth, three : the Third and Fourth dorsal and Second palmar interosseous. To the fifth, five ; the Extensor carpi ulnaris, Flexor carpi ulnaris, Flexor ossis metacarpi minimi digiti. Fourth dorsal and Third palmar interosseous. 272 THE SKELETON. The Phalanges. The Phalanges (internodid) are the bones of the fingers; they are fourteen in number, three for each finger, and two for the thumb. They are long bones, and present for examination a shaft and two extremities. The shaft tapers from above downward, is convex posteriorly, concave in front from above downward, fiat from side to side, and marked laterally by rough ridges, which give attachment to the fibrous sheaths of the Flexor tendons. The metacarpal extremity, or base, in the first row presents an oval, concave, articular surface, broader from side to side than from before backward; and the same extremity in the other two row's, a double concavity, separated by a longitudinal median ridge, extending from before backward. The digital extremities are smaller than the others, and terminate, in the first and second row's, in tw'o small, lateral condyles, separated by a slight groove; the articular surface being prolonged farther forward on the palmar than on the dorsal surface, especially in the first row. The Ungual Phalanges are convex on their dorsal, flat on their palmar, surfaces; they are recognized by their small size and by a roughened, elevated surface of a horseshoe form on the palmar aspect of their ungual extremity, which serves to support the sensitive pulp of the finger. Articulations.-The first row, with the metacarpal bones and the second row of phalanges; the second row, with the first and third; the third, with the second row. Attachment of Muscles.-To the base of the first phalanx of the thumb, five muscles : the Extensor brevis pollicis, Flexor brevis pollicis, Abductor pollicis, Adductor transversus and obliquus pollicis. To the second phalanx, two: the Flexor longus pollicis and the Extensor longus pollicis. To the base of the first phalanx of the index finger, the First dorsal and the First palmar interosseous ; to that of the middle finger, the Second and Third dorsal interosseous; to that of the ring finger, the Fourth dorsal and the Second palmar interosseous; and to that of the little finger, the Third palmar interosseous, the Flexor brevis minimi digiti, and Abductor minimi digiti. To the second phalanges, the Flexor sublimis digi- torum, Extensor communis digitorum, and, in addition, the Extensor indicis to the index finger, the Extensor minimi digiti to the little finger. To the third phalanges, the Flexor profundus digitorum and Extensor communis digitorum. Surface Form.-On the front of the wrist are two subcutaneous eminences, one on the radial side, the larger and flatter, due to the tuberosity of the scaphoid and the ridge on the trapezium; the other, on the ulnar side, caused by the pisiform bone. The tubercle of the scaphoid is to be felt just below and in front of the apex of the styloid process of the radius. It is best perceived by extending the hand on the forearm. Immediately below is to be felt another prominence, better marked than the tubercle ; this is the ridge on the trapezium which gives attachment to some of the short muscles of the thumb. On the inner side of the front of the wrist the pisiform bone is to be felt, forming a small but prominent projection in this situa- tion. It is some distance below the styloid process of the ulna, and may be said to be just below the level of the styloid process of the radius. The rest of the front of the carpus is covered by tendons and the annular ligament, and entirely concealed, with the exception of the hooked pro- cess of the unciform, which can only be made out with difficulty. The back of the carpus is convex and covered by the Extensor tendons, so that none of the posterior surfaces of the bones are to be felt, with the exception of the cuneiform on the inner side. Below the carpus the dorsal surfaces of the metacarpal bones, except the fifth, are covered by tendons, and are scarcely visible except in very thin hands. The dorsal surface of the fifth is, however, subcutaneous throughout almost its whole length, and is plainly to be perceived and felt. Tn addition to this, slightly external to the middle line of the hand, is a prominence, frequently well marked, but occasionally indistinct, formed by the base of the metacarpal of the middle finger. The heads of the metacarpal bones are plainly to be felt and seen, rounded in contour and standing out in bold relief under the skin, when the fist is clenched. It should be borne in mind that when the fin- gers are flexed on the hand, the articular surfaces of the first phalanges glide off the heads of the metacarpal bones on to their anterior surfaces, so that the heads of these bones form the prom- inence of the knuckles and receive the force of any blow which may be given. The head of the third metacarpal bone is the most prominent, and receives the greater part of the shock of the blow. This bone articulates with the os magnum, so that the concussion is carried through this bone to the scaphoid and semilunar, with which the head of the os magnum articulates, and by these bones is transferred to the radius, along which it may be carried to the capitellum of the humerus. The enlarged extremities of the phalanges are to be plainly felt: they form the DEVELOPMENT OF THE BONES OF THE HAND. 273 joints of the fingers. When the digits are bent the proximal phalanges of the joints form prominences, which in the joint between the first and second phalanges is slightly hollowed, in accordance with the grooved shape of their articular surfaces, whilst at the last row the prominence is flattened and square-shaped. In the palm of the hand the four inner metacarpal bones are covered by muscles, tendons, and the palmar fascia, and no part of them but their heads is to be distinguished. With regard to the thumb, on the dorsal aspect the base of the metacarpal bone forms a prominence below the styloid process of the radius; the shaft is to be felt, covered by tendons, terminating at its head in a flattened prominence, in front of which can be felt the sesamoid bones. Surgical Anatomy.-The carpal bones are little liable to fracture, except from extreme violence, when the parts are so comminuted as to necessitate amputation. Occasionally they are the seat of tubercular disease. The metacarpal bone and the phalanges are not unfrequently broken from direct violence. The first metacarpal bone is the one most commonly fractured; then the second, the fourth, and the fifth, the third being the one least frequently broken. There are two diseases of the metacarpal bones and phalanges which require special mention on account of the frequency of their occurrence. One is tubercular dactylitis, consisting in a deposit of tubercular material in the medullary canal, expanding the bone, with subsequent caseation and resulting necrosis. The other is chondroma, which is perhaps more frequently found in connection with the metacarpal bones and phalanges than with any other bones. They are commonly multiple, and may spring either from the medullary canal or from the periosteum. The Carpal Bones are each developed by a single centre. At birth they are all cartilaginous. Ossification proceeds in the following order (Fig. 206): In the Development of the Bones of the Hand Carpus. One centre for each bone. All cartilaginous at birth. .Appears 3rd year. Unite 30th year. Appears 8th week. Metacarpus. Two centres for each bone: One for shaft, One for digital extremity, except first. __ Appears '8th week. Unite 20th year. Phalanges. Appears 3rd year. Two centres for each bone One for shaft, Appears 3rd-hth £ year. One for metacarpal extremity. Unite 18th-20th year. 1st Row. Appears 8th week. -Appears Uh-5th year. 3rd Row. 2nd Row. Unite 18th-20th year. Appears 8th week. Appears ith-5th year. Unite 18th-20 year. -Appears 8th week. Fig. 206.-Plan of the development of the hand. os magnum and unciform an ossific point appears during the first year, the former preceding the latter ; in the cuneiform, at the third year; in the trapezium and semilunar, at the fifth year, the former preceding the latter; in the scaphoid, at 274 THE SKELETON. the sixth year; in the trapezoid, during the eighth year; and in the pisiform, about the twelfth year. The Metacarpal Bones are each developed by two centres : one for the shaft and one for the digital extremity for the .four inner metacarpal bones; one for the shaft and one for the base for the metacarpal bone of the thumb, which in this respect resembles the phalanges.1 Ossification commences in the centre of the shaft about the eighth or ninth week, and gradually proceeds to either end of the bone: about the third year the digital extremities of the four inner metacarpal bones and the base of the first metacarpal begin to ossify, and they unite about the twentieth year. The Phalanges are each developed by two centres: one for the shaft and one for the base. Ossification commences in the shaft, in all three rows, at about the eighth week, and gradually involves the whole of the bone excepting the upper extremity. Ossification of the base commences in the first row between the third and fourth years, and a year later in those of the second and third rows. The two centres become united, in each row, between the eighteenth and twentieth years. THE LOWER EXTREMITY. The Lower Extremity consists of three segments, the thigh, leg, and/eot, which correspond to the arm, forearm, and hand in the upper extremity. It is con- nected to the trunk through the os innominatum, or hip-bone, which forms the pelvic girdle. THE HIP. The Os Innominatum. The Os Innominatum (m, not; nomino, I name), or nameless bone, so called from bearing no resemblance to any known object, is a large, irregularly-shaped, flat bone, constricted in the centre and expanded above and below. With its fellow of the opposite side it forms the sides and anterior wall of the pelvic cavity. In young subjects it consists of three separate parts, which meet and form the large, cup-like cavity situated near the middle of the outer surface of the bone; and, although in the adult these have become united, it is usual to describe the bone as divisible into three portions-the ilium, the ischium, and the os pubis. The ilium, so called from its supporting the flank (z7za), is the superior, broad and expanded portion which runs upward from the upper and back part of the acetabulum and forms the prominence of the hip. The ischium the hip) is the inferior and strongest portion of the bone; it proceeds downward from the acetabulum, expands into a large tuberosity, and then, curving upward, forms with the descending ramus of the os pubis, a large aperture, the obturator foramen. The os pubis is that portion which runs horizontally inward from the inner side of the acetabulum for about two inches, then makes a sudden bend, and descends for about one inch : it forms the front of the pelvis, supports the external organs of generation, and has received its name from being covered with hair. The Ilium presents for examination two surfaces, an external and an internal; a crest, and two borders, an anterior and a posterior. External Surface or Dorsum of the Ilium (Fig. 207).-The back part of this surface is directed backward, downward, and outward; its front part, forward, downward, and outward. It is smooth, convex in front, deeply concave behind; bounded above by the crest, below by the upper border of the acetabulum ; in front and behind by the anterior and posterior borders. This surface is crossed in an arched direction by three semicircular lines-the superior, middle, and inferior curved lines. The superior curved line, the shortest of the three, commences at 1 Allan Thomson has demonstrated the fact that the first metacarpal bone is often developed from three centres ; that is to say, there is a separate nucleus for the distal end, forming a distinct epiph- ysis, visible at the age of seven or eight years. He also states that there are traces of a proximal epiphysis in the second metacarpal bone.-Journal of Anatomy, 1869. THE OS INNOMINATUM. 275 the crest, about two inches in front of its posterior extremity ; it is at first distinctly marked, but as it passes downward and outward to the upper part of the great sacro-sciatic notch, where it terminates, it becomes less marked, and is often altogether lost. Behind this line is a narrow semilunar surface, the upper part of which is rough and affords attachment to part of the Gluteus maximus; the lower Cr est Posterior superior, spine. Anterior superior spine. Posterior inferior- spine. Anterior inferior spine. GEMELLUS SUPERIOR. < Spine of ischium.r Ilio-pectineal line for Gimbernat's ligament. Spine of os pubis for POUpart'S LIGAMENT. GEMELLUS INFERIOR.' .Angle of os pubis. RECTUS ABDOMINIS. PYRAMIDALIS. Fig. 207.-Right os innominatum. External surface. part is smooth and has no muscular fibres attached to it. The middle curved line, the longest of the three, commences at the crest, about an inch behind its anterior extremity, and, taking a curved direction downward and backward, terminates at the upper part of the great sacro-sciatic notch. The base between the superior and middle curved lines and the crest is concave, and affords attachment to the Gluteus medius muscle. Near the central part of this line may often be observed the ori- fice of a nutrient foramen. The inferior curved line, the least distinct of the three, commences in front at the upper part of the anterior inferior spinous process, and, 276 THE SKELETON. taking a curved direction backward and downward, terminates at the middle of the great sacro-sciatic notch. The surface of bone included between the middle and inferior curved lines is concave from above downward, convex from before backward, and affords attachment to the .Gluteus minimus muscle. Beneath the inferior curved line, and corresponding to the upper part of the acetabulum, is a roughened surface (sometimes a depression), to which is attached the reflected tendon of the Rectus femoris muscle. The Internal Surface (Fig. 208) of the ilium is bounded above by the crest ; below it is- continuous with the pelvic surface of the os pubis and ischium, a faint ANI. / COMPRESSOR URETHRAE. Crus penis. 'transversus perinei. Fig. 208.-Right os innominatum. Internal surface. ERECTOR PENIS. line only indicating the place of union; and before and behind it is bounded by the anterior and posterior borders. It presents anteriorly a large, smooth, concave surface, called the internal iliac fossa, or venter of the ilium, which lodges the Iliacus muscle, and presents at its lower part the orifice of a nutrient canal; and below this a smooth, rounded border, the linea ilio-pectinea, which separates the iliac fossa from that portion of the internal surface which enters into the formation THE OS INNOMINATUM. 277 of the true pelvis, and which gives attachment to part of the Obturator internus muscle. Behind the iliac fossa is a rough surface divided into two portions, an anterior and a posterior. The anterior or auricular portion, so called from its resemblance in shape to the ear, is coated with cartilage in the recent state, and articulates with a surface of similar shape on the side of the sacrum. The posterior portion is rough, for the attachment of the posterior sacro-iliac ligaments and for a part of the origin of the Erector spinae. The crest of the ilium is convex in its general outline and sinuously curved, being bent inward anteriorly, outward posteriorly. It is longer in the female than in the male, very thick behind, and thinner at the centre than at the extrem- ities. It terminates at either end in a prominent eminence, the anterior superior and posterior superior spinous process. The surface of the crest is broad, and divided into an external lip, an internal lip, and an intermediate space. To the external lip is attached the Tensor vagina femoris, Obliquus externus abdominis, and Latissimus dorsi, and by its whole length the fascia lata; to the space between the lips, the Internal oblique ; to the internal lip, the Transversalis, Quadratus lumborum, and Erector spinae, the Iliacus, and the fascia iliaca. The anterior border of the ilium is concave. It presents two projections, separated by a notch. Of these, the uppermost, situated at the junction of the crest and anterior border, is called the anterior superior spinous process of the ilium, the outer border of which gives attachment to the fascia lata and the origin of the Tensor vaginae femoris; its inner border, to the Iliacus; whilst its extremity affords attachment to Poupart's ligament and the origin of the Sartorius. Beneath this eminence is a notch which gives attachment to the Sartorius muscle, and across which passes the external cutaneous nerve. Below the notch is the anterior inferior spinous process, which terminates in the upper lip of the acetabulum ; it gives attachment to the straight tendon of the Rectus femoris muscle and the ilio-femoral ligament. On the inner side of the anterior inferior spinous process is a broad, shallow groove, over which passes the Iliacus muscle. This groove is bounded internally by an eminence, the ilio-pectineal, which marks the point of union of the ilium and os pubis. The posterior border of the ilium, shorter than the anterior, also presents two projections separated by a notch, the posterior superior and the posterior inferior spinous processes. The former corresponds with that portion of the posterior surface of the ilium which serves for the attachment of the oblique portion of the sacro-iliac ligaments and the Multifidus spinee; the latter to the auricular portion which articulates with the sacrum. Below the posterior inferior spinous process is a deep notch, the great sacro-sciatic. The Ischium forms the lower and back part of the os innominatum. It is divisible into a thick and solid portion, the body ; a large, rough eminence, on which the body rests in sitting, the tuberosity; and a thin, ascending part, the ramus. The body, somewhat triangular in form, presents three surfaces, external, internal, and posterior; and three borders, external, internal, and posterior. The external surface corresponds to that portion of the acetabulum formed by the ischium ; it is smooth and concave, and forms a little more than two-fifths of the acetabular cavity ; its outer margin is bounded by a prominent rim or lip, the external border, to which the cotyloid fibro-cartilage is attached. Below the acetabulum, between it and the tuberosity, is a deep groove, along which the tendon of the Obturator externus muscle runs as it passes outward to be inserted into the digital fossa of the femur. The internal surface is smooth, concave, and enters into the formation of the lateral boundary of the true pelvic cavity. This surface is perforated by two or three large, vascular foramina, and affords attachment to part of the Obturator internus muscle. The posterior surface is quadrilateral in form, broad and smooth. Below, where it joins the tuberosity, it presents a groove continuous with that on the external surface, for the tendon of the Obturator externus muscle. The lower edge of this groove is formed by the tuberosity of the ischium, and affords attachment to the Gemellus inferior muscle. This surface is 278 THE SKELETON. limited, in front, by the margin of the acetabulum ; behind, by the posterior border; it supports the Pyriformis, the two Gemelli, and the Obturator internus muscles in their passage outward to the great trochanter. The external border forms the prominent rim of the acetabulum, and separates the posterior from the external surface. To it is attached the cotyloid fibro-cartilage. The internal border is thin, and forms the outer circumference of the obturator foramen. The posterior border of the body of the ischium presents, a little below the centre, a thin and pointed, triangular eminence, the spine of the ischium, more or less elongated in different subjects; its external surface gives attachment to the Gemellus superior, its internal surface to the Coccygeus and Levator ani; whilst to the pointed extremity is connected the lesser sacro-sciatic ligament. Above the spine is a notch of a large size, the great sacro-sciatic, converted into a foramen by the lesser sacro-sciatic ligament; it transmits the Pyriformis muscle, the gluteal vessels and superior gluteal nerve passing out of the pelvis above the muscles; the sciatic vessels, the greater and lesser sciatic nerves, the internal pudic vessels and nerve, and muscular branches from the sacral plexus below it. Below the spine is a smaller notch, the lesser sacro-sciatic; it is smooth, coated in the recent state with cartilage, the surface of which presents numerous markings corresponding to the subdivisions of the tendon of the Obturator internus, which winds over it. It is converted into a foramen by the sacro-sciatic ligaments, and transmits the tendon of the Obturator internus, the nerve which supplies that muscle, and the internal pudic vessels and nerve. The tuberosity presents for examination three surfaces: external, internal, and inferior. The external surface is quadrilateral in shape, and rough for the attach- ment of muscles. It is bounded above by the groove for the tendon of the Obturator externus ; in front it is limited by the posterior margin of the obturator foramen, and below it is continuous with the ramus of the bone; behind, it is bounded by a prominent margin which separates it from the inferior surface. In front of this margin the surface gives attachment to the Quadratus femoris, and anterior to this to some of the fibres of origin of the Obturator externus. The lower part of the surface gives origin to part of the Adductor magnus. The internal surface forms part of the bony wall of the true pelvis. In front it is limited by the posterior margin of the obturator foramen. Behind, it is bounded by a sharp ridge, for the attachment of a falciform prolongation of the great sacro-sciatic ligament; it presents a groove on the inner side of this for the lodgment of the internal pudic vessels and nerve; and, more anteriorly, has attached the Transversus perinaei and Erector penis muscles. The inferior surface is divided into two portions-an anterior, rough, somewhat triangular part, and a posterior, smooth, quadrilateral portion. The anterior surface is subdivided by a prominent vertical ridge, passing from base to apex, into two parts; the outer one gives attachment to the Adductor magnus; the inner to the great sacro-sciatic ligament. The posterior portion is subdivided into two facets by an oblique ridge which runs forward and outward; from the upper and outer facet arises the Semimembranosus; from the lower and inner, the Biceps and Semitendinosus. The ramus, or ascending ramus, is the thin, flattened part of the ischium which ascends from the tuberosity upward and inward, and joins the ramus of the os pubis, their point of junction being indicated in the adult by a rough line. The outer surface of the ramus is rough, for the attachment of the Obturator externus muscle, and also some fibres of the Adductor magnus; its inner surface forms part of the anterior wall of the pelvis. Its inner border is thick, rough, slightly everted, forms part of the outlet of the pelvis, and presents two ridges and an intervening space. The ridges are continuous with similar ones on the descending ramus of the os pubis : to the outer one is attached the deep layer of the superficial perineal fascia, and to the inner the anterior layer of the triangular ligament of the perinaeum. If these two ridges are traced downward, they will be found to join with each other just behind the point of origin of the Transversus perinaei muscle; here the two layers of fascia are continuous behind the posterior border of the muscle. To the inter- THE OS INNO MINA TUM. 279 vening space, just in front of the point of junction of the ridges, is attached the Transversus perinaei muscle, and in front of this a portion of the crus penis vel clitoridis and the Erector penis vel clitoridis muscle. Its outer border is thin and sharp, and forms part of the inner margin of the obturator foramen. The Os Pubis forms the anterior part of the os innominatum, and, with the bone of the opposite side, forms the front boundary of the true pelvic cavity. It is divisible into a body, a horizontal ramus, and a descending ramus. The body is somewhat quadrilateral in shape, and presents for examination two surfaces and three borders. The anterior surface is rough, directed forward and outward, and serves for the attachment of various muscles. To the upper and inner angle, immediately below the crest, is attached the Adductor longus; lower down, from without inward, are attached the Obturator externus, the Adductor brevis, and the upper part of the Gracilis. The posterior surface, convex from above downward, concave from side to side, is smooth, and forms part of the anterior wall of the pelvis. It gives attachment to the Levator ani, Obturator internus, a few muscular fibres prolonged from the bladder, and the pubo-prostatic ligaments. The upper border presents for examination a prominent tubercle, which projects forward and is called the spine ; to it is attached the outer pillar of the external abdominal ring and Poupart's ligament. Passing outward from this is a promi- nent ridge, forming part of the ilio-pectineal line, which, running outward, marks the brim of the true pelvis: to it is attached a portion of the conjoined tendon of the Internal oblique and Transversalis muscles, Gimbernat's ligament, and the triangular ligament of the abdomen. Internal to the spine of the os pubis is the crest, which extends from this process to the inner extremity of the bone. It affords attachment anteriorly to the conjoined tendon of the Internal oblique and Transversalis, and posteriorly to the Rectus and Pyramidalis muscles. The point of junction of the crest with the inner border of the bone is called the angle ; to it, as well as to the symphysis, is attached the internal pillar of the external abdominal ring. The interior border is the symphysis; it is oval, covered by eight or nine transverse ridges, or a series of nipple-like processes arranged in rows, separated by grooves; they serve for the attachment of a thin layer of cartilage placed between it and the central fibro-cartilage. The outer border presents a sharp margin which forms part of the circumference of the obturator foramen and affords attachment to the obturator membrane. The horizontal ramus extends from the body to the point of junction of the os pubis with the ilium, and forms the upper part of the circumference of the obturator foramen. It presents for examination a superior, inferior, and posterior surface, and an outer extremity. The superior surface presents a continuation of the ilio-pectineal line, already mentioned as commencing on the body of the bone. In front of this ridge the surface of bone is triangular in form, wider externally than internally, smooth, and affords attachment to the Pectineus muscle. The surface is bounded externally by a rough eminence, the ilio-pectineal, which serves to indicate the point of junction of the ilium and pubes, and gives attachment to the Psoas parvus when this muscle is present. The inferior surface forms the upper boundary of the obturator foramen, and presents externally a broad and deep oblique groove, for the passage of the obturator vessels and nerve; and internally a sharp margin which forms part of the circumference of the obturator foramen, and to which the obturator membrane is attached. The posterior surface forms part of the anterior boundary of the true pelvis. It is smooth, convex from above downward, and affords attachment to the upper fibres of the obturator internus. The outer extremity, the thickest part of the ramus, forms one-fifth of the cavity of the acetabulum. The descending ramus of the os pubis is thin and flattened. It passes outward and downward, becoming narrower as it descends, and joins with the ramus of the ischium. Its anterior surface is rough, for the attachment of muscles-the Gracilis along its inner border ; a portion of the Obturator externus where it enters into the formation of the foramen of that name; and between these two muscles the 280 THE SKELETON. Adductores brevis and magnus from within outward. The posterior surface is smooth, and gives attachment to the Obturator internus and, close to the inner margin, to the Compressor urethrae. The inner border is thick, rough, and everted, especially in females. It presents two ridges, separated by an intervening space. The ridges extend downward, and are continuous with similar ridges on the ascending ramus of the ischium; to the external one is attached the deep layer of the superficial perineal fascia, and to the internal one the anterior layer of the triangular ligament of the perinmum. The outer border is thin and sharp, forms part of the circumference of the obturator foramen, and gives attachment to the obturator membrane. The cotyloid cavity, or acetabulum, is a deep, cup-shaped, hemispherical depression, directed downward, outward, and forward ; formed internally by the os pubis, above by the ilium, behind and below by the ischium, a little less than two-fifths being formed by the ilium, a little more than two-fifths by the ischium, and the remaining fifth by the pubic bone. It is bounded by a prominent, uneven rim, which is thick and strong above, and serves for the attachment of a fibro- cartilaginous structure which contracts its orifice and deepens the surface for articulation. It presents, on its inner side, a deep notch, the cotyloid notch, w hich is continuous with a circular depression, the fossa acetabuli, at the bottom of the cavity: this depression is perforated by numerous apertures, lodges a mass of fat, and its margins, as well as those of the notch, serve for the attachment of the ligamentum teres. The notch is converted, in the natural state, into a foramen by a dense ligamentous band which passes across it. Through this foramen the nutrient vessels and nerves enter the joint. The obturator or thyroid foramen is a large aperture situated between the ischium and os pubis. In the male it is large, of an oval form, its longest diameter being obliquely from above downward; in the female it is smaller and more triangular. It is bounded by a thin, uneven margin to which a strong membrane is attached; and presents at its upper and outer part a deep groove which runs from the pelvis obliquely forward, inward, and downward. This groove is converted into a foramen by the obturator membrane, and transmits the obturator vessels and nerve. Structure.-This bone consists of much cancellous tissue, especially where it is thick, enclosed between two layers of dense, compact tissue. In the thinner parts of the bone, as at the bottom of the acetabulum and centre of the iliac fossa, it is usually semitransparent, and composed entirely of compact tissue. Development (Fig. 209).-By eight centres : three primary-one for the ilium, one for the ischium, and one for the os pubis ; and five secondary-one for the crest of the ilium, one for the anterior inferior spinous process (said to occur more frequently in the male than the female), one for the tuberosity of the ischium, one for the symphysis pubis (more frequent in the female than the male), and one for the Y-shaped piece at the bottom of the acetabulum. These various centres appear in the following order: First, in the ilium, at the lower part of the bone, imme- diately above the sciatic notch, at about the eighth or ninth week ; secondly, in the body of the ischium, at about the third month of foetal life ; thirdly, in the body of the os pubis, between the fourth and fifth months. At birth the three primary centres are quite separate, the crest, the bottom of the acetabulum, and the rami of the ischium and pubes being still cartilaginous. At about the seventh or eighth year the rami of the os pubis and ischium are almost completely ossified. About the thirteenth or fourteenth year the three divisions of the bone have extended their growth into the bottom of the acetabulum, being separated from each other by a Y-shaped portion of cartilage, which now presents traces of ossification, often by two or more centres. The ilium and ischium then become joined, and lastly the os pubis, through the intervention of this Y-shaped portion. At about the age of puberty ossification takes place in each of the remaining portions, and they become joined to the rest of the bone about the twenty-fifth year. Articulations.-With its fellow of the opposite side, the sacrum, and femur. THE PELVIS. 281 Attachment of Muscles.-To the ilium, sixteen. To the outer lip of the crest, the Tensor vaginae femoris, Obliquus externus abdominis, and Latissimus dorsi; to the internal lip, the Iliacus, Transversalis, Quadratus lumborum, and Erector spinae ; to the interspace between the lips, the Obliquus internus. To the outer surface of the ilium, the Gluteus maximus, Gluteus medius, Gluteus minimus, reflected tendon of the Rectus; to the upper part of the great sacro-sciatic notch, a portion of the Pyriformis; to the internal surface, the Iliacus; to that portion of the internal surface below the linea ilio-pectinea, the Obturator internus, and the Multifidus spinae to the internal surface of the posterior superior spine; to the anterior border, the Sartorius and straight tendon of the Rectus. To thewAium, fourteen. To the outer surface of the ramus, the Obturator externus and Adductor magnus ; to the internal surface, the Obturator internus and Erector penis. To the spine, the Gemellus superior, Levator ani, and Coccygeus. To the tuberosity, the Biceps, Semitendinosus, Semimembranosus, Quadratus femoris, Adductor magnus, By eight centres Three primary (Ilium, Ischium, and Os Pubis'). Five Secondary. 8. Symphysis pubis. The three primary centres unite through Y-shaped piece about puberty. Epiphyses appear about puberty, and unite about 25th year. Fig. 209.-Plan of the development of the os Innominatum. Gemellus inferior, Transversus perinaei, Erector penis. To the os ptibis, sixteen: Obliquus externus, Obliquus internus, Transversalis, Rectus, Pyramidalis, Psoas parvus, Pectineus, Adductor magnus, Adductor longus. Adductor brevis, Gracilis, Obturator externus and internus, Levator ani, Compressor urethrae, and occasion- ally a few fibres of the Accelerator urinae. The Pelvis, so called from its resemblance to a basin (L. pelvis), is stronger and more massively constructed than either the cranial or thoracic cavity; it is a bony ring, interposed between the lower end of the spine, which it supports, and the lower extremities, upon which it rests. It is composed of four bones : the two ossa innominati, which bound it on either side and in front, and the sacrum and coccyx, which complete it behind. The pelvis is divided by a plane passing through the prominence of the sacrum, The Pelvis (Figs. 210, 211). 282 THE SKELETON. • . . . . the linea ilio-pectinea, and the upper margin of the symphysis pubis into the false and true pelvis. The false pelvis is all that expanded portion of the pelvic cavity which is situated above this plane. It is bounded on each side by the ossa ilii; in front it Fig. 210.-Male pelvis (adult). is incomplete, presenting a wide interval between the spinous processes of the ilia on either side, which is filled up in the recent state by the parietes of the abdomen ; Fig. 211.-Female pelvis (adult). behind, in the middle line, is a deep notch. This broad, shallow cavity is fitted to support the intestines and to transmit part of their weight to the anterior wall of the abdomen, and is, in fact, really a portion of the abdominal cavity. The term false pelvis is incorrect, and this space ought more properly to be regarded as part of the hypogastric region of the abdomen. The true pelvis is all that part of the pelvic cavity which is situated beneath THE PELVIS. 283 the plane. It is smaller than the false pelvis, but its walls are more perfect. For convenience of description it is divided into a superior circumference or inlet, an inferior circumference or outlet, and a cavity. The superior circumference forms the margin or brim of the pelvis, the included space being called the mZet It is formed by the linea ilio-pectinea, completed in front by the crests of the pubic bones, and behind by the anterior margin of the base of the sacrum and sacro-vertebral angle. The inlet of the pelvis is somewhat heart- shaped, obtusely pointed in front, diverging on either side, and encroached upon behind by the projection forward of the promontory of the sacrum. It has three principal diameters : antero-posterior (sacro-pubic), transverse, and oblique. The antero-posterior extends from the sacro-vertebral angle to the symphysis pubis; its average measurement is four inches in the male, four and three-quarters in the female. The transverse extends across the greatest width of the inlet, from the middle of the brim on one side to the same point on the opposite; its average measurement is four and a half in the male, five and a quarter in the female. The oblique extends from the margin of the pelvis, corresponding to the ilio- pectineal eminence on one side, to the sacro-iliac symphysis on the opposite side; its average measurement is four and a quarter in the male, and five in the female. The cavity of the true pelvis is bounded in front by the symphysis pubis; behind, by the concavity of the sacrum and coccyx, which, curving forward above and below, contracts the inlet and outlet of the canal; and laterally it is bounded by a broad, smooth, quadrangular surface of bone, corresponding to the inner surface of the body of the ischium and that part of the ilium which is below the ilio-pectineal line. The cavity is shallow in front, measuring at the symphy- sis an inch and a half in depth, three inches and a half in the middle, and four inches and a half posteriorly. From this description it will be seen that the cavity of the pelvis is a short, curved canal, considerably deeper on its posterior than on its anterior wall, and broader in the middle than at either extremity, from the projection forward of the sacro-coccygeal column above and below. This cavity contains, in the recent subject, the rectum, bladder, and part of the organs of generation. The rectum is placed at the back of the pelvis, and corresponds to the curve of the sacro-coccygeal column ; the bladder in front, behind the symphysis pubis. In the female the uterus and vagina occupy the interval between these parts. The lower circumference of the pelvis is very irregular, and forms what is called the outlet. It is bounded by three prominent eminences: one posterior, formed by the point of the coccyx ; and one on each side, the tuberosities of the ischia. These eminences are separated by three notches; one in front, the pubic arch, formed by the convergence of the rami of the ischia and pubic bones on each side. The other notches, one on each side, are formed by the sacrum and coccyx behind, the ischium in front, and the ilium above ; they are called the sacro-sciatic notches ; in the natural state they are converted into foramina by the lesser and greater sacro-sciatic ligaments. In the recent state, when the ligaments are m situ, the outlet of the pelvis is lozenge-shaped, bounded in front by the subpubic liga- ment and the rami of the os pubis and ischium ; on each side by the tuberosities of the ischia ; and behind by the great sacro-sciatic ligaments and the tip of the coccyx. The diameters of the outlet of the pelvis are two, antero-posterior and trans- verse. The antero-posterior extends from the tip of the coccyx to the lower part of the symphysis pubis; its average measurement is three and a quarter inches in the male and five in the female. The antero-posterior diameter varies with the length of the coccyx, and is capable of increase or diminution on account of the mobility of that bone.1 The transverse extends from the posterior part of one 1 The measurements of the pelvis given above are, I believe, fairly accurate, but different meas- urements are given by various authors, no doubt due in a great measure to differences in the phys- ique and stature of the population from whom the measurements have been taken. The accompany- 284 THE SKELETON. ischiatic tuberosity to the same point on the opposite side : the average measurement is three and a half inches in the male and four and three-quarters in the female. Position of the Pelvis.-In the erect posture the pelvis is placed obliquely with regard to the trunk of the body : the bony ring, which separates the true from the false pelvis, and which forms the essential part of the pelvis, is placed so as to form an angle of about 60° to 65° with the ground on which we stand. The pelvic surface of the symphysis pubis looks upward and backward, the concavity of the sacrum and coccyx downward and forward, the base of the sacrum in well- formed female bodies being nearly four inches above the upper border of the symphysis pubis, and the apex of the coccyx a little more than half an inch above its lower border. The obliquity is much greater in the foetus and at an early period of life than in the adult. In consequence of this obliquity of the pelvis the line of gravity of the head, which passes through the middle of the odontoid process of the axis and through the points of junction of the curves of the vertebral column to the sacro-vertebral angle, descends toward the front of the cavity, so that it bisects a line drawn transversely through the middle of the heads of the thigh-bones. And thus the centre of gravity of the head is placed immediately over the heads of the thigh-bones on which the trunk is supported. Axes of the Pelvis (Fig. 212).-The plane of the inlet of the true pelvis will be represented by a line drawn from the base of the sacrum to the upper margin of the symphysis pubis. A line carried at right angles with this at its middle would correspond at one extremity with the umbilicus, and at the other with the middle of the coccyx : the axis of the inlet is therefore directed downward and backward. The axis of the outlet, produced upward, would touch the base of the sacrum, and is therefore directed downward and forward. The axis of the cavity is curved like the cavity itself: this curve corresponds to the concavity of the sacrum and coccyx, the extremities being indicated by the central points of the inlet and outlet. A knowledge of the direction of these axes serves to explain the course of the foetus in its passage through the pelvis during parturition. It is also important to the surgeon, as indicating the direction of the force required in the removal of calculi from the bladder, and as determining the direction in which instruments should be used in operations upon the pelvic viscera. Differences between the Male and Female Pelvis.-The female pelvis, looked at as a whole, is distinguished from the male by the bones being more delicate, by its width being greater and its depth smaller. The whole pelvis is less massive, and its bones are lighter and more slender, and its muscular impressions are slightly marked. The iliac fossae are broad and expanded, and the anterior iliac spines widely separated; hence the greater prominence of the hips. The inlet in the female is larger than in the male; it is more nearly circular, and the sacro-vertebral angle projects less forward. The cavity is shallower and wider; the sacrum is shorter and wider, and its lower half forms a greater angle with its upper; the obturator foramina are triangular, and smaller in size than in the male. The outlet is larger and the coccyx more movable. The spines of the ischia project less in- Fig. 212.-Vertical section of the pel- vis, with lines indicating the axes of the pelvis. ing chart has been formulated to show the measurements of the pelvis, which are adopted by many obstetricians.-Ed. a. p. Obi. Tr. Inlet 4 41 5 Cavity 4J 4| 4£ Outlet 5 41 4 THE PELVIS. 285 ward. The tuberosities of the ischia and the acetabula are wider apart. The pubic arch is wider and more rounded than in the male, where it is an angle rather than an arch ; its pillars are somewhat excavated, and sloped from within outward, so that their inner surfaces look forward. In consequence of this the width of the fore part of the pelvic outlet is much increased and the passage of the foetal head facilitated. The size of the pelvis varies, not only in the two sexes, but also in different members of the same sex. This does not appear to be influenced in any way by the height of the individual. Women of short stature, as a rule, have broad pelves. Occasionally the pelvis is equally contracted in all its dimensions, so much so that all its diameters measure an inch less than the average, and this even in women of average height and otherwise well formed. The principal divergences, however, are found at the inlet, and affect the relation of the antero-posterior to the transverse diameter. Thus we may have a pelvis the inlet of which is elliptical either in a transverse or antero-posterior direction ; the transverse diameter in the former and the antero-posterior in the latter greatly exceeding the other diameters. Again, the inlet of the pelvis in some instances is seen to be almost circular. The same differences are found in various races. European women are said to have the most roomy pelves. That of the negress is smaller, circular in shape, and with a narrow pubic arch. The Hottentots and Bushwomen possess the smallest pelves. In the foetus and for several years after birth the pelvis is small in proportion to that of the adult. The cavity is deep, and the projection of the sacro-vertebral angle less marked. The antero-posterior and transverse diameters are nearly equal. About puberty the pelvis in both sexes presents the general characters of the adult male pelvis; but after puberty it acquires its proper sexual characters. Surface Form.-The pelvic bones are so thickly covered with muscles that it is only at cer- tain points that they approach the surface and can be felt through the skin. In front, the anterior superior spinous process is easily to be recognized; a portion of it is subcutaneous, and in thin subjects may be seen to stand out as a prominence at the outer extremity of the fold of the groin. In fat subjects its position'is marked by an oblique depression amongst the sur- rounding fat, at the bottom of which the bony process may be felt. Proceeding upward and outward from this process, the crest of the ilium may be traced throughout its whole length, sinuously curved. It is represented, in muscular subjects, on the surface, by a groove or fur- row, the iliac furrow, caused by the projection of fleshy fibres of the External oblique muscle of the abdomen. It terminates behind in the posterior superior spinous process, the position of which is indicated by a slight depression on a level with and on each side of the spinous process of the second sacral vertebra. Between the two posterior superior spinous processes, but at a lower level, is to be felt the spinous process of the third sacral vertebra (see page 164). Another part of the bony pelvis which is easily accessible to the touch is the tuberosity of the ischium, situated beneath the gluteal fold, and, when the hip is flexed, easily to be felt, as it is then to a great extent uncovered by muscle. Finally, the spine of the os pubis can always be readily felt, and constitutes an important surgical guide, especially in connection with the sub- ject of hernia. It is nearly in the same horizontal line with the upper edge of the great tro- chanter. In thin subjects it is very apparent, but in the obese it is obscured by the pubic fat. It can, however, be detected by following up the tendon of origin of the Adductor longus muscle. Surgical Anatomy.-There is arrest of development in the bones of the pelvis in cases of extroversion of the bladder; the anterior part of the pelvic girdle being deficient, the bodies of the pubic bones imperfectly developed, and the symphysis absent. The pubic bones are separated to the extent of from two to four inches, the superior rami shortened and directed forward, and the obturator foramen diminished in size, narrowed, and turned outward. The iliac bones are straightened out more than normal. The sacrum is very peculiar. The lateral curve, instead of being concave, is flattened out or even convex, with the ilio-sacral facets turned more outward than normal, while the vertical curve is straightened.1 Fractures of the pelvis are divided into fractures of the false pelvis and of the true pelvis. Fractures of the false pelvis vary in extent: a small portion of the crest may be broken or one of the spinous processes may be torn off, and this may be the result of muscular action ; or the bone may be extensively comminuted. This latter accident is the result of some crushing vio- lence, and may be complicated with fracture of the true pelvis. These cases may be accom- panied by injury to the intestine as it lies in the hollow of the bone, or to the iliac vessels as they course along the margin of the true pelvis. Fractures of the true pelvis generally occur through the horizontal ramus of the os pubis and the ascending ramus of the ischium, as this is the weakest part of the bony ring, and may be caused either by crushing violence applied 1 Wood. Heath's Dictionary of Practical Surgery, i. 426. 286 THE SKELETON. in an antero-posterior direction, when the fracture occurs from direct force, or by compression laterally, when the acetabula are pressed together, and the bone gives way in the same place from indirect violence. Occasionally the fracture may be double, occurring on both sides of the body. It is in these cases that injury to the contained viscera is liable to take place : the urethra, the bladder, the rectum, the vagina in the female, the small intestines, and even the uterus, have all been lacerated by a displaced fragment. Fractures of the acetabulum are occasionally met with : either a portion of the rim may be broken off, or a fracture may take place through the bottom of the cavity, and the head of tRe femur driven inward and project into the pelvic cavity. Separation of the Y-shaped cartilage at the bottom of the acetabulum may also occur in the young subject, separating the bone into its three anatomical portions. The sacrum is occasionally, but rarely, broken by direct violence-i. e. blows, kicks, or falls on the part. The lesion may be complicated with injury to the nerves of the sacral plexus, leading to paralysis and loss of sensation in the lower extremity, or to incontinence of faeces from paralysis of the sphincter ani. The pelvic bones often undergo important deformity in rickets, the effect of which in the adult woman may interfere seriously with childbearing. In consequence of the yielding nature of the bones, the acetabula become approximated, the symphysis is pushed forward, and the antero-posterior diameter lessened. In osteo-malacia also great deformity may occur, the pelvis becoming beak-shaped. The promontory of the sacrum is pushed forward by the weight of the body, and the sides of the pelvis are approximated by the pressure of the two thigh-bones: this gives to the pelvis the peculiar deformity which is characteristic of this disease. The Femur, or Thigh-Bone. THE THIGH. The Femur (femur, the thigh) is the longest,1 largest, and strongest bone in the skeleton, and almost perfectly cylindrical in the greater part of its extent. In the erect posture it is not vertical, being separated from its fellow above by a considerable interval, which corresponds to the- entire breadth of the pelvis, but inclining gradually downward and inward, so as to approach its fellow toward its lower part, for the purpose of bringing the knee-joint near the line of gravity of the body. The degree of this inclination varies in different persons, and is greater in the female than the male, on account of the greater breadth of the pelvis. The femur, like other long bones, is divisible into a shaft and two extremities. The Upper Extremity presents for examination a head, a neck, and the great and lesser trochanters. The head, which is globular, and forms rather more than a hemisphere, is directed upward, inward, and a little forward, t"he greater part of its convexity being above and in front. Its surface is smooth, coated with cartilage in the recent state, except at a little behind and below its centre, where is an ovoid depression, for the attachment of the ligamentum teres. The neck is a flattened pyramidal process of bone which connects the head with the shaft. It varies in length and obliquity at various periods of life and under different circumstances. The angle is widest in infancy, and becomes lessened during growth, so that at puberty it forms a gentle curve from the axis of the shaft. In the adult it forms an angle of about 130° with the shaft, but varies in inverse proportion to the development of the pelvis and the stature. In consequence of the prominence of the hips and widening of the pelvis in the female, the neck of the thigh-bone forms more nearly a right angle with the shaft than it does in man. It has been stated that the angle diminishes in old age and the direction of the neck becomes horizontal, but this statement is founded on insufficient evidence. Sir George Humphry states that the angle decreases during the period of growth, but after full growth has been attained it does not usually undergo any change, even in old age. He further states that the angle varies considerably in different persons of the same age. It is smaller in short than in long bones, and when the pelvis is wide.2 The neck is flattened from before backward, contracted in the middle, and broader at its outer extremity, where it is connected with the shaft, than at its summit, where it is attached to the head. The vertical diameter of the outer 1 Ina man six feet high it measures eighteen inches-one-fourth of the whole body. 2 Journal of Anatomy and Physiology. THE FEMUR, OR THIGH-BONE. 287 OBTURATOR INTERNUS and QEMELLI PYRIFORMIS. half is increased by the thicken- ing of the lower edge, which slopes downward to join the shaft at the lesser trochanter, so that the outer half of the neck is flattened from before backward, and its vertical diameter measures one-third more than the antero-posterior. The inner half is smaller and of a more circular shape. The anterior surface of the neck is perforated by numerous vascular foramina. The posterior surface is smooth, and is broader and more concave than the anterior ; it gives attachment to the posterior part of the capsular ligament of the hip-joint, about half an inch above the posterior intertrochanteric line. The superior border is short and thick, and terminates exter- nally at the great trochanter; its surface is per- forated by large foramina. The inferior border, long and narrow, curves a little backward, to terminate at the lesser trochanter. The Trochanters (rpoydco, to run or roll) are prominent processes of bone which afford lever- age to the muscles which rotate the thigh on its axis. They are two in number, the great and the lesser. The Great Trochanter is a large, irregular, quadrilateral eminence, situated at the outer side of the neck, at its junction with the upper part of the shaft. It is directed a little out- ward and backward, and in the adult is about three-quarters of an inch lower than the head. It presents for examination two surfaces and four borders. The external surface, quadri- lateral in form, is broad, rough, convex, and marked by a prominent diagonal line, which extends from the posterior superior to the anterior inferior angle; this line serves for the attachment of the tendon of the Gluteus medius. Above the line is a triangular surface, some- times rough for part of the tendon of the same muscle, sometimes smooth for the interposition of a bursa between that tendon and the bone. Below and behind the diagonal line is a smooth, triangular surface, over which the tendon of the Gluteus maximus muscle plays, a bursa being interposed. The internal surface is of much less extent than the external, and presents at its base a deep depression, the digital or tro- chanteric fossa, for the attachment of the tendon of the Obturator externus muscle, and in front of this an impression for the attachment of the Obturator internus and Gemelli. The superior border is free; it is thick and irregular, and marked near the centre by an impression for the attachment of the Pyriformis. The inferior border corresponds to the point of Junction of , Depression for C LIQAMENTUM TERES. Outer Tuberosity. Inner Tuberosity. Outer Condyle. Fig. 213.-Right femur. Anterior surface. 288 THE SKELETON. the base of the trochanter with the outer surface of the shaft; it is marked by a rough, prominent, slightly curved ridge, which gives attachment to the upper part of the Vastus externus muscle. The anterior border is prominent, somewhat irregular, as well as the surface of bone immediately below it; it aifords attach- ment at its outer part to the Gluteus minimus. The posterior border is very prominent, and appears as a free, rounded edge, which forms the back part of the digital fossa. The Lesser Trochanter is a conical eminence which varies in size in different subjects; it projects from the lower and back part of the base of the neck. Its base is triangular, and connected with the adjacent parts of the bone by three well-marked borders: two of these are above-the internal continuous with the lower border of the neck, the external with the posterior intertrochanteric line- while the inferior border is continuous with the middle division of the linea aspera. Its summit, which is directed inward and backward, is rough, and gives insertion to the tendon of the Psoas magnus. The Iliacus is inserted into the shaft below the lesser trochanter between the Vastus internus in front and the Pectineus behind. A well-marked prominence of variable size, which projects from the upper and front part of the neck at its junction with the great trochanter, is called the tubercle of the femur; it fs the point of meeting of five muscles: the Gluteus minimus externally, the Vastus externus below, and the tendon of the Obturator internus and Gemelli above. Running obliquely downward and inward from the tubercle is the spiral line of the femur, or anterior intertrochanteric line ; it winds round the inner side of the shaft, below the lesser trochanter, and termi- nates in the linea aspera, about two inches below this eminence. Its upper half is rough, and affords attachment to the capsular ligament of the hip-joint; its lower half is less prominent, and gives attachment to the upper part of the Vastus internus. Running obliquely downward and inward from the summit of the great trochanter on the posterior surface of the neck is a very prominent, well- marked ridge, the posterior intertrochanteric line. Its upper half forms the posterior border of the great trochanter, and its lower half runs downward and inward across the neck of the bone to the upper and back part of the lesser trochanter. A slight ridge sometimes commences about the middle of the posterior intertrochanteric line, and passes vertically downward for about two inches along the back part of the shaft: it is called the linea quadrata, and gives attachment to the Quadratus femoris and a few fibres of the Adductor magnus muscles.1 The Shaft, almost cylindrical in form, is a little broader above than in the centre, and somewhat flattened below, from before backward. It is slightly arched, so as to be convex in front and concave behind, where it is strengthened by a prominent longitudinal ridge, the linea aspera. It presents for examination three borders, separating three surfaces. Of the three borders, one, the linea aspera, is posterior; the other two are placed laterally. The linea aspera (Fig. 214) is a prominent longitudinal ridge or crest, on the middle third of the bone, presenting an external lip, an internal lip, and a rough intermediate space. Above, this crest is prolonged by three ridges. The most external one is very rough, and is continued almost vertically upward to the base of the great trochanter. It is sometimes termed the gluteal ridge, and gives attach- ment to part of the Gluteus maximus muscle; its upper part is often elongated into a roughened crest, on which is a more or less well-marked, rounded tubercle, a rudimental third trochanter. The middle ridge, the least distinct, is continued to the base of the trochanter minor, and the internal one is lost above in the spiral line of the femur. Below, the linea aspera is prolonged by two ridges, which enclose between them a triangular space, the popliteal space, upon which rests the popliteal artery. Of these two ridges, the outer one is the more prominent, and 1 Generally there is merely a slight thickening about the centre of the intertrochanteric line, marking the point of attachment of the Quadratus femoris. This is termed by some anatomists the tubercle of the Quadratus. THE FEMUR, OR THIGH-BONE 289 descends to the summit of the outer condyle. The inner one is less marked, especially at its upper part, where it is crossed by the femoral artery. It ter- minates, below, at the summit of the internal condyle, in a small tubercle, the Adductor tubercle, which affords attach- ment to the tendon of the Ad- ductor magnus. To the inner lip of the linea aspera and its inner prolongation above and below is attached the Vastus internus, and to the outer lip and its outer prolongation above is attached the Vastus externus. The Adductor magnus is attached to the linea aspera, to its outer prolongation above and its inner prolongation below. Between the Vastus externus and the Adductor magnus are attached two muscles-viz. the Gluteus maximus above, and the short head of the Biceps below. Between the Adductor magnus and the Vastus internus four muscles are attached: the Iliacus and Pectineus above (the latter to the middle of the upper divis- ions) ; below these, the Adductor brevis and Adductor longus. The linea aspera is perforated a little below its centre by the nutrient canal, which is directed obliquely upward. The tivo lateral borders of the femur are only slightly marked, the outer one extending from the anterior inferior angle of the great trochanter to the anterior extremity of the external condyle; the inner one from the spiral line, at a point opposite the trochanter minor, to the an- terior extremity of the internal condyle. The internal border marks the limit of attachment of the Crureus muscle internally. The anterior surface includes that portion of the shaft which is situated between the two lateral borders. It is smooth, convex, broader above and below than in the centre, slightly twisted, so that its upper part is Groove for tendon of i POPLITEUS. Fig. 214.-Right femur. Posterior surface. 290 THE SKELETON. directed forward and a little outward, its lower part forward, and a little inward. To the upper three-fourths of this surface the Crureus is attached; the lower fourth is separated from the muscle by the intervention of the synovial membrane of the knee-joint and a bursa, and affords attachment to the Subcrureus to a small extent. The external surface includes the portion of bone between the external border and the outer lip of the linea aspera: it is continuous above with the outer surface of the great trochanter, below with the outer surface of the external condyle; to its upper three-fourths is attached the outer portion of the Crureus muscle. The internal surface includes the portion of bone between the internal border and the inner lip of the linea aspera; it is continuous above with the lower border of the neck, below with the inner side of the internal condyle : it is covered by the Vastus internus muscle. The Lower Extremity, larger than the upper, is of a cuboid form, flattened from before backward, and divided into two large eminences, the condyles (xbi'dtj/.o?, a knuckle), by an interval which presents a smooth depression in front called the trochlea, and a notch of considerable size behind-the intercondyloid notch. The external condyle is the more prominent anteriorly, and is the broader both in the antero-posterior and transverse diameters. The internal condyle is the narrower, longer, and more prominent inferiorly. This difference in the length of the two condyles is only observed when the bone is perpendicular, and depends upon the obliquity of the thigh-bones, in consequence of their separation above at the articulation with the pelvis. If the femur is held obliquely, the surfaces of the two condyles will be seen to be nearly horizontal. The two condyles are directly continuous in front, and form a smooth trochlear surface, which articulates with the patella. It presents a median groove, which extends downward and back- ward to the intercondyloid notch; and two lateral convexities, of which the external is the broader, more prominent, and prolonged farther upward upon the front of the outer condyle. The external border is also more prominent, and ascends higher than the internal one. The intercondyloid notch lodges the crucial liga- ments ; it is bounded laterally by the opposed surfaces of the two condyles, and in front by the lower end of the shaft. Outer Condyle.-The outer surface of the external condyle presents, a little behind its centre, an eminence, the outer tuberosity ; it is less prominent than the inner tuberosity, and gives attachment to the external lateral ligaments of the knee. Immediately beneath it is a groove which commences at a depression a little behind the centre of the lower border of this surface : the front part of this depression gives origin to the Popliteus muscle, the tendon of which is lodged in the groove during flexion of the knee. The groove is smooth, covered with cartilage in the recent state, and runs upward and backward to the posterior extremity of the condyle. The inner surface of the outer condyle forms one of the lateral boundaries of the intercondyloid notch, and gives attachment, by its posterior part, to the anterior crucial ligament. The inferior surface is convex, smooth, and broader than that of the internal condyle. The posterior extremity is convex and smooth: just above the articular surface is a depression for the tendon of the outer head of the Gastrocnemius, above which is the origin of the Plantaris. Inner Condyle.-The inner surface of the inner condyle presents a convex eminence, the inner tuberosity, rough for the attachment of the internal lateral ligament. The outer side of the inner condyle forms one of the lateral boundaries of the intercondyloid notch, and gives attachment, by its anterior part, to the posterior crucial ligament. Its inferior or articular surface is convex, and presents a less extensive surface than the external condyle. Just above the articular surface of the condyle, behind, is a depression for the tendon of origin of the inner head of the Gastrocnemius. Structure.-The shaft of the femur is a cylinder of compact tissue, hollowed by a large medullary canal. The cylinder is of great thickness and density in the middle third of the shaft, where the bone is narrowest and the medullary canal well formed; but above and below this the cylinder gradually becomes thinner, THE FEMUR, OR THIGH-BONE. 291 owing to a separation of the layers of the bone into cancelli, which project into the medullary canal and finally obliterate it, so that the upper and lower ends of the shaft, and the articular extremities more especially, consist of cancellated tissue invested by a thin, compact layer. The arrangement of the cancelli in the ends of the femur is remarkable. In the upper end they are arranged in two sets. One, starting from the top of the head, the upper surface of the neck, and the great trochanter, converge to the inner circumference of the shaft (Fig. 215); these are placed in the direction of greatest pressure, and serve to support the vertical weight of the body. The second set are planes of lamellae intersecting the former nearly at right angles, and are situ- ated in the line of the greatest tension-that is to say, along the lines in which the muscles and ligaments exert their traction. In the head of the bone these .Great trochanter. Digital fossa. I Lesser trochanter. Calcar femorale. \ Tension Pressure planes. planes. Fig. 215.-Diagram showing the arrange- ment of the cancelli of the neck of the femur. Fig. 216.-Calcar femorale. planes are arranged in a curved form, in order to strengthen the bone when exposed to pressure in all directions. In the midst of the cancellous tissue of the neck is a vertical plane of compact bone, the femoral spur (calcar femorale) which com- mences at the point where the neck joins the shaft midway between the lesser trochanter and the internal border of the shaft of the bone, and extends in the direction of the digital fossa (Fig. 216). This materially strengthens this portion of the bone. Another point in connection with the structure of the neck of the femur requires mention, especially on account of its influence on the production of fracture in this situation. It will be noticed that a considerable portion of the great trochanter lies behind the level of the posterior surface of the neck ; and if a section be made through the trochanter at this level, it will be seen that the posterior wall of the neck is prolonged into the trochanter. This prolongation is termed by Bigelow' the " true neck," 1 and forms a thin, dense plate of bone, which passes beneath the posterior intertrochanteric ridge toward the outer surface of the bone. In the lower end the cancelli spring on all sides from the inner surface of the cylinder, and descend in a perpendicular direction to the articular surface, the cancelli being strongest and having a more accurately perpendicular course above the condyles. In addition to this, however, horizontal planes of cancellous tissue 1 Bigelow on the Hip, p. 121. 292 THE SKELETON. are to be seen, so that the spongy tissue in this situation presents an appearance of being mapped out into a series of rectangular areas. Articulations.-With three bones : the os innominatum, tibia, and patella. Development (Fig. 217).-The femur is developed by/wc centres: one for the shaft, one for each extremity, and one for each trochanter. Of all the long bones, except the clavicle, it is the first to show traces of ossification: this commences in the shaft, at about the fifth week of foetal life, the centres of ossification in the epiphyses appearing in the following order: First, in the lower end of the bone, at the ninth month of foetal life1 (from this the condyles and tuberosities are formed); in the head at the end of the first year after birth ; in the great trochanter, during the fourth year; and in the lesser trochanter, between the thirteenth and fourteenth. The order in which the epiphyses are joined to the shaft is the reverse of that of their appear- ance : their junction does not com- mence until after puberty, the lesser trochanter being first joined, then the great, then the head, and, lastly, the inferior extremity (the first in which ossification commenced), which is not united until the twentieth year. Attachment of Muscles.-To twenty-three. To the great tro- chanter : the Gluteus medius, Gluteus minimus, Pyriformis, Obturator inter- nus, Obturator externus, Gemellus superior, Gemellus inferior, and Quadratus femoris. To the lesser trochanter: the Psoas magnus and the Iliacus below it. To the shaft: the Vastus externus. Gluteus maximus, short head of the Biceps, Vastus internus, Adductor magnus, Pectineus, Adductor brevis, Adductor longus, Crureus, and Subcrureus. To the condyles : the Gastrocnemius, Plantaris, and Popliteus. Surface Form.-The femur is covered with muscles, so that in fairly muscular subjects the shaft is not to be detected through its fleshy covering, and the only parts accessible to the touch are the outer surface of the great trochanter and the lower expanded end of the bone. The external surface of the great trochanter is to be felt, especially in certain positions of the limb. Its position is generally indicated by a depression, owing to the thickness of the Gluteus medius and minimus, which project above it. When, however, the thigh is flexed, and especially if crossed over the opposite one, the trochanter produces a blunt eminence on the surface. The upper border is about on a line with the spine of the os pubis, and its exact level is indicated by a line drawn from the anterior superior spinous process of the ilium, over the outer side of the hip, to the most prominent point of the tuberosity of the ischium. This is known as Nelaton's line. The outer and inner condyles of the lower extremity are easily to be felt. The outer one is more subcutaneous than the inner one, and readily felt. The tuberosity on it is comparatively little developed, but can be more or less easily recognized. The inner condyle is more thickly covered, and this gives a general convex outline to this part, especially when the knee is flexed. The tuberosity on it is easily felt, and at the upper part of the condyle the sharp tubercle for the insertion of the tendon of the Adductor magnus can be recognized without difficulty. When the knee is flexed, and the patella situated in the interval between the con- dyles and the upper end of the tibia, a part of the trochlear surface of the femur can be made out above the patella. Surgical Anatomy.-There are one or two points about the ossification of the femur Appears at end of 1st year; joins shaft about 18th year. Appears at jth year; joins shaft about 18th year.. Appears year; ■ joins shaft about 18th year. Appears at 9th month (foetal). I Joins shaft at 20th year' Lower extremity. Fig. 217-Plan of the development of the femur. By five centres. 1 This is the only epiphysis in which ossification begins before birth. THE PATELLA. 293 bearing on practice to which allusion must be made. Tt has been stated above that the lower end of the femur is the only epiphysis in which ossification has commenced at the time of birth. The presence of this ossific centre is, therefore, a proof, in newly-born children found dead, that the child has arrived at the full period of utero-gestation, and is always relied upon in medico-legal investigations. The position of the epiphysial line should be carefully noted. It is on a level with the adductor tubercle, and the epiphysis does not, therefore, form the whole of the cartilage-clad portion of the lower end of the bone. It is essential to bear this point in mind in performing excision of the knee, since growth in length of the femur takes place chiefly from the lower epiphysis, and any interference with the epiphysial cartilage in a young child would involve such ultimate shortening of the limb, from want of growth, as to render it almost useless. Separation of the lower epiphysis may take place up to the age of twenty, at which time it becomes completely joined to the shaft of the bone ; but. as a matter of fact, few cases occur after the age of sixteen or seventeen. The upper epiphysis of the femur is of interest principally on account of its being the seat of origin of a large number of cases of tubercular disease of the hip-joint. The disease commences in the majority of cases in the highly vascular and growing tissue in the neighborhood of the epiphysis, and from here extends into the joint. Fractures of the femur are divided, like those of the other long bones, into fractures of the upper end; of the shaft; and of the lower end. The fractures of the upper end may be classified into (1) fracture of the neck; (2) fracture at the junction of the neck with the great trochanter; (3) fracture of the great trochanter; and (4) separation of the epiphysis, either of the head or of the great trochanter. The first of these, fracture of the neck, is usually termed intracapsular fracture, but this is scarcely a correct designation, as, owing to the attach- ment of the capsular ligament, the fracture may be partly within and partly without the cap- sule, when the fracture occurs at the lower part of the neck. It generally occurs in old people, principally women, and usually from a very slight degree of indirect violence. Probably the main cause of the fracture taking place in old people is in consequence of the degenerative changes which the bone has undergone. Merkel believes that it is mainly due to the absorp- tion of the calcar femorale. These fractures are occasionally impacted. As a rule they unite by fibrous tissue, and frequently no union takes place, and the surfaces of the fracture become smooth and eburnated. Fractures at the junction of the neck with the great trochanter are usually termed extra- capsular, but this designation is also incorrect, as the fracture is partly within the capsule, owing to its attachment in front to the anterior intertrochanteric line, which is situated below the line of fracture. These fractures are produced by direct violence to the great trochanter, as from a blow or fall laterally on the hip. From the manner in which the accident is caused, the neck of the bone is driven into the trochanter, where it may remain impacted, or the trochanter may be split up into two or more fragments, and thus no fixation takes place. Fractures of the great trochanter may be either "oblique fracture through the trochanter major, without implicating the neck of the bone" (Astley Cooper), or separation of the great trochanter. Most of the recorded cases of this latter injury occurred in young persons, and were probably cases of separation of the epiphysis of the great trochanter. Separation of the epiphysis of the head of the femur has been said to occur, but, as far as I know, has never been verified by post-mortem examination. Fractures of the shaft may occur at any part, but the most usual situation is at or near the centre of the bone. They may be caused by direct or indirect violence or by muscular action. Fractures of the upper third of the shaft are almost always the result of indirect violence, whilst those of the lower third are the result, for the most part, of direct violence. In the middle third fractures occur from both forms of injury in about equal proportions. Fractures of the shaft are generally oblique, but they may be transverse, longitudinal, or spiral. The transverse fracture occurs most frequently in children. The fractures of the lower end of the femur include transverse fracture above the condyles, the most common ; and this may be com- plicated by a vertical fracture between the condyles, constituting the T-shaped fracture. In these cases the popliteal artery is in danger of being wounded. Oblique fracture, separating either the internal or external condyle, and a longitudinal incomplete fracture between the con- dyles, may also take place. The femur as well as the other bones of the leg are frequently the seat of acute necrosis in young children. This is no doubt due to their greater exposure to injury, which is often the exciting cause of this disease. Tumors not unfrequently are found growing from the femur: the most common forms being sarcoma, which may grow either from the periosteum or from the medullary tissue within the interior of the bone ; and exostosis, which is commonly found originating in the neighborhood of the epiphysial cartilage of the lower end. The skeleton of the Leg consists of three bones : the Patella, a large sesamoid bone, placed in front of the knee ; the Tibia; and the Fibula. THE LEG. The Patella (Figs. 218, 219.) The Patella (patella, a small pan) is a flat, triangular bone, situated at the 294 THE SKELETON. anterior part of the knee-joint. It is usually regarded as a sesamoid bone, developed in the tendon of the Quadriceps extensor. It resembles these bones (1) in its being developed in a tendon ; (2) in its centre of ossi- fication presenting a knotty or tuberculated outline similar to other sesamoid bones; (3) in its structure being composed mainly of dense cancellous tissue, as in the other sesamoid bones. It serves to protect the front of the joint, and increases the leverage of the Quadriceps ex- tensor by making it act at a greater angle. It presents an anterior and posterior surface, three borders, and an apex. The anterior surface is convex, perforated by small apertures, for the passage of nutrient vessels, and marked by numerous rough, longitudinal striae. This surface is covered, in the recent state, by an expansion from the tendon of the Quadriceps extensor, which is continuous below with the superficial fibres of the ligamentum patellae. It is separated from the integument by a bursa. The posterior surface presents a smooth, oval-shaped, articular surface, covered with cartilage in the recent state, and divided into two facets by a vertical ridge, which descends from the superior border toward the inferior angle of the bone. The ridge corresponds to the groove on the trochlear surface of the femur, and the two facets to the articular surfaces of the two condyles ; the outer facet, for articulation with the outer condyle, being the broader and deeper. This character serves to indicate the side to which the bone belongs. Below the articular surface is a rough, convex, non-articular depression, the lower half of which gives attachment to the ligamentum patellae, the upper half being separated from the head of the tibia by adipose tissue. The superior border is thick, and sloped from behind, downward and forward: it gives attachment to that portion of the Quadriceps extensor which is derived from the Rectus and Crureus muscles. The lateral borders are thinner, converging below. They give attachment to that portion of the Quadriceps extensor derived from the external and internal Vasti muscles. The apex is pointed, and gives attachment to the ligamentum patellae. Structure.-It consists of a nearly uniform dense cancellous tissue covered by a thin compact lamina. The cancelli immediately beneath the anterior surface are arranged parallel with it. In the rest of the bone they radiate from the posterior articular surface toward the other parts of the bone. ' Development.-By a single centre, which makes its appearance, according to Beclard, about the third year. In two instances I have seen this bone cartilagi- nous throughout, at a much later period (six years). More rarely, the bone is developed by two centres, placed side by side. Ossification is completed about the age of puberty. Articulations.-With the two condyles of the femur. Attachment of Muscles.-To four: the Rectus, Crureus, Vastus internus, and Vastus externus. These muscles, joined at their insertion, constitute the Quadriceps extensor cruris. Surface Form.-The external surface of the patella can be seen and felt in front of the knee. In the extended position of the limb the internal border is a little more prominent than the outer, and if the Quadriceps extensor is relaxed, the bone can be moved from side to side and appears to be loosely fixed. If the joint is flexed, the patella recedes into the hollow between the condyles of the femur and the upper end of the tibia, and becomes firmly fixed against the femur. Surgical Anatomy.-The main surgical interest about the patella is in connection with fractures; which are of common occurrence. They may be produced by muscular action ; that Fig. 218.-Right patella. An terior surface. Fig. 219.-Right patella. Posterior surface. THE TIBIA. 295 is to say, by violent contraction of the Quadriceps extensor while the limb is in a position of semi-flexion, so that the bone is snapped across the condyles; or by direct violence, such as falls on the knee. In the former class of cases the fracture is transverse; in the latter it may be oblique, longitudinal, stellate, or the bone variously comminuted. The principal interest in these cases attaches to their treatment. Owing to the wide separation of the fragments, and the difficulty there is in maintaining them in apposition, union takes place by fibrous tissue, and this may subsequently stretch, producing wide separation of the fragments and permanent lameness. Various plans, including opening the joint and suturing the fragments, have been advocated for overcoming this difficulty. In the larger number of cases of fracture of the patella the knee-joint is involved, the car- tilage which covers its posterior surface being also torn. In some cases of fracture from direct violence, however, this need not necessarily happen, the lesion involving only the superficial part of the bone; and, as Morris has pointed out, it is an anatomical possibility, in complete fracture, if the lesion involve only the lower and non-articular part of the bone, for it to take place without injury to the synovial membrane. The Tibia (Figs. 220, 221). The Tibia (tibia, a flute or pipe) is situated at the front and inner side of the leg, and, excepting the femur, is the longest and largest bone in the skeleton. It is prismoid in form, expanded above, where it enters into the knee-joint, more slightly enlarged below. In the male its direction is vertical and parallel with the bone of the opposite side; but in the female it has a slightly oblique direction downward and outward, to compensate for the oblique direction of the femur inward. It presents for examination a shaft and two extremities. The Upper Extremity, or Head, is large, and expanded on each side into two lateral eminences, the tuberosities. Superiorly, the tuberosities present two smooth, concave surfaces, which articulate with the condyles of the femur ; the internal, articular surface is longer, deeper, and narrower than the external, oval from before backward, to articulate with the internal condyle; the external one is broader, flatter, and more circular, to articulate with the external condyle. Between the two articular surfaces, and nearer the posterior than the anterior aspect of the bone, is an eminence, the spinous process of the tibia, surmounted by a prominent tubercle on each side, which gives attachment to the extremities of the semilunar fibro-cartilages; in front and behind the spinous process is a rough depression for the attachment of the anterior and posterior crucial ligaments and the semilunar fibro-cartilages. The anterior surfaces of the tuberosities are continuous with one another, forming a single large surface, which is somewhat flattened: it is triangular, broad above, and perforated by large vascular foramina ; narrow below, where it terminates in a prominent oblong elevation of large size, the tubercle of the tibia; the lower half of this tubercle is rough, for the attachment of the ligamentum patellae; the upper half presents a smooth facet supporting, in the recent state, a bursa which separates the ligament from the bone. Posteriorly the tuberosities are separated from each other by a shallow depression, the popliteal notch, which gives attachment to part of the posterior crucial ligament and part of the posterior ligament of the knee-joint. The inner tuberosity presents posteriorly a deep transverse groove, for the insertion of one of the fasciculi of the tendon of the Semi-membranosus. Its lateral surface is convex, rough, and prominent: it gives attachment to the internal lateral ligament. The outer tuber- osity presents posteriorly a flat articular facet, nearly circular in form, directed downward, backward, and outward, for articulation with the fibula. Its lateral surface is convex and rough, more prominent in front than the internal: it presents a prominent rough eminence, situated on a level with the upper border of the tubercle of the tibia, for the attachment of the ilio-tibial band. Just below this the Extensor longus digitorum and a slip from the Biceps are attached. The Shaft of the tibia is of a triangular prismoid form, broad above, gradually decreasing in size to its most slender part, at the commencement of its lower fourth, where fracture most frequently occurs; it then enlarges again toward its lower extremity. It presents for examination three borders and three surfaces. The anterior border, the most prominent of the three, is called the crest of the 296 THE SKELETON. tibia, or, in popular language, the shin ; it commences above at the tubercle, and terminates below at the anterior margin of the inner malleolus. This border is very prominent in the upper two- thirds of its extent, smooth and rounded below. It presents a very flexuous course, being usually curved outward above and inward below; it gives attachment to the deej) fascia of the leg. The internal border is smooth and rounded above and below, but more prominent in the centre; it commences at the back part of the inner tuberosity, and terminates at the posterior border of the internal malleolus; its upper part gives attachment to the internal lateral ligament of the knee to the extent of about two inches, and to some fibres of the Popliteus muscle; its middle third to some fibres of the Soleus and Flexor longus digitorum muscles. The external border, or in- terosseous ridge, is thin and prominent, especially its central part, and gives attachment to the interosseous membrane; it commences above in front of the fibular articular facet, and bifur- cates below, to form the bounda- ries of a triangular rough surface, for the attachment of the inter- osseous ligament connecting the tibia and fibula. The internal surface is smooth, convex, and broader above than below; its upper third, directed forward and inward, is covered by the aponeurosis derived from the tendon of the Sartorius, and by the tendons of the Gracilis and Semitendinosus, all of which are inserted nearly as far forward as the anterior border; in the rest of its extent it is subcutaneous. The external surface is nar- rower than the internal; its upper two-thirds presents a shallow groove for the attachment of the Tibialis anticus muscle; its lower third is smooth, convex, curves gradually forward to the anterior part of the bone, and is covered from within Head. Head. Styloid process.- EXTERNAL- LATERAL LIGAMENT. FIBULA. TIBIA. Internal malleolus. External malleolus. Fig. 220.-Bones of the right leg. Anterior surface. THE TIBIA 297 outward by the tendons of the fol- lowing muscles: Tibialis anticus, Extensor proprius hallucis, Ex- tensor longus digitorum. The posterior surface (Fig. 221) presents, at its upper part, a prom- inent ridge, the oblique line of the tibia, which extends from the back part of the articular facet for the fibula obliquely downward, to the internal border, at the junction of its upper and middle thirds. It marks the limit for the insertion of the Popliteus muscle, and serves for the attachment of the popliteal fascia and part of the Soleus, Flexor longus digitorum, and Tib- ialis posticus muscles; the tri- angular concave surface, above and to the inner side of this line, gives attachment to the Popliteus mus- cle. The middle third of the pos- terior surface is divided by a vertical ridge into two lateral halves : the ridge is well marked at its commencement at the oblique line, but becomes gradually indis- tinct below; the inner and broader half gives attachment to the Flexor longus digitorum, the outer and narrower to part of the Tibialis posticus. The remaining part of the bone presents a smooth surface covered by the Tibialis posticus, Flexor longus digitorum, and Flexor longus hallucis muscles. Immediately below the oblique line is the medullary foramen, which is directed obliquely downward. The Lower Extremity, much smaller than the upper, presents five surfaces; it is prolonged downward, on its inner side to a strong pro- cess, the internal malleolus. The inferior surface of the bone is quadrilateral, and smooth for artic- ulation with the astragalus. This surface is concave from before back- ward, and broader in front than be- hind. It is traversed from before backward by a slight elevation, separating two lateral depressions. It is narrow internally, where the articular surface becomes continu- ous with that on the inner malleolus. The anterior surface of the lowrer extrem- ity is smooth and rounded above, and covered by the tendons of the Extensor muscles of the toes; its lower margin presents a rough transverse depression, for Styloid process. TIBIA. FIBULA. Fig. 221.-Bones of the right leg. Posterior surface. 298 THE SKELETON. the attachment of the anterior ligament of the ankle-joint; the posterior surface presents a superficial groove directed obliquely downward and inward, continuous with a similar groove on the posterior extremity of the astragalus, and serving for the passage of the tendon of the Flexor longus hallucis; the external surface presents a triangular rough depression for the attachment of the inferior inter- osseous ligament connecting it with the fibula; the lower part of this depression is smooth, covered with cartilage in the recent state, and articulates with the fibula. This surface is bounded by two prominent ridges, continuous above with the interosseous ridge ; they afford attachment to the anterior and posterior infe- rior tibio-fibular ligaments. The internal surface of the lower extremity is pro- longed downward to form a strong pyramidal process, flattened from without inward-the inner malleolus. The inner surface of this process is convex and sub- cutaneous ; its outer surface is smooth and slightly concave, and articulates with the astragalus; its anterior border is rough, for the attachment of the anterior fibres of the Deltoid ligament; its posterior border presents a broad and deep groove, directed obliquely downward and inward, which is occasionally double: this groove transmits the tendons of the Tibialis posticus and Flexor longus digi- torum muscles. The summit of the internal malleolus is marked by a rough depression behind, for the attachment of the internal lateral ligament of the ankle-joint. Structure.-Like that of the other long bones. At the junction of the middle and lower third, where the bone is smallest, the wall of the shaft is thicker than in other parts, in order to compensate for the smallness of the calibre of the bone. Development.-By three centres (Fig. 222): one for the shaft, and one for each extremity. Ossification commences in the centre of the shaft about the seventh week, and gradually extends to- ward either extremity. The centre for the upper epiphysis appears during the first year; it is flattened in form, and has a thin, tongue-shaped process in front which forms the tubercle. That for the lower epiphysis appears in the second year. The lower epiphysis joins the shaft at about the eighteenth, and the upper one about the twentieth, year. Two additional centres occasionally exist -one for the tongue-shaped process of the upper epiphysis, which forms the tubercle, and one for the inner malleolus. Articulations.-With three bones: the femur, fibula, and astragalus. Attachment of Muscles.-To twelve: to the inner tuberosity, the Semimem- branosus ; to the outer tuberosity, the Tibialis anticus and Extensor longus digi- torum and Biceps ; to the shaft, its inter- nal surface, the Sartorius, Gracilis, and Semitendinosus ; to its external surface, the Tibialis anticus; to its posterior sur- face, the Popliteus, Soleus, Flexor longus digitorum, and Tibialis posticus ; to the tubercle, the ligamentum patellae. Appears at_ birth. .Joins shaft about 20th year. Appears at 2nd_ year. Joins shaft about 18th year. Lower extremity Fig. 222.-Plan of the development of the tibia. By three centres. Surface Form.-A considerable portion of the tibia is subcutaneous and easily to be felt. At the upper extremity the tuberosities are to be recognized just below the knee. The internal one is broad and smooth, and merges into the subcutaneous surface of the shaft below. The external one is narrower and more prominent, and on it, about midway between the apex of the patella and the head of the fibula, may be felt a prominent tubercle for the insertion of the ilio- THE FI BEL A. 299 tibial band. In front of the upper end of the bone, between the tuberosities, is the tubercle of the tibia, forming an oval eminence, which is continuous below with the anterior border or crest of the bone. This border can be felt, forming the prominence of the shin, in the upper two- thirds of its extent being sharp and presenting a somewhat flexuous course, being curved out- ward above and inward below. In the lower third of the leg the border disappears, and the bone is concealed by the tendons of the muscles on the front of the leg. Internal to the ante- rior border is to be felt the broad internal surface of the tibia, slightly encroached upon by the muscles in front and behind. It commences above at the wide expanded inner tuberosity, and terminates below at the internal malleolus. The internal malleolus is a broad prominence situ- ated on a higher level and somewhat farther forward than the external malleolus. It overhangs the inner border of the arch of the foot. Its anterior border is nearly straight; its posterior border presents a sharp edge, which forms the inner margin of the groove for the tendon of the Tibialis posticus muscle. The Fibula (Figs. 220, 221). The Fibula {fibula, a clasp) is situated at the outer side of the leg. It is the smaller of the two bones, and, in proportion to its length, the most slender of all the long bones; it is placed nearly parallel but behind the level of the tibia. Its upper extremity is small, placed toward the back of the head of the tibia and below the level of the knee-joint, and excluded from its formation ; the lower extremity inclines a little forward, so as to be on a plane anterior to that of the upper end, projects below the tibia, and forms the outer ankle. It presents for examination a shaft and two extremities. The Upper Extremity, or Head, is of an irregular quadrate form, presenting above a flattened articular facet, directed upward, forward, and inward, for artic- ulation with a corresponding facet on the external tuberosity of the tibia. On the outer side is a thick and rough prominence, continued behind into a pointed eminence, the styloid process, which projects upward from the posterior part of the head. The prominence gives attachment to the tendon of the Biceps muscle and to the long external lateral ligament of the knee, the ligament dividing the tendon into two parts. The summit of the styloid process gives attachment to the short external lateral ligament. The remaining part of the circumference of the head is rough, for the attachment of the anterior superior tibio-fibular ligament, presenting, in front, a tubercle for the attachment of the upper and anterior part of the Peroneus longus; and behind, another tubercle for the attachment of the posterior superior tibio-fibular ligament and the upper fibres of the Soleus muscle. The shaft presents four borders-the antero-external, the antero-internal, the postero-external, and the postero-internal ; and four surfaces-anterior, posterior, internal, and external. The antero-external border commehces above in front of the head, runs verti- cally downward to a little below the middle of the bone, and then, curving some- what outward, bifurcates so as to embrace the triangular subcutaneous surface immediately above the outer surface of the external malleolus. This border gives attachment to an intermuscular septum, which separates the extensor muscles on the anterior surface of the leg from the Peroneus longus and brevis muscles. The antero-internal border, or interosseous ridge, is situated close to the inner side of the preceding, and runs nearly parallel with it in the upper third of its extent, but diverges from it so as to include a broader space in the lower two-thirds. It commences above just beneath the head of the bone (sometimes it is quite indistinct for about an inch below the head), and terminates below at the apex of a rough triangular surface immediately above the articular facet of the external malleolus. It serves for the attachment of the interosseous membrane, and sepa- rates the extensor muscles in front from the flexor muscles behind. The postero-external border is prominent; it commences above at the base of the styloid process, and terminates below in the posterior border of the outer malleolus. It is directed outward above, backward in the middle of its course, backward and a little inward below, and gives attachment to an aponeurosis which separates the Peronei muscles on the outer surface of the shaft from the flexor muscles on its posterior surface. 300 THE SKELETON. The postero-internal border, sometimes called the oblique line, commences above at the inner side of the head, and terminates by becoming continuous with the antero-internal border or interosseous ridge 4t the lower fourth of the bone. It is well marked and prominent at the upper and middle parts of the bone. It gives attachment to an aponeurosis which separates the Tibialis posticus from the Soleus above and the Flexor longus hallucis below. The anterior surface is the interval between the antero-external and antero- internal borders. It is extremely narrow and flat in the upper third of its extent; broader and grooved longitudinally in its lower third; it serves for the attachment of three muscles, the Extensor longus digitorum, Peroneus tertius, and Extensor proprius hallucis. The external surface is the space between the antero-external and postero- external borders. It is much broader than the preceding, and often deeply grooved, is directed outward in the upper two-thirds of its course, backward in the lower third, where it is continuous with the posterior border of the external malleolus. This surface is completely occupied by the Peroneus longus and brevis muscles. The internal surface is the interval included between the antero-internal and the postero-internal borders. It is directed inward, and is grooved for the attach- ment of the Tibialis posticus muscle. The posterior surface is the space included between the postero-external and the postero-internal borders; it is continuous ..below with the rough triangular surface above the articular facet of the outer malleolus; it is directed backward above, backward and inward at its middle, directly inward below. Its upper third is rough, for the attachment of the Soleus muscle ; its lower part presents a triangular rough surface, connected to the tibia by a strong interosseous ligament, and between these two points the entire surface is covered by the fibres of origin of the Flexor longus hallucis muscle. At about the middle of this surface is the nutrient foramen, which is directed downward. The Lower Extremity, or external malleolus, is of a pyramidal form, somewhat flattened from without inward, and is longer, and descends lower than the internal malleolus. Its external surface is convex, subcutaneous, and continuous with the triangular (also subcutaneous) surface on the outer side of the shaft. The internal surface presents in front a smooth triangular facet, broader above than below, and convex from above downward, which articulates with a corresponding surface on the outer side of the astragalus. Behind and beneath the articular surface is a rough depression which gives attachment to the posterior fasciculus of the external lateral ligament of the ankle. The anterior border is thick and rough, and marked below by a depression for the attachment of the anterior fasciculus of the external lateral ligament. The posterior border is broad and marked by a shallow groove, for the passage of the tendons of the Peroneus longus and brevis muscles. The summit is rounded, and gives attachment to the middle fasciculus of the external lateral ligament. In order to distinguish the side to which the bone belongs, hold it with the O C5 7 lower extremity downward and the broad groove for the Peronei tendons back- ward-i. e. toward the holder: the triangular subcutaneous surface will then be directed to the side to which the bone belongs. Articulations.-With two bones : the tibia and astragalus. Development.-By three centres (Fig. 223): one for the shaft, and one for each extremity. Ossification commences in the shaft about the eighth week of foetal life, a little later than in the tibia, and extends gradually toward the extremities. At birth both ends are cartilaginous. Ossification commences in the lower end in the second year, and in the upper one about the fourth year. The lower epiphysis, the first in which ossification commences, becomes united to the shaft about the twentieth year; the upper epiphysis joins about the twenty- fifth year. Ossification appearing first in the lower epiphysis is contrary to the rule which prevails with regard to the commencement of ossification in epiphyses -viz. that that epiphysis toward which the nutrient artery is directed commences THE TARSUS: THE CALCANEUM. 301 to ossify last; but it follows the rule which prevails with regard to the union of epiphyses, by uniting first. Attachment of Muscles.-To nine : to the head, the Biceps, Soleus, and Peroneus longus; to the shaft, its anterior surface, the Extensor longus digi- torum, Peroneus tertius, and Extensor proprius hallucis; to the internal surface, the Tibialis pos- ticus ; to the posterior surface, the Soleus and Flexor longus hallucis ; to the external surface, the Peroneus longus and brevis. Surface Form.-The only parts of the fibula which are to be felt are the head and the lower part of the external sur- face of the shaft and the external malleolus. The head is to be seen and felt behind and to the outer side of the outer tuberosity of the tibia. It presents a small, prominent triangular eminence slightly above the level of the tubercle of the tibia. The external malleolus presents a narrow elon- gated prominence, situated on a plane posterior to the internal malleolus and reaching to a lower level. From it may be traced the lower third or half of the external surface of the shaft of the bone in the interval between the Peroneus tertius in front and the other two Peronei tendons behind. Surgical Anatomy.-In fractures of the bones of the leg both bones are usually fractured, but each bone may be broken separately, the fibula more frequently than the tibia. Fracture of both bones may be caused either by direct or indirect violence. When it occurs from indirect force, the fracture in the tibia is at the junction of the middle and lower third of the bone. Many causes conduce to render this the weakest part of the bone. The fracture of the fibula is usually at rather a higher level. These fractures present great variety, both as regards their direction and condition. They may be oblique, transverse, longitudinal, or spiral. When oblique, they are usually the result of indirect violence, and the direction of the fracture is from behind, downward, forward, and inward in many cases, but may be downward and outward or downward and backward. When transverse, the fracture is often at the upper part of the bone, and is the result of direct violence. The spiral fracture usually comfnences as a vertical fissure, involving the ankle-joint, and is associated with fracture of the fibula higher up. It is the result of torsion, from twisting of the body whilst the foot is fixed. Fractures of the tibia alone are almost always the result of direct violence, except where the malleolus is broken off by twists of the foot. Fractures of the fibula alone may arise from indirect or direct force, those of the lower end being usually the result of the former, and those higher up being caused by a direct blow on the part. The tibia and fibula, like the femur, are frequently the seat of acute necrosis. Chronic abscess is more frequently met with in the cancellous tissue of the head and lower end of the tibia than in any other bone of the body. The abscess is of small size, very chronic, and the result of rarefying osteitis of a localized portion of the cancellous tissue. The tibia is the bone which is most frequently and most extensively distorted in rickets. It gives way at the junction of the middle and lower third, its weakest part, and presents a curve forward and outward. Upper extremity. Appears about Jfth year. Unites about 25th year. Appears at~_ 2nd year. Unites about 20th year. Lower extremity. Fig. 2'23.-Plan of the develop- ment of the fibula. By three centres. THE FOOT (Figs. 224, 225). The skeleton of the Foot consists of three divisions: the Tarsus, Metatarsus, and Phalanges. The bones of the Tarsus are seven in number: viz. the calcaneum or os calcis, astragalus, cuboid, navicular, internal, middle, and external cuneiform bones. The Tarsus. The Calcaneum. The Calcaneum, or Os Calcis (calx, the heel), is the largest and strongest of the tarsal hones. It is irregularly cuboidal in form, having its long axis directed forward and outward. It is situated at the lower and back part of the foot, serving to transmit the weight of the body to the ground, and forming a strong 302 THE SKELETON. Groove for tendon of FLEXOR LONGUS HALLUClS. Groove for peroneus longus. Groove for peroneus brevis.- Tarsus. PERONEUS TERTIUS. PERONEUS BREVIS. \ Metatarsus. Innermost tendon of """e XT ENSOR BREVIS DlGlTORUM. Phalanges. EXTENSOR LONGUS HALLUClS. Fig. 224.-Bones of the right foot. Dorsal surface. THE TARSUS: THE CALCANEUM. 303 lever for the muscles of the Calf. It presents for examination six surfaces: superior, inferior, external, internal, anterior, and posterior. The superior surface is formed behind by the upper aspect of that part of the 'os calcis which projects backward to form the heel. It varies in length in differ- ent individuals; is convex from side to side, concave from before backward, and corresponds above to a mass of adipose substance placed in front of the tendo Achillis. In the middle of the superior surface are two (sometimes three) articular facets, separated by a broad shallow groove, which is directed obliquely forward and outward, and is rough for the attachment of the interosseous ligament connecting the astragalus and os calcis. Of the two articular surfaces, the external is the larger, and situated on the body of the bone: it is of an oblong form, wider behind than in front, and convex from before backward. The internal articular surface is supported on a projecting process of bone, called the lesser process of the calcaneum (sustentaculum tali); it is also oblong, concave longitudinally, and sometimes subdivided into two parts, which differ in size and shape. More anteriorly is seen the upper surface of the greater process, marked by a rough depression for the attachment of numerous ligaments, and a tubercle for the origin of the Extensor brevis digitorum muscle. The inferior surface is narrow, rough, uneven, wider behind than in front and convex from side to side; it is bounded posteriorly by two tubercles separated by a rough depression ; the external, small, prominent, and rounded, gives attach- ment to part of the Abductor minimi digiti: the internal, broader and larger, for the support of the heel, gives attachment, by its prominent inner margin, to the Abductor hallucis, and in front to the Flexor brevis digitorum muscles; the depression between the tubercles gives attachment to the Abductor minimi digiti and plantar fascia. The rough surface in front of the tubercles gives attachment to the long plantar ligament and to the outer head of the Flexor accessorius muscle; and to a prominent tubercle nearer the anterior part of this surface, as well as to a transverse groove in front of it, is attached the short plantar liga- ment. The external surface is broad, flat, and almost subcutaneous; it presents near its centre a tubercle, for the attachment of the middle fasciculus of the external lateral ligament. At its upper and anterior part this surface gives attachment to the external calcaneo-astragaloid ligament; and in front of the tubercle it presents a narrow surface marked by two oblique grooves, separated by an elevated ridge which varies much in size in different bones; it is named the peroneal ridge, and gives attachment to a fibrous process from the external annular ligament. The superior groove transmits the tendon of the Peroneus brevis ; the inferior, the tendon of the Peroneus longus. The internal surface presents a deep concavity, directed obliquely downward and forward, for the transmission of the plantar vessels and nerves into the sole of the foot; it affords attachment to part of the Flexor accessorius muscle. This surface presents an eminence of bone, the lesser process or sustentaculum tali, which projects horizontally inward from its upper and fore part, and to which a slip of the tendon of the Tibialis posticus is attached. This process is concave above, and supports the anterior articular surface of the astragalus; below, it is grooved for the tendon of the Flexor longus hallucis. Its free margin is rough, for the attachment of part of the internal lateral ligament of the ankle-joint. The anterior surface, of a somewhat triangular form, articulates with the cuboid. It is concave from above downward and outward, and convex in the opposite direction. Its inner border gives attachment to the inferior calcaneo- navicular ligament. The posterior surface is rough, prominent, convex, and wider below than above. Its lower part is rough, for the attachment of the tendo Achillis and of the Plan- taris muscle; its upper part is smooth, and is covered by a bursa which separates the tendon from the bone. Articulations.-With two bones: the astragalus and cuboid. 304 THE SKELETON. ABDUCTOR HALLUCIS. 1 [OUTER HEAD OF ACCESSORIUS. BREVIS HALLUCIS. Tubercle of navicular. TIBIALIS ANTICUS.< FLEXOR BREVIS and ABDUCTOR MINIMI DIQITI. Two bones. FLEXOR BREVIS DlQlTORUM. FLEXOR LONQUS DlQITORUM Fig. 225.-Bones of the right foot. Plantar surface. Attachment of Muscles.-To eight: part of the Tibialis posticus, the tendo THE TARSUS: THE ASTRAGALUS, THE CUBOID. 305 Achillis, Plantaris, Abductor hallucis, Abductor minimi digiti, Flexor brevis digi- torum, Flexor accessorius, and Extensor brevis digitorum. The Astragalus. The Astragalus (darpdyaAo', a die) is the largest of the tarsal bones, next to the os calcis. It occupies the middle and upper part of the tarsus, supporting the tibia above, articulating with the malleoli on either side, resting below upon the os calcis, and joined in front to the navicular. This bone may easily be recognized by its large rounded head, by the broad articular facet on its upper convex surface, or by the two articular facets separated by a deep groove on its under concave surface. It presents six surfaces for examination. The superior surface presents, behind, a broad smooth trochlear surface for articulation with the tibia. The trochlea is broader in front than behind, convex from before backward, slightly concave from side to side ; in front of it is the upper surface of the neck of the astragalus, rough for the attachment of ligaments. The inferior surface presents two articular facets separated by a deep groove. The groove runs obliquely forward and outward, becoming gradually broader and deeper in front: it corresponds with a similar groove upon the upper surface of the os calcis, and forms, when articulated with that bone, a canal, filled up in the recent state by the interosseous calcaneo-astragaloid ligament. Of the two articular facets, the posterior is the larger, of an oblong form and deeply concave from side to side ; the anterior, although nearly of equal length, is narrower, of an elongated oval form, convex longitudinally, and often subdivided into two by an elevated ridge; of these, the posterior articulates with the lesser process of the os calcis ; the anterior, with the upper surface of the inferior calcaneo-navicular liga- ment. The internal surface presents at its upper part a pear-shaped articular facet for the inner malleolus, continuous above with the trochlear surface; below the articular surface is a rough depression, for the attachment of the deep portion of the internal lateral ligament. The external surface presents a large triangular facet, concave from above downward for articulation with the external malleolus; it is continuous above with the trochlear surface; and in front of it is a rough depression for the attachment of the anterior fasciculus of the external lateral ligament of the ankle-joint. The anterior surface, convex and rounded, forms the head of the astragalus; it is smooth, of an oval form, and directed obliquely inward and downward; it articulates with the navicular. On its under surface is a small facet, continuous in front with the articular surface of the head, and behind with the smaller facet for the os calcis. This rests on the inferior calcaneo- navicular ligament, being separated from it by the synovial membrane, which is prolonged from the anterior calcaneo-astragaloid joint to the astragalo-navicular joint. The head is surrounded by a constricted portion, the neck of the astragalus. The posterior surface is narrow, and traversed by a groove, which runs obliquely downward and inward, and transmits the tendon of the Flexor longus hallucis, external to which is a prominent tubercle, to which the posterior fasciculus of the external lateral ligament is attached. To the inner side of the groove is a second, but less marked tubercle. To ascertain to which foot the bone belongs, hold it with the broad articular surface upward, and the rounded head forward; the lateral triangular articular surface for the external malleolus will then point to the side to which the bone belongs. Articulations.-With four bones: tibia, fibula, os calcis, and navicular. The Cuboid. The Cuboid (xy/9oc, a cube; eZdoc, like) bone is placed on the outer side of the foot, in front of the os calcis, and behind the fourth and fifth metatarsal bones. It is of a pyramidal shape, its base being directed upward and inward, its apex downward and outward. It may be distinguished from the other tarsal bones by 306 7777/ SKELETON. the existence of a deep groove on its under surface, for the tendon of the Peroneus longus muscle. It presents for examination six surfaces: three articular and three non-articular. The non-articular surfaces are the superior, inferior, and external. The superior or dorsal surface, directed upward and outward, is rough, for the attach- ment of numerous ligaments. The inferior or plantar surface presents in front a deep groove, which runs obliquely from without, forward and inward ; it lodges the tendon of the Peroneus longus, and is bounded behind by a prominent ridge, to which is attached the long calcaneo-cuboid ligament. The ridge terminates externally in an eminence, the tuberosity of the cuboid, the surface of which presents a convex facet, for articulation with the sesamoid bone of the tendon contained in the groove. The surface of bone behind the groove is rough, for the attachment of the short plantar ligament, a few fibres of the Flexor brevis hallucis, and a fasciculus from the tendon of the Tibialis posticus. The external surface, the smallest and narrowest of the three, presents a deep notch formed by the commencement of the peroneal groove. The articular surfaces are the posterior, anterior, and internal. The posterior surface is smooth, triangular, and concavo-convex, for articulation with the anterior surface of the os calcis. The anterior, of smaller size, but also irregu- larly triangular, is divided by a vertical ridge into two facets: the inner one, quadrilateral in form, articulates with the fourth metatarsal bone; the outer one, larger and more triangular, articulates with the fifth metatarsal. The internal surface is broad, rough, irregularly quadrilateral, presenting at its middle and upper part a smooth oval facet, for articulation with the external cuneiform bone; and behind this (occasionally) a smaller facet, for articulation with the navic- ular; it is rough in the rest of its extent, for the attachment of strong interosseous ligaments. To ascertain to which foot the bone belongs, hold it so that its under surface, marked by the peroneal groove, looks downward, and the large concavo-convex articular surface backward toward the holder: the narrow non-articular surface, marked by the commencement of the peroneal groove, will point to the side to which the bone belongs. Articulations.-With four bones: the os calcis, external cuneiform, and the fourth and fifth metatarsal bones; occasionally with the navicular. Attachment of Muscles.-Part of the Flexor brevis hallucis and a slip from the tendon of the Tibialis posticus. The Navicular or Scaphoid bone is situated at the inner side of the tarsus, between the astragalus behind and the three cuneiform bones in front. It may be distinguished by its form, being concave behind, convex and subdivided into three facets in front. The anterior surface, of an oblong form, is convex from side to side, and sub- divided by two ridges into three facets, for articulation with the three cuneiform bones. The posterior surface is oval, concave, broader externally than internally, and articulates with the rounded head of the astragalus. The superior surface is convex from side to side, and rough for the attachment of ligaments. The inferior is irregular, and also rough for the attachment of ligaments. The internal surface presents a rounded tubercular eminence, the tuberosity of the navicular, the lower part of which projects, and gives attachment to part of the tendon of the Tibialis posticus. The external surface is rough and irregular, for the attachment of ligamentous fibres, and occasionally presents a small facet for articulation with the cuboid bone. To ascertain to which foot the bone belongs, hold it with the concave articular surface backward, and the convex dorsal surface upward; the external surface- i. e. the surface opposite the tubercle-will point to the side to which the bone belongs. The Navicular. 7777? CUNEIFORM BONES. 307 Articulations.-With four bones : astragalus and three cuneiform ; occasionally also with the cuboid. Attachment of Muscles.-Part of the Tibialis posticus. The Cuneiform Bones have received their name from their wedge-like shape (cuneus, a wedge; forma, likeness). They form, with the cuboid, the anterior row of the tarsus, being placed between the navicular behind, the three innermost metatarsal bones in front, and the cuboid externally. They are called the first, second, and third, counting from the inner to the outer side of the foot, and, from their position, internal, middle, and external. The Internal Cuneiform is the largest of the three. It is situated at the inner side of the foot, between the navicular behind and the base of the first metatarsal in front. It may be distinguished from the other two by its large size, and its more irregular, wedge-like form. Without the others, it may be known by the large kidney-shaped anterior articulating surface and by the prominence on the inferior or plantar surface for the attachment of the Tibialis posticus. It presents for examination six surfaces. The internal surface is subcutaneous, and forms part of the inner border of the foot; it is broad, quadrilateral, and presents at its anterior inferior angle a smooth oval facet, into which the tendon of the Tibialis anticus is partially inserted; in the rest of its extent it is rough, for the attachment of ligaments. The external surface is concave, presenting, along its superior and posterior borders, a narrow reversed L-shaped surface for articulation with the middle cuneiform behind, and second metatarsal bone in front; in the rest of its extent it is rough for the attachment of ligaments and part of the tendon of the Peroneus longus. The anterior surface, kidney-shaped, much larger than the posterior, articulates with the metatarsal bone of the great toe. The posterior surface is triangular, concave, and articulates with the innermost and largest of the three facets on the anterior surface of the navicular. The inferior or plantar surface is rough, and presents a prominent tuberosity at its back part for the attachment of part of the tendon of the Tibialis posticus. It also gives attachment in front to part of the tendon of the the Tibialis anticus. The superior surface is the narrow-pointed end of the wedge, which is directed upward and outward ; it is rough for the attachment of ligaments. To ascertain to which side the bone belongs, hold it so that its superior narrow edge looks upward, and the long, kidney-shaped, articular surface forward; the external surface, marked by its vertical and horizontal articular facets, will point to the side to which it belongs. Articulations.-With four bones: navicular, middle cuneiform, first and second metatarsal bones. Attachment of Muscles.-To three: the Tibialis anticus and posticus, and Peroneus longus. The Middle Cuneiform, the smallest of the three, is of very regular wedge-like form, the broad extremity being placed upward, the narrow end downward. It is situated between the other two bones of the same name, and articulates with the navicular behind and the second metatarsal in front. It may be distinguished from the external cuneiform bone, which it much resembles in general appearance, by the articular facet, of angular form, which runs round the upper and back part of its inner surface; and if the two bones from the same foot are together, the middle cuneiform is much the smaller. The anterior surface, triangular in form and, narrower than the posterior, articulates with the base of the second metatarsal bone. The posterior surface, also triangular, articulates with the navicular. The internal surface presents a reversed L-shaped articular facet, running along the superior and posterior borders, for articulation with the internal cuneiform, and is rough in the rest of its extent for the attachment of ligaments. The external surface presents posteriorly a smooth facet for articulation with the external cuneiform bone. The superior The Cuneiform Bones. 308 THE SKELETON. surface forms the base of the wedge; it is quadrilateral, broader behind than in front, and rough for the attachment of ligaments. The inferior surface, pointed and tubercular, is also rough for ligamentous attachment and for the insertion of a slip from the tendon of the Tibialis posticus. To ascertain to which foot the bone belongs, hold its superior or dorsal surface upward, the broadest edge being toward the holder: the smooth facet (limited to the posterior border) will then point to the side to which it belongs. Articulations.-With four bones: navicular, internal and external cuneiform, and second metatarsal bone. Attachment of Muscles.-A slip from the tendon of the Tibialis posticus is attached to this bone. The External Cuneiform, intermediate in size between the two preceding, is of a very regular wedge-like form, the broad extremity being placed upward, the narrow' end downward. It occupies the centre of the front rowr of the tarsus between the middle cuneiform internally, the cuboid externally, the navicular behind, and the third metatarsal in front. It is distinguished from the internal cuneiform bone by its more regular wedge-like shape and by the absence of the kidney-shaped articular surface: from the middle cuneiform, by the absence of the reversed L-shaped facet, and by the two articular facets which are present on both its inner and outer surfaces. It has six surfaces for examination. The anterior surface, triangular in form, articulates with the third metatarsal bone. The posterior surface articulates with the most external facet of the navicular, and is rough below for the attachment of ligamentous fibres. The internal surface presents two articular facets, separated by a rough depression ; the anterior one, sometimes divided into two, articulates with the outer side of the base of the second metatarsal bone; the posterior one skirts the posterior border and articulates with the middle cuneiform ; the rough depression between the two gives attachment to an interosseous ligament. The external surface also presents tw'o articular facets, separated by a rough non-articular surface; the anterior facet, situated at the superior angle of the bone, is small, and articulates with the inner side of the base of the fourth metatarsal; the posterior and larger one articulates with the cuboid; the rough, non-articular surface serves for the attachment of an interosseous ligament. The three facets for articulation with the three metatarsal bones are continuous with one another, and covered by a prolongation of the same cartilage; the facets for articulation with the middle cuneiform and navicular are also continuous, but that for articulation with the cuboid is usually separate. The superior or dorsal surface is of an oblong square form, its posterior external angle being prolonged backward. The inferior or plantar surface is an obtuse rounded margin, and serves for the attachment of part of the tendon of the Tibialis posticus, part of the Flexor brevis hallucis, and ligaments. To ascertain to which side the bone belongs, hold it with the broad dorsal surface upward, the prolonged edge backward; the separate articular facet for the cuboid will point to the proper side. Articulations.-With six bones: the navicular, middle cuneiform, cuboid, and second, third, and fourth metatarsal bones. Attachment of Muscles.-To two: part of the Tibialis posticus, and Flexor brevis hallucis. The Metatarsal Bones. The Metatarsal Bones are five in number; they are long bones, and present for examination a shaft and two extremities. Common Characters.-The shaft is prismoid in form, tapers gradually from the tarsal to the phalangeal extremity, and is slightly curved longitudinally, so as to be concave below, slightly convex above. The posterior extremity, or base, is wedge-shaped, articulating by its terminal surface with the tarsal bones, and by its lateral surfaces with the contiguous metatarsal bones, its dorsal and plantar surfaces being rough for the attachment of ligaments. The anterior extremity, THE METATARSAL BONES. 309 or head, presents a terminal rounded articular surface, oblong from above downward and extending farther backward below than above. Its sides are flattened, and present a depression, surmounted by a tubercle, for ligamentous attachment. Its under surface is grooved in the middle line for the passage of the Flexor tendon, and marked on each side by an articular eminence continuous with the terminal articular surface. Peculiar Characters.-The First is remarkable for its great thickness, but is the shortest of all the metatarsal bones. The shaft is strong and of well-marked prismoid form. The posterior extremity presents no lateral articular facets; its terminal articular surface is of large size, kidney-shaped; its circumference is grooved, for the tarso-metatarsal ligaments, and internally gives attachment to part of the tendon of the Tibialis anticus: its inferior angle presents a rough oval prominence for the insertion of the tendon of the Peroneus longus. The head is of large size; on its plantar surface are two grooved facets, over which glide sesamoid bones; the facets are separated by a smooth elevated ridge. This bone is known by the single kidney-shaped articular surface on its base, the deeply grooved appearance of the plantar surface of its head, and its great thickness relatively to its length. When it is placed in its natural position, the concave border of the kidney-shaped articular surface on its base points to the side to which the bone belongs. The Second is the longest and largest of the remaining metatarsal bones, being prolonged backward into the recess formed between the three cuneiform bones. Its tarsal extremity is broad above, narrow and rough below. It presents four articular surfaces: one behind, of a triangular form, for articulation with the middle cuneiform; one at the upper part of its internal lateral surface, for articu- lation with the internal cuneiform: and two on its external lateral surface, a posterior and anterior, separated by a vertical ridge. Each of these external articular surfaces is divided by a rough depression into two parts; the two anterior facets articulate with the third metatarsal; the two posterior (sometimes continuous) with the external cuneiform. The facets on the tarsal extremity of the second metatarsal bone serve at once to distinguish it from the rest, and to indicate the foot to which it belongs ; there being one facet at the upper angle of the internal surface, and two facets, each subdivided into two parts, on the external surface, pointing to the side to which the bone belongs. The fact that the two posterior subdivisions of these external facets sometimes run into one should not be forgotten. The Third articulates behind, by means of a triangular smooth surface, with the external cuneiform; on its inner side, by two facets, with the second meta- tarsal ; and on its outer side, by a single facet, with the fourth metatarsal. The latter facet is of circular form and situated at the upper angle of the base. The third metatarsal is known by its having at its tarsal end two undivided facets on the inner side, and a single facet on the outer. This distinguishes it from the second metatarsal, in which the two facets, found on one side of its tarsal end, are each subdivided into two. The single facet (when the bone is put in its natural position) is on the side to which the bone belongs. The Fourth is smaller in size than the preceding; its tarsal extremity presents a terminal quadrilateral surface, for articulation with the cuboid ; a smooth facet on the inner side, divided by a ridge into an anterior portion for articulation with the third metatarsal, and a posterior portion for articulation with the external cunei- form ; on the outer side a single facet, for articulation with the fifth metatarsal. The fourth metatarsal is known bv its having a' single facet on either side of the tarsal extremity, that on the inner side being divided into two parts. If this subdivision be not recognizable, the fact that its tarsal end is bent somewhat outward will indicate the side to which it belongs. The Fifth is recognized by the tubercular eminence on the outer side of its base. It articulates behind, by a triangular surface cut obliquely from without inward, with the cuboid, and internally with the fourth metatarsal. 310 THE SKELETON. The projection on the outer side of this bone at its tarsal end at once distin- guishes it from the others, and points to the side to which it belongs. Articulations.-Each bone articulates with the tarsal bones by one extremity, and by the other with the first row of phalanges. The number of tarsal bones with which each metatarsal articulates is one for the first, three for the second, one for the third, two for the fourth, and one for the fifth. Attachment of Muscles.-To the first metatarsal bone, three : part of the Tibialis anticus, the Peroneus longus, and First dorsal interosseous. To the second, four : the Adductor obliquus hallucis and First and Second dorsal inter- osseous, and a slip from the tendon of the Tibialis posticus, and occasionally a slip from the Peroneus longus. To the third, five: the Adductor obliquus hallucis, Second and Third dorsal, and First plantar interosseous, and a slip from the tendon of the Tibialis posticus. To the fourth, five : the Adductor obliquus hallucis. Third and Fourth dorsal, and Second plantar interosseous, and a slip from the tendon of the Tibialis posticus. To the fifth, six : the Peroneus brevis, Peroneus tertius, Flexor brevis minimi digiti, Adductor transversus hallucis, Fourth dorsal, and Third plantar interosseous. The Phalanges. The Phalanges of the foot, both in number and general arrangement, resemble those in the hand ; there being two in the great toe and three in each of the other toes. The phalanges of the first row resemble closely those of the hand. The shaft is compressed from side to side, convex above, concave below. The posterior extremity is concave; and the anterior extremity presents a trochlear surface, for articulation with the second phalanges. The phalanges of the second row are remarkably small and short, but rather broader than those of the first row. The ungual phalanges in form resemble those of the fingers; but they are smaller, flattened from above downward, presenting a broad base for articulation with the second row, and an expanded extremity for the support of the nail and end of the toe. Articulation.-The first row, with the metatarsal bones behind and second phalanges in front; the second row of the four outer toes, with the first and third phalanges ; of the great toe, with the first phalanx; the third row of the four outer toes, with the second phalanges. Attachment of Muscles.-To the first phalanges. Great toe, five muscles: innermost tendon of Extensor brevis digitorum, Abductor hallucis, Adductor obliquus hallucis, Flexor brevis hallucis, Adductor transversus hallucis. Second toe, three muscles: First and Second dorsal interosseous and First lumbrical. Third toe, three muscles : Third dorsal and First plantar interosseous and Second lumbrical. Fourth toe, three muscles : Fourth dorsal and Second plantar inter- osseous and Third lumbrical. Fifth toe, four muscles : Flexor brevis minimi digiti, Abductor minimi digiti, and Third plantar interosseous, and Fourth lumbrical.-Second phalanges. Great toe; Extensor longus hallucis, Flexor longus hallucis. Other toes; Flexor brevis digitorum, one slip of the common tendon of the Extensor longus and brevis digitorum.1-Third phalanges : two slips from the common tendon of the Extensor longus and Extensor brevis digitorum, and the Flexor longus digitorum. The Tarsal bones are each developed by a single centre, excepting the os calcis, which has an epiphysis for its posterior extremity. The centres make their appear- ance in the following order: os calcis, at the sixth month of foetal life ; astragalus, Development of the Foot (Fig. 226). 1 Except the second phalanx of the fifth toe, which receives no slip from the Extensor brevis digitorum. CONSTRUCTION OF THE FOOT AS A WHOLE. 311 about the seventh month; cuboid, at the ninth month; external cuneiform, during the first year; internal cuneiform in the third year; middle cuneiform and navicular in the fourth year. The epiphysis for the posterior tuberosity of .Appears 10th year: unites after puberty. Tarsus. One centre for each bone, except os calcis. Metatarsus. Two centres for each bone: '' One for shaft, One for digital extremity except 1st. Appears 5th year. Unite 18th-20 year. Appears 7th week. Appears 7th week. Unite 18th-20th year. Appears 3rd year. Appears 4th year.. Phalanges. Appears 2nd~4th month.- Unite 17-18th year. 1st row. Two centres for each bone: One for shaft, One for metatarsal extremity. Appears 6th-7th year. Unite 17th-18th year. &ra row. 2nd row. Appears 2nd~4th month.' Appears 6th year.' Unite 17 th-18 th year. Appears 7th week. Fig. 226.-Plan of the development of the foot. the os calcis appears at the tenth year, and unites with the rest of the bone soon after puberty. The Metatarsal bones are each developed by two centres: one for the shaft and one for the digital extremity in the four outer metatarsal; one for the shaft and one for the base in the metatarsal bone of the great toe.1 Ossification commences in the centre of the shaft about the ninth week, and extends toward either extremity. The centre in the proximal end of the first metatarsal bone appears about the third year, the centre in the distal end of the other bones between the fifth and eighth years; they become joined between the eighteenth and twentieth years. The Phalanges are developed by two centres for each bone: one for the shaft and one for the metatarsal extremity. Construction of the Foot as a Whole. The foot is constructed on the same principles as the hand, but modified to form a firm basis of support for the rest of the body when in the erect position. It 1 As was noted in the first metacarpal bone, so in the first metatarsal, there is often to be observed a tendency to the formation of a second epiphysis in the distal extremity. (See footnote, p. 274). 312 THE SKELETON. is more solidly constructed, and its component parts are less movable on each other than in the hand. This is especially the case with the great toe, which has to assist in supporting the body, and is therefore constructed with greater solidity ; it lies parallel with the other toes, and has a very limited degree of mobility, whereas the thumb, which is occupied in numerous and varied movements, is constructed in such a manner as to permit of great mobility. Its metacarpal bone is directed away from the others, so as to form an acute angle with the second, and it enjoys a considerable range of motion at its articulation with the carpus. The foot is placed at right angles to the leg-a position which is almost peculiar to man, and has relation to the erect position which he maintains. In order to allow' of its supporting the weight of the whole body in this position with the least expenditure of material, it is constructed in the form of an arch. This arch is not, however, made up of two equal limbs. The hinder one, which is made up of the os calcis and the posterior part of the astragalus, is about half the length of the anterior limb, and measures about three inches. The anterior limb consists of the rest of the tarsal and the metatarsal bones, and measures about six inches. It may be said to consist of two parts, an inner segment made up of the head of the astragalus, the navicular, the three cuneiform, and the three inner metatarsal bones; and an outer segment composed of the cuboid and the two outer metatarsal bones. The summit of the arch is at the superior articular surface of the astragalus; and its two extremities-that is to say, the two points on which the arch rests in standing- are the tubercles on the under surface of the os calcis posteriorly, and the heads of the metatarsal bones anteriorly. The weakest part of the arch is the joint between the astragalus and scaphoid, and here it is more liable to yield in those who are overweighted, and in those in whom the ligaments which complete and preserve the arch are relaxed. This w eak point in the arch is braced on its concave surface by the inferior calcaneo-navicular ligament, which is more elastic than most other ligaments, and thus allows the arch to yield from jars or shocks applied to the anterior portion of the foot and quickly restores it to its pristine condition. This ligament is supported on its under surface by the tendon of the Tibialis posticus muscle, which is spread out into a fan-shaped insertion, and prevents undue tension of the ligament or such an amount of stretching as would permanently elongate it. In addition to this longitudinal arch the foot presents a transverse arch, at the anterior part of the tarsus and hinder part of the metatarsus. This, how ever, can scarcely be described as a true arch, but presents more the character of a half-dome. The inner border of the central portion of the longitudinal arch is elevated from the ground, and from this point the bones arch over to the outer border, which is in contact w ith the ground, and, assisted by the longitudinal arch, produce a sort of rounded niche on the inner side of the foot, which gives the appearance of a transverse as well as a longitudinal arch. The arch of the foot, from the point of the heel to the toes, is not quite straight, but is directed a little outward, so that the inner border is a little convex and the outer border concave. This disposition of the bones becomes more marked when the longitudinal arch of the foot is lost, as in the disease known under the name of "flat-foot." Surface Form.-On the dorsum of the foot the individual bones are not to be distinguished with the exception of the head of the astragalus, which forms a rounded projection in front of the ankle-joint when the foot is forcibly extended. The whole surface forms a smooth convex outline, the summit of which is the ridge formed by the head of the astragalus, the navicular, the middle cuneiform, and the second metatarsal bones; from this it gradually inclines outward and more rapidly inward. On the inner side of the foot, the internal tuberosity of the os calcis and the ridge separating the inner from the posterior surface of the bone may be felt most pos- teriorly. In front of tbis, and below the internal malleolus, may be felt the projection of the sustentaculum tali. Passing forward is the well-marked tuberosity of the navicular bone, situ- ated about an inch or an inch and a quarter in front of the internal malleolus. Further toward the front, the ridge formed by the base of the first metatarsal bone can be obscurely felt, and from this the shaft of the bone can be traced to the expanded head articulating with the base of the first phalanx of the great toe. Immediately beneath the base of this phalanx, the SURGICAL ANATOMY OF THE FOOT 313 internal sesamoid bone is to be felt. Lastly, the expanded ends of the bones forming the last joint of the great toe are to be felt. On the outer side of the foot the most posterior bony point is the outer tuberosity of the os calcis, with the ridge separating the posterior from the outer surface of the bone. In front of this the greater part of the external surface of the os calcis is subcutaneous; on it, below and in front of the external malleolus, may be felt the pero- neal ridge, when this process is present. Farther forward, the base of the fifth metatarsal bone forms a prominent and well-defined landmark, and in front of this the shaft of the bone, with its expanded head, and the base of the first phalanx may be defined. The sole of the foot is almost entirely covered by soft parts, so that but few bony parts are to be made out, and these somewhat obscurely. The hinder part of the under surface of the os calcis and the heads of the metatarsal bones, with the exception of the first, which is concealed by the sesamoid bones, may be recognized. Surgical Anatomy.-Considering the injuries to which the foot is subjected, it is surpris- ing how seldom the tarsal bones are fractured. This is no doubt due to the fact that the tarsus is composed of a number of bones, articulated by a considerable extent of surface and joined together by very strong ligaments, which serve to break the force of violence applied to this part of the body. When fracture does occur, these bones, being composed for the most part of a soft cancellous structure, covered only bj7 a thin shell of compact tissue, are often extensively comminuted, especially as most of the fractures are produced by direct violence. And having only a very scanty amount of soft parts over them, the fractures are very often compound, and amputation is frequently necessary. When fracture occurs in the anterior group of tarsal bones, it is almost invariably the result of direct violence ; but fractures of the posterior group, that is, of the calcaneum and astrag- alus, are most frequently produced by falls from a height on to the feet; though fracture of the os calcis may be caused by direct violence or by muscular action. The posterior part of the bone, that is, the part behind the articular surfaces, is almost always the seat of the fracture, though some few cases of fracture of the sustentaculum tali and of vertical fracture between the two articulating facets have been recorded. The neck of the astragalus, being the weakest part of the bone, is most frequently fractured, though fractures may occur in any part and almost in any direction, either associated or not with fracture of other bones. In cases of club-foot, especially in congenital cases, the bones of the tarsus become altered in shape and size, and displaced from their proper positions. This is especially the case in con- genital equino-varus, in which the astragalus, particularly about the head, becomes twisted and atrophied, and a similar condition may be present in the other bones, more especially the navic- ular. The tarsal bones are peculiarly liable to become the seat of tubercular caries from com- paratively trivial injuries. There are several reasons to account for this. They are composed of a delicate cancellated structure, surrounded by intricate synovial membranes. They are situ- ated at the farthest point from the central organ of the circulation and exposed to vicissitudes of temperature; and, moreover, on their dorsal surface are thinly clad with soft parts which have but a scanty blood-supply. And finally, after slight injuries, they are not maintained in a condition of rest to the same extent as similar injuries in some other parts of the body. Caries of the calcaneum and astragalus may remain limited to the one bone for a long period, but when one of the other bones is affected, the remainder frequently become involved, in consequence of the disease spreading through the large and complicated synovial membrane which is more or less common to these bones. Amputation of the whole or a part of the foot is frequently required either for injury or disease. The principal amputations areas follow: (1) Syme's: amputation at the ankle-joint by a heel-flap, with removal of the malleoli and sometimes a thin slice from the lower end of the tibia. (2) Roux's: amputation at the ankle-joint by a large internal flap. (3) Pirogoff's amputation : removal of the whole of the tarsal bones, except the posterior part of the os calcis and a thin slice from the tibia and fibula including the two malleoli. The sawn surface of the os calcis is then turned up and united to the similar surface of the tibia. (4) Subastragaloid amputation : removal of the foot below the astragalus through the joint between it and the os calcis. This operation has been modified by Hancock, who leaves the posterior third of the os calcis and turns it up against the denuded surface of the astragalus. This latter operation is of doubtful utility and is rarely performed. (5) Chopart's or medio-tarsal: removal of the ante- rior part of the foot with all the tarsal bones except the os calcis and astragalus; disarticula- tion being effected through the joints between the scaphoid and cuboid in front, and the astrag- alus and os calcis behind. (6) Lisfranc's: amputation of the anterior part of the foot through the tarso-metatarsal joints. This has been modified by Hey, who disarticulated through the joints of the four outer metatarsal bones with the tarsus, and sawed off' the projecting internal cuneiform; and by Skey, who sawed off the base of the second metatarsal bone and disarticu- lated the others. The bones of the tarsus occasionally require removal'individually. This is especially the case with the astragalus and os calcis for disease limited to the one bone, or again the astragalus may require excision in cases of subastragaloid dislocation, or, as recommended by Mr. Lund, in cases of inveterate talipes. The cuboid has been removed for the same reason by Mr. Solly. But both these two latter operations have fallen very much into disuse, and have been super- seded by resection of a wedge-shaped piece of bone from the outer side of the tarsus. Finally. Mickulicz and Watson have devised operations for the removal of more extensive portions of the tarsus. Mickulicz's operation consists in the removal of the os calcis and astragalus, along 314 THE SKELETON. with the articular surfaces of the tibia and fibula, and also of the scaphoid and cuboid. The remaining portion of the tarsus is then brought into contact with the sawn surfaces of the tibia and fibula, and fixed there. The result is a position of the shortened foot resembling talipes equinus. Watson's operation is adapted to those cases where the disease is confined to the anterior tarsal bones. By two lateral incisions he saws through the bases of the metatarsal bones in front and opens up the joints between the scaphoid and astragalus, and the cuboid and os calcis, and removes the intervening bones. The metatarsal bones and phalanges are nearly always broken by direct violence, and in the majority of cases the injury is the result of severe crushing accidents, necessitating amputation. The metatarsal bones and especially the one of the great toe, are frequently diseased, either in tubercular subjects or in perforating ulcer of the foot. Sesamoid Bones. These are small rounded masses, cartilaginous in early life, osseous in the adult, which are developed in those tendons which exert a great amount of pressure upon the parts over which they glide. It is said that they are more commonly found in the male than in the female, and in persons of an active muscular habit than in those who are weak and debilitated. They are invested throughout their whole surface by the fibrous tissue of the tendon in which they are found, excepting upon that side which lies in contact with the part over which they play, where they present a free articular facet. They may be divided into two kinds: those which glide over the articular surfaces of joints, and those which play over the cartilag- inous facets found on the surfaces of certain bones. The sesamoid bones of the joints in the upper extremity, are two on the palmar surface of the metacarpo-phalangeal joint in the thumb, developed in the tendons of the Flexor brevis pollicis; occasionally one or two opposite the metacarpo- phalangeal articulations of the fore and little fingers; and, still more rarely, one opposite the same joints of the third and fourth fingers. In the lower extremity, the patella, which is developed in the tendon of the Quadriceps extensor; two small sesamoid bones, found in the tendons of the Flexor brevis hallucis, opposite the metatarso-phalangeal joint of the great toe ; and occasionally one in the metatarso- phalangeal joint of the second toe, the little toe, and, still more rarely, the third and fourth toes. Those found in the tendons which glide over certain bones occupy the following situations: one sometimes found in the tendon of the Biceps cubiti, opposite the tuberosity of the radius : one in the tendon of the Peroneus longus, where it glides through the groove in the cuboid bone ; one appears late in life in the tendon of the Tibialis anticus, opposite the smooth facet of the internal cuneiform bone; one is found in the tendon of the Tibialis posticus, opposite the inner side of the head of the astragalus; one in the outer head of the Gastrocnemius, behind the outer condyle of the femur; and one in the conjoined tendon of the Psoas and Iliacus, where it glides over the os pubis. Sesamoid bones are found occasionally in the tendon of the Gluteus maximus, as it passes over the great trochanter, and in the tendons which wind round the inner and outer malleoli. THE ARTICULATIONS. THE various bones of which the Skeleton consists are connected together at different parts of their surfaces, and such a connection is designated by the name of JoiW or Articulation. If the joint is immovable, as between the cranial and most of the facial bones, the adjacent margins of the bones are applied in almost close contact, a thin layer of fibrous membrane, the sutural ligament, and, at the base of the skull, in certain situations, a thin layer of cartilage, being interposed. Where slight movement is required, combined with great strength, the osseous surfaces are united by tough and elastic fibro-cartilages, as in the joints of the spine, the sacro-iliac and interpubic articulations; but in the movable joints the bones forming the articulation are generally expanded for greater convenience of mutual connection, covered by cartilage, held together by strong bands or capsules of fibrous tissue called ligaments, and partially lined by a membrane, the synovial membrane, which secretes a fluid to lubricate the various parts of which the joint is formed; so that the structures which enter into the formation of a joint are bone, cartilage, fibro-cartilage, ligament, and synovial membrane. Bone constitutes the fundamental element of all the joints. In the long bones the extremities are the parts which form the articulations; they are generally somewhat enlarged, consisting of spongy cancellous tissue, with a thin coating of compact substance. In the fiat bones the articulations usually take place at the edges, and, in the short bones at various parts of their surface. The layer of compact bone which forms the articular surface, and to which the cartilage is attached, is called the articular lamella. It is of a white color, extremely dense, and varies in thickness. Its structure differs from ordinary bone-tissue in this respect, that it contains no Haversian canals, and its lacunae are much larger than in ordinary bone and have no canaliculi. The vessels of the cancellous tissue, as they approach the articular lamella, turn back in loops, and do not perforate it; this layer is consequently more dense and firmer than ordinary bone, and is evi- dently designed to form a firm and unyielding support for the articular cartilage. The cartilage, which covers the articular surfaces of bone, and is called the articular, will be found described, with the other varieties of cartilage, in the section on General Anatomy (page 51). Ligaments consist of bands of various forms, serving to connect together the articular extremities of bones, and composed mainly of bundles of white fibrous tissue placed parallel with, or closely interlaced with, one another, and presenting a white, shining, silvery aspect. A ligament is pliant and flexible, so as to allow of the most perfect freedom of movement, but strong, tough, and inextensile, so as not readily to yield under the most severely applied force ; it is consequently well adapted to serve as the connecting medium between the bones. Some liga- ments consist entirely of yellow elastic tissue, as the ligamenta subflava, which connect together the adjacent arches of the vertebrae and the ligamentum nuchae in the lower animals. In these cases it will be observed that the elasticity of the ligament is intended to act as a substitute for muscular power. Synovial membrane is a thin, delicate membrane of connective tissue, with branched connective-tissue corpuscles. Its secretion is thick, viscid, and glairy, like the white of egg, and is hence termed synovia. The synovial membranes found in the body admit of subdivision into three kinds-articular, bursal, and vaginal. The articular synovial membranes are found in all the freely movable joints. In the foetus this membrane is said, by Toynbee, to be continued over the surface 315 316 THE ARTICULATIONS. of the cartilages; but in the adult it is wanting, excepting at their circumference, upon which it encroaches for a short distance, and to which it is firmly attached; it then invests the inner surface of the capsular or other ligaments enclosing the joint, and is reflected over the surface of any tendons passing through its cavity, as the tendon of the Popliteus in the knee and the tendon of the Biceps in the shoulder. Hence the articular synovial membrane may be regarded as a short wide tube, attached by its open ends to the margins of the articular cartilages, and covering the inner surface of the various ligaments which connect the articular surfaces, so that along with the cartilages it completely encloses the joint-cavity. In some of the joints the synovial membrane is thrown into folds, which pass across the cavity. They are called synovial ligaments, and are especially distinct in the knee. In other joints there are flattened folds, subdivided at their margins into fringe-like processes, the vessels of which have a convoluted arrangement. These latter generally project from the synovial membrane near the margin of the cartilage and lie flat upon its surface. They consist of connective tissue covered with endothelium, and contain fat-cells in variable quantities, and, more rarely, isolated cartilage-cells. The larger folds often contain considerable quantities of fat. They were described by Clopton Havers as mucilaginous glands, and as the source of the synovial secretion. Under certain diseased conditions similar pro- cesses are found covering the entire surface of the synovial membrane, forming a mass of pedunculated fibro-fatty growths which project into the joint. Similar structures are also found in some of the bursal and vaginal synovial membranes. The bursal synovial membranes are found interposed between surfaces which move upon each other, producing friction, as in the gliding of a tendon or of the integument over projecting bony surfaces. They admit of subdivision into two kinds, the bursce mucosce and the bursce synovice. The bursce mucosce are large, simple, or irregular cavities in the subcutaneous areolar tissue, enclosing a clear viscid fluid. They are found in various situations, as between the integument and the front of the patella, over the olecranon, the malleoli, and other prominent parts. The bursce synovice are found interposed between muscles or tendons as they play over projecting bony surfaces, as between the Glutei muscles and the surface of the great trochanter. They consist of a thin wall of connective tissue, partially covered by patches of cells, and contain a viscid fluid. Where one of these exists in the neighborhood of a joint, it usually communicates with its cavity, as is gen- erally the case with the bursa between the tendon of the Psoas and Iliacus and the capsular ligament of the hip, or the one interposed between the under surface of the Subscapularis and the neck of the scapula. The vaginal synovial membranes (synovial sheaths) serve to facilitate the gliding of tendons in the osseo-fibrous canals through which they pass. The membrane is here arranged in the form of a sheath, one layer of which adheres to the wall of the canal, and the other is reflected upon the surface of the contained tendon, the space between the two free surfaces of the membrane being partially filled with synovia. These sheaths are chiefly found surrounding the tendons of the flexor and extensor muscles of the fingers and toes as they pass through the osseo-fibrous canals in the hand or foot. Synovia is a transparent, yellowish-white or slightly reddish fluid, viscid like the white of egg, having an alkaline reaction and slightly saline taste. It consists, according to Frerichs, in the ox, of 94.85 water, 0.56 mucus and epithelium, 0.07 fat, 3.51 albumen and extractive matter, and 0.99 salts. The articulations are divided into three classes: synarthrosis, or immovable ; amphiarthrosis, or mixed; and diarthrosis, or movable joints. ' Synarthrosis includes all those articulations in which the surfaces of the bones are in almost direct contact, fastened together by an intervening mass of connective tissue, and in which there is no appreciable motion, as the joints between the bones . 1. Synarthrosis. Immovable Articulations. CLASSIFICATION OF JOINTS. 317 of the cranium and face, excepting those of the lower jaw. The varieties of synar- throsis are four in number : Sutura, Schindylesis, Gomphosis, and Synchondrosis. Sutura (a seam) is that form of articulation where the contiguous margins of flat bones are united by a thin layer of fibrous tissue. It is met with only in the skull. Where the articulating surfaces are connected by a series of processes and indentations interlocked together, it is termed sutura vera, of which there are three varieties: sutura dentata, serrata, and limbosa. The surfaces of the bones are not in direct contact, being separated by a layer of membrane continuous externally with the pericranium, internally with the dura mater. The sutura dentata [dens, a tooth) is so called from the tooth-like form of the projecting articular processes, as in the suture between the parietal bones. In the sutura serrata (serra, a saw) the edges of the two bones forming the articulation are serrated like the teeth of a fine saw, as between the two portions of the frontal bone. In the sutura limbosa [limbus, a selvage), besides the dentated processes, there is a certain degree of bevelling of the articular surfaces, so that the bones overlap one another, as in the suture between the parietal and frontal bones. When the articulation is formed by roughened surfaces placed in apposition with one another, it is termed the false suture (sutura notha), of which there are two kinds: the sutura squamosa (squama, a scale), formed by the overlapping of two contiguous bones by broad bevelled margins, as in the squamo-parietal (squamous) suture; and the sutura liarmonia (&pp.ovta, a joining together), where there is simple apposition of two contiguous rough bony surfaces, as in the articulation between the two superior maxillary bones or of the horizontal plates of the palate bones. Schindylesis (aytvdutyati;, a fissure) is that form of articulation in which a thin plate of bone is received into a cleft or fissure formed by the separation of two laminae in another bone, as in the articulation of the rostrum of the sphenoid and perpendicular plate of the ethmoid with the vomer, or in the reception of the latter in the fissure between the superior maxillary and palate bones. Gomphosis a nail) is an articulation formed by the insertion of a conical process into a socket, as a nail is driven into a board ; this is not illustrated by any articulation between bones, properly so called, but is seen in the articulation of the teeth with the alveoli of the maxillary bones. Synchondrosis.-Where the connecting medium is cartilage the joint is termed a synchondrosis. This is a temporary form of joint, for the cartilage becomes con- verted into bone before adult life. Such a joint is found between the epiphyses and shafts of long bones. 2. Amphiarthrosis. Mixed Articulations. In this form of articulation the contiguous osseous surfaces are either con- nected together by broad flattened disks of fibro-cartilage, of a more or less complex structure, which adhere to the end of each bone, as in the articulation between the bodies of the vertebrae and the sacro-iliac and pubic symphyses. This is termed Symphysis. Or, secondly, the bony surfaces are united by an interosseous ligament, as in the inferior tibio-fibular articulation. To this the term Syndosmosis is applied. 3. Diarthrosis. Movable Articulations. This form of articulation includes the greater number of the joints in the body, mobility being their distinguishing character. They are formed by the approxi- mation of two contiguous bony surfaces covered with cartilage, connected by ligaments and lined by synovial membrane. The varieties of joints in this class have been determined by the kind of motion permitted in each. There are two varieties in which the movement is uniaxial; that is to say, all movements take place around one axis. In one form, the Ginglymus, this axis is, practically speaking, transverse; in the other, the trochoid or pivot-joint, it is longitudinal. There are two varieties where the movement is biaxial, or around two horizontal 318 THE ARTICULATIONS. axes at right angles to each other or at any intervening axis between the two. These are the condyloid and saddle-joint. There is one form of joint where the movement is polyaxial, the enarthrosis or ball-and-socket joint. And finally there are the Arthrodia or Gliding joints. Ginglymus or Hinge-joint (y/yyZu/zoc, a hinge).-In this form of joint the articular surfaces are moulded to each other in such a manner as to permit motion only in one plane, forward and backward; the extent of motion at the same time being considerable. The direction which the distal bone takes in this motion is never in the same plane as that of the axis of the proximal bone, but there is always a certain amount of alteration from the straight line during flexion. The articular surfaces are connected together by strong lateral ligaments, which form their chief bond of union. The most perfect forms of ginglymus are the inter- phalangeal joints and the joint between the humerus and ulna ; the knee and ankle are less perfect, as they allow a slight degree of rotation or lateral movement in certain positions of the limb. Trochoides (pivot-joint).-Where the movement is limited to rotation,-the joint is formed by a pivot-like process turning within a ring, or the ring on the pivot, the ring being formed partly of bone, partly of ligament. In the superior radio-ulnar articulation the ring is formed partly by the lesser sigmoid cavity of the ulna; in the rest of its extent, by the orbicular ligament; here the head of the radius rotates within the ring. In the articulation of the odontoid process of the axis with the atlas the ring is formed in front by the anterior arch of the atlas; behind, by the transverse ligament; here the ring rotates round the odontoid process. Condyloid Articulations.-In this form of joint an ovoid articular head, or condyle, is received into an elliptical cavity in such a manner as to permit of flexion and extension, adduction and abduction and circumduction, but no axial rotation. The articular surfaces are connected together by anterior, posterior, and lateral ligaments. An example of this form of joint is found in the wrist. Articulations by Reciprocal Reception (saddle-joint).-In this variety the articular surfaces are concavo-convex ; that is to say, they are inversely convex in one direction and concave in the other. The movements are the same as in the preceding form ; that is to say, there is flexion, extension, adduction, abduction, and circumduction, but no axial rotation. The articular surfaces are connected by a capsular ligament. The best example of this form of joint is the carpo-meta- carpal joint of the thumb. Enarthrosis is that form of joint in which the distal bone is capable of motion around an indefinite number of axes which have one common centre. It is formed by the reception of a globular head into a deep cup-like cavity (hence the name " ball-and-socket "), the parts being kept in apposition by a capsular ligament strengthened by accessory ligamentous bands. Examples of this form of articulation are found in the hip and shoulder. Arthrodia is that form of joint which admits of a gliding movement; it is formed by the approximation of plane surfaces or one slightly concave, the other slightly convex, the amount of motion between them being limited by the ligaments, or osseous processes, surrounding the articulation; as in the articular processes of the vertebrae, the carpal joints, except that of the os magnum with the scaphoid and semilunar bones, and the tarsal joints with the exception of the joint between the astragalus and the navicular. On the next page, in a tabular form, are the names, distinctive characters, and examples of the different kinds of articulations. The Kinds of Movement admitted in Joints. The movements admissible in joints may be divided into four kinds : gliding, angular movement, circumduction, and rotation. These movements are often, however, more or less combined in the various joints, so as to produce an infinite variety, and it is seldom that we find only one kind of motion in any particular joint. CLASSIFICATION OF JOINTS. 319 Dentata, having tooth-like processes. As in interparietal suture. Serrata, having ser- rated edges like the teeth of a saw. As in interfrontal suture. Limbosa, having bevelled margins and dentated processes. As in fronto-parie- tal suture. Sutura vera (true), articulate by indented bor- ders. Sutura. Ar- ticulation by processes and indentations interlocked to- gether. Synarthrosis, or Immovable Joint. Surfaces separated by fibrous mem- brane, without any intervening synovial cavity, and immovably connected with each other. As in joints of cranium and face (except lower jaw). Squamosa, formed by thin bevelled mar- gins, overlapping each other. As in squamo-parie- tal suture. Zfarmtmhz,formedby the apposition of con- tiguousrough surfaces. As in intermaxil- lary suture. Sutura notha (false), articulate by rough surfaces. Schindylesis.-Articulation formed by the reception of a thin plate of one bone into a fissure of another. As in articulation of rostrum of sphenoid with vomer. G-omphosis.-Articulation formed by the insertion of a conical process into a socket. The teeth. Symphysis.-Surfaces connected by fibro-cartilage, not separated by synovial membrane, and having limited motion. As in joints between bodies of vertebrae. Syndesmosis.-Surfaces united by an interosseous ligament. As in the inferior tibio-fibular articulation. Amphiarthrosis, Mixed Articula- tion. Gringlymus.-Hinge-joint ; motion limited to two directions, forward and backward. Articular surfaces fitted togethei' so as to permit of movement in one plane. As in the inter- phalangeal joints and the joint between the humerus and the ulna. Trochoides, or Pivot-joint.-Articulation by a pivot process turning within a ring or ring around a pivot. As in superior radio-ulnar articulation and atlanto-axial joint. Condyloid.-Ovoid head received into elliptical cavity. Movements in every direction except axial rotation. As the wrist-joint. Reciprocal Reception (saddle-joint).-Articular surfaces inversely convex in one direction and concave in the other. Movement in every direction except axial rotation. As in the carpo-metacarpal joint of the thumb. Enarthrosis.-Ball-and-socket joint; capable of motion in all directions. Articulations by a globular head received into a cup-like cavity. As in hip- and shoulder-joints. Arthrodia.-Gliding joint; articulations by plane surfaces, which glide upon each other. As in carpal and tarsal articu- lations. Diarthrosis, Movable Joint. 320 THE ARTICULATIONS Gliding movement is the most simple kind of motion that can take place in a joint, one surface gliding or moving over another without any angular or rotatory movement. It is common to all movable joints, but in some, as in the articu- lations of the carpus and tarsus, it is the only motion permitted. This movement is not confined to plane surfaces, but may exist between any two contiguous surfaces, of whatever form, limited by the ligaments which enclose the articu- lation. Angular movement occurs only between the long bones, and by it the angle between the two bones is increased or diminished. It may take place in four directions : forward and backward, constituting flexion and extension, or inward and outward, from the mesial line of the body (or in the fingers and toes from the middle line of the hand or foot), constituting adduction and abduction. The strictly ginglymoid or hinge-joints admit of flexion and extension only. Abduction and adduction, combined with flexion and extension, are met with in the more movable joints; as in the hip, shoulder, and metacarpal joint of the thumb, and partially in the wrist. Circumduction is that limited degree of motion which takes place between the head of a bone and its articular cavity, whilst the extremity and sides of the limb are made to circumscribe a conical space, the base of which corresponds with the inferior extremity of the limb, the apex with the articular cavity; this kind of motion is best seen in the shoulder- and hip-joints. Rotation is the movement of a bone upon an axis, which is the axis of the pivot on which the bone turns, as in the articulation between the atlas and axis, when the odontoid process serves as a pivot around which the atlas turns; or else is the axis of a pivot-like process which turns within a ring, as in the rotation of the radius upon the humerus. Ligamentous Action of Muscles.-The movements of the different joints of a limb are combined by means of the long muscles which pass over more than one joint, and which, when relaxed and stretched to their greatest extent, act to a certain extent as elastic ligaments in restraining certain movements of one joint, except when combined with corresponding movements of the other, these latter movements being usually in the opposite direction. Thus the shortness of the hamstring muscles prevents complete flexion of the hip, unless the knee-joint be also flexed, so as to bring their attachments nearer together. The uses of this arrangement are threefold: 1. It co-ordinates the kinds of movement which are the most habitual and necessary, and enables them to be performed with the least expendi- ture of power. " Thus in the usual gesture of the arms, whether in grasping or rejecting, the shoulder and the elbow are flexed simultaneously, and simultaneously extended," in consequence of the passage of the Biceps and Triceps cubiti over both joints. 2. It enables the short muscles which pass over only one joint to act upon more than one. "Thus, if the Rectus femoris remain tonically of such length that, when stretched over the extended hip, it compels extension of the knee, then the Gluteus maximus becomes not only an extensor of the hip, but an extensor of the knee as well." 3. It provides the joints with ligaments which, while they are of very great power in resisting movements to an extent incompatible with the mechanism of the joint, at the same time spontaneously yield when necessary. " Taxed beyond its strength, a ligament will be ruptured, whereas a contracted muscle is easily relaxed; also, if neighboring joints be united by ligaments, the amount of flexion or extension of each must remain in constant proportion to that of the other; while, if the union be by muscles, the separation of the points of attach- ment of those muscles may vary considerably in different varieties of movement, the muscles adapting themselves tonically to the length required." The quotations are from a very interesting paper by Dr. Cleland in the Journal of Anatomy and Physiology, No. 1, 1866, p. 85; by whom I believe this important fact in the mechanism of joints was first clearly pointed out, though it has been independently observed afterward by other anatomists. Dr. W. W. Keen points out how important it is " that the surgeon should remember this ligamentous action of OF THE VERTEBRAL COLUMN. 321 muscles in making passive motion-for instance, at the wrist after Colles's fracture. If the fingers be extended, the wrist can be flexed to a right angle. If, however, they be first flexed, as in " making a fist," flexion at the wrist is quickly limited to from forty to fifty degrees in different persons, and is very painful beyond that point. Hence passive motion here should be made with the fingers extended. In the leg, when flexing the hip, the knee should be flexed.' Dr. Keen further points out that " a beautiful illustration of this is seen in the perching of birds, whose toes are forced to clasp the perch by just such a passive ligamentous action so soon as they stoop. Hence they can go to sleep and not fall off the perch." The articulations may be arranged into those of the trunk, those of the upper extremity, and those of the lower extremity. ARTICULATIONS OF THE TRUNK. I. Of the vertebral column. II. Of the atlas with the axis. III. Of the atlas with the occipital bone. IV. Of the axis with the occipital bone. V. Of the lower jaw. VI. Of the ribs with the vertebrae. These may be divided into the following groups, viz.: VII. Of the cartilages of the ribs with the sternum and with each other. VIII. Of the sternum. IX. Of the vertebral column with the pelvis. X. Of the pelvis. I. Articulations of the Vertebral Column. The different segments of the spine are connected together by ligaments, which admit of the same arrangement as the vertebrae. They may be divided into five sets: 1. Those connecting the bodies of the vertebrae. 2. Those connecting the lamina?. 3. Those connecting the articular processes. 4. Those connecting the spinous processes. 5. Those of the transverse processes. The articulations of the bodies of the vertebrae with each other form a series of amphiarthrodial joints ; those between the articular processes form a series of arthrodial joints. 1. Tiie Ligaments of the Bodies. Anterior Common Ligament. Posterior Common Ligament. Intervertebral Substance. The Anterior Common Ligament (Figs. 227, 228, 235, 239) is a broad and strong band of ligamentous fibres which extends along the front surface of the bodies of the vertebrae from the axis to the sacrum. It is broader below' than above, thicker in the dorsal than in the cervical or lumbar regions, and somewhat thicker opposite the front of the body of each vertebra than opposite the inter- vertebral substance. It is attached, above, to the body of the axis by a pointed process, where it is continuous with the anterior atlanto-axial ligament, and is connected with the tendon of insertion of the Longus colli muscle, and extends down as far'as the upper bone of the sacrum. It consists of dense longitudinal fibres, which are intimately adherent to the intervertebral substance and the prominent margins of the vertebrae, but less closely to the middle of the bodies. In the latter situation the fibres are exceedingly thick, and serve to fill up the concavities on their front surface and to make the anterior surface of the spine more even. This ligament is composed of several layers of fibres, which vary in length, but are closely interlaced with each other. The most superficial or longest fibres extend between four or five vertebrae. A second subjacent set extend between two or three vertebrae, whilst a third set, the shortest and deepest, extend from one vertebra to the next. At the side of the bodies the ligament consists of a few short fibres, which pass from one vertebra to the next, separated from the median portion by large oval apertures for the passage of vessels. The Posterior Common Ligament (Figs. 227, 231) is situated within the spinal 322 THE A11TICULA TIONS canal, and extends along the posterior surface of the bodies of the vertebrae from the body of the axis above, where it is continuous with the occipito-axial ligament, to the sacrum below. It is broader above than below', and thicker in the dorsal than in the cervical or lumbar regions. In the situation of the intervertebral substance and contiguous margins of the vertebrae, where the ligament is more intimately adherent, it is broad, and presents a series of dentations with inter- vening concave margins; but it is narrow' and thick over the centre of the bodies, from which it is separated by the vena basis vertebra. This ligament is composed of smooth, shining, longitudinal fibres, denser and more compact than those of the anterior ligament, and composed of a superficial layer occupying the interval between three or four vertebrae, and of a deeper layer which extends between one vertebra and the next adjacent to it. It is separated from the dura mater of ANTERIOR COMMON . LIGAMENT. POSTERIOR COMMON LIGAMENT. Fig. 227.-Vertical section of two vertebree and their ligaments, from the lumbar region. the spinal cord by some loose connective tissue which is very liable to serous infiltration. The Intervertebral Substance (Figs. 227, 236) is a lenticular disk of composite structure interposed between the adjacent surfaces of the bodies of the vertebrae from the axis to the sacrum, and forming the chief bond of connection between those bones. These disks vary in shape, size, and thickness in different parts of the spine. In shape they accurately correspond with the surfaces of the bodies between which they are placed, being oval in the cervical and lumbar regions, and circular in the dorsal. Their size is greatest in the lumbar region. In thickness they vary not only in the different regions of the spine, but in different parts of the same disk: thus, they are much thicker in front than behind in the cervical and lumbar regions, while they are uniformly thick in the dorsal region. The intervertebral disks form about one-fourth of the spinal column, exclusive of the first two vertebrae; they are not equally distributed, however, betw een the various bones; the dorsal portion of the spine having, in proportion to its length, a much smaller quantity than in the cervical and lumbar regions, which necessarily gives to the latter parts greater pliancy and freedom of movement. The intervertebral disks are adherent, by their surfaces, to a thin layer of hyaline cartilage which covers the upper and under surfaces of the bodies of the vertebrae, and in which the epiphysial plate develops, and by their circumference are closely connected in OF THE VERTEBRAL COLUMN. 323 front to the anterior, and behind to the posterior common ligament; whilst in the dorsal region they are connected laterally, by means of the interarticular ligament, to the heads of those ribs which articulate with two vertebrae ; they, consequently, form part of the articular cavities in which the heads of these bones are received. Structure of the Intervertebral Substance.-The intervertebral substance is composed, at its circumference, of laminae of fibrous tissue and fibro-cartilage; ami, at its centre, of a soft, pulpy, highly elastic substance, of a yellowish color, which rises up considerably above the surrounding level when the disk is divided horizontally. This pulpy substance, which is especially well developed in the lumbar region, is the remains of the chorda dorsalis, and, according to Luschka, contains a small synovial cavity in its centre. The laminae are arranged concen- trically one within the other, the outermost consisting of ordinary fibrous tissue, but the others and more numerous consisting of white fibro-cartilage. These plates are not quite vertical in their direction, those near the circumference being curved outward and closely approximated; whilst those nearest the centre curve in the opposite direction, and are somewhat more widely separated. The fibres of which each plate is composed are directed, for the most part, obliquely from above downward, the fibres of adjacent plates passing in opposite directions and varying in every layer; so that the fibres of one layer are directed across those of another, like the limbs of the letter X. This laminar arrangement belongs to about the outer half of each disk. The pulpy substance presents no concentric arrangement, and consists of a fine fibrous matrix, containing angular cells, united to form a reticular structure. 2. Ligaments connecting the Laminjs. Ligamenta Subflava. The Ligamenta Subflava (Fig. 227) are interposed between the laminae of the vertebrae, from the axis to the sacrum. They are most distinct when seen from the interior of the spinal canal; when viewed from the outer surface they appear short, being overlapped by the laminae. Each ligament consists of two lateral portions, which commence on each side at the root of either articular process, and pass backward to the point where the laminae converge to form the spinous process, where their margins are in contact and to a certain extent united; slight intervals being left for the passage of small vessels. These ligaments consist of yellow elastic tissue, the fibres of which, almost perpendicular in direction, are attached to the anterior surface of the laminae above, some distance from its inferior margin, and to the posterior surface, as well as to the margin of the lamina below. In the cervical region they are thin in texture, but very broad and long ; they become thicker in the dorsal region, and in the lumbar acquire very considerable thickness. Their highly elastic property serves to preserve the upright posture and to assist in resuming it after the spine has been flexed. These ligaments do not exist between the occiput and atlas or between the atlas and axis. 3. Ligaments connecting the Articular Processes. Capsular. The Capsular Ligaments (Fig. 229) are thin and loose ligamentous sacs, attached to the contiguous margins of the articulating processes of each vertebra through the greater part of their circumference, and completed internally by theligamenta subflava. They are longer and looser in the cervical than in the dorsal or lumbar regions. The capsular ligaments are lined on their inner surface bv svnovial membrane. 4. Ligaments connecting the Spinous Processes Supraspinous. Interspinous. The Supraspinous Ligament (Fig. 227) is a strong fibrous cord, which connects 324 THE ARTICULATIONS together the apices of the spinous processes from the seventh cervical to the spinous processes of the sacrum. It is thicker and broader in the lumbar than in the dorsal region, and intimately blended, in both situations, with the neighboring aponeu- rosis. The most superficial fibres of this ligament connect three or four vertebrae ; those deeper-seated pass between twTo or three vertebrae ; whilst the deepest connect the contiguous extremities of neighboring vertebrae. It is continued upward to the external occipital protuberance, as the ligamentum nuchae, which, in the human subject, is thin and forms merely an intermuscular septum. The Interspinous Ligaments (Fig. 227), thin and membranous, are interposed between the spinous processes. Each ligament extends from the root to the summit of each spinous process and connects together their adjacent margins. They are narrow and elongated in the dorsal region ; broader, quadrilateral in form, and thicker in the lumbar region ; and only slightly developed in the neck. 5. Ligaments connecting the Transverse Processes. Intertransverse. The Intertransverse Ligaments consist of bundles of fibres interposed between the transverse processes. In the cervical region they consist of a few irregular, scattered fibres ; in the dorsal, they are rounded cords intimately con- nected with the deep muscles of the back ; in the lumbar region they are thin and membranous. Actions.-The movements permitted in the spinal column are, Flexion, Exten- sion, Lateral Movement, Circumduction, and Rotation. In Flexion, or movement of the spine forward, the anterior common ligament is relaxed, and the intervertebral substances are compressed in front, while the posterior common ligament, the ligamenta subflava, and the inter- and supra- spinous ligaments are stretched, as well as the posterior fibres of the intervertebral disks. The interspaces between the laminae are widened, and the inferior articular processes of the vertebrae above glide upward upon the articular processes of the vertebrae below. Flexion is the most extensive of all the movements of the spine. In Extension, or movement of the spine backward, an exactly opposite dis- position of the parts takes place. This movement is not extensive, being limited By the anterior common ligament and by the approximation of the spinous processes. Flexion and extension are most free in the lower part of the lumbar region between the third and fourth and fourth and fifth lumbar vertebrae; above the third they are much diminished, and reach their minimum in the middle and upper part of the back. They increase again in the neck, the capability of motion backward from the upright position being in this region greater than that of the motion forward, whereas in the lumbar region the reverse is the case. In Lateral Movement, the sides of the intervertebral disks are compressed, the extent of motion being limited by the resistance offered by the surrounding liga- ments and by the approximation of the transverse processes. This movement may take place in any part of the spine, but is most free in the neck and loins. Circumduction is very limited, and is produced merely by a succession of the preceding movements. Rotation is produced by the twisting of the intervertebral substances ; this, although only slight between any two vertebrae, produces a great extent of move- ment when it takes place in the whole length of the spine, the front of the column being turned to one or the other side. This movement takes place only to a slight extent in the neck, but is freer in the upper part of the dorsal region, and is altogether absent in the lumbar region. It is thus seen that the cervical region enjoys the greatest extent of each variety of movement, flexion and extension especially being very free. In the dorsal region the three movements of flexion, extension, and circumduction are only permitted to a slight extent, while rotation is very free in the upper part and OF THE ATLAS WITH THE AXIS. 325 ceases below. In the lumbar region there is free flexion, extension, and lateral movement, but no rotation. As Sir George Humphry has pointed out, the movements permitted are mainly due to the shape and position of the articulating processes. In the loins the inferior articulating processes are turned outward and embraced by the superior; this renders rotation in this region of the spine impossible, while there is nothing to prevent a sliding upward and downward of the surfaces on each other, so as to allow of flexion and extension. In the dorsal region, on the other hand, the articulating processes, by their direction and mutual adaptation, especially at the upper part of the series, permit of rotation, but prevent extension and flexion, while in the cervical region the greater obliquity and lateral slant of the articular processes allow not only flexion and extension, but also rotation. The principal muscles which produce flexion are the Sterno-mastoid, Rectus capitis anticus major, and Longus colli; the Scaleni; the abdominal muscles and the Psoas magnus. Extension is produced by the fourth layer of the muscles of the back, assisted in the neck by the Splenius, Semispinalis dorsi et colli, and the Multifidus spinae. Lateral motion is produced by the fourth layer of the muscles of the back, by the Splenius and the Scaleni, the muscles of one side only acting; and rotation by the action of the following muscles of one side only-viz. the Sterno-mastoid, the Rectus capitis anticus major, the Scaleni, the Multifidus spinae, the Complexus, and the abdominal muscles. II. Articulation of the Atlas with the Axis. The articulation of the Atlas with the Axis is of a complicated nature, comprising no fewer than four distinct joints. There is a pivot articulation between the odontoid process of the axis and the ring formed between the anterior arch of the atlas and the transverse ligament (see Fig. 230). Here there are two joints: one in front between the posterior surface of the anterior arch of the atlas and the front of the odontoid process (the atlo-odontoid joint of Cruveilhier); the other between the anterior surface of the transverse ligament and the back of the process (the syndesmo-odontoid joint). Between the articulating processes of the two bones there is a double arthrodia or gliding joint. The ligaments which connect these bones are the Two Anterior Atlanto-axial. Posterior Atlanto-axial. Transverse. Two Capsular. Of the Two Anterior Atlanto-axial Ligaments (Fig. 228), the more superficial is a rounded cord, situated in the middle line; it is attached, above, to the tubercle on the anterior arch of the atlas ; below, to the base of the odontoid process and to the front of the body of the axis. The deeper ligament is a membranous layer, attached, above, to the lower border of the anterior arch of the atlas; below, to the base of the odontoid process and front of the body of the axis. These ligaments are in relation, in front, with the Recti antici majores. The Posterior Ligament (Fig. 229) is a broad and thin membranous layer, attached, above, to the lower border of the posterior arch of the atlas; below, to the upper edge of the laminae of the axis. This ligament supplies the place of the ligamenta subflava, and is in relation, behind, with the Inferior oblique muscles. The Transverse Ligament1 (Figs. 230, 231) is a thick and strong ligamentous band, which arches across the ring of the atlas, and serves to retain the odontoid process in firm connection with its anterior arch. This ligament is flattened from before backward, broader and thicker in the middle than at either extremity, and 1 It has been found necessary to describe the transverse ligament with those of the atlas and axis; but the student must remember that it is really a portion of the mechanism by which the movements of the head on the spine are regulated ; so that the connections between the atlas and axis ought always to be studied together with those between the latter bones and the skull. 326 THE ARTICULATIONS firmly attached on each side to a small tubercle on the inner surface of the lateral mass of the atlas. As it crosses the odontoid process, a small fasciculus is derived from its upper and lower borders; the former passing upward, to be inserted into the basilar process of the occipital bone ; the latter, downward, to be attached to the posterior surface of the body of the axis; hence, the whole ligament has received the name of cruciform. The transverse ligament divides the ring of the atlas into two unequal parts: of these, the posterior and larger serves for the transmission of the cord and its membranes and the spinal accessory nerves; the anterior and smaller contains the odontoid process. Since the space between the anterior arch of the atlas and the transverse ligament is smaller at the lower Basilar process. OCCIPITO- ATLANTAL CAPSULAR LIGA- MENT and synovial mem- brane. ATLANTO- AXIAL. CAPSULAR LIGAMENT and synovial membrane. Fig. 228.-Occipito-atloid and atlo-axoid ligaments. Front view. part than the upper (because the transverse ligament embraces firmly the narrow neck of the odontoid process), this process is retained in firm connection with the atlas after all the other ligaments have been divided. The Capsular Ligaments are two thin and loose capsules connecting the articular processes of the atlas and axis, the fibres being strongest on the anterior and external part of the articulation. There are four Synovial Membranes in this articulation : one lining the inner surface of each of the capsular ligaments; one between the anterior surface of the odontoid process and the anterior arch of the atlas, the atlo-odontoid joint; and one between the posterior surface of the odontoid process and the transverse ligament, the syndesmo-odontoid joint. The latter often communicates with those between the condyles of the occipital bone and the articular surfaces of the atlas. Actions.-This joint allows the rotation of the atlas (and, with it, of the cra- nium) upon the axis, the extent of rotation being limited by the odontoid liga- ments. The principal muscles by which this action is produced are the Sterno-mastoid and Complexus of one side, acting with the Rectus capitis anticus major, Splenius, Trachelo-mastoid, Rectus capitis posticus major, and Inferior oblique of the other side. OF THE ATLAS WITH THE OCCIPITAL BONE. 327 ARTICULATIONS OF THE SPINE WITH THE CRANIUM. The ligaments connecting the spine with the cranium may be divided into two sets-those connecting the occipital bone with the atlas, and those connecting the occipital bone with the axis. III. Articulation of the Atlas with the Occipital Bone. This articulation is a double condyloid joint. Its ligaments are the Two Anterior Occipito-atlantal. Posterior Occipito-atlantal. Two Lateral Occipito-atlantal. Two Capsular. Of the Two Anterior Occipito-atlantal Ligaments (Fig. 228), the superficial is a strong, narrow, rounded cord, attached, above, to the basilar process of the Arch for passage of vertebral artery and 1st cervical nerve. Fig. 229.-Occipito-atloid and atlo-axoid ligaments. Posterior view. occiput; below, to the tubercle on the anterior arch of the atlas: the deeper liga- ment is a broad and thin membranous layer which passes between the anterior margin of the foramen magnum above, and the whole length of the upper border of the anterior arch of the atlas below. This ligament is in relation, in front, with the Recti antici minores; behind, with the odontoid ligaments. The Posterior Occipito-sttlantal Ligament (Fig. 229) is a very broad but thin membranous lamina intimately blended with the dura mater. It is connected, above, to the posterior margin of the foramen magnum ; below, to the upper border of the posterior arch of the atlas. This ligament is incomplete at each side, and forms, with the superior intervertebral notch, an opening for the passage of the vertebral artery and suboccipital nerve. It is in relation, behind, with the Recti postici minores and Obliqui superiores ; in front, with the dura mater of the spinal canal, to which it is intimately adherent. The Lateral Ligaments are strong fibrous bands, directed obliquely upward and inward, attached above to the jugular process of the occipital bone ; below, to the base of the transverse process of the atlas. The Capsular Ligaments surround the condyles of the occipital bone, and con- 328 THE ARTICULATIONS. nect them with the articular processes of the atlas; they consist of thin, and loose capsules, which enclose the synovial membrane of the articulation. Synovial Membranes.-There are two synovial membranes in this articulation, one lining the inner surface of each of the capsular ligaments. These occasionally communicate with that between the posterior surface of the odontoid process and the transverse ligament. Actions.-The movements permitted in this joint are flexion and extension, which give rise to the ordinary forward and backward nodding of the head, besides For Spinal Cord and v its Membranes. J Fig. 230.-Articulation between odontoid process and atlas slight lateral motion to one or the other side. When either of these actions is carried beyond a slight extent, the whole of the cervical portion of the spine assists in its production. Flexion is mainly produced by the action of the Rectus capitis anticus major et minor and the Sterno-mastoid muscles ; extension by the Rectus capitis posticus major et minor, the Superior oblique, the Complexus, Splenius, and upper fibres of the Trapezius. The Recti laterales are concerned in the lat- eral movement, assisted by the Trapezius, Splenius, Complexus, Sterno-mastoid, and the Recti laterales of the same side, all acting together. According to Cru- veilhier, there is a slight motion of rotation in this joint. IV. Articulation of the Axis with the Occipital Bone. Occipito-axial. Three Odontoid. To expose these ligaments the spinal canal should be laid open by removing the posterior arch of the atlas, the laminae and spinous process of the axis, and the portion of the occipital bone behind the foramen magnum, as seen in Fig. 231. The Occipito-axial Ligament (apparatus ligamentosus colli} is situated within the spinal canal. It is a broad and strong ligamentous band, which covers the odontoid process and its ligaments, and appears to be a prolongation upward of the posterior common ligament of the spine. It is attached, below, to the posterior surface of the body of the axis, and, becoming expanded as it ascends, is inserted into the basilar groove of the occipital bone, in front of the foramen magnum, where it becomes blended with the dura mater of the skull. Relations.-By its anterior surface with the transverse ligament, by its posterior surface with the dura mater. The Odontoid or Check Ligaments (alar ligaments} are strong, rounded, fibrous cords, which arise one on either side of the upper part of the odontoid process, and, passing obliquely upward and outward, are inserted into the rough depres- sions on the inner side of the condyles of the occipital bone. In the triangular interval left between these ligaments and the margin of the foramen magnum a strong fibro-cartilaginous cord (ligamentum suspensorium} may be seen, which passes almost perpendicularly from the apex of the odontoid process to the anterior margin of the foramen, being intimately blended with the deep portion of the TEMPORO-MAXILLARY ARTICVLATION. 329 anterior occipito-atloid ligament and upper fasciculus of the transverse ligament of the atlas. Actions.-The odontoid ligaments serve to limit the extent to which rotation occipito-axoid ligament, divided and turned buck. I \ The vertical portion of ODONTOID LIGAMENTS. OCCIPITO ATLANTAL < CAPSULAR LIGAMENT and synovial [ membrane. ATLANTO- X AXIAL CAPSULAR LIGAMENT and synovial membrane. Fig. 231.-Occipito-axoid and atlo-axoid ligaments. Posterior view, obtained by removing the arches of the vertebra and the posterior part of the skull. of the cranium may be carried; hence they have received the name of check ligaments. In addition to these ligaments, which connect the atlas and axis to the skull, the ligamentum nuchre must be regarded as one of the ligaments by which the spine is connected with the cranium. It is described on a subsequent page. Surgical Anatomy.-The ligaments which unite the component parts of the vertebrae together are so strong, and these bones are so interlocked by the arrangement of their articulating processes, that dislocation is very uncommon, and, indeed, unless accompanied by fracture, rarely occurs, except in the upper part of the neck. Dislocation of the occiput from the atlas has only been recorded in one or two cases; but dislocation of the atlas from the axis, with rupture of the transverse ligament, is much more common: it is the mode in which death is produced in many cases of execution by hanging. In the lower part of the neck- that is, below the third cervical vertebra-dislocation unattended by fracture occasionally takes place. V. Temporo-maxillary Articulation. This is a double or bilateral condyloid joint: the parts entering into its formation on each side are, above, the anterior part of the glenoid cavity of the temporal bone and the eminentia articularis; and, below, the condyle of the lower jaw. The ligaments are the following: External Lateral. Internal Tjateral. Stylo-maxillary. Capsular. Interarticular Fibro-cartilage. The External Lateral Ligament (Fig. 232) is a short, thin, and narrow fasciculus, attached, above, to the outer surface of the zygoma and to the rough tubercle on its lower border; below, to the outer surface and posterior border of the neck of the lower jaw. It is broader above than below; its fibres are placed 330 THE ARTICULATIONS. parallel with one another, and directed obliquely downward and backward. Ex- ternally, it is covered by the parotid gland and by the integument. Internally, Temporal bone. Inferior maxilla. L t Fig. 232.-Temporo-maxillary articulation. External view. it is in relation with the capsular ligament, of which it is an accessory band, and not separable from it. The Internal Lateral Ligament (Fig. 233) is a specialized band of cervical fascia which is attached above to the spinous process of the sphenoid bone, and, becoming broader as it descends, is inserted into the lingula and margin of the dental foramen. Its outer surface is in relation, above, with the Ex- ternal pterygoid muscle; lower down, it is separated from the neck of the condyle by the internal maxillary artery; and still more inferiorly, the inferior dental ves- sels and nerve separate it from the ramus of the jaw. The inner sur- face is in relation with the Inter- nal pterygoid. The Stylo-maxillary Ligament is also a specialized band of the cervical fascia, which extends from near the apex of the styloid pro- cess of the temporal bone to the angle and posterior border of the ramus of the lower jaw, between the Masseter and Internal pterygoid muscles. This ligament separates the parotid from the submaxillary gland, and has attached to its inner side part of the fibres of origin of the Stylo-glossus muscle. Although usually classed among the ligaments of the jaw, it can only be considered as an accessory in the articulation. Fig. 233.-Temporo-maxillary articulation. Internal view. TEMPORO-MAXILLAR Y ARTICULA TION. 331 The Capsular Ligament forms a thin and loose ligamentous capsule, attached above to the circumference of the glenoid cavity and the articular surface im- mediately in front; below, to the neck of the condyle of the lower jaw. It consists of a few thin scattered fibres, and can hardly be considered as a distinct ligament; it is thickest at the back part of the articulation.1 The Interarticular Fibro-cartilage (Fig. 234) is a thin plate of an oval form, placed horizontally between the condyle of the jaw and the glenoid cavity. Its upper surface is concavo-convex from before backward, and a little convex transversely, to accommodate itself to the form of the glenoid cavity. Its under surface, where it is in con- tact with the condyle, is concave. Its circumference is connected to the capsular ligament, and in front to the tendon of the External pterygoid muscle. It is thicker at its circum- ference, especially behind, than at its centre. The fibres of which it is composed have a concentric arrange- ment, more apparent at the circum- ference than at the centre. Its surfaces are smooth. It divides the joint into two cavities, each of which is furnished with a separate synovial membrane. The Synovial Membranes, two in number, are placed, one above, and the other below, the fibro-cartilage. The upper one, the larger and looser of the two, is continued from the margin of the cartilage covering the glenoid cavity and eminentia articularis on to the upper surface of the fibro-cartilage. The lower one passes from the under surface of the fibro-cartilage to the neck of the condyle of the jaw, being prolonged downward a little farther behind than in front. The nerves of this joint are derived from the auriculo-temporal and masseteric branches of the inferior maxillary. The arteries are derived from the temporal branch of the external carotid. Actions.-The movements permitted in this articulation are very extensive. Thus, the jaw may be depressed or elevated, or it may be carried forward or backward or from side to side. It is by the alternation of these movements, performed in succession, that a kind of rotatory motion of the lower jaw upon the upper takes place, which materially assists in the mastication of the food. If the movement of depression is carried only to a slight extent, the condyles remain in the glenoid cavities, rotating on a transverse axis against the inter- articular fibro-cartilage; but if the depression is considerable, the condyles glide from the glenoid fossae on to the articular eminences, carrying with them the interarticular fibro-cartilages, so that in opening the mouth widely the two move- ments are combined-i. e. the condyle rotates on a transverse axis against the fibr o-cartilage, and at the same time glides forward, carrying the fibro-cartilage with it. When the jaw is elevated after forced depression, the condyles and fibro-cartilages return to their original position. When the jaw is carried hori- zontally forward and backward or from side to side, a horizontal gliding move- ment of the fibro-cartilages and condyles upon the glenoid cavities takes place in the corresponding direction. The lower jaw is depressed by its own weight, assisted by the Platysma, the Digastric, the Mylo-hyoid, and the Genio-hyoid. It is elevated by the anterior part of the Temporal, Masseter, and Internal pterygoid. It is drawn forward by Fig. 234.-Vertical section of temporo-maxillary ar- ticulation. 1 Sir G. Humphry describes the internal portion of the capsular ligament separately, as the short internal lateral ligament; and it certainly seems as deserving of a separate description as the external lateral ligament is. 332 THE A R TICULA TIONS the simultaneous action of the External pterygoid and the superficial fibres of the Masseter; and it is drawn backivard by the deep fibres of the Masseter and the posterior fibres of the Temporal muscle.. The grinding movement is caused by the alternate action of the two External pterygoids. Surface Form.-The temporo-maxillary articulation is quite superficial, situated below the base of the zygoma, in front of the tragus and external auditory meatus, and behind the posterior border of the upper part of the Masseter muscle. Its exact position can be at once ascer- tained by feeling for the condyle of the jaw, the working of which can be distinctly felt in the movements of the lower jaw either vertically or from side to side. When the mouth is opened wide, the condyle advances out of the glenoid fossa on to the eminentia articularis and a depres- sion is felt in the situation of the joint. Surgical Anatomy.-The lower jaw is dislocated only in one direction-viz. forward. The accident is caused by violence or muscular action. When the mouth is open, the condyle is situated on the eminentia articularis, and any sudden violence, or even a sudden muscular spasm, as during a convulsive yawn, may displace the condyle forward into the zygomatic fossa. The displacement may be unilateral or bilateral, according as one or both of the condyles are dis- placed. The latter of the two is the more common. Sir Astley Cooper described a condition which he termed "subluxation." It occurs principally in delicate women, and is believed by some to be due to the relaxation of the liga- ments, permitting too free movement of the bone, and possibly some displacement of the fibro- cartilage. Others have believed that it is due to gouty or rheumatic changes in the joint. In close relation to the condyle of the jaw is the external auditory meatus and the tympanum ; any force, therefore, applied to the bone is liable to be attended with damage to these parts, or inflammation in the joint may extend to the ear, or on the other hand inflammation of the middle ear may involve the articulation and cause its destruction, thus leading to ankylosis of the joint. In children, arthritis of this joint may also follow the exanthemata, and in adults occurs as the result of some constitutional conditions, as rheumatism or gout. The temporo-maxillary joint is also frequently the seat of osteo-arthritis, leading to great suffering during efforts of mastication. A peculiar affection sometimes attacks the neck and condyle of the lower jaw, consisting in hypertrophy and elongation of these parts and consequent protrusion of the chin to the oppo- site side. VI. Articulations of the Ribs with the Vertebrae. The articulations of the ribs with the vertebral column may be divided into two sets: 1. Those which connect the heads of the ribs with the bodies of the vertebrae. 2. Those which connect the necks and tubercles of the ribs with the transverse processes. 1. Articulations between the Heads of the Ribs and the Bodies of the Vertebrae (Fig. 235). These constitute a series of arthrodial joints, formed by the articulation of the heads of the ribs with the cavities on the contiguous margins of the bodies of the dorsal vertebrae, connected together by the following ligaments: Anterior Costo-vertebral or Stellate. Capsular. Interarticular. The Anterior Costo-vertebral or Stellate Ligament connects the anterior part of the head of each rib with the sides of the bodies of two vertebrae and the inter- vertebral disk between them. It consists of three flat bundles of ligamentous fibres, which radiate from the anterior part of the head of the rib. The superior fasciculus passes upward to be connected with the body of the vertebra above; the inferior one descends to the body of the vertebra below; and the middle one, the smallest and least distinct, passes horizontally inward, to be attached to the intervertebral substance. Relations.-In front, with the thoracic ganglia of the sympathetic, the pleura, and, on the right side, with the vena azygos major; behind, with the interarticular ligament and synovial membranes. In the first rib, which articulates with a single vertebra only, this ligament does not present a distinct division into three fasciculi; its fibres, however, radiate, and are attached to the body of the last cervical vertebra, as well as to the body of the vertebra with which the rib articulates. In the tenth, eleventh, and twelfth ribs also, which likewise articulate with a single vertebra, the division does not OF THE RIBS WITH THE VERTEBRAE. 333 exist; but the fibres of the ligament in each case radiate and are connected with the vertebra above, as well as that with which the ribs articulate. The Capsular Ligament is a thin and loose ligamentous bag, which surrounds the joint between the head of the rib and the articular cavity formed by the intervertebral disk and the adjacent vertebra. It is very thin, firmly connected with the anterior ligament, and most distinct at the upper and lower parts of the articulation. Behind, some of its fibres pass through the intervertebral foramen to the back of the intervertebral disk. This is the analogue of the liga- mentuin conjugale of some mammals, which unites the heads of opposite ribs across the back of the interverte- bral disk. The Interarticular Liga- ment is situated in the interior of the joint. It consists of a short band of fibres, flattened from above downward, attached by one extremity to the sharp crest on the head of the rib, and by the other to the intervertebral disk. It divides the joint into two cavities, which have no communication with each other. In the first, tenth, eleventh, and twelfth ribs the interarticular ligament does not exist; consequently, there is but one synovial membrane. The Synovial Membrane.-There are two synovial membranes in each of the articulations in which there is an interarticular ligament, one on each side of this structure. ' Upper synovial/ cavity. j . INTERARTICULAR LIGAMENT./ Lower synovial cavity. Fig. 235-Costo-vertebral and costo-transverse articulations. Ante- rior view. 2. Articulations of the Necks and Tubercles of the Ribs with the Transverse Processes (Fig. 236). The articular portion of the tubercle of the rib and adjacent transverse process form an arthrodial joint. In the eleventh and twelfth ribs this articulation is wanting. The ligaments connecting these parts are the- Anterior Costo-transverse. Middle Costo-transverse (Interosseous). Posterior Costo-transverse. Capsular. The Anterior Costo-transverse Ligament {superior or long) consists of two sets of fibres: the one is attached below to the sharp crest on the upper border of the neck of each rib, and passing obliquely upward and outward, to the lower border of the transverse process immediately above; the other is attached below to the neck of the rib, and passes upward and inward to the base of the transverse pro- cess and border of the lower articular process of the vertebra above. This liga- ment is in relation, in front, with the intercostal vessels and nerves; behind, with the Longissimus dorsi. Its internal border completes an aperture formed between it and the articular processes, through which pass the posterior branches of the 334 THE ARTICULATIONS intercostal vessels and nerves. Its external border is continuous with a thin aponeurosis which covers the External intercostal muscle. The/zrst rib has no anterior costo-transverse ligament. The Middle Costo-transverse or Interosseous Ligament consists of short but strong fibres which pass between the rough surface on the posterior part of the neck of each rib and the anterior surface of the adjacent transverse process. In ANTERIOR COSTO-TRANSVERSE LIGAMENT DIVIDED. MIDDLE COSTO-TRANSVERSE or INTEROSSEOUS.X. POSTER OR COSTO- TRANSVERSE LIGAMENT. V evictral \ Foramen /■ SYNOVIAL CAVITY. I CAPSULAR MEMBRANE. Fig. 236.-Costo-transverse articulation. Seen from above. order fully to expose this ligament, a horizontal section should be made across the transverse process and corresponding part of the rib ; or the rib may be forcibly separated from the transverse process and its fibres put on the stretch. In the eleventh and twelfth ribs this ligament is quite rudimentary or wanting. The Posterior Costo-transverse Ligament is a short but thick and strong fascic- ulus which passes obliquely from the summit of the transverse process to the rough non-articular portion of the tubercle of the rib. This ligament is shorter and more oblique in the upper than in the lower ribs. Those corresponding to the superior ribs ascend, while those of the inferior ribs descend slightly. In the eleventh and twelfth ribs this ligament is wanting. The Capsular Ligament is a thin, membranous sac attached to the circumference of the articular surfaces, and enclosing a small synovial membrane. In the eleventh and tivelfth ribs this ligament is absent. Actions.-The heads of the ribs are so closely connected to the bodies of the verte- brae by the stellate and interarticular ligaments, and the necks and tubercles of the ribs to the transverse processes, that only a slight gliding movement of the articular surfaces on each other can take place in these articulations. The result of this gliding movement is an elevation of the front and middle portion of the rib, the hinder part being prevented from performing any upward movement by its close connection with the spine. In this gliding movement there are two axes of rotation- that is to say, the rib rotates on an axis corresponding with a line drawn through the two articulations, Costo-vertebral and Costo-transverse, which the rib forms with the spine ; and, secondly, it rotates on an axis corresponding with a line drawn from the head of the rib to the sternum. By the first movement-that of rotation of the rib on an axis corresponding with a line drawn through the two articulations which this bone forms with the spine-an elevation of the anterior part of the OF THE RIBS WITH THE VERTEBRAE. 335 rib takes place, and a consequent enlargement of the antero-posterior diameter of the chest. None of the ribs lie in a truly horizontal plane; they are all directed more or less obliquely, so that their anterior extremities lie on a lower level than their pos- terior, and this obliquity increases from the first to the seventh, and then again decreases. If we ex- amine any one rib-say, that in which there is the greatest obliq- uity-we shall see that it is ob- vious that as its sternal extremity is carried upward, it must also be thrown forward; so that the rib may be regarded as a radius mov- ing on the vertebral joint as a cen- tre, and causing the sternal attach- ment to describe an arc of a circle in the vertical plane of the body. Since all the ribs are oblique and connected in front to the sternum by the elastic costal cartilages, they must have a tendency to thrust the sternum forward, and so increase the antero-posterior diameter of the chest. By the second move- ment-that of the rotation of the rib on an axis corresponding with a line drawn from the head of the rib to the sternum-an elevation of the middle portion of the rib takes place, and consequently an increase in the transverse diameter of the chest. For the ribs not only slant downward and forward from their vertebral attachment, but they are also oblique in relation to their transverse plane-that is to say, their middle is on a lower level than either their vertebral or sternal extremities. It results from this that when the ribs are raised the centre portion is thrust outward, somewhat after the fashion in which the handle of a bucket is thrust away from the side when raised to a horizontal position, and the lateral diameter of the chest is increased (see Fig. 237). The mobility of the different ribs varies very much. The first rib is more fixed than the others, on account of the weight of the upper extremity and the strain of the ribs beneath ; but on the freshly dissected thorax it moves as freely as the others. From the same causes the movement of the second rib is also not very extensive. In the other ribs this mobility increases successively down to the last two, which are very movable. The ribs are generally more movable in the femalq than in the male. Fig. 237.-Diagrams showing the axis of rotation of the ribs in the movements of respiration. The one axis of rota- tion corresponds with a line drawn through the two articu- lations which the rib forms with the spine (a, b), and the other with a line drawn from the head of the rib to the sternum (a, b). (From Kirke's Handbook of Physiology.) VII. Articulation of the Cartilages of the Ribs with the Sternum, etc. (Fig. 238). The articulations of the cartilages of the true ribs with the sternum are arthro- dial joints, with the exception of the first, in which the cartilage is almost always directly united with the sternum, and which must therefore be regarded as a synarthrodial articulation. The ligaments connecting them are- 336 THE ARTICULATIONS Anterior Chondro-sternal. Posterior Chondro-sternal. Capsular. Interarticular Chondro-sternal. Anterior Chondro-xiphoid. Posterior Chondro-xiphoid. The Anterior Chondro-sternal Ligament is a broad and thin membranous band that radiates from the front of the inner extremity of the cartilages of the true ribs to the anterior surface of the sternum. It is composed of fasciculi which pass in different directions. The superior fasciculi ascend obliquely, the inferior pass obliquely downward, and the middle fasciculi horizontally. The superficial fibres of this ligament are the longest: they intermingle with the fibres of the ligaments above and below them, with those of the opposite side, and with the tendinous fibres of origin of the Pectoralis major, forming a thick fibrous membrane which covers the surface of the sternum. This is more distinct at the lower than at the upper part. The Posterior Chondro-sternal Ligament, less thick and distinct than the anterior, is composed of fibres which radiate from the posterior surface of the sternal end of the cartilages of the true ribs to the posterior surface of the sternum, becoming blended with the periosteum. The Capsular Ligament surrounds the joints formed between the cartilages of the true ribs and the sternum. It is very thin, intimately blended with the anterior and posterior ligaments, and strengthened at the upper and lower part of the articulation by a few fibres which pass from the cartilage to the side of the sternum. These ligaments protect the synovial membranes. The Interarticular Chondro-sternal Ligaments.-These are only found between the second and third costal cartilages and the sternum. The cartilage of the second rib is connected with the sternum by means of an interarticular ligament attached by one extremity to the cartilage of the second rib, and by the other extremity to the cartilage which unites the first and second pieces of the sternum. This articulation is provided with two synovial membranes. The cartilage of the third rib is connected with the sternum by means of an interarticular ligament which is attached by one extremity to the cartilage of the third rib, and by the other extremity to the point of junction of the second and third pieces of the sternum. This articulation is provided with two synovial membranes. The Anterior Chondro-xiphoid.-This is a band of ligamentous fibres which connects the anterior surface of the seventh costal cartilage, and occasionally also that of the sixth, to the anterior surface of the ensiform appendix. It varies in length and breadth in different subjects. The Posterior Chondro-xiphoid is a similar band of fibres on the internal or posterior surface, though less thick and distinct. Synovial Membranes.-There is no synovial membrane between the first costal cartilage and the sternum, as this cartilage is directly continuous with the sternum. There are two synovial membranes, both in the articulation of the second and third costal cartilages to the sternum. There is generally one synovial membrane in each of the joints between the fourth, fifth, sixth, and seventh costal cartilages to the sternum; but it is sometimes absent in the sixth and seventh chondro-sternal joints. Thus there are eight synovial cavities on each side in the articulations between the costal cartilages of the true ribs and the sternum. After middle life the articular surfaces lose their polish, become roughened, and the synovial membranes appear to be wanting. In old age the articulations do not exist, the cartilages of most of the ribs becoming continuous with the sternum. Actions.-The movements which are permitted in the chondro-sternal articu- lations are limited to elevation and depression, and these only to a slight extent. Articulations of the Cartilages of the Ribs with each other (Interchondral) (Fig. 238). The contiguous borders of the sixth, seventh, and eighth, and sometimes the ninth and tenth, costal cartilages articulate with each other by small, smooth, OF THE RIBS WITH THEIR CARTILAGES. 337 oblong-shaped facets. Each articulation is enclosed in a thin capsular ligament lined by synovial membrane, and strengthened externally and internally by liga- mentous fibres (interchondral ligaments) which pass from one cartilage to the other. Sometimes the fifth costal cartilage, more rarely that of the ninth, articu- lates, by its lower border, with the adjoining cartilage by a small oval facet; more The synovial cavities exposed by a vertical section of the sternum and cartilages. Cartilage contino us with sternum. INTERARTICULAR LIGAMENT and tico synovial membravrjs. Single synovial membrane. Intercostal synovial membranes. Fig. 238.-Chondro-sternal, chondro-xiphoid, and interchondral articulations. Anterior view. frequently they are connected together by a few ligamentous fibres. Occasionally the articular surfaces above mentioned are wanting. Articulations of the Ribs with their Cartilages (Costo-chondral) (Fig. 238). The outer extremity of each costal cartilage is received into a depression in the sternal end of the ribs, and the two are held together by the periosteum. 338 777/,' A R TIC I rLA TIONS VIII. Ligaments of the Sternum. The first piece of the sternum is united to the second either by an amphi- arthrodial joint-a single piece of true, fibro-cartilage uniting the segments-or by a diarthrodial joint, in which each bone is clothed with a distinct lamina of cartilage, adherent on one side, free and lined with synovial membrane on the other. In the latter case the cartilage covering the gladiolus is continued without interruption on to the cartilages of the second ribs. Mr. Rivington has found the diarthrodial form of joint in about one-third of the specimens examined by him ; Mr. Maisonneuve more frequently. It appears to be rare in childhood, and is formed, in Mr. Rivington's opinion, from the amphiarthrodial form by absorption. The diarthrodial joint seems to have no tendency to ossify at any age, while the amphiarthrodial is more liable to do so, and has been found ossified as early as thirty-four years of age. The two segments are further connected by an Anterior Intersternal Ligament and a Posterior Intersternal Ligament. The Anterior Intersternal Ligament consists of a layer of fibres, having a longitudinal direction; it blends with the fibres of the anterior chondro-sternal ligaments on both sides, and with the tendinous fibres of origin of the Pectoralis major. This ligament is rough, irregular, and much thicker below than above. The Posterior Intersternal Ligament is disposed in a somewhat similar manner on the posterior surface of the articulation. The ligaments connecting the last lumbar vertebra with the sacrum are similar to those which connect the segments of the spine with each other-viz: 1. The continuation downward of the anterior and posterior common ligaments. 2. The intervertebral substance connecting the flattened oval surfaces of the two bones and forming an amphiarthrodial joint. 3. Ligamenta subflava, connecting the arch of the last lumbar vertebra with the posterior border of the sacral canal. 4. Capsular ligaments connecting the articulating processes and forming a double arthrodia. 5. Inter- and supraspinous ligaments. The two proper ligaments connecting the pelvis with the spine are the lumbo- sacral and ilio-lumbar. The Lumbo-sacral Ligament (Fig. 239) is a short, thick, triangular fasciculus, which is connected above to the lower and front part of the transverse process of the last lumbar vertebra, passes obliquely outward, and is attached below to the lateral surface of the base of the sacrum, becoming blended with the anterior sacro-iliac ligament. This ligament is in relation, in front, with the Psoas muscle. The Ilio-lumbar Ligament (Fig. 239) passes horizontally outward from the apex of the transverse process of the last lumbar vertebra to the crest of the ilium immediately in front of the sacro-iliac articulation. It is of a triangular form, thick and narrow internally, broad and thinner externally. It is in relation, in front, with the Psoas muscle ; behind, with the muscles occupying the vertebral groove; above, with the Quadratus lumborum. IX. Articulation of the Pelvis with the Spine. X. Articulations of the Pelvis. The ligaments connecting the bones of the pelvis with each other may be divided into four groups: 1. Those connecting the sacrum and ilium. 2. Those passing between the sacrum and ischium. 3. Those connecting the sacrum and coccyx. 4. Those between the two pubic bones. 1. Articulations of the Sacrum and Ilium. The sacro-iliac articulation is an amphiarthrodial joint formed between the lateral surfaces of the sacrum and ilium. The anterior or auricular portion of OF THE PELVIS. 339 each articular surface is covered with a thin plate of cartilage, thicker on the sacrum than on the ilium. The surfaces of these cartilages in the adult are rough and irregular, and separated from one another by a soft, yellow, pulpy substance. At an early period of life, occasionally in the adult, and in the female during pregnancy, they are smooth and lined by a delicate synovial membrane. The ligaments connecting these surfaces are the anterior and posterior sacro-iliac. The Anterior Sacro-iliac Ligament (Fig. 239) consists of numerous thin ligamentous bands which connect the anterior surfaces of the sacrum and ilium. Aperture of communication with Bursa of psoas and iliacus Fig. 239.-Articulations of pelvis and hip. Anterior view. The Posterior Sacro-iliac {Fig. 240) is a strong interosseous ligament, situated in a deep depression between the sacrum and ilium behind, and forming the chief bond of connection between those bones. It consists of numerous strong fasciculi which pass between the bones in various directions. Three of these are of large size: the two superior, nearly horizontal in direction, arise from the first and second transverse tubercles on the posterior surface of the sacrum, and are inserted into the rough, uneven surface at the posterior part of the inner surface of the ilium. The third fasciculus, oblique in direction, is attached by one extremity to the third transverse tubercle on the posterior surface of the sacrum, and by the other to the posterior superior spine of the ilium; it is sometimes called the oblique sacro-iliac ligament. The position of the sacro-iliac jpint is indicated by the posterior superior spine of the ilium. This process is immediately behind the centre of the articulation. 2. Ligaments passing between the Sacrum and Ischium (Fig. 240). The Great Sacro-sciatic (Posterior). The Lesser Sacro-sciatic (Anterior). The Great or Posterior Sacro-sciatic Ligament is situated at the lower and back part of the pelvis. It is thin, flat, and triangular in form; narrower in the 340 THE ARTICULATIONS middle than at the extremities; attached by its broad base to the posterior inferior spine of the ilium, to the fourth and fifth transverse tubercles of the sacrum, and to the lower part of the lateral margin of that bone and the coccyx. Passing obliquely downward, outward, and forward, it becomes narrow and thick, and at its insertion into the inner margin of the tuberosity of the ischium it increases in breadth, and is prolonged forward along the inner margin of the ramus, forming what is known as the falciform ligament. The free concave edge of this prolonga- tion has attached to it the obturator fascia, with which it forms a kind of groove, protecting the internal pudic vessels and nerve. One of its surfaces is turned toward the perinseum, the other toward the Obturator internus muscle. The posterior surface of this ligament gives origin, by its whole extent, to fibres of the Gluteus maximus. Its anterior surface is united to the lesser sacro-sciatic ANTERIOR Or LESSER S ACRO-SCl ATIC LIGAMENT. Fig. 240.-Articulations of pelvis and hip. Posterior view. ligament. Its external border forms, above, the posterior boundary of the great sacro-sciatic foramen, and, below, the lower boundary of the lesser sacro-sciatic foramen. Its loioer border forms part of the boundary of the perimeum. It is pierced by the coccygeal branch of the sciatic artery and coccygeal nerve. The Lesser or Anterior Sacro-sciatic Ligament, much shorter and smaller than the preceding, is thin, triangular in form, attached by its apex to the spine of the ischium, and internally, by its broad base, to the lateral margin of the sacrum and coccyx, anterior to the attachment of the great sacro-sciatic ligament, with which its fibres are intermingled. It is in relation, anteriorly, with the Coccygeus muscle; posteriorly, it is covered by the great sacro-sciatic ligament and crossed by the internal pudic vessels and nerve. Its superior border forms the lower boundary of the great sacro-sciatic foramen; its inferior border, part of the lesser sacro-sciatic foramen. These two ligaments convert the sacro-sciatic notches into foramina. The superior or great sacro-sciatic foramen is bounded, in front and above, by the OF THE PELVIS. 341 posterior border of the os innominatum ; behind, by the great sacro-sciatic ligament; and below, by the lesser sacro-sciatic ligament, It is partially filled up, in the recent state, by the Pyriformis muscle, which passes through it. Above this muscle the gluteal vessels and superior gluteal nerve emerge from the pelvis, and, below it, the sciatic vessels and nerves, the internal pudic vessels and nerve, and muscular branches from the sacral plexus. The inferior or lesser sacro-sciatic foramen is bounded, in front, by the tuber ischii; above, by the spine and lesser sacro-sciatic ligament; behind, by the greater sacro-sciatic ligament. It transmits the tendon of the Obturator internus muscle, its nerve, and the internal pudic vessels and nerve. 3. Articulation of the Sacrum and Coccyx. This articulation is an amphiarthrodial joint, formed between the oval surface at the apex of the sacrum and the base of the coccyx. It is analogous to the joints between the bodies of the vertebrae, and is connected by similar ligaments. They are the Anterior Sacro-coccygeal. Posterior Sacro-coccygeal. Lateral Sacro-coccygeal. Interposed Fibro-cartilage. The Anterior Sacro-coccygeal Ligament consists of a few irregular fibres which descend from the anterior surface of the sacrum to the front of the coccyx, becoming blended with the periosteum. The Posterior Sacro-coccygeal Ligament is a flat band of ligamentous fibres, of a pearly tint, which arises from the margin of the lower orifice of the sacral canal and descends to be inserted into the posterior surface of the coccyx. This ligament completes the lower and back part of the sacral canal. Its superficial fibres are much longer than the more deeply seated. This ligament is in relation, behind, with the Gluteus maximus. The Lateral Sacro-coccygeal Ligaments are ligamentous bands which pass from the cornua of the last sacral vertebra to the cornua of the first piece of the coccyx. A Fibro-cartilage is interposed between the contiguous surfaces of the sacrum and coccyx ; it differs from that interposed between the bodies of the vertebrae in being thinner and its central part firmer in texture. It is somewhat thicker in front and behind than at the sides. Occasionally, a synovial membrane is found when the coccyx is freely movable, which is more especially the case during pregnancy. The different segments of the coccyx are connected together by an extension downward of the anterior arid posterior sacro-coccygeal ligaments, a thin annular disk of fibro-cartilage being interposed between each of the bones. In the adult male all the pieces become ossified, but in the female this does not commonly occur until a later period of life. The separate segments of the coccyx are first united, and at a more advanced age the joint between the sacrum ami coccyx is obliterated. Actions.-The movements which take place between the sacrum and coccyx, and between the different pieces of the latter bone, are slightly forward and backward; they are very limited. Their extent increases during pregnancy. 4. Articulation of the Ossa Pubis (Fig. 241). The articulation between the pubic bones is an amphiarthrodial joint, formed by the junction of the two oval articular surfaces of the ossa pubis. The articular surface has been described on a former page under the name of symphysis, and the same name is given to the joint. The ligaments of this articulation are the Anterior Pubic. Superior Pubic. Posterior Pubic. Subpubic. Interpubic disk. 342 THE ARTICULATIONS. The Anterior Pubic Ligament consists of several superimposed layers which pass across the front of the articulation. The superficial fibres pass obliquely from one bone to the other, decussating and forming an interlacement with the fibres of the aponeurosis of the Ex- ternal oblique and the tendon of the Rectus muscles. The deep fibres pass transversely across the symphysis, and are blended with the fibro-cartilage. The Posterior Pubic Ligament con- sists of a few thin, scattered fibres which unite the two pubic bones pos- teriorly. The Superior Pubic Ligament is a band of fibres which connects together the two pubic bones superiorly. v The Subpubic Ligament is a thick, triangular arch of ligamentous fibres, connecting together the two pubic bones below and forming the upper boundary of the pubic arch. Above, it is blended with the interarticular fibro-cartilage; laterally it is united with the rami of the os pubis. Its fibres are closely connected and have an arched direction. The Interpubic Disk consists of a disk of cartilage and fibro-cartilage con- necting the surfaces of the pubic bones in front. Each pubic symphysis is covered by a thin layer of hyaline cartilage which is firmly connected to the bone by a series of nipple-like processes which accurately fit within corresponding depres- sions on the osseous surfaces. These opposed cartilaginous surfaces are connected together by an intermediate stratum of fibrous tissue and fibro-cartilage which varies in thickness in different subjects. It often contains a cavity in its centre, probably formed by the softening and absorption of the fibro-cartilage, since it rarely appears before the tenth year of life, and is not lined by synovial membrane. It is larger in the female than in the male, but it is very questionable whether it enlarges, as was formerly supposed, during pregnancy. It is most frequently limited to the upper and back part of the joint, but it occasionally reaches to the front, and may extend the entire length of the cartilage. This cavity may be easily demonstrated by making a vertical section of the symphysis pubis near its posterior surface. The Obturator Ligament is more properly regarded as analogous to the muscular fasciae, with which it will be described. Hyaline cartilage covering bone, intermediate fibro-cartilage. Cavity at upper and back part. Fig. 241.-Vertical section of the symphysis pubis. Made near its posterior surface. The articulations of the upper extremity may be arranged in the following groups: I. Sterno-clavicular articulation. II. Acromio-clavicular articulation. III. Ligaments of the Scapula. IV. Shoulder-joint. V. Elbow-joint. VI. Radio-ulnar articulations. VII. Wrist-joint. VIII. Articulations of the Carpal Bones. IX. Carpo-metacarpal articulations. X. Metacarpo-phalangeal articula- tions. XI. Articulations of the Phalanges. ARTICULATIONS OF THE UPPER EXTREMITY. The Sterno-clavicular is regarded by most anatomists as an arthrodial joint, but Cruveilhier considers it to be an articulation by reciprocal reception. Probably the former opinion is the correct one, the varied movement which the joint enjoys being due to the interposition of an interarticular fibro-cartilage between the joint surfaces. The parts entering into its formation are the sternal end of the I. Sterno-clavicular Articulation (Fig. 242). STERNO- CL A V1CULA R AR TICULA TION. 343 clavicle, the upper and lateral part of the first piece of the sternum, and the cartilage of the first rib. The articular surface of the clavicle is much larger than Fig. 242- Sternoclavicular articulation. Anterior view. that of the sternum, and invested with a layer of cartilage 1 which is considerably thicker than that on the latter bone. The ligaments of this joint are the Anterior Sterno-clavicular. Posterior Sterno-clavicular. Interclavicular. Costo-clavicular (rhomboid). Interarticular Fibro-cartilage. The Anterior Sterno-clavicular Ligament is a broad band of fibres which covers the anterior surface of the articulation, being attached, above, to the upper and front part of the inner extremity of the clavicle, and, passing obliquely downward and inward, is attached, below, to the upper and front part of the first piece of the sternum. This ligament is covered, in front, by the sternal portion of the Sterno-cleido-mastoid and the integument; behind, it is in relation with the interarticular fibro-cartilage and the two synovial membranes. The Posterior Sterno-clavicular Ligament is a similar band of fibres which covers the posterior surface of the articulation, being attached, above, to the upper and back part of the inner extremity of the clavicle, and, passing obliquely downward and inward, is attached, below, to the upper and back part of the first piece of the sternum. It is in relation, in front, with the interarticular fibro- cartilage and synovial membranes; behind, with the Sterno-hyoid and Sterno- thyroid muscles. The Interclavicular Ligament is a flattened band which varies considerably in form and size in different individuals ; it passes in a curved direction from the upper part of the inner extremity of one clavicle to the other, and is closely attached to the upper margin of the sternum. It is in relation, in front, with the integument; behind, with the Sterno-thyroid muscles. The Costo-clavicular Ligament (rhomboid) is short, flat, and strong: it is of a rhomboid form, attached, below, to the upper and inner part of the cartilage of the first rib : it ascends obliquely backward and outward, and is attached, above, to the rhomboid depression on the under surface of the clavicle. It is in relation, in front, with the tendon of origin of the Subclavius; behind, with the subclavian vein. The Interarticular Fibro-cartilage is a flat and nearly circular disk, interposed between the articulating surfaces of the sternum and clavicle. It is attached, 1 According to Bruch, the sternal end of the clavicle is covered by a tissue which is rather fibrous than cartilaginous in structure. 344 THE ARTICULATIONS. above, to the upper and posterior border of the articular surface of the clavicle ; below, to the cartilage of the first rib, at its junction with the sternum; and by its circumference, to the anterior and posterior sterno-clavicular and interclavicular ligaments. It is thicker at the circumference, especially its upper and back part, than at its centre or below. It divides the joint into two cavities, each of which is furnished with a separate synovial membrane. Of the two Synovial Membranes found in this articulation, one is reflected from the sternal end of the clavicle over the adjacent surface of the fibro-cartilage and cartilage of the first rib ; the other is placed between the articular surface of the sternum and adjacent surface of the fibro-cartilage; the latter is the larger of the two. They seldom contain much synovia. Actions.-This articulation is the centre of the movements of the shoulder, and admits of a limited amount of motion in nearly every direction-upward, down- ward, backward, forward-as well as circumduction. When these movements take place in the joint, the clavicle in its motion carries the scapula with it, this bone gliding on the outer surface of the chest. This joint therefore forms the centre from which all movements of the supporting arch of the shoulder originate, and is the only point of articulation of this part of the skeleton with the trunk. " The movements attendant on elevation and depression of the shoulder take place between the clavicle and the interarticular fibro-cartilage, the bone rotating upon the ligament on an axis drawn from before backward through its own articular facet. When the shoulder is moved forward and backward, the clavicle, with the interarticular fibro-cartilage, rolls to and fro on the articular surface of the sternum, revolving, with a sliding movement, round an axis drawn nearly vertically through the sternum. In the circumduction of the shoulder, which is compounded of these two movements, the clavicle revolves upon the interarticular fibro-cartilage, and the latter, with the clavicle, rolls upon the sternum." 1 Elevation of the clavicle is principally limited by the costo-clavicular ligament; depression, by the inter- clavicular. The muscles which raise the clavicle, as in shrugging the shoulders, are the upper fibres of the Trapezius, the Levator anguli scapulae, the clavicular head of the Sterno-mastoid, assisted to a certain extent by the two Rhomboids, which pull the inferior angle of the Scapula backward and upward, and so raise the clavicle. The depression of the clavicle is principally effected by gravity, assisted by the Subclavius, Pectoralis minor, and lower fibres of the Trapezius. It is drawn backrvard by the Rhomboids and the middle and lower fibres of the Trapezius, and forward by the Serratus magnus and Pectoralis minor. Surface Form.-The position of the sterno-clavicular joint maybe easily ascertained by feel- ing the enlarged sternal end of the collar-bone just external to the long, cord-like, sternal origin of the Sterno-mastoid muscle. If this muscle is relaxed by bending the head forward, a depres- sion just internal to the end of the clavicle, and between it and the sternum, can be felt, indica- ting the exact position of the joint, which is subcutaneous. When the arm hangs by the side, the cavity of the joint is V-shaped. If the arm is raised, the bones become more closely approx- imated, and the cavity becomes a mere slit. Surgical Anatomy.-The strength of this joint mainly depends upon its ligaments, and it is to this, and to the fact that the force of the blow is generally transmitted along the long axis of the clavicle, that dislocation rarely occurs, and that the bone is generally broken rather than displaced. When dislocation does occur, the course which the displaced bone takes depends more upon the direction in which the violence is applied than upon the anatomical construction of the joint; it may be either forward, backward, or upward. The chief point worthy of note, as regards the construction of the joint, in regard to dislocations, is the fact that, owing to the shape of the articular surfaces being so little adapted to each other, and that the strength of the joint mainly depends upon the ligaments, the displacement when reduced is very liable to recur, and hence it is extremely difficult to keep the end of the bone in its proper place. II. Acromio-clavicular Articulation (Fig. 243). The Acromio-clavicular is an arthrodial joint formed between the outer extremity of the clavicle and the upper edge of the acromion process of the scapula. Its ligaments are the 1 Humphry, On the Human Skeleton, p. 402. A CROMIO-CLA VICULAR ARTICULA TION. 345 Superior Acromio-clavicular. Inferior Acromio-clavicular. Interarticular Fibro-cartilage. Trapezoid and Conoid. Coraco-clavicular The Superior Acromio-clavicular Ligament is a broad band, of a quadrilateral form, which covers the superior part of the articulation, extending between the upper part of the outer end of the clavicle and the adjoining part of the upper surface of the acromion. It is composed of parallel fibres which interlace with the aponeurosis of the Trapezius and Deltoid muscles; below, it is in contact with the interarticular fibro-cartilage (when it exists) and the synovial membranes. The Inferior Acromio-clavicular Ligament, somewhat thinner than the pre- ceding, covers the under part of the articulation, and is attached to the adjoining surfaces of the two bones. It is in relation, above, with the synovial membranes, and in rare cases with the interarticular fibro-cartilage; below, with the tendon Fig. 243.-The left shoulder-joint, scapulo-clavieular articulations, and proper ligaments of scapula. of the Supraspinatus. These two ligaments are continuous with each other in front and behind, and form a complete capsule round the joint. The Interarticular Fibro-cartilage is frequently absent in this articulation. When it exists it generally only partially separates the articular surfaces, and occupies the upper part of the articulation. More rarely it completely separates the joint into two cavities. The Synovial Membrane.-There is usually only one synovial membrane in this articulation, but when a complete interarticular fibro-cartilage exists there are two synovial membranes. The Coraco-clavicular Ligament serves to connect the clavicle with the coracoid process of the scapula. It does not properly belong to this articulation, but as it forms a most efficient means in retaining the clavicle in contact with the acromial 346 THE ARTICULATIONS. process, it is usually described with it. It consists of two fasciculi, called the trapezoid and conoid ligaments. The Trapezoid Ligament, the anterior and external fasciculus, is broad, thin, and quadrilateral; it is placed obliquely between the coracoid process and the clavicle. It is attached, below, to the upper surface of the coracoid process; above, to the oblique line on the under surface of the clavicle. Its anterior border is free; its posterior border is joined with the conoid ligament, the two forming by their junction a projecting angle. The Conoid Ligament, the posterior and internal fasciculus, is a dense band of fibres, conical in form, the base being turned upward, the summit downward. It is attached by its apex to a rough impression at the base of the coracoid process, internal to the preceding; above, by its expanded base, to the conoid tubercle on the under surface of the clavicle, and to a line proceeding internally from it for half an inch. These ligaments are in relation, in front, with the Subclavius and Deltoid; behind, with the Trapezius. They serve to limit rotation of the scapula, the Trapezoid limiting rotation forward, and the Conoid backward. Actions.-The movements of this articulation are of two kinds : 1. A gliding motion of the articular end of the clavicle on the acromion. 2. Rotation of the scapula forward and backward upon the clavicle, the extent of this rotation being limited by the two portions of the coraco-clavicular ligament. The acromio-clavicular joint has important functions in the movements of the upper extremity. It has been well pointed out by Sir George Humphry that if there had been no joint between the clavicle and scapula the circular movement of the scapula on the ribs (as in throwing both shoulders backward or forward) would have been attended with a greater alteration in the direction of the shoulder than is consistent with the free use of the arm in such position, and it would have been impossible to give a blow straight forward with the full force of the arm ; that is to say, with the combined force of the scapula, arm, and forearm. " This joint," as he happily says, "is so adjusted as to enable either bone to turn in a hinge-like manner upon a vertical axis drawn through the other, and it permits the surfaces of the scapula, like the baskets in a roundabout swing, to look the same way in every position or nearly so." Again, when the whole arch formed by the clavicle and scapula rises and falls (in elevation or depression of the shoulders), the joint between these two bones enables the scapula still to maintain its lower part in contact with the ribs. Surface Form.-The position of the acromio-clavicular joint can generally be ascertained by the slightly enlarged extremity of the outer end of the clavicle, which causes it to project above the level of the acromion process of the scapula. Sometimes this enlargement is so considerable as to form a rounded eminence, which is easily to be felt. The joint lies in the plane of a ver- tical line passing up the middle of the front of the arm. Surgical Anatomy.-Owing to the slanting shape of the articular surfaces of this joint, dislocation generally occurs downward; that is to say, the acromion process of the scapula is dislocated under the outer end of the clavicle; but dislocations in the opposite direction have been described. The displacement is often incomplete, on account of the strong coraco-claviculai ligaments, which remain untorn. The same difficulty7 exists, as in the sterno-clavicular disloca- tion, in maintaining the ends of the bone in position after reduction. The proper ligaments of the scapula are the III. Proper Ligaments of the Scapula (Fig. 243). Coraco-acromial. Transverse. The Coraco-acromial Ligament is a broad, thin, flat band, of a triangular shape, extended transversely above the upper part of the shoulder-joint, between the coracoid and acromial processes. It is attached, by its apex, to the summit of the acromion just in front of the articular surface for the clavicle, and by its broad base to the whole length of the outer border of the coracoid process. Its posterior fibres are directed obliquely backward and inward, its anterior fibres transversely inward. This ligament completes the vault formed by the coracoid and acromion THE SHOULDER-JOINT. 347 processes for the protection of the head of the humerus. It is in relation, above, with the clavicle and under surface of the Deltoid ; below, with the tendon of the Supraspinatus muscle, a bursa being interposed. Its anterior border is continuous with a dense cellular lamina that passes beneath the Deltoid upon the tendons of the Supra- and Infraspinatus muscles. This ligament is sometimes described as consisting of two marginal bands and a thinner intervening portion, the two bands being attached respectively to the apex and base of the coracoid process, and joining together at their attachment into the acromion process. When the Pectoralis minor is inserted, as sometimes is the case, into the capsule of the shoulder-joint, instead of into the coracoid process, it passes between these two bands, and the intervening portion is then deficient. The Transverse or Coracoid Ligament converts the suprascapu- lar notch into a foramen. It is a thin and flat fasciculus, narrower at the mid- dle than at the extremities, attached by one end to the base of the coracoid process, and by the other to the inner extremity of the scapular notch. The suprascapular nerve parses through the foramen ; the suprascapular vessels pass over the ligament. Movements of Scapula.-The scapula is capable of being moved upward and downward, forward and backward, or, by a combination of these movements, cir- cumducted on the wall of the chest. The muscles which raise the scapula are the upper fibres of the Trapezius, the Levator anguli scapulae, and the two Rhom- boids; those which depress it are the lower fibres of the Trapezius, the Pectoralis minor, and, through the clavicle, the Subclavius. The scapula is drawn backward by the Rhomboids and the middle and lower fibres of the Trapezius, and forward by the Serratus magnus and Pectoralis minor, assisted, when the arm is fixed, by the Pectoralis major. The mobility of the scapula is very considerable, and greatly assists the movements of the arm at the shoulder-joint. Thus, in raising the arm from the side the Deltoid and Supraspinatus can only lift it to a right angle with the trunk, the further elevation of the limb being effected by the Trapezius moving the scapula on the wall of the chest. This mobility is of special importance in ankylosis of the shoulder-joint, the movements of this bone com- pensating to a very great extent for the immobility of the joint. IV. Shoulder-Joint (Fig. 243). The Shoulder is an enarthrodial or ball-and-socket joint. The bones entering into its formation are the large globular head of the humerus, which is received CORACO ACROMIAL LIGAMENT. BICEPS. GLENOID 'LIGAMENT. SUPRA SPINATUS DELTOID DELTOID. SUPRA SPINATUS. 1 I SUB- SCAPULARIS TERES MAvOR TRICEPS SU BSCA PU LARIS. teres major. Circumflex vessels. TRICEPS Circumflex vessels. HenleG) 244,-Vertical sections through the shoulder joint, the arm being vertical and horizontal. (After into the shallow glenoid cavity of the scapula-an arrangement which permits of very considerable movement, whilst the joint itself is protected against displacement 348 THE ARTICULATIONS. by the tendons which surround it and by atmospheric pressure. The ligaments do not maintain the joint surfaces in apposition, because when they alone remain the humerus can be separated to a considerable extent from the glenoid cavity ; their use, therefore, is to limit the amount of movement. Above, the joint is protected by an arched vault, formed by the under surface of the coracoid and acromion processes, and the coraco-acromial ligament. The articular surfaces are covered by a layer of cartilage : that on the head of the humerus is thicker at the centre than at the circumference, the reverse being the case in the glenoid cavity. The liga- ments of the shoulder are the Capsular. Glenoid.1 Coraco-humeral. Transverse humeral. The Capsular Ligament completely encircles the articulation, being attached, above, to the circumference of the glenoid cavity beyond the glenoid ligament; below, to the anatomical neck of the humerus, approaching nearer to the articular cartilage above than in the rest of its extent. It is thicker above and below than elsewhere, and is remarkably loose and lax, and much larger and longer than is necessary to keep the bones in contact, allowing them to be separated from each other more than an inch-an evident provision for that extreme freedom of move- ment which is peculiar to this articulation. Its external surface is strengthened, above, by the Supraspinatus; below, by the long head of the Triceps; externally, by the tendons of the Infraspinatus and Teres minor; and internally, by the tendon of the Subscapularis. The capsular ligament usually presents three openings; one at its inner side, below the coracoid process, partially filled up by the tendon of the Subscapularis; it establishes a communication between the synovial membrane of the joint and a bursa beneath the tendon of that muscle. The second, which is not constant, is at the outer part, where a communication sometimes exists between the joint and a bursal sac belonging to the Infra- spinatus muscle. The third is seen in the lower border of the ligament, between the two tuberosities, for the passage of the long tendon of the Biceps muscle. The Coraco-humeral or Accessory Ligament is a broad band which strengthens the upper part of the capsular ligament. It arises from the outer border of the coracoid process, and passes obliquely downward and outward to the front of the great tuberosity of the humerus, being blended with the tendon of the Supra- spinatus muscle. This ligament is intimately united to the capsular in the greater part of its extent. The Transverse Humeral Ligament.-This is a broad band of fibrous tissue passing from the lesser to the greater tuberosity of the humerus, and always limited to that portion of the bone which lies above the epiphysial line. It converts the bicipital groove into an osseo-aponeurotic canal, and is the analogue of the strong process of bone which connects the summits of the two tuberosities in the musk ox. Supplemental Bands of the Capsular Ligament.-In addition to the coraco- humeral or accessory ligament, the capsular ligament is strengthened by supple- mental bands in the interior of the joint. One of these bands is situated on the inner side of the joint, and passes from the inner edge of the glenoid cavity to the lower part of the lesser tuberosity of the humerus. This is sometimes known as Flood's ligament, and is supposed to correspond with the ligamentum teres of the hip-joint. A second of these bands is situated at the lower part of the joint, and passes from the under edge of the glenoid cavity to the under part of the neck of the humerus, and is known as Schlemm's ligament. The Glenoid Ligament is a fibro-cartilaginous rim attached round the margin of the glenoid cavity. It is triangular on section, the thickest portion being fixed to the circumference of the cavity, the free edge being thin and sharp. It is continuous above with the long tendon of the Biceps muscle, which bifurcates at 1 The long tendon of origin of the Biceps muscle also acts as one of the ligaments of this joint. See the observations on p. 320 on the function of the muscles passing over more than one joint. 77ZA SHOULDER-JOINT. 349 the upper part of the cavity into two fasciculi, and becomes continuous with the fibrous tissue of the glenoid ligament. This ligament deepens the cavity for articula- tion, and protects the edges of the bone. It is lined by the synovial membrane. The Synovial Membrane is reflected from the margin of the glenoid cavity over the fibro-cartilaginous rim surrounding it: it is then reflected over the internal surface of the capsular ligament, covers the lower part and sides of the neck of the humerus, and is continued a short distance over the cartilage covering the head of the bone. The long tendon of the Biceps muscle which passes through the capsular ligament is enclosed in a tubular sheath of synovial membrane, which is reflected upon it at the point where it perforates the capsule, and is continued around it as far as the summit of the glenoid cavity. The tendon of the Biceps is thus enabled to traverse the articulation, but it is not contained in the interior of the synovial cavity. The synovial membrane communicates with a large bursal sac beneath the tendon of the Subscapularis, by an opening at the inner side of the capsular ligament; it also occasionally communicates with another bursal sac, beneath the tendon of the Infraspinatus, through an orifice at its outer part. A third bursal sac, which does not communicate with the joint, is placed between the under surface of the Deltoid and the outer surface of the capsule. The Muscles in relation with the joint are, above, the Supraspinatus; below, the long head of the Triceps; internally, the Subscapularis; externally, the Infra- spinatus and Teres minor; within, the long tendon of the Biceps. The Deltoid is placed most externally, and covers the articulation on its outer side, as well as in front and behind. The Arteries supplying the joint are articular branches of the anterior and posterior circumflex, and suprascapular. The Nerves are derived from the circumflex and suprascapular. Actions.-The shoulder-joint is capable of movement in every direction, forward, backward, abduction, adduction, circumduction, and rotation. The humerus is drawn forward by the Pectoralis major, anterior fibres of the Deltoid, Coraco- brachialis, and by the Biceps when the forearm is flexed; backward, by the Latis- simus dorsi, Teres major, posterior fibres of the Deltoid, and by the Triceps when the forearm is extended ; it is abducted (elevated) by the Deltoid and Supraspinatus ; it is adducted (depressed) by the Subscapularis, Pectoralis major, Latissimus dorsi, and Teres major ; it is rotated outwardly Aw Infraspinatus and Teres minor; and it is rotated inward by the Subscapularis, Latissimus dorsi, Teres major, and Pectoralis major. The most striking peculiarities in this joint are : 1. The large size of the head of the humerus in comparison with the depth of the glenoid cavity, even when supplemented by the glenoid ligament. 2. The looseness of the capsule of the joint. 3. The intimate connection of the capsule with the muscles attached to the head of the humerus. 4. The peculiar relation of the biceps tendon to the joint. It is in consequence of the relative size of the two articular surfaces that the joint enjoys such free movement in every possible direction. When these movements of the arm are arrested in the shoulder-joint by the contact of the bony surfaces and by the tension of the corresponding fibres of the capsule, together with that of the muscles acting as accessory ligaments, they can be carried considerably farther by the movements of the scapula, involving, of course, motion at the acromio- and sterno-clavicular joints. These joints are therefore to be regarded as accessory structures to the shoulder-joint.1 The extent of these movements of the scapula is very considerable, especially in extreme elevation of the arm, which movement is best accomplished when the arm is thrown somewhat forward, since the articular surface of the humerus is broader in the middle than at either end. especially the lower, so that the range of elevation directly forward is less, and that directly backward still more restricted. The great width of the central portion of the humeral head also allows of very free horizontal movement when the arm is raised to a right angle, in which movement the arch formed by the acromion, the 1 See p. 346. 350 THE ARTICULATIONS. coracoid process, and the coraco-acromial ligament constitutes a sort of supple- mental articular cavity for the head of the bone. The looseness of the capsule is so great that the arm will fall about an inch from the scapula when the muscles are dissected from the capsular ligament and an opening made in it to remove the atmospheric pressure. The movements of the joint, therefore, are not regulated by the capsule so much as by the surrounding muscles and by the pressure of the atmosphere-an arrangement which " renders the movements of the joint much more easy than they would otherwise have been, and permits a swinging, pendulum-like vibration of the limb when the muscles are at rest " (Humphry). The fact, also, that in all ordinary positions of the joint the capsule is not put on the stretch enables the arm to move freely in all direc- tions. Extreme movements are checked by the tension of appropriate portions of the capsule, as well as by the interlocking of the bones. Thus it is said that " abduction is checked by the contact of the great tuberosity with the upper edge of the glenoid cavity, adduction by the tension of the coraco-humeral ligament" (Beaunis et Bouchard). The intimate union of the tendons of the four short muscles with the capsule converts these muscles into elastic and spontaneously acting ligaments of the joint, and it is regarded as being also intended to prevent the folds into which all portions of the capsule would alternately fall in the varying positions of the joint from being driven between the bones by the pressure of the atmosphere. The peculiar relations of the Biceps tendon to the shoulder-joint appear to sub- serve various purposes. In the first place, by its connection with both the shoulder and elbow the muscle harmonizes the action of the two joints, and acts as an elastic ligament in all positions, in the manner previously adverted to.1 Next, it strengthens the upper part of the articular cavity, and prevents the head of the humerus from being pressed up against the acromion process, when the Deltoid contracts, instead of forming the centre of motion in the glenoid cavity. By its passage along the bicipital groove it assists in rendering the head of the humerus steady in the various movements of the arm. When the arm is raised from the side it assists the Supra- and Infraspinatus in rotating the head of the humerus in the glenoid cavity. It also holds the head of the bone firmly in contact with the glenoid cavity, and prevents its slipping over its lower edge, or being displaced by the action of the Latissimus dorsi and Pectoralis major, as in climbing and many other movements. Surface Form.-The direction and position of the shoulder-joint may be indicated by a line drawn from the middle of the coraco-acromial ligament, in a curved direction, with its con- vexity inward, to the innermost part of that portion of the head of the humerus which can be felt in the axilla when the arm is forcibly abducted from the side. When the arm hangs by the side, not more than one-third of the head of the bone is in contact with the glenoid cavity, and three-quarters of its circumference is in front of a vertical line drawn from the anterior border of the acromion process. Surgical Anatomy.-Owing to the construction of the shoulder-joint and the freedom of movement which it enjoys, as well as in consequence of its exposed situation, it is more frequently dislocated than any other joint in the body. Dislocation occurs when the arm is abducted, and when, therefore, the head of the humerus presses against the lower and front part of the cap- sule, which is the thinnest and least supported part of the ligament. The rent in the capsule almost invariably takes place in this situation, and through it the head of the bone escapes, so that the dislocation in most instances is primarily subglenoid. The head of the bone does not usually remain in this situation, but generally assumes some other position, which varies accord- ing to the direction and amount of force producing the dislocation and the relative strength of the muscles in front and behind the joint. In consequence of the muscles at the back being stronger than those in front, and especially on account of the long head of the Triceps pre- venting the bone passing backward, dislocation forward is much more common than back- ward. The most frequent position which the head of the humerus ultimately assumes is on the front of the neck of the scapula, beneath the coracoid process, and hence named subcora- coid. Occasionally, in consequence probably of a greater amount of force being brought to bear on the limb, the head is driven farther inward, and rests on the upper part of the front of the chest, beneath the clavicle (subclavicular). Sometimes it remains in the position in which it was primarily displaced, resting on the axillary border of the scapula (subglenoid), 1 See p. 320. TWA? EL BOW-JOINT. 351 and rarely it passes backward and remains in the infraspinatous fossa, beneath the spine (sub- spinous). The shoulder-joint is sometimes the seat of all those inflammatory affections, both acute and chronic, which attack joints, though perhaps less frequently than some other joints of equal size and importance. Acute synovitis may result from injury, rheumatism, or pyaemia, or may fol- low secondarily on the so-called acute epiphysitis of infants. It is attended with effusion into the joint, and when this occurs the capsule is evenly distended and the contour of the joint rounded. Special projections may occur at the site of the openings in the capsular ligament. Thus a swelling may appear just in front of the joint, internal to the lesser tuberosity, from effu- sion into the bursa beneath the Subscapularis muscle; or, again, a swelling which is sometimes bilobed may be seen in the interval between the Deltoid and Pectoralis major muscles, from effu- sion into the diverticulum, which runs down the bicipital groove with the tendon of the biceps. The effusion into the synovial membrane can be best ascertained by examination from the axilla, where a soft, elastic, fluctuating swelling can usually be felt. Tubercular arthritis not unfrequently attacks the shoulder-joint, and may lead to total de- struction of the articulation, when ankylosis may result or long-protracted suppuration may necessitate excision. This joint is also one of those which is most liable to be the seat of osteo- arthritis, and may also be affected in gout and rheumatism; or in locomotor ataxy, when it becomes the seat of Charcot's disease. Excision of the shoulder-joint may be required in cases of arthritis (especially the tuber- cular form) which have gone on to destruction of the articulation: in compound dislocations and fractures, particularly those arising from gunshot injuries, in which there has been extensive injury to the head of the bone; in some cases of old unreduced dislocation, where there is much pain ; and possibly in some few cases of growth connected with the upper end of the bone. The operation is best performed by making an incision from the middle of the coraco-acromial liga- ment down the arm for about three inches: this will expose the bicipital groove and the tendon of the Biceps, which may be either divided or hooked out of the way, according as to whether it is implicated in the disease or not. The capsule is then freely opened, and the muscles attached to the greater and lesser tuberosities of the humerus divided. The head of the bone can then be thrust out of the wound and sawn off, or divided with a narrow saw in situ and subsequently removed. The section should be made, if possible, just below the articular surface, so as to leave the bone as long as possible. The glenoid cavity must then be examined, and gouged if carious. V. Elbow-Joint. 'ITie Elbow is a ginglymus or hinge-joint. The bones entering into its forma- tion are the trochlear surface of the humerus, which is received into the greater sigmoid cavity of the ulna, and admits of the movements peculiar to this joint-viz. flexion and extension ; whilst the lesser, or radial, head of the humerus articulates with the cup-shaped depression on the head of the radius ; the circumference of the head of the radius articulates with the lesser sigmoid cavity of the ulna, allowing of the movement of rotation of the radius on the ulna, the chief action of the supe- rior radio-ulnar articulation. The articular surfaces are covered with a thin layer of cartilage, and connected together by a capsular ligament of unequal thickness, being especially thickened on its two sides and, to a less extent, in front and behind. These thickened portions are usually described as distinct ligaments under the following names: Anterior. Posterior. Internal Lateral. External Lateral. The orbicular ligament of the upper radio-ulnar articulation must also be reckoned among the ligaments of the elbow. 'fhe Anterior Ligament (Fig. 245) is a broad and thin fibrous layer which covers the anterior surface of the joint. It is attached to the front of the internal condyle and to the front of the humerus immediately above the coronoid fossa; below, to the anterior surface of the coronoid process of the ulna and orbicular ligament, being continuous on each side with the lateral ligaments. Its superficial fibres pass obliquely from the inner condyle of the humerus outward to the orbicular ligament. The middle fibres, vertical in direction, pass from the upper part of the coronoid depression and become partly blended with the preceding, but mainly inserted into the anterior surface of the coronoid process. The deep or transverse set intersects these at right angles. This ligament is in relation, in front, with the Brachialis anticus, except at its outermost part; behind, with the synovial membrane. 352 THE ARTICULA TIONS. The Posterior Ligament (Fig. 246) is a thin and loose membranous fold, attached, above, to the lower end of the humerus, on a level with the upper part of the olecranon fossa; below, to the margin of the olecranon. The superficial or trans- verse fibres pass between the adjacent margins of the olecranon fossa. The deeper portion consists of vertical fibres, which pass from the upper part of the olecranon fossa to the margin of the olecranon. This ligament is in relation, behind, with the tendon of the Tri- ceps and the Anconeus ; in front, with the synovial membrane. Fig. 245.-Left elbow-joint, showing anterior and internal ligaments. Fig. 246.-Left elbow-joint, showing posterior and external ligaments. The Internal Lateral Ligament (Fig. 245) is a thick triangular band consisting of two portions, an anterior and posterior, united by a thinner intermediate por- tion. The anterior portion, directed obliquely forward, is attached, above, by its apex, to the front part of the internal condyle of the humerus; and, below, by its broad base, to the inner margin of the coronoid process. The posterior portion, also of triangular form, is attached, above, by its apex, to the lower and back part of the internal condyle; below, to the inner margin of the olecranon. Between these two bands a few intermediate fibres descend from the internal con- dyle to blend with a transverse band of ligamentous tissue which bridges across the notch between the olecranon and coronoid processes. This ligament is in relation, internally, with the Triceps and Flexor carpi ulnaris muscles and the ulnar nerve, and gives origin to part of the Flexor sublimis digitorum. The External Lateral Ligament (Fig. 246) is a short and narrow fibrous band, less distinct than the internal, attached, above, to a depression below the external condyle of the humerus; below, to the orbicular ligament, some of its most pos- terior fibres passing over that ligament, to be inserted into the outer margin of the THE ELB O H- JOINT. 353 ulna. This ligament is intimately blended with the tendon of origin of the Supinator brevis muscle. The Synovial Membrane is very extensive. It covers the margin of the articular surface of the humerus, and lines the coronoid and olecranon fossae on that bone; from these points it is reflected over the anterior, posterior, and lateral ligaments, and forms a pouch between the lesser sigmoid cavity, the internal surface of the orbicular ligament, and the circumference of the head of the radius. Between the capsular ligament and the synovial membrane are three masses of fat; one, the largest, above the olecranon fossa, which is pressed into the fossa by the triceps during flexion ; a second, over the coronoid fossa; and a third, over the radial fossa. These are pressed into their respective fossae during extension. The Muscles in relation with the joint are, in front, the Brachialis anticus; behind, the Triceps and Anconeus; externally, the Supinator brevis and the common tendon of origin of the Extensor muscles; internally, the common tendon of origin of the Flexor muscles, and the Flexor carpi ulnaris, with the ulnar nerve. The Arteries supplying the joint are derived from the communicating branches between the superior profunda, inferior profunda, and anastomotica magna arteries, branches of the brachial, with the anterior, posterior, and interosseous recurrent branches of the ulnar and the recurrent branch of the radial. These vessels form a complete chain of inosculation around the joint. The Nerves are derived from the ulnar as it passes between the internal con- dyle and the olecranon ; a filament from the musculo-cutaneous (Riidinger), and two from the median (Macalister). Actions.-The elbow-joint comprises three different portions-viz, the joint between the ulna and humerus, that between the head of the radius and the humerus, and the superior radio-ulnar articulation, described below. All these articular surfaces are in- vested by a common synovial membrane, and the movements of the whole joint should be studied together. The combination of the movements of flexion and extension of the forearm with those of pronation and supina- tion of the hand, which is ensured by the two being performed at the same joint, is essen- tial to the accuracy of the various minute movements of the hand. The portion of the joint between the ulna and humerus is a simple hinge-joint, and allows of movements of flexion and extension only. Owing to the obliquity of the trochlear surface of the humerus, this movement does not take place in a straight line; so that when the forearm is extended and supinated the axis of the arm and forearm is not in the same line, but the one portion of the limb forms an angle with the others, and the hand, with the forearm, is directed outward. Dur- ing flexion, on the other hand, the forearm and the hand tend to approach the middle line of the body, and thus enable the hand to be easily carried to the face. The shape of the articular surface of the humerus, with its prominences and depressions accurately adapted to the opposing surfaces of the olecranon, prevents any lateral movement. Flexion is produced by the action of the Biceps and Brachialis Median -cephalic vein. Head of ■radius. Radial ' nerve. Fig. 247.-Sagittal section of the right elbow-joint, taken somewhat obliquely and seen from the radial aspect. (After Braune.) 354 THE ARTICULATIONS. anticus, assisted by the muscles arising from the internal condyle of the humerus and the Supinator longus; extension, by the Triceps and Anconeus, assisted by the extensors of the wrist and by the Extensor communis digitorum and Extensor minimi digiti. The joint between the head of the radius and the capitellum or radial head of the humerus is an arthrodial joint. The bony surfaces would of themselves con- stitute an enarthrosis, and allow of movement in all directions were it not for the orbicular ligament by which the head of the radius is bound down firmly to the sigmoid cavity of the ulna, and which prevents any separation of the two bones laterally. It is to the same ligament that the head of the radius owes its security from dislocation, which would otherwise constantly occur as a consequence of the shallowness of the cup-like surface on the head of the radius. In fact, but for this ligament the tendon of the biceps would be liable to pull the head of the radius out of the joint.1 In complete extension the head of the radius glides so far back on the outer condyle that its edge is plainly felt at the back of the articulation. Flexion and extension of the elbow-joint are limited by the tension of the structures on the front and back of the joint, the limitation of flexion being also aided by the soft structures of the arm and forearm coming in contact. In combination with any position of flexion or extension the head of the radius can be rotated in the upper radio-ulnar joint, carrying the hand with it. The hand is articulated to the lower surface of the radius only, and the concave or sigmoid surface on the lower end of the radius travels round the lower end of the ulna. The latter bone is excluded from the wrist-joint (as will be seen in the sequel) by the interarticular fibro-cartilage. Thus, rotation of the head of the radius round an axis which passes through the centre of the radial head of the humerus imparts circular movement to the hand through a very considerable arc. Surface Form.-If the forearm be slightly flexed on the arm, a curved crease or fold with its convexity downward may be seen running across the front of the elbow, extending from one condyle to the other. The centre of this fold is some slight distance above the line of the joint. The position of the radio-humeral portion of the joint can be at once ascertained by feeling for a slight groove or depression between the head of the radius and the capitellum of the humerus at the back of the articulation. Surgical Anatomy.-From the great breadth of the joint, and the manner in which the articular surfaces are interlocked, and also on account of the strong lateral ligaments and the support which the joint derives from the mass of muscles attached to each condyle of the humerus, lateral displacement of the bones is very uncommon, whereas antero-posterior disloca- tion, on account of the shortness of the antero-posterior diameter, the weakness of the anterior and posterior ligaments, and the want of support of muscles, much more frequently takes place, dislocation backward taking place when the forearm is in a position of extension, and forward when in a position of flexion. For, in the former position, that of extension, the coronoid pro- cess is not interlocked into the coronoid fossa, and loses its grip to a certain extent, whereas the olecranon process is in the olecranon fossa, and entirely prevents displacement forward. On the other hand, during flexion, the coronoid process is in the coronoid fossa, and prevents dislocation backward, while the olecranon loses its grip and is not so efficient, as during exten- sion, in preventing a forward displacement. When lateral dislocation does take place, it is gen- erally incomplete. Dislocation of the elbow-joint is of common occurrence in children, far more common than dislocation of any other articulation, for, as a rule, fracture of a bone more frequently takes place, under the application of any severe violence, in young persons than dislocation. In lesions of this joint there is often very great difficulty in ascertaining the exact nature of the injury. The elbow-joint is occasionally the seat of acute synovitis. The synovial membrane then becomes distended with fluid, the bulging showing itself principally around the olecranon pro- cess ; that is to say, on its inner and outer sides and above, in consequence of the laxness of the posterior ligament. Occasionally a well-marked, triangular projection may be seen on the outer side of the olecranon, from bulging of the synovial membrane beneath the Anconeus muscle. Again, there is often some swelling just above the head of the radius, in the line of the radio- humeral joint. There is generally not much swelling at the front of the joint, though sometimes deep-seated fulness beneath the Brachialis anticus may be noted. When suppuration occurs the abscess usually points at one or other border of the Triceps muscle; occasionally the pus discharges itself in front, near the insertion of the Brachialis anticus muscle. Chronic synovitis, 1 Humphry, op. cit., p. 419. THE RADIO-ULNAR ARTICULATIONS. 355 usually of tubercular origin, is of common occurrence in the elbow-joint: under these circum- stances the forearm tends to assume the position of semi-flexion, which is that of greatest ease and relaxation of ligaments. It should be borne in mind, that should ankylosis occur in this or the extended position, the limb will not be nearly so useful as if ankylosed in a position of rather less than a right angle. Loose cartilages are sometimes met with in the elbow-joint, not so commonly, however, as in the knee; nor do they, as a rule, give rise to such urgent symptoms as in this articulation, and rarely require operative interference. The elbow-joint is also some- times affected with osteo-arthritis, but this affection is less common in this articulation than in some other of the larger joints. Excision of the elbow is principally required for three conditions: viz. tubercular arthritis, injury and its results, and faulty ankylosis; but may be necessary for some other rarer condi- tions, such as disorganizing arthritis after pysemia. unreduced dislocations, and osteo-arthritis. The results of the operation are, as a rule, more favorable than those of excision of any other joint, and it is one, therefore, that the surgeon should never hesitate to perform, especially in the first three of the conditions mentioned above. The operation is best performed by a single vertical incision down the back of the joint, a transverse incision, over the outer condyle, being added if the parts are much thickened and fixed. A straight incision is made about four inches long, the mid-point of which is on a level with and a little to the inner side of the tip of the olecranon. This incision is made down to the bone, through the substance of the Triceps muscle. The operator with the point of his knife, and guarding the soft parts with his thumb- nail, separates them from the bone. In doing this there are two structures which he should carefully avoid: the ulnar nerve, which lies parallel to his incision, but a little internal, as it courses down between the internal condyle and the olecranon process, and the prolongation of the Triceps into the deep fascia of the forearm over the Anconeus muscle. Having cleared the bones and divided the lateral and posterior ligaments, the forearm is strongly flexed and the ends of the bone turned out and sawn off. The section of the humerus should be through the base of the condyles, that of the ulna and radius should be just below the level of the lesser sigmoid cavity of the ulna and the neck of the radius. In this operation the object is to obtain such union as shall allow free motion of the bones of the forearm; and, therefore, passive motion must be commenced early, that is to say, about the tenth day. VI. Radio-ulnar Articulations. The articulation of the radius with the ulna is effected by ligaments which connect together both extremities as well as the shafts of these bones. They may, consequently, be subdivided into three sets: 1, the superior radio-ulnar, which is a portion of the elbow-joint; 2, the middle radio-ulnar; and, 3, the inferior radio- ulnar articulations. 1. Superior Radio-ulnar Articulation. This articulation is a trochoid or pivot-joint. The bones entering into its formation are the inner side of the circumference of the head of the radius rotating within the lesser sigmoid cavity of the ulna. Its only ligament is the annular or orbicular. The Orbicular Ligament (Fig. 246) is a strong, flat band of ligamentous fibres, which surrounds the head of the radius, and retains it in firm connection with the lesser sigmoid cavity of the ulna. It forms about four-fifths of a fibrous ring, attached by each end to the extremities of the lesser sigmoid cavity, and is smaller at the lower part of its circumference than above, by which means the head of the radius is more securely held in its position. Its outer surface, is strengthened by the external lateral ligament of the elbow, and affords origin to part of the Supinator brevis muscle. Its inner surface is smooth, and lined by synovial membrane. The synovial membrane is continuous with that which lines the elbow-joint. Actions.-The movement which takes place in this articulation is limited to rotation of the head of the radius within the orbicular ligament, and upon the lesser sigmoid cavity of the ulna, rotation forward being called pronation; rotation backward, supination. Supination is performed by the Biceps and Supinator brevis, assisted to a slight extent by the Extensor muscles of the thumb and, in certain positions, by the Supinator longus. Pronation is performed by the Pro- nator radii teres and the Pronator quadratus, assisted, in some positions, by the Supinator longus. Surface Form.-The position of the superior radio-ulnar joint is marked on the surface of 356 THE A R TICULA TIONS. the body by the little dimple on the back of the forearm which indicates the position of the head of the radius. Surgical Anatomy.-Dislocation of the head of the radius alone is not an uncommon accident, and occurs most frequently in young persons from falls on the hand when the forearm is extended and supinated, the head of the bone being displaced forward. It is attended by rupture of the orbicular ligament. The interval between the shafts of the radius and ulna is occupied by two ligaments. Oblique. Interosseous. The Oblique or Round Ligament (Fig. 245) is a small, flattened fibrous band which extends obliquely downward and outward from the tubercle of the ulna at the base of the coronoid process to the radius a little below the bicipital tuberosity. Its fibres run in the opposite direction to those of the interosseous ligament, and it appears to be placed as a substitute for it in the upper part of the interosseous interval. This ligament is sometimes wanting. The Interosseous Membrane is a broad and thin plane of fibrous tissue descending obliquely downward and inward, from the interosseous ridge on the radius to that 2. Middle Radio-ulnar Articulation Inferior radio-ulnar articulation. Wrist-joint. articulations. Carpo-metacarpal Fig. 248.-Ligaments of wrist and hand. Anterior view. on the ulna. It is deficient above, commencing about an inch beneath the tubercle of the radius; is broader in the middle than at either extremity; and presents an oval aperture just above its lower margin for the passage of the anterior inter- osseous vessels to the back of the forearm. This ligament serves to connect the bones and to increase the extent of surface for the attachment of the deep muscles. Between its upper border and the oblique ligament an interval exists through which the posterior interosseous vessels pass. Two or three fibrous bands are occasionally found on the posterior surface of this membrane which descend obliquely from the ulna toward the radius, and which have consequently a direc- tion contrary to that of the other fibres. It is in relation, in front, by its upper three-fourths with the Flexor longus pollicis on the outer side, and with the Flexor profundus digitorum on the inner, lying upon the interval between which are the anterior interosseous vessels and nerve ; by its lower fourth, with the Pronator quadratus; behind, with the Supinator brevis, Extensor ossis metacarpi R J DIO- ULNA R ARTICULA TIONS. 357 pollicis, Extensor brevis pollicis, Extensor longus pollicis, Extensor indicis; and, near the wrist, with the anterior interosseous artery and posterior interosseous nerve. 3. Inferior Radio-ulnar Articulation. This is a pivot-joint, formed by the head of the ulna received into the sigmoid cavity at the inner side of the lower end of the radius. The articular surfaces are covered by a thin layer of cartilage, and connected together by the following lig- aments : Anterior Radio-ulnar. Posterior Radio-ulnar. Interarticular Fibro-cartilage. The Anterior Radio-ulnar Ligament (Fig. 248) is a narrow band of fibres extending from the anterior margin of the sigmoid cavity of the radius to the anterior surface of the head of the ulna. The Posterior Radio-ulnar Ligament (Fig. 249) extends between similar points on the posterior surface of the articulation Inferior radio-ulnar articulation. Wrist-joint. Carpal articulations. Carpo-metacarpal articulations. Fig. 249.-Ligaments of wrist and hand. Posterior view The Interarticular Fibro-cartilage (Fig. 251) is triangular in shape, and is placed transversely beneath the head of the ulna, binding the lower end of this bone and the radius firmly together. Its circumference is thicker than its centre, which is thin and occasionally perforated. It is attached by its apex to a depression which separates the styloid process of the ulna from the head of that bone; and by its base, which is thin, to the prominent edge of the radius, which separates the sigmoid cavity from the carpal articulating surface. Its margins are united to the ligaments of the wrist-joint. Its upper surface, smooth and concave, articulates with the head of the ulna, forming an arthrodial joint; its under surface, also concave and smooth, forms part of the wrist-joint and articulates with the cuneiform bone. Both surfaces are lined by a synovial membrane-the upper surface, by one peculiar to the radio-ulnar articulation ; the under surface, by the synovial membrane of the wrist. The Synovial Membrane (Fig. 251) of this articulation has been called, from its extreme looseness, the membrana sacciformis ; it extends horizontally inward between the head of the ulna and the interarticular fibro-cartilage, and upward between the radius and the ulna, forming here a very loose cul-de-sac. The quan- tity of synovia which it contains is usually considerable. Actions.-The movement in the inferior radio-ulnar articulation is just the reverse of that between the two bones above. It consists of a movement of rota- 358 THE ARTICULATIONS tion of the lower end of the radius round an axis which corresponds to the centre of the head of the ulna. When the radius rotates forward, pronation of the fore- arm and hand is the result; and when backward, supination. It will thus be seen that in pronation and supination of the forearm and hand the radius describes a segment of a cone, the axis of which extends from the centre of the head of the radius to the middle of the head of the ulna. In this movement, however, the ulna is not quite stationary, but rotates a little in the opposite direction. So that it also describes the segment of a cone, though of smaller size than that described by the radius. The movement which causes this alteration in the position of the head of the ulna takes place principally at the shoulder-joint by a rotation of the humerus, but possibly also to a slight extent at the elbow-joint.1 Surface Form.-The position of the inferior radio-ulnar joint may be ascertained by feeling for a slight groove at the back of' the wrist, between the prominent head of the ulna and the lower end of the radius, when the forearm is in a state of almost complete prona- tion. VII. Radio-carpal or Wrist-joint. The Wrist is a condyloid articulation. The parts entering into its formation are the lower end of the radius and under surface of the interarticular fibro-cartilage, which form together the receiving cavity, and the scaphoid, semilunar, and cuneiform bones, which form the condyle. The articular surface of the radius and the under surface of the inter-articular fibro-car- tilage are the receiving cavity, forming together a transversely elliptical concave surface. The articular surfaces of the scaphoid, semilunar, and cuneiform bones form together a smooth, convex surface, the condyle, which is received into the concavity above mentioned. All the bony sur- faces of the articulation are covered with cartilage, and connected together by a capsule, which is divided into the following ligaments: External Lateral. Anterior. Internal Lateral. Posterior. The External Lateral Ligament (radio-carpal} (Fig. 248) extends from the summit of the styloid process of the radius to the outer side of the scaphoid, some of its fibres being prolonged to the trapezium and annular ligament. The Internal Lateral Ligament (ulno-carpal) is a rounded cord, attached, above, to the extremity of the styloid process of the ulna, and dividing below into two fasciculi, which are attached, one to the inner side of the cuneiform bone, the other to the pisiform bone and annular ligament. The Anterior Ligament is a broad membranous band, attached, above, to the anterior margin of the lower end of the radius, its styloid process and the ulna: its fibres pass downward and inward to be inserted into the palmar surface of the scaphoid, semilunar, and cuneiform bones, some of the fibres being continued to the os magnum. In addition to this broad membrane, there is a distinct rounded fasciculus, superficial to the rest, which passes from the base of the styloid process of the ulna to the semilunar and cuneiform bones. This ligament is per- Fig. 250.-Longitudinal section of the right forearm, hand, and third finger, viewed from the ulnar aspect. (After Braune.) 1 See Journ. of Anat. and Phys., vol. xix,, parts ii., iii., and iv. OF THE CARPUS. 359 forated by numerous apertures for the passage of vessels, and is in relation, in front, with the tendons of the Flexor profundus digitorum and Flexor longus pol- licis; behind, with the synovial membrane of the wrist-joint. The Posterior Ligament (Fig. 249), less thick and strong than the anterior, is attached, above, to the posterior border of the lower end of the radius ; its fibres pass obliquely downward and inward, to be attached to the dorsal surface of the scaphoid, semilunar, and cuneiform bones, being continuous with those of the dorsal carpal ligaments. This ligament is in relation, behind, with the extensor tendons of the fingers; in front, with the synovial membrane of the wrist. The Synovial Membrane (Fig. 251) lines the inner surface of the ligaments above described, extending from the lower end of the radius and interarticular fibro-cartilage above to the articular surfaces of the carpal bones below. It is loose and lax, and presents numerous folds, especially behind. Relations.-The wrist-joint is covered in front by the flexor and behind by the ••extensor tendons ; it is also in relation with the radial and ulnar arteries. The Arteries supplying the joint are the anterior and posterior carpal branches of the radial and ulnar, the anterior and posterior interosseous, and some ascending branches from the deep palmar arch. The Nerves are derived from the ulnar and posterior interosseous. Actions.-The movements permitted in this joint are flexion, extension, abduc- tion, adduction, and circumduction. Its actions will be further studied with those of the carpus, with which they are combined. Surface Form.-The line of the radio-carpal joint is on a level with the apex of the styloid process of the ulna. Surgical Anatomy.-The wrist-joint is rarely dislocated, its strength depending mainly upon the numerous strong tendons which surround the articulation. Its security is further pro- vided for by the number of small bones of which the carpus is made up, and which are united by very strong ligaments. The slight movement which takes place between the several bones serves to break the jars that result from falls or blows on the hand. Dislocation backward, which is the more common, simulates to a considerable extent Colles' fracture of the radius, and is liable to be mistaken for it. The diagnosis can be easily made out by observing the relative position of the styloid processes of the radius and the ulna. In the natural condition the styloid process of the radius is on a lower level-i. e. nearer the ground-when the arm hangs by the side, than that of the ulna, and the same would be the case in dislocation. In Colles' frac- ture, on the other hand, the styloid process of the radius is on the same, or even a higher level than that of the ulna. The wrist-joint is occasionally the seat of acute synovitis, the result of traumatism or arising in the rheumatic or pyaemic state. When the synovial sac is distended with fluid, the swelling is greatest on the dorsal aspect of the wrist, showing a general fulness, with some bulging between the tendons. The inflammation is prone to extend to the intercarpal joints and to attack also the sheaths of the tendons in the neighborhood. Chronic inflammation of the wrist is generally tubercular, and often leads to similar disease in the synovial sheaths of adjacent tendons and of the intercarpal joints. The disease, therefore, when progressive, often leads to necrosis of the carpal bones, and the result is often unsatisfactory. VIII. Articulations of the Carpus. These articulations may be subdivided into three sets: 1. The Articulations of the First Row of Carpal Bones. 2. The Articulations of the Second Row of Carpal Bones. 3. The Articulations of the Two Rows with each other. 1. Articulations of the First Row of Carpal Bones. These are arthrodial joints. The ligaments connecting the scaphoid, semilunar, and cuneiform bones are- Dorsal. Palmar. Two Interosseous. The Dorsal Ligaments are placed transversely behind the bones of the first row ; they connect the scaphoid and semilunar and the semilunar and cuneiform. The Palmar Ligaments connect the scaphoid and semilunar and the semilunar 360 THE A R TICULA TIONS. and cuneiform bones; they are less strong than the dorsal, and placed very deeply under the anterior ligament of the wrist. The Interosseous Ligaments (Fig. 251) are two narrow bundles of fibrous tissue connecting the semilunar bone on one side with the scaphoid, and on the other with the cuneiform. They are on a level with the superior surfaces of these bones, and close the upper part of the spaces between them. Their upper surfaces are smooth, and form with the bones the convex articular surfaces of the wrist- joint. The ligaments connecting the pisiform bone are- Capsular. Two Palmar ligaments. The Capsular Ligament is a thin membrane which connects the pisiform bone to the cuneiform. It is lined with a separate synovial membrane. The two Palmar Ligaments are two strong fibrous bands which connect the pisiform to the unciform, the piso-uncinate, and to the base of the fifth metacarpal bone, the piso-metacarpal ligament (Fig. 248). 2. Articulations of the Second Row of Carpal Bones. These are also arthrodial joints. The articular surfaces are covered with carti- lage, and connected by the following ligaments: Dorsal. Palmar. Three Interosseous. The Dorsal Ligaments extend transversely from one bone to another on the dorsal surface, connecting the trapezium with the trapezoid, the trapezoid with the os magnum, and the os magnum with the unciform. The Palmar Ligaments have a similar arrangement on the palmar surface. The three Interosseous Ligaments, much thicker than those of the first row, are placed one between the os magnum and the unciform, a second between the os magnum and the trapezoid, and a third between the trapezium and trapezoid. The first of these is much the strongest, and the third is sometimes wanting. Sometimes a slender interosseous band connects the os magnum and the scaphoid. 3. Articulations of the Two Rows of Carpal Bones with each Other. The joint between the scaphoid, semilunar, and cuneiform, and the second row of the carpus, or the mid-carpal joint, is made up of three distinct portions; in the centre the head of the os magnum and the superior surface of the unciform articulate with the deep, cup-shaped cavity formed by the scaphoid and semilunar bones, and constitute a sort of ball-and-socket joint. On the outer side the trapezium and trapezoid articulate with the scaphoid, and on the inner side the unciform articulates with the cuneiform, forming gliding joints. The ligaments are- Anterior or Palmar. Posterior or Dorsal. External Lateral. Internal Lateral. The Anterior or Palmar Ligaments consist of short fibres, which pass, for the most part, from the palmar surface of the bones of the first row to the front of the os magnum. The Posterior or Dorsal Ligaments consist of short, irregular bundles of fibres passing between the bones of the first and second row on the dorsal surface of the carpus. The Lateral Ligaments are very short: they are placed, one on the radial, the other on the ulnar side of the carpus; the former, the stronger and more distinct, connecting the scaphoid and trapezium bones, the latter the cuneiform and unciform ; they are continuous with the lateral ligaments of the wrist-joint. The Synovial Membrane of the Carpus is very extensive: it passes from the CARPO-META CARPA L AR TICVLA TIONS. 361 under surface of the scaphoid, semilunar, and cuneiform bones to the upper surface of the bones of the second row, sending upward two prolongations-between the scaphoid and semilunar and the semilunar and cuneiform ; sending downward three prolongations between the four bones of the second row, which are further continued onward into the carpo-metacarpal joints of the four inner metacarpal bones, and also for a short distance between the metacarpal bones. There is a separate synovial membrane between the pisiform and cuneiform bones. Actions.-The articulation of the hand and wrist, considered as a whole, is divided into three parts: (1) the radius and the interarticular fibro-cartilage; (2) the meniscus, formed by the scaphoid, semilunar, and cuneiform, the pisiform bone having no essential part in the movements of the hand; (3) the hand proper, the metacarpal bones with the four carpal bones on which they are supported-viz. the trapezium, trapezoid, os magnum, and unciform. These three elements form two joints: (1) the superior (wrist-joint proper), between the meniscus and bones of the forearm; (2) the inferior, between the hand and meniscus (transverse or mid-carpal joint). (1) The articulation between the forearm and carpus is a true condyloid artic- ulation, and therefore all movements but rotation are permitted. Flexion and extension are the most free, and of these a greater amount of extension than flexion is permitted on account of the articulating surfaces extending farther on the dorsal than on the palmar aspect of the carpal bones. In this movement the carpal bones rotate on a transverse axis drawn between the tips of the styloid processes of the radius and ulna. A certain amount of adduction (or ulnar flexion) and abduction (or radial flexion) is also permitted. Of these the former is considerably greater in extent than the latter. In this movement the carpus revolves upon an antero-posterior axis drawn through the centre of the wrist. Finally, circumduction is permitted by the consecutive movements of adduction, extension, abduction, and flexion, with intermediate movements between them. There is no rotation, but this is provided for by the supination and pronation of the radius on the ulna. The movement of flexion is performed by the Flexor carpi radialis, the Flexor carpi ulnaris, and the Palmaris longus; extension, by the Extensor carpi radialis longior et brevior and the Extensor carpi ulnaris ; adduction (ulnar flexion), by the Flexor carpi ulnaris and the Extensor carpi ulnaris ; and abduction (radial flexion), by the Extensors of the thumb and the Extensor carpi radialis longior et brevior and the Flexor carpi radialis. (2) The chief movements permitted in the transverse or mid-carpal joint are flexion and extension and a slight amount of rotation. In flexion and extension, which is the movement most freely enjoyed, the trapezium and trapezoid on the radial side and the unciform on the ulnar side glide forward and backward on the scaphoid and cuneiform respectively, while the head of the os magnum and the superior surface of the unciform rotate in the cup-shaped cavity of the scaphoid and semilunar. Flexion at this joint is freer than extension. A very trifling amount of rotation is also permitted, the head of the os magnum rotating round a vertical axis drawn through its own centre, while at the same time a slight gliding movement takes place in the lateral portions of the joint. IX. Carpo-metacarpal Articulations. 1. Articulation of the Metacarpal Bone of the Thumb with the Trapezium. This is a joint of reciprocal reception, and enjoys great freedom of movement, on account of the configuration of its articular surfaces, which are saddle-shaped, so that, on section, each bone appears to be received into a cavity in the other, according to the direction in which they are cut. Its ligaments are a capsular ligament and a synovial membrane. The Capsular Ligament is a thick but loose capsule which passes from the circumference of the upper extremity of the metacarpal bone to the rough edge 362 THE A R TIC ULA TIONS. bounding the articular surface of the trapezium; it is thickest externally and behind, and lined by a separate synovial membrane. Movements.-In the articulation of the metacarpal bone of the thumb with the trapezium the movements permitted are flexion, extension, adduction, abduction, and circumduction. When the joint is flexed the metacarpal bone is brought in front of the palm and the thumb is gradually turned to the fingers. It is by this peculiar movement that the tip of the thumb is opposed to the other digits; for by slightly flexing the fingers the palmar surface of the thumb can be brought in contact with their palmar surfaces one after another. 2. Articulations of the Metacarpal Bones of the Four Inner Fingers with the Carpus. The joints formed between the carpus and four inner metacarpal bones are arthrodial joints. The ligaments are- Dorsal. Palmar. Interosseous. The Dorsal Ligaments, the strongest and most distinct, connect the carpal and metacarpal bones on their dorsal surface. The second metacarpal bone receives two fasciculi-one from the trapezium, the other from the trapezoid; the third metacarpal receives two-one from the trapezoid and one from the os magnum ; the fourth two-one from the os magnum and one from the unciform ; the fifth receives a single fasciculus from the unciform bone, which is continuous with a similar ligament on the palmar surface, forming an incomplete capsule. The Palmar Ligaments Lave a somewhat similar arrangement on the palmar surface, with the exception of the third metacarpal, which has three ligaments-an external one from the trapezium, situated above the sheath of the tendon of the Flexor carpi radialis; a middle one, from the os magnum ; and an inter- nal one, from the unciform. The Interosseous Ligaments con- sist of short, thick fibres, which are limited to one part of the carpo- metacarpal articulation; they con- nect the contiguous inferior angles of the os magnum and unciform with the adjacent surfaces of the third and fourth metacarpal bones. The Synovial Membrane is a con- tinuation of that between the two rows of carpal bones. Occasionally, the articulation of the unciform with the fourth and fifth metacarpal bones has a separate synovial membrane. The synovial membranes of the wrist and carpus (Fig. 251) are thus seen to be five in number. The first, the membrana sacciformis, passes from the lower end of the ulna to the sigmoid cavity of the radius, and lines the upper surface of the interarticular fibro-cartilage. The second passes from the lower end of the radius and interarticular fibro-cartilage above to the bones of the first row below. The third, the most extensive, passes between the contiguous margins of the two rows of carpal bones-between the bones of the second row to the carpal Fig. 251.-Vertical section through the articulations at the wrist, showing the five synovial membranes. META CA RPO-PHA LA NGEAL A R TICULA TIONS. 363 extremities of the four inner metacarpal bones. The fourth, from the margin of the trapezium to the metacarpal bone of the thumb. The fifth, between the adjacent margins of the cuneiform and pisiform bones. Actions.-The movement permitted in the carpo-metacarpal articulations of the four inner fingers is limited to a slight gliding of the articular surfaces upon each other, the extent of which varies in the different joints. Thus the articulation of the metacarpal bone of the little finger is most movable, then that of the ring finger. The metacarpal bones of the index and middle fingers are almost immovable. 3. Articulations of the Metacarpal Bones with each other. The carpal extremities of the four inner metacarpal bones articulate with one another at each side by small surfaces covered with cartilages, and connected together by dorsal, palmar, and interosseous ligaments. The Dorsal and Palmar Ligaments pass transversely from one bone to another on tbe dorsal and palmar surfaces. The Interosseous Ligaments pass between their contiguous surfaces, just beneath their lateral articular facets. The Synovial Membrane between the lateral facets is a reflection from that between the two rows of carpal bones. The Transverse Metacarpal Ligaments (Fig. 252) is a narrow fibrous band which passes transversely across the anterioi' surfaces of the digital extremities of the four inner metacarpal bones, connecting them together. It is blended an- teriorly with the anterior (glenoid) ligament of the metacarpal-phalan- geal articulations. To its posterior border is connected the fascia which covers the Interossei muscles. Its superficial surface is concave where the flexor tendons pass over it. Be- neath it the tendons of the Inter- ossei muscles pass to their insertion. X. Metacarpo-phalangeal Articu- lations (Fig. 252). These articulations are of the condyloid kind, formed by the re- ception of the rounded head of the metacarpal bone into a superficial cavity in the extremity of the first phalanx. The ligaments are- Anterior. Two Lateral. The Anterior Ligaments (Glenoid Ligaments of Cruveilhier) are thick, dense, fibrous structures, placed on the palmar surface of the joints in the intervals between the lateral ligaments, to which they are con- nected ; they are loosely united to the metacarpal bone, but very firmly to the base of the first phalanges. Their palmar surface is intimately blended with the transverse metacar- pal ligament, and presents a groove for the passage of the flexor tendons, the LATERAL LIGAMENT.- Metacarpo-phalangeal articulation. Grooves for flexor tendons.- LATERAL LIGAMENT." Phalangeal articulations. LATERAL LIGAMENT.- Fig. 252.-Articulations of the phalanges 364 THE ARTICULATIONS. sheath surrounding which is connected to each side of the groove. By their deep surface they form part of the articular surface for the head of the metacarpal bone, and are lined by a synovial membrane. The Lateral Ligaments are strong, rounded cords placed one on each side of the joint, each being attached by one extremity to the posterior tubercle on the side of the head of the metacarpal bone, and by the other to the contiguous extremity of the phalanx. Actions.-The movements which occur in these joints are flexion, extension, adduction, abduction, and circumduction ; the lateral movements are very limited. Surface Form.-The prominences of the knuckles do not correspond to the position of the joints either of the metacarpo-phalangeal or interphalangeal articulations. These prominences are invariably formed by the distal ends of the proximal bone of each joint, and the line indi- cating the position of the joint must be sought considerably in front of the middle of the knuckle. The usual rule for finding these joints is to flex the distal phalanx on the proximal one to a right angle ; the position of the joint is then indicated by an imaginary line drawn along the middle of the lateral aspect of the proximal phalanx. These are ginglymus joints. The ligaments are- Anterior. Two Lateral. The arrangement of these ligaments is similar to those in the metacarpo- phalangeal articulations; the extensor tendon supplies the place of a posterior ligament. Actions.-The only movements permitted in the phalangeal joints are flexion and extension ; these movements are more extensive between the first and second phalanges than between the second and third. The movement of flexion is very considerable, but extension is limited by the anterior and lateral ligaments. XI. Articulations of the Phalanges. ARTICULATIONS OF THE LOWER EXTREMITY. The articulations of the Lower Extremity comprise the following groups : I. The hip-joint. II. The knee-joint. III. The articulations between the tibia and fibula. IV. The ankle-joint. V. The articulations of the tarsus. VI. The tarso-metatarsal articulations. VII. The metatarso-phalangeal articulations. VIII. The articulations of the phalanges. I. Hip-joint (Fig. 253). This articulation is an enarthrodial or ball-and-socket joint, formed by the reception of the head of the femur into the cup-shaped cavity of the acetabulum. The articulating surfaces are covered with cartilage, that on the head of the femur being thicker at the centre than at the circumference, and covering the entire surface, with the exception of a depression just below its centre for the ligamentum teres; that covering the acetabulum is much thinner at the centre than at the circumference. It forms an incomplete cartilaginous ring of a horseshoe shape, deficient below and in front, and having in its centre a circular depression, which is occupied in the recent state by a mass of fat covered by synovial membrane. The ligaments of the joints are the Capsular. Ilio-femoral. Teres. Cotyloid. Transverse. The Capsular Ligament is a strong, dense, ligamentous capsule, embracing the margin of the acetabulum above and surrounding the neck of the femur below. Its upper circumference is attached to the acetabulum, above and behind, two or three lines external to the cotyloid ligament; but in front it is attached to the outer margin of this ligament, and opposite to the notch where the margin of this cavity is deficient, it is connected to the transverse ligament, and by a few fibres THE HIP-JOINT. 365 to the edge of the obturator foramen. Its lower circumference surrounds the neck of the femur, being attached, in front, to the spiral or anterior intertrochanteric line ; above, to the base of the neck ; behind, to the neck of the bone, about half an inch above the posterior intertrochanteric line. From this insertion the fibres are reflected upward over the neck of the femur, forming a sort of tubular sheath (the cervical reflection), which blends with the periosteum and can be traced as far as the articular cartilage. It is much thicker at the upper and fore part of the joint, where the greatest amount of resistance is required, than below and internally, where it is thin, loose, and longer than in any other part. It consists of two sets of fibres, circular and longitudinal. The circular fibres are most abundant at the lower and back part of the capsule, while the longitudinal fibres are greatest in Fig. 253.-Left hip-joint laid open. amount at the upper and front part of the capsule, where they form distinct bands or accessory ligaments, of which the most important is the ilio-femoral. The other accessory bands are known as the pubo-femoral, passing from the ilio- pectineal eminence to the front of the capsule ; ilio-troclianteric, from the anterior inferior spine of the ilium to the front of the great trochanter ; and ischio-capsular, passing from the ischium, just below the acetabulum, to blend with the circular fibres at the lower part of the joint. The external surface (Fig- 239, page 339) is rough, covered by numerous muscles, and separated in front from the Psoas and Iliacus by a synovial bursa, which not unfrequently communicates, by a circular aperture, with the cavity of the joint. It differs from the capsular ligament of the shoulder in being much less loose and lax, and in not being perforated for the passage of a tendon. The Ilio-femoral Ligament (Figs. 239 and 254) is an accessory band of fibres extending obliquely across the front of the joint; it is intimately connected with the capsular ligament, and serves to strengthen it in this situation. It is attached, above, to the lower part of the anterior inferior spine of the ilium ; and, diverging below, forms two bands, of which one passes downward to be inserted into the 366 77/Z? ARTICULATIONS. lower part of the anterior intertrochanteric line ; the other passes downward and outward to be inserted into the upper part of the same line and adjacent part of the neck of the femur. Between the two bands is a thinner part of the capsule. Sometimes there is no division, but the ligament spreads out into a flat, triangular band, which is attached below into the whole length of the anterior inter- trochanteric line. This ligament is frequently called the Y-shaped ligament of Bigelow. The Ligamentum Teres is a triangular band implanted by its apex into the depression a little behind and below the centre of the head of the femur, and by its broad base into the margins of the cotyloid notch, becoming blended with the transverse ligament. It is formed of connective tissue, surrounded bv a tubular sheath of synovial membrane. Sometimes only the synovial fold exists, or the ligament may be altogether absent. The ligament is made tense when the hip is semiflexed, and the limb then adducted and rotated outward; it is, on the other hand, relaxed when the limb is abducted. It has, however, but little influence as a ligament, though it may to a certain extent limit move- ment, and would appear to be merely a modi- fication of the folds which in other joints COTYLOID LIGAMENT.X RECTUS MUSCLE CAPSULAR LIGAMENT. ~TERES. OBTURATOR * MEMBRANE. Fig. 254.-Hip-joint, showing the ilio-femoral ligament. (After Bigelow.) Fig. 255.-Vertical section through hip-joint. (Henle.) fringe the margins of reflection of synovial membranes (see page 316). The Cotyloid Ligament is a fibro-cartilaginous rim attached to the margin of the acetabulum, the cavity of which deepens; at the same time it protects the edges of the bone and fills up the inequalities on its surface. It bridges over the notch as the transverse ligament, and thus forms a complete circle, which closely surrounds the head of the femur, and assists in holding it in its place, acting as a sort of valve. It is prismoid in form, its base being attached to the margin of the acetabulum, and its opposite edge being free and sharp; whilst its two surfaces are invested by synovial membrane, the external one being in contact with the capsular ligament, the internal one being inclined inward, so as to narrow the acetabulum and embrace the cartilaginous surface of the head of the femur. It is much thicker above and behind than below and in front, and consists of close, compact fibres, which arise from different points of the circumference of the acetabulum and interlace with each other at very acute angles. The Transverse Ligament is in reality a portion of the cotyloid ligament, THE HIP-JOINT. 367 though differing from it in having no nests of cartilage-cells amongst its fibres. It consists of strong, flattened fibres, which cross the notch at the lower part of the acetabulum and convert it into a foramen. Thus an interval is left beneath the ligament for the passage of nutrient vessels to the joint. The Synovial Membrane is very extensive. Commencing at the margin of the cartilaginous surface of the head of the femur, it covers all that portion of the neck which is contained within the joint; from the neck it is reflected on the internal surface of the capsular ligament, covers both surfaces of the cotyloid liga- ment and the mass of fat contained in the depression at the bottom of the acetab- Fig. 256.-Relation of muscles to the capsule of the hip-joint. From a drawing by Mr. F. A. Barton ulum, and is prolonged in the form of a tubular sheath around the ligamentum teres as far as the head of the femur. The muscles in relation with the joint are, in front, the Psoas and Iliacus, separated from the capsular ligament by a synovial bursa; above, the reflected head of the Rectus and Gluteus minimus, the latter being closely adherent to the capsule; internally, the Obturator externus and Pectineus ; behind, the Pyriformis, Gemellus superior, Obturator internus, Gemellus inferior, Obturator externus, and Quadratus femoris (Fig. 256). The arteries supplying the joint are derived from the obturator, sciatic, internal circumflex, and gluteal. The nerves are articular branches from the sacral plexus, great sciatic, obtu- rator, accessory obturator, and a filament from the branch of the anterior crural supplying the Rectus. Actions.-The movements of the hip, like those of all enarthrodial joints, are very extensive ; they are flexion, extension, adduction, abduction, circumduction, and rotation. The hip-joint presents a very striking contrast to the other great enarthrodial joint-the shoulder-in the much more complete mechanical arrangements for its security and for the limitation of its movements. In the shoulder, as we have seen, the head of the humerus is not adapted at all in shape to the glenoid cavity, and is 368 THE ARTICULATIONS. hardly restrained in any of its ordinary movements by the capsular ligament. In the hip-joint, on the contrary, the head of the femur is closely fitted to the acetab- ulum for a distance extending over nearly half a sphere, and at the margin of the bony cup it is still more closely embraced by the ligamentous ring of the cotyloid ligament, so that the head of the femur is held in its place by that ligament even when the fibres of the capsule have been quite divided (Humphry). The anterior portion of the capsule, described as the ilio-femoral or accessory ligament, is the strongest of all the ligaments in the body, and is put on the stretch by any attempt to extend the femur beyond a straight line with the trunk. That is to say, this ligament is the chief agent in maintaining the erect position without muscular fatigue, the action of the extensor muscles of the buttock being balanced by the tension of the ilio-femoral and capsular ligaments. The security of the joint may be also provided for by the two bones being directly united through the ligamentum teres; but it is doubtful whether this so-called ligament can have much influence upon the mechanism of the joint. Flexion of the hip-joint is arrested by the soft parts of the thigh and abdomen being brought into contact;1 extension, by the tension of the ilio-femoral ligament and front of the capsule; adduction, by the thighs coming into contact; adduction, with flexion by the outer band of the ilio-femoral ligament, the ilio-trochanteric ligament, the outer part of the capsular ligament; abduction, by the inner band of the ilio-femoral ligament and the pubo-femoral band; rotation outward, by the outer band of the ilio-femoral ligament; and rotation inward, by the ischio-capsular ligament and the hinder part of the capsule. The muscles which flex the femur on the pelvis are the Psoas, Iliacus, Rectus, Sartorius, Pectineus, Adductor longus and brevis, and the anterior fibres of the Gluteus medius and minimus. Extension is mainly performed by the Gluteus maximus, assisted by the hamstring muscles. The thigh is adducted by the Adductor magnus, longus and brevis, the Pectineus, and Gracilis, and abducted by the Gluteus maximus, medius, and minimus. The muscles which rotate the thigh inward are the anterior fibres of the Gluteus medius, the Gluteus minimus, and the Tensor vaginae femoris; while those which rotate it outward are the posterior fibres of the Gluteus medius, the Pyriformis, Obturator extern us and internus, Gemellus superior and inferior, Quadratus femoris, Psoas, Iliacus, Gluteus maximus, the three Adductors, the Pectineus, and the Sartorius. Surface Form.-A line drawn from the anterior superior spinous process of the ilium to the most prominent part of the tuberosity of the ischium (Nelaton's line) runs through the centre of the acetabulum, and would, therefore, indicate the level of the hip-joint; or, in other words, the upper border of the great trochanter, which lies on Nelaton's line, is on a level with the centre of the hip-joint. Surgical Anatomy.-Tn dislocation of the hip " the head of the thigh-bone may rest at any point around its socket" (Bryant); but whatever position the head ultimately assumes, the primary displacement is generally downward and inward, the capsule giving way at its weakest- that is, its lower and inner-part. The situation that the head of the bone subsequently assumes is determined by the degree of flexion or extension, and of outward or inward rotation of the thigh at the moment of luxation, influenced, no doubt, by the ilio-femoral ligament, which is not easily ruptured. When, for instance, the head is forced backward, this ligament forms a fixed axis, round which the head of the bone rotates, and is thus driven on to the dorsum of the ilium. The ilio-femoral ligament also influences the position of the thigh in the various disloca- tions : in the dislocations backward it is tense, and produces inversion of the limb; in the dislocation on to the pubes it is relaxed, and therefore allows the external rotators to evert the thigh; while in the thyroid dislocation it is tense and produces flexion. The muscles inserted into the upper part of the femur, with the exception of the Obturator interims, have very little direct influence in determining the position of the bone. But Bigelow has endeavored to show that the Obturator interims is the principal agent in determining whether, in the backward dislocations, the head of the bone shall be ultimately lodged on the dorsum of the ilium or in or near the sciatic notch. In both dislocations the head passes, in the first instance, in the same direction; but, as Bigelow asserts, in the displacement on to the dorsum, the head of the bone travels up behind the acetabulum, between the muscle and the pelvis; while in the disloca- 1 The hip-joint cannot be completely flexed, in most persons, without at the same time flexing the knee, on account of the shortness of the hamstring muscles.-Cleland, Journ. of Anat. and Phys., No. 1, Old Series, p. 87. THE HIP-JOINT. 369 tion into the sciatic notch, the head passes behind the muscle, and is therefore prevented from reaching the dorsum, in consequence of the tendon of the muscle arching over the neck of the bone, and so remains in the neighborhood of the sciatic notch. Bigelow, therefore, distinguishes these two forms of dislocation by describing them as dislocations backward, " above and below," the Obturator internus. The ilio-femoral ligament is rarely torn in dislocations of the hip, and this fact is taken advantage of by the surgeon in reducing these dislocations by manipulation. It is made to act as a fulcrum to a lever, of which the long arm is the shaft of the femur, and the short arm the neck of the bone. The hip-joint is rarely the seat of acute synovitis from injury, on account of its deep position and its thick covering of soft parts. Acute inflammation may, and does, frequently occur as the result of constitutional conditions, as rheumatism, pyaemia, etc. When, in these cases, effusion takes place, and the joint becomes distended with fluid, the swelling is not very easy to detect on account of the thickness of the capsule and the depth of the articulation. It is principally to be found on the front of the joint, just internal to the ilio-femoral ligament; or behind, at the lower and back part. In these two places the capsule is thinner than elsewhere. Disease of the hip-joint is much more frequently of a chronic character and is usually of a tubercular origin. It begins either in the bones or in the synovial membrane, more frequently in the former, and probably, in most cases, at the growing, highly vascular tissue in the neighborhood of the epiphysial cartilage. In this respect it differs very materially from tubercular arthritis of the knee, where the disease usually commences in the synovial membrane. The reasons for this are twofold : first, this part being the centre of rapid growth, its nutrition is unstable and apt to pass into inflammatory action; and, secondly, great strain is thrown upon it, from the frequency of falls and blows upon the hip, which causes crushing of the epiphysial cartilage or the cancellous tissue in its neighborhood, with the results likely to follow such an injury. In addition to these, the depth of the joint protects it from the causes of synovitis. In chronic hip-disease the affected limb assumes an altered position, the cause of which it is important to understand. In the early stage of a typical case the limb is flexed, abducted, and rotated outward. In this position all the ligaments of the joint are relaxed : the front of the capsule by flexion; the outer band of the ilio-femoral ligament by abduction; and the inner band of this ligament and the back of the capsule by rotation outward. It is, therefore, the- position of the greatest ease. The condition is not quite obvious at first upon examining a patient. If the patient is laid in the supine position, the affected limb will be found to be extended and parallel with the other. But it will be found that the pelvis is tilted downward on the diseased side and the limb apparently longer than its fellow, and that the lumbar spine is arched forward (lordosis). If now the thigh is abducted and flexed, the tilting down- ward and the arching forward of the pelvis disappears. The condition is thus explained. A limb which is flexed and abducted is obviously useless for progression, and, in order to over- come the difficulty, the patient depresses the affected side of his pelvis in order to produce parallelism of his limbs, and at the same time rotates his pelvis on its transverse horizontal axis, so as to direct the limb downward instead of forward. In the latter stages of the disease the limb becomes flexed and abducted and inverted. This position probably depends upon muscular action, at all events as regards the adduction. The Adductor muscles are supplied by the obturator nerve, which also largely supplies the joint. These muscles are therefore thrown into reflex action by the irritation of the peripheral terminations of this nerve in the inflamed artic- ulation. Osteo-arthritis is not uncommon in the hip-joint, and it is said to be more common in the male than in the female, in whom the knee-joint is more frequently affected. It is a disease of middle age or more advanced period of life. Congenital dislocation is more commonly met with in the hip-joint than in any other articula- tion. The displacement usually takes place on to the dorsum ilii. It gives rise to extreme lordosis, and a waddling gait is noticed as soon as the child commences to walk. Excision of the hip may be required for disease or for injury, especially gunshot. It may be performed either by an anterior incision or a posterior one. The former one entails less interference with important structures, especially muscles, than the posterior one, but permits of less efficient drainage. In these days, however, when the surgeon aims at securing healing of his wound without suppuration, this second desideratum is not of so much import- ance. In the operation in front the surgeon makes an incision three to four inches in length, starting immediately below and external to the anterior superior spinous process of the ilium, downward and inward between the Sartorius and Tensor vaginae femoris, to the neck of the bone, dividing the capsule at its upper part. A narrow-bladed saw now divides the neck of the femur, and the head of the bone is extracted with sequestrum forceps. All diseased tissue is carefully removed with a sharp spoon or scissors, and the cavity thoroughly flushed out with a hot antiseptic fluid. The posterior method consists in making an incision three or four inches long, commencing midway between the top of the great trochanter and the anterior superior spine, and ending over the shaft, just below the trochanter. The muscles are detached from the great trochanter, and the capsule opened freely, 'rhe head and neck are freed from the soft parts and the bone sawn through just below the top of the trochanter with a narrow saw. The head of the bone is then levered out of the acetabulum. In both operations, if the acetabulum is eroded, it must be freely gouged. 370 THE ARTICULATIONS. The knee-joint was formerly described as a ginglymus or hinge-joint, but is really of a much more complicated character. It must be regarded as consisting of three articulations together: one between each condyle of the femur and the corresponding tuberosity of the tibia, which are condyloid joints, and one between the patella and the femur, which is partly arthrodial, but not completely so, since the articular surfaces are not mutually adapted to each other, so that the movement is not a simple gliding one. This view of the construction of the knee-joint receives confirmation from the study of the articulation in some of the lower mammals, where three synovial membranes are sometimes found, corresponding to these three subdivisions, either entirely distinct or only connected together by small communi- cations. This view is further rendered probable by the existence of the two crucial ligaments within the joint, which must be regarded as the external and internal lateral ligaments of the inner and outer joints respectively. The existence of the ligamentum mucosum would further indicate a tendency to separation of the synovial cavity into two minor sacs, one corresponding to each joint. The bones entering into the formation of the knee-joint are the condyles of the femur above, the head of the tibia b.elow, and the patella in front. The bones are connected together by ligaments, some of which are placed on the exterior of the joint, while others occupy its interior. II. Knee-joint. External Ligaments. Anterior, or Ligamentum Pa- tellae. Posterior, or Ligamentum Pos- ticum Winslowii. Internal Lateral. Two External Lateral. Capsular. Interior Ligaments. Anterior, or External Crucial. Posterior, or Internal Crucial. Two Semilunar Fibro-cartilages. Transverse. Coronary. Ligamentum mucosum. Ligamenta alaria. The Anterior Ligament, or Ligamentum Patellae (Fig. 257), is the central portion of the common tendon of the Extensor muscles of the thigh which is continued from the patella to the tubercle of the tibia, supplying the place of an anterior ligament. It is a strong, flat, ligamentous band about three inches in length, attached, above, to the apex of the patella and the rough depression on its posterior surface ; below, to the lower part of the tubercle of the tibia, its superficial fibres being continuous over the front of the patella with those of the tendon of the Quadriceps extensor. The lateral portions of the tendon of the Extensor muscles pass down on either side of the patella, attached to the borders of this bone and its ligament, to be inserted into the upper extremity of the tibia on each side of the tubercle; externally, these portions merge into the capsular ligament. They are termed lateral patellar ligaments. The posterior surface of the ligamentum patellae can usually be easily separated from the front of the capsular ligament. The Posterior Ligament (Ligamentum Posticum Winslowii) (Fig. 258) is a broad, flat, fibrous band formed of fasciculi, obliquely directed, and separated from one another by apertures for the passage of vessels and nerves. The strongest of these fasciculi is derived from the tendon of the Semimembranosus, and passes from the back part of the inner tuberosity of the tibia obliquely upward and outward to the back part of the outer condyle of the femur. The posterior ligament forms part of the floor of the popliteal space, and the popliteal artery rests upon it. The Internal Lateral Ligament is a broad, flat, membranous band, thicker behind than in front, and situated nearer to the back than the front of the joint. It is attached, above, to the inner tuberosity of the femur; below, to the inner tuberosity and inner surface of the shaft of the tibia to the extent of about two inches. It is crossed, at its lower part, by the tendons of the Sartorius, Gracilis, and Semitendinosus muscles, a synovial bursa being interposed. Its deep surface covers the anterior portion of the tendon of the Semimembranosus, the synovial THE KNEE-JOINT. 371 membrane of the joint, and the inferior internal articular vessels and nerve; it is intimately adherent to the internal semilunar fibro-cartilage. Fig. 257.-Right knee-joint. Anterior view. Fig. 258.-Right knee-joint. Posterior view. The Long External Lateral Ligament is a strong, rounded, fibrous cord situated nearer to the back than the front of the joint. It is attached, above, to the back part of the outer tuberosity of the femur; below, to the outer part of the head of the fibula. Its outer surface is covered by the tendon of the Biceps, which divides at its insertion into two parts, separated by the ligament. The ligament has, passing beneath it, the tendon of the Popliteus muscle and the inferior external articular vessels and nerve. The Short External Lateral Ligament is an accessory bundle of fibres placed behind and parallel with the preceding, attached, above, to the lower and back part of the outer tuberosity of the femur; below, to the summit of the styloid process of the fibula. This ligament is intimately connected with the capsular ligament, and has, passing beneath it, the tendon of the Popliteus muscle and the inferior external articular vessels and nerve. The Capsular Ligament consists of an exceedingly thin but strong, fibrous membrane which fills in the intervals left between the stronger bands above described, and is inseparably connected with them. In front it blends with the lateral patellar ligaments and fills in the interval between the anterior and lateral ligaments of the joint, with which latter structures it is closely connected. Behind, it is strong, and formed chiefly of vertical fibres, which arise above from the condyles and intercondyloid notch of the femur, and is connected below with the back part of the head of the tibia, being closely united with the origins of the Gastrocnemius, Plantaris, and Popliteus muscles. It passes in front of, but is inseparably connected with, the posterior ligament. The Crucial are two interosseous ligaments of considerable strength situated O O 372 THE J R TICULA TIONS. in the interior of the joint, nearer its posterior than its anterior part. They are called crucial because they cross each other somewhat like the lines of the letter X ; and have received the names anterior and posterior, from the position of their attachment to the tibia. The Anterior, or External Crucial Liga- ment (Fig. 259), is attached to the depres- sion in front of the spine of the tibia, being blended with the anterior extremity of the external semilunar fibro-cartilage, and, pass- ing obliquely upward, backward, and out- ward, is inserted into the inner and back part of the outer condyle of the femur. Its direction is upward, backward, and outward. The Posterior, or Internal Crucial Lig- ament, is stronger, but shorter and less ob- lique in its direction, than the anterior. It is attached to the back part of the depres- sion behind the spine of the tibia, to the popliteal notch, and to the posterior extrem- ity of the external semilunar fibro-cartilage; and passes upward, forward, and inward, to be inserted into the outer and fore part of the inner condyle of the femur. As it crosses the anterior crucial ligament a fas- ciculus is given off from it, which blends with the posterior part of that ligament. It is in relation, in front, with the anterior crucial ligament; behind, with the capsular ligament. The Semilunar Fibro-cartilages (Fig. 260) are two crescentic lamellae which serve to deepen the surface of the head of the tibia, for articulation with the condyles of the femur. The circumference of each cartilage is thick, convex, and attached to the inside of the capsule of the knee ; the inner border is thin, concave and free. Their upper rurfaces are concave, and in relation with the condyles of the femur; their lower surfaces are flat, and rest upon the head of the tibia. Each car- tilage covers nearly the outer two-thirds of the correspond- ing articular surface of the tibia, leaving the inner third uncovered ; both surfaces are smooth and invested by syno- vial membrane. The Internal Semilunar Fibro-cartilage is nearly sem- icircular in form, a little elongated from before back- ward, and broader behind than in front; its anterior extremity, thin and pointed, is attached to a depression on the anterior margin of the head of the tibia, in front of the anterior crucial ligament; its posterior extremity is attached to the depression behind the spine, between the attachments of the external semilunar fibro-cartilage and the posterior crucial ligaments. Fig. 259.-Right knee-joint. Showing inter- nal ligaments. Fig. 260.-Head of tibia, with semilunar cartilages, etc. Seen from above. Right side. THE KNEE-JOINT. 373 The External Semilunar Fibro-cartilage forms nearly an entire circle, covering a larger portion of the articular surface than the internal one. It is grooved on its outer side for the tendon of the Popliteus muscle. Its extremities, at their insertion, are interposed between the two extremities of the inter- nal semilunar fibro-cartilage; the anterior extremity being attached in front of the spine of the tibia to the outer side of, and behind, the anterior crucial ligament, with which it blends; the posterior ex- tremity being attached behind the spine of the tibia, in front of the posterior extremity of the internal semilunar fibro- cartilage. Just before its in- sertion posteriorly it gives off a strong fasciculus, which passes obliquely upward and outward, to be inserted into the inner condyle of the femur, close to the attach- ment of the posterior crucial ligament. Occasionally a small fasciculus is given off which passes forward to be inserted into the back part of the anterior crucial lig- ament. The external semi- lunar fibro-cartilage gives off from its anterior convex mar- gin a fasciculus which forms the transverse ligament. Th * Transverse Ligament is a band of fibres which passes transversely from the anterior convex margin of the external semilunar fibro-cartilage to the anterior convex margin of the internal semilunar fibro-cartilage; its thickness varies considerably in different subjects, and it is sometimes absent altogether. The Coronary Ligaments are merely portions of the capsular ligament, which connect the circumference of each of the semilunar fibro-cartilages with the margin of the head of the tibia. The Synovial Membrane of the knee-joint is the largest and most extensive in the body. Commencing at the upper border of the patella, it forms a short cul-de- sac beneath the Quadriceps extensor tendon of the thigh, on the lower part of the front of the shaft of the femur : this communicates with a synovial bursa inter- posed between the tendon and the front of the femur by an orifice of variable size. On each side of the patella the synovial membrane extends beneath the aponeurosis of the Vasti muscles, and more especially beneath that of the Vastus internus. Below the patella it is separated from the anterior ligament by the anterior part of the capsule and a considerable quantity of adipose tissue. In this situation it sends off a triangular prolongation, containing a few ligamentous fibres, which extends from the anterior part of the joint below the patella to the front of the intercondyloid notch. This fold has been termed the lig amentum mucosum. It External popliteal nerve. •Popliteal artery. Fig. 261.-Longitudinal section through the middle of the right knee-joint. (After Braune.) 374 THE ARTICULATIONS. also sends off two fringe-like folds, called the ligamenta alaria, which extend from the sides of the ligamentum mucosum, upward and laterally between the patella and femur. On either side of the joint it passes downward from the femur, lining the capsule to its point of attachment to the semilunar cartilages ; it may then be traced over the upper surfaces of these cartilages to their free borders, and from thence along their under surfaces to the tibia. At the back part of the external one it forms a cul-de-sac between the groove on its surface and the tendon of the Popliteus; it surrounds the crucial ligaments and lines the inner surface of the ligaments which enclose the joints. The pouch of synovial membrane between the Extensor tendon and front of the femur is supported, during the movements of the knee, by a small muscle, the Subcrureus, which is inserted into the upper part of the capsular ligament. The folds of synovial membrane and the fatty processes contained in them act, as it seems, mainly as padding to fill up interspaces and obviate concussions. Sometimes the bursa beneath the Quadriceps extensor is completely shut off' from the rest of the synovial cavity, thus forming a closed sac between the Quadriceps and the lower part of the front of the femur, or it may communicate with the synovial cavity by a minute aperture. The bursae about the knee-joint are the following: In front there are three bursae: one is interposed between the patella and the skin; another, of small size, between the upper part of the tuberosity of the tibia and the ligamentum patellae ; and a third between the lower part of the tuberosity of the tibia and the skin. On the outer side there are four bursae : (1) one beneath the outer head of the Gastrocnemius (which sometimes communicates with the joint); (2) one above the external lateral ligament between it and the tendon of the Biceps; (3) one beneath the external lateral ligament between it and the ten- don of the Popliteus (this is sometimes only an expansion from the next bursa) ; (4) one beneath the tendon of the Popliteus between it and the condyle of the femur, which is almost always an extension from the synovial membrane. On the inner side there are five bursae : (1) one beneath the inner head of the Gastrocnemius, which sends a prolongation between the tendons of the Gastro- cnemius and Semimembranosus: this bursa often communicates with the joint; (2) one above the internal lateral ligament between it and the tendons of the Sartorius, Gracilis, and Semitendinosus; (3) one beneath the internal lateral ligament between it and the tendon of the Semimembranosus: this is sometimes only an expansion from the next bursa ; (4) one beneath the tendon of the Semi- membranosus, between it and the head of the tibia; (5) sometimes there is a bursa between the tendons of the Semimembranosus and of the Semitendinosus. Structures around the Joint.-In front and at the sides, the Quadriceps exten- sor ; on the outer side, the tendons of the Biceps and the Popliteus and the external popliteal nerve; on the inner side, the Sartorius, Gracilis, Semitendinosus,* and Semimembranosus ; behind, an expansion from the tendon of the Semimembra- nosus, the popliteal vessels, and the internal popliteal nerve, Popliteus, Plantaris, and inner and outei' heads of the Gastrocnemius, some lymphatic glands, and fat. The Arteries supplying the joint are derived from the anastomotica magna branch of the femoral, articular branches of the popliteal, anterior and posterior recurrent branches of the anterior tibial, and descending branch from the external circumflex of the Profunda. The Nerves are derived from the obturator, anterior crural, and external and internal popliteal. Actions.-The knee-joint permits of movements of flexion and extension, and, in certain positions, of slight rotation inward and outward. The movement of flexion and extension does not, however, take place in a simple, hinge-like man- ner, as in other joints, but is a complicated movement, consisting of a certain amount of gliding and rotation ; so that the same part of one articular surface is not always applied to the same part of the other articular surface, and the axis THE KNEE-JOINT. 375 of motion is not a fixed one. If the joint is examined while in a condition of extreme flexion, the posterior part of the articular surfaces of the tibia will be found to be in contact with the posterior rounded extremities of the condyles of the femur ; and if a simple hinge-like movement were to take place, the axis, round which the revolving movement of the tibia occurs, would be in the back part of the condyle. If the leg is now brought forward into a position of semiflexion, the upper surface of the tibia will be seen to glide over the condyles of the femur, so that the middle part of the articular facets are in contact, and the axis of rotation must therefore have shifted forward to nearer the centre of the condyles. If the leg is now brought into the extended position, a still further gliding takes place and a further shifting forward of the axis of rotation. This is not, however, a simple movement, but is accompanied by a certain amount of rotation outward round a vertical axis drawn through the centre of the head of the tibia. This rotation is due to the greater length of the internal condyle, and to the fact that the anterior portion of its articular surface is inclined obliquely outward. In consequence of this it will be seen that toward the close of the movement of extension-that is to say, just before complete extension is effected-the tibia glides obliquely upward and outward over this oblique surface of the inner condyle, and the leg is therefore necessarily rotated outward. In flexion of the joint the converse of these movements takes place: the tibia glides backward round the end of the femur, and at the commencement of the movement the tibia is directed downward and inward along the oblique curve of the inner condyle, thus causing an inward rotation to the leg. During flexion and extension the patella moves on the lower end of the femur, but this movement is not a simple gliding one; for if the articular surface of this bone is examined, it will be found to present on each side of the central vertical ridge two less marked transverse ridges, which divide the surface, except a small portion along the inner border, which is cut off by a slight vertical ridge into six facets (see Fig. 262), and therefore does not present a uniform curved sur- face, as would be the case if a simple gliding movement took place. These six facets-three on each side of the median vertical ridge-correspond to and denote the parts of the bone respectively in contact with the condyles of the femur during flexion, semiflexion, and extension. In flexion only the upper facets on the patella are in contact with the condyles of the femur ; the lower two-thirds of the bone rests upon the mass of fat which occupies the space between the femur and tibia. In the semiflexed position of the joint the middle facets on the patella rest upon the most prominent portion of the condyles, and thus afford greater leverage to the Quadriceps by increasing its distance from the centre of motion. In complete extension the patella is drawn up, so that only the lower facets are in contact with the articular surfaces of the condyles. The narrow strip along the inner border is an exception to this, and would appear to be in contact with the internal condyle throughout its whole extent in every position of the joint. As in the elbow, so it is in the knee-the axis of rotation in flexion and extension is not precisely at right angles to the axis of the bone, but during flexion there is a certain amount of alteration of plane; so that, wrhereas in flexion the femur and tibia are in the same plane, in extension the one bone forms an angle of about ten degrees with the other. There is, however, this difference between the two extremities: that in the upper, during extension, the humeri are parallel and the bones of the forearm diverge; in the lower, the femora converge below and the tibia are parallel. In addition to the slight rotation during flexion and extension, the tibia enjoys an independent rotation on the condyles of the femur in certain positions of the joint. This movement takes place between the interarticular fibro-cartilages and Fig. 262.-View of the posterior surface of the pa- tella, showing diagrammat- ically the areas of contact with the femur in different positions of the knee. 376 THE ARTICULATIONS. the tibia, whereas the movement of flexion and extension takes place between the interarticular fibro-cartilages and the femur. So that the knee may be said to consist of two joints, separated by the fibro-cartilages : an upper (menisco-femoral), in which flexion and extension take place; and a lower (menisco-tibial), allowing of a certain amount of rotation. This latter movement can only take place in the semiflexed position of the limb, when all the ligaments are relaxed. During flexion the ligamentum patellae is put upon the stretch, as is also the posterior crucial ligament in extreme flexion. The other ligaments are all relaxed by flexion of the joint, though the relaxation of the anterior crucial ligament is very trifling. Flexion is only checked during life by the contact of the leg with the thigh. In extension the ligamentum patellae becomes relaxed, and, in extreme extension completely so, so as to allow free lateral movement to the patella, which then rests on the front of the lower end of the femur. The other ligaments, with the exception of the posterior crucial, which is partly relaxed, are all on the stretch. When the limb has been brought into a straight line, extension is checked mainly by the tension of all the ligaments except the posterior crucial and ligamentum patellae. The movements of rotation, of which the knee is capable, are permitted in the semiflexed condition by the partial relaxation of both crucial ligaments, as well as the lateral ligaments. Rotation inward appears to be limited by the tension of the anterior crucial ligament, and by the interlocking of the two liga- ments ; but rotation outward does not appear to be checked by either crucial ligament, since they uncross during the execution of this movement, but by the lateral ligaments, especially the internal. The main function of the crucial liga- ments is to act as a direct bond of union between the tibia and femur, preventing the former bone from being carried too far backward or forward. Thus the anterior crucial ligament prevents the tibia being carried too far forward by the extensor tendons, and the posterior crucial checks too great movement backward by the flexors. They also assist the lateral ligaments in resisting any lateral bending of the joint. The interarticular cartilages are intended, as it seems, to adapt the surface of the tibia to the shape of the femur to a certain extent, so as to fill up the intervals which would otherwise be left in the varying positions of the joint, and to interrupt the jars which would be so frequently transmitted up the limb in jumping or falls on the feet; also to permit of the two varieties of motion, flexion and extension, and rotation, as explained above. The patella is a great defence to the knee-joint from any injury inflicted in front, and it distributes upon a large and tolerably even surface during kneeling the pressure which would otherwise fall upon the prominent ridges of the condyles; it also affords leverage to the Quadriceps extensor muscle to act upon the tibia; and Mr. Ward has pointed out 1 how this leverage varies in the various positions of the joint, so that the action of the muscles produces velocity at the expense of force in the commencement of extension, and, on the contrary, at the close of extension tends to diminish velocity, and therefore the shock to the ligaments; whilst in the standing position it draws the tibia powerfully forward, and thus maintains it in its place. Extension of the leg on the thigh is performed by the Quadriceps extensor ; flexion by the hamstring muscles, assisted by the Gracilis and Sartorius, and, indirectly, by the Gastrocnemius, Popliteus, and Plantaris; rotation outward, by the Biceps; and rotation inward by the Popliteus, Semitendinosus, and, to a slight extent, the Semimembranosus, the Sartorius, and the Gracilis. Surface Form.-The interval between the two bones entering into the formation of the knee-joint can always easily be felt. If the limb is extended, it is situated on a slightly higher level than the apex of the patella; but if the limb is slightly flexed, a knife carried horizontally back- ward immediately below the apex of the patella would pass directly into the joint. When the knee-joint is distended with fluid, the outline of the synovial membrane at the front of the knee may be fairly well mapped out. Surgical Anatomy.-From a consideration of the construction of the knee-joint it would at first sight appear to be one of the least secure of any of the joints in the body. It is formed 1 Human Osteology, p. 405. THE KNEE-JOINT. 377 between the two longest bones, and therefore the amount of leverage which can be brought to bear upon it is very considerable ; the articular surfaces are but ill adapted to each other, and the range and variety of motion which it enjoys is great. All these circumstances tend to render the articulation very insecure ; but, nevertheless, on account of the very powerful ligaments which bind the bones together, the joint is one of the strongest in the body, and dislocation from traumatism is of very rare occurrence. When, on the other hand, the ligaments have been softened or destroyed by disease, partial displacement is very liable to occur, and is frequently brought about by the mere action of the muscles displacing the articular surfaces from each other. The tibia may be dislocated in any direction from the femur-forward, back- ward, inward, or outward ; or a combination of two of these dislocations may occur-that is, the tibia may be dislocated forward and laterally, or backward and laterally; and any of these dis- locations may be complete or incomplete. As a rule, however, the antero-posterior dislocations are complete, the lateral ones incomplete. One or other of the semilunar cartilages may become displaced and nipped between the femur and tibia. The accident is produced by a twist of the leg when the knee is flexed, and is accompanied by a sudden pain and fixation of the knee in a flexed position. The cartilage may be displaced either inward or outward : that is to say, either inward toward the tibial spine, so that the cartilage becomes lodged in the intercondyloid notch ; or outward, so that the cartilage projects beyond the margin of the two articulating bones. Acute synovitis, the result of traumatism or exposure to cold, is very common in the knee, on account of its superficial posi- tion. When distended with fluid, the swelling shows itself above and at the sides of the patella, reaching about an inch or more above the trochlear surface of the femur, and extending a little higher under the Vastus internus than the Vastus externus. Occasionally the swelling may extend two inches or more. At the sides of the patella the swelling extends lower at the inner side than it does on the outer side. The lower level of the synovial membrane is just above the level of the upper part of the head of the fibula. In the middle line it covers the upper third of the ligamentum patellae, being separated from it, however, by the capsule and a little fat. Chronic synovitis principally shows itself in the form of pulpy degeneration of the synovial membrane, leading to tubercular arthritis. The reasons why tubercular disease of the knee usually commences in the synovial membrane appear to be the complex and extensive nature of this sac; the extensive vascular supply to it; and the fact that injuries are generally diffused and applied to the front of the joint rather than to the ends of the bones. Syphilitic disease not unfrequently attacks the knee-joint. In the hereditary form of the disease it is usually symmetrical, attacking both joints, which become filled with synovial effusion, and is very intractable and difficult of cure. In the tertiary form of the disease gummatous infiltration of the synovial membrane may take place. The knee is one of the joints most commonly affected with osteo-arthritis; and is said to be more frequently the seat of this disease in women than in men. The occurrence of the so-called loose cartilage is almost confined to the knee, though they are occasionally met with in the elbow, and, rarely, in some other joints. Many of them occur in cases of osteo-arthritis, in which calcareous or cartilaginous material is formed in one of the synovial fringes and constitutes the foreign body, and may or may not become detached, in the former case only meriting the usual term, "loose" cartilage. In other cases they have their origin in the exudation of inflammatory lymph, and possibly, in some rare instances, a portion of the articular cartilage or one of the semilunar cartilages becomes detached and constitutes the foreign body. Genu valgum, or knock-knee, is a common deformity of childhood, in which, owing to changes in and about the joint, the angle between the outer border of the tibia and femur is diminished, so that as the patient stands the two internal condyles of the femora are in contact, but the two internal malleoli of the tibiae are more or less widely separated from each other. When, however, the knees are flexed to a right angle, the two legs are practically parallel with each other. At the commencement of the disease there is a yielding of the internal lateral liga- ment and other fibrous structures on the inner side of the joint; as a result of this there is a constant undue pressure of the outer tuberosity of the tibia against the outer condyle of the femur. This extra pressure causes arrest of growth and, possibly, wasting of the outer con- dyle, and a consequent tendencj7 for the tibia to become separated from the internal condyle. To prevent this the internal condyle becomes depressed; probably, as was first pointed out by Mikulicz, by an increased growth of the lower end of the diaphysis on its inner side, so that the line of the epiphysis becomes oblique instead of transverse to the axis of the bone, with a direc- tion downward and inward. Excision of the knee-joint is most frequently required for tubercular disease of this articula- tion, but is also practised in cases of disorganization of the knee after rheumatic fever, pyaemia, etc., in osteo-arthritis, and in ankylosis. It is also occasionally called for in cases of injury, gun- shot or otherwise. The operation is best performed either by a horseshoe incision, starting from one condyle, descending as low as the tubercle of the tibia, where it crosses the leg, and is then carried upward to the other condyle; or by a transverse incision across the patella. In this latter incision the patella is either removed or sawn across, and the halves subsequently sutured together. The bones having been cleared, and in those cases where the operation is performed for tubercular disease all pulpy tissue having been carefully removed, the section of the femur is first made. This should never include, in children, more than, at the most, two-thirds of the articular surface, otherwise the epiphysis will be included, with disastrous results as far as regards the growth of the limb. Afterward a thin slice should be removed from the upper 378 THE ARTICULATIONS. end of the tibia, not more than half an inch. If any diseased tissue still appears to be left in the bones, it should be removed with the gouge rather than that a further section of the bones should be made. III. Articulations between the Tibia and Fibula. The articulations between the tibia and fibula are effected by ligaments which connect both extremities, as well as the shafts of the bones. They may, con- sequently, be subdivided into three sets: 1. The Superior Tibio-fibular articula- tion. 2. The Middle Tibio-fibular ligament or interosseous membrane. 3. The Inferior Tibio-fibular articulation. This articulation is an arthrodial joint. The contiguous surfaces of the bones present two flat, oval facets covered with cartilage, and connected together by the following ligaments: Anterior Superior Tibio-fibular. Posterior Superior Tibio-fibular. The Anterior Superior Ligament (Fig. 259) consists of two or three broad and flat bands which pass obliquely upward and inward from the front of the head of the fibula to the front of the outer tuberosity of the tibia. The Posterior Superior Ligament (Fig. 258) is a single thick and broad band which passes upward and inward from the back part of the head of the fibula to the back part of the outer tuberosity of the tibia. It is covered by the tendon of the Popliteus muscle. A Synovial Membrane lines this articulation, which at its upper and back part is occasionally continuous with that of the knee-joint. 1. Superior Tibio-fibular Articulation. 2. Middle Tibio-fibular Ligament or Interosseous Membrane. An interosseous membrane extends between the contiguous margins of the tibia and fibula, and separates the muscles on the front from those on the back of the leg. It consists of a thin, aponeurotic lamina composed of oblique fibres which pass downward and outward between the interosseous ridges on the two bones. It is broader above than below. Above its upper border is a large, oval aperture for the passage of the anterior tibial vessels forward to the anterior aspect of the leg; and at its lower part an opening for the passage of the anterior pero- neal vessels. It is continuous below with the inferior interosseous ligament, and is perforated in numerous parts for the passage of small vessels. It is in relation, in front, with the Tibialis anticus, Extensor longus digitorum, Extensor proprius hallucis, Peroneus tertius, and the anterior tibial vessels and nerve; behind, with the Tibialis posticus and Flexor longus hallucis. 3. Inferior Tibio-fibular Articulation. This articulation is formed by the rough, convex surface of the inner side of the lower end of the fibula, connected with a concave rough surface on the outer side of the tibia. Below, to the extent of about two lines, these surfaces are smooth, and covered with cartilage, which is continuous with that of the ankle- joint. The ligaments of this joint are- Anterior Inferior Tibio-fibular. Posterior Inferior Tibio-fibular. Transverse. Inferior Interosseous. The Anterior Inferior Ligament (Fig. 264) is a flat, triangular band of fibres, broader below than above, which extends obliquely downward and outward between the adjacent margins of the tibia and fibula, on the front aspect of the articulation. It is in relation, in front, with the Peroneus tertius, the aponeurosis THE ANKLE-JOINT. 379 of the leg, and the integument; behind, with the inferior interosseous ligament; and lies in contact with the cartilage covering the astragalus. The Posterior Inferior Ligament, smaller than the preceding, is disposed in a similar manner on the posterior surface of the articulation. The Transverse Ligament is a long, narrow band, continuous with the preceding, passing transversely across the back of the joint, from the external malleolus to the posterior border of the articular surface of the tibia, almost as far as its mal- leolar process. This ligament projects below the margin of the bones, and forms part of the articulating surface for the astragalus. The Inferior Interosseous Ligament consists of numerous short, strong, fibrous bands which pass between the contiguous rough surfaces of the tibia and fibula, and constitute the chief bond of union between the bones. This ligament is con- tinuous above with the interosseous membrane. The Synovial Membrane lining the articular surface is derived from that of the ankle-joint. Actions.-The movement permitted in these articulations is limited to a very slight gliding of the articular surfaces one upon another. IV. Ankle-joint. The Ankle is a ginglymus or hinge-joint. The bones entering into its forma- tion are the lower extremity of the tibia and its malleolus and the external mal- leolus of the fibula. These bones are united above, and form a mortise to receive the upper convex surface of the astragalus and its two lateral facets. The bony surfaces are covered with cartilage, and connected together by a capsule, which in places forms thickened bands constituting the following ligaments: Anterior. Posterior. Internal Lateral. External Lateral. The Anterior Tibio-tarsal Ligament (Fig. 263) is a broad, thin, membranous layer, attached, above, to the margin of the articular surface of the tibia; below, Ankle-joint Tarsal Tarso-metatarsal articulations. X Fig. 263.-Ankle-joint: tarsal and tarso-metatarsal articulations. Internal view. Right side. to the margin of the astragalus, in front of its articular surface. It is in relation, in front, with the Extensor tendons of the toes, with the tendons of the Tibialis 380 THE A R TICULA TIONS. anticus and Peroneus tertius, and the anterior tibial vessels and nerve ; behind, it lies in contact with the synovial membrane. The Posterior Tibio-tarsal Ligament is very thin, and consists principally of transverse fibres. It is attached, above, to the margin of the articular surface of the tibia, blending with the transverse tibio-fibular ligament; below, to the astragalus, behind its superior articular facet. Externally it is thicker than internally, where a somewhat thickened band of transverse fibres is attached to the hollow on the inner surface of the external malleolus. The Internal Lateral or Deltoid Ligament is a strong, flat, triangular band, attached, above, to the apex and anterior and posterior borders of the inner mal- leolus. The most anterior fibres pass forward to be inserted into the navicular bone and the inferior calcaneo-navicular ligament; the middle descend almost perpendicularly to be inserted into the sustentaculum tali of the os calcis ; and the posterior fibres pass backward and outward to be attached to the inner side of the astragalus. This ligament is covered by the tendons of the Tibialis posticus and Flexor longus digitorum muscles. . Inferior tibio-fibular articulation. /A nkle-joint. z Tarsal articulations. Tarso-metatarsal articulations. Fig. 264.-Ankle-joint: tarsal and tarso-metatarsal articulations. External view. Right side. The External Lateral Ligament (Fig. 264) consists of three distinctly special- ized fasciculi of the capsule, taking different directions and separated by distinct intervals; for which reason it is described by some anatomists as three distinct ligaments.1 The anterior fasciculus (anterior astragalo-fibular), the shortest of the three, passes from the anterior margin of the summit of the external malleolus, downward and forward, to the astragalus, in front of its external articular facet. The posterior fasciculus (posterior astragalo-fibular), the most deeply seated, passes from the depression at the inner and back part of the external malleolus to a prominent tubercle on the posterior surface of the astragalus. Its fibres are almost horizontal in direction. The middle fasciculus (calcaneo-fibular), the longest of the three, is a narrow, rounded cord passing from the apex of the external malleolus downward and slightly backward to a tubercle on the outer surface of the os calcis. It is covered by the tendons of the Peroneus longus and brevis. 1 Humphry, On the Skeletonp. 559. THE ANKLE-JOINT. 381 The Synovial Membrane invests the inner surface of the ligaments, and sends a duplicature upward between the lower extremities of the tibia and fibula for a short distance. Relations.-The tendons, vessels, and nerves in connection with the joint are, in front, from within outward, the Tibialis anticus, Extensor proprius hallucis, anterior tibial vessels, anterior tibial nerve, Extensor communis digitorum, and Peroneus tertius ; behind, from within outward, the Tibialis posticus, Flexor longus digitorum, posterior tibial vessels, posterior tibial nerve, Flexor longus hallucis; and, in the groove behind the external malleolus, the tendons of the Peroneus longus and brevis. The Arteries supplying the joint are derived from the malleolar branches of the anterior tibial and the peroneal. The Nerves are derived from the anterior and posterior tibial. Actions.-The movements of the joint are those of flexion and extension. The malleoli tightly embrace the astragalus in all positions of the joint, so that any slight degree of lateral movement which may exist is simply due to stretching of the inferior tibio-fibular ligaments and slight bending of the shaft of the fibula. Of the ligaments, the internal, or deltoid, is of very great power-so much so that it usually resists a force which fractures the process of bone to which it is attached. Its middle portion, together with the middle fasciculus of the external lateral ligament, binds the bones of the leg firmly to the foot and resists displacement in every direction. Its anterior and posterior fibres limit extension and flexion of the foot respectively, and the anterior fibres also limit abduction. The posterior portion of the external lateral ligament assists the middle portion in resisting the displacement of the foot backward, and deepens the cavity for the reception of the astragalus. The anterior fasciculus is a security against the dis- placement of the foot forward, and limits extension of the joint. The movements of abduction and adduction of the foot, together with the minute changes inform by which it is applied to the ground or takes hold of an object in climbing, etc., are mainly effected in the tarsal joints, the one which enjoys the greatest amount of motion being that between the astragalus and os calcis behind and the navicular and cuboid in front. This is often called the transverse or medio-tarsal joint, and it can, with the subordinate joints of the tarsus, replace the ankle-joint in a great measure when the latter has become ankylosed. Extension of the tarsal bones upon the tibia and fibula is produced by the Gastrocnemius, Soleus, Plantaris, Tibialis posticus, Peroneus longus and brevis, Flexor longus digitorum, and Flexor longus hallucis; flexion, by the Tibialis anti- cus, Peroneus tertius, Extensor longus digitorum, and Extensor proprius hallucis;1 adduction, in the extended position, is produced by the Tibialis anticus and posti- cus ; and abduction by the Peronei. Surface Form.-The line of the ankle-joint may be indicated by a transverse line drawn across the front of the lower part of the leg, about half an inch above the level of the tip of the internal malleolus. Surgical Anatomy.-Displacement of the trochlear surface of the astragalus from the tibio-fibular mortise is not of common occurrence, as the ankle-joint is a very strong and powerful articulation, and great force is required to produce it. Nevertheless, dislocation does occasionally occur, both in an antero-posterior and a lateral direction. In the latter, which is the most com- mon, fracture is a necessary accompaniment of the injury. The dislocation in these cases is somewhat peculiar, and is not a displacement in a horizontally lateral direction, such as usually occurs in lateral dislocations of ginglymoid joints, but the astragalus undergoes a partial rotation round an antero-posterior axis drawn through its own centre, so that the superior surface, instead of being directed upward, is inclined more or less inward or outward according to the variety of the displacement. The ankle-joint is more frequently sprained than any joint in the body, and this may lead to acute synovitis. In these cases, when the synovial sac is distended with fluid, the bulging appears principally in the front of the joint, beneath the anterior tendons, and on either side, between the Tibialis anticus and the internal lateral ligament on the inner side, and between the 1 The student must bear in mind that the Extensor longus digitorum and Extensor proprius hal- lucis are extensors of the toes, hut flexors of the ankle, and that the Flexor longus digitorum and Flexor longus hallucis are flexors of the toes, but extensors of the ankle. 382 THE ARTICULATIONS Peroneus tertius and the external lateral ligament on the outer side. In addition to this, bulging frequently occurs posteriorly, and a fluctuating swelling may be detected on either side of the tendo Achillis. Chronic synovitis may result from frequent sprains, and when once this joint has been sprained it is more liable to a recurrence of the injury than it was before ; or it may be tuber- Flexor longus digitorum..' Ext. plantar vessels.- Abductor minimi digiti.1 Flexor brevius hallucis. Fig. 265.-Section of the right foot near its inner border, dividing the tibia, astragalus, navicular, internal cuneiform, and first metatarsal bone, and the first phalanx of the great toe. (After Braune.) cular in its origin, the disease usually commencing in the astragalus and extending to the joint, though it may commence as a tubercular synovitis the result probably of some slight strain in a tubercular subject. Excision of the ankle-joint is not often performed for two reasons. Tn the first place, disease of the articulation for which this operation is indicated is frequently associated with disease of the tarsal bones, which prevents its performance; and, secondly, the foot after excision is frequently of very little use; far less, in fact, than after a Symes's amputation, which is often, therefore, a preferable operation in these cases. Excision may, however, be attempted in cases of tubercular arthritis, in a young and otherwise healthy subject, where the disease is limited to the bones forming the joint. It may also be required after injury where the vessels and nerves have not been damaged and the patient is young and free from visceral disease. The excision is best performed by two lateral incisions. One commencing two and a half inches above the external malleolus, carried down the posterior border of the fibula, round the end of the bone, and then forward and downward as far as the calcaneo-cuboid joint, midway between the tip of the external malleolus and the tuberosity on the fifth metatarsal bone. Through this incision the fibula is cleared, the external lateral ligament-is divided, and the bone sawn through at the upper end of the incision and removed. A similar curved incision is now made on the inner side of the foot, commencing two and a half inches above the lower end of the tibia, carried down the posterior border of the bone, round the internal malleolus, and forward and downward to the tuberosity of the navicular bone. Through this incision the tibia is cleared in front and behind, the internal lateral, the anterior and posterior ligaments divided, and the end of the tibia protruded through the wound by displacing the foot outward, and sawn off sufficiently high to secure a healthy section of bone. The articular surface of the astragalus is now to be sawn off or the whole bone removed. In cases where the operation is performed for tubercular arthritis the latter course is probably preferable, as the injury done by the saw is frequently the starting point of fresh caries; and after removal of the whole bone the shortening is not appreci- ably increased, and the result as regards union appears to be as good as when two sawn surfaces of bone are brought into apposition. VArticulations of the Tarsus. 1. Articulations of the Os Calcis and Astragalus The articulations between the os calcis and astragalus are two in number- anterior and posterior. They are arthrodial joints. The bones are connected together by four ligaments: External Calcaneo-astragaloid. Internal Calcaneo-astragaloid. Posterior Calcaneo-astragaloid. Interosseous. OF THE TARSUS. 383 The External Calcaneo-astragaloid Ligament (Fig. 264) is a short, strong, fasciculus passing from the outer surface of the astragalus, immediately beneath its external malleolar facet, to the outer surface of the os calcis. It is placed in front of the middle fasciculus of the external lateral ligament of the ankle-joint, with the fibres of which it is parallel. The Internal Calcaneo-astragaloid Ligament is a band of fibres connecting the internal tubercle of the back of the astragalus with the back of the sustentaculum tali. Its fibres blend with those of the inferior calcaneo-navicular ligament. The Posterior Calcaneo-astragaloid Ligament (Fig. 263) connects the posterior external tubercle of the astragalus with the upper and inner part of the os calcis; it is a short, narrow band, the fibres of which radiate from their narrow attach- ment to the astragalus. The Interosseous Ligament forms the chief bond of union between the bones. It consists of numerous vertical and oblique fibres attached by one extremity to the groove between the articulating facets on the under surface of the astragalus; by the other to a corresponding depression on the upper surface of the os calcis. It is very thick and strong, being at least an inch in breadth from side to side, and serves to unite the os calcis and astragalus solidly together. The Synovial Membranes (Fig. 267) are two in number: one for the posterior calcaneo-astragaloid articulation; a second for the anterior calcaneo-astragaloid joint. The latter synovial membrane is continued forward between the contiguous surfaces of the astragalus and navicular bones. Actions.-The movements permitted between the astragalus and os calcis are limited to a gliding of the one bone on the other in a direction from before back- ward, and from side to side. 2. Articulations of the Os Calcis with the Cuboid. The ligaments connecting the os calcis with the cuboid are four in number: Dorsal Superior Calcaneo-cuboid. Internal Calcaneo-cuboid (Interosseous). p, Long Calcaneo-cuboid. Short Calcaneo-cuboid. The Superior Calcaneo-cuboid Ligament (Fig. 264) is a thin and narrow fasciculus which passes between the contiguous surfaces of the os calcis and cuboid on the dorsal surface of the joint. The Internal Calcaneo-cuboid (Interosseous) Ligament (Fig. 264) is a short but thick and strong band of fibres arising from the os calcis, in the deep hollow which intervenes between it and the astragalus, and closely blended, at its origin, with the superior calcaneo-navicular ligament. It is inserted into the inner side of the cuboid bone. This ligament forms one of the chief bonds of union between the first and second rows of the tarsus. The Long Calcaneo-cuboid (Long Plantar) Ligament (Fig. 266), the more super- ficial of the two plantar ligaments, is the longest of all the ligaments of the tarsus : it is attached to the under surface of the os calcis, from near the tuberosities, as far forward as the anterior tubercle; its fibres pass forward to be attached to the ridge on the under surface of the cuboid bone, the more superficial fibres being continued onward to the bases of the second, third, and fourth metatarsal bones. This ligament crosses the groove on the under surface of the cuboid bone, convert- ing it into a canal for the passage of the tendon of the Peroneus longus. The Short Calcaneo-cuboid (Short Plantar) Ligament lies nearer to the bones than the preceding, from which it is separated by a little adipose tissue. It is exceedingly broad, about an inch in length, and extends from the tubercle and the depression in front of it, on the fore part of the under surface of the os calcis, to the inferior surface of the cuboid bone behind the peroneal groove. 384 77/Z-; ARTICULATIONS Synovial Membrane.-The synovial membrane in this joint is distinct. It lines the inner surface of the ligaments. Actions.-The movements permitted between the os calcis and cuboid are limited to a slight gliding upon each other. 3. The Ligaments connecting the Os Calcis and Navicular. Though these two bones do not directly articulate, they are connected together by two ligaments : Superior or External Calcaneo-navicular. Inferior or Internal Calcaneo-navicular. The Superior or External Calcaneo-navicular (Fig. 264) arises, as already mentioned, with the internal calcaneo-cuboid in the deep hollow between the astragalus and os calcis; it passes forward from the inner side of the anterior ex- tremity of the os calcis to the outer side of the navicular bone. These two liga- ments resemble the letter Y, being blended together behind, but separated in front. The Inferior or Internal Calcaneo-navicular (Fig. 266) is by far the larger and stronger of the two ligaments between these bones; it is a broad and thick band of fibres, which passes forward and inward from the anterior margin of the sustentaculum tali of the os calcis to the under surface of the navicular bone. This ligament not only serves to connect the os calcis and navicular, but supports the head of the astragalus, form- ing part of the articular cavity in which it is received. The upper surface presents a fibro- cartilaginous facet, lined by the synovial membrane continued from the anterior cal- caneo-astragaloid articulation, upon which the head of the astragalus rests. Its under surface is in contact with the tendon of the Tibialis posticus muscle ; 1 its inner border is blended with the fore part of the Deltoid ligament, thus completing the socket for the head of the astragalus. Surgical Anatomy.-The inferior calcaneo-nav- icular ligament, by supporting the head of the astrag- alus, is principally concerned in maintaining the arch of the foot, and when it yields the head of the astragalus is pressed downward, inward, and for- ward by the weight of the body, and the foot becomes flattened, expanded, and turned outward, constituting the disease known as flat-foot. This ligament con- tains a considerable amount of elastic fibre, so as to give elasticity to the arch and spring to the foot; hence it is sometimes called the "spring" ligament. It is supported, on its under surface, by the tendon of the Tibialis posticus, which spreads out at its insertion into a number of fasciculi which are attached to most of the tarsal and metatarsal bones; this pre- vents undue stretching of the ligament and is a pro- tection against the occurrence of flat-foot. Fig. 266.-Ligaments of the plantar surface of the foot. 4. Articulation of the Astragalus with the Navicular Bone The articulation between the astragalus and navicular is an arthrodial joint: the rounded head of the astragalus being received into the concavity formed by 1 Mr. Hancock describes an extension of this ligament upward on the inner side of the foot, which completes the socket of the joint in that direction {Lancet, 1866, vol. i. p. 618). OF THE TARSUS. 385 the posterior surface of the navicular, the anterior articulating surface of the calcaneum, and the upper surface of the inferior calcaneo-navicular ligament, which fills up the triangular interval between those bones. The only ligament of this joint is the superior astragalo-navicular. It is a broad band, which passes obliquely forward from the neck of the astragalus to the superior surface of the navicular bone. It is thin, and weak in texture, and covered by the Extensor ten- dons. The inferior calcaneo-navicular supplies the place of an inferior ligament. The Synovial Membrane which lines the joint is continued forward from the anterior calcaneo-astragaloid articulation. Actions.-This articulation permits of considerable mobility, but its feebleness is such as to allow' occasionally of dislocation of the other bones of the tarsus from the astragalus. The transverse tarsal or medio-tarsal joint is formed by the articulation of the os calcis with the cuboid, and by the articulation of the astragalus with the nav- icular. The movement which takes place in this joint is more extensive than that in the other tarsal joints, and consists of a sort of rotation by means of which the sole of the foot may be slightly flexed and extended or carried inward and outward. 5. The Articulation of the Navicular with the Cuneiform Bones. The navicular is connected to the three cuneiform bones by Dorsal and Plantar ligaments. The Dorsal Ligaments are small, longitudinal bands of fibrous tissue arranged as three bundles, one to each of the cuneiform bones. That bundle of fibres which connects the navicular with the internal cuneiform is continued round the inner side of the articulation to be continuous with the plantar ligament which connects these two bones. The Plantar Ligaments have a similar arrangement to those on the dorsum. They are strengthened by processes given off from the tendon of the Tibialis posticus. Actions.-The movements permitted between the navicular and cuneiform bones are limited to a slight gliding upon each other. The Synovial Membrane of these joints is part of the great tarsal synovial membrane. 6. The Articulation of the Navicular with the Cuboid. The navicular bone is connected w ith the cuboid by Dorsal, Plantar, and Interosseous ligaments. The Dorsal Ligament consists of a band of fibrous tissue which passes obliquely forward and outward from the navicular to the cuboid bone. The Plantar Ligament consists of a band of fibrous tissue which passes nearly transversely between these two bones. The Interosseous Ligament consists of strong transverse fibres which pass between the rough non-articular portions of the lateral surfaces of these two bones. Actions.-The movements permitted between the navicular and cuboid bones are limited to a slight gliding upon each other. The Synovial Membrane of this joint is part of the great tarsal synovial membrane. 7. The Articulation of the Cuneiform Bones with each other. These bones are connected together by Dorsal, Plantar, and Interosseous ligaments. The Dorsal Ligaments consist of two bands of fibrous tissue which pass trans- versely, one connecting the internal with the middle cuneiform, and the other connecting the middle with the external cuneiform. The Plantar Ligaments have a similar arrangement to those on the dorsum. 386 7V7A ARTICULATIONS. They are strengthened by the processes given off from the tendon of the Tibialis posticus. The Interosseous Ligaments consist of strong transverse fibres which pass between the rough non-articular portions of the lateral surfaces of the adjacent cuneiform bones. The Synovial Membrane of these joints is part of the great tarsal synovial membrane. Actions.-The movements permitted between the cuneiform bones are limited to a slight gliding upon each other. 8. The Articulation of the External Cuneiform Bone with the Cuboid. These bones are connected together by The Dorsal Ligament consists of a band of fibrous tissue which passes trans- versely between these two bones. The Plantar Ligament has a similar arrangement. It is strengthened by a process given off from the tendon of the Tibialis posticus. The Interosseous Ligament consists of strong transverse fibres which pass between the rough non-articular portions of the lateral surfaces of the adjacent sides of these two bones. The Synovial Membrane of this joint is part of the great tarsal synovial membrane. Actions.-The movements permitted between the external cuneiform and cuboid are limited to a slight gliding upon each other. Nerve-supply.-All the joints of the tarsus are supplied by the anterior tibial nerve. Dorsal, Plantar, and Interosseous ligaments. Surgical Anatomy.-In spite of the great strength of the ligaments which connect the tarsal bones together, dislocation at some of the tarsal joints does occasionally occur; though, on account of the spongy character of the bones, they are more frequently broken than dislocated, as the result of violence. When dislocation does occur, it is most commonly in connection with the astragalus; for not only may this bone be dislocated from the tibia and fibula at the ankle- joint, but the other bones may be dislocated from it, the trochlear surface of the bone remaining in situ in the tibio-fibular mortise. This constitutes what is known as the subastragaloid dislocation. Or, again, the astragalus may be dislocated from all its connections-from the tibia and fibula above, the os calcis below, and the navicular in front-and may even undergo a rotation, either on a vertical or horizontal axis. In the former case the long axis of the bone becoming directed across the joint, so that the head faces the articular surface on one or other malleolus; or, in the latter, the lateral surfaces becoming directed upward and down- ward, so that the trochlear surface faces to one or the other side. Finally, dislocation may occur at the medio-tarsal joint, the anterior tarsal bones being luxated from the astragalus and calcaneum. The other tarsal bones are also, occasionally, though rarely, dislocated from their connections. VI. Tarso-metatarsal Articulations. These are arthrodial joints. The bones entering into their formation are four tarsal bones-viz. the internal, middle, and external cuneiform and the cuboid- which articulate with the metatarsal bones of the five toes. The metatarsal bone of the great toe articulates with the internal cuneiform ; that of the second is deeply wedged in between the internal and external cuneiform, resting against the middle cuneiform, and being the most strongly articulated of all the metatarsal bones; the third metatarsal articulates with the extremity of the external cunei- form ; the fourth with the cuboid and external cuneiform ; and the fifth, with the cuboid. The articular surfaces are covered with cartilage, lined by synovial membrane, and connected together by the following ligaments: Dorsal. Plantar. Interosseous. The Dorsal Ligaments consist of strong, flat, fibrous bands, which connect the tarsal with the metatarsal bones. The first metatarsal is connected to the internal cuneiform by a single broad, thin, fibrous band; the second has three dorsal TA RSO-META TA RS A L AR TICULA TIONS. 387 ligaments, one from each cuneiform bone; the third has one from the external cuneiform; the fourth has two, one from the external cuneiform and one from the cuboid; and the fifth, one from the cuboid. The Plantar Ligaments consist of longitudinal and oblique fibrous bands connecting the tarsal and metatarsal bones, but disposed with less regularity than on the dorsal surface. Those for the first and second metatarsal are the most strongly marked; the second and third metatarsal receive strong fibrous bands which pass obliquely across from the internal cuneiform ; the plantar ligaments of the fourth and fifth metatarsal consist of a few scanty fibres derived from the cuboid. The Interosseous Ligaments are three in number-internal, middle, and external. The internal one passes from the outer extremity of the internal cuneiform to the adjacent angle of the second metatarsal. The middle one, less strong than the preceding, connects the external cuneiform with the adjacent angle of the second metatarsal. The external interosseous ligament connects the outer angle of the external cuneiform with the adjacent side of the third metatarsal. The Synovial Membrane between the internal cuneiform bone and the first metatarsal bone is a distinct sac. The synovial membrane between the middle and external cuneiform behind, and the second and third metatarsal bones in front, is part of the great tarsal synovial membrane. Two prolongations are sent forward from it-one between the adjacent sides of the second and third metatarsal bones, and one between the third and fourth metatarsal bones. The synovial membrane between the cuboid and the fourth and fifth metatarsal bones is a distinct sac. From it a prolongation is sent forward between the fourth and fifth metatarsal bones. Actions.-The movements permitted between the tarsal and metatarsal bones are limited to a slight gliding upon each other. The base of the first metatarsal bone is not connected with the second meta- tarsal bone by any ligaments; in this respect it resembles the thumb. The bases of the four outer metatarsal bones are connected together by dorsal, plantar, and interosseous ligaments. The Dorsal Ligaments consist of bands of fibrous tissue which pass transversely between the adjacent metatarsal bones. The Plantar Ligaments have a similar arrangement to those on the dorsum. The Interosseous Ligaments consist of strong transverse fibres which pass between the rough non-articular portions of the lateral surfaces. The Synovial Membrane between the second and third and the third and fourth metatarsal bones is part of the great tarsal synovial membrane. The synovial membrane between the fourth and fifth metatarsal bones is a prolongation of the synovial membrane of the cubo-metatarsal joint. Actions.-The movement permitted in the tarsal ends of the metatarsal bones is limited to a slight gliding of the articular surfaces upon one another. Articulations of the Metatarsal Bones with each other. The Synovial Membranes (Fig. 267) found in the articulations of the tarsus and metatarsus are six in number: one for the posterior calcaneo-astragaloid articulation ; a second for the anterior calcaneo-astragaloid and astragalo-navicular articulations; a third for the calcaneo-cuboid articulation ; and a fourth for the articulations of the navicular with the three cuneiform, the three cuneiform with each other, the external cuneiform with the cuboid, and the middle and external cuneiform with the bases of the second and third metatarsal bones, and the lateral surfaces of the second, third, and fourth metatarsal bones with each other ; a fifth for the internal cuneiform with the metatarsal bone of the great toe; and a sixth for the articulation of the cuboid with the fourth and fifth metatarsal bones. A The Synovial Membranes in the Tarsal and Metatarsal Joints. 388 THE ARTICULATIONS small synovial membrane is sometimes found between the contiguous surfaces of the navicular and cuboid bones. Nerve-supply.-The nerves supplying the tarso-metatarsal joints are derived from the anterior tibial. The digital extremities of all the metatarsal bones are connected together by the transverse metatarsal ligament. The Transverse Metatarsal Ligament is a narrow fibrous band which passes transversely across the anterior extremities of all the metatarsal bones, connecting Fig. 267.-Oblique section of the articulations of the tarsus and metatarsus. Showing the six synovial membranes. them together. It is blended anteriorly with the plantar (glenoid) ligament of the metatarso-phalangeal articulations. To its posterior border is connected the fascia covering the Interossei muscles. Its superficial surface is concave where the Flexor tendons pass over it. Beneath it the tendons of the Interossei muscles pass to their insertion. It differs from the transverse metacarpal ligament in that it connects the metatarsal bone of the great toe with the rest of the metatarsal bones. The metatarsophalangeal articulations are of the condyloid kind, formed by the reception of the rounded head of the metatarsal bone into a superficial cavity in the extremity of the first phalanx. The ligaments are- Plantar. Two Lateral. The Plantar Ligaments (Glenoid ligaments of Cruveilhier) are thick, dense, fibrous structures. Each is placed on the plantar surface of the joint in the interval between the lateral ligaments, to which they are connected; they are loosely united to the metatarsal bone, but very firmly to the base of the first phalanges. Their plantar surface is intimately blended with the transverse meta- tarsal ligament, and presents a groove for the passage of the Flexor tendons, the sheath surrounding which is connected to each side of the groove. By their deep surface they form part of the articular surface for the head of the metatarsal bone, and are lined by a synovial membrane. The Lateral Ligaments are strong, rounded cords, placed one on each side of the joint, each being attached, by one extremity, to the posterior tubercle on the side of the head of the metatarsal bone ; and, by the other, to the contiguous extremity of the phalanx. The Posterior Ligament is supplied by the extensor tendon placed over the back of the joint. Actions.-The movements permitted in the metatarso-phalangeal articulations are flexion, extension, abduction, and adduction. VII. Metatarso-phalangeal Articulations. OF THE PHALANGES. 389 The articulations of the phalanges are ginglymus joints. The ligaments are- Plantar. Two Lateral. The arrangement of these ligaments is similar to those in the metatarso- phalangeal articulations ; the extensor tendon supplies the place of a posterior ligament. Actions.-The only movements permitted in the phalangeal joints are flexion and extension; these movements are more extensive between the first and second phalanges than between the second and third. The movement of flexion is very considerable, but extension is limited by the anterior and lateral ligaments. VIII. Articulations of the Phalanges. Surface Form.-The principal joints which it is necessary to distinguish, with regard to the surgery of the foot, are the medio-tarsal and the tarso metatarsal joints. The joint between the astragalus and the navicular is best found by means of the tubercle of the navicular bone, for the line of the joint is immediately behind this process. If the foot is grasped and forcibly extended, a rounded prominence, the head of the astragalus, will appear on the inner side of the dorsum in front of the ankle-joint, and if a knife is carried downward, just in front of this prominence and behind the line of the navicular tubercle, it will enter the astragalo-navicular joint. The calcaneo-cuboid joint is situated midway between the external malleolus and the prominent end of the fifth metatarsal bone. The plane of the joint is in the same line as that of the astragalo-navicular. The position of the joint between the fifth metatarsal bone and the cuboid is easily found by the projection of the fifth metatarsal bone, which is the guide to it. The direction of the line of the joint is very oblique, so that, if continued onward, it would pass through the head of the first metatarsal bone. The joint between the fourth metatarsal bone and the cuboid and external cuneiform is the direct continuation inward of the previous joint, but its plane is less oblique ; it would be represented by a line drawn from the outer side of the articulation to the middle of the first metatarsal bone. The plane of the joint between the third metatarsal bone and the external cuneiform is almost transverse. It would be repre- sented by a line drawn from the outer side of the joint to the base of the first metatarsal bone. The tarso-metatarsal articulation of the great toe corresponds to a groove which can be felt by making firm pressure on the inner side of the foot one inch in front of the tubercle on the navicular bone; and the joint between the second metatarsal bone and the middle cuneiform is to be found on the dorsum of the foot, half an inch behind the level of the tarso-metatarsal joint of the great toe. The line of the joints between the metatarsal bones and the first phalanges is about an inch behind the webs of the corresponding toes. THE MUSCLES AND FASCLE.1 THE Muscles are connected with the bones, cartilages, ligaments, and skin, either directly or through the intervention of fibrous structures called tendons or aponeuroses. Where a muscle is attached to bone or cartilage, the fibres ter- minate in blunt extremities upon the periosteum or perichondrium, and do not come into direct relation with the osseous or cartilaginous tissue. Where muscles are connected with the skin, they either lie as a flattened layer beneath it, or are connected with its areolar tissue by larger or smaller bundles of fibres, as in the muscles of the face. The muscles vary extremely in their form. In the limbs, they are of consid- erable length, especially the more superficial ones, the deep ones being generally broad ; they surround the bones and form an important protection to the various joints. In the trunk they are broad, flattened, and expanded, forming the parietes of the cavities which they enclose; hence the reason of the terms, long, broad, short, etc., used in the description of a muscle. There is a considerable variation in the arrangement of the fibres of certain muscles with reference to the tendons to which they are attached. In some, the fibres are parallel and run directly from their origin to their insertion; these are quadrilateral muscles, such as the Thyro-hyoid. A modification of these is found in the fusiform muscles, in which the fibres are not quite parallel, but slightly curved, so that the muscle tapers at each end; in their action, however, they resemble the quadrilateral muscles. Secondly, in other muscles the fibres are convergent; arising by a broad origin, they converge to a narrow or pointed insertion. This arrangement of fibres is found in the triangular muscles-e. g. the Temporal. In some muscles, which otherwise wrould belong to the quadrilateral or triangular type, the origin and insertion are not in the same plane, but the plane of the line of origin intersects that of their insertion ; such is the case in the Pectineus muscle. Thirdly, in some muscles the fibres are oblique and converge, like the plumes of a pen, to one side of a tendon, which runs the entire length of the muscle. Such a muscle is rhomboidal or penniform, as the Peronei. A modification of these rhomboidal muscles is found in those cases where oblique fibres converge to both sides of a central tendon which runs down the middle of the muscle ; these are called bipenniform, and an example is afforded in the Rectus femoris. Finally, we have muscles in which the fibres are arranged in curved bundles in one or more planes, as in the Sphincter muscles. The arrangement of the muscular fibres is of considerable importance in respect to their relative strength and range of movement. Those muscles where the fibres are long and few in number have great range, but diminished strength; where, on the other hand, the fibres are short and more numerous, there is great power, but lessened range. Muscles differ much in size: the Gastrocnemius forms the chief bulk of the back of the leg, and the fibres of the Sartorius are nearly two feet in length, whilst 1 The Muscles and Fasciae are described conjointly, in order that the student may consider the arrangement of the latter in his dissection of the former. It is rare for the student of anatomy in this country to have the opportunity of dissecting the fasciae separately; and it is for this reason, as well as from the close connection that exists between the muscles and their investing sheaths, that they are considered together. Some general observations are first made on the anatomy of the muscles and fasciae, the special description being given in connection with the different regions. 390 GENERAL ANATOMY. 391 the Stapedius, a small muscle of the internal ear, weighs about a grain, and its fibres are not more than two lines in length. The names applied to the various muscles have been derived-1, from their situation, as the Tibialis, Radialis, Ulnaris, Peroneus; 2, from their direction, as the Rectus abdominis, Obliqui capitis, Transversalis; 3, from their uses, as Flexors, Extensors, Abductors, etc.; 4, from their shape, as the Deltoid, Trapezius, Rhom- boideus; 5, from the number of their divisions, as the Biceps, the Triceps ; 6, from their points of attachment, as the Sterno-cleido-mastoid, Sterno-hyoid, Stern o-thyroid. In the description of a muscle the term origin is meant to imply its more fixed or central attachment, and the term insertion, the movable point to which the force of the muscle is directed; but the origin is absolutely fixed in only a very small number of muscles, such as those of the face, which are attached by one extremity to the bone and by the other to the movable integument; in the greater number the muscle can be made to act from either extremity. In the dissection of the muscles the student should pay especial attention to the exact origin, insertion, and actions of each, and its more important relations with surrounding parts. An accurate knowledge of the points of attachment of the muscles is of great importance in the determination of their action. By a knowledge of the action of the muscles the surgeon is able to explain the causes of displacement in various forms of fracture and the causes which produce distortion in various deformities, and, consequently, to adopt appropriate treat- ment in each case. The relations, also, of some of the muscles, especially those in immediate apposition with the larger blood-vessels, and the surface-markings they produce, should be especially remembered, as they form useful guides in the application of a ligature to those vessels. Tendons are white, glistening, fibrous cords, varying in length and thickness, sometimes round, sometimes flattened, of considerable strength, and devoid of elasticity. They consist almost entirely of white fibrous tissue, the fibrils of which have an undulating course parallel with each other and are firmly united together. They are very sparingly supplied with blood-vessels, the smaller tendons presenting in their interior not a trace of them. Nerves also are not present in the smaller tendons, but the larger ones, as the tendo Achillis, receive nerves which accompany the nutrient vessels. The tendons consist principally of a substance which yields gelatin. Aponeuroses are flattened or ribbon-shaped tendons, of a pearly-white color, iridescent, glistening, and similar in structure to the tendons. They are destitute of nerves, and the thicker ones only sparingly supplied with blood-vessels. The tendons and aponeuroses are connected, on the one hand, with the muscles, and, on the other hand, with the movable structures, as the bones, cartilages, ligaments, fibrous membranes (for instance, the sclerotic), and the synovial mem- branes (subcrureus). Where the muscular fibres are in a direct line with those of the tendon or aponeurosis, the two are directly continuous, the muscular fibre being distinguishable from that of the tendon only by its striation. But where the muscular fibre joins the tendon or aponeurosis at an oblique angle the former terminates, according to Kolliker, in rounded extremities, which are received into corresponding depressions on the surface of the latter, the connective tissue between the fibres being continuous with that of the tendon. The latter mode of attachment occurs in all the penniform and bipenniform muscles, and in Sthose muscles the tendons of which commence in a membranous form, as the Gastrocnemius and Soleus. 'The fasciae (fascia, a bandage) are fibro-areolar or aponeurotic laminae of variable thickness and strength, found in all regions of the body, investing the softer and more delicate organs. The fasciae have been subdivided, from the situation in which they are found, into two groups, superficial and deep. The superficial fascia is found immediately beneath the integument over almost the entire surface of the body. It connects the skin with the deep or aponeurotic 392 THE MUSCLES AND FASCIAE. fascia, and consists of fibro-areolar tissue, containing in its meshes pellicles of fat in varying quantity. In the eyelids and scrotum, where adipose tissue is rarely deposited, this tissue is very liable to serous infiltration. The superficial fascia varies in thickness in different parts of the body: in the groin it is so thick as to be capable of being subdivided in several laminae, but in the palm of the hand it is of extreme thinness and intimately adherent to the integument. The superficial fascia is capable of separation into two or more layers, between which are found the superficial vessels and nerves, as the superficial epigastric vessels in the abdominal region, the radial and ulnar veins in the forearm, the saphenous veins in the leg and thigh, and the superficial lymphatic glands ; certain cutaneous muscles also are situated in the superficial fascia, as the Platysma myoides in the neck, and the Orbicularis palpebrarum around 'the eyelids. This fascia is most distinct at the lower part of the abdomen, the scrotum, perinaeum, and extremities; is very thin in those regions where muscular fibres are inserted into the integument, as on the side of the neck, the face, and around the margin of the anus. It is very dense in the scalp, in the palms of the hands, and soles of the feet, forming a fibro-fatty layer which binds the integument firmly to the subjacent structure. The superficial fascia connects the skin to the subjacent parts, facilitates the movement of the skin, serves as a soft nidus for the passage of vessels and nerves to the integument, and retains the warmth of the body, since the fat contained in its areolae is a bad conductor of caloric. The deep fascia is a dense, inelastic, unyielding fibrous membrane, forming sheaths for the muscles and affording them broad surfaces for attachment. It consists of shining tendinous fibres, placed parallel with one another, and connected together by other fibres disposed in a rectilinear manner. It is usually exposed on the removal of the superficial fascia, forming a strong investment, which not only binds down collectively the muscles in each region, but gives a separate sheath to each, as well as to the vessels and nerves. The fasciae are thick in unprotected situations, as on the outer side of a limb, and thinner on the inner side. The deep fasciae assist the muscles in their action by the degree of tension and pressure they make upon their surface; and in certain situations this is increased and regulated by muscular action; as, for instance, by the Tensor vaginae femoris and Gluteus maximus in the thigh, by the Biceps in the upper and lower extremities, and Palmaris longus in the hand. In the limbs the fasciae not only invest the entire limb, but give off septa which separate the various muscles, and are attached beneath to the periosteum: these prolongations of fasciae are usually spoken of as intermuscular septa. The Muscles and Fasciae may be arranged, according to the general division of the body, into those of the cranium, face, and neck ; those of the trunk ; those of the upper extremity; and those of the lower extremity. MUSCLES AND FASCLE OF THE CRANIUM AND FACE. The muscles of the Cranium and Face consist of ten groups, arranged according to the region in which they are situated: 1. Cranial Region. 2. Auricular Region. 3. Palpebral Region. 4. Orbital Region. 5. Nasal Region. 6. Superior Maxillary Region. 7. Inferior Maxillary Region. 8. Intermaxillary Region. 9. Temporo-maxillary Region. 10. Pterygo-maxillary Region. The muscles contained in each of these groups are the following: 1. Cranial Region. Occipitofrontalis. 2. Auricular Region. Attollens aurem. Attrahens aurem. Retrahens aurem. CRANIAL REGION. 393 3. Palpebral Region. Orbicularis palpebrarum. Corrugator supercilii. Tensor tarsi. 4. Orbital Region. Levator palpebrae. Rectus superior. Rectus inferior. Rectus internus. Rectus externus. Obliquus superior. Obliquus inferior. 5. Nasal Region. Pyramidalis nasi. Levator labii superioris alaeque nasi. Dilatator naris posterior. Dilatator naris anterior. Compressor nasi. Compressor narium minor. Depressor alae nasi. 6. Superior Maxillary Region. Levator labii superioris. Levator anguli oris. Zygomaticus major. Zygomaticus minor. 7. Inferior Maxillary Region. Levator labii inferioris. Depressor labii inferioris. Depressor anguli oris. 8. Intermaxillary Region. Buccinator. Risorius. Orbicularis oris. 9. Temporo-maxillary Region. Masseter. Temporal. 10. Pterygo-maxillary Region. Pterygoideus externus. Pterygoideus internus. Dissection (Fig. 268).-The head being shaved, and a block placed beneath the back of the neck, make a vertical incision through the skin from before backward, commencing at the root of the nose in front, and terminating behind at the occipital protuberance; make 1. Cranial Region-Occipito-frontalis. 1. Dissection of scalp. 2, 3, of auricular region. 4, 5, 6, of face. 7, 8, of neck. Fig. 268.-Dissection of the head, face, and neck. a second incision in a horizontal direction along the forehead and round the side of the head, from the anterior to the posterior extremity of the preceding. Raise the skin in front, from the subjacent muscle, from below upward; this must be done with extreme care, removing the integument from the outer surface of the vessels and the nerves which lie between the two. The Skin of the Scalp.-This is thicker than in any other part of the body. It is intimately adherent to the superficial fascia. The hair-follicles are very closely 394 THE MUSCLES AND FASCEE. set together, and extend throughout the whole thickness of the skin. It also con- tains a number of sebaceous glands. The superficial fascia in the cranial region is a firm, dense, fibro-fattv layer, intimately adherent to the integument, and to the Occipito-frontalis and its tendi- CORRUQATOR SUPERCILII- DILATATOR NARIS ANTERIOR. DILATATOR NARIS POSTERIOR. COMPRESSOR NARIUM MINOR DEPRESSOR ALXE NASI. LEVATOR MENTI.' nous aponeurosis; it is continuous, behind, with the superficial fascia at the back part of the neck; and, laterally, is continued over the temporal fascia. It con- tains between its layers the superficial vessels and nerves and much granular fat. The Occipito-frontalis (Fig. 269) is a broad musculo-fibrous layer, which covers the whole of one side of the vertex of the skull, from the occiput to the eyebrow. It consists of two muscular slips, separated by an intervening tendinous aponeurosis. The occipital portion, thin, quadrilateral in form, and about an inch and a half in length, arises from the outer two-thirds of the superior curved line of the occipital bone, and from the mastoid portion of the temporal. Its fibres of origin are tendinous, but they soon become muscular, and ascend in a parallel direction to Fig. 269.-Muscles of the head, face, and neck. THE AURICULAR REGION. 395 terminate in a tendinous aponeurosis. The frontal portion is thin, of a quadri- lateral form, and intimately adherent to the superficial fascia. It is broader, its fibres are longer, and their structure paler than the occipital portion. Its internal fibres are continuous with those of the Pyramidalis nasi. Its middle fibres become blended with the Corrugator supercilii and Orbicularis palpebrarum; and the outer fibres are also blended with the latter muscle over the external angular pro- cess. According to Theile, the innermost fibres are attached to the nasal bones, the outer to the external angular process of the frontal bone. From these attachments the fibres are directed upward, and join the aponeurosis below the coronal suture. The inner margins of the frontal portions of the two muscles are joined together for some distance above the root of the nose ; but between the occipital portions there is a considerable, though variable, interval, which is occupied by the aponeurosis. The aponeurosis covers the upper part of the vertex of the skull, being continuous across the middle line with the aponeurosis of the opposite muscle. Behind, it is attached, in the interval between the occipital origins, to the occipital protuberance and superior curved lines above the attachment of the Trapezius ; in front, it forms a short and narrow prolongation between the frontal portions; and on each side it has connected with it the Attollens and Attrahens aurem muscles ; in this situation it loses its aponeurotic character, and is continued over the temporal fascia to the zygoma as a layer of laminated areolar tissue. This aponeurosis is closely connected to the integument by the firm, dense, fibro- fatty layer, which forms the superficial fascia ; it is connected with the pericranium by loose cellular tissue, which allows of a considerable degree of movement of the integument. Nerves.-The frontal portion of the Occipito-frontalis is supplied by the facial nerve; its occipital portion by the posterior auricular branch of the facial, and sometimes by the occipitalis minor. Actions.-The frontal portion of the muscle raises the eyebrows and the skin over the root of the nose, and at the same time draws the scalp forward, throwing the integument of the forehead into transverse wrinkles. The posterior portion draws the scalp backward. By bringing alternately into action the frontal and occipital portions the entire scalp may be moved forward and backward. In the ordinary action of the muscles, the eyebrows are elevated, and at the same time the aponeurosis is fixed by the posterior portion, thus giving to the face the expression of surprise: if the action is more exaggerated, the eyebrows are still further raised, and the skin of the forehead thrown into transverse wrinkles, as in the expression of fright or horror. 2. Auricular Region (Fig. 269). Attrahens aurem. Attollens aurem. Retrahens aurem. These three small muscles are placed immediately beneath the skin around the external ear. In man, in whom the external ear is almost immovable, they are rudimentary. They are the analogues of large and important muscles in some of the mammalia. Dissection.-This requires considerable care, and should be performed in the following manner: To expose the Attollens aurem, draw the pinna or broad part of the ear downward, when a tense band will be felt beneath the skin, passing from the side of the head to the upper part of the concha; by dividing the skin over this band, in a direction from below upward, and then reflecting it on each side, the muscle is exposed. To bring into view the Attrahens aurem, draw the helix backward by means of a hook, when the muscle will be made tense, and may be exposed in a similar manner to the preceding. To expose the Retrahens aurem, draw the pinna forward, when the muscle, being made tense, may be felt beneath the skin at its insertion into the back part of the concha, and may be exposed in the same manner as the other muscles. The Attrahens aurem (ylurzcuZam anterior), the smallest of the three, is thin, fan-shaped, and its fibres pale and indistinct; they arise from the lateral edge of 396 THE MUSCLES AND EASCIAE. file aponeurosis of the Occipito-frontalis, and converge to be inserted into a projection on the front of the helix. Relations.-Superficially, with the skin ; deeply, with the areolar tissue derived from the aponeurosis of the Occipito-frontalis, beneath which are the temporal artery and vein and the temporal fascia. The Attollens aurem (Auricularis superior), the largest of the three, is thin and fan-shaped: its fibres arise from the aponeurosis of the Occipito-frontalis and converge to be inserted by a thin, flattened tendon into the upper part of the cranial surface of the pinna. Relations.-Superficially, with the integument; deeply, with the areolar tissue derived from the aponeurosis of the Occipito-frontalis, beneath which is the temporal fascia. The Retrahens aurem (AurzcwZarzs posterior) consists of two or three fleshy fasciculi, which arise from the mastoid portion of the temporal bone by short aponeurotic fibres. They are inserted into the lower part of the cranial surface of the concha. Relations.-Superficially, with the integument; deeply, with the mastoid portion of the temporal bone. Nerves.-The Attrahens and Attollens aurem are supplied by the temporal branch of the facial; the Retrahens aurem is supplied by the posterior auricular branch of the same nerve. Actions.-In man, these muscles possess very little action : the Attrahens aurem draws the ear forward and upward; the Attollens aurem slightly raises it; and the Retrahens aurem draw's it backward. 3. Palpebral Region (Fig. 269). Orbicularis palpebrarum. Corrugator supercilii. Levator palpebrae. Tensor tarsi. Dissection (Fig. 256).-In order to expose the muscles of the face, continue the longi- tudinal incision made in the dissection of the Occipito-frontalis down the median line of the face to the tip of the nose, and from this point onward to the upper lip; and carry another incision along the margin of the lip to the angle of the mouth, and transversely across the face to the angle of the jaw. Then make an incision in front of the external ear, from the angle of the jaw upward, to join the transverse incision made in exposing the Occipito-frontalis. These incisions include a square-shaped flap, which should be removed in the direction marked in the figure, with care, as the muscles at some points are intimately adherent to the integument. The Orbicularis palpebrarum is a sphincter muscle, which surrounds the cir- cumference of the orbit and eyelids. It arises from the internal angular process of the frontal bone, from the nasal process of the superior maxillary in front of the lachrymal groove for the nasal duct, and from the anterior surface and borders of a short tendon, the tendopalpebrarum, placed at the inner angle of the orbit. From this origin the fibres are directed outward, forming a broad, thin, and flat layer, which covers the eyelids, surrounds the circumference of the orbit, and spreads out over the temple and downward on the cheek. The palpebral portion (ciliaris) of the Orbicularis is thin and pale ; it arises from the bifurcation of the tendo palpebrarum, and forms a series of concentric curves, which are united on the outer side of the eye- lids at an acute angle by a cellular raphe, some being inserted into the external tarsal ligament and malar bone. The orbicular portion (orbicularis latus) is thicker and of a reddish color : its fibres are well developed, and form complete ellipses. The upper fibres of this portion blend with the Occipito-frontalis and Corrugator supercilii. Relations.-By its superficial surface, with the integument. By its deep surface, above, with the Occipito-frontalis and Corrugator supercilii, with which it is intimately blended, and -with the supra-orbital vessels and nerve ; below', it covers the lachrymal sac, and the origin of the Levator labii superioris alaeque nasi, the Levator labii superioris, and the Zygomaticus minor muscles. Inter- 77//< PALPEBRAL REGION'. 397 nally, it is occasionally blended with the Pyramidalis nasi. Externally, it lies on the temporal fascia. On the eyelids it is separated from the conjunctiva by the Levator palpebne, the tarsal ligaments, the tarsal plates, and the Meibomian glands. The tendo palpebrarum (tendo oculi) is a short tendon, about two lines in length and one in breadth, attached to the nasal process of the superior maxillary bone in front of the lachrymal groove for the nasal duct. Crossing the lachrymal sac, it divides into two parts, each division being attached to the inner extremity of the corresponding tarsal plate. As the tendon crosses the lachrymal sac, a strong aponeurotic lamina is given off from the posterior surface, which expands over the sac, and is attached to the ridge on the lachrymal bone. This is the reflected aponeurosis of the tendo palpebrarum. Use of Tendo oculi.-Besides giving attachment to part of the Orbicularis palpebrarum, and to the tarsal plates, it serves to suck the tears into the lachrymal sac, by its attachment to the sac. Thus, each time the eyelids are closed, the tendo oculi becomes tightened, and draws the wall of the lachrymal sac outward and forward, so that a vacuum is made in the sac, and the tears are sucked along the lachrymal canals into it. The Corrugator supercilii is a small, narrow, pyramidal muscle, placed at the inner extremity of the eyebrow, be- neath the Occipito-frontalis and Orbicularis palpebrarum muscles. It arises from the inner extremity of the superciliary ridge; from whence its fibres pass upward and outward, to be inserted into the under surface of the orbicularis, op- posite the middle of the orbital arch. Relations.-By its anterior sur- face with the Occipito-frontalis and Orbicularis palpebrarum muscles; by its posterior surface, with the frontal bone and supratrochlear nerve. The Levator palpebrse will be described with the muscles of the orbital region. The Tensor tarsi (Horner's muscle) (Fig. 270) is a small thin muscle about three lines in breadth and six in length, situated at the inner side of the orbit, behind the tendo oculi. It arises from the crest and adjacent part of the orbital sur- face of the lachrymal bone, and, pass- ing across the lachrymal sac, divides into two slips, which cover the lachrymal canals, and are inserted into the tarsal plates internal to the puncta lachrymalia. Its fibres appear to be continuous with those of the palpebral portion of the Orbicularis palpebrarum; it is occasionally very indistinct. Nerves.-The Orbicularis palpebrarum, Corrugator supercilii, and Tensor tarsi are supplied by the facial nerve. Actions.-The Orbicularis palpebrarum is the sphincter muscle of the eyelids. The palpebral portion acts involuntarily, closing the lids gently, as in sleep or in blinking; the orbicular portion is subject to the will. When the entire muscle is brought into action, the skin of the forehead, temple, and cheek is drawn inward toward the inner angle of the orbit, and the eyelids are firmly closed as in photophobia. When the skin of the forehead, temple, and cheek is thus drawn inward by the < HORNER'S MUSCLE. ORBICULARIS PALPEBRARUM. I Puncta lachrymalia. ORBICULARIS PALPEBRARUM. LEVATOR LABII SUPERIORIS ALXEQUE NASI. Fig. 270.-Horner's muscle. (From a preparation in the Museum of the Royal College of Surgeons of England.) 398 THE MUSCLES AND FASCIAE. action of the muscle it is thrown into folds, especially radiating from the outer angle of the eyelids, which give rise in old age to the so-called " crow's feet." The Levator palpebrae is the direct antagonist of this muscle; it raises the upper eyelid and exposes the globe. The Corrugator supercilii draws the eyebrow downward and inward, producing the vertical wrinkles of the forehead. It is the " frowning " muscle, and may be regarded as the principal agent in the expression of suffering. The Tensor tarsi draws the eyelids and the extremities of the lachrymal canals inward and compresses them against the surface of the globe of the eye; thus placing them in the most favorable situation for receiving the tears. It serves, also, to compress the lachrymal sac. Levator palpebrge superioris. Rectus superior. Rectus inferior. 4. Orbital Region (Fig. 271). Rectus internus. Rectus externus. Obliquus oculi superior. Obliquus oculi inferior. Dissection.-To open the cavity of the orbit, remove the skull-cap and brain ; then saw through the frontal bone at the inner extremity of the supraorbital ridge, and externally at its junction with the malar. Break in pieces the thin roof of the orbit by a few slight blows of the hammer, and take it away; drive forward the superciliary portion of the frontal bone by a smart stroke, but do not remove it, as that would destroy the pulley of the Obliquus superior. When the fragments are cleared away, the periosteum of the orbit will be exposed; this being removed, together with the fat which fills the cavity of the orbit, the several muscles of this region can be examined. The dissection will be facilitated by distending the globe of the eye. In order to effect this, puncture the optic nerve near the eyeball with a curved needle, and push the needle onward into the globe; insert the point of a blowpipe through this aperture, and force a little air into the cavity of the eyeball; then apply a ligature round the nerve so as to prevent the air escaping. The globe being now drawn forward, the muscles will be put upon the stretch. The Levator palpebrae superioris is thin, flat, and triangular in shape. It arises from the under surface of the lesser wing of the sphenoid, above and in front of the optic foramen, from w hich it is separated by the origin of the Superior rectus, and is inserted, by a broad aponeurosis, into the anterior surface of the superior tarsal plate. From this aponeurosis a thin expansion is continued onward, passing between the fibres of the Orbicularis to be inserted into the skin of the lid. At its origin it is narrow and tendinous, but soon becomes broad and fleshy, and finally terminates in a broad aponeurosis. Relations.-By its upper surface, with the frontal nerve and supraorbital Fig. 271.-Muscles of the right orbit. THE ORBITAL REGION. 399 artery, the periosteum of the orbit, and, in the lid, with the inner surface of the tarsal ligament; by its under surface, with the Superior rectus, and, in the lid, with the conjunctiva. A small branch of the third nerve enters its under surface. The Superior rectus, the thinnest and narrowest of the four Recti, arises from the upper margin of the optic foramen beneath the Levator palpebrae and Superior oblique, and from the fibrous sheath of the optic nerve, and is inserted by a tendinous expansion into the sclerotic coat, about three or four lines from the margin of the cornea. Relations.-By its upper surface, with the Levator palpebrse ; by its under sur- face, with the optic nerve, the ophthalmic artery, the nasal nerve, and the branch of the third nerve which supplies it; and, in front, with the tendon of the Superior oblique and the globe of the eye. The Inferior and Internal Recti arise by a common tendon (the ligament of Zinn),1 which is attached round the circumference of the optic foramen, except at its upper and outer part. The External rectus has two heads: the upper one arises from the outer margin of the optic foramen immediately beneath the Superior rectus; the lower head, partly from the ligament of Zinn and partly from a small pointed process of bone on the lower margin of the sphenoidal fissure. Each muscle passes forward in the position implied by its name, to be inserted by a tendinous expansion (the tunica albuginea) into the sclerotic coat, about three or four lines from the margin of the cornea. Between the two heads of the Ex- ternal rectus is a narrow interval, through which passes the third, the nasal branch of the ophthalmic division of the fifth and sixth nerves, and the ophthalmic vein. Although nearly all of these muscles present a common origin and are inserted in a similar manner into the sclerotic coat, there are certain differ- ences to be observed in them as regards their length and breadth. The Internal rectus is the broadest, the External is the longest, and the Superior is the thinnest and narrowest. The Superior oblique is a fusiform muscle placed at the upper and inner side of the orbit, internal to the Levator palpebrse. It arises about a line above the inner margin of the optic foramen, and, passing forward to the inner angle of the orbit, terminates in a rounded tendon, which plays in a ring or pulley formed by cartilaginous tissue attached to a depression beneath the internal angular process of the frontal bone, the contiguous surfaces of the tendon and ring being lined by a delicate synovial membrane and enclosed in a thin fibrous investment. The tendon is reflected backward, outward, and downward beneath the Superior rectus to the outer part of the globe of the eye, and is inserted into the sclerotic coat, midway between the cornea and entrance of the optic nerve, the insertion of the muscle lying between the Superior and External recti. Relations.-By its upper surface, with the periosteum covering the roof of the orbit and the fourth nerve: the tendon, where it lies on the globe of the eye is covered by the Superior rectus; by its under surface, with the nasal nerve and the upper border of the internal rectus. The Inferior oblique is a thin, narrow muscle placed near the anterior margin of the orbit. It arises from a depression on the orbital plate of the superior Rectus superior. Levator I palpebrce superior. I Obliquus superior) Rectus- internus. Its upper head. •Lower head. Rectus inferior Fig. 272.-The relative position and attach- ment of the muscles of the left eyeball. 1 The ligament of Zinn ought, perhaps more appropriately, to be termed the aponeurosis or tendon of Zinn. Mr. C. B. Lockwood has described a somewhat similar structure on the under surface of the Superior rectus muscle, which is attached to the lesser wing of the sphenoid, forming the upper and outer margin of the optic foramen. This superior tendon gives origin to the Superior rectus, the superior head of the External rectus, and the upper part of the Internal rectus. {Journal of Anatomy and Physiology, vol. xx. part i. p. 1.) 400 THE MUSCLES AND EASCEE. maxillary bone, external to the lachrymal groove for the nasal duct. Passing out- ward, backward, and upward beneath the Inferior rectus, and then between the eyeball and the External rectus, it is inserted into the outer part of the sclerotic coat between the Superior and External recti, near to, but somewhat behind, the tendon of insertion of the Superior oblique. Relations.-By its ocular surface, with the globe of the eye and with the Inferior rectus ; by its orbital surface, with the periosteum covering the floor of the orbit, and with the External rectus. Its borders look forward and backward; the posterior one receives a branch of the third nerve. Nerves.-The Levator palpebrae, Inferior oblique, and all the Recti excepting the External, are supplied by the third nerve ; the Superior oblique, by the fourth ; the External rectus, by the sixth. Actions.-The Levator palpebrae raises the upper eyelid, and is the direct antagonist of the Orbicularis palpebrarum. The four Recti muscles are attached in such a manner to the globe of the eye that, acting singly, they will turn it either upward, downward, inward, or outward, as expressed by their names. The movement produced by the Superior or Inferior rectus is not quite a simple one, for, inasmuch as they pass obliquely outward and forward to the eyeball, the elevation or depression of the cornea must be accompanied by a certain deviation inward, with a slight amount of rotation, which, however, is corrected by the Oblique muscles, the Inferior oblique correcting the deviation inward of the Superior rectus, and the Superior oblique that of the Inferior rectus. The con- traction of the External and Internal recti, on the other hand, produces a purely horizontal movement. If any two contiguous recti of one eye act together, they carry the globe of the eye in the diagonal of these directions-viz. upward and inward, upward and outward, downward and inward, or downward and outward. The movement of circumduction, as in looking round a room, is performed by the alternate action of the four Recti. The Oblique muscles rotate the eyeball on its antero-posterior axis, this kind of movement being required for the correct viewing of an object when the head is moved laterally, as from shoulder to shoulder, in order that the picture may fall in all respects on the same part of the retina of each eye.1 Surgical Anatomy.-The position and exact point of insertion of the tendons of the Internal and External recti muscles into the globe should be carefully examined from the front of the eyeball, as the surgeon is often required to divide the one or the other muscle for the cure of strabismus. In convergent strabismus, which is the more common form of the disease, the eye is turned inward, requiring the division of the Internal rectus. In the divergent form, which is more rare, the eye is turned outward, the External rectus being especially implicated. The deformity produced in either case is to be remedied by division of one or the other muscle. The operation is thus performed: The lids are to be well separated ; the eyeball being rotated outward or inward, the conjunctiva should be raised by a pair of forceps and divided immediately beneath the lower border of the tendon of the muscle to be divided, a little behind its insertion into the sclerotic; the submucous areolar tissue is then divided, and into the small aperture thus made a blunt hook is passed upward between the muscle and the globe, and the tendon of the muscle and conjunctiva covering it divided by a pair of blunt-pointed scissors. Or the tendon may be divided by a subconjunctival incision, one blade of the scissors being passed upward between the tendon and the conjunctiva, and the other between the tendon and the sclerotic. The student, when dissecting these muscles, should remove on one side of the subject the conjunctiva from the front of the eye, in order to see more accurately the position of the tendons, while on the opposite side the operation may be performed. 5. Nasal Region (Fig. 269). Pyramidalis nasi. Levator labii superioris alaeque nasi. Dilatator naris posterior. Dilatator naris anterior. Compressor nasi. Compressor narium minor. 1 " On the Oblique Muscles of the Eye in Man and Vertebrate Animals," by John Struthers, M. D., in Anatomical and Physiological Observations. For a fuller account of the various co-ordinate actions of the muscles of a single eye and of both eyes than our space allows, the reader may be referred to Dr. M. Foster's Text-book of Physiology. Depressor alae nasi. THE NASAL REGION. 401 The Pyramidalis nasi is a small pyramidal slip prolonged downward from the Occipito-frontalis upon the side of the nose, where it becomes tendinous and blends with the Compressor nasi. As the two muscles descend they diverge, leaving an angular interval between them. Relations.-By its upper surface, with the skin ; by its under surface, with the frontal and nasal bones. The Levator labii superioris alaeque nasi is a thin triangular muscle placed by the side of the nose, and extending between the inner margin of the orbit and upper lip. It arises by a pointed extremity from the upper part of the nasal process of the superior maxillary bone, and, passing obliquely downward and outward, divides into two slips, one of which is inserted into the cartilage of the ala of the nose; the other is prolonged into the upper lip, becoming blended with the Orbicularis oris and Levator labii superioris proprius. Relations.-In front, with the integument, and with a small part of the Orbicularis palpebrarum above. The Dilatator naris posterior is a small muscle which is placed partly beneath the elevator of the nose and lip. It arises from the margin of the nasal notch of the superior maxilla and from the sesamoid cartilages, and is inserted into the skin near the margin of the nostril. The Dilatator naris anterior is a thin delicate fasciculus passing from the cartilage of the ala of the nose to the integument near its margin. This muscle is situated in front of the preceding. The Compressor nasi is a small, thin, triangular muscle arising by its apex from the superior maxillary bone, above and a little external to the incisive fossa; its fibres proceed upward and inward, expanding into a thin aponeurosis which is attached to the fibro-cartilage of the nose and is continuous on the bridge of the nose with that of the muscle of the opposite side and with the aponeurosis of the Pyramidalis nasi. The Compressor narium minor is a small muscle attached by one end to the alar cartilage, and by the other to the integument at the end of the nose. The Depressor alae nasi is a short radiated muscle arising from the incisive fossa of the superior maxilla; its fibres ascend to be inserted into the septum and back part of the ala of the nose. This muscle lies between the mucous membrane and muscular structure of the lip. Nerves.-All the muscles of this group are supplied by the facial nerve. Actions.-The Pyramidalis nasi draws down the inner angle of the eyebrows and produces transverse wrinkles over the bridge of the nose ; by some anatomists it is also considered as an elevator of the ala, and, consequently, a dilator of the nose.1 The Levator labii superioris alaeque nasi draws upward the upper lip and ala of the nose : its most important action is upon the nose, which it dilates to a considerable extent. The action of this muscle produces a marked influence over the countenance, and it is the principal agent in the expression of contempt and disdain. The two Dilatatores nasi enlarge the aperture of the nose. Their action in ordinary breathing is to resist the tendency of the nostrils to close from atmospheric pressure, but in difficult breathing they may be noticed to be in violent action, as well as in some emotions, as anger. The Depressor alae nasi is a direct antagonist of the other muscles of the nose, drawing the ala of the nose downward, and thereby constricting the aperture of the nares. The Com- pressor nasi depresses the cartilaginous part of the nose and compresses the alae together. 1 Although this muscle anatomically seems to be a continuation of the Occipito-frontalis down- ward, it is really the reverse. Its origin is from the nose below, and its insertion into the Occipito- frontalis and skin. If one pole of a battery be placed in front of the lobe of the ear, and the other (a small pointed one) be carried up and down over the nose and forehead in the middle line, it is easy to find a nodal point of indifference above which the Occipito-frontal draws the parts upward, and below which the Pyramidalis draws them downward (W. W. Keen, M. D., American edition). 402 THE MUSCLES A El) FASCIAE. 6. Superior Maxillary Region (Fig. 269). Levator labii superioris. Levator anguli oris. Zygomaticus major. Zygomaticus minor. The Levator labii superioris (proprius) is a thin muscle of a quadrilateral form. It arises from the lower margin of the orbit immediately above the infraorbital foramen, some of its fibres being attached to the superior maxilla, others to the malar bone; its fibres converge to be inserted into the muscular substance of the upper lip. Relations.-By its superficial surface above, with the lower segment of the Orbicularis palpebrarum; below, it is subcutaneous. By its deep surface it conceals the origin of the Compressor nasi and Levator anguli oris muscles, and the infraorbital vessels and nerve, as they escape from the infraorbital foramen. The Levator anguli oris arises from the canine fossa immediately below the infraorbital foramen ; its fibres incline downward and a little outward, to be inserted into the angle of the mouth, intermingling with those of the Zygomaticus major, the Depressor anguli oris, and the Orbicularis. Relations.-By its superficial surface, with the Levator labii superioris and the infraorbital vessels and nerves; by its deep surface, with the superior maxilla, the Buccinator, and the mucous membrane. The Zygomaticus major is a slender fasciculus which arises from the malar bone, in front of the zygomatic suture, and, descending obliquely downward and inward, is inserted into the angle of the mouth, where it blends with the fibres of the Levator anguli oris, the Orbicularis oris, and the Depressor anguli oris. Relations.-By its superficial surface, with the subcutaneous adipose tissue; by its deep surface, with the malar bone and the Masseter and Buccinator muscles. The Zygomaticus minor arises from the malar bone immediately behind the maxillary suture, and, passing downward and inward, is continuous with the Orbicularis oris at the outer margin of the Levator labii superioris. It lies in front of the preceding. Relations.-By its superficial surface, with the integument and the Orbicularis palpebrarum above; by its deep surface, with the Masseter, Buccinator, and Levator anguli oris. Nerves.-This group of muscles is supplied by the facial nerve. Actions.-The Levator labii superioris is the proper elevator of the upper lip, carrying it at the same time a little forward. It assists in forming the naso-labial ridge, which passes from the side of the nose to the upper lip and gives to the face an expression of sadness. The Levator anguli oris raises the angle of the mouth, and assists the Levator labii superioris in producing the naso-labial ridge. The Zygomaticus major draws the angle of the mouth backward and upward, as in laughing; whilst the Zygomaticus minor, being inserted into the outer part of the upper lip and not into the angle of the mouth, draws it backward, upward, and outward, and thus gives to the face an expression of sadness. 7. Inferior Maxillary Region (Fig. 269). Levator labii inferioris (Levator menti). Depressor labii inferioris (Quadratus menti). Depressor anguli oris (Triangularis menti). Dissection.-The muscles in this region may be dissected by making a vertical incision through the integument from the margin of the lower lip to the chin : a second incision should then be carried along the margin of the lower jaw as far as the angle, and the integument care- fully removed in the direction shown in Fig. 268. The Levator labii inferioris (Levator menti) is to be dissected by everting the lower lip and raising the mucous membrane. It is a small conical fasciculus placed on the side of the fraenum of the lower lip. It arises from the incisive fossa, INFERIOR MAXILLARY AND INTERMAXILLARY REGIONS. 403 external to the symphysis of the lower jaw; its fibres descend to be inserted into the integument of the chin. Relation.-On its inner surface, with the mucous membrane; in the median line, it is blended with the muscle of the opposite side; and on its outer side, with the Depressor labii inferioris. The Depressor labii inferioris (Quadratus menti) is a small quadrilateral muscle. It arises from the external oblique line of the lower jaw, between the symphysis and mental foramen, and passes obliquely upward and inward, to be inserted into the integument of the lower lip, its fibres blending with the Orbicularis oris and with those of its fellow of the opposite side. It is continuous with the fibres of the Platysma at its origin. This muscle contains much yellow fat inter- mingled with its fibres. Relations.-By its superficial surface, with part of the Depressor anguli oris and with the integument, to which it is closely connected; by its deep surface, with the mental vessels and nerves, the mucous membrane of the lower lip, the labial glands, and the Levator menti, with which it is intimately united. The Depressor anguli oris (Triangularis menti) is triangular in shape, arising, by its broad base, from the external oblique line of the lower jaw, from whence its fibres pass upward, to be inserted, by a narrow fasciculus, into the angle of the mouth. It is continuous with the Platysma at its origin and with the Orbicu- laris oris and Risorius at its insertion, and some of its fibres are directly continuous with those of the Levator anguli oris. Relations.-By its superficial surface, with the integument; by its deep surface, with the Depressor labii inferioris and Buccinator. Nerves.-This group of muscles is supplied by the facial nerve. Actions.-The Levator labii inferioris raises the lower lip and protrudes it forward, and at the same time wrinkles the integument of the chin, expressing doubt or disdain. The Depressor labii inferioris draws the lower lip directly downward and a little outward, as in the expression of irony. The Depressor anguli oris depresses the angle of the mouth, being the antagonist to the Levator anguli oris and Zygomaticus major; acting with these muscles, it will draw the angle of the mouth directly backward. Orbicularis oris. 8. Intermaxillary Region. Buccinator. Risorius. Dissection.-The dissection of these muscles may be considerably facilitated by filling the cavity of the mouth with tow, so as to distend the cheeks and lips ; the mouth should then be closed by a few stitches and the integument carefully removed from the surface. The Orbicularis oris (Fig. 269) is not a sphincter muscle, like the Orbicularis palpebrarum, but consists of numerous strata of muscular fibres, having different directions, which surround the orifice of the mouth. These fibres are partially derived from the other facial muscles which are inserted into the lips, and are partly fibres proper to the lips themselves. Of the former, a considerable number are derived from the Buccinator and form the deeper stratum of the Orbicularis. Some of them-namely, those near the middle of the muscle-decussate at the angle of the mouth, those arising from the upper jaw passing to the lower lip, and those from the lower jaw to the upper lip. Other fibres of the muscle, situated at its upper and lower part, pass across the lips from side to side without interruption. Superficial to this stratum is a second, formed by the Levator and Depressor anguli oris, which cross each other at the angle of the mouth, those from the Depressor passing to the upper lip, and those from the Levator to the lower lip, along which they run to be inserted into the skin near the median line. In addition to these there are fibres from the other muscles inserted into the lips-the Levator labii superioris, the Levator labii superioris alaeque nasi, the Zygomatici, and the Depressor labii inferioris; these intermingle with the transverse fibres above described, and have principally an oblique direction. The proper fibres of 404 THE MUSCLES AND FASCIAE. the lips are oblique, and pass from the under surface of the skin to the mucous membrane through the thickness of the lip. And in addition to these are fibres by which the muscle is connected directly with the maxillary bones and the septum of the nose. These consist, in the upper lip, of four bands, two of which {Accessor ii orbicularis superioris} arise from the alveolar border of the superior maxilla, opposite the lateral incisor tooth, and, arching outward on each side, are continuous at the angles of the mouth with the other muscles inserted into this part. The two remaining muscular slips, called the Naso-labialis, connect the upper lip to the back of the septum of the nose: as they descend from the septum an interval is left between them. It is this interval which forms the depression seen on the surface of the skin beneath the septum of the nose. The additional fibres for the lower segment (Accessorii orbicularis inferioris} arise from the inferior maxilla, externally to the Levator labii inferioris, and arch outward to the angles of the mouth, to join the Buccinator and the other muscles attached to this part. Relations.-By its superficial surface, with the integument, to which it is closely connected; by its deep surface, with the buccal mucous membrane, the labial glands, and coronary vessels; by its outer circumference it is blended with the numerous muscles which converge to the mouth from various parts of the face. Its inner circumference is free, and covered by the mucous membrane. The Buccinator (Fig. 282) is a broad, thin muscle, quadrilateral in form, which occupies the interval between the jaws at the side of the face. It arises from the outer surface of the alveolar processes of the upper and lower jaws, corresponding to the three molar teeth, and, behind, from the anterior border of the pterygo-maxillary ligament. The fibres converge toward the angle of the mouth, where the central fibres intersect each other, those from below being continuous with the upper segment of the Orbicularis oris, and those from above with the inferior segment; the highest and lowest fibres continue forward uninter- ruptedly into the corresponding segment of the lip, without decussation. Relations.-By its superficial surface, behind, with a large mass of fat, which separates it from the ramus of the lower jaw, the Masseter, and a small portion of the Temporal muscle; anteriorly, with the Zygomatici, Risorius, Levator anguli oris, Depressoi* anguli oris, and Stenson's duct, which pierces it opposite the second molar tooth of the upper jaw ; the facial artery and vein cross it from below upward. It is also crossed by the branches of the facial and buccal nerves by its internal surface, with the buccal glands and mucous membrane of the mouth. The pterygo-maxillary ligament separates the Buccinator muscle from the Superior constrictor of the pharynx. It is a tendinous band, attached by one extremity to the apex of the internal pterygoid plate, and by the other to the posterior extremity of the internal oblique line of the lower jaw. Its inner surface corresponds to the cavity of the mouth, and is lined by mucous membrane. Its outer surface is separated from the ramus of the jaw by a quantity of adipose tissue. Its posterior border gives attachment to the Superior constrictor of the pharynx; its anterior border, to the fibres of the Buccinator (see Fig. 282). The Risorius (Santorini) (Fig. 269) consists of a narrow bundle of fibres which arises in the fascia over the Masseter muscle, and, passing horizontally forward, is inserted into the skin at the angle of the mouth. It is placed superficial to the Platysma, and is broadest at its outer extremity. This muscle varies much in its size and form. Nerves.-The Orbiculaiis oris and the Risorius are supplied by the facial, the Buccinator by the facial and by the buccal branch of the inferior maxillary nerve ; which latter, however, is by many anatomists regarded as a sensory nerve only. Actions.-The Orbicularis oris in its ordinary action produces the direct closure of the lips; by its deep fibres, assisted by the oblique ones, it closely applies the lips to the alveolar arch. The superficial part, consisting principally of the decussating fibres, brings the lips together and also protrudes them forward. The Buccinators contract and compress the cheeks, so that, during the process of mastication, the food is kept under the immediate pressure of the teeth. When THE TEMPORO-MAXILLARY REGION. 405 the cheeks have been previously distended with air, the Buccinator muscles expel it from between the lips, as in blowing a trumpet. Hence the name (buccina, a trumpet). The Risorius retracts the angles of the mouth, and is therefore regarded as the "smiling" muscle. 9. Temporo-maxillary Region. Masseter. Temporal. Masseteric Fascia.-Covering the Masseter muscle, and firmly connected with it, is a strong layer of fascia derived from the deep cervical fascia. Above, this fascia is attached to the lower border of the zygoma, and, behind, it covers the parotid gland, constituting the parotid fascia. The Masseter is exposed by the removal of this fascia (Fig. 269); it is a short, thick muscle, somewhat quadrilateral in form, consisting of two portions, super- ficial and deep. The superficial portion, the larger, arises by a thick, tendinous aponeurosis from the malar process of the superior maxilla, and from the anterior two-thirds of the lower border of the zygomatic arch: its fibres pass downward and backward, to be inserted into the angle and lower half of the outer surface of the ramus of the jaw. The deep portion is much smaller and more muscular in texture; it arises from the posterior third of the lower border and the whole of the inner surface of the zygomatic arch; its fibres pass downward and forward, to be inserted into the upper half of the ramus and outer surface of the coronoid process of the jaw. The deep portion of the muscle is partly concealed, in front by the superficial portion; behind, it is covered by the parotid gland. The fibres of the two portions are united at their insertion. Relations.-By its superficial surface, with the Zygomatici, the Socia parotidis, and Stenson's duct; the branches of the facial nerve and the transverse facial vessels, which cross it; the masseteric fascia; the Risorius, Santorini, Platysma myoides, and the integument; by its deep surface, with the Temporal muscle at its insertion, the ramus of the jaw, and the Buccinator, from which it is separated by a mass of fat. The masseteric nerve and artery entei' it on its under surface. Its posterior margin is overlapped by the parotid gland. Its anterior margin projects over the Buccinator muscle, and the facial vein lies on it below. The temporal fascia is seen, at this stage of the dissection covering in the Temporal muscle. It is a strong, fibrous investment, covered, on its outer surface, by the Attrahens and Attollens aurem muscles, the aponeurosis of the Occipito- frontalis, and by part of the Orbicularis palpebrarum. The temporal vessels and the auriculo-temporal nerve cross it from below upward. Above, it is a single layer, attached to the entire extent of the upper temporal ridge; but below, where it is attached to the zygoma, it consists of two layers, one of which is inserted into the outer, and the other into the inner, border of the zygomatic arch. A small quantity of fat, the orbital branch of the temporal artery, and a filament from the orbital, or temporo-malar, branch of the superior maxillary nerve, are contained between these two layers. It affords attachment by its inner surface to the superficial fibres of the Temporal muscle. Dissection.-In order to expose the Temporal muscle, remove the temporal fascia, which may be effected by separating it at its attachment along the upper border of the zygoma, and dissecting it upward from the surface of the muscle. The zygomatic arch should then be divided in front at its junction with the malar bone, and behind near the external auditory meatus, and drawn downward with the Masseter, which should be detached from its inser- tion into the ramus and angle of the jaw. The whole extent of the Temporal muscle is then exposed. The Temporal (Fig. 273) is a broad, radiating muscle situated at the side of the head and occupying the entire extent of the temporal fossa. It arises from the whole of the temporal fossa except that portion of it that is formed by the malar bone. Its attachment extends from the external angular process of the frontal in front to the mastoid portion of the temporal behind, and from the curved line on the frontal and parietal bones above to the pterygoid ridge on the great wing of 406 7VZZ? MUSCLES AND FASCEE. the sphenoid below. It is also attached to the inner surface of the temporal fascia. Its fibres converge as they descend, and terminate in an aponeurosis, the fibres of Fig. 273.-The Temporal muscle, the zygoma and Masseter having been removed. which, radiated at its commencement, converge into a thick and flat tendon, which is inserted into the inner surface, apex, and anterior border of the coronoid process of the jaw, nearly as far forward as the last molar tooth. Relations.-By its superficial surface, with the integument, the Attrahens and Attollens aurem muscles, the temporal vessels and nerves, the aponeurosis of the Occipito-frontalis, the temporal fascia, the zygoma, and Masseter ; by its deep surface, with the temporal fossa, the External pterygoid and part of the Buccinator muscles, the internal maxillary artery, its deep temporal branches, and the deep temporal nerves. Behind the tendon are the masseteric vessels and nerve, and in front of it the buccal vessels and nerve. Its anterior border is separated from the malar bone by a mass of fat. Nerves.-Both muscles are supplied by the inferior maxillary nerve. 10. Pterygo-maxillary Region (Fig. 274). Dissection.-The Temporal muscle having been examined, saw through the base of the coronoid process, and draw it upward, together with the Temporal muscle, which should be detached from the surface of the temporal fossa. Divide the ramus of the jaw just below the condyle, and also, by a transverse incision extending across the middle, just above the dental foramen; remove the fragment, and the Pterygoid muscles will be exposed. The External Pterygoid is a short, thick muscle, somewhat conical in form, which extends almost horizontally between the zygomatic fossa and the condyle of the jaw. It arises from the pterygoid ridge on the great wing of the sphenoid and the portion of bone included between it and the base of the pterygoid process, and from the outer surface of the external pterygoid plate. Its fibres pass horizontally backward and outward, to be inserted into a depression in front of the neck of the condyle of the lower jaw and into the corresponding part of the interarticular fibro-cartilage. This muscle, at its origin, appears to consist of two portions separated by a slight interval; hence the terms upper and lower head sometimes used in the description of the muscle. Relations.-By its external surface, with the ramus of the lower jaw, the External Pterygoid. Internal Pterygoid. THE PTERYGO-MAXILLARY REGION. 407 internal maxillary artery, which crosses it,1 the tendon of the Temporal muscle, and the Masseter; by its internal surface it rests against the upper part of the Internal pterygoid, the internal lateral ligament, the middle meningeal artery, Fig. 274.-The Pterygoid muscles, the zygomatic arch and a portion of the ramus of the jaw having been removed. and inferior maxillary nerve ; by its upper border it is in relation with the temporal and masseteric branches of the inferior maxillary nerve; by its lower border it is in relation with the inferior dental and gustatory nerves, and it is pierced by the buccal nerve. In the interval between the two portions of the muscle the internal maxillary artery passes, when this vessel lies on the muscle (see Fig. 274). The Internal Pterygoid is a thick, quadrilateral muscle, and resembles the Masseter in form. It arises from the pterygoid fossa, being attached to the inner surface of the external pterygoid plate and to the grooved surface of the tuberosity of the palate bone, and by a second slip from the outer surface of the tuberosity of the palate bone and from the tuberosity of the superior maxillary bone ; its fibres pass downward, outward, and backward, to be inserted, by a strong, tendinous lamina, into the lower and back part of the inner side of the ramus and angle of the lower jaw, as high as the dental foramen. Relations.-By its external surface, with the ramus of the lower jaw, from which it is separated, at its upper part, by the External pterygoid, the internal lateral ligament, the internal maxillary artery, the dental vessels and nerves, and the lingual nerve; by its internal surface, with the Tensor palati, being separated from the Superior constrictor of the pharynx by a cellular interval. Nerves.-These muscles are supplied by the inferior maxillary nerve. Actions.-The Temporal and Masseter and Internal pterygoid raise the lower jaw against the upper with great force. The superficial portion of the Masseter assists the External pterygoid in drawing the lower jaw forward upon the upper, the jaw being drawn back again by the deep fibres of the Masseter and posterior fibres of the Temporal. The External pterygoid muscles are the direct agents in the trituration of the food, drawing the lower jaw directly forward, so as to make the lower teeth project beyond the upper. If the muscle of one side acts, the corresponding side of the jaw is drawn forward, and, the other condyle remaining fixed, the symphysis deviates to the opposite side. The alternation of these movements on the two sides produces trituration. 1 This is the usual relation, but in many cases the artery will be found below the muscle. 408 THE MUSCLES AND FASCIAE. Surface Form.-The outline of the muscles of the head and face cannot be traced on the surface of the body, except in the case of two of the masticatory muscles. Those of the head are thin, so that the outline of the bone is perceptible beneath them. Those in the face are small, covered by soft skin, and often by a considerable layer of fat, so that their outline is con- cealed, but they serve to round off and smooth prominent borders and to fill up what would be otherwise unsightly angular depressions. Thus, the Orbicularis palpebrarum rounds off the prominent margin of the orbit, and the Pyramidalis nasi fills in the sharp depression beneath the glabella, and thus softens and tones down the abrupt depression which is seen on the unclothed bone. In like manner, the labial muscles, converging to the lips and assisted by the superimposed fat, fill in the sunken hollow of the lower part of the face. Although the muscles of the face are usually described as arising from the bones and inserted into the nose, lips, and corners of the mouth, they have fibres inserted into the skin of the face along their whole extent, so that almost every point of the skin of the face has its muscular fibre to move it; hence it is that when in action the facial muscles produce alterations in the skin-surface, giving rise to the formation of various folds or wrinkles, or otherwise altering the relative position of parts, so as to produce the varied expressions with which the face is endowed; hence these muscles are termed the ''muscles of expression." The only twro muscles in this region which greatly influence surface form are the Masseter and the Temporal. The Masseter is a quadrilateral muscle, which imparts fulness to the hinder part of the cheek. When the muscle is firmly contracted, as when the teeth are clenched, its outline is plainly visible; the anterior border forms a prominent vertical ridge, behind which is a considerable fulness, especially marked at the lower part of the muscle; this fulness is entirely lost when the mouth is opened and the muscle no longer in a state of contraction. The Temporal muscle is fan-shaped, and fills the Temporal fossa, substituting for it a somewhat convex form, the anterior part of which, on account of the absence of hair, over the temple, is more marked than the posterior, and stands out in strong relief when the muscle is in a state of con- traction. MUSCLES AND FASCIJE OF THE NECK. The muscles of the neck may be arranged into groups corresponding with the region in which they are situated. These groups are nine in number: 1. Superficial cervical region. 2. Depressors of the Os Hyoides and Larynx. 3. Elevators of the Os Hyoides and Larynx. 4. Muscles of the Tongue. 5. Muscles of the Pharynx. 6. Muscles of the Soft Palate. 7. Muscles of the Anterior Ver- tebral Region. 8. Muscles of the Lateral Ver- tebral Region. 9. Muscles of the Larynx. The muscles contained in each of these groups are the following: 1. Superficial Region. Platysma myoides. Sterno-cleido-mastoid. Infra-hyoid Region. 2. Depressors of the Os hyoides and Larynx. Sterno-hyoid. Sterno-thyroid. Thyro-hyoid. Omo-hyoid. Supra-hyoid Region. 3. Elevators of the Os hyoides and Larynx. Digastric. Stylo-hyoid. Mylo-hyoid. Genio-hyoid. Lingual Region. 4. Muscles of the Tongue. Genio-hyo-glossus. Hyo-glossus. Lingualis. Stylo-glossus. Palato-glossus. 5. Muscles of the Pharynx. Constrictor inferior. Constrictor medius. Constrictor superior. Stylo-pharyngeus. Palato-pharyngeus. 6. Muscles of the Soft Palate. Levator palati. Tensor palati. Azygos uvulae. Palato-glossus. Palato-pharyngeus. THE SUPERFICIAL CERVICAL REGION. 409 7. Muscles of the Anterior Vertebral Region. Rectus capitis anticus major. Rectus capitis anticus minor. Rectus lateralis. Longus colli. 8. Muscles of the Lateral Vertebral Region. Scalenus anticus. Scalenus medius. Scalenus posticus. 9. Muscles of the Larynx. Included in the description of the Larynx. 1. Superficial Cervical Region. Dissection.-A block having been placed at the back of the neck, and the face turned to the side opposite that to be dissected, so as to place the parts upon the stretch, make two trans- verse incisions: one from the chin, along the margin of the lower jaw, to the mastoid process, and the other along the upper border of the clavicle. Connect these by an oblique incision made in the course of the Sterno-mastoid muscle, from the mastoid process to the sternum; the two flaps of integument having been removed in the direction shown in Fig. 268, the superficial fascia will be exposed. The Superficial Cervical Fascia is a thin, aponeurotic lamina which is hardly demonstrable as a separate membrane. Beneath it is found the Platysma myoides muscle. The Platysma myoides (Fig. 269) is a broad, thin plane of muscular fibres placed immediately beneath the superficial fascia on each side of the neck. It arises by thin, fibrous bands from the fascia covering the upper part of the Pectoral and Deltoid muscles; its fibres proceed obliquely upward and inward along the side of the neck. The anterior fibres interlace, in front of the jaw, with the fibres of the muscle of the opposite side; the posterior fibres pass over the lower jaw, a few of them being attached to the bone below the external oblique line, the greater number passing on to be inserted into the skin and subcutaneous tissue of the lower part of the face, many of these fibres blending with the muscles about the angle and lower part of the mouth. Sometimes fibres can be traced to the Zygomatic muscles or to the margin of the Orbicularis palpebrarum. Beneath the Platysma the external jugular vein may be seen descending from the angle of the jaw to the clavicle. Surgical Anatomy.-It is essential to remember the direction of the fibres of the Platysma in connection with the operation of bleeding from the external jugular vein; for if the point of the lancet is introduced in the direction of the muscular fibres, the orifice made will be filled up by the contraction of the muscle, and blood will not flow; but if the incision is made across the course of the fibres, they will retract and expose the orifice in the vein, and so allow the flow of blood. Relations.-By its external surface, with the integument, to which it is united more closely below than above; by its internal surface, with the Pectoralis major, Deltoid, and Trapezius, and with the clavicle; in the neck, with the external and anterior jugular veins, the deep cervical fascia, the superficial branches of the cervical plexus, the Sterno-mastoid, Sterno-hyoid, Omo-hyoid, and Digastric muscles; behind the Sterno-mastoid muscle it covers the Scaleni muscles and the nerves of the brachial plexus; on the face it is in relation with the parotid gland, the facial artery and vein, and the Masseter and Buccinator muscles. Action.-The Platysma myoides produces a slight wrinkling of the surface of the skin of the neck, in an oblique direction, when the entire muscle is brought into action. Its anterior portion, the thickest part of the muscle, depresses the lower jaw ; it also serves to draw down the lower lip and angle of the mouth on each side, being one of the chief agents in the expression of melancholy. The Deep Cervical Fascia (Fig. 275) is a strong, fibrous layer which invests the muscles of the neck and encloses the vessels and nerves. It commences, as an extremely thin layer, at the back part of the neck, where it is attached to the Platysma myoides. Sterno-cleido-mastoid. 410 77/7-; MUSCLES AND FA SCIE. ligamentum nuchae and to the spinous process of the seventh cervical vertebrae, and, passing forward, invests the Trapezius muscle; from the anterior border of OMO-HYOID. Thyroid body. Anterior jugular vein. STERNO-HYOID. -STER NO-THYROID. . Trachea. ■ (Esophagus. ■ LONGUS COLLI. ■6th cervical. ■Vertebral vessels. -SEMI-SPINALIS COLLI. COMPLEXUS. SPLENIUS CAPITIS. Common carotid artery.*. Internal jugular vein. STER NO-MASTOID.\ Pneumogas-| trie nerve. J External 1 jugtilar >■ vein. J SCALENUS 1 ANTICUS. J SCALENUS I MEOIUS. J SPLENIUS 1 COLLI. J LEVATOR ) ANGULI > SCAPULZE. ) TRAPEZIUS. . Fig. 275.-Section of the neck at about the level of the sixth cervical vertebra, showing the arrangement of the deep cervical fascia. this muscle it forms a layer which covers in the posterior triangle of the neck ; and, passing forward to the posterior border of the Sterno-mastoid muscle, divides into two layers, one of which passes in front, and the other behind, that muscle. The layer which passes in front of the muscle is continued forward to the front of the neck, and blends with the fascia of the opposite side, covering the anterior triangle. It is joined on its under surface, except for about an inch below, by a lamella derived from the layer covering the posterior surface of the Sterno-mastoid muscle. Where these two layers do not meet a little space is left between them, as they both pass inward to the middle line of the neck. This is Burns s space, and contains a little areolar tissue and fat, and occasionally a small lymphatic gland. If traced upward, the anterior layer of the cervical fascia is found to pass across the parotid gland and Masseter muscle, forming the parotid and masseteric fascice, ami is attached to the lower border of the zygoma, and, more anteriorly, to the lower border of the body of the jaw ; if traced downward, it is seen to pass to the upper border of the clavicle and sternum, being pierced just above the former bone by the external jugular vein. In the middle line of the neck the fascia is connected to the THE SUPERFICIAL CERVICAL REGION. 411 symphysis of the inferior maxilla, and, lower down, to the hyoid bone, between which points it is thin ; below the hyoid bone it becomes thicker, and is attached below to the anterior margin of the upper border of the sternum. The layer of the deep cervical fascia which passes behind the Sterno-mastoid covers the anterior surface of the Scalenus anticus muscle. At the outer side of the carotid vessels it divides into two, one layer passing in front of the vessels, the other behind them. The layer which passes in front of the vessels again divides into three lamellae. Of these, the anterior lamella, except for an inch below where it forms the posterior boundary of Burns's space, joins the layer of cervical fascia passing in front of the Sterno-mastoid, and with it passes to the middle line covering the anterior surface of the Depressor muscles of the hyoid bone. The portion of this lamella which invests the Omo-hyoid is continued downward as a distinct process, which descends to be inserted into the sternum and cartilage of the first rib, and becomes connected with the Costo-coracoid membrane. The middle lamella passes behind the depressors of the hyoid bone and in front of the thyroid body to meet its fellow of the opposite side, in front of the trachea. At the root of the neck this middle lamella can be traced downward into the thorax to become continuous with the fibrous layer of the pericardium. The posterior lamella passes on the inner side of the carotid vessels, and speedily joins the layer passing behind them, thus enclosing them in a sheath. The layer of cervical fascia which passes behind the carotid vessels, having been joined by the posterior of the three lamellae from the layer of fascia passing in front of the vessels, is prolonged inward, behind the pharynx and oesophagus, forming a sheath for the Prevertebral muscles, the prevertebral fascia. The layer of the deep cervical fascia, which passes behind the Sterno-mastoid, gives off another lamella, which passes downward and outward over the brachial plexus and subclavian vessels, to assist in forming the axillary sheath. The two layers of the deep cervical fascia, where they unite opposite the angle of the lower jaw, bind the Sterno-mastoid muscle to this part of the bone. From that portion of the cervical fascia which is attached to the angle of the jaw a process of extreme density is found passing behind to the inner side of the parotid gland, to be attached to the apex of the styloid process of the temporal bone ; this is termed the Stylo-maxillary liga- ment. The Sterno-mastoid or Sterno-cleido-mastoid (Fig. 276) is a large, thick muscle, which passes obliquely across the side of the neck, being enclosed between the two layers of the deep cervical fascia. It is thick and narrow at its central part, but is broader and thinnei- at each extremity. It arises, by two heads, from the sternum and clavicle. The sternal portion is a rounded fasciculus, tendinous in front, fleshy behind, which arises from the upper and anterior part of the first piece of the sternum, and is directed upward, outward, and backward. The clavicular portion arises from the inner third of the superior border of the clavicle, being composed of fleshy and aponeurotic fibres ; it is directed almost vertically upward. These two portions are separated from one another, at their origin, by a triangular cellular interval, but become gradually blended, below the middle of the neck, into a thick, rounded muscle, which is inserted, by a strong tendon, into the outer surface of the mastoid process, from its apex to its superior border, and by a thin aponeurosis into the outer two-thirds of the superior curved line of the occipital bone. The Sterno-mastoid varies much in its extent of attachment to the clavicle : in one case the clavicular may be as narrow as the sternal portion ; in another, as much as three inches in breadth. When the clavicular origin is broad it is occasionally subdivided into numerous slips separated by narrow intervals. More rarely, the corresponding margins of the Sterno-mastoid and Trapezius have been found in contact. In the application of a ligature to the third part of the sub- clavian artery it will be necessary, where the muscles come close together, to divide a portion of one or of both. This muscle divides the quadrilateral space at the side of the neck into two triangles, an anterior and a posterior. The boundaries of the anterior triangle 412 THE MUSCLES AND FASCIAE are, in front, the median line of the neck ; above, the lower border of the body of the jaw, and an imaginary line drawn from the angle of the jaw to the mastoid Fig. 276.-Muscles of the neck and boundaries of the triangles. process ; behind, the anterior border of the Sterno-mastoid muscle. The boundaries of the posterior triangle are, in front, the posterior border of the Sterno-mastoid; below, the upper border of the clavicle; behind, the anterior margin of the Trapezius.1 Relations.-By its superficial surface, with the integument and Platysma, from which it is separated by the external jugular vein, the superficial branches of the cervical plexus, and the anterior layer of the deep cervical fascia. By its deep surface it is in relation with the Sterno-clavicular articulation; a process of the deep cervical fascia; the Sterno-hyoid, Sterno-thyroid, Omo-hyoid, posterior belly of the Digastric, Levator anguli scapulae, Splenius and Scaleni muscles ; common carotid artery, internal jugular vein, commencement of the internal and external carotid arteries, the occipital, subclavian, transversalis colli, and supra- scapular arteries and veins; the pneumogastric, hypoglossal, descendens and communicans hypoglossi nerves, and the spinal accessory nerve, which pierces its upper third; the cervical, plexus, part of the parotid gland and deep lymphatic glands. Nerves.-The Platysma myoides is supplied by the facial and superficial branches of the cervical plexus ; the Sterno-cleido-mastoid, by the spinal accessory and deep branches of the cervical plexus. Actions.-A\ hen only one Sterno-mastoid muscle acts, it flexes the head and draws it toward the shoulder of the same side, assisted by the Splenius and the Obliquus capitis inferior of the opposite side. At the same time it rotates the head so as to carry the face toward the opposite side. When both muscles are brought 1 I he anatomy of these triangleswill be more exactly described with that of the vessels of the neck. 77ZZ7 INFRA-HYOID REGION 413 into action they serve to depress the head upon the neck and the neck upon the chest. If the head is fixed, they assist in elevating the thorax in forced inspiration. Surface Form.-The anterior edge of the muscle forms a very prominent ridge beneath the skin, which it is important to notice, as it forms a guide to the surgeon in making the neces- sary incisions for ligature of the common carotid artery and for oesophagotomy. Surgical Anatomy.-The relations of the sternal and clavicular parts of the Sterno-mastoid should be carefully examined, as the surgeon is sometimes required to divide one or both por- tions of the muscles in wry-neck. One variety of this distortion is produced by spasmodic con- traction or rigidity of the Sterno-mastoid ; the head being carried down toward the shoulder of the same side, and the face turned to the opposite side and fixed in that position. When there is permanent shortening subcutaneous division of the muscle is resorted to. This is performed by introducing a tenotomy knife beneath it, close to its origin, and dividing it from behind for- ward whilst the muscle is put well upon the stretch. There is seldom any difficulty in dividing the sternal portion, by making a puncture on the inner side of the tendon, and then pushing a blunt tenotome behind it, and cutting forward. In dividing the clavicular portion care must be taken to avoid wounding the external jugular vein, which runs parallel with the posterior border of the muscle in this situation, or the anterior jugular vein, which crosses beneath it. If the external jugular vein lies near the muscle, it is safer to make the first puncture at the outer side of the tendon, and introduce a blunt tenotome from without inward. Some of the fibres of the Sterno-mastoid muscle are occasionally torn during birth, especially in breech presentations; this is accompanied by haemorrhage and formation of a swelling within the substance of the muscle. This by some is believed to be one of the causes of wry-neck. 2. Infra-hyoid Region (Figs. 276, 277). Depressors of the Os Hyoides and Larynx. Sterno-hyoid. Sterno-thyroid. Thyro-hyoid. Omo-hyoid. Dissection.-The muscles in this region may be exposed by removing the deep fascia from the front of the neck. In order to see the entire extent of the Omo-hyoid it is necessary to divide the Sterno-mastoid at its centre, and turn its ends aside, and to detach the Trapezius from the clavicle and scapula. This, however, should not be done until the Trapezius has been dissected. The Sterno-hyoid is a thin, narrow, ribbon-like muscle, which arises from the inner extremity of the clavicle and the upper and posterior part of the first piece of the sternumpassing upward and inward, it is inserted, by short, tendinous fibres, into the lower border of the body of the os hyoides. This muscle is separated, below, from its fellow by a considerable interval; but they approach one another in the middle of their course, and again diverge as they ascend. It sometimes presents, immediately above its origin, a transverse tendinous intersection, like those in the Rectus abdominis. Relations.-By its superficial surface, below, with the sternum, the sternal end of the clavicle, and the Sterno-mastoid; and above, with the Platysma and deep cervical fascia ; by its deep surface, with the Sterno-thyroid, Crico-thyroid, and Thyro-hyoid muscles, the thyroid gland, the superior thyroid vessels, the thyroid cartilage, the crico-thyroid and thyro-hyoid membranes. The Sterno-thyroid is situated beneath the preceding muscle, but is shorter and wider than it. It arises from the posterior surface of the first bone of the sternum, below the origin of the Sterno-hyoid, and from the edge of the cartilage of the first rib, and is inserted into the oblique line on the side of the ala of the thyroid cartilage. This muscle is in close contact with its fellow at the lower part of the neck, and is occasionally traversed by a transverse or oblique tendinous intersection, like those in the Rectus abdominis. Relations.-By its anterior surface, with the Sterno-hyoid, Omo-hyoid, and Sterno-mastoid; by its posterior surface, from below upward, with the trachea, vena innominata, common carotid (and on the right side the arteria innominata), the thyroid gland and its vessels, and the lower part of the larynx. 1 he middle thyroid vein lies along its inner border, a relation which it is important to remember in the operation of tracheotomy. The Thyro-hyoid is a small, quadrilateral muscle appearing like a continuation 414 THE MUSCLES AND FASCIA?. of the Sterno-thyroid. It arises from the oblique line on the side of the thyroid cartilage, and passes vertically upward to be inserted into the lower border of the body and greater cornu of the hyoid bone. Relations.-By its external surface, with the Sterno-hyoid and Omo-hyoid muscles; by its internal surface, with the thyroid cartilage, the thyro-hyoid membrane, and the superior laryngeal vessels and nerve. The Omo-hyoid passes across the side of the neck, from the scapula to the Symphysis of jaw. Fig. 277.-Muscles of the neck. Anterior view. hyoid bone. It consists of two fleshy bellies, united by a central tendon. It arises from the upper border of the scapula, and occasionally from the transverse ligament which crosses the suprascapular notch ; its extent of attachment to the scapula varying from a few lines to an inch. From this origin the posterior bellv forms a flat, narrow fasciculus, which inclines forward and slightly upward across the lower part of the neck, behind the Sterno-mastoid muscle, where it becomes tendinous; it then changes its direction, forming an obtuse angle, and terminates in the anterior belly, which passes almost vertically upward, close to the outer border of the Sterno-hyoid, to be inserted into the lower border of the body of the os hyoides, just external to the insertion of the Sterno-hyoid. The central tendon of this muscle, which varies much in length and form, is held in position by a process of the deep cervical fascia, which includes it in a sheath. This process is prolonged down, to be attached to the cartilage of the first rib and the sternum. It is by this means that the angular form of the muscle is main- tained. I his muscle subdivides each of the two large triangles at the side of the neck into two smaller triangles; the two posterior ones being the posterior superior or occipital, and the posterior inferior or subclavian : the two anterior, the anterior superior or superior carotid, and the anterior inferior or inferior carotid triangle. Relations. By its superficial surface, with the Trapezius, the Sterno-mastoid, deep cervical fascia, Platysma, and integument; by its deep surface, with the Scaleni muscles, phrenic nerve, lower cervical nerves, which go to form the brachial THE SUPRA-HYOID REGION. 415 plexus, the suprascapular vessels and nerve, sheath of the common carotid artery and internal jugular vein, the Sterno-thyroid and Thyro-hyoid muscles. Nerves. - The Thyro-hyoid is supplied by the hypoglossal; the other muscles of this group by branches from the loop of communication between the descendens and communicans hypoglossi. Actions.-These muscles depress the larynx and hyoid bone, after they have been drawn up with the pharynx in the act of deglutition. The Omo-hyoid muscles not only depress the hyoid bone, but carry it backward and to one or the other side. It is concerned especially in the act of sucking, and is also a tensor of the cervical fascia. 1 he 1 hyro-hyoid may act as an elevator of the thyroid cartilage when the hyoid bone ascends, drawing upward the thyroid cartilage, behind the os hyoides.1 The Sterno-thyroid acts as a depressor* of the thvroid cartilage. 3. Supra-hyoid Region (Figs. 276, 277). Elevators of the Os Hyoides-Depressors of the Lower Jaw. Digastric. Stylo-hyoid. Mylo-hyoid. Genio-hyoid. Dissection.-To dissect these muscles a block should be placed beneath the back of the neck, and the head drawn backward and retained in that position. On the removal of the deep fascia the muscles are at once exposed. The Digastric consists of two fleshy bellies united by an intermediate, rounded tendon. It is a small muscle, situated below the side of the body of the lower jaw, and extending, in a curved form, from the side of the head to the symphysis of the jaw. The posterior belly, longer than the anterior, arises from the digastric groove on the inner side of the mastoid process of the temporal bone, and passes downward, forward, and inward. The anterior belly arises from a depression on the inner side of the lower border of the jaw, close to the symphysis, and passes downward and backward. The two bellies terminate in the central tendon which perforates the Stylo-hyoid, and is held in connection with the side of the body and the greater cornu of the hyoid bone by a fibrous loop, lined by a synovial membrane. A broad aponeurotic layer is given off from the tendon of the Digastric on each side, which is attached to the body and great cornu of the hyoid bone: this is termed the supra-hyoid aponeurosis. It forms a strong layer of fascia between the anterior portion of the two muscles, and a firm investment for the other muscles of the supra-hyoid region which lie deeper. The Digastric muscle divides the anterior superior triangle of the neck into two smaller triangles; the upper, or submaxillary, being bounded, above, bv the lower border of the body of the jaw, and a line drawn from its angle to the mastoid process; below, by the posterior belly of the Digastric and the Stylo- hyoid muscles; in front, by the middle line of the neck and anterior belly of the Digastric, the lower or superior carotid triangle being bounded above by the posterior belly of the Digastric, behind by the Sterno-mastoid, below by the Omo- hyoid. Relations.-By its superficial surface, with the Platysma, Sterno-mastoid. part of the Splenius, Trachelo-mastoid, and Stylo-hyoid muscles, and the parotid gland. By its deep surface, the anterior belly lies on the Mylo-hyoid; the posterior bellv on the Stylo-glossus, Stylo-pharyngeus, and Hyo-glossus muscles, the external carotid artery and its lingual and facial branches, the internal carotid artery, internal jugular vein, and hypoglossal nerve. The Stylo-hyoid is a small, slender muscle, lying in front of, and above, the posterior belly of the Digastric. It arises from the back and outer surface of the styloid process, near the base; and, passing downward and forward, is inserted into the body of the hyoid bone, just at its junction with the greater cornu, and 1 It is this action of the Thyro-hyoid muscle which, as Dr. Buchanan has pointed out, " causes or permits the folding back of the epiglottis over the upper orifice of the larynx." (Journ. of Anat. and Phys. 2d series, No. III. p. 255). 416 THE MUSCLES AND FASCIAE. immediately above the Omo-hyoid. This muscle is perforated, near its insertion, by the tendon of the Digastric. Relations.-The relations are the same as those of the posterior belly of the Digastric. The Stylo-hyoid Ligament.-In connection with the Stylo-hyoid muscle may be described a ligamentous band, the Stylo-hyoid ligament. It is a fibrous cord, often containing a little cartilage in its centre, which continues the styloid process down to the hyoid bone, being attached to the tip of the former and the small cornu of the latter. It is often more or less ossified. The Digastric and Stylo-hyoid should be removed, in order to expose the next muscle. The Mylo-hyoid is a flat, triangular muscle, situated immediately beneath the anterior belly of the Digastric, and forming, with its fellow of the opposite side, a muscular floor for the cavity of the mouth. It arises from the whole length of the mylo-hyoid ridge, extending from the symphysis in front to the last molar tooth behind. The posterior fibres pass obliquely forward, to be inserted into the body of the os hyoides. The middle and anterior fibres are inserted into a median fibrous raphe, extending from the symphysis of the lower jaw to the hyoid bone, where they join at an angle with the fibres of the opposite muscle. This median raphe is sometimes wanting; the muscular fibres of the two sides are then directly continuous with one another. Relations.-By its cutaneous surface, with the Platysma, the anterior belly of the Digastric, the supra-hyoid aponeurosis, the submaxillary gland, submental vessels, and mylo-hyoid vessels and nerve; by its deep or superior surface, with the Genio-hyoid, part of the Hyo-glossus, and Stylo-glossus, muscles, the hypo- glossal and lingual nerves, the submaxillary ganglion, the sublingual gland, the deep portion of the submaxillary gland and Wharton's duct; the sublingual and ranine vessels, and the buccal mucous membrane. Dissection.-The Mylo-hyoid should now be removed, in order to expose the muscles which lie beneath : this is effected by detaching it from its attachments to the hyoid bone and jaw, and separating it by a vertical incision from its fellow of the opposite side. The Genio-hyoid is a narrow, slender muscle, situated immediately beneath 1 the inner border of the preceding. It arises from the inferior genial tubercle on the inner side of the symphysis of the jaw, and passes downward and backward, to be inserted into the anterior surface of the body of the os hyoides. This muscle lies in close contact with its fellow of the opposite side, and increases slightly in breadth as it descends. Relations.-It is covered by the Mylo-hyoid, and lies on the Genio-hyo- glossus. Nerves.-The Digastric is supplied: its anterior belly, by the mylo-hyoid branch of the inferior dental; its posterior belly, by the facial; the Stylo-hyoid, by the facial; the Mylo-hyoid, by the mylo-hyoid branch of the inferior dental; the Genio- hyoid, by the hypoglossal. Actions.-This group of muscles performs two very important actions. They raise the hyoid bone, and with it the base of the tongue, during the act of degluti- tion ; or, when the hyoid bone is fixed by its depressors and those of the larynx, they depress the lower jaw. During the first act of deglutition, when the mass is being driven from the mouth into the pharynx, the hyoid bone, and with it the tongue, is carried upward and forward by the anterior belly of the Digastric, the Mylo-hyoid, and Genio-hyoid muscles. In the second act, when the mass is pass- ing through the pharynx, the direct elevation of the hyoid bone takes place by the combined action of all the muscles; and after the food has passed the hyoid bone is carried upward and backward by the posterior belly of the Digastric and Stylo-hyoid muscles, which assist in preventing the return of the morsel into the mouth. 1 This refers to the depth of the muscles from the skin in the order of dissection. In the erect position of the body each of these muscles lies above the preceding. THE LINGUAL REGION. 417 4. Lingual Region. Genio-hyo-glossus. Hyo-glossus. Stylo-glossus. Palato-glossus. Chondro-glossus. Dissection.-After completing the dissection of the preceding muscles, saw through the lower jaw just external to the symphysis. Then draw the tongue forward, and attach it, by a stitch, to the nose; when its muscles, which are thus put on the stretch, may be examined. The Genio-hyo-glossus has received its name from its triple attachment to the jaw, hyoid bone, and tongue, but it would be better named the Grenio-glossus, since its attachment to the hyoid bone is very slight or altogether absent. It is a flat, triangular muscle, placed vertically on either side of the middle line, its apex corresponding with its point of attachment to the lower jaw, its base with its insertion into the tongue and hyoid bone. It arises by a short tendon from the superior genial tubercle on the inner side of the symphysis of the jaw, immediately above the Genio-hyoid ; from this point the muscle spreads out in a fan-like form, a few of the inferior fibres passing downward, to be attached by a thin aponeurosis into the upper part of the body of the hvoid bone; the middle fibres passing back- ward, and the superior ones upward and forward, to enter the whole length of the under surface of the tongue, from the base to the apex. The two muscles lie on either side of the median plane ; behind, they are quite distinct from each other, and are separated at their insertion into the under surface of the tongue by a ten- dinous raphe, which extends through the middle of the organ; in front, the two muscles are more or less blended : distinct fasciculi are to be seen passing off from one muscle, crossing the middle line, and intersecting with bundles of fibres derived from the muscle on the other side (Fig. 279). Relations.-By its internal surface it is in contact with its fellow of the opposite Fig. 278.-Muscles of the tongue. Left side. 418 THE MUSCLES AND FASCIAE. side; by its external surf ace, with the Inferior lingualis, the Hyo-glossus, the lin- gual artery and hypoglossal nerve, the lingual nerve, and sublingual gland; by its upper border, with the mucous membrane of the floor of the mouth (fraenum linguae) ; by its lower border, with the Genio-hyoid. The Hyo-glossus is a thin, flat, quadrilateral muscle which arises from the side of the body and whole length of the greater cornu of the hyoid bone, and passes almost vertically upward to enter the side of the tongue, between the Stylo-glossus and Lingualis. Those fibres of this muscle which arise from the body are direct- ed upward and backward, overlapping those arising from the greater cornu, which are direct- ed upward and forward. Relations.-By its external surface, with the Digastric, the Stylo-hyoid, Stylo-glossus, and Mylo-hyoid muscles, the submaxillary ganglion, the lingual and hypoglossal nerves, Wharton's duct, and the deep portion of the submaxillary gland ; by its deep surface, with the Stylo-hyoid ligament, the Genio-hyo-glossus, Lingualis, and Middle constrictor, the lingual vessels, and the glosso-pharyngeal nerve. The Chondro-glossus is a distinct muscular slip, about three-quarters to an inch in length, which arises from the inner side and base of the lesser cornu of the hyoid bone and contiguous portion of the body of the bone, and passes directly upward to blend with the intrinsic mus- cular fibres of the tongue, between the Hyo- glossus and Genio-hyo-glossus. A small slip of muscular fibre is occasionally found, arising from the cartilage triticea in the thyro-hyoid ligament, and passing upward and forward to enter the tongue with the hindermost fibres of the Hyo-glossus. The Stylo-glossus, the shortest and smallest of the three styloid muscles, arises from the anterior and outer side of the styloid process, near its apex, and from the stylo-maxillary ligament, to which its fibres, in most cases, are attached by a thin aponeurosis. Passing downward and forward between the internal and external carotid arteries, and becoming nearly horizontal in its direction, it divides upon the side of the tongue into two portions : one longitudinal, which enters the side of the tongue near its dorsal surface, blending with the fibres of the Lingualis in front of the Hyo-glossus; the other oblique, which overlaps the Hyo-glossus muscle and decussates with its fibres. Relations.-By its external surface, from above downward, with the parotid gland, the Internal pterygoid muscle, the lingual nerve, and the mucous membrane of the mouth; by its internal surface, with the tonsil, the Superior constrictor, and the Hyo-glossus muscle. I he Palato-glossus, or Constrictor isthmi faucium, although it is one of the muscles of the tongue, serving to draw its base upward during the act of degluti- tion, is more nearly associated with the soft palate, both in its situation and func- tion; it will consequently be described with that group of muscles. Nerves. I he Palato-glossus is probably innervated by the spinal accessory nerve, through the pharyngeal plexus; the Inferior lingualis, according to some authors, by the chorda tympani; the remaining muscles of this group, by the hypoglossal. Muscular Substance of Tongue.-The muscular fibres of the tongue run in vari- ous directions. These fibres are divided into two sets-Extrinsic and Intrinsic. / CHONDRO-GLOSSUS. Fig. 279.-Muscles of the tongue from be- low. (From a preparation in the Museum of the Royal College of Surgeons of England.) THE LINGUAL REGION 419 'rhe extrinsic muscles of the tongue are those which have their origin external, and only their terminal fibres contained in the substance of the organ. They are: the Stylo-glossus, the Hyo-glossus, the Palato-glossus, the Genio-hyo-glossus, and part of the Superior constrictor of the pharynx (Pharyngeo-glossus). The intrinsic are those which are contained entirely within the tongue, and form the greater part of its muscular structure. The tongue consists of symmetrical halves separated from each other in the middle line by a fibrous septum. Each half is composed of muscular fibres arranged in various directions, containing much interposed fat and supplied by vessels and nerves. To demonstrate the various fibres of the tongue, the organ should be sub- jected to prolonged boiling, in order to soften the connective tissue; the dis- section may then be commenced from the dorsum (Fig. 280). Immediately beneath the mucous membrane is a submucous, fibrous layer, into which the muscular fibres which terminate on the surface of the tongue are inserted. Upon removing this, with the mucous mem- brane, the first stratum of muscular fibres is exposed. This belongs to the group of intrin- sic muscles, and has been named the Superior lingualis. It consists of a thin layer of Fig. 281.-Coronal section of tongue. Showing intrinsic muscles. (Altered from Krause.) a, lingual artery: b, Inferior lingualis, cut through; c, fibres of Hyo-glossus; d, oblique fibres of Stylo-glossus; e, insertion of Transverse lingualis; f, Supe- rior lingualis ; g, papillae to tongue ; h, vertical fibres of Genio- hyo-glossus intersecting Transverse lingualis ; i, septum. Cut edge of Superficial lingualis. Fig. 280.-Muscles on the dorsum of the tongue. oblique and longitudinal fibres which arise from the submucous fibrous layer, close to the Epiglottis, and from the fibrous septum, and pass forward and outward to the edges of the tongue. Between its fibres pass some vertical fibres derived from the Genio-hvo-glossus and from the vertical intrinsic muscle, which will be described later on. Beneath this layer is the second stratum of muscular fibres, derived prin- cipally from the extrinsic muscles. In front it is formed by the fibres derived from the Stylo-glossus, running along the side of the tongue, and sending one set of fibres over the dorsum which runs obliquely forward and inward to the middle line, and another set of fibres, seen at a later period of the dissection, on to the under surface of the sides of the anterior part of the tongue, which run forward and inward, between the fibres of the Hyo-glossus, to the middle line. Behind this layer of fibres, derived from the Stylo-glossus, are fibres derived from the Hyo-glossus, assisted by some few fibres of the Palato-glossus. The Hyo-glossus, entering the side of the under surface of the tongue, between the Stylo-glossus and Inferior lin- 420 THE MUSCLES AND FASCIAE. gualis, passes round its margin and spreads out into a layer on the dorsum, which occupies the middle third of the organ, and runs almost transversely inward to the septum. It is reinforced by some fibres from the Palato-glossus; other fibres of this muscle pass more deeply and intermingle with the next layer. The posterior part of the second layer of the muscular fibres of the tongue is derived from those fibres of the Hyo-glossus which arise from the lesser cornu of the hyoid bone, and are here described as a separate muscle-the Chondro-glossus. The fibres of this muscle are arranged in a fan-shaped manner, and spread out over the posterior third of the tongue. Beneath this layer is the great mass of the intrinsic muscles of the tongue, intersected at right angles by the terminal fibres of one of the extrinsic muscles-the Genio-hyo-glossus. This portion of the tongue is paler in color and softer in texture than that already described, and is sometimes designated the medullary portion in contradistinction to the firmer superficial part, which is termed the cortical portion. It consists largely of transverse fibres, the Transverse lingualis, and of vertical fibres, the Vertical lingualis. The Transverse lingualis forms the largest portion of the third layer of muscular fibres of the tongue. The fibres arise from the median septum, and pass outward to be inserted into the submucous fibrous layer at the sides of the tongue. Intermingled with these transverse intrinsic fibres are transverse extrinsic fibres derived from the Palato-glossus and the Superior constrictor of the pharynx. These transverse extrinsic fibres, however, run in the opposite direction, passing inward, toward the septum. Intersecting the transverse fibres are a large number of vertical fibres derived partly from the Genio-hyo-glossus and partly from vertical intrinsic fibres, the Vertical lingualis. The fibres derived from the Genio-hyo-glossus enter the under surface of the tongue on each side of the median septum from base to apex. They ascend in a radiating manner to the dorsum, being inserted into the sub- mucous fibrous laver covering the tongue on each side of the middle line. The Vertical lingualis is found only at the borders of the fore part of the tongue, external to the fibres of the Genio-hyo-glossus. Its fibres extend from the upper to the under surface of the tongue, decussating with the fibres of the other muscles, and especially with the Transverse lingualis. The fourth layer of muscular fibres of the tongue consists partly of extrinsic fibres derived from the Stylo-glossus, and partly of intrinsic fibres, the Inferior lingualis. At the sides of the under surface of the tongue are some fibres derived from the Stylo-glossus, which, as it runs forward at the side of the tongue, gives off fibres which, passing forward and inward between the fibres of the Hyo-glossus, form an inferior oblique stratum which joins in front with the anterior fibres of the Inferior lingualis. The Inferior lingualis is a longi- tudinal band, situated on the under surface of the tongue, lying in the interval between the Stylo-glossus, in front of the Hyo-glossus, and the Genio-hyo-glossus, and extending from the base to the apex of the organ. Posteriorly, some of the fibres are lost in the base of the tongue, and others are occasionally attached to the hyoid bone. It blends with the fibres of the Hyo-glossus, and is continued forward as far as the apex of the tongue. It is in relation by its under surface with the ranine artery. Surgical Anatomy.-The fibrous septum which exists between the two halves of the tongue is very complete, so that the anastomosis between the two lingual arteries is not very free, a fact often illustrated by injecting one-half of the tongue with colored size, while the other half is left uninjected or is injected with size of a different color. 1 his is a point of considerable importance in connection with removal of one-half of the tongue for cancer, an operation which is now frequently resorted to when the disease is strictly confined to one side of the tongue. If the mucous membrane is divided longitudinally exactly in the middle line, the tongue can be split into halves along the median raphe without any appreciable haemorrhage, and the diseased half can then be removed. Actions.-I he movements of the tongue, although numerous and complicated, may be understood by carefully considering the direction of the fibres of its muscles. The G-enio-hyo-glossi muscles, by means of their posterior fibres, draw the base of the tongue forward, so as to protrude the apex from the mouth. The anterior fibres draw the tongue back into the mouth. The whole length of these THE PHARYNGEAL REGION. 421 two muscles, acting along the middle line of the tongue, draw it downward, so as to make it concave from side to side, forming a channel along which fluids may pass toward the pharynx, as in sucking. The Hyo-glossi muscles depress the tongue and draw down its sides, so as to render it convex from side to side. The Stylo- glossi muscles draw the tongue upward and backward. The Palato-glossi muscles draw the base of the tongue upward. With regard to the intrinsic muscles, both the Superior and Inferior linguales tend to shorten the tongue, but the former, in addition, turn the tip and sides upward so as to render the dorsum concave, while the latter pull the tip downward and cause the dorsum to become convex. The Transverse lingualis narrows and elongates the tongue, and the Vertical lingualis flattens and broadens it. The complex arrangement of the muscular fibres of the tongue, and the various directions in which they run, give to this organ the power of assuming the various forms necessary for the enunciation of the different consonantal sounds; and Dr. Macalister states that " there is reason to believe that the musculature of the tongue varies in different races owing to the hereditary practice and habitual use of certain motions required for enunciating the several vernacular languages." 5. Pharyngeal Region. Inferior constrictor. Middle constrictor. Superior constrictor. Stylo-pharyngeus. Palato-pharyngeus. Salpingo-pharyngeus. (See next section.) Dissection (Fig. 282).-In order to examine the muscles of the pharynx, cut through the trachea and oesophagus just above the sternum, and draw them upward by dividing the loose areolar tissue connecting the pharynx with the front of the vertebral column. The parts being drawn well forward, apply the edge of the saw immediately behind the styloid pro- cesses, and saw the base of the skull through from below upward. The pharynx and mouth should then be stuffed with tow, in order to distend its cavity and render the muscles tense and easier of dissection. The Inferior constrictor, the most superficial and thickest of the three constrictors, arises from the sides of the cricoid and thyroid cartilages. To the cricoid cartilage it is attached in the interval between the Crico-thyroid mus- cle in front and the articular facet for the thyroid cartilage behind. To the thyroid cartilage it is attached to the oblique line on the side of the great ala, the cartilaginous surface behind it, near- ly as far as its posterior border, and to the inferior cornu. From these attach- ments the fibres spread backward and inward, to be inserted into the fibrous raphe in the posterior median line of the pharynx. The inferior fibres are horizontal, and continuous with the fibres of the oesophagus : the rest as- cend, increasing in obliquity, and over- lap the Middle constrictor. The supe- rior laryngeal nerve and artery pass near the upper border, and the inferior, or recurrent laryngeal, beneath the lower border of this muscle, previous to their entering the larynx. Relations.-It is covered by a dense cellular membrane which surrounds the Fig. 282.-Muscles of the pharynx. External view. 422 THE MUSCLES AND FA SOLE. entire pharynx. Behind, it is in relation with the vertebral column and the Longus colli muscle; laterally, with the thyroid gland, the common carotid artery, and the Sterno-thyroid muscle ; by its internal surface, with the Middle constrictor, the Stylo-pharyngeus, Palato-pharyngeus, the fibrous coat and mucous membrane of the pharynx. The Middle constrictor is a flattened, fan-shaped muscle, smaller than the pre- ceding. It arises from the whole length of the upper surface of the greater cornu of the hvoid bone, from the lesser cornu, and from the stylo-hyoid ligament. The fibres diverge from their origin, the lower ones descending beneath the Infe- rior constrictor, the middle fibres passing transversely, and the upper fibres ascending and overlapping the Superior constrictor. The muscle is inserted into the posterior median fibrous raphe, blending in the middle line with the one of the opposite side. Relations.-This muscle is separated from the Superior constrictor by the glosso-pharyngeal nerve and the Stylo-pharyngeus muscle, and from the Inferior constrictor by the superior laryngeal nerve. Behind, it lies on the vertebral column, the Longus colli, and the Rectus capitis anticus major. On each side it is in relation with the carotid vessels, the pharyngeal plexus, and some lymphatic glands. Near its origin it is covered by the Hyo-glossus, from which it is separated by the lingual vessels. It lies upon the Superior constrictor, the Stylo-pharyngeus, the Palato-pharyngeus, the fibrous coat, and the mucous membrane of the pharynx. The Superior Constrictor is a quadrilateral muscle, thinner and paler than the other constrictors, and situated at the upper part of the pharynx. It arises from the lower third of the posterior margin of the internal pterygoid plate and its hamular process, from the contiguous portion of the palate bone and the reflected tendon of the Tensor palati muscle, from the pterygo-maxillary ligament, from the alveolar process above the posterior extremity of the mylo-hyoid ridge, and by a few fibi •es from the side of the tongue. From these points the fibres curve back- ward, to be inserted into the median raphe, being also prolonged by means of a fibrous aponeurosis to the pharyngeal spine on the basilar process of the occipital bone. The superior fibres arch beneath the Levator palati and the Eustachian tube, the interval between the upper border of the muscle and the basilar process being deficient in muscular fibres and closed by fibrous membrane. This interval is known as the sinus of Morgagni. Relations.-By its outer surface, with the vertebral column, the internal carotid artery, the internal jugular vein, the glosso-pharyngeal, pneumogastric, spinal accessory, hypoglossal, and sympathetic nerves, the Middle constrictor, which overlaps it, and the Stylo-pharyngeus; by its internal surface, with the Palato- pharyngeus, the tonsil, the fibrous coat and mucous membrane of the pharynx. The Stylo-pharyngeus is a long, slender muscle, round above, broad and thin below. It arises from the inner side of the base of the styloid process, passes downward along the side of the pharynx between the Superior and Middle constrictors, and spreads out beneath the mucous membrane, where some of its fibres are lost in the Constrictor muscles; and others, joining with the Palato- pharyngeus, are inserted into the posterior border of the thyroid cartilage. The glosso-pharyngeal nerve runs on the outer side of this muscle, and crosses over it in passing forward to the tongue. Relations.-Externally, with the Stylo-glossus muscle, the parotid gland, the external carotid artery, and the Middle constrictor; internally, with the internal carotid, the internal jugular vein, the Superior constrictor, Palato-pharyngeus, and mucous membrane. Nerves.-The Constrictors are supplied by branches from the pharyngeal plexus, the Stylo-pharyngeus by the glosso-pharyngeal nerve, and the Inferior constrictor by an additional branch from the external laryngeal nerve and by the recurrent laryngeal. Actions.-V hen deglutition is about to be performed, the pharynx is drawn THE PALATAL REGION. 423 upward and dilated in different directions, to receive the morsel propelled into it from the mouth. The Stylo-pharyngei, which are much farther removed from one another at their origin than at their insertion, draw the sides of the pharynx upward and outward, and so increase its transverse diameter, its breadth in the antero-posterior direction being increased by the larynx and tongue being carried forward in their ascent. As soon as the morsel is received in the pharynx, the Elevator muscles relax, the bag descends, and the Constrictors contract upon the morsel, and convey it gradually downward into the oesophagus. Besides its action in deglutition, the pharynx also exerts an important influence in the modulation of the voice, especially in the production of the higher tones. 6. Palatal Region. Levator palati. Tensor palati. Azygos uvulae. Palato-glossus. Palato-pharyngeus. Salpingo-pharyngeus. Dissection (Fig. 283).-Lay open the pharynx from behind by a vertical incision extending from its upper to its lower part, and partially divide the occipital attachment by a transverse incision on each side of the vertical one ; the posterior surface of the soft palate is then exposed. Having fixed the uvula so as to make it tense, the mucous membrane and glands should be care- fully removed from the posterior surface of the soft palate, and the muscles of this part are at once exposed. The Levator palati is a long, thick, rounded muscle, placed on the outer side Fig. 283.-Muscles of the soft palate, the pharynx being laid open from behind. of the posterior nares. It arises from the under surface of the apex of the petrous portion of the temporal bone, and from the adjoining cartilaginous portion of the Eustachian tube; after passing into the pharynx, above the upper concave margin 424 THE MUSCLES AND FASCLE. of the Superior constrictor, it passes obliquely downward and inward, its fibres spreading out in the soft palate as far as the middle line, where they blend with those of the opposite side. Relations.-Externally, with the Tensor palati and Superior constrictor; internally, with the mucous membrane of the pharynx; posteriorly, with the posterior fasciculus of the Palato-pharyngeus, the Azygos uvulae, and the mucous lining of the soft palate. The Circumflexus or Tensor palati is a broad, thin, ribbon-like muscle, placed on the outer side of the Levator palati, and consisting of a vertical and a horizontal portion. The vertical portion arises by a broad, thin, and flat lamella from the scaphoid fossa at the base of the internal pterygoid plate ; from the spine of the sphenoid ; the vaginal process of the temporal bone and the anterior aspect of the cartilaginous portion of the Eustachian tube : descending vertically between the internal pterygoid plate and the inner surface of the Internal pterygoid muscle, it terminates in a tendon, which winds round the hamular process, being retained in this situation by some of the fibres of origin of the Internal pterygoid muscle, and lubricated by a bursa. The tendon or horizontal portion then passes horizontally inward, and is inserted into a broad aponeurosis, the palatine aponeurosis, and into the transverse ridge on the horizontal portion of the palate bone. Relations.-Externally, with the Internal pterygoid; internally, with the Levator palati, from which it is separated by the Superior constrictor, and with the internal pterygoid plate. In the soft palate its tendon and the palatine aponeurosis is anterior to that of the Levator palati, being covered by the Palato- glossus and the mucous membrane. Palatine Aponeurosis.-Attached to the posterior border of the hard palate is a thin, firm, fibrous lamella which supports the muscles and gives strength to the soft palate. It is thicker above than below, where it becomes very thin and difficult to define. Laterally, it is continuous with the pharyngeal aponeurosis. The Azygos uvulae is not a single muscle, as would be inferred from its name, but a pair of narrow cylindrical fleshy fasciculi placed side by side in the median line of the soft palate. Each muscle arises from the posterior nasal spine of the palate bone and from the contiguous tendinous aponeurosis of the soft palate, and descends to be inserted into the uvula. Relations.-Anteriorly, with the tendinous expansion of the Levatores palati; behind, with the posterior fasciculus of the Palato-pharyngeus and the mucous membrane. The two next muscles are exposed by removing the mucous membrane from the pillars of the soft palate throughout nearly their whole extent. The Palato-glossus (Constrictor isthmi faucium) is a small fleshy fasciculus, narrower in the middle than at either extremity, forming, with the mucous membrane covering its surface, the anterior pillar of the soft palate. It arises from the anterior surface of the soft palate on each side of the uvula, and, passing downward, forward, and outward in front of the tonsil, is inserted into the side of the tongue, some of its fibres spreading over the dorsum, and others passing deeply into the substance of the organ to intermingle with the Transversus linguae. In the soft palate the fibres of this muscle are continuous with those of the muscle of the opposite side. The Palato-pharyngeus is a long, fleshy fasciculus, narrow er in the middle than at either extremity, forming, with the mucous membrane covering its surface, the- posterior pillar of the soft palate. It is separated from the Palato-glossus by an angular interval, in which the tonsil is lodged. It arises from the soft palate by an expanded fasciculus, which is divided into two parts by the Levator palati and Azygos uvulae. T he posterior fasciculus lies in contact with the mucous membrane, and also joins with the corresponding muscle in the middle line ; the anterior fasciculus, the thicker, lies in the soft palate between the Levator and Tensor, and THE PALATAL REGION. 425 joins in the middle line the corresponding part of the opposite muscle. Passing outward and downward behind the tonsil, the Palato-pharyngeus joins the Stylo- pharyngeus, and is inserted with that muscle into the posterior border of the thyroid cartilage, some of its fibres being lost on the side of the pharynx, and others passing across the middle line posteriorly to decussate with the muscle of the opposite side. The Salpingo-pharyngeus.-This muscle arises from the inferior part of the Eustachian tube near its orifice ; it passes downward and blends with the posterior fasciculus of the Palato-pharyngeus. Relations.- In the soft palate its posterior surface is covered bv mucous membrane, from which it is separated by a layer of palatine glands. By its anterior surface it is in relation with the Tensor palati. Where it forms the posterior pillar of the fauces it is covered by mucous membrane, excepting on its outer surface. In the pharynx it lies between the mucous membrane and the Constrictor muscles. In a dissection of the soft palate from its posterior or nasal surface to its anterior or oral surface, the muscles would be exposed in the following order: viz. the posterior fasciculus of the Palato-pharyngeus, covered over by the mucous membrane reflected from the floor of the nasal fossae ; the Azygos uvulae; the Levator palati; the anterior fasciculus of the Palato-pharyngeus; the aponeurosis of the Tensor palati, and the Palato-glossus covered over by a reflection from the oral mucous membrane. Nerves.-The Tensor palati is supplied by a branch from the otic ganglion; the remaining muscles of this group are in all probability supplied by the internal branch of the spinal accessory, whose fibres are distributed along with certain branches of the pneumogastric through the pharyngeal plexus.1 Actions.-During the first stage of deglutition the morsel of food is driven back into the fauces by the pressure of the tongue against the hard palate, the base of the tongue being, at the same time, retracted, and the larynx raised with the pharynx, and carried forward under it. During the second stage the epiglottis is pressed over the superior aperture of the larynx, and the morsel glides past it; then the Palato-glossi muscles, the constrictors of the fauces, contract behind the food ; the soft palate is slightly raised by the Levator palati, and made tense by the Tensor palati; and the Palato-pharyngei, by their contraction, pull the pharynx upward over the morsel of food, and at the same time come nearly together, the uvula filling up the slight interval between them. By these means the food is prevented passing into the upper part of the pharynx or the posterior nares; at the same time the latter muscles form an inclined plane, directed obliquely down- ward and backward, along the under surface of which the morsel descends into the lower part of the pharynx. The Salpingo-pharyngeus raises the upper and lateral part of the pharynx-i. e. that part which is above the point where the Stylo-pharyngeus is attached to the pharynx. Surgical Anatomy.-The muscles of the soft palate should be carefully dissected, the rela- tions they bear to the surrounding parts especially examined, and their action attentively studied upon the dead subject, as the surgeon is required to divide one or more of these muscles in the operation of staphylorraphy. Sir W. Fergusson was the first to show that in the congenital deficiency called cleft palate the edges of the fissure are forcibly separated by the action of the Levatores palati and Palato-pharyngei muscles, producing very considerable impediment to the healing process after the performance of the operation for uniting their margins by adhesion ; he, consequently, recommended the division of these muscles as one of the most important steps in the operation. This he effected by an incision made with a curved knife introduced behind the soft palate. The incision is to be halfway between the hamular process and Eustachian tube, and perpendicular to a line drawn between them. This incision perfectly accomplishes the division of the Levator palati. The Palato-pharyngeus may be divided by cutting across the posterior pillar of the soft palate, just below the tonsil, with a pair of blunt-pointed curved scissors; and the anterior pillar may be divided also. To divide the Levator palati the plan recommended by Mr. Pollock is to be greatly preferred. The soft palate being put upon the stretch, a double-edged knife is passed through it just on the inner side of the hamular process 1 Journal of Anatomy and Physiology, vol. xxiii. p. 523. 426 THE MUSCLES AND FASCIAE. and above the line of the Levator palati. The handle being now alternately raised and depressed, a sweeping cut is made along the posterior surface of the soft palate, and the knife withdrawn, leaving only a small opening in the mucous membrane on the anterior surface. If this operation is performed on the dead body and the parts afterward dissected, the Levator palati will be found completely divided. In the present day, however, this division of the muscles, as part of the operation of staphylorraphy, is not so much insisted upon. All tension is prevented by making longitudinal incisions on either side, parallel to the cleft and just internal to the hamular process, in such a position as to avoid the posterior palatine artery. 7. Anterior Vertebral Region. Rectus capitis anticus major. Rectus capitis anticus minor. Rectus capitis lateralis. Longus colli. The Rectus capitis anticus major (Fig. 284), broad and thick above, narrow below, appears like a continuation upward of the Scalenus anticus. It arises by Fig. 284.-The prevertebral muscles. four tendinous slips from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and ascends, converging toward its fellow of the opposite side, to be inserted into the basilar process of the occip- ital bone. Relations.-By its anterior surface, with the pharynx, the sympathetic nerve, and the sheath enclosing the internal and common carotid artery, internal jugular vein, and pneumogastric nerve ; by its posterior surface, with the Longus colli, the Rectus capitis anticus minor, and the upper cervical vertebrae. lhe Rectus capitis anticus minor is a short, flat muscle, situated immediately behind the upper part of the preceding. It arises from the anterior surface of the lateral mass of the atlas and from the root of its transverse process, and, passing THE LATERAL VERTEBRAL REGION. 427 obliquely upward and inward, is inserted into the basilar process immediately behind the preceding muscle. Relations.-By its anterior surface, with the Rectus capitis anticus major; by its posterior surface, with the front of the occipito-atlantal articulation. The Rectus capitis lateralis is a short, flat muscle, which arises from the upper surface of the transverse process of the atlas, and is inserted into the under surface of the jugular process of the occipital bone. Relations.-By its anterior surface, with the internal jugular vein ; by its pos- terior surface, with the vertebral artery. On its outer side lies the occipital artery; on its inner side, the suboccipital nerve. The Longus colli is a long, flat muscle, situated on the anterior surface of the spine, between the atlas and the third dorsal vertebra. It is broad in the middle, narrow and pointed at each extremity, and consists of three portions: a superior oblique, an inferior oblique, and a vertical portion. The superior oblique portion arises from the anterior tubercles of the transverse processes of the third, fourth, and fifth cervical vertebrae, and, ascending obliquely inward, is inserted by a nar- row tendon into the tubercle on the anterior arch of the atlas. The inferior oblique portion, the smallest part of the muscle, arises from the front of the bodies of the first two or three dorsal vertebrae, and, ascending obliquely outward, is inserted into the anterior tubercles of the transverse processes of the fifth and sixth cervical vertebrae. The vertical portion lies directly on the front of the spine ; it arises, below, from the front of the bodies of the upper three dorsal and lower three cervical vertebrae, and is inserted above into the front of the bodies of the second, third, and fourth cervical vertebrae above. Relations.-By its anterior surface, with the pharynx, the oesophagus, sympa- thetic nerve, the sheath of the great vessels of the neck, the inferior thyroid artery, and recurrent laryngeal nerve; by its posterior surface, with the cervical and dorsal portions of the spine. Its inner border is separated from the opposite muscle by a considerable interval below, but they approach each other above. 8. Lateral Vertebral Region. Scalenus anticus. Scalenus posticus. Scalenus medius. The Scalenus anticus is a conical-shaped muscle, situated deeply at the side of the neck, behind the Sterno-mastoid. It arises from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and, descending almost vertically, is inserted by a narrow, flat tendon into the impression on the inner border and upper surface of the first rib. The lower part of this muscle separates the subclavian artery and vein, the latter being in front, and the former, with the brachial plexus, behind. Relations.-In front, with the clavicle, the Subclavius, Sterno-mastoid, and Omo-hyoid muscles, the transversalis colli, the suprascapular and ascending cer- vical arteries, the subclavian vein, and the phrenic nerve ; its posterior surface, with the Scalenus medius, pleura, the subclavian artery, and brachial plexus of nerves. It is separated from the Longus colli, on the inner side, by the vertebral artery. On the anterior tubercles of the transverse processes of the cervical ver- tebrae, between the attachments of the Scalenus anticus and Longus colli, lies the ascending cervical branch of the inferior thyroid artery. The Scalenus medius, the largest and longest of the three Scaleni, arises from the posterior tubercles of the transverse processes of the lower six cervical vertebrae, and, descending along the side of the vertebral column, is inserted by a broad attachment into the upper surface of the first rib, behind the groove for the sub- clavian artery, as far back as the tubercle. It is separated from the Scalenus anticus by a subclavian artery below and the cervical nerves above. The pos- terior thoracic, or nerve of Bell, is formed in the substance of the Scalenus medius and emerges from it. 428 THE MUSCLES AND FASCIAE Relations.-By its anterior surface, with the Sterno-mastoid; it is crossed by the clavicle, the Omo-hyoid muscle, subclavian artery, and the cervical nerves. To its outer side is the Levator anguli scapulae and the Scalenus posticus muscle. The Scalenus posticus, the smallest of the three Scaleni, arises, by two or three separate tendons, from the posterior tubercles of the transverse processes of the lower two or three cervical vertebrae, and, diminishing as it descends, is inserted by a thin tendon into the outer surface of the second rib, behind the attachment of the Serratus magnus. This is the most deeply placed of the three Scaleni, and is occasionally blended with the Scalenus medius. Nerves.-The Rectus capitis anticus major and minor and the Rectus lateralis are supplied by the first cervical nerve, and from the loop formed between it and STY LO-G LOSSUS. / STYLO-HYOID. OBLIQUUS CAPITIS z I SUPERIOR. -STERNO-H YOI D.. TRANSVERSALIS COLLI. CRICO-THYROID. Trachea. "(Esophagus. STERNO-CLEI DO- ST MASTOID. SERRATUS MAGNUS. England2)85 ~Muscles of the neck> <From a preparation in the Museum of the Royal College of Surgeons of the second ; the Longus colli and Scaleni, by branches from the anterior divisions of the lower cervical nerves (fifth, sixth, seventh, and eighth) before they form the brachial plexus. 1 he Scalenus medius also receives a filament from the deep external branches of the cervical plexus. Actions.- I he Rectus anticus major and minor are the direct antagonists of the muscles at the back of the neck, serving to restore the head to its natural position after it has been drawn backward. These muscles also serve to flex the head, and, OF THE TRUNK. 429 from their obliquity, rotate it, so as to turn the face to one or the other side. The Longus colli flexes and slightly rotates the cervical portion of the spine. The Scaleni muscles, when they take their fixed point from above, elevate the first and second ribs, and are, therefore, inspiratory muscles. When they take their fixed point from below, they bend the spinal column to one or the other side. If the muscles of both sides act, lateral movement is prevented, but the spine is slightlv flexed. The Rectus lateralis, acting on one side, bends the head laterally. Surface Form.-The muscles in the neck, with the exception of the Platysma myoides, are invested by the deep cervical fascia, which softens down their form, and is of considerable importance in connection with deep cervical abscesses and tumors, modifying the direction of their growth and causing them to extend laterally instead of toward the surface. The Platysma myoides doesnot influence surface form except it is in action, when it produces wrinkling of the skin of the neck, which is thrown into oblique ridges parallel with the fasciculi of the muscle. Sometimes this contraction takes place suddenly and repeatedly as a sort of spasmodic twitching, the result of a nervous habit. The Sterno-deido-mastoid is the most important muscle of the neck as regards its surface form. If the muscle is put into action by drawing the chin down- ward and to the opposite shoulder, its surface form will be plainly outlined. The sternal origin will stand out as a sharply-defined ridge, while the clavicular origin will present a flatter and not so prominent an outline. The fleshy middle portion will appear as an oblique roll or elevation, with a thick rounded anterior border gradually becoming less marked above. On the opposite side-i. e. on the side to which the head is turned-the outline is lost, its place being occupied by an oblique groove in the integument. When the muscle is at rest its anterior border is still ■visible, forming an oblique rounded ridge, terminating below in the sharp outline of the sternal head. The posterior border of the muscle does not show above the clavicular head. The anterior border is defined by drawing a line from the tip of the mastoid process to the sterno- clavicular joint. It is an important surface-marking in the operation of ligature of the common carotid artery and some other operations. Between the sternal and clavicular heads is a slight depression, most marked when the muscle is in action. This is bounded below by the prominent sternal extremity of the clavicle. Between the sternal origins of the two muscles is a V-shaped space, the suprasternal notch, more pronounced below, and becoming toned down above, where the Sterno-hyoid and Sterno-thyroid muscles, lying upon the trachea, become more prominent. Above the hyoid bone, in the middle line, the anterior belly of the Digastric to a certain extent influences surface form. It corresponds to a line drawn from the symphysis of the lower jaw to the side of the body of the hyoid bone, and renders this part of the hyo-mental region convex. In the posterior triangle of the neck, the posterior belly of the Omo-hyoid, when inaction, forms a conspicuous object, especially in thin necks, presenting a cord-like form running across this region, almost parallel with, and a little above, the clavicle. MUSCLES AND FASCIA OF THE TRUNK. The muscles of the Trunk may be arranged in four groups : the muscles of the Back, of the Thorax, of the Abdomen, and of the Perinaeum. The muscles of the Back are very numerous, and may be subdivided into five layers. THE BACK. First Layer. Trapezius. Latissimus dorsi. Second Layer. Levator anguli scapulae. Rhomboideus minor. Rhomboideus major. Third Layer. Serratus posticus superior. Serratus posticus inferior. Splenius capitis. Splenius colli. Fourth Layer. Sacral and Lumbar Regions. Erector spinae. Dorsal Region. Ilio-costalis. Musculus accessorius ad ilio-costalem. Longissimus dorsi. Spinalis dorsi. Cervical Region. Cervicalis ascendens. Transversalis colli. 430 THE MUSCLES AND FASCIAE Trachelo-mastoid. Complexus. Biventer cervicis. Spinalis colli. Fifth Layer. Semispinalis dorsi. Semispinalis colli. Multifidus spin®. Rotatores spin®. Supraspinales. Interspinales. Extensor coccygis. Intertransversales. Rectus capitis posticus major. Rectus capitis posticus minor. Obliquus capitis superior. Obliquus capitis inferior. First Layer. Trapezius. Latissimus dorsi. Dissection (Fig. 286).-Place the body in a prone position, with the arms extended over the sides of the table, and the chest and abdomen supported by several blocks, so as to render the muscles tense. Then make an incision along the middle line of the back from the occipital protuberance to the coccyx. Make a transverse incision from the upper end of this to the mastoid process, and a third incision from its lower end, along the crest of the ilium to about its middle. This large intervening space should, for convenience of dissection, be sub- divided by a fourth incision, extending obliquely from the spinous process of the last dorsal vertebra, upward and outward, to the acromion process. This incision corresponds with the lower border of the Trapezius muscle. The flaps of integument are then to be re- moved in the direction shown in the figure. The superficial fascia is exposed upon re- moving the skin from the back. It forms a layer of considerable thickness and strength, in which a quantity of granular pinkish fat is contained. It is continuous with the super- ficial fascia in other parts of the body. The deep fascia is a dense fibrous layer attached to the occipital bone, the spines of the vertebrse, the crest of the ilium, and the spine of the scapula. It covers over the superficial muscles, forming sheaths for them, and is continuous, in the neck at the anterior border of the Tra- pezius, with the deep cervical fascia; in the thorax, with the deep fascia of the axilla and chest, and in the abdomen with that covering the abdominal muscles. The Trapezius (Fig. 287) is a broad, flat, triangular muscle, placed immediately be- neath the skin and fascia, and covering the upper and back part of the neck and shoulders. iFarises from the inner third of the superior curved line of the occipital bone; from the ligamentum nuchae, the spinous process of the seventh cervical, and those of all the dorsal vertebrae; and from the corresponding portion of the supraspinous ligament. From this origin the superior fibres proceed downward and outward, the inferior ones -upward and outward, and the middle fibres horizontally, and are inserted, the superior ones into the outer third of the posterior border of the clavicle; the middle fibres into the inner margin of the acromion process, and into the superior lip of the posterior border or crest of the spine of the scapula; the inferior fibres converge near the scapula, and terminate in a triangular aponeurosis, which glides over a smooth surface at the inner extremity of the spine, to be inserted into a tubercle at the outer part of this smooth surface. The Trapezius is fleshy in the greater part of its extent, but tendinous at its origin baCk.IG-286-Dissectionofthemusclesofthe OF THE BACK. 431 Triangle of Petit.~ Fig. 287.-Muscles of the back. On the left side is exposed the first layer; on the right side, the second layer and part of the third. and insertion. At its occipital origin it is connected to the bone by a thin fibrous lamina, firmly adherent to the skin, and wanting the lustrous, shining appearance 432 THE MUSCLES AND FASCLE of aponeuroses. At its origin from the spines of the vertebrae it is connected to the bones by means of a broad semi-elliptical aponeurosis, which occupies the space between the sixth cervical and the third dorsal vertebrae, and forms, with the aponeurosis of the opposite muscle, a tendinous ellipse. The rest of the muscle arises by numerous short tendinous fibres. If the Trapezius is dissected on both sides, the two muscles resemble a trapezium or diamond-shaped quadrangle; two angles corresponding to the shoulders; a third to the occipital protuberance; and the fourth to the spinous process of the last dorsal vertebra. The clavicular insertion of this muscle varies as to the extent of its attach- ment ; it sometimes advances as far as the middle of the clavicle, and may even become blended with the posterior edge of the Sterno-mastoid or overlap it. This should be borne in mind in the operation for tying the third part of the subclavian artery. Relations.-By its superficial surface, with the integument; by its deep surface, in the neck, with the Complexus, Splenius, Levator anguli scapulae, and Rhomboideus minor; in the back, with the Rhomboideus major, Supraspinatus, Infraspinatus, and Vertebral aponeurosis (which separates it from the prolongations of the Erector spinae), and the Latissimus dorsi. The spinal accessory nerve and the superficial cervical artery pass beneath the anterior border of this muscle, near the clavicle. The anterior margin of its cervical portion forms the posterior boundary of the posterior triangle of the neck, the other boundaries being the Sterno- mastoid in front and the clavicle below. The Ligamentum nuchae (Fig. 287) is a thin band of condensed cellulo-fibrous membrane placed in the line of union between the two Trapezii in the neck. It extends from the external occipital protuberance to the spinous process of the seventh cervical vertebra, where it is continuous with the supraspinous ligament. From its anterior surface a fibrous lamina is given off, which is attached to the spinous process of each of the cervical vertebrae, excepting the atlas, so as to form a septum between the muscles on each side of the neck. In man it is merely the rudiment of an important elastic ligament which, in some of the lower animals, serves to sustain the weight of the head. The Latissimus dorsi is a broad flat muscle which covers the lumbar and the lower half of the dorsal regions, and is gradually contracted into a narrow fasciculus at its insertion into the humerus. It arises by an aponeurosis from the spinous processes of the six inferior dorsal, from those of the lumbar and sacral vertebrae, and from the supraspinous ligament. Over the sacrum the aponeurosis of this muscle blends with the posterior layer of the lumbar fascia. It also arises from the external lip of the crest of the ilium, behind the origin of the External oblique, and by fleshy digitations from the three or four lower ribs, which are interposed between similar processes of the External oblique muscle (Fig. 292, page 451). From this extensive origin the fibres pass in different directions, the upper ones horizontally, the middle obliquely upward, and the lower vertically upward, so as to converg'e and form a thick fasciculus, which crosses the inferior angle of the scapula, and occasionally receives a few fibres from it. The muscle then curves around the lower border of the Teres major, and is twisted upon itself, so that the superior fibres become at first posterior and then inferior, and the vertical fibres at first anterior and then superior. It then terminates in a short quadrilateral tendon, about three inches in length, which, passing in front of the tendon of the Teres major, is inserted into the bottom of the bicipital groove of the humerus, its insertion extending higher on the humerus than that of the tendon of the Pectoralis major. The lower border of the tendon of this muscle is united with that of the Teres major, the surfaces of the two being separated bv a bursa; another bursa is sometimes interposed between the muscle and the inferior angle of the scapula. This muscle at its insertion gives off an expansion to the deep fascia of the arm. A muscular slip, varying from 3 to 4 inches in length, and from f to i of an inch in breadth, occasionally arises from the upper edge of the Latissimus dorsi about the middle of the posterior OF THE BACK. 433 fold of the axilla, and crosses the axilla in front of the axillary vessels and nerves, to join the under surface of the tendon of the Pectoralis major, the Coraco-brachialis, or the fascia over the Biceps. The position of this abnormal slip is a point of interest in its relation to the axillary artery, as it crosses the vessel just above the spot usually selected for the application of a ligature, and may mislead the surgeon during the operation. It may be easily recognized by the transverse direction of its fibres. Dr. Struther found it, in 8 out of 105 subjects, occurring seven times on both sides. Relations.-Its superficial surface is subcutaneous, excepting at its upper part, where it is covered by the Trapezius, and at its insertion, where its tendon is crossed by the axillary vessels and the brachial plexus of nerves. By its deep surface it is in relation with the Lumbar fascia, the Serratus posticus inferior, the lower external intercostal muscles and ribs, inferior angle of the scapula, Rhom- boideus major, Infraspinatus, and Teres major. Its outer margin is separated below from the External oblique by a small triangular interval; and another triangular interval exists between its upper border and the margin of the Trapezius, in which the Rhomboideus major muscle is exposed. Nerves.-The Trapezius is supplied by the spinal accessory, and by branches from the anterior divisions of the third and fourth cervical nerves: the Latissimus dorsi, by the middle or long subscapular nerve. Second Layer. Levator anguli scapulae. Rhomboideus major. Rhomboideus minor. Dissection.-The Trapezius must be removed, in order to expose the next layer; to effect this, detach the muscle from its attachment to the clavicle and spine of the scapula, and turn it back toward the spine. The Levator anguli scapulae is situated at the back part and side of the neck. It arises by tendinous slips from the posterior tubercles of the transverse processes of the four upper cervical vertebrae; these, becoming fleshy, are united so as to form a flat muscle, which, passing downward and backward, is inserted into the posterior border of the scapula, between the superior angle and the triangular smooth surface at the root of the spine. Relations.-By its superficial surface, with the integument, Trapezius, and Sterno-mastoid; by its deep surface, with the Splenius colli, Transversalis colli, Cervicalis ascendens, and Serratus posticus superior muscles, and with the trans- versalis colli and posterior scapular arteries. The Rhomboideus minor arises from the ligamentum nuchae and spinous processes of the seventh cervical and first dorsal vertebrae. Passing downward and outward, it is inserted into the margin of the triangular smooth surface at the root of the spine of the scapula. This small muscle is usually separated from the Rhomboideus major by a slight cellular interval. Relations.-By its superficial (posterior) surface, with the Trapezius; by its deep surface, with the same structures as the Rhomboideus major. The Rhomboideus major is situated immediately below the preceding, the adjacent margins of the two being occasionally united. It arises by tendinous fibres from the spinous processes of the four or five upper dorsal vertebrae and the supraspinous ligament, and is inserted into a narrow tendinous arch attached above to the lower part of the triangular surface at the root of the spine; below, to the inferior angle, the arch being connected to the border of the scapula by a thin membrane. When the arch extends, as it occasionally does, but a short distance, the muscular fibres are inserted into the scapula itself. Relations.-By its superficial (posterior) surface, with the Latissimus dorsi; by its deep (anterior) surface, with the Serratus posticus superior, posterior scapular artery, the vertebral aponeurosis which separates it from the prolongations from the Erector spinae, the Intercostal muscles, and ribs. Nerves.-The Rhomboid muscles are supplied by branches from the anterior 434 7777? MUSCLES AND FAS CEE division of the fifth cervical nerve; the Levator anguli scapulae, by the anterior division of the third and fourth cervical nerves. Actions.-The movements effected by the preceding muscles are numerous, as may be conceived from their extensive attachment. The whole of the Trapezius when in action retracts the scapula and rotates it on a sagittal axis ; if the head is fixed, the upper part of the Trapezius will elevate the point of the shoulder, as in supporting weights; when the lower fibres are brought into action, they assist in depressing the bone. If the scapula is prevented from gliding on the chest, the middle and lower fibres of the muscle cause it to rotate, so that the acromion is raised. If the shoulders are fixed, both Trapezii, acting together, will draw the head directly backward; or if only one acts, the head is drawn to the corresponding side. The Latissimus dorsi, when it acts upon the humerus, draws it backward, adducts, and at the same time rotates it inward. It is the muscle which is principally employed in giving a downward blow, as in felling a tree or in sabre practice. If the arm is fixed, the muscle may act in various ways upon the trunk ; thus, it may raise the lower ribs and assist in forcible inspiration ; or, if both arms are fixed, the two muscles may assist the Abdominal and great Pectoral muscles in suspending and drawing the whole trunk forward, as in climbing or walking on crutches. The Levator anguli scapulce raises the superior angle of the scapula, assisting the Trapezius in bearing weights or in shrugging the shoulders. If the shoulder be fixed, the Levator anguli scapulae inclines the neck to the corresponding side and rotates it in the same direction. The Rhomboid muscles carry the inferior angle backward and upward, thus producing a slight rotation of the scapula upon the side of the chest, the Rhomboideus major acting especially on the lower angle of the scapula through the tendinous arch by which it is inserted. The Rhomboid muscles, acting together with the middle and inferior fibres of the Trapezius, will draw the scapula directly backward toward the spine. Third Layer. Serratus posticus superior. Splenius Splenius capitis. rjL . L. Splenius colli. Serratus posticus inferior. Dissection.-To bring into view the third layer of muscles, remove the whole of the second, together with the Latissimus dorsi, by cutting through the Levator anguli scapulae and Rhom- boid muscles near their insertion, and reflecting them upward, and by dividing the Latissimus dorsi in the middle by a vertical incision carried from its upper to its lower part, and reflecting the two halves of the muscle. The Serratus posticus superior is a thin, flat, quadrilateral muscle situated at the upper and back part of the thorax. It arises by a thin and broad aponeurosis from the ligamentum nuchae, and from the spinous processes of the last cervical and two or three upper dorsal vertebrae and from the supraspinous ligament. Inclining downward and outward, it becomes muscular, and is inserted, by four fleshy digitations into the upper borders of the second, third, fourth, and fifth ribs, a little beyond their angles. Relations.-By its superficial surface, with the Trapezius, Rhomboidei, and Levator anguli scapulae; by its deep surface, with the Splenius and the vertebral aponeurosis, which separates it from the prolongations of the Erector spinae, and with the Intercostal muscles and ribs. The Serratus posticus inferior is situated at the junction of the dorsal and lumbar regions; it is of an irregularly quadrilateral form, broader than the preceding, and separated from it by a considerable interval. It arises by a thin aponeurosis from the spinous processes of the last two dorsal and two or three upper lumbar vertebrae, and from the supraspinous ligaments. Passing obliquely upward and outward, it becomes fleshy, and divides into four flat digitations, which are inserted into the lower borders of the four lower ribs, a little beyond their angles. OF THE BACK. 435 The thin aponeurosis of origin is intimately blended with the tendon of origin of the Latissimus dorsi muscle and with the lumbar fascia. Relations.-By its superficial surface, with the Latissimus dorsi, with the aponeurosis of which its own aponeurotic origin is inseparably blended; by its deep surface, with the lumbar fascia, the Erector spinae, ribs, and Intercostal muscles. Its upper margin is continuous with the vertebral aponeurosis. The Vertebral aponeurosis is a thin, fibrous lamina extending along the whole length of the back part of the thoracic region, serving to bind down the long extensor muscles of the back which support the spine and head, and separate them from those muscles which connect the spine to the upper extremity. It con- sists of longitudinal and transverse fibres blended together, forming a thin lamella, which is attached in the median line to the spinous processes of the dorsal vertebrae ; externally, to the angles of the ribs ; and below, to the upper border of the Serratus posticus inferior and tendon of origin of the Latissimus dorsi; above, it passes beneath the Serratus posticus superior and the Splenius, and blends with the deep fascia of the neck. The Lumbar fascia (Fig.288) is a thick and strong lamella occupying the interval between the last rib and crest of the ilium. It is attached internally to the spinous processes of the lumbar and sacral vertebrae; above, to the last rib and to the cartilage of the eleventh rib ; below, to the posterior third of the crest of the ilium. Externally, it blends with the Transversalis abdominis muscle. The posterior or superficial surface of this fascia gives attachment to part of the origin of the Latissimus dorsi, to the Serratus posticus inferior, and to the Internal oblique muscle of the abdomen. The anterior or deep surface gives off two layers : one lies between the Erector spinae and Quadratus lumborum, and is attached to the tips of the transverse processes of the lumbar vertebrae ; the other lies on the anterior or internal surface of the Quadratus lumborum, and is attached to the front part of the same transverse processes. The upper portion of this layer, which extends from the transverse process of the first lumbar vertebra to the apex and lower border of the last rib, constitutes the ligamentum arcuatum externum. Therefore these three layers of the lumbar fascia form two spaces : between the posterior and middle layer is situated the Erector spinae and the Multifidus spinae; between the middle and anterior layers is situated the Quadratus lumborum. • Now detach the Serratus posticus superior from its origin, and turn it outward, when the Splenius muscle will be brought into view. The Splenius is situated at the back of the neck and upper part of the dorsal region. At its origin it is a single muscle, narrow, and pointed in form ; but it soon becomes broader, and divides into two portions, which have separate inser- tions. It arises, by tendinous fibres, from the lower half of the ligamentum nuchae, from the spinous processes of the last cervical and of the six upper dorsal vertebrae, and from the supraspinous ligament. From this origin the fleshy fibres proceed obliquely upward and outward, forming a broad flat muscle, which divides as it ascends into two portions, the Splenius capitis and Splenius colli. The Splenius capitis is inserted into the mastoid process of the temporal bone, and into the rough surface on the occipital bone just beneath the superior curved line. The Splenius colli is inserted, by tendinous fasciculi, into the posterior tubercles of the transverse processes of the two or three upper cervical vertebrae. The Splenius is separated from its fellow of the opposite side by a triangular interval, in which is seen the Complexus. Relations.-By its superficial surface, with the Trapezius, from which it is separated below by the Rhomboidei and the Serratus posticus superior. It is covered at its insertion by the Sterno-mastoid, and at the lower and back part of the neck by the Levator anguli scapulae; by its deep surface, with the Spinalis dorsi, Longissimus dorsi, Semispinalis colli, Complexus, Trachelo-mastoid, and Transversalis colli. 436 THE MUSCLES AND FASCIAE Nerves.-The Splenius is supplied from the external branches of the posterior divisions of the cervical nerves; the Serratus posticus superior is supplied by the external branches of the posterior divisions of the upper dorsal nerves ; the Serratus posticus inferior by the external branches of the posterior divisions of the lower dorsal nerves. Actions.-The Serrati are respiratory muscles. The Serratus posticus supe- rior elevates the ribs; it is therefore an inspiratory muscle; while the Serratus inferior draws the lower ribs downward and backward, and thus elongates the thorax. It also fixes the lower ribs, thus aiding the downward action of the diaphragm and resisting the tendency which it has to draw the lower ribs upward and forward. It must therefore be regarded as a muscle of inspiration. This muscle is also probably a tensor of the vertebral aponeurosis. The Splenii muscles of the two sides, acting together, draw the head directly backward, assisting the Trapezius and Complexus ; acting separately, they draw the head to one or the other side, and slightly rotate it, turning the face to the same side. They also assist in supporting the head in the erect position. Fourth Layer. Sacral and Lumbar Regions. Erector spin®. Dorsal Region. Ilio-costalis. Musculus accessorius ad ilio-costalem. Longissimus dorsi. Spinalis dorsi. Cervical Region. Cervicalis ascendens. Transversalis colli. Trachelo-mastoid. Complexus. Biventer cervicis. Spinalis colli. Dissection.-To expose the muscles of the fourth layer, remove entirely the Serrati and the vertebral and lumbar fasciae. Then detach the Splenius by separating its attachment to the spinous processes and reflecting it outward. The Erector spin® (Fig. 288) and its prolongations in the dorsal and cervical regions fill up the vertebral groove on each side of the spine. It is covered in the lumbar region by the lumbar fascia; in the dorsal region, by the Serrati muscles and the vertebral aponeurosis; and in the cervical region, by a layer of cervical fascia continued beneath the Trapezius and the Splenius. This large muscular and tendinous mass varies in size and structure at different parts of the spine. In the sacral region the Erector spin® is narrow and pointed, and its origin chiefly tendinous in structure. In the lumbar region the muscle becomes enlarged, and forms a large fleshy mass. In the dorsal region it subdivides into two parts, which gradually diminish in size as they ascend to be inserted into the vertebrae and ribs. In the cervical region it is gradually lost, where a number of small muscles are continued upward to the head to support it upon the spine. The Erector spin® arises from the sacro-iliac groove, and from the anterior surface of a very broad and thick tendon, which is attached, internally, to the spines of the sacrum, to the spinous processes of the lumbar vertebr®, and the supraspinous ligament; externally, to the back part of the inner lip of the crest of the ilium, and to the series of eminences on the posterior part of the sacrum, which represents the transverse processes, where it blends with the great sacro- sciatic ligament. The muscular fibres form a single large fleshy mass, bounded in front by the transverse processes of the lumbar vertebr® and by the middle lamella of the lumbar fascia. Opposite the last rib it divides into two parts, the Ilio- costalis and the Longissimus dorsi. The Ilio-costalis (Sacro-lumbalis}, the external and smaller portion of the Erector spin®, is inserted, generally, by six or seven flattened tendons into the angles of the six or seven lower ribs. The number of the tendons of this muscle is, however, very variable, and therefore the number of ribs into which it is inserted. Frequently it is found to possess nine or ten tendons, and sometimes as many tendons as there are ribs, and is then inserted into the angles of all the ribs. Or THE BACK. 437 Occipital bone. MULTIFIDUS SPIN'S. First dorsal vertebra. 1st rib. -2nd. \3rd. First lumbar vertebra.- First sacral vertebra.- Fig. 288.-Muscles of the back. Deep layers. If this muscle is reflected outward, it will be seen to be reinforced by a series of muscular slips which arise from the angles of the ribs ; by means of these the Ilio- 438 THE MUSCLES AND FASCIAE costalis is continued upward to the upper ribs and cervical portion of the spine. The accessory portions form two additional muscles, the Musculus accessorius and the Cervicalis ascendens. The Musculus accessorius ad ilio-costalem arises, by separate flattened tendons, from the angles of the six lower ribs; these become muscular, and are finally inserted, by separate tendons, into the angles of the six upper ribs. The Cervicalis ascendens1 is the continuation of the Accessorius upward into the neck ; it is situated on the inner side of the tendons of the Accessorius, arising from the angles of the four or five upper ribs, and is inserted by a series of slender tendons into the posterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae. The Longissimus dorsi is the inner and larger portion of the Erector spinae. In the lumbar region, where it is as yet blended with the Ilio-costalis, some of the fibres are attached to the whole length of the posterior surface of the transverse processes of the lumbar vertebrae, to the tubercles at the back of the articular processes, and to the middle layer of the lumbar fascia. In the dorsal region the Longissimus dorsi is inserted, by long thin tendons, into the tips of the transverse processes of all the dorsal vertebrae, and into from seven to eleven of the lower ribs between their tubercles and angles. This muscle is continued upward, to the cranium and cervical portion of the spine by means of two additional muscles, the Transversalis colli and Trachelo-mastoid. The Transversalis colli (or cervicis), placed on the inner side of the Longis- simus dorsi, arises by long thin tendons from the summits of the transverse pro- cesses of the six upper dorsal vertebrae, and is inserted by similar tendons into the posterior tubercles of the transverse processes of the cervical vertebrae from the second to the sixth. The Trachelo-mastoid lies on the inner side of the preceding, between it and the Complexus muscle. It arises, by four tendons, from the transverse processes of the third, fourth, fifth, and sixth dorsal vertebrae, and by additional separate tendons from the articular processes of the three or four lower cervical. The fibres form a small muscle, which ascends to be inserted into the posterior margin of the mastoid process, beneath the Splenius and Sterno-mastoid muscles. This small muscle is almost always crossed by a tendinous intersection near its insertion into the mastoid process.2 Relations.-The Erector spinae and its prolongations are bound down to the vertebrae and ribs in the lumbar and dorsal regions by the lumbar fascia and the vertebral aponeurosis. The inner part of these muscles covers the muscles of the fifth layer. In the neck they are in relation, by their superficial surface, with the Trapezius and Splenius; by their deep surface, with the Semispinalis dorsi et colli and the Recti and Obliqui. The Spinalis dorsi connects the spinous processes of the upper lumbar and the dorsal vertebrae together by a series of muscular and tendinous slips which are intimately blended with the Longissimus dorsi. It is situated at the inner side of the Longissimus dorsi, arising, by three or four tendons, from the spinous pro- cesses of the first two lumbar and the last two dorsal vertebrae: these, uniting, form a small muscle, which is inserted, by separate tendons, into the spinous pro- cesses of the dqrsal vertebrae, the number varying from four to eight. It is intimately united with the Semispinalis dorsi, which lies beneath it. The Spinalis colli is a small muscle, connecting together the spinous processes of the cervical vertebrae, and analogous to the Spinalis dorsi in the dorsal region. It varies considerably in its size and in its extent of attachment to the vertebrae, not only in different bodies, but on the two sides of the same body. It usually arises by fleshy or tendinous slips, varying from two to four in number, from the 'This muscle is sometimes called " Cervicalis descendens." The student should remember that these long muscles take their fixed point from above or from below according to circumstances. 2 .These two muscles are sometimes described as one, having a common origin, but dividing above at their insertion. The Trachelo-mastoid is then termed the Transversalis capitis. OF THE BACK. 439 spinous processes of the fifth, sixth, and seventh cervical vertebrae, and occasionally from the first and second dorsal, and is inserted into the spinous process of the axis, and occasionally into the spinous processes of the two vertebrae below it. This muscle was found absent in five cases out of twenty-four. The Complexus is a broad thick muscle, situated at the upper and back part of the neck, beneath the Splenius, and internal to the Transversalis colli and Trachelo- mastoid. It arises, by a series of tendons, about seven in number, from the tips of the transverse processes of the upper three dorsal and seventh cervical vertebrae, and from the articular processes of the three cervical above this. The tendons, uniting, form a broad muscle, which passes obliquely upward and inward, and is inserted into the innermost depression between the two curved lines of the occipital bone. This muscle, about its middle, is traversed by a transverse tendi- nous intersection. The Biventer cervicis is a small fasciculus, situated on the inner side of the preceding, and in the majority of cases blended with it; it has received its name from having a tendon intervening between two fleshy bellies. It is sometimes described as a separate muscle, arising, by from two to four tendinous slips, from the transverse processes of as many of the upper dorsal vertebrae, and inserted, on the inner side of the Complexus, into the superior curved line of the occipital bone. Relations.-The Complexus is covered by the Splenius and the Trapezius. It lies on the Rectus capitis posticus major and minor, the Obliquus capitis superior and inferior, and on the Semispinalis colli, from which it is separated by the pro- funda cervicis artery, the princeps cervicis artery, and branches of the posterior cervical plexus of nerves. The Biventer cervicis is separated from its fellow of the opposite side by the ligamentum nuchae. Nerves.-The Erector spinae and its subdivisions in the dorsal region are supplied by the external branches of the posterior divisions of the lumbar and dorsal nerves, while its subdivisions in the cervical region, the Transversalis colli and Trachelo-mastoid, are supplied by the external branches of the posterior divisions of the cervical nerves ; the Complexus, by the internal branches of the posterior divisions of the cervical nerves, the suboccipital and great occipital. The Spinalis colli is supplied by the internal branches of the posterior divisions of the cervical nerves ; and the Spinalis dorsi, by the internal branches of the pos- terior divisions of the dorsal nerves. Fifth Layer. Semispinalis dorsi. Semispinalis colli. Multifidus spinae. Rotatores spinae. Supraspinales. Interspinales. Extensor coccygis. Intertransversales. Rectus capitis posticus major. Rectus capitis posticus minor. Obliquus capitis superior. Obliquus capitis inferior. Dissection.-Remove the muscles of the preceding layer by dividing and turning aside the Complexus; then detach the Spinalis and Longissimus dorsi from their attachments, divide the Erector spinae at its connection below to the sacral and lumbar spines, and turn it outward. The muscles filling up the interval between the spinous and transverse processes are then exposed. The Semispinalis dorsi (Fig. 288) consists of thin, narrow, fleshy fasciculi interposed between tendons of considerable length. It arises by a series of small tendons from the transverse processes of the lower dorsal vertebrae, from the tenth or eleventh to the fifth or sixth; and is inserted, by five or six tendons, into the spinous processes of the upper four dorsal and lower two cervical vertebrae. The Semispinalis colli, thicker than the preceding, arises by a series of tendinous and fleshy fibres from the transverse processes of the upper four dorsal vertebrae and from the'articular processes of the lower four cervical vertebrae; and is inserted into the spinous processes of four cervical vertebrae, from the axis to the 440 THE MUSCLES AND FASCIAE fifth cervical. The fasciculus connected with the axis is the largest, and chiefly muscular in structure. Relations.-By their superficial surface, from below upward, with the Spinalis dorsi, Longissimus dorsi, Splenius, Complexus, the profunda cervicis artery, the princeps cervicis artery, and the internal branches of the posterior divisions of the first, second, and third cervical nerves; by their deep surface, with the Mul- tifidus spinae. The Multifidus spinae consists of a number of fleshy and tendinous fasciculi which fill up the groove on either side of the spinous processes of the vertebrae, from the sacrum to the axis. In the sacral region these fasciculi arise from the back of the sacrum, as low as the fourth sacral foramen, and from the aponeurosis of origin of the Erector spinae; in the iliac region, from the inner surface of the posterior superior spine of the ilium and posterior sacro-iliac ligaments ; in the lum- bar regions, from the articular processes; in the dorsal region, from the trans- verse processes ; and in the cervical region, from the articular processes. Each fasciculus, passing obliquely upward and inward, is inserted into the lamina and whole length of the spinous process of one of the vertebrae above. These fasciculi vary in length : the most superficial, the longest, pass from one vertebra to the third or fourth above ; those next in order pass from one vertebra to the second or third above ; whilst the deepest connect two contiguous vertebrae. Relations.-By its superficial surface, with the Longissimus dorsi, Spinalis dorsi, Semispinalis dorsi, and Semispinalis colli ; by its deep surface, with the laminae and spinous processes of the vertebrae, and with the Rotatores spinae in the dorsal region. The Rotatores spinae are found only in the dorsal region of the spine, beneath the Multifidus spinae; they are eleven in number on each side. Each muscle is small and somewhat quadrilateral in form ; it arises from the upper and back part of the transverse process, and is inserted into the lower border and outer surface of the lamina of the vertebra above, the fibres extending as far inward as the root of the spinous process. The first is found between the first and second dorsal; the last, between the eleventh and twelfth. Sometimes the number of these muscles is diminished by the absence of one or more from the upper or lower end. The Supraspinales consist of a series of fleshy bands which lie on the spinous processes in the cervical region of the spine. The Interspinales are short muscular fasciculi, placed in pairs between the spinous processes of the contiguous vertebrae, one on each side of the interspinous ligament. In the cervical region they are most distinct, and consist of six pairs, the first being situated between the axis and third vertebra, and the last between the last cervical and the first dorsal. They are small narrow bundles, attached, above and below, to the apices of the spinous processes. In the dorsal region they are found between the first and second vertebrae, and occasionally between the second and third; and below, between the eleventh and twelfth. In the lumbar region there are four pairs of these muscles in the intervals between the five lumbar vertebrae. There is also occasionally one in the interspinous space, between the last dorsal and first lumbar, and between the fifth lumbar anti the sacrum. The Extensor coccygis is a slender muscular fasciculus, occasionally present, which extends over the lower part of the posterior surface of the sacrum and coccyx. It arises by tendinous fibres from the last bone of the sacrum or first piece of the coccyx, and passes downward to be inserted into the lower part of the coccyx. It is a rudiment of the Extensor muscle of the caudal vertebrae which exists in some animals. The Intertransversales are small muscles placed between the transverse pro- cesses of the vertebrae. In the cervical region they are most developed, consisting of rounded muscular and tendinous fasciculi, which are placed in pairs, passing between the two anterior and the two posterior tubercles of the transverse processes OF THE BACK. 441 of two contiguous vertebrae, separated from one another by the anterior division of the cervical nerve, which lies in the groove between them. In this region there are seven pairs of these muscles, the first pair being between the atlas and axis, and the last pair between the seventh cervical and first dorsal vertebrae. In the dorsal region they are least developed, consisting chiefly of rounded tendinous cords in the intertransverse spaces of the upper dorsal vertebrae; but between the transverse processes of the lower three dorsal vertebrae, and between the transverse processes of the last dorsal and the first lumbar, they are muscular in structure. In the lumbar region they are four in number, and consist of a single muscular layer, which occupies the entire interspace between the transverse processes of the lower lumbar vertebrae, whilst those between the transverse processes of the upper lumbar are not attached to more than half the breadth of the process. The Rectus capitis posticus major arises by a pointed tendinous origin from the spinous process of the axis, and, becoming broader as it ascends, is inserted into the inferior curved line of the occipital bone and the surface of bone immediately below it. As the muscles of the two sides pass upward and outward, they leave between them a triangular space, in which are seen the Recti capitis postici minores muscles. Relations.-By its superficial surface, with the Complexus, and, at its inser- tion, with the Superior oblique ; by its deep surface, with part of the Rectus capitis posticus minor, the posterior arch of the atlas, the posterior occipito-atlantal liga- ment, and part of the occipital bone. The Rectus capitis posticus minor, the smallest of the four muscles in this region, is of a triangular shape ; it arises by a narrow pointed tendon from the tubercle on the posterior arch of the atlas, and, becoming broader as it ascends, is inserted into the rough surface beneath the inferior curved line, nearly as far as the foramen magnum, nearer to the middle line than the preceding. Relations.-By its superficial surface, with the Complexus and the Rectus capitis posticus major; by its deep surface, with the posterior occipito-atlantal ligament. The Obliquus capitis inferior, the larger of the two Oblique muscles, arises from the apex of the spinous process of the axis, and passes almost horizontally outward, to be inserted into the lower and back part of the transverse process of the atlas. Relations.-By its superficial surface, with the Complexus and with the pos- terior division of the second cervical nerve, which crosses it; by its deep surface, with the vertebral artery and posterior atlanto-axial ligament. The Obliquus capitis superior, narrow below, wide and expanded above, arises by tendinous fibres from the upper surface of the transverse process of the atlas, joining with the insertion of the preceding, and, passing obliquely upward and inward, is inserted into the occipital bone, between the two curved lines, external to the Complexus. Relations.-By its superficial surface, with the Complexus and Trachelo-mastoid. By its deep surface, with the posterior occipito-atlantal ligament. The Suboccipital Triangle.-Between the two oblique muscles and the Rectus capitis posticus major a triangular interval exists, the suboccipital triangle. This triangle is bounded, above and internally, by the Rectus capitis posticus major; above and externally, by the Obliquus capitis superior; below and externally, by the Obliquus capitis inferior. It is covered in by a layer of dense fibro-fatty tissue, situated beneath the Complexus muscle. The floor is formed by the posterior occipito-atlantal ligament, the posterior arch of the atlas, and the posterior atlanto- axial ligament. It contains the vertebral artery, as it runs in a deep groove on the upper surface of the posterior arch of the atlas, and the posterior division of the suboccipital nerve. Nerves.-The Semispinalis dorsi and Rotatores spinae are supplied by the internal branches of the posterior divisions of the dorsal nerves; the Semispinalis colli, by the internal branches of the posterior divisions of the cervical nerves ; the 442 THE MUSCLES AND FASCLE. Supraspinales and Interspinales are supplied by the internal branches of the posterior divisions of the cervical, dorsal, and lumbar nerves in the respective regions; the Intertransversales, by the internal branches of the posterior divisions of the cervical, dorsal, and lumbar nerves; the Multifidus spinae, by the same, with the addition of the internal branches of the posterior divisions of the sacral nerves. The Recti and Obliqui muscles are all supplied by the suboccipital nerve ; the Inferior oblique is also supplied by the great occipital nerve. Actions.-When both the Spinales dorsi contract, they extend the dorsal region of the spine; when only one muscle contracts, it helps to bend the dorsal portion of the spine to one side. The Erector spinae, comprising the Ilio-costalis and the Longissimus dorsi with their accessory muscles, serves, as its name implies, to maintain the spine in the erect posture; it also serves to bend the trunk back- ward when it is required to counterbalance the influence of any weight at the front of the body, as, for instance, when a heavy weight is suspended from the neck, or when there is any great abdominal distension, as in pregnancy or dropsy ; the peculiar gait under such circumstances depends upon the spine being drawn backward by the counterbalancing action of the Erector spinae muscles. The muscles which form the continuation of the Erector spinae upward steady the head and neck, and fix them in the upright position. If the Ilio-costalis and Longissimus dorsi of one side act, they serve to draw down the chest and spine to the corresponding side. The Cervicales ascendens, taking their fixed points from the cervical vertebrae, elevate those ribs to which they are attached; taking their fixed points from the ribs, both muscles help to extend the neck ; while one muscle bends the neck to its own side. The Transversalis colli, when both muscles act, taking their fixed point from below, bend the neck backward. The Trachelo- mastoid, when both muscles act, taking their fixed point from below, bend the head backward; while, if only one muscle acts, the face is turned to the side on which the muscle is acting, and then the head is bent to the shoulder. The two Recti muscles draw the head backward. The Rectus capitis posticus major, owing to its obliquity, rotates the cranium, with the atlas, round the odontoid process, turning the face to the same side. The Multifidus spinae acts successively upon the different parts of the spine; thus, the sacrum furnishes a fixed point from which the fasciculi of this muscle act upon the lumbar region; these then become the fixed points for the fasciculi moving the dorsal region, and so on throughout the entire length of the spine; it is by the successive contraction and relaxation of the separate fasciculi of this and other muscles that the spine preserves the erect posture without the fatigue that would necessarily have been produced had this position been maintained by the action of a single muscle. The Multifidus spinae, besides preserving the erect position of the spine, serves to rotate it, so that the front of the trunk is turned to the side opposite to that from which the muscle acts, this muscle being assisted in its action by the Obliquus externus abdominis. The Complexi draw the head directly backward : if one muscle acts, it draws the head to one side, and rotates it so that the face is turned to the opposite side. The Superior oblique draws the head backward, and, from the obliquity in the direction of its fibres, will slightly rotate the cranium, turning the face to the opposite side. The Obliquus capitis inferior rotates the atlas, and with it the cranium, round the odontoid process, turning the face to the same side. The Semispinales, when the muscles of the two sides act together, help to extend the spine ; when the muscles of one side only act, they rotate the dorsal and cervical parts of the spine, turning the body to the opposite side. The Supraspinales and Interspinales by approximating the spinous processes help to extend the spine. The Intertransversales approximate the transverse processes, and help to bend the spine to one side. The Rotatores spinae assist the Multifidus spinae to rotate the spine, so that the front of the trunk is turned to the side opposite to that from which the muscle acts. Surface Forms.-The surface forms produced by the muscles of the back are numerous and difficult to analyze unless they are considered in systematic order. The most superficial layer, OF THE THORAX. 443 consisting of large strata of muscular substance, influences to a certain extent the surface form, and at the same time reveals the forms of the layers beneath. The Trapezius at the upper part of the back, and in the neck, covers over and softens down the outline of the underlying muscles. Its anterior border forms the posterior boundary of the posterior triangle of the neck. It forms a slight undulating ridge which passes downward and forward from the occiput to the junction of the middle and outer third of the clavicle. The tendinous ellipse formed by a part of the origin of the two muscles at the back of the neck is always to be seen as an oval depression, more marked when the muscle is in action. A slight dimple on the skin opposite the interval between the spinous processes of the third and fourth dorsal vertebrae marks the triangular aponeurosis by which the inferior fibres are inserted into the root of the spine of the scapula. From this point the inferior border of the muscle may be traced as an undulating ridge to the spinous process of the twelfth dorsal vertebra. In like manner, the Latissimus dorsi softens down and modulates the underlying structures at the lower part of the back and lower part of the side of the chest. In this way it modulates the outline of the Erector spinae; of the Serratus posticus inferior, which is sometimes to be discerned through it, and is sometimes entirely obscured by it; of part of the Serratus magnus and Superior oblique, which it covers ; and of the convex oblique ridges formed by the ribs with the intervening intercostal spaces. The anterior border of the muscle is the only part which gives a distinct surface form. This border may be traced, when the muscle is in action, as a rounded edge, starting from the crest of the ilium, and passing obliquely forward and upward to the posterior border of the axilla, where it combines with the Teres major in forming a thick rounded fold, the posterior boundary of the axillary space. The muscles in the second layer influence to a very considerable extent the surface form of the back of the neck and upper part of the trunk. The Levator anguli scapulae reveals itself as a prominent divergent line, running downward and outward, from the transverse pro- cesses of the upper cervical vertebrae to the angle of the scapula, covered over and toned down by the overlying Trapezius. The Rhomboidei produce, when in action, a vertical eminence between the internal border of the scapula and the spinal furrow, varying in intensity according to the condition of contraction or relaxation of the Trapezius muscle, by which they are for the most part covered. The lowermost part of the Rhomboideus major is uncovered by the Trapezius, and forms on the surface an oblique ridge running upward and inward from the inferior angle of the scapula. Of the muscles of the third layer of the back, the Serratus posticus superior does not in any way influence surface form. The Serratus posticus inferior, when in strong action, may occasionally be revealed as an elevation beneath the Latissimus dorsi. The Splenii by their divergence serve to broaden out the upper part of the back of the neck and produce a local fulness in this situation, but do not otherwise influence surface form. Beneath all these muscles those of the fourth layer-the Erector spinor and its continuations-influence the surface form in a decided manner. In the loins, the Erector spinae, bound down by the lumbar fascia, forms a rounded vertical eminence, which determines the depth of the spinal furrow, and which below tapers to a point on the posterior surface of the sacrum and becomes lost there. In the back it forms a flattened plane which gradually becomes lost. • In the neck the only part of this group of muscles which influences surface form is the Trachelo-mastoid, which produces a short convergent line across the upper part of the posterior triangle of the neck, appearing from under cover of the posterior border of the Sterno-mastoid and being lost below beneath the Trapezius. THE THORAX The Muscles exclusively connected with the bones in this region are few in number. They are the Intercostales externi. Intercostales interni. Infracostales. Triangularis sterni. Levatores costarum. Intercostal Fasciae.-A thin but firm layer of fascia covers the outer surface of the External intercostal and the inner surface of the Internal intercostal muscles; and a third layer, the middle intercostal fascia, more delicate, is interposed between the two planes of muscular fibres. These are the intercostal fasciae ; they are best marked in those situations where the muscular fibres are deficient, as between the External intercostal muscles and sternum, in front, and between the Internal intercostals and spine, behind. The Intercostal muscles (Fig. 299) are two thin planes of muscular and tendinous fibres, placed one over the other, filling up the intercostal spaces, and being directed obliquely between the margins of the adjacent ribs. They have received the name "external" and " internal " from the position they bear to one another. The tendinous fibres are longer and more numerous than the muscular; hence the walls of the intercostal spaces possess very considerable strength, to which the crossing of the muscular fibres materially contributes. 444 THE MUSCLES AND EASCEE The External Intercostals are eleven in number on each side. They extend from the tubercles of the ribs, behind, to the commencement of the cartilages of the ribs, in front, where they terminate in a thin membranous aponeurosis, which is continued forward to the sternum. They arise from the lower border of each rib, and are inserted into the upper border of the rib below. In the two lowest spaces they extend to the end of the cartilages. Their fibres are directed obliquely downward and forward, in a similar direction with those of the External oblique muscle of the abdomen. They are thicker than the Internal intercostals. Relations.-By their outer surface, with the muscles which immediately invest the chest-viz. the Pectoralis major and minor, Serratus magnus, and Rhomboideus major, Serratus posticus superior and inferior, Scalenus posticus, Ilio-costalis, Longissimus dorsi, Cervicalis ascendens, Transversalis colli, Levatores costarum, and the Obliquus externus abdominis; by their internal surface, with the middle intercostal fascia, which separates them from the intercostal vessels and nerve, and the Internal intercostal muscles, and, behind, from the pleura. The Internal intercostals are also eleven in number on each side. They commence anteriorly at the sternum, in the interspaces between the cartilages of the true ribs, and from the anterior extremities of the cartilages of the false ribs, and extend backward as far as the angles of the ribs, whence they are continued to the vertebral column by a thin aponeurosis. They arise from the ridge on the inner surface of each rib, as well as from the corresponding costal cartilage, and are inserted into the upper border of the rib below. Their fibres are directed obliquely downward and backward, passing in the opposite direction to the fibres of the External intercostal muscle. Relations.-By their external surface, with the intercostal vessels and nerves, and the middle intercostal fascia, which separates them from the External inter- costal muscles ; by their internal surface, with the internal intercostal fascia, which separates them from the pleura costalis, Triangularis sterni, and Diaphragm. The Infracostales (subcostales) consist of muscular and aponeurotic fasciculi, which vary in number and length : they are placed on the inner surface of the ribs, where the Internal intercostal muscles cease; they arise from the inner surface of one rib, and are inserted into the inner surface of the first, second, or third rib below. Their direction is most usually oblique, like the Internal intercostals. They are most frequent between the lower ribs. The Triangularis sterni is a thin plane of muscular and tendinous fibres, situated upon the inner wall of the front of the chest. It arises from the lower part of the side of the sternum, from the inner surface of the ensiform cartilage, and from the sternal ends of the costal cartilages of the three or four lower true ribs. Its fibres diverge upward and outward, to be inserted by fleshy digitations into the lower border and inner surfaces of the costal cartilages of the second, third, fourth, and fifth ribs. The lowest fibres of this muscle are horizontal in their direction, and are continuous with those of the Transversalis ; those which succeed are oblique, whilst the superior fibres are almost vertical. This muscle varies much in its attachment, not only in different bodies, but on opposite sides of the same body. Relations.-In front, with the sternum, ensiform cartilage, costal cartilages, Internal intercostal muscles, and internal mammary vessels; behind, with the pleura, pericardium, and anterior mediastinum. The Levatores Costarum (Fig. 288), twelve in number on each side, are small tendinous and fleshy bundles, which arise from the extremities of the transverse processes of the seventh cervical and eleven upper dorsal vertebrae, and, passing obliquely downward and outward, are inserted into the upper border of the rib below them, between the tubercle and the angle. That for the first rib arises from the transverse process of the last cervical vertebra, and that for the last from the eleventh dorsal. The Inferior levatores divide into two fasciculi, one of which is inserted as above described; the other fasciculus passes down to the second rib OF THE THORAX. 445 below its origin ; thus, each of the lower ribs receives fibres from the transverse processes of two vertebrae. Nerves. I he muscles of this group are supplied by the intercostal nerves. Actions. I he Intercostals are the chief agents in the movement of the ribs SCALENUS MEDIUS. SCALENUS ANTICUS. STERNO-MASTOI D. ZSTERNO-HYOID. PECTORALIS MAJOR. - \ \ r i / TRIANGULARIS STERNI. TRANSVERSALIS ABDOMINIS Fig. 289.-Posterior surface of sternum and costal cartilages, showing Triangularis sterni muscle. (From a preparation in the Museum of the Royal College of Surgeons of England.) in ordinary respiration. When the first rib is elevated and fixed by the Scaleni, the External intercostals raise the other ribs, especially their fore part, and so increase the capacity of the chest from before backward ; at the same time they evert their lower borders, and so enlarge the thoracic cavity transversely. The Internal intercostals, at the side of the thorax, depress the ribs and invert their lower borders, and so diminish the thoracic cavity ; but at the fore part of the chest these muscles assist the External intercostals in raising the cartilages.1 The Levatores 1 The view of the action of the Intercostal muscles given in the text is that which is taught by Hutchinson (Q/cZ. of Anat. and Phys., art. " Thorax "), and is usually adopted in our schools. It is, however, much disputed. Hamberger believed that the External intercostals act as elevators of the ribs, or muscles of inspiration, while the Internal act in expiration. Haller taught that both sets of muscles act in common-viz. as muscles of inspiration-and this view is adopted by many of the best anatomists of the Continent, and appears supported by many observations made on the human subject under various conditions of disease, and on living animals after the muscles have been exposed under chloroform. The reader may consult an interesting paper by Dr. Cleland in the Journal of Anat. and Phys. No. IL, May, 1867, p. 209, " On the Hutchinsonian Theory of the Action of the Intercostal Muscles," who refers also to Henle, Luschka, Budge, and Baumler, Observations on the Action of the Intercostal Muscles, Erlangen, 1860. (In NetvSyd. Soc.'s Year-Book for 1861, p. 69.) Dr. W. W. Keen has come to the conclusion, from experiments made upon a criminal executed by hanging, that the Exter- 446 THE MUSCLES AND FASCIAE. costarum assist the External intercostals in raising the ribs. The Triangularis sterni draws down the costal cartilages; it is therefore an expiratory muscle. Muscles of Inspiration and Expiration.-The muscles which assist the action of the Diaphragm in ordinary tranquil inspiration are the Intercostals and the Levatores costarum, as above stated, and the Scaleni. hen the need for more forcible action exists, the shouldersand the base of the scapula are fixed, and then the powerful muscles of forced inspiration come into play; the chief of these are the Trapezius, the Pectoralis minor, the Serratus posticus superior and inferior, and the Rhomboidei. The lower fibres of the Serratus magnus may possibly assist slightly in dilating the chest by raising and everting the ribs. The Sterno- mastoid also, when the head is fixed, assists in forced inspiration by drawing up the sternum and by fixing the clavicle, and thus affording a fixed point for the action of the muscles of the chest. The Ilio-costalis and Quadratus lumborum assist in forced inspiration by fixing the last rib (see page 460). The ordinary action of expiration is hardly effected by muscular force, but results from a return of the walls of the thorax to a condition of rest, owing to their own elasticity and to that of the lungs. Forced expiratory actions are performed mainly by the flat muscles (Obliqui and Transversalis) of the abdomen, assisted also by the Rectus. Other muscles of forced expiration are the Internal intercostals and Triangularis sterni (as above mentioned), the Quadratus lumborum, and the Ilio-costalis. THE DIAPHRAGMATIC REGION. The Diaphragm (duiippaypa, a partition wall) (Fig. 290) is a thin musculo- fibrous septum, placed obliquely at the junction of the upper with the middle third of the trunk, and separating the thorax from the abdomen, forming the floor of the former cavity and the roof of the latter. It is elliptical, its longest diameter being from side to side, somewhat fan-shaped, the broad elliptical portion being hori- zontal, the narrow part, which represents the handle of the fan, vertical, and joined at right angles to the former. It is from this circumstance that some anatomists describe it as consisting of two portions, the upper or great muscle of the Diaphragm, and the lower or lesser muscle. It arises from the whole of the internal circumference of the thorax; being attached, in front, by fleshy fibres to the ensiform cartilage; on either side, to the inner surface of the cartilages and bony portions of the six or seven inferior ribs, interdigitating with the Transver- salis; and behind, to two aponeurotic arches, named the ligamentum arcuatum externum et internum, and to the lumbar vertebrae. The fibres from these sources vary in length; those arising from the ensiform appendix are very short and occasionally aponeurotic; those from the ligamenta arcuata, and more especially those from the cartilages of the ribs at the side of the chest, are longer, describe well-marked curves as they ascend, and finally converge to be inserted into the circumference of the central tendon. Between the sides of the muscular slip from the ensiform appendix and the cartilages of the adjoining ribs the fibres of the Diaphragm are deficient, the interval being filled by areolar tissue, covered on the thoracic side by the pleurae; on the abdominal, by the peritoneum. This is, consequently, a weak point, and a portion of the contents of the abdomen may protrude into the chest, forming phrenic or diaphragmatic hernia, or a collection of pus in the mediastinum may descend through it, so as to point at the epigastrium,. The ligamentum arcuatum internum is a tendinous arch, thrown across the upper part of the Psoas magnus muscle, on each side of the spine. It is connected, by one end, to the outer side of the body of the first lumbar vertebra, being continuous with the outer side of the tendon of the corresponding crus; and, by Diaphragm. nal intercostals are muscles of expiration, as they pulled the ribs down, while the Internal intercostals pulled the ribs up and are muscles of inspiration ( Trans. Coll. Phys. Philadelphia, Third Series, vol. i., 1875, p. 97). THE DIAPHRAGMATIC REGION. 447 the other end, to the front of the transverse process of the first, and sometimes also to that of the second, lumbar vertebra. The ligamentum arcuatum externum is the thickened upper margin of the ante- rior lamella of the lumbar fascia; it arches across the upper part of the Quadratus lumborum, being attached, by one extremity, to the front of the transverse process of the first lumbar vertebra, and, by the other, to the apex and lower margin of the last rib. The Crura.-The Diaphragm is connected to the spine by two crura or pillars, which are situated on the bodies of the lumbar vertebrae, on each side of the aorta. The crura, at their origin, are tendinous in structure; the right crus, larger and longer than the left, arising from the anterior surface of the bodies and inter- vertebral substances of the three or four upper lumbar vertebrae; the left, from Fig. 290-The Diaphragm. Under surface. the two upper; both blending with the anterior common ligament of the spine. These tendinous portions of the crura pass forward and inward, and gradually converge to meet in the middle line, forming an arch, beneath which passes the aorta, vena azygos major, and thoracic duct. From this tendinous arch muscular fibres arise, which diverge, the outermost portion being directed upward and outward to the central tendon; the innermost decussating in front of the aorta, and then diverging, so as to surround the oesophagus before ending in the central tendon. The fibres derived from the right crus are the most numerous and pass in front of those derived from the left. The Central or Cordiforni Tendon of the Diaphragm is a thin but strong tendinous aponeurosis, situated at the centre of the vault formed by the muscle, immediately below the pericardium, with which its circumference is blended. It is shaped somewhat like a trefoil leaf, consisting of three divisions, or leaflets, 448 THE MUSCLES AND FASCIAE. separated from one another by slight indentations. The right leaflet is the largest: the middle one, directed toward the ensiform cartilage, the next in size; and the left, the smallest. In structure, the tendon is composed of several planes of fibres, which intersect one another at various angles, and unite into straight or curved bundles-an arrangement which affords it additional strength. The Openings connected with the Diaphragm are three large and several smaller apertures. The former are the aortic, the oesophageal, and the opening for the vena cava. The aortic opening is the lowest and the most posterior of the three large aper- tures connected with this muscle. It is situated in the middle line, immediately in front of the bodies of the vertebrae; and is, therefore, behind the Diaphragm, not in it. It is an osseo-aponeurotic aperture, formed by a tendinous arch thrown across the front of the bodies of the vertebrae, from the crus on one side to that on the other, and transmits the aorta, vena azygos major, thoracic duct, and sometimes the left sympathetic nerve. Occasionally some tendinous fibres are prolonged across the bodies of the vertebrae from the inner part of the lower end of the crura, passing behind the aorta, and thus converting the opening into a fibrous ring. The oesophageal opening, elliptical in form, muscular in structure, and formed by the two crura, is placed above, and, at the same time, anterior, and a little to the left of, the preceding. It transmits the oesophagus and pneumogastric nerves. The anterior margin of this aperture is occasionally tendinous, being formed by the margin of the central tendon. The opening for the vena cava (foramen qiiadratum) is the highest; it is quad- rilateral in form, tendinous in structure, and placed at the junction of the right and middle leaflets of the central tendon, its margins being bounded by four bundles of tendinous fibres, which meet at right angles. The right crus transmits the sympathetic and the greater and lesser splanchnic nerves of the right side; the left crus, the greater and lesser splanchnic nerves of the left side and the vena azygos minor. The Serous Membranes in relation with the Diaphragm are four in number: three lining its upper or thoracic surface; one, its abdominal. The three serous membranes on its upper surface are the pleura on either side and the serous layer of the pericardium, which covers the middle portion of the tendinous centre. The serous membrane covering its under surface is a portion of the general peritoneal membrane of the abdominal cavity. The Diaphragm is arched, being convex toward the chest and concave to the abdomen. The right portion forms a complete arch from before backward, being accurately moulded over the convex surface of the liver, and having resting upon it the concave base of the right lung. The left portion is arched from before back- ward in a similar manner; but the arch is narrower in front, being encroached upon by the pericardium, and lower than the right, at its summit, by about three-quarters of an inch. It supports the base of the left lung, and covers the great end of the stomach, the spleen, and left kidney. At its circumference the Diaphragm is higher in the mesial line of the body than at either side; but in the middle of the thorax the central portion, which supports the heart, is on a lower level than the two lateral portions. Nerves.-The Diaphragm is supplied by the phrenic nerves and phrenic plexus of the sympathetic. Actions.-The Diaphragm is the principal muscle of inspiration. When in a condition of rest the muscle presents a domed surface, concave toward the abdo- men ; and consists of a circumferential muscular and a central tendinous part. When the muscular fibres contract, they become less arched, or nearly straight, and thus cause the central tendon to descend, and in consequence the level of the chest-wall is lowered, the vertical diameter of the chest being proportionally increased. In this descent the different parts of the tendon move unequally. The left leaflet descends to the greatest extent; the right to a less extent, on OF THE ABDOMEN. 449 account of the liver; and the central leaflet the least, because of its connection to the pericardium. In descending the diaphragm presses on the abdominal viscera, and so to a certain extent causes a projection of the abdominal wall; but in conse- quence of these viscera not yielding completely, the central tendon becomes a fixed point, and enables the circumferential muscular fibres to nd from it, and so elevate the lower ribs and expand the lower part of the thoracic cavity; and Duchenne has shown that the Diaphragm has the power of elevating the ribs, to which it is attached, by its contraction, if the abdominal viscera are in situ, but that if these organs are removed, this power is lost. When at the end of inspiration the Dia- phragm relaxes, the thoracic walls return to their natural position in consequence of their elastic reaction and of the elasticity and weight of the displaced viscera.1 In all expulsive acts the Diaphragm is called into action, to give additional power to each expulsive effort. Thus, before sneezing, coughing, laughing, and crying, before vomiting, previous to the expulsion of the urine and feces, or of the fetus from the womb, a deep inspiration takes place. The height of the Diaphragm is constantly varying during respiration, the muscle being carried upward or downward from the average level; its height also varies according to the degree of distension of the stomach and intestines, and the size of the liver. After a forced expiration, the right arch is on a level, in front, with the fourth costal cartilage ; at the side, with the fifth, sixth, and seventh ribs ; and behind, with the eighth rib, the left arch being usually from one to two ribs' breadth below the level of the right one. In a forced inspiration, it descends from one to two inches; its slope would then be represented by a line drawn from the ensiform cartilage toward the tenth rib. THE ABDOMEN. Superficial Muscles. The Muscles in this region are, the Obliquus Externus. Obliquus Interims. Transversalis. Rectus. Pyramidalis. Dissection (Fig. 291).-To dissect the abdominal muscles, make a vertical incision from the ensiform car- tilage to the pubes; a second incision from the umbilicus obliquely upward and outward to the outer surface of the chest, as high as the lower border of the fifth or sixth rib : and a third, commencing midway between the umbilicus and pubes, transversely outward to the anterior superior iliac spine, and along the crest of the ilium as far as its posterior third. Then reflect the three flaps included be- tween these incisions from within outward, in the lines of direction of the muscular fibres. If necessary, the abdom- inal muscles may be made tense by inflating the peritoneal cavity through the umbilicus. The Superficial fascia of the abdomen consists over the greater part of the abdominal wall of a single layer of fascia, which contains a variable amount of fat; but as this layer approaches the groin it is easily divisible into two layers, be- tween which are found the superficial vessels and nerves and the superficial inguinal lymphatic glands. The superficial layer is thick, areolar in texture, containing adipose tissue in its meshes, the quantity of which varies in different subjects. Below it passes over Poupart's ligament, and is continuous with the outer layer of the superficial fascia of the thierh. In the male this fascia is continued over tho nonis and nntnr 3. Dis- I lection of' inguinal hernia. Fig. 291.-Dissection of abdomen 1 For a detailed description of the general relations of the Diaphragm, and its action, refer to Dr. Sibson's Medical Anatomy. 450 THE MUSCLES AND FASCIAE surface of the cord to the scrotum, where it helps to form the dartos. As it passes to the scrotum it changes its character, becoming thin, destitute of adipose tissue and of a pale reddish color, and in the scrotum it acquires some involuntary mus- cular fibres. From the scrotum it may be traced backward to be continuous with the superficial fascia of the perinaeum. In the female this fascia is continued into the labia majora. The deeper layer (fascia of Scarpa) is thinner and more mem- branous in character than the superficial layer. In the middle line it is intimately adherent to the linea alba; above, it is continuous with the superficial fascia over the rest of the trunk ; below, it blends with the fascia lata of the thigh a little below Poupart's ligament; and below and internally it is continued over the penis and spermatic cord to the scrotum, where it helps to form the dartos. From the scrotum it may be traced backward to be continuous with the deep layer of the superficial fascia of the perinaeum. In the female it is continued into the labia majora. The External or Descending Oblique muscle (Fig. 292) is situated on the side and fore part of the abdomen ; being the largest and the most superficial of the three flat muscles in this region. It is broad, thin, and irregularly quadrilateral, its muscular portion occupying the side, its aponeurosis the anterior wall, of the abdomen. It arises, by eight fleshy digitations, from the external surface and lower borders of the eight inferior ribs; these digitations are arranged in an oblique line running downward and backward ; the upper ones being attached close to the cartilages of the corresponding ribs ; the lowest, to the apex of the cartilage of the last rib; the intermediate ones, to the ribs at some distance from their cartilages. The five superior serrations increase in size from above down- ward, and are received between corresponding processes of the Serratus magnus; the three lower ones diminish in size from above downward, receiving between them corresponding processes from the Latissimus dorsi. From these attachments, the fleshy fibres proceed in various directions. Those from the lowest ribs pass nearly vertically downward, to be inserted into the anterior half of the outer lip of the crest of the ilium ; the middle amPupper fibres, directed downward and for- ward, terminate in tendinous fibres, opposite a line drawn from the prominence of the ninth costal cartilage to the anterior superior spinous process of the ilium, which then spread out into a broad aponeurosis. The Aponeurosis of the External Oblique is a thin, but strong membranous aponeurosis, the fibres of which are directed obliquely downward and outward. It is joined with that of the opposite muscle along the median line, covers the whole of the front of the abdomen; above, it is connected with the lower border of the Pectoral's major ; below, its fibres are closely aggregated together, and extend obliquely across from the anterior superior spine of the ilium to the spine of the os pubis and the linea ilio-pectinea. In the median line it interlaces with the aponeurosis of the opposite muscle, forming the linea alba, which extends from the ensiform cartilage to the symphysis pubis. That portion of the aponeurosis which extends between the anterior superior spine of the ilium and the spine of the os pubis is a broad band, folded inward, and continuous below with the fascia lata; it is called Poupart's ligament. The portion which is reflected from Poupart's ligament at the spine of the os pubis along the pectineal line is called Gimbernat's ligament. From the point of attach- ment of the latter to the pectineal line, a few fibres pass upward and inward, behind the inner pillar of the ring, to the linea alba. They diverge as they ascend, and form a thin, triangular, fibrous band, which is called the triangular ligament of the abdomen. In the aponeurosis of the External oblique, immediately above the crest of the os pubis, is a triangular opening, the external abdominal ring, formed by a separa- tion of the fibres of the aponeurosis in this situation. Relations.-By its external surface, with the superficial fascia, superficial epigastric and circumflex iliac vessels, and some cutaneous nerves; by its internal surface, with the Internal oblique, the lower part of the eight inferior ribs, and OF THE ABDOMEN. 451 Intercostal muscles, the Cremaster, the spermatic cord in the male, and round liga- ment in the female. Its posterior border, extending from the last rib to the crest of the ilium, is fleshy throughout and free; it is occasionally overlapped by the Latissimus dorsi, though generally a triangular interval exists between the two muscles near the crest of the ilium, in which is seen a portion of the internal oblique. This triangle, Petit's triangle, is therefore bounded in front by the External abdo- minal ring. ... Gimbernat's- ligament. ' Pubes. Fig. 292-The External oblique muscle. External oblique, behind by the Latissimus dorsi, below by the crest of the ilium, while its floor is formed by the Internal oblique (Fig. 281). The following parts of the aponeurosis of the External oblique muscle lequne to be further described : viz. the external abdominal ring, the intercolumnai fibies and fascia, Poupart's ligament, Gimbernat s ligament, and the triangulai ligament of the abdomen. The External Abdominal Ring.-Just above, and to the outer side of the crest of the os pubis, an interval is seen in the aponeurosis of the External oblique, called the External abdominal ring. The aperture is oblique in direction, some- 452 THE MUSCLES AND FASCIAE what triangular in form, and corresponds with the course of the fibres of the aponeurosis. It usually measures from base to apex about an inch, and transversely about half an inch. It is bounded below by the crest of the os pubis; above, by a series of curved fibres, the intercolumnar, which pass across the upper angle of the ring, so as to increase its strength ; and on each side, by the margins of the opening in the aponeurosis, which are called the columns or pillars of the ring. The external pillar, which is at the same time inferior from the obliquity of its direction, is the stronger: it is formed by that portion of Poupart's ligament which is inserted into the spine of the os pubis; it is curved so as to form a kind of groove, upon which the spermatic cord rests. The internal or superior pillar is a broad, thin, flat band which is attached to the front of the symphysis pubis, interlacing with its fellow of the opposite side, that of the right side being super- ficial. The external abdominal ring gives passage to the spermatic cord in the male, and round ligament in the female: it is much larger in men than in women, on account of the large size of the spermatic cord, and hence the greater frequency of inguinal hernia in men. The intercolumnar fibres are a series of curved tendinous fibres, which arch across the lower part of the aponeurosis of the External oblique. They have received their name from stretching across between the two pillars of the external ring, describing a curve with the convexity downward. They are much thicker and stronger at the outer margin of the external ring, where they are connected to the outer third of Poupart's ligament, than internally, where they are inserted into the linea alba. They are more strongly developed in the male than in the female. The intercolumnar fibres increase the strength of the lower part of the aponeurosis, and prevent the divergence of the pillars from one another. These intercolumnar fibres as they pass across the external abdominal ring are themselves connected together by delicate fibrous tissue, thus forming a fascia, which as it is attached to the pillars of the ring covers it in, and is called the intercolumnar fascia. This intercolumnar fascia is continued down as a tubular prolongation around the outer surface of the cord and testis, and encloses them in a distinct sheath; hence it is also called the external spermatic fascia. The sac of an inguinal hernia, in passing through the external abdominal ring, receives an investment from the intercolumnar fascia. If the finger is introduced a short distance into the external abdominal ring and the limb is then extended and rotated outward, the aponeurosis of the External oblique, together with the iliac portion of the fascia lata, will be felt to become tense, and the external ring much contracted; if the limb is on the con- trary flexed upon the pelvis and rotated inward, this aponeurosis will become lax and the external abdominal ring sufficiently enlarged to admit the finger with comparative ease: hence the patient should always be put in the latter position when the taxis is applied for the reduction of an inguinal hernia in order that the abdominal walls may be relaxed as much as possible. Poupart's ligament, or the crural arch, is the lower border of the aponeurosis of the External oblique muscle, which extends from the anterior superior spine of the ilium to the os pubis. From this latter point it is reflected outward to be attached to the pectineal line for about half an inch, forming Gimbernat's liga- ment. Its general direction is curved downward toward the thigh, where it is continuous w ith the fascia lata. Its outer half is rounded and oblique in direction. Its inner half gradually w idens at its attachment to the os pubis, is more horizontal in direction, and lies beneath the spermatic cord. Nearly the wrhole of the space included between the crural arch and the innominate bone is filled in by the parts which descend from the abdomen into the thigh. These will be referred to again on a subsequent page. Gimbernat's ligament is that part of the aponeurosis of the External oblique OF THE ABDOMEN 453 muscle which is reflected downward and outward from the spine of the os pubis to be inserted into the pectineal line. It is about half an inch in length, larger in the male than in the female, almost horizontal in direction in the erect posture, and of a triangular form with the base directed outward. Its base, or outer margin, is concave, thin, and sharp, and lies in contact with the crural sheath. Its apex corresponds to the spine of the os pubis. Its posterior margin is attached to the pectineal line, and is continuous with the pubic portion of the fascia lata. Its anterior margin is continuous with Poupart's ligament. The triangular ligament of the abdomen is a band of tendinous fibres of a triangular shape, which is attached by its apex to the pectineal line, where it is continuous with Gimbernat's ligament. It passes inward beneath the spermatic cord, and expands into a somewhat fan-shaped fascia, lying behind the inner pillar of the external abdominal ring, and in front of the conjoined tendon, and interlaces with the ligament of the other side at the linea alba. Dissection.-Detach the External oblique by dividing it across, just in front of its attach- ment to the ribs, as far as its posterior border, and separate it below from the crest of the ilium as far as the anterior superior spine ; then separate the muscle carefully from the Internal oblique, which lies beneath, and turn it toward the opposite side. The Internal or Ascending oblique muscle (Fig. 293), thinner and smaller than the preceding, beneath which it lies, is of an irregularly quadrilateral form, Conjoined tendon. CREM ASTER. Pubes. Fig. 293.-The internal oblique muscle. and situated at the side and fore part of the abdomen. It arises, by fleshy fibres, from the outer half of Poupart's ligament, being attached to the groove on its 454 THE MUSCLES AND FASCIAE upper surface; from the anterior two-thirds of the middle lip of the crest of the ilium, and from the posterior lamella of the lumbar fascia. From this origin the fibres diverge: those from Poupart's ligament, few in number and paler in color than the rest, arch downward and inward across the spermatic cord, and, becoming tendinous, are inserted, conjointly with those of the Transversalis, into the crest of the os pubis and pectineal line, to the extent of half an inch, forming what is known as the conjoined tendon of the Internal oblique and Transversalis; those from the anterior third of the iliac origin are horizontal in their direction, and. becoming tendinous along the lower fourth of the linea semilunaris, pass in front of the Rectus muscle to be inserted into the linea alba; those which arise from the middle third of the origin from the crest of the ilium pass obliquely upward and inward, and terminate in an aponeurosis, which divides opposite the linea semilunaris into two lamellae, which are continued forward, in front and behind the Rectus muscle, to the linea alba; the posterior lamella, being also connected to the cartilages of the seventh, eighth, and ninth ribs; the most posterior fibres pass almost vertically upward, to be inserted into the lower borders of the cartilages of the three lower ribs, being continuous with the Internal intercostal muscles. The conjoined tendon of the Internal oblique and Transversalis is inserted into the crest of the os pubis and pectineal line, immediately behind the external abdominal ring, serving to protect what would otherwise be a weak point in the abdominal wall. Sometimes this tendon is insufficient to resist the pressure from within, and is carried forward in front of the protrusion through the external ring, forming one of the coverings of direct inguinal hernia; or the hernia forces its way through the fibres of the conjoined tendon. The aponeurosis of the Internal oblique is continued forward to the middle line of the abdomen, where it joins with the aponeurosis of the opposite muscle at the linea alba, and extends from the margin of the thorax to the os pubis. At the outer margin of the Rectus muscle, this aponeurosis, for the upper three-fourths of its extent, divides into two lamellae, which pass, one in front and the other behind the muscle, enclosing it in a kind of sheath, and reuniting on its inner border at the linea alba; the anterior layer is blended with the aponeurosis of the External oblique muscle; the posterior layer with that of the Transversalis. Along the lower fourth the aponeurosis passes altogether in front of the Rectus without any separation. Relations.-By its external surface, with the External oblique, Latissimus dorsi, spermatic cord, and external ring; by its internal surface, with the Trans- versalis muscle, the lower intercostal vessels and nerves, the ilio-hypogastric and the ilio-inguinal nerves. Near Poupart's ligament it lies on the fascia transversalis, internal ring, and spermatic cord. Its lower border forms the upper boundary of the spermatic canal. The Cremaster muscle is a thin muscular layer, composed of a number of fasciculi which arise from the middle of Poupart's ligament at the inner side of the Internal oblique, being connected with that muscle, and also occasionally with the Transversalis. It passes along the outer side of the spermatic cord, descends with it through the external abdominal ring upon the front and sides of the cord, and forms a series of loops which differ in thickness and length in different subjects. Those at the upper part of the cord are exceedinglv short, but they become in succession longer and longer, the longest reaching down as low as the testicle, where a few are inserted into the tunica vaginalis. These loops are united together by areolar tissue, and form a thin covering over the cord and testis, the fascia cremasterica. The fibres ascend along the inner side of the cord, and are inserted by a small pointed tendon into the crest of the os pubis and front of the sheath of the Rectus muscle. It will be observed that the origin and insertion of the Cremaster is precisely similar to that of the lower fibres of the Internal oblique. This fact affords an easy explanation of the manner in which the testicle and cord are invested by this muscle. At an early period of foetal life the testis is placed at the lower and back OF THE ABDOMEN 455 part of the abdominal cavity, but during its descent toward the scrotum, which takes place before birth, it passes beneath the arched fibres of the Internal oblique. In its passage beneath this muscle some fibres are derived from its lower part which accompany the testicle and cord into the scrotum. It occasionally happens that the loops of the Cremaster surround the cord, some lying behind as well as in front. It is probable that under these circumstances the testis, in its descent, passed through instead of beneath the fibres of the Internal oblique. In the descent of an oblique inguinal hernia, which takes the same course as the spermatic cord, the Cremaster muscle forms one of its coverings. This muscle becomes largely developed in cases of hydrocele and large old scrotal hernia. No such muscles exist in the female, but an analogous structure is developed in those cases where an oblique inguinal hernia descends beneath the margin of the Internal oblique. Dissection.-Detach the Internal oblique in order to expose the Transversalis beneath. This may be effected by dividing the muscle, above, at its attachment to the ribs; below, at its con- nection with Poupart's ligament and the crest of the ilium; and behind, by a vertical incision extending front the last rib to the crest of the ilium. The muscle should previously be made tense by drawing upon it with the fingers of the left hand, and if its division is carefully effected, the cellular interval between it and the Transversalis, as well as the direction of the fibres of the latter muscle, will afford a clear guide to their separation ; along the crest of the ilium the cir- cumflex iliac vessels are interposed between them, and form an important guide in separating them. The muscle should then be thrown forward toward the linea alba. The Transversalis muscle (Fig. 294), so called from the direction of its fibres, is the most internal flat muscle of the abdomen, being placed immediately beneath the Internal oblique. It arises by fleshy fibres from the outer third of Poupart's ligament; from the inner lip of the crest of the ilium for its anterior three- fourths ; from the inner surface of the cartilages of the six lower ribs, interdigitating with the Diaphragm ; and by the lumbar fascia from the spinous and transverse processes of the lumbar vertebrae. The muscle terminates in front in a broad aponeurosis, the lower fibres of which curve downward and inward, and are inserted, together with those of the Internal oblique, into the lower part of the linea alba, the crest of the os pubis and pectineal line, forming what is known as the conjoined tendon of the Internal oblique and Transversalis. Throughout the rest of its extent the aponeurosis passes horizontally inward, and is inserted into the linea alba; its upper three-fourths passing behind the Rectus muscle, blending with the posterior lamella of the Internal oblique; its lower fourth passing in front of the Rectus. Relations.-By its external surface, with the Internal oblique, and the inner surface of the cartilages of the lower ribs; by its internal surface, with the fascia transversalis, which separates it from the peritoneum. Its lower border forms the upper boundary of the spermatic canal. Dissection.-To expose the Rectus muscle, open its sheath by a vertical incision extending from the margin of the thorax to the os pubis, and then reflect the two portions from the surface of the muscle, which is easily done, excepting at the lineae transversae, where so close an adhesion exists that the greatest care is requisite in separating them. Now raise the outer edge of the muscle, in order to examine the posterior layer of the sheath. By dividing the muscle in the centre, and turning its lower part downward, the point where the posterior wall of the sheath terminates in a thin curved margin will be seen. The Rectus abdominis is a long flat muscle, which extends along the whole length of the front of the abdomen, being separated from its fellow of the opposite side by the linea alba. It is much broader, but thinner, above than below, and arises by two tendons, the external or larger being attached to the crest of the os pubis, the internal, smaller portion interlacing with its fellow of the opposite side, and being connected with the ligaments covering the front of the symphysis pubis. The fibres ascend, and the muscle is inserted by three portions of unequal size into the cartilages of the fifth, sixth, and seventh ribs. Some fibres are occasion- ally connected with the costo-xiphoid ligaments and side of the ensiform cartilage. 1 The Rectus muscle is traversed by tendinous intersections, three in number, 456 THE MUSCLES AND EASCIAE which have received the name of Unece transversce. One of these is usually situated opposite the umbilicus, and two above that point; of the latter, one corresponds to the extremity of the ensiform cartilage, and the other to the interval between the ensiform cartilage and the umbilicus. These intersections pass transversely or obliquely across the muscle in a zigzag course; they rarely extend completely through its substance, sometimes pass only halfway across Linea alba.~ Fig. 294.-The Transversalis, Rectus, and Pyramidalis muscles. it, and are intimately adherent in front to the sheath in which the muscle is enclosed. The Rectus is enclosed in a sheath (Fig. 295) formed by the aponeuroses of the Oblique and Transversalis muscles, which are arranged in the following manner. When the aponeurosis of the Internal oblique arrives at the outer margin of the Rectus, it divides into two lamellae, one of which passes in front of the Rectus, blending with the aponeurosis of the External oblique; the other, behind it, blending with the aponeurosis of the Transversalis; and these, joining again at its OF THE ABDOMEN. 457 inner border, are inserted into the linea alba. This arrangement of the aponeuroses exists along the upper three-fourths of the muscle: at the commencement of the lower fourth, the posterior wall of the sheath terminates in a thin curved margin, the semilunar fold of Douglas, the concavity of which looks downward toward the pubes; the aponeuroses of all three muscles passing in front of the Rectus without any separation. rl he extremities of the fold of Douglas descend as pillars to the os pubis. The inner pillar is attached to the symphysis pubis; the outer pillar, which is named by Braune the ligament of Hesselbach, divides below to enclose the internal abdominal ring; the internal fibres are attached to the horizontal ramus of the os pubis and the pectineal fascia; the external ones pass to the Psoas fascia and to the Transversalis where it arises from Poupart's ligament on the outer side of the ring. The Rectus muscle, in the situation Fig. 295.-A transverse section of the abdomen in the lumbar region where its sheath is deficient, is separated from the peritoneum by the transversalis fascia. The Pyramidalis is a small muscle, triangular in shape, placed at the lower part of the abdomen, in front of the Rectus, and contained in the same sheath with that muscle. It arises by tendinous fibres from the front of the os pubis and the anterior pubic ligament; the fleshy portion of the muscle passes upward, diminishing in size as it ascends, and terminates by a pointed extremity, which is inserted into the linea alba, midway between the umbilicus and the os pubis. This muscle is sometimes found wanting on one or both sides; the lower end of the Rectus then becomes proportionately increased in size. Occasionally it has been found double on one side, or the muscles of the two sides are of unequal size. Sometimes its length exceeds what is stated above. Relations.-Its anterior surface (or rather the fascia which covers its anterior surface) is in relation with the colon, the kidney, the Psoas muscle, and the Diaphragm. Its posterior surface is in relation with the middle lamella of the lumbar fascia, which separates it from the Erector spinae. The Quadratus lumborum extends, however, beyond the outer border of the Erector spinae. Nerves.-The abdominal muscles are supplied by the lower intercostal nerves. The Internal oblique also receives a filament from the ilio-inguinal nerve. The Cremaster is supplied by the genital branch of the Genito-crural. In the description of the abdominal muscles mention has frequently been made of the linea alba, lineae semilunares, and lineae transversae ; when the dissection of the muscles is completed these structures should be examined. The linea alba is a tendinous raphe seen along the middle line of the abdomen, extending from the ensiform cartilage to the symphysis pubis, to which it is 458 THE MUSCLES AND FASCIAE attached. It is placed between the inner borders of the Recti muscles, and is formed by the blending of the aponeuroses of the Obliqui and Transversales muscles. It is narrow below, corresponding to the narrow interval existing between the Recti; but broader above, as these muscles diverge from one another in their ascent, becoming of considerable breadth after great distension of the abdomen from pregnancy or ascites. It presents numerous apertures for the passage of vessels and nerves: the largest of these is the umbilicus, which in the foetus transmits the umbilical vessels, but in the adult is obliterated, the cicatrix being stronger than the neighboring parts; hence umbilical hernia occurs in the adult near the umbilicus, whilst in the foetus it occurs at the umbilicus. The linea alba is in relation, in front, with the integument, to which it is adherent, especially at the umbilicus ; behind, it is separated from the peritoneum by the transversalis fascia ; and below, by the urachus, and the bladder when that organ is distended. The linese semilunares are two curved tendinous lines placed one on each side of the linea alba. Each corresponds with the outer border of the Rectus muscle, extends from the cartilage of the ninth rib to the pubic spine, and is formed by the aponeurosis of the Internal oblique at its point of division to enclose the Rectus, where it is reinforced in front by the External oblique and behind by the Transversalis. The lineae transversae are three narrow transverse lines which intersect the Recti muscles, as already mentioned; they connect the lineae semilunares with the linea alba. Actions.-The abdominal muscles perform a threefold action: When the pelvis and thorax are fixed, they compress the abdominal viscera, by constricting the cavity of the abdomen, in which action they are materially assisted by the descent of the diaphragm. By these means the foetus is expelled from the uterus, the faeces from the rectum, the urine from the bladder, and the contents of the stomach in vomiting. If the pelvis and spine are fixed, these muscles compress the lower part of the thorax, materially assisting expiration. If the pelvis alone is fixed, the thorax is bent directly forward when the muscles of both sides act, or to either side when those of the two sides act alternately, rotation of the trunk at the same time taking place to the opposite side. If the thorax is fixed, these muscles, acting together, draw the pelvis upward, as in climbing; or, acting singly, they draw the pelvis upward, and rotate the vertebral column to one side or the other. The Recti muscles, acting from below, depress the thorax, and consequently flex the vertebral column ; when acting from above, they flex the pelvis upon the vertebral column. The Pyramidales are tensors of the linea alba. The fascia transversalis is a thin aponeurotic membrane which lies between the inner surface of the Transversalis muscle and the peritoneum. It forms part of the general layer of fascia which lines the interior of the abdominal and pelvic cavities, and is directly continuous with the iliac and pelvic fasciae. In the inguinal region the transversalis fascia is thick and dense in structure, and joined by fibres from the aponeurosis of the Transversalis muscle, but it becomes thin and cellular as it ascends to the diaphragm. Below, it has the following attachments : external to the femoral vessels it is connected to the posterior margin of Poupart's ligament, and is there continuous with the iliac fascia. Internal to the femoral vessels it is thin and attached to the os pubis and pectineal line, behind the conjoined tendon, with which it is united ; and, corresponding to the point where the femoral vessels pass into the thigh, this fascia descends in front of them, forming the anterior wall of the crural sheath. The spermatic cord in the male and the round ligament in the female pass through this fascia: the point where they pass through is called the internal abdominal ring. This opening is not visible externally, owing to a prolongation of the transversalis fascia on the structures, forming the infundib- uliform process. The internal or deep abdominal ring is situated in the transversalis fascia, OF THE ABDOMEN 459 midway between the anterior superior spine of the ilium and the spine of the os pubis, and about half an inch above Poupart's ligament. It is of an oval form, the extremities of the oval directed upward and downward, varies in size in different subjects, and is much larger in the male than in the female. It is bounded, above and externally, by the arched fibres of the Transversalis ; below and internally, by the deep epigastric vessels. It transmits the spermatic cord in the male and the round ligament in the female. From its circumference a thin funnel-shaped membrane, the zn/'un<7z6zzZz/brm fascia, is continued round the cord and testis, enclosing them in a distinct pouch. When the sac of an oblique inguinal hernia passes through the internal or deep abdominal ring, the infundibuliform process of the transversalis fascia forms one of its coverings. I he inguinal or spermatic canal contains the spermatic cord in the male and the round ligament in the female. It is an oblique canal about an inch and a half in length, directed downward and inward, and placed parallel to and a little above Poupart's ligament. It commences above at the internal or deep abdominal ring, which is the point where the cord enters the spermatic canal, and terminates below at the external ring. It is bounded in front by the integument and superficial fascia, by the aponeurosis of the External oblique throughout its whole length, and by the Internal oblique for its outer third ; behind, by the triangular ligament, the conjoined tendon of the Internal oblique and Transversalis, transversalis fascia, and the subperitoneal fat and peritoneum; above, by the arched fibres of the Internal oblique and Transversalis ; below, by the union of the fascia transversalis with Poupart's ligament. That form of protrusion in which the intestine follows the course of the spermatic cord along the spermatic canal is called oblique inguinal hernia. The Deep Crural Arch.-Passing across the front of the crural arch, on the abdominal side of Poupart's ligament and closely connected with it, is a thickened band of fibres called the deep crural arch. It is apparently a thickening of the fascia transversalis, joining externally to the centre of Poupart's ligament, and arching across the front of the crural sheath to be inserted by a broad attachment into the pectineal line, behind the conjoined tendons. In some subjects this structure is not very prominently marked, and not unfrequently it is altogether wanting. Surface Form.-The only two muscles of this group which have any considerable influ- ence on surface form are the External oblique and Rectus muscles of the abdomen. With regard to the External oblique, the upper digitations of its origin from the ribs are well marked, intermingled with the serrations of the Serratus magnus; the lower digitations are not visible, being covered by the thick border of the Latissimus dorsi. Its attachment to the crest of the ilium, in conjunction with the Internal oblique, forms a thick oblique roll, which determines the iliac furrow. Sometimes on the front of the lateral region of the abdomen an undulating out- line marks the spot where the muscular fibres terminate and the aponeurosis commences. The outer border of the Rectus is defined by the tinea semilunaris, which may be exactly defined by putting the muscle into action. It corresponds with a curved line, with its convexity outward, drawn from the lowest part of the cartilage of the seventh rib to the spine of the os pubis, so that the centre of the line, at or near the umbilicus, is three inches from the median line. The inner border of the Rectus corresponds to the tinea alba, marked on the surface of the body by a groove, the abdominal furrow, which extends from the infrasternal fossa to, or to a little below, the umbilicus, where it gradually becomes lost. The surface of the Rectus presents three trans- verse furrows, the lineoe transverse. The upper two of these, one opposite or a little below the tip of the ensiform cartilage, and another, midway between this point and the umbilicus, are usually well marked ; the third, opposite the umbilicus, is not so distinct. The umbilicus, situ- ated in the linea alba, varies very much in position as regards its height. It is always situated above a zone drawn round the body opposite the highest point of the crest of the ilium, gene- rally being about three-quarters of an inch to an inch above this line. It generally corresponds, therefore, to the fibro-cartilage between the third and fourth lumbar vertebrae. Deep Muscles of the Abdomen. Psoas parvus. Psoas magnus. Iliacus. Quadratus lumborum. 460 THE MUSCLES AND EASCEE The Psoas magnus, the Psoas parvus, and the Iliacus muscles, with the fascia covering them, will be described with the Muscles of the Lower Extremity (see page 506). The Fascia covering the Quadratus Lumborum.-This is the most internal of the two layers of fascia which are given off from the anterior or deep surface of the lumbar fascia. It is a thin layer of fascia which, passing over the anterior surface of the Quadratus lumborum, is attached, internally, to the anterior surface of the transverse processes of the lumbar vertebrae; below to the ilio-lumbar ligament ; and above, to the apex and lower border of the last rib. The portion of this fascia which extends from the transverse process of the first lumbar vertebra to the apex and lower border of the last rib constitutes the ligamentum arcuatum externum. The Quadratus lumborum (Fig. 288, page 437) is situated in the lumbar region. It is irregularly quadrilateral in shape, and broader below than above. It arises by aponeurotic fibres from the ilio-lumbar ligament and the adjacent portion of the crest of the ilium for about two inches, and is inserted into the lower border of the last rib for about half its length and by four small tendons, into the apices of the transverse processes of the four upper lumbar vertebrae. Occasionally a second portion of this muscle is found situated in front of the preceding. It arises from the upper borders of the transverse processes of the lumbar vertebrae, and is inserted into the lower margin of the last rib. The Quadratus lumborum is contained in a sheath formed by the anterior and middle lamellae of the lumbar fasciae. Relations.-Its anterior surface (or rather the fascia which covers its anterior surface) is in relation with the colon, the kidney, the Psoas muscle, and the Diaphragm. Its posterior surface is in relation with the middle lamella of the lumbar fascia, which separates it from the Erector spinae. The Quadratus lumborum extends, however, beyond the outer border of the Erector spinae. Nerve-supply.-The anterior branches of the lumbar nerves. Actions.-The Quadratus lumborum draws down the last rib. and acts as a muscle of forced expiration ; but, at the same time, by fixing the last rib, it opposes the tendency of the Diaphragm to draw it upward, and thus it becomes an assistant to inspiration. If the thorax and spine are fixed, it may act upon the pelvis, raising it toward its own side when only one muscle is put in action ; and when both muscles act together, either from below or above, they flex the trunk. Muscles of the Pelvic Outlet or of the Ischio-rectal Region and Perinaeum. Corrugator cutis ani. External sphincter ani. Internal sphincter ani Levator ani. "Transversus perinaei. Accelerator urinae. Erector penis. Compressor urethrae. Coccygeus. Transversus perinaei. Sphincter vaginae. Erector clitoridis. Compressor urethrae. In Male. In Female. The Corrugator Cutis Ani.-Around the anus is a thin stratum of involuntary muscular fibre, which surrounds it in a radiating manner. Internally, the fibres fade off into the submucous tissue, whilst externally they blend with the true skin. By its contraction it raises the skin into ridges radiating from the margin of the anus. The External sphincter ani is a thin, flat plane of muscular fibres, elliptical in shape and intimately adherent to the integument surrounding the margin of the anus. It measures about three or four inches in length from its anterior to its posterior extremity, being about an inch in breadth opposite the anus. It arises from the tip of the coccyx by a narrow tendinous band, and from the superficial fascia in front of that bone ; and is inserted into the central tendinous point of the perinteum, joining with the Transversus perinsei, the Levator ani, and the Accelera- tor urinne. Like other sphincter muscles, it consists of two planes of muscular OF THE PERINEUM AND PELVIC OUTLET. 461 fibre, which surround the margin of the anus, and join in a commissure in front and behind. Nerve-supply.-A branch from the anterior division of the fourth sacral and the inferior haemorrhoidal branch of the internal pudic. Actions.-The action of this muscle is peculiar: 1. It is, like other muscles, always in a state of tonic contraction, and having no antagonistic muscle it keeps the anal orifice closed. 2. It can be put into a condition of greater contraction under the influence of the will, so as to more firmly occlude the anal aperture. 3. Taking its fixed point at the coccyx, it helps to fix the central point of the perinaeum, so that the Accelerator may act from this fixed point. The Internal sphincter is a muscular ring which surrounds the lower extremity of the rectum for about an inch, its inferior border being contiguous to, but quite separate from, the External sphincter. This muscle is about two lines in thickness, and is formed by an aggregation of the involuntary circular fibres of the intestine. It is paler in color and less coarse in texture than the External sphincter. Actions.-Its action is entirely involuntary. It helps the External sphincter to occlude the anal aperture. The Levator ani (Fig. 296) is a broad, thin muscle, situated on each side of the pelvis. It is attached to the inner surface of the sides of the true pelvis, and Spermatic vessels. „ Adductor longus. \ Ureter. ramus pubis.l Internal pudic vessels and nerve. Fig. 296.-Side view of pelvis, showing Levator ani. (From a preparation in the Museum of the Royal Col- lege of Surgeons.) descending unites with its fellow of the opposite side to form the floor of the pelvic cavity. It supports the viscera in this cavity and surrounds the various structures which pass through it. It arises, in front, from the posterior surface of the body and ramus of the os pubis on the outer side of the symphysis; posteriorly, from the inner surface of the spine of the ischium; and between these two points from the angle of division between the obturator and recto-vesical layers of the pelvic fascia at their under part. The fibres pass downward to the middle line of the floor of the pelvis, and are inserted, the most posterior into the sides of the apex of the coccyx; those placed more anteriorly unite with the muscles of the opposite side, in a median fibrous raphe, which extends between the coccyx and the margin of the anus. The middle fibres, which form the larger portion of the muscle, are 462 THE MUSCLES AND FASCIAE inserted into the side of the rectum, blending with the fibres of the Sphincter muscles; lastly, the anterior fibres, the longest, descend upon the side of the prostate gland to unite beneath it with the muscle of the opposite side, blending with the fibres of the External sphincter and Transversus perinaei muscles at the central tendinous point of the perinaeum. The anterior portion is occasionally separated from the rest of the muscle by connective tissue. From this circumstance, as well as from its peculiar relation with the prostate gland, descending by its side, and surrounding it as in a sling, it has been described by Santorini and others as a distinct muscle, under the name of Levator prostatae. In the female, the anterior fibres of the Levator ani descend upon the side of the vagina. Relations.-By its inner or pelvic surface, with the recto-vesical fascia, which separates it from the viscera of the pelvis and from the peritoneum. By its outer or perineal surface, it forms the inner boundary of the ischio-rectal fossa, and is covered by a thin layer of fascia, the ischio-rectal or anal fascia, given off from the obturator fascia. Its posterior border is continuous with the Coccygeus muscle. Its anterior border is separated from the muscle of the opposite side by a triangular space, through which the urethra, and in the female the vagina, passes from the pelvis. Nerve-supply.-A branch from the anterior division of the fourth sacral nerve. Actions.-This muscle supports the lower end of the rectum and vagina, and also the bladder during the efforts of expulsion. It elevates and inverts the lower end of the rectum after it has been protruded and everted during the expulsion of the faeces. It is also a muscle of forced expiration. The Coccygeus is situated behind and parallel with the preceding. It is a tri- angular plane of muscular and tendinous fibres, arising, by its apex, from the spine of the ischium and lesser sacro-sciatic ligament, and inserted, by its base, into the margin of the coccyx and into the side of the lower piece of the sacrum. This muscle is continuous with the posterior border of the Levator ani, and closes in the back part of the outlet of the pelvis. Relations.-By its inner or pelvic surface, with the rectum; by its external surface, with the lesser sacro-sciatic ligament; by its posterior border, with the Pyriformis. Nerve-supply.-A branch from the fourth and fifth sacral nerves. Action.-The Coccygei muscles raise and support the coccyx after it has been pressed backward during defecation or parturition. Superficial Fascia.-The superficial fascia of the perinaeum consists of two layers, superficial and deep, as in other regions of the body. The superficial layer is thick, loose, areolar in texture, and contains much adipose tissue in its meshes, the amount of which varies in different subjects. In front, it is continuous with the dartos of the scrotum; behind, it is continuous with the subcutaneous areolar tissue surrounding the anus ; and, on either side, with the same fascia on the inner side of the thighs. This layer should be care- fully removed after it has been examined, when the deep layer will be exposed. The deep layer of superficial fascia (Fascia of Colles) is thin, aponeurotic in structure, and of considerable strength, serving to bind down the muscles of the root of the penis. It is continuous, in front, with the dartos of the scrotum; on either side it is firmly attached to the margins of the rami of the os pubis and ischium, external to the crus penis, and as far back as the tuberosity of the isch- ium ; posteriorly, it curves down behind the Transversus perinaei muscles to join the lower margin of the deep perineal fascia. This fascia not only covers the muscles in this region, but sends down a vertical septum from its under surface, which separates the back part of the subjacent space into two, being incomplete in front. The Central Tendinous Point of the Perinseum.-This is a fibrous point in the middle line of the perinaeum, between the urethra and the rectum, being about half an inch in front of the anus. At this point four muscles converge and are attached : viz. the External sphincter ani, the Accelerator urinae, and the two OF THE PERINUM. 463 Transversus perinaei; so that by the contraction of these muscles, which extend in opposite directions, it serves as a fixed point of support. I he Transversus perinaei is a narrow muscular slip, which passes more or less transversely across the back part of the perineal space. It arises by a small tendon from the inner and fore part of the tuberosity of the ischium, and, passing inward, is inserted into the central tendinous point of the perinaeum, joining in this situation Fig. 297.-The perinseum. The integument and superficial layer of superficial fascia reflected. with the muscle of the opposite side, the External sphincter ani behind, and the Accelerator urinae in front. Nerve-supply.-The perineal branch of the internal pudic. Actions.-By their contraction they serve to fix the central tendinous point of the perimeum. The Accelerator urinae (Ejaculator s eminis, or Bulbo-cavernosus) is placed in the middle line of the perinaeum, immediately in front of the anus. It consists of two symmetrical halves, united along the median line by a tendinous raphe. It arises from the central tendon of the perinaeum, and from the median raphe in front. From this point its fibres diverge like the plumes of a pen; the most posterior form a thin layer, which are lost on the anterior surface of the triangular ligament; the middle fibres encircle the bulb and adjacent parts of the corpus spongiosum, and join with the fibres of the opposite side, on the upper part of the corpus spongiosum, in a strong aponeurosis; the anterior fibres, the longest and most distinct, spread out over the sides of the corpus cavernosum, to be inserted partly into that body, anterior to the Erector penis, occasionally extending to the os pubis; partly terminating in a tendinous expansion, which covers the dorsal vessels of the penis. The latter fibres are best seen by dividing the muscle longitudinally, and dissecting it outward from the surface of the urethra. Action.-This muscle serves to empty the canal of the urethra, after the bladder has expelled its contents ; during the greater part of the act of micturition its fibres are relaxed, and it only comes into action at the end of the process. The middle fibres are supposed, by Krause, to assist in the erection of the corpus 464 THE MUSCLES AND FAS CEE spongiosum, by compressing the erectile tissue of the bulb. The anterior fibres, according to Tyrrel, also contribute to the erection of the penis, as they are inserted into, and continuous with, the fascia of the penis, compressing the dorsal vein during the contraction of the muscle. The Erector penis covers the unattached part of the crus penis. It is an elongated muscle, broader in the middle than at either extremity, and situated on either side of the lateral boundary of the perinaeum. It arises by tendinous and RECTUS ABDOMINIS .CREMASTER. Fig. 298.-The muscles attached to the front of the pelvis. (From a preparation in the Museum of the Royal College of Surgeons of England.) lieshy fibres from the inner surface of the tuberosity of the ischium, behind the crus penis, from the surface of the crus, and from the adjacent portion of the ramus of the ischium. From these points fleshy fibres succeed, which end in an aponeurosis which is inserted into the sides and under surface of the crus penis. Nerve-supply.-The perineal branch of the internal pudic. Actions.-It compresses the crus penis and retards the return of the blood through the veins, and thus serves to maintain the organ erect. Between the muscles just examined a triangular space exists, bounded internally by the Accelerator urinae, externally by the Erector penis, and behind OF THE PERINEUM. 465 by the Transversus perinaei. The floor of this space is formed by the triangular ligament of the urethra (deep perineal fascia), and running from behind forward in it are the superficial perineal vessels and nerve, and the transverse perineal artery coursing along the posterior boundary of the space on the Transversus perinaei muscle. The Triangular Ligament (Deep perineal fascia) is a dense membranous lamina, which closes the front part of the outlet of the pelvis. It is triangular in shape, about an inch and a half in depth, attached above, by its apex, to the under surface of the symphysis pubis and subpubic ligament; and on each side to the rami of the ischium and pubes, beneath the crura penis. Its inferior margin, or base, is directed toward the rectum, and connected to the central tendinous point of the perinseum. It is continuous with the deep layer of the superficial fascia behind the Transversus perinaei muscle, and with a thin fascia which covers the cutaneous surface of the Levator ani muscle (anal or ischio-rectal fascia). ■Superficial perineal artery. ■Superficial perineal nerve. .Internal pudic nerve. Internal pudic artery. GREAT SACRO- SCIATIC LIGAMENT. Fig. 299.-The superficial muscles and vessels of the perineeum. The Triangular ligament is perforated by the urethra, about an inch below the symphysis pubis. The aperture is circular in form, and about three or four lines in diameter. Above this is the aperture for the dorsal vein of the penis , and, outside the latter, branches of the pudic nerve and artery pierce it. The triangular ligament consists of two layers, superficial or inferior, and deep or superior ; these are separated in front, but united behind. The superficial layer is continued forward, around the anterior pait of the membranous portion of the urethra, becoming lost upon the bulb. It is pierced by the duct of Cowper's gland. . . . The deep layer is derived from the obturator fascia;1 it is continued back- ward around the posterior part of the membranous portion of the urethra and the outer surface of the prostate gland. Structures between the Two Layers of the Triangular Ligament. If the superficial layer of this fascia is detached on either side, the following structuies 1 "On the Anatomy of the Posterior Layer of the Triangular Ligament," see a paper by Mr. Carrington, Guy's Hospital Reports. 466 THE MUSCLES AND FASCIAE will be seen between it and the deep layer: the subpubic ligament above, close to the pubes; the dorsal vein of the penis; the membranous portion of the urethra, and the Compressor urethrae muscle; Cowper's glands and their ducts; the pudic vessels and nerve; the artery and nerve of the bulb, and a plexus of veins. The Compressor urethrae (Constrictor urethra?) surrounds the whole length of the membranous portion of the urethra, and is contained between the two layers Anterior layer of deep perineal fascia removed showing .COMPRESSOR URETHRX. internal pudic artery. -Artery of the bulb. "Cowper's gland. Fig. 300.-Triangular ligament or deep perineal fascia. On the left side the superficial layer has been removed. of the triangular ligament. It arises, by aponeurotic fibres, from the upper part of the ramus of the os pubis on each side, to the extent of half or three-quarters of an inch : each segment of the muscle passes inward, and divides into two fasciculi, which surround the urethra from the prostate gland behind to the bulbous portion of the urethra in front; and unite, at the upper and lower surfaces of this tube, with the muscle of the opposite side, by means of a tendinous raphe. Actions.-The muscles of both sides act together as a sphincter, compressing the membranous portion of the urethra. During the transmission of fluids they, like the Acceleratores urinae, are relaxed, and only come into action at the end of the process to eject the last of the fluid. Muscles of the Perinaeum in the Female. The Transversus perinsei in the female is a narrow muscular slip, which passes more or less transversely across the back part of the perineal space. It arises by a small tendon from the inner and fore part of the tuberosity of the ischium, and, passing inward, is inserted into the central line of the perinaeum, joining in this situation with the muscle of the opposite side, the External sphincter ani behind, and the Sphincter vaginae in front. Nerve-supply.-The perineal branch of the internal pudic. Actions.-By their contraction they serve to fix the central tendinous point of the perinaeum. The Sphincter vaginae surrounds the orifice of the vagina, and is analogous to the Accelerator urinae in the male. It is attached posteriorly to the central OF THE UPPER EXTREMITY. 467 tendinous point of the perinaeum, where it blends with the External sphincter ani. Its fibres pass forward on each side of the vagina, to be inserted into the corpora cavernosa of the clitoris, a fasciculus crossing over the body of the organ so as to compress the dorsal vein. Nerve-supply.-The perineal branch of the internal pudic. Actions.-It diminishes the orifice of the vagina. The anterior fibres contribute to the erection of the clitoris, as they are inserted into and are continuous with the fascia of the clitoris; compressing the dorsal vein during the contraction of the muscle. The Erector clitoridis resembles the Erector penis in the male, but is smaller than it. It covers the unattached part of the crus clitoridis. It is an elongated muscle, broader at the middle than at either extremity, and situated on either side of the lateral boundary of the perinaeum. It arises by tendinous and fleshy fibres from the inner surface of the tuberosity of the ischium, behind the crus clitoridis from the surface of the crus, and from the adjacent portion of the ramus of the ischium. From these points fleshy fibres succeed, which end in an aponeurosis, which is inserted into the sides and under surface of the crus clitoridis. Nerve-supply.-The perineal branch of the internal pudic. Actions.-It compresses the crus clitoridis and retards the return of blood through the veins, and thus serves to maintain the organ erect. The triangular ligament (deep perineal fascia) in the female is not so strong as in the male. It is attached to the pubic arch, its apex being connected with the sym- physis pubis. It is divided in the middle line by the aperture of the vagina, with the external coat of which it becomes blended, and in front of this is perforated by the urethra. Its posterior border is continuous, as in the male, with the deep layer of the superficial fascia around the Transversus perinaei muscle. Structures between the Two Layers of the Triangular Ligament.-The subpubic ligament above, the dorsal vein of the clitoris, the membranous portion of the urethra and the Compressor urethrae muscle, the glands of Bartholin and their ducts; the pudic vessels and the dorsal nerve of the clitoris ; the artery of the bulbi vestibuli, and a plexus of veins. The Compressor urethrae (constrictor urethrce) arises on each side from the margin of the descending ramus of the os pubis. The fibres, passing inward, divide into two sets; those of the fore part of the muscle are directed across the subpubic arch in front of the urethra to blend with the muscular fibres of the opposite side ; while those of the hinder and larger part pass inward to blend with the wall of the vagina behind the urethra. MUSCLES AND FASCL® OF THE UPPER EXTREMITY. The Muscles of the Upper Extremity are divisible into groups, corresponding with the different regions of the limb. Of the Shoulder. Anterior Thoracic Region. Pectoralis major. Pectoralis minor. Subclavius. Lateral Thoracic Region. Serratus magnus. Acromial Region. Deltoid. Anterior Scapular Region. Subscapularis. Of the Arm. Anterior Humeral Region. Coraco-brachialis. Biceps. Brachialis anticus. Posterior Humeral Region. Triceps. Subanconeus. Of the Forearm. Anterior Brachial Region. < Pronator radii teres. Posterior Scapular Region. Superficial Layer. Flexor carpi radialis. Palmaris longus. Flexor carpi ulnaris. Flexor sublimis digitorum. Supraspinatus. Infraspinatus. Teres minor. Teres major. 468 THE MUSCLES AND FASCIAE. Flexor profundus digitorum. Flexor longus pollicis. Pronator quadratics. Of the Hand. Deep Layer. Radial Region. Abductor pollicis. Flexor ossis metacarpi pollicis (Opponens pollicis). Flexor brevis pollicis. Adductor pollicis. Radial Region. Supinator longus. Extensor carpi radialis longior. Extensor carpi radialis brevior. Posterior Brachial Region. Ulnar Region. Superficial Layer. Extensor communis digitorum. Extensor minimi digiti. Extensor carpi ulnaris. Anconeus. Palmaris brevis. Abductor minimi digiti. Flexor brevis minimi digiti. Flexor ossis metacarpi minimi digiti (Opponens minimi digiti). Palmar Region. Lumbricales. Interossei palmares. Interossei dorsales. Supinator brevis. Extensor ossis metacarpi pollicis. Extensor brevis pollicis. Extensor longus pollicis. Extensor indicis. Deep Layer. Dissection of Pectoral Region and Axilla (Fig. 301).-The arm being drawn away from the side nearly at right angles with the trunk, and rotated outward, make a vertical incision through the integument in the median line of the chest, from the upper to the lower part of the sternum ; a second incision along the lower border of the Pectoral muscle, from the ensiform cartilage to the inner side of the axilla; a third, from the sternum along the clavicle, as far as its centre; and a fourth, from the middle of the clavicle obliquely downward, along the interspace between the Pectoral and Del- toid muscles, as low as the fold of the armpit. The flap of integument is then to be dissected off in the direction indi- cated in the figure, but not entirely removed, as it should be replaced on com- pleting the dissection. If a transverse incision is now made from the lower end of the sternum to the side of the chest, as far as the posterior fold of the armpit, and the integument reflected outward, the axillary space will be more completely exposed. Fasciae of the Thorax. The superficial fascia of the thoracic region is a loose cellulo- fibrous layer enclosing masses of fat in its spaces. It is continu- ous with the superficial fascia of the neck and upper extremity above, and of the abdomen below. Opposite the mamma, it divides into two layers, one of which passes in front, the other behind that gland ; and from both of these layers numerous septa pass into its substance, supporting its various lobes : from the anterior layer fibrous processes pass forward to the integument and nipple. These processes were called by Sir A. Cooper the ligamenta suspensoria, from the support they afford to the gland in this situation. The deep fascia of its thoracic region is a thin aponeurotic lamina, covering the surface of the great Pectoral muscle, and sending numerous prolongations 3. Dissection of Shoulder and Arm. 1. Dissection of Pectoral Region and Axilla. 2. Bend of Elbow. 4- Forearm. \5. Palm of Hand. Fig. 301.-Dissection of upper extremity. THE SHOULDER. 469 between its fasciculi: it is attached, in the middle line, to the front of the sternum; and, above, to the clavicle. It is very thin over the upper part of the muscle, thicker in the interval between the Pectoralis major and Latissimus dorsi, where it closes in the axillary space, and divides at the outer margin of the latter muscle into two layers, one of which passes in front, and the other behind it; these proceed as far as the spinous processes of the dorsal vertebrae, to which they are attached. At the lower part of the thoracic region this fascia is well developed, and is continuous with the fibrous sheath of the Recti muscles. Anterior Thoracic Region. THE SHOULDER. Pectoralis major. Pectoralis minor. The Pectoralis major (Fig. 302) is a broad, thick, triangular muscle, situated at the upper and fore part of the chest, in front of the axilla. It arises from the anterior surface of the sternal half of the clavicle; from half the breadth of the anterior surface of the sternum, as low down as the attachment of the cartilage of the sixth or seventh rib ; this portion of its origin consists of aponeurotic fibres, which intersect with those of the opposite muscle ; it also arises from the cartilages of all the true ribs, with the exception, frequently, of the first or of the seventh, or both ; and from the aponeurosis of the External oblique muscle of the abdomen. The fibres from this extensive origin converge toward its insertion, giving to the muscle a radiated appearance. Those fibres which arise from the clavicle pass obliquely outward and downward, and are usually separated from the rest by a cellular interval: those from the lower part of the sternum, and the cartilages of the lower true ribs, pass upward and outward, whilst the middle fibres pass horizontally. They all terminate in a flat tendon, about two inches broad, which is inserted into the anterior bicipital ridge of the humerus. This tendon consists of two laminae, placed one in front of the other, and usually blended together below. The anterior, the thicker, receives the clavicular and upper half of the sternal portion of the muscle ; and its fibres are inserted in the same order as that in which they arise; that is to say, the outermost fibres of origin from the clavicle are inserted at the uppermost part of the tendon ; the upper fibres of origin from the sternum pass down to the lowermost part of this anterior lamina of the tendon and extend as low as the tendon of the Deltoid and join with it. The posterior lamina of the tendon receives the attachment of the lower half of the sternal portion and the deeper part of the muscle from the costal cartilages. These deep fibres, and particularly those from the lower costal carti- lages, ascend the higher, turning backward successively behind the superficial and upper ones, so that the tendon appears to be twisted. The posterior lamina reaches higher on the humerus than the anterior one, and from it an expansion is given off which covers the bicipital groove and blends with the capsule of the shoulder-joint. Another expansion passes downward to the fascia of the arm. Relations.-By its anterior surface, with the integument, the superficial fascia, the Platysma, the mammary gland, and the deep fascia ; by its posterior surface : its thoracic portion, with the sternum, the ribs and costal cartilages, the costo- coracoid membrane, the Subclavius, Pectoralis minor, Serratus magnus, and the Intercostals ; its axillary portion forms the anterior wall of the axillary space, and covers the axillary vessels and nerves, the Biceps and Coraco-brachialis muscles. Its upper border lies parallel with the Deltoid, from which it is separated by a slight interspace in which lie the cephalic vein and descending branch of the acromial thoracic artery. Its lotver border forms the anterior margin of the axilla, being at first separated from the Latissimus dorsi by a considerable interval; but both muscles gradually converge toward the outer part of the space. Subclavius. Dissection.-Detach the Pectoralis major by dividing the muscle along its attachment to the clavicle, and by making a vertical incision through its substance a little external to its line of 470 THE MUSCLES AND FASCIAE. attachment to the sternum and costal cartilages. The muscle should then be reflected outward, and its tendon carefully examined. The Pectoralis minor is now exposed, and immediately above it, in the interval between its upper border and the clavicle, a strong fascia, the costo- coracoid membrane. The costo-coracoid membrane is a strong fascia placed between the clavicle and the upper border of the Pectoralis minor muscle, which protects the axillary Fig. 302.-Muscles of the chest and front of the arm. Superficial view. vessels and nerves. Above, it is attached to the anterior margin of the Subclavian groove on the under surface of the clavicle, and is connected with a layer of cervical fascia which overlies the Omo-hyoid muscle, and forms the posterior layer of the sheath of the Subclavius muscle. Internally, it is attached to the first rib internal to the origin of the Subclavius muscle. Externally it is very thick and dense, and is attached to the coracoid process. The portion extending from its attachment to the first rib to the coracoid process is often whiter and denser than the rest; this is sometimes called the costo-coracoid ligament. Below, it is thin, and at the upper border of the Pectoralis minor it splits into two layers to invest the muscle; from the lower border of the Pectoralis minor it is continued down- THE ANTERIOR THORACIC REGION. 471 ward to join the axillary fascia, and outward to join the fascia over the short head of the Biceps. The costo-coracoid membrane is pierced by the cephalic vein, the aciomial thoracic artery and vein, superior thoracic artery, and anterior thoracic nerves. The Pectoralis minor (Fig. 303) is a thin, flat, triangular muscle, situated at the upper part of the thorax, beneath the Pectoralis major. It arises by three Fig. 303.-Muscles of the chest and front of the arm, with the boundaries of the axilla. tendinous digitations from the upper margin and outer surface of the third, fourth, and fifth ribs, near their cartilages, and from the aponeurosis covering the Intercostal muscles ; the fibres pass upward and outward, and converge to form a flat tendon, which is inserted into the inner border and upper surface of the cora- coid process of the scapula. Relations.-By its anterior surface, with the Pectoralis major and the superior thoracic vessels and nerves ; by its posterior surface, with the ribs, Intercostal muscles, Serratus magnus, the axillary space, and the axillary vessels and nerves. Its upper border is separated from the clavicle by a triangular interval, broad internally, narrow externally, bounded in front by the costo-coracoid membrane, and internally by the ribs. In this space are the first part of the axillary vessels and nerves. The costo-coracoid membrane should now be removed, when the Subclavius muscle will be seen. The Subclavius is a long, thin, spindle-shaped muscle, placed in the interval between the clavicle and the first rib. It arises by a short, thick tendon from the first rib and its cartilage at their junction, in front of the rhomboid ligament; the 472 THE MUSCLES AND FASCIAE. fleshy fibres proceed obliquely upward and outward, to be inserted into a deep groove on the under surface of the middle third of the clavicle. Relations.-By its upper surface, with the clavicle. By its under surface it is separated from the first rib by the subclavian vessels and brachial plexus of nerves. Its anterior surface is separated from the Pectoralis major by the costo-coracoid membrane, which, with the clavicle, forms an osseo-fibrous sheath in which the muscle is enclosed. If the costal attachment of the Pectoralis minor is divided across, and the muscle reflected outward, the axillary vessels and nerves are brought fully into view, and should be examined. Nerves.-The Pectoral muscles are supplied by the anterior thoracic nerves; the Subclavius, by a filament from the cord formed by the union of the fifth and sixth cervical nerves. Actions.-If the arm has been raised by the Deltoid, the Pectoralis major will, con- jointly with the Latissimus dorsi and Teres major, depress it to the side of the chest. If acting alone, it adducts and draws for- ward the arm, bringing it across the front of the chest, and at the same time rotates it inward. The Pectoralis minor depresses the point of the shoulder, drawing the scapula downward and inward to the thorax, and throwing the inferior angle backward. The Subclavius depresses the shoulder, drawing the clavicle downward and forward. When the arms are fixed, all three muscles act upon the ribs, drawing them upward and expand- ing the chest, and thus becoming very important agents in forced inspiration. Asthmatic patients always assume an atti- tude which fixes the shoulders, so that all these muscles may be brought into action to assist in dilating the cavity of the chest. Lateral Thoracic Region. Serratus magnus. The Serratus magnus (Fig. 304) is a broad, thin, and irregularly quadrilateral muscle, situated at the upper part and side of the chest. It consists of two tri- angular or fan-shaped portions; the upper one having the apex of the triangle at- tached to the first and second ribs, and the base to the upper angle and vertebral border of the scapula; the lower with its apex behind attached to the inferior angle of the scapula, and its base in front con- nected vith the ribs from the second to the eighth. It arises by nine fleshy digitations from the outer surface and upper border of the eight upper ribs (the second rib having two), and from the aponeurosis covering the upper intercostal muscles, and is inserted into the whole length of the anterior aspect of the poste- rior border of the scapula. The upper fan-shaped portion is attached to the fore part of the outer surfaces of the first and second ribs ; its fibres spread out, the upper ones forming a thick fasciculus, which passes upward and backward, and is attached to the triangular smooth surface on the anterior aspect of the superior angle of the scapula ; the remaining fibres proceed backward and downward to Slip Of SERRATUS MAGNUS to 1st rib. Spine of scapula. HXTERNVS OBLIQUUS. 8th rib. nrnJnn'i^CMy.ratus prep; aration in the Museum of the Royal College of Surgeons of England.) THE ACROMIAL REGION. 473 be attached to the posterior border of the scapula between the superior and inferior angles. I he lower fan-shaped portion is attached posteriorly by its apex to the anterior surface of the inferior angle of the scapula, partly by muscular, partly by tendinous fibres; it spreads out like a fan, the upper fibres passing forward and upward, the lower horizontally forward to be inserted into the outer surface of the fore part of the ribs from the second to the eighth, by a series of muscular digitations. In the intervals between the four lower of these are received cor- responding processes of the External oblique. Relations.-This muscle is covered, in front, by the Pectoral muscle; behind by the Subscapularis; above, by the axillary vessels and nerves. Its deep surface rests upon the ribs and Intercostal muscles. Nerves.-The Serratus magnus is supplied by the posterior thoracic nerve. Actions.-The Serratus magnus, as a whole, carries the scapula forward, and at the same time raises the vertebral border of the bone. It is therefore concerned in the action of pushing. Its lower and stronger fibres move forward the lower angle and assist the Trapezius in rotating the bone round an axis through its centre, and thus assists this muscle in raising the acromion and supporting weights upon the shoulder. It is possible that when the shoulders are fixed the lower fibres may assist in raising and everting the ribs ; but it is not the important inspiratory muscle which it was formerly believed to be. Surgical Anatomy.--When the muscle is paralyzed the vertebral border, and especially the lower angle, leave the ribs and stand out prominently on the surface, giving a peculiar " winged" appearance to the back. The patient is unable to raise the arm above a right angle, and an attempt to do so is followed by a revolution of the scapula, instead of by the elevation of the arm. Dissection.-After completing the dissection of the axilla, if the muscles of the back have been dissected, the upper extremity should be separated from the trunk. Saw through the clavicle at its centre, and then cut through the muscles which connect the scapula and arm with the trunk, viz. : the Pectoralis minor in front, Serratus magnus at the side, and the Levator anguli scapulae, the Rhomboids, Trapezius, and Latissimus dorsi behind. These muscles should be cleaned and traced to their respective insertions. Then make an incision through the integu- ment, commencing at the outer third of the clavicle, and extending along the margin of that bone, the acromion process, and spine of the scapula; the integument should be dissected from above downward and outward, when the fascia covering the Deltoid is exposed (Fig. 301, No. 3). The superficial fascia of the upper extremity is a thin cellulo-fibrous layer, containing the superficial veins and lymphatics, and the cutaneous nerves. It is most distinct in front of the elbow, and contains very large superficial veins and nerves; in the hand it is hardly demonstrable, the integument being closely adherent to the deep fascia by dense fibrous bands. Small subcutaneous bursae are found in this fascia over the acromion, the olecranon, and the knuckles. The deep fascia of the upper extremity comprises the aponeurosis of the shoulder, arm, and forearm, the anterior and posterior annular ligaments of the carpus, and the palmar fascia. These will be considered in the description of the muscles of the several regions. Acromial Region. The deep fascia covering the Deltoid (deltoid aponeurosis) is a fibrous layer which covers the outer surface of the muscle, thick and strong behind, where it is continuous with the infraspinatus fascia, thinner over the rest of its extent. It sends down numerous prolongations between the fasciculi of the muscle. In front, it is continuous with the fascia covering the great Pectoral muscle; behind, with that covering the Infraspinatus; above, it is attached to the clavicle, the acromion, and spine of the scapula ; below, it is continuous with the deep fascia of the arm. The Deltoid (Fig. 302) is a large, thick, triangular muscle, which gives the rounded outline to the shoulder, and has received its name from its resemblance to the Greek letter A reversed. It surrounds the shoulder-joint in the greater part of its extent, covering it on its outer side, and in front and behind. It arises from Deltoid. 474 THE MUSCLES AND EASCIrE. the outer third of the anterior border and upper surface of the clavicle; from the outer margin and upper surface of the acromion process, and from the lower lip of the posterior border of the spine of the scapula, as far back as the triangular surface at its inner end. From this extensive origin the fibres converge toward their insertion, the middle passing vertically, the anterior obliquely backward, the posterior obliquely forward; they unite to form a thick tendon, which is inserted into a rough prominence on the middle of the outer side of the shaft of the humerus. At its insertion the muscle gives off an expansion to the deep fascia of the arm. This muscle is remarkably coarse in texture, and the arrangement of its muscular fibres is somewhat peculiar; the central portion of the muscle-that is to say, the part arising from the acromion process-consists of oblique fibres, which arise in a bipenniform manner from the sides of tendinous intersections, generally four in number, which are attached above to the acromion process and pass downward parallel to one another in the substance of the muscle. The oblique muscular fibres thus formed are inserted into similar tendinous intersec- tions, generally three in number, which pass upward from the insertion of the muscle into the humerus and alternate with the descending septa. The lateral portions of the muscle-that is to say, the fibres arising from the clavicle and spine of the scapula-are not arranged in this manner, but consist of parallel fasciculi passing from their origin above, to be inserted into the margins of the inferior tendon. Relations.-By its superficial surfac'd} with the integument, the superficial fascia, Platysma, and supra-acromial nerves. Its deep surface is separated from the head of the humerus by a large sacculated synovial bursa, and covers the coracoid process, coraco-acromial ligament, Pectoralis minor, Coraco-brachialis, both heads of the Biceps, the tendon of the Pectoralis major, the insertions of the Supraspinatus, Infraspinatus, and Teres minor, the scapular and external heads of the Triceps, the circumflex vessels and nerve, and the humerus. Its anterior border is separated at its upper part from the Pectoralis major by a cellular interspace, which lodges the cephalic vein and descending branch of the acromial thoracic artery: lower down the two muscles are in close contact. Its posterior border rests on the Infraspinatus and Triceps muscles. Nerves.-The Deltoid is supplied by the circumflex nerve. Actions.-The Deltoid raises the arm directly from the side, so as to bring it at right angles with the trunk. Its anterior fibres, assisted by the Pectoralis major, draw the arm forward; and its posterior fibres, aided by the Teres major and Latissimus dorsi, draw it backward. Surgical Anatomy.-The Deltoid is very liable to atrophy, and when in this condition simulates dislocation of the shoulder-joint, as there is flattening of the shoulder and apparent prominence of the acromion process; upon examination, however, it will be found that the relative position of the great tuberosity of the humerus to the acromion and coracoid process is unchanged. Atrophy of the Deltoid may be due to disuse or loss of trophic influence, either from injury to the circumflex nerve or cord lesions, as in infantile paralysis. Dissection.-Divide the Deltoid across, near its upper part, by an incision carried along the margin of the clavicle, the acromion process, and spine of the scapula, and reflect it downward : the bursa will be seen on its under surface, as well as the circumflex vessels and nerve. Anterior Scapular Region. The subscapular fascia is a thin membrane attached to the entire circumference of the subscapular fossa, and affording attachment by its inner surface to some of the fibres of the Subscapularis muscle: when this is removed, the Subscapularis muscle is exposed. The Subscapularis (Fig. 303) is a large triangular muscle which fills up the subscapular fossa, arising from its internal two-thirds, with the exception of a narrow margin along the posterior border, and the surfaces at the superior and inferior angles which afford attachment to the Serratus magnus. Some fibres Subscapularis. THE POSTERIOR SCAPULAR REGION. 475 arise from tendinous laminae, which intersect the muscle, and are attached to ridges on the bone; and others from an aponeurosis, which separates the muscle from the Teres major and the long head of the Triceps. The fibres pass outward, and gradually converging, terminate in a tendon, which is inserted into the lesser tuberosity of the humerus. Those fibres which arise from the axillary border of the scapula are inserted into the neck of the humerus to the extent of an inch below the tuberosity. The tendon of the muscle is in close contact with the capsular ligament of the shoulder-joint, and glides over a large bursa, which separates it from the base of the coracoid process. This bursa communicates with the cavity of the joint by an aperture in the capsular ligament. Relations.-By its anterior surface, with the Serratus magnus, Coraco- brachialis, and Biceps, the axillary vessels and nerves, and the subscapular vessels and nerves; by its posterior surface, with the scapula and the capsular ligament of the shoulder-joint. Its lower border is contiguous with the Teres major and Latissimus dorsi. Nerves.-It is supplied by the upper and lower subscapular nerves. Actions.-The Subscapularis rotates the head of the humerus inward ; when the arm is raised, it draws the humerus downward. It is a powerful defence to the front of the shoulder-joint, preventing the displacement of the head of the bone forward. Supraspinatus. Infraspinatus. Posterior Scapular Region (Fig. 305) Teres minor. Teres major. Dissection.-To expose these muscles, and to examine their mode of insertion into the humerus, detach the Deltoid and Trapezius from their attachment to the spine of the scapula and acromion process. Remove the clavicle by dividing the ligaments connecting it with the coracoid process, and separate it at its articulation with the scapula: divide the acromion process near its root with a saw. The fragments being removed, the tendons of the posterior Scapular muscles will be fully exposed, and can be examined. A block should be placed beneath the shoulder-joint, so as to make the muscles tense. The Supraspinous fascia is a thick and dense membranous layer, which com- pletes the osseo-fibrous case in which the Supraspinatus muscle is contained, affording attachment, by its inner surface, to some of the fibres of the muscle. It is thick internally, but thinner externally under the coraco-acromial ligament. When this fascia is removed, the Supraspinatus muscle is exposed. The Supraspinatus muscle occupies the whole of the supraspinous fossa, arising from its internal two-thirds and from the strong fascia which covers its sur- face. The muscular fibres converge to a tendon which passes across the capsular ligament of the shoulder-joint, to which it is intimately adherent, and is inserted into the highest of the three facets on the great tuberosity of the humerus. Relations.-By its upper surface, with the Trapezius, the clavicle, the acromion, the coraco-acromial ligament, and the Deltoid; by its under surface, with the scapula, the suprascapular vessels and nerve, and upper part of the shoulder-joint. The Infraspinous fascia is a dense fibrous membrane, covering in the Infra- spinatus muscle and attached to the circumference of the infraspinous fossa ; it affords attachment, by its inner surface, to some fibres of that muscle. At the point where the Infraspinatus commences to be covered by the Deltoid, this fascia divides into two layers: one layer passes over the Deltoid muscle, helping to form the Deltoid fascia already described ; the other passes beneath the Deltoid to the shoulder-joint. The Infraspinatus is a thick, triangular muscle, which occupies the chief part of the infraspinous fossa, arising by fleshy fibres from its internal two-thirds, and by tendinous fibres from the ridges on its surface : it also arises from a strong fascia which covers it externally, and separates it from the Teres major and minor, 'fhe fibres converge to a tendon which glides over the external border of the spine of the scapula, and, passing across the capsular ligament of the shoulder- 476 77/A' MUSCLES AND FASCIAE. joint, is inserted into the middle facet on the great tuberosity of the humerus. The tendon of this muscle is occasionally separated from the spine of the scapula bv a synovial bursa which communicates with the synovial cavity of the shouldei- joint. Relations.-Bv its posterior surface, with the Deltoid, the Irapezius, Latissimus dorsi, and the integument; by its anterior surface, with the scapula, from which Fig. 305.-Muscles on the dorsum of the Scapula and the Triceps. it is separated by the suprascapular and dorsalis scapulae vessels, and with the capsular ligament of the shoulder-joint. Its lower border is in contact with the Teres minor, and occasionally united with it, and with the Teres major. The Teres minor is a narrow, elongated muscle, which lies along the inferior border of the scapula. It arises from the dorsal surface of the axillary border of the scapula for the upper two-thirds of its extent, and from two aponeurotic laminae, one of which separates this muscle from the Infraspinatus, the other from the Teres major; its fibres pass obliquely upward and outward, and terminate in a tendon which is inserted into the lowest of the three facets on the great tuberosity of the humerus, and, by fleshy fibres, into the humerus immediately below it. The tendon of this muscle passes across the capsular ligament of the shoulder-joint. Relations.-By its posterior surface, with the Deltoid, and the integument; by its anterior surface, with the scapula, and dorsal branch of the subscapular artery, the long head of the Triceps, and the shoulder-joint; by its upper border, with the Infraspinatus; by its lowei' border, with the Teres major, from which it is separated anteriorly by the long head of the Triceps. The Teres major is a broad and somewhat flattened muscle, which arises from the dorsal aspect of the inferior angle of the scapula, and from the fibrous septa interposed between it and the Teres minor and Infraspinatus; the fibres are THE ARM. 477 directed upward and outward, and terminate in a flat tendon, about two inches in length, which is inserted into the posterior bicipital ridge of the humerus. The tendon of this muscle, at its insertion into the humerus, lies behind that of the Latissimus dorsi, from which it is separated by a synovial bursa, the two tendons being, however, united along their lower borders for a short distance. Relations.-By its posterior surface, with the integument, from which it is separated, internally, by the Latissimus dorsi; and externally, by the long head of the Triceps; by its anterior surface, with the Subscapularis, Latissimus dorsi, Coraco-brachialis, short head of the Biceps, the axillary vessels, and brachial plexus of nerves. Its upper border is at first in relation with the Teres minor, from which it is afterward separated by the long head of the Triceps. Its lower border forms, in conjunction with the Latissimus dorsi, part of the posterior boundary of the axilla. Nerves.-The Supra- and Infraspinatus muscles are supplied by the suprascap- ular nerve ; the Teres minor, by the circumflex ; and the Teres major, by the lower subscapular. Actions.-The Supraspinatus assists the Deltoid in raising the arm from the side, and fixes the head of the humerus in its socket. The Infraspinatus and Teres minor rotate the head of the humerus outward : when the arm is raised, they assist in retaining it in that position and carrying it backward. One of the most important uses of these three muscles is the great protection they afford to the shoulder-joint, the Supraspinatus supporting it above, and preventing displacement of the head of the humerus upward, whilst the Infraspinatus and Teres minor protect it behind, and prevent dislocation backward. The Teres major assists the Latissimus dorsi in drawing the humerus downward and backward, when pre- viously raised, and rotating it inward; when the arm is fixed, it may assist the Pectoral and Latissimus dorsi muscles in drawing the trunk forward. Anterior Humeral Region (Fig. 303). THE ARM. Coraco-brachialis. Biceps. Brachialis anticus. Dissection.-The arm being placed on the table, with the front surface uppermost, make a vertical incision through the integument along the middle line, from the outer extremity of the anterior fold of the axilla, to about two inches below the elbow-joint, where it should be joined by a transverse incision, extending from the inner to the outer side of the forearm ; the two flaps being reflected on either side, the fascia should be examined (Fig. 301). The deep fascia of the arm is continuous with that covering the shoulder and front of the great Pectoral muscle, by means of which it is attached, above, to the clavicle, acromion, and spine of the scapula; it forms a thin, loose, membranous sheath investing the muscles of the arm, sending down septa between them, and composed of fibres disposed in a circular or spiral direction, and connected together by vertical and oblique fibres. It differs in thickness at different parts, being thin over the Biceps, but thicker where it covers the Triceps, and over the condyles of the humerus : it is strengthened by fibrous aponeuroses, derived from the Pectoralis major and Latissimus dorsi on the inner side, and from the Deltoid externally. On either side it gives off a strong intermuscular septum, which is attached to the condyloid ridge and condyle of the humerus. These septa serve to separate the muscles of the anterior from those of the posterior brachial region. The external intermuscular septum extends from the lower part of the anterior bicipital ridge, along the external condyloid ridge, to the outer condyle ; it is blended with the tendon of the Deltoid, gives attachment to the Triceps behind, to the Brachialis anticus, Supinator longus, and Extensor carpi radialis longior, in front; and is perforated by the musculo-spiral nerve and superior profunda artery. The internal intermuscular septum, thicker than the preceding, extends from the lower part of the posterior lip of the bicipital groove below the Teres major, along the internal condyloid ridge to the inner condyle; it is blended with the tendon of the Coraco- brachialis, and affords attachment to the Triceps behind, and the Brachialis anticus 478 THE MUSCLES AND EASCLE. in front. It is perforated by the ulnar nerve and the inferior profunda and anasto- motic arteries. At the elbow the deep fascia is attached to all the prominent points round the joint-viz. the condyles of the humerus and the olecranon process of the ulna-and is continuous with the deep fascia of the forearm. Just below the middle of the arm, on its inner side, in front of the internal intermuscular septum, is an oval opening in the deep fascia which transmits the basilic vein and some lymphatic vessels. On the removal of this fascia the muscles, vessels, and nerves of the anterior humeral region are exposed. The Coraco-brachialis, the smallest of the three muscles in this region, is sit- uated at the upper and inner part of the arm. It arises by fleshy fibres from the apex of the coracoid process, in common with the short head of the Biceps, and from the intermuscular septum between the two muscles; the fibres pass downward, backward, and a little outward, to be inserted by means of a flat ten- don into a rough ridge at the middle of the inner surface and internal border of the shaft of the humerus between the origins of the Triceps and Brachialis anticus. It is perforated by the musculo-cutaneous nerve. The inner border of the muscle forms a guide to the position of the brachial artery in tying the vessel in the upper part of its course. Relations.-By its anterior surface, with the Pectoralis major above, and at its insertion with the brachial vessels and median nerve which cross it; by its posterior surface, with the tendons of the Subscapularis, Latissimus dorsi, and Teres major, the inner head of the Triceps, the humerus, and the anterior circum- flex vessels; by its inner border, with the brachial artery, and the median and musculo-cutaneous nerves; by its outer border, with the short head of the Biceps and Brachialis anticus. The Biceps (Biceps flexor cubiti) is a long fusiform muscle, occuping the whole of the anterior surface of the arm, and divided above into two portions or heads, from which circumstance it has received its name. The short head arises by a thick flattened tendon from the apex of the coracoid process, in common with the Coraco-brachialis. The long head arises from the supraglenoid tubercle on the upper margin of the glenoid cavity, by a long rounded tendon, which is continuous with the glenoid ligament. This tendon arches over the head of the humerus, being enclosed in a special sheath of the synovial membrane of the shoulder-joint; it then passes through an opening in the capsular ligament at its attachment to the humerus, and descends in the bicipital groove, in which it is retained by a fibrous prolongation from the tendon of the Pectoralis major. The fibres from this tendon form a rounded belly, and, about the middle of the arm, join with the portion of the muscle derived from the short head. The belly of the muscle, narrow and somewhat flattened, terminates above the elbow in a flattened tendon, which is inserted into the back part of the tuberosity of the radius, a synovial bursa being interposed between the tendon and the front of the tuberosity. The tendon of the muscle is thin and broad ; as it approaches the radius it becomes narrow and twisted upon itself, so that its external border becomes anterior, and its posterior flat sur- face is applied to the back of the tuberosity: opposite the bend of the elbow the tendon gives off, from its inner side, a broad aponeurosis, the bicipital fascia (semi- lunar fascia), which passes obliquely downward and inward across the brachial artery, and is continuous with the deep fascia of the forearm (Fig. 302). The inner border of this muscle forms a guide to the position of the vessel in tying the brachial artery in the middle of the arm.1 Relations.-Its anterior surface is overlapped above by the Pectoralis major and Deltoid ; in the rest of its extent it is covered by the superficial and dee]) fasciae and the integument. Its posterior surface rests on the shoulder-joint and 1A third head to the Biceps is occasionally found (Theile says as often as once in eight or nine subjects), arising at the upper and inner part of the Brachialis anticus, with the fibres of which it is continuous, and inserted into the bicipital fascia and inner side of the tendon of the Biceps. In most cases this additional slip passes behind the brachial artery in its course down the arm. Occa- sionally the third head consists of two slips which pass down, one in front, the other behind the artery, concealing the vessel in the lower half of the arm. THE POSTERIOR HUMERAL REGION. 479 humerus, from which it is separated by the Subscapularis, Teres major, Latissimus dorsi, Brachialis anticus, and the musculo-cutaneous nerve. Its inner border is in relation with the Coraco-brachialis, the brachial vessels, and median nerve ; its outer border, with the Deltoid and Supinator longus. The Brachialis anticus is a broad muscle, which covers the elbow-joint and the lower half of the front of the humerus. It is somewhat compressed from before backward, and is broader in the middle than at either extremity. It arises from the lower half of the outer and inner surfaces of the shaft of the humerus, and commences above at the insertion of the Deltoid, which it embraces by two angular processes. Its origin extends below, to within an inch of the margin of the articular surface, and is limited on each side by the external and internal borders of the shaft of the humerus. It also arises from the intermuscular septa on each side, but more extensively from the inner than the outer, from which it is separated below by the Supinator longus and Extensor carpi radialis longior. Its fibres converge to a thick tendon, which is inserted into a rough depression on the anterior surface of the coronoid process of the ulna, being received into an interval between two fleshy slips of the Flexor digitorum profundus. Relations.-By its anterior surface, with the Biceps, the brachial vessels, musculo-cutaneous, and median nerves; by its posterior surface, with the humerus and front of the elbow-joint; by its inner border, with the Triceps, ulnar nerve, and Pronator radii teres, from which it is separated by the intermuscular septum ; by its outer border, with the musculo-spiral nerve, radial recurrent artery, the Supinator longus, and Extensor carpi radialis longior. Nerves.-The muscles of this group are supplied by the musculo-cutaneous nerve. The Brachialis anticus usually receives an additional filament from the musculo-spiral. Actions.-The Coraco-brachialis draws the humerus forward and inward, and at the same time assists in elevating it toward the scapula. The Biceps is a flexor of the forearm: it is also a supinator, and serves to render tense the deep fascia of the forearm by means of the broad aponeurosis given off from its tendon. The Brachialis anticus is a flexor of the forearm, and forms an important defence to the elbow-joint. When the forearm is fixed, the Biceps and Brachialis anticus flex the arm upon the forearm, as is seen in efforts of climbing. Posterior Humeral Region. Triceps. Subanconeus. The Triceps (Triceps extensor cubiti) (Fig- 305) is situated on the back of the arm, extending the entire length of the posterior surface of the humerus. It is of large size, and divided above into three parts; hence its name. These three portions have been named (1) the middle, scapular, or long head; (2) the external, or long humeral; and (3) the internal, or short humeral head. The middle or scapular head arises, by a flattened tendon, from a rough triangular depression immediately below the glenoid cavity, being blended at its upper part with the capsular ligament; the muscular fibres pass downward between the two other portions of the muscle, and join with them in the common tendon of insertion. The external head arises from the posterior surface of the shaft of the humerus, between the insertion of the Teres minor and the upper part of the musculo-spiral groove; from the external border of the humerus and the external intermuscular septum : the fibres from this origin converge toward the common tendon of insertion. The internal head arises from the posterior surface of the shaft of the humerus, below the groove for the musculo-spiral nerve; commencing above, narrow and pointed, below the insertion of the Teres major, and extending to within an inch of the trochlear surface: it also arises from the internal border of the humerus and internal intermuscular septum. The fibres of this portion of the muscle are 480 THE MUSCLES AND FASCIAE. directed, some downward to the olecranon, whilst others converge to the common tendon of insertion. The common tendon of the Triceps commences about the middle of the back part of the muscle: it consists of two aponeurotic laminae, one of which is subcutaneous and covers the posterior surface of the muscle for the lower half of its extent; the other is more deeply seated in the substance of the muscle : after receiving the attachment of the muscular fibres, they join together above the elbow, and are inserted, for the most part, into the back part of the upper surface of the olecranon process ; a band of fibres is, however, continued downward, on the outer side, over the Anconeus, to blend with the deep fascia of the forearm. A small bursa, occasionally multilocular, is situated on the front part of this surface, beneath the tendon. The long head of the Triceps descends between the Teres minor and Teres major, dividing the triangular space between these two muscles and the humerus into two smaller spaces, one triangular, the other quadrangular (Fig. 305). The triangular space contains the dorsalis scapulae vessels; it is bounded by the Teres minor above, the Teres major below, and the scapular head of the Triceps externally: the quadrangular space transmits the posterior circumflex vessels and the circumflex nerve; it is bounded by the Teres minor above, the Teres major below, the scapular head of the Triceps internally, and the humerus exter- nally. Relations.-By its posterior surface, with the Deltoid above: in the rest of its extent it is subcutaneous ; by its anterior surface, with the humerus, musculo- spiral nerve, superior profunda vessels, and back part of the elbow-joint. Its middle or longhead is in relation, behind, with the Deltoid and Teres minor; in front, with the Subscapularis, Latissimus dorsi, and Teres major. The Subanconeus is a name given to a few fibres from the lower part of the Triceps muscle, which are inserted into the posterior ligament of the elbow-joint. By some authors it is regarded as the analogue of the Subcrureus in the lower limb, but it is not a separate muscle. Nerves.-The Triceps is supplied by the musculo-spiral nerve. Actions.-The Triceps is the great extensor muscle of the forearm, serving, when the forearm is flexed, to extend the elbow-joint. It is the direct antagonist of the Biceps and Brachialis anticus. When the ai m is extended the long head of the muscle may assist the Teres major and Latissimus dorsi in drawing the humerus backward and in adducting it to the thorax. The long head of the Triceps protects the under part of the shoulder-joint, and prevents displacement of the head of the humerus downward and backward. The Subanconeus draws up the posterior ligament during extension of the forearm. Surgical Anatomy.-The existence of the band of fibres from the Triceps to the fascia of the forearm is of importance in excision of the elbow, and should always be carefully preserved from injury by the operator, as by means of these fibres the patient is enabled to extend the forearm, a movement which would otherwise mainly be accomplished by gravity; that is to say, allowing the forearm to drop from its own weight. THE FOREARM. Dissection.-To dissect the forearm, place the limb in the position indicated in Fig. 301 ; make a vertical incision along the middle line from the elbow to the wrist, and a transverse incision at the extremity of this; the superficial structures being removed, the deep fascia of the forearm is exposed. The deep fascia of the forearm, continuous above with that enclosing the arm, is a dense, highly glistening aponeurotic investment, which forms a general sheath enclosing the muscles in this region ; it is attached, behind, to the olecranon and posterior border of the ulna, and gives off from its inner surface numerous inter- muscular septa, which enclose each muscle separately. Below, it is continuous in front with the anterior annular ligament, and forms a sheath for the tendon of the Palmaris longus muscle, which passes over the annular ligament to be inserted into the palmar fascia. Behind, near the wrist-joint, it becomes much thickened THE FOREARM. 481 by the addition of many transverse fibres, and forms the posterior annular liga- ment. It consists of circular and oblique fibres, connected together by numerous vertical fibres. It is much thicker on the dorsal than on the palmar surface, and at the lower than at the upper part of the forearm, and is strengthened by tendinous fibres derived from the Brachialis anticus and Biceps in front, and from the Triceps behind. Its inner surface gives origin to muscular fibres, especially at the upper part of the inner and outer sides of the forearm, and forms the boundaries of a series of conical-shaped cavities, in which the muscles are contained. Besides the vertical septa separating each muscle, transverse septa are given off both on the anterior and posterior surfaces of the forearm, separating the deep from the superficial layer of muscles. Numerous aperturesexist in the fascia for the passage of vessels and nerves; one of these, of large size, situated at the front of the elbow, serves for the passage of a communicating branch between the superficial and deep veins. The muscles of the forearm may be subdivided into groups corresponding to the region they occupy. One group occupies the inner and anterior aspect of the forearm, and comprises the Flexor and Pronator muscles. Another group occupies its outer side, and a third its posterior aspect. The two latter groups include all the Extensor and Supinator muscles. Anterior Brachial Region. Pronator radii teres. Flexor carpi radialis Superficial Layer. Flexor carpi ulnaris. Flexor sublimis digitorum. Palmaris longus These muscles take origin from the internal condyle of the humerus by a common tendon. The Pronator radii teres arises by two heads. One, the larger and more superficial, arises from the humerus, immediately above the internal condyle, and from the tendon common to the origin of the other muscles ; also from the fascia of the forearm and intermuscular septum between it and the Flexor carpi radialis. The other head is a thin fasciculus which arises from the inner side of the coronoid process of the ulna, joining the preceding at an acute angle. Between the two heads passes the median nerve. The muscle passes obliquely across the forearm from the inner to the outer side, and terminates in a flat tendon, which turns over the outer margin of the radius, and is inserted into a rough impression at the middle of the outer surface of the shaft of that bone. Relations.-By its anterior surface, with the deep fascia, the Supinator longus, and the radial vessels and nerve; by its posterior surface, with the Brachialis anticus, Flexor sublimis digitorum, the median nerve, and ulnar artery, the small or deep head being interposed between the two latter structures. Its outer border forms the inner boundary of a triangular space in which is placed the brachial artery, median nerve, and tendon of the Biceps muscle. Its inner border is in contact with the Flexor carpi radialis. Surgical Anatomy.-This muscle, when suddenly brought into very active use, as in the game of lawn tennis, is apt to be strained, producing slight swelling, tenderness, and pain on putting the muscle into action. This is known as "lawn-tennis arm." The Flexor carpi radialis lies on the inner side of the preceding muscle. It arises from the internal condyle by the common tendon, from the fascia of the fore- arm, and from the intermuscular septa between it and the Pronator radii teres, on the outside, the Palmaris longus internally, and the Flexor sublimis digitorum beneath. Slender and aponeurotic in structure at its commencement, it increases in size, and terminates in a tendon which forms the lower two-thirds of its length. This tendon passes through a canal on the outer side of the annular ligament, runs through a groove in the os trapezium (which is converted into a canal by a fibrous sheath, and lined by a synovial membrane), and is inserted into the base 482 THE MUSCLES AND EASCIxE. of the metacarpal bone of the index finger, and by a slip into the base of the metacarpal bone of the middle finger. The radial artery lies between the tendon of this muscle and the Supinator longus, and may easily be tied in this situation. Relations.-By its superficial surf ace, with the deep fascia and the integument; by its deep surface, with the Flexor sublimis digitorum, Flexor longus pollicis, and wrist-joint; by its outer border, with the Pronator radii teres and the radial vessels ; by its inner border, with the Palmaris longus above and the median nerve below. The Palmaris longus is a slender, fusiform muscle lying on the inner side of the preceding. It arises from the inner condyle of the humerus by the common tendon, from the deep fascia, and the intermuscular septa between it and the adjacent muscles. It terminates in a slender, flattened tendon which passes over the annular ligament to end in the palmar fascia, frequently sending a tendinous slip to the short, muscles of the thumb. This muscle is often absent. Relations.-By its superficial surface, with the deep fascia ; by its deep surface, with the Flexor sublimis digitorum; internally, with the Flexor carpi ulnaris ; externally, with the Flexor carpi radialis. The median nerve lies close to the ten- don, just above the wrist, on its inner and posterior side. The Flexor carpi ulnaris lies along the ulnar side of the forearm. It arises by two heads con- nected by a tendinous arch, beneath which pass the ulnar nerve and posterior ulnar recurrent artery. One head arises from the inner condyle of the humerus by the common tendon; the other, from the inner margin of the olecranon by an aponeurosis from the upper two-thirds of the posterior border of the ulna, in common with the Extensor carpi ulnaris and the Flexor profundus digitorum, and from the intermuscular septum between it and the Flexor sublimis digitorum. The fibres terminate in a tendon which occupies the anterior part of the lower half of the muscle, and is inserted into the pisiform bone, and is pro- longed from this to the fifth metacarpal and unci- form bones by the piso-metacarpal and piso-uncinate ligaments and to the annular ligament. The ulnar artery lies on the outer side of the tendon of this muscle, in the lower two-thirds of the forearm, the tendon forming a guide in tying the vessel in this situation. Relations.-By its superficial surface, with the deep fascia, with which it is intimately connected for a considerable extent; by its deep surface, with the Flexor sublimis digitorum, the Flexor profundus digitorum, the Pronator quadratus, and the ulnar vessels and nerve ; by its outer or radial border, with the Palmaris longus above, and the ulnar vessels and nerve below'. The Flexor sublimis digitorum (perforatus) is placed beneath the preceding muscles, which therefore must be removed in order to bring its attachment into view. It is the largest of the muscles of the super- ficial layer, and arises by three heads. One head arises from the internal condyle Fig. 306.-Front of the left forearm. Superficial muscles. THE ANTERIOR BRACHIAL REGION. 483 of the humerus by the common tendon, from the internal lateral ligament of the elbow-joint, and from the intermuscular septum common to it and the pre- ceding muscles. The second head arises from the inner side of the coronoid process of the ulna, above the ulnar origin of the Pronator radii teres (Fig. 200, p. 257). The third head arises from the oblique line of the radius, extending from the tubercle to the insertion of the Pronator radii teres. The fibres pass vertically downward, forming a broad and thick muscle, which divides into four tendons about the middle of the forearm; as these tendons pass beneath the annular ligament into the palm of the hand they are arranged in pairs, the anterior pair corresponding to the middle and ring fingers, the posterior pair to the index and little fingers. The tendons diverge from one another as they pass onward. Opposite the base of the first phalanges each tendon divides into two slips, to allow of the passage of the corresponding tendons of the Flexor profundus digitorum ; the two portions of the tendon then unite and form a grooved channel for the reception of the accompanying deep flexor tendon. Finally they subdivide a second time, to be inserted into the sides of the second phalanges about their middle. After leaving the palm these tendons, accompanied by the deep flexor tendons, lie in osseo-aponeurotic canals formed by the fibrous sheath of the tendons and the bones (Fig. 316). Relations.-In the forearm, by its superficial surface, with the deep fascia and all the preceding superficial muscles ; by its deep surface, with the Flexor profundus digitorum, Flexor longus pollicis, the ulnar vessels and nerve, and the median nerve. In the hand its tendons are in relation, in front, with the palmar fascia, superficial palmar arch, and the branches of the median nerve; behind, with the tendons of the deep Flexor and the Lumbricales. Fibrous Sheath of the Flexor Tendons.-The flexor tendons of the fingers as they run along the phalanges are retained against the bones by a fibrous sheath, forming osseo-aponeurotic canals. These sheaths are formed by strong fibrous bands which arch across the tendons and are attached on each side to the margins of the phalanges. Opposite the middle of the proximal and second phalanges the sheath is very strong, and the fibres pass transversely; but opposite the joints it is much thinner, and the fibres pass obliquely. Each sheath is lined by a synovial membrane, which is reflected on the contained tendon. Deep Layer. Flexor profundus digitorum. Pronator quadratus. Flexor longus pollicis. Dissection.-Divide each of the superficial muscles at its centre, and turn either end aside ; the deep layer of muscles, together with the median nerve and ulnar vessels, will then be exposed. The Flexor profundus digitorum (perforans) (Fig. 307) is situated on the ulnar side of the forearm, immediately beneath the superficial Flexors. It arises from the upper three-fourths of the anterior and inner surfaces of the shaft of the ulna, embracing the insertion of the Brachialis anticus above, and extending, below, to within a short distance of the Pronator quadratus. It also arises from a depression on the inner side of the coronoid process; by an aponeurosis from the upper three-fourths of the posterior border of the ulna, in common with the Flexor and Extensor carpi ulnaris ; and from the ulnar half of the interosseous membrane. The fibres form a fleshy belly of considerable size, which divides into four tendons : these pass under the annular ligament beneath the tendons of the Flexor sublimis digitorum. Opposite the first phalanges the tendons pass between the two slips of the tendons of the Flexor sublimis digitorum, and are finally inserted into the bases of the last phalanges. The tendon of the index finger is distinct; the rest are connected together by cellular tissue and tendinous slips as far as the palm of the hand. The tendons of this and those of the Flexor sublimis digitorum, whilst contained in the osseo-aponeurotic canals of the fingers, are invested in a synovial 484 THE MUSCLES AND EASCLE. sheath, and are connected to each other and to the phalanges by slender tendinous filaments, called vincula accessorial tendinum. One of these con- nects the deep tendon to the bone be- fore it passes through the superficial tendon; a second connects the two tendons together, after the deep ten- dons have passed through; and a third connects the deep tendon to the head of the second phalanx. This last consists largely of yellow elastic tissue, and may assist in drawing down the tendon after flexion of the finger.1 Four small muscles, the Lum- bricales, are connected with the ten- dons of the Flexor profundus in the palm. They will be described with the muscles in that region. Relations.-By its superficial sur- face, in the forearm, with the Flexor sublimis digitorum, the Flexor carpi ulnaris, the ulnar vessels and nerve, and the median nerve; and in the hand, with the tendons of the super- ficial Flexor; by its deep surface, in the forearm, with the ulna, the in- terosseous membrane, the Pronator quadratus; and in the hand, with the interossei, Adductor pollicis, and deep palmar arch ; by its ulnar border, with the Flexor carpi ulnaris ; by its radial border, with the Flexor longus pollicis, the anterior interosseous vessels and nerve being interposed. The Flexor longus pollicis is situ- ated on the radial side of the forearm, lying on the same plane as the pre- ceding. It arises from the grooved anterior surface of the shaft of the radius, commencing above, imme- diately below the tuberosity and ob- lique line, and extending below to within a short distance of the Pro- nator quadratus. It also arises from the adjacent part of the interosseous membrane, and generally by a fleshy slip from the base of the coronoid process. The fibres pass downward, and terminate in a flattened tendon which passes beneath . the annular ligament, is then lodged in the in- terspace between the outer head of the Flexor brevis pollicis and the Adductor obliquus pollicis, and en- tering an osseo-aponeurotic canal Fig. 307-Front of the left forearm. Deep muscles. 1 Marshall, Brit, and For. Med.-Chir. Rev., 1853. THE RADIAL REGION. 485 similar to those for the other flexor tendons, is inserted into the base of the last phalanx of the thumb. Relations.-By its superficial surface, with the Flexor sublimis digitorum, Flexor carpi radialis, Supinator longus, and radial vessels ; by its deep surface, with the radius, interosseous membrane, and Pronator quadratus; by its ulnar border, with the Flexor profundus digitorum, from which it is separated by the anterior interosseous vessels and nerve. The Pronator quadratus is a small, flat, quadrilateral muscle, extending trans- versely across the front of the radius and ulna, above their carpal extremities. It arises from the oblique or pronator ridge on the lower part of the anterior surface of the shaft of the ulna; from the lower fourth of the anterior surface and the anterior border of the ulna; and from a strong aponeurosis which covers the inner third of the muscle. The fibres pass horizontally outward, to be inserted into the lower fourth of the anterior surface and anterior border of the shaft of the radius. Relations.-By its superficial surface, with the Flexor profundus digitorum, the Flexor longus pollicis, Flexor carpi radialis, and the radial vessels; by its deep surface, with the radius, ulna, and interosseous membrane. Nerves.-All the muscles of the superficial layer are supplied by the median nerve, excepting the Flexor carpi ulnaris, which is supplied by the ulnar. Of the deep layer, the Flexor profundus digitorum is supplied conjointly by the ulnar and by the median through its branch, the anterior interosseous nerve, which also sup- plies the Flexor longus pollicis and Pronator quadratus. Actions.-These muscles act upon the forearm, the wrist, and hand. The Pronator radii teres helps to rotate the radius upon the ulna, rendering the hand prone: when the radius is fixed it assists the other muscles in flexing the forearm. The Flexor carpi radialis is one of the flexors of the wrist; when acting alone it flexes the wrist, inclining it to the radial side. It can also assist in pronating the forearm and hand, and, by continuing its action, to bend the elbow. The Flexor carpi ulnaris is one of the flexors of the wrist: when acting alone it flexes the wrist, inclining it to the ulnar side, and, by continuing to contract, to bend the elbow. The Palmaris longus is a tensor of the palmar fascia. It also assists in flexing the wrist and elbow. The Flexor sublimis digitorum flexes first the middle, and then the proximal, phalanx. It assists in flexing the wrist and elbow. The Flexor profundus digitorum is one of the flexors of the phalanges. After the Flexor sublimis has bent the second phalanx, the Flexor profundus flexes the terminal one, but it cannot do so until after the contraction of the superficial muscle. It also assists in flexing the wrist. The Flexor longus pollicis is a flexor of the phalanges of the thumb. When the thumb is fixed it also assists in flexing the wrist. The Pronator quadratus helps to rotate the radius upon the ulna, rendering the hand prone. Radial Region (Fig. 308). Supinator longus. Extensor carpi radialis longior. Extensor carpi radialis brevior. Dissection.-Divide the integument in the same manner as in the dissection of the anterior brachial region, and, after having examined the cutaneous vessels and nerves and deep fascia, remove all those structures. The muscles will then be exposed. The removal of the fascia will be considerably facilitated by detaching it from below upward. Great care should be taken to avoid cutting across the tendons of the muscles of the thumb, which cross obliquely the larger tendons running down the back of the radius. The Supinator longus is the most superficial muscle on the radial side of the forearm : it is fleshy for the upper two-thirds of its extent, tendinous below. It arises from the upper two-thirds of the external condyloid ridge of the humerus, and from the external intermuscular septum, being limited above by the 486 THE MUSCLES AND FASCIHi. musculo-spiral groove. The fibres terminate above the middle of the fore- arm in a flat tendon which is inserted into the outer side of the base of the styloid process of the radius. Relations.-By its superficial sur- face, with the integument and fascia for the greater part of its extent; near its insertion it is crossed by the Extensor ossis metacarpi pollicis and the Extensor brevis pollicis; by its deep surface, with the humerus, the Extensor carpi radialis longior and brevior, the insertion of the Pronator radii teres, and the Supinator brevis; by its inner border, above the elbow, with the Brachialis anticus, the musculo-spiral nerve, and radial re- current artery ; and in the forearm with the radial vessels and nerve. The Extensor carpi radialis longior is placed partly beneath the pre- ceding muscle. It arises from the lower third of the external condyloid ridge of the humerus, and from the external intermuscular septum. The fibres terminate at the upper third of the forearm in a flat tendon, which runs along the outer border of the radius, beneath the extensor tendons of the thumb; it then passes through a groove common to it and the Ex- tensor carpi radialis brevior, imme- diately behind the styloid process, and is inserted into the base of the meta- carpal bone of the index finger, on its radial side. Relations.-By its superficial sur- face, with the Supinator longus, and fascia of the forearm ; its outer side is crossed obliquely by the extensor ten- dons of the thumb ; by its deep surface, with the elbow-joint, the Extensor carpi radialis brevior, and back part of the wrist. The Extensor carpi radialis brevior is shorter, as its name implies, and thicker than the preceding muscle, be- neath which it is placed. It arises from the external condyle of the humerus by a tendon common to it and the three following muscles; from the external lateral ligament of the elbow-joint, from a strong aponeurosis which covers its surface, and from the intermuscular septa between it and the adjacent muscles. The fibres ter- Fig. 308-Posterior surface of the forearm. Super- ficial muscles. THE POSTERIOR BRACHIAL REGION. 487 minate about the middle of the forearm in a flat tendon which is closely connected with that of the preceding muscle, and accompanies it to the wrist, lying in the same groove on the posterior surface of the radius; it passes beneath the extensor tendons of the thumb, then beneath the annular ligament, and, diverging some- what from its fellow, is inserted into the base of the metacarpal bone of the middle finger, on its radial side. The tendons of the two preceding muscles pass through the same compartment of the annular ligament, and are lubricated by a single synovial membrane, but are separated from each other by a small vertical ridge of bone as they lie in the groove at the back of the radius. Relations.-By its superficial surface, with the Extensor carpi radialis longior, and with the Extensor muscles of the thumb which cross it; by its deep surface, with the Supinator brevis, tendon of the Pronator radii teres, radius, and wrist- joint; by its ulnar border, with the Extensor communis digitorum. Posterior Brachial Region (Fig. 308). Superficial Layer. Extensor communis digitorum. Extensor minimi digiti. Extensor carpi ulnaris. Anconeus. The Extensor communis digitorum is situated at the back part of the forearm. It arises from the external condyle of the humerus by the common tendon, from the deep fascia, and the intermuscular septa between it and the adjacent muscles. Just below the middle of the forearm it divides into three tendons, which pass, together with the Extensor indicis, through a separate compartment of the annular ligament, lubricated by a synovial membrane. The tendons then diverge, the innermost one dividing into two; and all, after passing across the back of the hand, are inserted into the second and third phalanges of the fingers in the following manner: Each tendon becomes narrow and thickened opposite the meta- carpo-phalangeal articulation, and gives off a thin fasciculus upon each side of the joint,which blends with the lateral ligaments and serves as the posterior ligament; after having passed the joint it spreads out into a broad aponeurosis, which covers the whole of the dorsal surface of the first phalanx, being reinforced, in this situation, by the tendons of the Interossei and Lumbricales. Opposite the first phalangeal joint this aponeurosis divides into three slips, a middle and two lateral : the former is inserted into the base of the second phalanx ; and the two lateral, which are continued onward along the sides of the second phalanx, unite by their contiguous margins, and are inserted into the dorsal surface of the last phalanx. As the tendons cross the phalangeal joints they furnish them with posterior ligaments. The tendons of the middle, ring, and little fingers are connected together, as they cross the hand, by small, oblique, tendinous slips, or vincula; those on each side of the ring finger are strong, and bind the tendon of this finger closely to those of the middle and little finger, so that it cannot, in general, be freely extended without moving the other two. Sometimes there is also a thin slip betkeen the tendons of the index and middle fingers. The tendons of the index and little fingers also receive, before their division, the special extensor tendons belonging to them. > Relations.-By its superficial surface, with the fascia of the forearm and hand, the posterior annular ligament, and integument; by its deep surface, with the Supinator brevis, the Extensor muscles of the thumb and index finger, the posterior interosseous vessels and nerve, the wrist-joint, carpus, metacarpus, and phalanges; by its radial border, with the Extensor carpi radialis brevior; by its ulnar border, with the Extensor minimi digiti and Extensor carpi ulnaris. The Extensor minimi digiti is a slender muscle placed on the inner side of the Extensor communis, with which it is generally connected. It arises from the common tendon by a thin, tendinous slip, and from the intermuscular septa between it and the adjacent muscles. Its tendon runs through a separate 488 THE MUSCLES AND FASCIAE. compartment in the annular ligament behind the inferior radio-ulnar joint, then divides into two as it crosses the hand, one slip being united to the common extensor by a cross-piece at the metacarpo-phalangeal articulation. Both finally spread into a broad aponeurosis which blends with the common extensor to the finger, and is inserted into the second and third phalanges. The tendon is situated on the ulnar side of, and somewhat more superficial than, the common extensor. The Extensor carpi ulnaris is the most superficial muscle on the ulnar side of the forearm. It arises from the external condyle of the humerus by the common tendon; from the middle third of the posterior surface of the ulna, below the Anconeus, and by an aponeurosis from the posterior border of the ulna in common with the Flexor carpi ulnaris and the Flexor profundus digitorum ; and from the deep fascia of the forearm. This muscle terminates in a tendon which runs through a groove behind the styloid process of the ulna, passes through a separate compart- ment in the annular ligament, and is inserted into the prominent tubercle on the ulnar side of the base of the metacarpal bone of the little finger. Relations.-By its superficial surface, with the deep fascia of the forearm ; by its deep surface, with the ulna and the muscles of the deep layer. The Anconeus is a small triangular muscle placed behind and below the elbow- joint, and appears to be a continuation of the external portion of the Triceps. It arises by a separate tendon from the back part of the outer condyle of the humerus, and is inserted into the side of the olecranon and upper fourth of the posterior surface of the shaft of the ulna; its fibres diverge from their origin, the upper ones being directed transversely, the lower obliquely inward. Relations.-By its superficial surface, with a strong fascia derived from the Triceps ; by its deep surface, with the elbow-joint, the orbicular ligament, the ulna, and a small portion of the Supinator brevis. Supinator brevis. Extensor ossis metacarpi pollicis. Deep Layer (Fig. 310) Extensor brevis pollicis. Extensor longus pollicis. Extensor indicis. The Supinator brevis is a broad muscle, of a hollow cylindrical form, curved round the upper third of the radius. It consists of two distinct planes of muscular fibres, between which lies the posterior interosseous nerve. The two planes arise in common: the superficial one by tendinous, and the deeper by muscular fibres from the external condyle of the humerus; from the external lateral ligament of the elbow-joint and the orbicular ligament of the radius; from the ridge on the ulna, which runs obliquely downward from the posterior extremity of the lesser sigmoid cavity ; from the triangular depression in front of it; and from a tendinous expansion which covers the surface of the muscle. The superficial fibres surround the upper part of the radius, and are inserted into the outer edge of the bicipital tuberosity and to the oblique line of the radius, as low down as the insertion of the Pronator radii teres. The upper fibres of the deeper plane form a sling-like fasciculus, which encircles the neck of the radius above the tuberosity and is attached to the back part of its inner surface: the greater part of this portion of the muscle is inserted into the posterior and external surface of the shaft, midway between the oblique line and the head of the bone. Between the insertion of the two planes the posterior interosseous nerve lies on the shaft of the bone. Relations.-By its superficial surface, with the superficial Extensor and Supinator muscles, and the radial vessels and nerve; by its deep surface, with the elbow-joint, the interosseous membrane, and the radius. The Extensor ossis metacarpi pollicis is the most external and the largest of the deep extensor muscles: it lies immediately below the Supinator brevis, with which it is sometimes united. It arises from the posterior surface of the shaft of the ulna below the insertion of the Anconeus, from the interosseous membrane, THE POSTERIOR BRACHIAL REGION. 489 and from the middle third of the posterior surface of the shaft of the radius. Passing obliquely downward and outward, it terminates in a tendon which runs through a groove on the outer side of the styloid process of the radius, accompanied by the tendon of the Extensor brevis pollicis, and is in- serted into the base of the meta- carpal bone of the thumb. It occa- sionally gives off two slips, near its insertion-one to the Trapezium, and the other to blend with the origin of the Abductor pollicis. Relations.-By its superficial surface, with the Extensor com- munis digitorum, Extensor minimi digiti, and fascia of the forearm, and with the branches of the pos- terior interosseous artery and nerve which cross it; by its deep surface, External Condyle. I I Internal Condyle. Internail condyle. I External condyle. CAPSULAR LIGAMENT. Ulna, < coronoid ' process. Head of , radius. EXTENSOR CARPI ULNARIS. Ulna. Radius. Fig. 309.-Supinator brevis. (From a prepara- tion in the Museum of the Royal College of Surgeons of England). Fig. 310.-Posterior surface of the forearm. Deep muscles. with the ulna, interosseous membrane, radius, the tendons of the Extensor carpi radialis longior and brevior, which it crosses obliquely, and, at the outer side of the wrist, with the radial vessels; by its upper border, with the Supinator brevis; by its lower border, with the Extensor brevis pollicis. 490 THE MUSCLES AND FASCJxE. The Extensor brevis pollicis {Extensor primi internodii pollicis), the smallest muscle of this group, lies on the inner side of the preceding. It arises from the pos- terior surface of the shaft of the radius, below the Extensor ossis metacarpi pollicis, and from the interosseous membrane. Its direction is similar to that of the Extensor ossis metacarpi pollicis, its tendon passing through the same groove on the outer side of the styloid process, to be inserted into the base of the first phalanx of the thumb. Relations.-The same as those of the Extensor ossis metacarpi pollicis. The Extensor longus pollicis {Extensor secundi internodii pollicis) is much larger than the preceding muscle, the origin of which it partly covers in. It arises from the posterior surface of the shaft of the ulna, below the origin of the Extensor ossis metacarpi pollicis, and from the interosseous membrane. It terminates in a tendon which passes through a separate compartment in the annular ligament, lying in a narrow, oblique groove at the back part of the lower end of the radius. It then crosses obliquely the tendons of the Extensor carpi radialis longior and brevior, being separated from the other extensor tendons of the thumb by a triangular interval, in which the radial artery is found, and is finally inserted into the base of the last phalanx of the thumb. Relations.-By its superficial surface, with the same parts as the Extensor ossis metacarpi pollicis; by its deep surface, with the ulna, interosseous membrane, the posterior interosseous nerve, radius, the wrist, the radial vessels, and metacarpal bone of the thumb. The Extensor indicis is a narrow, elongated muscle placed on the inner side of, and parallel with, the preceding. It arises from the posterior surface of the shaft of the ulna, below the origin of the Extensor longus pollicis and from the inter- osseous membrane. Its tendon passes with the Extensor communis digitorum through the same canal in the annular ligament, and subsequently joins the tendon of the Extensor communis which belongs to the index finger, opposite the lower end of the corresponding metacarpal bone, lying to the ulnar side of the tendon from the common Extensor. Relations.-The relations are similar to those of the preceding muscles. Nerves.-The Supinator longus, Extensor carpi radialis longior, and Anconeus are supplied by branches from the musculo-spiral nerve; the remaining muscles of the radial and posterior brachial regions, by the posterior interosseous nerve. Actions.-The muscles of the radial and posterior brachial regions, which comprise all the extensor and supinator muscles, act upon the forearm, wrist, and hand; they are the direct antagonists of the pronator and flexor muscles. The Anconeus assists the Triceps in extending the forearm. The chief action of the Supinator longus is that of a flexor of the elbow-joint, but in addition to this it may act both as a supinator or a pronator ; that is to say, if the forearm is-forcibly pronated it will act as a supinator, and bring the bones into a position midway between supination and pronation ; and, vice versd, if the arm is forcibly supinated, it will act as a pronator, and bring the bones into the same position, midway between supination and pronation. The action of the muscle is therefore to throw the forearm and hand into the position they naturally occupy when placed across the chest. The Supinator brevis is a supinator ; that is to say, when the radius has been carried across the ulna in pronation and the back of the hand is directed forward, this muscle carries the radius back again to its normal position on the outer side of the ulna, and the palm of the hand is again directed forward. The Extensor carpi radialis longior extends the wrist and abducts the hand. It may also assist in bending the elbow-joint; at all events, it serves to fix or steady this articulation. The Extensor carpi radialis brevior assists the Extensor carpi radi- alis longior in extending the wrist, and may also act slightly as an abductor of the hand. The Extensor carpi ulnaris helps to extend the hand, but when acting alone inclines it toward the ulnar side ; by its continued action it extends the elbow-joint. The Extensor communis digitorum extends the phalanges, then the wrist, and finally the elbow. It acts principally on the proximal phalanges, the THE HAND. 491 middle and terminal phalanges being extended mainly by the Interossei and Lum- bricales. It has also a tendency to separate the fingers as it extends them. The Extensor minimi digiti extends the little finger, and by its continued action it assists in extending the wrist. It is owing to this muscle that the little finger can be extended or pointed whilst the others are flexed. The chief action of the Extensor ossis metacarpi pollicis is to carry the thumb outward and backward from the palm of the hand, and hence it has been called the abductor longus pollicis. By its continued action it helps to extend and abduct the wrist. The Extensor brevis pollicis extends the proximal phalanx of the thumb. By its continued action it helps to extend and abduct the wrist. The Extensor longus pollicis extends the terminal phalanx of the thumb. By its continued action it helps to extend and abduct the wrist. The Extensor indicis extends the index finger, and by its continued action assists in extending the wrist. It is owing to this muscle that the index finger can be extended or pointed while the others are flexed. Surgical Anatomy.-The tendons of the Extensor muscles of the thumb are liable to become strained and their sheaths inflamed after excessive exercise, producing a sausage-shaped swelling along the course of the tendon, and giving a peculiar creaking sensation to the finger when the muscle acts. In consequence of its often being caused by such movements as wringing clothes, it is known as "washerwoman's sprain.'' THE HAND. Dissection (Fig. 301).-Make a transverse incision across the front of the wrist, and a second across the heads of the metacarpal bones : connect the two by a vertical incision in the middle line, and continue it through the cen- tre of the middle finger. The anterior and posterior annular ligaments and the palmar fascia should then be dissected. The Anterior Annular Ligament is a strong, fibrous band which arches over the carpus, converting the deep groove on the front of the carpal bones into a canal, beneath which pass the flexor tendons of the fingers. It is attached, internally, to the pisiform bone and unciform pro- cess of the unciform bone, and ex- ternally to the tuberosity of the scaphoid and to the inner part of the anterior surface and the ridge on the trapezium. It is continuous, above, with the deep fascia of the forearm, of which it may be regarded as a thickened portion, and, below, with the palmar fascia. It is crossed by the ulnar vessels and nerve and the cutaneous branches of the median and ulnar nerves. At its outer extremity is the tendon of the Flexor carpi radialis, which lies in the groove on the trapezium between the attachments of the annular ligament to the bone. It has inserted into its anterior surface the tendon of the Palmaris longus and part of the tendon of the Flexor carpi ulnaris, and has arising from it, below, the small muscles of the thumb and little finger. Beneath it pass the tendons of the Flexor sublimis and profundus digitorum, the Flexor longus pollicis, and the median nerve. The Synovial Membranes of the Flexor Tendons at the Wrist.-There are two synovial membranes which enclose all the tendons as they pass beneath this lig- ament-one for the Flexor sublimis and profundus digitorum, the other for the Flexor longus pollicis. They extend up into the forearm for about an inch above the annular ligament, and downward about halfway along the metacarpal bone, where they terminate in a blind diverticulum around each pair of tendons, with the exception of the thumb and sometimes the little finger-in these two fingers Fig. 311.-Transverse section through the wrist, show- ing the annular ligaments and the canals for the passage of the tendons. 492 THE MUSCLES AND FASCIAE. the diverticulum is continued on, and communicates with the synovial sheath of the tendons. In the other three fingers the synovial sheath of the tendons in the fingers begins as a blind pouch without communication with the large synovial sac (Fig. 313). Surgical Anatomy.-This arrangement of the synovial sheaths explains the fact that thecal abscess in the thumb and little finger is liable tobe followed by abscesses in the forearm, from exten- sion of the inflammation along the continuous synovial sheaths. Gan- glion is apt to occur in this situation, constitu- ting "compound palmar ganglion " '■ it presents an hour-glass outline, with a swelling in front of the wrist and in the palm of the hand, and a constriction correspond- ing to the annular liga- ment between the two. The fluid can be forced from the one swelling to the other under the liga- ment. The Posterior An- nular Ligament is a strong fibrous band extending transversely across the back of the wrist, and consisting of the deep fascia of the back of the forearm, strengthened by the addition of some transverse fibres. It forms a sheath for the extensor tendons in their passage to the fingers, being attached, internally, to the styloid process of the ulna, the cuneiform and pisiform bones; externally, to the margin of the radius; and, in its passage across the wrist, to the elevated ridges on the posterior surface of the radius. It pre- sents six compartments for the passage of tendons, each of which is lined by a separate synovial membrane. These are, from without inward-1. On the outer side of the styloid process, for the ten- dons of the Extensor ossis metacarpi and Extensor brevis pollicis ; 2. Behind the styloid process, for the tendons of the Extensor carpi radialis longior and brevior; 3. About the middle- of the posterior surface of the radius, for the tendon of the Extensor longus pollicis; 4. To the inner side of the latter, for the tendons of the Extensor communis digi- torum and Extensor indicis; 5. Oppo- site the interval between the radius and ulna, for the Extensor minimi digiti; 6. Grooving the back of the ulna, for the tendon of the Extensor carpi ulnaris. The synovial membranes lining these sheaths are usually very extensive, reach- ing from above the annular ligament, down upon the tendons for a variable distance on the back of the hand. The deep palmar fascia (Fig. 314) forms a common sheath which invests the muscles of the hand. It consists of a central and two lateral portions. The central portion occupies the middle of the palm, is triangulai* in shape, of FLEXOR LONGUS POLLICIS. FLEXOR CARPI RADIALIS. \ MUSCLES OF THUMB. \ \ ANNULAR LIGAMENT. Median nerve. ' .Ulnar vessels. / jPALMARIS BREVIS. MUSCLES OF </ LITTLE \\finger. 1st EXT. PRIM INTERNOD.' POLL. /ext. carpi ** ULNARIS. EXT. SEC.\ internod/ POLL. Trapezium. Radial vessels. (extensor >M I N I M I DIGITI. EXT. CARP. RAD. LONG. / * Trapezoid. EXTENSOR ''COMMUNIS DIGITORUM. EXTENSOR CARPI BREVIOR. / EXTENSOR INDICIS. Os magnum. Fig. 312.-Transverse section through the carpus, showing the relative posi- tions of the tendons, vessels, and nerves. (Henle.) Fig. 313.-Diagram showing the arrangement of the synovial sheaths of the palm and fingers. THE HAND. 493 great strength and thickness, and binds down the tendons in this situation. It is narrow above, being attached to the lower margin of the annular ligament, and receives the expanded tendon of the Palmaris longus muscle. Below, it is broad and expanded, and divides into four slips, for the four.fingers. Each slip gives off superficial fibres, which are inserted into the skin of the palm and finger, those to the palm joining the skin at the furrow corresponding to the metacarpo-phalangeal articulation, and those to the fingers passing into the skin at the transverse fold at the base of the fingers. The deeper part of each slip subdivides into two pro- cesses, which are inserted into the lateral margins of the anterior (glenoid) liga- ment of the metacarpo-phalangeal joint. From the sides of these processes Digital artery. abductor' H ✓ INDICIS. Digital artery. Digital nerve.- (add. trans* \ POLL. EXTENSOR METACARPI AND "extensor BREVIS POLLICIS. ■FLEXOR LONGUS POLLICIS. Fig. 314.-Palmar fascia. (Altered from a dissection in the Museum of the Royal College of Surgeons of England.) offsets are sent backward, to be attached to the borders of the lateral surfaces of the metacarpal bones at their distal extremities. By this arrangement short channels are formed on the front of the lower ends of the metacarpal bones, through which the flexor tendons pass. Dr. W. W. Keen describes a fifth slip as frequently found passing to the thumb. The intervals left in the fascia between the four fibrous slips transmit the digital vessels and nerves and the tendons of the Lumbricales. At the points of division of the palmar fascia into the slips above mentioned numerous strong, transverse fibres bind the separate processes together. The palmar fascia is intimately adherent to the integument by dense fibro-areolar tissue, forming the superficial palmar fascia, and gives origin bv its inner margin to the Palmaris brevis: it covers the superficial palmar arch, the 494 THE MUSCLES AND FA SC EE. tendons of the flexor muscles, and the branches of the median and ulnar nerves, and on each side it gives oft' a vertical septum, which is continuous with the interosseous aponeurosis and separates the lateral from the middle palmar group of muscles. The lateral portions of the palmar fascia are thin, fibrous layers, which cover, on the radial side, the muscles of the ball of the thumb, and, on the ulnar side, the muscles of the little finger; they are continuous with the dorsal fascia, and in the palm with the central portion of the palmar fascia. The Superficial Transverse Ligament of the Fingers is a thin, fibrous band which stretches across the roots of the four fingers, and is closely attached to the skin of the clefts, and internally to the fifth metacarpal bone, forming a sort of rudimentary web. Beneath it the digital vessels and nerves pass onward to their destination. Surgical Anatomy.-The palmar fascia is liable to undergo contraction, producing a very inconvenient deformity known as " Dupuytren's contraction." The ring and little fingers are most frequently implicated, but the middle, the index, and the thumb may be involved. The proximal phalanx is drawn down and cannot be straightened, and the two distal phalanges become similarly flexed as the disease advances. The Muscles of the Hand are subdivided into three groups: 1. Those of the thumb, which occupy the radial side; 2. Those of the little finger, which occupy the ulnar side; 3. Those in the middle of the palm and between the interosseous spaces. Radial Region (Figs. 315, 316). Muscles of the Thumb. Abductor pollicis. Opponens (Flexor ossis metacarpi) pollicis. Flexor brevis pollicis. Adductor obliquus pollicis. Adductor transversus pollicis. The Abductor pollicis is a thin, flat muscle placed immediately beneath the integument. It arises from the ridge of the os trapezium and annular ligament, and, passing outward and downward, is inserted by a thin, flat tendon into the radial side of the base of the first phalanx of the thumb, sending a slip to join the tendon of the Extensor longus pollicis. Relations.-By its superficial surface, with the palmar fascia ; by its deep surface, with the Opponens pollicis, from which it is separated by a thin apo- neurosis. Its inner border is separated from the Flexor brevis pollicis by a narrow cellular interval. The Opponens pollicis is a small, triangular muscle placed beneath the preceding. It arises from the palmar surface of the trapezium and annular ligament, passes downward and outward, and is inserted into the whole length of the metacarpal bone of the thumb on its radial side. Relations.-By its superficial surface, with the Abductor pollicis; by its deep surface, with the trapezio-metacarpal articulation; by its inner border, with the Flexor brevis pollicis. The Flexor brevis pollicis is much larger than either of the two preceding muscles, beneath which it is placed. It consists of two portions, outer and inner. The outer and more superficial portion arises from the trapezium and outer two- thirds of the annular ligament, and passes along the outer side of the tendon of the Flexor longus pollicis, and, becoming tendinous, has a sesamoid bone developed in its tendon, and is inserted into the outer side of the base of the first phalanx of the thumb. The inner and deeper portion of the muscle is very small, and arises from the ulnar side of the first metacarpal bone, and is inserted into the inner side of the base of the first phalanx with the Adductor obliquus pollicis. A sesamoid bone is developed in the common tendon of insertion. Relations.-By its superficial surface, with the palmar fascia; by its deep sur- THE RADIAL REGION. 495 face, with the tendon of the Flexor carpi radialis ; by its external surface, with the Opponens pollicis; by its internal surface, with the Adductor obliquus pollicis. The Adductor obliquus pollicis arises by several slips from the os magnum, the bases of the second and third metacarpal bones, the anterior annular ligament, and the sheath of the tendon of the Flexor carpi radialis. From this origin the greater number of fibres pass obliquely downward and converge to a tendon, which, uniting with the tendons of the deeper portion of the Flexor brevis pollicis and the Adductor transversus, is inserted into the inner side of the base of the first phalanx of the thumb, a sesamoid bone being developed in the tendon of insertion. A considerable fasciculus, however, passes more obliquely outward beneath the 3d Metacarpal bone. ADDUCTOR POLLICIS TRANSVERSUS. EXTENSOR POLLICIS- 1st Metacarpal bone. OPPONENS POLLICIS. ADDUCTOR POLLICIS TRANSVERSUS FLEXOR BREVIS POLLICIS. *' ABDUCTOR POLLICIS. Fig. 315.-Muscles of thumb. (From a preparation in the Museum of the Royal College of Surgeons of England.) tendon of the long flexor to join the superficial portion of the short flexor and the Abductor pollicis.1 Relations.-By its superficial surface, with the Flexor longus pollicis and the outer head of the Flexor brevis pollicis. Its deep surface covers the Adductor transversus pollicis, and is in relation with the deep palmar arch, which passes between the two adductors. The Adductor transversus pollicis (Fig. 315) is the most deeply seated of this group of muscles. It is of a triangular form, arising, by its broad base, from the lower two-thirds of the metacarpal bone of the middle finger on its palmar surface: the fibres, proceeding outward, converge, to be inserted, with the inner tendon of the Flexor brevis pollicis, and the Adductor obliquus pollicis, into the ulnar side of the base of the first phalanx of the thumb. From the common tendon of insertion a slip is prolonged to the Extensor longus pollicis. Relations.-By its superficial surface, with the Adductor obliquus pollicis, the tendons of the Flexor profundus, and the Lumbricales. Its deep surface covers the first two interosseous spaces, from which it is separated by a strong aponeurosis. Three of these muscles of the thumb, the Abductor, the Adductor transversus, 1 This muscle was formerly described as the deep portion of the Flexor brevis pollicis. 496 THE MUSCLES AND EASCLE. and the Flexor brevis pollicis, at their insertions give off* fibrous expansions which join the tendon of the Extensor longus pollicis. This permits of flexion of the proximal phalanx and extension of the terminal phalanx at the same time. These expansions, originally figured by Albinus, have been more recently described by M. Duchenne {Physiologic des Mouvements, page 299). Nerves.-The Abductor, Opponens, and outer head of the Flexor brevis pollicis are supplied by the median nerve ; the inner head of the Flexor brevis, and the Adductors, by the ulnar nerve. Actions.-The actions of the muscles of the thumb are almost sufficiently indi- cated by their names. This segment of the hand is provided with three extensors -an extensor of the metacarpal bone, an extensor of the first, and an extensor of the second phalanx; these occupy the dorsal surface of the forearm and hand. There are also three flexors on the palmar surface-a flexor of the metacarpal bone, a flexor of the proximal, and a flexor of the terminal phalanx ; there is also an Abductor and two Adductors. The Abductor pollicis moves the metacarpal bone of the thumb outward; that is, away from the index finger. The Flexor ossis metacarpi pollicis flexes the metacarpal bone-that is, draws it inward over the palm-and at the same time rotates the bone, so as to turn the ball of the thumb toward the fingers, thus producing the movement of opposition. The Flexor brevis pollicis flexes the proximal phalanx of the thumb. The Adductores pollicis move the metacarpal bone of the thumb inward; that is, toward the index finger. These muscles give to the thumb its extensive range of motion. It will be noticed, however, that in consequence of the position of the first meta- carpal bone these movements differ from the corresponding movements of the metacarpal bones of the other fingers. Thus extension of the thumb more nearly corresponds to the motion of abduction in the other fingers, and flexion to adduction. Ulnar Region (Fig. 31G). Muscles of the Little Finger. Palmaris brevis. Abductor minimi digiti. Flexor brevis minimi digiti. The Palmaris brevis is a thin quadrilateral muscle placed beneath the integu- ment on the ulnar side of the hand. It arises by tendinous fasciculi from the annular ligament and palmar fascia; the fleshy fibres pass inward, to be inserted into the skin on the inner border of the palm of the hand. Relations.-By its superficial surface, with the integument, to which it is intimately adherent, especially by its inner extremity; by its deep surface, with the inner portion of the palmar fascia, which separates it from the ulnar vessels and nerve, and from the muscles of the ulnar side of the hand. The Abductor minimi digiti is situated on the ulnar border of the palm of the hand. It arises from the pisiform bone, and teiminates in a flat tendon which divides into two slips: one passes under the lateral expansion of the extensor tendon, opposite the metacarpo-phalangeal articulation, and is inserted into the ulnar side of the base of the first phalanx of the little finger. The other slip passes over the expansion, and is inserted into the ulnar border of the shaft of the same phalanx. Relations.-By its superficial surface, with the inner portion of the palmar fascia, and the Palmaris brevis; by its deep surface, with the Flexor ossis meta- carpi minimi digiti; by its outer border, with the Flexor brevis minimi digiti. The Flexor brevis minimi digiti lies on the same plane as the preceding muscle, on its radial side. It arises from the tip of the unciform process of the unciform bone and anterior surface of the annular ligament, and is inserted into the base of the first phalanx of the little finger. It is separated from the Abductor at its origin by the deep branches of the ulnar artery and nerve. This muscle is some- times wanting; the Abductor is then, usually, of large size. Opponens (Flexor ossis metacarpi) minimi digiti. THE ULNAR REGION 497 Relations.-By its superficial surface, with the internal portion of the palmar fascia, and the Palmaris brevis; by its deep surface, with the Opponens. The Opponens minimi digiti (Fig. 307) is of a triangular form, and placed immediately beneath the preceding muscles. It arises from the unciform process Fig. 316-Muscles of the left hand. Palmar surface. of the unciform bone and contiguous portion of the annular ligament; its fibres pass downward and inward, to be inserted into the whole length of the meta- carpal bone of the little finger, along its ulnar margin. Relations.-By its superficial surface, with the Flexor brevis and Abductor minimi digiti; by its deep surface, with the Interossei muscles in the fourth 498 THE MUSCLES AND FASCLE. metacarpal space, the metacarpal bone, and the Flexor tendons of the little finger. Nerves.-All the muscles of this group are supplied by the ulnar nerve. Actions.-The Abductor minimi digiti abducts the little finger from the middle line of the hand. It corresponds to a dorsal interosseous muscle. It also assists in flexing the proximal phalanx. The Flexor brevis minimi digiti abducts the little finger from the middle line of the hand. It also assists in flexing the proximal phalanx. The Opponens minimi digiti draws forward the fifth meta- carpal bone, so as to deepen the hollow of the palm. The Palmaris brevis corrugates the skin on the inner side of the palm of the hand. Middle Palmar Region. Lumbricales. Interossei dorsales. Interossei palmares. The Lumbricales (Fig. 316) are four small fleshy fasciculi, accessories to the deep Flexor muscle. They arise by fleshy fibres from the tendons of the deep Flexor : the first and second, from the radial side and palmar surface of the tendons of the index and middle fingers; the third, from the contiguous sides of the ten- dons of the middle and ring fingers; and the fourth, from the contiguous sides of the tendons of the ring and little fingers. They pass to the radial side of the corresponding fingers, and opposite the metacarpo-phalangeal articulation each tendon terminates in a broad aponeurosis which is inserted into the tendinous expansion from the Extensor communis digitorum, covering the dorsal aspect of each finger. The Interossei muscles are so named from occupying the intervals between the metacarpal bones. They are divided into two sets, a dorsal and palmar; the former are four in number, one in each metacarpal space; the latter, three in number, lie upon the metacarpal bones. The Dorsal interossei are four in number, larger than the palmar, and occupy the intervals between the metacarpal bones. They are bipenniform muscles, arising by two heads from the adjacent sides of the metacarpal bones, but more extensively from that side of the metacarpal bone which corresponds to the side of the finger in which the muscle is inserted. They are inserted into the bases of the first phalanges and into the aponeurosis of the common extensor tendon. Between the double origin of each of these muscles is a narrow triangular interval, through the first of which passes the radial artery ; through the other three passes a perforating branch from the deep palmar arch. The First dorsal interosseous muscle, or Abductor indicis, is larger than the others. It is flat, triangular in form, and arises by two heads, separated by a fibrous arch, for the passage of the radial artery from the dorsum to the palm of the hand. The outer head arises from the upper half of the ulnar border of the first metacarpal bone; the inner head, from almost the entire length of the radial border of the second metacarpal bone; the tendon is inserted into the radial side of the index finger. The second and third dorsal interossei are inserted into the middle finger, the former into its radial, the latter into its ulnar side. The fourth is inserted into the ulnar side of the ring finger. The Palmar interossei, three in number, are smaller than the Dorsal, and placed upon the palmar surface of the metacarpal bones, rather than between them. They arise from the entire length of the metacarpal bone of one finger, and are inserted into the side of the base of the first phalanx and aponeurotic expansion of the common extensor tendon of the same finger. The first arises from the ulnar side of the second metacarpal bone, and is inserted into the same side of the index finger. The second arises from the radial side of the fourth metacarpal bone, and is inserted into the same side of the ring finger. The third arises from the radial side of the fifth metacarpal bone, and is inserted into the same side of the little finger. From this account it may be seen THE MIDDLE PALMAR REGION. 499 that each finger is provided with two Interossei muscles, with the exception of the little finger, in which the Abductor muscle takes the place of one of the pair. Nerves.-The two outer Lumbricales are supplied by the median nerve; the rest of the muscles of this group, by the ulnar. All the Interossei are supplied by the ulnar. Actions.-The Palmar interossei muscles adduct the fingers to an imaginary line drawn longitudinally through the centre of the middle finger; and the Dorsal interossei abduct the fingers from that line. In addition to this, the Interossei, in Fig. 317.-The Dorsal interossei of left hand. Fig. 318.-The Palmar interossei of left hand. conjunction with the Lumbricales, flex the first phalanx at the metacarpo-phalangeal joints, and extend the second and third phalanges in consequence of their insertion into the expansion of the extensor tendons. The Extensor communis digitorum is believed to act almost entirely on the first phalanges. SURFACE FORM OF THE UPPER EXTREMITY. The Pectoralis major largely influences surface form and conceals a considerable part of the thoracic wall in front. Its sternal origin presents a festooned border which bounds and deter- mines the width of the sternal furrow. Its clavicular origin is somewhat depressed and flattened, and between the two portions of the muscle is often an oblique depression which differentiates the one from the other. The outer margin of the muscle is generally well marked above, and bounds the infraclavicular fossa, a triangular interval which separates the Pectoralis major from the Deltoid. It gradually becomes less marked as it approaches the tendon of insertion, and becomes more closely blended with the Deltoid muscle. The lower border of the Pectoralis major forms the rounded anterior axillary fold, and corresponds with the direction of the fifth rib. The Pectoralis minor influences surface form. When the arm is raised its lowest slip of origin produces a local fulness just below the border of the anterior fold of the axilla, and so serves to break the sharp line of the lower border of the Pectoralis major muscle, which is produced when the arm is in this position. The origin of the Serratus magnits produces a very characteristic surface marking. When the arm is raised from the side in a well-developed subject, the five or six lower serrations are plainly discernible, forming a zigzag line, caused by the series of digitations, which diminish in size from above downward, and have their apices arranged in the form of a curve. When the arm is lying by the side, the first serration to appear, at the lower margin of the Pectoralis major, is the one attached to the fifth rib. The Deltoid, with the prominence of the upper extremity of the humerus, produces the rounded outline of the shoulder. It is rounder and fuller in front than behind, where it presents a somewhat flattened form. Its anterior border, above, presents a rounded, slightly curved eminence, which bounds externally the infraclavicular fossa; below, it is closely united with the 500 ttta; muscles and fa sole. Pectoralis major. Its posterior border is thin, flattened, and scarcely marked above ; below, it is thicker and more prominent. When the muscle is in action, the middle portion becomes irregular, presenting alternate longitudinal elevations and depressions, the elevations correspond- ing to the fleshy portions, the depressions to the tendinous intersections of the muscle. The insertion of the Deltoid is marked by a depression on the outer side of the middle of the arm. Of the scapular muscles, the only one which materially influences surface form is the Teres major, which assists the Latissimus dorsi in forming the thick, rounded fold of the posterior boundary of the axilla. When the arm is raised, the Coraco-brachialis reveals itself as a long, narrow elevation which emerges from under cover of the anterior fold of the axilla and runs downward, internal to the shaft of the humerus. When the arm is hanging by the side, its front and inner part presents the prominence of the Biceps, bounded on either side by an inter- muscular depression. This muscle determines the contour of the front of the arm, and extends from the anterior margin of the axilla to the bend of the elbow. Its upper tendons are con- cealed by the Pectoralis major and the Deltoid, and its lower tendon sinks into the space at the bend of the elbow. When the muscle is in a state of complete contraction-that is to say, when the forearm has been flexed and supinated-it presents a rounded convex form, bulged out laterally, and its length is diminished. On each side of the Biceps, at the lower part of the arm, the Brachialis anticus is discernible. On the outer side it forms a narrow eminence which extends some distance up the arm along the border of the Biceps. On the inner side it shows itself only as a little fulness just above the elbow. On the back of the arm the long head of the Triceps may be seen as a longitudinal eminence emerging from under cover of the Deltoid, and gradually merging into the longitudinal flattened plane of the muscle on the lower part of the back of the arm. On the anterior aspect of the elbow are to be seen two muscular eleva- tions. one on each side, separated above and converging below so as to form a triangular space. Of these, the inner elevation, consisting of the flexors and pronator, forms the prominence along the inner side and front of the forearm. It is a fusiform mass, pointed above at the internal condyle and gradually tapering off below. The Pronator radii teres, the innermost muscle of the group, forms the boundary of the triangular space at the bend of the elbow. It is shorter, less prominent, and more oblique than the outer boundary. The most prominent part of the eminence is produced by the Flexor carpi radialis, the muscle next in order on the inner side of the preceding one. It forms a rounded prominence above, and can be traced downward to its tendon, which can be felt lying on the front of the wrist, nearer to the radial than to the ulnar border, and to the inner side of the radial artery. The Palmaris longus presents no surface marking above, but below is the most prominent tendon on the front of the wrist, standing out, when the muscle is in action, as a sharp, tense cord beneath the skin. The Flexor sublimis digitorum does not directly influence surface form. The position of its four tendons on the front of the lower part of the forearm is indicated by an elongated depression between the tendons of the Palmaris longus and the Flexor carpi ulnaris. The Flexor carpi ulnaris occupies a small part of the posterior surface of the forearm, and is separated from the extensor and supinator group, which occupies the greater part of this surface, by the ulnar furrow, produced by the subcutaneous posterior border of the ulna. Its tendon can be perceived along the ulnar border of the front of the forearm, and is most marked when the hand is flexed and adducted. The deep muscles of the front of the forearm have no direct influence on surface form. The external group of muscles of the forearm, consisting of the extensors and supi- nators, occupy the outer and a considerable portion of the posterior surface of this region. They form a fusiform mass, which is altogether on a higher level than the pronato-flexor group. Its apex emerges from between the Triceps and Brachialis anticus muscles some distance above the elbow-joint, and acquires its greatest breadth opposite the external condyle, and thence gradually shades off into a flattened surface. About the middle of the forearm it divides into two longi- tudinal eminences which diverge from each other, leaving a triangular interval between them. The outer of these two groups of muscles consists of the Supinator longus and the Extensor carpi radialis longior et brevior, which form a longitudinal eminence descending from the exter- nal condyloid ridge in the direction of the styloid process of the radius. The other and more posterior group consists of the Extensor communis digitorum, the Extensor minimi digiti. and the Extensor carpi ulnaris. It commences above as a tapering form at the external condyle of the humerus, and is separated behind at its upper part from the Anconeus by a well-marked furrow, and below, from rhe pronato-flexor mass, by the ulnar furrow. In the triangular inter- val left between these two groups the extensors of the thumb and index finger are seen. The only two muscles of this region which require special mention as independently influencing surface form are the Supinator longus and the Anconeus. The inner border of the Supinator longus forms the outer boundary of the triangular space at the bend of the elbow. It com- mences as a rounded border above the condyle, and is longer, less oblique, and more prominent than the inner boundary. Lower down, the muscle forms a full fleshy mass on the outer side of the upper part of the forearm, and below tapers into a tendon, which may be traced down to the styloid process of the radius. The Anconeus presents a well-marked and characteristic surface form in the shape of a triangular, slightly elevated surface, immediately external to the subcutaneous posterior surface of the olecranon, and differentiated from the common extensor group by a well-marked oblique longitudinal depression. The upper angle of the triangle corre- sponds to the external condyle, and is marked by a depression or dimple in this situation. In the triangular interval caused by the divergence from each other of the two groups of muscles into which the extensor and supinator group is divided at the lower part of the forearm an SURGICAL ANATOMY OF THE UPPER EXTREMITY. 501 oblique elongated eminence is seen, caused by the emergence of two of the extensors of the thumb from their deep origin at the back of the forearm. This eminence, full above and be- coming flattened out and partially subdivided below, runs downward and outward over the back and outer surface of the radius to the outer side of the wrist-joint, where it forms a ridge, especially marked when the thumb is extended, which passes onward to the posterior aspect of the thumb. The tendons of most of the extensor muscles are to be seen and felt at the level of the wrist-joint. Most externally are the tendons of the Extensor ossis metacarpi pollicis and the Extensor brevis pollicis, forming a vertical ridge over the outer side of the joint from the styloid process of the radius to the thumb. Internal to this is the oblique ridge produced by the tendon of the Extensor longus pollicis, very noticeable when the muscle is in action. The Extensor carpi radialis longior is scarcely to be felt, but the Extensor carpi radialis brevior can be distinctly perceived as a vertical ridge emerging from under the inner border of the tendon of the Extensor longus pollicis, when the hand is forcibly extended at the wrist. Internal to this, again, can be felt the tendons of the Extensor indicis, Extensor communis digitorum, and Extensor minimi digiti; the latter tendon being separated from those of the common extensor by a slight furrow. The muscles of the hand are principally concerned, as far as regards sur- face-form, in producing the thenar and hypothenar eminences, and individually are not to be distinguished, on the surface, from each other. The Adductor transversus pollicis is, however, an exception to this; its anterior border gives rise to a ridge across the web of skin connecting the thumb to the rest of the hand. The thenar eminence is much larger and rounder than the hypothenar one, which presents a longer and narrower eminence along the ulnar side of the hand. When the Palmaris brevis is in action it produces a wrinkling of the skin over the hypo- thenar eminence, and a deep dimple on the ulnar border of the hand. The anterior extremities of the Lumbrical muscles help to produce the soft eminences just behind the clefts of the fingers, separated from each other by depressions corresponding to the flexor tendons in their sheaths. Between the thenar and hypothenar eminences, at the wrist-joint, is a slight groove or depression, widening out as it approaches the fingers; beneath this we have the strong central part of the palmar fascia. Here we have some furrows, which are pretty constant in their arrangement, and bear some resemblance to the letter M. One of these furrows passes obliquely outward from the groove between the thenar and hypothenar regions to the head of the metacarpal bone of the index finger. A second passes inward, with a slight inclination upward, from the termi- nation of the first to the ulnar side of the hand. A third runs parallel with the second and about three-quarters of an inch below it. Lastly, crossing these two latter furrows, is an oblique furrow parallel with the first. The skin of the palm of the hand differs considerably from that of the forearm. At the wrist it suddenly becomes hard and dense, and covered with a thick layer of cuticle. The skin in the thenar region presents these characteristics less than elsewhere. In spite of this hardness and density, the skin of the palm is exceedingly sensitive and very vascular. It is destitute of hair, and no sebaceous follicles have been found in this region. Over the fingers the skin again becomes thinner, especially at the flexures of the joints, and over the terminal phalanges it is thrown into numerous parallel ridges in consequence of the arrangement of the papillae in it. The superficial fascia in the palm is made up of dense fibro- fatty tissue. This tissue binds down the skin so firmly to the deep palmar fascia that very little movement is permitted between the two. On the back of the hand the Dorsal interossei pro- duce elongated swellings between the metacarpal bones. The first dorsal interosseous (Abductor indicis), when the thumb is closely adducted to the hand, forms a prominent fusiform bulging; the other interossei are not so marked. SURGICAL ANATOMY OF THE UPPER EXTREMITY. The student, having completed the dissection of the muscles of the upper extremity, should consider the effects likely to be produced by the action of the various muscles in fracture of the bones. In considering the actions of the various muscles upon fractures of the upper extremity, I have selected the most common forms of injury, both for illustration and description. Fracture of the middle of the clavicle (Fig. 319) is always attended with considerable dis- placement: the inner end of the outer fragment is displaced inward and backward, while the (»uter end of the same fragment is rotated forward, owing to the displacement backward of its inner end. The whole outer fragment is somewhat depressed. The displacement is produced as follows: inward, by the muscles passing from the chest to the outer fragment of the clavicle, to the scapula, and to the humerus-viz. the Subclavius, the Pectoralis minor and major, and the Latissimus dorsi: backward, with consequent rotation of the outer end of the outer fragment forward by the Pectoral muscles. The depression of the whole outer fragment is produced by the weight of the arm and by the contraction of the Deltoid. The outer end of the inner fragment appears to be elevated, the skin being drawn tensely over it; this is owing to the depression of the outer fragment, as the inner fragment is usually kept fixed by the costo-clavicular ligament and by the antagonism between the Sterno-mastoid and Pectoralis major muscles. But it may be raised by an unusually strong Sterno-mastoid, or by the inner end of the outer fragment getting below and behind it. The causes of displacement having been ascertained, it is easy to apply the appropriate treatment. The outer fragment is to be drawn outward, and, together with the scapula, raised upward to a level with the inner fragment, and retained in that position. 502 THE MUSCLES AND EASCLE. In fracture of the acromial end of the clavicle, between the conoid and trapezoid ligaments, only slight displacement occurs, as these ligaments, from their oblique insertion, serve to hold both portions of the bone in apposition. Fracture, also, of the sternal end, internal to the costo-clavicular liga- ment, is attended with only slight displacement, this ligament serving to retain the fragments in close appo- sition. Fracture of the acromion process usually arises from violence applied to the upper and outer part of the shoulder; it is generally known by the rotundity of the shoulder being lost, from the Deltoid drawing the frac- tured portion downward and forward; and the displace- ment may easily be discovered by tracing the margin of the clavicle outward, when the fragment will be found resting on the front and upper part of the head of the humerus. In order to relax the anterior and outer fibres of the Deltoid (the opposing muscle), the arm should be drawn forward across the chest and the elbow well raised, so that the head of the bone may press the acromion process upward and retain it in its position. Fracture of the coracoid process is an extremely rare accident, and is usually caused by a sharp blow on the point of the shoulder. Displacement is here produced by the combined actions of the Pectoralis minor, short head of the Biceps, and Coraco-brachialis, the former muscle drawing the fragment inward, and the latter directly downward, the amount of displacement being limited by the connection of this process to the acromion by means of the coraco-acromial ligament. In order to relax these muscles and replace the fragments in close apposition, the forearm should be flexed so as to relax the Biceps, and the arm drawn forward and inward across the chest, so as to relax the Coraco- brachialis; the humerus should then be pushed upward against the coraco-acromial ligament, and the arm retained in that position. Fracture of the surgical neck of the humerus (Fig. 320) is very common, is attended with considerable displacement, and its appearances correspond somewhat with those of dislocation of the head of the humerus into the axilla. The upper fragment is slightly elevated under the coraco-acromial ligament by the muscles attached to the greater and lesser tuberosities; the lower fragment is drawn inward by the Pectoralis major, Latissimus dorsi, and Teres major; and the humerus is thrown obliquely outward from the side by the Deltoid, and occasionally elevated so as to project beneath and in front of the coracoid process. The deformity is reduced by fixing the shoulder and drawing the arm outward and down- ward. To counteract the opposing muscles, and to keep the fragments in position, the arm should be drawn from the side and pasteboard splints applied on its four sides; a large conical- shaped pad should be placed in the axilla, with the base turned upward and the elbow' approximated to the side, and retained there by a broad roller passed round the chest; the forearm should then be flexed, and the hand supported in a sling, care being taken not to raise the elbow, otherwise the lower frag- ment may be displaced upward. In fracture of the shaft of the humerus below' the inser- tion of the Pectoralis major, Latissimus dorsi, and Teres major, and above the insertion of the Deltoid, there is also consider- able deformity, the upper fragment being drawn inward by the first-mentioned muscles, and the lower fragment upward and outward by the Deltoid, producing shortening of the limb and a considerable prominence at the seat of fracture, from the fractured ends of the bone riding over one another, especially if the fracture takes place in an oblique direction. The frag- ments may be brought into apposition by extension from the elbow, and retained in that position by adopting the same means as in the preceding injury. In fractures of the shaft of the humerus immediately below the insertion of the Deltoid, the amount of deformity depends greatly upon the direction of the fracture. If it occurs in a transverse direction, only slight displacement takes place, the upper fragment being drawn a little forward ; but in oblique fracture the combined actions of the Biceps and Brachialis anticus muscles in front and the Triceps behind draw' upward the lower fragment, causing it to glide over the upper fragment, either backward or forward, according to the direction of the fracture. Simple extension reduces the deformity, and the application of splints on the four sides of the arm will retain the fragments in apposition. Fig. 319.-Fracture of the middle of the clavicle. Fig. 320.-Fracture of the surgical neck of the humerus. SURGICAL ANATOMY OF THE UPPER EXTREMITY. 503 Care should be taken not to raise the elbow, but the forearm and hand may be supported in a sling. Fracture of the humerus (Fig. 321) immediately above the condyles deserves very attentive consideration, as the general appearances correspond somewhat with those produced by sep- aration of the epiphysis of the humerus, and with those of dislocation of the radius and ulna backward. If the direction of the fracture is oblique from above, downward and forward, the lower fragment is drawn upward and backward by the Brachialis anticus and Biceps in front and the Triceps behind. This injury may be diagnosed from dis- location by the increased mobility in fracture, the existence of crepitus, and the fact of the deformity being remedied by extension, on the discontinuance of which it is reproduced. The age of the patient is of importance in distinguishing this form of injury from separation of the epiphysis. If frac- ture occurs in the opposite direction to that shown in the accompanying figure, the lower fragment is drawn upward and forward, causing a considerable prominence in front, and the upper fragment projects backward beneath the tendon of the Triceps muscle. Fracture of the oZecranon. process (Fig. 322) is a frequent accident. The detached fragment is displaced upward, by the action of the Triceps muscle, from half an inch to two inches; the prominence of the elbow is consequently lost, and a deep hollow is felt at the back part of the joint, which is much increased on flexing the limb. The patient at the same time loses, more or less, the power of extending the forearm. The treatment consists in relaxing the Triceps by extending the limb, and retaining it in the extended posi- tion by means of a long- straight splint applied to the front of the arm ; the fragments are thus brought into close apposition, and may be further approxi- mated by drawing down the upper fragment. Union is generally ligamentous. Fracture of the neck of the radius is an exceedingly rare accident, and is generally caused by direct violence. Its diagnosis is somewhat obscure, on account of the slight deformity visible, the injured part being surrounded by a large number of muscles; but the movements of prona- tion and supination are entirely lost. The upper fragment is drawn outward by the Supinator brevis, its extent of displacement being limited by the attachment of the orbicular ligament. The lower fragment is drawn forward and slightly upward by the Biceps, and inward by the Pro- nator radii teres, its displacement forward and upward being counteracted in some degree by the Supinator brevis. The treatment essentially consists in relaxing the Biceps, Supinator brevis, and Pronator radii teres muscles by flexing the forearm, and placing it in a position midway between pronation and supination, extension having been previously made so as to bring the parts in apposition. In fracture of the radius (Fig. 323) near its centre, the upper fragment is drawn upward by the Biceps and inward by the Pronator radii teres, holding a position midway between pro- nation and supination, and a degree of fulness in the upper half of the forearm is thus pro- duced : the lower fragment is drawn downward and inward toward the ulna by the Pronator quadratus, and thrown into a state of pronation by the same muscle : at the same time, the Su- pinator longus, by elevating the styloid process, into which it is inserted, will serve to depress the upper end of the lower fragment still more toward the ulna. In order to relax the opposing muscles the forearm should be bent, and the limb placed in a position midway between prona- tion and supination ; the fracture is then easily reduced by extension from the wrist and elbow: well-padded splints should be applied on both sides of the forearm from the elbow to the wrist; the hand being allowed to fall, will, by its own weight, counteract the action of the Pronator quadratus and Supinator longus, and elevate the lower fragment to the level of the upper one. In fracture of the shaft of the ulna the upper fragment retains its usual position, but the lower fragment is drawn outward toward the radius by the Pronator quadratus, producing a well-marked depression at the seat of fracture and some fulness on the dorsal and palmar surfaces of the forearm. The fracture is easily reduced by extension from the wrist and forearm. The fore- arm should be flexed, and placed in a position midway between pronation and supination, and well-padded splints applied from the elbow to the ends of the fingers. Fig. 321.-Fracture of the humerus above the condyles. Fig. 322.-Fracture of the olecranon. 504 THE MUSCLES AND FASCIAE. In fracture of the shafts of the radius and ulna together the lower fragments are drawn upward, sometimes forward, sometimes backward, according to the direction of the fracture, by the combined actions of the Flexor and Extensor muscles, producing a degree of fulness on the dorsal or palmar surface of the forearm; at the same time the two fragments are drawn into contact by the Pronator quadratus, the radius being in a state of pronation : the upper frag- ment of the radius is drawn upward and inward by the Biceps and Pronator radii teres to a higher level than the ulna; the upper portion of the ulna is slightly elevated by the Brachialis anticus. The fracture may be reduced by extension from the wrist and elbow, and the forearm should be placed in the same position as in fracture of the ulna. In fracture of the lower end of the radius (Fig. 324) the displacement which is produced is very considerable, and bears some resemblance to dislocation of the carpus backward, from which it should be carefully distinguished. The lower fragment is drawn upward and backward behind the upper fragment by the combined actions of the Supinator longus and the flexors and the extensors of the thumb and carpus, producing a well-marked prominence on the back of the wrist, with a deep depression above it. The upper fragment projects forward, often lacerating the substance of the Pronator quadratus, and is drawn by this muscle into close contact with the lower end of the ulna, causing a projection on the anterior surface of the forearm, immediately Fig. 323.-Fracture of the shaft of the radius. Fig. 324.-Fracture of the lower end of the radius. above the carpus, from the flexor tendons being thrust forward. This fracture may be distin- guished from dislocation by the deformity being removed on making sufficient extension, when crepitus may be occasionally detected; at the same time, on extension being discontinued, the parts immediately resume their deformed appearance (see also page 234). The age of the patient will also assist in determining whether the injury is fracture or separation of the epiph- ysis. The treatment consists in flexing the forearm, and making powerful extension from the wrist and elbow, depressing at the same time the radial side of the hand, and retaining the parts in that position by well-padded pistol-shaped, splints. MUSCLES AND FASCLE OF THE LOWER EXTREMITY. The Muscles of the Lower Extremity are subdivided into groups, corresponding with the different regions of the limb. Iliac Region. Psoas magnus. Psoas parvus. Iliacus. Thigh. Anterior Femoral Region. Tensor vaginae femoris. Sartorius. Rectus. Vastus externus. Vastus internus. Crureus. Subcrureus. Internal Femoral Region. Gracilis. Pectineus. Adductor longus. Adductor brevis. Adductor magnus. Hip. Griuteal Region. Gluteus maximus. Gluteus medius. Gluteus minimus. Pyriformis. TWA ILIAC REGION. 505 Gemellus superior. Obturator internus. Gemellus inferior. Obturator externus. Quadratus femoris. Posterior Femoral Region. Biceps. Semitendinosus. Semimembranosus. Leg. Anterior Tibio-fibular Region. Tibialis anticus. Extensor longus digitorum. Extensor proprius hallucis. Peroneus tertius. Posterior Tibio-fibular Region. Superficial Layer. Gastrocnemius. Plantaris. Soleus. Deep Layer. Popliteus. Flexor longus hallucis. Flexor longus digitorum. Tibialis posticus. Fibular Region. Peroneus longus. Peroneus brevis. Foot. Dorsal Region. Extensor brevis digitorum. Plantar Region. First Layer. Abductor hallucis. Flexor brevis digitorum. Abductor minimi digiti. Second Layer. Flexor accessorius. Lumbricales. Third Layer. Flexor brevis hallucis. Adductor obliquus hallucis. Flexor brevis minimi digiti. Adductor transversus pedis. Fourth Layer. The Interossei. ILIAC REGION. Psoas magnus. Psoas parvus. Iliacus. Dissection.-No detailed description is required for the dissection of these muscles. On the removal of the viscera from the abdomen they are exposed, covered by the peritoneum and a thin layer of fascia, the iliac fascia. The iliac fascia1 is the aponeurotic layer which lines the back part of the abdominal cavity, and covers the Psoas and Iliacus muscles throughout their whole extent. It is thin above, and becomes gradually thicker below' as it approaches the crural arch. The portion covering the Psoas is attached, above, to the ligamentum arcuatum internum ; internally, by a series of arched processes to the intervertebral substances and prominent margins of the bodies of the vertebrae, and to the upper part of the sacrum, the intervals so left, opposite the constricted portions of the bodies, transmitting the lumbar arteries and filaments of the sympathetic nerve. Ex- ternally, above the crest of the ilium, this portion of the iliac fascia is continuous with the anterior lamella of the lumbar fascia (see page 435), but below the crest of the ilium it is continuous with the fascia covering the Iliacus. The portion investing the Iliacus is connected externally to the whole length of the inner border of the crest of the ilium, and internally to the brim of the true pelvis, where it is continuous with the periosteum, and at the ilio-pectineal eminence it receives the tendon of insertion of the Psoas parvus, when that muscle exists. External to the femoral vessels, this fascia is intimately connected to the posterior margin of Poupart's ligament, and is continuous with the fascia trans- versalis. Internal to the vessels it is attached to the ilio-pectineal line behind the conjoined tendon, where it is again continuous with the transversalis fascia; and, 1 The student must not confound this fascia with the iliac portion of the fascia lata (see p. 510). 506 THE MUSCLES AND FA SOLE. corresponding to the point where the femoral vessels pass into the thigh, this fascia descends behind them, forming the posterior wall of the crural sheath. This portion of the iliac fascia which passes behind the femoral vessels is also attached to the ilio-pectineal line beyond the limits of the attachment of the conjoined tendon ; at this part it is continuous with the pubic portion of the fascia lata of the thigh. The external iliac vessels lie in front of the iliac fascia, but all the branches of the lumbar plexus behind it; it is separated from the peritoneum bv a quantity of loose areolar tissue. The Psoas magnus (Fig. 326) is a long fusiform muscle placed on the side of the lumbar region of the spine and margin of the pelvis. It arises from the front of the bases and lower borders of the transverse processes of the lumbar vertebrae by five fleshy slips; also from the sides of the bodies and the corresponding intervertebral substances of the last dorsal and all the lumbar vertebrae. The muscle is connected to the bodies of the vertebrae by five slips ; each slip is attached to the upper and lower margins of two vertebrae, and to the intervertebral substance between them, the slips themselves being connected by the tendinous arches which extend across the constricted part of the bodies, and beneath which pass the lumbar arteries and sympathetic nerves. These tendinous arches also give origin to muscular fibres, and protect the blood-vessels and nerves from pressure during the action of the muscle. The first slip is attached to the contiguous margins of the last dorsal and first lumbar vertebrae ; the last to the contiguous margins of the fourth and fifth lumbar, and to the intervertebral substance. From these points the muscle passes down across the brim of the pelvis, and, diminishing gradually in size, passes beneath Poupart's ligament, and terminates in a tendon which, after receiving the fibres of the Iliacus, is inserted into the lesser trochanter of the femur. Relations.-In the lumbar region : by its anterior surface, which is placed behind the peritoneum, with the iliac fascia, the ligamentum arcuatum internum, the kidney, Psoas parvus, renal vessels, ureter, spermatic vessels, genito-crural nerve, and the colon ; by its posterior surface, with the transverse processes of the lumbar vertebrae and the Quadratus lumborum, from which it is separated by the anterior lamella of the lumbar fascia. The anterior crural nerve is at first situated in the substance of the muscle, and emerges from its outer border at the lower part. The lumbar plexus is situated in the posterior part of the substance of the muscle. By its inner side the muscle is in relation with the bodies of the lumbar vertebrae, the lumbar arteries, the ganglia of the sympathetic nerve, and their branches of communication with the spinal nerves; the lumbar glands; the vena cava inferior on the right and the aorta on the left side, and along the brim of the pelvis with the external iliac artery. In the thigh it is in relation, in front, with the fascia lata; behind, with the capsular ligament of the hip, from which it is separated by a synovial bursa, which frequently communicates with the cavity of the joint through an opening of variable size; by its inner border, with the Pectineus and the femoral artery, which slightly overlaps it: by its outer border, with the anterior crural nerve and Iliacus muscle. The Psoas parvus is a long slender muscle placed in front of the Psoas magnus. It arises from the sides of the bodies of the last dorsal and first lumbar vertebrae and from the intervertebral substance between them. It forms a small fiat muscular bundle, which terminates in a long flat tendon inserted into the ilio-pectineal eminence, and, by its outer border, into the iliac fascia. This muscle is often absent, and, according to Cruveilhier, sometimes double. Relations.-It is covered by the peritoneum, and, at its origin, by the ligamentum arcuatum internum; it rests on the Psoas magnus. The Iliacus is a flat, triangular muscle which fills up the whole of the iliac fossa. It arises from the upper two-thirds of this fossa and from the inner margin of the crest of the ilium; behind, from the ilio-lumbar ligament and base of the sacrum ; in front, from the anterior superior and anterior inferior spinous processes of the ilium, from the notch between them, and by a few fibres from the capsule THE THIGH. 507 of the hip-joint. The fibres converge to be inserted into the outer side of the tendon of the Psoas, some of them being prolonged into the oblique line which extends from the lesser trochanter to the linea aspera.1 Relations.- Within the pelvis : by its anterior surface, with the iliac fascia, which separates the muscle from the peritoneum, and with the external cutaneous nerve; on the right side, with the caecum; on the left side, with the sigmoid flexure of the colon; by its posterior surface, with the iliac fossa; by its inner border, with the Psoas magnus and anterior crural nerve. In the thigh, it is in relation, by its anterior surface, with the fascia lata, Rectus, and Sartorius; behind, with the capsule of the hip-joint, a synovial bursa common to it and the Psoas magnus being interposed. Nerves.-The Psoas magnus, and the Psoas parvus when it exists, are supplied by the anterior branches of the lumbar nerves; the Iliacus by the anterior crural. Actions.-The Psoas and Iliacus muscles, acting from above, flex the thigh upon the pelvis, and, at the same time, rotate the femur outward, from the obliquity of their insertion into the inner and back part of that bone. Acting from below, the femur being fixed, the muscles of both sides bend the lumbar portion of the spine and pelvis forward. They also serve to maintain the erect position, by supporting the spine and pelvis upon the femur, and assist in raising the trunk when the body is in the recumbent posture. The Psoas parvus is a tensor of the iliac fascia. Surgical Anatomy.-In the iliac fascia there is no definite septum between the portions of fascia covering the Psoas and Iliacus respectively, and the fascia is only connected to the subja- cent muscles by a quantity of loose connective tissue. When abscess forms beneath this fascia, as it is very apt to do, the matter is contained in an osseo-fibrous cavity which is closed on all sides within the abdomen, and is open only at its lower part, w7here the fascia is prolonged over the muscle into the thigh. Abscess within the sheath of the Psoas muscle (Psoas abscess) is generally due to tubercular caries of the bodies of the lower dorsal and lumbar vertebrae. When the disease is in the dorsal region, the matter tracts down the posterior mediastinum, in front of the bodies of the vertebrae, and, passing beneath the ligamentum arcuatum internum, enters the sheath of the Psoas muscle, down which it passes as far as the pelvic brim ; it then gets beneath the iliac portion of the fascia and fills up the iliac fossa. Tn consequence of the attachment of the fascia to the pelvic brim, it rarely finds its way into the pelvis, but passes by a narrow opening under Poupart's ligament into the thigh, to the outer side of the femoral vessels. It thus follows that a Psoas abscess may be described as consisting of four parts: (1) a somewhat narrow channel at its upper part, in the Psoas sheath ; (2) a dilated sac in the iliac fossa ; (3) a constricted neck under Poupart's liga- ment ; and (4) a dilated sac in the upper part of the thigh. When the lumbar vertebrae are the seat of the disease, the matter finds its way directly into the substance of the muscle. The muscular fibres are destroyed, and the nervous cords contained in the abscess are isolated and exposed in its interior; the femoral vessels which lie in front of the fascia remain intact, and the peritoneum seldom becomes implicated. All Psoas abscesses do not, however, pursue this course : the matter may leave the muscle above the crest of the ilium, and, tracking backward, may point in the loin (lumbar abscess); or it may point above Poupart's ligament in the inguinal region; or it may follow the course of the iliac vessels into the pelvis, and, passing through the great sacro-sciatic notch, discharge itself on the back of the thigh; or it may open into the bladder or find its way into the perinaeum. THE THIGH. Anterior Femoral Region. Tensor vaginae femoris. Sartorius. Rectus. Vastus externus. Vastus internus. Crureus. Dissection.-To expose the muscles and fasciae in this region, make an incision along Poupart's ligament, from the anterior superior spine of the ilium to the spine of the os pubis; a vertical incision from the centre of this, along the middle of the thigh to below the knee-joint; and a transverse incision from the inner to the outer side of the leg, at the lower end of the ver- tical incision. The flaps of integument having been removed, the superficial and deep fasciae Subcrureus. 1 The Psoas and Iliacus are sometimes regarded as a single muscle, the Hio-psoas, having two heads-of origin and a single insertion. 508 77ZA MUSCLES AND FASCIAE. should be examined. The more advanced student should commence the study of this region by an examination of the anatomy of femoral hernia and Scarpa's triangle, the incisions for the dissection of which are marked out in the figure below. The superficial fascia forms a continuous layer over the whole of the thigh, consisting of areolar tissue, containing in its meshes much fat, and capable of being separated into two or more layers, between which are found the superficial vessels and nerves. It varies in thickness in different parts of the limb: in the groin it is thick, and the two layers are separated from one another by the super- ficial inguinal lymphatic glands, the internal saphenous vein, and several smaller vessels. One of these two layers, the superficial, is continuous above with the superficial fascia of the abdomen. The deep layer of the superficial fascia is a very thin, fibrous layer, best marked on the inner side of the long saphenous vein and below Poupart's ligament. It is placed beneath the subcutaneous vessels and nerves and upon the surface of the fascia lata. It is intimately adherent to the fascia lata a little below Poupart's ligament. It covers the saphenous opening in the fascia lata, being closely united to its circumference, and is connected to the sheath of the femoral vessels, corresponding to its under surface. The portion of fascia covering this aperture is perforated by the internal saphenous vein and by numerous blood- and lymphatic vessels ; hence it has been termed the cribriform fascia, the openings for these vessels having been likened to the holes in a sieve. The cribriform fascia adheres closely both to the superficial fascia and to the fascia lata, so that it is described by some anatomists as part of the fascia lata, but is usually considered (as in this work) as belonging to the superficial fascia. It is not until the cribriform fascia has been cleared away that the saphenous opening is seen, so that this opening does not in ordinary cases exist naturally, but is the result of dissection. Mr. Callender, however, speaks of cases in which, probably as the result of pressure from enlarged inguinal lymphatic glands, the fascia has become atrophied, and a saphenous opening exists inde- pendent of dissection. A femoral hernia in pass- ing through the saphenous opening receives the cribriform fascia as one of its coverings. A large subcutaneous bursa is found in the superficial fascia over the patella. The deep fascia of the thigh is exposed on the removal of the superficial fascia, and is named, from its great extent, the fascia lata; it formsa uniform investment for the whole of this region of the limb, but varies in thickness in different parts ; thus, it is thicker in the upper and outer part of the thigh, where it receives a fibrous expansion from the Gluteus maximus muscle, and the Tensor vaginse femoris is inserted between its layers: it is very thin behind, and at the upper and inner part where it covers the Adductor muscles, and again becomes stronger around the knee, receiving fibrous expansions from the tendon of the Biceps externally, and from the Sartorius internally, and Quadriceps extensor cruris in front. The fascia lata is attached, above and behind, to the back of the sacrum and coccyx ; externally, to the crest of the ilium; in front, to Poupart's ligament and to the body of the os pubis; and internally, to the descending ramus 1. Dissection of femoralhernia, and Scarpa's triangle. 2. Front of thigh. 3. Front of leg. 4. Dorsum of foot. fig. 325.-Dissection of lower extremity, Front view. THE ANTERIOR FEMORAL REGION. 509 of the os pubis, to the ascending ramus and tuberosity of the ischium, and to the lower border of the great sacro-sciatic ligament. From its attachment to the crest of the ilium it passes down over the Gluteus medius muscle to the upper border of the Gluteus maximus, where it splits into two layers, one passing superficial to and the other beneath this muscle. At the lower border of the muscle the two layers unite. Externally, just below the great trochanter, the fascia lata receives the greater part of the tendon of insertion of the Gluteus maximus, and becomes proportionately thick- ened. The portion of the fascia lata arising from the front part of the crest of the ilium, corresponding to the origin of the Tensor vaginae femoris, passes down the outer side of the thigh as two layers, one superficial and the other beneath this muscle; these at its lower end become blended together into a thick and strong band, having first received the insertion of the muscle. This band is continued downward, under the name of the ilio-tibial band, to be inserted into the external tuberosity of the tibia. Below, the fascia lata is attached to all the prominent points around the knee-joint-viz. the condyles of the femur, tuberosities of the tibia, and head of the fibula. On each side of the patella it is strengthened by transverse fibres given off from the lower part of the Vasti muscles, which are attached to and support this bone. Of these the outer is the stronger, and is con- tinuous with the ilio-tibial band. From the inner surface of the fascia lata are given oft' two strong intermuscular septa, which are attached to the whole length of the linea aspera and its prolongations above and below: the external and stronger one, which extends from the insertion of the Gluteus maximus to the outer condyle, separates the Vastus ex- ternus in front from the short head of the Biceps behind, and gives partial origin to these muscles; the inner one, the thinner of the two, separates the Vastus internus from the Adductor and Pectineus muscles. Besides these there are numerous smaller septa, sepa- rating the individual muscles and enclosing each in a distinct sheath. At the upper and inner part of the thigh, a little below Poupart's ligament, a large oval-shaped aperture is observed after the superficial fascia has been cleared off: it transmits the internal saphenous vein and other smaller vessels, and is termed the saphenous opening. In order more correctly to consider the mode of formation of this aperture, the fascia lata in this part of the femorai S^uscles of the iliac and anterior 510 THE MUSCLES AND FASCIAE thigh is described as consisting of two portions-an iliac portion and a pubic portion. The iliac portion is all that part of the fascia lata on the outer side of the saphenous opening. It is attached, externally, to the crest of the ilium and its anterior superior spine, to the whole length of Poupart's ligament as far internally as the spine of the os pubis, and to the pectineal line in conjunction with Gimbernat's ligament. From the spine of the os pubis it is reflected down- ward and outward, forming an arched margin, the boundary or falciform process (superior cornu) of the saphenous opening; this margin overlies and is adherent to the anterior layer of the sheath of the femoral vessels: to its edge is attached the cribriform fascia; and, below, it is continuous with the pubic portion of the fascia lata. The pubic portion is situated at the inner side of the saphenous opening: at the lower margin of this aperture it is continuous with the iliac portion; traced upward, it covers the surface of the Pectineus, Adductor longus, and Gracilis muscles, and, passing behind the sheath of the femoral vessels, to which it is closely united, is continuous with the sheath of the Psoas and Iliacus muscles, and is attached above to the ilio-pectineal line, where it becomes continuous with the iliac fascia. From this description it may be observed that the iliac portion of the fascia lata passes in front of the femoral vessels, and the pubic portion behind them, so that an apparent aperture exists between the two, through which the internal saphenous joins the femoral vein.1 The fascia should now be removed from the surface of the muscles. This may be effected by pinching it up between the forceps, dividing it, and separating it from each muscle in the course of its fibres. The Tensor vaginae femoris arises from the anterior part of the outer lip of the crest of the ilium, and from the outer surface of the anterior superior spinous process, between the Gluteus medius and Sartorius. It is inserted into the fascia lata about one-fourth down the outer side of the thigh. From the point of inser- tion the fascia is continued downward to the head of the tibia as a thickened band, the ilio-tibial band. Relations.-By its superficial surface, with the fascia lata and the integument; by its deep surface, with the Gluteus medius, Bectus femoris, Vastus externus, and the ascending branches of the external circumflex artery; by its anterior border, with the Sartorius, from which it is separated below by a triangular space, in which is seen the Rectus femoris ; by its posterior border, with the Gluteus medius. The Sartorius, the longest muscle in the body, is flat, narrow, and ribbon-like; it arises by tendinous fibres from the anterior superior spinous process of the ilium and the upper half of the notch below it, passes obliquely across the upper and anterior part of the thigh, from the outer to the inner side of the limb, then descends vertically, as far as the inner side of the knee, passing behind the inner condyle of the femur, and terminates in a tendon which, curving obliquely forward, expands into a broad aponeurosis inserted into the upper part of the inner surface of the shaft of the tibia, nearly as far forward as the crest. This expansion is inserted into the bone by an inverted U-shaped aponeurosis: part of it is inserted behind the attachment of the Gracilis and Semitendinosus, and another part, arching over the upper border of the tendon of the Gracilis, is inserted into the tibia in front of these muscles. An offset is derived from the upper margin of this aponeurosis, which blends with the fibrous capsule of the knee-joint, and another, given off from its lower border, blends with the fascia on the inner side of the leg. The relations of this muscle to the femoral artery should be carefully examined, as it constitutes the chief guide in tying the artery. In the upper third of the thigh it forms the outer side of a triangular space, Scarpa's triangle, the inner 1 These parts will be again more particularly described with the anatomy of Hernia. THE ANTERIOR FEMORAL REGION. 511 side of which is formed by the Adductor longus, and the base, turned upward, by Poupart's ligament; the femoral artery passes perpendicularly through the middle of this space from its base to its apex. In the middle third of the thigh the femoral artery lies first along the inner border, and then behind the Sartorius. Relations.-By its superficial stirface, with the fascia lata and integument; by its deep surface, with the Rectus, Iliacus, Psoas, Vastus internus, anterior crural nerve, sheath of the femoral vessels, Adductor longus, Adductor magnus, Gracilis, Semitendinosus, long saphenous nerve, and internal lateral ligament of the knee-joint. The Quadriceps extensor includes the four remaining muscles on the front of the thigh. It is the great Extensor muscle of the leg, forming a large fleshy mass which covers the front and sides of the femur, being united below into a single tendon, attached to the patella, and above subdivided into separate poi> tions, which have received distinct names. Of these, one occupying the middle of the thigh, connected above with the ilium, is called the Rectus femoris, from its straight course. The other divisions lie in immediate connection with the shaft of the femur, which they cover from the trochanters to the condyles. The portion on the outer side of the femur is termed the Vastus externus ; that covering the inner side, the Vastus internus; and that covering the front of the femur, the Crureus. The two latter portions are, however, so intimately blended as to form but one muscle. The Rectus femoris is situated in the middle of the anterior region of the thigh: it is fusiform in shape, and its superficial fibres are arranged in a bipenni- form manner, the deep fibres running straight down to the deep aponeurosis. It arises by two tendons: one the straight tendon, or short head, from the anterior inferior spinous process of the ilium; the other is flattened, and curves outw ard, to be attached to a groove above the brim of the acetabulum; this is the reflected tendon, or long head, of the Rectus ; it unites with the straight tendon at an acute angle, and then spreads into an aponeurosis, from which the muscular fibres arise.1 The muscle terminates in a broad and thick aponeurosis which occupies the lower two-thirds of its posterior surface, and, gradually becoming narrowed into a flattened tendon, is inserted into the patella in common with the Vasti and Crureus. Relations.-By its superficial surface, with the anterior fibres of the Gluteus minimus, the Tensor vaginae femoris, the Sartorius, and the Psoas and Iliacus; by its lower three-fourths, with the fascia lata; by its posterior surface, with the hip-joint, the external circumflex vessels, and the Crureus and Vasti muscles. The three remaining muscles have been described collectively by some anat- omists, separate from the Rectus, under the name of the Triceps extensor cruris. The Vastus externus is the largest part of the Quadriceps extensor. It arises by a b]j|ad aponeurosis, which is attached to the tubercle of the femur, to the anterior and inferior borders of the great trochanter, to a rough line leading from the trochanter major to the linea aspera, and to the outer lip of the linea aspera: this aponeurosis covers the upper three-fourths of the muscle, and from its inner surface many fibres arise. A few additional fibres arise from the tendon of the Gluteus maximus and from the external intermuscular septum between the Vastus externus and short head of the Biceps. The fibres form a large fleshy mass which is attached to a strong aponeurosis, placed on the under surface of the muscle at its lower part: this becomes contracted and thickened into a flat tendon, which is inserted into the outer border of the patella, blending w ith the great extensor tendon. 1 Mr. W. R. Williams, in an interesting paper in the Journ. of Anat. and Phys., vol. xiii. p. 204, points out that the reflected tendon is the real origin of the muscle, and is alone present in early foetal life. The direct tendon is merely an accessory band of condensed fascia. The paper will well repay perusal, though in some particulars I think the description in the text more generally accurate.-Ed. 512 77ZA MUSCLES AND FASCEE. Relations.-By its superficial surface, with the Rectus, the Tensor vaginae femoris, the fascia lata, and the Gluteus maximus, from which it is separated by a synovial bursa; by its deep surface, with the Crureus, some large branches of the external circumflex artery and anterior crural nerve being interposed. The Vastus internus and Crureus are so inseparably connected together as to form but one muscle, as which it will be accordingly described. It is the smallest portion of the Quadriceps extensor. The anterior portion of it, covered by the Rectus, is called the Crureus; the internal portion, which lies immediately beneath the fascia lata, the Vastus internus. It arises by an aponeurosis, which is attached to the lower part of the line that extends from the inner side of the neck of the femur to the linea aspera, from the inner lip of the linea aspera, from the ridge leading from the linea aspera to the internal condyle and internal intermuscular septum. It also arises from nearly the whole of the internal, anterior, and external surfaces of the shaft of the femur, limited, above, by the line between the two trochanters, and extending, below, to within the lower fourth of the bone. From these different origins the fibres converge to a broad aponeurosis which covers the anterior surface of the middle portion of the muscle (the Crureus) and the deep surface of the inner division of the muscle (the Vastus internus), and which gradually narrows down to its insertion into the patella, where it blends with the other portions of the Quadriceps extensor. The muscular fibres of the Vastus internus extend lower down than those of the Vastus externus, so that the capsule of the joint is less covered with muscular fibres on the outer than on the inner side. Relations.-By its superficial surface, with the Psoas and Iliacus, the Rectus, Sartorius, Pectineus, Adductors, and fascia lata, femoral vessels, and saphenous nerve; by its deep surface, with the femur, Subcrureus, and synovial membrane of the knee-joint. The student will observe the striking analogy that exists between the Quadri- ceps extensor and the Triceps muscle in the upper extremity. So close is this similarity that M. Cruveilhier has described it under the name of the Triceps femoralis. Like the Triceps extensor cubiti, it consists of three distinct divisions, or heads: a middle or long head, the Rectus, analogous to the long head of the Triceps, attached to the ilium, and two other portions, which may be called the external and internal heads of the Triceps femoralis. These, it will be noticed, are strictly analogous to the outer and inner heads of the Triceps in the arm. The tendons of the different portions of the Quadriceps extensor unite at the lower part of the thigh, so as to form a single strong tendon which is inserted into the upper part of the patella. More properly, the patella may be regarded as a sesamoid bone, developed in the tendon of the Quadriceps, and the ligamentum patellae, which is continued from the lower part of the patella to the tuberosity of the tibia, as the proper tendon of insertion of the muscle. A synovial bursa, the post-patellar bursa, is interposed between the tendon and the upper part of the tuberosity of the tibia ; and another, the prepatellar bursa, is placed over the patella itself. This latter bursa often becomes enlarged, constituting " housemaid's knee." The Subcrureus is a small muscle, usually distinct from the Crureus, but occa- sionally blended with it, which arises from the anterior surface of the lower part of the shaft of the femur, and is inserted into the upper part of the cul-de-sac of the capsular ligament which projects upward beneath the Quadriceps for a variable distance. It sometimes consists of two separate muscular bundles. Nerves.-The Tensor vaginae femoris is supplied by the superior gluteal nerve ; the other muscles of this region by branches from the anterior crural. Actions.-The Tensor vaginae femoris is a tensor of the fascia lata; continuing its action, the oblique direction of its fibres enables it to abduct and to rotate the thigh inward. In the erect posture, acting from below, it will serve to steady the pelvis upon the head of the femur, and by means of the ilio-tibial band it steadies the condyles of the femur on the articular surfaces of the tibia, and assists the THE INTERNAL FEMORAL REGION 513 Gluteus maximus in supporting the knee in the extended position. The Sartorius flexes the leg upon the thigh, and, continuing to act, flexes the thigh upon the pelvis ; it next rotates the thigh outward. It was formerly supposed to adduct the thigh, so as to cross one leg over the other, and hence received its name of Sartorius, or tailor's muscle (sartor, a tailor), because it was supposed to assist in crossing the legs in the squatting position. When the knee is bent the Sartorius assists the Semitendinosus, Semimembranosus, and Popliteus in rotating the tibia inward. Taking its fixed point from the leg, it flexes the pelvis upon the thigh, and, if one muscle acts, assists in rotating the pelvis. The Quadriceps extensor extends the leg upon the thigh. Taking its fixed point from the leg, as in standing, this muscle will act upon the femur, supporting it perpendicularly upon the head of the tibia, and thus maintaining the entire weight of the body, or in the stooping position it will straighten the knee, and therefore assist the trunk in rising into the erect position. The Rectus muscle assists the Psoas and Iliacus in supporting the pel- vis and trunk upon the femur or in bending it forward. Surgical Anatomy.-A few fibres of the Rectus muscle are liable to be ruptured from severe strain. This accident is especially liable to occur during the games of football and cricket, and is sometimes known as "cricket thigh. " The patient experiences a sudden pain in the part, as if he had been struck, and the Rectus muscle stands out and is felt to be tense and rigid. The accident is often followed by considerable swelling from inflammatory effusion. Occasionally the Quadriceps extensor may be torn away from its insertion into the patella, or the tendon of the patella may be ruptured about an inch above the bone. This accident is caused in the same manner as fracture of the patella by muscular action is produced-viz. by a violent muscular effort to prevent falling whilst the knee is in a position of semiflexion. A distinct gap can be felt above the patella, and, owing to the retraction of the muscular fibres, union may fail to take place. Internal Femoral Region. Gracilis. Pectineus. Adductor longus. Adductor brevis. Adductor magnus. Dissection.-These muscles are at once exposed by removing the fascia from the fore part and inner side of the thigh. The limb should be abducted, so as to render the muscles tense and easier of dissection. The Gracilis (Figs. 326, 329) is the most superficial muscle on the inner side of the thigh. It is thin and flattened, broad above, narrow and tapering below. It arises by a thin aponeurosis, between two and three inches in breadth, from the lower half of the margin of the symphysis and the inner margin of the descending ramus of the os pubis. The fibres pass vertically downward, and terminate in a rounded tendon which passes behind the internal condyle of the femur, and, curving round the inner tuberosity of the tibia, becomes flattened, and is inserted into the upper part of the inner surface of the shaft of the tibia, below the tuber- osity. The tendon of this muscle is situated immediately above that of the Semitendinosus, and is surrounded by the tendon of the Sartorius, with which it is in part blended. As it passes across the internal lateral ligament of the knee-joint it is separated from it by a synovial bursa common to it and the Semitendinosus muscle. Relations.-By its superficial surface, with the fascia lata and the Sartorius below : the internal saphenous vein crosses it obliquely near its lower part, lying superficial to the fascia lata; the internal saphenous nerve emerges between its tendon and that of the Sartorius ; by its deep surface, with the Adductor brevis and the Adductor magnus and the internal lateral ligament of the knee-joint. The Pectineus (Fig. 326) is a flat, quadrangular muscle situated at the anterior part of the upper and inner aspect of the thigh. It arises from the linea ilio- pectinea, from the surface of the bone in front of it between the pectineal eminence and spine of the os pubis, and from the fascia covering the anterior surface of the muscle ; the fibres pass downward, backward, and outward, to be inserted into a rough line leading from the lesser trochanter to the linea aspera. Relations.-By its anterior surface, with the pubic portion of the fascia lata, 514 THE MUSCLES AND FASCIAE. which separates it from the femoral vessels and internal saphenous vein; by its posterior surface, with the capsular ligament of the hip-joint, the Adductor brevis and Obturator externus muscles, the obtura- tor vessels and nerve being interposed ; by its outer border, with the Psoas, a cellular interval separating them, through which passes the internal circumflex vessels; by its inner border, with the margin of the Adductor longus. The Adductor longus, the most super- ficial of the three Adductors, is a fiat tri- angular muscle lying on the same plane as the Pectineus. It arises, by a flat narrow tendon, from the front of the os pubis, at the angle of junction of the crest with the symphysis; and soon expands into a broad fleshy belly, which, passing downward, back- ward, and outward, is inserted, by an apo- neurosis, into the linea aspera, between the Vastus internus and the Adductor magnus, with which it is usually blended. Relations.-By its anterior surface, with the fascia lata, the Sartorius, and, near its insertion, with the femoral artery and vein; by its posterior surface, with the Adductor brevis and magnus, the anterior branches of the obturator nerve, and with the profunda artery and vein near its inser- tion ; by its outer border, with the Pecti- neus ; by its inner border, with the Gracilis. The Pectineus and Adductor longus should now be divided near their origin, and turned down- ward, when the Adductor brevis and Obturator ex- ternus will be exposed. The Adductor brevis is situated im- mediately behind the two preceding mus- cles. It is somewhat triangular in form, and arises by a narrow origin from the outer surface of the body and descending ramus of the os pubis, between the Gracilis and Obturator externus. Its fibres, passing backward, outward, and downward, are in- serted, by an aponeurosis, into the lower part of the line leading from the lesser trochanter to the linea aspera and the upper part of the linea aspera, immediately behind the Pectineus and upper part of the Adduc- tor longus. Relations.-By its anterior surface, with the Pectineus, Adductor longus, profunda femoris artery, and anterior branches of the obturator nerve; by its posterior sur- face, with the Adductor magnus and posterior branch of the obturator nerve; by its outer border, with the Obturator externus and conjoined tendon of the Psoas and Iliacus; by its inner border, with the Gracilis and Adductor magnus. Fig. 327.-Deep muscles of the internal femoral region. THE INTERNAL EEMORAL REGION 515 This muscle is pierced, near its insertion, by the middle perforating branch of the profunda femoris artery. The Adductor brevis should now be cut away near its origin, and turned outward, when the entire extent of the Adductor magnus will be exposed. The Adductor magnus is a large triangular muscle forming a septum between the muscles on the inner and those on the back of the thigh. It arises from a] small part of the descending ramus of the os pubis, from the ascending ramus of the ischium, and from the outer margin and under surface of the tuberosity of the ischium. Those fibres which arise from the ramus of the os pubis are very short, horizontal in direction, and are inserted into the rough line leading from the great trochanter to the linea aspera, internal to the Gluteus maximus; those from the ramus of the ischium are directed downward and outward with different degrees of obliquity, to be inserted, by means of a broad aponeurosis, into the linea aspera and the upper part of its internal prolonga- tion below. The internal portion of the muscle, consisting principally of those fibres which arise from the tuberosity of the ischium, forms a thick fleshy mass consisting of coarse bundles which descend almost vertically, and terminate about the lower third of the thigh in a rounded tendon, which is inserted into the Adductor tubercle on the inner condyle of the femur, being connected by a fibrous expansion to the line leading upward from the tubercle to the linea aspera. Between the two portions of the muscle an interval is left, tendinous in front, fleshy behind, for the passage of the femoral vessels into the popliteal space. The external portion of the muscle at its attachment to the femur presents three or four osseo-aponeurotic openings, formed by tendinous arches attached to the bone, from which muscular fibres arise. The three superior of these apertures are for the three perforating arteries, and the fourth, when it exists, for the terminal branch of the profunda. Relations.-By its anterior surface, with the Pectineus, Adductor brevis, Adductor longus, and the femoral and profunda vessels and obturator nerve; by its posterior surface, with the great sciatic nerve, the Gluteus maximus, Biceps, Semitendinosus, and Semimembranosus. By its superior or shortest border it lies parallel with the Quadratus femoris, the internal circumflex artery passing between them ; by its internal or longest border, with the Gracilis, Sartorius, and fascia lata; by its external or attached border it is inserted into the femur behind the Adductor brevis and Adductor longus, which separate it from the Vastus internus, and in front of the Gluteus maximus and short head of the Biceps, which separate it from the Vastus externus. Nerves.-All the muscles of this group are supplied by the obturator nerve. The Pectineus receives additional branches from the accessory obturator and ante- rior crural, and the Adductor magnus an additional branch from the great sciatic. Actions.-The Pectineus and three Adductors adduct the thigh powerfully; they are especially used in horse exercise, the flanks of the horse being grasped between the knees by the actions of these muscles. In consequence of the obliquity of their insertion into the linea aspera they rotate the thigh outward, assisting the external Rotators, and when the limb has been abducted they draw it inward, carrying the thigh across that of the opposite side. The Pectineus and Adductor brevis and longus assist the Psoas and Iliacus in flexing the thigh upon the pelvis. In progression, also, all these muscles assist in drawing forward the hinder limb. The Gracilis assists the Sartorius in flexing the leg and rotating it inward; it is also an adductor of the thigh. If the lower extremities are fixed, these muscles may take their fixed point from below and act upon the pelvis, serving to maintain the body in an erect posture, or, if their action is continued, to flex the pelvis forward upon the femur. Surgical Anatomy.-The Adductor longus is liable to be severelj' strained in those who ride much on horseback, or its tendon to be ruptured by suddenly gripping the saddle. And, occasionally, especially in cavalry soldiers, the tendon may become ossified, constituting the " rider's bone." 516 77ZA MUSCLES AND FASCIAE. THE HIP. Gluteal Region Gluteus maximus. Gluteus medius. Gluteus minimus. Pyriformis. Gemellus superior. Obturator internus. Gemellus inferior. Obturator externus. Quadratus femoris Dissection (Fig. 328).-The subject should be turned on its face, a block placed beneath the pelvis to make the buttocks tense, and the limbs allowed to hang over the end of the table, with the foot inverted and the thigh abducted. Make an incision through the integument along the crest of the ilium to the middle of the sacrum, and thence downward to the tip of the coccyx, and carry a second incision from that point obliquely downward and outward to the outer side of the thigh, four inches below the great trochanter. The portion of integument included between these incisions is to be removed in the direction shown in the figure. The Gluteus maximus (Fig. 329), the most superficial muscle in the gluteal region, is a very broad and thick, fleshy mass of a quadrilateral shape, which forms the prominence of the nates. Its large size is one of the most characteristic points in the muscular system in man, connected as it is with the power he has of maintaining the trunk in the erect posture. In structure the muscle is remarkably coarse, being made up of muscular fasciculi lying parallel with one another, and collected together into large bundles, separated by deep cellular intervals. It arises from the superior curved line of the ilium and the por- tion of bone, including the crest, immediately behind it; from the posterior surface of the lower part of the sacrum, the side of the coccyx, the aponeurosis of the Erector spinse muscle, and the great sacro-sciatic ligament. The fibres are directed obliquely downward and outward; those forming the upper and larger portion of the muscle (after converging somewhat) terminate in a thick tendinous lamina, which passes across the great trochanter, and is inserted into the fascia lata covering the outer side of the thigh, the lower portion of the muscle being inserted into the rough line leading from the great trochanter to the linea aspera between the Vastus externus and Ad- ductor magnus. Three synovial bursce are usually found in relation with this muscle. One of these, of large size, and generally multilocular, separates it from the great trochanter. A second, often wanting, is situated on the tuberosity of the ischium. A third is found between the tendon of this muscle and the Vastus externus. Relations.-By its superficial surface, with a thin fascia, which separates it from the sub- cutaneous tissue; by its deep surface, from above downward, wdth the ilium, sacrum, coccyx, and great sacro-sciatic ligament, part of the Gluteus medius, Pyriformis, Gemelli, Obturator internus, Quadratus femoris, the tuberosity of the ischium, great trochanter, the origin of the Biceps, Semitendinosus, Semimembranosus, and Adductor magnus muscles. The gluteal vessels and superior gluteal nerve are seen issuing from the pelvis above the Pyriformis muscle, the sciatic and 1. Dissection of gluteal region. I 3. Back of thigh. 2. Popliteal space. ' 4. Back of leg. 5. Sole of foot. Fig. 328-Dissection of lower extremity. Posterior view. THE GLUTEAL LEGION. 517 internal pudic vessels and nerves, and muscular branches from the sacral plexus below it. Its upper border is thin, and connected with the Gluteus medius by the fascia lata; its lower border is free and prominent. Dissection.-Now divide the Glu- teus maximus near its origin by a ver- tical incision carried from its upper to its lower border; a cellular interval will be exposed, separating it from the Gluteus medius and External rotator muscles beneath. The upper portion of the muscle is to be alto- gether detached, and the lower portion turned outward; the loose areolar tissue filling up the interspace be- tween the trochanter major and tuber- osity of the ischium being removed, the parts already enumerated as ex- posed by the removal of this muscle will be seen. The Gluteus medius is a broad, thick, radiated muscle, situated on the outer surface of the pelvis. Its posterior third is covered by the Gluteus maximus; its anterior two-thirds by the fascia lata, which separates it from the integument. It arises from the outer surface of the ilium, between the superior and middle curved lines, and from the outer lip of that portion of the crest which is between them ; it also arises from the dense fascia (Gluteal aponeurosis) cover- ing its outer surface. The fibres converge to a strong flattened tendon which is inserted into the oblique line which traverses the outer surface of the great tro- chanter. A synovial bursa sepa- rates the tendon of the muscle from the surface of the trochanter in front of its insertion. Relations.-By its superficial surface, with the Gluteus maxi- mus behind, the Tensor vaginae femoris and deep fascia in front; by its deep surface, with the Gluteus minimus and the gluteal vesselsand superior gluteal nerve. Its anterior border is blended with the Gluteus minimus. Its posterior border lies parallel with the Pyriformis, the gluteal ves- sels intervening. Inner hamstring tendons. SARTORIUS. GRACILIS. SEMITENDINOSUS. SEMIMEMBRA- NOSUS. Older hamstring tendon. -biceps. Fig. 329.-Muscles of the hip and thigh. 518 77/A' MUSCLES AND FASCIAE. This muscle should now be divided near its insertion and turned upward, when the Gluteus minimus will be exposed. The Gluteus minimus, the smallest of the three Glutei, is placed immediately beneath the preceding. It is fan-shaped, arising from the outer surface of the ilium, between the middle and inferior curved lines, and behind, from the margin of the great sacro-sciatic notch; the fibres converge to the deep surface of a radiated aponeurosis, which, terminating in a tendon, is inserted into an impres- sion on the anterior border of the great trochanter. A synovial bursa is inter- posed between the tendon and the great trochanter. Relations.-By its superficial surface, with the Gluteus medius, and the gluteal vessels and superior gluteal nerve ; by its deep surface, with the ilium, the reflected tendon of the Rectus femoris, and capsular ligament of the hip-joint. Its anterior margin is blended with the Gluteus medius; its, posterior margin is often joined with the tendon of the Pyriformis. The Pyriformis is a flat muscle, pyramidal in shape, lying almost parallel with the posterior margin of the Gluteus medius. It is situated partly within the pelvis at its posterior part and partly at the back of the hip-joint. It arises from the front of the sacrum by three fleshy digitations attached to the portions of bone between the first, second, third, and fourth anterior sacral foramina, and also from the groove leading from the foramina: a few fibres also arise from the margin of the great sacro-sciatic foramen and from the anterior surface of the great sacro- sciatic ligament. The muscle passes out of the pelvis through the great sacro- sciatic foramen, the upper part of which it fills, and is inserted by a rounded tendon into the upper border of the great trochanter, behind, but often blended with, the tendon of the Obturator internus and Gemelli muscles. Relations.-By its anterior surface, within the pelvis, with the Rectum (espe- cially on the left side), the sacral plexus of nerves, and the branches of the internal iliac vessels ; external to the pelvis, with the os innominatum and capsular liga- ment of the hip-joint; by its posterior surface, within the pelvis, with the sacrum, and external to it, with the Gluteus maximus; by its upper border, with the Gluteus medius, from which it is separated by the gluteal vessels and superior gluteal nerve ; by its lower border, with the Gemellus superior and Coccygeus, the sciatic vessels and nerves, the internal pudic vessels and nerve, and muscular branches from the sacral plexus, passing from the pelvis in the interval between the two muscles. * The Obturator membrane is a thin layer of interlacing fibres which closes the obturator foramen. It is attached, externally, to the margin of the foramen; internally, to the posterior surface of the ischio-pubic ramus, internal to the inner margin of the foramen. It is occasionally incomplete, and presents at its upper and outer part a small canal, which is bounded below by a thickened band of fibres, for the passage of the obturator vessels and nerve. Each obturator muscle is connected with this membrane. Dissection.-The next muscle, as well as the origin of the Pyriformis, can only be seen when the pelvis is divided and the viscera removed. The Obturator internus, like the preceding muscle, is situated partly within the cavity of the pelvis and partly at the back of the hip-joint. It arises from the inner surface of the anterior and external wall of the pelvis, around the inner side of the obturator foramen, being attached to the descending ramus of the os pubis and the ascending ramus of the ischium, and at the side to the inner surface of the body of the ischium, between the margin of the obturator foramen in front and the great sacro-sciatic notch behind, and to the inner surface of the ilium below the brim of the true pelvis. It also arises from the inner surface of the obturator membrane, except at its lower part, and from the tendinous arch which completes the canal for the passage of the obturator vessels and nerve. The fibres are directed backward and downward, and terminate in four or five tendinous bands which are found on its deep surface: these bands are reflected at a right THE GLUTEAL REGION. 519 angle over the inner surface of the tuberosity of the ischium, which is grooved for their reception : the groove is covered with cartilage and lined with a synovial bursa. The muscle leaves the pelvis by the lesser sacro-sciatic notch, and the tendinous bands unite into a single flattened tendon, which passes horizontally outward, and, after receiving the attachment of the Gemelli, is inserted into the inner surface of the great trochanter in front of the Obturator externus. A synovial bursa, narrow and elongated in form, is usually found between the tendon of this muscle and the capsular ligament of the hip : it occasionally communicates with the bursa between the tendon and the tuberosity of the ischium, the two forming a single sac. In order to display the peculiar appearances presented by the tendon of this muscle, it must be divided near its insertion and reflected outward. Relations.- Within the pelvis this muscle is in relation, by its anterior surface, with the obturator membrane and inner surface of the anterior wall of the pelvis; by its posterior surface, with the pelvic and obturator fasciae, which separate it from the Levator ani; and it is crossed by the internal pudic vessels and nerve. This surface forms the outer boundary of the ischio-rectal fossa. External to the pelvis it is covered by the great sciatic nerve and Gluteus maximus, and rests on the back part of the hip-joint. The Gemelli are two small muscular fasciculi, accessories to the tendon of the Obturator internus, which is received into a groove between them. They are called superior and inferior. The Gemellus superior, the smaller of the two, arises from the outer surface of the spine of the ischium, and, passing horizontally outward, becomes blended with the upper part of the tendon of the Obturator internus, and is inserted with it into the inner surface of the great trochanter. This muscle is sometimes wanting. Relations.-By its superficial surface, with the Gluteus maximus and the sciatic vessels and nerves ; by its deep surface, with the capsule of the hip-joint; by its upper border, with the lower margin of the Pyriformis ; by its lower border, with the tendon of the Obturator internus. The Gemellus inferior arises from the upper part of the tuberosity of the ischium, where it forms the lower edge of the groove for the Obturator internus tendon, and, passing horizontally outward, is blended with the lower part of the tendon of the Obturator internus, and is inserted with it into the inner surface of the great trochanter. Relations.-By its superficial surface, with the Gluteus maximus and the sciatic vessels and nerves; by its deep surface, with the capsular ligament of the hip-joint; by its upper border, with the tendon of the Obturator internus ; by its lower border, with the tendon of the Obturator externus and Quadratus femoris. The Quadratus femoris is a short, flat muscle, quadrilateral in shape (hence its name), situated between the Gemellus inferior and the upper margin of the Adductor magnus. It arises from the external lip of the tuberosity of the ischium, and, proceeding horizontally outward, is inserted into the upper part of the linea quadrata ; that is, the line which crosses the posterior intertrochanteric line. A synovial bursa is often found between the under surface of this muscle and the lesser trochanter, which it covers. Relations.-By its posterior surface, with the Gluteus maximus and the sciatic vessels and nerves; by its anterior surface, with the tendon of the Obturator externus and trochanter minor and with the capsule of the hip-joint; by its upper border, with the Gemellus inferior. Its lower border is separated from the Adductor magnus by the terminal branches of the internal circumflex vessels. Dissection.-In order to expose the next muscle (the Obturator externus), it is necessary to remove the Psoas, Iliacus, Pectineus, and Adductor brevis and longus muscles from the front and inner side of the thigh, and the Gluteus maximus and Quadratus femoris from the back part. Its dissection should, consequently, be postponed until the muscles of the anterior and internal femoral regions have been explained. 520 THE MUSCLES AND FASCINE. The Obturator externus (Fig. 327) is a flat, triangular muscle which covers the outer surface of the anterior wall of the pelvis. It arises from the margin of bone immediately around the inner side of the obturator foramen-viz. from the body and ramus of the os pubis, and the ramus of the ischium ; it also arises from the inner two-thirds of the outer surface of the obturator membrane, and from the tendinous arch which completes the canal for the passage of the obturator vessels and nerves. The fibres converging pass backward, outward, and upward, and terminate in a tendon which runs across the back part of the hip-joint and is inserted into the digital fossa of the femur. Relations.-By its anterior surface, with the Psoas, Iliacus, Pectineus, Adductor magnus, Adductor brevis, and Gracilis, and more externally, with the neck of the femur and capsule of the hip-joint; by its posterior surface, with the obturator membrane and Quadratus femoris. Nerves.-The Gluteus maximus is supplied by the inferior gluteal nerve from the sacral plexus; the Gluteus medius and minimus, by the superior gluteal; the Pyriformis, Gemelli, Obturator internus, and Quadratus femoris, by branches from the sacral plexus; and the Obturator externus, by the obturator nerve. Actions.-The Gluteus maximus, when it takes its fixed point from the pelvis, extends the femur and brings the bent thigh into a line with the body. Taking its fixed point from below, it acts upon the pelvis, supporting it and the whole trunk upon the head of the femur, which is especially obvious in standing on one leg. Its most powerful action is to cause the body to regain the erect position after stooping by drawing the pelvis backward, being assisted in this action by the Biceps, Semitendinosus, and Semimembranosus. The Gluteus maximus is a tensor of the fascia lata, and by its connection with the ilio-tibial band it steadies the femur on the articular surface of the tibia during standing, when the extensor muscles are relaxed. The lower part of the muscle also acts as an abductor and external rotator of the limb. The Gluteus medius and minimus abduct the thigh when the limb is extended, and are principally called into action in supporting the body on one limb, in conjunction with the Tensor vaginae femoris. Their anterior fibres, by drawing the great trochanter forward, rotate the thigh inward, in which action they are also assisted by the Tensor vaginae femoris. The remaining muscles are powerful rotators of the thigh outward. In the sitting posture, when the thigh is flexed upon the pelvis, their action as rotators ceases, and they become abductors, with the exception of the Obturator externus, which still rotates the femur outward. When the femur is fixed, the Pyriformis and Obturator muscles serve to draw the pelvis forward if it has been inclined backward, and assist in steadying it upon the head of the femur. Biceps. Posterior Femoral Region. Semitendinosus. Semimembranosus. Dissection (Fig. 328).-Make a vertical incision along the middle of the thigh, from the lower fold of the nates to about three inches below the back of the knee-joint, and there connect it with a transverse incision carried from the inner to the outer side of the leg. Make a third incision transversely at the junction of the middle with the lower third of the thigh. The integument having been removed from the back of the knee and the boundaries of the popliteal space examined, the removal of the integument from the remaining part of the thigh should be continued, when the fascia and muscles of this region will be exposed. The Biceps (Biceps flexor cruris) is a large muscle, of considerable length, situated on the posterior and outer aspect of the thigh (Fig. 329). It arises by two heads. One, the long head, arises from the lower and inner facet on the back part of the tuberosity of the ischium by a tendon common to it and the Semitendinosus. The femoral, or short head, arises from the outer lip of the linea aspera, between the Adductor magnus and Vastus externus, extending up almost as high as the insertion of the Gluteus maximus, and from its outer pro- longation below to within two inches of the outer condyle; it also arises from the THE POSTERIOR FEMORAL REGION. 521 external intermuscular septum. The fibres of the long head form a fusiform belly, which, passing obliquely downward and a little outward, terminates in an aponeurosis which covers the posterior surface of the muscle and receives the fibres of the short head: this aponeurosis becomes gradually contracted into a tendon, which is inserted into the outer side of the head of the fibula, and by a small slip into the lateral surface of the external tuberosity of the tibia. At its insertion the tendon divides into two portions, which embrace the long external lateral ligament of the knee-joint, a strong prolongation being sent for- ward to the outer tuberosity of the tibia, which gives off an expansion to the fascia of the leg. The tendon of this muscle forms the outer hamstring. Relations.-By its superficial surface, with the Gluteus maximus above, with the fascia lata and integument in the rest of its extent; by its deep surface, with the Semimembranosus, Adductor magnus, and Vastus externus, the great sciatic nerve, and, near its insertion, with the external head of the Gastro- cnemius, Plantaris, the superior external articular artery, and the external popliteal nerve. The Semitendinosus, remarkable for the great length of its tendon, is situated at the posterior and inner aspect of the thigh. It arises from the lower and inner facet on the tuberosity of the ischium by a tendon common to it and the long head of the Biceps; it also arises from an aponeurosis which connects the adjacent surfaces of the two muscles to the extent of about three inches after their origin. It forms a fusiform muscle, which, passing downward and inward, terminates a little below the middle of the thigh in a long round tendon which lies along the inner side of the popliteal space, then curves around the inner tuberosity of the tibia, and is inserted into the upper part of the inner surface of the shaft of that bone nearly as far forward as its anterior border. This tendon is surrounded by the tendon of the Sartorius, and lies below that of the Gracilis, to which it is united. A tendinous intersection is usually observed about the middle of the muscle. Relations.-By its superficial surface, with the Gluteus maximus and fascia lata; by its deep surface, with the Semimembranosus, Adductor magnus, inner head of the Gastrocnemius, and internal lateral ligament of the knee-joint. The Semimembranosus, so called from the membranous expansion on its anterior and posterior surfaces, is situated at the back part and inner side of the thigh. It arises by a thick tendon from the upper and outer facet on the back part of the tuberosity of the ischium, above and to the outer side of the Biceps and Semitendinosus, and is inserted into the groove on the inner and back part of the inner tuberosity of the tibia, beneath the internal lateral ligament. The tendon of the muscle at its origin expands into an aponeurosis which covers the upper part of its anterior surface: from this aponeurosis muscular fibres arise, and converge to another aponeurosis, which covers the lower part of its posterior surface and contracts into the tendon of insertion. The tendon of the muscle at its insertion gives off two fibrous expansions; one of these, of considerable size, passes upward and outward to be inserted into the back part of the outer con- dyle of the femur, forming part of the posterior ligament of the knee-joint. The second is continued downward to the fascia which covers the Popliteus muscle. The tendon also sends a few fibres to join the internal lateral ligament of the joint. The tendons of the two preceding muscles, with that of the Gracilis, form the inner hamstring. Relations.-By its superficial surface, with the Semitendinosus, Biceps, and fascia lata; by its deep surface, with the popliteal vessels, Adductor magnus, and inner head of the Gastrocnemius, from which it is separated by a synovial bursa; by its inner border, with the Gracilis; by its outer border, with the great sciatic nerve and its internal popliteal branch. Nerves.-The muscles of this region are supplied by the great sciatic nerve. Actions.-The hamstring muscles flex the leg upon the thigh. When the 522 THE MUSCLES AND FASCIAE. knee is semiflexed, the Biceps, in consequence of its oblique direction downward and outward, rotates the leg slightly outward; and the Semi- tendinosus, and to a slight extent the Semimem- branosus, rotate the leg inward, assisting the Pop- liteus. Taking their fixed point from below, these muscles serve to support the pelvis upon the head of the femur and to draw the trunk directly back- ward, as in feats of strength, when the body is thrown backward in the form of an arch. Surgical Anatomy.-The tendons of these muscles occasionally require subcutaneous division in some forms of spurious ankylosis of the knee-joint dependent upon per- manent contraction and rigidity of the Flexor muscles, or from stiffening of the ligamentous and other tissues sur- rounding the joint, the result of disease. This is effected by putting the tendon upon the stretch, and inserting a nar- row, sharp-pointed knife between it and the skin : the cut- ting edge being then turned toward the tendon, it should be divided, taking great care that the wound in the skin is not at the same time enlarged. The relation of the external popliteal nerve to the tendon of the Biceps must always be borne in mind in dividing this tendon. THE LEG. Dissection (Fig. 325).-The knee should be bent, a block placed beneath it, and the foot kept in an extended position; then make an incision through the integument in the middle line of the leg to the ankle, and continue it along the dorsum of the foot to the toes. Make a second incision transversely across, the ankle, and a third in the same direc- tion across the bases of the toes; remove the flaps of integu- ment included between these incisions in order to examine the deep fascia of the leg. The Deep fascia of the Leg forms a complete investment to the muscles, but is not continued over the subcutaneous surfaces of the bones. It is continuous above with the fascia lata, receiving an expansion from the tendon of the Biceps on the outer side, and from the tendons of the Sartorius, Gracilis, and Semitendinosus on the inner side; in front it blends with the periosteum covering the subcutaneous surface of the tibia, and with that covering the head and external malleolus of the fibula; below it is continuous with the annular ligaments of the ankle. It is thick and dense in the upper and anterior part of the leg, and gives attachment, by its deep surface, to the Tibialis anticus and Extensor longus digitorum muscles, but thinner behind, where it covers the Gastro- cnemius and Soleus muscles. Over the popliteal space it is much strengthened by transverse fibres which stretch across from the inner to the outer hamstring muscles, and it is here perforated by the external saphenous vein. Its deep surface gives off. on the outer side of the leg, two strong inter- muscular septa which enclose the Peronei muscles, and separate them from the muscles on the anterior and posterior tibial regions and several smaller and more slender processes which enclose the indi- Fig. 330.-Muscles of the front of the leg. THE ANTERIOR TIBIO-FIBULAR REGION. 523 vidual muscles in each region; at the same time a broad transverse intermuscular septum, called the deep transverse fascia of the leg, intervenes between the super- ficial and deep muscles in the posterior tibio-fibular region. Now remove the fascia by dividing it in the same direction as the integument, excepting opposite the ankle, where it should be left entire. Commence the removal of the fascia from below, opposite the tendons, and detach it in the line of direction of the muscular fibres. Muscles of the Leg.-These may be subdivided into three groups : those on the anterior, those on the posterior, and those on the outer side. Tibialis anticus. Extensor proprius hallucis. Anterior Tibio-fibular Region. Extensor longus digitorum. Peroneus tertius. The Tibialis anticus is situated on the outer side of the tibia; it is thick and fleshy at its upper part, tendinous below. It arises from the outer tuberosity and upper two-thirds of the external surface of the shaft of the tibia; from the adjoin- ing part of the interosseous membrane ; from the deep surface of the fascia ; and from the intermuscular septum between it and the Extensor longus digitorum : the fibres pass vertically downward, and terminate in a tendon which is apparent on the anterior surface of the muscle at the lower third of the leg. After passing through the innermost compartment of the anterior annular ligament, it is inserted into the inner and under surface of the internal cuneiform bone and base of the metatarsal bone of the great toe. Relations.-By its anterior surface, with the fascia and with the annular liga- ment; by its posterior surface, with the interosseous membrane, tibia, ankle-joint, and inner side of the tarsus: this surface also overlaps the anterior tibial vessels and nerve in the upper part of the leg. By its inner surface, with the tibia; by its outer surface, with the Extensor longus digitorum and Extensor proprius hal- lucis, and the anterior tibial vessels and nerve. The Extensor proprius hallucis is a thin, elongated, and flattened muscle situ- ated between the Tibialis anticus and Extensor longus digitorum. It arises from the anterior surface of the fibula for about the middle two-fourths of its extent, its origin being internal to that of the Extensor longus digitorum; it also arises from the interosseous membrane to a similar extent. The fibres pass downward, and terminate in a tendon which occupies the anterior border of the muscle, passes through a distinct compartment in the horizontal portion of the annular ligament, crosses the anterior tibial vessels near the bend of the ankle, and is inserted into the base of the last phalanx of the great toe. Opposite the metatarso-phalangeal articulation the tendon gives oft' a thin prolongation on each side, which covers the surface of the joint. It usually sends an expansion from the inner side of the tendon, to be inserted into the base of the first phalanx. Relations.-By its anterior surface, with the fascia and the anterior annular ligament; by its posterior surface, with the interosseous membrane, fibula, tibia, ankle-joint, and Extensor brevis digitorum ; by its outer side, with the Extensor longus digitorum above, the dorsalis pedis vessels and anterior tibial nerve below; by its inner side, with the Tibialis anticus and the anterior tibial vessels above. The Extensor longus digitorum is an elongated, flattened, semipenniform muscle situated the most externally of all the muscles on the fore part of the leg. It arises from the outer tuberosity of the tibia ; from the upper three-fourths of the anterior surface of the shaft of the fibula; from the interosseous membrane; from the deep surface of the fascia ; and from the intermuscular septa between it and the Tibialis anticus on the inner and the Peronei on the outer side. The tendon enters a canal in the annular ligament with the Peroneus tertius, and divides into four slips, which run across the dorsum of the foot and are inserted into the second and third phalanges of the four lesser toes. The mode in which the tendons are inserted is the following: The three inner tendons opposite the metatarso- phalangeal articulation are joined, on their outer side, by a tendon of the Extensor 524 THE MUSCLES AND FASCIAE. brevis digitorum. They all receive a fibrous expansion from the Interossei and Lumbricales, and then spread out into a broad aponeurosis, which covers the dorsal surface of the first phalanx: this aponeurosis, at the articulation of the first with the second phalanx, divides into three slips-a middle one, which is inserted into the base of the second phalanx, and two lateral slips, which, after uniting on the dorsal surface of the second phalanx, are continued onward, to be inserted into the base of the third. Relations.-By its anterior surface, with the fascia and the annular ligament; by its posterior surface, with the fibula, interosseous membrane, ankle-joint, and Extensor brevis digitorum; by its inner side, with the Tibialis anticus, Extensor proprius hallucis, and anterior tibial vessels and nerve; by its outer side, with the Peroneus longus and brevis. The Peroneus tertius is a part of the Extensor longus digitorum, and might be described as its fifth tendon. The fibres belonging to this tendon arise from the lower fourth of the anterior surface of the fibula, from the lower part of the interosseous membrane, and from an intermuscular septum between it and the Peroneus brevis. The tendon, after passing through the same canal in the annular ligament as the Extensor longus digitorum, is inserted into the dorsal surface of the base of the metatarsal bone of the little toe, on its inner side. This muscle is sometimes wanting. © Nerves.-These muscles are supplied by the anterior tibial nerve. Actions.-The Tibialis anticus and Peroneus tertius are the direct flexors of the tarsus upon the leg; the former muscle, from the obliquity in the direction of its tendon, raises the inner border of the foot; and the latter, acting with the Peroneus brevis and longus, draws the outer border of the foot upward and the sole outward. The Extensor longus digitorum and Extensor proprius hallucis extend the phalanges of the toes, and, continuing their action, flex the tarsus upon the leg. Taking their fixed point from below in the erect posture, all these muscles serve to fix the bones of the leg in the perpendicular position and give increased strength to the ankle-joint. Posterior Tibio-fibular Region. Dissection (Fig. 328).-Make a vertical incision along the middle line of the back of the leg, from the lower part of the popliteal space to the heel, connecting it below by a transverse incision extending between the two malleoli; the flaps of integument being removed, the fascia and muscles should be examined. The muscles in this region of the leg are subdivided into two layers-super- ficial and deep. The superficial layer constitutes a powerful muscular mass, forming the calf of the leg. Their large size is one of the most characteristic features of the muscular apparatus in man, and bears a direct connection with his ordinary attitude and mode of progression. Superficial Layer. The Gastrocnemius is the most superficial muscle, and forms the greater part of the calf. It arises by two heads, which are connected to the condyles of the femur by two strong flat tendons. The inner head, the larger and a little the more posterior, arises from a depression at the upper and back part of the inner condyle. The outer head arises from the upper and back part of the external condyle, immediately above the origin of the Popliteus. Both heads, also, arise by a few tendinous and fleshy fibres from the ridges which are continued upward from the condyles to the linea aspera. Each tendon spreads out into an aponeurosis which covers the posterior surface of that portion of the muscle to which it belongs, that covering the inner head being longer and thicker than the outer. From the anterior surface of these tendinous expansions muscular fibres are given off. The fibres in the median line, which correspond to the Gastrocnemius. Soleus. Plantaris. THE POSTERIOR TIBIO-FIBULAR REGION. 525 accessory portions of the muscle derived from the bifurcations of the linea aspera, unite at an angle upon a median tendinous raphe below : the remaining fibres converge to the posterior surface of an aponeurosis which covers the anterior surface of the muscle, and this, gradually contracting, unites with the tendon of the Soleus, and forms with it the tendo Achillis. Relations.-By its superficial surface, with the fascia of the leg, which separates it from the external saphenous vein and nerve; by its deep surface, with the posterior ligament of the knee-joint, the Popliteus, Soleus, Plantaris, popliteal vessels, and in- ternal popliteal nerve. The tendon of the inner head corresponds with the back part of the inner condyle, from which it is sepa- rated by a synovial bursa, which, in some cases, communicates with the cavity of the knee-joint. The tendon of the outer head contains a sesamoid fibro-cartilage (rarely osseous) where it plays over the correspond- ing outer condyle ; and one is occasionally found in the tendon of the inner head. The Gastrocnemius should be divided across, just below its origin, and turned downward, in order to expose the next muscles. The Soleus is a broad flat muscle situated immediately beneath the Gastrocnemius. It has received its name from its resemblance in shape to a sole-fish. It arises by ten- dinous fibres from the back part of the head of the fibula and from the upper third of the posterior surface of its shaft; from the oblique line of the tibia and from the middle third of its internal border; some fibres also arise from a tendinous arch placed between the tibial and fibular origins of the muscle, be- neath which the posterior tibial vessels and nerve pass. The fibres pass backward to an aponeurosis which covers the posterior sur- face of the muscle, and this, gradually be- coming thicker and narrower, joins with the tendon of the Gastrocnemius, and forms with it the tendo Achillis. Relations.-By its superficial surface, with the Gastrocnemius and Plantaris; by its deep surface, with the Flexor longus digitorum, Flexor longus hallucis, Tibialis posticus, and posterior tibial vessels and nerve, from which it is separated by the transverse intermuscular septum or deep transverse fascia of the leg. The Tendo Achillis, the common tendon of the Gastrocnemius and Soleus, is the thickest and strongest tendon in the body. It is about six inches in length, and commences about the middle of the leg, but receives fleshy fibres on its anterior surface nearly to its lower end. Gradually becoming contracted below, it is inserted into the lower part of the posterior surface of the os calcis, a synovial FLEXOR LONGUS HALLUCIS. I FLEXOR LONGUS DIGITORUM. I TIBIALIS POSTICUS. =- Tendons of PERONEUS LONGUS k and brevis. Tendons of < Fig. 331.-Muscles of the back of the leg. Superficial layer. 526 THE MUSCLES AND FASCIAE. bursa being interposed betw een the tendon and the upper part of this surface. The tendon spreads out somewhat at its lower end, so that its narrowest part is usually about an inch and a half above its insertion. The tendon is covered by the fascia and the integument, and is separated from the deep muscles and vessels by a considerable interval filled up with areolar and adipose tissue. Along its outer side, but superficial to it, is the external saphenous vein. The Plantaris is an extremely diminutive muscle placed between the Gastro- cnemius and Soleus, and remarkable for its long and delicate tendon. It arises from the lower part of the outer prolongation of the linea aspera and from the posterior ligament of the knee-joint. It forms a small fusiform belly, about three or four inches in length, terminating in a long slender tendon which crosses obliquely between the two muscles of the calf, and, running along the inner border of the tendo Achillis, is inserted with it into the posterior part of the os calcis. This muscle is occasionally double, and is sometimes wanting. Occasionally, its tendon is lost in the internal annular ligament or in the fascia of the leg. Nerves.-These muscles are supplied by the internal popliteal nerve. Actions.-The muscles of the calf possess considerable power, and are constantly called into use in standing, walking, dancing, and leaping; hence the large size they usually present. In walking these muscles draw powerfully upon the os calcis, raising the heel, and with it the entire body, from the ground; the body being thus supported on the raised foot, the opposite limb can be carried forward. In standing, the Soleus, taking its fixed point from below, steadies the leg upon the foot, and prevents the body from falling forward, to which there is a constant tendency from the superincumbent weight. The Gastrocnemius, acting from belowr, serves to flex the femur upon the tibia, assisted by the Popliteus. The Plantaris is the rudiment of a large muscle which exists in some of the lower animals and serves as a tensor of the plantar fascia. In man it is merely an accessory to the Gastrocnemius, extending the ankle if the foot is free or bending the knee if the foot is fixed. Deep Layer. Popliteus. Flexor longus hallucis. Flexor longus digitorum. Tibialis posticus. Dissection.-Detach the Soleus from its attachment to the fibula and tibia, and turn it downward, when the deep layer of muscles is exposed, covered by the deep transverse fascia of the leg. The Deep Transverse Fascia of the leg is a broad, transverse, intermuscular septum interposed between the superficial and deep muscles in the posterior tibio-fibular region. On either side it is connected to the margins of the tibia and fibula. Above, where it covers the Popliteus, it is thick and dense, and receivesan expansion from the tendon of the Semimembranosus; it is thinner in the middle of the leg, but below, where it covers the tendons passing behind the malleoli, it is thickened. It is continued onward in the interval between the ankle and the heel, where it covers the vessels and is blended with the internal annular ligament. This fascia should now be.removed, commencing from below opposite the tendons, and detaching it from the muscles in the direction of their fibres. The Popliteus is a thin, flat, triangular muscle, which forms part of the floor of the popliteal space, and is covered by a tendinous expansion derived from the Semimembranosus muscle. It arises by a strong tendon, about an inch in length, from a deep depression on the outer side of the external condyle of the femur, and from the posterior ligament of the knee-joint, and is inserted into the inner two-thirds of the triangular surface above the oblique line on the posterior surface of the shaft of the tibia, and into the tendinous expansion covering the surface of the muscle. The tendon of the muscle is covered by that of the Biceps and the external lateral ligament of the knee-joint; it grooves the outer border of the THE POSTERIOR TIBIO-FIBULAR REGION. 527 external semilunar fibro-cartilage, and is invested by the synovial membrane of the knee-joint. Relations.-By its superficial surface, with the fascia above mentioned, which separates it from the Gastrocnemius, Plantaris, popliteal vessels, and internal popliteal nerve; by its deep sur- face, with the superior tibio-fibular articulation and back of the tibia. The Flexor longus hallucis is situated on the fibular side of the leg, and is the most superficial and largest of the next three muscles. It arises from the lower two-thirds of the posterior surface of the shaft of the fibula, with the exception of an inch at its lowest part; from the lower part of the interosseous mem- brane ; from an intermuscular septum between it and the Peronei, externally; and from the fascia covering the Tibialis posticus, which is attached to the inner border of the fibula externally and to the posterior surface of the tibia between the origins of the Tibialis posticus and the Flexor longus digitorum, internally. The fibres pass obliquely downward and backward, and terminate round a tendon which occupies nearly the whole length of the posterior surface of the muscle. This tendon passes through a groove on the posterior surface of the tibia; it then passes through another groove on the posterior surface of the astragalus, and along a third groove, beneath the sustentaculum tali of the os calcis, into the sole of the foot, where it runs forward between the two heads of the Flexor brevis hallucis, and is inserted into the base of the last phalanx of the great toe. The grooves in the astragalus and os calcis, which contain the tendon of the muscle, are converted by tendinous fibres into distinct canals lined by synovial membrane; and as the tendon crosses the sole of the foot, it is connected to the common flexor by a tendinous slip. Relations.-By its superficial surface, with the Soleus and tendo Achillis, from which it is sepa- rated by the deep transverse fascia; by its deep sur- face, with the fibula, Tibialis posticus, the peroneal vessels, the lower part of the interosseous membrane, and the ankle-joint; by its outer border, with the Peronei; by its inner border, with the Tibialis posticus and posterior tibial vessels and nerve. The Flexor longus digitorum (perforans) is situated on the tibial side of the leg. At its origin it is thin and pointed, but gradually increases in size as it descends. It arises from the posterior surface of the shaft of the tibia, immediately below the oblique line, to within three inches of its extremity internal to the tibial origin of the Tibialis posticus; some fibres also arise from the fascia covering the Tibialis posticus. The fibres terminate in a tendon which runs nearly the whole length of the posterior surface of the muscle. This tendon passes behind the internal malleolus in a groove common to it and the Tibialis posticus, but separated from the latter by a fibrous septum, each tendon being contained in a special sheath lined by a separate synovial Fig. 332.-Muscles of the back of the leg. Deep layer. 528 THE MUSCLES AND FASCLE. membrane. It then passes obliquely forward and outward, crossing over the internal lateral ligament into the sole of the foot (Fig. 334), where, crossing superficially to the tendon of the Flexor longus hallucis,1 to which it is connected by a strong tendinous slip, it becomes expanded, is joined by the Flexor acces- sorius, and finally divides into four tendons which are inserted into the bases of the last phalanges of the four lesser toes, each tendon passing through a fissure in the tendon of the Flexor brevis digitorum opposite the base of the first phalanges. Relations.-In the leg : by its superficial surface, with the posterior tibial vessels and nerve, and the deep transverse fascia, which separates it from the Soleus muscle; by its deep surface, with the Tibia and Tibialis posticus. In the foot it is covered by the Abductor hallucis and Flexor brevis digitorum, and crosses superficial to the Flexor longus hallucis. The Tibialis posticus lies between the two preceding muscles, and is the most deeply seated of all the muscles in the leg. It commences above by two pointed processes, separated by an angular interval, through which the anterior tibial vessels pass forward to the front of the leg. It arises from the whole of the posterior surface of the interosseous membrane, excepting its lowest part, from the posterior surface of the shaft of the tibia, external to the Flexor longus digitorum, between the commencement of the oblique line above, and the middle of the external border of the bone below, and from the upper two-thirds of the internal surface of the fibula; some fibres also arise from the deep transverse fascia and from the intermuscular septa, separating it from the adjacent muscles on each side. This muscle, in the lower fourth of the leg, passes in front of the Flexor longus digitorum, and terminates in a tendon which passes through a groove behind the inner malleolus with the tendon of that muscle, but enclosed in a separate sheath ; it then passes through another sheath, over the internal lateral ligament into the foot, and then beneath the inferior calcaneo-navicular ligament, and is inserted into the tuberosity of the navicular and internal cuneiform bones. The tendon of this muscle contains a sesamoid fibro-cartilage as it passes over the navicular bone, and gives off fibrous expansions, one of which passes backward to the sustentaculum tali of the os calcis, others outward to the middle and external cuneiform and cuboid, and some forw ard to the bases of the second, third, and fourth metatarsal bones (Fig. 335). Relations.-By its superficial surface, with the Soleus, from which it is separated by the deep transverse fascia, the Flexor longus digitorum, the posterior tibial vessels and nerve, and the peroneal vessels; by its deep surface, with the interosseous ligament, the tibia, fibula, and ankle-joint. Nerves.-The Popliteus is supplied by the internal popliteal nerve, the remaining muscles of this group by the posterior tibial nerve. Actions.-The Popliteus assists in flexing the leg upon the thigh ; when the leg is flexed it will rotate the tibia inward. It is especially called into action at the commencement of the act of bending the knee, inasmuch as it produces a slight inward rotation of the tibia, which is essential in the early stage of this movement. The Tibialis posticus is a direct extensor of the tarsus upon the leg; acting in conjunction with the Tibialis anticus, it turns the sole of the foot inward, antagonizing the Peroneus- longus, which turns it outward. The Flexor longus digitorum and Flexor longus hallucis are the direct Flexors of the phalanges, and, continuing their action, extend the foot upon the leg; they assist the Gastro- cnemius and Soleus in extending the foot, as in the act of walking or in standing on tiptoe. In consequence of the oblique direction of the tendon of the long flexor the toes would be drawn inward were it not for the Flexor accessorius muscle, which is inserted into the outer side of its tendon and drawsit to the middle line of the foot during its action. Taking their fixed point from the foot, these muscles serve to maintain the upright posture by steadying the tibia and fibula perpendicularly 1 That is, in the order of dissection of the sole of the foot. THE OUTER OR FIBULAR REGION. 529 upon the ankle-joint. They also serve to raise these bones from the oblique position they assume in the stooping posture. Outer or Fibular Region. Peroneus longus. Peroneus brevis. Dissection.-The muscles are readily exposed by removing the fascia covering their surface, from below upward, in the line of direction of their fibres. The Peroneus longus is situated at the upper part of the outer side of the leg, and is the more superficial of the two muscles. It arises from the head and upper two-thirds of the outer surface of the shaft of the fibula, from the deep surface of the fascia, and from the intermuscular septa between it and the muscles on the front, and those on the back of the leg. It terminates in a long tendon which passes behind the outer malleolus, in a groove common to it and the Peroneus brevis, the groove being converted into a canal by a fibrous band, and the tendons invested by a common synovial membrane ; it is then reflected, obliquely forward, across the outer side of the os calcis, being contained in a separate fibrous sheath lined by a prolongation of the synovial membrane from that which lines the groove behind the malleolus. Having reached the outer side of the cuboid bone, it runs in a groove on the under surface of that bone, which is converted into a canal by the long calcaneo-cuboid ligament, and is lined by a synovial membrane: the tendon then crosses obliquely the sole of the foot, and is inserted into the outer side of the base of the metatarsal bone of the great toe and the internal cuneiform bone. Occasionally it sends a slip to the base of the second metatarsal bone. The tendon changes its direction at two points ; first, behind the external malleolus; secondly, on the outer side of the cuboid bone; in both of these situations the tendon is thickened, and in the latter a sesamoid fibro-cartilage, or sometimes a bone, is usually developed in its substance. Relations.-By its superficial surface, w'ith the fascia and integument; by its deep surface, with the fibula, the Peroneus brevis, os calcis, and cuboid bone; by its anterior border, with an intermuscular septum which intervenes between it and the Extensor longus digitorum ; by its posterior border, with an intermuscular septum which separates it from the Soleus above and the Flexor longus hallucis below. The Peroneus brevis lies beneath the Peroneus longus, and is shorter and smaller than it. It arises from the lower two-thirds of the external surface of the shaft of the fibula, internal to the Peroneus longus, and from the intermuscular septa separating it from the adjacent muscles on the front and back part of the leg. The fibres pass vertically downward, and terminate in a tendon which runs in front of that of the preceding muscle through the same groove, behind the external malleolus, being contained in the same fibrous sheath and lubricated by the same synovial membrane. It then passes through a separate sheath on the outer side of the os calcis, above that for the tendon of the Peroneus longus, and is finally inserted into the tuberosity at the base of the metatarsal bone of the little toe, on its outer side. Relations.-By its superficial surface, with the Peroneus longus and the fascia of the leg and foot; by its deep surface, with the fibula and outer side of the os calcis. Nerves.-The Peroneus longus and brevis are supplied by the musculo-cuta- neous branch of the external popliteal nerve. Actions.-The Peroneus longus and brevis extend the foot upon the leg in conjunction with the Tibialis posticus, antagonizing the Tibialis anticus and Peroneus tertius, which are flexors of the foot. The Peroneus longus also everts the sole of the foot; hence the extreme eversion occasionally observed in fracture of the lower end of the fibula, where that bone offers no resistance to the action of this muscle. Taking their fixed point below, the Peronei serve to steady the leg upon the foot. This is especially the case in standing upon one leg, when the 530 THE MUSCLES AND FASCIAE tendency of the superincumbent weight is to throw the leg inward: the Peroneus longus overcomes this tendency by draw ing on the outer side of the leg, and thus maintains the perpendicular direction of the limb. Surgical Anatomy.-The student should now consider the position of the tendons of the various muscles of the leg, their relation with the ankle-joint and surrounding blood-vessels, and especially their action upon the foot, as their rigidity and contraction give rise to one or other of the kinds of deformity known as club-foot. The most simple and common deformity, and one that is rarely, if ever, congenital, is the talipes equinus, the heel being raised by rigidity and con- traction of the Gastrocnemius muscle, and the patient walking upon the ball of the foot. Tn the talipes varus the foot is forcibly adducted and the inner side of the sole raised, sometimes to a right angle with the ground, by the action of the Tibialis anticus and posticus. In the talipes valgus the outer edge of the foot is raised by the Peronei muscles, and the patient walks on the inner ankle. In the talipes calcaneus the toes are raised by the extensor muscles, the heel is depressed, and the patient walks upon it. Other varieties of deformity are met with, as the talipes equino-varus, equino-valgus, and calcaneo-valgus, whose names sufficiently indicate their nature. Of these, the talipes equino-varus is the most common congenital form : the heel is raised by the tendo Achillis, the inner border of the foot drawn upward by the Tibialis anticus, the anterior two-thirds twisted inward by the Tibialis posticus, and the arch increased by the contraction of the plantar fascia, so that the patient walks on the middle of the outer border of the foot. Each of these deformities may be successfully relieved (after other remedies fail) by division of the opposing tendons and fascia : by this means the foot regains its proper position, and the tendons heal by the organization of lymph thrown out between the divided ends. The operation is easily performed by putting the contracted tendon upon the stretch, and dividing it by means of a narrow, sharp-pointed knife inserted beneath it. Rupture of a few of the fibres of the Gastrocnemius or rupture of the Plantaris tendon not uncommonly occurs, especially in men somewhat advanced in life, from some sudden exertion, and frequently occurs during the game of lawn tennis, and is hence known as "lawn-tennis leg." The accident is accompanied by a sudden pain, and produces a sensation as if the individual had been struck a violent blow on the part. The tendo Achillis is also sometimes ruptured. It is stated that John Hunter ruptured his tendo Achillis whilst dancing at the age of forty. THE FOOT. The fibrous bands which bind down the tendons in front of and behind the ankle in their passage to the foot should now be examined ; they are termed the annular ligaments, and are three in number-anterior, internal, and external. The Anterior Annular Ligament consists of a superior or vertical portion, which binds down the extensor tendons as they descend on the front of the tibia and fibula, and an inferior or horizontal portion, which retains them in connection with the tarsus, the two portions being connected by a thin intervening layer of fascia. The vertical portion is attached externally to the lower end of the fibula, internally to the tibia, and above is continuous with the fascia of the leg; it con- tains only one synovial sheath, for the tendon of the Tibialis anticus, the other tendons and the anterior tibial vessels and nerve passing beneath it, but without any distinct synovial sheath. The horizontal portion is attached externally to the upper surface of the os calcis, in front of the depression for the interosseous ligament; it passes upward and inward as a double layer, one lamina passing in front, and the other behind, the Peroneus tertius and Extensor longus digitorum. At the inner border of the latter tendon these two layers join together, forming a sort of loop or sheath in which the tendons are enclosed, surrounded by a synovial membrane. From the inner extremity of this loop two bands are given off: one passes upward and inward to be attached to the internal malleolus, passing over the Extensor proprius hallucis and vessels and nerves, but enclosing the Tibialis anticus and its synovial sheath by a splitting of its fibres. The other limb passes downward and inward to be attached to the navicular and internal cuneiform bones, and passes over both the tendon of the Extensor proprius hallucis and the Tibialis anticus, and also the vessels and nerves. These two tendons are contained in separate synovial sheaths situated beneath the ligament. It will thus be seen that the horizontal portion of the ligament is like the letter Y. the foot of the letter being attached to the os calcis, and the two diverging arms to the tibia and navic- ular and internal cuneiform respectively. The Internal Annular Ligament is a strong fibrous band which extends from the inner malleolus above to the internal margin of the os calcis below, converting OF THE FOOT. 531 a series of grooves in this situation into canals for the passage of the tendons of the Flexor muscles and vessels into the sole of the foot. It is continuous by its upper border with the deep fascia of the leg, and by its lower border with the plantar fascia and the fibres of origin of the Abductor hallucis muscle. The three canals which it forms transmit, from within outward, first, the tendon of the Tibi- alis posticus; second, the tendon of the Flexor longus digitorum ; then the pos- terior tibial vessels and nerve, which run through a broad space beneath the liga- ment ; lastly, in a canal formed partly by the astragalus, the tendon of the Flexor longus hallucis. Each of these canals is lined by a separate synovial membrane. The External Annular Ligament extends from the extremity of the outer mal- leolus to the outer surface of the os calcis : it binds down the tendons of the Pero- nei muscles in their passage beneath the outer ankle. The two tendons are enclosed in one synovial sac. Dissection of the Sole of the Foot.-The foot should be placed on a high block with the sole uppermost, and firmly secured in that position. Carry an incision round the heel and along the inner and outer borders of the foot to the great and little toes. This incision should divide the integument and thick layer of granular fat beneath until the fascia is visible ; the skin and fat should then be removed from the fascia in a direction from behind forward, as seen in Fig. 328. The Plantar Fascia, the densest of all the fibrous membranes, is of great strength, and consists of dense pearly-white glistening fibres, disposed, for the most part, longitudinally: it is divided into a central and two lateral portions. The central portion, the thickest, is narrow behind and attached to the inner tubercle of the os calcis, behind the origin of the Flexor brevis digitorum, and, becoming broader and thinner in front, divides near the heads of the metatarsal bones into five processes, one for each of the toes. Each of these processes divides opposite the metatarso-phalangeal articulation into two strata, superficial and deep. The superficial stratum is inserted into the skin of the transverse sulcus which divides the toes from the sole. The deeper stratum divides into two slips which embrace the sides of the flexor tendons of the toes, and blend with the sheaths of the tendons, and laterally with the transverse metatarsal ligament, thus forming a series of arches through which the tendons of the short and long flexors pass to the toes. The intervals left between the five processes allow the digital vessels and nerves and the tendons of the Lumbricales muscles to become superficial. At the point of division of the fascia into processes and slips numerous transverse fibres are superadded, which serve to increase the strength of the fascia at this part by binding the processes together and connecting them with the integument. The central portion of the plantar fascia is continuous with the lateral portions at each side, and sends upward into the foot, at their point of junction, twostrong vertical intermuscular septa, broader in front than behind, which separate the middle from the external and internal plantar group of muscles ; from these, again, thinner transverse septa are derived, which separate the various layers of muscles in this region. The upper surface of this fascia gives attachment behind to the Flexor brevis digitorum muscle. The lateral portions of the plantar fascia are thinner than the central piece, and cover the sides of the foot. The outer portion covers the under surface of the Adductor minimi digiti; it is thick behind, thin in front, and extends from the os calcis, forward, to the base of the fifth metatarsal bone, into the outer side of which it is attached ; it is con- tinuous internally with the middle portion of the plantar fascia, and externally with the dorsal fascia. The inner portion is very thin, and covers the Abductor hallucis muscle ; it is attached behind to the internal annular ligament, and is continuous around the side of the foot with the dorsal fascia, and externally with the middle portion of the plantar fascia. The Muscles of the Foot are found in two regions: 1. On the dorsum ; 2. On the plantar surface. 532 THE MUSCLES AND FASCIAE Extensor brevis digitorum. 1. Dorsal Region. The Fascia on the dorsum of the foot is a thin membranous layer continuous above with the anterior margin of the annular ligament; it becomes gradually lost opposite the heads of the metatarsal bones, and on each side blends with the lateral portions of the plantar fascia; it forms a sheath for the tendons placed on the dorsum of the foot. On the removal of this fascia the muscles and tendons of the dorsal region of the foot are exposed. The Extensor brevis digitorum (Fig. 330) is a broad thin muscle which arises from the fore part of the upper and outer surfaces of the os calcis, in front of the groove for the Peroneus brevis, from the external calcaneo-astragaloid ligament, and from the horizontal portion of the anterior annular ligament. It passes obliquely across the dorsum of the foot, and terminates in four tendons. The innermost, which is the largest, is inserted into the dorsal surface of the base of the first phalanx of the great toe, crossing the Dorsalis pedis artery ; the other three, into the outer sides of the long extensor tendons of the second, third, and fourth toes. Relations.-By its superficial surface, with the fascia of the foot, the tendons of the Extensor longus digitorum and Extensor proprius hallucis ; by its deep surface, with the tarsal and metatarsal bones and the Dorsal interossei muscles. Nerves.-It is supplied by the anterior tibial nerve. Actions.-The Extensor brevis digitorum is an accessory to the long Extensor, extending the phalanges of the four inner toes, but acting only on the first phalanx of the great toe. The obliquity of its direction counteracts the oblique movement given to the toes by the long Extensor, so that, both muscles acting together, the toes are evenly extended. 2. Plantar Region. The muscles in the plantar region of the foot may be divided into three groups, in a similar manner to those in the hand. Those of the internal plantar region are connected with the great toe, and correspond with those of the thumb ; those of the external plantar region are connected with the little toe, and correspond with those of the little finger ; and those of the middle plantar region are con- nected with the tendons intervening between the two former groups. But in order to facilitate the dissection of these muscles it will be found more convenient to divide them into four layers, as they present themselves, in the order in which they are successively exposed. First Layer. Abductor hallucis. Abductor minimi digiti. Flexor brevis digitorum. Dissection.-Remove the fascia on the inner and outer sides of the foot, commencing in front over the tendons and proceeding backward. The central portion should be divided trans- versely in the middle of the foot, and the two flaps dissected forward and backward. The Abductor hallucis lies along the inner border of the foot. It arises from the inner tubercle on the under surface of the os calcis; from the internal annular ligament; from the plantar fascia; and from the intermuscular septum between it and the Flexor brevis digitorum. The fibres terminate in a tendon which is inserted, together with the innermost tendon of the Flexor brevis hallucis, into the inner side of the base of the first phalanx of the great toe. Relations.-By its superficial surface, with the plantar fascia; by its deep sur- face, with the Flexor brevis hallucis, the Flexor accessorius, and the tendons of the Flexor longus digitorum and Flexor longus hallucis, the Tibialis anticus and posticus, the plantar vessels and nerves, and the articulations of the tarsus. The Flexor brevis digitorum (perforatus) lies in the middle of the sole of the foot, immediately beneath1 the plantar fascia, with which it is firmly united. It 1 That is. in order of dissection of the sole of the foot. OF THE FOOT. 533 arises by a narrow tendinous process, from the inner tubercle of the os calcis, from the central part of the plantar fascia, and from the intermuscular septa between it and the adjacent muscles. It passes forward, and divides into four tendons. Opposite the bases of the first phalanges each tendon divides into two slips, to allow of the passage of the corresponding tendon of the Flexor longus digitorum ; the two portions of the tendon then unite and form a grooved channel for the reception of the accompanying long flexor tendon. Finally, they divide a second time, to be inserted into the sides of the second phalanges about their middle. The mode of division of the tendons of the Flexor brevis digitorum and their insertion into the phalanges is analogous to the Flexor sublimis in the hand. Relations.-By its superficial surface, with the plantar fascia; by its deep surface, with the Flexor accessorius, the Lumbricales, the tendons of the Flexor longus digitorum, and the external plantar vessels and nerve, from which it is separated by a thin layer of fascia. The outer and inner borders are separated from the adjacent muscles by means of vertical pro- longations of the plantar fascia. Fibrous Sheaths of the Flexor Tendons.- These are not so well marked as in the fingers. The flexor tendons of the toes as they run along the phalanges are retained against the bones by a fibrous sheath, forming osseo-apo- neurotic canals. These sheaths are formed by strong fibrous bands which arch across the tendons and are attached on each side to the margins of the phalanges. Opposite the middle of the proximal and second phalanges the sheath is very strong, and the fibres pass transversely, but opposite the joints it is much thinner, and the fibres pass obliquely. Each sheath is lined by a synovial membrane which is reflected on the contained tendon. The Abductor minimi digiti lies along the outer border of the foot. It arises, by a very broad origin, from the outer tuber- cle of the os calcis, from the under surface of the os calcis in front of both tuber- cles, from the fore part of the inner tubercle, from the plantar fascia and the intermuscular septum between it and the Flexor brevis digitorum. Its tendon, after gliding over a smooth facet on the under surface of the base of the fifth metatarsal bone, is inserted with the short Flexor of the little toe into the outer side of the base of the first phalanx of the little toe. Relations.-By its superficial surface, with the plantar fascia; by its deep sur- face, with the Flexor accessorius, the Flexor brevis minimi digiti, the long plantar ligament, and the tendon of the Peroneus longus. On its inner side are the external plantar vessels and nerve, and it is separated from the Flexor brevis digitorum by a vertical septum of fascia. Dissection.-The muscles of the superficial layer should be divided at their origin by insert- ing the knife beneath each, and cutting obliquely backward, so as to detach them from the bone; they should then be drawn forward, in order to expose the second layer, but not cut Fig. 333.-Muscles of the sole of the foot. First Layer. 534 7777? MUSCLES AND FASCIAE. away at their insertion. The two layers are separated by a thin membrane, the deep plantar fascia, on the removal of which is seen the tendon of the Flexor longus digitorum, the Flexor accessorius, the tendon of the Flexor longus hallu- cis, and the Lumbricales. The long flexor tendons cross each other at an acute angle, the Flexor longus hallucis running along the inner side of the foot, on a plane superior to that of the Flexor longus digitorum, the direction of which is ob- liquely outward. Second Layer. Flexor accessorius. Lumbricales. The Flexor accessorius arises by two heads; the inner or larger, which is mus- cular, being attached to the inner concave surface of the os calcis, and to the inferior calcaneo-navicular ligament; the outer head, flat and tendinous, to the under surface of the os calcis, in front of its outer tubercle, and to the long plantar ligament; the two portions join at an acute angle, and are inserted into the outer margin and upper and under surfaces of the tendon of the Flexor longus digitorum, forming a kind of groove in which the tendon is lodged.1 Relations.-By its superficial surface, with the muscles of the superficial layer, from which it is separated by the external plantar vessels and nerves ; by its deep sur- face, with the os calcis and long calcaneo- cuboid ligament. The Lumbricales are four small muscles accessory to the tendons of the Flexor longus digitorum: they arise from the tendons of the long Flexor, as far back as their angle of division, each arising from two tendons, except the internal one. Each muscle terminates in a tendon, which passes forward on the inner side of each of the lesser toes, and is inserted into the expansion of the long Extensor and base of the first phalanx of the cor- responding toe. Dissection.-The flexor tendons should be divided at the back part of the foot, and the Flexor accessorius at its origin, and drawn forward, in order to expose the third layer. Fig. 334.-Muscles of the sole of the foot. Second layer. Flexor brevis hallucis. Adductor obliquus hallucis. Flexor brevis minimi digiti. Adductor transversus hallucis. Third Layer. The Flexor brevis hallucis arises, by a pointed tendinous process, from the inner border of the cuboid bone, from the contiguous portion of the external cuneiform, and from the prolongation of the tendon of the Tibialis posticus, which 1 According to Turner, the fibres of the Flexor accessorius end in aponeurotic bands, which con- tribute slips to the second, third, and fourth digits. OF THE FOOT. 535 is attached to that bone. The muscle divides, in front, into two portions, which are inserted into the inner and outer sides of the base of the first phalanx of the great toe, a sesamoid bone being developed in each tendon at its insertion. The inner portion of this muscle is blended with the Abductor hallucis pre- vious to its insertion, the outer with the Adductor obliquus hallucis, and the ten- don of the Flexor longus hallucis lies in a groove between them. Relations.-By its superficial surface, with the Abductor hallucis, the tendon of the Flexor longus hallucis, and plantar fas- cia ; by its deep surface, with the tendon of the Peroneus longus and metatarsal bone of the great toe; by its inner bor- der, with the Abductor hallucis; by its outer border, with the Adductor obliquus hallucis. The Adductor obliquus hallucis is a large, thick, fleshy mass passing obliquely across the foot and occupying the hollow space between the four inner metatarsal bones. It arises from the tarsal extrem- ities of the second, third and fourth met- atarsal bones, and from the sheath of the tendon of the Peroneus longus, and is inserted, together with the outer portion of the Flexor brevis hallucis, into the outer side of the base of the first phalanx of the great toe. The small muscles of the great toe, the Abductor, Flexor brevis, Adductor obliquus, and Adductor transversus, like the similar muscles of the thumb, give off fibrous expansions, at their inser- tions, to blend with the long Extensor tendon. The Flexor brevis minimi digiti lies on the metatarsal bone of the little toe, and much resembles one of the Interossei. It arises from the base of the metatarsal bone of the little toe, and from the sheath of the Peroneus longus; its tendon is inserted into the base of the first phalanx of the little toe on its outer side. Relations.-By its superficial surface, with the plantar fascia and tendon of the Abductor minimi digiti; by its deep surface, with the fifth metatarsal bone. The Adductor transversus hallucis (Transversus pedis} is a narrow, flat, muscular fasciculus, stretched transversely across the heads of the metatarsal bones, between them and the flexor tendons. It arises from the inferior metatarso-phalangeal ligaments of the three outer toes, sometimes only from the third and fourth and from the transverse ligament of the metatarsus ; and is inserted into the outer side of the first phalanx of the great toe, its fibres being blended with the tendon of insertion of the Adductor obliquus hallucis. Relations.-By its superficial surface, with the tendons of the long and short Flexors and Lumbricales; by its deep surface, with the Interossei. Fig. 335.-Muscles of the sole of the foot. Third layer. 536 THE MUSCLES AND FASCIAE. Fourth Layer. The Interossei The Interossei muscles in the foot are similar to those in the hand, with this exception, that they are grouped around the middle line of the second toe, instead of the middle line of the third finger, as in the hand. They are seven in number, and consist of two groups, dorsal and plantar. The Dorsal interossei, four in number, are situated between the metatarsal bones. They are bipenniform muscles, arising by two heads from the adjacent sides of the metatarsal bones, between which they are placed ; their tendons are inserted into the bases of the first phalanges, and into the aponeurosis of the common extensor tendon. In the angular interval left between the heads of Fig. 336.-The Dorsal interossei. Left foot. Fig. 337.-The Plantar interossei. Left foot. each muscle at its posterior extremity the perforating arteries pass to the dorsum of the foot, except in the First interosseous muscle, where the interval allows the passage of the communicating branch of the dorsalis pedis artery. The First dorsal interosseous muscle is inserted into the inner side of the second toe; the other three are inserted into the outer sides of the second, third, and fourth toes. The Plantar interossei, three in number, lie beneath, rather than between, the metatarsal bones. They are single muscles, and are each connected with but one metatarsal bone. They arise from the base and inner sides of the shaft of the third, fourth, and fifth metatarsal bones, and are inserted into the inner sides of the bases of the first phalanges of the same toes, and into the aponeurosis of the common extensor tendon. Nerves.-The Flexor brevis digitorum, the Flexor brevis and Abductor hallucis, and the two inner Lumbricales are supplied by the internal plantar nerve; all the other muscles in the sole of the foot by the external plantar. The First and Second dorsal interossei muscles receive extra filaments from the gan- glionic enlargement of the anterior tibial nerve on the dorsum of the foot. Actions.-All the muscles of the foot act upon the toes, and for purposes of description as regards their action may be grouped as Abductors, Adductors, SURFACE FORM OF THE LOWER EXTREMITY. 537 Flexors, or Extensors. The Abductors are the Dorsal interossei, the Abductor hallucis, and the Abductor minimi digiti. The Dorsal interossei are abductors from an imaginary line passing through the axis of the second toe, so that the first muscle draws the second toe inward, toward the great toe; the second muscle draws the same toe, outward; the third draws the third toe, and the fourth draws the fourth toe, in the same direction. Like the interossei in the hand, they also assist in flexing the proximal phalanx and extending the two terminal phalanges. The Abductor hallucis abducts the great toe from the others, and also flexes the proximal phalanx of this toe. And in the same way the action of the Abductor minimi digiti is twofold-as an abductor of this toe from the others, and also as a flexor of the proximal phalanx. The Adductors are the Plantar interossei, the Adductor obliquus hallucis, and the Adductor transversus hallucis. The plantar interosseous muscles adduct the third, fourth, and fifth toes toward the imaginary line passing through the second toe, and by means of their insertion into the aponeurosis of the extensor tendon they assist in flexing the prox- imal phalanx and extending the two terminal phalanges. The Adductor obliquus hallucis is chiefly concerned in adducting the great toe toward the second one, but also assists in flexing this toe. The Adductor transversus hallucis approximates all the toes, and thus increases the curve of the transverse arch of the metatarsus. The Flexors are the Flexor brevis digitorum, the Flexor accessorius, the Flexor brevis hallucis, the Flexor brevis minimi digiti, and the Lumbricales. The Flexor brevis digitorum flexes the second phalanges upon the first, and, continuing its action, flexes the first phalanges also and brings the toes together. The Flexor accessorius assists the Long flexor of the toes, and converts the oblique pull of the tendons of that muscle into a direct backward pull upon the toes. The Flexor brevis minimi digiti flexes the little toe and draws its metatarsal bone downward and inward. The Lumbricales, like the corresponding muscles in the hand, assist in flexing the proximal phalanx, and by their insertion into the long Extensor tendon aid that muscle in straightening the two terminal phalanges. The only muscle in the Extensor group is the Extensor brevis digitorum. It extends the first phalanx of the great toe, and assists the long Extensor in extending the next three toes, and at the same time gives to the toes an outward direction when they are extended. Surface Form.-Of the muscles of the thigh, those of the iliac region have no influence on surface form, while those of the anterior femoral region, being to a great extent superficial, largely contribute to the surface form of this part of the body. The Tensor vaginae femoris produces a broad elevation immediately below the anterior portion of the crest of the ilium and behind the anterior superior spinous process. From its lower border a longitudinal groove, corresponding to the ilio-tibial band, may be seen running down the outer side of the thigh to the outer side of the knee-joint. The Sartorius muscle, when it is brought into action by flexing the leg on the thigh and the thigh on the pelvis, and rotating the thigh outward, presents a well-marked surface form. At its upper part, where it constitutes the outer boundary of Scarpa's triangle, it forms a prominent oblique ridge, which becomes changed into a flattened plane below, and this gradually merges in a general fulness on the inner side of the knee-joint. When the Sartorius is not in action, a depression exists between the Extensor quadriceps and the Adductor muscles, running obliquely downward and inward from the apex of Scarpa's triangle to the inner side of the knee, which corresponds to this muscle. In the depressed angle formed by the divergence of the Sartorius and Tensor vaginae femoris muscles, just below the anterior superior spinous process of the ilium, the Rectus femoris muscle appears, and, below this, determines to a great extent the convex form of the front of the thigh. Tn a well-developed subject the borders of the muscle, when in action, are clearly to be defined. The Dtttus externus forms a long flattened plane on the outer side of the thigh, traversed by the longitudinal groove formed by the ilio-tibial band. The Vastus interims, on the inner side of the lower half of the thigh, gives rise to a considerable prominence, which increases toward the knee and terminates somewhat abruptly in this situation with a full, curved outline. The Crureus and Subcrureus are completely hidden, and do not directly influence surface form. The Adductor muscles, constituting the internal femoral group, are not to be individually distin- guished from each other, with the exception of the upper tendon of the Adductor longus and the lower tendon of the Adductor magnus. The upper tendon of the Adductor longus, when the muscle is in action, stands out as a prominent ridge, which runs obliquely downward and outward from the neighborhood of the pubic spine, and forms the inner boundary of a flattened triangular space on the upper part of the front of the thigh, known as Scarpa's triangle. The 538 TFIE MUSCLES AND FASCLE. lower tendon of the Adductor magnus can be distinctly felt as a short ridge extending down to the Adductor tubercle on the internal condyle, between the Sartorius and Vastus internus. The Adductor group of muscles fills in the triangular space at the upper part of the thigh, formed between the oblique femur and the pelvic 'wall, and to them is due the contour of the inner border of the thigh, the Gracilis largely contributing to the smoothness of the outline. These muscles are not marked off on the surface from those of the posterior femoral region by any intermuscular marking; but on the outer side of the thigh these latter muscles are defineil from the Vastus externus by a distinct marking, corresponding to the external intermuscular septum. The Gluteus maximus and a part of the Gluteus medius are the only muscles of the buttock which influence surface form. The other part of the Gluteus medius, the Gluteus minimus, and the External rotators are completely hidden. The Gluteus maximus forms the full rounded outline of the buttock: it is more prominent behind, compressed in front, and terminates at its tendinous insertion in a depression immediately behind the great trochanter. Its lower border does not correspond to the gluteal fold, but is much more oblique, being marked by a line drawn from the side of the coccyx to the lower part of the great trochanter. From beneath the fold of the buttock the hamstring muscles appear, at first narrow and not well marked, but as they descend becoming more prominent and widened out. and eventually divid- ing into two well-marked ridges, which form the upper boundaries of the popliteal space, being formed by the tendons of the inner and outer hamstring muscles respectively. In the upper part of the thigh these muscles are not to be individually distinguished from each other, but lower down, the separation between the Semitendinosus and Semimembranosus is denoted by a slight intermuscular marking. The external hamstring tendon formed by the Biceps is seen as a thick cord running down to the head of the fibula. The inner hamstring tendons comprise the Semitendinosus, the Semimembranosus, and the Gracilis. The Semitendinosus is the most internal of these, and can be felt, in certain positions of the limb, as a sharp cord ; the Semimembranosus is thick, and the Gracilis is situated a little farther forward than the other two. All the muscles on the front of the leg appear to a certain extent somewhere on the surface, but the form of this region is mainly dependent upon the Tibialis anticus and the Extensor longus digitorum. The Tibialis anticus is well marked, and presents a fusiform enlargement at the outer side of the tibia, and projects beyond the crest of the shin-bone. From the muscular mass its tendon may be traced downward, standing out boldly, when the muscle is in action, on the front of the tibia and ankle-joint, and coursing down to its insertion along the inner border of the foot. A well-marked groove separates this muscle externally from the Extensor longus digitorum, which fills up the rest of the space between the upper part of the shaft of the tibia and fibula. It does not present so bold an outline as the Tibialis anticus, and its tendon below, diverging from the tendon of the Tibialis anticus, forms a sort of plane, in which may be seen the tendon of the Extensor proprius hallucis. A groove on the outer side of the Extensor longus digitorum, seen most plainly when the muscle is in action, separates from it a slight eminence corresponding to the Peroneus tertius. The fleshy fibres of the Peroneus longus are strongly marked at the upper part of the outer side of the leg, especi- ally when the muscle is in action. It forms a bold swelling, separated by furrows from the Extensor longus digitorum in front and the Soleus behind. Below, the fleshy fibres terminate abruptly in a tendon which overlaps the more flattened form of the Peroneus brevis. At the external malleolus the tendon of the Peroneus brevis is more marked than that of the Peroneus longus. On the dorsum of the foot the tendons of the Extensor muscles, emerging from beneath the anterior annular ligament, spread out and can be distinguished in the following order: The most internal and largest is the Tibialis anticus, then the Extensor proprius hallucis: next comes the Extensor longus digitorum, dividing into four tendons to the four outer toes; and lastly, most externally, is the Peroneus tertius. The flattened form of the dorsum of the foot is relieved by the rounded outline of the fleshy belly of the Extensor brevis digitorum, which forms a soft fulness on the outer side of the tarsus in front of the external malleolus, and by the Dorsal interossei, which bulge between the metatarsal bones. At the back of the knee is the popliteal space, bounded above by the tendons of the hamstring muscle; below, by the two heads of the Gastrocnemius. Below this space is the prominent fleshy mass of the calf of the leg, produced by the Gastrocnemius and Soleus. When these muscles are in action, as in standing on tiptoe, the borders of the Gastrocnemius are well defined, presenting two curved lines, which converge to the tendon of insertion. Of these borders, the inner is more prominent than the outer. The fleshy mass of the calf terminates somewhat abruptly below in the tendo Achillis, which stands out prominently on the lower part of the back of the leg. It presents a somewhat tapering form in the upper three-fourths of its extent, but widens out slightly below. V hen the muscles of the calf are in action, the lateral portions of the Soleus may be seen, forming curved eminences, of which the outer is the longer, on either side of the Gastrocnemius. Behind the inner border of the lower part of the shaft of the tibia a well-marked ridge, pro- duced by the tendon of the Tibialis posticus, is visible when this muscle is in a state of con- traction. On the sole of the foot the superficial layer of muscles influences surface form; the Abductor minimi digit! most markedly. This muscle forms a narrow rounded elevation along the outer border of the foot, while the Abductor hallucis does the same, though to a less ex- tent, on the inner side. The Flexor brevis digitorum, bound down by the plantar fascia, is not very apparent ; it produces a flattened form, covered by the thickened skin of the sole, which is here thrown into numerous wrinkles. SURGICAL ANATOMY OF THE LOWER EXTREMITY. 539 SURGICAL ANATOMY OF THE LOWER EXTREMITY. The student should now consider the effects produced by the action of the various muscles in fractures of the bones of the lower extremity. The more common forms of fractures are selected for illustration and description. In fracture of the neck of the femur internal to the capsular ligament (Fig. 338) the characteristic marks are slight shortening of the limb and eversion of the foot, neither of which symp- toms occurs, however, in some cases until some time after the injury. The eversion is caused by the weight of the limb rotating it outward. The shorten- ing is produced by the action of the Glutei, and by the Rectus femoris in front and the Biceps, Semitendinosus, and Semi- membranosus behind. In fracture of the femur just below the trochan- ters (Fig. 339) the upper fragment, the portion chiefly displaced, is tilted forward PYRIFORMIS. -GEMELLUS SUPERIOR OBTURATOR INTERNUS GEMELLUS INFERIOR. OBTURATOR EXTERNUS QUADRATUS FEMORIS. Fig. 338.-Fracture of the neck of the femur within the capsular ligament. almost at right angles with the pelvis by the combined action of the Psoas and Iliacus, and, at the same time, everted and drawn outward by the External rotator and Glutei muscles, causing a marked prominence at the upper and outer side of the thigh, and much pain from the bruising and laceration of the muscles. The limb is shortened, in consequence of the lower fragment being drawn upward by the rectus in front, and the Biceps, Semi- membranosus, and Semitendinosus behind, and, at the same time, everted, and the upper end thrown outward and the lower inward by the Pectineus and Adductor muscles. This fracture may be reduced in two different methods: either by direct relax- ation of all the opposing muscles, to effect which the limb should be placed on a double inclined plane; or by overcoming the con- traction of the muscles by continued extension, which may be effected bj7 means of the long splint. Oblique fracture of the femur immediately above the condyles (Fig. 340) is a formidable injury, and attended with considerable displacement. On examination of the limb the lower fragment may be felt deep in the popliteal space, being drawn backward by the Gastrocnemius and Plantaris muscles, and upward by the posterior Femoral and Rectus muscles. The pointed end of the upper fragment is drawn inward by the Pectineus and Ad- ductor muscles, and tilted forward by the Psoas and Iliacus, pierc- ing the Rectus muscle and occasionally the integument. Relaxation of these muscles and direct approximation of the broken frag- ments are effected by placing the limb on a double inclined plane. The greatest care is requisite in keeping the pointed extremity of the upper fragment in proper position ; otherwise, after union of the fracture, the power of extension of the limb is partially destroyed, from the Rectus muscle being held down by the frac- tured end of the bone, and from the patella, when elevated, being drawn upward against the projecting fragment. In fracture of the patella (Fig. 341) the fragments are sepa- rated by the effusion which takes place into the joint, and possibly by the action of the Quadriceps extensor; the extent of separation of the two SEMI- MEMBRANOSUS SEMI- TENDINOSUS. Fig. 339.-Fracture of the femur below the trochanters. 540 THE MUSCLES AND FASCIFE. fragments depending upon the degree of laceration of the ligamentous structures around the bone. In oblique fracture of the shaft, of the tibia (Fig. 342), if the fracture has taken place obliquely from above, downward and forward, the fragments ride over one another, the lower fragments being drawn backward and upward by the powerful action of the muscles of the calf; the pointed extremity of the upper fragment projects forward immediately be- neath the integument, often protruding through it and rendering the fracture a compound one. If the direction of the fracture is the reverse of that shown in the figure, the pointed extremity of the lower fragment projects forward, riding upon the lower end of the upper one. By bending the knee, which relaxes the opposing muscles, and making extension from the ankle and counter-extension at the knee, the fragments may be brought into apposition. It is often necessary, however, in compound fracture, to remove a portion of the projecting bone with the saw before complete adaptation can be effected. Fracture of the fibula with dislocation of the foot outward (Fig. 343), commonly known as "Pott's Fracture," is one of the most frequent injuries of the ankle-joint. The end of the tibia is displaced from the corresponding surface of the astragalus; the internal lateral ligament is ruptured; and the inner malleolus projects inward beneath the integument, which is tightly stretched over it and in danger of bursting. The fibula is broken, usually from two to three inches above the ankle, and occasionally that portion of the tibia with which it is more directly connected below; the foot is everted by the action of the Peroneus longus, its inner border resting upon the ground, and at the same time the heel is drawn up by the muscles of the calf. This injury may be at once reduced by flexing the leg at right angles with the thigh, which relaxes all the opposing muscles, and by making extension from the ankle and counter-extension at the knee. Fig. 340.-Fracture of the femur above the condyles. Fig. 341. -Fracture of the patella. Fig. 342.-Oblique fracture of the shaft of the tibia. Fig. 343.-Fracture of the fibula with dislocation of the foot outward-" Pott's Fracture." THE ARTERIES. THE Arteries are cylindrical tubular vessels which serve to convey blood from both ventricles of the heart to every part of the body. These vessels were named arteries air; rqpetv, to contain) from the belief entertained by the ancients that they contained air. To Galen is due the honor of refuting this opinion ; he showed that these vessels, though for the most part empty after death, contain blood in the living body. The pulmonary artery, which arises from the right ventricle of the heart, carries venous blood directly into the lungs, whence it is returned by the pul- monary veins into the left auricle. This constitutes the lesser or pulmonic circu- lation. The great artery which arises from the left ventricle, the aorta, conveys arterial blood to the body generally, whence it is brought back to the right side of the heart by means of the veins. This constitutes the greater or systemic circulation. The distribution of the systemic arteries is like a highly ramified tree, the common trunk of which, formed by the aorta, commences at the left ventricle of the heart, the smallest ramifications corresponding to the circumference of the body and the contained organs. The arteries are found in nearly every part of the body, with the exception of the hairs, nails, epidermis, cartilages, and cornea ; and the larger trunks usually occupy the most protected situa- tions, running, in the limbs, along the flexor side, where they are less exposed to injury. There is considerable variation in the mode of division of the arteries : occa- sionally a short trunk subdivides into several branches at the same point, as we observe in the coeliac and thyroid axes ; or the vessel may give off several branches in succession, and still continue as the main trunk, as is seen in the arteries of the limbs; but the usual division is dichotomous; as, for instance, the aorta dividing into the two common iliacs, and the common carotid into the external and internal. The branches of arteries arise at very variable angles: some, as the superior intercostal arteries from the aorta, arise at an obtuse angle: others, as the lumbar arteries, at a right angle; or, as the spermatic, at an acute angle. An artery from which a branch is given off is smaller in size, but retains a uniform diameter until a second branch is derived from it. A branch of an artery is smaller than the trunk from which it arises; but if an artery divides into two branches, the com- bined area of the two vessels is, in nearly every instance, somewhat greater than that of the trunk ; and the combined area of all the arterial branches greatly exceeds the area of the aorta; so that the arteries collectively may be regarded as a cone, the apex of which corresponds to the aorta, the base to the capillary system. The arteries, in their distribution, communicate freely with one another, form- ing what is called an anastomosis (dvd, between; aropa, mouth), or inosculation ; and this communication is very free between the large as well as between the smaller branches. The anastomosis between trunks of equal size is found where great freedom and activity of the circulation are requisite, as in the brain; here the two vertebral arteries unite to form the basilar, and the two internal carotid arteries are connected by a short communicating trunk; it is also found in the abdomen, the intestinal arteries having very free anastomoses between their larger 541 542 THE ARTERIES. branches. In the limbs the anastomoses are most frequent and of largest size around the joints, the branches of an artery above freely inosculating with branches from the vessels below; these anastomoses are of considerable interest to the surgeon, as it is by their enlargement that a collateral circulation is established after the application of a ligature to an artery for the cure of aneurism. The smaller branches of arteries anastomose more frequently than the larger, and between the smallest twigs these inosculations become so numerous as to constitute a close network that pervades nearly every tissue of the body. Throughout the body generally the larger arterial branches pursue a perfectly straight course, but in certain situations they are tortuous; thus, the facial artery in its course over the face, and the arteries of the lips, are extremely tortuous in their course, to accommodate themselves to the movements of the parts. The uterine arteries are also tortuous, to accommodate themselves to the increase of size which the organ undergoes during pregnancy. Again, the internal carotid and vertebral arteries, previous to their entering the cavity of the skull, describe a series of curves, which are evidently intended to diminish the velocity of the current of blood by increasing the extent of surface over which it moves and adding to the amount of impediment which is produced by friction. The arteries are dense in structure, of considerable strength, highly elastic, and, wThen divided, they preserve, although empty, their cylindrical form. The minute structure of these vessels has been described in the chapter on General Anatomy. In the description of the arteries we shall first consider the efferent trunk of the pulmonic circulation, the pulmonary artery, and then the efferent trunk of the systemic circulation, the aorta and its branches. THE PULMONARY ARTERY (Fig. 344). The pulmonary artery conveys the venous blood from the right side of the heart to the lungs. It is a short, wide vessel, about two inches in length, arising from the left side of the base of the right ventricle, in front of the aorta. It passes obliquely upward and backward, passing at first in front of, and then to the left of, the ascending part of the arch of the aorta as far as the under surface of the transverse portion of the arch, where it divides into two branches of nearly equal size-the right and left pulmonary arteries. Relations.-The whole of this vessel is contained, together with the ascending part of the arch of the aorta, in the pericardium, being enclosed with it in a tube of serous membrane, continued upward from the base of the heart, and has attached to it, above, the fibrous layer of the membrane. Behind, it rests at first upon the ascending aorta, and higher up lies in front of the left auricle. On each side of its origin is the appendix of the corresponding auricle and a coronary artery; and higher up it passes to the left side of the ascending aorta. The right pulmonary artery, longer and larger than the left, pierces the peri- cardium and runs horizontally outward, behind the ascending aorta and superior vena cava, to the root of the right lung, where it divides into two branches, of which the lower, which is the smaller, supplies the lower lobe; the upper supplies the upper lobe, giving a branch to the middle lobe. The left pulmonary artery, shorter and somewhat smaller than the right, pierces the pericardium and passes horizontally in front of the descending aorta and left bronchus to the root of the left lung, where it divides into two branches for the two lobes. The root of the left pulmonary artery is connected to the under surface of the arch of the aorta by a short fibrous cord, the remains of a vessel peculiar to foetal life, the ductus arteriosus. The terminal branches of the pulmonary artery will be described with the anatomy of the lung. THE AORTA. 543 THE AORTA. The aorta (doprtf, arteria magna) is the main trunk of a series of vessels which convey the oxygenated blood to every part of the body for its nutrition. This vessel commences at the upper part of the left ventricle, and, after ascending for a short distance, arches backward to the left side, over the root of the left lung, then descends within the thorax on the left side of the vertebral column, passes through the aortic opening in the Diaphragm, and, entering the abdominal cavity, terminates, considerably diminished in size, opposite the fourth lumbar vertebra, Right vagus. Recurrent laryngeal. Left vagus. Left phrenic. Thoracic duct. Arch Aorta, Right coronary. ' Left coronary. Fig. 345.-Plan of the branches. Fig. 344.-The arch of the aorta and its branches. where it divides into the right and left common iliac arteries. Hence its division into the ascending aorta, the arch of the aorta, and the descending aorta, which last is again divided into thoracic aorta and abdominal aorta, from the position of these parts. THE ASCENDING AORTA. The ascending aorta is about two inches in length. It commences at the upper part of the left ventricle, on a level with the lower border of the third costal cartilage behind the left half of the sternum ; it passes obliquely upward, forward, 544 THE ARTERIES. and to the right in the direction of the heart's axis, as high as the upper border of the second right costal cartilage, describing a slight curve in its course, and being situated, when distended, about a quarter of an inch behind the posterior surface of the sternum. A little above its commencement it is somewhat enlarged, and presents three small dilatations, called the sinuses of the aorta (sinuses of Valsalva), opposite to which are attached the three semilunar valves, which serve the purpose of preventing any regurgitation of blood into the cavity of the ventricle. A section of the aorta opposite this part has a somewhat triangular figure, but below the attachment of the valves it is circular. This portion of the aorta is contained in the cavity of the pericardium, and, together with the pul- monary artery, is invested in a tube of serous membrane, continued on to them from the surface of the heart. Relations.-The ascending aorta is covered at its commencement by the trunk of the pulmonary artery and the right auricular appendix, and, higher up, is separated from the sternum by the pericardium, the right pleura, and anterior margin of right lung, some loose areolar tissue, and the remains of the thymus gland; behind, it rests upon the root of the right lung and left auricle. On the right side it is in relation with the superior vena cava and right auricle; on the left side, with the pulmonary artery. Plan of the Relations of the Ascending Aorta. In front. Pulmonary artery. Right auricular appendix. Pericardium. Right pleura and lung. Remains of thymus gland. Right side. Superior cava. Right auricle. 'Arch of Aorta. Ascending Portion. Left side. Pulmonary artery. Behind. Root of right lung. Left auricle. Branches of the Ascending Aorta The only branches of the ascending aorta are the two coronary arteries. They supply the heart, and are two in number, right and left, arising near the commencement of the aorta immediately above the free margin of the semilunar valves. THE CORONARY ARTERIES. The Right Coronary Artery, about the size of a crow's quill, arises from the aorta immediately above the free margin of the anterior semilunar valve. It passes forward between the pulmonary artery and the right auricular appendix, then runs obliquely to the right side in the groove between the right auricle and ventricle, and, curving around the right border of the heart, runs along its posterior surface as far as the posterior interventricular groove, where it divides into two branches, one of which continues onward in the groove between the left auricle and ventricle, and anastomoses with the left coronary; the other descends along the posterior interventricular furrow, supplying branches to both ventricles and to the septum, and anastomosing at the apex of the heart with the descending branches of the left coronary. This vessel sends a large branch along the thin margin of the right ventricle to the apex, and numerous small branches to the right auricle and ventricle, and the commencement of the pulmonary artery. The Left Coronary, larger than the former, arises immediately above the free THE ARCH OF THE AORTA. 545 edge of the left semilunar valve, a little higher than the right; it passes forward between the pulmonary artery and the left auricular appendix, and divides into two branches. Of these, one passes transversely outward in the left auriculo- ventricular groove, and winds around the left border of the heart into its posterior surface, where it anastomoses with the transverse branch of the right coronary; the other descends along the anterior interventricular groove to the apex of the heart, where it anastomoses with the descending branches of the right coronary. The left coronary supplies the left auricle and its appendix, both ventricles, and numerous small branches to the pulmonary artery, and commencement of the aorta.1 Peculiarities.-These vessels occasionally arise by a common trunk, or their number may be increased to three, the additional branch being of small size. More rarely, there are two additional branches. THE ARCH OF THE AORTA. The arch, or transverse aorta, commences at the upper border of the second chondro-sternal articulation of the right side, and passes from right to left, and from before backward, to the left side of the lower border of the fourth dorsal vertebra behind. Its upper border is usually about an inch below the upper mar- gin of the sternum. Relations.-Its anterior surface is covered by the pleurae and lungs and the remains of the thymus gland, and crossed toward the left side by the left pneumo- gastric and phrenic nerves and superior cardiac branches of the left sympathetic, and by the left superior intercostal vein. Its posterior surface lies on the trachea, just above its bifurcation, on the great, or deep, cardiac plexus, the oesophagus, thoracic duct, and left recurrent laryngeal nerve. Its upper border is in relation with the left innominate vein, and from its upper part are given off the innom- inate, left common carotid, and left subclavian arteries. Its lower border is in relation with the bifurcation of the pulmonary artery, the remains of the ductus arteriosus, which is connected with the left division of that vessel, and the super- ficial cardiac plexus; the left recurrent laryngeal nerve winds round it from before backward, whilst the left bronchus passes below it. Plan of the Relations of the Arch of the Aorta Above. Left innominate vein. Innominate artery. Left carotid. Left subclavian. In Front. Pleurae and lungs. Remains of thymus gland. Left pneumogastric nerve. Left phrenic nerve. Left superior cardiac nerves. Left superior intercostal vein. Behind. Trachea. Deep cardiac plexus. (Esophagus. Thoracic duct. Left recurrent nen[e. Arch of Aorta. Transverse Portion. Below. Bifurcation of pulmonary artery. Remains of ductus arteriosus. Superficial cardiac plexus. Left recurrent nerve. Left bronchus. Peculiarities.-The height to which the aorta rises in the chest is usually about an inch below the upper border of the sternum; but it may ascend nearly to the top of that bone. Occasionally it is found an inch and a half, more rarely two or even three inches, below this point. 1 According to Dr. Samuel West, there is a very free and complete anastomosis between the two coronary arteries (Lancet, June 2, 1883, p. 945). This, however, is not the view generally held by anatomists, for, with the exception of the anastomosis mentioned above in the auriculo-ventricular and interventricular grooves, it is believed that the two arteries only communicate by very small vessels in the substance of the heart. 546 THE ARTERIES. In Direction.-Sometimes the aorta arches over the root of the right instead of the left lung, as in birds, and passes down on the right side of the spine. In such cases all of the viscera of the thoracic and abdominal cavities are transposed. Less frequently, the aorta, after arching over the root of the right lung, is directed to its usual position on the left side of the spine, this peculiarity not being accompanied by any transposition of the viscera. In Conformation.-The aorta occasionally divides, as in some quadrupeds, into an ascend- ing and descending trunk, the former of which is directed vertically upward, and subdivides into three branches, to supply the head and upper extremities. Sometimes the aorta subdivides soon after its origin into two branches, which soon reunite. In one of these cases the oesophagus and trachea were found to pass through the interval left by their division ; this is the normal condition of the vessel in the reptilia. Surgical Anatomy.-Of all the vessels of the arterial system, the aorta, and more espe- cially its arch, is most frequently the seat of disease ; hence it is important to consider some of the consequences that may ensue from aneurism of this part. It will be remembered that the ascending aorta is contained in the pericardium, just behind the sternum, being crossed at its commencement by the pulmonary artery and right auricular appendix, and having the root of the right lung behind, the vena cava on the right side, and the pulmonary artery and left auricle on the left side. Aneurism of the ascending aorta, in the situation of the aortic sinuses, in the great majority Right pulmonary reins. ] Vein azygos major. Right innom. vein. 'Left subclav. Right subclav. Right common carotid. ''Left common carotid. Inferior thyroid. I Left innominate rein. Fig. 346.-Relation of great vessels at base of heart, seen from above. (From a preparation in the Museum of the Royal College of Surgeons.) of cases, affects the right anterior sinus ; this is mainly owing to the fact that the regurgitation of blood upon the sinuses takes place chiefly on the right anterior aspect of the vessel. As the aneurismal sac enlarges it may compress any or all of the structures in immediate proximity with it, but chiefly projects toward the right anterior side, and, consequently, interferes mainly with those structures that have a corresponding relation with the vessel. In the majority of cases it bursts into the cavity of the pericardium, the patient suddenly drops down dead, and, upon a post-mortem examination, the pericardial sac is found full of blood; or it may compress the right auricle, or the pulmonary artery, and adjoining part of the right ventricle, and open into one or the other of these parts, or may press upon the superior vena cava. Aneurism of the ascending aorta, originating above the sinuses, most frequently implicates the right anterior wall'of the vessel; this is probably mainly owing to the blood being impelled against this part. The direction of the aneurism is also chiefly toward the right of the median line. If it attains a large size and projects forward, it may absorb the sternum and the cartilages of the ribs, usually on the right side, and appear as a pulsating tumor on the front of the chest, just below the manubrium ; or it may burst into the pericardium, or may compress or open into the right lung, the trachea, bronchi, or oesophagus. Regarding the transverse aorta, the student is reminded that the vessel lies on the trachea, the oesophagus, and thoracic duct; that the recurrent laryngeal nerve winds around it; and that from its upper part are given off three large trunks, which supply the head, neck, and upper extremities. Now, an aneurismal tumor, taking origin from the posterior part or right aspect of the vessel, its most usual site, may press upon the trachea, impede the breathing, or produce cough, haemoptysis, or stridulous breathing, or it may ultimately burst into that tube, producing fatal haemorrhage. Again, its pressure on the laryngeal nerves may give rise to symptoms which so accurately resemble those of laryngitis that the operation of tracheotomy has in some cases THE INNOMINATE ARTERY. 547 been resorted to, from the supposition that disease existed in the larynx; or it may press upon the thoracic duct and destroy life by inanition ; or it may involve the oesophagus, producing dysphagia; or may burst into the oesophagus, when fatal haemorrhage will occur. Again, the innominate artery, or the subclavian, or left carotid, may be so obstructed by clots as to produce a weakness, or even a disappearance, of the pulse in one or the other wrist or in the left tem- poral artery; or the tumor may present itself at or above the manubrium, generally either in the median line or to the right of the sternum, and may simulate an aneurism of one of the arteries of the neck. The branches given off from the arch of the aorta are three in number : the innominate artery, the left common carotid, and the left subclavian. Peculiarities.-Position ofthe Branches.-The branches, instead of arising from the high- est part of the arch (their usual position), may be moved more to the right, arising from the commencement of the transverse or upper part of the ascending portion: or the distance from one another at their origin may be increased or diminished, the most frequent change in this respect being the approximation of the left carotid toward the innominate artery. The Number of the primary branches may be reduced to two : the left carotid arising from the innominate artery, or (more rarely) the carotid and subclavian arteries of the left side aris- ing from a left innominate artery. But the number may be increased to four, from the right carotid and subclavian arteries arising directly from the aorta, the innominate being absent. Tn most of these latter cases the right subclavian has been found to arise from the left end of the arch ; in other cases it was the second or third branch given off instead of the first. Lastly, the number of trunks from the arch may be increased to five or six; in these instances the external and internal carotids arise separately from the arch, the common carotid being absent on one or both sides. Number Usual, Arrangement Different.-When the aorta arches over to the right side, the three branches have an arrangement the reverse of what is usual, the innominate supplying the left side, and the carotid and subclavian (which arise separately) the right side. In other cases, where the aorta takes its usual course, the two carotids may be joined in a common trunk, and the subclavians arise separately from the arch, the right subclavian generally arising from the left end of the arch. Secondary Branches sometimes arise from the arch ; most commonly such a secondary branch is the left vertebral, which usually takes origin between the left carotid and left subcla- vian, or beyond them. Sometimes, a thyroid branch is derived from the arch, or the right internal mammary, or right vertebral, or, more rarely, both vertebral.1 Branches of the Arch of the Aorta (Figs. 344, 345). THE INNOMINATE ARTERY. The innominate artery (brachio-cephalic) is the largest branch given off' from the arch of the aorta. It arises opposite the fourth dorsal vertebra from the commencement of the arch of the aorta in front of the left carotid, and, ascending obliquely to the upper border of the right sterno-clavicular articulation, divides into the right common carotid and right subclavian arteries. This vessel varies from an inch and a half to two inches in length. Relations.-In front, it is separated from the first bone of the sternum by the Sterno-hyoid and Sterno-thyroid muscles, the remains of the thymus gland, the left innominate and right inferior thyroid veins which cross its root, and some- times the inferior cervical cardiac branch of the right pneumogastric. Behind, it lies upon the trachea, which it crosses obliquely. On the right side is the right innominate vein, right pneumogastric nerve, and the pleura; and on the left side, the remains of the thymus gland, the origin of the left carotid artery, the left inferior thyroid vein, and the trachea. Branches.-The innominate usually gives off no branches, but occasionally a small branch, the thyroidea ima, is given off from this vessel. It also sometimes gives off a thymic or bronchial branch. The Thyroidea ima ascends in front of the trachea to the lower part of the thyroid body, which it supplies. It varies greatly in size, and appears to compensate for deficiency or absence of one of the other thyroid vessels. It occasionally is found to arise from the subclavian or internal mammary vessel. 1 The anomalies of the aorta and its branches are minutely described by Krause in Henle's Anatomy (Brunswick, 1868), vol. iii. p. 203 et seq. 548 THE ARTERIES. Plan of the Relations of the Innominate Artery. In front. Sternum. Sterno-hyoid and Sterno-thyroid muscles. Remains of thymus gland. Left innominate and right inferior thyroid veins. Inferior cervical cardiac branch from right pneumogastric nerve. Right side. Left side. Remains of thymus. Left carotid. Left inferior thyroid vein. Trachea. Right innominate vein. Right pneumogastric nerve. Pleura. Innominate Artery. Behind. Trachea. Peculiarities in Point of Division.-When the bifurcation of the innominate artery varies from the point above mentioned, it sometimes ascends a considerable distance above the sternal end of the clavicle ; less frequently it divides below it. In the former class of cases its length may exceed two inches, and in the latter be reduced to an inch or less. These are points of con- siderable interest for the surgeon to remember in connection with the operation of tying this vessel. Position.-When the aorta arches over to the right side, the innominate is directed to the left side of the neck instead of the right. Collateral Circulation.-Allan Burns demonstrated, on the dead subject, the possibility of the establishment of the collateral circulation after ligature of the innominate artery, by tying and dividing that artery, after which, he says, "Even coarse injection, impelled into the aorta, passing freely by the anastomosing branches into the arteries of the right arm, filling them and all the vessels of the head completely" {Surgical Anatomy of the Head and Neck, p. 62). The branches by which this circulation would be carried on are very numerous; thus, all the communications across the middle line between the branches of the carotid arteries of opposite sides would be available for the supply of blood to the right side of the head and neck ; while the anastomosis between the superior intercostal of the subclavian and the first aortic intercostal (see infra on the collateral circulation after obliteration of the thoracic aorta) would bring the blood, by a free and direct course, into the right subclavian: the numerous connections, also, between the intercostal arteries and the branches of the axillary and internal mammary arteries would, doubtless, assist in the supply of blood to the right arm, while the epigastric, from the external iliac, would, by means of its anastomosis with the internal mammary, compensate for any deficiency in the vascularity of the wall of the chest. Surgical Anatomy.-Although the operation of tying the innominate artery has been performed by several surgeons for aneurism of the right subclavian extending inward as far as the Scalenus, in only two instances has the patient survived.1 Mott's patient, however, on whom the operation was first performed, lived nearly four weeks, and Graefe's more than two months. The main obstacles to the operation are, as the student will perceive from his dissection of this vessel, the deep situation of the artery behind and beneath the sternum and the number of important structures which surround it in every part. In order to apply a ligature to this vessel, the patient is to be placed upon his back, with the thorax slightly raised, the head bent a little backward, and the shoulder on the side of the aneu- rism strongly depressed, so as to draw out the artery from behind the sternum into the neck. An incision three or more inches long is then made along the anterior border of the Sterno-mas- toid muscle, terminating at the sternal end of the clavicle. From this point a second incision is carried about the same length along the upper border of the clavicle. The skin is then dissected back, and the Platysma divided on a director: the sternal end of the Sterno-mastoid is now brought into view, and, a director being passed beneath it and close to its under surface, so as to avoid any small vessels, it is to be divided ; in like manner the clavicular origin is to be divided throughout the whole or greater part of its attachment. By pressing aside any loose cellular tissue or vessels that may now appear the Sterno-hyoid and Sterno-thyroid muscles will be exposed, and must be divided, a director being previously passed beneath them. The inferior thyroid veins may come into view, and must be carefully drawn, either upward or downward, by means of a blunt hook, or tied with double ligatures and divided. After tearing through a strong fibro-cellular lamina, the right carotid is brought into view, and, being traced downward, the arteria innominata is arrived at. The left innominate vein should now be depressed ; the right innominate vein, the internal jugular vein, and the pneumogastric nerve drawn to the right side ; and a curved aneurism needle may then be passed around the vessel, close to its surface, and in a direction from below upward and inward, care being taken to avoid the right pleural sac, the trachea, and cardiac nerves. The ligature should be applied to the artery as high as possible, in order to allow room between it and the aorta for the formation of the coagulum. 1 In one of these the operation was performed by Dr. Smyth of New Orleans. See the New Sydenham Society's Biennial Retrospect for 1865-6, p. 346. In the other, the operation was performed by Dr. Mitchell Banks in the Liverpool Infirmary. The case is recorded by Mr. Jacobson in Oper- ations of Surgery, p. 536. THE COMMON CAROTID ARTERIES. 549 The importance of avoiding the thyroid plexus of veins during the primary steps of the opera- tion, and the pleural sac whilst including the vessel in the ligature, should be most carefully borne in mind. The most frequent cause of death after operation is secondary haemorrhage, which has occurred in almost every case. Other causes are pleurisy, pericarditis, and suppura- tive cellulitis. The common carotid arteries, although occupying a nearly similar position in the neck, differ in position, and, consequently, in their relation at their origin. The right carotid arises from the innominate artery, behind the right sterno- clavicular articulation ; the left from the highest part of the arch of the aorta. The left carotid is, consequently, longer, and at its origin is contained within the thorax. The course and relations of that portion of the left carotid which inter- venes between the arch of the aorta and the left sterno-clavicular articulation will first be described (see Fig. 344). The left carotid within the thorax ascends obliquely outward from the arch of the aorta to the root of the neck. In front, it is separated from the first piece of the sternum by the Sterno-hyoid and Sterno-thyroid muscles, the left innominate vein, and the remains of the thymus gland; behind, it lies on the trachea, oesoph- agus, and thoracic duct. Internally, it is in relation with the innominate artery, inferior thyroid veins and remains of thymus gland; externally, with the left pneumogastric nerve, left pleura, and lung. The left subclavian artery is posterior and external to it. THE COMMON CAROTID ARTERIES. Plan of the Relations of the Left Common Carotid. Thoracic Portion. In front. Sternum. Sterno-hyoid and Sterno-thyroid muscles. Left innominate vein. Remains of thymus gland. Internally. Innominate artery. Inferior thyroid veins. Remains of thymus gland. Left Common ' Carotid. Thoracic Portion. , Externally. Left pneumogastric nerve. Left pleura and lung. Left subclavian artery. Behind. Trachea. (Esophagus. Thoracic duct. In the neck the two common carotids resemble each other so closelv that one description will apply to both. Each vessel passes obliquely upward from behind the sterno-clavicular articulation to a level with the upper border of the thyroid cartilage, opposite the third cervical vertebra, where it divides into the external and internal carotid; these names being derived from the distribution of the arteries to the external parts of the head and face and to the internal parts of the cranium and orbit respectively. At the lower part of the neck the two common carotid arteries are separated from each other by a very small interval, which contains the trachea; but at the upper part, the thyroid body, the larynx and pharynx project forward between the two vessels, and give the appearance of their being placed farther back in that situation. The common carotid artery is contained in a sheath derived from the deep cervical fascia, which also encloses the internal jugular vein and pneumo- gastric nerve, the vein lying on the outer side of the artery, and the nerve between the artery and vein, on a plane posterior to both. On opening the sheath these three structures are seen to be separated from one another, each being enclosed in a separate fibrous investment. Relations.-At the lower part of the neck the common carotid artery is very 550 THE A R TERIES. deeply seated, being covered by the integument, superficial fascia, Platysma, and deep cervical fascia, the Sterno-mastoid, Sterno-hyoid, and Sterno-thyroid muscles, and by the Omo-hyoid, opposite the cricoid cartilage ; but in the upper part of its course, near its termination, it is more superficial, being covered merely by the integument, the superficial fascia, Platysma, deep cervical fascia, and inner margin of the Sterno-mastoid, and is contained in a triangular space, bounded behind by Orico-thyroid artery. Fig. 348.-Plan of the branches of the external carotid. Fig. 347.-Surgical anatomy of the arteries of the neck. Right side. the Sterno-mastoid, above by the posterior belly of the Digastric, and below by the anterior belly of the Omo-hyoid. This part of the artery is crossed obliquely, from within outward, by the sterno-mastoid artery; it is crossed also by one, or sometimes two superior thyroid veins, which terminate in the internal jugular; and, descending on its sheath in front, is seen the descendens hypoglossi nerve, this filament being joined by one or two branches from the cervical nerves, which cross the vessel from without inward. Sometimes the descendens hypoglossi is contained within the sheath. The middle thyroid vein crosses the artery about THE COMMON CAROTID ARTERIES. 551 its middle, and the anterior jugular vein below. Behind, the artery lies in front of the cervical portion of the spine, resting first on the Longus colli muscle, then on the Rectus capitis anticus major, from which it is separated by the sympathetic nerve. The recurrent laryngeal nerve and inferior thyroid artery cross behind the vessel at its lower part. Internally, it is in relation with the trachea and thyroid gland, the inferior thyroid artery and recurrent laryngeal nerve being interposed: higher up, with the larynx and pharynx. On its outer side are placed the internal jugular vein and pneumogastric nerve At the lower part of the neck the internal jugular vein on the right side diverges from the artery, but on the left side it approaches it, and often crosses its lower part. This is an important fact to bear in mind during the performance of any operation on the lower part of the left common carotid artery. Plan of the Relations of the Common Carotid Artery. Integument, and superficial fascia. Deep cervical fascia. Platysma. Sterno-mastoid. Sterno-hyoid. Sterno-thyroid. In front. Omo-hyoid. Descendens and Communicans hypoglossi nerves. Sterno-mastoid artery. Superior and middle thyroid veins. Anterior jugular vein. Internally. Trachea. Thyroid gland. Recurrent laryngeal nerve. Inferior thyroid artery. Larynx. Pharynx. Externally. Internal jugular vein. Pneumogastric nerve. Common Carotid. Behind. Longus colli. Sympathetic nerve. Rectus capitis anticus major. Inferior thyroid artery. Recurrent laryngeal nerve. Peculiarities as to Origin.-The right common carotid may arise above or below its usual point, the upper border of the sterno-clavicular articulation. This variation occurs in one out of about eight cases and a half, and the origin is more frequently above than below the usual point; or the artery may arise as a separate branch from the arch of the aorta or in conjunction with the left carotid. The left common carotid varies more frequently in its origin than the right. In the majority of abnormal cases it arises with the innominate artery, or, if the innominate artery is absent, the two carotids arise usually by a single trunk. The left carotid is occasionally the first branch given off from the arch of the aorta. It rarely joins with the left subclavian, except in cases of transposition of the arch. Peculiarities as to Point of Division.-The most important peculiarities of this vessel, in a surgical point of view, relate to its place of division in the neck. In the majority of abnormal cases this occurs higher than usual, the artery dividing into two branches opposite the hyoid bone, or even higher; more rarely, it occurs below its usual place, opposite the middle of the larynx or the lower border of the cricoid cartilage; and one case is related by Morgagni where the common carotid, only an inch and a half in length, divided at the root of the neck. Very rarely the common carotid ascends in the neck without any subdivision, the internal carotid being wanting; and in a few cases the common carotid has been found to be absent, the external and internal carotids arising directly from the arch of the aorta. This peculiarity existed on both sides in some instances, on one side in others. Occasional Branches.-The common carotid usually gives off no branch previous to its bifurcation ; but it occasionally gives origin to the superior thyroid or its laryngeal branch, the inferior thyroid, or, more rarely, the vertebral artery. Surface Marking.-The carotid arteries are overlapped throughout their entire extent by the anterior border of the Sterno-mastoid muscle, but their course does not correspond to the border of the muscle, which passes in a somewhat curved direction from the mastoid process to the sterno-clavicular joint. The course of the artery is indicated more exactly by a line drawn from the sternal end of the clavicle below, to a point midway between the angle of the jaw and the mastoid process above. That portion of the line below the lovel of the upper border of the thyroid cartilage would represent the course of the vessel. < Surgical Anatomy.-The operation of tying the common carotid artery may be necessary in a case of wound of that vessel or its branches, in aneurism, or in a case of pulsating tumor of the orbit or skull. If the wound involves the trunk of the common carotid, it will be necessary to tie the artery above and below the wounded part. But in cases of aneurism, or where one of 552 THE ARTERIES. the branches of the common carotid is wounded in an inaccessible situation, it may be judged necessary to tie the trunk. In such cases the whole of the artery is accessible, and any part may be tied except close to either end. When the case is such as to allow of a choice being made, the lower part of the carotid should never be selected as the spot upon which to place a ligature, for not only is the artery in this situation placed very deeply in the neck, but it is covered by three layers of muscles, and, on the left side, the internal jugular vein, in the great majority of cases, passes obliquely in front of it. Neither should the upper end be selected, for here the superior thyroid vein and its tributaries would give rise to very considerable difficulty in the application of a ligature. The point most favorable for the operation is that part of the vessel which is at the level of the cricoid cartilage. It occasionally happens that the carotid artery bifurcates below its usual position: if the artery be exposed at its point of bifurcation, both divisions of the vessel should be tied near their origin, in preference to tying the trunk of the artery near its termination ; and if, in consequence of the entire absence of the common carotid or from its early division, two arteries, the external and internal carotids, are met with, the ligature should be placed on that vessel which is found on compression to be connected with the disease. In this operation the direction of the vessel and the inner margin of the Sterno-mastoid are the chief guides to its performance. The patient should be placed on his back with the head thrown back and turned slightly to the opposite side: an incision is to be made, three inches long, in the direction of the anterior border of the Sterno-mastoid, so that the centre corresponds to the level of the cricoid cartilage: after dividing the integument, superficial fascia, and Platysma, the deep fascia must be cut through on a director, so as to avoid wounding numerous small veins that are usually found beneath. The head may now be brought forward so as to relax the parts somewhat, and the margins of the wound held asunder by retractors. The descendens hypoglossi nerve may now be exposed, and must be avoided, and, the sheath of the vessel having been raised by forceps, is to be opened to a small extent over the artery at its inner side. The internal jugular vein may present itself alternately distended and relaxed ; this should be compressed both above and below, and drawn outward, in order to facilitate the opera- tion. The aneurism needle is passed from the outside, care being taken to keep the needle in close contact with the artery, and thus avoid the risk of injuring the internal jugular vein or including the vagus nerve. Before the ligature is tied it should be ascertained that nothing but the artery is included in it. Ligature of the Common Carotid at the Lower Part of the Neck.-This operation is sometimes required in cases of aneurism of the upper part of the carotid, especially if the sac is of large size. It is best performed by dividing the sternal origin of the Sterno-mastoid muscle, but may be done in some cases, if the aneurism is not of very large size, by an incision along the anterior border of the Sterno-mastoid, extending down to the sterno-clavicular articula- tion, and by then retracting the muscle. The easiest and best plan, however, is to make an incision two or three inches long down the lower part of the anterior border of the Sterno- mastoid muscle to the sterno-clavicular joint, and a second incision, starting from the termination of the first, along the upper border of the clavicle for about two inches. This incision is made through the superficial and deep fascia, and the sternal origin of the muscle exposed. This is to be divided on a director, and turned up, with the superficial structures, as a triangular flap. Some loose connective tissue is to be divided or torn through, and the outer border of the Sterno-hyoid muscle exposed. In doing this care must be taken not to wound the anterior jugular vein, which crosses the muscle to reach the external jugular or subclavian vein. The Sterno-hyoid, and with it the Sterno-thyroid. are to be drawn inward by means of a retractor, and the sheath of the vessel is exposed. This must be opened with great care on its inner or tracheal side, so as to avoid the internal jugular vein. This is especially necessary on the left side, where the artery is commonly overlapped by the vein. On the right side there is usually an interval between the artery and the vein, and not the same risk of wounding the latter. The common carotid artery, being a long vessel without any branches, is particularly suitable for the performance of Brasdor's operation for the cure of an aneurism of the lower part of the vessel. Brasdor's procedure consists in ligaturing the artery on the distal side of the aneurism, and in the case of the common carotid there are no branches given off from the vessel between the aneurism and the site of the ligature; hence little or no blood passes through the sac of the aneurism, and consequently it and the vessel shrinks, and a cure is effected. Collateral Circulation.-After ligature of the common carotid the collateral circulation can be perfectly established, by the free communication which exists between the carotid arteries of opposite sides, both without and within the cranium, and by enlargement of the branches of the subclavian artery on the side corresponding to that on which the vessel has been tied-the chief communication outside the skull taking place between the superior and inferior thyroid arteries, and the profunda cervicis and arteria princeps cervicis of the occipital; the vertebral taking the place of the internal carotid within the cranium. Sir A. Cooper had an opportunity of dissecting, thirteen years after the operation, the case in which he first successfully tied the common carotid (the second case in which he performed the operation).1 The injection, however, does not seem to have been a successful one. It showed merely that the arteries at the base of the brain (circle of Willis) were much enlarged on 1 Guy's Hospital Reports, i. 56. THE EXTERNAL CAROTID ARTERY. 553 the side of the tied artery, and that the anastomosis between the branches of the external carotid on the affected side and those of the same artery on the sound side was free, so that the external carotid was pervious throughout. The external carotid artery (Fig. 847) commences opposite the upper border of the thyroid cartilage, and taking a slightly curved course, passes upward and for- ward, and then inclines backward to the space between the neck of the condyle of the lower jaw and the external meatus, where it divides into the temporal and internal maxillary arteries. It rapidly diminishes in size in its course up the neck, owing to the number and large size of the branches given off from it. In the child it is somewhat smaller than the internal carotid, but in the adult the two vessels are of nearly equal size. At its commencement this artery is more superficial, and placed nearer the middle line than the internal carotid, and is contained in the triangular space bounded by the Sterno-mastoid behind, the Omo-hyoid below, and the posterior belly of the Digastric and Stylo-hyoid above. Relations.-It is covered by the skin, superficial fascia, Platysma, deep fascia, and anterior margin of the Sterno-mastoid, crossed by the hypoglossal nerve, and by the lingual and facial veins; it is afterward crossed by the Digastric and Stylo-hyoid muscles, and higher up passes deeply into the substance of the parotid gland, where it lies beneath the facial nerve and the junction of the temporal and internal maxillary veins. Internally is the hyoid bone, wall of the pharynx, the superior laryngeal nerve, and the ramus of the jaw, from which it is separated by a portion of the parotid gland. Externally, in the lower part of its course, is the internal carotid artery. Behind it, near its origin, is the superior laryngeal nerve; and higher up it is separated from the internal carotid by the Stylo-glossus and Stylo-pharyngeus muscles, the glosso-pharyngeal nerve, and part of the parotid gland. Surface Marking.-The position of the external carotid artery may be marked out with sufficient accuracy by a line drawn from the front of the meatus of the external ear to the side of the cricoid cartilage, slightly arching the line forward. Surgical Anatomy.-The application of a ligature to the external carotid may be required in case of wounds of this vessel, or of its branches when these cannot be tied, and in some cases of pulsating tumor of the scalp or face. The operation has not received the attention which it deserves, owing to the fear which surgeons have entertained of secondary haemorrhage, on account of the number of branches given off from the vessel. This fear, however, has been shown by Mr. Cripps not to be well founded.1 To tie this vessel near its origin, below the point where it is crossed by the Digastric, an incision about three inches in length should be made along the margin of the Sterno-mastoid, from the angle of the jaw to the upper border of the thyroid cartilage. The ligature should be applied between the lingual and superior thyroid branches. To tie the vessel above the Digastric, between it and the parotid gland, an incision should be made, from the lobe of the ear to the great cornu of the os hyoides, dividing succes- sively the skin, Platysma, and fascia. By drawing the Sterno-mastoid outward, and the posterior belly of the Digastric and Stylo hyoid muscles downward, and separating them from the parotid gland, the vessel will be exposed, and a ligature may be applied to it. The circulation is at once re-established by the free communication between most of the large branches of the artery (facial, lingual, superior thyroid, occipital) and the corresponding arteries of the opposite side, and by the anastomosis of its branches with those of the internal carotid, and of the occipital with the branches of the subclavian, etc. The External Carotid Artery. Plan of the Relations of the External Carotid Skin, superficial fascia. Platysma and deep fascia. Anterior border of Sterno-mastoid. Hypoglossal nerve. Lingual and facial veins. Digastric and Stylo-hyoid muscles. Parotid gland with facial nerve and temporo-maxillary vein in its substance. Li front. 1 Med.-Chir. Trans., Ixi. 229. 554 THE ARTERIES. Internally. Hyoid bone. Pharynx. Superior laryngeal nerve. Parotid gland. Ramus of jaw. Externally. Internal carotid artery. External Carotid. Behind. Superior laryngeal nerve. Stylo-glossus. Stylo- ph ary ngeus. Glosso-pharyngeal nerve. Parotid gland. Branches.-The external carotid artery gives off eight branches, which, for convenience of description, may be divided into four sets. (See Fig. 348, Plan of the Branches). Anterior. Superior Thyroid. Lingual. Facial. Posterior. Occipital. Posterior Auricular. Ascending. Ascending Pha- ryngeal. Terminal. Superficial Temporal. Internal Maxillary. The student is here reminded that many variations are met with in the number, origin, and course of these branches in different subjects; but the above arrangement is that which is found in the great majority of cases. The Superior Thyroid Artery (Figs. 347 and 352) is the first branch given off from the external carotid, being derived from that vessel just below' the great cornu of the hyoid bone. At its commencement it is quite superficial, being covered by the integument, fascia, and Platysma, and is contained in the triangular space bounded by the Sterno-mastoid, Digastric, and Omo-hyoid muscles. After running upward and inward for a short distance, it curves downward and forward, in an arched and tortuous manner, to the upper part of the thyroid gland, passing beneath the Omo-hyoid, Sterno-hyoid, and Sterno-thyroid muscles, and distributes numerous branches to the anterior surface of the gland, anastomosing with its fellow of the opposite side and with the inferior thyroid arteries. Besides the arteries distributed to the muscles by which it is covered and the substance of the gland, the branches of the superior thyroid are the following: Hyoid. Superficial descending branch (Sterno-mastoid). Superior Laryngeal. Crico-thyroid. The hyoid is a small branch which runs along the lower border of the os hyoides beneath the Thyro-hyoid muscle; after supplying the muscles connected to that bone it forms an arch, by anastomosing with the vessels of the opposite side. The superficial descending branch runs downward and outward across the sheath of the common carotid artery, and supplies the Sterno-mastoid and neigh- boring muscles and integument. There is also often a distinct branch from the external carotid distributed to the Sterno-mastoid muscle. The superior laryngeal, larger than either of the preceding, accompanies the superior laryngeal nerve, beneath the Thyro-hyoid muscle: it pierces the thyro- hyoid membrane, and supplies the muscles, mucous membrane, and glands of the larynx, anastomosing with the branch from the opposite side. The crico-thyroid is a small branch which runs transversely across the crico- thyroid membrane, communicating with the artery of the opposite side. Surgical Anatomy.-The superior thyroid, or some of its branches, is often divided in cases of cut throat, giving rise to considerable haemorrhage. In such cases the artery should be secured, the wound being enlarged for that purpose, if necessary. The operation may be easily performed, the position of the artery being very superficial, and the only structures of importance covering it being a few small veins. The operation of tying the superior thyroid artery in bronchocele has been performed in numerous instances with partial or temporary success. When, BRANCHES OF THE EXTERNAL CAROTID. 555 however, the collateral circulation between this vessel and the artery of the opposite side, and the inferior thyroid, is completely re-established, the tumor usually regains its former size. The position of the superficial descending branch is of importance in connection with the operation of ligature of the common carotid artery. It crosses and lies on the sheath of this vessel, and may chance to be wounded in opening the sheath. The position of the crico-thyroid branch should be remembered, as it may prove the source of troublesome haemorrhage during the operation of laryngotomy. The Lingual Artery (Fig. 352) arises from the external carotid between the superior thyroid and facial; it runs obliquely upward and inward to the great cornu of the hyoid bone, then passes horizontally forward parallel with the great cornu, and, ascending perpendicularly to the under surface of the tongue, turns forward on its under surface as far as the tip of that organ, under the name of the ranine artery. Relations.-Its first, or oblique, portion is superficial, being contained in the triangular space already described, resting upon the middle constrictor of the pharynx, and covered by the Platysma and fascia of the neck. Its second, or horizontal, portion also lies upon the middle constrictor, being covered at first by the tendon of the Digastric and the Stylo-hyoid muscle, and afterward by the Hyo-glossus, the latter muscle separating it from the hypoglossal nerve. Its third, or ascending, portion lies between the Hyo-glossus and Genio-hyo-glossus muscles. The fourth, or terminal, part, under the name of the ranine, runs along the under surface of the tongue to its tip : it is very superficial, being covered only by the mucous membrane, and rests on the Lingualis on the outer side of the Genio-hyo-glossus. The hypoglossal nerve crosses the lingual artery, and then becomes separated from it, in the second part of its course, by the Hyo-glossus muscle. The branches of the lingual artery are-the Hyoid. Dorsalis Linguae. Sublingual Ranine. The hyoid branch runs along the upper border of the hyoid bone, supplying the muscles attached to it and anastomosing with its fellow of the opposite side. The dorsalis linguae (Fig. 352) arises from the lingual artery beneath the Hyo- glossus muscle (which, in the figure, has been partly cut away to show the vessel) ; ascending to the dorsum of the tongue, it supplies the mucous membrane, the tonsil, soft palate, and epiglottis, anastomosing with its fellow from the opposite side. The sublingual, which may be described as a branch of bifurcation of the lingual artery, arises at the anterior margin of the Hyo-glossus muscle, and runs forward between the Genio-hyo-glossus and the sublingual gland. It supplies the substance of the gland, giving branches to the Mylo-hyoid and neighboring muscles, the mucous membrane of the mouth and gums. One branch runs behind the alveolar process of the lower jaw in the substance of the gum to anastomose with a similar artery from the other side. The ranine may be regarded as the other branch of bifurcation, or, as is more usual, as the continuation of the lingual artery ; it runs along the under surface of the tongue, resting on the Inferior lingualis, and covered by the mucous membrane of the mouth; it lies on the outer side of the Genio-hyo-glossus, accompanied by the lingual nerve. On arriving at the tip of the tongue it has been said to anastomose with the artery of the opposite side, but this is denied by Hyrtl. These vessels in the mouth are placed one on each side of the fraenum. Surgical Anatomy.-The lingual artery may be divided near its origin in eases of cut throat, a complication that not unfrequently happens in this class of wounds; or severe haemorrhage which cannot be restrained by ordinary means may ensue from a wound or deep ulcer of the tongue. ' In the former case the primary wound may be enlarged if necessary, and the bleeding vessels secured. In the latter case it has been suggested that the lingual artery should be tied near its origin. Ligature of the lingual artery is also occasionally practised, as a palliative measure, in cases of cancer of the tongue, in order to check the progress of the disease by starving the growth, and it is sometimes tied as a preliminary measure to removal of 556 7T7A ARTERIES. the tongue. The operation is a difficult one, on account of the depth of the artery, the number of important parts by which it is surrounded, the loose and yielding nature of the parts upon which it is supported, and its occasional irregularity of origin. An incision is to be made in a curved direction from a finger's breadth external to the symphysis of the jaw downward to the cornu of the hyoid bone, and then upward to near the angle of the jaw. Care must be taken not to carry this incision too far backward, for fear of endangering the facial vein. In the first incision the skin, superficial fascia, and Platysma will be divided, and the deep fascia exposed. This is then to be incised and the submaxillary gland exposed and pulled upward by retractors. A triangular space is now exposed, bounded internally by the posterior border of the Mylo- hyoid muscle: below and externally, by the tendon of the Digastric; and above, by the hypo- glossal nerve. The floor of the space is formed by the Hyo-glossus muscle, beneath which the artery lies. The fibres of this muscle are now to be cut through horizontally and the vessel exposed, care being taken, while near the vessel, not to open the pharynx. Troublesome haemorrhage may occur in the division of the fraenum in children if the ranine artery, which lies on each side of it, is wounded. The student should remember that the opera- tion is always to be performed with a pair of blunt-pointed scissors, and the mucous membrane only is to be divided by a very superficial cut, which cannot endanger any vessel. The scissors, also, should be directed away from the tongue. Any further liberation of the tongue which majr be necessary can be effected by tearing. The Facial Artery (Fig. 349) arises a little above the lingual, and passes obliquely upward, beneath the Digastric and Stylo-hyoid muscles ; it then runs . Angular. \Lateralis nasi. -Arteria septi nasi. Superior coronary. Inferior coronary. -Inferior labial. Fig. 349.-The arteries of the face and scalp.1 forward under cover of the body of the lower jaw, lodged in a groove on the posterior surface of the submaxillary gland; this may be called the cervical part of the artery. It then curves upward over the body of the jaw at the anterior inferior angle of the Masseter muscle; passes forward and upward across the 1 The muscular tissue of the lips must be supposed to have been cut away, in order to show the course of the coronary arteries. BRANCHES OF THE EXTERNAL CAROTID. 557 cheek to the angle of the mouth, then upward along the side of the nose, and terminates at the inner canthus of the eye, under the name of the angular artery. This vessel, both in the neck and on the face, is remarkably tortuous: in the former situation, to accommodate itself to the movements of the pharynx in deglutition, and in the latter to the movements of the jaw and the lips and cheeks. Relations.-In the neck its origin is superficial, being covered by the integument, Platysma, and fascia ; it then passes beneath the Digastric and Stylo- hvoid muscles and the submaxillary gland. On the face, where it passes over the body of the lower jaw, it is comparatively superficial, lying immediately beneath the Platysma. In this situation its pulsation may be distinctly felt, and com- pression of the vessel effectually made against the bone. In its course over the face it is covered by the integument, the fat of the cheek, and, near the angle of the mouth, by the Platysma, Risorius, and Zygomatic muscles. It rests on the Buccinator, the Levator anguli oris, and the Levator labii superioris (sometimes piercing or else passing under this last muscle). It is accompanied by the facial vein throughout its entire course; the vein is not tortuous like the artery, and, on the face, is separated from that vessel by a considerable interval, lying to its outer side. The branches of the facial nerve cross the artery, and the infra-orbital nerve lies beneath it. The branches of this vessel may be divided into two sets : those given off below the jaw (cervical), and those on the face (facial). Cervical Branches. Inferior or Ascending Palatine. Tonsillar. Submaxillary. Submental. Muscular. Facial Branches. Muscular. Inferior Labial. Inferior Coronary. Superior Coronary. Lateralis Nasi. Angular. The inferior or ascending palatine (Fig. 352) passes up between the Stylo- glossus and Stylo-pharyngeus to the outer side of the pharynx. After supplying these muscles, the tonsil, and Eustachian tube, it divides, near the Levator palati, into two branches : one follows the course of the Levator palati, and, winding over the upper border of the Superior constrictor, supplies the soft palate and the pal- atine glands; the other pierces the Superior constrictor, supplies the tonsil, anas- tomosing with the tonsillar artery. These vessels also anastomose with the pos- terior palatine branch of the internal maxillary artery. The tonsillar branch (Fig. 352) passes up between the Internal Pterygoid and Stylo-glossus, and then ascends along the side of the pharynx, perforating the Superior constrictor, to ramify in the substance of the tonsil and root of the tongue. The submaxillary consists of three or four large branches, which supply the submaxillary gland, some being prolonged to the neighboring muscles, lymphatic glands, and integument. The submental, the largest of the cervical branches, is given off from the facial artery just as that vessel quits the submaxillary gland : it runs forward upon the Mylo-hyoid muscle, just below the body of the jaw and beneath the Digastric; after supplying the surrounding muscles, and anastomosing with the sublingual artery by branches which perforate the Mylo-hyoid muscle, it arrives at the sym- physis of the chin, where it turns over the border of the jaw and divides into a superficial and a deep branch ; the former passes between the integument and Depressor labii inferioris, supplies both, and anastomoses with the inferior labial. The deep branch passes between the latter muscle and the bone, supplies the lip, and anastomoses with the inferior labial and mental arteries. The muscular branches are distributed to the Internal pterygoid and Stylo-hyoid in the neck, and to the Masseter and Buccinator on the face. The inferior labial passes beneath the Depressor anguli oris, to supply the 558 THE ARTERIES. muscles and integument of the lower lip, anastomosing with the inferior coronary and submental branches of the facial, and with the mental branch of the inferior dental artery. The inferior coronary is derived from the facial artery, near the angle of the mouth : it passes upward and inward beneath the depressor anguli oris, and, pen- etrating the Orbicularis oris muscle, runs in a tortuous course along the edge of the lower lip between this muscle and the mucous membrane, inosculating with the artery of the opposite side. This artery supplies the labial glands, the mucous membrane, and muscles of the lower lip, and anastomoses with the inferior labial and the mental branch of the inferior dental artery. The superior coronary is larger and more tortuous in its course than the pre- ceding. It follows the same course along the edge of the upper lip, lying between the mucous membrane and the Orbicularis oris, and anastomoses with the artery of the opposite side. It supplies the textures of the upper lip, and gives off in its course two or three vessels which ascend to the nose. One, named the inferior artery of the septum, ramifies on the septum of the nares as far as the point of the nose ; another, the artery of the ala, supplies the ala of the nose. The lateralis nasi is derived from the facial, as that vessel is ascending along the side of the nose; it supplies the ala and dorsum of the nose, anastomosing with its fellow, the nasal branch of the ophthalmic, the inferior artery of the septum, the artery of the ala, and the infra-orbital. The angular artery is the termination of the trunk of the facial; it ascends to the inner angle of the orbit, imbedded in the fibres of the Levator labii superioris alaeque nasi, and accompanied by a large vein, the angular ; it distributes some branches on the cheek which anastomose with the infra-orbital, and after supplying the lachrymal sac and Orbicularis palpebrarum muscle, terminates by anastomos- ing with the nasal branch of the ophthalmic artery. The anastomoses of the facial artery are very numerous, not only with the vessel of the opposite side, but, in the neck, with the sublingual branch of the lingual; with the ascending pharyngeal ; with the posterior palatine, a branch of the internal maxillary, by its inferior or ascending palatine and tonsillar branches ; on the face, with the mental branch of the inferior dental as it emerges from the mental foramen, with the transverse facial, a branch of the temporal; with the infra-orbital, a branch of the internal maxillary, and with the nasal branch of the ophthalmic. Peculiarities.-The facial artery not unfrequentlj' arises by a common trunk with the lingual. This vessel is also subject to some variations in its size and in the extent to which it supplies the face. Lt occasionally terminates as the submental, and not unfrequently supplies the face only as high as the angle of the mouth or nose. The deficiency is then supplied by enlargement of one of the neighboring arteries. Surgical Anatomy.-The passage of the facial artery over the body of the jaw would appear to afford a favorable position for the application of pressure in case of haemorrhage from the lips, the result either of an accidental wound or during an operation ; but its applica- tion is useless, except for a very short time, on account of the free communication of this vessel with its fellow and with numerous branches from different sources. Tn a wound involv- ing the lip it is better to seize the part between the fingers, and evert it, when the bleeding vessel may be at once secured with pressure-forceps. In order to prevent haemorrhage in cases of removal of diseased growths from the part, the lip should be compressed on each side between the fingers and thumb or by a pair of specially devised clamp-forceps, whilst the surgeon excises the diseased part. In order to stop haemorrhage where the lip has been divided in an operation, it is necessary, in uniting the edges of the wound, to pass the sutures through the cut edges, almost as deep as its mucous surface ; by these means not only are the cut surfaces more neatly and securely adapted to each other, but the possibility of haemorrhage is prevented by including in the suture the divided artery. If the suture is, on the contrary, passed through merely the cutaneous portion of the wound, haemorrhage occurs into the cavity of the mouth. The student should, lastly, observe the relation of the angular artery to the lachrymal sac, and it will be seen that, as the vessel passes up along the inner margin of the orbit, it ascends on its nasal side. In operating for fistula lachrymalis the sac should always be opened on its outer side-, in order that this vessel may be avoided. The Occipital Artery (Fig. 349) arises from the posterior part of the external carotid, opposite the facial near the lower margin of the Digastric muscle. At its origin it is covered by the posterior belly of the Digastric and Stylo-hyoid muscles, BRANCHES OF THE EXTERNAL CAROTID. 559 and the hypoglossal nerve winds around it from behind forward; higher up, it passes across the internal carotid artery, the internal jugular vein, and the pneumo- gastric and spinal accessory nerves; it then ascends to the interval between the transverse process of the atlas and the mastoid process of the temporal bone, and passes horizontally backward, grooving the surface of the latter bone, being covered by the Sterno-mastoid, Splenius, Trachelo-mastoid, and Digastric muscles, and resting upon the Rectus lateralis, the Superior oblique, and Complexus muscles; it then changes its course and passes vertically upward, pierces the fascia which connects the cranial attachment of the Trapezius with the Sterno-mastoid, and ascends in a tortuous course over the occiput, as high as the vertex, where it divides into numerous branches. It is accompanied in the latter part of its course by the great occipital and a cutaneous filament from the suboccipital nerve. The branches given off from this vessel are- Muscular. Sterno-mastoid. Auricular. Meningeal. Arteria Princeps Cervicis. The Muscular branches supply the Digastric, Stylo-hyoid, Splenius, and Trachelo-mastoid muscles. The sterno-mastoid is a large and constant branch, generally arising from the artery close to its commencement. It first passes upward and backward, and then turns downward over the hypoglossal nerve, and enters the substance of the muscle, frequently in company with the spinal accessory nerve. The auricular branch supplies the back part of the concha. It frequently gives off a branch, which enters the skull through the mastoid foramen and supplies the dura mater. The meningeal branch ascends with the internal jugular vein, and enters the skull through the foramen lacerum posterius, to supply the dura mater in the posterior fossa. The arteria princeps cervicis (Fig. 352) is a large branch which descends along the back part of the neck and divides into a superficial and deep branch. The former runs beneath the Splenius, giving off branches which perforate that muscle to supply the Trapezius, anastomosing with the superficial cervical artery, a branch of the transversalis colli: the latter passes beneath the Complexes between it and the Semispinalis colli, and anastomoses with branches from the vertebral and with the deep cervical artery, a branch of the superior intercostal. The anastomosis between these vessels serves mainly to establish the collateral circula- tion after ligature of the carotid or subclavian artery. The cranial branches of the occipital artery are distributed upon the occiput; they are very tortuous, and lie between the integument and Occipito-frontalis, anastomosing with the artery of the opposite side, the posterior auricular and temporal arteries. They supply the back part of the Occipito-frontalis muscle, the integument, and pericranium. The Posterior Auricular Artery (Fig. 349) is a small vessel which arises from the external carotid, above the Digastric and Stylo-hyoid muscles, opposite the apex of the styloid process. It ascends, under cover of the parotid gland, to the groove between the cartilage of the ear and the mastoid process, immediately above which it divides into two branches: an anterior, auricular, passing forward to supply the back of the auricle and anastomose with the posterior division of the temporal; and a posterior, mastoid, to the scalp above and behind the ear, communicating with the occipital. Just before arriving at the mastoid process this artery is crossed by the portio dura, and has beneath it the spinal accessory nerve. Besides several small branches to the Digastric, Stylo-hyoid, and Sterno-mastoid muscles and to the parotid gland, this vessel gives off three branches: Stylo-mastoid. Auricular. Mastoid. The stylo-mastoid branch enters the stylo-mastoid foramen, and supplies the 560 THE ARTERIES. tympanum, mastoid cells, and semicircular canals. In the young subject a branch from this vessel forms, with the tympanic branch from the internal maxillary, a vascular circle, which surrounds the auditory meatus, and from which delicate vessels ramify on the membrana tympani. It anastomoses with the petrosal branch of the middle meningeal artery by a twig which enters the hiatus Fallopii. The auricular branch is distributed to the back part of the cartilage of the ear, upon which it ramifies minutely, some branches curving round the margin of the fibro-cartilage, others perforating it, to supply its anterior surface. It anastomoses with the anterior auricular branches of the temporal. The mastoid branch passes backward, over the Sterno-mastoid muscle, to the scalp above and behind the ear. It supplies the posterior belly of the Occipito-fron- talis muscle and the scalp in this situation. It anastomoses with the occipital artery. The Ascending Pharyngeal Artery (Fig. 352), the smallest branch of the external carotid, is a long, slender vessel, deeply seated in the neck, beneath the other branches of the external carotid and the Stylo-pharyngeus muscle. It arises from the back part of the external carotid, near the commencement of that vessel, and ascends vertically between the internal carotid and the side of the pharynx, to the under surface of the base of the skull, lying on the Rectus capitis anticus major. Its branches may be subdivided into three sets: The prevertebral branches are numerous small vessels which supply the Recti capitis antici and Longus colli muscles, the sympathetic, hypoglossal, and pneumogastric nerves, and the lymphatic glands of the neck, anastomosing with the ascending cervical artery. The pharyngeal branches are three or four in number. Two of these descend to supply the middle and inferior Constrictors and the Stylo-pharyngeus, ramifying in their substance and in the mucous membrane lining them. The largest of the pharyngeal branches passes inward, running upon the Superior constrictor, and sends ramifications to the soft palate and tonsil, which take the place of the ascending palatine branch of the facial artery when that vessel is of small size. A twig from this branch passes up the Eustachian tube to supply the tympanum. The meningeal branches consist of several small vessels, which pass through foramina in the base of the skull, to supply the dura mater. One, the posterior meningeal, enters the cranium through the foramen lacerum posterius; a second passes through the foramen lacerum medium ; and occasionally a third through the anterior condyloid foramen. They are all distributed to the dura mater. Surgical Anatomy.-The ascending pharyngeal artery has been wounded from the throat, as in the case in which the stem of a tobacco-pipe was driven into the vessel, causing fatal haemorrhage. The Superficial Temporal Artery (Fig. 349), the smaller of the two terminal branches of the external carotid, appears, from its direction, to be the continu- ation of that vessel. It commences in the substance of the parotid gland, in the interspace between the neck of the condyle of the lower jaw and the external meatus, crosses over the posterior root of the zygoma, passes beneath the Attra- hens aurem muscle, and divides, about two inches above the zygomatic arch, into two branches, an anterior and a posterior. The anterior temporal inclines forward over the forehead, supplying the muscles, integument, and pericranium in this region, and anastomoses with the supra-orbital and frontal arteries. The posterior temporal, larger than the anterior, curves upward and backward along the side of the head, lying superficial to the temporal fascia, and inosculates with its fellow of the opposite side, and with the posterior auricular and occipital arteries. The superficial temporal artery, as it crosses the zygoma, is covered by the Attrahens aurem muscle and by a dense fascia given off from the parotid gland: it is also usually crossed by one or two veins, and accompanied by branches of the Prevertebral. Pharyngeal. Meningeal. BRANCHES OF THE EXTERNAL CAROTID. 561 facial and auriculo-temporal nerves. Besides some twigs to the parotid gland, the articulation of the jawy, and the Masseter muscle, its branches are-the Transverse Facial. Anterior Auricular. Middle Temporal. The transverse facial is given off from the temporal before that vessel quits the parotid gland; running forward through its substance, it passes transversely across the face, between Stenson's duct and the lower border of the zygoma, and divides on the side of the face into numerous branches, which supply the parotid gland, the Masseter muscle, and the integument, anastomosing with the facial, masseteric, and infra-orbital arteries. This vessel rests on the Masseter, and is accompanied by one or two branches of the facial nerve. It is sometimes a branch of the external carotid. The middle temporal artery arises immediately above the zygomatic arch, and, perforating the temporal fascia, supplies the Temporal muscle, anastomosing with the deep temporal branches of the internal maxillary. It occasionally gives off an orbital branch, which runs along the upper border of the zygoma, between the tw'o layers of the temporal fascia, to the outer angle of the orbit. This branch supplies the Orbicularis palpebrarum, and anastomoses with the lachrymal and palpebral branches of the ophthalmic artery. The anterior auricular branches are distributed to the anterior portion of the pinna, the lobule, and part of the external meatus, anastomosing with branches of the posterior auricular. Surgical Anatomy.-It occasionally happens that the surgeon is called upon to perform the operation of arteriotomy upon this vessel in cases of inflammation of the eye or brain. If the student will consider the relations of the trunk of this vessel as it crosses the zygomatic arch with the surrounding structures, he will observe that it is covered by a thick and dense fascia, crossed by one or two veins, and accompanied by branches of the facial and auriculo-tem- poral nerves. Bleeding should not be performed in this situation, as much difficulty may arise from the dense fascia over the vessel preventing a free flow of blood, and considerable pressure is requisite afterward to repress the haemorrhage. Again, a varicose aneurism may be formed by the accidental opening of one of the veins in front of the artery, or severe neuralgic pain may arise from the operation implicating one of the nervous filaments in the neighborhood. The anterior branch, on the contrary, is subcutaneous, is a large vessel, and is readily compressed ; it should consequently always be selected for the operation. The Internal Maxillary (Fig. 350), the larger of the two terminal branches of the external carotid, passes inward, at right angles from that vessel, to the inner side of the neck of the condyle of the lower jaw, to supply the deep structures of the face. At its origin, it is imbedded in the substance of the parotid gland, being on a level with 'the lower extremity of the lobule of the ear. In the first part of its course (maxillary portion) the artery passes horizontally forward and inward, between the ramus of the jaw and the internal lateral lig- ament. The artery here lies parallel with the auriculo-temporal nerve; it crosses the inferior dental nerve, and lies along the lower border of the External pterygoid muscle. In the second part of its course (pterygoid portion) it runs obliquely forward and upward upon the outer surface of the External pterygoid muscle, being covered by the ramus of the lower jaw and low'er part of the Temporal muscle. In the third part of its course (spheno-maxillary portion) it approaches the superior maxillary bone, and enters the spheno-maxillary fossa in the interval between the two heads of the External pterygoid, where it lies in relation with Meckel's ganglion, and gives off its terminal branches. Peculiarities.-Occasionally, this artery passes between the two Pterygoid muscles. The vessel in this case passes forward to the interval between the processes of origin of the External pterygoid, in order to reach the superior maxillary bone. Sometimes the vessel escapes from beneath the External pterygoid by perforating the middle of that muscle. The branches of this vessel may be divided into three groups, corresponding with its three divisions. 562 THE ARTERIES. Branches of the First or Maxillary Portion of the Internal Max illary (Fig. 351). Tympanic (anterior). Middle Meningeal. Small Meningeal. Inferior Dental. The tympanic branch passes upward behind the articulation of the lower jaw, enters the tympanum through the Glaserian fissure, and ramifies upon the mem- --Incisior. Fig. 350.-The internal maxillary artery, and its branches. Ptery go-Palatine. I Vidian. Descending Palatine. _Spheno Palatine. Middle Meningea Parva.- Tympanic.-- Deep Temporal.\ Inferior Dental. Fig. 351.-Plan of the branches. brana tympani, forming a vascular circle around the membrane with the stylo- mastoid artery, and anastomosing with the Vidian and the tympanic branch from the internal carotid. It gives off an auricular branch to the external meatus, supplying its cuticular lining and the outer surface of the membrana tympani. The middle meningeal is the largest of the branches which supply the dura mater. It arises from the internal maxillary, between the internal lateral liga- ment and the neck of the jaw, and passes vertically upward between the two roots of the auriculo-temporal nerve to the foramen spinosum of the sphenoid bone. On entering the cranium it divides into two branches, anterior and poste- rior. The anterior branch, the larger, crosses the great ala of the sphenoid, and reaches the groove, or canal, in the anterior inferior angle of the parietal bone : it then divides into branches which spread out between the dura mater and internal surface of the cranium, some passing upward over the parietal bone as far as the vertex, and others backward to the occipital bone. The posterior branch crosses the squamous portion of the temporal, and on the inner surface of the parietal BRANCHES OF THE EXTERNAL CAROTID. 563 bone divides into branches which supply the posterior part of the dura mater and cranium. The branches of this vessel are distributed partly to the dura mater, but chiefly to the bones ; they anastomose with the arteries of the opposite side, and with the anterior and posterior meningeal. The middle meningeal on entering the cranium gives off the following collat- eral branches : 1. Numerous small vessels to the ganglion of the fifth nerve and to the dura mater in this situation; 2. A branch branch), which enters the hiatus Fallopii, supplies the facial nerve, and anastomoses with the stylo- mastoid branch of the posterior auricular artery; 3. Orbital branches, which pass through the sphenoidal fissure or through separate canals in the great wing of the sphenoid to anastomose with the lachrymal or other branches of the ophthalmic artery; 4. Temporal branches, which pass through foramina in the great wing of the sphenoid, and anastomose in the temporal fossa with the deep temporal arteries. Surgical Anatomy.-The middle meningeal is an artery of considerable surgical import- ance, as it may be injured in fractures of the temporal region of the skull, and the injury may be followed by considerable haemorrhage between the bone and dura mater, which may cause compression of the brain and require the operation of trephining for its relief. This artery crosses the anterior inferior angle of the parietal bone at a point 1| inches behind the external angular process of the frontal bone, and 1 j inches above the zygoma. From this point the ante- rior branch passes upward and slightly backward to the sagittal suture, lying about J inch to | inch behind the coronal suture. The posterior branch passes upward and backward over the squamous portion of the temporal bone. In order to expose the artery as it lies in the canal in the parietal bone, a semilunar incision, with its convexity upward, should be made, commencing an inch behind the external angular process, and carried backward for 2 inches. The structures cut through are : (1) skin ; (2) superficial fascia, with branches of the superficial temporal vessels and nerves; (3) the fascia continued down from the aponeurosis of the Occipito-frontalis; (4) the two layers of the temporal fascia; (5) the temporal muscle ; (6) the deep temporal vessels ; (7) the pericranium; and (8) the bone. The small meningeal is sometimes derived from the preceding. It enters the skull through the foramen ovale, and supplies the Gasserian ganglion and dura mater. Before entering the cranium it gives off a branch to the nasal fossa, soft palate, and tonsil. The inferior dental descends with the dental nerve to the foramen on the inner side of the ramus of the jaw. It runs along the dental canal in the substance of the bone, accompanied by the nerve, and opposite the first bicuspid tooth divides into two branches, incisor and mental; the former is continued forward beneath the incisor teeth as far as the symphysis, where it anastomoses with the artery of the opposite side; the mental branch escapes with the nerve at the mental foramen, supplies the structures composing the chin, and anastomoses with the submental, inferior labial, and inferior coronary arteries. As the dental artery enters the foramen it gives off a mylo-hyoid branch, which runs in the mylo-hyoid groove, and ramifies on the under surface of the Mylo-hyoid muscle. The dental and incisor arteries during their course through the substance of the bone give off a few twigs which are lost in the cancellous tissue, and a series of branches which correspond in number to the roots of the teeth : these enter the minute apertures at the extremities of the fangs and supply the pulp of the teeth. Branches of the Second or Pterygoid Portion of Internal Maxillary. Deep Temporal. Pterygoid. Masseteric. Buccal. These branches are distributed, as their names imply, to the muscles in the maxillary region. The deep temporal branches, two in number, anterior and posterior, each occupy that part of the temporal fossa indicated by its name. Ascending between the Temporal muscle and pericranium, they supply that muscle and anastomose with the other temporal arteries, the anterior branch communicating with the lachrymal through small branches which perforate the malar bone and great wing of the sphenoid. 564 THE ARTERIES. The pterygoid branches, irregular in their number and origin, supply the Pterygoid muscles. The masseteric is a small branch which passes outward, above the sigmoid notch of the lower jaw, to the deep surface of the Masseter. It supplies that muscle, and anastomoses with the masseteric branches of the facial and with the transverse facial artery. The buccal is a small branch which runs obliquely forward between the Internal pterygoid and the ramus of the jaw, to the outer surface of the Buccinator, to which it is distributed, anastomosing with branches of the facial artery. Branches of the Third or Spheno-maxillary Portion of Internal Maxillary. Alveolar. Infra-orbital. Posterior or Descending Palatine. Vidian. Pterygo-palatine. Naso- or Spheno-palatine. The alveolar or posterior dental branch is given off from the internal maxillary by a common branch with the infra-orbital, and just as the trunk of the vessel is passing into the spheno-maxillary fossa. Descending upon the tuberosity of the superior maxillary bone, it divides into numerous branches, some of which enter the posterior dental canals, to supply the molar and bicuspid teeth and the lining of the antrum, and others are continued forward on the alveolar process to supply the gums. The infra-orbital appears, from its direction, to be the continuation of the trunk of the internal maxillary. It arises from that vessel by a common trunk with the preceding branch, and runs along the infra-orbital canal with the superior maxil- lary nerve, emerging upon the face at the infra-orbital foramen, beneath the Levator labii superioris. Whilst contained in the canal, it gives off branches which ascend into the orbit, and supply the Inferior rectus and Inferior oblique muscles and the lachrymal gland. Other branches {anterior dental) descend through canals in the bone to supply the mucous membrane of the antrum and the front teeth of the upper jaw. On the face some branches pass inward toward the nose, anasto- mosing with the angular branch of the facial artery and nasal branch of the ophthalmic; and other branches descend beneath the Levator labii superioris and anastomose with the transverse facial and buccal branches. The four remaining branches arise from that portion of the internal maxillary which is contained in the spheno-maxillary fossa. The descending palatine passes down the posterior palatine canal with the anterior palatine branch of Meckel's ganglion, and, emerging from the posterior palatine foramen, runs forward in a groove on the inner side of the alveolar border of the hard palate to the anterior palatine canal, where the terminal branch of the artery passes upward through the foramen of Stenson to anastomose with the naso-palatine artery. Its branches are distributed to the gums, the mucous membrane of the hard palate, and the palatine glands. Whilst it is contained in the palatine canal it gives off branches, which descend in the accessory palatine canals to supply the soft palate and tonsil, anastomosing with the ascending palatine artery. The Vidian branch passes backward along the Vidian canal with the Vidian nerve. It is distributed to the upper part of the pharynx and Eustachian tube, sending a small branch into the tympanum, which anastomoses with the anterior tympanic. The pterygo-palatine is also a very small branch, which passes backward through the pterygo-palatine canal with the pharyngeal nerve, and is distributed to the upper part of the pharynx and Eustachian tube. The spheno-palatine passes through the spheno-palatine foramen into the cavity of the nose, at the back part of the superior meatus, and divides into two branches: one internal, the naso-palatine or superior artery of the septum, passes THE ANTERIOR TRIANGLE OE THE NECK. 565 obliquely downward and forward along the septum nasi, supplies the mucous membrane, and anastomoses in front with the terminal branch of the descending palatine. The external branches, two or three in number, supply the mucous membrane covering the lateral wall of the nose, the antrum, and the ethmoid and sphenoid cells. SURGICAL ANATOMY OF THE TRIANGLES OF THE NECK. The student having considered the relative anatomy of the large arteries of the neck and their branches, and the relations they bear to the veins and nerves, should now examine these structures collectively, as they present themselves in certain regions of the neck, in each of which important operations are constantly being performed. The side of the neck presents a somewhat quadrilateral outline, limited, above, by the lower border of the body of the jaw, and an imaginary line extending from the angle of the jaw to the mastoid process ; below, by the prominent upper border of the clavicle ; in front, by the median line of the neck; behind, by the anterior margin of the Trapezius muscle. This space is subdivided into two large triangles by the Sterno-mastoid muscle, which passes obliquely across the neck, from the sternum and clavicle below to the mastoid process above. The triangular space in front of this muscle is called the anterior triangle ; and that behind it, the posterior triangle. Anterior Triangle of the Neck. The anterior triangle is bounded, in front, by a line extending from the chin to the sternum; behind, by the anterior margin of the Sterno-mastoid; its base, directed upward, is formed by the lower border of the body of the jaw and a line extending from the angle of the jaw to the mastoid process; its apex is below, at the sternum. This space is subdivided into three smaller triangles by the Digastric muscle above and the anterior belly of the Omo-hyoid below. These smaller triangles are named, from below upward, the inferior carotid, the superior carotid, and the submaxillary triangle. The Inferior Carotid Triangle is bounded, in front, by the median line of the neck ; behind, by the anterior margin of the Sterno-mastoid ; above, by the anterior belly of the Omo-hyoid ; and is covered by the integument, superficial fascia, Platysma, and deep fascia, ramifying between which is the descending branch of the superficialis colli nerve. Beneath these superficial structures are the Sterno- hyoid and Sterno-thyroid muscles, which, together with the anterior margin of the Sterno-mastoid, conceal the lower part of the common carotid artery.1 This vessel is enclosed within its sheath, together with the internal jugular vein and pneumogastric nerve; the vein lying on the outer side of the artery on the right side of the neck, but overlapping it, or passing directly across it on the left side; the nerve lying between the artery and vein, on a plane posterior to both. In front of the sheath are a few filaments descending from the loop of com- munication between the descendens and communicans hypoglossi; behind the sheath are seen the inferior thyroid artery, the recurrent laryngeal nerve, and the sym- pathetic nerve; and on its inner side, the trachea, the thyroid gland-much more prominent in the female than in the male-and the lower part of the larynx. By cut- ting into the upper part of this space and slightly displacing the Sterno-mastoid muscle the common carotid artery may be tied below the Omo-hyoid muscle. The floor of the inferior carotid triangle is formed by the Longus colli muscle below, by the Scalenus anticus above (see Fig. 284, page 426), between which 1 Therefore the common carotid artery and internal jugular vein are not, strictly speaking, con- tained in this triangle, since they are covered by the Sterno-mastoid muscle; that is to say, lie behind the anterior border of that muscle, which forms the posterior border of the triangle. But as they lie very close to the structures which are really contained in the triangle, and whose position it is essential to remember in operating on this part of the artery, it has seemed expedient to study the relations of all these parts together. 566 THE ARTERIES. muscles the vertebral artery and vein will be found passing into the foramen in the sixth transverse process ; a small portion of the origin of the Rectus capitis anticus major may also be seen in the floor of the, space. The Superior Carotid Triangle is bounded, behind, by the Sterno-mastoid; below, by the anterior belly of the Omo-hyoid; and above, by the posterior belly of the Digastric muscle. It is covered by the integument, superficial fascia, Platysma, and deep fascia, ramifying between which are branches of the facial and superficialis colli nerves. Its floor is formed by parts of the Thyro-hyoid, Hyo-glossus, and the inferior and middle Constrictor muscles of the pharynx. This space contains the upper part of the common carotid artery, which bifurcates opposite the upper border of the thyroid cartilage into the external and internal carotid. These vessels are occasionally somewhat concealed from view by the anterior margin of the Sterno-mastoid muscle, which overlaps them. The external and internal carotids lie side by side, the external being the more anterior of the two. The following branches of the external carotid are also met with in this space: the superior thyroid, running forward and downward; the lingual, directly forward; the facial, forward and upward; the occipital, backward; and the ascending pharyngeal directly upward on the inner side of the internal carotid. The veins met with are: the internal jugular, which lies on the outer side of the common and internal carotid arteries, and veins corresponding to the above-mentioned branches of the external carotid-viz. the superior thyroid, the lingual, facial, ascending pharyngeal, and sometimes the occipital,-all of which accompany their corresponding arteries and terminate in the internal jugular. The nerves in this space are the following: In front of the sheath of the common carotid is the descendens hypoglossi. The hypoglossal nerve crosses both carotids above, curving round the occipital artery at its origin. Within the sheath, between the artery and vein, and behind both, is the pneumogastric nerve; behind the sheath, the sympathetic. On the outer side of the vessels the spinal accessory nerve runs for a short distance before it pierces the Sterno-mastoid muscle ; and on the inner side of the external carotid, just below the hyoid bone, may be seen the superior laryngeal nerve; and, still more inferiorly, the external laryngeal nerve. The upper part of the larynx and lower part of the pharynx are also found in the front part of this space. The Submaxillary Triangle corresponds to the part of the neck immediately beneath the body of the jaw. It is bounded, above, by the lower border of the body of the jaw and a line drawn from its angle to the mastoid process; below, by the posterior belly of the Digastric and Stylo-hyoid muscles; in front, by the middle line of the neck. It is covered by the integument, superficial fascia, Pla- tysma, and deep fascia, ramifying between which are branches of the facial and ascending filaments of the superficial cervical nerves. Its floor is formed by the anterior belly of the Digastric, the Mylo-hyoid, and the Hyo-glossus muscles. This space contains, in front, the submaxillary gland, imbedded in the substance of which are the facial artery and vein and their glandular branches; beneath this gland, on the surface of the Mylo-hyoid muscle, are the submental artery and the mylo-hyoid artery and nerve. The back part of this space is separated from the front part by the stylo-maxillary ligament: it contains the external carotid artery, ascending deeply in the substance of the parotid gland: this vessel here lies in front of, and superficial to, the internal carotid, being crossed by the facial nerve, and gives off in its course the posterior auricular, temporal, and internal maxil- lary branches: more deeply are the internal carotid, the internal jugular vein, and the pneumogastric nerve, separated from the external carotid by the Stylo- glossus and Stylo-pharyngeus muscles and the glosso-pharyngeal nerve.1 1 The same remark will apply to this triangle as was made about the inferior carotid triangle. The structures enumerated as contained in the back part of the space lie, strictly speaking, beneath the muscles which form the posterior boundary of the triangle; but as it is very important to bear in mind their close relation to the parotid gland and its boundaries (on account of the frequency of sur- gical operations on this gland), all these parts are spoken of together. THE INTERNAL CAROTID ARTERY. 567 Posterior Triangle of the Neck. The posterior triangle is bounded, in front, by the Sterno-mastoid muscle; behind, bv the anterior margin of the Trapezius; its base corresponds to the upper border of the clavicle; its apex, to the occiput. The space is crossed, about an inch above the clavicle, by the posterior belly of the Omo-hyoid, which divides it unequally into two, an upper or occipital and a lower or subclavian triangle. The Occipital, the larger of the two posterior triangles, is bounded, in front, by the Sterno-mastoid ; behind, by the Trapezius ; below, by the Omo-hyoid. Its floor is formed from above downward by the Splenius, Levator anguli scapulae, and the middle and posterior Scaleni muscles. It is covered by the integument, the Platysma below, the superficial and deep fasciae, and by the spinal acces- sorv nerve, which is directed obliquely across the space from the Sterno-mastoid, which it pierces, to the under surface of the Trapezius; below, the descending branches of the cervical plexus and the transversalis colli artery and vein cross the space. A chain of lymphatic glands is also found running along the pos- terior border of the Sterno-mastoid, from the mastoid process to the root of the neck. The Subclavian, the smaller of the two posterior triangles, is bounded, above, by the posterior belly of the Omo-hyoid; below, by the clavicle, its base, directed forward, being formed by the Sterno-mastoid. The size of the subclavian trian- gle varies according to the extent of attachment of the clavicular portion of the Sterno-mastoid and Trapezius muscles, and also according to the height at which the Omo-hyoid crosses the neck above the clavicle. Its height also varies much according to the position of the arm, being much diminished by raising the limb, on account of the ascent of the clavicle, and increased by drawing the arm down- ward, when that bone is depressed. This space is covered by the integument, superficial and deep fasciae, and crossed by the descending branches of the cervical plexus. Just above the level of the clavicle the third portion of the subclavian artery curves outward and downward from the outer margin of the Scalenus anticus, across the first rib, to the axilla. Sometimes this vessel rises as high as an inch and a half above the clavicle, or to any point intermediate between this and its usual level. Occasionally, it passes in front of the Scalenus anticus or pierces the fibres of that muscle. The subclavian vein lies behind the clavicle, and is usually not seen in this space; but it occasionally rises as high up as the artery, and has even been seen to pass with that vessel behind the Scalenus anticus. The brachial plexus of nerves lies above the artery, and in close contact with it. Passing transversely across the clavicular margin of the space are the suprascapular vessels, and traversing its upper angle in the same direction, the transversalis colli artery and vein. The external jugular vein runs vertically downward behind the posterior border of the Sterno-mastoid, to terminate in the subclavian vein; it receives the transverse cervical and suprascapular veins, which occasionally form a plexus in front of the artery, and a small vein which crosses the clavicle from the cephalic. The small nerve to the Subclavius muscle also crosses this triangle about its middle. A lymphatic gland is also found in the space. Its floor is formed by the first rib with the first digitation of the Serratus magnus. The Internal Carotid Artery. The internal carotid artery supplies the anterior part of the brain, the eye, and its appendages, and sends branches to the forehead and nose. Its size in the adult is equal to that of the external carotid, though in the child it is larger than that vessel. It is remarkable for the number of curvatures that it presents in different parts of its course. In its cervical portion it occasionally presents one or two flexures near the base of the skull, whilst through the rest of its extent it describes a double curvature which resembles the italic letter s placed horizon- tally. These curvatures most probably diminish the velocity of the current of 568 THE ARTERIES. blood, by increasing the extent of surface over which it moves and adding to the amount of impediment produced from friction. In considering the course and relations of this vessel it may be conveniently divided into four portions: a cervical, petrous, cavernous, and cerebral. Cervical Portion.-This portion of the internal carotid commences at the bifur- cation of the common carotid, opposite the upper border of the thyroid cartilage, and runs perpendicularly upward, in front of the transverse processes of the three upper cervical vertebrae, to the carotid canal in the petrous portion of the temporal bone. It is superficial at its commencement, being contained in the superior carotid triangle, and lying on the same level as the external carotid, but behind that artery overlapped by the Sterno-mastoid and covered by the deep fascia, Platysma, and integument: it then passes beneath the parotid gland, being crossed by the hypoglossal nerve, the Digastric and Stylo-hyoid muscles, and the external carotid and occipital arteries. Higher up, it is separated from the external carotid by the Stylo-glossus and Stylo-pharyngeus muscles, the glosso-pharyngeal nerve, and pharyngeal branch of the pneumogastric. It is in relation, behind, with the Rectus capitis anticus major, the superior cervical ganglion of the sympathetic, and superior laryngeal nerve; externally, with the internal jugular vein and pneu- mogastric nerve ; internally, with the pharynx, tonsil, the superior laryngeal nerve, and ascending pharyngeal artery. Petrous Portion.-When the internal carotid artery enters the canal in the petrous portion of the temporal bone, it first ascends a short distance, then curves forward and inward, and again ascends as it leaves the canal to enter the cavity of the skull. In this canal the artery lies at first anterior to the tympanum, from which it is separated by a thin, bony lamella, which is cribriform in the young subject, and often absorbed in old age. It is separated from the bony wall of the carotid canal by ajirolongation of dura mater, and is surrounded by filaments of the carotid plexus. Cavernous Portion.-The internal carotid artery in this part of its course is situated between the layers of the dura mater forming the cavernous sinus, but covered by the lining membrane of the sinus. It at first ascends to the posterior clinoid process, then passes forward by the side of the body of the sphenoid bone, and again curves upward on the inner side of the anterior clinoid process, ami perforates the dura mater forming the roof of the sinus. In this part of its course it is surrounded by filaments of the sympathetic nerve, and has in relation with it externally the sixth nerve. Cerebral Portion.-Having perforated the dura mater on the inner side of the anterior clinoid process, the internal carotid enters the inner extremity of the fissure of Sylvius, where it gives off its terminal or cerebral branches. This portion of the artery has the optic nerve on its inner side, and the third nerve externally. Plan of the Relations of the Internal Carotid Artery in the Neck. In front. Skin, superficial and deep fasciae. Platysma. Sterno-niastoid. External carotid and occipital arteries. Hypoglossal nerve. Parotid gland. Stylo-glossus and Stylo-pharyngeus muscles. Glosso-pharyngeal nerve. Pharyngeal branch of the pneumogastric. Externally. Internal jugular vein. Pneumogastric nerve. Internal Carotid Artery. Internally. Pharynx. Superior laryngeal nerve. Ascending pharyngeal artery. Tonsil. THE INTERNAL CAROTID ARTERY. 569 Behind. Rectus capitis anticus major. Sympathetic. Superior laryngeal nerve. Peculiarities.-The length of the internal carotid varies according to the length of the neck, and also according to the point of bifurcation of the common carotid. Its origin some- Fig. 352.-The internal carotid and vertebral arteries. Right side. times takes place from the arch of the aorta ; in such rare instances this vessel has been found to be placed nearer the middle line of the neck than the external carotid, as far upward as the larynx, when the latter vessel crossed the internal carotid. The course of the vessel, instead of being straight, may be very tortuous. A few instances are recorded in which this vessel was altogether absent: in one of these the common carotid passed up the neck, and gave off the usual branches of the external carotid, the cranial portion of the internal carotid being replaced by two branches of the internal maxillary, which entered the skull through the foramen rotundum and ovale and joined to form a single vessel. 570 THE ARTERIES. Surgical Anatomy.-The cervical part of the internal carotid is very rarely wounded. Mr. Cripps, in an interesting paper in the Medico-Chirurgical Transactions, compares the rare- ness of a wound of the internal carotid with one of the external or its branches. It is, however, sometimes injured by a stab or gunshot wound in the neck, or even occasionally by a stab from within the mouth, as when a person receives a thrust from the end of a parasol or falls down with a tobacco-pipe in his mouth. The relation of the internal carotid with the tonsil should be especially remembered, as instances have occurred in which the artery has been wounded during the operation of scarifying the tonsil, and fatal haemorrhage has supervened. The indications for ligature are wounds, when the vessel should be exposed by a careful dissection and tied above and below the bleeding point; and aneurism, which if non-traumatic may be treated by ligature of the common carotid, but if traumatic in origin by exposing the sac and tying the vessel above and below. The incision for ligature of the cervical portion of the internal carotid should be made along the anterior border of the Sterno-mastoid, from the angle of the jaw to the upper border of the thyroid cartilage. The superficial structures being divided and the Sterno-mastoid defined and drawn outward, the cellular tissue must be carefully separated and the posterior belly of the Digastric and hypoglossal nerve sought for as guides to the vessel. When the artery is found the external carotid should be drawn inward and the Digastric muscles upward, and the aneurism needle passed from without inward. The branches given off from the internal carotid are- From the Petrous portion . Tympanic (internal or deep). Arteriae Receptaculi. Anterior Meningeal. Ophthalmic. From the, Cavernous portion Anterior Cerebral. Middle Cerebral. Posterior Communicating. Anterior Choroid. From the Cerebral portion The cervical portion of the internal carotid gives off no branches. The tympanic is a small branch which enters the cavity of the tympanum through a minute foramen in the carotid canal, and anastomoses with the tympanic branch of the internal maxillary, and with the stylo-mastoid artery. The arteriae receptaculi are numerous small vessels, derived from the internal carotid in the cavernous sinus; they supply the pituitary body, the Gasserian ganglion, and the walls of the cavernous and inferior petrosal sinuses. Some of these branches anastomose with branches of the middle meningeal. The anterior meningeal is a small branch which passes over the lesser wing of the sphenoid to supply the dura mater of the anterior fossa; it anastomoses with the meningeal branch from the posterior ethmoidal artery. The Ophthalmic Artery arises from the internal carotid, just as that vessel is emerging from the cavernous sinus, on the inner side of the anterior clinoid process, and enters the orbit through the optic foramen, below and on the outer side of the optic nerve. It then passes over the nerve to the inner wall of the orbit, and thence horizontally forward, beneath the lower border of the Superior oblique muscle, to a point behind the internal angular process of the frontal bone, where it divides into two terminal branches, the/rontoZ and nasal. Branches.-The branches of this vessel may be divided into an orbital group, which are distributed to the orbit and surrounding parts, and an ocular group, which supply the muscles and globe of the eye: Orbital Group. Lachrymal. Supra-orbital. Posterior Ethmoidal. Anterior Ethmoidal. Palpebral. Frontal. Nasal. Ocular Group. Muscular. Anterior Ciliary. Short Ciliary. Long Ciliary. Arteria Centralis Retinae. The lachrymal is the first and one of the largest branches derived from the ophthalmic, arising close to the optic foramen: not unfrequently it is given off' BRANCHES OF THE INTERNAL CAROTID. 571 from the artery before it enters the orbit. It accompanies the lachrymal nerve along the upper border of the External rectus muscle, and is distributed to the lachrymal gland. Its terminal branches, escaping from the gland, are distributed to the eyelids and conjunctiva, anastomosing with the palpebral arteries. The lachrymal artery gives off one or two malar branches, one of which passes through a foramen in the malar bone, to reach the temporal fossa, and anastomoses with the deep temporal arteries; the other appears on the cheek and anastomoses with Nasal. Palpebral. I Frontal. Supra-orbital. Anterior ethmoidal. Posterior ethmoidal. j-A rteri<v**-J centralis retina. -Lachrymal. Temporal branches of lachrymal. Muscular. ■Ophthalmic. Internal carotid. Fig. 353.-The ophthalmic artery and its branches, the roof of the orbit having been removed, the transverse facial. A branch is also sent backward through the sphenoidal fissure to the dura mater, which anastomoses with a branch of the middle menin- geal artery. Peculiarities.-The lachrymal artery is sometimes derived from one of the anterior branches of the middle meningeal artery. The supra-orbital artery arises from the ophthalmic as that vessel is crossing over the optic nerve. Ascending so as to arise above all the muscles of the orbit, it passes forward, with the supra-orbital nerve, between the periosteum and Levator palpebrae; and, passing through the supra-orbital foramen, divides into a superficial and deep branch, which supply the integument, the muscles, and the pericranium of the forehead, anastomosing with the frontal, the anterior branch of the temporal, and the artery of the opposite side. This artery in the orbit supplies the Superior rectus and the Levator palpebrae, and sends a branch inward, across the pulley of the Superior oblique muscle, to supply the parts at the inner canthus. At the supra-orbital foramen it frequently transmits a branch to the diploe. The ethmoidal branches are two in number-posterior and anterior. The former, which is the smaller, passes through the posterior ethmoidal foramen, supplies the posterior ethmoidal cells, and, entering the cranium, gives off a meningeal branch, which supplies the adjacent dura mater, and nasal branches which descend into the nose through apertures in the cribriform plate, anasto- 572 THE ARTERIES. mosing with branches of the spheno-palatine. The anterior ethmoidal artery accompanies the nasal nerve through the anterior ethmoidal foramen, supplies the anterior ethmoidal cells and frontal sinuses, and, entering the cranium, gives off a meningeal branch, which supplies the'adjacent dura mater, and nasal branches, which descend into the nose, through apertures in the cribriform plate. The palpebral arteries, two in number, superior and inferior, arise from the ophthalmic, opposite the pulley of the Superior oblique muscle; they leave the orbit to encircle the eyelids near their free margin, forming a superior and an inferior arch, which lie between the Orbicularis muscle and tarsal plates; the superior palpebral inosculating at the outer angle of the orbit with the orbital branch of the temporal artery, and with a branch from the lachrymal artery-the inferior palpebral inosculating, at the outer angle of the orbit with a branch from the lachrymal and transverse facial arteries, and at the inner side of the lid with a branch from the angular artery. From this anastomosis a branch passes to the nasal duct, ramifying in its mucous membrane, as far as the inferior meatus. The frontal artery, one of the terminal branches of the ophthalmic, passes from the orbit at its inner angle, and, ascending on the forehead, supplies the integument, muscles, and pericranium, anastomosing with the supraorbital artery and with the artery of the opposite side. The nasal artery, the other terminal branch of the ophthalmic, emerges from the orbit above the tendo oculi, and, after giving a branch to the upper part of the lachrymal sac, divides into two branches, one of which anastomoses with the angular artery; the other, the dorsalis nasi, runs along the dorsum of the nose, supplies its entire surface, and anastomoses with the artery of the opposite side. The ciliary arteries are divisible into three groups, the short, the long, and ante- rior. The short ciliary arteries, from six to twelve in number, arise from the ophthal- mic or some of its branches ; they surround the optic nerve as they pass forward to the posterior part of the eyeball, pierce the sclerotic coat around the entrance of the nerve, and supply the choroid coat and ciliary processes. The long ciliary arteries, two in number, also pierce the posterior part of the sclerotic, and run forward, along each side of the eyeball, between the sclerotic and choroid, to the ciliary muscle, where they divide into twro branches ; these form an arterial circle around the circumference of the iris, from which numerous radiating branches pass forw ard, in its substance, to its free margin, where they form a second arterial circle around its pupillary margin. The anterior ciliary arteries are derived from the muscular branches; they pierce the sclerotic a short distance from the cornea, and terminate in the great arterial circle of the iris. The arteria centralis retinae is one of the smallest branches of the ophthalmic artery. It arises from the ophthalmic as that vessel is about to cross over the optic nerve ; it pierces the optic nerve obliquely, and runs forward in the centre of its substance, and enters the globe of the eye through the porus opticus. Its mode of distribution will be described in the account of the anatomy of the eye. The muscular branches, two in number, superior and inferior, supply the mus- cles of the eyeball. The superior, the smaller, often wanting, supplies the Levator palpebrse, Superior rectus, and Superior oblique. The inferior, more constant in its existence, passes forward between the optic nerve and Inferior rectus, and is distributed to the External, Internal, and Inferior recti, and Inferior oblique. This vessel gives off most of the anterior ciliary arteries. The cerebral branches of the internal carotid are-the anterior cerebral, the middle cerebral, the posterior communicating, and the anterior choroid. The anterior cerebral arises from the internal carotid at the inner extremity of the fissure of Sylvius. It passes forward in the great longitudinal fissure between the two anterior lobes of the brain, being connected, soon after its origin, with the vessel of the opposite side by a short anastomosing trunk, about two lines in length, the anterior communicating. The two anterior cerebral arteries, lying side by side, curve round the anterior border of the corpus callosum, and run along its BRANCHES OF THE INTERNAL CAROTID. 573 upper surface to its posterior part, where they terminate by anastomosing with the posterior cerebral arteries. In their course they give off the following branches: Antero-median and Ganglionic. Anterior and Internal Frontal. Middle and Internal Frontal. Posterior and Internal Frontal. Longitudinal Fissure. Fig. 354.-The arteries of the base of the brain. The right half of- the cerebellum and pons have been removed. N.B.-It will be noticed that in the illustration the two anterior cerebral arteries have been drawn at a considerable distance from each other: this makes the anterior communicating artery appear very much longer than it really is. The antero-median ganglionic is a group of small arteries which arise at the 574 THE ARTERIES. commencement of the anterior cerebral artery ; they pierce the anterior perforated space and lamina cinerea,' and supply the head of the caudate nucleus. The anterior and internal frontal branches supply the two inferior frontal convolutions. The middle and internal frontal branches supply the corpus callosum, the convolution of the corpus callosum, the inner surface of the first frontal convolution, and the upper part of the ascending frontal convolution. The posterior and internal frontal branches supply the lobus quadratus. The anterior communicating artery is a short branch, about two lines in length, but of moderate size, connecting together the two anterior cerebral Fig. 355.-Vascular area: of the internal surface of the cerebrum. (After Charcot.) The regions marked off by the line ( ) represent the area of distribution of the anterior cerebral artery: I. Anterior and internal frontal arteries. II. Middle and internal frontal arteries. III. Posterior and internal frontal arteries. The regions marked off by the line ( ) represent the area of distribution of the posterior cerebral arteries : IV. to the temporo-sphenoidal lobe; V. to the cuneus and occipital lobe ; a third branch supplies the uncinate gyrus. arteries across the longitudinal fissure. Sometimes this vessel is wanting, the two arteries joining together to form a single trunk, which afterward divides. Or the vessel may be wholly or partially divided into two; frequently it is longer and smaller than usual. It gives off' some of the antero-median ganglionic group of vessels, which are, however, principally derived from the anterior cerebral. The middle cerebral artery (Fig. 356), the largest branch of the internal car- otid, passes obliquely outward along the fissure of Sylvius, and opposite the island of Reil divides into its terminal branches. The branches of the middle cerebral artery are- Antero-lateral Ganglionic. External and Inferior Frontal. Ascending Frontal. Ascending Parietal. Parieto-sphenoidal. The antero-lateral ganglionic branches are a group of small arteries which arise at the commencement of the middle cerebral artery ; they pierce the ante- rior perforated space and supply the greater part of the caudate nucleus, the len- ticular nucleus, the internal capsule, and a part of the optic thalamus. One artery of this group, distributed to the lenticular nucleus, is of larger size than the rest, and is of special importance, as being the artery in the brain most fre- quently ruptured; it has been termed by Charcot the " artery of cerebral hcemor- rhage." The external and inferior frontal supplies the third or inferior frontal convolution (Broca's convolution). The ascending frontal supplies the ascending frontal convolution. The ascending parietal supplies the ascending parietal con- THE BLOOD-VESSELS OF THE BRAIN. 575 volution. The parieto-sphenoidal supplies the superior temporo-sphenoidal con- volution and the angular gyrus. The posterior communicating artery arises from the back part of the internal carotid, runs directly backward, and anastomoses with the posterior cerebral, a FISSURE OF ROLANDO. Perforating Branches. , Middle Cerebral Artery. Fig. 356.-The distribution of the middle cerebral artery. (After Charcot.) branch of the basilar. This artery varies considerably in size, being sometimes small, and occasionally so large that the posterior cerebral may be considered as arising from the interna] carotid rather than from the basilar. It is frequently larger on one side than on the other side. From the posterior half of this vessel are given oft' a number of small branches, the postero-median ganglionic branches, which, with similar vessels from the posterior cerebral, pierce the posterior perfo- rated space and supply the internal surfaces of the optic thalami and the walls of the third ventricle. The anterior choroid is a small but constant branch which arises from the back part of the internal carotid, near the posterior communicating artery. Passing backward and outward, it enters the descending horn of the lateral ven- tricle beneath the edge of the middle lobe of the brain. It is distributed to the hippocampus major, corpus fimbriatum, velum interpositum, and choroid plexus. Recent investigations have tended to show that the mode of distribution of the vessels of the brain has an important bearing upon a considerable number of the anatomical lesions of which this part of the nervous system may be the seat; it therefore becomes important to consider a little more in detail the way in which the cerebral vessels are distributed. The cerebral arteries are derived from the internal carotid and the vertebral, which at the base of the brain form a remarkable anastomosis known as the circle of Willis. It is formed in front by the anterior cerebral arteries, branches of the internal carotid, which are connected together by the anterior communicating; behind by the two posterior cerebrals, branches of the basilar which are connected on each side with the internal carotid by the posterior communicating (Fig. 354, p. 573). The parts of the brain included within this arterial circle are the lamina cinerea, the commissure of the optic nerves, the infundibulum, the tuber cinereum, the corpora albicantia, and the posterior perforated space. From the circle of Willis arise the three trunks which together supply each cerebral hemisphere. From its anterior part proceed the two anterior cerebrals, from its antero-lateral part the middle cerebral, and from its posterior part the The Blood-vessels of the Brain. 576 THE ARTERIES. posterior cerebrals. Each of these principal arteries gives origin to two very different systems of secondary vessels. One of these systems has been named the central ganglionic system, and the vessels belonging to it supply the central ganglia of the brain ; the other has been named the cortical arterial system, and its vessels ramify in the pia mater and supply the cortex and subjacent medullary matter. These two systems, though they have a common origin, do not communicate at anv point of their peripheral distribution, and are entirely independent of each other. Though some of the arteries of the cortical system approach, at their terminations, the regions supplied by the central ganglionic system, no communication between the two sets of vessels takes place, and there is between the parts supplied by the two systems a borderland of diminished nutritive activity, where, it is said, softening is especially liable to occur in the brains of old people. The Central Ganglionic System.-All the vessels belonging to this system are given off from the circle of Willis or from the vessels immediately after their origin --Anterior cerebral artery. /Internaf'carotid artery. \ Middle cerebral artery. I /Posterior cerebral artery. \Vertebral artery. Fig. 357.-Diagram of the arterial circulation at the base of the brain. (After Charcot.) I. Antero-median group of ganglionic branches. II. Postero-median group. III. Right and left antero-lateral group. IV. Right and left postero-lateral group. The dotted line shows the limit of the ganglionic circle. from it, so that if a circle is drawn at a distance of about an inch from the circle of Willis, it will include the origin of all the arteries belonging to this system (Fig. 357). The vessels of this system form six principal groups : (I.) the antero-median group, derived from the anterior cerebrals and anterior communicating; (II.) the po»tero-median group, from the posterior cerebrals and posterior communicating; (HL) the right and left antero-lateral group, from the middle cerebrals: and (IV.) the right and left postero-lateral group, from the posterior cerebrals, after they have wound round the crura cerebri. The vessels belonging to this system are larger than those of the cortical system, and are what Cohnheim has termed " terminal " arteries; that is to say, vessels which from their origin to their termination neither supply nor receive any anastomotic branch, so that by one of the small vessels only a limited area of the central ganglia can be injected ; and the injection cannot be driven beyond the area of the part supplied by the particular vessel which is the subject of the experiment. The Cortical Arterial System.-The vessels forming this system are the terminal branches of the anterior, middle, and posterior cerebral arteries, described above. THE ARTERIES OF THE UPPER EXTREMITY. 577 These vessels divide and ramify in the substance of the pia mater, and give off nutrient arteries which penetrate the cortex perpendicularly. These nutrient vessels are divisible into two classes-the long and short. The long-or, as they are some- times called, the medullary-arteries pass through the gray matter to penetrate the centrum ovale to the depth of about an inch and a half, without intercommunica- ting otherwise than by very fine capillaries, and thus constitute so many independ- Fig. 358.-Distribution of the cortical arteries. (After Charcot.) 1. Medullary arteries. 1'. Group of medullary arteries in the sulcus between two adjacent convolutions. 1". Arteries situated among Gratiolet's commis- sural fibres. 2, 2. Cortical arteries, a. Capillary network with fairly wide meshes, situated beneath the pia mater, b. Network with more compact, polygonal meshes, situated in the cortex, c. Transitional network with wider meshes, d. Capillary network in the white matter. ent small systems. The short vessels are confined to the cortex, where they form with the long vessels a compact network in the middle zone of the gray matter, the outer and inner zones being sparingly supplied with blood (Fig. 358). The vessels of the cortical arterial system are not so strictly "terminal" as those of the central ganglionic system, but they approach this type very closely, so that injec- tion of one area from the vessel of another area, though it may be possible, is frequently very difficult, and is only effected through vessels of small calibre. As a result of this, obstruction of one of the main branches or its divisions may have the effect of producing softening in a very limited area of the cortex.1 ARTERIES OF THE UPPER EXTREMITY. The artery which supplies the upper extremity continues as a single trunk from its commencement down to the elbow, but different portions of it have received different names according to the region through which it passes. That part of the vessel which extends from its origin to the lower border of the first rib is termed the subclavian; beyond this point to the lower border of the axilla it is termed the axillary; and from the lower margin of the axillary space to the bend of the elbow it is termed brachial; here the single trunk terminates by dividing into two branches, the radial and ulnar-an arrangement precisely similar to what occurs in the lower limb. 1 The student who desires further information on this subject is referred to Charcot's Localization of Cerebral and Spinal Diseases, p. 42 et seq., whence the facts above given have been principally derived. 578 THE ARTERIES. THE SUBCLAVIAN ARTERIES (Fig. 359). , The subclavian artery on the right side arises from the innominate artery opposite the right sterno-clavicular articulation ; on the left side it arises from the arch of the aorta. It follows, therefore, that these two vessels must, in the first part of their course, differ in their length, their direction, and their relation with neighboring parts. In order to facilitate the description of these vessels, more especially from a Phrenic nerve. / Vertebral artery. t i Inferior thyroid artery. Supra-scapular artery. Supra-scapular nerve.' Pneumogastric y nerve. - Subclavian artery. v -.Int. mammary artery. , Innominate vein. .Innominate artery. Musculo-cutaneous i nerve. / -Subscapular artery. \ Profunda artery. Fig. 359.-The subclavian artery, showing its relations. (From a preparation in the Museum of the Royal College of Surgeons.) surgical point of view, each subclavian artery has been divided into three parts. The first portion, on the right side, passes upward and outward from the origin of the vessel to the inner border of the Scalenus anticus. On the left side it ascends nearly vertically, to gain the inner border of that muscle. The second part passes outward, behind the Scalenus anticus; and the third part passes from the outer margin of that muscle, beneath the clavicle, to the lower border of the first rib, where it becomes the axillary artery. The first portion of these two vessels differs so much in its course and in its relation with neighboring parts that it will be described separately. The second and third parts are alike on the two sides. THE SUBCLAVIAN ANTE HIES. 579 First Part of the Right Subclavian Artery (Figs. 344, 359). The right subclavian artery arises from the arteria innominata, opposite the right sterno-clavicular articulation, and passes upward and outward to the inner margin of the Scalenus anticus muscle. In this part of its course it ascends a little above the clavicle, the extent to which it does so varying in different cases. It is covered, in front, by the integument, superficial fascia, Platysma, deep fascia, the clavicular origin of the Sterno-mastoid, the Sterno-hyoid, and Sterno-thyroid muscles, and another layer of the deep fascia. It is crossed by the internal jugular and vertebral veins and by the pneumogastric. the cardiac branches of the sympathetic, and the phrenic nerve. Beneath, the artery is invested by the pleura, and behind, it is separated by a cellular interval from the Longus colli, the neck of the first rib, and the cord of the sympathetic nerve; the recurrent laryngeal nerve winds round the lower and back part of the vessel. The subclavian vein lies below the subclavian artery, immediately behind the clavicle. Plan of Relations of First Portion of the Right Subclavian Artery. In front. Skin, superficial fascia. Platysma, deep fascia. Clavicular origin of Sterno-mastoid. Sterno-hyoid and Sterno-thyroid. Internal jugular and vertebral veins. Pneumogastric, cardiac, and phrenic nerves. : Right , Subclavian I Artery. \ First Portion. Beneath. Pleura. Behind. Recurrent laryngeal nerve. Sympathetic. Longus colli. Neck of first rib. First Part of tiie Left Subclavian Artery (Fig. 344). The left subclavian artery arises from the end of the arch of the aorta, opposite the fourth dorsal vertebra, and ascends nearly vertically to the inner margin of the Scalenus anticus muscle. This part of the vessel is, therefore, longer than the right, situated more deeply in the cavity of the chest, and directed nearly vertically upward, instead of arching outward like the vessel of the opposite side. It is in relation, in front, with the pleura, the left lung, the pneumogastric, cardiac, and phrenic nerves, which lie parallel with it; the left carotid artery, left internal jugular and vertebral veins, and the commencement of the left innominate vein; and is covered by the Sterno-thyroid, Sterno-hyoid, and Sterno-mastoid muscles; it has the left carotid in front of, but not in contact with, it; behind, it is in relation with the oesophagus, thoracic duct, inferior cervical ganglion of the sympathetic, Longus colli, and vertebral column. To its inner side are the oesophagus, trachea, and thoracic duct; to its outer side, the pleura. Plan of Relations of First Portion of Left Subclavian Artery. In front. Pleura and left lung. Pneumogastric, cardiac, and phrenic nerves. Left carotid artery. Left internal jugular, vertebral, and innominate veins. Sterno-thyroid, Sterno-hyoid, and Sterno-mastoid muscles. 580 THE ARTERIES. Inner side. Trachea. (Esophagus. Thoracic duct. Left Subclavian Artery. i Outer side. Pleura. Behind. (Esophagus and thoracic duct. Inferior cervical ganglion of sympathetic. Longus colli and vertebral column. Second and Third Parts of the Subclavian Artery (Fig. 347). The Second Portion of the Subclavian Artery lies behind the Scalenus anticus muscle; it is very short, and forms the highest part of the arch described by that vessel. Relations.-It is covered, in front, by the skin, superficial fascia, Platysma, deep cervical fascia, Sterno-mastoid, and by the phrenic nerve, which is separated from the artery by the Scalenus anticus muscle. Behind, it is in relation with the pleura and the middle Scalenus; above, with the brachial plexus of nerves; below, with the pleura. The subclavian vein lies below and in front of the artery, separated from it by the Scalenus anticus. Plan of Relations of Second Portion of Subclavian Artery. In front. Skin and superficial fascia. Platysma and deep cervical fascia. Sterno-mastoid. Phrenic nerve. Scalenus anticus. Subclavian vein. Above. Brachial plexus. Subclavian Artery. Second Portion. , Below. Pleura. Behind. Pleura and Middle Scalenus. The Third Portion of the Subclavian Artery passes downward and outward from the outer margin of the Scalenus anticus to the lower border of the first rib, where it becomes the axillary artery. This portion of the vessel is the most superficial, and is contained in a triangular space, the base of which is formed in front by the Sterno-mastoid, and the two sides by the Omo-hyoid above and the clavicle below. Plan of Relations of Third Portion of Subclavian Artery. In front. Skin and superficial fascia. Platysma and deep cervical fascia. Descending branches of cervical plexus. Nerve to Subclavius muscle. Subclavius muscle, suprascapular artery, and vein. The external jugular and transverse cervical veins. The clavicle. Above. Brachial plexus. Omo-hyoid. Subclavian Artery. Third Portion. Below. First rib. Behind. Scalenus niedius. THE SUBCLAVIAN ARTERIES. 581 Relations.-It is covered, in front, by the skin, the superficial fascia, the Platysma, deep cervical fascia ; by the clavicle, the Subclavius muscle and the suprascapular artery and vein, and the transverse cervical vein ; the clavicular descending branches of the cervical plexus and the nerve to the Subclavius muscle pass vertically downward in front of the artery. The external jugular vein crosses it at its inner side, and receives the suprascapular and transverse cervical veins, which occasionally form a plexus in front of it. The subclavian vein is below the artery, lying close behind the clavicle. Behind, it lies on the middle Scalenus muscle; above it, and to its outer side, is the brachial plexus and Omo-hyoidmus- cle ; beloiv, it rests on the upper surface of the first rib. Peculiarities.-The subclavian arteries vary in their origin, their course, and the height to which they rise in the neck. The origin of the right subclavian from the innominate takes place, in some cases, above the sterno-clavicular articulation, and occasionally, but less frequently, in the cavity of the thorax, below that joint. Or the artery may arise as a separate trunk from the arch of' the aorta. In such cases it may be either the first, second, third, or even the last branch derived from that ves- sel; in the majority of cases it is the first or last, rarely the seconder third. When it is the first branch, it occupies the ordinary position of the innominate artery; when the second or third, it gains its usual position by passing behind the right carotid ; and when the last branch, it arises from the left extremity of the arch, at its upper or back part, and passes obliquely toward the right side, usually behind the oesophagus and right carotid, sometimes between the oesophagus and trachea to the upper border of the first rib. whence it follows its ordinary course. In very rare instances this vessel arises from the thoracic aorta, as low down as the fourth dorsal verte- bra. Occasionally it perforates the anterior Scalenus ; more rarely it passes in front of that muscle. Sometimes the subclavian vein passes with the artery behind the Scalenus. The artery sometimes ascends as high as an inch and a half above the clavicle or any intermediate point between this and the upper border of the bone, the right subclavian usually ascending higher than the left. The left subclavian is occasionally joined at its origin with the left carotid. Surface Marking.-The course of the subclavian artery in the neck may be mapped out by describing a curve, with its convexity upward at the base of the posterior triangle. The inner end of this curve corresponds to the sterno-clavicular joint, the outer end to the centre of the lower border of the clavicle. The curve is to be drawn with such an amount of convexity that its mid-point reaches half an inch above the upper border of the clavicle. The left subclavian artery is more deeply placed than the right in the first part of its course, and, as a rule, doesnot reach quite as high a level in the neck. It should be borne in mind that the posterior border of the Sterno-mastoid muscle corresponds to the outer border of the Scalenus anticus, so that the third portion of the artery, that part most accessible for operation, lies immediately external to the posterior border of the Sterno-mastoid. Surgical Anatomy.-The relations of the subclavian arteries of the two sides having been examined, the student should direct his attention to a consideration of the best position in which compression of the vessel may be effected, or in what situation a ligature may be best applied in cases of aneurism or wound. Compression of the subclavian artery is required in cases of operations about the shoul- der. in the axilla, or at the upper part of the arm ; and the student will observe that there is only one situation in which it can be effectually applied-viz. where the artery passes across the outer surface of the first rib. In order to compress the vessel in this situation, the shoulder should be depressed, and the surgeon, grasping the side of the neck, should press with his thumb in the angle formed by the posterior border of the Sterno-mastoid with the upper border of the clavicle, downward, backward, and inward against the rib ; if from any cause the shoulder cannot be sufficiently depressed, pressure may be made from before backward, so as to compress the artery against the middle Scalenus and transverse process of the seventh cervical vertebra. In appropriate cases, a preliminary incision may be made through the cervical fascia, and the finger may be pressed down directly upon the artery. Ligature of the subclavian artery may be required in cases of wounds or of aneurism in the axilla, or in cases of aneurism on the cardiac side of the point of ligature; and the third part of the artery is that which is most favorable for an operation, on account of its being compara- tively superficial and most remote from the origin of the large branches. In those cases where the clavicle is not displaced, this operation maybe performed with comparative facility; but where the clavicle is pushed up by a large aneurismal tumor in the axilla the artery is placed at a great depth from the surface, which materially increases the difficulty of the operation. 1 nder these circumstances it becomes a matter of importance to consider the height to which this vessel reaches above the bone. In ordinary cases its arch is about half an inch above the clavicle, occasionally as high as an inch and a half, and sometimes so low as to be on a level with its upper border. If the clavicle is displaced, these variations will necessarily make the opera- tion more or less difficult according as the vessel is more or less accessible. The chief points in the operation of tying the third portion of the subclavian artery are as follows: The patient being placed on a table in the horizontal position, with the head drawn 582 THE ARTERIES. over to the opposite side and the shoulder depressed as much as possible, the integument should be drawn downward upon the clavicle, and an incision made through it, upon that bone, from the anterior border of the Trapezius to the posterior border of the Sterno-mastoid, to which may be added a short vertical incision meeting the preceding in its centre. The object in drawing the skin downward is to avoid any risk of wounding the external jugular vein, for as it perforates the deep fascia above the clavicle, it cannot be drawn downward with the skin. The cervical fascia should be divided upon a director, and if the interval between the Trapezius and Sterno- mastoid muscles be insufficient for the performance of the operation, a portion of one or both may be divided. The external jugular vein will now be seen toward the inner side of the wound : this and the suprascapular and transverse cervical veins, which terminate in it, should be held aside. If the external jugular vein is at all in the way and exposed to injury, it should be tied in two places and divided. The suprascapular artery should be avoided, and the Omo-hyoid muscle held aside if necessary. In the space beneath this muscle careful search must be made for the vessel: a deep layer of fascia and some connective tissue having been divided carefully, the outer margin of the Scalenus anticus muscle must be felt for, and, the finger being guided by it to the first rib, the pulsation of the subclavian artery will be felt as it passes over the rib. The aneurism needle may then be passed around the vessel from above downward and inward, so as to avoid including any of the branches of the brachial plexus. If the clavicle is so raised by the tumor that the application of the ligature cannot be effected in this situation, the artery may be tied above the first rib, or even behind the Scalenus anticus muscle ; the difficulties of the ope- ration in such a case will be materially increased, on account of the greater depth of the artery and the alteration in position of the surrounding parts. The second part of the subclavian artery, from being that portion which rises highest in the neck, has been considered favorable for the application of the ligature when it is difficult to tie the artery in the third part of its course. There are, however, many objections to the ope- ration in this situation. It is necessary to divide the Scalenus anticus muscle, upon which lies the phrenic nerve, and at the inner side of which is situated the internal jugular vein ; and a wound of either of these structures might lead to the most dangerous consequences. Again, the artery is in contact, below, with the pleura, which must also be avoided; and, lastly, the proximity of so many of its large branches arising internal to this point must be a still further objection to the operation. In cases, however, where the sac of an axillary aneurism encroaches on the neck, it may be necessary to divide the outer half or two-thirds of the Scalenus anticus muscle, so as to place the ligature on the vessel at a greater distance from the sac. The opera- tion is performed exactly in the same way as ligature of the third portion, until the Scalenus anticus is exposed, when it is to be divided on a director (never to a greater extent than its outer two-thirds), and it immediately retracts. The operation is therefore merely an extension of liga- ture of the third portion of the vessel. In those cases of aneurism of the axillary or subclavian artery which encroach upon the outer portion of the Scalenus muscle to such an extent that a ligature cannot be applied in that situation, it may be deemed advisable, as a last resource, to tie the first portion of the subcla- vian artery. On the left side this operation is almost impracticable; the great depth of the artery from the surface, its intimate relation with the pleura, and its close proximity to the thoracic duct and to so many important veins and nerves, present a series of difficulties which it is next to impossible to overcome.1 On the right side the operation is practicable, and has been performed, though never with success. The main objection to the operation in this situation is the smallness of the interval which usually exists between the commencement of the vessel and the origin of the nearest branch. The operation may be performed in the following manner: The patient being placed on the table in the horizontal position with the neck extended, an incis- ion should be made along the upper border of the inner part of the clavicle, and a second along the inner border of the Sterno-mastoid, meeting the former at an angle. The sternal attachment of the Sterno-mastoid may now be divided on a director and turned outward; a few small arteries and veins, and occasionally the anterior jugular, must be avoided, or, if necessary, ligatured in two places and divided, and the Sterno-hyoid and Sterno-thyroid muscles divided in the same manner as the preceding muscle. After tearing through the deep fascia with the finger- nail, the internal jugular vein will be seen crossing the subclavian artery; this should be pressed aside and the artery secured by passing the needle from below upward, by which the pleura is more effectually avoided. The exact position of the vagus nerve, the recurrent laryngeal, the phrenic and sympathetic nerves should be remembered, and the ligature should be applied near the origin of the vertebral, in order to afford as much room as possible for the formation of a coagulum between the ligature and the origin of the vessel. It should be remembered that the right subclavian artery is occasionally deeply placed in the first part of its course when it arises from the left side of the aortic arch, and passes in such cases behind the oesophagus or between it and the trachea. Collateral Circulation.-After ligature of the third part of the subclavian artery the col- lateral circulation is mainly established by three sets of vessels, thus described in a dissection: "1. A posterior set, consisting of the suprascapular and posterior scapular branches of the subclavian, anastomosing with the median branch from the subscapular from the axillary. " 2. An internal set produced by the connection of the internal mammary on the one hand, 1 The operation was, however, performed in New York by Dr. J. K. Rodgers, and the case is related in A System of Surgery, edited by T. Holmes, 2d ed. vol. iii. pp. 620, etc. BRANCHES OF THE SUBCLAVIAN ARTERY. 583 with the superior and long thoracic arteries, and the branches from the subscapular on the other. "3. A middle or axillary set, which consisted of a number of small vessels derived from branches of the subclavian, above, and, passing through the axilla, terminated either in the main trunk or some of the branches of the axillary below. This last set presented most con- spicuously the peculiar character of newly-formed or, rather, dilated arteries, being excessively tortuous, and forming a complete plexus. " The chief agent in the restoration of the axillary artery below the tumor was the sub- scapular artery, which communicated most freely with the internal mammary, suprascapular, and posterior scapular branches of the subclavian, from all of which it received so great an influx of blood as to dilate it to three times its natural size." 1 When a ligature is applied to the first part of the subclavian artery, the collateral circula- tion is carried on by-1, the anastomosis between the superior and inferior thyroid ; 2, the anas- tomosis of the two vertebrals; 3, the anastomosis of the internal mammary with the deep epigastric and the aortic intercostals; 4, the superior intercostal anastomosing with the aortic intercostals; 5, the profunda cervicis anastomosing with the princeps cervicis; 6, the scapular branches of the thyroid axis anastomosing with the branches of the axillary; and 7, the thoracic branches of the axillary anastomosing with the aortic intercostals. Branches of the Subclavian Artery. These aTe four in number. On the left side all four branches, the vertebral, the internal mammary, the thyroid axis, and the superior intercostal, generally arise from the first portion of the vessel; but on the right side the superior inter- costal usually arises from the second portion of the vessel. On both sides of the body the first three branches arise close together at the inner margin of the Sca- lenus anticus, in the majority of cases a free interval of half an inch to an inch existing between the commencement of the artery and the origin of the nearest branch ; in a smaller number of cases an interval of more than an inch exists, never exceed- ing an inch and three-quarters. In a very few instances the interval had been found to be less than half an inch. The Vertebral Artery (Fig. 352) is gen- erally the first and largest branch of the subclavian; it arises from the upper and back part of the first portion of the vessel, and, passing upward, enters the foramen in the transverse process of the sixth cerv- ical vertebra,2 and ascends through the for- amina in the transverse processes of all the vertebrae above this. Above the upper bor- der of the axis it inclines outward and upward to the foramen in the transverse process of the atlas, through which it passes ; it then winds backward behind its articular process, runs in a deep groove on the upper surface of the posterior arch of this bone, and, passing beneath the posterior occipito-atlantal* ligament, pierces the dura mater and enters the skull through the foramen magnum. It then passes forward and upward to the front of the medulla oblongata, and unites with the vessel of the opposite side at the lower border of the pons Varolii to form the basilar artery. Relations.-At its origin it is situated behind the internal jugular vein and inferior thyroid artery and near the spine; it lies between the Longus colli and Scalenus anticus muscles, having the thoracic duct in front of it on the left side, ithin the foramina formed by the transverse processes of the vertebrae it is accompanied by a plexus of nerves from the inferior cervical ganglion of the sympathetic, and is surrounded by a dense plexus of veins which unite to form the Fig. 360.-Plan of the branches of the right subclavian artery. 1 Guy's Hospital Reports, vol. i. 1836: case of axillary aneurism, in which Mr. Aston Key had tied the subclavian artery on the outer edge of the Scalenus muscle twelve years previouslv. 2 The vertebral artery sometimes enters the foramen in the transverse process of the fifth ver- tebra. Dr. Smyth, who tied this artery in the living subject, found it, in one of his dissections, pass- ing into the foramen in the seventh vertebra. 584 THE ARTE RIES. vertebral vein at the lower part of the neck. It is situated in front of the cervical nerves as they issue from the intervertebral foramina. Whilst winding round the articular process of the atlas it is contained in a triangular space (suboccipital triangle') formed by the Rectus capitis posticus major, the Superior and the Inferior oblique muscles; and at this point is covered by the Complexus muscle. Within the skull, as it winds round the medulla oblongata, it is placed between the hypo- glossal nerve and the anterior root of the suboccipital nerve, beneath the first digitation of the ligamentum denticulatum, and finally lies between the dura mater covering the basilar process of the occipital bone and the anterior surface of the medulla oblongata. Branches.-These may be divided into two sets-those given off in the neck and those within the cranium. Cervical Branches. Lateral Spinal. Muscular. Cranial Branches. Posterior Meningeal. Anterior Spinal. Posterior Spinal. Posterior Inferior Cerebellar. The lateral spinal branches enter the spinal canal through the intervertebral foramina and divide into two branches. Of these, one passes along the roots of the nerves to supply the spinal cord and its membranes, anastomosing with the other arteries of the spinal cord; the other divides into an ascending and a descending branch, which unite with similar branches from the artery above and below, so that two lateral anastomotic chains are formed on the posterior surface of the bodies of the vertebrae near the attachment of the pedicles. From these anastomotic chains branches are given off to supply the periosteum and the bodies of the vertebrae, and to communicate with similar branches from the opposite side ; from these latter small branches are given off which join similar branches above and below, so that a central anastomotic chain is formed on the posterior surface of the bodies of the vertebrae. Muscular branches are given off to the deep muscles of the neck, where the vertebral artery curves round the articular process of the atlas. They anastomose with the occipital and with the ascending and deep cervical arteries. The posterior meningeal are one or two small branches given off from the vertebral opposite the foramen magnum. They ramify between the bone and dura mater in the cerebellar fossae, and supply the falx cerebelli. The anterior spinal is a small branch, though larger than the posterior spinal, which arises near the termination of the vertebral, and, descending in front of the medulla oblongata, unites with its fellow of the opposite side at about the level of the foramen mao-num. The single trunk, thus formed, descends on the front of the spinal cord, and is reinforced by a succession of small branches which enter the'spinal canal through the intervertebral foramina; these branches are derived from the vertebral and ascending cervical of the inferior thyroid in the neck; from the intercostal in the dorsal region ; and from the lumbar, ilio- lumbar, and lateral sacral arteries in the lower part of the spine. They unite, by means of ascending and descending branches, to form a single anterior median artery, which extends as far as the lower part of the spinal cord. This vessel is placed in the pia mater along the anterior median fissure: it supplies that mem- brane and the substance of the cord, and sends off' branches at its lower part to be distributed to the cauda equina, and ends on the central fibrous prolongation of the cord. The posterior spinal arises from the vertebral at the side of the medulla oblongata : passing backward to the posterior aspect of the spinal cord, it descends on each side, lying behind the posterior roots of the spinal nerves, and is reinforced by a succession of small branches which enter the spinal canal through the intervertebral foramina, and by which it is continued to the lower part of the BRANCHES OF THE SUBCLAVIAN ARTERY. 585 cord and to the cauda equina. Branches from these vessels form a free anasto- mosis round the posterior roots of the spinal nerves, and communicate, by means of very tortuous transverse branches, with the vessel of the opposite side. At its commencement it gives off an ascending branch, which terminates on the side of the fourth ventricle. The posterior inferior cerebellar artery (Fig. 354), the largest branch of the vertebral, winds backward round the upper part of the medulla oblongata, passing between the origin of the pneumogastric and spinal accessory nerves, over the restiform body to the under surface of the cerebellum, where it divides into two branches-an internal one, which is continued backward to the notch between the two hemispheres of the cerebellum ; and an external one, which supplies the under surface of the cerebellum as far as its outer border, where it anastomoses with the anterior inferior cerebellar and the superior cerebellar branches of the basilar artery. Branches from this artery supply the choroid plexus of the fourth ventricle. Surgical Anatomy.-The vertebral artery has been tied in several instances: 1, for wounds or traumatic aneurism ; 2, after ligature of the innominate, either at the same time to prevent haemorrhage, or later on to arrest bleeding where it has occurred at the seat of ligature; and 3, in epilepsy. In these latter cases the treatment has been recommended by Dr. Alexander of Liverpool, in the hope that by diminishing the supply of blood to the posterior part of the brain and the spinal cord a diminution or cessation of the epileptic fits would result. The operation of ligature of the vertebral is performed by making an incision along the posterior border of the Sterno-mastoid muscle, just above the clavicle. The muscle is pulled to the inner side, and the anterior tubercle of the transverse process of the sixth cervical vertebra sought for. A deep layer of fascia being now divided, the interval between the Scalenus anticus and the Longus colli just below their insertion into the tubercle is defined, and the artery and vein found in the interspace. The vein is to be drawn to the outer side, and the aneurism needle passed from without inward. Drs. Ramskill and Bright have pointed out that severe pain at the back of the head may be symptomatic of disease of the vertebral artery just before it enters the skull. This is explained by the close connection of the artery with the sub- occipital nerve in the groove on the posterior arch of the atlas. Disease of the same artery has been also said to affect speech, from pressure on the hypoglossal where it is in relation with the vessel, leading to paralysis of the muscles of the tongue. The Basilar Artery, so named from its position at the base of the skull, is a single trunk formed by the junction of the two vertebral arteries; it extends from the posterior to the anterior border of the pons Varolii, lying in its median groove, under cover of the arachnoid. It ends by dividing into two branches, the posterior cerebral arteries. Its branches are, on each side, the following: Transverse. Anterior Inferior Cerebellar. Superior Cerebellar. Posterior Cerebral. The transverse branches supply the pons Varolii and adjacent parts of the brain, one branch, the internal auditory, accompanies the auditory nerve into the internal auditory meatus; and another, the anterior inferior cerebellar artery, passes across the crus cerebelli, to be distributed to the anterior border of the under surface of the cerebellum. The superior cerebellar arteries arise near the termination of the basilar. They wind round the crus cerebri close to the fourth nerve, and, arriving at the upper surface of the cerebellum, divide into branches which ramify in the pia mater and anastomose with the branches of the inferior cerebellar artery. Sev- eral branches are given to the pineal gland and also to the velum interpositum. 'fhe posterior cerebral arteries, the two terminal branches of the basilar, are larger than the preceding, from which they are separated near their origin by the third nerves. Winding round the crus cerebri, they pass to the under surface of the occipital lobes of the cerebrum and divide into three main branches. Near their origin they receive the posterior communicating arteries from the internal carotid. The branches of the posterior cerebral artery are- Postero-median Ganglionic. Posterior Choroid. Postero-lateral Ganglionic. Three Terminal. 586 THE ARTERIES. The postero-median ganglionic branches (Fig. 357) are a group of small arteries which arise at the commencement of the posterior cerebral artery; these, with similar branches from the posterior communicating, pierce the posterior perforated space and supply the internal surfaces of the optic thalami and the walls of the third ventricle. The posterior choroid enters the interior of the brain beneath the posterior border of the corpus callosum and supplies the velum interpositum and the choroid plexus. The postero-lateral ganglionic branches are a group of small arteries which arise from the posterior cerebral artery after it has turned round the crus cerebri; they supply a considerable portion of the optic thalamus. The terminal branches are distributed as follows : the first to the uncinate gyrus; the second to the temporo-sphenoidal lobe; and the third to the cuneus or the occip- ital lobule. Circle of Willis.-The remarkable anastomosis which exists between the branches of the internal carotid and vertebral arteries at the base of the brain constitutes the circle of Willis. It is formed, in front, by the anterior cerebral arteries, branches of the internal carotid, which are connected together by the anterior communicating; behind, by the two posterior cerebrals, branches of the basilar, which are connected on each side with the internal carotid by the pos- terior communicating arteries (Fig. 354). It is by this anastomosis that the cere- bral circulation is equalized, and provision made for effectually carrying it on if one or more of the branches are obliterated. The parts of the brain included within this arterial circle are-the lamina cinerea, the commissure of the optic nerves, the infundibulum, the tuber cinereum, the corpora albicantia, and the posterior perforated space. The Thyroid Axis (Fig. 347) is a short thick trunk which arises from the fore part of the first portion of the subclavian artery, close to the inner border of the Scalenus anticus muscle, and divides, almost immediately after its origin, into three branches-the inferior thyroid, suprascapular, and transversalis colli. The Inferior Thyroid Artery passes upward, in a serpentine course, behind the sheath of the common carotid vessel and sympathetic nerve (the middle cervical ganglion resting upon it), and in front of the vertebral artery, recurrent laryngeal nerve, and Longus colli muscle, and is distributed to the under surface of the thyroid gland, anastomosing with the superior thyroid and with the corresponding artery of the opposite side. Its branches are-the Inferior Laryngeal. Tracheal. (Esophageal. Ascending Cervical Muscular. The inferior laryngeal branch ascends upon the trachea to the back part of the larynx, in company with the recurrent laryngeal nerve, and supplies the muscles and mucous membrane of this part, anastomosing with the branch from the oppo- site side and with the laryngeal branch from the superior thyroid artery. The tracheal branches are distributed upon the trachea, anastomosing below with the bronchial arteries. The oesophageal branches are distributed to the oesophagus, and anastomose with the oesophageal branches of the aorta. The ascending cervical is a small branch which arises from the inferior thyroid just where that vessel is passing behind the common carotid artery, and runs up on the anterior tubercles of the transverse processes of the cervical vertebrae in the interval between the Scalenus anticus and Rectus capitis anticus major. It gives branches to the muscles of the neck, which anastomose with branches of the vertebral, and sends one or two branches into the spinal canal through the inter- vertebral foramina to be distributed to the spinal cord and its membranes, and to the bodies of the vertebrae in the same manner as the lateral spinal branches from the vertebral. It anastomoses with the ascending pharyngeal artery. The muscular branches supply the depressors of the hyoid bone, the Longus colli, the Scalenus anticus, and the Inferior constrictor of the pharynx. BRANCHES OF THE SUBCLAVIAN ARTERY. 587 Surgical Anatomy.-This artery is sometimes tied, in conjunction with the superior thy- roid, in cases of bronchocele. An incision is made along the anterior border of the Sterno-mas- toid down to the clavicle. After the deep fascia has been divided, the Sterno-mastoid and caro- tid vessels are drawn outward and the carotid (Chassaignac's) tubercle sought for. The vessel will be found just below this tubercle, between the carotid sheath on the outer side of the trachea and oesophagus on the inner side. In passing the ligature great care must be exercised to avoid including the recurrent laryngeal nerve. The Suprascapular Artery (transversalis humeri), smaller than the transversalis colli, passes obliquely from within outward, across the root of the neck. It at first lies on the lower part of the Scalenus anticus, being covered by the Sterno- mastoid ; it then crosses the subclavian artery, and runs outward behind and par- allel with the clavicle and Subclavius muscle, and beneath the posterior belly of the Omo-hyoid, to the superior border of the scapula, where it passes over the transverse ligament of the scapula to the supraspinous fossa. In this situation it lies close to the bone, and ramifies between it and the Supraspinatus muscle, to which it is mainly distributed, giving off a communicating branch which crosses Posterior scapular. Suprascapular. Acromial branch of Thoracico-acromialis. Anterior \circumflex. Termination of subscapular. Fig. 361-The scapular and circumflex arteries. the neck of the scapula, to reach the infraspinous fossa, where it anastomoses with the dorsal branch of the subscapular artery. Besides distributing branches to the Sterno-mastoid and neighboring muscles, it gives off a supra-acroniial branch, which, piercing the Trapezius muscle, supplies the cutaneous surface of the acro- mion, anastomosing with the acromial thoracic artery. As the artery passes over the transverse ligament of the scapula a branch descends into the subscapular fossa, ramifies beneath that muscle, and anastomoses with the posterior and sub- scapular arteries. It also supplies the shoulder-joint and a nutrient branch to the clavicle. The Transversalis Colli passes transversely outward, across the upper part of the subclavian triangle, to the anterior margin of the Trapezius muscle, beneath which it divides into two branches, the superficial cervical and the posterior scap- ular. In its passage across the neck it crosses in front of the Scaleni muscles and the brachial plexus, between the divisions of which it sometimes passes, and is covered by the Platysma, Sterno-mastoid, Omo-hyoid, and Trapezius muscles. The superficial cervical ascends beneath the anterior margin of the Trapezius, distributing branches to it and to the neighboring muscles and glands in the neck, and anastomoses with the superficial branch of the arteria princeps cervicis. The posterior scapular, the continuation of the transversalis colli, passes 588 THE ARTERIES. beneath the Levator anguli scapulae to the superior angles of the scapula. It now descends along the posterior border of that bone as far as the inferior angle, where it anastomoses with the subscapular branch of the axillary. In its course it is covered by the Rhomboid muscles, supplying them and the Latissimus dorsi and Trapezius, and anastomosing with the suprascapular and subscapular arteries and with the posterior branches of some of the intercostal arteries. Peculiarities.-The superficial cervical frequently arises as a separate branch from the thyroid axis; and the posterior scapular, from the third, more rarely from the second, part of the subclavian. The Internal Mammary arises from the under surface of the first portion of the subclavian artery, opposite the thyroid axis. It descends behind the costal cartilage of the first rib to the inner surface of the anterior wall of the chest, resting against the costal cartilages about half an inch from the margin of the sternum; and at the interval between the sixth and seventh cartilages divides into two branches, the musculo-phrenic and superior epigastric. Relations.-At its origin it is covered by the internal jugular and subclavian veins and crossed by the phrenic nerve. In the upper part of the thorax it lies against the costal cartilages and Internal intercostal muscles in front, and is covered by the pleura behind. At the lower part of the thorax the Triangularis sterni separates the artery from the pleura. The branches of the internal mammary are- Comes Nervi Phrenici (Superior Phrenic). Mediastinal. Pericardiac. Sternal. Anterior Intercostal. Perforating. Musculo-phrenic. Superior Epigastric. The comes nervi phrenici (superior phrenic), is a long slender branch which accompanies the phrenic nerve, between the pleura and pericardium, to the Diaphragm, to which it is distributed, anastomosing with the other phrenic arteries from the internal mammary and abdominal aorta. The mediastinal branches are small vessels which are distributed to the areolar tissue and lymphatic glands in the anterior mediastinum and the remains of the thymus gland. The pericardiac branches supply the upper part of the anterior surface of the pericardium, the lower part receiving branches from the musculo-phrenic artery. The sternal branches are distributed to the Triangularis sterni and to the posterior surface of the sternum. The mediastinal, pericardiac, and sternal branches, together with some twigs from the comes nervi phrenici, anastomose with branches from the intercostal and bronchial arteries, and form a minute plexus beneath the pleura, which has been named by Turner the subpleural mediastinal plexus. The anterior intercostal arteries supply the five or six upper intercostal spaces. The branch corresponding to each space soon divides into two, or the two branches may come off separately from the parent trunk. The small vessels pass outward in the intercostal spaces, one lying near the lower margin of the rib above, and the other near the upper margin of the rib below, and anastomose with the intercostal arteries from the aorta. They are at first situated between the pleura and the Internal intercostal muscles, and then between the Internal and External intercostal muscles. They supply the Intercostal muscles, and, by branches which perforate the External intercostal muscle, the Pectoral muscles and the mammary gland. The perforating arteries correspond to the five or six upper intercostal spaces. They arise from the internal mammary, pass forward through the intercostal spaces, and, curving outward, supply the Pectoralis major and the integument. Those which correspond to the second, third, and fourth spaces are distributed to the mammary gland. In females, during lactation, these branches are of large size. The musculo-phrenic artery is directed obliquely downward and outward, SURGICAL ANATOMY OF THE AXILLA. 589 behind the cartilages of the false ribs, perforating the Diaphragm at the eighth or ninth rib, and terminating, considerably reduced in size, opposite the last inter- costal space. It gives off anterior intercostal arteries to each of the intercostal spaces across which it passes; these diminish in size as the spaces decrease in length, and are distributed in a manner precisely similar to the anterior intercostals from the internal mammary. The musculo-phrenic also gives branches to the lower part of the pericardium, and others which run backward to the Diaphragm and downward to the abdominal muscles. The superior epigastric continues in the original direction of the internal mammary ; it descends through the cellular interval between the costal and sternal attachments of the Diaphragm, and enters the sheath of the Rectus abdominis muscle, at first lying behind the muscle, and then perforating it and supplying it, and anastomosing with the deep epigastric artery from the external iliac. Some vessels perforate the sheath of the Rectus, and supply the muscles of the abdomen and the integument, and a small branch, which passes inward upon the side of the ensiform appendix, anastomoses in front of that cartilage with the artery of the opposite side. Surgical Anatomy.-The course of the internal mammary artery may be defined by draw- ing a line across the six upper intercostal spaces half an inch from and parallel with the sternum. The position of the vessel must be remembered, as it is liable to be wounded in stabs of the chest-wall. It is most easily reached by a transverse incision in the second intercostal space. The Superior Intercostal (Fig. 352) arises from the upper and back part of the subclavian artery, behind the Anterior scalenus on the right side, and to the inner side of the muscle on the left side. Passing backward, it gives off the deep cervical branch, and then descends behind the pleura in front of the necks of the first two ribs, and inosculates with the first aortic intercostal.1 In the first intercostal space it gives off a branch which is distributed in a manner similar to the distri- bution of the aortic intercostals. The branch for the second intercostal space usually joins with one from the aortic intercostals. Each intercostal gives off a branch to the posterior spinal muscles, and a small one which passes through the corresponding intervertebral foramen to the spinal cord and its membranes. The deep cervical branch (profunda cervicis) arises, in most cases, from the superior intercostal, and is analogous to the posterior branch of an aortic inter- costal artery. Passing backward, between the transverse process of the seventh cervical vertebra and the first rib, it runs up the back part of the neck, between the Complexus and Semispinalis colli muscles, as high as the axis, supplying these and adjacent muscles, and anastomosing with the deep branch of the arteria princeps cervicis of the occipital and with branches which pass outward from the vertebral. SURGICAL ANATOMY OF THE AXILLA. The Axilla is a pyramidal space, situated between the upper and lateral part of the chest and the inner side of the arm. Boundaries.-Its apex, which is directed upward toward the root of the neck, corresponds to the interval between the first rib, the upper edge of the scapula, and the clavicle, through which the axillary vessels and nerves pass. The base, directed downward, is formed by the integument, and a thick layer of fascia extending between the lower border of the Pectoralis major in front, and the lower border of the Latissimus dorsi behind; it is broad internally at the chest, but narrow and pointed externally at the arm. The anterior boundary is formed by the Pectoralis major and minor muscles, the former covering the whole of the anterior wall of the axilla, the latter covering only its central part. The posterior boundary, which extends somewhat lower than the anterior, is formed by the Sub- scapularis above, the Teres major and Latissimus dorsi below. On the inner side are the first four ribs with their corresponding Intercostal muscles, and part of the Serratus magnus. On the outer side, where the anterior and posterior boundaries 1 See foot-note, p. 609. 590 THE ARTERIES. converge, the space is narrow, and bounded by the humerus, the Coraco-brachialis and Biceps muscles. Contents.-This space contains the axillary vessels and brachial plexus of nerves, with their branches, some branches of the intercostal nerves, and a large number of lymphatic glands, all connected together by a quantity of fat and loose areolar tissue. Their Position.-The axillary artery and vein, with the brachial plexus of nerves, extend obliquely along the outer boundary of the axillary space, from its apex to its base, and are placed much nearer the anterior than the posterior wall, the vein lying to the inner or thoracic side of the artery and partially concealing it. At the fore part of the axillary space, in contact with the Pectoral muscles, are the thoracic branches of the axillary artery, and along the anterior margin Anterior circumflex.' of the axilla the long thoracic artery extends to the side of the chest. At the back part, in contact with the lower margin of the Subscapularis muscle, are the subscapular vessels and nerves; winding around the lower border of this muscle is the dorsalis scapulae artery and veins; and toward the outer extremity of the muscle the posterior circumflex vessels and the circumflex nerve are seen curving backward to the shoulder. Along the inner or thoracic side no vessel of any importance exists, the upper part of the space being crossed merely by a few small branches from the superior thoracic artery. There are some important nerves, however, in this situation- viz. the posterior thoracic or external respiratory nerve, descending on the sur- face of the Serratus magnus, to which it is distributed; and perforating the upper and anterior part of this wall, the intercosto-humeral nerve or nerves, passing across the axilla to the inner side of the arm. The cavity of the axilla is filled by a quantity of loose areolar tissue and a large number of small arteries and veins, all of which are, however, of inconsiderable Fig. 362.-The axillary artery and its branches. THE AXILLARY ARTERY. 591 size, and numerous lymphatic glands : these are from ten to twelve in number, and situated chiefly on the thoracic side and lower and back part of this space. Surgical Anatomy.-The axilla is a space of considerable surgical importance. It trans- mits the large vessels and nerves to the upper extremity, and these may be the seat of injury or disease: it contains numerous lymphatic glands which may require removal when diseased ; in it is a quantity of loose connective and adipose tissue which may be readily infiltrated with blood or inflammatory exudation, and it may be the seat of rapidly-growing tumors. Moreover, it is covered at its base by thin skin, largely supplied with sebaceous and sweat glands, which is fre- quently the seat of small cutaneous abscesses and boils, and of eruptions due to irritation. In suppuration in the axilla the arrangement of the fasciae plays a very important part in the direction which the pus takes. As described on page 470, the costo-coracoid membrane, after covering in the space between the clavicle and the upper border of the Pectoralis minor, splits to enclose this muscle, and, reblending at its lower border, becomes incorporated with the fascia covering the Pectoralis major muscle at the anterior fold of the axilla. This is known as the clavi-pectoral fascia. Suppuration may take place either superficial to or beneath this layer of fascia ; that is, either between the pectorals or below the pectoralis minor: in the former case, it would point either at the anterior border of the axillary fold or in the groove between the Del- toid and the Pectoralis major; in the latter, the pus would have a tendency to surround the vessels and nerves and ascend into the neck, that being the direction in which there is least resistance. Its progress toward the skin is prevented by the axillary fascia ; its progress backward, by the Serratus magnus; forward, by the clavi-pectoral fascia ; inward, by the wall of the thorax; and outward, by the upper limb. The pus in these cases, after extending into the neck, has been known to spread through the superior opening of the thorax into the mediastinum. In opening an axillary abscess the knife should be entered in the floor of the axilla, midway between the anterior and posterior margins and near the thoracic side of the space. It is well to use a director and dressing forceps after an incision has been made through the skin and fascia in the manner directed by the late Mr. Hilton. The student should attentively consider the relation of the vessels and nerves in the several parts of the axilla, for it not unfrequently happens that the surgeon is called upon to extirpate diseased glands or to remove a tumor from this situation. In performing such an operation it will be necessary to proceed with much caution in the direction of the outer wall and apex of the space, as here the axillary vessels will be in danger of being wounded. Toward the posterior wall it will be necessary to avoid the subscapular, dorsalis scapulae, and posterior circumflex vessels. Along the anterior wall it will be necessary to avoid the thoracic branches. It is only along the inner or thoracic wall, and in the centre of the axillary cavity, that there are no vessels of any importance-a fortunate circumstance, for it is in this situation more especially that tumors requiring removal are usually situated. THE AXILLARY ARTERY. The Axillary Artery, the continuation of the subclavian, commences at the lower border of the first rib, and terminates at the lower border of the tendon of the Teres major muscle, where it takes the name of brachial. Its direction varies with the position of the limb: when the arm lies by the side of the chest, the vessel forms a gentle curve, the convexity being upward and outward; when it is directed at right angles with the trunk, the vessel is nearly straight; and when it is elevated still higher, the artery describes a curve the concavity of which is directed upward. At its commencement the artery is very deeply situated, but near its termination is superficial, being covered only by the skin and fascia. The description of the relations of this vessel is facilitated by its division into three portions, the first portion being that above the Pectoralis minor; the second por- tion. behind; and the third below, that muscle. The first portion of the axillary artery is in relation, in front, with the clavic- ular portion of the Pectoralis major, the costo-coracoid membrane, the external anterior thoracic nerve, and the acromio-thoracic and cephalic veins; behind, with the first intercostal space, the corresponding Intercostal muscle, the second and third serrations of the Serratus magnus, and the posterior thoracic nerve; on its outer side, with the brachial plexus, from which it is separated by a little cellular interval; on its inner or thoracic side, with the axillary vein. Relations of the First Portion of the Axillary Artery. In front. Pectoralis major. Costo-coracoid membrane. External anterior thoracic nerve. Acromio-thoracic and Cephalic veins. 592 THE ARTERIES. Outer side. Brachial plexus. / Axillary Artery. First Portion. Inner side. Axillary vein. Behind. First Intercostal space, and Intercostal muscle. Second and third serrations of Serratus magnus. Posterior thoracic nerve. The second portion of the axillary artery lies behind the Pectoralis minor. It is covered, in front, by the Pectoralis major and minor muscles; behind, it is separated from the Subscapularis by a cellular interval; on the inner side is the axillary vein. The brachial plexus of nerves surrounds the artery, and separates it from direct contact with the vein and adjacent muscles. Relations of the Second Portion of the Axillary Artery. In front. Pectoralis major and minor. Outer side. Outer cord of plexus. Axillary Artery. Second Portion Inner side. Axillary vein. Inner cord of plexus. Behind. Subscapularis. Posterior cord of plexus. The third portion of the axillary artery lies below the Pectoralis minor. It is in relation, in front, with the lower part of the Pectoralis major above, being covered only by the integument and fascia below, where it is crossed by the inner head of the median nerve; behind, with the lower part of the Subscapularis and the tendons of the Latissimus dorsi and Teres major; on its outer side, with the Coraco-brachialis; on its inner or thoracic side, with the axillary vein. The nerves of the brachial plexus bear the following relation to the artery in this part of its course: on the outer side is the median nerve, and the musculo-cutaneous for a short distance; on the inner side, the ulnar, the internal, and lesser internal cutaneous nerves; and behind, the musculo-spiral and circumflex, the latter extending only to the lower border of the Subscapularis muscle. Peculiarities.-The axillary artery, in about one case out of every ten, gives off a large branch, which forms either one of the arteries of the forearm or a large muscular trunk. In the first set of cases this artery is most frequently the radial (1 in 33), sometimes the ulnar (1 in 72), and, very rarely, the interosseous (1 in 506). In the second set of cases the trunk has been found to give origin to the subscapular, circumflex, and profunda arteries of the arm. Some- times only one of the circumflex, or one of the profunda arteries, arose from the trunk. In these cases the brachial plexus surrounded the trunk of the branches, and not the main vessel. Relations of the Third Portion of the Axillary Artery In front. Integument and fascia. Pectoralis major. Inner head of median nerve. Outer side. Coraco-brachialis. Median nerve. Musculo-cutaneous nerve. Axillary Artery. Third Portion, i Inner side. Ulnar nerve. Internal cutaneous nerves. Axillary veins. Behind. Subscapularis. Tendons of Latissimus dorsi and Teres major. Musculo-spiral and circumflex nerves. THE AXILLARY ARTERY. 593 Surface Marking.-The course of the axillary artery may be marked out by raising the arm to a right angle and drawing a line from the middle of the clavicle to the point where the tendon of the Pectoralis major crosses the prominence caused by the Coraco-brachialis as it emerges from under cover of the anterior fold of the axilla. The third portion of the artery can be felt pulsating beneath the skin and fascia, at the junction of the anterior with the middle third of the space between the anterior and posterior folds of the axilla, close to the inner border of the Coraco-brachialis. Surgical Anatomy.-The student, having carefully examined the relations of the axillary artery in its various parts, should now consider in what situation compression of this vessel may be most easily effected, and the best position for the application of a ligature to it when necessary. Compression of the vessel may be required in the removal of tumors or in amputation of the upper part of the arm ; and the only situation in which this can be effectually made is in the lower part of its course; by pressing on it in this situation from within outward against the humerus the circulation may be effectually arrested. The axillary artery is perhaps more frequently lacerated than any other artery in the body, with the exception of the popliteal, by violent movements of the upper extremity, especially in those cases where its coats are diseased. It has occasionally been ruptured in attempts to reduce old dislocations of the shoulder-joint. This lesion is most likely to occur during the preliminary breaking down of adhesions, in consequence of the artery having contracted adhesions to the capsule of the joint. Aneurism of the axillary artery is of frequent occurrence, a large percentage of the cases being traumatic in their origin, due to the violence to which it is exposed in the varied, extensive, and often violent movement of the limb. The application of a ligature to the axillary artery may be required in cases of aneurism of the upper part of the brachial or as a distal operation for aneurism of the sub- clavian ; and there are only two situations in which it can be secured-viz. in the first and in the third parts of its course ; for the axillary artery at its central part is so deeply seated, and, at the same time, so closely surrounded with large nervous trunks, that the application of a ligature to it in that situation would be almost impracticable. In the third part of its course the operation is most simple, and may be performed in the following manner: The patient being placed on a bed and the arm separated from the side, with the hand supinated, an incision is made through the integument forming the floor of the axilla about two inches in length, a little nearer to the anterior than the posterior fold of the axilla. After carefully dissecting through the areolar tissue and fascia, the median nerve and axillary vein are exposed ; the former having been displaced to the outer and the latter to the inner side of the arm, the elbow being at the same time bent, so as to relax the structures and facilitate their separation, the ligature may be passed round the artery from the ulnar to the radial side. This portion of the artery is occasionally crossed by a muscular slip derived from the Latissimus dorsi, which may mislead the surgeon during an operation. The occasional existence of this muscular fasciculus was spoken of in the description of the muscles. It may easily be recognized by the transverse direction of its fibres. The first portion of the axillary artery may be tied in cases of aneurism encroaching so far upward that a ligature cannot be applied in the lower part of its course. Notwithstanding that this operation has been performed in some few cases, and with success, its performance is attended with much difficulty and danger. The student will remark that in this situation it would be necessary to divide a thick muscle, and, after separating the costo-coracoid membrane, the artery would be exposed at the bottom of a more or less deep space, with the cephalic and axillary veins in such relation with it as must render the application of a ligature to this part of the vessel particularly hazardous. Under such circumstances it is an easier, and at the same time more advisable, operation to tie the subclavian arteiy in the third part of its course. The vessel can be best secured by a curved incision with the convexity downward from a point half an inch external to the Sterno-clavicular joint to a point half an inch internal to the coracoid process. The limb is to be well abducted and the head inclined to the opposite side, and this incision carried through the superficial structures, care being taken of the cephalic vein at the outer angle of the incision. The clavicular origin of the Pectoralis major is then divided in the whole extent of the wound. The arm is now to be brought to the side, and the upper edge of the Pectoralis minor defined and drawn downward. The costo-coracoid membrane is to be carefully torn through with a director close to the coracoid process, and the axillary sheath exposed ; this is to be opened with especial care on account of the vein overlapping the artery. The needle should be passed from below, so as to avoid wounding the vein. In a case of wound of the vessel the general practice of cutting down upon, and tying it above and below the wounded point should be adopted in all cases. Collateral Circulation after Ligature of the Axillary Artery.-If the artery be tied above the origin of the acromial thoracic, the collateral circulation will be carried on by the same branches as after the ligature of the subclavian ; if at a lower point, between the acromial thoracic and subscapular arteries, the latter vessel, by its free anastomoses with the other scapular arteries, branches of the subclavian, will become the chief agent in carrying on the cir- culation, to which the long thoracic, if it be below the ligature, will materially contribute by its anastomoses with the intercostal and internal mammary arteries. If the point included in the ligature be below the origin of the subscapular artery, it will most probably also be below the origins of the two circumflex arteries. The chief agents in restoring the circulation will then be 594 THE ARTERIES. the subscapular and the two circumflex arteries anastomosing with the superior profunda from the brachial, which will be afterward referred to as performing the same office after ligature of the brachial. The cases in which the operation has been performed are few in number, and no published account of dissection of the collateral circulation appears to exist. Branches of the Axillary Artery. The branches of the axillary nerve are- 77 /• , , Irom first part r Superior Thoracic. Acromial Thoracic. r . brom second part L Long Thoracic. Alar Thoracic. Subscapular. Anterior Circumflex. Posterior Circumflex. From third part The superior thoracic is a small artery which arises from the axillary sepa- rately or by a common trunk with the acromial thoracic. Running forward and inward along the upper border of the Pectoralis minor, it passes between it and the Pectoralis major to the side of the chest. It supplies these muscles and the parietes of the thorax, anastomosing with the internal mammary and intercostal arteries. The acromial thoracic is a short trunk which arises from the fore part of the axillary artery. Projecting forward to the upper border of the Pectoralis minor, it divides into three sets of branches-thoracic, acromial, and descending. The thoracic branches, two or three in number, are distributed to the Serratus magnus and Pectoral muscles, anastomosing with the intercostal branches of the internal mammary. The acromial branches are directed outward toward the acromion, supplying the Deltoid muscle, and anastomosing, on the surface of the acromion, with the suprascapular and posterior circumflex arteries. The descending branch passes in the space between the Pectoralis major and Deltoid in the same groove as the cephalic vein, and supplies both muscles. The artery also gives off a very small branch, the clavicular, which passes upward to the Subclavius muscle. The long thoracic passes downward and inward along the lower border of the Pectoralis minor to the side of the chest, supplying the Serratus magnus, the Pectoral muscles, and mammary gland, and sending branches across the axilla to the axillary glands and Subscapularis ; it anastomoses with the internal mammary and intercostal arteries. The alar thoracic is a small branch which supplies the glands and areolar tissue of the axilla. Its place is frequently supplied by branches from some of the other thoracic arteries. The subscapular, the largest branch of the axillary artery, arises opposite the lower border of the Subscapularis muscle, and passes downward and backward along its lower margin to the inferior angle of the scapula, where it anastomoses with the long thoracic and intercostal arteries and with the posterior scapular, a branch of the transversalis colli, from the thyroid axis of the subclavian. About an inch and a half from its origin it gives off a large branch, the dorsalis scapula?, and terminates by supplying branches to the muscles in the neighborhood. The dorsalis scapulae is given off from the subscapular about an inch from its origin, and is generally larger than the continuation of the vessel. It curves round the axillary border of the scapula, leaving the axilla through the space between the Teres minor above, the Teres major below, and the long head of the Triceps externally (Fig. 361), and enters the infraspinous fossa, where it anastomoses with the posterior scapular and suprascapular arteries. In its course it gives off two sets of branches: one enters the subscapular fossa beneath the Subscapularis, which it supplies, anastomosing with the posterior scapular and suprascapular arteries; the other is continued along the axillary border of the scapula, between the Teres major and minor, and, at the dorsal surface of the inferior angle of the bone, anastomoses with the posterior scapular. In addition to these, small branches are distributed to the back part of the Deltoid muscle and the long head of the Triceps, anastomosing with an ascending branch of the superior profunda of the brachial. THE BRACHIAL ARTERY. 595 The circumflex arteries wind round the neck of the humerus. The posterior circumflex (Fig. 361), the larger of the two, arises from the back part of the axillary opposite the lower border of the Subscapularis muscle, and, passing backward with the circumflex veins and nerve through the quadrangular space bounded by the Teres major and minor, the scapular head of the Triceps and the humerus, winds round the neck of that bone and is distributed to the Deltoid muscle and shoulder- joint, anastomosing with the anterior circumflex and acromial thoracic arteries, and with the superior profunda branch of the brachial artery. The anterior circumflex (Figs. 361, 362), considerably smaller than the preceding, arises just below that vessel from the outer side of the axillary artery. It passes horizontally outward beneath the Coraco-brachialis and short head of the Biceps, lying upon the fore part of the neck of the humerus, and, on reaching the bicipital groove, gives off an ascending branch which passes upward along the groove to supply the head of the bone ami the shoulder-joint. The trunk of the vessel is then continued outward beneath the Deltoid, which it supplies, and anastomoses with the posterior circum- flex artery. The Brachial Artery commences at the lower margin of the tendon of the Teres major, and, passing down the inner and anterior aspect of the arm, terminates about half an inch below the bend of the elbow, where it divides into the radial and ulnar arteries. THE BRACHIAL ARTERY (Fig. 363). Plan of the Relations of the Brachial Artery. In front. Integument and fasciae. Bicipital fascia, median basilic vein. Median nerve. Outer side. Median nerve (above). Coraco- brach i al is. Biceps. • Inner side. Internal cutaneous and ulnar nerve. Median nerve (below). Basilic vein. Brachial Artery. Behind. Triceps. Musculo-spiral nerve. Superior profunda artery. Coraco-brachialis. Brachialis anticus. Relations.-This artery is superficial throughout its entire extent, being covered, in front, by the integument, the superficial and deep fascia; the bicipital fascia separates it opposite the elbow from the median basilic vein ; the median nerve crosses it at its middle. Behind, it is separated from the inner side of the humerus, above, by the long and inner heads of the Triceps, the musculo-spiral nerve and superior profunda artery intervening, and from the front of the bone, below, by the insertion of the Coraco-brachialis muscle and by the Brachialis anticus. By its outer side it is in relation with the commencement of the median nerve and the Coraco-brachialis and Biceps muscles, which slightly overlap the artery. By its inner side its upper half is in relation with the inter- nal cutaneous and ulnar nerves, its lower half with the median nerve. The basilic vein lies on the inner side of the artery, but is separated from it in the lower part of the arm by the deep fascia. It is accompanied by two venae comites, which lie in close contact with the artery, being connected together at inter- vals by short transverse communicating branches. SURGICAL ANATOMY OF THE BEND OF THE ELBOW. At the bend of the elbow the brachial artery sinks deeply into a trian- gular interval, the base of which is directed upward toward the humerus, 596 77AE? A RTE HIES. and the sides of which are bounded, externally, by the Supinator longus; internally, by the Pronator radii teres; its floor'is formed by the Brachialis anticus and Supinator brevis. This space contains the brachial artery, with its accompanying veins, the radial and ulnar arteries, the median and musculo- spiral nerves, and the tendon of the Biceps. The brachial artery occupies the middle line of this space, and divides opposite the neck of the radius into the radial and ulnar arteries; it is covered, in front, by the integument, the super- ficial fascia, and the median basilic vein, the vein being separated from direct contact with the artery by the bicipital fascia. Behind, it lies on the Brachialis anticus, which separates it from the elbow-joint. The median nerve lies on the inner side of the artery, close to it above, but separated from it below by the coronoid head of the Pronator radii teres. The tendon of the Biceps lies to the outer side of the space, and the musculo-spiral nerve still more ex- ternally, lying upon the Supinator brevis and partly concealed by the Supinator longus. Peculiarities of the Brachial Artery as regards its Course.-The brachial artery, ac- companied by the median nerve, may leave the inner border of the Biceps, and descend toward the inner condyle of the humerus, where it usually curves round a prominence of bone, to which it is connected by a fibrous band ; it then inclines outward, beneath or through the sub- stance of the Pronator radii teres muscle, to the bend of the elbowr. The variation bears considerable analogy with the normal condition of the artery in some of the carnivora: it has been referred to above in the description of the humerus (page 252). As regards its Division.-Occasionally, the artery is divided for a short distance at its upper part into two trunks, which are united above and below. A similar peculiarity occurs in the main vessel of the lower limb. The point of bifurcation may be above or below the usual point, the former condition being by far the more frequent. Out of 481 exam- inations recorded by Mr. Quain, some made on the right and some on the left side of the body, in 386 the artery bifurcated in its normal position. In one case only was the place of division lower than usual, being two or three inches below the elbow-joint. " In 94 cases out of 481, or about 1 in 5|. there were two arteries instead of one in some part or in the whole of the arm." There appears, however, to be no correspondence between the arteries of the two arms with respect to their irregular division ; for in 61 bodies it occurred on one side only in 43; on both sides, in different positions, in 13; on both sides, in the same position, in 5. The point of bifurcation takes place at different parts of the arm, being most frequent in the upper part, less so in the lower part, and least so in the middle, the most usual point for the application of a ligature : under any of these circumstances two large arteries would be found in the arm instead of one. The most frequent (in three out of four) of these peculiarities is the high division of the radial. That artery often arises from the inner side of the brachial, and runs parallel with the main trunk to the elbow, where it crosses it, lying beneath the fascia; orit may perforate the fascia and pass over the artery immediately beneath the integument. The ulnar sometimes arises from the brachial high up, and then occasionally leaves that ves- sel at the lower part of t lio arm, and descends toward the inner condyle. In the forearm it Internal cutaneous nerve. Musculo- spiral nerve. Superior profunda. Inferior ' profunda. Anastomotica magna. Fig. 363.-The surgical anatomy of the brachial artery. BRANCHES OF THE BRACHIAL. 597 erally lies beneath the deep fascia, superficial to the flexor muscles; occasionally between the integument and deep fascia, and very rarely beneath the flexor muscles. The interosseous artery sometimes arises from the upper part of the brachial or axillary ; as it passes down the arm it lies behind the main trunk, and at the bend of the elbow regains its usual position. In some cases of high division of the radial the remaining trunk (ulnar interosseous) occa- sionally passes, together with the median nerve, along the inner margin of the arm to the inner condyle, and then passing from within outward, beneath or through the Pronator radii teres, regains its usual position at the bend of the elbow. Occasionally the two arteries representing the brachial are connected at the bend of the elbow by a short transverse branch, and are even sometimes reunited. Sometimes, long slender vessels, vasa aberrantia, connect the brachial or axillary arteries with one of the arteries of the forearm or a branch from them. These vessels usually join the radial. Varieties in Muscular Relations.1-The brachial artery is occasionally concealed in some part of its course by muscular or tendinous slips derived from the Coraco-brachialis, Biceps, Brachialis anticus and Pronator radii teres muscles. Surface Marking.-The direction of the brachial artery is marked, when the arm is extended and supinated, by a line drawn from the junction of the anterior and middle third of the space between the anterior and posterior folds of the axilla; that is to say from the inner side of the prominence of the Coraco-brachialis muscle to the point midway between the condyles of the humerus which corresponds to the depression along the inner border of the Coraco-bra- chialis and Biceps. In the upper part of its course the artery lies internal to the humerus, but below it is in front of that bone. Surgical Anatomy.-Compression of the brachial artery is required in cases of amputation and some other operations in the arm and forearm ; and it will be observed that it maybe effected in almost any part of the course of the artery. If pressure is made in the upper part of the limb, it should be directed from within outward ; and if in the lower part, from before backward, as the artery lies on the inner side of the humerus above and in front below. The most favor- able situation is about the middle of the arm, where it lies on the tendon of the Coraco-brachialis on the inner flat side of the humerus. The application of a ligature to the brachial artery may be required in case of wound of the vessel and in some cases of wound of the palmar arch. It is also sometimes necessary in cases of aneurism of the brachial, the radial, ulnar, or interosseous arteries. The artery may be 'secured in any part of its course. The chief guides in determining its position are the sur- face markings produced by the inner margin of the Coraco-brachialis and Biceps, the known course of the vessel, and its pulsation, which should be carefully felt for before any operation is performed, as the vessel occasionally deviates from its usual position in the arm. In whatever situation the operation is performed, great care is necessary, on account of the extreme thinness of the parts covering the artery and tbe intimate connection which the vessel has throughout its whole course with important nerves and veins. Sometimes a thin layer of muscular fibre is met with concealing the artery; if such is the case, it must be cut across in order to expose the vessel. In the upper third of the arm the artery may be exposed in the following manner: The patient being placed horizontally upon a table, the affected limb should be raised from the side and the hand supinated. An incision about two inches in length should be made on the inner side of the Coraco-brachialis muscle, and the subjacent fascia cautiously divided, so as to avoid wounding the internal cutaneous nerve or basilic vein, which sometimes runs on the surface of the artery as high as the axilla. The fascia having been divided, it should be remembered that the ulnar and internal cutaneous nerves lie on the inner side of the artery, the median on the outer side, the latter nerve being occasionally superficial to the artery in this situation, and that the venae comites are also in relation with the vessel, one on either side. These being carefully separated, the aneurism needle should be passed round the artery from the inner to the outer side. If two arteries are present in the arm in consequence of a high division, they are usually placed side by side: and if they are exposed in an operation, the surgeon should endeavor to ascertain, by alternately pressing on each vessel, which of the two communicates with the wound or aneurism, when a ligature may be applied accordingly; or if pulsation or haemorrhage ceases only when both vessels are compressed, both vessels may be tied, as it may be concluded that the two communicate above the seat of disease or are reunited. It should also be remembered that two arteries may be present in the arm in a case of high division, and that one of these may be found along the inner intermuscular septum, in a line toward the inner condyle of the humerus, or in the usual position of the brachial, but deeply placed beneath the common trunk: a knowledge of these facts will suggest the precautions necessary in every case, and indicate the measures to be adopted when anomalies are met with. In the middle of the arm the brachial artery may be exposed by making an incision along the inner margin of the Biceps muscle. The forearm being bent so as to relax the muscle, it should be drawn slightly aside, and, the fascia being carefully divided, the median nerve will be 1 See Struther's Anatomical and Physiological Observations. 598 THE ARTERIES. exposed lying upon the artery (sometimes beneath); this being drawn inward and the muscle outward, the artery should be separated from its accompanying veins and secured. In this situation the inferior profunda may be mistaken for the main trunk, especially if enlarged, from the collateral circulation having become established; this may be avoided by directing the incis- ion externally toward the Biceps, rather than inward or backward toward the Triceps. The lower part of the brachial artery is of interest in a surgical point of view, on account of the relation which it bears to the veins most commonly opened in venesection. Of these vessels, the median basilic is the largest and most prominent, ami, consequently, the one usually selected for the operation. It should be remembered that this vein runs parallel with the brachial artery, from which it is separated by the bicipital fascia, and that care should be taken in opening the vein not to carry the incision too deeply, so as to endanger the artery. Collateral Circulation.-After the application of a ligature to the brachial artery in the upper third of the arm, the circulation is carried on by branches from the circumflex and subscapular arteries, anastomosing with ascending branches from the superior profunda. If the brachial is tied below the origin of the profunda arteries, the circulation is maintained by the branches of the profundae, anastomosing with the recurrent radial, ulnar, and interosseous arteries. In two cases described by Mr. South,1 in which the brachial artery had been tied some time previously, in one ''a long portion of the artery had beenobliterated, and sets of vessels are descending on either side from above the obliteration, to be received into others which ascend in a similar manner from below it. In the other the obliteration is less extensive, and a single curved artery about as big as a crow-quill passes from the upper to the lower open part of the artery. '' The branches of the brachial artery are-the Superior Profunda. Nutrient. Inferior Profunda. Anastomotica Magna. The superior profunda arises from the inner and back part of the brachial, just below the lower border of the Teres major, and passes backward to the interval between the outer and inner heads of the Triceps muscle, accompanied by the musculo-spiral nerve; it winds round the back part of the shaft of the humerus in the spiral groove, between the Triceps and the bone, to the outer side of the humerus just above the external condyle, where it divides into two terminal branches. One of these pierces the external intermuscular septum, and descends to the space between the Brachialis anticus and Supinator longus, w here it anasto- moses with the recurrent branch of the radial artery; while the other, the posterior articular, descends along the back of the external intermuscular septum to the back part of the elbow-joint, where it anastomoses with the posterior interosseous recurrent, and across the back of the humerus with the posterior ulnar recurrent, the anastomotica magna, and inferior profunda (Fig. 366). The superior profunda supplies the Triceps muscle and gives off a nutrient artery to the upper end of the humerus. Near its commencement it sends off a branch which passes upward between the external and long heads of the Triceps muscle to anastomose with the posterior circumflex artery, and, while in the groove, a small branch which accompanies a branch of the musculo-spiral nerve through the substance of the Triceps muscle and ends in the Anconeus below the outer condyle of the humerus. The nutrient artery of the shaft of the humerus arises from the brachial, about the middle of the arm. Passing downward it enters the nutrient canal of that bone near the insertion of the Coraco-brachialis muscle. The inferior profunda, of small size, arises from the brachial, a little below the middle of the arm; piercing the internal intermuscular septum, it descends on the surface of the inner head of the Triceps muscle to the space between the inner condyle and olecranon, accompanied by the ulnar nerve, and terminates by anasto- mosing with the posterior ulnar recurrent and anastomotica magna. It also supplies a branch to the front of the internal condyle, which anastomoses with the anterior ulnar recurrent. The anastomotica magna arises from the brachial about two inches above the Muscular. 1 Chelius's Surgery, vol. ii. p. 254. See also White's engraving, referred to by Mr. South, of the anastomosing branches after ligature of the brachial, in White's Cases in Surgery. Porta also gives a case (with drawings) of the circulation after ligature of both brachial and radial (Alterazioni Patoligiche delle Arterie). THE RADIAL ARTERY. 599 elbow-joint. It passes transversely inward upon the Brachialis anticus, and, piercing the internal intermuscular septum, winds round the back part of the humerus between the Triceps and the bone, forming an arch above the olecranon fossa by its junction with the posterior articular branch of the superior profunda. As this vessel lies on the Brachialis anticus, branches ascend to join the inferior profunda, and others descend in front of the inner condyle to anastomose with the anterior ulnar recurrent. Behind the internal condyle an offset is given off which anastomoses with the inferior profunda and posterior ulnar recurrent arteries and supplies the Triceps. The muscular are three or four large branches, which are distributed to the muscles in the course of the artery. They supply the Coraco-brachialis, Biceps, and Brachialis anticus muscles. The Anastomosis around the Elbow-joint (Fig. 366).-The vessels engaged in this anastomosis may be conveniently divided into those situated in front and behind the internal and external condyles. The branches anastomosing in front of the internal condyle are the anastomotica magna, the anterior ulnar recurrent, and the anterior terminal branch of the inferior profunda. Those behind the internal condyle are the anastomotica magna, the posterior ulnar recurrent, and the posterior terminal branch of the inferior profunda. The branches anastomosing in front of the external condyle are the radial recurrent and one of the terminal branches of the superior profunda. Those behind the external condyle (perhaps more properly described as being situated between the external condyle and the olecranon) are the anastomotica magna, the interosseous recurrent, and one of the terminal branches of the superior profunda. There is also a large arch of anastomosis above the olecranon, formed by the interosseous recurrent, joining with the anastomotica magna and posterior ulnar recurrent (Fig. 366). From this description it will be observed that the anastomotica magna is the vessel most engaged, the only part of the anastomosis in which it is not employed being that in front of the external condyle. Radial Artery. The Radial Artery appears, from its direction, to be the continuation of the brachial, but in size it is smaller than the ulnar. It commences at the bifurca- tion of the brachial, just below the bend of the elbow, and passes along the radial side of the forearm to the wrist; it then winds backward, round the outer side of the carpus, beneath the extensor tendons of the thumb, and, finally, passes forward, between the two heads of the First dorsal interosseous muscle, into the palm of the hand, where it crosses the metacarpal bones to the ulnar border of the hand, to form the deep palmar arch. At its termination it inosculates with the deep branch of the ulnar artery. The relations of this vessel may thus be con- veniently divided into three parts-viz. in the forearm, at the back of the wrist, and in the hand. Relations.-In the forearm this vessel extends from opposite the neck of the radius to the fore part of the styloid process, being placed to the inner side of the shaft of the bone above and in front of it below. It is superficial throughout its entire extent, being covered by the integument, the superficial and deep fascine, and slightly overlapped above by the Supinator longus. In its course downward it lies upon the tendon of the Biceps, the Supinator brevis, the radial origin of the Flexor sublimis digitorum, the Pronator radii teres, the Flexor longus pollicis, the Pronator quadratus, and the lower extremity of the radius. In the upper third of its course it lies between the Supinator longus and the Pronator radii teres; in its lower two-thirds, between the tendons of the Supinator longus and the Flexor carpi radialis. The radial nerve lies along the outer side of the artery in the middle third of its course, and some filaments of the musculo-cutaneous nerve, after piercing the deep fascia, run along the lower part of the artery as it winds round the wrist. The vessel is accompanied by venae comites throughout its whole course. 600 THE ARTERIES. Plan of the Relations of the Radial Artery in the Forearm, In front. Skin, superficial and deep fasciae. Supinator longus. ' Inner side. Pronator radii teres. Flexor carpi radialis. Outer side. Supinator longus. Radial nerve (middle third). Radial Artery in Forearm. Behind. Tendon of Biceps. Supinator brevis. Flexor sublimis digitorum. Pronator radii teres. Flexor longus pollicis. Pronator quadratus. Radius. At the wrist, as it winds round the outer side of the carpus from the styloid process to the first interosseous space, it lies upon the external lateral ligament, and then upon the scaphoid bone and trapezium, being covered by the extensor tendons of the thumb, subcutaneous veins, some filaments of the radial nerve, and the integument. It is accompanied by two veins and a filament of the musculo- cutaneous nerve. In the hand it passes from the upper end of the first interosseous space, between the heads of the Abductor indicis or First dorsal interosseous muscle, transversely across the palm, to the base of the metacarpal bone of the little finger, where it inosculates with the communicating branch from the ulnar artery, forming the deep palmar arch. It lies upon the carpal extremities of the metacarpal bones and the Interossei muscles, being covered by the Adductor obliquus pollicis, the flexor tendons of the fingers, the Lumbricales, the Opponens, and Flexor brevis minimi digiti. Alongside of it is the deep branch of the ulnar nerve, but running in the opposite direction; that is to say, from within outward. Peculiarities.-The origin of the radial artery, according to Quain. is, in nearly one case in eight, higher than usual; more frequently arising from the axillary or upper part of the brachial than from the lower part of this vessel. The variations in the position of this vessel in the arm and at the bend of the elbow have been already mentioned. In the forearm it deviates less frequently from its position than the ulnar. It has been found lying over the fascia instead of beneath it. It has also been observed on the surface of the Supinator longus, instead of along its inner border; and in turning round the wrist it has been seen lying over, instead of beneath, the extensor tendons. Surface Marking.-The position of the radial artery in the forearm is represented by a line drawn from the outer border of the tendon of the Biceps in the centre of the hollow in front of the elbow-joint with a straight course to the inner side of the fore part of the styloid process of the radius. Surgical Anatomy.-The radial artery is much exposed to injury in its lower third, and is frequently wounded by the hand being driven through a pane of glass, by the slipping of a knife or chisel held in the other hand, and such-like accidents. The injury is often followed by a traumatic aneurism, for which the old operation of laying open the sac and securing the vessel above and below is required. The operation of tying the radial artery is required in cases of wounds either of its trunk or of some of its branches, or for aneurism ; and it will be observed that the vessel may be exposed in any part of its course through the forearm without the division of any muscular fibres. The operation in the middle or inferior third of the forearm is easily performed, but in the upper third, near the elbow, it is attended with some difficulty, from the greater depth of the vessel and from its being overlapped by the Supinator longus muscle. To tie the artery in the upper third an incision three inches in length should be made through the integument, in a line drawn from the centre of the bend of the elbow to the front of the styloid process of the radius, avoiding the branches of the median vein; the fascia of the arm being divided and the Supinator longus drawn a little outward, the artery will be exposed. The venae comites should be carefully separated from the vessel, and the ligature passed from the radial to the ulnar side. In the middle third of the forearm the artery may be exposed by making an incision of similar length on the inner margin of the Supinator longus. In this situation the radial nerve 1 THE RADIAL ARTERY. 601 lies in close relation with the outer side of the artery, and should, as well as the veins, be care- fully avoided. P ' In the lower third the artery is easily secured by dividing the integument and tascia in the interval between the tendons of the Su- pinator longus and Flexor carpi radialis muscles. The branches of the radial ar- tery may be divided into three groups, corresponding with the three regions in which the vessel is situated. Radial Recurrent. Muscular. Anterior Carpal. Superficialis Volte. In the Forearm. Wrist. Posterior Carpal. Metacarpal. Dorsales Pollicis. Dorsalis Indicis. Radial recurrent. Princeps Pollicis. Radialis Indicis. Perforating. Interosseous. Palmar Recurrent. Hand. The radial recurrent is given off immediately below the elbow. It ascends between the branches of the musculo-spiral nerve lying on the Supinator brevis, and then between the Supinator longus and Brachialis anticus, supplying these muscles and the elbow-joint, and anastomosing with one of the ter- minal branches of the superior profunda. The muscular branches are dis- tributed to the muscles on the ra- dial side of the forearm. The anterior carpal is a small vessel which arises from the radial artery near the lower border of the Pronator quadratus, and, running inward in front of the radius, an- astomoses with the anterior carpal branch of the ulnar artery. From the arch thus formed branches de- scend to supply the articulations of the wrist. The superficialis volae arises from the radial artery, just where this vessel is about to wind round the wrist. Running forward, it passes between the muscles of the thumb, which it supplies, and some- times anastomoses with the palmar portion of the ulnar artery, com- pleting the superficial palmar arch. This vessel varies considerably in size Deep branch of ulnar. Superficialis wise. Fig. 364.-The surgical anatomy of the radial and ulnar arteries. 602 TH Fl A RTE HI FIS. usually it is very small, and terminates in the muscles of the thumb; sometimes it is as large as the continuation of the radial. The posterior carpal is a small vessel which arises from the radial artery beneath the extensor tendons of the thumb; crossing the carpus transversely to the inner border of the hand, it anastomoses with the posterior carpal branch of the ulnar, forming the posterior carpal arch, which is joined by the termi- nation of the posterior interosseous artery. From this arch are given off' descending branches, the dorsal interosseous arteries for the third and fourth interosseous spaces, which run forward on the Third and Fourth dorsal interossei mus- cles and divide into dorsal digital branches which supply the adjacent sides of the middle, ring, and little fingers respectively, communica- ting with the digital arteries of the superficial palmar arch. At their origin they anastomose with the perforating branches from the deep palmar arch. The metacarpal (first dorsal interosseous branch) arises beneath the extensor tendons of the thumb, sometimes with the posterior carpal artery; running forward on the Second dorsal interosseous muscle, it communicates, behind, with the corresponding perforating branch of the deep palmar arch; and in front it divides into two dorsal digital branches, which supply the adjoining sides of the index and middle fingers, inosculating with the digital branch of the super- ficial palmar arch. The dorsales pollicis are two small vessels which run along the sides of the dorsal aspect of the thumb. They arise separately, or occasionally by a common trunk, near the base of the first metacar- pal bone. The dorsalis indicis, also a small branch, runs along the radial side of the back of the index finger, sending a few branches to the Abductor indicis. The princeps pollicis arises from the radial just as it turns inward to the deep part of the hand; it descends between the Abductor indicis and Adductor obliquus pollicis, then between the Adductor transversus pollicis and Adductor obliquus pollicis, along the ulnar side of the metacarpal bone of the thumb, to the base of the first phalanx, where it divides into two branches, which run along the sides of the palmar aspect of the thumb and form an arch on the under surface Anastomotica magna. Radial recurrent. Anterior ulnar recurrent. Posterior ulnar recurrent. Posterior interosseous. Muscular Muscular. Anterior carpal. Superficiahs volte. ■Anterior carpal. Deep branch of ulnar. Fig. 365.-Ulnar and radial arteries. Deep view. THE ULNAR ARTERY. 603 of the last phalanx, from which branches are distributed to the integument and pulp of the thumb. The radialis indicis arises close to the preceding, descends between the Abductor indicis and Adductor transversus pollicis, and runs along the radial side of the index finger to its extremity, where it anastomoses with the collateral digital artery from the superficial palmar arch. At the lower border of the Adductor transversus pollicis this vessel anastomoses with the princeps pollicis, and gives a communicating branch to the superficial palmar arch. The perforating arteries, three in number, pass backward between the heads of the last three Dorsal interossei muscles, to inosculate with the dorsal inter- osseous arteries. The palmar interosseous, three or four in number, are branches of the deep palmar arch; they run forward upon the Interossei muscles, and anastomose at the clefts of the fingers with the digital branches of the superficial arch. The palmar recurrent branches arise from the concavity of the deep palmar arch. They pass upward in front of the wrist, supplying the carpal articulations and anastomosing with the anterior carpal arch. The Ulnar Artery, the larger of the two terminal branches of the brachial, commences a little below the bend of the elbow, and crosses obliquely the inner side of the forearm, to the commencement of its lower half; it then runs along its ulnar border to the wrist, crosses the annular ligament on the radial side of the pisiform bone, and immediately beyond this bone divides into two branches, superficial and deep palmar. Relations in the Forearm.-In its upper half it is deeply seated, being covered by all the superficial flexor muscles, excepting the Flexor carpi ulnaris ; it is crossed by the median nerve, which lies to its inner side for about an inch, and it lies upon the Brachialis anticus and Flexor profundus digitorum muscles. In the lower half of the forearm it lies upon the Flexor profundus, being covered by the integument, the superficial and deep fasciae, and is placed between the Flexor carpi ulnaris and Flexor sublimis digitorum muscles. It is accompanied by two venae comites; the ulnar nerve lies on its inner side for the lower two- thirds of its extent, and a small branch from the nerve descends on the lower part of the vessel to the palm of the hand. Ulnar Artery. Pla*< of Relations of the Ulnar Artery in the Forearm. In front. Superficial layer of flexor muscles. Median nerve. Superficial and deep fascia;. Lower half. Upper half. Inner side. Flexor carpi ulnaris. Ulnar nerve (lower two-thirds). Ulnar Artery in Forearm. Outer side. Flexor sublimis digitorum. Behind. Brachialis anticus. Flexor profundus digitorum. At the wrist (Fig. 364) the ulnar artery is covered by the integument and fascia, and lies upon the anterior annular ligament. On its inner side is the pisiform bone. The ulnar nerve lies at the inner side, and somewhat behind the artery. Peculiarities.-The ulnar artery has been found to vary in its origin nearly in the propor- tion of one in thirteen cases, in one case arising lower than usual, about two or three inches below the elbow, and in all other cases much higher, the brachial being a more frequent source of origin than the axillary. 604 THE ARTERIES. Variations in the position of this vessel are more frequent than in the radial. When its origin is normal the course of the vessel is rarely changed. When it arises high up it is almost invariably superficial to the flexor muscles in the forearm, lying commonly beneath the fascia, more rarely between the fascia and integument. In a few cases its position was subcutaneous in the upper part of the forearm, subaponeurotic in the lower part. Surface Marking.-On account of the curved direction of the ulnar artery the line on the sur- face of the body which indicates its course is somewhat complicated. First, draw a line from the front of the internal condyle of the humerus to the radial side of the pisiform bone ; the lower two-thirds of this line represents the course of the middle and lower third of the ulnar artery. Secondly, draw a line from the centre of the hollow in front of the elbow-joint to the junction of the upper and middle third of the first line ; this represents the course of the upper third of the artery. Surgical Anatomy.-The application of a ligature to this vessel is required in cases of wound of the artery or of its branches, or in consequence of aneurism. In the upper half of the forearm the artery is deeply seated beneath the superficial flexor muscles, and the applica- tion of a ligature in this situation is attended with some difficulty. An incision is to be made in the course of a line drawn from the front of the internal condyle of the humerus to the outer side of the pisiform bone, so that the centre of the incision is three fingers' breadth below the internal condyle. The skin and superficial fascia having been divided and the deep fascia exposed, the white line which separates the Flexor carpi ulnaris from the other flexor muscles is to be sought for, and the fascia incised in this line. The Flexor carpi ulnaris is now to be carefully separated from the other muscles, when the ulnar nerve will be exposed, and must be drawn aside. Some little distance below the nerve the artery will be found accompanied by its venae comites, and may be ligatured by passing the needle from within outward. In the middle and lower third of the forearm this vessel may be easily secured by making an incision on the radial side of the tendon of the Flexor carpi ulnaris : the deep fascia being divided, and the Flexor carpi ulnaris and its companion muscle, the Flexor sublimis, being separated from each other, the vessel will be exposed, accompanied by its venae comites, the ulnar nerve lying on its inner side. The veins being separated from the artery, the ligature should be passed from the ulnar to the radial side, taking care to avoid the ulnar nerve. The branches of the ulnar artery may be arranged in the following groups : Anterior Ulnar Recurrent. Posterior Ulnar Recurrent. Forearm. Interosseous Anterior Interosseous. Posterior Interosseous. Muscular. -nr ■ . Anterior Carpal. Posterior Carpal. Hand Superficial Palmar Arch. Deep Palmar or Communicating. The anterior ulnar recurrent (Fig. 365) arises immediately below the elbow- joint, passes upward and inward between the Brachialis anticus aryl Pronator radii teres, supplies those muscles, and, in front of the inner condyle, anastomoses with the anastomotica magna and inferior profunda. The posterior ulnar recurrent is much larger, and arises somewhat lower than the preceding. It passes backward and inward, beneath the Flexor sublimis, and ascends behind the inner condyle of the humerus. In the interval between this process and the olecranon it lies beneath the Flexor carpi ulnaris, ascend- ing between the heads of that muscle, beneath the ulnar nerve; it supplies the neighboring muscles and joint, and anastomoses with the inferior profunda, anas- tomotica magna, and interosseous recurrent arteries (Fig. 366). The interosseous artery (Fig. 365) is a short trunk about an inch in length, and of considerable size, which arises immediately below the tuberosity of the radius, and, passing backward to the upper border of the interosseous membrane, divides into two branches, the anterior and posterior interosseous. The anterior interosseous passes down the forearm on the anterior surface of the interosseous membrane, to which it is connected by a thin aponeurotic arch. It is accompanied by the interosseous branch of the median nerve, and overlapped by the contiguous margins of the Flexor profundus digitorum and Flexor longus pollicis muscles, giving off in this situation muscular branches and the nutrient arteries of the radius and ulna. At the upper border of the Pronator quadratus a branch descends beneath the muscle to anastomose in front of the carpus with BRANCHES OF THE ULNAR ARTERY. 605 branches from the anterior carpal and deep palmar arch. The continuation of the artery passes behind the Pronator quadratus, and, piercing the interosseous membrane, gets to the back of the forearm, and anastomoses with the posterior interosseous artery (Fig- 366). It then descends to the back of the wrist to join the posterior carpal arch. The anterior interosseous gives off a long, slender branch, the median artery, which accom- panies the median nerve and gives offsets to its substance. This artery is sometimes much enlarged. It also gives off nutrient branches to the radius and ulna about the middle of the forearm. The posterior interosse- ous artery passes backward through the interval between the oblique ligament and the upper border of the interos- seous membrane. It appears between the contiguous bor- ders of the Supinator brevis and the Extensor ossis meta- carpi pollicis, and runs down the back part of the forearm, between the superficial and deep layer of muscles, to both of -which it distributes branches. At the lower part of the forearm it anastomoses with the termination of the anterior interosseous artery. Then, continuing its course over the head of the ulna, it joins the posterior carpal branch of the ulnar artery. This artery gives off, near its origin, the interosseous recur- rent branch. The interosseous recurrent artery is a large vessel which ascends to the interval be- tween the external condyle and olecranon, on or through the fibres of the Supinator brevis, but beneath the Anco- neus, anastomosing with a 7 branch from the superior pro- funda, and with the posterior ulnar recurrent and anas- tomotica magna. The muscular branches are distributed to the muscles along the ulnar side of the forearm. The anterior carpal is a small vessel which crosses the front of the carpus beneath the tendons of the Flexor profundus, and inosculates with a correspond- ing branch of the radial artery. Descending branch from superior profunda. Anastomotica magna. Posterior ulnar recurrent. ■Posterior interosseous. Termination of an- terior interosseous. Posterior carpal__ (ulnar). . ~ Posterior carpal (radial). -Radial. poll ids. indicis. Fig. 366.-Arteries of the back of the forearm and hand. 606 THE ARTERIES. The posterior carpal arises immediately above the pisiform bone, and winds backward beneath the tendon of the Flexor carpi ulnaris: it passes across the dorsal surface of the carpus beneath the extensor tendons, anastomosing with a corresponding branch of the radial artery; and forming the posterior carpal arch. Immediately after its origin it gives off a small branch which runs along the ulnar side of the metacarpal bone of the little finger, forming one of the meta- carpal arteries, and supplies the ulnar side of the dorsal surface of the little finger. The deep palmar or communicating branch (Fig. 365) passes deeply inward between the Abductor minimi digiti and Flexor brevis minimi digiti near their origins ; it anastomoses with the termination of the radial artery, completing the deep palmar arch. The Superficial Palmar Arch.-The superficial palmar arch passes outward across the palm of the hand, describing a curve, with its convexity forward to the space between the ball of the thumb and the index finger, where the arch is com- pleted by its anastomosing with a branch from the radialis indicis, though some- times the arch is completed by its anastomosing with the superficial volte branch of the radial artery. Relations.-The superficial palmar arch is covered by the skin, the Palmaris brevis, and the palmar fascia. It lies upon the annular ligament, origin of the muscles of the little finger, the tendons of the superficial flexor of the fingers, and, the divisions of the median and ulnar nerves. Relations of the Superficial Palmar Arch. In front. Skin. Palmaris brevis. Palmar fascia. Superficial Palmar Arch. Behind. Annular ligament. Origin of muscles of little finger. Superficial flexor tendons. Divisions of median and ulnar nerves. Branches of the Superficial Palmar Arch. Digital. The digital branches (Fig. 364), four in number, are given off from the con- vexity of the superficial palmar arch. They supply the ulnar side of the little finger and the adjoining sides of the little, ring, middle, and index fingers, the radial side of the index finger and thumb being supplied from the radial artery. The digital arteries at first lie superficial to the flexor tendons, but as they pass forward with the digital nerves to the clefts between the fingers they lie between them, and are there joined by the interosseous branches from the deep palmar arch. The digital arteries on the sides of the fingers lie beneath the digital nerves; and about the middle of the last phalanx the two branches for each finger form an arch, from the convexity of which branches pass to supply the pulp of the finger. Surface Marking.-The superficial palmar arch is represented by a curved line, starting from the outer side of the pisiform bone and carried downward as far as the middle third of the palm, and then curved outward on a level with the upper end of the cleft between the thumb and index finger. The deep palmar arch is situated about half an inch nearer to the carpus. THE THORACIC AORTA. 607 Surgical Anatomy.-Wounds of the palmar arches are of special interest, and are always difficult to deal with. When the wound in the superficial tissues is extensive, it may be possible to secure the bleeding ends of the vessel; but when there is a small punctured wound, as from a penknife or piece of glass, pressure systematically applied is probably the best course of treat- ment, as there is difficulty in reaching the wounded vessel without damaging important struc- tures. At the same time it must be admitted that pressure applied to the palm of the hand to arrest haemorrhage from a wound of one of the palmar arches, especially the deep arch, is apt to be followed by sloughing, owing to the rigidity of the parts and the facility with which a con- siderable amount of pressure can be applied. In wounds of the deep palmar arch a ligature may be applied to the bleeding points from the dorsum of the hand by resection of the upper part of the third metacarpal bone. It is useless in these cases to ligature one of the arteries of the forearm alone, and indeed simultaneous ligature of both radial and ulnar arteries above the wrist is often unsuccessful, on account of the anastomosis carried on by the carpal arches. Therefore, upon the failure of pressure to arrest haemorrhage it is expedient to apply a liga- ture to the brachial artery. THE DESCENDING AORTA. ARTERIES OF THE TRUNK. The Descending Aorta is divided into two portions, the thoracic and abdominal, in correspondence with the two great cavities of the trunk in which it is situated. THE THORACIC AORTA. The Thoracic Aorta commences at the lower border of the fourth dorsal ver- tebra, on the left side, and terminates at the aortic opening in the Diaphragm, in front of the last dorsal vertebra. At its commencement it is situated on the left side of the spine ; it approaches the median line as it descends, and at its termina- tion lies directly in front of the column. The direction of this vessel being influ- enced by the spine, upon which it rests, it describes a curve which is concave forward in the dorsal region. As the branches given off from it are small, the diminution in the size of the vessel is inconsiderable. It is contained in the back part of the posterior mediastinum. Relations.-It is in relation, in front, from above downward, with the left pul- monary artery, the left bronchus, the pericardium, and the oesophagus; behind, with the vertebral column and the vena azygos minor; on the right side, with the vena azygos major and thoracic duct; on the left side, with the left pleura and lung. The oesophagus, with its accompanying nerves, lies on the right side of the aorta above, but at the lower part of the thorax it gets in front of the aorta, and close to the Diaphragm is situated to its left side. Plan of the Relations of the Thoracic Aorta. In front. Left pulmonary artery. Left bronchus. Pericardium. (Esophagus. Righ t side. (Esophagus (above). Vena azygos major. Thoracic duct. Thoracic Aorta. Left side. Pleura. Left lung. (Esophagus (below). Behind. Vertebral column. Vena azygos minor. The aorta is occasionally found to be obliterated at a particular snot-viz. at the junction of the arch with the thoracic aorta, just below the ductus arteriosus. Whether this is the result of disease or of congenital malformation is immaterial to our present purpose ; it affords an interest- ing opportunity of observing the resources of the collateral circulation. The course of the anas- tomosing vessels, by which the blood is brought from the upper to the lower part of the artery, will be found well described in an account of two cases in the Pathological Transactions, vols. viii. and x. In the former (p. 162) Mr. Sydney Jones thus sums up the detailed description of the 608 777/v ARTERIES. anastomosing vessels: "The principal communications by which the circulation was carried on, were-Firstly, the internal mammary, anastomosing with the intercostal arteries, with the phrenic of the abdominal aorta by means of the musculo-phrenic and comes nervi phreniei, and largely with the deep epigastric. Secondly, the superior intercostal, anastomosing anteriorly by means of a large branch with the first aortic intercostal, and posteriorly with the posterior branch of the same artery. Thirdly, the inferior thyroid, by means of a branch about the size of an ordinary radial, formed a communication with the first aortic intercostal. Fourthly, the transversalis colli, by means of very large communications with the posterior branches of the intercostals. Fifthly, the branches (of the subclavian and axillary) going to the side of the chest were large, and anastomosed freely with the lateral branches of the intercostals.'' In the second case also (vol. x. p. 97) Mr. Wood describes the anastomoses in a somewhat similar manner, adding the remark that "the blood which was brought into the aorta through the anastomoses of the intercostal arteries appeared to be expended principally in supplying the abdomen and pelvis, while the sup- ply to the lower extremities had passed through the internal mammary and epigastrics. " Surgical Anatomy.-The student should now consider the effects likely to be produced by aneurism of the thoracic aorta, a disease of common occurrence. When we consider the great depth of the vessel from the surface and the number of important structures which surround it on every side, it may easily be conceived what a variety of obscure symptoms may arise from dis- ease of this part of the arterial system, and how they may be liable to be mistaken for those of other affections. Aneurism of the thoracic aorta most usually extends backward along the left side of the spine, producing absorption of the bodies of the vertebrae, with curvature of the spine; whilst the irritation or pressure on the cord will give rise to pain, either in the chest, back, or loins, with radiating pain in the left upper intercostal spaces, from pressure on the intercostal nerves; at the same time the tumor may project backward on each side of the spine, beneath the integument, as a pulsating swelling, simulating abscess connected with diseased bone, or it may displace the oesophagus and compress the lung on one or the other side. If the tumor extend forward, it may press upon and displace the heart, giving rise to palpitation and other symptoms of disease of that organ ; or it may displace, or even compress, the oesophagus, causing pain and difficulty of swallowing, as in stricture of that tube; and ultimately even open into it by ulcera- tion, producing fatal haemorrhage. If the disease extends to the right side, it may press upon the thoracic duct; or it may burst into the pleural cavity or into the trachea or lung ; and lastly, it may open into the posterior mediastinum. Branches of the Thoracic Aorta. Pericardiac. Bronchial. (Esophageal. Posterior Mediastinal. Intercostal. The pericardiac are a few small vessels, irregular in their origin, distributed to the pericardium. The bronchial arteries are the nutrient vessels of the lungs, and vary in num- ber, size, and origin. That of the right side arises from the first aortic intercostal, or by a common trunk with the left bronchial from the front of the thoracic aorta. Those of the left side, usually two in number, arise from the thoracic aorta, one a little lower than the other. Each vessel is directed to the back part of the corre- sponding bronchus along which it runs, dividing and subdividing upon the bron- chial tube, supplying them, the cellular tissue of the lungs, the bronchial glands, and the oesophagus. The oesophageal arteries, usually four or five in number, arise from the front of the aorta, and pass obliquely downward to the oesophagus, forming a chain of anastomoses along that tube, anastomosing with the oesophageal branches of the inferior thyroid arteries above, and with ascending branches from the phrenic and gastric arteries below. The posterior mediastinal arteries are numerous small vessels which supply the glands and loose areolar tissue in the mediastinum. The Intercostal arteries arise from the back part of the aorta. They are usu- ally eleven in number on each side, the superior intercostal space being supplied by the superior intercostal, a branch of the subclavian, and the second intercostal space being supplied by a branch from the superior intercostal joining with the first aortic intercostal. The lowest of these branches, the subcostal artery, underlies the last rib. The right intercostals are longer than the left, on account of the position of the aorta on the left side of the spine: they pass outward, across the bodies of the vertebrae, to the intercostal spaces, being covered by the pleura, the BRANCHES OF THE THORACIC AORTA. 609 oesophagus, thoracic duct, sympathetic nerve, and the vena azygos major; the left passing beneath the superior intercostal vein, the vena azygos minor, and sympa- thetic. In the intercostal spaces each artery divides into two branches-an ante- rior, or proper intercostal branch; and a posterior, or dorsal branch.1 The anterior branch passes outward, at first lying upon the External inter- Fig. 367.-The abdominal aorta and its branches. costal muscle, covered in front by the pleura and a thin fascia. It then passes between the two layers of Intercostal muscles, and, having ascended obliquely to the lower border of the rib above, divides, near the angle of that bone, into two branches: of these the larger runs in the groove on the lower border of the rib above; the smaller branch along the upper border of the rib below; passing 1 Mr. W. J. Walsham describes a small twig as being given off from each intercostal close to its origin. He states that they can be traced running between the neck of the rib and the transverse process of the corresponding vertebra ; they anastomose with similar twigs given off from the inter- costal artery next below. In the first and second spaces similar anastomosing twigs are given off' from the superior intercostal (Journal of Anatomy and Physiology, vol. xvi. part iii. p. 443). 610 THE ARTERIES. forward, they supply the Intercostal muscle, and anastomose with the anterior intercostal branches of the internal mammary, and with the thoracic branches of the axillary artery. The first aortic intercostal anastomoses with the superior intercostal, and the last three pass between the abdominal muscles, inosculating with the epigastric in front and with the phrenic and lumbar arteries. Each intercostal artery is accompanied by a vein and nerve, the former being above, and the latter below, except in the upper intercostal spaces, where the nerve is at first above the artery. The arteries are protected from pressure during the action of the Intercostal muscles by fibrous arches thrown across, and attached by each extremity to the bone. The lower intercostal arteries are continued anteriorly from the intercostal spaces into the abdominal wall, except the last, the subcostal, which lies throughout its whole course in the abdominal wall, since it is placed below the last rib. They pass behind the costal cartilages between the Internal oblique and Transversalis muscle to the sheath of the Rectus, where they anastomose with the internal mammary and the deep epigastric arteries. Behind, the subcostal artery anastomoses with the first lumbar artery. The posterior or dorsal branch of each intercostal artery passes backward to the inner side of the anterior costo-transverse ligament, and divides into a muscular branch which is distributed to the muscles and integument of the back, and a spinal branch which enters the spinal canal through the intervertebral foramina to be distributed to the spinal cord and its membranes, and to the bodies of the vertebrae in the same manner as the lateral spinal branches from the vertebral. The Abdominal Aorta commences at the aortic opening of the Diaphragm, in front of the body of the last dorsal vertebra, and, descending a little to the left side of the vertebral column, terminates on the body of the fourth lumbar vertebra, commonly a little to the left of the middle line,1 where it divides into the two common iliac arteries. It diminishes rapidly in size, in consequence of the many large branches which it gives off. As it lies upon the bodies of the vertebrae the curve which it describes is convex forward, the greatest convexity correspond- ing to the third lumbar vertebra, which is a little above and to the left side of the umbilicus. Relations.-It is covered, in front, by the lesser omentum and stomach, behind which are the branches of the coeliac axis and the solar plexus; below these, by the splenic vein, the pancreas, the left renal vein, the transverse portion of the duodenum, the mesentery, and aortic plexus. Behind, it is separated from the lumbar vertebrae by the left lumbar veins, the receptaculum chyli, and thoracic duct. On the right side it is in relation with the inferior vena cava (the right crus of the Diaphragm being interposed above), the vena azygos major, thoracic duct, and right semilunar ganglion; on the left side, with the sympathetic nerve and left semilunar ganglion. THE ABDOMINAL AORTA (Fig. 367). Plan of the Relations of the Abdominal Aorta. In front. Lesser omentum and stomach. Branches of the coeliac axis and solar plexus. Splenic vein. Pancreas. Left renal vein. Transverse duodenum. Mesentery. Aortic plexus. 1 Sir Joseph Lister, having accurately examined 30 bodies in order to ascertain the exact point of termination of this vessel, found it "either absolutely, or almost absolutely, mesial in 15, while in 13 it deviated more or less to the left, and in 2 was slightly to the right" (System of Surgery, edited by T. Holmes, 2d ed. vol. v. p. 652). THE ABDOMINAL AORTA. 611 Right side. Right crus of Diaphragm. Inferior vena cava. Vena azygos major. Thoracic duct. Right semilunar ganglion. Abdominal Aorta. ft side. [sympathetic nerve. Left semilunar ganglion. Behind. Left lumbar veins. Receptaculum chyli. Thoracic duct. Vertebral column. Surface Marking.-In order to map out the abdominal aorta on the surface of the abdomen, a line must be drawn from the middle line of the body, on a level with the distal extremity of the seventh costal cartilage, downward and slightly to the left, so that it just skirts the umbilicus, to a zone drawn round the body opposite the highest point of the crest of the ilium. This point is generally half an inch below and to the left of the umbilicus, but as the position of this structure varies with the obesity of the individual, it is not a reliable landmark as to the situation of the bifurcation of the aorta. Surgical Anatomy.-Aneurisms of the abdominal aorta near the coeliac axis communicate in nearly equal proportion with the anterior and posterior parts of the artery. When an aneurismal sac is connected with the back part of the abdominal aorta, it usually produces absorption of the bodies of the vertebrae, and forms a pulsating tumor that presents itself in the left hypochondriac or epigastric regions, and is accompanied by symptoms of dis- turbance in the alimentary canal. Pain is invariably present, and is usually of two kinds-a fixed and constant pain in the back, caused by the tumor pressing on or displacing the branches of the solar plexus and splanchnic nerves ; and a sharp lancinating pain, radiating along those branches of the lumbar nerves which are pressed on by the tumor; hence the pain in the loins, the testes, the hynogastrium, and in the lower limb (usually of the left side). This form of aneurism usually bursts into the peritoneal cavity or behind the peritoneum in the left hypo- chondriac region; or it may form a large aneurismal sac, extending down as low as Poupart's ligament; haemorrhage in these cases being generally very extensive, but slowly produced, and not rapidly fatal. When an aneurismal sac is connected with the front of the aorta near the coeliac axis, it forms a pulsating tumor in the left hypochondriac or epigastric regions, usually attended with symptoms of disturbance of the alimentary canal, as sickness, dyspepsia, or constipation, and accompanied by pain, which is constant, but nearly always fixed in the loins, epigastrium, or some part of the abdomen; the radiating pain being rare, as the lumbar nerves are seldom implicated. This form of aneurism may burst into the peritoneal cavity or behind the peritoneum, between the layers of the mesentery, or, more rarely, into the duodenum ; it rarely extends back- ward so as to affect the spine. The abdominal aorta has been tied several times, and although none of the patients perma- nently recovered, still, as one of them lived as long as ten days, the possibility of the re- establishment of the circulation may be considered to be proved. In the lower animals this artery has been often successfully tied. The vessel may be reached in several ways. In the original operation, performed by Sir A. Cooper, an incision was made in the linea alba, the peritoneum opened in front, the finger carried down amongst the intestines toward the spine, the peritoneum again opened behind by scratching through the mesentery, and the vessel thus reached. Or either of the operations described below for securing the common iliac artery may, by extend- ing the dissection a sufficient distance upward, be made use of to expose the aorta. The chief difficulty in the dead subject consists in isolating the artery in consequence of its great depth ; but in the living subject the embarrassment resulting from the proximity of the aneurismal tumor, and the great probability of disease in the vessel itself, add to the dangers and difficulties of this for- midable operation so greatly that it is very doubtful whether it ought ever to be performed. The collateral circulation would be carried on by the anastomosis between the internal mammary and the deep epigastric ; by the free communication between the superior and inferior mesenteries if the ligature were placed above the latter vessel; or by the anastomosis between the inferior mesenteric and the internal pudic when (as is more common) the point of ligature is below the origin of the inferior mesenteric; and possibly by the anastomoses of the lumbar arteries with the branches of the internal iliac. The circulation through the abdominal aorta may be commanded, in thin persons, by firm pressure with the fingers. A tourniquet has been invented for this purpose which is sometimes used in amputation at the hip-joint and some other operations. Branches of the Abdominal Aorta. Phrenic. Gastric. Hepatic. Splenic. Superior Mesenteric. Suprarenal. Renal. Spermatic in male. Ovarian in female. Inferior Mesenteric. Lumbar. Sacra Media. Coeliac Axis, 612 THE A RTE HIES. The branches may be divided into two sets : 1. Those supplying the viscera. 2. Those distributed to the walls of the abdomen. Visceral Branches. Gastric. Hepatic. Splenic. Renal. Spermatic or Ovarian. Parietal Branches. Phrenic. Lumbar. Sacra Media. Coeliac Axis. Superior Mesenteric. Inferior Mesenteric. Suprarenal. Visceral Branches of the Abdominal Aorta. The Coeliac Axis (Fig. 368). To expose this artery raise the liver, draw down the stomach, and then tear through the layers of the lesser omentum. The Coeliac Axis is a short thick trunk, about half an inch in length, which Cystic artery. , -I Probe passed through foramen of Winslow. Fig. 368.-The coeliac axis and its branches, the liver having been raised and the lesser omentum removed arises from the aorta opposite the margin of the Diaphragm, and, passing nearly horizontally forward (in the erect posture), divides into three large branches, the gastric, hepatic, and splenic, occasionally giving off one of the phrenic arteries. Relations.-It is covered by the lesser omentum. On the right side it is in relation with the right semilunar ganglion, and the lobus Spigelii; on the left side, with the left semilunar ganglion and cardiac end of the stomach. Below, it rests upon the upper border of the pancreas. THE (XELIAC AXIS. 613 The Gastric Artery (Coronaria ventriculi), the smallest of the three branches of the coeliac axis, passes upward and to the left side, to the cardiac orifice of the stomach, distributing branches to the oesophagus which anastomose with the aortic oesophageal arteries; others supply the cardiac end of the stomach, inoscu- lating with branches of the splenic artery ; it then passes from left to right, along the lesser curvature of the stomach to the pylorus, lying in its course between the layers of the lesser omentum, and giving branches to both surfaces of the organ : at its termination it anastomoses with the pyloric branch of the hepatic. The Hepatic Artery in the adult is intermediate in size between the gastric and splenic; in the foetus it is the largest of the three branches of the coeliac axis. It is first directed forward and to the right, to the upper margin of the pyloric end of the stomach, forming the lower boundary of the foramen of Winslow. It then passes upward between the layers of the lesser omentum, and in front of the fora- men of Winslow, to the transverse fissure of the liver, where it divides into two branches, right and left, which supply the corresponding lobes of that organ, accompanying the ramifications of the vena portae and hepatic duct. The hepatic artery, in its course along the right border of the lesser omentum, is in relation with the ductus communis choledochus and portal veins, the duct lying to the right of the artery and the vena portae behind. Its branches are-the Pyloric. Gastro-epiploica Dextra. Pancreatico-duodenalis Superior. x , j Gastro-duodenalis Cystic. The pyloric branch arises from the hepatic, above the pylorus, descends to the pyloric end of the stomach, and passes from right to left along its lesser curvature, supplying it with branches and inosculating with the gastric artery. The gastro-duodenalis (Fig. 369) is a short but large branch which descends, near the pylorus, behind the first portion of the duodenum, and divides at the lower border of the stomach into two branches, the gastro-epiploica dextra and the pan- creatico-duodenalis superior. Previous to its division it gives off two or three small inferior pyloric branches to the pyloric end of the stomach and pancreas. The gastro-epiploica dextra runs from right to left along the greater curvature of the stomach, between the layers of the great omentum, anastomosing about the middle of the lower border of the stomach with the gastro-epiploica sinistra from the splenic artery. This vessel gives oft' numerous branches, some of which ascend to supply both surfaces of the stomach, whilst others descend to supply the great omentum. The pancreatico-duodenalis superior descends between the contiguous margins of the duodenum and pancreas. It supplies both these organs, and anastomoses with the inferior pancreatico-duodenal branch of the superior mesenteric artery and with the pancreatic branches of the splenic. The cystic artery (Fig. 368), usually a branch of the right hepatic, passes upward and forward along the neck of the gall-bladder, and divides into two branches, one of which ramifies on its free surface, the other between it and the substance of the liver. The Splenic Artery, in the adult, is the largest of the three branches of the coeliac axis, and is remarkable for the extreme tortuosity of its course. It passes horizontally to the left side along the upper border of the pancreas, accompanied by the splenic vein, which lies below it, and on arriving near the spleen divides into branches, some of which enter the hilum of that organ to be distributed to its structure, whilst others are distributed to the great end of the stomach. Its branches are-the Pancreaticae Parvae. Pancreatica Magna. Gastric (Vasa Brevia). Gastro-epiploica Sinistra. 614 THE ARTERIES. The pancreatic are numerous small branches derived from the splenic as it runs behind the upper border of the pancreas, supplying its middle and left parts. One of these, larger than the rest, is given off from the splenic near the left extremity of the pancreas; it runs from left to right near the posterior surface of the gland, following the course of the pancreatic duct, and is called the pancreatica magna. These vessels anastomose with the pancreatic branches of the pancreatico- Fig. 369.-The coeliac axis and its branches, the stomach having been raised and the transverse meso-colon removed. duodenal arteries, derived from the hepatic on the one hand and superior mesenteric on the other. The gastric (vasa brevia) consists of from five to seven small branches, which arise either from the termination of the splenic artery or from its terminal branches, and, passing from left to right, between the layers of the gastro-splenic omentum, are distributed to the great curvature of the stomach, anastomosing with branches of the gastric and gastro-epiploica sinistra arteries. The gastro-epiploica sinistra, the largest branch of the splenic, runs from left to right along the great curvature of the stomach, between the layers of the great omentum, and anastomoses with the gastro-epiploica dextra. In its course it distributes several branches to the stomach, which ascend upon both surfaces; others descend to supply the omentum. In order to expose this vessel raise the great omentum and transverse colon, draw down the small intestines, and cut through the peritoneum where the transverse meso-colon and mesen- The Superior Mesenteric Artery (Fig. 370). THE SUPERIOR MESENTERIC ARTERY. 615 tery join : the artery will then be exposed just as it issues from beneath the lower border of the pancreas. The Superior Mesenteric Artery supplies the w hole length of the small intestine, except the first part of the duodenum ; it also supplies the caecum, ascending and transverse colon; it is a vessel of large size, arising from the fore part of the aorta about a quarter of an inch below the coeliac axis; being covered at its origin by the splenic vein and pancreas. It passes forward, between the pancreas and transverse portion of the duodenum, crosses in front of this portion of the intes- Fig, 370.-The superior mesenteric artery and its branches. tine, and descends between the layers of the mesentery to the right iliac fossa, where it terminates, considerably diminished in size. In its course it forms an arch, the convexity of which is directed forward and downward to the left side, the concavity backward and upward to the right. It is accompanied by the superior mesenteric vein, and is surrounded by a superior mesenteric plexus of nerves. Its branches are-the Inferior Pancreatico-duodenal. Vasa Intestini Tenuis. Ileo-colic. Colica Dextra. Colica Media. The Inferior pancreatico-duodenal is given off from the superior mesenteric behind the pancreas, and is distributed to the head of the pancreas with the 616 THE ARTERIES. transverse and descending portions of the duodenum, anastomosing with the superior pancreatico-duodenal artery. The vasa intestini tenuis arise from the convex side of the superior mesenteric artery. They are usually from twelve to fifteen in number, and are distributed to the jejunum and ileum. They run parallel with one another between the layers of the mesentery, each vessel dividing into two branches, which unite with a sim- ilar branch on each side, forming a series of arches the convexities of which are directed toward the intestine. From this first set of arches branches arise, which again unite with similar branches from either side, and thus a second series of arches is formed ; and from these latter, a third, and a fourth, or even fifth, series of arches is constituted, diminishing in size the nearer they approach the intestine. From the terminal arches numerous small straight vessels arise which encircle the intestine, upon which they are distributed, ramifying thickly between its coats. The ileo-colic artery is the lowest branch given off from the concavity of the superior mesenteric artery. It descends between the layers of the mesentery to the right iliac fossa, where it divides into two branches. Of these, the inferior one inosculates with the lowest branches of the vasa intestini tenuis, from the convexity of which branches proceed to supply the termination of the ileum, the caecum and appendix caeci, and the ileo-caecal valve. The superior division inos- culates with the colica dextra and supplies the commencement of the colon. The colica dextra arises from about the middle of the concavity of the superior mesenteric artery, and, passing behind the peritoneum to the middle of the ascending colon, divides into two branches-a descending branch, which inoscu- lates with the ileo-colic; and the ascending branch, which anastomoses w ith the colica media. These branches form arches, from the convexity of which vessels are distributed to the ascending colon. The branches of this vessel are covered with peritoneum only on their anterior aspect. The colica media arises from the upper part of the concavity of the superior mesenteric, and, passing forward between the layers of the transverse meso-colon, divides into two branches, the one on the right side inosculating with the colica dextra; that on the left side, with the colica sinistra, a branch of the inferior mesenteric. From the arches formed by their inosculation branches are distrib- uted to the transverse colon. The branches of this vessel lie between two layers of peritoneum. The Inferior Mesenteric Artery (Fig. 371). In order to expose this vessel draw the small intestines and mesentery over to the right side of the abdomen, raise the transverse colon toward the thorax, and divide the peritoneum covering the left side of the aorta. The Inferior Mesenteric Artery supplies the descending and sigmoid flexure of the colon and the greater part of the rectum. It is smaller than the superior mesenteric, and arises from the left side of the aorta, between one and two inches above its division into the common iliacs. It passes downward to the left iliac fossa, and then descends, between the layers of the meso-rectum, into the pelvis, under the name of the superior hemorrhoidal artery. It lies at first in close relation with the left side of the aorta, and then passes as the superior haemor- rhoidal in front of the left common iliac artery. Its branches are-the Colica Sinistra. Sigmoid. Superior Haemorrhoidal. The colica sinistra passes behind the peritoneum, in front of the left kidney, to reach the descending colon, and divides into two branches-an ascending branch, which inosculates with the colica media; and a descending branch, which anastomoses with the sigmoid artery. From the arches formed by these inoscu- lations branches are distributed to the descending colon. The sigmoid artery runs obliquely downward across the Psoas muscle to the THE SUPRARENAL ARTERIES. 617 sigmoid flexure of the colon, and divides into branches which supply that part of the intestine, anastomosing above with the colica sinistra, and below with the superior haemorrhoidal artery. This vessel is sometimes replaced by three or four small branches. The superior haemorrhoidal artery, the continuation of the inferior mesenteric, descends into the pelvis between the layers of the meso-rectum, crossing, in its Middle hxmorrhoidal. • Inferior haemorrhoidal. < Fig. 371.-The inferior mesenteric and its branches. course, the ureter and left common iliac vessels. It divides into twm branches, which descend one on each side of the rectum, and about five inches from the anus break up into several small branches, which are distributed between the mucous and muscular coats of that tube, nearly as far as its lower end, anastomosing with each other, with the middle haemorrhoidal arteries, branches of the internal iliac, and with the inferior haemorrhoidal branches of the internal pudic. The Suprarenal Arteries. The suprarenal arteries (Fig. 367) are two small vessels which arise, one on each side of the aorta, opposite the superior mesenteric artery. They pass obliquely upward and outward, over the crura of the Diaphragm, to the under surface of the suprarenal capsules, to which they are distributed, anastomosing with capsular branches from the phrenic and renal arteries. In the adult these arteries are of small size; in the foetus they are as large as the renal arteries. 618 THE ARTERIES. The Renal Arteries. The renal arteries are two large trunks which arise from the sides of the aorta immediately below the superior mesenteric artery. Each is directed outward across the crus of the Diaphragm, so as to form nearly a right angle with the aorta. The right is longer than the left, on account of the position of the aorta; it passes behind the inferior vena cava. The left is somewhat higher than the right. Previously to entering the kidney each artery divides into four or five branches which are distributed to its substance. At the hilum these branches lie between the renal vein and ureter, the vein being usually in front, the ureter behind. Each vessel gives off some small branches to the suprarenal capsule, the ureter, and the surrounding cellular tissue and muscles. Frequently there is a second renal artery, which is given off from the abdominal aorta at a lower level and supplies the lower portion of the kidney. It is termed the inferior renal artery. The spermatic arteries are distributed to the testes in the male and to the ovaria in the female. They are two slender vessels, of considerable length, which arise from the front of the aorta a little below the renal arteries. Each artery passes obliquely outward and downward behind the peritoneum, resting on the Psoas muscle, the right spermatic lying in front of the inferior vena cava, the left behind the sigmoid flexure of the colon. It then crosses obliquely over the ureter and the lower part of the external iliac artery to reach the internal abdominal ring, through which it passes, and accompanies the other constituents of the spermatic cord along the inguinal canal to the scrotum, where it becomes tortuous, and divides into several branches, two or three of which accompany the vas deferens and supply the epididymis, anastomosing with the artery of the vas deferens ; others pierce the back part of the tunica albuginea, and supply the substance of the testis. The Spermatic Arteries. The ovarian arteries are shorter than the spermatic, and do not pass out of the abdominal cavity. The origin and course of the first part of the artery are the same as the spermatic in the male, but on arriving at the margin of the pelvis the ovarian artery passes inward, between the two laminae of the broad ligament of the uterus, to be distributed to the ovary. One or two small branches supply the Fallopian tube ; another passes on to the side of the uterus and anastomoses with the uterine arteries. Other offsets are continued along the round ligament, through the inguinal canal, to the integument of the labium and groin. At an early period of foetal life, when the testes or ovaries lie by the side of the spine below the kidneys, the spermatic or ovarian arteries are short; but as these organs descend from the abdomen into the scrotum the arteries become gradually lengthened. Parietal Branches of the Abdominal Aorta. The Ovarian Arteries. The Phrenic Arteries. The phrenic arteries are two small vessels which present much variety in their origin. They may arise separately from the front of the aorta, immediately above the coeliac axis, or by a common trunk, which may spring either from the aorta or from the coeliac axis. Sometimes one is derived from the aorta, and the other from one of the renal arteries. In only one out of thirty-six cases examined did these arteries arise as two separate vessels from the aorta. They diverge from one another across the crura of the Diaphragm, and then pass obliquely upward and outward upon its under surface. The left phrenic passes behind the oesoph- agus and runs forward on the left side of the oesophageal opening. The right phrenic passes behind the inferior vena cava, and ascends along the right side of the aperture for transmitting that vein. Near the back part of the central tendon each vessel divides into two branches. The internal branch runs forward to the front of the thorax, supplying the Diaphragm and anastomosing with its fellow of THE SACRA MEDIA. 619 the opposite side, and with the musculo-phrenic and comes nervi phrenici, branches of the internal mammary. The external branch passes toward the side of the thorax and inosculates with the intercostal arteries. The internal branch of the right phrenic gives off a few vessels to the inferior vena cava, and the left one some branches to the oesophagus. Each vessel also sends capsular branches to the suprarenal capsule of its own side. The spleen on the left side and the liver on the right also receive a few branches from these vessels. The lumbar arteries are analogous to the intercostal. They are usually four in number on each side, and arise from the back part of the aorta, nearly at right angles with that vessel. They pass outward and backward, around the sides of the body of the lumbar vertebra, behind the sympathetic nerve and the Psoas magnus muscle, those on the right side being covered by the inferior vena cava, and the two upper ones on each side by the crura of the Diaphragm. In the interval between the transverse processes of the vertebrae each artery divides into a dorsal and an abdominal branch. The dorsal branch gives off, immediately after its origin, a spinal branch, which enters the spinal canal; it then continues its course backward between the trans- verse processes, and is distributed to the muscles and integument of the back, anastomosing with the similar branches of the adjacent lumbar arteries and with the posterior branches of the intercostal arteries. The spinal branch enters the spinal canal through the intervertebral foramen, to be distributed to the spinal cord and its membranes and to the bodies of the vertebrae in the same manner as the lateral spinal branches from the vertebral (see page 584). The abdominal branches pass outward, having a variable relation to the Quadratus lumborum muscle. Most frequently the first branch passes in front of the muscle and the others behind it; sometimes the order is reversed and the lowest branch passes in front of the muscle. At the outer border of the Quadratus they are continued between the abdominal muscles, anastomose with branches of the epigastric and internal mammary in front, the intercostals above, and those of the ilio-lumbar and circumflex iliac below. The Lumbar Arteries. The Middle Sacral Artery is a small vessel about the size of a crow-quill, which arises from the back part of the aorta just at its bifurcation. It descends upon the last lumbar vertebra, and along the middle line of the front of the sacrum, to the upper part of the coccyx, where it anastomoses with the lateral sacral arteries, and terminates in a minute branch, which runs down to the situation of the body presently to be described as "Luschka's gland." From it branches arise which run through the meso-rectum to supply the posterior surface of the rec- tum. Other branches are given off on each side, which anastomose with the lateral sacral arteries, and send off small offsets which enter the anterior sacral foramina. The artery is the representative of the caudal prolongation of the aorta of animals, and its lateral branches correspond to the intercostal and lumbar arteries in the dorsal and lumbar regions. Coccygeal Gland, or Luschka's Gland.-Lying near the tip of the coccyx in a small tendinous interval formed by the union of the Levator ani muscles of each side, and just above the coccygeal attachment of the Sphincter ani, is a small conglobate body about as large as a lentil or a pea, first described by Luschka,1 and named by him the coccygeal gland. Its most obvious connections are with the arteries of the part. Structure.-It consists of a congeries of small arteries with little aneurismal dilatations derived from the middle sacral and freely communicating with each 1 Der Himanhang und die Steissdriise des Menschen, Berlin, 1860; Anatomic des Menschen, Tubingen, 1864, vol. ii. pt. 2, p. 187. The Sacra Media. 620 THE A RTE HIES. other. These vessels are enclosed in one or more layers of polyhedral granular cells, and the whole structure is invested in a capsule of connective tissue which sends in trabeculae, dividing the interior into a number of spaces in which the vessels and cells are contained. Nerves pass into this little body from the sympathetic, but their mode of termination is unknown. Macalister believes the glomerulus of vessels " consists of the condensed and convoluted metameric dorsal arteries of the caudal segments imbedded in tissue which is possibly a small persisting fragment of the neurenteric canal." The abdominal aorta divides into the two common iliac arteries. The bifurca- tion usually takes place on the left side of the body of the fourth lumbar vertebra. This point corresponds to the left side of the umbilicus, and is on a level with a line drawn from the highest point of one iliac crest to the other. The common iliac arteries are about two inches in length; diverging from the termination of the aorta, they pass downward and outward to the margin of the pelvis, and divide opposite the intervertebral substance, between the last lumbar vertebra and the sacrum into two branches, the external and internal iliac arteries, the former supplying the lower extremity ; the latter, the viscera and parietes of the pelvis. The right common iliac is somewhat larger than the left, and passes more obliquely across the body of the last lumbar vertebra. In front of it are the peritoneum, the small intestine, branches of the sympathetic nerve, and, at its point of division, the ureter. Behind, it is separated from the last lumbar vertebra by the two common iliac veins. .On its outer side, it is in relation with the inferior vena cava and the right common iliac vein above, and the Psoas magnus muscle below. The left common iliac is in relation, in front, with the peritoneum, branches of the sympathetic nerve and the superior haemorrhoidal artery, and is crossed at its point of bifurcation by the ureter. The left common iliac vein lies partly on the inner side and partly beneath the artery ; on its outer side the artery is in relation with the Psoas magnus muscle. THE COMMON ILIAC ARTERIES. Plan of the Relations of the Common Iliac Arteries. In front. Peritoneum. Small intestines. Sympathetic nerves. Ureter. Iii front. Peritoneum. Sympathetic nerves. Superior haemorrhoidal artery. Ureter. Outer side. Vena cava. Right common iliac vein. Psoas muscle. Inner side. Left common iliac vein. Left Common Iliac. Outer side. Psoas muscle. Right Common Iliac. Behind. Last lumbar vertebra. Right and left common iliac veins. Behind. Last lumbar vertebra. Left common iliac vein. Branches.-The common iliac arteries give off small branches to the peritoneum Psoas magnus, ureters, and the surrounding cellular tissue, and occasionally give origin to the ilio-lumbar or renal arteries. Peculiarities.-The potato/ origin varies according to the bifurcation of the aorta. In three-fourths of a large number of cases the aorta bifurcated either upon the fourth lumbar vertebra or upon the intervertebral disk between it and the fifth, the bifurcation being, in one case out of nine below, and in one out of eleven above, this point. In ten out of every thirteen cases the vessel bifurcated within half an inch above or below the level of the crest of the ilium more frequently below than above. The point of division is subject to great variety. Tn two-thirds of a large number of cases it was between the last lumbar vertebra and the upper border of the sacrum being above that THE COMMON ILIAC ARTERIES. 621 point in one case out of eight; and below it in one case out of six. The left common iliac artery divides lower down more frequently than the right. The relative length, also, of the two common iliac arteries varies. The right common iliac was the longer in sixty-three cases, the left in fifty-two, whilst they were both equal in fifty- three. The length of the arteries varied in five-sevenths of the cases examined from an inch and a half to three inches; in about half of the remaining cases the artery was longer and in the other half shorter, the minimum length being less than half an inch, the maximum four and a half inches. In two instances the right common iliac has been found wanting, the external and internal iliacs arising directly from the aorta. Surface Marking.-Draw a zone round the body opposite the highest part of the crest of the ilium ; in this line take a point half an inch to the left of the middle line. From this Ileo-lumbar. -Gluteal. Fig. 372.-Arteries of the pelvis. draw two lines to points midway between the anterior superior spines of the ilium and the symphysis pubis. These two diverging lines will represent the course of the common and external iliac arteries. Draw a second zone round the body corresponding to the level of the anterior superior spines of the ilium : the portion of the diverging lines between the two zones will represent the course of the common iliac artery; the portion below the lower zone, that of the external iliac artery. Surgical Anatomy.-The application of a ligature to the common iliac artery may be required on account of aneurism or haemorrhage implicating the external or internal iliacs. The artery may be tied by one or two incisions: 1, an anterior or iliac incision, by which the vessel is approached more directly from the front; and 2, a posterior abdominal or lumbar incision, by which the vessel is reached from behind. If the surgeon select the iliac region, a curved incis- ion, from five to eight inches in length according to the amount of fat, is made, commencing just outside the middle of Poupart's ligament and a finger's breadth above it, and carried outward toward the anterior superior iliac spine, then upward toward the ribs, and finally curving inward 622 THE ARTERIES. toward the umbilicus. The abdominal muscles and transversahsfascia are div ded, and the peri- toneum raised upward and inward until the Psoas is reached. The artery will be found on the inner side of this muscle, and is to be cleared with a director, especial care being taken on the right side, as here the common iliac veins lie behind the artery, lhe aneurism needle is to be passed from within outward. But if the aneunsmal tumor should extend high up in the abdomen, along the external iliac, it is better to select the posterior or lumbar, by making an incision partly in the abdomen, partly in the loin. The incision is commenced at the anterior extremity of the last rib proceeding directly downvrard to the ilium, it is. then curved foiwaid along the crest of the ilium and a little above it to the anterior superior spine of that bone. The abdominal mus- cles having been cautiously divided in succession, the transversalis fascia must be carefully cut through, and the peritoneum, together with the ureter, separated from the artery and pushed aside ■' the sacro-iliac articulation must then be felt for, and upon it the vessel will be felt pulsat- ing, and may be fully exposed in close connection with its accompanying vein. On the right side both common iliac veins, as well the inferior vena cava, are in close connection with the artery, and must be carefully avoided. On the left side the vein usually lies on the inner side and behind the artery ; but it occasionally happens that the two common iliac veins are joined on the left instead of the right side, which would add much to the difficulty of an operation in such a case. The common iliac artery may be so short that danger may be apprehended from second- ary haemorrhage if a ligature is applied to it. It would be preferable, in such a case, to tie both the external and internal iliacs near their origin. Collateral Circulation.-The principal agents in carrying on the collateral circulation after the application of a ligature to the common iliac are-the anastomoses of the haemorrhoidal branches of the internal iliac with the superior haemorrhoidal from the inferior mesenteric; the anastomoses of the uterine and ovarian arteries and of the vesical arteries of opposite sides ; of the lateral sacral with the middle sacral artery ; of the epigastric with the internal mammary, inferior intercostal, and lumbar arteries; of the circumflex iliac with the lumbar arteries ; of the ilio-lumbar with the last lumbar artery; of the obturator artery, by means of its pubic branch, with the vessel of the opposite side and with the deep epigastric. Compression of the Common Iliac Arteries.-The common iliac arteries are most effi- ciently compressed by Davy's lever. The instrument consists of a gum-elastic tube about two feet long, in which fits a round wooden "lever " considerably longer than the tube. A small quantity of olive oil having been injected into the rectum, the gum-elastic tube, softened in hot water, is passed into the bowel sufficiently far to permit its pressing upon the common iliac artery as it lies in the groove between the last lumbar vertebra and the Psoas muscle. The wooden lever is then inserted into the tube, and the projecting end carried toward the opposite thigh and raised, when it acts as a lever of the first order, the anus being the fulcrum. In cases where the meso-rectum is abnormally short it may be impossible, without unjustifiable force, to compress the artery on the right side. The internal iliac artery supplies the walls and viscera of the pelvis, the gen- erative organs, and inner side of the thigh. It is a short, thick vessel, smaller in the adult than the external iliac, and about an inch and a half in length. It arises at the point of bifurcation of the common iliac, and, passing downward to the upper margin of the great sacro-sciatic foramen, divides into two large trunks an anterior and posterior ; from its point of bifurcation a partially obliterated cord' the hypogastric artery, extends forward to the bladder. Relations.-In front, with the ureter, which separates it from the peritoneum Behind, with the internal iliac vein, the lumbo-sacral nerve, and Pvriformis mus- cle. By its outer side, near its origin, with the Psoas magnus muscle Internal Iliac Artery (Fig. 372). Plan of the Relations of the Internal Iliac Artery. In front. Peritoneum. Ureter. Outer side. Psoas magnus. Internal Iliac. Behind. Internal iliac vein. Lumbo-sacral nerve. Pyriformis muscle. THE INTERNAL ILIAC ARTERY. 623 In the foetus the internal iliac artery (hypogastric) is twice as large as the external iliac, and appears to be the continuation of the common iliac. Instead of into the pelvis, it passes forward to the bladder, and ascends along the sides of that viscus to its summit, to which it gives branches; it then passes upward along the back part of the anterior wall of the abdomen to the umbilicus, converging toward its fellow of the opposite side. Having passed through the umbilical opening, the two arteries twine round the umbilical vein, forming with it the umbilical cord, and ultimately ramify in the placenta. The portion of the vessel within the abdomen is called the hypogastric artery, and that external to that cavity, the umbilical artery. At birth, when the placental circulation ceases, the upper portion of the hypogastric artery, extending from the summit of the bladder to the umbilicus, contracts, and ultimately dwindles to a solid fibrous cord; but the lower portion, extending from its origin (in what is now the internal iliac artery) for about an inch and a half to the wall of the bladder, and thence to the summit of that organ, is not totally impervious, though it becomes considerably reduced in size, and serves to convey blood to the bladder under the name of the superior vesical artery. Peculiarities as regards Length.-In two-thirds of a large number of cases the length of the internal iliac varied between an inch and an inch and a half; in the remaining third it was more frequently longer than shorter, the maximum length being three inches, the minimum half an inch. The lengths of the common and internal iliac arteries bear an inverse proportion to each other, the internal iliac artery being long when the common iliac is short, and vice versa. As regards its Place of Division.-The place of division of the internal iliac varies between the upper margin of the sacrum and the upper border of the sacro-sciatic for- amen. . . . The arteries of the two sides in a series of cases often differed in length, but neither seemed pnnQtan11v tn pypppii flip nt I) PT' Surgical Anatomy-The application of a ligature to the internal iliac artery may be required in cases of aneurism or haemorrhage affecting one of its branches. The vessel may be secured by making an incision through the abdominal parietes in the iliac region in a direction and to an extent similar to that for securing the common iliac; the transversalis fascia having been cautiously divided, and the peritoneum pushed inward from the ihac fossa toward the pelvis, the finger may feel the pulsation of the external iliac at the bottom of the wound,. and by tracing this vessel upward the internal iliac is arrived at, opposite the sacro-ihac articulation. It should be remembered that the vein lies behind and on the right side, a little external to the artery, and in close contact with it; the ureter and peritoneum, which he in front, must also be avoided. The degree of facility in applying a ligature to this vessel will mainly depend upon its length. It has been seen that in the great majority of the cases examined the artery was short, varying from an inch to an inch and a half; in these cases the artery is deeply seated in the pelvis; when, on the contrary, the vessel is longer, it is found partly above that cavity, it the artery is very short, as occasionally happens, it would be preferable to apply a ligature to the common iliac or upon the external and internal iliacs at then ongm. . . Probably a better method of tying the internal iliac artery is by an abdomina section in the median line and reaching the vessel through the peritoneal cavity. Tins plan has been advocated by Dennis of New York on the following grounds: (1) It no way increases the danger of the operation; (2) it prevents a series of accidents which have occurred during ligature of artery by the older methods; (3) it enables the surgeon to ascertam the exact extent of disease in the main arterial trunk, and select his spot for the application of the ligature, and (4) it "coilateral'cireulation.-In Professor Owen's dissection of a case in which the '"fo™1 iliac artery had been tied by Stevens ten years before death for aneurism of the sciatic artery, ihac was found impervious for about an inch above the point where hedigatnre had St" p"r£ ' Xliteratedas far Z& point of connection with the aneurism.) tumor, but on the distal side of the St was continued down along the back of the thigh nearly as large in size as the femoral, . • ■ ki-nrf an inoh below the sac bv receiving an anastomosing vessel from the pro »f ",m"e and o™ria" arterle8; 1 Medico-Chirurgical Trans., vol. xvi. 624 THE ARTERIES. of the opposite vesical arteries; of the haemorrhoidal branches of the internal iliac with those from the inferior mesenteric; of the obturator artery, by means of its pubic branch, with the vessel of the opposite side and with the epigastric and internal circumflex, o e circumflex and perforating branches of the profunda femoris with the sciatic; of the gluteal with the posterior branches of the sacral arteries; of the iho-lumbar with the last lumbar, of the lateral sacral with the middle sacral; and of the circumflex iliac with the iho-lumbar and gluteal. Branches of the Internal Iliac. From the Anterior Trunk. Superior Vesical. Middle Vesical. Inferior Vesical. Middle Haemorrhoidal. Obturator. Internal Pudic. Sciatic. From the Posterior Trunk. Ilio-lumbar. Lateral Sacral. Gluteal. In female ■ Uterine. Vaginal. The superior vesical is that part of the foetal hypogastric artery which remains pervious after birth. It extends to the side of the bladder, distributing numerous branches to the apex and body of the organ. From one of these a slender vessel is derived which accompanies the vas deferens in its course to the testis, where it anastomoses with the spermatic artery. This is the artery of the vas deferens. Other branches supply the ureter. The middle vesical, usually a branch of the superior, is distributed to the base of the bladder and under surface of the vesiculae seminales. The inferior vesical arises from the anterior division of the internal iliac, frequently in common with the middle haemorrhoidal, and is distributed to the base of the bladder, the prostate gland, and vesiculae seminales. The branches distributed to the prostate communicate with the corresponding vessel of the opposite side. The middle hsemorrhoidal artery usually arises together with the preceding vessel. It supplies the rectum, anastomosing with the other hsemorrhoidal arteries. The uterine artery passes inward from the anterior trunk of the internal iliac to the neck of the uterus. Ascending, in a tortuous course on the side of this viscus, between the layers of the broad ligament, it distributes branches to its substance, anastomosing, near its termination, with a branch from the ovarian artery. Branches from this vessel are also distributed to the bladder and ureter. The vaginal artery is analogous to the inferior vesical in the male; it descends upon the vagina, supplying its mucous membrane, and sending branches to the neck of the bladder and contiguous part of the rectum. The Obturator Artery usually arises from the anterior trunk of the internal iliac, frequently from the posterior. It passes forward, below the brim of the pelvis, to the upper part of the obturator foramen, and, escaping from the pelvic cavity through a short canal formed by a groove on the under surface of the horizontal ramus of the os pubis and the arched border of the obturator mem- brane, it divides into an internal and external branch. In the pelvic cavity this vessel lies upon the pelvic fascia, beneath the peritoneum, and a little below the obturator nerve. Branches.- the pelvis, the obturator artery gives off an iliac branch to the iliac fossa, which supplies the bone and the Iliacus muscle, and anastomoses with the iho-lumbar artery; a branch, which runs backward to sunnlv the bladder; and a pubic branch, which is given off' from the vessel just before it leaves the pelvic cavity. Ibis branch ascends upon the back of the os pubis BRANCHES OF THE INTERNAL ILIAC. 625 communicating with offsets from the deep epigastric artery and with the corre- sponding vessel of the opposite side. This branch is placed on the inner side of the femoral ring External to the pelvis, the obturator artery divides into an internal and an external branch, which are deeply situated beneath the Obturator externus muscle. 1 he internal branch curves downward along the inner margin of the obturator foramen, distributing branches to the Obturator externus muscle, Pectineus Adductors, and Gracilis, and anastomoses with the external branch and with the internal circumflex artery. 1 he external branch curves round the outer margin of the foramen to the space between the Gemellus inferior and Quadratus femoris, where it anastomoses with the sciatic artery. It supplies the Obturator muscles, anastomoses, as it passes backward, with the internal branch and with the internal circumflex, and Fig. 373.-Variations in origin and course of obturator artery sends a branch to the hip-joint through the cotyloid notch, which ramifies on the round ligament as far as the head of the femur. Peculiarities.-In two out of every three cases the obturator arises from the internal iliac : in one case in three and a half from the epigastric ; and in about one in seventy-two cases by two roots from both vessels. It arises in about the same proportion from the external iliac artery. The origin of the obturator from the epigastric is not commonly found on both sides of the same body. When the obturator artery arises at the front of the pelvis from the epigastric, it descends almost vertically to the upper part of the obturator foramen. The artery in this course usually lies in contact with the external iliac vein and on the outer side of the femoral ring (Fig. 373, a) ; in such cases it would not be endangered in the operation for femoral hernia. Occasionally, however, it curves inward along the free margin of Gimbernat's ligament (Fig. 373, b), and under such circumstances would almost completely encircle the neck of a hernial sac (supposing a hernia to exist in such a case), and would be in great danger of being wounded if an operation was performed. The internal pudic is the smaller of the two terminal branches of the anterior trunk of the internal iliac, and supplies the external organs of generation. Though the course of the artery is the same in the two sexes, the vessel is much smaller in the female than in the male, and the distribution of its branches somewhat different. The description of its arrangement in the male will first be given, and subsequently the differences which it presents in the female will be mentioned. The Internal Pudic Artery in the Male passes downward and outward to the lower border of the great sacro-sciatic foramen, and emerges from the pelvis between the Pyriformis and Coccygeus muscles : it then crosses the spine of the ischium and re-enters the pelvis through the lesser sacro-sciatic foramen. The artery now crosses the Obturator internus muscle along the outer wall of the ischio- rectal fossa, being situated about an inch and a half above the lower margin of the ischial tuberosity. It is here contained in a sheath of the obturator fascia, and gradually approaches the margin of the ramus of the ischium, along which it passes forward and upward, pierces the posterior layer of the deep perineal fascia, and runs forward along the inner margin of the ramus of the os pubis ; finally, it perforates the anterior layer of the deep perineal fascia and divides into its two 626 THE ARTERIES. terminal branches, the dorsal artery of the penis and the artery of the corpus cavernosum. Relations.-In the first part of its course, within the pelvis, it lies in front of the Pyriformis muscle and sacral plexus of nerves, and on the outer side of the rectum (on the left side). As it crosses the spine of the ischium it is covered by Spine of Obtur- In- External ischium. ator. ternal iliac. iliac. I PSOAS MAGNUS Dorsal artery. Artery of \ the corpus cavernosum.'' Superficial perineal. Internal pudic. Inferior hsemorr- hoidal. Internal pudic. Sciatic. Small sciatic. Fig. 374.-The internal pudic artery and its branches in the male the Gluteus maximus. In the pelvis it lies on the outer side of the ischio-rectal fossa, upon the surface of the Obturator internus muscle, contained in a fibrous canal formed by the obturator fascia and the falciform process of the great sacro- sciatic ligament. It is accompanied by the pudic veins and the internal pudic nerve. Peculiarities.-The internal pudic is sometimes smaller than usual, or fails to give off one or two of its usual branches ; in such cases the deficiency is supplied by branches derived from an additional vessel, the accessory pudic, which generally arises from the internal pudic artery before its exit from the great sacro-sciatic foramen. It passes forward along the lower part of the bladder and across the side of the prostate gland to the root of the penis, where it perforates the triangular ligament and gives off the branches usually derived from the pudic artery. The deficiency most frequently met with is that in which the internal pudic ends as the artery of the bulb, the artery of the corpus cavernosum and arteria dorsalis penis being derived from the accessory pudic. Or the pudic may terminate as the superficial perineal, the artery of the bulb being derived, with the other two branches, from the accessory vessel. Surgical Anatomy.-The relation of the accessory pudic to the prostate gland and urethra is of the greatest interest in a surgical point of view, as this vessel is in danger of being wounded in the lateral operation of lithotomy. The student should also study the position of the internal pudic artery and its branches, when running a normal course, with regard to the same operation. The superficial and the transverse perineal arteries are, of necessity, divided in this operation, but the haemorrhage from these vessels is seldom excessive; should a ligature be required, it can readily be applied on account of their superficial position. The artery of the bulb may be divided if the incision be carried too far forward, and injury of this vessel maybe attended with serious or even fatal consequences. The main trunk of the internal pudic artery may be wounded if the incision be carried too far outward ; but, being bound down by the strong obturator fascia and under cover of the ramus of the ischium, the accident is not very likely to occur unless the vessel runs an anomalous course. BRANCHES OF THE INTERNAL ILIAC. 627 Branches.-The branches of the internal pudic artery are- Muscular. Inferior Haemorrhoidal. Superficial Perineal. Transverse Perineal. Artery of the Bulb. Artery of the Corpus Cavernosum. Dorsal Artery of the Penis. The muscular branches consist of two sets-one given off in the pelvis, the other as the vessel crosses the ischial spine. The former are several small offsets which supply the Levator ani, the Obturator interims, the Pyriformis, and the Coccygeus muscles. The branches given off outside the pelvis are distributed to the adjacent part of the Gluteus maximus and External rotator muscles. They anastomose with branches of the sciatic artery. The inferior hsemorrhoidal are two or three small arteries which arise from the internal pudic as it passes above the tuberosity of the ischium. Crossing the ischio-rectal fossa, they are distributed to the muscles and integument of the anal region. The superficial perineal artery supplies the scrotum and muscles and integu- ment of the perinaeum. It arises from the internal pudic in front of the preceding branches, and turns upward, crossing either over or under the Transversus perinaei muscle, and runs forward, parallel to the pubic arch, in the interspace between the Accelerator urinae and Erector penis muscles, both of which it supplies, and is finally distributed to the skin and dartos of the scrotum. In its passage through the perinaeum it lies beneath the superficial perineal fascia. The transverse perineal is a small branch which arises either from the internal pudic or from the superficial perineal artery as it crosses the Transversus perinaei muscle. It runs transversely inward along the cutaneous surface of the Trans- versus perinaei muscle, which it supplies, as well as the structures between the anus and bulb of the urethra, and anastomoses with the one of the opposite side. The artery of the bulb is a large but very short vessel which arises from the internal pubic between the two layers of the deep perineal fascia, and, passing nearly transversely inward, pierces the bulb of the urethra, in which it ramifies. It gives off a small branch which descends to supply Cowper's gland. Surgical Anatomy.-This artery is of considerable importance in a surgical point of view, as it is in danger of being wounded in the lateral operation of lithotomy-an accident usually attended in the adult with alarming haemorrhage. The vessel is sometimes very small, occasion- ally wanting, or even double. It sometimes arises from the internal pudic earlier than usual, and crosses the perinaeum to reach the back part of the bulb. In such a case the vessel could hardly fail to be wounded in the performance of the lateral operation of lithotomy. If, on the contrary, it should arise from an accessory pudic, it lies more forward than usual and is out of danger in the operation. The artery of the corpus cavernosum, one of the terminal branches of the inter- nal pudic, arises from that vessel while it is situated between the crus penis and the ramus of the os pubis ; piercing the crus penis obliquely, it runs forward in the centre of the corpus cavernosum, to which its branches are distributed. The dorsal artery of the penis ascends between the crus and pubic symphysis, and, piercing the suspensory ligament, runs forward on the dorsum of the penis to the glans, where it divides into two branches which supply the glans and prepuce. On the dorsum of the penis it lies immediately beneath the integument, parallel with the dorsal vein and the corresponding artery of the opposite side. It supplies the integument and fibrous sheath of the corpus cavernosum, sending branches through the sheath to anastomose with the preceding vessel. The Internal Pudic Artery in the Female is smaller than in the male. Its origin and course are similar, and there is considerable analogy in the distribution of its branches. The superficial artery supplies the labia pudendi; the artery of the bulb supplies the bulbi vestibuli and the erectile tissue of the vagina; the artery of the corpus cavernosum supplies the cavernous body of the clitoris; and the arteria dorsalis clitoridis supplies the dorsum of that organ, and terminates in the glans and in the membranous fold corresponding to the prepuce of the male. 628 THE ARTERIES. The Sciatic Artery (Fig. 375), the larger of the two terminal branches of the anterior trunk of the internal iliac, is distributed to the muscles at the back of the pelvis. It passes down to the lower part of the great sacro-sciatic foramen behind the internal pudic artery, resting on the sacral plexus of nerves and Pvriformis muscle, and escapes from the pelvis through this foramen between the Pyriformis and Coccygeus. It then descends in the interval between the trochanter major and tuberosity of the ischium, ac- companied by the sciatic nerves, and covered by the Gluteus maximus, and is continued down the back of the thigh supplying the skin, and anastomosing with branches of the perforating arte- ries. Within the pelvis it distrib- utes branches to the Pyriformis, Coccygeus, and Levator ani muscles; some haemorrhoidal branches, which supply the rectum, and occasionally take the place of the middle haemor- rhoidal artery; and vesical branches to the base and neck of the bladder, vesiculae semi- nales, and prostate gland. Ex- ternal to the pelvis it gives off the following branches: Coccygeal. Inferior Gluteal. Comes Nervi Ischiadici. Muscular. Articular. The coccygeal branch runs inward, pierces the great sacro- sciatic ligament, and supplies the Gluteus maximus, the in- tegument, and other structures on the back of the coccyx. The inferior gluteal branches, three or four in number, supply the Gluteus maximus muscle, anastomosing with the gluteal artery in the substance of the muscle. The comes nervi ischiadici is a long, slender vessel which accompanies the great sciatic nerve for a short distance; it then penetrates it and runs in its substance to the lower part of the thigh. The muscular branches supply the muscles on the back part of the hip, anas- tomosing with the gluteal, external branch of the obturator, internal and exter- nal circumflex, and superior perforating arteries. Some articular branches are distributed to the capsule of the hip-joint. The Ilio-lumbar Artery, given off from the posterior trunk of the internal Termination of internal circumflex. Superior perforating. Middle perforating. Inferior perforating. Termination of profunda. -Superior muscular. Superior internal, articular. Superior external articular. - Inferior muscular. Fig. 375.-The arteries of the gluteal and posterior femoral regions. BRANCHES OF THE INTERNAL ILIAC. 629 iliac, turns upward and outward between the obturator nerve and lumbo-sacral cord, to the inner margin of the Psoas muscle, behind which it divides into a lum- bar and an iliac branch. The lumbar branch supplies the Psoas and Quadratus lumborum muscles, anastomosing with the last lumbar artery, and sends a small spinal branch through the intervertebral foramen, between the last lumbar vertebra and the sacrum, into the spinal canal, to supply the spinal cord and its membranes. The iliac branch descends to supply the Iliacus muscle; some offsets, running between the muscle and the bone, anastomose with the iliac branch of the obturator; one of these enters an oblique canal to supply the diploe, whilst others run along the crest of the ilium, distributing branches to the Gluteal and Abdom- inal muscles, and anastomose in their course with the gluteal, circumflex iliac, and external circumflex arteries. The Lateral Sacral Arteries (Fig. 372) are usually two in number on each side, superior and inferior. The superior, which is of large size, passes inward, and, after anastomosing with branches from the middle sacral, enters the first or second sacral foramen, is distributed to the contents of the sacral canal in the same manner as the lateral spinal branches from the vertebral, and, escaping by the corresponding posterior sacral foramen, supplies the skin and muscles on the dorsum of the sacrum, anas- tomosing with the gluteal. The inferior passes obliquely across the front of the Pyriformis muscle and sacral nerves to the inner side of the anterior sacral foramina, descends on the front of the sacrum, and anastomoses over the coccyx with the sacra media and opposite lateral sacral arteries. In its course it gives off branches which enter the anterior sacral foramina; these, after giving off branches to be distributed to the contents of the sacral canal in the same manner as the lateral spinal branches from the vertebral, escape by the posterior sacral foramina, and are distributed to the muscles and skin on the dorsal surface of the sacrum, anastomosing with the gluteal. The Gluteal Artery is the largest branch of the internal iliac, and appears to be the continuation of the posterior division of that vessel. It is a short, thick trunk, which passes out of the pelvis above the upper border of the Pyriformis muscle, and immediately divides into a superficial and deep branch. Within the pelvis it gives off a few muscular branches to the Iliacus, Pyriformis, and Obtu- rator internus, and, just previous to quitting that cavity, a nutrient artery, which enters the ilium. The superficial branch passes beneath the Gluteus maximus and divides into numerous branches, some of which supply that muscle, whilst others perforate its tendinous origin, and supply the integument covering the posterior surface of the sacrum, anastomosing with the posterior branches of the sacral arteries. The deep branch runs between the Gluteus medius and minimus, and sub- divides into two. Of these, the superior division, continuing the original course of the vessel, passes along the upper border of the Gluteus minimus to the anterior superior spine of the ilium, anastomosing with the circumflex iliac and ascending branches of the external circumflex artery. The inferior division crosses the Gluteus minimus obliquely to the trochanter major, distributing branches to the Glutei muscles, and inosculates with the external circumflex artery. Some branches pierce the Gluteus minimus to supply the hip-joint. Surface Marking.-The position of the three main branches of the internal iliac, the sciatic, internal pudic, and gluteal, which may occasionally be the object of surgical interference, is indicated on the surface in the following way: A line is to be drawn from the posterior supe- rior iliac spine to the posterior superior angle of the great trochanter, with the limb slightly flexed and rotated inward: the point of emergence of the gluteal artery from the upper part of the sciatic notch will correspond with the junction of the upper with the middle third of this line. A second line is to be drawn from the same point to the middle of the tuberosity of the ischium ; the junction of the lower with the middle third marks the point of emergence of the sciatic and pudic arteries from the great sciatic notch. 630 THE ARTERIES. Surgical Anatomy.-Any of these three vessels may require ligaturing for a wound or for aneurism, which is generally traumatic, and the operation may be performed by an incision, three or four inches long, in the direction of the fibres of the Gluteus maximus muscle, the middle of the cut corresponding to the point indicating their respective positions. The external iliac artery is larger in the adult than the internal iliac, and passes obliquely downward and outward along the inner border of the Psoas muscle, from the bifurcation of the common iliac to Poupart's ligament, where it enters the thigh and becomes the femoral artery. Relations.-In front, with the peritoneum, subperitoneal areolar tissue, the intestines, and a thin layer of fascia derived from the iliac fascia, which surrounds the artery and vein. At its origin it is occasionally crossed by the ureter. The spermatic vessels descend for some distance upon it near its termination, and it is crossed in this situation by the genital branch of the genito-crural nerve and the circumflex iliac vein ; the vas deferens curves down along its inner side. Behind, it is in relation with the external iliac vein, which, at Poupart's ligament, lies at its inner side; on the left side the vein is altogether internal to the artery. Externally, it rests against the Psoas muscle, from which it is separated by the iliac fascia. The artery rests upon this muscle, near Poupart's ligament. Numer- ous lymphatic vessels and glands are found lying on the front and inner side of the vessel. The External Iliac Artery (Fig. 372). Plan of the Relations of the External Iliac Artery. In front. Near Poupart's Ligament. Peritoneum, intestines, and fascia. i Spermatic vessels. Genito-crural nerve (genital branch). Circumflex iliac vein. Lymphatic vessels and glands. Outer side. Psoas magnus. Iliac fascia. External Iliac. Inner side. External iliac vein and vas deferens at femoral arch. Behind. External iliac vein. Psoas magnus. Surface Marking.-The surface line indicating the course of the external iliac artery has been already given (see page 621). Surgical Anatomy.-The application of a ligature to the external iliac may be required in cases of aneurism of the femoral artery or for a wound of the artery. This vessel may be secured in any part of its course, excepting near its upper end, which is to be avoided on account of the proximity of the great stream of blood in the internal iliac, and near its lower end, which should also be avoided, on account of the proximity of the epigastric and circumflex iliac vessels. One of the chief points in the performance of the operation is to secure the ves- sel without injury to the peritoneum. The patient having been placed in the recumbent posi- tion, an incision should be made, commencing below at a point about three-quarters of an inch above Poupart's ligament, and a little external to its middle, and running upward and outward, parallel to Poupart's ligament, to a point above the anterior superior spine of the ilium. When the artery is deeply seated more room will be required, and may be obtained by curving the incision from the point last named inward toward the umbilicus for a short distance, or, if the lower part of the artery is to be reached, the surgeon may adopt the plan advocated by Sir Astley Cooper, by making an incision close to Poupart's ligament from about half an inch out- side of the external abdominal ring to one inch internal to the anterior superior spine of the ilium. This incision, being made in the course of the fibres of the aponeurosis of the external oblique, is less likely to be followed by a ventral hernia, but there is danger of wounding the epigastric artery. Abernethy, who first tied this artery, made his incision in the course of the vessel. The abdominal muscles and transversalis fascia having been cautiously divided, the peri- toneum should be separated from the iliac fossa and raised toward the pelvis; and on introducing the finger to the bottom of the wound the artery may be felt pulsating along the inner border of the Psoas muscle. The external iliac vein is generally found on the inner side of the artery, THE EXTERNAL ILIAC ARTERY. 631 and must be cautiously separated from it by the finger-nail or handle of the knife, and the aneu- rism needle should be introduced on the inner side, between the artery and the vein. Ligature of the external iliac artery has recently been performed in three or more cases by a transperitoneal method. An incision four inches in length is made in the semilunar line, com- mencing about an inch below the umbilicus and carried through the abdominal wall into the peritoneal cavity. The intestines are then pushed upward and held out of the way by a broad abdominal retractor, and an incision made through the peritoneum at the margin of the pelvis in the course of the artery, and the vessel secured in any part of its course which may seem desirable to the operator. The advantages of this operation appear to be that if it is found necessary the common iliac artery can be ligatured instead of the external iliac without extension or modification of the incision; and secondly, that the vessel can be ligatured without in any way interfering with the coverings of the sac. Possibly a disadvantage may exist in the greater risk of hernia after this method. Collateral Circulation.-The principal anastomoses in carrying on the collateral circulation, after the application of a ligature to the external iliac, are-the ilio-lumbar with the circumflex iliac; the gluteal with the external circumflex ; the obturator with the internal circumflex ; the sciatic with the superior perforating and circumflex branches of the profunda artery; and the internal pudic with the external pudic. When the obturator arises from the epigastric, it is supplied with blood by branches, either from the internal iliac, the lateral sacral, or the inter- nal pudic. The epigastric receives its supply from the internal mammary and inferior intercostal arteries, and from the internal iliac by the anastomoses of its branches with the obturator. In the dissection of a limb eighteen years after the successful ligature of the external iliac artery by Sir A. Cooper, which is to be found in Guys Hospital Reports, vol. i. p. 50, the anastomosing branches are described in three sets: An anterior set.-1, a very large branch from the ilio-lumbar artery to the circumflex iliac; 2, another branch from the ilio-lumbar, joined by one from the obturator, and breaking up into numerous tortuous branches to anastomose with the external circumflex; 3, two other branches from the obturator, which passed over the brim of the pelvis, communicated with the epigastric, and then broke up into a plexus to anas- tomose with the internal circumflex. An internal set.-Branches given off from the obturator, after quitting the pelvis, which ramified among the adductor muscles on the inner side of the hip-joint, and joined most freely with branches of the internal circumflex. A posterior set.- 1, three large branches from the gluteal to the external circumflex; 2, several branches from the sciatic around the great sciatic notch to the internal and external circumflex, and the perforating branches of the profunda. Branches.-Besides several small branches to the Psoas muscle and the neigh- boring lymphatic glands, the external iliac gives oft' two branches of considerable size-the Deep Epigastric and Deep Circumflex Iliac. The Deep Epigastric Artery arises from the external iliac a few lines above Poupart's ligament. It at first descends to reach this ligament, and then ascends obliquely along the inner margin of the internal abdominal ring, lying between the transversalis fascia and peritoneum, and, continuing its course upward, it pierces the transversalis fascia, and, passing over the semilunar fold of Douglas, enters the sheath of the Rectus muscle. It then ascends on the posterior surface of the muscle, and finally divides into numerous branches, which anastomose, above the umbilicus, with the terminal branches of the internal mammary and inferior intercostal arteries. The deep epigastric artery bears a very important relation to the internal abdominal ring as it passes obliquely upward and inward from its origin from the external iliac. In this part of its course it lies along the lower and inner margin of the ring and beneath the commencement of the sper- matic cord. As it winds round the internal abdominal ring it is crossed by the vas deferens in the male and the round ligament in the female. Branches.-The branches of this vessel are the following : The cremasteric, which accompanies the spermatic cord, and supplies the Cremaster muscle and other coverings of the cord, anastomosing with the spermatic artery; a pubic branch, which runs along Poupart's ligament, and then descends behind the pubes to the inner side of the femoral ring, and anastomoses with offsets from the obturator artery ; muscular branches, some of which are distributed to the abdominal muscles and peritoneum, anastomosing with the lumbar and circumflex iliac arteries; others perforate the tendon of the External oblique, and supply the integument, anastomosing with branches of the superficial epigastric. 632 THE ARTERIES. Peculiarities.-The origin of the epigastric may take place from any part of the external iliac between Poupart's ligament and two inches and a half above it, or it may arise below this ligament, from the femoral or from the deep femoral. Union with Branches.-It frequently arises ■ from the external iliac by a common trunk with the obturator. Sometimes the epigastric arises from the obturator, the latter vessel being furnished by the internal iliac, or the epigastric may be formed of two branches, one derived from the external iliac, the other from the internal iliac. Surgical Anatomy.-The deep epigastric artery follows a line drawn from the middle of Poupart's ligament toward the umbilicus; but shortly after this line crosses thelineasemilunaris the direction changes, and the course of the vessel is directly upward in the line of junction of the inner third with the outer two-thirds of the Rectus muscle. It has important surgical relations, in addition to the fact that it is one of the principal means, through its anastomosis with the internal mammary, in establishing the collateral circulation after ligature of either the common or external iliac arteries. It lies close to the internal abdominal ring, and is therefore internal to an oblique inguinal hernia, but external to a direct inguinal hernia, as it emerges from the abdomen. It forms the outer boundary of Hesselbach's triangle. It is in close rela- tionship with the spermatic cord, which lies in front of it in the inguinal canal, separated only by the transversalis fascia. The vas deferens hooks round its outer side. The Deep Circumflex Iliac Artery arises from the outer side of the external iliac nearly opposite the epigastric artery. It ascends obliquely outward behind Poupart's ligament, contained in a fibrous sheath formed by the junction of the transversalis and iliac fasciae, to the anterior superior spinous process of the ilium. It then runs along the inner surface of the crest of the ilium to about its middle, where it pierces the Transversalis, and runs backward between that muscle and the Internal oblique, to anastomose with the ilio-lumbar and gluteal arteries. Opposite the anterior superior spine of the ilium it gives off a large branch, which ascends between the Internal oblique and Transversalis muscles, supplying them, and anastomosing with the lumbar and epigastric arteries. ARTERIES OF THE LOWER EXTREMITY. The Femoral Artery (Fig. 376). The femoral artery is the continuation of the external iliac. It commences immediately behind Poupart's ligament, midway between the anterior superior spine of the ilium and the symphysis pubis, and, passing down the fore part and inner side of the thigh, terminates at the opening in the Adductor magnus, at the junction of the middle with the lower third of the thigh, where it becomes the popliteal artery. The vessel, at the upper part of thigh, lies a little internal to the head of the femur; in the lower part of its course, on the inner side of the shaft of the bone, and between these two parts the vessel is far away from the bone. In the upper third of the thigh it is contained in a triangular space called Scarpa's triangle. In the middle third of the thigh it is contained in an aponeurotic canal called Hunter's canal. Scarpa's Triangle.-Scarpa's triangle corresponds to the depression seen immediately below the fold of the groin. It is a triangular space, the apex of which is directed downward, and the sides formed externally by the Sartorius, internally by the Adductor longus, and above by Poupart's ligament. The floor of the space is formed from without inward by the Iliacus, Psoas, Pectineus, a small part of the Adductor brevis and the Adductor longus muscles ; and it is divided into two nearly equal parts by the femoral vessels, which extend from the middle of its base to its apex, the artery giving off in this situation its cutaneous and profunda branches, the vein receiving the deep femoral and internal saphenous. On the outer side of the femoral artery is the anterior crural nerve dividing into its branches. Besides the vessels and nerves, this space contains some fat and lymphatics. Hunter's Canal.-This is the aponeurotic space in the middle third of the thigh, extending from the apex of Scarpa's triangle to the femoral opening in the Adductor magnus muscle. It is bounded, externally, by the Vastus internus ; internally, by the Adductor longus and magnus muscles; and covered in by a strong aponeurosis which extends transversely from the Vastus internus, across THE FEMORAL ARTERY. 633 the femoral vessels to the Adductor longus and magnus muscles, lying on which aponeurosis is the Sartorius muscle. It contains the femoral artery and vein enclosed in their own sheath of areolar tissue, the vein being behind and on the outer side of the artery, and the internal or long saphenous nerve lying on the outer side of the vessels. For convenience of description, and also in reference to its surgical anatomy, the femoral artery is divided into a short trunk, about an inch and a half or two inches long, which is known as the common femoral artery, and the remainder of the vessel, which is known as the superficial femoral, to distinguish it from the deep femoral (pro- funda femoris), which is a large branch given off from the com- mon femoral at its termination, and which by its derivation from the parent trunk marks the com- mencement of the superficial fem- oral artery. The common femoral artery is very superficial, being covered by the skin and superficial fascia, superficial inguinal lym- phatic glands, the iliac portion of the fascia lata, and the prolon- gation downward of the Trans- versalis fascia, which forms the sheath of the vessels. It has in front of it filaments from the crural branch of the genito- crural nerve, the superficial cir- cumflex iliac vein, and occa- sionally the superficial epigastric vein. It rests on the inner mar- gin of the Psoas muscle, which separates it from the capsular ligament of the hip-joint, and a little lower on the Pectineus muscle; and crossing behind it is the branch to the Pectineus from the anterior crural nerve. Separating the artery from the Psoas and Pectineus muscles is the pubic portion of the fascia lata and the prolongation from the fascia covering the Iliacus muscle, which forms the poste- rior layer of the sheath of the vessels. The anterior crural nerve lies about half an inch to the outer side of the common femoral artery, lying between the Psoas and Iliacus muscles. To the inner side of the artery is the femoral vein, between the margins of the Pectineus and Psoas muscles. The two vessels are enclosed in a strong fibrous sheath formed bv the proper sheath of the vessels strengthened by the fascia lata (see page 509); the | Scrota m. Long saphenous nerve. Anastomotica magna. Superior external articular. Anastomotica magna. Superior internal articular. Inferior internal, articular. Inferior internal articular. Anterior tibial recurrent. Fig. 376.-Surgical anatomy of the femoral artery. 634 7V/7< ARTERIES. artery and vein are separated, however, from one another by a thin fibrous partition. Plan of Relations of the Common Femoral Artery. In front. Skin and superficial fascia. Superficial inguinal glands. Iliac portion of fascia lata. Prolongation of transversalis fascia. Crural branch of genito-crural nerve. Superficial circumflex iliac vein. Superficial epigastric vein. Inner side. Femoral vein. Common Femoral Artery. Outer side. Anterior crural nerve. Behind. Prolongation of fascia covering Iliacus muscle. Pubic portion of fascia lata. Nerve to Pectineus. Psoas muscle. Pectineus muscle. Capsule of hip-joint. The superficial femoral artery is only superficial where it lies in Scarpa's tri- angle. Here it is covered by the skin, superficial and deep fascia, and crossed by the internal cutaneous branch of the anterior crural nerve. In Hunter's canal it is more deeply seated, being covered by the integument, the superficial and deep fascia, the Sartorius and aponeurotic covering of Hunter's canal. The internal saphenous nerve crosses the artery from without inward. Behind, the artery lies at its upper part on the femoral vein and the profunda artery and vein, which separate it from the Pectineus muscle, and lower down on the Adduc- tor longus and Adductor magnus muscles. To the outer side is the long saphe- nous nerve and the nerve to the Vastus internus, the Vastus internus muscle, and, at its lower part, the femoral vein. To the inner side is the Adductor longus above and the Adductor magnus and Sartorius below. Plan of Relations of the Superficial Femoral Artery. In front. Skin, superficial and deep fasciae. Internal cutaneous nerve. Sartorius. Aponeurotic covering of Hunter's canal. Internal saphenous nerve. Inner side. Adductor longus. Adductor magnus. Sartorius. Outer side. Long saphenous nerve. Nerve to vastus internus. Vastus internus. Femoral vein (below). Superficial Femoral Artery. Behind. Femoral vein. Profunda artery and vein. Pectineus muscle. Adductor longus. Adductor magnus. The femoral vein, at Poupart's ligament, lies close to the inner side of the artery, separated from it by a thin fibrous partition; but lower down it is behind it, and then to its outer side. The internal saphenous nerve is situated on the outer side of the artery, in the THE FEMORAL ARTERY. 635 middle third of the thigh, beneath the aponeurotic covering of Hunter's canal, but not usually within the sheath of the vessels. The internal cutaneous nerve passes obliquely across the upper part of the sheath of the femoral artery. Peculiarities.-Double Femoral reunited.-Several cases are recorded in which the femoral artery divided into two trunks below the origin of the profunda, and became reunited near the opening in the Adductor magnus so as to form a single popliteal artery. One of them occurred in a patient operated upon for popliteal aneurism. Change of Position.-A few cases have been recorded in which the femoral artery was situated at the back of the thigh, the vessel being continuous above with the internal iliac, escaping from the pelvis through the great sacro-sciatic foramen, and accompanying the great sciatic nerve to the popliteal space, where its division occurred in the usual manner. The external iliac in these cases was small, and terminated in the profunda. Position of the Vein.-The femoral vein is occasionally placed along the inner side of the artery, throughout the entire extent of Scarpa's triangle, or it may be slit so that a large vein is placed on each side of the artery for a greater or less extent. Origin of the Profunda.-This vessel occasionally arises from the inner side, and, more rarely, from the back of the common trunk; but the more important peculiarity, in a surgical point of view, is that which relates to the height at which the vessel arises from the femoral. In three-fourths of a large number of cases it arose between one or two inches below Poupart's ligament; in a few cases the distance was less than an inch ; more rarely, opposite the ligament; and in one case, above Poupart's ligament, from the external iliac. Occasionally, the distance between the origin of the vessel and Poupart's ligament exceeds two inches, and in one case it was found to be as much as four inches. Surface Marking.-The upper two-thirds of a line drawn from a point midway between the anterior superior spine of the ilium and the symphysis pubis to the prominent tuberosity on the inner condyle of the femur, with the thigh abducted and rotated outward, will indicate the course of the femoral artery. Surgical Anatomy.- Compression of the femoral artery, which is constantly requisite in amputations and other operations on the lower limb, and also for the cure of popliteal aneurisms, is most effectually made immediately below Poupart's ligament. In this situation the artery is very superficial, and is merely separated from the horizontal ramus of the os pubis by the Psoas muscle : so that the surgeon, by means of his thumb or a compressor, may effectually control the circulation through it. This vessel may also be compressed in the middle third of the thigh by placing a compress over the artery, beneath the tourniquet, and directing the pressure from within outward, so as to compress the vessel against the inner side of the shaft of the femur. The application of a ligature to the femoral artery may be required in the cases of wound or aneurism of the arteries of the leg, of the popliteal or femoral;1 and the vessel may be exposed and tied in any part of its course. The great depth of this vessel at its lower part, its close connection with important structures, and the density of its sheath render the opera- tion in this situation one of much greater difficulty than the application of a ligature at its upper part, where it is more superficial. Ligature of the common femoral artery is usually considered unsafe, on account of the con- nection of large branches with it-viz. the deep epigastric and the deep circumflex iliac arising just above Poupart's ligament; on account of the number of small branches which arise from it in its short course ; and on account of the uncertainty of the origin of the profunda femoris, which, if it arise high up, would be too close to the ligature for the formation of a firm coagu- lum. The profunda sometimes arises higher than the point above mentioned, and rarely between two or three inches (in one case four) below Poupart's ligament. It would appear, then, that the most favorable situation for the application of a ligature to the femoral is between four and five inches from its point of origin. In order to expose the artery in this situation, an incision between two and three inches long should be made in the course of the vessel, the patient lying in the recumbent position, with the limb slightly flexed and abducted. A large vein is frequently met with, passing in the course of the artery to join the saphena: this must be avoided, and, the fascia lata having been cautiously divided and the Sartorius exposed, that muscle must be drawn outward in order to fully expose the sheath of the vessels. The finger being introduced into the wound and the pulsation of the artery felt, the sheath should be opened on the outer side of the vessel to a sufficient extent to allow of the introduction of the ligature, but no farther; otherwise the nutrition of the coats of the vessel may be interfered with, or muscular branches which arise from the vessel at irregular intervals may be divided. In this part of the operation the long saphenous nerve and the nerve to the Vastus internus, which is in close relation with the sheath, should be avoided. The aneurism needle must be carefully introduced and kept close to the artery, to avoid the femoral vein, which lies behind the vessel in this part of its course. To expose the artery, in Hunter's canal, an incision should be made through the integument, between three and four inches in length, a finger's breadth internal to the line of the artery, in the middle of the thigh-i. e. midway between the groin and the knee. The fascia lata having been divided and the Sartorius muscle exposed, it should be drawn inward, when the strong 1 Ligature of the femoral artery has been also recommended and performed for elephantiasis of the leg and acute inflammation of the knee-joint (Maunder, Clin. Soc. Trans., vol. ii. p. 37). 636 THE ARTERIES. fascia which is stretched across from the Adductors to the Vastus internus will be exposed, and must be freely divided ; the sheath of the vessels is now seen, and must be opened, and the artery secured by passing the aneurism needle between the vein and artery in the direction from without inward. The femoral vein in this situation lies on the outer side of the artery, the long saphenous nerve on its anterior and outer side. It has been seen that the femoral artery occasionally divides into two trunks below the origin of the profunda. If in the operation for tying the femoral two vessels are met with, the surgeon should alternately compress each, in order to ascertain which vessel is connected with the aneurismal tumor or with the bleeding from the wound, and that one only should be tied which controls the pulsation or haemorrhage. If, however, it is necessary to compress both vessels before the circulation in the tumor is controlled, both should be tied, as it would be probable that they became reunited, as in the instances referred to above. In wounds of the femoral artery the question of the mode of treatment is of considerable importance. If the wound in the superficial structures is a large one, the injured vessel must be exposed and tied; but if the wound is a punctured one and the bleeding has ceased, the question will arise whether to cut down upon the artery or to trust to pressure. Mr. Cripps1 advises that if the wound is in the " upper part of the thigh-that is to say, in a position where the femoral artery is comparatively superficial-the surgeon may enlarge the opening with a good prospect of finding the wounded vessel without an extensive or prolonged operation. If the wound be in the lower half of the thigh, owing to the greater depth of the artery and the possibility of its being the popliteal that is wounded, the search is rendered a far more severe and hazardous operation, and it should not be undertaken until a thorough trial of pressure has proved ineffectual." Great care and attention are necessary for the successful application of pressure. The limb should be carefully bandaged from the foot upward to the wound, which is not covered, and then onward to the groin. The wound is then dusted with iodoform or boracic powder and a conical pad applied over the wound. Rollers the thickness of the index finger are then placed along the course of the vessel above and below the wound, and the whole carefully bandaged to a back splint with a foot-piece. Collateral Circulation.-When the common femoral is tied the main channels for carrying on the circulation are the anastomoses of the gluteal and circumflex iliac arteries above with the external circumflex below; of the obturator and sciatic above with the internal circumflex below; and of the comes nervi ischiadici with the arteries in the ham. The principal agents in carrying on the collateral circulation after ligature of the superficial femoral artery are, according to Sir A. Cooper, as follows : " The arteria profunda formed the new channel for the blood." "The first artery sent off passed down close to the back of the thigh-bone, and entered the two superior articular branches of the popliteal artery. ' ' "The second new large vessel, arising from the profunda at the same part with the former, passed down by the inner side of the Biceps muscle to a branch of the popliteal which was dis- tributed to the Gastrocnemius muscle; whilst a third artery, dividing into several branches, passed down with the sciatic nerve behind the knee-joint, and some of its branches united them- selves with the inferior articular arteries of the popliteal, with some recurrent branches of those arteries, with arteries passing to the Gastrocnemii, and, lastly, with the origin of the anterior and posterior tibial arteries." " It appears, then, that it is those branches of the profunda which accompany the sciatic nerve that are the principal supporters of the new circulation." 2 In Porta's work 3 (tab. xii., xiii.) is a good representation of the collateral circulation after the ligature of the femoral artery. The patient had survived the operation three years. The lower part of the artery is at least as large as the upper ; about two inches of the vessel appear to have been obliterated. The external and internal circumflex arteries are seen anastomosing by a great number of branches with the lower branches of the femoral (muscular and anasto- motica magna) and with the articular branches of the popliteal. The branches from the external circumflex are extremely large and numerous. One very distinct anastomosis can be traced between this artery on the outside and the anastomotica magna on the inside through the intervention of the superior external articular artery, "with which they both anastomose ; and blood reaches even the anterior tibial recurrent from the external circumflex by means of anastomosis with the same external articiilar artery. The perforating branches of the profunda are also seen bringing blood round the obliterated portion of the artery into long branches (muscular) which have been given off-just below that portion. The termination of the profunda itself anastomoses most freely with the superior external articular. A long branch of anasto- mosis is also traced down from the internal iliac by means of the comes nervi ischiadici of the sciatic, which anastomoses on the popliteal nerves with branches from the popliteal and posterior tibial arteries. In this case the anastomosis had been too free, since the pulsation and growth of the aneurism recurred, and the patient died after ligature of the external iliac. There is an interesting preparation in the Museum of the Royal College of Surgeons of a limb on which John Hunter had tied the femoral artery fifty years before the patient's death. The whole of the superficial femoral and popliteal artery seems to have been obliterated. The 1 Heath's Dictionary of Practical Surgery, vol. i. p. 525. * Med.-Chir. Trans., vol. ii. 1811. 3 Alterazioni patologiche delle Arterie. 77777 EEJfORAL ARTERY. 637 anastomosis by means of the comes nervi ischiadici, which is shown in Porta's plate, is distinctly seen: the external circumflex and the termination of the profunda artery, seem to have been the chief channels of anastomosis; but the injection has not been a very successful one, Branches.-The branches of the femoral artery are-the Superficial Epigastric. Superficial Circumflex Iliac. Superficial External Pudic. Deep External Pudic. External Circumflex. Internal Circumflex. Three Perforating. Profunda Anastomotica Magna. Muscular. The superficial epigastric arises from the femoral about half an inch below Pou- part's ligament, and, passing through the saphenous opening in the fascia lata, ascends on the abdomen, in the superficial fascia covering the External oblique muscle, nearly as high as the umbilicus. It distributes branches to the superficial inguinal glands, the superficial fascia, and the integument, anastomosing with branches of the deep epigastric. The superficial circumflex iliac, the smallest of the cutaneous branches, arises close to the preceding, and, piercing the fascia lata, runs outward, parallel with Poupart's ligament, as far as the crest of the ilium, dividing into branches which supply the integument of the groin, the superficial fascia, and the superficial ingui- nal lymphatic glands, anastomosing with the circumflex iliac and with the gluteal and external circumflex arteries. The superficial external pudic (superior) arises from the inner side of the femoral artery, close to the preceding vessels, and, after passing through the saphenous opening, courses inward, across the spermatic cord or round ligament, to be dis- tributed to the integument on the lower part of the abdomen, the penis and scro- tum in the male, and the labium in the female, anastomosing with branches of the internal pudic. The deep external pudic (inferior), more deeply seated than the preceding, passes inward on the Pectineus muscle, covered by the fascia lata, which it pierces at the inner border of the thigh, its branches being distributed, in the male, to the integument of the scrotum and perinteum ; and in the female, to the labium, anas- tomosing with branches of the superficial perineal artery. The Profunda Femoris (deep femoral artery) nearly equals the size of the superficial femoral. It arises from the outer and back part of the femoral artery, from one to two inches below Poupart's ligament. It at first lies on the outer side of the superficial femoral, and then passes behind it and the femoral vein to the inner side of the femur, and, passing downward beneath the Adductor longus, terminates at the lower third of the thigh in a small branch which pierces the Adductor magnus (and from this circumstance is sometimes called the fourth perforating artery), and is distributed to the flexor muscles on the back of the thigh, anastomosing with branches of the popliteal and inferior perforating arteries. Relations.-Behind, it lies first upon the Iliacus, and then on the Pectineus, Adductor brevis, and Adductor magnus muscles. In front, it is separated from the femoral artery, above by the femoral and profunda veins, and below by the Adductor longus. On its outer side the origin of the Vastus internus separates it from the femur. 638 THE ARTERIES. Plan of the Relations of the Profunda Artery. In front. Femoral and Profunda veins. Adductor longus. Outer side. Vastus internus. Profunda. Behind. Iliacus. Pectineus. Adductor brevis. Adductor magnus. The External Circumflex Artery supplies the muscles on the front of the thigh. It arises from the outer side of the profunda, passes horizontally outward, between the divisions of the anterior crural nerve and behind the Sartorius and Rectus muscles, and divides into three sets of branches-ascending, transverse, and descending. The ascending branches pass upward, beneath the Tensor vaginae femoris muscle, to the outer side of the hip, anastomosing with the terminal branches of the gluteal and circumflex iliac arteries. The descending branches, three or four in number, pass downward, behind the Rectus, upon the Vasti muscles, to which they are distributed, one or two passing beneath the Vastus externus as far as the knee, anastomosing with the superior articular branches of the popliteal artery. These are accompanied by the branch of the anterior crural nerve to the Vastus externus. The transverse branches, the smallest and least numerous, pass outward over the Crureus, pierce the Vastus externus, and wind round the femur to its back part, just belowr the great trochanter, anastomosing at the back of the thigh with the internal circumflex, sciatic, and superior perforating arteries. The Internal Circumflex Artery, smaller than the external, arises from the inner and back part of the profunda, and winds round the inner side of the femur, between the Pectineus and Psoas muscles. On reaching the upper border of the Adductor brevis it gives off two branches, one of which passes inward to be dis- tributed to the Adductor muscles, the Gracilis, and Obturator externus, anasto- mosing with the obturator artery; the other descends, and passes beneath the Adductor brevis, to supply it and the great Adductor ; while the continuation of the vessel passes backward, between the Quadratus femoris and upper border of the Adductor magnus, anastomosing with the sciatic, external circumflex, and superior perforating arteries (" the crucial anastomosis "). Opposite the hip-joint this branch gives off an articular vessel, which enters the joint beneath the trans- verse ligament, and, after supplying the adipose tissue, passes along the round ligament to the head of the bone. The Perforating Arteries (Fig. 375), usually three in number, are so called from their perforating the tendon of the Adductor magnus muscle to reach the back of the thigh. The first is given off above the Adductor brevis, the second in front of that muscle, and the third immediately below' it. The first or superior perforating artery passes backward between the Pectineus and Adductor brevis (sometimes perforates the latter); it then pierces the Adductor magnus close to the linea aspera, and divides into branches which supply the Adductor brevis, the Adductor magnus, the Biceps, and Gluteus maximus muscles, anastomosing with the sciatic, internal and external circumflex, and middle per- forating arteries. The second or middle perforating artery, larger than the first, pierces the tendons of the Adductor brevis and Adductor magnus muscles, and divides into ascending and descending branches, which supply the flexor muscles of the thigh. THE POPLITEAL ARTERY. 639 anastomosing with the superior and inferior perforating. The nutrient artery of the femur is usually given off from this branch. The third or inferior perforating artery is given off below the Adductor brevis; it pierces the Adductor magnus, and divides into branches which supply the flexor muscles of the thigh, anastomosing above with the perforating arteries, and below with the terminal branches of the profunda and the muscular branches of the popliteal. Muscular branches are given off from the superficial femoral throughout its entire course. They vary from two to seven in number, and supply chiefly the Sartorius and Vastus internus. The Anastomotica Magna arises from the femoral artery just before it passes through the tendinous opening in the Adductor magnus muscle, and divides into a superficial and deep branch. The superficial branch accompanies the long saphenous nerve beneath the Sartorius, and, piercing the fascia lata, is distributed to the integument. The deep branch descends in the substance of the Vastus internus, lying in front of the tendon of the Adductor magnus, to the inner side of the knee, where it anastomoses with the superior internal articular artery and anterior recurrent branch of the anterior tibial. A branch from this vessel crosses outward above the articular surface of the femur, forming an anastomotic arch with the superior external articular artery, and supplies branches to the knee-joint. Popliteal Artery. The popliteal artery commences at the termination of the femoral at the opening in the Adductor magnus, and, passing obliquely downward and outward behind the knee-joint to the lower border of the Popliteus muscle, divides into the anterior and posterior tibial arteries. A portion of the artery lies in the popliteal space; but above, to a slight extent, and below, to a considerable extent, it is covered by the muscles which form the boundaries of the space, and is therefore beyond the confines of the hollow. Dissection.-A vertical incision about eight inches in length should be made along the back part of the knee-joint, connected above and below by a transverse incision from the inner to the outer side of the limb. The flaps of integument included between these incisions should be reflected in the direction shown in Fig. 328, page 516. Boundaries.-The popliteal space, or the ham, is a lozenge-shaped space, widest at the back part of the knee-joint and deepest above the articular end of the femur. It is bounded externally, above the joint, by the Biceps, and, below the joint, by the Plantaris and external head of the Gastrocnemius; internally, above the joint, by the Semimembranosus, Semitendinosus, Gracilis, and Sartorius ; below the joint, by the inner head of the Gastrocnemius. Above, it is limited by the apposition of the inner and outer hamstring muscles; below, by the junction of the two heads of the Gastrocnemius. The floor is formed by the lower part of the posterior surface of the shaft of the femur, the posterior ligament of the knee-joint, the upper end of the tibia, and the fascia covering the Popliteus muscle, and the space is covered in by the fascia lata. Contents.-It contains the popliteal vessels and their branches, together with the termination of the external saphenous vein, the internal and external popliteal nerves and some of their branches, the lower extremity of the small sciatic nerve, the articular branch from the obturator nerve, a few small lymphatic glands, and a considerable quantity of loose adipose tissue. Position of Contained Parts.-The internal popliteal nerve descends in the middle line of the space, lying superficial and crossing the artery from without inward. The external popliteal nerve descends on the outer side of the space, THE POPLITEAL SPACE (Fig. 377) 640 THE ARTERIES. lying close to the tendon of the Biceps muscle. More deeply at the bottom of the space are the popliteal vessels, the vein lying superficial and a little external to the artery, to which it is closely united by dense areolar tissue ; sometimes the vein is placed on the inner instead of the outer side of the artery ; or the vein may be double, the artery lying between the two venae comites, which are usually connected by short transverse branches. More deeply, and, at its upper part, close to the surface of the bone, is the popliteal artery, and passing off from it at right angles are its articular branches. The articular branch from the obturator nerve descends upon the popliteal artery to supply the knee, and occasionally there is found deep in the space an articular filament from the great sciatic nerve. The popliteal lymphatic glands, foui' or five in number, are found surrounding the artery: one usually lies superficial to the vessel; another is situated between it and the bone, and the rest are placed on either side of it. The Popliteal Artery, in its course downward from the aperture in the Adductor magnus to the lower border of the Popliteus muscle, rests first on the inner surface of the femur, and is then separated by a little fat from the hollowed popliteal surface of the bone; in the middle of its course it rests on the posterior ligament of the knee-joint, and below on the fascia covering the Popliteus muscle. Super- ficially, it is covered above by the Semimembranosus ; in the middle of its course, by a quantity of fat, which separates it from the deep fascia and integument; and below it is overlapped by the Gastrocnemius, Plantaris, and Soleus muscles, the popliteal vein, and the internal popliteal nerve. The popliteal vein, which is intimately attached to the artery, lies superficial and external to it until near the termination of the artery, when the vein crosses it and lies to its inner side. The popliteal nerve is still more superficial and external above, but below the joint it crosses the artery and lies on its inner side. Laterally, the artery is bounded by the muscles which are situated on either side of the popliteal space. Plan of Relations of Popliteal Artery. In front. Femur. Ligamentum posticum. Popliteus. Inner side. Semimembranosus. Internal condyle. Gastrocnemius (inner head). Duter side. Biceps. Outer condyle. Gastrocnemius (outer head). Plantaris. Popliteal Artery. Behind. Semimembranosus. Fascia. Popliteal vein. Internal popliteal nerve. Gastrocnemius. Plantaris. Soleus. Peculiarities in Point of Division.-Occasionally the popliteal artery divides prematurely into its terminal branches; this unusual division occurs most frequently opposite the knee-joint. Unusual Branches.-The artery sometimes divides into the anterior tibial and peroneal, the posterior tibial being wanting or very small. Occasionally the popliteal is found to divide into three branches, the anterior and posterior tibial and peroneal. Surface Marking.-The course of the upper part of the popliteal artery is indicated by a line drawn from the outer border of the Semimembranosus muscle at the junction of the middle and lower third of the thigh obliquely downward to the middle of the popliteal space, exactly behind the knee-joint. From this point it passes vertically downward to the level of a line drawn through the lower part of the tubercle of the tibia. Surgical Anatomy.-The popliteal artery is not infrequently the seat of injury. It may be torn by direct violence, as by the passage of a cart-wrheel over the knee or by hyper-extension of the knee ; and in the dead body, at all events, the middle and internal coats may be ruptured by extreme flexion. It may also be lacerated by fracture of the lower part of the shaft of the BRANCHES OF THE POPLITEAL ARTERY. 641 femur or by antero-posterior dislocation of the knee-joint. It has been torn in breaking down adhesions in cases of fibrous ankylosis of the knee, and is in danger of being wounded, and in fact has been wounded, in performing Macewen's operation of osteotomy of the lower end of the femur for genu valgum. In addition, Spencer records a case in which the popliteal artery was wounded from in front by a stab just below the knee, the knife passing through the interosseous space. The popliteal artery is more frequently the seat of aneurism than is any other artery in the body, with the exception of the thoracic aorta. This is due no doubt, in a great measure to the amount of movement to which it is subjected, and to the fact that it is supported by loose and lax tissue only, and not by muscles, as is the case with most arteries. Ligature of the popliteal artery is required in cases of wound of that vessel, but for aneurism of the posterior tibial it is preferable to tie the superficial femoral. The popliteal may be tied in the upper or lower part of its course ; but in the middle of the ham the operation is attended with considerable difficulty, from the great depth of the artery and from the extreme degree of tension of the lateral boundaries of the space. In order to expose the vessel in the upper part of its course the patient should be placed in the prone position, with the limb extended. An incision about three inches in length should then be made through the integument, along the posterior margin of the Semimembranosus, and, the fascia lata having been divided, this muscle must be drawn inward. The internal pop- liteal nerve will be first exposed, lying very superficial and external to the artery ; beneath this will be seen the popliteal vein, and, still deeper and to its inner side, the artery. The vein and nerve must be cautiously separated from the artery, and the aneurism needle passed around the vessel from without inward. To expose the vessel in the lower part of its course, where the artery lies between the two heads of the Gastrocnemius, the patient should be placed in the same position as in the preceding operation. An incision should then be made through the integument in the middle line, com- mencing opposite the bend of the knee-joint, care being taken to avoid the external saphenous vein and nerve. After dividing the deep fascia and separating some dense cellular membrane, the artery, vein, and nerve will be exposed, descending between the two heads of the Gastrocne- mius. Some muscular branches of the popliteal should be avoided if possible, or, if divided, tied immediately. The leg being now flexed, in order the more effectually to separate the two heads of the Gastrocnemius the nerve should be drawn inward and the vein outward, and the aneurism needle passed between the artery and vein from without inward. In cases where the artery has been wounded during an osteotomy of the lower end of the femur it would be most conveniently secured from the front at the inner side of the thigh. The knee is flexed and the limb placed on its outer side. An incision, three inches long, is made parallel to and immediately behind the tendon of the Adductor magnus from the junction of the middle and lower third of the thigh. Skin, superficial and deep fascia are to be divided, care being taken of the internal saphenous vein; the Adductor magnus is to be drawn forward and the inner hamstring tendons backward, and the artery will be found surrounded by fat. The nerve and vein are usually not seen, as they lie to the outer side of the artery. The branches of the popliteal artery are-the Superior. Inferior or Sural. Superior Internal Articular. Azygos Articular. Inferior External Articular. Inferior Internal Articular. Ar , Muscular Cutaneous. Superior External Articular. The superior muscular branches, two or three in number, arise from the upper part of the popliteal artery, and are distributed to the Vastus externus and flexor muscles of the thigh, anastomosing with the inferior perforating and terminal branches of the profunda. The inferior muscular (sural) are two large branches which are distributed to the two heads of the Gastrocnemius and to the Plantaris muscle. They arise from the popliteal artery opposite the knee-joint. Cutaneous branches descend on each side and in the middle of the limb, between the Gastrocnemius and integument; they arise separately from the popliteal artery or from some of its branches, and supply the integument of the calf. The superior articular arteries, two in number, arise one on each side of the popliteal, and wind round the femur immediately above its condyles to the front of the knee-joint. The internal branch passes beneath the tendon of the Adductor magnus, and divides into two, one of which supplies the Vastus internus, inoscu- lating with the anastomotica magna and inferior internal articular ; the other ramifies close to the surface of the femur, supplying it and the knee-joint, and anastomosing with the superior external articular artery. The external branch passes above the outer condyle, beneath the tendon of the Biceps, and divides into 642 THE ARTERIES. a superficial and deep branch: the superficial branch supplies the Vastus exter Inferior external articular Inferior internal articular. Sural arteries. Anterior tibial recurrent. Internal malleolar. Anterior peroneal. External malleolar. ■Anterior peroneal. Internal calcanean. ( Communicating. Fig. 377.-The popliteal, posterior tibial, and peroneal arteries. Fig. 378.-Surgical anatomy of the anterior tibial and dorsalis pedis arteries. nus, and anastomoses with the descending branch of the external circumflex, and the inferior external articular arteries; the deep branch supplies the lower part THE ANTERIOR TIBIAL ARTERY. 643 of the femur and knee-joint, and forms an anastomotic arch across the bone with the anastomotica magna and the inferior internal articular arteries. The azygos articular is a small branch arising from the popliteal artery oppo- site the bend of the knee-joint. It pierces the posterior ligament, and supplies the ligaments and synovial membrane in the interior of the articulation. The inferior articular arteries, two in number, arise from the popliteal beneath the Gastrocnemius, and wind round the head of the tibia below the joint. The one passes below the inner tuberosity, beneath the internal lateral lig- ament, at the anterior border of which it ascends to the front and inner side of the joint, to supply the head of the tibia and the articulation of the knee, anasto- mosing with the inferior external articular and superior internal articular arteries. The external one passes outward above the head of the fibula, to the front of the knee-joint, passing in its course beneath the outer head of the Gastrocnemius, the external lateral ligament, and the tendon of the Biceps muscle, and divides into branches which anastomose with the inferior internal articular artery, the superior external articular artery, and the anterior recurrent branch of the anterior tibial. Circumpatellar Anastomosis.-Around and above the patella, and on the con- tiguous ends of the femur and tibia, is a large network of vessels, forming a superficial and deep plexus from which numerous offsets proceed into the interior of the joint. The arteries from which this plexus is formed are the two internal and two external articular branches of the popliteal, the anastomotica magna, the terminal branch of the profunda, the descending branch from the external cir- cumflex, and the anterior recurrent branch of the anterior tibial. The Anterior Tibial Artery (Fig. 378). The anterior tibial artery commences at the bifurcation of the popliteal at the lower border of the Popliteus muscle, passes forward between the two heads of the Tibialis posticus, and through the large oval aperture above the upper border of the interosseous membrane to the deep part of the front of the leg: it then descends on the anterior surface of the interosseous membrane, gradually approaching the tibia ; and at the lower part of the leg lies on this bone, and then on the anterior ligament of the ankle to the bend of the ankle-joint, where it lies more superficially, and becomes the dorsalis pedis. Relations.-In the upper two-thirds of its extent it rests upon the interosseous membrane, to which it is connected by delicate fibrous arches thrown across it; in the lower third, upon the front of the tibia and the anterior ligament of the ankle-joint. In the upper third of its course it lies between the Tibialis anticus and Extensor longus digitorum; in the middle third, between the Tibialis anticus and Extensor proprius hallucis. At the bend of the ankle it is crossed by the tendon of the Extensor proprius hallucis, and lies between it and the innermost tendon of the Extensor longus digitorum. It is covered, in the upper two-thirds of its course, by the muscles which lie on either side of it and by the deep fascia; in the lower third, by the integument, anterior annular ligament, and fascia. The anterior tibial artery is accompanied by two veins (venae comites), which lie one on each side of the artery ; the anterior tibial nerve lies at first to its outer side, and about the middle of the leg is placed superficial to it; at the lower part of the artery the nerve is generally again on the outer side. 644 77/E ARTERIES. Plan of the Relations of the Anterior Tibial Artery. In front'. Integument, superficial and deep fasciae. Anterior tibial nerve. Extensor longus digitorum Extensor proprius hallucis Tibialis anticus (overlaps it in the upper part of the leg). (overlap it slightly). Anterior annular ligament. Inner side. Tibialis anticus. Extensor proprius hallucis (crosses it at its lower part). Outer side. Anterior tibial nerve. Extensor longus digitorum. Extensor proprius hallucis. Anterior Tibial. Behind. Interosseous membrane. Tibia. Anterior ligament of ankle-joint. Peculiarities in Size.-This vessel may be diminished in size, may be deficient to a greater or less extent, or may be entirely wanting, its place being supplied by perforating branches from the posterior tibial or by the anterior division of the peroneal artery. Course.-The artery occasionally deviates in its course toward the fibular side of the leg, regaining its usual position beneath the annular ligament at the front of the ankle. In two instances the vessel has been found to approach the surface in the middle of the leg, being covered merely by the integument and fascia below that point. Surface Marking.-A line drawn from the inner side of the head of the fibula to midway between the two malleoli will mark the course of the artery, the point where the artery comes in front of the interosseous membrane being in this line, one and a quarter inches below the level of the head of the fibula. Surgical Anatomy.-The anterior tibial artery may be tied in the upper or lower part of the leg. In the upper part the operation is attended with great difficulty, on account of the depth of the vessel from the surface. An incision about four inches in length, should be made through the integument, midway between the spine of the tibia and the outer margin of the fibula, the fascia and intermuscular septum between the Tibialis anticus and Extensor longus digitorum being divided to the same extent. The foot must be flexed to relax these muscles, and they must be separated from each other by the finger. The artery is then exposed deeply seated, lying upon the interosseous membrane, the nerve lying externally, and one of the venae comites on either side; these must be separated from the artery before the aneurism needle is passed round it. To tie the vessel in the lower third of the leg above the ankle-joint an incision about three inches in length should be made through the integument between the tendons of the Tibialis anticus and Extensor proprius hallucis muscles, the deep fascia being divided to the same extent. The tendon on either side should be held aside, when the vessel will be seen lying upon the tibia, with the nerve superficial to it and one of the venae comites on either side. The branches of the anterior tibial artery are-the Posterior Recurrent Tibial. Superior Fibular. Anterior Recurrent Tibial. Muscular. Internal Malleolar. External Malleolar, The posterior recurrent tibial is not a constant branch, and is given off from the anterior tibial before that vessel passes through the interosseous space. It ascends beneath the Popliteus muscle, which it supplies, and anastomoses with the lower articular branches of the popliteal artery, giving off an offset to the superior tibio-fibular joint. The superior fibular is sometimes given off from the anterior tibial, sometimes from the posterior tibial. It passes outward, round the neck of the fibula, through the Soleus, which it supplies, and ends in the substance of the Peroneus longus muscle. The anterior recurrent tibial branch arises from the anterior tibial as soon as that vessel has passed through the interosseous space; it ascends in the Tibialis anticus muscle, and ramifies on the front and sides of the knee-joint, anastomos- ing with the articular branches of the popliteal and with the anastomotica magna. The muscular branches are numerous: they are distributed to the muscles THE DORSALIS PEDIS ARTERY. 645 which lie on each side of the vessel, some piercing the deep fascia to supply the integument, others passing through the interosseous membrane, and anastomosing with branches of the posterior tibial and peroneal arteries. The malleolar arteries supply the ankle-joint. The internal arises about two inches above the articulation, and passes beneath the tendons of the Extensor proprius hallucis and Tibialis anticus to the inner ankle, upon which it ramifies, anastomosing with branches of the posterior tibial and internal plantar arteries and with the internal calcanean from the posterior tibial. The external passes beneath the tendons of the Extensor longus digitorum and Peroneus tertius, and supplies the outer ankle, anastomosing with the anterior peroneal artery and with ascending branches from the tarsal branch of the dorsalis pedis. The Dorsalis Pedis Artery (Fig. 378). The dorsalis pedis, the continuation of the anterior tibial, passes forward from the bend of the ankle along the tibial side of the foot to the back part of the first intermetatarsal space, where it divides into two branches, the dorsalis hallucis and communicating. Relations.-This vessel, in its course forward, rests upon the astragalus, navic- ular, and internal cuneiform bones and the ligaments connecting them, being cov- ered by the integument and fascia, anterior annular ligament, and crossed near its termination by the innermost tendon of the Extensor brevis digitorum. On its tibial side is the tendon of the Extensor proprius hallucis; on its fibular side, the innermost tendon of the Extensor longus digitorum, and the termination of the anterior tibial nerve. It is accompanied by two veins. Plan of the Relations of the Dorsalis Pedis Artery. In front. Integument and fascia. Anterior annular ligament. Innermost tendon of Extensor brevis digitorum. Fibular side. Extensor longus digitorum. Anterior tibial nerve. Tibial side. Extensor proprius hallucis. Dorsalis Pedis. Behind. Astragalus. Navicular. Internal cuneiform, and their ligaments. Peculiarities in Size.-The dorsal artery of the foot may be larger than usual, to compen- sate for a deficient plantar artery; or it may be deficient in its terminal branches to the toes, which are then derived from the internal plantar; or its place may be supplied altogether by a large anterior penmeal artery. Position.-This artery frequently curves outward, lying external to the line between the middle of the ankle and the back part of the first interosseous space. Surface Marking.-The dorsalis pedis artery is indicated on the surface of the dorsum of the foot by a line drawn from the centre of the space between the two malleoli to the back of the first intermetatarsal space. Surgical Anatomy.-This artery may be tied, by making an incision through the integu- ment between two and three inches in length, on the fibular side of the tendon of the Extensor proprius hallucis, in the interval between it and the inner border of the short Extensor muscle. The incision should not extend farther forward than the back part of the first intermetatarsal space, as the artery divides in that situation. The deep fascia being divided to the same extent, the artery will be exposed, the nerve lying upon its outer side. 646 THE ARTERIES. Branches.-The branches of the dorsalis pedis are-the Tarsal. Metatarsal-Interosseous. Dorsalis Hallucis. Communicating. The tarsal artery arises from the dorsalis pedis, as that vessel crosses the navic- ular bone; it passes in an arched direction outward, lying upon the tarsal bones, and covered by the Extensor brevis digitorum; it supplies that muscle and the articulations of the tarsus, and anastomoses with branches from the metatarsal, external malleolar, peroneal, and external plantar arteries. The metatarsal arises a little anterior to the preceding; it passes outward to the outer part of the foot, over the bases of the metatarsal bones, beneath the ten- dons of the short Extensor, its direction being influenced by its point of origin; and it anastomoses with the tarsal and external plantar arteries. This vessel gives off three branches, the interosseous arteries, which pass forward upon the three outer Dorsal interossei muscles, and, in the clefts between the toes, divide into two dorsal collateral branches for the adjoining toes. At the back part of each interosseous space these vessels receive the posterior perforating branches from the plantar arch, and at the fore part of each interosseous space they are joined by the anterior perforating branches from the digital arteries. The outer- most interosseous artery gives off a branch which supplies the outer- side of the little toe. The dorsalis hallucis runs forward along the outer border of the first metatarsal bone, and at the cleft between the first and second toes divides into two branches, one of which passes inward, beneath the tendon of the Extensor proprius hallucis, and is distributed to the inner border of the great toe; the outer branch bifurcates, to supply the adjoining sides of the great and second toes. The communicating artery dips down into the sole of the foot, between the two heads of the First dorsal interosseous muscle, and inosculates with the termina- tion of the external plantar artery to complete the plantar arch. It here gives off two digital branches: one runs along the inner side of the great toe on its plantar surface; the other passes forward along the first interosseous space, and bifurcates for the supply of the adjacent sides of the great and second toes. The Posterior Tibial Artery. The posterior tibial is an artery of large size, which extends obliquely down- ward from the lower border of the Popliteus muscle, along the tibial side of the leg, to the fossa between the inner ankle and the heel, where it divides beneath the origin of the Abductor hallucis, on a level with a line drawn from the point of the internal malleolus to the centre of the convexity of the heel, into the internal and external plantar arteries. At its origin it lies opposite the interval between the tibia and fibula; as it descends, it approaches the inner side of the leg, lying behind the tibia, and, in the lower part of its course, is situated midway between the inner malleolus and the tuberosity of the os calcis. Relations.-It lies successively upon the TibialiA posticus, the Flexor longus digitorum, the tibia, and the back part of the ankle-joint. It is covered by the deep transverse fascia, which separates it above from the Gastrocnemius and Soleus muscles. In the lower third, where it is more superficial, it is covered only by the integument and fascia, and runs parallel with the inner border of the tendo Achillis. It is accompanied by two veins, and by the posterior tibial nerve, which lies at first to the inner side of the artery, but soon crosses it, and is, in the greater part of its course, on its outer side. THE POSTERIOR TIBIAL ARTERY. 647 Plan of the Relations of the Posterior Tibial Artery. In front. Tibialis posticus. Flexor longus digitorum. Tibia. Ankle-joint. Inner side. Posterior tibial nerve, upper third. Outer side. Posterior tibial nerve, lower two-thirds. Posterior Tibial. Behind. Integument and fascia. Gastrocnemius. Soleus. Deep transverse fascia. Posterior tibial nerve. Behind the Inner ankle the tendons and blood-vessels are arranged in the following order, from within outward: First, the tendons of the Tibialis posticus and Flexor longus digitorum, lying in the same groove, behind the inner malleolus, the former being the most internal. External to these is the posterior tibial artery, having a vein on either side ; and, still more externally, the posterior tibial nerve. About half an inch nearer the heel is the tendon of the Flexor longus hallucis. Peculiarities in Size.-The posterior tibial is not unfrequently smaller than usual, or absent, its place being supplied by a large peroneal artery which passes inward at the lower end of the tibia, and either joins the small tibial artery or continues alone to the sole of the foot. Surface Marking.-The course of the posterior tibial artery is indicated by a line drawn from a point one inch below the centre of the popliteal space to midway between the tip of the internal malleolus and the centre of the convexity of the heel. Surgical Anatomy.-The application of a ligature to the posterior tibial may be required in cases of wound of the sole of the foot attended with great haemorrhage, when the vessel should be tied at the inner ankle. In cases of wound of the posterior tibial it will be necessary to enlarge the opening so as to expose the vessel at the wounded point, excepting where the vessel is injured by a punctured wound from the front of the leg. In cases of aneurism from wound of the artery low down, the vessel should be tied in the middle of the leg. But in aneurism of the posterior tibial high up it would be better to tie the femoral artery. To tie the posterior tibial artery at the ankle, a semilunar incision should be made through the integument, about two inches and a half in length, midway between the heel and inner ankle or a little nearer the latter. The subcutaneous cellular tissue having been divided, a strong and dense fascia, the internal annular ligament, is exposed. This ligament is continuous above with the deep fascia of the leg, covers the vessels and nerves, and is intimately adherent to the sheaths of the tendons. This having been cautiously divided upon a director, the sheath of the vessels is exposed, and, being opened, the artery is seen with one of the venae comites on each side. The aneurism needle should be passed round the vessel from the heel toward the ankle, in order to avoid the posterior tibial nerve, care being at the same time taken not to include the venae comites. The vessel may also be tied in the lower third of the leg by making an incision, about three inches in length, parallel with the inner margin of the tendo Achillis. The internal saphenous vein being carefully avoided, the two layers of fascia must be divided upon a director, when the artery is exposed along the outer margin of the Flexor longus digitorum, with one of its venae comites on either side and the nerve lying external to it. To tie the posterior tibial in the middle of the leg is a very difficult operation, on account of the great depth of the vessel from the surface. The patient being placed in the recumbent posi- tion, the injured limb should rest on its outer side, the knee being partially bent and the foot extended, so as to relax the muscles of the calf. An incision about four inches in length should then be made through the integument a finger's breadth behind the inner margin of the tibia, taking care to avoid the internal saphenous vein. The deep fascia having been divided, the margin of the Gastrocnemius is exposed, and must be drawn aside, and the tibial attachment of the Soleus divided, a director being previously passed beneath it. The artery may now be felt pulsating beneath the deep fascia about an inch from the margin of the tibia. The fascia having been divided, and the limb placed in such a position as to relax the muscles of the calf as much as possible, the veins should be separated from the artery, and the aneurism needle passed round the vessel from without inward, so as to avoid wounding the posterior tibial nerve. 648 THE ARTERIES. The branches of the posterior tibial artery are-the Peroneal. Muscular. Nutrient. Communicating. Internal Calcanean. The Peroneal Artery lies, deeply seated, along the back part of the fibular side of the leg. It arises from the posterior tibial about an inch below the lower border of the Popliteus muscle, passes obliquely outward to the fibula, and then descends along the inner border of that bone to the lower third of the leg, where it gives off the anterior peroneal. It then passes across the articulation between the tibia and fibula to the outer side of the os calcis, where it gives off its terminal branches, the external calcanean. Relations.-This vessel rests at first upon the Tibialis posticus, and then, for the greater part of its course, in a fibrous canal between the origins of the Flexor longus hallucis and Tibialis posticus, covered or surrounded by the fibres of the Flexor longus hallucis. It is covered, in the upper part of its course, by the Soleus and deep transverse fascia; below, by the Flexor longus hallucis. Plan of the Relations of the Peroneal Artery In front. Tibialis posticus. Flexor longus hallucis, Outer side. Fibula. Flexor longus hallucis. Peroneal Artery. Inner side. Flexor longus hallucis. Behind. Soleus. Deep transverse fascia. Flexor longus hallucis. Peculiarities in Origin.-The peroneal artery may arise three inches below the Popliteus, or from the posterior tibial high up, or even from the popliteal. Its size is more frequently increased than diminished; and then it either reinforces the posterior tibial by its junction with it, or altogether takes the place of the posterior tibial in the lower part of the leg and foot, the latter vessel only existing as a short muscular branch. In those rare cases where the peroneal artery is smaller than usual a branch from the posterior tibial supplies its place, and a branch from the anterior tibial compensates for the diminished anterior peroneal artery. In one case the peroneal artery has been found entirely wanting. The anterior peroneal is sometimes enlarged, and takes the place of the dorsal artery of the foot. The branches of the peroneal are-the Muscular. Nutrient. Anterior Peroneal. Communicating. Posterior Peroneal. External Calcanean. Muscular Branches.-The peroneal artery, in its course, gives off branches to the Soleus, Tibialis posticus, Flexor longus hallucis, and Peronei muscles. The nutrient artery supplies the fibula. The Anterior peroneal pierces the interosseous membrane, about two inches above the outer malleolus, to reach the fore part of the leg, and, passing down beneath the Peroneus tertius to the outer ankle, ramifies on the front and outer side of the tarsus, anastomosing with the external malleolar and tarsal arteries. The communicating is given off from the peroneal about an inch from its lower end, and, passing inward, joins the communicating branch of the posterior tibial. The Posterior peroneal passes down behind the outer ankle to the back of the external malleolus, to terminate in branches which ramify on the outer surface and back of the os calcis. THE PLANTAR ARTERIES. 649 The External calcanean are the terminal branches of the peroneal artery ; they pass to the outer side of the heel, and communicate writh the external malleolar, and, on the back of the heel, with the internal calcanean arteries. The nutrient artery of the tibia arises from the posterior tibial near its origin, and, after supplying a few muscular branches, enters the nutrient canal of that bone, wThich it traverses obliquely from above downward. This is the largest nutrient artery of bone in the body. The muscular branches of the posterior tibial are distributed to the Soleus and deep muscles along the back of the leg. The communicating branch, to join a similar branch of the peroneal, runs trans- versely across the back of the tibia, about two inches above its lower end, passing beneath the Flexor longus hallucis. The internal calcanean are several large arteries which arise from the posterior Communicating branch of dorsalis pedis. Its digital branches. Fig. 379.-The plantar arteries. Superficial view Fig. 380.-The plantar arteries. Deep view tibial just before its division: they are distributed to the fat and integument behind the tendo Achillis and about the heel, and to the muscles on the inner side of the sole, anastomosing with the peroneal and internal malleolar, and, on the back of the heel, with the external calcanean arteries. The Internal Plantar Artery (Figs. 379, 380), much smaller than the external, passes forward along the inner side of the foot. It is at first situated above 1 the Abductor hallucis, and then between it and the Flexor brevis digitorum, both of which it supplies. At the base of the first metatarsal bone, where it has become much diminished in size, it passes along the inner border of the great toe, inoscu- lating with its digital branch. The External Plantar Artery, much larger than the internal, passes obliquely outward and forward to the base of the fifth metatarsal bone. It then turns obliquely inward to the interval between the bases of the first and second meta- tarsal bones, where it anastomoses with the communicating branch from the dorsalis pedis artery, thus completing the plantar arch. As this artery passes 1 This refers to the erect position of the body. In the ordinary position for dissection the artery is deeper than the muscle. 650 THE ARTERIES. outward, it is first placed between the os calcis and Abductor hallucis, and then between the Flexor brevis digitorum and Flexor accessorius, and as it passes forward to the base of the little toe, it lies more superficially between the Flexor brevis digitorum and Abductor minimi digiti, covered by the deep fascia and integument. The remaining portion of the vessel is deeply situated: it extends from the base of the metatarsal bone of the little toe to the back part of the first interosseous space, and forms the plantar arch; it is convex forward, lies upon the Interossei muscles opposite the tarsal ends of the metatarsal bones, and is covered by the Adductor obliquus hallucis, the flexor tendons of the toes, and the Lumbricales. Surface Marking.-The course of the internal plantar artery is represented by a line drawn from the mid-point between the tip of the internal malleolus and the centre of the con- vexity of the heel to the middle of the under surface of the great toe; the external plantar by a line from the same point to within a finger's breadth of the tuberosity of the fifth metatarsal bone. The plantar arch is indicated by a line drawn from this point; t. e. a finger's breadth internal to the tuberosity of the fifth metatarsal bone transversely across the foot to the back of the first interosseous space. Surgical Anatomy.-Wounds of the plantar arch are always serious, on account of the depth of the vessel and the important structures which must be interfered with in an attempt to ligature it. Delorme has shown that it may be ligatured from the dorsum of the foot in almost any part of its course by removing a portion of one of the three middle metatarsal bones. Branches.-The plantar arch, besides distributing numerous branches to the muscles, integument, and fasciae in the sole, gives off the following branches: Posterior Perforating. Digital-Anterior Perforating. The Posterior Perforating are three small branches which ascend through the back part of the three outer interosseous spaces, between the heads of the Dorsal interossei muscles, and anastomose with the interosseous branches from the meta- tarsal artery. The Digital Branches are four in number, and supply the three outer toes and half the second toe. The first passes outward from the outer side of the plantar arch, and is distributed to the outer side of the little toe, passing in its course beneath the Abductor and short Flexor muscles. The second, third, and fourth run forward along the interosseous spaces, and on arriving at the clefts between the toes divide into collateral branches, which supply the adjacent sides of the three outer toes and the outer side of the second. At the bifurcation of the toes each digital artery sends upward, through the fore part of the corresponding interosseous space, a small branch, which inosculates with the interosseous branches of the metatarsal artery. These are the anterior perforating branches. From the arrangement already described of the distribution of the vessels to the toes it will be seen that both sides of the three outer toes and the outer side of the second toe are supplied by branches from the plantar arch ; both sides of the great toe and the inner side of the second are supplied by the communi- cating branch of the dorsalis pedis. THE VEINS. rpiiE Veins are the vessels which serve to return the blood from the capillaries 1 of the different parts of the body to the heart. They consist of two distinct sets of vessels, the pulmonary and systemic. The Pulmonary Veins are concerned in the circulation in the lungs. Unlike other vessels of this kind, they contain arterial blood, which they return from the lungs to the left auricle of the heart. The Systemic Veins are concerned in the general circulation; they return the venous blood from the body generally to the right auricle of the heart. The Portal Vein, an appendage to the systemic venous system, is confined to the abdominal cavity, returning the venous blood from the viscera of digestion, and carrying it to the liver by a single trunk of large size, the vena portce. This vessel ramifies in the substance of the liver and breaks up into a minute network of capillaries. These capillaries then re-collect to form the hepatic veins, by which the blood is conveyed to the inferior vena cava. The veins, like the arteries, are found in nearly every tissue of the body. They commence by minute plexuses which receive the blood from the capillaries. The branches which have their commencement in these plexuses unite together into trunks, and these, in their passage toward the heart, constantly increase in size as they receive tributaries or join other veins. The veins are larger and altogether more numerous than the arteries ; hence the entire capacity of the venous system is much greater than that of the arterial, the pulmonary veins excepted, which do not exceed in capacity the pulmonary arteries. From the combined area of the smaller venous branches being greater than the main trunks, it results that the venous system represents a cone, the summit of which corresponds to the heart, its base to the circumference of the body. In form the veins are not perfectly cylindrical like the arteries, their walls being collapsed when empty, and the uniformity of their surface being interrupted at intervals by slight constric- tions, which indicate the existence of valves in their interior. They usually retain, however, the same calibre as long as they receive no branches. The veins communicate very freely with one another, especially in certain regions of the body, and this communication exists between the larger trunks as well as between the smaller branches. Thus, in the cavity of the cranium and between the veins of the neck, where obstruction would be attended with immi- nent danger to the cerebral venous system, we find that the sinuses and larger veins have large and very frequent anastomoses. The same free communication exists between the veins throughout the whole extent of the spinal canal, and between the veins composing the various venous plexuses in the abdomen and pel- vis, as the spermatic, uterine, vesical, and prostatic. The systemic veins are subdivided into three sets : superficial, deep, and sinuses. The Superficial or Cutaneous Veins are found between the layers of the super- ficial fascia, immediately beneath the integument; they return the blood from these structures, and communicate with the deep veins by perforating the deep fascia. The Deep Veins accompany the arteries, and are usually enclosed in the same sheath with those vessels. With the smaller arteries-as the radial, ulnar, brachial, tibial, peroneal-they exist generally in pairs, one lying on each side of the ves- sel, and are called vence comites. The larger arteries-as the axillary, subclavian, popliteal, and femoral-have usually only one accompanying vein. In certain 652 THE VEINS organs of the body, however, the deep veins do not accompany the arteries; for instance, the veins in the skull and spinal canal, the hepatic veins in the liver, and the larger veins returning blood from the osseous tissue. Sinuses are venous channels which, in their structure and mode of distribution, differ altogether from the veins. They are found only in the interior of the skull, and are formed by a separation of the layers of the dura mater, their outer coat consisting of fibrous tissue, their inner of an endothelial layer continuous with the lining membrane of the veins. Veins have thinner walls than arteries, the difference in thickness being due to the small amount of elastic and muscular tissues which the veins contain. The superficial veins usually have thicker coats than the deep veins, and the veins of the lower limb are thicker than those of the upper. The minute structure of these vessels has been described in the section on General Anatomy. The Pulmonary Veins return the arterial blood from the lungs to the left auricle of the heart. They are four in number, two for each lung. The pulmo- nary differ from other veins in several respects: 1. They carry arterial instead of venous blood. 2. They are destitute of valves. 3. They are only slightly larger than the arteries they accompany. 4. They accompany those vessels singly. They commence in a capillary network upon the walls of the air-cells, where they are continuous with the ramifications of the pulmonary artery, and, uniting together, form a single trunk for each lobule. These branches, uniting succes- sively, form a single trunk for each lobe, three for the right and two for the left lung. The vein from the middle lobe of the right lung unites with that from the upper lobe, in most cases forming two trunks on each side, which open separately into the left auricle. Occasionally they remain separate; there are then three veins on the right side. Not unfrequently the two left pulmonary veins termi- nate by a common opening. Within the lung, the branches of the pulmonary artery are in front, the veins behind, and the bronchi between the two. At the root of the lung, the veins are in front, the artery in the middle, and the bronchus behind. Within the pericardium, their anterior surface is invested by the serous layer of this membrane. The right pulmonary veins pass behind the right auricle and ascending aorta; the left pass in front of the thoracic aorta with the left pulmo- nary artery. THE PULMONARY VEINS. THE SYSTEMIC VEINS. The systemic veins may be arranged into three groups: 1. Those of the head and neck, upper extremity, and thorax, which terminate in the superior vena cava. 2. Those of the lower limb, pelvis, and abdomen, which terminate in the inferior vena cava. 3. The cardiac veins, which open directly into the right auricle of the heart. VEINS OF THE HEAD AND NECK. The veins of the head and neck may be subdivided into three groups: 1. The veins of the exterior of the head and face. 2. The veins of the neck. 3. The veins of the diploe and interior of the cranium. Veins of the Exterior of the Head. The veins of the exterior of the head and face are-the Frontal. Supra-orbital. Angular. Facial. Temporal. Internal Maxillary. Temporo-maxillary. Posterior Auricular. Occipital. OF THE EXTERIOR OF THE HEAD. 653 The frontal vein commences on the anterior part of the skull by a venous plexus which communicates with the anterior tributaries of the temporal vein. The veins converge to form a single trunk, which runs downward near the middle line of the forehead parallel with the vein of the opposite side, and unites with it at the root of the nose by a transverse branch called the nasal arch. Occasionally the frontal veins join to form a single trunk, which bifurcates at the 'Communicating branch with [ophthalmic rein. JL ~~ Angular. -Lingual. Laryngeal. ■'Superior thyroid. Fig. 381.-Veins of the head and neck. root of the nose into the two angular veins. At the root of the nose the veins diverge, and join the supra-orbital vein, at the inner angle of the orbit, to form the angular vein. The supra-orbital vein commences on the forehead, communicating with the anterior temporal vein, and runs downward and inward, superficial to the Occipito-frontalis muscle, receiving tributaries from the neighboring structures, and joins the frontal vein at the inner angle of the orbit to form the angular vein. The angular vein, formed by the junction of the frontal and supra-orbital veins, runs obliquely downward and outward on the side of the root of the nose, and receives the veins of the ala nasi on its inner side and the superior palpebral veins on its outer side; it moreover communicates with the ophthalmic vein, thus 654 THE VEINS establishing an important anastomosis between this vessel and the cavernous sinus. Some small veins from the dorsum. of the nose terminate in the nasal arch. The facial vein commences at the side of the root of the nose, being a direct continuation of the angular vein. It passes obliquely downward and outward beneath the Zygomaticus major and minor muscles, descends along the anterior border of the Masseter, crosses over the body of the lower jaw with the facial artery, and, passing obliquely outward and backward beneath the Platysma and cervical fascia, unites with a branch of communication from the temporo-max- illary vein to form a trunk of large size which enters the internal jugular. From near its termination a communicating branch often runs down the anterior border of the Sterno-mastoid to join the lower part of the anterior jugular. Tributaries.-The facial vein receives, near the angle of the mouth, communi- cating tributaries of considerable size (the deep facial or anterior internal maxil- lary vein) from the pterygoid plexus. It is also joined by the inferior palpebral, the superior and inferior labial veins, the buccal veins from the cheek, and the masseteric veins. Below the jaw it receives the submental; the inferior palatine, which returns the blood from the plexus around the tonsil and soft palate; the submaxillary vein, which commences in the submaxillary gland ; and, generally, the ranine vein. Surgical Anatomy.-There are some points about the facial vein which render it of great importance in surgery. It is not so flaccid as are most superficial veins, and, in consequence of this, remains more patent when divided. It has, moreover, no valves. It communicates freely with the intracranial circulation, not only at its commencement by its tributaries, the angular and supra-orbital veins, communicating with the ophthalmic vein, a tributary of the cavernous sinus, but also by its deep branch, which communicates through the pterygoid plexus with the cavernous sinus by branches which pass through the foramen ovale and foramen lacerum medium (see page 663). These facts have an important bearing upon the surgery of some diseases of the face, for on account of its patency the facial vein favors septic absorption, and therefore any phlegmonous inflammation of the face following a poisoned wound is liable to set up thrombosis in the facial vein. And on account of its communications with the cerebral sinuses these thrombi are apt to extend upward into them, and detached portions may give rise to purulent foci in other parts of the body, and so induce a fatal issue. The Temporal Vein commences by a minute plexus on the side and vertex of the skull, which communicates with the frontal and supra-orbital veins in front, the corresponding vein of the opposite side, and the posterior auricular and occipital veins behind. From this network anterior and posterior branches are formed which unite above the zygoma, forming the trunk of the vein. This trunk is joined in this situation by a large vein, the middle temporal, which receives the blood from the substance of the Temporal muscle and pierces the fascia at the upper border of the zygoma. The temporal vein then descends between the external auditory meatus and the condyle of the jaw, enters the sub- stance of the parotid gland, and unites with the internal maxillary vein to form the temporo-maxillary vein. Tributaries.-The temporal vein receives in its course some parotid veins, an articular branch from the articulation of the jaw, anterior auricular veins from the external ear, and a vein of large size, the transverse facial, from the side of the face. The middle temporal vein, previous to its junction with the temporal vein, receives a branch, the orbital vein, which is formed by some external palpe- bral branches, and passes backward between the layers of the temporal fascia. The Internal Maxillary Vein is a vessel of considerable size, receiving branches which correspond with those of the internal maxillary artery. Thus it receives the middle meningeal veins, the deep temporal, the pterygoid, masseteric, buccal, alveolar, some palatine veins, and the inferior dental. These branches form a large plexus, the pterygoid, which is placed between the Temporal and External pterygoid and partly between the Pterygoid muscles. This plexus communicates very freely with the facial vein and with the cavernous sinus by branches through the foramen Vesalii at the base of the skull. The trunk of the vein then passes OF THE NECK. 655 backward behind the neck of the lower jaw, and unites with the temporal vein, forming the temporo-maxillary vein. The Temporo-Maxillary Vein, formed by the union of the temporal and internal maxillary veins, descends in the substance of the parotid gland on the outer surface of the external carotid artery, between the ramus of the jaw and the Sterno-mastoid muscle, and divides into two branches, one of which passes inward to join the facial vein; the other is joined by the posterior auricular vein and becomes the external jugular. The Posterior Auricular Vein commences upon the side of the head by a plexus which communicates with the tributaries of the temporal and occipital veins. The vein descends behind the external ear and joins the temporo-maxillary vein, forming the external jugular. This vessel receives the stylo-mastoid vein and some tributaries from the back part of the external ear. The Occipital Veins commence at the back part of the vertex of the skull by a plexus in a similar manner to the other veins. These unite and form one or two veins, which follow the course of the occipital artery, passing deeply beneath the muscles of the back part of the neck, and terminate in the internal jugular, occasionally in the external jugular vein. As these veins pass across the mastoid portion of the temporal bone, one of them receives the mastoid vein, which thus establishes a communication with the lateral sinus. The Veins of the Neck. The veins of the neck, which return the blood from the head and face, are-the External Jugular. Posterior External Jugular. Anterior Jugular. Internal Jugular. Vertebral. The External Jugular Vein receives the greater part of the blood from the exterior of the cranium and deep parts of the face, being formed by the junction of the posterior division of the temporo-maxillary and posterior auricular veins. It commences in the substance of the parotid gland, on a level with the angle of the lower jaw, and runs perpendicularly down the neck in the direction of a line drawn from the angle of the jaw to the middle of the clavicle. In its course it crosses the Sterno-mastoid muscle, and runs parallel with its posterior border as far as its attachment to the clavicle, where it perforates the deep fascia, and terminates in the subclavian vein, on the outer side of or in front of the Scalenus anticus muscle. In the neck it is separated from the Sterno-mastoid by the anterior layer of the deep cervical fascia, and is covered by the Platysma, the superficial fascia, and the integument. This vein is crossed about its middle by the super- ficialis colli nerve, and its upper half is accompanied by the auricularis magnus nerve. The external jugular vein varies in size, bearing an inverse proportion to that of the other veins of the neck ; it is occasionally double. It is provided with two pairs of valves, the lower pair being placed at its entrance into the subclavian vein, the upper pair in most cases about an inch and a half above the clavicle. The portion of vein between the two sets of valves is often dilated, and is termed the sinus. These valves do not prevent the regurgitation of the blood or the passage of injection from below upward.1 Surgical Anatomy.-Venesection used formerly to be performed on the external jugular vein, but is now probably never resorted to. The anatomical point to be remembered in per- forming this operation is to cut across the fibres of the Platysma myoides in opening the vein, so that by their contraction they will expose the orifice in the vein and so allow the flow of blood. Tributaries.-This vein receives the occipital occasionally, the posterior external jugular, and near its termination, the suprascapular and transverse cervical veins. 4 ' The student may refer to an interesting paper by Dr. Struthers, " On Jugular Venesection in Asphyxia, anatomically and experimentally considered, including the Demonstration of Valves in the Veins of the Neck," in the Edinburgh Medical Journal for November, 1856. 656 7V/J-; VEINS It communicates with the anterior jugular, and, in the substance of the parotid, receives a large branch of communication from the internal jugular. The Posterior External Jugular Vein commences in the occipital region, and returns the blood from the integument and superficial muscles in the upper and back part of the neck, lying between the Splenitis and Trapezius muscles. It runs down the back part of the neck, and opens into the external jugular just below the middle of its course. The Anterior Jugular Vein commences near the hyoid bone from the con- vergence of several superficial veins from the submaxillary region. It passes down between the median line and the anterior border of the Sterno-mastoid, and at the lower part of the neck passes beneath that muscle to open into the termination of the external jugular or into the subclavian vein (Fig. 388). This vein varies considerably in size, bearing almost always an inverse proportion to the external jugular. Most frequently there are two anterior jugulars, a right and left, but occasionally only one. This vein receives some laryngeal veins, and occasionally a small thyroid vein. Just above the sternum the two anterior jugular veins communicate by a transverse trunk, which receives tributaries from the inferior thyroid veins. It also communicates with the internal jugular. There are no valves in this vein. The Internal Jugular Vein collects the blood from the interior of the cranium, from the superficial parts of the face, and from the neck. It commences just external to the jugular foramen, at the base of the skull, being formed by the coalescence of the lateral and inferior petrosal sinuses (Fig. 386). At its origin it is somewhat dilated, and this dilatation is called the sinus, or gulf, of the internal jugular vein. It runs down the side of the neck in a vertical direction, lying at first on the outer side of the internal carotid, and then on the outer side of the common carotid, and at the root of the neck unites with the subclavian vein to form the innominate vein. The internal jugular vein, at its commencement, lies upon the Rectus capitis lateralis, and behind the internal carotid and the nerves passing through the jugular foramen ; lower down, the vein and artery lie upon the same plane, the glosso-pharyngeal and hypoglossal nerves passing forward between them; the pneumogastric descends between and behind them in the same sheath, and the spinal accessory passes obliquely outward behind the vein. At the root of the neck the vein of the right side is placed at a little distance from the artery; on the left side it usually lies over the artery at its lower part. The right internal jugular vein crosses the first part of the subclavian artery. The vein is of considerable size, but varies in different individuals, the left one being usually the smaller. It is provided with a pair of valves, which are placed at its point of termination or from half to three-quarters of an inch above it. Tributaries.-This vein receives in its course the facial, lingual, pharyngeal, superior and middle thyroid veins, and sometimes the occipital. At its point of junction with the branch common to the temporo-maxillary and facial veins it becomes greatly increased in size. The lingual veins commence on the dorsum, sides, and under surface of the tongue, and, passing backward, following the course of the lingual artery and its branches, terminate in the internal jugular. Sometimes the ranine vein, which is a branch of considerable size commencing below the tip of the tongue, joins the lingual. Generally, however, it passes backward, crosses the Hyo-glossus muscle in company with the hypoglossal nerve, and joins the facial. The pharyngeal vein commences in a minute plexus, the pharyngeal, at the back part and sides of the pharynx, and, after receiving meningeal tributaries and the Vidian and spheno-palatine veins, terminates in the internal jugular. It occasionally opens into the facial, lingual, or superior thyroid vein. The superior thyroid vein commences in the substance and on the surface of the thyroid gland by tributaries corresponding with the branches of the superior thyroid artery, and terminates in the upper part of the internal jugular vein. OF THE DIPLOE. 657 The middle thyroid vein collects the blood from the lower part of the lateral lobe of the thyroid gland, and, being joined by some veins from the larynx and trachea, terminates in the lower part of the internal jugular vein. The facial and occipital veins have been described above. Surgical Anatomy.-The internal jugular vein occasionally requires ligature in cases of septic thrombosis of the lateral sinus from suppuration in the middle ear, in order to prevent embolism of the thoracic viscera. This operation has been performed recently in several cases with the most satisfactory results. The cases are generally those of chronic disease of the middle ear, with discharge of pus which perhaps has existed for many years. The patient is seized with acute septic inflammation, spreading to the mastoid cells, and consequent on this septic throm- bosis of the lateral sinus extending to the internal jugular vein. Such cases are always extremely grave, for there is a danger of a portion of the septic clot being detached and causing septic embolism in the thoracic viscera. This may be mechanically prevented by ligature of the inter- nal jugular vein in the middle of the neck. The operation is a comparatively simple one, and may be performed by an incision similar to that employed in ligature of the common carotid artery. « The Vertebral Vein commences in the occipital region by numerous small tributaries from the .deep muscles at the upper and back part of the neck; these pass outward and enter the foramen in the transverse process of the atlas, and descend, forming a dense plexus around the vertebral artery in the canal formed by the transverse processes of the cervical vertebrae. This plexus unites at the lower part of the neck into two main trunks, one of which emerges from the foramen in the transverse process of the sixth cervical vertebra, and the others through that of the seventh, and, uniting, form a single vessel, which terminates at the root of the neck in the back part of the innominate vein near its origin, its mouth being guarded by a pair of valves. On the right side it crosses the first part of the subclavian artery. Tributaries.-The vertebral vein receives in its course a vein from the inside of the skull through the posterior condyloid foramen; muscular veins from the muscles in the prevertebral region ; dorsi-spinal veins, from the back part of the cervical portion of the spine; meningo-rachidian veins, from the interior of the spinal canal; the anterior and posterior vertebral veins; and close to its termina- tion it is joined by a small vein from the first intercostal space which accompanies the superior intercostal artery. The anterior vertebral vein commences in a plexus around the transverse pro- cesses of the upper cervical vertebrae, descends in company with the ascending cervical artery between the Scalenus anticus and Rectus capitis anticus major muscles, and opens into the vertebral vein just before its termination. The posterior vertebral vein (the deep cervical) accompanies the profunda cer- vicis artery, lying between the Complexus and Semispinalis colli. It commences in the suboccipital region by communicating branches from the occipital vein and tributaries from the deep muscles at the back of the neck. It receives tribu- taries from the plexuses around the spinous processes of the cervical vertebrae, and terminates in the lower end of the vertebral vein. The diploe of the cranial bones is channelled in the adult by a number of tortuous canals, which are lined by a more or less complete layer of compact tissue. The veins they contain are large and capacious, their walls being thin, and formed only of endothelium resting upon a layer of elastic tissue, and they pre- sent at irregular intervals pouch-like dilatations, or culs-de-sac, which serve as reservoirs for the blood. These are the veins of the diploe; they can only be displayed by removing the outer table of the skull. In adult life, as long as the cranial bones are distinct and separable, these veins are confined to the particular bones; but in old age, when the sutures are united, they communicate with each other and increase in size. These vessels communicate, in the interior of the cranium, with the meningeal veins and with The Veins of the Diploe. 658 THE VEINS. the sinuses of the dura mater, and on the exterior of the skull with the veins of the pericranium. They are divided into the frontal, which opens into the supra- orbital vein by an aperture in the supra-orbital notch ; the anterior temporal, which is confined chiefly to the frontal bone, and opens into one of the deep temporal veins, after escaping by an aperture in the great wing of the sphenoid ; Fig. 382.-Veins of the Diploe as displayed by the removal of the outer table of the skull the posterior temporal, which is confined to the parietal bone, and terminates in the lateral sinus by an aperture at the posterior inferior angle of the parietal bone ; and the occipital, the largest of the four, which is confined to the occipital bone, and opens either into the occipital vein or internally into the lateral sinus or torcular Herophili. The Cerebral Veins. The Cerebral Veins are remarkable for the extreme thinness of their coats in consequence of the muscular tissue in them being wanting, and for the absence of valves. They may be divided into two sets: the superficial, which are placed on the surface, and the deep veins, which occupy the interior of the organ. The Superficial Cerebral Veins ramify upon the surface of the brain, being lodged in the sulci between the convolutions, a few running across the convolu- tions. They receive branches from the substance of the brain and terminate in the sinuses. They are named, from the position they occupy, superior, median, and inferior cerebral veins. The Superior Cerebral Veins, eight to twelve in number on each side, return the blood from the convolutions on the superior surface of the hemisphere; they pass forward and inward toward the great longitudinal fissure, where they receive the median cerebral veins ; near their termination they become invested with a tubular sheath of the arachnoid membrane, and open into the superior longitudi- nal sinus in the opposite direction to the course of the blood. The Median Cerebral Veins return the blood from the convolutions of the mesial surface of the corresponding hemisphere; they open into the superior cerebral veins, or occasionally into the inferior longitudinal sinus. The Inferior Cerebral Veins ramify on the lower part of the outer and on the under surface of the cerebral hemisphere. Some, collecting tributaries from the under surface of the anterior lobes of the brain, terminate in the cavernous sinus. One vein of large size, the middle cerebral vein, commences on the under surface THE SINUSES OF THE DURA MATER. 659 of the temporo-sphenoidal lobe, and, running along the fissure of Sylvius, opens into the cavernous sinus. Another large vein, the great anastomotic vein of Tro- lard, commences on the parietal lobe, runs along the horizontal limb of the fissure of Sylvius, and opens into the anterior part of the cavernous sinus under the lesser wing of the sphenoid. Others commence on the under surface of the base of the brain, and unite to form from three to five veins, which open into the superior petrosal and lateral sinuses from before backward. The Deep Cerebral, or Ventricular Veins (pence Galeni), are two in number. They are formed by the union of two veins, the vena corporis striati, and the choroid vein, on either side. They run backward, parallel with one another, between the layers of the velum interpositum, and pass out of the brain at the great transverse fissure, between the posterior extremity, or splenium, of the corpus callosum and the tubercula quadrigemina, to enter the straight sinus. The two veins usually unite to form one before opening into the straight sinus. The vena corporis striati commences in the groove between the corpus striatum and thalamus opticus, receives numerous veins from both of these parts, and unites behind the anterior pillar of the fornix with the choroid vein to form one of the venae Galeni. The choroid vein runs along the whole length of the outer border of the choroid plexus, receiving veins from the hippocampus major, the fornix and corpus callosum, and unites, at the anterior extremity of the choroid plexus, with the vein of the corpus striatum. The Cerebellar Veins occupy the surface of the cerebellum, and are disposed in three sets, superior, inferior, and lateral. The superior pass forward and inward across the superior vermiform process, and terminate in the straight sinus; some open into the venae Galeni. The inferior cerebellar veins, of large size, run trans- versely outward, and terminate by two or three trunks in the lateral sinuses. The lateral anterior cerebellar veins terminate in the superior petrosal sinuses. The perivascular lymph-sheaths alluded to above (see page 87) are especially found in con- nection with the vessels of the brain. These vessels are enclosed in a sheath which acts as a lymphatic channel, through which the lymph is carried to the subarachnoid and subdural spaces, from which it is returned into the general circulation. The Sinuses of the Dura Mater. The sinuses of the dura mater are venous channels, analogous to the veins, their outer coat being formed by the dura mater; their inner, by a continuation of the lining membrane of the veins. They are fifteen in number, and are divided into two sets: 1, those situated at the upper and back part of the skull; 2, those at the base of the skull. The former are-the Superior Longitudinal. Inferior Longitudinal. Straight Sinus. Lateral Sinuses. Occipital Sinus. The Superior Longitudinal Sinus occupies the attached margin of the falx cerebri. Commencing at the foramen caecum, through which it constantly com- municates by a small branch with the veins of the nasal fossae, it runs from before backward, grooving the inner surface of the frontal, the adjacent margins of the two parietal, and the superior division of the crucial ridge of the occipital bone, and terminates by opening into the torcular Herophili. The sinus is triangular in form, narrow in front, and gradually increasing in size as it passes backward. On examining its inner surface it presents the internal openings of the superior cerebral veins, which run, for the most part, from behind forward,«and open chiefly at the back part of the sinus, their orifices being concealed by fibrous folds; numerous fibrous bands (chorda1 Willisii) are also seen, extending transversely across the inferior angle of the sinus; and, lastly, some small, white, projecting bodies, the glandule? Pacchioni. This sinus receives the superior cerebral veins, numerous veins from the diploe and dura mater, and, at the posterior extremity 660 THE VEINS. of the sagittal suture, veins from the pericranium, which pass through the parietal foramen. The torcular Herophili is the dilated extremity of the superior longitudinal sinus. It is of irregular form, and is lodged on one side (generally the right) of the internal occipital protuberance. From it the lateral sinus of the side to which it is deflected is derived. It receives also the blood from the occipital sinus. The Inferior Longitudinal Sinus, more correctly described as the inferior longi- tudinal vein, is contained in the posterior part of the free margin of the falx cerebri. It is of a cylindrical form, increases in size as it passes backward, and terminates in the straight sinus. It receives several veins from the falx cerebri, and occasionally a few from the mesial surface of the hemispheres. The Straight Sinus is situated at the line of junction of the falx cerebri with the tentorium. It is triangular in form, increases in size as it proceeds backward, and runs obliquely downward and backward from the termination of the inferior longitudinal sinus to the lateral sinus of the opposite side to that into which the superior longitudinal sinus is prolonged. It communicates by a cross branch ■Foramen cxcum. Torcular herophili. Fig. 383.-Vertical section of the skull, showing the sinuses of the dura mater. with the torcular Herophili. Beside the inferior longitudinal sinus, it receives the venae Galeni and the superior cerebellar veins. A few transverse bands cross its interior. The Lateral Sinuses are of large size, and are situated in the attached margin of the tentorium cerebelli. They commence at the internal occipital protuberance, the one, generally the right, being the direct continuation of the superior longi- tudinal sinus, the other of the straight sinus. They pass horizontally outward to the base of the petrous portion of the temporal bone, then curve downward and inward on each side to reach the jugular foramen, where they terminate in the internal jugular vein. Each sinus rests, in its course, upon the inner surface of the occipital, the posterior inferior angle of the parietal, the mastoid portion of the temporal, and on the occipital, again just before its termination. These sinuses are frequently of unequal size, that formed by the superior longitudinal sinus being the larger, and they increase in size as they proceed from behind forward. The horizontal portion is of a triangular form, the curved portion semicylindrical. Their inner surface is smooth, and not crossed by the fibrous bands found in the other sinuses. These sinuses receive the blood from the superior petrosal sinuses at the base of the petrous portion of the temporal bone, and they unite with the inferior petrosal sinus, just external to the jugular foramen, to form the internal THE SINUSES OF THE DURA MATER. 661 jugular vein (Fig. 386). They communicate with the veins of the pericranium by means of the mastoid and posterior condyloid veins, and they receive some of the inferior cerebral and inferior cerebellar veins and some veins from the diploe. The Occipital is the smallest of the cranial sinuses. It is generally single, but occasionally there are two. It is situated in the attached margin of the falx cere- belli. It commences by several small veins around the margin of the foramen magnum, one of which joins the termination of the lateral sinus; it communicates with the posterior spinal veins and terminates in the torcular Ilerophili. The sinuses at the base of the skull are-the Cavernous. Circular. Superior Petrosal. Inferior Petrosal. Transverse. The Cavernous Sinuses are named from their presenting a reticulated structure. They are two in number, of large size, and placed one on each side of the sella /Lining membrane of sinus. Dura mater lining' pituitary fossa. 'Third nerve. 'Fourth nerve. Sixth nerve.'- Internal carotid. ■First division of fifth nerve. Fig. 384.-Plan showing the relative position of the structures in the right cavernous sinus, viewed from behind. turcica, extending from the sphenoidal fissure to the apex of the petrous portion of the temporal bone; they receive anteriorly the ophthalmic vein through the sphenoidal fissure, and open behind into the petrosal sinuses. On the inner wall of each sinus is found the internal carotid artery, accompanied by filaments of the carotid plexus and by the sixth nerve ; and on its outer wall, the third, fourth, and ophthalmic division of the fifth nerve. These parts are separated from the blood flowing along the sinus by the lining membrane, which is continuous with the inner coat of the veins. The cavity of the sinus, which is larger behind than in front, is intersected by filaments of fibrous tissue and small vessels. The cavernous sinuses receive some of the cerebral veins ; they communicate with the lateral sinuses by means of the superior and inferior petrosal, and with the facial vein through the ophthalmic. They also communicate with each other by means of the circular sinus. Surgical Anatomy.-An arterio-venous communication may be established between the cavernous sinus and the carotid artery, as it lies in it, giving rise to a pulsating tumor in the orbit. These communications may be the result of injury, such as a bullet wound, a stab, or a blow or fall sufficiently severe to cause a fracture of the base of the skull in this situation, or they may occur idiopathically from the rupture of an aneurism or a diseased condition of the internal carotid artery. The disease begins with sudden noise and pain in the head, followed by exophthalmos, and development of a pulsating tumor at the margin of the orbit, with thrill and the characteristic bruit. In some cases the opposite orbit becomes affected by the passage of the arterial blood into the opposite sinus by means of the circular sinus. Or the arterial blood may find its way through the emissary veins (see page 663) into the pterygoid plexus, and thence into the veins of the face. Pulsating tumors of the orbit may also be due to traumatic aneurism of one of the orbital arteries, and symptoms resembling those of pulsating tumor may be produced by pressure on the ophthalmic vein, as it enters the sinus, by an aneurism of the internal carotid artery. The ophthalmic is a large vein which connects the angular vein at the inner angle of the orbit with the cavernous sinus; it pursues the same course as the ophthalmic artery, and receives tributaries corresponding to the branches derived from that vessel. Forming a short single trunk, it passes through 662 THE VEINS. the inner extremity of the sphenoidal fissure and terminates in the cavernous sinus. The Inferior Ophthalmic Vein.-Sometimes the veins from the floor of the orbit collect into a separate trunk, the inferior ophthalmic vein, which either passes out of the orbit through the spheno-maxillary fissure to join the pterygoid plexus of veins, or else, passing backward through the sphenoidal fissure, it enters the cavernous sinus, either by a separate opening or in common with the ophthalmic vein. The Circular Sinus is formed by two transverse vessels which connect together the two cavernous sinuses, the one passing in front and the other behind the pituitary body, and thus forming with the cavernous sinuses a venous circle around the body. The anterior one is usually the larger of the two, and one or other is occasionally found to be absent. The Superior Petrosal Sinus is situated along the superior border of the petrous portion of the temporal bone, in the front part of the attached margin of the tentorium. It is small and narrow, and connects together the cavernous Opening of mastoid vein. Torcular Herophili. Fig. 385.-The sinuses at the base of the skull. and lateral sinuses at each side. It receives a cerebellar vein (anterior lateral cerebellar) from the anterior border of the cerebellum, and a vein from the internal ear. The Inferior Petrosal Sinus is situated in the groove formed by the junction of the posterior border of the petrous portion of the temporal with the basilar process of the occipital. It commences in front at the termination of the cavernous sinus, and behind joins the lateral sinus after it has passed through the jugular foramen, the junction of these two sinuses forming the commencement of the internal jugular vein. The junction of the two sinuses takes place at the lower border of, or just external to, the jugular foramen. The exact relation of the parts to one another in the foramen is as follows: The inferior petrosal sinus is in front, with the meningeal branch of the ascending pharyngeal artery, and is directed obliquely downward and backward; the lateral sinus is situated at the back part of the fora- THE SINUSES OF THE DURA MATER. 663 men with a meningeal branch of the occipital artery, and between the two are the glosso-pharvngeal, pneumogastric, and spinal accessory nerves. These three sets of structures are divided from each other by two processes of fibrous tissue. The junction of the sinuses takes place superficial to the nerves, so that these latter lie a little internal to the venous channels in the foramen (see Fig. 386). These sinuses are semicylindrical in form. The Transverse Sinus, or basilar sinus, consists of several interlacing veins between the layers of the dura mater over the basilar process of the occipital bone, which serve to connect the two inferior petrosal sinuses. With them the anterior spinal veins communicate. Emissary Veins.-The emissary veins are vessels which pass through apertures Styloid process. Fig. 386.-Relation of structures in jugular foramen. in the cranial wall and establish communications between the sinuses inside the skull and the veins external to it. Some of these are always present, others only occasionally so. They vary much in size in different individuals. The principal emissary veins are the following: 1. A vein, almost always present, which passes through the mastoid foramen and connects the lateral sinus with the posterior auricular or with an occipital vein. 2. A vein which passes through the parietal foramen and connects the superior longitudinal sinus with thff veins of the scalp. 3. A plexus of minute veins which pass through the anterior condyloid foramen and connect the occipital sinus with the vertebral vein and deep veins of the neck. 4. An inconstant vein which passes through the posterior condyloid foramen and connects the lateral sinus with the deep veins of the neck. 5. One or two veins of considerable size which pass through the foramen ovale and connect the cav- ernous sinus with the pterygoid and pharyngeal plexuses. 6. Two or three small veins which pass through the foramen lacerum medium and connect the cavernous sinus with the pterygoid and pharyngeal plexuses. 7. There is sometimes a small 664 THE VEINS vein passing through the foramen of Vesalius connecting the same parts. 8. A plexus of veins passing through the carotid canal and connecting the cav- ernous sinus with the internal jugular vein. Surgical Anatomy.-These emissary veins are of great importance in surgery. In addition to them there are. however, other com- munications between the intra- and extra-cra- nial circulation, as. for instance, the communi- cation of the angular and supra-orbital veins with the ophthalmic vein at the inner angle of the orbit (page 653), and the communication of the veins of the scalp with the diploic veins (page 658). Through these communications inflammatory processes commencing on the out- side of the skull may travel inward, leading to osteo-phlebitis of the diploe and inflammation of the membranes of the brain. To this must be attributed one of the principal dangers of seal]) wounds and other injuries of the scalp. By means of these emissary veins blood may be abstracted almost directly from the intracranial circulation. For instance, leeches applied behind the ear abstract blood almost directly from the lateral sinus through the vein passing through the mastoid foramen. Again, epistaxis in children will frequently relieve severe headache, the blood which flows from the nose being derived from the longitudinal sinus by means of the vein which passes through the foramen caecum, which is another communica- tion between the intracranial and extracranial circulation which is constantly found in children. VEINS OF THE UPPER EXTREMITY AND THORAX. The veins of the Upper Extremity are divided into two sets, superficial andtfee/?. The Superficial Veins are placed im- mediately beneath the integument be- tween the two layers of superficial fascia. The Deep Veins accompany the ar- teries. and constitute the venae comites of those vessels. Both sets of vessels are provided with valves, which are more numerous in the deep than in the superficial. The superficial veins of the upper extremity are-the Superficial veins of the Hand. Anterior Ulnar. Posterior Ulnar. Common Ulnar. Radial. Median. Median Basilic. Median Cephalic. Basilic. Cephalic. The Superficial Veins of the Hand and Fingers are principally situated on the Median cephalic. External/ cutaneous nerve. [ Internal cutaneous nerve. -Median i basilic. Fig. 387.-The superficial veins of the upper extremity. OF THE UPPER EXTREMITY AND THORAX. 665 dorsal surface, and form two plexuses, an inner and outer, on the back of the hand. The inner plexus is formed by the veins from the little finger {vena salva- telld), the ring finger, and the ulnar side of the middle finger ; from it the anterior and posterior ulnar veins are derived. The outer plexus is formed by veins from the thumb, the index finger, and radial side of the middle finger; from it the radial vein is derived. These two plexuses communicate on the back of the hand, forming the superficial arch of veins in this situation. The superficial veins from the palm of the hand form a plexus in front of the wrist, from which the median vein is derived. The Anterior Ulnar Vein commences on the anterior surface of the ulnar side of the hand and wrist, and ascends along the anterior surface of the ulnar side of the forearm to the bend of the elbow, where it joins with the posterior ulnar vein to form the common ulnar. Occasionally it opens separately into the median basilic vein. It communicates with branches of the median vein in front and with the posterior ulnar behind. The Posterior Ulnar Vein commences on the posterior surface of the ulnar side of the wrist. It runs on the posterior surface of the ulnar side of the forearm, and just below the elbow unites with the anterior ulnar vein to form the common ulnar, or else joins the median basilic to form the basilic. It communicates with the deep veins of the palm by a branch which emerges from beneath the Abductor minimi digiti muscle. The Common Ulnar is a short trunk which is not constant. When it exists it is formed by the junction of the two preceding veins, and, passing upward and outward, joins the median basilic to form the basilic vein. When it does not exist the anterior and posterior ulnar veins open separately into the median basilic vein. The Radial Vein commences from the dorsal surface of the wrist, communi- cating with the deep veins of the palm by a branch which passes through the first interosseous space. It forms a large vessel, which ascends along the radial side of the forearm and receives numerous veins from both its surfaces. At the bend of the elbow it unites with the median cephalic to form the cephalic vein. The Median Vein ascends on the front of the forearm, and communicates with the anterior ulnar and radial veins. At the bend of the elbow it receives a branch of communication from the deep veins, and divides into two branches, the median cephalic and median basilic, which diverge from each other as they ascend. The Median Cephalic, usually the smaller of the two, passes outward in the groove between the Supinator longus and Biceps muscles, and joins with the radial to form the cephalic vein. The branches of the external cutaneous nerve pass beneath this vessel. The Median Basilic Vein passes obliquely inward, in the groove between the Biceps and Pronator radii teres, and joins the common ulnar to form the basilic. This vein passes in front of the brachial artery, from which it is separated by a fibrous expansion (the bicipital fascia} which is given off from the tendon of the Biceps to the fascia covering tbe Flexor muscles of the forearm. Filaments of the internal cutaneous nerve pass in front as well as behind this vessel.1 Venesection is usually performed at the bend of the elbow, and as a matter of practice the largest vein in this situation is commonly selected. This is usually the median basilic, and there are anatomical advantages and disadvantages in selecting this vein. The advantages are, that in addition to its being the largest, and therefore yielding a greater supply of blood, it is the least movable and can be easily steadied on the bicipital fascia on which it rests. The disadvan- tages are, that it is in close relationship with the brachial artery, separated only by the bicipital fascia; and formerly, when venesection was frequently practised, arterio-venous aneurism was 1 Cruveilhier says: "Numerous varieties are observed.in the disposition of the veins of the elbow; sometimes the common median vein is wanting; but in those cases its two branches are fur- nished by the radial vein, and the cephalic is almost always in a rudimentary condition. In other cases only two veins are found at the bend of the elbow, the radial and ulnar, which are continuous, without any demarcation, with the cephalic and basilic." 666 THE VEINS. no uncommon result of this practice. Another disadvantage is, that the median basilic is crossed by some of the branches of the internal cutaneous nerve, and these may be divided in the operation, giving rise to ''traumatic neuralgia of extreme intensity " (Tillaux). The Basilic Vein is of considerable size, formed by the coalescence of the common ulnar vein with the median basilic. It passes upward along the inner side of the Biceps muscle, pierces the deep fascia a little below the middle of the arm, and, ascending in the course of the brachial artery, terminates by joining the venae comites of that vessel to form the axillary vein. The Cephalic Vein courses along the outer border of the Biceps muscle, lying in the same groove with the upper external cutaneous branch of the musculo-spiral nerve, to the upper third of the arm ; it then passes in the interval between the Pectoralis major and Deltoid muscles, lying in the same groove with the descending branch of the acromial-thoracic artery. It pierces the costo-coracoid membrane, and terminates in the axillary vein just below the clavicle. This vein is occa- sionally connected with the external jugular or subclavian by a branch which passes from it upward in front of the clavicle. The Deep Veins of the Upper Extremity follow the course of the arteries, forming their venae comites. They are generally two in number, one lying on each side of the corresponding artery, and they are connected at intervals by short transverse branches. There are two digital veins accompanying each artery along the sides of the fingers: these, uniting at their base, pass along the interosseous spaces in the palm, and terminate in the two venae comites which accompany the superficial palmar arch. Branches from these vessels on the radial side of the hand accom- pany the superficialis volae, and on the ulnar side terminate in the deep ulnar veins. The deep ulnar veins, as they pass in front of the wrist, communicate with the interosseous and superficial veins, and at the elbow unite with the deep radial veins to form the venae comites of the brachial artery. The Interosseous Veins accompany the anterior and posterior interosseous arteries. The anterior interosseous veins commence in front of the wrist, where they communicate with the deep radial and ulnar veins ; at the upper part of the forearm they receive the posterior interosseous veins, and terminate in the venae comites of the ulnar artery. The Deep Palmar Veins accompany the deep palmar arch, being formed by tributaries which accompany the ramifications of that vessel. They communicate with the deep ulnar veins at the inner side of the hand, and on the outer side terminate in the venae comites of the radial artery. At the wrist they receive a dorsal and a palmar tributary from the thumb, and unite with the deep radial veins. Accompanying the radial artery, these vessels terminate in the venae comites of the brachial artery. The Brachial Veins are placed one on each side of the brachial artery, receiving tributaries corresponding with the branches given off from that vessel; at the lower margin of the axilla they unite with the basilic to form the axillary vein. These deep veins have numerous anastomoses, not only with each other, but also with the superficial veins. The Axillary Vein is of large size, and formed by the junction of the venae comites of the brachial artery with the basilic vein. It commences at the lower part of the axillary space, increases in size as it ascends by receiving tributaries corresponding with the branches of the axillary artery, and terminates imme- diately beneath the clavicle at the lower border of the first rib, where it becomes the subclavian vein. This vessel is covered in front by the Pectoral muscles and costo-coracoid membrane, and lies on the thoracic side of the axillary artery, which it partially overlaps. Near its termination it receives the cephalic vein. This vein is provided with a pair of valves opposite the lower border of the Sub- scapularis muscle; valves are also found at the termination of the cephalic and subscapular veins. THE INNOMINATE VEINS. 667 Surgical Anatomy.-There are several points of surgical interest in connection with the axillary vein. Being more superficial, larger, and slightly overlapping the axillary artery, it is more liable to be wounded in the operation of extirpation of the axillary glands, especially as these glands, when diseased, are apt to become adherent to the vessel. When wounded there is always a danger of air being drawn into its interior, and death resulting. This is due not only to the fact that it is near the thorax, and therefore liable to be influenced by the respiratory movements, but also because it is adherent by its anterior surface to the costo-coracoid membrane, and therefore if wounded is likely to remain patulous and favor the chance of air being sucked in. This adhesion of the vein to the fascia prevents its collapsing, and therefore favors the furious bleeding which takes place in these cases. To avoid wounding the axillary vein in the extirpation of cancerous glands from the axilla, no sharp cutting instruments should be used after the axillary cavity has been freely exposed, and care should be taken to use no undue force in isolating the glands. Should the vein be so imbedded in the malignant deposit that the latter cannot be removed without taking away a part of the vein, this must be done, the vessel having been first ligatured above and below. The Subclavian Vein, the continuation of the axillary, extends from the lower border of the first rib to the inner end of the sterno-clavicular articulation, where it unites with the internal jugular to form the innominate vein. It is in relation, in front, with the clavicle and Subclavius muscle; behind, with the subclavian artery, from which it is separated internally by the Scalenus anticus muscle and phrenic nerve. Below, it rests in a depression on the first rib and upon the pleura. Above, it is covered by the cervical fascia and integument. The subclavian vein occasionally rises in the neck to a level with the third part of the subclavian artery, and in two instances has been seen passing with this vessel behind the Scalenus anticus. This*vessel is usually provided with valves about an inch from its termination in the innominate, just external to the entrance of the external jugular vein. Tributaries.-It receives the external and anterior jugular veins and a small branch from the cephalic, outside the Scalenus, and on the inner side of that muscle the internal jugular vein. At the angle of junction with the internal jugular the left subclavian vein receives the thoracic duct, while the right sub- clavian vein receives the right lymphatic duct. The Innominate or Brachio-cephalic Veins (Fig. 888) are two large trunks, placed one on each side of the root of the neck, and formed by the union of the internal jugular and subclavian veins of the corresponding side. The Right Innominate Vein is a short vessel, an inch in length, which com- mences at the inner end of the clavicle, and, passing almost vertically downward, joins with the left innominate vein just below the cartilage of the first rib, close to the right border of the sternum, to form the superior vena cava. It lies superficial and external to the innominate artery; on its right side the pleura is interposed between it and the apex of the lung. This vein, at the angle of junction of the internal jugular with the subclavian, receives the right vertebral vein, and, lower down, the right internal mammary, right inferior thyroid, and sometimes the right superior intercostal veins. The Left Innominate Vein, about two and a half inches in length, and larger than the right, passes from left to right across the upper and front part of the chest, at the same time inclining downward, to unite with its fellow of the opposite side, forming the superior vena cava. It is in relation, in front, with the first piece of the sternum, from which it is separated by the Sterno-hyoid and Sterno- thyroid muscles, the thymus gland or its remains, and some loose areolar tissue. Behind, it lies across the roots of the three large arteries arising from the arch of the aorta. This vessel is joined by the left vertebral, left internal mammary, left inferior thyroid, and the left superior intercostal veins, and occasionally some thymic and pericardiac veins. There are no valves in the innominate veins. Peculiarities.-Sometimes the innominate veins open separately into the right auricle ; in such cases the right vein takes the ordinary course of the superior vena cava ; but the left vein, after communicating by a small branch with the right one, passes in front of the root of the left lung, and. turning to the back of the heart, receives the cardiac veins and terminates in the back of the right auricle. This occasional condition of the veins in the adult is a regular one in the foetus at an early period, and the two vessels are persistent in birds and some mammalia. The 668 7777T VEINS. subsequent changes which take place in these vessels are the following: The communicating branch between the two trunks enlarges and forms the future left innominate vein; the re- maining part of the left trunk is obliterated as far as the heart, where it remains pervious and forms the coronary sinus: a remnant of the obliterated vessel is seen in adult life as a fibrous band passing along the back of the left auricle and in front of the root of the left lung, called by Mr. Marshall the vestigial fold of the pericardium. The internal mammary veins, two in number to each artery, follow the course of that vessel, and re- ceive branches correspond- ing with those derived from it. The two veins of each side unite into a single trunk, which terminates in the innominate vein. The inferior thyroid veins, two, frequently three or four, in number, arise in the venous plexus on the thyroid body, communicat- ing with the middle and superior thyroid veins. The left one descends in front of the trachea behind the Sterno-thyroid muscle, com- municating with its fellow by transverse branches, and terminates in the left in- nominate vein. The right one, which is placed a little to the right of the median line, opens into the right innominate vein just at its junction with the superior vena cava. These veins receive oesophageal, tra- cheal, and inferior laryn- geal veins, and are pro- vided with valves at their termination in the innom- inate veins. The Superior Intercos- tal Veins return the blood from the upper intercostal spaces. The rigid superior inter- costal, much smaller than the left, closely corresponds with the superior intercos- tal artery, receiving the blood from the first or first and second intercostal spaces, and, passing down- .Anterior jugular. x a , _ Superior thyroid. Middle thyroid. ■External jugular. Mediastinal. and \ pericardiac. < Suprarenal.- -Suprarenal. Fig. 388.-The venee cavee and azygos veins, with their formative branches. 77/VENA CA VA. 669 ward, terminates in the vena azygos major. Occasionally it opens into the right innominate vein. The left superior intercostal is always larger than the right, but varies in size in different subjects, being small when the left upper azygos vein is large, and vice versa. It is usually formed by branches from the two or three upper intercostal spaces, and, passing across the arch of the aorta, terminates in the left innominate vein. The left bronchial vein and the left superior phrenic open into it. The Superior Vena Cava receives the blood which is conveyed to the heart from the whole of the upper half of the body. It is a short trunk, varying from two inches and a half to three inches in length, formed by the junction of the two innominate veins. It commences immediately below the cartilage of the first rib close to the sternum on the right side, and, descending vertically, enters the peri- cardium about an inch and a half above the heart, and terminates in the upper part of the right auricle opposite the upper border of the third left costal cartilage. In its course it describes a slight curve, the convexity of which is turned to the right side. Relations.-In front, with the pericardium and process of cervical fascia which is continuous with it: this separates it from the thymus gland and from the ster- num; behind, with the root of the right lung; on its right side, with the phrenic nerve and right pleura ; on its left side, with the commencement of the innominate artery and ascending part of the aorta. The portion contained within the peri- cardium is covered by the serous layer of that membrane in its anterior three- fourths. It receives the vena azygos major just before it enters the pericardium, and several small veins from the pericardium and parts in the mediastinum. The superior vena cava has no valves. The Azygos Veins connect together the superior and inferior venae cavae, sup- plying the place of those vessels in the part of the chest which is occupied by the heart. The larger, or right azygos vein (vena azygos major), commences opposite the first or second lumbar vertebra by a branch from the right lumbar veins (the ascending lumbar); sometimes by a branch from the right renal vein or from the inferior vena cava. It enters the thorax through the aortic opening in the Dia- phragm, and passes along the right side of th • vertebral column to the fourth dorsal vertebra, where it arches forward over the root of the right lung, and terminates in the superior vena cava just before that vessel enters the pericardium. Whilst passing through the aortic opening of the Diaphragm it lies with the thoracic duct on the right side of the aorta, and'in the thorax it lies upon the intercostal arteries on the right side of the aorta and thoracic duct, and is partly covered by pleura. Tributaries.-It receives nine or ten lower intercostal veins of the right side, the vena azygos minor, several oesophageal, mediastinal, and pericardial veins; near its termination, the right bronchial vein; and generally the right superior intercostal vein. A few imperfect valves are found in this vein, but its tributaries are provided with complete valves. The intercostal veins on the left side, below the two or three upper intercostal spaces, usually form two trunks, named the left lower and the left upper azygos veins. The left lower, or smaller azygos vein (vena azygos minor), commences in the lumbar region by a branch from one of the lumbar veins (ascending lumbar) or from the left renal. It passes into the thorax through the left crus of the Dia- phragm, and, ascending on the left side of the spine as high as the seventh or eighth dorsal vertebra, passes across the column, behind the aorta and thoracic duct, to terminate in the right azygos vein. It receives the four or five lower inter- costal veins of the left side, and some oesophageal and mediastinal veins. The left upper azygos vein varies according to the size of the left superior intercostal. It receives veins from the intercostal spaces between the left superior intercostal vein and highest tributary of the left lower azygos. They are usually 670 THE VEINS. two or three in number, and join to form a trunk which ends in the right azygos vein or in the left lower azygos. It sometimes receives the left bronchial vein. When this vein is small or altogether wanting, the left superior intercostal vein will extend as low as the fifth or sixth intercostal space.1 Surgical Anatomy.-In obstruction of the superior vena cava the azygos veins are one of the principal means by which the venous circulation is carried on, connecting as they do the superior and inferior venae cavae. and communicating with the common iliac veins by the ascending lumbar veins, and with many of the tributaries of the inferior vena cava. The bronchial veins return the blood from the substance of the lungs; that of the right side opens into the vena azygos major near its termination ; that of the left side, into the left superior intercostal vein or left upper azygos vein. THE SPINAL VEINS. The numerous venous plexuses placed upon and within the spine may be arranged into four sets : 1. Those placed on the exterior of the spinal column (the dorsi-spinal veins). 2. Those situated in the interior of the spinal canal, between the vertebrae and the theca vertebralis (meningo-rachidian veins'). 3. The veins of the bodies of the vertebrae (pence basis vertebrarum). 4. The veins of the spinal cord (medulli-spinal). 1. The Dorsi-spinal Veins commence by small branches which receive their The dorsi-spinal veins. Fig 389.-Transverse section of a dorsal vertebra, showing the spinal veins blood from the integument of the back of the spine and from the muscles in the vertebral grooves. They form a complicated network, which surrounds the spinous processes, the laminae, and the transverse and articular processes of all the ver- tebrae. At the bases of the transverse processes they communicate, by means of ascending and descending branches, with the veins surrounding the contiguous vertebrae, and they join with the veins in the spinal canal by branches which perforate the ligamenta subflava. Other branches pass obliquely forward, between the transverse processes, and communicate with the intraspinal veins through the intervertebral foramina. They terminate by joining the vertebral 1 For an account of the arrangement of the azygos and superior intercostal veins in a number of consecutive cases from the same dissecting-room, see a paper by Mr. B. G. Morison (Journal of Anat- omy and Physiology, vol. xiii. p. 346). The most important difference between his description and that in the text is, that he always found two superior intercostal veins on both sides, the vein from the first space being separate, and joining the corresponding innominate vein. The lower (and larger) supe- rior intercostal vein he describes as opening into the azygos on the right and innominate on the left side. THE SPINAL VEINS. 671 veins in the neck, the intercostal veins in the thorax, and the lumbar and sacral veins in the loins and pelvis. 2. The Meningo-rachidian Veins.-The principal veins contained in the spinal canal are situated between the theca vertebralis and the vertebrae. They consist of two longitudinal plexuses, one of which runs along the posterior surface of the bodies of the vertebrae (anterior longitudinal spinal veins). The other plexus (posterior longitudinal spinal veins) is placed on the inner or anterior surface of the laminae of the vertebrae. The Anterior Longitudinal Spinal Veins consist of two large, tortuous veins which extend along the whole length of the vertebral column, from the foramen magnum, where they communicate by a venous ring around that opening, to the base of the coccyx, being placed one on each side of the posterior surface of the bodies of the vertebrae along the margin of the posterior common ligament. These veins communicate together opposite each vertebra by transverse trunks which pass beneath the ligament, and receive the large vence basis vertebrarum from the interior of the body of each vertebra. The anterior longitudinal spinal veins are least developed in the cervical and sacral regions. They are not of Dorsi-spinal. uniform size throughout, being alternately enlarged and constricted. At the intervertebral foramina they communicate with the dorsi-spinal veins, and with the vertebral veins in the neck, with the intercostal veins in the dorsal region, and with the lumbar and sacral veins in the corresponding regions. The Posterior Longitudinal Spinal Veins, smaller than the anterior, are situated one on each side, between the inner surface of the laminae and the theca vertebralis. They communicate (like the anterior) opposite each vertebra by transverse trunks, and with the anterior longitudinal veins by lateral transverse branches which pass from behind forward. These veins, by branches which per- forate the ligamenta subflava, join with the dorsi-spinal veins. From them branches are given off which pass through the intervertebral foramina and join the vertebral, intercostal, lumbar, and sacral veins. 3. The Veins of the Bodies of the Vertebrae (vena? basis vertebrarum) emerge from the foramina on their posterior surface, and join the transverse trunk con- necting the anterior longitudinal spinal veins. They are contained in large, tor- tuous channels in the substance of the bones, similar in every respect to those found in the diploe of the cranial bones. These canals lie parallel to the upper and lower surface of the bones. They commence by small openings on the front and sides of the bodies of the vertebrae, through which communicating branches from the veins external to the bone pass into its substance, and converge to the principal canal, which is sometimes double toward its posterior part, and open into the corresponding transverse branch uniting the anterior longitudinal veins. They become greatly developed in advanced age. 4. The Veins of the Spinal Cord (medulli-spinal) consist of a minute, tortuous, Fig. 390.-Vertical section of two dorsal vertebrae, showing the spinal veins 672 tw; VEINS venous plexus which covers the entire surface of the cord, being situated between the pia mater and arachnoid. These vessels emerge chiefly from the median furrows, and are largest in the lumbar region. Near the base of the skull they unite and form two or three small trunks, which communicate with the vertebral veins, and then terminate in the inferior cerebellar veins or in the inferior petro- sal sinuses. Each of the spinal nerves is accompanied by a branch as far as the intervertebral foramina, where they join the other veins from the spinal canal. There are no valves in the spinal veins. VEINS OF THE LOWER EXTREMITY, ABDOMEN, AND PELVIS. The Veins of the Lower Extremity are subdivided, like those of the upper, into two sets, superficial and deep, the superficial veins being placed beneath the integument, between the two layers of superficial fascia, the deep veins accom- panying the arteries and forming the venae comites of those vessels. Both sets of veins are provided with valves, which are more numerous in the deep than in the superficial set. These valves are also more numerous in the lower than in the upper limb. The Superficial Veins of the Lower Extremity are the internal or long saphen- ous and the external or short saphenous. On the dorsum of the foot is a venous arch situated in the superficial struc- tures over the anterior extremities of the metatarsal bones. It has its convexity directed forward, and receives digital tributaries from the upper surface of the toes; at its concavity it is joined by numerous small veins which form a plexus on the dorsum of the foot. The arch terminates internally in the long saphenous, externally in a short saphenous vein. The internal or long saphenous vein (Fig. 391) commences at the inner side of the arch on the dorsum of the foot; it ascends in front of the inner malleolus and along the inner side of the leg, behind the inner margin of the tibia, accom- panied by the internal saphenous nerve. At the knee it passes backward behind the inner condyle of the femur, ascends along the inside of the thigh, and, pass- ing through the saphenous opening in the fascia lata, terminates in the femoral vein about an inch and a half below Poupart's ligament. This vein receives in its course cutaneous tributaries from the leg and thigh, and at the saphenous opening the superficial epigastric, superficial circumflex iliac, and external pudic veins. The veins from the innei* and back part of the thigh frequently unite to form a large vessel, which enters the main trunk near the saphenous opening; and sometimes those on the outer side of the thigh join to form another large vessel; so that occasionally three large veins are seen converging from different parts of the thigh toward the saphenous opening. The internal saphenous vein communicates in the foot with the internal plantar vein ; in the leg, with the posterior tibial veins by branches which perforate the tibial origin of the Soleus muscle, and also with the anterior tibial veins; at the knee, with the articular veins ; in the thigh, with the femoral vein by one or more branches. The valves in this vein vary from two to six in number; they are more numerous in the thigh than in the leg. The external or short saphenous vein (Fig. 392) commences at the outer side of the arch on the dorsum of the foot; it ascends behind the outer malleolus, and along the outer border of the tendo Achillis, across which it passes at an acute angle to reach the middle line of the posterior aspect of the leg. Passing directly upward, it perforates the deep fascia in the lower part of the popliteal space, and terminates in the popliteal vein, between the heads of the Gastro- cnemius muscle.1 It receives numerous large tributaries from the back part of 1 Mr. Gay calls attention to the fact that the external saphenous vein often (he says invariably) penetrates the fascia at or about the point where the tendon of the Gastrocnemius commences, and runs below the fascia in the rest of its course, or sometimes among the muscular fibres, to join the popliteal vein. (See Gay on Varicose Disease of the Lower Extremities, p. 24, where there is also a careful and elaborate description of the branches of the saphena veins.) OF THE LOWER EXTREMITY. 673 the leg, and communicates with the deep veins on the dorsum of the foot and behind the outer malleolus. Before it perforates the deep fascia it gives oft a communicating branch, which passes upward and inward to join the internal saphenous vein. This vein has a variable number of valves, from three to nine (Gay), one of which is always found near its termination in the popliteal vein. The external saphenous nerve lies close beside this vein. Surgical Anatomy.-The saphena veins are of considerable surgical import- ance, since a varicose condition of these vessels is more frequently met with than those in other parts of the body, except perhaps the spermatic and haemorrhoidal veins. The course of the internal saphenous is in front of the tip of the malleolus, over the subcutaneous surface of the lower end of the tibia, and then along the internal border of this bone to the back part of the internal condyle of the femur, whence it follows the course of the Sartorius muscle, and is represented on the surface by a line drawn from the posterior border of the Sartorius on a level with the internal condyle to the saphenous opening. The short saphenous lies behind the external malleolus, and from this follows the middle line of the calf to just below the ham. It is not generally so apparent beneath the skin as the internal saphenous. Both these veins in the leg are accompanied by nerves, the internal saphenous being joined by its companion nerve just below the level of the knee-joint. No doubt much of the pain of varicose veins in the leg is due to this fact. On the Continent the internal saphenous vein as it rests on the tibia just above the malleolus is sometimes selected for venesection. The Deep Veins of the Lower Extremity accompany the arteries and their branches, and are called the vence comites of those vessels. The external and internal plantar veins unite to form the posterior tibial. They accompany the posterior tibial artery and are joined by the peroneal veins. The anterior tibial veins are formed by a con- tinuation upward of the venae comites of the dorsalis pedis artery. They pass between the tibia and fibula, through the large oval aperture above the interosse- ous membrane, and form, by their junction with the posterior tibial, the popliteal vein. The valves in the deep veins are very numerous. The Popliteal Vein'is formed by the junction of the venae comites of the anterior and posterior tibial ves- sels ; it ascends through the popliteal space to the tendinous aperture in the Adductor magnus, where it becomes the femoral vein. In the lower part of its course it is placed internal to the artery; between the Fig. 392-External or short saphenous vein. Fig. 391.-The internal or long saphenous vein and its branches. 674 77M7 VEINS heads of the Gastrocnemius it is superficial to that vessel; but above the knee- joint it is close to its outer side. It receives the sural veins from the Gastro- cnemius muscle, the articular veins, and the external saphenous. The valves in this vein are usually four in number. The Femoral Vein accompanies the femoral artery through the upper two- thirds of the thigh. In the lower part of its course it lies external to the artery; higher up it is behind it; and at Poupart's ligament it lies to its inner side and on the same plane. It receives numerous muscular tributaries: the profunda femoris and deep external pudic veins join it near Poupart's ligament and about an inch and a half below the internal saphenous vein. The valves in this vein are four or five in number. The External Iliac Vein commences at the termination of the femoral, beneath the crural arch, and, passing upward along the brim of the pelvis, terminates opposite the sacro-iliac synchondrosis by uniting with the internal iliac to form the common iliac vein. On the right side it lies at first along the inner side of the external iliac artery, but as it passes upward gradually inclines behind it. On the left side it lies altogether on the inner side of the artery. It receives, immediately above Poupart's ligament, the deep epigastric and deep circumflex iliac veins and a small pubic vein, corresponding to the pubic branch of the obturator artery. According to Friedreich, it frequently contains one, and some- times two valves. The Deep Epigastric Veins.-Two veins accompany the deep epigastric artery; they usually unite into a single trunk before their termination in the external iliac vein. The Deep Circumflex Iliac Veins.-Two veins accompany the deep circumflex iliac artery. These unite into a single trunk which crosses the external iliac artery just above Poupart's ligament and terminates in the external iliac vein. The Internal Iliac Vein is formed by the venae comites of the branches of the internal iliac artery, the umbilical arteries excepted. It receives the blood from the exterior of the pelvis by the gluteal, sciatic, internal pudic, and obturator veins, and from the organs in the cavity of the pelvis by the haemorrhoidal and vesico-prostatic plexuses in the male, and the uterine and vaginal plexuses in the female. The vessels forming these plexuses are remarkable for their large size, their frequent anastomoses, and the number of valves which they contain. The internal iliac vein lies at first on the inner side, and then behind the inter- nal iliac artery, and terminates opposite the sacro-iliac articulation by uniting with the external iliac to form the common iliac vein. This vessel has no valves. The internal pudic veins (yence comites') have the same course as the internal pudic artery. They receive tributaries corresponding to the branches of the artery, except the tributary corresponding to the dorsal artery of the penis; that is, the dorsal vein of the penis, which opens into the prostatic plexus. The haemorrhoidal plexus surrounds the lower end of the rectum, being formed by the superior haemorrhoidal veins (tributaries of the inferior mesenteric), and the middle and inferior haemorrhoidal, which terminate in the internal iliac. The portal and general venous, systems have a free communication by means of the branches composing this plexus. Surgical Anatomy.-The veins of this plexus are apt to become dilated and varicose and form piles. This is partly due to the free communication between the portal and systemic circu- lation which here exists, so that any obstruction to the flow of blood through either the inferior vena cava or its main tributaries, or through the portal vein, tends to produce passive congestion of this plexus. The condition is also partly due to the fact that the vessels are contained in very loose, lax connective tissue, so that they get less support from surrounding structures than most other veins, and are less capable of resisting increased blood-pressure. And, finally, the condition is favored by gravitation, inasmuch as the portal vein contains no valves. OF THE LOWER EXTREMITY. 675 The vesico-prostatic plexus surrounds the neck and base of the bladder and prostate gland. It communicates with the haemorrhoidal plexus behind, and receives the dorsal vein of the penis, which enters the pelvis beneath the subpubic ligament. This plexus is supported upon the sides of the bladder by a reflection of the pelvic fascia. The veins composing it are very liable to become varicose, and often contain hard, earthy concretions, called phleboliths. Surgical Anatomy.-This plexus is wounded in the lateral operation of lithotomy, and it is through it that septic matter finds its way into the general circulation after this operation. The dorsal vein of the penis is a vessel of large size which returns the blood from the body of that organ. At first it consists of two branches, which are contained in the groove on the dorsum of the penis, and it receives veins from the glans, the corpus spongiosum, and numerous superficial veins ; these unite near the root of the penis into a single trunk, which passes through the suspensory ligament of the penis, pierces the triangular ligament beneath the pubic arch, and divides into two branches, which enter the prostatic plexus. The vaginal plexus surrounds the mucous membrane, being especially developed at the orifice of the vagina; it communicates with the vesical plexus in front, and with the hmmorrhoidal plexus behind. The uterine plexus is situated along the sides and superior angles of the uterus, between the layers of the broad ligament, receiving large venous canals (the uterine sinuses) from the substance of the uterus. The veins composing this plexus anastomose frequently with each other and with the ovarian veins. They are not tortuous like the arteries. The Common Iliac Veins are formed by the union of the external and internal iliac veins in front of the sacro-iliac articulation: passing obliquely upward toward the right side, they terminate upon the intervertebral substance between the fourth and fifth lumbar vertebrae, where the veins of the two sides unite at an acute angle to form the inferior vena cava. The right common iliac is shorter than the left, nearly vertical in its direction, and ascends behind and then to the outer side of its corresponding artery. The left common iliac, longer and more oblique in its course, is at first situated on the inner side of the corresponding artery, and then behind the right common iliac. Each common iliac receives the ilio-lumbar, and sometimes the lateral sacral, veins. The left receives, in addition, the middle sacral vein. No valves are found in these veins. The middle sacral veins accompany the corresponding artery along the front of the sacrum, and terminate in the left common iliac vein ; occasionally in the angle of junction of the two iliac veins. Peculiarities.-The left common iliac vein, instead of joining with the right in its usual position, occasionally ascends on the left side of the aorta as high as the kidney, where, after receiving the left renal vein, it crosses over the aorta, and then joins with the right vein to form the vena cava. In these cases the two common iliacs are connected by a small communicating branch at the spot where they are usually united.1 The Inferior Vena Cava returns to the heart the blood from all the parts below the Diaphragm. It is formed by the junction of the two common iliac veins on the right side of the intervertebral substance between the fourth and fifth lumbar vertebrae. It passes upward along the front of the spine on the right side of the aorta, and, having reached the under surface of the liver, is contained in a groove in its posterior surface. It then perforates the central tendon of the Diaphragm, enters the pericardium, where it is covered by its serous layer, and terminates in the lower and back part of the right auricle. At its termination in the auricle it is provided with a valve, the Eustachian, which is of large size during foetal life. Relations.-In front, from below upward, with the mesentery, right spermatic artery, transverse portion of the duodenum, the pancreas, portal vein, and the 1 See two cases which have been described by Mr. Walsham in the St. BartholomeW s Hospital Reports, vols. xvi. and xvii. 676 THE VEINS. posterior surface of the liver, which partly and occasionally completely surrounds it; behind, with the vertebral column, the right crus of the Diaphragm, the right renal and lumbar arteries, right semilunar ganglion ; on the left side, with the aorta. Tributaries.-It receives in its course the following veins: Lumbar. Right Spermatic. Renal. Suprarenal. Phrenic. Hepatic. Peculiarities.-In Position.-This vessel is sometimes placed on the left side of the aorta, as high as the left renal veins, after receiving which it crosses over to its usual position on the right side ; or it may be placed altogether on the left side of the aorta, as far upward as its ter- mination in the heart: in such cases the abdominal and thoracic viscera, together with the great vessels, are all transposed. Point of Termination.-Occasionally the inferior vena cava joins the right azygos vein, which is then of large size. In such cases the superior cava receives the whole of the blood from the body before transmitting it to the right auricle, except the blood from the hepatic veins, which passes directly into the right auricle. The lumbar veins, four in number on each side, collect the blood by dorsal tributaries from the muscles and integument of the loins and by abdominal tribu- taries from the walls of the abdomen, where they communicate with the epigastric veins. At the spine they receive veins from the spinal plexuses, and then pass forward, round the sides of the bodies of the vertebrae beneath the Psoas magnus, and terminate at the back part of the inferior cava. The left lumbar veins are longer than the right, and pass behind the aorta. The lumbar veins are connected together by a longitudinal vein which passes in front of the transverse processes of the lumbar vertebrae, and is called the ascending lumbar. It forms the most frequent origin of the corresponding vena azygos, and serves to connect the common iliac, ilio-lumbar, lumbar, and azygos veins of the corresponding side of the body. The spermatic veins emerge from the back of the testis, and receive tributaries from the epididymis ; they unite and form a convoluted plexus called the spermatic plexus {plexus pampiniformis), which forms the chief mass of the cord : the vessels composing this plexus are very numerous, and ascend along the cord in front of the vas deferens ; below the external abdominal ring they unite to form three or four veins, which pass along the spermatic canal, and, entering the abdomen through the internal abdominal ring, coalesce to form two veins, which ascend on the Psoas muscle behind the peritoneum, lying one on each side of the spermatic artery, and unite to form a single vein, which opens on the right side into the inferior vena cava at an acute angle; on the left side into the left renal vein at a right angle. The spermatic veins are provided with valves.1 The left spermatic vein passes behind the sigmoid flexure of the colon, and is thus exposed to pressure from the contents of that bowel. Surgical Anatomy.-The spermatic veins are very frequently varicose, constituting the disease known as varicocele. Though it is quite possible that the originating cause of this affection may be a congenital abnormality either in the size or number of the veins of the pampiniform plexus, still it must be admitted that there are many anatomical reasons why these veins should become varicose-viz. the imperfect support afforded to them by the loose tissue of the scrotum ; their great length ; their vertical course ; their dependent position ; their plexiform arrangement in the scrotum, with their termination in one small vein in the abdomen ; their few and imperfect valves; and the fact that they maybe subjected to pressure in their passage through the abdominal wall. The ovarian veins are analogous to the spermatic in the male ; they form a plexus near the ovary and in the broad ligament and Fallopian tube, communi- cating with the uterine plexus. They terminate in the same way as the spermatic veins in the male. Valves are occasionally found in these veins. These vessels, like the uterine veins, become much enlarged during pregnancy. 1 Rivington has pointed out that a valve is usually found at the orifices of both the right and left spermatic veins. When no valves exist at the opening of the left spermatic vein into the left renal vein, valves are generally present in the left renal vein within a quarter of an inch from the orifice of the spermatic vein (Journal of Anatomy and Physiology, vol. vii. p. 163). THE PORTAL SYSTEM. 677 The renal veins are of large size, and placed in front of the renal arteries.1 The left is longer than the right, and passes in front of the aorta, just below the origin of the superior mesenteric artery. It receives the left spermatic, the left inferior phrenic, and, generally, the left suprarenal veins. It opens into the vena cava a little higher than the right. The suprarenal veins terminate, on the right side, in the vena cava ; on the left side, in the left renal or phrenic vein. The phrenic veins follow the course of the phrenic arteries. The two superior, of small size, accompany the phrenic nerve and comes nervi phrenici artery, and join the internal mammary. The two inferior phrenic veins follow the course of the phrenic arteries, and terminate, the right in the inferior vena cava, the left in the left renal vein. The hepatic veins commence in the substance of the liver, in the capillary terminations of the portal vein and hepatic artery: these tributaries, gradually uniting, usually form three large veins, which converge toward the posterior surface of the liver and open into the inferior vena cava, whilst that vessel is situated in the groove at the back part of this organ. Of these three veins, one from the right, and another from the left lobe, open obliquely into the inferior vena cava, that from the middle of the organ and lobulus Spigelii having a straight course. The hepatic veins run singly, and are in direct contact with the hepatic tissue. They are destitute of valves. The Portal System of Veins. The portal venous system is composed of four large veins which collect the venous blood from the viscera of digestion. The trunk formed by their union (vena portce) enters the liver and ramifies throughout its substance, and its branches, again emerging from that organ as the hepatic veins, terminate in the inferior vena cava. The branches in this vein are in all cases single and destitute of valves. The veins forming the portal system are-the Superior Mesenteric. Splenic. Inferior Mesenteric. Gastric. The superior mesenteric vein returns the blood from the small intestines and from the caecum and ascending and transverse portions of the colon, correspond- ing with the distribution of the branches of the superior mesenteric artery. The large trunk formed by the union of these branches ascends along the right side and in front of the corresponding artery, passes in front of the transverse por- tion of the duodenum, and unites, behind the upper border of the pancreas, with the splenic vein to form the vena portae. It receives the right gastro-epiploic vein. The splenic vein commences by five or six large branches which return the blood from the substance of the spleen. These, uniting, form a single vessel, which passes from left to right, grooving the upper and back part of the pancreas below the artery, and terminates at its greater end by uniting at a right angle with the superior mesenteric to form the vena portae. The splenic vein is of large size, and not tortuous like the artery. It receives the vasa brevia from the left extremity of the stomach, the left gastro-epiploic vein, pancreatic branches from the pancreas, the pancreatico-duodenal vein, and the inferior mesenteric vein. The inferior mesenteric vein returns the blood from the rectum, sigmoid flexure, and descending colon, corresponding with the ramifications of the branches of the inferior mesenteric artery. Ascending beneath the peritoneum in the lumbar region, it passes behind the transverse portion of the duodenum and pancreas and terminates in the splenic vein. Its htemorrhoidal branches inosculate with those 1 The student may observe that all veins above the Diaphragm, which do not lie on the same plane as the arteries which they accompany, lie in front of them, and that all veins below the Diaphragm, which do not lie on the same plane as the arteries which they accompany, lie behind them, except the renal and profunda femoris vein. 678 THE VEINS. of the internal iliac, and thus establish a communication between the portal and the general venous system.1 The gastric veins are two in number-: one, a small vein, corresponds to the pyloric branch of the hepatic artery ; the other, considerably larger, corresponds to the gastric artery. The former {pyloric, Walsham) runs along the lesser cur- Fig. 393.-Portal vein and its branches. Note.-In this diagram the right gastro-epiploic vein opens into the splenic vein ; generally it empties itself into the superior mesenteric, close to its termination. vature of the stomach toward the pyloric end, receives branches from the pylorus and duodenum, and ends in the vena portte. The latter [coronary, Walsham) begins near the pylorus, runs along the lesser curvature of the stomach toward the 1 Besides this anastomosis between the portal vein and the branches of the vena cava, other anastomoses between the portal and systemic veins are formed by the communication between the gastric veins and the oesophageal veins, which empty themselves into the vena azygos minor ; between the left renal vein and the veins of the intestines, especially of the colon and duodenum; between the veins of the round ligament of the liver and the portal veins ; and between the superficial branches of the portal veins of the liver and the phrenic veins, as pointed out by Mr. Kiernan. (See Physio- logical Anatomy, by Todd and Bowman, 1859, vol. ii. p. 348.) THE CARDIAC VEINS. 679 oesophageal opening, and then curves downward and backward between the folds of the lesser omentum, to end in the vena portae. The Portal Vein is formed by the junction of the superior mesenteric and splenic veins, their union taking place in front of the vena cava and behind the upper border of the great end of the pancreas. Passing upward through the right border of the lesser omentum to the under surface of the liver, it enters the trans- verse fissure, where it is somewhat enlarged, forming the sinus of the portal vein, and divides into two branches which accompany the ramifications of the hepatic artery and hepatic duct throughout the substance of the liver. Of these two branches, the right is the larger, but the shorter, of the two. The portal vein is about three or four inches in length, and, whilst contained in the lesser omentum, lies behind and between the hepatic duct and artery, the former being to the right, the latter to the left. These structures are accompanied by filaments of the hepatic plexus of nerves and numerous lymphatics, surrounded by a quantity of loose areolar tissue (capsule of Grlisson), and placed between the layers of the lesser omentum. The vena portse receives the gastric and cystic veins : the latter vein sometimes terminates in the right branch of the vena portse. Within the liver the portal vein receives the blood from the branches of the hepatic artery. THE CARDIAC VEINS. The veins which return the blood from the substance of the heart are-the Anterior Cardiac Vein. Posterior Cardiac Vein. Left Cardiac Veins. Right Cardiac Veins. Right or Small Coronary Sinus. Left or Great Coronary Sinus. Venae Thebesii. The Anterior Cardiac Vein (sometimes called Grreat. Cardiac Vein') is a vessel of considerable size which commences at the apex of the heart and ascends along the anterior interventricular groove to the base of the ventricles. It then curves to the left side, around the auriculo-ventricular groove, between the left auricle and ventricle, to the back part of the heart, and opens into the great coronary sinus, its aperture being guarded by two valves. It receives, in its course, tribu- taries from both ventricles, but especially the left, and also from the left auricle ; one of these, ascending along the thick margin of the left ventricle, is of consider- able size. The vessels joining it are provided with valves. The Posterior Cardiac Vein commences by small tributaries at the apex of the heart, communicating with those of the preceding. It ascends along the posterior interventricular groove to the base of the heart, and terminates in the great coro- nary sinus, its orifice being guarded by a valve. It receives the veins from the posterior surface of both ventricles. The Left Cardiac Veins are three or four small vessels which collect the blood from the posterior surface of the left ventricle, and open into the lower border of the great coronary sinus. The Right Cardiac Veins are three or four small vessels which collect the blood from the anterior surface of the right ventricle. One of these (the vein of G-alen), larger than the rest, runs along the right border of the heart. They open sepa- rately into the lower part of the right auricle. The Right or Small Coronary Sinus runs along the groove between the right auricle and ventricle, to open into the right extremity of the great coronary sinus. It receives blood from the back part of the right auricle and ventricle. The Left or Great Coronary Sinus is that portion of the anterior cardiac vein which is situated in the posterior part of the left auriculo-ventricular groove. It is about an inch in length, presents a considerable dilatation, and is covered by the muscular fibres of the left auricle. It receives the veins enumerated above, and an oblique vein from the back part of the left auricle, the remnant of the obliterated left innominate trunk of the foetus, described by Mr. Marshall. The 680 THE VEINS. great coronary sinus terminates in the right auricle between the inferior vena cava and the auriculo-ventricular aperture, its orifice being guarded by a semilunar fold of the lining membrane of the heart, the coronary valve. All the veins join- ing this vessel, excepting the oblique vein above mentioned, are provided with valves. The Vense Thebesii are numerous minute veins, which return the blood directly from the muscular substance, without entering the venous current. They open by minute orifices {foramina Thebesii) on the inner surface of the right auricle. THE LYMPHATICS. THE Lymphatics have derived their name from the appearance of the fluid con- tained in their interior (lympha, water). They are also called absorbents, from the property they possess of absorbing certain materials from the tissues and conveying them into the circulation. The lymphatic system includes not only the lymphatic vessels and the glands through which they pass, but also the lacteal or chyliferous vessels. The lacteals are the lymphatic vessels of the small intestine, and differ in no respect from the lymphatics generally, excepting that they contain a milk-white fluid, the chyle, during the process of digestion, and convey it into the blood through the thoracic duct. The lymphatics are exceedingly delicate vessels, the coats of which are so transparent that the fluid they contain is readily seen through them. They retain a nearly uniform size, being interrupted at intervals by constrictions, which give them a knotted or beaded appearance. These constrictions are due to the pres- ence of valves in their interior. Lymphatics have been found in nearly every texture and organ of the body which contain blood-vessels. Such non-vascular structures as cartilage, the nails, cuticle, and hair have none, but with these exceptions it is probable that eventually all parts will be found to be permeated by these vessels. The lymphatics are arranged into a superficial and deep set. The superficial lymphatics, on the surface of the body, are placed immediately beneath the integ- ument, accompanying the superficial veins; they join the deep lymphatics in cer- tain situations by perforating the deep fascia. In the interior of the body they lie in the submucous areolar tissue throughout the whole length of the gastro- pulmonary and genito-urinary tracts, and in the subserous tissue in the cranial, thoracic, and abdominal cavities. The method of their origin has been described along with the other details of their minute anatomy (page 86). Here it will be sufficient to say that a plexiform network of minute lymphatics may be found interspersed among the proper elements and blood-vessels of the several tissues, the vessels composing which, as w'ell as the meshes between them, are much larger than those of the capillary plexus. From these networks small vessels emerge, which pass either to a neighboring gland or to join some larger lymphatic trunk. The deep lymphatics, fewer in number and larger than the superficial, accompany the deep blood-vessels. Their mode of origin is probably similar to that of the superficial vessels. The lymphatics of any part or organ exceed the veins in number, but in size they are much smaller. Their anastomoses also, especially those of the large trunks, are more frequent, and are effected by vessels equal in diameter to those which they connect, the continuous trunks retaining the same diameter. The lymphatic or absorbent glands, named also conglobate glands, are small, solid, glandular bodies situated in the course of the lymphatic and lacteal ves- sels. In size they vary from a hemp-seed to an almond, and their color, on sec- tion, is of a pinkish-gray tint, excepting the bronchial glands, which in the adult are mottled with black. Each gland has a layer or capsule of cellular tissue investing it, from which prolongations dip into its substance, forming partitions. The lymphatic and lacteal vessels pass through these bodies in their passage to the thoracic and lymphatic ducts. A lymphatic or lacteal vessel, previous to 681 682 THE LYMPHATICS entering a gland, divides into several small branches, which are named afferent vessels. As they enter their external coat becomes continuous with the capsule of the gland, and the vessels, much thinned, and consisting only of their internal or endothelial coat, pass into the gland, and branch out upon and in the tissue of the capsule, these branches opening into the lymph-sinuses of the gland. From these sinuses fine branches proceed to form a plex- us, the vessels of which unite to form a single efferent vessel, which, on emerging from the gland, is again invested with an external coat. (Further details on the mi- nute anatomy of the lymphatic ves- sels and glands will be found in the chapter on General Anatomy.) THE THORACIC DUCT. The thoracic duct (Fig. 394) conveys the great mass of lymph and chyle into the blood. It is the common trunk of all the lymphatic vessels of the body, excepting those of the right side of the head, neck, and thorax, and right upper ex- tremity, the right lung, right side of the heart, and the convex sur- face of the liver. It varies in length from fifteen to eighteen inches in the adult, and extends from the second lumbar vertebra to the root of the neck. It com- mences in the abdomen by a trian- gular dilatation, the receptaculum chyli (reservoir or cistern of Pec- quet), which is situated upon the front of the body of the second lumbar vertebra, to the right side and behind the aorta, by the side of the right crus of the Diaphragm. It ascends into the thorax through the aortic opening in the Dia- phragm, lying to the right of the aorta, and is placed in the pos- terior mediastinum in front of the vertebral column, lying between the aorta and vena azygos major. Opposite the fourth dorsal ver- tebra it inclines toward the left side, and ascends behind the arch of the aorta on the left side of the oesophagus, and behind the first portion of the left subclavian artery, to the upper orifice of the thorax. Opposite the seventh cervical vertebra it turns outward and then curves downward over the subclavian artery and in front of the Scalenus anticus muscle, so as to form an arch, and terminates in the left Right lymphatic duct. - Intercostal 4 glands. Lumbar glands.' Fig. 394.-The thoracic and right lymphatic duct. OF THE HEAD, FACE, AND NECK. 683 subclavian vein at its angle of junction with the left internal jugular vein. The thoracic duct, at its commencement, is about equal in size to the diameter of a goosequill, diminishes considerably in its calibre in the middle of the thorax, and is again dilated just before its termination. It is generally flexuous in its course, and constricted at intervals so as to present a varicose appearance. The thoracic duct not unfrequently divides in the middle of its course into two branches of unequal size, which soon reunite, or into several branches, which form a plexiform interlacement. It occasionally divides, at its upper part, into two branches, of which the one on the left side terminates in the usual manner, while that on the right opens into the right subclavian vein, in connection with the right lymphatic duct. The thoracic duct has numerous valves throughout its whole course, but they are more numerous in the upper than in the lower part: at its termination it is provided with a pair of valves, the free borders of which are turned toward the vein, so as to prevent the passage of venous blood into the duct. Tributaries.-The thoracic duct, at its commencement, receives four or five large trunks from the abdominal lymphatic glands, and also the trunk of the lacteal vessels. Within the thorax it is joined by the lymphatic vessels from the left half of the wall of the thoracic cavity, the lymphatics from the sternal and intercostal glands, those of the left lung, left side of the heart, trachea, and oesophagus; and, just before its termination, it receives the lymphatics of the left side of the head and neck and left upper extremity. Structure (Fig. 61).-The thoracic duct is composed of three coats, which differ in some respects from those of the lymphatic vessels. The internal coat consists of a single layer of flattened lanceolate-shaped endothelial cells with serrated borders; of a subendothelial layer, similar to that found in the arteries; and an elastic fibrous coat, the fibres of which run in a longitudinal direction. The middle coat consists of a longitudinal layer of white connective tissue with elastic fibres, external to which are several laminae of muscular tissue, the fibres of which are for the most part disposed transversely, but some are oblique or longitudinal and intermixed with elastic fibres. The external coat is composed of areolar tissue, with elastic fibres and isolated fasciculi of muscular fibres. The Right Lymphatic Duct is a short trunk, about half an inch in length and a line or a line and a half in diameter. It terminates in the right subclavian vein at its angle of junction with the right internal jugular vein. Its orifice is guarded by two semilunar valves, which prevent the passage of venous blood into the duct. Tributaries.-It receives the lymph from the right side of the head and neck, the right upper extremity, the right side of the thorax, the right lung and right side of the heart, and from part of the convex surface of the liver. LYMPHATICS OF THE HEAD, FACE, AND NECK. The Lymphatic Glands of the Head (Fig. 395) are of small size, few in number, and confined to its posterior region. They are the occipital and posterior auricular. The occipital set are placed at the back of the head along the attach- ment of the Occipito-frontalis muscle. The posterior auricular set are placed near the upper end of the Sterno-mastoid muscle. Both these sets of glands are affected in cutaneous eruptions and other diseases of the scalp. In the face the superficial lymphatic glands are more numerous : they are the parotid, some of which are superficial, and others deeply placed in the substance of the parotid gland; the zygomatic, situated under the zygoma ; the buccal, on the surface of the Buccinator muscle ; and the internal maxillary, the largest, beneath the ramus of the lower jaw. The lymphatic vessels of the scalp are divided into an anterior and a posterior set, which follow the course of the temporal and occipital vessels. The temporal set accompany the temporal artery in front of the ear, to the parotid lymphatic glands, from which they proceed to the lymphatic glands of the neck. The occipital set follow the course of the occipital artery, descend to the occipital 684 THE L YMPHA TICS and posterior auricular lymphatic glands, and from thence join the cervical glands. The Lymphatic Vessels of the Face are divided into two sets, superficial and deep. The superficial lymphatic vessels of the face are more numerous than those of the head, and commence over its entire surface. Those from the frontal region accompany the frontal vessels ; they then pass obliquely across the face, running Fig. 395.-The superficial lymphatics and glands of the head, face, and neck. with the facial vein, pass through the buccal glands on the surface of the Bucci- nator muscle, and join the submaxillary lymphatic glands. The latter receive the lymphatic vessels from the lips, and are often found enlarged in cases of malignant disease of those parts. The deep lymphatic vessels of the face are derived from the pituitary membrane of the nose, the raucous membrane of the mouth and pharynx, and the contents of the temporal and orbital fossae ; they accompany the branches of the internal maxillary artery, and terminate in the internal maxillary and cervical lymphatic glands. The lymphatic vessels of the cranium consist of two sets, the meningeal and cerebral. The meningeal lymphatics accompany the meningeal vessels, escape through foramina at the base of the skull, and join the deep cervical lymphatic glands. The cerebral lymphatics are described by Eshmann as being situated between the arachnoid and pia mater, as well as in the choroid plexuses of the OF THE NECK. 685 lateral ventricles ; they accompany the trunks of the carotid and vertebral arteries, and probably pass through foramina at the base of the skull to terminate in the deep cervical glands. They have not at present been demonstrated in the dura mater or in the substance of the brain. The Lymphatic Glands of the Neck are divided into two sets, superficial and deep. The superficial cervical glands may be arranged in three sets: (1) The submaxillary, ten to fifteen in number, situated beneath the body of the lower Fig. 396-The deep lymphatics and glands of the neck and thorax. jaw in the submaxillary triangle ; (2) suprahyoid, situated in the middle line of the neck, between the anterior bellies of the two digastric muscles; and (3) cervical, placed in the course of the external jugular vein between the Platysma and deep fascia. They are most numerous at the root of the neck, in the triangular interval between the clavicle, the Sterno-mastoid, and the Trapezius, where they are continuous with the axillary glands. A few small glands are also found on the front and sides of the larynx. The deep cervical glands (Fig. 396) are numerous and of large size; they form a chain along the sheath of the carotid artery and internal jugular vein, lying by the side of the pharynx, oesophagus, and trachea, and extending from the base of the skull to the thorax, where they communicate with the lymphatic glands in that cavity. They are subdivided into two sets: an upper, ten to twenty in number, 686 THE LYMPHATICS situated about the bifurcation of the common carotid and along the upper part of the internal jugular vein ; and a lotver, ten to fifteen in number, clustered around the lower part of the internal jugular vein, and extending outward into the supra- clavicular fossa, where they are continuous with the axillary glands. Internally, this set is continuous with the mediastinal glands. The superficial and deep cervical lymphatic vessels are a continuation of those already described on the cranium and face. After traversing the glands in those regions, they pass through the chain of glands which lie along the sheath of the carotid vessels, being joined by the lymphatics from the pharynx, oesophagus, larynx, trachea, and thyroid gland. At the lower part of the neck, after receiving some lymphatics from the thorax, they unite into a single trunk, which terminates, on the left side, in the thoracic duct; on the right side, in the right lymphatic duct. Surgical Anatomy.-The cervical glands are very frequently the seat of tuberculous trouble. This condition is most usually set up by some lesion in those parts from which they receive their lymph. This excites some inflammation, which subsequently takes on a tuberculous character. It is very desirable, therefore, for the surgeon, in dealing with these cases, to possess a knowledge of the relation of the respective groups of glands to the periphery. The following table is extracted from Mr. Treves's work on Scrofula and its Gland Diseases: Scalp.-Posterior part = suboccipital and mastoid glands. Frontal and parietal portions = parotid glands. Lymphatic vessels from the scalp also enter the superficial cervical set of glands. Skin of face and neck = submaxillary, parotid, and superficial cervical glands. External ear = superficial cervical glands. Lower lip = submaxillary and suprahyoid glands. Buccal cavity = submaxillary and upper set of deep cervical glands. Gums of lower jaw = submaxillary glands. Tongue.-Anterior portion = suprahyoid and submaxillary glands. Posterior portion = upper set of deep cervical glands. Tonsils and palate = upper set of deep cervical glands. Pharynx.-Upper part = parotid and retro-pharyngeal glands. Lower part = upper set of deep cervical glands. Larynx, orbit, and roof of mouth = upper set of deep cervical glands. Nasal fossae = retro-pharyngeal glands, upper set of deep cervical glands. Some lymphatic vessels from posterior part of the fossae enter the parotid glands. LYMPHATICS OF THE UPPER EXTREMITY. The Lymphatic Glands of the Upper Extremity (Fig. 397) are divided into two sets, superficial and deep. The superficial lymphatic glands are few and of small size. There are occa- sionally two oi' three in front of the elbow, and one or two above the internal condyle of the humerus, near the basilic vein. The deep lymphatic glands are few in number, and are subdivided into those in the forearm, the arm, and the axilla. In the forearm a few small ones are occasionally found in the course of the radial and ulnar vessels. In the arm there is a chain of small glands along the inner side of the brachial artery. One, sometimes two, fairly constant glands are situated a little above and in front of the inner condyle of the humerus. In the axilla they are of large size, and usually ten or twelve in number. A chain of these glands surrounds the axillary vessels, imbedded in a quantity of loose areolar tissue; they receive the lymphatic vessels from the arm; others are dispersed in the areolar tissue of the axilla; the remainder are arranged in two series, a small chain running along the lower border of the Pectoralis major, receiving the lymphatics from the front of the chest and mamma ; and others are placed along the lower margin of the posterior wall of the axilla, which receive the lymphatics from the integument of the back. Two or three subclavian lymphatic glands are placed immediately beneath the clavicle; it is through these that the axillary and deep cervical glands communi- cate with each other. Surgical Anatomy.-Tn malignant diseases, tumors, or other affections implicating the upper part of the back and shoulder, the front of the chest and mamma, the upper part of the OF THE UPPER EXTREMITY. 687 front and side of the abdomen, or the hand, forearm, and arm, the axillary glands are liable to be found enlarged. The lymphatic vessels of the upper extremity are divided into two sets, super- ficial and deep. The superficial lymphatic vessels of the upper extremity commence on the fin- gers, two vessels running along either side of each finger, one on the palmar and the other on the dorsal surface. Those on the palmar surface form an arch in the Axillary glands Fig. 397.-The superficial lymphatics and glands of the upper extremity. palm of the hand, from which are derived two sets of vessels, which pass up the forearm, taking the course of the subcutaneous veins. The lymphatics from the dorsal surface of the fingers form a plexus on the back of the hand, and, winding around the inner and outer borders of the forearm, unite with those in front. Those from the inner border of the hand accompany the ulnar veins along the inner side of the forearm to the bend of the elbow, where they are joined by some lymphatics from the outer side of the forearm : they then follow the course of the basilic vein, communicate with the glands immediately above the elbow, and terminate in the axillary glands, joining with the deep lymphatics. The superficial lymphatics from 688 THE LYMPHATICS the outer and back part of the hand accompany the radial veins to the bend of the elbow. They are less numerous than the preceding. At the bend of the elbow the greater number join the basilic gfoup ; the rest ascend with the cephalic vein on the outer side of the arm, some crossing the upper part of the Biceps obliquely, to terminate in the axillary glands, whilst one or two accompany the cephalic vein in the cellular interval between the Pectoralis major and Deltoid, and entei' the subclavian lymphatic glands. The deep lymphatic vessels of the upper extremity accompany the deep blood- vessels. In the forearm they consist of four sets, corresponding with the radial, ulnar, and interosseous arteries ; they pass through the glands occasionally found in the course of those vessels, and communicate at intervals with the superficial lymphatics. In their course upward some of them pass through the glands which lie upon the brachial artery; they then enter the axillary and subclavian glands, and at the root of the neck terminate on the left side in the thoracic duct, and on the right side in the right lymphatic duct. The Lymphatic Glands of the Lower Extremity are divided into two sets, super- ficial and deep. The superficial are confined to the inguinal region, forming the superficial inguinal lymphatic glands. The superficial inguinal lymphatic glands, placed immediately beneath the integument, are of large size, and vary from eight to ten in number. They are divisible into two groups : an upper oblique set, disposed irregularly along Pou- part's ligament, which receive the lymphatic vessels from the integument of the scrotum, penis, parietes of the abdomen, perineal and gluteal regions, and the mucous membrane of the urethra ; and an inferior vertical set, which surround the saphenous opening in the fascia lata, a few being sometimes continued along the saphenous vein to a variable extent. This latter group receive the superficial lymphatic vessels from the lower, extremity. Surgical Anatomy.-These glands frequently become enlarged in diseases implicating the parts from which their lymphatics originate. Thus in malignant or syphilitic affections of the prepuce and penis, or of the labia majora in the female, in cancer scroti, in abscess in the peri- meuin, or in any other diseases affecting the integument and superficial structures in those parts, or the subumbilical part of the abdominal wall or the gluteal region, the upper chain of glands is almost invariably enlarged, the lower chain being implicated in diseases affecting the lower limb. The deep lymphatic glands are the anterior tibial, popliteal, deep inguinal, gluteal, and ischiatic. The anterior tibial gland is not constant in its existence. It is gener- ally found by the side of the anterior tibial artery, upon the interosseous mem- brane at the upper part of the leg. Occasionally, two glands are found in this situation. The popliteal glands, four or five in number, are of small size; they surround the popliteal vessels, imbedded in the cellular tissue and fat of the popliteal space. The deep inguinal glands are placed beneath the deep fascia around the femoral artery and vein. They are of small size, and communicate with the superficial inguinal glands through the saphenous opening. The gluteal and ischiatic glands are placed, the former above, the latter below, the Pyriformis muscle, resting on their corresponding vessels as they pass through the great sacro-sciatic foramen. The Lymphatic Vessels of the Lower Extremity, like the veins, may be divided into two sets, superficial and deep. The superficial lymphatic vessels are placed beneath the integument in the superficial fascia, and are divisible into two groups: an internal group, which follow the course of the internal saphenous vein ; and an external group, which accompany the external saphenous. The internal group, the larger, commence on the inner side and dorsum of the foot; they pass, some in front and some behind LYMPHATICS OF THE LOWER EXTREMITY. OF THE LOWER EXTREMITY. 689 the inner ankle, run up the leg with the internal saphenous vein, pass with it behind the inner condyle of the femur, and accompany it to the groin, where they terminate in the group of super- ficial inguinal lymphatic glands which surround the saphenous opening. Some of the efferent vessels from these glands pierce the cribriform fascia and sheath of the femoral vessels, and terminate in a lymphatic gland contained in the femoral canal, thus establishing a com- munication between the lymphatics of the lower extremity and those of the trunk ; others pierce the fascia lata and join the deep inguinal glands. The ex- ternal group arise from the outer side of the foot, ascend in front of the leg, and, just below the knee, cross the tibia from without inward, to join the lym- phatics on the inner side of the thigh. Others commence on the outer side of the foot, pass behind the outer malleolus, and accompany the external saphenous vein along the back of the leg, where they enter the popliteal glands. The deep lymphatic vessels of the lower extremity are few in number and accompany the deep blood-vessels. In the leg they consist of three sets, the anterior tibial, peroneal, and posterior tibial, which accompany the correspond- ing blood-vessels, two or three to each artery; they ascend with the blood- vessels and enter the lymphatic glands in the popliteal space; the efferent vessels from these glands accompany the femoral vein and join the deep inguinal glands; from these, the vessels pass beneath Poupart's ligament and com- municate with the chain of glands sur- rounding the external iliac vessels. The deep lymphatic vessels of the gluteal and ischiatic regions follow the course of the blood-vessels, and join the gluteal and ischiatic glands at the great sacro-sciatic foramen. LYMPHATICS OF THE PELVIS AND ABDOMEN. The Lymphatic Glands in the Pelvis are the external iliac, the internal iliac, and the sacral. Those of the abdomen are the lumbar glands. The external iliac glands form an unin- terrupted chain round the external iliac vessels, three being placed round the commencement of the vessels just behind the Superficial inguinal glands. Fig. 398.-The superficial lymphatics and glands of the lower extremity. 690 THU LYMPHATICS crural arch. They communicate below with the deep inguinal lymphatic glands, and above with the lumbar glands. The internal iliac glands surround the internal iliac vessels; they receive the lymphatic vessels corresponding to the branches of the internal iliac artery, and communicate with the lumbar glands. The sacral glands occupy the sides of the anterior surface of the sacrum, some Lumbar glands. Sacral glands. \ Internal 5;. iliac glands. External iliac Deep inguinal* glands. Deep lymphatics of penis. Fig. 399-The deep lymphatic vessels and glands of the abdomen and pelvis. being situated in the meso-rectal fold. These and the internal iliac glands are affected in malignant disease of the bladder, rectum, or uterus. The lumbar glands are very numerous; they are situated on the front of the lumbar vertebrae, surrounding the common iliac vessels, the aorta, and vena cava; they receive the lymphatic vessels from the lower extremities and pelvis, as well as from the testes and some of the abdominal viscera: the efferent vessels from these glands unite into a few large trunks, which, with the lacteals, form the commence- OF THE ABDOMEN AND PELVIS. 691 ment of the thoracic duct. In addition to these there are a few small lateral lum- bar glands which lie between the transverse processes of the vertebrae, behind the Psoas muscle, and receive lymphatics from the back. In some cases of malignant disease these glands become enormously enlarged, completely surrounding the aorta and vena cava, and occasionally greatly contracting the calibre of those vessels. In all cases of malignant disease of the testes and in malignant disease of the lower limb, before any operation is attempted, careful examination of the abdomen should be made, in order to ascertain if any enlargement exists; and if any should be detected, all operative measures should be avoided as fruitless. The Lymphatic Vessels of the Abdomen and Pelvis may be divided into two sets, superficial and deep. The superficial lymphatic vessels of the walls of the abdomen and pelvis follow the course of the superficial blood-vessels. Those derived from the integument of the lower part of the abdomen below the umbilicus follow the course of the superficial epigastric vessels and converge to the superior group of the superficial inguinal glands; a deeper set accompany the deep epigastric vessels, and commu- nicate with the external ibac glands. The superficial lymphatics from the sides of the lumbar part of the abdominal wall wind round the crest of the ilium, accompanying the superficial circumflex iliac vessels, to join the superior group of the superficial inguinal glands; the greater number, however, run back- ward along with the ilio-lumbar and lumbar vessels, to join the lateral lumbar glands. The superficial lymphatic vessels of the gluteal region turn horizontally round the outer side of the nates, and join the superficial inguinal glands. The superficial lymphatic vessels of the scrotum and perinaeum follow the course of the external pudic vessels, and terminate in the superficial inguinal glands. The superficial lymphatic vessels of the penis occupy the sides and dorsum of the organ, the latter receiving the lymphatics from the skin covering the glans penis ; they all converge to the upper chain of the superficial inguinal glans. The deep lymphatic vessels of the penis follow the course of the internal pudic vessels, and join the internal iliac glands. In the female the lymphatic vessels of the mucous membrane of the labia, nymphte, and clitoris terminate in the upper chain of the inguinal glands. The deep lymphatic vessels of the abdomen and pelvis take the course of the principal blood-vessels. Those of the parietes of the pelvis, which accompany the gluteal, ischiatic, and obturator vessels, follow the course of the internal iliac artery, and ultimately join the lumbar lymphatics. The efferent vessels from the inguinal glands enter the pelvis beneath Poupart's ligament, where they lie in close relation with the femoral vein ; they then pass through the chain of glands surrounding the external iliac vessels, and finally ter- minate in the lumbar glands. They receive the deep epigastric and circumflex iliac lymphatics. The lymphatic vessels of the bladder arise from the entire surface of the organ;1 the greater number run beneath the peritoneum on its posterior surface, and, after passing through the lymphatic glands in that situation, join with the lymphatics from the prostate and vesiculae seminales, and enter the internal iliac glands. The lymphatic vessels of the rectum are of large size; after passing through some small glands that lie upon its outer wall and in the meso-rectum they pass to the sacral glands. The lymphatic vessels of the uterus consist of two sets, superficial and deep, the former being placed beneath the peritoneum, the latter in the substance of the organ. The lymphatics of the cervix uteri, together with those from the vagina, enter the internal iliac and sacral glands; those from the body and fundus of the uterus pass outward in the broad ligaments, and, being joined by the lymphatics 1 Curnow states that they are confined to the base of the organ. 692 THE LYMPHATICS from the ovaries, broad ligaments, and Fallopian tubes, ascend with the ovarian vessels to open into the lumbar glands. In the unimpregnated uterus they are small, but during gestation they become very greatly enlarged. The lymphatic vessels of the testicle consist of two sets, superficial and deep: the former commence on the surface of the tunica vaginalis, the latter in the epididy- mis and body of the testis. They form several large trunks which ascend with the spermatic cord, and, accompanying the spermatic vessels into the abdomen, terminate into the lumbar glands; hence the enlargement of these glands in malignant disease of the testis. The lymphatic vessels of the kidney arise on the surface, and also in the inte- rior of the organ ; they join at the hilum, and, after receiving the lymphatic vessels from the ureter and suprarenal capsules, open into the lumbar glands. The lymphatic vessels of the liver are divisible into two sets, superficial and deep. The former arise in the subperitoneal areolar tissue over the entire surface of the organ. Those on the convex surface may be divided into four groups: 1. Those which pass from behind forward, consisting of three or four branches, which ascend in the longitudinal ligament and unite to form a single trunk, which passes up between the fibres of the Diaphragm, behind the ensiform cartilage, to enter the anterior mediastinal glands, and finally ascends to the root of the neck, to ter- minate in the right lymphatic duct. 2. Another group, which also incline from behind forward, are reflected over the anterior margin of the liver to its under surface, and from thence pass along the longitudinal fissure to the glands in the gastro-hepatic omentum. 3. A third group incline outward to the right lateral ligament, and, uniting into one or two large trunks, pierce the Diaphragm, and run along its upper surface to enter the anterior mediastinal glands, or, instead of entering the thorax, turn inward across the crus of the Diaphragm and open into the commencement of the thoracic duct. 4. The fourth group incline out- ward from the surface of the left lobe of the liver to the left lateral ligament, pierce the Diaphragm, and, passing forward, terminate in the glands in the ante- rior mediastinum. The superficial lymphatics on the under surface of the liver are divided into three sets : 1. Those on the right side of the gall-bladder enter the lumbar glands. 2. Those surrounding the gall-bladder form a remarkable plexus; they accom- pany the hepatic vessels, and open into the glands in the gastro-hepatic omentum. 3. Those on the left of the gall-bladder pass to the oesophageal glands and to the glands which are situated along the lesser curvature of the stomach. The deep lymphatics accompany the branches of the portal vein and the hepatic artery and duct through the substance of the liver; passing out at the transverse fissure, they enter the lymphatic glands along the lesser curvature of the stomach and behind the pancreas, or join with one of the lacteal vessels previous to its termination in the thoracic duct. The lymphatic glands of the stomach are of small size; they are placed along the lesser and greater curvatures, some within the gastro-splenic omentum, whilst others surround the cardiac and pyloric orifices. The lymphatic vessels of the stomach consist of two sets, superficial and deep, the former originating in the subserous, and the latter in the submucous, coat. They follow the course of the blood-vessels, and may consequently be arranged into three groups: The first group accompany the gastric vessels along the lesser curvature, receiving branches from both surfaces of the organ, and pass to the glands around the pylorus. The second group pass from the great end of the stomach, accompanying the vasa brevia, and enter the splenic lymphatic glands. The third group run along the greater curVature with the right gastro-epiploic vessels, and terminate at the root of the mesentery in one of the principal lacteal vessels. The lymphatic glands of the spleen occupy the hilum. Its lymphatic vessels consist of two sets, superficial and deep : the former are placed beneath its peritoneal covering, the latter in the substance of the organ ; they accompany the OF THE THORAX. 693 blood-vessels, passing through a series of small glands, and, after receiving the lymphatics from the pancreas, ultimately pass into the thoracic duct. THE LYMPHATIC SYSTEM OF THE INTESTINES. The lymphatic glands of the small intestine are placed between the layers of the mesentery, occupying the meshes formed by the superior mesenteric vessels, and hence called mesenteric glands. They vary in number from a hundred to a hundred and fifty, and in size from that of a pea to that of a small almond. These glands are most numerous, and largest above, near the duodenum, and below, opposite the termination of the ileum in the colon. This latter group becomes enlarged and infiltrated with deposit in cases of fever accompanied with ulceration of the intestines. The lymphatic glands of the large intestine are much less numerous than the mesenteric glands; they are situated along the vascular arches formed by the arteries previous to their distribution, and even sometimes upon the intestine itself. They are fewest in number along the transverse colon, where they form an uninterrupted chain with the mesenteric glands. The lymphatic vessels of the small intestine are called lacteals, from the milk- white fluid they usually contain: they consist of two sets, superficial and deep, the former lie between the layers of the muscular coat and between the muscular and peritoneal coats, taking a longitudinal course along the outer side of the intestine ; the latter occupy the submucous tissue, and course transversely round the intestine, accompanied by the branches of the mesenteric vessels; they pass between the layers of the mesentery, enter the mesenteric glands, and finally unite to form two or three large trunks which terminate in the thoracic duct. The lymphatic vessels of the large intestine consist of two sets: those of the caecum, ascending and transverse colon, which, after passing through their proper glands, enter the mesenteric glands ; and those of the descending colon, sigmoid flexure, and rectum, which pass to the lumbar glands. THE LYMPHATICS OF THE THORAX. The Lymphatic Glands of the Thoracic Wall are the intercostal, internal mam- mary, anterior mediastinal, and posterior mediastinal. The intercostal glands are small, irregular in number, and situated on each side of the spine, near the costo-vertebral articulations, some being placed between the two planes of intercostal muscles. The internal mammary glands are placed at the anterior extremity of each intercostal space, by the side of the internal mammary vessels. The anterior mediastinal glands are placed in the loose areolar tissue of the anterior mediastinum, some lying upon the Diaphragm in front of the pericardium, and others round the great vessels at the base of the heart. The posterior mediastinal glands are situated in the areolar tissue in the poste- rior mediastinum, forming a continuous chain by the side of the aorta and oesoph- agus ; they communicate on each side with the intercostal, below with the lumbar, and above with the deep cervical glands. The Superficial Lymphatic Vessels of the Front of the Thorax run across the great Pectoral muscle, and those on the back part of this cavity lie upon the Trapezius and Latissimus dorsi; they all converge to the axillary glands. The lymphatics from the greater part of the mammary gland pass outward to the lower border of the Pectoralis major muscle, where they enter a chain of small glands situated in the axillary space along the lower border of its anterior boundary. Some few lymphatics from the inner side of the mammary gland pass through the intercostal spaces to reach the anterior mediastinal glands. The Deep Lymphatic Vessels of the Thoracic Wall are the intercostal, internal mammary, and diaphragmatic. The intercostal lymphatic vessels follow the course of the intercostal vessels, 694 THE L YMPHA TICS. receiving lymphatics from the intercostal muscles and pleura ; they pass backward to the spine, and unite with lymphatics from the back part of the thorax and spinal canal. After traversing the intercostal glands, they pass down the spine and terminate in the thoracic duct. The internal mammary lymphatic vessels follow the course of the internal mammary vessels; they commence in the muscles of the abdomen above the umbilicus, communicating with the epigastric lymphatics, ascend between the fibres of the Diaphragm at its attachment to the ensiform appendix, and in their course behind the costal cartilages are joined by the intercostal lymphatics; they terminate on the right side in the right lymphatic duct, on the left side in the thoracic duct. The lymphatic vessels of the Diaphragm follow the course of their correspond- ing vessels, and terminate, some in front in the anterior mediastinal and internal mammary glands, some behind, in the intercostal and posterior mediastinal lymph- atics. The Lymphatic Glands of the Viscera are the bronchial glands. The bronchial glands are situated round the bifurcation of the trachea and roots of the lungs. They are ten or twelve in number, the largest being placed opposite the bifurcation of the trachea, the smallest round the bronchi and their primary divisions for some little distance within the substance of the lungs. In infancy they present the same appearance as lymphatic glands in other situations ; in the adult they assume a brownish tinge, and in old age a deep black color. Occasionally they become sufficiently enlarged to compress and narrow the canal of the bronchi, and they are often the seat of tubercle or cretaceous deposits. The lymphatic vessels of the lung consist of two sets, superficial and deep : the former are placed beneath the pleura, forming a minute plexus which covers the outer surface of the lung; the latter accompany the blood-vessels and run along the bronchi: they both terminate at the root of the lungs in the bronchial glands. The efferent vessels from these glands, two or three in number, ascend upon the trachea to the root of the neck, traverse the tracheal and oesophageal glands, and terminate on the left side in the thoracic duct and on the right side in the right lymphatic duct. The cardiac lymphatic vessels consist of two sets, superficial and deep : the former arise in the subserous areolar tissue of the surface, and the latter in the deeper tissues of the heart. They follow the course of the coronary vessels: those of the right side unite into a trunk at the root of the aorta, which, ascending across the arch of that vessel, passes backward to the trachea, upon which it ascends, to terminate at the root of the neck in the right lymphatic duct. Those of the left side unite into a single vessel at the base of the heart, which, passing along the pulmonary artery and traversing some glands at the root of the aorta, ascends on the trachea to terminate in the thoracic duct. The thymic lymphatic vessels arise from the under surface of the thymus gland, and terminate on each side in the internal jugular veins. The thyroid lymphatic vessels arise from either lateral lobe of this organ: they converge to form a short trunk, which terminates on the right side in the right lymphatic duct, on the left side in the thoracic duct. The lymphatic vessels of the oesophagus form a plexus round that tube, traverse the glands in the posterior mediastinum, and, after communicating with the pulmonary lymphatic vessels near the roots of the lungs, terminate in the thoracic duct. THE NERVOUS SYSTEM. mHE Nervous System is composed-1. Of a series of large centres of nerve-matter, 1 called, collectively, the cerebrospinal centre or axis. 2. Of smaller centres, termed ganglia. 3. Of nerves, connected either with the cerebro-spinal axis or the ganglia. And 4. Of certain modifications of the peripheral terminations of the nerves, forming the organs of the external senses. The Cerebro-spinal Centre consists of two parts, the spinal cord and the encephalon ; the latter may be subdivided into the cerebrum, the cerebellum, the pons Varolii, and the medulla oblongata. THE SPINAL CORD AND ITS MEMBRANES. Dissection.-To dissect the cord aud its membranes it will be necessary to lay open the whole length of the spinal canal. For this purpose the muscles must be separated from the vertebral grooves, so as to expose the spinous processes and laminae of the vertebrae; and the latter must be sawn through on each side, close to the roots of the transverse processes, from the third or fourth cervical vertebra above to the sacrum below. The vertebral arches having been displaced by means of a chisel and the separate fragments removed, the dura mater will be exposed, covered by a plexus of veins and a quantity of loose areolar tissue, often infiltrated with serous fluid. The arches of the upper vertebrae are best divided by means of a strong pair of cutting bone-forceps. The membranes which envelop the spinal cord are three in number. The most external is the cZura mater, a strong fibrous membrane which forms a loose sheath around the cord. The most internal is the pia mater, a cellulo-vascular membrane which closely invests the entire surface of the cord. Between the two is the arachnoid membrane, a non-vascular membrane which envelops the cord and is connected to the pia mater by slender filaments of connective tissue. The Dura Mater of the cord, continuous with that which invests the brain, is a loose sheath which surrounds the cord, and is separated from the bony walls of the spinal canal by a quantity of loose areolar tissue and a plexus of veins. It is attached to the circumference of the foramen magnum and to the posterior common ligament, especially at the lower end of the spinal canal, by fibrous slips, and extends below as far as the third piece of the sacrum; but beyond this point it is impervious, being continued in the form of a slender cord to the back of the coccyx, where it blends with the periosteum. This sheath is much larger than is necessary for its contents, and its size is greater in the cervical and lumbar regions than in the dorsal. Its inner surface is smooth. On each side may be seen the double openings which transmit the two roots of the corresponding spinal nerve, the fibrous layer of the dura mater being continued in the form of a tubular prolongation on them as they pass through these apertures. These prolongations of the dura mater are short in the upper part of the spine, but become gradually longer below, forming a number of tubes of fibrous membrane which enclose the sacral nerves and are contained in the spinal canal. The chief peculiarities of the dura mater of the cord, as compared with that investing the brain, are the following: © ■ © The dura mater of the cord is not adherent to the bones of the spinal canal, which have an independent periosteum. It does not send partitions into the fissures of the cord, as in the brain. MEMBRANES OF THE CORD. 695 696 THE NERVOUS SYSTEM. Its fibrous laminae do not separate to form venous sinuses, as in the brain. Structure.-The dura mater consists of white fibrous and elastic tissue arranged in bands or lamellae, which, for the most part, are par- allel with one another. Its internal surface is covered by a layer of endothelial cells which gives this surface its smooth appearance. It is sparingly supplied with vessels, and some few nerves have been traced into it. The Arachnoid is exposed by slitting up the dura mater and reflecting that membrane to either side (Fig. 400). It is a thin, delicate, tubular membrane which invests the surface of the cord, and is connected to the pia mater by slender filaments of connective tissue. Above, it is continuous with the cerebral arachnoid; on each side it is continued on the various nerves, so as to form a sheath for them as they pass outward to the intervertebral foramina. The outer surface of the arachnoid is in contact with the inner surface of the dura mater, and the two are, here and there, connected together by isolated connective-tissue trabeculae, especi- ally on the posterior surface of the cord. For the most part, however, the membranes are not connected together, and the interval between them is named the subdural space. The inner surface of the arachnoid is separated from the pia mater by a considerable interval, which is called the subarachnoidean space. The space is the largest at the lower part of the spinal canal, and encloses the mass of nerves which form the cauda equina. Superiorly it is continuous with the cranial subarachnoid space, and communicates with the general ventricular cavity of the brain by means of an opening in the pia mater at the inferior boundary of the fourth ventricle (for- amen of Majendie). It contains an abundant serous secretion, the cerebrospinal fluid. This secretion is sufficient in amount to expand the arachnoid membrane, so as to com- pletely fill up the whole of the space included in the dura mater. The subarachnoidean space is occupied by trabecuhe of delicate connective tissue, connecting the pia mater on the one hand with the arachnoid membrane on the other. This is named subarachnoid tissue. In addition to this it is partially subdivided by a longitudinal membranous partition, which serves to connect the arachnoid with the pia mater, opposite the posterior median fissure. This partition is in- complete and cribriform in structure, consisting of bundles of white fibrous tissue interlacing with each other. This space is to be regarded as, in reality, a great lymph-space, from which the lymph carried to it by the perivascular lymph- sheath (see page 87) is conveyed back into the circulation. Structure.-The arachnoid is a delicate membrane made up of closely arranged interlacing bundles of connective tissue in several layers. The Pia Mater of the cord is exposed on the removal of the arachnoid (Fig. 400). It covers the entire surface of the cord, to which it is very intimately adherent, forming its neurilemma, and sending a process downward into its anterior fissure. It also forms a sheath for each of the filaments of the spinal nerves, and invests the nerves themselves. A longitudinal fibrous band extends along the middle line on its anterior surface, called by Haller the linea splendens ; and a somewhat similar band, the ligamentum denticulatum, is situated on each side. At the point where the cord terminates the pia mater becomes contracted, and is con- It Dura j Mater. Fig. 400.-The spinal cord and its membranes. Dura Mater Lio. Denticu- LATUM Pia Mater Fig. 401.-Transverse section of the spinal cord and its membranes. THE SPINAL CORD. 697 tinned down as a long, slender filament (filum terminate), which descends through the centre of the mass of nerves forming the cauda equina, and is blended with the impervious sheath of dura mater on a level with the third sacral vertebra. It assists in maintaining the cord in its position during the movements of the trunk, and is from this circumstance called the central ligament of the spinal cord. It contains a little gray nervous substance, which may be traced for some dis- tance into its upper part, and is accompanied by a small artery and vein. At the upper part of the cord the pia mater presents a grayish, mottled tint, which is owing to yellow or brown pigment-cells scattered among the elastic fibres. Structure.-The pia mater of the cord is less vascular in structure, but thicker and denser, than the pia mater of the brain, with which it is continuous. It consists of two layers: an outer composed of bundles of connective-tissue fibres, arranged for the most part longitudinally; and an inner, consisting of stiff bundles of the same tissue, which present peculiar angular bends, and is covered on both surfaces by a layer of endothelium. Between the two layers are a number of cleftlike lymphatic spaces wrhich communicate with the subarachnoid cavity, and a number of blood-vessels which are enclosed in a perivascular sheath, derived from the inner layer of the pia mater, into which the lymphatic spaces open. It is also supplied with nerves, which are derived from the sympa- thetic. The Ligamentum Denticulatum (Fig. 400) is a narrow fibrous band, situated on each side of the spinal cord, throughout its entire length, and separating the anterior from the posterior roots of the spinal nerves. It has received its name from the serrated appearance which it presents. Its inner border is continuous with the pia mater at the side of the cord. Its outer border presents a series of triangular, dentated serrations, the points of which are fixed at intervals to the dura mater. These serrations are twenty-one in number on each side, the first being attached to the dura mater, opposite the margin of the foramen magnum between the vertebral artery and the hypoglossal nerve, and the last near the lower end of the cord. Its use is to support the cord in the fluid by which it is surrounded. THE SPINAL CORD. The Spinal Cord {medulla spinalis) is the cylindrical, elongated part of the cerebro-spinal axis which is contained in the vertebral canal. Its length is usually about seventeen or eighteen inches, and its weight, when divested of its membranes and nerves, about one ounce and a half, its proportion to the encepha- lon being about 1 to 33. It does not nearly fill the canal in which it is con- tained, its investing membranes being separated from the surrounding walls by areolar tissue and a plexus of veins. It occupies, in the adult, the upper two- thirds of the vertebral canal, extending from the upper border of the atlas to the lower border of the body of the first lumbar vertebra, where it terminates in a slender filament of gray substance, which is continued for some distance into the filum terminale. In the foetus, before the third month, it extends to the bottom of the sacral canal, but after this period it gradually recedes from below', as the growth of the bones composing the canal is more rapid in proportion than that of the cord, so that in the child at birth the cord extends as far as the third lumbar vertebra. Its position varies also according to the degree of curvature of the spinal column, being raised somewhat in flexion of the spine. On examin- ing its surface it presents a difference in its diameter in different parts, being marked by two enlargements, an upper or cervical, and a lower or lumbar. The cervical enlargement, which is the larger, extends from about the third cervical to the first or second dorsal vertebra: its greatest diameter is in the transverse direction, and it corresponds with the origin of the nerves which supply the upper extremities. The lower, or lumbar, enlargement is situated opposite the last two or three dorsal vertebrae, its greatest diameter being from before back- 698 THE NERVOUS SYSTEM. ward. It corresponds with the origin of the nerves which supply the lower extremities. In form the spinal cord is a flattened cylinder. Fissures.-It presents on its anterior surface, along the middle line, a longi- tudinal fissure, the anterior median fissure, and on its posterior surface another fissure, which also extends along the entire length of the cord, the posterior median fissure. These fissures penetrate through the greater part of the thickness of the cord, and incompletely divide the cord into two symmetrical halves, united in the middle line by a transverse band of nervous substance, the commissure. The Anterior Median Fissure is wider, but of less depth, than the posterior, extending into the cord for about one-third of its thickness, and is deepest at the lower part of the cord. It contains a prolongation from the pia mater, and its floor is formed by the anterior white commissure, which is perforated by numerous blood-vessels passing to the centre of the cord. The Posterior Median Fissure is not an actual fis- sure, as the space between the lateral halves of the posterior part of the cord is crossed by connective tissue and numerous blood-vessels, so that no actual hiatus exists, and there is consequently no prolonga- tion of the pia mater into it. It extends into the cord to about one half its depth, and its floor is formed by the posterior gray commissure. Lateral Fissures-On each side of the anterior median fissure a linear series of foramina may be observed, indicating the points where the anterior roots of the spinal nerves emerge from the cord. This is called, by some anatomists, the antero-lateral fissure of the cord, although no actual fissure exists in this situation. And on each side of the posterior median fissure, along the line of attachment of the posterior roots of the nerves, a delicate fissure may be seen, leading down to the gray matter which approaches the surface in this situation ; this is called the postero-lateral fissure of the spinal cord. On the posterior surface of the spinal cord, between the posterior median fissure and the postero-lateral fissure on each side, is a slight longitudinal furrow marking off two slender tracts, the posterior median columns. These are most distinct in the cervical region, but are stated by Foville to exist throughout the whole length of the cord. Columns of the Cord.-Each half of the spinal cord is thus divided into four columns : an anterior column, a lateral column, a posterior column, and a poste- rior median column. The anterior column includes all the portion of the cord between the anterior median fissure and the line from which the anterior roots of the nerves arise. It is continuous with the pyramid of the medulla oblongata. The lateral column, the largest segment of the cord, includes all the portion between the line of origin of the anterior roots of the spinal nerves and the pos- tero-lateral fissure. By some anatomists the anterior and lateral columns are included together under the name of the antero-lateral column, which forms rather more than two-thirds of the entire circumference of the cord. The posterior column is situated between the posterior median and postero- lateral fissures. The posterior median column is that narrow segment of the cord which is seen on each side of the posterior median fissure, usually included with the preceding as the posterior column. Structure of the Cord.-If a transverse section of the spinal cord be made, it will be seen to consist of white and gray nervous substance. The white matter is situated externally, and constitutes the greater part. The gray substance occupies the centre, and is so arranged as to present on the surface of the section two crescentic masses, placed one in each lateral half of the cord, united together by a Anterior Median Fissure. Anterior Lateral Fissure. Posterior ■Median Fissure. I J Posterior Lateral Fissure. 1 Post. Fig. 402.-Spinal cord. Side view. Plan of the Assures and columns. THE SPINAL CORD. 699 transverse band of gray matter, the gray commissure. Each crescentic mass has an anterior and posterior horn. The posterior horn is long and narrow, and approaches the surface of the postero-lateral fissure, near which it presents a slight enlargement, the caput cornu : from this it tapers to form the apex cornu, which at the surface of the cord becomes continuous with the fibres of the posterior roots of the spinal nerves. The anterior horn is short and thick, and does not quite reach the surface, but extends toward the point of attachment of the anterior roots of the nerves. Its margin presents a dentate or stellate appearance. Owing to the pro- jections toward the surface of the anterior and posterior horns of the gray matter, each half of the cord is divided, more or less completely, into three columns, anterior, middle, and posterior, the anterior and middle being joined to form the antero-lateral column, as the anterior horn does not quite reach the surface. Opposite middle of cervical region. Fig. 404.-From a transverse section through the spinal cord of a calf. Magnified about 180 diameters, showing part of the central canal and the tissue immediately around it-viz. the cen- tral gray nucleus. (Klein and Noble Smithd The canal is lined with epithelium, composed of ciliated, more or less conical, cells ; in most in- stances a filamentous processjpasses from the cell into the tissue underneath. This tissue contains, in a hyaline matrix, a network of fibrils : most of these run horizontally, others have a longitu- dinal course, and appear therefore here cut trans- versely-?. e. as small dots. The nuclei corre- spond to the cells of the neuroglia, the cell-sub- stance not being shown. Both the nuclei of the neuroglia-cells and those of the epithelium con- tain three or more large disk-shaped particles. Opposite middle of dorsal region. Opposite lumbar region. Fig. 403.-Transverse sections of the cord. The commissure of the spinal cord is composed of white and gray fibres, hence called the white and gray commissures. The white commissure is formed of fibres, which pass horizontally between the gray matter of the anterior horn of one side and the anterior white column of the opposite side. The gray commissure, which connects the two crescentic masses of gray matter, is separated from the bottom of the anterior median fissure by the anterior white commissure. It consists of transverse fibres, with a considerable quantity of neuroglia between them. The fibres when they reach the lateral crescents diverge : some pass backward to the posterior roots ; others spread out, at various angles, into the cervix cornu. Running through the gray commissure of the whole length of the cord is a minute canal, which is barely visible to tlie naked eye in the human cord, but is proportionally larger in some of the lower vertebrata. It is called the central canal, and opens above into the fourth ventricle, and terminates below in a some- what dilated extremity. It is lined in the foetus by columnar ciliated epithelium, but in the adult the cilia have disappeared, and the canal is filled with their remains. The cells are supported on a layer of neuroglia, which is sometimes called the substantia gelatinosa centralis. The mode of arrangement of the gray matter, and its amount in proportion to the white, vary in different parts of the cord. Thus, the posterior horns are long and narrow in the cervical region; short and narrower in the dorsal; short, but wider, in the lumbar region. In the cervical region the crescentic portions are small, and the white matter more abundant than in any other region of the cord. In the dorsal region the gray matter is least developed, the white matter being also small in quantity. In the lumbar region the gray matter is more abundant than in any other region of the cord. Toward the lower end of the cord the white matter gradually ceases. The crescentic portions of the gray matter soon blend into a single mass, which forms the only constituent of the extreme point of the cord. 700 THE NERVOUS SYSTEM. Minute Anatomy of the Cord.-The cord consists of an outer part, composed of medullated nerve-fibres, -which is the white substance ; and of a central part, the gray matter, both supported in a peculiar kind of connective tissue, called neuroglia. The neuroglia consists of a homogeneous transparent matrix, of a network of very delicate fibrillae, and of small stellate or branched cells, the neuroglia-cells. In addition to forming a ground substance, in which the nerve-fibres, nerve- White matter. Septa of connectives' tissue. I canal. Gray matter. Divided nerve- fibres. Fig. 405.-Transverse section through the cervical portion of the spinal cord of the calf. Magnified 40 diameters. (Klein and Noble Smith.) cells, and blood-vessels are imbedded, a considerable accumulation of neuroglia takes place in three situations-(1) on the surface of the cord, beneath the pia mater; (2) around the central canal; and (3) in the posterior part of the posterior horn, forming the substantia cinerea gelatinosa. The white substance of the cord consists of medullated nerve-fibres, with blood-vessels and neuroglia. On transverse section of the white substance of the cord a very striking object is presented. It is seen to be studded all over with minute dots, surrounded by a white area, and this again by a dark circle (Fig. 409). This is due to the longitudinal medullated fibres seen on section. The dot is the axis-cylinder, the white area the substance of Schwann, and the dark circle the tubular membrane of the fibres, which seems to consist of several laminae. Externally, the neuroglia is seen to form a delicate connective sheath round the outer surface of the cord immediately beneath the pia mater, from which numerous THE SPINAL CORD. 701 septa pass in to separate the respective bundles of fibres and extend between the individual nerve-fibres, acting as a supporting medium in which they are imbedded. Thus it will be seen that the greater bulk of the white matter of the cord is made up of longitudinal medullated fibres, which are arranged in groups forming the anterior, lateral, and posterior columns. There are, however, also oblique and transverse fibres in the white substance. These are principally found (1) at the bottom of the anterior median fissure, forming the white commissure, the fibres passing from the gray matter of the anterior horn on one side to the white matter of the anterior column of the opposite side; (2) horizontal or oblique fibres passing from the roots of the nerves into the gray matter; and (3) fibres leaving the gray matter, and pursuing a longer or shorter Postr. Medn. Fissure. Cervix Cornu i JPoxtx. Tractus.- Intermedia- lateralis. Fig. 407.-Transverse section of the gray substance of the spinal cord, near the middle of the dorsal region. Mag- nified 13 diameters. Antr. Medn. Fissure. Fig. 406-Columns of the cord. horizontal course between the bundles of longitudinal fibres, with which many of them are continuous. The investigation of pathological lesions has shown that the white matter of the cord consists of certain columns or tracts of fibres, for it has been found that separate lesions are strictly limited to certain well-determined parts of the organ without involving neighboring regions. That these parts or fasciculi correspond to so many distinct anatomical systems, each endowed with special functions, seems abundantly proved by the researches of Flechsig and others on the develop- ment of the cord during the later periods of utero-gestation and in the newly-born infant. Thus, on either side of the anterior median fissure a portion of the anterior column is divided off as the Direct pyramidal fasciculus (fasciculus of Tiirck), which can be traced to be continuous with the non-decussating fibres of the pyramid of the medulla. The remainder of the anterior column of the cord forms the fundamental fasciculus, which is continued into the deeper part of the medulla. The lateral column of the cord is divided into four tracts, the anterior division of which is called the anterior radicular zone, the peripheral portion of the posterior part the cerebellar column, and the internal part, next the gray substance, is termed the mixed lateral column ; whilst an intermediate portion, between these last two, is the crossed pyramidal fasciculus, its fibres when traced upward forming the decussating portion of the pyramid of the medulla oblongata. The other three portions of the lateral column can be traced into the lateral tract of the medulla, the peripheral fibres, or those forming the cerebellar column, passing through it to the cerebellum. The posterior column of the cord is divided into two: the portion which lies next the posterior median fissure is called the column of Groll (posterior median), 702 THE NERVOUS SYSTEM. and if traced upward is- found to be continuous with the fasciculus gracilis of the medulla. The remainder of the posterior column is called the cuneate fasciculus, or Burdach's column (posterior external), and is prolonged into the medulla under the same name. The gray substance of the cord occupies its central part in the shape of two crescentic horns, joined together by a commissure. Each of these crescents has an anterior and posterior cornu. The posterior horn consists of two parts-the caput cornu, or expanded extremity of the horn (Fig. 408), round which is a lighter space or lamina of Gelatinous. tfliPorfr. 'M Wafer, jtota Cervix Cornus Posts. ' Anterior Anterior Roots. dlan Fissure. Fig. 408.-Transverse section of the gray substance of the spinal cord through the middle of the lumbar enlargement. On the left side of the figure groups of large cells are seen ; on the right side, the course of the fibres is shown without the cells. Magnified 13 diameters. gelatinous substance; and the cervix cornu, or narrower portion, which connects it with the rest of the gray substance. The gelatinous substance is a peculiar accumulation of neuroglia (Klein), and has been named by Rolando the substantia cinerea gelatinosa. The anterior horn of the gray substance in the cervical and lumbar swellings, where it gives origin to the nerves of the extremities, is much larger than in any other region, and contains several distinct groups of large and variously shaped cells. In addition to this, in certain parts of the cord other horns or projections of the gray matter may be seen on transverse section. One of these, the lateral horn, is found projecting outward from the lateral region of the gray matter on a level with the gray commissure in the cervical and upper part of the dorsal region of the cord; and a second, Clarke's vesicular column, is found on the inner side of the posterior horn near the gray commissure, in the upper cervical or dorsal regions or at the point of exit of the lower lumbar nerves. The gray commissure is situated behind the white commissure, which sep- arates it from the bottom of the anterior median fissure. The gray substance of the cord consists of-(1) nerve-fibres of variable but smaller average diameter than those of the columns; (2) nerve-cells of various shapes and sizes, with from two to eight processes; (3) blood-vessels and connec- tive tissue. 777A' SPINAL CORD. 703 The nerve-fibres of the gray matter of the posterior horn are for the most part composed of a minute and dense network of minute fibrils, which is termed "Gerlach's nerve-network," intermingled with nerves of a larger size. This net- work is continuous with the medullated fibres of the posterior nerve-roots on the one hand (Dieters), and with the branched processes of the ganglion-cells on the other (Gerlach), so that the ganglion-cells are connected with the medullated fibres of the posterior nerve-roots only indirectly through the nerve-network. The arrangement of the fibres in the anterior horn of the gray matter appears to be somewhat different; here the medullated fibres of the anterior nerve-roots are directly continuous with some of the processes of the ganglion-cells, others of the processes of the ganglion-cells communicating with Ger- lach's nerve-network. Posterior Poots. Posterior Column. Gelatinous. Substance. Gray . Substance. Fig. 410.-Transverse section through the white matter of the spinal cord of a calf. Magnified about 300 diameters. (Klein and Noble Smith.) In the upper part are shown two isolated flattened nucleated cells of the neuroglia, under a somewhat higher power than the rest. In the bulk of the figure the nerve-fibres are seen in transverse section. They are of different sizes, and possess a laminated medullary sheath surrounding the axis-cylinder, which was deeply stained in the preparation, and is' here represented by a black dot. The nerve-fibres are imbedded in the neuroglia. This contains, in a matrix which appears sometimes granular, sometimes homogeneous, numerous elastic fibrils, seen here in transverse section as minute dots, on account of their having a course parallel to the long axis of the cord. Amongst the neuroglia are also seen two branched connec- tive-tissue cells-neuroglia-cells. Anterior Column. Anterior Roots. Fig. 409.-Longitudinal section of the white and gray substance of the spinal cord, through the middle of the lumbar enlarge- ment. Magnified 14 diameters. The nerve-cells of the gray matter are of two kinds, large branched nerve-vesicles which are collected into groups, and small round cells which resemble free nuclei and are found scattered throughout the whole of the gray matter. In the anterior horn is a constant group, situated at the anterior part of the cornu, and sometimes termed the vesicular column of the anterior cornu. It con- sists of two groups of cells: one mesial, near the anterioi* column; the other lateral, near the lateral column. At the base of the posterioi' horn on its inner side, and joining the gray commissure, is a group of nerve-cells, which give rise to the projection mentioned above as being seen on transverse section in the upper part of the cord, which is called Clarke's posterior vesicular column. At the junction of the anterior and posterior cornu, in the outer portion of the gray matter, is a third group of cells, the tractus intermedio-lateralis. In cer- tain regions of the cord these cells extend in amongst the fibres of the white matter of the lateral column, and give rise to the lateral horn. In addition to these groups a few large scattered cells are found in the posterior horn, extending into the substantia cinerea gelatinosa. 704 THE NERVOUS SYSTEM. THE BRAIN AND ITS MEMBRANES. Dissection.-To examine the brain with its membranes the skull-cap must be removed. In order to effect this, saw through the external table, the section commencing, in front, about an inch above the margin of the orbit, and extending, behind, to a level with the occipital protu- berance. Then break the internal table with the chisel and hammer, to avoid injuring the invest- ing membranes or brain ; loosen and forcibly detach the skull-cap, when the dura mater will be exposed. The adhesion between the bone and the dura mater is very intimate, and much more so in the young subject than in the adult. MEMBRANES OF THE BRAIN. The membranes of the brain are the dura mater, arachnoid membrane, and pia mater. The Dura Mater. The Dura Mater is a thick and dense inelastic fibrous membrane which lines the interior of the skull. Its outer surface is rough and fibrillated, and adheres closely to the inner surface of the bones, forming their internal periosteum, this adhesion being most marked opposite the sutures and at the base of the skull. Its inner surface is smooth and lined by a layer of endothelial cells. It sends three processes inward, into the cavity of the skull, for the support and protection of the different parts of the brain, and is prolonged to the outer surface of the skull through the various foramina which exist at the base, and thus becomes continuous with the pericranium; its fibrous layer forms sheaths for the nerves which pass through these apertures. At the base of the skull it sends a fibrous prolongation into the foramen caecum; it sends a series of tubular prolongations round the filaments of the olfactory nerves as they pass through the cribriform plate, and also round the nasal nerve as it passes through the nasal slit; a prolongation is also continued through the sphenoidal fissure into the orbit, and another is con- tinued into the same cavity through the optic foramen, forming a sheath for the optic nerve, which is continued as far as the eyeball. In the posterior fossa it sends a process down the internal auditory meatus, ensheathing the facial and auditory nerves; another through the jugular foramen, forming a sheath for the structures which pass through this opening; and a third through the anterior condyloid foramen. Around the margin of the foramen magnum i.t is closely adherent to the bone, and is continuous with the dura mater lining the spinal canal. In certain situations, as already mentioned (page 652), the fibrous layers of this membrane separate, to form sinuses for the passage of venous blood. Upon the outer surface of the dura mater, in the situation of the longitudinal sinus, may be seen numerous small whitish bodies, the glandulce Pacchioni. Structure.-The dura mater consists of white fibrous and elastic tissues arranged in flattened laminae, which are divisible into two layers, the fibres of the two layers intersecting each other obliquely. A layer of nucleated endothelial cells, similar to those found on serous membranes, lines its inner surface; these were formerly regarded as belonging to the arachnoid membrane. Its arteries are very numerous, but are chiefly distributed to the bones. Those found in the anterior fossa are the anterior meningeal branches of the anterior and posterior ethmoidal and internal carotid, and a branch from the middle meningeal. In the middle fossa are the middle and small meningeal branches of the internal maxillary, a branch from the ascending pharyngeal, which enters the skull through the foramen lacerum medium basis cranii, branches from the internal carotid, and a recurrent branch from the lachrymal. In the posterior fossa are meningeal branches from the occipital, one of which enters the skull through the jugular foramen, and the other through the mastoid foramen; the posterior meningeal, from the vertebral; occasionally meningeal branches from the ascending pharyngeal, which enter the skull, one at the jugular foramen, the other at the anterior condyloid foramen, and a branch from the middle meningeal. The veins, which return the blood from the dura mater, and partly from the bones, anastomose with the diploic veins. These vessels terminate in the various THE BRAIN AND ITS MEMBRANES. 705 sinuses, with the exception of two which accompany the middle meningeal artery, and pass out of the skull at the foramen spinosum to join the internal maxillary vein. The nerves of the dura mater are, the recurrent branch of the fourth and filaments from the Gasserian ganglion, from the ophthalmic and hypoglossal nerves, and from the sympathetic. The so-called glandulse Pacchioni are numerous small whitish granulations, usually collected into clusters of variable size, which are found in the following situations: 1. Upon the outer surface of the dura mater, in the vicinity of the superior longitudinal sinus, being received into little depressions on the inner surface of the calvarium. 2. On the inner surface of the dura mater. 3. In the superior longitudinal sinus. 4. On the pia mater, near the margin of the hemispheres. These bodies are not glandular in structure, but simply enlarged normal villi of the arachnoid. In their growth they perforate the dura mater, and are thus found on its outer surface, and when of large size they cause absorption of the bone, and come to be lodged in pits or depressions on the inner table of the skull. The manner in which they perforate the dura mater is as follows: At an early period of their growth they project through minute holes in the inner layer of the dura mater, which open into large venous spaces situated in the tissues of the membrane on either side of the longitudinal sinus and communicating with it. In their onward growth the villi push the outer layer of the dura mater before them, and this forms over them a delicate membranous sheath. In structure they consist of trabeculae of connective tissue covered over by a layer of endothelium. The spongy tissue of which they are composed is continuous with the trabecular tissue of the subarachnoid space. These bodies are not found in infancy, and very rarely until the third year. They are usually found after the seventh year, and from this period they increase in number as age advances. Occasionally they are wanting. Processes of the Dura Mater.-The processes of the dura mater, sent inward into the cavity of the skull, are three in number: the falx cerebri, the tentorium cerebelli, and the falx cerebelli. ThefaZz cerebri, so named from its sickle-like form, is a strong arched process of the dura mater, which descends vertically in the longitudinal fissure between the two hemispheres of the brain. It is narrow in front, where it is attached to the crista galli of the ethmoid bone, and broad behind, where it is connected with the upper surface of the tentorium. Its upper margin is convex, and attached to the inner surface of the skull as far back as the internal occipital protuberance. In this situation it is broad, and contains the superior longitudinal sinus. Its lower margin is free, concave, and presents a sharp curved edge, which contains the inferior longitudinal sinus. The tentorium cerebelli is an arched lamina of dura mater, elevated in the middle and inclining downward toward the circumference. It covers the upper surface of the cerebellum, and supports the occipital lobes of the brain, and prevents them pressing upon the cerebellum. It is attached, behind, by its convex border to the transverse ridges upon the inner surface of the occipital bone, and there encloses the lateral sinuses; in front, to the superior margin of the petrous portion of the temporal bone, enclosing the superior petrosal sinuses; and at the apex of this bone the free or internal border and the attached or external border meet, and, forming two processes, cross one another and are continued forward, to be attached to the anterior and posterior clinoid processes respectively. Along the middle line of its upper surface the posterior border of the falx cerebri is attached, the straight sinus being placed at their point of junction. Its anterior border is free and concave, and presents a large oval opening for the transmission of the crura cerebri. The falx cerebelli is a small triangular process of dura mater received into the indentation between the two lateral lobes of the cerebellum behind. Its base is 706 THE NERVOUS SYSTEM. attached, above, to the under and back part of the tentorium ; its posterior margin, to the lower division of the vertical crest on the inner surface of the occipital bone. As it descends it sometimes divides into two smaller folds, which are lost on the sides of the foramen magnum. The Arachnoid Membrane. The arachnoid eidoc;, like a spider's web), so named from its extreme thinness, is a delicate membrane which envelops the brain, lying between the pia mater internally and the dura mater externally; from this latter membrane it is separated by a space, the subdural space. It invests the brain loosely, being separated from direct contact with the cerebral substance by the pia mater, and a quantity of loose areolar tissue, the subarachnoidean. On the upper surface of the cerebrum the arachnoid is thin and transparent, and may be easily demonstrated by injecting a stream of air beneath it by means of a blowpipe ; it passes over the convolutions without dipping down into the sulci between them. At the base of the brain the arachnoid is thicker, and slightly opaque toward the central part; it covers the anterior lobes, and extends across between the two temporo-sphenoidal lobes, so as to leave a consid- erable interval between it and the brain, the anterior subarachnoidean space; it is in contact with the pons and under surfaqe of the cerebellum, but between the hemispheres of the cerebellum and the medulla oblongata another considerable interval is left between it and the brain, called the posterior subarachnoidean space. These two spaces communicate together across the crura cerebelli. The arachnoid membrane surrounds the nerves which arise from the brain, and encloses them in loose sheaths as far as their point of exit from the skull. The subarachnoid space is the interval between the arachnoid and pia mater : this space is narrow on the surface of the hemispheres, but at the base of the brain a wide interval is left between the two temporo-sphenoidal lobes, and, behind, between the hemispheres of the cerebellum and the medulla oblongata. This space is the seat of an abundant serous secretion, the cerebro-spinal fluid, which fills up the interval between the arachnoid and pia mater. The subarachnoid space usually communicates with the general ventricular cavity of the brain by means of an opening in the inferior boundary of the fourth ventricle. The subdural space also contains fluid; this is, however, small in quantity compared with the cerebro-spinal fluid. Structure.-The arachnoid consists of bundles of white fibrous and elastic tissue intimately blended together. Its outer surface is covered with a layer of endothelium. From its inner surface are given off a number of bundles of fine connective tissue, which form a sponge-like trabecular network in the subarachnoid space, in the interstices of which the cerebro-spinal fluid is contained. Vessels of considerable size, but few in number, and, according to Bochdalek, a rich plexus of nerves derived from the motor division of the fifth, the facial, and the spinal accessory nerves, are found in the arachnoid. The cerebrospinal fluid fills up the subarachnoid space. It is a clear, limpid fluid, having a saltish taste and a slightly alkaline reaction. According to Lassaigne, it consists of 98.5 parts of water, the remaining 1.5 per cent, being solid matters, animal and saline. It varies in quantity, being most abundant in old persons, and is quickly reproduced. Its chief use is probably to afford mechanical protection to the nervous centres and to prevent the effects of concus- sions communicated from without. The Pia Mater. The pia mater is a vascular membrane, and derives its blood from the internal carotid and vertebral arteries. It consists of a minute plexus of blood-vessels, held together by an extremely fine areolar tissue. It invests the entire surface of the brain, dipping down between the convolutions and laminae, and is prolonged THE DIVISIONS OF THE DRAIN 707 into the interior, forming the velum interpositum and choroid plexuses of the fourth ventricle. Upon the surfaces of the hemispheres, where it covers the gray matter of the convolutions, it is very vascular, and gives off from its inner surface a multitude of minute vessels, which extend perpendicularly for some distance into the cerebral substance. At the base of the brain, in the situation of the anterior and posterior perforated spaces, a number of long straight vessels are given off, which pass through the white matter to reach the gray substance in the interior. On the cerebellum the membrane is more delicate, and the vessels from its inner surface are shorter. Upon the crura cerebri and pons Varolii its characters are altogether changed; it here presents a dense fibrous structure, marked only by slight traces of vascularity. According to Fohmann and Arnold, this membrane contains numerous lymphatic vessels. Its nerves are derived from the sympathetic, and also from the third, fifth, sixth, facial, glosso-pharyngeal, pneumogastric, and spinal acces- sory. They accompany the branches of the arteries. The brain (encephalon) is that portion of the cerebro-spinal axis which is con- tained in the cranial cavity. It is divided into four principal parts-viz. the cerebrum, the cerebellum, the pons Varolii, and the medulla oblongata. The cerebrum forms the largest portion of the encephalon, and occupies a considerable part of the cavity of the cranium, resting in the anterior and middle fossae of the base of the skull, and separated posteriorly from the cerebellum by the tentorium cerebelli. About the middle of its under surface is a narrow constricted portion, part of which, the crura cerebri, is continued onward into the pons Varolii below, and through it to the medulla oblongata and spinal cord ; whilst another portion, the crura cerebelli, passes down into the cerebellum. The cerebellum (little-brain or after-brain) is situated in the inferior occipital fossae, being separated from the under surface of the occipital lobes of the cerebrum by the tentorium cerebelli. It is connected to the rest of the encephalon by means of connecting bands, called crura: of these, two ascend to the cerebrum, two descend to the medulla oblongata, and twro blend together in front, forming the pons Varolii. The pons Varolii is that portion of the encephalon which rests upon the upper part of the basilar process of the occipital bone and body of the sphenoid bone. It constitutes the bond of union of the various segments above named, receiving, above, the crura from the cerebrum; at the sides, the crura from the cerebellum; and below, the medulla oblongata. The medulla oblongata extends from the lower border of the pons Varolii to the upper part of the spinal cord. It lies beneath the cerebellum, resting on the lower part of the basilar groove of the occipital bone. Weight of the Encephalon.-The average weight of the brain in the adult male is 49£ oz., or a little more than 3 lbs. avoirdupois; that of the female 44 oz.; the average difference between the two being from 5 to 6 oz. The prevailing weight of the brain in the male ranges between 46 oz. and 53 oz., and in the female between 41 oz. and 47 oz. In the male the maximum weight out of 278 cases was 65 oz., and the minimum weight 34 oz. The maximum weight of the adult female brain, out of 191 cases, was 56 oz., and the minimum w'eight 31 oz. According to Luschka, the average weight of a man's brain is 1424 grammes (about 45 oz.), of a woman's 1272 grammes (about 41 oz.), and, according to Krause, 1570 grammes (about 48J oz.) for the male, and 1350 (about 43 oz.) for the female. It appears that the weight of the brain increases rapidly up to the seventh year, more slowly to between sixteen and twenty, and still more slowly to between thirty and forty, when it reaches its maximum. Beyond this period, as age advances and the mental faculties decline, the brain diminishes slowly in weight, about an ounce for each subsequent decennial period. These results apply alike to both sexes. The size of the brain was formerly said to bear a general relation to the intel- THE DIVISIONS OF THE BRAIN. 708 THE NERVOUS SYSTEM. lectual capacity of the individual. Cuvier's brain weighed rather more than 64 oz., that of the late Dr. Abercrombie 63 oz., and that of Dupuytren 62| oz. On the other hand, the brain of an idiot seldom weighs more than 23 oz. But these facts are by no means conclusive, and it is well known that these weights have been equalled by the brains of persons who never displayed any remarkable intellect. Dr. Haldennan of Cincinnati has recorded the case of a mulatto, aged forty-five, whose brain weighed 68f oz.; he had been a slave, and was never regarded as particularly intelligent; he was illiterate, but is said to have been reserved, medi- tative, and economical. Dr. Ensor, district medical officer at Port Elizabeth, reports that the brain of Carey, the Irish informer, weighed 61 oz. M. Nikiforoff has published an article on the subject of the weight of brains in the Novosti. According to him, the weight of the brain has no influence whatever on the mental faculties. It ought to be remembered that the significance of the weight of the brain should depend upon the proportion it bears to the dimensions of the whole body and to the age of the individual. It is equally important to know what was the cause of death, for long illness or old age exhausts the brain. To define the real degree of development of the brain it is therefore necessary to have a knowledge of the condition of the whole body, and, as this is usually lacking, the mere record of weight possesses little significance. The human brain is heavier than that of all the lower animals, excepting the elephant and whale. The brain of the former weighs from eight to ten pounds; and that of a whale, in a specimen seventy-five feet long, weighed rather more than five pounds. The Medulla Oblongata. The Medulla Oblongata, or bulb, is the upper enlarged part of the spinal cord, and extends from the lower margin of the foramen magnum to the lower border of the pons Varolii. It is directed from above obliquely downward and backward; its anterior surface rests on the basilar groove of the occipital bone, its posterior surface is received into the fossa between the hemispheres of the cerebellum, forming the floor of the fourth ventricle. It is pyramidal in form, its broad extremity directed upward, its lower end being narrow at its point of connection with the cord. It measures an inch in length, three-quarters of an inch in breadth at its widest part, and half an inch in thickness. Its surface is marked, in the median line, in front and behind, by an anterior and posterior median fissure, which are continuous with those of the spinal cord. The anterior fissure contains a fold of pia mater, and terminates just below the pons in a cul-de-sac, the foramen ccecum. It is interrupted at its lower part by some bundles of fibres, which cross obliquely from one side to the other, forming the decussation of the pyramids. The posterior is a deep but narrow fissure, continued upward to about the middle of the medulla, where it expands into the fourth ventricle. These two fissures divide the medulla into two symmetrical halves, each lateral half presenting elongated eminences which are continuous with the columns of the cord. By taking the lines along which some of the cranial nerves emerge from the medulla as landmarks, we may divide the surface of this portion of the nervous system into three columns, just in the same way as the spinal cord is divided into three columns by the lines corresponding to the points of exit of the anterior and posterior roots of the spinal nerves. The anterior column comprises that portion which is situated between the anterior median fissure and the fibres of origin of the hvpoglossal nerve : this column is called the pyramid. The lateral column comprises that portion which is situated between the fibres of origin of the hypoglossal nerve and the fibres of origin of the glosso-pharyngeal, pneumogastric, and spinal accessory nerves. In the lower part of the medulla this column is single, and is called the lateral tract; but in the upper part an oval-shaped body comes forward between it and the pyramid, pushing aside the lateral tract. This is called the olivary body. The posterior column comprises that portion which is situated between the fibres of origin of the glosso-pharyngeal, pneumogastric, and spinal THE MEDULLA OBLONGATA 709 accessory nerves, and the posterior median fissure. This column is marked by slight furrows marking off smaller columns, and these in the lower part of the medulla are named, from without inward, the funiculus of Rolando, the /um'euZus cuneatus, and due funiculus gracilis ; in the upper part of the medulla the funiculus of Rolando and the funiculus cuneatus appear to become fused together, forming a single body called the restiform body. The Pyramids are two pyramidal bundles of white matter, placed one on either side of the anterior median fissure, and separated from the olivary body, which is external to them, by a slight depression. At the lower border of the pons they are somewhat con- stricted ; they then become enlarged, and taper as they descend, being continuous below, by their outer portion, with the anterior columns of the cord {direct pyr- amidal tract), and by their inner portion with the decussating fibres, seen in the anterior median fissure, which are derived from the lateral column of the cord {crossed pyramidal tract). For, on separating the pyramids below, it will be observed that their innermost fibres form from four to five bundles on each side, which decussate with one another across the anterior median fissure; this decussation, however, is not formed of fibres from the anterior column of the cord, but from the deep portion of the lateral columns which pass forward to the surface on the inner side of the anterior columns. The outermost fibres do not decussate; they are derived, as just stated, from the anterior column of the cord. The lateral column, in the lower part of the medulla, is of the same width as the lateral column of the cord, and appears on the surface to be a direct continuation of it. In the upper part of the medulla the lateral tract, on account of the inter- polation of the olivary body, is reduced to a narrow strip, lying between the olivary and restiform bodies. The olivary body is a prominent oval mass, situated behind the pyramid, from which it is separated by a slight groove, along which the hypoglossal nerve arises. It is separated externally from the restiform body by a longitudinal narrow band of fibres, the continuation upward of the lateral tract, and by a groove from which the glosso-pharyngeal, pneumogastric, and spinal accessory nerves arise. It is equal in breadth to the pyramid ; is a little broader above than below, and is about half an inch in length, being separated above from the pons Varolii by a slight depression, in which is sometimes to be seen a band of arched fibres. Numerous white fibres {superficial arciform fibres) are seen winding across the lower half of the pyramid and the olivary body to enter the restiform body. The funiculus of Rolando is a longitudinal prominence, on the outer side of the lateral tract. It begins at the lower end of the medulla by a tapering extremity, and gradually enlarging as it ascends, forms at a level with the lower border of the olivary body a slight prominence, known as the tubercle of Rolando. About half an inch below the pons it appears to blend with the funiculus cuneatus. In front, it is separated from the lateral tract by a distinct groove, the continuation upward of the postero-lateral groove of the cord ; behind, the separation from the funiculus cuneatus is much less distinct. The funiculus cuneatus is the direct continuation upward of the posterior lateral column of the cord. It is situated between the funiculus of Rolando and the funiculus gracilis; it enlarges as it ascends, and forms, opposite the 1 Middle 'peduncle of cerebellum. Fig. 411.-Medulla oblongata and pons Varolii. Anterior surface. 710 THE NERVOUS SYSTEM. lower extremity of the fourth ventricle, a slight eminence or enlargement, the tuberculum cuneatum, which is best marked in children. About half an inch below the pons it appears to blend with the funiculus of Rolando. The restiform bodies appear on the surface to be the direct continuation upward of the funiculus of Rolando and the funiculus cune- atus. But they also receive the arched fibres (arciform), presently to be described, and fibres derived from the lateral column of the cord, or the lateral cerebellar tract. The restiform bodies are the largest prominences of the medulla, and are placed between the lateral tracts in front and the funiculus gracilis behind, from both of which they are separated by slight grooves. As they ascend they diverge from each other, assist in forming the lower part of the lateral boundaries of the fourth vent- ricle, and then enter the corresponding hemi- sphere of the cerebellum, forming its inferior peduncles. The funiculus gracilis is the direct con- tinuation upward of the posterior median column of the cord. It is a narrow white cord, placed parallel to and along the side of the posterior median fissure. It is sep- arated from the funiculus cuneatus below and the restiform body above by a slight groove, which is continuous with the groove on the surface of the cord, which marks off the pos- terior median column. It consists entirely of white fibres, and is the direct continuation of the posterior median column of the cord. At first the funiculi of the two sides lie in close contact on either side of the posterior median fissure. Opposite the apex of the fourth ventricle they form an enlarge- ment (cZuvu), and then diverging, form the lateral boundaries of the lower part of the fourth ventricle, and gradually tapering off they soon become no longer traceable. The posterior surface of the medulla oblongata forms part of the floor of the fourth ventricle. This portion is of a triangular form, bounded on each side by the diverging funiculi graciles and restiform bodies, and is that part of the ventricle which, from its resemblance to the point of a pen, is called calamus scrip- torius. The divergence of the funiculi graciles and restiform bodies opens to view the gray matter of the medulla, which is continuous below with the gray matter of the cord. In the middle line is seen a longitudinal furrow, which ends below, near the point of the calamus, in a somewhat cleft-like space, the ventricle of Arantius, which opens by a minute hole into the central canal of the cord. The arciform or arcuate fibres, which have been mentioned as forming part of the restiform body, are found in the upper half of the medulla, both crossing its surface and traversing its substance. They are divided for the purpose of descrip- tion into two sets-superficial and deep. The superficial arciform fibres have already been alluded to as crossing the pyramid and olivary body on each side. They emerge from the anterior median fissure, in which they can be traced to enter the raphe and cross it, after which they become no longer traceable. After emerging from the anterior median fissure they cross the pyramid and olivary body, and enter the restiform body. As they cross the olivary body they are reinforced -Clava. - Cuneate tubercle. -Restiform body. -Funiculus of Rolando. - Funiculus cuneatus. ~ Funiculus gracilis. Fig. 412.-Posterior surface of the me- dulla oblongata. THE MEDULLA OBLONGATA. 711 by some of the deep arciform fibres which come to the surface on the inner side of, or through, this structure. The deep arciform fibres are described with the Microscopic Anatomy of the Medulla. Structure.-The medulla oblongata, like the spinal cord, consists of both gray and white matter, and exhibits in sections both these structures arranged in certain definite masses. The fibres of the several columns of the cord enter the medulla, and in it undergo a rearrangement, some of them passing through it to the pons Varolii, the cerebrum, and the cerebellum, while others end in its gray substance. Some fibres take origin in the medulla, and are continued onward to the cerebrum and cerebellum. The structure of the medulla will be best understood by tracing its several parts upward from the spinal cord. The pyramid is composed of fibres derived from the direct pyramidal tract of the anterior column of the cord of its own side, and from the crossed pyramidal tract of the lateral column of the opposite half of the cord. Those fibres which are derived from the direct pyramidal tract, and which in the cord lie close to the median fissure, are in the medulla placed to the outer side of the pyramid, being pushed aside, as it were, by the interpolation of the fibres derived from the crossed pyramidal tract, which are much more numerous. The crossed pyramidal fibres ascend from the lateral column of the spinal cord, and, passing through the anterior gray cornua and across the median fissure, form the inner part of the pyramid. The fibres of the pyramid may be traced upward through the pons to the crus cerebri of its own side. All the fibres of the anterior column of the cord are not continued into the pyramid of the medulla; some of them pass backward, and enter the formatio reticularis, which is described with the Microscopic Anatomy of the Medulla. The olivary body when cut across obliquely is seen to be composed, externally of white fibres, internally of a gray layer, the corpus dentatum, which is arranged in the form of a hollow capsule, open at its upper and inner part and presenting a zigzag or deritated outline. White fibres enter the interior of this capsule by the aperture at its upper and inner part, constituting the olivary peduncle. The lateral tract of the medulla is the continuation upward of the lateral column of the cord. The fibres from it divide into three sets: one set, the most numerous, pass deeply behind the olivary body, and ascend through the formatio reticularis to the pons; a second set pass across the anterior median fissure to join the pyramid, forming the crossed pyramidal set; the third set, few in number, form a small band, which passes backward to the restiform body to enter the cerebellum, forming the lateral cerebellar tract. The funiculus of Rolando, which is a longitudinal prominence on the outer side of the lateral tract, is now seen to be the enlarged head of the posterior cornu of the gray matter, which is displaced laterally in consequence of the increase in size of the posterior columns of the medulla, so that it lies almost at right angles to the posterior median fissure, and approaching the surface forms a prominence which is covered over by a very thin layer of white matter derived from the funiculus cuneatus. Its most prominent part on the surface is called the tubercle of Holando. The funiculus cuneatus is the direct continuation upward of the postero- lateral column of the cord. Its white fibres are derived from this region of the cord. The fibres appear to end in the gray matter which forms the so-called nucleus of this column; this nucleus, at first narrow, gradually enlarges, and produces, externally, the eminence mentioned above as the tuberculum cuneatum. The funiculus gracilis is the direct continuation upward of the posterior median column of the cord. It consists entirely of white fibres, which are continuous with those of this region of the cord. Like the funiculus cuneatus, its fibres appear to end in its so-called nucleus, which produces externally the prominence mentioned above as the clava. The restiform body is mainly constituted by the fusing together of the funiculus 712 THE NERVOUS SYSTEM. of Rolando and the funiculus cuneatus, to which are added the arciform fibres of the medulla and the lateral cerebellar tract from the lateral tract of the medulla. In addition to these, a bundle of fibres has been described by Solly as passing from the anterior column of the cord obliquely upward below the olivary body to the restiform body. The white fibres of the restiform body are continued upward to the cerebellum, forming its inferior peduncle. Microscopic Anatomy of the Medulla.-If the cranial nerves emerging from the medulla are traced into its substance, it will be seen that they divide each hemisphere of the medulla into three wedge-shaped areas, which have been named the anterior, lateral, and posterior areas of the medulla. The anterior area comprises that portion which is situated between the anterior median fissure and the fibres of origin of the hypoglossal nerve. On the surface of the medulla this area corresponds to the pyramid. The lateral area comprises that portion which is situated between the fibres of origin of the hypoglossal nerve and the fibres of origin of the glosso-pharyngeal, pneumogastric, and spinal accessory nerves. On the surface of the medulla, in its lower part, this area is single, and is called the lateral tract; but in the upper part an oval-shaped body comes forward between it and the pyramid, pushing aside the lateral tract. This oval-shaped body is the olivary body. The posterior area comprises that portion which is situated between the fibres of origin of the glosso-pharyngeal, pneumogastric, and spinal accessory nerves and the posterior median fissure. On the surface of the medulla, this area is marked by slight furrows marking off smaller columns ; these, in the lower part of the medulla, are named, from without inward, the funiculus of Rolando, the funiculus cuneatus, and the funiculus gracilis ; in the upper part of the medulla the funiculus of Rolando and the funiculus cuneatus appear to become fused together, forming a single body, called the restiform body. The Arciform Fibres.-Deep Set.-The deep arciform fibres are more numerous than the superficial set; they traverse the whole area of the upper half of the medulla, except the pyramid. They pass from the raphe : some become superficial and join the superficial arciform fibres ; while others remain deep and pass to the restiform body and to the nuclei of the funiculus cuneatus and funiculus gracilis. The Raphe.-The raphe is situated in the middle line of the medulla, above the decussation of the pyramids. It consists of nerve-fibres intermingled with nerve-cells. The fibres have different directions which can only be seen in suitable microscopic sections ; thus : 1. Some are antero-posterior ; these are continuous in front w ith the superficial arciform fibres. 2. Some are longitudinal; these are derived from the arciform fibres, which on entering the raphe change their direction and become longitudinal. 3. Some are oblique; these are continuous with the deep arciform fibres which pass from the raphe. Some of the fibres of the raphe arise from the nuclei on the floor of the fourth ventricle. The Formatio Reticularis.-In the substance of the medulla behind the pyramid and olivary body is a peculiar reticulated structure, which has received the name of formatio reticularis ; the appearance it presents in sections of the medulla is due to its being composed of bundles of fibres running at right angles to each other, some being longitudinal, others transverse. The longitudinal fibres are derived- 1. From the anterior column of the cord after the direct pyramidal tract has passed into the pyramid. 2. From the olivary body. 3. From the lateral column of the cord after the crossed pyramidal tract has passed into the pyramid. 4. From the funiculus cuneatus and funiculus gracilis. MICROSCOPIC ANATOMY OF THE MEDULLA. 713 The transverse fibres are the deep arciform fibres. In the lateral part of this reticular structure gray matter containing large nerve-cells is found. The Gray Matter of the Medulla Oblongata.-The gray matter of the medulla oblongata is partly continuous with the gray matter of the cord, and partly arranged in independent masses. It contains many multipolar ganglion-cells. In the lower part of the medulla the gray matter, which is continuous with that of the cord, is arranged in the shape of two crescentic horns, with their convexities toward each other, and connected by a central commissure; but in the upper part it loses its crescentic arrangement, becomes more abundant, and is disposed with less regularity. The caput of the posterior horns becomes enlarged, and gradually shifted Hypo- glossal Nucleus of funiculus teres, nucleus. Vagus . nuclei. Ligula. Nucleus gracilis. Nucleus cuneatus. Corpus restiforme. Raphe.- Formatlo reticularis. Ascending root of fifth nerve. Continuation of anterior column. Vagus root. Arciform fibres. Accessory olivary Olivary nucleus. Hypoglossal nerve. Fig. 413.-Section of the medulla oblongata at about the middle of the olivary body. (Schwalbe.) Anterior median fissure. -outward, so that they form rounded masses, close under the lateral tract, and pro- duce the prominence on the surface called the funiculus of Rolando. The neck of the cornu diminishes in size, and is broken up into a reticular formation by the passage of longitudinal and transverse fibres through it, so that the caput is sep- arated from the rest of the gray matter. As the central canal expands into the fourth ventricle, the rest of the posterior horn of gray matter is pushed outward into the funiculus cuneatus and funiculus gracilis; in each of these funiculi it forms a distinct accumulation of gray matter, constituting the nucleus cuneatus and the nucleus gracilis. The anterior horn of gray matter is broken up by the passage through it of the crossed pyramidal tract from the lateral column of the cord. By this means the anterior portion of the horn is completely isolated from the remainder, and constitutes the lateral nucleus of gray matter which is situated near the surface of the lateral tract. The greater part of the rest of the anterior horn, being permeated by the decussating fibres, presents a reticular formation. A small part of the base of the anterior cornu comes to the surface of the floor of the fourth ventricle, and is 714 THE NERVOUS SYSTEM. exposed to view by the divergence of the funiculus cuneatus and funiculus gracilis. It forms a continuous mass, which gradually increases in size and forms the eminence of the fasciculus teres. In it is a group of nerve-cells, which form the nucleus from which the roots of the hypoglossal nerve arise. At the base of the posterior cornu, in the lower part of the medulla, is a group of cells, which, if traced upward, are found to be pushed on one side; so that in the floor of the fourth ventricle they are outside the hypoglossal nucleus and form a second eminence, the ala cinerea: from it arise the roots of the accessory portion of the spinal accessory, pneumogastric, and glosso-pharyngeal nerves. Outside this, again, and toward the upper part of the medulla, is another group of cells, from which most of the fibres of the auditory nerve take origin. Another independent mass of gray matter is found in the olivary body, forming the corpus dentatum. It consists of a gray layer arranged in the form of a hollow capsule, open at its upper and inner part, and presenting a zigzag or dentated outline. White fibres enter the interior of this capsule by the aperture at its upper and inner part, constituting the olivary peduncles. Some of these fibres terminate in the cells of the corpus dentatum, while others are continued through the gray layer to join the arciform fibres. Furthermore, two small isolated bands of gray matter are seen, one on the dorsal and the other on the mesial aspect of the corpus dentatum: these are known as accessory olivary nuclei. The Pons Varolii. The pons Varolii (tuber annulare) is the bond of union of the various segments of the encephalon, connecting the cerebrum above, the medulla oblongata below, and the cerebellum behind. It is situated above the medulla oblongata, below the crura cerebri, and between the hemispheres of the cerebellum. Its anterior surface presents a broad transverse band of white fibres, which arches like a bridge across the upper part of the medulla, extending between the two hemispheres of the cerebellum. This surface projects considerably beyond the level of these parts, is of quadrangular form, rests upon the clivus of the sphenoid bone, and is limited before and behind by very prominent margins. It presents along the middle line a longitudinal groove, wider in front than behind, which lodges the basilar artery: numerous transverse striae are also observed on each side, which indicate me course of its superficial fibres. Its posterior surface forms part of the floor of the fourth ventricle. At each side its fibres become contracted into a thick rounded cord, the crus cerebelli, which enters the substance of the cerebellum, constituting its middle peduncle. Structure.-The pons Varolii consists of two parts, which differ in appearance and structure from each other : the anterior or ventral half consists for the most part of fibres arranged in transverse and longitudinal bundles with a small amount of gray matter; the posterior or dorsal half is a continuation of the reticular forma- tion of the medulla with the gray matter of the floor of the fourth ventricle. The anterior or ventral half consists of three layers of fibres : (1) superficial transverse fibres ; (2) superficial longitudinal fibres; (3) deep transverse fibres. These three layers are not, however, completely differentiated from each other, for some trans- verse fibres may be seen between the bundles of the longitudinal fibres. The superficial transverse fibres (Fig. 414) pass from the crus or middle peduncle of the cerebellum to the median raphe of the pons, where they meet and interlace with those coming from the opposite side. They then dip deeply into the substance of the pons and pass to the crus cerebri of the opposite side. The superficial longi- tudinal fibres enter the pons below as a single mass, being the continuation upward of the fibres of the pyramids of the medulla; as they ascend they become broken up into bundles by some of the transverse fibres passing through them, and are continued into the superficial portion of the crus cerebri, much increased in THE PONS VAR0L1I. 715 number from being reinforced by the fibres derived from the nerve-cells in the deej) transverse strata. The deep transverse fibres form a much thicker layer than the superficial set, and contain much gray matter between them. The fibres pass from the crus or middle peduncle of the cerebellum to the median raphe of the pons, where they meet and interlace with those coming from the opposite side. The posterior or dorsal portion of the pons is chiefly constituted by a continua- tion upward of the reticular formation of the medulla and by the gray matter of the floor of the fourth ventricle. Microscopic Anatomy of the Pons.-This presents the same reticular structure as in the medulla, consisting of longitudinal fibres continued upward from the medulla, with interlacing transverse fibres, between which is interspersed gray Superficial 1 fibres ofponsl reflected. I Fig. 414.-Superficial dissection of the medulla oblongata and pons. (Ellis.) matter with nerve-cells, especially in the deeper layers. Many of the deep trans- verse fibres join the nerve-cells, which are situated in the gray matter (nuclei pontis) of this layer. From these cells other fibres are given off which ascend through the pons to the crus cerebri. In the lower part of this portion of the pons is a small isolated collection of gray matter, the superior olivary nucleus, enclosed by some of the deep transverse fibres, called the trapezium. It is situated close to the medulla, behind the super- ficial longitudinal fibres from the pyramid and immediately above the olivary body. The fibres of the trapezium, which are probably connected with the cells of the nucleus, pass to the middle peduncle of the cerebellum. Near the floor of the fourth ventricle important collections of nerve-cells are found, from which some of the cranial nerves arise. One of these forms the nucleus of the sensory root of the fifth nerve; a second, the nucleus of the motor part of the same nerve ; a third, the nucleus of the sixth nerve; and a fourth, the nucleus of the facial nerve. The nucleus of the auditory nerve, situated just at the junction of the pons and medulla, is prolonged upward into the pons. 716 THE NERVOUS SYSTEM. Septum.-The posterior part of the pons is subdivided into lateral halves by a medium septum, but this does not extend into the anterior half, being here oblite- rated by the transverse fibres. It is formed mainly by the decussation and change in the direction of fibres as they cross the middle line. The Cerebrum (Fig. 415). The cerebrum constitutes the largest portion of the encephalon. Its under sur- face or base is of an irregular form, resting in front on the anterior and middle fossm of the skull, behind upon the tentorium cerebelli. Its upper surface is of an ovoid form, broader behind than in front, convex in its general outline, and Lower frontal Fissure of Rolando. 'Parieto-occipital fissure. divided into lateral halves or hemispheres, right and left, by the great longitudinal fissure, which extends throughout the entire length of the cerebrum in the middle line, reaching down to the base of the brain in front and behind, but interrupted in the middle by a broad transverse commissure of white matter, the corpus cal- losum, which connects the two hemispheres together. This fissure lodges the falx cerebri, and indicates the original development of the brain by two lateral halves. Each hemisphere presents an outer surface, which is convex to correspond with the vault of the cranium ; an inner surface, which is flattened, and in contact with the opposite hemisphere (the two inner surfaces forming the sides of the longitudinal fissure) ; and an under surface or base, of an irregular form, which rests in front on the anterior and middle fossae of the base of the skull, and behind upon the tentorium cerebelli. Fig. 415.-Upper surface of the brain, the arachnoid having been removed. CONVOLUTIONS OF THE CEREBRUM. 717 Upper Surface of the Cerebrum. If the arachnoid and pia mater are removed, the entire surface of each hemi- sphere will be seen to present a number of depressions (fissures and sulci) sepa- rating a number of convoluted eminences (the convolutions or gyri). The depressions are of two kinds, fissures and sulci. The fissures are few' in number; they are constant in their arrangement, and are produced by the foldings of the cerebrum during the process of development. They involve both gray and white matter. The sulci are more numerous ; they are superficial depressions of the gray matter, which is folded inward and only indents the central white sub- stance ; they vary in different brains and in different parts of the same brain. The Convolutions.-There is no accurate resemblance between the convolutions in different brains, nor are they exactly symmetrical on the twro sides of the same brain, but their general arrangement or plan is fairly constant. Certain infoldings of the cerebrum take place at an early period of development and form important landmarks, which are constant and can without difficulty be recognized, but the secondary depressions and convolutions vary considerably. The number and extent of the convolutions, as well as their depth, appear to bear a close relation to the intellectual power of the individual, as is shown in their increasing complexity of arrangement as w e ascend from the low est mammalia up to man. Thus they are absent in some of the lower orders of mammalia, and they increase in number and extent through the higher orders. In man they present the most complex arrangement. Again, in the child at birth before the intellectual faculties are exercised the convolutions have a very simple arrangement, presenting few undulations, and the sulci between them are less deep than in the adult. In old age, when the mental faculties have diminished in activity, the convolutions become much less prominently marked. The convolutions on the outer convex surface of the hemisphere are the largest and most complicated convolutions of the brain ; their general direction is more or less oblique ; they frequently branch like the letter Y in their course upward and backward toward the longitudinal fissure: these convolutions attain their greatest development in man, and are especially characteristic of the human brain. Structure of the Convolutions.-The outer surface of each convolution, as well as the sides and bottom of the sulci between them, are composed of gray matter, which is here called the cortical substance. The interior of each convolution is composed of w hite matter, and white fibres also blend with the gray matter at the sides and bottom of the sulci. By this arrangement the convolutions are adapted to increase the amount of gray matter without occupying much additional space, while they also afford a greater extent of surface for the termination of the white fibres in gray matter. The Lobes and Fissures of the Brain.-Each hemisphere of the brain on its external surface is divided into five lobes, the division being made by the main fissures and by imaginary lines drawn to connect them (Fig. 416). The fissures dividing the five lobes on the external surface of the hemispheres are three in number, and are named fissure of Sylvius, fissure of Holando, and parieto-occipital fissure. The fissure of Sylvius begins at the base of the brain at the anterior perforated space, and passes outward to the external surface of the hemisphere. It gives off a short anterior limb, which passes forward, and another, ascending limb, which passes upward into the inferior frontal convolution. It is then continued back- ward as the horizontal limb, and terminates in the parietal lobe after curving upward for a short distance. It separates the frontal and parietal lobes from the temporo-sphenoidal, and occupies the middle third of the lateral surface of the hemisphere. The fissure of Rolando is situated about the middle of the outer surface of the hemisphere. It commences at or near the longitudinal fissure, and runs downward and forward to terminate a little above the horizontal limb of the fissure of Sylvius,. 718 THE NERVOUS SYSTEM. and about half an inch behind the ascending limb of the same fissure. It separates the frontal from the parietal lobe. The parieto-occipital fissure is only seen to a slight extent on the outer surface of the hemisphere, and is not so distinctly marked as the others. The portion on the outer surface of the hemisphere is sometimes called the external parieto-occip- ital fissure, to distinguish it from the continuation of the sulcus on the internal surface of the hemisphere, which would then be termed the internal parieto-occip- ital fissure. It commences about midway between the posterior extremity of the brain and the fissure of Rolando, and runs downward and forward for about an inch. It divides the parietal and occipital lobes. These three fissures divide the external surface of the hemisphere into five lobes -the frontal, the parietal, the occipital, the temporo-sphenoidal, and the central or island of Reil. The frontal lobe is that portion of the brain which is situated in front of the End of calloso- marginal fissure. Parieto- occipital fissure. Ascending fissure of Sylvius. Fissure °f Sylvius. Fig. 416.-Convolutions and fissures of the outer surface of the cerebral hemisphere. fissure of Rolando and above the horizontal limb of the fissure of Sylvius. Its under surface rests on the orbital plate of the frontal bone, and is termed the orbital lobe. The outer surface of the frontal lobe presents three sulci, which divide it into four primary convolutions : 1. The precentral sulcus runs upward through this lobe, parallel to the lower half of the fissure of Rolando. It divides off a convo- lution which lies between it and the fissure of Rolando, and which is called the ascending frontal convolution. 2 and 3. From it two sulci, the superior and infe- rior frontal sulci, run forward and downward, and divide the remainder of the outer surface of the lobe-namely, that part in front of the precentral sulcus- into three principal convolutions, named respectively the superior, middle, and inferior frontal convolutions. The under surface of the frontal lobe, which rests on the orbital plate of the CONVOLUTIONS OF THE CEREBRUM. 719 frontal bone, is named the orbital lobe (Fig. 417). It presents a well-marked groove or sulcus for the olfactory tract. The convolution internal to this sulcus forms part of the marginal gyrus, hereafter to be described. External to the sulcus this surface of the frontal lobe is divided into three convolutions by a well- marked sulcus, the orbital sulcus. These are named, from their positions, the internal, anterior, and posterior orbital convolutions, and are the continuation respectively of the superior, middle, and inferior frontal convolutions. The ascending frontal convolution is a simple convolution, bounded in front by the precentral sulcus, behind by the fissure of Rolando, and extending from the Aiitei ior Perforated Space. Fig. 417.-Convolutions and fissures of the under surface of the anterior lobe. upper margin of the hemisphere above to a little behind the bifurcation of the fissure of Sylvius below. The superior frontal convolution is situated between the margin of the longitu- dinal fissure and the superior frontal sulcus. It extends above on to the inner aspect of the hemisphere, forming the marginal convolution, and in front on to the orbital surface, forming the internal orbital convolution. It is much divided by secondary sulci. The middle frontal convolution is situated between the superior and inferior frontal sulci, and extends from the precentral sulcus to the lower margin of the lobe, where it forms the anterior orbital convolution. The inferior frontal convolution is situated below the inferior frontal sulcus, and extends from the lower part of the precentral sulcus, circling round the ascend- ing and anterior limbs of the fissure of Sylvius, to the under surface of the lobe, where it forms the posterior orbital convolution. The parietal lobe is situated between the frontal and occipital lobes, and is not 720 THE NERVOUS SYSTEM. much more than half the size of the former. It is bounded in front by the fissure- of Rolando; behind, by the external parieto-occipital fissure and a line drawn in continuation of that sulcus over the hemisphere; and below, by the horizontal limb of the fissure of Sylvius and a line connecting this with the lower end of the superior occipital sulcus. Above, it extends to the longitudinal fissure. It pre- sents for examination two sulci and three convolutions. The intraparietal sulcus commences close to the horizontal limb of the fissure of Sylvius, about midway between the fissure of Rolando and the upturned extremity of the fissure of Sylvius. It first runs upward parallel to and behind the lower half of the fissure of Rolando, and then turns backward, extending nearly to the termination of the external parieto-occipital fissure, where it sometimes becomes continuous with the superior occipital sulcus. The ascending portion of this sulcus separates off a convolution, the ascending parietal, which lies between it and the fissure of Rolando, whilst the horizontal portion divides the remainder of the parietal lobe into two other convolutions, the superior and inferior parietal. The post-central sulcus is a slightly marked groove, which is sometimes a branch of the intraparietal sulcus, being given off where the ascending portion of this sulcus turns backward. It lies parallel to and behind the upper part of the fissure of Rolando, and separates the ascending from the superior parietal convolution.1 The ascending parietal convolution is bounded in front by the fissure of Rolando, behind by the ascending portion of the intraparietal and the post-central sulci. It extends from the great longitudinal fissure above to the horizontal limb of the fissure of Sylvius below. It lies parallel with the ascending frontal convolution, with which it is connected below, and also generally above, the termination of the fissure of Rolando. The superior parietal convolution is bounded in front by the post-central sulcus, which separates it from the previous convolution, but with which it is usually connected above the upper extremity of the sulcus; behind, it is bounded by the external parieto-occipital fissure, below the termination of which it is connected with the occipital lobe by a narrow convolution, the first anneetant gyrus. Below, it is separated from the inferior parietal convolution by the horizontal portion of the intraparietal sulcus; and above it is continuous on the inner surface of the hemisphere with the quadrate lobe. The inferior parietal convolution is that portion of the parietal lobe which is situated between the ascending portion of the intraparietal sulcus in front, the horizontal portion of the same sulcus above, the horizontal limb of the fissure of Sylvius below, and the posterior boundary of the parietal lobe behind. It is sub- divided into two convolutions by an indistinct groove. One, the supramarginal, lies behind the lower end of the intraparietal sulcus and above the horizontal limb of the fissure of Sylvius. It is connected, in front, with the ascending parietal convolution beneath the intraparietal sulcus, and with the superior temporo-sphe- noidal convolution behind, round the posterior extremity of the fissure of Sylvius. The other, the angular, is connected in front with the foregoing, and with the middle temporo-sphenoidal convolution by a process which curves round the supe- 1 Professor Cunningham describes these two sulci, intraparietal and post-central, somewhat differ- ently. He regards them as both belonging to the intraparietal sulcus, which he divides into three parts: the ascending portion of the intraparietal, as described above, he terms the ramws verticalis infe- rior; the horizontal portion as the ramus horizontal is ; while the post-central sulcus he denominates the ramus verticalis superior. He states that considerable variability is exhibited in the relation to each other of these different parts of the intraparietal sulcus, but that the one in which the three parts of the sulcus are confluent is by far the most constant condition. Sometimes, however, the three parts of the sulcus may be all separate, or the ramus horizontalis confluent with the ramus verticalis infe- rior, the ramus verticalis superior remaining separate; or, again, the vertical limbs may be confluent and the horizontal limb separate; or, finally, the ramus horizontalis may be joined to the lower end of the ramus verticalis superior, while the lower vertical limb is separate. The connection which sometimes exists between the intraparietal sulcus and the occipital lobe he calls the ramus occipitalis. In the majority of cases, however, the occipital ramus is separated from the main portion of the intra- parietal sulcus by a superficial or deep bridging convolution (Journal of Anatomy and Physiology, vol. xxiv. part ii. p. 135). CONVOLUTIONS OF THE CEREBRUM. 721 rior temporo-sphenoidal or parallel sulcus. It is connected with the occipital lobe by the second annectant gyrus. The occipital lobe is triangular in shape and forms the posterior extremity of the hemisphere. It is bounded in front by the external parieto-occipital fissure and a line drawn from the extremity of this in the direction of the fissure across the outer surface of the hemisphere. It is continuous below' and in front with the temporo-sphenoidal lobe, and above with the parietal. It is divided on the outer surface of the hemisphere into three convolutions by two indistinct sulci-the superior and middle occipital sulci. They are directed backward across the lobe, being frequently small and ill-marked; the superior is sometimes continuous with the horizontal portion of the intraparietal sulcus. The superior occipital convolution is situated above the superior sulcus, and is connected to the superior parietal convolution by the first annectant gyrus. The middle occipital convolution is situated betw'een the superior and middle occipital sulci, and is connected to the angular convolution by the second annectant gyrus, and to the middle temporo-sphenoidal by the third annectant gyrus. The inferior occipital convolution is situated below' the middle occipital sulcus, and is sometimes separated from the external occipito-temporal convolution on the under surface of the hemisphere by an inconstant sulcus, the inferior occipital sul- cus. It is connected to the inferior temporo-sphenoidal convolution by the fourth annectant gyrus. The temporo-sphenoidal lobe is that portion of the hemisphere which is lodged in the middle fossa of the base of the skull. In front and above it is limited by the fissure of Sylvius ; behind, it is connected w ith the parietal and occipital lobes, and is limited artificially by a line continuing the direction of the external parieto- occipital fissure across the outer surface of the hemisphere. It is divided into three convolutions by two sulci. The superior of these runs parallel to the horizontal limb of the fissure of Sylvius. It is named the superior temporo- sphenoidal or parallel sulcus, and it is well marked and constant. The second, the middle temporo-sphenoidal, is not so well marked or constant; it takes the same course at a lower level. The superior temporo-sphenoidal convolution is situated between the horizontal limb of the fissure of Sylvius and the superior temporo-sphenoidal sulcus. It is continuous behind with the supramarginal convolution. The middle temporo-sphenoidal convolution is situated between the superior and middle sulci of the same name, and is continuous behind w ith the angular and middle occipital convolutions. The inferior temporo-sphenoidal convolution is situated below the middle temporo-sphenoidal sulcus, and is separated from the external occipito-temporal convolution, on the under surface of the hemisphere, by a sulcus which is called the inferior temporo-sphenoidal sulcus. It is connected with the inferior occipital convolution. The central lobe, or island of Beil (Fig. 417), is situated in the fissure of Sylvius, at the base of the brain ; it is separated, in front, from the posterior orbital convolution by a nearly transverse sulcus, the anterior sulcus of Heil; externally, from the inferior frontal convolution and the low'er ends of the ascending frontal and parietal convolutions by another deep sulcus, the external sulcus of Reil; and posteriorly, from the temporo-sphenoidal lobe, by a third sulcus, the posterior sulcus of Heil. It is a triangular-shaped prominent cluster of about six convolutions, the gyri operti, so called from being covered in by the fissure. By the removal of these convolutions the extraventricular part of the corpus striatum would be reached. On the inner or median surface of the hemispheres the arrangement of the convolutions is less complex; they are generally well defined, and some of them being of great length, there is not the same subdivision into smaller lobes as on the external surface (Fig. 418). The fissures in the internal surface are five in 722 THE NERVOUS SYSTEM. number, and are named the calloso-marginal, the parieto-occipital, the calcarine, the collateral, and the dentate. The calloso-marginal fissure is seen in front, commencing below the anterior extremity of the corpus callosum; it at first runs forward and upward, parallel with the rostrum of the corpus callosum, and, winding round the genu of that body, it continues from before backward, between the upper margin of the hemisphere and the convolution of the corpus callosum, to about midway between the anterior and posterior extremities of the brain, where it turns upward to reach the upper margin of the inner surface of the hemisphere a short distance behind the superior extremity of the furrow of Rolando. It separates the marginal convolution from the gyrus fornicatus or convolution of the corpus callosum. The parieto-occipital fissure (internal parieto-occipitaV) is the continuation of the fissure of the same name seen on the outer surface of the hemisphere. It Fig. 418.-Convolutions and fissures of the inner surface of the cerebral hemisphere. extends in an oblique direction downward and forward to join the calcarine fissure on a level with the hinder end of the corpus callosum. It separates the quadrate from the cuneate lobe. The calcarine fissure commences, usually by two branches, at the back of the hemisphere, runs nearly horizontally forward, and is joined by the parieto-occipital fissure, and continues nearly as far as the posterior extremity of the corpus callosum, to terminate a little belowr the level of this commissure. It separates the cuneate lobe from the uncinate gyrus, and causes the prominence known as the hippocampus minor or calcar avis, whence its name. The collateral fissure is situated belowr the preceding, being separated from it by the uncinate gyrus. It runs forward, from the posterior extremity of the brain, nearly as far as the commencement of the fissure of Sylvius. It runs between the internal and external occipito-temporal convolutions. It lies below the posterior and middle horn of the lateral ventricle, and causes the prominence known as the eminentia collateralis. The dentate or hippocampal fissure commences immediately below the posterior extremity of the corpus callosum, and runs forward to terminate at the recurved part of the uncinate gyrus. It corresponds with the prominence of the hippo- campus major in the descending horn of the lateral ventricle. The lobes or convolutions seen on the internal surface of the hemisphere are CONVOLUTIONS OF THE CEREBRUM. 723 six in number, and are named gyrus fornicatus, marginal, quadrate, cuneate, uncinate, or internal occipito-temporal, and the external occipito-temporal. The gyrus fornicatus, or convolution of the corpus callosum, is a well-marked lobe which begins just in front of the anterior perforated space at the base of the brain; it ascends in front of the genu of the corpus callosum, and runs backward along the upper surface of this body to its posterior extremity, where it joins the uncinate convolution. It is bounded above in the greater part of its extent by the calloso-marginal fissure, which separates it from the marginal convolution ; behind the spot where this fissure turns upward it is continuous with the quadrate lobe. The marginal convolution is situated above the preceding, and has received its Fig. 419.-Side view of the brain of man, showing the localization of various functions. (After Ferrier.) I. Centre for movements of opposite leg and foot. 2, 3,4. Centres for complex movements of the arms and legs, as in swimming. 5. Extension forward of the arm and hand. 6. Supination of the hand and flexion of the forearm. 7, 8. Elevators and depressors of the angle of the mouth. 9, 10. Movements of the lips and tongue. II. Retraction of the angle of the mouth. 12. Movements of the eyes. 13,13'. Vision. 14. Hearing, a, b. c, d. Movements of the wrists and fingers. name from its position along the border of the hemisphere. It commences in front of the anterior perforated space, runs along the margin of the longitudinal fissure on the under surface of the orbital lobe, being bounded externally by the sulcus for the olfactory tract; it then turns upward to the upper surface of the hemisphere and runs backward, forming the marginal convolution, on the inner surface, to the point where the calloso-marginal fissure turns upward to reach the superior border of the hemisphere. The quadrate lobe (precuneus') is the marginal convolution of the longitudinal fissure behind the calloso-marginal sulcus, lying between this fissure in front and the internal parieto-occipital behind. It joins the gyrus fornicatus below, and is continuous above with the superior parietal convolution. The cuneate or occipital lobule is triangular in shape, being situated between the internal parieto-occipital and calcarine fissures, which, as above mentioned, meet behind the posterior extremity of the gyrus fornicatus. The uncinate or internal occipito-temporal convolution extends from the posterior extremity of the hemisphere to the fissure of Sylvius, being bounded 724 THE NERVOUS SYSTEM. above by the calcarine and dentate fissure, and separated below from the external occipito-temporal convolution by the collateral fissure. From the anterior extremity a narrow portion is recurved or bent backward in the form of a hook, which is sometimes called the crochet or uncus. The back part of this convolu- tion-that is, the part below the calcarine fissure-is sometimes known as the lingual lobule or gyrus. The external occipito-temporal convolution is of considerable length, and lies between the collateral fissure and the inferior temporo-sphenoidal sulcus, which Fig. 420.-Top view of the brain of man, showing the localization of various functions. (After Ferrier.) References the same as in the preceding figure. latter separates it from the inferior temporo-sphenoidal convolution on the outer surface of the hemisphere. Besides the great primary convolutions above named and described, and which can be recognized in almost any well-developed brain, there are a great number of secondary convolutions which pass from one primary convolution to another, and often render the arrangement of the latter somewhat obscure ; of these, the connections of the occipital lobe, above mentioned, and which are named annectant convolutions, may be taken as examples. Cerebral Localization and Topography.-Within the last few years physiological and pathological research have gone far to prove that the surface of the brain may be mapped out into series of definite areas, each one of which is intimately connected with some well-defined function. And this is especially true with regard to the convolutions on either side of the fis- sure of Rolando, which are believed by most physiologists of the present day to be concerned in motion, those grouped around the fissure being associated with movements of the extremities of the opposite side of the body, and those around the lower end of the fissure being related to movements of the mouth and tongue. This is not the place, nor can space be given, to describe these localities. But the two accompanying woodcuts from Ferrier (Figs. 419, 420) have been introduced, and will serve to indicate the position of these areas as far as they have been at present ascertained. The relation of the principal fissures and convolutions of the cerebrum to the outer surface TOPOGRAPHY OF THE CEREBRAL CONVOLUTIONS. 725 of the scalp has been the subject of much recent investigation, and many systems have been devised by which one may localize these parts from an examination of the external surface of the head. These plans can only be regarded as approximately correct for several reasons : in the first place, because the relations of the convolutions and sulci to the surface are found to be very variable in different individuals; secondly, because the surface area of the scalp is greater than the surface area of the brain, so that lines drawn on the one cannot correspond exactly to sulci or convolutions on the other ; and thirdly, because the sulci and convolutions in two individuals are never precisely alike. Nevertheless, the principal fissures and convolutionscan be mapped out with sufficient accuracy for all practical purposes, so that any particular convolution can be generally exposed by removing with the trephine a certain portion of the skull's area. The various landmarks on the outside of the skull, which can be easily felt, and which serve Superior frontal fissure, i End of calloso- marginal Inferior frontal ' lobe. Parieto- occipital fissure. Fissure of Sylvius. Fig. 421.-Drawing to illustrate cranio-cerebral topography. (Macalister.) Taken from a cast prepared by Professor Cunningham. as indications of the position of the parts beneath, have been already referred to (see page 224), and the relation of the fissures and convolutions to these landmarks is as follows: Longitudinal Fissure.-This corresponds to a line drawn from the glabella at the root of the nose to the external occipital protuberance. The Fissure of Sylvius.-The position of the fissure of Sylvius and its horizontal limb is marked by a line starting from a point one inch and a quarter horjzontally behind the external angular process of the frontal bone to a point three-quarters of an inch below the most promi- nent point of the parietal eminence. The first three-quarters of an inch will represent the main fissure, the remainder the horizontal limb. The bifurcation of the fissure is, therefore, two inches behind and about a quarter of an inch above the level of the external angular process. The ascending limb of the fissure passes upward from this point parallel to, and immediately behind, the coronal suture. Fissure of Rolando.-To find the upper end of the fissure of Rolando, a measurement should be taken from the glabella to the external occipital protuberance. The position of the top of the sulcus will be, measuring from in front. 55.6 per cent, of the whole distance from the glabella to the external occipital protuberance. Professor Thane adopts a somewhat simpler method. He divides the distance from the glabella to the external occipital protuberance over the top of the head into two equal parts, and, having thus defined the middle point of the ver- 726 THE NERVOUS SYSTEM. tex, he takes half an inch behind it as the top of the sulcus. This is not quite so accurate as the former method, but it is sufficiently so for all practical purposes, and on account of its sim- plicity is very generally adopted. From this point the fissure runs downward and forward for 3$ inches, its axis making an angle of 67° with the middle line. In order to mark this groove, two strips of metal may be employed-one, the shorter, being fixed to the middle of the other at the angle mentioned. If the longer strip is now placed along the sagittal suture so that the junction of the two strips is over the point corresponding to the top of the furrow, the shorter, oblique strip will indicate the direction and 3| inches will mark the length of the furrow. Dr. Wilson has devised an instrument, called a cystometer, which combines the scale of measurements for localizing the fissure with data for representing its length and direction.1 Professor Thane gives the lower end of the furrow as "close to the posterior limb, and about half an inch behind the bifurcation of the fissure of Sylvius." So that, according to this anatomist, a line drawn from a point half an inch behind the mid-point between the glabella and external occipi- tal protuberance to this snot would mark out the fissure of Rolando. Dr. Reid adopts a differ- ent method (Fig. 422). He first indicates, on the surface the longitudinal fissure and the hori- zontal limb of the fissure of Sylvius (as above). He then draws two perpendicular lines from Fig. 422.-Relations of the principal fissures and convolutions of the cerebrum to the outer surface of the scalp. (Reid.) his "base-line" (that is, a line from the lowest part of the infra-orbital margin through the middle of the external auditory meatus to the back of the head) to the top of the cranium, one (d e, Fig. 422) from the depression in front of the external auditory meatus, and the other (f g, Fig. 422) from the posterior border of the mastoid process at its root. He has thus described on the surface of the head a four-sided figure (f d g e, Fig. 422), and a diagonal line from the posterior superior angle to the anterior perpendicular line where it is crossed by the fissure of Sylvius will represent the furrow. The parieto-occipital fissure on the upper surface of the cerebrum runs outward at right angles to the great longitudinal fissure for about an inch, from a point one-fifth of an inch in front of the lambda (posterior fontanelle). Reid states that if the horizontal limb of the fissure of Sylvius be continued onward to the sagittal suture, the last inch of this line will indicate the position of the sulcus. The precentral sulcus lies in a line drawn vertically downward from the point of junction of the sagittal and coronal sutures. It begins four-fifths of an inch in front of the middle of the fissure of Rolando, and extends nearly, but not quite, to the horizontal limb of the fissure of Sylvius. The superior frontal fissure runs backward from the supra-orbital notch, parallel with the line of the longitudinal fissure to two-fifths of an inch in front of the line indicating the position of the fissure of Rolando. 1 Lancet, vol. i., 1888, p. 408. THE UNDER SURFACE OR THE BASE OF THE BRAIN. 727 The inferior frontal fissure follows the course of the superior temporal ridge on the frontal bone. The intraparietal fissure begins on a level with the junction of the middle and lower third of the fissure of Rolando, on a line carried across the head from the back of the root of one auricle to that of the other. After passing upward it curves backward, lying parallel to the longitudinal fissure, midway between it and the parietal eminence; it then curves downward to end midway between the posterior fontanelle and the parietal eminence. Under Surface or Base or the Cerebrum (Fig. 423). The under surface of each hemisphere presents a subdivision into three lobes, named, from their position, anterior, middle, and posterior. The anterior or frontal lobe, of a triangular form, with its apex backward, is -Frontal lobe. ■Posterior division °f Sylvian fissure. • Temporo- sphenoidal lobe. -Occipital lobe. Fig. 423.-Base of the brain. somewhat concave, and rests upon the convex surface of the roof of the orbit, being separated from the middle lobe by the fissure of Sylvius. The middle lobe, which is more prominent, is received into the middle fossa of the base of the skull, and comprises the under part of the temporo-sphenoidal lobe. The posterior or occip- ital lobe rests upon the tentorium, its extent forward being limited by the ante- rior margin of the cerebellum. The various objects exposed to view on the under surface of the cerebrum, in and near the middle line, are here arranged in the order in which they are met with from before backward: 728 THE NERVOUS SYSTEM. Longitudinal fissure. Corpus callosum and its peduncles. Lamina cinerea. Olfactory tract. Fissure of Sylvius. Anterior perforated space. Optic commissure. Tuber cinereum. Infundibulum. Pituitary body. Corpora albicantia. Posterior perforated space. The longitudinal fissure partially separates the two hemispheres from each other: it divides the two frontal lobes in front, and on raising the cerebellum and pons it will be seen completely separating the two occipital lobes. Of these two portions of the longitudinal fissure, that which separates the occipital lobes is the longer. The intermediate portion of the fissure is filled up by the great transverse band of white matter, the corpus callosum. In the fissure between the two frontal lobes the anterior cerebral arteries ascend on the corpus callosum. The corpus callosum terminates at the base of the brain by a concave margin which is connected with the tuber cinereum through the intervention of a thin layer of gray substance, the lamina cinerea. This may be exposed by gently raising and drawing back the optic commissure. A white band may be observed on each side, passing from the under surface of the corpus callosum, backward and out- ward to the commencement of the fissure of Sylvius : these bands are called the peduncles of the corpus callosum. They may be traced upward around the genu to become continuous with the strice longitudinales. or nerves of Lancisi, on the upper surface of the corpus callosum (page 732). Laterally, this portion of the corpus callosum extends into the frontal lobe. The lamina cinerea is a thin layer of gray substance, extending backward above the optic commissure from the termination of the corpus callosum to the tuber cinereum ; it is continuous on each side with the gray matter of the anterior per- forated space, and forms the anterior part of the inferior boundary of the third ventricle. The olfactory tract, with its bulb, is seen on each side of the longitudinal fissure upon the under surface of each frontal lobe. The fissure of Sylvius separates the frontal from the temporo-sphenoidal lobe, and lodges the middle cerebral artery. It begins at the outer side of a depression, at the bottom of which is the anterior perforated space. This depression is called the vallecula Sylvii. At its commencement is seen a point of medullary substance, corresponding to a subjacent band of white fibres, connecting the frontal and temporo-sphenoidal lobes, and called the fasciculus unciformis. On following this fissure outward, it divides into two branches, enclosing portions of the frontal and parietal lobes, which overhang and cover the upper part of a prominent cluster of isolated convolutions called the island of Reil or central lobe. The overhanging portion of the frontal and parietal lobe is called the operculum of the insula. The anterior perforated space is situated at the inner side of the fissure of Sylvius. It is of a triangular shape, bounded in front, by the orbital convolutions of the frontal lobe and the roots of the olfactory tract; behind, by the optic tract; externally, by the temporo-sphenoidal lobe and commencement of the fissure of Sylvius; internally, it is continuous with the lamina cinerea and crossed by the peduncle of the corpus callosum. It is of a grayish color, and corresponds to the under surface of the corpus striatum, a large mass of gray matter situated in the interior of the brain ; it has received its name from being perforated by numerous minute apertures for the transmission of small straight vessels into the substance of the corpus striatum, constituting the antero-median and antero-lateral ganglionic branches of the anterior and middle cerebral arteries. The optic commissure is situated in the middle line, immediately in front of the tuber cinereum and below the lamina cinerea.1 It is the point of junction between the two optic nerves. Crura cerebri 1 That is to say, the commissure is superficial to the lamina in the order of dissection when the base is uppermost. THE BASE OF THE BRAIN. 729 Immediately behind the diverging optic tracts, and between them and the peduncles of the cerebrum (crura cerebri), is a lozenge-shaped interval, the inter- peduncular space, in which are found the following parts: the tuber cinereum, infundibulum, pituitary body, corpora albicantia, and the posterior perforated space. The tuber cinereum is an eminence of gray matter situated between the optic tracts and the corpora albicantia ; it is connected with the surrounding parts of the cerebrum, forms part of the floor of the third ventricle, and is continuous with the gray substance in that cavity. From the middle of its under surface a conical tubular process of gray matter, about two lines in length, is continued downward and forward, to be attached to the posterior lobe of the pituitary body : this is the infundibulum. Its canal, which is funnel-shaped, communicates with the third ventricle. The pituitary body (hypophysis cerebri) is a small reddish-gray vascular mass weighing from five to ten grains, and of an oval form, situated in the sella Turcica, in connection with which it is retained by a process of dura mater derived from the inner wall of the cavernous sinus. This process covers in the pituitary fossa, enclosing the pituitary body, and having a small hole in its centre through which the infundibulum passes. Structure.-The pituitary body is very vascular, and consists of two lobes, separated from one another by a fibrous lamina. Of these, the anterior is the larger, of an oblong form and somewhat concave behind, where it receives the posterior lobe, which is round. The two lobes differ both in development and structure. The anterior lobe, of a dark, yellowish-gray color, is developed from the ectoderm of the buccal cavity, and resembles to a considerable extent, in micro- scopic structure, the thyroid body. It consists of a number of isolated vesicles and slightly convoluted alveoli lined by epithelium and united together by connective tissue. The epithelium is columnar, and occasionally ciliated. The alveoli some- times contain a colloid material, similar to that found in the thyroid body, and their walls are surrounded by a close network of lymphatics and capillary blood- vessels. The posterior lobe is developed by an outgrowth from the embryonic brain, and during foetal life contains a cavity which communicates through the infundibulum with the cavity of the third ventricle. In the adult it becomes firmer and more solid, and consists of a sponge-like connective tissue arranged in the form of reticulating bundles, between which are branched cells, some of them containing pigment. In the lower animals the two lobes are quite distinct, and it is only in the mammalia that they become connected together. The corpora albicantia, or mammillaria, are two small, round, white masses, each about the size of a pea, placed side by side immediately behind the tuber cinereum. They are formed by the anterior crura of the fornix, hence called the bulbs of the fornix, which, after descending to the base of the brain, are folded upon themselves before passing upward to the thalami optici. They are composed externally of white substance and internally of gray matter, the gray matter of the two being connected by a transverse commissure of the same material. At an early period of foetal life they are blended together into one large mass, but become separated about the seventh month. The posterior perforated space (pons Tarini) corresponds to a whitish-gray substance placed between the corpora albicantia in front, the ponsVarolii behind, and the crura cerebri on each side. It forms the back part of the floor of the third ventricle. It is perforated by numerous small orifices for the passage of the postero-median ganglionic branches of the posterior cerebral and posterior communicating arteries. The crura cerebri (peduncles of the cerebrum) are two thick cylindrical bundles of white matter which emerge from the anterior border of the pons and diverge as they pass forward and outward to enter the under part of either hemisphere. Each crus is about three-quarters of an inch in length, and somewhat broader in front than behind. They are marked upon their surface with longitudinal striae, 730 THE NERVOUS SYSTEM. and each is crossed, just before entering the hemisphere, by a flattened white band, the optic tract, which is adherent by its upper border to the peduncle. The third nerve may be seen emerging from a groove on the inner side of each crus, and the fourth nerve winding round its outer side from above. Structure of the Crura.-Each crus consists of a superficial layer of longitudinal white fibres, the crusta, continued upward from the pons; of a deeper layer, a prolongation of the reticular formation, termed the tegmentum ; and of an inter- mediate stratum of gray matter, the locus niger. The crusta, or the superficial layer of longitudinal fibres, consists of coarse bundles of nerve-fibres which are collected on the under or free surface of the crus. It is formed almost entirely of longitudinal fibres continuous with the pyramidal fibres of the medulla and pons, those derived from the medulla occupying the central portion of the crusta, those added in the pons being placed laterally. The fibres pass to the cerebral hemispheres, entering the internal capsule. The tegmentum forms the deeper part of the crus cerebri, and is united below with its fellow of the opposite side by a prolongation of the septum of the pons, but separated above by the posterior perforated space. It consists of longitudinal bundles of white fibres interlaced by transverse fibres, together with a quantity of gray matter with scattered nerve-cells. It forms a well-marked formatio reticularis similar to that found in the pons and medulla, with which it is continuous, receiving, however, a bundle of fibres (superior peduncle} from the cerebellum. Above, the fibres enter the optic thalamus. The locus niger is a mass of gray matter situated between the crusta and tegmentum, and projecting here and there between the bundles of the former. It is thicker at the inner than at the outer side, and is traversed in its mesial part by the fibres of origin of the third nerve. It contains irregular nerve-cells, in which are lodged numerous dark pigment-granules. The posterior lobes of the cerebrum are concealed from view by the upper surface of the cerebellum and pons Varolii. When these parts are raised, the two hemispheres are seen to be separated by the great longitudinal fissure, this fissure being interrupted by the posterior rounded border of the corpus callosum. General Arrangement of the Parts composing the Cerebrum. As the peduncles or crura of the cerebrum enter the hemispheres they diverge from one another, so as to leave an interval between them, the interpeduncular space. As they ascend the component fibres of each pass through two large masses of gray matter, the ganglia of the brain, called the thalamus opticus and corpus striatum, which project as rounded eminences from the upper and inner side of each peduncle. The hemispheres are connected together, above these masses, by the great transverse commissure, the corpus callosum ; the interval left between its under surface, the upper surface of the ganglia, and the parts closing the inter- peduncular space forms the general ventricular cavity. The upper part of this cavity is subdivided into two by a vertical septum, the septum lucidum ; and thus the two lateral ventricles are formed. The lower part of the cavity forms the third ventricle, which communicates with the lateral ventricles above and with the fourth ventricle behind. The fifth ventricle is the interval left between the two layers composing the septum lucidum. The Interior of the Cerebrum. If the upper part of either hemisphere is removed with a scalpel about half an inch above the level of the corpus callosum, its internal white matter will be exposed. It is an oval-shaped centre, of white substance, surrounded on all sides by a narrow convoluted margin of gray matter, which presents an equal thickness in nearly every part. This white central mass has been called the centrum ovale minus. Its surface is studded with numerous minute red dots (puncta vasculosd), produced by the escape of blood from divided blood-vessels. In inflammation or 7VZZ? INTERIOR OF THE CEREBRUM. 731 great congestion of the brain these are very numerous and of a dark color. If the remaining portion of one hemisphere is slightly separated from the other, a broad band of white substance will be observed connecting them at the bottom of the longitudinal fissure; this is the corpus callosum. The margins of the hemi- spheres which overlap this portion of the brain are called the labia cerebri. Each labium is part of the convolution of the corpus callosum (gyrus fornicatus), already described, and the space between it and the upper surface of the corpus callosum has been termed the ventricle of the corpus callosum (Fig. 427). The hemispheres should now be sliced off to a level with the corpus callosum, when the white substance of that structure will be seen connecting the two hemispheres. The large expanse of medullary matter now exposed, surrounded by the convoluted margin of gray substance, is called the centrum ovale majus of Vieussens. The corpus callosum is a thick stratum of transverse fibres exposed at the bottom of the longitudinal fissure. It connects the two hemispheres of the brain, Fig. 424.-Section of the brain. Made on a level with the corpus collosum. forming their great transverse commissure, and forms the roof of a space in the interior of each hemisphere, the lateral ventricle. It is about four inches in length, extending to within an inch and a half of the anterior, and to within two inches and a half of the posterior, part of the brain. It is somewhat broader behind than in front, and is thicker at either end than in its central part, being thickest behind. It presents a somewhat arched form (Fig. 431, 5) from before backward, terminating anteriorly in a rounded border, which curves, downward and backward, between the frontal lobes to the base of the brain. In its course it forms a distinct bend, named the genu, and is then continued downward and 732 THE NERVOUS SYSTEM. backward to the base of the brain, where it is connected, through the lamina cinerea, with the tuber cinereum. The reflected portion of the corpus callosum is called the beak or rostrum: it becomes gradually narrower as it descends, and is attached by its lateral margins to the frontal lobes. At its termination the corpus callosum gives off two bundles of white substance, which, diverging from one another, pass backward, across the anterior perforated space, to the entrance of the fissure of Sylvius. They are called the peduncles of the corpus callosum. Posteriorly, the corpus callosum forms a thick rounded fold, called the splenium or pad, which is free for a little distance as it curves forward, and is then continuous with the fornix. On its upper surface the structure of the corpus callosum is very apparent, being collected into coarse transverse bundles. Along the middle line is a linear depression, the raphe, bounded laterally by two or more slightly elevated longitudinal bands, called the strice longitudinales or nerves of Lancisi; and, still more externally, other longitudinal striae are seen beneath the convolutions which rest on the corpus callosum. These are the strice longitudinales laterales or tcenice tectce. The under surface of the corpus callosum is continuous behind with the fornix, being separated from it in front by the septum lucidum, which forms a vertical partition between the two ventricles. On each side the fibres of the corpus callosum extend into the substance of the hemispheres, connecting them together. The greater thickness of the two extremities of this commissure is explained by the fact that the fibres from the anterior and posterior parts of each hemisphere cannot pass directly across, but have to take a curved direction. An incision should now be made through the corpus callosum on either side of the raphe, when two large irregular-shaped cavities will be exposed, which extend through a great part of the length of each hemisphere. These are the lateral ventricles. The lateral ventricles are serous cavities, formed by the upper part of the general ventricular space in the interior of the brain. They are lined by a thin diaphanous lining membrane (the ependyma), covered by nucleated epithelium, with cilia scattered here and there in patches. It is moistened by a serous fluid, which is sometimes, even in health, secreted in considerable quantity. These cavities are two in number, one in each hemisphere, and they are separated from each other by a vertical septum, the septum lucidum. Each lateral ventricle consists of a central cavity, or body, and three smaller cavities or cornua, which extend from it in different directions. The anterior cornu curves forward and outward into the substance of the frontal lobe. The posterior cornu, called the digital cavity, curves backward into the occipital lobe. The middle cornu descends into the temporo-sphenoidal lobe. The central cavity, or body of the lateral ventricle, is triangular in form. It is bounded, above, by the under surface of the corpus callosum, which forms the roof of the cavity. Internally is a vertical partition, the septum lucidum, which separates it from the opposite ventricle, and connects the under surface of the corpus callosum with the fornix. Its floor is formed by the following parts, enumerated in their order of position from before backward: the corpus striatum, tcenia semicircularis, optic thalamus, choroid plexus, fornix, and commencement of its corpus fimbriatum. The anterior cornu is triangular in form, passing outward into the frontal lobe and curving round the anterior extremity of the corpus striatum. It is bounded, above, by the corpus callosum; below and externally, by the corpus striatum; and in front, by the reflected portion of the corpus callosum. The posterior cornu, or digital cavity, curves backw'ard into the substance of the occipital lobe, its direction being backward and outward, and then inward. On its inner wall is seen a longitudinal eminence, which is produced by the extension inward of the calcarine sulcus; this is called the hippocampus minor, or calcar avis. Between the middle and posterior horns a smooth eminence is observed which varies considerably in size in different subjects. It is called the eminentia collateralis. THE INTERIOR OF THE CEREBRUM. 733 The middle or descending cornu, the largest of the three, traverses the middle lobe of the brain, forming in its course a remarkable curve round the back of the optic thalamus. It passes, at first, backward, outward, and downward, and then curves round the crus cerebri, forward and inward, nearly to the point of the middle lobe, close to the fissure of Sylvius. Its upper boundary, or roof, is formed by the fibres of the corpus callosum, passing downward and outward into the temporo-sphenoidal lobe, with which are incorporated the posterior fibres of the nucleus caudatus and taenia semicircularis, which are prolonged into it. Its lower boundary, or floor, presents for examination the following parts: the hippocampus major, pes hippocampi, eminentia collateralis or pes accessorius, corpus fimbriatum of the fornix, choroid plexus, fascia dentata, transverse fissure. The corpus striatum has received its name from the striped appearance which Fig. 425.-The lateral ventricles of the brain. its section presents, in consequence of diverging white fibres being mixed with the gray matter which forms the greater part of its substance. The greater portion of this body is imbedded in the white substance of the hemisphere, and is there- fore external to the ventricle. It is termed the extraventricular portion, or the nucleus lenticularis ; a part, however, is visible in the ventricle and its anterior cornu ; this is the intraventricular portion, or the nucleus caudatus. The intra- ventricular portion is a pear-shaped mass of gray matter: its broad extremity is directed forward into the fore part of the body and anterior cornu of the lateral ventricle; its narrow end is directed outward and backward, and lies on the outer side of the optic thalamus, and is continued into the roof of the descending cornu ; it is covered by the serous lining of the cavity and crossed by some veins of con- siderable size. It is separated from the extraventricular portion by a lamina of 734 THE NERVOUS SYSTEM. white matter, which is called the internal capsule, in contradistinction to a lamina of white matter which covers the outer surface of the extraventricular portion of the corpus striatum, and which is called the external capsule. The internal capsule is formed by fibres of the crusta of the crus cerebri, supplemented by fibres derived from the nuclei on each side. In horizontal section it is seen to be somewhat abruptly curved, with its convexity inward; the prominence of the curve is called the genu, and projects between the intraventricular portion of the corpus striatum and the optic thalamus (Fig. 426). The extraventricular portion of the corpus striatum, or nucleus lenticularis, is oval in form. It does not extend as far forward or backward as the nucleus caudatus. It is bounded externally by a lamina of white matter called the external capsule, which is covered on its outer surface Genu of Corp. Callosum. Caudate Splemum of Corp. Callosum. Mid. Cor'nui of lat.Vent.t Fig. 426.-Middle part of a horizontal section through the cerebrum at the level of the dotted line in the small figure of one hemisphere. (From Ellis, after Dalton.) by a thin layer of gray matter termed the claustrum. The claustrum presents ridges and furrows on its outer surface, corresponding to the convolutions and sulci of the island of Reil, with the white matter of which it is in immediate relation. The taenia semicircularis is a narrow, whitish, semi-transparent band of medullary substance situated in the depression between the nucleus caudatus and optic thalamus. Anteriorly, it descends, in connection with the anterior pillar of the fornix, to below the level of the foramen of Monro, where it enters a mass of gray matter, the nucleus amygdalae. Behind, it is continued into the roof of the middle or descending horn of the lateral ventricle, and is lost near the bottom of the cornua. Beneath it is a large vein (vena corporis striati), which receives numerous small veins from the surface of the corpus striatum and optic thalamus, and joins the venae Galeni. THE INTERIOR OF THE CEREBRUM. 735 The choroid plexus is a highly vascular, fringe-like membrane, occupying the margin of the fold of pia mater (velum interpositum) in the interior of the brain. It extends, in a curved direction, across the floor of the lateral ventricle. In front, where it is small and tapering, it communicates with the choroid plexus of the opposite side through an oval aperture, the foramen of Monro. Posteriorly, it descends into the middle horn of the lateral ventricle, where it joins with the pia mater through the transverse fissure. In structure it consists of minute and highly vascular villous processes, composed of large round corpuscles, containing, besides a central nucleus, several yellowish granules and fat-molecules, and covered by a single layer of flattened epithelium. The arteries of the choroid plexus enter Gray matter White matter Ventricle of corpus callosum. Corpus callosum. Lateral ventricle. Hippocampus major. Pons Parolii. Cerebellum. Auditory nerve. Pneumogastric nerve. Fig. 427-Transverse vertical section of the brain, through the fore part of the foramen magnum, looked at from the front. (After Hirschfeld and Leveille.) the ventricle at the descending cornu, and, after ramifying through its substance, send branches into the substance of the brain. The veins of the choroid plexus terminate in the venae Galeni. The corpus fimbriatum (tcenia hippocampi) is a narrow, white, tape-like band situated immediately behind the choroid plexus. It is the thin lateral edge of the posterior pillar of the fornix, and is attached along the inner border of the hippo- campus major as it descends into the middle horn of the lateral ventricle. It may be traced as far as the crochet oi' hook of the uncinate convolution. The optic thalamus and fornix will be described on a subsequent page. The middle cornu should now be exposed throughout its entire extent, by introducing the little finger gently into it, and cutting outward along the finger through the substance of the hemisphere, which should be removed to an extent sufficient to expose the entire cavity. The hippocampus major, or cornu Ammonis (Fig. 428), so called from its resem- blance to a ram's horn, is a white eminence, of a curved elongated form, extending throughout the entire length of the floor of the middle horn of the lateral ventricle. At its lower extremity it becomes enlarged, and presents a number of rounded elevations with intervening depressions, which, from presenting some resemblance to the paw of an animal, is called the pcs hippocampi. If a transverse section is made through the hippocampus major (Fig. 427), it will be seen that this 736 THE NERVOUS SYSTEM. eminence is produced by the extension inward of the dentate (hippocampal) sulcus on the exterior of the brain. This sulcus is filled with gray substance, which projects along the free margin of the hippocampus major, forming a notched ridge, the/ascm dentata. The hippocampus is covered on its ventricular surface by a thin lamina of gray matter, w'hich is continuous with the corpus fimbriatum of the fornix. The eminentia collateralis, or pes accessorius, has already been mentioned as a white eminence, varying in size, placed between the hippocampus major and hippocampus minor, at the junction of the posterior with the descending cornu. It is formed by the protrusion inward of the collateral fissure. Fascia Dentata.-On separating the inner border of the corpus fimbriatum from the choroid plexus, and raising the edge of the former, a serrated band of gray substance, the edge of the gray substance in the dentate fissure, will be seen beneath it: this is the fascia dentata. Correctly speaking, it is placed external to the cavity of the descending cornu. The transverse fissure is of a horseshoe shape, extending from the end of the descending cornu on one side to the same point on the opposite side. Its Eminentia I collateralis. J Hippocampus major. Fascia dentata. Gray matter of the hippocampus. Uncinate convolution. Uncinate process. Fig. 428.-Transverse section of the middle horn of the lateral ventricle. (From a drawing by Mr. F. A. Barton.) horizontal portion (which extends from the commencement of the descending cornu on one side to the same point on the opposite side) is bounded, above, by the splenium, or rounded posterior extremity of the corpus callosum and the fornix; below, by the corpora quadrigemina, pineal gland, and the posterior extremity of the optic thalamus. Its lateral portions curve downward, forward, and inward, and are bounded above by the crura cerebri and optic thalamus, below by the hippocampus major and the corpus fimbriatum of the fornix. Through this fissure the pia mater passes from the exterior of the brain into the ventricles, to form the velum interpositum and the choroid plexuses. Where the pia mater projects into the lateral ventricle, beneath the edge of the fornix, it is connected with the lining membrane of these cavities, so as to exclude all communication with the exterior of the brain. The septum lucidum (Fig. 431, 6) forms the internal boundary of the lateral ventricles. It is a thin, semitransparent septum, attached, above, to the under surface of the corpus callosum; below, to the anterior part of the fornix ; and, in front of this, to the reflected portion of the corpus callosum. It is triangular in form, broad in front, and narrow behind, its surfaces looking toward the cavi- ties of the ventricles. The septum consists of twTo laminae, separated by a narrow interval, the fifth ventricle. THE INTERIOR OF THE CEREBRUM. 737 Fifth Ventricle.-The fifth ventricle was originally a part of the great longi- tudinal fissure, which has become shut off' by the union of the hemispheres in the formation of the corpus callosum above and the fornix below. Its walls are there- fore formed by the median wall of the hemispheres, and consist of an internal layer of gray matter, derived from the gray matter of the cortex and an external layer of white substance continuous with the white matter of the cerebral hemi- spheres. This is lined on its external surface by the ependyma of the lateral ventricles. The fifth ventricle is not lined by epithelium. In the foetus and in some animals this space communicates, below, with the third ventricle, but in the adult it forms a separate cavity. In cases of serous effusion into the ven- tricles the septum is often found softened and partially broken down. The fifth ventricle may be exposed by cutting through the septum and attached portion of the corpus callosum with scissors: after its examination the corpus callosum should be cut across, toward its anterior part, and the two portions carefully dissected, the one forward, the other backward, when the fornix will be exposed. The fornix (Figs. 425, 431) is a longitudinal lamella of white fibrous matter situated beneath the corpus callosum, with which it is continuous behind, but separated in front by the septum lucidum. It may be described as consisting of two symmetrical halves, one for either hemisphere. These two portions are joined together in the middle line, "where they form the body, but are separated from one another in front and behind, forming the anterior and posterior crura. The body of the fornix is triangular ; narrow in front, broad behind. Its upper surface is connected, in the median line, to the septum lucidum in front and the corpus callosum behind, while laterally this surface forms part of the floor of each lateral ventricle. Its under surface rests upon the velum interposition, which separates it from the third ventricle, and the inner portion of the optic thalami. Its outer edge, on each side, is in contact with the choroid plexuses. The anterior crura arch downward toward the base of the brain, separated from each other by a narrow interval. They are composed of white fibres, which descend through a quantity of gray matter in the lateral walls of the third ven- tricle, and are placed immediately behind the anterior commissure. At the base of the brain the white fibres of each crus form a sudden curve upon themselves, and spread out and form the outer part of the corresponding corpus albicans, from which point they may be traced upward into the substance of the corresponding optic thalamus (Fig. 431). The anterior crura of the fornix are connected in their course with the peduncle of the pineal gland and the superficial fibres of the taenia semicircularis, and receive fibres from the septum lucidum. Between the anterior crura or pillars of the fornix and the anterior extremities of the optic thalami an oval aperture is seen on each side : this is the foramen of Monro (Fig. 430). The two openings descend toward the middle line and lead into the upper part of the third ventricle. Through these openings the lateral ventricles on each side communicate with the third ventricle, and consequently with each other. The posterior crura, at their commencement, are intimately connected by their upper surfaces with the corpus callosum ; diverging from one another, they pass downward into the descending horn of the lateral ventricle, being continuous with the concave border of the hippocampus major. The lateral thin edges of the posterior crura have received the name of corpus fimbriatum. Upon examining the under surface of the fornix, between its diverging posterior crura, a triangular portion of the under surface of the corpus callosum may be seen. On it are a number of lines, some transverse, others longitudinal or oblique. This portion has been termed the lyra, from the fancied resemblance it bears to the strings of a harp. Divide the fornix across anteriorly, and reflect the two portions, the one forward, the other backward, when the velum interpositum will be exposed. The velum interpositum (Fig. 429) is a vascular membrane, a prolongation from 738 THE NERVOUS SYSTEM. the pia mater into the interior of the brain through the transverse fissure, passing beneath the posterior rounded border of the corpus callosum and fornix, and above the corpora quadrigemina, pineal gland, and optic thalami. It is of a triangular form, and separates the under surface of the body of the fornix from the cavity of the third ventricle. Its posterior border forms an almost complete investment for the pineal gland. Its anterior extremity, or apex, is bifid : each bifurcation has attached to it the anterior extremity of the choroid plexus of the lateral ventricle through the foramen of Monro. On its under surface are the choroid plexuses of the third ventricle. To its lateral margins are connected the choroid plexuses of the lateral ventricles. Of the arteries of the velum interpositum some branches Fig. 429.-The fornix, velum interpositum, and middle or descending cornu of the lateral ventricle. from the superior cerebellar and posterior cerebral enter from behind beneath the corpus callosum ; another constant branch, the anterior choroid, enters the velum interpositum at the extremity of the middle horn of the lateral ventricle, and supplies this structure and the choroid plexus. The veins of the velum interpositum, the vena? G-aleni, two in number, run between its layers ; they are formed by the venae corporis striati and the veins of the choroid plexuses; the venae Galeni unite posteriorly into a single trunk, which terminates in the straight sinus (Fig. 383). The velum interpositum should now be removed. This must be effected carefully, especially at its posterior part, where it invests the pineal gland ; the optic thalami will then be exposed, with the cavity of the third ventricle between them (Fig. 430). The optic thalami are two large oblong masses, placed between the diverging portions of the corpora striata ; they are of a white color superficially ; internally THE INTERIOR OF THE CEREBRUM. 739 they are composed chiefly of gray matter. Each thalamus rests upon its corre- sponding crus cerebri, which it embraces. Externally, it is separated from the corpus striatum by the teenia semicircularis. Internally, it forms the lateral boundary of the third ventricle, and running along its upper and inner border is seen the peduncle of the pineal gland. Its upper surf ace is free, being partly seen in the lateral ventricle; it is partially covered by the velum interpositum and fornix, and marked in front by an eminence, the anterior tubercle. Its under sur- face is united with the tegmentum of the crus cerebri. Its posterior extremity projects above the level of the corpora quadrigemina and crus cerebri, and inter- nally forms a well-marked prominence, the posterior tubercle or pulvinar, and below and outside this it presents two small rounded eminences, the internal and external geniculate bodies. Its anterior extremity, which is narrow, forms the posterior boundary of the foramen of Monro. Fig. 430.-The third and fourth ventricles. An arrow has been placed in the position of the foramen of Monro. The Third Ventricle is the narrow oblong fissure placed between the optic thalami and extending to the base of the brain. It is bounded, above, by the under surface of the velum interpositum, from which are suspended the choroid plexuses of the third ventricle. Its floor, somewhat oblique in its direction, is formed, from before backward, by the parts which are contained in the interpe- duncular space-viz. the lamina cinerea, the tuber cinereum and infundibulum, the corpora albicantia and the locus perforatus posticus-and behind these by the tegmenta of the crura cerebri; its sides are formed by the optic thalami, along the upper and inner border of which are two white tracts, one on each side, the pedun- cles of the pineal gland. It is bounded, in front, by the anterior crura of the 740 THE NERVOUS SYSTEM. fornix and part of the anterior commissure; behind, by the posterior commissure and the iter a tertio ad quartum ventriculum. The cavity of the third ventricle is crossed by three commissures, named, from their position, anterior, middle, and posterior. The anterior commissure is a round bundle of white fibres, placed in front of the anterior crura of the fornix, and appears to connect together the corpora striati. It passes outward through the corpus striatum on each side, and then curves back- ward into the substance of the temporo-sphenoidal lobe. The middle or soft commissure consists almost entirely of gray matter. It connects together the optic thalami, and is continuous with the gray matter lining the anterior part of the third ventricle. It is frequently broken in examining the brain, and might then be supposed to be wanting. The posterior commissure, smaller than the anterior, is a flattened white band of fibres, and appears to connect together the optic thalami posteriorly. It con- sists of decussating fibres which come from the tegmentum of the crus cerebri on one side, and pass through the optic thalami, across the back part of the third ventricle, to the white substance of the temporo-sphenoidal lobe of the other side. Some of the fibres may also serve as commissural fibres between the optic thal- ami. It bounds the third ventricle posteriorly, above the opening of the Sylvian aqueduct. The pineal gland is placed above it and connected to its upper surface. The third ventricle has four openings connected with it. In front are the two oval apertures of the foramina of Monro, one on each side, through which the third communicates with the lateral ventricles. Behind is a third opening, leading into the fourth ventricle by a canal, the aqueduct of Sylvius, or iter a tertio ad quartum ventriculum. The fourth, situated in the anterior part of the floor of the ventricle, is a deep pit, which leads downward to the funnel-shaped cavity of the infundibulum (iter ad infundibulum). A fifth opening existed in the foetus, which communicated behind with a cavity in the pineal gland. A sixth opening also existed in the foetus, which communicated in front with the fifth ventricle. The lining membrane of the lateral ventricles is continued through the foramen of Monro into the third ventricle, and extends along the iter a tertio into the fourth ventricle; at the bottom of the iter ad infundibulum it ends in a cul-de-sac. The foramen of Monro is a foramen by which each lateral ventricle communi- cates with the third ventricle. It is formed by the anterior extremity of the body of the fornix, which, dividing into its two crura, arches downward in front of the anterior extremity of the optic thalami; the crus is not, however, in con- tact with the thalamus, but an interval is left between the two, which is the fora- men of Monro. Its boundaries are, therefore, in front, the anterior pillars of the fornix ; behind, the anterior extremity of the optic thalamus; above, the body of the fornix ; and below, the groove between the anterior pillars of the fornix and the optic thalamus. Behind the third ventricle, and in front of the cerebellum, are the corpora quadrigemina, and, resting upon these, the pineal gland. The pineal gland (epiphysis cerebri), so named from its peculiar shape (pinus, a fir-cone), is a small reddish-gray body, conical in form (hence its synonym, conarium), placed immediately behind the posterior commissure and between the nates, upon which it rests. It is retained in its position by a duplicature of pia mater, derived from the under surface of the velum interpositum, which almost completely invests it. The pineal gland is about four lines in length and from two to three in width at its base, and is said to be larger in the child than in the adult, and in the female than in the male. Its base is connected to the cerebrum by two peduncles (the peduncles of the pineal gland), which pass forward upon the upper and inner margin of the optic thalami to the anterior crura of the for- nix, with which they become blended; these two peduncles join together at their posterior extremity, in front of the pineal gland, forming a sort of festoon, and THE INTERIOR OF THE CEREBRUM. 741 the base of the gland is connected to their posterior margin at the point of junc- tion. In front the band of union is joined to the posterior commissure. Structure.-The pineal gland consists of a number of follicles lined by epithe- lium and connected together by ingrowths of connective tissue. The follicles contain a transparent viscid fluid, and a quantity of sabulous matter, named acervulus cerebri, composed of phosphate and carbonate of lime, phosphate of magnesia and ammonia, with a little animal matter. These concretions are almost constant in their existence, and are found at all periods of life. When Fig. 431.-Vertical median section of the encephalon, showing the parts in the middle line. 1. Convolution of the corpus callosum. Above it is the cal- loso-marginal fissure, running out at 2 to join the fissure of Rolando. 3. The parieto-occipital fissure. 4. 4 point to the calcarine fissure, which is just above the numbers Between 2 and 3 are the convolutions of the quadrate lobe. Between 3 and 4 is the cuneate lobe. 5. The corpus callosum. 6. The septum lucidum. 7. The fornix. 8. Anterior crus of the fornix, descending to the base of the brain, and turning on itself to form the corpus albicans. Its course to the optic thalamus is indicated by a dotted line. 9. The optic thalamus. Behind the anterior crus of the for- nix a shaded part indicates tlie foramen of Monro; in front of the number an oval mark shows the position of the gray matter continuous with the middle commissure. 10. The velum interpositum. 11. The pineal gland. 12. The corpora quadrigemina. 13. The crus cerebri. 14. The valve of Vieussens (above the number). 15. The pons Varolii. 16. The third nerve. 17. The pituitary body. 18. The optic nerve. 19 points to the anterior commissure, indicated by an oval mark behind the number. this body is solid the sabulous matter is found upon its surface, and occasionally upon its peduncles. On the removal of the pineal gland and adjacent portion of the pia mater the corpora quadrigemina are exposed. The corpora or tubercula quadrigemina [optic lobes) are four rounded eminences placed in pairs, two in front and two behind, and separated from one another by a crucial depression. They are situated immediately behind the third ventricle and posterior commissure, and beneath the posterior border of the corpus cal- losum. Below, they are separated in the middle line from the crura cerebri by the aqueduct of Sylvius, but on each side are continuous with the tegmentum of the crura. The anterior or upper pair, the nates, are the larger, oblong from before backward, and of a gray color. The posterior or lower pair, the testes, are 742 THE NERVOUS SYSTEM. hemispherical in form, and lighter in color than the preceding. From the outer side of each of these eminences a prominent white band, termed JracAzum, is con- tinued forward and outward. Those from the nates (brachia anteriora) are the larger, and pass obliquely outward, between the inner and outer geniculate bodies, into the optic tract. Those from the testes (brachia posteriora) pass beneath an oval prominence, the internal geniculate body, and are no longer traceable. Both pairs, in the adult, are quite solid, being composed of white matter externally and gray matter within. These bodies are larger in the lower animals than in man. In fishes, reptiles, and birds they are only two in number, are called the optic lobes, from their connection with the optic nerves, and are hollowr in their interior ; but in mammalia they are four in number, as in man, and quite solid. In the human foetus they are developed at a very early period, and form a large proportion of the cerebral mass; at first they are only two in number, as in the lower vertebrata, and hollow in their interior. These bodies are connected with the cerebellum by means of a large white cord on each side, the processus ad testes, or superior peduncles of the cere- bellum, which is continued onward to the optic thalami through the tegmentum of the crus cerebri. Beneath the corpora quadrigemina some fibres from it decussate with those of the opposite side across the middle line. Arching over these peduncles is a flattish band of white fibres, the which issues from beneath the transverse fibres of the pons, and in sections of this body can be seen lying between the deep transverse fibres and the reticular formation. If these fibres are traced upward through the pons, the outer ones will be seen to become superficial at its upper border, to pass obliquely round the superior peduncle of the cerebellum, and become lost in the quadrigeminal body, while the inner are continued upward in the crus to the cerebral hemi- sphere. The corpora geniculata are twro small, flattened, oblong masses, placed on the under and back part of each optic thalamus, and named, from their positions, corpus geniculatum externum and internum. The two bodies are separated from one another by one of the roots of the optic tract, the brachia anterior, from the nates. Structure of the Cerebrum. The cerebrum, like the other parts of the great nerve-centre, is composed of gray and white matter. In order to give some general idea of its construction-at all events, in part-it may be compared, for the sake of illustration, to a tree, the trunk of which divides into two main branches, and these break up into smaller branches, which finally end in twigs, to which are attached the leaves, forming an investment to the branches and covering the whole tree. The trunk is represented by the medulla oblongata as it passes through the foramen magnum; the two main branches, by the crura cerebri, which break up into smaller branches, which diverge from each other, dividing and subdividing, until they reach the surface of the hemispheres, where they terminate in single nerve-fibres, to which are attached the basal axial cylinder processes of the nerve-cells, represented by the leaves. These cells are arranged on the surface, resembling a cap covering the hemispheres, and constitute the cerebral cortex. But here the analogy ends, for in the cerebrum we have, in addition to this cortex, other masses of gray matter situated in the middle of the brain, and other white fibres besides these diverging ones which have been mentioned, and which serve either to connect together the two hemispheres of which the cerebrum consists or else serve to connect different structures in the same hemisphere. The white matter of the cerebrum consists of medullated fibres, varying in size and arranged in bundles, separated by neuroglia. They may be divided into three distinct systems, according to the course which they take : 1. Diverging or peduncular fibres, which connect the hemispheres with the medulla oblongata and cord. 2. Transverse commissural fibres, which connect together the two hemi- THE STRUCTURE OE THE CEREBRUM. 743 spheres. 3. Commissural fibres, which connect different structures in the same hemisphere. 1. The diverging or peduncular fibres consist of a main body, which originates in the cord and medulla oblongata, forms the longitudinal fibres of the pons, and divides into two main branches, which, diverging from each other, constitute the crura cerebri or cerebral peduncles. In the crura cerebri, as has been before described, the diverging fibres derived from the longitudinal fibres of the pons Varolii are arranged in two strata, which are separated by the locus niger, the anterior or superficial stratum forming the crusta of these bodies, and the posterior or deeper stratum, the tegmentum. The fibres derived from these two sources take a different course, and will have to be separately considered. The fibres of the crusta are derived from the pyramid of the medulla, which fibres are continued upward through the pons to form the crusta ; they are reinforced in their passage through the crus by accessory fibres derived from the central gray matter around the Sylvian aqueduct and from the locus niger. When they emerge from the crus (1) some of the fibres pass directly upward as radiating fibres to the gray matter of the cerebral hemisphere, forming the corona radiata; (2) some of the fibres pass to the internal capsule, between the nucleus caudatus and lenticularis, where they give off fibres to these ganglia and receive others from them, and then, issuing from the capsule, diverge to form a part of the corona radiata, passing to the cerebral cortex. The fibres which arise from the ganglia are more numerous than those which terminate in the ganglia, so that more fibres pass out of the ganglia than pass into them. The fibres of the tegmentum are continuous with those longitudinal fibres of the pons which are derived from the formatio reticularis of the medulla, which is formed by fibres-(1) from the anterior column of the cord; (2) from the olivary body; (3) from the lateral column of the cord; and (4) from the funiculus cuneatus and funiculus gracilis. They are reinforced by fibres from the corpora quadrigemina and corpora geniculata, and from the superior peduncle of the cerebellum, and enter the optic thalamus. Some of these fibres pass through the optic thalamus, and, being augmented by other fibres arising within this body, pass out of it and spread out to form part of the corona radiata, especially joining the ganglion-cells of the cortex of the temporo-sphenoidal and occipital lobes; other fibres terminate in the optic thalamus. 2. The transverse commissural fibres connect together the two hemispheres. They include (a) the transverse fibres of the corpus callosum ; (J) the anterior commissure; (c) the posterior commissure. The corpus callosum, which has already been described, connects together the two hemispheres of the brain, forming their great transverse commissure, pene- trating into the substance of the convolutions and intersecting the fibres of the corona radiata. The anterior commissure is a round bundle of white fibres which is placed in front of the anterior crura of the fornix, and appears to connect the corpora striata. It passes outward through the corpus striatum on each side, and then curves backward into the substance of the temporo-sphenoidal lobe. The posterior commissure, smaller than the anterior, is a flattened white band of fibres, which appears to connect together the optic thalami posteriorly. It consists of decussating fibres which come from the tegmentum of the crus cerebri on one side, and pass through the optic thalamus, across the back part of the third ventricle, to the white substance of the temporo-sphenoidal lobe of the other. Some of the fibres may also serve as commissural fibres between the optic thalami. 3. Commissural Fibres connecting Different Structures in the Same Hemisphere. -These fibres are of two kinds: (1) those which connect adjacent convolu- tions, and which are termed arcuate or association fibres; (2) those which con- nect more distant parts in the same hemisphere-the longitudinal or collateral fibres. The arcuate or association fibres are situated immediately beneath the gray 744 THE NERVOUS SYSTEM. substance of the cortex of the hemispheres, and connect together adjacent con- volutions. The longitudinal or collateral fibres include the following: (a) the uncinate fasciculus; (6) the fillet of the gyrus fornicatus; (c) the longitudinal fibres of the corpus callosum; (c?) the taenia semicircularis; (e) the fornix; (/) the inferior longitudinal fasciculus. (а) The uncinate fasciculus connects the convolutions of the frontal and temporo-sphenoidal lobe. It passes across the bottom of the Sylvian fissure and traverses the claustrum. (б) The fillet of the gyrus fornicatus is a band of white matter which encircles the hemisphere in an antero-posterior direction, lying in the substance of the con- volution of the corpus callosum. Commencing in front at the anterior perforated space, it passes forward and upward parallel with the rostrum, winds round the genu, runs in the convolution from before backward, immediately above the corpus callosum, turns round its posterior extremity, and is continued downward and forward in the temporo-sphenoidal lobe to again reach the perforated space. In its course it is connected with the secondary convolutions of the gyrus fornicatus by short arcuate fibres. (c) The longitudinal fibres of the corpus callosum, or nerves of Lancisci, connect the anterior and posterior extremities of the gyrus fornicatus or convolution of the corpus callosum. (cZ) The tcenia semicircularis is a narrow whitish, semitransparent band, of medullary substance, situated in the depression between the nucleus caudatus and the optic thalamus. Anteriorly, it descends in connection with the anterior pillar of the fornix to below the level of the foramen of Monro, where it enters a mass of gray matter, the nucleus amygdalai ; behind, it is continued into the roof of the middle or descending horn of the lateral ventricle, and is lost near the bottom of the cornua. (e) The fornix connects the optic thalamus with the hippocampus major and uncinate convolution. It has already been described as arising from the gray matter of the optic thalamus ; it then emerges from the under surface of this body, forms the corpus albicans, where the fibres are arranged in loops, between which nerve-cells are to be found: it then passes upward into the third ventricle and joins with the fibres of the other side forming the body of the fornix; from this the posterior pillars diverge, and, entering the middle cornu of the lateral ventricle, part of its fibres are distributed to the hippocampus major, and the remainder end as the taenia hippocampi or fimbria, which is continued as a distinct piece to the crochet or uncus of the uncinate convolution. (/) The inferior longitudinal fasciculus is a collection of fibres which connects the temporo-sphenoidal and occipital lobes, running along the outer wall of the middle and posterior cornu. The gray matter of the cerebrum is disposed in three great groups: 1. The gray matter of the cerebral cortex. 2. The gray matter of the basal ganglia; that is, the great ganglia of the base of the cerebrum. 3. The gray matter which lines the internal surface of the upper part of the cerebro-spinal tube; that is, the remains of the cavity in the original vesicles from which the brain was formed, and which constitutes the central cavities of the organ. 1. The gray matter of the cortex (Fig. 432) invests the surface of the hemi- spheres and gives them external form. When vertical sections are made through it and examined microscopically, it is found to consist of five separate layers, but to this there are some exceptions. According to Meynert these exceptions are to be found : (1) in the posterior portion of the occipital lobe; (2) in the gray cortex of the hippocampus major; (3) in the wall of the fissure of Sylvius; and (4) in the olfactory bulb. The five layers in the common type are as follows: (1) The first layer is principally composed of a matrix or neuroglia, through which a few small ganglion-cells are irregularly distributed, and a nerve-fibre network. (2) The second layer consists of numerous small pyramidal cells, which have their THE STRUCTURE OF THE CEREBRUM. 745 long axes vertical to the surface of the convolutions, and are closely aggregated together so as to completely fill the layer with a number of closely compressed cells. (3) The third layer is named by Meynert the formation of the cornu Ammonis, as it is made up of cells, which are the only mor- phological element found in this part. It con- sists of the same sort of pyramidal cells, arranged vertically to the surface, as was found in the pre- ceding layer, but they are of very much larger size, and increase progressively toward the deeper parts of the layer, and they are much more widely separated from each other. This layer is the principal and broadest one of the series, and is at least twice as deep as the preceding layer. (4) The fourth layer is termed the granular formation by Meynert, and consists of numerous small, irregular, rarely triangular or elongated cells, which resemble the nerve-corpuscles found in the internal granule layer of the retina, and which are closely aggre- gated together. (5) The fifth layer is termed the claustral formation, and consists of a very large proportion of spindle-shaped cells, which are the peculiar elements of this layer. They are espe- cially numerous in the inner half, and are arranged horizontally, extending parallel to the surface. They have received their name from the fact that the claustrum is made up almost entirely of an accumulation of these cells. It will be seen, therefore, that the differences in these layers depend upon the varying form and size of the cells and the closeness of their arrangement, and that the typical form of cell, and the only one which is admitted by some observers, is the pyra- midal cell or nerve-corpuscle. Character of the Pyramidal Cell or Nerve-cor- puscle.-These nerve-corpuscles are destitute of a cell-wall; they present a nucleus, sometimes round or oval, sometimes angular, and give off many processes. One of these, which, in the cells arranged vertically to the surface, projects outward and is named the process of the apex, is strong and branched, and, according to Cleland, is continuous with the nerve-fibre network in the first or super- ficial layer of the cortex. Another process pro- jects inward toward the white matter of the hemisphere and from the opposite extremity of the cell. It is termed the process of the centre of the base. It is more slender than the preceding and remains unbranched. It is an axis-cylinder process, and, becoming invested with a medullary sheath, constitutes a nerve-fibre, extending into the central white matter. In addition to these, lateral processes are given off, forming the processes of the basal angle, which can be traced for a longer or shorter distance, and break up into a network of extremely minute nerve-fibres. Special Types of the dray Matter of the Cortex.-The special types of gray mat- ter of the cortex are the following: (1) On the posterior portion of the occipital lobe the gray matter consists of eight layers. This is produced by the intercalation of intermediate granule layers, similar to those forming the fourth layer of the typical cortex. (2) In the gray matter of the cortex of the hippocampus major or cornu Ammonis pyramidal cells are alone found, such as have been described in the Fig. 432-Gray matter of the cerebral cortex. (Meynert.) 746 THE NERVOUS SYSTEM. third layer of the typical cortex. This constitutes the greater part of the structure in this situation, the fourth and fifth layers being absent and the second layer containing no cells. (3) In the wall of the Sylvian fissure the gray matter is termed the claustrum ; it separates the white matter of the convolutions of the island of Reil from the external capsule of the corpus striatum. This presents peculiarities of structure, consisting mainly of spindle-shaped cells, such as consti- tute the fifth layer. (4) In the olfactory bulb, which may be regarded as a portion of the cerebral hemispheres, forming " a cap superimposed upon a conical process of the cerebrum," is another variety of structure, differing from the type of the cortex of the hemispheres. The bulb consists of both gray and white matter, and sometimes retains a central cavity lined by epithelium. The lower part is gray matter, and consists of the following layers from below upward : (1) The olfactory nerve-layer, consisting of a layer of non-medullated nerve-fibres derived from the nerves which supply the olfactory region. (2) The stratum glomerulosum, consisting of nodulated masses, containing small nuclear cells and a convoluted olfactory nerve-fibre amongst the cells. (3) The stratum gelatinosum, consisting of pyramidal or spindle-shaped nerve-cells and a fine network of nerve-fibre. (4) The granular layer, consisting of small irregular nerve-cells resembling the fourth layer of the cerebrum or the granular layer of the retina. 2. The Gray Matter of the Basal Ganglia.-The great ganglia of the base of the brain are the corpus striatum, the optic thalamus, the corpora quadrigemina, the corpora geniculata, and the locus niger. Only a part, however, of the gray matter of the corpora quadrigemina-that found on the periphery of this body- belongs to this group ; the remainder, that contained in its centre around the Sylvian aqueduct, belongs properly to the third group, which will be discussed immediately. The corpus striatum presents two distinct and separate masses, the nucleus caudatus, which is the intraventricular portion of the corpus striatum, and the nucleus lenticularis, which is the extraventricular portion. The two are separated from each other by a distinct lamina of white matter, the internal capsule, which also separates the nucleus lenticularis from the outer part of the optic thalamus. The gray matter of the corpus striatum is permeated by tracts of medullated nerve- fibres, some of which probably originate in it, though the actual connection of the nerve-fibres with the cells has not been demonstrated. The nerve-cells are multi- polar, both large and small, the larger being principally found in the lenticular nucleus. The optic thalamus is chiefly formed of gray matter, covered over by a super- ficial layer of white, which on the outer side separates it from the internal capsule. The gray matter is arranged in two masses, the outer and inner nuclei, partially divided by a vertical white septum. It is traversed by numerous nerve-fibres, which for the most part have no definite direction; some, however, converge and form a bundle which passes downward to form the anterior root of the fornix. It contains comparatively large nerve-cells, both multipolar and fusiform. The inner nucleus is connected across the middle line writh the inner nucleus of the opposite side by the middle commissure of the third ventricle, which, however, belongs to the third group of gray matter. The corpora quadrigemina consist of two distinct and separate collections of gray matter, one at or near the surface, which belongs to the basal ganglia, and one in the centre around the aqueduct of Sylvius. The former will only be considered at present. The peripheral gray matter of the corpora quadrigemina differs somewhat in the posterior and anterior lobes. The posterior lobes or testes are composed almost entirely of gray matter, covered over by a thin stratum of white matter, and separated from the central gray matter by tracts of transverse white fibres derived from, and forming part of, the fillet. The anterior lobes or nates are covered superficially by a thin stratum of white matter; beneath this is a layer of gray matter, termed the stratum cinereum, and consisting, as well as the gray matter of the posterior lobes, of small multipolar cells imbedded in a fine THE CEREBELL UM. 747 network of nerves. Beneath this, again, is a characteristic mass of gray matter, termed the stratum opticum, which is made up of fine nerve-fibres, coursing in a longitudinal direction, and containing between them small masses of gray substance, consisting of small multipolar nerve-cells imbedded in gray matter. Lastly, between this body and the central gray matter around the Sylvian aqueduct is a thin lamina of white matter, derived from the fillet. The geniculate bodies are continuous with the gray substance of the optic thalamus, and the external one {corpus geniculatum externum) is peculiar on account of its dark color, due to its cells containing pigment. It presents a laminated arrangement, and consists of alternate thick layers of gray matter and thin layers of white matter. Its cells are multipolar. The internal body {corpus geniculatum internum) is of lighter color, does not present a laminated arrangement, and its cells are smaller in size and fusiform in shape. The locus niger, or gray matter of the crus cerebri, like the external geniculate body, is peculiar from the large amount of dark pigment-granules which are contained in its ganglion-cells, and which give to it its dark color, from which it has derived its name. Its cells are small and multipolar. 3. The central gray matter of the cerebrum lines the upper part of the cerebro-spinal tube, which is the remains of the cavity in the original vesicles from which the brain was formed, and is continuous with the gray matter of the floor of the fourth ventricle, and through it with the gray matter of the cord. This central gray matter is found lining the aqueduct of Sylvius, by which the third communi- cates with the fourth ventricle; it covers the inner wall of each optic thalamus, forming the middle or gray commissure of the third ventricle; it also lines the floor of the third ventricle ; it covers behind the upper surface of the tegmentum of the crus, and in front it approaches the surface of the brain, forming the posterior perforated space and lamina cinerea. It forms also the tuber cinereum and the infundibulum, and in the lower vertebrata, especially fishes, the posterior lobe of the pituitary body. In the higher vertebrates this lobe does not present any nervous structure, being encroached upon and obliterated by an ingrowth of con- nective tissue and vessels. The gray matter surrounding the Sylvian aqueduct, which has been before mentioned as the central gray matter of the corpora quadrigemina, presents some features requiring especial mention. It forms a tolerably thick layer surrounding the canal, but is thicker on the lower wall-that is, below the canal-than above. The cells, which are multipolar, are here collected into groups, and form nuclei for the origin of the third and fourth cranial nerves. The nucleus for the third and fourth consists of a column of cells of large size on either side of, and close to, the median line. In addition to these cells there are found at the periphery of the zone of gray matter surrounding the aqueduct some other, and larger, cells, sometimes single, sometimes grouped in twos or threes, or even more. They are globular, and lie in the midst of well-marked nerve-fibres, with which their processes appear to be continuous. The Cerebellum. The Cerebellum, or little brain, is that portion of the encephalon which is contained in the inferior occipital fossae. It is situated beneath the occipital lobes of the cerebrum, from which it is separated by the tentorium. In form the cerebellum is oblong, and flattened from above downward, its great diameter being from side to side. It measures from three and a half to four inches trans- versely, and from two to two and a half inches from before backward, being about two inches thick in the centre, and about six lines at the circumference, which is the thinnest part. It consists of gray and white matter: the former, darker than that of the cerebrum, occupies the surface ; the latter, the interior. The surface of the cerebellum is not convoluted like the cerebrum, but traversed by numerous 748 THE NERVOUS SYSTEM. curved furrows or sulci, which vary in depth at different parts, and separate the laminae of which its exterior is composed. Weight of the Cerebellum.-Its average weight in the male is 5 ozs. 4 drs. It attains its maximum weight between the twenty-fifth and fortieth year, its increase in weight after the fourteenth year being relatively greater in the female than in the male. The proportion between the cerebellum and cerebrum is, in the male, as 1 to ; and in the female, as 1 to 8|. In the infant the cerebellum is propor- tionately much smaller than in the adult, the relation between it and the cerebrum being, according to Chaussier, between 1 to 13 and 1 to 26 ; by Cruveilhier the proportion was found to be 1 to 20. Lobes of the Cerebellum.-The cerebellum is divided into an upper and a lower portion by the great horizontal fissure, which commences in front at the pons, and passes horizontally round the free margin of the hemisphere to the middle line behind. From this primary fissure numerous secondary fissures proceed, which separate the cerebellum into lobes. Its upper surface (Fig. 433) is somewhat elevated in the median line, and sloped toward its circumference; it consists of two lateral hemispheres, connected Incisura cerebelli anterior. . Incisura cerebelli posterior. Fig. 433.-Upper surface of the cerebellum together by an elevated median portion or lobe, the superior vermiform process. The median lobe is the fundamental part, and in some animals, as fishes and reptiles, the only part which exists, the hemispheres being additions, and attaining their maximum size in man. The hemispheres are separated, in front, by a deep notch, the incisura cerebelli anterior, which encircles the posterior part of the corpora quadrigemina; they are also separated by a similar notch behind, the incisura cerebelli posterior, in which is received the upper part of the falx cere- belli. The superior vermiform process (upper part of the median lobe of the cere- bellum) extends from the notch on the anterior to that on the posterior border. Upon the upper surface of each hemisphere there are two lobes, separated from each other by a fissure. These are the anterior or square lobe, which extends as far back as the posterior edge of the vermiform process; and the posterior or semilunar lobe, which passes from the termination of the preceding to the great horizontal fissure. The under surface of the cerebellum (Fig. 434) is subdivided into two lateral hemispheres by a depression, the vallecula or valley, which extends from before backward in tbe middle line. These lateral hemispheres are lodged in the infe- rior occipital fossae; the median depression, or valley, receives the back part of the medulla oblongata, is broader in the centre than at either extremity, and has THE CEREBELLUM. 749 projecting from its floor part of the median lobe of the cerebellum, called the inferior vermiform process. Upon the under surface of each hemisphere there are five lobes, separated by sulci; these are, from before backward, (1) the flocculus or subpeduncular lobe, a prominent tuft situated behind and below the middle peduncle of the cerebellum ; its surface is composed of gray matter, subdivided into a few small laminae; it is sometimes called the pneumogastric lobule, from being situated behind the pneu- mogastric nerve: (2) the amygdala or tonsil, situated on either side of the great median fissure or valley, and projecting into the fourth ventricle: (3) the digas- tric lobe, situated on the outside of the tonsil, and connected in part with the pyramid: (4) the slender lobe, behind the digastric, and connected with the back part of the pyramid and the commissura brevis, and, more posteriorly, (5) the infe- rior posterior lobe, which also joins the commissura brevis in the valley. Fig. 434.-Under surface of the cerebellum. The Inferior Vermiform Process.-The parts entering into the composition of the inferior vermiform process, from behind forward, are-the tuber valvulce or commissura brevis, a transverse lamina uniting the inferior posterior and slender lobes of the two sides; in front of this, a laminated conical projection, the pyra- mid; more anteriorly, a larger eminence, the uvula, which is placed between two rounded lobes, the amygdalae or tonsils, which occupy the sides of the valley, and which is connected with them by a commissure of gray matter, indented on the surface, called the furrowed band. In front of the uvula is the nodule; it is the anterior pointed termination of the inferior vermiform process, and projects into the cavity of the fourth ventricle; it has been named by Malacarne the laminated tubercle. On each side of the nodule is a thin layer of white substance, attached externally to the flocculus, and internally to the nodule; these form together the posterior medullary velum, or commissure of the flocculus. It is usually covered in and concealed by the amygdalae, and cannot be seen until they are drawn aside. This band is of a semilunar form on each side, its anterior margin being free and concave, its posterior attached just in front of the furrowed band. Between it and the nodule and uvula behind is a deep fossa called the swallow's nest (nidus hirundinis'). Internal Structure of the Cerebellum.-The cerebellum consists both of white and gray matter. If a vertical section (Fig. 435) is made through either hemisphere of the cere- bellum, midway between its centre and the superior vermiform process, the inte- rior will be found to consist of a central stem of white matter, which contains in its interior a gray mass, the corpus dentatum. From the surface of this central stem a series of plates of medullary matter are detached, which, covered with gray matter, form the laminae. From the anterior part of each hemisphere arise 750 THE NERVOUS SYSTEM. three large processes or peduncles-superior, middle, and inferior-by which the cerebellum is connected with the rest of the encephalon. The white matter includes two varieties of nerve-matter: (1) the peduncular fibres, which are directly continuous with the fibres of the peduncles of the cere- bellum ; (2) the fibres (fibrce proprice) proper to the cerebellum itself. The peduncles of the cerebellum-superior, middle, and inferior-serve to con- nect it with the rest of the encephalon. The superior peduncles (processus e cerebello ad testes) arise from the middle of the white matter of the cerebral hemispheres; they run beneath the testes of the corpora quadrigemina, and, emerging at its posterior border, pass outward and backward to the cerebellum. Each peduncle forms the upper part of the lateral boundary of the fourth ventricle, and is connected with its fellow of the opposite side by the valve of Vieussens. Beneath the corpora quadrigemina the innermost fibres of each peduncle decussate with each other, so that some fibres from the one half of the cerebrum are continued into the other half of the cerebellum. Upon Fig. 435.-Vertical section of the cerebellum. entering the cerebellum the fibres of this peduncle pass to a great extent into the interior of the corpus dentatum, though some wind round it and reach the gray cortical matter, especially on its inferior surface. The valve of Vieussens, or superior medullary velum, is a thin translucent lamina of white matter, marked superficially by a few transverse streaks of gray substance, stretched between the two processus e cerebello ad testes; it forms part of the roof of the fourth ventricle. It is narrow in front, where it is connected with the testes, and broader behind, at its connection with the vermiform process of the cerebellum. A slight elevated ridge, doe frcenulum, descends upon the upper part of the valve from the corpora quadrigemina, and on either side of it may be seen the fourth nerve, which is connected with its fellow of the opposite side by a transverse band of fibres forming a partial decussation. Its lower half is covered by a thin, transversely-grooved lobule of gray matter prolonged from the anterior border of the cerebellum ; this is called the lingula. The middle peduncles (processus ad pontem), the largest of the three, connect together the two hemispheres of the cerebellum, forming their great transverse commissure. They consist of a mass of curved fibres, which arise in the gray matter of the foliated cortex of the hemispheres of the cerebellum, and pass across the pons Varolii, forming its transverse fibres. The inferior peduncles (processus ad medullani) connect the cerebellum with the medulla oblongata. As the restiform bodies they pass upward and outward, THE CEREBELLUM 751 forming part of the lateral wall of the fourth ventricle ; entering the cerebellum, they end in the gray cortex of the upper surface of this organ. The fibres proprice of the cerebellum are of two kinds: (1) commissural fibres, which cross the middle line to connect the opposite halves of the hemispheres, some at the anterior part, and others at the posterior part of the vermiform pro- cess; (2) arcuate or association fibres, which connect one lamina with another, arching across the fissures between the laminae. The gray matter of the cerebellum is found in two situations : (1) on the surface, forming the cortex ; (2) as independent masses in the interior. 1. The gray matter of the cortex presents a characteristic foliated appearance, External gray or cellular layer. Corpuscles of Purkinje. ■Internal or rust- colored layer. White substance. Fig. 436.-Vertical section through the gray matter of the human cerebellum. Magnified about 100 diame ters. (Klein and Noble Smith.) due to the series of laminae which are given off from the central white matter; these laminae give off secondary laminae which are covered with gray matter. This arrangement gives to the cut surface of the organ a foliated appearance, to which the name arbor vita has been applied (Fig. 435). Externally the cortex is covered by pia mater, and internally is the medullary centre, consisting mainly of nerve-fibres. Microscopical Appearance of the Cortex.-The cortex presents a remarkable structure, consisting of two distinct layers-viz. an external gray or cellular layer, and an internal rust-colored granular layer. Between the two layers, or rather 752 THE NERVOUS SYSTEM. situated in the deepest part of the gray or cellular layer, is an incomplete stratum of the characteristic cells of the cerebellum, the corpuscles of Purkinje. The external gray or cellular layer (Fig. 436) consists of a transparent tissue- like neuroglia containing fibres and cells. The fibres are delicate fibrillae running at right angles to the surface, and many of them connected with the processes of the large nerve-cells immediately below ; others are delicate supporting connective- tissue-like fibres, which spread out into a broad base against the inner surface of the pia mater. The cells are granular bodies, some very small, and probably belonging to the neuroglia; others, according to Lockhart Clarke, connected with the processes of the corpuscles of Purkinje which lie immediately beneath. The corpuscles of Purkinje (Fig. 436) are flask-shaped cells in the deepest part of the external gray or cellular layer, resting against the internal rust-colored layer. From their under surface a slight slender process arises, which passes through the internal layer, and becomes continuous with the axial cylinder of a medullated nerve-fibre in the medullary substance beneath. From the other extremity two peripheral processes are given off, which branch in an antler-like manner in the external layer, some of the finer processes becoming connected with the cells in this layer. The internal or rust-colored layer (Fig. 436) is characterized by containing multitudes of granular-looking bodies imbedded in a gelatinous matrix. They are minute stellate cells, consisting of a well-defined nucleus with a thin protoplasmic envelope. Between the cells is a fine nerve-network, with which the processes of the cells are supposed to be continuous. 2. The independent centres of gray matter in the cere- bellum are-(1) the corpus dentatum ; (2) the roof nuclei of Stilling. The corpus dentatum, or ganglion of the cerebellum, is situated a little to the inner side of the centre of the stem of white matter. It consists of an open bag or capsule of gray matter, the section of which presents a gray den- tated outline, open at its anterior part. It is surrounded by white fibres ; white fibres are also contained in its interior, which issue from it to join the superior pedun- cles. The roof nuclei of Stilling are two small gray masses, situated at the anterior end of the superior vermiform process, and projecting into the valve of Vieussens, so as to assist in the formation of the roof of the fourth ven- tricle. These can only be seen in microscopic preparations. Fig. 437.-A corpuscle of Purkinje, with its dichotom- ously branched processes. The Fourth Ventricle (Fig. 430) The Fourth Ventricle, or ventricle of the cerebellum, is the space between the posterior surface of the medulla oblongata and pons in front and the cerebellum behind. It is lozenge or diamond-shaped ; that is to say, it is composed of two tri- angles, with their bases opposed to each other. The lower triangle is formed by the divergence of the funiculi graciles and the restiform bodies of the medulla oblongata on either side. These columns pass upward and outward at an acute angle to the lateral hemispheres of the cerebellum, leaving by their divergence a triangular space which forms the lower half of the fourth ventricle. In like man- ner the upper triangle is formed by the divergence of the superior peduncles (pro- cessus e cerebello ad testes) of the cerebellum. These crura as they emerge from the corpora quadrigemina are in contact by their lateral margins, but they gradu- ally diverge, passing downward, backward, and outward, to reach the cerebellum, thus enclosing a triangular space which forms the upper half of the fourth THE FOURTH VENTRICLE. 753 ventricle. This cavity is therefore bounded laterally by the processus e cere- bello ad testes above, and by the diverging funiculi graciles and restiform bodies below. It presents four angles. The upper angle reaches as high as the upper border of the pons ; it presents the lower opening of the aqueduct of Sylvius, by which this ventricle communicates with the third ventricle. The lower angle is on a level with the lower border of the olivary body, and presents a minute opening, the aperture of the central canal of the spinal cord. At its lateral angles the fourth ventricle is extended for a short distance between the side of the medulla and the cerebellum, where these two structures come in contact. The roof is arched, and is formed in the upper triangle by part of the superior peduncles of the cerebellum and the valve of Vieussens (superior medullary velum), a lamina of white matter streaked with gray, which bridges across from one supe- rior peduncle to the other. The roof of the lower half is formed by a reflection of pia mater passing from the under surface of the inferior vermiform process of the cerebellum to the lower part of the medulla oblongata. Above this is the inferior vermiform process itself. This pia-matral covering is lined on its under or ven- tricular surface by a layer of epithelium, which is continuous with that lining the sides and base of the cavity, and is perforated by a hole, the foramen of Majendie, by which the cavity of the ventricle communicates with the subarachnoidean space. The floor is formed by the posterior surface of the medulla oblongata and pons. In the median line is seen a fissure which gradually becomes obliterated above and terminates below, near the point of the calamus scriptorius, in a somewhat cleft- like space, the ventricle of Arantius, which opens by a minute hole into the central canal of the spinal cord. From the resemblance that there is in the diverging lower boundaries of the space and the central fissure to the nib of a writing-pen the lower triangle has been named the calamus scriptorius. On each side of the median fissure are two spindle-shaped longitudinal eminences, the/«sczewZz teretes ; they extend the entire length of the floor, being indistinct below and of a grayish color, but well marked and whiter, above. Each eminence consists of a portion of the base of the anterior cornu of gray matter of the medulla, which comes to the surface of the floor of the fourth ventricle, where the central canal of the spinal cord opens out into this cavity. External to this eminence there is a slight groove which terminates below in a little fossa, called the/ovea inferior ; and in the same groove, opposite the widest part of the ventricle, there is a second depression or fossa, called the fovea superior. Above the superior fovea, and external to the fasciculi teretes, is a small eminence of dark-gray substance, which presents a bluish tint through the thin stratum covering it; this is called the locus cceruleus ; and a thin streak of the same color, continuing up from this on either side of the fasciculi teretes as far as the top of the ventricle is called the tcenia violacea. The lower part of the floor of the ventricle is crossed by several white transverse lines, linece transversce or auditory strice ; they emerge from the posterior median fissure and enter the roots of origin of the auditory nerve. The lining membrane of the fourth ventricle is continuous with that of the third through the aqueduct of Sylvius, and its cavity communicates below with the subarachnoidean space of the brain and cord through an aperture in the layer of pia mater extending between the cerebellum and medulla oblongata. Laterally, this membrane is reflected outward a short distance between the cerebellum and medulla. The choroid plexuses of the fourth ventricle are two in number: they are del- icate vascular fringes which project into the ventricle on each side, passing from the point of the inferior vermiform process to the outer margin of the restiform bodies. The gray matter in the floor of the ventricle consists of a tolerably thick stra- tum, continuous below with the gray commissure of the cord, and extending up as high as the aqueduct of Sylvius, and, in addition, of some special deposits connected with the deep origin of certain of the cranial nerves. 754 THE NERVOUS SYSTEM. These special deposits produce little elevations on the floor of the ventricle. The nucleus of the fifth is placed the highest; the deep origin of the larger or sensory root is from a nucleus on a level with the middle of the superior peduncle of the cerebellum, just internal to the margin of the ventricle ; the deep origin of the smaller root is from a nucleus internal to the sensory root, and just external to the fasciculus teres on the floor of the ventricle. The origin of the sixth is a little lower than the motor root of the fifth, and close to the median line beneath the anterior portion of the fasciculus teres. The deep origin of the seventh, or facial, is a little below and external to the nucleus of the sixth, above the level of the auditory striae. The deep origin of the eighth, or auditory, is twofold: one from a prominence, the auditory tubercle, on the outer side of the inferior fovea; the other is situated at the lateral angle of the ventricle. Into 'this latter run the auditory striae. The deep origin of the ninth, or glosso-pharyngeal, is from a nucleus of gray matter at the lower part of the ventricle, beneath the inferior fovea, below the inner nucleus of the eighth or auditory nerve. The deep origin of the tenth, or pneumogastric, is from a nucleus of gray mat- ter at the lower part of the ventricle, below and continuous with the nucleus of origin of the ninth or glosso-pharyngeal nerve. The deep origin of the eleventh or accessory portion of the spinal accessory is from a nucleus of gray matter at the back of the medulla, extending from the level of the top of the calamus scriptorius as far down as the intermedio-lateral tract of the spinal cord. The deep origin of the twelfth, or hypoglossal, is from a nucleus of gray matter on the floor of the ventricle, on either side of the middle line, extending from the level of the auditory striae to the lowest point of the ventricle of Aran tins. THE CRANIAL NERVES. The cranial nerves arise from some part of the cerebro-spinal centre, and are transmitted through foramina in the base of the cranium. They have been named numerically, according to the order in which they pass through the dura mater lining the base of the skull. Other names are also given to them, derived from the parts to which they are distributed or from their functions. Taken in their order, from before backward, they are as follows : 1st. Olfactory. 2d. Optic. 3d. Motor oculi. 4th. Pathetic. 5th. Trifacial (Trigeminus). 6th. Abducent. 7th. Facial (Portio dura). 8th. Auditory (Portio mollis). 9th. Glosso-pharyngeal. 10th. Pneumogastric (Par vagum). 11th. Spinal accessory. 12th. Hypoglossal. All the cranial nerves are connected to some part of the surface of the brain. This is termed their superficial or apparent origin. But their fibres may, in all cases, be traced deeply into the substance of the brain to some special centre of gray matter, termed a nucleus. This is called their deep or real origin. The nerves, after emerging from the brain at their apparent origin, pass through foramina or tubular prolongations in the dura mater, leave the skull through foramina in its base, and pass to their final distribution. The First Cranial or Olfactory Nerves, the special nerves of the sense of smell, are about twenty in number. They are given off' from the under surface of the olfactory bulb, an oval mass of a grayish color, which rests on the cribriform plate of the ethmoid bone, and forms the anterior expanded extremity of a slender process of brain-substance, named the olfactory tract (see page 728). The olfactory tract, when traced backward, divides into three slips or roots at its base. The middle root is attached to the under surface of the frontal lobe, just in front of First Nerve (Fig. 423, page 727). THE CRANIAL NERVES. 755 the anterior perforated space. The external root passes outward, round the anterior perforated space, across the fissure of Sylvius to the temporo-sphenoidal lobe. The internal root passes inward, and joins the lower end of the corpus callosum. These three roots unite and form a flat band, narrower in the middle than at either extremity, and of a somewhat prismoid form on section. It is soft in texture and contains a considerable amount of gray matter in its substance. As it passes forward it is contained in a deep sulcus, the olfactory sulcus, between two convolutions, lying on the under surface of the frontal lobe, on either side of the longitudinal fissure, and is retained in position by the arachnoid membrane, which covers it. On reaching the cribriform plate of the ethmoid bone it expands into the olfactory bulb. From the under part of this bulb are given oft' the olfactory nerves, which pass through the cribriform foramina and are distributed to the mucous membrane of the nose. Each nerve is surrounded by a tubular prolonga- tion from the dura mater and pia mater; the former being lost on the periosteum lining the nose; the latter, in the neurilemma of the nerve. The nerves, as they enter the nares, are divisible into three groups : an inner group, larger than those on the outer wall, spread out over the upper third of the septum ; a middle set, confined to the roof of the nose; and an outer set, which are distributed over the superior and middle turbinated bones and the surface of the ethmoid in front of them. As the filaments descend they unite in a plexiform network, and are believed by most observers to terminate in the cells of Schultze. The olfactory differs in structure from other nerves in being composed exclu- sively of non-medullated fibres. They are deficient in the white substance of Schwann, and consist of axis-cylinders, with a distinct nucleated sheath, in which there are, however, fewer nuclei than in ordinary non-medullated fibres. Surgical Anatomy.-In severe injuries to the head the olfactory bulb may become sepa- rated from the olfactory nerves, thus producing loss of the sense of smelling (anosmia), and with this a considerable loss in the sense of taste, as much of the perfection of the sense of taste is due to the sapid substances being also odorous and simultaneously exciting the sense of smell. The Second or Optic Nerve, the special nerve of the sense of sight, is distributed exclusively to the eyeball. The nerves of opposite sides are connected together at the commissure, and from the back of the commissure they may be traced to the brain, under the name of the optic tracts. The optic tract, at its connection with the brain, is divided into two bands. One of these arises from the stratum opticum of the corpora quadrigemina, and emerges from the nates of this body as the anterior brachium, and passes obliquely outward between the inner and outer geniculate bodies ; the second arises from the optic thalamus, and passes through the inner geniculate body, from which it derives fibres, and joins with the other band to form the optic tract. From this origin the tract winds ob- liquely across the under surface of the crus cerebri in the form of a flattened band, desti- tute of neurilemma and attached to the crus by its anterior margin. It then assumes a cylindrical form, and, as it passes forward is connected with the tuber cinereum and lamina cinerea, from both of which it receives fibres. It finally joins with the tract of the opposite side to form the optic commissure. Second Nerve (Fig. 438). Fig. 438.-The left optic nerve and optic tracts. 756 THE NERVOUS SYS TEAL. The commissure or chiasma, somewhat quadrilateral in form, rests upon the optic groove of the sphenoid bone, being bounded, above, by the lamina cinerea; behind, by the tuber cinereum; on either side, by the anterior perforated space. Within the commissure the optic nerves of the two sides undergo a partial decus- sation. The fibres which form the inner margin of each tract are continued across from one to the other side of the brain, and have no connection with the optic nerves. These may be regarded as commissural fibres {intercerebral} between the thalami of opposite sides. Some fibres are continued across the anterior border of the chiasma, and connect the optic nerves of the two sides, having no relation with the optic tracts.1 They may be regarded as commissural fibres between the two retinae {inter-retinal fibres}. The outer fibres of each tract are continued into the optic nerve of the same side. The central fibres of each tract are continued into the optic nerve of the opposite side, decussating in the commissure with similar fibres of the opposite tract.2 The optic nerves arise from the fore part of the commissure, and, diverging from one another, become rounded in form and firm in texture, and are enclosed in a sheath derived from the arachnoid. -As each nerve passes through the correspond- ing optic foramen it receives a sheath from the dura mater ; and as it enters the orbit this sheath subdivides into two layers, one of which becomes continuous with the periosteum of the orbit; the other forms the proper sheath of the nerve and surrounds it as far as the sclerotic. The nerve passes through the cavity of the orbit, pierces the sclerotic and choroid coats at the back part of the eyeball, a little to the nasal side of its centre, and expands into the retina. Arnold describes a communication between the optic nerve in the orbit and the ascending branches of Meckel's ganglion. A small artery, the arteria centralis retinoe, perforates the optic nerve a little behind the globe, and runs along its interior in a tubular canal of fibrous tissue. It supplies the inner surface of the retina, and is accompanied by corresponding veins. Surgical Anatomy.-The optic nerve is peculiarly liable to become the seat of neuritis or undergo atrophy in affections of the central nervous system, and, as a rule, the pathological relationship between the two affections is exceedingly difficult to trace. There are, however, certain points in connection with the anatomy of this nerve which tend to throw light upon the frequent association of these affections with intracranial disease: (1) From its mode of development (see page 123) and from its structure the optic nerve must be regarded as a prolonga- tion of the brain-substance, rather than as an ordinary cerebro-spinal nerve. (2) As it passes from the brain it receives sheaths from the three cerebral membranes-a perineural sheath from the pia mater, an intermediate sheath from the arachnoid, and an outer sheath from the dura mater, which is also connected with the periosteum as it passes through the optic foramen. These sheaths are separated from each other by spaces which communicate with the subdural and subarachnoid spaces respectively. The innermost or perineural sheath sends a process around the arteria centralis retinae into the interior of the nerve, and enters intimately into the struc- ture of the nerve. Thus inflammatory affections of the meninges or of the brain may readily extend themselves along these spaces or along the interstitial connective tissue in the nerve. The course of the fibres in the optic commissure has an important pathological bearing, and has been the subject of much controversy. Microscopic examination, experiments, and pathology all seem to point to the fact that there is a partial decussation of the fibres, each tract supplying the corresponding half of each eye, so that the right tract supplies the right half of each eye, and the left tract the left half of each eye. At the same time, Charcot believes-and his view has met with general acceptation-that the fibres which do not decussate at the optic commis- sure have already decussated in the corpora quadrigemina, so that lesion of the cerebral centre of one side causes complete blindness of the opposite eye, because both sets of decussating fibres are destroyed. Whereas should one tract-say the right-be destroyed by disease, there will be blindness of the right half of both retinae. An antero-posterior section through the commissure would divide the decussating fibres, and would therefore produce blindness of the inner half of each eye ; while a section at the - To optic nerve of same side. *-0f opposite side. Fig. 439.-Course of the fibres in the optic commissure. 1 The presence of these fibres has been doubted by some observers, but they have been recently asserted to exist by Stilling. 2 A specimen of congenital absence of the optic commissure is to be found in the Museum of the Westminster Hospital. (See also Henle, Nervenlehre, p. 393, ed. 2.) THE THIRD OR MOTOR OCULI NERVE. 757 margin of the side of the optic commissure would produce blindness of the external half of the retina of the same side. The optic nerve may also be affected in injuries or diseases involving the orbit, in fractures of the anterior fossa of the base of the skull, in tumors of the orbit itself, or those invading this cavity from neighboring parts. Third Nerve (Figs. 440, 441, 442). The Third or Motor Oculi Nerve supplies all the muscles of the orbit, except the Superior oblique and External rectus ; it also sends motor filaments to the iris and the ciliary muscle. It is a rather large nerve, of rounded form and firm texture. Its apparent origin is from the inner surface of the crus cerebri, immediately in front of the pons Varolii. The deep origin may be traced through the locus niger and teg- mentum of the crus to a nucleus situated on either side of the median line beneath the floor of the aqueduct of Sylvius. On emerging from the brain the nerve is invested with a sheath of pia mater, and enclosed in a prolonga- tion from the arachnoid. It then pierces the dura mater in front of and external to the posterior clinoid process, passing between the two processes from the free and attached borders of the tentorium, which are prolonged forward to be connected with the anterior and posterior clinoid processes of the sphenoid bone. It passes along the outer wall of the cavernous sinus, above the other orbital nerves, receiving in its course one or two filaments from the cavernous plexus of the sympathetic. It then divides into two branches, which enter the orbit through the sphenoidal fissure be- tween the two heads of the Exter- nal rectus muscle. On passing through the fissure the nerve is placed below the fourth and the frontal and lachrymal branches of the ophthalmic nerve, and has passing between its two divisions the nasal nerve. The superior division, the smaller, passes inward over the optic nerve, and supplies the Superior rectus and Levator palpebrae. It occasionally communi- cates with the ganglionic branch of the nasal nerve. The inferior division, the larger, divides into three branches. One passes beneath the optic nerve to the Internal rectus ; another, to the Inferior rectus ; and the third, the largest of the three, passes forward between the Inferior and External recti to the Inferior oblique. From this latter a short, thick branch is given off to the lower part of the lenticular ganglion, which forms its inferior root. It also gives off one or two filaments to the Inferior rectus. All these branches enter the muscles on their ocular surface. Surgical Anatomy.-Paralysis of the third nerve may be the result of many causes: as cerebral disease; conditions causing pressure on the cavernous sinus; periostitis of the bones Infratrochlearl nerve. "z Motor root. / Sensory root. Recurrent filament to dura mater. Fig. 440.-Nerves of the orbit. Seen from above. 758 THE NERVOUS SYSTEM. entering into the formation of the sphenoidal fissure. It results, when complete, in (1) ptosis, or drooping of the upper eyelid, in consequence of the Levator palpebrae being paralyzed; (2) external strabismus, on account of the unopposed action of the External rectus muscle, which is not supplied by the third nerve, and is not therefore paralyzed; (3) dilatation of the pupil, because the sphincter fibres of the iris are paralyzed; (4) loss of power of accommodation, as the sphincter pupillae, the ciliary muscle, and the Internal rectus are paralyzed; (5) slight prominence of the eyeball, from the compressing action of the Superior oblique, which is not paralyzed. Occasionally paralysis may affect only a part of the nerve ; that is to say, there may be, for example, a dilated and fixed pupil, with ptosis, but no other signs. Irritation of the nerve causes spasm of one or other of the muscles supplied by it; thus, there may be internal strabismus from spasm of the Internal rectus; accommodation for near objects only from spasm of the ciliary muscle, or myosis, contraction of the pupil, from irritation of the sphincter of the pupil. Fourth Nerve (Fig. 440). The Fourth or Trochlear Nerve (pathetic), the smallest of the cranial nerves, supplies the Superior oblique muscle. Its apparent origin, at the base of the brain, is on the outer side of the crus cerebri, just in front of the pons Varolii, but the fibres can be traced backward behind the corpora quadrigemina to the valve of Vieussens, on the upper surface of which the two nerves decussate. Its deep origin may be traced to the nucleus in the floor of the aqueduct of Sylvius Lenticulan ganglion, t Fig. 441.-Plan of the motor oculi nerve. (After Flower.) immediately below that of the third nerve, with which it is continuous. The nerve winds round the outer side of the crus cerebri, immediately above the pons Varolii, pierces the dura mater in the free border of the tentorium cerebelli, just behind, and external to, the posterior clinoid process, and passes forward in the outer wall of the cavernous sinus, between the third nerve and the ophthalmic division of the fifth. It crosses the third nerve, and enters the orbit through the sphenoidal fissure. It now becomes the highest of all the nerves, lying at the inner extremity of the fissure internal to the frontal nerve. In the orbit it passes inward above the origin of the Levator palpebrae, and finally enters the orbital surface of the Superior oblique muscle. In the outer wall of the cavernous sinus this nerve is not unfrequently blended with the ophthalmic division of the fifth. Branches of Communication.-In the outer wall of the cavernous sinus it receives some filaments from the cavernous plexus of the sympathetic. In the sphenoidal fissure it occasionally gives off' a branch to assist in the formation of the lachrymal nerve. Branches of Distribu- tion.-It gives off a recurrent branch, which passes backward between the layers of the tentorium, dividing into two or three filaments which may be traced as far back as the wall of the lateral sinus. THE FIFTH OR TRIFACIAL NERVE. 759 Surgical Anatomy.-The fourth nerve when paralyzed causes loss of function in the Superior oblique, so that the patient is unable to turn his eye downward and outward. Should the patient attempt to do this, the eye on the affected side is twisted inward, producing diplopia or double vision. Accordingly, it is said that the first symptom of this disease which presents itself is giddiness when going down hill or in descending stairs, owing to the double vision induced by the patient looking at his steps while descending. Fifth Nerve. The Fifth or Trifacial Nerve (trigeminus) is the largest cranial nerve. It resembles a spinal nerve (1) in arising by two roots; (2) in having a ganglion developed on its posterior root; and (3) in its function, since it is a compound nerve. It is the great sensory nerve of the head and face and the motor nerve of the muscles of mastication. Its upper two divisions are entirely sensory ; the third division is partly sensory and partly motor. It arises by two roots: of these the anterior is the smaller, and is the motor root; the posterior, the larger and sensory. Its superficial origin is from the side of the pons Varolii, nearer to the upper than the lower border. The smaller root consists of three or four bundles; the larger root consists of numerous bundles of fibres, varying in number from seventy to a hundred. The two roots are separated from one another by a few of the transverse fibres of the pons. The deep origin of the larger or sensory root is from a nucleus on a level with the middle of the superior peduncle of the cere- bellum, just internal to the margin of the fourth ventricle. The deep origin of the smaller or motor root is from a nucleus internal to the sensory root, and just external to the fasciculus teres on the floor of the fourth ventricle. The two roots of the nerve pass forward through an oval opening in the dura mater, on the superior border of the petrous portion of the temporal bone, above the internal auditory meatus: they then run between the bone and the dura mater to the apex of the petrous portion of the temporal bone, where the fibres of the sensory root form a large, semilunar ganglion (Grasserian), while the motor root passes beneath the ganglion without having any connection with it, and joins outside the cranium with one of the trunks derived from it. The Gasserian or semilunar ganglion1 is lodged in a depression near the apex of the petrous portion of the temporal bone. It is of somewhat crescentic form, with its convexity turned forward. Its upper surface is intimately adherent to the dura mater. Besides the small or motor root, the large superficial petrosal nerve lies underneath the ganglion. Branches of Communication.-This ganglion receives, on its inner side, fila- ments from the carotid plexus of the sympathetic. Branches of Distribution.-It gives off' minute branches to the tentorium cerebelli and the dura mater in the middle fossa of the cranium. From its anterior border, which is directed forward and outward, three large branches proceed-the ophthalmic, superior maxillary, and inferior maxillary. The ophthalmic and superior maxillary consist exclu- sively of fibres derived from rhe larger root and ganglion, and are solely nerves of common sensation. The third division, or inferior maxillary, is joined outside the cranium by the motor root. This, therefore, strictly speaking, is the only portion of the fifth nerve which can be said to resemble a spinal nerve. Ophthalmic Nerve (Figs. 440, 442, 443). The Ophthalmic, or first division of the fifth, is a sensory nerve. It supplies the eyeball, the lachrymal gland, the mucous lining of the eye and nasal fossae, and the integument of the eyebrow, forehead, and nose. It is the smallest of the three divisions of the fifth, arising from the upper part of the Gasserian 1 A Viennese anatomist, Raimund Balthasar Hirsch (1765), was the first who recognized the ganglionic nature of the swelling on the sensory root of the fifth nerve, and called it, in honor of his otherwise unknown teacher, Jon. Laur. Gasser, the " Ganglion Gasseri." Julius Casserius, whose name is given to the musculo-cutaneous nerve of the arm, was professor at Padua, 1545-1605. (See Hyrtl, Lehrbuch der Anatomic, p. 895 and p. 55.) 760 THE NERVOUS SYSTEM. ganglion. It is a short, flattened band, about an inch in length, which passes forward along the outer wall of the cavernous sinus, below the other nerves, and just before entering the orbit, through the sphenoidal fissure, divides into three branches-lachrymal, frontal, and nasal. Branches of Communication.-The ophthalmic nerve is joined by filaments from the cavernous plexus of the sympathetic, communicates with the third and sixth nerves, and is not unfrequently joined with the fourth. Branches of Distribution.-It gives off recurrent filaments which pass between the layers of the tentorium along with a branch from the fourth nerve, and then divides into Lachrymal. Frontal. Nasal. The Lachrymal is the smallest of the three branches of the ophthalmic. Not unfrequently it arises by two filaments, one from the ophthalmic, the other from the fourth. It passes forward in a separate tube of dura mater and enters the Internal carotid artery and carotid plexus.\ Upper division of third nerve. root. Motor root Lower division of third nerve. Orbital nerve. Fig. 442.-Nerves of the orbit and ophthalmic ganglion. Side view. orbit through the narrowest part of the sphenoidal fissure. In the orbit it runs along the upper border of the External rectus muscle with the lachrymal artery, and sends off a recurrent branch which joins the orbital branch of the superior maxillary nerve, and occasionally takes the place of the temporal branch of this nerve, which is then absent. Within the lachrymal gland it gives off several filaments, which supply the gland and the conjunctiva. Finally, it pierces the tarsal ligaments, and terminates in the integument of the upper eyelid, joining with filaments of the facial nerve. The Frontal is the largest division of the ophthalmic, and may be regarded, both from its size and direction, as the continuation of the nerve. It enters the orbit above the muscles through the highest and broadest part of the sphenoidal fissure, and runs forward along the middle line, between the Levator palpebrae and the periosteum. Midway between the apex and base of the orbit it divides into two branches, supratrochlear and supra-orbital. The supratrochlear branch, the smaller of the two, passes inward above the pulley of the Superior oblique muscle, and gives off a descending filament, which joins with the infratrochlear branch of the nasal nerve. It then escapes from the orbit between the pulley of the Superior oblique and the supra-orbital foramen, curves up on to the forehead close to the bone, and ascends beneath the Corrugator BRANCHES OF THE FIFTH NERVE. 761 supercilii and Occipito-frontalis muscles, and supplies the integument of the lower part of the forehead on either side of the middle line. The supra-orbital branch passes forward through the supra-orbital foramen, and gives off, in this situation, palpebral filaments to the upper eyelid. It then ascends upon the forehead, and terminates in cutaneous and pericranial branches. The cutaneous branches, two in number, an inner and an outer, supply the integument of the cranium as far back as the occiput. They are at first situated beneath the Occipito-frontalis, the inner branch perforating the frontal portion of the muscle, the outer branch its tendinous aponeurosis. The pericranial branches are distributed to the pericranium over the frontal and parietal bones. The Nasal nerve is intermediate in size between the frontal and lachrymal, and more deeply placed than the other branches of the ophthalmic. It enters the orbit between the two heads of the External rectus, and passes obliquely inward across the optic nerve, beneath the Levator palpebrae and Superior rectus muscles, to the inner wall of the orbit, where it enters the anterior ethmoidal foramen, immediately below the- Superior oblique. It then enters the cavity of the cranium, traverses a shallow' groove on the front of the cribriform plate of the ethmoid bone, and passes down, through the slit by the side of the crista galli, into the nose, where it divides into two branches, an internal and an external. The internal branch supplies the mucous membrane near the fore part of the septum of the nose. The external branch descends in a groove on the inner surface of the nasal bone, and supplies a few filaments to the mucous membrane covering the fore part of the outer wall of the nares as far as the inferior spongy bone; it then leaves the cavity of the nose, between the lower border of the nasal bone and the upper lateral cartilage of the nose, and, passing down beneath the Compressor nasi, supplies the integument of the ala and the tip of the nose, joining with the facial nerve. The branches of the nasal nerve are the ganglionic, ciliary, and infratrochlear. The ganglionic is a slender branch, about half an inch in length, which usually arises from the nasal, between the two heads of the External rectus. It passes forward on the outer side of the optic nerve, and enters the superior and posterior angle of the ciliary ganglion, forming its superior or long root. It is sometimes joined by a filament from the cavernous plexus of the sympathetic or from the superior division of the third nerve. The long ciliary nerves, two or three in number, are given off from the nasal as it crosses the optic nerve. They join the short ciliary nerves from the ciliary ganglion, pierce the posterior part of the sclerotic, and, running forward between it and the choroid, are distributed to the ciliary muscles, iris, and cornea. The infratrochlear branch is given off just before the nasal nerve passes through the anterior ethmoidal foramen. It runs forward along the upper border of the Internal rectus, and is joined, beneath the pulley of the Superior oblique, by a filament from the supratrochlear nerve. It then passes to the inner angle of the eye, and supplies the integument of the eyelids and side of the nose, the conjunctiva, lachrymal sac, and caruncula lachrymalis. Ophthalmic Ganglion (Figs. 442, 443). Connected with the three divisions of the fifth nerve are four small ganglia. With the first division is connected the ophthalmic ganglion ; with the second division, the spheno-palatine or Meckel's ganglion; and with the third, the otic and submaxillary ganglia. All the four receive sensory filaments from the fifth, and motor and sympathetic filaments from various sources ; these filaments are called the roots of the ganglia. The Ophthalmic, Lenticular, or Ciliary Ganglion is a small, quadrangular, flattened ganglion, of a reddish-gray color, and about the size of a pin's head, situated at the back part of the orbit between the optic nerve and the External rectus muscle, lying generally on the outer side of the ophthalmic artery. It is enclosed in a quantity of loose fat, which makes its dissection somewhat difficult. 762 THE NERVOUS SYSTEM. _ To ciliary muscle and iris. \Sub-maxillary ' ganglion. Fig. 443.-Plan of the fifth cranial nerve. (After Flower.) Its branches of communication, or roots, are three, all of which enter its posterior border. One, the long or sensory root, is derived from the nasal branch BRANCHES OF THE FIFTH NERVE. 763 of the ophthalmic and joins its superior angle. The second, the short or motor root, is a short, thick nerve, occasionally divided into two parts, which is derived from the branch of the third nerve to the Inferior oblique muscle, and is connected with the inferior angle of the ganglion. The third, the sympathetic root, is a slender filament from the cavernous plexus of the sympathetic. This is frequently blended with the long root, though it sometimes passes to the ganglion separately. According to Tiedemann, this ganglion receives a filament of communication from the spheno-palatine ganglion. Its branches of distribution are the short ciliary nerves. These are delicate filaments, from six to ten in number, which arise from the fore part of the ganglion in two bundles, connected with its superior and inferior angles; the lower bundle is the larger. They run forward with the ciliary arteries in a wavy course, one set above and the other below the optic nerve, and are joined by the long ciliary nerves from the nasal. They pierce the sclerotic at the back part of the globe, pass forward in delicate grooves on its inner surface, and are distributed to the ciliary muscle, iris, and cornea. Tiedemann has described one small branch as penetrating the optic nerve with the arteria centralis retinee. The Superior Maxillary, or second division of the fifth, is a sensory nerve. It is intermediate, both in position and size, between the ophthalmic and inferior maxillary. It commences at the middle of the Gasserian ganglion as a flattened plexiform band, and passes forward through the foramen rotundum, where it becomes more cylindrical in form and firmer in texture. It then crosses the spheno-maxillary fossa, enters the orbit through the spheno-maxillary fissure, traverses the infra-orbital canal in the floor of the orbit, and appears upon the face at the infra-orbital foramen.1 At its termination the nerve lies beneath the Levator labii superioris muscle, and divides into a leash of branches, which spread out upon the side of the nose, the lower eyelid, and upper lip, joining with filaments of the facial nerve. Branches of Distribution.-The branches of this nerve may be divided into four groups : 1. Those given off in the cranium. 2. Those given off in the spheno- maxillary fossa. 3. Those in the infra-orbital canal. 4. Those on the face. Superior Maxillary Nerve (Fig. 444). In the cranium Meningeal. Orbital or temporo-malar. Spheno-palatine. Posterior superior dental. Spheno-maxillary fossa Middle superior dental. Anterior superior dental. Infra-orbital canal \ Palpebral. Nasal. Labial. On the face The meningeal branch is given off directly after its origin from the Gasserian ganglion, and supplies the dura mater, communicating with a meningeal branch from the inferior maxillary nerve. The orbital or temporo-malar branch arises in the spheno-maxillary fossa, enters the orbit by the spheno-maxillary fissure, and divides at the back of that cavity into two branches, temporal and malar. The temporal branch runs in a groove along the outer wall of the orbit (in the malar bone), receives a branch of communication from the lachrymal, and, passing through a foramen in the malar bone, enters the temporal fossa. It ascends between the bone and substance of the Temporal muscle, pierces this muscle and the temporal fascia about an inch above the zygoma, and is distributed to the integument covering the temple and side of the forehead, communicating 1 After it enters the infra-orbital canal, the nerve is frequently called the infra-orbital. 764 THE NERVOUS SYSTEM. with the facial and auriculo-temporal branch of the inferior maxillary nerve. As it pierces the temporal fascia it gives off a slender twig, which runs between the two layers of the fascia to the outer angle of the orbit. The malar branch passes along the external inferior angle of the orbit, emerges upon the face through a foramen in the malar bone, and, perforating the Orbicu- laris palpebrarum muscle, supplies the skin on the prominence of the cheek, and is named subcutaneus malce. It joins with the facial and the palpebral branches of the superior maxillary. The spheno-palatine branches, two in number, descend to the spheno-palatine ganglion. The posterior superior dental branches arise from the trunk of the nerve just as it is about to enter the infra-orbital canal; they are generally two in number, Sensory root. Motor root. Auriculo-temporal nerve. Fig. 444.-Distribution of the second and third divisions of the fifth nerve and submaxillary ganglion. but sometimes arise by a single trunk, and immediately divide and pass downward on the-tuberosity of the superior maxillary bone. They give off several twigs to the gums and neighboring parts of the mucous membrane of the cheek (superior gingival branches}. They then enter the posterior dental canals on the zygomatic surface of the superior maxillary bone, and, passing from behind forward in the substance of the bone, communicate with the middle dental nerve, and give off branches to the lining membrane of the antrum and three twigs to each of the molar teeth. These twigs enter the foramina at the apices of the fangs and supply the pulp. The middle superior dental branch is given off from the superior maxillary nerve in the back part of the infra-orbital canal, and runs downward and forward in a special canal in the outer wall of the antrum to supply the two bicuspid teeth. It communicates with the posterior and anterior dental branches. At its point of BRANCHES OF THE FIFTH NERVE. 765 communication with the posterior branch is a slight thickening which has received the name of the ganglion of Valentin ; and at its point of communication with the anterior branch is a second enlargement, which is called the ganglion oj Bochdalek. Neither of these is probably a true ganglion. The anterior superior dental branch, of large size, is given off from the supe- rior maxillary nerve just before its exit from the infra-orbital foramen ; it enters a special canal in the anterior wall of the antrum, and, coursing from before back- ward, divides into a series of branches which supply the incisor and canine teeth. It communicates with the middle dental branch, and gives off a nasal branch, which passes through a minute canal into the nasal fossa, and supplies the mucous mem- brane of the fore part of the inferior meatus and the floor of this cavity, communi- cating with the naso-palatine nerve from Meckel's ganglion. Termination of naso-palatine ' nerre. i Fig. 445.-The spheno-palatine ganglion and its branches. The palpebral branches pass upward beneath the Orbicularis palpebrarum. They supply the integument and conjunctiva of the lower eyelid with sensation, joining at the outer angle of the orbit with the facial nerve and malar branch of the orbital. The nasal branches pass inward; they supply the integument of the side of the nose and join with the nasal branch of the ophthalmic. The labial branches, the largest and most numerous, descend beneath the Levator labii superioris, and are distributed to the integument of the upper lip, the mucous membrane of the mouth, and labial glands. All these branches are joined, immediately beneath the orbit, by filaments from the facial nerve, forming an intricate plexus, the infra-orbital. The spheno-palatine ganglion (Meckel' s'), the largest of the cranial ganglia, is deeply placed in the spheno-maxillary fossa, close to the spheno-palatine foramen. It is triangular or heart-shaped, of a reddish-gray color, and is situated just below the superior maxillary nerve as it crosses the fossa. Its Branches of Communication.-Like the other ganglia of the fifth nerve, it Spheno-palatine Ganglion (Fig. 445). 766 THE NERVOUS SYSTEM. possesses a motor, a sensory, and a sympathetic root. Its sensory root is derived from the superior maxillary nerve through its two spheno-palatine branches. These branches of the nerve, given off in the spheno-maxillary fossa, descend to the ganglion. Their fibres, for the most part, pass in front of the ganglion, as they proceed to their destination, in the palate and nasal fossa, and are not incorporated in the ganglionic mass; some few of the fibres, however, enter the ganglion, constituting its sensory root. Its motor root is derived from the facial nerve through the large superficial petrosal nerve, and its sympathetic root from the carotid plexus, through the large deep petrosal nerve. These two nerves join together to form a single nerve, the Vidian, before theii' entrance into the ganglion. The large superficial petrosal branch (nervus petrosus superficialis major) is given off' from the intumescentia ganglioformis in the aqueductus Fallopii; it passes through the hiatus Fallopii; enters the cranial cavity, and runs forward contained in a groove on the anterior surface of the petrous portion of the temporal bone, lying beneath the dura mater and the Gasserian ganglion. It then enters the cartilaginous substance which fills in the foramen lacerum medium basis cranii, and, joining with the large deep petrosal branch, forms the Vidian nerve. The large deep petrosal branch (nervus petrosus profundus) is given off from the carotid plexus, and runs through the carotid canal on the outer side of the internal carotid artery. It then enters the cartilaginous substance which fills in the foramen lacerum medium, and joins with the large superficial petrosal nerve to form the Vidian. The Vidian nerve, formed in the cartilaginous substance which fills in the middle lacerated foramen by the junction of the two preceding nerves, passes forward through the Vidian canal, with the artery of the same name, and, entering the spheno-maxillary fossa, joins the posterior angle of Meckel's ganglion. Its branches of distribution are divisible into four groups : ascending, which pass to the orbit; descending, to the palate; internal, to the nose; and posterior branches, to the pharynx and nasal fossae. The ascending branches are two or three delicate filaments which enter the orbit by the spheno-maxillary fissure and supply the periosteum. Arnold describes and delineates these branches as ascending to the optic nerve. Bock describes a branch as going to the cavernous sinus to communicate with, the sixth nerve, and Tiedemann, a communicating branch to the ophthalmic ganglion. The descending or palatine branches are distributed to the roof of the mouth, the soft palate, tonsil, and dining membrane of the nose. They are almost a direct continuation of the spheno-palatine branches of the superior maxillary nerve, and are three in number-anterior, middle, and posterior. The anterior or large palatine nerve descends through the posterior palatine canal, emerges upon the hard palate at the posterior palatine foramen, and passes forward through a groove in the hard palate nearly as far as the incisor teeth. It supplies the gums, the mucous membrane and glands of the hard palate, and communicates in front with the termination of the naso-palatine nerve. While in the posterior palatine canal it gives off inferior nasal branches, which enter the nose through openings in the palate bone, and ramify over the middle meatus and the middle and inferior spongy bones; and, at its exit from the canal a palatine branch is distributed to both surfaces of the soft palate. The middle or external palatine nerve descends through one of the accessory palatine canals, distributing branches to the uvula, tonsil, and soft palate. It is occasionally wanting. The posterior or small palatine nerve descends with a small artery through the small posterior palatine canal, emerging by a separate opening behind the posterior palatine foramen. It supplies the Levator palati and Azygos uvulae muscles, the soft palate, tonsil, and uvula. The middle and posterior palatine join with the BRANCHES OF THE FIFTH NERVE. 767 tonsillar branches of the glosso-pharyngeal to form the plexus around the tonsil (circulus tonsillaris). The internal branches are distributed to the septum and outer wall of the nasal fossae. They are the superior nasal (anterior) and the naso-palatine. The superior nasal branches {anterior), four or five in number, enter the back part of the nasal fossa by the spheno-palatine foramen. They supply the mucous membrane covering the superior and middle spongy bones, and that lining the posterior ethmoidal cells, a few being prolonged to the upper and back part of the septum. One branch is continued on to the inner surface of the anterior wall of the antrum, and there forms a communication with the anterior dental nerve. At the point of communication a swelling exists, denominated "the ganglion of Bochdalek," the nature of which seems to be, however, uncertain. -The naso-palatine nerve (Cotunnius) also enters the nasal fossa through the spheno-palatine foramen, and passes inward across the roof of the nose, below the orifice- of the sphenoidal sinus, to reach the septum ; it then runs obliquely downward and forward along the lower part of the septum, to the anterior palatine foramen, lying between the periosteum and mucous membrane. It descends to the roof of the mouth through the anterior palatine canal. The two nerves are here contained in separate and distinct canals, situated in the intermaxillary suture, and termed the foramina of Scarpa, the left nerve being usually anterior to the right one. In the mouth they become united, supply the mucous membrane behind the incisor teeth, and join with the anterior palatine nerve. The naso- palatine nerve occasionally furnishes a few small filaments to the mucous mem- brane of the septum. The posterior branches are the pharyngeal (pterygo-palatine) and the upper posterior nasal branches. The pharyngeal nerve (pterygo-palatine) is a small branch arising from the back part of the ganglion, being generally blended with the Vidian nerve. It passes through the pterygo-palatine canal with the pterygo-palatine artery, and is distributed to the mucous membrane of the upper part of the pharynx, behind the Eustachian tube. The upper posterior nasal branches are a few twigs given off from the posterior part of the ganglion, which run backward in the sheath of the Vidian nerve to the mucous membrane at the back part of the roof, septum, and superior meatus of the nose and that covering the end of the Eustachian tube. The Inferior Maxillary Nerve distributes branches to the teeth and gums of the lower jaw, the integument of the temple and external ear, the lower part of the face and lower lip, and the muscles of mastication; it also supplies the tongue with a large branch. It is the largest of the three divisions of the fifth, and is made up of two roots: a large or sensory root proceeding from the inferior angle of the Gasserian ganglion; and a small or motor root, which passes beneath the ganglion, and unites with the sensory root just after its exit through the foramen ovale. Immediately beneath the base of the skull this nerve divides into two trunks, anterior and posterior. Previous to its division the primary trunk gives off from its inner side a recurrent (meningeal) branch and the nerve to the Internal pterygoid muscle. The recurrent branch is given off' directly after its exit from the foramen ovale. It passes backward into the skull through the foramen spinosum with the middle meningeal artery. It divides into two branches, anterior and posterior, which accompany the main divisions of the artery and supply the dura mater. The anterior branch communicates with the meningeal branch of the superior maxillary nerve. The Internal Pterygoid Nerve, given off from the inferior maxillary previous to its division, is intimately connected at its origin with the otic ganglion. It is a Inferior Maxillary Nerve (Fig. 444). 768 THE NERVOUS SYSTEM. long and slender branch, which passes inward to enter the deep surface of the Internal pterygoid muscle. The anterior and smaller division, which receives nearly the whole of the motor root, divides into branches which supply the muscles of mastication. They are the masseteric, deep temporal, buccal, and external pterygoid. The masseteric branch passes outward, above the External pterygoid muscle, in front of the temporo-maxillary articulation, and crosses the sigmoid notch with the masseteric artery to the Masseter muscle, in which it ramifies nearly as far as its anterior border. It occasionally gives a branch to the Temporal muscle and a filament to the articulation of the jaw. The deep temporal branches, two in number, anterior and posterior, supply the deep surface of the Temporal muscle. The posterior branch, of small size, is placed at the back of the temporal fossa. It is sometimes joined with the masse- teric branch. The anterior branch is reflected upward at the pterygoid ridge of the sphenoid to the front of the temporal fossa. Sometimes there are three deep temporal branches, the third branch (middle deep temporal} passing outward over the External pterygoid muscle to enter the deep surface of the Temporal muscle. The buccal branch passes forward between the two heads of the External pterygoid, and downward beneath the inner surface of the coronoid process of the lower jaw, or through the fibres of the Temporal muscle, to reach the surface of the Buccinator, upon which it divides into a superior and an inferior branch. It gives a branch to the External pterygoid during its passage through that muscle, and a few ascending filaments to the Temporal muscle, one of which occasionally joins with the anterior branch of the deep temporal nerve. The upper branch supplies the integument and upper part of the Buccinator muscle, joining with the facial nerve round the facial vein. The lower branch passes forward to the angle of the mouth : it supplies the integument and Buccinator muscle, as wrell as the mucous membrane lining the inner surface of that muscle, and joins the facial nerve.1 The External Pterygoid Nerve is most frequently derived from the buccal, but it may be given off separately from the anterior trunk of the nerve. It enters the muscle on its inner surface. The posterior and larger division of the inferior maxillary nerve is for the most part sensory, but receives a few7 filaments from the motor root. It divides into three branches : auriculo-temporal, lingual (gustatory), and inferior dental. The Auriculo-temporal Nerve generally arises by two roots, beneath which the middle meningeal artery passes. It runs backward beneath the External ptery- goid muscle to the inner side of the neck of the lower jaw7. It then turns upw ard with the temporal artery, between the external ear and condyle of the jaw7, under cover of the parotid gland, and, escaping from beneath this structure, ascends over the zygoma and divides into two temporal branches. The branches of communication are with the facial and with the otic ganglion. The branches of communication with the facial, usually two in number, pass forward from behind the neck of the condyle of the jaw7, to join this nerve at the posterior border of the Masseter muscle. They form one of the principal branches of communication between the facial and the fifth nerve. The filaments of communication with the otic ganglion are derived from the commencement of the auriculo-temporal nerve. The branches of distribution are- Auricular, inferior and superior. Branches to the meatus auditorius. Articular. Parotid. The inferior auricular arises behind the articulation of the jaw, and is distrib- Temporal, anterior and posterior. 1 There seems to be no reason to doubt that the branch supplying the Buccinator muscle is entire- ly a nerve of ordinary sensation, and that the true motor-supply of this muscle is from the facial. BRANCHES OF THE FIFTH NERVE. 769 uted to the ear below the external meatus: other filaments twine round the internal maxillary artery and communicate with the sympathetic. The superior auricular arises in front of the external edr, and supplies the integument cover- ing the tragus and pinna. Branches to the meatus auditorius, two in number, arise from the point of communication between the auriculo-temporal and facial nerves, and are distrib- uted to the meatus. A branch to the temporo-majcillary articulation is usually derived from the auriculo-temporal nerve. The parotid branches supply the parotid gland. The anterior temporal accompanies the temporal artery to the vertex of the skull, and supplies the integument of the temporal region, communicating with the facial nerve and the temporal branch of the temporo-malar from the superior maxillary. The posterior temporal, the smaller of the two, is distributed to the upper part of the pinna and the neighboring tissues. The Lingual Nerve (gustatory) supplies the papillae and mucous membrane of the tongue. It is deeply placed throughout the whole of its course. It lies at first beneath the External pterygoid muscle, together with the inferior dental nerve, being placed to the inner side of the latter nerve, and is occasionally joined to it by a branch which crosses the internal maxillary artery. The chorda tympani also joins it at an acute angle in this situation. The nerve then passes between the Internal pterygoid muscle and the inner side of the ramus of the jaw, and crosses obliquely to the side of the tongue over the Stylo-glossus muscle, and then between the Hyo-glossus muscle and deep part of the submaxil- lary gland: the nerve lastly runs across Wharton's duct, and along the side of the tongue to its apex, lying immediately beneath the mucous membrane. The branches of communication are with the facial through the chorda tympani, the inferior dental and hypoglossal nerves, and the submaxillary ganglion. The branches to the submaxillary ganglion are two or three in number ; those con- nected with the hypoglossal nerve form a plexus at the anterior margin of the Hyo-glossus muscle. The branches of distribution are few in number. They supply the mucous membrane of the mouth, the gums, the sublingual gland, the filiform and fungi- form papillse and mucous membrane of the tongue; the terminal filaments com- municate, at the tip of the tongue, with the hypoglossal nerve. The Inferior Dental is the largest of the three branches of the inferior max- illary nerve. It passes downward with the inferior dental artery, at first beneath the External pterygoid muscle, and then between the internal lateral ligament and the ramus of the jaw to the dental foramen. It then passes forward in the dental canal of the inferior maxillary bone, lying beneath the teeth, as far as the mental foramen, where it divides into two terminal branches, incisor and mental. The branches of the inferior dental are, the mylo-hyoid, dental, incisive, and mental. The mylo-hyoid is derived from the inferior dental just as that nerve is about to enter the dental foramen. It descends in a groove on the inner surface of the ramus of the jaw, in which it is retained by a process of fibrous membrane. It reaches the under surface of the Mylo-hyoid muscle, and supplies it and the anterior belly of the Digastric, occasionally sending one or two filaments to the submaxillary gland. The dental branches supply the molar and bicuspid teeth, They correspond in number to the fangs of those teeth: each nerve entering the orifice at the point of the fang and supplying the pulp of the tooth. The incisive branch is continued onward within the bone to the middle line, and supplies the canine and incisor teeth. The mental branch emerges from the bone at the mental foramen, and divides beneath the Depressor anguli oris into two or three branches; one descends to supply the skin of the chin, and another (sometimes two) ascends to supply the 770 THE NERVOUS SYSTEM. skin and mucous membrane of the lower lip. These branches communicate freely with the facial nerve. Two small ganglia are connected with the inferior maxillary nerve-the otic with the trunk of the nerve, and the submaxillary with its lingual branch. Otic Ganglion (Fig. 446). The Otic Ganglion (Arnold's) is a small, oval-shaped, flattened ganglion of a reddish-gray color, situated immediately below the foramen ovale, on the inner surface of the inferior maxillary nerve, and round the origin of the internal ptery- goid nerve. It is in relation, externally, with the trunk of the inferior maxillary nerve, at the point where the motor root joins the sensory portion; internally, with the cartilaginous part of the Eustachian tube, and the origin of the Tensor palati muscle; behind it is the middle meningeal artery. Branches of Communication.-This ganglion is connected with the internal pterygoid branch of the inferior maxillary nerve by two or three short, delicate filaments. From this it may obtain a motor root, and possibly also a sensory root, as these filaments from the nerve to the Internal pterygoid may contain sensory Fig. 446.-The otic ganglion and its branches. fibres. It communicates with the glosso-pharyngeal and facial nerves through the small superficial petrosal nerve continued from the tympanic plexus (page 779), and through this communication it probably receives its sensory root from the glosso-pharyngeal and its motor root from the facial; its communication with the sympathetic is effected by a filament from the plexus surrounding the middle meningeal artery. The ganglion also communicates with the auriculo-temporal nerve. This is probably a branch from the glosso-pharyngeal which passes to the ganglion, and through it and the auriculo-temporal nerve to the parotid gland. Its branches of distribution are a filament to the Tensor tympani and one to the Tensor palati. The former passes backward on the outer side of the Eustachian tube; the latter arises from the ganglion, near the origin of the internal pterygoid nerve, and passes forward. The fibres of these nerves are, however, mainly derived from the nerve to the Internal pterygoid muscle. It also gives off a small com- municating branch to the chorda tympani. BRANCHES OF THE FIFTH NERVE. 771 Submaxillary Ganglion (Fig. 444). The submaxillary ganglion is of small size, fusiform in shape, and situated above the deep portion of the submaxillary gland, near the posterior border of the Mylo-hyoid muscle, being connected by filaments with the lower border of the lingual (gustatory) nerve. Branches of Communication.-This ganglion is connected with the lingual (gustatory) nerve by a few filaments which join it separately at its fore and back part. It also receives a branch from the chorda tympani, by which it communicates with the facial, and communicates with the sympathetic by filaments from the sympathetic plexus around the facial artery. Branches of Distribution.-These are five or six in number: they arise from the lower part of the ganglion, and supply the mucous membrane of the mouth and Wharton's duct, some being lost in the submaxillary gland. The branch of com- munication from the lingual to the fore part of the ganglion is by some regarded as a branch of distribution, by which filaments of the chorda tympani pass from the ganglion to the nerve, and by it are conveyed to the sublingual gland and the tongue. Surface Marking.-It will be seen from the above description that the three terminal branches of the three divisions of the fifth nerve emerge from foramina in the bones of the skull and face on to the face: the terminal branch of the first division emerging through the supra- orbital foramen ; that of the second through the infra-orbital foramen; and the third through the mental foramen. The supra-orbital foramen is situated at the junction of the internal and middle third of the supra-orbital arch between the internal and external angular processes. If a straight line is drawn from this point to the lower border of the inferior maxillary bone, so that it passes between the two bicuspid teeth in both jaws, it will pass over the infra-orbital and mental foramina, the former being situated about one centimetre (two-fifths of an inch) below the margin of the orbit, and the latter varying in position according to the age of the individual. In the adult it is midway between the upper and lower borders of the inferior maxillary bone ; in the child it is nearer the lower border; and in the edentulous jaw of old age it is close to the upper margin. Surgical Anatomy.-The fifth nerve may be affected in its entirety, or its sensory or motor root may be affected, or one of its primary main divisions. In injury to the sensory root there is anaesthesia of the whole of the side of the face on the side of the lesion, with the exception of the skin over the parotid gland ; insensibility of the conjunctiva, followed by destructive inflam- mation of the cornea, partly from loss of trophic influence, and partly from the irritation pro- duced by the presence of foreign bodies on it, which are not perceived by the patient, and there- fore not expelled by the act of winking ; dryness of the nose, loss to a considerable extent of the sense of taste, and diminished secretion of the lachrymal and salivary glands. In injury to the motor root there is impaired action of the lower jaw from paralysis of the muscles of mastication on the affected side. The fifth nerve is often the seat of neuralgia, and each of the three divisions has been divided or a portion of the nerve excised for this affection. The supra-orbital nerve may be exposed by making an incision an inch and a half in length along the supra-orbital margin below the eyebrow, which is to be drawn upward, the centre of the incision corresponding to the supra- orbital notch. The skin and Orbicularis palpebrarum having been divided, the nerve can be easily found emerging from the notch and lying in some loose cellular tissue. It should be drawn up by a blunt hook and divided, or, what is better, a portion of it removed. The infra-orbital nerve has been divided at its exit by an incision on the cheek ; or the floor of the orbit has been exposed, the infra-orbital canal opened up, and the anterior part of the nerve resected ; or the whole nerve, together with Meckel's ganglion as far back as the foramen rotundum, has been removed. This latter operation, though undoubtedly a severe proceeding, appears to have been followed by the best results. The operation is performed as follows: The superior maxillary bone is first exposed by a T-shaped incision, one limb passing along the lower margin of the orbit, the other from the centre of this vertically down the cheek to the angle of the mouth. The nerve is then found, divided, and a piece of silk tied to it as a guide. A small trephine (one- half inch) is then applied to the bone below, but including, the infra-orbital foramen, and the antrum opened. The trephine is now applied to the posterior wall of the antrum, and the spheno-maxillary fossa exposed. The infra-orbital canal is now opened up from below by fine cutting-pliers or a chisel, and the nerve drawn down into the trephine hole, it being held on the stretch by means of the piece of silk; it is severed with fine curved scissors as near the foramen rotundum as possible, any branches coming off from the ganglion being also divided.1 The inferior dental nerve has been divided at its exit from the foramen by an incision made through the mucous membrane where it is reflected from the alveolar process on to the lower lip; or a portion of the nerve has been resected by an incision on the cheek through the Masseter muscle, 1 Carnochan, Amer. Joum. Med. Science, 1858, p. 136. 772 THE NERVOUS SYSTEM. exposing the outer surface of the ramus of the jaw. A trephine was then applied over the position of the inferior dental foramen and the outer table removed, so as to expose the inferior dental canal. The nerve was dissected out of the portion of the canal exposed, and, having been divided after its exit from the mental foramen, it was by traction on the end exposed in the trephine hole, drawn out entire, and cut off as high up as possible.1 The inferior dental nerve has also been divided by an incision within the mouth, the bony point guarding the inferior dental foramen forming the guide to the nerve. The buccal nerve may be divided by an incision through the mucous membrane of the mouth and the Buccinator just in front of the anterior border of the ramus of the lower jaw (Stimson). The lingual (gustatory) nerve is occasionally divided with the view of relieving the pain in cancerous disease of the tongue. This may be done in that part of its course where it lies below and behind the last molar tooth. If a line is drawn from the middle of the crown of the last molar tooth to the angle of the jaw, it will cross the nerve, which lies about half an inch behind the tooth, parallel to the bulging alveolar ridge on the inner side of the body of the bone. If the knife is entered three-quarters of an inch behind and below the last molar tooth and carried down to the bone, the nerve will be divided. Hilton divided it opposite the second molar tooth, where it is covered only by the mucous membrane, and Lucas pulls the tongue forward and over to the opposite side, when the nerve can be seen standing out as a firm cord under the mucous membrane by the side of the tongue, and can be easily seized with a sharp hook and divided or a portion excised. This is a simple enough operation on the cadaver, but when the disease is extensive and has extended to the floor of the mouth, as is generally the case when division of the nerve is required, the operation is not practicable. Sixth Nerve (Fig. 442). The Sixth or Abducent Nerve supplies the External rectus muscle. Its super- ficial origin is by several filaments from the constricted part of the pyramid close to the pons, or from the lower border of the pons itself in the groove between this body and the medulla. Its deep origin is a little lower than the motor root of the fifth, and close to the median line, beneath the anterior portion of the fasciculus teres on the floor of the fourth ventricle. The nerve pierces the dura mater on the basilar surface of the sphenoid bone, runs through a notch immediately below the posterior clinoid process, and enters the cavernous sinus. It passes forward through the sinus, lying on the outer side of the internal carotid artery. It enters the orbit through the sphenoidal fissure, and lies above the ophthalmic vein, from which it is separated by a lamina of dura mater. It then passes between the two heads of the External rectus, and is dis- tributed to that muscle on its ocular surface. Branches of Communication.-It is joined by several filaments from the carotid and cavernous plexus, by one from Meckel's ganglion (Bock), and another from the ophthalmic nerve. The above-mentioned nerve, as well as the third, fourth, and the ophthalmic division of the fifth, as they pass to the orbit, bear a certain relation to each other in the cavernous sinus, at the sphenoidal fissure, and in the cavity of the orbit, which will now be described. In the cavernous sinus (Fig. 384) the third, fourth, and ophthalmic division of the fifth are placed on the outer wall of the sinus, in their numerical order both from above downward and from within outward. The sixth nerve lies at the outer side of the internal carotid artery. As these nerves pass forward to the sphenoidal fissure, the third and fifth nerves become divided into branches, and the sixth approaches the rest, so that their relative position becomes considerably changed. In the sphenoidal fissure (Fig. 447) the fourth and the frontal and lachrymal divisions of the ophthalmic lie upon the same plane, the former being most internal, the latter external, and they enter the cavity of the orbit above the mus- cles. The remaining nerves enter the orbit between the two heads of the External rectus. The superior division of the third is the highest of these; beneath this lies the nasal branch of the ophthalmic; then the inferior division of the third; and the sixth lowest of all. In the orbit the fourth and the frontal and lachrymal divisions of the ophthal- 1 Mears, Trans. Amer. Surg. Assoc., vol. ii. p. 469. THE SEVENTH OR FACIAL NERVE. 773 mic lie on the same plane immediately beneath the periosteum, the fourth nerve being internal and resting on the Superior oblique, the frontal resting on the Levator palpebrge, and the lachrymal on the External rectus. Next in order comes the superior division of the third nerve, lying immediately beneath the Lachrymal. Frontal. 4th. ' Superior division of 3d. Nasal. "Inferior division of 3d. "6th. Ophthal mic rein. Fig. 447.-Relations of structures passing through the sphenoidal fissure. Superior rectus, and then the nasal branch of the ophthalmic, crossing the optic nerve from the outer to the inner side of the orbit. Beneath these is found the optic nerve, surrounded in front by the ciliary nerves, and having the lenticular ganglion on its outer side, between it and the External rectus. Below the optic is the inferior division of the third and the sixth, which lies on the outer side of the orbit. Surgical Anatomy.-The sixth nerve is more frequently involved in fractures of the base of the skull than any other of the cranial nerves. The result of paralysis of this nerve is internal or convergent squint. When injured so that its function is destroyed, there is, in addition to the paralysis of the External rectus muscle, often a certain amount of contraction of the pupil, because some of the sympathetic fibres to the radiating muscle of the iris pass along with this nerve. Seventh Nerve (Figs. 448, 449, 450). The Seventh or Facial Nerve (portio dura) is the motor nerve of all the mus- cles of expression in the face and of the Platysma and Buccinator, the muscles of the External ear, the posterior belly of the Digastric, and the Stylo-hyoid. Through its chorda tympani it sup- plies the Lingualis; by its tympa- nic branch the Stapedius. Its super- ficial origin is from the lateral tract of the medulla oblongata, in the groove between the olivary and restiform bodies. Its deep origin is from a nucleus on the floor of the fourth ventricle, a little below and external to the nucleus of the sixth, above the level of the auditory striae. The auditory nerve (portio mollis) lies to its outer side, and between the two is a small fasciculus (portio inter duram etmollem of Wrisberg, or pars intermedia), which arises from the medulla and joins the facial nerve in the internal auditory meatus. At its origin it is frequently connected with both the nerves between which it lies. I The facial nerve, firmer, rounder, and smaller than the auditory, passes forward and outward upon the middle peduncle of the cerebellum, and enters the internal auditory meatus with the auditory nerve. Within the meatus the facial nerve lies first to the inner side of the auditory, and then in a groove upon that nerve. The pars intermedia is placed between the facial and auditory nerves in the internal auditory meatus ; a few of its fibres frequently pass into the auditory nerve, while External petrosal... Small superficial petrosal.- Large superficial petrosal.' Intumescentia ganglioformis. ~ Seventh pair f Facial. ' I Auditory. Fig. 448.-The course and connections of the facial nerve in the temporal bone. 774 THE NERVOUS SYSTEM. the remainder join the facial. At the bottom of the meatus it is connected to this nerve by one or two slender filaments. At the bottom of the meatus the facial nerve enters the aqueductus Fallopii, and follows the serpentine course of that canal through the petrous portion of the temporal bone, from its commencement at the internal meatus to its termination at the stylo-mastoid foramen. It is at first directed outward toward the inner wall of the tympanum, where it forms a reddish gangliform swelling (intumescentia ganglioformis, or geniculate ganglion), and is joined by several nerves ; then bending suddenly backward, it runs in the internal wall of the tympanum, above the fenestra ovalis, and at the back of that cavity passes vertically downward behind the tympanum to the stylo-mastoid foramen. On emerging from this aperture it runs forward in the substance of the parotid gland, crosses the external carotid artery, and divides behind the ramus of the lower jaw into two primary branches, temporo-facial and cervico-facial, from which numerous offsets are distributed over the side of the head, face, and upper part of the neck, supplying the superficial muscles in these regions. As the primary branches and their offsets diverge from each other they present somewhat the appearance of a bird's claw ; hence the name of pes anserinus is given to the divisions of the facial nerve in and near the parotid gland. The communications of the facial nerve may be thus arranged : In the internal auditory meatus . With the auditory nerve. With Meckel's ganglion by the large superficial petrosal nerve. With the otic ganglion by the small superficial petrosal nerve. With the sympathetic on the middle meningeal by the external superficial petrosal nerve. In the aqueductus Fallopii . With the glosso-pharyngeal. With the pneumogastric. With the carotid plexus. With the auricularis magnus. With the auriculo-temporal. At its exit from the stylo-mastoid foramen On the face With the three divisions of the fifth. In the internal auditory meatus some minute filaments pass between the facial and auditory nerves. Opposite the hiatus Fallopii the gangliform enlargement on the facial nerve communicates with Meckel's ganglion by means of the large superficial petrosal nerve, which forms its motor root; with the otic ganglion, by the small superficial petrosal nerve ; and with the sympathetic filaments accompanying the middle meningeal artery, by the external petrosal (Bidder). From the gangliform enlarge- ment, according to Arnold, a twig is sent back to the auditory nerve. At its exit from the stylo-mastoid foramen it sends a twig to the glosso- pharyngeal, another to the pneumogastric nerve, and communicates with the carotid plexus of the sympathetic, with the great auricular branch of the cervical plexus, with the auriculo-temporal branch of the inferior maxillary nerve in the parotid gland, and on the face with the terminal branches of the three divisions of the fifth. Branches of Distribution Tympanic. Chorda Tympani. Within the aqueductus Fallopii . 1 1 . x .x .,r ,, ,i . At its exit from the stvlo-mastoid r J foramen Posterior Auricular. Digastric. Stylo-hyoid. 77ZA AEPfi'ATVZ OR FACIAL NERVE. 775 Temporal. Malar. Infra-orbital. Temporo-facial On the face Buccal. Supramaxillary. Inframaxillary. Cervico-facial The tympanic branch arises from the nerve opposite the pyramid ; it passes through a small canal in the pyramid and supplies the Stapedius muscle. The chorda tympani is given off from the facial as it passes vertically down- ward at the back of the tympanum, about a quarter of an inch before its exit from the stylo-mastoid foramen. It passes from belowr upward and forward in a distinct canal, and enters the cavity of the tympanum through an aperture (iter chordce postering) on its posterior wall between the opening of the mastoid cells and the attachment of the membrana tympani, and becomes invested with mucous membrane. It passes forward through the cavity of the tympanum, between the handle of the malleus and vertical ramus of the incus, to its anterior inferior angle, and emerges from that cavity through a foramen at the inner end of the Glaserian fissure, which is called the iter chordce anterius, or canal of Huguier. It then descends between the two Pterygoid muscles, meets the lingual nerve at an acute angle, and accompanies it to the submaxillary gland; part of it then joins the submaxillary ganglion ; the rest is continued onward into the proper muscular fibres of the tongue-the Inferior lingualis muscle. A few of its fibres probably pass through the submaxillary ganglion to the sublingual gland. Before joining the lingual nerve it receives a small communicating branch from the otic ganglion. The Posterior auricular nerve arises close to the stylo-mastoid foramen, and passes upward in front of the mastoid process, where it is joined by a filament from the auricular branch of the pneumogastric, and communicates with the Fig. 449.-Plan of the facial nerve. (After Flower.) 776 THE NERVOUS SYSTEM. mastoid branch of the auricularis magnus and with the small occipital. As it ascends between the meatus and mastoid process it divides into two branches. The auricular branch supplies the Retrahens aurem and the small muscles on the cranial surface of the pinna. The occipital branch, the larger, passes backward along the superior curved line of the occipital bone, and supplies the occipital portion of the Occipito-frontalis. The digastric branch usually arises by a common trunk with the Stylo-hyoid branch: it divides into several filaments, which supply the posterior belly of the Terminations of supratrochlear, of infratrochlear \ of nasal. Fig. 450.-The nerves of the scalp, face, and side of the neck. Digastric; one of these perforates that muscle to join the glosso-pharyngeal nerve. The stylo-hyoid is a long slender branch, which passes inward, entering the Stylo-hyoid muscle about its middle; it communicates with the sympathetic filaments on the external carotid artery. The Temporo-facial, the larger of the two terminal branches, passes upward and forward through the parotid glands, crosses the external carotid artery and temporo-maxillary vein, and passes over the neck of the condyle of the jaw, being connected in this situation with the auriculo-temporal branch of the inferior maxillary nerve, and divides into branches which are distributed over the temple and upper part of the face ; these are divided into three sets-temporal, malar, and infra-orbital. THE SEVENTH OR FACIAL NERVE. 777 The temporal branches cross the zygoma to the temporal region, supplying the Attrahens and Attollens aurem muscles, and join with the temporal branch of the temporo-maxillary, a branch of the superior maxillary, and with the auriculo- temporal branch of the inferior maxillary. The more anterior branches supply the frontal portion of the Occipito-frontalis, the Orbicularis palpebrarum, and Corruga- tor supercilii muscles, joining with the supra-orbital and lachrymal branches of the ophthalmic. The malar branches pass across the malar bone to the outer angle of the orbit, where they supply the Orbicularis palpebrarum muscle, joining with filaments from the lachrymal nerve; others supply the lower eyelid, joining with filaments of the malar branch (subcutaneus malce) of the superior maxillary nerve. The infra-orbital, of larger size than the rest, pass horizontally forward to be distributed between the lower margin of the orbit and the mouth. The superficial branches run beneath the skin and above the superficial muscles of the face, which they supply : some branches are distributed to the Pyramidalis nasi, joining at the inner angle of the orbit with the infratrochlear and nasal branches of the ophthalmic. The deep branches pass beneath the Zygomatici and the Levator labii superioris, supplying them and the Levator anguli oris, and form a plexus (infra- orbital} by joining with the infra-orbital branch of the superior maxillary nerve and the buccal branches of the cervico-facial. This branch also supplies the Levator labii superioris alaeque nasi and the small muscles of the nose. The Cervico-facial division of the facial nerve passes obliquely downward and forward through the parotid gland, crossing the external carotid artery. In this situation it is joined by branches from the great auricular nerve. Opposite the angle of the lower jaw it divides into branches which are distributed on the lower half of the face and upper part of the neck. These may be divided into three sets -buccal, supramaxillary, and inframaxillary. The buccal branches cross the Masseter muscle. They supply the Buccinator and Orbicularis oris, and join with the infra-orbital branches of the temporo-facial division of the nerve, and with filaments of the buccal branch of the inferior maxillary nerve. The supramaxillary branches pass forward beneath the Platysma and Depressor anguli oris, supplying the muscles of the lower lip and chin, and communicating with the mental branch of the inferior dental nerve. CJ The inframaxillary branches run forward beneath the Platysma, and form a series of arches across the side of the neck over the suprahyoid region. One of these branches descends vertically to join with the superficialis colli nerve from the cervical plexus; others supply the Platysma. Surgical Anatomy.-The facial nerve is more frequently paralyzed than any of the other of the cranial nerves. The paralysis may depend either upon (1) central causes-i. e. blood-clots or intracranial tumors pressing on the nerve before its entrance into the internal auditory meatus. It is also one of the nerves involved in " bulbar paralysis." Or (2) it may be paralyzed in its passage through the petrous bone by damage due to middle-ear disease or by fractures of the base. Or (3) it may be affected at or after its exit from the stylo-mastoid foramen. This is commonly known as " Bell's paralysis." It may be due to exposure to cold or to injury of the nerve, either from accidental wounds of the face or during some surgical operation, as removal of parotid tumors, opening of abscesses, or operations on the lower jaw. When the cause is central the sixth nerve is usually also paralyzed, and there is hemiplegia on the opposite side. In these cases the electrical reactions are the same as in health ; whereas when the paralysis is in the course of the nerve the reaction is usually lost. When the nerve is paralyzed in the petrous bone, in addition to the paralysis of the muscles of expression there is loss of taste in the anterior part of the tongue, and the patient is unable to recognize the differ- ence between bitters and sweets, acids and salines, from involvement of the chorda tympani. The mouth is dry, because the salivary glands are not secreting, and the sense of hearing is affected from paralysis of the Stapedius. When the cause of the paralysis is from fracture of the base of the skull, the auditory nerve and the petrosal nerves, which are connected with the intumescentia ganglioformis, are also involved. When the injury Is after the exit of the nerve from the stylo-mastoid foramen, all the muscles of expression, except the Levator palpebrae, together with the posterior belly of the Digastric and Stylo-hyoid, are paralyzed. There is smoothness of the forehead and the patient is unable to frown: the eyelids cannot be closed and the lower lid droops, so that the punctum is no longer in contact with the globe, and the 778 THE NERVOUS SYSTEM. tears run down the cheek; there is smoothness of the cheek and loss of the naso-Iabial furrow ; the nostril cannot be dilated; the mouth is drawn to the sound side, and there is inability to whistle ; food collects between the cheek and gum from paralysis of the Buccinator. The facial nerve is at fault in cases of so-called " histrionic spasm," which consists in an almost constant and uncontrollable twitching of the muscles of the face. This twitching is sometimes so severe as to cause great discomfort and annoyance to the patient and to interfere with sleep, and for its relief the facial nerve has been stretched. The operation is performed by making an incision behind the ear from the root of the mastoid process to the angle of the jaw. The parotid is turned forward, and the dissection carried along the anterior border of the Sterno-mastoid mus- cle and mastoid process until the upper border of the posterior belly of the Digastric is found, 'fhe nerve is parallel to this on about a level of the middle of the mastoid process. When found, the nerve must be stretched by passing a blunt hook beneath it and pulling it forward and out- ward. Too great force must not be used, for fear of permanent injury to the nerve. Eighth Nerve. The Eighth or Auditory Nerve (portio mollis} is the special nerve of the sense of hearing, being distributed exclusively to the internal ear. Its superficial origin is from the groove between the olivary and restiform bodies at the lower border of the pons. It lies external to the facial nerve. It has two deep origins: 1. From a prominence, the auditory tubercle, on the outer side of the inferior fovea on the floor of the fourth ventricle. 2. From a nucleus situated at the lateral angle of the same ventricle. The auditory nerve winds round the restiform body, and passes forward across the posterior border of the middle peduncle of the cerebellum, in company with the facial nerve, from which it is partially separated by a small artery (auditory). It then enters the internal auditory meatus with the facial nerve. At the bottom of the meatus it receives one or two filaments from the facial nerve, and then divides into two branches, cochlear and vestibular, which are distributed, the former to the cochlea, the latter to the vestibule and semicircular canals. The auditory nerve is soft in texture (hence the mollis}, and is destitute of neurilemma. The distribution of the auditory nerve in the internal ear will be found described along with the anatomy of that organ in a subsequent page. Surgical Anatomy.-The auditory nerve is frequently injured, together with the facial nerve, in fractures of the middle fossa of the base of the skull implicating the internal auditory meatus. The nerve may be either torn across, producing permanent deafness, or it may be bruised or pressed upon by extravasated blood or inflammatory exudation, when the deafness will in all probability be temporary. The nerve may also be injured by violent blows on the head without fracture, and deafness may arise from loud explosions from dynamite, etc., prob ably from some lesion of this nerve, which is more liable to be injured than the other cranial nerves on account of its structure. The test that the nerve is destroyed and that the deafness is not due to some lesion of the auditory apparatus is obtained by placing a vibrating tuning-fork on the head. The vibrations will be heard in cases where the auditory apparatus is at fault, but not in cases of destruction of the auditory nerve. Ninth Pair (Figs. 451, 452, 453). The Ninth or Glosso-pharyngeal Nerve (Figs. 451, 452, 453) is distributed, as its name implies, to the tongue and pharynx, being the nerve of sensation to the mucous membrane of the pharynx, fauces, and tonsil, and a special nerve of taste to all the parts of the tongue to which it is distributed. Its superficial origin is by three or four filaments closely connected together, from the upper part of the medulla oblongata, in the groove between the olivary and the restiform body. Its deep origin may be traced through the fasciculi of the lateral tract to a nucleus of gray matter at the lower part of the floor of the fourth ventricle, beneath the inferior fovea, below the inner nucleus of the auditory nerve, and above that of the pneumogastTic. From its superficial origin it passes outward across the flocculus, and leaves the skull at the central part of the jugular fora- men, in a separate sheath of the dura mater, in front of the pneumogastric and spinal accessory nerves (Fig. 386). In its passage through the jugular foramen it grooves the lower border of the petrous portion of the temporal bone, and 77/A NINTH OR GLOSSO-PHARYNGEAL NERVE. 779 at its exit from the skull passes forward between the jugular vein and internal carotid artery, and descends in front of the latter vessel, and beneath the styloid process and the muscles connected with it, to the lower border of the Stylo- pharyngeus. The nerve now curves inward, forming an arch on the side of the neck, and lying upon the Stylo-pharyngeus and Mid- dle constrictor of the pharynx, above the superior laryngeal nerve. It then passes beneath the Hyo- glossus, and is finally distributed to the mucous membrane of the fauces and base of the tongue, and the mucous glands of the mouth and tonsil. In passing through the jugular foramen the nerve presents, in succession, two gangliform enlarge- ments. The superior, the smaller, is called the Ju/y- ular ganglion; the inferior and larger, the petrous ganglion, or the ganglion of Andersch. ' The superior, or jugular, ganglion is situated in the uppei' part of the groove in which the nerve is lodged during its passage through the jugular foramen. It is of very small size, and involves only the lower part of the trunk of the nerve. It is usually regarded as a segmentation from the lower ganglion. The inferior, or petrous, ganglion is situated in a depression in the lower bor- der of the petrous portion of the temporal bone; it is larger than the former and involves the whole of the fibres of the nerve. From this ganglion arise those filaments which connect the glosso-pharyngeal with the pneumogastric and sym- pathetic nerves. The branches of communication are with the pneumogastric, sympathetic, and facial. The branches to the pneumogastric are two filaments, arising from the petrous ganglion, one to its auricular branch, and one to the upper ganglion of the pneumogastric. The branch to the sympathetic, also arising from the petrous ganglion, is con- nected with the superior cervical ganglion. The branch of communication with the facial perforates the posterior belly of the Digastric. It arises from the trunk of the nerve below the petrous ganglion, and joins the facial just after its exit from the stylo-mastoid foramen. The branches of distribution are the tympanic, carotid, pharyngeal, muscular, tonsillar, and lingual. The tympanic branch (Jacobson s nerve) arises from the petrous ganglion, and enters a small bony canal in the lower surface of the petrous portion of the tem- poral bone, the lower opening of which is situated on the bony ridge which sep- arates the carotid canal from the jugular fossa. It ascends to the tympanum, enters that cavity by an aperture in its floor close to the inner wall, and divides into branches which are contained in grooves upon the surface of the promontory, forming the tympanic plexus. Its branches of distribution are-one to the fenestra rotunda, one to the fenestra ovalis, and one to the lining membrane of the tympanum and Eustachian Its branches of communication are three, and occupy separate grooves on the surface of the promontory. One branch, the small deep petrosal, arches forward and downward to the carotid canal to join the carotid plexus. A second, the long petrosal nerve, runs forward through a canal close to or in the processus cochleariformis and enters the foramen lacerum medium, where it joins the carotid plexus of the sympathetic, and generally the large superficial petrosal nerve. The third branch runs upward through the substance of the petrous por- tion of the temporal bone. In its course it passes by the gangliform enlargement of the facial nerve, and, receiving a connecting filament from it, becomes the small superficial petrosal nerve. This nerve enters the skull through a small aperture situated external to the hiatus Fallopii on the anterior surface of the .Jugular ganglion. Petrous ganglion. Tympanic br. Fig. 451.-Nerves of the eighth pair, their origin, ganglia, and communica- tions. 780 THE NERVOUS SYSTEM. Branches I from cer- p viced plead -\ms. I [superior \cervical cardiac. Thoracic/ cardiac.' To || STERNO- MASTOID. Posterior} pulmonary.} Fig. 452.-Plan of the glosso-pharyngeal, pneumogastric, and spinal accessory nerves. (After Flower.) petrous bone, courses forward across the base of the skull, and emerges through a foramen in the middle fossa (sometimes in the foramen ovale), and joins the otic ganglion. THE TENTH OR PNEUMOGASTRIC NERVE. 781 The carotid branches descend along the trunk of the internal carotid artery as far as its commencement, communicating with the pharyngeal branch of the pneumogastric and with branches of the sympathetic. The pharyngeal branches are three or four filaments which unite opposite the Middle con- strictor of the pharynx with the pharyngeal branches of the pneu- mogastric, the external laryngeal, and sympathetic nerves to form the pharyngeal plexus, branches from which perforate the muscu- lar coat of the pharynx to sup- ply the muscles and mucous membran'e. The muscular branch is dis- tributed to the Stylo-pharyngeus. The tonsillar branches supply the tonsil, forming a plexus (czr- culus tonsillaris') around this body, from which branches are distributed to the soft palate and fauces, where they communicate with the palatine nerves. The lingual branches are two in number: one supplies the circumvallate papillae and the mucous membrane covering the surface of the base of the tongue; the other perforates its substance, and supplies the mucous mem- brane and follicular glands of the tongue and anterior surface of the epiglottis. Tenth Pair (Figs. 452, 453). The Tenth or Pneumogastric Nerve (nervus vagus or par vagum) has a more extensive distribution than any of the other cranial nerves, passing through the neck and thorax to the upper part of the abdomen. It is composed of both motor and sensory fibres. It supplies the organs of voice and respiration with motor and sensory fibres, and the pharynx, oesophagus, stomach, and heart with motor fibres. Its superficial origin is by eight or ten filaments from the groove between the olivary and the restiform body below the glosso-pharyn- geal; its deep origin may be traced through the fasciculi of the medulla, to terminate in a nucleus of gray matter at the lower part of the floor of the fourth ventricle, below' and continuous with the nucleus of origin of the Glosso-pharyngeal. . Pneumogastric. Spinal accessory. 'Superior laryngea nerve. 'External laryngeal. ''Inferior laryngeal. *-Car diac. Fig. 453.-Course and distribution of the eighth pair of nerves. 782 77777 NERVOUS SYSTEM. glosso-pharyngeal. The filaments become united and form a flat cord, which passes outward beneath the flocculus to the jugular foramen, through which it emerges from the cranium. In passing through this opening the pneu- mogastric accompanies the spinal accessory, being contained in the same sheath of dura mater with it, a membranous septum separating it from the glosso-pharyngeal, which lies in front (Fig. 386). The nerve in this situation presents a well-marked ganglionic enlargement, which is called the jugular gan- glion, or the ganglion of the root of the pneumogastric: to it the accessory part of the spinal accessory nerve is connected by one or two filaments. After the exit of the nerve from the jugular foramen the nerve is joined by the accessory portion of the spinal accessory, and enlarged into a second gangliform swelling, called the ganglion inferius, or the ganglion of the trunk of the nerve, through which the fibres of the spinal accessory pass unchanged, being principally distributed to the pharyngeal and superior laryngeal branches of the vagus; but some of the fila- ments from it are continued into the trunk of the vagus below the ganglion, to be distributed with the recurrent laryngeal nerve, and probably also with the cardiac nerves. The nerve passes vertically down the neck within the sheath of the carotid vessels lying between the internal carotid artery and internal jugular vein as far as the thyroid cartilage, and then between the same vein and the common carotid to the root of the neck. Here the course of the nerve becomes different on the two sides of the body. On the right side the nerve passes across the subclavian artery between it and the right innominate vein, and descends by the side of the trachea to the back part of the root of the lung, where it spreads out in a plexiform network (posterior pul- monary), from the lower part of which two cords descend upon the oesophagus, on which they divide, forming, with branches from the opposite nerve, the oesophageal plexus (plexus gulce); below, these branches are collected into a single cord, which runs along the back part of the oesophagus, enters the abdomen, and is distributed to the posterior surface of the stomach, joining the left side of the solar plexus, and sending filaments to the splenic plexus and a considerable branch to the coeliac plexus. On the left side the pneumogastric nerve enters the chest between the left carotid and subclavian arteries, behind the left innominate vein. It crosses the arch of the aorta and descends behind the root of the left lung, forming the poste- rior pulmonary plexus, and'along the anterior surface of the oesophagus, where it unites with the nerve of the right side in forming the plexus gulae, to the stomach, distributing branches over its anterior surface, some extending over the great cul-de-sac, and others along the lesser curvature. Filaments from these branches enter the gastro-hepatic omentum and join the hepatic plexus. The ganglion of the root is of a grayish color, circular in form, about two lines in diameter, and resembles the ganglion on the large root of the fifth nerve. Connecting Branches.-To this ganglion the accessory portion of the spinal accessory nerve is connected by several delicate filaments; it also has a communi- cating twig with the petrous ganglion of the glosso-pharyngeal, with the facial nerve by means of its auricular branch, and with the sympathetic by means of an ascending filament from the superior cervical ganglion. The ganglion of the trunk (inferior) is a plexiform cord, cylindrical in form, of a reddish color, and about an inch in length ; it involves the whole of the fibres of the nerve, and passing through it is the accessory portion of the spinal accessory nerve, which blends xvith the pneumogastric below the ganglion, and is then principally continued into its pharyngeal and superior laryngeal branches. Connecting Branches.-This ganglion is connected with the hypoglossal, the superior cervical ganglion of the sympathetic, and the loop between the first and second cervical nerves. The branches of the pneumogastric are- THE TENTH OR PNEUMO GASTRIC NERVE. 783 Meningeal. Auricular. In the jugular fossa . Pharyngeal. Superior laryngeal. Recurrent laryngeal. Cervical cardiac. In the neck Thoracic cardiac. Anterior pulmonary. Posterior pulmonary. (Esophageal. In the thorax In the abdomen . Gastric. The meningeal branch is a recurrent branch given off from the ganglion of the root in the jugular foramen. It passes backward, and is distributed to the dura mater covering the posterior fossa of the base of the skull. The auricular branch (Arnold's) arises from the ganglion of the root, and is joined soon after its origin by a filament from the petrous ganglion of the glosso- pharyngeal; it passes outward behind the jugular vein, and enters a small canal on the outer wall of the jugular fossa. Traversing the substance of the temporal bone, it crosses the aqueductus Fallopii about two lines above its termination at the stylo-mastoid foramen ; here it gives off an ascending branch, which joins the facial: the continuation of the nerve reaches the surface by passing through the auricular fissure between the mastoid process and the external auditory meatus, and divides into two branches, one of which communicates with the posterior auricular nerve, while the other supplies the integument at the back part of the pinna and the posterior part of the external auditory meatus. The pharyngeal branch, the principal motor nerve of the pharynx, arises from the upper part of the inferior ganglion of the pneumogastric. It consists principally of filaments from the accessory portion of the spinal accessory: it passes across the internal carotid artery (in front or behind) to the upper border of the Middle constrictor, where it divides into numerous filaments, which join with those from the glosso-pharyngeal, superior laryngeal (its external branch), and sympathetic, to form the pharyngeal plexus, from which branches are distributed to the muscles and mucous membrane of the pharynx and the muscles of the soft palate. From the pharyngeal plexus a minute filament is given off, which descends and joins the hypoglossal nerve as it winds round the occipital artery. The superior laryngeal is the nerve of sensation to the larynx. It is larger than the preceding, and arises from the middle of the inferior ganglion of the pneumo- gastric. It consists principally of filaments from the accessory portion of the spinal accessory. In its course it receives a branch from the superior cervical ganglion of the sympathetic. It descends by the side of the pharynx behind the internal carotid, where it divides into two branches, the external and internal laryngeal. The external laryngeal branch, the smaller, descends by the side of the larynx, beneath the Sterno-thyroid, to supply the Crico-thyroid muscle. It gives branches to the pharyngeal plexus and the Inferior constrictor, and communicates with the superior cardiac nerve, behind the common carotid. The internal laryngeal branch descends to the opening in the thyro-hyoid membrane, through which it passes with the superior laryngeal artery, and is distributed to the mucous membrane of the larynx. A small branch communicates with the recurrent laryngeal nerve. The branches to the mucous membrane are distributed, some in front to the epiglottis, the base of the tongue, and the epiglottidean glands ; while others pass backward, in the aryteno-epiglottidean fold, to supply the mucous membrane surrounding the superior orifice of the larynx, as well as the membrane which lines the cavity of the larynx as low down as the vocal cord. The filament which joins with the recurrent laryngeal descends beneath the mucous membrane on the inner surface of the thyroid cartilage, where the two nerves become united. 784 THE NERVOUS SYSTEM. The inferior or recurrent laryngeal, so called from its reflected course, is the motor nerve of the larynx. It arises on the right side, in front of the subclavian artery ; winds from before backward round that vessel, and ascends obliquely to the side of the trachea, behind the common carotid and inferior thyroid arteries. On the left side it arises in front of the arch of the aorta, and winds from before backward round the aorta at the point where the remains of the ductus arteriosus are connected with it, and then ascends to the side of the trachea. The nerves on both sides ascend in the groove between the trachea and oesophagus, and, passing under the lowei' border of the Inferior constrictor muscle, enter the larynx behind the articulation of the inferior cornu of the thyroid cartilage with the cricoid, being distributed to all the muscles of the larynx, except the Crico-thyroid. It communicates with the Superior laryngeal nerve. The recurrent laryngeal, as it winds round the subclavian artery and aorta, gives 011 several cardiac filaments, which unite with the cardiac branches from the pneumogastric and sympathetic. As it ascends in the neck it gives off oesophageal branches, more numerous on the left than on the right side, which supply the mucous membrane and muscular coat of the oesophagus ; tracheal branches to the mucous membrane and muscular fibres of the trachea : and some pharyngeal filaments to the Inferior constrictor of the pharynx. The cervical cardiac branches, two or three in number, arise from the pneumo- gastric, at the upper and lower part of the neck. The superior branches are small, and communicate with the cardiac branches of the sympathetic. They can be traced to the great or deep cardiac plexus. The inferior branches, one on each side, arise at the lower part of the neck, just above the first rib. On the right side this branch passes in front or by the side of the arteria innominata, and communicates with one of the cardiac nerves proceeding to the great or deep cardiac plexus. On the left side it passes in front of the arch of the aorta and joins the superficial cardiac plexus. The thoracic cardiac branches, on the right side, arise from the trunk of the pneumogastric as it lies by the side of the trachea, and from its recurrent laryngeal branch, but on the left side from the recurrent nerve only; passing inward, they terminate in the deep cardiac plexus. The anterior pulmonary branches, two or three in number, and of small size, are distributed on the anterior aspect of the root of the lungs. They join w ith filaments from the sympathetic, and form the anterior pulmonary plexus. The posterior pulmonary branches, more numerous and larger than the anterior, are distributed on the posterior aspect of the root of the lung : they are joined by filaments from the third and fourth (sometimes also first and second) thoracic ganglia of the sympathetic, and form the posterior pulmonary plexus. Branches from both plexuses accompany the ramification of the air-tubes through the substance of the lungs. The oesophageal branches are given off from the pneumogastric both above and below the pulmonary branches. The lower are more numerous and larger than the upper. They form, together w ith branches from the opposite nerve, the oesophageal plexus or plexus gulai. The gastric branches are the terminal filaments of the pneumogastric nerve. The nerve on the right side is distributed to the posterior surface of the stomach, and joins the left side of the coeliac plexus and the splenic plexus. The nerve on the left side is distributed over the anterior surface of the stomach, some filaments passing across the great cul-de-sac, and others along the lesser curvature. They unite with branches of the right nerve and with the sympathetic, some fila- ments passing through the lesser omentum to the hepatic plexus. Surgical Anatomy.-The laryngeal nerves are of considerable importance in considering some of the morbid conditions of the larynx. When the peripheral terminations of the superior laryngeal nerve are irritated by some foreign body passing over them, reflex spasm of the glottis is the result. When the trunk of this same nerve is pressed upon by, for instance, a goitre or an aneurism of the upper part of the carotid, we have a peculiar dry, brassy cough. When the 7777? ELEVENTH OR SPINAL ACCESSORY NERVE. 785 nerve is paralyzed, we have anaesthesia of the mucous membrane of the larynx, so that foreign bodies can readily enter the cavity, and, in consequence of its supplying the crico-thyroid muscle, the vocal cords cannot be made tense, and the voice is deep and hoarse. Paralysis of the superior laryngeal nerves may be the result of bulbar paralysis, may be a sequel to diphtheria, when both nerves are usually involved, or it may, though less commonly, be caused by the pressure of tumors or aneurisms, when the paralysis is generally unilateral. Irritation of the inferior laryngeal nerves produces spasm of the muscles of the larynx. When both these recurrent nerves are paralyzed, the vocal cords are motionless, in the so-called " cadaveric posi- tion "-that is to say, in the position in which they are found in ordinary tranquil respiration- neither closed as in phonation, nor open as in deep inspiratory efforts. When one recurrent nerve is paralyzed, the cord of the same side is motionless, while the opposite one crosses the middle line to accommodate itself to the affected one; hence phonation is present, but the voice is altered and weak in timbre. The recurrent laryngeal nerves may be paralyzed in bulbar paralysis or after diphtheria, when it usually affects both sides; or they may be affected by the pressure of aneurisms of the aorta, innominate or subclavian arteries ; by mediastinal tumors ; by bronchocele ; or by cancer of the upper part of the oesophagus, when the paralysis is often unilateral. The "Eleventh, or Spinal Accessory Nerve consists of two parts-one the accessory part to the vagus, and the other the spinal portion. The accessory part is the smaller of the two. Its superficial origin is by four or five delicate filaments from the side of the medulla, below the roots of the vagus. Its deep origin may be traced to a nucleus of gray matter at the back of the medulla, extending from the level of the top of the calamus scriptorius as far down as the intermedio-lateral tract of the spinal cord. It passes outward to the jugular foramen, where it joins with the spinal portion and with the upper ganglion of the vagus by one or two filaments, and is then continued over the surface of this ganglion to join the trunk of the vagus after its exit from the jugular foramen. The fibres of the accessory part then pass unchanged through the inferior ganglion, or ganglion of the trunk of the vagus, to be distributed principally to the pharyngeal and superior laryngeal branches of the pneumogastric. Through the pharyngeal branch it probably supplies the muscles of the soft palate (see page 425). Some few filaments from it are continued into the trunk of the vagus below the ganglion, to .be distributed with the recurrent laryngeal nerve and probably also with the cardiac nerves. The spinal portion is firm in texture. Its superficial origin is by several filaments from the lateral tract of the cord, as low down as the sixth cervical nerve. Its deep origin may be traced to the intermedio-lateral tract of the gray matter of the cord. This portion of the nerve ascends between the ligamentum denticulatum and the posterior roots of the spinal nerves, enters the skull through the foramen magnum, and is then directed outward to the jugular foramen, through which it passes, lying in the same sheath as the pneumogastric, but separated from it by a fold of the arachnoid. In the jugular foramen it receives one or two filaments from the accessory portion. At its exit from the jugular foramen it passes backward, either in front of or behind the internal jugulai' vein, and descends obliquely behind the Digastric and Stylo-hyoid muscles to the upper part of the Sterno-mastoid. It pierces that muscle, and passes obliquely across the occipital triangle, to terminate in the deep surface of the Trapezius. This nerve gives several branches to the Sterno-mastoid during its passage through it, and joins in its substance with branches from the second cervical, which supplv the muscle. In the occipital triangle it joins with the second and third cervical nerves and assists in the formation of the cervical plexus. Beneath the Trapezius it joins with the third and fourth cervical nerves to form a sort of plexus, from which fibres are distributed to the muscle. Eleventh Pair (Figs. 452, 453). Surgical Anatomy.-In cases of spasmodic torticollis in which all previous palliative treat- ment has failed, and the spasms are so severe as to undermine the patient's health, division or excision of a portion of the spinal accessory nerve has been resorted to. This may be done either along the anterior or posterior border of the Sterno-mastoid muscle. The former operation is performed by making an incision from the apex of the mastoid process, three inches in length, along the anterior border of the Sterno-mastoid muscle. The anterior border of the muscle is 786 THE NERVOUS SYSTEM. defined and pulled backward, so as to stretch the nerve, which is then to be sought for beneath the Digastric muscle, about two inches below the apex of the mastoid process. The other operation consists in making an incision along the posterior border of the muscle, so that the centre of the incision corresponds to the middle of this border of the muscle. The superficial structures having been divided and the border of the muscle defined, the nerve is to be sought for as it emerges from the muscle to cross the occipital triangle. When found, it is to be traced upward through the muscle, and a portion of it excised above the point where it gives off its branches to the Sterno-mastoid. In this operation one of the descending branches of the super- ficial cervical plexus is liable to be mistaken for the nerve. Twelfth Pair (Figs. 453, 454). The Twelfth or Hypoglossal Nerve is the motor nerve of the tongue. Its superficial origin is by several filaments, from ten to fifteen in number, from the To .G E N IO-H YO-G LOSSUS. To ganglion of trunk of tenth. To HYO-GLOSSUS. sGE N IO-H YO I D. To Stylo-glossus. To dura- mater. To loop between first and second, cervical = spinal nerves. THYRO- HYOID. DMO-HYOID (ant. part). To upper cervical ganglion of sympathetic.t To lingual. (.POST. part). From second cervical From third cervical nerve. Fig. 454.-Plan of the hypoglossal nerve. (After Flower.) groove between the pyramidal and olivary bodies, in a continuous line with the anterior roots of the spinal nerves. Its deep origin can be traced to a nucleus of gray matter on the floor of the fourth ventricle, on either side of the median line, extending from the level of the auditory striae to the lowest point of the ventricle of Arantius. The filaments of this nerve are collected into two bundles which perforate the dura mater separately, opposite the anterior condyloid foramen, and unite together after their passage through it. In those cases in which the anterior condyloid foramen in the occipital bone is double these two portions of the nerve are separated by the small piece of bone which divides the foramen. The nerve descends almost vertically to a point corresponding with the angle of the jaw. It is at first deeply seated beneath the internal carotid artery and internal jugular vein, and intimately connected with the pneumogastric nerve ; it then passes forward between the vein and artery, and lower down in the neck becomes super- ficial below the Digastric muscle. The nerve then loops round the occipital artery, and crosses the external carotid below the tendon of the Digastric muscle. It THE TWELFTH OR HYPOGLOSSAL NERVE. 787 passes beneath the Mylo-hyoid muscle, lying between it and the Hyo-glossus, and communicates at the anterior border of the latter muscle with the lingual (gus- tatory) nerve; it is then continued forward in the fibres of the Genio-hyo-glossus muscle as far as the tip of the tongue, distributing branches to its substance. The branches of communication are-with the Pneumogastric. Sympathetic. First and Second Cervical Nerves. Lingual (gustatory). The communication with the pneumogastric takes place close to the exit of the nerve from the skull, numerous filaments passing between the hypoglossal and Hypo-glossal nerve. Pneumogastric nerve. s-- Glosso-pharyngeal nerve. Fig. 455.-Hypoglossal nerve, cervical plexus, and their branches. lower ganglion of the pneumogastric; sometimes the two nerves are united so as to form one mass. It also communicates with the pharyngeal plexus by a minute filament as it winds round the occipital artery. The communication with the sympathetic takes place opposite the atlas by branches derived from the superior cervical ganglion, and in the same situation the nerve is joined by a filament derived from the loop connecting the first two cervical nerves. The communication with the lingual (gustatory) takes place near the anterior border of the Hyo-glossus muscle by numerous filaments which ascend upon it. The branches of distribution are-the Meningeal. Descendens hypoglossi. Thyro-hyoid. Muscular. Meningeal Branches.-As the hypoglossal nerve passes through the anterior 788 77Z7f NERVOUS SYSTEM. condyloid foramen it gives off, according to Luschka, several filaments to the dura mater in the posterior fossa of the base of the skull. The descendens hypoglossi is a long slender branch which quits the hypoglossal where it turns round the occipital artery. It descends obliquely across the sheath of the carotid vessels, and joins the communicating branches from the second and third cervical nerves, just below the middle of the neck, to form a loop. From the convexity of this loop branches pass forward to supply the Sterno-hyoid, Sterno- thyroid, and both bellies of the Omo-hyoid. According to Arnold, another filament descends in front of the vessels into the chest and joins the cardiac and phrenic nerves. The descendens hypoglossi is occasionally contained in the sheath of the carotid vessels, being sometimes placed over, and sometimes beneath, the internal jugular vein. The thyro-hyoid is a small branch arising from the hypoglossal near the poste- rior border of the Hyo-glossus; it passes obliquely across the great cornu of the hyoid bone and supplies the Thyro-hyoid muscle. The muscular branches are distributed to the Stylo-glossus, Hyo-glossus, Genio- hyoid, and Genio-hyo-glossus muscles. At the under surface of the tongue numer- ous slender branches pass upward into the substance of the organ to supply its muscular structure. Surgical Anatomy.-The hypoglossal nerve is an important guide in the operation of liga- ture of the lingual artery (see page 555). It runs forward just above the great cornu of the hyoid bone, and forms the upper boundary of the triangular space in which the artery is to be sought for. The spinal nerves are so called because they take their origin from the spinal cord, and are transmitted through the intervertebral foramina on either side of the spinal column. There are thirty-one pairs of spinal nerves, which are arranged into the following groups, corresponding to the region of the spine through which they pass: THE SPINAL NERVES. Cervical 8 pairs. Dorsal 12 " Lumbar 5 " Sacral , 5 " Coccygeal 1 pair. It will be observed that each group of nerves corresponds in number with the vertebrae in that region, except the cervical and coccygeal. Each spinal nerve arises by two roots, an anterior or motor root, and a.pos- terior or sensory root. Roots of the Spinal Nerves. The Anterior Roots.-The superficial origin is from a somewhat irregular series of depressions which map out a longitudinal area on the antero-lateral column of the spinal cord, gradually approaching toward the anterior median fissure as they descend. The deep origin can be traced to the anterior part of the antero-lateral column ; the roots, after penetrating horizontally through the longitudinal fibres of this tract, enter the gray substance, where their fibrils diverge in several directions : some, passing mwartZ, are continued across the anterior commissure in front of the cen- tral canal, to become continuous with the axis-cylinder processes of the large cells of the anterior cornua of the opposite side ; others terminate in the mesial group of cells of the anterior column of the same side ; other fibrils pass outward, some to become continuous with the axis-cylinder processes of the group of cells in the lateral part of the anterior column ; and others enter the lateral column of the same side, where, turning upward, they pursue their course as longitudinal fibres. The remaining fibrils pass backward to the posterior horn, where they are continuous with the axis-cylinders of the cells at the base of the posterior cornu. THE SPINAL NERVES. 789 The Posterior Roots.-The superficial origin is from the postero-lateral fissure of the cord. The deep origin is from the gray substance of the posterior cornu, either directly through the substantia gelatinosa, or indirectly, by first passing through the white matter of the posterior column and winding round in front of the caput cornu. Those which enter the gray matter at once for the most part turn upward and downward, and become continuous with the fine nerve-plexus in the central portion of the gray matter; some few fibres pass transversely through the posterior commissure to the opposite side, and others into the anterior cornu of the same side. Those fibres which enter the gray matter in front of the caput cornu reach the posterior vesicular column (Clark's column) and blend with it, a few fibres passing through it, to become longitudinal in the posterior column of the cord. The anterior roots are smaller than the posterior, devoid of ganglionic enlarge- ment, and their component fibrils are collected into two bundles near the inter- vertebral foramina. The posterior roots of the nerves are larger, but the individual filaments are finer and more delicate than those of the anterior. As their component fibrils pass outward, toward the aperture in the dura mater, they coalesce into two bun- dles, receive a tubular sheath from that membrane, and enter the ganglion which is developed upon root. The posterior root of the first cervical nerve forms an exception to these cha- racters. It is smaller than the anterior, has frequently no ganglion developed upon it, and when the ganglion exists it is often situated within the dura mater. Ganglia of the Spinal Nerves. A ganglion is developed upon the posterior root of each of the spinal nerves. These ganglia are of an oval form and of a reddish coloi*; they bear a proportion in size to the nerves upon which they are formed, and are placed in the interver- tebral foramina, external to the point where the nerves perforate the dura mater. Each ganglion is bifid internally, where it is joined by the two bundles of the posterior root, the two portions being united into a single mass externally. The ganglion upon the first and second cervical nerves forms an exception to these characters, being placed on the arches of the vertebrae over which the nerves pass. The ganglia, also, of the sacral nerves are placed within the spinal canal; and that on the coccygeal nerve, also in the canal, about the middle of its posterior root. Distribution of the Spinal Nerves. Immediately beyond the ganglion the two roots coalesce, their fibres inter- mingle, and the trunk thus formed passes out of the intervertebral foramen, and divides into a posterior division for the supply of the posterior part of the body, and an anterior division for the supply of the anterior part of the body, each con- taining fibres from both roots. The posterior divisions of the spinal nerves are generally smaller than the anterior; they arise from the trunk resulting from the union of the roots in the intervertebral foramina, and, passing backward, divide into internal and external branches, which are distributed to the muscles and integument behind the spine. The first cervical and lower sacral nerves are exceptions to these characters. The anterior divisions of the spinal nerves supply the parts of the body in front of the spine, including the limbs. They are for the most ,part larger than the posterior divisions, this increase of size being proportioned to the larger extent of structures they are required to supply. Each division is connected by slender filaments with the sympathetic. In the dorsal region the anterior divisions of the spinal nerves are completely separate from each other, and are uniform in their distribution; but in the cervical, lumbar, and sacral regions they form intricate plexuses previous to their distribution. 790 TWA' NERVOUS SYSTEM. Points of Emergence of the Spinal Nerves. The roots of the spinal nerves from their origin in the cord run obliquely downward to their point of exit from the intervertebral foramina, the amount of obliquity varying in different regions of the spine, and being greater in the lower than the upper part. The level of their emergence from the cord is within certain limits variable, and of course does not correspond to the point of emergence of the nerve from the intervertebral foramina. The accompanying table, from Macalister, shows as accurately as can be shown the relation of these points of origin from the spinal cord to the bodies and spinous processes of the vertebrae : Level of Body of No. of Nerve. Level of tip of Spine of Level of Body of No. of Nerve. Level of tin of Spine or C. 1 C. 1 - D. 8 9 7 d. 0 / 2 - 9 10 8 d. "I 3 1 c. 10 11 9 d. 3 4 2 c. - 12 10 d. 4 5 3 c. 11 L. 1 11 d. 5 6 4 c. 2 - 6 7 5 c. 12 { 3 8 6 c. 4 | 12 d. 7 I). 1 7 c. 5 D. 1 2 1 d. S. 1 2 3 - L.1-! 2 3 4 2d. 1 3 4 5 3 d. I 4 | 1 L. 5 6 4 d. 5 6 7 5d. - G. 1 7 8 6 d. L. 2 - THE CERVICAL NERVES The roots of the cervical nerves increase in size from the first to the fifth, and then remain the same size to the eighth. The posterior roots bear a proportion to the anterior as 3 to 1, which is much greater than in any other region, the individual filaments being also much larger than those of the anterior roots. In direction the roots of the cervical are less oblique than those of the other spinal nerves. The first cervical nerve is directed a little upward and outward; the second is horizontal; the others are directed obliquely downward and outward, the lowest being the most oblique, and consequently longer than the upper, the distance between their place of origin and their point of exit from the spinal canal never exceeding the depth of one vertebra. The trunk of the first cervical nerve (suboccipital) leaves the spinal canal between the occipital bone and the posterior arch of the atlas; the second, between the posterior arch of the atlas and the lamina of the axis; and the eighth (the last), between the last cervical and first dorsal vertebrae. Each nerve, at its exit from the intervertebral foramen, divides into a posterior and an anterior division. The anterior divisions of the four upper cervical nerves form the cervical plexus. The anterior divisions of the four lower cervical nerves, together with the first dorsal, form the brachial plexus. Posterior Divisions of the Cervical Nerves (Fig. 456). The posterior division of the first cervical (suboccipital) nerve differs from the posterior divisions of the other cervical nerves in not dividing into an internal and external branch. It is larger than the anterior division, and escapes from the spinal canal between the occipital bone and the posterior arch of the atlas, lying behind the vertebral artery. It enters the suboccipital triangle formed by the Rectus capitis posticus major, the Obliquus superior, and Obliquus inferior, and supplies the Recti and Obliqui muscles, and the Complexus. From the branch which supplies the Inferior oblique a filament is given off which joins the second 77/CERVICAL NERVES. 791 cervical nerve. This nerve also occasionally gives off a cutaneous filament, which accompanies the occipital artery and communicates with the occipitalis major and minor nerves. The posterior division of the second cervical nerve is three or four times greater than the anterior division, and the largest of all the posterior cervical divisions. It emerges from the spinal canal between the posterior arch of the atlas and Fig. 456.-Posterior divisions of the upper cervical nerves. lamina of the axis, below the Inferior oblique. It supplies this muscle, and receives a communicating filament from the first cervical. It then divides into an internal and external branch. The internal branch, called, from its size and distribution., the occipitalis major, ascends obliquely inward between the Obliquus inferior and Complexus, and pierces the latter muscle and the Trapezius near their attachments to the cranium. It is now joined by a filament from the posterior division of the third cervical nerve, and, ascending on the back part of the head with the occipital artery, divides into two branches, which supply the integument of the scalp as far forward as the vertex, communicating with the occipitalis minor. It gives off an auricular 792 THE NERVOUS SYSTEM. branch to the back part of the ear and muscular branches to the Complexus. The external branch is often joined by the external branch of the posterior division of the third, and supplies the Splenitis, Trachelo-mastoid, and Complexus. The posterior division of the third cervical is smaller than the preceding, but larger than the fourth ; it differs from the posterior divisions of the remaining cervical nerves in its supplying an additional filament, the third occipital nerve, to the integument of the occiput. The posterior division of the third nerve, like the others, divides into an internal and external branch. The internal branch passes between the Complexus and Semispinalis, and, piercing the Splenius and Trapezius, supplies the skin over the latter muscle ; the external branch joins with that of the posterior division of the second to supply the Splenius, Trachelo-mas- toid, and Complexus. The third occipital nerve arises from the internal or cutaneous branch beneath the Trapezius; it then pierces that muscle, and supplies the skin on the lower and back part of the head. It lies to the inner side of the occipitalis major, with which it is connected. The posterior division of the suboccipital nerve and the internal branches of the posterior divisions of the second and third cervical nerves are occasionally joined beneath the Complexus by communicating branches. This communication is described by Cruveilhier as the posterior cervical plexus. The posterior divisions of the fourth, fifth, sixth, seventh, and eighth cervical nerves (Fig. 463) pass backward, and divide, behind the Posterior intertransverse muscles, into internal and external branches. The internal branches, the larger, are distributed differently in the upper and lower part of the neck. Those derived from the fourth and fifth nerves pass between the Complexus and Semi- spinalis muscles, and, having reached the spinous processes, perforate the aponeurosis of the Splenius and Trapezius, and are continued outward to the integument over the Trapezius, whilst those derived from the three lowest cervical nerves are the smallest, and are placed beneath the Semispinalis colli, which they supply, and then pass into the Interspinales, Multifidus spinae, and Complexus, and send twigs through this latter muscle to supply the integument near the spinous processes (Hirschfeld). The external branches supply the muscles at the side of the neck-viz. the Cervicalis ascendens, Transversalis colli, and Trachelo- mastoid. Anterior Division of the Cervical Nerves. The anterior division of the first or suboccipital nerve is of small size. It escapes from the spinal canal through a groove upon the posterior arch of the atlas. In this groove it lies beneath the vertebral artery, to the inner side of the Rectus capitis lateralis. As it crosses the foramen in the transverse process of the atlas it receives a filament from the sympathetic. It then descends, in front of this process, to communicate with an ascending branch from the second cervical nerve. Communicating filaments from this nerve join the pneumogastric, the hypo- glossal, and sympathetic, and some branches are distributed to the Rectus lateralis and the two Anterior recti. According to Valentin, the anterior division of the suboccipital also distributes filaments to the occipito-atlantal articulation and mastoid process of the temporal bone. The anterior division of the second cervical nerve escapes from the spinal canal, between the posterior arch of the atlas and the lamina of the axis, and, passing forward on the outer side of the vertebral artery, divides in front of the Intertransverse muscle into an ascending branch, which joins the first cervical, and one or two descending branches, which join the third. It gives off the small occipital; a branch to assist in forming the great auricular; another to assist in forming the superficial cervical; one of the communicantes hypoglossi, and a filament to the Sterno-mastoid w hich communicates in the substance of the muscle writh the spinal accessory. THE CERVICAL PLEXUS. 793 The anterior division of the third cervical nerve is double the size of the preceding. At its exit from the intervertebral foramen it passes downward and outward beneath the Sterno-mastoid, and divides into two branches. The ascend- ing branch joins the anterior division of the second cervical; the descending branch passes down in front of the Scalenus anticus, and communicates with the fourth. It gives off the greater part of the great auricular and superficial cervical nerves; one of the communicantes hypoglossi; a branch to the supraclavicular nerves; a filament to assist in forming the phrenic; and muscular branches to the Levator anguli scapulae and Trapezius : this latter nerve communicates beneath the muscle with the spinal accessory. Sometimes the nerve to the Scalenus medius is derived from this source. The anterior division of the fourth cervical is of the same size as the preceding. It receives a branch from the third, sends a communicating branch to the fifth cervical, and, passing downward and outward, divides into numerous filaments which cross the posterior triangle of the neck, forming the supraclavicular nerves. It gives a branch to the phrenic nerve whilst it is contained in the intertransverse 'space, and sometimes a branch to the Scalenus medius muscle. It also gives a branch to the Levator anguli scapulae and to the Trapezius, which unites with the branch given off from the third nerve, and communicates beneath the muscle with the spinal accessory. The anterior divisions of the fifth, sixth, seventh, and eighth cervical nerves are remarkable for their large size. They are much larger than the preceding nerves, and are all of equal size. They assist in the formation of the brachial plexus. The Cervical Plexus. The cervical plexus (Fig. 457) is formed by the anterior divisions of the four upper cervical nerves. It is situated opposite the four upper cervical vertebrae, resting upon the Levator anguli scapulae and Scalenus medius muscles, and covered in by the Sterno-mastoid. Its branches may be divided into two groups, superficial and deep, which may be thus arranged: Ascending ' Occipitalis minor. Auricularis magnus. Superficialis colli. Superficial Suprasternal. Supraclavicular. Supra-acromial. Descending . Supraclavicular r Communicating. Muscular. Communicans hypoglossi. I Phrenic. Internal . Deep r Communicating. [_ Muscular. External . Superficial Branches of the Cervical Plexus. The Occipitalis minor (Fig. 463, page 809) arises from the second cervical nerve; it curves round the posterior border of the Sterno-mastoid, and ascends, running parallel to the posterior border of the muscle, to ,the back part of the side of the head. Near the cranium it perforates the deep fascia, and is continued upward along the side of the head behind the ear, supplying the integument, and communicating with the occipitalis major, the auricularis magnus, and with the posterior auricular branch of the facial. This nerve gives off an auricular branch, which supplies the integument of the upper and back part of the auricle, communicating with the mastoid branch 794 THE NERVOUS SYSTEM. of the auricularis magnus. This branch is occasionally derived from the great occipital nerve. The occipitalis minor varies in size; it is occasionally double. The Auricularis Magnus is the largest of the ascending branches. It arises from the second and third cervical nerves, winds round the posterior border of the Sterno-mastoid, and, after perforating the deep fascia, ascends upon that muscle beneath the Platysma to the parotid gland, where it divides into facial, auricular, and mastoid branches. facial branches pass across the parotid, and are distributed to the integ- ument of the face over the parotid gland; others penetrate the substance of the gland and communicate with the facial nerve. The auricular branches ascend to supply the integument of the back part of RCCT. CAP . LAT. I u HL n V RECT.ANT. MAJOR j RECT. ANT. MINOR TO SYMPATHETIC TO HYPOGLOSSAL TO VAGUS __ ,'O SCALP <?k OCCIPITO FRONTALIS TO AURICLE 5TERNO-MASTOID WITH SPIN. AURICULAR FACIAL >CUMMUNICANS HYPOGLOSSI 3LEV. ANG. SCAR. C. WITH SPIN. ACCESSORY ASTERNAL ACROMIAL SCALEN. MEDIUS Fig. 457.-Plan of the cervical plexus. the pinna, except at its upper part, communicating with the auricular branches of the facial and pneumogastric nerves. The mastoid branch communicates with the occipitalis minor and the posterior auricular branch of the facial, and is distributed to the integument behind the ear. The Superficialis Colli arises from the second and third cervical nerves, turns round the posterior border of the Sterno-mastoid about its middle, and, passing obliquely forward beneath the external jugular vein to the anterior border of that muscle, perforates the deep cervical fascia, and divides beneath the Platysma into two branches which are distributed to the antero-lateral parts of the neck. The ascending branch gives a filament which accompanies the external jugular vein ; it then passes upward to the submaxillary region, and divides into branches, some of which form a plexus with the cervical branches of the facial nerve beneath DEEP BRANCHES OF THE CERVICAL PLEXUS. 795 the Platysma; others pierce that muscle, supply it, and are distributed to the integument of the uppex' half of the neck, at its fore part, as high as the chin. The descending branch (occasionally represented by two or more filaments) pierces the Platysma, and is distributed to the integument of the side and front of the neck, as low as the sternum. The Descending ox* supraclavicular branches arise from the third and fourth cervical nerves: emerging beneath the posterior border of the Sterno-mastoid, they descend in the interval between that muscle and the Trapezius, and divide into branches, which are arranged, according to their position, into three groups. The inner or suprasternal branches cross obliquely over the clavicular and sternal attachments of the Sterno-mastoid, and supply the integument as far as the median line. The middle or supraclavicular branches cross the clavicle, and supply the integument over the Pectoral and Deltoid muscles, communicating with the cutaneous branches of the upper intercostal nerves. The external or supra-acromial branches pass obliquely across the outer surface of the Trapezius and the acromion, and supply the integument of the upper and back part of the shoulder. The communicating branches consist of several filaments which pass from the loop between the first and second cervical nerves in front of the atlas to the pneumogastric, hypoglossal, and sympathetic, and a communicating branch between the fourth and fifth cervical. Muscular branches supply the Anterior recti and Rectus lateralis muscles; they proceed from the first cervical nerve and from the loop formed between it and the second. The Communicans Hypoglossi (Fig. 455) consists usually of two filaments, one being derived from the second, and the other from the third cervical. These filaments pass downward on the outer side of the internal jugular vein, cross in front of the vein a little below the middle of the neck, and form a loop with the descendens hypoglossi in front of the sheath of the carotid vessels (see page 787). Occasionally, the junction of these nerves takes place within the sheath. The Phrenic Nerve (internal respiratory of Bell) arises chiefly from the fourth cervical nerve, with a few filaments from the third and a communicating branch from the fifth. It descends to the root of the neck, running obliquely across the front of the Scalenus anticus, passes over the first part of the subclavian artery, between it and the subclavian vein, and, as it enters the chest, crosses the internal mammary artery near its origin. Within the chest it descends nearly vertically in front of the root of the lung and by the side of the pericardium, between it and the mediastinal portion of the pleura, to the Diaphragm, where it divides into branches, which separately pierce that muscle and are distributed to its under surface. The two phrenic nerves differ in their length, and also in their relations at the upper part of the thorax. The right nerve is situated more deeply, and is shorter and more vertical in direction than the left; it lies on the outer side of the right vena innominata and superior vena cava. The left nerve is rather longer than the right, from the inclination of the heart to the left side, and from the Diaphragm being lower on this than on the opposite side. At the upper part of the thorax it crosses in front of the arch of the aorta to the root of the lung. Each nerve supplies filaments to the pericardium and pleura, and near the chest is joined by a filament from the sympathetic, and occasionally by one from the union of the descendens hypoglossi with the spinal nerves : this filament is found, according to Swan, only on the left side. It is also usually connected by Deep Branches of the Cervical Plexus. Internal Series. 796 THE NERVOUS SYSTEM. a filament with the nerve to the Subclavius muscle. Branches have been described as passing to the peritoneum. From the right nerve one or two filaments pass to join in a small ganglion with phrenic branches of the solar plexus ; and branches from this ganglion are distributed to the hepatic plexus, the suprarenal capsule, and inferior vena cava. From the left nerve filaments pass to join the phrenic plexus of the sympathetic, but without any ganglionic enlargement. Deep Branches of the Cervical Plexus. External Series. Communicating Branches.-The deep branches of the external series of the cervical plexus communicate with the spinal accessory nerve, in the substance of the Sterno-mastoid muscle, in the occipital triangle, and beneath the Trapezius. Muscular branches are distributed to the Sterno-mastoid, Trapezius, Levator anguli scapulae, and Scalenus medius. The branch for the Sterno-mastoid is derived from the second cervical; the Trapezius and Levator anguli scapulae receive branches from the third and fourth. The Scalenus medius is supplied sometimes from the third, sometimes the fourth, and occasionally from both nerves. The Brachial Plexus (Fig. 458). The Brachial Plexus is formed by the union of the anterior branches of the four lower cervical and the greater part of the first dorsal nerves, receiving also a fasciculus from the fourth cervical nerve. It extends from the lower part of the side of the neck to the axilla. It is very broad, and presents little of a plexiform arrangement at its commencement. It is narrow opposite the clavicle, becomes broad and forms a more dense interlacement in the axilla, and divides opposite the coracoid process into numerous branches for the supply of the upper limb. The nerves which form the plexus are all similar in size, and their mode of com- munication is subject to considerable variation, so that no one plan can be given as applying to every case. The following appears, however, to be the most con- stant arrangement: the fifth and sixth cervical unite together soon after their exit from the intervertebral foramina to form a common trunk. The eighth cervi- cal and first dorsal also unite to form one trunk. So that the nerves forming the plexus, as they lie on the Scalenus medius external to the outer border of the Scalenus anticus, are blended into three trunks-an outer one, formed by the junction of the fifth and sixth cervical nerves ; a middle one, consisting of the seventh cervical nerve; and an inner one, formed by the junction of the eighth cervical and first dorsal nerves. As they pass beneath the clavicle, each of these three trunks divides into two branches, an anterior and a posterior. The anterior divisions of the outer and middle trunks then unite to form a common cord, which is situated on the outer side of the middle part of the axillary artery, and is called the outer cord of the brachial plexus. The anterior division of the inner trunk, formed by the union of the eighth cervical and first dorsal, passes down on the inner side of the axillary artery in the middle of the axilla, and forms the inner cord of the brachial plexus. The posterior divisions of the outer trunk (formed by the junction of the fifth and sixth nerves) and of the middle trunk (the seventh nerve) unite together to form the posterior cord of the brachial plexus, which is situated behind the second portion of the axillary artery. From this posterior cord are given off the two lower subscapular nerves, the upper sub- scapular nerve being given off from the posterior division of the outer trunk prior to its junction with the posterior division of the middle trunk. The pos- terior cord divides into the circumflex and musculo-spiral nerves. The musculo- spiral nerve is subsequently joined by the posterior division of the innei' trunk, formed by the union of the eighth cervical and first dorsal. The brachial plexus communicates with the cervical plexus by a branch from the fourth to the fifth nerve, and with the phrenic nerve by a branch from the fifth cervical, which joins that nerve on the Anterior scalenus muscle: the cervi- THE BRACHIAL PLEXUS. 797 cal and first dorsal nerves are also joined by filaments from the middle and inferior cervical ganglia of the sympathetic, close to their exit from the interver- tebral foramina. Relations.-In the neck the brachial plexus lies at the first between the Anterior and Middle scaleni muscles, and then above and to the outer side of the subclavian artery: it then passes behind the clavicle and Subclavius muscle, lying upon the first serration of the Serratus magnus, and the Subscapularis muscles. In the axilla it is placed on the outer side of the first portion of the axillary artery; it FROM 4IM RHOMBOID SUB-CLAVIAN SUPRA-SCAPULAR c. WITH BRS TO LONG/ US COLLI A; V SCALENI X jext: ant: thoracic UPPER SUB-SCAPULAR •jUB -SCAPULAR |SJ DORSAL ''i CIRCUMFLEX j POSTERIOR THORACIC INT. ANT. THORACIC INTERNAL CUTANEOUS ilesser INTERNAL cutaneous MUSCULO-CUTANEOUS MUSCULO- SPIRAI- ULNAR < MEDIAN Fig. 458.-Plan of the brachial plexus surrounds the artery in the second part of its course, one cord lying upon the outer side of that vessel, one on the inner side, and one behind it, and at the lower part of the axillary space gives off its terminal branches to the upper extremity. Branches.-The branches of the brachial plexus are arranged in two groups- viz. those given off above the clavicle, and those below that bone. Branches above the Clavicle. Communicating. Muscular. Posterior thoracic. Suprascapular. The communicating branch with the phrenic is derived from the fifth cervical nerve or from the loop between the fifth and sixth ; it joins the phrenic on the Anterior scalenus muscle. The muscular branches supply the Longus colli, Scaleni, Rhomboidei, and Subclavius muscles. Those for the Longus colli and Scaleni arise from the lower 798 THE NERVOUS SYSTEM. cervical nerves at their exit from the intervertebral foramina. The Rhomboid branch arises from the fifth cervical, pierces the Scalenus medius, and passes beneath the Levator anguli scapulae, which it occasionally supplies, to the Rhomboid muscles. The nerve to the Subclavius is a small filament which arises from the Fig. 459.-Cutaneous nerves of right upper extremity. Anterior view. Fig. 460.-Cutaneous nerves of right upper extremity. Posterior view. fifth cervical at its point of junction with the sixth nerve; it descends in front of the subclavian artery to the Subclavius muscle, and is usually connected by a filament with the phrenic nerve. The posterior thoracic nerve (long thoracic, external respiratory of Belt) (Fig. 461) supplies the Serratus magnus, and is remarkable for the length of its course. It sometimes arises by two roots from the fifth and sixth cervical nerves THE BRACHIAL PLEXUS. 799 .External anterior thoracic. "Internal anterior thoracic. -Median. Internal cutaneous. Musculo-spiral. Posterior interosseous. -Radial. -Anterior interosseous. Ulnar. Dorsal branch.- Deep branch.- Fig. 461.-Nerves of the left upper extremity. immediately after their exit from the intervertebral foramina, but generally by three roots from the fifth, sixth, and seventh nerves. These unite in the substance 800 THE NERVOUS SYSTEM. of the Middle scalenus muscle, and, after emerging from it, the nerve passes down behind the brachial plexus and the axillary vessels, resting on the outer surface of the Serratus magnus. It extends along the side of the chest to the lower border of that muscle, supplying filaments to each of its digitations. The suprascapular nerve (Fig. 462) arises from the cord formed by the fifth and sixth cervical nerves; passing obliquely outward beneath the Trapezius, it enters the supraspinous fossa, through the notch in the upper border of the scapula, and, passing beneath the Supraspinatus muscle, curves in front of the spine of the scapula to the infraspinous fossa. In the supraspinous fossa it gives off two branches to the Supraspinatus muscle, and an articular filament to the shoulder- joint ; and in the infraspinous fossa it gives off two branches to the Infraspinatus muscle, besides some filaments to the shoulder-joint and scapula. Branches below the Clavicle. The branches given off below the clavicle are derived from the three cords of the brachial plexus, in the following mannei-: From the outer cord arise the external of the two anterior thoracic nerves, the musculo-cutaneous nerve, and the outer head of the median. From the inner cord arise the internal of the two anterior thoracic nerves, the internal cutaneous, the lesser internal cutaneous (nerve of Wrisberg), the ulnar, and inner head of the median. From the posterior cord arise two of the three subscapular nerves, the third arising from the posterior division of the trunk formed by the fifth and sixth cervical nerves; the cord then divides into the musculo-spiral and circumflex nerves. These may be arranged according to the parts they supply: To the chest . . . . . Anterior thoracic. Subscapular. Circumflex. To the shoulder . . . . Musculo-cutaneous. Internal cutaneous. Lesser internal cutaneous. Median. Ulnar. Musculo-spiral. To the arm, forearm, and hand . The fasciculi of which these nerves are composed may be traced through the plexus to the spinal nerves from which they originate. They are as follows : External anterior thoracic from 5th, 6th, and 7th cervical. Internal anterior thoracic " 8th cervical and 1st dorsal. Subscapular " 5th, 6th, 7th, and 8th cervical. Circumflex " 5th, 6th, 7th, and 8th cervical. Musculo-cutaneous " 5th, 6th, and 7th cervical. Internal cutaneous " 8th cervical and 1st dorsal. Lesser internal cutaneous " 1st dorsal. Median " 6th, 7th, and 8th cervical, and 1st dorsal. Ulnar " 8th cervical and 1st dorsal. Musculo-spiral " 6th, 7th, and 8th cervical, and 1st dorsal. The Anterior Thoracic Nerves (Fig. 461), two in number, supply the Pectoral muscles. The external or superficial nerve, the larger of the two, arises from the outer cord of the brachial plexus, through which its fibres may be traced to the fifth, sixth, and seventh cervical nerves. It passes inward, across the axillary artery and vein, pierces the costo-coracoid membrane, and is distributed to the under surface of the Pectoralis major. It sends down a communicating filament to join THE BRACHIAL PLEXUS. 801 the internal nerve, which forms a loop round the inner side of the axillary artery. The internal or deep nerve arises from the inner cord, and through it from the eighth cervical and first dorsal. It passes upward between the axillary artery and vein, and joins with the filament from the superficial nerve. It then passes to the under surface of the Pectoralis minor muscle, where it divides into a number of branches, which supply the muscle on its under surface. Some of the branches pass through the muscle ; others wind round its upper border and pierce the costo- coracoid membrane to supply the Pectoralis major. The Subscapular Nerves, three in number, supply the Subscapularis, Teres major, and Latissimus dorsi muscles. The fasciculi of which they are composed may be traced to the fifth, sixth, seventh, and eighth cervical nerves. The upper subscapular nerve, the smallest, enters the upper part of the Sub- scapularis muscle. The lower subscapular nerve enters the axillary border of the Subscapularis and terminates in the Teres major. The latter muscle is sometimes supplied by a separate branch. The middle or long subscapular, the largest of the three, follows the course of the subscapular artery, along the posterior wall of the axilla to the Latissimus dorsi, through which it may be traced as far as its lower border. The Circumflex Nerve (Fig. 462) supplies some of the muscles and the integu- ment of the shoulder and the shoulder-joint. It arises from the posterior cord of the brachial plexus, in common with the musculo-spiral nerve, and its fibres may be traced through the posterior cord to the fifth, sixth, seventh, and eighth cer- vical nerves. It is at first placed behind the axillary artery, between it and the Subscapularis muscle, and passes downward and outward to the lower border of that muscle. It then winds backward in company with the posterior circumflex artery, through a quadrilateral space bounded above by the Teres minor, below by the Teres major, internally by the long head of the Triceps, and externally by the neck of the humerus, and divides into two branches. The upper branch winds round the surgical neck of the humerus, beneath the Deltoid, with the posterior circumflex vessels, as far as the anterior border of that muscle, supplying it, and giving off cutaneous branches, which pierce the muscle and ramify in the integument covering its lower part. The lower branch, at its origin, distributes filaments to the Teres minor and back part of the Deltoid muscles. Upon the filament to the former muscle a gangliform enlargement usually exists. The nerve then pierces the deep fascia, and supplies the integument over the lower two-thirds of the posterior surface of the Deltoid, as well as that covering the long head of the Triceps. The circumflex nerve, before its division, gives off an articular filament, which enters the shoulder-joint below the Subscapularis. The Musculo-cutaneous Nerve (Fig. 461) (external cutaneous or perforans Cas- serii)x supplies some of the,muscles of the arm and the integument of the fore- arm. It arises from the outer cord of the brachial plexus, opposite the lower border of the Pectoralis minor, receiving filaments from the fifth, sixth, and seventh cervical nerves. It perforates the Coraco-brachialis muscle, passes obliquely between the Biceps and Brachialis anticus to the outer side of the arm, and, a little above the elbow, winds round the outer border of the tendon of the Biceps, and, perfo- rating the deep fascia, becomes cutaneous. This nerve in its course through the arm supplies the Coraco-brachialis, Biceps, and part of the Brachialis anticus muscles. It sends a small branch to the bone, which enters the nutrient foramen with the accompanying artery and a filament, from the branch supplying the Brachialis anticus, to the elbow-joint. The cutaneous portion of the nerve passes behind the median cephalic vein, and divides, opposite the elbow-joint, into an anterior and a posterior branch. The anterior branch descends along the radial border of the forearm to the 1 See foot-note, page 759. 802 THE NERVOUS SYSTEM. wrist, and supplies the integument over the outer half of the anterior surface. At the wrist-joint it is placed in front of the radial artery, and some filaments, piercing the deep fascia, accompany that vessel to the back of the wrist, supplying the carpus. The nerve then passes downward to the ball of the thumb, where it terminates in cutaneous filaments. It communicates with a branch from the radial nerve and the palmar cutaneous branch of the median. The posterior branch passes downward along the back part of the radial side of the forearm to the wrist. It supplies the integument of the lower third of the forearm, communicating with the radial nerve and the external cutaneous branch of the musculo-spiral. The Internal Cutaneous Nerve (Fig. 461) is one of the smallest branches of the brachial plexus. It arises from the inner cord in common with the ulnar and internal head of the median, and at its commencement is placed on the inner side of the brachial artery. It derives its fibres from the eighth cervical and first dorsal nerves. It passes down the inner side of the arm, pierces the deep fascia with the basilic vein, about the middle of the limb, and, becoming cutaneous, divides into two branches, anterior and posterior. This nerve gives off, near the axilla, a cutaneous filament, which pierces the fascia and supplies the integument covering the Biceps muscle nearly as far as the elbow. This filament lies a little external to the common trunk, from which it arises. The anterior branch, the larger of the two, passes usually in front of, but occasionally behind, the median basilic vein. It then descends on the anterior surface of the ulnar side of the forearm, distributing filaments to the integument as far as the wrist, and communicating with a cutaneous branch of the ulnar nerve. The posterior branch passes obliquely downward on the inner side of the basilic vein, passes in front of, or over, the internal condyle of the humerus to the back of the forearm, and descends on the posterior surface of its ulnar side as far as the wrist, distributing filaments to the integument. It communicates, above the elbow, with the lesser internal cutaneous, and above the wrist with the dorsal cutaneous branch of the ulnar nerve (Swan). The Lesser Internal Cutaneous Nerve (nerve of Wrisberg) (Fig. 461) is distrib- uted to the integument on the inner side of the arm. It is the smallest of the branches of the brachial plexus, and, arising from the inner cord with the internal cutaneous and ulnar nerves, receives its fibres from the first dorsal nerve. It passes through the axillary space, at first lying behind, and then on the inner side of, the axillary vein, and communicates with the intercosto-humeral nerve. It descends along the inner side of the brachial artery to the middle of the arm, where it pierces the deep fascia, and is distributed to the integument of the back part of the lower third of the arm, extending as far as the elbow, where some filaments are lost in the integument in front of the inner condyle, and others over the olecranon. It communicates with the posterior branch of the internal cutaneous nerve. In some cases the nerve of Wrisberg and intercosto-humeral are connected by two or three filaments which form a plexus at the back part of the axilla. In other cases the intercosto-humeral is of large size, and takes the place of the nerve of Wrisberg, receiving merely a filament of communication from the brachial plexus, which represents the latter nerve. In other cases this filament is wanting, the place of the nerve of Wrisberg being supplied entirely from the intercosto- humeral. The Median Nerve (Fig. 461) has received its name from the course it takes along the middle of the arm and forearm to the hand, lying between the ulnar and the musculo-spiral and radial nerves. It arises by two roots, one from the outer, and one from the inner, cord of the brachial plexus ; these embrace the lower part of the axillary artery, uniting either in front or on the outer side of that vessel. It receives filaments from the sixth, seventh, and eighth cervical and the THE BRACHIAL PLEXUS. 803 first dorsal. As it descends through the arm, it lies at first on the outer side of the brachial artery, crosses that vessel in the middle of its course, usually in front, but occasionally behind it, and lies on its inner side to the bend of the elbow, where it is placed beneath the bicipital fascia, and is separated from the elbow-joint by the Brachialis anticus. In the forearm it passes between the two heads of the Pronator radii teres, and descends beneath the Flexor sublimis, lying on the Flexor profundus, to within two inches above the annular ligament, where it becomes more superficial, lying between the tendons of the Flexor sublimis and Flexor carpi radialis, beneath, or rather to the ulnar side of, the tendon of the Palmaris longus, covered by the integument and fascia. It then passes beneath the annular ligament into the hand. In its course through the forearm it is accompanied by a small artery. Branches.-No branches are given off from the median nerve in the arm. In the forearm its branches are muscular, anterior interosseous, and palmar cuta- neous, and, according to Rudinger and Macalister, two articular twigs to the elbow-joint. The muscular branches supply all the superficial muscles on the front of the forearm, except the Flexor carpi ulnaris. These branches are derived from the nerve near the elbow. The branch furnished to the Pronator radii teres often arises above the joint. The anterior interosseous supplies the deep muscles on the front of the fore- arm, except the inner half of the Flexor profundus digitorum. It accompanies the anterior interosseous artery along the interosseous membrane, in the interval between the Flexor longus pollicis and Flexor profundus digitorum muscles, both of which it supplies, and terminates below in the Pronator quadratus. The palmar cutaneous branch arises from the median nerve at the lower part of the forearm. It pierces the fascia above the annular ligament, and, descending over that ligament, divides into two branches; of which the outer supplies the skin over the ball of the thumb, and communicates with the anterior cutaneous branch of the musculo-cutaneous nerve; and the inner supplies the integument of the palm of the hand, communicating with the cutaneous branch of the ulnar. In the palm of the hand the median nerve is covered by the integument and palmar fascia and crossed by the superficial palmar arch. It rests upon the tendons of the flexor muscles. In this situation it becomes enlarged, somewhat flattened, of a reddish color, and divides into two branches. Of these, the external supplies a muscular branch to some of the muscles of the thumb and digital branches to the thumb and index finger; the internal supplies digital branches to the contiguous sides of the index and middle and of the middle and ring fingers. The branch to the muscles of the thumb is a short nerve which subdivides to supply the Abductor, Opponens, and outer head of the Flexor brevis pollicis muscles, the remaining muscles of this group being supplied by the ulnar nerve. The digital branches are five in number. The first and second pass along the borders of the thumb, the external branch communicating with branches of the radial nerve. The third passes along the radial side of the index finger, and supplies the First lumbricalis muscle. The fourth subdivides to supply the adjacent sides of the index and middle fingers, and sends a branch to the Second lumbrical muscle. The fifth supplies the adjacent sides of the middle and ring fingers, and communicates with a branch from the ulnar nerve. Each digital nerve, opposite the base of the first phalanx, gives off a dorsal branch, which joins the dorsal digital nerve from the radial and runs along the side of the dorsum of the finger, to end in the integument over the last phalanx. At the end of the finger the digital nerve divides into a palmar and a dorsal branch, the former of which supplies the extremity of the finger, and the latter ramifies round and beneath the nail. The digital nerves, as they run along the fingers, are placed superficial to the digital arteries. 804 THE NERVOUS SYSTEM. The Ulnar Nerve (Fig. 461) is placed along the inner or ulnar side of the upper limb, and is distributed to the muscles and integument of the forearm and hand. It is smaller than the median, behind which it is placed, diverging from it in its course down the arm. It arises from the inner cord of the brachial plexus, in common with the inner head of the median and the internal cutaneous nerve, and derives its fibres from the eighth cervical and first dorsal nerves. At its commence- ment it lies at the inner side of the axillary artery, and holds the same relation with the brachial artery to the middle of the arm. From this point it runs obliquely across the internal head of the Triceps, pierces the internal intermuscular septum, and descends to the groove between the internal condyle and the olecranon, accom- panied by the inferior profunda artery. At the elbow it rests upon the back of the inner condyle, and passes into the forearm between the two heads of the Flexor carpi ulnaris. In the forearm it descends in a perfectly straight course along its ulnar side, lying upon the Flexor profundus digitorum, its upper half being covered by the Flexor carpi ulnaris, its lower half lying on the outer side of the muscle, covered by the integument and fascia. The ulnar artery, in the upper third of its course, is separated from the ulnar nerve by a considerable interval, but in the rest of its extent the nerve lies to its inner side. At the wrist the ulnar nerve crosses the annular ligament on the outer side of the pisiform bone, to the inner side and a little behind the ulnar artery, and immediately beyond this bone divides into two branches, superficial and deep palmar. The branches of the ulnar nerve are- Articular (elbow). Muscular. Cutaneous. Dorsal cutaneous. Articular (wrist). In the forearm In the hand Superficial palmar. Deep palmar. The articular branches distributed to the elbow-joint consist of several small filaments. They arise from the nerve as it lies in the groove between the inner condyle and olecranon. The muscular branches are two in number-one supplying the Flexor carpi ulnaris; the other, the inner half of the Flexor profundus digitorum. They arise from the trunk of the nerve near the elbow. The cutaneous branch arises from the ulnar nerve about the middle of the fore- arm, and divides into two branches. One branch (frequently absent) pierces the deep fascia near the wrist, and is distributed to the integument, communicating with a branch of the internal cutaneous nerve. The second branch (palmar cutaneous) lies on the ulnar artery, which it accompanies to the hand, some filaments entwining round the vessel; it ends in the integument of the palm, communicating with branches of the median nerve. The dorsal cutaneous branch arises about two inches above the wrist; it passes backward beneath the Flexor carpi ulnaris, perforates the deep fascia, and, running along the ulnar side of the back of the wrist and hand, supplies the inner side of the little finger and the adjoining sides of the little and ring fingers; it communi- cates with the posterior branch of the internal cutaneous nerve, and sends a com- municating filament to that branch of the radial nerve which supplies the adjoining sides of the middle and ring fingers. The articular filaments to the wrist are also supplied by the ulnar nerve. The superficial palmar branch supplies the Palmaris brevis and the integu- ment on the inner side of the hand, and terminates in two digital branches, which are distributed, one to the ulnar side of the little finger, the other to the adjoining sides of the little and ring fingers, the latter communicating with a branch from the median. The digital branches are distributed to the fingers in the same manner as the digital branches of the median. The deep palmar branch passes between the Abductor and Flexor brevis THE BRACHIAL PLEXUS. 805 minimi digiti muscles, and follows the course of the deep palmar arch beneath the flexor tendons. At its origin it supplies the muscles of the little finger. As it crosses the deep part of the hand it sends two branches to each interosseous space, one for the Dorsal and one for the Palmar interosseous muscle, the branches to the Second and Third palmar interossei supplying filaments to the two inner Lumbrical muscles. At its termination between the thumb and index finger it supplies the Adductores transversus et obliquus pollicis and the inner head of the Flexor brevis pollicis. It will be remembered that the inner part of the Flexor profundus digitorum is supplied by the ulnar nerve ; the two inner Lumbricales, which are connected with the tendons of this part of the muscle, are therefore supplied by the same nerve. The outer part of the Flexor profundus is supplied by the median nerve; the two outer Lumbricales, which are connected with the tendons of this part of the muscle, are therefore supplied by the same nerve. The Musculo-spiral Nerve (Fig. 462), the largest branch of the brachial plexus, supplies the muscles of the back part of the arm and forearm and the integument of the same parts, as well as that of the back of the Hand. It arises from the posterior cord of the brachial plexus by a common trunk with the circumflex nerve, and is afterward joined by the posterior division of the trunk, formed by the junction of the eighth cervical and first dorsal nerves. It receives filaments from the sixth, seventh, and eighth cervical and first dorsal nerves. At its commence- ment it is placed behind the axillary and upper part of the brachial arteries, passing down in front of the tendons of the Latissimus dorsi and Teres major. It winds round the humerus in the musculo-spiral groove with the superior pro- funda artery, passing from the inner to the outer side of the bone, between the internal and external heads of the Triceps muscle. It pierces the external inter- muscular septum, and descends between the Brachialis anticus and Supinator longus to the front of the external condyle, where it divides into the radial and posterior interosseous nerves. The branches of the musculo-spiral nerve are- Muscular. Cutaneous. Radial. Posterior interosseous. The muscular branches are divided into internal, posterior, and external; they supply the Triceps, Anconeus, Supinator longus, Extensor carpi radialis longior, and Brachialis anticus. These branches are derived from the nerve at the inner side, back part, and outer side of the arm. The internal muscular branches supply the inner and middle heads of the Triceps muscle. That to the inner head of the Triceps is a long, slender filament which lies close to the ulnar nerve, as far as the lower third of the arm, and is often intimately connected with it. The posterior muscular branch, of large size, arises from the nerve in the groove between the Triceps and the humerus. It divides into branches which supply the outer head of the Triceps and Anconeus muscles. The branch for the latter muscle is a long, slender filament which descends in the substance of the Triceps to the Anconeus. The external muscular branches supply the Supinator longus, Extensor carpi- radialis longior, and (usually) the outer part of the Brachialis anticus. The cutaneous branches are three in number, one internal and two external. The internal cutaneous branch arises in the axillary space with the inner mus- cular branch. It is of small size, and passes through the axilla to the inner side of the arm, supplying the integument on its posterior aspect nearly as far as the olecranon. In its course it crosses beneath the intercosto-humeral, with which it communicates. The two external cutaneous branches perforate the outer head of the Triceps at its attachment to the humerus. The upper and smaller one passes to the front of the elbow, lying close to the cephalic vein, and supplies the integu- 806 THE NERVOUS SYSTEM. ment of the lower half of the arm on its anterior aspect. The lower branch pierces the deep fascia below the insertion of the Deltoid, and passes down along the outer side of the arm and elbow, and then along the back part of the radial side of the forearm to the wrist, supplying the integument in its course, and joining, near its termination, with the pos- terior cutaneous branch of the musculo-cutaneous nerve. The radial nerve passes along the front of the radial side of the forearm to the commencement of its lower third. It lies at first a little to the outer side of the radial artery, concealed beneath the Supinator longus. In the middle third of the forearm it lies beneath the same mus- cle, in close relation with the outer side of the artery. It quits the artery about three inches above the wrist, passes beneath the tendon of the Supinator longus, and, pier- cing the deep fascia at the outer border of the forearm, divides into two branches. The external branch, the smaller of the two, supplies the integument of the radial side and ball of the thumb, joining wTith the anterior branch of the musculo-cuta- neous nerve. The internal branch com- municates, above the wrist, with the posterior cutaneous branch from the musculo- cutaneous, and on the back of the hand forms an arch with the dorsal cutaneous branch of the ulnar nerve. It then divides into three digital nerves, which are dis- tributed as follows : The first supplies the ulnar side of the thumb and the radial side of the index finger; the second, the adjoining sides of the index and middle fingers; and the third, the adjacent borders of the middle and ring fingers.1 The latter nerve communicates with a filament from the dorsal branch of the ulnar nerve. Suprascapular - Circumflex. ■ Musculo-spiral. Posterior 'interosseous. Fig. 462.-The suprascapular, circumflex, and musculo-spiral nerves. 1 According to Hutchinson, the digital nerve to the thumb reaches only as high as the root of the nail; the one to the forefinger as high as the middle of the second phalanx; and the one to the mid- dle and ring lingers not higher than the first phalangeal joint (London Hosp. Gaz. vol. iii. p. 319.) THE BRACHIAL PLEXUS. 807 The Posterior Interosseous Nerve winds to the back of the forearm through the fibres of the Supinator brevis, and passes down, between the superficial and deep layer of muscles, to the middle of the forearm. Considerably dimin- ished in size, it descends on the interosseous membrane, beneath the Extensor longus pollicis, to the back of the carpus, where it presents a gangliform enlargement from which filaments are distributed to the ligaments and artic- ulations of the carpus. It supplies all the muscles of the radial and posterior brachial regions, excepting the Anconeus, Supinator longus, and Extensor carpi radialis longior. Surgical Anatomy.-The brachial plexus may be ruptured by traction on the limb leading to complete paralysis. In these cases the lesion would appear to be rather a tearing away of the nerves from the spinal cord than a solution of continuity of the nerve-fibres themselves. In the axilla any of the nerves forming the brachial plexus may be injured in a wound of this part, the median being the one which is most frequently damaged from its exposed position, and the musculo-spiral, on account of its sheltered and deep position, being the least often wounded. The brachial plexus in the axilla is often damaged from the pressure of a crutch, producing the condition known as "crutch paralysis." In these cases the musculo-spiral appears to be the nerve which is most frequently implicated to the greatest extent, the ulnar nerve being the one that appears to suffer next in frequency. The circumflex nerve is of particular surgical interest. On account of its course round the joint it is liable to be torn in fractures of the surgical neck of the humerus and in dislocations of the shoulder-joint, leading to paralysis of the deltoid, and, according to Erb, inflammation of the shoulder-joint is liable to be followed by a neuritis of this nerve from extension of the inflammation to it. Mr. Hilton takes the circumflex nerve as an illustration of a law which he lays down, that " the same trunks of nerves whose branches supply the groups of muscles moving a joint furnish also a distribution of nerves to the skin over the insertions of the same muscles, and the interior of the joint receives its nerves from the same source." In this way he explains the fact that an inflamed joint becomes rigid, because the same nerves which supply the interior of the joint supply the muscles also which move that joint. The median nerve is liable to injury in wounds of the forearm. When paralyzed, there is loss of flexion of the second phalanges of all the fingers and of the terminal phalanges of the index and middle fingers. Flexion of the terminal phalanges of the ring and middle fingers is effected by that portion of the Flexor profundus digitorum which is supplied by the ulnar nerve. There is power to flex the proximal phalanges through the Interossei. The thumb cannot be flexed or opposed, and is maintained in a position of extension and adduction. All power of pronation is lost. The wrist can be flexed, if the hand is first adducted, by the action of the Flexor carpi ulnaris. There is loss or impairment of sensation on the palmar surface of the thumb, index, middle, and outer half of the ring fingers, and on the dorsal surface of the same fingers over the last two phalanges ; except in the thumb, where the loss of sensation would be limited to the back of tpe last phalanx. In order to expose the median nerve for the purpose of stretching an incision should be made along the ulnar side of the tendon of the Palmaris longus, which serves as a guide to the nerve. The nerve is also liable to be injured in wounds of the forearm. When paralyzed, there is loss of power of flexion in the ring and little fingers ; there is impaired power of ulnar flexion and adduction ; there is inability to spread out the fingers from paralysis of the Inter- ossei ; and there is inability to adduct the thumb. Sensation is lost or impaired in the skin sup- plied by the nerve. In order to expose the nerve in the lower part of the forearm, an incision should be made along the outer border of the tendon of the Flexor carpi ulnaris, and the nerve will be found lying on the ulnar side of the ulnar artery. The musculo-spiral nerve is probably more frequently injured than any other nerve of the upper extremity. In consequence of its close relationship to the humerus as it lies in the mus- culo-spiral groove, it is frequently torn or injured in fractures of this bone, or subsequently involved in the callus that may be thrown out around a fracture, and thus pressed upon and its functions interfered with. It is also liable to be contused against the bone by kicks or blows or to be divided by wounds of the arm. When paralyzed, the hand is flexed at the wrist and lies flaccid. This is known as " drop-wrist." The fingers are also flexed, and on an attempt being made to extend them the last two phalanges only will be extended through the action of the Inter- ossei, the first phalanges remaining flexed. There is no power of extending the wrist. Supina- tion is completely lost when the forearm is extended on the arm, but it is possible to a certain extent if the forearm is flexed so as to allow of the action of the Biceps. The power of exten- sion of the forearm is lost on account of paralysis of the Triceps. The best position in which to expose the nerve for the purpose of stretching is to make an incision along the inner border of the Supinator longus, just above the level of the elbow-joint. The skin and super- ficial structures are to be divided and the deep fascia exposed. The white line in this struc- ture indicating the border of the muscle is to be defined, and the deep fascia divided in this line. By now raising the Supinator longus the nerve will be found lying beneath it, on the Brachialis anticus. 808 7777? NERVOUS SYSTEM. THE DORSAL NERVES (Fig. 463). The Dorsal Nerves are twelve in number on each side. The first appears between the first and second dorsal vertebrae, and the last between the last dorsal and first lumbar. The roots of the. dorsal nerves are of small size, and vary but slightly from the second to the last. Both roots are very slender, the posterior roots only slightly exceeding the anterior in thickness. They gradually increase in length from above downward, and pass down in contact with the spinal cord for a distance equal to the height of, at least, two vertebrae, in the lower part of the dorsal region, before they emerge from the spinal canal. They then join in the intervertebral foramen, and at their exit divide into two primary divisions, a posterior (dorsal) and an anterior (intercostal). The first and last dorsal nerves are peculiar in some respects. The posterior divisions of the dorsal nerves, which are smaller than the ante- rior, pass backward between the transverse processes, and divide into internal and external branches. The mternaZ branches of the six upper nerves pass inward between the Semi- spinalis dorsi and Multifidus spinae muscles, which they supply, and then, piercing the origins of the Rhomboidei and Trapezius muscles, become cutaneous by the side of the spinous processes and ramify in the integument. The internal branches of the six lower nerves are distributed to the Multifidus spinae, without giving off' any cutaneous filaments. The external branches increase in size from above downward. They pass through the Longissimus dorsi to the cellular interval between it and the llio- costalis, and supply those muscles, as well as their continuations upward to the head, and the Levatores costarum; the five or six lower nerves also give off cutaneous filaments, which pierce the Serratus posticus inferior and Latissimus dorsi in a line with the angles of the ribs, and then ramify in the integument. The cutaneous branches of the dorsal nerves are twelve in number. The six upper cutaneous nerves are derived from the internal branches of the posterior divisions of the dorsal nerves. They pierce the origins of the Rhomboidei and Trapezius muscles, and become cutaneous by the side of the spinous processes, and then ramify in the integument. They are frequently furnished with gangliform enlargements. The six lower cutaneous nerves are derived from the external branches of the posterior divisions of the dorsal nerves. They pierce the Serratus posticus inferior and Latissimus dorsi in a line with the angles of the ribs, and then ramify in the integument. Posterior Divisions of the Dorsal Nerves. Anterior Divisions of the Dorsal Nerves. The anterior divisions of the dorsal nerves {intercostal nerves) are twelve in number on each side. They are, for the most part, distributed to the parietes of the thorax and abdomen, separately from each other, without being joined in a plexus; in which respect they differ from the other spinal nerves. Each nerve is connected with the adjoining ganglia of the sympathetic by one or two filaments. The intercostal nerves may be divided into two sets, from the difference they present in their distribution. The six upper, with the exception of the first and the intercosto-humeral branch of the second, are limited in their distribution to the parietes of the chest. The six lower supply the parietes of the chest and abdomen, the last one sending a cutaneous filament to the hip. The First Dorsal Nerve.-The anterior division of the first dorsal nerve divides into two branches: one, the larger, leaves the thorax in front of the neck of the first rib, and enters into the formation of the brachial plexus ; the other and smaller branch runs along the first intercostal space, forming the first intercostal nerve, and terminates on the front of the chest by forming the first anterior THE DORSAL NERVES. 809 Fig. 463.-Superficial and deep distribution of the posterior branches of the spinal nerves (after Hirschfeld and Leveill6). On the left side the cutaneous branches are represented lying on the superficial layer of mus- cles. On the right side the superficial muscles have been removed, the Splenius capitis and Complexus divided in the neck, and the Erector spime divided and partly removed in the back, so as to expose the posterior divis- ions of the spinal nerves near their origin, a a. Lesser occipital nerve from the cervical plexus. 1. External muscular branches of the first cervical nerve, and union by a loop with the second. 2, placed on the Rectus capitis posticus major muscle, marks the great occipital nerve, passing round the short muscles and piercing the Complexus : the external branch is seen to the outside. 3. External branch from the posterior division of the third nerve. 3'. Its internal branch, sometimes called the third occipital. 4' to 8'. The internal branches of the several corresponding nerves on the left side. The external branches of these nerves, proceeding to muscles, are displayed on the right side, d 1 to d 6, and thence to d 12; External muscular branches of the pos- terior divisions of the twelve dorsal nerves on the right side, d 1' to d 6'. The internal cutaneous branches of the six upper dorsal nerves on the left side, d T to d 12'. Cutaneous twigs from the external branches of the six lower dorsal nerves. 11. External branches from the posterior divisions of several lumbar nerves on the right side, piercing the muscles, the lower descending over the gluteal region. I' I'. The same, more super- ficially, on the left side, s s. The issue and union by loops of the posterior divisions of four sacral nerves on the right side, s' s'. Some of those distributed to the skin on the left side. cutaneous nerve of the thorax. Occasionally this anterior cutaneous branch is wanting. The first intercostal nerve, as a rule, gives off no lateral cutaneous 810 THE NERVOUS SYSTEM. branch, but sometimes a small branch is given oft' which communicates with the intercosto-humeral. The Upper Dorsal Nerves.-The anterior divisions of the second, third, fourth, fifth, and sixth dorsal nerves and the small branch from the first dorsal are confined to the parietes of the thorax, and are named upper or pectoral intercostal nerves. They pass forward in the intercostal spaces with the intercostal vessels, being situated below them. At the back of the chest they lie between the pleura and the External intercostal muscle, but are soon placed between the two planes of Intercostal muscles as far as the middle of the rib. They then enter the substance of the Internal intercostal muscles, and, running amidst their fibres as far as the costal cartilages, they gain the inner surface of the muscles and lie between them and the pleura. Near the sternum they cross the internal mammary artery and Triangularis sterni muscle, pierce the Internal intercostal and Pectoralis major muscles, and supply the integument of the front of the chest and over the mammary gland, forming the anterior cutaneous nerves of the thorax, the branch from the second nerve becoming joined with the supraclavicular nerves of the cervical plexus. Branches.-Numerous slender muscular filaments supply the Intercostals, the Infracostales, theLevatores costarum, Serratus posticus superior, and Triangularis sterni muscles. Some of these branches, at the front of the chest, cross the costal cartilages from one to another intercostal space. Lateral Cutaneous Nerves.-These are derived from the intercostal nerves, midway between the vertebrae and sternum : they pierce the External intercostal and Serratus magnus muscles, and divide into two branches, anterior and posterior. The anterior branches are reflected forward to the side and the fore part of the chest, supplying the integument of the chest and mamma and the upper digitations of the External oblique. The posterior branches are reflected backward to supply the integument over the scapula and over the Latissimus dorsi. The lateral cutaneous branch of the second intercostal nerve is of large size, and does not divide, like the other nerves, into an anterior and posterior branch. It is named, from its origin and distribution, the intercosto-humeral nerve (Fig. 461). It pierces the External intercostal muscle, crosses the axilla to the inner side of the arm, and joins with a filament from the nerve of Wrisberg. It then pierces the fascia, and supplies the skin of the upper half of the inner and back part of the arm, communicating with the internal cutaneous branch of the musculo-spiral nerve. The size of this nerve is in inverse proportion to the size of the other cutaneous nerves, especially the nerve of Wrisberg. A second intercosto-humeral nerve is frequently given off from the third intercostal. It supplies filaments to the armpit and inner side of the arm. The Lower Dorsal Nerves.-The anterior divisions of the seventh, eighth, ninth, tenth, and eleventh dorsal nerves are continued anteriorly from the intercostal spaces into the abdominal wall, and the twelfth dorsal is continued throughout its whole course in the abdominal wall, since it is placed below the last rib ; hence these nerves are named loiver or abdominal intercostal nerves. They have (with the exception of the last) the same arrangement as the upper ones as far as the anterior extremities of the intercostal spaces, where they pass behind the costal cartilages, and between the Internal oblique and Transversalis muscles, to the sheath of the Rectus, which they perforate. They supply the Rectus muscle, and terminate in branches which become subcutaneous near the linea alba. These branches are named the anterior cutaneous nerves of the abdomen. They are directed outward as far as the lateral cutaneous nerves, supplying the integument of the front of the belly. The lower intercostal nerves supply the Intercostals, Serratus posticus inferior, and Abdominal muscles, and about the middle of their course give off lateral cutaneous branches, which pierce the External intercostal and External oblique muscles, in the same line as the lateral cutaneous nerves of the thorax, and divide into anterior and posterior branches, which are distributed THE LUMBAR NERVES. 811 to the integument of the abdomen and back, the anterior branches passing nearly as far forward as the margin of the Rectus, the posterior branches passing backward to supply the skin over the Latissimus dorsi, where they join the dorsal cutaneous nerves. The last dorsal is larger than the other dorsal nerves. Its anterior division runs along the lower border of the last rib in front of the Quadratus lumborum. perforates the Transversalis, and passes forward between it and the Internal oblique to be distributed in the same manner as the lower intercostal nerves. It communicates with the ilio-hypogastric branch of the lumbar plexus, and is frequently connected with the first lumbar nerve by a slender branch, the dorsi- lumbar nerve, which descends in the substance of the Quadratus lumborum. The lateral cutaneous branch of the last dorsal is remarkable for its large size: it perforates the Internal and External oblique muscles, passes downward over the crest of the ilium in front of the iliac branch of the ilio-hypogastric (Fig. 470), and is distributed to the integument of the front of the hip, some of its filaments extending as low down as the trochanter major. It does not divide into an anterior and posterior branch like the other lateral cutaneous branches of the intercostal nerves. Surgical Anatomy.-The lower seven intercostal nerves and the ilio-hypogastric from the first lumbar nerve supply the skin of the abdominal wall. They run downward and inward fairly equidistant from each other. The sixth and seventh supply the skin over the " pit of the stomach;" the eighth corresponds to about the position of the middle linea transversa; the tenth to the umbilicus ; and the ilio-hypogastric supplies the skin over the pubes and external abdominal ring. There are several points of surgical importance about the distribution of these nerves, and it is important to remember their origin and course, for in many diseases affecting the nerve-trunks at or near the origin the pain is referred to their peripheral terminations. Thus in Pott's disease of the spine children will often be brought to the surgeon suffering from pain in the belly. This is due to the fact that the nerves are irritated at the seat of disease as they issue from the spinal canal. When the irritation is confined to a single pair of nerves, the sensation complained of is often a feeling of constriction, as if a cord were tied round the abdo- men ; and in these cases the situation of the sense of constriction may serve to localize the disease in the spinal column. In other cases, where the bone disease is more extensive and two or more nerves are involved, a more general diffused pain in the abdomen is complained of. A similar condition is sometimes present in affections of the cord itself, as in tabes dorsalis. Again, it must be borne in mind that the same nerves which supply the skin of the abdomen supply also the planes of muscle which constitute the greater part of the abdominal wall. Hence it follows that any irritation applied to the peripheral terminations of the cutaneous branches in the skin of the abdomen is immediately followed by reflex contraction of the abdominal muscles. A good practical illustration of this may sometimes be seen in watching two surgeons examine the abdomen of the same patient. One, whose hand is cold, causes the muscles of the abdominal wall to at once contract and the belly to become rigid, and thus not nearly so suitable for examina- tion; the other, who has taken the precaution to warm his hand, examines the abdomen with- out exciting any reflex contraction. The supply of both muscles and skin from the same source is of importance in protecting the abdominal viscera from injury. A blow on the abdomen, even of a severe character, will do no injury to the viscera if the muscles are in a condition of firm contraction; whereas in cases where the muscles have been taken unawares, and the blow has been struck "while they were in a state of rest, an injury insufficient to produce any lesion of the abdominal wall has been attended with rupture of some of the abdominal contents. The importance, therefore, of immediate reflex contraction upon the receipt of an injury cannot be overestimated, and the intimate association of the cutaneous and muscular fibres in the same nerve produces a much more immediate response on the part of the muscles to any peripheral stimulation of the cutaneous filaments than would be the case if the two sets of fibres were derived from independent sources. Again, the nerves supplying the abdominal muscles and skin derived from the lower inter- costal nerves are intimately connected with the sympathetic supplying the abdominal viscera through the lower thoracic ganglia from which the splanchnic nerves are derived. In con- sequence of this, in laceration of the abdominal viscera and in acute peritonitis the muscles of the belly-wall become firmly contracted, and thus as far as possible preserve the abdominal contents in a condition of rest. THE LUMBAR NERVES. The lumbar nerves are five in number on each side. The first appears between the first and second lumbar vertebrae, and the last between the last lumbar and the base of the sacrum. The roots of the lumbar nerves are the largest, and their filaments the most 812 THE NERVOUS SYSTEM. numerous, of all the spinal nerves, and they are closely aggregated together upon the lower end of the cord. The anterior roots are the smaller, but there is not the same disproportion between them and the posterior roots as in the cervical nerves. The roots of these nerves have a vertical direction, and are of consider- able length, more especially the lower ones, since the spinal cord does not extend beyond the first lumbar vertebra. The roots become joined in the intervertebral foramina, and the nerves so formed divide at their exit into two divisions, pos- terior and anterior. Posterior Divisions of the Lumbar Nerves. The posterior divisions of the lumbar nerves (Fig. 463) diminish in size from above downward; they pass backward between the transverse processes, and divide into internal and external branches. The internal branches, the smaller, pass inward close to the articular processes of the vertebrae, and supply the Multifidus spinae and Interspinales muscles. The external branches supply the Erector spinae and Intertransverse muscles. From the three upper branches cutaneous nerves are derived which pierce the aponeurosis of the Latissimus dorsi muscle and descend over the back part of the crest of the ilium, to be distributed to the integument of the gluteal region, some of the filaments passing as far as the trochanter major. Anterior Divisions of the Lumbar Nerves. The anterior divisions of the lumbar nerves increase in size from above down- ward. At their origin they communicate with the lumbar ganglia of the sympathetic by long, slender filaments, which accompany the lumbar arteries round the sides of the bodies of the vertebrae, beneath the Psoas muscle. The nerves pass obliquely outward behind the Psoas magnus or between its fasciculi, distributing filaments to it and the Quadratus lumborum. The anterior divisions of the four upper nerves are connected together in this situation by anastomotic loops, and form the lumbar plexus. The anterior division of the fifth lumbar, joined with a branch from the fourth, descends across the base of the sacrum to join the anterior division of the first sacral nerve and assist in the formation of the sacral plexus. The cord resulting from the union of the fifth lumbar and the branch from the fourth is called the lumbo-sacral nerve. The lumbar plexus is formed by the loops of communication between the anterior divisions of the four upper lumbar nerves. The plexus is narrow above, and often connected with the last dorsal by a slender branch, the dorsi-lumbar nerve ; it is broad below, where it is joined to the sacral plexus by the lumbo- sacral cord. It is situated in the substance of the Psoas muscle near its posterior part, in front of the transverse processes of the lumbar vertebrae. The mode in which the plexus is formed is the following: The first lumbar nerve receives a branch from the last dorsal, and gives off a larger branch, which subdivides into the ilio-hypogastric and ilio-inguinal; a communicating branch, which passes down to the second lumbar nerve; and a third branch, which unites with a branch of the second lumbar to form the genito-crural nerve. The second, third, and fourth lumbar nerves divide into an anterior and a posterior division. The anterior division of the second divides into two branches, one of which joins with the above-mentioned branch of the first nerve to form the genito-crural; the other unites with the anterior division of the third nerve and a part of the anterior division of the fourth nerve to form the obturator nerve. The remainder of the anterior division of the fourth nerve passes down to communicate with the fifth lumbar nerve. The posterior divisions of the second and third nerve divide into two branches, a smaller branch from each uniting to form the external The Lumbar Plexus THE LUMBAR PLEXUS. 813 cutaneous nerve, and a larger branch from each, which join with the whole of the posterior division of the fourth lumbar nerve to form the anterior crural. The accessory obturator, wrhen it exists, is formed by a small branch from the third nerve joining with a small branch from the fourth. From this arrangement it fol- lows that the ilio-hypogastric and ilio-inguinal are derived entirely from the first lumbar nerve; the genito-crural from the first and second nerves; the external cuta- neous from the second and third; the anterior crural and obturator by fibres derived from the second, third, and fourth ; and the accessory obturator, when it exists, from the •third and fourth. The branches of the lumbar plexus are-the Ilio-hypogastric. Ilio-inguinal. Genito-crural. External cutaneous. Anterior crural. Obturator. Accessory obturator. The Ilio-hypogastric Nerve (su- perior musculo-cutaneous} arises from the first lumbar nerve. It emerges from the outer border of the Psoas muscle at its upper part, and crosses obliquely in front of the Quadratus lumborum to the crest of the ilium. It then perforates the Transversalis muscle at its posterior part, near the crest of the ilium, and divides between it and the Internal oblique into two branches, iliac and hypogastric. The iliac branch pierces the Internal and External oblique muscles imme- diately above the crest of the ilium, and is distributed to the integument of the gluteal region, behind the lateral cutaneous branch of the last dorsal nerve (Fig. 470). The size of this nerve bears an inverse proportion to that of the cutaneous branch of the last dorsal nerve. The hypogastric branch (Fig. 466) continues onward between the Internal oblique and Transversalis muscles. It then pierces the Internal oblique, and near the middle line perforates the aponeurosis of the External oblique, about an inch above and a little to the outer side of the external abdominal ring, and is distributed to the integument of the hypogastric region. The ilio-hypogastric nerve communicates with the last dorsal and ilio-inguinal nerves. The Ilio-inguinal Nerve (inferior musculo-cutaneous\ smaller than the pre- ceding, arises with it from the first lumbar nerve. It emerges from the outer border of the Psoas just below the ilio-hypogastric, and, passing obliquely across the Quadratus lumborum and Iliacus muscles, perforates the Transversalis near the fore part of the crest of the ilium, and communicates with the ilio-hypogastric nerve betwmen that muscle and the Internal oblique. The nerve then pierces the Internal oblique, distributing filaments to it; and, accompanying the spermatic cord through the inguinal canal, it escapes at the external abdominal ring, and is Fig. 464.-Plan of the lumbar plexus. 814 THE NERVOUS SYSTEM. distributed to the integument of the upper and inner part of the thigh, and to the scrotum in the male and to the labium in the female. The size of this nerve is in inverse proportion to that of the ilio-hypogastric. Occasionally it is very small, and ends by joining the ilio-hypogastric; in such cases a branch from the ilio- hypogastric takes the place of the ilio-inguinal, or the latter nerve may be alto- gether absent. The Genito-crural Nerve arises from the first and second lumbar nerves. It passes obliquely through the substance of the Psoas, descends on its surface for some distance, and divides into a genital and crural branch. The genital branch passes outward on the Psoas magnus, and it then pierces Fig. 465.-The lumbar plexus and its branches. the fascia transversalis or passes through the internal abdominal ring, descends along the back part of the spermatic cord to the scrotum, and supplies, in the male, the Cremaster muscle. In the female it accompanies the round ligament, and is lost upon it. The crural branch descends on the external iliac artery, sending a few fila- ments round it, and, passing beneath Poupart's ligament into the thigh, enters the sheath of the femoral vessels, lying superficial and a little external to the femoral artery. It pierces the anterior layer of the sheath of the vessels, and, becoming superficial by passing through the fascia lata, it supplies the skin of the anterior aspect of the thigh as far as midway between the pelvis and knee. On the front of the thigh it communicates with the outer branch of the middle cutaneous nerve, derived from the anterior crural. THE LUMBAR PLEXUS. 815 External cutaneous. Anterior crural. Middle cutaneous. Anterior division of obturator. . Internal cutaneous. Internal saphenous. Musculo- cutaneous. Anterior tibial. External saphenous. ■Anterior tibial. Fig. 466.-Cutaneous nerves of lower ex tremity. Front view. Fig. 467.-Nerves of the lower extremity. Front view. A few filaments from this nerve may be traced on to the femoral artery; they are derived from the nerve as it passes beneath Poupart's ligament. 816 THE NERVOUS SYSTEM. The External Cutaneous Nerve arises from the second and third lumbar nerves. It emerges from the outer border of the Psoas muscle about its middle, and crosses the Iliacus muscle obliquely, to the notch immediately beneath the ante- rior superior spine 'of the ilium, where it passes under Poupart's ligament into the thigh, and divides into two branches,-anterior and posterior. The anterior branch descends in an aponeurotic canal formed in the fascia lata, becomes superficial about four inches below Poupart's ligament, and divides into branches which are distributed to the integument along the anterior and outer part of the thigh, as far down as the knee. This nerve occasionally com- municates with a branch of the long saphenous nerve in front of the knee- joint. The posterior branch pierces the fascia lata, and subdivides into branches which pass backward across the outer and posterior surface of the thigh, supplying the integument from the crest of the ilium as far as the middle of the thigh. The Obturator Nerve supplies the obturator externus and Adductor muscles of the thigh, the articulations of the hip and knee, and occasionally the integument of the thigh and leg. It arises by three branches-from the third, the fourth, and the fifth lumbar nerves. It descends through the inner fibres of the Psoas muscle, and emerges from its inner border near the brim of the pelvis; it then runs along the lateral wall of the pelvis, above the obturator vessels, to the upper part of the obturator foramen, where it enters the thigh, and divides into an anterior and a posterior branch, separated by some of the fibres of the Obturator externus, and lower down by the Adductor brevis muscle. The anterior branch (Fig. 467) passes down in front of the Adductor brevis, being covered by the Pectineus and Adductor longus, and at the lower border of the latter muscle communicates with the internal cutaneous and internal saphenous nerves, forming a kind of plexus. It then descends upon the femoral artery, upon which it is finally distributed. The nerve, near the obturator foramen, gives off an articular branch to the hip-joint. Behind the Pectineus it distributes muscular branches to the Adductor longus and Gracilis, and occasionally to the Adductor brevis and Pectineus, and receives a communicating branch from the accessory obturator nerve. Occasionally the communicating branch to the internal cutaneous and internal saphenous nerves is continued down, as a cutaneous branch, to the thigh and leg. When this is so, this occasional cutaneous branch emerges from beneath the lower border of the Adductor longus, descends along the posterior margin of the Sartorius to the inner side of the knee, where it pierces the deep fascia, communicates with the long saphenous nerve, and is distributed to the integument of the inner side of the leg as low down as its middle. When this communicating branch is small, its place is supplied by the internal cutaneous nerve. The posterior branch of the obturator nerve pierces the Obturator externus, sending branches to supply it, and passes behind the Adductor brevis on the front of the Adductor magnus, where it divides into numerous muscular branches, which supply the Adductor magnus, and occasionally the Adductor brevis. One of the branches gives off a filament to the knee-joint. The articular branch for the knee-joint perforates the lower part of the Adductor magnus and enters the popliteal space; it then descends upon the popliteal artery as far as the back part of the knee-joint, where it perforates the posterior ligament, and is distributed to the synovial membrane. It gives filaments to the artery in its course. The Accessory Obturator Nerve (Fig. 465) is not constantly present. It is of small size, and arises by separate filaments from the third and fourth lumbar nerves. It descends along the inner border of the Psoas muscle, crosses the horizontal ramus of the os pubis, and passes under the outer border of the Pectineus muscle, where it divides into numerous branches. One of these supplies the Pectineus. penetrating its under surface; another is distributed to the hip-joint; while a third communicates with the anterior branch of the obturator nerve. When this nerve THE LUMBAR PLEXUS. 817 is absent the hip-joint receives two branches from the obturator nerve. ■ Occasion- ally it is very small, and becomes lost in the capsule of the hip-joint. The Anterior Crural Nerve (Figs. 465, 467) is the largest branch of the lumbar plexus. It supplies muscular branches to the Iliacus, Pectineus, and all the muscles on the front of the thigh, excepting the Tensor vagi me femoris ; cutaneous filaments to the front and inner side of the thigh and to the leg and foot; and articular branches to the hip and knee. It arises from the second, third, and fourth lumbar nerves. It descends through the fibres of the Psoas muscle, emerging from it at the lower part of its outer border, and passes down between it and the Iliacus, and beneath Poupart's ligament, into the thigh, where it becomes somewhat flattened, and divides into an anterior part which passes superficial to the external circumflex vessels, and a posterior part which passes beneath these vessels. Under Poupart's ligament it is separated from the femoral artery by the Psoas muscle, and lies beneath the iliac fascia. Within the pelvis the anterior crural nerve gives off from its outer side some small branches to the Iliacus, and a branch to the femoral artery which is distrib- uted upon the upper part of that vessel. The origin of this branch varies : it occasionally arises higher than usual, or it may arise lower down in the thigh. External to the pelvis the following branches are given off: From the Anterior Division. Middle cutaneous. Internal cutaneous. From the Posterior Division. Long saphenous. Muscular. Articular. The middle cutaneous nerve (Fig. 466) pierces the fascia lata (generally the Sartorius also) about three inches below Poupart's ligament, and divides into two branches, which descend in immediate proximity along the fore part of the thigh, distributing numerous branches to the integument as low as the front of the knee, where it communicates with the nervus cutaneus patelice, a branch of the internal saphenous nerve, helping to form the patellar plexus. Its outer branch communicates, above, with the crural branch of the genito-crural nerve, and the inner branch with the internal cutaneous nerve below. The Sartorius muscle is supplied by this or the following nerve. The internal cutaneous nerve passes obliquely across the upper part of the sheath of the femoral artery, and divides in front or at the inner side of that vessel into two branches, anterior and posterior or internal. The anterior branch runs downward on the Sartorius, perforates the fascia lata at the lower third of the thigh, and divides into two branches, one of which supplies the integument as low down as the inner side of the knee ; the other crosses to the outer side of the patella, communicating in its course with the nervus cutaneus patellae, a branch of the internal saphenous nerve. The posterior or internal branch descends along the inner border of the Sartorius muscle to the knee, where it pierces the fascia lata, communicates with the long saphenous nerve, and gives off several cutaneous branches. The nerve then passes down the inner side of the leg, to the integument of which it is distributed. This nerve, beneath the fascia lata, at the lower border of the Adductor longus, joins in a plexiform network by uniting with branches of the long saphenous and obturator nerves (Fig. 467). When the communicating branch from the obturator nerve is large and continued to the integument of the leg, the inner branch of the internal cutaneous is small and terminates at the plexus, occasionally giving off a few cutaneous filaments. The internal cutaneous nerve, before dividing, gives off a few filaments, which pierce the fascia lata, to supply the integument of the inner side of the thigh, accompanying the long saphenous vein. One of these filaments passes through the saphenous opening; a second becomes subcutaneous about the middle of the thigh; and a third pierces the fascia at its lower third. 818 THE NERVOUS SYSTEM. The long or internal saphenous nerve is the largest of the cutaneous branches of the anterior crural. It approaches the femoral artery where this vessel passes beneath the Sartorius, and lies on its outer side, beneath the aponeurotic cover- ing of Hunter's canal, as far as the opening in the lower part of the Adductor magnus. It then quits the artery, and descends vertically along the inner side of the knee, beneath the Sartorius, pierces the fascia lata, opposite the interval between the tendons of the Sartorius and Gracilis, and becomes subcutaneous. The nerve then passes along the inner side of the leg, accompanied by the internal saphenous vein, descends behind the internal border of the tibia, and, at the lower third of the leg, divides into two branches : one continues its course along the margin of the tibia, terminating at the inner ankle; the other passes in front of the ankle, and is distributed to the integument along the inner side of the foot, as far as the great toe, communicating with the internal branch of the musculo- cutaneous nerve. Branches.-The long saphenous nerve about the middle of the thigh gives off a communicating branch which joins the plexus formed by the obturator and internal cutaneous nerves. At the inner side of the knee it gives off a large branch (nervus cutaneus patellaf which pierces the Sartorius and fascia lata, and is distributed to the integument in front of the patella. This nerve communicates above the knee with the anterior branch of the internal cutaneous and with the middle cutaneous ; below the knee, with other branches of the long saphenous; and on the outer side of the joint, with branches of the external cutaneous nerve, forming a plexiform network, the plexus patellae. The cutaneous nerve of the patella is occasionally small, and terminates by joining the internal cutaneous, which supplies its place' in front of the knee. Below the knee the branches of the long saphenous nerve are distributed to the integument of the front and inner side of the leg, communicating with the cutaneous branches from the internal cutaneous or from the obturator nerve. The muscular branches supply the Pectineus and all the muscles on the front of the thigh, except the Tensor vaginae femoris, which is supplied from the superior gluteal nerve, and the Sartorius, which is supplied by filaments from the middle or internal cutaneous nerves. The branches to the Pectineus, usually two in number, pass inward behind the femoral vessels, and enter the muscle on its anterior surface. Sometimes one of these nerves is given off in the pelvis, and is then often united with the accessory obturator. The branch to the Rectus muscle enters its under surface high up, sending off a small filament to the hip-joint. The branch to the Vastus externus, of large size, follows the course of the descending branch of the external circumflex artery to the lower part of the muscle. It gives off an articular filament to the knee-joint. The branch to the Vastus internus is a long branch which runs down on the outer side of the femoral vessels in company with the internal saphenous nerve for its upper part. It enters the muscle about its middle, and gives off a filament which can usually be traced downward on the surface of the muscle to the knee- joint. The branch to the Crureus enters the muscle on its anterior surface about the middle of the thigh, and sends a filament through the muscle to the Sub- crureus. The articular branch to the hip-joint is derived from the nerve to the Rectus. The articular branches to the knee-joint are two in number. One, a long, slender filament, is derived from the nerve to the Vastus externus. It penetrates the capsular ligament of the joint on its anterior aspect. The other is derived from the nerve to the Vastus internus. It can usually be traced downward on the surface of this muscle to near the joint; it then penetrates the muscular fibres, 77//< SACRAL NERVES. 819 and accompanies the deep branch of the anastomotica magna artery, pierces the capsular ligament of the joint on its inner side, and supplies the synovial membrane. THE SACRAL AND COCCYGEAL NERVES. The sacral nerves are five in number on each side. The four upper ones pass from the sacral canal through the sacral foramina; the fifth through the foramen between the sacrum and coccyx. The roots of origin of the upper sacral {and lumbar) nerves are the largest of all the spinal nerves, whilst those of the lowest sacral and coccygeal nerve are the smallest. The roots of these nerves are of very considerable length, being longer than those of any of the other spinal nerves, on account of the spinal cord not extending beyond the first lumbar vertebra. From their great length and the appearance they present in connection with the spinal cord the roots of origin of these nerves are called collectively the cauda equina. Each sacral and coccygeal nerve divides into two divisions, posterior and anterior. The posterior divisions of the sacral nerve (Fig. 468) are small, diminish in Fig. 468.-The posterior sacral nerves. size from above downward, and emerge, except the last, from the sacral canal by the posterior sacral foramina. The three upper ones are covered, at their exit from the sacral canal, by the Multifidus spin;®, and divide into internal and external branches. The internal branches are small, and supply the Multifidus spinse. The external branches join "with one another and with the last lumbar and fourth sacral nerves by means of communicating loops. These branches pass out- ward to the outer surface of the great sacro-sciatic ligament, where they form a second series of loops beneath the Gluteus maximus. Cutaneous branches from this second series of loops, usually three in number, pierce the Gluteus maximus: 820 777A NERVOUS SYSTEM. one near the posterior inferior spine of the ilium; another opposite the end of the sacrum; and the third midway between the other two. They supply the integu- ment over the posterior part of the gluteal region. The posterior divisions of the two lower sacral nerves are situated below the Multifidus spinae. They are of small size, and do not divide into internal and external branches, but join with each other, and with the coccygeal nerve, so as to form loops on the back of the sacrum, filaments from which supply the Extensor coccygis and the integument over the coccyx. The coccygeal nerve divides into its anterior and posterior divisions in the spinal canal. The posterior division is the smaller. It does not divide, but receives, as already mentioned, a communicating branch from the last sacral, and is lost in the fibrous structure on the back of the coccyx. The anterior divisions of the sacral nerves diminish in size from above down- Femoral artery. to COCCYGEUS. to' LEVATOR ANI. Br. to SPHINCTER ANI Fig. 469.-Side view of pelvis, showing sacral nerves. ward. The four upper ones emerge from the anterior sacral foramina: the ante- rior division of the fifth, after emerging from the spinal canal through its termi- nal opening, curves forward between the sacrum and the coccyx. All the anterior sacral nerves communicate with the sacral ganglia of the sympathetic at their exit from the sacral foramina. The first nerve, of large size, unites with the lumbo-sacral cord, formed by the fifth lumbar, and a branch from the fourth. The second, equal in size to the preceding, and the third, about one-fourth the size of the second, unite with this trunk, and form, with a small fasciculus from the fourth, the sacral plexus, a visceral branch being given off from the third nerve to the bladder. The fourth anterior sacral nerve sends a branch to join the sacral plexus. The remaining portion of the nerve divides into visceral and muscular branches, and a communicating filament descends to join the fifth sacral nerve. The visceral branches are distributed to the viscera of the pelvis, communicating with the THE SAC11AL PLEXUS. 821 sympathetic nerve. These branches ascend upon the rectum and bladder, and in the female upon the vagina, communicating with branches of the sympathetic from the pelvic plexus. The muscular branches are distributed to the Levator ani, Coccygeus, and Sphincter ani. The branch to the Sphincter ani pierces the Levator ani, so as to reach the ischio-rectal fossa, where it is found lying in front of the coccyx. Cutaneous filaments arise from the latter branch, which supply the integument between the anus and coccyx. Another cutaneous branch is fre- quently given off from this nerve, though sometimes from the pudic (Schwalbe). It perforates the great sacro-sciatic ligament, and, winding round the lower bor- der of the Gluteus maximus, supplies the skin over the lower and inner part of this muscle. The fifth anterior sacral nerve, after passing from the lower end of the sacral canal, curves forward through the fifth sacral foramen, formed between the lower part of the sacrum and the transverse process of the first piece of the coccyx. It pierces the Coccygeus muscle, and descends upon its anterior surface to near the tip of the coccyx, where it again perforates the muscle, to be distributed to the integument over the back part and side of the coccyx. This nerve communicates above with the fourth sacral and below with the coccygeal nerve, and supplies the Coccygeus muscle. The anterior division of the coccygeal nerve is a delicate filament which escapes at the termination of the sacral canal; it passes downward behind the rudiment- ary transverse process of the first piece of the coccyx, and curves forward through the notch between the first and second pieces, piercing the Coccygeus muscle, and descending on its anterior surface to near the tip of the coccyx, where it again pierces the muscle, to be distributed to the integument over the back part and side of the coccyx. It is joined by a branch from .the fifth anterior sacral as it descends on the surface of the Coccygeus muscle. The sacral plexus is formed by the lumbo-sacral cord, the anterior divisions of the three upper sacral nerves, and part of that of the fourth. These nerves proceed in different directions; the upper ones obliquely downward and outward, the lower one nearly horizontally, and they all unite into a single, broad, flat cord. The sacral plexus is triangular in form, its base corresponding with the exit of the nerves from the sacrum, its apex with the lowTer part of the great sacro- sciatic foramen. It rests upon the anterior surface of the Pyriformis, and is covered in front by the pelvic fascia, which separates it from the sciatic and pudic branches of the internal iliac artery and from the viscera of the pelvis. The branches of the sacral plexus are- The Sacral Plexus (Fig. 469). Muscular. Superior gluteal. Inferior gluteal. Pudic. Small sciatic. Great sciatic. The muscular branches supply the Pyriformis, Obturator internus, the two Gemelli, and the Quadratus femoris. The branch to the Pyriformis arises either from the plexus or from the upper sacral nerves before they enter the plexus; the branch to the Obturator internus arises at the junction of the lumbo- sacral and first sacral nerves: it passes out of the pelvis through the great sacro- sciatic foramen, crosses the spine of the ischium, and re-enters the pelvis through the lesser sacro-sciatic foramen to the inner surface of the Obturator internus; the branch to the Gemellus superior arises in common with the nerve to the Obtu- rator internus: it enters the muscle at the upper part of its posterior surface; the small branch to the Gemellus inferior and Quadratus femoris also arises from the upper part of the plexus: it passes through the great sacro-sciatic foramen, and courses down beneath the Gemelli and tendon of the Obturator internus, and sup- plies the muscles on their deep or anterior surface. It gives off an articular 822 THE NEU VO US SYSTEM. Superior gluteal. Pudic. Nerve to obturator internus. Small sciatic. Inferior. pudendal. Descending- cutaneous. Internal . popliteal. i External -popliteal, or peroneal. External saphenous. Posterior tibial. ~~ _Communicans peronei. Plantar cutaneous. Fig. 470.-Cutaneous nerves of lower extremity. Posterior view. Fig. 471.-Nerves of the lower extremity.1 Posterior view. 1 N. B.-In this diagram the external saphenous and communicans peronei are not in their nor mal position. They have been displaced by the removal of the superficial muscles. THE SACRAL PLEXUS. 823 branch to the hip-joint. This articular branch is occasionally derived from the upper part of the great sciatic nerve. The Superior Gluteal Nerve (Fig. 471) arises from the back part of the lumbo- sacral cord, with some filaments from the first sacral nerve: it passes from the pelvis through the great sacro-sciatic foramen above the Pyriformis muscle, accompanied by the gluteal vessels, and divides into a superior and an inferior branch. The superior branch follows the line of origin of the Gluteus minimus, and supplies the Gluteus medius. The inferior branch crosses obliquely between the Gluteus minimus and medius, distributing filaments to both these muscles, and terminates in the Tensor vaginae femoris, extending nearly to its lower end. The Inferior Gluteal arises from the lumbo-sacral cord and first and second sacral nerves, and is intimately connected with the small sciatic at its origin. It passes out of the pelvis through the great sciatic notch, beneath the Pyriformis muscle, and, dividing into a number of branches, enters the Gluteus maximus muscle on its under surface. It gives off a cutaneous branch, which winds round the lower border of the Gluteus maximus muscle to supply the skin of the buttock. It is said also to give an articular branch to the hip-joint. The Pudic Nerve arises from the lower part of the sacral plexus, and leaves the pelvis, through the great sacro-sciatic foramen, below the Pyriformis. It then crosses the spine of the ischium, and re-enters the pelvis through the lesser sacro- sciatic foramen. It accompanies the pudic vessels upward and forward along the outer wall of the ischio-rectal fossa, being contained in a sheath of the Obturator fascia, and divides into two terminal branches, the perineal nerve and the dorsal nerve of the penis. Before its division it gives off the inferior haemorrhoidal nerve. The inferior hcemorrhoidal nerve is occasionally derived separately from the sacral plexus. It passes across the ischio-rectal fossa, with its accompanying ves- sels, toward the lower end of the rectum, and is distributed to the integument round the anus. Branches of this nerve communicate with the inferior pudendal and superficial perineal nerves at the fore part of the perinaeum. The perineal nerve, the inferior and larger of the two terminal branches of the pudic, is situated below the pudic artery. It accompanies the superficial perineal artery in the perinaeum, dividing into cutaneous and muscular branches. The cutaneous branches (superficial perineal) are two in number, posterior and anterior. The posterior or external branch passes forward along the outer side of the perineal space parallel to the inferior pudendal nerve, and is distrib- uted to the skin of the scrotum. It communicates with the inferior haemorrhoid- al, the inferior pudendal, and the other superficial perineal nerve. The anterior or internal branch passes forward nearer to the middle line, to be distributed to the inner and back part of the scrotum. Both these nerves supply the labia majora in the female. The muscular branches are distributed to the Transversus perinaei, Accelerator urinae, Erector penis, and Compressor urethrae. A distinct branch is given off from the nerve to the Accelerator urinae, which pierces this muscle and supplies the corpus spongiosum, ending in the mucous membrane of the urethra. This is the nerve to the bulb. The dorsal nerve of the penis is the deepest division of the pudic nerve ; it accompanies the pudic artery along the ramus of the ischium: piercing the pos- terior layer of the deep perineal fascia, it runs forward along the inner margin of the ramus of the os pubis, between the two layers of the deep fascia. It then pierces the anterior layer, and, in company with the dorsal artery of the penis, passes through the suspensory ligament, and, running forward, is distributed to the glans. On the penis this nerve gives off a cutaneous branch which runs along the side of the organ; it is joined with branches of the sympathetic, and supplies the integument of the upper surface and sides of the penis and prepuce, giving a large branch to the corpus cavernosum. 824 THE NERVOUS SYSTEM. In the female the dorsal nerve is very small and supplies the clitoris. The Small Sciatic Nerve (Fig. 471) supplies the integument of the perinaeum and back part of the thigh and leg. It is usually formed by the union of two branches, which arise from the second and third nerves of the sacral plexus. It issues from the pelvis through the great sacro-sciatic foramen below the Pvri- formis muscle, descends beneath the Gluteus maximus with the sciatic artery, and at the lower border of that muscle passes along the back part of the thigh, beneath the fascia lata, to the lower part of the popliteal region, where it pierces the fascia and becomes cutaneous. It then accompanies the external saphenous vein to about the middle of the leg, its terminal filaments communicating with the external saphenous nerve. The branches of the small, sciatic nerve are all cutaneous, and consist of four groups-internal, external, ascending, and descending. The internal cutaneous branches are distributed to the skin at the upper and inner side of the thigh, on its posterior aspect. One branch, longer than the rest, the inferior pudendal, curves forward below the tuber ischii, pierces the fascia lata, and passes forward beneath the superficial fascia of the perinaeum to be distributed to the integument of the scrotum in the male and the labium in the female, communicating with the superficial perineal and inferior haemorrhoidal nerves. The external cutaneous branches consist of two or three filaments, which are distributed to the skin at the upper and outer side of the thigh on its posterior aspect, as far down as the middle of that region. The ascending cutaneous branches consist of two or three filaments, which turn upward round the lower border of the gluteus maximus, to supply the integument covering its surface. The descending cutaneous branches are given off from the lesser sciatic nerve as it descends beneath the fascia of the thigh ; they supply the integument of the back part of the thigh, popliteal region, and upper part of the leg. The Great Sciatic Nerve (Fig. 471) supplies nearly the whole of the integu- ment of the leg, the muscles of the back of the thigh, and those of the leg and foot. It is the largest nervous cord in the body, measuring three-quarters of an inch in breadth, and is the continuation of the lower part of the sacral plexus. It passes out of the pelvis through the great sacro-sciatic foramen, below the Pyriformis muscle. It descends between the trochanter major and tuberosity of the ischium, along the back part of the thigh to about its lower third, where it divides into two large branches, the internal and external popliteal nerves. This division may take place at any point between the sacral plexus and the lower third of the thigh. When the division occurs at the plexus, the two nerves descend together, side by side; or they may be separated at their commencement by the interposition of part or the whole of the Pyriformis muscle. As the nerve descends along the back of the thigh it rests at first upon the External rotator muscles, in company with the small sciatic nerve and artery, being covered by the Gluteus maximus ; lower down, it lies upon the Adductor magnus and is covered by the long head of the Biceps. The branches of the nerve, before its division, are articular and muscular. The articular branches arise from the upper part of the nerve; they supply the hip-joint, perforating its fibrous capsule posteriorly. These branches are sometimes derived from the sacral plexus. The muscular branches are distributed to the Flexors of the leg-viz. the Biceps, Semitendinosus, and Semimembranosus, and a branch to the Adductor magnus. These branches are given off beneath the Biceps muscle. The Internal Popliteal Nerve, the larger of the two terminal branches of the great sciatic, descends along the back part of the thigh, through the middle of the popliteal space, to the lower part of the Popliteus muscle, where it passes with the artery beneath the arch of the Soleus and becomes the posterior tibial. It is overlapped by the hamstring muscles above, and then becomes more super- THE TIBIAL AND PLANTAR NERVES. 825 ficial, and lies to the outer side of, and some distance from, the popliteal vessels; opposite the knee-joint it is in close relation with the vessels, and crosses to the inner side of the artery. Below, it is overlapped by the Gastrocnemius. The branches of this nerve are-articular, muscular, and a cutaneous branch, the communicans poplitei nerve. The articular branches, usually three in number, supply the knee-joint: two of these branches accompany the superior and inferior internal articular arteries, and a third, the azygos articular artery. The muscular branches, four or five in number, arise from the nerve as it lies between the two heads of the Gastrocnemius muscle; they supply that muscle, the Plantaris, Soleus, and Popliteus. The filaments which supply the Popliteus turn round its lower border and are distributed to its deep surface. The commum'cans poplitei descends between the two heads of the Gastrocne- mius muscle, and about the middle of the back of the leg pierces the deep fascia, and joins a communicating branch (communicans peronei} from the external popliteal nerve to form the external or short saphenous (Fig. 470). The exter- nal saphenous nerve, formed by the cutaneous branches of the internal and external popliteal nerves, passes downward and outward near the outer margin of the tendo Achillis, lying close to the external saphenous vein, to the interval between the external malleolus and the os calcis. It winds round the outer mal- leolus, and is distributed to the integument along the outer side of the foot and little toe, communicating on the dorsum of the foot with the musculo-cutaneous nerve. In the leg its branches communicate with those of the small sciatic. The Posterior Tibial Nerve (Fig. 471) commences at the lower border of the Popliteus muscle, and passes along the back part of the leg with the posterior tibial vessels to the interval between the inner malleolus and the heel, where it divides into the external and internal plantar nerves. It lies upon the deep muscles of the leg, and is covered in the upper part by the muscles of the calf, lower down by the skin and fascia. In the upper part of its course it lies to the inner side of the posterior tibial artery, but it soon crosses that vessel, and lies to its outer side as far as the ankle. In the lower third of the leg it is placed parallel with the innei* margin of the tendo Achillis. The branches of the posterior tibial nerve are-muscular, plantar cutaneous, and articular. The muscular branches arise either separately or by a common trunk from the upper part of the nerve. They supply the Tibialis posticus, Flexor longus digito- rum, and Flexor longus hallucis muscles, the branch to the latter muscle accompanying the peroneal artery. The joZantar cutaneous branch perforates the internal annular ligament and supplies the integument of the heel and inner side of the sole of the foot. The articular branch is given off just above the bifurcation of the nerve and supplies the hnkle-joint. The internal plantar nerve (Fig. 472), the larger of the two terminal branches of the posterior tibial, accompanies the internal plantar artery along the inner side of the foot. From its origin at the inner ankle it passes beneath the Abductor hallucis, and then forward between this muscle and the Flexor brevis digitorum, divides opposite the bases of the metatarsal bones into four digital branches, and communicates with the external plantar nerve. Branches.-In its course the internal plantar nerve gives off cutaneous branches, which pierce the plantar fascia and supply the integument of the sole of the foot; muscular branches, which supply the Abductor hallucis and Flexor brevis digitorum; articular branches, to the articulations of the tarsus and meta- tarsus ; and four digital branches. These pass between the divisions of the plantar fascia in the clefts between the toes, and are distributed in the fol- lowing manner: The first supplies the inner border of the great toe, and sends a filament to the Flexor brevis hallucis muscle; the second bifurcates to supply the adjacent sides of the great and second toes, sending a filament 826 THE NERVOUS SYSTEM. to the First lumbrical muscle; the third digital branch supplies the adjacent sides of the second and third toes, and the Second lumbrical muscle; the fourth supplies the corresponding sides of the third and fourth toes, and receives a communicating branch from the external plantar nerve. It will be observed that the distribution of these branches is pre- cisely similar to that of the median nerve in the hand. Each digital nerve gives off cutaneous and articular filaments, and oppo- site the last phalanx sends a dorsal branch, which supplies the structure round the nail, the continuation of the nerve being dis- tributed to the ball of the toe. The external plantar nerve, the smaller of the two, completes the nervous supply to the structures of the sole of the foot, being distributed to the little toe and one-half of the fourth, as well as to most of the deep muscles, its distribution being similar to that of the ulnar in the hand. It passes obliquely forward with the external plantar artery to the outer side of the foot, lying between the Flexor brevis digitorum and Flexor accessorius, and in the interval be- tween the former muscle and Abductor minimi digiti divides into a superficial and a deep branch. Before its division it sup- plies the Flexor accessorius and Abductor minimi digiti. The superficial branch separates into two digital nerves: one, the smaller of the two, supplies the outer side of the little toe, the Flexor brevis minimi digiti, and the two Interosseous muscles of the fourth metatarsal space ; the other and larger digital branch supplies the adjoining sides of the fourth and fifth toes, and communicates with the internal plantar nerve. The deep or muscular branch accompanies the external plantar artery into the deep part of the sole of the foot, beneath the tendons of the Flexor muscles and Adductor transversus hallucis, and supplies all the Interossei (except those in the fourth metatarsal space), the two outer Lumbricales, the Adductor obliquus hal- lucis, and the Adductor transversus hallucis. The External Popliteal or Peroneal Nerve (Fig. 471), about one-half the size of the internal popliteal, descends obliquely along the outer sides of the popliteal space to the head of the fibula, close to the inner margin of the Biceps muscle. It is easily felt beneath the skin behind the head of the fibula at the inner side of the tendon of the Biceps. It passes between the tendon of the Biceps and outer head of the Gastrocnemius muscle, winds round the neck of the fibula, pierces the origin of the Peroneus longus, and divides beneath that muscle into the anterior tibial and musculo-cutaneous nerves. • The branches of the peroneal nerve, previous to its division, are articular and cutaneous. The articular branches are three in number; two of these accompany the superior and inferior external articular arteries to the outer side of the knee. The upper one occasionally arises from the great sciatic nerve before its bifurcation. The third (recurrent) articular nerve is given off at the point of division of the peroneal nerve; it ascends with the anterior recurrent tibial artery through the Tibialis anticus muscle to the front of the knee, which it supplies. Internal plantar.' External plantar. Deep 'branch. Fig. 472.-The plantar nerves. SURGICAL ANA TOMY OF NERVES OF LO WER EXTREMITY. 827 The cutaneous branches, two or three in number, supply the integument along the back part and outer side of the leg as far as its middle or lower part; one of these, larger than the rest, the communicans peronei, arises near the head of the fibula, crosses the external head of the Gastrocnemius to the middle of the leg, and joins with the communicans poplitei to form the external saphenous. This nerve occasionally exists as a separate branch, which is continued down as far as the heel. The Anterior Tibial Nerve (Fig. 467) commences at the bifurcation of the per- oneal nerve, between the fibula and upper part of the Peroneus longus, passes obliquely forward beneath the Extensor longus digitorum to the fore part of the interosseous membrane, and reaches the outer side of the anterior tibial artery above the middle of the leg; it then descends with the artery to the front of the ankle-joint, where it divides into an external and an internal branch. This nerve lies at first on the outer side of the anterior tibial artery, then in front of it, and again at its outer side at the ankle-joint. The branches of the anterior tibial nerve in its course through the leg are the muscular branches to the Tibialis anticus, Extensor longus digitorum, Peroneus tertius, and Extensor proprius hallucis muscles, and an articular branch to the ankle-joint. The external or tarsal branch of the anterior tibial passes outward across the tarsus, beneath the Extensor brevis digitorum, and, having become ganglionic, like the posterior interosseous nerve at the wrist, supplies the Extensor brevis digitorum. From the ganglion are given off' three minute interosseous branches which supply the tarsal joints and the metatarso-phalangeal joints of the second, third, and fourth toes. The first of these sends a filament to the second dorsal interosseous muscle. The internal branch, the continuation of the nerve, accompanies the dorsalis pedis artery along the inner side of the dorsum of the foot, and at the first inter- osseous space divides into two branches, which supply the adjacent sides of the great and second toes, communicating with the internal branch of the musculo- cutaneous nerve. Before it divides it gives off an interosseous branch to the first space, which supplies the metatarso-phalangeal joint of the great toe and sends a filament to the First dorsal interosseous muscle. The Musculo-cutaneous Nerve (Fig. 467) supplies the muscles on the fibular side of the leg and the integument of the dorsum of the foot. It passes forward between the Peronei muscles and the Extensor longus digitorum, pierces the deep fascia at the lower third of the leg on its front and outer side, and divides into two branches. This nerve in its course between the muscles gives off muscular branches to the Peroneus longus and brevis, and cutaneous filaments to the integument of the lower part of the leg. The internal branch of the musculo-cutaneous nerve passes in front of the ankle-joint and along the dorsum of the foot, supplying the inner side of the great toe and the adjoining sides of the second and third toes. It also supplies the integument of the inner ankle and inner side of the foot, communicating with the internal saphenous nerve, and joins with the anterior tibial nerve between the great and second toes. The external branch, the larger, passes along the outer side of the dorsum of the foot, to be distributed to the adjoining sides of the third, fourth, and fifth toes. It also supplies the integftment of the outer ankle and outer side of the foot, com- municating with the short saphenous nerve. The-. distribution of these branches of the musculo-cutaneous nerve will be found to vary; together, they supply all the toes excepting the outer side of the little toe and the adjoining sides of the great and second toes, the former being supplied by the external saphenous, and the latter by the internal branch of the anterior tibial. Surgical Anatomy.-The lumbar plexus passes through the Psoas muscle, and, therefore in psoas abscess any or all of its branches may be irritated, causing severe pain in the part to 828 THE NERVOUS SYSTEM. which the irritated nerves are distributed. The genito-crural nerve is the one which is most frequently implicated. This nerve is also of importance, as it is concerned in one of the princi- pal reflexes employed in the investigation of diseases of the spine. If the skin over the inner side of the thigh just below Poupart's ligament, the part supplied by the crural branch of the genito-crural nerve, be gently tickled in a male child, the testicle will be noticed to be drawn upward through the action of the Cremaster muscle, supplied by the genital branch of the same nerve. The same result may sometimes be noticed in adults, and can almost always be produced by severe stimulation. This reflex, when present, shows that the portion of the cord from which the first and second lumbar nerves are derived is in a normal condition. The anterior crural nerve is in danger of being injured in fractures of the true pelvis, since the fracture most commonly takes place through the horizontal ramus of the os pubis, at or near the point where this nerve crosses the bone. It is also liable to be injured in fractures and dislocations of the femur, and is likely to be pressed upon and its functions impaired in some tumors growing in the pelvis. Moreover, on account of its superficial position it is exposed to injury in wounds and stabs in the groin. When this nerve is paralyzed, the patient is unable to flex his hip completely, on account of the loss of motion in the Iliacus, or to extend the knee on the thigh, on account of paralysis of the Quadriceps extensor cruris; there is complete paralysis of the Sartorius and partial paralysis of the Pectineus. There is loss of sensation down the front and inner side of the thigh, except in that part supplied by the crural branch of the genito-crural and by the ilio-inguinal. There is also loss of sensation down the inner side of the leg and foot as far as the ball of the great toe. The obturator nerve is of special surgical interest. It is rarely paralyzed alone, but occa- sionally in association with the anterior crural. The principal interest attached to it is in con- nection with its supply to the knee, pain in the knee being symptomatic of many diseases in which the trunk of this nerve or one of its branches is irritated. Thus it is well known that in the earlier stages of hip-joint disease the patient does not complain of pain in that articulation, but on the inner side of the knee, or in the knee-joint itself, both these articulations being supplied by the obturator nerve, the final distribution of the nerve being to the knee-joint. Again, the same thing occurs in sacro-iliac disease: pain is complained of in the knee-joint or on its inner side. The obturator nerve is in close relationship with the sacro-iliac articulation, pass- ing over it, and, according to some anatomists, distributing filaments to it. Again, in cancer of the sigmoid flexure, and even in cases where masses of hardened faeces are impacted in this portion of the gut, pain is complained of in the knee. The obturator nerve lies beneath the sigmoid flexure, and is readily pressed upon and irritated when disease exists in this part of the intestine. Finally, pain in the knee forms an important diagnostic sign in obturator hernia. The hernial protrusion as it passes out through the opening in the obturator membrane presses upon the nerve and causes pain in the parts supplied by its peripheral filaments. When the obturator nerve is paralyzed, the patient is unable to press his knees together or to cross one leg over the other, on account of paralysis of the Adductor muscles. Rotation outward of the thigh is impaired from paralysis of the Obturator externus. Sometimes there is loss of sensation in the upper half of the inner side of the leg. The great sciatic nerve is liable to be pressed upon by various forms of pelvic tumors, giv- ing rise to pain along its trunk, to which the term sciatica is applied. Tumors growing from the pelvic viscera or bones, aneurisms of some of the branches of the internal iliac artery, calcu- lus in the bladder when of large size, accumulation of faeces in the rectum, may all cause pressure on the nerve inside the pelvis and give rise to sciatica. Outside the pelvis exposure to cold, violent movements of the hip-joint, exostoses or other tumors growing from the margin of the sacro-sciatic foramen, may also give rise to the same condition. When paralyzed there is loss of motion in all the muscles below the knee, and loss of sensation in the same situation, except the upper half of the back of the leg, supplied by the small sciatic and the upper half of the inner side of the leg, when the communicating branch of the obturator is large (see page 816). The sciatic nerve has been frequently cut down upon and stretched, or has been acupunctured for the relief of sciatica. The nerve has also been stretched in cases of locomotor ataxy, the anaesthesia of leprosy, etc. In order to define it on the surface, a point is taken at the junction of the middle and lower third of a line stretching from the posterior superior spine of the ilium to the outer part of the tuber ischii, and a line drawn from this to the middle of the upper part of the popliteal space. The line must be slightly curved with its convexity outward, and as it passes downward to the lower border of the Gluteus maximus is slightly nearer the tuber ischii than the great trochanter, as it bisects a line drawn between these two points. The operation of stretching the sciatic nerve is performed by making an incision over the course of the nerve about the centre of the thigh. The skin, superficial structures, and deep fascia having been divided, the interval between the inner and outer hamstrings is to be defined, and these muscles pulled inward and outward with retractors. The nerve will be found a little to the inner side of the Biceps. It is to be separated from the surrounding structures, hooked up with the finger, and stretched by steady and continuous traction for two or three minutes. The sciatic nerve may also be stretched by what is known as the "dry" plan. The patient is laid on his back, the foot is extended, the leg flexed on the thigh, and the thigh strongly flexed on the abdomen. While the thigh is maintained in this position the leg is forcibly extended to its full extent and the foot as fully flexed on the leg. The position of. the external popliteal, close behind the tendon of the Biceps on the outer THE SYMPATHETIC NERVE. 829 side of the ham, should be remembered in subcutaneous division of the tendon. After it is divided a cord often rises up close beside it, which might be mistaken for a small undivided portion of the tendon, and the surgeon might be tempted to reintroduce his knife and divide it. This must never be done, as the cord is the external popliteal nerve, which becomes prominent as soon as the tendon is divided. THE SYMPATHETIC NERVE The Sympathetic Nervous System consists of (1) a series of ganglia, connected together by intervening cords, extending from the base of the skull to the coccyx, one on each side of the middle line of the body, partly in front and partly on each side of the vertebral column ; (2) of three great gangliated plexuses or aggregations of nerves and ganglia, situated in front of the spine in the thoracic, abdominal, and pelvic cavities respectively; (3) of smaller ganglia, situated in relation with the abdominal viscera; and (4) of numerous nerve-fibres. These latter are of two kinds: communicating, by which the ganglia communicate with each other and with the cerebro-spinal nerves; and distributory, supplying, in general, all the internal viscera and the coats of the blood-vessels. Each gangliated cord may be traced upward from the base of the skull into its cavity by an ascending branch, which passes through the carotid canal, forms a plexus on the internal carotid artery, and communicates with the ganglia on the first and second divisions of the fifth nerve. According to some anatomists, the two cords are joined, at their cephalic extremities, by these ascending branches communicating in a small ganglion (the ganglion of Ribes\ situated upon the anterior communicating artery. The ganglia of these cords are distinguished as cervical, dorsal, lumbar, and sacral, and except in the neck they correspond pretty nearly in number to the vertebrae against which they lie. They may be thus arranged: Cervical portion . . 3 pairs of ganglia. Dorsal " . . 12 " " Lumbar " . . 4 " " Sacral " . .4 or 5 " " In the neck they are situated in front of the transverse processes of the verte- brae ; in the dorsal region, in front of the heads of the ribs ; in the lumbar region, on the sides of the bodies of the vertebrae ; and in the sacral region, in front of the sacrum. As the two cords pass into the pelvis they converge and unite together in a single ganglion {ganglion impar) placed in front of the coccyx. Each ganglion may be regarded as a distinct centre, and, in addition to its branches of distribution, possesses also branches of communication which communicate with other ganglia and with the cerebro-spinal nerves. The branches of communication between the ganglia are composed of gray and white nerve-fibres, the latter being continuous with those fibres of the spinal nerves which pass to the ganglia. The brandies of communication between the ganglia and the cerebro-spinal nerves also consist of a white and gray portion, the former proceeding from the spinal nerve to the ganglion, the latter passing from the ganglion to the spinal nerve, so that a double interchange takes place between the two systems. The three great gangliated plexuses are situated in front of the spine in the thoracic, abdominal, and pelvic regions, and are named, respectively, the cardiac, the solar or epigastric, and the hypogastric plexus. They consist of collections of nerves and ganglia, the nerves being derived from the gangliated cords and from the cerebro-spinal nerves. They distribute branches to the viscera. Smaller ganglia are also found lying amidst the nerves, some of them of microscopic size, in certain viscera-as, for instance, in the heart, the stomach, and the uterus. They serve as additional centres for the origin of nerve-fibres. The branches of distribution derived from the gangliated cords, from the prevertebral plexuses, and also from the smaller ganglia, are principally destined for the blood-vessels and thoracic and abdominal viscera, supplying the involuntary 830 THE NERVOUS SYSTEM. Carotid plexus.. Superior cervical ganglion.- Pharyngeal branches. Middle cervical ganglion. Inferior cervical ganglion. -Cardiac branches. Deen cardiac plexus. •Superficial cardiac plexus. Dorsal ganglia. / ' \ -Solar plexus. Aortic plexus. Lumbar ganglia.<. Hypogastric plexus. Sacral ganglia. Ganglion impar. Fig. 473.-The sympathetic nerve. muscular fibre of the coats of the vessels and the hollow viscera, and the secreting cells, as well as the muscular coats of the vessels in the glandular viscera. CERVICAL PORTION OF THE GANGLIATED CORD. 831 In addition to these various divisions of the sympathetic, the ganglia con- nected with the three branches of the fifth cranial nerve are believed by some to constitute a part of the sympathetic system. These ganglia have already been described (page 763 et seq.). THE GANGLIATED CORD. Cervical Portion of the Gangliated Cord. The cervical portion of the gangliated cord consists of three ganglia on each side, which are distinguished, according to their position, as the superior, middle, and inferior cervical. The Superior Cervical Ganglion, the largest of the three, is placed opposite the second and third cervical vertebrae, and sometimes as low as the fourth or fifth. It is of a reddish-gray color, and usually fusiform in shape, sometimes broad, and occasionally constricted at intervals, so as to give rise to the opinion that it consists of the coalescence of several smaller ganglia ; and it is usually believed that it is formed by the coalescence of the four ganglia, corresponding to the four upper cervical nerves. It is in relation, in front, with the sheath of the internal carotid artery and internal jugular vein; behind, it lies on the Rectus capitis anticus major muscle. Its branches may be divided into superior, inferior, external, internal, and anterior. The superior branch appears to be a direct prolongation of the ganglion. It is soft in texture and of a reddish color. It ascends by the side of the internal carotid artery, and, entering the carotid canal in the temporal bone, divides into two branches, which lie, one on the outer, and the othei- on the inner, side of that vessel. The outer branch, the larger of the two, distributes filaments to the internal carotid artery and forms the carotid plexus. The inner branch also distributes filaments to the internal carotid, and, con- tinuing onward, forms the cavernous plexus. The carotid plexus is situated on the outer side of the internal carotid. Fila- ments from this plexus occasionally form a small gangliform swelling on the under surface of the artery, which is called the carotid ganglion. The carotid plexus communicates with the Gasserian ganglion, with the sixth nerve, and the spheno- palatine ganglion, and distributes filaments to the wall of the carotid artery and to the dura mater (Valentin), while in the carotid canal it communicates with Jacobson's nerve, the tympanic branch of the glosso-pharyngeal. The communicating branches ivith the sixth nerve consist of one or two fila- ments which join that nerve as it lies upon the outer side of the internal carotid. Other filaments are also connected with the Gasserian ganglion. The communi- cation with the spheno-palatine ganglion is effected by a branch, the large deep petrosal, which is given off from the plexus on the outer side of the artery, and which passes through the cartilage filling up the foramen lacerum medium, and joins the great superficial petrosal to form the Vidian nerve. The Vidian nerve then proceeds along the pterygoid or Vidian canal to the spheno-palatine ganglion. The communication with Jacobson's nerve is effected by two branches, one of which is called the small deep petrosal nerve, and the other the long petrosal. The Carotid Plexus The cavernous plexus is situated below and internal to that part of the internal carotid which is placed by the side of the sella Turcica in the cavernous sinus, and is formed chiefly by the internal division of the ascending branch from the superior cervical ganglion. It communicates with the third, the fourth, the ophthalmic division of the fifth, and the sixth nerves, and with the ophthalmic The Cavernous Plexus. 832 THE NERVOUS SYSTEM. Accompanying branches of internal carotid artery. // //If, To tympanic branch of glosso-pharyngeal. To sixth nerve. To ophthalmic ganglion. -To fifth nerve. fourth nerve. To ganglion of root of pneumogastric. \ To petrosal ganglion of glosso pharyngeal.- -.To third nerve. Vidian nerve to -spheno-palatlne gangl. ; To ganglion of trunk of pneumogastric. To hypoglossal. Large superficial petrosal from facial nerve. From 1st cervical nerve From 2d cervical nerve. From 3d cervical nerve. Accompanying branches of carotid artery. From tth cervical nerve.-. - Uniting with branches of pneumogas- =tric and glosso-pharyngeal, to Jorm =the pharyngeal plexus. From 5th cervical nerve.', Plexus sur- 2 rounding vert- ebral artery. From 6th cervical nerve. Inferior thyroid branches surrounding artery. 7 From 7th [cervical nerve. From 8th cerv- ical nerve. Plexus surround- ing subclavian art- ery and its n branches. I II To re- current iftaryng- eal. From Isba dorsal nerve. From 2d dorsal nerve.-. Cardiac branches from pneumo- ll gastric and recurrent laryngeal // nerves. From 3d dorsal < nerve. .Ganglion of Wrisberg. •To left an- terior pul- monary From l>th dorsal-- nerve.-\ x To aorta, \ vertebrae, oesophagus, and ■ posterior . pulmonary ' plexus. Cardiac plexus. From 5th dorsal -■< nerve. =< To right anterior plexus, F'om 6th dorsal nerve. Anterior or right coronary plexus. From 7th dorsal=z nerve. - Fig. 474.-Plan of the cervical portion of the sympathetic. (After Flower.) THE SYMPATHETIC, MIDDLE CERVICAL GANGLION. 833 ganglion, and distributes filaments to the wall of the internal carotid. The branch of communication with the third nerve joins it at its point of division; the branch to the fourth nerve joins it as it lies on the outer wall of the cavernous sinus; other filaments are connected with the under surface of the trunk of the ophthalmic nerve ; and a second filament of communication joins the sixth nerve. The filament of connection with the ophthalmic ganglion arises from the anterior part of the cavernous plexus; it accompanies the nasal nerve or con- tinues forward as a separate branch. The terminal filaments from the carotid and cavernous plexuses are prolonged along the internal carotid, forming plexuses which entwine round the cerebral and ophthalmic arteries; along the former vessels they may be traced on to the pia mater; along the latter, into the orbit, where they accompany each of the sub- divisions of the vessel, a separate plexus passing, with the arteria centralis retinae, into the interior of the eyeball. The filaments prolonged on to the anterior com- municating artery form a small ganglion, the ganglion of Ribesd which serves, as mentioned above, to connect the sympathetic nerves of the right and left sides. The inferior or descending branch of the superior cervical ganglion communi- cates with the middle cervical ganglion. The external branches are numerous, and communicate with the cranial nerves and with the four upper spinal nerves. Sometimes the branch to the fourth spinal nerve may come from the cord connecting the upper and middle cervical ganglia. The branches of communication with the cranial nerves consist of delicate filaments, which pass from the superior cervical ganglion to the ganglion of the trunk of the pneumogastric and to the hypoglossal nerve. A separate filament from the cervical ganglion subdivides and joins the petrosal ganglion of the glosso-pharyngeal and the ganglion of the root of the pneumogastric in the jugular foramen. The internal branches are three in number-the pharyngeal, laryngeal, and superior cardiac nerve. The pharyngeal branches pass inward to the side of the pharynx, where they join with branches from the glosso-pharyngeal, pneumogastric, and external laryngeal nerves to form the pharyngeal plexus. The laryngeal branches unite with the superior laryngeal nerve and its branches. The superior cardiac nerve (nervus superficialis cordis} arises by two or more branches from the superior cervical ganglion, and occasionally receives a filament from the cord of communication between the first and second cervical ganglia. It runs down the neck behind the common carotid artery, lying upon the Longus colli muscle, and crosses in front of the inferior thyroid artery and recurrent laryngeal nerve. The right superior cardiac nerve, at the root of the neck, passes either in front of or behind the subclavian artery, and along the arteria innominata, to the back part of the arch of the aorta, w here it joins the deep cardiac plexus. This nerve, in its course, is connected with other branches of the sympathetic : about the middle of the neck it receives filaments from the external laryngeal nerve; lower down, one or two tw'igs from the pneumogastric ; and as it enters the thorax it is joined by a filament from the recurrent laryngeal. Filaments from this nerve communicate with the thyroid branches from the middle cervical ganglion. The left superior cardiac nerve, in the chest, runs by the side of the left com- mon carotid artery and in front of the arch of the aorta to the superficial cardiac plexus, but occasionally it passes behind the aorta and terminates in the deep cardiac plexus. The anterior branches ramify upon the external carotid artery and its branches, forming round each a delicate plexus, on the nerves composing which small ganglia are occasionally found. These ganglia have been named, according to their posi- tion, intercarotid2 (placed at the angle of bifurcation of the common carotid), lingual, temporal, and pharyngeal. The plexuses accompanying some of these 1 The existence of this ganglion is doubted by some observers. 2 This ganglion is of the same structure as the coccygeal gland (Luschka). 834 THE NERVOUS SYSTEM. arteries have important communications with other nerves. That surrounding the external carotid is connected with the branch of the facial nerve to the stylo-hyoid muscle ; that surrounding the facial communicates with the submaxillary ganglion by one or two filaments; and that accompanying the middle meningeal artery sends offsets which pass to the otic ganglion and to the intumescentia ganglioformis of the facial nerve (external petrosal). The Middle Cervical Ganglion (thyroid ganglion) is the smallest of the three cervical ganglia, and is occasionally altogether wanting. It is placed opposite the sixth cervical vertebra, usually upon', or close to, the inferior thyroid artery; hence the name, "thyroid ganglion," assigned to it by Haller. It is probably formed by the coalescence of two ganglia corresponding to the fifth and sixth cer- vical nerves. Its superior branches ascend to communicate with the superior cervical gan- glion. Its inferior branches descend to communicate with the inferior cervical ganglion. Its external branches pass outward to join the fifth and sixth spinal nerves. These branches are not constantly found. Its internal branches are the thyroid and the middle cardiac nerve. The thyroid branches are small filaments which accompany the inferior thyroid artery to the thyroid gland; they communicate, on the artery, with the superior cardiac nerve, and, in the gland, with branches from the recurrent and external laryngeal nerves. The middle cardiac nerve (nervus cardiacus magnus), the largest of the three cardiac nerves, arises from the middle cervical ganglion or from the cord between the middle and inferior ganglia. On the right side it descends behind the common carotid artery, and at the root of the neck passes either in front of or behind the subclavian artery; it then descends on the trachea, receives a few filaments from the recurrent laryngeal nerve, and joins the deep cardiac plexus. In the neck it communicates with the superior cardiac and recurrent laryngeal nerves. On the left side the middle cardiac nerve enters the chest between the left carotid and sub- clavian arteries, and joins the left side of the deep cardiac plexus. The Inferior Cervical Ganglion is situated between the base of the transverse process of the last cervical vertebra and the neck of the first rib on the inner side of the superior intercostal artery. Its form is irregular; it is larger in size than the preceding, and frequently joined with the first thoracic ganglion. It is proba- bly formed by the coalescence of two ganglia which correspond to the two last cervical nerves. Its superior branches communicate with the middle cervical ganglion. Its inferior branches descend, some in front of, others behind, the subclavian artery, to join the first thoracic ganglion. Its internal branch is the inferior cardiac nerve. The inferior cardiac nerve (nervus cardiacus minor) arises from the inferior cervical or first thoracic ganglion. It passes down behind the subclavian artery and along the front of the trachea to join the deep cardiac plexus. It communi- cates freely behind the subclavian artery with the recurrent laryngeal and middle cardiac nerves. The external branches consist of several filaments, some of which communi- cate with the seventh and eighth spinal nerves; others accompany the vertebral artery along the vertebral canal, forming a plexus round the vessel, supplying it with filaments, and communicating with the cervical spinal nerves as high as the fourth. Thoracic Portion of the Gangliated Cord. The thoracic portion of the gangliated cord consists of a series of ganglia which usually correspond in number to that of the vertebrae, but, from the occa- sional coalescence of two, their number is uncertain. These ganglia are placed on each side of the spine, resting against the heads of the ribs and covered by the THE LUMBAR PORTION OF THE GANGLIATED CORD. 835 pleura costalis; the last two are, however, anterior to the rest, being placed on the side of the bodies of the eleventh and twelfth dorsal vertebrae. The ganglia are small in size and of a grayish color. The first, larger than the rest, is of an elongated form and frequently blended with the last cervical. They are connected together by cord-like prolongations from their substance. The external branches from each ganglion, usually two in number, communi- cate with each of the dorsal spinal nerves. The internal branches from the six upper ganglia are very small; they supply filaments to the thoracic aorta and its branches, besides small branches to the bodies of the vertebrae and their ligaments. Branches from the third and fourth, and sometimes also from the first and second ganglia, form part of the posterior pulmonary plexus. The internal branches from the six lower ganglia are large and white in color; they distribute filaments to the aorta and unite to form the three splanchnic nerves. These are named the great, the lesser, and the smallest or renal splanchnic. The great splanchnic nerve is of a white color, firm in texture, and bears a marked contrast to the ganglionic nerves. It is formed by branches from the thoracic ganglia between the sixth and tenth, receiving filaments (according to Dr. Beck) from all the thoracic ganglia above the sixth. These roots unite to form a large round cord of considerable size. It descends obliquely inward in front of the bodies of the vertebrae along the posterior mediastinum, perforates the crus of the Diaphragm, and terminates in the semilunar ganglion, distributing filaments to the renal and suprarenal plexus. The lesser splanchnic nerve is formed by filaments from the tenth and eleventh ganglia and from the cord between them. It pierces the Diaphragm with the preceding nerve and joins the coeliac plexus. It communicates in the chest with the great splanchnic nerve, and occasionally sends filaments to the renal plexus. The smallest, or renal, splanchnic nerve arises from the last ganglion, and, piercing the Diaphragm, terminates in the renal plexus and lower part of the coeliac plexus. It occasionally communicates with the preceding nerve. A striking analogy appears to exist between the splanchnic and the cardiac nerves. The cardiac nerves are three in number; they arise from the three cervical ganglia, and are distributed to a large and important organ in the thoracic cavity. The splanchnic nerves, also three in number, are connected probably with all the dorsal ganglia, and are distributed to important organs in the abdominal cavity. The Lumbar Portion of the Gangliated Cord. The lumbar portion of the gangliated cord is situated in front of the vertebral column along the inner margin of the Psoas muscle. It consists usually of four ganglia, connected together by interganglionic cords. The ganglia are of small size, of a grayish color, shaped like a barleycorn, and placed much nearer the median line than the thoracic ganglia. The superior and inferior branches of the lumbar ganglia serve as communi- cating branches between the chain of ganglia in this region. They are usually single and of a white color. The external branches communicate with the lumbar spinal nerves. From the situation of the lumbar ganglia these branches are longer than in the other regions. They are usually two in number.from each ganglion, but their connection with the spinal nerves is not so uniform as in other regions. They accompany the lumbar arteries around the sides of the bodies of the vertebrae, passing beneath the fibrous arches from which some of the fibres of the Psoas muscle arise. Of the internal branches, some pass inward, in front of the aorta, and help to form the aortic plexus. Othei- branches descend in front of the common iliac arteries, and join over the promontory of the sacrum, helping to form the hypo- gastric plexus. Numerous delicate filaments are also distributed to the bodies of the vertebrae and the ligaments connecting them. o o 836 THE NERVOUS SYSTEM. Pelvic Portion of the Gangliated Cord. The pelvic portion of the gangliated cord is situated in front of the sacrum along the inner side of the anterior sacral foramina. It consists of four or five small ganglia on each side, connected together by interganglionic cords. Below, these cords converge and unite on the front of the coccyx by means of a small ganglion (the coccygeal ganglion or ganglion impar}. The superior and inferior branches are the cords of communication between the ganglia above and below. The external branches, exceedingly short, communicate with the sacral nerves. They are two in number from each ganglion. The coccygeal nerve communicates either with the last sacral or coccygeal ganglion. The internal branches communicate, on the front of the sacrum, with the corresponding branches from the opposite side; some, from the first two ganglia, pass to join the pelvic plexus, and others form a plexus which accompanies the middle sacral artery and sends filaments to the coccygeal gland. THE GREAT PLEXUSES OF THE SYMPATHETIC. The great plexuses of the sympathetic are the large aggregations of nerves and ganglia, above alluded to, situated in the thoracic, abdominal, and pelvic cavities respectively. From them are derived the branches which supply the viscera. The Cardiac Plexus. The cardiac plexus is situated at the base of the heart, and is divided into a superficial part, which lies in the concavity of the arch of the aorta, and a deep part, which lies between the trachea and aorta. The great or deep cardiac plexus (plexus magnus profundus, Scarpa) is situated in front of the trachea at its bifurcation, above the point of division of the pulmonary artery and behind the arch of the aorta. It is formed by the cardiac nerves derived from the cervical ganglia of the sympathetic and the cardiac branches of the recurrent laryngeal and pneumogastric. The only cardiac nerves which do not enter into the formation of this plexus are the left superior cardiac nerve and the left inferior cervical cardiac branch from the pneumogastric. The branches from the rigid side of this plexus pass, some in front of, and others behind, the right pulmonary artery; the former, the more numerous, transmit a few filaments to the anterior pulmonary plexus, and are then continued onward to form part of the anterior coronary plexus ; those behind the pulmonary artery distribute a few filaments to the right auricle, and are then continued onward to form part of the posterior coronary plexus. The branches from the left side of the deep cardiac plexus distribute a few filaments to the superficial cardiac plexus, to the left auricle of the heart, and to the anterior pulmonary plexus, and then pass on to form the greater part of the posterior coronary plexus. The superficial (anterior) cardiac plexus lies beneath the arch of the aorta, in front of the right pulmonary artery. It is formed by the left superior cardiac nerve, the left (and occasionally the right) inferior cervical cardiac branches of the pneumogastric, and filaments from the deep cardiac plexus. A small ganglion (cardiac ganglion of Wrisberg} is occasionally found connected with these nerves at their point of junction. This ganglion, when present, is situated immediately beneath the arch of the aorta, on the right side of the ductus arteriosus. The superficial cardiac plexus forms the chief part of the anterior coronary plexus, and several filaments pass along the pulmonary artery to the left anterior pulmonary plexus. The posterior coronary plexus is chiefly formed by filaments prolonged from the left side of the deep cardiac plexus, and by a few from the right side. It surrounds the branches of the coronary artery at the back of the heart, and its THE EPIGASTRIC OR SOLAR PLEXUS. 837 filaments are distributed with those vessels to the muscular substance of the ventricles. The anterior coronary plexus is formed chiefly from the superficial cardiac plexus, but receives filaments from the deep cardiac plexus. Passing forward between the aorta and pulmonary artery, it accompanies the left coronary artery on the anterior surface of the heart. Valentin has described nervous filaments ramifying under the endocardium; and Remak has found, in several mammalia, numerous small ganglia on the cardiac nerves, both on the surface of the heart and in its muscular substance. The Epigastric or Solar Plexus (Figs. 473, 475). The Epigastric or Solar plexus supplies all the viscera in the abdominal cavity. It consists of a great network of nerves and ganglia, situated behind the stomach and in front of the aorta and crura of the Diaphragm. It surrounds the coeliac axis and root of the superior mesenteric artery, extending downward as Ioav as the pancreas and outward to the suprarenal capsules. This plexus, and the ganglia connected with it, receive the great splanchnic nerve of both sides, and some filaments from the right pneumogastric. It distributes filaments which accompany, under the name of plexuses, all the branches from the front of the abdominal aorta. The semilunar ganglia of the solar plexus, two in number, one on each side, are the largest ganglia in the body. They are large irregular gangliform masses formed by the aggregation of smaller ganglia, having interspaces between them. They are situated in front of the crura of the Diaphragm, close to the suprarenal capsules: the one on the right side lies beneath the inferior vena cava; the upper part of each ganglion is joined by the greater splanchnic nerve, and to the inner side of each the branches of the solar plexus are connected. From the epigastric or solar plexus are derived the following : Phrenic or Diaphragmatic plexus. Suprarenal plexus. Renal plexus. Spermatic plexus. Coeliac plexus Gastric plexus. Splenic plexus. Hepatic plexus. Aortic plexus. The phrenic plexus accompanies the phrenic artery to the Diaphragm, which it supplies, some filaments passing to the suprarenal capsule. It arises from the upper part of the semilunar ganglion, and is larger on the right than on the left side. It receives one or two branches from the phrenic nerve. In connection with this plexus, on the right side, at its point of junction with the phrenic nerve, is a small ganglion (ganglion diaphragmaticuni). This ganglion is placed on the under surface of the Diaphragm, near the suprarenal capsule. Its branches are distributed to the inferior vena cava, suprarenal capsule, and hepatic plexus. There is no ganglion on the left side. The suprarenal plexus is formed by branches from the solar plexus, from the semilunar ganglion, and from the phrenic and great splanchnic nerves, a ganglion being formed at the point of junction of the latter nerve. It supplies the supra- renal capsule. The branches of this plexus are remarkable for their large size in comparison with the size of the organ they supply. The renal plexus is formed by filaments from the solar plexus, the outer part of the semilunar ganglion, and the aortic plexus. It is also joined by filaments from the lesser and smallest splanchnic nerves. The nerves from these sources, fifteen or twenty in number, have numerous ganglia developed upon them. They accompany the branches of the renal artery into the kidney, some filaments on the right side being distributed to the inferior vena cava, and others to the sper- matic plexus on both sides. The spermatic plexus is derived from the renal plexus, receiving branches from the aortic plexus. It accompanies the spermatic vessels to the testes. Superior mesenteric plexus. 838 THE NERVOUS SYSTEM. Hepatic artery. \ Diaphragmatic ganglion Suprarenal capsule Left semilunar ganglion. Superior mesenteric artery. Great splanchnic nerve. splanchnic nerve. Great splanchnic' nerve. Right semilunar ganglion. Renal ganglion. Small splanchnic nerve. Renal ganglion. 'Renal artery. Renal artery, " mesenteric ganglion. Gangliated cord.- Communicating branch.- ■.Branch to aortic plexus. Gangliated cord of sympathetic. Branch to aortic plexus. - Inferior mesenteric artery. .Inferior mesenteric ganglion. Sacro-vertebral angle. Common iliac vein. Common iliac artery. Fig. 475.-Lumbar portion of the gangliated cord, with the solar and hypogastric plexuses. (After Henle.) In the female the ovarian plexus is distributed to the ovaries and fundus of the uterus. The coeliac plexus, of large size, is a direct continuation from the solar plexus: it surrounds the coeliac axis and subdivides into the gastric, hepatic, and splenic THE HYPOGASTRIC PLEXUS. 839 plexuses. It receives branches from the lesser splanchnic nerves, and, on the left side, a filament from the right pneumogastric. The gastric or coronary plexus accompanies the gastric artery along the lesser curvature of the stomach, and joins with branches from the left pneumogastric nerve. It is distributed to the stomach. The hepatic plexus, the largest offset from the coeliac plexus, receives filaments from the left pneumogastric and right phrenic nerves. It accompanies the hepatic artery, ramifying in the substance of the liver upon its branches and upon those of the vena portae. Branches from this plexus accompany all the divisions of the hepatic artery. Thus there is a pyloric plexus accompanying the pyloric branch of the hepatic, which joins wdth the gastric plexus and pneumogastric nerves. There is also a gastro-duodenal plexus, which subdivides into the pancreatico-duodenal plexus, which accompanies the pancreatico-duodenal artery, to supply the pancreas and duodenum, joining with branches from the mesenteric plexus; and a gastro-epi- ploic plexus, which accompanies the right gastro-epiploic artery along the greater curvature of the stomach and anastomoses with branches from the splenic plexus. A cystic plexus, which supplies the gall-bladder, also arises from the hepatic plexus near the liver. The splenic plexus is formed by branches from the coeliac plexus, the left semi- lunar ganglia, and from the right pneumogastric nerve. It accompanies the splenic artery and its branches to the substance of the spleen, giving off, in its course, filaments to the pancreas (pancreatic plexus') and the left gastro-epiploic plexus, which accompanies the gastro-epiploica sinistra artery along the convex border of the stomach. The superior mesenteric plexus is a continuation of the lower part of the great solar plexus, receiving a branch from the junction of the right pneumogastric nerve with the coeliac plexus. It surrounds the superior mesenteric artery, which it accompanies into the mesentery, and divides into a number of secondary plexuses, which are distributed to all the parts supplied by the artery-viz. pancreatic branches to the pancreas ; intestinal branches, which supply the whole of the small intestine; and ileo-colic, right colic, and middle colic branches, which supply the correspond- ing parts of the great intestine. The nerves composing this plexus are white in color and firm in texture, and have numerous ganglia developed upon them near their origin. The aortic plexus is formed by branches derived, on each side, from the solar plexus and the semilunar ganglia, receiving filaments from some of the lumbar ganglia. It is situated upon the sides and front of the aorta, between the origins of the superior and inferior mesenteric arteries. From this plexus arise part of the spermatic, the inferior mesenteric, and the hypogastric plexuses; and it dis- tributes filaments to the inferior vena cava. The inferior mesenteric plexus is derived chiefly from the left side of the aortic plexus. It surrounds the inferior mesenteric artery, and divides into a number of secondary plexuses, which are distributed to all the parts supplied by the artery- viz. the left colic and sigmoid plexuses, which supply the descending and sigmoid flexure of the colon ; and the superior haemorrhoidal plexus, which supplies the upper part of the rectum and joins in the pelvis with branches from the pelvic plexus. The Hypogastric Plexus. The Hypogastric Plexus supplies the viscera of the pelvic cavity. It is situated in front of the promontory of the sacrum, between the two common iliac arteries, and is formed by the union of numerous filaments, which descend on each side from the aortic plexus and from the lumbar ganglia. This plexus contains no ganglia, and bifurcates, below, into two lateral portions, which form the pelvic plexuses. 840 THE NERVOUS SYSTEM. The Pelvic Plexus (sometimes called inferior hypogastric) supplies the viscera of the pelvic cavity, is situated at the side of the rectum and bladder in the male, and at the side of the rectum, vagina, and bladder in the female. It is formed by a continuation of the hypogastric plexus, by branches from the second, third, and fourth sacral nerves, and by a few filaments from the first two sacral ganglia. At the point of junction of these nerves small ganglia are found. From this plexus numerous branches are distributed to all the viscera of the pelvis. They accom- pany the branches of the internal iliac artery. The inferior hsemorrhoidal plexus arises from the back part of the pelvic plexus. It supplies the rectum, joining with branches of the superior hremor- rhoidal plexus. The vesical plexus arises from the fore part of the pelvic plexus. The nerves composing it are numerous, and contain a large- proportion of spinal nerve-fibres. They accompany the vesical arteries, and are distributed at the side and base of the bladder. Numerous filaments also pass to the vesiculae seminales and vas deferens; those accompanying the vas deferens join, on the spermatic cord, with branches from the spermatic plexus. The prostatic plexus is continued from the lower part of the pelvic plexus. The nerves composing it are of large size. They are distributed to the pros- tate gland, vesiculae seminales, and erectile structure of the penis. The nerves supplying the erectile structure of the penis consist of two sets, the small and large cavernous nerves. They are slender filaments, which arise from the fore part of the prostatic plexus, and, after joining with branches from the internal pudic nerve, pass forward beneath the pubic arch. The small cavernous nerves perforate the fibrous covering of the penis near its roots. The large cavernous nerve passes forward along the dorsum of the penis, joins with the dorsal branch of the pudic nerve, and is distributed to the corpus cavernosum and spongiosum. The vaginal plexus arises from the lower part of the pelvic plexus. It is lost on the walls of the vagina, being distributed to the erectile tissue at its anterior part and to the mucous membrane. The nerves composing this plexus contain, like the vesical, a large proportion of spinal nerve-fibres. The uterine plexus arises from the upper part of the pelvic plexus above the point where the branches from the sacral nerves join the plexus. Its branches accompany the uterine arteries to the side of the organ between the layers of the broad ligament, and are distributed to the cervix and lower part of the body of the uterus, penetrating its substance. Other filaments pass separately to the body of the uterus and Fallopian tube. Branches from the plexus accompany the uterine arteries into the substance of the uterus. Upon these filaments ganglionic enlargements are found. The Pelvic Plexus. THE ORGANS OF SENSE. milE Organs of the Senses are five in number-viz. those of Touch, of Taste, of I Smell, of Hearing, and of Sight. The skin, which is the principal seat of the sense of touch, has been described in the chapter on General Anatomy. THE TONGUE. The Tongue is the organ of the special sense of taste. It is situated in the floor of the mouth, in the interval between the two lateral portions of the body of the lower jaw. Its base or root is directed backward, and connected with the os hyoides by the Hyo-glossi and Genio-hyo-glossi muscles and the hyo-glossal membrane; with Fig. 476.-Upper surface of the tongue. the epiglottis by three folds of mucous membrane which form the glosso-epiglottic ligaments; with the soft palate by means of the anterior pillars of the fauces; and with the pharynx by the Superior constrictor and the mucous membrane. Its apex or tip, thin and narrow, is directed forward against the inner surface of the lower incisor teeth. The under surface of the tongue is connected with the lower jaw by the Genio-hyo-glossi muscles; from its sides the mucous membrane is reflected to the inner surface of the gums; and in front a distinct fold of that membrane, the frcenum is formed beneath its under surface. 841 842 THE ORGANS OF SENSE. The tip of the tongue, part of the under surface, its sides and dorsum, are free. The dorsum of the tongue is convex, marked along the middle line by a raphe, ■which divides it into symmetrical halves; this raphe terminates behind, about an inch from the base of the organ, in a depression, the foramen ccecum. The anterior two-thirds of this surface are rough and covered with papillae ; the posterior third is smoother, and covered by the projecting orifices of numerous muciparous glands. Structure of the Tongue.-The tongue is partly invested by mucous membrane and a submucous fibrous layer. It consists of symmetrical halves, separated from each other, in the middle line, by a fibrous septum. Each half is composed of muscular fibres arranged in various directions, containing much interposed fat, and supplied by vessels and nerves. The mucous membrane invests the entire extent of the free surface of the tongue. On the dorsum it is thicker behind than in front, and is continuous with the sheath of the muscles attached to it, through the submucous fibrous layer. On the under surface of the organ it can be traced on each side of the fraenum through the ducts of the submaxillary and the sublingual glands. As it passes over the borders of the organ it gradually assumes its papillary character. The structure of the mucous membrane of the tongue differs in different parts. That covering the under surface of the organ is thin, smooth, and identical in structure with that lining the rest of the oral cavity. The mucous membrane on the anterior part of the dorsum of the tongue is thin and intimately adherent to the muscular tissue, whilst that at the root is much thicker and looser. It consists Filiform Fungiform. Secondary f'f papillae. Circumvallate. Fig. 477.-The three kinds of papillae, magnified. of a layer of connective tissue, the corium or mucosa, supporting numerous papilla? and covered, as well as the papillae, with epithelium. The epithelium is of the scaly variety, like that of the epidermis. It covers the free surface of the tongue, as may be easily demonstrated by maceration or boiling, when it can be easily detached entire : it is much thinner than on the skin : the intervals between the large papillae are not filled up by it, but each papilla has a separate investment from root to summit. The deepest cells may sometimes be detached as a separate layer, corresponding to the rete mucosum, but they never contain coloring matter. The corium consists of a dense feltwork of fibrous connective tissue, with numerous elastic fibres, firmly connected with the fibrous tissue forming the septa between the muscular bundles of the tongue. It contains the ramifications of the numerous vessels and nerves from which the papillae are supplied, large plexuses of lymphatic vessels, and the glands of the tongue. The Papillce of the Tongue.-These are papillary projections of the corium. They are thickly distributed over the anterior two-thirds of its upper surface, giving THE TONGUE. 843 to it its characteristic roughness. The varieties of papillae met with are-the papillae maximae (circumvallatce), papillae mediae {fungiformes}, papillae minimae (conicce or filiformes}, and papillae simplices. The papillce maxima3 (circumvallatae) are of large size, and vary from eight to twelve in number. They are situated at the back part of the dorsum of the tongue, near its base, forming a row on each side, which, running backward and inward, meet in the middle line, like the two lines of the letter V inverted. Each papilla consists of a projection of mucous membrane from of an inch wide, attached to the bottom of a cup-shaped depression of the mucous membrane; the papilla is in shape like a truncated cone, the smaller end being directed down- ward and attached to the tongue, the broader part or base projecting on the sur- face and being studded with numerous small secondary papillae, which, however, are covered by a smooth layer of the epithelium. The cup-shaped depression forms a kind of fossa round the papilla, having a circular margin of about the same elevation covered with smaller papillae. At the point of junction of the two rows of papillae is the deep depression, the foramen ccecum, mentioned above. The papillce medice (fungiformes), more numerous than the preceding, are scattered irregularly and sparingly over the dorsum of the tongue, but are found chiefly at its sides and apex. They are easily recognized among the other papillae, by their large size, rounded eminences, and deep-red color. They are narrow' at their attachment to the tongue, but broad and rounded at their free extremities, and covered with secondary papillae. Their epithelial investment is very thin. The papillce minimce (conicae or filiformes) cover the anterior two-thirds of the dorsum of the tongue. They are very mi- nute, more or less conical or filiform in shape, and arranged in lines corresponding in di- rection with the two rows of the papillae cir- cumvallatae, excepting at the apex of the organ, where their direction is transverse. They have projecting from their apices nu- merous filiform processes or secondary pa- pillae, which are of a whitish tint, owing to the thickness and density of the epithelium of which they are composed, and which has here undergone a peculiar modification, the cells having become cornified and elongated into dense, imbricated, brush-like processes. They contain also a number of elastic fibres, which render them firmer and more elastic than the papillae of mucous membrane gen- erally. Simple papilla3, similar to those of the skin, cover the whole of the mucous'mem- brane of the tongue, as well as the larger papillae. They consist of closely-set, microscopic elevations of the corium, con- taining a capillary loop, covered by a layer of epithelium. Structure of the Papillce.-The papillae apparently resemble in structure those of the cutis, consisting of a cone-shaped projection of connective tissue, covered with a thick layer of squamous epithelium, and contain one or more capillary loops, amongst which nerves are distributed in great abundance. If the epithe- lium is removed, it will be found that they are not simple elevations like the papillae of the skin, for the surface of each is studded with minute conical pro- cesses of the mucous membrane, which form secondary papillae (Todd and Bow- man). In the papillae circumvallatae the nerves are numerous and of large size; in the papillae fungiformes they are also numerous, and terminate in a plexiform network, from which brush-like branches proceed ; in the papillae filiformes their Fig. 478.-Circumvallate papillae of tongue of rabbit, showing position of taste-goblets. (Stohr.) a. Duct of gland, d. Serous gland. <7. Taste-goblets. I. Primary septa, and I, second- ary septa, of papillae, n. Medullated nerve. M. Muscular fibres. 844 THE ORGANS OF SENSE. mode of termination is uncertain. Buried m the epidermis of the papillae circum- vallatae, and in some of the fungiformes, certain peculiar bodies called taste-gob- lets have been described.1 They are flask-like in shape, their broad base resting on the corium, and their neck opening by an orifice between the cells of the epi- thelium. They are formed by two kinds of cells: the external (cortical) are arranged in several layers; they are long and flattened, with tapering ends, and in contact by their edges, the tapering extremities extending from the base to the apex of the organ. They thus enclose the central cells (gustatory cells), which are spindle-shaped and have a large spherical nucleus about the middle of the cell. Both extremities are filamentous ; the inner process is described as continuous with the terminal fibril of a nerve, while the outer one projects as an extremely fine hair through the orifice of the taste- goblet.2 Glands of the Tongue.-The tongue is provided with mucous and serous glands and lymphoid follicles. The mucous glands are similar in structure to the labial and buccal glands. They are found all over the surface of the raucous membrane of the tongue, especially at the back part, behind the cir- cumvallate papillae, but also at the apex and mar- ginal parts. In connection with these glands a special one has been described by Blandin and Nuhn. It is situated near the apex of the tongue on either side of the fraenum, and is covered over by a fasciculus of muscular fibre derived from the Stylo-glossus and Inferior lingualis. It is from half an inch to nearly an inch long and about the third of an inch broad. It has from four to six ducts, which open on the under surface of the apex. The serous glands occur only at the back of the tongue in the neighborhood Fig. 479.-Taste-gohlets. a. Cen- tral cell. b. Cortical cell. 'Bristles in Gland Ducts. ~Gland of Blandin and Nuhn. T ~Ranine Artery.' Lingual Nerve. Fig. 480.-Under surface of tongue, showing position and relations of gland of Blandin and Nuhn. (From a preparation in the Museum of the Royal College of Surgeons.) of the taste-goblets, their ducts opening for the most part into the fossae of the circumvallate papillae. These glands are racemose, the duct branching into sev- eral minute ducts, which terminate in alveoli lined by a single layer of more or less columnar epithelium. Their secretion is of a watery nature, and probably 1 These bodies are also found in considerable numbers at the side of the base of the tongue, just in front of the anterior pillars of the fauces. 2 See Englemann, in Stricker's Handbook (New Syd. Soc. Trans.), vol. iii. p. 2. THE TONGUE. 845 assists in the distribution of the substance to be tasted over the taste-area (Ebner). The Lymphoid Follicles.-The lymphoid tissue is situated, for the most part at the back of the tongue, between the epiglottis and the circumvallate papillae, and is collected at numerous points into distinct masses known as lymphoid follicles. Here and there in this situation are depressions in the mucous membrane, surrounded bv nodules of lymphoid tissue, similar to the structure found in the tonsil: into them open some of the ducts of the mucous glands. The fibrous septum consists of a vertical layer of fibrous tissue, extending throughout the entire length of the middle line of the tongue, from the base to the Submaxillary artery. Submaxillary ganglion. Hypoglossal nerve. Glosso- pharyngeal nerve. Lingual artery. • Lingual artery. Superior laryngeal nerve. Fig. 481.-Under surface of the tongue, showing the distribution of nerves to this organ. (From a prepara- tion in the Museum of the Royal College of Surgeons.) apex, though not quite reaching the dorsum. It is thicker behind than in front, and occasionally contains a small fibro-cartilage about a quarter of an inch in length. It is well displayed by making a vertical section across the organ. The Hyo-glossal membrane is a strong fibrous lamina which connects the under surface of the base of the tongue to the body of the hyoid bone. This membrane receives, in front, some of the fibres of the Genio-hyo-glossi. Vessels of the Tongue.-The arteries of the tongue are derived from the lingual, the facial, and ascending pharyngeal. The veins of the tongue accompany the arteries. Muscles of the Tongue.-The muscular fibres of the tongue run in various directions. These fibres are divided into two sets, Extrinsic and Intrinsic. The Extrinsic muscles of the tongue are those which have their origin external 846 THE ORGANS OF SENSE. to it, and only their terminal fibres contained in the substance of the organ. They are the Stylo-glossus, the Hyo-glossus, the Palato-glossus, the Genio-hyo-glossus, and part of the Superior constrictor of the pharynx (Pharyngo-glossus). The muscles are those which are contained entirely within the tongue and form the greater part of its substance. Both sets have been already described (page 417). The lymphatic vessels from the tongue pass to one or two small glands situated on the Hyo-glossus muscle in the submaxillary region, and from thence to the deep glands of the neck. The nerves of the tongue are four in number in each half: the lingual branch of the fifth, which is distributed to the papillae at the fore part and sides of the tongue ; the lingual branch of the glosso-pharyngeal, which is distributed to the mucous membrane at the base and side of the tongue and to the papillae circum- vaHatae; the hypoglossal nerve, which is distributed to the muscular substance of the tongue; and the chorda tympani to the Lingualis muscle. Sympathetic filaments also pass to the tongue from the nervi molies on the lingual and other arteries supplying it. The glosso-pharyngeal branch is the special nerve of the sense of taste, the lingual (gustatory) is the nerve of common sensation, and the hypoglossal is the motor nerve of the tongue, except for the Inferior lingualis, which is supplied by the chorda tympani. Surgical Anatomy.-The diseases to which the tongue is liable are numerous, and its surgical anatomy of importance, since any or all the structures of which it is composed-muscles, connective tissue, mucous membrane, glands, vessels, nerves, and lymphatics-may be the seat of morbid changes. It is not often the seat of congenital defects, though a few cases of vertical cleft have been recorded, and it is occasionally, though much more rarely than is commonly sup- posed, the seat of "tongue-tie," from shortness of the fraenum. (See page 556.) There is, however, one condition which must be regarded as congenital, though it does not sometimes evidence itself until a year or two after birth, which is not uncommon. This is an enlargement of the tongue which is due primarily to a dilatation of the lymph-channels and a greatly increased development of the lymphatic tissue throughout the tongue. This is often aggravated by inflammatory changes induced by injury or exposure, and the tongue may assume enormous dimensions and hang out of the mouth, giving the child an imbecile expression. The treatment consists in excising a V-shaped portion and bringing the cut surfaces together with deeply-placed silver sutures. Compression has been resorted to in some cases and with success, but it is difficult to apply. Acute inflammation of the tongue, which may be caused by injury and the introduction of some septic or irritating matter, is attended by great swelling from infiltration of its connective tissue, which is in considerable quantity. This renders the patient incapable of swallowing or speaking, and may seriously impede respiration. It may run on to suppuration and the formation of an acute abscess. Chronic abscess, which has been mistaken for cancer, may also occur in the substance of the tongue. The mucous membrane of the tongue may become chronically inflamed, and presents different appearances in different stages of the disease, to which the terms leucoplakia, psoriasis, and ichthyosis have been given. The tongue, being very vascular, is often the seat of naevoid growths,and these have a tend- ency to grow rapidly. The tongue is frequently the seat of ulceration, which may arise from many causes, as from the irritation of jagged teeth, dyspepsia, tubercle, syphilis, and cancer. Of these the cancerous ulcer is the most important, and probably also the most common. The variety is the squamous epithelioma, which soon develops into an ulcer with an indurated base. It produces great pain, which speedily extends to all parts supplied with sensation by the fifth nerve, especially to the region of the ear. The pain in these cases is conducted to the ear and temporal region by the lingual nerve, and from it to the other branches of the inferior maxillary nerve, especially the auriculo-temporal. Possibly pain in the ear itself may be due to implication of the fibres of the glosso-pharyngeal nerve, which by its tympanic branch is conducted to the tympanic plexus. Cancer of the tongue may necessitate removal of a part or the whole of the organ, and many different methods have been adopted for its excision. It may be removed from the mouth by the ecraseur or the scissors. Probably the better method is by the scissors, usually known as Whitehead's method. The mouth is widely opened with a gag, the tongue transfixed with a stout silk ligature, by which to hold and make traction on it and the reflection of mucous mem- brane from the tongue to the jaw, and the insertion of the Genio-hyo-glossus first divided with a pair of curved blunt scissors. The Palato-glossus is also divided. The tongue can now be pulled well out of the mouth. The base of the tongue is cut through by a series of short snips, each bleeding vessel being dealt with as soon as divided, until the situation of the ranine artery is reached. The remaining undivided portion of tissue is to be seized with a pair of Wells's forceps, the tongue removed, and the vessel secured. In the event of the ranine artery being THE NOSE. 847 accidentally injured haemorrhage can be at once controlled by passing two fingers over the dorsum of the tongue as far as the epiglottis and dragging the root of the tongue forcibly forward. In cases where the disease is confined to one side of the tongue this" operation may be modified by splitting the tongue down the centre and removing only the affected half. In eases where the submaxillary glands are involved Kocher's operation should be performed. He removes the tongue from the neck, having performed a preliminary tracheotomy, by an incis- ion from near the lobule of the ear, down the anterior border of the Sterno-mastoid to the level of the great cornu of the hyoid bone, then forward to the body of the hyoid bone, and upward to near the symphysis of the jaw. The lingual artery is now secured, and by a careful dissec- tion the submaxillary lymphatic glands and the tongue removed. Regnoli advocated the removal of the tongue by a semilunar incision in the submaxillary triangle along the line of the lower jaw, and a vertical incision from the centre of the semilunar one backward to the hyoid bone. Care must be taken not to carry the first incision too far backward, so as to wound the facial arteries. The tongue is thus reached through the floor of the mouth, pulled out through the external incision, and removed with the ecraseur or knife. The great objection to this operation is that all the muscles which raise the hyoid bone and larynx are divided, and that therefore the movements of deglutition and respiration are interfered with. Finally, where both sides of the floor of the mouth are involved in the disease, or where very free access is required on account of the extension backward of the disease to the pillars of the fauces and the tonsil, or where the lower jaw is involved, the operation recommended by Syme must be performed. This is done by an incision through the central line of the lip, across the chin, and down as far as the hyoid bone. The lower jaw is sawn through at the symphysis, and the two halves of the bone forcibly separated from each other. The mucous membrane is separated from the bone, and the Genio-hyo-glossi detached from the bone, and the Hyo-glossi divided. The tongue is then drawn forward and removed close to its attachment to the hyoid bone. Any glands which are enlarged can be removed, and if the bone is implicated in the disease, it can also be removed by freeing it from the soft parts externally and internally, and making a second section with the saw beyond the diseased part. Formerly many surgeons before removing the tongue performed a preliminary tracheotomy: (1) to prevent blood entering the air-passages ; and (2) to allow the patient to breathe through the tube and not inspire air which had passed over a sloughy wound, and which was loaded with septic organisms and likely to induce septic pneumonia. By the judicious use of iodoform this secondary evil may be obviated, and the preliminary tracheotomy is now usually dispensed with. THE NOSE. The nose is the special organ of the sense of smell : by means of the peculiar properties of its nerves it protects the lungs from the inhalation of deleterious gases and assists the organ of taste in discriminating the properties of food. Seen from below Side view. Lower lateral cartilage. ■Sesamoid cartilages. Figs. 482, 483.-Cartilages of the nose. The organ of smell consists of two parts-one external, the nose ; the other internal, the nasal fossce. The nose is the more anterior and prominent part of the organ of smell. It is of a triangular form, directed vertically downward, and projects from the centre 848 THE ORGANS OF SENSE. of the face immediately above the upper lip. Its summit or root is connected directly yith the forehead. Its inferior part, the base of the nose, presents two elliptical orifices, the nostrils, separated from each other by an antero-posterior septum, the columna. The margins of these orifices are provided with a number of stiff hairs, or vibrissa?, which arrest the passage of foreign substances carried with the current of air intended for respiration. The lateral surfaces of the nose form, by their union, the dorsum, the direction of which varies considerably in different individuals. The dorsum terminates below in a rounded eminence, the lobe of the nose. The nose is composed of a framework of bones and cartilages, the latter being slightly acted upon by certain muscles. It is covered externally by the integument, internally by mucous membrane, and supplied with vessels and nerves. The bony framework occupies the upper part of the organ: it consists of the nasal bones and the nasal processes of the superior maxillary. The cartilaginous framework consists of five pieces, the two upper and the two lower lateral cartilages and the cartilage of the septum. The upper lateral cartilages are situated below the free margin of the nasal bones ; each cartilage is flattened and triangular in shape. Its anterior margin is thickei* than the posterior, and connected with the fibro-cartilage of the septum. Its posterior margin is attached to the nasal process of the superior maxillary and nasal bones. Its inferior margin is connected by fibrous tissue with the lower lateral cartilage : one surface is turned outward, the other inward toward the nasal cavity. The lower lateral cartilages are two thin, flexible plates situated immediately below the preceding, and bent upon themselves in such a manner as to form the inner and outer walls of each orifice of the nostril. The portion which forms the inner wall, thicker than the rest, is loosely connected with the same part of the opposite cartilage, and forms a small part of the columna. Its infe- rior border, free, rounded, and pro- jecting, forms, with the thickened integument and subjacent tissue and the corresponding parts of the opposite side, the tip of the nose. The part which forms the outer wall is curved to correspond with the ala of the nose ; it is oval and flattened, narrow behind, where it is connected with the nasal process of the superior maxilla by a tough fibrous membrane, in which are found three or four small cartilaginous plates (sesamoid cartilages), cartilag- ines minores. Above, it is connected to the upper lateral cartilage and front part of the cartilage of the septum; below, it is separated from the margin of the nostril by dense cellular tissue; and in front, it forms, with its fellow, the lobe of the nose. The cartilage of the septum is somewhat quadrilateral in form, thicker at its margins than at its centre, and completes the separation between the nasal fossae in front. Its anterior margin, thickest above, is connected from above downward with the nasal bones, the anterior margin of the two upper lateral cartilages, and the inner portion of the two lower lateral cartilages. Its posterior margin is connected with the perpendicular lamella of the ethmoid, its inferior margin with the vomer and the palate processes of the superior maxillary bones. These various cartilages are connected to each other and to the bones by a Fig. 484.-Bones and cartilages of septum of nose. Right side. THE NASAL FOSSfE. 849 tough fibrous membrane, which allows the utmost facility of movement between them. The muscles of the nose are situated immediately beneath the integument: they are (on each side) the Pyramidalis nasi, the Levator labii superioris alaeque nasi, the Dilatator naris, anterior and posterior, the Compressor nasi, the Com- pressor narium minor, and the Depressor alae nasi. They have been described above (page 401). The integument covering the dorsum and sides of the nose is thin, and loosely connected with the subjacent parts, but where it forms the tip or lobe and the alae of the nose it is thicker and more firmly adherent. It is furnished W'ith a large number of sebaceous follicles, the orifices of which are usually very distinct. The mucous membrane lining the interior of the nose is continuous with the skin externally and with that which lines the nasal fossae within. The arteries of the nose are the lateralis nasi from the facial, and the inferior artery of the septum from the superior coronary, which supply the alae and septum, the sides and dorsum being supplied from the nasal branch of the ophthalmic and the infra-orbital. The veins of the nose terminate in the facial and ophthalmic. The nerves of the nose are branches from the facial, infra-orbital, and infra- trochlear, and a filament from the nasal branch of the ophthalmic. Nasal Fossae. The nasal fossae are two irregular cavities situated in the middle of the face and extending from before backward. They open in front by the two anterior Superior turbin- ated bone. Ethmoidal sinus. Middle turbin- ated bone. ■Inferior turbin- ated bone. Fig. 485.-Transverse vertical section of the nasal fossae. (Henle.) nares, and terminate in the pharynx, behind, by the posterior nares. The anterior nares are somewhat pear-shaped apertures, each measuring about one inch vertically and half an inch transversely at their widest part. The posterior nares are two oval openings situated at the upper part of the anterior wall of the pharynx. They are smaller in the body than in the skeleton, because narrowed by the mucous membrane. Each opening measures an inch in the vertical and half an inch in the transverse direction in a well-developed adult skull. 850 THE ORGANS OF SENSE. The mucous membrane lining the nasal fossae is called the pituitary, from the nature of its secretion ; or Schneiderian, from Schneider, the first anatomist who showed that the secretion proceeded from the mucous membrane, and not, as was formerly imagined, from the brain. It is intimately adherent to the periosteum or perichondrium, over which it lies. It is continuous externally with the skin through the anterior nares, and with the mucous membrane of the pharynx through the posterior nares. From the nasal fossae its continuity may be traced with the conjunctiva through the nasal duct and lachrymal canals; with the lining membrane of the tympanum and mastoid cells through the Eustachian tube; and with the frontal, ethmoidal, and sphenoidal sinuses, and the antrum of Highmore through the several openings in the meatuses. The mucous membrane is thickest and most vascular over the turbinated bones. It is also thick over the septum, but in the intervals between the spongy bones and on the floor of the nasal fossae it is very thin. Where it lines the various sinuses and the antrum of Highmore it is thin and pale. Owing to the great thickness of this membrane, the nasal fossae are much narrower, and the turbinated bones, especially the lower ones, appear larger and more prominent than in the skeleton. From the same circumstance also the various apertures communicating with the meatuses are either narrowed or completely closed. In the superior meatus the aperture of communication with the posterior ethmoidal cells is considerably diminished in size, and the spheno-palatine foramen completely covered in. In the middle meatus the opening of the infundibulum is partially hidden by a projecting fold of mucous membrane, and the orifice of the antrum is contracted to a small circular aperture, much narrower than in the skeleton. In the inferior meatus the orifice of the nasal duct is partially hidden by either a single or double valvular mucous fold, and the anterior palatine canal either completely closed in or a tubular cul-de-sac of mucous membrane is continued a short distance into it. This cul-de-sac is termed the organ of Jacobson, and is present in all mammals as well as man. In the former it consists of a bilateral tube, situated in the nasal septum and supported by hyaline cartilage, the cartilage of Jacobson. In the roof the opening leading to the sphenoidal sinus is narrowed, and the apertures in the cribriform plate of the ethmoid completely closed in. Structure of the Mucous Membrane.-The epithelium covering the mucous membrane differs in its character according to the functions of the part of the nose in which it is found. Near the orifice of the nostril, the vestibule, where common sensation is chiefly or alone required, the epithelium is of the ordinary pavement or scaly variety. In the rest of the cavity, below the distribution of the olfactory nerves-i.e. in the respiratory portion of the nasal cavity-the epithelium is columnar and ciliated. This is the case also in the meatuses of the nose. In this region, beneath the epithelium and its basement membrane, is a fibrous layer infiltrated with lymph-corpuscles, so as to form in many parts a diffuse adenoid tissue, and beneath this a nearly continuous layer of smaller and larger glands, some mucous and some serous, the ducts of which open upon the surface. In the olfactory region-i.e. the region in which the terminal filaments from the olfactory nerves are distributed (see page 755)-the epithelial cells are columnar and, for the most part, non-ciliated: their free surface presents a sharp outline, and their deep extremity is prolonged into a process which runs inward, branching to commu- nicate with similar processes from neighboring cells, so as to form a network in the deep part of the mucous membrane. Eying between them are cells (termed by Max Schultze, olfactory cells), which consist of a nucleated body and two processes, of which one runs outward between the columnar epithelial cells and projects on the surface of the mucous membrane; the other (the deep) process runs inward, is frequently beaded like a nerve-fibre, and is believed by most observers to be in connection with one of the terminal filaments of the olfactory nerve. Amongst THE NASAL FOSSAE. 851 the branched ends of the columnar cells there is a deep layer of epithelial cells of a conical shape, their broad end resting on the basement membrane, and their tapering extremity projecting between the other cells. Beneath the epithelium, extending through the thickness of the mucous membrane, is a layer of glands, the glands of Borvman, identical in structure with serous glands. The mucous membrane is pigmented in the olfactory, but not in the other regions, being of a light yellow color, at least in the white races.1 The arteries of the nasal fossce are the anterior and posterior ethmoidal, from the ophthalmic, which supply the ethmoidal cells, frontal sinuses, and roof of the nose; a minute twig from the small meningeal; the spheno-palatine, from the internal maxillary, which supplies the mucous membrane covering the spongy bones, the meatuses, and septum; the inferior artery of the septum from the superior coronary of the facial; and the alveolar branch of the internal maxillary, which supplies the lining membrane of the antrum. The ramifica- tions of these vessels form a close, plexiform network beneath and in the substance of the mucous mem- brane. The veins of the nasal fossoe form a close network beneath the mucous membrane. They pass, some with the veins accompanying the spheno- palatine artery, through the spheno- palatine foramen, and others through the alveolar branch, to join the facial vein ; some accompany the ethmoidal arteries and terminate in the ophthal- mic vein; and, lastly, a few communi- cate with the veins in the interior of the skull through the foramina in the cribriform plate of the ethmoid bone and the foramen caecum. The nerves are-the olfactory, the nasal branch of the ophthalmic, filaments from the anterior dental branch of the superior maxillary, the Vidian, naso-palatine, descending anterior palatine, and nasal branches of Meckel's ganglion. The olfactory, the special nerve of the sense of smell, is distributed over the upper third of the septum and over the surface of the superior and middle spongy bones. The nasal branch of the ophthalmic distributes filaments to the fore part of the septum and outer wall of the nasal fossae. Filaments from the anterior dental branch of the superior maxillary supply the inferior meatus and inferior turbinated bone. The Vidian nerve supplies the upper and back part of the septum and superior spongv bone, and the upper anterior nasal branches from the spheno-palatine ganglion have a similar distribution. The naso-palatine nerve supplies the middle of the septum. The larger or anterior palatine nerve supplies the middle and lower spongy bones. Surgical Anatomy.-Instances of congenital deformity of the nose are occasionally met with, such as complete absence of the nose, an aperture only being present, or perfect develop- ment on one side, and suppression or malformation on the other; or there may be imperfect apposition of the nasal bones, so that the nose presents a median cleft or furrow. Deformities which have been acquired are much more common, such as flattening of the nose, the result of Fig. 486.-Nerves of septum of nose. Right side. 1 An interesting speculation has been suggested by Dr. W. Ogle, {Med. Chir. Trans., vol. liii. p. 277) as to the possible connection between the presence and abundance of this pigment and the per- fection of the sense of smell. 852 THE ORGANS OF SENSE. syphilitic necrosis, or imperfect development of the nasal bones in cases of congenital syphilis, or a lateral deviation of the nose may result from fracture. The skin over the alae and tip of the nose is thick and closely adherent to subjacent parts. Inflammation of this part is therefore very painful, on account of the tension. It is largely sup- plied with blood, and, the circulation here being terminal, vascular engorgement is liable to occur, especially in women at the menopause and in both sexes from disorders of digestion, exposure to cold, etc. The skin of the nose also contains a large number of sebaceous follicles, and these, as the result of intemperance, are apt to become affected and the nose reddened, congested, and irregularly swollen. To this the term ' ' grog-blossom ' ' is popularly applied. In some of these cases there is enormous hypertrophy of the skin and subcutaneous tissues, producing pendulous masses, termed lipomata nasi. Epithelioma and rodent ulcer may attack the nose, the latter being the more common of the two. Lupus and syphilitic ulceration frequently attack the nose, and may destroy the whole of the cartilaginous portion. In fact, lupus vulgaris begins more frequently on the ala of the nose than in any other situation. Cases of congenital occlusion of one or both nostrils, or adhesion between the ala and septum may occur, and may require immediate operation, since the obstruction much interferes with suck- ing. Bony closure of the posterior nares may also occur. To examine the nasal cavities, the head should be thrown back and the nose drawn upward, the parts being dilated by some form of speculum. It can also be examined with the little finger or a probe, and in this way foreign bodies detected. A still more extensive examination can be made by Rouge's operation, which was introduced for the cure of ozaena by the removal of any dead bone which may be present in this disease. The whole framework of the nose is lifted up by an incision made inside the mouth, through the junction of the upper lip with the bone; the septum nasi and the lateral cartilages are divided with strong scissors till the anterior nares are completely exposed. The posterior nares can be explored by reflected light from the mouth, by which the posterior nares can be illuminated. The examination is very difficult to carry out, and, as a rule, sufficient information regarding the presence of foreign bodies or tumors in the naso-pharynx can be obtained by the introduction of the finger behind the soft palate through the mouth. The septum of the nose may be displaced or deviate from the middle line: this may be the result of an injury or from some congenital defect in its development. Sometimes the deviation may be so great that the septum may come in contact with the outer wall of the nasal fossae, and may even become adherent to it, thus producing complete obstruction. Per- foration of the septum is not an uncommon affection, and may arise from several causes: syph- ilitic or tubercular ulceration, blood-tumor or abscess of the septum, and especially in workmen exposed to the vapor of bichromate of potash, from the irritating and corrosive action of the fumes. When small, the perforation may cause a peculiar whistling sound during respiration. When large, it may lead to the falling in of the bridge of the nose. Epistaxis is a very common affection in children. It is rarely of much consequence, and will almost always subside, but in the more violent haemorrhages of later life it may be necessary to plug the posterior nares. In performing this operation it is desirable to remember the size of the posterior nares. A ready method of regulating the size of the plug to fit the opening is to make it of the same size as the terminal phalanx of the thumb of the patient to be operated on. Nasal polypus is a very common disease, and presents itself in three forms: the gelatinous, the fibrous, and the malignant. The first is by far the most common. It grows from the mucous membrane of the outer wall of the nasal fossa, where there is an abundant layer of highly vascular submucous tissue; rarely from the septum, where the mucous membrane is closely adherent to the cartilage and bone, without the intervention of much, if any, submucous tissue. Their most common seat is probably the middle turbinated bone. The fibrous polypus generally grows from the base of the skull behind the posterior nares or from the roof of the nasal fossae. The malignant polypi, both sarcomatous or carcinomatous, may arise in the nasal cavities and the naso-pharynx; or they may originate in the antrum, and protrude through its inner wall into the nasal fossa. Rhinoliths, or nose-stones, may sometimes be found in the nasal cavities, from the formation of phosphate of lime upon either a foreign body or a piece of inspissated secretion. The eyeball is contained in the cavity of the orbit. In this situation it is securely protected from injury, whilst its position is such as to ensure the most extensive range of sight. It is acted upon by numerous muscles, by which it is capable of being directed to any part; it is supplied by vessels and nerves, and is additionally protected in front by several appendages, such as the eyebrow, eye- lids, etc. The eyeball is imbedded in the fat of the orbit, but is surrounded by a thin membranous sac, the capsule, of Tenon, which isolates it, so as to allow of free movement. The capsule of Tenon (tunica vaginalis oculi) may be regarded as a distinct THE EYE. THE EYE. 853 serous membrane, consisting of a parietal and visceral layer. The latter invests the posterior part of the globe from the ciliary margin of the cornea backward to the entrance of the optic nerve, and is connected to it by very delicate connective tissue: the former (parietal) lines the hollow in the fat in which the eyeball is imbedded. Both layers are lined on their free surfaces by endothelial cells. The cavity between them is continuous with the spaces between the different layers of the sheath of the optic nerve-that is to say, with the subarachnoidean between the pia-matral and the arachnoid sheath, and the subdural between the arachnoid and dural sheath-and into it empty the lymphatic vessels of the sclerotic. The capsule is pierced by the muscles of the eyeball near their insertion, and sends tubular prolongations on them, which become continuous with the sheath of the muscles. From the outer surface of these sheaths expansions, consisting of elastic fibres and muscle-cells, are given off to the margin of the orbit, which serve to limit the degree of contraction of the muscles.1 The eyeball is composed of segments of two spheres of different sizes. The anterior segment is one of a small sphere, and forms about one-sixth of the eyeball. It is more prominent than the posterior segment, which is one of a much larger sphere, and forms about five-sixths of the globe. The segment of the larger sphere is opaque, and formed by the sclerotic, the tunic of protection to the eyeball; the smaller sphere is transparent, and formed by the cornea. The axes of the eyeballs are nearly parallel, and do not correspond to the axes of the orbits, which are directed outward. The optic nerves follow the direction of the axes of the orbits, and are therefore not parallel; they enter the eyeball a little to their inner or nasal side. The eyeball measures rather more in its transverse than in its antero- posterior and vertical diameters, the former amounting to about an inch, the latter to about nine-tenths of an inch. The eyeball is composed of several investing tunics, and of fluid and solid refracting media, called humors. The tunics are three in number: 1. Sclerotic and Cornea. 2. Choroid, Iris, and Ciliary Processes. 3. Retina. The refracting media, or humors, are also three: Aqueous. Crystalline (lens) and Capsule. Vitreous. The sclerotic and cornea form the external tunic of the eyeball; they are essentially fibrous in structure, the sclerotic being opaque, and forming the posterior five-sixths of the globe ; the cornea, which forms the remaining sixth, being transparent. The Sclerotic hard) (Fig. 487) has received its name from its extreme density and hardness ; it is a firm, unyielding, fibrous membrane, serving to main- tain tbe form of the globe. It is much thicker behind than in front. Its external surface is of a white color, quite smooth, except at the points where the Recti and Obliqui muscles are inserted into it, and covered, for part of its extent, by the conjunctival membrane; hence the whiteness and brilliancy of the front of the eyeball. Its inner surface is stained of a brown color, marked by grooves, in which are lodged the ciliary nerves, and connected by an exceedingly fine cellular tissue (lamina fused) with the outer surface of the choroid. Behind, it is pierced by the optic nerve a little to its inner or nasal side, and is continuous with the fibrous sheath of the nerve, which is derived from the dura mater. At the point where the optic nerve passes through the sclerotic this membrane forms a thin cribriform lamina (the lamina cribrosd); the minute orifices in this layer serve for the transmission of the nervous filaments, and the fibrous septa dividing them from one another are continuous with the membranous processes which separate the bundles of nerve-fibres. One of these openings, larger than the rest, occupies 1 See a paper by Mr. C. B. Lockwood (Journal of Anatomy and Physiology, vol. xx., part i. p. 1). 854 THE ORGANS OF SENSE. the centre of the lamella; it is called the porus opticus, and transmits the arteria centralis retinae to the interior of the eyeball. Around the cribriform lamella are numerous small apertures for the transmission of the ciliary vessels and nerves. In front the sclerotic is continuous with the cornea by direct continuity of tissue, but the opaque sclerotic overlaps the cornea rather more on its outer than on its inner surface. Structure.-The sclerotic is formed of white fibrous tissue intermixed with fine elastic fibres, and of flattened connective-tissue corpuscles, some of which are pigmented, contained in cell-spaces between the fibres. These fibres are aggre- gated into bundles which are arranged chiefly in a longitudinal direction. It yields gelatin on boiling. Its vessels are not numerous, the capillaries being of small size, uniting at long and wide intervals. The existence of nerves in it is doubtful. ffforneg. Posterior chamber.~~ Anterior chamber. ''Canal of Schlemm. Ciliary body. " Ciliary 'processes. Crystalline lens. Canal of Petit. Cavity occupied by vitreous humor. INTERNAL " RECTUS MUSCLE. Retina.' Choroid coat.' Canal for ""central artery. Sclerotic coat. Nerve sheath- ■Optic nerve. Fig. 487.-A horizontal section of the eyeball. (Allen.) The Cornea is the projecting transparent part of the external tunic of the eyeball, and forms the anterior sixth of the globe. It is almost circular in shape, occasionally a little broader in the transverse than in the vertical direction. It is convex anteriorly, and projects forward from the sclerotic in the same manner that a watch-glass does from its case. Its degree of curvature varies in different individuals, and in the same individual at different periods of life, it being more prominent in youth than in advanced life, when it becomes flattened. The cornea is dense and of uniform thickness throughout; its posterior surface is perfectly circular in outline, and exceeds the anterior surface slightly in extent, from the latter being overlapped by the sclerotic. Structure.-The cornea consists of four layers-namely, (1) several strata of epithelial cells, continuous with those of the conjunctiva ; (2) a thick central fibrous structure, the cornea proper; (3) a homogeneous elastic lamina; and (4) a single layer of epithelial cells, forming part of the lining membrane of the anterior chamber of the eyeball. The name of membrane of Descemet or Demours is given to this posterior elastic lamina and its endothelial coating. THE CORNEA. 855 The conjunctival epithelium, which covers the front of the cornea proper, consists of several strata of epithelial cells. The lowermost cells are columnar : then follow two or three layers of polyhedral cells, some of which present ridges and furrows similar to those found in the cuticle. Lastly, there are three or four layers of scaly epithelium with flattened nuclei. The proper substance of the cornea is fibrous, tough, unyielding, perfectly transparent, and continuous with the sclerotic, with which it is identical in structure. It is composed of about sixty flattened lamellae, superimposed one on another. These lamellae are made up of bundles of fibrous connective tissue, the fibres of which are directly continuous with the fibres of the sclerotic. The fibres of each lamella are for the most part parallel with each other; those of alternat- ing lamellae at right angles to each other. Fibres, however, frequently pass from one lamella to the next. The lamellae are connected with each other by an interstitial cement-substance,* in which are spaces, the corneal spaces. The spaces are stellate in shape, and have numerous offsets by which they communicate with other spaces. Each space contains a cell, the corneal corpuscle, which resembles in form the space in which it is contained, but does not entirely fill it. Immediately beneath the conjunctival epithelium the cornea proper presents certain characteristic differences, which have led some anatomists to regard it as a distinct membrane, and it has been named by Bowman the anterior elastic lamina. It differs, however, from the true elastic lamina or membrane of Descemet in many essential particulars, presenting evidence of fibrillar structure, and not having the same tendency to curl inward or to undergo fracture when detached from the other layers of the cornea. It consists of extremely closely interwoven fibrils, similar to those found in the rest of the cornea proper, but contains no corneal corpuscles. It seems, therefore, more proper to regard it as a part of the proper tissue of the cornea.1 The posterior elastic lamina, which covers the proper structure of the cornea behind, presents no structure recognizable under the microscope. It consists of a hard, elastic, and perfectly transparent homogeneous membrane, of extreme thin- ness, which is not rendered opaque by either water, alcohol, or acids. It is very brittle, but its most remarkable property is its extreme elasticity, and the tend- ency which it presents to curl up or roll upon itself, with the attached surface innermost, when separate from the proper substance of the cornea. Its use appears to be (as suggested by Dr. Jacob) " to preserve the requisite permanent correct curvature of the flaccid cornea proper." At the margin of the cornea this posterior elastic membrane breaks up into fibres to form a reticular structure at the outer angle of the anterior chamber, the intervals between the fibres forming small cavernous spaces, the spaces of Fontana. These little recesses communicate with a somewhat larger space in the substance of the sclerotic close to its junction with the cornea. This is the canal of Schlemm, or sinus circularis iridis, and, according to some authors, is a lymph- canal, but according to others is a venous sinus. Some of the fibres of this reticulated structure are continued into the front of the iris, forming the liga- mentum pectinatum iridis, while others are connected with the fore part of the sclerotic and choroid. The endothelial lining of the aqueous chamber covers the posterior surface of the posterior elastic lamina. It consists of a single layer of polygonal flattened transparent nucleated cells, similar to those found lining other serous cavities. Arteries and Nerves.-The cornea is a non-vascular structure, the capillary vessels terminating in loops at its circumference. Lymphatic vessels have not as yet been demonstrated in it, but are represented by the channels in which the bundles of nerves run ; these are lined by an endothelium and are continuous with the cell-spaces. The nerves are numerous, twenty-four to thirty-six in 1 This layer has been called by Reichert the " anterior limiting layer "-a name which appears more applicable to it than that of "anterior elastic lamina." 856 THE ORGANS OF SENSE. number (Kblliker), forty to forty-five (Waldeyer and Sumisch); they are derived from the ciliary nerves and enter the laminated tissue of the cornea. They ramify throughout its substance in a delicate network, and their terminal fila- ments form a firm and closer plexus on the surface of the cornea proper beneath the epithelium. This is termed the subepithelial plexus, and from it fibrils are given off which ramify between the epithelial cells, forming a network which is termed the intra-epithelial plexus. Dissection.-In order to separate the sclerotic and cornea, so as to expose the second tunic, the eyeball should be immersed in a small vessel of water and held between the finger and thumb. The sclerotic is then carefully incised, in the equator of the globe, till the choroid is exposed. One blade of a pair of probe-pointed scissors is now introduced through the opening thus made, and the sclerotic divided around its entire circumference, and removed in separate portions. The front segment being then drawn forward, the handle of the scalpel should be pressed gently against it at its connection with the iris, and, these being separated, a quantity of perfectly transparent fluid will escape; this is the aqueous humor. In the course of the dissection the ciliary nerves may be seen lying in the loose cellular tissue between the choroid and sclerotic or contained in delicate grooves on the inner surface of the latter membrane. Second Tunic.-This is formed by the choroid behind, the iris and ciliary processes in front, and by the Ciliary muscle, opposite the junction of the scle- rotic and cornea. Fig. 488-The choroid and iris. (Enlarged.) The choroid is the vascular and pigmentary tunic of the eyeball investing the posterior five-sixths of the globe, and extending as far forward as the cornea, the ciliary processes being appendages of the choroid developed from its inner surface in front. The iris is the circular muscular septum which hangs vertical- ly behind the cornea, presenting in its centre a large circular aperture, the pupil. The Ciliary muscle forms the white ring observed at the point where the choroid and iris join with each other and with the sclerotic and cornea. The Choroid is a thin, highly vascular membrane, of a dark brown or chocolate color, which invests the posterior five-sixths of the central part of the globe. It is pierced behind by the optic nerve, and extends in front as far forward as the ciliary ligament, where it is connected with the iris, and bends inward, forming on its inner surface a series of folds or plaitings, the ciliary processes. It is thicker THE EYE. 857 behind than in front. Externally it is connected by a fine cellular web (membran a fused) with the inner surface of the sclerotic. Its inner surface is smooth and lies in contact with the retina. Structure.-The choroid consists mainly of a dense capillary plexus and of small arteries and veins, carrying the blood to and returning it from this plexus. On its external surface-i. e. the surface next the sclerotic-is a thin membrane of fine elastic fibres arranged in lamellae, which are covered with endothelium and form spaces, which communicate by perforations in the sclerotic, through which the vessels and nerves enter, with the capsule of Tenon. This layer is named the lamina, suprachoroidea, and is continuous with the lamina fusca of the sclerotic. Internal to this is the choroid proper, and, in consequence of the small arteries and veins being arranged on the outer surface of the capillary network, it is cus- tomary to describe this as consisting of two layers, the outermost composed of small arteries and veins, with pigment-cells interspersed between them, and the Fig. 489.-The veins of the choroid. (Enlarged.) inner consisting of a capillary plexus. The external layer consists, in part, of the larger branches of the short ciliary arteries, which run forward between the veins before they bend inward to terminate in the capillaries ; but is formed principally of veins, which are named, from their arrangement, vence vorticosce. They converge to four or five equidistant trunks, which pierce the sclerotic mid- way between the margin of the cornea and the entrance of the optic nerve. Inter- spersed between the vessels are lodged dark star-shaped pigment-cells, the fibrous offsets from which, communicating with similar branchings from neighboring cells, form a delicate network or stroma, which toward the inner surface of the choroid loses its pigmentary character. The internal layer consists of an exceedingly fine capillary plexus, formed by the short ciliary vessels, and is known as the tunica Ruyschiana. The network is close, and finer at the hinder part of the choroid than in Front. About half an inch behind the cornea its meshes become larger, and are continuous with those of the ciliary processes. On the inner surface of this tunic is a very thin, structureless-or, according to Kolliker, faintly fibrous- membrane, called the lamina vitrea ; it is closely connected with the stroma of the choroid, and separates it from the pigmentary layer of the retina. The ciliary processes should now be examined. They may be exposed, either by detaching the iris from its connection with the Ciliary muscle, or by making a transverse section of the globe and examining them from behind. The ciliary processes are formed by the plaiting and folding inward of the various layers of the choroid (z. e. the choroid proper and the lamina vitrea) at its anterior margin, and are received between corresponding foldings of the suspensory 858 THE ORGANS OF SENSE. ligament of the lens, thus establishing a connection between the choroid and inner tunic of the eye. They are arranged in a circle, and form a sort of plaited frill behind the iris round the margin of the lens. They vary between sixty and eighty in number, lie side by side, and may be divided into large and small; the latter, consisting of about one-third of the entire number, are situated in the spaces between the former, but without regular alternation. The larger processes are each about one-tenth of an inch in length, and are attached by their periphery to the Ciliary muscle, and are continuous with the layers of the choroid: the opposite margin is free, and rests upon the circumference of the lens. Their anterior surface is turned toward the back of the iris, with the circumference of which they are continuous. The posterior surface is closely connected with the suspensory ligament of the lens. Structure.-The ciliary processes are similar in structure to the choroid, but the vessels are larger, and have chiefly a longitudinal direction. They are covered Anterior ciliary artery. Short ciliary arteries. interior ciliary artery. Fig. 490.-The arteries of the choroid and iris. The sclerotic has been mostly removed. (Enlarged.) on their inner surface with a layer of black pigment-cells continuous with the cells of the pigmentary layer of the retina, and in their stroma are also other, stellate, pigment-cells, which, however, are not so numerous as in the choroid itself, and toward the free extremities of the folds are devoid of pigment. The Iris (iris, a rainbow) has received its name from its various colors in dif- ferent individuals. It is a thin, circular-shaped, contractile curtain, suspended in the aqueous humor behind the cornea and in front of the lens, being perforated a little to the nasal side of its centre by a circular aperture, the pupil, for the transmission of light. By its circumference it is intimately connected with the choroid ; externally to this is the Ciliary muscle, by which it is connected to the sclerotic and cornea ; its inner edge forms the margin of the pupil; its surfaces are flattened, and look forward and backward, the anterior surface toward the cornea, the posterior toward the ciliary processes and lens. The circumference of the iris is connected to the cornea by a reticular structure denominated the ligamentum pectinatum iridis. The anterior surface of the iris is variously colored in different individuals, and marked by lines which converge toward the pupil. The posterior surface is of a deep purple tint, from being covered by dark pigment; it is hence named uvea, from its resemblance in color to a ripe grape. Structure.-The iris is composed of the following structures : 1. In front is a layer of polyhedral cells on a delicate hyaline basement membrane. This layer is continuous with the epithelial layer of the membrane of Descemet, and in men with dark-colored irides the cells contain pigment-granules. 2. Stroma.-The stroma consists of fibres and cells. The former are made up THE EYE. 859 of fine delicate bundles of fibrous tissue, of which some few fibres have a circular direction at the circumference of the iris, but the chief mass consists of fibres radiating toward the pupil. They form, by their interlacement, a delicate mesh, in which the vessels and nerves are contained. Interspersed between the bundles of connective tissue are numerous branched cells with fine processes. Many of them in dark eyes contain pigment-granules, but in blue eyes and the pink eyes of albinos they are unpigmented. 3. The muscular fibre is involuntary, and consists of circular and radiating fibres. The circular fibres (sphincter of the pupil) surround the margin of the pupil on the posterior surface of the iris, like a sphincter, forming a narrow band Circ. fibres Canal of ' Spaces of of sclerotic. Schlevmi. Fontana.' Ciliary artery. Radiating fibres of Ciliary muscle. Pars ciliaris retinae. Circ. fibres / ™ of Ciliary muscle. Fig. 491.-Section of the eye, showing the relations of the cornea, sclerotic, and iris, together with the Ciliary muscle and the cavernous spaces near the angle of the anterior chamber. (Waldeyer.) about one-thirtieth of an inch in width, those near the free margin being closely aggregated; those more external somewhat separated, and forming less complete circles. The radiating fibres (dilator of the pupil) converge from the circumfer- ence toward the centre, and blend with the circular fibres near the margin of the pupil. 4. Pigment.-The situation of the pigment-cells differs in different irides. In the various shades of blue eyes the only pigment-cells are several layers of small round or polyhedral cells filled with dark pigment, situated on the posterior surface of the iris and continuous with the pigmentary lining of the ciliary processes. The color of the eye in these individuals is due to this coloring matter showing more or less through the texture of the iris. In the albino even this pigment is absent. In the gray, brown, and black eye there are, as mentioned above, pigment-granules to be found in the cells of the stroma and in the epithelial layer on the front of the iris, to which the color of the eye is due. The arteries of the iris are derived from the long and anterior ciliary and from the vessels of the ciliary processes (see page 572). The nerves of the iris are derived from the ciliary branches of the lenticular ganglion and the long ciliary from the nasal branch of the ophthalmic division of the fifth. After reaching the iris in the manner described above (page 763) they form a plexus around the attached margin of the iris; from this are derived non- 860 THE ORGANS OF SENSE. medullated fibres which terminate in the circular and radiating muscular fibres. Their exact mode of termination has not been ascertained. Other fibres from the plexus terminate in a network on the anterior surface of the iris. The fibres derived from the motor root of the lenticular ganglion (third nerve) supply the circular fibres, while those derived from the sympathetic supply the radiating fibres. Membrana Pupillaris.-In the foetus the pupil is closed by a delicate transparent vascular membrane, the membrana pupillaris, which divides the space into which the iris is suspended into two distinct chambers. This membrane contains numerous minute vessels, continued from the margin of the iris to those on the front part of the capsule of the lens. These vessels have a looped arrangement, and converge toward each other without anastomosing. Between the seventh and eighth months the membrane begins to disappear, by its gradual absorption from the centre toward the circumference, and at birth only a few fragments remain. It is said sometimes to remain permanent and produce blindness. The Ciliary muscle (Bowman) consists of unstriped fibres : it forms a grayish, semitransparent, circular band, about one-eighth of an inch broad, on the outer surface of the fore part of the choroid. It is thickest in front, and gradually becomes thinner behind. It consists of two sets of fibres, radiating and circular. The former, much the more numerous, arise at the point of junction of the cornea and sclerotic, and, passing backward, are attached to the choroid opposite to the ciliary processes. One bundle, according to Waldeyer, is continued backward to be inserted into the sclerotic. The circular fibres are internal to the radiating ones, ami to some extent unconnected with them, and have a circular course around the attachment of the iris. They are sometimes called the " ring muscle " of Muller, and were formerly described as the ciliary ligament. The Ciliary muscle is admitted to be the chief agent in accommodation-i. e. in adjusting the eye to the vision of near objects. Mr. Bowman believed that this was effected by its compressing the vitreous body, and so causing the lens to advance; but the view which now prevails is that the contraction of the muscle, by drawing on the ciliary processes, relaxes the suspensory ligament of the lens, thus allowing the anterior surface of the lens to become more convex. The pupil is at the same time slightly contracted.1 The Retina is a delicate nervous membrane upon the surface of which the images of external objects are received. Its outer surface is in contact with the choroid, the inner surface with the vitreous body. Behind it is continuous with the optic nerve ; it gradually diminishes in thickness from behind forward, and in front extends nearly as far forward as the Ciliary muscle, where it terminates by a jagged margin, the ora serrata. It is soft, and semitransparent in the fresh state, but soon becomes clouded, opaque, and of a pinkish tint. 'Exactly in the centre of the posterior part of the retina, and at a point corresponding to the axis of the eye, in which the sense of vision is most perfect, is a round, elevated, yellowish spot, called, after its discoverer, the yelloiv spot or limbus luteus (macula lutea) of Sbmmerring, having a central depression at its summit, the fovea centralis. The retina in the situation of the fovea centralis is exceedingly thin ; so much so that the dark color of the choroid is distinctly seen through it; so that it presents more the appearance of a foramen, and hence the name " foramen of Sbmmerring " at first given to it. It exists only in man, the quadrumana, and some saurian reptiles. About one-tenth of an inch to the inner side of the yellow spot is the point of entrance of the optic nerve (porus opticus); here the nervous substance is slightly raised so as to form an eminence (colliculus nervi optici); the arteria centralis retinse pierces its centre. This is the only part of the surface of the retina from which the power of vision is absent. Structure.-The retina is an exceedingly complex structure, and, when exam- ined microscopically by means of sections made perpendicularly to its surface, 1 See explanation and diagram in Power's Illustrations of Some of the Principal Diseases of the Eye, p. 590. THE EYE. 861 is found to consist of ten layers, which are named from within outward as follows : 1. Membrana limitans interna. 2. Fibrous layer, consisting of nerve-fibres. 3. Vesicular layer, consisting of nerve-cells. 4. Inner molecular, or granular, layer. 5. Inner nuclear layer. 6. Outer molecular, or granular, layer. 7. Outer nuclear layer. 8. Membrana limitans externa. 9. Layer of rods and cones (Jacob's membrane). 10. Pigmentary layer. 1. The membrana limitans interna is the most internal layer of the retina, and is in contact with the hyaloid membrane of the vitreous humor. It is derived from the supporting framework of the retina, with which tissue it will be described. - Sclerotic. Choroid. Fig. 492.-The arteria centralis retinae, yellow spot, etc., the anterior half of the eyeball being removed (Enlarged.) 2. The fibrous layer is made up of nerve-fibres, the direct continuation of the fibres of the optic nerve. This nerve therefore passes through all the other layers of the retina, except the one previously mentioned, to reach its destination in the fibrous layer. As the nerve passes through the lamina cribrosa of the sclerotic coat the fibres of which it is composed lay aside their medullary sheaths and are continued onward, through the choroid and retina, as simple axis-cylinders. When these non-medullated fibres reach the internal surface of the retina, they radiate from their point of entrance over the surface of the retina, grouped in bundles, and in many places, according to Michel, arranged in plexuses. The layer is thickest at the optic nerve entrance, and gradually diminishes in thick- ness toward the ora serrata. 3. The vesicular layer consists of a single layer of large ganglion-cells, except in the macula lutea, where there'are several layers. The cells are somewhat flask- shaped ; their rounded internal margin resting on the preceding layer, and sending off a single process, which is prolonged into the fibrous layer, and is believed to be continuous with a nerve-fibre. From the opposite extremity of the cell one or more thicker processes extend into the inner molecular layer, where they divide dichotomously and become lost in its reticulum, or, according to some, pass through this layer to reach the inner nuclear layer. 4. The inner molecular layer consists of a stratum of granular-looking sub- stance, from which circumstance it is sometimes called the " inner granular" layer. 862 THE ORGANS OF SENSE. It is made up of a dense reticulum of minute fibrils, intermingled with the fine processes of the ganglion-cells and also processes derived from certain cells contained in the next layer, immediately to be described. No direct connection between these sets of processes has yet been demonstrated, but it is considered probable that they do communicate, and that there is therefore a direct connection between the ganglion-cells of the vesicular layer and the nuclear cells of the inner nuclear layer. Within the reticulum formed by these fibrils minute clear granules, of unknown nature, are imbedded. 5. The inner nuclear layer is made up of nuclear bodies, of which there are Figs. 493, 494.-Vertical sections of the human retina. Fig. 493, half an inch from the entrance of the optic nerve. Fig. 494, close to the latter. 1. Layer of rods and cones (columnar layer), bounded underneath by the membrana limitans externa. 2. External nuclear layer. 3. Outer molecular layer. 4. Internal nuclear layer. 5. Inner molecular layer. 6. Layer of the ganglion-cells. 7. Expansion of optic fibres. 8. Sustentacular fibres of Muller. 9. Their attachment'to the membrana limitans interna. three different kinds : (1) A large number of oval nuclei, which are commonly- regarded as bipolar nerve-cells, and are much more numerous than either of the other kind. They consist of a large oval nuclear body placed vertically to the surface, containing a distinct nucleolus : they are surrounded by a small amount of protoplasm, which is prolonged into two processes: one of these passes inward into the inner molecular layer, is varicose in appearance, and, as stated above, is believed to be continuous with the processes of the ganglion-cells. The other process passes outward into the outer molecular layer, and there bifurcates. According to some observers, the divisions thus formed communicate with the rod- and cone-fibres (Merkel). (2) At the innermost part of this inner nuclear layer is a stratum of cells which are not branched. (3) Some few cells are also found in this layer connected with the fibres of Muller, and will be described with those structures. 6. The outer molecular layer is much thinner than the inner molecular layer, but, like it, consists of a dense network of minute fibrils, and presents the same granular appearance. It differs, however, from the inner molecular layer in con- taining branched stellate cells, the processes of which are extremely fine and exhibit varicosities like nerve-fibrils. They are therefore considered by Schultze to be ganglion-cells. 7. The Outer Nuclear Layer.-Like the inner nuclear layer, this layer contains several strata of clear oval nuclear bodies; they are of two kinds, and, on account of their being respectively connected with the rods and cones of Jacob's membrane, THE EYE. 863 are named rod-granules and cone-granules. The rod-granules are much the more numerous, and are placed at different levels throughout the layer. They present a peculiar cross-striped appearance, and have prolonged from either extremity a fine process : the outermost is continuous with a single rod of Jacob's membrane; the innermost passes inward toward the outer molecular layer, and terminates in an enlarged extremity, from which are given off a number of minute fibrils, which enter the outer molecular layer. In its course it presents numerous varicosities. The cone-granules, fewer in number than the rod-granules, are placed close to the membrana limitans externa, and are closely connected with the cones of Jacob's membrane. They do not present any cross-striping, but contain a pyriform nucleus, which almost completely fills the cell. From their inner extremity a thick process passes inward to the outer molecular layer, where, like the processes of the rod-cells, it terminates in an enlargement, from which are given off numerous fine fibrils which enter the outer molecular layer. 8. The Membrana Limitans Externa.-This layer, like the membrana limitans interna, is derived from the fibres of Muller, with which structures it will be described. 9. Jacob's Membrane (bacillary layer).-The elements which compose this layer are of two kinds, rods and cones, the former being much more numerous than the latter. The rods are solid, of nearly uniform size, ? nd arranged perpendicularly to the surface. Each rod consists of two portions, an outer and inner, which are joined together by a cement-substance and are of about equal length. They differ from each other as regards refraction and in their behavior with coloring reagents, the inner portion becoming stained by carmine, iodine, etc., the outer portion remaining unstained. The outer portion of each rod is marked by transverse striae, and is made up of a number of thin disks superimposed on one another. It also exhibits faint longitudinal markings. The inner portion of each rod at its inner extremity, where it is joined to the processes of the rod-granules, is indistinctly granular ; at its outer extremity it presents a fine longitudinal striation, being composed of fine, bright, highly refracting fibrils. The cones are conical or flask-shaped, their broad ends resting upon the membrana limitans externa, the narrow pointed extremity being turned to the choroid. Like the rods, they are made up of two portions, outer and inner; the outer portion being a short conical process, which, like the outer segment of the rods, presents transverse strife. The inner portion resembles the inner portion of the rods in structure, presenting an outer striated and an inner granular appearance, but differs from it in size, being bulged out laterally and presenting a flask shape. 10. The Pigmentary Layer, or Tapetum Nigrum.-The most external layer of the retina, formerly regarded as a part of the choroid, consists of a single layer of hexagonal epithelium cells loaded with pigment-granules (Fig. 21). In the eyes of albinos the cells of the pigmentary layer are present, but they contain no coloring matter. In many of the mammals also, as in the horse, and many of the carnivora, there is no pigment in the cells of this layer, and the choroid possesses a beautiful iridescent lustre, which is termed the tapetum lucidum. Connective-tissue Framercork of the Retina.-Almost all these layers of the retina are connected together by a sort of supporting connective tissue, which has been named the fibres of Muller, or radiating fibres, from which the membrana limitans interna et externa are derived. These fibres are found stretched between the two limiting layers, " as columns between a floor and a ceiling," and passing through all the nervous layers except Jacob's membrane. They commence on the inner surface of the retina by a conical base, the edges of the bases of adjoining fibres being united, and thus forming a boundary-line which is the membrana limitans interna. As they pass through the various layers they present a roughness on their surface, as if a number of membranous processes had been abruptly broken off. By these they are continuous with the reticulum of the inner and outer molecular layer and with a sponge-like stroma, in which the nuclei of the inner nuclear layers are imbedded. In the inner nuclear layer each fibre of Muller 864 THE ORGANS OF SENSE. presents a clear oval nucleus, referred to above, which is sometimes situated at the side of, sometimes altogether within, the fibre. In the outer nuclear layer the fibre breaks up into fine lamellae, which form a fenestrated or sponge-like tissue, in which the rod- and cone-granules are enclosed, and at the outer border of this layer these lamellae unite along a definite line, forming the membrana limitans externa. Macula Lutea and Fovea Centralis.-The structure of the retina at the yellow spot presents some modifications. In the macula lutea (1) the nerve-fibres are Pigmentary layer. Jacob's membrane. Membrana limitans externa. Outer nuclear layer. Outer molecular layer. Inner nuclear layer. Fibre of Muller. Inner molecular layer. Vesicular layer. Fibrous layer. Membrana limitans interna. Fig. 495.-The layers of the retina (diagrammatic). (After Schultze.) wanting as a continuous layer; (2) the vesicular layer consists of several strata of cells, instead of a single layer; (3) in Jacob's membrane there are no rods, but only cones, and these are longer and narrower than in other parts; and (4) in the outer nuclear layer there are only cone-fibres, which are very long and arranged in curved lines. At the fovea centralis the only parts which exist are the cones of Jacob's membrane, the outer nuclear layer, the cone-fibres of which are almost horizontal in direction, and an exceedingly thin inner granular layer. The color of the spot seems to imbue all the layers except Jacob's membrane; it is of a rich yellow, deepest toward the centre, and does not appear to consist of pigment-cells, but simply a staining of the constituent parts. At the ora serrata the layers of the retina for the most part terminate abruptly, and the radiating fibres of Muller, covered by the pigmentary layer, can be traced forward, as the pars ciliar is, to the iris. The fibres of Muller here present the appearance of columnar epithelial cells arranged in a single stratum. The arteria centralis retince and its accompanying vein pierce the optic nerve, and enter the globe of the eye through the porus opticus. It immediately divides THE VITREOUS BODY. 865 into four or five branches, which at first run between the hyaloid membrane and the nervous layer, but they soon enter the latter membrane, and pass forward, dividing dichotomously. From these branches a minute capillary plexus is given off, which does not extend beyond the inner nuclear layer. In the foetus a small vessel passes forward, through the vitreous humor, to the posterior surface of the capsule of the lens. Humors of the Eye. The aqueous humor completely fills the anterior and posterior chambers of the eyeball. It is small in quantity (scarcely exceeding, according to Petit, four or five grains in weight), has an alkaline reaction, in composition is little more than water, less than one-fiftieth of its weight being solid matter, chiefly chloride of sodium. The anterior chamber is a space bounded in front by the cornea, behind by the front of the iris. The posterior chamber was the name formerly given to a space which was believed to exist between the iris in front and the capsule of the lens, its suspensory ligament, and the ciliary processes behind. It is now known that the posterior surface of the iris is in immediate contact with the lens throughout the greater part of its extent. The only space which remains to represent the posterior chamber is a narrow chink between the peripheral part of the iris, the suspensory ligament, and the ciliary processes. In the adult these two chambers communicate through the pupil; but in the foetus in the seventh month, when the pupil is closed by the membrana pupillaris, the two chambers are quite separate. The vitreous body forms about four-fifths of the entire globe. It fills the con- cavity of the retina, and is hollowed in front for the reception of the lens and its capsule. It is perfectly transparent, of the consistence of thin jelly, and is com- posed of an albuminous fluid enclosed in a delicate transparent membrane, the hyaloid. This membrane invests the outer surface of the vitreous body; it is inti- mately connected in front with the suspensory ligament of the lens, and is con- tinued into the back part of the capsule of the lens. It has been supposed, by Hannover, that from its inner surface numerous thin lamellae are prolonged inward in a radiating manner, forming spaces in which the fluid is contained. In the adult these lamellae cannot be detected even after careful microscopic examination ; but in the foetus a peculiar fibrous texture pervades the mass, the fibres joining at numerous points, and presenting minute nuclear granules at their point of junction. In the centre of the vitreous humor, running from the position of the entrance of the optic nerve on the retina to the posterior surface of the lens, is a canal filled with fluid and lined by a prolongation of the hyaloid membrane. This is the canal of Stilling, and is the canal which in the embryonic vitreous humor conveyed the minute artery from the central artery of the retina to the back of the lens. The fluid from the vitreous body resembles nearly pure water ; it contains, however, some salts and a little albumen. The hyaloid membrane encloses the whole of the vitreous humor, except its anterior surface, which is hollowed out for the reception of the lens ; it passes from the margin of this surface to the margin of the lens, forming the suspensory ligament. It is a delicate structureless membrane, except where it forms the sus- pensory ligament, where it contains longitudinal elastic fibres. Immediately beneath the hyaloid membrane are found small, granular, nucleated cells which are said to be possessed of amoeboid movements. In the foetus the centre of the vitreous humor presents a tubular canal, through which a minute artery passes along the vitreous body to the capsule of the lens. In the adult no vessels penetrate its substance, so that its nutrition must be carried on by the vessels of the retina and ciliary processes situated upon its exterior. The Vitreous Body. 866 THE ORGANS OF SENSE. The Crystalline Lens and its Capsule. The crystalline lens, enclosed in its capsule, is situated immediately behind the pupil, in front of the vitreous body, and surrounded by the ciliary processes, which slightly overlap its margin. The capsule of the lens is a transparent, highly elastic, and brittle membrane which closely surrounds the lens. It rests, behind, in a depression in the fore part of the vitreous body ; in front it is in contact with the free border of the iris, this latter receding from it at the circumference, thus forming the posterior chamber of the eye ; and it is retained in its position chiefly by the suspensory ligament of the lens. The capsule is much thicker in front than behind, structureless in text- ure, and when ruptured the edges roll up with the outer surface innermost, like the elastic lamina of the cornea. The anterior surface of the lens is connected to the inner surface of the capsule by a single layer of transparent, polygonal, nucle- ated cells. At the circumference of the lens these cells undergo a change in form : they become elongated, and Babucin states that he can trace the gradual transition of the cells into proper lens-fibres, with which they are directly continuous. There is no epithelium on the posterior surface. In the foetus a small branch from the arteria centralis retinae runs forward, as already mentioned, through the vitreous humor to the posterior part of the capsule of the lens, where its branches radiate and form a plexiform network which covers its surface, and they are continu- ous round the margin of the capsule with the vessels of the pupillary membrane and with those of the iris. In the adult no vessels enter its substance. The lens is a transparent, double-convex body, the convexity being greater on the posterior than on the anterior surface. It measures about a third of an inch in the transverse diameter, and about one-fourth in the antero-posterior. It con- sists of concentric layers, of which the external in the fresh state are soft and easily detached; those beneath are firmer, the central ones forming a hardened nucleus. These laminae are best demonstrated by boiling, or immersion in alcohol. The same reagents demonstrate that the lens consists of three triangular segments, the sharp edges of which are directed toward the centre, the bases toward the circumference. The laminae consist of minute parallel fibres which are hexagonal prisms, the edges being dentated, and the dentations fitting accurately into each other; their breadth is about of an inch. They run from the sutures or lines of junction of the triangular segments on the one surface to the periphery of the lens, and, curving round its margin, they terminate at the line of junction of the segments on the other. No fibres pass from pole to pole, but they are arranged in such a way that fibres which commence near the pole on the one aspect of the lens-that is to say, near the apex of the triangular segment- terminate near the peripheral extremity of the plane on the other, or near the base of the triangular segment, and vice versa. The fibres of the outer layers of the lens each contain a nucleus, which together form a layer (nuclear layer) on the surface of the lens, most distinct toward its circumference. The meridians, or lines of junction of the three segments, are composed of an amorphous granular substance which sometimes becomes opaque, when the lines are seen forming a distinct star on the lens. The lines on one surface do not lie immediately opposite those on the other, but are intermediate. The changes produced in the lens by age are the following: In the foetus its form is nearly spherical, its color of a slightly reddish tint, it is not perfectly transparent, and is so soft as to break down readily on the slightest pressure. Fig. 496.-The crystalline lens, hardened and divided. (Enlarged.) THE CRYSTALLINE LENS AND ITS CAPSULE. 867 In the adult the posterior surface is more convex than the anterior; it is color- less, transparent, and firm in texture. In old age it becomes flattened on both surfaces, slightly opaque, of an amber tint, and increases in density. The suspensory ligament of the lens is a thin, transparent, membranous struc- ture placed between the vitreous body and the ciliary processes of the choroid; it connects the anterior margin of the vitreous humor with the anterior surface of the lens near its circumference. It assists in retaining the lens in its position. Its outer surface presents a number of folds or plaitings in which the corresponding folds of the ciliary processes are received. These plaitings are arranged round the lens in a radiating form, and are stained by the pigment of the ciliary processes. The suspensory ligament is a part of the hyaloid membrane, which, as described above, is continued forward to the anterior part of the margin of the lens. It is covered on its outer surface by the pars ciliaris, or connective-tissue framework of the retina, prolonged forward from the ora serrata. That portion of this mem- brane which intervenes between the ciliary processes and the capsule of the lens forms part of the boundary of the posterior chamber of the eye. The posterior surface of this layer is turned toward the vitreous humor, being separated from it at the circumference of the lens by a space called the canal of Petit. The canal of Petit is about one-tenth of an inch wide. It is bounded in front by the suspensory ligament; behind by the vitreous humor, its base being formed by the capsule of the lens. When inflated with air it is sacculated at intervals, owing to the foldings on its anterior surface. The arteries of the globe of the eye are the short, long, and anterior ciliary arteries and the arteria centralis retinae. They have been already described (see page 572). The ciliary veins are seen on the outer surface of the choroid, and are named, from their arrangement, the vence vorticosce. They converge to four or five equidistant trunks, which pierce the sclerotic midway between the margin of the cornea and the entrance of the optic nerve. Another set of veins accompany the anterior ciliary arteries and open into the ophthalmic vein. The ciliary nerves are derived from the nasal branch of the ophthalmic and from the ciliary or ophthalmic ganglion. Surgical Anatomy.-Foreign bodies frequently get into the conjunctival sac and cause great pain, especially if they come in contact with the corneal surface during the movements of the lid and the eye on each other. The conjunctiva is frequently involved in severe injuries of the eyeball, but is seldom ruptured alone ; the most common form of injury to the conjunctiva alone is from a burn, either from fire, strong acids, or lime. In these cases union is liable to take place between the eyelid and the eyeball. The conjunctiva is often the seat of inflammation arising from many different causes, and the arrangement of the conjunctival vessels should be remembered as affording a means of diagnosis between this condition and injection of the sclero- tic, which is present in inflammations of the deeper structures of the globe. The inflamed con- junctiva is bright red; the vessels are large and tortuous, and greatest at the circumference, shading off toward the corneal margin; they anastomose freely and form a dense network, and they can be emptied or displaced by gentle pressure. From a surgical point of view the cornea may be regarded as consisting of three layers: (1) of an external epithelial layer, developed from the epiblast, and continuous with the external epithelial covering of the rest of the body, and therefore in its lesions resembling those of the epidermis and superficial layers of the derma; (2) of the cornea proper, derived from the meso- blast, and associated in its diseases with the fibro-vascular structures of the body; and (3) the posterior elastic layer with its endothelium, also derived from the mesoblast and having the characters of a serous membrane, so that inflammation of it resembles inflammation of the other serous and synovial membranes of the body. The cornea contains no blood-vessels, except at its periphery, where numerous delicate loops, derived from the anterior ciliary arteries, may be demonstrated on the anterior surface of the cornea. The rest of the cornea is nourished by lymph, which gains access to the proper sub- stance of the cornea and the posterior layer through the spaces of Fontana. This lack of a direct blood-supply renders the cornea very apt to inflame in the cachectic and ill-nourished. Tn cases of granular lids there is a peculiar affection of the cornea, called pannus, in which the anterior layers of the cornea become vascularized, and a rich network of blood-vessels may be seen on the cornea; and in interstitial keratitis new vessels extend into the cornea, giving it a pinkish hue, to which the term " salmon patch " is applied. The cornea is richly supplied with 868 THE ORGANS OF SENSE. nerves, derived from the ciliary, which enter the cornea through the fore part of the sclerotic and form plexuses in the stroma, terminating between the epithelial cells by free ends or in cor- puscles. In cases of glaucoma the ciliary nerves may be pressed upon as they course between the choroid and sclerotic, and the cornea becomes anaesthetic. The sclerotic has very few blood- vessels and nerves. The blood-vessels are derived from the anterior ciliary, and form an open plexus in its substance. As they approach the corneal margin this arrangement is peculiar. Some branches pass through the sclerotic to the ciliary body; others become superficial and lie in the episcleral tissue, and form arches, by anastomosing with each other, some little distance behind the corneal margin. From these arches numerous straight vessels are given off, which run forward to the cornea, forming its marginal plexus. In inflammation of the sclerotic and episcleral tissue these vessels become conspicuous, and form a pinkish zone of straight vessels radiating from the corneal margin, commonly known as the zone of ciliary injection. In inflam- mation of the iris and ciliary body this zone is present, since the sclerotic speedily becomes involved when these structures are inflamed. But in inflammation of the cornea the sclerotic is seldom much affected, though the cornea and sclerotic are structurally continuous. This would appear to be due to the fact that the nutrition of the cornea is derived from a different source from that of the sclerotic. The sclerotic may be ruptured subcutaneously without any laceration of the conjunctiva, and the rupture usually occurs near the corneal margin, where the tunic is thin- nest. It may be complicated with lesions of adjacent parts-laceration of the choroid, retina, iris, or suspensory ligament of the lens-and is then often attended with haemorrhage into the anterior chamber, which masks the nature of the injury. In some cases the lens has escaped through the rent in the sclerotic, and has been found under the conjunctiva. Wounds of the sclerotic are always dangerous, and are often followed by inflammation, suppuration, and by sympathetic ophthalmia. The function of the choroid is to provide nutrition for the retina and to convey vessels and nerves to the ciliary body and iris. Inflammation of the choroid is therefore followed by grave disturbance in the nutrition of the retina, and is attended with early interference with vision. In its diseases it bears a considerable analogy to those which affect the skin, and, like it, is one of the places from which melanotic sarcomata may grow. These tumors contain a large amount of pigment in their cells, and grow only from those parts where pigment is naturally present. The choroid may be ruptured without injury to the other tunics, as well as participa- ting in general injuries of the eyeball. In cases of uncomplicated rupture the injury is usually at its posterior part, and is the result of a blow on the front of the eye. It is attended by con- siderable haemorrhage, which for a time may obscure vision, but in most cases this is restored as soon as the blood is absorbed. The iris is the seat of a malformation, termed coloboma, which consists in a deficiency or cleft, which in a great number of cases is clearly due to an arrest in development. In these cases it is found at the lower aspect, extending directly downward from the pupil, and the gap frequently extends through the choroid to the entrance of the optic nerve. In some rarer cases the gap is found in other parts of the iris, and is then not associated with any deficiency of the choroid. The iris is abundantly supplied with blood-vessels and nerves, and is therefore very prone to become inflamed. And when inflamed, in consequence of the intimate relationship which exists between the vessels of the iris and choroid this latter tunic is very apt to participate in the inflammation. And, in addition, inflammation of adjacent structures, the cornea and sclerotic, is apt to spread into the iris. The iris is covered with epithelium, and partakes of the character of a serous membrane, and, like these structures, is liable to pour out a plastic exuda- tion when inflamed, and contract adhesions, either to the cornea in front {synechia anterior}, or to the capsule of the lens behind {synechia posterior}. In iritis the lens may become involved, and the condition known as secondary cataract maybe set up. Tumors occasionally commence in the iris; of these, cysts, which are usually congenital and sarcomatous tumors, are the most common and require removal. Gummata are not unfrequently found in this situa- tion. In some forms of injury of the eyeball, as the impact of a spent shot, the rebound of a twig, or a blow with a whip, the iris may be detached from the Ciliary muscle, the amount of detachment varying from the slightest degree to the separation of the whole iris from its ciliary connection. The retina, with the exception of its pigment-layer and its vessels, is perfectly transparent, so as to be invisible when examined by the ophthalmoscope, so that its diseased conditions are recognized by its loss of transparency. In retinitis, for instance, there is more or less dense and extensive opacity of its structure, and not unfrequently extravasations of blood into its sub- stance. Haemorrhages may also take place into the retina from rupture of a blood-vessel with- out inflammation. The retina may become displaced from effusion of serum between it and the choroid or by blows on the eyeball, or may occur without apparent cause in progressive myopia, and in this case the ophthalmoscope shows an opaque, tremulous cloud. Glioma, a form of sarcoma, and essentially a disease of early life, is occasionally met with in connection with the retina. The lens has no blood-vessels, nerves, or connective tissue in its structure, and therefore is not subject to those morbid changes to which tissues containing these structures are liable. It does, however, present certain morbid or abnormal conditions of various kinds. Thus, variations in shape, absence of the whole or a part of the lens, and displacements are amongst its congeni- tal defects. Opacities may occur from injury, senile changes, malnutrition, or errors in growth or development. Senile changes may take place in the lens, impairing its elasticity and render- THE APPENDAGES OF THE EYE. 869 ing it harder than in youth, so that its curvature can only be altered to a limited extent by the Ciliary muscle. And, finally, the lens may be dislocated or displaced by blows upon the eyeball, and its relations to surrounding structures altered by adhesions or the pressure of new growths. There are two particular regions of the eye which require special notice: one of these is known as the " filtration area," and the other as the " dangerous area." The filtration area is the circumcorneal zone immediately in front of the iris. Here are situated the cavernous spaces of Fontana, which communicate with the canal of Schlemm, through which the chief transuda- tion of fluid from the eye is now believed to take place. The dangerous area of the eye is the region in the neighborhood of the ciliary body, and wounds or injuries in this situation are peculiarly dangerous ; for inflammation of the ciliary body is liable to spread to many of the other structures of the eye, especially to the iris and choroid, which are intimately connected by nervous and vascular supplies. Moreover, wounds which involve the ciliary region are especially liable to be followed by sympathetic ophthalmia, in which destructive inflammation of one eye is excited by some irritation in the other. The Appendages of the Eye. The appendages of the eye (tutamina oculi) include the eyebrows, the eyelids, the conjunctiva, and the lachrymal apparatus-viz. the lachrymal gland, the lachrymal sac, and the nasal duct. The eyebrows (supercilia) are two arched eminences of integument which surmount the upper circumference of the orbit on each side, and support numer- ous short, thick hairs, directed obliquely on the surface, In structure the eye- brow's consist of thickened integument, connected beneath with the Orbicularis palpebrarum, Corrugator supercilii, and Occipito-frontalis muscles. These mus- cles serve, by their action on this part, to control to a certain extent the amount of light admitted into the eye. The eyelids (palpebrce) are two thin, movable folds placed in front of the eye, protecting it from injury by their closure. The upper lid is the larger and the more movable of the twro, and is furnished with a separate elevator muscle, the Levator palpebrce superioris. When the eyelids are opened an elliptical space (fissura palpebrarum) is left between their margins, the angles of which correspond to the junction of the upper and lower lids, and are called eanthi. The outer canthus is more acute than the inner, and the lids here lie in close contact with the globe; but the inner canthus is prolonged for a short distance inward toward the nose, and the two lids are separated by a triangular space, the lacus lachrymalis. At the commencement of the lacus lachrymalis, on the margin of each eyelid, is a small conical elevation, the lachrymal papilla, or tubercle, the apex of which is pierced by a small orifice, the punctual lachrymale, the com- mencement of the lachrymal canal. The eyelashes (cilia) are attached to the free edges of the eyelids ; they are short, thick, curved hairs, arranged in a double or triple row at the margin of the lids: those of the upper lid, more numerous and longer than the lower, curve upward; those of the lower lid curve downward, so that they do not interlace in closing the lids. Near the attachment of the eyelashes are the openings of a number of glands, glands of Mohl, arranged in several rows close to the free margin of the lid. They resemble in structure a portion of a sweat-gland, and are regarded as the modified sweat-glands of this region. Structure of the Eyelids.-The eyelids are composed of the following struc- tures, taken in their order from without inward : Integument, areolar tissue, fibres of the Orbicularis muscle, tarsal plate (cartilage), and its ligament, Meibomian glands and conjunctiva. The upper lid has, in addition, the aponeurosis of the Levator palpebrae. The mtet/ument is extremely thin, and continuous at the margin of the lids with the conjunctiva. The subcutaneous areolar tissue is very lax and delicate, seldom contains any fat, and is extremely liable to serous infiltration. of the Orbicularis muscle, where they cover the palpebrae, are thin, pale in color, and possess an involuntary action. 870 THE ORGANS OF SENSE. The tarsal plates {cartilages)1 are two thin elongated plates of dense connect- ive tissue about an inch in length. They are placed one in each lid, contribut- ing to their form and support. The superior, the larger, is of a semilunar form, about one-third of an inch in breadth at the centre, and becoming gradually narrowed at each extremity. Into the anterior surface of this plate the aponeurosis of the Levator palpebrm is attached. The inferior tarsal plate, the smaller, is thinner and of an elliptical form. The/ree or ciliary margin of these plates is thick, and presents a perfectly straight edge. The attached or orbital margin is connected to the circumference of the orbit by the fibrous membrane of the lids with which it is continuous. The outer angle of each plate is attached to the malar bone by the external palpebral or tarsal ligament. The inner angles of the two plates terminate at the com- mencement of the lacus lachrymalis, being fixed to the margins of the orbit by the tendo oculi. The tarsal ligament, or fibrous membrane of the lids, is a layer of fibrous membrane beneath the Orbicularis, attached marginally to the edge of the orbit, where it becomes continuous with the periosteum, and centrally to the tarsal plate, near its ciliary margin, with the tissue of which it is continuous. It is thickest and densest at the outer part of the orbit. Upon its under surface is a layer of unstriped muscle, which in the upper lid passes from the aponeurosis of the Levator palpebrae muscle to the tarsal plate. This ligament serves to support the eyelids, and retains the tarsal plates in their position. The Meibomian glands (Fig- 497) are situated upon the inner surface of the eyelids between the tarsal plates and conjunctiva, and may be distinctly seen through the mucous membrane on everting the eyelids, presenting the appear- ance of parallel strings of pearls. They are about thirty in number in the upper eyelid, and somewhat fewer in the lower. They are imbedded in grooves in the inner surface of the tarsal plates, and correspond in length with the breadth of each plate ; they are, consequently, longer in the upper than in the lower eyelid. Their ducts open on the free margin of the lids by minute foramina, which cor- respond in number to the follicles. The peculiar parallel arrangement of these glands, side by side, forms a smooth layer adapted to the surface of the globe, over which they constantly glide. The use of their secretion is to prevent adhe- sions of the lids. Structure of the Meibomian Glands.-These glands are a variety of the cuta- neous sebaceous glands, each consisting of a single straight tube or follicle, hav- ing a caecal termination, and with numerous small secondary follicles opening into it. The tubes consist of basement membrane, covered by a layer of scaly epithelium; the secondary follicles are lined by a layer of polyhedral cells con- tinuous with the cells of the tube. The remainder of the follicle is filled with large polyhedral cells charged with fat. They are thus identical in structure with the sebaceous glands. The conjunctiva is the mucous membrane of the eye. It lines the inner surface of the eyelids, and is reflected over the fore part of the sclerotic and cornea. In each of these situations its structure presents some peculiarities. The palpebral portion of the conjunctiva is thick, opaque, highly vascular, and covered with numerous papillae, its deeper parts presenting a considerable amount of lymphoid tissue. At the margin of the lids it becomes continuous with the lining membrane of the ducts of the Meibomian glands, and, through the lachrymal canals, with the lining membrane of the lachrymal sac and nasal duct. At the outer angle of the upper lid it may be traced along the lachrymal ducts into the lachrymal gland, and at the inner angle of the eye it forms a semilunar fold, the plica semilunaris. The folds formed by the reflection of the conjunctiva from the lids on to the eye are called the superior and inferior palpebral folds, the 1 Recent observations have proved that the so-called " tarsal cartilages" do not contain any carti- lage-cells, and that the name is a misnomer. THE LACHRYMAL APPARATUS. 871 former being the deeper of the two. Upon the sclerotic the conjunctiva is loosely connected to the globe: it becomes thinner, loses its papillary structure, is transparent, and only slightly vascular in health. Upon the cornea the con- junctiva consists only of epithelium, constituting the anterior layer of the cornea (conjunctival epithelium) already described (see page 855). Lymphatics arise in the conjunctiva in a delicate zone around the cornea, from which the vessels run to the ocular conjunctiva. At the point of reflection of the conjunctiva from the lid on to the globe of the eye, termed the fornix conjunctiva;, are a number of mucous glands which are much convoluted. They are chiefly found in the upper lid. Other glands, analogous to Puncta lachrymalia. Fig. 497.-The Meibomian glands, etc., seen from the inner surface of the eyelids lymphoid follicles, and called by Henle trachoma glands, are found in the con- junctiva, and, according to Strohmeyer, are chiefly situated near the inner canthus of the eye. They were first described by Brush, in his description of Peyer's patches of the small intestines, as " identical structures existing in the under eye- lid of the ox." The nerves in the conjunctiva are numerous and form rich plexuses. According to Krause, they terminate in a peculiar form of tactile corpuscle, which he terms the "terminal bulb." The caruncula lachrymalis is a small, reddish, conical-shaped body, situated at the inner canthus of the eye, and filling up the small triangular space in this situa- tion, the lacus lachrymalis. It consists of a cluster of follicles similar in structure to the Meibomian, covered with mucous membrane, and is the source of the whitish secretion which constantly collects at the inner angle of the eye. A few slender hairs are attached to its surface. On the outer side of the caruncula is a slight semilunar fold of mucous membrane, the concavity of which is directed toward the cornea ; it is called the plica semilunaris. Muller found smooth muscular fibres in this fold, and in some of the domesticated animals a thin plate of cartilage has been discovered. This structure is considered to be the rudiment of the third eyelid in birds, the membrana nictitans. The Lachrymal Apparatus (Fig. 498). The lachrymal apparatus consists of the lachrymal gland, which secretes the tears, and its excretory ducts, which convey the fluid to the surface of the eye. This fluid is carried away by the lachrymal canals into the lachrymal sac, and along the nasal duct into the cavity of the nose. The lachrymal gland is lodged in a depression at the outer angle of the orbit, on the inner side of the external angular process of the frontal bone. It is of an 872 THE ORGANS OF SENSE. oval form, about the size and shape of an almond. Its upper convex surface is in contact with the periosteum of the orbit, to which it is connected by a few fibrous bands. Its under concave surface rests upon the convexity of the eyeball and upon the Superior and External recti muscles. Its vessels 'and nerves enter its posterior border, whilst its anterior margin is closely adherent to the back part of the upper eyelid, where it is covered to a slight extent by the reflection of the con- junctiva. The fore part of the gland is separated from the rest by a fibrous septum ; hence it is sometimes described as a separate lobe, called the palpebral portion of the gland (accessory gland of Rosenmuller). Its ducts, about seven in number, run obliquely beneath the mucous membrane for a short distance, and, separating from each other, open by a series of minute orifices on the upper and outer half Pun eta lachrymalia.' Fig. 498.-The lachrymal apparatus. Right side. of the conjunctiva near its reflection on to the globe. These orifices are arranged in a row, so as to disperse the secretion over the surface of the membrane. Structure of the Lachrymal G-land.-In structure and general appearance the lachrymal resembles the serous salivary glands (page 908). In the recent state the cells are so crowded with granules that their limits can hardly be defined. They contain an oval nucleus, and the cell-protoplasm is finely fibrillated. The lachrymal canals commence at the minute orifices, puncta lachrymalia, on the summit of a small conical elevation, the lachrymal papilla, seen on the margin of the lids at the outer extremity of the lacus lachrymalis. The superior canal, the smaller and shorter of the two, at first ascends, and then bends at an acute angle, and passes inward and downward to the lachrymal sac. The inferior canal at first descends, and then, abruptly changing its course, passes almost horizontally inward to the lachrymal sac. These canals are dense and elastic in structure and somewhat dilated at their angle. The mucous membrane is covered with scaly epithelium. The lachrymal sac is the upper dilated extremity of the nasal duct, and is lodged in a deep groove formed by the lachrymal bone and nasal process of the superior maxillary. It is oval in form, its upper extremity being closed in and rounded, whilst below it is continued into the nasal duct. It is covered by a fibrous expansion derived from the tendo oculi. and on the inner side it is crossed by the Tensor tarsi muscle (Horner's muscle, page 397), which is attached to the ridge on the lachrymal bone. Structure.-It consists of a fibrous elastic coat, lined internally by mucous membrane, the latter being continuous, through the lachrymal canals, with the mucous lining of the conjunctiva, and, through the nasal duct, with the pituitary membrane of the nose. THE LACHRYMAL APPARATUS. 873 The nasal duct is a membranous canal, about three-quarters of an inch in length, which extends from the lower part of the lachrymal sac to the inferior meatus of the nose, where it terminates by a somewhat expanded orifice, provided with an imperfect valve, the valve of Hasner, formed by the mucous membrane. It is contained in an osseous canal formed by the superior maxillary, the lachrymal, and the inferior turbinated bones, is narrower in the middle than at each extremity, and takes a direction downward, backward, and a little outward. It is lined by mucous membrane, which is continuous below with the pituitary lining of the nose. This membrane in the lachrymal sac and nasal duct is covered with ciliated epithelium as in the nose. Surface Form.-The palpebral fissure, or opening between the eyelids, is elliptical in shape, and differs in size in different individuals and in different races of mankind. In the Mongolian races, for instance, the opening is very small, merely a narrow fissure, and this makes the eye- ball appear small in these races, whereas the size of the eye is relatively very constant. The normal direction of the fissure is slightly oblique, in a direction upward and outward, so that the outer angle is on a slightly higher level than the inner. This is especially noticeable in the Mon- golian races, in whom, owing to the upward projection of the malar bone and the shortness of the external angular process of the frontal bone, the tarsal plate of the upper lid is raised at its outer part and gives an oblique direction to the palpebral fissure. When the eyes are directed forward, as in ordinary vision, the upper part of the cornea is covered by the upper lid, and the lower margin of the cornea corresponds to the level of the lower lid, so that about the lower three-fourths of the cornea is exposed under ordinary circum- stances. On the margins of the lids, about a quarter of an inch from the inner canthus, are two small openings, the puncta lachrymalia, the commencement of the lachrymal canals. They are best seen by everting the eyelids. In the natural condition they are in contact with the con- junctiva of the eyeball, and are maintained in this position by the Tensor tarsi muscle, so that the tears running over the surface of the globe easily find their way into the lachrymal canals. The position of the lachrymal sac into which the canals open is indicated by a little tubercle (page 226), which is plainly to be felt on the lower margin of the orbit. The lachrymal sac lies immediately above and to the inner side of this tubercle, and a knife passed through the skin in this situation would open the cavity. The position of the lachrymal sac may also be indicated by the tendo oculi or internal tarsal ligament. If both lids be drawn outward, so as to tense the skin at the inner angle, a prominent cord will be seen beneath the tightened skin. This is the tendo oculi, which lies immediately over the lachrymal sac, bisecting it, and thus forming a use- ful guide to its situation. A knife entered immediately beneath the tense cord would open the lower part of the sac. A probe introduced through this opening can be readily passed down- ward through the duct into the inferior meatus of the nose. The direction of the duct is down- ward, outward, and backward, and this course should be borne in mind in passing the probe, otherwise the point may be driven through the thin bony walls of the canal. A convenient plan is to direct the probe in such a manner that if it were pushed onward it would strike the first molar tooth of the lower jaw on the same side of the body. In other words, the surgeon standing in front of his patient should carry in his mind the position of the first molar tooth, and should push his probe onward in such a way as if he desired to reach this structure. Beneath the internal angular process of the frontal bone the pulley of the Superior oblique muscle of the eye can be plainly felt by pushing the finger backward between the upper and inner angle of the eye and the roof of the orbit; passing backward and outward from this pulley, the tendon can be felt for a short distance. Surgical Anatomy.-The eyelids are composed of various tissues, and consequently are liable to a variety of diseases. The skin which covers them is exceedingly thin and delicate, and is supported on a quantity of loose and lax subcutaneous tissue which contains no fat. In conse- quence of this it is very freely movable, and is liable to be drawn down by the contraction of neighboring cicatrices, and thus produce an eversion of the lid known as ectropion. Inversion of the lids [entropion] from spasm of the Orbicularis palpebrarum or from chronic inflammation of the palpebral conjunctiva may also occur. The eyelids are richly supplied with blood, and are often the seat of vascular growths, such as naevi. Rodent ulcer also frequently commences in this situation. The loose cellular tissue beneath the skin is liable to become extensively infil- trated either with blood or inflammatory products, producing very great swelling. Even from very slight injuries to this tissue the extravasation of blood may be so great as to produce consid- erable swelling of the lids and complete closure of the eye, and the same is the case when inflam- matory products are poured out. The follicles of the eyelashes or the sebaceous glands associated with these follicles maybe the seat of inflammation, constituting the ordinary "sty." The Meibomian glands are affected in the so-called "tarsal tumor ; " the tumor, according to some, being caused by the retained secretion of these glands; by others it is believed to be a neoplasm connected with the gland. The ciliary follicles are liable to become inflamed, constituting the disease known as blepharitis ciliaris, or "blear-eye. " Irregular or disorderly growth of the eye- lashes not unfrequently occurs, some of them being turned toward the eyeball and producing inflammation and ulceration of the cornea, and jxjssibly eventually complete destruction of the eye. The Orbicularis palpebrarum may be the seat of spasm, either in the form of slight quiv- 874 THE ORGANS OF SENSE. ering of the lids or repeated twitchings, most commonly due to errors of refraction in children, or more continuous spasm, due to some irritation of the fifth or seventh cranial nerve. The Orbicularis may be paralyzed, generally associated with paralysis of the other facial muscles. Under these circumstances the patient is unable to close the lids, and, if he attempts to do so, rolls the eyeball upward under the upper lid., The tears overflow from displacement of the lower lid, and the conjunctiva and cornea, being constantly exposed and the patient being unable to wink, become irritated from dust and foreign bodies. In paralysis of the Levator palpebrm superioris there is drooping of the upper eyelid and other symptoms of implication of the third nerve. The eyelids may be the seat of bruises, wounds, or burns. Tn these latter injuries adhe- sions of the margins of the lids to each other or adhesion of the lids to the globe may take place. The eyelids are sometimes the seat of emphysema after fracture of some of the thin bones forming the inner wall of the orbit. If shortly after such an injury the patient blows his nose, air is forced from the nostril through the lacerated structures into the connective tissue of the eyelids, which suddenly swell up and present the peculiar crackling characteristic of this affection. The lachrymal gland is occasionally, though rarely, the seat of inflammation, either acute or chronic; it is also sometimes the seat of tumors, benign or malignant, and for these may require removal. This may be done by an incision through the skin just below the eyebrow ; and the gland, being invested with a special capsule of its own, may be isolated and removed without opening the general cavity of the orbit. The canaliculi may be obstructed, either as a congenital defect or by some foreign body, as an eyelash or a dacryolith, causing the tears to run over the cheek. The canaliculi may also become occluded as the result of burns or injury; over- flow of the tears may in addition result from deviation of the puncta or from chronic inflamma- tion of the lachrymal sac. This latter condition is set up by some obstruction to the nasal duct frequently occurring in tubercular subjects. In consequence of this the tears and mucus accumu- late in the lachrymal sac, distending it. Suppuration in the lachrymal sac is sometimes met with ; this may be the sequel of a chronic inflammation ; or may occur after some of the erup- tive fevers in cases where the lachrymal passages were previously quite healthy. It may lead to lachrymal fistula. THE EAR. The organ of hearing is divisible into three parts-the external ear, the middle ear or tympanum, and the internal ear or labyrinth. The external ear consists of an expanded portion named pinna or auricle, and the auditory canal, or meatus. The former serves to collect the vibrations of the air by which sound is produced ; the latter conducts those vibrations to the tympanum. The pinna, or auricle (Fig. 498), is of an ovoid form, with its larger end directed upward. Its outer surface is irregularly concave, directed slightly forward, and presents numerous eminences and depressions which result from the foldings of its fibro-cartilaginous element. To each of these names have been assigned. Thus the external prominent rim of the auricle is called the helix. Another curved prominence, parallel with and in front of the helix, is called the antihelix; this bifurcates above, so as to enclose a triangular depression, the fossa of the antihelix. Thenarrow curved depression between the helix and antihelix is called the fossa of the helix (fossa innominata or scaphoidea}; the antihelix describes a curve round a deep, capacious cavity, the concha, which is partially divided into two parts by the commencement of the helix. In front of the concha, and projecting backward over the meatus, is a small pointed eminence, the tragus, so called from its being generally covered on its under surface with a tuft of hair resem- bling a goat's beard. Opposite the tragus, and separated from it by a deep notch (incisura intertragicafxs a small tubercle, the antitragus. Below this is the lobule, composed of tough areolar and adipose tissue, wanting the firmness and elasticity of the rest of the pinna. Structure of the Pinna.-The pinna is composed of a thin plate of yellow fibro- cartilage covered with integument, and connected to the surrounding parts by the extrinsic ligaments and muscles, and to the commencement of the external auditory canal. The integument is thin, closely adherent to the cartilage, and furnished with sebaceous glands, which are most numerous in the concha and scaphoid fossa. The cartilage of the pinna consists of one single piece: it gives form to this part of the ear, and upon its surface are found all the eminences and depressions above described. It does not enter into the construction of all parts of the auricle: thus it does not form a constituent part of the lobule; it is deficient THE EAR. 875 also between the tragus and beginning of the helix, the notch between them being filled up by dense fibrous tissue. At the front part of the pinna, where the helix bends upward, is a small projection of cartilage, called the process of the helix. The cartilage of the pinna presents several intervals or fissures in its substance which partially separate the different parts. The fissure of the helix is a short vertical slit situated at the fore part of the pinna, immediately behind a small conical projection of cartilage, opposite the first curve of the helix (process of the helix). Another fissure, the fissure of the tragus, is seen upon the anterior sur- face of the tragus. The antihelix is divided below, by a deep fissure, into two parts : one part termi- nates by a pointed, tail-like ex- tremity (processus caudatus) ; the other is continuous with the anti- tragus. The cartilage of the Fig. 499.-The pinna, or auricle. Outer surface. Fig. 500.-The muscles of the pinna. pinna is very pliable, elastic, of a yellowish color, and belongs to that form of cartilage which is known under the name of yellow fibro-cartilage. The ligaments of the pinna consist of two sets: 1. The extrinsic set, or those connecting it to the side of the head. 2. The intrinsic set, or those connecting the various parts of its cartilage together. The extrinsic ligaments, the most important, are two in number, anterior and posterior. The anterior ligament extends from the process of the helix to the root of the zygoma. A few fibres connect the tragus to the root of the zygoma. The posterior ligament passes from the posterior surface of the concha to the outer surface of the mastoid process of the temporal bone. The intrinsic ligaments are also two in number. Of these, one is a strong fibrous band stretching across from the tragus to the commencement of the helix, completing the meatus in front and partly encircling the boundary of the concha; the other extends between the concha and the processus caudatus. The muscles of the pinna (Fig- 477) consist of two sets : 1. The extrinsic, which connect it with the side of the head, moving the pinna as a whole-viz. the Attollens, Attrahens, and Retrahens aurem (page 396); and 2. The intrinsic, which extend from one part of the auricle to another-viz. : Helicis major. Helicis minor. Tragic us. Antitragicus. Transversus auriculae. Obliquus auris. 876 THE ORGANS OF SENSE. The Musculus helicis major is a narrow vertical band of muscular fibres, situated upon the anterior margin of the helix. It arises below from the process of the helix, and is inserted into the anterior border of the helix, just where it is about to curve backward. It is pretty constant in its existence. The Musculus helicis minor is an oblique fasciculus, attached to that part of the helix which commences from the bottom of the concha. The Tragicus is a short, flattened band of muscular fibres situated upon the outer surface of the tragus, the direction of its fibres being vertical. The Antitragicus arises from the outer part of the antitragus: its fibres are inserted into the processus caudatus of the helix. This muscle is usually very distinct. The Transversus auriculce is placed on the cranial surface of the pinna. It consists of radiating fibres, partly tendinous and partly muscular, extending from the convexity of the concha to the prominence corresponding with the groove of the helix. The Obliquus auris (Todd) consists of a few fibres extending from the upper and back part of the concha to the convexity immediately above it. The arteries of the pinna are-the posterior auricular from the external carotid, the anterior auricular from the temporal, and an auricular branch from the occipital artery. The veins accompany the corresponding arteries. The nerves are-the auricularis magnus, from the cervical plexus ; the posterior auricular, from the facial to the muscles of the pinna; the auricular branch of the pneumogastric; the auriculo-temporal branch of the inferior maxillary nerve; the occipitalis minor from the cervical plexus ; and the occipitalis major or internal branch of the posterior division of the second cervical nerve. The Auditory Canal (meatus auditorius externus) (Fig. 500) extends from the bottom of the concha to the membrana tympani. It is about an inch and a quarter in length, its direction is obliquely forward and inward, and it is slightly curved upon itself, so as to be higher in the middle than at either extremity. It forms an oval cylindrical canal, the greatest diameter being in the vertical direction at the external orifice, but in the transverse direction at the tympanic end. The calibre of the canal is narrowest about the middle. The membrana tympani, which occupies the termination of the meatus, is obliquely directed, in consequence of which the floor of the canal is longer than the roof, and the anterior wall longer than the posterior. The auditory canal is formed partly by cartilage and mem- brane, and partly by bone, and is covered by skin. The cartilaginous portion is about half an inch in length, being rather less than half the canal; it is formed by the cartilage of the concha and tragus, prolonged inward, and firmly attached to the circumference of the auditory process of the temporal bone. The cartilage is deficient at its upper and back part, its place being supplied by fibrous membrane. This part of the canal is rendered extremely movable by two or three deep fissures (incisura; Santorini), which extend through the cartilage in a vertical direction. The osseous portion is about three-quarters of an inch in length, and narrower than the cartilaginous portion. It is directed inward and a little forward, forming a slight curve in its course, the convexity of which is upward and back- ward. Its inner end, which communicates, in the dry bone, with the cavity of the tympanum, is smaller than the outer and sloped, the anterior wall projecting beyond the posterior about two lines; it is marked, except at its upper part, by a narrow groove for the insertion of the membrana tympani. Its outer end is dilated, and rough, in the greater part of its circumference, for the attachment of the cartilage of the pinna. Its vertical transverse section is oval, the greatest diameter being from above downward. The front and lower parts of this canal are formed by a curved plate of bone, which, in the foetus, exists as a separate ring (tympanic plate), incomplete at its upper part. The skin lining the meatus is very thin, adheres closely to the cartilaginous THE EAR. 877 and osseous portion of the tube, and covers the surface of the membrana tympani, forming its outer layer. After maceration the thin pouch of epidermis, when withdrawn, preserves the form of the meatus. In the thick subcutaneous tissue of the cartilaginous part of the meatus are numerous ceruminous glands, which Incus. I I Malleus. i { \ Stapes. ■Semi-circular Canals. , Vestibule. r i \ Cavity of \ Tympanum\ secrete the ear-wax. They resemble in structure sweat-glands, and their ducts open on the surface of the skin. The arteries supplying the meatus are branches from the posterior auricular, internal maxillary, and temporal. The nerves are chiefly derived from the auriculo-temporal branch of the inferior maxillary nerve. Surface Form.-At the point of junction of the osseous and cartilaginous portions the tube forms an obtuse angle, which projects into the tube at its antero-inferior wall. This produces a sort of constriction in this situation, and renders it the narrowest portion of the canal-an im- portant point to be borne in mind in connection with the presence of foreign bodies in the ears. The cartilaginous is connected to the bony part by fibrous tissue, which renders the outer part of the tube very movable, and therefore by drawing the pinna upward and backward the canal is rendered almost straight. At the external orifice are a few short, crisp hairs which serve to prevent the entrance of small particles of dust, or flies or other insects. In the external auditory meatus the secretion of the ceruminous glands serves to catch any small particles which may find their way into the canal, and prevent their reaching the membrana tympani, where their presence might excite irritation. In young children the meatus is very short, the osseous part being very deficient, and consisting merely of a bony ring (the tympanic plate}, which supports the membrana tympani. In the foetus the osseous part is entirely absent. The shortness of the canal in children should be borne in mind in introducing the aural speculum, so that it be not pushed in too far, at the risk of injuring the membrana tympani; indeed, even in the adult the speculum should never be introduced beyond the constriction which marks the junction of the osseous and cartilaginous portions. In using this instrument it is advisable that the pinna should be drawn upward, backward, and a little outward, so as to render the canal as straight as possible, and thus assist the operator in obtaining, by the aid of reflected light, a good view of the membrana tympani. Just in front of the membrane is a well-marked depression, situated on the floor of the canal and bounded by a somewhat prominent ridge; in this foreign bodies may become lodged. By aid of the speculum, combined with traction of the auricle upward and backward, the whole of the membrana tympani is rendered visible. It is a pearly-gray mem- brane, slightly glistening in the adult, placed obliquely, so as to form with the floor of the meatus a very acute angle, while with the roof it forms an obtuse angle. At birth it is more horizontal, situated in almost the same plane as the base of the skull. About midway between the anterior and posterior margins of the membrane, and extending from the centre obliquely upward, is a reddish-yellow streak ; this is the handle of the malleus, which is inserted into the membrane. At the upper part of this streak, close to the roof of the meatus, a little white rounded promi- nence is plainly to be seen ; this is the processus brevis of the malleus, projecting against the membrane. The membrana tympani does not present a plane surface ; on the contrary, its centre is drawn inward, on account of its connection with the handle of the malleus, and thus the external surface is rendered concave. Fig. 501.-A front view of the organ of hearing. Right side. 878 THE ORGANS OF SENSE. Middle Ear, or Tympanum. The middle ear, or tympanum, is an irregular cavity, compressed from without inward, and situated within the petrous bone. It is placed above the jugular fossa; the carotid canal lying in front, the mastoid cells behind, the meatus auditorius externally, and the labyrinth internally. It is filled with air, and communicates with the pharynx by the Eustachian tube. The tympanum is traversed by a chain of movable bones, which connect the membrana tympani with the labyrinth, and serve to convey the vibrations communicated to the membrana tympani across the cavity of the tympanum to the internal ear. The cavity of the tympanum measures about five lines from before backward, three lines in the vertical direction, and between two and three in the transverse, being a little broader behind and above than it is below and in front. It is bounded externally by the membrana tympani and meatus, internally, by the outer surface of the internal ear, and communicates, behind, with the mastoid cells, and in front with the Eustachian tube and canal for the Tensor tympani. Its roof and floor are formed by thin osseous laminae, the one forming the roof being a thin plate situated on the anterior surface of the petrous portion of the temporal bone, close to its angle of junction with the squamous portion of the same bone. The roof is broad, flattened, and formed of a thin plate of bone which separates the cranial and tympanic cavities. The floor is narrow, and corresponds to the jugular fossa, which lies beneath. It presents, near the inner wall, a small aperture for the passage of Jacobson's nerve. The outer wall is formed mainly by the membrana tympani, partly by the ring of bone into which this membrane is inserted. Close to it are three small apertures- the iter chord® posterius, the Glaserian fissure, and the iter chord® anterius. The aperture of the iter chordce posterius is in the angle of junction between the posterior and external walls of the tympanum, immediately behind the membrana tympani and on a level with its centre ; it leads into a minute canal, which descends in front of the aqueductus Fallopii and terminates in that canal near the stylo- mastoid foramen. Through it the chorda tympani nerve enters the tympanum. The Glaserian fissure opens just above and in front of the ring of bone into which the membrana tympani is inserted; in this situation it is a mere slit about a line in length. It lodges the long process of the malleus and gives passage to some tympanic vessels. The aperture of the iter chordce anterius is seen just above the preceding fissure ; it leads into a canal (canal of Huguier), which runs parallel with the Glaserian fissure. Through it the chorda tympani nerve leaves the tympanum. The internal wall of the tympanum (Fig. 502) is vertical in direction and looks directly outward. It presents for examination the following parts : Fenestra ovalis. Fenestra rotunda. Promontory. Ridge of the aqueductus Fallopii. Pyramid. Opening for the Stapedius. The fenestra ovalis is a reniform opening leading from the tympanum into the vestibule; its long diameter is directed horizontally, and its convex border is upward. The opening in the recent state is occupied by the base of the stapes, which is connected to the margin of the foramen by an annular ligament. The/mestra rotunda is an aperture placed at the bottom of a funnel-shaped depression leading into the cochlea. It is situated below and rather behind the fenestra ovalis, from which it is separated by a rounded elevation, the promontory ; it is closed in the recent state by a membrane (membrana tympani secundaria, Scarpa). This membrane is concave toward the tympanum, convex toward the cochlea. It consists of three layers: the external, or mucous, derived from the mucous lining of the tympanum ; the internal, or serous, from the lining membrane of the cochlea ; and an intermediate, or fibrous layer. THE TYMPANUM. 879 The promontory is a rounded hollowT prominence, formed by the projection outward of the first turn of the cochlea ; it is placed between the fenestrae, and is furrowed on its surface by three small grooves which lodge branches of the tympanic plexus. The rounded eminence of the aqueductus Fallopii, the prominence of the bony canal in which the portio dura is contained, traverses the inner wall of the tym- panum above the fenestra ovalis, and behind that opening curves nearly vertically downward along the posterior wall. The pyramid is a conical eminence situated immediately behind the fenestra ovalis, and in front of the vertical portion of the eminence above described ; it is hollow in the interior, and contains the Stapedius muscle ; its summit projects forward toward the fenestra ovalis, and presents a small aperture which transmits the tendon of the muscle. The cavity in the pyramid is prolonged into a minute canal, which communicates with the aqueductus Fallopii and transmits the nerve which supplies the Stapedius. The posterior wall of the tympanum is wider above than below, and presents for examination the Openings of the mastoid cells These consist of one large irregular aperture and several smaller openings, Chorda tympani. Fig. 502.-View of inner wall of tympanum. (Enlarged.) situated at the upper part of the posterior wall; they lead into canals which communicate with large irregular cavities contained in the interior of the mas- toid process. These cavities vary considerably in number, size, and form ; they are lined by mucous membrane continuous with that lining the cavity of the tympanum. The anterior wall of the tympanum is wider above than below; it corresponds with the carotid canal, from which it is separated by a thin plate of bone, perforated by the tympanic branch of the internal carotid. It presents for examination the Canal for the Tensor tympani. Orifice of the Eustachian tube. The processus cochleariformis. The orifice of the canal for the Tensor tympani and the orifice of the Eustachian tube are situated at the upper part of the anterior wall, being separated from each other by a thin, delicate, horizontal plate of bone, the processus cochleariformis. These canals run from the tympanum, forward, inward, and a little downward, to the retiring angle between the squamous and petrous portions of the temporal bone. The canal for the Tensor tympani is the superior and the smaller of the two ; it is rounded, and lies beneath the upper surface of the petrous bone, close to the 880 THE ORGANS OF SENSE. hiatus Fallopii. The tympanic end of this canal forms a conical eminence which is prolonged backward into the cavity of the tympanum, and is perforated at its summit by an aperture which transmits the tendon of the muscle contained in it. This eminence is sometimes called the anterior pyramid. The canal contains the Tensor tympani muscle. The Eustachian tube is the channel through which the tympanum communi- cates with the pharynx. Its length is from an inch and a half to two inches, and its direction downward, forward, and inward. It is formed partly of bone, partly of cartilage and fibrous tissue. The osseous portion is about half an inch in length. It commences in the lower part of the anterior wall of the tympanum, below the processus cochleari- formis, and, gradually narrowing, terminates in an oval dilated opening at the angle of junction of the petrous and squamous portions, its extremity presenting a jagged margin which serves for the attachment of the cartilaginous portion. The cartilaginous portion, about an inch in length, is formed of a triangular plate of elastic fibro-cartilage, curled upon itself, an interval being left below, between the margins of the cartilage, which is completed by fibrous and muscular tissue. Its canal is narrow behind, wide, expanded, and somewhat trumpet-shaped in front, terminating by an oval orifice at the upper part and side of the pharynx, behind the back part of the inferior meatus. Through this canal the mucous membrane of the pharynx is continuous with that which lines the tympanum. The mucous membrane is covered with ciliated epithelium. The membrana tympani separates the cavity of the tympanum from the bottom of the external meatus. It is a thin, semi-transparent membrane, nearly oval in form, somewhat broader above than below, and directed very obliquely downward and inward. Its circumference is contained in a groove at the inner end of the meatus, which skirts the circumference of this part, excepting above. The handle of the malleus descends vertically between the inner and middle layers of this membrane as far down as its centre, where it is firmly attached, drawing the membrane inward, so that its outer surface is concave, its inner convex. Structure.-This membrane is composed of three layers, an external (cuticular), a middle (fibrous), and an internal (mucous). The cuticular lining is derived from the integument lining the meatus. The fibrous layer consists of fibrous and elastic tissues ; some of the fibres radiate from near the centre to the circumference; others are arranged, in the form of a dense circular ring, round the attached margin of the membrane. The mucous lining is derived from the mucous lining of the tympanum. The vessels pass to the membrana tympani along the handle of the malleus, and are distributed between its layers. Ossicles of the Tympanum (Fig. 503). The tympanum is traversed by a chain of movable bones three in number, the malleus, incus, and stapes. The former is attached to the membrana tympani, the latter to the fenestra ovalis, the incus being placed between the two, to both of which it is connected by delicate articulations. The Malleus, so named from its fancied resemblance to a hammer, consists of a head, neck, and three processes-the handle or manubrium, the processus gracilis, and the processus brevis. The head is the large upper extremity of the bone; it is oval in shape, and articulates posteriorly with the incus, being free in the rest of its extent. The neck is the narrow contracted part just beneath the head, and below this is a prominence to which the various processes are attached. The manubrium is a vertical process of bone which is connected by its outer margin with the membrana tympani. It decreases in size toward its extremity, where it is curved slightly forward, and flattened from within outward. On the inner side, near its upper end, is a slight projection, into which the tendon of the Tensor tympani is inserted. THE TYMPANUM. 881 The processus gracilis is a long and very delicate process which passes from the eminence below the neck forward and outward to the Glaserian fissure, to which it is connected by bone and ligamentous fibres. The processus brevis is a slight conical projection which springs from the root of the manubrium, and lies in contact with the membrana tympani. The Incus has received its name from its supposed resemblance to an anvil, but it is more like a bicuspid tooth, with two roots, which differ in length and are widely separated from each other. It consists of a body and two processes. The body is somewhat quadrilateral, but compressed laterally. On the anterior surface of its summit is a deeply concavo-convex facet, which articulates with the malleus ; in the fresh state it is covered with cartilage and lined with synovial membrane. The two processes diverge from one another nearly at right angles. The short process, somewhat conical in shape, projects nearly horizontally backward, and is attached to the margin of the opening leading into the mastoid cells by ligamentous fibres. The long process, longer and more slender than the preceding, descends nearly vertically behind and parallel to the handle of the mal- leus, and, bending inward, terminates in a rounded globular projection, the os orbiculare, or lenticular process, which is tipped with cartilage and articulates with the head of the stapes. In the foetus the os orbiculare exists as a separate bone, but becomes united to the long process of the incus in the adult. The Stapes, so called from its close resemblance to a stirrup, consists of a head, neck, two branches, and a base. The head presents a depression, tipped with cartilage, which articulates with the os orbiculare. The neck, the constricted part of the bone below the head, receives the insertion of the Stapedius muscle. The two branches (crura) diverge from the neck, and are connected at their extremities by a flattened, oval-shaped plate (the base), which forms the foot of the stirrup, and is fixed to the margin of the fenestra ovalis by ligamentous fibres. Ligaments of the Ossicula.-These small bones are connected with each other and with the walls of the tympanum by ligaments, and moved by small muscles. The articular surfaces of the malleus and incus and the orbicular process of the incus and head of the stapes are covered with cartilage, connected together by delicate capsular ligaments and lined by synovial membrane. The ligaments con- necting the ossicula with the walls of the tympanum are four in number-two for the malleus, one for the incus, and one for the stapes. The anterior ligament of the malleus was formerly described by Sbmmerring as a muscle (Laxator tympani). It is now, however, believed by most observers to consist of ligamentous fibres only. It is attached by one extremity to the neck of the malleus, just above the processus gracilis, and by the other to the anterior wall of the tympanum, close to the Glaserian fissure, some of its fibres being pro- longed through the fissure. The suspensory ligament of the malleus is a delicate, round bundle of fibres which descends perpendicularly from the roof of the tympanum to the head of the malleus. The posterior ligament of the incus is a short, thick, ligamentous band which connects the extremity of the short process of the incus to the posterior wall of the tympanum, near the margin of the opening of the mastoid cells. The annular ligament of the stapes connects the circumference of the base of this bone to the margin of the fenestra ovalis. Processus brevis. Stapes' Os orbiculare. / Head. Crura. Fig. 503.-The small bones of the ear, seen from the outside. (Enlarged.) 882 THE ORGANS OF SENSE. A suspensory ligament of the incus has been described by Arnold, descending from the roof of the tympanum to the upper part of the incus, near its articulation with the malleus. The muscles of the tympanum are two : Tensor tympani. Stapedius. The Tensor tympani, the larger, is contained in the bony canal above the osseous portion of the Eustachian tube, from which it is separated by the processus cochleariformis. It arises from the under surface of the petrous bone, from the cartilaginous portion of the Eustachian tube, and from the osseous canal in which it is contained. Passing backward through the canal, it terminates in a slender tendon which enters the tympanum and makes a sharp bend outward round the extremity of the processus cochleariformis, and is inserted into the handle of the malleus near its root. It is supplied by a branch from the otic ganglion. The Stapedius arises from the side of a conical cavity hollowed out of the inte- rior of the pyramid; its tendon emerges from the orifice at the apex of the pyra- mid, and, passing forward, is inserted into the neck of the stapes. Its surface is aponeurotic, its interior fleshy, and its tendon occasionally contains a slender bony spine, which is constant in some mammalia. It is supplied by the tympanic branch of the facial nerve. Actions.-The Tensor tympani draws the membrana tympani inward and thus heightens its tension. The Stapedius draws the head of the stapes backward, and thus causes the base of the bone to rotate on a vertical axis drawn through its own centre: in doing this the back part of the base would be pressed inward toward the vestibule, while the fore part would be drawn from it. It probably compresses the contents of the vestibule. The mucous membrane of the tympanum is thin, slightly vascular, and continuous with the mucous membrane of the pharynx through the Eustachian tube. It invests the ossicula and the muscles and nerves contained in the tympanic cavity, forms the internal layer of the membrana tympani, covers the foramen rotundum, and is reflected into the mastoid cells, which it lines throughout. In the tympanum and mastoid cells this membrane is pale, thin, slightly vascular, and covered with ciliated epithelium. In the osseous portion of the Eustachian tube the membrane is thin, but in the cartilaginous portion it is very thick, highly vascular, covered with laminar ciliated epithelium, and provided with numerous mucous glands. The arteries supplying the tympanum are six in number. Three of them are larger than the rest-viz. the tympanic branch of the internal maxillary, which supplies the membrana tympani; the Vidian and the stylo-mastoid branch of the posterior auricular, which supplies the back part of the tympanum and mastoid cells. The smaller branches are-the petrosal branch of the middle meningeal, which enters through the hiatus Fallopii ; a branch from the ascending pharyngeal, and another from the Vidian which pass up the Eustachian tube; and the tympanic branch from the internal carotid, given off in the carotid canal and perforating the thin anterior wall of the tympanum. The veins of the tympanum terminate in the temporo-maxillary vein and in the superior petrosal sinus. The nerves of the tympanum may be divided into-1, those supplying the muscles ; 2, those distributed to the lining membrane ; 3, branches communicating with other nerves. Nerves to Muscles.-The Tensor tympani is supplied by a branch from the otic ganglion; the Stapedius, by the tympanic branch of the facial (Sbmmerring). The nerves distributed to the lining membrane are derived from the tympanic plexus. The communications which take place in the tympanum are between the tympanic branch of the glosso-pharyngeal with the sympathetic and with filaments derived from the intumescentia ganglioformis of the facial. The tympanic branch of the glosso-pharyngeal (Jacobson's nerve) enters the THE INTERNAL EAR. 883 tympanum by an aperture in its floor, close to the inner wall, and divides into branches w'hich are contained in grooves upon the surface of the promontory forming the tympanic plexus. Its branches of distribution are-one to the fenestra rotunda, one to the fenestra ovalis, and one to the lining membrane of the tympanum and Eustachian tube. Its branches of communication are three, and occupy separate grooves on the surface of the promontory. One branch, the small deep petrosal, arches forward and downward to the carotid canal to join the carotid plexus. A second, the Zony petrosal nerve, runs forward through a canal close to or in the processus cochleari- formis, and enters the foramen lacerum medium, where it joins the carotid plexus of the sympathetic, and generally the large superficial petrosal nerve. The third branch runs upward through the substance of the petrous portion of the temporal bone. In its course it passes by the gangliform enlargement of the facial nerve, and, receiving a connecting filament from it, becomes thesznaZZ sitperficial petrosal nerve. It then enters the skull through a small aperture, situated external to the hiatus Fallopii on the anterior surface of the petrous bone, courses forward across the base of the skull, and emerges through a foramen in the middle fossa (sometimes through the foramen ovale) and joins the otic ganglion. Tbe chorda tympani is given off from the facial as it passes vertically down- ward at the back of the tympanum, about a quarter of an inch before its exit from the stylo-mastoid foramen. It passes from below upward and forward in a distinct canal, and enters the cavity of the tympanum through an aperture, iter chordceposterius, on its posterior wall between the opening of the mastoid cells and the attachment of the membrana tympani, and becomes invested with mucous membrane. It passes forward through the cavity of the tympanum, between the handle of the malleus and vertical ramus of the incus, to its anterior inferior angle, and emerges from that cavity through a foramen at the inner end of the Glaserian fissure, which is called the iter chordae anterius, or canal of Huguier. The Internal Ear, or Labyrinth. The internal ear is the essential part of the organ, receiving the ultimate distribution of the auditory nerve. It is called the labyrinth, from the complexity of its shape, and consists of three parts-the vestibule, semicircular canals, and cochlea. It is formed by a series of cavities channelled out of the substance of the petrous bone, communicating externally with the cavity of the tympanum through the fenestra ovalis and rotunda, and internally with the meatus auditorius internus, which contains the auditory nerve. Within the osseous labyrinth is contained the membranous labyrinth, upon which the ramifications of the auditory nerve are distributed. The Vestibule (Fig. 504) is the common central cavity of communication between the parts of the internal ear. It is situated on the inner side of the tympanum, behind the cochlea, and in front of the semicircular canals. It is somewhat ovoidal in shape from before backward, flattened from within outward, and measures about one-fifth of an inch from before backward, as well as from above downward, being narrower from without inward. On its outer or tympanic wall is the fenestra ovalis, closed, in the recent state, by the base of the stapes and its annular ligament. On its inner wall, at the fore part, is a small circular depression, fovea hemispherica, which is perforated, at its anterior and inferior part, by several minute holes (macula cribrosai) for the passage of the filaments of the auditory nerve ; and behind this depression is a vertical ridge, the pyramidal eminence (crista vestibuli). At the hinder part of the inner wall is the orifice of the aque- ductus vestibuli, which extends to the posterior surface of the petrous portion of the temporal bone. It transmits a small vein, and, according to some, contains a tubular prolongation of the lining membrane of the vestibule, which ends in a cul-de-sac between the layers of the dura mater within the cranial cavity. On the upper wall or roof is a transversely oval depression, fovea semi-elliptica, 884 THE ORGANS OF SENSE. separated from the fovea hemispherica by the pyramidal eminence already mentioned. Behind, the semicircular canals open into the vestibule by five orifices. In front is a large oval opening which communicates with the scala vestibuli of the cochlea by a single orifice, apertura scales vestibuli cochleae. The Semicircular canals are three bony canals situated above and behind the vestibule. They are of unequal length, compressed from side to side, and describe the greater part of a circle. They measure about one-twentieth of an inch in diameter, and each presents a dilatation at one end, called the ampulla, which measures more than twice the diameter of the tube. These canals open into the vestibule by five orifices, one of the apertures being common to two of the canals. The superior semicircular canal is vertical in direction, and stretches across the petrous portion of the temporal bone, at right angles to its posterior surface; its arch forms a round projection on the anterior surface of the petrous bone. It describes about two-thirds of a circle. Its outer extremity, which is ampullated, commences by a distinct orifice in the upper part of the vestibule ; the opposite end Opening of aqueductus vestibuli. Bristle passed through foramen rotundum Opening of aqueductus cochleae. Fig. 504.-The osseous labyrinth laid open. (Enlarged.) of the canal, which is not dilated, joins with the corresponding part of the pos- terior canal, and opens by a common orifice with it in the back part of the vestibule. The posterior semicircular canal, also vertical in direction, is directed back- ward, nearly parallel to the posterior surface of the petrous bone; it is the longest of the three: its ampullated end commences at the lower and back part of the vestibule, its opposite end joining to form the common canal already mentioned. The external or horizontal canal is the shortest of the three, its arch being directed outward and backward; thus each semicircular canal stands at right angles to the other two. Its ampullated end corresponds to the upper and outer angle of the vestibule, just above the fenestra ovalis; its opposite end opens by a distinct orifice at the upper and back part of the vestibule. The Cochlea bears some resemblance to a common snail-shell: it forms the anterior part of the labyrinth, is conical in form, and placed almost horizontally in front of the vestibule; its apex is directed forward and outward toward the upper and front part of the inner wall of the tympanum ; its base corresponds with the anterior depression at the bottom of the internal auditory meatus, and is perforated by numerous apertures for the passage of the cochlear branch of the THE INTERNAL EAR. 885 auditory nerve. It measures about a quarter of an inch in length, and its breadth toward the base is about the same. It consists of a conical-shaped central axis, the modiolus or columella ; of a canal wound spirally round the axis for two turns and a half, from the base to the apex ; and of a delicate lamina (the lamina spiralis) contained within the canal, which follows its windings and partially subdivides it into two. The central axis, or modiolus, is conical in form, and extends from the base to the apex of the cochlea. Its base is broad, corresponds with the first turn of the cochlea, and is perforated by numerous orifices, which transmit filaments of the cochlear branch of the auditory nerve; the axis diminishes rapidly in size in the second coil, and terminates within the last half-coil, or cupola, in an expanded delicate, bony lamella, which resembles the half of a funnel divided longitudinally, and is called the infundibulum ; the broad part of this funnel is directed toward the summit of the cochlea, and blends with the cupola or last half-turn of the spiral canal of the cochlea. At this point the two larger scahe of the cochlea, the scala tympani and scala vestibuli, communicate by an opening called the helico- trema. The outer surface of the modiolus forms part of the wall of the spiral canal, and is dense in structure; but its centre is channelled, as far as the last half-coil, by numerous branching canals, which transmit nervous filaments in regular succession into the canal of the cochlea or on to the surface of the lamina spiralis. One of these, larger than the rest, occupies the centre of the modiolus, and is named the canalis centralis modioli; it extends from the base to the extremity of the modiolus, and transmits a small nerve and artery (arteria centralis modioli). The spiral canal (Fig. 505) takes two turns and a half round the modiolus. It is about an inch and a half in length, measured along its outer wall, and Fig. 505.-The cochlea laid open. (Enlarged.) diminishes gradually in size from the base to the summit, where it terminates in a cul-de-sac, the cupola, which forms the apex of the cochlea. The commence- ment of this canal is about the tenth of an inch in diameter; it diverges from the modiolus toward the tympanum and vestibule and presents three open- ings. One, the fenestra rotunda, communicates with the tympanum; in the recent state this aperture is closed by a membrane, the membrana tympani secundaria. Another aperture, of an oval form, enters the vestibule. The third is the aperture of the aqueductus cochlea*, leading to a minute funnel-shaped canal, which opens on the basilar surface of the petrous bone and transmits a small vein. The interior of the spiral canal (Fig. 506) is partially divided into two, in the dry state, by a thin bony plate, the lamina spiralis, which consists of two thin lamellae of bone, between which are numerous canals for the passage of nerve- fibres. This lamina projects from the modiolus into the canal, but does not reach more than halfway toward the outer wall of the tube. From its extremity a thin membrane extends to the outer wall, and completes the division of the canal into an upper compartment, the scala vestibuli, and a lower one, the scala tympani. 886 THE ORGANS OF SENSE. By a second membrane a portion of the upper of these two canals is cut off from the rest, constituting the scala media. The lamina spiralis ends above in a hook- shaped process which partly bounds the helicotrema. At the point where the osseous lamina is attached to the modiolus is a small canal, which winds round the modiolus, and was denominated by Rosenthal the canalis spiralis modioli; it is occupied by a swelling of the cochlear nerve, the ganglion spirale, in which Fig. 506.-Longitudinal section of the cochlea, showing the relations of the scalae, the ganglion spirale, etc. S. V. Scala vestibuli. S. T. Scala tympani. S. M. Scala media. L. S. Ligamentum spirale. G. S. Ganglion spi- rale. ganglion-cells are found, and from which the nerves pass to the osseous lamina and organ of Corti. The osseous lamina, as above stated, extends only part of the distance between the modiolus and the outer bony wall of the cochlea. Near its outer end the periosteum on the upper or vestibular surface of the lamina swells up into an elevation which is called the limbus laminae spiralis (" denticulate lamina " of Todd and Bowman). The lamina spiralis terminates in a grooved extremity, the sulcus spiralis, which presents the form of the letter C: the upper part of the letter, being formed by the overhanging extremity of the limbus, is named the labium vestibulare; the lower part, prolonged and tapering, is called the labium tympani- cum (Fig. 507). From the labium tympanicum a thin membrane extends over to the bony wall of the cochlea, completing the scala tympani. This membrane is called the membrana basilaris. At its outer attachment it swells out so as to form a thick triangular structure, which was regarded as a muscle by Todd and Bowman (cochlearis), but is now recognized as ligamentous-the ligamentum spirale. Between the labium vestibulare and the attachment of the membrane of Reissner, presently to be described, a very delicate membrane extends over to the outer wall of the cochlea, running nearly parallel to the membrana basilaris. It was described by Corti, and covers over the organ which is called after his name, and is therefore called membrane of Corti, or membrana tectoria. Farther inward, near the commencement of the limbus lamime spiralis, another delicate mem- brane, the membrane of Reissner, is attached to the vestibular surface of the periosteum of the osseous lamina and stretches across to the outer wall of the cochlea. The canal which lies below the osseous lamina and membrana basilaris is the scala tympani; that which is bounded by the osseous lamina and membrane of Reissner, the scala vestibuli; while the space between the membrane of Reissner and membrana basilaris is generally described as the Scala media, Can- alis membranacea, or Canalis cochleae, and this is the nomenclature which will be used here. Others, however, apply the name canalis cochleae only to the canal THE INTERNAL EAR. 887 lying between the membrane of Reissner and the membrana tectoria, which con- tains no object for description, while the space lying between the membrana tec- toria and membrana basilaris is described by itself as a fourth canal-the ductus cochlearis or ductus auditorius} The latter is the space in which the organ of Corti2 is contained. This organ (Fig. 507) is situated upon the membrana basila- ris, and appears at first sight as a papilla, winding spirally with the turns of this membrane throughout the whole length of the cochlea, from which circumstance it has been designated the papilla spiralis. More accurately viewed, it is seen to Membrane of Corti. [Sulcus spiralis. Organ of Membrana basilaris. Fig. 507.-Floor of scala media, showing the organ of Corti, etc. be composed of a remarkable arrangement of cells which may be likened to the keyboard of a pianoforte. Of these cells, the two central ones are rod-like bodies, and are called the inner and outer rods of Corti. They are placed erect on the basilar membrane at some little distance from each other, the space between them being denominated the zona arcuata; they are inclined toward each other, so as to meet at their opposite extremities and form a series of arches roofing over the zona arcuata, thus forming a minute tunnel between them and the basilar membrane, which ascends spirally through the whole length of the cochlea. They are estimated at over three thousand in number. The inner rods, which are more numerous than the outer ones, rest on the basilar membrane, close to the labium tympanicum; they project obliquely for- ward and outward, and terminate above in expanded extremities, which resemble in shape the upper end of the ulna, with its sigmoid cavity, coronoid and olecra- non processes. On the outer side of the rod, in the angle formed between it and the basilar membrane, is a protoplasmic cell, whilst on the inner side is a row of epithelial cells surmounted by a brush of fine, stiff, hair-like processes, these cells being continuous with the cubical cells lining the sulcus spiralis. The outer rods also rest by a broad foot on the basilar membrane; they incline forward and inward, and their upper extremity resembles the head and bill of a swan, the head fitting into the concavity-the analogue of the sigmoid cavity-of one or more of the internal rods, and the bill resting against the phalanges of the lamina reticularis, presently to be described. In the head of these outer rods is an oval portion, where the fibres of which the rod appears to be composed are deficient, and which stains more deeply with carmine than the rest of the rod. This is supposed to represent the nucleus of the cell from which the rod was originally developed. At the base of the rod, on its internal side-that is to say, in the angle formed by the rod with the basilar membrane-is a similar protoplasmic cell to that found on the outer side of the base of the inner rod, whilst external to the outer rod are three or four successive 1 In reading the older descriptions of the organ of hearing the student must bear in mind that the membranes bounding the ductus auditorius, together with the organ contained between them, were de- scribed together as the " lamina spiralis membranacea," while the membrane of Reissner was not recog- nized, the parts being, in fact, as shown in the second turn of the cochlea on the right hand of Fig. 506. 2 Corti's original paper is in the Zeitschrift f. JKissea. Zool., iii. 109. 888 THE ORGANS OF SENSE. rows of epithelial cells, more elongated than those found on the internal side of the inner rod, but, like them, furnished with minute hairs or cilia. These are termed the outer hair-cells, in contradistinction to the inner set, which are termed the inner hair-cells. They are attached by their bases to the basilar membrane, whilst from the opposite extremity a bru&h of hairs or cilia projects through the reticular membrane. They are continuous externally with the cubical cells on the lateral part of the basilar membrane. The reticular lamina or membrane of Kolliker is a delicate framework perfo- rated by rounded holes. It extends from the inner rods of Corti to the external row of the outer hair-cells, and is formed by several rows of " minute fiddle- shaped cuticular structures," called phalanges, between which are holes for the projection of the cilise of the outer hair-cells. Covering over these structures, but not touching them, is the membrana tec- toria, or membrane of Corti, which is attached to the vestibular surface of the lamina spiralis close to the attachment of the membrane of Reissner; it courses over the denticulate lamina, and, passing outward parallel to the basilar mem- brane, is blended with the ligamentum spirale on the outer wall of the spiral canal.1 The inner surface of the osseous labyrinth is lined by an exceedingly thin fibro-serous membrane, analogous to a periosteum from its close adhesion to the inner surfaces of these cavities, and performing the office of a serous membrane by its free surface. It lines the vestibule, and from this cavity is continued into the semicircular canals and the scala vestibuli of the cochlea, and through the helicotrema into the scala tympani. A delicate tubular process is prolonged along the aqueduct of the vestibule to the inner surface of the dura mater. This membrane is continued across the fenestra ovalis and rotunda, and consequently has no communication with the lining membrane of the tympanum. Its attached surface is rough and fibrous, and closely adherent to the bone ; its free surface is smooth and pale, covered with a layer of epithelium, and secretes a thin, limpid fluid, the aqua labyrinthi, liquor Cotunnii, or perilymph (Blainville). The scala media is closed above and below. The upper blind extremity is attached to the cupola at the upper part of the helicotrema; the lower end fits into the angle at the commencement of the osseous lamina on the floor of the ves- tibule. Near this blind extremity, the scala media receives the canalis reunions (Fig. 508), a very delicate canal by which the ductus cochlearis is brought into continuity with the saccule. The membranous labyrinth (Fig. 508) is a closed membranous sac, containing fluid, on the walls of which the ramifications of the auditory nerve are distributed. It has the same general form as the vestibule and semicircular canals in which it is enclosed and to which it is limited; but is considerably smaller, and separated from their lining membrane by the perilymph. The vestibular portion consists of two sacs, the utricle and the saccule. The utricle is the larger of the two, of an oblong form, compressed laterally, and occupies the upper and back part of the vestibule, lying in contact with the fovea semi-elliptica. Numerous filaments of the auditory nerve are distributed on the wall of this sac, and its cavity communicates behind with the membranous semicircular canals by five orifices. The saccule is the smaller of the two vestibular sacs ; it is globular in form, lies in the fovea hemispherica near the opening of the vestibular scala of the cochlea, and receives numerous nervous filaments which enter from the bottom of the depression in which it is contained. Its cavity is apparently distinct from that of the utricle. The membranous semicircular canals are about one-third the diameter of the The Membranous Labyrinth. 1 In Fig. 507 only the inner half of the membrane is represented. THE MEMBRANOUS LABYRINTH OF THE EAR. 889 osseous canals, but in number, shape, and general form they are precisely similar; they are hollow, and open by five orifices into the utricle, one opening being common to two canals. Their ampullae are thicker than the rest of the tubes, and nearly fill the cavities in which they are contained. The membranous labyrinth is held in position by numerous fibrous bands which stretch across the space between the membranous and bony labyrinths. These fibrous bands convey the blood-vessels and nervous filaments distributed to the utricle, to the saccule, and to the ampulla of each canal. The nerves enter the vestibule through the minute apertures on its inner wall. Structure.-The wall of the membranous labyrinth is semi-transparent, and consists of three layers. The outer layer is a loose and flocculent structure, apparently composed of ordinary fibrous tissue, containing blood-vessels and numerous pigment-cells analogous to those in the pigment-coat of the retina. The middle layer, thicker and more transparent, bears some resemblance to the hyaloid CANALIS REUNIENS Fig. 508.-The membranous labyrinth. (Enlarged.) membrane, but it presents on its internal surface numerous papilliform projections, and on the addition of acetic acid presents an appearance of longitudinal fibrilla- tion and elongated nuclei. The inner layer is formed of polygonal nucleated epi- thelial cells, which secrete the endolymph. The endolymph (liquor Scarpce) is a limpid serous fluid which fills the membra- nous labyrinth ; in composition it closely resembles the perilymph. The otoliths are two small rounded bodies consisting of a mass of minute crys- talline grains of carbonate of lime, held together in a mesh of delicate fibrous tissue, and contained in the walls of the utricle and saccule, opposite the distribu- tion of nerves. A calcareous material is also, according to Bowman, sparingly scattered in the cells lining the ampulla of each semicircular canal. The arteries of the labyrinth are-the internal auditory, from the basilar; the stylo-mastoid, from the posterior auricular ; and, occasionally, branches from the occipital. The internal auditory divides at the bottom of the internal meatus into two branches, cochlear and vestibular. The cochlear branch subdivides into from twelve to fourteen twigs, which traverse the canals in the modiolus, and are distributed, in the form of a capillary network, in the substance of the lamina spiralis. The vestibular branches accompany the nerves, and are distributed, in the form of a minute capillary network, in the substance of the membranous labyrinth. The veins (auditory) of the vestibule and semicircular canals accompany the arteries, and, receiving those of the cochlea at the base of the modiolus, terminate in the superior petrosal sinus. The auditory nerve, the special nerve of the sense of hearing, divides, at the 890 THE ORGANS OF SENSE. bottom of the internal auditory meatus, into two branches, the cochlear and ves- tibular. The trunk of the nerve, as well as the branches, contains numerous ganglion-cells with caudate prolongations. The vestibular nerve, the posterior of the two, divides into three branches- superior, middle, and inferior. The superior vestibular branch, the largest, divides into numerous filaments, which pass through minute openings at the upper and back part of the cul-de- sac at the bottom of the meatus, and, entering the vestibule, are distributed to the utricle and to the ampulla of the external and superior semicircular canals. The middle vestibular branch consists of numerous filaments, which enter the vestibule by a smaller cluster of foramina placed below those above mentioned, and which correspond to the bottom of the fovea hemispherica; they are distributed to the saccule. The inferior and smallest branch passes backward in a canal behind the fora- mina for the nerves of the saccule, and is distributed to the ampulla of the pos- terior semicircular canal. The nervous filaments enter the ampullary enlargements at a deep depression seen on their external surface, with a corresponding elevation when seen from within ; the nerve-fibres ending in loops and in free extremities. In the utricle and saccule the nerve-fibres spread out, some blending with the calcareous matter; others, radiating on the inner surface of the wall of each cavity, become blended with a layer of nucleated cells and terminate in a thin fibrous film. The cochlear nerve divides into numerous filaments at the base of the modiolus, which ascend along its canals, and then, bending outward at right angles, pass between the plates of the bony lamina spiralis, close to its tympanic surface. Between the plates of the spiral lamina the nerves form a plexus which contains ganglion cells forming the ganglion spirale. From this ganglion delicate filaments pass between the layers of the osseous lamina to the sulcus spiralis and pass out- ward to the organ of Corti. Their exact termination is uncertain. Waldeyer describes them as collected into two groups, one group ending in the outer and the other in the inner hair-cells. Surgical Anatomy.-Malformations, such as imperfect development of the external parts, absence of the meatus, or supernumerary auricles, are occasionally met with. Or the pinna may present a congenital fistula which is due to defective closure of the first visceral cleft, or rather of that portion of it which is not concerned in the formation of the Eustachian tube, tympanum, and meatus. The skin of the auricle is thin and richly supplied with blood, but in spite of this it is frequently the seat of frost-bite, due to the fact that it is much exposed to cold, and lacks the usual covering of subcutaneous fat found in most other parts of the body. A collection of blood is sometimes found between the cartilage and perichondrium (hceviatoma auris), usually the result of traumatism, but not necessarily due to this cause. It is said to occur most fre- quently in the ears of the insane. Keloid sometimes grows in the auricle around the puncture made for earrings, and epithelioma occasionally affects this part. Deposits of urate of soda are often met with in the pinna in gouty subjects. The external auditory meatus can be most satisfactorily examined by light reflected down a funnel-shaped speculum; by gently moving the latter in different directions th'e whole of the canal and membrana tympani can be brought into view. The points to be noted are, the presence of wax or foreign bodies, the size of the canal, and the condition of the mem- brana tympani. The accumulation of wax is often the cause of deafness, and may give rise to very serious consequences, causing ulceration of the membrane and even absorption of the bony wall of the canal. Foreign bodies are not infrequently introduced into the ear by children, and, when situated in the first portion of the canal, may be removed with tolerable facility by means of a minute hook or loop of fine wire, with reflected light; but when they have slipped beyond the narrow middle part of the meatus, their removal is in no wise easy, and attempts to effect it, in inexperienced hands, may be followed by destruction of the membrana tympani and possi- bly the contents of the tympanum. The calibre of the external auditory canal maybe narrowed by inflammation of its lining membrane, running on to suppuration ; by periostitis ; by polypi,, sebaceous tumors, and exostoses. The membrana tympani, when seen in a healthy ear, "reflects light strongly, and, owing to its peculiar curvature, presents a bright spot of triangular shape at its lower and anterior portion." From the apex of this, proceeding upward and slightly forward, is a white streak formed by the handle of the malleus, wdiile at the upper and middle part of the membrane may be seen a slight projection, caused by the short process of the malleus. In SURGICAL ANATOMY OF THE EAR. 891 disease alterations in color, lustre, curvature or inclination, and perforation must be noted. Such perforations may be caused by a blow or a loud report or by a wound. The upper wall of the meatus is separated from the cranial cavity by a thin plate of bone; the anterior wall is separated from the temporo-maxillary joint and parotid gland by the bone forming the glenoid fossa ; and the posterior wall is in relation with the mastoid cells; hence inflammation of the external auditory meatus may readily extend to the membranes of the brain, to the temporo-maxillary joint, or to the mastoid cells ; and, in addition to this, blows on the chin may cause fracture of the wall of the meatus. The nerves supplying the meatus are the auricular branch of the pneumogastric, the auriculo-temporal, and the auricularis magnus. The connections of these nerves explain the fact of the occurrence, in cases of any irritation of the meatus, of constant coughing and sneez- ing from implication of the pneumogastric, or of yawning from implication of the auriculo- temporal. No doubt also the association of earache with toothache in cancer of the tongue is due to implication of the same nerve, a branch of the fifth, which supplies also the teeth and the tongue. The vessels of the meatus and membrana tympani are derived from the posterior auricular, temporal, and internal maxillary arteries. The upper half of the membrana tympani is much more richly supplied with blood than the lower half. For this reason, and also to avoid the chorda tympani nerve and ossicles, incisions through the membrane should be made at the lower and posterior part. The principal point in connection with the surgical anatomy of the tympanum is its relations to other parts. Its roof is formed by a thin plate of bone, which, with the dura mater, is all that separates it from the temporo-sphenoidal lobe of the brain. Its floor is immediately above the jugular fossa behind and the carotid canal in front. Its posterior wall presents the openings of the mastoid cells. On its anterior wall is the opening of the Eustachian tube. Thus it follows that in disease of the middle ear we may get subdural abscess, septic meningitis, or abscess of the cerebrum or cerebellum from extension of the inflammation through the bony roof; throm- bosis of the lateral sinus, with or without pyaamia, by extension through the floor; or mastoid abscess by extension backward. In addition to this, we may get fatal haemorrhage from the internal carotid in destructive changes of the middle ear; and in throat disease we may get the inflammation extending up the Eustachian tube to the middle ear. The Eustachian tube is accessible from the nose. If the nose and mouth be closed and an attempt made to expire air, a sense of pressure with dulness of hearing is produced in both ears, from the air finding its way up the Eustachian tube and bulging out the membrana tympani. During the act of swallowing the pharyngeal orifice of the tube, which is normally closed, is opened, probably by the action of the Tensor tympani. This fact was employed by Politzer in devising an easy method of inflating the tube. The nozzle of an india-rubber syringe is inserted into the nostril; the patient takes a mouthful of water and holds it in his mouth ; both nostrils are closed with the finger and thumb to prevent the escape of air, and the patient is then requested to swallow ; as he does so the air is forced out of the syringe into his nose, and is driven into the Eustachian tube, which is now open. The impact of the air against the membrana tympani can be heard, if the membrane is sound, by means of a piece of india-rubber tubing, one end of which is inserted into the meatus of the patient's ear, the other into that of the surgeon. The direct examination of the Eustachian tube is made by the Eustachian catheter. This is passed along the floor of the nostril, with the curve downward, to the posterior wall of the pharynx. When this is felt, the catheter is to be withdrawn about half an inch, and the point rotated outward through a quarter of a circle, and pushed again slightly backward, when it will enter the orifice of the tube, and will be found to be caught, and air forced into the catheter will be heard impinging on the tympanic membrane if the ears of the patient and surgeon are connected by an india-rubber tube. THE ORGANS OF DIGESTION. THE Apparatus for the Digestion of the Food consists of the alimentary canal and of certain accessory organs. The alimentary canal is a musculo-membranous tube, about thirty feet in length, extending from the mouth to the anus, and lined throughout its entire extent by mucous membrane. It has received different names in the various parts of its course : at its commencement, the mouth, we find provision made for the mechanical division of the food (mastication), and for its admixture with a fluid secreted by the salivary glands (insalivation); beyond this are the organs of deglutition, the pharynx and the oesophagus, which convey the food into that part of the alimentary canal (the stomach) in which the principal chemical changes occur, and in which the reduction and solution of the food take place ; in the small intestines the nutritive principles of the food (the chyle) are separated, by its admixture with the bile and pancreatic fluid, from that portion which passes into the large intestine, most of which is expelled from the system. Alimentary Canal. Mouth. Pharynx. (Esophagus. Stomach. Small intestine- Duodenum. Jejunum. Ileum. Caecum. Colon. Rectum. Large intestine < Teeth. Accessory Organs. Salivary glands- Parotid. Submaxillary. Sublingual. Liver. Pancreas. Spleen. THE MOUTH. The mouth (oral or buccal cavity') (Fig. 509) is placed at the commencement of the alimentary canal; it is a nearly oval-shaped cavity, in which the mastication of the food takes place. It is bounded, in front, by the lips; laterally, by the cheeks and alveolar processes of the upper and lower jaws ; above, by the hard palate and teeth of the upper jaw ; belowT, by the tongue and by the mucous membrane stretched between the under surface of that organ and the inner surface of the jaws, and by the teeth of the lower jaw; behind, by the soft palate and fauces. The mucous membrane lining the mouth is continuous with the integument at the free margin of the lips and with the mucous lining of the fauces behind ; it is of a rose-pink tinge during life, and very thick where it covers the hard parts bounding the cavity. It is covered by stratified epithelium. The lips are two fleshy folds which surround the orifice of the mouth, formed externally of integument and internally of mucous membrane, between which are found the Orbicularis oris muscle, the coronary vessels, some nerves, areolar tissue, and fat, and numerous small labial glands. The inner surface of each lip is con- 892 THE MOUTH. 893 nected in the middle line to the gum of the corresponding jaw by a fold of mucous membrane, the frcenum labii superioris and inferioris-the former being the larger of the two. The labial glands are situated between the mucous membrane and the Orbicu- laris oris round the orifice of the mouth. They are rounded in form, about the size of small peas, their ducts opening by small orifices upon the mucous mem- brane. In structure they resemble the salivary glands. The cheeks form the sides of the face and are continuous in front with the lips. They are composed externally of integument, internally of mucous membrane, and between the two of a muscular stratum, besides a large quantity of fat, areolar tissue, vessels, nerves, and buccal glands. The mucous membrane lining the cheek is reflected above and below upon the gums, and is continuous behind with the lining membrane of the soft palate. Opening of nasal duct. rBristle passed through Stenson's duct. Fig. 509.-Sectional view of the nose, mouth, pharynx, etc. Opposite the second molar tooth of the upper jaw is a papilla, the summit of which presents the aperture of the duct of the parotid gland. The principal muscle of the cheek is the Buccinator, but numerous other muscles enter into its formation-viz. the Zygomatici, Risorius Santorini, and Platysma myoides. The buccal glands are placed between the mucous membrane and Buccinator muscle: they are similar in structure to the labial glands, but smaller. Two or three of larger size than the rest are placed between the Masseter and Buccinator muscles; their ducts open into the mouth opposite the last molar tooth. They are called molar glands. The gums are composed of a dense fibrous tissue closely connected to the 894 THE ORGANS OF DIGESTION. periosteum of the alveolar processes and surrounding the necks of the teeth. They are covered by smooth and vascular mucous membrane, which is remark- able for its limited sensibility. Around the necks of the teeth this membrane presents numerous fine papillae, and from this point it is reflected into the alve- olus, where it is continuous with the periosteal membrane lining that cavity. THE TEETH. The human subject is provided with two sets of teeth, which make their appearance at different periods of life. The first set appear in childhood, and are called the temporary, deciduous, or milk teeth. The second set, which also appear at an early period, continue until old age, and are named permanent. The temporary teeth are twenty in number-four incisors, two canine, and four molars, in each jaw. The permanent teeth are thirty-two in number-four incisors (two central and two lateral), two canines, four bicuspids, and six molars in each jaw. General Characters.-Each tooth consists of three portions : the crown, or body, projecting above the gum ; the root, or fang, entirely concealed within the alveolus ; and the neck, the constricted portion, between the other two. The roots of the teeth are firmly implanted within the alveoli; these depres- sions are lined with periosteum, which is reflected on to the tooth at the point of the fang and covers it as far as the neck. At the margin of the alveolus the peri- osteum becomes continuous with the fibrous structure of the gums. Permanent Teeth. The incisors, or cutting teeth, are so named from their presenting a sharp cut- ting edge, adapted for biting the food. They are eight in number, and form the four front teeth in each jaw. The croton is directed vertically and is wedge-like in form, being bevelled at the expense of its posterior surface, so as to terminate in a sharp horizontal cut- ting edge, which, before being subject to attrition, presents three small prominent points. It is convex, smooth, and highly polished in front; concave behind, where it is frequently marked by slight longitudinal furrows. The neck is constricted. The fang is long, single, conical, transversely flattened, thicker before than behind, and slightly grooved on each side in the longitudinal direction. The incisors of the upper jaw are altogether larger and stronger than those of the lower jaw. They are directed obliquely downward and forward. The two central ones are larger than the two lateral, and their free edges are sharp and chisel-like, being bevelled at the expense of their posterior edge: the root is more rounded. The incisors of the lower jaw are smaller than the upper: the two central ones are smaller than the two lateral, and are the smallest of all the incisor teeth. The canine teeth (cuspidati) are four in number-two in the upper and two in the lower jaw, one being placed behind each lateral incisor. They are larger and stronger than the incisors, especially the root, which sinks deeply into the jaw and causes a well-marked prominence upon its surface. The crown is large and conical, very convex in front, a little hollowed and uneven posteriorly, and tapering to a blunted point or cusp, which rises above the level of the other teeth. The root is single, but longer and thicker than that of the incisors, conical in form, compressed laterally, and marked by a slight groove on each side. The upper canine teeth (vulgarly called eye-teeth) are larger and longer than the two lower, and situated a little behind them. The lower canine teeth are placed in front of the upper, so that their summits correspond to the interval between the upper canine tooth and the neighboring incisors on each side. THE TEETH. 895 The bicuspid teeth (premolars, small, or false molars) are eight in number- four in each jaw, two being placed immediately behind each of the canine teeth. They are smaller and shorter than the canine. The crown is compressed from without inward, and surmounted by two pyram- idal eminences, or cusps, separated by a groove; hence their name, bicuspidate. The outer of these cusps is larger and more prominent than the inner. The neck is oval. The root is generally single, compressed, and presents a deep groove on each side, which indicates a tendency in the root to become double. The apex is generally bifid. The upper bicuspids are larger, and present a greater tendency to the division of their roots than the lower; this is especially marked in the second upper bicuspid. The molar teeth (multiciispidati, true or large molars) are the largest of the permanent set, and are adapted from the great breadth of their crowns for grinding Upper Jaw. Molars. Bicuspids. Canine. Incisors. Wisdom tooth. -Fang. _Neck. |- Crown. Lower Jaw. I Crown. - Neck. - Fang. Wisdom tooth. J Molars. Bicuspids. Canine. Incisors. Fig. 510.-The permanent teeth. External view. and pounding the food. They are twelve in number-six in each jaw, three being placed behind each of the posterior bicuspids. The crown is nearly cubical in form, rounded on each of its lateral surfaces, flattened in front and behind, the upper surface being surmounted by four or five tubercles, or cusps (four in the upper, five in the lower molars), separated from each other by a crucial depression; hence their name, multicuspidati. The neck is distinct, large, and rounded. The root is subdivided into from two to five fangs, each of which presents an aperture at its summit. The first molar tooth is the largest and broadest of all ; its crown has usually five cusps, three outer and two inner. In the upper jaw the root consists of three fangs, widely separated from one another, two being external, the other internal. The latter is the largest and longest, slightly grooved, and sometimes bifid. In the lower jaw the root consists of two fangs, one being placed in front, the other behind: they are both compressed from before backward, and grooved on their contiguous faces, indicating a tendency to division. 896 THE ORGANS OF DIGESTION. The second molar is a little smaller than the first. The crown has four cusps in the upper and five in the lower jaw. The root has three fangs in the upper jaw and two in the lower, the characters of which are similar to the preceding tooth. The third molar tooth is called the wisdom tooth {dens sapiential), from its late appearance through the gum. It is smaller than the others, and its axis is directed inward. The crown is small and rounded and furnished with three tubercles. The root is generally single, short, conical, slightly curved, and grooved so as to present traces of a subdivision into three fangs in the upper and two in the lower jaw. Temporary Teeth. The temporary or milk teeth are smaller, but resemble in form those of the permanent set. The hinder of the two temporary molars is the largest of all the milk teeth, and is succeeded by the second permanent bicuspid. The first upper molar has only three cusps-two external, one internal; the second upper molar has four cusps. The first lower molar has four cusps; the second lower molar Upper Jaw. Molars. Canine. Incisors. - Fang. -Neck. I- Crown. Loxver Jaxv. Crown. ~ Fang. Molars. Canine. Incisors. Fig. 511.-The temporary, or milk teeth. External view. has five. The fangs of the temporary molar teeth are smaller and more diverging than those of the permanent set, but in other respects bear a strong resemblance to them. Structure of the Teeth. On making a vertical section of a tooth (Fig. 512) a cavity will be found in the interior. This cavity is situated in the interior of the crown and the centre of each fang, and opens by a minute orifice at the extremity of the latter. The shape of the cavity corresponds somewhat with that of the tooth ; it forms what is called the pulp-cavity, and contains a soft, highly vascular, and sensitive substance, the dental pulp. The pulp consists of a loose connective tissue and cells; it is richly supplied with vessels and nerves, which enter the cavity through the small aperture at the point of each fang. The cells of the pulp are partly found permeating the connective tissue, and partly arranged as a layer on the wall of the pulp-cavity. These latter cells are of two kinds: some, columnar in shape, are named the odontoblasts of Waldeyer, and will be referred to hereafter; others, fusiform in shape, are wedged in between the columnar cells, and have two fine processes, the outer or distal one passing into a dentine tubule ; the inner being continuous with the processes of the connective-tissue cells of the pulp-matrix. STRUCTURE OF THE TEETH. 897 According to some anatomists, the processes of the odontoblasts are also continued into the dentine tubuli. The solid portion of the tooth consists of three distinct structures-viz. the proper dental substance, which forms the larger portion of the tooth, the ivory or dentine ; a layer which covers the exposed part of the crown, the enamel; and a thin layer, which is disposed on the surface of the fang, the cement or crusta petrosa. The ivory, or dentine (Fig. 513), forms the principal mass of a tooth; in its central part is the cavity enclosing the pulp. It is a modification of osseous tissue, from which it differs, however, in structure. On microscopic examination it is seen to consist of a number of minute wavy and branching tubes having distinct parietes. They are called the dental tubuli, and are imbedded in a dense homogeneous substance, the intertubu- lar tissue. The dental tubuli (Fig. 514) are placed parallel with one another, and open at their inner ends into the pulp-cavity. In their course to the periphery they present two or three curves, and are twisted on themselves in a spiral direction. The direction of these tubes varies: they are vertical in the upper portion of the crown, oblique in the neck and upper part of the root, and toward the lower part of the ~ Grown. -Neck. -Fang. Fig. 512.-Vertical sec- tion of a molar tooth. - Cement. Interglobular spaces. -Crown. -Neck. -Fang. Dental tubules. Fig. 513.-Vertical section of a bicuspid tooth. (Magnified.) Fig. 514.-Canine tooth of man, presenting a transverse section of a portion of the root. (Magnified 300 diameters.) root they are inclined downward. The tubuli, at their commencement, are about of an inch in diameter; in their course they divide and subdivide dichotomously, so as to give to the cut surface of the dentine a striated appear- ance. From the sides of the tubes, especially in the fang, ramifications of extreme minuteness are given off, which join together in loops in the intertubular substance, or terminate in small dilatations, from which branches are given off. Near the periphery of the dentine the finer ramifications of the tubuli terminate in a layer of irregular branched spaces which communicate with each other. 898 THE ORGANS OF DIGESTION. These are called the interglobular spaces of Czermak, or the granular layer of Purkinje (Fig. 514). The dental tubuli have comparatively thick walls, and contain slender cylindrical prolongations from the cells of the pulp-tissue, first described by Mr. Tomes, and named Tomes's fibres or dentinal fibres. These dentinal fibres are analogous to the soft contents of the canaliculi of bone. Between Tomes's fibres and the ivory of the canals there is an elastic homo- geneous membrane which resists the action of acids-the dentinal sheath of Neumann. The intertubular substance is translucent, finely granular, and contains the chief part of the earthy matter of the dentine. After the earthy matter has been removed by steeping a tooth in weak acid the animal basis remaining may be torn into laminae which run parallel with the pulp-cavity across the direction of the tubes. A section of dentine often displays a series of somewhat parallel lines -the incremental lines of Salter. These lines are composed of a number of masses of imperfectly calcified dentine arranged in layers. In consequence of the imperfection in the calcifying process little irregular cavities are left, termed interglobular spaces, similar to those in the granular layer, but larger. They have received their name from the fact that they are surrounded by minute nodules or globules of dentine. Other curved lines may be seen parallel to the surface. These are the lines of Schreger, and are due to the optical effect of simultaneous curvature of the dentinal fibres. Chemical Composition.-According to Berzelius and Bibra, dentine consists of 28 parts of animal and 72 of earthy matter. The animal matter is resolvable by boiling into gelatin. The earthy matter consists of phosphate of lime, carbonate of lime, a trace of fluoride of calcium, phosphate of magnesia, and other salts. The enamel is the hardest and most compact part of a tooth, and forms a thin crust over the exposed part of the crown as far as the commencement of the fang. It is thickest on the grinding surface of the crown until worn away by attrition, and becomes thinner toward the neck. It consists of a congeries of minute hexagonal rods. They lie parallel with one another, resting by one extremity upon the dentine, which presents a number of minute depressions for their reception, and forming the free surface of the crown by the other extremity. These fibres are directed vertically on the summit of the crown, horizontally at the sides; they are about the of an inch in diameter, and pursue a more or less wavy course. The enamel is marked by a series of undulating lines, which cross each other, or "decussate;" these lines are doubtless formed by the variation in the course of the enamel-rods. Another series of lines, having a brown appearance, and denominated the parallel strice of Retzius, are seen on a section of the enamel. Their exact significance is uncertain. Numerous minute interstices intervene between the enamel-fibres near their dentinal surface, a provision calculated to allow of the permeation of fluids from the dentinal tuBhle into the substance of the enamel. It is a disputed point whether the dentinal fibres penetrate a certain distance between the rods of the enamel or not. No nutritive canals exist in the enamel. Chemical Composition.-According to Bibra, enamel consists of 96.5 per cent, of earthy matter and 3.5 percent, of animal matter. The earthy matter con- sists of phosphate of lime, with traces of fluoride of calcium, carbonate of lime, phosphate of magnesia, and other salts. The cortical substance, or cement (crusta petrosa), is disposed as a thin layer on the roots of the teeth, from the termination of the enamel as far as the apex of the fang, where it is usually very thick. Tn structure and chemical composition it resembles bone. It contains, sparingly, the lacunae and canaliculi which characterize true bone; the lacunae placed near the surface have the canaliculi radiating from the side of the lacunae toward the periodontal membrane, and those more deeply placed join with the adjacent dental tubuli. In the thicker portions of the crusta petrosa the lamellae and Haversian canals peculiar to bone are also found. DEVELOPMENT OF THE TEETH. 899 As age advances the cement increases in thickness, and gives rise to those bony growths, or exostoses, so common in the teeth of the aged ; the pulp-cavity becomes also partially filled up by a hard substance intermediate in structure between dentine and bone (psteo-dentine, Owen ; secondary dentine, Tomes). It appears to be formed by a slow conversion of the dental pulp, which shrinks or even disappears. Development of the Teeth. In describing the development of the teeth we have first to consider the mode of formation of the temporary or milk teeth, and then that of the permanent series. Development of the Temporary Teeth.-The development of these teeth in the foetus begins at a very early period. About the seventh week the margin of the jaw presents a slight longitudinal depression or groove with rounded borders. This is termed the primitive dental groove of Goodsir, and is caused by an involution of the epithelium of the oral cavity into the subjacent connective tissue. The projecting borders of the groove are called the dental ridges. The groove consists, therefore, superficially, of a collection of epithelial cells, beneath which is a gelatinous connective tissue, which is taken to represent the corium and connective tissue of the mucous membrane ; and deeper than this is the ossifying substance of the jaw. The essential structures of the teeth are derived from these elements-the enamel from the epithelium which covers the surface of the dental groove ; the dentine and crusta petrosa from the deeper structures. First, as to the enamel. The primitive dental groove increases in size by the growing up of the corium in front and behind, and is filled up and covered in by the epithelium, which becomes greatly increased in quantity, so that the groove is only indicated by a shallow superficial furrow. Secondary ridges of corium rise at intervals along the floor of the groove, dividing it into a series of pits. As the dental ridges-that is to say, the sides of the groove-rise up, epithelial masses are contained within the separate pits; these are called enamel-germs, and seem to pass deeper and deeper into the substance of the jaw, and at last meet with the papillae, presently to be described. The lower part of these masses of epithelial cells-that is, the part farthest from the margin of the jaw-spreads out in all directions, and the epithelial cells here increase in number. Each mass thus assumes a flask shape, which is connected by a narrow neck, embraced by the dental ridges, with the epithelial lining of the mouth. It may now be compared to a tubular gland, consisting of a dilated extremity filled with epithelium and opening by a narrow duct, also filled with epithelium, on the margin of the jaw. This narrow, constricted portion is called the neck of the enamel-organ, and is of importance as being the part from which the enamel-organ of the future perma- nent tooth is derived. The lower expanded portion of the mass of epithelial cells, the body of the flask, now inclines outward, so as to form an angle with the neck or more superficial part. In the soft connective tissue beneath this mass of epithelial cells small papillae, corresponding in number to the pits in the primitive dental groove, arise by an increased development and growth of the corpuscles of the part. They grow upward, become vascular, and come in contact with the epithelial cells of the enamel-germ, and are received into dimples on its under surface. By continued growth they push their way up into the enamel-germs, which become folded over them like a hood or cap. We have then, at this stage, vascular papillae which have already begun to assume somewhat the shape of the crowns of the future teeth, surmounted by domes or caps of epithelial cells, which were originally the cells contained in the lower or expanded part of the flask-shaped masses in the primi- tive dental groove (Fig. 515). These cells now undergo a differentiation into three classes or varieties. Those which are in contact with the papilla, and which are continuous through the neck of the enamel-germ with the deepest layer of cells of the oral epithelium, become elongated and form a layer of well-marked and regular columnar epithelium coating the papilla. These are named the 900 THE ORGANS OF DIGESTION. internal enamel epithelium. The outer layer of cells of the enamel-germ, which are in contact with the inner surface of the dentinal sac, presently to be described, are much shorter, cubical in form, and are named the external enamel epithelium. All the intermediate round cells of the enamel-germ between these two layers undergo a peculiar change. They become stellate in shape, and their processes unite to form a network which resembles gelatinous connective tissue. While these changes have been going on the soft embryonic tissue from which the papillae arose, and which is situated beneath the enamel-germs, grows upward in the form of ridges, surrounding the rudimentary teeth and becoming converted into a vascular membrane, constituting a sac-the dentinal sac-which encloses each tooth. As they grow upward the two ridges approach one another, and, penetrating the lips of the primitive groove, they cause the neck of the enamel- organ to atrophy and disappear, so that all communication between the enamel- germ and the superficial epithelium is cut off. Dental groove.- Remains of enamel germ. Enamel organ. ■Dental germ. Secondary enamel germ. Meckel's cartilage. Lower jaw. Fig. 515.-Vertical section of the inferior maxilla of an early human foetus. (Magnified 25 diameters.) We have now vascular papillae surmounted by inverted caps or capsules of epithelial cells, the whole being surrounded by membranous sacs. The cap or capsule consists of an internal layer of cells-the internal enamel epithelium-in contact with the papilla; of an external layer of cells-the external enamel epithelium-lining the interior of the dentinal sac; and of an intermediate mass of stellate cells with anastomosing processes (Fig. 516). The enamel is formed exclusively from the internal enamel epithelium, the columnar cells of which undergo direct calcification and become elongated into the hexagonal rods of the enamel. The intermediate cells atrophy and disappear, so that the calcified internal enamel epithelium and the external enamel epithelium come into close apposition, and the cells of this latter layer form a distinct mem- brane, named the cuticula dentis or Nasmyth's membrane, which long remains perceptible, and, after the tooth has emerged from the gums, forms a horny layer which may be separated from the calcified mass below by the action of strong acids. It is marked by the hexagonal impressions of the enamel-prisms, and when stained by nitrate of silver shows the characteristic appearance of epithelium. It soon, however, wears away from the surface of the tooth. Formation of the Dentine.-While these changes are taking place in the epithelium to form the enamel contemporaneous changes are occurring in the blastema or corium which result in the formation of the dentine and cement. As before stated, the first germ of the dentine consists in the formation of papillae, DEVELOPMENT OE THE TEETH. 901 corresponding in number to the teeth, from the soft connective tissue which bounds the depressions containing the enamel-germ. The papillae growT upward into the enamel-organ, and become coated by it and enclosed in a vascular connective tis- sue, the dentinal sac, in the manner above described. They then constitute the formative pulp from which the dentine and permanent pulp are derived. Each papilla consists of rounded cells, and is very vascular, and soon begins to assume the shape of the tooth which is to be developed from it. The next step is the formation of the odontoblasts, which have a relation to the development of the teeth similar to that of the osteoblasts in the formation of bone. They are formed first from the cells of the periphery of the papilla, which become enlarged and of an elongated form and provided with numerous processes. These processes as they grow become calcified externally, the calcified portion forming the walls of the dentinal tubules, and the uncalcified axial portion forming the dentinal fibres (Tomes's fibres), which are contained within the tubules. In addition to this, the lateral processes from the odontoblasts form the branches of anastomosis whereby the denti- nal canals communicate. In this way the peripheral layer of the papilla becomes coated with a solid shell of dentine, on the inner surface of which a second layer of odonto- blasts is arranged, and in its turn calcifies; and thus the process goes on through the entire thickness of the dentine, the processes of one odontoblast being directly continuous with those in succeeding layers, so that each dental fibre must be regarded as formed by several continuous odontoblasts. The central part of the papilla does not undergo calcifi- cation ; its cells proliferate, nerve-fibres are developed in it, and it remains persistent as the pulp of the tooth. The cement is formed from the wall of the dentinal sac, which is developed from the embryonic mass at the bottom of the dental groove from which the papilla originally sprung. So that the dentine and cement may be said to originate from analogous structures. In this membranous sac ossification goes on in a manner identical with the intra- membranous ossification of bone, and the cement formed is simply ordinary bone containing canaliculi and lacunae. The germs of the milk teeth make their appearance in the following order: At the seventh week the germ of the first molar of the upper jaw appears: at the eighth w'eek that for the canine tooth is developed; the two incisor papillae appear about the ninth week (the central preceding the lateral); lastly, the second molar papilla is seen at the tenth week, behind the anterior molar. The teeth of the lower jaw appear rather later, the first molar papilla being only just visible at the seventh week, and the second molar papilla not being developed before the eleventh week. Development of the Permanent Teeth.-The permanent teeth as regards their development may be divided into two sets : (1) those which replace the temporary teeth, and which, like them, are ten in number: these are the successionalpermanent teeth ; and (2) those which have no temporary predecessors, but are superadded at the back of the dental series. These are three in number on either side in each jaw, and are termed the superadded permanent teeth. They are the three molars of the permanent set, the molars of the temporary set being replaced by the pre- molars or bicuspids of the permanent set. The development of the successional Fig. 516-Dental sac of a human embryo at an advanced stage of development. Partly diagrammatic, a. Wall of the sac, formed of connective tissue, with its outer stratum a1 and its inner a2, b. Enamel-organ with its papil- lary and parietal layer of cells, c. d. The en- amel-membrane and enamel-prisms, e. Den- tine cells, f. Dental germ and capillaries, gr. i. Transition of the wall of the follicle into the tissue of the dental germ. 902 THE ORGANS OF DIGESTION. permanent teeth-the ten anterior ones in either jaw-will be first considered. In the neck of the enamel-organ of the temporary tooth, prior to the meeting of the two dental ridges and the obliteration of this portion of the primitive dental groove, an indentation of the epithelium takes place in the layer of cells forming the posterior wall of the neck of the sac. This forms a groove or indentation similar to the groove in the oral epithelium of the margin of the jaw which formed the primitive dental groove, and from its resemblance is termed by Goodsir the secondary dental groove. These grooves or depressions are ten in number in each jaw, and are formed successively from before backward. They become filled with epithelial cells, and recede into the substance of the gum behind the germs of the temporary teeth. They constitute the enamel-germs of the permanent teeth. As they recede they become flask-shaped, from an expansion of their distal extremity, and finally meet a papilla, which has been formed in the corium, just in the same manner as was the case in the temporary teeth. The apex of the papilla indentates the enamel-germ, which encloses it, and forming a cap for it, undergoes analogous changes to those described in the development of the milk teeth, and becomes converted into the enamel, whilst the papilla forms the dentine of the permanent tooth. In its development it becomes enclosed in a dental sac which adheres to the back of the sac of the temporary tooth. The sac of each permanent tooth remains connected with the fibrous tissue of the gum by a slender band or guber- naculum, which passes to the margin of the jaw behind the corresponding milk tooth. The superadded permanent teeth-three on each side in each jaw-arise from successive extensions backward of the back part of the enamel-germ of the imme- diately preceding tooth. During the fourth month that portion of the enamel- germ of the last temporary molar tooth which lies behind the tooth, and which has remained unaltered, is prolonged backward and forms the enamel-germ of the first permanent molar into which a papilla projects. From this tooth, in a similar manner, about the seventh month after birth the second molar is formed, and about the third year the third molar is formed by an extension backward of the enamel-germ of the second molar. Eruption.-When the calcification of the different tissues of the tooth is suffi- ciently advanced to enable it to bear the pressure to which it will be afterward subjected, its eruption takes place, the tooth making its way through the gum. The gum is absorbed by the pressure of the crown of the tooth against it, which is itself pressed up by the increasing size of the fang. At the same time the septa between the dental sacs, at first fibrous in structure, ossify, and constitute the alveoli; these firmly embrace the necks of the teeth and afford them a solid basis of support. The eruption of the temporary teeth commences at the seventh month, and is complete about the end of the second year,, those of the lower jaw preceding the upper. The periods for the eruption of the temporary set are- 7th month, central incisors. 7th to 10th month, lateral incisors. 12th to 14th month, anterior molars. 14th to 20th month, canine. 18th to 36th month, posterior molars. Calcification of the permanent teeth commences a little before birth, and pro- ceeds in the following order in the upper jaw-in the lower jaw a little earlier: First molar, fifth or sixth month ; the central incisor, a little later ; lateral incisors and canine, about the eighth or ninth month ; the bicuspids at the second year ; second molar, fifth or sixth year ; wisdom tooth about the twelfth year. Previous to the permanent teeth penetrating the gum the bony partitions which separate their sacs from the deciduous teeth are absorbed, the fangs of the temporary teeth disappear by absorption through the agency of particular multinucleated cells, called odontoclasts, which are developed at the time in the neighborhood of the fang, and the permanent teeth become placed under the loose crowns of the THE PALATE. 903 deciduous teeth ; the latter finally become detached, and the permanent teeth take their place in the mouth. The eruption of the permanent teeth takes place at the following periods, the teeth of the lower jaw preceding those of the upper by a short interval : 6J years, first molars. 7th year, two middle incisors. 8th year, two lateral incisors. 9th year, first bicuspid. 10th year, second bicuspid. 11th to 12th year, canine. 12th to 13th year, second molars. 17th to 21st year, wisdom teeth. THE PALATE. The palate forms the roof of the mouth: it consists of two portions, the hard palate in front, the soft palate behind. The hard palate is hounded in front and at the sides by the alveolar arches and gums ; behind, it is continuous with the soft palate. It is covered by a dense structure formed by the periosteum and mucous membrane of the mouth, which are intimately adherent together. Along the middle line is a linear ridge or raphe, which terminates anteriorly in a small papilla corresponding with the inferior opening of the anterior palatine fossa. This papilla receives filaments from the naso-palatine and anterior palatine nerves. On either side and in front of the raphe the mucous membrane is thick, pale in color, and corrugated ; behind, it is thin, smooth, and of a deeper color: it is covered with squamous epithelium, and furnished with numerous glands (palatal glands), which lie between the mucous membrane and the surface of the bone. The soft palate (velum pendulum palati) is a movable fold suspended from the posterior border of the hard palate, and forming an incomplete septum between the mouth and pharynx. It consists of a fold of mucous membrane enclosing muscular fibres, an aponeurosis, vessels, nerves, adenoid tissue, and mucous glands. When occupying its usual position (i. e. relaxed and pendent) its anterior surface is concave, continuous with the roof of the mouth, and marked by a median ridge or raphe, which indicates its original separation into two lateral halves. Its posterior surface is convex, and continuous with the mucous membrane covering the floor of the posterior nares. Its upper border is attached to the posterior margin of the hard palate, and its sides are blended with the pharynx. Its lower border is free. Hanging from the middle of its lower border is a small, conical-shaped pendulous process, the uvula, and arching outward and downward from the base of the uvula on each side are two curved folds of mucous membrane, containing muscular fibres, called the arches or pillars of the soft palate. The anterior pillars run downward, outward, and forward to the sides of the base of the tongue, and are formed by the projection of the Palato-glossi muscles, covered by mucous membrane. The posterior pillars are nearer to each other and larger than the anterior; they run downward, outward, and backward to the sides of the pharynx, and are formed by the projection of the Palato-pharyngei muscles, covered by mucous membrane. The anterior and posterior pillars are separated below by a triangular interval in which the tonsil is lodged. The space left between the arches of the palate on the two sides is called the isthmus of the fauces. It is bounded, above, by the free margin of the soft palate ; below, by the back of the tongue; and on each side, by the pillars of the soft palate and the tonsil. The mwcous membrane of the soft palate is thin, and covered with squamous epithelium on both surfaces, excepting near the orifice of the Eustachian tube, where it is columnar and ciliated.1 Beneath the mucous membrane on the oral surface 1 According to Klein, the mucous membrane on the nasal surface of the soft palate is in the foetus covered throughout by columnar ciliated epithelium. 904 THE ORGANS OF DIGESTION. of the soft palate is a considerable amount of adenoid tissue. The palatine glands form a continuous layer on its posterior surface and round the uvula. The aponeurosis of the soft palate is a thin but firm fibrous layer attached above to the posterior border of the hard palate,, and becoming thinner toward the free margin of the velum. Laterally, it is continuous with the pharyngeal aponeurosis. It forms the framework of the soft palate, and is joined by the tendon of the Tensor palati muscle. The muscles of the soft palate are five on each side: the Levator palati, Tensor palati, Azygos uvuhe, Palato-glossus, and Palato-pharyngeus (see page 423). The following is the relative position of these structures in a dissection of the soft palate from the posterior or nasal to the anterior or oral surface: Immediately beneath the nasal mucous membrane is a thin stratum of muscular fibres, the posterior fasciculus of the Palato-pharyngeus muscle, joining with its fellow of the opposite side in the middle line. Beneath this is the Azygos uvulae, consisting of two rounded fleshy fasciculi, placed side by side in the median line of the soft palate. Next comes the aponeurosis of the Levator palati, joining with the muscle of the opposite side in the middle line. Fourthly, the anterior fasciculus of the Palato-pharyngeus, thicker than the posterior, and separating the Levator palati from the next muscle, the Tensor palati. This muscle terminates in a tendon which, after winding round the hamular process, expands into a broad aponeurosis in the soft palate, anterior to the other muscles which have been enumerated. Finally, we have a thin muscular stratum, the Palato-glossus muscle, placed in front of the aponeurosis of the Tensor palati, and separated from the oral mucous membrane by adenoid tissue. The tonsils (amygdalai) are two glandular organs, situated one on each side of the fauces, between the anterior and posterior pillars of the soft palate. They are of a rounded form, and vary considerably in size in different individuals. Exter- nally the tonsil is in relation with the inner surface of the Superior constrictor, which separates it from the internal carotid and ascending pharyngeal arteries. It corresponds to the angle of the lower jaw. Its inner surface presents from twelve to fifteen orifices, leading into small recesses, from which numerous follicles branch out into the substance of the gland. These follicles are lined by a continua- tion of the mucous membrane of the pharynx, covered with epithelium; around each follicle is a layer of closed capsules imbedded in the submucous tissue. These capsules are analogous to those of Peyer's glands, consisting of adenoid tissue. No openings from the capsules into the follicles can be recognized. They contain a thick grayish secretion. Surrounding each follicle is a close plexus of lymphatic vessels. From these plexuses the lymphatic vessels pass to the deep cervical glands in the upper part of the neck, which frequently become enlarged in affec- tions of these organs. The arteries supplying the tonsil are the dorsalis linguae from the lingual, the ascending palatine and tonsillar from the facial, the ascending pharyngeal from the external carotid, the descending palatine branch of the internal maxillary, and a twig from the small meningeal. The veins terminate in the tonsillar plexus, on the outer side of the tonsil. The nerves are derived from Meckel's ganglion and from the glosso-pharyngeal. THE SALIVARY GLANDS (Fig. 517). The principal salivary glands communicating with the mouth and pouring their secretion into its cavity are the parotid, submaxillary, and sublingual. The parotid gland, so called from being placed near the ear (napd, near ; oo', wtoj, the ear), is the largest of the three salivary glands, varying in weight from half an ounce to an ounce. It lies upon the side of the face immediately below and in front of the external ear. It is limited above by the zygoma; below, by the angle of the jaw and by a line drawn between it and the mastoid process: anteriorly, it extends to a variable extent over the Masseter muscle; posteriorly, THE SALIVARY GLANDS. 905 it is bounded by the external meatus, the mastoid process, and the Sterno-mastoid and Digastric muscles, slightly overlapping the latter. Its anterior surface is grooved to embrace the posterior margin of the ramus of the lower jaw, and advances forward beneath the ramus, between the two Pterygoid muscles and in front of the ramus over the Masseter muscle. Its outer surface, slightly lobulated, is covered by the integument and parotid fascia, and has one or two lymphatic glands resting on it. Its inner surface extends deeply into the neck by means of two large processes, one of which dips behind the styloid process and projects beneath the mastoid process and the Sterno-mastoid muscle; the other is situated in front of the styloid process, and passes into the back part of the glenoid fossa, behind the articulation of the lower jaw. The structures passing through the parotid gland are-the external carotid artery, giving off its three terminal branches : the posterior auricular artery emerges from the gland behind; the temporal artery above; the transverse facial, a branch of the temporal, in front; Fig. 517.-The salivary glands. and the internal maxillary winds through it as it passes inward, behind the neck of the jaw. Superficial to the external carotid is the trunk formed by the union of the temporal and internal maxillary veins; a branch, connecting this trunk with the internal jugular, also passes through the gland. It is also traversed by the facial nerve and its branches, which emerge at its anterior border ; branches of the great auricular nerve pierce the gland to join the facial, and the auriculo- temporal branch of the inferior maxillary nerve emerges from the upper part of the gland. The internal carotid artery and internal jugular vein lie close to its deep surface. The duct of the parotid gland (Stenson «) is about two inches and a half in length. It commences by numerous branches from the anterior part of the gland, crosses the Masseter muscle, and at its anterior border dips down into the substance of the Buccinator muscle, which it pierces; it then runs for a short distance obliquely forward between the Buccinator and mucous membrane of the mouth, and opens upon the inner surface of the cheek by a small orifice opposite the second molar 906 THE ORGANS OF DIGESTION. tooth of the upper jaw. While crossing the Masseter it receives the duct of a small detached portion of the gland, socia parotidis, which occasionally exists as a separate lobe, just beneath the zygomatic arch. In this position it has the transverse facial artery above it and some branches of the facial nerve below it. Structure.-The parotid duct is dense, of considerable thickness, and its canal about the size of a crowquill; it consists of an external or fibrous coat, of considerable density, containing contractile fibres, and of an internal or mucous coat lined with short columnar epithelium. Surface Form.-The direction of the duct corresponds to a line drawn across the face about a finger's breadth below the zygoma; that is, from the lower part of the tragus to midway between the free margin of the upper lip and the ala of the nose. Vessels and Nerves.-The arteries supplying the parotid gland are derived from the external carotid, and from the branches given off by that vessel in or near its substance. The veins empty themselves into the external jugular through some of its tributaries. The lymphatics terminate in the superficial and deep cervical Alveolus. Orescent of Gianuzzi. i Salivary duct. Fig. 518.-A highly magnified section of the submaxillary gland of the dog, stained with carmine. (Kolliker.) glands, passing in their course through two or three lymphatic glands placed on the surface and in the substance of the parotid. The nerves are derived from the carotid plexus of the sympathetic, the facial, the auriculo-temporal, and great auricular nerves. It is probable that the branch from the auriculo-temporal nerve is derived from the glosso-pharyngeal through the otic ganglion (see page 770). At all events, in some of the lower animals this has been proved experimentally to be the case. The submaxillary gland is situated below the jaw, in the anterior part of the submaxillary triangle of the neck. It is irregular in form and weighs about two drachms. It is covered by the integument, Platysma, deep cervical fascia, and the body of the lower jaw, corresponding to a depression on the inner surface of that bone, and lies upon the Mylo-hyoid, Hyo-glossus, and Stylo-glossus muscles, a portion of the gland passing beneath the posterior border of the Mylo-hyoid. In front of it is the anterior belly of the Digastric; behind, it is separated from the parotid gland by the stylo-maxillary ligament, and from the sublingual gland in front by the Mylo-hyoid muscle. The facial artery lies imbedded in a groove in its posterior and upper border. The duct of the submaxillary gland (Wharton s') is about two inches in length, and its walls are much thinner than those of the parotid duct. It commences by numerous branches from the deep portion of the gland, and passes forward and inward between the Mylo-hyoid and the Hyo-glossus and Genio-hyo-glossus mus- cles, then between the sublingual gland and the Genio-hyo-glossus, and opens by a narrow orifice on the summit of a small papilla at the side of the fraenum linguae. On the Hyo-glossus muscle it lies between the lingual and hypoglossal nerves, but THE SALIVARY GLANDS. 907 at the anterior border of the muscle it crosses under the lingual nerve, and is then placed above it. Vessels and Nerves.-The arteries supplying the submaxillary gland are branches of the facial and lingual. Its veins follow the course of the arteries. The nerves are derived from the submaxillary ganglion, through which it receives filaments from the chorda tympani of the facial and lingual branch of the inferior maxillary, from the mylo-hyoid branch of the inferior dental, and from the sympathetic. The sublingual gland is the smallest of the salivary glands. It is situated beneath the mucous membrane of the floor of the mouth, at the side of the fraenum linguae, in contact with the inner surface of the lower jaw, close to the symphysis. It is narrow, flattened, in shape somewhat like an almond, and weighs about a drachm. It is in relation, above, with the mucous membrane ; below, with the Mylo-hyoid muscle; in front, with the depression on the side of the symphysis of the lower jaw, and with its fellow of the opposite side; behind, with the deep part of the submaxillary gland; and internally, with the Genio-hyo-glossus, from which it is separated by the lingual nerve and Wharton's duct. Its excretory ducts (ducts of Rivini), from eight to twenty in number, open separately into the mouth, on the elevated crest of mucous membrane caused by the projection of the gland, on either side of the frgenum linguae. One or more join to form a tube which opens into the Whartonian duct; this is called the duct of Bartholin. Vessels and Nerves.-The sublingual gland is supplied with blood from the sublingual and submental arteries. Its nerves are derived from the lingual. Structure of Salivary Glands.-The salivary are compound racemose glands, consisting of numerous lobes, which are made up of smaller lobules connected together by dense areolar tissue, vessels, and ducts. Each lobule consists of the ramifications of a single duct, "branching frequently in a tree-like manner," the branches terminating in dilated ends or alveoli, on which the capillaries are distributed. These alveoli, however, as Pfliiger points out, are not necessarily spherical, though sometimes they assume that form; sometimes they are perfectly cylindrical, and very often they are mutually compressed. The alveoli are enclosed by a basement membrane which is continuous with the membrana propria of the duct. It presents a peculiar reticulated structure, having the appearance of a basket with open meshes, and consisting of a network of branched and flattened nucleated cells. The alveoli of the salivary glands are of two kinds, which differ both in the appearance of their secreting cells, in their size, and in the nature of their secretion. The one variety secretes a ropy fluid which contains mucin, and has therefore been named the mucous, whilst the other secretes a thinner and more watery fluid, which contains serum-albumin, and has been named serous or albuminous. The sublingual gland may be regarded as an example of the former variety, the parotid of the latter. The submaxillary is of the mixed variety, containing both mucous and serous alveoli, the latter, however, prepon- derating. Both alveoli are lined by cells, and it is by the character of these cells that the nature of the gland is chiefly to be determined. In addition, however, the alveoli of the serous glands are smaller than those of the mucous ones. The cells in the mucous alveoli are spheroidal in shape, glassy, transparent, and dimly striated in appearance. The nucleus is usually situated in the part of the cell which is next the basement membrane, against which it is sometimes flattened. The most remarkable peculiarity presented by these cells is, that they give off an extremely fine process, which is curved in a direction parallel to the surface of the alveolus, lies in contact with the membrana propria, and overlaps the process of neighboring cells. The cells contain a quantity of mucin, to which their clear, transparent appearance is due. Here and there in the alveoli are seen peculiar half-moon-shaped bodies lying 908 THE ORGANS OF DIGESTION between the cells and the membrana propria of the alveolus. They are termed the crescents of Grianuzzi or the demilunes of Heidenhain (Fig. 518), and are regarded by Pfiiiger as due to post-mortem change, but by most other later observers they are believed to be composed of polyhedral granular cells, which Heidenhain regards as young epithelial cells destined to supply the place of those salivary cells which have undergone disintegration. This view, however, is not accepted by Klein. Serous Alveoli.-In the serous alveoli the cells almost completely fill the cavity, so that there is hardly any lumen perceptible. Instead of presenting the clear, transparent appearance of the cells of the mucous alveoli, they present a granular appearance, due to distinct granules of an albuminous nature imbedded in a closely- reticulated protoplasm. The ducts which originate out of the alveoli are lined at their commencement by epithelium which differs little from the pavement type. As the ducts enlarge the epithelial cells change to the columnar type, and they are described by Pfiiiger as attached to the basement membrane by a brush of fine hair-like processes, which he believes to be continuous with the nerve-fibres. Other anatomists regard these cells as merely striated on their deep surface. The lobules of the salivary glands are richly supplied with blood-vessels which form a dense network in the interalveolar spaces. Fine plexuses of nerves are also found in the interlobular tissue. Pfiiiger describes the nerves as being directly continuous with the salivary cells of the alveolus, the nerve some- Fig. 519.-Illustrating Pfl tiger's views of the termination of the nerves in the alveolar cells. (From Stricker's 'Handbook.") a. Direct passage of nerve into a salivary cell. b. By the medium of a multipolar ganglion-cell, g. times passing through a ganglion-cell just before joining the alveolus (Fig. 519, a and b). This fact has not, however, been corroborated by other observers. There is no doubt that ganglia are to bo found in some salivary glands in connec- tion with the nerve-plexuses in the interlobular tissue; thus they are to be found in the submaxillary, but not in the parotid, but whether the ultimate fibrils are connected with the salivary cells, as asserted by Pfliiger, remains to be proved In the submaxillary and sublingual glands the lobes are larger and more loosely united than in the parotid. Mucous Glands.-Besides the salivary glands proper, numerous other glands are found in the mouth. They appear to secrete mucus only, which serves to keep the mouth moist during the intervals of the salivary secretion, and which is mixed with that secretion in swallowing. Many of these glands are found at the posterior part of the dorsum of the tongue, behind the circumvallate papillae, and also along its margins as far forward as the apex.1 Others lie around and in the tonsil between its crypts, and a large number in the soft palate. These glands are of the ordinary compound racemose type. 1 It has recently been shown by Ebner that many of these glands open into the trenches around the circumvallate papillae, and that their secretion is more watery than that of ordinary mucous glands. He supposes that they assist in the more rapid distribution of the substance to be tasted over the region where the special apparatus of the sense of taste is situated. FORM OF THE MOUTH. 909 Surface Form.-The orifice of the mouth is bounded by the lips, two thick, fleshy folds covered externally by integument and internally by mucous membrane, and consisting of muscles, vessels, nerves, areolar tissue, and numerous small glands. The size of the orifice of the mouth varies considerably in different individuals, but seems to bear a close relation to the size and prominence of the teeth. Its corners correspond pretty accurately to the outer border of the canine teeth. In the Mongolian tribes, where the front teeth are large and inclined for- ward, the mouth is large; and this, combined with the thick and everted lips which appear to be associated with prominent teeth, gives to the negro's face much of the peculiarity by which it is characterized. The smaller teeth and the slighter prominence of the alveolar arch of the more highly civilized races render the orifice of the mouth much smaller, and thus a small mouth is an indication of intelligence, and is regarded as an evidence of the higher civilization of the individual. Upon looking into the mouth, the first thing we may note is the tongue, the upper surface of which will be seen occupying the floor of the cavity. This surface is convex, and is marked along the middle line by a raphe which divides it into two symmetrical portions. The anterior two-thirds is rough and studded with papillae; the posterior third smooth and tuberculated, covered by numerous glands which project from the surface. Upon raising the tongue the mucous membrane which invests the upper surface may be traced covering the sides of the under surface, and then reflected over the floor of the mouth on to the inner surface of the lower jaw, a part of which it covers. As it passes over the borders of the tongue it changes its character, becoming thin and smooth and losing the papillae which are to be seen on the upper surface. In the middle line the mucous membrane on the under surface of the tip of the tongue forms a distinct fold, the fraenum linguae, by which this organ is connected to the sym- physis of the jaw. Occasionally it is found that this fraenum is rather shorter than natural, and, acting as a bridle, prevents the complete protrusion of the tongue. When this condition exists and an attempt is made to protrude the organ, the tip will be seen to remain buried in the floor of the mouth, and the dorsum of the tongue is rendered very convex, and more or less extruded from the mouth ; at the same time a deep furrow will be noticed to appear in the middle line of the anterior part of the dorsum. Sometimes, a little external to the fraenum, the ranine vein may be seen immediately beneath the mucous membrane. The corresponding artery, being more deeply placed, does not come into view, nor can its pulsation be felt with the finger. On either side of the fraenum, in the floor of the mouth, is a longitudinal elevation or ridge, produced by the projection of the sublingual gland, which lies immediately beneath the mucous membrane. And close to the attachment of the fraenum to the tip of the tongue may be seen on either side the slit-like orifices of Wharton's ducts, into which a fine probe may be passed without much difficulty. By everting the lips the smooth mucous membrane lining them may be examined, and may be traced from them on to the outer surface of the alveolar arch. In the middle line, both of the upper and lower lip, a small fold of mucous membrane passes from the lip to the bone, constituting the frcena; these are not so large as the fraenum linguae. By pulling outward the angle of the mouth, the mucous membrane lining the cheeks can be seen, and on it may be perceived a little papilla which marks the position of the orifice of Sten- son's duct-the duct of the parotid gland. The exact position of the orifice of the duct will be found to be opposite the second molar tooth of the upper jaw. The introduction of a probe into this duct is attended with considerable difficulty. The teeth are the next objects which claim our attention upon looking into the mouth. There are, as stated above, ten in either jaw in the temporary set, and sixteen in the permanent set. The gums, in which they are implanted, are dense, firm, and vascular. At the back of the mouth is seen the isthmus of the fauces, or, as it is popularly called, " the throatthis is the space between the pillars of the fauces on either side, anil is the means by which the mouth communicates with the pharynx. Above, it is bounded by the soft palate, the anterior surface of which is concave and covered with mucous membrane, which is continuous with that lining the roof of the mouth. Projecting from the middle of its lower border is a conical-shaped projection, the uvula. On either side of the isthmus of the fauces are the anterior and posterior pillars, formed by the Palato-glossus and Palato-pharyngeus muscles respectively, covered over by mucous membrane. Between the two pillars on either side is situated the tonsil. By their external surface these glands are in close relationship with the internal carotid artery, being separated from this vessel only by the thin plane of muscular fibres forming the wall of the pharynx. It is stated that this vessel may be wounded in remov- ing the tonsil. The extirpation of this glandular body is not unattended with danger of haemorrhage from other sources. Dr. Weir has stated that he believes that when haemorrhage occurs after their removal it arises from one of the palatine arteries having been wounded. These vessels are large: they lie in the muscular tissue of the palate, and when wounded are constantly exposed to disturbance from the contraction of the palatine muscles. The vessels of the tonsil, Dr. Weir states, are small and lie in the soft tissue, and readily contract when wounded. When the mouth is wide open a prominent tense fold of mucous membrane may be seen and felt, extending upward and backward from the position of the fang of the last molar tooth to the posterior part of the hard palate. This is caused by the Pterygo-maxillary ligament, which is attached by one extremity to the apex of the internal pterygoid plate, and by the other to the posterior extremity of the mylo-hyoid ridge of the lower jaw. It connects the Buccina- tor with the Superior constrictor of the pharynx. The fang of the last molar tooth indicates 910 THE ORGANS OF DIGESTION the position of the lingual (gustatory) nerve, where it is easily accessible, and can with readiness be divided in cases of cancer of the tongue (see page 772). On the inner side of the last molar tooth we can feel the hamular process of the internal pterygoid plate of the sphenoid bone, around which the tendon of the Tensor palati plays. The exact position of this process is of importance in performing the operation of staphylorraphy. About one-third of an inch in front of the hamular process, and the same distance directly inward from the last molar tooth, is the situation of the opening of the posterior palatine canal, through which emerges the pos- terior or descending palatine branch of the internal maxillary artery and one of the descending palatine nerves from Meckel's ganglion. The exact position of the opening on the subject may be ascertained by driving a needle through the tissues of the palate in this situation, when it will be at once felt to enter the canal. The artery emerging from the opening runs forward in a groove in the bone just internal to the alveolar border of the hard palate, and may be wounded in the operation for the cure of cleft palate. Under these circumstances the palatine canal may require plugging. By introducing the finger into the mouth the anterior border of the coronoid process of the jaw can be felt, and is especially prominent when the jaw is dislocated. By throwing the head well back a considerable portion of the posterior wall of the pharynx may be seen through the isthmus faucium, and on introducing the finger the anterior surface of the bodies of the upper cervical vertebrae may be felt immediately beneath the thin muscular stra- tum forming the wall of the pharynx. The finger can be hooked around the posterior border of the soft palate, and by turning it forward the posterior nares, separated by the septum, can be felt, or the presence of any adenoid or other growths in the naso-pharynx ascertained. THE PHARYNX. The pharynx is that part of the alimentary canal which is placed behind the nose, mouth, and larynx. It is a musculo-membranous sac, somewhat conical in form, with the base upward and the apex downward, extending from the under surface of the skull to the cricoid cartilage in front and the intervertebral disk between the fifth and sixth cervical vertebrae behind. The pharynx is about four inches and a half in length, and broader in the transverse than in the antero-posterior diameter. Its greatest breadth is opposite the cornua of the hyoid bone; its narrowest point, at its termination in the oesophagus. It is limited, above, by the body of the sphenoid and basilar process of the occipital bone; below, it is continuous with the oesophagus; posteriorly, it is connected by loose areolar tissue with the cervical portion of the vertebral column and the Longi colli and Recti capitis antici muscles; anteriorly, it is incomplete, and is attached in succession to the internal pterygoid plate, the pterygo-maxillary ligament, the lower jaw, the tongue, hyoid bone, and thyroid and cricoid cartilages; laterally, it is connected to the styloid processes and their mus- cles, and is in contact with the common and internal carotid arteries, the internal jugular veins, and the glosso-pharyngeal, pneumogastric, hypoglossal, and sym- pathetic nerves, and above with a small part of the Internal pterygoid muscles. It has seven openings communicating with it-the two posterior nares, the two Eustachian tubes, the mouth, larynx, and oesophagus. The posterior nares are the two oval openings (see page 224) situated at the upper part of the anterior wall of the pharynx. The two Eustachian tubes open one at each side of the upper part of the pharynx, at the back part of the inferior meatus. Below' the posterior nares are the posterior surface of the soft palate and uvula, the large aperture of the mouth, the base of the tongue, the epiglottis, and the cordiform opening of the larynx. The oesophageal opening is the lower contracted portion of the pharynx. Structure.-The pharynx is composed of three coats-mucous, fibrous, and muscular. The pharyngeal aponeurosis, or fibrous coat, is situated between the mucous and muscular layers. It is thick above, where the muscular fibres are wanting, and is firmly connected to the basilar process of the occipital and petrous portion of the temporal bones. As it descends it diminishes in thickness, and is gradually lost. It is strengthened posteriorly by a strong fibrous band which is attached above to the pharyngeal spine on the under surface of the basilar portion of the occipital bone, and passes downward, forming a median raphe, which gives attachment to the Constrictor muscles of the pharynx. THE (ESOPHAGUS. 911 The mucous coat is continuous with that lining the Eustachian tubes, the nares, the mouth, and the larynx. It is covered by columnar ciliated epithelium, as low down as on a level with the floor of the nares ; below that point the epithelium is of the squamous variety. Beneath the mucous membrane are found racemose mucous glands ; they are especially numerous at the upper part of the pharynx around the orifices of the Eustachian tubes. Throughout the pharynx are also numerous crypts or recesses, the walls of which are surrounded by lymphoid tissue similar to what is found in the tonsils. Across the back part of the pharyngeal cavity, between the two Eustachian tubes, a considerable mass of this tissue exists, and has been named the pharyngeal tonsil. Above this in the middle line is an irregular, flask-shaped depression of the mucous membrane, extending up as far as the basilar process of the occipital bone. It is known as the bursa pharyngea, and is the remains of the diverticulum of the alimentary canal, which is concerned in the development of the pituitary body (see page 121). The muscular coat has been already described (page 421). Surgical Anatomy.-The internal carotid artery is in close relation with the pharynx, so that its pulsations can be felt through the mouth. It has been occasionally wounded by sharp- pointed instruments introduced into the mouth and thrust through the wall of the pharynx. In aneurism of this vessel in the neck the tumor necessarily bulges into the pharynx, as this is the direction in which it meets with the least resistance, nothing lying between the vessel and the mucous membrane except the thin Constrictor muscle, whereas on the outer side there is the dense cervical fascia, the muscles descending from the styloid process, and the margin of the Sterno-mastoid. The mucous membrane of the pharynx is very vascular, and is often the seat of inflamma- tion, frequently of a septic character, and dangerous on account of its tendency to spread to the larynx. On account of the tissue which surrounds the pharyngeal wall being loose and lax, the inflammation is liable to spread through it far and wide, extending downward into the posterior mediastinum along the oesophagus. Abscess may form in the connective tissue behind the pharynx, between it and the vertebral column, constituting what is known as post-pharyngeal abscess. This is most commonly due to caries of the cervical vertebrae, but may also be caused by suppuration of a lymphatic gland which is situated in this position opposite the axis, and which receives lymphatics from the nares, or by a gumma or by acute pharyngitis. The abscess may be most easily evacuated by an incision, with a guarded bistoury, through the mouth. It has recently been proposed to open the abscess aseptically by an incision in the neck behind the Sterno-mastoid. The operation, however, is a difficult one, unless the abscess is pointing later- ally, and does not give such free access to the seat of disease for the removal of necrosed bone, if any exists, and does not appear to present sufficient advantages to warrant its performance. Foreign bodies not unfrequently become lodged in the pharynx, and most usually at its termination at about the level of the cricoid cartilage, just beyond the reach of the finger, as the distance from the arch of the teeth to the commencement of the oesophagus is about six inches. The position of the opening of the Eustachian tubes should be carefully studied with a view to catheterism of these tubes, and the student should practise passing a catheter into them. This is to be done by introducing the instrument through the anterior nares, so that its point rests on the floor of the nasal cavity close to the septum ; it is then pushed gradually and slowly back- ward until the posterior wall of the pharynx is reached. Then, having been slightly withdrawn so as to free the point from the wall of the pharynx, it is rotated outward and upward, so that the ring of the instrument is turned toward the external ear, and it can then be made to glide into the Eustachian tube. The oesophagus, or gullet, is a muscular canal, about nine inches in length, extending from the pharynx to the stomach. It commences at the upper border of the cricoid cartilage, opposite the intervertebral disk between the fifth and sixth cervical vertebrae, descends along the front of the spine through the posterior mediastinum, passes through the Diaphragm, and, entering the abdomen, terminates at the cardiac orifice of the stomach, opposite the tenth dorsal vertebra or the intervertebral disk between the tenth and eleventh dorsal vertebrae. The general direction of the oesophagus is vertical, but it presents two or three slight curves in its course. At its commencement it is placed in the median line, but it inclines to the left side as far as the root of the neck, gradually passes to the middle line again, and finally again deviates to the left as it passes forward to the oesophageal opening of the Diaphragm. The oesophagus also presents an antero-posterioi THE (ESOPHAGUS. 912 THE ORGANS OF DIGESTION. flexure, corresponding to the curvature of the cervical and thoracic portions of the spine. It is the narrowest part of the alimentary canal, being most contracted at its commencement and at the point where it passes through the Diaphragm. Relations.-In the neck the oesophagus is in relation, in front, with the trachea, and at the lower part of the neck, where it projects to the left side, with the thyroid gland and thoracic duct; behind, it rests upon the vertebral column and Longi colli muscles; on each side, it is in relation with the common carotid artery (especially the left, as it inclines to that side) and part of the lateral lobes of the thyroid gland; the recurrent laryngeal nerves ascend between it and the trachea. In the thorax it is at first situated a little to the left of the median line ; it then passes behind the left side of the aortic arch, and descends in the posterior mediastinum, along the right side of the aorta, nearly to the Diaphragm, where it passes in front and a little to the left of the artery, previous to entering the abdomen. It is in relation, in front, with the trachea, the arch of the aorta, left carotid, and left subclavian arteries, the left bronchus, and the posterior surface of the pericardium; behind, it rests upon the vertebral column, the Longi colli muscles, and the intercostal vessels, and below, near the Diaphragm, upon the front of the aorta; laterally, it is covered by the pleurse : the vena azygos major lies on the right and the descending aorta on the left side. The pneumogastric nerves descend in close contact with it, the right nerve passing down behind, and the left nerve in front of it. Structure.-The oesophagus has three coats-an external or muscular; a middle or areolar; and an internal or mucous coat. The muscular coat is composed of two planes of fibres of considerable thickness, an external longitudinal and an internal circular. The longitudinal fibres are arranged, at the commencement of the tube, in three fasciculi: one in front, which is attached to the vertical ridge on the posterior surface of the cricoid cartilage; and one at each side, which is continuous with the fibres of the Inferior constrictor : as they descend they blend together and form a uniform layer, which covers the outer surface of the tube. Accessory slips of muscular fibres are described by Dr. Cunningham as passing between the oesophagus and the pleura, where it covers the thoracic aorta (almost always), or the root of the left bronchus (usually), or the back of the pericardium or corner of the mediastinum (more rarely), as well as other still more rare accessory fibres. In Fig. 520, taken from a dissection in the Museum of the Royal College of Surgeons, several of these accessory slips may be seen passing from the oesophagus to the pleura, and two slips to the back of the trachea just above its bifurcation. The circular fibres are continuous above with the Inferior constrictor; their direction is transverse at the upper and lower parts of the tube, but oblique in the central part. The muscular fibres in the upper part of the oesophagus are of a red color, and consist chiefly of the striped variety, but below they consist for the most part of involuntary muscular fibre. The areolar coat connects loosely the mucous and muscular coats. The mucous coat is thick, of a reddish color above and pale below. It is disposed in longitudinal folds, which disappear on distension of the tube. Its surface is studded with minute papillae, and it is covered throughout with a thick layer of stratified pavement epithelium. Beneath the mucous membrane, between it and the areolar coat, is a layer of longitudinally arranged non-striped muscular fibres. This is the muscularis mucosae. At the commencement it is absent, or only represented by a few scattered bundles; lower down it forms a considerable stratum. The oesophageal glands are numerous small compound racemose glands scattered throughout the tube; they are lodged in the submucous tissue, and open upon the surface by a long excretory duct. They are most numerous at the lower part of the tube, where they form a ring round the cardiac orifice. THE (ESOPHAGUS. 913 Vessels of the (Esophagus.-The arteries supplying the oesophagus are derived from the inferior thyroid branch of the thyroid axis of the subclavian, from the descending thoracic aorta, and from the gastric branch of the coeliac axis from the abdominal aorta. They have for the most part a longitudinal direction. Nerves of the (Esophagus.-The nerves are derived from the pneumogastric and from the sympathetic; they form a plexus in which are groups of ganglion- cells between the two layers of the muscular coats, and also a second plexus in the submucous tissue. Surgical Anatomy.-The relations of the oesophagus are of considerable practical interest to the surgeon, as he is frequently required, in cases of stricture of this tube, to dilate the canal by a bougie, when it is of importance that the direction of the oesophagus and its relations to surrounding parts should be remembered. In cases of malignant disease of the oesophagus, where its tissues have become softened from infiltration of the morbid deposit, the greatest care is requisite in directing the bougie through the strictured part, as a false passage may easily be made, and the instrument may pass into the medi- astinum, or into one or the other pleural cavity, or even into the pericardium. The student should also remember that contraction of the oesophagus, and consequent symptoms of stricture, are occa- sionally produced by an aneurism of some part of the aorta pressing upon this tube. In such a case the passage of a bougie could only hasten the fatal issue. In passing a bougie the left fore finger should be intro- duced into the mouth and the epiglottis felt for, care being taken not to throw the head too far backward. The bougie is then to be passed beyond the finger until it touches the pos- terior wall of the pharynx. The patient is now asked to swal- low, and at the moment of swallowing the bougie is passed gently onward, all violence being carefully avoided. It occasionally happens that a foreign body becomes im- pacted in the oesophagus which can neither be brought upward nor moved downward. When all ordinary means for its re- moval have failed, excision is the only resource. This, of course, can only be performed when it is not very low down. If the foreign Body is allowed to remain, extensive inflamma- tion and ulceration of the oesophagus may ensue. In one case the foreign body ultimately penetrated the intervertebral sub- stance, and destroyed life by inflammation of the membranes and substance of the cord. The operation of oesophagotomy is thus performed : The patient being placed upon his back, with the head and shoul- ders slightly elevated, an incision, about four inches in length, should be made on the left side of the trachea, from the thy- roid cartilage downward, dividing the skin and Platysma. The edges of the wound being separated, the Omo-hyoid muscle should, if necessary, be divided, and the fibres of the Sterno-hyoid and Sterno-thyroid muscles drawn inward; the sheath of the carotid vessels, being, exposed, should be drawn outward, and retained in that position by retractors : the oesoph- agus will now he exposed, and should be divided over the foreign body, which can then be removed. Great care is necessary to avoid wounding the thyroid vessels, the thyroid gland, and the laryngeal nerves. The oesophagus may be obstructed not only by foreign bodies, but also by changes in its coats, producing stricture, or by pressure on it from without of new growths or aneurism, etc. The different forms of stricture are: (1) the spasmodic, usually occurring in nervous women, and intermittent in character, so that the dysphagia is not constant; (2) fibrous, due to cicatrization after injuries, such as swallowing corrosive fluids or boiling water ; and (3) malig- nant, usually epitheliomatous in its nature. This is situated generally either at the upper end of the tube, opposite to the cricoid cartilage, or at its lower end at the cardiac orifice, but is also occasionally found at that part of the tube where it is crossed by the left bronchus. The operation of oesophagostomy has occasionally been performed in cases where the stricture in the oesophagus is at the upper part, with a view to making a permanent opening below the stricture through which to feed the patient, but the operation has been far from a successful one, and the risk of setting up diffuse inflammation in the loose planes of connective tissue deep in the neck is so great that it would appear to be better, if any operative interference Fig. 520.-Accessory muscular fi- bres between the oesophagus and pleura, and oesophagus and trachea. (From a preparation in the Museum of the Royal College of Surgeons.) 914 THE ORGANS OF DIGESTION. Fig. 521.--Topography of thoracic and abdominal viscera. THE ABDOMEN. 915 is undertaken, to perforin gastrostomy. The operation is performed in the same manner as oesophagotomy, but the edges of the opening in the oesophagus are stitched to the skin incision. THE ABDOMEN. The Abdomen is the largest cavity in the body. It is of an oval form, the extremities of the oval being directed upward and downward, the upper one being formed by the under surface of the Diaphragm, the lower by the upper concave surface of the Levator ani. In order to facilitate description it is arti- ficially divided into two parts-an upper and larger part, the abdomen proper; and a lower and smaller part, the pelvis. These two cavities are not separated from each other, but the limit between them is marked by the brim of the true pelvis. The space is wider above than below, and measures more in the vertical than in the transverse diameter. Boundaries.-The abdomen proper is bounded, in front and at the sides, by the lower ribs, the abdominal muscles, and the venter ilii; behind, by the vertebral column and the Psoas and Quadratus lumborum muscles; above, by the Dia- phragm ; below, by the brim of the pelvis. The muscles forming the boundaries of the cavity are lined upon their inner surface by a layer of fascia, differently named according to the part which it covers. The abdomen contains the greater part of the alimentary canal; some of the accessory organs to digestion-viz. the liver, pancreas, and spleen; and the kid- neys and suprarenal capsules. Most of these structures, as well as the wall of the cavity in which they are contained, are covered by an extensive and compli- cated serous membrane, the peritoneum. The apertures found in the walls of the abdomen for the transmission of struc- tures to or from it are-the umbilicus, for the transmission (in the foetus) of the umbilical vessels ; the caval opening in the Diaphragm, for the transmission of the inferior vena cava ; the aortic opening, for the passage of the aorta, vena azygos, and thoracic duct; and the oesophageal opening, for the oesophagus and pneumogastric nerves. Below, there are two apertures on each side, one for the passage of the femoral vessels, and the other for the transmission of the spermatic cord in the male and the round ligament in the female. Regions.-For convenience of description of the viscera, as well as of reference to the morbid condition of the contained parts, the abdomen is artificially divided into nine regions. Thus, if two circular lines are drawn round the body, the one through the extremities of the ninth ribs where they join their costal cartilages, and the other through the highest point of the crests of the ilia, the abdominal cavity is divided into three zones-an upper, a middle, and a lower. If two par- allel lines are drawn perpendicularly upward from the centre of Poupart's liga- ment, each of these zones is subdivided into three parts-a middle and two lateral. The middle region of the upper zone is called the epigastric (lire, over; the stomach); and the two lateral regions, the right and left hypochondriac (bnb, under; yovopot, the cartilages). The central region of the middle zone is the umbilical, and the two lateral regions, the right and left lumbar. The middle region of the lower zone is the hypogastric or pubic region, and the lateral regions are the right and left inguinal or iliac. The viscera contained in these different regions are the following (Fig. 522): Right Hypochondriac. The right lobe of the liver and the gall-bladder, hepatic flexure of the colon, and part of the right kidney. Epigastric Region. The pyloric end of the stomach, left lobe of the liver, and lobulus Spigelii, the pancreas, the duode- num, parts of the kidneys and the suprarenal cap- sules. Left Hypochondriac. The splenic end of the stomach, the spleen and extremity of the pancreas, the splenic flexure of the colon, and part of the left kidney. 916 THE ORGANS OF DIGESTION. Right Lumbar. Ascending colon, part of the right kidney, and some convolutions of the small intestines. Umbilical Region. The transverse colon, part of the great omentum and mesentery, .transverse part of the duodenum, and some convolutions of the jejunum and ileum, and part of both kidneys. Left Lumbar. Descending colon, part of the omentum, part of the left kidney, and some convolutions of the small intestines. Right Inguinal (Iliac). The caecum, appendix caeci. Hypogastric Region. Convolutions of the small intestines, the blad- der in children, and in adults if distended, and the uterus during pregnancy. Left Inguinal (Iliac). Sigmoid flexure of the colon. Fig. 522.-The regions of the abdomen and their contents. (Edge of costal cartilages in dotted outline.) THE PERITONEUM. The peritoneum to extend around) is a serous membrane, and partially invests all the viscera contained in the abdominal and pelvic cavities. In consequence of the number and different shapes of these viscera the reflections of the peritoneum, as it invests them, are exceedingly complex and difficult to understand. The peritoneum partially invests all the viscera contained in the abdominal and pelvic cavities, forming the visceral layer of the membrane ; it is then reflected upon the internal surface of the parietes of those cavities, forming the parietal THE PERITONEUM. 917 layer. The free surface of the peritoneum is smooth, moist, and covered by a layer of flattened endothelial cells ; its attached surface is rough, being connected to the viscera and inner surface of the parietes by means of areolar tissue called the subserous areolar tissue. The parietal portion is loosely connected with the fascia lining the abdomen and pelvis, but more closely to the under surface of the Diaphragm and in the middle line of the abdomen. In order to get a first general idea of the peritoneum and its reflections the student should bear in mind that all the abdominal and pelvic viscera are placed external to it, and that it is a shut sac superimposed upon the viscera.1 Let the student imagine that all the viscera are in their proper positions in the abdominal cavity, but uninvested by peritoneum. Upon the top of them is Pleura. Liver. through foramen of Winslow. .Lesser omentum. Stomach. Fig. 523.-The reflections of the peritoneum, as seen in a vertical section of the abdomen. placed a large closed sac, the walls of which are of extreme thinness, and wherever there is a cleft between two viscera a process of peritoneum derived from the part of the sac in contact with the viscera is tucked in between them, so as to cover the adjacent surfaces of the two viscera and separate them from each other, and at the same time, by becoming adherent to the viscera, form an investment for them. Thus in Fig. 523 such a diverticulum or process may be seen tucked in between the under surface of the liver and the upper surface of the stomach, and extending between the two as far backward as the portal vein, hepatic artery, and hepatic duct, which it covers on their anterior surfaces, forming the anterior layer of what is termed the lesser omentum. Another diverticulum or process is tucked in round the hepatic artery as it passes forward and upward to the liver, and afterward expands into a large 1 We may disregard, for the present, the fact that the peritoneum in the female is not an absolutely closed sac, since the Fallopian tubes open into it at their free extremities. 918 THE ORGANS OF DIGESTION. sac or bag, which covers the posterior surface of the liver and stomach and the upper part of the posterior wall of the abdomen, separating these structures from each other. This large cul-de-sac of peritoneum is called the lesser cavity of the peritoneum, but is only a part of the general cavity, differentiated from it by the constriction produced at the situation of the hepatic artery. In this respect the peritoneum may be compared to an hour-glass with two unequal globes, the smaller one constituting the lesser cavity of the peritoneum, the larger one the greater cavity, and the constriction where the two globes communicate corre- sponding to the constriction in the peritoneum where it hooks round the hepatic artery. This constriction is called the foramen of Winslow. Between the transverse fissure of the liver and the lesser curvature of the stomach there is thus a double layer of peritoneum, the anterior layer being part of the greater bag of the peritoneum, where it is tucked in between the liver and the stomach from the front, while the posterior layer is part of the lesser bag of the peritoneum where it is tucked in round the hepatic artery. These two layers constitute the lesser omentum. Between the two layers are situated the hepatic artery, the portal vein, and the hepatic duct. A process of this lesser bag of the peritoneum is pushed backward and upward behind the liver, extending as far as the under surface of the Diaphragm, the posterior part of which it covers. At its extremity this process is in contact with a process of the greater bag of the peritoneum, which is pushed in from the front, in the cleft between the upper surface of the liver and the under surface of the Diaphragm. Where these two layers are in contact (passing down from the Diaphragm to the liver) they form some of the ligaments of the liver, thus supporting and holding it in position. Another process of this lesser bag is pushed downward between the stomach and the transverse colon, and forms the two inner of the four layers of the great omentum. Thus the lesser cavity of the peritoneum is seen to be a complete sac or bag, separating the back and part of the under surface of the liver, the posterior wall of the stomach, and the upper surface of the transverse colon from the back part of the under surface of the Diaphragm and the upper part of the posterior wall of the abdomen. The greater cavity of the peritoneum separates the anterior surfaces of the viscera from the front wall of the abdomen; so that in our comparison of the two cavities to an hour-glass it must be borne in mind that they are not in the same straight line as the two globes of the hour-glass, but that at the point of constriction the smaller cavity is bent round the hepatic artery, so as to lie behind the greater cavity. The greater sac of the peritoneum is placed in front of the viscera, one layer being in contact with them, the other lining the inner surface of the anterior wall of the abdomen. The layer which is in relation with the viscera sends backward diverticula which pass between the various organs, and in certain places comes in contact with the peritoneum forming the lesser bag, in the manner described above. Thus we have one of these diverticula sent backward between the liver and Dia- phragm, covering the anterior part of the under surface of the Diaphragm, until it meets the peritoneum of the lesser cavity, and covering the upper surface of the liver as far backward as the ligaments. The extremity of this diverticulum is in contact with a similar diverticulum of the lesser bag, already described, and the two layers, when in apposition, form the coronary and lateral ligaments of the liver. Another process, which has already been mentioned, is sent backward between the under surface of the liver and the stomach to meet a similar process of the lesser cavity prolonged from behind forward. Where the two are in apposition the lesser or gastro-hepatic omentum is formed. A third diverticulum is carried backward to the posterior wall of the abdomen between the transverse colon and the small intestine. This prolongation covers the under surface of the transverse colon, and forms the under layer of the transverse meso-colon and the upper layer of the mesentery; by its extremity it is in contact with the posterior wall of the abdomen and covers a part of the abdominal aorta. Between the greater curvature THE PERITONEUM. 919 of the stomach and the transverse colon there is a fold or reduplication of the peritoneum, which contains between its layers a similar fold from the lesser cavity, and forms the apron or great omentum. Another fold of the greater bag of the peritoneum is pushed backward to the spine between the small intestines and the pelvic viscera. This fold forms the lower layer of the mesentery, covers a considerable portion of the lowrer part of the abdominal wall, and passes over the sacro-vertebral angle into the pelvis. Below, wThere it covers the upper part of the pelvic viscera, it sends diverticula downward between them, separating them from one another; thus one is sent downward between the back of the rectum and the sacrum, another between the rectum and the bladder. In the female one is sent down between the rectum and uterus, another between the uterus and bladder. These, then, are the various diverticula sent off' from the posterior layer of the greater bag of the peritoneum; the anterior layer simply lines the anterior wall of the abdomen, and is continuous at its extremities with the posterior layer. The student will perhaps be better able to follow these various folds or reflections of the peritoneum by a reference to the accompanying plan (Fig. 524), which should Process between. Diaphragm and liver.' liver and Diaphragm. Between Uteri and stomach* Between liver stomach.. Between transverse colon and small intestine] Between small intestine and pelvic viscera.. Between sacrum, and rectum. Between rectum and uterus. Fig. 524.-Plan of the peritoneum. be studied in conjunction with Fig. 523. He must not forget, however, that though the lesser and greater cavities of the peritoneum are here represented, for the sake of clearness, as quite distinct from each other, they are not really so, but that they both form part of one great cavity. The reflections of the peritoneum may be traced in two different ways, either by considering the folds which form each cavity separately or by describing them together. According to the first plan (Fig. 523), the liver should be raised and supported in that position, and the stomach should be depressed, when a thin membranous layer is seen passing from the transverse fissure of the liver to the upper border of the stomach : this is the lesser or gastro-hepatic omentum. It consists of two delicate layers of peritoneum, an anterior and a posterior, between which are contained the 920 THE ORGANS OF DIGESTION. hepatic vessels and nerves. Of these two layers, the anterior should first be traced, and then the posterior. The anterior layer descends to the lesser curvature of the stomach, and covers its anterior surface as far as the great curvature: it descends for some distance in front of the small intestines, and, returning - upon itself to the transverse colon, forms the external layer of the great omentum ; it then covers the under surface of the transverse colon, and, passing to the back part of the abdominal cavity, forms the inferior layer of the transverse meso-colon. It then descends in front of the duodenum, the aorta, and vena cava, as far as the superior mesenteric artery, along which it passes to invest the small intestines, and, returning to the vertebral column, forms the mesentery ; whilst on either side it covers the ascending and descending colon, and is thus continuous with the peritoneum lining the walls of the abdomen. From the root of the mesentery it descends along the front of the spine into the pelvis, and surrounds the upper part of the rectum, which it holds in its position by means of a distinct fold, the meso-rectum. Its course in the male and female now differs. In the male it forms a fold between the rectum and bladder, the recto-vesical fold, and ascends over the posterior surface of the latter organ as far as its summit. In the female it descends into the pelvis in front of the rectum, forms a fold between the rectum and vagina, the recto-vaginal fold (pouch of Douglas), covers a small part of the posterior wall of the vagina, and passes on to the uterus, the fundus and body of which it covers. From the sides of the uterus it is reflected to the wall of the pelvis, forming the broad ligaments, and from the anterior surface of the uterus it ascends upon the posterior wall of the bladder as far as its summit. From this point it may be traced, as in the male, ascending upon the anterior parietes of the abdomen, to the under surface of the Diaphragm, from which it is reflected upon the liver, forming the upper layer of the coronary and the lateral and longitudinal ligaments. It then covers the upper and under surfaces of the liver, and at the transverse fissure becomes continuous with the anterior layer of the lesser omentum, the point whence its reflection was originally traced. The posterior layer of the lesser omentum descends to the lesser curvature of the stomach, and covers its posterior surface as far as the great curvature; it then descends for some distance in front of the small intestines, and, returning upon itself to the transverse colon, forms the internal layer of the great omentum ; it covers the upper surface of the transverse colon, and, passing backward to the spine, forms the upper layer of the transverse meso-colon. Ascending in front of the pancreas and crura of the Diaphragm, it lines the back part of the under surface of that muscle, from which it is reflected on to the posterior border of the liver, forming the inferior layer of the coronary ligament. From the under surface of the liver it may be traced to the transverse fissure, where it is continuous with the posterior layer of the lesser omentum, the point whence its reflection was originally traced. The space included in the reflections of this layer of the peritoneum is called the lesser cavity of the peritoneum, or cavity of the great omentum. It is bounded, in front, by the lesser omentum, the stomach, and the descending part of the great omentum ; behind, by the ascending part of the great omentum, the transverse colon, transverse meso-colon, and its ascending layer; above, by the liver; and beloiv, by the folding of the great omentum. This space communicates with the general peritoneal cavity through the foramen of Winslow, which is situated behind the right or free border of the lesser omentum. In order to trace the two layers together, we commence at the top of the abdominal cavity ; that is to say, the under surface of the Diaphragm. This muscle is covered throughout the greater part of its extent by peritoneum, one layer extending from its anterior border backward, the other from its posterior border forward. Where the two layers meet they are reflected downward to the liver, THE PERITONEUM. 921 forming the coronary and lateral ligaments of this organ. When these two layers reach the liver, they again separate to enclose this viscus, the one passing in front and the other behind, and they meet again on its under surface at the transverse fissure. From this fissure they turn downward to the lesser curvature of the stomach, forming the gastro-hepatic or lesser omentum, and enclosing the hepatic artery, the portal vein, and the hepatic duct, which are contained between the two folds in this situation. From the lesser curvature of the stomach the two layers pass over the anterior and posterior surfaces of the viscus, enclosing it and meet- ing again at the greater curvature. From this point they pass down in front of the small intestines, between this tube and the abdominal wall, and are reflected on themselves, passing upward to the transverse colon, and forming the apron or great omentum. This reflection, therefore, consists of/our layers of peritoneum. When the two posterior layers of the great omentum, in their reflection upward, reach the transverse colon, they separate to enclose this portion of the intestinal tube, the one layer passing above it and the other below. They meet on its pos- terior surface and pass backward to the vertebral column, forming what is called the transverse meso-colon. At this point the two layers separate. The one which formed the upper surface of the transverse meso-colon, and which belongs to the lesser cavity, passes upward in front of the pancreas and crura of the Diaphragm to the back part of the under surface of the Diaphragm, the point from which the description of this layer was commenced. The other, which formed the inferior layer of the transverse meso-colon, turns downward in front of the duodenum, aorta, and inferior vena cava, and can be traced, as a single layer, in the manner above described, investing the small intestines and forming the mesentery; then passing over the sacro-vertebral angle into the pelvis, the viscera of which it partially invests, and finally over the posterior surface of the front wall of the abdomen to the under surface of the Diaphragm, the point from which the description of this layer was commenced. In addition to tracing the peritoneum vertically, as has now been done, it is necessary to trace it horizontally. If this is done below the transverse colon, the circle is extremely simple, as it includes only the greater bag of the peritoneum (Fig. 523). Above the level of the transverse colon the arrangement is more com- plicated, on account of the existence of two sacs. Starting from the linea alba, below the level of the transverse colon, and tra- cing the continuity in a horizontal direction to the right, we find the peritoneum covering the internal surface of the abdominal wall almost as far as the anterior border of the Quadratus lumborum muscle; it encloses the caecum, forming the meso-caecum, and is reflected over the sides and anterior surface of the ascending colon, fixing it to the abdominal wall, thus forming the meso-caecum and the ascending meso-colon, from which it can be traced over the kidney to the front of the bodies of the vertebrae. It then passes along the mesenteric vessels to invest the small intestines, and back again to the spine, forming the mesentery, between the layers of which are contained the blood-vessels, nerves, lacteals, and glands. Lastly, it passes over the left kidney to the sides and anterior surface of the descending colon, and, reaching the abdominal wall, it passes along it to the mid- dle line of the abdomen. Above the transverse colon (Fig. 525) the peritoneum can be traced, forming the greater and lesser cavities, and their communication through the foramen of Winslow can be demonstrated. Commencing in the middle line of the abdomen the membrane may be traced lining its anterior wall, and on the right side sending a process backward to encircle the obliterated umbilical vein (the round ligament of the liver), forming the falciform or longitudinal ligament of the liver. Con- tinuing its course to the right, it is reflected over the front of the upper part of the right kidney, across the vena cava inferior and aorta, and over the left kidney to the hilum of the spleen. From this point it is reflected on to the posterior surface of the stomach, which it covers, and from its right extremity it passes around the vessels passing to the transverse fissure of the liver, and back again to the stomach 922 THE ORGANS OF DIGESTION. as the lesser omentum, and thus it forms the anterior boundary of the foramen of Winslow. It now covers the front of the stomach, and upon reaching the cardiac extremity it passes to the spleen, which it encloses, forming the gastro- splenic omentum. From the hilum of the spleen it turns backward to reach the abdominal wall, along which it courses to reach the median line of the abdomen. The foramen of Winslow is bounded, in front, by the lesser omentum, enclosing Hepatic artery, portal vein and hepatic duct, Lesser omentum, Round ligament of liver. Abdominal aorta. '-Lv 7- Vena cava. CVura of Diaphragm. Fig. 525.-Transverse section of peritoneum. (An arrow has been introduced into the foramen of Winslow.) the vena portte and the hepatic artery and duct; behind, by the inferior vena cava; above, by the lobulus Spigelii and lobulus caudatus; below, by the hepatic artery curving forward from the coeliac axis. The reflections of the peritoneum over the transverse colon are somewhat differently described by some authors (Luschka, Holden), and there is no doubt, as was long ago pointed out by Haller, that the arrangement in the foetus is different from that which has been described above. In the foetus, and even in the young child, the two ascending layers of the great omentum can be traced passing together over the transverse colon, instead of embracing it, as described above, and passing back to the spine as a double fold, which can be separated from the transverse colon and transverse meso-colon. Upon reaching the spine the two layers separate : the upper one (the inner of the two ascending layers of the great omentum) passes upward in front of the pancreas and crura of the Diaphragm, forming the posterior boundary of the lesser bag of the peritoneum, in a similar manner to the upper layer of the transverse meso-colon in the former description. The other fold (the outer of the ascending layer of the great omentum) after reaching the spine is turned forward again on itself as far as the transverse colon, which it covers, and is again reflected back to the spine, to pass down in front of the aorta to form the mesentery, in a similar manner to the lower layer of the transverse meso-colon in the former description. Thus the transverse colon is invested by a distinct fold of peritoneum, prolonged forward from the spine to surround it, in a very similar manner to the way in which the small intestines are surrounded. In the adult, however, as a rule, this arrangement disappears. Probably adhesion of the layers of which the foetal duplication is composed takes place, and then absorption, and thus the arrangement is brought about which has been described above as most frequently seen in the adult subject. It may be that the foetal duplicature is " drawn or pushed forward from its place in the progress of visceral development, and thus effaced." 1 Viscera covered by Peritoneum.-The viscera thus shown to be almost entirely 1 Quain's Anatomy, vol. ii. p. 485, 8th ed. THE PER J TONE UM. 923 invested by peritoneum are, the liver, stomach, spleen, first portion of the duodenum, the jejunum and ileum, the transverse colon, the caecum, sigmoid flexure, upper half of the rectum, the uterus, and ovaries. Viscera Partially covered by Peritoneum.-The viscera only partially invested by peritoneum are-the descending and transverse portions of the duodenum, the ascending and descending colon, the middle portion of the rectum, and the upper part of the vagina and posterior wall of the bladder. The kidneys, suprarenal capsules, and pancreas are covered by the membrane without receiving any special investment from it. Viscera uncovered by Peritoneum.-The lower end of the rectum, the neck, base, and anterior surface of the bladder, the whole of the front, and the lower part of the posterior wall of the vagina have no peritoneal covering. Numerous folds are formed by the peritoneum, extending between the various organs. These serve to hold them in position, and at the same time enclose the vessels and nerves proceeding to each part. Some of the folds are called ligaments, from their serving to support the organs in position ; others, which connect certain parts of the intestine with the abdominal wall, constitute the mesenteries; and lastly, those which proceed from the stomach to certain viscera in its neighborhood are called omenta. The Ligaments, formed by folds of the peritoneum, include those of the liver, spleen, bladder, and uterus. They will be found described with their respective organs. The Omenta are-the lesser omentum, the great omentum, and the gastro-splenic omentum. The lesser omentum (gastro-hepatic) is the duplicature which extends between the transverse fissure of the liver and the lesser curvature of the stomach. It is extremely thin, and consists of two layers of peritoneum. At the left border its two layers pass on to the end of the oesophagus ; but at the right border, where it is free, they are continuous, and form a free rounded margin, which contains between its layers the hepatic artery, the common bile-duct, the portal vein, lymphatics, and the hepatic plexus of nerves,-all these structures being enclosed in loose areolar tissue, called Grlissons capsule. Between the layers where they are attached to the stomach lie the gastric artery and the pyloric branch of the hepatic, anastomosing with it. The great omentum (gastro-colic) is the largest peritoneal fold. It consists of four layers of peritoneum, two of which descend from the stomach, one from its anterior, the other from its posterior surface, and, uniting at its lower border, descend in front of the small intestines as low down as the pelvis; they then turn upon themselves, and ascend again as far as the transverse colon, where they separate and enclose that part of the intestine. These separate layers may be easily demonstrated in the young subject, but in the adult they are more or less inseparably blended. The left border of the great omentum is continuous with the gastro-splenic omentum; its right border extends as far only as the duodenum. The great omentum is usually thin, presents a cribriform appearance, and always contains some adipose tissue, which in fat subjects accumulates in considerable quantity. Its use appears to be to protect the intestines from the cold and to facilitate their movement upon each other during their vermicular action. Between its twro anterior layers is the anastomosis between the right and left gastro-epiploica arteries. The gastro-splenic omentum is the fold which connects the concave surface of the spleen to the cul-de-sac of the stomach, being continuous by its lower border with the great omentum. It contains the splenic vessels and vasa brevia. The Mesenteries are-the mesentery proper, the meso-caecum, the ascending, transverse, and descending meso-colon, the sigmoid meso-colon, and the meso- rectum. The mesentery (gsaov, evrepov), so called from being connected to the middle of the cylinder of the small intestine, is the broad fold of peritoneum which connects 924 THE ORGANS OF DIGESTION. the convolutions of the jejunum and ileum with the posterior wall of the abdomen. Its root, the part connected with the vertebral column, is narrow, about six inches in length, and directed obliquely from the left side of the second lumbar vertebra to the right sacro-iliac symphysis (Fig. 526). Its intestinal border is much longer, and here its two layers separate, so as to enclose the intestine and form its peri- toneal coat. Its breadth between its vertebral and intestinal border is about four inches. Its upper border is continuous with the under surface of the transverse Right lateral liaament of liver. Falciform ligament of liver. Left lateral ligament of liver. "'Peritoneum. 'Extra-peritoneal tissue. ( Diaphragmatic end of 2 gastro-hepatic omentum. ' Gastro-phrenic ligament. ■Gastro-splenic omentum. •Foramen of Winslow. "Duodenum {1st part). - Costo-colic ligament. y Dot between two anterior layers of great omentum. Transverse meso-colon. m ( Bare surface for descend- < ing colon. . ( The two layers of the " ( mesentery proper. J Bare surface for ascend- ( ing colon. ..Sigmoid meso-colon. .Bare surf ace for caecum. ■Meso rectum. 5 Bare surface for 2nd part ' t of rectum. 5 Left lateral false liga- ' ( ment of bladder. Vena cava inferior. (Esophagus. Right phrenic artery. Coronary artery. Hepatic artery. Splenic artery. Pancreas. Inf. pane.-duo. artery. Colica media. Superior mesenteric. Duodenum (3rd part). Aorta. Duodenum (2nd part). Right and left kidneys. Superior mesenteric. Aorta. Colica sinistra. Colica dextra. Vasa intest ini. j Sigmoid artery. Sup. hcemorrhoidal artery.. Common iliac artery.' Internal iliac artery. External iliac artery. Epigastric artery. Bladder. Fig. 52fi.-Diagram devised by Dr. Deldpine to show the lines along which the peritoneum leaves the wall of the abdomen to invest the viscera. meso-colon; its lower border, with the peritoneum, covering the caecum and ascending colon. It serves to retain the small intestines in their position, and contains between its layers the mesenteric vessels and nerves, the lacteal vessels, and mesenteric glands. The meso-cceeum serves to connect the back part of the caecum with the pos- terior wall of the abdomen, being continuous with the ascending meso-colon. The ascending meso-colon is the fold which connects the back part of the ascending colon with the posterior wall of the abdomen, and the descending meso- colon retains the descending colon in connection with the posterior abdominal THE STOMACH. 925 wall; more frequently the peritoneum merely covers the anterior surface and sides of these two portions of the intestine. At the place where the transverse colon turns downward to form the descending colon, a fold of peritoneum is continued upwrard to the under surface of the Diaphragm opposite the tenth and eleventh ribs. This is the costo-colic ligament; it passes below the spleen, and serves to support this organ and prevent it moving. The transverse meso-colon is a broad fold which connects the transverse colon to the posterior wall of the abdomen. It is formed by the two ascending layers of the great omentum, which, after separating to surround the transverse colon, join behind it, and are continued backward to the spine, where they diverge in front of the duodenum. This fold contains between its layers the vessels which supply the transverse colon. The sigmoid meso-colon is the fold of peritoneum which retains the sigmoid flexure in connection with the left iliac fossa. The meso-rectum is the narrow fold which connects the upper part of the rectum with the front of the sacrum. It contains the superior haemorrhoidal vessels. The appendices epiploicce are small pouches of the peritoneum filled with fat and situated along the colon and upper part of the rectum. They are chiefly appended to the transverse colon. THE STOMACH. The Stomach is the principal organ of digestion. It is the most dilated part of the alimentary canal. Its form is irregularly conical, curved upon itself, and presenting a rounded base, turned to the left side. It is placed, in part, immediately behind the anterior wall of the abdomen, and, in part, beneath the liver and Diaphragm and above the transverse colon. It is placed almost vertically in the abdomen, so that the fundus which projects upward and to the left of the oesophageal opening touches the Diaphragm, while the pyloric or lesser extremity is directed downward and to the right, so that the opening by which the stomach communicates with the small intestine is situated slightly to the right of the median line of the body (Fig. 527) : the stomach is situated, there- fore, for the most part, in the left hypo- chondriac region, the pyloric extremity occupying, however, the epigastric region. Its size varies considerably in different subjects, and also according to its state of distension. When moderately full its vertical diameter is about twelve inches, its transverse diameter about four. Its weight, according to Clendenning, is about four ounces and a half. It presents for examination two extremities, two orifices, two borders, and two surfaces. Its upper extremity is called the greater or splenic end. This is the largest part of the stomach, and extends two or three inches to the left of the point of entrance of the oesophagus. This expanded part is called the great cul-de-sac, or fundus. It lies behind the lower ribs, in contact with the Diaphragm, and is connected posteriorly to the spleen by the gastro-splenic omentum. The lesser or pyloric end is much smaller than the fundus, and situated on a plane anterior and inferior to it. It lies in contact with the wall of the abdomen and the under surface of the liver. Its position on the surface of the body varies with the degree of distension of the organ. Near the pyloric end there is a double bend in the stomach, attended by an appearance of constriction. The distal bend corresponds to the situation of the pyloric valve, and between the two there is a bulging which is named the lesser cul-de-sac or antrum pylori. Cardiac orifice._l_ \ Fundus. Pylorus. Lesser cul-de-sac Fig. 527.-Diagrammatic outline of the stomach. 926 THE ORGANS OF DIGESTION. The oesophageal or cardiac orifice communicates with the oesophagus; it is somewhat funnel-shaped. The pyloric orifice communicates with the duodenum, the aperture being guarded by a kind of valve-the pylorus. The lesser curvature extends between the oesophageal and pyloric orifices, along the right border of the organ, and is connected to the under surface of the liver by the lesser omentum. The greater curvature extends between the same two points, along the left border, and gives attachment to the great omentum. The surfaces of the organ are limited by these two curvatures. The anterior surface is directed upward and forward, and is in relation with the Diaphragm, the under surface of the left lobe of the liver, and with the abdominal parietes. The posterior surface is directed downward and backward, and is in relation with the spleen, the pancreas, the left kidney and suprarenal capsule, and the transverse meso-colon. The stomach is held in position by the lesser omentum, which extends from the transverse fissure of the liver to its lesser curvature, and by a fold of peritoneum, which passes from the Diaphragm on to the oesophageal end of the stomach, the gastro-phrenic ligament: this constitutes the most fixed point of the stomach, whilst the pyloric end and greater curvature are the most movable parts. To its greater curvature is attached the great omentum, by which it is connected to the transverse colon. Alterations in Position.-There is no organ in the body the position and connections of which present such frequent alterations as the stomach. During inspiration it is displaced downward by the descent of the Diaphragm and elevated by the pressure of the abdominal muscles during expiration. Its position in relation to the surrounding viscera is also changed according to the empty or distended state of the organ. When empty it lies at the back part of the abdomen, some distance from the surface. The left lobe of the liver covers it in front, and the under surface of the heart rests upon it above and in front, being separated from it by the left lobe of the liver, besides the Diaphragm and pericardium. This close relation between the stomach and the heart explains the fact that in gastralgia the pain is generally referred to the heart, and is often accompanied by palpitation and intermission of the pulse. When the stomach is (listended the greater curvature is elevated and carried forward, so that the anterior surface is turned upward and the posterior surface downward, and the stomach brought well against the anterior wall of the abdomen.1 The Diaphragm at the same time is forced upward, contracting the cavity of the chest; hence the dyspnoea complained of, from inspiration being impeded. The heart is also displaced upward; hence the oppression in this region and the palpitation experienced in extreme distension of the stomach. Pressure from without, as from tight lacing, pushes the stomach down toward the pelvis. In disease also the position and con- nections of the organ may be greatly changed, from the accumulation of fluid in the chest or abdomen or from alteration in size of any of the surrounding viscera. On looking into the pyloric end of the stomach the mucous membrane is found projecting inward in the form of a circular fold, the pylorus, leaving a narrow cir- cular aperture, about half an inch in diameter, by which the stomach communicates with the duodenum. The pylorus is formed by a reduplication of the mucous membrane of the stomach, containing numerous muscular fibres, which are aggregated into a thick circular ring, the longitudinal fibres and serous membrane being continued over the fold without assisting in its formation. The aperture is occasionally oval. Sometimes the circular fold is replaced by two crescentic folds, placed one above and the other below the pyloric orifice; and more rarely there is only one cres- centic fold. Structure.-The stomach consists of four coats-serous, muscular, areolar, and mucous, together with vessels and nerves. The serous coat is derived from the peritoneum, and covers the entire sur- 1 This is denied by Dr. Lesshaft of St. Petersburg, who states that " if the stomach is enlarged, no one part can be alone displaced, but all parts are equally moved by the distension" (Lancet, March 11, 1882, p. 406). THE STOMACH. 927 face of the organ, excepting along the greater and lesser curvatures, at the points of attachment of the greater and lesser omenta; here the two layers of peritoneum leave a small triangular space along which the nutrient vessels and nerves pass. The muscular coat (Fig. 529) is situated immediately beneath the serous covering. It consists of three sets of fibres-longitudinal, circular and oblique. Hepatic ducts. Cystic duct. - 'Pylorus. Fig. 528.-The mucous membrane of the stomach and duodenum with the bile-ducts. The longitudinal fibres are most superficial; they are continuous with the longitudinal fibres of the oesophagus, radiating in a stellate manner from the cardiac orifice. They are most distinct along the curvatures, especially the lesser, but are very thinly distributed over the surfaces. At the pyloric end they are more thickly distributed, and continuous with the longitudinal fibres of the small intestine. The circular fibres form a uniform layer over the whole extent of the stomach beneath the longitudinal fibres. At the pylorus they are most abundant, and are aggregated into a circular ring, which projects into the cavity and forms, with the fold of mucous membrane covering its surface, the pyloric valve. The oblique fibres are limited chiefly to the cardiac end of the stomach, where they are disposed as a thick uniform layer covering both surfaces, some passing obliquely from left to right, others from right to left, round the cardiac end. They are continuous with the circular fibres of the oesophagus. The areolar coat consists of a loose, filamentous, areolar tissue, connecting the mucous and muscular layers. It is sometimes called the submucous coat. It sup- ports the blood-vessels previous to their distribution to the mucous membrane; hence it is sometimes called the vascular coat. The mucous membrane is thick, its surface smooth, soft, and velvety. In the fresh state it is of a pinkish tinge at the pyloric end, and of a red or reddish- 928 THE ORGANS OF DIGESTION. brown color over the rest of its surface. In infancy it is of a brighter hue, the vascular redness being more marked. It is thin at the cardiac extremity, but thicker toward the pylorus. During the contracted state of the organ it is thrown into numerous plaits or rugae, which for the most part have a longitudinal direc- tion, and are most marked toward the lesser end of the stomach and along the greater curvature (Fig. 528). These folds are entirely obliterated when the organ becomes distended. Structure of the Mucous Membrane.-When examined with a lens the inner surface of the mucous membrane presents a peculiar honeycomb appearance, from being covered with small shallow depressions or alveoli of a polygonal or hexagonal form, which vary from to of an inch in diameter, and are separated by slightly elevated ridges. In the bottom of the alveoli are seen the orifices of minute tubes, the gastric follicles, which are situated perpendicularly side by side throughout the entire substance of the mucous mem- brane. The gastric follicles are of two kinds, which differ from each other in structure. Fig. 529.-The muscular coat of the stomach. and it is believed also in the nature of their secretion. They are named respectively pyloric and peptic glands. They are both tubular in character, and are formed of a delicate basement membrane, supporting epithelium. The basement membrane consists of flattened transparent endothelial cells, with processes which extend and support the epithelium. The pyloric glands (Fig- 530) are most numerous at the pyloric end of the stomach, and from this fact have received their name. They were formerly termed mucous glands, and were supposed to secrete mucus ; but, as Klein points out, " the cells are serous, not mucous, and the secretion of the glands cannot therefore be mucus." They consist of two or three short closed tubes opening into a common duct, the external orifice of which is situated at the bottom of an alveolus. The caecal tubes are wavy, and are of about equal length with the duct. The tubes and duct are lined throughout with epithelium, the duct being lined by columnar cells continuous with the epithelium lining the surface of the mucous membrane of the stomach, the tubes with shorter and more cubical cells, which are finely granular. The peptic glands (Fig. 531) are found all over the surface of the stomach. Like the pyloric glands, they consist of a duct into which open two or more caecal tubes. The duct, however, in these glands is shorter than in the other THE STOMACH 929 variety, sometimes not amounting to more than one-sixth of the whole length of the gfand ; it is lined throughout by columnar epithelium. At the point where the terminal tubes open into the duct, and which is termed the neck, the epithe- lium alters, the cells becoming much shorter and opaque: the lumen also becomes suddenly constricted, and is continued down to the bottom of the tubes as a very fine channel. Here also are found, between the epithelium and the basement membrane, large spheroidal, coarsely granular cells, which were formerly termed peptic cells, and which produce an outward bulging of the basement membrane. They are seen throughout the remainder of the tube at intervals, and give it a beaded or varicose appearance. Below the neck the terminal tubes, in addition to these isolated spheroidal cells, are occupied with finely granular, angular cells Fig. 530.-Pyloric gland. Fig. 531.-Peptic gastric gland. (columnar, Klein), leaving only a small channel in the centre. They are continuous with the short columnar cells of the neck, and are termed the central or chief cells, because they are believed to be principally concerned in the secretion of the gastric juice. The peptic cells, which were formerly supposed to possess this office, are now termed parietal or oxyntic cells. Between the glands the mucous membrane consists of a connective-tissue framework, with lymphoid tissue. In places this latter tissue, especially in early life, is collected into little masses, which to a certain extent resemble the solitary glands of the intestine, and are by some termed the lenticular glands of the stomach. They are not, however, so distinctly circum- scribed as the solitary glands. The epithelium lining the mucous membrane of the stomach and its alveoli is of the columnar variety. Beneath the mucous membrane, and between it and the submucous coat, is a thin stratum of involuntary muscular fibre (muscularis mucosce), which in some parts consists only of a single longitudinal layer ; in others, of two layers, an inner, circular, and an outer, longitudinal. Vessels and Nerves.-The arteries supplying the stomach are-the gastric, the pyloric and right gastro-epiploic branches of the hepatic, the left gastro-epiploic and vasa brevia from the splenic. They supply the muscular coat, ramify in the 930 THE ORGANS OF DIGESTION. submucous coat, and are finally distributed to the mucous membrane. The arrangement of the vessels in the mucous membrane is somewhat peculiar. The arteries break up at the base of the gastric tubules into a plexus of fine capillaries which run upward between the tubules, anastomosing with each other, and ending in a plexus of larger capillaries, which surround the mouths of the tubes and also form hexagonal meshes around the alveoli. From these latter the veins arise, and , pursue a straight course backward between the tubules, to the submucous tissue, and terminate either in the splenic and superior mesenteric veins or directlv in the portal vein. The lymphatics are numerous; they consist of a superficial and deep set, which pass through the lymphatic glands found along the two curvatures of the organ. The nerves are the terminal branches of the right and left pneumo- gastric, the former being distributed upon the back, and the latter upon the front part of the organ. A great number of branches from the sympathetic also supply the organ. Surface Form.-The stomach lies for the most part in the left hypochondriac region, but also slightly in the epigastric region, and is partly in contact with the abdominal wall, partly under cover of the lower ribs on the left side, and partly under the left lobe of the liver. Its cardiac orifice is behind the seventh costal cartilage of the left side, about one inch from its junction with the sternum, on a level with the tenth dorsal vertebra. The pyloric orifice is in a vertical line drawn from the right border of the sternum, two and a half or three inches below the level of the sterno-xiphoid articulation. According to Braune, when the stomach is dis- tended the pylorus moves considerably to the right, as much sometimes as three inches. The lesser curvature of the stomach is represented by a curved line with its convexity downward from the cardiac to the pyloric extremities; the greater curvature by a similarly curved line between the same points, but with a curve of much greater extent, so that its lowest point reaches a horizontal line drawn betweeri the tips of the tenth costal cartilages. The fundus of the stomach reaches, on the left side, as high as the level of the sixth chondro-sternal articula- tion, being a little below and behind the apex of the heart. The portion of the stomach which is in contact with the abdominal walls, and is therefore accessible for opening in the operations of gastrotomy and gastrostomy, is represented by a triangular .space, the base of which is formed by a line drawn from the tip of the tenth costal cartilage on the left side to the tip of the ninth costal cartilage on the right, and the sides by two lines drawn from the extremity of the eighth costal cartilage on the left side to the ends of the base line. Surgical Anatomy.-Operations on the stomach are frequently performed. By "gastrotomy" is meant an incision into the stomach for the removal of a foreign body, the opening being immediately afterward closed-in contradistinction to "gastrostomy," the making of a more or less permanent fistulous opening. Gastrotomy is probably best performed by an incision in the linea alba, especially if the foreign body is large, by a cut from the ensiform cartilage to the umbilicus, but may be performed by an incision over the body itself, where this can be felt, or by one of the incisions for gastrostomy, to be mentioned immediately. The peritoneal cavity is opened, and the point at which the stomach is to be incised decided upon. This portion is then brought out of the abdominal wound and sponges carefully packed around. The stomach is now opened by a transverse incision and the foreign body extracted. The wound in the stomach is then closed by Lembert's sutures-i. e. by sutures passed through the peritoneal and muscular coats in such a way that the peritoneal surfaces on each side of the wound are brought into apposition, and in this way the wound is closed. Gastrostomy is performed in two stages: The first stage consists in opening the peritoneal cavity and stitching the stomach to the abdominal wall. The second stage consists in opening the stomach after a lew days have elapsed and adhesions formed between the peritoneal surfaces of lhe stomach and abdominal wall. The operation is usually performed by an oblique incision about one finger s breadth below and parallel with the margin of the left costal cartilages, commencing an inch and a half from the median line and being about three inches in length. Some surgeons prefer a straight incision, beginning opposite to the end of the eighth intercostal space, and passing down for three inches over the Rectus abdominis muscle. The skin, fasciae, and muscles are to be severally divided down to the peritoneum. Howse recommends that the sheath of the Rectus should be opened longitudinally, and the fibres of this muscle separated, and not cut, in the same direction, so as to secure a sphincter-like action around the opening. After the peritoneum has been opened the stomach is recognized by its pink-red color and smooth surface. It is to be pulled up into the wound and sutured to the opening. This may be done in several ways, but in whatever way it is done the following points should be carefully attended to : (1) In taking up the stomach only to pass the needle through the serous and muscular coats, and avoid puncturing the mucous membrane. (2) To take up plenty of the muscular coat. (3) In passing the needle through the parietes of the abdomen to be careful to include the parietal peritoneum. (4) To enclose a circle of the stomach at least an inch in diameter. If the symptoms admit of it. the parts are now to be left quiet for four or five days, and a small puncture is then to be made through the exposed portion of the stomach, and a gum elastic catheter passed through it into the viscus, through which fluid can be injected, THE SMALL INTESTINE. 931 in small quantities at first. In more urgent cases it may be necessary to make the opening much earlier. Excision of the pylorus has occasionally been performed, but the results of this operation are by no means favorable, and in cases of cancer of the pylorus gastro-enterostomy is generally pre- ferred. The object of this operation is to make a fistulous communication between the stomach, on the cardiac side of the disease, and the small intestine, as high up as is possible. The small intestine is a convoluted tube, about twenty feet in length,1 which gradually diminishes in size from its commencement to its termination. It is contained in the central and lower parts of the abdominal and pelvic cavities, surrounded above and at the sides by the large intestine; it is in relation, in front, with the great omentum and abdominal parietes, and connected to the spine by a fold of peritoneum, the mesentery. The small intestine is divisible into three portions-the duodenum, the jejunum, and ileum. The duodenum has received its name from being about equal in length to the breadth of twelve fingers (eight or ten inches). It is the shortest, the widest, and the most fixed part of the small intestine ; it has no mesentery, and is only partially covered by the peritoneum. Its course presents a remarkable curve, somewhat like a horseshoe in form, the convexity being directed toward the right, and the concavity to the left, embracing the head of the pancreas. Commencing at the pylorus, it passes obliquely upward, backward, and to the right, to the under surface of the liver; it then descends in front of the right kidney, and passes nearly transversely across the front of the spine, terminating in the jejunum on the left side of the second lumbar vertebra. Hence the duodenum has been divided into three portions-ascending, descending, and transverse. The first, or ascending portion (Fig. 532), about two inches in length, is free, movable, and nearly completely invested by the peritoneum, which forms the lesser omentum. It is in relation, above and in front, with the liver and neck of the gall-bladder; behind, with the vessels which run between the layers of the lesser omentum-viz. the hepatic artery and duct, and vena portae. This portion of the intestine is usually found after death stained with bile, especially on its anterior surface. The second, or descending portion, about three inches in length, is firmly fixed by the peritoneum and pancreas. It passes from the neck of the gall-bladder vertically downward, in front of the right kidney, as far as the third lumbar vertebra. It is covered by peritoneum only on its anterior surface. It is in relation, in front, with the right arch of the colon and the meso-colon ; behind, with the front of the right kidney; at its inner side is the head of the pancreas and the ductus communis choledochus. The common bile-duct and the pancreatic duct perforate the inner side of this portion of the intestine obliquely, a little below its middle. The third, or transverse portion, the longest and narrowest part of the duo- denum, passes across the front of the spine, ascending from the third to the second lumbar vertebra, and terminating in the jejunum on the left side of the latter bone. In front, though at some distance from it, is the descending layer of the transverse meso-colon, or the divergence of the two layers of that structure, and it is crossed by the superior mesenteric vessels; behind, it rests upon the aorta, the vena cava inferior, and the crura of the Diaphragm; above it is the lower border of the pancreas, the superior mesenteric vessels passing forward between the two. The point of junction of the duodenum and jejunum is said to correspond to the spot where the gut receives a complete investment of peritoneum. From this point a fairly constant portion, about an inch in length, ascends on the left side of THE SMALL INTESTINE. 1 Treves states that in one hundred cases the average length of the small intestine in the adult male was 22 feet 6 inches, and in the adult female 23 feet 4 inches: but that it varies very much, the extremes in the male being 31 feet 10 inches in one case and 15 feet 6 inches in another, a difference of over 15 feet. He states that he has convinced himself that the length of the bowel is independent, in the adult, of age, height, and weight. 932 THE ORGANS OF DIGESTION. the vertebral column, and is by some regarded as a fourth part of the duodenum. This portion is fixed in this position by a band which extends upward from it, obliquely across the aorta to the connective tissue around the coeliac axis and the left crus of the Diaphragm, and is termed the muse ulus suspensorius duodeni, from possessing, according to Treitz, plain muscular fibres, mixed with the fibrous tissue of which it is principally made up. Vessels and Nerves.-The arteries supplying the duodenum are the pyloric and pancreatico-duodenal branches of the hepatic and the inferior pancreatico-duodenal Portal vein. Hepatic duct. Pound ligament. Hepatic artery. Cystic artery. Fig. 532.-Relations of the duodenum. (A portion of the stomach has been cut away.) branch of the superior mesenteric. The veins terminate in the splenic and superior mesenteric. The nerves are derived from the solar plexus. The jejunum (jejunus, empty), so called from being usually found empty after death, includes the upper two-fifths of the small intestine below the duo- denum. It commences at the duodenum on the left side of the second lumbar vertebra, and terminates in the ileum, its convolutions being chiefly confined to the umbilical and left iliac regions. The jejunum is wider, its coats thicker, more vascular, and of a deeper color than those of the ileum ; but there is no character- istic mark to distinguish the termination of the one and the commencement of the other. THE SMALL INTESTLNE. 933 The ileum (sr'AsZy, to twist), so called from its numerous coils or convolutions, includes the remaining three-fifths of the small intestine. It occupies chiefly the umbilical, hypogastric, right iliac, and occasionally the pelvic regions, and termi- nates in the right iliac fossa by opening into the inner side of the commencement of the large intestine. The ileum is narrower, its coats thinner and less vascular than those of the jejunum, a given length of it weighing less than the same length of the jejunum. Meckel's diverticulum.-Occasionally there may be found connected with the lower part of the ileum, from one to three feet from its termination, a blind diverticulum or tube varying in length. It is attached to and communicates with the free margin of the bowel by one extremity, and by the other is unattached, or may be connected with the abdominal wall or some other portion of the intestine by a fibrous band. This is Meckel's diverticulum, and represents the remains of the vitelline duct, or duct of communication between the umbilical vesicle and the alimentary canal (see page 109). Structure.-The wall of the small intestine is composed of four coats-serous, muscular, areolar, and mucous. The serous coat is derived from the peritoneum. The first or ascending por- tion of the duodenum is almost completely surrounded by that membrane; the second or descending portion is covered by it only in front; and the third or transverse portion lies behind the descending layer of the transverse meso-colon, which passes over it without being closely incorporated with the other coats of this part of the intestine. The remaining portion of the small intestine is sur- rounded by the peritoneum, excepting along its attached or mesenteric border; here a space is left for the vessels and nerves to pass to the gut. The muscular coat consists of two layers of fibres, an external or longitudinal and an internal or circular layer. The longitudinal fibres are thinly scattered over the surface of the intestine, and are more distinct along its free border. The circular fibres form a thick, uniform layer; they surround the cylinder of the intestine in the greater part of its circumference, but do not form complete rings. The muscular coat is thicker at the upper than at the lower part of the small intestine. The areolar or submucous coat connects together the mucous and muscular layers. It consists of loose, filamentous areolar tissue, which forms a nidus for the sub- division of the nutrient vessels previous to their distribution to the mucous surface. The mucous membrane is thick and highly vascular at the upper part of the small intestine, but somewhat paler and thinner below. It consists of the following structures : next the areolar or submucous coat is a layer of unstriped muscular fibres, the muscularis mucosce; internal to this is a quantity of retiform tissue, enclosing in its meshes lymph-corpuscles, and in which the blood-vessels and nerves ramify. Lastly, a basement membrane, supporting a single layer of epithelial cells, which throughout the intestines are columnar in character. They are granular in appearance and possess a clear oval nucleus. At their superficial or unattached end they present a distinct layer of highly refracting material, marked by vertical striae, which were formerly believed to be minute channels, by which the chyle was taken up into the interior of the cell, and by them transferred to the lacteal vessels of the mucous membrane. The mucous membrane presents for examination the following structures, con- tained within it or belonging to it: Valvulse conniventes. Villi. Simple follicles. Duodenal glands. Solitary glands. Agminate or Peyer's glands. Glands The valvulae conniventes (valves of Kerkring) are reduplications or foldings of the mucous membrane and submucous tissue. Unlike the folds in the stomach, they are permanent, and are not obliterated when the intestine is distended. They extend transversely across the cylinder of the intestine for about one-half 934 THE ORGANS OF DIGESTION. or two-thirds of its circumference. The larger folds are about two inches in length and one-third of an inch in depth at their broadest part, but the greater number are of smaller size. The larger and smaller folds alternate with each other. They are not found at the commencement of the duodenum, but begin to appear about one or two inches beyond the pylorus. In the lower part of the descending portion, below the point where the common choledic and pancreatic ducts enter the intestine, they are very large and closely approximated. In the transverse portion of the duodenum and upper half of the jejunum they are large and numerous, and from this point, down to the middle of the ileum, they Fig. 533.-Diagrammatic section of a villus. (Watney.) ep. Epithelium only partially shaded in. I. Cen- tral chyle-vessel; the cells forming the vessel have been less shaded to distinguish them from the cells of the parenchyma of the villus, m. Muscle-fibres running up by the side of the chyle-vessel. It will be noticed that each muscle-fibre is surrounded by the reticulum, ana by this reticulum the muscles are attached to the cells forming the membrana propria, as at e', or to the reticulum of the villus. Ic. Lymph-corpuscles, marked by a spherical nucleus and a clear zone of protoplasm. I'. Upper limit of the chyle-vessel, e, e, e'. Cells forming the membrana propria. It will be seen that there is hardly any difference between the cells of the parenchyma, the endothelium of the upper part of the chyle-vessel, and the cells of the membrana propria, v. Blood-vessels. z. Dark line at the base of the epithelium formed by the reticulum. It will be seen that the reticulum pene- trates between all the other elements of the villus. The reticulum contains thickenings or " nodal points." The diagram shows that the cells of the upper part of the villus are larger and contain a larger zone of proto- plasm than those of the lower part. The cells of the upper part of the chyle-vessel differ somewhat from those of the lower part, in that they more nearly resemble the cells of the parenchyma. diminish considerably in size. In the lower part of the ileum they almost entirely disappear; hence the comparative thinness of this portion of the intestine as compared with the duodenum and jejunum. The valvulae conniventes retard the passage of the food along the intestines and afford a more extensive surface for absorption. The villi are minute, highly vascular processes projecting from the mucous membrane of the small intestine throughout its whole extent, and giving to its surface a velvety appearance. In shape some are triangular and laminated, others conical or cylindrical, with clubbed or filiform extremities. They are largest and most numerous in the duodenum and jejunum, and become fewer and smaller in the ileum. Krause estimates their number in the upper part of the small intestine at from fifty to ninety in a square line, and in the lower part from forty to seventy, the total number for the whole length of the intestine being about four millions. 77/7-7 SMALL INTESTINE. 935 Structure of the Villi (Fig. 533).-The structure of the villi has been studied recently by many eminent anatomists. We shall here follow the description of Dr. Watney,1 whose researches have a most important bearing on the physiology Capillaries. Lymph trunk. -Lymph trunk. Capillaries. Fig. 534.-Villi of small intestine. (Cadiat.) Small artery. '' 'Lymphatic plexus. of that which is the peculiar function of this part of the intestine, the absorp- tion of fat. The essential parts of a villus are-the lacteal vessel, the blood-vessels, the epithelium, the basement membrane and muscular tissue of the mucosa, these structures being supported and held together by retiform lymphoid tissue. These structures are arranged in the following manner: Situated in the centre of the villus is the lacteal, terminating near the summit in a blind extremity; running along this vessel are unstriped muscular fibres ; surrounding it is a plexus of capillary vessels, the whole being enclosed by a basement membrane, supporting columnar epithelium. Those structures which are contained within the basement membrane-namely, the lacteal, the muscular tissue, and the blood-vessels-are surrounded and enclosed by a delicate reticulum which forms the matrix of the villus, and in the meshes of which are fouhd large flattened cells, with an oval nucleus, and, in smaller numbers, lymph-corpuscles. These latter are to be distinguished from the larger cells of the villus by their behavior with reagents, by their size, and by the shape of their nucleus, which is spherical. Transitional forms, however, of all kinds are met with between the lymph-corpuscle and the proper cells of the villus. The lacteals are in some cases double, and in some animals multiple. Situated in the axis of the villi, they commence by dilated caecal extremities near to, but not quite at, the summit of the villus. The walls are composed of a single layer of endothelial cells, the interstitial substance between the cells being continuous with the reticulum of the matrix. The muscular fibres are derived from the muscularis mucosae, and are arranged in bundles around the lacteal vessel, extending from the base to the summit of the villus, and giving off laterally, individual muscle-cells, which are enclosed by the reticulum, and by it are attached to the basement membrane. The blood-vessels form a plexus between the lacteal and the basement mem- 1 Phil. Trans., vol. clxvi. pt. ii. 936 77/A' ORGANS OF DIGESTION. brane, and are enclosed in the reticular tissue; in the interstices of the capillary plexus, which they form, are contained the cells of the villus. These structures are surrounded by the basement membrane, which is made up of a stratum of endothelial cells, and upon which is placed a layer of columnar epithelium. The reticulum of the matrix is continuous through the basement membrane (that is, through the interstitial substance between the individual endothelial cells) with the interstitial cement substance of the columnar cells on the surface of the villus. Thus we are enabled to trace a direct continuity between the interior of the lacteal and the surface of the villus by means of the reticular tissue, and it is along this path that, according to Dr. Watney, the chyle passes in the process of absorption by the villi. That is to say, it passes through the interstitial substance between the epithelium cells, through the interstitial sub- stance of the basement membrane, the reticulum of the matrix, and the interstitial substance between the endothelial plates of the lacteal, all which structures have been shown to be continuous with one another, and, being probably semifluid, do not offer any obstacle to the passage of the molecular basis of the chyle. The simple follicles, or crypts of Lieberkuhn (Figs. 535, 536), are found in con- siderable numbers over every part of the mucous membrane of the small intestine. They consist of minute tubular depressions of the mu- cous membrane, arranged perpendicularly to the sur- face, upon which they open by small circular apertures. They may be seen with the aid of a lens, their orifices appearing as minute dots scattered between the villi. Their walls are thin, consisting of a layer of basement membrane (which is, in fact, an endothelial membrane) lined by columnar epithelium, and covered on their ex- terior by capillary vessels. The duodenal or Brunner's glands are limited to the duodenum and commencement of the jejunum. They are small, flattened, granular bodies imbedded in the submucous areolar tissue, and open upon the surface of the mucous membrane by minute excretory ducts. They are most numerous and largest near the pylorus. They may be compared to the elementary lobules of a salivary gland spread out over a broad surface, Fig. 535.- Transverse section of crvpts of Lieberkuhn. (Klein and Noble Smith.) Fig. 536.-Longitudinal section of crypts of Lieberkuhn. Goblet-cells seen among the columnar epithelial cells. (Klein and Noble Smith.) instead of being collected in a mass. They consist of a number of tubular alveoli lined by epithelium, and opening by a single duct on the inner surface of the intestine. The solitary glands (glandules solitaries) are found scattered throughout the mucous membrane of the small intestine, but are most numerous in the lower part of the ileum. They are small, round, whitish bodies, from half a line to a line in diameter. Their free surface is covered with villi, and each gland is surrounded by the openings of the follicles of Lieberkuhn. They are now recognized as lymph-follicles, and consist of a dense interlacing retiform tissue, closely packed with lymph-corpuscles and permeated with an abundant capillary network (Fig. 537). The interspaces of the retiform tissue are continuous with larger lymph- spaces at the base of the gland through which they communicate with the lacteal system. They are situated partly in the submucous tissue, partly in the mucous 77ZL' iSJ/yfZZ INTESTINE. 937 membrane, where they form slight projections of its epithelial layer after having penetrated the muscularis mucosae. The villi which are situated on them are generally absent from the very summit (or "cupola," as Frey calls it) of the gland. Peyer's glands (Figs. 536-540) may be regarded as aggregations of solitary glands, forming circular or oval patches from twenty to thirty in number, and varying in length from half an inch to four inches. They are largest and most numerous in the ileum. In the lower part of the jejunum they are small, of a circular form, and few in number. They are occasionally seen in the duodenum. They are placed lengthwise in the intes- tine, covering the portion of the tube most distant from the attachment of the mesentery. Each patch is formed of a group of the above-described solitary glands covered with mucous membrane, and in almost every respect are similar in structure to them. They do not, how- ever, as a rule, possess villi on their free surface. Each patch is surrounded by a circle of the crypts of Lieberkuhn. They are best marked in the young subject, becoming indistinct in middle age, and sometimes altogether disappearing in ■■Capillary network. Large circular-' vessel. Fig. 537.-Transverse section through the equa- torial plane of three of Peyer's follicles from the rabbit. Fig. 538.-Patch of Peyer's glands. From the lower part of the ileum. Fig. 539.-A portion of the above magnified. advanced life. They are largely supplied with blood-vessels, which form an abundant plexus around each follicle, from which fine branches are given off which permeate the lymphoid tissue in the interior of the follicle. Vessels and Nerves.-The jejunum and ileum are supplied by the superior mesenteric artery, the branches of which, having reached the attached border of the bowel, run between the serous and muscular coats, with frequent inoscula- tions to the free border, where they also anastomose with other branches running round the opposite surface of the gut. From these vessels numerous branches are given off which pierce the muscular coat, supplying it and forming an intricate plexus in the submucous tissue. From this plexus minute vessels 938 THE ORGANS OF DIGESTION pass to the glands and villi of the mucous membrane. The veins have a similar course and arrangement to the arteries. The lymphatics of the small Fig. 540.-Vertical section of one of Peyer's patches from man, injected through its lymphatic canals, a. Villi with their chyle-passages, b. Follicles of Lieberkuhn, c. Muscular mucosee. a. Cupola or apex of solitary glands, e. Mesial zone of glands, f. Base of glands, g. Points of exit of the chyle-passages from the villi, anil entrance into the true mucous membrane, h. Retiform arrangement of the lymphatics in the mesial zone. i. Course of the latter at the base of the glands, k. Confluence of the lymphatics opening into the vessels of the submucous tissue. I. Follicular tissue of the latter. intestine (lacteals) are arranged in two sets, those of the villi and those of the 'Multipolar ganglion-cells. Single ganglion-cell. Fig. 541.-Meissner's plexus. (Klein and Noble Smith.) muscular coat. The lymphatics of the villi commence in these structures in the manner described above, and form an intricate plexus in the mucous and THE LARGE INTESTINE. 939 submucous tissue, being joined by the lymphatics from the lymph-spaces at the bases of the solitary glands (Fig. 540), and from this pass to larger vessels at the mesenteric border of the gut. The lymphatics of the muscular coats are situated to a great extent between the two layers of muscular fibres, where they form a close plexus, and throughout their course communicate freely with the lymphatics from the mucous membrane, and empty themselves in the same manner into the commencement of the lacteal vessels at the attached border of the gut. The nerves of the small intestine are derived from the plexuses of sympathetic nerves around the superior mesenteric artery. From this source they run to a plexus of nerves and ganglia situated between the circular and longitudinal muscular fibres (Auerbach's plexus) from which the nervous branches are distributed to the muscular coats of the intestine. From this plexus a secondary plexus is derived (Meissner's plexus), which is formed by branches which have perforated the circular muscular fibres (Fig. 541). This plexus lies between the muscular and mucous coats of the intestine. It is also gangliated, and from it the ultimate fibres pass to the muscularis mucosae and to the mucous membrane. THE LARGE INTESTINE. The large intestine extends from the termination of the ileum to the anus. It is about five feet in length, being one-fifth of the whole extent of the intestinal canal. It is largest at its commencement at the caecum, and gradually diminishes as far as the rectum, where there is a dilatation of considerable size just above the anus. It differs from the small intestine in its greater size, its more fixed position and its sacculated form. The large intestine in its course describes an arch, which surrounds the convolutions of the small intestine. It com- mences in the right inguinal region, in a dilated part, the c cecum. It ascends through the right lumbar and hypochondriac regions to the under surface of the liver; passes transversely across the abdomen, on the confines of the epigastric and umbilical regions, to the left hypochondriac region; descends through the left lumbar region to the left iliac fossa, where it becomes convoluted and forms the sigmoid flexure; finally it enters the pelvis, and descends along its posterior wall to the anus. The large intestine is divided into the caecum, colon, and rectum. The caecum (ccecus, blind) (Fig. 542) is the large blind pouch, or cul-de-sac, in which the large intestine commences. It is the most dilated part of the tube, measuring about two and a half inches both in its vertical and transverse diameters. Its position varies somewhat; usually it is found lying upon the Psoas muscle, and so placed that its apex or lowest point is just projecting beyond the inner border of that muscle, corresponding to a point a little to the inner side of the middle of Poupart's ligament. Sometimes, however, it is situated external to this, in the right iliac fossa, in relation with the Iliacus muscle; and at other times it lies internal to both Psoas and Iliacus, either resting on the pelvic brim or altogether contained within the pelvis. It is entirely enveloped on all sides by peritoneum, which after enclosing it is reflected on to the posterior wall of the abdomen, being continuous with the ascending meso-colon when this fold exists. The caecum, therefore, lies quite free in the abdominal cavity, and enjoys a considerable amount of movement. On its inner side it is joined by the ileum, while attached to its lower and back part is the appendix vermi- formis. The appendix vermiformis is a long, narrow, worm-shaped tube, the rudiment of the lengthened caecum found in nearly all the mammalia. The appendix varies from three to six inches in length, its average diameter being about equal to that of a goosequill. It is usually directed upward and inward behind the caecum, coiled upon itself, and terminates in a blunt point, being retained in its position by a fold of peritoneum, which sometimes forms a mesentery for it. 940 THE ORGANS OF DIGESTION Its canal is small, and communicates with the caecum by an orifice which is placed below and behind that of the ileum. It is sometimes guarded with an incomplete valve formed of a fold of mucous mem- brane. Its coats are thick, and its mucous lining furnished with a large number of solitary glands. In the neighborhood of the caecum, and especially in the vicinity of the ileo-caecal valve, are certain pouches of peritoneum or fossae which are of surgical importance. Three of these fossae have been described. The ileo-colic fossa (superior ileo-caecal) is situated at the junction of the ileum and colon, in the angle between the ascending colon, which forms the outer boundary of the pouch, and the ileum which forms the lower boundary. Often a fold of peritoneum, arch- ing over a branch of the ileo-colic artery, roofs in this angle, and thus forms a pouch the floor of which is formed by the mesen- tery. The ileo-coecal fossa (inferior ileo- caecal) is situated behind the angle of junc- tion of the ileum and caecum. It is formed by a fold of peritoneum (ileo-caecal fold), which extends from the border of the ileum, and, passing over the ileo-caecal junction, joins the mesentery of the appendix. Between this fold and the appendix is the fossa, which is bounded to the right by the ascending meso-colon and to the left by the mesentery. It may extend a con- siderable distance upward, behind and parallel with the colon. The subccecal fossa (retro-caecal) is situated immediately beneath the caecum, which has to be raised to bring it into view. It lies close to the ileo-caecal fossa, from which it is separated by the meso-caecum and ascending meso-colon. It is not so constant as either the ileo-caecal or ileo-colic fossae. Hernia of the vermiform appendix into one of these pouches frequently takes place, when it is often concealed and might escape the search of the surgeon were he not familiar with their existence. Moreover, a herniated appendix into one of these pouches is very liable to become strangulated. The presence of these pouches also explains the course which pus has been known to take in cases of perforation of the appendix, where it travels upward behind the ascending colon as far as the Diaphragm.1 Ileo-caecal valve.-The lower end of the ileum terminates at the inner and back part of the large intestine, opposite the junction of the caecum with the colon. At this point the mucous membrane forms two valvular folds, which project into the large intestine and are separated from each other by a narrow, elongated aperture. These folds form the ileo-caecal valve (valvula Bauhini). Each fold is semilunar in form. The upper one, nearly horizontal in direction, is attached by its convex border to the point of junction of the ileum with the colon ; the lower segment, to the point of junction of the ileum with the caecum. Their free concave margins project into the intestine, separated from one another by a narrow slit-like aperture directed transversely. At each end of this aperture the two segments of the valve coalesce, and are continued as a narrow membranous ridge round the canal of the intestine for a short distance, forming the frcen a, or retinacula, of the valve. The left or anterior end of this aperture is rounded ; the right or posterior end is narrow and pointed. Each segment of the valve is formed by a reduplication of the mucous Fig. 542.-The caecum and colon laid open to show the ileo-caecal valve. 1 On the anatomy of these fossae see a paper by Dr. Rolleston and Mr. Lockwood (Journal of Anatomy and Physiology, vol. xxvi. p. 130). THE LARGE INTESTINE. 941 membrane and of the circular muscular fibres of the intestine, the longitudinal fibres and peritoneum being continued uninterruptedly across from one intestine to the other. When these are divided or removed the ileum may be drawn outward, and all traces of the valve will be lost, the ileum appearing to open into the large intestine by a funnel-shaped orifice of large size. The surface of each segment of the valve directed toward the ileum is covered with villi, and presents the characteristic structure of the mucous membrane of the small intestine, whilst that turned toward the large intestine is destitute of villi, and marked with the orifices of the numerous tubular glands peculiar to the membrane in the large intestine. These differences in structure continue as far as the free margin of the valve. When the caecum is distended the margins of the opening are approximated, so as to prevent any reflux into the ileum. The colon is divided into four parts-the ascending, transverse, descending, and the sigmoid flexure. The ascending colon is smaller than the caecum. It passes upward from its commencement at the caecum, opposite the ileo-caecal valve, to the under surface of the liver on the right of the gall-bladder, where it bends abruptly inward to the left, forming the hepatic flexure. It is retained in contact with the posterior wall of the abdomen by the peritoneum, which covers its anterior surface and sides, its posterior surface being connected by loose areolar tissue with the Quadratus lumborum, right kidney, and descending portion of the duodenum (Figs. 543, 544) : sometimes the peritoneum almost completely invests it and forms a distinct but narrow meso-colon.1 It is in relation, in front, with the convolutions of the ileum and the abdominal parietes; behind, it lies on the Quadratus lumborum muscle and right kidney and descending portion of the duodenum. The transverse colon, the longest part of the large intestine, passes trans- versely from right to left across the abdomen, opposite the confines of the epigastric and umbilical zones, into the left hypochondriac region, where it curves downward beneath the lower end of the spleen, forming the splenic flexure. In its course it describes an arch, the concavity of which is directed backward toward the vertebral column ; hence the name transverse arch of the colon. This is the most movable part of the colon, being almost completely invested by peritoneum, and connected to the spine behind by a large and wide duplicature of that membrane, the transverse meso-colon. It is in relation, by its upper surface, with the liver and gall-bladder, the great curvature of the stomach, and the lower end of the spleen; by its under surface, with the small intestines; by its anterior surface, with the anterior layers of the great omentum and the abdominal parietes; by its posterior surface, with the transverse meso-colon and third portion of the duodenum. The descending colon passes almost vertically downward through the left hypochondriac and lumbar regions to the upper part of the left iliac fossa, where it terminates in the sigmoid flexure. It is retained in position by the peritoneum, which covers its anterior surface and sides, its posterior surface being connected by areolar tissue with the left crus of the Diaphragm, the left kidney, and the Quadratus lumborum (Figs. 542, 543). It is smaller in calibre and more deeply placed than the ascending colon, and is more frequently covered with peritoneum on its posterior surface than the ascending colon (Treves). The sigmoid flexure is the narrowest part of the colon: it is situated in the left iliac fossa, commencing from the termination of the descending colon at the 1 Mr. Treves states that, after a careful examination of one hundred subjects, he found that in fifty-two there was neither an ascending nor a descending meso-colon. In twenty-two there was a descending meso-colon, but no trace of a corresponding fold on the other side. In fourteen subjects there was a meso-colon to both the ascending and the descending segments of the bowel, while in the remaining twelve there was an ascending meso-colon, but no corresponding fold on the left side. It follows, therefore, that in performing lumbar colotomy a meso-colon may be expected upon the left side in 36 per cent, of all cases, and on the right in 26 per cent. (The Anatomy of the Intestinal Canal and Peritoneum in Alan, 1885, p. 55.) 942 THE ORGANS OF DIGESTION. margin of the crest of the ilium, and ending in the rectum opposite the left sacro- iliac symphysis. It curves in the first place inward, across the Psoas muscle; it Posterior lamella of lumbar fascia. Middle lamella of lumbar fascia. Anterior lamella of lumbar fascia. --QUADRATUS LUMBORUM. LATISSIMUS DORSI. Ureter. Fig. 543.-Diagram of the relations of the large intestine and kidney, from behind. then descends vertically along the left wall of the pelvis, and finally again passes inward to the left sacro-iliac joint, where it becomes the rectum. It is retained in its place by a loose fold of peritoneum, the segmoid meso-colon. It is in relation in front, with the small intestines and abdominal parietes.1 1 Treves describes the sigmoid flexure somewhat differently. He includes in his description of THE LARGE INTESTINE. 943 The rectum is the terminal part of the large intestine, and extends from the Receptaculum chyli. Great splanchnic nerve piercing crus. Great splanchnic nerve piercing crus. Semilunar ganglion. Semilunar ganglion. Fig. 544.-The relations of the viscera and large vessels of the abdomen. (Seen from behind, the last dorsal vertebra being well raised.) sigmoid flexure to the anus: it varies in length from six to eight inches, and has received its name from being less flexuous than any other part of the intestinal this portion of the bowel the upper part of the rectum, and makes it terminate opposite the third portion of the sacrum. Instead of forming a sigmoid curve, he describes it as a large loop or bend, more like the Greek letter 12 (omega). 944 THE ORGANS OF DIGESTTON. canal. It commences opposite the left sacro-iliac symphysis, passes obliquely downward from left to right to the middle of the sacrum, forming a gentle curve to the right side; it then descends in front of the lower part of the sacrum and coccyx, presenting a curve with its concavity forward, and near the extremity of the latter bone inclines backward to terminate at the anus. The rectum is, therefore, not straight, *the upper part being directed obliquely from the left side to the median line, the middle portion being curved in the direction of the hollow of the sacrum and coccyx, and the lowrer portion presenting a short curve in the opposite direction. The rectum is cylindrical, not sacculated like the rest of the large intestine; it is narrower at its upper part than the sigmoid flexure, gradually increases in size as it descends, and immediately above the anus presents a considerable dilatation, capable of acquiring an enormous size. The rectum is divided into three portions-upper, middle, and lower. The tipper portion, which includes about half the length of the tube, extends obliquely from the left sacro-iliac symphysis to the middle of the third piece of the sacrum. It is almost completely surrounded by peritoneum, and connected to the sacrum behind by a duplicature of that membrane, the meso-rectum. It is in relation, behind, with the Pyriformis muscle, the sacral plexus of nerves, and the branches of the internal iliac artery of the left side, which separate it from the sacrum and sacro-iliac symphysis ; in front, it is separated, in the male, from the posterior surface of the bladder; in the female, from the posterior surface of the uterus and its appendages by some convolutions of the small intestine. The middle portion of the rectum is about three inches in length, and extends as far as the tip of the coccyx. It is closely connected to the concavity of the sacrum, and covered by peritoneum only on the upper part of its anterior surface. It is in relation, in front, in the male, with the triangular portion of the base of the bladder, the vesiculae seminales, and vasa deferentia ; more anteriorly, with the under surface of the prostate. In the female, with the posterior wall of the vagina, to which it is adherent. The lower portion is about an inch or an inch and a half in length : it curves backward at the fore part of the prostate gland and terminates at the anus. This portion of the intestine receives no peritoneal covering. It is invested by the Internal sphincter, supported by the Levatores ani muscles, and surrounded at its termination by the External sphincter. In the male it is separated from the membranous portion and bulb of the urethra by a triangular space, and in the female a similar space intervenes between it and the vagina. The base of this space forms the perinaeum. The rectum in the female is more capacious and less curved than in the male. Structure.-The large intestine has four coats-serous, muscular, areolar, and mucous. The serous coat is derived from the peritoneum, and invests the different portions of the large intestine to a variable extent. The caecum is completely covered by the serous membrane. The ascending and descending colon are usually covered only in front.1 The transverse colon is almost completely invested, the parts corresponding to the attachment of the great omentum and transverse meso-colon being alone excepted. The sigmoid flexure is nearly completely surrounded, the point corresponding to the attachment of the sigmoid meso-colon being excepted. The upper part of the rectum is almost completely invested by the peritoneum: the middle portion is covered only on its anterior surface, and the lower portion is entirely devoid of any serous covering. In the course of the colon and upper part of the rectum the peritoneal coat is thrown into a number of small pouches filled w ith fat, called appendices epiploicce. They are chiefly appended to the transverse colon. The muscular coat consists of an external longitudinal and an internal circular layer of muscular fibres. The longitudinal fibres, although found to a certain extent all round the intes- 1 See foot-note, page 941. THE LARGE INTESTINE. 945 tine, do not form a uniform layer over the whole surface of the large intestine. In the caecum and colon they are especially collected into three flat longitudinal bands, each being about half an inch in width. These bands commence at the attachment of the appendix vermiformis to the caecum : one, the posterior, is placed along the attached border of the intestine ; the anterior band, the largest, corresponds along the arch of the colon to the attachment of the great omentum, but is in front in the ascending and descending colon and sigmoid flexure; the third, or lateral band, is found on the inner side of the ascending and descending colon and on the under border of the transverse colon. These bands are nearly one-half shorter than the other parts of the intestine, and serve to produce the sacculi which are characteristic of the caecum and colon ; accordingly, when they are dissected off, the tube can be lengthened, and its sacculated character becomes lost. In the sigmoid flexure the longitudinal fibres become more scattered, but upon its lower part and round the rectum they spread out and form a thick uniform layer. The circular fibres form a thin layer over the caecum and colon, being especially accumulated in the intervals between the sacculi; in the rectum they form a thick layer, especially at its lower end, where they become numerous and form the Internal sphincter. The areolar coat connects the muscular and mucous layers closely together. The mucous membrane in the caecum and colon is pale, and of a grayish or pale yellow color. It is quite smooth, destitute of villi, and raised into numerous cres- centic folds which correspond to the intervals between the sacculi. In the rectum it is thicker, of a darker color, more vascular, and connected loosely to the muscular coat, as in the oesophagus. When the lower part of the rectum is contracted, its mucous membrane is thrown into a number of folds, some of which, near the anus, are longitudinal in direction and are effaced by the distension of the gut. Besides these there are certain permanent folds, of a semilunar shape, known as Houston's valves.1 They are usually three in number; sometimes a fourth is found, and occasionally only two are present. One is situated near the commencement of the rectum, on the right side; another extends inward from the left side of the tube, opposite the middle of the sacrum ; the largest and most constant one projects back- ward from the fore part of the rectum, opposite the base of the bladder. When a fourth is present, it is situated about an inch above the anus on the back of the rectum. These folds are about half an inch in width, and contain some of the circular fibres of the gut. In the empty state of the intestine they overlap each other, as Mr. Houston remarks, so effectually as to require considerable manoeuvring to conduct a bougie or the finger along the canal of the intestine. Their use seems to be " to support the w eight of faecal matter, and prevent its urging toward the anus, where its presence always excites a sensation demanding its discharge." As in the small intestine, the mucous membrane consists of a muscular layer, the muscularis mucosae ; of a quantity of retiform tissue, in which the vessels ramify; of a basement membrane and epithelium, which is of the columnar variety and exactly resembles the epithelium found in the small intestine. The mucous membrane of this portion of the bowel presents for examination simple follicles and solitary glands. The simple follicles are minute tubular prolongations of the mucous membrane, arranged perpendicularly, side by side, over its entire surface; they are longer, more numerous, and placed in much closer apposition than those of the small intestine, and they open by minute rounded orifices upon the surface, giving it a cribriform appearance. The solitary glands (Fig. 545) in the large intestine are most abundant in the ccecum and appendix vermiformis, but are irregularly scattered also over the rest of the intestine. They are similar to those of the small intestine. Vessels and Nerves.-The arteries supplying the large intestine give off large branches, which ramify between the muscular coats, supplying them, and, after dividing into small vessels in the submucous tissue, pass to the mucous membrane. 1 Dublin Hosp. Reports, vol. v. p. 163. 946 THE ORGANS OF DIGESTION. In the lower part of the rectum, however, the arrangement is somewhat different. Here the vessels run in a longitudinal direction, parallel with each other, to the external orifice, where they are joined by large transverse branches. In their course they communicate with each other. The veins of the rectum form an intricate interlacement (the hcemorrhoidal' plexus}, and, pursuing from it a longitu- dinal course similar to the arteries, empty themselves partly into the internal iliac vein (systemic circulation) and partly into the inferior mesenteric vein (portal circulation). The nerves are derived from the plexuses of the sympathetic nerve around the branches of the superior and inferior mesenteric arteries that are Surface of mucous membrane, with opening of Lieberkuhn's follicles. Lieberkuhn's follicles. Muscularis mucosce (two layers). Submucous connective tissue. Solitary gland. Fig. 545.-Minute structure of large intestine. distributed to the large intestine. They are distributed in a similar way as those in the small intestine. Surface Form.-The coils of the small intestine occupy the front of the abdomen below the transverse colon, and are covered more or less completely by the great omentum. For the most part the coils of the jejunum occupy the left side of the abdominal cavity-i. e. the left lumbar and inguinal regions and the left half of the umbilical region-whilst the coils of the ileum are situated to the right, in the right lumbar and inguinal regions, in the right half of the umbilical region, and also the hypogastric. The caecum is situated in the right inguinal region. Its posi- tion varies slightly, but the mid-point of a line drawn from the anterior superior spinous process of the ilium to the symphysis pubis will about mark the middle of its lower border. It is com- paratively superficial. From it the ascending colon passes upward through the right lumbar and hypochondriac regions, and becomes more deeply situated as it ascends to the hepatic flexure, which is deeply placed under cover of the liver. The transverse colon crosses the belly trans- versely on the confines of the umbilical and epigastric regions, its lower border being on a level slightly above the umbilicus, its upper border just below the greater curvature of the stomach. The splenic flexure of the colon is situated behind the stomach in the left hypochondrium, and is on a higher level than the hepatic flexure. The descending colon is deeply seated, passing- down through the left hypochondriac and lumbar regions to the sigmoid flexure, which is situ- ated in the left inguinal regions, and which can be felt in thin persons, with relaxed abdominal walls, rolling under the fingers when empty, and when distended forming a distinct tumor. Surgical Anatomy.-The small intestines are much exposed to injury, but, in consequence of their elasticity and the ease with which one fold glides over another, they are not so frequently ruptured as would otherwise be the case. Any part of the small intestine may be ruptured, but probably the most common situation is the transverse duodenum, on account of its being more fixed than other portions of the bowel, and because it is situated in front of the bodies of the vertebrae, so that if this portion of the abdomen is struck by a sharp blow, as from the kick of a horse, it is unable to glide out of the way, but is compressed against the bone and so lacerated. Wounds of the intestine sometimes occur. If the wound is a small puncture, under, it is said, three lines in length, no extravasation of the contents of the bowel takes place. The mucous membrane becomes everted and plugs the little opening. The bowels, therefore, may be safely punctured with a fine capillary trocar, in cases of excessive distension of the intestine with gas, without fear of extravasation. A longitudinal wound gapes more than a transverse, owing to the greater amount of circular muscular fibres. The small intestine, and most frequently the ileum, may become strangulated by internal bands, or through apertures, normal or abnormal. The bands may be formed in several different ways: they may be old peritoneal adhesions from SURGICAL ANATOMY OF THE LARGE INTESTINE. 947 previous attacks of peritonitis; or an adherent omentum from the same cause ; or the band may be formed by Meckel's diverticulum, which has contracted adhesions at its distal extremity; or the band may be the result of the abnormal attachment of some normal structure, as the adhesion of two appendices epiploicae, or an adherent vermiform appendix or Fallopian tube. Intussusception or invagination of the small intestine may take place in any part of the jejunum and ileum, but the most frequent situation is at the ileo-caecal valve, the valve forming the apex of the entering tube. This form may attain great size, and it is not uncommon in these cases to find the valve projecting from the anus. Stricture, the impaction of foreign bodies, and twist- ing of the gut (volvulus) may lead to intestinal obstruction. Foreign bodies and small hardened masses of faecal matter are very liable to become lodged in the vermiform appendix. Here they set up inflammation, often cause perforation of the appendix and formation of abscess in the loose connective tissue around. This may require operative interference, and in some cases of recurrent attacks of appendicitis this little divertic- ulum of the bowel has been removed. In external hernia the ileum is the portion of bowel most frequently herniated. When a part of the large intestine is involved, it is usually the caecum, and this may occur even on the left side. In some few cases the vermiform appendix has been the part implicated in cases of strangulated hernia, and has given rise to serious symp- toms of obstruction. Occasionally ulceration of the duodenal glands may occur in cases of burns, but is not a very common complication. The ulcer may perforate one of the large duodenal vessels, and may cause death from haemorrhage, or it may perforate the coats of tbe intestine and produce fatal acute peritonitis. The diameter of the large intestine gradually diminishes from the caecum, which has the greatest diameter of any part of the bowel, to the point of junction of the sigmoid flexure with the rectum, at or a little below which point stricture most commonly occurs and diminishes in frequency as one proceeds upward to the caecum. When distended by some obstruction low down, the outline of the large intestine can be defined throughout nearly the whole of its course-all, in fact, except the hepatic and splenic flexures, which are more deeply placed; the distension is most obvious in the two flanks and on the front of the abdomen just above the umbilicus. The caecum, however, is that portion of the bowel which is, of all, most distended. It sometimes assumes enormous dimensions, and has been known to be perforated from the pressure, causing fatal peritonitis. The hepatic flexure and the right extremity of the transverse colon is in close relationship with the liver, and abscess of this viscus sometimes bursts into the gut in this situation. The gall-bladder may become adherent to the colon, and gall-stones may find their way through into the gut, where they may become impacted or may be discharged per anum. The mobility of the sigmoid flexure renders it more liable to become the seat of a volvulus or twist than any other part of the intestine. It gener- ally occurs in patients who have been the subjects of habitual constipation, and in whom, there- fore, the meso-sigmoid flexure is elongated. The gut at this part being loaded with faeces, from its weight falls over the gut below, and so gives rise to the twist. The surgical anatomy of the rectum is of considerable importance. There may be congen- ital malformation due to arrest or imperfect development. Thus, there may be no inflection of the epiblast (see page 134), and consequently a complete absence of the anus; or the hind-gut may be imperfectly developed, and there may be an absence of the rectum, though the anus is developed; or the inflection of the epiblast may not communicate with the termination of the hind-gut from want of solution of continuity in the septum which in early foetal life exists between the two. The mucous membrane is thick and but loosely connected to the muscular coat beneath, and thus favors prolapse, especially in children. The vessels of the rectum are arranged, as mentioned above, longitudinally, and are contained in the loose cellular tissue between the mucous and muscular coats, and receive no support from surrounding tissues, and this favors varicosity. Moreover, the blood from these vessels is returned into the general circulation through two distinct channels-part through the systemic system and part through the portal system-so that they may be said to be placed between the portal and systemic circulations, and thus predisposed to congestion and consequent dilatation. In addition to this, there are no valves in the superior haemorrhoidal veins, and the vessels of the rectum are placed in a depend- ent position, and are liable to be pressed upon and obstructed by hardened faeces. The anatom- ical arrangement, therefore, of the haemorrhoidal vessels explains the great tendency to the occurrence of piles. Again, the presence of the Sphincter ani is of surgical importance, since it is the constant contraction of this muscle which prevents an ischio-rectal abscess from healing and causes it to become a. fistula. Also, the reflex contraction of this muscle is the cause of the severe pain complained of in fissure of the anus. The relations of the peritoneum to the rectum are of importance in connection with the operation of removal of the lower end of the rectum for malignant disease. This membrane gradually leaves the rectum as it descends into the pelvis; first leaving its posterior surface, then the sides, and then the anterior surface to become reflected in the male on to the posterior wall of the bladder, forming the recto-vesical pouch, ami in the female on to the posterior wall of the vagina, forming Douglas's pouch. The recto-vesical pouch of peritoneum extends to within three and a half or four inches from the anus, so that it is not safe to remove more than three inches of the entire circumference of the bowel for fear of the risk of opening the peritoneum. When, however, the disease is confined to the posterior surface of the rectum, or extends farther in this direction, a greater amount of the posterior wall of the gut may be removed, as the peritoneum does not extend on this surface to a lower level than five inches from the margin of the anus. The recto-vaginal or Douglas's pouch in the female extends somewhat lower than the recto-vesical pouch of the male, and therefore it is 948 THE ORGANS OF DIGESTION. necessary to remove a less length of the tube in this sex.1 Upon introducing the finger into the rectum the membranous portion of the urethra can be felt, if an instrument has been introduced into the bladder, exactly in the middle line; behind this the prostate gland can be recognized by its shape and hardness and any enlargement detected; behind the prostate the fluctuating wall of the bladder when full can be felt, and if thought desirable it can be tapped in this situ- ation ; on either side and behind the prostate the vesicufe seminales can be readily felt, espe- cially if enlarged by tubercular disease. Behind, the coccyx is to be felt, and on the mucous membrane one or two of Houston's folds. The ischio-rectal fossae can be explored on either side, with a view to ascertaining the presence of deep-seated collections of pus. Finally, it will be noted that the finger is firmly gripped by the sphincter for about an inch up the bowel. By gradual dilatation of the sphincter the whole hand can be introduced into the rectum so as to reach the descending colon. This method of exploration is rarely, however, required for diagnostic purposes. The colon frequently requires opening in cases of intestinal obstruction, the descending colon being usually the portion of bowel selected for this operation. The operation of colotomy may be performed either without opening the peritoneum by an incision in the loin (lumbar colotomy), or by an opening through the peritoneum (inguinal colotomy). Lumbar colotomy is performed by placing the patient on the side opposite to the one to be operated on, with a firm pillow under the loin. A line is then drawn from the anterior superior to the posterior superior spine of the ilium, and the mid-point of this line (Heath) or half an inch behind the mid-point (Allingham) is taken, and a line drawn vertically upward from it to the last rib. This line represents, with sufficient correctness, the position of the normal colon. An oblique incision four inches in length is now made midway between the last rib and the crest of the ilium, so that its centre bisects the vertical line, and the following parts successively divided: (1) Tbe skin, superficial fascia, with cutaneous vessels and nerves and deep fascia. (2) The posterior fibres of the External oblique and anterior fibres of the Latissimus dorsi. (3) The Internal oblique. (4) The lumbar fascia and the external border of the Quadratus lumborum. The edges of the wound are now to be held apart with retractors, and the transversalis fascia will be exposed. This is to be opened with care, commencing at the posterior angle of the incision. If the bowel is distended, it will bulge into the wound, and no difficulty will be found in dealing with it. If, however, the gut is empty, this bulging will not take place, and the colon will have to be sought for. The guides to it are the lower end of the kidney, which will be plainly felt, and the outer edge of the Quadratus lumborum. The bowel having been found, is to be drawn well up into the wound, and it may be opened at once and the margins of the openings stitched to the skin at the edge of the wound; or, if the case is not an urgent one, it may be retained in this position by two harelip pins passed through the muscular coat, the rest of the wound closed, and the bowel opened in three or four days, when adhesion of the bow'd to the edges of the wound has taken place. Inguinal colotomy is preferred by many surgeons in those cases where there is no urgent obstruction, and where, therefore, there is no necessity to open the bowel at once. The main reason for preferring this operation is that a spur-shaped process of the meso-colon can be formed which prevents any faecal matter finding its way past the artificial anus and becoming lodged on the diseased structures below. The sigmoid flexure being almost entirely surrounded by peri- toneum, a coil can be drawn out of the wound and the greater part of its calibre removed, leav- ing the remainder attached to the meso-colon, which forms a spur, much the same as in an artificial anus caused by sloughing of the gut after a strangulated hernia, and this prevents any faecal matter finding its way from the gut above the opening into that below. The operation is performed by making an incision two or three inches in length from a point one inch internal to the anterior superior spinous process of the ilium, parallel to Poupart's ligament. The various layers of abdominal muscles are cut through, and the peritoneum opened and sewn to the external skin. The sigmoid flexure is now sought for, and pulled out of the wound and fixed by passing a needle threaded with carbolized silk through the meso-colon close to the gut and then through the abdominal wall. The intestine is now sewn to the skin all round, the suture passing only through the serous and muscular coats. Tbe wound is dressed, and on the second to the fourth day, according to the requirements of the case, the protruded coil of intestine is opened and removed with scissors. THE LIVER. The Liver is a glandular organ of large size, intended mainly for the secretion of the bile, but effecting also important changes in certain constituents of the blood in their passage through the gland. It is situated in the right hypochondriac and epigastric regions, but in the child extends across the epigastrium into the left hypochondrium. It is the largest gland in the body, weighing from three to four pounds (from fifty to sixty ounces avoirdupois). It measures in its transverse diameter from ten to twelve inches, from six to seven in its antero-posterior, and is about three inches thick at the back part of the right lobe, which is the thickest part. 1 A Hingham says one inch less in the female. THE LIVER. 949 Its upper or diaphragmatic surface is convex, directed upward and forward, smooth, covered by peritoneum. It is in relation with the under surface of the Diaphragm, and below, to a small extent, with the abdominal parietes. The sur- face is divided into two unequal lobes, the right and left, by a fold of peritoneum, the suspensory or broad ligament. It presents on the left lobe a shallow depres- sion corresponding to the heart. Its under or visceral surface is concave, directed downward and backward, and is in relation with the stomach and duodenum, the hepatic flexure of the colon, and the right kidney and suprarenal capsule. The surface is divided by a longi- tudinal fissure into a right and left lobe. The posterior surface is rounded and broad over the right lobe, but narrow on the left. It is not covered by peritoneum, and is in contact with the Diaphragm and posterior wall of the abdomen, and is marked off from the upper surface by the line of reflection of the peritoneum from the under surface of the Diaphragm to the upper surface of the liver. On the right lobe this surface, which is here broad, is marked off from the under surface of the liver by the line of reflection of peritoneum from the posterior portion of the Diaphragm on to the liver, which forms the posterior layer of the coronary ligament. In its centre this posterior surface is deeply notched for the vertebral column, and to the right of this it is indented for the inferior vena cava, which is partly embedded in its substance. Close to the right of the vein is a slight depression for the right suprarenal cap- sule. To the left of the vena cava is the narrow ridge bounding the lobus Spi- gelii behind, and to the left of this a groove indicating the position of the oeso- phageal orifice of the stomach. The anterior border is thin and sharp, and marked opposite the attachment of the longitudinal ligament by a deep notch, and opposite the cartilage of the ninth rib by a second notch for the fundus of the gall-bladder. In adult males this border usually corresponds with the margin of the ribs, but in women and children it usually projects below the ribs. The right extremity of the liver is thick and rounded, whilst the left is thin and flattened. Ligaments.-The ligaments of the liver (Fig. 546) are five in number, four being formed of folds of peritoneum ; the fifth, the Ramentum teres, is a round Right Lobe. Left Lobe. Fig. 546.-The liver. Upper surface. fibrous cord resulting from the obliteration of the umbilical vein. The ligaments are the longitudinal, two lateral, coronary, and round. The longitudinal ligament (broad, falciform, or suspensory ligament) is a broad and thin antero-posterior peritoneal fold, falciform in shape, its base being directed 950 THE ORGANS OF DIGESTION. forward, its apex backward. It is attached by one margin to the under surface of the Diaphragm and the posterior surface of the sheath of the Right rectus muscle as low7 down as the umbilicus; by its hepatic margin it extends from the notch on the anterior margin of the liver as far back as its posterior surface. It consists of two layers of peritoneum closely united together. Its anterior free edge contains the round ligament between its layers. The lateral ligaments, two in number, right and left, are triangular in shape. They are formed of two layers of peritoneum united, and extend from the sides of the Diaphragm to the extremities of the posterior surface of the organ. The left is the longer of the tw7o, and lies in front of the oesophageal opening in the Diaphragm. The coronary ligament connects the posterior surface of the liver to the Dia- phragm. It is formed by the reflection of the peritoneum from the Diaphragm on to the upper and lower margins of the posterior surface of the organ. The coronary ligament consists of tw7o layers, which are continuous on each side with the lateral ligaments, and in front with the longitudinal ligament. Between the layers a ig h t Lobe Left Lobe Fig. 547.-The liver. Under surface. large oval space is left uncovered by peritoneum, and is connected to the Diaphragm by firm areolar tissue. The round ligament (Fig. 546) is a fibrous cord resulting from the obliteration of the umbilical vein. It ascends from the umbilicus, in the anterior free margin of the longitudinal ligament, to the notch in the anterior border of the liver, from which it may be traced along the longitudinal fissure on the under surface of the liver as far back as the inferior vena cava. Fissures (Fig. 547).-Five fissures are seen upon the under and posterior surfaces of the liver, which serve to divide it into five lobes. They are the longitudinal fissure, the fissure of the ductus venosus, the transverse fissure, the fissure for the gall-bladder, and the fissure for the inferior vena cava. They are arranged in the form of the letter A, the apex of the letter corresponding to the posterior surface of the liver, its base to the anterior free border. The connecting bar would represent the transverse fissure; the two converging limbs posterior to this would represent, the left one the fissure for the ductus venosus; the right one the fissure for the inferior vena cava ; the two diverging limbs anterior to the cross-bar would represent the umbilical fissure (left} and the fissure for the gall-bladder (right}. The longitudinal fissure is a deep groove which extends from the notch on the THE LIVER. 951 anterior margin of the liver to the posterior surface of the organ. It separates the right and left lobes; the transverse fissure joins it, at right angles, about one- third from its posterior extremity, and divides it into two parts. The anterior half is called the umbilical fissure ; it is deeper than the posterior part, and lodges the umbilical vein in the foetus or its remains (the round ligament) in the adult. This fissure is often partially bridged over by a prolongation of the hepatic substance, thejoons hepatis. The fissure of the ductus venosus is the back part of the longitudinal fissure, and is situated partly on the posterior surface of the liver ; it is shorter and shallower than the anterior portion. It lodges in the foetus the ductus venosus, and in the adult a slender fibrous cord, the obliterated remains of that vessel. The transverse or portal fissure is a short but deep fissure, about two inches in length, extending transversely across the undersurface of the right lobe, nearer to its posterior surface than its anterior border. It joins, nearly at right angles, Lobus Caudatus. i Suprarenal I Impression. (Esophageal Portal Vein. Gastric / Small Omentum. RIGHT LATERAL k/ LIGAMENT. I Lohus j Renat Omental Tuberosity globus J Quad- irat us fRladdeji Colic Impress LIGAMENTUM TERES. I Hepatic Artery. Common Bile Duct. Fig. 548.-Under surface of the liver. (From Ellis.) with the longitudinal fissure. By the older anatomists this fissure was considered the gateway (portai) of the liver; hence the large vein which enters at this point was called the portal vein. Besides this vein, the fissure transmits the hepatic artery and nerves and the hepatic duct and lymphatics. At their entrance into the fissure the hepatic duct lies in front and to the right, the hepatic artery to the left, and the portal vein behind and between the duct and artery. The fissure for the gall-bladder (fossa cystis fellece) is a shallow oblong fossa placed on the under surface of the right lobe parallel with the longitudinal fissure. It extends from the anterior free margin of the liver, which is occasionally notched for its reception, to near the right extremity of the transverse fissure. The fissure for the inferior vena cava is a short deep fissure, occasionally a complete canal, which extends obliquely upward from a little behind the right extremity of the transverse fissure on to the posterior surface of the liver, where it joins the fissure for the ductus venosus. On slitting open the inferior vena cava which is contained in it, a deep fossa is seen, at the bottom of which the hepatic veins communicate with this vessel. This fissure is separated from the transverse fissure by the lobus caudatus, and from the longitudinal fissure by the lobulus Spigelii. 952 THE ORGANS OF DIGESTION. Lobes.-The lobes of the liver, like the ligaments and fissures, are five in number-the right lobe, the left lobe, the lobus quadratus, the lobulus Spigelii, and the lobus caudatus. The right lobe is much larger than the left, the proportion between them being as six to one. It occupies the right hypochondrium, and is separated from the left lobe, on its upper surface, by the longitudinal ligament, on its under and posterior surfaces by the longitudinal fissure, and in front by a deep notch. It is of a quadrilateral form, its under surface being marked by three fissures-the transverse fissure, the fissure for the gall-bladder, and the fissure for the inferior vena cava ; and by three shallow impressions, one in front {impressio colica), for the hepatic flexure of the colon; one behind {impressio renalis), for the right kidney, and one internal, between the last-named and the gall-bladder {impressio duodenalis), for the second part of the duodenum. The left lobe is smaller and more flattened than the right. It is situated in the epigastric region. Its upper surface is convex ; its under surface is concave, and presents a shallow depression for the stomach {gastric impression). This is situated in front of the groove for the oesophagus, and is separated from the longitudinal fissure by a well-marked prominence, the omental tuberosity, which lies against the small omentum and lesser curvature of the stomach. The lobus quadratus, or square lobe, is situated on the under surface of the right lobe, bounded in front by the free surface of the liver, behind by the transverse fissure, on the right by the fissure of the gall-bladder, and on the left by the umbilical fissure. The lobulus Spigelii projects from the back part of the under surface of the right lobe. It is bounded in front by the transverse fissure, on the right by the fissure for the vena cava, and on the left by the fissure for the ductus venosus. The lobus caudatus, or tailed lobe, is a small elevation of the hepatic substance extending obliquely outward from the base of the lobulus Spigelii to the under surface of the right lobe. It separates the right extremity of the transverse fissure from the commencement of the fissure for the inferior vena cava. Vessels.-The vessels connected with the liver are also five in number: they are the hepatic artery, the portal vein, the hepatic vein, the hepatic duct, and the lymphatics. The hepatic artery and portal vein, accompanied by numerous lymphatics and nerves, ascend to the transverse fissure between the layers of the gastro-hepatic omentum. The hepatic duct, lying in company with them, descends from the transverse fissure between the layers of the same omentum. The relative position of the three structures is as follows : The hepatic duct lies to the right, the hepatic artery to the left, and the portal vein behind and between the other two. They are enveloped in a loose areolar tissue, the capsule of Glisson, which accompanies the vessels in their course through the portal canals in the interior of the organ. The hepatic veins convey the blood from the liver. They commence in the substance of the liver, in the capillary terminations of the portal vein and hepatic artery; these tributaries, gradually uniting, usually form three large veins, which converge toward the posterior surface of the liver and open into the inferior vena cava, whilst that vessel is situated in the groove at the back part of this organ. Of these three veins, one from the right and another from the left lobe open obliquely into the vena cava, that from the middle of the organ and lobulus Spigelii having a straight course. The hepatic veins have no cellular investment, consequently their parietes are adherent to the walls of the canals through which they run ; so that, on a section of the organ, these veins remain widely open and solitary, and may be easily dis- tinguished from the branches of the portal vein, which are more or less collapsed and always accompanied by an artery and duct. The hepatic veins are destitute of valves. The lymphatics are large and numerous, consisting of a deep and superficial set. They have been already described. tvta; liver. 953 Nerves.-The nerves of the liver are derived from the hepatic plexus of the sympathetic, from the pneumogastric nerves, especially the left, and from the right phrenic. Structure.-The substance of the liver is composed of lobules held together by an extremely fine areolar tissue, and of the ramifications of the portal vein, hepatic duct, hepatic artery, hepatic veins, lymphatics, and nerves, the whole being invested by a serous and a fibrous coat. The serous coat is derived from the peritoneum, and invests the greater part of the surface of the organ. It is intimately adherent to the fibrous coat. The fibrous coat lies beneath the serous investment and covers the entire sur- face of the organ. It is difficult of demonstration, excepting where the serous coat is deficient. At the transverse fissure it is continuous with the capsule of Glisson, and on the surface of the organ with the areolar tissue separating the lobules. The lobules form the chief mass of the hepatic substance; they may be seen either on the surface of the organ or by making a section through the gland. Hepatic artery. Portal vein.-] Portion of canal from which vein has been removed. Orifices of intralobular veins. Fig. 549.-Longitudinal section of an hepatic vein. (After Kiernan.) Fig. 550.-Longitudinal section of a small portal vein and canal. (After Kiernan.) They are small granular bodies about the size of a millet-seed, measuring from one-twentieth to one-tenth of an inch in diameter. In the human subject their outline is very irregular, but in some of the lower animals (for example, the pig) they are well-defined, and when divided transversely have a polygonal outline. If divided longitudinally they are more or less foliated or oblong. The bases of the lobules are clustered round the smallest radicles (sublobular) of the hepatic veins, to which each is connected by means of a small branch which issues from the centre of the lobule (intralobular). The remaining part of the surface of each lobule is imperfectly isolated from the surrounding lobules by a thin stratum of areolar tissue in which is contained a plexus of vessels (the interlobular plexus) and ducts. In some animals, as the pig, the lobules are completely isolated one from another by this interlobular areolar tissue. If one of the sublobular veins be laid open, the bases of the lobules may be seen through the thin wall of the vein on which they rest, arranged in the form of a tesselated pavement, the centre of each polygonal space presenting a minute aperture, the mouth of an intralobular vein (Fig. 549). Microscopic Appearance.-Each lobule is composed of a mass of cells (hepatic cells) surrounded by a dense capillary plexus, composed of vessels which penetrate from the circumference to the centre of the lobule, and terminate in a single 954 THE ORGANS OF DIGESTION. straight vein, which runs through its centre, to open at its base into one of the radicles of the hepatic vein. Between the cells are also the minute com- mencements of the bile-ducts. Therefore in the lobule we have all the essen- tials of a secreting gland; that is to say: (1) cells, by which the secretion is formed; (2) blood-vessels, in close relation' with the cells, containing the blood from which the secretion is derived; and (3) ducts, by which the secretion, when formed, is carried away. Each of these structures will have to be further considered. (1) The hepatic cells are of more or less spheroidal form, but may be rounded, flattened, or many-sided from mutual compression. They vary in size from the TiroTT t0 t^ie nW an 'nch in diameter. They consist of a honeycomb net- work (Klein) without any cell-wall, and contain one or sometimes two distinct nuclei. In the nucleus is a highly refracting nucleolus with granules. Embedded in the honeycomb network are numerous yellow particles, the coloring matter of the bile, and oil-globules. The cells adhere together by their surfaces so as to form rows, which radiate from the centre to the circumference of the lobules. As stated above, they are the chief agents in the secretion of the bile. (2) The Blood-vessels.-The blood in the capillary plexus around the liver- cells is brought to the liver principally by the portal vein, but also to a certain extent by the hepatic artery. For the sake of clearness the distribution of the blood derived from the hepatic artery may be considered first. The hepatic artery, entering the liver at the transverse fissure with the portal vein and hepatic duct, ramifies with these vessels through the portal canals. It gives off vaginal branches which ramify in the capsule of Glisson, and appear to be destined chiefly for the nutrition of the coats of the large vessels, the ducts, and the investing membranes of the liver. It also gives off capsular branches which reach the surface of the organ, terminating in its fibrous coat in stellate plexuses. Finally it gives off interlobular branches which form a plexus on the outer side of each lobule, to supply its wall and the accompanying bile-ducts. From this, lobulaj* branches enter the lobule and end in the capillary network between the cells. Some anatomists, however, doubt whether it transmits any blood directly to the capillary network. The portal vein (Fig. 550) also enters at the transverse fissure and runs through the portal canals, enclosed in Glisson's capsule, dividing into branches in its course, which finally break up into a plexus (the interlobular plexus} in the interlobular spaces between the lobules. In their course these branches receive the vaginal and capsular veins, corresponding to the vaginal and capsular branches of the hepatic artery (Fig. 550). Thus it will be seen that all the blood carried to the liver by the portal vein and hepatic artery, except perhaps that derived from the interlobular branches of the hepatic artery, directly or indirectly finds its way into the interlobular plexus. From this plexus the blood is carried into the lobule by fine branches which pierce its wall and then converge from the circumference to the centre of the lobule, forming a number of longitu- dinal vessels which are connected by transverse or horizontal branches (Fig. 551). In the interstices of the network of vessels thus formed are situated, as before said, the liver-cells : and here it is that, the blood being brought into intimate connection with the liver-cells, the bile is secreted. Arrived at the centre of the lobule, all these minute vessels empty themselves into one vein, of considerable size, which runs down the centre of the lobules from apex to base and is called the intralobular vein. At the base of the lobule this vein opens directly into the sublobular vein, with which the lobule is connected, and which, as before men- tioned, is a radicle of the hepatic vein. The sublobular veins, uniting into larger and larger trunks, end at last in the hepatic veins, which do not receive any intralobular veins. Finally, the hepatic veins, as mentioned at page 677, converge to form three large trunks which open into the inferior vena cava, while that ves- sel is situated in the fissure appropriated to it at the back of the liver. (3) The Ducts.-Having shown how the blood is brought into intimate relation 77//; LIVJilt. 955 with the hepatic cells in order that the bile may be secreted, it remains now only to consider the way in which the secretion, having been formed, is carried away. L Interlobular' vein. Trunk of intralobular k vein. Intralobular reinJi Fig. 551.-Horizontal section of liver (dog.) Several views have prevailed as to the mode of origin of the hepatic ducts ; it seems, however, to be clear that they commence by little passages which are formed between the cells, and which have been termed intercellular biliary pas- ~ Biliary duct. -Hepatic cells. -Capillary. Biliary duct. Fig. 553.-A transverse section of a small portal canal and its vessels. (After Kiernan.) 1. Portal vein. 2. Inter- lobular branches. 3. Vaginal branches. 4. Hepatic duct. 5. Hepatic artery. Fig. 552.-Section of liver. sages or bile-capillaries (Fig. 552). These passages are merely little channels or interspaces left between the contiguous surfaces of two cells or in the angle where three or more liver-cells meet (Fig. 552), and it seems doubtful whether there is any delicate membrane forming the wall of the space. The channels thus formed radiate to the circumference of the lobule, and, piercing its wall, form a plexus (interlobular) between the lobules. From this plexus ducts are derived which pass into the portal canals, become enclosed in Glisson's capsule, and, accompanying the portal vein and hepatic artery (Fig. 553), join with other ducts to form two main trunks, which leave the liver at the transverse fissure, and by their union form the hepatic duct. 956 THE ORGANS OF DIGESTION. THE GALL-BLADDER. The Gall-bladder is the reservoir for the bile ; it is a conical or pear-shaped musculo-membranous sac, lodged in a fossa on the under surface of the right lobe of the liver, and extending from near the right extremity of the transverse fissure to the anterior border of the organ. It is about four inches in length, one inch in breadth at its widest part, and holds from eight to ten drachms. It is divided into a fundus, body, and neck. The fundus, or broad extremity, is directed downward, forward and to the right, and occasionally projects beyond the anterior border of the liver; the body and neck are directed upward and backward to the left. The gall-bladder is held in its position by the peritoneum, which, in the majority of cases, passes over its under surface, but the serous membrane occasionally invests the gall-bladder, which is then connected to the liver by a kind of mesentery. Relations.-The body of the gall-bladder is in relation, by its upper surface, with the liver, to which it is connected by areolar tissue and vessels; by its under surface, with the first portion of the duodenum, occasionally the pyloric end of the stomach, and the hepatic flexure of the colon. The fundus is completely invested by peritoneum ; it is in relation, in front, with the abdominal parietes, immedi- ately below the ninth costal cartilage; behind, with the transverse arch of the colon. The neck is narrow, and curves upon itself like the letter S ; at its point of connection with the cystic duct it presents a well-marked constriction. When the gall-bladder is distended with bile or calculi, the fundus may be felt through the abdominal parietes, especially in an emaciated subject: the relations of this sac will also serve to explain the occasional occurrence of abdominal biliary fistulas, through which biliary calculi may pass out, and of the passage of calculi from the gall-bladder into the stomach, duodenum, or colon, which occasionally happens. Structure.-The gall-bladder consists of three coats-serous, fibrous and mus- cular, and mucous. The external or serous coat is derived from the peritoneum; it completely invests the fundus, but covers the body and neck only on their under surface. The f bro-muscular coat is a thin but strong layer which forms the framework of the sac, consisting of dense fibrous tissue which interlaces in all directions and is mixed with plain muscular fibres which are disposed chiefly in a longitudinal direction, a few running transversely. The internal or mucous coat is loosely connected with the fibrous layer. It is generally tinged with a yellowish-brown color, and is everywhere elevated into minute rugae, by the union of which numerous meshes are formed, the depressed intervening spaces having a polygonal outline. The meshes are smaller at the fundus and neck, being most developed about the centre of the sac. Opposite the neck of the gall-bladder the mucous membrane projects inward in the form of oblique ridges or folds, forming a sort of screw-like valve. The mucous membrane is covered with columnar epithelium and secretes an abundance of thick viscid mucus; it is continuous through the hepatic duct with the mucous membrane lining the ducts of the liver, and through the ductus com- munis choledochus with the mucous membrane of the alimentary canal. The Biliary Ducts are the hepatic, the cystic, and the ductus communis choledochus. The Hepatic Duct.-Two main trunks of nearly equal size issue from the liver at the transverse fissure, one from the right, the other from the left lobe ; these unite to form the hepatic duct, which then passes downward and to the right for about an inch and a half between the layers of the lesser omentum, where it joins at an acute angle with the cystic duct, and so forms the ductus communis choledochus. The hepatic duct, as it descends from the transverse fissure of the liver between the two layers of the lesser omentum, lies in company with the hepatic artery and portal vein. The cystic duct, the smallest of the three biliary ducts, is about an inch and a half in length. It passes obliquely downward and to the left from the neck of THE GALL-BLADDER. 957 the gall-bladder, and joins the hepatic duct to form the common duct. It lies in the gastro-hepatic omentum in front of the vena portae, the hepatic artery lying to its left side. The mucous membrane lining its interior is thrown into a series of crescentic folds, from five to twelve in number, similar to those found in the neck of the gall-bladder. They project into the duct in regular succession, and are directed obliquely round the tube, presenting much the appearance of a continuous spiral valve. When the duct has been distended the spaces between the folds are dilated so as to give to its exterior a sacculated appearance. The ductus communis choledochus, the largest of the three, is the common excretory duct of the liver and gall-bladder. It is about three inches in length, of the diameter of a goosequill, and formed by the junction of the cystic and hepatic ducts. It descends along the right border of the lesser omentum behind the first portion of the duodenum, in front of the vena porta, and to the right of the hepatic artery ; it then passes between the pancreas and descending portion of the duodenum, and, running for a short distance along the right side of the pancreatic duct near its termination passes with it obliquely between the mucous and muscular coats. The two ducts open by a common orifice upon the summit of a papilla, situated at the inner side of the descending portion of the duodenum, a little below its middle. Structure.-The coats of the biliary ducts are an external or fibrous and an internal or mucous. The fibrous coat is composed of strong fibro-areolar tissue, with a certain amount of muscular tissue arranged for the most part in a circular manner around the duct. The mucous coat is continuous with the lining membrane of the hepatic ducts and gall-bladder, and also with that of the duodenum, and, like the mucous membrane of these structures, its epithelium is of the columnar variety. It is provided with numerous mucous glands which are lobulated and open by minute orifices scattered irregularly in the larger ducts. In the smaller ducts, which lie in the portal canals in the substance of the liver, are also a number of orifices, disposed in two longitudinal row's, which were formerly regarded as the openings of mucous glands, but which are merely the orifices of tubular recesses. They occasionally anastomose, and from the sides of them saccular dilatations are given off. Surface Form.-The liver is situated in the right hypochondriac and the epigastric regions, and is moulded to the arch of the Diaphragm. In the greater part of its extent it lies under cover of the lower ribs and- their cartilages, but in the epigastric region it comes in contact with the abdominal wall in the subcostal angle. The upper limit of the right lobe of the liver may be defined by a line drawn from the articulation of the fifth right costal cartilage to the sternum horizontally outward to a little below the nipple, and then inclined downward to reach the seventh rib at the side of the chest. The upper limit of the left lobe may be defined by continu- ing this line to the left, with an inclination downward as it crosses the gladiolus, to a point about two inches to the left of the sternum on a level with the sixth left costal cartilage. The lower limit of the liver may be indicated by a line drawn half an inch below the lower border of the thorax on the right side as far as the ninth right costal cartilage, and thence obliquely upward across the subcostal angle to the eighth left costal cartilage. A slight curved line with its con- vexity to the left from this point-i. e. the eighth left costal cartilage-to the termination of the line indicating the upper limit will denote the left margin of the liver. The fundus of the gall- bladder approaches the surface behind the anterior extremity of the ninth costal cartilage, close to the outer margin of the Right rectus muscle. It must be remembered that the liver is subject to considerable alterations in position, and the student should make himself acquainted with the different circumstances under which this occurs, as they are of importance in determining the existence of enlargement or other diseases of the organ. Its position varies according to the posture of the body. In the erect position in the adult male the edge of the liver projects about half an inch below the lower edge of the right costal cartilages, and its anterior border can be often felt in this situation if the abdominal wall is thin. In the supine position the liver gravitates backward and recedes above the lower margin of the ribs, and cannot then be detected by the finger. In the prone position it falls forward, and can then generally be felt in a patient with loose and lax abdominal walls. Its position varies also with the ascent or descent of the Diaphragm. In a deep inspiration the liver descends below the ribs; in expiration it is raised behind them. Again, in emphysema, where the lungs are distended and the Diaphragm descends very low, the liver is pushed down; in some other 958 THE ORGANS OF DIGESTION. diseases, as phthisis, where the Diaphragm is much arched, the liver rises very high up. Pres- sure from without, as in tight-lacing, by compressing the lower part of the chest, displaces the liver considerably, its anterior edge often extending as low as the crest of the ileum ; and its convex surface is often at the same time deeply indented from the pressure of the ribs. Again, its position varies greatly according to the greater or less distension of the stomach and intestines. When the intestines are empty the liver descends in-the abdomen, but when they are distended it is pushed upward. Its relations to surrounding organs may also be changed by the growth of tumors or by collections of fluid in the thoracic or abdominal cavities. Surgical Anatomy.-On account of its large size, its fixed position, and its friability, the liver is more frequently ruptured than any of the abdominal viscera. The rupture may vary considerably in extent, from a slight scratch to an extensive laceration completely through its substance, dividing it into two parts. Sometimes an internal rupture without laceration of the peritoneal covering takes place, and such injuries are most susceptible of repair ; but small tears of the surface may also heal; when, however, the laceration is extensive, death usually takes place from haemorrhage, on account of the fact that the hepatic veins are contained in rigid canals in the liver-substance and are unable to contract, and are moreover unprovided with valves. The liver may also be torn by the end of a broken rib perforating the Diaphragm. The liver may be injured by stabs or other punctured wounds, and when these are inflicted through the chest-wall both pleural and peritoneal cavities may be opened up and both lung and liver be wounded. In cases of wound of the liver from the front, hernia of a part of thisviscus may take place, but can generally easily be replaced. Abscess of the liver is of not unfrequent occurrence, and may open in many different ways on account of the relations of this viscus to other organs. Thus, it has been known to burst into the lungs, and the pus been coughed up, or into the stomach and the pus vomited ; it may burst into the colon or into the duodenum : or, by perforating the Diaphragm, it may empty itself into the pleural cavity. Frequently it makes its way forward and points on the anterior abdominal wall, and finally it may burst into the peritoneal or pericardiac cavities. Abscesses of the liver frequently require opening, and this should be done preferably by an incision in the right semilunar line, in two stages: the peritoneal cavity being opened and the liver over the summit of the abscess being stitched to the parietal peritoneum on the first occasion, and three or four days subsequently the abscess being- evacuated. Hydatid cysts are more often found in the liver than in any other of the viscera. The reason of this is not far to seek. The embryo of the egg of the taenia echinococcus, being- liberated in the stomach by the disintegration of its shell, bores its way through the gastric walls, and usually enters a blood-vessel and is carried by the blood-stream to the hepatic capil- laries, where its onward course is arrested, and where it undergoes development into the fully- formed hydatid. When the gall-bladder is ruptured, or one of its main ducts, which may occur indepen- dently of laceration of the liver, the injury is necessarily fatal from peritonitis caused by the extravasation of bile into the peritoneal cavity. The gall-bladder may become distended with bile in cases of obstruction of its duct or the common bile-duct, or from a collection of gall-stones within its interior, thus forming a large tumor. The swelling is pear-shaped, and projects downward and forward to the umbilicus. It moves with respiration, since it is attached to the liver. To relieve this condition the gall-blad- der must be opened and the gall-stones removed. The operation is performed by an incision two or three inches long in the right semilunar line, commencing an inch below the costal mar- gin. The peritoneal cavity is opened, and, the tumor having been found, sponges are packed round it to protect the peritoneal cavity, and it is aspirated. When the contained fluid has been evacuated the flaccid bladder is drawn out of the abdominal wound and its wall incised to the extent of an inch ; any gall-stones in the bladder are now removed and the interior of the sac sponged dry. If the ease is one of obstruction of the duct, an attempt must be made to dislodge the stone by manipulation through the wall of the duct, or it must be crushed from without by carefully padded forceps. After all obstruction has been removed a drainage-tube is to be inserted and the external wound closed around it, the stitches being passed through the parietal peritoneum and also through the peritoneum covering the gall-bladder around the incision, so as to bring these two surfaces into apposition. The fistulous opening generally closes in the course of a few weeks. THE PANCREAS. Dissection.-The pancreas may be exposed for dissection in three different ways : 1. By raising the liver, drawing down the stomach, and tearing through the gastro-hepatic omentum and the ascending layer of the transverse meso-colon. 2. By raising the stomach, the arch of the colon, and great omentum, and then dividing the inferior layer of the transverse meso-colon and raising the ascending layer of the transverse meso-colon. 3. By dividing the two layers of peritoneum which descend from the great curvature of the stomach to form the great omentum, turning the stomach upward, and then cutting through the ascending layer of the transverse meso-colon (see Fig. 523, page 917). The Pancreas all flesh) is a compound racemose gland analogous in its structure to the salivary glands, though softer and less compactly arranged than those organs. In shape it is transversely oblong, flattened from before back- ward, and bears some resemblance to a dog's tongue, its right extremity being THE PANCREAS. 959 broad and presenting a sort of angular bend from above downward called the head, whilst its left extremity gradually tapers to form the tail, the intermediate portion being called the body. It is situated transversely across the posterior wall of the abdomen, at the back of the epigastric and left hypochondriac regions. Its length varies from six to eight inches, its breadth is an inch and a half, and its thickness from half an inch to an inch, being greater at its right extremity and along its upper border. Its weight varies from two to three and a half ounces, but it may reach six ounces. The right extremity or head of the pancreas (Fig. 554) is curved upon itself from above downward, and is embraced by the concavity of the duodenum. The common bile-duct descends behind, between the duodenum and pancreas, and the pancreatico-duodenal artery descends in front between the same parts. The lesser end or tail of the pancreas is narrow'; it extends to the left as far as the spleen, and is placed over the left kidney and suprarenal capsule. The body of the pancreas is somewhat prismatic in shape, and has three surfaces -anterior, posterior, and inferior. The anterior surface is somewhat concave, and is covered by the posterior surface of the stomach, which rests upon it. The posterior surface is separated from the vertebral column by the aorta, vena cava, the commencement of the vena porta, the pillars of the Diaphragm, and the superior mesenteric artery and vein. These latter vessels are surrounded by a lobular fold of the gland which passes transversely to the left behind them, and thus these vessels are embraced by the substance of the gland. This portion is sometimes detached from the rest of the organ, and is called the lesser pancreas. To the left of the vertebral column the posterior surface of the pancreas is in contact with the left renal vessels, the left suprarenal capsule, and the left kidney. Near the upper border of this surface is a groove, running from the centre of the gland to the left, in which is lodged the splenic artery and vein. The inferior surface is narrow, and lies above the third portion of the duodenum, from which it is separated in the middle line by the superior mesenteric vessels, which tilt it somewhat forward. The left extremity of this surface rests on the splenic flexure of the colon. Fig. 554.-The pancreas and its relations. 960 7777? ORGANS OF DIGESTTON. Projecting above the pancreas, where it crosses the aorta, is the coeliac axis. The pancreatic duct, called the canal of Wirsung, from its discoverer, extends transversely from left to right through the substance of the pancreas, nearer to its lower than its upper border, and lying nearer its anterior than its posterior sur- face. In order to expose it the superficial portion of the gland must be removed. It commences by the junction of the small ducts of the lobules situated in the tail of the pancreas, and, running from right to left, it constantly receives the ducts of the various lobules composing the gland, and, considerably augmented in size, it leaves the head of the pancreas, and, descending slightly, it gets into relation with the common bile-duct, lying to its left side, and, passing very obliquely through the mucous and muscular coats of the duodenum, it terminates by an orifice com- mon to it and the ductus communis choledochus upon the summit of an elevated papilla situated at the inner side of the descending portion of the duodenum, a little below its middle. Sometimes the pancreatic duct and ductus communis choledochus open sepa- rately into the duodenum. The excretory duct of the lesser pancreas is called the ductus pancreaticus minor ; it opens into the main duct near the duodenum, and sometimes separately into that intestine, at a distance of an inch or more from the termination of the principal duct. The pancreatic duct, near the duodenum, is about the size of an ordinary quill : its walls are thin, consisting of two coats, an external fibrous and an internal mucous ; the latter is thin, smooth, and furnished near its termination with a few scattered follicles. Sometimes the pancreatic duct is double up to its point of entrance into the duodenum. In structure the pancreas resembles the salivary glands. It differs from them, however, in certain particulars, and is looser and softer in its texture. It is not RECTUS MUSCLE. 8th Costal Cartilage. '' 7th Costal Cartilage. ,7th Rib. .'8th Rib. -9th Rib. '10th Rib. 'diaphragm. Abdominal Aorta. i ' 12th Rib. llth Rib. Fig. 555.-Transverse section through the middle of the first lumbar vertebra, showing the relations of the pancreas. (Braune.) enclosed in a distinct capsule, but is surrounded by areolar tissue, which dips down into its interior and connects together the various lobules of which it is composed. Each lobule, like the lobules of the salivary glands, consists of one of the ultimate THE SPLEEN. 961 ramifications of the main duct, terminating in a number of caecal pouches or acini. The minute ducts are lined by short columnar epithelium, shorter than that found in the salivary ducts. The acini are wavy and convoluted, and are also lined by columnar cells which present certain characteristics; each cell shows an outer homogeneous or faintly striated portion which becomes deeply stained with dyes and contains the nucleus, and an inner granular portion which does not easily stain. The lumen of the alveolus is hardly visible, being filled with an interstitial substance containing spindle-shaped cells, the centro-acinar cells of Langerhans. Vessels and Nerves.-The arteries of the pancreas are derived from the splenic and the pancreatico-duodenal branches of the hepatic and the superior mesenteric. Its veins open into the splenic and superior mesenteric veins. Its lymphatics terminate in the lumbar glands. Its nerves are filaments from the splenic plexus. Surface Form.-The pancreas lies in front of the first lumbar vertebra, and can sometimes be felt, in emaciated subjects, when the stomach and colon are empty, by making deep pressure in the middle line about three inches above the umbilicus. Surgical Anatomy.-The pancreas presents but little of surgical importance. It is occa- sionally the seat of cancer, which usually affects the head or duodenal end, and therefore often speedily involves the common bile-duct, leading to persistent jaundice. Cysts are also occasion- ally found in it, which may present in the epigastric region, above and to the right of the umbil- icus. and may require opening and draining. The fluid in them contains some of the elements of the pancreatic secretion and is very irritating, so that, if allowed to come in contact with the skin of the abdominal wall, it is likely to produce intractable eczema. It has been said that the pancreas is the only abdominal viscus which has never been found in a hernial protrusion ; but even this organ has been found, in company with other viscera, in rare cases of diaphragmatic hernia. The pancreas has been known to become invaginated into the intestine, and portions of the organ have sloughed off. In cases of excision of the pylorus great care must be exer- cised to avoid wounding the pancreas, as the escape of the pancreatic fluid may be attended with serious results. According to Billroth, it is likely, in consequence of its peptonizing quali- ties, to dissolve the cicatrix of the stomach. THE SPLEEN. The Spleen was formerly classified, together with the thyroid, thymus, and suprarenal capsules, as one of the ductless or blood-glands. It possesses no excretory duct. It is of an oblong flattened form, soft, of very brittle consistence, highly vascular, of a dark bluish-red color, and situated in the left hypochondriac region, embracing the cardiac end of the stomach. It is invested by peritoneum and connected with the stomach by the gastro-splenic omentum. Relations.-The external and posterior surface is convex, smooth, and in rela- tion with the under surface of the Diaphragm, which separates it from the ninth, tenth, and eleventh ribs of the left side. The internal surface is concave, and divided by a vertical fissure, the hilum, into an anterior or larger and a posterior or smaller portion. The hilum is pierced by several irregular apertures for the entrance and exit of vessels and nerves. At the margins of the hilum the two layers of peritoneum are reflected from the surface of the spleen on to the cardiac end of the stomach, forming the gastro-splenic omentum, which contains between its layers the splenic vessels and nerves and the vasa brevia. In front of the hilum the internal surface, which is directed somewhat forward, is broad and concave and in contact with the great end of the stomach, and below this with the tail of the pancreas and splenic flexure of the colon. Behind the hilum the internal surface, which is here directed inward, presents a smooth concave fossa which rests on the upper and outer border of the left kidney. The upper end, thick and rounded, is in relation with the Diaphragm, to which it is connected by a fold of peritoneum, the suspensory ligament. The lower end is pointed and rests on the costo-colic ligament. The anterior margin is free, rounded, and often notched, especially below. The spleen is held in its position by two folds of peritoneum : one, the gastro- splenic omentum, connects it with the stomach; and the other, the suspensory 962 THE ORGANS OF DIGESTION ligament, with the under surface of the Diaphragm. It is also supported by the costo-colic ligament, upon which its lower end rests (see page 925). The size and weight of the spleen are liable to very extreme variations at different periods of life, in different individuals, and in the same individual under different conditions. In the adult, in whom it attains its greatest size, it is usually about five inches in length, three or four inches in breadth, and an inch or an inch and a half in thickness, and weighs about seven ounces. At birth its weight, in proportion to the entire body, is almost equal to what is observed in the adult, being as 1 to 350; whilst in the adult it varies from 1 to 320 and 400. In old age the organ not only decreases in weight, but decreases considerably in proportion to the entire body, being as 1 to 700. The size of the spleen is increased during and after digestion, and varies considerably according to the state of nutrition of the body, being large in highly-fed and small in starved animals. In intermittent and other fevers it becomes much enlarged, weighing occasionally from 18 to 20 pounds. Fig. 556.-Transverse section of the spleen, showing the trahecular tissue and the splenic vein and its branches, Structure.-The spleen is invested by two coats-an external serous and an internal fibro-elastic coat. The external or serous coat is derived from the peritoneum; it is thin, smooth, and in the human subject intimately adherent to the fibro-elastic coat. It invests almost the entire organ, being reflected from it, at the hilum, on to the great end of the stomach, and at the upper end of the organ on to the Diaphragm. The fibro-elastic coat forms the framework of the spleen. It invests the exterior of the organ, and at the hilum is reflected inward upon the vessels in the form of vaginae or sheaths. From these sheaths, as well as from the inner surface of the fibro-elastic coat, numerous small fibrous bands, trabeculce (Fig. 556), are given off in all directions; these, uniting, constitute the areolar framework of the spleen. The framework of the spleen resembles, therefore, a sponge-like material, consisting of a number of small spaces or areolce, formed by the trabeculae which are given off from the inner surface of the capsule, or from the sheaths prolonged inward on the blood-vessels. And in these spaces or areolae is contained the splenic pulp. The proper coat, the sheaths of the vessels and the trabeculae, consist of a dense mesh of white and yellow elastic fibrous tissues, the latter considerably pre- dominating. It is owing to the presence of this tissue that the spleen possesses a considerable amount of elasticity, which allows of the very great variations in size that it presents under certain circumstances. In addition to these con- THE SPLEEN. 963 stituents of this tunic, there is found in man a small amount of non-striped muscu- lar fibre, and in some mammalia (e. g. dog, pig, and cat) a very considerable amount, so that the trabeculae appear to consist chiefly of muscular tissue. It is probably owing to this structure that the spleen exhibits, when acted upon by the galvanic current, faint traces of contractility. The proper substance of the spleen or spleen-pulp is a soft mass of a dark reddish-brown color, resembling grumous blood. When examined, by means of a thin section, under a microscope, it is found to consist of a number of branching cells and an intercellular substance. The cells are connective-tissue corpuscles, and have been named the sustentacular or supporting cells of the pulp. The processes of these branching cells communicate with each other, thus forming a delicate reticulated tissue in the interior of the areolae formed by the trabeculae of the capsule; so that each primary space may be considered to be divided into a number of smaller spaces by the junction of these processes of the branching corpuscles. These secondary spaces contain blood, in which, however, the white corpuscles are found to be in larger proportions than they are in ordinary blood. The sustentacular cells are either small uni-nucleated or larger multi-nucleated cells; they do not become deeply stained with carmine, like the cells of the Malpighian bodies, presently to be described (W. Muller), but like them they pos- sess amoeboid movements (Cohnheim). In many of them may be seen deep red or reddish-yellow granules of various sizes which present the characters of the haematin of the blood. Sometimes, also, unchanged blood-disks are seen included in these cells, but more frequently blood-disks are found which are altered both in form and color. In fact, blood-corpuscles in all stages of disintegration may be noticed to occur within them. Klein has recently pointed out that some- times these cells in the young spleen contain a proliferating nucleus; that is to say, the nucleus is of large size, and presents a number of knob-like projections, as if small nuclei were budding from it by a process of gemmation. This observa- tion is of importance, as it may explain one possible source of the colorless blood- corpuscles. The interspaces or areolae formed by the framework of the spleen are thus filled by a delicate reticulum of branched connective-tissue corpuscles the interstices of which are occupied by blood, and in which the blood-vessels terminate in the manner now to be described. Blood-vessels of the Spleen.-The splenic artery is remarkable for its large size in proportion to the size of the organ, and also for its tortuous course. Fig. 557.-Transverse section of the human spleen, showing the distribution of the splenic artery and its branches. It divides into from four to six branches which enter the hilum of the spleen and ramify throughout its substance (Fig. 557), receiving sheaths from an 964 THE ORGANS OF DIGESTION involution of the external fibrous tissue. Similar sheaths also invest the nerves and veins. Each branch runs in the transverse axis of the organ from within outward, diminishing in size during its transit, and giving off in its passage smaller branches, some of which pass to the anterior, others to the posterior part. These ultimately leave the trabecular sheaths, and terminate in the proper substance of the spleen in small tufts or pencils of minute arterioles, which open into the interstices of the reticulum formed by the branched sustentacular cells. Each of the larger branches of the artery supplies chiefly that region of the organ in which the branch ramifies, having no anastomosis with the majority of the other branches. The arterioles, supported by the minute trabeculae, traverse the pulp in all directions in bundles or penicilli of straight vessels. Their external coat, on leaving the trabecular sheaths, consists of ordinary connective tissue, but it gradu- ally undergoes a transformation, becomes much thickened, and is converted into a lymphoid material.1 This change is effected by the conversion of the con- nective tissue into a cystogenous tissue, the bundles of connective tissue becoming looser and laxer, their fibrils more delicate, and containing in their interstices an abundance of lymph-corpuscles (W. Muller). This lymphoid material is supplied with blood by minute vessels derived from the artery with which they are in contact, and which terminates by breaking up into a network of capillary vessels. The altered coat of the arterioles, consisting of lymphoid tissue, presents here and there thickenings of a spheroidal shape, the Malpighian bodies of the spleen. These bodies vary in size from about the of an inch to the of an inch in diameter. They are merely local expansions or hyperplasiae of the lymphoid tissue of which the external coat of the smaller arteries of the spleen is formed. They are most frequently found surrounding the arteriole, which thus seems to tunnel them, but occasionally they grow from one side of the vessel only, and present the appearance of a sessile bud growing from the arterial wall. Klein, however, denies this, and says it is incorrect to describe the Malpighian bodies as isolated masses of adenoid tissue, but that they are always formed around an artery, though there is generally a greater amount on one side than the other, and that therefore in transverse sections the artery in the majority of cases is found in an eccentric position. These bodies are visible to the naked eye on the sur- face of a fresh section of the organ, appearing as minute dots of semi-opaque whitish color in the dark substance of the pulp. In minute structure they resemble the adenoid tissue of lymphatic glands, consisting of a delicate retic- ulum in the meshes of which lie ordinary lym- phoid cells. The reticulum of the tissue is made up of extremely delicate fibrils, and is comparatively open in the centre of the corpuscle, becoming closer at the periphery of the body. The cells which it encloses, like the supporting cells of the pulp, are possessed of amoeboid movements, but when treated with carmine become deeply stained, and can thus easily be recognized from those of the pulp. The arterioles terminate in capillaries which traverse the pulp in all directions ; their walls become much attenuated, lose their tubular character, and the cells of Fig. 558.-Part of a Malpighian capsule of the spleen of man. (Klein and Noble Smith.) a. Arterial branch in longitudinal section, b. Adenoid tissue, still containing the lymph-corpuscles; only their nuclei are shown, c. Adenoid reticulum, the lymph-corpuscles accidentally removed. 1 According to Klein, it is the sheath of the small vessel which undergoes this transformation, and forms a "solid mass of adenoid tissue which surrounds the vessel like a cylindrical sheath " {Atlas of Histology, p. 424). THE SPLEEN. 965 the lymphoid tissue of which they are composed become altered, presenting a branched appearance and acquiring processes which are directly connected with the processes of the sustentacular cells of the pulp (Fig. 559). In this manner the capillary vessels terminate, and the blood flowing through them finds its way into the interstices of the reticulated tissue formed by the branched connective-tissue corpuscles of the splenic pulp. Thus the blood passing through the spleen is Supporting cell. Vessel undergoing lymphoid change. Vessel continuous with processes of supporting cells. Small artery. Supporting cell. Supporting- cell. Fig. 559.-Section of spleen, showing the termination of the small blood-vessels. brought into intimate relation with the elements of the pulp, and no doubt under- goes important changes. After these changes have taken place the blood is collected from the interstices of the tissue by the rootlets of the veins, which commence much in the same way as the arteries terminate. Where a vein is about to commence the connective- tissue corpuscles of the pulp arrange themselves in rows in such a way as to form an elongated space or sinus. They become changed in shape, being elongated and spindle-shaped, and overlap each other at their extremities. They thus form a sort of endothelial lining of the path or sinus, which is the radicle of a vein. On the outer surface of these cells are seen delicate transverse lines or markings which are due to minute elastic fibrillae arranged in a circular manner around the sinus. Thus the channel obtains a continuous external investment, and gradually becomes converted into a small vein, which after a time presents a coat of ordinary connective tissue, lined by a layer of fusiform epithelial cells which are continuous with the supporting cells of the pulp. The smaller veins unite to form larger ones which do not accompany the arteries, but soon enter the trabecular sheaths of the capsule, and by their junction form from four to six branches which emerge from the hilum and, uniting, form the splenic vein, the largest radicle of the vena porta. The veins are remarkable for their numerous anastomoses, while the arteries hardly anastomose at all. The lymphatics originate in two ways-i. e. from the sheaths of the arteries and in the trabeculae. The former accompany the blood-vessels; the latter pass to the superficial lymphatic plexus which may be seen on the surface of the organ. The two sets communicate in the interior of the organ. They pass through the lymphatic glands at the hilum and terminate in the thoracic duct. The nerves are derived from branches of the right and left semilunar ganglia and from the right pneumogastric nerve. Surface Form.-The spleen is situated under cover of the ribs of the left side, being sepa- rated from them by the Diaphragm, and above by a small portion of the lower margin of the left lung. Its position corresponds to the ninth, tenth, and eleventh ribs. It is placed very obliquely. " It is oblique in two directions, viz. from above downward and outward, and also from above downward and forward" (Cunningham). "Its highest and lowest points are on a 966 THE ORGANS OF DIGESTION. level respectively with the ninth dorsal and first lumbar spines; its inner end is distant about an inch and a half from the median plane of the body, and its outer end about reaches the mid- axillary line " (Quain). Surgical Anatomy.-Injury of the spleen is less common than that of the liver, on account of its protected situation and connections. It may be ruptured by direct or indirect violence, torn by a broken rib, or injured by a punctured or gunshot wound. When the organ is enlarged the chance of rupture is increased. The great risk is haemorrhage, owing to the great vascu- larity of the organ, and the absence of a proper system of capillaries. The injury is not, how- ever, necessarily fatal, and this would appear to be due in a great measure to the contractile power of its capsule, which narrows the wound and prevents the escape of blood. In cases where the diagnosis is clear and the symptoms indicate danger to life laparotomy must be per- formed ; and if the haemorrhage cannot be stayed by ordinary surgical methods the spleen must be removed. The spleen may become displaced, producing great pain from stretching of the vessels and nerves, and this may require removal of the organ. The spleen may become enor- mously enlarged in certain diseased conditions, such as ague, syphilis, valvular disease of the heart, or without any obtainable history of previous disease. It may also become enlarged in lymphadenoma as a part of a general blood-disease. In these cases the tumor may sometimes fill the abdomen and extend into the pelvis, and may be mistaken for ovarian or uterine disease. The spleen is sometimes the seat of cystic tumors, especially hydatids, and of abscess. These cases require treatment by incision and drainage; and in abscess great care must be taken if there are no adhesions between the spleen and abdominal cavity, to prevent the escape of any of the pus into the peritoneal cavity. If possible, the operation should be performed in two stages, as in abscess of the liver. Sarcoma and carcinoma are occasionally found in the spleen, but very rarely as a primary disease. Extirpation of the spleen has been performed for wounds or injuries, in floating spleen, in simple hypertrophy, and in leukaemic enlargement; but in these latter cases the operation is now regarded as unjustifiable, as every case in which it has been performed has terminated fatally. The incision is best made in the left semilunar line : the spleen is isolated from its sur- roundings, and the pedicle transfixed and ligatured in two portions, before the tumor is turned out of the abdominal cavity, if this is possible, so as to avoid any traction on the pedicle, which may cause tearing of the splenic vein. In applying the ligature care must be taken not to include the tail of the pancreas, and in lifting out the organ to avoid rupturing the capsule. THE THORAX. Fill IE Thorax is a cone-shaped cavity containing and protecting the heart, I enclosed in its membranous bag, the pericardium, and the lungs, invested by the pleura. Its shape and boundaries have already been described (see page 230). The Cavity of the Thorax.-The size of the cavity of the thorax does not correspond with its apparent size externally, because (1) the space enclosed by the lower ribs is occupied by some of the abdominal viscera, and (2) the cavity extends above the first rib into the neck. The size of the cavity of the thorax is constantly varying during life with the movements of the ribs and Diaphragm and with the degree of distension of the abdominal viscera. From the collapsed state of the lungs in the dead body it would appear as if the viscera only partly filled the cavity of the thorax, but during life there is no vacant space, that which is seen after death being filled up by the expanded lungs. The Upper Opening of the Thorax.-The parts which pass through the upper opening of the thorax are, from before backward in the middle line, the Sterno- hyoid and Sterno-thyroid muscles, the remains of the thymus gland, the trachea, oesophagus, thoracic duct, and the Longus colli muscle of each side; at the sides, the innominate artery, the left common carotid and left subclavian arteries, the internal mammary and superior intercostal arteries, the right and left innom- inate veins, and the inferior thyroid veins, the pneumogastric, cardiac, phrenic, and sympathetic nerves, the anterior branch of the first dorsal nerve, and the recurrent laryngeal nerve of the left side. The apex of each lung, covered by the pleura, also projects through this aperture, a little above the margin of the first rib. The lower opening of the thorax is wider transversely than from before back- ward. It slopes obliquely downward and backward, so that the cavity of the thorax is much deeper behind than in front. The Diaphragm (see page 446) closes in the opening, forming the floor of the thorax. The floor is flatter at the centre than at the sides, and is higher on the right side than on the left, corresponding in the dead body to the upper border of the fifth costal cartilage on the former, and to the corresponding part of the sixth costal cartilage on the latter. From the highest point on each side the floor slopes suddenly downward to the attachment of the Diaphragm to the ribs; this is more marked behind than in front, so that only a narrow space is left between it and the wall of the thorax. The Pericardium (Figs. 560, 561) is a conical membranous sac in which the heart and the commencement of the great vessels are contained. It is placed behind the sternum and the cartilages of the third, fourth, fifth, sixth, and seventh ribs of the left side, in the interval between the pleurae. Its apex is directed upward, and surrounds the great vessels about two inches above their origin from the base of the heart. Its base is attached to the central tendon and part of the adjoining muscular structure of the Diaphragm, extending a little farther to the left than to the right side. In front it is separated from the sternum by the remains of the thymus gland above and a little loose areolar tissue below, and is covered by the margins of the lungs, especially the left. Behind, it rests upon the bronchi, the oesophagus, and the descending aorta. Laterally, it is covered by the pleurae, the phrenic nerve with its accompanying vessels descending between the two membranes on either side. THE PERICARDIUM. 968 THE THORAX. Structure of the Pericardium.-The pericardium is a fibro-serous membrane, and consists, therefore, of two layers, an external fibrous and an internal serous. The fibrous layer is a strong, dense membrane. Above, it surrounds the great vessels arising from the base of the heart, on which it is continued in the form of tubular prolongations which are gradually lost upon their external coat, the strongest being that which encloses the aorta. The pericardium may be traced over these vessels, to become continuous with the deep layer of the cervical fascia. On each side of the ascending aorta it sends upward a diverticulum : the one on Right common carotid , artery. {Right subclavian artery. ]Left carotid. Inf. thyroid vein. .Left subclavian. Right innom" vein. Ductus /arteriosus. Left innom. vein. Sup. vena~- cava. Right pulmonary* vein. -Pulm. vein. Fig. 560.-Pericardium, from in front. The sac has been distended with plaster. (From a preparation in the Museum of the Royal College of Surgeons.) the left side, somewhat conical in shape, passes upward and outward, between the arch of the aorta and the pulmonary artery, as far as the ductus arteriosus, where it terminates in a caecal extremity, which is attached by loose connective tissue to the obliterated duct (Fig. 560). The one on the right side passes upward and to the right, between the ascending aorta and vena cava superior, and also terminates in a caecal extremity. Below, the fibrous layer is attached to the central tendon of the Diaphragm, and on the left side to its muscular fibres. The vessels receiving fibrous prolongations from this membrane are the aorta, the superior vena cava, the right and left pulmonary arteries, and the four pulmonary veins. As the inferior vena cava enters the pericardium through the central tendon of the Diaphragm it receives no covering from the fibrous layer. THE PERICARDIUM. 969 The serous layer invests the heart, and is then reflected on the inner surface of the pericardium. It consists, therefore, of a visceral and parietal portion. The former invests the surface of the heart and the commencement of the great vessels to the extent of two inches from their origin; from these it is reflected upon the inner surface of the fibrous layer, lining, below, the upper surface of the central tendon of the Diaphragm. The serous membrane encloses the aorta and pul- monary artery in a single tube, but it only partially covers the superior and inferior vena cava and the four pulmonary veins. Its inner surface is smooth and Right subclavian artery. Left comm, carotid artery. Right comm. ' carotid art. Left subclavian art. Right pulmonary art.\ (.Left innom. vein. Inf. thyr. Rt. innom. S' vein. Sup. vena cava. • Vena .azygos maj. Rt. pulm. vein. Fig. 561.-Pericardium, from behind. (From the same preparation as the preceding figure.) glistening, and secretes a thin fluid which serves to facilitate the movements of the heart. Arteries of the Pericardium.-These are derived from the internal mammary and its musculo-phrenic branch and from the descending thoracic aorta. Nerves of the Pericardium.-These are branches from the vagus, the phrenic, and the sympathetic. The Vestigial Fold of the Pericardium.-In front of the root of the left lung there is a vertical fibrous band, the vestigial fold of Marshall. It is formed by the remnant of the lower part of the trunk of the left innominate vein, which after birth became obliterated, between the branch communicating with the right innominate vein and the back of the heart. 970 7777f THORAX. Surgical Anatomy.-Paracentesis of the pericardium is sometimes required in cases of effu- sion into its cavity. The operation is best performed in the fifth intercostal space, one inch to the left of the sternum. The operation has been performed, however, in the fourth, sixth, and seventh spaces, and also on the right side of the sternum. THE HEART. The Heart is a hollow muscular organ, of a conical form, placed between the lungs and enclosed in the cavity of the pericardium. Position.-The heart is placed obliquely in the chest: the broad attached end, or base, is directed upward, backward, and to the right, and corresponds to the Fig. 562.-Front view of the thorax. The ribs and sternum are represented in relation to the lungs, heart, and other internal organs. 1. Pulmonary orifice. 2. Aortic orifice. 3. Left auriculo-ventricular orifice. 4. Right auriculo-ventricular orifice. interval between the fifth and eighth dorsal vertebrae; the apex is directed downward, forward, and to the left, and corresponds to the space between the cartilage of the fifth and sixth ribs, three-quarters of an inch to the inner side, and an inch and a half below the left nipple. The heart is placed behind the lower two-thirds of the sternum, and projects farther into the left than into the right cavity of the chest, extending from the median line about three inches in the former direction, and only one and a half in the latter. The anterior surface of the heart is round and convex, directed upward and forward, and formed chiefly by the right ventricle and part of the left. Its posterior surface is flat- tened and rests upon the Diaphragm, and is formed chiefly by the left ventricle. The right border is long, thin, and sharp ; the left border short, but thick and round. THE HEART. 971 Size.-The heart in the adult measures five inches in length, three inches and a half in breadth in the broadest part, and two inches and a half in thickness. The prevalent weight, in the male, varies from ten to twelve ounces ; in the female, from eight to ten : its proportions to the body being as 1 to 169 in males, 1 to 149 in females. The heart continues increasing in weight, and also in length, breadth, and thickness, up to an advanced period of life: this increase is more marked in men than in women. Component Parts.-The heart is subdivided by a longitudinal muscular septum into two lateral halves, which are named respectively, from their position, right and left; and a transverse constriction subdivides each half of the organ into two cavities, the upper cavity on each side being called the auricle, the lower the ven- tricle. The right is the venous side of the heart, receiving into its auricle the Foramina, Thebesii 1 Tubercle of Lower. Bristle passed through Right Auriculo- Ventricular opening. Fig. 563.-The right auricle and ventricle laid open, the anterior walls of both being removed. dark venous blood from the entire body, by the superior and inferior vena cava and coronary sinus. From the right auricle the blood passes into the right ventricle, and from the right ventricle, through the pulmonary artery, into the lungs. The blood, arterialized by its passage through the lungs, is returned to the left side of the heart by the pulmonary veins, which open into the left auricle; from the left auricle the blood passes into the left ventricle, and from the left ventricle is distributed, by the aorta and its subdivisions, through the entire body. This constitutes the circulation of the blood in the adult. The division of the heart into four cavities is indicated by grooves upon its surface. The great transverse groove separating the auricles from the ventricles is called the auriculo-ventricular groove. It is deficient, in front, from being crossed by the root of the pulmonary artery. It contains the trunks of the nutrient vessels of the heart. The auricular portion occupies the base of the heart, and is subdivided into two cavities by a median septum. The two ventricles are also separated into a right and left by two longitudinal furrows, the interven- tricular grooves, which are situated one on the anterior, the other on the posterior surface ; these extend from the base to the apex of the organ, the former being situated nearer to the left border of the heart, and the latter to the right. It fol- 972 THE THORAX. lows, therefore, that the right ventricle forms the greater portion of the anterior surface of the heart, and the left ventricle more of its posterior surface. Each of these cavities should now be separately examined. To examine the interior of the right auricle, an incision should be made along its right bor- der from the entrance of the superior vena cava to that of the inferior. A second cut is to be made from the centre of this first incision to the tip of the auricular appendix, and the flaps raised. The Right Auricle is a little larger than the left, its walls somewhat thinner, measuring about one line, and its cavity is capable of containing about two ounces. It consists of two parts-a principal cavity, or sinus venosus, and an appendix auriculae. The sinus is the large quadrangular cavity placed between the two vense cavse ; its walls are extremely thin; it is connected below with the right ventricle, and internally with the left auricle, being free in the rest of its extent. The appendix auricula;, so called from its fancied resemblance to a dog's ear, is a small conical muscular pouch the margins of which present a dentated edge. It projects from the sinus forward and to the left side, overlapping the root of the aorta. The internal surface of the right auricle is smooth, except in the appendix and adjacent part of the anterior wall of the sinus venosus, where it is thrown into parallel ridges. It presents the following parts for examination : Superior cava. Inferior cava. Coronary sinus. Foramina Thebesii. Auriculo-ventricular. Openings Valves Eustachian. Coronary. Relics of foetal structure Annulus ovalis. Fossa ovalis. Musculi pectinati. Tuberculum Loweri. The superior vena cava returns the blood from the upper half of the body, and opens into the upper and back part of the auricle, the direction of its orifice being downward and forward. The inferior vena cava, larger than the superior, returns the blood from the lower half of the body, and opens into the lowest part of the auricle near the septum, the direction of its orifice being upward and inward. The direction of a current of blood through the superior vena cava would consequently be toward the auriculo-ventricular orifice, whilst the direction of the blood through the inferior cava would be toward the auricular septum. This is the normal direction of the two currents in foetal life. The tuberculum Loweri is a small projection on the right wall of the auricle, between the two venae cavae. It is most distinct in the hearts of quadrupeds; in man it is scarcely visible. It was supposed by Lower to direct the blood from the superior cava toward the auriculo-ventricular opening. The coronary sinus opens into the auricle, between the inferior vena cava and the auriculo-ventricular opening. It returns the blood from the substance of the heart, and is protected by a semicircular fold of the lining membrane of the auricle, the coronary valve. The sinus, before entering the auricle, is considerably dilated-nearly to the size of the end of the little finger. Its wall is partly muscular, and at its junction with the great coronary vein is somewhat constricted and furnished with a valve consisting of two unequal seg- ments. The foramina Thebesii are numerous minute apertures, the mouths of small veins (pence cordis minima!), which open on various parts of the inner surface of the auricle. They return the blood directly from the muscular substance of the THE HEART. 973 heart. Some of these foramina are minute depressions in the walls of the heart, presenting a closed extremity. The auriculo-ventricular opening is the large oval aperture of communication between the auricle and the ventricle, to be presently described. The Eustachian valve is situated between the anterior margin of the inferior vena cava and the auriculo-ventricular orifice. It is semilunar in form, its convex margin being attached to the wall of the vein; its concave margin, which is free, terminating in two cornua, of which the left is attached to the anterior edge of the annulus ovalis, the right being lost on the wall of the auricle. The valve is formed by a duplicature of the lining membrane of the auricle containing a few muscular fibres. In the foetus this valve is of large size, and serves to direct the blood from the inferior vena cava, through the foramen ovale, into the left auricle. In the adult it is occasionally persistent, and may assist in preventing the reflux of blood into the inferior vena cava; more commonly it is small, and its free margin presents a cribriform or filamentous appearance; occasionally it is altogether wanting. The coronary valve (valve of Thebesius) is a semicircular fold of the lining membrane of the auricle, protecting the orifice of the coronary sinus. It prevents the regurgitation of blood into the sinus during the contraction of the auricle. This valve is occasionally double. The fossa ovalis is an oval depression corresponding to the situation of the foramen ovale in the foetus. It is situated at the lower part of the septum auricu- larum, above and to the left of the orifice of the inferior vena cava. The annulus ovalis is the prominent oval margin of the foramen ovale. It is most distinct above and at the sides; below, it is deficient. A small slit-like valvular opening is occasionally found, at the upper margin of the fossa ovalis, which leads upward beneath the annulus into the left auricle, and is the remains of the aperture between the two auricles in the foetus. The musculi pectinati are small, prominent muscular columns which run across the inner surface of the appendix auriculae and adjoining portion of the wall of the sinus. They have received the name pectinati from the fancied resemblance they bear to the teeth of a comb. The Right Ventricle is triangular in form, and extends from the right auricle to near the apex of the heart. Its anterior or upper surface is rounded and convex, and forms the larger part of the front of the heart. Its under surface is flattened, rests upon the Diaphragm, and forms only a small part of the back of the heart. Its posterior wall is formed by the partition between the two ventricles, the septum ventriculorum, the surface of which is convex and bulges into the cavity of the right ventricle. Its upper and inner angle is prolonged into a conical pouch, the infundibulum or conus arteriosus, from which the pul- monary artery arises. The walls of the right ventricle are thinner than those of the left, the proportion between them being as 1 to 3. The wall is thickest at the base, and gradually becomes thinner toward the apex. The cavity, which equals that of the left ventricle, is capable of containing about three fluidounces.1 To examine the interior of the right ventricle, an incision should be made a little to the right of the anterior interventricular groove from the pulmonary artery to the apex of the heart, and should be carried up from thence a little to the right of the posterior interventricular groove, as far as the auriculo-ventricular opening. The following parts present themselves for examination: ~ . penings Auriculo-ventricular. Opening of the pulmonary artery. Valves Tricuspid. Semilunar. 1 Morrant Baker says that " taking the means of varions estimates, it may be inferred that each ventricle is able to contain four to six ounces of blood" (Kirke's Physiology, 10th edition, p. 156). 974 THE THORAX. And a muscular and tendinous apparatus connected with the tricuspid valve: Columns carnern. Ch or dm tendineae. The auriculo-ventricular orifice is the large oval aperture of communication between the auricle and ventricle. It is situated at the base of the ventricle, near the right border of the heart. The opening is about an inch in diameter,1 oval from side to side, surrounded by a fibrous ring, covered by the lining membrane of the heart, and rather larger than the corresponding aperture on the left side, being sufficiently large to admit the ends of four fingers. It is guarded by the tricuspid valve. The opening of the pulmonary artery is circular in form, and situated at the summit of the conus arteriosus, close to the septum ventriculorum. It is placed on the left side .of the auriculo-ventricular opening, upon the anterior aspect of the heart. Its orifice is guarded by the pulmonary semilunar valves. The tricuspid valve consists of three segments of a triangular or trapezoidal shape, formed by a duplicature of the lining membrane of the heart, strengthened by a layer of fibrous tissue, and containing, according to Kurschner and Senac, muscular fibres. These segments are connected by their bases to the auriculo- ventricular orifice, and by their sides with one another, so as to form a continuous annular membrane which is attached round the margin of the auriculo-ventricular opening, their free margins and ventricular surfaces affording attachment to a number of delicate tendinous cords, the chordce tendinece. The largest and most movable segment is placed toward the left side of the auriculo-ventricular opening, interposed between that opening and the pulmonary artery. Anothei' segment corresponds to the front of the ventricle, and a third to its posterior wall. The central part of each segment is thick and strong; the lateral margins are thin and indented. The chordae tendineae are connected with the adjacent margins of the principal segments of the valve, and are further attached to each segment in the following manner: 1. Three or four reach the attached margin of each segment, where they are continuous with the auriculo-ventricular tendinous ring. 2. Others, four to six in number, are attached to the central thickened part of each segment.. 3. The most numerous and finest are connected with the marginal portion of each segment. The columnce carnece are the rounded muscular columns which project from nearly the whole of the inner surface of the ventricle, excepting near the opening of the pulmonary artery, where the wall becomes smooth. They may be classified, according to their mode of connection with the ventricle, into three sets: The first set merely form prominent ridges on the inner surface of the ventricle, being attached by their entire length on one side, as well as by their extremities; the second set are attached by their two extremities, but are free in the rest of their extent; whilst the third set (musculi papillares), three or four in number, are attached by one extremity to the wall of the heart, the opposite extremity giving attachment to the chordce tendinece. The semilunar valves, three in number,2 guard the orifice of the pulmonary artery. They consist of three semicircular folds, two anterior (right and left) and one posterior, formed by a duplicature of the lining membrane strengthened by fibrous tissue. They are attached by their convex margins to the wall of the artery at its junction with the ventricle, the straight border being free, and directed 1 In the Pathological Transactions, vol. vi. p. 119, Dr. Peacock has given some careful researches upon the weight and dimensions of the heart in health and disease. He states, as the result of his investigations, that in the healthy adult heart the right auriculo-ventricular aperture has a mean cir- cumference of 54.4 lines, or 42 ° inches; the left auriculo-ventricular aperture, a mean circumference of 44.3 lines, or 3jf inches; the pulmonic orifice, of 40 lines, or 311 inches; and the aortic orifice, of 35.5 lines, or 3/T inches; but the dimensions of the orifices varied greatly in different cases, the auriculo-ventricular aperture having a range of from 45 to 60 lines, and the others in the same proportion. 2 The pulmonary semilunar valves have been found to be two in number, instead of three (Dr. Hand, of St. Paul, Minn., in the North-Western ■ Med. and Surg. Jour., July, 1873), and the same variety is more frequently noticed in the aortic semilunar valves. THE HEART. 975 upward in the course of the vessel, against the sides of which the valve-flaps are pressed during the passage of the blood along the artery. The free margin of each is somewhat thicker than the rest of the valve, is strengthened by a bundle of tendinous fibres, and presents at its middle a small projecting thickened nodule called corpus Arantii.1 From this nodule tendinous fibres radiate through the valve to its attached margin, and these fibres form a constituent part of its substance throughout its whole extent, excepting two narrow lunated portions placed on each side of the nodule immediately behind the free margin; here the valve is thin and formed merely by the lining membrane. During the passage of the blood along the pulmonary artery these valves are pressed against the sides of the cylinder and the course of the blood along the tube is uninterrupted ; but during the ventricular diastole, when the current of blood along the pulmonary artery is checked and partly thrown back by its elastic walls, these valves become immediately expanded and effectually close the entrance of the tube. When the valves are closed the lunated portions of each are brought into contact with one another by their opposed surfaces, the three corpora Arantii filling up the small triangular space that would be otherwise left by the approximation of the three semilunar valves. Between the semilunar valves and the commencement of the pulmonary artery are three pouches or dilatations, one behind each valve. These are the pulmonary sinuses (sinuses of Valsalva). Similar sinuses exist between the semilunar valves and the commencement of the aorta; they are larger than the pulmonary sinuses. The blood, in its regurgitation toward the heart, finds its way into these sinuses, and so shuts down the valve-flaps. In order to examine the interior of the left auricle, make an incision on the posterior surface of the auricle from the pulmonary veins on one side to those on the other, the incision being carried a little way into the vessels. Make another incision from the middle of the horizontal one to the appendix. The Left Auricle is rather smaller than the right; its walls thicker, measuring about one line and a half; it consists, like the right, of two parts, a principal cavity or sinus and an appendix auriculae. The sinus is cuboidal in form, and concealed in front by the pulmonary artery and aorta; internally, it is separated from the right auricle by the septum auricu- larum ; behind, it receives on each side the pulmonary veins, being free in the rest of its extent. The appendix auriculce is somewhat constricted at its junction with the auricle ; it is longer, narrower, and more curved than that of the right side, and its margins more deeply indented, presenting a kind of foliated appearance. Its direction is forward and toward the right side, overlapping the root of the pulmonary artery. The following parts present themselves for examination: The openings of the four pulmonary veins. Auriculo-ventricular opening. Musculi pectinati. The pulmonary veins, four in number, open, two into the right, and two into the left side of the auricle. The two left veins frequently terminate by a common opening. They are not provided with valves. The auriculo-ventricular opening is the large oval aperture of communication between the auricle and ventricle. It is rather smaller than the corresponding opening on the opposite side (see note, page 974). 1 In former editions, as well as in other text-books on anatomy, these little nodules have been described as fibro-cartilaginous in structure. At my request, Dr. Le Cronier Lancaster, Demonstrator of Anatomy at St. George's Hospital, has investigated this subject, and reports that the "corpora Arantii" appear to consist of bundles of interlacing connective-tissue fibres with branched connective- tissue cells, and some few elastic fibres. Occasionally a rounded cell, with indistinct capsule, resem- bling a cartilage-cell was seen ; but there were not many of them. At the free edge of the corpus the structure is denser, there being a larger proportion of fibres to cells than in the central portion. He thinks the structure of the corpus should be put down as fibrous and not fibro-cartilaginous. 976 THE THORAX. The musculi pectinati are fewer in number and smaller than on the right side ; they are confined to the inner surface of the appendix. On the inner surface of the septum auricularum may be seen a lunated impression bounded below by a crescentic ridge the concavity of which is turned upward. The depression is just above the fossa ovalis in the right auricle. To examine the interior of the left ventricle, make an incision a little to the left of the anterior interventricular groove from the base to the apex of the heart, and carry it up from thence, a little to the left of the posterior interventricular groove, nearly as far as the auriculo- ventricular groove. The Left Ventricle is longer and more conical in shape than the right ventricle. It forms a small part of the left side of the anterior surface of the Bristle passed through left auriculo-ventricular opening. Passed through aortic opening. Fig. 564.-The left auricle and ventricle laid open, the posterior walls of both being removed heart, and a considerable part of its posterior surface. It also forms the apex of the heart by its projection beyond the right ventricle. Its walls are much thicker than those of the right side, the proportion being as 3 to 1. They are also thickest in the broadest part of the ventricle, becoming gradually thinner toward the base, and also toward the apex, which is the thinnest part. The following parts present themselves for examination: Openings Auriculo-ventricular. Aortic. Valves Mitral. Semilunar. Chordae tendineae. Columnae carneae. The auriculo-ventricular opening is placed below and to the left of the aortic orifice. It is a little smaller than the corresponding aperture of the opposite side, and, like it, is broader in the transverse than in the antero-posterior diameter. It is surrounded by a dense fibrous ring, covered by the lining membrane of the heart, and guarded by the mitral valves. The aortic opening is a circular aperture in front and to the right side of the auriculo-ventricular, from which it is separated by one of the segments of the mitral valve. Its orifice is guarded by the semilunar valves. 77777 HEART. 977 The 'mitral valve is attached to the circumference of the auriculo-ventricular orifice in the same way that the tricuspid valve is on the opposite side. It is formed by a duplicature of the lining membrane strengthened by fibrous tissue, and contains a few muscular fibres. It is larger in size, thicker, and altogether stronger than the tricuspid, and consists of two segments of unequal size. The larger seg- ment is placed in front, between the auriculo-ventricular and aortic orifices, and is said to prevent the filling of the aorta during the distension of the ventricle. Two smaller segments are usually found at the angles of junction of the larger. The mitral valve-flaps are furnished with chordae tendineae, the mode of attach- ment of which is precisely similar to that of those on the right side, but they are thicker, stronger, and less numerous. The semilunar valves surround the orifice of the aorta; two are posterior (right and left), and one anterior: they are similar in structure and in their mode of attachment to those of the pulmonary artery. They are, however, larger, thicker, and stronger than those of the right side, the lunulae are more distinct, and the corpora Arantii larger and more prominent. Between each valve and the cylinder of the aorta is a deep depression, the sinus aortici (sinuses of Valsalva); they are larger than those of the root of the pulmonary artery. The columnce carneoe admit of a subdivision into three sets, like those upon tlie right side, but they are smaller, more numerous, and present a dense interlace- ment, especially at the apex and upon the posterior wall. Those attached by one extremity only, the musculipapillares, are two in number, being connected one to Pulmonary artery. Musculi pectinati. Fig. 565.-Section of the heart, showing the interauricular and interventricular septa. the anterior, the other to the posterior wall; they are of large size, and terminate by free rounded extremities from which the chordae tendineae arise. The septum between the two ventricles is thick, especially below (Fig. 565). 978 THE THORAX. At its upper part it suddenly tapers off and becomes destitute of muscular fibres, consisting only of fibrous tissue covered by two layers of endocardium, and on the right side also covered by one of the flaps of the tricuspid valve. It is continued upward, and forms the septum between the aortic vestibule and the right auricle. It is derived from the lower part of the aortic septum of the foetus, and an abnormal communication may exist at this part owing to defective development of this septum. The Endocardium is a thin membrane which lines the internal surface of the heart; it assists in forming the valves by its reduplications, and is continuous with the lining membrane of the great blood-vessels. It is a smooth, transparent membrane, giving to the inner surface of the heart its glistening appearance. It is more opaque on the left than on the right side of the heart, thicker in the auricles than in the ventricles, and thickest in the left auricle. It is thin on the musculi pectinati and on the column® carne®, but thicker on the smooth part of the auricular and ventricular walls and on the tips of the musculi papillares. Structure.-The heart consists of muscular fibres and of fibrous rings which serve for their attachment. The fibrousrings surround the auriculo-ventricular and arterial orifices : they are stronger upon the left than on the right side of the heart. The auriculo-ventricular rings serve for the attachment of the muscular fibres of the auricles and ventricles, and also for the mitral and tricuspid valves; the ring on the left side is closely connected by its right margin with the aortic arterial ring. Between these and the right auriculo-ventricular ring is a mass of fibrous tissue, and in some of the larger animals, as the ox and elephant, a nodule of bone. The fibrous rings surrounding the arterial orifices serve for the attachment of the great vessels and semilunar valves. Each ring receives, by its ventricular margin, the attachment of the muscular fibres of the ventricles; its opposite margin presents three deep semicircular notches, within which the middle coat of the artery (which presents three convex semicircular segments) is firmly fixed, the attachment of the artery to its fibrous ring being strengthened by the thin cellular coat and serous membrane externally and by the endocardium within. It is opposite the margins of these semicircular notches, in the arterial rings, that the endocardium by its reduplication, forms the semilunar valves, the fibrous structure of the ring being continued into each of the segments of the valve at this part. The middle coat of the artery in this situation is thin, and the sides of the vessel are dilated to form the sinuses of Valsalva. The muscular structure of the heart consists of bands of fibres which present an exceedingly intricate interlacement. They are of a deep red color and marked with transverse striae (page 67). The muscular fibres of the heart admit of a subdivision into two kinds, those of the auricles and those of the ventricles, which are quite independent of one another. Fibres of the Auricles.-These are disposed in two layers-a superficial layer common to both cavities, and a deep layer proper to each. The superficial fibres are more distinct on the anterior surface of the auricles, across the bases of which they run in a transverse direction, forming a thin, but incomplete layer. Some of these fibres pass into the septum auricularum. The internal or deep fibres proper to each auricle consist of two sets, looped and annular fibres. The looped fibres pass upward over each auricle, being attached by two extremities to the corre- sponding auriculo-ventricular rings in front and behind. The annular fibres surround the whole extent of the appendices auricularum, and are continued upon the wralls of the venae cav® and coronary sinus on the right side, and upon the pulmonary veins on the left side, at theii* connection with the heart. In the appendices they interlace with the longitudinal fibres. The of the ventricles are arranged in an exceedingly complex manner, and the accounts given by various anatomists differ considerably. This is probably due partly to the fact that the various layers of muscular fibre of which the THE HEART. 979 heart is said to be composed are not independent, but their fibres are interlaced to a considerable extent, and therefore any separation into layers must be to a great extent artificial; and also no doubt partly due to the fact, pointed out by Henle, that there are varieties in the arrangement due to individual differences. If the epicardium (visceral layer of pericardium) and the subjacent fat is removed from a heart which has been subjected to prolonged boiling, so as to dissolve the connective tissues, the superficial fibres of the ventricles will be exposed. They will be seen to commence at the base of the heart, where they are attached to the tendinous rings around the orifices, and to pass obliquely downward toward the apex, with a direction from right to left. At the apex the fibres turn suddenly inward, forming what is called the vortex, into the interior of the ventricle. On the back of the heart it will be seen that the fibres pass continuously from one ventricle to the other over the interventricular groove ; and the same thing will be noticed on the front of the heart at the upper and lower end of the anterior interventricular groove, but in the middle portion of this groove the fibres passing from one ventricle to the other are interrupted by fibres emerging from the septum along the groove ; many of the superficial fibres pass in also at this groove to the septum. The vortex is produced, as stated above, by the sudden turning inward of the superficial fibres in a peculiar spiral manner into the interior of the ventricle. Those fibres which descended on the posterior surface of the heart enter, at the vortex, the left ventricle, and, ascending, form the posterior part of the inner layer of muscular fibres lining this cavity and the right (posterior) musculus papillaris ; those fibres which descend on the front of the heart, and which pass to the apex, also pass, at the vortex, into the interior of the ventricle, where they form the remainder of the innermost layer of the ventricle and the left (anterior) musculus papillaris. The fibres forming the inner layer of the wall of the ventricle ascend to be attached to the fibrous rings around the orifices. By dissection these superficial fibres may be removed as a thin stratum, and it will then be found that the ventricles are made up of oblique fibres superimposed in layers one on the top of another, and assuming gradually a less oblique direction as they pass to the middle of the thickness of the ventricular wall, so that in the centre of the wall the fibres are transverse. Internal to this central transverse layer the fibres become oblique again, but in the opposite direction to the external ones. This division into distinct layers is, however, to a great extent artificial, as the fibres pass across from one layer to another, and have therefore to be divided in the dissection, and the change in the direction of the fibres is very gradual. These oblique fibres commence above at the fibrous rings at the base of the heart, and, descending toward the apex, they enter the septum near its lower end. In the septum the fibres which form the left ventricle may be traced in three directions: 1. Some pass upward to be attached to the central fibro-cartilage. 2. Others pass through the septum to become continuous with the fibres of the right ventricle. 3. The remainder pass through the septum to encircle the ventricle as annular fibres. Of the fibres of the right ventricle, some on entering the septum pass upward to be attached to the central fibro-cartilage; some, entering the septum from behind, pass forward to become continuous with the fibres on the anterior surface of the left ventricle ; and others, entering in front, pass backward to join the fibres on the posterior wall of the left ventricle. The septum therefore consists of three varieties of fibres-viz. annular fibres, special to the left ventricle ; ascending fibres, derived from both ventricles and ascending through the septum to the central fibro-cartilage ; and decussating fibres, derived from the anterior wall of one ventricle and passing to the posterior wall of the other ventricle, or from the posterior wall of the right ventricle and passing to the anterior wall of the left. In addition to these fibres there are a considerable number which appear to encircle both ventricles and which pass across the septum without turning into it. Vessels and Nerves.-The arteries supplying the heart are the left or anterior and right or posterior coronary (page 544). The veins accompany the arteries, and terminate in the right auricle. They are 980 THE THORAX. the anterior, posterior, left and right cardiac veins, the right or small and the left or great coronary sinuses, and the vense cordis minimae (pence Thebesii) (page 679). The lymphatics terminate in the thoracic and right lymphatic ducts. The nerves are derived from the cardiac plexuses, which are formed partly from the cranial nerves and partly from the sympathetic. They are freely distributed both on the surface and in the substance of the heart, the separate filaments being furnished with small ganglia. Surface Form.-In order to show the extent of the heart in relation to the front of the chest, draw a line from the lower border of the second left costal cartilage, one inch from the sternum, to the upper border of the third right costal cartilage, half an inch from the sternum. This represents the base-line or upper limit of the organ. Take a point, an inch and a half below and three-quarters of an inch internal to the left nipple-that is, about three and a half inches to the left of the median line of the body. This represents the apex of the heart. Draw a line from this apex-point, with a slight convexity downward, to the junction of the seventh right costal cartilage to the sternum. This represents the lower limit of the heart. Join the right extremity of the first line-that is, the base-line-with the right extremity of this line-that is, to the seventh right chondro-sternal joint-with a slight curve outward, so that it projects about an inch and a half from the middle line of the sternum. Lastly, join the left extremity of the base-line and the apex-point by a line curved slightly to the left. The position of the various orifices is as follows: viz. the pulmonary orifice is situated in the upper angle formed by the articulation of the third left costal cartilage with the sternum ; the aortic orifice is a little below and internal to this, behind the left border of the sternum, close to the articulation of the third left costal cartilage to this bone. The left auriculo-ventric- ular opening is behind the sternum, rather to the left of the median line, and opposite the fourth costal cartilages. The right auriculo-ventricular opening is a little lower, opposite the fourth interspace and in the middle line of the body. A portion of the area of the heart thus mapped out is uncovered by lung, and therefore gives a dull note on percussion; the remainder, being overlapped by the lung, gives a more or less resonant note. The former is known as the area of superficial cardiac dulness ; the latter as the area of deep cardiac dulness. The area of superficial cardiac dulness is included between a line drawn from the centre of the sternum, between the fourth costal cartilages, to the apex of the heart and a line drawn from the same point down the lower third of the middle line of the sternum. Below, this area merges into the dulness which corresponds to the liver. Dr. Latham lays down the following rule as a sufficient practical guide for the definition of the por- tion of the heart which is uncovered by lung or pleura: " Make a circle of two inches in diam- eter round a point midway between the nipple and the end of the sternum," that is, the gladiolus. The chief peculiarities in the heart of the foetus are the direct communication between the two auricles through the foramen ovale and the large size of the Eustachian valve. There are also several minor peculiarities. Thus, the position of the heart is vertical until the fourth month, when it commences to assume an oblique direction. Its size is also very considerable as compared with the body, the proportion at the second month being 1 to 50; at birth it is as 1 to 120; whilst in the adult the average is about 1 to 160. At an early period of fietal life the auricular portion of the heart is larger than the ventricular, the right auricle being more capacious than the left; but toward birth the ventricular portion becomes the larger. The thickness of both ventricles is at first about equal, but toward birth the left becomes much the thicker of the two. The foramen ovale is situated at the lower and back part of the septum auricu- larum, forming a communication between the auricles. It remains as a free oval opening from the time of the formation of the auricular septum (about the eighth week) until the middle period of foetal life. About this period a fold grows up from the posterior wall of the auricle to the left of the foramen ovale, and advances over the opening so as to form a sort of valve, which allows the blood to pass only from the right to the left auricle, and not in the opposite direction. The Eustachian valve is developed from the anterior border of the inferior vena cava at its entrance into the auricle. It is directed upward on the left side of the opening of this vein, and serves to direct the blood from the inferior vena cava through the foramen ovale into the left auricle. The peculiarities in the arterial system of the foetus are the communication between the pulmonary artery and the descending aorta by means of the ductus Peculiarities in the Vascular System of the Foetus. THE HEART. 981 arteriosus, and the communication between the internal iliac arteries and the placenta by means of the umbilical arteries. The ductus arteriosus is a short tube, about half an inch in length at birth, and of the diameter of a goosequill. In the early condition it forms the continuation of the pulmonary artery, and opens into the descending aorta just below the origin of the left subclavian artery, and so conducts the chief part of the blood from the right ventricle into this vessel. When the branches of the pulmonary artery have become larger relatively to the ductus arteriosus, the latter is chiefly connected to the left pulmonary artery; and the fibrous cord, which is all that remains of the ductus arteriosus in later life, will be found to be attached to the root of that vessel. The umbilical or hypogastric arteries arise from the internal iliacs, in addition to the branches given off from those vessels in the adult. Ascending along the sides of the bladder to its fundus, they pass out of the abdomen at the umbilicus, and are continued along the umbilical cord to the placenta, coiling round the umbilical vein. They return to the placenta the blood which has circulated in the system of the foetus. The peculiarity in the venous system of the foetus is the communication estab- lished between the placenta and the liver and portal vein through the umbilical vein, and the inferior vena cava through the ductus venosus. Fcetal Circulation. The blood destined for the nutrition of the foetus is carried from the placenta to the foetus, along the umbilical cord, by the umbilical vein. The umbilical vein enters the abdomen at the umbilicus, and passes upward along the free margin of the suspensory ligament of the liver to the under surface of that organ, where it gives off two or three branches to the left lobe, one of which is of large size, and others to the lobus quadratus and lobulus Spigelii. At the transverse fissure it divides into two branches : of these, the larger is joined by the portal vein and enters the right lobe ; the smaller branch continues onward, under the name of the ductus venosus, and joins the left hepatic vein at the point of junction of that vessel with the inferior vena cava. The blood, therefore, which traverses the umbilical vein reaches the inferior vena cava in three different ways: the greater quantity circulates through the liver with the portal venous blood before entering the vena cava by the hepatic veins; some enters the liver directly, and is also returned to the inferior cava by the hepatic veins; the smaller quantity passes directly into the vena cava by the junction of the ductus venosus with the left hepatic vein. In the inferior cava the blood carried by the ductus venosus and hepatic veins becomes mixed with, that returning from the lower extremities and viscera of the abdomen. It enters the right auricle, and, guided by the Eustachian valve, passes through the foramen ovale into the left auricle, where it becomes mixed with a small quantity of blood returned from the lungs by the pulmonary veins. From the left auricle it passes into the left ventricle, and from the left ventricle into the aorta, by means of which it is distributed almost entirely to the head and upper extremities, a small quantity being probably carried into the descending aorta. From the head and upper extremities the blood is returned by the branches of the superior vena cava to the right auricle, where it becomes mixed with a small portion of the blood from the inferior cava. From the right auricle it descends over the Eustachian valve into the right ventricle, and from the right ventricle passes into the pulmonary artery. The lungs of the foetus being solid and almost impervious, only a small quantity of the blood of the pulmonary artery is distrib- uted to them by the right and left pulmonary arteries, and is returned by the pulmonary veins to the left auricle; the greater part passes through the ductus arteriosus into the commencement of the descending aorta, where it becomes mixed with a small quantity of blood transmitted by the left ventricle into the aorta. 982 77/A' THORAX. Along this vessel it descends to supply the lower extremities and viscera of the abdomen and pelvis, the chief portion being, however, conveyed by the umbilical arteries to the placenta. From the preceding account of the circulation of the blood in the foetus it will be seen- 1. That the placenta serves the double purpose of a respiratory and nutritive IDucfws arteriosus. '"Internal iliac artery. Fig. 566.-Plan of the foetal circulation. In this plan the figured arrows represent the kind of blood, as well as the direction which it takes in the vessels. Thus, arterial blood is figured -->; venous blood, >; mixed (arterial and venous) blood, >. organ, receiving the venous blood from the foetus, and returning it again re-oxy- genated and charged with additional nutritive material. 2. That nearly the whole of the blood of the umbilical vein traverses the liver THE HEART. 983 before entering the inferior cava; hence the large size of this organ, especially at an early period of foetal life. 3. That the right auricle is the point of meeting of a double current, the blood in the inferior cava being guided by the Eustachian valve into the left auricle, whilst that in the superior cava descends into the right ventricle. At an early period of foetal life it is highly probable that the two streams are quite dis- tinct, for the inferior cava opens almost directly into the left auricle, and the Eustachian valve would exclude the current along the vein from entering the right ventricle. At a later period, as the separation between the two auricles becomes more distinct, it seems probable that some mixture of the two streams must take place. 4. The blood carried from the placenta to the foetus by the umbilical vein, mixed with the blood from the inferior cava, passes almost directly to the arch of the aorta, and is distributed by the branches of that vessel to the head and upper extremities; hence the large size and perfect development of those parts at birth. 5. The blood contained in the descending aorta, chiefly derived from that which has already circulated through the head and limbs, together with a small quantity from the left ventricle, is distributed to the lower extremities; hence the small size and imperfect development of these parts at birth. Changes in the Vascular System at Birth. At birth, when respiration is established, an increased amount of blood from the pulmonary artery passes through the lungs, which now perform their office as respiratory organs, and at the same time the placental circulation is cut off. The foramen ovale becomes gradually closed by about the tenth day after birth; the valvular fold above mentioned becomes adherent to the margins of the foramen for the greater part of its circumference, but above a slit-like opening is left between the two auricles which sometimes remains per- sistent. The ductus arteriosus begins to contract immediately after respiration is estab- lished, becomes completely closed from the fourth to the tenth day, and ultimately degenerates into an impervious cord which serves to connect the left pulmonary artery to the descending aorta. Of the umbilical or hypogastric arteries, the portion continued on to the bladder from the trunk of the corresponding internal iliac remains pervious as the superior vesical artery, and the part between the fundus of the bladder and the umbilicus becomes obliterated between the second and fifth days after birth, and projects into the peritoneal sac so as to form 'the two fossae of the peritoneum spoken of in the section on the surgical anatomy of direct inguinal hernia. The umbilical vein and ductus venosus become completely obliterated between the second and fifth days after birth, and ultimately dwindle to fibrous cords, the former becoming the round ligament of the liver, the latter the fibrous cord, which in the adult may be traced along the fissure of the ductus venosus. THE ORGANS OF VOICE AND RESPIRATION. THE LARYNX. THE Larynx is the organ of voice, placed at the upper part of the air-passage. It is situated between the trachea and base of the tongue, at the upper and fore part of the neck, where it forms a considerable projection in the middle line. On either side of it lie the great vessels of the neck ; behind, it forms part of the boundary of the pharynx, and is covered by the mucous membrane lining that cavity. The larynx is broad above, wrhere it presents the form of a triangular box, flattened behind and at the sides, and bounded in front by a prominent vertical ridge. Below, it is narrow and cylindrical. It is composed of cartilages which are connected together by ligaments and moved by numerous muscles ; the interior is lined by mucous membrane and supplied with vessels and nerves. The Cartilages of the Larynx are nine in number, three single and three pairs: Thyroid. Cricoid. Epiglottis. Two Arytenoid. Two Cornicula Laryngis. Two Cuneiform. The Thyroid (Oupebt;, a shield) is the largest cartilage of the larynx. It consists of two lateral lamellae or alae, united at an acute angle in front, forming a vertical projection in the middle line which is prominent above and called the pomum Adami. This projec- tion is subcutaneous, more distinct in the male than in the female, and occasionally separated from the integument by a bursa mucosa. Each lamella is quadrilateral in form. Its outer surface presents an oblique ridge which passes downward and forward from a tubercle situated near the root of the superior cornu. This ridge gives attachment to the Sterno- thyroid and Thyro-hyoid muscles, and the por- tion of cartilage included between it and the posterior border, to part of the Inferior con- strictor muscle. The inner surface of each ala is smooth, slightly concave, and covered by mucous mem- brane above and behind; but in front, in the receding angle formed by their junction, are attached the epiglottis, the true and false vocal cords, the Thyro-arytenoid and Thyro-epiglot- tidean muscles. The upper border of the thyroid cartilage is sinuously curved, being concave at its posterior part, just in front of the superior cornu, then rising into a convex outline, which dips in front to form the sides of a notch in the middle line imme- diately above the pomum Adami. This border gives attachment throughout its whole extent to the thyro-hyoid membrane. Fig. 567.-Side view of the thyroid and cricoid cartilages. 984 THE LARYNX. 985 The lower border is connected to the cricoid cartilage, in the median line, by the crico-thyroid membrane, and on each side by the Crico-thyroid muscle. The posterior borders, thick and rounded, terminate above in the superior cornua, and below in the inferior cornua. The two superior cornua are long and nar- row, directed upward, backward, and inward, and terminate in a conical extremity which gives at- tachment to the thyro-hyoid liga- ment. The two inferior cornua are short and thick; they pass downward, with a slight inclination forward and inward, and present on their inner surfaces a small oval articular facet for articulation with the side of the cricoid carti- lage. The posterior border re- ceives the insertion of the Stylo- pharyngeus and Palato-pharyn- geus muscles on each side. The Cricoid Cartilage is so called from its resemblance to a signet-ring (xpixot;, a ring). It is smaller, but thicker and stronger, than the thyroid cartilage, and forms the lower and back part of the cavity of the larynx. Its anterior half is narrow, convex, affording attachment in front and at the sides to the Crico- thyroid muscles, and behind to part of the Inferior constrictor. Its posterior half is very broad both from side to side and from above downward; it presents in the middle line a vertical ridge for the attachment of the longitudinal fibres of the oesophagus, and on either side a broad depression for the Crico-arytenoideus posticus muscle. At the point of junction of the two halves of the cartilage on either side is a small round elevation for articulation with the inferior cornu of the thyroid car- tilage. The lower border of the cricoid cartilage is horizontal and connected to the upper ring of the trachea by fibrous membrane. Its upper border is directed obliquely upward and backward, owing to the great depth of its posterior surface. It gives attachment in front to the crico- thyroid membrane; at the sides, to part of the same membrane and to the lateral Crico-arytenoid muscle; behind, the highest point of the upper border is sur- mounted on each side by a smooth oval surface for articulation with the arytenoid cartilage. Between the articular surfaces is a slight notch for the attachment of part of the Arytenoideus muscle. The inner surface of the cricoid cartilage is smooth and lined by mucous mem- brane. Epiglottis. Thyroid. Cornicula laryngis. Cuneiform cartilage. Arytenoid. Insertion of CRICO-ARYTENOIDEUSX POSTICUS ET LATERALIS. Posterior ~ surface. Arytenoid cartilages, base. Cricoid. Articular facet for arytenoid cartilage. Articular facet for inferior cornu of thyroid cartilage. Fig. 568.-The cartilages of the larynx. Posterior view 986 THE ORGANS OF VOICE AND RESPIRATION. The Arytenoid Cartilages are so called from the resemblance they bear, when approximated, to the mouth of a pitcher (djourcum, a pitcher). They are two in number, and situated at the upper border of the cricoid cartilage, at the back of the larynx. Each cartilage is pyramidal in form, and presents for examination three surfaces, a base, and an apex. Vhe posterior surface is triangular, smooth, concave, and gives attachment to the Arytenoid muscle. The anterior surface, somewhat convex and rough, gives attachment to the Thyro-arytenoid muscle and to the false vocal cord. The internal surface is narrow, smooth, and flattened, covered by mucous mem- brane, and lies almost in apposition with the cartilage of the opposite side. The base of each cartilage is broad, and presents a concave smooth surface for articulation with the cricoid cartilage. Of its three angles, the external is short, rounded, and prominent, receiving the insertion of the Posterior and Lateral crico-arytenoid muscles. The anterior angle, also prominent, but more pointed, gives attachment to the true vocal cord. This angle is sometimes called the vocal process. The apex of each cartilage is pointed, curved backward and inward, and sur- mounted by a small, cone-shaped, cartilaginous nodule, the corniculum laryngis. The cornicula laryngis (cartilages of Santorini) are two small, conical nodules, consisting of yellow fibro-cartilage, which articulate with the summit of the aryt- enoid cartilages and serve to prolong them backward and inward. To them are attached the aryteno-epiglottidean folds. They are sometimes united to the arytenoid cartilages. The cuneiform cartilages (cartilages of Wrisberg) are two small, elongated, cartilaginous bodies, placed one on each side, in the fold of mucous membrane which extends from the apex of the arytenoid cartilage to the side of the epiglottis (aryteno-epiglottidean fold); they give rise to small whitish elevations on the inner surface of the mucous membrane, just in front of the arytenoid cartilages. The epiglottis is a thin lamella of fibro-cartilage, of a yellowish color, shaped like a leaf, and placed behind the tongue, in front of the superior opening of the larynx. During respiration its direction is vertically upward, its free extremity curving forward toward the base of the tongue ; but when the larynx is drawn up beneath the base of the tongue during deglutition it is carried downward and backward so as to completely close the opening of the larynx. Its free extremity is broad and rounded ; its attached end is long and narrow, and connected to the receding angle between the two alae of the thyroid cartilage, just below the median notch, by a long, narrow, ligamentous band, the thyro-epiglottic ligament. It is also connected to the posterior surface of the body of the hyoid bone by an elastic ligamentous band, the hyo-epiglottic ligament. Its anterior or lingual surface is curved forward toward the tongue, and covered at its upper part by mucous membrane, which is reflected on to the sides and base of the organ, forming a median and two lateral folds, the glosso-epiglottidean ligaments. Its posterior or laryngeal surface is smooth, concave from side to side, concavo- convex from above downward, and covered by mucous membrane ; when this is removed the surface of the cartilage is seen to be studded with a number of small mucous glands which are lodged in little pits upon its surface. To its sides the aryteno-epiglottidean folds are attached. Structure.-The cornicula laryngis, cuneiform cartilages, and epiglottis are composed of yellow fibro-cartilage which shows little tendency to calcification, but the other cartilages resemble in structure the costal cartilages, becoming more or less calcified in old age. Ligaments.-The ligaments of the larynx are extrinsic-i. e. those connecting the thyroid cartilage and epiglottis with the hyoid bone, and the cricoid cartilage with the trachea; and intrinsic-those which connect the several cartilages of the larynx to each other. 777/7 LARYNX. 987 The ligaments connecting the thyroid cartilage with the hyoid bone are three in number-the thyro-hyoid membrane, and the two lateral thyro-hyoid ligaments. The thyro-hyoid membrane is a broad, fibro-elastic, membranous layer, attached below to the upper part of the posterior surface of the thyroid cartilage, and above to the upper border of the hyoid bone, passing behind the posterior surface, and being separated from it by a synovial bursa. It is thicker in the middle line than at either side, in which situation it is pierced by the superior laryngeal vessels and nerve. The two lateral thyro-hyoid ligaments are rounded elastic cords which pass between the superior cornua of the thyroid cartilage and the extremities of the greater cornua of the hyoid bone. A small cartilaginous nodule (cartilago triticeaf sometimes bony, is frequently found in each. The ligament connecting the epiglottis with the hyoid bone is the hyo-epiglottic. In addition to this extrinsic ligament, the epiglottis is connected to the tongue by the three glosso-epiglottidean folds of mucous membrane, which may also be considered as extrinsic ligaments of the epiglottis. The hyo-epiglottic ligament is an elastic fibrous band which extends from the anterior surface of the epiglottis, near its apex, to the upper border of the body of the hyoid bone. The ligaments connecting the thyroid cartilage to the cricoid are also three in number-the crico-thyroid membrane and the capsular ligaments. The crico-thyroid membrane is composed mainly of yellow elastic tissue. It is of triangular shape, thick in front, where it connects together the contiguous margins of the thyroid and cricoid cartilages ; thinner at each side, where it extends from the superior border of the cricoid cartilage to the inferior margin of the true vocal cords, with which it is closely united in front. The anterior portion of the crico-thyroid membrane is convex, concealed on each side by the Crico-thyroid muscle, subcutaneous in the middle line, and crossed horizontally by a small anastomotic arterial arch formed by the junction of the two crico-thyroid arteries. The lateral portions are lined internally by mucous membrane, and covered by the lateral Crico-arytenoid and Thyro-arytenoid muscles. A capsular ligament encloses the articulation of the inferior cornu of the thyroid with the cricoid cartilage on each side. The articulation is lined by synovial membrane. The ligaments connecting the arytenoid cartilages to the cricoid are two capsular ligaments and two posterior crico-arytenoid ligaments. The capsular crico-arytenoid ligaments are thin and loose capsules attached to the margin of the articular surfaces ; they are lined internally by synovial membrane. The posterior crico-arytenoid ligaments extend from the cricoid to the inner and back part of the base of the arytenoid cartilage. The ligament connecting the epiglottis with the thyroid cartilage is the thyro- epiglottic. The thyro-epiglottic ligament is a long, slender, elastic cord which connects the apex of the epiglottis with the receding angle of the thyroid cartilage imme- diately beneath the median notch, above the attachment of the vocal cords. The crico-tracheal ligament connects the cricoid cartilage with the first ring of the trachea. It resembles the fibrous membrane which connects the cartilaginous rings of the trachea to each other. Interior of the Larynx.-The superior aperture of the larynx (Fig. 569) is a triangular or cordiform opening, wide in front, narrow behind, and sloping obliquely downward and backward. It is bounded in front by the epiglottis, behind by the apices of the arytenoid cartilages and the cornicula laryngis, and laterally by a fold of mucous membrane enclosing ligamentous and muscular fibres, stretched between the sides of the epiglottis and the apex of the arytenoid cartilages : these are the aryteno-epiglottidean folds, on the margins of which the cuneiform cartilages form a more or less distinct whitish prominence. 988 THE ORGANS OF VOICE AND RESPIRATION. The cavity of the larynx extends from the superior aperture to the lower border of the cricoid cartilage. It is divided into two parts by the projection inward of the vocal cords; between the two cords is a long and narrow triangular fissure or chink, the rima glottidis. The portion of the cavity of the larynx above the true vocal cords is broad and triangular in shape, and corresponds to the interval between the alae of the thyroid cartilage ; it contains the false vocal cords, and between these and the true vocal cords are the ventricles of the larynx. The portion below the true vocal cords is at first of an elliptical, and lower down of a circular, form. The rima glottidis is the narrow fissure or chink between the inferior or true vocal cords. It is the narrow- est part of the cavity of the larynx, and corresponds to the lower level of the arytenoid cartilages. Its length in the male measures rather less than an inch, its breadth when dilated varying at its widest part from a third to half an inch. In the female these measurements are less by two or three lines. The form of the rima glottidis va- ries. In its half-closed condi- tion it is a narrow fissure, a little enlarged and rounded be- hind. In quiet breathing it is widely open, somewhat trian- gular, the base of the triangle directed backward, and corre- sponding to the space between the separated arytenoid cartilages. In forcible expiration it is smaller than during inspiration. When sound is produced it is more narrowed, the margins of the arytenoid cartilages being brought into contact and the edges of the vocal cords approximated and made parallel, the degree of approximation and tension corre- sponding to the height of the note produced.1 The superior or false vocal cords, so called because they are not directly concerned in the production of the voice, are two folds of mucous membrane enclosing a delicate narrow fibrous band, the superior thyro-arytenoid ligament. This ligament consists of a thin band of elastic tissue, attached in front to the angle of the thyroid cartilage below the epiglottis, and behind to the anterior surface of the arytenoid cartilage. The lower border of this ligament, enclosed in mucous membrane, forms a free crescentic margin, which constitutes the upper boundary of the ventricle of the larynx. The inferior or true vocal cords, so called from their being concerned in the production of sound, are two strong fibrous bands (inferior thyro-arytenoid ligaments}, covered on their surface by a thin layer of mucous membrane. Each ligament consists of a band of yellow elastic tissue, attached in front to the depression between the two alie of the thyroid cartilage, and behind to the anterior angle of the base of the arytenoid. Its lower border is continuous with the thin lateral part of the crico-thyroid membrane. Its upper border forms the lower boundary of the ventricle of the larynx. Externally, the Thyro-arytenoideus- muscle lies parallel with it. It is covered internally by mucous membrane, which is extremely thin and closely adherent to its surface. The ventricle of the larynx is an oblong fossa situated between the superior and inferior vocal cords on each side, and extending nearly their entire length. Arytenoid cart. Rima glottidis. Superior and inferior vocal cords. Ventricle be- tween them. Aryteno-epi glottidean fold. Fig. 569.-The larynx and adjacent parts, seen from above. 1 On the shape of the rima glottidis in the various conditions of breathing and speaking, see- Czermak, On the Laryngoscope, translated for the New Sydenham Society. 7V/A LARYNX. 989 This fossa is bounded above by the free crescentic edge of the superior vocal cord, below by the straight margin of the true vocal cord, externally by the corresponding Thyro-arytenoideus muscle. The anterior part of the ventricle leads up by a narrow opening into a caecal pouch of mucous membrane of variable size called the laryngeal pouch. The sacculus laryngis, or laryngeal pouch, is a membranous sac placed be- tween the superior vocal cord and the inner surface of the thyroid cartilage, occasionally extending as far as its up- per border; it is conical in form, and curved slightly backward like a Phryg- ian cap. On the surface of its mu- cous membrane are the openings of sixty or seventy small follicular glands which are lodged in the submucous areolar tissue. This sac is enclosed in a fibrous capsule continuous below with the superior thyro-arytenoid liga- ment; its laryngeal surface is covered by the Aryteno-epiglottideus inferior muscle (Compressor sacculi laryngis, Hilton), whilst its exterior is covered by the Thyro-arytenoideus and Thyro- epiglottideus muscles. These muscles compress the sacculus laryngis and discharge the secretion it contains upon the chordae vocales, the surfaces of which it is intended to lubricate. Muscles.-The intrinsic muscles of the larynx are nine in number, six of which are the muscles of the vocal cords and rima glottidis, and three are con- nected with the epiglottis. The six muscles of the vocal cords and rima glottidis are-the Glosso-epiglottic Ar fold. 1 Aryteno- .epiglottic fold. Arytenoid cartilage. Vocal cords, ventricle - between them ARYTENClDEUS t MUSCLE Orico-thyroidy membrane. ~~ Trachea. Fig. 570.-Vertical section of the larynx and upper part of the trachea. Crico-thyroid. Crico-arytenoideus posticus. Crico-arytenoideus lateralis. Arytenoideus. Thyro-arytenoideus. Arytenoideus rectus The Crico-thyroid is triangular in form, and situated at the fore part and side of the cricoid cartilage. It arises from the front and lateral part of the cricoid cartilage; its fibres diverge, passing obliquely upward and outward to be inserted into the lower border of the thyroid cartilage and into the anterior border of the lower cornua. The inner borders of these two muscles are separated in the middle line by a triangular interval occupied by the crico-thyroid membrane. The Crico-arytenoideus posticus arises from the broad depression occupying each lateral half of the posterior surface of the cricoid cartilage; its fibres pass upward and outward, converging to be inserted into the outer angle of the base of the arytenoid cartilage. The upper fibres are nearly horizontal, the middle oblique, and the lower almost vertical.1 1 Dr. Merkel of Leipsic has described a muscular slip which occasionally extends between the outer border of the posterior surface of the cricoid cartilage and the posterior margin of the inferior cornu of the thyroid; this he calls the " Musculus kerato-cricoideus." It is not found in every larynx, and when present exists usually only on one side, but is occasionally found on both sides. Sir William Turner (Edinburgh Medical Journal, Feb., 1860) states that it is found in about one case in five. Its action is to fix the lower horn of the thyroid cartilage backward and downward, opposing in some measure the part of the Crico-thyroid muscle which is connected to the anterior margin of the horn. 990 THE ORGANS OF VOICE AND RESPIRATION. The Crico-arytenoideus lateralis is smaller than the preceding, and of an oblong form. It arises from the upper border of the side of the cricoid cartilage, and, passing obliquely upward and backward, is inserted into the outer angle of the base of the arytenoid cartilage in front of the preceding muscle. The Arytenoideus is a single mus- cle filling up the posterior concave surface of the arytenoid cartilages. It arises from the posterior surface and outer border of one arytenoid cartilage, and is inserted into the cor- responding parts of the opposite car- tilage. It consists of three planes of fibres, two oblique and one transverse. The oblique fibres, the most superficial, form two fasciculi, which pass from the base of one cartilage to the apex of the opposite one. The transverse fibres, the deepest and most numerous, pass transversely across between the two cartilages; hence the Arytenoi- deus was formerly considered as several muscles, under the name of transversi and obliqui. A few of the oblique fibres are occasionally con- tinued round the outer margin of the cartilage, and blend with the Thyro- arytenoid or the Aryteno-epiglottideus muscle. The Thyro-arytenoideus is a broad, flat muscle which lies parallel with the outer side of the true vocal cord. It arises in front from the lower half of the receding angle of the thyroid car- tilage and from the crico-thyroid mem- brane. Its fibres pass horizontally back- ward and outward, to be inserted into the base and anterior surface of the aryt- enoid cartilage. This muscle consists of two fasciculi. The inner or inferior portion, the thicker, is inserted into the anterior angle of the base of the aryt- enoid cartilage and into the adjacent portion of its anterior surface; it lies parallel with the true vocal cord, to which it is adherent. The outer or superior fasciculus, the thinner, is in- serted into the anterior surface and outer border of the arytenoid cartilage above the preceding fibres; it lies on the outer side of the sacculus laryngis, immediately beneath the mucous mem- brane.1 Arytenoideus Rectus.- This is a small but fairly constant muscle which Cornicula laryngis. .4 rticular facet for inferior cornu of thyroid cartilage. Fig. 571.-Muscles of larynx. Side view. Right ala of thyroid cartilage removed. Fig. 572.-Interior of the larynx, seen from above. (Enlarged.) 1 Henle describes these two portions as separate muscles, under the names of External and Internal thyro-arytenoid. THE LARYNX. 991 was first described by Luschka, and named by him the Arytenoideus rectus. It is attached below to the posterior concave surface of the arytenoid cartilage beneath the Arytenoideus muscle, and, passing upward, emerges at the upper border of this muscle, and is inserted into the posterior surface of the cartilage of Santorini.1 The muscles of the epiglottis are the Thyro-epiglottideus. Aryteno-epiglottideus superior. Aryteno-epiglottideus inferior. The Thyro-epiglottideus is a delicate fasciculus which arises from the inner surface of the thyroid cartilage, just external to the origin of the Thyro-arytenoid muscle, and spreads out upon the outer surface of the sacculus laryngis; some of its fibres are lost in the aryteno-epiglottidean fold, whilst others are continued for- ward to the margin of the epiglottis (Depressor epiglottidis). The Aryteno-epiglottideus superior consists of a few delicate muscular fasciculi which arise from the apex of the arytenoid cartilages and become lost in the fold of mucous membrane extending between the arytenoid cartilage and side of the epiglottis (aryteno-epiglottidean folds). The Aryteno-epiglottideus inferior (Compressor sacculi laryngis, Hilton) arises from the arytenoid cartilage just above the attachment of the superior vocal cord; passing forward and upward, it spreads out upon the anterior surface of the epiglottis. This muscle is separated from the preceding by an indistinct areolar interval.2 Actions.-In considering the action of the muscles of the larynx, they may be conveniently divided into two groups, viz.: 1. Those which open and close the glottis. 2. Those which regulate the .degree of tension of the vocal cords. 1. The muscles which open the glottis are the Crico-arytenoidei postici; and those which close it are the Arytenoideus and the Crico-arytenoidei laterales. 2. The muscles which regulate the tension of the vocal cords are the Crico- thyroidei, which tense and elongate them ; and the Thyro-arytenoidei, which relax and shorten them. The Thyro-epiglottideus is a depressor of the epiglottis, and the Aryteno-epiglottidei constrict the superior aperture of the larynx, compress the sacculi laryngis, and empty them of their contents. The Crico-arytenoideipostici separate the chordae vocales, and consequently open the glottis, by rotating the arytenoid cartilages outward around a vertical axis passing through the crico- arytenoid joints, so that their anterior angles and the ligaments attached to them become widely separated, the vocal cords at the same time being made tense. The Crico-arytenoidei laterales close the glottis by rotating the arytenoid cartilages inward so as to approximate their anterior angles. The Arytenoideus muscles approximate the arytenoid cartilages, and thus dose the opening of the glottis, especially at its back part. The Crico-thyroid muscles produce tension and elongation of the vocal cords. This is effected as follows: the thyroid cartilage is fixed by the Thyro-hyoid muscles; then the Crico-thyroid muscles, when they act, draw upward the front of the cricoid cartilage, and so depress the posterior portion, which carries with it the arytenoid cartilages, and thus elongate the vocal cords. The Thyro-arytenoidei muscles, consisting of two parts having different attachments and different directions, are rather complicated as regards their action. Their main use is to draw the arytenoid cartilages forward toward the thyroid, and thus shorten and relax the vocal cords. But, owing to the connection of the inner portion with the vocal cord, this part, if acting sep- arately, is supposed to modify its elasticity and tension, and the outer portion, being inserted into the outer part of the anterior surface of the arytenoid cartilage, may rotate it inward, and thus narrow the rima glottidis by bringing the two cords together. The Thyro-epiylottidei depress the epiglottis and assist in compressing the sacculi laryngis. The Aryteno-epiglottideus superior constricts the superior aperture of the larynx, when it 1 Anatomy, by Hyrtl, page 718. 2 Musculus triticeq-glossus. Bochdalek, jun. {Prager Vierteljahrsschrift, 2d part, 1866), describes a muscle hitherto entirely overlooked, except a brief statement in Henle's Anatomy, which arises from the nodule of cartilage {corpus triticeum) in the posterior thyro-hyoid ligament, and passes forward and upward to enter the tongue along with the Hyo-glossus muscle. He met with this muscle eight times in twenty-two subjects. It occurred in both sexes, sometimes on both sides, at others on one only. 992 7777? ORGANS OF VOICE AND RESPIRATION. is drawn upward, during deglutition, and the opening closed by the epiglottis. The Aryteno- epiglottideus inferior, together with some fibres of the Thyro-arytenoidei, compress the sacculus laryngis. The Mucous Membrane of the Larynx is continuous above with that lining the mouth and pharynx, and is prolonged through the trachea and bronchi into the lungs. It lines the posterior and upper part of the anterior surface of the epiglottis, to which it is closely adherent, and forms the aryteno-epiglottidean folds which encircle the superior aperture of the larynx. It lines the whole of the cavity of the larynx; forms, by its reduplication, the chief part of the superior or false vocal cord; and, from the ventricle, is continued into the sacculus laryngis. It is then reflected over the true vocal cords, where it is thin and very intimately adherent; covers the inner surface of the crico-thyroid membrane and cricoid cartilage; and is ultimately continuous with the lining membrane of the trachea. It is covered with columnar ciliated epithelium below the superior vocal cord, but above this point the cilia are found only in front, as high as the middle of the epiglottis. In the rest of its extent the epithelium is of the squamous variety. Glands.-The mucous membrane of the larynx is furnished with numerous muciparous glands, the orifices of which are found in nearly every part; they are very numerous upon the epiglottis, being lodged in little pits in its substance; they are also found in large numbers along the posterior margin of the aryteno- epiglottidean fold, in front of the arytenoid cartilages, where they are termed the arytenoid glands. They exist also in large numbers upon the inner surface of the sacculus laryngis. None are found on the vocal cords. Vessels and Nerves.-The arteries of the larynx are the laryngeal branches derived from the superior and inferior thyroid. The veins accompany the arteries : those accompanying the superior laryngeal artery join the superior thyroid vein which opens into the internal jugular vein ; while those accompanying the inferior laryngeal artery join the inferior thyroid vein which opens into the innominate vein. The lymphatics terminate in the deep cervical glands. The nerves are the superior laryngeal and the inferior or recurrent laryngeal branches of the pneumo- gastric nerves, joined by filaments from the sympathetic. The superior laryngeal nerves supply the mucous membrane of the larynx and the Crico-thyroid muscles. The inferior laryngeal nerves supply the remaining muscles. The Arytenoid muscle is supplied by both nerves. THE TRACHEA (Fig. 573). The Trachea, or Windpipe, is a cartilaginous and membranous cylindrical tube, flattened posteriorly, which extends from the lower part of the larynx, on a level with the sixth cervical vertebra, to opposite the fourth, or sometimes the fifth, dorsal, where it divides into the two bronchi, one for each lung. The trachea measures about four inches and a half in length ; its diameter, from side to side, is from three-quarters of an inch to an inch, being always greater in the male than in the female. Relations.-The anterior surface of the trachea is convex, and covered in the neck, from above downward, by the isthmus of the thyroid gland, the inferior thyroid veins, the arteria thyroidea ima (when that vessel exists), the Sterno-hyoid and Sterno-thyroid muscles, the cervical fascia, and more superficially, by the anastomosing branches between the anterior jugular veins : in the thorax it is covered from before backward by the first piece of the sternum, the remains of the thymus gland, the left innominate vein, the arch of the aorta, the innominate and left carotid arteries, and the deep cardiac plexus. Posteriorly, it is in relation with the oesophagus; laterally, in the neck, it is in relation with the common carotid arteries, the lateral lobes of the thyroid gland, the inferior thyroid arteries and recurrent laryngeal nerves; and in the thorax it lies in the space between the pieurge, having the pneumogastric nerve on each side of it. The Right Bronchus, wider, shorter, and more horizontal in direction than the THE TRACHEA. 993 left, is about an inch in length, and enters the right lung opposite the fifth dorsal vertebra. The vena azygos major arches over it from behind, and the right pulmonary artery lies below and then in front of it. The Left Bronchus is smaller, longer, and more oblique than the right, being nearly two inches in length. It enters the root of the left lung opposite the sixth dorsal vertebra, about an inch lower than the right bronchus. It passes beneath the arch of the aorta, crosses, in front of the oesophagus, the thoracic duct and Superior. Cornu. ' Inferior Cornu. Fig. 573.-Front view of cartilages of larynx; the trachea and bronchi. the descending aorta, and has the left pulmonary artery lying at first above and then in front of it. If a transverse section is made across the trachea a short distance above its point of bifurcation, and a bird's-eye view taken of its interior (Fig. 574), the septum placed at the bottom of the trachea and separating the two bronchi will be seen to occupy the left of the median line, so that any solid body dropping into the trachea would naturally be directed toward the right bronchus. This tendency is aided by the larger size of the right tube as compared with its fellow. This fact serves to explain why a foreign body in the trachea generally falls into the right bronchus.1 1 Reigel asserts that the entry of a foreign body into the left bronchus is by no means so infre- quent as is generally supposed. 994 THE ORGANS OF VOICE AND RESPIRATION. Structure.-The trachea is composed of imperfect cartilaginous rings, fibrous membrane, muscular fibres, longitudinal yellow elastic fibres, mucous membrane, and glands. The cartilages vary from sixteen to twenty in number: each forms an imper- fect ring which surrounds about two-thirds of the cylinder of the trachea, being imperfect behind, where the tube is completed by fibrous membrane. The cartilages are placed horizontally above each other, separated by narrow membranous intervals. They measure about two lines in depth and half a line in thickness. Their outer surfaces are flattened, but internally they are convex from being thicker in the middle than at the margins. Two or more of the cartilages often unite partially or completely, and are sometimes bifurcated at their extremities. They are highly elastic, but sometimes become calcified in advanced life. In the right bronchus the cartilages vary in number from six to eight; in the left, from nine Left. Right. Fig. 574-Transverse section of the trachea, just above its bifurcation, with a bird's-eye view of the interior. to twelve. They are shorter and narrower than those of the trachea. The peculiar cartilages are the first and the last. The first cartilage is broader than the rest, and sometimes divided at one end; it is connected by fibrous membrane with the lower border of the cricoid cartilage, with which or with the succeeding cartilage it is sometimes blended. The last cartilage is thick and broad in the middle, in consequence of its lower border being prolonged into a triangular hook-shaped process which curves down- ward and backward between the two bronchi. It terminates on each side in an imperfect ring which encloses the commencement of the bronchi. The cartilage above the last is somewhat broader than the rest at its centre. The Fibrous Membrane.-The cartilages are enclosed in an elastic fibrous membrane which forms a double layer, one layer, the thicker of the two, passing over the outer surface of the ring, the other over the inner surface : at the upper and lower margins of the cartilages these two layers blend together to form a single membrane which connects the rings one with another. They are thus, as it were, imbedded in the membrane. In the space behind, between the extremities of the rings, the membrane forms a single distinct layer. The muscular fibres are disposed in two layers, longitudinal and transverse. The longitudinal fibres are the most external, and arise by minute tendons from the inner surfaces of the ends of the tracheal cartilages and from the fibrous membrane. The transverse fibres (Trachealis muscle, Todd and Bowman), the most internal, form a thin layer which extends transversely between the ends of the cartilages and the intervals between them at the posterior part of the trachea. The muscular fibres are of the unstriped variety. The elastic fibres form a complete lining to the entire cylinder of the trachea, external to the mucous membrane; they are most abundant at the posterior part of the tube between the extremities of the rings, where they are collected into distinct longitudinal bundles, and are especially numerous about the bifurcation of the trachea. They may be traced downward as a continuous membrane to the ultimate ramifications of the bronchial tubes. The fibres are contained in a loose submucous tissue which contains numerous mucous glands. The Mucous Membrane is continuous above with that of the larynx, and below THE TRACHEA. 995 with that of the bronchi. Microscopically, it presents a well-marked basement membrane supporting a layer of columnar ciliated epithelium, between the deeper ends of which are smaller round or elongated cells. It contains a large amount of lymphoid tissue and some tracheal glands. The Tracheal Glands are found in great abundance at the posterior part of the trachea. They are small, flattened, ovoid bodies placed upon the outer surface of the fibrous layer; each is furnished with an excretory duct which pierces the fibrous and muscular layers and opens on the surface of the mucous membrane. Some glands of smaller size are also found at the sides of the trachea, between the layers of fibrous tissue connecting the rings, and others immediately beneath the mucous coat. The secretion from these glands serves to lubricate the inner surface of the trachea. Vessels and Nerves.-The trachea is supplied with blood by the inferior thyroid arteries. The veins terminate in the thyroid venous plexus. The nerves are derived from the pneumogastric and its recurrent branches and from the sympa- thetic. Surface Form.-In the middle line of the neck some of the cartilages of the larynx can be readily distinguished. In the receding angle below the chin the hyoid bone can easily be made out (see page 230), and a finger's breadth below it is the pomum Adami, the prominence between the upper borders of the two alae of the thyroid cartilage. About an inch below this, in the middle line, is a depression corresponding to the crico-thyroid space, in which the operation of laryngotomy is performed. This depression is bounded below by a prominent arch, the anterior ring of the cricoid cartilage, below which the trachea can be felt, though it is only in the emaciated adidt that the separate rings can be distinguished. The lower part of the trachea is not easily made out, for as it descends in the neck it takes a deeper position and is farther removed from the surface. The level of the vocal cords corresponds to the middle of the ante- rior margin of the thyroid cartilage. With the laryngoscope the following structures can be seen : The base of the tongue and the upper surface of the epiglottis, with the glosso-epiglottic ligaments, the superior aperture of the larynx, bounded on either side by the aryteno-epiglottidean ligaments, in which may be seen two rounded eminences corresponding to the cornicula and cuneiform cartilages. Beneath these, the true and false vocal cords, with the ventricle between them. Still deeper, the cricoid carti- lage and some of the anterior parts of the rings of the trachea, and sometimes, in deep inspira- tion, the bifurcation of the trachea. Surgical Anatomy.-Foreign bodies often find their way into the air-passages. These may be either large soft substances, as a piece of meat, when they become lodged in the upper aper- ture of the larynx or in the rima glottidis, and cause speedy suffocation unless rapidly got rid of or unless an opening is made into the air-passages below, so as to enable the patient to breathe. Smaller bodies, and frequently of a hard nature, such as cherry- or plum-stones, small pieces of bone, buttons, etc., may find their way through the rima glottidis into the trachea or bronchus, or may become lodged in the ventricle of the larynx. The dangers then depend not so much upon the mechanical obstruction as upon the spasm of the glottis which they excite from reflex irritation. When lodged in the ventricle of the larynx they may produce very few symptoms beyond sudden loss of voice or alteration in the voice sounds immediately following the inhala- tion of the foreign body. When, however, they are situated in the trachea, they are constantly striking against the vocal cords during expiratory efforts, and produce attacks of dyspnoea from spasm of the glottis. When lodged in the bronchus they usually become fixed there, and, occluding the lumen of the tube, cause a loss of the respiratory murmur on the affected side, which is, as stated above, usually the right. Beneath the mucous membrane of the upper part of the air-passages there is a considerable amount of submucous tissue which is liable to become much swollen from effusion in inflamma- tory affections, constituting the disease known as "oedema of the glottis." This effusion does not extend below the level of the vocal cords, on account of the fact that the mucous membrane is closely adherent to these structures, without the intervention of any submucous tissue. So that, in cases of this disease in which it is necessary to open the air-passages to prevent suffoca- tion, the operation of laryngotomy is sufficient. Chronic laryngitis is an inflammation of the mucous glands of the larynx which occurs in those who speak much in public, and is known as "clergyman's sore throat." It is due to the dryness induced by the large amount of cold air draw into the air-passages during prolonged speaking, which excites the increased activity of the mucous glands to keep the parts moist, and this eventually terminates in inflammation of these structures. Ulceration of the larynx may occur from syphilis, either superficial ulceration or from the softening of a gumma, from tubercular disease (laryngeal phthisis), or from malignant disease (epithelioma). The air-passages may be opened in two different situations: through the crico-thyroid mem- brane {laryngotomy), or in some part of the trachea {tracheotomy); and to these some surgeons 996 THE ORGANS OF VOICE AND RESPIRATION. have added a third method, by opening the crico-thyroid membrane and dividing the cricoid cartilage with the upper ring of the trachea {laryngo-tracheotomy). The student should care- fully consider the relative anatomy of the air-tube in each of these situations (Fig. 575). Thyroid cartilage- Crico-thyroid membrane_ and artery. Cricoid cartilage.- Superior thyroid vein.- Inferior thyroid vein- innominate artery.. Thyroid body (isthmus). Fig. 575.-Surgical anatomy of laryngo-traelieal region. In the infant. Laryngotomy is anatomically the most simple operation : it can most readily be performed, and should always be preferred when particular circumstances do not render the operation of tracheotomy absolutely necessary. The crico-thyroid membrane is very superficial, being covered only in the middle line by the skin, superficial fascia, and the deep fascia. On each side of the middle line it is also covered by the Sterno-hyoid and Sterno-thyroid muscles, which diverge slightly from each other at their upper parts, leaving a slight interval between them. On these muscles rests the anterior jugular vein. The only vessel of any importance in connection with this operation is the crico-thyroid artery, which crosses the crico-thyroid membrane, and which may be wounded, but rarely gives rise to any trouble. The operation is performed thus: The head being thrown back and steadied by an assistant, the finger is passed over the front of the neck and the crico-thyroid depression felt for. A vertical incision is then made through the skin in the middle line over this spot, and carried down through the fascia until the crico- thyroid membrane is exposed. A cross cut is then made through the membrane, close to the upper border of the cricoid cartilage, so as to avoid, if possible, the crico-thyroid artery, ami a tracheotomy-tube introduced. It has been recommended, as a more rapid way of performing the operation, to make a transverse instead of a longitudinal cut through the superficial structures, and thus to open at once the air-passages. It will be seen, however, that in operating in this way the anterior jugular veins would be in danger of being wounded. Tracheotomy may be performed either above or below the isthmus of the thyroid body, or this structure may be divided and the trachea opened beneath it. The isthmus of the thyroid gland usually crosses the second and third rings of the trachea; along its upper border is frequently to be found a large transverse communicating branch between the superior thyroid veins; and the isthmus itself is covered by a venous plexus formed between the thyroid veins of the opposite sides. Theoretically, therefore, it is advisable to avoid dividing this structure in opening the trachea. Above the isthmus the trachea is comparatively superficial, being covered by the skin, superficial fascia, deep fascia. Sterno-hyoid and Sterno-thyroid muscles, and a second layer of the deep fascia, which, attached above to the lower border of the hyoid bone, descends beneath the muscles to the thyroid body, where it divides into two layers and encloses the isthmus. Below the isthmus the trachea lies much more deeply, and is covered by the Sterno-hyoid and the Sterno-thyroid muscles and a quantity of loose areolar tissue in which is a plexus of veins, some of them of large size; they converge to two trunks, the inferior thyroid veins, which descend on either side of the median line on the front of the trachea and open into the innomi- nate veins. In the infant the thymus gland ascends a variable distance along the front of the trachea, and opposite the episternal notch the windpipe is crossed by the left innominate vein. Occasionally also, in young subjects, the innominate artery crosses the tube obliquely above the level of the sternum. The thyroidea ima artery, when that vessel exists, passes from below upward along the front of the trachea. THE PLEUHJE. 997 From these observations it must be evident that the trachea can be more readily opened above than below the isthmus of the thyroid body. Tracheotomy above the isthmus is performed thus: The patient should, if possible, be laid on his back on a table in a good light. A pillow is to be placed under the shoulders and the head thrown back and steadied by an assistant. The surgeon, standing on the right side of his patient, makes an incision from an inch and a half to two inches in length in the median line of the neck from the top of the cricoid cartilage. The incision must be made exactly in the middle line, so as to avoid the anterior jugular veins, and after the superficial structures have been divided the interval between the Sterno-hyoid muscles must be found, the raphe divided, and the muscles drawn apart. The lower border of the cricoid cartilage must now be felt for, and the upper part of the trachea exposed from this point downward in the middle line. Bose has recommended that the layer of fascia in front of the trachea should be divided transversely at the level of the lower border of the cricoid cartilage, and, having been seized with a pair of forceps, pressed downward with the handle of the scalpel. By this means the isthmus of the thyroid gland is depressed, and is saved from all danger of being wounded, and the trachea cleanly exposed. The trachea is now transfixed with a sharp hook and drawn forward in order to steady it, and is then opened by inserting the knife into it and dividing the two or three upper rings from below upward. If the trachea is to be opened below the isthmus, the incision must be made from a little below the cricoid cartilage to the top of the sternum. In the child the trachea is smaller, more deeply placed, and more movable than in the adult. In fat or short-necked people, or in those in whom the muscles of the neck are prominently developed, the trachea is more deeply placed than in the opposite conditions. A portion of the larynx or the whole of it has been removed for malignant disease. The results which have been obtained from the removal of the whole of it have not been very satis- factory, and the cases in which the operation is justifiable are very few. It may be removed by a median incision through the soft parts, freeing the cartilage from the muscles and other structures in front, separating the larynx from the trachea below, and dissecting off the deeper structure from below upward. THE PLEURAE. Each lung is invested, upon its external surface, by an exceedingly delicate serous membrane, the pleura, which encloses the organ as far as its root, and is then reflected upon the inner surface of the thorax. The portion of the serous membrane investing the surface of the lung is called the pleura pulmonalis (visceral layer of pleura), while that which lines the inner surface of the chest is called the pleura costalis (parietal layer of pleura). The space between these two layers is called the cavity of the pleura, but it must be borne in mind that in the healthy condition the two layers are in contact, and there is no real cavity until the lung becomes collapsed and a separation of it from the wall of the chest takes place. Each pleura is therefore a shut sac, one occupying the right, the other the left half of the thorax, and they are perfectly separate, not communicating with each other. The two pleurae do not meet in the middle line of the chest, excepting anteriorly opposite the upper part of the second piece of the sternum-a space being left between them, which contains all the viscera of the thorax excepting the lungs: this is the mediastinum. Reflections of the Pleura (Fig. 576).-Commencing at the sternum, the pleura passes outward, covers the costal cartilages, the inner surface of the ribs and Intercostal muscles, and at the back part of the thorax passes over the thoracic ganglia and their branches, and is reflected upon the sides of the bodies of the vertebrae, where it is separated by a narrow interval, the posterior mediastinum, from the opposite pleura. From the vertebral column the pleura passes to the side of the pericardium, which it covers to a slight extent; it then covers the back part of the root of the lung, from the lower border of which a triangular fold descends vertically by the side of the posterior mediastinum to the Diaphragm. This fold is the broad ligament of the lung, the ligamentum latum pulmonis, and serves to retain the lower part of that organ in position. From the root the pleura may be traced over the convex surface of the lung, the summit and base, and also over the sides of the fissures between the lobes on to its anterior surface and the front part of its root; from this it is reflected upon the side of the pericardium to the inner surface of the sternum. Below, it covers the upper surface of the Diaphragm, and extends in front as low as the costal cartilage of the seventh rib ; at the side of the chest, as low as the tenth rib on the left side and the ninth on the right side; and 998 THE ORGANS OF VOICE AND RESPIRATION. behind, it reaches as low as the twelfth rib, and sometimes even beyond it, as low as the transverse process of the first lumbar vertebra. Above, its apex projects, in the form of a cul-de-sac, through the superior opening of the thorax into the neck, extending from one to two inches above the margin of tha first rib, and receives the summit of the corresponding lung; this sac is strengthened, according to Dr. Sibson, by a dome-like expansion of fascia, attached in front to the posterior border of the first rib, and behind to the anterior border of the transverse process of the TRIANGULARIS STERNI. Internal Mammary Vessels. Left Phrenic Nerve. /Pleura Pulmonalis. 'Pleura Costalis. Mediastinum I Sympathetic Nerve. / Meaiasttnum | Thoracic Duct.' \ Vena Azygos Major} posteriQr Pneumogasinc Nerves) Fig. 576.-A transverse section of the thorax, showing the relative position of the viscera and the reflections of the nleurae. seventh cervical vertebra. This is covered and strengthened by a few spreading muscular fibres derived from the Scaleni muscles. A little above the middle of the sternum, the contiguous surfaces of the two pleurae are sometimes in contact for a slight extent; but above and below this point the interval left between them forms part of the mediastinum. The inner surface of the pleura is smooth, polished, and moistened by a serous fluid; its outer surface is intimately adherent to the surface of the lung and to the pulmonary vessels as they emerge from the pericardium; it is also adherent to the upper surface of the Diaphragm : throughout the rest of its extent it is somewhat thicker, and may be separated from the adjacent parts with extreme facility. The right pleural sac is shorter, wider, and reaches higher in the neck than the left. Vessels and Nerves.-The arteries of the pleura are derived from the inter- costal, the internal mammary, the musculo-phrenic, thymic, pericardiac, and bronchial. The veins correspond to the arteries. The lymphatics are very numerous. The nerves are derived from the phrenic and sympathetic (Luschka). Kolliker states that nerves accompany the ramification of the bronchial arteries in the pleura pulmonalis. Surgical Anatomy.-In operations upon the kidney it must be borne in mind that tbe pleura may sometimes extend below the level of the last rib. and may therefore be opened in these operations, especially when the last rib is removed in order to give more room. THE MEDIASTINUM. 999 THE MEDIASTINUM. The Mediastinum is the space left in the median line of the chest by the non- approximation of the two pleurae. It extends from the sternum in front to the spine behind, and contains all the viscera in the thorax excepting the lungs. The mediastinum may be divided for purposes of description into two parts-an Fig. 577.-The posterior mediastinum. upper portion, above the upper level of the pericardium, which is named the Superior mediastinum (Struthers); and a lower portion, below the upper level of the pericardium. This lower portion, is again subdivided into three-that part which contains the pericardium and its contents, the middle mediastinum; that part which is in front of the pericardium, the anterior mediastinum; and that part which is behind the pericardium, the posterior mediastinum. 1000 THE ORGANS OF VOICE AND RESPIRATION. The superior mediastinum is that portion of the interpleural space which lies above the upper level of the pericardium, between the manubrium sterni in front and the upper dorsal vertebrae behind. It is bounded below by a plane passing back- ward from the junction of the manubrium and gladiolus sterni to the lower part of the body of the fourth dorsal vertebra. It contains the origins of the Sterno- hyoid and Sterno-thyroid muscles and the lower ends of the Longi colli muscles; the transverse portion of the arch of the aorta ; the innominate, the thoracic portion of the left carotid and subclavian arteries ; the upper half of the superior vena cava and the innominate veins, and the left superior intercostal vein; the pneumogastric, cardiac, phrenic, and left recurrent laryngeal nerves ; the trachea, oesophagus, and thoracic duct; the remains of the thymus gland and lymphatics. The anterior mediastinum is bounded in front by the sternum, on each side by the pleura, and behind by the pericardium. Owing to the oblique position of the Left Inom- inate Vein. Left Carotid Artery. Thymus Gland. Pneumogastric Nerve. Pneumogastric Nerve. Internal Mammary Artery. Right Innom- -inate Pein. 1st Rib. Trachea. Vertebral . 1 rtery - Left Sublcavian, A rtery. (Esophagus. '2nd Rib. 3rd Rib. Fig. 578.-Transverse section through the upper margin of the third dorsal vertebra. (Braune.) heart toward the left side, this space is not parallel with the sternum, but directed obliquely from above downward and to the left of the median line ; it is broad below, narrow above, very narrow opposite the first segment of the gladiolus of the sternum, the contiguous surfaces of the two pleurae being occasionally united over a small space. The anterior mediastinum contains the origins of the Triangularis sterni muscles, and a quantity of loose areolar tissue in which some lymphatic vessels are found ascending from the convex surface of the liver, and two or three lymphatic glands (anterior mediastinal glands). The middle mediastinum is the broadest part of the interpleural space. It contains the heart enclosed in the pericardium, the ascending aorta, the lower half of the superior vena cava, with the vena azygos major opening into it, the bifurcation of the trachea and the two bronchi, the pulmonary artery dividing into its two branches and the right and left pulmonary veins, the phrenic nerves, and some bronchial lymphatic glands. The posterior mediastinum is an irregular triangular space running parallel with the vertebral column; it is bounded in front by the pericardium and roots of THE LUNGS. 1001 the lungs, behind by the vertebral column from the lower border of the fourth dorsal vertebra, and on either side by the pleura. It contains the descend- ing thoracic aorta, the greater and lesser azygos veins, the pneumogastric and splanchnic nerves, the oesophagus, thoracic duct, and some lymphatic glands. THE LUNGS. The Lungs are the essential organs of respiration ; they are two in number, placed one on each side of the chest, separated from each other by the heart and other contents of the mediastinum. Each lung is conical in shape, and presents for examination an apex, a base, two borders, and two surfaces (Fig- 579). Fig. 579.-Front view of the heart and lungs. The apex forms a tapering cone which extends into the root of the neck about an inch to an inch and a half above the level of the first rib. The base is broad, concave, and rests upon the convex surface of the Dia- phragm ; its circumference is thin, and fits into the space between the lower ribs and the costal attachment of the Diaphragm, extending lower down externally and behind than in front. The external or thoracic surface is smooth, convex, of considerable extent, and corresponds to the form of the cavity of the chest, being deeper behind than in front. The inner surface is concave. It presents in front a depression corresponding to the convex surface of the pericardium, and behind a deep fissure (the hilum pulmonis) which gives attachment to the root of the lung. The posterior border is rounded and broad, and is received into the deep con- cavity on either side of the spinal column. It is much longer than the anterior border, and projects below between the ribs and the Diaphragm. 1002 7777s ORGANS OF VOICE AND RESPIRATION The anterior border is thin and sharp, and overlaps the front of the peri- cardium. Each lung is divided into two lobes, an upper and lower, by a long and deep fissure wThich extends from the upper part of the posterior border of the organ, about three inches from its apex, downward and forward to the lower part of its anterior border. This fissure penetrates nearly to the root. In the right lung the upper lobe is partially subdivided by a second and shorter fissure which extends from the middle of the preceding, forward and upward, to the anterior margin of the organ, marking off' a small triangular portion, the middle lobe. The right lung is the larger and heavier; it is broader than the left, owing to the inclination of the heart to the left side ; it is also shorter by an inch, in conse- quence of the Diaphragm rising higher on the right side to accommodate the liver. The Root of the Lungs.-A little above the middle of the inner surface of each lung, and nearer its posterior than its anterior border, is its root, by which the lung is connected to the heart and the trachea. The root is formed by tbe bronchial tube, the pulmonary artery, the pulmonary veins, the bronchial arteries and veins, the pulmonary plexus of nerves, lymphatics, bronchial glands, and areolar tissue, all of which are enclosed by a reflection of the pleura. The root of the right lung lies behind the superior vena cava and ascending portion of the aorta and below the vena azygos major. That of the left lung passes beneath the arch of the aorta and in front of the descending aorta; the phrenic nerve and the anterior pulmonary plexus lie in front of each, and the pneumogastric and posterior pulmonary plexus behind each. The chief structures composing the root of each lung are arranged in a similar manner from before backward on both sides-viz. the pulmonary veins most anterior; the pulmonary artery in the middle; and the bronchus, together with the bronchial vessels, behind. From above downward, on the two sides, their arrangement differs, thus: On the right side their position is-bronchus, pulmonary artery, pulmonary veins ; but on the left side their position is-pulmonary artery, bronchus, pul- monary veins ; this is accounted for by the bronchus being placed on a lower level on the left than on the right side, in order that it may pass under the arch of the aorta. The weight of both lungs together is about forty-two ounces, the right lung being two ounces heavier than the left; but much variation is met with according to the amount of blood or serous fluid they may contain. The lungs are heavier in the male than in the female, their proportion to the body being in the former as 1 to 37, in the latter as 1 to 43. The specific gravity of the lung-tissue varies from 0.345 to 0.746, water being 1000. The color of the lungs at birth is a pinkish-white; in adult life a dark shite-color, mottled in patches; and as age advances this mottling assumes a black color. The coloring matter consists of granules of a carbonaceous substance deposited in the areolar tissue near the surface of the organ. It increases in quantity as age advances, and is more abundant in males than in females. The posterior border of the lung is usually darker than the anterior. The surface of the lung is smooth, shining, and marked out into numerous polyhedral spaces, indicating the lobules of the organ; the area of each of these spaces is crossed by numerous lighter lines. The substance of the lung is of a light, porous, spongy texture; it floats in water and crepitates when handled, owing to the presence of air in the tissue; it is also highly elastic; hence the collapsed state of these organs when they are removed from the closed cavity of the thorax. Structure.-The lungs are composed of an external serous coat, a subserous areolar tissue, and the pulmonary substance or parenchyma. The serous coat is derived from the pleura; it is thin, transparent, and invests the entire organ as far as the root. The subserous areolar tissue contains a large proportion of elastic fibres; THE LUNGS. 1003 it invests the entire surface of the lung, and extends inward between the lobules. The parenchyma is composed of lobules which, although closely connected together by an interlobular areolar tissue, are quite distinct from one another, and may be teased asunder without much difficulty in the foetus. The lobules vary in size: those on the surface are large, of pyramidal form, the base turned toward the surface; those in the interior smaller and of various forms. Each lobule is composed of one of the ramifications of a bronchial tube and its ter- minal air-cells, and of the ramifications of the pulmonary and bronchial vessels, lymphatics, and nerves, all of these structures being connected together by areolar tissue. The bronchus, upon entering the substance of the lung, divides and subdivides dichotomously throughout the entire organ. Sometimes three branches arise together, and occasionally small lateral branches are given off from the sides of a main trunk. Each of the smaller subdivisions of the bronchi enters a pulmonary lobule, and is termed a lobular bronchial tube. Its wall now begins to present irregular dilatations, at first sparingly and on one side of the tube only, but as it proceeds onward these dilatations become more numerous and surround the tube on all sides, so that it loses its cylindrical character, and, becoming enlarged, terminates in a sacculated alveolar passage beset in all directions, both laterally and terminally, by caecal pouches or air-cells. The enlarged terminations-that is, the alveolar passages from which the caecal pouches or air-cells spring-are termed infundibula. Within the lungs the bronchial tubes are circular, not flat- tened, and present certain peculiarities of structure. Changes in the Structure of the Bronchi in the Lungs.-1. In the Lobes of the Lungs.-In the lobes of the lungs the following changes take place : The cartilages are not imperfect rings, but consist of thin laminae, of varied form and size, scattered irregularly along the sides of the tube, being most distinct at the points of division of the bronchi. They may be traced into tubes the diameter of which is only one-fourth of a line. Beyond this point the tubes are wholly membranous. The fibrous coat and the longitudinal elastic fibres are continued into the smallest ramifications of the bronchi. The muscular coat is disposed in the form of a continuous layer of annular fibres, which may be traced upon the smallest bronchial tubes, and consists of the unstriped variety of muscular tissue. The mucous membrane lines the bronchi and its ramifications throughout, and is covered with columnar ciliated epithelium. 2. In the Lobules of the Lung.-In the lobular bronchial tubes and in the infundibula the following changes take place: The muscular tissue begins to disappear, so that in the infundibula there is scarcely a trace of it. The longitudinal elastic fibres begin to break up, so that in the infundibula they form an interlacement around the mouths of the air-cells which spring from it. The epithelium becomes non-ciliated and flattened. This occurs gradually ; thus, in the lobular bronchial tubes patches of non-ciliated flattened epithelium may be found scattered amongst the columnar ciliated epithelium ; then these patches of non-ciliated flattened epithelium become more and more numerous, until in the infundibula and air-cells all the epithelium is of the non-ciliated pavement variety. In addition to these flattened cells, there are small polyg- onal granular cells in the air-sacs, in clusters of two or three, between the others. The air-cells are small, polyhedral, alveolar recesses composed of a fibrillated connective tissue and surrounded by a few involuntary muscular and elastic fibres. In their walls are granular, rounded, amoeboid cells often containing carbonaceous particles. The air-cells are well seen on the surface of the lung, and vary from Yihj-th to th of an inch in diameter, being largest on the surface at the thin borders and at the apex, and smallest in the interior. The pulmonary artery conveys the venous blood to the lungs; it divides into branches which accompany the bronchial tubes, and terminates in a dense capillary 1004 THE ORGANS OF VOICE AND RESPIRATION. network upon the walls of the intercellular passages and air-cells. In the lung the branches of the pulmonary artery are usually above and in front of a bronchial tube, the vein below. The pulmonary capillaries form plexuses which lie immediately beneath the mucous membrane in the walls and septa of the air-cells and of the infundibula. In the septa between the air-cells the capillary network forms a single layer. The capillaries form a very minute network, the meshes of which are smaller than the vessels themselves ;l their walls are also exceedingly thin. The vessels of neighboring lobules are distinct from each other, and do not anastomose; and, according to Dr. Waters,2 those of the separate groups of infundibula with their air-cells (which groups he denominates lobulettes) are also independent, so that in the septa between two adjoining lobulettes there would be a double layer of capillaries, one layer belonging to each of the adjacent infundibula with their air- cells. If this is really the arrangement of the vessels, it would follow that, in the septa between the air-cells, the blood in the capillaries would be exposed on all sides to the action of the air, since it is circulating in a single layer of vessels which is in contact with the membrane of the air-cells on both sides; but that, in the septa between the neighboring infundibula, with their air-cells, the blood being in a double layer of capillaries, it will be in contact with the air on one side only. The pulmonary veins commence in the pulmonary capillaries, the radicles coalescing into larger branches, which accompany the arteries and return the oxygenated blood to the left auricle of the heart. The bronchial arteries supply blood for the nutrition of the lung: they are derived from the thoracic aorta, and, accompanying the bronchial tubes, are distributed to the bronchial glands and upon the walls of the larger bronchial tubes and pulmonary vessels. Those supplying the bronchial tubes form a capillary plexus in the muscular coat, from which branches are given off to form a second plexus in the mucous coat. This plexus communicates with branches of the pulmonary artery and empties itself into the pulmonary vein. Others are distributed in the interlobular areolar tissue, and terminate partly in the deep, partly in the superficial, bronchial veins. Lastly, some ramify upon the surface of the lung beneath the pleura, where they form a capillary network. The bronchial vein is formed at the root of the lung, receiving superficial and deep veins corresponding to branches of the bronchial artery. It does not, however, receive all the blood supplied by the artery, as some of it passes into the pulmonary vein. It terminates on the right side in the vena azygos major, and on the left side in the superior intercostal vein. The lymphatics consist of a superficial and deep set: they terminate at the root of the lung, in the bronchial glands. Nerves.-The lungs are supplied from the anterior and posterior pulmonary plexuses, formed chiefly by branches from the sympathetic and pneumogastric. The filaments from these plexuses accompany the bronchial tubes, upon which they are lost. Small ganglia are found upon these nerves. Surface Form.-The apex of the lung is situated in the neck, behind the interval between the two heads of origin of the Sterno-mastoid. The height to which it rises above the clavicle varies very considerably, but is generally about one inch. It may, however, extend as much as an inch and a half or an inch and three-quarters, of, on the other hand, it may scarcely project above the level of this bone. Tn order to mark out the anterior margin of the lung, a line is to be drawn from the apex-point, one inch above the level of the clavicle, and rather nearer the posterior than the anterior border of the Sterno-mastoid muscle, downward and inward across the sterno-clavicular articulation and first piece of the sternum until it meets, or almost meets, its fellow of the other side opposite the articulation of the manubrium and gladiolus. From this point the two lines are to be drawn downward, one on either side of the mesial line and close to 1 The meshes are only 0.002,// to 0.008/// in width, while the vessels are 0.003/// to 0.005//z ifKolliker, Human Microscopic Anatomy}. 2 Med.-Chir. T> •ans., vol. xxviii., 1845. THE LUNGS. 1005 i Recurrent laryngeal nerve. First dorsal vertebra. Thoracic duct. \ (Esophagus. Thoracic duct. Fig. 580.-The roots of the lungs and posterior pulmonary plexus, seen from behind. 1006 THE ORGANS OF VOICE AND RESPIRATION. it, as far as the level of the articulation of the fourth costal cartilages to the sternum. From here the two lines diverge; the left is to be drawn at first passing outward with a slight inclina- tion downward, and then taking a bend downward with a slight inclination outward to the apex of the heart, and thence to the sixth costo-chondral articulation. The direction of the anterior border of this part of the left lung is denoted with sufficient accuracy by a curved line with its convexity directed upward and outward from the articulation of the fourth right costal cartilage of the sternum to the fifth intercostal space, an inch and a half below and three-quarters of an inch internal to the left nipple. The continuation of the anterior border of the right lung is marked by a prolongation of its line from the level of the fourth costal cartilages vertically downward as far as the sixth, when it slopes off along the line of the sixth costal cartilage to its articulation with the rib. The lower border of the lung is marked out by a slightly curved line with its convexity down- ward from the articulation of the sixth costal cartilage to its rib to the spinous process of the tenth dorsal vertebra. If vertical lines are drawn downward from the nipple, the mid-axillary line, and the apex of the scapula, while the arms are raised from the sides, they should intersect this convex line, the first at the sixth, the second at the eighth, and the third at the tenth rib. It will thus be seen that the pleura (see page 997) extends farther down than the lung, so that it may be wounded, and a wound pass through its cavity into the Diaphragm, and even injure the abdominal viscera, without the lung being involved. The posterior border of the lung is indicated by a line drawn from the level of the spinous process of the seventh cervical vertebra, down either side of the spine, corresponding to the costo-vertebral joints as low as the spinous process of the tenth dorsal vertebra. 'The trachea bifurcates opposite the spinous process of the fourth dorsal vertebra, and from this point the two bronchi are directed outward, the right one almost horizontally, the left with a considerable inclination downward. The position of the great fissure in the right lung may be indicated by a line drawn from the fourth dorsal vertebra round the side of the chest to the anterior margin of the lung opposite the seventh rib, and the smaller or secondary fissure by a line drawn from the preceding where it bisects the mid-axillary line to the junction of the fourth costal cartilage to the sternum. The great fissure in the left lung is a little higher, extending from the third dorsal vertebra round the side of the chest to reach the anterior margin of the lung opposite the sixth costal cartilage. Surgical Anatomy.-The lungs may be wounded or torn in three ways: (1) By compres- sion of the chest, without any injury to the ribs. (2) By a fractured rib penetrating the lung. (3) By stabs, gunshot wounds, etc. The first form, where the lung is ruptured by external compression without any fracture of the ribs, is very rare, and usually occurs in young children, and affects the root of the lung-i. e. the most fixed part-and thus, implicating the great vessels, is frequently fatal. It would seem a priori a most unusual injury, and its exact mode of causation is difficult to interpret. The prob- able explanation is that immediately before the compression is applied a deep inspiration is taken and the lungs are fully inflated; owing then to spasm of the glottis at the moment of compres- sion, the air is unable to escape from the lung, which is not able to recede, and consequently gives way. In the second variety, when the wound in the lung is produced by the penetration of a broken rib, both the pleura costalis and puhnonalis must necessarily be injured, and consequently the air taken into the wounded air-cells may find its way through these wounds into the cellular tissue of the parietes of the chest. This it may do without collecting in the pleural cavity; the two layers of the pleura are so intimately in contact that the air passes straight through from the wounded lung into the subcutaneous tissue. Emphysema constitutes therefore the most important sign of injury to the lung in cases of fracture of the ribs. Pneumothorax, or air in the pleural cavity, is much more likely to occur in injuries to the lung of the third variety; that is to say, from external wounds, from stabs, gunshot injuries, and such like, in which cases air passes either from the wound of the lung or from the external wound into the cavity of the pleura during the respiratory movements. In these cases there is generally no emphysema of the subcutaneous tissue unless the external wound is small and valvular, so that the air is drawn into the wound during inspiration, and then forced into the cellular tissue around during expiration because it cannot escape from the external wound. Occasionally in wounds of the parietes of the chest no air finds its way into the cavity of the pleura, because the lung at the time of the accident protrudes through the wound and blocks the opening. This occurs where the wound is large, and constitutes one form of hernia of the lung. Another form of hernia of the lung occurs, though very rarely, after wounds of the chest-wall, when the wound has healed and the cicatrix subsequently yields from the pressure of the viscus behind. It forms a globular, elastic, crepitating swelling, which enlarges during expiratory efforts,.falls in during inspiration, and disappears on holding the breath. THE THYROID GLAND. The thyroid gland bears much resemblance in structure to other glandular organs, and was formerly classified, together with the thymus, suprarenal capsules, and spleen, under the head of ductless glands, since when fully developed it has no excretory duct. From its situation in connection with the trachea and larynx, THE THYROID GLAND. 1007 the thyroid body is usually described with those organs, although it takes no part in the function of respiration. It is situated at the upper part of the trachea, and consists of two lateral lobes placed one on each side of that tube and connected together by a narrow transverse portion, the isthmus. Its anterior surface is convex, and covered by the Sterno-hyoid, Sterno-thyroid, and Omo- hyoid muscles. Its lateral surfaces, also convex, lie in con- tact with the sheath of the common carotid artery. Its posterior surface is concave, and embraces the trachea and larynx. The posterior borders of the gland extend as far back as the lower part of the pharynx, and on the left side to the oesophagus. The thyroid varies in weight from one to two ounces. It is larger in females than in males, and becomes slightly increased in size during menstruation. Each lobe is somewhat conical in shape, about two inches in length, and three-quarters of an inch to an inch and a quarter in breadth, the right lobe being the larger of the two. The isthmus connects the lower third of the two lateral lobes', it measures about half an inch in breadth and the same in depth, and usually covers the second and third rings of the trachea. Its situation presents, however, many variations- a point of importance in the operation of tracheotomy. Sometimes the isthmus is altogether wanting. A third lobe, of conical shape, called the pyramid, occasionally arises from the upper part of the isthmus or from the adjacent portion of either lobe, but most commonly the left, and ascends as high as the hyoid bone. It is occasionally quite detached, or divided into two parts, or altogether wanting. A few muscular bands are occasionally found attached above to the body of the hyoid bone, and below to the isthmus of the gland or its pyramidal process. These form a muscle which was named by Sbmmerring the Levator glandule? thyroidece. Structure.-The thyroid body is invested by a thin capsule of connective tissue which projects into its substance and imperfectly divides it into masses of irregular form and size. When the organ is cut into, it is of a brownish-red color, and is seen to be made up of a number of closed Vesicles containing a yellow glairy fluid and separated from each other by intermediate connective tissue. According to Dr. Baber, who has recently published some important observa- tions on the minute structure of the thyroid,1 the vesicles of the thyroid of the adult animal are generally closed cavities; but in some young animals (e.g. young dogs) the vesicles are more or less tubular and branched. This appearance he supposes to be due to the mode of growth of the gland, and merely indicating that an increase in the number of vesicles is taking place. Each vesicle is lined by a single layer of epithelium, the cells of which, though differing somewhat in shape in different animals, have always a tendency to assume a columnar form. Between the epithelial cells exists a delicate reticulum. The vesicles are of various sizes and shapes, and contain as a normal product a viscid, homogeneous, semi-fluid, slightly yellowish material which frequently contains blood, the red corpuscles of which are found in it in various stages of disintegration and decolorization, the yellow tinge being probably due to the haemoglobin, which is thus set free from the colored corpuscles. Baber has also described in the thyroid gland of the Fig. 581.-Two lobules from the thyroid of an infant, a. Small glandular vesicles with their cells, b. The same with incipi- ent colloid metamorphosis, more strongly marked at c. d. Coarse lymph-canals, e. Fine radicles of the same. f. An efferent vessel of considerable size. 1 " Researches on the Minute Structure of the Thyroid Gland," Phil. Trans., part iii., 1881. 1008 THE ORGANS OF VOICE AND RESPIRATION dog large round cells (" parenchymatous cells "), each provided with a single oval- shaped nucleus, which migrate into the interior of the gland-vesicles. The capillary blood-vessels form a dense plexus in the connective tissue around the vesicles, between the epithelium of the vesicles and the endothelium of the lymph-spaces, which latter surround a greater or smaller part of the circumference of the vesicle. These lymph-spaces empty themselves into lymphatic vessels which run in the interlobular connective tissue, not uncommonly surrounding the arteries which they accompany, and communicate with a network in the capsule of the gland. Baber has found in the lymphatics of the thyroid a viscid mate- rial which is morphologically identical with the normal constituent of the vesicle. Vessels and Nerves.-The arteries supplying the thyroid are the superior and inferior thyroid, and sometimes an additional branch (thyroidea media or ima) Lymphatic vessel. Vesicle. -Artery. Wall of gland-vesicle. Fig. 582.-Minute structure of thyroid. From a transverse section of the thyroid of a dog. (Semi-diagram matic.) (Baber.) from the innominate artery or the arch of the aorta, which ascends upon the front of the trachea. The arteries are remarkable for their large size and frequent anastomoses. The veins form a plexus on the surface of the gland and on the front of the trachea, from which arise the superior, middle, and inferior thyroid veins, the two former terminating in the internal jugular, the latter in the innom- inate vein. The lymphatics are numerous, of large size, and terminate in the thoracic and right lymphatic ducts. The nerves are derived from the middle and inferior cervical ganglia of the sympathetic. Surgical Anatomy.-The thyroid gland is subject to enlargement, which is called goitre. This may be due to hypertrophy of any of the constituents of the gland. The simplest (parenchymatous goitre) is due to an enlargement of the follicles. The fibroid is due to increase of the interstitial connective tissue. The cystic is that form in which one or more large cysts are formed from dilatation and possibly coalescence of adjacent follicles. The pulsating goitre is where the vascular changes predominate over the parenchymatous, and the vessels of the gland are especially enlarged. Finally, there is exophthalmic goitre (Graves's disease), where there is great vascularity and often pulsation, accompanied by exophthalmos, palpitation, and rapid pulse. For the relief of these growths various operations have been resorted to, such as injection of tincture of iodine or perchloride of iron, especially applicable to the cystic form of the disease, ligature of the thyroid arteries, excision of the isthmus, and extirpation of the whole or a part of the gland. This latter operation is one of difficulty, and when the entire gland has been removed the operation has been followed by a condition resembling myxoedema. In removing the organ great care must be taken to avoid tearing the capsule, as if this happens the gland- tissue bleeds profusely. The thyroid arteries should be ligatured before an attempt is made to remove the mass, and in ligaturing the inferior thyroids the position of the recurrent laryngeal nerve must be borne in mind, so as not to include it in the ligature. THE THYMUS GLAND. 1009 THE THYMUS GLAND. The thymus gland presents much resemblance in structure to other glandular organs, and is another of the organs which used formerly to be denominated ductless glands. The thymus gland is a temporary organ, attaining its full size at the end of the sec' /nd year, when it ceases to grow, and gradually dwindles, until at puberty it has almost disappeared. If examined when its growth is most active, it will be found to consist of two lateral lobes placed in close contact along the middle line, situated partly in the superior mediastinum, partly in the neck, and extending from the fourth costal cartilage upward as high as the lower border of the thyroid gland. It is covered by the sternum and by the origins of the Sterno- hyoid and Sterno-thyroid muscles. Below, it rests upon the pericardium, being separated from the arch of the aorta and great vessels by a layer of fascia. In the neck it lies on the front and sides of the trachea, behind the Sterno-hyoid and Sterno-thyroid muscles. The two lobes generally differ in size; they are Fig. 583.-1. Upper portion of the thymus of a foetal pig of 2" in length, showing the bud-like lobuli and glandular elements. 2. Cells of the thymus, mostly from a man. a. Free nuclei, b. Small cells, c. Larger. d. Larger, with oil-globules, from the ox. e,/. Cells completely filled with fat, at f without a nucleus, g, h. Concentric bodies, g. An encapsulated nucleated cell. h. A composite structure of a similar nature. occasionally united so as to form a single mass, and sometimes separated by an intermediate lobe. The thymus is of a pinkish-gray color, soft, and lobulated on its surfaces. It is about two inches in length, one and a half in breadth below, and about three or four lines in thickness. At birth it weighs about half an ounce. Structure.-Each lateral lobe is composed of numerous lobules held together by delicate areolar tissue, the entire gland being enclosed in an investing capsule of a similar but denser structure. The primary lobules vary in size from a pin's head to a small pea, and are made up of a number of small nodules or follicles which are irregular in shape and are more or less fused together, especially toward the interior of the gland. According to Watney, each follicle consists of a medullary and cortical portion, which differ in many essential particulars from each other. The cortical portion is mainly composed of lymphoid cells supported by a delicate reticulum. In addition to this reticulum, of which traces onlv are found in the medullary portion, there is also a network of finely-branched cells which is continuous with a similar network in the medullary portion. This network forms an adventitia to the blood-vessels. In the medullary portion there are but few lymphoid cells, but there are, especially toward the centre, granular cells and concentric corpuscles. The granular cells are rounded or flask-shaped masses attached (often by fibrillated extremities) to blood-vessels and to newly- formed connective tissue. The concentric corpuscles are composed of a central 1010 THE ORGANS OF VOICE AND RESPIRATION mass consisting of one or more granular cells, and of a capsule which is formed of epithelioid cells which are continuous with the branched cells forming the network mentioned above. Each follicle is surrounded by a capillary plexus from which vessels pass into the interior and radiate from the periphery toward the centre, and form a second zone just within the margin of the medullary portion. In the centre of the medulla there are very few vessels, and they are of minute size. Dr. Watney has recently made the important observation that haemoglobin is found in the thymus either in cysts or in cells situated near to or forming part / Vein. Artery. Concentric corpuscle. Artery.- ■Granular cells. -Artery. Vein. Vein.-- Artery.- Fig. 584.-Minute structure of the thymus gland. Follicle of injected thymus from calf, four days old, slightly diagrammatic, magnified about 50 diameters. The large vessels are disposed in two rings, one of which surrounds the follicle, the other lies just within the margin of the medulla. (Watney.) A and B. From thy- mus of camel, examined without addition of any reagent. Magnified about 400 diameters. A. Large colorless cell containing small oval masses of haemoglobin. Similar cells are found in the lymph-glands, spleen, and medulla of bone. B. Colored blood-corpuscles. of the concentric corpuscles. This haemoglobin varies from granules to masses exactly resembling colored blood-corpuscles, oval in the bird, reptile, and fish ; circular in all mammals except in the camel. Dr. Watney has also discovered in the lymph issuing from the thymus similar cells to those found in the gland, and, like them, containing haemoglobin either in the form of granules or masses. From these facts he arrives at the physiological conclusion that the thymus is one source of the colored blood-corpuscles. Vessels and Nerves.-The arteries supplying the thymus are derived from the internal mammary and from the superior and inferior thyroid. The veins terminate in the left innominate vein and in the thyroid veins. The lymphatics are of large size, arise in the substance of the gland, and are said to terminate in the internal jugular vein. The nerves are exceedingly minute; they are derived from the pneumogastric and sympathetic. Branches from the descendens hypo- glossi and phrenic reach the investing capsule, but do not penetrate into the sub- stance of the gland. THE URINARY ORGANS. THE KIDNEYS. milE Kidneys, two in number, are situated in the back part of the abdomen, and I are for the purpose of separating from the blood certain materials which, when dissolved in a quantity of water, also separated from the blood by the kid- neys, constitute the urine. They are placed in the loins, one on each side of the vertebral column, behind the peritoneum, and surrounded by a mass of fat and loose areolar tissue. Their upper extremity is on a level with the upper border of the twelfth dorsal vertebra, their lower extremity on a level with the third lumbar. The right kidney is usually on a slightly lower level than the left, probably on account of the vicinity of the liver. The kidneys rest on the lower part of the Diaphragm and the fascia covering the Quadratus lumborum and the Psoas magnus muscles. The right one is covered in front by the right lobe of the liver, the descending portion of the duodenum, and the ascending colon; the left one has in front the fundus of the stomach, the tail of the pancreas, and the descending colon. Each kidney is about four inches in length, two to two and a half in breadth, and rather more than one inch in thickness. The left is somewhat longer, though narrower, than the right. The weight of the kidney in the adult male varies from 4J ounces to 6 ounces, in the adult female from 4 ounces to 5| ounces. The com- bined weight of the two kidneys in proportion to the body is about 1 in 240. The kidney has a characteristic form. It is flattened on its sides, and pre- sents at one part of its circumference a hollow. It is larger at its upper than its lower extremity. It presents for examination two surfaces, two borders, and an upper and lower extremity. Its anterior surface is convex, looks forward and outward, and is partially covered by peritoneum. The upper part of this surface on the right side is in contact with the under surface of the right lobe of the liver, on which it produces a slight concave impression, the impressio renalis (page 952) ; below this the descending portion of the duodenum and the upper part of the ascending colon are connected to this surface by a quantity of loose areolar tissue. On the left side the upper part of the anterior surface of the kidney is in contact with the under surface of the stomach, and below this with the left extremity of the pan- creas, whilst the lower part is connected to the descending colon by loose areolar tissue. The posterior surface is flatter than the anterior, and is imbedded in areolar tissue which separates it from the Diaphragm covering the twelfth rib and from the anterior lamellae of the lumbar fascia covering the Quadratus lumborum mus- cle, and internally from the fascia covering the Psoas magnus muscle. The external border is convex, and is directed outward and backward toward the postero-lateral wall of the abdomen. On the left side it is in contact, at its upper part, with the spleen. 'Phe internal border is concave, and is directed forward and a little downward. It presents a deep longitudinal fissure bounded by a prominent overhanging ante- rior and posterior lip. This fissure is named the hilum, and allows of the passage of the vessels, nerves, and ureter into and out of the kidney. The superior extremity, directed slightly inward as well as upward, is thick 1011 1012 77/7; URINARY ORGANS. and rounded, and is surmounted by the suprarenal capsule, which covers also a small portion of the anterior surface. The inferior extremity, directed a little outward as well as downward, is smaller and thinner than the superior. It extends to within two inches of the crest of the ilium. At the hilum of the kidney the relative position of the main structures passing into and out of the kidney is as follows : the vein is in front, the artery in the middle, and the duct or ureter behind and toward the lower part. By a knowledge of these relations the student may distinguish between the right and left kidney. The kidney is to be laid on the table before the student on its posterior surface, with its lower extremity toward the observer-that is to say, with the ureter behind and below the other vessels; the hilum will then be directed to the side to which the kidney belongs. General Structure of the Kidney.-The kidney is surrounded by a distinct investment of fibrous tissue which forms a firm, smooth covering to the organ. It closely invests it, but can be easily stripped off, in doing which, however, numerous fine processes of connective tissue and small blood-vessels are torn through. Beneath this coat a thin wide-meshed network of unstriped muscular fibre forms an incomplete covering to the organ. When the fibrous coat is stripped off, the surface of the kidney is found to be smooth and even and of a deep-red color. In infants fissures extending for some depth may be seen on the surface of the organ, a remnant of the lobular construction of the gland. The kidney is dense in texture, but is easily lacerable by mechanical force. In order to obtain a knowledge of the structure of the gland, a vertical section must be made from its convex to its concave border, and the loose tissue and fat removed from around the vessels and the excretory duct (Fig. 585). It will be then seen that the kidney consists of a central cavity surrounded at all parts but one by the proper kidney-substance. This central cavity is called the sinus, and is lined by a pro- longation of the fibrous coat of the kidney, which enters through a longitudinal fissure, the hilum (before mentioned), which is situated at that part of the cavity which is not surrounded by kidney-structure. Through this fissure the blood-vessels of the kidney and its excretory duct pass, and therefore these structures, upon entering the kidney, are contained within the sinus. The excretory duct, or ureter, after entering, dilates into a wide, funnel-shaped sac named the pelvis. This divides into two or three tubular divisions, which subdivide into several short, truncated branches named calices or in- fundibula, all of which are contained in the central cavity of the kidney. The blood-vessels of the kidney, after passing through the hilum, are contained in the sinus or central cavity, lying between its lining membrane and the excretory apparatus, before entering the kidney-substance. This central cavity, as before mentioned, is surrounded on all sides except at the hilum by the substance of the kidney, which is at once seen to consist of two parts-viz. of an external granular investing part, which is called the cortical portion ; and of an internal part, the medullary portion, made up of a number of dark-colored pyramidal masses, with their bases resting on the cortical part and their apices converging toward the centre, where they form prominent papillae ■which project into the interior of the calices. Fig. 585.-Vertical section of kidney. THE KIDNEYS. 1013 The cortical substance is of a bright reddish-brown color, soft, granular, and easily lacerable. It is found everywhere immediately beneath the capsule, and is seen to extend in an arched form over the base of each medullary pyramid. The part separating the sides of any two pyramids through which the arteries and nerves enter, and the veins and lymphatics emerge, from the kidney, is called a cortical column or column of Bertini (a, a' Fig. 585); whilst that portion which stretches from one cortical column to the next, and intervenes between the base of the pyramid and the capsule (which is marked by the dotted line extending from A to a' in Fig. 585), is called a cortical arch, the depth of which varies from a third to half an inch. The medullary substance, as before stated, is seen to consist of pale red-colored, striated, conical masses, the pyramids of Malpighi,the number of which, varying from eight to eighteen, correspond to the number of lobes of which the organ in the foetal state is composed. The base of each pyramid is surrounded by a cortical arch, and directed toward the circumference of the kidney; the sides are contigu- ous with the cortical columns ; whilst the apex, known as the papilla or mammilla of the kidney, projects into one of the calices of the ureter. These two parts, cortical and medullary, so dissimilar in appearance, are very similar in structure, being made up of urinary tubes and blood-vessels united and bound together by a connecting matrix or stroma. Minute Anatomy.-The tubuli uriniferi, of which the kidney is for the most part made up, commence in the cortical portion of the kidney, and, after pursuing a very circuitous course through the cortical and med- ullary parts of the kidney, finally terminate at the apices of the Malpighian pyramids by open mouths (Fig. 586), so that the fluid which they contain is emptied into the dilated extremity of the ureter con- tained in the sinus of the kidney. If the surface of one of the papillae is examined with a lens, it will be seen to be studded over with a number of small depres- sions from sixteen to twenty in number, and in a fresh kidney, upon pressure being made, fluid will be seen to exude from these depressions. They are the orifices of the tubuli uriniferi, which terminate in this situation. They commence in the cortical portion of the kidney as the Malpighian bodies, which are small rounded masses, varying in size, but of an average of about of an inch in diameter. They are of a deep-red color, and are found only in the cortical portion of the kidney. Each of these little bodies is composed of two parts-a central glomerulus of vessels, called a Mal- pighian tuft, and a membranous envelope, the Mal- pighian capsule, or capsule of Bowman, which latter is a small pouch-like commencement of a uriniferous tubule. The Malpighian tuft, or vascular glomerulus, is a network of convoluted capillary blood-vessels held together by scanty connective tissue and grouped into from two to five lobules. This capillary network is derived from a small arterial twig, the afferent vessel, which pierces the wall of the capsule, generally at a point opposite that at which the latter is connected with the tube ; and the resulting vein, the efferent vessel, emerges from the capsule at the same point. The afferent vessel is usually the larger of the two (Fig. 587). The Malpighian or Bowman s capsule, which surrounds the glomerulus, is formed of a hyaline membrane sup- ported by a small amount of connective tissue which is continuous with the con- nective tissue of the tube. It is lined on its inner surface by a layer of squa- Fig. 586.--a, a. Malpighian bodies, b, b. Margin of medullary- structure. c; c, c. Loops of Henle. D, D, D. Straight tubes cut off. e. Commencing straight tubes, f. Termination of straight tube. 1014 THE URINARY ORGANS. mous epithelial cells which are reflected from the lining membrane on to the glomerulus at the point of entrance or exit of the afferent and efferent vessels. The whole surface of the glomerulus is covered with a continuous layer of the same cells on a delicate supporting membrane, which with the cells dips in between the lobules of the glomerulus, closely surrounding them (Fig. 588). Thus, between the glomerulus and the capsule a space is left, forming a cavity lined by a con- tinuous layer of cells, which varies in size according to the state of secretion and the amount of fluid present in it. The cells, as above stated, are -squamous in Fig. 587.-Minute structure of kidney Fig. 588.-Malpighian body. the adult, but in the foetus and young subject they are polyhedral or even co- lumnar. The tubuli uriniferi, commencing in the Malpighian bodies, in their course present many changes in shape and direction, and are contained partly in the medullary and partly in the cortical portions of the organ. At their junction with the Malpighian capsule they present a somewhat constricted portion which is termed the neck. Beyond this the tube becomes convoluted, and pursues a con- siderable course in the cortical structure, constituting the proximal convoluted tube. After a time the convolutions disappear, and the tube approaches the medullary portion of the kidney in a more or less spiral manner. This section of the tube has been called the spiral tube of Schachowa. Throughout this portion of their course the tubuli uriniferi have been contained entirely in the cortical structure, and have presented a pretty uniform calibre. They now enter the medullary portion, and suddenly become much smaller, quite straight in direction, and dip down for a variable depth into the pyramids, constituting the descending limb of Henle's loop. Bending on themselves, they form a kind of loop, the loop of Henle, and, reascending, become suddenly enlarged and again spiral in direction, forming the ascending limb of Henle's loop, and re-enter the cortical structure. This portion of the tube does not present a uniform calibre, but becomes narrower as it ascends and irregular in outline. As a narrow tube it enters the cortex and ascends for a short distance, when it again becomes dilated, irregular, and angular. This section is termed the irregular tubule; it terminates in a convoluted tube which exactly resembles the proximal convoluted tubule, and is called the distal convoluted tubule. This again terminates in a narrow curved tube which enters the straight or collecting tube. Each straight, otherwise called a collecting or receiving, tube commences by a small orifice on the summit of one of the papillae, thus opening and discharging its contents into the interior of one of the calices. Traced into the substance of the pyramid, these tubes are found to run from apex to base, dividing dichotomously in their course and slightly diverging from each other. Thus dividing and sub- dividing, they reach the base of the pyramid, and enter the cortical structure greatly increased in number. Upon entering the cortical portion they continue a straight course for a variable distance, and are arranged in groups called medullary THE KIDNEYS. 1015 rays, several of these groups corresponding to a single pyramid. The tubes in the centre of the group are the longest, and reach almost to the surface of the kidney, Distal conyo- luted tubule. Curved collecting tubule. Malpighian \ corpuscle. Neck.' Proximal I convoluted >■ tubule.) Irregular L tubule. (Spired part of ascending L limb. Spiral tubule of '\ Schachoua. j Straight ] collecting tube. J Ascending limb. Descending limb of Henle's loop. Fig. 589-Uriniferous tube. For the sake of clearness the epithelial cells have been represented more highly magnified than the tubes in which they are contained. while the external ones are shorter, and advance only a short distance into the cortex. In consequence of this arrangement the cortical portion presents a number of conical masses, the apices of which reach the periphery of the organ, and the bases are applied to the medullary portion. These are termed the pyramids of Ferrein. As they run through the cortical portion the straight tubes receive on either side the curved extremity of the convoluted tubes, which, as stated above, commence at the Malpighian bodies. It will be seen from the above description that there is a continuous series of tubes from their commencement in the Malpighian bodies to their termination at the orifices on the apices of the pyramids of Malpighi, and that the urine, the secretion of which commences in the capsule, finds its way through these tubes into the calices of the kidney, and so into the ureter. Commencing at the capsule, the tube first presents a narrow constricted portion, (1) the neck. 2. It forms a wide convoluted tube, the proximal convoluted tube. 3. It becomes spiral, the spiral tubule of Schachowa. 4. It enters the medullary structure as a narrow, straight tube, the descending limb of Henle's loop. 5. Forming a loop and becoming dilated, it ascends somewhat spirally, and, gradually diminishing in calibre, again enters the cortical structure, the ascending limb of Henle's loop. 6. It now becomes irregular and angular in outline, the irregular tubule. 7. It then becomes convoluted, the distal convoluted tubule. 8. Diminishing in size, it forms a curve, the curved tubule. 9. Finally, it joins a straight tube, the straight collecting tube, which is continued downward through the medullary substance to open at the apex of a pyramid. The Tubuli Uriniferi: their Structure.-The tubuli uriniferi consist of base- 1016 THE URINARY ORGANS. ment membrane lined with epithelium. The epithelium varies considerably in different sections of the uriniferous tubes. In the neck the epithelium is con- tinuous with that lining the Malpighian capsule, and, like it, consists of flattened cells with an oval nucleus (Fig. 589 a). The cells are, however, very indistinct and difficult to trace, and the tube has here the appearance of a simple basement membrane unlined by epithelium. In the proximal convoluted tubule and the spiral tubule of Schachowa the epithelium is polyhedral in shape, the sides of the cells not being straight, but fitting into each other, and in some animals so fused Fig. 590.1-Longitudinal section of Henle's descending limb. a. Membrana propria, b. Epithelium. Fig. 591.-Longitudinal section of straight tube. a. Cylindrical or cubical epithelium. b. Membrana propria. together that it is impossible to make out the lines of junction. In the human kidney the cells often present an angular projection of the surface next the base- ment membrane. These cells are made up of more or less rod-like fibres, which rest by one extremity on the basement membrane, whilst the other projects toward the lumen of the tube. This gives to the cells the appearance of distinct striation (Heidenhain) (Fig. 589 b). In the descending limb of Henle's loop the epithelium resembles that found in the Malpighian capsule and the commencement of the tube, consisting of flat transparent epithelial plates with an oval nucleus (Figs. 589 A, 590). In the ascending limb, on the other hand, the cells partake more of the character of those described as existing in the proximal convoluted tubule, being polyhedral in shape and presenting the same appearance of striation. The nucleus, however, is not situated in the centre of the cell, but near the lumen (Fig. 589 c). After the ascending limb of Henle's loop becomes narrower upon entering the cortical structure, the striation appears to be confined to the outer part of the cell; at all events, it is much more distinct in this situation, the nucleus, which appears flattened and angular, being still situated near the lumen (Fig. 589 d). In the irregular tubule the cells undergo a still farther change, becoming very angular, and presenting thick bright rods or markings, which render the striation much more distinct than in any other section of the urinary tubules (Fig. 589 h). In the distal convoluted tubule the epithelium appears to be identical with that which has been described as existing in the proximal con- voluted tubule (Fig. 589 b). In the curved tubule, just before its entrance into the straight collecting tube, the epithelium varies greatly as regards the shape of the cells, some being angular with short processes, others spindle-shaped, others polyhedral (Fig. 589 e). In the straight tubes the epithelium is more or less columnar; in its papillary portion the cells are distinctly columnar and transparent (Figs. 591, 592), but as the tube approaches the cortex the cells are less uniform in shape; some are polyhedral, and others angular with short processes (Fig. 589 F and g). 1 From the Handbook for the Physiological Laboratory. THE KIDNEYS. 1017 The Renal Blood-vessels.-The kidney is plentifully supplied with blood by the renal artery, a large offset of the abdominal aorta. Previously to entering Fig. 592.-Transverse section of pyramidal substance of kidney of pig, the blood-vessels of which are injected. a. Large collecting tube cut across, lined with cylindrical epithelium, b. Branch of collecting tube cut across, lined with epithelium with shorter cylinders, c and d. Henle's loops cut across, e. Blood-vessels cut across. i>. Connective-tissue ground-substance. the kidney, each artery divides into four or five branches, which are distributed to its substance. At the hilum these branches lie between the renal vein and ureter, the vein being usually in front, the ureter behind. Each vessel gives off some small branches to the suprarenal capsules, the ureter, and the sur- Fig. 593.-Diagrammatical sketch of kidney, Fig. 594.-A portion of Fig. 593 enlarged. (The references are the same.) a, a. Proper renal artery and vein, the former giving off the renal afferent®, the latter receiving the renal efferents, b, b. Interlobular artery and vein, the latter commencing from the stellate veins, and receiving branches from the plexus around the tubuli contorti, the former giving off renal afferents. c. Straight tube, sur- rounded by tubuli contorti, with which it communicates, as more fully shown in Fig. 586. d. Margin of medul- lary substance, e, e, e. Receiving tubes cut off. f,/. Arteriolae et venae rectae, the latter arising from (g) the plexus at the medullary apex. rounding cellular tissue and muscles. Frequently there is a second renal artery, which is given off from the abdominal aorta at a lower level, and supplies the lower portion of the kidney. It is termed the inferior renal artery. The branches of the renal artery whilst in the sinus give off a few twigs for the nutrition of the surrounding tissues, and terminate in the arterice proprice renales, which enter the kidney proper in the columns of Bertini. Two of these pass to each pyramid of Malpighi and run along its sides for its entire length, 1018 THE URINARY ORGANS. giving off as they advance the afferent vessels of the Malpighian bodies in the columns. Having arrived at the bases of the pyramids, they make a bend in their course, so as to lie between the bases of the pyramids and the cortical arches, where they break up into two distinct sets of branches devoted to the supply of the remaining portions of the kidney. The/W set, the interlobular arteries (Figs. 593, 594 b), are given off at right angles from the side of the arteriae proprise re- nales looking toward the cortical substance, and, passing directly outward between the pyramids of Ferrein, they reach the capsule, where they terminate in the capillary network of this part. In their outward course thev give off lateral branches; these are the afferent vessels for the Malpighian bodies (see page 1014), and, having pierced the capsule, end in the Malpighian tufts. From each tuft the corresponding renal efferent arises, and, having made its egress from the capsule near to the point where the afferent ves- sel entered, anastomoses with other efferents from other tufts, and contributes to form a dense venous plexus around the adjacent urin- ary tubes (Fig. 595). The second set of branches from the arteriae propiae renales are for the supply of the medul- lary pyramids, which they enter at their bases; and, passing straight through their substance to their apices, terminate in the venous plex- uses found in that situation. They are called the arteriole? rectce (Figs. 593, 594 f). The Renal Veins arise from three sources-the veins beneath the capsule, the plexuses around the tubuli contorti in the cortical arches, and the plexuses situated at the apices of the pyramids of Malpighi. The veins beneath the capsule are stellate in arrangement, and are derived from the capillary network of the capsule, into which the terminal branches of the interlobular arteries break up. These join to form the vence interlobular es, which pass inward between the pyramids of Ferrein, receive branches from the plexuses around the tubuli contorti, and, having arrived at the bases of the Malpighian pyramids, join with the venae rectae, next to be described (Figs. 593, 594 6). The Fente Rectce are branches from the plexuses at the apices of the medullary pyramids, formed by the terminations of the arteriolae rectae. They pass outward in a straight course between the tubes of the medullary structure, and joining, as above stated, the venae interlobulares, form the proper renal veins (Figs. 593,594/). These vessels, Vence Proprice Renales, accompany the arteries of the same name, running along the entire length of the sides of the pyramids ; and, having received in their course the efferent vessels from the Malpighian bodies in the cortical structure adjacent, quit the kidney substance to enter the sinus. In this cavity they inosculate with the corresponding veins from the outer pyramids to form the renal vein, which emerges from the kidney at the hilum and opens into the inferior vena cava, the left being longer than the right, from having to cross in front of the abdominal aorta. Nerves of the Kidney.-The nerves of the kidney, although small, are about fifteen in number. They have small ganglia developed upon them, and are derived from the renal plexus, which is formed by branches from the solar plexus, the lower and outer part of the semilunar ganglion and aortic plexus, and from the lesser and smallest splanchnic nerves. They communicate with the spermatic plexus, a circumstance which may explain the occurrence of pain in the testicle in affections of the kidney. So far as they have been traced, they seem to accompany Fig. 595.-Diagrammatic representation of the blood-vessels in the substance of the cortex of the kidney, m. Region of the medullary ray. b. Region of the tortuous portion of the tubules, ai. Arteria inter- lobularis. vi. Vena interlobularis. va. Vas afferens. gl. Glomerulus, ve. Vas efferens. vz. Venous twig of the interlobularis. (From Ludwig, in Stricker's Handbook.) THE KIDNEYS. 1019 the renal artery and its branches, but their exact mode of termination is not known. The lymphatics consist of a superficial and deep set which terminate in the lumbar glands. Connective Tissue, or Intertubular Stroma.-Although the tubules and vessels are closely packed, a certain small amount of connective tissue, continuous with the capsule, binds them firmly together. This tissue was first described by Goodsir, and subsequently by Bowman. Ludwig and Zawarykin have observed distinct fibres passing around the Malpighian bodies, and Henle has seen them between the straight tubes composing the medullary structure. Surface Form.-The kidneys, being situated at the back part of the abdominal cavity and deeply placed, cannot be felt unless enlarged or misplaced. They are situated on the confines of the epigastric and umbilical regions internally, with the hypochondriac and lumbar regions externally. The left is somewhat higher than the right. According to Morris, the position of the kidney may be thus defined: Anteriorly: "1. A horizontal line through the umbilicus is below the lower edge of each kidney. 2. A vertical line carried upward to the costal arch from the middle of Poupart's ligament has one-third of the kidney to its outer side and two-thirds to its inner side-i. e. between this line and the median line of the body." In adopting these lines it must be borne in mind that the axes of the kidneys are not vertical, but oblique, and if con- tinued upward would meet about the ninth dorsal vertebra. Posteriorly : The upper end of the left kidney would be defined by a line drawn horizontally outward from the spinous process of the eleventh dorsal vertebra, and its lower end by a point two inches above the iliac crest. The right kidney would be half to three-quarters of an inch lower. Morris lays down the following rules for indicating the position of the kidney on the posterior surface of the body : "1. A line par- allel with, and one inch from, the spine, between the lower edge of the tip of the spinous pro- cess of the eleventh dorsal vertebra and the lower edge of the spinous process of the third lumbar vertebra. 2. A line from the top of this first line outward at right angles to it for 2| inches. 3. A line from the lower end of the first transversely outward for 2f inches. 4. A line parallel to the first and connecting the outer extremities of the second and third lines just described. ' ' The hilum of the kidney lies about two inches from the middle line of the back, at the level of the spinous process of the first lumbar vertebra. Surgical Anatomy.-The kidney is imbedded in a large quantity of loose fatty tissue, and is but slightly covered by peritoneum ; hence rupture of this organ is not nearly so serious an accident as rupture of the liver or spleen, since the extravasation of blood and urine which follows is outside the peritoneal cavity. Occasionally the kidney may be bruised by blows in the loin or by being compressed between the lower ribs and the ilium when the body is violently bent forward. This is followed by a little transient haematuria, which, however, speedily passes oft'. Occasionally, when rupture involves the pelvis of the kidney or the commencement of the ureter, this duct may become blocked, and hydronephrosis follow. The loose cellular tissue around the kidney may be the seat of suppuration, constituting perinephritic abscess. This may be due to injury, to disease of the kidney itself, or to extension of inflammation from neighboring parts. It may burst into the pleura, constituting empyema; into the colon or bladder; or may point externally in the groin or loin. Tumors of the kidney, of which, perhaps, sarcoma in children is the most common, may be recognized by their position and fixity; by the resonant colon lying in front of it; by their not moving with respiration ; and by their rounded outline, not presenting a notched anterior margin like the spleen, with which they are most likely to be confounded. The examination of the kidney should be bimanual; that is to say, one hand should be placed in the flank and firm pressure made forward, while the other hand is buried in the abdominal wall just external to the semilunar line. Manipulation of the kidney frequently produces a peculiar sickening sensation, with sometimes faintness. The kidney is mainly held in position by the mass of fatty matter in which it is imbedded and over which the peritoneum is stretched. If this fatty matter is loose or lax or is absorbed, the kidney may become movable and may give rise to great pain. This condition occurs, there- fore, in badly-nourished people or in those who have become emaciated from any cause, and is more common in women than in men. It must not be confounded with the floating kidney: this is a congenital condition due to the development of a meso-nephron, which permits the organ to move more or less freely. The two conditions cannot, however, be distinguished until the abdomen is opened or the kidney explored from the loin. The kidney has, of late years, been frequently the seat of surgical interference. It may be exposed for exploration or the evacuation of pus (nephrotomy); it maybe incised for the removal of stone (nephro-lithotomy); it maybe sutured when movable or floating (nephrorraphy); or it may be removed (nephrectomy). The kidney may be exposed either by a lumbar or abdominal incision. The lumbar opera- tion is the one which is generally adopted, unless in cases of very large tumors or of wandering kidneys with a loose meso-nephron, on account of the advantages which it possesses of not opening the peritoneum and of affording admirable drainage. It may be performed either by an oblique, a vertical, or a transverse incision. Perhaps the preferable, as affording the best 1020 THE URINARY ORGANS. means for exploring the whole surface of the kidney, is an incision from the tip of the last rib backward to the edge of the Erector spinae. This incision must not be quite parallel to the rib, but its posterior end must be at least three-quarters of an inch below it, lest the pleura be wounded. This cut is quite sufficient for an exploration of the organ. Should it require removal, a vertical incision can be made downward to the crest of the ilium, along the outer border of the Quadratus lumborum. The structures divided are the skin, the superficial fascia with the cutaneous nerves, the deep fascia, the posterior border of the External oblique muscle of the abdomen, and the outer border of the Latissimus dorsi; the Internal oblique and the posterior aponeurosis of the Transversalis muscle ; the outer border of the Quadratus lumborum, and the deep layer of the transversalis aponeurosis, and the transversalis fascia. The fatty tissue around the kidney is now exposed to view, and must be separated by the fingers or a director in order to reach the kidney. The abdominal operation is best performed by an incision in the linea semilunaris on the side of the kidney to be removed, as recommended by Langenbuch. The incision is made of varying length according to the size of the kidney; its mid-point should be on a level with the umbilicus. The abdominal cavity is opened. The intestines are then held aside and the outer layer of the meso-colon opened, so that the fingers can be introduced behind the peritoneum and the renal vessels sought for. These are then to be ligatured; if tied separately, care must be taken to ligature the artery first. The kidney must now be enucleated, and the vessels and ureter divided, and the latter tied or, if thought necessary, stitched to the edge of the wound. THE URETERS. The Ureters are the two tubes which conduct the urine from the kidneys into the bladder. They commence within the sinus of the kidney by a number of short truncated branches, the calices or infundibula, which unite either directly or indirectly to form a dilated pouch, the pelvis, from which the ureter, after passing through the hilum of the kidney, descends to the bladder. The calices are cup-like tubes encircling the apices of the Malpighian pyramids; but inasmuch as one calyx may include two or even more papillae, their number is generally less than the pyramids themselves, the former being from seven to thirteen, whilst the latter vary from eight to eighteen. These calices converge into two or three tubular divisions which by their junction form the pelvis or dilated portion of the ureter. The portion last mentioned, where the pelvis merges into the ureter proper, is found opposite the spinous process of the first lumbar vertebra, in which situation it is accessible behind the peritoneum (see Fig. 543, page 942). The ureter proper is a cylindrical membranous tube, about sixteen inches in length and of the diameter of a goosequill, extending from the pelvis of the kidney to the bladder. Its course is obliquely downward and inward through the lumbar region into the cavity of the pelvis, where it passes downward, forward, and inward across that cavity to the base of the bladder, into which it then opens by a constricted orifice, after having passed obliquely for nearly an inch between its muscular and mucous coats. Relations.-In its course it rests upon the Psoas muscle, being covered by the peritoneum, and crossed obliquely, from within outward, by the spermatic vessels; the right ureter lying close to the outer side of the inferior vena cava. Opposite the first piece of the sacrum it crosses either the common or external iliac artery, lying behind the ileum on the right side and the sigmoid flexure of the colon on the left. In the pelvis it enters the posterior false ligament of the bladder below the obliterated hypogastric artery, the vas deferens in the male passing between it and the bladder. In the female the ureter passes along the sides and cervix of the uterus and upper part of the vagina. At the base of the bladder it is situated about two inches from its fellow, lying, in the male, about an inch and a half behind the base of the prostate, at the posterior angle of the trigone. Structure.-The ureter is composed of three coats-a fibrous, muscular, and mucous. The fibrous coat is the same throughout the entire length of the duct, being continuous at one end with the capsule of the kidney at the floor of the sinus, whilst at the other it is lost in the fibrous structure of the bladder. In the pelvis of the kidney the muscular coat consists of two layers, longitudinal and circular : the longitudinal fibres become lost upon the sides of the papillae at THE SUPRARENAL CAPSULES. 1021 the extremities of the calices; the circular fibres may be traced surrounding the medullary structure in the same situation. In the ureter proper the muscular fibres are very distinct, and are arranged in three layers-an external longitudinal, a middle circular, and an internal layer, less distinct than the other two, but having a general longitudinal direction. According to Kblliker, this internal layer is only found in the neighborhood of the bladder. The mucous coat is smooth, and presents a few longitudinal folds which become effaced by distension. It is continuous with the mucous membrane of the bladder below, whilst it is prolonged over the papillae of the kidney above. Its epithelium is of a peculiar character, and resembles that found in the bladder. It is known by the name of " transitional " epithelium. It consists of several layers of cells, of which the innermost-that is to say, the cells in contact with the urine-are quadrilateral in shape, with a concave margin on their outer surface, into which fits the rounded end of the cells of the second layer. These, the inter- mediate cells, more or less resemble columnar epithelium, and are pear-shaped, with a rounded internal extremity which fits into the concavity of the cells of the first layer, and a narrow external extremity which is wedged in between the cells of the third layer. The external or third layer consists of conical or oval cells varying in number in different parts, and presenting processes which extend down into the basement membrane. The arteries supplying the ureter are branches from the renal, spermatic, internal iliac, and inferior vesical. The nerves are derived from the inferior mesenteric, spermatic, and pelvic plexuses. The Suprarenal Capsules were formerly classified, together with the spleen, thymus, and thyroid, under the head of " ductless glands," as they have no excretory duct. They are two small flattened glandular bodies, of a yellowish color, situated at the back part of the abdomen, behind the peritoneum and immediately in front of the upper part of each kidney; hence their name. The right one is somewhat triangular in shape, bearing a resemblance to a cocked hat; the left is more semilunar, and usually larger and higher than the right. They vary in size in different individuals, being sometimes so small as to be scarcely detected; their usual size is from an inch and a quarter to nearly two inches in length, rather less in width, and from two to three lines in thickness. Their average weight is about a drachm each. Relations.-The relations of the suprarenal capsules differ on the two sides of the body. The right suprarenal presents on its anterior surface two areas: along its upper and inner borders a depressed area, which is in contact in front with the under surface of the right lobe of the liver, and along its inner border with the inferior vena cava (Rolleston), and behind rests on the crus of the Diaphragm ; over the remainder of the anterior surface is an elevated area, which is covered in front by peritoneum passing from the upper part of the kidney to the under sur- face of the liver, and behind rests on the upper and inner part of the kidney. The left suprarenal is in contact by its anterior surface, superiorly, with the spleen; below and internal to this it is in contact with the peritoneum forming the lesser sac, which separates it from the cardiac extremity of the stomach ; and at its lower part it is covered by the pancreas and splenic artery, and is therefore not in contact with the peritoneum. By its posterior surface, at its outer and back part, it rests upon the kidney, whilst below and internally it is in contact with the left crus of the Diaphragm. The surface of the suprarenal gland is sur- rounded by areolar tissue containing much fat, and closely invested by a thin fibrous coat, which is difficult to remove on account of the numerous fibrous pro- cesses and vessels which enter the organ through the furrows on its anterior sur- face and base. Small accessory suprarenals are often to be found in the connective tissue THE SUPRARENAL CAPSULES. 1022 THE URINARY ORGANS. around the suprarenals. The smaller of these, on section, show a uniform surface but in some of the larger a distinct medulla can be made out. Structure.-On making a perpendicular section, the gland is seen to consist of two substances-external or cortical and internal or medullary. The former which constitutes the chief part of the organ, is of a deep-yellow color. The medullary sub- stance is soft, pulpy, and of a dark-brown or black color, whence the name atrabiliary cap- sules formerly given to these organs. In the centre is often seen a space, not natural, but formed by the breaking down after death of the medullary substance. Connective tissue. -Capsule. Zona glomerulosa. " Zona \ fasciculata. Gland cylinders. Fig. 597. Framework. * Zona reticularis. -Nuclei. Capillary. I Medulla. Gland cells. Fig. 596.-Vertical section of the suprarenal capsule. From Elberth, in Stricker's Manual. Fig. 598. The cortical portion consists chiefly of narrow columnar masses placed perpen- dicularly to the surface. This arrangement is due to the disposition of the cap- sule, which sends into the interior of the gland processes passing in vertically and communicating with each other by transverse bands so as to form spaces which open into each other. These spaces are of slight depth near the surface of the organ, so that there the section somewhat resembles a net; this is termed the zona glomerulosa; but they become much deeper or longer farther in, so as to resemble pipes or tubes placed endwise, the zona fasciculata. Still deeper down, near the medullary part, the spaces become again of small extent; this is named the zona reticularis. These processes or trabeculae, derived from the capsule and forming the framework of the spaces, are composed of fibrous connective tissue with longitudinal bundles of unstriped muscular fibres. Within the interior of the spaces are contained groups of polyhedral cells, which are finely granular in appearance, and contain a spherical nucleus, and not unfrequently fat-molecules. These groups of cells do not entirely fill the spaces in which they are contained. THE BLADDER. 1023 but between them and the trabeculae of the framework is a channel which is believed to be a lymph-path or sinus, and which communicates with certain passages between the cells composing the group. The lymph-path is supposed to open into a plexus of efferent lymphatic vessels which are contained in the capsule. In the medullary portion the fibrous stroma seems to be collected together into a much closer arrangement, and forms bundles of connective tissue which are loosely applied to the large plexus of veins of which this part of the organ mainly consists. In the interstices lie a number of cells compared by Frey to those of columnar epithelium. They are coarsely granular, do not contain any fat- molecules, and some of them are branched. Luschka has affirmed that these branches are connected with the nerve-fibres of a very intricate plexus which is found in the medulla: this statement has not been verified by other observers, 'for the tissue of the medullary substance is less easy to make out than that of the cortical, owing to its rapid decomposition. The numerous arteries which enter the suprarenal bodies from the sources mentioned belowr penetrate the cortical part of the gland, where they break up into capillaries in the fibrous septa, and these converge to the very numerous veins of the medullary portion, which are collected together into the suprarenal vein, which usually emerges as a single vessel from the centre of the gland. The arteries supplying the suprarenal capsules are numerous and of large size; they are derived from the aorta, the phrenic, and the renal; they sub- divide into numerous minute branches previous to entering the substance of the gland. The suprarenal vein returns the blood from the medullary venous plexus, and receives several branches from the cortical substance; it opens on the right side into the inferior vena cava, on the left side into the renal vein. The lymphatics terminate in the lumbar glands. The nerves are exceedingly numerous : they are found chiefly, if not entirely, in the medulla, and are derived from the solar and renal plexuses, and, according to Bergmann, from the phrenic and pneumogastric nerves. They have numerous small ganglia developed upon them, from which circumstance the organ has been conjectured to have some function in connection with the sympathetic nervous system. THE CAVITY OF THE PELVIS. The cavity of the pelvis is that part of the general abdominal cavity which is below the level of the linea ilio-pectinea and the promontory of the sacrum. Boundaries.-It is bounded behind by the sacrum, the coccyx, the Pyriformis muscle, and the great sacro-sciatic ligaments ; in front and at the sides by the ossa pubis and ischia, covered by the Obturator muscles ; above, it communicates with the cavity of the abdomen; and below, the outlet is closed by the triangular ligament, the Levatores ani and Coccygei muscles, and the visceral layer of the pelvic fascia, which is reflected from the wall of the pelvis on to the viscera. Contents.-The viscera contained in this cavity are-the urinary bladder, the rectum, and some of the generative organs peculiar to each sex, and some convo- lutions of the small intestines ; they are partially covered by the peritoneum, and supplied with blood-vessels, lymphatics, and nerves. The bladder is the reservoir for the urine. It is a musculo-membranous sac situated in the pelvis, behind the pubes, and in front of the rectum in the male, the uterus and vagina intervening between it and that intestine in the female. The shape, position, and relations of the bladder are greatly influenced by age, sex, and the degree of distension of the organ. During infancy it is conical in shape, and projects above the upper border of the os pubis into the hypogastric region. In the adult, when quite empty and contracted, it is a small triangular THE BLADDER. 1024 THE URINARY ORGANS. sac, placed deeply in the pelvis, flattened from before backward, its apex reaching as high as the upper border of the symphysis pubis. When slightly distended it has a rounded form, and is still contained within the pelvic cavity; and when greatly distended it is ovoid in shape, rising into the abdominal cavity, and often extending nearly as high as the umbilicus. It is larger in its vertical diameter than from side to side, and its long axis is directed from above obliquely downward and backward, in a line directed from some point between the os pubis and umbilicus (according to its distension) to the end of the coccyx. The bladder, when distended, is slightly curved forward toward the anterior wall of the abdomen, so as to be more convex behind than in front. In the female it is larger in the transverse than in the vertical diameter, and its capacity is said to be greater than in the male.1 Prostatic portion of urethra. Suspensory tig. Ejaculatory duct/ • Urethra. SPHINCTER ANI. * Prostatics sinuses. Cowper's gland. Crus penis. Membranous portion of urethra. '/ Fossa -navicularis. Prepuce. Fig. 599.-Vertical section of bladder, penis, and urethra. When moderately distended it measures about five inches in length and three inches across, and the ordinary amount which it contains is about a pint. The bladder is divided into a summit, body, base, and neck. The summit or apex of the bladder is rounded and directed forward and upward; it is connected to the umbilicus by a fibro-muscular cord, the urachus. The summit of the bladder behind the urachus is covered by peritoneum, w'hilst the portion in front of the urachus has no peritoneal covering, but rests against the abdominal wall. The urachus is the obliterated remains of a tubular canal -which exists in the embryo, and connects the cavity of the bladder with a membranous sac placed external to the abdomen, opposite the umbilicus, called the allantois. It passes upward from the apex of the bladder between the transversalis fascia and peri- toneum, becoming thinner as it ascends. On each side of it is placed a fibrous 1 According to Henle, the bladder is considerably smaller in the female than in the male. THE BLADDER. 1025 cord, the obliterated portion of the hypogastric artery, which, passing upward from the side of the bladder, approaches the urachus above its summit. In the infant, at birth, it is occasionally found pervious, so that the urine escapes at the umbilicus, and calculi have been found in its canal. The body of the bladder is not covered in front by peritoneum, but is in relation with the triangular ligament, the posterior surface of the symphysis pubis, the Internal obturator muscles, and, when distended, with the abdominal parietes. The posterior surface is covered by peritoneum. It corresponds, in the male, with the rectum; in the female, with the uterus, some convolutions of the small intestine being interposed. The side of the bladder is crossed obliquely from below, upward and forward,' Vermiform appendix. External iliac artery. Anterior crural ! nerve. External oblique muscle. V I M Profunda vessels, levator anl Corpora Urethra, cavernosa. Fig. 600.-Frontal section of the lower part of the abdomen. Viewed from the front. (Braune.) by the obliterated hypogastric artery; above and behind this cord the bladder is covered by peritoneum, but below and in front of it the serous covering is wanting, and it is connected to the pelvic fascia. The vas deferens passes, in an arched direction, from before backward, along the side of the bladder, toward its base, crossing in its course the obliterated hypogastric artery, and passing along the inner side of the ureter. The base of the bladder is directed downward and backward. It varies in extent according to the state of distension of the organ, being very broad when full, but much narrower when empty. In the male it rests upon the second portion of the rectum, from which it is separated by a reflection of the recto-vesical fascia. It is covered posteriorly, for a slight extent, by the peritoneum, which is reflected from it upon the rectum, forming the recto-vesical fold. The portion of the bladder in relation with the rectum corresponds to a triangular space bounded 1026 THE URINARY ORGANS. in front by the prostate gland, behind by the recto-vesical fold of the peritoneum, and on each side by the vesicula seminalis and vas deferens. It is separated from direct contact with the rectum by the recto-vesical fascia. When the bladder is very full the peritoneal fold is raised with it, and the distance between its reflection and the anus is about four inches ; but this distance is much diminished when the bladder is empty and contracted. In the female the base of the bladder lies in contact with the lower part of the cervix uteri, is adherent to the anterior wall of the vagina, and separated from the upper part of the anterior surface of the cervix uteri by a fold of the peritoneum. The so-called neck (cervix) of the bladder is the point of commencement of the urethra; there is, however, no tapering part, which would constitute a true Peritoneum. Vesicula seminalis. Symphysis pubis. Dorsal vein of penis. Septum pectiniforme. Urethra. gland. J SPHINCTER ANI. Accelerator urinse. Prostatic sinus. Fjg. 601.-Vertical median section of the male pelvis. (Henle.) neck, but the bladder suddenly contracts to the opening of the urethra. In the male its direction is oblique in the erect posture, and it is surrounded by the prostate gland. In the female its direction is obliquely downward and forward. Ligaments.-The bladder is retained in its place by ligaments which are divided into true and false. The true ligaments are five in number : two anterior, two lateral, and the urachus. The false ligaments, also five in number, are formed by folds of the peritoneum. The anterior ligaments (pubo-prostatic) extend from the back of the os pubis, one on each side of the symphysis, to the front of the neck of the bladder, over the upper surface of the prostate gland. These ligaments are formed by the recto- vesical fascia, and contain a few muscular fibres prolonged from the bladder. THE BLADDER. 1027 The lateral ligaments, also formed by the recto-vesical fascia, are broader and thinner than the preceding. They are attached to the lateral parts of the prostate and to the sides of the base of the bladder. The urachus is the fibro-muscular cord already mentioned, extending between the summit of the bladder and the umbilicus. It is broad below, at its attach- ment to the bladder, and becomes narrower as it ascends. The false ligaments of the bladder are-two posterior, two lateral, and one superior. The two posterior pass forward, in the male, from the sides of the rectum ; in the female, from the sides of the uterus to the posterior and lateral aspect of the bladder; they form the lateral boundaries of the recto-vesical fold of the perito- neum, and contain the obliterated hypogastric arteries and the ureters, together with vessels and nerves. The two lateral ligaments are reflections of the peritoneum from the iliac fossae to the sides of the bladder. The superior ligament is the prominent fold of peritoneum extending from the summit of the bladder to the umbilicus. It covers thevurachus and the obliterated hypogastric arteries. Structure.-The bladder is composed of four coats-serous, muscular, sub- mucous, and mucous. The serous coat is partial, and derived from the peritoneum. It invests the posterior surface, from opposite the termination of the two ureters to its summit, and is reflected from this point and from the sides on to the abdominal and pelvic walls. The muscular coat consists of three layers of unstriped muscular fibre: an external layer, composed of fibres having for the most part a longitudinal arrange- ment ; a middle layer, in which the fibres are arranged, more or less, in a circular manner; and an internal layer, in which the fibres have a general longitudinal arrangement. The fibres of the external longitudinal layer arise from the posterior surface of the body of the os pubis in both sexes (musculipubo-vesicalis), and in the male from the adjacent part of the prostate gland and its capsule. They pass, in a more or less longitudinal manner, up the anterior surface of the bladder, over its apex, and then descend along its posterior surface to its base, where they become attached to the prostate in the male and to the front of the vagina in the female. At the sides of the bladder the fibres are arranged obliquely and intersect one another. This layer has been named the detrusor urince muscle. The middle circular layers are very thinly and irregularly scattered on the body of the organ, and, though to some extent placed transversely to the long axis of the bladder, are for the most part arranged obliquely. Toward the lower part of the bladder, round the cervix and commencement of the urethra, they are disposed in a thick circular layer, forming the sphincter vesicce, which is continuous with the muscular fibres of the prostate gland. The internal longitudinal layer is thin, and its fasciculi have a reticular arrangement, but with a tendency to assume for the most part a longitudinal direction. Two bands of oblique fibres, originating behind the orifices of the ureters, converge to the back part of the prostate gland, and are inserted, by means of a fibrous process, into the middle lobe of that organ. They are the muscles of the ureters, described by Sir C. Bell, who supposed that during the contraction of the bladder they served to retain the oblique direction of the ureters, and so prevent the reflux of the urine into them. The submucous coat consists of a layer of areolar tissue connecting together the muscular and mucous coats, and intimately united to the latter. The mucous coat is thin, smooth, and of a pale rose color. It is continuous through the ureters with the lining membrane of the uriniferous tubes, and below with that of the urethra. It is connected loosely to the muscular coat by a layer 1028 THE URINARY ORGANS. of areolar tissue, excepting at the trigone, where its adhesion is more close. It is provided with a few mucous follicles, and numerous small racemose glands lined with columnar epithelium exist near the neck of the organ. The epithelium covering it is of the transitional variety, consisting of a superficial layer of poly- hedral, flattened cells, each with one, two, or three nuclei; beneath these a stratum of large club-shaped cells, with the narrow7 extremity directed downward Fig. 602.-Superficial layer of the epithelium of the bladder. Composed of polyhedral cells of vari- ous sizes, each with one, two, or three nuclei. (Klein and Noble Smith.) Fig. 603.-Deep layers of epithelium of bladder showing large club-shaped cells above, and smaller, more spindle-shaped cells below, each with an oval nucleus. (Klein and Noble Smith.) and wedged in between smaller spindle-shaped cells, containing an oval nucleus (Figs. 602, 603). Objects Seen on the Inner Surface.-Upon the inner surface of the bladder are seen the orifices of the ureters, the trigone, and the commencement of the urethra. The Orifices of the Ureters.-These are situated at the base of the trigone, being distant from each other by about two inches ; they are about an inch and a half from the base of the prostate and the commencement of the urethra. The trigonum vesicce, or trigone vesical, is a triangular smooth surface, with the apex directed forward, situated at the base of the bladder immediately behind the urethral orifice. It is paler in color than the rest of the mucous membrane, and never presents any rugae, even in the collapsed condition of the organ, owing to its intimate adhesion to the subjacent tissue. It is bounded at each posterior angle by the orifices of the ureters, which are placed nearly two inches from each other and about an inch and a half behind the orifice of the urethra. The trigone corresponds with the interval at the base of the bladder, bounded by the prostate in front and the vesiculae seminales and vasa deferentia on the sides. Projecting from the lower and anterior part of the bladder into the orifice of the urethra is a slight elevation of mucous membrane called the uvula vesicce. It is formed by a thickening of the submucous tissue. The arteries supplying the bladder are the superior, middle, and inferior vesi- cal in the male, with additional branches from the uterine and vaginal in the female. They are all derived from the anterior trunk of the internal iliac. The obturator and sciatic arteries also supply small visceral branches to the bladder. The veins form a complicated plexus round the neck, sides, and base of the bladder, and terminate in the internal iliac vein. The lymphatics accompany the blood-vessels, passing through the glands sur- rounding them. The nerves are derived from the pelvic plexus of the sympathetic and from the third and the fourth sacral nerves; the former supplying the upper part of the organ, the latter its base and neck. According to F. Darwin, the sympa- thetic fibres have ganglia connected with them, which send branches to the ves- sels and muscular coat. Surface Form.-The surface form of the bladder varies with its degree of distension and under other circumstances. In the young child it is represented by a conical figure, the apex THE BLADDER. 1029 of which, even when the viscus is empty, is situated in the hypogastric region, about an inch above the level of the symphysis pubis. In the adult, when the bladder is empty, its apex does not reach above the level of the upper border of the symphysis pubis, and the whole organ is situated in the pelvis; the neck, in the male, corresponding to a line drawn horizontally backward through the symphysis a little below its middle. As the bladder becomes dis- tended it gradually rises out of the pelvis into the abdomen, and forms a swelling in the hypogastric region which is perceptible to the hand as well as to percussion. In extreme distension it reaches into the umbilical region. Under these circumstances it is closely applied to the abdominal wall, without the intervention of peritoneum, so that it can be tapped by an opening in the middle line just above the pubes without any fear of wounding the serous membrane. When the rectum is distended the prostatic portion of the urethra is elongated and the bladder lifted out of the pelvis and the peritoneum pushed upward. Ad- vantage is taken of this in performing the operation of suprapubic cystotomy. The rectum is distended by an india-rubber bag, which is introduced into this cavity empty, and then filled with ten or twelve ounces of water. If now the bladder is injected with about half a pint of some antiseptic fluid, it will appear above the pubes, plainly perceptible to the sight and touch. The peritoneum will be pushed out of the way, and an in- cision three inches long may be made in the linea alba from the symphysis pubis upward without any great risk of wounding the peritoneum. When distended the bladder can be felt in the male, from the rectum, behind the prostate, and fluc- tuation can be perceived by a bimanual examination, one finger being introduced into the rectum and the distended bladder tapped on the front of the abdomen with the finger of the other hand. This portion of the bladder-that is, the portion felt in the rectum by the finger-is also uncovered by peritoneum, and the blad- der may here be punctured from the rectum, in the middle line, without risk of wounding the serous mem- brane. Surgical Anatomy.-A defect of development in which the bladder is implicated is known under the name of extroversion of the bladder. In this condition the lower part of the abdominal wall and the anterior wall of the bladder are wanting, so that the posterior surface of the bladder presents on the abdominal sur- face, and is pushed forward by the pressure of the vis- cera within the abdomen, forming a red vascular tumor on which the openings of the ureters are visible. The penis, except the glans, is rudimentary and is cleft on its dorsal surface, exposing the floor of the urethra-a condition known as epispadias. The pelvic bones are also arrested in develop- ment (see page 285). The bladder may be ruptured by violence applied to the abdominal wall, when the viscus is distended without any injury to the bony pelvis, ojpt may be torn in cases of fracture of the pelvis. The rupture may be either intraperitoneal or extraperitoneal-that is, may implicate the posterior surface of the bladder in the former case, or the anterior surface in the latter. Rupture of the anterior surface alone is, however, very rare. Until recently intraperitoneal rupture was uniformly fatal, but now abdominal section and suturing the rent with Lembert's suture is resorted to, with a very considerable amount of success. The sutures are inserted only through the peri- toneal and muscular coats in such a way as to bring the serous surfaces at the margins of the wound into apposition, and one is inserted just beyond each end of the wound. The bladder should be tested as to whether it is water-tight before closing the external wound. The muscular coat of the bladder undergoes hypertrophy in cases in which there is any obstruction to the flow of urine. Under these circumstances the bundles of which the muscular coat consists become much increased in size, and, interlacing in all directions, give rise to what is known as the fasciculated bladder. Between these bundles of muscular fibres the mucous mem- brane may bulge out, forming sacculi, constituting the sacculated bladder, and in these little pouches phosphatic secretions may collect, forming encysted calculi. The mucous membrane is very loose and lax, except over the trigone, to allow of the distension of the viscus. Various forms of tumor have been found springing from the wall of the bladder. The Cowper's Gland. Orifices of ducts , j of Cowper's Glands. Fig. 604.-The bladder and urethra laid open. Seen from above. Meatus. 1030 THE URINARY ORGANS. innocent tumors are the papilloma and the mucous polypus, arising from the mucous membrane; the fibrous, from the submucous tissue ; and the myoma, originating in the muscular tissue; and, very rarely, dermoid tumors, the exact origin of which it is difficult to explain. Of the malignant tumors, epithelioma is the most common, but sarcomata are occasionally found in the bladder of children. Puncture of the bladder may be performed either above the pubes or through the rectum, in both cases without wounding the peritoneum. The former plan is generally to be preferred, since in puncture by the rectum a permanent fistula may be left from abscess forming between the rectum and the bladder; or pelvic cellulitis may be set up; moreover, it is exceedingly inconvenient to keep a cannula in the rectum. In some cases in performing this operation the recto-vesical pouch of peritoneum has been wounded, inducing fatal peritonitis. The operation, therefore, has been almost completely abandoned. THE MALE URETHRA. The urethra in the male extends from the neck of the bladder to the meatus urinarius. It presents a double curve in the flaccid state of the penis, but in the erect state it forms only a single curve, the concavity of which is directed upward (Fig. 599). Its length varies from eight to nine inches, and it is divided into three portions, the prostatic, membranous, and spongy, the structure and relations of which are essentially different. Except during the passage of the urine or semen the urethra is a mere transverse cleft or slit, with its upper and under surfaces in contact. At the orifice of the urethra at the end of the penis the slit is vertical, and in the prostatic portion somewhat arched. The Prostatic Portion is the widest and most dilatable part of the canal. It passes through the prostate gland, from its base to its apex, lying nearer its upper than its lower surface. It is about an inch and a quarter in length ; the form of the canal is spindle-shaped, being wider in the middle than at either extremity, and narrowest in front, where it joins the membranous portion. A transverse section of the canal as it lies in the prostate is horseshoe in shape, the convexity being directed upward (Fig. 605). Fpon the floor of the canal is a narrow longitudinal ridge, the verumontanum, or caput gallinaginis, formed by an elevation of the mucous membrane and its subjacent tissue. It is eight or nine lines in length and a line and a half in height, and contains, according to Kobelt, muscular and erectile tissues. When distended it may serve to prevent the passage of the semen backward into the bladder. On each side of the verumontanum is a slightly depressed fossa, the prostatic sinus, the floor of which is perforated by numerous apertures, the orifices of the prostatic ducts, the ducts of the middle lobe opening behind the verumon- tanum. At the fore part of the verumontanum, in the middle line, is a depression, the sinus pocularis (yesicula prostaticd), and upon or within its margins are the slit-like openings of the ejaculatory ducts. The sinus pocularis forms a cul-de-sac about a quarter of an inch in length, which runs upward and backward in the substance of the prostate beneath the middle lobe ; its prominent upper wall partly forms the verumontanum. Its walls are composed of fibrous tissue, muscular fibres, and mucous membrane, and numerous small glands open on its inner surface. It has been called by Weber, who discovered it, the uterus masculinus, from its being developed from the united ends of the rudimentary Mullerian ducts, and therefore homologous with the uterus in the female. The Membranous portion of the urethra extends between the apex of the prostate and the bulb of the corpus spongiosum. It is the narrowest part of the canal (excepting the orifice), and measures three-quarters of an inch along its upper and half an inch along its lower surface, in consequence of the bulb projecting backward beneath it. Its upper concave surface is placed about an inch beneath the pubic arch, from which it is separated by the dorsal vessels and nerves of the penis and some muscular fibres. Its lower convex surface is separated from the rectum by a triangular space, which constitutes the perinaeum. The membranous portion of the urethra perforates both the anterior and posterior layers of the deep perineal fascia, and receives an investment from them. As it pierces the posterior layer, the fibres around the opening are prolonged backward 1031 THE MALE URETHRA. over the posterior part of the membranous portion of the urethra, and as it pierces the anterior layer, a similar prolongation takes place in the opposite direction, investing the anterior part of the membranous portion. It is also surrounded by the Compressor urethrae muscle. The Spongy portion is the longest part of the urethra, and is contained in the corpus spongiosum. It is about six inches in length, and extends from the termination of the membranous portion to the meatus urinarius. Commencing below7 the symphysis pubis, it ascends for a short distance and then curves down- ward. It is narrow and of uniform size in the body of the penis, measuring about a quarter of an inch in diameter, being dilated behind, within the bulb, and again anteriorly within the glans penis, where it forms the fossa navicularis. The Bulbous portion is a name given, in some descriptions of the urethra, to the posterior part of the spongy portion contained within the bulb. The meatus urinarius is the most contracted part of the urethra ; it is a vertical slit, about three lines in length, bounded on each side by two small labia. The inner surface of the lining membrane of the urethra, especially on the floor of the spongy portion, presents the orifices of numerous mucous glands and follicles situated in the submucous tissue, and named the glands of Littre. They vary in size, and their orifices are directed forward, so that they may easily intercept the point of a catheter in its passage along the canal. One of these lacunae, larger than the rest, is situated in the upper surface of the fossa navicularis, about an inch and a half from the orifice; it is called the lacuna magna. Into the btdbous portion are found opening the ducts of Cowper's glands. Structure.-The urethra is composed of a continuous mucous membrane, supported by a submucous tissue which connects it with the various structures through which it passes. The mucous coat forms part of the genito-urinary mucous membrane. It is continuous with the mucous membrane of the bladder, ureters, and kidneys; externally with the integument covering the glans penis ; and is prolonged into the ducts of the glands which open into the urethra-viz. Cowper's glands and the prostate gland-and into the vasa deferentia and vesiculae seminales through the ejaculatory ducts. In the spongy and membranous portions the mucous membrane is arranged in longitudinal folds when the organ is contracted. Small papillae are found upon it near the orifice, and its epithelial lining is of the columnar variety, excepting near the meatus, where it is squamous. The submucous tissue consists of a vascular erectile layer, outside which is a layer of unstriped muscular fibres, arranged in a circular direction, which sepa- rates the mucous membrane and submucous tissue from the tissue of the corpus spongiosum. Surgical Anatomy.-The urethra may be ruptured by the patient falling astride of any hard substance and striking his perinaeum,so that the urethra is crushed against the pubic arch. Bleeding will at once take place from the urethra, and this, together with the bruising in the perinaeum and the history of the accident, will at once point to the nature of the injury. The surgical anatomy of the urethra is of considerable importance in connection with the passage of instruments into the bladder. Otis was the first to point out that the urethra is capable of great dilatability, so that, excepting through the external meatus, an instrument cor- responding to 18 English gauge (29 French) can usually be passed without damage. The orifice of the urethra is not so dilatable, and therefore frequently requires slitting. A recognition of this dilatability caused Bigelow to very considerably modify the operation of lithotrity and intro- duce that of litholapaxy. In passing catheters, especially fine ones, the point of the instrument should be kept as far as possible along the upper wall of the canal, as the point is otherwise very liable to enter one of the lacunae. Stricture of the urethra is a disease of very common occur- rence, and is generally situated in the spongy portion of the urethra, most commonly in the bulbous portion, just in front of the membranous urethra, but in a very considerable number of cases in the penile or ante-scrotal part of the canal. MALE GENERATIVE ORGANS. milE Prostate Gland (Ttpoiavrjpi, to stand before) is a pale, firm, glandular body, _L which is placed immediately in front of the neck of the bladder and around the commencement of the urethra. It is placed in the pelvic cavity, behind and below the symphysis pubis, posterior to the deep perineal fascia, and rests upon the THE PROSTATE GLAND. Fig. 605 -Transverse section of the prostate gland showing the urethra, with the eminence of the caput gallinaginis : beneath it the sinus pocularis and ejaculatory ducts. rectum, through which it may be distinctly felt, especially when enlarged. In shape and size it resembles a chestnut. Its base is directed backward toward the neck of the bladder. Its apex is directed forward to the deep perineal fascia, which it touches. Its under surface is smooth, marked by a slight longitudinal furrow, and rests on the rectum, to which it is connected by dense areolar tissue. Its upper surface is flattened, marked by a slight longitudinal furrow, and placed about three-quarters of an inch below the pubic symphysis. It measures about an inch and a half in its transverse diameter at the base, an inch in its antero-posterior diameter, and three-quarters of an inch in depth. Its weight is about six drachms. It is held in its position by the anterior ligaments of the bladder (pubo-prostatic); by the posterior layer of the deep perineal fascia, which invests the commencement of the membranous portion of the urethra and prostate 1032 77/// PROSTATE GLAND. 1033 gland; and by the anterior portion of the Levator ani muscle (levator prostatte), which passes down on each side from the symphysis pubis and anterior ligament of the bladder to the sides of the prostate. The prostate consists of two lateral lobes and a middle lobe. The two lateral lobes are of equal size, separated by a deep notch behind, and by a slight furrow upon their upper and lower surfaces, which indicates the bilobed condition of the organ in some animals. The third, or middle lobe, is a small transverse band, occasionally a rounded or triangular prominence, placed between the two lateral lobes at the posterior part of the organ. It lies immediately beneath the neck of the bladder, behind the commencement of the urethra, and above and between the ejaculatory ducts. Its existence is not constant, but it is occasionally found at an early period of life, as well as in adults and in old age. The prostate gland is perforated by the urethra and the ejaculatory ducts. The urethra usually lies about one-third nearer its upper than its lower surface; occasionally, the prostate surrounds only the lower three-fourths of this tube, and more rarely the urethra runs through the lower instead of the upper part of the gland. The ejaculatory ducts pass forward obliquely through the lower part of the prostate and open into the prostatic portion of the urethra. Structure.-The prostate is enclosed in a thin but firm fibrous capsule, distinct from that derived from the posterior layer of the deep perineal fascia, and separated from it by a plexus of veins. Its substance is of a pale reddish-gray color, of great density and not easily torn. It consists of glandular substance and muscular tissue. The muscular tissue, according to Kolliker, constitutes the proper stroma of the prostate, the connective tissue being very scanty, and simply forming thin trabeculae between the muscular fibres, in which the vessels and nerves of the gland ramify. The muscular tissue is arranged as follows : Immediately beneath the fibrous capsule is a dense layer, wThich forms an investing sheath for the gland ; secondly, around the urethra, as it lies in the prostate, is another dense layer of circular fibres, continuous behind with the internal layer of the muscular coat of the bladder, and in front blending with the fibres surrounding the membranous portion of the urethra. Between these two layers strong bands of muscular tissue, which decussate freely, form meshes in which the glandular structure of the organ is imbedded. In that part of the gland which is situated above the urethra the muscular tissue is especially dense, and there is here little or no gland tissue; while in that part which is below the urethra the muscular tissue presents a wide- meshed structure, which is densest at the upper part of the gland-that is, near the bladder-becoming looser and more sponge-like toward the apex of the organ. The glandular substance is composed of numerous follicular pouches, opening into elongated canals, which join to form from twelve to twenty small excretory ducts. The follicles are connected together by areolar tissue, supported by prolongations from the fibrous capsule and muscular stroma, and enclosed in a delicate capillary plexus. The epithelium lining of both the canals and the terminal vesicles is of the columnar variety. The prostatic ducts open into the floor of the prostatic portion of the urethra. Vessels and Nerves.-The arteries supplying the prostate are derived from the internal pudic, vesical, and haemorrhoidal. Its veins form a plexus around the sides and base of the gland; they receive in front the dorsal vein of the penis, and terminate in the internal iliac vein. The nerves are derived from the pelvic plexus. Surgical Anatomy.-The relation of the prostate to the rectum should be noted : by means of the finger introduced into the gut the surgeon detects enlargement or other disease of this organ; he can feel the apex of the gland, which is the guide to Cock's operation for stricture ; he is enabled also by the same means to direct the point of a catheter when its introduction is attended with difficulty either from injury or disease of the membranous or prostatic portions of 1034 MALE GENERATIVE ORGANS. the urethra. When the finger is introduced into the bowel the surgeon may, in some cases, especially in boys, learn the position, as well as the size and weight, of a calculus in the bladder; and in the operation for its removal, if, as is not unfrequently the case, it should be lodged behind an enlarged prostate, it may be displaced from its position by pressing upward the base of the bladder from the rectum. The prostate gland is occasionally the seat of suppuration, either due to injury, gonorrhoea, or tuberculous disease. The gland, being enveloped in a dense unyielding capsule, determines the course of the abscess, and also explains the great pain which is present in the acute form of the disease. The abscess most frequently bursts into the urethra, the direction in which there is least resistance, but may occasionally burst into the rectum, or more rarely in the perinaeum. In advanced life the prostate becomes considerably enlarged, and pro- jects into the bladder so as to impede the passage of the urine. According to Dr. Messer's researches, conducted at Greenwich Hospital, it would seem that such obstruction exists in 20 per cent, of all men over sixty years of age. In some cases the enlargement affects principally the lateral lobes, which may undergo considerable enlargement without causing much incon- venience. In other cases it would seem that the middle lobe enlarges most, and even a small enlargement of this lobe may act injuriously, by forming a sort of valve over the urethral orifice, preventing the passage of the urine, and blocking more completely the orifice the more the patient strains. In consequence of the enlargement of the prostate a pouch is formed at the base of the bladder behind the projection, in which water collects and cannot be entirely expelled. It becomes decomposed and ammoniacal, and leads to cystitis. For this condition ''prostatec- tomy " is sometimes done. The bladder is opened by an incision above the symphysis pubis, the mucous membrane incised, and the enlarged and projecting middle lobe enucleated. COWPER'S GLANDS. Cowper's Glands are two small rounded and somewhat lobulated bodies of a yellow color, about the size of peas, placed beneath the fore part of the mem- branous portion of the urethra, between the two layers of the deep perineal fascia. They lie close behind the bulb, and are enclosed by the transverse fibres of the Compressor urethrae muscle. Their existence is said to be constant: they gradually diminish in size as age advances. Structure.-Each gland consists of several lobules held together by a fibrous investment. Each lobule consists of a number of acini lined by columnar epithelial cells, opening into one duct, which, joining with the ducts of other lobules outside the gland, form a single excretory duct. The excretory duct of each gland, nearly an inch in length, passes obliquely forward beneath the mucous membrane, and opens by a minute orifice on the floor of the bulbous portion of the urethra. Their existence is said to be constant; they gradually diminish in size as age advances. THE PENIS. The Penis is the organ of copulation. It consists of a root, body, and extremity, or glans penis. The root is firmly connected to the rami of the os pubis and ischium by two strong tapering, fibrous processes, the crura, and to the front of the symphysis pubis by the suspensory ligament, a strong band of fibrous tissue which passes downward from the front of the symphysis pubis to the upper surface of the root of the penis, where it blends with the fascial sheath of the organ. The extremity or glans penis, presents the form of an obtuse cone, flattened from above downward. At its summit is a vertical fissure, the orifice of the urethra (meatus urinarius). The base of the glans forms a rounded projecting border, the corona glandis, and behind the corona is a deep constriction, the cervix. Upon both of these parts numerous small sebaceous glands are found, the glandules Tysonii odoriferce. They secrete a sebaceous matter of very peculiar odor, which probably contains caseine and becomes easily decomposed. The body of the penis is the part between the root and extremity. In the flaccid condition of the organ it is cylindrical, but when erect has a triangular prismatic form with rounded angles, the broadest side being turned upward, and called the dorsum. The body is covered by integument, and contains in its interior a large portion of the urethra. The integument covering the penis is remarkable for its thinness, its dark color, its looseness of connection with the deeper parts of the organ, and its containing no adipose tissue. At the root of the penis the THE PENIS. 1035 integument is continuous with that upon the pubes and scrotum, and at the neck of the glans it leaves the surface and becomes folded upon itself to form the prepuce. The internal layer of the prepuce is attached behind to the cervix, and approaches in character to a mucous membrane ; from the cervix it is reflected over the glans penis, and at the meatus urinarius is continuous with the mucous lining of the urethra. The mucous membrane covering the glans penis contains no sebaceous glands, but projecting from its free surface are a number of small, highly sensitive papillae. At the back part of the meatus urinarius a fold of mucous membrane passes back- ward to the bottom of a depressed raphe, where it is continuous with the prepuce; this fold is termed the frcenum prceputii. Structure of the Penis.-The penis is composed of a mass of erectile tissue enclosed in three cylindrical fibrous compartments. Of these, two, the corpora cavernosa, are placed side by side along the upper part of the organ; the third, or corpus spongiosum, encloses the urethra and is placed below. The Corpora Cavernosa form the chief part of the body of the penis. They consist of two fibrous cylindrical tubes, placed side by side, and intimately connected along the median line for their anterior three-fourths, whilst at their back part they separate from each other to form the crura, which are two strong tapering fibrous processes firmly connected to the rami of the os pubis and ischium. Each crus commences by a blunt - pointed process in front of the tuberosity of the ischium, and before its junction with its fellow to form the body of the penis it presents a slight enlargement, named by Kobelt the bulb of the corpus cavernosum. Just beyond this point they become constricted, and retain an equal diameter to their anterior extremity, where they form a single rounded end which is received into a fossa in the base of the glans penis. A median groove on the upper surface lodges the dorsal vein of the penis, and the groove on the under surface receives the corpus spongiosum. The root of the penis is connected to the symphysis pubis by the suspensory ligament. Structure.-The corpora cavernosa are surrounded by a strong fibrous envelope, consisting of two sets of fibres-the one, longitudinal in direction, being common to the two corpora cavernosa, and investing them in a common covering; the other, internal, being circular in direction, and being proper to each corpus cavernosum. The internal circular fibres by their junction at one part form an incomplete partition or septum between the twro bodies. The septum between the two corpora cavernosa forms an imperfect partition; it is thick and complete behind, but in front it is incomplete, and consists of a number of vertical bands, which are arranged like the teeth of a comb, whence the name which it has received, septum pectiniforme. These bands extend between the dorsal and the urethral surface of the corpora cavernosa. This fibrous invest- ment is extremely dense, of considerable thickness, and consists of bundles of shining white fibres, with an admixture of well-developed elastic fibres, so that it is possessed of great elasticity. From the internal surface of the fibrous envelope, as well as from the sides of the septum, are given off a number of bands or cords which cross the interior of the corpora cavernosa in all directions, subdividing them into a number of separate compartments, and giving the entire structure a spongy appearance. These bands and cords are called trabeculoe, and consist of white fibrous tissue, elastic fibres, and plain muscular fibres. In them are contained numerous arteries and nerves. The component fibres of which the trabeculae are composed are larger and stronger round the circumference than at the centre of the corpora cavernosa; they are also thicker behind than in front. The interspaces, on the contrary, are larger at the centre than at the circumference, their long diameter being directed transversely ; they are largest anteriorly. They are occupied by venous blood, and are lined by a layer of flattened cells similar to the endothelial lining of veins. 1036 MALE GENERATIVE ORGANS. The whole of the structure of the corpora cavernosa contained within the fibrous sheath consists, therefore, of a sponge-like tissue of areolar spaces freely communicating with each other and filled with venous blood. The spaces may therefore be regarded as large cavernous veins. The arteries bringing the blood to these spaces are the arteries of the corpora cavernosa and branches from the dorsal artery of the penis, which perforate the fibrous capsule, along the upper surface, especially near the fore part of the organ. These arteries on entering the cavernous structure divide into branches which are supported and enclosed by the trabeculae. Some of these terminate in a capillary network, the branches of which open directly into the cavernous spaces ; others assume a tendril-like appearance, and form convoluted and somewhat dilated vessels, which were named by Muller helicine arteries. They project into the spaces, and from them are given off' small capillary branches to supply the trabecular structure. They are bound down in the spaces by fine fibrous processes, and are more abundant in the back part of the corpora cavernosa (Fig. 606). The blood from the cavernous spaces is returned by a series of vessels, some of which emerge in considerable numbers from the base of the glans penis and Fig. 606.-From the peripheral portion of the corpus cavernosum penis under a low magnifying power. (Copied from Langer.) 1. a. Capillary network, b. Cavernous spaces. 2. Connection of the arterial twigs (a) with the cavernous spaces. converge on the dorsum of the organ to form the dorsal vein; others pass out on the upper surface of the corpora cavernosa and join the dorsal vein ; some emerge from the under surface of the corpora cavernosa, and, receiving branches from the corpus spongiosum, wind round the sides of the penis to terminate in the dorsal vein; but the greater number pass out at the root of the penis and join the prostatic plexus. The Corpus Spongiosum encloses the urethra, and is situated in the groove on the under surface of the corpora cavernosa. It commences posteriorly in front of the deep perineal fascia, between the diverging crura of the corpora cavernosa, where it forms a rounded enlargement, the bulb, and terminates anteriorly in another expansion, the glans penis, which overlaps the anterior rounded extremity of the corpora cavernosa. The central portion, or body of the corpus spongiosum, is cylindrical, and tapers slightly from behind forward. The bulb varies in size in different subjects ; it receives a fibrous investment from the anterior layer of the deep perineal fascia, and is surrounded by the Accelerator urinae muscle. The urethra enters the bulb nearer its upper than its lower surface, being surrounded by a layer of erectile tissue, a thin prolongation of which is continued backward round the membranous and prostatic portions of the canal to the neck of the bladder, lying between the two layers of muscular tissue. The portion of the bulb below the urethra presents a partial division into two lobes, being marked externally by a linear raphe, whilst internally there projects inward, for a short distance, a thin fibrous septum, more distinct in early life. THE TESTES. 1037 Structure.-The corpus spongiosum consists of a strong fibrous envelope, enclosing a trabecular structure, which contains in its meshes erectile tissue. The fibrous envelope is thinner, whiter in color, and more elastic than that of the corpora cavernosa. The trabeculae are delicate, uniform in size, and the meshes between them small, their long diameter, for the most part, corresponding with that of the penis. The external envelope or outer coat of the corpus spongiosum is formed partly of unstriped muscular fibre, and a layer of the same tissue imme- diately surrounds the canal of the urethra. The lymphatics of the penis consist of a superficial and deep set; the former are derived from a dense network on the skin of the glans and prepuce and from the mucous membrane of the urethra, and terminate in the superficial inguinal glands; the latter emerge from the corpora cavernosa and corpus spongiosum, and, passing beneath the pubic arch, join the deep lymphatics of the pelvis. The nerves are derived from the internal pudic nerve and the pelvic plexus. On the glans and bulb some filaments of the cutaneous nerves have Pacinian bodies connected with them, and, according to Krause, many of them terminate in a peculiar form of end-bulb. Surgical Anatomy.-The penis occasionally requires removal for malignant disease. Usually, removal of the ante-scrotal portion is all that is necessary, but sometimes it is requisite to remove the whole organ from its attachment to the rami of the os pubis and ischium. The former operation is performed either by cutting off the whole of the anterior part of the penis with one sweep of the knife, or, what is better, cutting through the corpora cavernosa from the dorsum, and then separating the corpus spongiosum from them, dividing it at a level nearer the glans penis. The mucous membrane of the urethra is then slit up, and the edges of the flap attached to the external skin, in order to prevent contraction of the orifice, which would other- wise take place. The vessels which require ligature are the two dorsal arteries of the penis, the arteries of the corpora cavernosa, and the artery of the septum. When the entire organ requires removal the patient is placed in the lithotomy position, and an incision is made round the root of the penis, and carried down the median line of the scrotum as far as the perinaeum. The two halves of the scrotum are then separated from each other, and, a catheter having been intro- duced into the bladder as a guide, the membranous portion of the urethra in front of the trian- gular ligament is separated from the corpora cavernosa and divided, the catheter having been withdrawn, just behind the bulb. The suspensory ligament is now severed, and the crura sepa- rated from the bone with a periosteum scraper, and the whole penis removed. The membranous portion of the urethra, which has not been removed, is now to be attached to the skin at the posterior extremity of the incision in the perinaeum. The remainder of the wound is to be brought together, free drainage being provided for. THE TESTES AND THEIR COVERINGS (Fig. 607). The Testes are two small glandular organs which secrete the semen; they are situated in the scrotum, being suspended by the spermatic cords. At an early period of foetal life the testes are contained in the abdominal cavity, behind the peritoneum. Before birth they descend to the inguinal canal, along which they pass with the spermatic cord, and, emerging at the external abdominal ring, they descend into the scrotum, becoming invested in their course by numerous coverings derived from the serous, muscular, and fibrous layers of the abdominal parietes, as well as by the scrotum. The coverings of the testes are-the Skin ' Dartos Scrotum. Intercolumnar, or External spermatic fascia. Cremasteric fascia. Infundibuliform, or Fascia propria (Internal spermatic fascia). Tunica vaginalis. o The Scrotum is a cutaneous pouch which contains the testes and part of the spermatic cords. It is divided into two lateral halves by a median line, or raphe, which is continued forward to the under surface of the penis and backward along the middle line of the perinaeum to the anus. Of these two lateral portions, the left is longer than the right, and corresponds with the greater length of the spermatic cord on the left side. Its external aspect varies under different circumstances : 1038 MALE GENERATIVE ORGANS. thus, under the influence of warmth and in old and debilitated persons it becomes elongated and flaccid, but under the influence of cold and in the young and robust it is short, corrugated, and closely applied to the testes. The scrotum consists of two layers, the integument and the dartos. The integument is very thin, of a brownish color, and generally thrown into folds or rugae. It is provided with sebaceous follicles, the secretion of which has a peculiar odor, and is beset with thinly-scattered, crisp hairs, the roots of which are seen through the skin. The dartos is a thin layer of loose reddish tissue, endowed with contractility : it forms the proper tunic of the scrotum, is continuous, around the base of the scrotum, with the two layers of the superficial fascia of the groin and perinaeum, Skin. Dartos. External spermatic fascia.' Cremasteric fascia.- Infundibuliform fascia. Parietal tunica vaginalis.- Visceral tunica vaginalis.- Tunica albuginea. A lobule of the testicle.. A septum. Mediastinum. Digital fossa. Spermatic vein. Epididymis. Vas deferens. Artery to vas. Spermatic artery. Internal muscular tunic of Kolliker. Fig. 607.-Transverse section through the left side of the scrotum and the left testicle. The sac of the tunica vaginalis represented in a distended condition. (DelOpine.) and sends inward a distinct septum, septum scroti, which divides it into two cavities for the two testes, the septum extending between the raphe and the under surface of the penis as far as its root. The dartos is closely united to the skin externally, but connected with the subjacent parts by delicate areolar tissue, upon which it glides with the greatest facility. The dartos is very vascular, and consists of a loose areolar tissue con- taining unstriped muscular fibre, but no fat. Its contractility is slow, and excited by cold and mechanical stimuli, but not by electricity. The intercolumnar fascia is a thin membrane derived from the margin of the pillars of the external abdominal ring, during the descent of the testes in the foetus, which is prolonged downward around the surface of the cord and testis. It is separated from the dartos by loose areolar tissue, which allows of considerable movement of the latter upon it, but is intimately connected with the succeeding layers. The cremasteric fascia consists of scattered bundles of muscular fibres (Cremaster muscle) connected together into a continuous covering by intermediate areolar tissue. The muscular fibres are derived from the lower border of the Internal oblique muscle during the descent of the testis. The fascia propria is a thin membranous layer which loosely invests the surface of the cord. It is a continuation downward of the infundibuliform process of the fascia transversalis and the subperitoneal areolar tissue, and is also acquired during the descent of the testis in the foetus. 77//; TESTES. 1039 The tunica vaginalis is described with the proper covering of the testis. Vessels and Nerves.-The arteries supplying the coverings of the testis are : the superficial and deep external pudic, from the femoral; the superficial perineal branch of the internal pudic; and the cremasteric branch from the epigastric. The veins follow the course of the corresponding arteries. The lymphatics terminate in the inguinal glands. The nerves are : the ilio-inguinal branch of the lumbar plexus, the two superficial perineal branches of the internal pudic nerve, the inferior pudendal branch of the small sciatic nerve, and the genital branch of the genito- crural nerve. The Spermatic Cord extends from the internal abdominal ring, where the structures of which it is composed converge, to the back part of the testicle. In the abdominal wall the cord passes obliquely along the inguinal canal, lying at first beneath the Internal oblique, and upon the fascia transversalis ; but nearer the pubes it rests upon Poupart's ligament, having the aponeurosis of the External oblique in front of it and the conjoined tendon behind it. It then escapes at the external ring, and descends nearly vertically into the scrotum. The left cord is rather longer than the right, consequently the left testis hangs somewhat lower than its fellow. Structure of the Spermatic Cord.-The spermatic cord is composed of arteries, veins, lymphatics, nerves, and the excretory duct of the testicle. These structures are connected together by areolar tissue, and invested by the fasciae brought down by the testicle in its descent. The arteries of the cord are: the spermatic, from the aorta ; the artery of the vas deferens, from the superior vesical; and the cremasteric, from the deep epigastric. The spermatic artery, a branch of the abdominal aorta, escapes from the abdomen at the internal or deep abdominal ring, and accompanies the other con- stituents of the spermatic cord along the inguinal canal and through the external abdominal ring into the scrotum. It then descends to the testicle, and, becoming tortuous, divides into several branches, two or three of which accompany the vas deferens and supply the epididymis, anastomosing with the artery of the vas deferens ; others pierce the back of the tunica albuginea and supply the substance of the testis. The cremasteric artery is a branch of the deep epigastric artery. It accom- panies the spermatic cord and supplies the Cremaster muscle and other coverings of the cord, anastomosing with the spermatic artery. The artery of the vas deferens, a branch of the superior vesical, is a long slender vessel which accompanies the vas deferens, ramifying upon the coats of that duct, and anastomosing with the spermatic artery near the testis. The spermatic veins emerge from the back of the testis and receive tributaries from the epididymis; they unite and form a convoluted plexus (plexus pampini- formis), which forms the chief mass of the cord : the vessels composing this plexus are very numerous, and ascend along the cord in front of the vas deferens ; below the external or superficial abdominal ring they unite to form three or four veins, which pass along the spermatic canal, and, entering the abdomen through the internal or deep abdominal ring, coalesce to form two veins. These again unite to form a single vein, which opens on the right side into the inferior vena cava at an acute angle, and on the left side into the renal vein at a right angle. The lymphatic vessels terminate in the lumbar glands. The nerves are the spermatic plexus from the sympathetic, joined by filaments from the pelvic plexus which accompany the artery of the vas deferens. Surgical Anatomy.-The scrotum forms an admirable covering for the protection of the testicle. This body, lying suspended and loose in the cavity of the scrotum and surrounded by a serous membrane, is capable of great mobility, and can therefore easily slip about within the scrotum, and thus avoid injuries from blows or squeezes. The skin of the scrotum is very elastic and capable of great distension, and on account of the looseness and amount of subcu- taneous tissue the scrotum becomes greatly enlarged in cases of oedema, to which this part is especially liable on account of its dependent position. The scrotum is frequently the seat of 1040 MALE GENERATIVE ORGANS. epithelioma; this is no doubt due to the rugae on its surface, which favor the lodgment of dirt, and this, causing irritation, is the exciting cause of the disease, which is especially common in chimney-sweeps from the lodgment of soot. The scrotum is also the part most frequently affected by elephantiasis. On account of the looseness of the subcutaneous tissue considerable extravasations of blood may take place from very slight injuries. It is therefore generally recommended never to apply leeches to the scrotum, since they may lead to considerable ecchymosis, but rather to puncture one or more of the superficial veins of the scrotum in cases where local bloodletting from this part is judged to be desirable. The muscular fibre in the dartos causes contraction and consider- able diminution in the size of a wound of the scrotum, as after the operation of castration, and is of assistance in keeping the edges together and covering the exposed parts. THE TESTES. The Testes are suspended in the scrotum by the spermatic cords. As the left spermatic cord is rather longer than the right one, the left testicle hangs somewhat lower than its fellow. Each gland is of an oval form, compressed laterally, and having an oblique position in the scrotum, the upper extremity being directed forward and a little outward, the lower, backward and a little inward; the anterior convex border looks forward and downward; the posterior or straight border, to which the cord is attached, backward and upward. The anterior and lateral surfaces, as well as both extremities of the organ, are convex, free, smooth, and invested by the tunica vaginalis. The posterior border, to which the cord is attached, receives only a partial investment from that mem- brane. Lying upon the outer edge of this posterior border is a long, narrow, flattened body, named from its relation to the testis, the epididymis testis). It consists of a central portion, or body ; an upper enlarged extremity, the globus major, or head ; and a lower pointed extremity, the tail, or globus minor. The globus major is intimately connected with the upper end of the testicle by means of its efferent ducts, and the globus minor is connected with its lower end by cellular tissue and a reflection of the tunica vaginalis. The outer surface and upper and lower ends of the epididymis are free and covered by serous membrane ; the body is also completely invested by it, excepting along its posterior border. The epididymis is connected to the back of the testis by a fold of the serous mem- brane. Attached to the upper end of the testis or to the epididymis are one or more small pedunculated bodies. One of them is pretty constantly found between the globus major of the epididymis and the testicle, and is believed to be the remains of the upper extremity of the Mullerian duct (page 138). It is termed the hydatid of Morgagni? When the testicle is removed from the body, the position of the vas deferens, on the posterior surface of the testicle and inner side of the epididymis, marks the side to which the gland has belonged. Size and Weight.-The average dimensions of this gland are from one and a half to two inches in length, one inch in breadth, and an inch and a quarter in the antero-posterior diameter, and the weight varies from six to eight drachms, the left testicle being a little the larger. The testis is invested by three tunics-the tunica vaginalis, tunica albuginea, and tunica vasculosa. The Tunica Vaginalis is the serous covering of the testis. It is a pouch of serous membrane, derived from the peritoneum during the descent of the testis in the foetus from the abdomen into the scrotum. After its descent that portion of the pouch which extends from the internal ring to near the upper part of the gland becomes obliterated, the lower portion remaining as a shut sac, which invests the outer surface of the testis, and is reflected on to the internal surface of the scrotum; hence it may be described as consisting of a visceral and parietal portion. The meeraZ portion {tunica vaginalis propria) covers the outer surface of the testis, as wrell as the epididymis, connecting the latter to the testis by means of a distinct fold. From the posterior border of the gland it is reflected on to the internal surface of the scrotum. THE TESTES. 1041 The parietal portion of the serous membrane (tunica vaginalis reflexa) is far more extensive than the visceral portion, extending upward for some distance in front and on the inner side of the cord, and reaching below the testis. The inner surface of the tunica vaginalis is free, smooth, and covered by a layer of endothelial cells. The interval between the visceral and parietal layers of this membrane constitutes the cavity of the tunica vaginalis. The obliterated portion of the pouch may generally be seen as a fibro-cellular thread lying in the loose areolar tissue around the spermatic cord; sometimes this may be traced as a distinct band from the upper end of the inguinal canal, where it is connected with the peritoneum, down to the tunica vaginalis; sometimes it gradually becomes lost on the spermatic cord. Occasionally no trace of it can be detected. In some cases it happens that the pouch of peri- toneum does not become obliterated, but the sac of the peritoneum communicates with the tunica vaginalis. This may give rise to one of the varieties of oblique inguinal hernia (page 1073). Or in other cases the pouch may contract, but not become entirely obliterated ; it then forms a minute canal leading from the peritoneum to the tunica vaginalis.1 The Tunica Albuginea is the fibrous cover- ing of the testis. It is a dense fibrous mem- brane, of a bluish-white color, composed of bundles of white fibrous tissue, which interlace in every direction. Its outer surface is covered by the tunica vaginalis, except along its poste- rior border, at the points of attachment of the epididymis; hence the tunica albuginea is usually considered as a fibro-serous membrane, like the pericardium. This membrane sur- rounds the glandular structure of the testicle, and at its posterior border is reflected into the interior of the gland, forming an incomplete vertical septum, called the mediastinum testis (corpus Highmorianum). The testis extends from the upper, nearly to the lower, border of the gland, and is wider above than below. From the front and sides of this septum numerous slender fibrous cords and imperfect septa (trabeculce) are given off, which radiate toward the surface of the organ, and are attached to the inner surface of the tunica albuginea. They therefore divide the interior of the organ into a number of incomplete spaces, which are somewhat cone-shaped, being broad at their bases at the surface of the gland, and becoming narrower as they converge to the mediastinum. The mediastinum supports the vessels and ducts of the testis in their passage to and from the substance of the gland. The Tunica Vasculosa (pia mater testis) is the vascular layer of the testis, consisting of a plexus of blood-vessels held together by a delicate areolar tissue. It covers the inner surface of the tunica albuginea and the different septa in the interior of the gland, and therefore forms an internal investment to all the spaces of which the gland is composed. Structure.-The glandular structure of the testis consists of numerous lobules (lobuli testis). Their number, in a single testis, is estimated by Berres at 250, and by Krause at 400. They differ in size according to their position, those in the middle of the gland being larger and longer. The lobules are conical in shape, the base being directed toward the circumference of the organ, the apex toward the Spermatic cord. Artery of cord. Tunica vaginalis, parietal layer. vaghmiiS6having%eenTaid^pin.th^tumca 1 It is recorded that in the post-mortem examination of Sir Astley Cooper this minute canal was found on both sides of the body. Sir Astley Cooper states that when a student he suffered from inguinal hernia; probably this was of the congenital variety, and the canal found after death was the remains of the one down which the hernia travelled (Lancet, vol. ii., 1824, p. 116). 1042 MALE GENERATIVE ORGANS. mediastinum, Each lobule is contained in one of the intervals between the fibrous cords and vascular processes which extend between the mediastinum testis and the tunica albuginea, and consists of from one to three or more minute convoluted tubes, the tubuli seminiferi. The tubes may be separately unravelled by careful dissection under water, and maybe seen to commence either by free caecal ends or by anastomotic loops. The total number of tubes is considered by Munro to be about 300, and the length of each about sixteen feet; by Lauth their number is estimated at 840, and their average length two feet and a quarter. The diameter varies from to of an inch. The tubuli are pale in color in early life, but in old age they acquire a deep yellow tinge from containing much fatty matter. They consist of a membrana propria, inside which are several layers of epithelial cells, the seminal cells. The membrana propria is a hyaline structure, consisting of several membranous layers, containing oval flattened nuclei at regular intervals, super- imposed on one another. The seminal cells or lining epithelium differ in different tubules. In some tubes they may be seen to consist of an outer layer, next the membrana propria, and two or more layers of inner cells. The former cells are more or less polyhedral in shape, uniform in size, and contain an oval or spherical nucleus; the latter cells, those comprising the inner layers, are spherical and more loosely connected together. The nucleus of most or all of them is in the process of indirect division (karyokinesis, page 40), and in consequence of this numerous small spherical daughter-cells are to be seen, lying nearest to the lumen and closely connected together. These small daughter-cells are named spermatoblasts, and by a series of changes become converted into spermatozoa. In other tubes the gradual transition of the spermatoblasts into spermatozoa may be traced. In some tubes or parts of tubes the daughter-cells may be seen to have assumed a pear shape, with the pointed end, in which the nucleus is to be found, directed toward the inner seminal cells, while the broad part is directed into the lumen of the tube. In other parts of a tube the broad end may be seen to have become elongated into a rod-shaped body, which constitutes the middle piece of the spermatozoon, while the nucleus forms the head. Again, in other parts of the tubes these young spermatozoa may be seen collected together into fan-shaped groups, and from their distal end-that is to say, the end projecting into the lumen of the tube-a thin long filament, called the tail, is growing out. In the young subject the seminal cells present somewhat the appearance of an epithelial lining, and do not almost fill the tube, as in the adult testis. The tubules are enclosed in a delicate plexus of capillary vessels, and are held together by an intertubular connective tissue, which presents large interstitial spaces lined by endothelium, which are believed to be the rootlets of lymphatic vessels of the testis. In the apices of the lobules the tubuli become less convoluted, assume a nearly straight course, and unite together to form from twenty to thirty larger ducts, of about Jq of an inch in diameter, and these, from their straight course, are called vasa recta. The vasa recta enter the fibrous tissue of the mediastinum, and pass upward and backward, forming, in their ascent, a close network of anastomosing tubes, which are merely channels in the fibrous stroma, having no proper walls ; this constitutes the rete testis. At the upper end of the mediastinum the vessels of the rete testis terminate in from twelve to fifteen or twenty ducts, the vasa efferentia : they perforate the tunica albuginea, and carry the seminal fluid from the testis to the epididymis. Their course is at first straight; they then become enlarged and exceedingly convoluted, and form a series of conical masses, the coni vasculosi, which, together, constitute the globus major of the epididymis. Each cone consists of a single convoluted duct from six to eight inches in length, the diameter of which gradually decreases from the testis to the epididymis. Oppo- site the bases of the cones the efferent vessels open at narrow intervals into a single duct, which constitutes, by its complex convolutions, the body and globus minor of the epididymis. When the convolutions of this tube are unravelled it THE TESTES. 1043 measures upward of twenty feet in length, and increases in breadth and thick- ness as it approaches the vas deferens. The convolutions are held together by fine areolar tissue and by bands of fibrous tissue. The vasa recta are of smaller diameter than the seminal tubes, and have very thin parietes. They, as well as the channels of the rete testis, are lined by a single layer of flattened epithe- lium. The vasa efferentia and the tube of the epididymis have walls of considerable thickness, on account of the presence in them of muscular tissue, which is principally arranged in a circular manner. These tubes are lined by columnar ciliated epithelium. The Vas Deferens, the excretory duct of the testis, is the continuation of the epididymis. Commencing at the lower part of the globus minor, it ascends along the posterior surface of the testis and inner side of the epididymis, and along the back part of the spermatic cord, through the spermatic canal to the internal or deep abdominal ring. From the ring it curves round the outer side of the epigastric artery, crosses the external iliac vessels, and descends into the pelvis at the side of the bladder; it arches backward and downward to its base, crossing over the obliterated hypogastric artery and to the inner side of the ureter. At the base of the bladder it lies between that viscus and the rectum, running along the inner border of the vesicula seminalis. In this situation it becomes enlarged and sacculated, forming the ampulla, and then, becoming narrowed at the base of the prostate, unites with the duct of the vesicula seminalis to form the ejaculatory duct. The vas deferens presents a hard and cord-like sensation to the fingers; it is about two feet in length, of cylindrical form, and about a line and a quarter in diameter. Its walls are dense, measuring one-third of a line, and its canal is extremely small, measuring about half a line. Structure.-The vas deferens consists of three coats : 1. An external or cellular coat. 2. A muscular coat, which in the greater part of the tube consists of two layers of unstriped muscular fibre : an outer, longitudinal in direction, and an inner, circular ; but in addition to these, at the .commencement of the vas deferens, there is a third layer, consisting of longitudinal fibres, placed internal to the circular stratum, between it and the mucous membrane. 3. An internal or mucous coat, which is pale, and arranged in longitudinal folds; its epithelial covering is of the columnar variety. A long narrow tube, the vas aberrans of Haller, is occasionally found connected with the lower part of the canal of the epididymis or with the commencement of the vas deferens. It extends up into the cord for about two or three inches, where it terminates by a blind extremity, which is occasionally bifurcated. Its length varies from an inch and a half to fourteen inches, and sometimes it becomes dilated toward its extremity; more commonly it retains the same diameter throughout. Its structure is similar to that of the vas deferens. Occasionally it is found unconnected with the epididymis. Surgical Anatomy.-The testicle frequently requires removal for malignant disease; in tuberculous disease, to prevent systemic infection; in cystic disease ; in cases of large hernia testis, and in some instances of incompletely descended or misplaced testicle. The operation is a comparatively simple one. An incision is made from the external ring to the bottom of the scrotum into the tunica vaginalis. The coverings are shelled off the organ, and the mesorchium, stretching between the back of the testicle and the scrotum, divided. The cord is then isolated, and an aneurism needle, armed with a double ligature, passed under it, as high as is thought Tunica Vaginalis. Tunica Albuginea. Its Septa. Fig. 609.-Vertical section of the testi- cle, to show the arrangement of the ducts. 1044 MALE GENERATIVE ORGANS. necessary, and the cord tied, in two. places, and divided between the ligatures. Sometimes, in cases of malignant disease, it is desirable to open the inguinal canal and tie the cord as near the internal abdominal ring as possible. vesicula: seminales. The Seminal Vesicles are two lobulated membranous pouches placed between the base of the bladder and the rectum, serving as reservoirs for the semen, and secreting a fluid to be added to the secretion of the testicles. Each sac is somewhat pyramidal Right Ejaculatory duct. Fig. 610.-Base of the bladder, with the vasa deferentia and vesiculae seminales in form, the broad end being directed backward and the narrow end forward toward the prostate. They measure about twm and a half inches in length, about five lines in breadth, and two or three lines in thickness. They vary, however, in size, not only in different individuals, but also in the same individual on the two sides. Their upper surface is in contact with the base of the bladder, extending from near the termination of the ureters to the base of the prostate gland. Their under surface rests upon the rectum, from which they are separated by the recto-vesical fascia. Their posterior extremities diverge from each other. Their anterior extremities are pointed, and converge toward the base of the prostate gland, where each joins with the corresponding vas deferens to form the ejaculatory duct. Along the inner margin of each vesicula runs the enlarged and convoluted vas deferens. The inner border of the vesiculm and the corresponding vas deferens form the lateral boundaries of a triangular space, limited behind by the recto-vesical peritoneal fold; the portion of the bladder included in this space rests on the rectum, and corresponds with the trigonum vesicse in its interior. Each vesicula consists of a single tube, coiled upon itself and giving off several irregular caecal diverticula, the separate coils, as well as the diverticula, being connected together by fibrous tissue. When uncoiled this tube is about the diameter of a quill, and varies in length from four to six inches; it terminates posteriorly in a cul-de-sac; its anterior extremity becomes constricted into a nar- row straight duct, which joins on its inner side with the corresponding vas deferens, and forms the ejaculatory duct. The ejaculatory ducts, two in number, one on each side, are formed by the junction of the ducts of the vesiculae seminales with the vasa deferentia. Each duct is about three-quarters of an inch in length ; it commences at the base of the prostate, and runs forward and upward in a canal in its substance, and along the side of the sinus pocularis, to terminate by a separate slit-like orifice close to or DESCENT OF THE TESTES. 1045 just within the margins of the sinus. The ducts diminish in size and converge toward their termination. Structure.-The vesiculae seminales are composed of three coats : an external or fibro-cellular ; a middle or muscular coat, which is thinner than in the vas deferens: the muscular fibres are arranged in three layers, consisting of an inner and outer longitudinal stratum and an intermediate layer of circular fibres; and an internal or mucous coat, which is pale, of a whitish-brown color, and presents a delicate reticular structure, like that seen in the gall-bladder, but the meshes are finer. The epithelium is columnar. The coats of the ejaculatory ducts are extremely thin. They are: an outer fibrous layer, which is almost entirely lost after their entrance into the prostate; a layer of muscular fibres, consisting of an outer thin circular and an inner longitudinal layer; and the mucous membrane, forming the only constituents of the tubes. Vessels and Nerves.-The arteries supplying the vesiculae seminales are derived from the middle and inferior vesical and middle haemorrhoidal. The veins and lymphatics accompany the arteries. The nerves are derived from the pelvic plexus. Surgical Anatomy.-The vesiculae seminales are often the seat of an extension of the disease in cases of tuberculous disease of the testicle, and should always be examined from the rectum before coming to a decision with regard to castration in this affection. Descent of the Testes. The testes at an early period of foetal life are placed at the back part of the abdominal cavity, behind the peritoneum, in front and a little below the kidneys. The anterior surface and sides are invested by peritoneum. At about the third month of intra-uterine life a peculiar structure, the gubernaculum testis, makes its appearance. This structure is at first a slender band which extends from the situation of the internal ring to the epididymis and body of the testicle, and is then continued upward in front of the kidney toward the Diaphragm. As development advances the peritoneum covering the testicle encloses it and forms a mesentery, the mesorchium, which also encloses the gubernaculum and forms two folds-one above the testicle, and the other below it. The one above the testicle is the plica vascularis, and contains ultimately the spermatic vessels ; the one below, the plica gubernatrix, contains the lower part of the gubernaculum, which has now grown into a thick cord ; it terminates below at the internal ring in a sort of tube, the processus vaginalis, which protrudes itself down the inguinal canal. The lower part of the gubernaculum by the fifth month has become a thick cord, whilst the upper part has disappeared. The lower part can now be seen to consist of a cen- tral core of unstriped muscle-fibre, and outside this of a firm layer of striped elements, connected, behind the peritoneum, with the abdominal wall. Later on, about the sixth month, the lower end of the gubernaculum can be traced into the inguinal canal, extending to the pubes, and, at a later period, to the bottom of the scrotum. The fold of peritoneum constituting the processus vaginalis pro- jects itself downward into the inguinal canal, forming a gradually elongating depression or cul-de-sac, which eventually reaches the bottom of the scrotum, and into this the testicle is drawn by the growth of the body of the foetus, for the gubernaculum does not grow commensurately with the growth of other parts, and therefore the testicle, being attached by the gubernaculum to the bottom of the scrotum, is prevented from rising as the body grows, and is drawn first into the inguinal canal, and eventually into the scrotum. By the eighth month the testicle has reached the scrotum, preceded by the lengthened pouch of peritoneum, the processus vaginalis, which communicates by its upper extremity with the per- itoneal cavity. Just before birth the upper part of the pouch usually becomes closed, and this obliteration extends gradually downward to within a short dis- tance of the testis. The process of peritoneum surrounding the testis, which is 1046 MALE GENERATIVE ORGANS. now entirely cut off from the general peritoneal cavity, constitutes the tunica vaginalis.1 In the female, a small cord, corresponding to the gubernaculum in the male, descends to the inguinal region, and ultimately forms the round ligament of the uterus. A pouch of peritoneum accompanies it along the inguinal canal, analogous to the processus vaginalis in the male: it is called the canal of Nuck. Surgical Anatomy.-Abnormalities in the formation and in the descent of the testicle may occur. The testicle may fail to be developed, or the testicle may be fully developed and the vas deferens may be undeveloped in whole or part; or, again, both testicle and vas deferens may be fully developed, but the duct may not become connected to the gland. The testicle may fail in its descent or it may descend into some abnormal position. Thus it may be retained in the position where it was primarily developed, below the kidney; or it may descend to the internal abdominal ring, but fail to pass through this opening ; it may be retained in the inguinal canal, which is perhaps the most common position; or it may pass through the external abdominal ring and remain just outside it, failing to pass to the bottom of the scrotum. On the other hand, it may get into some abnormal position: it may pass the scrotum and reach the perinaeum, or it may fail to enter the inguinal canal, and may find its way through the femoral ring into the crural canal, and present itself on the thigh at the saphenous opening. There is still a third class of cases of abnormality of the testicle, where the organ has descended in due course into the scrotum, but is malplaced. The most common form of this is where the testicle is inverted ; that is to say, the organ is rotated, so that the epididymis is connected to the front of the scrotum, and the body, surrounded by the tunica vaginalis, is directed backward. In these cases the vas deferens is to be felt in the front of the cord. The condition is of importance in connection with hydrocele and hmmatocele, and the position of the testicle should always be carefully ascertained before performing any operation for these affections. Again, more rarely, the testicle may be reversed. This is a condition in which the top of the testicle, indicated by the globus major of the epididymis, is at the bottom of the scrotum, and the vas deferens comes off from the summit of the organ. 1 The obliteration of the process of peritoneum which accompanies the cord, and is hence called the funicular process, is often incomplete. See section on Inguinal Hernia. THE FEMALE GENERATIVE ORGANS. THE External Organs of Generation in the Female are: the mons Veneris, the labia majora and minora, the clitoris, the meatus urinarius, and the orifice of EXTERNAL ORGANS. ;3y Orifice ff urethra of vayina Fig. 611.-The vulva. External female organs of generation. the vagina. The term " vulva " or " pudendum," as generally applied, includes all these parts. The Mons Veneris is the rounded eminence in front of the pubic symphysis, formed by a collection of fatty tissue beneath the integument. It surmounts the vulva, and becomes covered with hair at the time of puberty. The Labia Majora are two prominent longitudinal cutaneous folds extending downward from the mons Veneris to the anterior boundary of the perinaeum, and 1047 1048 FEMALE GENERATIVE ORGANS. enclosing the common urino-sexual opening. Each labium is formed, externally, of integument covered with hair; internally, of mucous membrane 1 which is continuous with the genito-urinary mucous tract, and, between the two, of a considerable quantity of areolar tissue, fat, and a tissue resembling the dartos of the scrotum, besides vessels, nerves, and glands. The labia are thicker in front, where they form by their meeting the anterior commissure. Posteriorly they are not really joined, but appear to become lost in the neighboring terminating close to, and nearly parallel with, each other. Together with the connecting skin between them, they form the posterior commissure or posterior boundary of the vulval orifice. The interval between the posterior commissure and ''Vagina. Fig. 612.-Vertical median section of the female pelvis. the anus, about an inch to an inch and a quarter in length, constitutes the perimeum. The fourchette is the anterior edge of the perinieum, and between it and the hymen is a depression, the fossa navicularis. The labia correspond to the scrotum in the male. The Labia Minora, or Nymphse, are two small cutaneous folds, situated within the labia majora, and extending from the clitoris obliquely downward, outward, and backward for about an inch and a half on each side of the orifice of the vagina, between which and the labia majora they are lost. Anteriorly, the two labia minora meet and form the frcenum of the clitoris. T he prepuce of the clitoris, passing backward on each side, is inserted, as it were, into the labia, but is not actually a part of them. The nymplue are really modified skin. .1 heir internal surfaces have numerous sebaceous follicles. The Clitoris is an erectile structure analogous to the corpora cavernosa of the 1 The term mucous membrane is used here in its broad sense to denote an internal surface kept continuously moist by secretion, and communicating directly or indirectly with the external air. TTZAZ URETHRA. 1049 penis. It is situated beneath the anterior commissure, partially hidden between the anterior extremities of the labia minora. It is connected to the rami of the os pubis and ischium on each side by a crus ; the body is short and concealed beneath the labia; the free extremity, or glans clitoridis, is a small rounded tubercle, consisting of spongy erectile tissue, and highly sensitive. It is provided, like the penis, with a suspensory ligament, and with two small muscles, the Erectores clitoridis, which are inserted into the crura of the clitoris. The clitoris consists of two corpora cavernosa, composed of erectile tissue enclosed in a dense layer of fibrous membrane, united together along their inner surfaces by an incomplete fibrous pectiniform septum. Between the clitoris and the entrance of the vagina is a triangular smooth surface, bounded on each side by the nymphee; this is the vestibule. The orifice of the urethra (meatus urinarius) is situated at the back part of the vestibule, about an inch below the clitoris and near the margin of the vagina, surrounded by a prominent elevation of the mucous membrane. Below the meatus urinarius is the orifice of the vagina, more or less closed in the virgin by a mem- branous fold, the hymen. The Hymen is a membranous fold which closes to a greater or less extent the opening of the vagina. It varies much in shape. Its commonest form is that of a ring, generally broadest posteriorly : sometimes it is represented by a semilunar fold, with its concave margin turned toward the pubes. A complete septum stretched across the lower part of the vaginal orifice is called " imperferate hymen.'' Occasionally it is cribriform, or its free margin forms a membranous fringe, or it may be entirely absent. It may persist after copulation, so that it cannot be considered as a test of virginity. After parturition the small rounded elevations known as the carunculce myrtiformes are found as the remains of the hymen. Glands of Bartholin.-On each side of the commencement of the vagina, and behind the hymen, is a round or oblong body, of a reddish-yellow color, and of the size of a horse-bean, analogous to Cowper's gland in the male. It is called the gland of Bartholin. Each gland opens by means of a long single duct on each side external to the hymen. Bulbi Vestibuli.-Extending from the clitoris, along either side of the vestibule, and lying a little behind the nymphse, are two large oblong masses, about an inch in length, consisting of a plexus of veins enclosed in a thin layer of fibrous membrane. These bodies are narrow in front, rounded below, and are connected with the crura of the clitoris and rami of the pubes : they are termed by Kobelt the bulbi vestibuli, and he considers them analogous to the bulb of the corpus spongiosum in the male. Immediately in front of these bodies is a smaller venous plexus, continuous with the bulbi vestibuli behind and the glans clitoridis in front: it is called by Kobelt the pars intermedia, and is considered by him as analogous to that part of the body of the corpus spongiosum which immediately succeeds the bulb. RELATIONS OF THE BLADDER. The Bladder is situated at the anterior part of the pelvis. It is in relation, in front, with the symphysis pubis; behind, with the utero-vesical pouch of peritoneum, which separates it from the body of the uterus ; its base lies in contact with the connective tissue in front of the cervix and upper part of the vagina. Laterally, is the recto-vesical fascia. The bladder is said by some anatomists to be larger in the female than in the male. At any rate, it does not rise above the symphysis pubis till more distended than in the male, but this is perhaps owing to the more capacious pelvis rather than to its being of actually larger size. THE URETHRA. The Urethra is a narrow membranous canal, about an inch and a half in length, extending from the neck of the bladder to the meatus urinarius. It is placed beneath the symphysis pubis, imbedded in the anterior wall of the vagina; 1050 FEMALE GENERATIVE ORGANS. and its direction is obliquely downward and forward, its course being slightly curved, the concavity directed forward and upward. Its diameter when undilated is about a quarter of an inch. The urethra perforates the triangular ligament precisely as in the male. Structure.-The urethra consists of three coats : muscular, erectile, and mucous. The muscular coat is continuous with that of the bladder; it extends the whole length of the tube, and consists of a circular stratum of muscular fibres. In addition to this, between the two layers of the triangular ligament, the female urethra is surrounded by the Compressor urethrae, as in the male. A thin layer of spongy erectile tissue, containing a plexus of large veins inter- mixed with bundles of unstriped muscular fibre, lies immediately beneath the mucous coat. The mucous coat is pale, continuous externally with that of the vulva, and internally with that of the bladder. It is thrown into longitudinal folds, one of which, placed along the floor of the canal, resembles the verumontanum in the male urethra. It is lined by laminated epithelium, which becomes transitional near the bladder. Its external orifice is surrounded by a few mucous follicles. The urethra, from not being surrounded by dense resisting structures, as in the male, admits of considerable dilatation, which enables the surgeon to remove with considerable facility calculi or other foreign bodies from the cavity of the bladder. The Rectum is more capacious and less curved in the female than in the male. The first portion extends from the left sacro-iliac symphysis to the middle of the sacrum. Its connections are similar to those in the male. The second portion extends to the tip of the coccyx. It is covered in front by the peritoneum for a short distance, at its upper part: it is in relation with the posterior wall of the vagina. The third portion curves backward from the vagina to the anus, leaving a space which corresponds on the surface of the body to the perinseum. Its extremity is surrounded by the Sphincter muscles, and its sides are supported by the Levatores ani. THE RECTUM. INTERNAL ORGANS. The Internal Organs of Generation are-the vagina, the uterus and its append- ages, the Fallopian tubes, the ovaries and their ligaments, and the round ligaments. The Vagina extends from the vulva to the uterus. It is situated in the cavity of the pelvis, behind the bladder and in front of the rectum. Its direction is curved upward and backward, at first in the line of the outlet, and afterward in that of the axis of the cavity of the pelvis. Its walls are ordinarily in contact, and its usual shape on transverse section is that of an H, the transverse limb being slightly curved forward or backward, whilst the lateral limbs are somewhat convex toward the median line. Its length is about two inches along its anterior wall, and two and three-quarter inches along its posterior wall. It is constricted at its commencement, and becomes dilated medially, and narrowed near its uterine extremity ; it surrounds the vaginal portion of the cervix uteri, a short distance from the os, its attachment extending higher up on the posterior than on the anterior wall of the uterus. Relations.-Its anterior surface is in relation with the base of the bladder and with the urethra. Its posterior surface is connected for the lower three-fourths of its extent to the anterior wall of the rectum, the upper fifth being separated from that tube by the recto-vaginal fold of peritoneum, which forms a cul-de-sac between the vagina and rectum. Its sides give attachment superiorly to the broad ligaments, and inferiorly to the Levatores ani muscles and recto-vesical fascia. Structure.-The vagina consists of an internal mucous lining, of a muscular coat, and between the two of a layer of erectile tissue. THE UTERUS. 1051 The mucous membrane' is continuous above with that lining the uterus. Its inner surface presents, along the anterior and posterior walls, a longitudinal ridge or raphe, called the columns of the vagina, and numerous transverse ridges or rugae, extending outward from the raphe on either side. These rugae are divided by furrows of variable depth, giving to the mucous membrane the appearance of being studded over with conical projections or papillae ; they are most numerous near the orifice of the vagina, especially in females before parturition. The epithelium covering the mucous membrane is of the squamous variety. The submucous tissue is very loose, and contains numerous large veins, which by their anastomoses form a plexus, together with smooth muscular fibres derived from the muscular coat; it is regarded by Gussenbauer as an erectile tissue. It contains a number of mucous crypts, but no true glands. The muscular coat consists of two layers: an external longitudinal, which is far the stronger, and an internal circular layer. The longitudinal fibres are continuous with the superficial muscular fibres of the uterus. The strongest fasciculi are those attached to the recto-vesical fascia on each side. The two layers are not distinctly separable from each other, but are connected by oblique decus- sating fasciculi which pass from the one layer to the other. In addition to this the vagina at its lower end is surrounded by a band of striped muscular fibres, the sphincter vagina* (see page 466). External to the muscular coat is a layer of connective tissue containing a large plexus of blood-vessels. The erectile tissue consists of a layer of loose connective tissue situated between the mucous membrane and the muscular coat; imbedded in it is a plexus of large veins, and numerous bundles of unstriped muscular fibres derived from the circular muscular layer. The arrangement of the veins is similar to that found in other erectile tissues. THE UTERUS. The Uterus is the organ of gestation, receiving the fecundated ovum in its cavity, retaining and supporting it during the development of the foetus, and becoming the principal agent in its expulsion at the time of parturition. In the virgin state it is pear-shaped, flattened from before backward, and situated in the cavity of the pelvis between the bladder and the rectum ; it is retained in its position by the round and broad ligaments on each side, and projects into the upper end of the vagina below. Its upper end, or base, is directed upward and forward; its lower end, or apex, downward and backward, in the line of the axis of the inlet of the pelvis. It therefore forms an angle with the vagina, since the direction of the vagina corresponds to the axis of the cavity and outlet of the pelvis. The uterus measures about three inches in length, two in breadth at its upper part, and nearly an inch in thickness, and it weighs from an ounce to an ounce and a half. It consists of two parts : (1) the body, with its upper broad extremity, the fundus ; and (2) the cervix, or neck, which is partly above the vagina and partly in the vagina. The fundus is placed on a line below' the level of the brim of the pelvis, being directed forward behind the upper portion of the anterior pelvic wall. The division betw'een the body and cervix is indicated externally by a slight constriction, and by the reflection of the peritoneum from the anterior surface of the uterus on to the bladder, and internally by a narrowing of the canal, called the internal os. The body gradually narrows from the fundus to the neck. Its anterior surface is flattened, covered by peritoneum in the upper three-fourths of its extent, and separated from the bladder by the utero-vesical pouch. Its posterior surface is convex transversely, covered by peritoneum throughout, and separated from the rectum by some convolutions of the intestine. Its lateral margins are concave, and 1 See foot-note, page 1048. 1052 FEMALE GENERATIVE ORGANS. give attachment to the Fallopian tube above, the round ligament below and in front of this, and the ligament of the ovary behind and between both of these structures. The cervix is the lower constricted segment of the uterus ; around its circum- ference is attached the upper end of the vagina, which extends upward a greater distance behind than in front. The supravaginal portion is not covered by peritoneum in front; a pad of cellular tissue is interposed between it and the bladder. Behind, the peritoneum is extended over it. The vaginal portion is the rounded lower end projecting into the vagina. On its surface is a small aperture, the os uteri, generally circular in shape, but sometimes oval or almost linear. The margin of the opening is, in the absence of past parturition or disease, quite smooth. Ligaments.-The ligaments of the uterus are eight in number: one anterior ; Round Ureter. * External iliac artery. Apex of Douglas' pouch. External iliac artery. Fig. 613.-Douglas's pouch. (From a preparation in the Museum of the Royal College of Surgeons.) one posterior; two lateral or broad; two sacro-uterine,-all these being formed of peritoneum-and, lastly, two round ligaments. The anterior ligament (vesico-uterine) is reflected on to the bladder from the front of the uterus, at the junction of the.supra vaginal cervix and body. The posterior ligament (recto-uterine) passes from the posterior wall of the uterus over the upper fifth of the vagina, and thence on to the rectum and sacrum. It thus forms a pouch called Douglas s pouch (Fig- 613), the boundaries of which are, in front, the posterior wall of the uterus, the supravaginal cervix, and the upper fifth of the vagina ; behind, the rectum and sacrum; above, the small intestine; and, laterally, the sacro-uterine ligaments. The two lateral or broad ligaments pass from the sides of the uterus to the lateral walls of the pelvis, forming a septum across the pelvis, which divides that cavity into two portions. In the anterior part are contained the bladder,. THE UTERUS. 1053 urethra, and vagina; in the posterior part, the rectum. Between the two layers of each broad ligament are contained-(1) the Fallopian tubes superiorly ; (2) the round ligament; (3) the ovary and its ligament; (4) the parovarium, or organ of Rosenmuller; (5) connective tissue; and (6) unstriped muscular fibre. Between the fimbriated extremity of the tube and the lower attachment of the broad ligament is a concave rounded margin called the infundibulo-pelvic liga- ment (Fig. 616). The sacro-uterine ligaments pass from the second and third bones of the sacrum, downward and forward, to be attached one on each side of the uterus at the junc- tion of the supravaginal cervix and the body, this point corresponding internally to the position of the os internum. The cavity of the uterus is small in comparison with the size of the organ: ■ Urachus. External Uiac artery. Labia minora. 7 SPHINCTER VAGIN/E. Fig. 614.-Side view of the female pelvic organs. (From a preparation in the Museum of the Royal College ■of Surgeons.) that portion of the cavity which corresponds to the body is triangular, flattened from before backward, so that its walls are closely approximated, and having its base directed upward toward the fundus. At each superior angle is a funnel- shaped cavity, which constitutes the remains of the division of the body of the uterus into two cornua, and at the bottom of each cavity is the minute orifice of the Fallopian tube. At the inferior angle of the uterine cavity is a small con- stricted opening, the internal orifice (ostium internum'), which leads into the cavity of the cervix. The cavity of the cervix is somewhat fusiform, flattened from before backward, broader at the middle than at either extremity, and communicates below with the vagina. The wall of the canal presents, anteriorly and posteriorly, a longitudinal column, from which proceed a number of small oblique columns, giving the appearance of branches from the stem of a tree; and hence the name arbor vitae uterina applied to it. These folds usually become very indistinct after the first labor. Structure.-The uterus is composed of three coats-an external serous coat, a middle or muscular, and an internal mucous coat. 1054 FEMALE GENERATIVE ORGANS. The serous coat is derived from the peritoneum ; it invests the fundus and the whole of the posterior surface of the body of the uterus, but only the upper three-fourths of its anterior surface. In the lower fourth of the posterior sur- face the peritoneum, though covering the uterus, is not closely connected with it, being separated from it by a layer of loose cellular tissue and some large veins. The muscular coat forms the chief bulk of the substance of the uterus. In the unimpregnated state it is dense, firm, of a grayish color, and cuts almost like cartilage. It is thick opposite the middle of the body and fundus, and thin at the orifices of the Fallopian tubes. It consists of bundles of unstriped muscular fibres, disposed in layers, intermixed with areolar tissue, blood-vessels, lymphatic vessels, and nerves. In the impregnated state the muscular tissue becomes more prominently developed, and is disposed in three layers-external, middle, and internal. The external layer is placed beneath the peritoneum, disposed as a thin plane on the anterior and posterior surfaces. It consists of fibres which pass trans- versely across the fundus, and, converging at each superior angle of the uterus, are continued on the Fallopian tube, the round ligament, the ligament of the ovary: some passing at each side into the broad ligament, and others running backward from the cervix into the recto-uterine ligaments. The middle layer of fibres, which is thickest, presents no regularity in its arrangement, being disposed longitudinally, obliquely, and transversely. It con- tains most blood-vessels. The internal or deep layer consists of circular fibres arranged in the form of two hollow' cones, the apices of which surround the orifices of the Fallopian tubes, their bases intermingling with one another on the middle of the body of the uterus. At the internal os these circular fibres form a distinct sphincter. The mucous membrane is thin, smooth, and closely adherent to the subjacent tissue. It is continuous, through the fimbriated extremity of the Fallopian tubes, with the peritoneum, and through the os uteri with the lining of the vagina. In the body of the uterus it is smooth, soft, of a pale red color, lined by colum- nar ciliated epithelium, and presents, when viewed with a lens, the orifices of numerous tubular follicles arranged perpendicularly to the surface. It is unpro- vided with any submucosa, but is intimately connected with the innermost layer of the muscular coat, which by some anatomists is regarded as the muscularis mucosae. In structure it differs from ordinary mucous membrane, consisting of an embryonic nucleated and highly cellular form of connective tissue in which run numerous large lymphatics. In it are the tube-like uterine glands, which are of small size in the unimpregnated uterus, but shortly after impregnation become enlarged, elongated, presenting a contorted or waved appearance toward their closed extremities, which reaches into the muscularis, and may be single or bifid. They consist of a delicate membrane, lined by an epithelium, which becomes ciliated toward the orifices. In the impregnated uterus the epithelium loses its ciliated character, is thicker and tougher, and is provided with a submucous layer of areolar tissue. In the cervix the mucous membrane is sharply differentiated from that of the uterine cavity. It is thrown into numerous transverse folds, which are arranged along an anterior and posterior longitudinal raphe, presenting an appearance which has received the name of arbor vitce. In the upper two-thirds of the canal the mucous membrane is provided with numerous deep glandular follicles, which secrete a clear viscid alkaline mucus; and in addition, extending through the whole length of the canal, are a variable number of little cysts, presumably follicles, which have become occluded and distended with retained secretion. They are called the ovula Nabothi. The mucous membrane covering the lover half of the cervical canal presents numerous papillae. The epithelium of the upper two-thirds is cylindrical and ciliated, but below this it loses its cilia, and gradually changes to squamous epithelium close to the external os. THE UTERUS. 1055 Vessels and Nerves.-The arteries of the uterus are the uterine, from the internal iliac, and the ovarian, from the aorta. They are remarkable for their tortuous course in the substance of the organ and for their frequent anastomoses. The termination of the ovarian artery meets the termination of the uterine artery, and forms an anastomotic trunk from which branches are given off to supply the uterus, their disposition being, as shown by John Williams, circular. The veins are of large size, and correspond with the arteries. In the impregnated uterus these vessels are termed the uterine sinuses, consisting of the lining membrane of the veins adhering to the walls of the canal channelled through the substance of the uterus. They terminate in the uterine plexuses. The lymphatics of the body terminate in the lumbar glands, those of the cervix in the pelvic glands. The 'Uterine .artery. Ovarian artery. \Ronnd ligament. Internal iliac artery. Fig. 615.-The arteries of the internal organs of generation of the female, seen from behind. (After Hyrtl.) nerves are derived from the inferior hypogastric and ovarian plexuses, and from the third and fourth sacral nerves. The form, size, and situation of the uterus vary at different periods of life and under dif- ferent circumstances. In the foetus the uterus is contained in the abdominal cavity, projecting beyond the brim of the pelvis. The cervix is considerably larger than the body. At puberty the uterus is pyriform in shape, and weighs from eight to ten drachms. It has descended into the pelvis, the fundus being just below the level of the brim of this cavity. The arbor vitae is distinct, and extends to the upper part of the cavity of the organ. During menstruation the organ is enlarged, and more vascular, its surfaces rounder ; the os externum is rounded, its labia swollen, and the lining membrane of the body thickened, softer and of a darker color. According to J. Williams, at each recurrence of menstruation a molecular disintegration of the mucous membrane takes place, which leads to its complete removal, only the bases of the glands imbedded in the muscle being left. At the cessation of menstruation by a proliferation of the remaining structures a fresh mucous membrane is formed. During pregnancy the uterus becomes enormously enlarged, and in the ninth month reaches the epigastric region. The increase in size is partly due to growth of pre-existing muscle and partly to development of new fibres. After parturition the uterus nearly regains its usual size, weighing about an ounce and a half; but its cavity is larger than in the virgin state, the external orifice is more marked, its edges present a fissured surface, its vessels are tortuous, and its muscular layers are more defined. 1056 FEMALE GENERATIVE ORGANS. In old age the uterus becomes atrophied, and paler and denser in texture ; a more distinct constriction separates the body and cervix. The ostium internum and, occasionally, the vaginal orifice often become obliterated, and its labia almost entirely disappear. APPENDAGES OF THE UTERUS. The appendages of the uterus are the Fallopian tubes, the ovaries and their ligaments, and the round ligaments. They are placed in the following order: in front is the round ligament; the Fallopian tube occupies the upper margin of the broad ligament; the ovary and its ligament are behind and below both. THE FALLOPIAN TUBES. The Fallopian Tubes, or Oviducts, convey the ova from the ovaries to the cavity of the uterus. They are two in number, one on each side, situated in the upper margin of the broad ligament, extending from each superior angle of the uterus to the sides of the pelvis. Each tube is about four inches in length ; and is described as consisting of three portions : (1) the isthmus, or inner constricted half; (2) the ampulla, or outer dilated portion, which curves over the ovary; and (3) the Parovarium. Fimbriated extremity. Uterus. Ostium abdominale. Fimbria ovarica. Fig. 616.-Uterine appendages, seen from behind. (Henle.) infundibulum with its ostium abdominale, surrounded by fimbriae, one of which is attached to the ovary, the fimbria ovarica. The general direction of the Fallopian tube is outward, backward, and downward. The uterine opening is minute, and will only admit a fine bristle; the abdominal opening is comparatively much larger. In connection with the fimbriae of the Fallopian tube or with the broad ligament close to them there is frequently one or more small vesicles floating on a long stalk of peritoneum. These are termed the hydatids of Morgagni, and are probably the remains of the terminal sacs of the Mullerian ducts. Structure.-The Fallopian tube consists of three coats-serous, muscular, and mucous. The external or serous coat is peritoneal. The middle or muscular coat consists of an external longitudinal and an internal circular layer of muscular fibres continuous with those of the uterus. The internal or mucous coat is continuous with the mucous lining of the uterus and, at the free extremity of the tube, with the peritoneum. It is thrown into longitudinal folds, which in the outer, larger part of the tube, or ampulla, are much more extensive than in the narrow canal of the isthmus. The lining epithelium is columnar ciliated. This form of epithelium is also found on the inner surface of the fimbriae, while on the outer or serous surfaces of these processes the epithelium gradually merges into the endothelium of the peritoneum. THE OVARIES. 1057 THE OVARIES. The Ovaries (tcsfcs muliebres, Galen) are analogous to the testes in the male. They are oval-shaped bodies of an elongated form, flattened from above down- ward, situated one on each side of the uterus, in the posterior part of the broad ligament behind and below the Fallopian tubes. Each ovary is connected by its anterior straight margin to the broad ligaments; by its inner extremity to the uterus by a proper ligament, the ligament of the ovary ; and by its outer end to the fimbriated extremity of the Fallopian tube by the ovarian fimbria; its superior and inferior surfaces and posterior convex border are free. The ovaries are of a grayish-pink color, and present either a smooth or puckered, uneven surface. They are each about an inch and a half in length, three-quarters of an inch in width, and about a third of an inch thick, and weigh from one to two drachms. The exact position of the ovary has been the subject of considerable difference of opinion, and writers differ much as to what is to be regarded as the normal posi- tion. The fact appears to be that it is differently placed in different individuals. Hasse has described it as being situated with its long axis transverse, or almost transverse, to the pelvic cavity. Schultze, on the other hand, believes that its Fimbriated extremity of tube. Fallopian tube. Ligament of the ovary. Uterus Broad ligament, upper part. Fimbria ovarica. Uterine Ovarian vessels. Vaginal! artery. 1 -Os externum. Artery. Vein. Anterior wall of vagina. Fig. 617.-The uterus and its appendages. Posterior view. The parts have been somewhat displaced from their proper position in the preparation of the specimen; thus the right ovary has been raised above the Fallopian tube, and the fimbriated extremities of the tubes have been turned upward and outward. (From a preparation in the Royal College of Surgeons.) long axis is antero-posterior. Kolliker asserts that the truth lies between these two views, and that the ovary is placed obliquely in the pelvis, its long axis lying parallel to the external iliac vessels, with its surface directed inward and outward, and its convex free border upward. His has made some important observations on this subject, and his views are largely accepted. He teaches that the uterus rarely lies symmetrically in the middle of the pelvic cavity, but is generally inclined to one or other side, most frequently to the left, in the proportion of three to two. The position of the two ovaries varies according to the inclination of the uterus. When the uterus is inclined to the left, the ovary of this side lies with its long axis vertical and with one side closely applied to the outer wall of the pelvis, while the ovary of the opposite side, being dragged upon by the inclination of the uterus, lies obliquely, its outer extremity being retained in close apposition to the side of the pelvis by the infundibulo-pelvic ligament (page 1053). When, on the other hand, the uterus is inclined to the right, the position of the two ovaries is exactly reversed, the right being vertical and the left oblique. In whichever position the ovary is placed, the Fallopian tube forms a loop around it, the uterine half ascending obliquely over it. and the outer half, including the dilated extremity, descending and bulging freely behind it. From this extremity the fimbriae pass upward on to the ovary and closely embrace it. Structure.-The ovary consists of a number of Graafian vesicles imbedded in 1058 FEMALE GENERATIVE ORGANS. the meshes of a stroma or framework, and invested by a serous covering derived from the peritoneum. Serous Covering.-Though the investing membrane of the ovary is derived from the peritoneum, it differs essentially from that structure, inasmuch as its epithelium consists of a single layer of columnar cells, instead of the flattened endothelial cells of other parts of the membrane; this has been termed the ger- minal epithelium of Waldeyer, and gives to the surface of the ovary a dull gray aspect instead of the shining smoothness of serous membranes generally. Stroma.-The stroma is a peculiar soft tissue, abundantly .supplied with blood- vessels, consisting for the most part of spindle-shaped cells, with a small amount of ordinary connective tissue. These cells have been regarded by some anatomists as unstriped muscle-cells, which, indeed, they most resemble (His); by others as connective-tissue cells (Waldeyer, Henle, and Kolliker). On the surface of the organ this tissue is much condensed, and forms a layer composed of short connec- tive-tissue fibres, with fusiform cells between them. This was formerly regarded as a distinct fibrous covering, and was termed the tunica albuginea, but is nothing more than a condensed layer of the stroma of the ovary. Graafian Vesicles.-Upon making a section of an ovary numerous round trans- parent vesicles of various sizes are to be seen ; they are the Graafian vesicles, the ovisacs containing the ova. Immediately beneath the superficial covering is a layer of stroma, in which are a large number of minute vesicles, of uniform size, about -jf-Q of an inch in diameter. These are the Graafian vesicles in their earliest condition, and the layer where they are found has been termed the cortical layer. They are especially numerous in the ovary of the young child. After puberty and during the whole of the child- bearing period large and mature, or almost mature, Graafian vesi- cles are also found in the cortical layer in small numbers, and also "corpora lutea," the remains of vesicles which have burst and are t/L'UWt.' Granular zone. Fluid of the : vesicle. Peritoneum. / Coats of the Graafian vesicle. Fig. 618.-Section of the ovary. (After Schron.) 1. Outer covering. 1'. Attached border. 2. Central stroma. 3. Peripheral stroma. 4. Blood-vessels. 5. Graafian fol- licles in their earliest stage. 6, 7, 8. More advanced folli- cles. 9. An almost mature follicle. 9'. Follicle from which the ovum has escaped. 10. Corpus luteum. Stroma of the ovary with blood-vessels. Membrana granulosa. Fig. 619.-Section of the Graafian ves- icle. (After Von Baer.) undergoing atrophy and absorption. Beneath this superficial stratum other large and more mature Graafian vesicles are found imbedded in the ovarian stroma. These increase in size as they recede from the surface toward a highly vascular stroma in the centre of the organ, termed the medullary substance {zona vasculosa, Waldeyer). This stroma forms the tissue of the hilum by which the ovary is attached, and through which the blood-vessels enter; it does not contain any Graafian vesicles. The Graafian vesicles consist of an external fibro-vascular coat connected with the surrounding stroma of the ovary by a network of blood-vessels; and an internal coat, named ovicapsule, which is lined by a layer of nucleated cells, called the membrana granulosa. The fluid contained in the interior of the vesicles is transparent and albuminous, and in it is suspended the ovum. In that part of the mature Graafian vesicle which is nearest the surface of the ovary the cells of the membrana granulosa are collected into a mass which projects into the cavity THE OVARIES. 1059 of the vesicle. This is termed the discus proligerus, and in this the ovum is imbedded.1 The ova are formed from the germ-epithelium on the surface of the ovary: the cells become enlarged and involuted, forming little depressions on the surface of the ovary As they sink deeper into the tissue they become enclosed by the out- growth of processes from the stroma of the ovary, and, becoming surrounded, their connection with the surface is cut off, and the germ-epithelium forming the involution is contained in a cavity, the future Graafian follicle. The germ-cell or cells now form the ovum ; the cell-wall forms the vitelline membrane ; the nucleus, the germinal area; and a nucleolus, which soon appears, the germinal spot. A clear homogeneous protoplasm is formed within the cell, constituting the yelk, and thus the primordial ovum is developed. According to Dr. Foullis, the cells of the membrana granulosa are formed out of the nuclei of the fibro-cellular stroma of the ovary.2 The development and maturation of the Graafian vesicles and ova continue uninterruptedly from puberty to the end of the fruitful period of woman's life, while their formation commences before birth. Before puberty the ovaries are small, the Graafian vessels contained in them are disposed in a comparatively thick layer in the cortical substance ; here they present the appearance of a large number of minute closed vesicles, constituting the early condition of the Graafian vesicle; many, however, never attain full development, but shrink and disappear, their ova being incapable of impregnation. At puberty the ovaries enlarge, are more vascular, the Graafian vesicles are developed in greater abundance, and their ova are capable of fecundation. Discharge of the Ovum.-The Graafian vesicles, after gradually approaching the surface of the ovary, burst: the ovum and fluid contents of the vesicles are liberated, and escape on the exterior of the ovary, passing thence into the Fallo- pian tube.3 In the foetus the ovaries are situated, like the testes, in the lumbar region, near the kidneys. They may be distinguished from those bodies at an early period by their elongated and flattened form, and by their position, which is at first oblique and then nearly transverse. They gradually descend into the pelvis. Lying above the ovary in the broad ligament between it and the Fallopian tube is the organ of Rosenmuller, called also the parovarium or epoophoron. This is the remnant of a foetal structure, the development of which has been described at a former page (page 139). In the adult it consists of a few closed convoluted tubes lined with epithelium, some of them atrophied, and one, usually distinguishable from the rest, ends in a bulbous or hydatid swelling. The parovarium is con- nected at its uterine extremity with the remains of the Wolffian duct-the duct of Gartner. The Ligament of the Ovary is a rounded cord which extends from each superior angle of the uterus to the inner extremity of the ovary ; it consists of fibrous tissue and a few muscular fibres derived from the uterus. The Round Ligaments are two rounded cords, between four and five inches in length, situated between the layers of the broad ligament in front of and below the Fallopian tube. Commencing on each side at the superior angle of the uterus, this ligament passes forward, upward, and outward through the internal abdominal ring, along the inguinal canal, to the labia majora, in which it becomes lost. The round ligament consists principally of muscular tissue prolonged from the uterus; also of some fibrous and areolar tissue, besides blood-vessels and nerves, enclosed in a duplicature of peritoneum, which in the foetus is prolonged in the form of a tubular process for a short distance into the inguinal canal. This process is called the canal of Nuck. It is generally obliterated in the adult, but sometimes remains 1 For a description of the ovum, see page 100. 2 Proceedings of the Royal Society of Edinburgh, April, 1875. 3 This is effected either by application of the tube to the ovary, or by a curling upward of the fimbriated extremity, so that the ovum is caught as it falls. 1060 FEMALE GENERATIVE ORGANS. pervious even in advanced life. It is analogous to the peritoneal pouch which accompanies the descent of the testis. Vessels and Nerves.-The arteries of the ovaries and Fallopian tubes are the ovarian from the aorta. They enter the attached border, or hilum, of the ovarv. The veins follow the course of the arteries ; they form a plexus near the ovary, the pampiniform plexus. The nerves are derived from the inferior hypogastric or pelvic plexus, and from the ovarian plexus, the Fallopian tube receiving a branch from one of the uterine nerves. The mammae, or breasts, are accessory glands of the generative system, which secrete the milk. They exist in the male as well as in the female, but in the former only in the rudimentary state, unless their growth is excited by peculiar circumstances. In the female they are two large hemispherical eminences situated THE MAMMARY GLANDS. Fat. ' Lobule unravelled. Lobule. '•Lactiferous duct. 'Loculi in connective tissue. ''Ampulla. Fig. 620.-Dissection of the lower half of the female breast during the period of lactation. (From Luschka.) toward the lateral aspect of the pectoral region, corresponding to the intervals between the third and sixth or seventh ribs, and extending from the side of the sternum to the axilla. Their weight and dimensions differ at different periods of life and in different individuals. Before puberty they are of small size, but enlarge as the generative organs become more completely developed. They increase during pregnancy, and especially after delivery, and become atrophied in old age. The left mamma is generally a little larger than the right. Their base is nearly circular, flattened or slightly concave, and has its long diameter directed upward and outward toward the axilla; they are separated from the Pectoral muscles by a thin layer of superficial fascia. The outer surface of the mamma is convex, and presents, just below the centre, a small conical prominence, the nipple (znammYZa). The surface of the nipple is dark-colored and surrounded by an areola having a colored tint. In the virgin the areola is of a delicate rosy hue; about the second month after impregnation it enlarges and acquires a darker tinge, which increases as pregnancy advances, becoming in some cases of a dark-brown or even black color. This color diminishes as soon as lactation is over, but is never entirely lost throughout life. These changes in the color of the areola are of importance in forming a conclusion in a case of suspected first pregnancy. 1061 THE MAMMARY GLANDS. The nipple is a cylindrical or conical eminence capable of undergoing a sort of erection from mechanical excitement, a change mainly due to the contraction of its muscular fibres. It is of a pink or brownish hue, its surface wrinkled and provided with papillae, and it is perforated by numerous orifices, the apertures of the lactiferous ducts. Near the base of the nipple and upon the surface of the areola are numerous sebaceous glands, which become much enlarged during lactation, and present the appearance of small tubercles beneath the skin. These glands secrete a peculiar fatty substance which serves as a protection to the integument of the nipple during the act of sucking. The nipple consists of numerous vessels, inter- mixed with plain muscular fibres, which are principally arranged in a circular man- ner around the base, some few fibres radiating from base to apex. Structure.-The mamma consists of gland-tissue ; of fibrous tissue, connecting its GJ 7 7 GJ lobes; and of fatty tissue in the intervals between the lobes. The gland-tissue, when freed from fibrous tissue and fat, is of a pale reddish color, firm in texture, circular in form, flattened from before backward, thicker in the centre than at the circumference, and presenting several inequalities on its surface, especially in front. It consists of numerous lobes, and these are composed of lobules connected together by areolar tissue, blood-vessels, and ducts. The smallest lobules consist of a cluster of rounded vesicles, which open into the smallest branches of the lactiferous ducts ; these ducts, uniting, form larger ducts, which terminate in a single canal, correspond- ing with one of the chief subdivisions of the gland. The number of excretory ducts varies from fifteen to twenty : they are termed the tubuli lactiferi, or galactophori. They converge toward the areola, beneath which they form dilatations, or ampulla, which serve as reservoirs for the milk, and at the base of the nipple become contracted and pursue a straight course to its summit, perforating it by separate orifices considerably narrower than the ducts themselves. The ducts are composed of areolar tissue, with longitudinal and transverse elastic fibres and longitudinal muscular fibres : their mucous lining is continuous, at the point of the nipple, with the integument. The epithelium of the mammary gland differs according to the state of activity of the organ. In the gland of a woman who is not pregnant or suckling the alveoli are very small and solid, being filled with a mass of granular polyhedral cells. During pregnancy the alveoli enlarge and the cells undergo rapid multiplication. At the commencement of lactation the cells in the centre of the alveolus undergo fatty degeneration, and are eliminated in the first milk as colostrum-corpuscles. The peripheral cells of the alveolus remain, and form a single layer of granular, short columnar cells, with a spherical nucleus, lining the limiting membrana propria. These cells during the state of activity of the gland are capable of forming, in their interior, oil-globules, which are then ejected into the lumen of the alveolus and constitute the milk-globules. The fibrous tissue invests the entire surface of the breast, and sends down septa between its lobes, connecting them together. The/arty tissue surrounds the surface of the gland and occupies the interval between its lobes. It usually exists in considerable abundance, and determines the form and size of the gland. There is no fat immediately beneath the areola and nipple. Vessels and Nerves.-The arteries supplying the mammae are derived from the thoracic branches of the axillary, the intercostals, and internal mammary. The veins describe an anastomotic circle round the base of the nipple, called by Haller the circulus venosus. From this large branches transmit the blood to the circumference of the gland and end in the axillary and internal mammary veins. The lymphatics, for the most part, run along the lower border of the Pectoralis major to the axillary glands ; some few, from the inner side of the breast, perforate the intercostal spaces and empty themselves into the anterior mediastinal glands. The nerves are derived from the anterior and lateral cutaneous nerves of the thorax. THE SURGICAL ANATOMY OF HERNIA. Dissection (Fig. 621).-For dissection of the parts concerned in inguinal hernia a male subject, free from fat, should always be selected. The body should be placed in the supine posi- tion, the abdomen and pelvis raised by means of blocks placed beneath them, and the lower extremities rotated outward, so as to make the parts as tense as possible. If the abdominal walls are flaccid, the cavity of the abdomen should be inflated by an aperture through the umbilicus. An incision should be made along the middle line from the umbilicus to the symphysis pubis, and continued along the front of the scrotum, and a second incision from the anterior superior spine of the ilium to just below the umbilicus. These incisions should divide the integument, and the triangular-shaped flap included between them should be reflected downward and outward, when the superficial fascia will be exposed. The Superficial Fascia of the Abdomen.-This, over the greater part of the abdominal wall, consists of a single layer of fascia, which contains a variable amount of fat; but as it approaches the groin it is easily divisible into two layers, between which are found the superficial vessels and nerves and the superficial inguinal lymphatic glands. The superficial layer is thick, areolar in texture, containing adipose tissue in its meshes, the quantity of which varies in different subjects. Below, it passes over Poupart's ligament, and is continuous with the outer layer of the superficial fascia of the thigh. In the male this fascia is continued over the penis and over the outer surface of the cord to the scrotum, -where it helps to form the dartos. As it passes to the penis and over the cord to the scrotum it changes its character, becoming thin, destitute of adipose tissue, and of a pale reddish color ; and in the scrotum it acquires some involuntary muscular fibres. F rom the scrotum it may be traced backward, to be continuous with the superficial fascia of the perimeum. In the female this fascia is continued into the labia majora. The hypogastric branch of the ilio-hypogastric nerve perforates the aponeurosis of the External oblique muscle about an inch above and a little to the outer side of the external abdominal ring, and is distributed to the integument of the hypogastric region. The ilio-inguinal nerve escapes at the external abdominal ring, and is distributed to the integument of the upper and inner part of the thigh, to the scrotum in the male and to the labium in the female. The superficial epigastric artery arises from the femoral about half an inch below Poupart's ligament, and, passing through the saphenous opening in the fascia lata, ascends on to the abdomen, in the superficial fascia covering the External oblique muscle, nearly as high as the umbilicus. It distributes branches to the superficial inguinal lymphatic glands, the superficial fascia, and the integument, anastomosing with branches of the deep epigastric and internal mammary arteries. The superficial circumflex iliac artery, the smallest of the cutaneous branches, arises close to the preceding, and, piercing the fascia lata, runs outward, parallel with Poupart's ligament, as far as the crest of the ilium, dividing into branches which supply the superficial inguinal lymphatic glands, the superficial fascia, and the integument, anastomosing with the deep circumflex iliac and with the gluteal and external circumflex arteries. The superficial external pudic (superior) artery arises from the inner side of the femoral artery close to the preceding vessels, and, after passing through the saphenous opening, courses inward across the spermatic cord, to be distributed to the integument on the lower part of the abdomen, the penis and scrotum in the male, and the labium in the female, anastomosing with branches of the internal pudic. The Superficial Veins.-The veins accompanying these superficial vessels are 1062 THE SUPERFICIAL FASCIA. 1063 usually much larger than the arteries; they terminate in the internal saphenous vein. The superficial inguinal lymphatic glands are placed immediately beneath the integument, are of large size, and vary from eight to ten in number. They are divisible into two groups: an upper, disposed irregularly along Poupart's liga- ment, which receive the lymphatic vessels from the integument of the scrotum, penis, parietes of the abdomen, perineal and gluteal regions, and the mucous membrane of the urethra; and an inferior group, which surround the saphenous opening in the fascia lata, a few being sometimes continued along the saphenous Superficial circumflex- iliac rein.I External abdominal ring. Superficial epigastric vein. Fig. 621.-Inguinal hernia. Superficial dissection. vein to a variable extent. This latter group receive the superficial lymphatic vessels from the lower extremity. The deep layer of the superficial fascia (fascia of Scarpa') is thinner and more membranous in character than the superficial layer. In the middle line it is intimately adherent to the linea alba; above, it is continuous with the superficial fascia over the rest of the trunk ; below, it blends with the fascia lata of the thigh, a little below Poupart's ligament; below and internally, in the male, it is continued over the penis and over the outer surface of the cord to the scrotum, where it helps to form the dartos. From the scrotum it may be traced backward to be continu- ous with the deep layer of the superficial fascia of the perinaeum. In the female it is continuous with the labia majora. The scrotum is a cutaneous pouch which contains the testes and part of the spermatic cords, and into which an inguinal hernia frequently descends (see page 1037). The Aponeurosis of the External Oblique Muscle.-This is a thin but strong 1064 THE SURGICAL ANATOMY OF HERNIA. membranous aponeurosis, the fibres of which are directed obliquely downward and inward. That portion of the aponeurosis which extends between the anterior superior spine of the ilium and the spine of the os pubis is a broad band, folded inward and continuous below with the fascia lata; it is called Poupart's ligament. The portion which is reflected from Poupart's ligament at the spine of the os pubis, along the pectineal line, is called Grimbernat's ligament. From the point of attach- ment of the latter to the pectineal line a few fibres pass upward and inward, behind the inner pillar of the ring, to the linea alba. They diverge as they ascend, and form a thin, triangular, fibrous band, which is called the triangular ligament of the abdomen. In the aponeurosis of the External oblique, immediately above the crest of the os pubis, is a triangular opening, the external or superficial abdominal ring, formed by the separation of the fibres of the aponeurosis in this situation. The External or Superficial Abdominal Ring.-Just above and to the outer side of the crest of the os pubis an interval is seen in the aponeurosis of the External oblique, called the external abdominal ring. This aperture is oblique in direction, somewhat triangular in form, and corresponds with the course of the fibres of the aponeurosis. It usually measures from base to apex about an inch, and trans- versely about half an inch. It is bounded below by the crest of the os pubis; above, by a series of curved fibres, the inter columnar, which pass across the upper angle of the ring, so as to increase its strength; and on either side, by the mar- gins of the opening in the aponeurosis, which are called the columns or pillars of the ring. The external pillar, which at the same time is inferior from the obliquity of its direction, is the stronger; it is formed by that portion of Poupart's ligament which is inserted into the spine of the os pubis; it is curved, so as to form a kind of groove, upon which the spermatic cord rests. The internal or superior pillar is a broad, thin, flat band, which is attached to the front of the body of the os pubis, interlacing with its fellow of the oppo- site side in front of the symphysis pubis, that of the right side being superficial. The external abdominal ring gives passage to the spermatic cord in the male and round ligament in the female ; it is much larger in men than in women, on account of the large size of the spermatic cord, and hence the great frequency of inguinal hernia in men. The intercolumnar fibres are a series of curved tendinous fibres which arch across the lower part of the aponeurosis of the External oblique. They have received their name from stretching across between the two pillars of the external ring; they increase the strength of the lower part of the aponeurosis and prevent the divergence of the pillars from one another. They are thickest below, where they are connected to the outer third of Poupart's ligament, and are inserted into the linea alba, describing a curve, with the convexity downward. They are much thicker and stronger at the outer angle of the external ring than internally, and are more strongly developed in the male than in the female. These intercolumnar fibres, as they pass across the external abdominal ring, are themselves connected together by delicate fibrous tissue, thus forming a fascia which, as it is attached to the pillars of the ring, covers it in, and is called the intercolumnar fascia. This intercolumnar fascia is continued downward as a tubular prolongation around the outer surface of the cord and testis, and encloses them in a distinct sheath; hence it is also called the external spermatic fascia. The sac of an inguinal hernia in passing through the external abdominal ring receives an investment from the intercolumnar fascia. If the finger is introduced a short distance into the external ring, and then, if the limb is extended and rotated outward, the aponeurosis of the External oblique, together with the iliac portion of the fascia lata, will be felt to become tense and the external ring much contracted; if the limb is, on the contrary, flexed upon the pelvis and rotated inward, this aponeurosis will become lax, and the external ring sufficiently enlarged to admit the finger with comparative ease ; hence the patient should always be put in the latter position when the taxis is applied for the reduc- G/AfBURNA T'S LIGAMUNT. 1065 tion of an inguinal hernia, in order that the abdominal walls may be relaxed as much as possible. The aponeurosis of the External oblique should be removed by dividing it across in the same direction as the external incisions, and reflecting it downward and outward : great care is requisite in separating it from the aponeurosis of the muscle beneath. The lower part of the Internal oblique and the Cremaster are then exposed, together with the inguinal canal, which contains the spermatic cord (Fig. 622). The mode of insertion of Poupart's and Gimbernat's ligaments into the os pubis should also be examined. Poupart's ligament, or the crural arch, is the lower border of the aponeurosis of the External oblique muscle, which extends from the anterior superior spine of the ilium to the spine of the os pubis. From this latter point it is reflected outward to be attached to the pectineal line for about half an inch, forming Fig. 622.-Inguinal hernia, showing the Internal oblique, Cremaster, and spermatic canal. Gimbernat's ligament. Its general direction is curved downward toward the thigh, where it is continuous with the fascia lata. Its outer half is rounded and oblique in direction; its inner half gradually widens at its attachment to the os pubis, is more horizontal in direction, and lies beneath the spermatic cord. Gimbernat's ligament (Fig. 629) is that portion of the External oblique muscle which is reflected downward and outward from the spine of the os pubis to be inserted into the pectineal line. It is about half an inch in length, larger in the male than in the female, almost horizontal in direction in the erect posture, and of a triangular form, with the base directed outward. Its base or outer margin is concave, thin, and sharp, and lies in contact with the crural sheath, forming the inner boundary of the crural ring (see Fig. 630). Its apex corresponds to the spine of the os pubis. Its posterior margin is attached to the pectineal line, and is continuous with the pubic portion of the fascia lata. Its anterior margin is continuous with Poupart's ligament. The triangular ligament of the abdomen is a band of tendinous fibres, of a triangular shape, which is attached by its apex to the pectineal line, where it is 1066 THE SURGICAL ANATOMY OF HERNIA. continuous with Gimbernat's ligament. It passes inward beneath the spermatic cord, and expands into a somewhat fan-shaped fascia, lying behind the inner pillar of the external abdominal ring and in front of the conjoined tendon, and interlaces with the ligament of the other side at the linea alba. The Internal oblique muscle has been previously described (page 453). The part which is now exposed is partly muscular and partly tendinous in structure. Those fibres which arise from Poupart's ligament, few in number and paler in color than the rest, arch downward and inward across the spermatic cord, and, becoming tendinous, are inserted, conjointly with those of the Transversalis, into the crest of the os pubis and pectineal line, forming what is known as the conjoined tendon of the Internal oblique and Transversalis. This tendon is inserted imme- diately behind the external abdominal ring, serving to protect what would other- wise be a weak point in the abdominal wall. Sometimes this tendon is insufficient to resist the pressure from within, and is carried forward in front of the protrusion through the external ring, forming one of the coverings of direct inguinal hernia, or the hernia forces its way through the fibres of the conjoined tendon. The Cremaster is a thin muscular layer composed of a number of fasciculi which arise from the middle of Poupart's ligament at the inner side of the Internal oblique, being connected with that muscle and also occasionally with the Transversalis. It passes along the outer side of the spermatic cord, descends with it through the external ring upon the front and sides of the cord, and forms a series of loops which differ in thickness and length in different subjects. Those at the upper part of the cord are exceedingly short, but they become in succession longer and longer, the longest reaching down as low as the testicle, where a few are inserted into the tunica vaginalis. These loops are united together by areolar tissue, and form a thin covering over the cord and testis, the fascia cr emast eric a. The fibres ascend along the inner side of the cord, and are inserted by a small pointed tendon into the crest of the os pubis and front of the sheath of the Rectus muscle. It will be observed that the origin and insertion of the Cremaster is precisely similar to that of the lower fibres of the Internal oblique. This fact affords an easy explanation of the manner in which the testicle and cord are invested by this muscle. At an early period of fietal life the testis is placed at the lower and back part of the abdominal cavity, but during its descent toward the scrotum, which takes place before birth, it passes beneath the arched border of the Internal oblique. In its passage beneath this muscle some fibres are derived from its lower part which accompany the testicle and cord into the scrotum. It occasionally happens that the loops of the Cremaster surround the cord, some lying behind as well as in front. It is probable that under these circumstances the testis in its descent passes through, instead of beneath, the fibres of the Internal oblique. In the descent of an oblique inguinal hernia, which takes the same course as the spermatic cord, the Cremaster muscle forms one of its coverings. This muscle becomes largely developed in cases of hydrocele and large old scrotal herniae. No such muscle exists in the female, but an analogous structure is developed in those cases where an oblique inguinal hernia descends beneath the margin of the Internal oblique. The Internal oblique should be detached from Poupart's ligament, separated from the Transversalis to the same extent as in the previous incisions, and reflected inward on to the sheath of the Rectus (Fig. 623). The circumflex iliac vessels, which lie between these two muscles, form a valuable guide to their separation. The Transversalis muscle has been previously described (page 455). The part which is now exposed is partly muscular and partly tendinous in structure ; this portion arises from the outer third of Poupart's ligament, its fibres curve down- ward and inward, and are inserted, together with those of the Internal oblique, into the lower part of the linea alba, into the crest of the os pubis and pectineal line, forming what is known as the conjoined tendon of the Internal oblique and THE FASCIA TRANSVERSALIS, 1067 Transversalis. Between the lower border of this muscle and Poupart's ligament a space is left in which is seen the fascia transversalis. The inguinal or spermatic canal contains the spermatic cord in the male and the round ligament in the female. It is an oblique canal, about an inch and a half in length, directed downward and inward and placed parallel with, and a little above, Poupart's ligament. It commences above at the internal abdominal ring, which is the point where the cord enters the spermatic canal, and terminates below at the external ring. It is bounded, in front, by the integument and superficial fascia, by the aponeurosis of the External oblique throughout its whole length, and by the Internal oblique for its outer third; behind, by the triangular ligament, the conjoined tendon of the Internal oblique and Transversalis, trans- versalis fascia, and the subperitoneal fat and peritoneum ; above, by the arched fibres of the Internal oblique and Transversalis ; below, by the union of the fascia transversalis with Poupart's ligament. That form of protrusion in which the Internal abdominal ring. Epigastric artery. Fig. 623.-Inguinal hernia showing the Transversalis muscle, the transversalis fascia, and the internal abdominal ring. intestine follows the course of the spermatic cord along the spermatic canal is called oblique inguinal hernia. The fascia transversalis is a thin aponeurotic membrane which lies between the inner surface of the Transversalis muscle and the peritoneum. It forms part of the general layer of fascia which lines the interior of the abdominal and pelvic cavities, and is directly continuous with the iliac and pelvic fasciae. In the inguinal region the transversalis fascia is thick and dense in structure, and joined by fibres from the aponeurosis of the Transversalis muscle; but it becomes thin and cellular as it ascends to the Diaphragm. Below, it has the following attachments : external to the femoral vessels it is connected to the posterior margin of Poupart's ligament, and is there continuous with the iliac fascia. Internal to the vessels it is thin, and attached to the os pubis and pectineal line behind the conjoined tendon, with which it is united; and, corresponding to the points where the femoral vessels pass into the thigh, this fascia descends in front of them, forming the anterior wall of the crural sheath. The spermatic cord 1068 THE SURGICAL ANATOMY OF HERNIA. in the male and the round ligament in the female pass through this fascia; the point where they pass through is called the internal or deep abdominal ring. This opening is not visible externally, owing to a prolongation of the transversalis fascia on these structures, forming the infundibuliform process. The internal or deep abdominal ring is situated in the transversalis fascia, midway between the anterior superior spine of the ilium and the symphysis pubis, and about half an inch above Poupart's ligament. It is of an oval form, the extremities of the oval directed upward and downward; it varies in size in dif- ferent subjects, and is much larger in the male than in the female. It is bounded above and externally by the arched fibres of the Transversalis muscle, below and internally by the deep epigastric vessels. It transmits the spermatic cord in the male and the round ligament in the female. From its circumference a thin, funnel-shaped membrane, the infundibuliform fascia, is continued round the cord and testis, enclosing them in a distinct pouch. When the sac of an oblique inguinal hernia passes through the internal or deep abdominal ring, the infundi- buliform process of the transversalis fascia forms one of its coverings. The Subperitoneal Areolar Tissue.-Between the fascia transversalis and the peritoneum is a quantity of loose areolar tissue. In some subjects it is of con- siderable thickness and loaded with adipose tissue. Opposite the internal ring it is continued round the surface of the cord, forming a loose sheath for it. The deep epigastric artery arises from the external iliac artery a few lines above Poupart's ligament. It at first descends to reach this ligament, and then ascends obliquely along the inner margin of the internal or deep abdominal ring, lying between the transversalis fascia and the peritoneum, and passing upward pierces the transversalis fascia and enters the sheath of the Rectus muscle just below the semilunar fold of Douglas. Consequently the deep epigastric artery bears a very important relation to the internal abdominal ring as it passes obliquely upward and inward from its origin from the external iliac. In this part of its course it lies along the lower and inner margin of the internal ring and beneath the commencement of the spermatic cord. As it winds round the internal abdominal ring it is crossed by the vas deferens in the male and by the round ligament in the female. The peritoneum, corresponding to the inner surface of the internal ring, presents a well-marked depression, the depth of which varies in different subjects. A thin fibrous band is continued from it along the front of the cord for a variable distance, and becomes ultimately lost. This is the remains of the pouch of peritoneum which, in the foetus, accompanies the cord and testis into the scrotum, the obliteration of which commences soon after birth. In some cases the fibrous band can only be traced a short distance, but occasionally it may be followed, as a fine cord, as far as the upper end of the tunica vaginalis. Sometimes the tube of peritoneum is only closed at intervals and presents a sacculated appearance, or a single pouch may extend along the whole length of the cord, which may be closed above, or the pouch may be directly continuous with the peritoneum by an opening at its upper part. In the female (in the foetus) the peritoneum is also prolonged in the form of a tubular process for a short distance into the inguinal canal. This process is called the canal of Nuck. It is generally obliterated in the adult, but sometimes it remains pervious even in advanced life. It is analogous to the peritoneal pouch which accompanies the descent of the testis. Inguinal hernia is that form of protrusion which makes its way through the abdomen in the inguinal region. There are two principal varieties of inguinal hernia-external or oblique, and internal or direct. External or oblique inguinal hernia, the more frequent of the two, takes the INGUINAL HERNIA OBLIQUE INGUINAL HERNIA. 1069 same course as the spermatic cord. It is called external from the neck of the sac being on the outer or iliac side of the deep epigastric artery. Internal or direct inguinal hernia does not follow the same course as the cord, but protrudes through the abdominal wall on the inner or pubic side of the deep epigastric artery. Oblique Inguinal Hernia. In oblique inguinal hernia the intestine escapes from the abdominal cavity at the internal ring, pushing before it a pouch of peritoneum, which forms the hernial Femoral vein. 'Femoral artery. Fig. 624.-Oblique inguinal hernia, showing its various coverings. (From a preparation in the Museum of the Royal College of Surgeons.) sac (Fig. 625, a). As it enters the inguinal canal it receives an investment from the subserous areolar tissue, and is enclosed in the infundibuliform process of the transversalis fascia. In passing along the inguinal canal it displaces upward the arched fibres of the Transversalis and Internal oblique muscles, and is surrounded by the fibres of the Cremaster. It then passes along the front of the cord, and escapes from the inguinal canal at the external ring, receiving an investment from the intercolumnar fascia. Lastly, it descends into the scrotum, receiving coverings from the superficial fascia and the integument. The coverings of this form of hernia, after it has passed through the external ring, are, from without inward, the integument, superficial fascia, intercolumnar fascia, Ci emaster muscle, infundibuliform fascia, subserous a reolar tissue, and peritoneum. This form of hernia lies in front of the vessels of the spermatic cord and 1070 THE SURGICAL ANATOMY OF HERNIA. seldom extends below the testis, on account of the intimate adhesion of the cover- ings of the cord to the tunica vaginalis. Sac of hernia. Tunica vaginalis. Tunica naainalix A. Common scrotal hernia. B. Congenital hernia. Sac of hernia. -Tunica vaginalis. Sac of hernia Tunica "vaginalis. C. Infantile hernia. D. Encysted hernia. Tunica vaginalls. -Sac of hernia. E. Hernia into the funicular process. Fig. 625.-Varieties of oblique inguinal hernia. The seat of stricture in oblique inguinal hernia is either at the external ring; in the inguinal canal, caused by the fibres of the Internal oblique or Trans- DIRECT INGUINAL HERNIA. 1071 versalis; or at the internal ring, most frequently in the latter situation. If it is situated at the external ring, the division of a few fibres at one point of its circumference is all that is necessary for the replacement of the hernia. If in the inguinal canal or at the internal ring, it may be necessary to divide the aponeurosis of the External oblique so as to lay open the inguinal canal. In dividing the stricture the direction of the incision should be upward. When the intestine passes along the spermatic canal and escapes from the external ring into the scrotum, it is called complete oblique inyuinal or scrotal hernia. If the intestine does not escape from the external ring, but is retained in the inguinal canal, it is called incomplete inguinal hernia, or bubonocele. In each of these cases the coverings which invest it will depend upon the extent to which it descends in the inguinal canal. There are some other varieties of oblique inguinal hernia depending upon con- genital defects in the processus vaginalis. The testicle in its descent from the abdomen into the scrotum is accompanied by a pouch of peritoneum, which about the period of birth becomes shut off from the general peritoneal cavity by a closure of that portion of the pouch which extends from the internal abdominal ring to near the upper part of the testicle, the lower portion of the pouch remaining per- sistent as the tunica vaginalis. It would appear that this closure commences at two points-viz. at the internal abdominal ring and at the top of the epididymis- and gradually extends until, in the normal condition, the whole of the inter- vening portion is converted into a fibrous cord. From failure in the completion of this process variations in the relation of the hernial protrusion to the testicle and tunica vaginalis are produced, which constitute distinct varieties of inguinal hernia, and which have received separate names and are of surgical importance. These are congenital, infantile, encysted, and hernia of the funicu- lar process. Congenital Hernia (Fig. 625, b).-Where the pouch of peritoneum which accompanies the cord and testis in its descent remains patent throughout and is unclosed at any point, the cavity of the tunica vaginalis communicates directly with the peritoneum. The intestine descends along this pouch into the cavity of the tunica vaginalis, which constitutes the sac of the hernia, and the gut lies in contact with the testicle. Infantile and Encysted Hernia.-Where the pouch of peritoneum is occluded at the internal ring only, and remains patent throughout the rest of its extent, two varieties of oblique inguinal hernia may be produced, which have received the names of infantile and encysted hernia. In the infantile form (Fig. 625, c) the bowel, pressing upon the septum and the peritoneum in its immediate neighborhood, causes it to yield and form a sac, which descends behind the tunica vaginalis, so that in front of the bowel there are three layers of per- itoneum, the two layers of the tunica vaginalis and its own sac. In the encysted form (Fig. 625, d) pressure in the same position-namely, at the occluded spot in the pouch-causes the septum to yield and form a sac which projects into and not behind the tunica vaginalis, as in the infantile form, and thus it constitutes a sac within a sac, so that in front of the bowel there are two layers of peritoneum-one layer of the tunica vaginalis and its own sac. Hernia into the Funicular Process (Fig. 625, e).-Where the pouch of perito- neum is occluded at the lower point only-that is, just above the testicle-the intestine descends into the pouch of peritoneum as far as the testicle, but is pre- vented from entering the sac of the tunica vaginalis by the septum which has formed between it and the pouch, so that it resembles the congenital form in all respects, except that, instead of enveloping the testicle, that body can be felt below the rupture. Direct Inguinal Hernia. In direct inguinal hernia the protrusion makes its way through some part of the abdominal wall internal to the epigastric artery. 1072 THE SURGICAL ANATOMY OF HERNIA. At the lower part of the abdominal wall is a triangular space {Hesselbach's triangle) bounded externally by the deep epigastric artery, internally by the margin of the Rectus muscle, below by Poupart's ligament. The conjoined tendon is stretched across the inner two-thirds of this space, the remaining portion of the space having only the subperitoneal areolar tissue and the trans- versalis fascia between the peritoneum and the aponeurosis of the External oblique muscle. In some cases the hernial protrusion escapes from the abdomen on the outer side of the conjoined tendon, pushing before it the peritoneum, the subserous areolar tissue, and the transversalis fascia. It then enters the inguinal canal, passing along nearly its whole length, and finally emerges from the external ring, receiving an investment from the intercolumnar fascia. The coverings of this form of hernia are precisely similar to those investing the oblique form, with the insignificant difference that the infundibuliform fascia is replaced by a portion derived from the general layer of the fascia transversalis. In other cases-and this is the more frequent variety-the hernia is either forced through the fibres of the conjoined tendon or the tendon is gradually distended in front of it so as to form a complete investment for it. The intestine then enters the lower end of the inguinal canal, escapes at the external ring lying on the inner side of the cord, and receives additional coverings from the superficial fascia and the integument. This form of hernia has the same coverings as the oblique variety, excepting that the conjoined tendon is substituted for the Cremaster, and the infundibuliform fascia is replaced by a portion derived from the general layer of the fascia transversalis. The difference between the position of the neck of the sac in these two forms of direct inguinal hernia has been referred, with some probability, to a difference in the relative positions of the obliterated hypogastric artery and the deep epigastric artery. When the course of the obliterated hypogastric artery cor- responds pretty nearly with that of the deep epigastric-which is regarded as the normal arrangement-the projection of these arteries toward the cavity of the abdomen produces two fossae in the peritoneum. The bottom of the external fossa of the peritoneum corresponds to the position of the interna] abdominal ring, and a hernia which distends and pushes out the peritoneum lining this fossa is an oblique hernia. When, on the other hand, the obliterated hypogastric artery lies considerably to the inner side of the deep epigastric artery, corresponding to the outer margin of the conjoined tendon, it divides the triangle of Hesselbach into two parts, so that three depressions will be seen on the inner surface of the lower part of the abdominal wall-viz. an external one, on the outer side of the deep epigastric artery; a middle one, between the deep epigastric and the obliterated hypogastric arteries; and an internal one, on the inner side of the obliterated hypogastric artery. In such a case a hernia may distend and push out the peritoneum forming the bottom of either fossa. When the hernia distends and pushes out the peritoneum forming the bottom of the external fossa, it is an oblique or external inguinal hernia. When the hernia distends and pushes out the peritoneum forming the bottom of either the middle or the internal fossa, it is a direct or internal hernia. The anatomical difference between these two forms of direct or internal inguinal hernia is that, when the hernia protrudes through the middle fossa-that is, the fossa between the deep epigastric and the obliterated hypogastric arteries- it will enter the upper part of the inguinal canal; consequently its coverings will be the same as those of an oblique hernia, with the insignificant difference that the infundibuliform fascia is replaced by a portion derived from the general layer of the fascia transversalis, whereas when the hernia protrudes through the internal fossa it is either forced through the fibres of the conjoined tendon or the tendon is gradually distended in front of it so as to form a complete investment for it. The intestine then enters the lower part of the inguinal canal, and escapes from the external abdominal ring lying on the inner side of the cord. FEMORAL HERNIA. 1073 This form of hernia has the same coverings as the oblique variety, excepting that the conjoined tendon is substituted for the Cremaster, and the infundibuli- forrn fascia is replaced by a portion derived from the general layer of the fascia transversalis. The seat of stricture in both varieties of direct hernia is most frequently at the neck of the sac or at the external ring. In that form of hernia which perforates the conjoined tendon it not unfrequently occurs at the edges of the fissure through which the gut passes. In dividing the stricture the incision should in all cases be directed upward.1 If the hernial protrusion passes into the inguinal canal, but does not escape from the external abdominal ring, it forms what is called incomplete direct hernia. This form of hernia is usually of small size, and in corpulent persons very difficult of detection. Direct inguinal hernia is of much less frequent occurrence than the oblique, their comparative frequency being, according to Cloquet, as one to five. It occurs far more frequently in men than in women, on account of the larger size of the external ring in the former sex. It differs from the oblique in its smaller size and globular form, dependent most probably on the resistance offered to its progress by the transversalis fascia and conjoined tendon. It differs also in its position, being placed over the os pubis and not in the course of the inguinal canal. The deep epigastric artery runs on the outer or iliac side of the neck of the sac, and the spermatic cord along its external and posterior side, not directly behind it, as in oblique inguinal hernia. FEMORAL HERNIA. The dissection of the parts comprised in the anatomy of femoral hernia should be per- formed, if possible, upon a female subject free from fat. The subject should lie upon its back ; a block is first placed under the pelvis, the thigh everted, and the knee slightly bent and retained in this position. An incision should then be made from the anterior superior spinous process of the ilium along Poupart's ligament to the symphysis pubis; a second incision should be carried transversely across the thigh about six inches beneath the preceding; and these are to be connected together by a vertical one carried along the inner side of the thigh. These several incisions should divide merely the integument; this is to be reflected outward, when the superficial fascia will be exposed. The superficial fascia forms a continuous layer over the whole of the thigh, consisting of areolar tissue, containing in its meshes much fat, and capable of being separated into two or more layers, between which are found the superficial vessels and nerves. It varies in thickness in different parts of the limb. In the groin it is thick, and the two layers are separated from one another by the super- ficial inguinal lymphatic glands, the internal saphenous vein, and several smaller vessels. One of these layers, the superficial, is continuous with the superficial fascia of the abdomen. The superficial layer should be detached by dividing it across in the same direction as the external incisions; its removal will be facilitated by commencing at the lower and inner angle of the space, detaching it at first from the front of the internal saphenous vein, and dissecting it off from the anterior surface of that vessel and its tributaries; it should then be reflected out- ward in the same manner as the integument. The cutaneous vessels and nerves and superficial inguinal glands are then exposed, lying upon the deep layer of the superficial fascia. These are the internal saphenous vein and the superficial epigastric, superficial circumflex iliac, and super- ficial external pudic vessels, as well as numerous lymphatics, ascending with the saphenous vein to the inguinal glands. The internal or long saphenous vein ascends along the inner side of the thigh, and, passing through the saphenous opening in the fascia lata, terminates in th.e femoral vein about an inch and a half below Poupart's ligament. This vein 1 In all cases of inguinal hernia, whether oblique or direct, it is proper to divide the stricture directly upward : the reason of this is obvious, for by cutting in this direction the incision is made parallel to the deep epigastric artery-either external to it in the oblique variety, or internal to it in the direct form of hernia-and thus all chance of wounding the vessel is avoided. If the incision was made outward, the artery might be divided if the hernia was direct; and if made inward, it would stand an equal chance of injury if the case was one of oblique inguinal hernia. 1074 THE SURGICAL ANATOMY OF HERNIA. receives at the saphenous opening the superficial epigastric, the superficial circumflex iliac, and the superficial external pudic veins. The superficial external pudic artery (superior) arises from the inner side of the femoral artery, and, after passing through the saphenous opening, courses inward across the spermatic cord, to be distributed to the integument on the lower part of the abdomen, the penis and scrotum in the male anti the labium in the female, anastomosing with branches of the internal pudic. The superficial epigastric artery arises from the femoral about half an inch below Poupart's ligament, and, passing through the saphenous opening in the fascia lata, ascends on to the abdomen, in the superficial fascia covering the Fig. 626.-Femoral hernia. Superficial dissection. External oblique muscle, nearly as high as the umbilicus. It distributes branches to the superficial inguinal lymphatic glands, the superficial fascia, and the integu- ment, anastomosing with branches of the deep epigastric and internal mammary arteries. The superficial circumflex iliac artery, the smallest of the cutaneous branches, arises close to the preceding, and, piercing the fascia lata, runs outward, parallel with Poupart's ligament, as far as the crest of the ilium, dividing into branches which supply the superficial inguinal lymphatic glands, the superficial fascia, and the integument of the groin, anastomosing with the deep circumflex iliac, and with the gluteal and external circumflex arteries. The Superficial Veins.-The veins accompanying these superficial arteries are usually much larger than the arteries : they terminate in the internal or long saphenous vein at the saphenous opening. FEMORAL HERNIA. 1075 The superficial inguinal lymphatic glands, placed immediately beneath the integument, are of large size and vary from eight to ten in number. They are divisible into two groups : an upper, disposed irregularly along Poupart's ligament, which receive the lymphatic vessels from the integument of the scrotum, penis, parietes of the abdomen, perineal and gluteal regions, and the mucous membrane of the urethra ; and an inferior group, which surround the saphenous opening in the fascia lata, a few being sometimes continued along the saphenous vein to a variable extent. This latter group receive the superficial lymphatic vessels from the lower extremity. The nerve arises from the first lumbar nerve. It escapes at the external abdominal ring, and is distributed to the integument of the upper and inner part of the thigh-to the scrotum in the male and to the labium in the female. The size of this nerve is in inverse proportion to that of the ilio-hypo- gastric. Occasionally it is very small, and ends by joining the ilio-hypogastric : in such cases a branch of the ilio-hypogastric takes the place of the ilio-inguinal, or the latter nerve may be altogether absent. The crural branch of the genito- crural nerve passes along the inner margin of the Psoas muscle, beneath Poupart's ligament, into the thigh, entering the sheath of the femoral vessels, and lying superficial and a little external to the femoral artery. It pierces the anterior layer of the sheath of the vessels, and, becoming superficial by passing through the fascia lata, it supplies the skin of the anterior aspect of the thigh as far as midway between the pelvis and knee. On the front of the thigh it communicates with the outer branch of the middle cutaneous nerve, derived from the anterior crural. The deep layer of the superficial fascia is a very thin fibrous layer, best marked on the inner side of the long saphenous vein and below Poupart's ligament. It is placed beneath the subcutaneous vessels and nerves, and upon the surface of the fascia lata, to which it is intimately adherent at the lower margin of Poupart's ligament. It covers the saphenous opening in the fascia lata, is closely united to its circumference, and is connected to the sheath of the femoral vessels corre- sponding to its under surface. The portion of fascia covering this aperture is perforated by the internal saphenous vein and by numerous blood- and lymphatic vessels; hence it has been termed the cribriform fascia, the openings for these vessels having been likened to the holes in a sieve. The cribriform fascia adheres closely both to the superficial fascia and to the fascia lata, so that it is described by some anatomists as a part of the fascia lata, but it is usually considered (as in this work) as belonging to the superficial fascia. It is not till the cribriform fascia has been cleared away that the saphenous opening is seen, so that this opening does not in ordinary cases exist naturally, but is the result of dissection. A femoral hernia in passing through the saphenous opening receives the cribriform fascia as one of its coverings. The deep layer of superficial fascia, together with the cribriform fascia, having been removed, the fascia lata is exposed. The Fascia Lata has been already described with the muscles of the front of the thigh (page 508). At the upper and inner part of the thigh, a little below Poupart's ligament, a large oval-shaped aperture is observed after the superficial fascia has been cleared away ; it transmits the internal saphenous vein and other smaller vessels, and is called the saphenous opening. In order the more correctly to consider the mode of formation of this aperture, the fascia lata in this part of the thigh is described as consisting of two portions, an iliac portion and a pubic portion. The iliac portion is all that part of the fascia lata on the outer side of the saphenous opening. It is attached externally to the crest of the ilium and its anterior superior spine ; to the whole length of Poupart's ligament as far internally as the spine of the os pubis ; and to the pectineal line in conj unction with Gimbernat's ligament. From the spine of the os pubis it is reflected downward and outward, forming an arched margin, the outer boundary or falciform process or superior cornu of the saphenous opening. This margin overlies and is adherent to the anterior layer of the sheath of the femoral vessels; to its edge is attached the 1076 THE SURGICAL ANATOMY OF HERNIA. cribriform fascia, and below it is continuous with the pubic portion of the fascia lata. The pubic portion of the fascia lata is situated at the inner side of the saphenous opening : at the lower margin of this aperture it is continuous with the iliac portion : traced upward, it covers the surface of the Pectineus, Adductor longus, and Gracilis muscles; and, passing behind the sheath of the femoral vessels, to which it is closely united, is continuous with the sheath of the Psoas and Iliacus muscles, and is attached above to the ilio-pectineal line, where it becomes continuous with the fascia covering the Iliacus muscle. From this description it may be observed that the iliac portion of the fascia lata passes in front of the femoral vessels and the pubic portion behind them, so that an apparent aperture Fig. 627.-Femoral hernia, showing fascia lata and saphenous opening. consequently exists between the two, through which the internal saphenous joins the femoral vein. The Saphenous Opening is an oval-shaped aperture measuring about an inch and a half in length and half an inch in width. It is situated at the upper and inner part of the front of the thigh, below Poupart's ligament, and is directed obliquely downward and outward. Its outer margin is of a semilunar form, thin, strong, sharply defined, and lies on a plane considerably anterior to the inner margin. If this edge is traced upward, it will be seen to form a curved elongated process, the falciform process or superior cornu, which ascends in front of the femoral vessels, and, curving inward, is attached to Poupart's ligament and to the spine of the os pubis and pectineal line, where it is continuous with the pubic portion. If traced down- ward, it is found continuous with another curved margin, the concavity of which is directed upward and inward: this is the inferior cornu of the saphenous FEMORAL HERNIA. 1077 opening, and is blended with the pubic portion of the fascia lata covering the Pectineus muscle. The inner boundary of the opening is on a plane posterior to the outer margin and behind the level of the femoral vessels ; it is much less prominent and defined than the outer, from being stretched over the subjacent Pectineus muscle. It is through the saphenous opening that a femoral hernia passes after descending along the crural canal. If the finger is introduced into the saphenous opening while the limb is moved in different directions, the aperture will be found to be greatly constricted on extending the limb or rotating it outward, and to be relaxed on flexing the limb Fig. 628.-Femoral hernia. Iliac portion of fascia lata removed, and sheath of femoral vessels and femoral canal exposed. and inverting it: hence the necessity for placing the limb in the latter position in employing the taxis for the reduction of a femoral hernia. The iliac portion of the fascia lata, but not its falciform process, should now be removed by detaching it from the lower margin of Poupart's ligament, carefully dissecting it from the sub- jacent structures, and turning it inward, when the sheath of the femoral vessels is exposed, descending beneath Poupart's ligament (Fig. 628). Poupart's Ligament, or the Crural Arch, is the lower border of the aponeurosis of the External oblique muscle, which extends from the anterior superior spine of the ilium to the spine of the os pubis. From this latter point it is reflected outward, to be attached to the pectineal line for about half an inch, forming Gimbernat's ligament. Its general direction is curved downward toward the thigh, where it is continuous with the fascia lata. Its outer half is rounded and oblique in direction. Its inner half gradually widens at its attachment to the os pubis, is more horizontal in direction, and lies beneath the spermatic cord. Nearly the 1078 THE SURGICAL ANATOMY OF HERNIA. whole of the space included between the crural arch and innominate bone is filled in by the parts which descend from the abdomen into the thigh. The outer half of the space is occupied by the Iliacus and Psoas muscles, together with the external cutaneous and anterior crural nerves. The pubic half of the space is occupied by the femoral vessels included in their sheath, a small oval-shaped interval existing between the femoral vein and the inner wall of the sheath, which is occupied merely by a little loose areolar tissue, a few lymphatic vessels, Crural branch of genito- crural. External cutaneous nerve. Poupart's ligament. Anterior crural. Iliac portion of fascia lata. \ Femoral vein.\ Femoral ring. \ Gimbernat's ligament. ?<•... Sheath of ' vessels. Kp PSOAS Hmagnus. Fig. 629.-Structures which pass beneath the crural arch. Femoral artery. and occasionally by a small lymphatic gland : this is the crural ring, through which the gut descends in femoral hernia. Gimbernat's Ligament (Fig. 630) is that part of the aponeurosis of the External oblique muscle which is reflected downward and outward from the spine of the os pubis, to be inserted into the pectineal line. It is about half an inch in length, larger in the male than in the female, almost horizontal in direction in the erect posture, and of a triangular form, with the base directed outward. Its base, or outer margin, is concave, thin, and sharp, and lies in contact with the crural sheath. Its apex corresponds to the spine of the os pubis. Its posterior margin is attached to the pectineal line, and is continuous with the pubic portion of the fascia lata. Its anterior margin is continuous with Poupart's ligament. Crural Sheath.-The femoral or crural sheath is a continuation downward of the fasciae that line the abdomen, the transversalis fascia passing down in front of the femoral vessels, and the iliac fascia descending behind them ; these fasciae are directly continuous on the iliac side of the femoral artery, but a small space exists between the femoral vein and the point where they are continuous on the pubic side of that vessel, which constitutes the femoral or crural canal. The FEMORAL HERNIA. 1079 femoral sheath is closely adherent to the contained vessels about an inch below the saphenous opening, being blended with the areolar sheath of the vessels, but opposite Poupart's ligament it is much larger than is required to contain them ; hence the funnel-shaped form which it presents. The outer border of the sheath is perforated by the genito-crural nerve. Its inner border is pierced by the internal saphenous vein and numerous lymphatic vessels. In front it is covered by the iliac portion of the fascia lata ; and behind it is the pubic portion of the same fascia. If the anterior wall of the sheath is removed, the femoral artery and vein are seen lying side by side, a thin septum separating the two vessels, while another septum may be seen lying just internal to the vein, and cutting off a small space between the vein and the inner wall of the sheath. The septa are stretched between the anterior and posterior walls of the sheath, so that each vessel is enclosed in a separate compartment. The interval left between the vein and the inner wall of the sheath is not filled up by any structure, excepting a little loose areolar tissue, a few lymphatic vessels, and occasionally by a small lymphatic Fig. 630.-Hernia. The relations of the femoral and internal abdominal rings, seen from within the abdo- men. Right side. gland: this is the femoral or crural canal, through which the intestine descends in femoral hernia. Deep Crural Arch.-Passing across the front of the crural sheath on the abdominal side of Poupart's ligament, and closely connected with it, is a thickened band of fibres called the deep crural arch. It is apparently a thickening of the fascia transversalis, joining externally to the centre of Poupart's ligament, and arching across the front of the crural sheath, to be inserted by a broad attachment into the pectineal line behind the conjoined tendon. In some subjects this structure is not very prominently marked, and not unfrequently it is altogether wanting. The crural canal is the narrow interval between the femoral vein and the inner wall of the crural sheath. It exists as a distinct canal only when the sheath has been separated from the vein by dissection or by the pressure of a hernia or tumor. Its length is from a quarter to half an inch, and it extends from Gimbernat's liga- ment to the upper part of the saphenous opening. Its anterior wall is very narrow, and formed by a continuation downward of the fascia transversalis, under Poupart's ligament, covered by the falciform pro- cess of the fascia lata. 1080 THE SURGICAL ANATOMY OF HERNIA. Its posterior wall is formed by a continuation downward of the iliac fascia covering the pubic portion of the fascia lata. Its outer wall is formed by the fibrous septum separating it from the inner side of the femoral vein. Its inner wall is formed by the junction of the processes of the transversalis and iliac fasciae, which form the inner side of the femoral sheath, and lies in contact at its commencement with the outer edge- of Gimbernat's ligament. This canal has two orifices-an upper one, the femoral or crural ring, closed by the septum crurale; and a lower one, the saphenous opening, closed by the cribriform fascia. The femoral or crural ring (Fig. 630) is the upper opening of the femoral canal, and leads into the cavity of the abdomen. It is bounded in front by Poupart s ligament and the deep crural arch ; behind, by the os pubis, covered by the Pectineus muscle and the pubic portion of the fascia lata; internally, by the base of Gimbernat's ligament, the conjoined tendon, the transversalis fascia, and the deep crural arch; externally, by the fibrous septum lying on the inner side of the femoral vein. The femoral ring is of an oval form; its long diameter, directed transversely, measures about half an inch, and it is larger in the female than in the male, which is one of the reasons of the greater frequency of femoral hernia in the former sex. ' Position of Parts around the Ring.-The spermatic cord in the male and round ligament in the female lie immediately above the anterior margin of the femoral ring, and may be divided in an operation for femoral hernia if the incision for the relief of the stricture is not of limited extent. In the female this is of little importance, but in the male the spermatic artery and vas deferens may be divided. The femoral vein lies on the outer side of the ring. The deep epigastric artery in its passage upward and inward from the external iliac artery passes across the upper and outer angle of the crural ring, and is consequently in danger of being wounded if the stricture is divided in a direction upward and outward. The branch between the deep epigastric and obturator lies in front of the ring. The circumference of the ring is thus seen to be bounded by vessels in every part, excepting internally and behind. It is in the former position that the stricture is divided in cases of strangulated femoral hernia. The obturator artery, when it arises by a common trunk with the deep epigastric, which occurs once in every three subjects and a half, bears a very important relation to the crural ring. In some cases it descends on the inner side of the external iliac vein to the obturator foramen, and will consequently lie on the outer side of the crural ring, where there is no danger of its being wounded in the operation for dividing the stricture in femoral hernia (see Fig. 373, page 625, fig. a). Occasionally, however, the obturator artery curves along the free margin of Gimbernat's ligament in its passage to the obturator foramen: it would conse- quently skirt along the greater part of the circumference of the crural ring, and could hardly avoid being wounded in the operation (see Fig. 373, page 625, fig. b). Septum Crurale.-The femoral ring is closed by a layer of condensed areolar tissue called, by J. Cloquet, the septum crurale. This serves as a barrier to the protrusion of a hernia through this part. Its upper surface is slightly concave, and supports a small lymphatic gland by which it is separated from the subserous areolar tissue and peritoneum. Its under surface is turned toward the femoral canal. The septum crurale is perforated by numerous apertures for the passage of lymphatic vessels connecting the deep inguinal lymphatic glands with those surrounding the external iliac artery. The size of the femoral canal, the degree of tension of its orifices, and consequently the degree of constriction of a hernia, vary according to the position of the limb. If the leg and thigh are extended, abducted, or everted, the femoral FEMORAL HERNIA. 1081 canal and its orifices are rendered tense from the traction on these parts by Poupart's ligament and the fascia lata, as may be ascertained by passing the finger along the canal. If, on the contrary, the thigh is flexed upon the pelvis, and at the same time adducted and rotated inward, the femoral canal and its orifices become considerably relaxed; for this reason the limb should always be placed in the latter position when the application of the taxis is made in attempting the reduction of a femoral hernia. The subperitoneal areolar tissue is continuous with the subserous areolar tissue of surrounding parts. It is usually thickest and most fibrous where the iliac vessels leave the abdominal cavity. It covers over the small interval (crural ring) on the inner side of the femoral vein. In some subjects it contains a considerable amount of adipose tissue. In such cases, where it is protruded forward in front of the sac of a femoral hernia, it may be mistaken for a portion of omentum. The peritoneum lining the portion of the abdominal wall between Poupart's ligament and the brim of the pelvis is similar to that lining any other portion of the abdominal wall, being very thin. It has here no natural aperture for the escape of intestine. Descent of the Hernia.-From the preceding description it follows that the femoral ring must be a weak point in the abdominal wall: hence it is that when violent or long-continued pressure is made upon the abdominal viscera a portion of intestine may be forced into it, constituting a femoral hernia; and the changes in the tissues of the abdomen which are produced by pregnancy, together with the larger size of this aperture in the female, serve to explain the frequency of this form of hernia in women. When a portion of the intestine is forced through the femoral ring, it carries before it a pouch of peritoneum, which forms what is called the hernial sac ; it receives an investment from the subserous areolar tissue and from the septum crurale, and descends vertically along the crural canal in the inner compartment of the sheath of the femoral vessels as far as the saphenous opening ; at this point it changes its course, being prevented from extending farther down the sheath on account of the narrowing of the sheath and its close contact with the vessels, and also from the close attachment of the superficial fascia and crural sheath to the lower part of the circumference of the saphenous opening ; the tumor is conse- quently directed forward, pushing before it the cribriform fascia, and then curves upward on to the falciform process of the fascia lata and lower part of the tendon of the External oblique, being covered by the superficial fascia and integument. While the hernia is contained in the femoral canal it is usually of small size, owing to the resisting nature of the surrounding parts; but when it has escaped from the saphenous opening into the loose areolar tissue of the groin, it becomes considerably enlarged. The direction taken by a femoral hernia in its descent is at first downward, then forward and upward ; this should be borne in mind, as in the application of the taxis for the reduction of a femoral hernia pressure should be directed in the reverse order. Coverings of the Hernia.-The coverings of a femoral hernia, from within outward, are-peritoneum, subserous areolar tissue, the septum crurale, crural sheath, cribriform fascia, superficial fascia, and integument.1 Varieties of Femoral Hernia.-If the intestine descends along the femoral canal only as far as the saphenous opening, and does not escape from this aperture, it is called incomplete femoral hernia. The small size of the protrusion in this form of hernia, on account of the firm and resisting nature of the canal in which it is contained, renders it an exceedingly dangerous variety of the disease, from the 1 Sir Astley Cooper has described*an investment for femoral hernia, under the name of " fascia propria," lying immediately external to the peritoneal sac, but frequently separated from it by more or less adipose tissue. Surgically, it is important to remember the existence (at any rate, the occa- sional existence) of this layer, on account of the ease with which an inexperienced operator may mis- take the fascia for the peritoneal sac and the contained fat for omentum. Anatomically, this fascia appears identical with what is called in the text " subserous areolar tissue," the areolar tissue being thickened and caused to assume a membranous appearance by the pressure of the hernia. 1082 THE SURGICAL ANATOMY OF HERNIA. extreme difficulty of detecting the existence of the swelling, especially in corpulent subjects. The coverings of an incomplete femoral hernia would be, from without inward, integument, superficial fascia, falciform process of fascia lata, crural sheath, septum crurale, subserous areolar tissue, and peritoneum. When, however, the hernial tumor protrudes through the saphenous opening and directs itself forward and upward, it forms a complete femoral hernia. Occasionally the hernial sac descends on the iliac side of the femoral vessels or in front of these vessels, or even sometimes behind them. The seat of stricture of a femoral hernia varies : it may be in the peritoneum at the neck of the hernial sac; in the greater number of cases it would appear to be at the point of junction of the falciform process of the fascia lata with the lunated edge of Gimbernat's ligament, or at the margin of the saphenous opening in the thigh. The stricture should in every case be divided in a direction upward and inward, and the extent necessary in the majority of cases is about two or three lines. By these means all vessels or other structures of importance in relation with the neck of the hernial sac will be avoided. SURGICAL ANATOMY OF THE ISCHIO-RECTAL REGION AND PERMUM. Dissection.-The student should select a well-developed muscular subject, free from fat, and the dissection should be commenced early, in order that the parts may be examined in as recent a state as possible. A staff having been introduced into the bladder and the subject placed in the position shown in Fig. 631, the scrotum should be raised upward, and retained in that position, and the rectum moderately distended with tow. The space which is now to be examined corresponds to the inferior aperture or outlet of the pelvis. Its deep boundaries are, in front, the pubic arch and subpubic ligament; behind, the tip of the coccyx; and on each side, the rami of the pubes and ischium, the tuberosities of the ischium, and great sacro- sciatic ligaments. The space included by these boundaries is somewhat lozenge- shaped, and is limited on the surface of the body by the scrotum in front, by the buttocks behind, and on each side by the inner side of the thighs. A line drawn transversely between the anterior part of the tuberosity of the ischium on each side, in front of the anus, divides this space into tw'O portions. The anterior portion contains the penis and urethra, and is called the perinoeum. The posterior portion contains the termination of the rectum, and is called the ischio- rectal region. THE ISCHIO-RECTAL REGION. The ischio-rectal region corresponds to the portion of the outlet of the pelvis situated immediately behind the perineum: it contains the termination of the rectum and a deep fossa, filled with fat, on each side of the intestine, between it and the tuberosity of the ischium : this is called the ischio-rectal fossa. The ischio-rectal region presents in the middle line the aperture of the anus : around this orifice the integument is thrown into numerous folds, which are obliterated on distension of the intestine. The integument is of a dark color, continuous with the mucous membrane of the rectum, and provided with numerous follicles, which occasionally inflame and suppurate, and may be mistaken for fistulae. The veins around the margin of the anus are occasionally much dilated, forming a number of hard pendent masses, of a dark bluish color, covered partly by mucous membrane and partly by the integument. These tumors constitute the disease called external piles. Dissection (Fig. 631).-Make an incision through the integument, along the median line, from the base of the scrotum to the anterior extremity of the anus: carry it round the margins of this aperture to its posterior extremity, and continue it backward to about an inch behind the tip of the coccyx. A transverse incision should now be carried across the base of the scrotum, joining the anterior extremity of the preceding; a second, carried in the same direction, should be made in front of the anus; and a third at the posterior extremity of the first incision. These incisions shotdd be sufficiently extensive to enable the dissector to raise the integument from the inner side of the thighs. The flaps of skin corresponding to the ischio- rectal region should now be removed. In dissecting the integument from this region great care is required, otherwise the Corrugator cutis ani and External sphincter will be removed, as they are intimately adherent to the skin. The superficial fascia is exposed on the removal of the skin: it is very thick, areolar in texture, and contains much fat in its meshes. In it are found ramifying two or three cutaneous branches of the small sciatic nerve; these turn round the inferior border of the Gluteus maximus and are distributed to the integument around the anus. 1083 1084 SURGICAL ANATOMY OF THE PERINAEUM. In this region, and connected with the lower end of the rectum, are four muscles : the Corrugator cutis ani; the two Sphincters, External and Internal; and the Levator ani. These muscles have been already described (see pages 460 and 461). The ischio-rectal fossa is situated between the end of the rectum and the tuberosity of the ischium on each side. It is triangular in shape ; its base, directed to the surface of the body, is formed by the integument of the ischio-rectal region ; its apex, directed upward, corresponds to the point of division of the obturator fascia and the thin membrane given off from it, which covers the outer surface of the Levator ani (ischio-rectal or anal fascia). Its dimensions are about an inch in breadth at the base and about two inches in depth, being deeper behind than in front. It is bounded, internally, by the Sphincter ani, Levator ani, and Coc- cygeus muscles; externally, by the tuberosity of the ischium and the obturator fascia, which covers the inner surface of the Obturator internus muscle; in front, it is limited by the line of junction of the superficial and deep perineal fasciae; and behind, by the margin of the Gluteus maximus and the great sacro-sciatic liga- ment. This space is filled with a large mass of adipose tissue, which explains the frequency with which abscesses in the neighborhood of the rectum burrow to a considerable depth. If the subject has been injected, on placing the finger on the outer wall of this fossa the internal pudic artery, with its accompanying veins and nerve, will be felt about an inch and a half above the margin of the ischiatic tuberosity, but approaching nearer the surface as they pass forward along the inner margin of the pubic arch. These structures are enclosed in a sheath (canal of Alcock) formed by the obturator fascia, the pudic nerve lying below' the artery (Fig. 374). Cross- ing the space transversely, about its centre are the inferior haemorrhoidal vessels and nerves, branches of the internal pudic ; they are distributed to the integu- ment of the anus and to the muscles of the lower end of the rectum. These vessels are occasionally of large size, and may give rise to troublesome haemorrhage when divided in the operation of lithotomy or of fistula in ano. At the back part of this space may be seen a branch of the fourth sacral nerve, and, at the fore part of the space the superficial perineal vessels and nerves can be seen for a short distance. The perineal space is of a triangular form; its deep boundaries are limited, laterally, by the rami of the pubic bones and ischia, meeting in front at the pubic arch; behind, by an imaginary transverse line extending between the tuberosities of the ischia. The lateral boundaries are, in the adult, from three inches to three inches and a half in length, and the base from two to three inches and a half in breadth, the average extent of the space being twTo inches and three- quarters. The variations in the diameter of this space are of extreme interest in connection with the operation of lithotomy and the extraction of a stone from the cavity of the bladder. In those cases where the tuberosities of the ischia are near together it would be necessary to make the incisions in the lateral operation of lithotomy less oblique than if the tuberosities were widely separated, and the perineal space consequently wider. The perinaeum is subdivided by the median raphe into two equal parts. Of these, the left is the one in which the operation of lithotomy is performed. In the middle line the perinaeum is convex, and corresponds to the bulb of the urethra. The skin covering it is of a dark color, thin, freely movable upon the subjacent parts, and covered with sharp crisp hairs, which should be removed before the dissection of the part is commenced. In front of the anus a prominent line commences, the raphe, continuous in front with the raphe of the scrotum. Upon removing the skin and superficial structures from this region, in the manner shown in Fig. 631, a plane of fascia will be exposed, covering in the triangular space and stretching across from one ischio-pubic ramus to the other. This is the deep layer of the superficial fascia or fascia of Colles. It has already THE PERINEUM IN THE MALE. THE PERINEUM IN THE MALE. 1085 been described (page 462). It is a layer of considerable strength, and encloses and covers a space in which are contained muscles, vessels, and nerves. It is continuous in front with the dartos of the scrotum; on each side it is firmly attached to the margin of the ischio-pubic ramus and to the tuberosity of the ischium; and posteriorly it curves down behind the Transversus perinsei muscles to join the lower margin of the deep perineal fascia. It is between this layer of fascia and the next layer, the superficial layer of the deep perineal fascia, that extravasation of urine most frequently takes place in cases of rupture of the urethra. The superficial layer of the deep perineal fascia (see page 465) is also attached to the ischio-pubic rami, and in front to the subpubic ligament. It is clear, therefore, that when extravasation of fluid takes place between these two layers, it cannot pass backward, because the two layers are continuous with each other around the Transversus perimei muscles ; it cannot extend laterally, on account of the connection of both these layers to the rami of the os pubis and ischium; it cannot find its way into the pelvis, because the opening into this cavity is closed by the deep perineal fascia; and therefore, so long as these two layers remain intact, the only direction in which the fluid can make its way is forward into the areolar tissue of the scrotum and penis, and from thence on to the anterior wall of the abdomen. When the deep layer of the superficial fascia is removed, a space is exposed between this fascia and the deep perineal fascia in which are contained most of Fig. 631.-Dissection of perineeum and ischio-rectal region. the branches of the internal pudic artery, with their accompanying veins ; the terminal branches of the internal pudic nerve ; some of the muscles connected with the penis and urethra;-in the middle line, the Accelerator urinae ; on each side, the Erector penis; and behind, the Transversus perinaei;-the crura of the corpora cavernosa; and the bulb of the corpus spongiosum. Here also is seen the central tendinous point of the perinceum. This is a fibrous point in the middle line of the perinaeum between the urethra and the rectum, being about half an inch in front of the anus. At this point five muscles converge and are attached-viz. the External sphincter ani, the Acceleratores urinae, and the two Transversi perinaei muscles-so that by the contraction of these muscles, which extend in opposite directions, it serves as a fixed point of support. The Accelerator urinae, the Erector penis, and the Transversus perinaei muscles have been already described (page 463). They form a triangular space, bounded internally by the Accelerator urinae, externally by the Erector penis, and behind by the Transversus perinaei. The floor of this space is formed by the triangular ligament of the urethra (deep perineal fascia), and running from behind forward in it are the superficial perineal vessels and nerves, and the transverse perineal artery coursing along the posterior boundary of the space on the Transversus perinaei muscle. The two terminal branches of the internal pudic artery are also to be seen in this space: the dorsal artery of the penis ascending between the crus and the pubic arch, and the artery to the corpus cavernosum entering the crus immediately after the division of the parent trunk. The perineal nerve and dorsal nerve of the penis, the two terminal branches of the pudic nerve, are 1086 SURGICAL ANATOMY OF THE PERINEUM. also contained in this space: the perineal, dividing into muscular and cutaneous branches, and the dorsal nerve, accompanying the dorsal artery along the ischio- pubic ramus, and with it piercing the suspensory ligament to be distributed to the penis. The Accelerator urinae and Erector penis should now be removed, when the deep perineal fascia will be exposed, stretching across the front part of the outlet of the pelvis. The urethra is seen perforating its centre just behind the bulb, and on each side is the crus penis, connecting the corpus cavernosum with the rami of the ischium and os pubis. The deep perineal fascia (triangular ligament), which has already been described (see page 465), consists of two layers, the inferior or superficial layer of which, sometimes called the anterior layer of the triangular ligament, is now exposed. It is united to the superior or deep layer behind, but is separated in front by a sub- fascial space, in which are contained certain structures. The superficial layer of the deep perineal fascia consists of a strong fibrous membrane, the fibres of which are disposed transversely, which stretches across ■Superficial perineal artery. ■Superficial perineal nerve. .Internal pudic nerve. Internal pudic artery. GREAT SACRO- SCIATIC LIGAMENT. Fig. 632.-The superficial muscles and vessels of the perinaeum. from one ischio-pubic ramus to the other and completely fills in the pubic arch ; it is attached in front to the subpubic ligament, except just in the centre, where a small interspace is left for the dorsal vein of the penis. In the erect position of the body it is almost horizontal. It is perforated by the urethra in the middle line, and on each side by the ducts of Cowper's glands. It is pierced also by several branches of the internal pudic artery, the dorsal artery of the penis near the apex of the ligament, the artery to the corpus cavernosum more posteriorly, close to the lateral margin of the ligament, and the artery to the bulb in front of the opening for Cowper's duct. The dorsal nerve of the penis also passes through the ligament in company with the artery of the same name. The crura penis are exposed, lying superficial to this ligament. They will be seen to be attached by blunt-pointed processes to the rami of the os pubis and ischium, in front of the tuberosities, and, passing forward and inward, joining to form the body of the penis. In the middle line is the bulb and corpus spongiosum, exposed by the removal of the Accelerator urinae muscle. JAiS'CZd. 1087 If the superficial layer of the deep perineal fascia is detached on either side, the deep perineal interspace will be exposed and the following parts will be seen between it and the deep layer of the fascia : the subpubic ligament in front, close to the symphysis pubis ; the dorsal vein of the penis; the membranous portion of the urethra and the Compressor urethrae muscle; Cowper's glands and their ducts ; the pudic vessels and the dorsal nerve of the penis ; the artery and nerve of the bulb and a plexus of veins. The superior or deep layer of the deep perineal fascia is derived from the obturator fascia or is continuous w'ith it along the pubic arch. Behind, it joins with the superficial layer of the deep perineal fascia and is continuous with the anal fascia. Above it is the recto-vesical fascia, separated from it on each side by the anterior fibres of the Levator ani, but in the median line these two layers of fascia are continuous and form a median septum, in consequence of the recto-vesical fascia dipping down to join the deep layer of the deep perineal fascia. Thus on each Anterior layer of deep perineal fascia removed, showing URETHRAE. Jnternal pudic artery. -Artery of the bulb. 'Cowper's gland. side of the middle line, beneath this fascia, is a little interspace in which is contained the anterior fibres of the Levator ani (Levator prostatse). It is bounded, below, by the deep layer of the deep perineal fascia; above, by the recto-vesical fascia, and is separated internally from the space on the other side by the median septum. The deep layer of the deep perineal fascia is pierced by the urethra, and is continued backward around the posterior part of the membranous portion of the urethra and the outer surface of the prostate gland. The Compressor urethrae has already been described (page 466). In addition to this muscle and immediately beneath it circular muscular fibres surround the mem- branous portion of the urethra from the bulb in front to the prostate behind, and are continuous with the muscular fibres of the bladder. These fibres are involuntary. Cowper's glands are situated immediately below the membranous portion of the urethra, close behind the bulb, and below the artery of the bulb. The pudic vessels and dorsal nerve of the penis are placed along the inner margin of the pudic arch (pages 625 and 833). The artery of the bulb passes transversely inward, from the internal pudic along the base of the triangular ligament, between the two layers of fascia, Fig. 633.-Deep perineal fascia. On the left side the anterior layer has been removed 1088 SURGICAL ANATOMY OF THE PERINAEUM. accompanied by a branch of the pudic nerve (page 823). If the posterior layer of the deep perineal fascia is removed and the crus penis of one side detached from the bone, the under or perineal surface of the Levator ani is brought fullv into view. This muscle, with the triangular ligament in front and the Coccygeus and Pyriformis behind, closes the outlet of the pelvis. The Levator ani and Coccygeus muscles have already been described (page 461). Position of the Viscera at the Outlet of the Pelvis-Divide the central tendinous point of the perinaeum, separate the rectum from its connections by dividing the fibres of the Levator ani, which descend upon the sides of the prostate gland, and draw the gut backward toward the coccyx, when the under surface of the prostate gland, the neck and base of the bladder, the vesiculae seminales, and the vasa deferentia will be exposed. The Prostate Gland is a pale, firm, glandular body which is placed immediately in front of the neck of the bladder around the commencement of the urethra. It is Artery of corpus cavernosum. Dorsal artery of penis. Artery of bulb.- Internal pudic artery.. Cowper's gland.. Fig. 634.-A view of the position of the viscera at the outlet of the pelvis. placed in the pelvic cavity, behind and below the symphysis pubis, posterior to the deep perineal fascia, and rests upon the rectum, through which it may be distinctly felt, especially when enlarged. In shape and size it resembles a chestnut. Its base is directed backward toward the neck of the bladder. Its apex is directed forward to the deep perineal fascia, which it touches. Its under surface is smooth, marked by a slight longitudinal furrow, and rests on the rectum, to which it is connected by areolar tissue. Its upper surface is flattened, marked by a slight longitudinal furrow, and placed about three-quarters of an inch below the pubic symphysis. It measures about an inch and a half in its transverse diameter at the base, an inch in its antero-posterioi' diameter, and three-quarters of an inch in depth. Hence the greatest extent of incision that can be made in it without dividing its substance completely across is obliquely back- ward and outward. This is the direction in which the incision is made in it in the lateral operation of lithotomy. Behind the prostate is the posterior surface of the neck and base of the bladder, a small triangular portion of the bladder being seen, bounded, in front, by the prostate gland; behind, by the recto-vesical fold of the peritoneum; on each side, by the vesicula seminalis and the vas deferens. It is separated from direct contact THE FEMALE PERINAEUM. 1089 with the rectum by the recto-vesical fascia. The relation of this portion of the bladder to the rectum is of extreme interest to the surgeon. In cases of retention of urine this portion of the organ is found projecting into the rectum, between three and four inches from the margin of the anus, and may be easily perforated without injury to any important parts : this portion of the bladder is, consequently, occasionally selected for the performance of the operation of tapping the bladder. Surgical Anatomy.-The student should consider the position of the various parts in reference to the lateral operation of lithotomy. This operation is performed on the left side of the perinaeum, as it is most convenient for the right hand of the operator. A staff having been introduced into the bladder, the first incision is commenced midway between the anus ami the back of the scrotum (?. e. in an ordinary adult perinaeum about an inch and a half in front of the anus) a little on the left side of the raphe, and carried obliquely backward and outward to midway between the anus and tuberosity of the ischium. The incision divides the integument and superficial fascia, the inferior haemorrhoidal vessels and nerves, and the superficial and trans- verse perineal vessels. If the forefinger of the left hand is thrust upward and forward into the wound, pressing at the same time the rectum inward and backward, the staff may be felt in the membranous portion of the urethra. The finger is fixed upon the staff, and the structures covering it are divided with the point of the knife, which must be directed along the groove toward the bladder, the edge of the knife being turned outward and backward, dividing in its course the membranous portion of the urethra and part of the left lobe of the prostate gland to the extent of about an inch. The knife is then withdrawn, and the forefinger of the left hand passed along the staff into the bladder. The position of the stone having been ascertained, the staff is to be withdrawn, and the forceps is introduced over the finger into the bladder. If the stone is very large, the opposite side of the prostate may be notched before the forceps is intro- duced : the finger is now withdrawn, and the blades of the forceps opened and made to grasp the stone, which must be extracted by slow and cautious undulating movements. Parts Divided in the Operation.-The various structures divided in this operation are as follows : the integument, superficial fascia, inferior haemorrhoidal vessels and nerves, and prob- ably the superficial perineal vessels and nerves, the posterior fibres of the Accelerator urinae, the Transversus perinaei muscle and artery, the deep perineal fascia, the anterior fibres of the Levator ani, part of the Compressor urethrae, the membranous and prostatic portions of the urethra, and part of the prostate gland. Parts to be Avoided in the Operation.-In making the necessary incisions in the peri- naeum for the extraction of a calculus the following parts should be avoided: The primary incis- ion should not be made too near the middle line, for fear of wounding the bulb of the corpus spongiosum or the rectum ; nor too far externally, otherwise the pudic artery may be implicated as it ascends along the inner border of the pubic arch. If the incisions are carried too far forward, the artery of the bulb may be divided; if carried too far backward, the entire breadth of the prostate and neck of the bladder may be cut through, which allows the urine to become infiltrated behind the pelvic fascia into the loose areolar tissue between the bladder and rectum, instead of escaping externally ; diffuse inflammation is consequently set up, and peritonitis, from the close proximity of the recto vesical peritoneal fold, is the result. If. on the contrary, the prostate is divided in front of the base of the gland, the urine makes its way externally, and there is less danger of infiltration taking place. During the operation it is of great importance that the finger should be passed into the bladder before, the staff is removed; if this is neglected, and if the incision made in the prostate and neck of the bladder is too small, great difficulty may be experienced in introducing the finger afterward; and in the child, where the connections of the bladder to the surrounding parts are very loose, the force made in the attempt is sufficient to displace the bladder upward into the abdomen, out of the reach of the operator. Such a proceeding has not unfrequently occurred, producing the most embarrassing results and total failure of the operation. It is necessary to bear in mind that the arteries in the perinaeum occasionally take an abnor- mal course. Thus the artery of the bulb, when it arises, as sometimes happens, from the pudic opposite the tuber ischii, is liable to be wounded in the operation for lithotomy in its passage forward to the bulb. The accessory pudic may be divided near the posterior border of the pros- tate gland, if this is completely cut across; and the prostatic veins, especially in people advanced in life, are of large size, and give rise, when divided, to troublesome haemorrhage. THE FEMALE PERINEUM. The female perinaeum presents certain differences from that of the male, in consequence of the whole of the structures which constitute it being perforated in the middle line by the vulvo-vaginal passage. The superficial fascia, as in the male, consists of two layers, of which the superficial one is continuous with the superficial fascia over the rest of the body, and the deep layer, corresponding to the fascia of Colles in the male, is like it attached to the ischio-pubic ramus, and in front is continued forward through 1090 SURGICAL ANATOMY OF THE PERINEUM. the labia majora to the inguinal region. It is of less extent than the male, in consequence of being perforated by the aperture of the vulva. On removing this fascia the muscles of the female perinseum, which have already been described (page 466), are exposed. The Sphincter vaginae, corre- sponding to the Accelerator urinae in the male, consists of an attenuated plane of fibres, forming an orbicular muscle around the orifice of the vagina, instead of being united in a median raphe, as in the male. The Erector clitoridis is propor- tionately reduced in size, but differs in- no other respect, and the Transversus perinaei is similar to.the muscle of the same name in the male. The deep perineal fascia is not so strongly marked as in the male. It transmits the urethra, and is wide, separated in the median line by the aperture of the vagina. The Compressor Urethrae (Transversus perincei profundus) is the analogue of the Compressor urethrae in the male. It arises from the ischio-pubic ramus, and, passing inward, its anterior fibres blend with the muscle of the opposite side, in front of the urethra; its middle fibres, the most numerous, are inserted into the side of the vagina, and the posterior fibres join the central point of the perinaeum. The distribution of the internal pudic artery is the same as in the male (see page 627), and the pudic nerve has also a similar arrangement, the dorsal nerve being, however, very small and supplying the clitoris. The corpus spongiosum is divided into two lateral halves, which are represented by the bulbi vestibuli and partes intermediates (see page 1049). The perineal body fills up the interval between the lower part of the vagina and the rectum. Its base is covered by the skin lying between the anus and Crest of ilium. Anterior crural nerve. ' -Iliac Fascia. Femoral vessels. Brim of pelvis. Pelvic vfascia. •Bladder Obturator fascia. Internal pndic and nerve. Tuberosity of ischium. Fig. 635.-A transverse section of the pelvis, showing the pelvic fascia from behind. vagina on what is called the " perinaeum." Its anterior surface lies behind the posterior vaginal wall, and its posterior surface lies in front of the anterior rectal wall and the anus. It measures about an inch and a quarter from before backward, and laterally extends from one tuberosity of the ischium to the other. In it are situated the muscles belonging to the external organs of generation. Through its PELVIC FASCIA. 1091 centre runs the transverse perineal septum, which is of great strength in women, and forms on either side, behind the posterior commissure, a hard, ill-defined body, consisting of connective tissue, with much yellow elastic tissue and interlacing bundles of involuntary muscular fibres, in which the voluntary muscles of the perinaeum are inserted. PELVIC FASCIA. The Pelvic fascia (Fig. 635) is a thin membrane which lines the whole of the cavity of the pelvis and is continuous with the transversalis and iliac fasciae. It is attached to the brim of the pelvis, for a short distance, at the side of the cavity, and to the inner surface of the bone round the attachment of the Obturator internus. At the posterior border of this muscle it is continued backward as a very thin membrane in front of the Pyriformis muscle and sacral nerves to the front of the sacrum. In front it follows the attachment of the Obturator internus to the bone, arches beneath the obturator vessels, completing the orifice of the obturator canal, and at the front of the pelvis is attached to the lower part of the symphysis pubis. At the level of a line extending from the lower part of the symphysis pubis to the Fig. 636.-Side view of the pelvic viscera of the male subject, showing the pelvic and perineal fasciae. spine of the ischium is a thickened whitish band ; this marks the attachment of the Levator ani muscle to the pelvic fascia, and corresponds to its point of division into two layers, the obturator and recto-vesical. The obturator fascia descends and covers the Obturator internus muscle. It is a direct continuation of the pelvic fascia below the white line above mentioned, and is attached to the pubic arch and to the margin of the great sacro-sciatic liga- ment. From its attachment to the rami of the os pubis and ischium a process is given off which is continuous with a similar process from the opposite side, so as to close the front part of the outlet of the pelvis, forming the posterior layer of the triangular ligament. This fascia forms a canal for the pudic vessels and nerve in their passage forward to the perinaeum, and gives off a thin membrane 1092 SURGICAL ANATOMY OF THE PER I NYU UM. which covers the perineal aspect of the Levator ani muscle, called the ischio-rectal (anal} fascia. The recto-vesical fascia (visceral layer of the pelvic fascia} descends into the pelvis upon the upper surface of the Levator ani muscle, and invests the prostate, bladder, and rectum. From the inner surface of the symphysis pubis a short rounded band is continued to the upper surface of the prostate and neck of the bladder, forming the pubo-prostatic or anterior true ligaments of the bladder. At the side this fascia is connected to the side of the prostate, enclosing this gland and the vesico-prostatic plexus of veins, and is continued upward on the side of the bladder, forming the lateral true ligaments of the organ. Another prolonga- tion invests the vesicul<e seminales, and passes across between the bladder and rectum, being continuous with the same fascia of the opposite side. Another thin prolongation is reflected round the surface of the lower end of the rectum. The Levator ani muscle arises from the point of division of the pelvic fascia, the vis- ceral layer of the fascia descending upon and being intimately adherent to the upper surface of the muscle, while the under surface of the muscle is covered by a thin layer derived from the obturator fascia, called the ischio-rectal or anal fascia. In the female the vagina perforates the recto-vesical fascia, and receives a pro- longation from it. INDEX. A. Abdomen, 914 apertures found in, 914 boundaries of, 914 lymphatics of, 691 muscles of, 449 regions of, 914 viscera of, 918 Abdominal aorta, 610 branches of, 611 surgical anatomy of, 611 surface-marking of, 611 muscles, 449 ring, external, 451 internal, 1068 viscera, position of, 914, 916 Abdomino-thoracic arch, 239 Abducent nerve, 772 surgical anatomy of, 773 Abductor indicis muscle, 498 minimi digiti muscle, band, 496 foot, 533 pollicis muscle, 474 hallucis, 532 Aberrant duct of testis, 1023 Absorbent glands, 681 Absorbents, 681 Accelerator urinae muscle, 465 Accessorii orbicularis oris, 404 Accessorius ad ilio-costalem mus- cle, 438 pedis, 534 Accessory ligament of shoulder, 348 obturator nerve, 816 olivary nuclei, 714 descending palatine canals, 199 processes, 154 pudic artery, 625 Acervulus cerebri, 741 Acetabulum, 280 Acromatin, 39 Acromial end of clavicle, frac- ture of, 502 region, muscles of, 473 thoracic artery, 594 Acromio-clavicular joint, 344 surface form of, 346 surgical anatomy of, 346 Acromion process, 246 fracture of, 502 Actions of muscles. See each group of muscles. Adductor brevis muscle, 514 longus muscle, 514 magnus muscle, 515 obliquus pollicis, 495 hallucis, 535 transversus pollicis, 495 hallucis, 535 tubercle, 289 Adenoid connective tissue, 48 Adipose tissue, 49 Afferent nerves, 75 vessels of kidney, 1018 Air-cells, 1003 A he of vomer, 203 Alar ligaments, 328 of knee, 374 thoracic artery, 594 Alcock, canal of, 1084 Alimentary canal, 892 development of, 133 subdivisions of, 892 Allantoic vessels, 113 vesicle, 113 Allantois, 113, 1024 Alveolar artery, 564 process, 195, 205 Alveoli of lower jaw, 205 of upper jaw, 195 formation of, 902 of stomach, 928 Amnion, 111 Amniotic cavity, 112 Amphiarthrosis, 317 Ampullae of semicircular canals, 884 of tubuli lactiferi, 1061 Amygdalae, 904 of cerebellum, 749 Anal fascia, 1092 Anastomosis of arteries, 541 Anastomotica magna of brachial, 598 of femoral, 639 Anatomical neck of humerus, 249 fracture of, 255 Anconeus muscle, 488 Andersch, ganglion of, 779 Aneurisms of abdominal aorta, 611 of arch of aorta, 546 of thoracic aorta, 608 Angle of jaw, 208 of pubes, 280 of rib, 235 sacro-vertebral, 157 Angular artery, 558 convolution, 720 movement, 20 process, external, 173 internal, 173 vein, 653 Ankle-joint, 379 relations of tendons and ves- sels to, 381 surface form of, 381 surgical anatomy of, 381 Annectant gyrus, 721, 724 Annular ligament of radius and ulna, 355 Annular ligament of wrist, ante- rior, 491 posterior, 492 of ankle, anterior, 530 external, 531 internal, 530 of stapes, 881. Annulus ovalis, 973 Anterior annular ligament, wrist, 491 ankle, 530 chamber of eye, 865 crural nerve, 817 surgical anatomy of, 827 dental canal, 192 ethmoidal cells, 188 fontanelle. 190 fossa of skull, 212 and internal frontal artery, 574 nasal spine, 196 palatine canal, 196 fossa, 196, 215 radicular zone, 701 region of skull, 219 triangle of neck, 565 Antero-lateral ganglionic artery, 574 Antero-median ganglionic artery. 573 Antihelix, 874 fossa of, 874 Antitragicus muscle, 876 Antitragus, 874 Antrum of Highmore, 192 Anus, 1083 development of, 134 muscles of, 460, 461 Aorta, 543 abdominal, 611 branches of, 611 development of, 129 surgical anatomy of arch of, 545 arch of, 543 branches of, 547 peculiarities of, 545 of branches of, 547 sinuses of, 544 surgical anatomy of, 545 descending, 607 thoracic, 607 branches of, 608 sinuses of, 544 surgical anatomy of, 608 Aortic opening of diaphragm, 448 of heart, 976 plexus, 840 semilunar valves, 977 sinuses, 977 Apertura sea he vestibuli cochleae, 884 1093 1094 INDEX. Aponeurosis, 391 of deltoid, 473 of external oblique in inguinal region, 450 of occipito-frontalis, 395 suprahyoid, 415 of soft palate, 904 Apophysis, 146 Apparatus ligamentosus colli, 328 Appendages of eye, 869 surgical anatomy of, 873 of skin, 92 of uterus, 1056 Appendices epiploicse, 925 Appendix of right auricle, 972 of left auricle, 975 vermiformis, 939 Aqua labyrinthi, 888 Aquaeductus cochleae, 180, 885 vestibuli, 179, 883 Fallopii, 179, 879 Sylvii, 740 Aqueous humor, 865 Arachnoid of brain, 706 of cord, 696 Arantii corpora, 975 Arantius, ventricle of, 710 Arbor vitae uterina, 1053 of cerebellum, 757 Arch of aorta, 543 peculiarities of, 545 branches of, 547 surgical anatomy, 545 of os pubes, 283 of a vertebra, 146 supraorbital, 173 crural or femoral, 1077 palmar superficial, 656 deep, 600 plantar, 649 zygomatic, 218 Arches, pharyngeal, 118 aortic, foetal, 129 Arciform or arcuate fibres of me- dulla oblongata, 712 Arcuate fibres of cerebrum, 743 of cerebellum, 751 Area, germinal, 103 Areas of Cohnheim, 66 Areola of breast, 1060 Areolae of bone, primary, 60 secondary, 61 Areolar tissue, 47 Arm, back of, muscles of, 479 front of, muscles of, 477 arteries of, 578 bones of, 249 fascia of, 477 lymphatic glands of, 686 lymphatics of, 686 superficial fascia of, 472 nerves of, 801 veins of, 664 Arnold's nerve, 783 canal for, 180 ganglion, 770 Arrectores pili, 94 Arteria magna, 543 centralis retinae, 572 Arteriae propriae renales, 1017 receptaculi, 570 Arteries, development of, 129 general anatomy of, 80 anastomoses of, 541 capillary, 82 Arteries, development of, 129 distribution of, 541 mode of division, 541 mode of origin of branches, 541 nerves of, 82 sheath of, 82 structure of, 80 subdivision of, 541 systemic, 541 vessels of, 82 Arteries or artery, accessory pu- dic, 625 acromial thoracic, 594 alar thoracic, 594 alveolar, 564 anastomotica magna of bra- chial, 599 of femoral, 639 angular, 558 anterior and internal frontal, 672 cerebral, 572 choroid, 567 ciliary, 572 communicating, 574 inferior cerebellar, 585 intercostal, 589 spinal, 585 antero-lateral ganglionic, 574 antero-median ganglionic, 573 aorta, 543 abdominal, 610 arch of, 543 ascending part, 543 descending part, 607 thoracic, 607 articular, knee, 641 ascending cervical, 586 pharyngeal, 560 auditory, 585, 889 auricular anterior, 561 posterior, 559 axillary, 591 azygos of knee, 643 basilar, 585 brachial, 595 bronchial, 607, 1004 buccal, 564 of bulb, 627 calcanean, external, 649 internal, 649 carotid, common, 549 external, 553 internal, 567 carpal ulnar, 605 radial, 601 of cavernous body, 627 centralis retinge, 570 cerebellar, 585 cerebral, 572, 575, 585 ascending cervical, 586 superficial, 587 princeps, 559 profunda, 589 choroid anterior, 575 posterior, 586 ciliary, 572 circle of Willis, 575, 586 circumflex, of arm, 595 of thigh, 638 iliac, deep, 602 superficial, 637 cochlear, 889 coccygeal, 628 Arteries or artery, colica dextra, 616 media, 616 sinistra, 616 cceliac axis, 612 comes nervi iscliiadici, 628 phrenici, 588 common carotid, 549 iliac, 620 communicating, anterior cere- bri, 574 posterior cerebri, 575 communicating branch of ul- nar, 606 coronary, of heart, 544 of lip, 558 cremasteric, 631 crico-thyroid, 554 cystic, 613 deep branch of ulnar, 607 cervical, 589 palmar arch, 599 temporal, 563 deferent, 624 dental inferior, 563 anterior, 564 descending aorta, 607 palatine, 564 digital plantar, 650 of ulnar, 606 dorsal, of penis, 626 of scapula, 594 dorsalis hallucis, 646 indicia, 602 linguae, 555 pedis, 645 pollicis, 602 epigastric, deep, 631 superior, 589 superficial, 637 ethmoidal, 571 external carotid, 553 plantar, 649 iliac, 630 facial, 556 femoral, 632 deep, 637 frontal, 572 gastric, 613, 614 gastro-duodenalis, 613 gastro-epiploica dextra, 613 sinistra, 614 gluteal, 629 inferior, 628 helicine, 1036 hemorrhoidal inferior, 627 middle, 624 superior, 617 hepatic, 613 hyoid branch of lingual, 555 of superior thyroid, 554 hypogastric in foetus, 623, 981 ileo-colic, 616 iliac, common, 620 external, 630 internal, 622 ilio-lumbar, 628 inferior cerebellar, 585 dental, 563 labial, 558 laryngeal, 586 mesenteric, 616 profunda, 598 pyloric, 613 thyroid, 586 INDEX. 1095 Arteries or artery, infraorbital, 564 innominate, 547 intercostal, 608 anterior, 588 superior, 589 internal auditory, 889 carotid, 568 iliac, 622 mammary, 588 maxillary, 561 plantar, 649 interosseous ulnar, 604 of foot, 646 of hand,604 intestini tenuis, 616 labial inferior, 558 lachrymal, 570 laryngeal superior, 554 inferior, 586 lateral sacral, 629 spinal, 584 lateralis nasi, 558 lingual, 555 long ciliary, 572 thoracic, 594 lumbar, 619 malleolar, 645 mammary, internal, 588 masseteric, 564 maxillary, internal, 561 median, of forearm, 604 of spinal cord, 585 mediastinal, 588 posterior, 608 meningeal anterior, 570 middle, 562 small, 563 from occipital, 559 from pharyngeal, 560 from vertebral, 583 mesenteric inferior, 616 superior, 615 metacarpal, 602 metatarsal, 646 middle cerebral, 574 sacral, 619 musculo-phrenic, 588 mylo-hyoid, 563 nasal, of ophthalmic, 572 of septum, 558 inferior, 558 superior, 564 nutrient, of humerus, 598 femur, 639 fibula, 648 radius and ulnar, 604 tibia, 648 obturator, 624 occipital, 558 oesophageal, 608 ophthalmic, 570 orbital, 564 ovarian, 618 palatine, ascending, 557 descending, 564 of pharyngeal, 560 palmar arch, superficial, 606 deep, 606 palmar interossei, 603 palpebral, 572 pancreatic, 614 panereatico-duodenalis, 613 inferior, 615 perforating, of hand, 603 Arteries or artery, perforating, of thigh, 638 of foot, 650 of intercostal, 588 plantar, 649 pericardiac, 588, 608 perineal, superficial, 627 transverse, 627 peroneal, 648 anterior, 648 pharyngea ascendens 560 phrenic, 618 popliteal, 639 posterior auricular, 559 cerebral, 585 communicating, 575 meningeal, from vertebral, 584 princeps cervicis, 559 pollicis, 602 profunda of arm, inferior, 598 superior, 598 cervicis, 589 femoris, 637 pterygoid, 564 pterygo-palatine, 564 pudic, deep external, 637 superficial external, 638 internal, 625 pulmonary, 542, 1003 pyloric inferior, 613 of hepatic, 613 radial, 599 radialis indicis, 603 ranine, 555 recurrent interosseous, 605 radial, 601 ulnar, anterior, 604 posterior, 604 tibial, 644 posterior, 644 renal, 618 sacral lateral, 629 middle, 619 scapular, posterior, 587 sciatic, 628 short ciliary, 572 sigmoid, 617 spermatic, 618, 1039 spheno-palatine, 564 spinal, anterior, 584 lateral, 584 posterior, 584 spinal, median, 584 splenic, 613 sterno-mastoid, 559 stylo-mastoid, 559 subclavian, 578 sublingual, 555 submaxillary, 557 submental, 557 subscapular, 594 superficial cervical, 587 circumflex iliac, 632 perineal, 627 palmar arch, 606 superficialis volae, 601 superior cerebellar, 585 epigastric, 589 haemorrhoidal, 617 intercostal, 589 laryngeal, 554 mesenteric, 615 profunda, 598 thoracic, 594 Arteries or artery, superior thy- roid, 564 supraorbital, 571 suprarenal, 617 suprascapular, 587 sural, 641 tarsal, 646 temporal, 560 anterior, 560 deep, 563 middle, 561 posterior, 560 thoracic, acromial, 594 alar, 594 aorta, 607 long, 594 superior, 594 thyroid axis, 586 inferior, 586 superior, 554 thyroidea ima, 547, 1008 tibial anterior, 643 posterior, 646 recurrent, 644 tonsillar, 557 transverse facial, 561 transversalis colli, 587 tympanic, from internal caro- tid, 571 from internal maxillary, 562 ulnar, 603 recurrent anterior, 604 posterior, 604 umbilical in foetus, 623, 983 uterine, 624 vagina], 624 vasa aberrantia of arm, 597 brevia, 614 intestini tenuis, 616 vertebral, 583 vesical inferior, 624 middle, 624 superior, 624 vestibular, 889 Vidian, 564 Arteriolae rectae, 1018 Arthrodia, 318 Articular arteries (knee), from popliteal, 643 cartilage, 145 end-btdbs, 76 lamella of bone, 315 processes of vertebrae, 148 Articulations in general, 315 different kinds of, 316 acromio-clavicular, 344 ankle, 379 astragalo-calcanean, 383 navicular, 384 atlanto-axial, 325 calcaneo-astragaloid, 383 calcaneo-cuboid, 383 navicular, 384 carpo-metacarpal, 361 carpal, 359 classification of, 316 coccygeal, 341 chondro-sternal, 336 costo transverse, 333 costo-vertebral, 332 of cuboid with external cunei- form, 386 of cuneiform with each other, 385 elbow, 351 1096 INDEX. Articulations, femoro-tibial, 370 hip, 364 immovable, 316 knee, 370 metacarpal, 359 metacarpo-phalangeal, 363 metatarso-phalangeal, 3SS metatarsal, 387 mixed, 317 movable, 317 movements of, 318 naviculo-cuboid, 385 naviculo-cuneiform, 385 occipito-atlantal, 327 occipito-axial, 328 pelvis, 338 with spine, 338 phalanges, 364 pubic, 341 radio-carpal, 358 radio-ulnar, inferior, 357 middle, 356 superior, 355 sacro-coccygeal, 341 sacro-iliac, 339 sacro-sciatic, 340 sacro-vertebral, 338 scapulo-clavicular, 345 scapulo-humeral, 347 shoulder, 347 sterno-clavicular, 343 of sternum, 338 tarso-metatarsal, 386 tarsal, 382 temporo-maxillary, 329 tibio-fibular, inferior, 378 middle, 378 superior, 378 of tympanic bones, 880 vertebral column, 321 wrist, 358 Arvtaeno-epiglottideus, superior, 991 inferior, 991 Arytaeno-epiglottidean folds, 991 Arytenoid cartilages, 986 glands, 992 muscle, 990 Arytenoideus rectus, 990 Ascending colon, 941 frontal artery, 574 oblique muscle of abdomen, 453 palatine artery, 558 parietal artery, 574 pharyngeal artery, 560 surgical anatomy of, 561 Association fibres of hemispheres of brain, 743 Astragalus, 305 development of, 310 Atlanto-axial articulation, 325 Atlanto-odontoid joint, 325 Atlas, 148 development of, 155 Atrabiliary capsules, 1021 Attollens aurem muscle, 396 Attrahens aurem muscle, 395 Auditory artery, 889 canal, 876 meatus, external, 179 internal, 179 nerve, 778, 890 surgical anatomy of, 778 process, 179 Auditory striae, 753 tubercle, 754 veins, 889 vesicle, 124 I Auerbach's plexus, 939 | Auricle of ear, 874 cartilage of, 874 ligaments of, 875 of heart, left, 975 appendix of, 975 sinus of. 975 right, 972 openings in, 972 valves in, 973 sinus of, 972 septum of, 973, 976 Auricular artery, posterior, 559 anterior, 561 ' fissure, 180, 216 lymphatic glands, 683 nerve of vagus, 783 posterior from facial, 775 surface of sacrum, 159 veins, anterior, 654 posterior, 655 1 Auricularis anterior muscle, 395 posterior, 396 superior, 396 magnus nerve, 793 Auriculo-temporal nerve, 768 Auriculo-ventricular groove of heart, 971 opening, left, 976 right, 973 Axes of the pelvis, 284 I Axilla, 589 dissection of, 468 surgical anatomy of, 591 | Axillary artery, 591 branches of, 594 surface-marking of, 593 peculiarities, 592 surgical anatomy of, 593 lymphatic glands, 686 space, 589 vein, 666 surgical anatomy of, 667 | Axis, or second vertebra, 149 development of, 156 cerebro-spinal, 695 cceliac, 612 thyroid, 586 Axis-cylinder of nerve-tubes, 71 Azygos artery, articular, 643 veins, 669 uvulae muscle, 424 B. Bacillary layer of retina, 863 Back muscles of, first layer, 430 second layer, 433 third layer, 434 fourth layer, 436 fifth layer, 439 Ball-and-socket joint. See Enar- throdia. j Bartholine, duct of, 907 glands of, 1049 Base of brain, 727 of skull, 210 external surface, 213 internal surface, 210 Basement membranes, 49 Basi-hyal of hyoid bone, 229 Basilar artery, 585 membrane of cochlea, 886 process, 167 suture, 209 Basilic vein, 665 median, 665 Basis vertebrarum venae, 670 Bauhin, valve of, 940 Beak of corpus callosum, 732 Beaunis et Bouchard, Table of Development of Foetus, from, 143 Bend of elbow, 595 Biceps flexor cruris, 520 cubiti, 478 Bicipital fascia, 478 groove, 249 tuberosity, 261 ridges, 249 Bicuspid teeth, 895 Biliary ducts, 955, 956 structure of, 957 Biventer cervicis muscle, 439 Bladder, 1023 female, 1049 ligaments of, 1026 trigone of, 1028 surface form of, 1028 surgical anatomy of, 1029 vessels and nerves of, 1028 Blastodermic membrane, 104 Blood, general composition of, 33' circulation of, in adult, 971 in foetus, 981 gases of, 37 Blood-corpuscles, 34 Blood-crystals, 37 Blood-globules, 34 Blood-plaques, 36 Blood-vessels of brain, 575 Bochdalek, ganglion of, 765, 767 on musculus triticeo-glossusr 991, note. Body of a tooth, 894 of a vertebra, 147 Bone, general anatomy of, 54 animal constituent of, 58 apophysis of, 146 articular lamella of, 315 canaliculi of, 56 cancellous tissue of, 54 cells, 58 chemical analysis of, 58 compact tissue of, 54 diploe of, 146 development of, 59 earthy constituent of, 59 eminences and depressions of,. 146 epiphysis of, 146 growth of, 63 Haversian canals of, 56 systems of, 56 inorganic constituent of, 59 lacunae of, 58 lamellae of, 57 lymphatics of, 56 marrow of, 55 medullary canal of, 54, 145 membrane of, 54 microscopic appearances, 55 nerves of, 55 organic constituent of, 59 ossification of, 60 ossific centres, number of, 64 INDEX. 1097 Bone, periosteum of, 54 spongy tissue of, 145 vessels of, 55 Bones, forms of-viz. long, short, flat, mixed, irregular, 145 number of, in the body, 145 Bones or bone, descriptive anat- omy of, 145 astragalus, 305 atlas, 148 axis, 149 calcaneum, 302 carpal, 264 clavicle, 240 coccyx, 161 cranial, 167 cuboid, 305 cuneiform, of carpus, 266 of tarsus, 307 ear, 878 ethmoid, 187 facial, 190 femur, 286 fibula, 299 frontal, 172 hand,264 humerus, 249 hyoid, 229 ilium, 274 incus, 881 inferior maxillary, 203 turbinated, 202 innominate, 274 ischium, 277 lachrymal, 197 lesser lachrymal, 197 lingual, 229 magnum, 268 malar, 198 malleus, 880 maxillary, inferior, 203 superior, 191 metacarpal, 269 metatarsal, 308 nasal, 191 navicular, 306 occipital, 166 orbicular, 882 palate, 199 parietal, 170 patella, 293 pelvic, 281 phalanges of foot, 310 of hand, 272 pisiform, 266 pubic, 279 radius, 261 ribs, 234 sacrum, 157 scaphoid, 264 scapula, 244 semilunar, 268 sesamoid, 314 sphenoid, 182 sphenoidal, spongy, 186 stapes, 881 sternum, 230 superior maxillary, 191 tarsal, 301 temporal, 175 tibia, 295 trapezium, 268 trapezoid, 268 triquetral, 190 Bones or bone, turbinate, infe- rior, 202 middle, 188 superior, 189 tympanic, 181 ulna, 256 unciform, 269 vertebra prominens, 151 vertebrae, cervical, 147 dorsal, 151 lumbar, 153 vomer, 203 Wormian, 190 Bowman, glands of, 851 sarcous elements of, 67 Bowman's capsule, 1013 Brachia of optic lobes, 739 Brachial artery, 595 branches of, 598 peculiarities of, 596 surface marking of, 597 surgical anatomy of, 597 lymphatic glands, 686 plexus, 796 surgical anatomy of, 807 region, posterior, muscles of, 487 anterior, 481, 483 veins, 666 Brachialis anticus muscle, 479 Brachio-cephalic artery. See Innominate. Brain, 704 base of, 727 convolutions of, 717 development of, 120 dura mater of, 704 general anatomy of, 73 interior of, 730 lobes of, 727 membranes and dissection, 704 subdivision into parts, 707 upper surface of, 717 weight of, 717 Branchial arches, 119 Breasts, 1060 Bregma, 210 Brim of pelvis, 283 Broad ligaments of uterus, 1052 formation of, 920 Bronchi, right and left, 993 septum of, 994 in lung, 1003 Bronchial arteries, 608, 1004 lymphatic glands, 694 septum, 994 tubes. See UroncAi. veins, 670, 1004 Brunner's glands, 936 Bubonocele, 1071 Buccal arteries, 564 cavity, 892 development of, 134 glands, 893 lymphatic glands, 683 nerve of facial, 777 of inferior maxillary, 768 veins, 655 Buccinator muscle, 404 Bulb, artery of, 627 of corpus cavernosum, 1035 of corpus spongiosum, 1036 olfactory, 728, 755 Bulbi vestibuli, 1049 Bulbo-cavernous muscle, 465 Bulbous portion of the urethra, 1031 Bulbs of the fornix, 729 Burdach's column, 702 Bursae mucosae, 316 of knee, 374 of shoulder, 348 Bursal synovial membranes, 316 C. Caecum, 939 Calamus scriptorius, 753 Calcanean arteries, internal, 649 external, 649 Calcaneo-astragaloid ligaments, 383 Calcaneo-cuboid ligaments, 383 Calcaneo-navicular ligaments, 384 Calcaneum, 301 Calcar fem or ale, 291 avis, 732 Calcarine fissure, 722 Calices of kidney, 1012 Calloso-marginal fissure, 722 Camper's ligament. See Trian- gular ligament of Urethra. Canals or canal, accessory pala- tine, 199 alimentary, 892 anterior dental, 193 palatine, 196 for Arnold's nerve, 180 auditory, 876 carotid, 179, 180 central, of modiolus, 885 for chorda tympani, 202, 878- of cochlea, 885 crural, 1079 dental posterior, 192 ethmoidal, 174 Haversian, of bone, 56 of Huguier, 177 incisive, 215 inferior dental, 205 infraorbital, 192 inguinal, 1067 for Jacobson's (tympanic) nerve, 180 lachrymal, 872 naso-palatine, 196 of Nuck, 1046, 1059 of Petit, 867 palatine, anterior, 196 posterior, 194 pterygo-palatine, 184 sacral, 159 of Sch 1 emm, 855 spermatic, 1067 of spinal cord, 121 spiral, of cochlea, 885 of Stilling, 865 of modiolus, 885 semicircular, 884, 885 for tensor tympani, 181, 857 temporo-malar, 199 vertebral, 164 Vidian, 185 of Wirsung, 898 Canaliculi of bone, 58 Canalis centralis modioli, 885 reuniens, 888 spiralis modioli, 886 Cancellous tissue of bone, 54 1098 INDEX. Canine eminence, 192 fossa, 192 teeth, 894 Canthi of eyelids, 869 Capillaries, 82 structure of, 83 Capitellum of humerus, 253 Capsular ligament of hip, 364 of knee, 371 of shoulder, 348 of thumb, 361 of vertebne, 323 Capsule, external, of brain, 734 internal, of brain, 734 in foetus, 124 of Glisson, 952 of kidney, 1012 of lens, 866 of Tenon, 852 Capsules, suprarenal, 1021 Caput cornu poster io ris, 702 gallinaginis, 1030 Cardiac lymphatics, 694 nerves, 833 from pneumogastric, 784 plexus of nerves, deep, 836 superficial, 836 veins, 679 Cardinal veins, foetal, 131 Carotid artery, common, 549 branches of (occasional), 551 peculiarities of, 551 surface marking of, 551 surgical anatomy of, 551 external, 553 branches of, 554 surface marking of, 553 surgical anatomy of, 553 internal, 567 branches of, 570 peculiarities of, 569 surgical anatomy of, 570 tubercle, 148 branch of Vidian, 766 canal, 180 ganglion, 831 groove, 183 plexus, 831 triangle, inferior, 565 superior, 566 Carpal arteries, from radial, 601 from ulnar, 604, 605 ligaments, 359 Carpo-metacarpal articulations, 361 Carpus, 264 development of, 273 articulations of, 359 surface form of, 272 surgical anatomy of, 273 Cartilage, general anatomy of, 51 articular, 52 cellular, 51 costal, 52 fibrous, 53 hyaline, 51 intercellular substance of, 51 reticular, 53 temporary, 54, 60 descriptive anatomy of, 51 arytenoid, 986 of auricle, 874 Cartilage of bronchi, 994 costal, 52, 238 cricoid, 985 cuneiform, 986 of ear, 874, 876, 880 ensiform, 230 of epiglottis, 986 fibro-, 52 hyaline, 51 of larynx, 984 of the nose, 848 of the pinna, 874 reticular, 53 of Santorini, 986 semilunar of knee, 372 of septum of nose, 848 tarsal, 870 temporary, 54 thyroid, 984 of trachea, 994 white fibro-, 52 of Wrisberg, 986 yellow elastic, 53 xiphoid, 230 Cartilage-cells, 51 Cartilage-lacunae, 51 Cartilagines minores, 848 Cartilago triticea, 987 Caruncula lachrymalis, 871 Carunculae myrtiformes, 1049 Cauda equina, 819 Cava, inferior, 675 peculiarities, 675 superior, 669 Cavernous body, artery of, 627 groove, 183 nerves of penis, 840 plexus, 831 sinus, 661 nerves in, 772 surgical anatomy of, 661 Cavity, cotyloid, 280 glenoid, 247 of the great omentum, 920 of pelvis, 283 sigmoid, 257 Cells, 38 of bone, 58 definition of, 38 division of, direct, 41 indirect, 40 ethmoidal, 188 mastoid, 178 prickle, 43 reproduction of, 40 structure of, 38 wall, 41 Cellular tissue, lymphoid, 48 mucoid, 48 retiform, 48 Cement of teeth, 901 formation of, 900 Central canal of cord, 699 ganglionic vessels of brain, 576 lobe of cerebrum, 721 Centres of ossification, 63 Centrifugal nerve-fibres, 75 Centripetal nerve-fibres, 75 Centrum ovale majus, 731 minus, 730 Cephalic vein, 665 median, 665 Cerato-hyal of hyoid bone, 229 Cerebellar arteries, anterior, 585 inferior, 585 Cerebellar arteries, superior, 585 column, 701 veins, 659 Cerebelli incisura, anterior, 748 posterior, 748 Cerebellum, 747 corpus dentatum of, 749, 752 hemispheres of, 748 laminae of, 751 lobes of, 748 median lobe of, 748 peduncles of, 750 structure of, 749 under surface of, 748 upper surface of, 748 the valley of, 748 ventricle of, 752 weight of, 748 Cerebral arteries, 572 anterior, 572 middle, 574 posterior, 585 convolutions, 717 lymphatics, 684 topography, 229 veins, 658 ventricles, 732, 737, 739, 752 Cerebro-spinal axis, 695 fluid, 706 nerves, 69 system, 69 Cerebrum, 707, 716 base of, 727 commissural fibres of, 743 commissures of, 743 convolutions of, 717 crura of, 730 fibres of, 743 fissures of, 717 general arrangement of its parts, 730 gray matter of, 73, 744 hemispheres of, 716 interior of, 730 labia of, 731 lobes of, 727 peduncles of, 729 structure of, 742 sulci, 717 under surface, 727 upper surface, 717 ventricles of, 733, 739, 752 Ceruminous glands, 878 Cervical artery, ascending, 586 superficial, 587 princeps, 559 profunda, 589 fascia, 409 ganglion, inferior, 834 middle, 834 superior, 831 lymphatic glands, deep, 686 superficial, 686 nerves, 790 anterior divisions of, 792 posterior divisions of, 790 roots of, 685 plexus, 793 deep branches of, 796 posterior, 790 superficial branches of, 793 veins, deep, 657 vertebrae, 147 surgical anatomy ot, 329 Cervicalis ascendens muscle, 438 INDEX. 1099 Cervico-facial nerve, 777 Cervix cornu posterioris, 702 uteri, 1053 Chalice cells, 43 Chambers of the eye, 865 Chassaignac's tubercle, 148 Check ligaments, 328 Cheek, muscles of, 403 Cheeks, structure of, 893 Chest, muscles of front, 469 of side, 472 surface form of, 238 surgical anatomy of, 239 Chiasma, or optic commissure, 756 Chondro-glossus muscle, 418 Chondro-sternal ligaments, 336 Chondro-xiphoid ligament, 336 Chorda dorsalis, 107, 115 tympani nerve, 775, 883 Chord® tendine®, of right ven- tricle, 974 of left ventricle, 976 vocales, 988 Willisii, 659 Chorion, 112 Choroid arteries, anterior, 575 posterior, 586 coat of eye, 856 plexus of lateral ventricle, 735 of fourth ventricle, 753 of third ventricle, 739 veins of brain, 658 Choroidal fissure, 123 Chromatin, 39 Chyle, 38 Chyli receptaculum, 682 Cilia, or eyelashes, 869 Ciliary arteries, 572, 867 ganglion, 761 muscle, 860 nerves, long, 761 short, 761 processes of eye, 857 Circle of Willis, 586 Circular sinus, 661 Circulation of blood in adult, 971 in foetus, 981 Circulus tonsillaris, 767 Circumduction, 318 Circumferential fibro-cartilage, 53 Circumflex artery of arm, ante- rior, 595 posterior, 595 of thigh, external, 638 internal, 638 iliac artery, 632 superficial, 637 nerve, 801 surgical anatomy of, 807 vein, 674 superficial, 672 Circumilexus palati muscle, 424 Circumvallate papill® of tongue, 843 Claustral formation of cortex, 745 Claustrum, 734 Clava of forniculus gracilis, 716 Clavicle, 240 development of, 243 fracture of, 501 peculiarities in sexes, 243 surface form of, 243 surgical anatomy of, 243 Cleft palate, 425 Clinoid processes, anterior, 185 middle, 182 posterior, 183 Clitoris, 1049 frenum of, 1048 lymphatics of, 691 muscles of, 467, 1049 prepuce of, 1048 Clivus, 183 Cloaca, 140 Coccygeal artery, 628 gland, 619 nerves, 820 Coccygeus muscle, 462 Coccyx, 161 development of, 162 Cochlea, 884 aqueduct of, 179 arteries of, 889 central axis of, 885 cupola of, 885 denticulate lamina of, 886 infundibulum of, 885 lamina spiralis of, 885 nerves of, 890 seal® of, 886 spiral canal of, 885 veins of, 890 Cochlear artery, 890 nerve, 890 Cochleariform process, 181, 878 Cceliac axis, 612 plexus, 838 Colica dextra artery, 616 media, 616 sinistra, 616 Collateral circulation. See Sur- gical Anatomy of each Artery. fibres of cerebrum, 744 fissure, 722 Collecting tubes of kidney, 1014 Colliculus nervi optici, 860 Colon, 941 Colostrum corpuscles, 1061 Columella cochleae, 885 Column of Goll, 701 of Burdach, 702 cerebellar, 701 Clarke's vesicular, of spinal cord, 703 mixed lateral, 701 vesicular of anterior cornu, 703 Columna nasi, 848 Columna? carne® of left ventricle, .977 of right ventricle, 974 papillaries, 974, 977 Columns of abdominal ring, 1064 of spinal cord, 698 of vagina, 1051 Comes nervi ischiadici artery, 628 phrenici artery, 588 Commissura, brevis, of cerebel- lum, 749 Commissural fibres of brain, 743 Commissures, of brain, anterior, 740 middle or soft, 740 posterior, 740 optic, 756 of spinal cord, gray, 698 white, 698 Common ligaments of vertebrae, 321 Communicans hypoglossi nerve, 796 peronei, 827 Communicating artery of brain, anterior, 574 posterior, 574 from dorsalis pedis, 645 ulnar, 606 Compact tissue of bone, 54, 145 Complexus muscle, 439 Compressor narium minor, 401 nasi, 401 sacculi laryngis, 991 urethrae, 466 in female, 1090 Conarium, 740 Concentric corpuscles of thymus, . 1009 Conception, where effected, 100 Concha, 874 Condyles of bones. See Bones. Condyloid articulations, 318 foramina, 167 fossae, 162 process, 206 ridge, external, 252 internal, 252 veins, posterior, 659, 660 Congenital fissures in cranium, 190 hernia, 1071 Conglobate glands, 681 Coni vasculosi, 1042 Conjoined tendon of internal ob- lique and transversalis, 453, 1066 Conjunctiva, 870 Connecting fibro-cartilages, 53 Connective tissue, 45 development of, 48 lymphatics of, 48 nerves of, 48 Conoid ligament, 346 tubercle, 241 Constrictor inferior muscle, 421 medius, 422 superior, 422 isthmi faucium, 424 urethrae, 466 Contractile fibre-cells, 68 Conus arteriosus, 974 Convolution of corpus callosum, 722 Convolutions, angular, 720 of cerebrum, structure of, 742 topography of, 724 of corpus callosum, 722 cuneate, 723 frontal, 719 marginal, 723 occipital, 721 occipito-temporal, 724 orbital, 719 parietal, 720 precuneus, 723 quadrate, 723 supramarginal, 720 temporo-sphenoidal, 727 uncinate, 723 Coraco-acromial ligament, 346 Coraco-brachialis muscle, 478 Coraco-clavicular ligament, 345 Coraco-humeral ligament, 348 1100 INDEX. Coracoid ligament, 347 process, 247 fracture of, 502 Cord, spermatic, 1039 umbilical, 115 Cordiform tendon of diaphragm, 447 Corium of skin, 91 of tongue, 842 Cornea, 854 Corneal corpuscles, 855 spaces, 855 Cornicula laryngis, 921 Cornu Ammonis, 735, 745 formation of, 745 Cornua of the coccyx, 161 of hyoid bone, 229 of the sacrum, 158 of thyroid cartilage, 920 Corona glandis, 1034 radiata, 73, 742 Coronal suture, 207 Coronaria ventriculi artery, 613 Coronary arteries of lip, 558 of heart, 544 peculiarities, 545 ligament of liver, 950 ligaments of knee, 370 plexus, anterior, 837 posterior, 836 sinus, 679 opening of, 972 valve, 680, 974 Coronoid depression, 253 process of .jaw, 206 of ulna, 257 Corpora albicantia, 724 Arantii, 975 mammillaria, 729 cavernosa penis, 1035 crura of, 1034 cavernosa clitoridis, 1049 geniculata, 742 quadrigemina, 746 striata, 733 veins of, 659 Corpus callosum, 731, 743 cavernosum, artery of, 527 convolution of, 723 genu of, 732 peduncles of, 732 ventricle of, 732 dentatum of cerebellum, 749 of olivary body, 710 fimbriatum, 735 Highmorianum, 1041 spongiosum, 1036 dentatum, 749, 752 Corpuscles, blood-, 34 colored, 34 development of, 126 of Herbst, 77 white, 35 Malpighian, of kidney, 1013 of Purkinje, 752 of spleen, 963 tactile, 76 of Vater, 77 Corrugator cutis ani, 460 supercilii muscle, 397 Cortex of cerebellum, 751 of cerebrum, 744 Corti, membrane of, 886 organ of. 887 rods of, 887 Cortical arteries of brain, 577 arches, 1013 columns, 1013 substance of brain, 744 of kidney, 1013 of suprarenal capsules, 1022 of teeth, 898 Costal cartilages, 52, 238 connection with ribs, 336 process, 148 vertebral ligaments, 332 Costo-chondral articulation, 337 Costo-clavicular ligament, 343 Costo-colic ligament, 925 Costo-coracoid fascia, 470 ligament, 470 Costo-transverse articulations, 333 Costo-vertebral articulations, 332 Chondro-xiphoid ligaments, 336 Cotunnius, nerve of, 767 Cotyloid cavity, 280 ligament, 366 notch, 280 Coverings of direct inguinal her- nia, 1072 of femoral hernia, 1081 of oblique, 1069 of testis, 1040 Cowper's glands, 1034, 1088 Cranial bones, 165 articulations of, 210 fossa*, 210 nerves, 754 development of, 117 eighth, 778 eleventh, 785 fifth, 759 first pair, 754 fourth, 758 ninth, 778 second, 755 seventh, 773 sixth, 772 tenth, 781 third, 757 twelfth, 786 sutures, 207 Cranium, 165 congenital fissures in, 190 development of, 189 lymphatics of, 684 Cremaster muscle, 454 formation of, 1066 Cremasteric artery, 621 fascia, 454 Crescents of Gianuzzi, 908 Crest, frontal, 173 of ilium, 274 lachrymal, 197 nasal, 191 occipital, 167 internal, 168 turbinated, of palate, 200 of the superior maxillary, 194 of pubes, 279 of tibia, 295, 296 Cribriform fascia, 1075 plate of ethmoid, 187 Crico-arytaenoideus lateralis mus- cle, 989 posticus muscle, 988 Crico-thyroid artery, 554 membrane, 987 Crico-thyroid muscle, 989 Cricoid cartilage, 985 Crista falciformis, 179 galli, 187, 210 pubis, 279 vestibuli, 883 Crochet of uncinate gyrus, 724 Cross pyramidal fasciculus, 709, ' 711 Crown of a tooth, 894 Crucial anastomosis, 638 ligaments of knee, 371 Cruciform ligament, 326 Crura cerebri, 729 of clitoris, 1049 of corpora cavernosa, 1035 of diaphragm, 447 of fornix, 737 Crural arch, 452, 1077 deep, 459, 1079 canal, 1079 nerve, anterior, 817 surgical anatomy of, 827 ring, 1080 sheath, 1078 septum, 1080 Crureus muscle, 512 Crus penis. 1035 Crusta petrosa of teeth, 898 of crus cerebri, 730, 743 Crypts of Lieberkuhn, 936 Crystalline lens, 866 Crystals, blood-, 37 Cuboid bone, 305 Cuneate lobe, 723 fasciculus, 711 Cuneiform bone, hand, 266 foot, external, 308 internal, 307 middle, 307 cartilages, 986 Cupola of cochlea, 885 Curvatures of the spine,. 163 Cuspidate teeth, 894 Cutaneous branches of accessory obturator, 817 of anterior tibial nerve, 827 of cervical plexus, 793 of circumflex, 801 of dorsal nerve of penis, 823 of dorsal nerves, 808 of external popliteal, 826 internal 825 of inferior hemorrhoidal nerve, 823 of ilio-hypogastric, 813 of ilio-inguinal, 813 of intercostal nerves, 810 of lesser sciatic nerve, 824 of lumbar nerves, 812 of median, 802 of musculo-spiral, 805 of ulnar nerve, 804 of arm, musculo-cutaneous, 801 internal, 802 lesser internal, 802 of buttock and thigh, 824 of inguinal region, 1075 of ischio-rectal region, 1083 from obturator, 816 of thigh, external, 814 internal, 818 middle, 818 of patella, 818 INDEX. 1101 Cutaneous branches of perineal nerve, 823 plantar nerve, 825 of posterior tibial, 825 of radial, 806 of sacral nerves, 819 of ulnar, 804 Cuticle of skin, 90 Cuticula dentis, 900 Cutis vera, 91 Cuvier, ducts of, 131 Cystic artery, 613 duct, 956 valve of, 957 plexus of nerves, 839 veins, 679 D. Dart os, 1038 Decidua, 114 reilexa, 114 serotina, 114 vera, 114 Deciduous teeth, 894 Decussation of optic nerves, 756 of pyramids, 710 Deep crural arch, 459, 1079 palmar arch, 600 perineal fascia, 465, 1086 Deferent artery, 624 Deglutition, actions of, 425 Deltoid aponeurosis, 473 muscle, 473 tubercle, 241 Demilunes of Heidenhain, 908 Demours, membrane of, 854 Dens sapientiae, 893 Dental artery, inferior, 563 posterior, 563 canal, anterior, 193 inferior, 205 posterior, 192 groove, 899, 902 nerves, anterior, 765 inferior, 769 middle, 764 posterior, 764 pulp, 896 ridges, 899 sacs, 902 tubuli, 897 vein, inferior, 655 Dentate fissure, 722 Denticulate lamina of cochlea, 886 Dentinal sac, 900 sheath, 898 Dentine, 897 formation of, 900 Depressions of Pacchionian bodies, 171 Depressor alee nasi, 401 anguli oris, 403 epiglottidis, 991 labii inferioris, 403 Derma, or true skin, 91 Descemet, membrane of, 854 Descendens hypoglossi nerve, 788 Descending aorta, 607 colon, 941 oblique muscle of abdomen, 450 Descent of testicle, 1045 Development of atlas, 156 Development, axis, 156 alimentary canal and its ap- pendages, 133 arteries, 129 bone, 59 carpus, 273 clavicle, 243 coccyx, 162 cranium, 117, 189 ear, 124 ethmoid, 189 eye, 122 face, 117 femur, 292 fibula, 300 foot, 310 frontal bone, 175 genital organs, 137 hand, 273 heart, 126 humerus, 254 hyoid bone, 229 inferior turbinated bone, 202 lachrymal bone, 198 lens, 123 lower jaw, 208 lumbar vertebne, 155 malar bone, 199 mammae, 125 metacarpus, 274 metatarsus, 311 muscles, 126 nasal bone, 191 nervous centres, 120 nose, 125 occipital bone, 169 os innominatum, 280 palate, 119 palate bone, 201 parietal bone, 172 patella, 294 permanent teeth, 901 phalanges of hand, 274 of foot, 311 radius, 262 ribs, 237 sacrum, 160 scapula, 248 seventh cervical, 156 skin, 125 sphenoid, 186 spine, 115 sternum, 233 superior maxillary bone, 196 tarsus, 311 temporal bone, 181 temporary teeth, 899 tibia, 298 ulna, 260 veins, 130 vertebrae, 154 vomer, 203 Wormian, 190 Development of Organs, Chron- ological Table of, 143 Diameters of pelvis, 282 Diaphragm, 446 development of, 134 lymphatics of, 694 Diaphysis, 64 Diarthrosis, 317 Digastric muscle, 415 fossa, 178 lobe of cerebellum, 749 nerve, from facial, 776 Digestion, organs of, 892 Digital arteries from ulnar, 606 from plantar, 649 cavity of lateral ventricle, 732 fossa, 287 nerves, from median, 803 from radial, 806 from ulnar, 804 of foot, 836 Dilatator naris, anterior, 401 posterior, 401 Diploe, 146 veins of, 657 Direct inguinal hernia, 1071 course of, 1072 coverings of, 1072 pyramidal fasciculus, 701 Discus proligerus, 100, 1059 Disks, blood, 36 development of, 127 Dissection of abdominal muscles, 449 arm, 477 auricular region, 395 axilla, 468 back, 430 epicranial region, 393 eye, 856 face, 396 femoral hernia, 1072 foot, 530 forearm, 480 gluteal region, 516 hand, 91 heart, left auricle, 975 left ventricle, 976 right auricle, 972 right ventricle, 973 hernia, femoral, 1072 inguinal, 1062 iliac region, 505 inferior maxillary region, 402 infrahyoid region, 413 inguinal hernia, 1062 intermaxillary region, 403 ischio-rectal region, 1083 leg, 522 lingual region, 417 neck, 408 orbit, 398 palatal region, 423 palm of hand, 492 palpebral region, 396 pancreas, 958 pectoral region, 468 perineum, 1083 pharynx, 421 pterygoid muscles, 406 radial region, 485 scalp, 393 sole of foot, 531 spinal cord and membranes, 695 suprahyoid region, 415 temporal muscle, 405 thigh, front of, 507 back of, 520 inner side of, 513 Diverticulum, Meckel's, 933 Division of cells, 40 direct, 41 indirect, 41 Dorsal artery of penis, 626 nerves of penis, 823 nerves, 808 1102 INDEX. Dorsal nerves, anterior divisions of, 808 posterior divisions of, 808 peculiar, 811 roots of, 808 vein of penis, 675 vertebrse, 151 peculiar, 153 Dorsales pollicis arteries. 602 Dorsalis hallucis artery, 646 indicis, 602 lingua?, 555 pedis, 645 branches of, 646 peculiarities of, 645 surface marking of, 645 surgical anatomy of, 645 scapulae, 594 Dorsi-lumbar nerve, 811 Dorsi-spinal veins, 670 Dorsum of scapula, 245 ephipii or sellae, 183 Douglas, pouch of, 1052 semilunar fold of, 457 Ducts or duct, of Bartholine, 907 biliary, 956 of Cowper's glands, 1031 of Cuvier, 131 cystic, 956 ejaculatory, 1044 of Gartner, 139 galactophorous, 1061 hepatic, 955, 956 of kidney, 1019 lactiferous, 1061 of liver, 955 lymphatics, 683 nasal, 873 of pancreas, 960 parotid, 904 Rivini, 907 seminal, 1043 Stenson's, 905 thoracic, 682 Wharton's, 906 Ductless glands: spleen, 962 suprarenal capsule, 1021 thyroid, 1006 thymus, 1009 Ductus arteriosus, 542, 981 how obliterated in foetus, 983 communis choledochus, 957 pancreaticus minor, 960 Rivini, 907 venosus, 981 how obliterated, 983 Duodenal glands, 936 Duodenum, 931 vessels and nerves of, 932 Dura mater of brain, 704 arteries of, 704 nerves of, 705 processes of, 705 veins of, 704 of cord, 695 peculiarities of, 695 E. Ear, 874 arteries of, 877, 882, 889 auditory canal, 876 cochlea, 885 internal, or labyrinth, 883 I Ear, membranous labyrinth, 888 muscles of auricle, 875 of tympanum, 880 ossicula of, 880 pinna or auricle of, 874 semicircular canals, 884 surface form of, 877 surgical anatomy of, 890 tympanum, 878 vestibule, 883 Earthy constituents of bone, 59 Ectoderm, 104 Eighth nerve, 778 Efferent nerves, 75 surgical anatomy of, 778 Ejaculator seminis muscle, 463 Ejaculatory ducts, 1044 Elastic lamina of cornea, 855 Elbow, cartilage, 586 anastomoses around, 599 bend of, 595 joint, 351 surface form of, 354 surgical anatomy of, 354 vessels and nerves of, 353 Eleventh nerve, 785 surgical anatomy of, 785 Embryo, first rudiments of, 107 Eminence of aquseductus Fal- lopii, 879 canine, 192 frontal, 173 ilio-pectineal, 279 nasal, 173 parietal, 170 Eminences and depressions of bones, 146 Eminentia articularis, 176 collateralis, 732 Emissary veins, 663 Enamel epithelium, 900 of teeth, 898 formation of, 900 germ, 899 organ, neck of, 899 rods, 898 Enarthrosis, 319 End-bulbs of Krause, 76 End-plates, motorial, of Kiihne, 78 Endocardium, 912 Endolymph, 889 Endomysium, 65 Endoneurism, 74 Endothelium, 45 Ensiform appendix, 230 Entoderm, 104 Epencephalon, 120 Ependyma, 732 Epiblast, 104 Epidermis, structure of, 90 development of, 125 Epididymis, 1043 development of, 125 Epigastric artery, deep, 631 peculiarities, 632 relation to femoral ring, 1080 with internal ring, 1068 superficial, 637 superior, 589 plexus, 837 region, 914 vein, 674 superficial, 672 Epiglottic glands, 992 Epiglottis, 986 Epineurium, 74 Epiphysial cartilage, 60 Epiphysis, 64, 146 cerebri, 740 Epithelium, 42 ciliated, 43 columnar, 43 pavement, 42 spheroidal or glandular, 43. See Various Organs. stratified, 44 Epoophoron, 139 Erectile tissue, its structure, 1035 of clitoris, 1049 of penis, 1035 Erector clitoridis, 466, 1049 penis, 464 spina1, 436 Eruption of the teeth, 902 Ethmo-sphenoidal suture, 209 Ethmoid bone, 187 articulations of, 188 cribriform plate of, 187 development of, 189 lateral masses of, 188 os planum of, 188 perpendicular plate of, 188 unciform process of, 188 Ethmoidal artery, 571 canal, anterior, 174 posterior, 174 cells, 188 notch, 174, 188 process of inferior turbinated, 202 spine, 182 Ethmo-frontal suture, 209 Eustachian tube, 181, 880 surgical anatomy of, 911 valve, 973 in foetal heart, 981 Expiration, muscles of, 446 Extensor coccygis, 440 brevis digitorum muscle, 532 carpi radialis brevior, 486 longior, 486 carpi ulnaris, 488 communis digitorum (hand), . 487 indicis, 490 longus digitorum (foot), 523 minimi digiti, 485 ossis metacarpi pollicis, 488 proprius hallucis, 523 pollicis, 490 External abdominal ring, 459, 1064 annular ligament, 531 capsule, 734 inguinal hernia, 1068 orbital foramina, 185 pterygoid plate, 185 spermatic fascia, 1064 sphincter ani, 460 External and inferior frontal ar- tery, 574 Extrinsic muscles of tongue, 419 Eye, 852 appendages of, 869 chambers of, 865 ciliary muscle, 860 processes of, 857 humors of, 865 INDEX. 1103 Eye, aqueous humors of, 865 crystalline lens, 866 vitreous, 865 membrana pupillaris, 860 choroid, 856 conjunctiva, 870 cornea, 854 hyaloid membrane, 865 iris, 858 Jacob's, 863 retina, 860 sclerotic, 853 pupil of, 858 surgical anatomy of, 867 tunics of, 853 uvea of, 858 vessels of globe of, 867 elastic lamina of cornea, 855 Eyeball, muscles of, 398 nerves of, 867 vessels of, 867 Eyebrows, 869 Eyelashes, 869 Eyelids, 869 cartilages or plates of, 870 Meibomian glands of, 870 muscles of, 397 tarsal ligament of, 870 Eye-teeth, 894 F. Face, arteries of, 556 bones of, 165, 190 development of, 116 lymphatics of, 684 muscles of, 397 nerves of, 735 veins of, 653 Facial artery, 556 peculiarities of, 558 surgical anatomy of, 558 transverse, 561 bones, 190 nerve, 773 surgical anatomy of, 777 vein, 653 surgical anatomy of, 555 Falciform process of fascia lata, 510 ligament of liver, 949 Fallopian tubes, 1056 development of, 138 fimbriated extremity of, 1056 lymphatics of, 691 nerves of, 1060 structure of, 1056 vessels of, 1060 False ligaments of bladder, 1027 pelvis, 282 ribs, 234 Falx cerebelli, 705 cerebri, 705 Fangs of teeth, 894 Fascia, anal, 1092 Fasciae, general description of, 391 of arm, 477 cervical, deep, 409 superficial, 409 of Colles, 464 costo-coracoid, 470 of cranial region, 394 cremasteric, 454 cribriform, 1075 Fasciae, deep, 392 dentata, 736 dorsal, of foot, 532 fibro-areolar, its structure, 391 iliac, 505 infundibuliform, 1068 intercolumnar, 452, 1064 intercostal, 443 intermuscular, of arm, 477 of foot, 531 ischio-rectal, 1092 lata, 510, 1076 falciform process of, 1076 iliac portion, 510, 1075 pubic portion, 510, 1076 of leg, 523 deep transverse, 526 lumbornm, 435 of mamma, 467 masseteric, 405 of neck, 408 obturator, 1092 palmar, 492 parotid, 405, 410 pelvic, 1091 perineal, deep, 1086 superficial, 1085 plantar, 532 of foot, 531 of forearm, 480 of hand, 492 propria of spermatic cord, 1039 of femoral hernia, 1072 recto-vesical, 1092 spermatic, 452, 1064 superficial, 391 of inguinal region, 1062 of ischio-rectal region, 1083 of thigh, 508 temporal, 405 of thigh, deep, 508 superficial, 508 of thorax, 443, 468 transversalis, 996 visceral layer of pelvic, 1092 Fasciculi teretes, 753 Fasciculus, crossed pyramidal, 701 cuneate, 702 fundamental, 701 direct pyramidal, 701 of Turck, 701 uncifonnis, 728 Fat, 50 Fat-cells, 50 Fauces, isthmus of, 903 Fecundation of ovum, 108 Female organs of generation : bulbi vestibuli, 1049 carunculae mvrtiformes, 1049 clitoris, 1048 development of, 138 fossa navicularis, 1048 glands of Bartholine, 1049 hymen, 1049 labia majora, 1047 minora, 1048 nymphae, 1048 uterus, 1051 vagina, 1050 vestibule, 1049 Femoral artery, 632 branches of, 637 common, 633 Femoral artery, deep, 637 peculiarities of, 635 superficial, 634 surface marking of, 635 surgical anatomy of, 635 or crural canal, 1080 variation in size of, accord- ing to position of limb, 1080 hernia, complete, 1081 coverings of, 1081 descent of, 1081 dissection of, 1072 incomplete, 1081 seat of stricture, 1082 surgical anatomy of, 1072 position of surrounding parts, 1080 region, muscles of anterior, 507 internal, 513 posterior, 520 ring, 1080 sheath, 1078 spur, 291 vein, 674 relation of femoral ring, 1080 Femur, 286 articulations of, 292 attachment of muscles to, 292 condyles of, 290 development of, 292 fracture of, above condyles, 539 below trochanters, 539 head of, 286 neck of, 286 structure of, 290 surface form of, 292 surgical anatomy of, 292 trochanters of, 287 Fenestra ovalis, 878 rotunda, 878, 885 Fenestrated membrane of Henle, 81 Ferrein, pyramids of, 1015 Fibre-cells, contractile, 68 Fibres of Muller, 863 of muscle, 67 of nerves, 69 Fibrin, 33 ferment, 33 Fibrinogen, 33 Fibro-cartilage, 52 interarticular, 53 connecting, circumferential, and stratiform, 53 yellow, 53 Fibro-cartilages, acromio-clavic- ular, 345 intercoccygean, 341 intervertebral, 322 of knee, 72, 373 of lower jaw, 331 pubic, 342 radio-ulnar, 357 sacro-coccygean, 341 sterno-clavicular, 345 Fibro-serous membranes, 96 Fibrous cartilage, 52 connective tissue, 45 nervous matter, 69 rings of heart, 978 tissue, white, 45 yellow, 46 Fibula, 299 1104 INDEX. Fibula, articulations of, 300 attachment of muscles to, 301 development of, 300 fracture of, with dislocation of the tibia, 540 surface form of, 301 Fibular region, muscles of, 529 Fifth nerve, 759 surface marking of, 771 surgical anatomy of, 771 ventricle of brain, 737 Filiform papillae of tongue, 843 Fillet of the gyrus fornicatus, 744 Filuin terminale of cord, 697 Fimbriae of Fallopian tube, 1056 First nerve, 754 surgical anatomy of, 755 Fissure, auricular, 181 for gall-bladder, 950 Glaserian, 176, 878 horizontal, of cerebellum, 749 of ductus venosus, 891 longitudinal, of cerebrum, 716, 725 of liver, 950 of lung, 1002 of medulla oblongata, 707 portal, 895 pterygo-maxillary, 218 sphenoidal, 184 spheno-maxillary, 218 of spinal cord, 698 Sylvian, 717 transverse, of cerebrum, 736 of liver, 951 umbilical, 951 for vena cava, 951 Fissures, congenital, in cranium, 190 calcarine, 722 collateral, 722 calloso-marginal, 722 dentate, 722 intraparietal, 720 parallel, 721 parieto-occipital, 722 precentral, 718 Rolando, 717 Sylvius, 717, 725 Flat bones, 145 Flexor accessorius muscle, 534 brevis digitorum, 532 minimi digiti (hand), 497 (foot), 535 pollicis, 494 hallucis, 534 carpi radialis, 481 ulnaris, 482 digitorum sublimis, 482 profundus, 483 longus digitorum, 527 pollicis (hand), 484 hallucis, 527 ossi metacarpi pollicis, 496 Floating ribs, 234 Flocculus, 749 Fluids of the body, 33 Foetus, circulation in, 981 Eustachian valve in, 980 foramen ovale in, 128, 980 liver of, distribution of its ves- sels, 981 ovaries in, 138 vascular system in, peculiari- ties, 981 Fold of Douglas, 457 Folds, aryteno-epiglottidean, 987 genital, 140 recto-uterine, 1052 recto-vesical, 1026 vesico-uterine, 1052 Follicle of hair, 94 of intestine, 936 Follicles, sebaceous, 94 Fontana, spaces 6f, 855 Fontanelles, 169, 190 Foot, arteries of, 645, 648 bones of, 301 development of, 310 dorsum, muscles of, 532 fascia of, 532 ligaments of, 530, 531 nerves of, 825 sole of, muscles of, 532 fascia of, 531 surface form of, 312 surgical anatomy of, 313 veins of, 672 Foramen caecum of frontal bone, 173, 210 of medulla oblongata, 708 of tongue, 843 carotid, 180 condyloid, 167 dental inferior, 205 ethmoidal, 211 incisive, 215 infraorbital, 192 intervertebral, 163 jugular, 213 lacerum anterius, 212 posterius, 213 magnum, 167 of Majendie, 896 mastoid, 177 medium, 213 mental, 204 of Monro, 734, 740 obturator, 280 optic, 185, 212 ovale of heart, 915 of sphenoid, 184 palatine, anterior, 195, 213 posterior, 200, 215 parietal, 171 pterygo-palatine, 184 rotundum, 184, 212 sacro-sciatic, 277, 339 of Scarpa, 196, 215 of Sommerring, 860 spheno-palatine, 201, 223 spinosum, 184, 212 of Stenson, 196, 215 sternal, 231 stylo-mastoid, 180 supraorbital, 173 thyroid, 280 Vesalii, 184, 212 of Winslow, 918 Foramina, sacral, 158 of diaphragm, 448 external orbital, 184 malar, 198 olfactory, 188 Thebesii, 680, 972 Forearm, arteries of, 598 bones of, 256 fascia of, 480 lymphatics of, 686 muscles of, 480 Forearm, nerves of, 801 veins of, 664 Form of bones, 145 For matio reticularis of medulla, 712 Formation of the cornu Ammo- nis, 745 Fornix, 737 bulbs of, 729 conjunctivae, 870 crura of, 737 Fossa acetabuli, 280 of antihelix, 874 canine, 192 condyloid, 167 cystis felleae, 951 digastric, 178 digital, 287 glenoid, 177 of helix, 874 iliac, 276 incisive, 192, 204 infra- and supraspinous, 246 innominata, 874 ischio-rectal, 1083 jugular, 181 lachrymal, 174 myrtiform, 192 navicularis of urethra, 1030 of vulva, 1048 occipital, 167 olfactory, of foetus, 125 ovalis, 973 palatine, anterior, 196 pituitary, 182 pterygoid, of sphenoid, 185 of lower jaw, 206 scaphoid, 185 scaphoidea, 874 sigmoidea, 178 spheno-maxillary, 218 of skull, anterior, 210 middle, 212 posterior, 213 sublingual, 204 submaxillary, 205 subscapular, 245 temporal, 217 trochanteric, 287 zygomatic, 218 Fossae, nasal, 221, 850 of skull, 210 Fourchette, 1048 Fourth nerve, 759 surgical anatomy of, 759 ventricle, 752 Fovea, anterior of fourth ven- tricle, 753 centralis retinae, 860 hemispherica, 883 posterior of fourth ventricle, 753 semi-elliptica, 883 Fracture of acromion process, 502 centre of clavicle, 501 acromial end of, 502 coracoid process, 502 coronoid process of ulna, 503 femur above condyles, 539 below trochanters, 539 fibula, with dislocation of tibia, 540 humerus, anatomical neck. 502 shaft of, 502 INDEX. 1105 Fracture of humerus, shaft, 502 non-union of, 255 surgical neck, 502 neck of femur, 539 olecranon process, 503 patella, 539 Pott's, 540 radius, 503 lower end of, 504 neck of, 503 shaft of, 503 and ulna, 504 Fraena of ileo-csecal valve, 940 Fraenulum of Vieussens' valve, 750 Fraenum clitoridis, 1048 labii superioris et inferioris, 893 linguae, 841 praeputii, 1034 Frontal artery, 572 bone, 172 articulations of, 175 attachment of muscles to, 175 development of, 175 structure of, 175 crest, 173 eminence, 173 lobe, 718 nerve, 760 process of malar, 198 sinuses, 175 suture, 173, 175 vein, 653 Fronto-nasal process, 119 Fronto-sphenoidal suture, 209 Fundamental fasciculus, 701 Fundus of bladder, 1025 of uterus, 1051 Fungiform papillae of tongue, 843 Funiculi of nerve, 73 Funiculus cuneatus, 709 gracilis, 710 of Rolando, 709 Furrow, auriculo-ventricular, 971 genital, 140 interventricular, 971 Furrowed band of cerebellum, 749 G. Galactophorous ducts, 1061 Galen, veins of, 659, 738 Gall-bladder, 956 development of, 135 fissure for, 951 structure of, 956 surface form of, 957 valve of, 956 Ganglion corpuscles, 80 Ganglion or ganglia, general anatomy of,' 79 of Andersch, 779 Arnold's, 770 of Bockdalek, 765, 767 cardiac, 836 carotid, 831 cephalic, 761 of the cerebellum, 752 cervical, inferior, 834 middle, 834 superior, 731 ciliary, 761 Ganglion or ganglia on circum- flex nerve, 801 diaphragmatic, 837 on facial nerve, 774 of fifth nerve, 761 Gasserian, 759 of glosso-pharyngeal, 779 impar, 827, 836 intercarotid, 834 on posterior interosseous nerve, 807 jugular, 779 lenticular, 761 lingual, 834 lumbar, 835 Meckel's, 765 mesenteric, 839 ophthalmic, 761 otic, 770 petrous, 779 pharyngeal, 833 of pneumogastric, 782 of portio dura, 774 of Ribes, 833 of root of vagus, 781 sacral, 835 semilunar, of abdomen, 837 of fifth nerve, 761 spheno-palatine, 765 of spinal nerves, 789 spirale, 890 submaxillary, 771 suprarenal, 837 of sympathetic nerve, 829 temporal, 834 thoracic, 834 thyroid, 834 of trunk of vagus, 781 of Wrisberg, 836 Ganglionic branch of nasal nerve, 761 Gartner, duct of, 139 Gases of the blood, 37 Gasserian ganglion, 759 depression for, 179 Gastric arteries (vasa brevia), 614 artery, 613 follicles, 928 impression of liver, 952 nerves from vagus, 784 plexus, 839 vein, 678 Gastrocnemius muscle, 524 Gastro-colic omentum, 923 Gastro-duodenal artery, 613 plexus, 839 Gastro-epiploic plexus, 839 veins, 677 Gastro-epiploica dextra artery, 613 sinistra, 614 Gastro-hepatic omentum, 923 Gastro-phrenic ligament, 926 Gastro-splenic omentum, 923 Gelatinous connective tissue, 48 nerve-fibres, 72 Gemellus inferior muscle, 519 superior, 519 Generative organs, development of, 137 female, 1047 male, 1032 Genial tubercles, 204 Geniculate bodies, 742 Geniculate ganglion, 774 Genio-hyo-glossus muscle, 417 Genio-hyoid muscle, 416 Genital cord, 136 corpuscles, 76 folds, 140 furrow, 140 ridge, 137 tubercle, 140 Genito-crural nerve, 814 Genu of the corpus callosum, 732 Gerlach's nerve network, 703 Germinal area, 104 disk, 104 spot, 101 vesicle, 101 Giant cells, 55 Gianuzzi, crescents of, 908 Gimbernat's ligament, 450, 1065 Ginglymus, 318 Giraldes, organ of, 138 Girdle, pelvic, 240 shoulder, 240 Glabella of frontal bone, 173, 219 Gladiolus, 231 Glands, development of, 125 ductless, 961 spleen, 961 suprarenal, 1021 thymus, 1009 thyroid, 1006 Glands, lymphatics, 87 Gland or glands, secreting, 98 accessory of parotid, 906 arytenoid, 992 of Bartholine, 1049 of biliary ducts, 956 Brunner's, 936 buccal, 893 ceruminous, 876 coccygeal, 619 Cowper's, 1034, 1086 duodenal, 936 epiglottic, 992 gastric, 928 of Havers, 316 labial, 893 lachrymal, 871 of larynx, 992 lingual, 844 of Littr£, 1031 of Luschka, 619 mammary, 1060 Meibomian, 870 molar, 895 mucilaginous, of Havers, 316 odori ferae, 1034 oesophageal, 912 of Pacchioni, 659, 705 palatial, 903, 910 parotid, 904 peptic, 929 Peyer's, 937 pharyngeal, 910 pineal, 740 pituitary, 729 prostate, 1032 salivary, 904 sebaceous, 94 solitary, 936 sublingual, 907 submaxillary. 906 sudoriferous, 95 suprarenal, 1021 1106 INDEX. Gland or glands, thymus, 1009 thyroid, 1006 tracheal, 995 of Tyson, 1034 uterine, 1054 of vulva, 1049 Glanduhe odoriferte, 1034 Pacchioni, 659, 705 Glans penis, 1034 clitoridis, 1049 Glaserian fissure, 176, 878 Glenoid cavity, 247 fossa, 177 ligament of shoulder, 348 of Cruveilhier, 363 of phalanges, 363 Gliding movement, 320 Glisson's capsule, 923, 952 Globules, blood-, 34 development of, 127 Globus major of epididymus, 1042 minor, 1042 Glosso-epiglottidean ligaments, 841, 987 Glosso-pharyngeal nerve, 778 Glottis, rima of, 988 Gluteal aponeurosis, 517 artery, 629 inferior, 628 lymphatic glands, 688 nerve, inferior, 823 superior, 823 region, lymphatics of, 691 muscles of, 516 ridge, 288 veins, 675 Gluteus maximus muscle, 516 medius, 517 minimus, 518 Goblet cells, 43 Golgi, organs of, 78 Goll's column, 701 Gomphosis, 317 Graafian vesicles, 1058 membrana granulosa of, 1058 ovicapsule of, 1058 . structure of, 1058 Gracilis muscle, 513 Granular formation of cortex, 745 Gray nervous substance, 69 matter of cerebellum, 751 of cerebrum, 743 of fourth ventricle, 753 of medulla oblongata, 713 of spinal cord. 702 Great omentum, 923 sciatic nerve, 824 surgical anatomy of, 328 Greater wings of sphenoid, 184 Groin, 1072 cutaneous vessels and nerves of, 1072 superficial fascia ofj 1072 surgical anatomy of, 1072 Groove, auriculo-ventricular, 971 biqipital, 249 cavernous, 183 infraorbital, 193 lachrymal, 194 mylo-hyoid, 205 nasal, 191 occipital, 178 optic, 182 primitive dental, 899 Groove, subclavian, 236 | Grooves in the radius, 262 interventricular, 971 Growth of bones, 63 Gubernaculum testis, 1045 Gums, 894 Gustatory nerve, 769 Gvri, or convolutions of brain, 721 annectant, 724' operati, 721 Gyrus fornicatus, 723 or lingual lobule, 724 H. Htematoidin crystals, 37 Htemin crystals, 37 Haemoglobin, 34 crystals, 37 Hair-cells of internal ear, 888 Hair-follicles, 94 Hairs, 93 root-sheath of, 93 shaft of, 94 structure of, 93 Ham, region of the, 639 Hamstring tendons, surgical anatomy of, 522 Hamular process of sphenoid, 185 of humerus, 252, note. of lachrymal, 197 Hand, arteries of, 603 bones of, 264 fascia of, 491 ligaments of, 358, 359 muscles of, 491 nerves of, from median, 802 from radial, 806 from ulnar, 804 surface form of, 272, 500 veins of, 664 Hard palate, 903 Harmonia, 317 Hasner, valve of, 873 Havers, glands of, 316 Haversian canals of bone, 56 Head, lymphatics of, 683 muscles of, 392 veins of, 652 Heart, 970 annular fibres of auricles, 978 arteries of, 547, 979 circular fibres of, 978 development of, 126 endocardium, 978 fibres of the auricles, 978 of the ventricles, 978 fibrous rings of, 978 foetal relics in, 972 infundibulum of, 973 left auricle, 975 ventricle, 976 looped fibres of auricles, 978 lymphatics of, 694, 980 muscular fibres of, 67 structure of, 978 nerves of, 784, 836, 979 position of, 970 right auricle, 972 ventricle, 973 septum yentriculorum, 973 size and weight, 971 spiral fibres of, 978 Heart, structure of, 978 subdivision into cavities, 971 surface marking of, 980 veins of, 679 vortex of, 979 Heidenhain, demilunes of, 908 Helicine arteries, 1056 Helicis major muscle, 876 1 minor, 876 Helicotrema of cochlea, 885 Helix, 874 fossa of, 874 muscles of, 875 process of, 875 Haemorrhoidal artery, inferior, 589 middle, 624 superior, 617 nerve, inferior, 823 plexus of nerves, 840 veins, inferior, 674 middle, 674 superior, 677 venous plexus, 676, 677 surgical anatomy of, 674 Henle, looped tubes of, 1014 Henle's layer of hair-follicle, 94 Hepatic artery, 613, 954 cells, 954 duct, 956 plexus, 839 veins, 677, 952, 954 Hernia, congenital, 1071 descent of, 1081 direct inguinal, 1071 dissection of, 1072 encysted, 1071 • femoral, coverings of, 1081 of funicular process, 1071 general remarks on, 997 infantile, 1071 inguinal, 1062 dissection of, 1062 oblique inguinal, 1069 scrotal, 1071 Hesselbach's triangle, 1072 Hiatus Fallopii, 179 Highmore, antrum of, 194 Hilton's muscle, 991 Hilum of kidney, 1011 of spleen, 961 Hinge-joint, 318 Hip-joint, 364 muscles of, 516 in relation with, 367 surface form of, 368 surgical anatomy of, 368 Hippocampus major, 735 minor, 732 Horizontal plate of ethmoid, 187 of palate, 199 Horner's muscle, 397 Houston's valves of rectum, 945 Howship's lacuna*, 55 Huguier, canal of, 177 Humerus, 249 anatomical neck, fracture of, 502 articulations of, 254 attachment of muscles to, 254 development of, 254 head of, 249 neck of, 249 nutrient artery of, 598 shaft, fracture of, 502 INDEX. 1107 Humerus, surgical anatomy of, 255 tuberosities of, greater and lesser, 249 Humors of the eye, 865 Hunter's canal, 632 Huxley's layer of hair-follicle, 94 Hyaline cartilage, 51 Hyaloid membrane of eye, 865 Hydatid of Morgagni, 138 Hymen, 1049 Hyo-epiglottic ligament, 987 Hyo-glossal membrane, 845 Hyo-glossus muscle, 418 Hyoid arch (foetal), 119 artery of superior thyroid, 557 bone, 229 attachment of muscles to, 229 cornua of, 229 development of, 229 branch of lingual artery, 555 region, muscles of, infra-, 413 supra-, 415 Hypoblast, 104 Hypochondriac regions, 914 Hypogastric arteries in foetus, 622, 981 how obliterated, 983 plexus, 839 inferior, 839 region, 916 Hypoglossal nerve, 786 surgical anatomy of, 788 Hypophysis cerebri, 729 of pituitary body, 121 I. Ileo-csecal fossa, 940 valve, 940 Ileo-colic artery, 616 fossa, 940 valve, 940 Ileum, 933 Iliac arteries, common, 620 peculiarities, 620- surface marking of, 621 surgical anatomy of, 621 external, 630 surface marking of, 621 surgical anatomy of, 630 internal, 622 at birth, 623 peculiaritv in the fuetus, 623 surgical anatomy of, 623 fascia, 505 portion of fascia lata, 505 fossa, 276 lymphatic glands, 690 region, muscles of, 505 veins, common, 675 peculiarities of, 675 external, 674 internal, 674 lliacus muscle, 506 Ilio-costalis muscle, 436 Il io-femoral ligament, 365 Ilio-hypogastric nerve, 813 Ilio-inguinal nerve, 813 Ilio-lumbar artery, 628 ligament, 338 vein, 675 Ilio-pectineal eminence, 279 Ilio-tibial band, 509, 510 Ilium, 274 crest of, 277 dorsum of, 274 spines, 274 venter of, 276 Impressio colica, 952 duodenalis, 952 renal is, 952 Incisive foramina, 215 fossa, 193, 204 Incisor teeth, 894 Incisura intertragica, 874 cerebelli, 748 Santorini, 876 Incremental lines of dentine, 898 Incus, 881 development of, 125 ligament of, 881 suspensory, 881 Infantile hernia, 1071 Inferior dental artery, 563 canal, 205 maxillary bone, 203 changes produced by age in, 206 meatus of nose, 223 occipital fossa, 168 profunda artery, 598 turbinated bones, 202 articulations of, 202 development of, 202 ethmoidal process of, 202 lachrymal process of, 202 maxillary process of, 202 vena cava, 675 Inferior-posterior lobe of cere- bellum, 749 Infracostal muscles, 444 Infraglenoid tubercle, 247 Inframaxillary nerves from fa- cial, 777 Infraorbital artery, 564 canal, 193 foramen, 192 groove, 193 plexus of nerves, 764 branches of facial, 777 Infraspinatus muscle, 475 Infraspinous fascia, 475 fossa, 246 Infratrochlear nerve, 761 Infundibula of kidney, 1012 Infundibuliform fascia, 459, 1068 Infundibulum of brain, 729 of cochlea, 885 of ethmoid, 189 of heart, 973 Ingrassias, processes of, 185 Inguinal canal, 1067 glands, deep, 688 superficial, 688, 1063 hernia, 1068 dissection of, 1062 region, 916 Inlet of pelvis, 283 Innominate artery, 547 peculiarities of, 548 surgical anatomy of, 548 bone, 274 articulations of, 280 attachment of muscles to, 281 development of, 280 Innominate veins, 667 peculiarities of, 667 Inorganic constituents of bone, 59 Inspiration, muscles of, 446 Interarticular fibro-cartilage, 53 of acromio-clavicular joint, 345 of jaw, 331 of knee, 372, 373 of radio-ulnar joint, 357 of sterno-clavicular joint, 345 ligament of ribs, 336 Intercarotid ganglion, 834 Intercellular substance of carti- lage, 51 biliary passages, 955 Interchondral ligaments, 336 Interclavicular ligament, 343 Intercolumnar fascia, 452, 1064 fibres, 452 Intercondyloid notch, 290 Intercostal arteries, 608 anterior, 609 superior, 589 fasciae, 444 lymphatic glands, 693 lymphatics, 694 muscles, 444 nerves, 810 spaces, 230 veins, superior, 668 Intercosto-humeral nerves, 802, 810 Interglobular spaces, 898 Interlobular arteries of kidney, 1018 biliary plexus, 955 Intermaxillary suture, 219 Intermediate disk of muscular fibre, 66 Intermembranous ossification, 63 Internal abdominal ring, 996 annular ligament, 530 capsule, 734 carotid artery, 567 cutaneous nerve, 802 inguinal hernia, 1069 mammary artery, 588 maxillary artery, 561 branches of, 562 peculiarities of, 561 surgical anatomy of, 563 mammary vein, 668 oblique muscle, 450 occipital crest, 168 pterygoid plate, 185 sphincter, 1011 Internasal suture, 219 Internodia or phalanges, 272 Internodal segment of nerves, 71 Interossei muscles, dorsal of hand, 498 of foot, 536 palmar, 498 plantar, 536 Interosseous artery of forearm, 603 of foot, 646 fibro-cartilages, 317 membrane of forearm, 356 of leg, 378 nerve, anterior, 803 posterior, 807 veins of forearm, 666 1108 INDEX. Interpeduncular space of brain, 729 Interspinales muscles, 440 Interspinous ligaments, 324 Intertransversales muscles, 440 Intertransverse ligaments, 324 Intertubular stroma of kidney, 1019 Intervertebral notches, 147 foramen, 164 substance, 322 Intestine, development of, 133 large, coats of, 944 lymphatics of, 693 small, 931 coats of, 893 surface marking of, 946 surgical anatomy of, 946 Intracartilaginous ossification, 60 Intralobular veins, 954 Intraparietal fissure, 720 Intrinsic muscle of tongue, 419 Intumescentia gangliformis, 774 Investing mass of Rathke, 118 Involuntary muscle, 68 Iris, 858 Irregular bones, 146 Ischiatic lymphatic glands, 688 Ischio-rectal fascia, 1092 fossa, 1084 position of vessels and nerves in, 1084 region, surgical anatomy of, 1083 Ischium, 277 body of, 277 ramus of, 278 spine of, 277 tuberosity of, 278 Island of Reil, 721 Isthmus of the fauces, 903 of thyroid gland, 1007 Iter ad infundibulum, 740 a tertio ad quartum ventricu- lum, 740 chord® anterius, 878 posterius, 878 Ivory of tooth, 897 J. Jacob's membrane, 863 Jacobson's nerve, 779, 883 canal for, 180 cartilage of, 850 organ of, 850 Jaw, lower, 203 articulations of, 206 attachment of muscles to, 206 changes produced in, bv age, 207 condyle of, 206 development of, 206 ligaments of, 329, 330 oblique line of, 204 pterygoid fossa of, 206 rami of, 205 sigmoid notch of, 206 symphysis of, 203 upper. See Maxillary Bone. Jejunum, 932 Joint. See .4 rticulations. Jugular foramen, 213 fossa, 181 ganglion, 779 Jugular process, 168 surface, 180 vein, anterior, 656 external, 655 surgical anatomy of, 655 internal, 656 surgical anatomy of, 657 sinus or gulf of, 656 posterior, external, 656 K. Karyokinesis, 40 Karyomitosis, 40 Kerkring, valves of, 933 Kidney, 1011 calices of, 1012 cortical substance of, 1013 development of, 135 ducts of, 1020 hilum of, 1011 infundibula of, 1012 lymphatics of, 692, 1019 Malpighian bodies of, 1013 mammillae of, 1013 medullary substance, 1013 nerves of, 1018 papillae of, 1013 pelvis of, 1012 pyramids of Ferrein, 1015 renal artery, 618, 1017 sinus of, 1012 surface marking of, 1019 surgical anatomy of, 1019 tubuli uriniferi, 1014 veins of, 677, 1018 weight and dimensions, 1011 Knee-joint, 370 surface form of, 377 surgical anatomy of, 377 Krause's membrane, 66 end-bulbs of, 76 Kiihne's views on the termina- tions of motor nerves, 78 Kiirschner, on structure of heart's valves, 974 L. Labia cerebri, 731 pudendi majora, 1047 minora, 1048 lymphatics of, 691 Labial artery, 558 glands, 893 veins, superior, 654 inferior, 654 Labium tympanicum, 883 vestibulare, 884 Labyrinth, 883 arteries of, 889 fibro-serous membrane of, 888 Lachrymal apparatus, 871 artery, 570 bone, 197 articulations of, 198 attachment of muscles to, 198 development of, 198 canals, 872 caruncula, 871 crest, 197 fossa, 174 gland, 871 groove, 194 Lachrymal nerve, 760 notch, 193 papilla, 869, 872 process of inferior turbinated bone, 202 puncta, 872 sac, 872 tubercle, 195 Lacteals, 681, 683, 935 Lactiferous ducts, 1061 Lacuna magna, 1031 Lacuna? of bone, 58 Howship's, 55 Lacus lachrymalis, 871 Lambda, 210 Lambdoid suture, 207 Lamella, horizontal, of ethmoid, 187 perpendicular, of ethmoid, 188 of bone, articular, 315 Lamellae of bone, 57 Lamina cinerea, 728 of cornea, elastic, 854 cribrosa, 179 of sclerotic, 853 fusca, 853 spiralis ossea of cochlea, 885 suprachoroidea, 857 membranacea, 887, note. of the vertebra?, 146 cerebellum, 749 vitrea, 857 Laminae dorsales, 107 Laminated tubercle of cerebel- lum, 749 Lancisi, nerves of, 728 Lanugo (foetal hairs), 125 Large intestine, 939 areolar coat, 945 caecum, 939 colon, 941 ilio-caecal valve, 940 mucous coat, 945 muscular coat, 944 rectum, 943 serous coat of, 944 Laryngeal artery, inferior, 586 superior, 554 nerve, external, 783 internal, 783 recurrent, 784 superior, 783 surgical anatomy of, 784 from sympathetic, 833 pouch, 989 veins, 668 Laryngo-tracheotomy, 996 Laryngotomy, 996 Larynx, 984 actions of muscles of, 991 arteries of, 992 cartilages of, 984 cavity of, 988 glands of, 992 interior of, 987 ligaments of, 986 lymphatics of, 992 mucous membrane of, 992 muscles of, 989 nerves of, 992 rima glottidis, 988 superior aperture of, 987 surface form of, 995 surgical anatomy of, 995 veins of, 992 INDEX. 1109 Larynx, ventricle of, 988 vocal chords of, false, 987 true, 987 Lateral disk of muscular fibre, 66 horn of spinal cord, 702 ligaments of liver, 950 masses of ethmoid, 188 region of skull, 216 sinus of brain, 660 tract of medulla oblongata, 709, 711 Lateralis nasi artery, 558 Latissimus dorsi muscle, 432 Leg, arteries of, 641 bones of, 293 fascia of, 522 deep transverse, 526 ligaments of, 364 lymphatics of, 688 muscles of, 522 back of, 524 front of, 523 nerves of, 782 veins of, 672 Lens, 866 changes produced in, by age, 866 development of, 126 suspensory ligament of, 867 Lenticular ganglion, 761 glands of stomach, 929 Lesser lachrymal bone, 197 omentum, 923 sciatic nerve, 824 wings of sphenoid, 185 Levator anguli oris, 402 scapulae, 433 ani, 461 glandulae thyroidie, 1007 labii inferioris, 402 superior alaeque nasi, 402 superioris, 402 menti, 402 palati, 423 palpebrse, 397 prostate, 462 Levatores costarum, 444 Lieberkuhn, crypts of, 936 Ligament, structure of, 315 acromio-clavicular, inferior, 345 . superior, 345 alar of knee, 374 of ankle, anterior, 379 lateral, 380 annular of radius, 355 of wrist, anterior, 358 posterior, 359 of ankle, 379 externa], 380 internal, 380 of stapes, 381 anterior, of knee, 370 arcuate, 446 aryteno-epiglottic, 986 astragalo-navicular, 385 atlanto-axial, anterior, 325 posterior, 325 of bladder, false, 1027 true, 1026 broad, of liver, 949 caleaneo-astragaloid, external, 383 interosseous, 383 posterior, 383 Ligament, calcaneo-cuboid, inter- nal, 383 long, 383 short, 383 superior, 383 calcaneo-navicular, inferior, 384 superior, 384 capsular. See Individual Joints. carpo-metacarpal, dorsal, 359 interosseous, 360 palmar, 359 of carpus, 359 central, of spinal cord, 697 check, 328 chondro-sternal, anterior, 336 posterior, 336 common vertebral, anterior, 321 posterior, 321 conoid, 346 coraco-acromial, 346 coraco-clavicular, 345 coraco-humeral, 348 coracoid, 347 coronary of liver, 950 costo-clavicular, 343 costo-colic, 925 costo-transverse, 333 costo-vertebral, or stellate, 332 cotyloid, 366 crico-arytenoid, 987 crico-thyroid, 987 crucial, of knee, 371 cruciform, 326 deltoid, 380 dorsal. See Individual Joints. of elbow, 351 anterior, 351 external lateral, 352 internal lateral, 352 posterior, 352 falciform of liver, 949 gastro-phrenic, 926 Gimbernat's, 450, 1065, 1078 glenoid, 348 glosso-epiglottidean, 986 of hip, 364 hyo-epiglottic, 986 ilio-femoral, 365 ilio-lumbar, 338 of incus, 881 interarticular of ribs, 333 interclavicular, 343 interchondral, 336 interosseous. See Individual Joints. interspinous, 324 intertransverse, 324 intervertebral, 322 of jaw, 329 of knee, 370 of larynx, 986 lateral. See Individual Joints. longitudinal of liver, 949 long plantar, 383 1 umbo-iliac, 338 lumbo-sacral, 338 of malleus, 881 metacarpo-phalangeal, 363 metacarpal, 363 metatarsal, 387 metatarso-phalangeal, 388 mucosum of knee, 370 nuchte, 432 Ligament, oblique, 356 obturator, 518 occipito-atlantal, anterior, 327 lateral, 327 posterior, 327 occipito-axial, 328 odontoid, 328 orbicular, 355 of ossicula, 881 of ovary, 1057 palpebral or tarsal, 870 of patella, 370 of pelvis, 338 of the phalanges, hand, 364 foot, 389 of the pinna, 375 plantar, 387 posterior of knee, or posticum Winslowii, 370 Poupart s, 450, 1065, 1077 pterygo-maxillary, 404 pubic, anterior, 342 posterior, 342 superior, 342 pubo-prostatic, 957 radio-carpal, 357 radio-ulnar joint, inferior, 357 middle, 357 superior, 357 recto-uterine, 1052 rhomboid, 343 round, of uterus, 1059 of liver, 950 of radius and ulna, 356 of hip, 365 sacro-coccygeal, anterior, 341 posterior, 341 sacro-iliac, anterior, 339 oblique, 339 posterior, 339 sacro-sciatic, greater, 339 lesser, 340 sacro-uterine, 1052 sacro-vertebral, 338 of scapula, 346 scapulo-clavicular, 345 of shoulder, 347 stellate, 332 sterno-clavicular, anterior, 343 posterior, 343 of sternum, 333 stylo-maxillary, 330 subpubic, 342 supraspinous, 324 suspensory, of incus, 881 of lens, 867 of liver, 949 of malleus, 881 of mamma, 468 of penis, 964 of spleen, 1034 sutural, 315 tarsal, of eyelids, 870 tarso-metatarsal, 386 of tarsus, 382 teres, of hip, 466 of thumb, 361 thyro-arytenoid, inferior, 988 superior, 988 thyro-epiglottic, 986 thyro-hyoid, 987 tibio-fibula, 380 tibio-tarsal, 379 transverse, of atlas, 325 of hip, 363 1110 INDEX. Ligament, transverse, ofknee, 373 of scapula, 347 trapezoid, 346 triangular, of urethra, 1086 of tympanic bones, 881 of uterus, 1052 of vertebrae, 322 vesico-uterine, 1052 of Winslow, 370 of wrist, anterior, 358 lateral external, 358 lateral internal, 358 posterior, 359 of Zinn, 399 Ligamenta alaria, 374 subflava, 323 suspensoria of mamma, 468 Ligamentum arcuatum exter- num, 447 internum, 446 denticulatum, 697 latum pulmonis, 997 mucosum, 374 nucha*, 432 patella*, 370 pectinatum iridis, 858 posticum Winslowii, 370 spirale, 887 suspensorium, 328 teres, 366 Ligature of arteries. See each Artery. Limbs, development of, 126 Limbus laminae spiralis, 886 luteus, 860 Linea alba, 457 aspera, 288 ilio-pectinea, 276 quadrat!, 288 splendens, 696 suprema, 166 Lineae semilunares, 458 transversae of abdomen, 458 Lingual artery, 555 surgical anatomy of, 555 bone, 229 ganglion, 834 nerve, 769 veins, 656 Lingualis muscle, inferior, 420 superior, 419 transverse, 420 vertical, 420 Lingula, 750 of sphenoid, 183 Lips, 892 arteries of, 558 Liquor amnii, 112 Cotunnii, 888 Scarpae, 889 sanguinis, 36 Lithotomy, parts concerned in operation of, 1089 avoided in operation, 1089 divided, 1089 Littre, glands of, 1031 Liver, 948 changes of position in, 957 development of, 134 distribution of vessels to, in foetus, 981 ducts of, 955 fibrous coat of, 953 fissures of, 950 hepatic artery, 613, 954 Liver, cells, 954 duct, 956 veins, 677, 974 ligaments of, 949 coronary, 950 lateral, 950 longitudinal, 949 round, 950 lobes of, 952 lobules of, 952 lymphatics of, 692 nerves of, 839 portal vein, 677 situation, size, and weight, 948 structure of, 953 surface marking of, 957 in surfaces and borders, 949 surgical anatomy of, 958 vessels of, 952 Lobe, central, 721 cuneate, 723 frontal, 718 marginal, 722 occipital, 721 orbital, 719 parietal, 719 quadrate, 723 temporo-sphenoidal, 721 uncinate, 723 Lobes of cerebrum, 717 of cerebellum, 748 of kidney, 1012 of liver, 950 of lung, 1002 of prostate, 1033 of testis, 1042 of thymus, 1009 of thyroid, 1007 Lobule of the ear, 874 Lobules of liver, 952 of kidney, 1012 of lung, 1003 Lobuli testes, 1042 Lobulus Spigelii, 952 Lobus caudatus, 952 quadratus, 952 Locus coeruleus, 753 niger, 730 Long bones, 145 saphenous nerve, 818 Longissimus dorsi muscle, 438 Longitudinal fissure, of brain, ' 716, 728 of liver, 950 ligament of liver, 950 sinus of brain, superior, 659 inferior, 660 Longus colli muscle, 427 Looped tubes of Henle, 1015 Lower extremity, arteries of, 632, 633 bones of, 274 fascia of, 504 ligaments of, 364 lymphatics of, 688 muscles of, 504 nerves of, 812 surface form of, 537 veins of, 672 Lower, tubercle of, 972 Lumbar arteries, 619 fascia, 435 ganglia, 835 glands, 690 nerves, 811 Lumbar, anterior divisions of, 812 posterior divisions of, 812 roots of, 811 plexus of nerves, 813 region, 916 surgical anatomy of, 827 vein, ascending, 676 veins, 676 vertebrae, 153 development of, 156 Lumbo-iliac ligament, 338 Lumbo-sacral ligament, 338 nerve, 812 Lumbricales muscles, hand, 498 foot, 534 Lungs, 1001 air-cells of, 1003 bronchial arteries, 1004 veins, 1004 capillaries of, 1003 development of, 135 in foetus, 981 lobes and fissures of, 1001 lobules of, 1003 lymphatics of, 694, 1004 nerves of, 1004 pulmonary artery, 1003 veins, 1004 root of, 1902 structure of, 1002 surface marking, 1004 weight, color, etc., 1002 Lunulae of nails, 92 Luschka's gland, 619 Lymph, 37 path or sinus, 88 Lymphatic duct, right, 683 glands, general anatomy of, 87 descriptive anatomy, anterior mediastinal, 693 auricular posterior, 683 axillary, 686 brachial, 686 bronchial, 694 buccal, 683 cervical, deep, 685 superficial, 685 in front of elbow, 686 gluteal, 688 of head, 683 iliac, external, 689 internal, 690 inguinal, deep, 688 superficial, 688 intercostal, 693 internal mammary, 693 ischiatic, 688 of large intestine, 693 of lower extremity, 688 lumbar, 690 of neck, 686 occipital, 683 parotid, 683 of pelvis, 689 popliteal, 688 radial, 686 sacral, 690 of small intestines, 693 of spleen, 692 of stomach, 692 submaxillary, 683 of thorax, 693 tibial anterior, 688 ulnar, 686, 687 of upper extremity, 686 INDEX. 1111 Lymphatic, zygomatic, 683 Lymphatics, general anatomy of, 85 origin of, 86 plexus of, 86 subdivision into deep and su- perficial, 681 terminations of, 87 valves of, 86 descriptive anatomy: abdomen, 689 arm, 686 bladder, 691 bone, 56 broad ligaments, 691 cardiac, 694 cerebral, 684 cervical, superficial and deep, 685 chest, 694 of clitoris, 691 of cranium, 684 diaphragm, 694 face, superficial, 684 deep, 684 Fallopian tubes, 691 gluteal region, 691 head, superficial, 683 heart, 694 intercostal, 693 internal mammary, 694 intestines, 693 kidneys, 692 labia, 692 lacteals, 693 large intestine, 693 leg, 688 liver, 692 lower extremity, 688 lung, 694 lymphatic duct, 683 meningeal, 684 mouth, 684 neck, 685 nose, 684 nymphae, 691 oesophagus, 694 ovaries, 692 pancreas, 692 pelvis, 689 penis, 691 perinaeuin, 691 pharynx, 685 pia mater, 684 prostate, 691 rectum, 691 scrotum, 691 small intestine, 693 spleen, 692 stomach, 692 testicle, 692 thoracic duct, 682 thorax, 693 thymic, 694 thyroid, 694 upper extremity, 686 deep, 686 superficial, 687 uterus, 691 vagina, 691 Lymphoid connective tissue, 48 of tongue, 845 of tonsil, 912 Lyra of fornix, 737 M. Macula cribrosa, 883 germinativa, 100 lutea, 864 Magnum of carpus, 268 Majendie, foramen of, 696 Malar bone, 198 articulations of, 199 attachment of muscles to, 199 development of, 199 frontal process of, 198 maxillary process of, 199 orbital process of, 198 zygomatic process of, 199 canals, 198 nerves, from facial, 777 process of superior maxillary, 194 Male urethra, 1030 Malleolar arteries, external and internal, 645 Malleolus, external, 299 internal, 299 Malleus, 880 development of, 125 suspensory ligament of, 881 Malpighi, pyramids of, 1013 Malp ighian bodies of kidney, 1013 capsules, 1013 corpuscles of spleen, 964 tufts, 1013 Mamma, areola of, 1060 lobules of, 1061 nerves of, 1061 nipple or mamilla of, 1060 vessels of, 1061 Mammae, development of, 125 Mammary artery, internal, 588 glands, 1060 lymphatic glands, 683 veins, internal, 668 Mammilla of breast, 1061 of kidney, 1013 Mammillary processes, 154 Mandibular arch, 119 Manubrium of sternum, 230 of malleus, 880 Marginal lobe, 723 Marrow of bone, 55 Marshall, vestigial fold of, 668 Masseter muscle, 405 Masseteric arteries, 564 nerve, 768 veins, 654 Mastoid cells, 178 openings of, 878, 879 foramen, 177 portion of temporal bone, 177 process, 178 vein, 655 Masto-occipital suture, 209 Masto-parjetal suture, 209 Matrix of nail, 92 Maxillary arch, foetal, 119 artery, internal, 561 bone, inferior, 203 superior, 191 development of, 196 nerve, inferior, 767 superior, 763 process of inferior turbinated, 202 Maxillary process of malar bone, 199 processes (foetal), 119 sinus, 192 tuberosity, 192 vein, internal, 654 Meatus auditorius externus, 179 internus, 179 of nose, inferior, 223, 850 middle, 223, 850 superior, 223, 850 urinarius, male, 1031 female, 1049 Meatuses of the nose, 223, 850 Meckel's cartilage, 120 diverticulum, 933 ganglion, 766 Median artery of forearm, 605 of spinal cord, 586 nerve, 802 surgical anatomy of, 807 vein, 665 disk of Hensen, 67 Mediastinal arteries, from inter- nal mammary, 588 posterior, from aorta, 608 lymphatic glands, 653 Mediastinum, anterior, 1000 middle, 1000 posterior, 1000 superior, 1000 testis, 1041 Medio-tarsal joint, 381 Medulla oblongata, 708 arcuate fibres of, 710 back of, 711 fissures of, 708 formatio reticularis of, 712 funiculus cuneatus, 711 of Rolando of, 711 gracilis of, 711 gray matter of, 713 lateral column, 709 tract, 710 olivary body, 709, 711 pyramids, 709 raphe of, 712 restiform bodies, 710, 711 structure of, 711 spinalis, 697 Medullary canal of bone, 62, 145 formation of, 63 of spine, development of, 120 membrane of bone, 54 plates, 107 sheath of nerve-fibres, 71 spaces of bone, 61 of kidney, 1012 of suprarenal capsules, 1022 velum, posterior of cerebel- lum, 749 superior, 750 Medullated nerve-fibres, 70 Medullo-spinal veins, 670 Meibomian glands, 870 Meissner's plexus, 939 Membrana basilaris, 886 fusca, 853 granulosa, of Graafian vesicle, 1058 limitans of retina, 861 nictitans, 870 pupillaris, 860 sacciformis, 362 tectoria, 886 1112 INDEX. Membrana tympani, 880 secundaria, 885 Membrane of aqueous chamber, 855 arachnoid, spinal, 696 cerebral, 705 choroid, 856 of Corti, 886 costo-coracoid, 470 crico-thyroid, 987 of Descemet. 854 fenestrated, 81 hyaloid, 865 Jacob's, 863 limiting, 861 pituitary, 850 pupillary, 860 of Reissner, 886 Schneiderian, 850 thyro-hyoid, 987 Membranes of spinal cord, 695 of brain, 704 Membranous labyrinth, 888 portion of urethra, 1030 semicircular canals, 888 Meningeal artery, from ascending pharyngeal, 560 anterior, from internal carotid, 570 lymphatics, 684 middle, from internal maxil- lary, 562 from occipital, 559 posterior, from vertebral, 584 small, from internal maxil- lary, 563 veins, 656, 704 Meninges. See Membranes. Menisci, 52 Mental foramen, 204, 219 process, 204 tubercles, 204 Mesencephalon, 121 Mesenteric artery, inferior, 616 superior, 615 glands, 693 plexus of nerves, inferior, 839 superior, 839 vein, inferior, 677 superior, 677 Mesenteries, 867 Mesoblast, 104 Mesoblastic somites, 107 Mesocaecum, 924 Mesocolon, ascending, 924 descending, 924 transverse, 925 Mesoderm, 104 Mesonephros, 135 Mesorchium, 138 Mesorectum, 925 Mesosternum, 231 Mesovarium, 138 Metacarpal artery, 602 articulations, 363 Metacarpo-phalangeal articula- tions, 363 Metacarpus, 269 common characters of, 269 development of, 274 peculiar bones of, 271 Metanepheros, 135 Metatarsal articulations, 387 artery, 646 bones, 308 Metatarso-phalangeal articula- tions, 388 Metatarsus, 308 development of, 311 Metasternum, 231 Metencephalon, 121 Middle and internal frontal artery, 574 Middle clinoid processes, 182 ear, or tympanum, 878 fossa of skull, 212 meatus, 223, 850 Mid-frontal process (foetal), 119 Milk teeth, 896 Mitral valve, 977 Mixed bones, 146 lateral column, 701 Modiolus of cochlea, 885 Mold, glands of, 869 Molar glands, 894 teeth, 895 Monro, foramen of, 740 Mons Veneris, 1045 Morgagni, hydatid of, 138 sinus of, 422 Motor nerves, 78 oculi nerve, 757 surgical anatomy of, 758 Motorial end-plates, 87 Mouth, 892 mucous membrane of, 892 muscles of, 402 surface form of, 909 Movement admitted in mints, 318 Mucilaginous glands, 316 Mucoid cellular tissue, 48 Mucous glands of tongue, 844 • membrane, 97 Muller, duct of, 135 fibres of, 864 Multicuspidati teeth, 895 Multifid us spinae muscle, 440 Muscle, general anatomy of, 64 of animal life, 64 arrangement of fibres of, 65 bipenniform, 390 blood-vessels of, 67 chemical composition of, 68 derivation of names, 390 development of, 126 fasciculi of, 65 fibres of, 65 fibrils of, 65 form of, 390 fusiform, 390 involuntary, 68 lymphatics of, 68 meaning of the terms " origin " and "insertion," 391 mode of connection of, with bone, cartilage, skin, etc., 391 nerves of, 68, 78 of organic life, 78 penniform, 390 quadrilateral, 390 rhomboidal, 390 sarcous elements of, 66 sheath of, 65 size of, 390 striped, 65 structure of, 65 tendons of, 391 triangular, 390 Muscle, unstriped, 68 voluntary, 64 Muscles or muscle, descriptive anatomy: of abdomen, 449 abductor minimi digiti (hand), 496 (foot), 533 indicis, 498 pollicis (hand), 494 hallucis, 532 accelerator u rinse, 463 accessorii orbicularis oris, 403 accessorius pedis, 534 ad ilio-costalem, 438 adductor brevis, 514 longus, 514 magnus, 515 obliquus pollicis (hand), 495 transversus pollicis, 495 obliquus hallucis, 535 transversus hallucis, 535 anconeus, 488 antitragicus, 876 arytaeno-epiglottideus, inferior, 991 superior, 991 arytaenoideus, 990 rectus, 990 attollens aurem, 396 atrrahens aurem, 395 azygos uvulae, 424 biceps (arm), 478 (thigh), 520 biventer cervicis, 439 brachialis anticus, 479 buccinator, 404 cervicalis ascendens, 438 chondro-glossus, 418 ciliary of eye, 860 circumflexus palati, 424 coccygeus, 462 complexus, 439 compressor narium minor, 401 nasi, 401 sacculi laryngis, 991 urethrae, 467 in female, 1090 constrictor isthmi faucium, 418 pharyngeus inferior, 421 medius, 422 superior, 422 coraco-brachialis, 478 corrugator supercilii, 397 of cranial region, 393 cremaster, 454 crico-arytaenoideus lateralis, 990 posticus, 989 crico-thyroid, 989 crureus, 511 cutis ani, 460 deltoid, 473 depressor anguli oris, 403 alse nasi, 401 epiglottidis, 926 labii inferioris, 403 diaphragm, 446 digastric, 415 dilatator naris, anterior, 401 posterior, 401 erector clitoridis, 467 penis, 464 spinae, 436 of external ear, 396 INDEX. 1113 Muscles or muscle, external sphincter, 460 extensor brevis digitorum, 532 carpi radialis brevior, 486 longior, 486, ulnaris, 488 coccygis, 440 digitorum communis, 487 indicia, 490 longus digitorum, 523 pollicis, 490 minimi digiti, 487 ossi metacarpi pollicis, 488 brevis pollicis, 490 primi internodii pollicis, 490 proprius hallucis, 523 of face, 396 femoral r tgion, anterior, 507 internal, 513 posterior, 520 fibular region, 529 flexor accessorius, 534 brevis minimi digiti (hand), 498 (foot), 535 hallucis, 534 digitorum, 532 pollicis (hand), 494 carpi radialis, 481 • ulnaris, 482 digitorum sublimis, 482 longus digitorum, 528 hallucis, 527 pollicis (hand), 484 ossis metacarpi pollicis, 494 profundus digitorum, 483 gastrocnemius, 524 gemellus superior, 519 inferior, 519 genio-hyo-glossus, 417 genio-hyoid, 416 gluteus maximus, 516 medius, 517 minimus, 518 gracilis, 513 of hand, 494 of head and face, 392 helicis, major, 876 minor, 876 Hilton's, 991 of hip, 516 Horner's, 397 hyo-glossus, 418 iliac region, 505 iliacus, 506 ilio-costalis, 436 infracostal, 444 infraspinatus, 475 intercostal, 443 internal sphincter, 461 interossei of foot, 536 of hand, 498 interspinales, 440 intertransversales, 440 labial, 402 of larynx, 989 latissimus dorsi, 432 of leg, 522 levator anguli oris, 402 ani, 416 glandulte thyroideae, 1007 labii inferioris, 402 superioris, 398 superioris alseque nasi, 401 Muscles or muscle, labii menti, 402 palati, 423 palpebrae, 397 prostatse, 462 levatores costarum, 444 lingualis, 417 longissimus dorsi, 438 longus colli, 427 lumbricales (hand), 498 (foot), 534 masseter, 405 multifidus spinae, 440 musculus accessorius ad ilio- costalem, 438 mylo-hyoid, 416 naso-labialis, 401 of neck, 408 obliquus auris, 876 abdominus externus, 450 internus, 453 capitis superior, 441 inferior, 441 obturator, externus, 520 internus, 518 occipito-frontalis, 393 oculi, inferior, 400 superior, 399 omo-hyoid, 414 opponens minimi digiti, 497 pollicis, 494 orbicularis oris, 403 palpebrarum, 396 palate, 423 palato-glossus, 424 palato-pharyngeus, 424 palmaris brevis, 496 longus, 482 pectineus, 513 pectoralis, major, 469 minor, 471 of perineum, male, 460 female, 466 peroneus brevis, 529 longus, 529 tertius, 524 of pharynx, 421 plantaris, 526 platysma myoides, 408 popliteus, 526 pronator quadratus, 485 radii teres, 481 psoas magnus, 506 parvus, 506 pterygoid, internal, 407 external, 406 pyramidalis abdominis, 457 nasi, 401 pyriformis, 518 quadratus femoris, 519 lumborum, 460 menti, 403 quadriceps extensor cruris, 511 rectus abdominis, 455 capitis anticis major, 426 minor, 426 femoris. 511 lateralis, 427 oculi, externus, superior, in- ferior, and internus, 399 posticus major, 441 minor, 441 retrahens aurem, 396 rhomboides major, 433 minor, 433 Muscles or muscle, risorius, 404 rotatores spinse, 440 sacro-lumbalis, 436 salpingo-pharyngeus, 424 sartorius, 510 scalenus anticus, 427 medius, 427 posticus, 428 scapulae, 433 semimembranosus, 521 semispinalis dorsi, 439 colli, 439 semitendinosus, 521 serratus magnus, 472 posticus, superior, 434 inferior, 434 sole of foot, 532 first layer, 532 fourth layer, 536 second layer, 534 third layer, 534 soleus, 525 sphincter, external, 461 internal, 461 vaginae, 466 spinalis dorsi, 438 colli. 438 splenius, 435 capitis, 435 colli, 435 stapedius, 882 sterno-cleido-mastoid, 411 sterno-hyoid, 413 sterno-thyroid, 413 stylo-glossus, 418 stylo-hyoid, 415 stylo-pharyngeus, 422 subanconeus, 480 subclavius, 471 subcrureus, 512 subscapularis, 474 supinator brevis, 488 longus, 485 supraspinales, 440 supraspinatus, 475 temporal, 405 tensor-palati, 424 tarsi, 397 tympani, 882 vaginae femoris, 510 teres major, 476 minor, 476 thyro-arytsenoideus, 990 thyro-epiglottideus, 991 thyro-hyoid, 413 tibialis anticus, 523 posticus, 528 of tongue, 418 trachelo-mastoid, 438 tragicus, 876 transversalis abdominis, 455 colli, 438 transversus auriculae, 876 perinaei, 612 (female), 466 profundus, 1090 trapezius, 430 triangularis sterni, 444 triceps, extensor cubiti, 479 extensor cruris, 511 fem oralis, 512 of tympanum, 882 of ureters, 1028 vastus externus, 511 internus and crureus, 512 1114 INDEX. Muscles or muscle, zygomaticus major, 402 minor, 402 Muscles of inspiration and ex- piration, 446 Muscular columns, 66 fibres of heart, 67 Muscularis mucosae, 97 Musculi papillares, left ventricle, 977 right, 974 pectinati in left auricle, 976 in right, 973 Musculo-cutaneous nerve of arm, 801 from peroneal, 827 Musculo-spiral groove, 252 surgical anatomy of, 807 nerve, 805 Musculo-phrenic artery, 588 Musculus accessorius ad ilio- costalem, 436 suspensorius duodeni, 932 Myelo-plaques, 55 Mylo-hyoid artery, 563 groove, 205 muscle, 416 nerve, 769 ridge, 205 Myrtiform fossa, 192 N. Nails, 92 Nares, anterior, 224, 849 posterior, 224, 849, 910 septum of, 223, 848 Nasal angle, 191 artery, of internal maxillary, 564 of ophthalmic, 572 of septum, 558 bones, 191 articulations of, 191 development of, 191 cartilages, 848 crest, 191 duct, 873 eminence, 173 fossae, 221, 849 arteries of, 851 mucous membrane of, 850 nerves of, 851 surgical anatomy of, 852 veins of, 851 groove, 191 nerve, 760 nerves from Meckel's ganglion, 765 notch, 173 process, 194 spine, 173 anterior, 196, 219 posterior, 198 venous arch, 653 Nasion, 219 Nasmyth's membrane, 9Q0 Naso-maxillary suture, 219 Naso-palatine nerve, 765 Nates of brain, 741 Navicular bone, 306 articulations of, 307 attachment of muscles to, 307 tuberosity of, 306 Neck, glands of, 685 lymphatics of, 685 muscles of, 408 triangle of, anterior, 565 posterior, 567 veins of, 655 Nerve-corpuscles, 69 Nerve-epithelium cells, 78 Nerves, general anatomy of, 73 cerebro-spinal, 73 endoneurium, 74 epineurium, 74 funiculi of, 73 origin of, 75 perineum, 74 plexus of, 75 sheath of, 74 spinal roots of, 789 sympathetic, 75 termination of, 75 vessels of, 74 Nerves or nerve, descriptive an- atomy of: abducens, 772 accessory obturator, 816 anterior crural, 817 auditory, 778 auricular, posterior, 775 of vagus, 783 auricularis magnus, 794 of auriculo-temporal, 768 of second cervical, 790 of small occipital, 793 of brachial plexus, 796 buccal, 768 of facial, 777 cardiac, 834 inferior, 834 middle, 834 plexus, deep, 836 superficial, 836 of pneumogastric, 781 superior, 833 cavernous, of penis, 840 cervical, anterior, 792 posterior, 790 superficial, 793 cervico-facial, 777 chorda tympani, 775, 883 ciliary, long, 763 short, 763 circumflex, 801 coccygeal, 820 cochlear, 890 communicans hypoglossi, 795 peronei, 825 of Cotunnius, 767 cranial, 754 crural anterior, 817 cutaneous. See that heading. deep palmar, 805 temporal, 768 dental anterior, 765 inferior, 769 posterior, 764 descendens hypoglossi, 788 digastric, from facial, 776 digital (foot), 825 dorsal (hand), 808 peculiar, 811 of penis, 823 spinal, 808 dorsi-lumbar, 811 of dura mater, 705 eighth pair, 778 eleventh pair, 785 Nerves or nerve of eyeball, 755 facial, 773 fifth, 759 fourth, 759 frontal, 760 ganglionic branch of nasal, 761 gastric branches of vagus, 839 gen ito-crural, 814 glosso-pharyngeal, 778 gluteal, inferior, 823 superior, 823 great petrosal, 766 great splanchnic, 835 gustatory, 769 hsemorrhoidal, inferior, 823 of heart. See Cardiac. hepatic, 839 hypoglossal, 786 ilio-hypogastric, 813 ilio-inguinal, 813 incisive, 769 inferior maxillary, 767 inframaxillary, of facial, 777 infraorbital, of facial, 777 infratrochlear, 761 intercostal, 810 intercosto-humeral, 811 interosseous, anterior, 803 posterior, S07 ischiadic, great, 824 small, 824 Jacobson's, 779 labial, 765 of labyrinth, 889 lachrymal, 760 of Lancisi, 728 large cavernous, 840 laryngeal, external, 783 internal, 783 recurrent, 784 superior, 783 lesser splanchnic, 835 lingual of fifth, 769 of glosso-pharyngeal, 781 long ciliary, 761 saphenous, 818 thoracic, 797 lumbar, 811 lumbo-sacral, 812 malar branch of orbital nerve, 764 of facial, 777 masseteric, 768 maxillary, inferior, 767 superior, 763 median, 802 mental, 769 middle cardiac, 834 motor of the eye, common, 757 external, 770 musculo-cutaneous, of arm, 801 leg, 827 musculo-spiral, 805 mylo-hyoid, 769 nasal, ophthalmic, 760 from Meckel's ganglion, 765 from Vidian, 766 naso-palatine, 767 ninth, 778 obturator, 816 occipital, great, 790 small, 793 of facial, 776 INDEX. 1115 Nerves or nerve, occipital, of third cervical, 792 oesophageal, 784 olfactory, 754 ophthalmic, 759 optic, 755 orbital nerves, their relation, 772 in cavernous sinus, 772 in orbit, 773 in sphenoidal fissure, 772 of superior maxillary, 763 palatine, anterior or large, 766 external, 766 posterior or small, 766 palmar, cutaneous, of median, 803 ulnar, 804 palpebral, 765 par vagum, 781 pathetic, 758 perforans Casserii, 801 perineal, 823 superficial, 823 peroneal, 826 petrosal, superficial, external, or large, 766 deep large, 766 deep small, 779 pharyngeal, of external laryn- geal, 783 of glosso-pharyngeal, 781 of Meckel's ganglion, 767 of pneumogastric, 783 of sympathetic, 833 phrenic, 795 plantar, cutaneous, 825 external, 826 internal, 825 pneumogastric, 781 popliteal, external, 826 internal, 824 portia inter duram et mollem, 773 portio dura, 773 mollis, 773 posterior auricular, 775 pterygoid, 767, 768 pterygo-palatine, 767 pudendal, inferior, 824 pudic, 823 pulmonary, from vagus, 784 radial, 806 recurrent laryngeal, 784 to tentorium,'758 renal splanchnic, 835 respiratory, external, 798 internal, 795 sacral, 819 . plexus, 821 saphenous, long or internal, 818 short or external, 825 sciatic, great, 824 small, 824 short ciliary, 761 sixth, 772 small cavernous, 840 spinal, 789 accessory, 785 splanchnic, great, 835 small, 835 smallest, 835 stylo-hyoid of facial, 776 Nerves or nerve, subclavian, 798 suboccipital, 790 posterior branch of, 790 subscapular, 800 superficialis colli, 794 superior cardiac, 834 maxillary, 763 supra-acromial, 795 supraclavicular, 795 supramaxillary of facial, 777 supra-orbital, 761 suprascapular, 800 suprasternal, 795 supratrochlear, 760 sympathetic, 828 temporal, deep, 768 of facial, 776 of auriculo-temporal, 768 temporo-facial, 776 temporo-malar, 764 tenth, 781 third, or motor oculi, 757 thoracic anterior, 800 posterior, 797 thyro-hyoid, 788 tibial, anterior, 827 posterior, 825 of tongue, 846 tonsillar, 781 trifacial or trigeminus, 759 trochlear, 759 twelfth, 786 tympanic of glosso-pharyn- geal, 779, 882 of facial, 775 ulnar, 804 uterine, 840 vaginal, 840 vagus, 781 vestibular, 890 Vidian, 766 of Wrisberg, 802 Nervi-nervorum, 74 Nervous substance, chemical analysis, 72 gray, 69 vesicular, 69 white, 70 layer of retina, 861 system, general anatomy of, 69 fibrous nervous matter, 70 ganglia, 79 gelatinous fibres, 69, 72 gray or cineritious substance, 69 sympathetic, 72 composition of, 72 vesicular nervous matter, 69 white or medullary substance, 70 Nervus cardiacus magnus, 834 minor, 834 petrosus profundus, 766 superficialis cordis, 833 Neural crest, 122 Neurilemma, 71, note. of cord, 697 Neumann, dentinal sheath of, 898 Neuroblasts, 122 Neuroglia, 73 of cord, 700 Nidus hirundinis, of cerebellum. 749 Ninth nerve, 778 Nipple, 1061 Nodes of Ranvier, 72 Nodule of cerebellum, 749 Non-medullated nerve-fibres, 72 Nose, 847 arteries of, 849 bones of, 191 cartilage of septum of, 848 cartilages of, 848 development of, 125 fossae of, 221, 849 mucous membrane of, 849 muscles of, 400 nerves of, 849 surgical anatomy of, 851 veins of, 849 Notch, cotyloid, 280 ethmoidal, 175, 187 intercondyloid, 290 nasal, 173 sacro-sciatic, greater, 278 lesser, 278 sigmoid, 206 spheno-palatine, 201 supra-orbital, 173 suprascapular, 247 Notochord, 107, 115 Nuck, canal of, 1046, 1059 Nuclei pontis, 715 Nucleus amygdalae, 734 caudatus, 733 of a cell, 39 lenticularis, 733 Nutrient artery of bone, 55 Nymphae, 1048 lymphatics of, 691 O. Obelion, 210 Oblique inguinal hernia, 1069 coverings of, 1069 ligament, 356 line of the clavicle, 241 of lower jaw, 204 of radius, 261 ridge of ulna, 257 Obliquus auris muscle, 876 externus abdominis, 450 internus, 451 inferior capitis, 441 superior, 441 inferior oculi, 399 superior, 399 Obturator artery, 624 peculiarities of, 624 relation of, to femoral ring, 1007 externus muscle, 520 internus, 518 fascia, 1091 foramen, 280 ligament or membrane, 518 nerve, 816 accessory, 816 surgical anatomy of, 827 veins, 675 Occipital artery, 558 bone, 166 articulations of, 170 attachment of muscles to, 170 development of, 169 crests, 166, 168 protuberances, 166, 168 1116 INDEX. Occipital fossae, 167 lobe, 721 lymphatic glands, 683 groove, 178 sinus, 661 triangle, 567 vein, 655 Occipitalis major nerve, 791 minor, 793 Occipito-atlantal articulation, 327 Occipital-axial articulation, 328 Occipito-frontalis muscle, 393 Occiput, arteries of, 558 Ocular cleft, 123 cup, 123 vesicle, primitive, 123 secondary, 123 Odontoblasts, 896, 901 Odontoid ligaments, 328 tubercle for, 168 process of axis, 150 (Esophageal arteries, 608 branches of vagus nerve, 785 glands, 912 opening of diaphragm, 448 plexus, 785 (Esophagus, 911 lymphatics of, 694 structure of, 912 surgical anatomy of, 913 Olecranon process, 256 fracture of, 503 Olfactory bulb, 746, 755 cells, 850 foramina, 187 fossa? (foetal), 125 nerve, 754 sulcus, 755 surgical anatomy of, 755 Olivary bodies of medulla ob- longata, 709, 711 nucleus, superior, 715 peduncle, 713 process, 182 Omenta, 867 Omental tuberosity of liver, 952 Omentum, gastro-colic, 923 gastro-hepatic, 923 gastro-splenic, 923 great, 923 lesser, 923 Omo-hyoid muscle, 414 Omphalo-mesenteric arteries, foe- tal, 127 duct, 109 veins, 128 Opening of aorta in left ventricle, 976 aortic, in diaphragm, 448 caval, in diaphragm, 448 of coronary sinus, 973 of inferior cava, 972 left auriculo-ventricular, 976 oesophageal in diaphragm, 526 of pulmonary artery, 974 veins, 975 right auriculo-ventricular, 974 saphenous, 509, 1076 of superior cava, 972 Operations : amputations of foot, 313 of penis, 1037 arteries, ligature of, abdominal aorta, 611 Operations: arteries, axillary, 593 brachial, 598 carotid, common, 552 external, 553 internal, 570 femoral, 635 iliac, common, 621 external, 630 internal, 623 innominate, 548 lingual, 555 popliteal, 640 radial, 600 subclavian, 581 thyroid, inferior, 587 tibial, anterior, 644 posterior, 647 ulnar, 604 catheterism of Eustachian tube, 911 cholecystotomy, 958 for cleft palate, 425 colotomy, 948 division of nerves, facial, 777 infraorbital, 771 lingual, 772 sciatic, great, 828 spinal accessory, 785 supra-orbital, 771 excision of ankle, 382 elbow, 355 hip, 369 knee, 377 of shoulder, 351 extirpation of thyroid, 1008 of spleen, 966 gastrostomy, 930 gastrotomy, 930 hamstring tendons, division of, 522 laryngotomy, 995 lithotomy, 1089 nephrotomy and nephrectomy, 1019 oesophagotomy, 913 paracentesis of pericardium, 970 prostatectomy, 1034 puncture of the bladder, 1029 removal of the clavicle, 243 lower jaw, 228 upper jaw, 228 tongue, 420, 846 scapula, 249 testis, 1043 for strabismus, 400 tapping chest, 240 for torticollis, 413 tracheotomy, 996 venesection, 665 Ophthalmic artery, 570 ganglion, 761 nerve, 759 vein, 662 Opponens minimi digiti muscle, 497 pollicis muscle, 494 Optic commissure, 756 foramen, 182, 212 groove, 182, 212 lobes, 741 nerve, 755 intercerebral fibres of, 756 inter-retinal fibres of, 756 Optic nerve, anatomy of, 755 thalami, 738 tract, 755 Ora serrata, 860 Oral cavity, 892 Orbicular bone, 881 ligament, 355 Orbicularis ciliaris, 398 latus, 398 oris muscle, 402 palpebrarum, 396 Orbit, 219 arteries of, 571 muscles of, 398 relation of nerves in, 773 Orbital artery, 564 foramina, 185 lobe, 719 nerve, 763 process of malar, 198 of palate, 201 Organs of Golgi, 78 Organic constituent of bone, 60 Orifice, oesophageal, of stomach, 926 pyloric, of stomach, 926 Os calcis, 301 development of, 310 hyoides, 229 innominatum, 274 development of, 280 magnum of carpus, 268 orbiculare, 881 planum, 188 unguis, 197 uteri, 1052 Ossa triquetra, 190 Ossicula auditus, 880 ligaments of, 881 Ossification of bone, 59 defects in, 165 intracartilaginons, 60 intramembranous, 63 period of, 63 of spine, progress in, 156 subperiosteal, 59 Osteoblasts, 55, 60 Osteoclasts, 55 Osteo-dentine, 899 Osteology, 145 Ostium abdominale of Fallopian tube, 1056 internum or uterinum, 1053 Otic ganglion, 770 vesicle, 124 Otoliths, 889 Outlet of pelvis, 283 Ovarian arteries, 618 plexus of nerves, 838 veins, 677 Ovary, 1057 development of, 138 Graafian vesicles of, 1058 ligament of, 1059 lymphatics of, 692 nerves of, 1060 ovicapsule of, 1058 shape, position, and dimen- sions, 1057 stroma of, 1058 tunica albuginea of, 1058 vessels of, 1060 Ovicapsule of Graafian vesicle, 1058 Oviducts, 1056 INDEX. 1117 Ovisacs of ovary, 1058 Ovula of Naboth, 1054 Ovum, 100 discharge of, 1059 discus proligerus of, 100 fecundation of, 102 germinal spot of, 101 vesicle of, 101 vitelline membrane of, 100 yolk of, 101 zona pellucida of, 100 Oxyntic cells of peptic glands, 929 P. Pacchionian depressions, 171 glands, 659, 700 Pacinian corpuscles, 77 Pad of corpus callosum, 732 Palatal glands, 903 Palate, arches of, 903 development of, 119 bone, 199 articulations of, 202 attachment of muscles to, 202 development of, 201 horizontal plate of, 199 orbital process of, 201 process of superior maxil- lary, 195 sphenoidal process of, 201 turbinated crest of, 200 vertical plate of, 200 hard, 903 muscles of, 423 soft, 903 sphenoidal process of, 201 aponeurosis, 424 Palatine artery, ascending, 557 descending or posterior, 564 canal, anterior, 196 accessory, 199 posterior, 199 fossa, anterior, 196 nerves, 766 process of superior maxillary, 195 veins, inferior, 654 Palato-glossus muscle, 418, 424 Palato-pharyngeus, 424 Palmar arch, deep, 600 superficial, 606 surface marking of, 606 cutaneous nerve, 803, 804 fascia, 492 interossei arteries, 603 nerve, deep, of ulnar, 805 superficial, 804 veins, 665 Palmaris brevis muscle, 496 longus muscle, 482 Palpebne, 819 Palpebral arteries, 572 cartilages or plates, 869 fissures, 869 surface form of, 873 folds of conjunctiva, 870 ligaments, 870 muscles, 396 veins, inferior, 654 superior, 654 Pampiniform plexus of veins, 676, 1039, 1060 Pancreas, 958 development of, 135 lymphatics of, 692 structure of, 960 surgical anatomy of, 961 surgical marking of, 961 vessels and nerves of, 961 Pancreatic arteries, 614 duct, 960 plexus of nerves, 839 veins, 677 Pancreatica magna artery, 614 Pancreatico-duodenal artery, 613 inferior, 615 plexus of nerves, 839 vein, 677 Papilla lachrymalis, 872 spiralis, 887 Papillae of tooth, 899 conicae vel filiformes, 843 fungiformes (mediae), 843 of kidney, 946 maximae (circumvallatae), 843 of skin, 91 of tongue, 842 Papillary layer of skin, 91 Par vagum, 781 Paraglobulin, 33 Parallel fissure, 721 Paramastoid process, 167 Parietal bones, 170 articulations of, 172 attachment of muscles to, 172 development of, 172 cells of peptic glands, 928 eminence, 170 foramen, 171 lobe, 719 veins, 131 Parieto-occipital fissure, 718, 722 Parieto-sphenoid artery, 575 Parotid duct, 905 fascia, 405, 410 gland, 904 accessory portion of, 906 nerves of, 906 vessels of, 906 lymphatic glands, 683 veins, 654 Parovarium, 139, 1059 Patella, 293 articulations of, 294 attachment of muscles to, 294 development of, 294 fracture of, 539 surface form of, 294 surgical anatomy of, 294 Pecquet, reservoir of, 682 Pectineus muscle, 513 Pectiniforme septum, 1035 Pectoral region, dissection of, 469 . Pectoralis major, 469 minor, 471 Peculiar dorsal vertebrae, 153 Pedicles of a vertebra, 146 Peduncles of cerebellum, 750 of cerebrum, 729 of corpus callosum, 732 of pineal gland, 740 Peduncular fibres of cerebrum, 743 of cerebellum, 750 Pelvic fascia, 1091 Pelvic fascia, parietal or obtu- rator layer, 1091 visceral layer, 1092 girdle, 240 plexus, 840 Pelvis, 281, 1023 arteries of, 622 articulations of, 338 axes of, 284 boundaries of, 282 brim of, 282 cavity of, 283 diameters of, 284 false, 282 inlet of, 283 ligaments of, 338 lymphatics of, 689 male and female, differences of, 284 outlet of, 283 position of, 284 of viscera at outlet of, 1088 surface form of, 285 surgical anatomy of, 285 Pelvis of kidney, 1012 Penis, 1034 arteries of, 1036 body of, 1034 corpora cavernosa, 1035 corpus spongiosum, 1036 development of, 141 dorsal artery of, 626 nerve of, 823 vein of, 675 lymphatics of, 691, 1037 muscles of, 464 nerves of, 1037 prepuce of, 1035 root of, 1034 surgical anatomy of, 1037 suspensory ligament, 1033 Penniform muscle, 390 Peptic glands, 928 Perforans Casserii nerve, 801 Perforated space, anterior, 728 posterior, 729 Perforating arteries of hand, 603 from mammary artery, 588 plantar, 649 profunda, 638 Pericardiac arteries. 588, 608 Pericardium, relations of, 967 diverticula of, 968 fibrous layer of, 968 nerves of, 969 serous layer' of. 969 structure of, 968 vessels of, 968 vestigial fold of,. 668, 969 Perichondrium, 51 Perilymph, 888 Perimysium, external, 65 internal, 65 Perineal artery, superficial, 627 transverse, 627 fascia, deep, 465, 1086 superficial, 462 nerve, 823 superficial, 823 Perineum, 1083 abnormal course of arteries in, 1090 deep boundaries of, 1085 in the female, 1089 1118 INDEX. Perineum, development of, 140 lymphatics of, 691 in the male, 1084 muscles of, 460, 461 surgical anatomy of, 1083 Perineurium, 74 Periosteum, 54 of teeth, 894 Peripheral termination of nerves, 76 Peritoneum, greater cavity of, 918 lesser cavity of, 918, 922 ligaments of, 923 mesenteries of, 923 omenta of, 923 reflections traced, 917 Perivascular lymph-sheaths, 87, 659 Permanent cartilage, 51 teeth, 894 Peroneal artery, 648 anterior, 648 peculiarities of, 648 nerve, 826 ridge, 303 veins, 673 Peroneus brevis muscle, 529 longus, 529 tertius, 524 Perpendicular plate of ethmoid, 188 line of ulna, 260 Pes accessorius, 733 anserinus, 774 hippocampi, 735 Petit, canal of, 867 triangle of, 451 Petrosal nerve, superficial or large, from Vidian, 766 small superficial, 779 deep large, 766 small, 779 long, 779 sinus inferior, 662 superior, 662 Petro-mastoid portion of tem- poral bone, 181 Petro-occipital suture, 209 Petro-sphenoidal suture, 209 Petrous ganglion, 779 portion of temporal bone, 178 Peyer's glands, 937 Phalanges, hand, 272 articulations of, 272, 364 development of, 274 foot, 310 articulations of, 310, 389 development of, 311 Pharyngeal aponeurosis, 910 arches, 118 artery, ascending, 560 clefts, 118 ganglion, 833 glands, 910 nerve, from external laryngeal, 783 from glosso-pharyngeal, 781 from Meckel's ganglion, 767 from sympathetic, 833 from vagus, 783 plexus of nerves, 783, 833 spine, 167 tonsil, 911 Pharyngeal vein, 656 Pharynx, 910 aponeurosis of, 910 arteries of, 560 development of, 132 mucous membrane of, 910 muscles of, 421 surgical anatomy of, 911 Phleboliths, 675 Phrenic arteries; 618 nerve, 795 plexus of nerves, 837 veins, 677 Pia mater of brain, 706 of cord, 696 testis, 988 Pigment, 50 of iris, 859 of skin, 91 Pigmentary layer of retina, 863 Pillars of diaphragm, 448 of external abdominal ring, 451, 1064 of fauces, 903 Pineal gland, 740 peduncles of, 740 Pinna of ear, 874 ligaments of, 875 muscles of, 875 nerves of, 856 vessels of, 876 Pisiform bone, 266 Pituitary body, 729 development of, 119 fossa, 182 membrane, 850 Pivot-joint, 318 Placenta, 114 Placental sinus, 114 circulation, 129 Plantar artery, external, 649 internal, 649 cutaneous nerve, 825 fascia, 531 ligaments, 383 nerve, external, 826 internal, 825 veins, external, 673 internal, 673 Plantaris muscle, 526 Plasma, 36 Plates, tarsal, 870 Platysma myoides, 409 Pleura, 997 cavity of, 997 costalis, 997 pulmonalis, 997 reflections of, traced, 997 surgical anatomy of, 998 vessels and nerves of, 998 Pleuro-peritoneal cavity, 112 Plexus of nerves, 75 aortic, 739 brachial, 796 cardiac, deep, 836 superficial, 836 carotid, 831 external, 831 cavernous, 831 cervical, 793 posterior, 792 coeliac, 839 colic, left, 840 middle, 840 right, 840 Plexus, coronary, anterior, 837 posterior, 836 cystic, 839 diaphragmatic, 837 epigastric or solar, 837 facial, 833 gastric, 839 gastro-duodenal, 839 gastro-epiploic, 839 left, 839 great cardiac, 836 haemorrhoidal superior, 840 inferior, 840 hepatic, 839 hypogastric, 839 inferior, 840 ileo-colic, 840 infra-orbital, 765 lumbar, 813 mesenteric, inferior, 839 superior, 839 oesophageal, 784 ophthalmic, 831 ovarian, 838 pancreatic, 839 pancreatico duodenal, 839 patellae, 818 pharyngeal, 783, 833 phrenic, 837 prostatic, 840 pulmonary, anterior, 784 posterior, 784 pyloric, 839 renal, 837 sacral, 820 sigmoid, 839 solar, 837 spermatic, 837 splenic, 839 superficial cardiac, 836 suprarenal, 837 tonsillar, 781 tympanic, 779 vaginal, 840 vertebral, 834 vesical, 840 Plexus magnus profundus, 836 of veins. See Veins. Plica semilunaris, 871 Pneumogastric lobule of cerebel- lum, 749 nerve, 781 Polar globules of Robin, 101 Pomum Adami, 984 Pons hepatis, 951 Tarini, 729 Varolii, 714 Popliteal artery, 639 branches of, 641 peculiarities of, 640 surface marking of, 640 surgical anatomy of, 640 lymphatic glands, 688 nerve, external, 826 surgical anatomy of, 827 internal, 824 space, 639 vein, 673 Popliteus muscle, 526 Pores of the skin, 95 Portal canals, 952 fissure, 951 vein, 679, 952, 954 Portio dura of seventh nerve, 773 inter duram et mollem, 773 INDEX. 1119 Portio mollis, 773 Porus opticus of sclerotic, 854 Posterior. See under each sepa- rate head. Posterior and internal frontal artery, 574 choroid artery, 586 glenoid process, 177 vertebral veins of Rathke, 132 vesicular column, 702 Postero-lateral ganglionic arte- ries, 586 median ganglionic arteries, 586 Post-oral arches (foetal), 118 Post-patellar bursa, 512 Pott's fracture, 540 Pouch of Douglas, 1052 Pouches, laryngeal, 989 Poupart's ligament, 1065, 1077 Praevertebral fascia, 411 Precentral fissure, 718 Pre-oral arches (foetal), 119 Prepatellar bursa, 512 Prepuce, 1035 of clitoris, 1048 Presternal notch, 231 Presternum, 231 Prickle cells, 43 Primary areolae of bone, 60 Primitive jugular veins, 132 aorta, 127 fibulae of Schultze, 71 otic vesicle, 124 sheath of nerve-fibre, 71 trace, 104 Princeps cervicis artery, 559 pollicis artery, 602 Processes or process, acromion, 246 alveolar, 195 angular, external, 173 internal, 173 auditory, 179 basilar, 167 ciliary, 857 clinoid, anterior, 185 middle, 182 posterior, 183 cochleariform, 186, 879 condyloid of lower jaw, 206 coracoid, 247 coronoid of lower jaw, 206 of ulna, 256 ethmoidal of inferior turbinat- ed, 202 frontal of malar, 198 hamular of lachrymal, 197 of sphenoid, 185 of helix, 875 of Ingrassias, 185 jugular, 168 lachrymal of inferior turbi- nated bone, 202 malar, 194 of malar bone, 198 mastoid, 178 mammillary, 154 maxillary of inferior turbi- nated, 202 mental, 204 nasal, 194 odontoid of axis, 151 olecranon, 256 olivary, 182 orbital of malar, 198 Processes or process, orbital, of palate, 201 palatine of superior maxillary, 195 post-glenoid, 177 pterygoid of palate bone, 200 of sphenoid, 185 sphenoidal of palate, 201 spinous of tibia, 295 of ilium, 277 of sphenoid, 184 styloid of temporal, 180 of ulna, 260 of radius, 262 unciform, 269 of ethmoid, 188 vaginal of sphenoid, 184 of temporal, 180 vermiform of cerebellum, in- ferior, 749 superior, 748 zygomatic, 199 Processes of Ingrassias, 185 Processus ad medullam, 750 ad pontem, 750 brevis of malleus, 881 caudatus, 875 cochleariformis, 181, 879 e cerebello ad testes, 750 gracilis of malleus, 881 Profunda cervicis artery, 589 femoris artery, 637 inferior artery of arm, 598 superior, 598 vein, 674 Promontory of tympanum, 879 of sacrum, 157 Pronator quadratus muscle, 485 radii teres muscle, 481 ridge, 257 Pronephros, 135 Pronucleus, female, 102 male, 102 Prosencephalon, 121 Prostate gland, 1032 levator muscle of, 462 lobes of, 1033 lymphatics of, 691 surgical anatomy of, 1033 vessels and nerves of, 1033 Prostatic plexus of nerves, 840 of veins, 675 portion of urethra, 1030 sinus, 1030 Protoplasm, 39 Proto vertebrae, 107 Protovertebral column, 115 somites, 107 Protuberance, occipital, external, 166 internal, 168 Psoas magnus muscle, 506 surgical anatomy of, 507 parvus, 506 Pterion ossicle, 190 Pterygoid arteries, 564 fossa of sphenoid, 185 of lower jaw, 206 muscles, 406 nerve, 67, 768 notch, 185 plexus of veins, 654 process of palate bone, 200 processes of sphenoid, 185 ridge, 184 j Pterygo-maxillary fissure, 218 ligament, 404 Pterygo-palatine artery, 564 canal, 184 nerve, 767 Pubes, angle of, 279 crest of, 279 os, 279 spine of, 279 symphysis of, 279, 341 Pubic arch, 283 articulations of, 342 portion of fascia lata, 510 Pubo-prostatic ligaments, 1026 Pudendum, 1047 Pudic artery in male, 625 peculiarities of, 626 accessory, 626 deep external, 637 in female, 627 superficial external, 637 nerve, 823 vein, external, 672 internal, 674 Pulmonary artery, 542, 1003 opening of, in right ventri- cle, 974 capillaries, 1004 nerves from vagus, 784 sinuses, 975 veins, 651, 652, 1004 openings of, left auricle, 975 Pulp-cavity of tooth, 896 of teeth, development of, 902 of spleen, 963 Pulvinar of optic thalamus, 739 Puncta vasculosa, 730 lachrymal ia, 873 Pupil of eye, 858 membrane of, 860 Purkinje, axis-cylinder of, 71 corpuscles of, 752 granular layer of, 898 vesicle of, 101 Pyloric artery, 613 inferior, 613 glands, 928 plexus, 839 Pylorus, 926 Pyramid in vestibule, 883 of cerebellum, 749 of thyroid gland, 1007 of tympanum, 878 Pyramidal cell or nerve-corpusle, 745 Pyramidalis muscle, 457 nasi, 401 Pyramids of medulla, 709, 711 decussation of, 709 of Ferrein, 1015 of Malpighi, 1013 of the spine, 163 Pyriformis muscle, 518 Q. Quadrate lobe, 723 Quadratus femoris muscle, 519 lumborum, 457 fascia covering, 460 menti, 403 Quadriceps extensor cruris mus* cle, 511 I Quadrigeminal bodies, 741 1120 INDEX. R. Racemose glands, 99 Radial artery, 599 branches of, 601 peculiarities of, 600 y surface marking of, 600 surgical anatomy of, 600 lymphatic glands, 686 nerve, 806 recurrent artery, 601 region, muscles of, 485 vein, 665 Radialis indicis artery, 603 Radicular zone, anterior, 701 Radio-carpal articulation, 358 surface form of, 359 surgical anatomy of, 359 Radio-ulnar articulations, infe- rior, 357 middle, 356 superior, 355 Radius, 261 articulations of, 263 development of, 262 fracture of, 503 grooves in lower end of, 262 muscles attached to, 263 oblique line of, 261 sigmoid cavity of, 262 surface form of, 263 surgical anatomy of, 263 tuberosity of, 261 and ulna, fracture of, 504 Rami of the lower jaw, 205 Ramus of ischium, 278 descending, 279 horizontal of pubes, 279 of pubes, 279 Ranine artery, 555 vein, 654, 656 Ranvier, nodes of, 71 Raphe of corpus callosum, 732 of medulla, 712 of palate, 903 of perineum, 1084 of scrotum, 1037 of tongue, 842 Rathke, posterior vertebral veins of, 132 Receiving tubes of kidney, 1014 Receptaculi arterise, 570 Receptaculum chyli, 682 Recessus labyrinthi, 124 Recto-uterine ligaments, 1052 Recto-vesical fascia, 1092 fold, peritoneal, 1026 Rectum, 943 development of, 133 folds of, 945 lymphatics of, 691 relations of, male, 944 female, 944, 1050 surgical anatomy of, 946 Rectus abdominis, 455 capitis anticus major, 426 minor, 426 femoris muscle, 511 surgical anatomy of, 513 lateralis, 427 oculi, internus, superior, infe- rior, and externus, 399 posticus major, 441 minor, 441 Recurrent artery, interosseous, 605 radial, 601 tibial anterior, 644 posterior, 644 ulnar, anterior, 604 posterior, 604 laryngeal nerve, 784 nerves to tentorium, 760 Region, abdominal, muscles of, 449 acromial, muscles of, 473 auricular, 395 back, muscles of, 429 brachial, anterior, 483 posterior, 487 cervical superficial, muscles of, 409 diaphragmatic, 446 epicranial, muscles of, 393 epigastric, 914 femoral, muscles of, anterior, 507 internal, 513 posterior, 520 fibular, 529 foot, dorsum of, 532 sole of, 532 gluteal, muscles of, 516 groin, 1072 of hand, muscles of, 505 humeral, anterior, 477 posterior, 479 hypochondriac, 914 hypogastric, 916 iliac, muscles of, 505 infrahyoid, 413 inguinal, 1072 intermaxillary, muscles of, 403 ischio-rectal, 1083 laryngo-tracheal, surgical an- atomy of, 995 lingual, muscles of, 417 lumbar, 916 maxillary, muscles of, inferior, 402 superior, 402 nasal, muscles of, 400 orbital, muscles of, 398 palatal, muscles of, 423 palmar, 491 palpebral, 396 perineum, 1083 pharyngeal, muscles of, 421 popliteal, 639 pterygo-maxillary, muscles of, 406 radial, muscles of, 485 scapular, muscles of, anterior, 474 posterior, 475 Scarpa's triangle, 632 suprahyoid, muscles of, 414 temporo-maxillary, muscles of, 405 thoracic, 443 anterior, 469 lateral, 472 tibio-fibular, anterior, 523 posterior, 524 ulnar, 496 umbilical, 916 vertebral, muscles of, anterior, 426 lateral, 427 Regions of abdomen, 914 Reil, island of, 718 Remak, fibres of, 72 Renal afferent vessels, 1013, 1018 artery, 618, 1017 efferent vessels, 1013, 1018 plexus, 837 veins, 677, 1018 Respiration, organs of, 984 muscles of, 446 Respiratory nerves of Bell, ex- ternal, 798 internal, 795 organs, development of, 135 Restiform bodies of medulla ob- longata, 711 Rete mucosum of skin, 90 Malpighii, 90 testis, 1042 Reticular cartilage, 53 layer of skin, 91 lamina of Kolliker, 888 Retiform connective tissue, 48 Retina, 860 arteria centralis of, 572, 865 externa, 863 fovea centralis of, 864 limbus luteus of, 860 membrana limitans of, 861 layers of, 861 structure of. 861 Retinacula of ileo-caecal valve, 940 Retrahens aurein muscle, 396 Rhomboid impression, 242 ligament, 343 Rhomboidal sinus, 120 Rhomboideus major, 433 minor, 433 Ribes. ganglion of, 829 Ribs, 234 angle of, 235 articulations of, 332 attachment of muscles to, 237 development of, 117, 237 false, 234 floating, 234 head of, 235 ligaments of, 332, 333 neck of, 235 peculiar, 236 true, 234 tuberosity of, 235 Ridge, internal occipital, 168 mylo-hyoidean, 204 pterygoid, 185 superciliary, 173 temporal, 176, 217 Rima glottidis, 988 Ring, abdominal, external, 451, 1064 internal, 1068 femoral or crural, 1080 fibrous, of heart, 978 Risorius muscle, 404 Rivini, ducts of, 907 Robin, polar globules of, 101 Rods of Corti, 867 Rolando, tubercle of, 711 fissure of, 717 funiculus of, 711 topography of, 725 ! Roof nuclei of Stilling, 752 Root of lung, 1102 I Root of spinal nerves, 788 INDEX. 1121 Root of teeth, 896 of zygomatic process, 176 Rosenmuller, organ of, 138, 1059 accessory gland of, 872 Rostrum of sphenoid bone, 184 of corpus callosum, 732 Rotation, 320 Rotatores spinae muscles, 440 Round ligaments of uterus, 1059 relations of, to femoral ring, 1080 of liver, 950 Rugae of stomach, 928 of vagina, 1051 Rupture of urethra, course taken by urine in, 1085 Rust-colored layer of cerebellar cortex, 752 S. Sac, lachrymal, 872 Saccular secretory glands, 98 Saccule of vestibule, 888 Sacculus laryngis, 924 Sacra-media artery, 619 Sacral arteries, lateral, 629 canal, 159 cornua, 158 foramina, 157 ganglia, 836 groove, 158 lymphatic glands, 690 nerves, 817 anterior divisions of, 820 posterior divisions of, 820 roots of, 819 plexus, 821 vein, lateral, 675 middle, 675 peculiarities of, 675 Sacro-coccygeal ligaments, 341 Sacro-iliac articulation, 339 Sacro-lumbalis muscle, 436 Sacro-sciatic foramen, greater, 278, 340 lesser, 278, 340 ligaments, 339, 340 notch, greater, 278 lesser, 278 Sacro uterine ligament, 1053 Sacro-vertebral angle, 157 ligament, 338 Sacrum. 157 ala of, 159 articulations of, 161 attachment of muscles to, 161 development of, 160 peculiarities of, 160 structure of, 160 Sacs, dental, 900 Saddle-joint, 318 Sagittal suture, 207 Salivary glands, 904 structure of, 907 Salpingo-pharyngeus, 425 Salter, incremental lines of, 898 Santorini, cartilages of, 986 Saphena veins, surgical anatomy of, 673 Saphenous nerve, long or inter- nal, 818 short, 824 opening, 509, 1076 Saphenous vein, external or short, 672 internal or long, 672, 1072 surgical anatomy of, 673 Sarcolemma, 65 Sarcoplasm, 66 Sarcostyles, 66 Sarcous elements of muscle, 66 Sartorius muscle, 510 Scala tympani of cochlea, 865 media, 886 vestibuli of cochlea, 886 Scalae of cochlea, 886 Scalenus anticus, 427 medius, 427 posticus, 428 Scaphoid hone, hand, 264 foot, 306 fossa of sphenoid, 185 Scapula, 244 articulations of, 249 attachment of muscles to, 249 development of, 248 dorsum of, 245 glenoid cavity of, 247 head of, 471 ligaments of, 346, 347 muscles of, 475 spine of. 246 surface form of, 249 surgical anatomy of, 249 venter of, 244 Scapular artery, posterior, 587 region, muscles of, anterior, 474 posterior, 475 veins, 668 Scapulo-clavicular articulation, 343 Scarfskin, 89 Scarpa, foramina of, 196, 215 Scarpa's triangle, 632 Schachowa, spiral tubes of, 1014 Schindylesis, 317 Schneiderian membrane, 850 Schlemm, canal of, 855 Schreger, lines of, 898 Schultze, cells of, 755, 830 primitive fibrillie of, 71 Schwann, white substance of, 71 Sciatic artery, 628 nerve, greater, 824 surgical anatomy of, 828 lesser, 824 veins, 675 Sclerotic; 853 Scrobiculus cordis, 239 Scrotal hernia, 1071 Scrotum, 1037 dartos of, 1038 development of, 141 lymphatics of, 691 nerves of, 1039 septum of, 1037 surgical anatomy of, 1039 vessels of, 1039 Sebaceous glands, 94 Second nerve, 755 surgical anatomy of, 756 Secreting glands, 98 Segmental organs, 135 Sella Turcica, 182, 212 Semicircular canals, 884 Semilunar bone, 265 cartilages of knee, 372 Semilunar fold of Douglas, 457 fascia, 478 ganglion of fifth nerve, 759 of abdomen, 834 valves, aortic, 977 pulmonic, 974 Semimembranosus muscle, 521 Seminal cells, 1042 tubes, 1042 vesicles, 1044 Semispinalis muscle, 439 Semitendinosus muscle, 521 Senac on structure of heart's valves, 974 Senses, organs of the, 841 Septum auricularum, 976 cartilage of, 848 crurale, 1080 lucidum, 736 of nose, 223 pectiniforme, 1035 of pons Varolii, 716 scroti, 1037 subarachnoid, 696 of tongue, 845 ventriculorum, 978 Septum between bronchi, 993 Serous glands of tongue, 844 Serous membranes, 96 Serratus magnus, 472 posticus, inferior, 434 superior, 434 Serum, 33, 37 globulin, 33 Sesamoid bones, 314 cartilages, 848 Seventh nerve, 773 surgical anatomy of, 777 Shaft of a bone, its structure, 145 Sheath of arteries, 81 femoral or crural, 1078 of muscles, 65 of nerves, 74 of rectus muscle, 455 Shin, 296 Short bones, 145 Shoulder, muscles of, 469 girdle, 240 joint, 347 surface form of, 350 surgical anatomy of, 350 vessels and nerves of, 349 Sigmoid artery, 616 cavity, greater and lesser, of ulna, 257 of radius, 262 flexure of colon, 941 mesocolon, 925 notch of lower jaw, 206 Sinus circularis iridis, 855 of external jugular vein, 655 internal, 656 of kidney, 1012 of Morgagni, 422 pocularis, 1030 prostaticus, 138, 1030 venosus, 131 Sinuses, cranial, 173, 652, 659 cavernous, 661 circular, 662 of coronary vein, 679, 972 ethmoidal, 187 frontal, 173 of heart, of right auricle, 972 of left, 975 1122 INDEX. Sinuses, lateral, 660 longitudinal inferior, 660 superior, 659 maxillary, 194 of nose, 173 occipital, 661 petrosal, inferior, 662 superior, 662 pulmonary, 975 sphenoidal, 183 straight, 660 transverse, 663 of Valsalva, 544, 977 Sixth nerve, 772 surgical anatomy of, 773 Skeleton, 145 number of its pieces, 145 Skin, general anatomy of, 89 appendages of, 92 arteries of, 92 corium of, 91 cuticle of, 89 derma, or true skin. 91 development of, 125 epidermis of, 89 furrows of, 91 hairs, 93 muscular fibres of, 94 nails, 92 nerves of, 92 papillary layer of, 91 rete mucosum of, 90 sebaceous glands of, 94 sudoriferous or sweat-glands of, 95 tactile corpuscles of, 76 vessels of, 92 Skull, 165, 210 anterior region, 219 base of, external surface, 210 internal surface, 210 fossa of, anterior, 210 middle, 212 posterior, 213 lateral region of, 216 surface marking of, 224 tables of, 145 vertex of, 210 vitreous table of, 146 Slender lobe of cerebellum, 749 Small intestine, areolar coat of, 933 mucous coat of, 933 muscular coat of, 933 serous coat of, 933 simple follicles, 936 valvula; conniventes, 933 villi of, 934 intestines, 931 duodenum, 931 ileum, 933 jejunum, 932 Socia parotidis, 906 Soft palate, 903 aponeurosis of, 904 arches or pillars of, 903 muscles of, 424 structure of, 903 Solar plexus, 837 Sole of foot, muscles of, first layer, 532 fourth layer, 536 second layer, 534 third layer, 534 Soleus muscle, 525 Solitary glands, 936 Somatopleure, 108 Sommerring, yellow spot of, 860 Space, anterior perforated, 728 axillary, 589 intercostal, 234 popliteal, 639 posterior perforated. 729 Spaces of Fontana, 855 Spermatic artery,- 618, 1039 canal, 1067 cord, 1039 arteries of, 1039 course of, 1039 fascia, external, 452, 1064 lymphatics of, 1039 nerves of, 1039 plexus of nerves, 837 of veins, 676 relation to femoral ring, 1080 of, in inguinal canal, 1039, 1067 veins, 676, 1039 surgical anatomy of, 676 Sphenoid bone, 182 articulations of, 187 attachment of muscles to, 187 body of, 182 development of, 186 greater wings of, 184 lesser wings of, 185 pterygoid processes of, 185 rostrum of, 184 spinous processes of, 184 vaginal processes of, 184 Sphenoidal fissure, 185 nerves in, 772 process of palate, 201 sinuses, 183 spongy or turbinated bones, " 186 Spheno-maxillary fissure, 218 fossa, 218 Spheno-palatine artery, 564 foramen, 201 ganglion, 765 nerves, 765 notch, 201 Spheno-parietal suture, 209 Sphincter muscle of bladder, 1027 of rectum, external, 460 internal, 461 of vagina, 466 Spina bifida, 164 Spinal accessory nerve, 785 surgical anatomy of, 785 foramen, 147 arteries, anterior, 584 lateral, 584 median, 584 posterior, 584 canal, 164 cord, 697 arachnoid of, 696 arrangement of gray and white matter in, 700 central canal of, 699 ligament of, 697 columns of, 698 development of, 115 dura mater of, 695 fissures of, 698 fcetal, pecidiarity of, 697 gray commissure of, 698 internal structure of, 698 Spinal cord, ligamentum dentic- ulatum of, 697 membranes of, 595 minute structure of, 700 neuroglia of, 700 pia mater of, 696 sections of, 698 white commissure of, 699 matter of, 700 nerves, 788 arrangement into groups, . 788 divisions of, anterior, 789 posterior, 789 development of, 122 distribution of, 789 origin of, in cord, 703 of roots, anterior, 788 posterior, 789 points of emergence of, 790 veins, 670 longitudinal, anterior, 671 posterior, 671 Spinalis colli muscle, 438 dorsi, 438 Spine, 146 articulations of, 321 development of, 115 general description of, 162 ossification of, 156 Spines of bones, ethmoidal, 182 of ischium, 278 nasal, 173 anterior, 196 posterior, 199 of os pubis, 279 pharyngeal, 167 of scapula, 246 Spinous process of ilium, 277 of sphenoid, 184 of tibia, 295 of vertebrae, 147 Spiral canal of cochlea, 885 Splanchnic nerve, greater, 835 lesser, 835 smallest or renal, 835 Splanchnopleure, 108 Spleen, 961 artery of, 964 capillaries of, 964 fibro-elastic coat of, 962 lymphatics of, 692, 965 Malpighian corpuscles of, 964 nerves of, 965 proper substance of, 963 relations of, 961 serous coat of, 962 size and weight, 962 structure of, 962 surface marking of, 965 surgical anatomy of, 966 trabeculae of, 962 veins of, 965 Splenic artery, 613 distribution of, 964 corpuscles, 964 plexus, 839 pulp, 963 vein, 677 Splenium of corpus callosum, 732 Splenius muscle, 435 Spongy portion of urethra, 1031 tissue of bone, 145 Squamo-parietal suture, 209 Squamo-sphenoidal suture, 209 INDEX. 1123 Squamo-zygomatic portion of temporal bone, 181 Squamous portion of temporal bone, 175 Stapedius muscle, 882 Stapes, 881 annular ligament of, 881 development of, 125 Stellate ligament, 332 plexus of kidney, 1018 Stenson, foramina of, 196, 215 Stenson's duct, 905 Sternal end of clavicle, fracture of, 501 foramen, 233 furrow, 238 ligaments, 338 Sterno-clavicular articulation, 342 surface form of, 344 surgical anatomy of, 344 Sterno-hyoid muscle, 413 Sterno-mastoid muscle, 411 artery, 559 Sterno-thyroid muscle, 413 Sternum, 230 articulations of, 234 attachment of muscles to, 234 development of, 117, 233 ligaments of, 338 Stilling, canal of, 865 Stomach, 925 alteration in position of, 926 alveoli of, 928 areolar coat of, 927 curvatures of, 926 development of, 133 fundus of, 925 gastric follicles of, 928 lenticular glands of, 929 ligaments of, 926 lymphatics of, 837 mucous membrane of, 927 muscular coat of, 927 orifices of, 926 peptic glands of, 928 pyloric end of, 925 glands of, 928 pylorus, 926 serous coat of, 926 splenic end of, 925 structure of, 926 surface marking of, 930 surfaces of, 925 surgical anatomy of, 930 vessels and nerves of, 929 Stomodoeum, 120 Straight sinus, 660 tubes of kidney, 1014 Stratiform fibro-cartilage, 53 Stratum cinereum, 746 corneum, 90 gelatinosum, 746 glomerulosum, 746 lucidum, 91 opticum, 747 Striae laterales, 732 longitudinales, 732 of muscle, 66 Striped muscle, 64 Stroma of ovary, 1058 Stylo-glossus muscle, 418 Stylo-hyoid ligament, 416 muscle, 416 Stylo-hyoid nerve from facial, 776 Stylo-mastoid artery, 559 foramen, 180 vein, 655 Stylo-maxillary ligament, 330, 341 Stylo-pharyngeus muscle, 422 Styloid process of radius, 262 of temporal bone, 180 of ulna, 260 Subanconeus muscle, 480 Subarachnoid of cord, 696 fluid, 706 space of brain, 706 septum, 696 tissue, 696 Subcaecal fossa, 940 Subclavian arteries, 577 branches of, 582 first part of, left, 580 right, 577 peculiarities of, 581 second portion of, 580 surface form of, 581 surgical anatomy of, 581 third, 580 groove, 236 nerve, 797 triangle, 567 vein, 667 Subclavius muscle, 471 Subcostal angle, 230 muscle, 444 Subcrureus muscle, 512 Subdural space, 696 Sublingual artery, 555 fossa, 204 gland, 907 vessels and nerves of, 907 Sublobular veins, 954 Submaxillary artery, 557 fossa, 205 ganglion, 771 gland, 906 nerves of, 907 vessels of, 907 lymphatic gland, 685 triangle, 566 vein, 654 Submental artery, 557 vein, 654 Suboccipital nerve, 789 posterior branch of, 789 triangle, 584 Subpeduncular lobe of cerebel- lum, 749 Subpleural mediastinal plexus, _ 588 Subpubic ligament, 342 Subscapular angle, 245 artery, 594 fascia, 474 fossa, 244 nerves, 801 Subscapularis muscle, 475 Substantia cinerea gelatinosa, 702 Sudoriferous glands, 95 Sulci of cerebrum, 717 Sulcus, frontal inferior, 788 superior, 718 intraparietal, 720 occipital inferior, 721 middle, 721 Sulcus, occipital superior, 721 for olfactory tract, 719 orbital, 719 parallel, 721 postcentral, 720 precentral, 718 of Keil, anterior, 721 external, 721 posterior, 721 temporo-sphenoidal, middle, 721 superior, 721 Sulcus spiralis, 886 Supercilia, 869 Superciliary ridge, 173 Superficial cervical artery, 587 circumflex iliac artery, 637 epigastric, 637 external pudic, 637 palmar arch, 606 perineal artery, 627 surgical anatomy of, 561 temporal artery, 560 transverse ligament of fingers, 494 Superficialis colli nerve, 794 volae artery, 601 Superior maxillary bone, 191 articulations of, 197 attachment of muscles to, 197 changes in, produced bv age, 197 development of, 196 maxillary nerve, 763 meatus, 223, 850 mediastinum, 1000 medullary velum, 750 profunda artery, 598 thyroid artery, 554 surgical anatomy of, 554 turbinated crest, 194 of palate, 200 vena cava, 669 Supinator brevis muscle, 488 longus, 485 Supraclavicular nerves, 785 Suprahyoid aponeurosis, 415 Supramarginal convolution, 720 Supramaxillary nerves from fa- cial, 777 Supraorbital arch, 173 artery, 571 foramen, 173, 219 nerve, 761 notch, 173 Suprarenal arteries, 617 capsules, 1021 development of, 137 nerves of, 1023 vessels of, 1023 plexus, 837 veins, 677 Suprascapular artery, 587 nerve, 800 notch, 247 Supraspinales muscles, 440 Supraspinatus muscle, 475 Supraspinous fascia, 475 fossa, 246 ligaments, 324 Supratrochlear foramen, 253 nerve, 760 Sural arteries, 641 veins, 674 1124 INDEX. Surface form or marking of ab- dominal aorta, 611 of acromio-clavicular joint, 346 of ankle-joint, 381 of anterior tibial artery, 644 of axillary artery, 593 of back, 442 of bladder, 1028 of brachial artery, 597 of branches of internal iliac artery, 629 of carpus, 272 of cerebral convolutions, 725 of clavicle, 243 of common carotid artery, 551 of common iliac artery, 621 of cranium, 224 of dorsalis pedis artery, 645 of elbow, 354 of external auditory meatus, 877 of external carotid artery, 553 of external iliac artery, 621 of femoral artery, 635 of femur, 292 of fibula, 301 of fifth cranial nerve, 771 of foot, 312 of head and face, 408 of heart, 980 of hip-joint, 368 of humerus, 255 of hyoid bone, 230 of intestines, 946 of kidney, 1019 of knee-joint, 376 of knuckles 364 of larynx, 995 of liver, 957 of lower extremity, 537 of lungs, 1004 of mouth, 909 of muscles of abdomen, 459 of neck, 429 of palmar arches, 606 of palpebral fissure, 873 of pancreas, 961 of patella, 294 of pelvis, 285 of plantar arch, 650 of popliteal artery, 640 of posterior tibial artery, 647 of radial artery, 600 of radio-ulnar joint, supe- rior, 355 inferior, 358 of radius, 263 of scapula, 249 of shoulder-joint, 350 of skull, 224 of spleen, 965 of spine, 164 of upper extremity, 499 of sterno-clavicular joint, 344 of sterno-mastoid, 413 of stomach, 930 of subclavian artery, 581 of tarsus and foot, 312 of temporo-maxillary joint, 332 of thorax, 238 of tibia, 298 Surface form or marking of ulna, 261 of ulnar artery, 604 of vertebral column, 164 of wrist and hand, 272 of wrist-joint, 359 Surgical anatomy of abdominal aorta, 611 of abducent nerve, 773 of acromio-dlavicular joint, 346 of adductor longus muscle, 516 of ankle-joint, 381 of anterior tibial artery, 644 of arch of aorta, 545 of artery of the bulb, 627 of ascending pharyngeal ar- tery, 560 of auditory nerve, 778 of axilla, 591 of axillary artery, 593 glands, 687 vein, 667 of azygos veins, 670 of base of bladder, 1089 of brachial artery, 597 plexus, 807 of branches of internal iliac, 629 of bend of elbow, 597 of bones of face, 227 of cavernous sinus, 661 of cervical glands, 686 vertebrae, 329 of clavicle, 243 of club-foot, 530. of common carotid, 551 iliac, 621 of dee}) epigastric, 632 of deltoid muscle, 474 of descending aorta, 607 of dorsalis pedis artery, 645 of elbow-joint, 354 of Eustachian tube, 911 of extensor muscles of thumb, 491 of external carotid artery, 553 ear, 890 iliac artery, 621 jugular vein, 655 of eye, 867 of facial artery, 558 vein, 654 nerve, 777 of femoral artery, 635 hernia, 1072 of femur, 293 of foot, bones of, 313 of forearm, bones of, 263 of gluteal artery, 629 of haemorrhoidal veins, 674 of hamstrings, 522 of hand, bones of, 273 of hip-joint, 368 of humerus, 255 of hyoid bone, 230 of hypoglossal nerve, 788 of iliac fascia, 507 of inferior thyroid artery, 587 vena cava, 670 of inguinal hernia, 1062 glands, 688 Surgical anatomy of innominate artery, 548 of intercostal nerves, 811 of internal carotid artery, 570 jugular vein, 657 mammary artery, 589 iliac artery, 623 pudic artery, 626 of intestines, 946 of ischio-rectal region, 1083 of joints of cervical verte- brae, 329 of kidneys, 1019 of knee-joint, 376 of lachrymal apparatus, 873 of laryngeal nerves, 784 of laryngo-tracheal region, 995 of larynx, 995 of leg, bones of, 301 of lingual artery, 555 of liver, 957 of lumbar plexus, 827 of lungs, 1006 of middle meningeal artery, 563 of motor oculi nerve, 758 of muscles of eye, 400 of lower extremity, 539 of soft palate, 425 of upper extremity, 501 of musculo-spiral nerve, 807 of nasal fossae, 852 of nose, 851 of oesophagus, 913 of olfactory nerve, 755 of optic nerve, 756 of palmar arch, 607 fascia, 494 of pancreas, 961 of patella, 294 of pelvis, bones of, 285 of penis, 1037 of perinaeum, 1083 of peroneal or external pop- liteal nerve, 828 of pharynx, 911 of plantar arch, 650 ligaments, 384 of pleura, 998 of popliteal artery, 640 of posterior tibial, 647 of pronator radii teres mus- cle, 481 of prostate gland, 1033 of psoas magnus, 507 of radial artery, 600 of radio-ulnar joint, 356 of rectus femoris muscle, 513 of ribs, 239 of saphena veins, 673 of scapula, 249 of Scarpa's triangle, 632 of sciatic artery, 630 (great) nerve, 828 of scrotum, 1039 of serratus magnus muscle, 473 of shoulder-joint, 350 of skull, 226 of spermatic veins, 676 of spinal accessory nerve, 784 INDEX. 1125 Surgical anatomy of spine, 164 of spleen, 966 of sterno-clavicular joint, 344 of sterno-mastoid muscle, 413 of sternum, 239 of stomach, 930 of subclavian artery, 581 of superior thyroid artery, 554 of synovial sheaths of ten- dons of wrist, 492 of talipes, 530 of tarsal joints, 384, 386 of temporal artery, 561 of temporo-maxillary joint, 332 of testis, 1043 of thoracic aorta, 607 of thorax, 239 of thyroid gland, 1008 of tongue, 420, 846 of triangles of neck, 565 of triceps, 480 of trifacial nerve, 771 of trochlear nerve, 759 of ulnar artery, 604 of urethra, 1031 of vertebral artery, 585 of vesico-prostatic plexus, 675 of vesicnlse seminales, 1045 of wrist-joint, 359 Suspensory ligament of incus, 882 of lens, 867 of liver, 949 of malleus, 881 of penis, 1035 Sustentacular cells of spleen, 963 Sustentaculum tali, 303 Sutura, 317 dentata, 317 harmonia, 317 limbosa, 317 notha, 317 serrata, 317 squamosa, 317 vera, 317 Suture, basilar, 209 coronal, 207 cranial, 207 frontal, 207 fronto-parietal, 207 fronto-sphenoidal, 209 intermaxillary, 219 internasal, 219 interparietal, 207 lambdoid, 207 masto-occipital, 209 masto-parietal, 209 occipito-parietal, 207 petro-occipital, 209 petro-sphenoidal, 209 sagittal, 207 spheno-parietal, 209 squamo-parietal, 209 squamo-sphenoidal, 209 temporal, 179 transverse facial, 209 Swallow's nest of cerebellum, 749 Sweat-glands, 95 Sylvius, aqueduct of, 740 fissure of, 728 surface marking of, 725 Sympathetic nerve, 75, 829 cervical portion, 831 cranial portion, 831 lumbar portion, 835 pelvic portion, 836 thoracic portion, 834 plexuses, 836 cardiac, 836 epigastric, 837 hypogastric, 839 pelvic, 840 solar, 837 Symphysis, 317 of jaw, 204 pubis, 279, 341 Synarthrosis, 316 Syndesmo-odontoid joint, 325 1 Syndosmosis, 317 j Synovia, 316 Synovial membrane, 96, 315 articular, 315 bursal, 316 vaginal, 316. See also Indi- vidual Joints. System, Haversian, 56 Systemic arteries, 541 veins, 651. T. Tables of the skull, 145 Tactile corpuscles, 76 of Grandy, 77 Tsenia hippocampi, 735 semicircularis, 734 violacea, 753 Tapetum lucidum, 863 nigrum, 863 Tarsal artery, 645 bones, 301 ligament of eyelid, 870 ligaments, 383 plates of eyelid, 870 ! Tarso-metatarsal articulations, 386 Tarsus, 301 articulations of, 382 surface form of, 312 surgical anatomy of, 313 synovial membranes of, 383 development of, 310 Taste-goblets, 844 1 Teeth, 894 bicuspid, 895 body of, 894 canine, 894 cement of, 898 cortical substance of, 898 crown of, 894 crusta petrosa of, 898 cuspidate, 894 deciduous, 894 dental tubuli of, 897 dentine of, 897 development of, 899 enamel of, 898 eruption of, 902 eye, 894 false molars, 895 fang of, 894 general characters of, 894 growth of, 901 incisors, 894 intertubular substance of, 898 ivory of, 897 Teeth, milk, 894, 896 molar, 895 multicuspidate, 895 permanent, 894 pulp-cavity of, 896 root of, 894 structure of, 896 temporary, 894, 896 true or large molars, 895 wisdom, 896 Tegmentum of crus cerebri, 730, 743 Tegmen tympani, 179 Temporal artery, 560 anterior, 560 deep, 563 middle, 561 posterior, 560 surgical anatomy of, 561 bone, 175 articulations of, 182 attachment of muscles to, 182 development of, 181 mastoid portion, 177 petrous portion, 178 squamous portion, 175 structure of, 181 fascia, 405 fossae, 217 ganglion, 833 muscle, 405 nerves of auriculo-temporal, 769 deep, 769 of facial, 777 ridge, 173, 176, 217 suture, 179 veins, 654 Temporary cartilage, 51 teeth, 894, 896 Temporo-facial nerve, 776 Temporo-malar, 763 Temporo-maxillary articulation, 329 surface form of, 332 surgical anatomy of, 332 vein, 655 Temporo-sphenoidal lobe, 721 Tendo Achillis, 525 palpebrarum or oculi, 396 Tendon, central, or cordiform, of diaphragm, 447 conjoined, of internal, oblique and transversalis, 453, 1066 structure of, 391 of wrist, relation of, 492 Tenon, capsule of, 852 Tensor palati muscle, 424 tarsi muscle, 397 tympani muscle, 882 canal for, 181, 879 vaginae femoris muscle, 510 Tenth nerve, 781 surgical anatomy of, 784 Tentorium cerebelli, 706 Teres major muscle, 476 minor, 475 Testes, 1040 coni vasculosi of, 1042 coverings of, 1037 development of, 138 gnbernaculum testis, 1045 lobules of, 1042 lymphatics of, 691 1126 INDEX. Testes, mode of descent, 1045 rete testis, 1042 size and weight of, 1040 structure of, 1041 surgical anatomy of, 1043 tubuli seminiferi of, 1042 tunica albuginea, 1041 vaginalis, 1040 vasculosa, 1041 vasa efferentia of, 1043 vas aberrans of, 1043 vas deferens of, 1042 vas recta of, 1042 Testes muliebres, 1057 Thalamencephalon, 121 Thalami optici, 738 Thebesii foramina, 680 venae, 680 Theca vertebral is, 695 Thigh, deep fascia, fascia lata, 508 muscles of back of, 520 of front of, 507 superficial fascia, 508, 1072 Third nerve, 757 surgical anatomy of, 758 ventricle of the brain, 739 Thoracic aorta, 607 surgical anatomy of, 608 artery, acromial, 594 alar, 594 long, 594 superior, 594 duct, 682 ganglia of sympathetic, 834 nerves, anterior, 800 posterior, or long, 798 region, muscles of anterior, 469 lateral, 472 Thorax, base of, 967 bones of, 230 boundaries of, 967 cavity of, 967 cutaneous nerves of, anterior, 810 lateral, 810 fasciae of, 443 general description of, 967 lymphatics of, 693 muscles of, 443 parts passing through upper opening of, 967 surface form of, 238 Thumb, articulation of, with carpus, 361 muscles of, 494 Thymus gland, 1009 lobes of, 1009 lymphatics of, 1010 Thyro-arytaenoideus muscle, 990 Thyro-arytenoid ligament, in- ferior, 988 superior, 988 Thyro-epiglottic ligament, 986 Thyro-epiglottideus muscle, 991 Thyro-hyal of hyoid bone, 229 Thyro-hyoid arch (foetal), 119 ligaments, 987 membrane, 987 muscle, 413 nerve, 788 Thyroid artery inferior, 586 superior, 554 surgical anatomy of, 554 axis, 586 Thyroid branches of sympathetic, 834 cartilage, 984 foramen, 280 ganglion, 834 gland,1006 isthmus of, 1007 lymphatics of, 694 veins, inferior, 668 middle, 657 superior, 656 Thyroidea ima artery, 547 Tibia, 295 articulations of, 298 attachment of muscles to, 298 crest of, 295, 296 development of, 298 fracture of shaft of, 540 nutrient artery of, 648 spinous process of, 295 surface, form of, 298 surgical anatomy of, 301 tubercle of, 295 tuberosities of, 295 Tibial artery, anterior, 643 branches of, 644 peculiarities of, 644 surface marking of, 644 surgical anatomy of, 644 lymphatic glands, 688 nerve, anterior, 827 posterior, 825 recurrent artery, 644 veins, anterior, 673 posterior, 673 Tibialis anticus muscle, 523 posticus muscle, 528 Tibio-fibular articulations, 378 region, anterior, muscles of, 523 posterior, 524 Tibio-tarsal ligament, 379, 380 Tongue, 841 arteries of, 845 fibrous septum of, 844 fraenum of, 841 mucous glands of, 844 membrane of, 842 muscles of, 418 nerves of, 846 papillae of, 742 serous glands of, 844 surgical anatomy of, 846 Tonsillar artery, 557 nerves, 781 Tonsils, 904 of cerebellum, 749 nerves of, 904 vessels of, 904 Torcular Herophili, 168, 660 Trabeculae of corpus cavernosum, 1035 of foetal skull, 118 of spleen, 962 of testis, 1041 Trachea, 992 cartilages of, 994 glands of, 995 relations of, 992 structure of, 994 surgical anatomy of, 996 vessels and nerves of, 995 Trachelo-mastoid muscle, 438 Tracheotomy, 976 Trachoma glands, 871 Tractus intermedio-lateral is, 703 opticus, 755 Tragicus muscle, 876 Tragus, 874 Transversalis colli artery, 587 muscle, 438 fascia, 1067 muscle, 455 Transverse arteries of basilar, 585 colon, 941 disks of muscular fibre, 66 facial artery, 561 vein, 654 fissure of brain, 736 of liver, 951 joint of foot, 381 ligament of atlas, 325 of hip, 367 of knee, 373 of scapula, 347 of shoulder, 348 superficial, of fingers, 494 tibio-fibular, 379 mesocolon, 925 process of a vertebra, 147 sinus, 663 suture, 209 Transversus auriculae, 876 perinaei, 463 (in female), 466 Trapezium bone, 268 of pons, 715 Trapezius muscle, 430 Trapezoid bone, 268 ligament, 346 Triangle of elbow, 595 of Hesselbach, 999 inferior carotid, 565 of neck, anterior, 565 posterior, 567 occipital, 567 Scarpa's, 632 subclavian, 567 submaxillary, 566 suboccipital, 584 superior carotid, 566 Triangular interarticular fibro- cartilage, 357 ligament of abdomen, 450, 1065 of urethra, 465, 1086 Triangularis sterni muscle, 444 Triceps extensor cruris, 511 extensor cubiti, 479 Tricuspid valves, 974 Trifacial or trigeminus nerves, 759 surface marking of, 771 surgical anatomy of, 771 Trigone of bladder, 1028 Trochanter, greater, 287 lesser, 288 Trochanteric fossa, 287 Trochlea of femur, 290 of humerus, 253 Trochlear nerve, 758 surgical anatomy of, 759 Trochoides, 318 True ligaments of bladder, 1026 pelvis, 282 ribs, 234 Trunk, articulations of, 321 muscles of, 429 Tube, Eustachian, 878 INDEX: 1127 Tube, Fallopian, 1056 Tuber annulare, 714 cinereuin, 729 ischii, 278 Tubercle, carotid or Chassaig- nac's, 148 of the clavicle, 241 of the femur, 288 genital, 140 of hyoid bone, 229 lachrymal, 195 laminated, of cerebellum, 749 of Lower, 972 of navicular, 306 for odontoid ligaments, 167 of ribs, 235 of Rolando, 711 of scaphoid of carpus, 264 of tibia, 295 of ulna, 256, 257 of zygoma, 176 Tubercles, genial, 204 mental, 204 of ribs, 235 Tubercula quadrigemina, 741 Tuberculum cuneatum, 710 Tuberosities of humerus, greater and lesser, 249 of tibia, 295 Tuberosity, cuboid, 306 of ischium, 278 maxillary, 192 of palate bone, 201 of radius, 261 of ribs, 235 Tubes, bronchial, 993 structure of, in lung, 1003 Tubular secreting glands, 98 substance of kidney, 1013 Tubuli, dental, 897 of Ferrein, 1015 lactiferi, 1061 seminiferi, 1042 uriniferi, 1013 Tuft, vascular, in Malpighian bodies of kidney, 1013 Tunica adventitia, 82 albuginea, 1041 of eye, 399 intima of arteries, 80 media, 81 of ovary, 1058 Ruyschiana, 857 vaginalis, 1040 oculi, 853 propria, 1040 reflexa, 1041 vasculosa testis, 1042 Turbinated bone, inferior, 202 middle, 188 superior, 189 crest, inferior, 194 superior, 194 Tiirck, fasciculus of, 701 surgical anatomy of, 788 Tutamina oculi, 869 Twelfth nerve, 786 Tympanic artery, from internal carotid, 570 from internal maxillary, 562 nerve, 779, 882 of facial, 775 plate, 176 Tympanum, 878 Tympanum, arteries of, 882 cavity of, 878 membrane of, 880 mucous membrane of, 882 muscles of, 882 nerves of, 882 ossicula of, 880 veins of, 882 Tyson's glands, 964 U. Ulna, 256 articulations of, 260 coronoid process of, 256 development of, 260 fracture of coronoid process of, 503 muscles attached to, 260 of olecranon, 503 process of, 256 of shaft, 503 sigmoid cavities of, 257 styloid process of, 260 surface form of, 261 surgical anatomy of, 263 tubercle of, 256, 257 Ulnar artery, 603 branches of, 604 peculiarities of, 603 recurrent, anterior, 604 posterior, 604 surface marking of, 604 surgical anatomy of, 604 lymphatic gland, 686 nerve, 804 surgical anatomy of, 807 vein, anterior, 665 posterior, 665 Umbilical arteries in foetus, 130, 981 how obliterated, 983 cord, 115 fissure of liver, 951 region, contents of, 916 vein, 131 vesicle, 108 Umbilicus, 108, 458 Unciform bone, 269 process of ethmoid, 188 Uncinate fasciculus, 744 lobe, 723 Uncus, 724 Ungual phalanges, 272 Unstriped muscle, 68 Upper extremity, arteries of, 577 bones of, 240 fascia of, 467 ligaments of, 342 lymphatics of, 686 muscles of, 467 nerves of, 800 surface form of, 499 surgical anatomy of, 501 veins of, 664 Urachus, 114, 1027 Ureters, 1020 muscles of, 1028 nerves of, 1021 vessels of, 1021 Urethra, bulbous portion of, 1031 caput gallinaginis, 1030 development of, 141 female, 1050 male, 1030 Urethra, membranous portion, 1030 prostatic portion, 1030 sinus of, 1030 rupture of, course taken by urine, 1085 sinus pocularis of, 1030 spongy portion of, 1031 structure of, 1031 surgical anatomy of, 1031 verumontanum, 1030 Urinary organs, 1011 development of, 135 Urogenital sinus, 141 Uterine arteries, 624 plexus, 840 of veins, 675 Uterus, 1051 appendages of, 1056 arbor vita of, 1053 broad ligaments of, 1052 cavity of, 1053 development of, 138 in foetus, 1055 fundus, body, and cervix of, 1051 ' ganglia of, 840 nerves of, 840 ligaments of, 1052 lymphatics of, 691 masculinus or utriculus hom- inis, 138, 1030 during menstruation, 1055 nerves of, 1055 in old age, 1056 after parturition, 1055 during pregnancy, 1055 at puberty, 1055 round ligaments of, 1059 shape, position, dimensions, 1051 structure of, 1053 vessels, 1055 Utricle of vestibule, 888 Uvea, 858 Uvula of cerebellum, 749 of throat, 903 vesicae, 1028 V. Vagina, 1050 columns of, 1051 lymphatics of, 691 orifice of, 1047 Vaginal arteries, 624 plexus of nerves, 840 of veins, 675 portal plexus, 954 process of temporal, 177, 180 processes of sphenoid, 184 synovial membranes, 315 Vagus, ganglion of root of, 782 nerve, 781 of trunk of, 782 Vallecula Sylvii, 728 Valley (vallecula) of cerebellum, 748 Valsalva, sinuses of, 544, 975, 977 Valve of Bauhin, 940 coronary, 972 of cystic duct, 957 Eustachian, 973 of gall-bladder, 956 1128 INDEX. Valve of Hasner, 873 ileo-caecal, 940 of Kerkring, 933 mitral, 977 of Vieussens, 750 Valves in right auricle, 972 of lymphatics, 86 pulmonic, 973 semilunar aortic, 977 tricuspid, 974 of veins, 84 Valvula? conniventes, 933 Vas aberrans, 1043 deferens, 1043 structure of, 1043 Vasa aberrantia, from brachial artery, 597 afferentia of lymphatic glands, 682 brevia arteries, 614 veins, 677 efferentia of testis, 1042 of lymphatic glands, 682 intestini tenuis arteries, 614 recta, 1042 vasorum of arteries, 82 of veins, 85 Vascular system, general anat- omy of, 80 changes in, at birth, 983 peculiarities in the foetus, 981 Vaso-motor nerves, 74 Vastus externus muscle, 511 internus and crureus, 512 Vater, corpuscles of, 77, Note Veins, general anatomy of, 84 anastomoses of, 651 coats of, 84 development of, 130 muscular tissue of 84 plexuses of, 651 size, form, etc., 651 structure of, 84 valves of, 84 vessels and nerves of, 85 Veins or vein, descriptive anat- omy of, 652 of alae nasi, 654 angular, 653 articular, of knee, 674 auditory, 889 auricular anterior, 654 posterior. 655 axillary, 666 azygos, left lower, 669 left upper, 669 right, 669 basilic, 666 basi-vertebral, 671 of bone, 56 brachial, 666 brachio-cephalic or innomi- nate, 667 bronchial, 670 buccal, 655 cardiac, 679 anterior, 679 left, 679 posterior, 679 right, 679 cardinal, 131 cava superior, 669 inferior, 675 cephalic, 665 Veins or vein, cerebellar, 659 cerebral, 658 cervical, ascending, 657 deep, 657 choroid of brain, 659 circumflex, iliac, 674 superficial, 672 condyloid posterior, 657, 661 of corpora cavernosa, 1036 of corpus spongiosum, 675 of corpus striatum, 659 cystic, 679 deep, or venie comites, 651 dental inferior, 655 digital, of hand, 665 of diploe, 657 dorsalis nasi, 654 pedis, 672 dorsi-spinal, 670 of penis, 675 emissary, 663 surgical anatomy of, 664 epigastric, 674 superficial, 672 of eyeball, 867 facial, 654 femoral, 674 frontal, 653 of Galen, 659 gastric, 678 gastro-epiploic, 678 gluteal, 674 hemorrhoidal, 674 of head, 652 hepatic, 677 iliac, common, 675 external, 674. internal, 674 ilio-lumbar, 676 inferior cava, 675 innominate, 667 intercostal, superior, 668 interlobular, of kidney, 1018 of liver, 954 interosseous of forearm, 666 intralobular of liver, 954 jugular, anterior, 656 external, 655 posterior, 656 internal, 656 of kidney, 1018 labial, inferior, 654 superior, 654 laryngeal, 668 lateral sacral, 675 lingual, 656 of liver, 952 longitudinal inferior, 660 lumbar, 676 ascending, 676 mammary internal, 668 masseteric, 654 mastoid, 655 maxillary internal, 654 median cutaneous, 665 basilic, 666 cephalic, 666 medulli-spinal, 670 meningeal, 655 meningo-rachidian, 670 mesenteric inferior, 677 superior, 677 nasal, 653 oblique, 679 obturator, 675 Veins or vein, occipital, 655 oesophageal, 669 ophthalmic, 661 ovarian, 676 palatine, inferior, 614 palmar, deep, 666 palpebral, inferior, 654 superior, 654 pancreatic, 677 pancreatico-duodenal, 677 parotid, 654 peroneal, 673 pharyngeal, 656 phrenic, 677 plantar, external, 673 internal, 673 popliteal, 673 portal, 651, 679, 954 profunda femoris, 674 pterygoid plexus, 654 pudic, external, 672 internal, 674 pulmonary, 652 radial, 665 ranine, 654, 656 renal, 677, 1018 sacral, middle, 675 lateral, 675 Salvatella, 665 saphenous, external, or short, 672 internal, or long, 672, 1072 sciatic, 674 spermatic, 676 spheno-palatine, 657 spinal, 670 splenic, 677 stylo-mastoid, 655 subclavian, 667 sublobular, 953, 954 submaxillary, 654 submental, 654 superficial, 651 supraorbital, 653 suprarenal, 677 suprascapular, 656 sural, 674 systemic, 651 temporal, 654 middle, 654 teinporo-maxillary, 655 thyroid inferior, 668 middle, 657 superior, 656 tibial anterior, 673 posterior, 673 transverse cervical, 656 facial, 654 ulnar anterior, 665 common, 665 deep, 666 posterior, 665 umbilical, 983 vaginal of liver, 954 vasa brevia, 677 vertebral, 657 Vidian, 616 Veins, plexuses of, ovarian, 677, 1060 pampiniform, 676, 1039, 1060 pharyngeal, 656 pterygoid, 654 spermatic, 676, 1039 uterine, 675 vaginal, 675 INDEX. 1129 Veins, vesico-prostatic, 657 Velum pendulum palati, 903 interposituin, 738 Vena cava, superior, 669 fcetal, 132 inferior, 675 peculiarities of, 676 Venae comites, 651 hepaticae advehentes, 131 revehentes, 131 interlobulares of kidney, 1018 rectae of kidney, 1018 Thebesii, or minimae cordis, 680, 972 vorticosae, 857 Venesection, 665 Venter of ilium, 276 of scapula, 244 Ventricle of Arantius, 710 Ventricle of brain, third, 739 fourth, 752 lining membrane of, 753 fifth, 737 lateral, 732 of corpus callosum, 731 of heart, left, 976 right, 973 of larynx, 988 Vermicular motion, 68 Vermiform process of cerebellum, inferior, 749 superior, 748 Vernix caseosa, 125 Vertebra prominens, 151 development of, 156 Vertebrae, 146 cervical, 147 development of, 154 dorsal, 151 general characters, 146 ligaments of, 321 lumbar, 153 sacral, 157 structure of, 154 Vertebral aponeurosis, 435 artery, 583 column, 162 articulation of, 321 ossification of, 154 surface form of, 164 ligaments, 321 region, muscles of, anterior, 426 lateral, 427 vein, 657 Vertex of skull, 210 Vertical plate of palate bone, 200 Verumontanum, 1036 Vesical artery, inferior, 624 middle, 624 Vesical artery, superior, 624 plexus of nerves, 840 Vesicle, auditory, 124 cerebral, 119 germinal, 101 ocular, 123 of Purkinje, 101 umbilical, 109 Vesicles, Graafian, 1058 Vesico-prostatic plexus of veins, 675 Vesico-uterine ligaments, 1052 Vesicula prostatica, 1030 Vesiculae seminales, 1044 surgical anatomy of, 1045 vessels and nerves of, 1045 Vesicular nervous matter, 69 column of anterior cornu of spine, 703 Vestibular artery, 889 nerve, 889 Vestibule of ear, 883 aqueduct of, 179, 883 Vestigial fold of pericardium, 668 Vibrissae, 848 Vidian artery, 564 canal, 186 nerve, 766 Vieussens, valve of, 750 Villi, 934 Viscera, position of, in abdom- inal regions, 914 pelvic position of, at outlet of pelvis, 1088 Visceral arches (foetal), 118 Vitelline circulation, 126 membrane, 100 spheres, 102 Vitellus, 100 Vitreous humor of the eye, 865 table of the skull, 146 Vocal cords, inferior or true, 988 superior or false, 988 Voice, organs of, 984 Voluntary muscles, 65 Vomer, 203 alae of, 203 articulations of, 203 development of, 203 Vortex of heart, 979 Vulva, 1047 development of, 140 W. Wagner, tactile corpuscles of, 76 Waters, researches on the lung, 1004 Watney on the structure of villi, 935 of thymus, 1010 Weight of organs. See Individ- ual organs. Wharton's duct, 906 White fibrous tissue, 45 substance of cord, 700 of Schwann, 71 nerve-substance, 70 Willis, circle of, 575, 586 Winslow, foramen of, 918 ligament of, 370 Wisdom tooth, 896 Wolffian body, 135 Womb. See Uterus. Wormian bones, 190 Wrisberg, cartilages of, 986 ganglion of, 836 nerve of, 802 Wrist-joint, 358 surface form of, 272, 359 surgical anatomy of, 359 Wry-neck, 413 Xiphoid appendix, 231 Y. Y-ligament, 366 Y-shaped centre of acetabulum, 280 Yellow elastic fibrous tissue, 46 cartilage, 53 spot of retina, 860 Yolk, 101 cleavage of, 102 sac, 109 Z. 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Published in four styles, Weekly (dated for 30 patients) ; Monthly (undated, for 120 patients per month ; Perpetual (undated, for 30 patients weekly per year) ; and Perpetual (undated, for 60 patients weekly per year). The 60-patient Perpetual consists of 256 pages of assorted blanks. The first three styles contain 32 pages of important data and 176 pages of assorted blanks. Each style is in one wallet- shaped book, leather-bound, with pocket, pencil, rubber, and catheter-scale. Price, each, $1.25. For convenience and elegance it is not surpassable.- Obstetric Gazette. This list is all that could be desired. It contains a vast , amount of useful information, especially for emergencies, i and gives good tables of doses and therapeutics.-Canadian Practitioner. Special Combinations of Periodicals with The Visiting List. The American Journal ($4) with Visiting List ($1.25), or Year-Book ($1.50), for $4.75 The Medical News ($4) " " " " " " " " 4.75 The Journal and News ($7.50) " " " " " " " 8.25 The Journal, News, Visiting List and Year-Book (see page 13) . . . 8.50 The Medical News Physicians' Ledger. Containing 300 pages of fine linen "ledger" paper, ruled so that all the accounts of a large practice may be conveniently kept in it, either by single or double entry, for a long period. Strongly bound in leather, with cloth sides, and with a patent flexible back, which permits it to lie perfectly flat when opened at any place. Price, $4.00. Subscribers can obtain at the close of each volume, cloth covers for The Journal (one annually), and for The News (one annually), free by mail, by remitting Ten Cents for The Journal cover, and Fifteen Cents for The News cover. The safest mode of remittance is by bank check or postal money order, drawn to the order of the undersigned ; where these are not accessible, remittance for subscriptions may be sent at the risk of the publishers by forwarding in registered lettters. Address Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. DICTIONARIES. 3 A NEW MEDICAL DICTIONARY. READY IN A FEW DAYS. THE STUDENTS' Dictionary of Medicine AND THE ALLIED SCIENCES. COMPRISING THE PRONUNCIATION, DERIVATION AND FULL EXPLANATION OF MEDICAL TERMS ; TOGETHER WITH MUCH COLLATERAL DESCRIPTIVE MATTER, NUMEROUS TABLES, ETC. By ALEXANDER DUANE, M.D., Assistant Surgeon to the New York Ophthalmic and Aural Institute; Reviser of Medical Terms for Webster's International Dictionary. In one Square Octavo Volume of about 650 pages. fVHIS handy volume gives succinct but full information concerning every word likely to be met -*• with by students or physicians in the course of medical reading. Especial care has been devoted to making the definitions clear and complete, this main service of a dictionary being expanded to include much descriptive and explanatory matter under headings which would be inadequately represented by a definition, however full. Thus under Diseases are given their causation, symptoms and treatment; under important Organs, an outline of their structure and functions; under each Drug, its action, uses and preparations. Extensive tables of Bacilli, Muscles, Arteries, Veins, etc., are included and the pronun- ciation and derivation of all words are given in a manner to be readily understood. Each page contains an extraordinary amount of matter set in type of great clearness and beauty. In every detail Duane's Medical Dictionary has been planned to furnish to the student a standard guide to medical terms on a level with the existing advanced condition of the medical sciences. The National Medical Dictionary, INCLUDING ENGLISH, FRENCH, GERMAN, ITALIAN AND LATIN TECHNICAL TERMS USED IN MEDICINE AND THE COLLATERAL SCIENCES, AND A SERIES OF TABLES OF USEFUL DATA. By JOHN S. BILLINGS, M.D., LL.D., Edin. and Harv., D.C.L., Oxon., Member of the National Academy of Sciences, Surgeon U. S. A., etc. In Two very Handsome Royal Octavo Volumes containing 1574 Pages, with Two Colored Plates. Per Volume-cloth, $6.00; leather, $7.00; half Morocco, marbled edges, $8.50. For sale by subscription only. Specimen pages on application. Address the Publishers. Its scope is one which will at once satisfy the student and meet all the requirements of the medical practitioner. The work is remarkable, too, for its fulness. It presents to the English reader a thoroughly scientific mode of acquiring a rich vocabulary and offers'an accurate and ready means of reference in consulting works in any of the three modem continental languages which are richest in medical litera- ture. Apart from the boundless stores of information which may be gained by the study of a good dictionary, one is enabled by the work under notice to read intelligently any technical treatise in any of the four chief modem languages. There cannot be two opinions as to the great value and usefulness of this dictionary as a book of ready reference for all sorts and conditions of medical men. So far as we have been able to see, no subject has been omitted, and in respect of completeness it will be found distinctly superior to any medical lexicon yet published.-The London Lancet, April 5, 1890. Hoblyn's Dictionary of Medicine. A Dictionary of the Terms Used in Medicine and the Collateral Sciences. By Richard D. Hoblyn, M. D. Revised, with numerous additions, by Isaac Hays, M. D., late Editor of the American Journal of the Medical Sciences. In one large royal 12mo. volume of 520 double-columned pages. Cloth, $1.50 ; leather, $2.00. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 4 DUNGLISON'S PRONOUNCING MEDICAL DICTIONARY. NEW (21ST) EDITION. THOROUGHLY REVISED. JUST READY. DUNGLISON'S DICTIONARY OF MEDICAL SCIENCE. CONTAINING A FULL EXPLANATION OF THE VARIOUS SUBJECTS AND TERMS OF ANATOMY, PHYSIOLOGY, MEDICAL CHEMISTRY, PHARMACY, PHARMACOLOGY, THERAPEUTICS, MEDICINE, HYGIENE, DIETETICS, PATHOLOGY, SURGERY, OPHTHALMOLOGY, OTOLOGY, LARYNGOLOGY, DERMATOLOGY, GYNE- COLOGY, OBSTETRICS, PEDIATRICS, MEDICAL JURISPRUDENCE AND DENTISTRY, ETC., ETC. By ROBLEY DUNGLISON, M.D., LL.D. Late Professor of Institutes of Medicine in the Jefferson Medical College of Philadelphia. Edited by RICHARD J. DUNGLISON, A.M., M.D. New (21st) edition. Thoroughly revised, greatly enlarged and improved, with the PRONUNCIATION, ACCENTUATION, AND DERIVATION OF THE TERMS. In one magnificent imperial octavo volume of 1191 pages. Cloth, $7.00; leather, $8.00. rpHIS great medical dictionary, which has been for more than two generations the standard of the English-speaking, race is now, after several years of incessant labor, issued in a thoroughly revised and greatly enlarged and improved edition. The new words and phrases aggregate 44,000, and by themselves would fill a large volume. Space has been gained by the excision of everything obsolete, and the page has been much enlarged, so that while the new edition contains far more matter than its predecessor, the whole is accommodated within a volume convenient for the hand. The revision has not only covered every word but it has resulted in a number of important new features designed to confer on the work the utmost usefulness, and to make it answer the most advanced demands of the times. Pronunciation, has been introduced throughout by means of a simple and obvious system of phonetic spelling. At a glance the proper sound of a word is clearly indicated and thus a most important desideratum is supplied. Derivation affords the utmost aid in recollecting the meanings of words, and gives the power of analyzing and understanding those which are unfamiliar. It is here indicated in the simplest manner. Greek words are spelled with English letters, and thus placed at the command of those unfamiliar with the Greek alphabet. Definitions, the essence of a dictionary, are clear and full, a characteristic in which' this work has always been preeminent. In this edition much explanatory and encyclopedic matter has been added, especially upon subjects of practical value. Thus under the various Diseases will be found their symptoms, treatment, etc. ; under Drugs their doses and effects, under Poisoning the symptoms, treatment and antidotes, etc., etc. A vast amount of information has been clearly and conveniently condensed into tables in the alphabet. The typography is thoroughly in keeping with the excellence of the literary material. In a word, both the editor and the publishers have felt that the world-wide reputation of Dunglison's Dictionary has rendered it incumbent on them to ensure that in its remodelled and enlarged shape it should be found equal to all that the student and practitioner can expect from such a work. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. GRAY'S ANATOMY. NEW EDITION. 5 New (Thirteenth) Edition. Just Ready. GRAY'S ANATOMY, IN COLORS OR IN BLACK. Anatomy, Descriptive and Surgical. By HENRY GRAY, F.R.S., LECTURER ON ANATOMY AT ST. GEORGE'S HOSPITAL, LONDON. Edited by T. PICKERING PICK, F.R.C.S., Surgeon to and Lecturer on Anatomy at St. Georgd s Hospital, London, Examiner in Anatomy, Royal College of Surgeons of England. A NEW AMERICAN FROM THE THIRTEENTH ENLARGED AND IMPROVED LONDON EDITION. In one imperial octavo volume of 1118 pages, with 635 large and elaborate engravings on wood. Price of edition with illustrations in colors (see below): Cloth, $7-00; leather, $8.00. Price of edition with illustrations in black: Cloth, $6.00; leather, $7.00. Q INCE 1857 Gray's Anatomy has been the standard work used by students of medicine and practitioners in all English-speaking races. So preeminent has it been among the many works on the subject that thirteen editions have been required to meet the demand. This opportunity for frequent revisions has been fully utilized and the work has thus been subjected to the careful scrutiny of many of the most distinguished anatomists of a generation, and thus a degree of completeness and accuracy has been secured which is not attainable in any other way. In no former revision has so much care been exercised as in the present to provide for the student all the assistance that a text-book can furnish. The engravings have always formed a distinguishing feature of the work, and in the present edition the series has been enriched and rendered complete by the addition of many new ones. The large scale on which the illustrations are drawn and the clearness of the execution render them of unequalled value in affording a grasp of the complex details of the subject. As heretofore the name of each part is printed in the engraving, thus conveying to the eye at once the position, extent and relations of each organ, vessel, muscle, bone or nerve with a clearness impossible when figures on lines of reference are employed. Distinctive colors have been used to give additional prominence to the attachments of muscles, and to the veins, arteries and nerves. For the sake of those who prefer not to pay the slight increase in cost necessitated by the use of colors the volume is published also in black alone. The illustrations thus constitute a complete and splendid series, which will greatly assist the student in forming a clear idea of Anatomy, and will also serve to refresh the memory of those who may find in the exigencies of practice the necessity of recalling the details of the dissecting-room. Combining, as it does, a complete Atlas of Anatomy with a thorough treatise on systematic, descriptive and applied Anatomy, the work will be found of great service to all physicians who receive students in their offices, relieving both preceptor and pupil of much labor in laying the groundwork of a thorough medical education. As this work covers a more extended range of subjects than is customary in the ordinary text-books, giving not only the details necessary for the student, but also the application of those details to the practice of medicine and surgery, it furnishes both a guide for the learner and an admirable work of reference for the active practitioner. A few notices of the previous edition are appended. A work which has had the lead of all other text-books on anatomy throughout the civilized world comes to hand in such beauty of execution and accuracy of text and illustration as more than to make good the large promise of the prospectus. It would be indeed difficult to name a feature wherein Gray could be mended or bettered, and it needs no prophet to see that the royal work is destined for many years to come to hold the first place among anatomical text-books. The work is published with black and colored plates. It is a marvel of book-making.-American Practi- tioner and News. The most popular work on anatomy ever written.-Jour- no? of the American Medical Association Gray's Anatomy is the most magnificent work upon anatomy which has ever been published in the English or any other language.-Cincinnati Medical News. As the book now goes to the purchaser he is receiving the best work on anatomy that is published in any language.- Virginia Medical Monthly. Gray's standard Anatomy has been and will be for years the text-book for students. The book needs only to be examined to be perfectly understood.-Medical Press of Western New York. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 6 ANATOMY, PHYSIOLOGY. Human Monstrosities. By BARTON C. HIRST, M.D., and GEORGE A. PIERSOL, M.D., Professor of Obstetrics in the University of . Professor of Anatomy and Embryology in the Pennsylvania. University of Pennsylvania. Magnificent folio, containing 220 pages of text, illustrated with 123 engravings and 39 full-page photographic plates from nature. In four parts, price, each, $5.00. Complete work just ready. Limited edition, for sale by subscription only. Address the Publishers. We have before us the fourth and last part of the latest and best work on human monstrosities. This completes one of the masterpieces of American medical literature. Typographically and from an artistic standpoint, the work is unexceptionable. In this last and final volume is pre- sented the most complete bibliography of teratological lit- erature extant. No library will be complete without this magnificent work.- Journal of the American Medical Asso- ciation, May 6, 1893. It will take its place as a standard work on teratology in medical libraries, and it must always retain the honor of being the first of its kind written in the English language. - The British Medical Journal, May 27, 1893. The authors have sought to present in a concise and con- venient form a treatise on Teratology which the obstetrician and pathologist can consult for an explanation and classifi- cation of the graver anomalies in development occasionally met with in medical practice. So far as we know there has been hitherto no comprehensive work on the subject in the English language, the literature of the subject in English being scattered and not always easy of access. The authors of the work before us have placed the English-speaking profession greatly in their debt by undertaking what must have largely been a labor of love and by producing a work which certainly fills a gap in English medical literature.- Boston Medical and Surgical Journal, January 12, 1893. This work promises to be one for which a place must be found in the library of every anatomist, pathologist, ob- stetrician, and teratologist. It is the joint production of an obstetrician, and an embryologist and histologist, and this fact makes it certain that both the obstetric and anato- mical sides of the subject will be fully represented and described. The book promises to be one of the greatest value to the English-speaking medical world.-Edinburgh Medical Journal, April, 1892. Allen's System of Human Anatomy. A System of Human Anatomy, Including its Medical and Surgical Relations. For the use of Practitioners and Students of Medicine. By Harrison Allen, M. D., Professor of Physiology in the University of Pennsylvania. With an Introductory Section on Histology by E. O. Shakespeare, M.D., Ophthalmologist to the Philadelphia Hospital. Comprising 813 double-columned quarto pages, with 380 illustrations on 109 full-page lithographic plates, many of which are in colors, and 241 engrav- ings in the text. In six Sections, each in a portfolio. Price, per Section, $3.50; also bound in one volume, cloth, $23.00 ; half Russia, $25.00. For sale by subscription only. Address the Publishers. Holden's Landmarks, Medical and Surgical. Landmarks, Medical and Surgical. By Luther Holden, F.R.C.S., Surgeon to St. Bartholomew's and the Foundling Hospitals, London. Second American from the third and revised English edition, with additions by W. W. Keen, M.D., Professor of Artistic Anatomy in the Penna. Academy of Fine Arts. In one 12mo. volume of 148 pages. Cloth, $1.00. Clarke <& Lockwood's Dissector's Manual. The Dissector's Manual. By W. B. Clarke, F.R.C.S., and C. B. Lockwood, F.R.C.S., Demonstrators of Anatomy at St. Bartholomew's Hospital Medical School, London. In one pocket-size 12mo. volume of 396 pages, with 49 illustrations. Limp cloth, red edges, $1.50. See Students' Series of Manuals, page 30. Treves' Surgical Applied Anatomy. Surgical Applied Anatomy. By Frederick Treves, F.R.C.S., Senior Demonstrator of Anatomy and Assistant Surgeon at the London Hospital. In one pocket-size 12mo. volume of 540 pages, with 61 illustrations. Limp cloth, red edges, $2.00. See Students' Series of Manuals, page 30. Bellamy's Surgical Anatomy. The Student's Guide to Surgical Anatomy: Being a Description of the most Important Surgical Regions of the Human Body, and intended as an Introduction to Operative Surgery. By Edward Bellamy, F.R.C.S., Senior Assistant-Surgeon to the Charing-Cross Hospital. In one 12mo. volume of 300 pages, with 50 illustrations. Cloth, $2.25. Wilson's Human Anatomy. A System of Human Anatomy, General and Special. By Erasmus Wilson, F.R.S. Edited by W. H. Gobrecht, M.D., Professor of General and Surgical Anatomy in the Medical College of Ohio. In one large and handsome octavo volume of 616 pages, with 397 illustrations. Cloth, $4.00 ; leather, $5.00. Cleland's Dissector. A Directory for the Dissection of the Human Body. By John Cleland, M.D., Professor of Anatomy, Queen's College, Galway. 12mo. 178 pages. Cloth, $1.25. HARTSHORNE'S HAND-BOOK OF ANATOMY AND | HORNER'S SPECIAL ANATOMY AND HISTOLOGY. PHYSIOLOGY. Second edition, revised. 12mo., 310 pages, Eighth edition. In two octavo volumes of 1007 pages, with 220 woodcuts. Cloth, 81.75. | 320 woodcuts. Cloth, 86.00. Lea Brothers & Co., Publishers, 706 708 & 710 Sansom Street, Philadelphia. PHYSICS, PHYSIOLOGY, ANATOMY, CHEMISTRY. 7 Draper's Medical Physics. Medical Physics. A Text-book for Students and Practitioners of Medicine. By John C. Draper, M.D., LL.D., Professor of Chemistry in the University of the City of New York. In one octavo volume of 734 pages, with 376 woodcuts, mostly original. Cloth, $4.00. While all enlightened physicians will agree that a knowl- edge of physics is desirable for the medical student, only those actually engaged in the teaching of the primary sub- jects can be fully aware of the difficulties encountered by students who attempt the study of these subjects without a knowledge of either physics or chemistry. These are especially felt by the teacher of physiology. It is, however, impossible for him to impart a knowledge of the main facts of his subject and establish them by reasons and experimental demonstration, and at the same time undertake to teach ab initio the principles of chem- istry or physics. Hence the desirability, we may say the necessity, for some such work as the present one. No man in America was better fitted than Dr. Draper for the task he undertook and he has provided the student and practitioner of medicine with a volume at once readable and thorough. Even to the student who has some knowl- edge of physics this book is useful, as it shows him its ap- plications to the profession that he has chosen. Dr. Draper, as an old teacher, knew well the difficulties to be encoun- tered in bringing his subject within the grasp of the average student, and that he has succeeded so well proves once more that the man to write for and examine students is the one who has taught and is teaching them. The book is well printed and fully illustrated, and in every way de- serves grateful recognition.-Montreal Med. Jour., July, 1890. Chemistry and Physics. Cloth, $1.00. See The Studentd Quiz Series, page 30. Power's Human Physiology.-Second Edition. Human Physiology. By Henry Power, M.B., F.R.C.S., Examiner in Physiology, Royal College of Surgeons of England. Second edition. In one 12mo. volume of 509 pages, with 68 illustra- tions. Cloth, $1.50. See Students' Series of Manuals, page 30. Robertson's Physiological Physics. Physiological Physics. By J. McGregor Robertson, M.A., M.B., Muirhead Demonstrator of Physiology, University of Glasgow. In one 12mo. volume of 537 pages, with 219 illustrations. Limp cloth, $2.00. See Studentd Series of Manuals, page 30. The title of this work sufficiently explains the nature of its contents. It is designed as a manual for the student of medicine, an auxiliary to his text-book in physiology, and it would be particularly useful as a guide to his laboratory experiments. It will be found of great value to the practi- tioner. It is a carefully prepared book of reference, concise and accurate, and as such we heartily recommend it.- Journal of the American Medical Association, Dec. 6, 1884. Dalton on the Circulation of the Blood. Doctrines of the Circulation of the Blood. A History of Physiological Opinion and Discovery in regard to the Circulation of the Blood. By John C. Dalton, M.D., Professor Emeritus of Physiology in the College of Physicians and Surgeons, New York. In one handsome 12mo. volume of 293 pages. Cloth, $2.00. Dr. Dalton's work is the fruit of the deep research of a cultured mind, and to the busy practitioner it cannot fail to be a source of instruction. It will inspire him with a feel- ing of gratitude and admiration for those plodding workers of olden times, who laid the foundation of the magnificent temple of medical science as it now stands.-New Orleans Medical and Surgical Journal, Aug. 1885. Bell's Comparative Anatomy and Physiology. Comparative Anatomy and Physiology. By F. Jeffrey Bell, M.A., Professor of Comparative Anatomy at King's College, London. In one 12mo. volume of 561 pages, with 229 illustra- tions. Limp cloth, $2.00. See Students' Series of Manuals, page 30. The manual is preeminently a student's book-clear and simple in language and arrangement. It is well and abundantly illustrated, and is readable and interesting. I On the whole we consider it the best work in existence in the English language to place in the hands of the medical I student.-Bristol Medico- Chirurgical Journal, March. 1886. Ellis' Demonstrations of Anatomy.-Eighth Edition. Demonstrations of Anatomy. Being a Guide to the Knowledge of the Human Body by Dissection. By George Viner Ellis, Emeritus Professor of Anatomy in University College, London. From the eighth and revised London edition. In one very handsome octavo volume of 716 pages, with 249 illustrations. Cloth, $4.25; leather, $5.25. Roberts' Compend of Anatomy. The Compend of Anatomy. For use in the dissecting-room and in preparing for examina- tions. By John B. Roberts, A.M., M.D., Lecturer in Anatomy in the University of Pennsylvania. In one 16mo. volume of 196 pages. Limp cloth, 75 cents. Wohler's Outlines of Organic Chemistry. Edited by Fittig. Translated by Ira Remsen, M.D., Ph.D. In one 12mo. volume of 550 pages. Cloth, $3.00. LEHMANN'S MANUAL OF CHEMICAL PHYSIOLOGY. In one octavo volume of 327 pages, with 41 illustrations. Cloth, 82.25. CARPENTER'S HUMAN PHYSIOLOGY. Edited by Henry Power. In one octavo volume. CARPENTER'S PRIZE ESSAY ON THE USE AND Abuse of Alcoholic Liquors in Health and Disease. With explanations of scientific words. Small 12mo. 178 pages. Cloth, 60 cents. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 8 PHYSIOLOGY, CHEMISTRY. Foster's Physiology.-Fifth Text-Book of Physiology. By Michael Foi Fellow of Trinity College, Cambridge, England. New and revised English edition, with notes and additions, with 282 illustrations. Cloth, $4.50; leather, $5.50.- Edition Foster, M.D., F.R.S., Prelector in Physiology and ew (fourth) and enlarged American from the fifth is. In one handsome octavo volume of 1072 pages, There can be no doubt that this text-book continues to lead all others in the English language. Although the work of the American editor in former editions has been by the author largely adopted in a modified form in this re- vision, much was still left to be done by the editor to render the work fully adapted to the wants of our American stu- dents, so that the American edition will undoubtedly con- tinue to supply the market on this side of the Atlantic. The work, owing to its enormous sale, is offered at an extremely low price.-Medical and Surgical Reporter, Jan. 9, 1892. Dr. Foster is unquestionably the leading English-speaking physiologist of to-day. In its original editions this work was intended principally for advanced students, and it was not fully appreciated in America until revised and enlarged to meet the wants of junior students also. This process of growth under the repeated revision by author and editor has resulted in a volume containing the matter necessary to constitute a complete text and reference book for student and physician. Notwithstanding the enormous amount now presented, the popularity of the work renders possible its publication at an extremely low price, a point in which the American student has greatly the advantage of his English confrere. It is in every respect an excellent and ideal text-book. The author has succeeded in giving a thoroughly practical and entertaining account of the science. The work is admirably and graphically illustrated. -Southern Practitioner, Dec. 1891. Dalton's Physiology.-Seventh Edition. A Treatise on Human Physiology. Designed for the use of Students and Practitioners of Medicine. By John C. Dalton, M.D., Professor of Physiology in the College of Physicians and Surgeons, New York, etc. Seventh edition, thoroughly revised and rewritten. In one very handsome octavo volume of 722 pages, with 252 beautiful engravings on wood. Cloth, $5.00 ; leather, $6.00. From the first appearance of the book it has been a favorite, owing as well to the author's renown as an oral teacher as to the charm of simplicity with which, as a writer, he always succeeds in investing even intricate sub- jects. It must be gratifiying to him to observe the frequency with which his work, written for students and practitioners, is quoted by other writers on physiology. This fact attests its value, and, in great measure, its originality. It now needs no such seal of approbation, however, for the thou- sands who have studied it in its various editions have never been in any doubt as to its sterling worth.- N. Y. Medical Journal, Oct. 1882. Professor Dalton's well-known and deservedly-appreciated work has long passed the stage at which it could be re- viewed in the ordinary sense. The work is eminently one for the medical practitioner, since it treats most fully of those branches of physiology which have a direct bearing on the diagnosis and treatment of disease. The work is one which we can highly recommend to all our readers.- Dublin Journal of Medical Sciences, Feb. 1883. Chapman's Human Physiology. A Treatise on Human Physiology. By Henry C. Chapman, M.D., Professor of Institutes of Medicine in the Jefferson Medical College of Philadelphia. In one octavo volume of 925 pages, with 605 engravings. Cloth, $5.50 ; leather, $6.50. Matters which have a practical bearing on the practice of medicine are lucidly expressed; technical matters are given in minute detail; elaborate directions are stated for the guidance of students in the laboratory. In every respect the work fulfils its promise, whether as a complete treatise for the student or for the physician; for the former it is so complete that he need look no farther, and the latter will find entertainment and instruction in an admirable book of reference.-North Carolina Medical Journal, Nov. 1887. Physiology. Cloth, $1.00. See The Students' Quiz Series, page 30. Schofield's Elementary Physiology.-Just Ready. Elementary Physiology for Students. By Alfred T. Schofield, M.D., Late House Physician London Hospital. In one 12mo. volume of 380 pages, with 227 engravings and 2 colored plates containing 30 figures. Cloth, $2.00. This volume is neither more nor less than its title implies. It is most skilfully put together and a vast deal of ground is covered. The language is clear and perspicuous, the I arrangement is natural and consecutive. The illustrations are numerous and well executed. The book deserves to | become popular.- The Medical News, July 1,1893. Frankland & Japp's Inorganic Chemistry. Inorganic Chemistry. By E. Frankland, D.C.L., F.R.S., Professor of Chemistry in the Normal School of Science, London, and F. R. Japp, F.I.C., Assistant Professor of Chemistry in the Normal School of Science, London. In one handsome octavo volume of 677 pages, with 51 woodcuts and 2 plates. Cloth, $3.75; leather, $4.75. This work should supersede other works of its class in the medical colleges. It is certainly better adapted than any work upon chemistry with which we are acquainted to impart that clear and full knowledge of the science which students of medicine should have. Physicians who feel that their chemical knowledge is behind the times would do well to study this work. The descriptions and demonstra- tions are made so plain that there is no difficulty in under- standing them.-Cincinnati Medical News, January, 1886. Clowes' Qualitative Analysis.-Third Edition. An Elementary Treatise on Practical Chemistry and Qualitative Inorganic Analysis. Specially adapted for use in the Laboratories of Schools and Colleges and by Beginners. By Frank Clowes, I).Sc., London, Senior Science-Master at the High School, Newcastle-under-Lyme, etc. Third American from the fourth and revised English edition. In one 12mo. volume of 387 pages, with 55 illustrations. Cloth, $2.50. CLASSEN'S ELEMENTARY QUANTITATIVE ANALYSIS. Translated, with notes and additions, by Edgar F. Smith, ph.D., Assistant Professor of Chemistry in the Towne Seien- tiflc School, University of Pennsylvania. In one 12mo. volume of 3'24 pages, with 36 illustrations. Cloth, 3'2.00. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. CH EM IS TR Y-(Continued). 9 Simon's Chemistry.-New (4th) Edition. Just Ready. Manual of Chemistry. A Guide to Lectures and Laboratory work for Beginners in Chemistry. A Text-book specially adapted for Students of Pharmacy and Medicine. By W. Simon, Ph.D., M.D., Professor of Chemistry and Toxicology Coll, of Phys, and Surg., Baltimore; Professor of Chemistry in the Maryland College of Pharmacy. New (fourth) edition. In one 8vo. volume of 490 pages, with 44 woodcuts and 7 colored plates illustrating 56 of the most important chemical tests. Cloth, $3.25. A work which rapidly passes to its fourth edition needs no further proof of having achieved a success. In the present case the claims to favor are obvious. Emanating from an experienced teacher of medical and pharmaceutical students the volume is closely adapted to their needs. This is shown not only by the "careful selection and clear presentation of its subject matter, but by the colored plates of reactions, which form a unique feature. Every teacher will appreciate the saving of his own time, and the advan- tages accruing to the student from a permanent and ac- curate standard of comparison for tests depending on colors, and frequently upon their changes. To the prac- titioner, who is likely to be confronted at any time with important pathological or toxicological questions to be answered by the test-tube, the volume will be of the utmost value. Such it has proved in the past, and the author has accordingly been enabled, through frequent and thorough revisions to keep his work constantly in touch with the progress of its science and the best methods of its presenta- tion.-Kansas City Medical Index, May, 1893. The appearance within a year of another (the fourth) edition of Professor Simon's work indicates that our favor- able opinion of the work as already expressed is shared both by teachers and students. The unique feature of representing color-reactions and colored precipitates by artistically-produced illustrations is attractive and cannot fail to become part of an object lesson, so necessary for the successful study of chemistry. It can be said to rank with the best text-books on pharmaceutic and medical chemistry in this country.-The Medical News, July 22, 1893. Fownes' Chemistry.-Twelfth Edition. A Manual of Elementary Chemistry; Theoretical and Practical. By George Fownes, Ph.D. Embodying Watts' Physical and Inorganic Chemistry. From the twelfth English edition. In one large 12mo. volume of 1061 pages, with 168 engravings and a colored plate. Cloth, $2.75 ; leather, $3.25. Fownes' Chemistry has been a standard text-book upon chemistry for many years. Its merits are very fully known by chemists and physicians everywhere in this country and in England. As the science has advanced by the making of new discoveries, the work has been revised" so as to keep it abreast of the times. It has steadily maintained its position as a text-book with medical students. In this work are treated fully: Heat, Light and Electricity, including Mag- netism. The influence exerted by these forces in chemical action upon health and disease, etc., is of the most impor- tant kind, and should be familiar to every medical practi- tioner. We can commend the work as one of the very best text-books upon chemistry extant.-Cincinnati Medical News, Oct. 1885. Attfield's Chemistry.-Twelfth Edition. Chemistry, General, Medical and Pharmaceutical; Including the Chemistry of the U. S. Pharmacopoeia. A Manual of the General Principles of the Science, and their application to Medicine and Pharmacy. By John Attfield, M.A., Ph.D., F.I.C., F.R.S., etc., Professor of Practical Chemistry to the Pharmaceutical Society of Great Britain, etc. A new American, from the twelfth English edition, specially revised by the Author for America. In one handsome royal 12mo. volume of 782 pages, with 88 illustrations. Cloth, $2.75 ; leather, $3.25. Attfield's Chemistry is the most popular book among stu- dents of medicine and pharmacy. This popularity rests upon real merits. Attfield's work combines in the happiest manner a clear exposition of the theory of chemistry with the practical application of this knowledge to the everyday dealings of the physician and pharmacist. His book is precisely what the title claims for it. The admirable arrangement of the text enables a reader to get a good idea of Chemistry without the aid of experiments, and again it is a good laboratory guide, and finally it contains such a mass of well-arranged information that it will always serve as a handy book of reference. He does not allow any un- utilizable knowledge to slip into his book ; his long years of experience have produced a work which is both scientific and practical, and which shuts out everything in the nature of a superfluity, and therein lies the secret of its success. This last edition shows the marks of the latest progress made in chemistry and chemical teaching.-New Orleans Medical and Surgical Journal, Nov. 1889. Chemistry & Physics. Cloth, $1.00. See Students' Quiz Series, page SO. Bloxam's Chemistry.-Fifth Edition. Chemistry, Inorganic and Organic. By Charles L. Bloxam, Professor of Chemistry in King's College, London. From the fifth London edition, thoroughly revised and much improved. In one octavo volume of 727 pages, with 292 illustrations. Cloth, $2.00 ; leather, $3.00. Comment from us on this standard work is almost super- fluous. It differs widely in scope and aim from that of Attfield, and in its way is equally beyond criticism. It adopts the most direct methods in stating the principles, hypotheses and facts of the science. Its language is so terse and lucid, and its arrangement of matter so logical in sequence that the student never has occasion to complain that chemistry is a hard study. Much attention is paid to experimental illustrations of chemical principles and phe- nomena, and the mode of conducting these experiments. The book maintains the position it has always held as one of the best manuals of general chemistry in the English language.-Detroit Lancet, Feb. 1884. Luff's Manual of Chemistry.-Just Ready. A Manual of Chemistry. For the use of Students of Medicine. By Arthur P. Luff, M.D., B.Sc., Lecturer on Medical Jurisprudence and Toxicological Chemistry, St. Mary's Hospital Medical School, London. In one 12mo. volume of 522 pages, with 36 engravings. Cloth, $2.00. See Students' Series of Manuals, page 30. Greene's Medical Chemistry. A Manual of Medical Chemistry. For the use of Students. By William H. Greene, M.D., Demonstrator of Chemistry in the Medical Department of the University of Pennsylvania. In one 12mo. volume of 310 pages, with 74 illustrations. Cloth, $1.75. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia, 10 CHEMISTRY-(Continued), PHARMACY. Vaughan & Novy on Ptomaines and Leucomaines.-2d Ed. Ptomaines, Leucomaines and Bacterial Proteids; or the Chemical Factors in the Causation of Disease. By Victor C. Vaughan, Ph.D., M.D., Professor of Physiological and Pathological Chemistry, and Associate Professor of Therapeutics and Materia Medica in the University of Michigan, and Frederick Gt. Novy, M.D., Instructor in Hygiene and Physiological Chemistry in the University of Michigan. New (second) edition. In one 12mo. volume of 389 pages. Cloth, $2.25. This book is one that is of the greatest importance, and the modern physician who accepts bacterial pathology cannot have a complete knowledge of this subject unless he has carefully perused it. To the toxicologist the sub- ject is alike of great import, as well as to the hygienist and sanitarian. It contains information which is not easily obtained elsewhere, and which is of a kind that no med- ical thinker should be without.-The American Journal of the Medical Sciences, April, 1892. This volume brings prominently to view the correct path- ology of a host of diseases. Modern chemistry has furnished no more striking evidence of its value than the discovery of these ultimate causes of disease, a step which necessarily precedes any rational knowledge of cure or prevention. The literature of these subjects, already vast, was before the preparation of this work scattered and unattainable by those who had most need of its help, namely general practi- tioners. For the student no more important branch of chemistry exists. The early demand for a second edition of a work on so new a department of science argues well tor the curriculum of those colleges which have already made it a branch of study and for the growing promptness on the part of the profession to recognize and use the most enlightened methods for the benefit of their patients.- Southern Practitioner, Dec. 1891. Remsen's Theoretical Chemistry.-New (4th) Edition. Principles of Theoretical Chemistry, with special reference to the Constitution of Chemical Compounds. By Ira Remsen, M.D., Ph.D., Professor of Chemistry in the Johns Hopkins University, Baltimore. Fourth and thoroughly revised edition. In one royal 12mo. vol. of 325 pages. Cloth, $2.00. The principles of theoretical chemistry need to be put very plainly to the student, for unless he gains a clear insight into the laws which govern the constitution of matter his idea of the whole subject is seldom sound, and he will probably lose the full benefit of a practical course. The book gives clear accounts of all theories and modern specu- lations. We have noticed this book favorably on a previous occasion, since which time four editions have been printed, and it has recently been translated into the German ana Italian languages.-London Lancet, May 6, 1893. The fourth edition of Professor Remsen's well-known book comes again, enlarged and revised. Each edition has enhanced its value. We may say without hesitation that it is a standard work on the theory of chemistry, not excelled and scarcely equalled by any other in any language. Its translation into German and Italian speaks for its exalted position and the esteem in which it is held by the most prominent chemists. We claim for this little work a lead- ing place in the chemical literature of this country.-The American Journal of the Medical Sciences, July, 1893. Charles' Physiological and Pathological Chemistry. The Elements of Physiological and Pathological Chemistry. A Hand-book for Medical Students and Practitioners. Containing a general account of Nutrition, Foods and Digestion, and the Chemistry of the Tissues, Organs, Secretions and Excretions of the Body in Health and in Disease. Together with the methods for preparing or separating their chief constituents, as also for their examina- tion in detail, and an outline syllabus of a practical course of instruction for students. By T. Cranstoun Charles, M.D., F.R.S., M.S., formerly Assistant Professor and Demonstrator of Chemistry and Chemical Physics, Queen's College, Belfast. In one handsome octavo volume of 463 pages, with 38 woodcuts and 1 colored plate. Cloth, $3.50. Dr. Charles is fully impressed with the importance and practical reach of his subject, and he has treated it in a competent and instructive manner. We cannot recom- mend a better book than the present. In fact, it fills a gap in medical text-books, and that is a thing which can rarely be said nowadays. Dr. Charles has devoted much space to the elucidation of urinary mysteries. He does this with much detail, and yet in a practical and intelligible manner. In fact, the author has filled his book with many practical hints.-Medical Record, December 20, 1884. Hoffmann and Powers' Medicinal Analysis. A Manual of Chemical Analysis, as applied to the Examination of Medicinal Chemicals and their Preparations. Being a Guide for the Determination of their Identity and Quality, and for the Detection of Impurities and Adulterations. For the use of Pharmacists, Physicians, Druggists and Manufacturing Chemists, and Pharmaceutical and Medical Students. By Frederick Hoffmann, A.M., Ph.D., Public Analyst to the State of New York, and Frederick B. Power, Ph.D., Professor of Analytical Chemistry in the Philadelphia College of Pharmacy. Third edition, entirely rewritten and much enlarged. In one octavo volume of 621 pages, with 179 illustrations. Cloth, $4.25. Parrish's Pharmacy.-Fifth Edition. A Treatise on Pharmacy: Designed as a Text-book for the Student, and as a Guide for the Physician and Pharmaceutist. With many Formulae and Prescriptions. By Edward Parrish, late Professor of the Theory of Practice of Pharmacy in the Philadelphia College of Pharmacy. Fifth edition, thoroughly revised, by Thomas S. Wiegand, Ph.G. In one handsome octavo volume of 1093 pages, with 256 illustrations. Cloth, $5.00 ; leather, $6.00. No thorough-going pharmacist will fail to possess himself of so useful a guide to practice, and no physician who properly estimates the value of an accurate knowledge of the remedial agents employed by him in daily practice, so far as their miscibility, compatibility and most effective ' methods of combination are concerned, can afford to leave this work out of the list of their works of reference. The country practitioner, who must always be in a measure his own pharmacist, will find it indispensable.- Louisinlle I Medical News, March 29, 1884. Ralfe's Clinical Chemistry. Clinical Chemistry. By Charles H. Ralfe, M.D., F.R.C.P., Assistant Physician at the London Hospital. In one pocket-size 12mo. volume of 314 pages, with 16 illustrations. Limp cloth, red edges, $1.50. See Series of Manuals, page 30. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. MATERIA MEDICA, THERAPEUTICS. 11 New (5th) Edition.-Preparing. The National Dispensatory. CONTAINING THE NATURAL HISTORY, CHEMISTRY, PHARMACY, ACTIONS AND USES OF MEDICINES, INCLUDING THOSE RECOGNIZED IN THE PHARMACOPCEIAS OF THE UNITED STATES, GREAT BRITAIN AND GERMANY, WITH NUMEROUS REFERENCES TO THE FRENCH CODEX. By ALFRED STILLE, M.D., LL.D., Professor Emeritus of the Theory and Practice of Medicine and of Clinical Medicine in the University of Pennsylvania. and JOHN M. MAISCH, Phar.D., Professor of Materia Medica and Botany in Philadelphia College of Pharmacy, Secretary to the American Pharmaceutical Association. New (fifth) edition thoroughly revised, and covering the new United States Pharmacopoeia. In one magnificent imperial octavo volume of about 1800 pages, with about 325 elaborate engravings. Preparing. We think it is a matter for congratulation that the pro- fession of medicine and that of pharmacy have shown such appreciation of this great work as to call for four editions within the comparatively brief period of eight years. The matters with which it deals are of so practical a nature that neither the physician nor the pharmaceutist can do without the latest text-books on them, especially those that are so accurate and comprehensive as this one. The book is in every way creditable both to the authors and to the pub- lishers.- The New York Medical Journal, May 21, 1887. The authors and publishers have reason to feel proud of A few notices of the previous edition are appended. this, the most comprehensive, elaborate and accurate work of the kind ever printed in this country. It is no wonder that it has become the standard authority for both the med- ical and pharmaceutical professions, and that four editions have been required to supply the constant and increasing demand since its first appearance in 1879. The entire field has been gone over and the various articles revised in accordance with the latest developments regarding the attributes and therapeutical action of drugs. The remedies of recent discovery have received due attention.-Kansas City Medical Index, November, 1887. Maisch's Materia Medica.-New (5th) Edition. A Manual of Organic Materia Medica; Being a Guide to Materia Medica of the Vegetable and Animal Kingdoms. For the use of Students, Druggists, Pharmacists and Physicians. By John M. Maisch, Phar.D., Professor of Materia Medica and Botany in the Philadelphia College of Pharmacy. New (fifth) edition, thoroughly revised. In one very handsome 12mo. volume of 544 pages, with 270 engravings. Cloth, $3.00. This is an excellent manual of organic materia medica, as are all the works that emanate from the skilful pen of such a successful teacher as John M. Maisch. The book speaks for itself in the most forcible language. In the edi- tion before us, which is the fifth one published within the comparatively short space of eight years (and this is the best proof of the great value of the work and the just favor with which it has been received and accepted), the original contents have been thoroughly revised and much good and new matter has been incorporated. We have nothing but praise for Professor Maisch's work. It presents no weak point, even for the most severe critic. The book fully sus- tains the wide and well-earned reputation of its popular author. In the special line of work of which it treats it is fully up to the most recent observations and investigations. After a careful perusal of the book, we do not hesitate to recommend Maisch's Manual of Organic Materia Medica as one of the best, if not the best work on the subject thus far published. Its usefulness cannot well be dispensed with, and students, druggists, pharmacists, and physicians should all possess a copy of such a valuable book.-Medical News, December 31,1892. Edes' Therapeutics and Materia Medica. A Text-Book of Therapeutics and Materia Medica. Intended for the Use of Student and Practitioners. By Robert T. Edes, M.D., Jackson Professor of Clinical Medicine in Harvard University. Octavo, 544 pages. Cloth, $3.50; leather, $4 50. Dr. Edes' book represents better than any older book the practical therapeutics of the present day. The book is a thoroughly practical one. The classification of remedies has reference to their therapeutic action.- Pharmaceutical Era, January, 1888. It possesses all the essentials which we expect in a book of its kind, such as conciseness, clearness, a judicious clas- silication, and a reasonable degree of dogmatism. All the newest drugs of promise are treated of. The clinical index at the end will be found very useful. We heartily com- mend the book and congratulate the author on having pro- duced so good a one.-A'. Y. Medical Journal, Feb., 18,1888. Bruce's Materia Medica and Therapeutics.-Fifth Edition. Materia Medica and Therapeutics. An Introduction to Rational Treatment. By J. Mitchell Bruce, M.D., F.R.C.P., Physician and Lecturer on Materia Medica and Therapeutics at Charing-Cross Hospital, London. Fifth edition. In one 12mo. volume of 591 pages. Cloth, $1.50. See Students? Series of Manuals, page 30. The pharmacology and therapeutics of each drug are given with great fulness, and the indications for its rational employment in the practical treatment of disease are pointed out. The Materia Medica proper contains all that is necessary for a medical student to know at the present day. The third part of the book contains an outline of general therapeutics, each of the symptoms of the body being taken in turn and the methods of treatment illus- trated. A lengthy notice of a book so well known is un- necessary.-Medical Chronicle, May, 1891. Materia Medica and Therapeutics, cioth, $1. see The students' Quiz Series, p 30. STILLE'S THERAPEUTICS AND MATERIA MEDICA. A Systematic Treatise on the Action and Uses of Medicinal Agents, including their Description and History. Fourth edition, revised and enlarged. In two octavo volumes, con- taining 1936 pages. Cloth, 810.00 ; leather, 812.00. HERMANN'S EXPERIMENTAL PHARMACOLOGY. A Handbook of Methods for Determining the Physiological Action of Drugs. Translated, with the Author's permission, and with extensive additions, by R. M. Smith, M.D. 12mo., 199 pages, with 32 illustrations. Cloth, 51.50. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 12 THERAPEUTICS, MATERIA MEDICA-(Continued). A System of Practical Therapeutics, BY AMERICAN AND FOREIGN AUTHORS. Edited by HOBART AMORY HARE, M.D., Professor of Therapeutics and Materia Medica in the Jefferson Medical College of Philadelphia. In a series of contributions by seventy-eight eminent authorities. In three large octavo volumes of 3544 pages, with 434 illustrations. Price, per volume: Cloth, $5.00; leather, $6.00; half Russia, $7.00. For sale by subscription only. Address the Publishers. Full prospectus free to any address on application. The various divisions have been elaborated by men se- lected in view of their special fitness. In every case there is to be found a clear and concise description of the disease under consideration, corresponding with the most recent and well-established views of the subject, embracing appo- site pictorial illustrations where these are necessary. In treating of the employment of remedies and therapeutical measures, the writers have been singularly happy in giving in a definite way the exact methods employed and the results obtained, both by themselves and others, so that one might venture with confidence to use remedies with which he was previously entirely unfamiliar. The practitioner could hardly desire a book on practical therapeutics which he could consult with more interest and profit.-7/ie North American Practitioner, September, 1892. The scope of this work is beyond that of any previous one on the subject. The goal, after all, is the treatment of disease, and a work which contributes to its successful management is to be looked upon as of vast use to hu- manity. It cannot be denied that therapeutic resources, whether the treatment be confined to the mere administra- tion of drugs, or allowed its more extended application to the management of disease, have so greatly multiplied within the last few years as to render previous treatises of little value. Herein will be found the great value of Hare's encyclopedic work, which groups together within a single series of volumes the most modern methods known in the management of disease, and especially deals with important subjects comprehensively, which could not be done in a more limited treatise. We cannot commend Hare's System of Practical Therapeutics too highly; it stands out first and foremost as a work to be consulted by authors, teachers and physicians throughout the world.-Buffalo Medical and Surgical Journal, August, 1892. Hare's Text=Book of Practical Therapeutics.-New (3d) Ed. A Text-Book of Practical Therapeutics; With Especial Reference to the Application of Remedial Measures to Disease and their Employment upon a Rational Basis. By Hobart Amory Hare, M.D., Professor of Therapeutics and Materia Medica in the Jefferson Medical College of Philadelphia; Secretary of Convention for Revision of United States Pharmacopoeia of 1890. With special chapters by Drs. G. E. de Schweinitz, Edward Martin, J. Howard Reeves, and Barton C. Hirst. New (third) and revised edition. In one octavo volume of 689 pages. Cloth, $3.75; leather, $4.75. Just Ready. Hare's works on Therapeutics are remarkably well known. As its name would indicate, the book before us is a Text- Book on Practical Therapeutics. Its pretensions are not voluminous nor exhaustive, but they are honest, valuable and practical. The student of other works has often, indeed, very often, longed for less of the abstract materia medica ana more of the practical application of drugs to disease. In this work that want is filled. The drugs are arranged alphabetically, which enables one to find any name quickly, and, with the excellent index at the end of the volume, naught is left to be desired in the way of quick reference. Each drug, including all the newer remedies which have been proven to possess true merit, is considered in a rational and scientific manner. This work also presents us with nearly 250 pages of practical therapeutics, as ap- plied to the individual diseases. The subjects are arranged alphabetically. It is in the chapter on Diseases that the is properly the complement of the former, in which each drug was presented with notes as to its usefulness in numerous diseases, while in the latter each disease is con- sidered very fully from a therapeutical stand-point, giving the applications and special indications of the different remedies in the different phases of that particular affec- tion. It is not a wonder that this work was quickly adopted by many colleges as a text-book and so liberally purchased as to necessitate the publication of a third edition within two years; it is not surprising, but instead, just what we should reasonably expect. The student will find its pages filled with the choicest of therapeu- tical lore, systematically arranged and clearly and forcibly presented; the practitioner will appreciate its rationality and its general utility as an elbow consultant. It contains, without question, the best exposition of modern thera- peutics of any text-book with which we are acquainted.- student finds the rationale of therapeutics. This section The Chicago Clinical .Review, March, 1893. Brunton's Therapeutics and Materia Medica.-Third Ed. A Text-Book of Pharmacology, Therapeutics and Materia Medica. By T. Lauder Brunton, M.D., D.Sc., F.R.S., F.R.C.P., Lecturer on Materia Medicaand Therapeutics at St. Bartholo- mew's Hospital, London, etc. Including the Pharmacy, the Physiological Action and the Therapeutical Uses of Drugs. Adapted to the United States Pharmacopoeia by Francis H. Wieliams, M.D., of Har- vard University Medical School. Third edition. Octavo, 1305 pages, with 230 illustrations. Leather, $6.50. Farquharson's Therapeutics and Materia Medica.-4th Ed. A Guide to Therapeutics and Materia Medica. By Robert Farquharson, M.D., F.R.C.P., LL.D., Lecturer on Materia Medica at St. Mary's Hospital Medical School, London. Fourth American, from the fourth English edition. Enlarged and adapted to the United States Pharmacopoeia, by Frank Woodbury, M.D., Professor of Materia Medica and Therapeutics and Clinical Medicine in the Medico-Chirurgical College of Philadelphia. In one handsome 12mo. volume of 581 pages. Cloth, $2.50. It may correctly be regarded as the most modern work of its kind. It is concise, vet complete. Containing an account of all remedies that have a place in the British and United States Pharmacopoeias, as well as considering all non-oliicial but important new drugs, it becomes in fact a miniature dispensatory.-Pacific Medical Journal, June, 1889. Farquharson's Therapeutics and Matena Medica has struck a happy medium between excessive brevity on the one hand and tedious prolixity on the other. It deals with the entire list of drugs embraced in the British Pharmacopeia in such a way as to give in a satisfactory form the established indi- cations of each, excluding all irrelevant matter. An espe- cially attractive feature is an arrangement by which the physiological and therapeutical action of various remedies are shown in parallel columns. This'aids greatly in fixing attention and facilitates study. The American editor has enlarged the work so as to include all the remedies and preparations in the United States Pharmacopma. Altogether the book is a most valuable addition to the list of treatises on this most important subject.- TAe American Practitioner and News, November 9,1889. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. PRACTICE OF MEDICINE. TREATMENT. 13 Flint's Practice of Medicine.-Sixth Edition. A Treatise on the Principles and Practice of Medicine. Designed for the use of Students and Practitioners of Medicine. By Austin Flint, M.D., LL.D., Professor of the Principles and Practice of Medicine, and of Clinical Medicine in Bellevue Hospital Medical College, N. Y. Sixth edition, thoroughly revised and rewritten by the Author, assisted by William H. Welch, M.D., Professor of Pathology, Johns Hopkins University, Baltimore, and Austin Flint, Jr., M.D., LL.D., Professor of Physiology, Bellevue Hospital Medical College, New York. In one very handsome octavo volume of 1160 pages, with illustrations. Cloth, $5.50; leather, $6.50. No text-book on the principles and practice of medicine has ever met in this country with such general approval by medical students and practitioners as the work of Professor Flint. In all the medical colleges of the United States it is the favorite work upon Practice; and, as we have stated before in alluding to it, there is no other medical work that can be so generally found in the libraries of physicians. In every State and Territory of this vast country the book that will be most likely to be found in the office of a medical man, whether in city, town, village, or at some cross-roads, is Flint's Practice. We make this statement to a consider- able extent from personal observation, and it is the testi- mony also of others. The work may undoubtedly be re- garded as fairly representing the present state of the science of medicine, and as reflecting the views of those who exemplify in their practice the present stage of progress of medical art.-Cincinnati Medical News, October, 1886. Fothergill's Handbook of Treatment.-Third Edition. The Practitioner's Handbook of Treatment; Or, The Principles of Therapeutics. By J. Milner Fothergill, M. D., Edinburgh, M. R. C. P., London, Physician to the City of London Hospital for Diseases of the Chest. Third edition. In one 8vo. volume of 661 pages. Cloth, §3.75 ; leather, §4.75. To have a description of the normal physiological pro- cesses of an organ and of the methods of treatment of its morbid conditions brought together in a single chapter, and the relations between the two clearly stated, cannot fail to prove a great convenience to many thoughtful but busy physicians. The practical value of the volume is greatly increased by the introduction of many prescriptions. That the profession appreciates that the author has undertaken an important work and has accomplished it is shown by the demand for this third edition.-New York Medical Journal, June 11, 1887. The Year=Book of Treatment for 1893. A Comprehensive and Critical Review for Practitioners of Medicine and Surgery. In one 12mo. vol. of 501 pages. Cloth, $1.50. ***Fbr special commutations with periodicals see pages 1 and 2. The Year-Book of Treatment for 1893 easily holds its ad- vanced place among the many annuals and abstracts form- ing so marked a feature of modern medical literature. Its pages give a critical and well-arranged review of the best that the year has brought forth in all departments of ther- apeutics. Among so much that is excellent one can scarcely choose. Commendable features are the Summary of Ther- apeutics and the Selected List of New Books. There is as usual a good index.-The Medical News, May 20, 1893. The Year=Books of Treatment for 1891 and 1892. 12mos., 485 pages. Cloth, $1.50 each. The Year= Books of Treatment for 1886 and 1887 Similar to above. 12mo., 320-341 pages. Cloth, §1.25 each. Hartshorne's Essentials of Practice. -Fifth Edition. Essentials of the Principles and Practice of Medicine. A Hand-book for Students and Practitioners. By Henry Hartshorne, M. D., LL. D., lately Professor of Hygiene in the University of Pennsylvania. Fifth edition, thoroughly revised and rewritten. In one 12mo. volume of 669 pages, with 144 illustrations. Cloth, §2.75; half leather, §3.00. . -Fifth Edition. Within the compass of 600 pages it treats of the history of medicine, general pathology, general symptomatology, and physical diagnosis (including laryngoscope, ophthal- moscope, etc.), general therapeutics, nosology, and special pathology and practice. There is a wonderful amount of information contained in this work, and it is one of the best of its kind that we have seen.-Glasgow Medical Jour- nal, November, 1882. Practice of Medicine, Including Nervous Diseases. Cloth, §1.00. See Students Quiz Series, page 30. BRISTOWE'S PRACTICE OF MEDICINE. Seventh Edi- tion. In one large octavo volume of 1325 pages. Cloth, 86.50; leather, 87.50. REYNOLDS' SYSTEM OF MEDICINE. By J. Russell Reynolds, M.D., Professor of the Principlesand Practice of Medicine in University College, London. With notes and additions by Henry Hartshorne, A.M., M.D., late Professor of Hygiene in the University of Pennsylvania. Three large octavo volumes, containing 3056 double-columned pages, with 317 illustrations. Price per volume, cloth, 85.00; sheep, 86.00; half Russia, raised bands, 86.50. Per set, cloth, 815.00 ; leather, 818.00 ; half Russia, 819.50. Sold only by subscription. WATSON'S LECTURES ON THE PRINCIPLES AND PRACTICE OF PHYSIC. From the fifth English edition. Edited with additions, and 190 illustrations, by Henry- Hartshorne, A.M., M.D., late Professor of Hygiene in the University of Pennsylvania. In two large octavo Volumes of 1840 pages. Cloth, 89.00; leather, 811.00. FLINT ON PHTHISIS: ITS MORBID ANATOMY, ETI- OLOGY, SYMPTOMATIC EVENTS AND COMPLICATIONS, FATALITY AND PROGNOSIS, TREATMENT AND PHYS- ICAL DIAGNOSIS ; in a series of Clinical Studies. In one octavo volume of 442 pages. Cloth, 83.50. FLINT'S PRACTICAL TREATISE ON THE DIAGNOSIS, PATHOLOGY AND TREATMENT OF DISEASES OF THE HEART. Second revised and enlarged edition. In one octavo volume of 550 pages, with a plate. Cloth, 84. FLINT'S ESSAYS ON CONSERVATIVE MEDICINE AND KINDRED TOPICS. In one very handsome royal 12mo. volume of 210 pages. Cloth, 81.38. STURGES' INTRODUCTION TO THE STUDY OF CLIN- ICAL MEDICINE. Being a Guide to the Investigation of Disease. In one handsome 12mo. volume of 127 pages. Cloth, 81.25. WALSHE ON THE DISEASES OF THE HEART AND GREAT VESSELS. Third American edition. In one oc- tavo volume of 416 pages. Cloth, 83.00. HOLLAND'S MEDICAL NOTES AND REFLECTIONS. One octavo volume of 493 pages. Cloth, 83.50. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 14 PRACTICE OF MEDICINE- ('Continued), DIAGNOSIS. Lyman's Practice of Medicine. The Principles and Practice of Medicine. For the Use ot Medical Students and Prac- titioners. By Henry M. Lyman, M.D., Professor of the Principles and Practice of Medicine, Rush Medical College, Chicago. In one octavo volume of 925 pages, with 170 illustrations. Cloth, $4.75; leather, $5.75. This is an excellent treatise on the practice of medicine, written by one who is not only familiar with his subject, but who has also learned, through practical experience in teaching, what are the needs of the student, and how to present the facts to his mind in the most readily assimilable form. Each subject is taken up in order, treated clearly but briefly, and dismissed when all has been said that need be said in order to give the reader a clean-cut picture of the disease under discussion. The reader is not confused by having presented to him a variety of different methods of treatment, among which he is left to choose the one most easy of execution, but the author describes the one which is in his judgment the best. This is as it should be. What the student should be taught is the one most approved method of treatment. We have spoken of the work as one for the student, and this because the author occupies so prominent a position as a teacher, but we would not be un- derstood that it is adapted only for students. He will find here each subject presented in its latest aspect, and only such theories mentioned as have been generally accepted by the highest authorities. The practical and busy man who wants to ascertain in a short time all the necessary facts concerning the pathology or treatment of any disease will find here a safe and convenient guide.-Medical Record, October 22, 1892. Flint on Auscultation and Percussion.-Fifth Edition. A Manual of Auscultation and Percussion; Of the Physical Diagnosis of Diseases of the Lungs and Heart, and of Thoracic Aneurism. By Austin Flint, M.D., LL.D., Professor of the Principles and Practice of Medicine in Bellevue Hospital Medical College, New York. Fifth edition. Edited by James C. Wilson, M.D., Lecturer on Physical Diagnosis in the Jefferson Medical College, Philadelphia. In one handsome royal 12mo. volume of 274 pages, with 12 illustrations. Cloth, $1.75. This little book through its various editions has probably done more to advance the science of physical exploration of the chest than any other dissertation upon the subject, and now in its fifth edition it is as nearly perfect as can be. The rapidity with which previous editions were sold shows how the profession appreciated the thoroughness of Pro- fessor Flint's investigations. For students it is excellent, Its value is shown both in the arrangement of the material and in the clear, concise style of expression. For the prac- titioner it is a ready manual for reference.-North American Practitioner, January, 1891. Musser's Medical Diagnosis-In Press. A Practical Treatise on Medical Diagnosis. For the Use of Students and Practitioners. By John H. Musser, M.D., Assistant Professor of Clinical Medicine, University of Pennsylvania, Philadelphia. In one octavo volume of about 650 pages, richly illustrated. Broadbent on the Pulse. The Pulse. By W. H. Broadbent, M.D., F.R.C.P., Physician to and Lecturer on Medicine at St. Mary's Hospital, London. In one 12mo. volume of 312 pages. Cloth, $1.75. See Series of Clinical Manuals, page 30. Pepper's System of Practical Medicine. BY AMERICAN AUTHORS. Edited by WILLIAM PEPPER, M.D., LL.D., Provost and Professor of the Theory and Practice of Medicine and of Clinical Medicine in the University of Pennsylvania. The complete work, in five volumes, containing Price per volume, cloth, $5.00 ; leather, $6.00 ; half . : 5573 pages, with 198 illustrations, is now ready. Russia, $7.00. For sale by subscription only. The feeling of proud satisfaction with which the Amer- ican profession sees this, its representative system of prac- tical medicine, issued to the medical world, is fully justified by the character of the work. The entire caste of the sys- tem is in keeping with the best thoughts of the leaders and followers of our home school of medicine, and the combi- nation of the scientific study of disease and the practical application of exact and experimental knowledge to the treatment of human maladies, makes every one of us share in the pride that has welcomed Dr. Pepper's labors. Sheared of the prolixity that wearies the readers of the German school, the articles glean these same fields for all that is valuable. It is the outcome of American brains, and is marked throughout by much of the sturdy independence of thought ana originality that is a national characteristic. Yet nowhere is there lack of study of the most advanced views of the day.-North Carolina Medical Journal, Septem- ber, 1886. Habershon on the Abdomen. On the Diseases of the Abdomen; Comprising those of the Stomach, and other parts of the Alimentary Canal, (Esophagus, Caecum, Intestines and Peritoneum. By S. O. Habershon, M.D., Senior Physician to and late Lecturer on Principles and Practice of Medicine at Guy's Hospital, London. Second American from third enlarged and revised English edition. In one handsome octavo volume of 554 pages, with illustrations. Cloth, $3.50. SMITH ON CONSUMPTION; its Early and Remediable Stages. 1 vol. 8vo., 253 pp. Cloth, $2.25. LA ROCHE ON PNEUMONIA. 1 vol. 8vo., 490 pages. Cloth, $3.00. WILLIAMS ON PULMONARY CONSUMPTION; its Na- ture, Varieties, and Treatment. With an analysis of one thousand cases to exemplify its duration. In one 8vo. vol. of 303 pp. Cloth, $2.50. FULLER ON DISEASES OF THE LUNGS AND AIR- PASSAGES. Their Pathology, Physical Diagnosis, Symp- toms and Treatment. From the second and revised English edition. In one octavo volume of 475 pages. Cloth, $3.50. SLADE ON DIPHTHERIA; its Nature and Treatment, with an account of the History of its Prevalence in various Countries. Second and revised edition. In one 12mo. vol., 158 pp. Cloth, $1.25 Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. PRACTICE- (Continued}. ELECTRICITY, CHOLERA, FOOD, HYGIENE. 15 A Dictionary of Treatment; or Therapeutic Index, including Medical and Surgical Therapeutics. By William Whitla, M.D., Professor of Materia Medica and Therapeutics in the Queen's College, Belfast. Revised and adapted to the United States Pharmacopoeia. In one square, octavo volume of 917 pages. Cloth, $4.00. Whitla's Dictionary of Treatment. The several diseased conditions are arranged in alphabet- tical order, and the methods, medical, surgical, dietetic and climatic, by which they may be met, are considered. On every page we find clear arid detailed directions for treatment. The book abounds with useful, practical hints and suggestions. The most experienced members of the profession may usefully consult its pages for the purpose of learning what is really trustworthy in the later thera- peutic developments. The Dictionary, is, in short, the recorded experience of a practical scientific therapeutist, who has carefully studied diseases and disorders at the bed-side and in the consulting-room, and has earnestly addressed himself to the cure and relief of his patients. The Glasgow Medical Journal, April, 1892. Bartholow on Cholera.-Just Ready. Cholera: Its Causes, Symptoms, Pathology and Treatment. By Roberts Bartholow, M.D., LL.D., Emeritus Professor of Materia Medica, General Therapeutics and Hygiene in the Jefferson Medical College of Philadelphia. In one 12mo. volume of 127 pages, with 9 illustrations. Cloth, $1.25. Dr. Bartholow has produced a little book on cholera at once authoritative and complete in its detail. He has shown how all that is absolutely necessary for the practitioner to know about cholera may be compressed into a few pages. Nearly one half the book is given to treatment.-Journal of the American Medical Association, July 15, 1893. We have here a practical book, iu small compass, con- taining the very latest ideas concerning the treatment of cholera, together with the personal experience of the author who has passed through two epidemics of this disease. Historical accounts and long discussions on dis- puted etiological points are omitted and only that which is of most use to the general practitioner is included.- The National Medical Review, August, 1893. BY THE SAME AUTHOR. Medical Electricity. A Practical Treatise on the Applications of Electricity to Medicine and Surgery. Third edition. In one octavo volume of 308 pages, with 110 illustrations. Cloth, $2.50. Professor Bartholow's practical treatise on the application of electricity to medicine and surgery, having reached a third edition, scarcely requires detailed notice. Originally intended for students and practitioners, it starts by assum- ing an " entire unacquaintance with the elements of the subject." The work is fitted by its extreme lucidity for the use of busy practitioners who require a guide in practi- cal electro-therapeutics. - London Lancet, January 14, 1888. Yeo's Manual of Medical Treatment.-Just Ready. A Manual of Medical Treatment or Clinical Therapeutics. By I. Burney Yeo, M.D., F.R.C.P., Professor of Therapeutics in King's College London. In two 12mo. volumes containing 1275 pages, with illustrations. Complete work, cloth, $5.50. In this work disease is studied from the standpoint of treatment, the rational indications for therapeusis being reached through an explanation of the causation and phenomena of disease and of the properties and mode of action of the agencies available for alleviation or cure. The work is rich in selections of formulae used by well-known physicians. BY THE SAME AUTHOR. Food in Health and Disease. In one 12mo. volume of 590 pages. Cloth, $2.00. See Series of Clinical Manuals, page 30. Dr. Yeo supplies in a compact form nearly all that the practitioner requires to know on the subject of diet. The work is divided into two parts-food in health and food in disease. Dr. Yeo has gathered together from all quarters an immense amount of useful information within a com- paratively small compass, and he has arranged and digested his materials with skill for the use of the practitioner. We have seldom seen a book which more thoroughly realizes the object for which it was written than this little work of Dr. Yeo.-British Medical Journal, February 8, 1890. Richardson's Preventive Medicine. Preventive Medicine. By B. W. Richardson, M.D., LL.D., F.R.S., Fellow of the Royal College of Physicians, London. In one 8vo. volume of 729 pages. Cloth, $4.00 ; leather, $5.00. SCHREIBER ON MASSAGE. A Manual of Treatment by Massage and Methodical Muscle Exercise. By Joseph Schreiber, M.D. Translated by Walter Mendelson, M.D., of New York. In one handsome octavo volume of 274 pages, with 117 fine engravings. STILLE ON CHOLERA: Its Origin, History, Causation, Symptoms, Lesions, Prevention and Treatment. In one handsome 12mo. vol. of 163 pages, with a chart. Cloth, $1.25. PAVY'S TREATISE ON THE FUNCTION OF DIGES- TION ; its Disorders and their Treatment. From the second London edition. In one octavo volume of 238 pages. Cloth, $2.00. BARLOW'S MANUAL OF THE PRACTICE OF MEDI- CINE. With additions by D. F. Condie, M.D. In one octavo volume of 603 pages. Cloth, $2.50. CHAMBERS' MANUAL OF DIET AND REGIMEN IN HEALTH AND SICKNESS. In one handsome octavo vol- ume of 302 pages. Cloth, $2.75. A TREATISE ON FEVER. By Robert D. Lyons, K.C.C. In one octavo volume of 354 pages. Cloth, $2.25. LECTURES ON THE STUDY OF FEVER. By A. Hud- son, M.D., M.R.I.A. In one octavo volume of 308 pages. Cloth, $2.50. LA ROCHE ON YELLOW FEVER, in its Historical, Path- ological, Etiological and Therapeutical Relations. Two octavo volumes, 1468 pages. Cloth, $7.00. TANNER'S MANUAL OF CLINICAL MEDICINE AND PHYSICAL DIAGNOSIS. Third American, from the second London edition. Revised and enlarged by Tilbury Fox, M.D. In one 12mo. volume of 362 pages, with illustrations. Cloth, $1.50. DAVIS' CLINICAL LECTURES ON VARIOUS IMPOR- TANT DISEASES. By N. S. Davis, M.D. Edited by Frank H. Davis, M.D. Second edition. 12mo., 287 pages. Cloth, $1.75. TODD'S CLINICAL LECTURES ON CERTAIN ACUTE DISEASES. In one 8vo. volume of 320 pages. Cloth, $2.50. FLINT'S PRACTICAL TREATISE ON THE PHYSICAL EXPLORATION OF THE CHEST AND THE DIAGNOSIS OF DISEASES AFFECTING THE RESPIRATORY ORGANS. Second and revised edition. In one handsome octavo vol- ume of 591 pages. Cloth, $4.50. Lea Brothers & Co., Publishers. 706, 708 & 710 Sansom Street, Philadelphia. 16 NERVOUS AND MENTAL DISEASES. Gray on Nervous and Mental Diseases.-Just Ready. A Practical Treatise on Nervous and Mental Diseases. By Landon Carter Gray, M.D., Professor of Diseases of the Mind and Nervous System in the New York Polyclinic. In one very handsome octavo volume of 681 pages, with 168 illustrations. Cloth, $4.50 ; leather, $5.50. It must have been felt by all that the time had come for a new and representative book, and that the author would be both happy and fortunate who would meet this want in the reading and teaching ranks of the profession. This want we can now say has been met. It is evident that the author has drawn, and drawn profitably, from many sources for illustration and enrichment of his text. This gives the book a special value for literary reference. Another merit consists m the originality and distinctness of many of the photographic illustrations. Dr. Gray always speaks with the dogmatism that marks the original observer and that carries conviction. This tone in the book, which is alwavs well modulated and thoroughly under control, will add attractiveness and weight to the author's utterances. An- other general characteristic that strikes us most favorably is the prominence given to the symptoms and the treat- ment of these diseases. Hence Dr. Gray's book is a very practical one. It does not devote undue space to the mi- croscopic appearances of diseases, nerves and tissues which the general practitioner and student sees hardly once in a lifetime. Pathology and morbid anatomy, so essential to the expert, are not neglected; but therapeutics, the goal of the practitioner, is completely and exhaustively dis- cussed. Dr. Gray's book closes with an important section on mental diseases. This is a unique feature for a text-book on nervous diseases, and one, we are sure, that will com- mend it to many readers. After all, the two classes of sub- jects are closely allied, and a concise treatment of both within the same covers is, for many, a desideratum.-Amer- ican Journal of the Medical Sciences, March, 1893. Ross on Diseases of the Nervous System. A Hand-book on Diseases of the Nervous System. By James Ross, M.D., F.R.C.P., LL.D., Senior Assistant Physician to the Manchester Royal Infirmary. In one octavo volume of 725 pages, with 184 illustrations. Cloth, $4.50; leather, $5.50. This admirable work is intended for students of medicine and for such medical men as have no time for lengthy treatises. In the present instance the duty of arranging the vast store of material at the disposal of the author, ana of abridging the description of the different aspects of ner- vous diseases, has been performed with singular skill, and the result is a concise and philosophical guide to the de- partment of medicine of which it treats. Dr. Ross holds such a high scientific position that any writings which bear his name are naturally expected to have the impress of a powerful intellect. In every part this handbook merits the highest praise, and will no doubt be found of the greatest value to the student as well as to the practitioner.-Edin- burgh Medical Journal, January, 1887. Hamilton on Nervous Diseases.-Second Edition. Nervous Diseases; Their Description and Treatment. By Allan McLane Hamilton, M.D., Attending Physician at the Hospital for Epileptics and Paralytics, Blackwell's Island, N. Y. Second edition, thoroughly revised and rewritten. In one octavo volume of 598 pages, with 72 illustrations. Cloth, $4.00. Savage on Insanity and Allied Neuroses. Insanity and Allied Neuroses, Practical and Clinical. By George H. Savage, M.D., Lecturer on Mental Diseases at Guy's Hospital, London. In one 12mo. volume of 551 pages, with 18 illustrations. Cloth, $2.00. See Series of Clinical Manuals, page 30. Tuke on the Influence of the Mind upon the Body. Illustrations of the Influence of the Mind Upon the Body in Health and Disease. Designed to elucidate the Action of the Imagination. By Daniel Hack Tuke, M.D., Joint Author of the Manual of Psychological Medicine, etc. New edition, thoroughly revised and rewritten. In one 8vo. volume of 467 pages, with 2 colored plates. Cloth, $3.00. Guided by an enlightened deduction, the author has reclaimed for science a most interesting domain in psy- chology, previously abandoned to charlatans and empirics. This book, Well conceived and well written, must com- mend itself to every thoughtful understanding.-New York Medical Journal, September 6, 1884. Clouston on Mental Diseases. Clinical Lectures on Mental Diseases. By Thomas S. Clouston, M.D., Lecturer on Mental Diseases in the University of Edinburgh. With an Appendix, containing an abstract of the Statutes of the United States and of the Several States and Territories relating to the Custody of the Insane. By Charles F. Folsom, M.D., Assistant Professor of Mental Diseases, Medical Department of Harvard University. In one octavo volume of 541 pages, with 8 lithographic plates, 4 of which are colored. Cloth, $4.00. Dr.'Folsom's Abstract also separate, in one 8vo. volume of 108 pages. Cloth, $1.50 The descriptions of the diseases and cases are simple and practical, but true ; and one sees as he reads that they are given by one perfectly familiar from daily observation'with the cases and diseases he is speaking of. One feature of the book which commends it highly, and which is not to be found in any other work on mental diseases, are the hints and descriptions given as to the practical management and care of the cases. We can heartily recommend it to the student and busy general practitioner. Dr. Folsom's work greatly increases the value of Dr. Clouston's book for the American practitioner.-Archives of Medicine, June, 1884. Playfair on Nerve Prostration and Hysteria. The Systematic Treatment of Nerve Prostration and Hysteria. By W. S. Playfair, M.D., F.R.C.P. In one 12mo. volume of 97 pages. Cloth, $1.00. BLANDFORD ON INSANITY AND ITS TREATMENT. Lectures on the Treatment, Medical and Legal, of Insane Patients. In one very handsome octave volume. JONES' CLINICAL OBSERVATIONS ON FUNCTIONAL NERVOUS DISORDERS. Second American edition. In one handsome octavo volume of 340 pages. Cloth, S3.25. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. PATHOLOGY, HISTOLOGY, BACTERIOLOGY. 17 Gibbes' Practical Pathology and Morbid Histology. Practical Pathology and Morbid Histology. By Heneage Gibbes, M.D., Professor of Pathology in the University of Michigan, Medical Department. In one very handsome 8vo. volume of 314 pages, with 60 illustrations, mostly photographic. Cloth, $2.75. This is, in part, an expansion of the little work published by the author some years ago, and his acknowledged skill as a practical microscopist will give weight to his instruc- tions. Indeed, in fullness of directions as to the modes of investigating morbid tissues, the book leaves little to be desired. The work is throughout profusely illustrated with reproductions of micro-photographs. We may say that the practical histologist will gain much useful information from the book.- The London Lancet, January 23,1892. Abbott's Bacteriology. The Principles of Bacteriology : a Practical Manual for Students and Physicians. By A. C. Abbott, M.D., First Assistant, Laboratory of Hygiene, University of Pennsylvania, Philadelphia. In one 12mo. volume of 259 pages, with 32 illustrations. Cloth, $2.00. To a person desiring to learn the technique of bacterio-1 logical work, we cannot recommend any work which will be more suitable than the one before us. Dr. Abbott has shown great judgment in the selection and arrangement of his material. The student who follows it closely will be in a condition to carry forward the work for himself. Medical practitioners generally could read the work with profit, especially the chapters on sterilization and disinfection, and those on tuberculosis and diphtheria in the second part.- The Canadian Practitioner, Nov. 1, 1892. Senn's Surgical Bacteriology.-Second Edition. Surgical Bacteriology. By Nicholas Senn, M.D., Ph.D., Professor of Surgery in Rush Medical College, Chicago. New (second) edition. In one handsome octavo volume of 268 pages, with 13 plates, of which 10 are colored, and 9 engravings. Cloth, $2.00. The book is really a systematic collection in the most con- cise form of such results as are published in current medi- cal literature by the ablest workers in this field of surgical progress; and to these are added the author's own views and the results of his clinical experience and original investigations. The book is valuable to the student, but its chief value lies in the fact that such a compilation makes it possible for the busy practitioner, whose time for reading is limited and whose' sources of information are often few, to become conversant with the most modern and advanced ideas in surgical pathology, which have "laid the founda- tion for the wonderful achievements of modern surgery."- Annals of Surgery, March, 1892. Green's Pathology and Morbid Anatomy.-Seventh Edition. Pathology and Morbid Anatomy. By T. Henry Green, M.D., Lecturer on Pathology and Morbid Anatomy at Charing-Cross Hospital Medical School, London. Sixth American from the seventh revised English edition. Octavo volume of 539 pages, with 167 engravings. Cloth, $2.75. There is scarcely an intelligent physician anywhere who has not the work in his library, for it is almost an essential. In fact it is better adapted to the wants of general prac- titioners than any work of the kind with which we are acquainted. The works of German authors upon pathology, which have been translated into English, are too abstruse for the physician. Dr. Green's work precisely meets his wishes. The fact that it is so generally employed as a text- book by medical students is evidence that we have not spoken too much in its favor.-Cincinnati Medical News, October, 1889. Payne's General Pathology. A Manual of General Pathology. Designed as an Introduction to the Practice of Medicine. By Joseph F. Payne, M.D., F.R.C.P., Lecturer on Pathological Anatomy, St. Thomas' Hospital, London. Octavo volume of 524 pages, with 152 illustrations and a colored plate. Cloth, $3.50. Knowing, as a teacher and examiner, the exact needs of medical students, the author has in the work before us prepared for their especial use what we do not hesitate to say is the best introduction to general pathology that we have yet examined. A departure which our author has taken is the greater attention paid to the causation of dis- ease, and more especially to the etiological factors in those diseases now with reasonable certainty ascribed to patho- genetic microbes. In this department he has been very full and explicit, not only in a descriptive manner, but in the technique of investigation. The Appendix, giving methods of research, is alone worth the price of the took, several times over, to every student of pathology.-St. Louis Medical and Surgical Journal, January, 1889. Coats' Treatise on Pathology. A Treatise on Pathology. By Joseph Coats, M.D., F.F.P.S., Pathologist to the Glasgow Western Infirmary. In one octavo volume of 829 pages, with 339 illustrations. Cloth, $5.50 ; leather, $6.50. We are very much pleased with this book, which, for general practitioners and students, comes nearer to our idea of perfection than any we know on this subject, within the same dimensions. The style is exceedingly good, being plain, concise and practical without being like a dictionary. We have pleasure in recommending it to students, as we think it well adapted for their use.-Canadian Practitioner, December, 1883. Klein's Histology.-Fourth Edition. Elements of Histology. By E. Klein, M.D., F.R.S., Joint Lecturer on General Anatomy and Physiology in the Medical School of St. Bartholomew's Hospital, London. Fourth edition. In one 12mo. volume of 376 pages, with 194 illus. Limp cloth, $1.75. See Series of Manuals, page 30. The large number of editions through which Dr. Klein's little handbook of histology has run since its first appear- ance in 1883 is ample evidence that it is appreciated by the medical student and that it supplies a definite want. The clear and concise manner in which it is written, the ab- sence of debatable matter, of conflicting views, and the con- venient size of the book and its moderate price, will account for its undoubted success.- Medical Chronicle, Feb., 1890. Histology, Pathology and Bacteriology. Cloth. $1. See Students! Quiz Series, p. 30. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 18 SURGERY. Roberts' Modern Surgery. The Principles and Practice of Modern Surgery. For the use of Students and Practi- tioners of Medicine and Surgery. By John B. Roberts, M.D., Professor of Anatomy and Surgery in the Philadelphia Polyclinic. Professor of the Principles and Practice of Surgery in the Woman's Medical College of Pennsylvania. Lecturer on Anatomy in the University of Pennsylvania. In one very handsome octavo volume of 780 pages, with 501 illustrations. Cloth, $4.50 ; leather, $5.50. This work is a very comprehensive manual upon general surgery, and will doubtless meet with a favorable reception by the"profession. It has a thoroughly practical character, the subjects are treated with rare judgment, its conclusions are in accord with those of the leading practitioners of the art, and its literature is fully up to all the advanced doc- trines and methods of practice of the present day. Its gen- eral arrangement follows this rule, and the author, in his desire to be concise and practical, is at times almost dog- matic, but this is entirely excusable considering the ad- mirable manner in which he has thus increased the useful- ness of his work.-Medical Record, January 17,1891. Ashhurst's Surgery.-New (Sixth) Edition. The Principles and Practice of Surgery. By John Ashhurst, Jr., M.D., Barton Professor of Surgery and Clinical Surgery in the University of Pennsylvania, Surgeon to the Pennsylvania Hospital, Philadelphia. New (6th) edition, enlarged and thoroughly revised. In one octavo volume of about 1150 pages, with about 650 illustrations. Heady very shortly. A notice of the previous edition is appended. A complete and most excellent work on surgery. It is only necessary to examine it to see at once its excellence and real merit either as text-book for the student or a guide for the general practitioner. It fully considers in detail every surgical injury and disease to which the body is liable, and every advance in surgery worth noting is to be found in its proper place. It is unquestionably the best and most complete single volume on surgery, in the English language, and cannot but receive that continued apprecia- tion which its merits justly demand.- Southern Practitioner, February, 1890. Druitt's Modern Surgery.-Twelfth Edition. Manual of Modem Surgery. By Robert Druitt, M.R.C.S. Twelfth edition, thoroughly revised by Stanley Boyd, M.B., B.S., F.R.C.S. In one 8vo. volume of 965 pages, with 373 illustrations. Cloth, $4.00 ; leather, $5.00. Druitt's Surgery has been an exceedingly popular work in the profession. It is stated that 50,000 copies have been sold in England, while in the United States, ever since its first issue, it has been used as a text-book to a very large extent. During the late war in this country it was so highly appreciated that a copy was issued by the Govern- ment to each surgeon. The present edition, while it has the same features peculiar to the work at first, embodies all recent discoveries in surgery, and is fully up to the times. -Cincinnati Medical News, September, 1887. Gross' System of Surgery.-Sixth Edition. A System of Surgery. By Samuel D. Gross, M.D., LL.D., Emeritus Professor of Surgery in the Jefferson Medical College of Philadelphia. Sixth edition. In two large imperial octavo volumes containing 2382 pages, illustrated with 1623 engravings. Leather, $15.00 ; half Russia, $16.00. Surgery. Cloth, $1.75. See Students' Quiz Series, page 30. Young's Orthopaedic Surgery.-In Press. A Manual of Orthopaedic Surgery, for Students and Practitioners. By James K. Young, M.D., Instructor in Orthopiedic Surgery, University of Pennsylvania, Philadelphia. In one 12mo. volume of about 400 pages, fully illustrated. Butlin on the Tongue. Diseases of the Tongue. By Henry T. Butlin, F.R.C.S., Assistant Surgeon to St. Bartho- lomew's Hospital, London. In one 12mo. volume of 456 pages, with 8 colored plates and 3 woodcuts. Cloth, $3.50. See Series of Clinical Manuals, page 30. Gould's Surgical Diagnosis. Elements of Surgical Diagnosis. By A. Pearce Gould, M.S., M.B., F.R.C.S., Assistant Surgeon to Middlesex Hospital, London. In one pocket-size 12mo. volume of 589 pages. Cloth, $2.00. See Studentd Series of Manuals, page 30. Schafer's Histology.-Third Edition. The Essentials of Histology. By Edward A. Schafer, M.D., F.R.S., Jodrell Professor of Physiology in University College, London. New (third) edition. In one octavo volume of 311 pages, with 325 illustrations. Cloth, $3.00. PEPPER'S SURGICAL PATHOLOGY. In one pocket-size 12mo. volume of 511 pages, with 81 illustrations. Limp cloth, red edges, $2.00. See Students' Series of Manuals, page 30. PIRRIE'S PRINCIPLES AND PRACTICE OF SURGERY. Edited bv John Neill, M.D. In one octavo volume of 784 pages, with 316 illustrations. Cloth, $3.75. GANT'S STUDENT'S SURGERY. By Frederick James Gant, F.R.C.S. Square octavo, 848 pages, 159 engravings. Cloth, $3.75. MILLER'S PRACTICE OF SURGERY. Fourth and re- vised American edition. In one large octavo volume of 682 pages, with 364 illustrations. Cloth, $3.75. MILLER'S PRINCIPLES OF SURGERY. Fourth Ameri- can from the third Edinburgh edition. In one octavo vol- ume of 638 pages, with 340 illustrations. Cloth, $3.75. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. SURGERY-(Continued}. 19 Erichsen's Science and Art of Surgery.-Eighth Edition. The Science and Art of Surgery; Being a Treatise on Surgical Injuries, Diseases and Operations. By John E. Erichsen, F.R.S., F.R.C.S., Professor of Surgery in the University College, London, etc. From the eighth and enlarged English edition. In two large octavo volumes of 2316 pages, with 984 engravings on wood. Cloth, $9.00 ; leather, $11.00. For many years this classic work has been made by pref- erence of teachers the principal text-book on surgery for medical students, while through translations into the lead- ing continental languages it may be said to guide the sur- gical teachings of the civilized world. No excellence of the former edition has been dropped and no discovery, de- vice or improvement which has marked the progress of surgery during the last decade has been omitted. The illustrations are many and executed in the highest style of art.- Louisville Medical News, February 14,1885. Bryant's Practice of Surgery.-Fourth Edition. The Practice of Surgery. By Thomas Bryant, F.R.C.S., Surgeon and Lecturer on Surgery at Guy's Hospital, London. Fourth American from the fourth and revised English edition. In one large imperial octavo volume of 1040 pages, with 727 illustrations. Cloth, $6.50 ; leather, $7.50. The fourth edition of this work is fully abreast of the times. The author handles his subjects with that degree of judgment and skill which is attained by years of patient toil and varied experience. The present edition is a thor- ough revision of those which preceded it, with much new matter added. His diction is so graceful and logical, and his explanations are so lucid, as to place the work among the highest order of text-books for the medical student. Almost every topic in surgery is presented in such a form as to enable the busy practitioner to review any subject in every-day practice in a short time. No time is lost with useless theories or superfluous verbiage. In short, the work is eminently clear, logical and practical.-Chicago Medical Journal and Examiner, April, 1886. Wharton's Minor Surgery and Bandaging.-New (2d) Ed. Minor Surgery and Bandaging. By Henry R. Wharton, M.D., Demonstrator of Surgery in the University of Pennsylvania. In one 12mo. volume of 529 pages, with 416 engravings, many being photographic. Cloth, $3.00. Just ready. A notice of the previous edition is appended. This new work must take a first rank as soon as exam- ined. Bandaging is well described by words, and the methods are illustrated by photographic drawings, so as to make plain each step taken in the application of bandages of various kinds to different parts of the body and extrem- ities-including the head. The various operations are like- wise described and illustrated, so that it would seem easy for the tyro to do the gravest amputation. The various es- tablished operations are described in detail. Hence this work becomes a most valuable companion-book to any of the more pretentious treatises on surgery, where simply the general advice is given to bandage, amputate, intubate, operate, etc. For the student and young surgeon, it is a very valuable instruction book from which to learn how to do what may be advised, in general terms, to be done.- Virginia Medical Monthly, October, 1891. Treves' Operative Surgery.-Two Volumes. A Manual of Operative Surgery. By Frederick Treves, F.R.C.S., Surgeon and Lecturer on Anatomy at the London Hospital. In two octavo volumes containing 1550 pages, with 422 engravings. Complete work, cloth, $9.00; leather, $11.00. Mr. Treves in this admirable manual of operative sur- gery has in each instance practically assumed that opera- tion has been decided upon and has then proceeded to give the various operative methods which tnay be employed, with a criticism of their comparative value and a detailed and careful description of each particular stage of their performance. Especial attention has been paid to the pre- paratory treatment of the patient and to the details of the after-treatment of the case, and this is one of the most dis- tinctive among the many excellent features of the book. We declare it the best work on the subject in the English language, and indeed, in many respects, the best in any language. It cannot fail to be of the greatest use both to practical surgeons and to those general practitioners who, owing to their isolation or to other circumstances, are forced to do much of their own operative work. We recommend the book so strongly for the excellent judgment displayed in the arduous task of selecting from among the thousands of varying procedures those most worthy of description; for the way in which the still more difficult task of choosing among the best of those has been accomplished ; and for the simple, clear, straightforward manner in which the information thus gathered from all surgical literature has been con- veyed to the reader.-Annals of Surgery, March, 1892. Treves' Student's Hand-Book of Surgical Operations. In one square 12mo. volume of 508 pages, with 94 illustrations. Cloth, $2.50. A Manual of Surgery. In Treatises by various Authors, edited by Frederick Treves, F.R.C.S. In three 12mo. volumes, containing 1866 pages, with 213 engravings. Price per set, cloth, $6.00. See Students' Series of Manuals, page 30. We have here the opinions of thirty-three authors, in an encyclopaedic form for easy and ready reference. The three volumes embrace every variety of surgical affections likely to be met with, the paragraphs are short and pithy, I and the salient points and the beginnings of new subjects are always printed in extra-heavy type, so that a person may And whatever information he may be in need of at a moment's glance.-Cincinnati Lancet-Clinic, August 21,1886. Treves on Intestinal Obstruction. In one 12mo. volume of 522 pages, with 60 illustrations. Limp cloth, blue edges, $2.00. See Series of Clinical Manuals, page 30. Holmes' System of Surgery.-American Edition. A System of Surgery; Theoretical and Practical. IN TREATISES BY VARIOUS AUTHORS. Edited by Timothy Holmes, M.A., Surgeon and Lecturer on Surgery at St. George's Hospital, London. American edition, thoroughly revised and re-edited by John H. Packard, M.D. Three large octavo volumes of 3137 pages, with 979 illustrations on wood and 13 lithographic plates. Per set, cloth, $18.00; leather, $21.00. Subscription only. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 20 SURGERY-(Continued), FRACTURES, DISLOCATIONS. Smith's Operative Surgery.-Revised Edition. The Principles and Practice of Operative Surgery. By Stephen Smith, M.D., Professor of Clinical Surgery in the University of the City of New York. Second and thoroughly revised edition. In one very handsome octavo volume of 892 pages, with 1005 illustrations. Cloth, $4.00 ; leather, $5.00. This excellent and very valuable book is one of the most satisfactory works on modern operative surgery yet pub- lished. The book is a compendium for the modern sur- geon. The present edition is much enlarged, and the text has been thoroughly revised, so as to give the most im- proved methods in aseptic surgery and the latest instru- ments known for operative work. It can be truly said that, as a handbook for the student, a companion for the sur- geon, and even as a book of reference for the physician not especially engaged in the practice of surgery, this volume will long hold a most conspicuous place, ana seldom will its readers, no matter how unusual the subject, consult its pages in vain. Its compact form, excellent print, numerous illustrations, and especially its decidedly practical char- acter, all combine to commend it.- Boston Medical and Sur- gical Journal, May 10, 1888. Holmes' Treatise on Surgery.-One Volume. A Treatise on Surgery; Its Principles and Practice. By Timothy Holmes, M.A., Surgeon and Lecturer on Surgery at St. George's Hospital London. From the fifth English edition, edited by T. Pickering Pick, F.R.C.S. In one octavo volume of 997 pages, with 428 illustrations. Cloth, $6.00 ; leather, $7.00. To the younger members of the profession and to others not acquainted with the book and its merits, we take pleasure in recommending it as a surgery complete, thor- ough, well written, fully illustrated, modem, a work suffi- ciently voluminous for the surgeon specialist, adequately concise for the general practitioner, teaching those things that are necessary to be known for the successful prosecu- tion of the surgeon's career, imparting nothing that in our present knowledge is considered unsafe, unscientific or inexpedient.-Pacific Medical Journal, July, 1889. Hamilton on Fractures and Dislocations.-Eighth Edition. A Practical Treatise on Fractures and Dislocations. By Frank H. Hamilton, M.D., LL.D., Surgeon to Bellevue Hospital, New York. New (eighth) edition, revised and edited by Stephen Smith, M.D., Professor of Clinical Surgery in the University of the City of New York. In one octavo volume of 832 pages, with 507 illustrations. Cloth, $5.50; leather, $6.50. Its numerous editions are convincing proof, if any is needed, of its value and popularity. It is preeminently'the authority on fractures and dislocations, and universally quoted as such. In the new edition it has lost none of its former worth. The additions it has received by its recent revision make it a work thoroughly in accordance with modern practice theoretically, mechanically, aseptically. The task of writing a complete treatise on a subject of such magnitude is no easy one. Dr. Smith has aimed to make the present volume a correct exponent of our knowl- edge of this-department of surgery. In examining the vol- ume one is at once struck with the evidence of the vast amount of labor its compilation and reconstruction must have necessitated. The more one reads the more one is impressed with its completeness. The work has been ac- complished, and has been done clearly, concisely and ex- cellently well.-Boston Medical and Surgical Journal, May 26, 1892. Stimson's Operative Surgery.-Second Edition. A Manual of Operative Surgery. By Lewis A. Stimson, B.A., M.D., Professor of Clinical Surgery in the University of the City of New York. Second edition. In one royal 12mo. volume of 503 pages, with 342 illustrations. Cloth, $2.50. The author knows the difficult art of condensation. Thus the manual serves as a work of reference, and at the same time as a handy guide. It teaches what it professes, the steps of operations. In this edition Dr. Stimson has sought to indicate the changes that have been effected in operative methods and procedures by the antiseptic sys- tern, and has added an account of many new operations and variations in the steps of older operations. We do not desire to extol this manual above many excellent standard British publications of the same class, still we believe that it contains much that is worthy of imitation.-British Med- ical Journal, January 22, 1887. Stimson on Fractures and Dislocations. A Treatise on Fractures and Dislocations. By Lewis A. Stimson, M.D. In two hand- some octavo volumes. Volume I., Fractures, 582 pages, 360 illustrations. Volume II., Dislocations, 540 pages, with 163 illustrations. Complete work, cloth, $5.50; leather, $7.50. Either volume separately, cloth, $3.00 ; leather, $4.00. The appearance of the second volume marks the comple- tion of the author's original plan of preparing a work which should present in the fullest manner all that is known on the cognate subjects of Fractures and Disloca- tions. The volume on Fractures assumed at once the posi- tion of authority on the subject, and its companion on Dislocations will no doubt be similarly received. This vol- ume exhibits the surgery of Dislocations as it is taught and practised by the most eminent surgeons of the present time. Containing the results of such extended researches, it must for a long time be regarded as an authority on all subjects pertaining to dislocations. Every practitioner of surgery will feel it incumbent on him to have it for constant reference.-Cincinnati Medical News, May, 1888. Pick on Fractures and Dislocations. Fractures and Dislocations. By T. Pickering Pick, F.R.C.S., Surgeon to and Lecturer on Surgery at St. George's Hospital, London. In one 12mo. volume of 530 pages, with 93 illustrations. Limp cloth, $2.00. See Series of Clinical Manuals, page 30. Marsh on the Joints. Diseases of the Joints. By Howard Marsh, F.R.C.S., Senior Assistant Surgeon to St. Bartholomew's Hospital, London. In one 12mo. volume of 468 pages, with 64 woodcuts and a colored plate. Cloth, $2.00. See Series of Clinical Manuals, page 30. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. OPHTHALMOLOGY. 21 A Text=book of Ophthalmology. JUST READY. By WILLIAM F. NORRIS, M.D., Professor of Ophthalmology in the University of Pennsylvania. and CHARLES A. OLIVER, M.D., Surgeon to Wills Eye Hospital, Philadelphia. In one very handsome octavo volume of 641 pages, with 357 engravings and 5 colored plates. Cloth, $5.00; leather, $6.00. The preparation of this magnificent work has engaged its eminent authors during a period exceeding seven years, their effort being to produce a guide for the student and practitioner which should represent the most advanced state of its science in the clearest possible manner. The volume embodies not only the results of large personal experience but also of most extensive acquaintance with the vast and rich literature of its department. By a careful selection of material and the employment of a terse style the Authors have presented an ample working knowledge of their subject in a volume of convenient size. The series of illustrations is singularly rich and is thoroughly in keeping with the literary material which it embellishes. The volume is assured of the foremost position as a text-book and work of reference. Berry on the Eye.-New Edition. Just Ready. Diseases of the Eye. A Practical Treatise for Students of Ophthalmology. By George A. Berry, M.B., F.R.C.S., Ed., Ophthalmic Surgeon, Edinburgh Royal Infirmary. New (second) edition. In one octavo volume of 750 pages, and 197 illustrations, mostly lithographic. Cloth, $8.00. The most notable feature of Berry's book is its wealth of beautifully colored illustrations introduced throughout in immediate connection with the related text. The present edition contains a large number of these that are entirely new, making in all eighty-seven, the finest collec- tion of such illustrations of the normal and pathological appearances of the eye to be found in any work published in the English language. To the practitioner who has not the advantage of a large special clinic in which to become familiar with the rarer forms of eye disease, such illustra- tions are invaluable.-Philadelphia Polyclinic, June 15,1893. We are glad to see that a new edition of Mr. Berry's excellent manual has been called for. It has been enlarged to the extent of about fifty pages. The chapters have been rearranged and in many instances considerably augmented. The work is extremely well written, so that it gives the stu- dent a fairly complete account of the diseases of the eye he is likely to meet with in practice, and the treatment recom- mended may be thoroughly relied on as the result of careful observation and of considerable experience.-The Lancet, London, April 29, 1893. Juler's Ophthalmic Science & Practice.-New Ed. Just Ready. A Handbook of Ophthalmic Science and Practice. By Henry E. Juler, F.R.C.S., Ophthalmic Surgeon to St. Mary's Hospital, Surgeon to the Royal Westminster Ophthalmic Hospital, London. New (second) edition, revised and enlarged. In one handsome octavo volume of 562 pages, with 201 engravings, 17 colored platgs, test-types and color blindness test. Cloth, $5.50 ; leather, $6.50. It is but comparatively a few years since the profession first had the opportunity of studying and appreciating the exhaustive and scientific work on ophthalmic science and practice from the pen of Mr. Juler. In that work, the second edition of which we now have the pleasure of notic- ing, the author was eminently successful in giving concise descriptions and typical illustrations of all the most im- portant affections of the eye and of its appendages. The second edition of Air. Jnler's work has, we know, been anxiously waited for. The author has made numerous alterations and additions, alike in the text and in the illus- trations, so that the reader is provided in a readable form, and with a conciseness thoroughly compatible with accur- acy of description, with all that is most modem on the subject of ophthalmology. We would especially refer our readers to tbe chapter on the refraction of the eye, a sub- ject of essential importance in the diagnosis and treatment of optical errors. We confidently anticipate a most cordial welcome to this work alike by students and practitioners of medicine.- The Practitioner, July, 1893. Nettleship on the Eye.-Fifth Edition. Diseases of the Eye. By Edward Nettleship, F.R.C.S., Ophthalmic Surgeon at St. Thomas' Hospital, London. Surgeon to the Royal London (Moorfields) Ophthalmic Hospital. Fourth American from the fifth English edition, thoroughly revised. With a Supplement on the Detection of Color Blindness, by William Thomson, M.D., Professor of Ophthalmology in the Jefferson Medical College, Philadelphia. In one 12mo. volume of 500 pages, with 164 illustrations, selections from Snellen's test-types and formulae, and a colored plate. Cloth, §2.00. This is a well-known and a valuable work. It was pri- marily intended for the use of students, and supplies their needs admirably, but it is as useful for the practi- tioner, or indeed more so. It does not presuppose the large amount of recondite knowledge to be present which seems to be assumed in some of our larger works, is not tedious from over-conciseness, and yet covers the more important Sarts of clinical ophthalmology.-New York Medical Journal, •ec. 13, 1890. Eye, Ear, Throat and Nose. Cloth, $1.00. See Student Quiz Series, page so. Carter & Frost's Ophthalmic Surgery. Ophthalmic Surgery. ByR. Brudenell Carter, F.R.C.S., Lecturer on Ophthalmic Surgery at St. George's Hospital, London, and W. Adams Frost, F.R.C.S., Joint Leet, on Oph. Surgery at St. George's Hospital, London. In one 12mo. volume of 559 pages, with 91 woodcuts, color-blindness test, test-types and dots, and appendix of formulae. Cloth, $2.25. See Series of Clinical Manuals, p. 30. WELLS ON THE EYE. In one octavo volume. LAWSON ON INJURIES TO THE EYE, ORBIT AND EYELIDS : Their Immediate and Remote Effects. Octavo of 404 pages, with 92 illustrations. Cloth, 83.50. LAURENCE AND MOON'S HANDY BOOK OF OPH- THALMIC SURGERY, for the use of Practitioners. Second edition. In one octavo volume of 227 pages, with 65 illus- trations. Cloth, 82.75. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 22 OTOLOGY AND LARYNGOLOGY. Burnett on the Ear.-Second Edition. The Ear; Its Anatomy, Physiology and Diseases. A Practical Treatise for the Use of Medical Students and Practitioners. By Charles H. Burnett, A. M., M. D., Professor of Otology in the Philadelphia Polyclinic; President of the American Otological Society. Second edition. In one handsome octavo volume of 580 pages, with 107 illustrations. Cloth, $4.00 ; leather, $5.00. We note with pleasure the appearance of a second edition of this valuable work. When it first came out it was accepted by the profession as one of the few standard works on modem aural surgery in the English language, and in his second edition Dr. Burnett has fully maintained his reputation, for the book is replete with valuable informa- tion and suggestion. The revision has been carefully car- ried out and much new matter added. Dr. Burnett's work must be regarded as a very valuable contribution to aural surgery, not only on account of its comprehensiveness, but because it contains the results of the careful personal ob- servation and experience of this eminent aural surgeon.- London Lancet, February 21,1885. We are very glad, after many years' use of the first, to welcome the second edition of this excellent text-book to our shelves. The first 138 pages are devoted to a lucid ac- count of the anatomy, histology and physiology of this most complex organ. The cuts which accompany this part of the work will prove of much use to the student. The second part of the work consists of a clear and terse account of the diseases of the ear and their treatment. In the latter department the rules laid down are eminentlv prac- tical. We can cordially commend the book to all who wish a text-book on the ear.-New Orleans Medical and Surgical Journal, February, 1885. Field's Manual of Diseases of the Ear.-Just Ready. A Manual of Diseases of the Ear. By George P. Field, M.R.C.S., Aural Surgeon and Lecturer on Aural Surgery in St. Mary's Hospital School, London. Fourth edition. In one octavo volume of 391 pages, with 73 engravings and 21 colored plates. Cloth, $3.75. There can be no question of the need of more perfect knowledge of the pathology of the ear, on the part of general practitioners of medicine. Professor Field has given us a work which makes clear the intricacies of aural anatomy and pathology by the exactness and multiplicity of its illustrations no less than by the explanations of the text, Its popularity is evidenced by the fact that three editions have already been disposed of, the last numbering 3000 copies. The work has, of course, been revised to keep pace with the times.-The Medical Age, July 25, 1893. This book is written by an authority on this subject, and may be recommended as a good text-book for the student and a safe and reliable guide for the practitioner.-Edin- burgh Medical Journal, May, 1893. Politzer's Text=Book of Diseases of the Ear.-New Ed. In Press. A Text-Book of Diseases of the Ear and Adjacent Organs. By Dr. Adam Politzer, Imperial-Royal Professor of Aural Therapeutics in the University of Vienna. Translated into English. In one large octavo volume of about 800 pages, with about 300 engravings. Browne on the Throat and Nose.-New Ed. Just Ready. The Throat and Nose and Their Diseases. By Lennox Browne, F.R.C.S., E., Senior Physician to the Central London Throat and Ear Hospital. Fourth and enlarged edition. In one imperial octavo volume of about 750 pages, with 120 illustrations in color, and 235 engravings on wood. Cloth, $6.50. A few notices of the previous edition are appended. The beautiful and typical colored plates form a valuable and instructive atlas, the equal of which is not to be found in any modern work treating of these subjects. Mr. Len- nox Browne is to be congratulated on having produced the best practical text-book on diseases of the throat and nose extant. We are glad to learn that it is being translated into French and German.-The Provincial Medical Journal, August 1,1890. As a practical work on the treatment of diseases of the throat and nose this will be found an exceedingly valuable volume. The methods are fully set forth in the text, and references are made to a very complete and valuable list of formulae. The engravings are upon wood, and all reproduc- tions from the author's pen and ink drawings, by the photo- engraving process. Fifteen colored lithographic plates con- taining one hundred and twenty illustrations give an added value to the volume. While this work will be of essential service to the specialist it is one that should find a place in the library of every practising physician. It serves admir- ably toillustrate the progress that is being made in medical literature and especially in the departments which are con- sidered.-Journal of the American Medical Asso., Dec. 6,1890. Seiler on the Throat and Nose.-New (4th) Ed. Just Ready. A Handbook of Diagnosis and Treatment of Diseases of the Throat, Nose and NaSO-Pharynx. By Carl Seiler, M.D., Lecturer on Laryngoscopy in the University of Pennsylvania. New (fourth) edition. In one handsome 12mo. volume of 414 pages, with 107 illustrations and 2 colored plates. Cloth, $2.25. The mere fact that this work has reached a fourth edi- tion is sufficient evidence that it fills a want long felt by "average general practitioners." As a book of quick, ready reference it has no rival in the field of laryngology, and the directions are usually such as to be readily carried out, even by comparative tyros in the work. The first five chapters deal with the anatomy, physiology and methods of examination of the upper respiratory tract, and are most clear and practical, and are also excellently illustrated. This edition will probably be eagerly welcomed by those for whom it was written, and will be a useful addition to libraries of students and general practitioners. -Medical News, July 15, 1893. The fourth edition of this work is up to the required standard, which is the highest for one of its scope. It is concise and practical, treating of the commoner diseases of the throat and naso-pharynx, and presenting the salient features in an intelligible and interesting manner.-Medical Record, June 24,1893. The fourth edition of Seiler's admirable work should be warmly received by both practitioners and students, as it well deserves. There is no special work of its size, on dis- eases of the throat and nose, that contains more informa- tiion; yet it is arranged in such a concise, compact form that it makes an exceedingly handy reference book for the busy practitioner as well as a good text-book for the stu- dent.- Pacific Medical Record, May, 1893. Diseases of the Eye, Ear, Throat and Nose. Cloth, $1.00. See Studentd Quiz Series, page 30. BROWNE ON KOCH'S REMEDY IN RELATION TO I pages, with 45 illustrations, 4 of which are colored, and 17 THROAT CONSUMPTION. In one octavo volume of 121 | charts. Cloth, SI.50. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. URINARY AND RENAL DISEASES, DENTISTRY. 23 Roberts on Urinary and Renal Diseases.-Fourth Edition. A Practical Treatise on Urinary and Renal Diseases, including Urinary Deposits. By Sir William Roberts, M. D., Lecturer on Medicine in the Manchester School of Medicine, etc. Fourth American from the fourth London edition. In one handsome octavo volume of 609 pages, with 81 illustrations. Cloth, $3.50. It may be said to be the best book in print on the subject of which it treats.- The American Journal of the Medical Sciences, January, 1886. The peculiar value and finish of the book are in a measure derived from its resolute maintenance of a clinical and practical character. It is an unrivalled exposition of every- thing which relates directly or indirectly to the diagnosis, prognosis and treatment of urinary diseases, and possesses a completeness not found elsewhere in our language in its account of the different affections.-The Manchester Medical Chronicle, July, 1885. Purdy on Bright's Disease and Allied Affections. Bright's Disease and Allied Affections of the Kidneys. By Charles W. Purdy, M.D., Professor of Genito-Urinary and Renal Diseases in the Chicago Polyclinic. In one octavo volume of 288 pages, with illustrations. Cloth, $2.00. The object of this work is to "furnish a systematic, prac- tical ana concise description of the pathology and treat- ment of the chief organic diseases of the kidney associated with albuminuria, which shall represent the most recent advances in our knowledge on these subjectsand this definition of the object is a fair description of the book. The work is a useful one, giving in a short space the theo- ries, facts and treatments, and going more fully into their later developments. On treatment the writer is particularly strong, steering clear of generalities, and seldom omitting, what text-books usually do, the unimportant items which are all important to the general practitioner.- The Manches- ter Medical Chronicle, October, 1886. Gross on the Urinary Organs. A Practical Treatise on the Diseases, Injuries and Malformations of the Urinary Bladder, the Prostate Gland and the Urethra. By Samuel D. Gross, M.D., LL.D., D.C.L., etc. Third edition, thoroughly revised by Samuel W. Gross, M.D. In one octavo volume of 574 pages, with 170 illustrations. Cloth, $4.50. Morris on Surgical Diseases of the Kidney. Surgical Diseases of the Kidney. By Henry Morris, F.R.C.S., Surgeon to the Middlesex Hospital, London. 12mo. 554 pages, with 40 woodcuts, and 6 colored plates. Limp cloth, $2.25. See Series of Clinical Manuals, page 30. Thompson on the Urinary Organs. Lectures on Diseases of the Urinary Organs. By Sir Henry Thompson, Surgeon and Professor of Clinical Surgery to University College Hospital, London. Second American from the third English edition. In one octavo volume of 203 pages, with 25 illustrations. Cloth, $2.25. Thompson on the Pathology and Treatment of Stricture of the Urethra and Urinary Fistulse. From the third English edition. In one octavo volume of 359 pages, with 47 engravings and 3 plates. Cloth, $3.50. The American System of Dentistry. In Treatises by Various Authors. Edited by Wilbur F. Litch, M.D., D.D.S., Professor of Prosthetic Dentistry, Materia Medica and Therapeutics in the Pennsylvania College of Dental Surgery. In three very handsome octavo volumes containing 3160 pages, with 1863 illustrations and 9 full-page plates. Per volume, cloth, $6.00 ; leather, $7.00 ; half Morocco, gilt top, $8.00. For sale by subscription only. As an encyclopaedia of Dentistry it has no superior. It should form a part of every dentist's library, as the infor- mation it contains is of the greatest value to" all engaged in the practice of dentistry.-American Journal of Dental Sci- ence, September, 1886. A grand system, big enough and good enough and hand- some enough for a monument (which doubtless it is) to mark an epoch in the history of dentistry. Dentists will be satisfied with it and proud "of it-they must. It is sure to be precisely what the student needs to put him and keep him in the right track, while the profession at large will receive incalculable benefit from it.-Odontographic Journal, January, 1887. Coleman's Dental Surgery.-American Edition. A Manual of Dental Surgery and Pathology. By Alfred Coleman, L.R.C.P., F.R.C.S., Exam. L. D. S., Senior Dental Surgeon and Lecturer on Dental Surgery at St. Bartholomew's Hospital and the Dental Hospital, London. Thoroughly revised and adapted to the use of American Students, by Thomas C. Stellwagen, M.A., M.D., D.D.S., Professor of Physiology in the Philadelphia Dental College. In one handsome octavo volume of 412 pages, with 331 illustrations. Cloth, $3.25. It should be in the possession of every practitioner in this country. The part devoted to first and second dentition and irregularities in the permanent teeth is fully worth the price. In fact, price should not be considered in purchasing such a work. If the money put into some of our so-called standard text-books could be converted into such publica- tions as this, much good would result.-Southern Dental Journal, May, 1882. BASHAM ON RENAL DISEASES: A Clinical Guide to their Diagnosis and Treatment.' In one 12mo. volume of 304 pages, with 21 illustrations. Cloth, 82.00. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 24 VENEREAL DISEASES, IMPOTENCE, STERILITY, ETC. Taylor's Clinical Atlas of Venereal and Skin Diseases. A Clinical Atlas of Venereal and Skin Diseases: Including Diagnosis, Prognosis and Treatment. By Robert W. Taylor, A.M., M.D., Clinical Professor of Genito-Urinary Diseases in the College of Physicians and Surgeons, New York; Surgeon to the Department of Venereal and Skin Diseases of the New York Hospital; President of .the American Dermatological Association. In eight large folio parts, measuring 14 x 18 inches, and comprising 58 beautifully colored plates with 213 figures, and 431 pages of text with 85 engravings. Price, per part, $2.50. Bound in one volume, half Russia, $27.00; half Turkey Morocco, $28.00. For sale by subscription only. Specimen plates sent on receipt of 10 cents. A full prospectus sent to any address on application. It would be hard to use words which would perspicuously enough convey to the reader the great value of this Clinical Atlas. This Atlas is more complete even than an ordinary course of clinical lectures, for in no one college or hospital course is it at all probable that all of the diseases herein represented would be seen. It is also more serviceable to the majority of students than attendance upon clinical lec- tures, for most of the students who sit on remote seats in the lecture hall cannot see the subject as well as the office student can examine these true-to-life chromo-lithographs. Comparing the text to a lecturer, it is more satisfactory in exactness and fulness than he would be likely to be in lec- turing over a single case. Indeed, this Atlas is invaluable to the general practitioner, for it enables the eye of the physician to make diagnosis of a given case of skin mani- festation by comparing the case with the picture in the Atlas, where will be found also the text of diagnosis, path- ology, and full sections on treatment.- Virginia Medical Monthly, December, 1889. Taylor on Venereal Diseases.-Sixth Edition. Preparing. The Pathology and Treatment of Venereal Diseases. Including the results of recent investigations upon the subject. By Robert W. Taylor, A.M., M.D., Clinical Professor of Genito- Urinary Diseases in the College of Physicians and Surgeons, New York, Professor of Venereal and Skin Diseases in the University of Vermont. Being the sixth edition of Bumstead and Taylor. Entirely rewritten by Dr. Taylor. Large octavo volume, about 900 pages, with about 150 engravings, as well as numerous chromo-lithographs. In active preparation. Gross on Impotence, Sterility, etc.-Fourth Edition. A Practical Treatise on Impotence, Sterility, and Allied Disorders of the Male Sexual Organs. By Samuel W. Gross, A.M., M.D., LL.D., Professor of the Principles of Surgery and of Clinical Surgery in the Jefferson Medical College of Philadelphia. Fourth edition, thoroughly revised by F. R. Sturgis, M.D., Professor of Diseases of the Genito-Urinary Organs and of Venereal Diseases, New York Post-Graduate Medical School. In one octavo volume of 165 pages, with 18 illustra- tions. Cloth, $1.50. Three editions of Professor Gross' valuable book have been exhausted, and still the demand is unsupplied.' Dr. Sturgis has revised and added to the previous editions, and the new one appears more complete and more valuable than before. Four important and generally misunderstood subjects are treated-impotence, sterility, spermatorrhoea, and prostatorrhoea. The book is a practical one and in addition to the scientific and very interesting discussions on etiology, symptoms, etc., there are lines of treatment laid down that any practitioner can follow and which have met with success in the hands of author and editor.-Medical Record, February 25, 1891. Culver & Hayden's Manual of Venereal Diseases. A Manual of Venereal Diseases. By Everett M. Culver, M.D., Pathologist and Assistant Attending Surgeon, Manhattan Hospital, New York, and James R. Hayden, M.D., Chief of Clinic, Venereal Department, College of Physicians and Surgeons, New York. In one 12mo. volume of 289 pages, with 33 illustrations. Cloth, $1.75. This book is a practical treatise, presenting in a con- densed form the essential features of our present knowledge of the three venereal diseases, syphilis, chancroid and gon- orrhea. We have examined this work carefully arid have come to the conclusion that it is the most concise, direct and able treatise that has appeared on the subject of vene- real diseases for the general practitioner to adopt as a guide. The general practitioner needs a few simple, concise and and clearly presented laws, in the execution of which he cannot fail either to cure or prevent the ravages of the mal- adies in question and their direful results.-Buffalo Medical and Surgical Journal, May, 1892. Genito=Urinary and Venereal Diseases. Cloth, $1.00. See Students' Quiz Series, page 30. Cornil on Syphilis. Syphilis, its Morbid Anatomy, Diagnosis and Treatment. By V. Cornil, Professor to the Faculty of Medicine of Paris, and Physician to the Lourcine Hospital. Specially revised by the Author, and translated with notes and additions by J. Henry C. Simes, M.D., Demonstrator of Patho- logical Histology in the University of Pennsylvania, and J. William White, M.D., Lecturer on Venereal Diseases, University of Pennsylvania. In one handsome octavo volume of 461 pages, with 84 very beautiful illustrations. Cloth, $3.75. Hutchinson on Syphilis. Syphilis, By Jonathan Hutchinson, F.R.S., F.R.C.S., Consulting Surgeon to the London Hoepital. In one 12mo. volume of 542 pages, with 8 chromo-lithographs. Cloth, $2.25. See Series of Clinical Manuals, page 30. HILL ON SYPHILIS AND LOCAL CONTAGIOUS DIS- ORDERS. In one octavo volume of 479 pages. Cloth, 83.25. LEE'S LECTURES ON SYPHILIS AND SOME FORMS I OF LOCAL DISEASE AFFECTING THE ORGANS OF GENERATION. In one octavo volume of 246 pages. Cloth, | 82.25. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. DISEASES OF THE SKIN. 25 Hyde on the Skin.-New (3d) Edition. Just Ready. A Practical Treatise on Diseases of the Skin. For the use of Students and Practitioners. By J. Nevins Hyde, A.M., M.D., Professor of Dermatology and Venereal Diseases in Rush Medical College, Chicago. New (3d) ed. In one 8vo. vol. of 802 pages, with 108 illustrations and 9 full-page plates, 3 of which are colored. Cloth, $5.00 ; leather, $6.00. A few notices of the previous edition are appended. We can heartily recommend it, not only as an admirable text-book for teacher and student, but in its clear and com- prehensive rules for diagnosis, its sound and independent doctrines in pathology, and its minute and judicious direc- tions for the treatment of disease, as a most satisfactory and complete practical guide for the physician.- The American Journal of the Medical Sciences, July, 1888. In this volume the author has supplied the student with a work of standard value. While thorough and compre- hensive in the description of disease, it is especially helpful in the matter of treatment. In this regard it leaves nothing to the presumed knowledge of the reader, but enters thor- oughly into the most minute descriptions, so that one is not only told what should be done under given conditions, but how to do it as well. Care has been taken also to render the nomenclature as clear and unconfusing as the present state of dermatology will admit. The book is one we can heartily recommend as a valuable and creditable addition to American dermatological literature, and a reliable guide to students and practitioners in the requirements of the cir- cumstances of both.-The American Practitioner and News, September 29, 1888. • Jackson's Ready=Reference Handbook of Skin Diseases. The Ready-Reference Handbook of Diseases of the Skin. By George Thomas Jackson, M.D., Professor of Dermatology, Woman's Medical College of the New York Infirmary. In one 12mo. volume of 544 pages, with 50 illustrations and a colored plate. Cloth, $2.75. Intended to serve as a reference book for the general practitioner, " no attempt has been made to discuss debate- able questions," and "hence pathology and etiology do not receive as full consideration as symptomatology, diagnosis and treatment." The alphabetical arrangement of diseases, so universal now in books of this class, has been followed by Dr. Jackson, and he has inserted so many synonyms and titles from foreign languages, that the book may be turned to even by the specialist in skin diseases as a convenient dictionary of dermatological nomenclature. After a short and condensed account of the anatomy and physiology of the skin, the author presents a few notes of common and practical importance on diagnosis and therapeutics, which are followed by his well-known and graphic dermatological "Don'ts." Part II. treats in alphabetical order of the dis- eases of the skin and their management. This book seems to us the best of its class that has yet appeared.-Boston Medical and Surgical Journal, May 18, 1893. Pye=Smith on Diseases of the Skin.-Just Ready. A Handbook of Diseases of the Skin. By P. H. Pye-Smith, M.D., F.R.S., Physician to Guy's Hospital, London. Octavo, 407 pages, with 26 illus., 18 of which are colored. Cloth, $2.00. The book is an excellent one, and we commend it to all interested in the subject. It is written by one entirely familiar with skin diseases, both from the stand-point of the specialist and the general practitioner. It is written in an easy and attractive style, showing familiarity with the whole field of general 'medicine as well as the particular diseases described, which is in striking contrast to the con- tents of the average handbook, from which, as a rule, the reader learns but little. Dr. Pye-Smith is favorably known as one of the eminent physicians to Guy's Hospital, and we have no hesitation in saying that he has written an original and valuable handbook of skin diseases, sound and practical in all its bearings.-International Med. Magazine, July, 1893. It is a plain, practical treatise on dermatology, written for the student and general practitioner by a general prac- titioner of broad experience in the special subject of which he writes. By grouping the various diseases in as easy and natural a manner as possible, and dropping many of the old, confusing terms, he simplifies the nomenclature and succeeds in removing much of the difficulty that lies in the way of its study. After reviewing the recent advances made in this department of medicine, he pays a merited compliment to the "important contributions made by the newest school of dermatology, that of America."-Pittsburg Medical Record, June, 1893. Hardaway's Manual of Skin Diseases. Manual of Skin Diseases. With Special Reference to Diagnosis and Treatment. For the Use of Students and General Practitioners. By W. A. Hardaway, M.D., Professor of Skin Diseases in the Missouri Medical College. In one 12mo. volume of 440 pages. Cloth, $3.00. Dr. Hardaway's large experience as a teacher and writer has admirably fitted him for the difficult task of preparing a book which, while sufficiently elementary for the student, is yet sufficiently thorough and comprehensive to serve as a book of reference for the general practitioner. It embraces all essential points connected with the diagnosis and treat- ment of diseases of the skin, and we have no hesitation in commending it as the best manual that has yet appeared in this department of medicine.-Journal of Cutaneous and Genito- Urinary Diseases. This little manual is divided into three parts, the first portion being devoted to a general introduction on Sympto- matology, Etiology, Diagnosis and Treatment, which is brief, practically complete and clearly stated. The second part considers the clinical characters of the various skin affections in a most satisfactory manner, special stress being placed upon diagnosis and treatment. It concludes with an appendix of special formulae, selected by the author, and a diet table.-Buffalo Medical and Surgical Jour- nal, April 1, 1893. Jamieson on Diseases of the Skin.-Third Edition. Diseases of the Skin. A Manual for Students and Practitioners. By W. Allan Jamieson, M.D., Lecturer on Diseases of the Skin, School of Medicine, Edinburgh. Third edition, revised and enlarged. In one octavo volume of 656 pages, with woodcut and 9 double-page chromo-lithographic illustrations. Cloth, $6.00. The first edition of this work appeared in 1888, and the following year a second. The scope of the work is essen- tially clinical, little reference being made to pathology or disputed theories. Almost every subject is followed by illustrative cases taken from the author's practice, and the reader is constantly reminded that he has before him a record of personal experience. The pages are filled with interest to all those occupied with skin diseases. The general practitioner will find the book of great value in matters of diagnosis and treatment. The latter is quite up to date, and the formulae have been selected with care.- Medical Record, April 9, 1892. Diseases of the Skin. Cloth, §1.00. See Students' Quiz Series, page 30. .FOX'S EPITOME OF SKIN DISEASES. W'ITH FORM- ULAE. Third edition, revised and enlarged. In one 12mo. volume of 238 pages. Cloth, 81.25. HILLIER'S HANDBOOK OF SKIN DISEASES; for Students and Practitioners. Second American edition. In one 12mo. volume of 353 pages, with plates. Cloth, 82.25. WILSON'S STUDENT'S BOOK OF CUTANEOUS MED- ICINE AND DISEASES OF THE SKIN. In one handsome small octavo volume of 535 pages. Cloth, 83.50. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 26 DISEASES OF WOMEN. THE AMERICAN SYSTEMS OF Gynecology and Obstetrics IN TREATISES BY VARIOUS AUTHORS. MATTHEW D. MANN, A.M., M.D., Professor of Obstetrics and Gynecology in the Medical Department of the University of Buffalo. Gynecology edited by Obstetrics edited by and BARTON COOKE HIRST, M.D., Professor of Obstetrics in the University of Pennsylvania, Philadelphia. In four very handsome octavo volumes, containing 3612 pages, 1092 engravings and 8 plates. Complete work now ready. Per volume: Cloth, $5.00; leather, $6.00; half Russia, $7.00. For sale by subscription only. Address the Publishers. Full descriptive circular free on application. These volumes are the contributions of the most eminent fgentlemen of this country in these departments of the pro- fession. Each contributor presents a monograph upon his special topic, so that everything in the way of history, theory, methods and results is presented to our fullest need. As a work of general reference, it will be found remarkably full and instructive in every direction of inquiry.-The Obstetric Gazette, September, 1889. One is at a loss to know what to say of this volume, for fear that just and merited praise may "be mistaken for flat- tery. The papers of Drs. Engelmann, Martin, Hirst, Jag- gard and Reeve are incomparably beyond anything that can be found in obstetrical works.- Journal of the American Medical Association, September 8, 1888. In our notice of the "System of Practical Medicine by American Authors," we made the following statement: "It is a work of which the profession in this country can feel proud. Written exclusively by American physicians who are acquainted with all the varieties of climate in the United States, the character of the soil, the manners and customs of the people, etc., it is peculiarly adapted to the wants of American practitioners of medicine, and it seems to us that every one of them would desire to have it." Every word thus expressed in regard to the "American System of Practical Medicine" is applicable to the "Sys- tem of Gynecology by American Authors." It, like the other, has been written exclusively by American physicians who are acquainted with all the characteristics of American people, who are well informed in regard to the peculiarities of American women, their manners, customs, modes of liv- ing, etc. As every practising physician is called upon to treat diseases of females, and as they constitute a class to which the family physician must give attention, and can- not pass over to a specialist, we do not know of a work in any department of medicine that we should so strongly recommend medical men generally to purchase.-Cincin- nati Medical News, July, 1887. Emmet's Gynaecology.-Third Edition. The Principles and Practice of Gynaecology; For the use of Students and Practitioners of Medicine. By Thomas Addis Emmet, M.D., LL.D., Surgeon to the Woman's Hospital, New York, etc. Third edition, thoroughly revised. In one large and very handsome octavo volume of 880 pages, with 150 illustrations. Cloth, $5.00; leather, $6.00. We are in doubt whether to congratulate the author more than the profession upon the appearance of the third edi- tion of this well-known work. Embodying, as it does, the life-long experience of one who has conspicuously distin- guished himself as a bold and successful operator, and who has devoted so much attention to the specialty, we feel sure the profession will not fail to appreciate the privilege thus offered them of perusing the views and practice of the author. His earnestness of purpose and conscientiousness are manifest. He gives not only his individual experience but endeavors to represent the actual state of gynaecological science and art.-British Medical Journal, May 16, 1885. Gynecology. Cloth, $1.00. See Student Quiz Series, page 30. Tait's Diseases of Women and Abdominal Surgery. Diseases of Women and Abdominal Surgery. By Lawson Tait, F.R.C.S., Professor of Gynecology in Queen's College, Birmingham, late President of the British Gynecological Society, Fellow of the American Gynecological Society. In two octavo volumes. Volume I., 554 pages, 62 engravings and 3 plates. Cloth, $3.00. Volume II., preparing. Mr. Tait never writes anything that does not command attention by reason of the originality of his ideas and the clear and forcible manner in which they are expressed. This is eminently true of the present work. Germs of truth are thickly scattered throughout; single happily worded sentences express what another author would have ex- panded into pages. Useful hints on the technique of sur- gical operations, ingenious theories on pathology, daring innovations on long-established rules-these succeed one another with a bewildering rapidity. His position has long been assured; it is hardly possible for him to add to his great reputation as a daring and original surgeon. Few reformers have ever enjoyed the present reward of their labors in such full measure as he. We cannot repress our admiration for the restless genius of the great surgeon.- American Journal of the Medical Sciences, June, 1890. The Diseases of Women. Including their Pathology, Causation, Symptoms, Diagnosis and Treatment. A Manual for Students and Practitioners. By Arthur W. Edis, M.D., Lond., F.R.C.P., M.R.C.S., Assistant Obstetric Physician to Middlesex Hospital, late Physician to British Lying-in- Hospital. In one octavo volume of 576 pages, with 148 illustrations. Cloth, $3.00 ; leather, $4.00. Edis on Diseases of Women. The special qualities which are conspicuous are thorough- ness in covering the whole ground, clearness of description and conciseness of statement. Another marked feature of the book is the attention paid to the details of many minor surgical operations and procedures, as, for instance, the use of tents, application of leeches, and use of hot-water injec- tions. These are among the more common methods of treatment, and yet very little is said about them in many of the text-books. The book is one to be warmly recom- mended, especially to students and general practitioners, who need a concise but complete resume of the whole sub- ject. Specialists, too, will find many useful hints in its pages.-Boston Medical and Surgical Journal, March 2,1882. HODGE ON DISEASES PECULIAR TO WOMEN Includ- I ing Displacements of the Uterus. Second edition, revised ami enlarged. In one beautifully printed octavo volume of 519 pages, with original illustrations. Cloth, 84.50. WEST'S LECTURES ON THE DISEASES OE WOMEN, Third American from the third London edition. In one octavo volume of 543 pages. Cloth, 83.75; leather, 84.75. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia, DISEASES OF WOMEN-(Continued}. 27 A Practical Treatise on the Diseases of Women. By T. Gaillard Thomas, M.D., LL.D., Emeritus Professor of Diseases of Women in the College of Physicians and Surgeons, New York, and Paul F. Munde, M.D., Professor of Gynecology in the New York Polyclinic. New (sixth) edition, thoroughly revised and rewritten by Dr. Munde. In one large and handsome octavo volume of 824 pages, with 347 illustrations, of which 201 are new. Cloth, $5.00; leather, $6.00. Thomas & Munde on Diseases of Women.-Sixth Edition. The profession has sadly felt the want of a text-book on diseases of women, which should be comprehensive and at the same time not diffuse, systematically arranged so as to be easily grasped by the student of limited experience, and which should embrace the wonderful advances which have been made within the last two decades. Thomas' work fulfilled these conditions, and the announcement that a new edition was about to be issued, revised by so competent a writer as Dr. Munde, was hailed with delight. Dr. Munde brings to his work a most practical knowledge of the sub- jects of which he treats and an exceptional acquaintance with the world's literature of this important branch of medicine. The result is what is, perhaps, on the whole, the best practical treatise on the subject in the English lan- guage. The original work is preserved as a basis, but am- plified and enriched with the results of modem research. Much has been interspersed with the old material and sev- eral new chapters added. It is, as we have said, the best text-book we know, and will be of especial value to the general practitioner as well as to the specialist. The illus- trations are very satisfactory. Many of them are new and are particularly clear and attractive. The book will un- doubtedly meet with a favorable reception from the profes- sion.-Boston Medical and Surgical. Journal, January 14,1892. This work, which has already gone through five large editions, and has been translated into French, German, Spanish and Italian, is too well known to require com- mendation now upon the appearance of this, the sixth edi- tion. It has been thoroughly revised and brought up to date by Dr. Munde, who is announced as joint author. Many new illustrations have been added, and the text has been increased by the addition of new chapters. The dis- tinctive features of the work, which made it so attractive when first issued, have in a measure been retained, so that it continues to be the most practical and -at the same time the most complete treatise upon the subject in print, the changes that have been made only increasing its value.- The Archives of Gynecology, Obstetrics and Pediatrics, Feb- ruary, 1891. Sutton on the Ovaries and Fallopian Tubes. Surgical Diseases of the Ovaries and Fallopian Tubes, including Tubal Pregnancy. By J. Bland Sutton, F.R.C.S., Assistant Surgeon to the Middlesex Hospital, London. In one crown octavo volume of 544 pages, with 119 engravings and 5 colored plates. Cloth, $3.00. This is not a book to be read and then shelved ; it is one to be studied. It is not based upon hypotheses but upon facts. It makes pathology practical, and inculcates a prac- tice based upon pathology. It is succinct, yet thorough; practical, yet scientific; conservative, yet bold. It is prob- ably on the table of all gynecologists; but it is not for them alone; the general practitioner needs just such a book. It will be of immense service to him in the study of pelvic diseases, and will assuredly open his eyes to the pro- gress made by conscientious, painstaking workers like Dr. Sutton in the field of pathology and differential diagnosis. -International Medical Magazine, September, 1892. Mr. Sutton has written a book which deserves unstinted praise for the clearness with which it presents the subject and for the originality of the material. No specialist should fail to read it, and it is so written as to be of the greatest service to the general practitioner who wishes to post him- self upon the subject of which it treats.-New York Journal of Gynecology and Obstetrics, June, 1892. Davenport's Non=Surgical Gynecology.-Second Edition. Diseases of Women, a Manual of Non-Surgical Gynecology. Designed especially for the Use of Students and General Practitioners. By Francis H. Davenport, M.D., Assistant in Gynecology in the Medical Department of Harvard University, Boston. Second edition. In one handsome 12mo. volume of 314 pages, with 107 illustrations. Cloth, $1.75. The first edition of Dr. Davenport's book, which was pub- lished three years ago, evidently met with the reception it deserved, or the second edition would not have followed so soon. The title is an attractive one, and the contents are of value to the student and general practitioner. One ad- vantage of it is that it teaches the physician or the student how to do the little things, or to remedy the minor evils in connection with gynecology. In these days, when major gynecology is so largely practised, minor gynecology is too frequently ignored. To those in the profession who are about to interest themselves particularly in this branch of surgery, and to the student who in the future intends to make gynecology his life-work, we believe that Davenport's book will be essential to his success, because it will teach him facts which larger works sometimes ignore.-The Ther- apeutic Gazette, October 15, 1892. Many valuable volumes already exist on the surgical aspects of gynecology, but scant a'ttenttion has been paid in recent years to the non-surgical treatment of women's diseases. The present volume, dealing with nothing which has not stood the actual test of experience, and being con- cisely and clearly written, conveys a great amount of infor- mation in a convenient space.-Annals of Gynxcology and Pxdiatry, June, 1893. May's Manual of Diseases of Women.-Second Edition. A Manual of the Diseases of Women. Being a Concise and Systematic exposition of the Theory and Practice of Gynecology. By Charles H. May, M. D., late House Surgeon to Mount Sinai Hospital, New York. Second edition, edited by L. S. Rau, M.D., Attending Gynecologist at the Harlem Hospital, New York. In one 12mo. volume of 360 pages, with 31 illustrations. Cloth, $1.75. The classification is so clear that the purpose of enabling I the student to review the subject, or the practitioner rapidly to refresh his memory, is admirably fulfilled. Taking as authority some of the best systematic writers, and giving in the main an opinion which is a consensus, there is an absence of personal bias which is not the least valuable point in the work. The book meets its purpose. Whole chapters have been written in other works without express- ing more ideas than do pages in this.-American Journal of the Medical Sciences, August, 1890. Duncan on Diseases of Women. Clinical Lectures on the Diseases of Women; Delivered in St. Bartholomew's Hospital. By J. Matthews Duncan, M.D., LL.D., F.R.S. E., etc. In one octavo volume of 175 pages. Cloth, $1.50. ASHWELL'S PRACTICAL TREATISE ON THE DIS- EASES PECULIAR TO WOMEN. Third American from the third and revised London edition. In one octavo vol- ume of 520 pages. Cloth, 83.50. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 28 OBSTETRICS. Parvin's Art and Science of Obstetrics.-Second Edition. The Science and Art of Obstetrics. By Theophilus Parvin, M.D., LL.D., Professor of Obstetrics and the Diseases of Women and Children in Jefferson Medical College, Philadelphia. Second edition. In one handsome octavo volume of 701 pages, with 239 engravings and a colored plate. Cloth, $4.25; leather, $5.25. Through his many able contributions to obstetric litera- ture and by reason of his eminence and popularity as a teacher ana practitioner, the author of this volume is well known to the profession of America and obstetricians every- where. Among his many great efforts this work is his master-piece. He has handled this subject, upon which so much has been written, with an attractiveness that is far from common. The science and art of obstetrics have been well and fully demonstrated. The more difficult and abstruse branches have been accorded deserved attention, while the minutiae, the very little points so im- portant to the practitioner at the bedside, yet so generally ignored by writers, have not been neglected. A number of new cuts have been inserted, and the treatment of every subject is in a manner so clear, so direct, so complete, that little is left to be told and nothing could be told better. The work is therefore, in our estimation, one of the most valuable and trustworthy to which the obstetrician can appeal.-Pacific Medical journal, November, 1890. The second edition of this work, following so soon after its first publication, demonstrates its real value and the favor bestowed upon it by the profession. We regard it as the most valuable text-book for the student of medicine yet published. The author has been a most successful teacher for a long period, and the discipline and training of the lecture room are observed in the clearness with which the often-obscure principles of the science and art of obstetrics are presented to the comprehension of the undergraduate. We think this feature is one of the strongest in the work and commends it especially to teachers. The present edi- tion is greatly improved and embodies all the advances made in this important department pf medicine up to the time of its publication.-Buffalo Medical and Surgical Jour- nal, December, 1890. Playfair's Midwifery.-New (8th) Edition. Just Ready. A Treatise on the Science and Practice of Midwifery. By W. S. Playfair, M.D., F.R.C.P., Professor of Obstetric Medicine in King's College, London. Sixth American from the eighth English edition. Edited, with additions, by Robert P. Harris, M.D. One 8vo. vol. of 697 pages, with 217 engravings and 5 plates. Cloth, $4.00 ; leather, $5.00. A few notices of the previous edition are appended. Truly a wonderful book ; an epitome of all obstetrical knowledge, full, clear and concise. In thirteen years it has reached seven editions. It is perhaps the most popular work of its kind ever presentea to the profession. Begin- ning with the anatomy and physiology of the organs con- cerned, nothing is left unwritten that the practical ac- coucheur should know. It seems that every conceivable physiological or pathological condition, from the moment of "conception to the time of complete involution, has had the author's patient attention. The plates and illustrations, carefully studied, will teach the science of midwifery. The reader of this book will have before him the very latest and best of obstetric practice, and also of all the coincident troubles connected therewith.- Southern Practitioner, De- cember, 1889. This work holds a leading place in all medical college catalogues as a standard text-book.-Columbus Medical Jour- nal, November, 1889. King's Manual of Obstetrics.-Fifth Edition. A Manual of Obstetrics. By A. F. A. King, M.D., Professor of Obstetrics and Diseases of Women in the Medical Department of the Columbian University, Washington, D.C., and in the University of Vermont, etc. New (fifth) edition. In one 12mo. volume of 446 pages, with 150 illustra-. tions. Cloth, $2.50. So comprehensive a treatise could not be brought within the limits of a book of this size were not two things espe- cially true. First, Dr. King is a teacher of many years' ex- perience, and knows just how to present his subjects in a manner for them to be best received; and, secondly, he can gut his ideas in a clear and concise form. In other words, e knows how to use the English language. He gives us the plain truth, free from unnecessary ornamentation. Therefore he says there are nine hundred pages of matter between the covers of this manual of four hundred and fifty pages. We cannot imagine a better manual for the hard-worked student, while its clear and practical teach- ings make it invaluable to the busy practitioner. The illus- trations add much to the subject matter.-The National Medical Review, October, 1892. This deservedly* popular manual has rapidly passed through five editions since its first appearance ten years ago. It is essentially a book for students' use, and is one of the very best of its kind. Its scope in topics is particu- larly wide, and, though each topic is necessarily treated in a brief manner, it forms an excellent index, so to say, to the complete study of obstetrics. The present edition bears marks of revision, several illustrations having been added and the text amplified.- The Chicago Medical Recorder, Oc- tober, 1892. Barnes' System of Obstetric Medicine and Surgery. A System of Obstetric Medicine and Surgery, Theoretical and Clinical. For the Student and the Practitioner. By Robert Barnes, M.D., Physician to the General Lying-in Hospital, London, and Fancourt Barnes, M.D., Obstetric Physician to St. Thomas' Hospital, London. The Section on Embryology by Professor Milnes Marshall. In one octavo volume of 872 pages with 231 illustrations. Cloth, $5.00; leather, $6.00. The immediate purpose of the work is to furnish a hand- book of obstetric medicine and surgery for the use of the student and practitioner. It is not an exaggeration to say of the book that it is the best treatise in the English lan- guage yet published, and this will not be a surprise to those who are acquainted with the work of the elder Barnes, Every practitioner who desires to have the best obstetrical opinions of the time in a readily accessible and condensed form, ought to own a copy of the book.-Journal of the American Medical Association, June 12, 1886. The authors have made a text-book which is in every way quite worthy to take a place beside the best treatises of the period.- New York Medical Journal, July 2, 1887. Obstetrics. Cloth, $1.00. See Quiz Series, page 30. Landis on Labor and the Lying=in Period. The Management of Labor, and of the Lying-in Period. By Henry G. Landis, A.M., M.D., Professor of Obstetrics and the Diseases of Women in Starling Medical College, Columbus, Ohio. In one handsome 12mo. volume of 334 pages, with 28 illustrations. Cloth, $1.75. WINCKEL'S COMPLETE TREATISE ON THE PATH- OLOGY AND TREATMENT OF CHILDBED. For Stu- dents and Practitioners. Translated from the second Ger- man edition, by J. R. Chadwick, M.D. In one octavo vol- ume of 484 pages. Cloth, S4.00. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. DISEASES OF CHILDREN, OBSTETRICS-(Continued), MANUALS. 29 Smith on Diseases of Children.-Seventh Edition. A Treatise on the Diseases of Infancy and Childhood. By J. Lewis Smith, M.D., Clinical Professor of Diseases of Children in the Bellevue Hospital Medical College, New York. Seventh edition, thoroughly revised and rewritten. In one handsome octavo volume of 881 pages, with 51 illustrations. Cloth, $4.50; leather, $5.50. We have always considered Dr. Smith's book as one of the very best oh the subject. It has always been prac- tical-a field book, theoretical where theory has been de- duced from practical experience. He takes his theory from the bedside and the pathological laboratory. The very practical character of this book has always appealed to us. It is characteristic of Dr. Smith in all his writings to collect whatever recommendations are found in medical literature, and his search has been wide. One seldom fails to find here a practical suggestion after search in other works has been in vain. In the seventh edition we note a variety of changes in accordance with the progress of the times. It still stands foremost as the American text-book. Its advice is always conservative and thorough, and the evidence of research has long since placed its author in the front rank of medical teachers.- The American Journal of the Medical Sciences, December, 1891. In the present edition we notice that many of the chap- ters have been entirely rewritten. Full notice is taken of all the recent advances that have been made. Many dis- eases not previously treated of have received special chap- ters. The work is a very practical one. Especial care has been taken that the directions for treatment shall be par- ticular and full. In no other work are such careful instruc- tions given in the details of infant hygiene and the artificial feeding of infants.-Montreal Medical Journal, February, 1891. Already in previous editions the treatise- of Dr. Smith on Diseases of Children held position undisputed at the head of its class. No book in any language could dispute with it the title to preeminence. A list of works on diseases of children, made up in any country, would have this work at its head, and for the purposes of the great majority of prac- titioners the list would be complete with this one alone.- The American Practitioner and News, May 9, 1891. As a text-book for students and a guide for young practi- tioners it is unsurpassed.-Buffalo Medical and Surgical Journal, January, 1891. Diseases of Children. Cloth, $1.00. See Students' Quiz Series, page 30. Herman's First Lines in Midwifery. First Lines in Midwifery: a Guide to Attendance on Natural Labor for Medical Students and Midwives. By G. Ernest Herman, M.B., F.R.C.P., Obstetric Physician to the London Hospital. In one 12mo. volume of 198 pages, with 80 illustrations. Cloth, $1.25. See Series of Manuals, page 30. This little book is intended for the use of midwives and for the guidance of medical students in the care of normal cases. The author is the well-known lecturer on obstetrics to the London Hospital, and he has produced a manual which will prove extremely useful to those for whom it has been prepared. The book is replete with practical advice, and no student can go wrong who follows its teachings. Much stress has been laid on the now generally approved aseptic management of labor; and it is clearly pointed out in what complications the student should send for assist- ance. The book is well made and fully illustrated.- The Boston Medical and Surgical Journal, February 9, 1893. Owen on Surgical Diseases of Children. Surgical Diseases of Children. By Edmund Owen, M.B., F.B.C.S., Surgeon to the Children's Hospital, Great Ormond Street, London. In one 12mo. volume of 525 pages, with 4 chromo-lithographic plates and 85 woodcuts. Cloth, $2.00. See Series of Clinical Manuals, page 30. It would not be easy on any subject to find a more clearly written work, where every word and sentence tells, and from which it seems few could be spared. The work is truly a conspectus of the branch of which it treats, and covers the field in a way that is done by no other, present- ing the gist of what is known of every surgical affection to which childhood and infancy are liable.-The American Practitioner and News, November 13, 1886. Hartshorne's Conspectus of the Medical Sciences. A Conspectus of the Medical Sciences; Containing Handbooks on Anatomy, Physiology, Chemistry, Materia Medica, Practice of Medicine, Surgery and Obstetrics. By Henry Hartshorne, A.M., M.D., LL.D., lately Professor of Hygiene in the University of Pennsylvania. Second edition, thoroughly revised and greatly improved. In one large royal 12mo. volume of 1028 pages, with 477 illustrations. Cloth, $4.25 ; leather, $5.00. Ludlow's Manual of Examinations. A Manual of Examinations upon Anatomy, Physiology, Surgery, Practice of Medicine, Obstetrics, Materia Medica, Chemistry, Pharmacy and Therapeutics. To which is added a Medical' Formulary. By J. L. Ludlow, M.D., Consulting Physician to the Philadelphia Hospital, etc. Third edition, thoroughly revised, and greatly enlarged. In one 12mo. volume of 816 pages, with 370 illus- trations. Cloth, $3.25; leather, $3.75. CONDIE'S PRACTICAL TREATISE ON THE DISEASES OF CHILDREN. Sixth edition, revised and augmented. In one octavo volume of 779 pages. Cloth, $5.25 ; leather, $6.25. LEISHMAN'S SYSTEM OF MIDWIFERY, INCLUDING THE DISEASES OF PREGNANCY AND THE PUERPE- RAL STATE. Fourth edition. Octavo. WEST ON SOME DISORDERS OF THE NERVOUS SYS- TEM IN CHILDHOOD. In one small 12mo. volume of 127 pages. Cloth, $1.00. PARRY ON EXTRA-UTERINE PREGNANCY : Its Clin- ical History, Diagnosis, Prognosis and Treatment. Octavo, 272 pages. Cloth, $2.50. RAMSBOTHAM'S PRINCIPLES AND PRACTICE OF OBSETRIC MEDICINE AND SURGERY. In Reference to the Process of Parturition. A new and enlarged edition, thoroughly revised by the author. With additions by W. V. Keating, M.D., Professor of Obstetrics, etc., in the Jefferson Medical College of Philadelphia. In one large and hand- some imperial octavo volume of 640 pages, with 64 full-page plates and 43 woodcuts in the text, containing in all nearly 200 beautiful figures. Strongly bound in leather, with raised bands, $7. CHURCHILL ON THE PUERPERAL FEVER AND OTHER DISEASES PECULIAR TO WOMEN. In one oc- tavo volume of 464 pages. Cloth, $2.50. TANNER ON PREGNANCY. Octavo, 490 pages, colored plates, 16 cuts. Cloth, $4.25. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. 30 QUIZ SERIES, MANUALS. The Students' Quiz Series. ANEW Series of Manuals, comprising all departments of medical science and practice, and pre- pared to meet the needs of students and practitioners. Written by prominent medical teachers and specialists in New York, volumes may be trusted as authoritative and abreast of the day. They enjoy the unique advantage of issue under careful editorial supervision which gives assurance, not only of accuracy, but of the completeness of the Series as a whole, and of the compactness of each volume by the avoidance of duplication. Cast in the form of suggestive questions, and concise and clear answers, the text will impress vividly upon the reader's memory the salient points of his subject, and the prominent and uniform headings will facilitate instant reference to any topic. To the student these volumes will be of the utmost service in preparing for examinations, and they will also be of great use to the practitioner in recalling forgotten details, and in gaining the latest knowledge, whether in theory or in the actual treatment of disease. Nothing has been left undone to make them in type and illustration most attractive and convenient for the eye and mind. Handsomely bound in limp cloth, and in size suitable for the hand and pocket, these volumes are assured of enormous popularity, and are accordingly placed at an exceedingly low price in comparison with their value. For details of subjects and prices see below. ANATOMY (Z>ouWe Number')-By Fred J. Brockway, M.D., Assistant Demonstrator of Anatomy, College of Phy- sicians and Surgeons, New York, and A. O'Malley, M.D., Instructor in Surgery, New York Polyclinic. 81.75. PH YS IO LOGY-By F. A. Manning, M.D., Attending Surgeon, Manhattan Hospital, N. Y. 81. CHEMISTRY AND PH YSICS-By Joseph Struthers, Ph. B., Columbia College School of Mines, N.Y., and D. W. Ward, Ph. B., Columbia College School of Mines, N. Y., and Charles H..Willmarth, M.S., N. Y. 81. HISTOLOGY, PATHOLOGY AND BACTERIOLOGY-By Bennett S. Beach, M.D., Lecturer on Histology, Pathology and Bacteriology, New York Polyclinic. 81. MATERIA MEDIC A AND THERAPEUTICS-By L. F. Warner, M.D., Attending Physician, St. Barthol- omew's Dispensary, N.Y. 81. PRACTICE OF MEDICINE, INCLUDING NERVOUS DISEASES-By Edwin T. Doubleday, M.D., Member N. Y. Pathological Society, and J. D. Nagel, M.D., Member N. Y. County Medical Association. 81. SURGERY (Double Number)-By Bern B. Gallaudet, M.D., Visiting Surgeon, Bellevue Hospital, New York, and Charles Dixon Jones, M.D., Surgeon Yorkville Dispensary, New York. 81.75. GENITO-URINARY AND VENEREAL DISEASES-By Charles H. Chetwood, M.D., Visiting Sur- geon, Demilt Dispensary, Department of Surgery and Genito-Urinary Diseases, New York. 81. DISEASES OF THE SKIN-By Charles C. Ransom, M.D., Assistant Dermatologist, Vanderbilt Clinic, New York. 81. DISEASES OF THE EYE, EAR, THROAT AND NOSE-By Frank E. Miller, M.D., Throat Sur- geon, Vanderbilt Clinic, New York, and James P. McEvoy, M.D., Throat Surgeon, Bellevue Hospital, Out-Patient Department, New York, and J. E. Weeks, M.D., Lecturer on Ophthalmology ana Otology, Bellevue Hospital Medical College. New York. 81. OBSTETRICS-By Charles W. Hayt, M.D., House Physician, Nursery and Child's Hospital, New York. 81. GYNECOLOGY-By G. W. Bratenahl, M.D., Assistant in Gynecology, Vanderbilt Clinic, New York, and Sinclair Tousey, M.D., Assistant Surgeon, Out-Patient Department, Roosevelt Hospital, New York. 81. DISEASES QF CHILDREN-By C. A. Rhodes, M.D., Instructor in Diseases of Children, New York Post- Graduate Medical College. 81. For special circulars, with full information and specimen pages, address the Publishers. The Student's Quiz Series enables a man in practice to give himself an occasional quiz and see how much he has forgotten. It is intended, however, more particularly for the use of the student, not only to show how much he has yet to learn, but to make its accomplishment easier; to enable him to give his whole attention to lectures on these subjects without note-taking, and to go over in a condensed form, before an examination or quiz, the essential facts per- taining to the special branch.-Medical Record, June 3,1893. This series of Quiz- Compends is undoubtedly the best that is published. They will repay the practitioner as well as the student for the time spent in a careful study of them, while to the lecturer or author they will very materially lessen his labors by presenting to him his subject in a brief and classified manner.-Cincinnati Med. Jour., May 15, 1893. Those who desire to review the salient points of medicine can do so by means of these books in the shortest possible time. The form of question and answer crystallizes the information they contain.-Brooklyn Med. Jour, April, 1893. Such books serve a useful purpose, not only to the student preparing for examination but to the practitioner, in recall- ing the more salient characteristics of the affections under consideration.-Journal of Cutaneous and Genito-Urinary Diseases, February, 1893. We know of no series that we would recommend more highly.-Memphis Medical Monthly, Feb. 1893. Student's Series of Manuals. A Series of Fifteen Manuals, for the use of Students and Practitioners of Medicine and Surgery, written by eminent Teachers or Examiners, and issued in pocket-size 12mo volumes of 300-540 pages, richly illustrated and at a low price. The following volumes are now ready: Luff's Manual of Chemistry, $2.; Herman's First Lines in Midwifery, $1.25; Treves' Manual of Surgery, by various'writers, in three volumes, per set, $6; Bell's Comparative Anatomy and Physi- ology, $2; Gould's Surgical Diagnosis, $2; Robertson's Physiological Physics, $2; Bruce's Materia Medica and Thera- peutics (fifth edition), $1.50; Power's Human Physiology (second edition), $1.50; Clarke and Lockwood's Dissector's Manual, $1.50; Ralfe'S Clinical Chemistry, $1.50 ; Treves' Surgical Applied Anatomy, $2; Pepper's Surgical Pathology, $2; and Klein's Elements of Histology (fourth edition), $1.75. The following is in press : Pepper's Forensic Medicine. For separate notices see index on last page. Series of Clinical Manuals. In arranging for this Series it has been the design of the publishers to provide the profession with a collection of authoritative monographs on important clinical subjects in a cheap and portable form. The volumes contain about 550 pages and are freely illustrated by chromo-lithographs and wood cuts. The following volumes are now ready : Yeo on Food in Health and Disease, $2; Broadbent on the Pulse, $1.75; Carter & Frost's Ophthalmic Surgery, $2.25 ; Hutchin- son on Syphilis, $2.25; Marsh on the Joints, $2; Owen on Surgical Diseases of Children, $2 ; Morris on Surgical Diseases of the Kidney, $2.25; Pick on Fractures and Dislocations, $2; Butlin on the Tongue, $3.50; Treves on Intestinal Obstruc- tion, $2; and Savage on Insanity and Allied Neuroses, $2. The following is in preparation : Lucas on Diseases of the Urethra. For separate notices see index on last page. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. MEDICAL JURISPRUDENCE, HISTORICAL 31 Taylor's Medical Jurisprudence.-New Edition. Just Ready. A Manual of Medical Jurisprudence. By Alfred S. Taylor, M.D., Lecturer on Medical Jurisprudence and Chemistry in Guy's Hospital, London. New American from the twelfth English edition. Thoroughly revised by Clark Bell, Esq., of the New York Bar. In one octavo volume of 787 pages, with 56 illustrations. Cloth, $4.50; leather, $5.50. This is a complete revision of all former American and English editions of this standard book. This edition con- tains a large amount of entirely new matter, many portions of the book having been rewritten by the editor. Many cases and authorities have been cited, and the citations brought down to the latest date. The book has so long been a standard treatise on the subject of medical jurispru- dence, and has gone through so many editions-twelve English and eleven American-that there is little left to criticise, unless it is to note the admirable manner in which Mr. Clark Bell, in editing this edition, has enlarged and improved what already seemed complete, by bringing his many citations of cases down to date to meet the present law; and by adding much new matter he has furnished the medical profession and the bar with a valuable book of ref- erence, one to be relied upon in daily practice, and quite up to the present needs, owing to its exhaustive character. It would seem that the book is indispensable to the library of both physician and lawyer, and particularly the legal practitioner whose duties take him into the criminal courts. Too much praise cannot be given to the editor for his thor- ough and painstaking labors, by which he has given to two professions a reference-book to be relied upon.-The Amer- ican Journal of the Medical Sciences, April, 1893. No library is complete without Taylor's Medical Jurispru- dence, as its authority is accepted and unquestioned by the courts.-Buffalo Medical and Surgical Journal, June, 1893. There is no other work upon the subject which has been so uniformly recognized or so widely quoted and followed by courts in England and this country. It would have been impossible to select anyone in this country better fitted for the task of revision than Mr. Bell. Profiting by the labors with which Dr. Stevenson has enriched the twelfth English edition, he has, in this eleventh American edition, given us a book fully abreast with the most recent thought and knowledge. On the basis of his own researches, of the investigations of scientists throughout the world, and of the decisions of our own courts, he has incorporated in it a wealth of practical suggestion and instructive illustration which cannot fail to strengthen the hold it has so long had upon the profession.-The Criminal Law Magazine and Re- porter, January, 1893. BY THE SAME AUTHOR. Poisons in Relation to Medical Jurisprudence and Medicine. Third American, from the third and revised English edition. In one large octavo volume of 788 pages. Cloth, $5.50 ; leather, $6.50. Lea's Superstition and Force.-New Edition. Just Ready. Superstition and Force: Essays on the Wager of Law, The Wager of Battle, The Ordeal and Torture. By Henry Charles Lea, LL.D. New (fourth) edition, revised and enlarged. Royal 12mo., 629 pages. Cloth, $2.75. Both abroad and at home the work has been accepted as a standard authority, and the author has endeavored, by a complete revision and considerable additions, to render it more worthy of the universal favor which has carried it to a fourth edition. The style is severe and simple, and yet delights with its elegance and reserved strength. The known erudition and fidelity of the author are guarantees that all possible original sources of information have been not only consulted but exhausted. The subject matter is handled in such an able and philosophic manner that to read and study it is a step toward liberal education. It is a comfort to read a book that is so thorough, well conceived and well done. We should like to see it made a text-book in our law schools and prescribed course for admission to the bar.-Legal Intelligencer, March 3, 1893. BY THE SAME AUTHOR. Chapters from the Religious History of Spain. In one 12mo. volume of 522 pages. Cloth, $2.50. The width, depth and thoroughness of research which have earned Dr. Lea a high European place as the ablest historian the Inquisition has yet found are here applied to some side-issues of that great subject. We have only to say of this volume that it worthily complements the author's earlier studies in ecclesiastical history. His extensive and minute learning, much of it from inedited manuscripts in Mexico, appears on every page.-London Antiquary, Jan- uary, 1891. The Formulary of the Papal Penitentiary. In one octavo volume of 221 pages, with a frontispiece. Cloth, $2.50. Just ready. The text is edited with the care and learning which we should have expected of the historian of the " Inquisition , of the Middle Ages," and is illustrated with valuable notes and an introduction of remarkable interest. If his judgment of the whole system is a hard one it is to be remembered that he is here in accord with a succession of the greatest religious teachers of the medieval church.- English Historical Review, July, 1893. Studies in Church History. The Rise of the Temporal Power-Benefit of Clergy- Excommunication-The Early Church and Slavery. Second and revised edition. In one royal octavo volume of 605 pages. Cloth, $2.50. The author is preeminently a scholar; he takes up every topic allied with the leading theme and traces it out to the minutest detail with a wealth of knowledge and imparti- ality of treatment that compel admiration. The amount of information compressed into the book is extraordinary, and the profuse citation of authorities and references makes the work particularly valuable to the student who desires an exhaustive review from original sources. In no other single volume is the development of the primitive church traced with so much clearness and with so definite a per- ception of complex or conflicting forces.-Boston Traveller. An Historical Sketch of Sacerdotal Celibacy in the Christian Church. Second edition, enlarged. In one octavo volume of 685 pages. Cloth, $4.50. This subject has recently been treated with very great learning and with admirable impartiality by an American author, Mr. Henry C. Lea, in his History of Sacerdotal Cel- ibacy, which is certainly one of the most valuable works that America has produced. Since the great history of Dean Milman, I know no work in English which has thrown more light on the moral condition of the Middle Ages, and none which is more fitted to dispel the gross illusions con- cerning that period which positive writers and writers of a certain ecclesiastical school have conspired to sustain.- Becky's History of European Morals, Chapter V. Lea Brothers & Co., Publishers, 706, 708 & 710 Sansom Street, Philadelphia. INDEX TO CATALOGUE OF MEDICAL PUBLICATIONS OF LEA BROTHERS & CO., PHILADELPHIA. Abbott's Bacteriology' 17 Alien's Anatomy 6 American Journal of the Medical Sciences 2 American Systems of Gynecology and Obstetrics 26 American System of Practical Med- icine 14 American System of Dentistry . . 23 Ashhurst's Surgery . . . . . . .18 Ashwell on Diseases of Women . .27 Attfield's Chemistry 9 Barlow's Practice of Medicine . . 15 Barnes' System of Obstetric Med- icine and Surgery 28 Bartholow on Cholera 15 Bartholow on Electricity . . . .15 Basham on Renal Diseases .... 23 Bell's Comparative Anatomy and Physiology . 7,30 Bellamy's Surgical Anatomy ... 6 Berry on the Eye 21 Billings' National Medical Dictionary 3 Blandford on Insanity 16 Bloxam's Chemistry 9 Bristowe's Practice of Medicine . . 13 Broadbent on the Pulse ... 14, 30 Browne on Koch's Remedy .... 22 Browne on the Throat, Nose and Ear 22 Bruce's Materia Medica and Thera- peutics 11, 30 Brunton's Materia Medica and Thera- peutics 12 Bryant's Practice of Surgery ... 19 Bumstead and Taylor on Venereal. See Taylor 24 Burnett on the Ear 22 Butlin on the Tongue .... 18, 30 Carpenter on the Use and Abuse of Alcohol 7 Carpenter's Human Physiology . . 7 Carter & Frost's Ophthalmic Sur- gery 21,30 Chambers on Diet and Regimen . . 15 Chapman's Human Physiology . . 8 Charles' Physiological and Patho- logical Chemistry 10 Churchill on Puerperal Fever . . 29 Clarke & Lockwood's Dissectors' Manual 6, 30 Classen's Quantitative Analysis . . 8 Cleland's Dissector 6 Clouston on Insanity 16 Clowes' Practical Chemistry ... 8 Coats' Pathology 17 Coleman's Dental Surgery . . . .23 Condie on Diseases of Children . . 29 Cornil on Syphilis 24 Culver & Hayden on Venereal Dis- eases 24 Dalton on the Circulation .... 7 Dalton's Human Physiology ... 8 Davenport on Diseases of Women . 27 Davis' Clinical Lectures 15 Draper's Medical Physics .... 7 Druitt's Modem Surgery 18 Duane's Medical Dictionary .... 3 Duncan on Diseases of Women . . 27 Dunglison's Medical Dictionary . . 4 Edes' Materia Medica and Thera- peutics 11 Edis on Diseases of Women ... 26 Ellis' Demonstrations of Anatomy . 7 Emmet's Gynecology 26 Erichsen's System of Surgery ... 19 Farquharsori's Therapeutics and Materia Medica 12 Field's Diseases of the Ear .... 22 Flint on Auscultation and Percus- sion 14 Flint on Phthisis 13 Flint on the Respiratory Organs . . 15 Flint on the Heart 13 Flint's Essays 13 Flint's Practice of Medicine ... 13 Foster's Physiology 8 Fothergill's Handbook of Treatment 13 Fownes' Elementary Chemistry . . 9 Fox on Diseases of the Skin ... 25 Frankland and Japp's Inorganic Chemistry 8 Fuller on Lungs and Air-Passages . 14 Gant's Student's Surgery .... 18 Gibbes' Practical Pathology ... 17 Gould's Surgical Diagnosis . . 18, 30 Gray on Nervous and Mental Dis- eases ■ 16 Gray's Anatomy 5 Greene's Medical Chemistry ... 9 Greene's Pathology and Morbid Anat- omy 17 Gross on Foreign Bodies in Air- Passages 18 Gross on Impotence and Sterility . 24 Gross on Urinary Organs . ... 23 Gross' System of Surgery .... 18 Haberstion on the Abdomen ... 14 Hamilton on Fractures and Disloca- tions 20 Hamilton on Nervous Diseases . . 16 Hardaway on the Skin 25 Hare's Practical Therapeutics . . 12 Hare's System of Practical Thera- peutics 12 Hartshorne's Anatomy 6 Hartshorne's Conspectus of the Med- ical Sciences . 29 Hartshorne's Essentials of Medicine 13 Herman's First Lines in Midwifery 29 Hermann's Experimental Pharma- cology 11 Hill on Syphilis 24 Hillier's Handbook of Skin Diseases 25 Hirst & Piersol on Human Mon- strosities 6 Hoblyn's Medical Dictionary ... 3 Hodge on Diseases of Women ... 26 Hoffmann and Power's Chemical Analysis 10 Holden's Landmarks 6 Holland's Medical Notes and Reflec- tions 13 Holmes' Principles and Practice of Surgery 20 Holmes' System of Surgery .... 19 Horner's Anatomy 6 Hudson on Fever 15 Hutchinson on Syphilis . . . 24, 30 Hyde on Diseases of the Skin ... 25 Jackson on the Skin 25 Jamieson on the Skin 25 Jones on Nervous Disorders ... 16 Juler's Ophthalmic Science and Practice M King's Manual of Obstetrics ... 28 Klein's Histology 17,30 Landis on Labor 28 La Roche on Pneumonia & Malaria, 14 La Roche on Yellow Fever .... 15 Laurence and Moon's Ophthalmic Surgery 21 Lawson on the Eye, Orbit and Eyelid 21 Lea's Chapters from the Religious History of Spain 31 Lea's Formulary of the Papal Peni- tentiary 31 Lea's Sacerdotal Celibacy .... 31 Lea's Studies in Church History . . 31 Lea's Superstition and Force . . .31 Lee on Syphilis 24 Lehmann's Chemical Physiology . 7 Leishmann's Midwifery 29 Ludlow's Manual of Examinations . 29 Luff's Manual of Chemistry . .9,30 Lyman's Practice of Medicine . . 14 Lyons on Fever 15 Maisch's Organic Materia Medica . 11 Marsh on the Joints .... 20, 30 May on Diseases of Women ... .27 Medical News 1 Medical News Physicians' Ledger . 2 Medical News Visiting List.... 2 Miller's Practice of Surgery ... 18 Miller's Principles of Surgery ... 18 Morrison Diseases of the Kidney 23, 30 Musser's Medical Diagnosis ... 14 National Dispensatory 11 National Medical Dictionary ... 3 Nettleship on Diseases of the Eye . 21 Norris and Oliver on the Eye . . .21 Owen on Diseases of Children. 29, 30 Parrish's Practical Pharmacy ... 10 Parry on Extra-Uterine Pregnancy . 29 Parvin's Midwifery 28 Pavy on Digestion and its Disorders 15 Payne's General Pathology .... 17 Pepper's Forensic Medicine ... 30 Pepper's Surgical Pathology . 18, 30 I Pepper's System of Medicine ... 14 Pick on Fractures and Disloca- tions 20, 30 Physician's Visiting List 2 Pirrie's System of Surgery .... 18 Playfair on Nerve Prostration and Hysteria 16 Playfair's Midwifery 28 Pohtzer's Diseases of the Ear ... 22 Power's Human Physiology . . 7, 30 Purdy on Bright's Disease . . . .23 Pye-Smith on the Skin 25 Quiz Series 30 Ralfe's Clinical Chemistry . . 10, 30 Ramsbotham on Parturition ... 29 Remsen's Theoretical Chemistry . . 10 Reynolds' System of Medicine . .13 Richardson's Preventive Medicine . 15 Roberts on Urinary Diseases ... 23 Roberts' Compend of Anatomy . . 7 Roberts' Surgery 18 Robertson's Physiological Physics 7, 30 Ross on Nervous Diseases . . . .16 Savage on Insanity and Hysteria 16, 30 Schafer's Essentials of Histology . 18 Schofield's Physiology 8 Schreiber on Massage 15 Seiler on the Throat, Nose and Naso- pharynx 22 Senn's Surgical Bacteriology ... 17 Series of Clinical Manuals '. . . .30 Simon's Manual of Chemistry . . 9 Slade on Diphtheria 14 Smith (Edward) on Consumption . 14 Smith (J. Lewis) on Children . . .29 Smith's Operative Surgery .... 20 Stille on Cholera ....... 15 Stills & Maisch's National Dispensa- tory 11 Stille's Therapeutics and Materia Medica 11 Stimson on Fractures and Disloca- tions 20 Stimson's Operative Surgery ... 20 Students' Quiz Series 30 Students' Series of Manuals ... 30 Sturges' Clinical Medicine .... 13 Sutton on the Ovaries and Fallopian Tubes 27 Tait's Diseases of Women and Ab- dominal Surgery 26 Tanner on Pregnancy 29 Tanner's Clinical Medicine ... 15 Taylor's Atlas of Venereal and Skin Diseases 24 Taylor on Poisons 31 Taylor on Venereal Diseases . . .24 Taylor's Medical Jurisprudence . . 31 Thomas & Munde on Women ... 27 Thompson on Stricture 23 Thompson on Urinary Organs . . 23 Todd on Acute Diseases 15 Treves' Manual of Surgery . . 19, 30 Treves on Intestinal Obstruction 19, 30 Treves' Operative Surgery .... 19 Treves' Students' Handbook of Sur- gical Operations 19 Treves' Surgical Applied Anatomy 6, 30 Tuke on the Influence of the Mind on the Body 16 Vaughan & Novy's Ptomaines and Leucomaines ' 10 Visiting List 2 Walshe on the Heart 13 Watson's Practice of Physic ... 13 Wells on the Eye 21 West on Diseases of Women ... 26 West on Nervous Disorders in Child- hood 29 Wharton's Minor Surgery and Band- aging ' 19 Whitla's Dictionary of Treatment . 15 Williams on Consumption .... 14 Wilson on Cutaneous Medicine . . 25 Wilson's Human Anatomy .... 6 Winckel on the Pathology and Treat- ment of Childbed 28 Wohler's Organic Chemistry ... 7 Year-Books of Treatment for '86, '87 '91, '92, '93 13 Yeo on Food in Health and Dis- ease 15,30 Yeo's Medical Treatment .... 15 Young's Orthopaedic Surgery ... 18