THE ANATOMIST'S YADE MECUM A SYSTEM OF HUMAN ANATOMY BY ERASMUS WILSON, F.R.S. GEORGE BUCHANAN, A.M., M.D. SURGEON AND LECTURER ON CLINICAL SURGERY AT THE GLASGOW ROYAL INFIRMARY PROFESSOR OF ANATOMY IN ANDERSON’S UNIVERSITY EDITED BY ASSISTED BY HENRY E. CLARK, M.R.C.S. NINTH*' EDlifiO+N PHILADELPHIA LINDSAY A N'T BL A'KIS’T ON 1873 PREFACE TO THE NINTH EDITION. .. new Edition of the Anatomist’s Yade Mecum being required, Messrs. Churchill, with the consent of Mr. Wilson, requested me to undertake its preparation. This I agreed to on the understanding that I was to avail myself as freely as I chose of the assistance of my demonstrator, Mr. Henry E. Clark. This Edition therefore is our joint work, and although I am the responsible editor, its merits or demerits belong equally to us both. In preparing it for the press I have been guided by the desire to keep it as nearly as possible, in design and size, the same as the last edition, being convinced by a considerable experience of the requirements of medical students that there is no text-book in our language which is better arranged, and none so handy and easy of reference. It does not profess to be a complete treatise on Anatomy, but to be a compendium of all the facts necessary for the student during his years of preparation, and for the practitioner in after life. Those who desire to study minutely the microscopic structure and development of any tissue or organ, while they will find in this work as much as is necessary to guide them in their research, are referred for details to treatises on these subjects. It is unnecessary to point out the changes that have been made in this edition. While no alteration has been made simply for the sake of variety, the information has been brought up to the present VI PREFACE. day, and many passages which could not have been altered have been entirely re-written. Lastly, a number of additional woodcuts have been introduced. Many of these are borrowed from Carpenter’s “ Manual of Physiology,” others from Heath’s “ Practical Anatomy.” The rest were drawn and engraved by Messrs. Tennent and Miller, of Glasgow. Geoege Buchanan. 193, Bath Street, Glasgow. CONTENTS. CHAPTER I. THE TISSUES OF THE BODY. Page Definition of anatomy .... 1 General anatomy 1 Cells . 1 Fibrous tissue 2 Ligament, tendon 3 Connective tissue 4 Serous membrane 5 Synovial membrane ..... 0 Page Mucous membrane...... 6 Submucous tissue 7 Epithelium 7 Columnar epithelium ...... 8 Spheroidal and ciliated ditto . . 9 Glands 10 Cartilage 11 Eat or adipose tissue 13 CHAPTER II. OSTEOLOGY. General plan of the skeleton . . 15 Composition of bone 16 Division of bones into classes . . 17 Structure of bone 17 Development of bone 21 Vertebral column 26 Cervical vertebrae 27 Dorsal vertebrae 29 Lumbar vertebrae 30 General considerations ... 31 Development 32 Attachment of muscles . . . 33 Sacrum 34 Coccyx 36 Bones of the cranium 37 Occipital bone 37 Parietal bone 40 Frontal bone 41 Temporal bone 44 Sphenoid bone 49 Ethmoid bone 54 Bones of the face 56 Nasal bone 56 Superior maxillary 56 Lachrymal bone 60 Malar bone 61 Palate bone 61 Inferior turbinated 64 Yomer 65 Inferior maxillary 66 Table of developments, articula- tions, &c 68 Sutures 68 Regions of the skull 70 Base of the skull 72 Face 76 Orbits 76 Nasal fossae 77 Development of cranium and face 79 Vertebral theory of skull ... 82 Teeth . . 84 Structure 86 Development . 88 Eruption 91 Succession 92 Os hyoides 93 Thorax and upper extremity . . 93 Sternum ........ 93 Ribs 95 Costal cartilages VIII CONTENTS, Page Clavicle 97 Scapula 98 Humerus 100 Ulna 102 Radius 104 Carpus 106 Metacarpus 110 Phalanges Ill Pelvis and lower extremity . . . 112 Os innominatum 112 Page Ilium 112 Ischium—Os pubis 114 Pelvis—Axes—Diameters . .116 Femur 118 Patella—Tibia 121 Fibula 123 Tarsus 124 Metatarsal bones 128 Phalanges 129 Sesamoid bones 130 CHAPTER III. THE LIGAMENTS. Forms of articulation 131 Synarthrosis—Amphi-arthrosis. 131 Di arthrosis 132 Movements of joints 133 Gliding—Angular movement— Circumduction—Rotation . .133 Structures composing a joint . .133 Synovial membrane . . . .134 Ligaments of the trunk . .134 Articulation of vertebral column 135 Atlas with occipital bone . . . 138 Axis with occipital bone . . .139 Atlas and axis 139 Lower jaw 141 Ribs with vertebrae 143 Costal cartilages, with sternum, and each other 144 Ribs with eostal cartilages . .145 Articulation of sternum . . . 145 Vertebral column with pelvis . 145 Articulations of pelvis .... 146 Uffer extremity 149 Sterno-clavicular 149 Scapulo-clavicular 150 Shoulder-joint 151 Elbow-joint 153 Radio-ulnar articulation . . .154 Wrist-joint 155 Carpal articulations . . . .157 Carpo-metacarpal 158 Metacarpo-phalangeal . . . .159 Articulation of phalanges. . . 159 Lower extremity 160 Hip-joint 160 Knee-joint 161 Tibio-fibular articulation . . . 166 Ankle-joint 167 Articulation of tarsus . . . .168 Tarso-metatarsal joints . . . 171 Metatarso-phalangeal . . . .172 Articulation of phalanges . .172 CHAPTER IY. THE MUSCLES. General anatomy of muscle. . . 173 Nomenclature—Structure . .174 Head and face 178 Cranial group 179 Orbital group 181 Ocular group 183 Nasal group 186 Superior labial group . . . .187 Inferior labial group .... 189 Maxillary group 190 Auricular group 193 Muscles of the neck . . . .194 Superficial group 195 Regional anatomy of neck . .197 Depressors of os hyoides and larynx 198 Elevators of os hyoides . . ,199 Muscles of the tongue . . . .202 Muscles of the pharynx . . . 204 Muscles of the soft palate . . 207 Prsevertebral muscles .... 209 Muscles of the trunk . . . 212 Muscles of the back 213 First layer 213 Second layer 216 Third layer 216 Fourth layer » , . . . .218 Fifth layer 221 CONTENTS. IX Page Sixth layer 222 Table of origins and insertions . .226 Muscles of the thorax . . . .228 Muscles of the abdomen . . .230 Muscles of male perineum . . 241 Muscles of female perineum . . 243 Upper extremity 248 Anterior thoracic region . . . 249 Lateral thoracic region . . .250 Anterior scapular region . . .251 Posterior scapular region . . .251 Acromial region 253 Anterior humeral region . . . 254 Posterior humeral region . . . 256 Page Anterior brachial region . . .257 Posterior brachial region . . .261 Muscles of the hand .... 266 Lower extremity 271 Gluteal region 272 Anterior femoral region . . .276 Internal femoral region . . .279 Posterior femoral region . . .282 Anterior tibial region . . . .284 Posterior tibial region . . . .286 Fibular region 290 Foot—Dorsal region . . . .291 Plantar region 292 CHAPTER V. THE EASCLE. General anatomy 298 Fasci.f: of the head and neck 299 Temporal fascia 299 Cervical fascia 299 Fascia of the trunk .... 300 Thoracic fascia 300 Abdominal fasciae 302 Fascia transversalis . . . .302 Oblique inguinal hernia .... 303 Congenital hernia 305 Infantile or encysted hernia. . . 305 Direct inguinal hernia . . . .305 Iliac fascia . 305 Pelvic fascia 306 Obturator fascia 306 Perineal fasciae 309 Fasciae of upper extremity . 311 Fasciae of lower extremity . 313 Fascia lata 313 Femoral hernia 316 Plantar fascia 317 CHAPTER VI. THE ARTERIES. General anatomy of arteries . .319 Inosculations—Structure . . .320 Aorta 325 Table of branches 327 Coronary arteries 328 Arteria innominata 328 Common carotid arteries . . . .329 External carotid artery .... 330 Table of branches 331 Superior thyroid artery . . .331 Lingual artery 332 Facial artery 334 Sterno-mastoid artery .... 335 Occipital artery 335 Posterior auricular artery . .336 Ascending pharyngeal artery . 336 Parotidean arteries 336 Temporal artery 336 Internal maxillary artery . .337 Internal carotid artery .... 340 Ophthalmic artery 342 Anterior cerebral artery . . . 344 Middle cerebral artery .... 344 Subclavian artery 344 Table of branches 346 Vertebral artery 346 Basilar artery 347 Circle of Willis 349 Internal mammary artery . . 349 Inferior thyroid artery . . .350 Supra-scapular artery .... 350 Transversalis colli artery . . . 350 Superior intercostal artery . .351 Axillary artery 352 Table of branches 353 Brachial artery 355 Radial artery 356 Ulnar artery 359 Thoracic aorta; branches . . . 362 Abdominal aorta ; branches . .363 Phrenic arteries 363 Cceliac axis 363 X CONTENTS. Page Gastric artery 363 Hepatic artery 364 Splenic artery 366 Superior mesenteric artery . .366 Spermatic arteries 368 Inferior mesenteric artery . .368 Renal arteries 370 Common iliac arteries . . . .371 Internal iliac artery 371 Obturator artery 373 Is chiatic artery 374 Page Internal pudic artery . . . .374 External iliac artery 37 7 Femoral artery . . . , • • .378 Popliteal space 383 Popliteal artery 383 Anterior tibial artery 385 Dorsalis pedis artery 386 Posterior tibial artery 388 Peroneal artery 388 Plantar arteries 390 Pulmonary artery 391 CHAPTER VII. THE VEINS. General anatomy 393 Veins of the head and neck . . . 396 Veins of the diploe 398 Cerebral and cerebellar veins . . 399 Sinuses of the dura mater . . .399 Veins of the neck 403 Veins of the upper extremity . .4 05 Veins of the lower extremity . .407 Veins of the trunk 408 Brachio-cephalic veins . . . .409 Superior vena cava 409 Iliac veins 409 Inferior vena cava 411 Azygos veins 412 Vertebral and spinal veins . . .413 Cardiac veins 414 Portal vein 415 Pulmonary veins 416 CHAPTER VIII. General anatomy ...... 418 Lymphatics of head and neck . .421 Lymphatics of upper extremity . 423 Lymphatics of lower extremity . 424 Lymphatics of the trunk . . . .425 THE LYMPHATICS. Lymphatics of the viscera . . .427 Lacteals 428 Thoracic duct 429 Ductus lymphaticus dexter . . . 430 CHAPTER IX. THE NERVOUS SYSTEM. General anatomy . . . * . .431 Spinal cord 439 Medulla oblongata 442 Mesocephalon .445 Cerebrum 449 Base of the brain. ..... 449 Convolutions . 452 Inner surface of hemisphere . . 455 Interior of cerebrum .... 457 Lining of ventricles 468 Cerebellum 469 Development of the brain . . . 471 Membranes of the encephalon . .473 Membranes of the spinal cord . .479 Cranial nerves . ...... 481 Olfactory 482 Optic 483 Motores oculorum 484 Pathetici 484 Trifacial ........ 485 Abducentes 493 Facial 494 Auditory .497 Glosso-pharyngeal 497 Pneumogastric 501 Spinal accessory 505 Hypoglossal ....... 60G Spinal nerves 507 CONTENTS. XI Page Cervical plexus 509 Brachial plexus 513 Dorsal nerves 522 Lumbar nerves 525 Sacral nerves 532 Sympathetic nerves 540 Page Cranial ganglia 541 Cervical ganglia .... 546 Thoracic ganglia 549 Lumbar ganglia 551 Sacral ganglia 551 CHAPTER X. THE ORGANS OF SENSE. Organ of smell 552 Nose 552 Nasal fossae 554 Organ of vision 556 Appendages of the eye . . .557 Lachrymal apparatus . . . .560 Globe of the eye 561 Sclerotic and cornea . . . .562 Choroid coat 563 Iris and ciliary muscle . . . .565 Retina 567 Refracting media 569 Vessels and nerves of eye . .571 Development of eye .... 571 Organ of hearing 572 External ear 572 Tympanum . . . . , . .575 Internal ear 580 Vestibule 580 Semicircular canals . . . .581 Cochlea 581 Vessels and nerves of internal ear 585 Organ of taste 587 Organ of touch 589 Derma 589 Epidermis 591 Appendages of the skin . . . .593 Nails 593 Hairs 594 Sebaceous glands 595 Sudoriparous glands . . . .596 CHAPTER XL THE VISCERA. Thorax 597 Heart 598 Structure of the heart .... 606 Organs of respiration and voice . 608 Larynx 608 Trachea and bronchi . . . .615 Thyroid gland 616 Lungs 617 Pleuras 621 Mediastinum 621 Abdomen 622 Peritoneum 624 Alimentary canal 628 Cheeks 628 Gums—Palate—Fauces. . 629 Tonsils—Mucous glands . 630 Salivary glands . . . .632 Pharynx 634 Stomach 635 Small intestine 638 Large intestine . . . .639 Structure of the intestinal canal 642 Liver 649 Gallbladder ....... 659 Pancreas 661 Spleen 662 Supra-renal capsules .... 664 Kidneys 666 Pelvis 671 Bladder 671 Prostate gland 674 Yesiculae seminales 675 Male organs of generation . 677 Penis 677 Urethra 679 Testes 683 Female pelvis ..’.... 687 Bladder—Urethra 687 Vagina 689 Uterus 690 Fallopian tubes 692 Ovaries . . . 693 External organs of generation . 696 Mammary glands . . . .698 XII CONTENTS. CHAPTER XII. ANATOMY OF THE FCETUS. Pape Osseous and ligamentous system . 701 Muscular system 701 Vascular system 701 Foetal circulation 701 Nervous system 704 Organs of Sense—Eye—Ear . .704 Thyroid gland . . .- . . . .705 Thymus gland 705 Foetal lungs 708 Pape Foetal heart 708 Viscera of the abdomen . . . .709 Omphalo-mesenteric vessels . . 709 Liver 710 Kidneys, supra-renal capsules . 710 Wolffian bodies 710 Viscera of the pelvis 712 Testes—Descent 712 Glossary of Anatomical Terms 715 Index 727 LIST OF ILLUSTEATIONS. PIGS. PAGE 1. White fibrous tissue . 2 2. Yellow fibrous tissue 3 3. Anastomosing yellow fibrous tissue ..... Gerber 4 4. Connective tissue 5. Plan of a serous membrane 6 6. Ideal section of a joint Carpenter 6 7. Epithelial scales from mouth 8 8. Columnar epithelium from small intestine . . . Kolliker 8 9. Separated cells do. do. .... Henle 9 10. Columnar epithelium viewed from surface of membrane ... 9 11. Spheroidal epithelium from hair tube 9 12. Cells of ciliated epithelium of nose ....... 9 13. Ciliated cells viewed from their bases ...... 9 14. 15. Diagrams of the several kinds of glands 10 16. Articular cartilage H 17. Arrangement of cells in articular cartilage 12 18. Ditto ditto near its free surface . 12 19. Elementary part from cartilage of frog .... Beale 12 20. Reticular cartilage ..... .... 12 21. Fibrous cartilage from symphysis pubi8 18 22. Areolar and adipose tissue Mandl 13 23. Caudal vertebra of a fish 15 24. Segment of skeleton at level of first dorsal vertebra . . Quain 16 25. Section of head of tibia 18 26. Section of the body of a vertebra 18 27. Plan of a section of a long bone 19 28. Vertical section of tibia, with Havei-fian canals . . Mandl 20 29. Minute structure of bone 20 30. Lacunae of osseous substance Mandl 21 31. Development of bone 22 32. Do. do. ......... 23 33. Do. do. 23 34. A central cervical vertebra 27 35. Upper surface of atlas . . . • • • ... 28 36. Lateral view of axis 29 37. Lateral view of a dorsal vertebra 30 38. Lateral view of a lumbar vertebra 30 39. Anterior surface of sacrum 34 40. Posterior surface of sacrum 35 41. Front view of coccyx 36 42. External surface of occipital bone 37 43. Internal do. do. .'•»••••• 39 44. External surface of parietal bone 40 45. Internal do. do. 44 XIV LIST OF ILLUSTRATIONS. FIGS. PAGE 46. External surface of frontal bone 42 47. Internal do. do. . . 43 48. External surface of temporal bone 4 4 49. Section through meatus auditorius externus ..... 45 50. Left temporal bone, seen from within . . . . . .46 51. Annulus membranae tympani 48 52. Superior surface of sphenoid bone 49 53. Antero-inferior view of do. ....... 50 54. Ethmoid bone 54 55. Jfasal bone of left side 56 56. Lateral view of superior maxillary bone 56 57. Internal view of do. do. . . . . .57 58. Right lachrymal bone 60 59. Right malar bone 61 60. Right palate bone .... ...... 62 61. Perpendicular plate of palate bone 63 62. Right inferior turbinated bone 64 63. Vomer 65 64. Inferior maxilla 67 65. Front view of skull 71 66. Cerebral surface of base of skull 72 67. Basilar surface of do. ....... 74 68. Longitudinal section of nasal loss* 78 69. Diagram of head of chick at fourth day . . Remote and Huxley 79 70. Head of embryo at end of third day . . Ecker and Huxley 80 71. Head of do. fifth week . . do. 80 72. Vertex of foetal skull 81 73. Cranial vertebras Humphry 82 74. Section of canine tooth ......... 85 75. Longitudinal section of dentine Kollileer 86 76. Transverse section of dentine Kollileer 87 77. Longitudinal section of enamel Kollileer 87 78. Transverse section of enamel Kollileer 88 79. Development of teeth Goodsir 89 80. Eruption of tooth Goodsir 92 81. Os hyoides 93 82. Anterior view of thorax 94 83. Vertebral extremity of seventh rib . . .... 96 84. Clavicle of right side 97 85. Anterior surface of scapula . 99 86. Posterior view of ditto 100 87. Front of humerus 101 88. Back of humerus . 101 89. Radius and ulna, front view . . . . . . . .103 90. Do. do. back view 104 91. Grooves on back of radius and ulna 105 92. Dorsal surface of carpus 107 93. Bones of carpus of left hand 108 94. Anterior view of hand . . . . . . . . .110 95. Os innominatum of right side 113 96. Female pelvis 117 97. Anterior aspect of femur 119 98. Diagram of back of femur ........ 120 99. Patella of right side . . .121 100. Tibia and fibula, front view ........ 122 101. Do. do. back view ........ 123 102. Dorsal surface of left foot 125 103. Plantar do. do. 127 LIST OF ILLUSTRATIONS. XV PIGS. PAGE 104. Anterior ligaments of vertebrae and ribs ..... 135 105. Posterior common ligament of vertebrae . . . . .136 106. Ligaments of laminae (ligamenta subflava) 137 107. Anterior view of ligaments of atlas and axis . . . .137 108. Posterior view of ligaments of atlas and axis .... 138 109. Occipito axoid ligament 139 110. Posterior view of odontoid and cruciform ligaments . . . 140 111. Articulation of lower jaw, external view 141 112. Do. do. internal view ..... 141 113. Do. do. (fibro-cartilage) ..... 142 114. Articulation of ribs and bodies of vertebrae 144 115. Ligaments of pelvis and hip-joint 146 116. Do. do. lateral view .... 147 117. Ligaments of sterno-clavicular joint ...... 149 118. Ligaments of scapula and shoulder-joint 151 119. Section through shoulder-joint 152 120. Ligaments of elbow-joint, inner side 153 121. External view of elbow-joint 154 122. Orbicular ligament 154 123. Triangular inter-articular fibro-cartilage 155 124. Ligaments of wrist and hand, front view 156 125. Synovial membranes of wrist-joint .... Qiiain 158 126. Anterior view of ligaments of knee-joint 162 127. Posterior view of do. do. ...... 163 128. Internal view of knee-joint 164 129. Synovial membrane of knee-joint 165 130. Posterior view of ankle-joint 166 131. Internal view of do. 167 132. External view of do. 168 133. Ligaments of plantar surface of foot . . . . .169 134. Synovial membranes of ankle-joint .... Quain 170 135. Striated muscular fibre ....... Carpenter 174 136. Ultimate fibre of biceps Bowman 175 137. Muscle splitting into disks Bowman 175 138. Nuclei of muscular fibre ...... Bowman 176 139. Structure of the ultimate muscular fibre 176 140. Nou-striated muscular fibre ...... Bowman 177 141. Muscles of the head and face 180 142. Muscles of the eyeball 184 143. Muscles of the nose ....... Arnold 186 144. Pterygoid muscles .......... 192 145. Muscles of anterior aspect of neck 196 146. Styloid muscles and muscles of tongue ...... 201 147. Side-view of muscles of pharynx 205 148. Muscles of soft palate ...... J. T. Gray 208 149. Prsevertebral muscles . . . . . • • • .210 150. Lateral view of prsevertebral muscles 211 151. First, second, and part of third layer of dorsal muscles . . .214 152. Fourth, fifth, and part of sixth layer of dorsal muscles . . .219 153. Muscles of front of trunk 231 154. Lateral view of muscles of trunk 235 155. Diaphragm viewed from front ....... 238 156. Diaphragm viewed from below 239 157. Muscles of male perineum 242 158. Yiew of compressor urethrse Santorini 244 159. Muscles of female perineum . 246 160. Muscles of front of upper arm 255 161. Muscles of back of upper aim 256 XVI LIST OF ILLUSTRATIONS. rIGS- PAGE 162. Superficial muscles of front of forearm ...... 258 163. Deep muscles of front of forearm ....... 260 164. Superficial muscles of back of forearm ...... 262 165. Deep muscles of back of forearm ....... 265 166. Deep muscles of palm of hand 267 167. Deep muscles of gluteal region ....... 273 168. Muscles of anterior femoral region . . . . . . .2 76 169. Muscles of posterior femoral region ...... 283 170. Muscles of anterior tibial region ....... 285 171. Superficial muscles of back of leg 287 172. Deep muscles of back of leg ........ 289 173. Tarts at inner malleolus . . . Hirschjdd and Leveille 290 174. Dorsal interosseous muscles of foot ...... 292 175. Jluscles of sole of foot—first layer . . . . . . .293 176. Muscles of sole of foot—deep layers ...... 294 177. Plantar interosseous muscles ........ 296 178. Section of neck, showing deep cervical fascia .... 300 179. Section of neck at level of first rib Heath 301 180. Diagram of a common scrotal hernia , . . J. T. Gray 304 181. Diagram of a congenital hernia . . . . J. T. Gray 304 182. Diagram of an infantile hernia ... J. T. Gray 304 183. Transverse section of pelvis, with pelvic fasciae .... 306 184. Diagram of layers of pelvic fascia; 307 185. Another view of the pelvic tascise . . . . J. T. Gray 308 186. Pelvic viscera, with the fascia covering them ..... 308 187. Pelvic arch and triangular ligament 310 188. Fasciae of the groin . . 313 189. Crural sheath laid open Wood 314 190. Structures passing beneath crural arch 315 191. Muscle fibres from middle coat of an artery . . . Kolliker 321 192. Elastic tissue from middle coat of an artery . . . Kolliker 321 193. Fenestrated elastic membrane from middle coat . . Kolliker 322 194. Epithelial cells of blood-vessels Kolliket 323 195. Minute artery and capillary, showing nuclei in the walls Kolliker 323 196. Thoracic aorta and its branches ....... 326 197. Carotid arteries, and branches of the external carotid . . . 332 198. Lingual artery and branches . . . Hirschfeld and LeveilU 333 199. Internal maxillary artery and branches 338 200. Basilar artery .......... 348 201. Branches of right subclavian artery ...... 351 202. Axillary and brachial artery and their branches .... 353 203. Arteries of the forearm . . . . . . . . .358 204. Abdominal aorta with its branches . ...... 364 205. Branches of the coeliac axis ........ 365 206. Superior mesenteric artery ........ 367 207. Inferior mesenteric artery ........ 369 208. Iliac arteries ........... 372 209. Irregular origin of obturator artery .... Wood 373 210. Arteries of the perineum 375 211. Femoral artery and branches ........ 379 212. Anterior tibial and dorsalis pedis arteries ..... 386 213. Posterior tibial and popliteal arteries ...... 389 214. Arteries of the sole of the foot ....... 390 215. Valves of veins Sharpey 396 216. Superficial veins of head and neck . .... Qvain 397 217. Sinuses of the upper and back part of skull 400 218. Sinuses of the base of the skull 401 219. Cross section of cavernous sinus Heath 402 LIST OF ILLUSTRATIONS. XVII PIGS. 220. Diagram showing the relative position of the nerves in the cavernous PAGE OQ! 17- • SinUAt. 402 221. Veins of the forearm and bend of elbow 222. Superficial veins of thigh and inner side of leg . , 407 223. External saphenous vein and its connexions ... ' 40a 224. Veins of the trunk and neck . " ' 410 225. Vertebra1 and spinai veins ! Breschet 413 226. Portal vein 4 227. View of a lymphatic gland .' .' Kolliker 421 2-8. Lymphatic vessels and glands of head and neck ... 492 229. Lymphatic vessels and glands of upper extremity . . . 423 230. Lymphatic vessels and glands of lower extremitv 231. Thoracic duct 4* 232. Nerve fibres and nerve cells 432 233. Gelatinous nerve fibres ' Ecker 433 234. Multi-nucleated cells from central substance of spinal cord Kolliker 434 235. Cells of substantia geiatiuosa Kolliker 434 -36. Nerve cells with branching processes .... Kolliker 435 III" ne™eT7ith Eacinian corpuscle . Kolliker 436 Lf' t!rUC!Ure 1 aciman corpuscle Kolliker 437 239. Structure of a sympathetic ganglion .... Kolliker 438 240. Section of spinal cord, showing origin of nerves . 440 241. Transverse section of columns of cord . . . ‘ 442 242. Front view of upper part of cranio-spinal axis . . Ecker 443 243. Diagrammatic section of medulla oblongata .... 445 244. Diagram of a section of medulla, crus cerebri, and cerebral ganglia 446 245. Diagram showing connexion between medulla and convolutions of brain 246. Distribution of fibres of brain 448 247. Base of the brain . . . LErschfeld and LeveilU 451 248. Cortical substance of the hemispheres .... Kolliker 452 249. Laterai view of brain of bush woman . . . .' Marshall 454 250. Upper surface of brain of bushwoman .... Marshall 455 251 Inner and under surface of the brain . Hirsclifeld and Leveille 456 252. Centrum ovale majus 253. Lateral ventricles of the brain 430 H4- longitudinal section of the brain . . Hirsclifeld 'and LeveiM 463 2o5. Third ventricle of the brain . . . Hirsclifeld and Leveille 465 256. Fourth ventricle of the bram . . Hirschfeld and Leveille 467 2o7. Upper surface of the cerebellum . . Hirschfeld and Leveille 470 HI' .'nu®jS of tho braln. • • • • Hirschfeld and Leveille 474 259. Tourth ventricle, spinal cord and its membranes „ . Hirschfeld and Leveille 479 260 1 ransverse section of spinal cord and its membranes . Hirschfeld and Leveille 480 261. Olfactory nerve ••..... 432 262. Dissection of the nerves of the orbit . Hirschfeld and Leveille 4S6 263. Diagram of the fifth nerve and its branches ... 4S7 264. Nerves of the orbit •' Arnold 488 Iff 1InfCri,0r maxilIaiT nerve • • • Hirschfeld and Leveille 490 266. lacia nerve . 496 Iff b l"bt l pa!r °{ nerves of "ffht «de . . Hirschfeld and Leveille 498 268. Eighth pair of nerves of left side . . Hirschfeld and Leveilli 500 269. Diagram of the origin and distribution of the eighth pair . 503 270. Diagram of the connexions of the eighth pair Hirschfeld and Leveilli 504 271. Nerves of the tongue ...... 5(1g 272. Spinal cord, membranes, and spinal nerves . ." ' ' "to* 273. Roots of the spinal nerves ’ .... XVIII LIST OF ILLUSTRATIONS. PIGS. PAGE 274. Nerves of the axilla .... Hirschfeld and Leveille 514 275. Brachial plexus 517 276. Nerves of front of forearm . . . Hirschfeld and Leveille 518 277. Nerves of back of forearm . . . Hirschfeld and Leveille 521 278. Nerves of the abdominal wall . . Hirschfeld and Leveille 524 279. Lumbar plexus Hirschfeld and LeveilU 526 280. Diagram of lumbar and sacral plexuses 528 281.. Nerves of the thigh .... Hirschfeld and Leveille 530 282. Nerves of the pelvis .... Hirschfeld and LeveilU 533 283. Nerves of back of thigh . . . Hirschfeld and Leveille 536 284. Nerves of back of leg . . . Hirschfeld and LeveilU 537 285. Nerves of sole of foot .... Hirschfeld and LeveilU 539 286. Cranial ganglia of the sympathetic 542 287. Fibro-cartilages of nose 553 288. Side view of cartilages of nose Arnold 554 289. Mucous membrane of olfactory region .... Ecker 555 290. Olfactory cells . SchuUze 555 291. Appendages of the eye 558 292. Meibomian glands Arnold 558 293. General diagram of the eye Allen Thomson 561 294. Section of the cornea ....... Bowman 563 295. Veins of the choroid ....... Arnold 564 296. Pigmentary layer of the choroid Kolliker 564 297. Iris and ciliary processes 565 298. View of the back part of the retina ...... 566 299. Cells of the pars ciliaris retinae ..... Kolliker 567 300. Section of the coats of the eye at entrance of optic nerve Ecker 567 301. Bods and cones seen from outer surface .... Kolliker 568 302. Structure of the retina ...... M. Schultze 568 303. Crystalline lens ........ Babuchin 570 304. Pinna and its muscles, front view Arnold 573 305. Pinna and its muscles from behind .... Arnold §74 306. Diagram of the ear 575 307. Small bones of the tympanum 676 308. Section of the cochlea Kolliker 581 309. Labyrinth of left ear ....... Breschet 583 310. Minute structures of the cochlea Henle 584 811. Tongue 689 312. Vertical section of the skin Ecker 590 313. Papillse of skin 591 314. Diagram of the development of epidermis 592 315. Hairs and their connexions Kolliker 595 316. Diagram of heart and circulation 598 317. Bight side of heart 601 318. Left side of heart 604 319. Epithelium of the endocardium Kolliker 607 320. Anastomosing fibres of heart Kolliker 608 321. Vertical section of the larynx 611 322. Posterior 'Mew of the larynx 612 323. Side view of the larynx 613 324. Ciliated epithelium of trachea . . . . . Kolliker 615 325. Heart and lungs 618 326. Intercellular passages of lung 620 327. Viscera of the abdomen ......... 623 328. Beflcxions of the peritoneum 624 329. Follicular gland of tongue ...... Kolliker f.30 830. Bacemose mucous gland ... . Kolliker 631 331. Plan of a racemose gland Kolliker 631 LIST OF ILLUSTKATIONS. XIX FIGS. PAGE 332. Pharynx * 333. Section of the stomach 636 334. Mucous membrane of stomach ....... 637 335. Section of coats of stomach ...... Kolliker 638 336. Gastric follicle ........ Kolliker 638 337. Caecum and appendix 640 338. Mucous membrane, showing- villi 645 339. Section of ileum ........ Kolliker 645 340. Section of duodenum ....... Ecker 646 341. Section of a solitary gland Kolliker 647 342. Solitary gland, seen from the surface 647 343. Surface view of Peyer’s glands Ecker 648 344. Section of Peyer’s glands Ecker 648 345. Capillaries of mucous membrane Kolliker 648 346. Upper surface of liver 650 347. Under surface of liver 652 348. Lobules of liver 654 349. Longitudinal section of lobules 654 350. Hepatic cells 655 351. Arrangement of hepatic cells ...... Kolliker 655 352. Biliary capillaries of rabbit .... Irminger and Frey 655 353. Arrangement of splenic corpuscles Kolliker 663 354. Structure of do. Kolliker 663 355. Section of kidney 667 356. Plan of structure of kidney ...... Ecker 668 357. Plan of renal circulation Bowman 669 358. Side view of male pelvic viscera . . . . . . .673 359. Bladder; vesiculse seminales 676 360. Anatomy of bladder and urethra 680 361. Urethra and neck of bladder ........ 681 362. Transverse section of testis 684 363. Diagram of testis 686 364. Viscera of female pelvis 688 365. Uterus and appendages 690 366. Foetal circulation . . . . . . . . . .702 367. Section of thymus gland ..... Astley Cooper 706 368. Ducts of thymus gland ...... Astley Cooper 708 369. Wolffian bodies Quain 711 370. Descent of testicle Curling 713 371. Do. later stage . . ... Curling 713 THE ANATOMIST’S YAEE MECTJM. CHAPTER I. THE TISSUES OF THE BODY. Anatomy is the science which treats of the structure of organized bodies. The word Anatomy (derived from am and refivco, I cut asunder,) was originally used as synonymous with dissection, but at present it refers to the subject rather than the method of study. Organized bodies are such as are composed of a collection of dis- similar parts or organs, each of which is necessary to our idea of a perfect whole; the absence of one of which would leave a fragment. Human Anatomy has been divided into Descriptive and General. Descriptive Anatomy is a consideration of the organs or parts of the body with reference to their position, shape, size, connexion, &c. General Anatomy is the study of the textures which are found in the body without reference to the organ in which they may exist. At the present day the term has been superseded by that of His- tology (tcrros, a web). GENERAL ANATOMY. The human body, complicated though it be, is made up of dif- ferent combinations of a very few elementary tissues—viz., simple membrane, fibres, cells, and granules or molecules. These in turn form textures a little more complex, the various arrangements of which constitute the organs. It will be convenient at the outset to describe the comparatively simple tissues, leaving the remainder to be taken in the sections devoted to them. The following will be comprised in the present section, viz.—Cells, Fibrous Tissue, Con- nective Tissue, Fat, Serous Membrane, Synovial Membrane, Mucous Membrane, and Cartilage. Cells.—Cells are minute vesicles, usually of a globular form, but often irregular from mutual pressure. They sometimes lie in abso- lute contiguity, sometimes are separated by an intervening matter, which is therefore called intercellular substance. They consist of a cell wall formed of simple membrane and its contents, which usually 2 FIBROUS TISSUE. present the appearance of minute grannies or molecules. The cell contains a nucleus which is itself a small cell, and that again has within it a small particle termed the nucleolus. The white cor- puscles of the blood and the cells of all structures undergoing deve- lopment are devoid of a cell wall, so that they consist simply of small masses of jelly-like material, called protoplasm, enclosing a nucleus. In the primary stage of their development all the tissues are cellular, but in most the cells undergo a transformation, so that in their fully developed state no trace can be discovered of their original condition. Nuclei are however found more or less nume- rously present in the tissues, whether they retain their original cellular structure or not. Cells play an important part in most of the vital processes, and are present in large numbers in many of the organs, forming the greater part of the bulk of compound membranes and glands. Their peculiarities in each situation will be noticed afterwards. Fibrous tissue is one of the most generally distributed of all the animal tissues; it is composed of fibres of extreme minuteness, and presents itself under two elementary forms—namely, white fibrous tissue, and yellow fibrous or elastic tissue. In white fibrous tissue, the fibres are cylindrical, exceedingly minute (about i of an inch in diameter), transparent and undulating; they are collected into small fasciculi (from -gcrooth to Uioooth of an inch), and these latter form larger fasciculi, which, according to their arrangement, give rise to the production of thin laminae, membranes, ligamentous bands, and tendinous cords. The connecting medium of the fibres in the formation of the primitive fasci- culi is a transparent, structureless, interfibrous substance or blastema, to which in most situations are added numerous minute dark fila- ments of elastic tissue. The elastic filaments are sometimes wound spirally round the fasciculi, or in- terlace with their separate fibres; at other times they are variously twisted, and run parallel with the fasciculi. The fasciculi are con- nected and held together in the for- mation of membranes and cords by loose fibres interwoven between them,, or by mutual interlacement. White fibrous tissue is con- verted by boiling into gelatine. Examples of white fibrous tissue are met with in three principal forms—namel3r, membrane, ligament, and tendon. Fig. 1.* * White or non-elastic fibrous tissue. FIBROUS TISSUE. 3 Tlie membranous form of white fibrous tissue is seen in the com- mon connecting medium of the body—namely, cellular membrane, fibro-cellular, cellular, areolar, or filamentous tissue, in which the membrane is extremely thin, and disposed in laminas, bands, or threads, leaving interstices of various size between them. It exhibits two principal forms, in one of which it is lax and serves to connect organs or parts of organs, or establish a medium of sepa- ration between them; in the other it constitutes the condensed covering of various organs, as the periosteum, perichondrium, capsulse proprise of glands, membranes of the brain, sclerotic coat of the eyeball, pericardium, fasciae; sheaths of muscles, tendons, vessels, nerves, and ducts; sheaths of the erectile organs, serous membrane, and the corium of the dermal and mucous membrane. Ligament is the name given to those bands of various breadth and thickness which retain the articular ends of bones in contact in the construction of joints. They are glistening, but slightly elastic, aud composed of fasciculi of fibrous tissue ranged in a parallel direction side by side, or in some situations interwoven with each other. The fasciculi are held together by separate fibres, by fine elastic fibres, and by areolar tissue. Tendon .is the collection of parallel fasciculi of fibrous tissue, by means of which muscles are attached to bones. They are constructed on the same principle*as ligaments, are usually rounded in their figure, but in some instances are spread out so as to assume a mem- branous form. In the latter state they are called aponeuroses. Yellow fibrous tissue, or elastic tissue, enters very generally into the structure of tissues and organs in which the‘ pro- perty of elasticity is an im- portant quality, and serves the additional purpose of binding structures together. As an elastic and binding element it is present in the common cellular tissue and superficial fascia, in the fas- cial sheaths of muscles, in the fibrous capsules of diffe- rent organs, as of the spleen, in the corium of the skin, in serous and mucous mem- branes, in the coats of bloodvessels and ducts; and, in certain situations, is the sole tissue present, as in the ligamenta subflava, chorda} vocales, thyro-epiglottic ligament, crico-thyroidean mem- brane, the membranous layers connecting the cartilaginous rings of the trachea and' bronchial tubes, the ligamentum nucha;, and ligamentum suspensorium penis. It is also met with around some Fig. 2.* * Yellow or elastic fibrous tissue, from ligamenttufi nuchas. 4 CONNECTIVE TISSUE. parts of the alimentary canal, as the oesophagus, cardia, and anus, and around the male and female urethra. The fibres of elastic tissue are cylindrical or flattened, brittle, colourless when single but yel- lowish in an aggregated form, elastic, admitting of being stretched to double their length and returning to their original size, and variable in dimensions, ranging from extreme fineness to a considerable breadth. They present themselves, therefore, in the two forms of fine and coarse, and are distributed among the textures of the body either as single and isolated filaments or as a network. Isolated elastic fibres of ex- treme fineness are met with coiled around or entwined among the fasciculi of areolar tissue, holding them together, and used to be called nuclear fibres, from their supposed origin in the nuclei of the formative cells. There seems, however, to be no reason for the belief of their origin being different from that of other primitive tissues. The elastic network formed by these fibres may be extremely fine and delicate as in thin membranes ; or it may be coarser, as in the various ligamentous bands composed of this tissue ; or it may be spread out like a membrane, the interstices forming but a small part of its extent, as in the fenestrated membrane of the arteries. In the construction of yellow elastic ligaments, the fibres communicate with each other by means of short oblique bands which unite with adjoining fibres at acute or obtuse angles without any enlargement of the fibre with which they are joined. This circumstance has given rise to the idea of the fibres giving off branches, an expression derived from the division of bloodvessels, and another term bor- rowed frojm the same source has been applied to their communication with each ether—namely, inosculation; but both these expressions m their literal meaning are incorrect. When yellow fibrous tissue is cut or torn, -the fibres, in consequence of their elasticity, become clubbed and curved at the extremity, presenting a curled appearance which is a special character of this tissue. Connective Tissue, to which reference has already been made, is composed of both of the preceding kinds of fibrous tissue, the white or waving largely predominating. In the midst of the fibres numerous small masses of protoplasm are found ; these are irregu- lar in shape, are nucleated, and communicate with each other by Fig. 3* * Anastomosing form of yellow fibrous tissue, a. The fibres drawn apart to show the reticulate arrangement, b. The fibres fn situ, SEROUS MEMBRANE. 5 long slender processes. They are called the connective tissue cor- puscles. The arrangement of these elementary filaments has already been pointed out, and it is only necessary to state that this connective tissue is perhaps the most constantly present structure in every organ of the body. Under the name of areolar tissue it forms a complete envelope to the body underneath the integument. The term areolar is applied to it because when slightly stretched its component fibres can be separated, and meshes or areolm can be produced, the interstices containing in small quantity a fluid which moistens the filaments. During life these meshes, which commu- nicate with each other, sometimes become distended with an abnor- mal effusion of fluid, and this constitutes Anasarca. Besides the subcutaneous layer just named, the connective tissue exists as a submucous and subserous layer under these tissues re- spectively, and it also invests and separates all bloodvessels, nerves, and muscles to which it forms sheaths ; forms capsules for glands, penetrates into all the interstices of the organs, and with the bloodvessels enters into their substance, dividing them into lobes and lobules in the case of glands, and into fasciculi in the case of muscles and nerves. In truth it forms a kind of soft framework or skeleton for the whole body, so that if we could conceive of any agent which could extract all the characteristic molecules from the various or- gans and leave intact the fibrous framework, there would remain a spider-weblike model of the human form. Serous Membrane.—This is a thin transparent web which lines the interior of cavities containing viscera, and is so disposed as to facilitate movement. A serous membrane consists of two parts, one which lines the cavity, called the parietal layer; the other, which is reflected from the wall of the cavity, and is prolonged over the con- tained organ, the visceral layer. These two layers are in contact on their free surfaces; and from this free surface a very small quantity of limpid fluid is secreted, which serves the purpose of a lubricating medium, and so facilitates the gliding of the enclosed organ in its cavity. The serous membranes are all closed sacs re- taining their fluid contents, when from any cause there is an ab- normal effusion. The only exception to this is the peritoneum in Fig. 4.* * Portion of connective tissue, showing it to be composed of bands of white fibrous tissue, and of isolated yellow fibres. 6 SYNOVIAL AND MUCOUS MEMBBANES. the female, where at the extremity of the Fallopian tube the serous membrane is continuous with the mucous lining of the tube. In some cases, as the serous membrane of the heart and lungs, its arrange- ment is very simple ; in others, as the peritoneum, it is very com- plex, owing to the number of organ s contained in the cavity ; but in all the two layers can easily be made out. At the place where the reflection takes place, the vessels of the con- tained organ enter it. The viscus, although said to be surrounded by the serous membrane, is in reality outside of it. The accompanying plan of such a sac will give an idea of the manner of arrangement. In structure serous membrane consists of two layers: one, the deep or attached part, formed of fine fibres, and sometimes called the areolar layer; the other forming the free surface, which consists of a layer of cells of scaly epithelium. Synovial Membranes.—These membranes are nearly identical in structure with the serous membranes, but the secretion is more viscid and something like the white of egg, whence the name. They line the cavities of joints, and are interposed between tendons and bones, when much friction or pressure is produced during their movements. Mucous Membrane is the tissue which lines all the internal passages which communicate with the surface of the body. It secretes a viscid fluid called mucus, which protects and lubricates its surface, so as to allow of the passage of sub- stances which otherwise would injure or irritate it. There are two great tracts of mucous mem- brane, called the gastro-pulmonary and genito- urinary. The first communicates with the sur- face of the body at the edge of the eyelid, nostril, mouth, and anus; the second, at the orifice of the urethra in the male, of the vagina in the female. Every duct which opens into either of these tracts is a tubular prolongation of the mucous mem- brane ; and the various glands which pour their secretions into the alimentary canal on the one hand, and those connected with the bladder and organs of generation on the other, are but complicated ramifications of that membrane continued to them through their respective ducts. Besides these two principal tracts, mucous membrane also forms Fig. 5* Fig. G.f * Plan of a serous membrane. 1. Wall of cavity. 2. Parietal layer of serous membrane. 3. Visceral layer. 4. Vessel entering at the reflection. 5. The contained organ. t Ideal section of a joint, a, a. The extremities of the two articulated bones. b, b. The layers of cartilage which cover them, c, c, c, c. Synovial membrane covering the articular surfaces, and passing from one to the other. EPITHELIUM. 7 the ducts and secreting surface of numerous glands of a more or less complex kind, connected with the surface of the body. Thus there is the mammary gland and the perspiratory and sebaceous glands of the skin and ceruminous glands of the outer ear. The structure of mucous membrane is analogous to that of serous membrane, but more complex. It consists of two portions—one, the corium, a tough fibro-vascular layer; the other the epithelium, composed of one or more layers of cells which rest on the corium. The corium in most situations is separated from the epithelial layer by a thin, structureless, transparent membrane—the basement membrane. Underneath this filmy structure lies the capillary plexus, and on it rest the epithelial cells. The true corium consists of a congeries of vessels—capillaries and lymphatics—woven into a compact tissue by interlacing fibres of connective tissue. The pink colour of mucous membrane depends on the capillary plexus seen through the semi-transparent cellular epithelium. In certain situations plain or involuntary muscular fibres occur among the other fibres, especially in the alimentary canal. The arrangement of the vessels of the capillary plexus differs in each situation, so that a portion of mucous membrane under examination can be recognised by its vessels alone—as for instance the villi of the intestines, the air-cells of the lung, &c. Submucous tissue.—The corium is connected to the structures on which it lies by a layer of areolar tissue, which is dense and firm in some situations, where its fibres are continuous with the interlacing fibres of the corium ; but in most it is loose, and permits the corium to glide on the surface on which it lies, so that it may be thrown into folds, or rugae. The laxity of this submucous tissue renders it liable to be distended with fluid, as a result of inflammation, as in the case of chemosis of the conjunctiva and oedema of the glottis. The nature of the submucous tissue can be best examined by inflat- ing a piece of the small intestine which has been inverted after the mesentery has been cut off close to its attachment to the bowel. Epithelium is analogous to the epidermis in forming a layer of protection to the structure which it invests; it constitutes the surface of the mucous membrane, and indeed of all the other inter- nal membranes of the body—namely, the serous and synovial mem- branes, the heart, the bloodvessels, and lymphatics. Like the epidermis also it is composed of minute cells, generated on the sur- face of the corium. These imbibing nutriment from the vascular corium increase in size, and are in turn succeeded by a fresh growth from below. In proportion as they are so pushed to the surface they get beyond the sphere of the corium, and thus become flat and shrivelled. This process of cell-formation being in constant opera- tion on all the surfaces of the body, the old cells of the surface of the epithelium are regularly cast off, while young cells take their place from below. A section of epithelium would, therefore, show cells in successive stages of formation and growth. The cells of epithelium present some differences of form and EPITHELIUM—SQUAMOUS AND COLUMNAR. arrangement which have given rise to their division into four varie- ties—namely, squamous, columnar, spheroidal, and ciliated. The Squamous. epithelium is so named from the conversion of its superficial cells into thin, flattened, polyhedral squamae or scales, in which the original structure of the cell, together with its nucleus, is more or less effaced. On the serous membranes of the cavities of the body and on that of the blood and lymph vessels, the squamae form a single layer, but on the mucous membrane, as on the skin, there are several superimposed layers; hence the names lamellated, tesselated, stratified, and pavement epi- thelium have been given to this variety. The squamous epithelium is found on the conjunctiva; in the cavity of the nose near its external apertures ; in the mouth, fauces, and lower half of the pharynx ; in the oesophagus, where it forms a thick layer, and terminates at the cardiac orifice of the stomach by a serrated border, ora serrata; in the vulva, vagina, cervix uteri, and entrance of the urethra. The squamae are somewhat larger in the mouth and fauces than elsewhere; in longest diameter they measure between and of an inch; in the vagina between and ; and on the skin g-i-Q. The nucleus, which is round or oval in shape, and flat- tened, measures in scales from the mouth of an inch. The Columnar epithelium (cylinder epithelium) consists of cells, which have an elongated or pyriform shape, their bases being directed to the free surface, and their apices to the corium. They are ranged side by side like columns, and their interstices are filled with a transparent jelly-like matrix, similar to that which connects the cells of the squamous epi- thelium. Each column contains near its middle a nucleus, which gives it a swollen appearance, and the nucleus possesses one or more nucleoli; from the trans- parency of the column the nucleus may be seen through its base. The columnar epithelium occurs in the stomach and bowels, urethra, gall-bladder, and ducts of glands. In the gall-bladder the nucleus is less apparent than in other parts. Fig. 7* Fig. 8.f * Epithelial scales from the mouth; the large scale, magnified 310 times, exhibits the structure of the scale, as consisting of a nucleus with nucleolus in the centre; and secondary nucleated cells, forming the body of the scale. Tn the other scales, magnified 155 times, the nucleus and nucleolus are alone seen distinctly; the secondary cells being reduced to the appearance of a few granules dispersed through the scale. t Portion of columnar epithelium from one of the villi of the small intestines. 1. Nucleus of the cell. 2. Membrane of the cell raised from its contents by the absorption of water. From, the puppy: after Kolliker. EPITHELIUM—SPHEROIDAL AND CILIATED. 9 The Spheroidal epithelium is composed of cells, which are spheroidal in shape, and more or less polyhedral from compression ; in other respects they resemble in structure the cells of the preceding varieties. They are found in situa- tions where the squamous and columnar epithelium are continuous, and on that account have been named by Henle transitional epithelium. The spheroidal epithe- lium also occurs in the excretory passages of the kidney, the bladder, and in the excretory ducts of the glands which open on the mucous membrane and skin. The Ciliated epithelium is characterized by the pre- sence of minute conical vibratile filaments (cilia) mounted on the broad ends of the columnar cells, or upon the free surface of those of the spheroidal kind. The cilia are in constant action, and produce a wave- like motion, which carries the secretions in contact with them towards the outlet of the organ in which they exist. They are found in the nose, and sinuses communicating with the nose ; in the nasal duct; upper or respiratory part of the pharynx; Eustachian tubes; larynx, trachea, and bronchial tubes; uterus and Fallopian tubes; and serous membrane of the ventricles of the braiu. Fig. 9.* Fig. lO.f Fig. 114 Fig. 12. § Fig. 13.|| The epithelium of the mucous membrane of the alimentary canal is squamous in the mouth, guttural part of the pharynx, and oesophagus ; and columnar in the stomach, intestines, and mucous glands. In the upper or nasal portion of the pharynx the epithelium is columnar and ciliated, as belonging to the apparatus of the air-passages. In the mouth it is thin and continuous at the outer edge of the lips with the epidermis; in the oesophagus it is * Columnar epithelium from the small intestine: after Henle. Separate columns, showing nucleus and nucleolus. t Appearance of the surface formed by the apposition of the bases of several columns. t Cells of spheroidal epithelium from the walls of a hair tube, magnified 155 times. § Cells of the columnar ciliated epithelium of the nose, magnified 310 times. || Appearance of the surface formed by the apposition of the bases of the columnar ciliated epithelium. 10 ARRANGEMENT OF MUCOUS MEMBRANE. thick, and terminates by an abrupt and serrated border, ora serrata, at the cardiac orifice of the stomach ; below this point the epithe- lium is thin and transparent. The arrangement of the mucous membrane varies very much in different situations. Sometimes it is closely adherent to the tissue on which it rests, as on the lips and cheeks ; at other places it is loosely connected with the inner surface of a cavity, as the stomach, the contraction of which throws it into temporary folds or rugae. In the small intestine it is raised into permanent folds called val- vuli conniventes, and in the same situation little projections called villi exist. These are small conical elevations, about l-60th of an inch long, and are so numerous that when moistened they cause the mucous surface to have the appearance of velvet. The recessions of the mucous membrane are more numerous and more varied than the projections, and may be classified as follows: Follicles, or simple involutions, like the finger of a glove. Tubules, or elongated follicles, which usually terminate by being convoluted like a ball of twine. Saccules, or pouch-like sacs, opening by a narrow neck on the surface. Each of these varieties may be found in a more complex form, and constitute a compound fol- licular, compound tubular, and compound saccular gland, or racemose gland. A compound follicular gland is just a follicle the termination of which is cleft into two or three divisions. In a compound tubular gland, such as the kid- ney, the tubules subdivide many times ; and to save space are usually convoluted, and along with some connective tissue form a Fig. 14 * Fig. 15.f very solid organ. The racemose glands consist of a number of saccules opening into the common duct. They are usually sur- * 1, simple follicle ; 2, tubular gland ; 3, saccular gland, t 1, compound follicle; 2, compound tubular gland; 3, compound saccular or racemose gland. CARTILAGE. 11 rounded by a pretty firm envelope, called the capsule, partitions of which project between the saccules or clusters of saccules, and form subdivisions called lobules. Other varieties of the mucous surface occur in special organs, and will be. alluded to in their description. Skin is essentially the same in structure as mucous membrane consisting of a deep layer called the cutis vera and the epidermis. Its description will be introduced in the chapter on the organs of sensation. Cartilage admits of classification into three kinds; true car- tilage, reticular cartilage, and fibrous cartilage. True cartilage is composed of a semi-transparent homogeneous substance (hyaline or vitreous substance, matrix) containing a Fig. 16.* number of minute cells (cartilage cells) dispersed at short intervals through its structure. The cells are oval, oblong, or polyhedral in shape, and more or less flattened; their membranous envelope is thick and sometimes laminated, and they contain in their interior a clear fluid, together with nuclei, oil globules, and more or less granular matter. Cartilage cells have an average measurement of of an inch in long diameter; they are sometimes isolated, sometimes grouped in pairs, and sometimes disposed in a linear group of three or four. According to the observations of Dr. Beale and others, there are some forms of cartilage, especially during the stage of development, in which true cells cannot be found. The appearance of cells is produced by small masses of protoplasm (“ germinal matter”), which at their surface become converted into “ formed material.” This substance separates the masses from each other, but there is no limiting membrane like a cell wall to separate them from the matrix or matter in which they lie. According to these observers the little mass of protoplasm is the essential part of * A portion of articular (true) cartilage from the head of the fibula. The section is made vertically to the surface, and magnified 155 times. It exhibits the appearance and arrangement of the cells near the bone. The flexuous line to the left is the boundary of the bone. 12 CARTILAGE. a cell, the existence of a cell wall being an accidental occurrence, or met with only occasionally. True cartilage is pearl-white or bluish Fig. 17.* Fig. 18. f Fig. 194 and opaline in colour, its intercellular substance being semi-trans- parent, and homogeneous, or finely granular. These characters, however, are changed when it exhibits a ten- dency to ossify; in which case the intercellular substance becomes fibrous and more or less opaque, its colour yellowish, and the cells filled with a greater number of oil-globules than in its natural state. The special chemical proximate principle of the matrix of cartilage is chondrine, its cells yielding gelatine. The true cartilages are, the articular, costal, ensiform, thyroid, cricoid, arytenoid, tracheal, bronchial, nasal, meatus auris, pulley of the trochlearis muscle, and temporary cartilage or the cartilage of bone previously to ossification. Reticular cartilage is composed of cells (-rsooth of an inch in diameter), separated from each other by an opaque, fibrous, inter- cellular network, the breadth of the cells being considerably greater than that of the intercellular structure. The cells contain nuclei, granular matter, and oil-globules, the latter in greater number than Fig. 20.§ * Arrangement of the cells in articular cartilage. The drawing is made from the same section as fig. 16, the part selected being midway between the free surface of the cartilage and the bone. t Arrangement of the cells in articular cartilage near to, and at its free surface. The figure is drawn from the same section as the two preceding. The edge to the right, where the cells are most condensed, represents the free surface. The cells exhibit the fusiform shape. t Elementary part from cartilage of frog, treated with carmine, showing successive stages of conversion of germinal matter into matrix. § A portion of reticular cartilage. The section is made from the pinna, and magnified 155 times. CAETILAGE—FAT OE ADIPOSE TISSUE. 13 in true cartilage ; the fibres are short, imperfect, loose in texture, and yellowish; and chemically there is an absence of chondrine. Instances of reticular cartilage are, the pinna, epiglottis, and Eus- tachian tube. Fibrous cartilage is composed of an interlacement of fasciculi of white fibrous tissue, containing in its meshes scattered groups of cartilage cells; and the difference of density of different fibrous car- Fig. 21.* tilages is referrible to the greater or less abundance and more or less condensed state of the fibrous tissue. In some, as in interarticular cartilages, the fibrous element exists in a concentrated form, while in the intervertebral substance it is loose, and contains an abun- dance of areolar spaces. Fibrous cartilages admit of arrangement into four groups: inter- articular, stratiform, interosseous, and free. Instances of inter- articular fibrous cartilages (menisci) are those of the lower jaw, sternal and acromial end of the clavicle, wrist, carpus, knee, to which may be added the fibrous cartilages of circumference, glenoid, and cotyloid. The stratiform fibrous cartilages are such as form a thin coating to the grooves on bone through which tendons play. The interosseous fibrous cartilages are the intervertebral substance and symphysis pubis. The free fibrous car- tilages are the tarsal cartilages of the eye- lids. Fat or Adipose tissue is composed of minute cells, aggregated together in clusters of various size within the areolae of common cellular tissue. The cells of adipose tissue are identical in manner of formation with other cells, being developed around nuclei, and increasing in size by the formation of fluid in their interior. In adipose cells, this Fig. 22,t * A portion of fibrous cartilage. The section is made from the symphysis pnibis, and magnified 155 times. t Areolar and adipose tissue, a, a, fat-cells ; b, b, fibres of areolar tissue. 14 FAT OR ADIPOSE TISSUE. fluid, instead of being albuminous as in other cells, is oleaginous, the oil at first appearing in separate globules, -which subsequently coalesce into a single drop. The size of adipose cells at their full development is about -5^0th of an inch in diameter; when isolated they are globular in form, but are hexagonal or polyhedral when compressed. They are perfectly transparent, the cell-membrane being structureless and their nucleus disappearing as they attain their full size. Bone, muscle, nerve, bloodvessels, and lymphatics being com- plex tissues will be explained in the sections which refer to them. 15 CHAPTER II. OSTEOLOGY. Tiie skeleton is the bony framework which forms the support of the body, a,nd affords points of attachment for the muscles by which the movements are effected. The fundamental part of the skeleton is the spine or vertebral column (from verto, I turn), because it is the axis around which all the other parts are disposed and on which they move. It exists in all animals possessing an internal skeleton, which are therefore called vertebrate animals. The vertebrate skeleton consists of a series of segments articu- lated with each other, each of which resembles its immediate neigh- bour in general plan, although there are great differences between those taken from different regions of the same skeleton. As a general rule each segment consists of three essential parts. A centre, centrum, one of the subdivisions of the vertebral column or the body of a vertebra. Behind and in front, from this centre two plates of bone project, so arranged as to enclose a canal. That behind being for the lodgment of the nerve centres is called the neural canal. That in front, for the lodgment of the organs for the circulation and preparation of the blood, is called the visceral or haemal canal or cavity. The plates of bone which enclose the neural canal are called the neurapo- physes, and together they constitute the neural arch. In like manner there is a haemal arch formed by hmnapo- physes. These elements of a vertebral segment are seen in their greatest simplicity and perfection in the caudal vertebra of a fish. In other parts of the same skeleton, and in the skeletons of other animals, great differences are found, some of the parts of either arch being absent, and many additional elements introduced; the only constant part being the centrum or body which exists as the only element in the last bone of the coccyx and the ex- tremity of the tails of animals. In the human skeleton the most perfect segment is that of which the first dorsal vertebra is a part. The body of the vertebra is the centrum; the vertebral ring is the neural arch; and.the haemal arch is constituted by the first rib and its cartilage along with the upper piece of the sternum. Such a segment is called a complete vertebra, because it has a Fig. 23.* * Caudal vertebra of a fish. 1. Centrum. 2. Neural spine. 3. Haemal spine. 4. Neural canal. 5. Haemal canal. 6. Neural arch. 7. Haemal arch. 16 BONE, haemal as well as a neural arch. The first seven dorsal are the only complete vertebrae in the human skeleton if we exclude the skull, the segments of which are usually considered as modi- fied vertebrae ; the parts of the base being the centra; the flat hones of the cranium the neural arches; and the jaws the haemal arches. The other vertebral segments are incomplete from the absence of the haemal arches ; in the cervical region their place being occupied by the structures forming the neck; and in the abdomen by the muscular walls of that ca- vity. In both, however, there are traces of the segmental plan, the anterior portions of the transverse processes of the cer- vical and lumbar vertebrae being rudimentary ribs, and the Zineee transversce in the rectus muscle being the analogues of costal cartilages. The trunk of the body thus formed of vertebral segments has connected with it the limbs which are reckoned as appendages for the purposes of movement, and which vary in different animals according as their locomotion is on the land, in the water, or in the air. Varied as are the modifications, there is a sufficient similarity between the limbs of terrestrial animals, the wings of birds, and the fins of fishes to enable us to see that they are all constructed on the same principle. Fig. 24.* BONE. Bone is composed of about one-third of animal substance, which is almost completely reducible to gelatine by boiling, and two-thirds of earthy and alkaline salts. The special constituents of bone are present in the following proportions:— Animal matter 33 parts. Calcium triphosphate 57 „ Calcium carbonate 8 „ Calcium fluoride 1 „ Magnesium phosphate 1 „ 100 „ Bones are divisible into four classes:—Long, flat, round, and irregular. * Segment of the skeleton at the level of the first dorsal vertebra. 1. Body or centrum. 2. Neural spine. 3. Haemal spine. 4. Neural canal. 5. Haemal canal 6. Neural arch. 7. Haemal arch. STRUCTURE OF BONE. 17 The Long bones are found principally in the limbs, and consist of a shaft and two extremities. The shaft is cylindrical or prismoid in form, dense and hard in texture, and hollowed in the interior into a medullary canal. The extremities are broad and expanded to articulate with adjoining bones ; and, in internal structure, are cellular or cancellous. Upon the exterior of the bones are processes and rough surfaces for the attachment of muscles, and foramina for the transmission of vessels and nerves. The character of long bones is, therefore, their general type of structure and their divisibility into a central portion and extremities, and not so much their length ; for there are certain long bones, as the second phalanges of the toes, which are less than a quarter of an inch in length, and which, in some instances, exceed in breadth their longitudinal axis. The long bones are, the clavicle, humerus, radius and ulna, femur, tibia and fibula, metacarpal bones, metatarsal, phalanges, and ribs. Flat bones are composed of two layers of dense bone with an intermediate cellular structure, and are divisible into, surfaces, borders, angles, and processes. They are adapted to enclose cavi- ties : have processes upon their surface for the attachment of muscles; and are perforated by foramina for the passage of nutrient vessels to their cells, and for the transmission of vessels and nerves. They articulate with long bones by means of smooth sur- faces plated with cartilage, and with each other, either by fibro- cartilaginous tissue, as at the symphysis pubis ; or by suture, as in the bones of the skull. The two condensed layers of the bones of the skull are named, tables ; and the intermediate cellular structure, diploe. The flat bones are, the occipital, parietal, frontal, nasal, lachrymal, vomer, sternum, scapulae, and ossa innominata. Short or round bones have an exterior shell of dense bone filled with spongy or cellular substance; of this sort are the bones of the carpus and tarsus, and the sesamoid bones, including the patella. The Irregular bones include all that remain after the long, short, and flat bones have been selected. They are essentially irregular in their form, in some parts flat, in others short and thick; and are constructed on the same general principle as other bones. The bones of this class are, the temporal, sphenoid, ethmoid, superior maxillary, inferior maxillary, palate, inferior turbinated, hyoid, ver- tebras, sacrum, and coccyx. Structure of Bone.—On examining the section of a bone it will be found that there are two varieties of osseous tissue ; one forming the exterior—hard, compact, dense; the other occupying the in- terior—spongy, cellular, cancellated. The best way to obtain a correct idea of the arrangement of bone substance is to study the appearance presented by a long bone, such as the tibia, which has been sawn longitudinally. The shaft is a hollow pillar, the walls of which are formed of dense bone. The hollow interior is the medullary cavity, and in the recent state is filled with marrow. The upper and lower enlarged ends are formed of an exterior thin shell of compact bone which surrounds a beautiful spider-weblike 18 STRUCTURE OF BONE. lattice-work of osseous threads, the meshes of which are also filled with oily marrow. After complete maceration all the membranous and oily matters are removed, and the dried bony structure alone is visible. On close observation it will be seen that the walls of the pillar consist of fibres or plates arranged in the direction of the bone, and that the cancellated texture of the ex- tremities is formed by the separation and divergence of threads of bone which proceed in the same direction as the walls till they reach and support the thin shell which encases the spongy texture of the end. The fibres diverge and decussate like the divisions of a Gothic window, and so enclose lozenge-shaped spaces, which are the cancelli. This arrange- ment, which always has reference to the direc- tion in which the bone is to bear pressure, adds greatly to the strength of the loose light part of the bones; and this is further secured by little cross bars, which tie together the long slender fibres just described. The dense and spongy tissues are essen- tially the same in structure, and the difference is simply in the degree of closeness with which the fibres are packed. A perpendicular section of the body of a vertebra shows an example of reticular or cancellated texture where the bars are parallel and straight in accordance with the direction of the pressure. In flat bones the osseous substance is arranged as two plates of dense tissue, in some parts closely contiguous to each other, as in the scapula, in others separated by reticular tissue, or even by hollow spaces, as in the bones of the skull, where the intervening substance, in which the bloodvessels run, is called the diploe. The simplest arrangement of bone substance is to be found in the ethmoid and spongy bones of the face, the thin parti- tions of which are formed of a single plate of bone. This is nourished from the outside, no vessels entering into its sub- stance. Bone substance consists of minute granules which cohere by the medium of some second matter, which can be dissolved by pro- longed boiling in a Papin’s digester, thus leaving the granules free for examination. They are minute angular bodies of from -6-q00 to 14 *„o °f an inch in diameter. This bone substance exists in the form of plates or lamellae, Fig. 25.* Fig. 2(5.t * Section of head of tibia, to show the cancellated texture, t Section of the body of a vertebra—perpendicular and transverse bar 1. Vena basis vertebra?. STRUCTUEE OF BONE. 19 which can he seen by examining a thin slice of bone which has been softened by having been steeped in diluted hydrochloric acid. The fibrous character of the lamella can be demonstrated by tearing strips from softened bones, by which it will be seen that the direc- tion of the plates is in that of the length of a bone. The further description of the minute structure of bone will be simplified by considering the mode of nourishment of bone. Periosteum.—This is a fibrous membrane which covers the ex- terior of all bones except where they are encrusted with cartilage. It is a tough unyielding tissue, which adds to the strength and elasticity of the bones, and adhering very firmly, forms the means of attachment of the muscles and tendons. Its principal use is to afford a support and bed to the vessels entering the bone, and it may therefore be called the nourishing membrane to the exterior of the bone. When the periosteum is removed from bone by accident or disease, necrosis, or death of the bone, usually happens; and conversely when a piece of diseased bone can be removed without destroying its periosteum; in many instances the bone or a portion of it is reproduced from the membrane. This has given rise to the subperiosteal method of excising bones. Medullary Membrane or Endosteum.—The hollow shafts of long bones and the open or spongy texture are filled up with marrow or bone fat. This consists of minute oil vesicles, among which blood- vessels ramify, contained in the meshes of a delicate areolar tissue, which also forms a thin lining membrane to the hollow of the bone, hence called the medullary cavity. This medullary membrane is freely supplied with bloodvessels, which reach it through openings numerous and small at the extremities of long bones, and by a single vessel of considerable size which enters about the centre of the shaft through a channel called the nutritious foramen. The inner surface of the bone and the walls of the cancelli on which this membrane is applied, derive their nourishment from its blood- vessels, and processes of it extend into small canals in the dense tissue presently to be noticed. A certain thickness of the exterior of a bone and a similar amount of the inner surface derives its nourishment from the above two membranes, but in most bones there is a con- siderable amount of dense tissue, which is too far removed from either to draw its sup- port from it. This intervening portion is supplied by bloodvessels which enter little channels pro- Fig. 27.* * Plan of a section of a long bone. 1. Periosteum. 2. Periosteal layer of bone. 3. Medullary membrane. 4. Medullary layer of bone. 5. Dense tissue beyond the reach of the periosteal and medullary vessels constituting the Haversian system. 6. Medullary cavity. 20 STRUCTURE OF BONE. vided for the purpose. These Haversian canals, as they are called, are little tubes running for the most part in the direction of the length of a bone, but so obliquely as to form frequent com- munication with each other, and those near the external and internal surfaces, with these surfaces respec- tively. The whole dense substance therefore is permeated by a network of tubules, so that when a thin trans- verse slice of bone is examined by the microscope, it is seen to be riddled with circular holes. The Haversian canals measure from ToVo to °f au inch in diameter. A perpendicular section shows the communications with each other and with the surfaces of the bone. That portion of the dense tissue which derives its nourishment from the Haversian canals is arranged in con- centric lamellae round these tubes, so that a long bone may be described as a series of hollow rods, the central canals of which are the Haversian tubes, bound together by an exterior wrapper consisting of several layers of lamellae (see Fig. 27). A further provision exists for bringing the nutritive fluid into more close relation to the bone substance than can be accomplished by the vascular mem- branes or Haversian canals. The whole of the dense tissue is per- meated by extremely miuute channels called canaliculi. These pass through the periosteal and medullary layers at right angles to their surfaces, and radiate from the Haversian canals. They are smaller in calibre than the smallest capilla- ries, and serve to con- duct the nutritive fluid m1 to the denser tissue. The canaliculi which radiate out from the Haversian canals are inter- Fig. 28.* Fig. 29. t * Vertical section of tibia, showing the net-work of Haversian canals, t 1 ransverse section of a long bone, showing the Haversian system, the canals, concentric lamellae, canaliculi, and the lacuna;. DEVELOPMENT OF BONE. 21 rupted in tlieir passage to the more distant concentric lamella} by pouring their contents into little oval cavities called the lacunae of bone. These are arranged in the form of circles between the lamellae, and into their sides next the canals numerous canaliculi enter, while from the further side still more numerous canaliculi diverge towards the lacunae or circles further out. The lacunae therefore serve as reservoirs into which fluid from the vessels in the Haversian canals is poured on the one hand, and on the other they pass it on to the outer circles of bone. In this way the nourish- ment of those parts of bone most distant from the nutiient mem- branes is provided for by this intricate series of little channels and communicating reservoirs (fig. 29). A thin section of bone is one of the most beautiful of all microscopic objects. These lacunae were at one time called the “osseous corpuscles,” from the idea that they were solid dark particles. The cause of the misconception was that, during the grinding of a layer of bone the finer porosities get filled up with the debris, and by transmitted light appear black, so that a very much magnified view of a “ corpuscle” and its canali- culi resembles a black insect —the lacuna representing the body, the canaliculi the legs. Virchow has shown that in fresh bones there is in every lacuna a delicate walled cell completely filling it with clear contents and a single nucleus. He believes that the canaliculi are small processes which connect neighbouring cells. The lacunae and their corresponding canaliculi are to be found in all parts of a bone, and in bones however thin—although Haver- sian canals are only found in those of some thickness. In the periosteal and medullai'y layers of long bones, and in very thin bones, their arrangement has reference to the surface of the bone, as it had in the Haversian system; the flat of the oval being turned toward the nutrient membrane, so that their canaliculi may com- municate with it for the absorption of fluid nourishment. Development of Bone.—Bone, in its earliest stage, is composed of an assemblage of minute cells, which are soft and transparent, and are disposed within the embryo in the site of the future skeleton. From the resemblance which the soft bone-tissue bears to jelly, this has been termed the gelatinous stage of osteo-genesis. As development advances, the cells, heretofore loosely connected together, become separated by the interposition of a transparent intercellular sub- stance, which, at first fluid, gradually becomes hard and condensed. Fig. 30.* * Lacunae of osseous substance, magnified 500 diameters :—a, central cavity; b, its ramifications or canaliculi. 22 DEVELOPMENT OF BONE. The cartilaginous stage of osteo-genesis is now established, and cartilage is shown to consist of a transparent basis-substance, having minute cells disseminated through it at pretty equal dis- tances, Coincident with the formation of cartilage is the develop- ment of vascular canals in its substance, the canals being formed by the union of the cells in rows, and the subsequent liquefaction of their adhering surfaces. The change which next ensues is the concentration of the vascular canals towards some one point; for example, the centre of the shaft in a long, or the mid-point of a flat bone, and here the punctum ossificationis, or centre of ossification, is established. What determines the vascular concentration now alluded to, is a question not easily solved, but that it takes place is certain, and the vascular punctum is the most easily demonstrable of all the phenomena of ossification. During the formation of the punctum ossificationis, changes begin to be apparent in the cartilage cells. Originally, they are simple nucleated cells (-50V0 20V0 an i in diameter), having a rounded form. As growth proceeds, they become elongated, and it is then perceived that each cell contains two and often three nucleoli, around which smaller cells are in progress of formation. If we examine them nearer the punctum ossificationis, we find that the young or secondary cells have each attained the size of the parent cell (aoVo of an inch), the membrane of the parent cell has disappeared, and the young cells are separated to a short distance by freshly effused intercellular substance. Nearer still to the punctum ossificationis a more remarkable change has ensued, the energy of cellule reproduction has augmented with proximity to the ossifying point, and each cell, in place of producing two, gives Fig. 31.* birtli to four, five, or six young cells, which rapidly destroy the * Figures illustrative of the development of bone ; magnified 155 times, and drawn with the camera lucida. A. A portion of c artilage the farthest removed from the seat of ossification, showing simple nucleated cells, having an ordinary size of saVo of an inch, long diameter. B. The same cartilage, nearer the seat of ossification ; each simple cell has produced two, a little larger than the cells in figure A. DEVELOPMENT OF BONE. 23 parent membrane and attain a greater size (yitoo °f an inch) than the parent cell, each cell being, as in the previous case, separated to a slight extent from its neighbour by intercellular substance. By one other repetition of the same process, each cell producing four, Fig. 32.* five, or six young cells, a cluster is formed, containing from thirty to fifty cells. These clusters lie in immediate relation with the punctum ossificationis; they are oval in figure (about T) of an inch in length by in breadth), and elongated in the Fig. 33. f direction, of the long axis of the bone. The cells composing the cluster lie transversely with regard to its axis. In the first in- * The same cartilage, still nearer the seat of ossification ; each single cell of B has given birth to four, five, or six cells, which form clusters. The clusters become larger towards the right of the figure, and their cells more numerous and larger, rrbo of an inch, long diameter. t The same cartilage at the seat of ossification; the clusters of cells are arranged in columns; the intercellular spaces, between the columns, being of an inch in breadth. To the right of the figure osseous fibres are seen occupying the intercellular spaces, at first bounding the clusters laterally, then splitting them longitudinally, and encircling each separate cell. The greater opacity of the right-hand border is due to a threefold cause—namely, increase of osseous fibres, opacity of the contents of the cells, and multiplication of oil globules. In the lower part of the figure some attempt has been made to show the texture of the cells. 24 PEEIODS OF OSSIFICATION. stance they are closely compressed, but by degrees are parted by a thin layer of intercellular substance, and each cluster is separated from neighbouring clusters by a broader layer (3 of an inch) of intercellular substance. Such are the changes which occur in car- tilage preparatory to the formation of bone. Ossification is accomplished by the formation of very fine and delicate fibres within the intercellular substance : this process com- mences at the punctum ossificationis, and extends from that point through every part of the bone, in a longitudinal direction in long, and in a radiated direction in flat bones. Starting from the punc- tum ossificationis, the fibres embrace each cluster of cells, and then send branches between the individual cells of each group. In this manner the network, characteristic of bone, is formed, while the cells by their conjunction constitute the permanent areolae and Haversian canals. With a high magnifying power, the delicate ossific fibres here alluded to are seen themselves to be composed of minute cells, having an elliptical form and central nuclei. These cells attract into their interior the calcareous salts of the blood, and their nuclei become developed into the future lacunae. It is possible also that some of the cartilage cells become lacunae in the fully developed bone. During the progress of the phenomena above described, the con- tents of the cells undergo certain changes. At first, they are trans- parent, then they become granular, and still later opaque, from the presence of amorphous matter mingled with nuclei, nucleoli, and the remains of secondary cells. In the latter state the cells contain an abundance of minute oil globules, which increase in size as the ossific changes advance, and in the newly formed osseous areolae, have attained the ordinary size of adipose cells. Cartilaginification is complete in the human embryo at about the sixth week ; and the first point of ossification is observed in the clavicle at about the fifth week. Ossification commences at the centre, and thence proceeds towards the surface; in flat bones the osseous tissue radiates between two membranes from a central point towards the periphery, in short bones from a centre towards the circumference, and in long bones from a central portion, diaphysis, towards a secondary centre, epiphysis, situated at each extremity. Large processes, as the trochanters, are provided with a distinct centre of development, which is named apophysis. The growth of bone in length takes place at the extremity of the diaphysis, and in bulk by fresh deposition on the surface; while the medullary canal is formed and increased by absorption from within. The period of ossification is different in different bones; the order of succession may be thus arranged :— During the fifth week, ossification commences in the clavicle, lower jaw, and upper jaw. During the sixth week, in the femur, humerus, tibia, radius, and ulna. NUMBER OF BONES, 25 During the seventh and eighth weeks, in the fibula, frontal, occi- pital, sphenoid, ribs, parietal, temporal, nasal, vomer, palate, ver- tebrae, first three pieces of sacrum, malar, metacarpus, metatarsus, third phalanges of the hands and feet, and ilium. During the third month, in the first and second phalanges of the hands and feet, lachrymal bone, and ischium. During the fifth month, in the mastoid portion of the temporal, ethmoid, inferior turbinated, sternum, os pubis, and last two pieces of sacrum. During the sixth month, in the body and odontoid process of the axis, and in the os calcis. During the seventh month, in the astragalus. During the tenth month, in the cuboid bone and os hyoides. During the first year, in the coracoid process of the scapula; first piece of the coccyx, inferior turbinated bone, last piece of the ster- num, anterior arch of the atlas, os magnum, os unciforme, and ex- ternal cuneiform bone. During the third year, in the cuneiform of the carpus, internal cuneiform of the tarsus, and patella. During the fourth year, in the middle cuneiform and scaphoid of the tarsus. During the fifth year, in the trapezium and os semilunare. During the seventh year, in the second piece of the coccyx. During the eighth year, in the scaphoid of the carpus. During the ninth year, in the os trapezoides. During the twelfth year, in the os pisiforme and third piece of the coccyx. During the eighteenth year, in the fourth piece of the coccyx. The ossicula auditus are the only bones completely ossified at birth; the vertebrae are not completed until the five-and-twentieth year. The entire osseous framework of the body constitutes the skeleton, which in the adult man is composed of two hundred distinct bones. They may be thus arranged :— Cranium 8 Face 14 Yertebral column . . .24 Sacrum and Coccyx . . 2 Sternum and ribs . . .25 Upper extremities . . .64 Lower extremities . . .60 Patellae 2 Os hyoides .... 1 200 Skull. The skeleton is divisible into : 1. The vertebral column, or central axis. 2. The head and face, or superior development of the central 26 VERTEBRAL COLUMN. axis. 3. The hyoid arch. 4. The thoracic arch and upper ex- tremities. 5. The pelvic arch and lower extremities. The vertebral column is the first and only rudiment of internal skeleton in the lower Vertebrata, and constitutes the type of that great division of the animal kingdom. It is also the first developed portion of the skeleton in man, and the centre around which all the other parts are produced. In its earliest formation it is a simple cartilaginous cylinder, surrounding and protecting the primitive trace of the nervous system; but as it advances in growth and organization, it becomes divided into distinct pieces, which con- stitute vertebrae.* The vertebras admit of a division into true and false. The true vertebrae are twenty-four in number, and are classed, according to the three regions of the trunk which they occupy, into cervical, dorsal, and lumbar. The false vertebrae consist of nine pieces united into two bones, the sacrum and coccyx. The arrangement of the vertebrae may be better comprehended by means of the accompanying table:— VERTEBRAL COLUMN. 7 Cervical, 12 Dorsal, 5 Lumbar. True vertebrae liue verteoiae False vertebrae 9 5 Sacrum, 4 Coccyx. Characters of a Vertebra.—A vertebra consists of a body, two laminm, a spinous process, two transverse processes, and four arti- cular processes. The body is the solid part of the vertebra; and, by its articulation with adjoining vertebras, gives strength and sup- port to the trunk. It is flattened above and below, convex in front, and slightly concave behind. Its anterior surface is constricted around the middle, and pierced by numerous small openings, which give passage to nutritious vessels. On its posterior surface is a single irregular opening, or several, for the exit of the venae basis vertebras. The laminae commence upon the sides of the posterior part of the body of the vertebra by two pedicles; they then expand ; and, arch- ing backwards, enclose a foramen, which serves for the protection of the spinal cord. The upper and lower border of the lam in as are rough for the attachment of the ligamenta subflava. The con- cavities above and below the pedicles are the intervertebral notches. The spinous process stands backwards from the angle of union of the laminas. It is the succession of these projecting processes along the middle line of the back, that has given rise to the common designa- tion of the vertebral column, the spine. The use of the spinous process is for the attachment of muscles. The transverse processes project one at each side from the laminae of the vertebra; they also * See description of the vertebrate skeleton, page 15. CERVICAL VERTEBRAE. 27 are intended for the attachment of muscles. The articular processes, four in number, stand upwards and downwards from the laminae, to articulate with the vertebra above and below. Cervical Vertebrce.—In a cervical vertebra the body is smaller than in the other regions; it is thicker before than behind, broad from side to side, concave on the upper sur- face, and convex below, so that, when articulated, the vertebrae lock the one into the other. The laminoe are narrow and long, and the in- cluded spinal foramen large and triangular. The superior inter- vertebral notches are slightly deeper than the inferior; the inferior being the broadest. The spinous process is short and bifid at the extremity, increasing in length from the fourth to the seventh. The transverse processes are also short and bifid, and deeply grooved along the upper surface for the cervical nerves. Piercing the base of the transverse process is the vertebral foramen,f which gives passage to the vertebral artery and vein, and vertebral plexus of nerves. The transverse processes in this region are formed by two small developments, which proceed, the one from the side of the body, the other from the pedicle of the lamina, and unite near their extremities to enclose the circular area of the vertebral foramen. The anterior of these developments is the rudiment of a cervical rib; the posterior, the analogue of the transverse processes in the dorsal region. The extremities of these developments are the anterior and posterior tubercle of the transverse process. The articular processes are oblique ; the superior looking upwards and backwards; the inferior, downwards and forwards. There are three peculiar vertebra in the cervical region:—The first, or atlas; the second, or axis; and the seventh, or vertebra prominens. The Atlas (named from supporting the head) is a simple ring of bone, without body, and composed of arches and processes. The anterior arch has a tubercle on its anterior surface, for the attach- Fig. 34.* * A central cervical vertebra, seen upon its upper surface. 1. The body, concave in the middle, and rising on each side into a sharp ridge. 2. The lamina. 3. The pedicle, rendered concave by the superior intervertebral notch. 4. The bifid spinous process. 5. The bifid transverse process. The number is placed in the concavity between the anterior and posterior tubercle, between the two processes which correspond with the rudimentary rib and the true transverse process. 6. The vertebral foramen. 7. The superior articular pro- cess, looking backwards and upwards. 8. The inferior articular process. f Sometimes, as in a vertebra now before me, a small additional opening exists by the side of the vertebral foramen, in which case it is traversed by a second vein. 28 ATLAS AND AXIS. ment of the longus colli muscle; and on its posterior aspect is a smooth surface, for articulation with the odontoid process of the axis. The posterior arch is longer and more slender than the anterior, and flattened from above downwards; at its middle is a rudimentary spinous process; and upon its upper surface, near the articular processes, a shallow groovef at each side, which represents a superior inter- vertebral notch, and supports the vertebral artery (just before it perforates the dura mater) and the first cer- vical nerve. The interver- tebral notches are peculiar, from being situated behind the articular processes, instead of before them as in the other vertebrae. The transverse processes are remarkably large and long, and pierced by the foramen for the vertebral artery. The articular processes are situated on the most bulky and strongest part of the atlas. The superior are oval and concave, and look inwards, so as to form a kind of cup for the condyles of the occipital bone, and are adapted to the nodding movements of the head; the inferior are circular, and nearly horizontal, to permit of the rota- tory movements. Upon the inner face of the lateral mass which supports the articular processes, is a small tubercle at each side, to which the extremities of the transverse ligament are attached, a ligament which divides the ring of the atlas into two unequal segments; the smaller and anterior, for receiving the odontoid pro- cess of the axis; the larger and posterior, to give passage to the spinal cord and its membranes. The Axis (vertebra dentata) is so named from having a process, shaped like a tooth, upon which the head turns on a pivot. The body is of large size, and supports a strong process, the odontoid, which rises perpendicularly from its upper surface. The odontoid process presents two articulating surfaces : one on its anterior face, to articulate with the anterior arch of the atlas; the other on its posterior face, for the transverse ligament; the latter surface con- stricts the base of the process, which has given rise to the term neck applied to this part. Upon each side of its apex is a rough Fig. 35.* * The upper surface of the atlas. 1. The anterior tubercle projecting from the anterior arch. 2. The articular surface for the odontoid process on the posterior surface of the anterior arch. 3. The posterior arch, with its rudi- mentary spinous process. 4. The intervertebral notch. 5. The transverse process. 6. The vertebral foramen. 7. Superior articular surface. 8. Tubercle for the attachment of the transverse ligament. The tubercle referred to is just above the head of the figure; the convexity below it is the margin of the inferior articulating process. t This groove is sometimes converted into a foramen. VERTEBRA PROMINENS. 29 depression, for the attachment of the alar ligaments ; and running down from its base, on the anterior surface of the body ot the vertebra, a vertical ridge, with a depression at each side for the attachment of the longus colli muscle. The laminae are large and strong, and unite posteriorly to form a long and bifid spinous process, which is concave beneath. The transverse processes are rudimentary, not bifid, and project only so far as to enclose the vertebral fora- men, which is directed obliquely out- wards instead of perpendicularly as in the other vertebra. The superior articulating processes are situated on the body of the vertebra, at each side of the odontoid process. They are circular and nearly horizontal, having a slight inclination outwards. The inferior articulating processes look downwards and forwards, as do the same processes in the other cervical vertebra;. The superior intervertebral notch is remarkably shallow, and lies behind the articular process as in the atlas. The lower surface of the body is convex, and is received into the concavity upon the upper surface of the third vertebra. The Vertebra prominens, or seventh cervical, approaches in cha- racter the upper dorsal vertebrae. It has received its designation from having a very long spinous process, which is single and termi- nated by a tubercle, and forms a projection on the back part of the neck; to the extremity of this process the ligamentum nuchae is attached. The transverse processes are but slightly grooved along the upper surface, have each a small foramen for the transmission of the vertebral vein, and present only a rudimentary bifurcation at their extremity. Sometimes the anterior tubercle represents a small but distinct rib. Dorsal Vertebrae.—The body of a dorsal vertebra is as long from before backwards as from side to side, particularly in the middle of the dorsal region; it is thicker behind than before, and marked on each side by two half articulating surfaces for the heads of two ribs. The pedicles are strong, and the laminae broad and thick ; the spinal foramen small and round, and the inferior intervertebral notch of large size, the superior can scarcely be said to exist. The spinous process is long, prismoid, directed very obliquely downwards, and terminated by a tubercle. The transverse processes are large and Fig. 36.* * A lateral view of the axis. 1. The body; the number is placed on the depression which gives attachment to the longus colli. 2. The odontoid pro- cess. 3. The smooth facet on the anterior surface of the odontoid process which articulates with the anterior arch of the atlas ; the facet for the trans- verse ligament is beneath No. 2, where the constriction called the neck of the odontoid process is seen : the bulk of the process between 2, 3, would repre- sent its head. 4. The lamina. 5. The spinous process. 6. The transverse process, pierced obliquely by the vertebral foramen. 7. The superior articular surface. 8. The inferior articular process. 30 DORSAL AND LUMBAR VERTEBRA. strong, and directed obliquely backwards. Upon the anterior and superior aspect of their summits is a small facet for the articulation of the tubercle of a rib. The arti- cular processes are vertical, the supe- rior facing directly backwards, the in- ferior directly forwards. The peculiar vertebral in the dorsal region are, the first, ninth, tenth, eleventh, and twelfth. The first dorsal vertebra approaches very closely in character the last cervical. The body is broad from side to side, and concave above. The superior articular pro- cesses are oblique, and the spinous process horizontal. It has an entire articular surface for the first rib, and a half surface for the second. The ninth dorsal vertebra has only one half articular surface at each side. The tenth has a single entire articular surface at each side. The eleventh and twelfth have each a single entire articular surface at each side; they approach in character the lumbar vertebras; their transverse processes are very short, trifid at their summit, and have no articulation with the corresponding ribs. The transverse processes of the twelfth dorsal vertebra are rudimentary, and its inferior articular processes look outwards. Lumbar Vertebrce.—These are the largest pieces of the vertebral column. The body is broad and large, and thicker before than behind. The pedicles very strong : the lamince short, thick, and broad; the inferior inter- vertebral notches very large, and the spinal foramen large and oval. The spinous process is thick and broad. The transverse processes (costiform processes) are slender, pointed, and directed very slightly backwards. The superior articular processes are concave, and look backwards and inwards ; the inferior convex, Fig. 37.* Fig. 38. f * Lateral view of a dorsal vertebra. 1. The body. 2, 2. Articular facets for the heads of ribs. 3. The pedicle. 4. The superior intervertebral notch. 5. The inferior intervertebral notch. 6. The spinous process. 7. The extre- mity of the transverse process, marked by an articular surface for the tubercle of a rib. 8. The two superior articular processes looking backwards. 9. The two inferior articular processes looking forwards. t Lateral view of a lumbar vertebra. 1. The body. 2. The pedicle. 3. The superior intervertebral notch. 4. The inferior intervertebral notch. 5. The spinous process. 6. The transverse process. 7. The superior articular pro- cesses. 8. The inferior articular processes. 9. The posterior transverse process. LUMBAR YERTEBEfiE. 31 looks forwards and outwards. Projecting backwards and up- wards from the superior articular process is a short and flattened tubercle or posterior transverse process, and in a strongly marked vertebra there is not unfrequently at the base of this a smaller tubercle which has a direction downwards. The last lumbar ver- tebra differs from the rest in having the body very much bevelled posteriorly, so as to be thick in front and thin behind, and the trans- verse process thick and large. General Considerations.—Viewed as a whole, the vertebral column represents two pyramids applied base to base, the superior being formed by all the vertebrae from the second cervical to the last lumbar, the inferior by the sacrum and coccyx. Examined more attentively, it will be seen to be composed of four irregular pyra- mids, applied to each other by their smaller extremities and by their bases. The smaller extremity of the uppermost pyramid is formed by the axis, or second cervical vertebra; and its base, by the first dorsal. The second pyramid is inverted; having its base at the first dorsal, and the smaller end at the fourth. The third pyramid commences at the fourth dorsal, and gradually enlarges to the fifth lumbar. The fourth pyramid is formed by the sacrum and coccyx. The bodies of the vertebras are broad in the cervical region; nar- rowed almost to an angle in the middle of the dorsal, and again broad in the lumbar region. The arches are broad and imbricated in the cervical and dorsal regions, the inferior border of each over- lapping the superior of the next; in the lumbar region an interval is left between them. A considerable interval exists between the cranium and atlas, and another between the last lumbar vertebra and sacrum. The spinous processes are horizontal in the cervical, and become gradually oblique in the upper part of the dorsal region. In the middle of the dorsal region they are nearly vertical, and imbricated, and towards its lower part assume the direction of the lumbar spines, which are quite horizontal. The transverse processes developed in their most rudimentary form in the axis, gradually increase in length to the first dorsal vertebra. In the dorsal region they pro- ject obliquely backwards, and diminish suddenly in length in the eleventh and twelfth vertebrae, where they are very small. In the lumbar region they increase in length to the middle vertebra, and again subside to the last. The transverse processes consist essentially of two parts, the anterior of which in the dorsal region is the rib, while the posterior retains the name of transverse process. In the cervical region these two elements are quite apparent, both by their different points of attachment to the vertebra, and by the vertebral foramen which divides them at their base. In the lumbar region the so-called transverse processes are in reality lumbar ribs, while the transverse processes will be found behind them in a rudimentary state, deve- loped like the true transverse processes in the cervical region, from 32 DEVELOPMENT OF VERTEBRAE. the superior articular processes. When the anterior and posterior transverse processes are examined in relation with each other, they will he observed to converge; if they were prolonged they would unite as in the cervical region and enclose a foramen, or they would rest in contact as in the dorsal region, or become consolidated as in the formation of the sacrum. Moreover, the posterior transverse processes are directed upwards, and if they were prolonged, they would come into contact with a small tubercle which is found at the base of the posterior transverse process (in strongly marked vertebras) in the vertebra above. This junction would form a pos- terior intervertebral foramen, as actually occurs in the sacrum. In brief, the lumbar vertebras exhibit those transitional changes which are calculated, by an easy gradation, to convert separate vertebras into a solid bone. The transverse processes of the eleventh and twelfth dorsal vertebrae are interesting in a transcendental point of view, as exhibiting a tendency, which exists obscurely in all the rest, to trifurcate. Now, supposing these three branches to be lengthened in order to fulfil their purposes, the anterior would con- stitute the articulation or union with a rib, while the superior and inferior would join similar branches in the vertebra above and below, and form a posterior invertebral foramen. The intervertebral foramina formed by the juxtaposition of the intervertebral notches are smallest in the cervical region, and gra- dually increase to the last lumbar. On either side of the spinous processes, and extending the whole length of the column, is the vertebral groove, which is shallow and broad in the cervical, and deeper and narrower in the dorsal and lumbar regions. It lodges the principal muscles of the back. Viewed from the side, the vertebral column presents several curves, the principal of which is situated in the dorsal region, the concavity looking forwards. In the cervical and lumbar regions the column is convex in front; and in the pelvis an anterior concave curve is formed by the sacrum and coccyx. Besides the antero- posterior curves, a slight lateral curve exists in the dorsal region, having its convexity towards the right side. Development.—The vertebrae are developed by three primary and five secondary centres or epiphyses. The primary centres are, one for each lamella, and one for the body; the epiphyses, one for the apex of the spinous process, one for that of each transverse process, one for the upper and one for the under surface of the body. Ex- ceptions to this mode of development are met with in the atlas, axis, vertebra prominens, and lumbar vertebras. The atlas has four centres: one for each lateral mass, one (sometimes two) for the an- terior arch, and one for the centre of the posterior arch. The axis has five: one (sometimes two) for the body, two for the odontoid process, appearing side by side in its base, and one for each lamella. The vertebra prominens has two additional centres for the anterior or costal segments of the transverse processes, and the lumbar ver- tebrae two for the posterior segments of the transverse processes. DEVELOPMENT OF VERTEBRAE. 33 The primary centres of the vertebrae make their appearance during the seventh or eighth week of embryonic existence, the lamella being somewhat in advance of the body. From the lamella are produced the spinous, transverse, and articular processes, and the sides of the body; they unite, to complete the arch, one year after birth, and with the body during the fifth year. The epiphyses for the extremities of the spinous and transverse processes make their appearance at fifteen or sixteen, and become united between twenty and twenty-five. The epiphyses of the body are somewhat later in appearance, and are consolidated between the periods of twenty-five and thirty years of age. The ossific centres, for the lateral masses, of the atlas, appear at the same time as those of the other vertebrae; they unite posteriorly at the end of the second year, by the intervention of the centre for the posterior arch. The one or two centres of the anterior arch appear during the first year, and become consolidated with the lateral pieces during the fifth or sixth year. The axis develops its lateral pieces at the same time as the other vertebrae; they join posteriorly soon after birth, and with the body during the fourth or fifth year. The centres for the body and odontoid process appear during the sixth month, and are consolidated during the third year. The body of the axis is more largely developed at birth than that of the other vertebrae. The costal segments of the vertebra promi- nens appea" during the second month, and become united to the body at the fifth or sixth year; they sometimes remain perma- nently separate, and constitute cervical ribs. The transverse pro- cess of the first lumbar vertebra has sometimes a distinct centre, which may remain permanently separate, in that case forming a lumbar rib. The ossification of the arches of the vertebra? commences from above, and proceeds gradually downwards; hence arrest of develop- ment gives rise to spina bifida, generally in the loins. Ossification of the bodies, on the contrary, commences at the centre, and proceeds from that point towards the extremities of the column; hence imperfection of the bodies occurs either in the upper or lower vertebrae. Attachment of Muscles.—To the atlas are attached nine pairs of muscles; the longus colli, rectus anticus minor, rectus lateralis, rectus posticus minor, obliquus superior and inferior, splenius colli, levator anguli scapulae, and first intertransversales. To the axis are attached eleven pairs—viz., longus colli, inter- transversales, obliquus inferior, rectus posticus major, interspinales, semi-spinalis colli, multifidus spinae, levator anguli scapulae, splenius colli, transversalis cervicis, and scalenus medius. To the remaining vertebrae collectively, thirty-one pairs and one single muscle—viz., posteriorly, trapezius, latissimus dorsi, levator anguli scapulae, rhomboideus minor and major, serratus posticus superior and inferior, splenius, sacro-lumbalis, longissimus dorsi, spinalis dorsi, cervicalis ascendens, transversalis cervicis, trachelo- 34 SACRUM. mastoideus, complexus, semispinalis dorsi and colli, multifidus spin®, interspinales, intertransversales, levatores costarura: ante- riorly, rectus anticus major, longus colli, scalenus anticus, medius, and posticus, psoas magnus, psoas parvus, quadratus lumborum, diaphragm, obliquus interims and transversalis. The Sacrum is a triangular bone, situated at the lower extremity of the vertebral column, and formed by the consolidation of five false vertebras. It is divisible into an anterior and posterior surface, two lateral and a superior border, and an inferior extremity. The anterior surface is concave, and marked by four transverse lines, which indicate its original constitution of five separative pieces. At the extremities .of these lines, on each side, are the four anterior sacral foramina, which diminish in size from above down- wards, and transmit the anterior sacral nerves. The projection of the superior piece is the sacro-vertebral angle or promontory. The posterior surface is narrower than the anterior, and convex. On the middle line is a rough crest formed by the rudiments of four spinous processes, the fifth remaining undeveloped and exposing the lower termination of the sacral canal. Immediately external to and parallel with the median crest, is a range of five small tubercles which represent the articular processes of the true ver- tebras ; beyond these is a shallow groove in which the four pos- terior sacral foramina open, and farther outwards, a range of five tubercles corresponding with the posterior transverse processes of the lumbar vertebrae. The lowest pair of articular tubercles bound on each side the termination of the sacral canal, and send each a process downwards to articulate with the coccyx. The two descend- ing processes are the sacral cornua. The posterior sacral foramina are smaller than the anterior, and transmit the posterior sacral nerves. Of the posterior transverse tubercles the first corresponds with the angle of the superior border of the bone: the second is small, and enters into the formation of the sacro-iliac articulation; the third is large, and gives attachment to the oblique sacro- Fig. 39.* * The sacrum seen upon its anterior surface. 1, 1. Transverse lines mark- ing the original constitution of the bone of four pieces. 2, 2. Anterior sacral foramina. 3. Promontory of the sacrum. 4. Ear-shaped surface to articulate with the ilium. 5. The sharp edge to which the sacro-ischiatie ligaments are attached. 6. The vertebral articular surface. 7. The broad triangular surface which supports the psoas muscle and lumbo-sacral nerve. 8. Articular pro- cess of the right side. 9. Inferior extremity, or apex of the sacrum. 10. One of the sacral cornua. 11. The notch which is converted into a foramen by the coccyx. SACRUM. 35 iliac ligament; tlie fourth and fifth are smaller, and serve for the attachment of the sacro-ischiatic ligaments. The lateral border of the sacrum presents superiorly a broad and ear-shaped (auricular) surface to ar- ticulate with the ilium; and inte- riorly a sharp edge, to which the greater and lesser sacro-ischiatic liga- ments are attached. On the superior border, in the mid- dle line, is an oval articular surface, corresponding with the under part of the body of the last lumbar vertebra; and on each side a broad triangular surface, which supports the lumbo- sacral nerve and psoas magnus muscle. Immediately behind the ver- tebral articular surface is the trian- gular entrance of the sacral canal; and, on each side of this opening, an articular process, which looks back- wards and inwards, like the superior articular processes of the lumbar vertebrae. In front of each articular process is an intervertebral notch. The inferior extremity of the bone presents a Small oval surface which articulates with the coccyx; and on each side, a notch, which, with a corresponding notch in the upper border of the coccyx, forms the foramen for the transmission of the fifth sacral nerve. The sacrum presents some variety in respect of curvature, and of the number of pieces which enter into its structure. The curve is often very slight, and situated only near the lower part of the bone; while in other subjects it is considerable, and occurs at the middle of the sacrum. The sexual differences in the sacrum relate to its greater breadth, and the greater angle which it forms with the rest of the vertebral column in the female, rather than to any peculiarity in shape. It is sometimes composed of six pieces, more rarely of four, and, occasionally,, the first and second pieces remain perma- nently separate. Development.—By twenty-one points of ossification; five for each of the first three pieces—viz., one for the body, one for each lateral portion, and one for each lamina; and three for each of the last Fig. 40.* * Posterior view of the sacrum. 1, 1. The four rudimentary spinous pro- cesses. 2, 2. The sacral canal. 3, 3. Rudimentary articular processes. The lowest of these processes, with the corresponding process of the opposite side, 4, are the sacral cornua. 5, 5. The four posterior sacral foramina. 6, 6. Pos- terior transverse tubercles. 7. The auricular surface. 8. Sharp edge for the attachment of the sacro-ischiatic ligaments. 9. Surface for articulation with the body of the last lumbar vertebra. 10, 10. Articulating facets of the arti- cular processes. 11. Apex of the sacrum by which it articulates with the coccyx. 12. Rough- surface for the attachment of the posterior sacro-iliac ligaments. 36 COCCYX. two—namely, one for the body and one for each lateral portion. In the progress of growth, and after puberty, fourteen epiphysal centres are added—namely, two for the surfaces of each body, one for each auricular surface, and one for the thin edge of each lateral border. Ossification begins in the bodies of the sacral pieces some- what later than in those of the true vertebrae: the first three appearing during the eighth and ninth week, and the last two at about the middle of intra-uterine existence. Ossification of the lamellae takes place during the interval between the sixth and ninth month. The epiphyses for the upper and under surface of the bodies are developed during the interval between the fifteenth and eighteenth year; and for the auricular and marginal piece, after twenty. The two lower vertebral pieces, although the last to appear, are the first to be completed (between the fourth and fifth yeai*), and unite by their bodies. The union of the bodies takes place from below upwards, and finishes, between the twenty-fifth and thirtieth year, with the first two pieces. Articulation.—With four bones ; the last lumbar vertebra, ossa innominata, and coccyx. Attachment of Muscles.—To seven pairs ; in front, pyriformis; on the side, coccygeus; and behind, gluteus maximus, latissimus dorsi, longissimus dorsi, sacro-lumbalis, and multifidus spinas. The Coccyx (kokkv£, cuckoo, resembling a cuckoo’s beak) is com- posed of four small pieces, which form the caudal termination of the vertebral column. The superior piece is broad, and expands laterally into two trans- verse processes ; it is surmounted by an oval articular surface and two cornua, the former to articulate with the apex of the sacrum, the latter with the sacral cornua. The lateral wings sometimes become connected with the sacrum, and convert the notches for the fifth pair of sacral nerves into foramina. The re- maining three pieces diminish in size from above downwards. Development.—By four centres, one for each piece. Ossification commences in the first piece soon after birth ; in the second, between five and ten years ; in the third, between ten and fifteen ; and in the fourth, between fifteen and twenty. The pieces unite at an earlier period than the bodies of the sacrum, the first two pieces first, then the third and fourth, and lastly the second and third. Between forty and sixty years, the coccyx becomes consolidated with the sacrum; this event taking place later in the female than in the male. Articulations.-—With the sacrum. Fig. 41.* * Front view of the coccyx. 1, 2, 3, 4. The four pieces of the bone. 5, 5. The transverse processes of the first piece. 6. Articular surface for the ex- tremity of the sacrum, 7, 7. The cornua which articulate with the sacral cornua. OCCIPITAL BONE. 37 Attachment of Muscles.—To three pairs, and one single muscle ; gluteus maximus, coccygeus, posterior fibres of the levator ani, and sphincter ani. OP THE SKULL. The skull is divisible into two parts, the cranium and the face ; the former being adapted, by its form, structure, and strength to contain and protect the brain; the latter, the chief organs of sense. The CiiANiuii is composed of eight separate bones—viz., the Occipital, Two parietal, Frontal, Two temporal, Sphenoid, Ethmoid. Occipital Bone.—This bone is situated at the posterior part and base of the cranium. It is trapezoid in figure, and divi- sible into two surfaces, four borders, and four angles. External Surface.—Cross- ing the middle of the bone transversely, from one lateral angle to the other, is a pro- minent ridge, the superior curved line. In the middle of the ridge is a projection called the external occipital protuberance, for the attach- ment of the Ligamentum un- due; and descending from it a small vertical ridge, the spine or crest. Above and be- low the superior curved line the surface is rough, for the attachment of muscles. About three-quarters of an inch below the superior curved line is another transverse ridge, the inferior curved line, and beneath the latter the foramen magnum. On each side of the foramen magnum, nearer its anterior than its posterior segment, and encroaching somewhat upon the opening, is an oblong articular surface, the condyle, for articulation with the atlas. The condyles approach towards each Fig. 42* * External surface of the occipital bone. 1. Superior curved Hue. 2. Ex- ternal occipital protuberance. 3. Spine. 4. Inferior curved line. 5. Foramen magnum. 6. Condyle of the right side. 7. Posterior condyloid fossa, in which the posterior condyloid foramen is found. 8. Anterior condyloid foramen, con- cealed by the margin of the condyle. 9. Transverse process; this process on the internal surface of the bone forms the jugular eminence. 10. The notch in front of the jugular eminence, forming part of the jugular foramen. 11. Basilar process. 12. Rough projections into which the odontoid ligaments are inserted. 38 OCCiriTAL BONE. other anteriorly, their articular surfaces looking downwards and outwards. Directly behind each condyle is an irregular fossa, and, sometimes, a small opening, the 'posterior condyloid foramen, for the transmission of a vein to the lateral sinus. In front of the condyle is the anterior condyloid foramen, for the hypoglossal nerve; on the outer side of each condyle, a projecting ridge, the transverse process, excavated in front by a notch which forms part of the jugular foramen; and directly behind the ridge, and forming its posterior boundary, a prominent process, the jugular tubercle. In front of the foramen magnum is a thick square mass, the basilar process, and in its centre a small tubercle, the pharyngeal tubercle or spine, for the attachment of the tendinous raphe and superior constrictor muscle of the pharynx. Internal Surface.—On the internal surface is a crucial ridge, which divides the bone into four fossae ; the two superior or cerebral fossae lodging the posterior lobes of the cerebrum ; the two inferior or cerebellar, the lateral lobes of the cerebellum. The superior arm of the crucial ridge is grooved for the superior longitudinal sinus, and gives attachment to the falx cerebri; the inferior arm is sharp and prominent for the attachment of the falx cerebelli, and slightly grooved for the two occipital sinuses. The transverse ridge gives attachment to the tentorium cerebelli, and is deeply grooved for the lateral sinuses. At the point of meeting of the four arms is a projection, the internal occipital protuberance, which corresponds with the similar process situated on the external surface of the bone. The convergence of the four grooves forms a slightly depressed fossa, upon which rests the torcular Herophili. In the centre of the basilar portion of the bone is the foramen magnum, oblong in form, and larger behind than before, transmitting the spinal cord and its membranes, the spinal accessory nerves, and vertebral arteries, and having its anterior constricted portion occu- pied by the tip of the odontoid process of the axis. Upon the lateral margins of the foramen magnum are two rough eminences, which give attachment to the odontoid ligaments, and immediately above these, the openings of the anterior condyloid foramina. In front of the foramen magnum is the basilar process, grooved on its sur- face for supporting the medulla oblongata, and along each lateral border for the inferior petrosal sinus. On each side of the foramen magnum is a groove, for the termination of the lateral sinus; a smooth surface, which forms part of the jugular fossa; and a pro- jecting process, which divides the two, and is called the jugular eminence. Into the jugular fossa will be seen opening the posterior condyloid foramen. The superior borders are strongly serrated, and assist in forming the lambdoidal suture; the inferior are rough, not serrated, and articulate with the mastoid portion of the temporal bones by means of the additamentum suturm lambdoidalis. The jugular eminence and side of the basilar process articulate with the petrous portion of the temporal bone, and the intervening space, which is irregu- OCCIPITAL BONE. 39 larly notched, forms the posterior boundary of the jugular foramen, or foramen lacerum posterius. The angles of the occipital bone are, the superior, inferior, and two lateral. The superior angle is received into the in- terval formed by the union of the posterior and superior angles of the parietal bones, and corresponds with that portion of the foetal head which is called the posterior fontanelle. The inferior angle is the articular extremity of the basilar process. The lateral angles, at each side, project into the interval formed by the articulation of the posterior and inferior angle of the parietal with the mastoid portion of the tem- poral bone. Development. — By seven centres; four for the four parts of the expanded por- tion divided by the crucial ridge, one for each condyle, and one for the basilar process. Ossi- fication commences in the expanded portion of the bone at a period anterior to the vertebrae ; at birth the bone consists of four distinct pieces ; which are united at about the fifth or sixth year. After twenty the basilar process unites with the body of the sphenoid. The part above the occipital protuberances is developed from membrane, the rest from cartilage. Articulations.—With six bones; two parietal, two temporal, sphenoid, and atlas. Attachment of Muscles.—To twelve pairs; to the rough surface above the superior curved line, the occipito-frontalis ; to the superior curved line, the trapezius and sterno-mastoid; to the rough space bettveen the curved lines, complexus, and splenius capitis; to the space between the inferior curved line and the foramen magnum, the Fig. 43.* * Internal surface of the occipital bone. 1. Left cerebral fossa. 2. Left cerebellar fossa. 3. Groove for the posterior part of the superior longitudinal sinus. 4. Spine for the falx cerebelli, and groove for the occipital sinuses. 5. Groove for the left lateral sinus. 6. Internal occipital protuberance, the groove on which lodges the torcular Herophili. 7. Foramen magnum. 8. Basilar process, grooved for the medulla oblongata. 9. Termination of the groove for the lateral sinus, bounded externally by the jugular eminence. 10. Jugular fossa ; this fossa is completed by the petrous portion of the temporal bone. 11. Superior border. 12. Inferior border. 13. Border which articu- lates with the petrous portion of the temporal bone, grooved by the inferior petrosal sinus. 14. Anterior condyloid foramen. 40 PAEIETAL BONE. rectus posticus major and minor, and obliquus superior; to the transverse process, the rectus lateralis ; and to the basilar process, the rectus anticus major and minor, and superior constrictor of the pharynx. Parietal Bone.—The parietal bone (paries, a wall), is situated at the side and vertex of the skull; it is quadrilateral in form, and divisible into an external and internal surface, four borders, and four angles. The superior border is straight, to ar- ticulate with its fellow of the opposite side. The inferior border is arched and thin, to articulate with the temporal bone. The anterior border is con- cave, and the posterior somewhat convex. External Surface. — Crossing the bone in a longitudinal direction from the anterior to the posterior border, is an arched line, the tem- poral ridge, to which the temporal fascia is attached. In the middle of this line, and nearly in the centre of the bone, is the pro- jection called the parietal eminence, which marks the centre of ossification. Above the temporal ridge the surface is rough, and covered by the aponeurosis of the occipito-frontalis; below the ridge the bone is smooth, for the attachment of the fleshy fibres of the temporal muscle. Near the superior border of the bone, and at about one-third from its posterior extremity, is the parietal fora- men, which transmits a vein to the superior longitudinal sinus. This foramen is often absent. Internal Surface.—The internal table is smooth; it is marked by numerous furrows, which lodge the ramifications of the arteria meningea media, and by digital fossae which correspond with the convolutions of the brain. Along the upper border is part of a shallow groove, completed by the opposite parietal bone, which serves to contain the superior longitudinal sinus. Near this groove, some slight pits, which lodge the glandulae Pacchioni, are also observable. The anterior inferior angle is thin and lengthened, and articu- Fy. 44.* * External surface of the left parietal bone. 1. Superior or sagittal border. 2. Inferior or squamous border. 3. Anterior or coronal border. 4. Posterior or lambdoidal border. 5. Temporal ridge ; the cipher is situated immediately in front of the parietal eminence. 6. The parietal foramen, unusually large in the bone from which this figure was drawn. 7. Anterior inferior angle. 8. Posterior inferior angle. FRONTAL BONE. 41 lates with the greater wing of the sphenoid hone. Its inner surface is deeply grooved for the trunk of the arteria meningea media; the groove being frequently con- verted into a closed canal. The 'posterior inferior ancjle is thick, and presents a broad and shallow groove for the lateral sinus. Development.—By a single centre. Ossification com- mences in the parietal emi- nence at the same time as in the bodies of the vertebra; (seventh or eighth week). The whole of this bone is de- veloped from membrane. Articulations.—With five bones; with the opposite parietal, occipital, frontal, temporal, and sphenoid. Attachment of Muscles.— To one only, the temporal. The aponeurosis of the occipito-frontalis glides over its upper surface. Frontal Bone.—The frontal bone bears some resemblance in form to the under valve of a scallop-shell. It is situated at the anterior part of the cranium, forming the forehead, and assisting in the construction of the roof of the orbits and nose. Hence it is divisible into a superior or frontal portion, and an inferior or orbito- nasal portion. Each of these portions presents for examination an external and internal surface, borders, and processes. External Surface.—At about the middle of each lateral half of the frontal portion is a projection, the frontal eminence. Below these points are the superciliary riclges, large towards their inner termination, where they become continuous with the nasal tubero- sity, and becoming gradually smaller as they arch outwards : they support the eyebrows. Beneath the superciliary ridges are the sharp and prominent arches which form the upper margin of the orbits, the supraorbital ridges. Externally the supraorbital ridge terminates in the external angular process, internally in the internal angular process; at the inner third of this ridge is a notch, some- times converted into a foramen, the supraorbital notch, which gives passage to the supraorbital artery, veins, and nerve. Between the Fig. 45.* * Internal surface of the left parietal bone. 1. Superior, or sagittal border. 2. Inferior, or squamous border. 3. Anterior, or coronal border. 4. Posterior, or lambdoidal border. 5. Part of the groove for the superior longitudinal sinus. 6. Internal termination of the parietal foramen. 7. Anterior inferior angle of the bone, on which is seen the groove for the trunk of the arteria meningea media. 8. Posterior inferior angle, on which is seen a portion of the groove for the lateral sinus. 42 FRONTAL BONE. two superciliary ridges is a rough projection, the nasal tuberosity; this portion of the bone denotes by its prominence the situation of the frontal sinuses. Extending upwards and backwards from the external angular process is a sharp ridge, the commencement of the temporal ridge, and beneath the ridge, a depressed surface, forming part of the temporal fossa. The orbito-nasal portion of the bone consists of two thin pro- cesses, the orbital plates, which form the roof of the orbits, and an intervening notch which lodges the ethmoid bone, and is called the ethmoidal fissure. The edges of the ethmoidal fissure are hollowed into cavities, which, by their union with the ethmoid bone, com- plete the ethmoidal cells. Crossing these edges transversely, are two small grooves, which are converted into canals by articulation with the ethmoid: these are the anterior and posterior eth- moidal canals; they open on the inner wall of the orbit,—the anterior trans- mitting the anterior eth- moidal artery and vein, and nasal nerre, the posterior giving passage to the pos- terior ethmoidal vessels. At th e anterior termination of these edges are the irre- gular openings which lead into the frontal sinuses; and between the two in- ternal angular processes is a rough excavation which receives the nasal bones, and a projecting process, the nasal spine. On each orbital plate, immediately beneath the external an- gular process, is a shallow depression which lodges the lachrymal gland; and beneath the internal angular process a small pit, some- times a tubercle, to which the cartilaginous pulley of the superior oblique muscle of the eye is attached. Internal Surface.—Along the middle line of this surface is a grooved ridge, the edges of the ridge giving attachment to the falx cerebri, the groove lodging the superior longitudinal sinus. At the Fig. 46.* * External surface of the frontal bone. 1. Situation of the frontal eminence of the right side. 2. Superciliary ridge. 3. Supraorbital ridge. 4. External angular process. 5. Internal angular process. 6. Supraorbital notch, for the transmission of the supraorbital nerve and artery; in the figure it is partly con- verted into a foramen by a spiculum of bone. 7. Nasal tuberosity; the swell- ing around this point denotes the situation of the frontal sinuses. 8. Temporal ridge, commencing from the external angular process (4). 9. Part of the temporal fossa. 10. Nasal spine. FEONTAL BONE. 43 commencement of the ridge is an opening, sometimes completed by the ethmoid hone, the foramen caecum. This opening lodges a process of the dura mater, and occasionally gives passage to a small vein which communicates with the nasal veins. On each side of the vertical ridge are some slight depressions which lodge the glan- dulse Pacchioni, and on the orbital plates a number of irregular pits called digital fossae, which correspond with the convolutions of the anterior lobes of the cerebrum. The superior border is thick and strongly serrated, bevelled at the expense of the internal table in the middle, where it rests on the junction of the two parietal, and at the ex- pense of the external table on each side where it re- ceives the lateral pressure of those bones. The infe- rior border is thin, irre- gular, and squamous, and articulates with the sphe- noid bone. Development.—By two centres, one for each late- ral half. Ossification be- gins in the orbital arches, somewhat before the ver- tebrae. The two pieces are separate at birth, and unite by suture during the first year, the suture sometimes remaining per- manent through life, fron- tal suture. The frontal sinuses make their appearance during the first year, and increase in size until old age. This bone is entirely developed in membrane. Articulations.—With twelve bones: two parietal, sphenoid, eth- moid, two nasal, two superior maxillary, two lachrymal, and two malar. jFig. 47.* * Internal surface of the frontal bone ; the bone is raised to show the orbito- nasal portion. 1. Grooved ridge for the lodgment of the superior longitudinal sinus and attachment of the falix. 2. Foramen caecum. 3. Superior or coronal border of the bone ; the figure is situated near that part which is bevelled at the expense of the internal table. 4. Inferior border of the bone. 5. Orbital plate of the left side. 6. Cellular border of the ethmoidal fissure. The foramen caecum (2) is seen through the ethmoidal fissure. 7. Anterior and posterior ethmoidal foramen; the anterior is seen leading into its canal. 8. Nasal spine. 9. The depression within the external angular process (12) for the lachrymal gland. 10. Depression for the pulley of the superior oblique muscle of the eye ; immediately to the left of this number is the supraorbital notch, and to its right the internal angular process. 11. Opening leading into the frontal sinuses ; the leading line crosses the internal angular process. 12. External an- gular process. The corresponding parts are seen on the other side of the figure. 44 TEMPOEAL BONE. Attachment of Muscles.—To three pairs: corrugator supercilii, temporal, and orbicularis palpebrarum. Temporal Bone.—The temporal bone is situated at the side and base of the skull, and is divisible into a squamous, mastoid, and petrous portion. The Squamous portion (squama, a scale), forming the anterior part of the bone, is thin, translucent, and contains no diploe. On its external surface it is smooth, gives attachment to the fleshy fibres of the tem- poral muscle, and has project- ing from it an arched and lengthened process, the zygo- ma (from (vyos, a yoke,because it joins the temporal and malar bones together). Near the commencement of the zygoma, upon its lower border, is a pro- jection called the tubercle, to which is attached the external lateral ligament of the lower jaw, and continued horizon- tally inwards from the tuber- cle, a rounded eminence, the eminentia articularis. The process of bone which is continued from the tubercle of the zygoma into the eminentia articularis is the inferior root of the zygoma. The superior root is continued upwards from the upper border of the zygoma, and forms the posterior part of the temporal ridge, serving by its projection to mark the division of the squamous from the mastoid portion of the bone; and the middle root is continued directly backwards, and terminates abruptly at a narrow fissure, the fissura Glaseri. The upper border of the zygoma is thin and sharp, and has attached to it the fibres of the temporal fascia; the lower border is thick, and gives origin to some fibres of the masseter muscle. The internal surface of the squamous portion is marked by several shallow fossae, which correspond with the convolutions of the cere- brum, and by a furrow for the posterior branch of the arteria meuingea Fig. 48.* * External surface of the temporal bone of the left side. 1. Squamous por- tion. 2. Mastoid portion. 3. Extremity of the petrous portion. 4. The zygoma. 5. Indicates the tubercle of the zygoma, and at the same time its anterior root turning inwards to form the eminentia articularis. 6. Superior root of the zygoma, forming the posterior part of the temporal ridge. 7. Middle root of the zygoma, terminating abruptly at the glenoid fissure. 8. Mastoid foramen. 9. Meatus auditorius externus, surrounded by the processus auditorius. 10. The digastric fossa, situated immediately to the inner side of (2) the mastoid process. 11. Styloid process. 12. Vaginal process or tympanic lamina. 13. Glenoid or Glaserian fissure; the leading line from this number crosses the rough posterior portion of the glenoid fossa. 14. The opening and part of the groove for the Eustachian tube. TEMPORAL BONE. 45 media. The superior or squamous border is very thin, and bevelled at the expense of the inner surface, so as to overlap the lower and arched border of the parietal bone. The inferior border is thick, and dentated to articulate with the spinous process of the sphenoid bone. The Mastoid portion (fuurros elbos, nipple-like) forms the posterior part of the bone ; it is thick and hollowed between its tables into a loose and cellular diploe. On its external surface it is rough for the attachment of muscles, and contrasts strongly with the smooth and polished surface of the squamous portion: every part of the surface is pierced by small foramina, which give passage to minute arteries and veins; one of these openings, oblique in direction, of large size, and situated near the posterior border of the bone, the mastoid foramen, transmits a vein to the lateral sinus. Not unfrequently this foramen is situated in the occipital bone, or is absent altogether. The inferior part of the mastoid portion is round and expanded, the mastoid process, and excavated in its interior into numerous cells, which form part of the organ of hearing. In front of the mastoid process, and between the superior and middle root of the zygoma, is the large oval opening of the meatus auditorius externus, sur- rounded by a rough lip, the processus auditorius. Directly to the inner side of, and partly concealed by, the mastoid process, is a deep groove, the digastric fossa, for the digastric muscle; and a little more internally the occipital groove, which lodges the occipital artery, a branch of the external carotid. On its internal surface the mastoid portion presents a broad and shallow groove (fossa sigmoidea) for the lateral sinus, and terminating in this groove the internal opening of the mastoid foramen. The superior border of the mastoid portion is dentated, and articulates with the posterior inferior angle of the parietal bone ; its posterior border is thick, and less serrated, and articulates with the in- ferior border of the occipital bone. The meatus auditorius externus is a slightly curved canal, somewhat more than half an inch in length, longer along its lower than its upper wall, and directed obliquely inwards and forwards. The canal is narrower at the middle than at the extremities, is broadest in its hori- zontal diameter, and terminates at the outer wall of the tympanum by an abrupt oval border. Within the margin of this border is a groove for the insertion of the membrana tympani. Fig. 49 * * Section of the temporal bone, right side, showing the curved direction of the meatus auditorius externus. 1. Edge of the processus auditorius. 2. Groove into which the membrana tympani is inserted. The obliquity of the line from 2 to 3 indicates the oblique termination of the meatus, and the con- sequent oblique direction of the membrana tympani. 4, 4. Cavity of the tym- panum. 5. Opening of the Eustachian tube. 6. Part of the aquseductus Fallopii. 7. Part of the carotid canal. 46 TEMPORAL BONE. The Petrous portion of the temporal bone is named from its ex- treme hardness and density (nerpos, a rock). It is a three-sided pyramid, projecting horizontally forwards into the base of the skull, the base being applied against the internal surface of the squamous and mastoid portions, and the apex being received into the triangu- lar interval between the spinous process of the sphenoid and the basilar process of the occipital bone. For convenience of descrip- tion it is divisible into three surfaces, anterior, posterior, and basilar; and three borders, superior, anterior, and posterior. The anterior surface, forming the posterior boundary of the middle fossa of the interior of the base of the skull, presents for examination from base to apex, firstly an eminence caused by the projection of the perpendicular semicir- cular canal; next, a groove leading to an irregular oblique opening, the hiatus Fallopii, for the transmission of the petrosal branch of the Vidian nerve; thirdly, another and smaller oblique foramen, im- mediately beneath the pre- ceding, for the passage of the nervus petrosus superficialis minor, a branch of Jacobson’s nerve; and lastly, a large foramen near the apex of the bone, the termination of the carotid canal. The posterior surface forms the front boundary of the posterior fossa of the base of the skull; near its middle is the oblique en- trance of the meatus auditorius interims, which gives passage to Fig. 50.* * Left temporal bone, seen from within. 1. Squamous portion. 2. Mastoid portion. The cipher is placed immediately above the inner opening of the mastoid foramen. 3. Petrous portion. 4. Groove for the posterior branch of the arteria meningea media. 5. Bevelled edge of the squamous border of the bone. 6. Zygoma. 7. Digastric fossa, immediately internal to the mastoid process. 8. Occipital groove. 9. Groove for the lateral sinus. 10. Elevation on the anterior surface of the petrous bone, marking the situation of the per- pendicular semicircular canal. 11. Opening of termination of the carotid canal. 12. Meatus auditorius internus. 13. A dotted line leads Upwards from this cipher to the narrow fissure which lodges a process of the dura mater. Another line leads downwards to the sharp edge which conceals the opening of the aquroductus cochleae, while the cipher itself is situated on the bony lamina which overlies the opening of the aquceductus vestibuli. 14. Styloid process. 15. Stylo-mastoid foramen. 16. Carotid foramen. 17. Jugular process. The deep excavation to the left of this process forms part of the jugular fossa, that to the right is the groove for the eighth pair of nerves. 18. Eotch for the fifth nerve on the upper border of the petrous bone, near its apex. 19. Extremity of the petrous bone, this part gives origin to the levator palati and tensor tym- pani muscle. TEMPORAL BONE. 47 the seventh pair of nerves and the auditory artery. Above the meatus auditorius internus is a small oblique fissure, and a minute foramen ; the former lodges a process of the dura mater, and the foramen gives passage to a small vein. Further outwards, towards the mastoid portion of the bone, is a small slit, almost hidden by a thin plate of bone, this is the aqucedudus vestibuli, and transmits a small artery and vein of the vestibule and a process of dura mater. Below the meatus, and partly concealed by the margin of the pos- terior border of the bone is the aqucedudus codilece, through which passes a vein from the cochlea to the internal jugular vein, and a process of dura mater. The basilar surface of the petrous portion is rough, irregular, and enters into the formation of the under surface of the base of the skull. Projecting downwards, near its middle, is a long sharp spine, the styloid process, occasionally connected with the bone only by cartilage, and lost during maceration, particularly in the young subject.* At the base of this process is a rough sheath-like ridge, into which the styloid process appears implanted, the vaginal pro- cess or tympanic lamina. In front of the vaginal process is a broad triangular depression, the glenoid fossa, bounded in front by the eminentia articularis, behind by the vaginal process, and externally by the rough lip of the processus auditorius. The glenoid fossa (yXgurj, a socket), is divided transversely by the glenoid fissure (fissura Glaseri), which receives the extremity of the processus gracilis of the malleus, and transmits the laxator tympani muscle, chorda tympani nerve, and anterior tympanic artery. The surface of the fossa in front of the fissure is smooth, to articulate with the condyle of the lower jaw; and that behind the fissure rough, for the reception of part of the parotid gland. At the ex- tremity of the inner angle of the glenoid fossa is the foramen of the Eustachian tube; and separated from it by a thin lamella of bone, called processus cochleariformis, a small canal for the transmission of the tensor tympani muscle. Directly behind, and at the root of the styloid process, is the stylo-mastoid foramen, the opening of exit of the facial nerve, and entrance of the stylo-mastoid artery; and a little in front of this, between the mastoid and vaginal processes, is a small slit, the auri- cular fissure, for the exit of the auricular branch of the pneumo- gastric (Arnold’s nerve). Nearer the apex of the bone is a large oval opening, the carotid foramen, the commencement of the carotid canal, which lodges the internal carotid artery and carotid plexus. And between the stylo-mastoid and carotid foramen, in the pos- terior border, is an irregular excavation forming part of the jugular fossa for the commencement of the internal jugular vein; on the inner wall of which will be found a minute foramen, for the entrance * Eetzius remarks that the styloid process, which is connected with the lesser cornu of the os hyoides by means of the stylo-hyoidean ligament, belongs in reality to the os hyoides, and completes the hyoid arch ; he also notes that the vaginal process or tympanic lamina is a distinct bone in many vertebrata. 48 TEMPORAL BONE. of Arnold’s nerve. The share of the jugular fossa formed by the petrous portion of the temporal bone is different in different bones; but in all the fossa presents a vertical ridge on its inner side, which cuts off a small portion from the rest. The upper part of this ridge forms a spinous projection, the jugular process, the groove to the inner side of the ridge lodges the eighth pair of nerves, and the lower part of the ridge is the septum of division between the jugular fossa and carotid foramen. Upon the latter portion of the ridge near the posterior margin of the carotid foramen is a small opening leading into a canal which transmits the tympanic branch (Jacobson’s nerve) of the glosso-pharyngeal nerve. The superior border of the petrous portion is sharp, and gives attachment to the tentorium cerebelli. It is grooved for the supe- rior petrosal sinus, and near its extremity is marked by a smooth notch upon which reclines the Casserian ganglion of the fifth nerve. The anterior border is grooved for the Eustachian tube, and forms the posterior boundary of the foramen lacerum basis cranii; by its sharp extremity it gives attachment to the tensor tympani, and levator palati muscle. The 'posterior border is grooved for the inferior petrosal sinus, and excavated for the jugular fossa: it forms the anterior boundary of the foramen lacerum posterius. Development.—By four centres : one for the squamous portion, one for the petrous and mastoid portions, one for the auditory pro- cess, which in the foetus is a mere bony ring incomplete superiorly, and serving for the attachment of the mem- brana tympani, annulus membranes tympani; and one for the styloid process. Ossification occurs in these pieces in the following order : in the squamous portion immediately after the vertebras, then in the tympanic, next in the petrous and mastoid, and last in the styloid. The tympanic ring is united by its extremities to the squamous por- tion during the last month of intra-uterine life; the squamous, petrous, and mastoid portions are consolidated during the first year; and the styloid some years after birth. It not unfrequently happens that the latter remains permanently separate, or is prolonged by a series of pieces to the os hyoides, and so completes the hyoid arch. The subsequent changes in the bone are, the increase of size of the glenoid fossa, the growth of the meatus auditorius externus, the levelling of the surfaces of the petrous portion, and the develop- ment of mastoid cells. Traces of the union of the petrous with the squamous portion of the bone are usually perceptible in the adult. Articulations.—With five bones: occipital, parietal, sphenoid, inferior maxillary, and malar. Attachment of Muscles.—To fourteen: by the squamous portion, to the temporal; by the zygoma, to the masseter; by the mastoid portion, to the occipito-frontalis, splenius capitis, sterno-mastoid, Fig. 51.* * The annulus membranse tympani or tympanic bone of the foetal skull, right side. SPHENOID BONE. 49 trachelo-mastoid, digastricus, and retrahens aurem; by the styloid process, to the stylo-pharyngeus, stylo-hyoideus, stylo-glossus, and two ligaments, stylo-hyoid and stylo-maxillary; and, by the petrous portion, to the levator palati, tensor tympani, and stapedius. Sphenoid Bone.—(The sphenoid (crfyrjv, a wedge) is an irregular bone, situated at the base of the skull, wedged between the other bones of the cranium, and entering into the formation both of the cranium and face. It bears some resemblance, in form, to a bat with its wings extended, and is divisible into body, wings, and processes. The body forms the central mass of the bone, from which the wings and processes are projected. From the upper and anterior part of the body extend, one to each side, two small triangular plates, the lesser wings; from either side and expanding laterally are the greater wings; proceeding backwards from the base of the greater wings, the spinous processes, and downwards, the pterygoid processes. The body presents for examination a superior or cerebral surface, an antero-inferior surface, and a posterior surface. Superior surface.—At the anterior extremity of this surface is a small projecting plate, the ethmoidal spine, and spreading out on either side the lesser wings. Behind the ethmoidal spine in the middle line is a rounded elevation, the olivary process, which sup- ports the commissure of the optic nerves; and on either side of the posterior margin of that process a tubercle, the middle clinoid process (leXlvrj, a bed). Passing outwards and forwards from the olivary process, are the optic foramina, which transmit the optic nerves and ophthalmic arteries. Behind the optic foramina are two sharp tubercles, the anterior clinoid processes, which are the inner terminations of the lesser wings. Beneath these processes, on the sides of the olivary process, are two depressions* for the last turn Fig• 52.t of the internal carotid arteries. Behind the olivary process is the sella turcica (ephippium), the deep fossa which lodges the pituitary * These depressions are occasionally converted into foramina by the exten- sion of a short bony pillar from the middle to the anterior clinoid process. t Superior or cerebral surface of the sphenoid bone. 1. Processus olivaris. 2. Ethmoidal spine. 3. Lesser wing of the left side. 4. Cerebral surface of 50 SPHENOID BONE. gland and circular sinus; behind and somewhat overhanging the sella turcica, is a broad rough plate (dorsum ephippii) bounded at each angle by a tubercle, the posterior clinoid processes; and behind this plate an inclined surface (clivus Blumenbachii), which is con- tinuous with the basilar process of the occipital bone. On each side of the sella turcica is a broad groove (carotid or cavernous groove) which lodges the internal carotid artery, cavernous sinus, orbital nerves, and cavernous plexus of the sympathetic. The nerves are contained in the walls of the sinus, the sixth and cavernous plexus being in the inner wall, the third, fourth, and ophthalmic division of the fifth (in the order here given, from above downwards) in the outer wall. They are separated from the blood of the sinus by its lining membrane. Upon the antero-inferior surface of the body of the sphenoid is a long flattened spine or crest, the superior part of which, crista sphe- Fig. 53.* noidalis, articulates with the central lamella of the ethmoid, while the inferior part, longer and sharper, the rostrum sphenoidale, is the greater wing of the same side. 5. Spinous process. 6. Extremity of the pterygoid process of the same side, projecting downwards from the under sur- face of the body of the bone. 7. Foramen opticum. 8. Anterior clinoid pro- cess. 9. Groove by the side of the sella turcica; for lodging the internal carotid artery, cavernous plexus, cavernous sinus, and orbital nerves. 10. Sella turcica; the two tubercles in front of the figure are the middle clinoid processes. 11. Posterior boundary of the sella turcica ; its projecting angles are the pos- terior clinoid processes. 12. Basilar portion of the bone. 13. Part of the sphenoidal fissure. 14. Foramen rotundum. 15. Foramen ovale. 1G. Fora- men spinosum. 17. The angular interval which receives the apex of the petrous portion of the temporal bone. The posterior extremity of the Vidian canal terminates at this angle. 18. Spine of the spinous process; it affords attachment to the internal lateral ligament of the lower jaw. 19. The border of the greater wing and spinous process, which articulates with the anterior part of the squamous portion of the temporal bone. 20. The internal border of the spinous process, which assists iu the formation of the foramen lacarum basis cranii. 21. That portion of the greater ala which articulates with the anterior inferior angle of the parietal bone. 22. The portion of the greater ala which articulates with the orbital process of the frontal bone. * Antero-inferior view of the sphenoid bone. 1. Ethmoid spine. 2. The rostrum. 3. Sphenoidal spongy bone, partly closing the left opening of the sphenoidal cells. 4. Lesser wing. 5. Foramen opticum, piercing the base of SPHENOID BONE. 51 intended to be inserted into the sheath formed by the upper border of the vomer. On either side of the crista sphenoidalis is an irre- gular opening leading into the sphenoidal cells. The sphenoidal cells, absent in the young subject, are divided by a median septum which is continuous with the crista, and are partially closed by two thin plates of bone (frequently broken away) the sphenoidal spongy hones (bones of Bertin). On each side of the sphenoidal cells are the outlets of the optic foramina, and other openings to be presently described; the lesser and greater wings; and, below, the pterygoid processes. At the under surface of the body are two thin plates of bone (processus vaginales) proceeding from the base of the pterygoid process at each side, and intended for articulation with the border of the vomer. On each of these plates, close to the root of the pterygoid process, is a groove (sometimes a canal) converted into a canal by the palate bone, the pterygo-palatine canal for the pterygo- palatine nerve and artery; and traversing the root of the pterygoid process at its union with the body of the bone, is the pterygoid or Vidian canal, which gives passage to the Yidian nerve and artery. The posterior surface of the body is fiat and rough, and articu- lates with the basilar process of the occipital bone. In the adult this union is usually completed by bone; from which circumstance the sphenoid, in conjunction with the occipital, is described by Soemmering and Meckel as a single bone, under the name of spheno- occipital. The posterior surface is continuous at each side with the spinous process, and in the angle of union is the termination of the Yidian canal. The lesser wings (processes of Ingrassias) are thin and triangular, the base being attached to the upper and anterior part of the body of the sphenoid; and the apex, prolonged outwards, terminating in an acute point. The anterior border is irregularly serrated, the posterior being free and rounded, and received into the fissure of Sylvius of the cerebrum. The inner extremity of this border is the anterior clinoid process; it is supported by a short pillar of bone, which forms the inferior boundary of the optic foramen, and gives attachment by its anterior surface to part of the common tendon of the muscles of the orbit. The lesser wing forms the posterior part of the roof of the orbit. Between the lesser and greater wings is a triangular slit, broad internally, but narrowing almost to a point at its outer extremity—this is the sphenoidal fissure; it transmits the third, fourth, three branches of the ophthalmic division of the fifth, and sixth nerves, with the ophthalmic vein. The greater wings present three surfaces ; a superior or cerebral, which forms part of the middle fossa of the base of the skull; an the lesser wing. 6. Sphenoidal fissure. 7. Foramen rotundum. 8. Orbital surface of the greater wing. 9. Its temporal surface. 10. The pterygoid ridge. 11. Pterygo-palatine canal. 12. Foramen of entrance of the Vidian canal. 13. Internal pterygoid plate. 14. Hamular process. 15. External pterygoid plate. 16. Foramen spinosum. 17. Foramen ovale. 18. Extremity of the spinous process of the sphenoid. 52 SPHENOID BONE. anterior surface, which assists in forming the outer wall of the orbit; and an external surface, divided into two parts by the 'pterygoid ridge. The superior surface is concave, and receives the anterior part of the middle lobe of the cerebrum; at its internal border, where the greater wing joins the body, and immediately behind the sphenoidal fissure, is a circular opening, foramen ro- tundum, through which passes the superior maxillary branch of the fifth nerve. Behind this, but nearer to the external border, a large foramen pierces the root of the spinous process; this is called foramen ovale; it transmits the inferior maxillary division of the fifth nerve, the small meningeal artery, and lesser petrosal nerve. The anterior surface looks into the orbit, it is quadrilateral in shape, and its posterior border, which bounds the sphenoidal fissure in- teriorly, is usually marked by a slight prominence, for the attach- ment of part of the external rectus muscle. The superior part of the external surface enters into the formation of the temporal fossa, the inferior portion forms part of the zygomatic fossa. The pterygoid ridge, dividing the two, gives attachment to the upper origin of the pterygoideus externus muscle. The spinous processes are the posterior terminations of the greater wings; they project backwards, and are received into the angular interval between the squamous and petrous portions of the temporal bones. Near its apex each process is pierced by a small opening, foramen spinosum, for the middle meningeal artery, and extending downwards from the apex is a short spine, which gives attachment to the internal lateral ligament of the lower jaw, and to the laxator tympani muscle. The external border of the spinous process is rough, to articulate with the lower border of the squamous portion of the temporal bone; the internal border forms the anterior boun- dary of the foramen lacerum basis cranii, and is somewhat grooved for the reception of the Eustachian tube. The pterygoid processes descend perpendicularly from the base of the greater wings, and form in the articulated skull the lateral boundary of the posterior nares. Each process consists of an ex- ternal and internal plate, and an anterior surface. The external plate is broad and thin, giving attachment, by its external surface, to the external pterygoid muscle, and by its internal surface to the internal pterygoid. This plate is sometimes pierced by a foramen, w'hich is not unfrequently formed by a process of communication passing between it and the spinous process. The internal ptery- goid plate is long and narrow, terminating at its extremity by a curved hook, the hamular process, around which plays the tendon of the tensor palati muscle; while from the lower third of its posterior border, some fibres of the superior constrictor muscle of the pharynx have their origin. At the base of the internal ptery- goid plate is a small oblong depression, the scaphoid fossa, from which arises the circumflexus or tensor palati muscle. The interval between the two pterygoid plates is the pterygoid fossa; and the two plates are separated interiorly by an angular notch (palatine) SPHENOID BONE. 53 which receives the tuberosity, or pterygoid process, of the palate bone. The anterior surface of the pterygoid process is broad near its base, and supports Meckel’s ganglion. The base of the process is pierced by the Yidian canal. Development.—Up to within a short time of the birth of the foetus, the anterior and posterior parts of the body of the sphenoid are distinct from each other;—the anterior part, extending from the posterior border of the olivary process to the ethmoidal spine, being called pre-splienoid, and the posterior portion, from the border of the olivary process to the spheno-occipital synchondrosis, the post- sphenoid. The centres of ossification from which the sphenoid is developed are so numerous, that it is difficult to give a concise description of the process. The following is Meckel’s account:—“ In the third month, the first osseous nuclei appear in the two great wings, and soon afterwards the internal pterygoid processes begin to ossify as separate bones. Next, a third pair of ossifications appears in the external circumference of the alee minores; and then, about the fourth month, a seventh and eighth nucleus, which lie side by side in the body of the sphenoid. In the fifth month is formed, along- side this fourth pair, a fifth, between it and the great wings. Upon this the two median nuclei of the body coalesce. Boon arises a sixth pair of nuclei on the inner side of the optic foramen, and then a seventh appears between this and the fourth, so that, about the beginning of the seventh month, the sphenoid consists of thirteen separate bony nuclei, since, notwithstanding seven pairs have arisen, the two primary nuclei of the body early coalesced into one. “ From this time forth the number of the nuclei diminishes still more considerably by coalescence. Those nuclei coalesce earliest which give rise to the portions of the sphenoid, which persist in a separate state longest. The fourth, fifth, and seventh pair soon unite into one piece; the first and second, coalescing on each side, constitute two other pieces; the third and sixth, two others; whereby in the eighth month, the sphenoid consists of five pieces— the two greater wings, the lesser wings, and the body. Somewhat later the two lesser wings coalesce into one, and the sphenoid now consists of four pieces ; thereupon the body and the anterior pieces unite, so that in the fully-formed foetus the sphenoid consists of three pieces, the greater wings and internal pterygoid processes being still distinct; but in the first month after birth these three pieces unite into one.” It should, however, be mentioned that the existence of the seventh pair of ossific centres here described, is doubted by many anato- mists ; and furthermore, it should be borne in mind, that the above account does not include the development of the cornua sphenoi- dalia. These latter each arise from a single centre, which makes its appearance between the period of birth and the second year; they become joined to the body of the sphenoid about the time of puberty. 54 ETHMOID BONE. Lastly, the sphenoid becomes joined to the occipital from the 18th to the 25th year. Articulations.—With twelve bones: that is, with all the bones of the head, and five of the face, viz., two malar, two palate, and vomer. Attachment of Muscles.—To twelve pairs: temporal, external pterygoid, internal pterygoid, superior constrictor, tensor palati, laxator tympani, levator palpebras, obliquus superior, superior rectus, internal rectus, inferior rectus, and external rectus. Ethmoid Bone.—The ethmoid (rjdgos, a sieve) is a square-shaped cellular bone, situated between the two orbits, at the root of the nose, and perforated on its upper surface by a number of small openings, from which peculiarity it has received its name. It con- sists of a perpendicular lamella and two lateral masses. The perpendicular lamella is a thin central plate, which articu- lates by its anterior border with the frontal spine, and crest of the nasal bones, and by its posterior border with the rostrum of the sphenoid and upper edge of the vomer. It assists in forming the septum of the nose. It is surmounted superiorly by a thick and strong process, the crista galli,which projects into the cavity of the skull, and gives attachment to the falx cerebri. From the base of the an- terior border of this process there pro- ject forward two small plates, alar pro- cesses, which are received into cor- responding depressions in the frontal bone, and often complete posteriorly the foramen caecum. At each side of the crista galli, on the upper surface of the bone, is a thin and grooved plate per- forated with a number of small openings, the cribriform lamella, which supports the bulb of the olfactory nerve, and gives passage to its filaments, and to the nasal branch of the ophthalmic nerve. In the middle of the groove of this lamella the foramina pierce the bone completely, but at either side they are the apertures of canals, which run for some distance in the substance of the central lamella, inner wall of the lateral mass, and spongy bones. The opening for the Fig. 54.* * Ethmoid bone, seen from above and behind. 1. Central lamella. 2, 2. Lateral masses ; the ciphers are placed on the posterior border of the lateral mass at each side. 3. Crista galli process. 4. Cribriform plate of the left side, pierced by its foramina. 5. The hollow space immediately above and to the left of this number is the superior meatus. 6. Superior turbinated bone. 7. Middle turbinated bone; the numbers 5, 6, 7 are situated on the 'internal surface of the left lateral mass, near its posterior part. 8. External surface of the lateral mass, or os planum. 9. Superior or frontal border of the lateral mass, grooved by the anterior and posterior ethmoidal canals. 10. Refers to the concavity of the middle turbinated bone, wliich is the upper boundary of the middle meatus. ETHMOID BONE. 55 nasal nerve is a narrow slit in tlie anterior part of the cribriform lamella, close to the crista galli. The cribriform lamella serves to connect the lateral masses with the perpendicular plate. It arti- culates by its posterior border with the ethmoidal spine of the sphenoid. The lateral masses (labyrinthi) are divisible into an internal and external surface, and four borders, superior, inferior, anterior, and posterior. The internal surface is rough, slightly convex, and forms the external boundary of the upper part of the nasal fossae. Towards the posterior border of this surface is a narrow horizontal fissure, the superior meatus of the nose; the upper margin of this fissure is thin, and somewhat curled inwards, hence it is named the superior turbinated bone (concha superior). Below the meatus is the convex surface of another thin plate, which is curled outwards, and forms the lower border of the mass, the middle turbinated bone (concha media). The external surface is quadrilateral and smooth; hence it is named os planum, and, from its thinness, lamina papyracea; it enters into the formation of the inner wall of the orbit. The superior border is uneven and cellular, the cells being com- pleted by the edges of the ethmoidal fissure of the frontal bone. This border is crossed by two grooves, sometimes complete canals, opening into the orbit by the anterior and posterior ethmoidal foramen. The inferior border is formed internally by the lower border of the middle turbinated bone, and externally by a concave irregular fossa, the upper boundary of the middle meatus. The anterior border presents a number of incomplete cells, which are closed by the superior maxillary and lachrymal bone; the posterior border is irregularly cellular, to articulate with the sphenoid and palate bone. From the anterior part of each lateral mass an irre- gular plate of bone descends backwards, terminating in a hook-like extremity: this is called the uncinate or cuneiform process. It assists in closing the orifice of the antrum, and articulates with the ethmoidal process of the inferior turbinated bone. The lateral masses are composed of cells, divided by a thin par- tition into anterior and posterior ethmoidal cells. The anterior, the most numerous, communicate with the frontal sinuses, and open by means of an irregular and incomplete tubular canal, the infundi- bulum, into the middle meatus. The posterior cells, fewer in number, open into the superior meatus. Development.—By three centres: one for each lateral mass, and one for the perpendicular lamella. Ossification commences in the lateral masses at about the beginning of the fifth month, appearing first in the os planum, and then in the spongy bones. At birth, the bone merely consists of two ill-developed lateral masses. During the latter half of the first year after birth, the central lamella and lamina cribrosa begin to ossify, and are united to the lateral masses by the beginning of the second year. The cells of the ethmoid are developed in the course of the fourth and fifth year. 56 NASAL BONES. Articulations.—With thirteen bones: two of the cranium, frontal and sphenoid; and eleven of the face, viz., two nasal, two superior maxillary, two lachrymal, two palate, two inferior turbinated, and vomer. No muscles are attached to this bone. The face is composed of fourteen bones; namely, bones of the face. Two nasal, Two superior maxillary, Two lachrymal, Two malar, Two palate. Two inferior turbinated, Vomer. Inferior maxillary. Nasal Bones.—The nasal are two small quadran- gular bones, forming by their union the bridge and base of the nose. On the upper surface they are convex, and pierced by a foramen for a small vein ; on the under surface they are somewhat concave, and marked by a groove which lodges the nasal branch of the ophthalmic nerve. The superior border is narrow and thick, the inferior broad, thin, and irregular. Development.—By a single centre for each bone, the first ossific deposition making its appearance at the same time as in the vertebra. Articulations.—With four bones: frontal, ethmoid, nasal, and superior maxillary. Attachment of Muscles.—It has in relation with it the pyrami- dalis nasi and compressor naris ; but neither is inserted into it. Superior Maxillary Bones. — The superior maxillary are the largest bones of the face, with the exception of the lower jaw; they form, by their union, the whole of the upper jaw, and assist in the con- struction of the nose, orbit, cheek, and palate. Each bone is divisible into a body and four processes. The body is triangular in form, and hollowed in its interior into a large cavity, the antrum maxiUare (antrum of High- more). It presents for examination four surfaces, external or facial, internal or nasal, posterior or zygomatic, and superior or orbital. The external, or facial surface, forms the anterior part of the bone; it is irregularly Fig. 55.* Fig. 56.t * Nasal bone of the left side ; its external or convex surface. 1. Superior border. 2. Internal or mesial border. 3. External border. 4. Inferior or free border. 5. Foramen for a small vein. t Superior maxillary bone of the right side, as seen on its lateral aspect. SUPERIOR MAXILLARY BONES. 57 concave, and presents a deep depression towards its centre, the canine fossa, which gives attachment to two muscles, compressor nasi and levator anguli oris. Immediately above this fossa is the in- fraorbital foramen, the termination of the infraorbital canal, trans- mitting the superior maxillary nerve and infraorbital artery; and above the infraorbital foramen is the lower margin of the orbit, con- tinuous externally with the rough articular surface of the malar process, and internally with a thick ascending plate, the nasal process. Between the infraorbital foramen and the margin of the orbit, the levator labii superioris proprius muscle has its origin. Towards the middle line of the face the external surface is bounded by the concave border of the opening of the nose, this border is projected forwards at its inferior termination into a sharp process, forming, with a simi- lar process of the opposite bone, the nasal spine. Beneath the nasal spine, and above the two superior incisor teeth, is a slight depression, the incisive, or myrtiform fossa, which gives origin to the depressor labii superioris alaeque nasi muscle. The myrtiform fossa is divided from the canine fossa by a perpendicular ridge, corresponding with the root of the canine tooth. The inferior boundary of the facial surface is the alveolar process which contains the teeth of the upper jaw; and the facial is separated from the zygomatic surface by a strong pro- jecting eminence, the malar process. The internal, or nasal surface, presents a large irregular opening, lig. 57.* I. External or facial surface ; the depression in which the cipher is placed is the canine fossa. 2. Posterior, or zygomatic surface. 3. Superior or orbital surface. 4. Infraorbital foramen, situated immediately below the cipher. 5. Infraorbital canal, leading to the infraorbital foramen. 6. Inferior border of the orbit. 7. Malar process. 8. Nasal process. 9. Concavity forming the lateral boundary of the anterior nares. 10. Nasal spine. 1L Incisive, or myrtiform fossa. 12. Alveolar process. 13. The internal border of the orbital surface, which articulates with the ethmoid and palate bone. 14. Concavity which articulates with the lachrymal bone, and forms the commencement of the nasal duct. 15. Crista nasalis of the palate process, i. Two incisor teeth, c. Canine. 6. Two bicuspidati. m. Three molares. * Eight superior maxillary bone; internal surface. 1. Antrum. 2. Nasal process. 3. Crista turbinalis superior. 4. Depression corresponding with the middle meatus. 5. Crista turbinalis inferior. 6,6. Inferior meatus. 7. Sulcus lachrymalis. 8. Notch for articulation with the lachrymal bone. 9. Superior border of the bone, in which are seen three ethmoidal cells. 10, 10. Posterior border; the lower 10 marks the articulating surface for the palate bone. II, 11. Groove of the posterior palatine canal. 12. Anterior border of the bone. 13, 13. Palate process. 14. Crista nasalis. 15. Nasal spine. 16. An- terior palatine canal. 17. Situation of the incisive foramen. lw, 18. Alveolar process. 58 SUPERIOR MAXILLARY BONES. leading into the antrum maxillare ; this opening is nearly closed in the articulated skull by the ethmoid, palate, lachrymal, and inferior turbinated bone. The cavity of the antrum is somewhat triangular, corresponding in shape with the form of the body of the bone. On its inner wall are numerous grooves, lodging branches of the superior maxillary nerve, and projecting into its floor several conical processes, corresponding with the roots of the first and second molar tooth. In front of the opening of the antrum is the strong ascend- ing plate of the nasal process, marked interiorly by a rough hori- zontal ridge (crista turbinalis inferior), which gives attachment to the inferior turbinated bone. The concave depression immediately above this ridge corresponds with the middle meatus of the nose, that below the ridge with the inferior meatus. Between the nasal process and the opening of the antrum is a deep vertical groove (sulcus lachrymalis), converted into a canal by the lachrymal and inferior turbinated bone, and constituting the nasal duct. The superior border of the nasal surface is irregularly cellular, and ar- ticulates with the lachrymal and ethmoid bone; the posterior border is rough, and articulates with the palate bone; the anterior border is sharp, and forms the free margin of the opening of the nose; and, from the inferior border, projects inwards a strong horizontal plate, the palate process. The posterior surface may be called zygomatic, as forming part of the zygomatic fossa; it is bounded externally by the malar process, and internally by a rough and rounded border, the tuberosity, which is pierced by a number of small foramina (foramina alveo- laria posteriora), giving passage to the posterior dental nerves and branches of the superior dental artery. The lower part of this tuberosity presents a rough oval surface, to articulate with the palate bone, and immediately above and to the inner side of this articular surface a smooth groove, which forms part of the posterior palatine canal. The superior border is smooth and rounded, form- ing the lower boundary of the spheno-maxillary fissure, and marked by a notch, the commencement of the infraorbital canal. The in- ferior boundary is the alveolar process, containing the last two molar teeth. The orbital surface is triangular and thin, and constitutes the floor of the orbit. It is bounded internally by an irregular edge, which articulates with the palate, ethmoid, and lachrymal bone ; posteriorly, by the smooth border which enters into the formation of the spheno-maxillary fissure ; and, anteriorly, by a convex mar- gin, partly smooth and partly rough, the smooth portion forming part of the lower border of the orbit, the rough portion articulating with the malar bone. The middle of this surface is channelled by a deep groove and canal, the infraorbital, which terminates at the infraorbital foramen ; and near the root of the nasal process is a slight depression, marking the origin of the inferior oblique muscle of the eyeball. The four processes of the superior maxillary bone are, the nasal, malar, alveolar, and palate. SUPERIOR MAXILLARY BONES. 59 The nasal process ascends by the side of the nose, to which it forms the lateral boundary, and articulates with the frontal and nasal bone. By its external surface it gives attachment to the levator labii superioris alasque nasi, and to the orbicularis palpe- brarum muscle. Its internal surface contributes to form the outer wall of the nares, and is marked transversely by a horizontal ridge (crista turbinalis superior), which divides it into two portions, one above the ridge irregular and uneven, for giving attachment to and completing the cells of the lateral mass of the ethmoid; the other below, smooth and concave, corresponding with the middle meatus. The posterior border is thick and grooved for the nasal duct; while the prominent margin in front of that groove is continuous with the lower border of the orbit; this margin is marked by a small tubercle, which serves as a guide to the introduction of the knife in the ope- ration for fistula lachrymalis. The malar process, large and irregular, is situated at the angle of separation between the facial and zygomatic surface, and presents a triangular surface for articulation with the malar bone. The alveolar process forms the lower margin of the bone; it is spongy and cellular in texture, and excavated into deep holes for the reception of eight teeth. By its outer surface, as far forwards as the first molar tooth, it gives origin to the buccinator muscle. The anterior portion of its process containing the sockets of the incisor teeth, together with a small portion of the palate process, has a separate centre of ossification, and in the lower animals it remains separate throughout life as the intermaxillary or premaxillary bone. In young human skulls a fissure running backwards from the outer edge of the second incisor nearly to the incisive foramen, indicates the line of junction of the premaxillary bone with the rest of the maxilla; and in cases of cleft palate (there being an arrest of development) this portion is present as a distinct bone. The palate process is thick and strong, and projects horizontally inwards from the inner surface of the body of the bone. Superiorly, it is concave and smooth, and forms the floor of the nares; in- fer iorly, it is also concave, but uneven, and assists in the formation of the roof of the palate. The latter surface is marked by a deep groove, which lodges the anterior palatine nerve and superior pala- tine artery. Its internal edge is raised into a ridge (crista nasalis), which, with a corresponding ridge in the opposite bone, forms a groove for the reception of the vomer. The prolongation of this ridge forwards beyond the level of the facial surface of the bone is the nasal spine. Near the anterior extremity of the internal border is seen a deep groove, which, expanding interiorly, forms with its fellow of the opposite side the incisive foramen. When the hard palate (completed by the junction of the two bones) is viewed from below, this foramen is seen to contain four smaller foramina, two of which are placed in the middle line, one before the other (fora- mina of Scarpa), the other two (foramina of Stenson), being placed laterally. These all open above into the inferior meatus of the 60 LACHRYMAL BONES. nose, the first pair (Scarpa’s) transmitting the naso-palatine nerves, the nerve of the left side occupying the anterior foramen, and that of the right side (the larger of the two) the posterior. The other foramina are the inferior terminations of the anterior palatine canals, they give passage to the anterior palatine arteries. Development.—By four centres : one for the anterior part of the palate and incisive portion of the alveolar process (intermaxillary); one for that portion of the bone lying internally to the infraorbital canal and foramen; one for that portion lying externally to the infraorbital groove and canal; and one for the palate process. The superior maxillary bone is one of the earliest to show signs of ossifi- cation, this action beginning in the alveolar process, and being associated with the early development of teeth. The early develop- ment of the alveolar process, and the consequent fusion at this point of the original pieces, explains the difficulties which have been felt by anatomists in determining the precise number of ossi- fying centres of the bone. Articulations.—With nine bones ; viz., two of the cranium, and all the bones of the face, excepting the inferior maxillary. These are, frontal and ethmoid; nasal, lachrymal, malar, inferior turbi- nated, palate, vomer, and its fellow of the opposite side. Attachment of Muscles.—To ten; orbicularis palpebrarum, obli- quus inferior oculi, levator labii superioris alaeque nasi, levator labii superioris proprius, levator anguli oris, compressor naris, dilatator naris, depressor ahe nasi, buccinator, masseter. Lachrymal Bones (os unguis, from an imagined resemblance to a finger nail).—The lachrymal is a thin oval-shaped plate of bone, situated in front and at the inner angle of the orbit. It may be divided into an external and internal surface and four borders. The external surface is smooth and marked by a vertical ridge, the lachrymal crest, into two por- tions, one of which is flat and enters into the forma- tion of the orbit, hence may be called the orbital portion; the other is concave, and lodges the lachry- mal sac, hence, the lachrymal portion. The crest is expanded interiorly into a hook-shaped process (hamu- lus lachrymalis), which forms part of the outer boun- dary of the fossa lachrymalis. The internal surface is uneven, and completes the anterior ethmoid cells ; it assists also in forming the wall of the nasal fossae and nasal duct. The four borders articulate with adjoining bones. Development.—By a single centre, appearing in the early part of the third month. Fig. 58.* * Lachrymal bone of the right side viewed on its external or orbital surface. 1. Orbital portion of the bone. 2. Lachrymal portion; the prominent ridge between these two portions is the crest. 3. Lower termination of the crest, the hamulus lachrymalis. 4. Superior border, which articulates with the frontal bone. 5. Posterior border, which articulates with the ethmoid bone. 6. Anterior border, which articulates with the superior maxillary bone. 7. The border which articulates with the inferior turbinated bone. MALAR AND PALATE BONES. 61 Articulations.—With four hones; two of the cranium, frontal and ethmoid; and two of the face, superior maxillary and inferior turbinated bone. Attachment of Muscles.—To one muscle, the tensor tarsi, and to an expansion of the tendo oculi, the former arising from the orbital surface, the other being attached to the lachrymal crest. Malar Bones (mala, the cheek).—The malar (os jugale) is the strong quadrangular bone which forms the prominence of the cheek. It is divisible into an external and internal surface, and four pro- cesses, frontal, orbital, maxillary, and zygomatic. The external surface is smooth and convex; it gives origin to the zygomaticus major and minor muscles, and is pierced by several small openings, which give passage to filaments of the temporo-malar nerve and minute arteries. The internal surface is concave, partly smooth and partly rough; smooth where it forms part of the temporal fossa, and rough where it articulates with the superior max- illary bone. The frontal process ascends perpen- dicularly to form the outer border of the orbit, and articulate with the ex- ternal angular process of the frontal bone. The orbital process is a thick plate, which projects inwards from the frontal process, and unites with the great ala of the sphenoid to constitute the outer wall of the orbit. It is pierced by several small foramina for the passage of temporo-malar filaments of the superior maxillary nerve. The maxillary process is broad, and articulates with the superior maxillary bone. The zygomatic process, narrower than the rest, projects backwards to unite with the zygoma of the tem- poral bone. Development.—By a single centre: in rare instances by two or three. In many animals the malar bone is permanently divided into two portions, orbital and malar. Ossification commences in the malar bone soon after the vertebrae. Articulations.—With four bones ; three of the cranium, frontal, temporal, and sphenoid; and one of the face, superior maxillary. Attachment of Muscles.—To five: levator labii superioris pro- prius, zygomaticus minor and major, masseter, and temporal. Palate Bone.—The palate bones are situated at the posterior part of the nares, where they enter into the formation of the palate, side of the nose, and posterior part of the floor of the orbit; hence Fig. 59.* * Malar bone of the right side. 1. External surface. 2. Opening for an artery and nerve. 3. Frontal process. 4. Outer border of the orbit. 5. In- ferior border of the orbit. 6, 6. Maxillary process. 7. Zygomatic process. 8. Sweep to which the temporal fascia is attached. 9, 9. Lower border of the bone, from which the deep portion of the masseter muscles arises. 62 PALATE BONES. they might be named the palato-naso-orbital bones. Each bone re- sembles in general form the letter L, and is divisible into a hori- zontal plate, a perpendicular plate, and a pterygoid process or tuberosity. The horizontal plate is quadrilateral; and presents two surfaces, one superior, which enters into the formation of the floor of the nares, the other inferior, forming the posterior part of the hard palate. The superior surface is concave, and rises towards the middle line, where it unites with its fellow of the opposite side and forms part of a crest (crista nasalis), which articulates with the vomer. Thti inferior surface is uneven, and marked by a slight transverse ridge, to which is attached the ten- dinous expansion of the tensor palati muscle. Near its external border are two openings, one large and one small, the posterior palatine fora- mina ; they are the terminations of two minute canals, and transmit the descending palatine artery and nerves. The posterior border is concave, and presents at its inner extremity a sharp point, which, with a corresponding point in the opposite bone, constitutes the palate spine for the attachment of the azygos uvulse muscle. The perpendicular plate is also quadrilateral; and presents two surfaces, one internal or nasal, forming part of the wall of the nares ; the other external, bound- ing the spheno-maxillary fossa and antrum. The internal surface is marked near its middle by a horizontal ridge (crista turbinalis inferior), to which is united the inferior turbinated bone; and, about half an inch above this, by another ridge (crista tur- binalis superior), for the attachment of the middle turbinated bone. The concave surface below the inferior ridge is the lateral boundary of the inferior meatus of the nose; that between the two ridges corresponds with the middle meatus, and the surface above the superior ridge with the superior meatus. The external surface, extremely irregular, is rough on each side for articulation Fig. 60.* * Posterior view of the right palate bone in its natural position; it is slightly- turned on one side, to obtain a sight of the internal surface of the perpendicular plate (2). 1. Horizontal plate of the bone; its upper or nasal surface. 2. Perpendicular plate; its internal or nasal surface. 3, 10, 11. Pterygoid pro- cess or tuberosity. 4. Internal border of the horizontal plate, which, articu- lating with the similar border of the opposite bone, forms the crista nasalis for the reception of the vomer. 5. The pointed process, which, with a similar process of the opposite bone, forms the palate spine. 6. The horizontal ridge which gives attachment to the inferior turbinated bone ; the concavity below this ridge enters into the formation of the inferior meatus; the concavity (2) above the ridge into that of the middle meatus. 7. Spheno-palatine notch. 8. Orbital portion. 9. Crista turbinalis superior for the middle turbinated bone. 10. The middle facet of the tuberosity, which enters into the formation of the pterygoid fossa. The facets 11 and 3 articulate with the two pterygoid plates, 11 with the internal, 3 with the external. PALATE BONES. 63 with neighbouring bones, and smooth in the middle to constitute the inner boundary of the spheno-maxillary fossa. This smooth surface terminates interiorly in a deep groove, which, being com- pleted by the tuberosity of the superior maxillary bone and ptery- goid process of the sphenoid, forms the posterior palatine canal. Near the upper part of the perpendicular plate is a large oval notch completed by the sphenoid, the spheno-palatine foramen, which transmits the superior nasal and naso-palatine nerves and spheno-palatine artery, and serves to divide the upper extremity of the bone into two portions, an anterior or orbital, and a posterior or sphenoidal portion. The orbital portion is hollow within, and presents five surfaces externally, three articular and two free; the three articular are, anterior, which looks forward and articulates with the superior maxillary bone, internal with the ethmoid, and posterior with the sphenoid. The free surfaces are, superior or orbital, which forms the posterior part of the floor of the orbit, and external, which looks into the spheno-maxillary fossa. The sphenoidal portion, much smaller than the orbital, has three surfaces, two lateral and one superior. The external lateral surface enters into the formation of the spheno- maxillary fossa; the internal lateral forms part of the lateral boundary of the nares; the superior surface articulates with the under part of the body of the sphenoid bone, and assists the sphenoidal spongy bones in closing the sphenoidal sinuses. This portion takes part in the formation of the pterygo- palatine canal. The pterygoid process or tuberosity of the palatine bone is the thick and rough process which stands backwards from the angle of union of the horizontal with the perpendicular portion of the bone. It is received into the angular fissure, which exists between the two plates of the pterygoid process at their inferior extremity, and presents three surfaces: one concave and smooth, which forms part of the pterygoid fossa, and gives origin to some fibres of the internal pterygoid muscle; and one at each side to articulate with the pterygoid plates. The anterior face of this process is rough, and articulates with the superior maxillary bone. Fig. 61.* * Perpendicular plate of the right palate bone, seen on its external or spheno- maxillary surface. 1. The rough surface of this plate, which articulates with the superior maxillary bone and bounds the antrum. 2. Posterior palatine canal; completed by the tuberosity of the superior maxillary bone and ptery- goid process. The rough surface to the left of the canal (2) articulates with the internal pterygoid plate. 3. Spheno-palatine notch. 4, 5, 6. Orbital portion of the perpendicular plate. 4. Spheno-maxillary facet of this portion. 5. Orbital facet. 6. Maxillary facet, to articulate with the superior maxillary bone. 7. Sphenoidal portion of the perpendicular plate. 8. Pterygoid pro- cess or tuberosity of the bone. 64 INFERIOR TURBINATED BONES. Development.—By a single centre, which appears in the angle of union between the horizontal and perpendicular portion, at the same time as ossification in the vertebrae. Articulations.—With six bones: two of the cranium, sphenoid and ethmoid; and four of the face, superior maxillary, inferior tur- binated, vomer, and the palate bone of the opposite side. Attachment of Muscles.—To four: tensor palati, azygos uvulae, internal and external pterygoid. Inferior Turbinated Bones.—The inferior turbinated or spongy bone, is a thin layer of light and porous bone, attached to the crista turbinalis inferior of the inner wall of the nares, and projecting inwards towards the septum narium. It is somewhat triangular in form, one angle being directed up- wards and the curved base down- wards ; and slightly curled upon it- self, so as to bear some resemblance to one valve of a bivalve shell, hence its designation, concha inferior. The bone presents for examination, two surfaces, internal and external; three borders, anterior, superior and inferior; and three angles, ante- rior, posterior, and superior. The internal or convex surface looks inwards and upwards, and forms the inferior boundary of the middle meatus naris; it is marked by one or two longitudinal grooves or canals for branches of the nasal nerves and spheno- palatine artery. The external or concave surface looks down- wards and outwards, and constitutes the roof of the inferior meatus. The anterior border looks upwards and forwards, is thin and somewhat concave, and articulates with the crista turbinalis of the superior maxillary and with the lachrymal bone. The superior border, long and uneven, articulates with the crista turbinalis of the palate bone, and with the superior maxil- lary. The inferior border is convex, rounded, and free, and thicker than the rest of the bone. The anterior angle, attached to the superior maxillary bone advances forward nearly to the anterior margin of the nares. The posterior angle, sharp and pointed, is prolonged backwards on the internal pterygoid plate. The superior angle, more or less rounded, gives origin to three thin and laminated processes. The most anterior of these processes, processus lachry- malis, derived from the upper extremity of the anterior border, articulates with the lachrymal bone, and assists in completing the Fip. 62* * Inferior turbinated bone of the right side. 1, 1. Its internal or convex surface. 2, 2, 3. Canal for a branch of the spheno-palatine artery, dividing into two deep grooves. The cipher 3 also denotes the anterior border of the bone. 4. Posterior border. 5, 5. Inferior border. 6. Anterior angle. 7. Posterior angle. 8. Superior angle. 9. Processus lachrymalis. 10. Processus ethmoi- dalis. 11. A large irregular process, appertaining to the ethmoidal pro- cess, and articulating with the ethmoid bone. 12. An opening into the antrum. VOMEK, 65 nasal duct; the posterior process, processus ethmoidalis, derived directly from the superior angle or border, often from both, articu- lates with the unciform process of the ethmoid bone; the middle process, processus maxillaris, proceeding also from the superior border, is reflected downwards, and assists in completing the inner wall of the antrum, articulating with the superior maxillary and palate bone. Development.—By a single centre, which appears at about the fifth month of foetal life. It affords no attachment to muscles. Articulations.—With four bones: ethmoid, superior maxillary, lachrymal, and palate. Vomer.—The vomer is a thin, quadrilateral plate of bone, forming the posterior and inferior part of the septum of the nares. The superior border is broad and expanded, to articulate, in the middle, with the under surface of the body of the sphenoid, and on each side (ala) with the pro- cessus vaginalis of the ptery- goid process. The anterior part of this border is hollowed into a sheath for the reception of the rostrum of the sphenoid. The inferior border is thin and un- even, and is received into the grooved summit of the crista n asalis of the superior maxillary and palate bones. The posterior border is sharp and free, and forms the posterior division of the two nares. The anterior border is more or less deeply grooved for the reception of the central lamella of the ethmoid and the cartilage of the septum. This groove is an indi- cation of the early constitution of the bone of two lamellae, united at the inferior border. The lateral surfaces are smooth and marked by small furrows for vessels; each has a groove which runs downwards and forwards, giving passage to the naso-palatine nerve, and terminates inferiorly at the upper opening of the anterior palatine canal. The vomer not unfrequently presents a convexity to one or the other side, generally, it is said, to the left. Development.—By a single centre, which makes its appearance at the same time with those of the vertebrae. Ossification begins from below and proceeds upwards. At birth, the vomer presents the form of a trough, in the concavity of which the cartila,ge of the Fig. 63.* * The vomer viewed on its left aspect. 1,1. Its superior border, with the two alee. 2, 2. Inferior border. 3. Posterior border. 4, 4. That portion of the anterior border which articulates with the central lamella of the ethmoid. 5, 5. Inferior portion of the anterior border, which unites with the cartilage of the septum. 6, 6. An elevation on the bone marking its point of separation into two layers; the two layers are seen along the whole length of the anterior border from 4 to the lower 5. 66 INFERIOR MAXILLARY BONE. septum nasi is placed; it is this disposition which subsequently enables the bone to embrace the rostrum of the sphenoid. The vomer has no muscles attached to it. Articulations.—With six bones: sphenoid, ethmoid, two superior maxillary, two palate; and the cartilage of the septum. Inferior Maxillary Bone.—The lower jaw is the arch of bone which contains the inferior teeth; it is divisible into a horizontal portion or body, and a perpendicular portion, the ramus, at each side. The body is divisible into two portions. That above the men- tal foramen (alveolar) is of spongy texture, and contains the sockets for the teeth—that below this foramen (basilar) is thick and rounded—it is dense in structure, and is marked by ridges for the attachment of muscles. The relative proportion of these two parts varies with the age of the individual: in childhood, in consequence of containing the two sets of teeth, the alveolar portion is large, and the mental foramen is near the lower border of the bone; in old age, on the contrary, from the loss of teeth and consequent absorption of the alveolar process, the basilar portion alone remains, and the mental foramen is situated near its upper border. In adult age the alveolar and basilar portions are of equal depth, the mental foramen being situated midway between the upper and lower border. Upon the external surface of the body, at the middle line, and extending from between the two first incisor teeth to the chin, is a slight ridge, crista mentalis, which indicates the point of con- junction of the lateral halves of the bone in the young subject, the symphysis. Immediately external to this ridge is a depression which gives origin to the depressor labii inferioris muscle; and, corre- sponding with the root of the lateral incisor- tooth, another de- pression, the incisive fossa,, for the levator labii inferioris. Farther outwards is an oblique opening,, the mental foramen, for the exit of the mental nerve and inferior dental artery; and below this foramen, the commencement of an oblique ridge, which runs up- wards and outwards to the base of the coronoid process, and gives attachment to the depressor anguli oris, platysma myoides, and buccinator muscle. Near the posterior part of this surface is a rough impression made by the masseter muscle; and, immediately in front of this impression, a groove for the facial artery. The pro- jecting tuberosity at the posterior extremity of the lower jaw, at the point where the body and ramus-meet, is the angle. Upon the internal surface of the body of the bone, at the sym- physis, are two small pointed tubercles; immediately beneath these, two other tubercles, less marked; beneath them, a ridge, and be- neath the ridge two rough depressions of some size. These four points give attachment, from above- downwards, to the genio-hyo- glossi, genio-hyoidei, part of the mylo-hyoidei, and digastric muscles. Running outwards into the body of the bone from the above ridge is a prominent line, the mylo-hyoidean ridge, which gives attachment to the mylo-hyoideus muscle, and by its extremity to the pterygo-maxillary ligament and superior constrictor muscle. INFERIOR MAXILLARY BONE'i 67 Immediately above the ridge, and by the side of the symphysis, is a smooth concave surface, which corresponds with the sublingual gland; and below the ridge, and more externally, a deeper fossa for the submaxillary gland. The superior border of the body of the bone is the alveolar pro- cess, furnished in the adult with alveoli for sixteen teeth. The inferior border or base is rounded and smooth; thick and everted in front to form the chin, and thin behind where it merges into the angle of the bone. The ramus is a strong square-shaped process, differing in direc- tion at various periods of life; thus,.in the foetus and infant, it is almost parallel with the body; in youth it is oblique, and gradually approaches the vertical direction until manhood; in old age, after the loss of the teeth, it again declines, and assumes the oblique direction. On its external surface it is rough, for the attachment of the masseter muscle-, and at the junction of its posterior border with the body of the bone, it has a rough tuberosity, the angle of the lower jaw, which gives attachment by its inner margin to the stylo-maxillary ligament. The upper extremity of the ramus presents two processes, sepa- rated by a concave sweep, the sigmoid notch. The anterior is the coronoidprocess; it is sharp and pointed, and gives attachment by its inner surface to the tem- poral muscle. The anterior bor- der of the coronoid process is grooved at its lower part for the buccinator muscle. The posterior process is the condyle, which is flattened from before backwards, oblique in direction, and smooth on its upper surface, to articulate with the glenoid cavity of the temporal bone. The constriction around the base of the condyle is its neck, into which is inserted the external pterygoid muscle. The sigmoid notch is crossed by the masseteric artery and nerve. The internal surface of the ramus is marked near its centre by a large oblique foramen, the inferior dental, for the entrance of the inferior dental artery and nerve into the dental canal. Bounding this opening is a sharp margin, to which is attached the internal Fig. 64.* * The lower jaw. 1. Body. 2. Ramus. 3. Symphysis. 4. Fossa for the depressor labii inferioris muscle. 5. Mental foramen. 6. External oblique ridge. 7. Groove for the facial artery; the situation of the groove is marked by a notch in the bone a little in front of the cipher. 8. The angle. 9. Ex- tremity of the mylo-hyoidean ridge.. 10. Coronoid process. 11. Condyle. 12. Sigmoid notch. 13. Inferior dental foramen. 14. Mylo-hyoidean groove. 15. Alveolar process, i. Middle and lateral incisor tooth of one side. c. Canine tooth, b.-Two bicuspids.- m.-Three-molars.. 68 TABLE OF DEVELOPMENTS, AKTICULATIONS, ETC. lateral ligament, and passing downwards from the opening a narrow groove which lodges the mylo-hyoidean nerve with a small artery and vein. To the uneven surface above and in front of the inferior dental foramen, is attached the temporal muscle, and to that below it, the internal pterygoid. The internal surface of the neck of the condyle gives attachment to the external pterygoid muscle, and its external surface to the external lateral ligament of the lower jaw. To the angle is attached the stylo-maxillary ligament. Development.—By two centres ; one for each lateral half, the two sides meeting at the symphysis, where they become united. The lower jaw is the earliest of the bones of the skeleton to exhibit ossification, with the exception of the clavicle; ossific union of the symphysis takes place during the first year. Aiiiculations.—With the glenoid fossae of the two temporal bones, through the medium of a fibro-cartilage. Attachment of Muscles.—To fourteen pairs; by the external sur- face, commencing at the symphysis and proceeding outwards, levator labii inferioris, depressor labii inferioris, depressor anguli oris, platysma myoides, buccinator, and masseter ; by the internal surface, also commencing at the symphysis, the genio-hyo-glossus, genio-hyoideus, mylo-hyoideus, digastricus, superior constrictor, temporal, external pterygoid, and internal pterygoid. TABLE SHOWING THE POINTS OF DEVELOPMENT, ARTICULATIONS, AND ATTACHMENT OP MUSCLES OP THE BONES OP THE HEAD. Development. Articulation. Attachment of Muscles. Occipital .... . 7 .. 6 ... 12 pairs. Parietal .... . 1 .. 5 ... 1 muscle. Frontal .... . 2 .. 12 ... 3 pairs. Temporal .... . 4 .. 5 ... 14 muscles. Sphenoid .... . . 15 .. 12 ... 12 pairs. Ethmoid .... . . 3 .. 13 ... none. Nasal . . 1 4 ... none. Superior maxillary . . 4 .. 9 ... 10 muscles. Lachrymal . . . . . 1 .. 4 ... 1 ib. Malar . . 1 .. 4 ... 5 ib. Palate . 1 .. 6 ... 4 ib. Inferior turbinated . . 1 .: 4 ... none. Yomer . 1 6 ... none. Lower jaw . . . . 2 ... 2 ... 14 pairs. The bones of the cranium and face are connected with each other by means of sutures (sutura, a seam), of which there are four prin- cipal varieties; serrated, squamous, harmonia, and schindylesis. The serrated suture is formed by the union of two borders possess- ing serrated edges, as in the coronal, sagittal, and lambdoidal sutures. In these sutures the serrations are formed almost wholly SUTURES. SUTURES—OSSA TRIQUETRA 69 by the external table, the edges of the internal table lying merely in apposition. The squamous suture (squama, a scale) is formed by the over- lapping of the bevelled edges of two contiguous bones, as in the articulation between the temporal and lower border of the parietal. In this suture the approximated surfaces are roughened, so as to adhere mechanically with each other. The harmonia suture (apeiv, to adapt) is the simple apposition of contiguous surfaces, the surfaces being more or less rough and retentive. This suture is seen in the connexion between the supe- rior maxillary bones, or of the palate processes of the palate bones with each other. The schindylesis suture (cns) is the most extensive in its range of motion of all the moveable joints. From the manner of connexion and form of the bones in this articulation, it is called the ball-and- socket joint. There are two instances in the body—namely, the hip and the shoulder. We may add to the preceding the carpo-metacarpal articulation of the thumb, although not strictly a ball-and-socket joint, from the great extent of motion which it enjoys, and from the nature of the ligament connecting the bones. As far as the articular surfaces are concerned, it is rather a double than a single ball-and-socket; and the whole of these considerations remove it from the simple arthrodial and ginglymoid groups. The ball-and-socket joint has a circular form; and, in place of the four distinct ligaments of the ginglymus, is enclosed in a bag of ligamentous membrane, called capsular ligament. The kinds of articulation may be shown in a tabular form, as follows: MOVEMENTS OF JOINTS—STRUCTURES. 133 Synarthrosis. ' Sutura bones of the skull. Harmonia .... superior maxillary bones. Schindylesis . . . vomer with rostrum. .Gomphosis . . . teeth with alveoli. Amphi-arthrosis . Bodies of the vertebrae. Symphyses. ' Arthrodia .... carpal and tarsal bones. Ginglymus .... elbow, wrist, knee, ankle. .Enarthrosis. . . . hip, shoulder. Diarthrosis. The motions of joints maybe referred to four heads—viz., Gliding, Angular movement, Circumduction, and Rotation. 1. Gliding is the simple movement of one articular surface on another, and exists to a greater or less extent in all the joints, bn the least moveable joints, as in the carpus and tarsus, this is the only motion which is permitted. 2. Angular movement may be performed in four different direc- tions, either forwards and backwards, as in flexion and extension ; or, inwards and outwards, constituting adduction and abduction. Flexion and extension are illustrated in the ginglymoid joint, and exist in a large proportion of the joints of the body. Adduction and abduction conjoined with flexion and extension, are met with complete only in the most moveable joints, as the shoulder, hip, and thumb. In the wrist and ankle, adduction and abduction are only partial. 3. Circumduction is most strikingly exhibited in the shoulder and hip joints; it consists in the slight degree of motion which takes place between the head of a bone and its articular cavity, while the extremity of the limb is made to describe a large circle on a plane surface. It is also seen, but in a less degree, in the carpo- metacarpal articulation of the thumb, metacarpo-phalangeal arti- culation of the fingers and toes, and in the elbow when that joint is flexed and the end of the humerus fixed. 4. Rotation is the movement of a bone on its own axis, and is illustrated in the hip and shoulder, or better, in the rotation of the cup of the radius against the eminentia capitata of the humerus. Rotation is also observed in the movements of the atlas upon the axis, where the odontoid process serves as a pivot around which the atlas turns. The structures entering into the composition of a joint are bone, cartilage, areolar tissue, fibrous tissue, yellow or elastic tissue, adipose tissue, and synovial membrane. Cartilage forms a thin coating to the articular extremities of bones, sometimes presenting a smooth surface which moves on a corresponding smooth surface of the articulating bone; sometimes forming a plate smooth on both surfaces and interposed between the car- tilaginous ends of two bones, interartimlar; and sometimes acting as the connecting medium between bones without any free surface, interosseous. While fibrous tissue enters into the construction of joints under the form of ligament, in one situation constituting bands of various breadth and thickness; in another it forms a 134 SYNOVIAL MEMBEANE—AETICULATIONS. layer which extends completely round the joint, and is then called a capsular ligament. All the ligaments of joints are composed of that variety of fibrous tissue termed white fibrous tissue; but in some situations ligaments are found which consist of yellow fibrous tissue, for example, the ligamenta subflava of the arches of the vertebral column. Adipose tissue exists in variable quantity in relation with joints, where it performs, among other offices, that of a valve or spring, which occupies any vacant space that may be formed during the movements of the joint, and prevents the occur- rence of a vacuum in those cavities. This purpose of adipose tissue is exemplified in the cushion of fat at the bottom of the acetabulum afid in the similar cushion behind the ligamentum patellae. Synovial membrane is a thin membranous layer, investing the articular extremities of bones, and the surface of the ligaments which surround and enter into the composition of a joint. It re- sembles the serous membranes in being a shut sac (capsula syno- vialis), and secretes a transparent and viscous fluid, which is named synovia. Synovia is an alkaline secretion, containing albumen and mucus, the albumen being coagulable at a boiling temperature. In some joints the synovial membrane is pressed into the articular cavity by a cushion of fat: this mass was called by Havers the synovial gland, from an idea of its being the source of the synovia; it is found in the hip and knee joint. In the knee, moreover, the synovial membrane forms folds, which are improperly named liga- ments, as the mucous and alar ligaments, the two latter being an appendage to the cushion of fat. Besides the synovial membranes entering into the composition of joints, there are numerous smaller sacs of a similar kind interposed between surfaces which move upon each other so as to cause friction; they are often associated with the articulations. These are the bursce mucosae; they are shut sacs, analogous in structure to synovial membranes, and secreting a similar synovial fluid. The epithelium of synovial membranes is of the kind termed tesselated or pavement epithelium; it is developed in the same manner as the epithelium of other free surfaces, but presents only a single stratum of cells. ARTICULATIONS. The joints may be arranged, according to a natural division, into those of the trunk, those of the upper extremity, and those of the lower extremity. Ligaments of the Trunk.—The articulations of the trunk are divisible into ten groups—namely : 1. Of the vertebral column. 2. Of the atlas, with the occipital bone. 3. Of the axis, with the occipital bone. 4. Of the atlas, with the axis. 5. Of the lower jaw. 6. Of the ribs, with the vertebrae. LIGAMENTS OF THE VEKTEBKAL COLUMN. 135 7. Of the ribs, with the sternum, and with each other. 8. Of the sternum. 9. Of the vertebral column, with the pelvis. 10. Of the pelvis. 1. Articulation of the Vertebral column.—The ligaments connect- ing together the different pieces of the vertebral column, admit of the same arrangement as the vertebras themselves. Thus the ligaments Of the bodies, are the Anterior common ligament, Posterior common ligament, Intervertebral substance. Of the arches, Ligamenta subflava. Of the articular processes, Capsular ligaments, Synovial membranes. Of the spinous processes, Inter-spinous, Supra-spinous, Of the transverse processes, Inter-transverse. Bodies.—The Anterior common ligament (fascia longitudinalis anterior) is a broad and riband-like band of ligamentous fibres, ex- tending along the front surface of the vertebral column, from the axis to the sacrum. It is intimately connected with the interver- tebral substance, and less closely with the bodies of the vertebrae. In the dorsal region it is thicker than in the cervical and lumbar, and consists of a median and two lateral portions separated from each other by a series of openings for the passage of vessels. The ligament is composed of fibres of various length closely interwoven with each other; the deeper and shorter crossing the intervertebral substance from one vertebra to the next; the superficial and longer fibres crossing three or four vertebras. The anterior common ligament is in re- lation by its posterior or vertebral surface with the intervertebral substance, bodies of vertebrae, and vessels, principally veins, which separate its central from its lateral portions. By its anterior or visceral surface it is in relation, in the neck, with the longus colli muscles, pharynx and oesophagus ; in the thoracic region, with the aorta, venae azygos, and thoracic duct; in the lumbar region, with the aorta, right renal artery, right lumbar arteries, arteria sacra media, vena cava inferior, left lumbar veins, receptaculum chyli, commence- Fig. 104.* * Anterior ligament of the vertebra}, and ligaments of the ribs. 1. Anterior common ligament. 2. Anterior costo-vertebral or stellate ligament. 3. Anterior costo-transverse ligament. 4. lnterarticnlar ligament connecting the head of the rib to the intervertebral substance, and separating the two synovial mem- branes of this articulation. 136 LIGAMENTS OF THE VERTEBRAL COLUMN. ment of the thoracic duct, and tendons of the diaphragm with the fibres of which the ligamentous fibres interlace. The Posterior common ligament (fascia longitudinalis posterior) lies on the posterior surface of the bodies of the vertebrae, and extends from the axis to the sacrum. It is broad opposite the intervertebral substance, to which it is closely adherent; narrow and thick over the bodies of the vertebrae, from which it is separated by the veins of the base of each vertebra; and composed, like the anterior ligament, of shorter and longer fibres, arranged in a similar manner. It is broader above than below, the reverse of the anterior common ligament. The posterior common ligament is in relation by its anterior surface, with the intervertebral substance, bodies of the vertebrae, and venae basium vertebrarum; by its posterior surface, with the dura mater of the spinal cord, some loose cellular tissue and numerous small veins being interposed. The Intervertebral substance (ligamentum in- tervertebrale) is a lenticular disk of fibrous car- tilage, interposed between the bodies of the vertebrae from the axis to the sacrum, and retaining them firmly in connexion with each other. It varies in thickness in different parts of the column, and at different points of the same disk, being thickest in tbe lumbar region, deepest in front in the cervical and lumbar regions, and behind in the dorsal region; and contributes to the formation of the natural curves of the vertebral column. The aggregate thickness of the intervertebral substance has been estimated at one-fourth that of the entire vertebral column, exclusive of the sacrum and coccyx. When the intervertebral substance is bisected either horizontally or vertically, it is seen to be composed of a series of layers of dense fibrous tissue, separated by interstices filled with the softer kind. The central part of each intervertebral disk is wholly made up of this softer fibrous cartilage, which has the appearance of pulp, and is so elastic as to rise above the level of the section as soon as its division is completed. Examined from the exterior, the layers are found to consist of fibres passing obliquely between the two ver- tebras, in one layer passing from left to right, in the next from right to left, alternating in each successive layer. Fig. 105.* * A posterior view of the bodies of three dorsal vertebrae, connected by their intervertebral substance 1, 1. The laminae (2) have been sawn through near the bodies of the vertebrae, and the arches and processes removed, in order to show (3) the posterior common ligament. Part of one of the openings in the posterior surface of the vertebra, for the transmission of the vena basis vertebrae, is seen at 4, by the side of the narrow and unattached portion of the ligament. LIGAMENTS OF THE VERTEBRAL COLUMN. 137 Arches.—The ligamenta subflava are two thin planes of yellow fibrous tissue, situated between the arches of the vertebrae, from the axis to the sacrum. From the imbri- cated position of the laminae, they are attached to the posterior surface of the vertebra below, and the anterior surface of the arch of the vertebra above, being separated from each other at the middle fine by a slight interspace. They coun- teract, by their elasticity, the efforts of the flexor muscles of the trunk ; and, preserving the upright position of the spine, limit the expenditure of muscular force. They are longest in the cervical and thickest in the lumbar region. The ligamenta subflava are in relation by both surfaces with the meningo- rachidian veins, and, internally, are separated from the dura mater of the spinal cord by those veins and some loose cellular and adipose tissue. Articular processes.—The ligaments of the articular processes of the vertebral are thin capsules of ligamentous fibres which sur- round and enclose the synovial membrane; the latter being looser in the cervical than in the other regions of the spine. Spinous processes.—The inter- spinous ligaments (membrana in- terspinalis), thin and membranous, are extended between the spinous processes in the dorsal and lumbar region; being thickest in the latter. They are in relation with the multifidus spinae muscle at each side. The Supraspinous ligament (ligamenta apicum, fig. 114) is a Fig. 106.* Fig. 107.f * Internal view of the arches of three vertebra. To obtain this view the laminae have been divided through their pedicles. 1. One of the ligamenta subflava. 2. The capsular ligament of one side. I Anterior view of the ligaments connecting the atlas, axis, and occipital bone. A transverse section has been carried through the base of the skull, dividing the basilar process of the occipital bone and the petrous portion of the temporal bones. 1. Anterior round occipito-atloid ligament. 2. Anterior broad occipito-atloid ligament. 3. Commencement of the anterior common ligament. 4. Anterior atlo-axoid ligament, continuous interiorly with the commencement of the anterior common ligament. 5. One of the atlo-axoid capsular ligaments ; that on the opposite side has been removed, to show the approximated surfaces of the articular processes (6). 7. One of the occipito- atloid capsular ligaments. The most external of these fibres constitute the lateral occipito-atloid ligament. 138 LIGAMENTS OF THE ATLAS AND AXIS. strong, fibrous cord, extending from the apex of the spinous process of the last cervical vertebra to the sacrum, and attached to each spinous process in its course. Like the anterior and posterior common ligaments, it is composed of fibres of unequal length, the deeper fibres passing from one vertebra to the next, the superficial fibres extending over several spinous processes. It is thickest in the lumbar region. The continuation of this ligament upwards to the tuberosity of the occipital bone, constitutes the rudimentary ligamentum nuchaj of man. The latter is strengthened, as in animals, by a thin slip from the spinous process of each cervical vertebra. Tkansveb.se pkocesses.—The intertransverse ligaments, thin and membranous, are found, only, between the transverse processes of the lower dorsal vertebrae. 2. Articulation of the Atlas with the Occipital bone.—The liga- ments of this articulation are seven in number : Two anterior occipito-atloid, Lateral occipito-atloid, Posterior occipito-atloid, Two capsular. Of the two anterior ligaments, one is a rounded cord, situated in the middle fine, and superficially to the other; it is attached above to the basilar process of the occipital bone ; below, to the anterior tubercle of the atlas. The deeper ligament is a broad membranous layer, attached above to the margin of the occipital foramen, be- tween the two condyles; and below, to the whole length of the anterior arch of the atlas. It is in relation in front with the recti antici minores, behind with the odontoid ligaments. The posterior ligament is thin and membranous ; attached above to the margin of the occipital foramen, between the two condyles, and below, to the posterior arch of the atlas. It is closely adherent to the dura mater, by its inner sur- face ; and forms a ligamentous arch at each side, for the passage of the vertebral artery and first cervical nerve. It is in relation posteriorly with the recti postici minores and obliqui superiores. The lateral ligaments are strong fasciculi of ligamentous fibres, at- tached below to the base of the transverse process of the atlas at each side; and above, to the transverse process of the occipital bone. With the assistance of a ligamentous expansion derived Fig. 108.* * Posterior ligaments of the occipito-atloid and atlo-axoid articulations. 1. Atlas. 2. Axis. 3. Posterior ligament of the occipito-atloid articulation. 4,' 4. Capsular and lateral ligaments of this articulation. 5. Posterior ligament of the atlo-axoid articulation. 6, 6. Its capsular ligaments. 7. The first pair of ligamenta subflava; passing between the axis and third cervical vertebra. 8, 8. Capsular ligaments of those vertebrae. LIGAMENTS OF THE ATLAS AND AXIS. 139 from the vaginal process of the temporal bone, these ligaments form a strong sheath around the vessels and nerves which pass through the carotid and jugular foramen. The capsular ligaments (condylo-atloidea) are the thin and loose ligamentous capsules which surround the synovial membranes of the articulations between the condyles of the occipital bone and the superior articular processes of the atlas. The ligamentous fibres are most numerous on the anterior and external part of .the articulation. The movements taking place between the cranium and atlas are those of flexion and erection, giving rise to the forward nodding of the head. When this motion is increased to any extent, the whole of the cervical region concurs in its production. 3. Articulation of the Axis with the Occipital bone.—The liga- ments of this articulation are three in number: Occipito-axoid, Two odontoid. The occipito-axoid ligament (apparatus ligamentosus colli) is a broad and strong band, which covers in the odontoid process and its ligaments. It is attached below to the body of the axis, where it is continuous with the posterior common liga- ment ; superiorly it is inserted by a broad expansion, into the basilar groove of the occipital bone, it is firmly connected opposite the body of the axis, with the dura mater; and is sometimes described as con- sisting of a central and two lateral portions. The odontoid ligaments (ala- ria) are two short and thick fasciculi, which pass outwards from the apex of the odontoid process, to the sides of the occipital fora- men and condyles. A third and smaller fasciculus (ligamentum dentis suspensorium) proceeds from the apex of the odontoid process to the anterior margin of the foramen magnum. These ligaments serve to limit the extent of rotation of the head, hence they are termed check ligaments. 4. Articulation of the Atlas with the Axis.—The ligaments of this articulation are five in number: Anterior atlo-axoid, Two capsular, Posterior atlo-axoid, Transverse. Fig. 109.* * Upper part of the vertebral canal, opened from behind in order to show the occipito-axoid ligament. 1. Basilar portion of the sphenoid bone. 2. Sec- tion of the occipital bone. 3. Atlas, its posterior arch removed. 4. Axis, posterior arch removed. 5. Occipito-axoid ligament, rendered prominent at its middle by the projection of the odontoid process. 6. Lateral and capsular ligament of the occipito-atloid articulation. 7. Capsular ligament of the arti- cular process of the atlas and axis. 140 LIGAMENTS OF THE ATLAS AND AXIS. The anterior ligament consists of ligamentous fibres, which pass from the anterior tubercle and arch of the atlas to the base of the odontoid process and body of the axis, where they are continuous with the commencement of the anterior common ligament. The posterior ligament is a thin, membranous layer, passing be- tween the posterior arch of the atlas and the lamina; of the axis ; it represents the ligamenta subflava in a rudimentary state. The capsular ligaments surround the articular processes of the atlas and axis; they are loose, to permit of the free movement which subsists between these vertebra;. The ligamentous fibres are most numerous on the outer and anterior part of the articulation; and the synovial membrane usually communicates with the synovial cavity between the transverse ligament and odontoid process. The transverse ligament is a strong ligamentous band, which arches across the area of the ring of the atlas from a rough tubercle on the inner surface of one articu- lar process to a corresponding tubercle on the other; and serves to retain the odontoid process of the axis, in connexion with the anterior arch of the atlas. As it crosses the neck of the odontoid process, some fibres are sent down- wards to be attached to the body of the axis, and others pass up- wards to be inserted into the basi- lar process of the occipital bone; hence the ligament has a cross- like appearance, and is termed cruciform. A synovial membrane is situated between the transverse ligament and odontoid process ; and another between that process and the anterior arch of the atlas. Actions.—It is the peculiar disposition of the transverse ligament in relation to the odontoid process, that enables the atlas, and with it the entire cranium, to rotate upon the axis; the perfect freedom of movement between these bones being ensured by the two synovial membranes. The lower part of the ring, formed by the transverse ligament with the atlas, is smaller than the upper, while the sum- mit of the odontoid process is larger than its base; hence the process is retained in its place by the transverse ligament, when the other ligaments are cut through. The extent to which rotation of the head upon the axis can be carried, is determined by the odontoid or Fig. 110.* * Posterior view of the ligaments connecting the atlas, axis, and occipital bone. The posterior part of the occipital bone has been sawn away, and the arches of the atlas and axis removed. 1. Superior part of the occipito-axoid ligament, which has been cut away in order to show the ligaments beneath. 2. Transverse ligament of the atlas. 3, 4. Ascending and descending slips of the transverse ligament, which have obtained for it the title of cruciform ligament. 5. One of the odontoid ligaments; the fellow ligament is seen on the opposite side. 6. One of the occipito-atloid capsular ligaments. 7. One of the atlo-axoid capsular ligaments. LIGAMENTS OF THE LOWER JAW. 141 check ligaments. The odontoid process with its ligaments is covered in by the occipito-axoid ligament. 5. Articulation of the Lower Jaw.— The lower jaw has properly but one ligament, the external lateral; the ligaments usually de- scribed are three in number ; to which may be added, as appertain- ing to the mechanism of the joint, an interarticular fibrous-cartilage and two synovial membranes, thus : External lateral, Capsular, Internal lateral, Interarticular fibrous cartilage, Two synovial membranes. The external lateral ligament is a short and thick band of fibres, passing obliquely backwards from the tubercle of the zygoma, to the external surface of the neck of the lower jaw. It is in relation, ex- ternally, with the integument of the face; internally, with the two synovial membranes of the articu- lation and the interarticular car- tilage. The external lateral liga- ment acts conjointly with its fellow of the opposite condyle in the movements of the jaw. The internal lateral ligament (spheno-maxillary) has no connexion with the articulation of the lower jaw, and is, therefore, incorrectly named; it is a thin aponeurotic ex- pansion extending from the extremity of the spinous process of the sphenoid bone to the margin of the dental fora- men ; and is pierced at its insertion by the mylo-hyoidean nerve. Between the internal lateral liga- ment and neck of the jaw is a trian- gular space, in which are situated the internal maxillary artery, auriculo- temporal nerve, inferior dental arteiy and nerve, and part of the external pterygoid muscle; internally the liga- ment is in relation with the internal pterygoid muscle. Fig. 111.* Fig. 112.f Fig. 112.t * External view of the articulation of the lower jaw. 1. Zygomatic arch. 2. Tubercle of the Zygoma. 3. Ramus of the lower jaw. 4. Mastoid portion of the temporal bone. 5. External lateral ligament. 6. Stylo-maxillary ligament. f Internal view of the articulation of the lower jaw. 1. Section through the petrous portion of the temporal bone and spinous process of the sphenoid. 2. Internal surface of the ramus and body of the lower jaw. 3. Capsular ligament. 4. Internal lateral ligament. 5. A small interval at its insertion through which the mylo-hyoidean nerve passes. 6. Stylo-maxillary ligament, a process of the deep cervical fascia. 142 LIGAMENTS OF THE LOWER JAW, The capsular ligament (membrana maxillae articularis) consists of numerous irregular ligamentous fibres, which pass from the edge of the glenoid cavity to the neck of the lower jaw, and surround the articulation; on the inner side of the joint they form a pretty strong fasciculus. The interarticular fibrous cartilage (cartilage intermedia) is a thin oval plate, thicker at the edges than in the centre, placed hori- zontally between the head of the condyle of the lower jaw and the glenoid cavity. It is connected by its outer border with the ex- ternal lateral ligament, and receives in front some fibres of insertion of the external pterygoid muscle. It divides the joint into two cavities, one being above, the other below the cartilage ; but it is occasionally incomplete in the centre. The synovial membranes are situated, one above, the other below the fibrous cartilage, the former being the larger of the two. When the fibrous cartilage is perforate, the synovial membranes com- municate. Besides the lower jaw, there are several other joints provided with a complete interarticular cartilage, and, consequently, with two synovial membranes; they are, the sterno-clavicular, acromio- clavicular, and the articulation of the ulna with the cuneiform bone. The interarticular fibrous cartilages of the knee-joint are partial, and there is but one synovial membrane. The articu- lations of the heads of the ribs with the vertebrae have two synovial mem- branes separated by an interarticular ligament without fibrous cartilage. Connected with the lower jaw, though not with the joint, is the stylo-maxillary ligament, a process of the deep cervical fascia extended be- tween the point of the styloid pro- cess and the angle of the jaw. It is attached to the jaw between the insertions of the masseter and internal pterygoid muscle, and separates the parotid from the submaxillary gland. Actions.—The movements of the lower jaw are depression, by which the mouth is opened, elevation, by which it is closed ; a for- ward and backward movement, and a movement fiom side to side. In the movement of depression the interarticular cartilage glides forward on the eminentia articularis, carrying with it the condyle. If this m ovement be carried too far, the superior synovial membrane Fig. 113.* * In this sketch a section has been made through the joint to show the position of the interarticular fibro-cartilage, and the manner of its adaptatio to the articulating surfaces. 1. Glenoid fossa. 2. Eminentia articularis. 3. Interarticular fibro-cartilage. 4. Superior synovial cavity. 5. Inferior synovial cavity. 6. An interarticular fibro-cartilage, removed from the joint, in order to show its oval and concave form; it is seen from below. LIGAMENTS OF THE RIBS. 143 is ruptured, and dislocation of the fibro-cartilage with its condyle into the zygomatic fossa occurs. In elevation the fibrous cartilage and condyle are returned to their original position. The forward and backward movement is a gliding of the fibro-cartilage on the glenoid articular surface, in the antero-posterior direction; and the movement from side to side, in the lateral direction. 6. Articulation of the Ribs with the Vertebrce.—The ligaments of these articulations are remarkable for their strength, being in fact so strong as to render dislocation impossible; the neck of the rib must break before displacement could occur : they are divisible into two groups :—1. Those connecting the head of the rib with the bodies of the vertebrce; and, 2. Those connecting the neck and tubercle of the rib with the transverse processes. 1st Group. Anterior costo-vertebral or stellate, Capsular, Interarticular ligament, 2nd Group. Anterior costo-transverse, Middle costo-transverse, Posterior costo-transverse. Two synovial membranes. The anterior costo-vertebral or stellate ligament (lig. capituli cos- tarum, fig. 104) consists of three short bands of ligamentous fibres which radiate from the anterior part of the head of the rib. The superior band passes upwards to be attached to the vertebra above; the middle fasciculus is attached to the intervertebral substance; the inferior to the vertebra below. In the first, eleventh, and twelfth rib, the three fasciculi are attached to the body of the corresponding vertebra. The capsular ligament is a thin layer of ligamentous fibres sur- rounding the joint in the interval left by the anterior ligament; it is thickest above and below the articulation, and protects the synovial membranes. The inter articular ligament is a thin band which passes between the sharp crest on the head of the rib and the intervertebral substance. It divides the joint into two cavities, each being furnished with a separate synovial membrane. The first, eleventh, and twelfth rib have no interarticular ligament, and consequently but one synovial membrane. The anterior costo-transverse ligament (lig. transversarium in- ternum) is a broad band composed of two fasciculi, which ascend from the crest-like ridge on the neck of the rib, to the transverse process immediately above. This ligament separates the anterior from the dorsal branch of the intercostal nerve. . The middle costo-transverse ligament (lig. cervicis externum) is a strong interosseous ligament passing directly between the posterior surface of the neck of the rib, and the transverse process against which is rests. It is absent in the first and two inferior ribs. The posterior costo-transverse ligament (lig. transversarium ex- ternum) is a small but strong fasciculus, passing obliquely from the tubercle of the rib to the apex of the transverse process. The 144 LIGAMENTS OF THE EIBS. articulation between the tubercle of the rib and the transverse pro- cess is provided with a small synovial membrane. There is no anterior costo-transverse ligament to the first or last rib ; and only rudimentary posterior costo-transverse ligaments to the eleventh and twelfth ribs. Several accessory bands (ligamenta acces- sorial are found passing between the transverse processes and the ribs; a broad band of this kind connects the last rib with the transverse pro- cess of the first or second lumbar vertebra. Actions. — The movements per- mitted by the articulations of the ribs are upwards, downwards, and slightly forwards and backwards; the movement increasing in extent from the head to the extremity of the rib. The forward and backward movement is trifling in the seven superior, but greater in the in- ferior ribs; the eleventh and twelfth are very moveable. 7. Articulation of the Costal Cartilages with the Sternum, and with each other.—The ligaments of the chondro-sternal articulations are: Fig. 114.* Anterior chondro-sternal, Posterior chondro-sternal, Superior chondro-sternal, Inferior chondro-sternal, The anterior cliondro-sternal ligament (anterior stellar ligament) is a thin band of ligamentous fibres, passing in a radiated direction from the extremity of the costal cartilage to the anterior surface of the sternum, and intermingling its fibres with those ot the ligament of the opposite side, and with the tendinous fibres of origin of the pectoralis major muscle. The posterior cliondro-sternal ligament, much smaller than the anterior, consists of a thin fasciculus of fibres, situated on the pos- terior surface of the articulation. The superior and inferior cliondro-sternal ligaments are narrow fasciculi corresponding with the breadth of the cartilage, and con- necting its superior and inferior border with the side of the sternum. The synovial membrane is absent in the articulation of the first rib, its cartilage being usually adherent to the sternum; that of the Synovial membranes. * Posterior view of part of the thoracic portion of the vertebral column, showing the ligaments connecting the vertebrae with each other and the ribs with the vertebrae. 1, 1. Supra-spinous ligament. 2, 2. Ligamenta subflava, connecting the laminae. 3. Anterior costo-transverse ligament. 4. Posterior costo-transverse ligaments. LIGAMENTS OF THE STEENUM. 145 second rib has an interarticular ligament, with two synovial mem- branes ; the synovial membranes of the other costal cartilages are single. The sixth and seventh ribs have several fasciculi of strong liga- mentous fibres, passing from the extremity of their cartilages to the anterior surface of the ensiform cartilage, which latter they are in- tended to support. They are named the chondro-xyphoid ligaments. The sixth, seventh, and eighth, and sometimes the fifth and the ninth costal cartilages, have articulations with each other, and a synovial membrane for each articulation. They are connected by ligamentous fibres (ligamenta corruscantia), which pass from one cartilage to the other, external and internal ligaments. The ninth and tenth are connected at their extremity by liga- mentous fibres, but have no synovial membrane. Actions.—The movements of the chondro-sternal articulations are very trifling, being limited to a slight degree of sliding motion. The first rib is the least, the second the most moveable. 8. Articulation of the Bibs with the Costal Cartilages.—The an- terior extremity of each rib is excavated, so as to receive the convex outer end of the costal cartilage ; there is no true ligament, but the periosteum is prolonged on to the cartilage, and takes the place of one. No motion takes place at this articulation. 9. Articulation of the Sternum.—The pieces of the sternum are connected by means of a thin plate of interosseous cartilage placed between each, and by an anterior and posterior ligament {membrana ossium sterni). The fibres of the anterior sternal ligament are longitudinal in direction, but so blended with the anterior eosto- sternal ligaments and tendinous fibres of origin of the pectoral muscles, as scarcely to be distinguished as a distinct ligament. The posterior sternal ligament is a broad smooth plane of longitudinal fibres, placed on the posterior surface of the bone, and extending from the manubrium to the ensiform cartilage. These ligaments contribute very materially to the strength of the sternum and elasticity of the front of the chest; their contin nation downwards on the ensiform cartilage constitutes the sterno-xyphoid ligaments. 10. Articidation of the Vertebral Column with the Pelvis.—The last lumbar vertebra is connected with the sacrum by the same ligaments as those with which the various vertebrae are connected to each other: viz., anterior and posterior common ligament, inter- vertebral substance, ligamenta subflava, capsular ligaments, inter- spinous and supra-spinous ligament. There are, however, two proper ligaments connecting the vertebral column with the pelvis; these are, the Lumbo-sacral, Lumbo-iliac, The lumbo-sacral or sacro-vertebral ligament is a thick triangular fasciculus of ligamentous fibres, connected above with the transverse process of the last lumbar vertebra, and below with the posterior part of the upper border of the sacrum. 146 LIGAMENTS OF THE PELVIS. The lumbo-iliac or ilio-lumbar ligament passes from the apex of the transverse process of the last lumbar vertebra to that part of the crest of the ilium which surmounts the sacro-iliac articulation. It is triangular in form. 11. Articulations of the Pelvis.—The ligaments of the articula- tions of the pelvis are divisible into four groups :—1, those con- necting the sacrum and ilium; 2, those passing between the sacrum and ischium; 3, between the sacrum and coccyx; and, 4, between the two pubic bones. 1st, Between the sacrum and ilium. Sacro-iliac anterior, Sacro-iliac posterior. 2nd, Between the sacrum and ischium. Sacro-ischiatic anterior {short), Sacro-ischiatic posterior {long). 3rd, Between the sacrum and coccyx. Sacro-coecygean anterior, Sacro-coccygean posterior. 4th, Between the ossa pubis. Anterior pubic, Posterior pubic, Superior pubic, Sub-pubic, Interosseous fibro-cartilage. 1. Between the Sacrum and Ilium.—The anterior sacro-iliac ligament consists of numerous short ligamentous bands and fibres, which pass from bone to bone on the anterior surface of the joint. The posterior sacro-iliacs or in- terosseous ligament (ileo-sacrale breve) is composed of numerous strong fasciculi of ligamentous fibres, which pass horizontally between the rough surfaces of the posterior half of the sacro- iliac articulation, and constitute the principal bond of connexion between the sacrum and ilium. One fasciculus of this ligament, longer and larger than the rest, is distinguished, from its direc- tion, by the name of oblique sacro-iliac ligament (ileo-sacrale longum). It is attached, by one Fig. 115.* * Ligaments of the pelvis and hip-joint. 1. Lower part of the anterior common ligament of the vertebras, extending downwards over the front of the sacrum. 2. Lumbo-sacral ligament. 3. Lumbo-iliac ligament. 4. Anterior sacro-iliac ligament. 5. Obturator membrane. 6. Poupart’s ligament. 7. Gim- bemat’s ligament. 8. Capsular ligament of the hip-joint. 9. Ilio-femoral or accessory ligament. LIGAMENTS OF THE PELVIS. 147 extremity, to the posterior superior spine of the ilium; and, by the other, to the third transverse tubercle on the posterior surface of the sacrum. The surfaces of the two bones forming the sacro-iliac articulation are partly covered with cartilage, and partly rough and connected by the interosseous ligament. The anterior or auricular half is coated with cartilage, which is thicker on the sacrum than on the ilium. The surface of the cartilage is uneven, and provided with a delicate synovial membrane, not demonstrable in the adult, but apparent in the young subject and in the female during pregnancy. 2. Between the Sacrum and Ischium.-—The anterior or lesser sacro- ischiatic ligament (sacro-ischiadicum minus) is thin, and triangular in form; it is attached by its apex to the spine of the ischium; and by its broad extremity to the side of the sacrum and coccyx, inter- lacing its fibres with the greater sacro-ischiatic ligament. The anterior sacro-ischiatic ligament is in relation, in front, with the coccygeus muscle ; behind, with the posterior ligament, with which its fibres are intermingled. By its upper border it forms part of the lower boundary of the great sacro-ischi- atic foramen, and by the lower, part of the lesser sacro-ischiatic foramen. The posterior or greater sacro-ischiatic ligament (sacro-ischia- dicum majus), larger, thicker, and posterior to the preceding, is nar- rower in the middle than at each extremity. It is attached, by its smaller end, to the inner margin of the tuberosity and ramus of the ischium; where it forms a falci- form process, which pro- tects the internal pudic artery, and is continu- ous with the obturator fascia. By its larger ex- Fig. 116* Ligaments of the pelvis and hip-joint; lateral view. 1. Oblique sacro-iliao ligament.. I he other fasciculi of the posterior sacro-iliac ligament are not seen m this view of the pelvis. 2. Posterior sacro-ischiatic ligament. 3. An- terior sacro-ischiatic ligament. 4. Great sacro-ischiatic foramen. 5. Lesser sacro-ischiatic foramen. 6. Cotyloid ligament of the acetabulum. 7. Liga- mentum teres. 8. Cut edge of the capsular ligament, showing its extent pos- teriorly, as compared with its anterior attachment. 9. Obturator membrane only partly seen. 148 LIGAMENTS OF THE PELVIS. tremity it is inserted into the side of the coccyx, sacrum, and pos- terior inferior spine of the ilium. The posterior sacro-ischiatic ligament is in relation, in front, with the anterior ligament; behind, with the gluteus maximus, to some fibres of which it gives origin. By its superior border it forms part of the boundary of the lesser ischiatic foramen, and by its lower border, part of the boundary of the perinseum. It is pierced by the coccygeal branch of the ischiatic artery. The two ligaments convert the sacro-ischiatic notches into foramina. 3. Between the Sacrum and Coccyx.—The anterior sacro-coccy- gean ligament is a thin fasciculus passing from the anterior surface of the sacrum to the front of the coccyx. The posterior sacro-coccygean ligament is a thick ligamentous layer, which completes the lower part of the sacral canal, and con- nects the sacrum with the coccyx posteriorly, extending as far as the apex of the latter bone. Between the two bones is a thin disk of soft fibrous cartilage; and in females not unfrequently a synovial membrane. The articu- lation admits of a certain degree of movement backwards during parturition. The ligaments connecting the different pieces of the coccyx consist of a few scattered anterior and posterior fibres, and a thin disk of interosseous cartilage; the latter exists only in the young subject, as, in the adult, the pieces become ossified. 4. Between the Ossa Pubis.—The anterior pubic ligament is composed of ligamentous fibres, which pass obliquely across the union of the two bones from side to side, and form an interlacement in front of the symphysis. The posterior pubic ligament consists of a few irregular bands of fibres uniting the pubic bones posteriorly. The superior pubic ligament is a thick band of fibres connecting the angles of the ossa pubis superiorly, and filling the inequalities of the surface of the bones. The sub-pubic ligament is a thick arch of fibres connecting the two bones interiorly, and forming the upper boundary of the pubic arch. The interosseous fibro-cartilage unites the two surfaces of the pubic bones, in the same manner as the intervertebral substance connects the bodies of the vertebrae. It resembles the inter- vertebral substance also in being composed of oblique fibres dis- posed in concentric layers, which are more dense towards the surface than near the centre. It is thick in front, and thin behind; and a synovial membrane is sometimes found in the posterior half of the articulation. This articulation becomes moveable towards the latter term of pregnancy, and admits of a slight degree of separation of its surfaces. The obturator ligament (membrana obturatoria) is not a ligament of articulation, but simply a ligamentous membrane stretched across LIGAMENTS OF THE UPPER EXTREMITY. 149 the obturator foramen. It gives attachment by its surfaces to the two obturator muscles, and leaves a space in the upper part of the foramen for the passage of the obturator vessels and nerve. The numerous vacuities in the walls of the pelvis, and their closure by ligamentous structures, as in the case of the sacro- ischiatic fissures and obturator foramina, serve to diminish, the pressure on the soft parts during the passage of the head of the foetus through the pelvis in parturition. LIGAMENTS OF THE UPPER EXTREMITY. The Ligaments of the upper extremity may be arranged in the order of the articulations of the different bones ; they are: 1. Sterno-clavicular articulation. 4. Shoulder joint. 2. Scapulo-clavicular articulation. 5. Elbow joint. 3. Ligaments of the scapula. 6. Radio-ulnar articulation. 7. Wrist-joint. 8. Articulation between the carpal bones. 9. Carpo-metacarpal articulation. 10. Metacarpo-phalangeal articulation. 11. Articulation of the phalanges. 1. Sterno-clavicular Articulation.—The sterno-clavicular is an arthrodial articulation; its ligaments are: Anterior sterno-clavicular, Inter-clavicular, Posterior sterno-clavicular, Costo-clavicular (rhomboid), Interarticular fibro-cartilage, Two synovial membranes. The anterior sterno-clavicular ligament is a broad ligamentous layer, extending obliquely downwards and inwards, and covering the antei’ior aspect of the ar- ticulation. This ligament is in relation by its anterior surface with the integument and sternal origin of the sterno-mastoid muscle; and behind with the interarticu- lar fibro-cartilage and syno- vial membranes. The posterior-stemo-clavi- cular ligament is a broad band covering the posterior surface ‘ , of the articulation. It is in relation by its anterior surface with the interarticular fibro-cartilage and synovial membranes; and behind, with the sterno-hyoid and sterno-thyroid muscle. * Ligaments of the stemo-elavicular and costo-stemal articulations. 1. An- terior stemo-clavicular ligament. 2. Inter-clavicular ligament. 3. Costo- clavicular or rhomboid ligament; seen on both sides. 4. Interarticular fibro- cartilage, brought into view by the removal of the anterior and posterior liga- ments. 5. Anterior costo-sternal ligaments of the first and second rib. 150 SCAPULOCLAVICULAR LIGAMENTS. The anterior and posterior ligaments are continuous at the upper and lower paid of the articulation, so as to form a capsule around the joint. The inter-clavicular ligament is a cord-like band which crosses from the extremity of one clavicle to that of the other, and is closely adherent to the upper border of the sternum. It is separated by cellular tissue from the sterno-thyroid muscles. The costo-clavicular or rhomboid ligament is a thick fasciculus of fibres, connecting the sternal extremity of the clavicle with the cartilage of the first rib. It is placed obliquely between the rib and under surface of the clavicle; and is in relation, in front, with the tendon of origin of the subclavius muscle, and behind with the subclavian vein. The rupture of the rhomboid ligament in dislocation of the sternal end of the clavicle gives rise to the peculiar deformity of that accident. The interarticular fibro-cartilage is nearly circular in form, and thicker at the edges than in the centre. It is attached above, to the clavicle; below, to the cartilage of the first rib ; and throughout the rest of its circumference to the anterior and posterior sterno- clavicular ligament. It divides the joint into two cavities, which are lined by separate synovial memlyranes; is sometimes pierced through its centre, and not unfrequently deficient, to a greater or less extent, at its lower part. Actions —The movements of the sterno-clavicular articulation are, a gliding movement of the fibro-cartilage with the clavicle, on the articular surface of the sternum, in the directions, forward, backward, upward, and downward; and circumduction. This articulation is the centre of the movements of the shoulder. 2. Scapulo-davicular Articulation.—The ligaments of the sca- pular end of the clavicle are: Superior acromio-clavicular, Inferior acromio-clavicular, Coraco-clavicular (trapezoid and conoid), Interarticular fibro-cartilage, Two synovial membranes. The superior acromio-clavicular ligament is a moderately thick plane of fibres passing between the extremity of the clavicle and the acromion, on the upper surface of the joint. The inferior acromio-clavicular ligament is a thin plane situated on the under surface. These two ligaments are continuous with each other in front and behind, and form a capsule around the articulation. The coraco-clavicular ligament (trapezoid* and conoid) is a thick fasciculus of ligamentous fibres, passing obliquely between the base of the coracoid process and under surface of the clavicle, and holding the end of the clavicle in firm connexion with the scapula. Seen from before, it has a quadrilateral form; hence its name trapezoid; • LIGAMENTS OF THE SCAPULA. 151 examined from behind, it is triangular, the base being upwards ; hence its other name, conoid. The inter articular fibro-cartilage is often indistinct, from having partial connexions with the fibro-cartilaginous surfaces of the two bones between which it is placed; and is not unfrequently absent. When partial, it occupies the upper part of the articulation. The synovial membranes are thin; and when the fibro-cartilage is incomplete, there is but one. Actions.—The acromio-clavicular ar- ticulation admits of two movements, gliding of the surfaces on each other, and rotation of the scapula on the ex- tremity of the clavicle. 3. The proper lic/aments of the sca- pula are: Coraco-acromial, Transverse. The coraco-acromial ligament (tri- angulare) is a broad and thick trian- gular band, which forms a protecting arch over the shoulder joint. It is attached by its apex to the point of the acromion process, and by its base to the external border of the coracoid process its whole length. This liga- ment is in relation above with the under surface of the deltoid muscle; and below with the tendon of the supra-spinatus muscle, a bursa mucosa being usually interposed. The transverse or coracoid ligament (supra-scapular) is a narrow but strong fasciculus which crosses the notch in the upper border of the scapula, from the base of the coracoid process, and converts it into a foramen. The supra-scapular nerve passes through this foramen, the artery over it. The omo-hyoid muscle takes origin from this ligament. 4. Shoulder Joint. — The scapulo-humeral articulation is an enarthrosis, or ball-and-socket joint; its ligaments are: Fig. 118.* Capsular, Coraco-humeral, Gleno-humeral. Glenoid, The capsular ligament encloses the articulating head of the scapula and head of the humerus, and is attached to the neck of each bone. It is thick above, where resistance is most required, * Ligaments of the scapula and shoulder joint. 1. Superior acromio-clavi- cular ligament. 2. Coraco-clhvicular ligament ; this aspect of the ligament is named trapezoid. 3. Coraco-acromial ligament. 4. Transverse ligament. 5. Capsular ligament. 6. Coraco-humeral ligament. 7. The loDg tendon of the biceps issuing from the capsular ligament, and entering the bicipital groove. 152 SHOULDER JOINT. and strengthened by the tendons of the supra-spinatus, infra-spina- tus, teres minor, and subscapularis muscles: below it is thin and loose. The capsule is incom- plete at the point of contact of the tendons, which consequently obtain on their inner surface a lining of synovial membrane. The coraco-humeral ligament is a broad band which descends obliquely outwards from the border of the coracoid process to the greater tuberosity of the hu- merus, and serves to strengthen the superior and anterior part of the capsular ligament. The gleno-liumeral ligament is an accessory slip of fibres which projects into the joint along the inner edge of the biceps tendon, and is inserted into the upper part of the bicipital groove. It is supposed to be the analogue of the ligamentum teres in the hip-joint. The glenoid ligament is the prismoid band of fibro-cartilage, which is attached around the margin of the glenoid surface for the purpose of protecting its edge and deepening its cavity. It divides superiorly into two slips which are continuous with the long tendon of the biceps; hence the ligament is sometimes described as being formed by the splitting of that tendon. The cavity of the articulation is traversed by the long tendon of the biceps which is enclosed in a sheath of synovial membrane in its passage through the joint. The synovial membrane of the shoulder joint is extensive; it com- municates anteriorly through an opening in the capsular ligament with a large bursal sac, which lines the under surface of the tendon of the subscapularis muscle. Superiorly it frequently communi- cates through another opening in the capsular ligament with a bursal sac belonging to the infra-spinatus muscle; and it moreover forms a sheath around that portion of the tendon of the biceps Avhich is included within the joint. The muscles immediately surrounding the shoulder joint are, the subscapularis, supra-spinatus, infra-spinatus, teres minor, long head of the triceps, and deltoid; the long tendon of the biceps is within the capsular ligament. Actions.—The shoulder joint is capable of every variety of mo- Fig. 119.* * Section through the shoulder joint. 1. The cut end of the clavicle. 2. Acromial end of the clavicle. 3. Articular surface of the glenoid cavity covered with cartilage and synovial membrane. 4. Cross section of the glenoid ligament. 5. Lower part of capsule and synovial sac. 6. Synovial mem- brane prolonged on biceps tendon. 7. Tendon of biceps muscle. ELBOW JOINT. 153 tion—viz., of movement forwards and backwards, of abduction and adduction, of circumduction and rotation. 5. Elbow Joint.—The elbow is a ginglymoid articulation; and its ligaments four in number—namely: Anterior, Posterior. Internal lateral, External lateral. The anterior ligament is a broad and thin membranous layer, descending from the anterior surface of the humerus immediately above the joint, to the coronoid process of the ulna and orbicular ligament. It is connected on each side with the lateral ligaments; and is composed of fibres which pass in three different directions, vertical, transverse, and oblique, the latter being extended downwards and outwards to the orbicular liga- ment, into which they are inserted interiorly. This ligament is covered in by the brachialis anticus muscle. The posterior ligament is a broad and loose layer passing between the posterior surface of the humerus and the anterior surface of the base of the olecranon, and connected at each side with the lateral ligaments. It is covered in by the tendon of the triceps. The internal lateral ligament (brachio-cubitale) is a thick triangular layer, attached above, by its apex, to the internal condyle of the humerus; and below, by its expanded border, to the margin of the greater sigmoid cavity of the ulna, extending from the coronoid process to the olecranon. At its insertion it is intermingled with some trans- verse fibres ; and posteriorly is in relation with the ulnar nerve. The external lateral ligament (brachio-radiale) is a strong and narrow band, which descends from the external condyle of the humerus, to be inserted into the orbicular ligament and the ridge on the ulna with which the posterior part of the latter liga- ment is connected. This ligament is closely united with the tendon of origin of the supinator brevis muscle. The synovial membrane is extensive, and is reflected from the cartilaginous surfaces of the bones upon the inner surface of the ligaments. It surrounds interiorly the head of the radius, and forms an articulating sac between it and the lesser sigmoid notch. The muscles immediately surrounding, and in contact with, the Fig. 120.* * Ligaments of the elbow joint; inner side. 1. Anterior ligament. 2. In- ternal lateral ligament. 3. Orbicular ligament. 4. Oblique ligament. 5. Inter- osseous ligament. 6. Internal condyle of the humerus, which conceals the posterior ligament. 154 RADIO-ULNAE ARTICULATION. elbow joint are, in front, bracbialis anticus; inner side, pronator radii teres, flexor sublimis digitorum, and flexor carpi ulnaris; externally, extensor carpi radialis brevior, extensor communis digitorum, extensor carpi ulnaris, anco- neus, and supinator brevis; behind, triceps. Actions.—The movements of the elbow joint are flexion and extension; the extent of these movements being limited, in front by the coronoid process, and behind by the olecranon. 6. Radio-ulnar Articulation. — The radius and ulna are firmly held together by ligaments, connected with both extremities of the bones, and with the shaft; they are: Orbicular, Oblique, Interosseous, Anterior inferior, Posterior inferior, Interarticular fibro'-cartilage. The orbicular ligament (annu- lar, coronary) is a firm band seve- ral lines in breadth, which sur- rounds the head of the radius, and is attached by each end to an extremity of the lesser sigmoid cavity. It is strongest behind where it receives the external lateral ligament, and is lined on its inner surface by a reflection of the synovial membrane of the elbow joint; it gives attachment to fibres of the supinator brevis muscle. The rupture of this ligament permits the dis- location of the head of the radius. The oblique ligament (called also ligamentum teres, in contradistinction to the interosseous ligament) is a narrow slip of ligamentous fibres, descending obliquely from the base of the coronoid process of the ulna to the inner side of the radius, a little below its tuberosity. The interosseous ligament (membrana interossea) is a broad and thin plane of aponeurotic fibres passing obliquely downwards from Fig. 121.* Fig. 122.f * External view of the elbow joint. 1. Humerus. 2. Ulna. 3. .Radius. 4. External lateral ligament inserted interiorly into (5) the orbicular ligament. 6. Posterior extremity of the orbicular ligament, spreading out at its insertion into the ulna. 7. Anterior ligament, scarcely apparent in this view of the articu- lation. 8. Posterior ligament, thrown into folds by the extension of the joint. t Upper part of ulna, and orbicular ligament. 1. Olecranon. 2. Tip of coronoid process. 3. Orbicular ligament. WRIST JOINT. 155 the sharp ridge on the radius to that on the ulna. It is deficient supe- riorly, broader in the middle than at each extremity, and perforated at its lower part for the passage of the anterior interosseous artery. The posterior interosseous artery passes backwards between the oblique ligament and upper border of the interosseous ligament. The interosseous ligament affords an extensive surface for the attachment of muscles ; and is in relation, in front, with the flexor profundus digitorum, flexor longus pollicis, pronator quadratus, and anterior interosseous artery and nerve ; behind, with the supinator brevis, extensor ossis metacarpi pollicis, extensor primi internodii pollicis, extensor secundi internodii pollicis, extensor indicis, and near the wrist with the anterior interosseous artery and posterior interosseous nerve. The anterior inferior ligament is a thin band of fibres, passing transversely between the radius and ulna. The posterior inferior ligament, also thin and loose, has the same disposition on the posterior surface of the articulation. The inter articular, or triangular fibro-cartilage, acts the part of a ligament between the lower extremity of the radius and ulna. It is inserted by its apex into a depression on the inner surface of the styloid pro- cess of the ulna, and attached by its base to the edge of the radius. This fibro-cartilage is lined on the upper sur- face by a synovial membrane, which forms a remarkably loose capsule be- tween the radius and ulna, and is called the membrana sacciformis. By its lower surface it enters into the articulation of the wrist joint. Actions. — The movements taking place between the radius and ulna are, rotation of the former upon the latter; rotation forwards being termed pronation, and rotation backwards supination; in the former the palm of the hand comes to be directed downwards, in the latter it looks upwards. In these movements the head of the radius turns upon its axis, within its orbicular ligament and lesser sigmoid notch of the ulna ; while interiorly, the radius presents a concavity which moves on the rounded head of the ulna. The movements of the radius are chiefly limited by the anterior and posterior inferior ligaments; hence these are not unfrequently rup- tured in great muscular efforts. 7. Wrist Joint.—The wrist is a ginglymoid articulation; the articular surfaces entering into its formation being the radius and triangular fibro-cartilage above, and the rounded surface of the sea- Fig. 123.* * Lower end of radius and ulna, with articular surfaces. 1. Eadius. 2. Ulna. 3. Interarticular fibro-cartilage. 4. Articular end of radius. 5. Membrana sacciformis. 156 CARPAL ARTICULATIONS. phoid, semilunar, and cuneiform bone, below; its ligaments are four in number: Anterior, Posterior, Internal lateral, External lateral. The anterior ligament is a broad and membranous layer consist- ing of three fasciculi, which pass between the lower part of the radius and the scaphoid, semilunar, and cuneiform bone. The posterior ligament, also thin and loose, passes between the posterior surface of the radius, and the posterior surface of the semilunar and cuneiform bone. The internal lateral ligament extends from the styloid process of the ulna to the cuneiform and pisi- form bone. The external lateral ligament is at- tached by one extremity to the sty- loid process of the radius, and by the other to the side of the scaphoid bone, some of its fibres being prolonged to the trapezium. The radial artery rests on this ligament as it passes backwards to the first metacarpal space. The synovial membrane of the wrist joint lines the under surface of the radius and interarticular cartilage above, and the first row of bones of the carpus below. The relations of the wrist joint are, the flexor and extensor tendons, by which it is surrounded, and the radial and ulnar artery. Actions.—The movements of the wrist joint are, flexion, extension, adduction, abduction and circum- duction. In these motions the ar- ticular surfaces glide upon each other. Fig. 124.* * Ligaments of the anterior aspect of the wrist and hand. 1. Lower part of the interosseous membrane. 2. Antero-inferior radio-ulnar ligament. 3. Anterior ligament of the wrist joint. 4. External lateral ligament. 5. In- ternal lateral ligament. 6. Palmar ligaments of the carpus. 7. Pisiform bone, with its ligaments. 8. Ligaments connecting the second range of carpal bones with the metacarpal, and the metacarpal with each other. 9. Capsular ligament of the carpo-metacarpal articulation of the thumb. 10. Anterior ligament of the metacarpo-plialangeal articulation of the thumb. 11. One of the lateral ligaments of that articulation. 12. Anterior ligament of the ineta- carpo-phalangeal articulation of the index finger; this ligament has been removed in the other fingers. 13. Lateral ligaments of the same articulation: the corresponding ligaments are seen in the other articulations. 14. Trans- verse ligament connecting the heads of the metacarpal bones of the index and CARPAL ARTICULATIONS. 157 8. Articulations between the Carpal Bones.—These are amphi- arthrodial joints, with the exception of the conjoined head of the os magnum and unciform, which is received into a cup formed by the scaphoid, semilunar, and cuneiform bone, and constitutes an enarthrosis. The ligaments are : Dorsal, Palmar, Interosseous fibro-cartilages, Annular. The dorsal ligaments are ligamentous hands that pass trans- versely and longitudinally from bone to bone on the dorsal surface of the carpus. The palmar ligaments are fasciculi of the same hind, but stronger than the dorsal, having the like disposition on the palmar surface. The interosseous ligaments are fibro-cartilaginous lamella; situated between the adjoining bones in each range: in the upper range they close the upper part of the space between the scaphoid, semi- lunar, and cuneiform bones ; in the lower range they are stronger than in the upper, and connect the os magnum on the one side to the unciform, on the other to the trapezoid, leaving intervals through which the synovial membrane is continued to the bases of the metacarpal bones. The proper annular ligament is a firm ligamentous band, which connects the bones of the two sides of the carpus. It is attached by one extremity to the trapezium and scaphoid, by the other to the unciform process of the unciforme and base of the pisiform bone, and forms an arch over the anterior surface of the carpus, beneath which the tendons of the long flexors and the median nerve pass into the palm of the hand. The articulation of the pisiform hone with the cuneiform is pro- vided with a separate synovial membrane, protected by fasciculi of ligamentous fibres, which form a kind of capsule around the joint; they are inserted into the cuneiform, unciform, and base of the metacarpal bone of the little finger. Synovial membranes.—There are five synovial membranes enter- ing into the composition of the articulations of the carpus :— The first is situated between the lower end of the ulna and the interarticular fibro-cartilage; it is called sacciform, on account of forming a sacculus between the ulna and radius. The second is situated between the lower surface of the radius and interarticular fibro-cartilage above, and the first range of bones of the carpus below. The third, the most extensive of the synovial membranes of the wrist, is situated between the two rows of carpal bones, and passes middle finger ; the same ligament is seen between the other fingers. 15. An- terior and one lateral ligament of the phalangeal articulation of the thumb. 16. Anterior and lateral ligaments of the phalangeal articulations of the index finger; the anterior ligaments are removed in the other fingers, but the lateral ligaments remain. 158 CARPO-METACARPAL ARTICULATIONS. between the bones of the second range, to invest the carpal extre- mities of the four metacarpal bones of the fingers. The fourth is the synovial membrane of the articulation of the metacarpal bone of the thumb with the trapezium. The fifth is situated between the pisiform and cuneiform bone. Actions.—Very little movement exists between the bones in each range, but more is permitted between the two ranges. The motions of the latter, are those of flexion and extension.’ 9. Carpo-metacarpal Articulations.—The second row of bones of the carpus articulates with the metacarpal bones of the four fingers by dorsal and palmar ligaments; and the metacarpal bone of the thumb with the trapezium by a capsular ligament. There is also in the carpo-metacarpal articula- tion a thin interosseous band, which passes from the ulnar edge of the os magnum to the base of the third and fourth metacarpal bones at their point of connexion. The dorsal ligaments are strong fasciculi which pass from the second range of carpal to the metacarpal bones; with the exception of the little finger there are two fasciculi to each bone—namely, to the index finger, one each from the trapezium and trapezoid; to the middle finger, one each from the trapezoid and os magnum; to the ring finger, one each from the os magnum and unciform; and to the little finger, one from the unciform. The palmar ligaments are thin fasciculi arranged according to the same plan on the palmar surface. The synovial membrane is a continuation of the great synovial membrane of the two rows of carpal bones. The capsular ligament of the thumb is one of the three true capsular ligaments of the skeleton; the other two being the shoulder and hip. The articulation has a proper synovial membrane. Fig. 125.* * Diagram showing the disposition of the chief synovial membranes of the wrist joint, i. Sacciform membrane, n. Second synovial membrane, in. Third or large synovial membrane, iv. Synovial membrane between the trapezium and metacarpal bone of thumb. That of the pisiform bone is here omitted. 1. Radius. 2. Ulna. 3. Internal lateral ligament. 4. External lateral ligament. 5. Cuneiform bone. 6. Semilunar. 7. Scaphoid. 8. Unciform. 9. Os magnum. 10. Trapezoid. 11. Trapezium. 12. Interarticular fibro-cartilage. 13. Meta- carpal bone of thumb. 14. Metacarpal of little finger. * Interosseous meta- carpal ligaments. Interosseous ligaments are also seen connecting the bones of each row of the carpus. METACARPO-PHALANGEAL ARTICULATIONS. 159 The matacarpal bones of the four fingers are firmly connected at their bases by means of dorsal and palmar ligaments, which extend transversely from one bone to the other, and by interosseous liga- ments which pass between their contiguous surfaces. Their lateral articular facets are lined by a reflection of the great synovial mem- brane of the two rows of carpal hones. Actions.—The movements of the metacarpal on the carpal bones are restricted to a slight degree of sliding motion, with the exception of the articulation of the metacarpal bone of the thumb with the trapezium. In the latter, the movements are flexion, extension, adduction, abduction, and circumduction. 10. Metacarpo-phalangeal Articulation.—The metacarpo-pha- langeal articulation is a ginglymoid joint; and its ligaments four in number: Anterior, Two lateral, Transverse. The anterior ligaments, thick and fibro-cartilaginous, form part of the articulating surface of the joints. They are grooved externally for the lodgment of the flexor tendons, and by their internal aspect form part of the articular surface for the head of the metacarpal bone. At each side they are continuous with the lateral ligaments. The lateral ligaments are strong narrow fasciculi, holding the bones together at each side. The transverse ligament is a strong ligamentous band passing across the heads of the metacarpal bones of the four fingers, and connected with the anterior ligaments. The expansion of the extensor tendon over the back of the fingers takes the place, and performs the office of a posterior ligament. Actions.—The chief motions which this articulation admits of are flexion and extension—there is also some power of abduction and adduction in the extended position, but little in the flexed. 11. Articulation of the Phalanges.—These articulations are ginglymoid joints ; and furnished with three ligaments : Anterior, Two lateral. The anterior ligament, firm and fibro-cartilaginous, forms part of the articular surface for the head of the phalanges: while externally it is grooved for the reception of the flexor tendons. The lateral ligaments are very strong; and the principal bond of connexion between the bones. The extensor tendon takes the place and performs the office of a posterior ligament. Actions.—The movements of the phalangeal joints are flexion and extension, these movements being more free between the first and second than between the second and thii-d. In connexion with the phalanges it will be proper to examine certain fibrous bands termed thecae or vaginal ligaments, which serve to retain the tendons of the flexor muscles agaiust the flat surface of the bones. These fibrous bands are attached at each side to the lateral margins of the phalanges; they are thick in the 160 HIP JOINT. interspaces of the joints, thin where the tendons lie upon the joints, and are lined on their inner surface by synovial membrane. LIGAMENTS OF THE LOWER EXTREMITY. The ligaments of the lower extremity, like those of the upper, may be arranged in the order of the joints to which they belong; these are: 1. Hip joint. 2. Knee joint. 3. Articulation between the tibia and fibula. 4. Ankle joint. 5. Articulation of the tarsal bones. 6. Tarso-metatarsal articulation. 7. Metatarso-phalangeal articulation. 8. Articulation of the phalanges. 1. Hip Joint.—The articulation of the head of the femur with the acetabulum constitutes an enartlirosis, or ball-and-socket joint. The articular surfaces are, the cup-shaped cavity of the acetabulum and the rounded head of the femur; the ligaments are jive in number, viz.: Capsular, Ilio-femoral, Teres, Cotyloid, Transverse. The capsular ligament (membrana capsularis, fig. 115, s) is a strong ligamentous capsule, embracing the acetabulum superiorly, the neck of the femur below, and connecting the two bones firmly together. It is much thicker on the upper part of the joint, where more resistance is required, than on the under part, and extends farther along the neck of the femur on the anterior and superior than on the posterior and inferior side, being attached to the inter- trochanteric line in front, to the base of the great trochanter above, and to the middle of the neck of the femur behind. The ilio-femoral ligament (fig. 115, 9) is an accessory and radi- ating band, which descends obliquely from the anterior inferior spinous process of the ilium to the anterior intertrochanteric line, and strengthens the anterior portion of the capsular ligament. The ligamentum teres (fig. 116, 7), triangular in shape, is attached by a round apex to the depression just below the middle of the head of the femur, gnd by its base, which separates into two fasci- culi, into the borders of the notch of the acetabulum. It is formed by a fasciculus of fibres of variable size, surrounded by synovial membrane ; sometimes the synovial membrane is present without the fibres, or the ligament is wholly absent. The round ligament limits adduction in the flexed position, and thus resists dislocation of the head of the femur on to the dorsum of the ilium; it also limits external rotation when the limb is partly flexed. The cotyloid ligament (fig. 116, e) is a prismoid cord of fibrocar- KNEE JOINT. 161 tilage, attached around the margin of the acetabulum, and serving to deepen that cavity and protect its edges. It is thicker at the upper and posterior border of the acetabulum than in front, is in- clined inwards towards the acetabulum, and consists of fibres which arise from the whole circumference of the brim, and interlace with each other at acute angles. The transverse ligament is a strong fasciculus of ligamentous fibres, continuous with the cotyloid ligament, and stretching across the notch of the acetabulum. It converts the notch into a foramen, through which the articular branches of the internal circumfiex and obturator artery enter the joint. The fossa at the bottom of the acetabulum is filled with a mass of fat, covered by synovial membrane, which serves as an elastic cushion for the head of the bone during its movements. This was described by Havers as the synovial gland. The synovial membrane is extensive; it invests the head of the femur, and is continued around the ligamentum teres into the ace- tabulum, whence it is reflected on the inner surface of the capsular ligament back to the head of the bone. The muscles immediately surrounding and in contact with the hip-joint are, in front, psoas and iliacus, separated from the cap- sular ligament by a large synovial bursa; above, short head of the rectus and gluteus minimus ; behind, pyriformis, gemellus superior, obturator internus, gemellus inferior, and quadratus femoris; and at the inner side, obturator externus and pectineus. Actions.—The movements of the hip-joint are very extensive; they are flexion, extension, adduction, abduction, circumduction, and rotation. 2. Knee Joint.—The knee is a ginglymoid articulation of large size, and provided with numerous ligaments; the latter are thirteen in number—namely, Anterior or ligamentum patellae, Posterior or ligamentum posticum Winslowii, Internal lateral, Two external lateral, Anterior or external crucial, Posterior or internal crucial, Transverse, Two coronary, Ligamentum mucosum, Ligamenta alaria, Two semilunar fibrocartilages, Synovial membrane. false ligaments. The first five are external to the articulation; the next five are internal; the remaining three are mere folds of synovial membrane, and have no title to the name of ligaments. In addition to the ligaments, there are two fibrocartilages, and a synovial membrane. The anterior ligament, or ligamentum patellae, is the prolongation 162 KNEE JOINT. of the tendon of the extensor muscles of the thigh downwards to the tubercle of the tibia. It is, therefore, no ligament; and, as the patella is simply a sesamoid bone developed in the tendon of the extensor muscles for the defence of the front of the knee joint, the ligamentum pa- tellae has no title to consideration, either as a ligament of the knee joiut or as a ligament of the patella. A small bursa mucosa is situated between the ligamentum patellae near its insertion and the front of the tibia: and another of larger size between the anterior surface of the patella and fascia lata. It is the latter which is en- larged in housemaid’s knee. The posterior ligament, ligamentum pos- ticum Winslowii, is a broad expansion of ligamentous fibres, which covers the whole of the posterior aspect of the joint. It is divi- sible into two lateral portions, which invest the condyles of the femur, and a central portion which is depressed, and formed by the interlacement of fasciculi passing in different directions. The strongest of these fasciculi is derived from the tendon of the semi- membranosus, and passes obliquely upwards and outwards from the posterior part of the inner tuberosity of the tibia to the ex- ternal condyle of the femur. Other accessory fasciculi are given off by the tendon of the popliteus and heads of the gastrocnemius. The middle portion of the ligament supports the popliteal artery and vein, and is perforated by several openings for the passage of branches of the azygos articular artery and the nerves of the joint. The internal lateral ligament is a broad and trapezoid layer of ligamentous fibres, attached above to the tubercle on the internal condyle of the femur, and below to the inner tuberosity of the tibia. It is crossed at its lower part by the tendons of the inner hamstring, from which it is separated by a synovial bursa, and it covers in the anterior slip of the semi-membranosus tendon and the inferior in- ternal articular artery. External lateral ligaments.—The long external lateral ligament is a strong and round cord, which descends from the posterior part of the tubercle on the external condyle of the femur to the outer part of the head of the fibula. The short external lateral ligament is an irregular fasciculus situated behind the preceding, arising from the external condyle near the origin of the head of the gastrocnemius muscle, and Fig. 126,* * Anterior view of the ligaments of the knee joint. 1. Tendon of the qua- driceps extensor muscle of the leg. 2. Patella, 3. Anterior ligament, or ligamentum patellae, near its insertion. 4, 4. Synovial membrane. 5. Internal lateral ligament. 6. Long external lateral ligament. 7. Antero-superior tibio-fibular ligament. KNEE JOINT, 163 inserted into the posterior part of the head of the fibula. It is firmly connected with the external semilunar fibrocartilage, and appears principally intended to connect that cartilage with the fibula: sometimes it is lost superiorly in the capsular ligament without reaching the femur. The long external lateral ligament is covered in by the tendon of the biceps, and lias passing beneath it the tendon of origin of the popliteus muscle, and the inferior external articular artery. The true ligaments within the joint are the crucial, transverse, and coronary. The anterior, or external crucial ligament, arises from the depression on the head of the tibia in front of the spinous process, and passes upwards and backwards to be inserted into the inner surface of the outer condyle of the femur, as far back as its posterior border. It is smaller than the posterior. The posterior, or internal crucial ligament, ai'ises from the depression on the head of the tibia behind the spinous process, and passes upwards and forwards to be inserted into the intercondyloid hollow, and outer surface of the inner con- dyle of the femur. This ligament is less oblique and larger than the anterior. The anterior crucial ligament limits extension, and the posterior limits flexion ; they also limit rotation when the leg is flexed. The transverse ligament is a small slip of fibres which extends transversely from the external semilunar fibrocartilage, near its anterior extremity, to the anterior convexity of the internal carti- lage. The coronary ligaments are the short fibres by which the convex borders of the semilunar cartilages are connected to the head of the tibia and ligaments surrounding the joint. The semilunar fibrocartilages are two falciform plates of fibro- cartilage, situated on the head of the tibia around its margin, and serving to deepen the surface of articulation for the condyles of the femur. They are thick along their convex border ; thin and sharp along their concave edge. The internal semilunar fibrocartilage forms an oval cup for the Fig. 127.* * Posterior view of the ligaments of the knee joint. 1. Fasciculus, of the ligamentum posticum Winslowii, derived from 2, the tendon of the semi- membranosus muscle ; the latter is cut thi-ough. 3. The process of the tendon which spreads out in the fascia of the popliteus muscle. 4. The process which is sent forwards beneath the internal lateral ligament. 5. Posterior border of the internal lateral ligament. 6. Long external lateral ligament,. 7. Short external lateral ligament. 8. Tendon of the popliteus muscle cut through. 9. Postero-superior tihio-fibular ligament. 164 KNEE JOINT. reception of the internal condyle of the femur : it is connected by its convex border with the head of the tibia and internal and pos- terior ligaments, by means of its coronary ligament; and by its two extremities is firmly implanted into the depression before and behind the spinous process. The external semilunar fibrocarti- lage bounds a circular fossa for the external condyle; it is connected by its convex border with the head of the tibia, and to the ex- ternal and posterior ligaments by its coro- nary ligament; by its two extremities it is inserted, into the depression between the two projections which constitute the spinous pro- cess of the tibia. The two extremities of the external cartilage being inserted into the same fossa, form an almost complete circle, and the cartilage being somewhat broader than the internal, nearly covers the articular surface of the tibia. The external semilunar fibrocartilage, be- sides giving off a fasciculus from its ante- rior border to constitute the transverse ligament, is continuous by some of its fibres with the extremity of the anterior crucial liga- ment ; posteriorly it divides into three slips; one, a strong cord, ascends obliquely forwards to be inserted into the anterior part of the inner condyle of the femur in front of the posterior crucial liga- ment ; another is the fasciculus of insertion into the fossa of the spinous process; while the third, of small size, is continuous with the posterior part of the anterior crucial ligament. The Ligamentum mucosum is a slender conical process of synovial membrane enclosing a few ligamentous fibres which proceed from the transverse ligament. It is connected, by its apex, with the an- terior part of the condyloid notch, and, by its base, is lost in the mass of fat which projects into the joint beneath the patella. The alar ligaments are two fringed folds of synovial membrane, extending from the ligamentum mucosum, along the edges of the mass of fat to the sides of the patella. The synovial membrane of the knee joint is by far the most ex- tensive in the body. It invests the cartilaginous surfaces of the Fir/. 128.* * The right knee joint laid open from the front in order to show the in- ternal ligaments. 1. Cartilaginous surface of the lower extremity of the femur with its two condyles; the figure 5 rests on the external; the figure 3 on the internal condyle. 2. Anterior crucial ligament. 3. Posterior crucial ligament. 4. Transverse ligament. 5. Attachment of the ligamentum mu- cosum ; the rest has been removed. 6. Internal semilunar fibrocartilage. 7. External fibrocartilage. 8. Part of the ligamentum patellae turned down. !). Bursa situated between the ligamentum patellae, and head of the tibia; laid open. 10. Antero-superior tibio-fibular ligament. 11. Intex-osseous mem- brane ; the opening above this membrane is for the passage of the anterior tibial artery. KNEE JOINT. 165 condyles of the femur, head of tibia, and inner surface of the patella; it covers both surfaces of the semilunar fibrocartilages; and is reflected upon the crucial ligaments, and inner surface of the ligaments which form the circumference of the joint. On each side of the patella it lines the tendinous aponeuroses of the vastus internus and vastus externus muscle, and forms a pouch of considerable size between the extensor tendon and front of the femur. It also forms the folds in the interior of the joint, called “ ligamentum mucosum,” and “ ligamenta alaria.” The superior pouch of the synovial membrane is supported and raised during the movements of the limb by a small muscle, the subcrureus, which is inserted into it. Between the ligamentum patellae and synovial membrane is a considerable mass of fat, which presses the membrane towards the interior of the joint, and occupies the fossa between the condyles. Besides the proper ligaments of the ar- ticulation, the joint is strengthened in front by the fascia lata, which is thicker at the outer than the inner side, by a tendinous expansion from the vastus internus, and some scattered ligamentous fibres inserted into the sides of the patella. This expansion has been termed the capsular ligament. Actions.—The knee joint is one of the strongest of the articula- tions of the body, while, at the same time, it admits of the most perfect degree of movement in the direction of flexion and extension. During flexion the articular surface of the tibia glides forward on the condyles of the femur; the lateral ligaments, the posterior, and Fig. 129.* * Longitudinal section of the left knee joint, showing the reflections of its synovial membrane. 1. Cancellous structure of the lower part of the femur. 2. Tendon of the extensor muscles of the leg. 3. Patella. 4. Ligamentum patella?. 5. Cancellous structure of the head of the tibia. 6. A bursa situated between the ligamentum patellae and head of the tibia. 7. Mass of fat pro- jecting into the cavity of the joint below the patella. ** The synovial mem- brane. 8. The pouch of synovial membrane which ascends between the tendon of the extensor muscles of the leg, and front of the lower extremity of the femur. 9. One of the alar ligaments; the other has been removed with the opposite section. 10. Ligamentum mucosum left entire ; the section being made to its inner side. 11. Anterior or external crucial ligament. 12. Posterior ligament. The plan of the synovial membrane, which is here pre- sented to the student, is divested of all unnecessary complications. It may be traced from the sacculus (at 8), along the inner surface of the patella; then over the adipose mass (7) from which it throws off the mucous ligament (10); then over the head of the tibia, forming a sheath to the crucial liga- ments ; then upwards along the posterior ligament and condyles of the femur, to the sacculus whence its examination commenced. 166 TIBIO-FIBULAR ARTICULATION. the crucial ligaments are relaxed; while the ligament! mi patellae being on the stretch, serves to press the adipose mass behind it into the vacuity formed in the front of the joint. In extension all the ligaments are put on the stretch, with the exception of the liga- mentum patellae. When the knee is semi-flexed, a partial degree of rotation is permitted. 3. Articulation between the Tibia and Fibula.—The tibia and fibula are held firmly connected by means of seven ligaments— namely, Anterior, Posterior, Anterior, Posterior, Interosseous membrane, Interosseous inferior, above. Transverse. below. The anterior superior tibio-fibular ligament is a strong fasciculus of parallel fibres passing obliquely downwards and outwards from the outer tuberosity of the tibia, to the anterior surface of the head of the fibula. The posterior superior tibio-fibular ligament, thicker and stronger than the anterior, is disposed in a similar manner on the posterior surface of the joint. Within the articulation there is a synovial membrane which is sometimes continuous with that of the knee joint. The interosseous membrane, or superior interosseous ligament, is a broad layer of aponeurotic fibres which pass obliquely downwards and outwards, from the sharp ridge on the tibia to the inner edge of the fibula, and are crossed at an acute angle by a few fibres taking the oppo- site direction. The ligament is deficient above, leaving a considerable interval between the bones, through which the anterior tibial artery takes its course forward to the anterior aspect of the leg ; and perforated beloiv, near its lower third, for the anterior peroneal artery and vein. The interosseous membrane is in relation, in front, with the tibialis anticus, extensor longus digitorum, extensor proprius pollicis, anterior tibial vessels and nerve, and anterior peroneal artery; behind, with the tibialis posticus, flexor longus pollicis, flexor longus digitorum, and pos- terior peroneal artery. The inferior interosseous ligament consists of short and strong fibres, which hold the bones firmly together in- teriorly, where they are nearly in contact. This articulation is so Fig. 130.* * Posterior view of the ankle joint. 1. Lower part of the interosseous membrane. 2. Postero-inferior ligament connecting the tibia and fibula. 3. Transverse ligament. 4. Internal lateral ligament. 5. Posterior fasciculus of the external lateral ligament. 6. Middle fasciculus of the external lateral ligament. 7. Synovial membrane of the ankle joint. 8. Posterior tuberosity of the os calcis. ANKLE JOINT. 167 firm, that the fibula is broken when an attempt is made to rupture the ligament. The anterior inferior tibio-fibular ligament is a broad band, con- sisting of two fasciculi of parallel fibres which pass obliquely across the anterior aspect of the articulation of the two bones at their in- ferior extremity, from tibia to fibula. The posterior inferior tibio-fibular ligament is a similar band on the posterior surface of the articulation. Both ligaments project somewhat below the margin of the bones, and serve to deepen the cavity of articulation with the astragalus. The transverse ligament is a narrow band of ligamentous fibres, contiuuous with the preceding, and passing transversely across the bach of the ankle joint between the two malleoli. The synovial membrane of the inferior tibio-fibular articulation, is a duplicature of the synovial membrane of the ankle joint, reflected upwards for a short distance between the two bones. Actions.—Between the tibia and fibula there exists a slight degree of movement, which is calculated to enable the latter to resist injury by yielding for a trifling extent to forcible pressure. 4. Ankle Joint.— The ankle is a ginglymoid articulation; the surfaces entering into its formation are the under surface of the tibia with its malleolus and the malleolus of the fibula, above ; and the surface of the astragalus with its two lateral facets, below. The ligaments are three in number : Anterior, Internal lateral, External lateral. The anterior ligament is a thin, membranous layer, passing from the margin of the tibia, to the astragalus, in front of its articular surface. It is in relation, in front, with the tendons of the extensors of the great and lesser toes, tibialis an- ticus, peroneus tertius, and anterior tibial vessels and nerves. Posteriorly it lies in contact with a stratum of extra-synovial adipose tissue and the synovial membrane. The internal lateral or deltoid liga- ment is a triangular layer of fibres, attached superiorly, by its apex, to the internal malleolus; inferiorly, by an expanded base, to the astragalus, os calcis, and scaphoid bone. Beneath the superficial layer of this ligament is a stronger and thicker fasciculus, which connects the apex of the internal malleolus with the side of the astragalus. Fig. 131.* * Internal view of the ankle joint. 1. Internal malleolus of the tibia. 2, 2. Astragalus. 3. Os calcis. 4. Scaphoid bone. 5. Internal cuneiform bone. 6. Internal lateral or deltoid ligament. 7. Anterior ligament. 8. Tendo A chillis; a small bursa is seen interposed between this tendon and the pos- terior tuberosity of the os calcis. 168 TAESAL AETICULATIONS. The internal lateral ligament is covered in and partly concealed by the tendon of the tibialis posticus, and, at its posterior part, is in relation with the tendon of the flexor longus digitorum, and flexor longus pollicis. The external lateral ligament consists of three strong fasciculi, which proceed from the inner side of the external malleolus, and radiate in three different directions. The anterior fasciculus passes forward, to be attached to the astragalus ; the posterior, backward, to be connected with the astragalus posteriorly; and the middle, longer than the other two, descends to be inserted into the outer side of the os calcis. “ It is the strong union of the fibula,” says Sir Astley Cooper, with the tarsal bones, by means of the external lateral ligaments, “ which leads to its being more frequently fractured than dislo- cated.” The transverse ligament of the tibia and fibula occupies the place of a posterior ligament of the ankle joint. It is in relation, behind, with the posterior tibial vessels and nerve, and tendon of the tibialis posti- cus muscle; in front, with the extra- synovial adipose tissue and synovial membrane. The synovial membrane invests the cartilaginous surfaces of the tibia and fibula (sending a duplicature upwards between their lower ends), and the upper surface and two sides of the astragalus. It is then reflected upon the anterior and lateral ligaments, and on the transverse ligament pos- teriorly. Actions.—The movements of the ankle joint are flexion and extension only, without lateral motion. 5. Articulation, of the Tarsal Bones.—The ligaments which con- nect the seven bones of the tarsus to each other are of three kinds.— Dorsal, Plantar, Interosseous. The dorsal ligaments are small fasciculi of parallel fibres, which pass from each bone to all the neighbouring bones with which it articulates. The only dorsal ligaments deserving of particular men- tion, are the external and posterior calcaneo-astragaloid, which, with the interosseous ligament, complete the articulation of the astraga- lus with the os calcis; the superior and internal calcaneo-cuboid Fig. 132.* * External view of the ankle joint. 1. Tibia. 2. External malleolus of the fibula. 3, 3. Astragalus. 4. Os caleis. 5. Cuboid bone. 6. Anterior fasci- culus of the external lateral ligament .attached to the astragalus. 7. Its middle fasciculus, attached to the os calcis. 8. Its posterior fasciculus, attached to the astragalus. 9. Anterior ligament of the ankle. TARSAL ARTICULATIONS. 169 ligaments ; and the superior astragalo-scaphoid ligament. The in- ternal calcaneocuboid, and superior calcaneo-scaphoid ligament, which are closely united posteriorly in the deep groove which inter- venes between the astragalus and os calcis, separate anteriorly to reach their respective bones ; they form the principal bond of con- nexion between the first and second range of bones of the foot. It is the division of this portion of these ligaments that demands the careful attention of the surgeon in performing Cliopart’s ope- ration. The plantar ligaments have the same disposition on the plantar surface of the foot; three of them, however, are of large size, and have especial names, viz., the Calcaneo-scaphoid, Long calcaneo-cuboid, Short calcaneo-cuboid. The inferior calcaneo-scaphoid ligament is a broad and fibrocar- tilaginous band of ligament, which passes forward from the anterior and inner border of the os calcis to the edge of the scaphoid bone. Besides connecting the os calcis and scaphoid, it supports the astragalus, and forms part of the cavity in which the rounded head of the latter bone is received. It is lined on its upper surface by the synovial membrane of the astragalo-scaphoid articula- tion. The firm connexion of the os calcis with the scaphoid bone, and the feebleness of the astra- galo-scaphoid articulation, are conditions fa- vourable to the occasional dislocation of the head of the astragalus. The long calcaneo-cuboid, or ligamentum longum plantae,, is a long band of ligamentous fibres, which proceeds from the under surface of the os calcis to the rough surface on the under part of the cuboid bone, its fibres being continued onwards to the base of the third and fourth metatarsal bones. This ligament forms the inferior boundary of a canal in the cuboid bone, through which the tendon of the peroneus longus passes to its in- sertion into the base of the metatarsal bone of the great toe. Fig. 183.* * Ligaments of the sole of the foot. 1. Os calcis. 2. Astragalus. 3. Tube- rosity of the scaphoid bone. 4. Long calcaneo-cuboid ligament. 5. Part of the short calcaneo-cuboid ligament. 6. Calcaueo-scaphoid ligament. 7. Plantar tarsal ligaments. 8, S. Tendon of the peroneus longus muscle. 9. 9. Plantar tarso-metatarsal ligaments. 10. Plantar ligament of the me- tatarso-phalangeal articulation of the great toe; the same ligament is seen 170 TARSAL ARTICULATIONS. The short calcaneo-cuboid, or ligamentum breve jplantce, is situated closer to the bones than the long plantar ligament, from which it is separated by adipose tissue; it is broad and extensive, and ties the under part of the os calcis and cuboid bone firmly together. The interosseous ligaments are five in number; they are short and strong ligamentous fibres situated between adjoining bones, and firmly attached to their rough surfaces. One of these, calca- Fig. 134.* neo-astragaloid, is lodged in the groove between the upper surface of the os calcis and the lower of the astragalus. It is large and very strong, consists of vertical and oblique fibres, and serves to unite the os calcis and astragalus solidly together. The second interosseous ligament, also very strong, is situated between the sides of the scaphoid and cuboid bone; the three remaining interosseous ligaments connect strongly together the three cuneiform bones and the cuboid. The synovial membranes of the tarsus are four in number; one, on the other toes. 11. Lateral ligaments of the metatarsal-phalangeal articu- lation. 12. Transverse ligament. 13. Lateral ligaments of the phalanges of the great toe; the same ligaments are seen on the other toes. * Diagram showing the arrangement of the synovial membranes of the tarsal joints. i. Synovial membrane between the tibia and astragalus. ii. That between the back of the astragalus and os calcis. in. That between the astragalus and scaphoid, and between the front of the astragalus and os calcis. iv. Between the os calcis and cuboid, v. Between the cuneiform bones and scaphoid, vi. Between the internal cuneiform and metatarsal of big toe. vii. Between the middle metatarsal and two outer cuneiform bones, vm. Be- tween the cuboid and outer metatarsals, ix. Between the third and fourth metatarsals. 1. Tibia. 2. Astragalus. 3. Os calcis. 4. Scaphoid. 5. Cuboid. G. External cuneiform. 7. Middle, and 8. Internal cuneiform. 9, 10, 11, 12, 13. Metatarsal bones. Interosseous ligaments are shown connecting the several bones of the tarsus and metatarsus. TARSO-METATARSAL ARTICULATION. 171 for the posterior calcaneo-astragaloid articulation; a second, for the anterior calcaneo-astragaloid and astragalo-scaphoid articulation; occasionally an additional small synovial membrane is found in the anterior calcaneo-astragaloid joint; a third, for the calcaneo-cuboid articulation; and a, fourth, the large tarsal synovial membrane for the articulations between the scaphoid and three cuneiform bones, the cuneiform bones with each other, the external cuneiform bone with the cuboid, and the two external cuneiform bones with the bases of the second and third metatarsal bones. The prolongation which reaches the metatarsal bones passes forward between the in- ternal and middle cuneiform bone. The synovial membrane between the two outer cuneiform and second and third metatarsal bones is often distinct from the large one ; it is so represented in Fig. 134, vii. A small synovial membrane is sometimes met with between the contiguous surfaces of the scaphoid and cuboid bone. Actions.— The movements permitted by the articulation between the astragalus and os calcis, are a slight degree of gliding, in the direction forwards and backwards, and laterally from side to side. The movements of the second range of tarsal bones are very trifling, being greater between the scaphoid and three cuneiform bones than in the other articulations. The movements occurring between the first and second range are the most considerable ; they are adduc- tion and abduction; and, in a minor degree, flexion, which increases the arch of the foot, and extension, which flattens the arch. 6. Tar so-metatar sal Articulation.—The ligaments of this articu- lation are, Dorsal, Plantar, Interosseous. The dorsal ligaments connect the metatarsal to the tarsal bones, and the metatarsal bones with each other. The base of the second metatarsal bone, articulating with the three cuneiform bones, re- ceives a ligamentous slipo from each, while the rest articulating with a single tarsal bone receive only a single tarsal slip. The plantar ligaments have a similar disposition on the plantar surface. The interosseous ligaments are situated between the bases of the metatarsal bones of the four lesser toes; also between the base of the second and third metatarsal bone and the internal and external cuneiform bone. The metatarsal bone of the second toe being implanted by its base between the internal and external cuneiform bone, is the most strongly articulated of all the metatarsal bones. This disposition must be recollected in amputation at the tarso-metatarsal articu- lation. The synovial membranes of the tarso-metatarsal articulation are three in number: one for the metatarsal bone of the great toe; one for the second and third metatarsal bone, which is continuous with the great tarsal synovial membrane ; and one for the fourth and fifth metatarsal bones. 172 ARTICULATION OF THE PHALANGES. Actions.—The movements of the metatarsal on the tarsal hones and on each other are very slight; they are such only as contribute to the strength of the foot, b}r permitting a certain degree of yield- ing to opposing forces. 7. Metatar so-phalangeal Articulation.—The ligaments of this articulation, like those between the first phalanges and metacarpal bones of the hand, are, Inferior or plantar, Two lateral, Transverse. The inferior or plantar ligaments, thick and fibrocartilaginous, form part of the articulating surface of the joint. The lateral ligaments, short and very strong, are situated one on each side of the joint. The transverse ligament is a strong hand, which passes trans- versely between the plantar ligaments. The expansion of the extensor tendon supplies the place of a dorsal ligament. Actions.—The movements of the first phalanges on the rounded heads of the metatarsal bones, are flexion, extension, adduct ion, and abduction. 8. Articulation of the Phalanges.—The ligaments of the pha- langes are the same as those of the fingers, and have the same dis- position ; their actions are also similar. They are, Inferior or plantar, and, Two lateral. 173 CHAPTER IV. OF THE MUSCLES. Muscles are the moving organs of the animal frame; they con- stitute by their size and number the great bulk of the body, upon which they bestow form and symmetry. In the limbs they are situated around the bones, which they invest and defend, while they form to some of the joints a principal protection. In the trunk they are spread out to enclose cavities and constitute a defensive wall, capable of yielding to internal pressure, and again returning to its original position. Their colour presents the deep red which is characteristic of flesh, and their form is variously modified, to execute the varied range of movements which they are required to effect. Muscle is composed of a number of parallel fibres placed side by side, and supported and held together by a delicate web of areolar tissue; so that, if it were possible to remove the muscular substance, we should have remaining a beautiful reticular framework, possess- ing the exact form and size of the muscle without its colour and solidity. Towards the extremity of the organ the muscular fibre ceases, and the fibrous structure becomes aggregated and modified, so as to constitute those glistening fibres and cords by which the muscle is tied to the surface of bone, and which are called tendons. Almost every muscle of the body is connected with bone, either by tendinous fibres, or by an aggregation of those fibres constituting a tendon; and the union is so firm that, under extreme violence, the bone itself breaks rather than permit the separation of the tendon from its attachment. In the broad muscle the tendon is spread out so as to form an expansion, called aponeurosis (arro, longe ; vevpov * uervus, a nerve widely spread out). Muscles present various modifications in the arrangement of their fibres in relation to their tendinous structure. Sometimes they are longitudinal, and terminate at each extremity in tendon, the entire muscle being fusiform in shape; in other situations they are dis- posed like the rays of a fan, converging to a tendinous point, as the temporal, pectoral, glutei, &c., and constitute a radiate muscle. Again, they are penniform, converging like the barbs of a feather to one side of a tendon, which runs the whole length of the muscle, as in the peronei; or bipenniform, converging to both sides of the * The ancients named all tbe -white fibres of the body vevpa: the term has since been limited to the nerves. 174 STRUCTURE OF MUSCLE. tendon. In other muscles the fibres pass obliquely from the sur- face of a tendinous expansion spread out on one side, to that of an- other extended on the opposite side, as in the semi-membranosus; or, they are composed of penniform or bipenniform fasciculi, as in the deltoid, and constitute a compound muscle. The nomenclature of muscles is defective and confused, and is generally derived from some prominent character which the muscle presents; thus, some are named from theii situation, as the tibialis, peroneus, brachialis, temporalis; others from their use, as the flexors, extensors, adductors, abductors, levators, tensors, sphincters, &c. Some again from their form, as the trapezius, triangularis, deltoid, rhomboideus, scalenus, orbicularis, &c.; and others from their direc- tion, as the rectus, obliquus, transversalis, &c. Certain muscles have received names expressive of their attachments, as the sterno-mas- toideus, sterno-hyhoideus, &c.; and others, of their divisions, as the biceps, triceps, digastricus, complexus, &c. In the description of a muscle we express its attachment by the words “ origin” and “ insertion” : the term origin is generally ap- plied to the more fixed or central attachment, or to the point to- wards which the motion is directed, while insertion is assigned to the more moveable point, or to that most distant from the centre ; but there are exceptions to this principle, and as many muscles pull equally towards both extremities, the use of such terms must be regarded as arbitrary. In structure, muscle is composed of bundles of fibres of variable size called fasciculi, which are enclosed in an areolar membranous investment or sheath, and the latter is continuous with the areolar frame- work of the fibres. Each fasciculus is composed of a number of smaller bun- dles, and these of single fibres, which from their minute size and inde- pendent appearance, have been distinguished by the name of ultimate fibres. The ultimate fibre is found by micro- scopic investigation to be itself a fasciculus (ultimate fasciculus), made up of a number of ultimate fibrils enclosed in a delicate sheath, the myolemma or sarcolemma. Two kinds of ultimate muscular fibre exist in the animal economy ; viz., that of voluntary or animal life, striated muscle; and that of involuntary or organic life, smooth muscle. The ultimate fibre of animal life is known by its size, by its uni- formity of calibre, and especially by the transverse markings which occur at minute and regular distances. It also presents other Fig. 135.* * Striated muscular fibre separating into fibrillar. STRUCTURE OF MUSCLE. 175 markings or strife, having a longitudinal direction, which indicate the existence of fibrillae within the myolemma. The myolemma, or sarcolemma, the investing sheath of the ultimate fibre, is thin, homogeneous, transparent, and elastic. According to Bowman,* the ultimate fibres or fasciculi are poly- hedral in shape and various in size; the polyhedral form being due to mutual pressure, and the variety of size besides being met with in a single muscle, being also charac- teristic of different classes, genera, and even sexes of animals : thus the average diameter of the ultimate fibre in the human female is in the male g-i^> the average of both being in round numbers The largest fibres are met with in fishes, in which they ave- rage » the next largest are found in man ; while in other classes they range in the following order:— insects; reptiles ; mammalia -g-iy ; birds s£y. The ultimate fibrils of voluntary muscle are seen under the microscope to be composed of alternate colourless and dark por- tions, of about equal breadth, the light portions having frequently a secondary faint line drawn across the middle of each. The composition of these ultimate fibrils is still uncertain. Some anatomists suppose that the dark portions occupied by a peculiar semi-fluid material, called “ sarcous matter ” (the individual dark spaces being called “ sarcous elements”), and the lighter portions of a more fluid and hence less highly refracting matter; in this opinion Erasmus Wilson fully concurs. But of the nature of the sarcous matter we know nothing, except that in it chiefly the con- tractility of the muscle resides. Carpenter thinks that he can distinguish a pellucid area at the sides of the sarcous elements as well as above and below, and hence he con- cludes that they are in reality cells, filled with a highly refracting substance ; this how- ever has not been confirmed by subsequent observers. The fibres of voluntary muscle cleave most readily in the longitudinal direction, pro- ducing fibrils, but they sometimes cleave transversely, so as to produce flat disks (Fig. 137). Bowman was of opinion that both Fig. 136.t Fig. 1374 * On the Minute Structure and Movements of Voluntary Muscle. Philo- sophical Transactions, 1840. f Transverse section of ultimate fibres of the biceps after Bowman. In this figure the polyhedral form of the fibres is seen, and their composition of ultimate fibrils. \ Ultimate fibre, in which the transverse splitting into disks, iu the direction of the constrictions of the ultimate fibrils, is seen. After Bowman. 176 STRUCTURE OF MUSCLE. the longitudinal and transverse cleavage were alike accidental, and that no such division existed in living muscle; other observers have however concluded that the fibrils do actually exist during life, but that the disks are the result of maceration. Under a high microscopic power numerous nuclei may be ob- served in the fibres ; they are connected with the inner surface of the sarcolemma,and are more distinctly visible in foetal muscle, but can also be traced in that of adult life by the addition of some weak acid. They frequently contain nucleoli, and there is little doubt that they are the nuclei of the cells from which the muscle was developed. Kolliker considers that each fibre arises from a single cell, by its longitudinal extension, and not as some sup- pose by the aggregation of several. The following is a brief account of Mr. Wilson’s own investigations:— “ The ultimate fibril of animal life is cylin- drical when isolated, and probably polyhedral from pressure when forming part of an ultimate fibre or fasiculus. It measures in diameter an inch, and is composed of a succession of cells connected by their flat surfaces. The cells are filled with a transparent substance, which may be termed myoline. The myoline differs in density in different cells, and from this circumstance bestows a peculiarity of character on certain of the cells. For ex- ample, when a fibril in its passive state is examined, there will be seen a series of dark oblong bodies separated by light spaces of equal length; now, the dark bodies are each composed of a pair of cells containing the densest form of myoline, and are hence highly refractive, while the transparent spaces are constituted by a pair of cells containing a more fluid myoline. When the fibrils are collected together so as to form an ultimate fibre or fasciculus, the appearance of the cell is altered: those which look dark in the single fibril, that is the most refractive, being ranged side by side, constitute the bright Fig. 138.* Fig. 139. f * Mass of ultimate fibres from the pectoralis major of the human foetus, at nine months. These fibres have been immersed in a solution of tartaric acid, and their “numerous corpuscles, turned in various directions, some presenting nucleoli,” are shown. After Bowman. f Structure of the ultimate muscular fibril and fibre of animal life. A. Ultimate muscular fibril iu the state of partial contraction. B. The same in the state of ordinary relaxation. This fibril measured snJmj of an inch in diameter, c. A similar fibril put upon the stretch, and measuring jB-ioo of STRUCTURE OF MUSCLE. 177 band; while the transparent cells of the single fibril are the shaded striae of the fibre. When the ultimate fibril is very much stretched, the two highly refractive cells appear each to be double; while the transparent space is evidently composed of four cells.” The ultimate fibre of organic life, or smooth muscular fibre, is a simple homogeneous filament much smaller than the fibre of animal life, fiat, smooth, and without transverse markings. It is of a fusiform shape, and various length, and consists of a thin external membrane, blended with a soft, homogeneous or finely granular contained substance. These fibres were originally round nucleated cells, which have become elongated into a fusiform shape, and sub- sequently grown into the dimensions of fibres. When of small size they have a single nucleus; but in the longer fibre a succession of nuclei may be observed from point to point, and the nucleus is sometimes so much elongated as to deserve the title of columnar. The fusiform cells are united into little bundles or fasciculi by an adhesive interstitial sub- stance, and the fasciculi, which are some- times round and sometimes flat, are bound together into larger bundles by areolar tissue and fine elastic fibres; the interspaces of the bundles being occupied by vessels and nerves, the former in great abundance. Organic or smooth muscle is distributed abundantly in the animal frame, and is met with in all situations where a distinct contractile power, independent of mere elasticity, is required; for example, in the alimentary canal, from the middle of the oesophagus to the internal sphincter ani; in the posterior segment of the trachea, and in the bronchial tubes to their finest Fig. 140.* an inch in diameter. D. Plan of a portion of an ultimate fibre, showing the manner in which the transverse strise are produced by the collocation of the fibrils. Nos. 1, 1. The pair of highly refractive cells; they form the dark parts of the single fibrils, but the bright parts of the fibre D. In the stretched fibril C, each cell has the appearance of being double. 2, 2. The pair of less re- fractive cells, light in the single fibrils, but forming the shaded stria in D. The transverse septum between these cells is very conspicuous ; and in c two other septa are seen to exist, making the number of transparent cells four. In d, the tier of cells immediately above t. te dark tier is partially illumined from the obliquity of the light. By an errc • on the part of the engraver the boundary lines of the fibril are omitted in A B and c. * Non-striated muscular fibre ; at 6, in its natural state; at a, showing the nuclei after the action of acetic acid. 178 MUSCLES OF THE HEAD AND NECK. ramifications; in the excretory ducts of various glands, as Wharton’s duct, the ductus communis clioledochus, thecalices and pelvis of the kidneys; the ureters, bladder, and urethra; on the testes around the vasa deferentia and vesicular seminales, the prostate, Cowper’s glands, and in the substance of the corpora cavernosa; in the Fallopian tubes, uterus and vagina ; in the middle coat of arteries, veins, and lymphatic vessels; in the iris; and in the corium of the skin, particularly in the areola and nipples of the mammary glands, in the dartos of the scrotum, and around the hair follicles, and many of the sudoriferous and sebaceous ducts. The development of muscular fibre is effected by means of the formation of nucleated cells out of an original blastema, and the conversion of those cells into the tubuli of ultimate fibres, while their contents, by a subsequent developmental action, are transformed into ultimate fibrils. In the muscular fibre of organic life the process seems to stop short of the formation of fibrillas; the cell-contents retaining their original homogeneous or granular character. Muscles are divided into two great classes, voluntary and in- voluntary, to which may be added, as an intermediate and connect- ing link, the muscle of the vascular system, the heart. The voluntary, or system of animal life, is developed from the intermediate or vascular layer of the germinal membrane, and com- prehends the whole of the muscles of the limbs and trunk. The involuntary, or organic system, is also developed from the inter- mediate layer, and constitutes the thin muscular structure of the intestinal canal, urinary passages, and internal organs of genera- tion. Near the commencement of the alimentary canal at the middle of the oesophagus, and near its termination at the anus, the muscular coat is formed by a blending of the fibres of both classes. The heart is also developed from the middle, or vascular layer of the germinal membrane; and although involuntary in its action is composed of ultimate fibres, having the transverse strice cf the muscle of animal life. Striated muscle is also found around the venae cavae near the heart, in the upper half of the oesophagus, and in the round ligaments of the uterus. The muscles may be arranged in conformity with the general division of the body into—1. Those of the head and neck. 2. Those of the trunk. 3. Those of the upper extremity. 4. Those of the lower extremity. MUSCLES OF THE HEAD AND NECK. The muscles of the head and neck admit of subdivision into those of the head and face and those of the neck. Muscles of the Head and Face.—These muscles may be divided iuto groups corresponding with the natural regions of the head and face; the groups are eight in number, namely, 1. Cranial group. 2. Orbital group. 3. Ocular group. 4. Nasal group. MUSCLES OF THE HEAD AND FACE. 179 5. Superior labial group. 6. Inferior labial group. 7. Maxillary group. 8. Auricular group. The muscles of each of these groups may be thus arranged— 1. Cranial group. Occipito-frontalis. 2. Orbital group. Orbicularis palpebrarum, Corrugator supercilii, Tensor tarsi. 3. Ocular group. Levator palpebrae, Bectus superior, Bectus inferior, Bectus internus, Bectus externus, Obliquus superior, Obliquus inferior. 4. Nasal group. Pyramidalis nasi, Compressor naris, Dilatator naris, Depressor aim nasi. 5. Superior labial group. (Orbicularis oris), Levator labii superioris alaeque nasi, Levator labii superioris proprius, Levator anguli oris, Zygomaticus major, Zygomaticus minor. 6. Inferior labial group. (Orbicularis oris),* Depressor labii inferioris, Depressor anguli oris, Bisorius Santorini, Levator labii inferioris. 7. Maxillary group. Masseter, Temporalis, Buccinator, Pterygoideus extern us, Pterygoideus internus. 8. Auricular group. Attollens aurem, Attrahens aurem, Betrahens aurem. 1. Cranial Group.—Occipito-frontalis. Dissection.—The occipito-frontalis is to be dissected by making a longitudinal incision along the vertex of the head, from the tubercle on the occipital bone to the root of the nose ; and a second incision along the forehead and around the side of the head, to join the two extremities of the preceding. Dissect the integument and superficial fascia carefully outwards, beginning at the anterior angle of the flap, where the muscular fibres are thickest, and remove it altogether. This dissection requires care; for the muscle is very thin, and without attention would be raised with the integument. There is no deep fascia on the face or head, nor is it required; for here the muscles are closely applied against the bones, upon which they depend for support, whilst in the extremities the support is derived from the dense layer of fascia by which they are invested, and which forms for each muscle a distinct sheath. * The orbicularis oris, from encircling the mouth, belongs necessarily to both the superior and inferior labial region; it is therefore enclosed within parantheses. 180 OCCIPITO-FEONTALIS. The Occipitofrontalis (epicramus) is a broad musculo-aponeu- rotic layer, which covers the whole side of the vertex of the skull, from the occiput to the eyebrow. It arises by tendinous fibres from the outer two-thirds of the superior curved line of the occipital, and from the mastoid portion of the temporal bone. Its insertion takes place by means of the blending of the fibres of its anterior portion with those of the orbicularis palpebrarum, corrugator supercilii, levator labii superioris akeque nasi, and pyramidalis nasi. The muscle is fleshy in front over the frontal bone (frontalis) and behind over the occipital (occipitalis), the two portions being connected by a broad aponeurosis. The two muscles, together with their apo- neurosis, cover the whole ver- tex of the skull, hence their designation galea capitis; they are loosely adherent to the pericranium, but closely to the integument, particularly on the forehead. At the sides of the head the aponeurosis (galea aponeurotica) is attached to the root of the mastoid process and processus auditorius, and, be- coming thin over the temporal fascia, is connected with the zygoma, malar bone, and ex- ternal boundary of the orbit. Relations.—This muscle is in relation by its external sur- face with the frontal and supra- orbital vessels, supraorbital and facial nerve, temporal vessels and auriculo-temporal nerve, occipital vessels and , nerves, and integument, to which last it is closely adherent. Its under surface is attached Fig. 141.* * Muscles of the head and face. 1. Frontal portion of the occipito-fron- talis. 2. Its occipital portion. 3. Its aponeurosis. 4. Orbicularis palpebra- rum, which conceals the corrugator supercilii and tensor tarsi. 5. Pyramidalis nasi. 6. Compressor naris. 7. Orbicularis oris. 8. Levator labii superioris aheque nasi; the adjoining fasciculus between ciphers 8 and 9 is the labial portion of the muscle. 9. Levator labii superioris proprius ; the lower part of the levator anguli oris is seen between the muscles 10 and 11. 10. Zygoma- ticus minor. 11. Zygomaticus major. 12. Depressor labii inferioris. 13. De- pressor anguli oris. 14. Levator labii inferioris. 15. Superficial portion of the masseter. 16. Part of its deep portion. 17. Attrahens aurem. 18. Buc- cinator. 19. Attollens aurem. 20. Temporal fascia covering the temporal muscle. 21. Retrahens aurem. 22. Anterior belly of the digastricus; the tendon is seen passing through its aponeurotic pulley. 23. Stylo-hyoid muscle pierced by the posterior belly of the digastricus. 24. Mylo-hvoideus. 25. Upper part of the stemo-mastoid." 26. Upper part of the trapezius. The muscle between 25 and 26 is the splenius. MUSCLES OF THE FACE. 181 to the pericranium by a loose cellular tissue, which permits con- siderable movement. Nerve Supply.—Posterior or occipital portion by the posterior auricular; frontal portion by the temporal—both branches of the facial. Action.—To raise the eyebrows, thereby throwing the integument of the forehead into transverse wrinkles. Some persons have the power of moving the entire scalp on the pericranium by means of these muscles. 2. Orbital Group.— Orbicularis palpebrarum, Corrugator supercilii, Tensor tarsi. Dissection.—The dissection of the face is to be effected by con- tinuing the longitudinal incision of the vertex of the previous dis- section onwards to the tip of the nose, and thence downwards to the margin of the upper lip; then carry an incision along the margin of the lip to the augle of the mouth, and transversely across the face to the angle of the lower-jaw. Lastly, divide the integument in front of the external ear upwards to the transverse incision which was made for exposing the occipito-frontalis. Dissect the integu- ment and superficial fascia carefully from the whole of the region included by these incisions, and the present and two following groups of muscles will be brought into view. The Orbicularis palpebrarum; is a sphincter muscle, surround- ing the orbit and eyelids, and consists of two portions, external and internal. The external or orbital portion arises from a short tendon, tendo palpebrarum (tendo oculi), situated at the inner angle of the eye, from the nasal process of the superior maxillary and angular process of the frontal bone; it encircles the orbit, and is inserted into the inner border of the orbit and lower border of the tendo palpebrarum, some of its fibres being continuous with the upper segment. The internal portion (palpebralis) forms a curved plane of fibres on the eyelids, thinner and paler than the orbital portion; externally these fibres are attached to the external palpebral ligament and border of the orbit, some being continuous with the orbital portion ; internally they are attached to the borders of the lacus lachrymalis and tendo palpebrarum. The borders of the palpebralis nearest the edges of the lids are thicker than the rest, and termed ciliaris. The ciliaris is redder than the rest of the palpebralis, and continuous with the tensor tarsi; it is probably the active cause in the production of entropium. The tendo palpebrarum (tendo oculi), about two lines in length and one in breadth, is attached by one end to the nasal process of the superior maxillary bone, close to the edge of the orbit; the other end bifurcates to be inserted into the inner extremities of the tarsal cartilages; from its inner side is given off a process which spreads over the lachrymal sac, and is attached to the crest of the lachrymal bone; this is the reflected aponeurosis of the tendo palpebrarum, and serves to protect the lachrymal sac. 182 MUSCLES OF THE FACE. Relations.—By its superficial surface it is closely adherent to the integument, from which it is separated on the eyelids by a loose cellular tissue. By its deep surface it lies in contact, above, with the upper border of the orbit, corrugator supercilii muscle, frontal and supraorbital vessels, and supraorbital nerve; below, with the lachrymal sac, levator labii superioris aheque nasi, levator labii superioris proprius, zygomaticus major and minor muscles, and malar bone; externally, with the temporal fascia. On the eyelids it is in relation with the broad tarsal ligament and tarsal cartilages, and by its upper border is connected with the occipito-frontalis. Nerve Supply.—Temporal and malar branches of the facial. The Corrugator supercilii is a small, narrow, and pointed muscle, situated immediately above the orbit and beneath the tipper segment of the orbicularis palpebrarum. It arises from the inner extremity cf the superciliary ridge, and is inserted into the under surface of the orbicularis palpebrarum. Its connexion with the orbicularis commences near the supraorbital foramen and is con- tinued outwards to the external angular process. Relations.—By its superficial surface, with the pyramidalis nasi, occipito-frontalis and orbicularis palpebrarum; by its deep surface, with the supraorbital vessels and nerve. The Tensor tarsi (Horner’s muscle) is a thin plane of muscular fibres, about three lines in breadth and six in length. It is best dissected (after the dissection of the orbit has been completed) by separating the eyelids from the eye, and turning them over the nose without disturbing the tendo palpebrarum oculi; then dissect away the small fold of mucous membrane called plica semilunaris, and some loose cellular tissue under which the muscle is concealed. It arises from the orbital surface of the lachrymal bone, and passing across the lachrymal sac, divides into two slips, which are con- tinuous with the margin of the ciliaris along the edges of the lids; some few of its fibres being attached to the lachrymal canals as far as the puncta. According to some anatomists the tensor tarsi is a process of the orbicularis consisting of two small fasciculi which enclose the lachrymal canals, and then spread out on the apo- neurosis of the lachrymal sac to be inserted into the crest and orbital surface of the lachrymal bone. Nerve Supply.—Infraorbital branch of facial. Actions.—The palpebral portion of the orbicularis acts involun- tarily in closing the lids, and from the greater curve of the upper lid, upon that principally. The entire muscle constitutes a sphincter, drawing at the same time, by means of its osseous attachment, the integument and lids inwards towards the nose. The corrugatores superciliorum draw the eyebrows downwards and inwards, and produce the vertical wrinkles of the forehead. The tensor tarsi, or lachrymal muscle, is an auxiliary to the orbicularis, and draws the extremities of the lachrymal canals inwards, so as to place the puncta in the best position for receiving the tears. It serves also to keep the lids in relation with the surface of the eye. OCULAR GROUP. 183 3. Ocular Gjroup.— Levator palpebrae, Rectus superior, Rectus inferior, Rectus internus, Rectus externus, Obliquus superior, Obliquus inferior. Dissection.—To open the orbit (tlie calvarium and brain having been removed) the frontal bone must be sawn through at the inner extremity of the orbital ridge, the saw being directed to the supra- orbital notch ; and, externally, at its outer extremity. The roof of the orbit may then be comminuted with the hammer; a process easily accomplished, on account of the thinness of the orbital plate of the frontal bone and lesser wing of the sphenoid. The super- ciliary portion of the orbit may next be driven forwards by a smart blow, and the external angular process and external wall of the orbit outwards in the same manner; the broken fragments of the roof of the orbit should then be removed. By this means the peri- osteum will be exposed unbroken and undisturbed. Remove the periosteum from the whole of the upper surface of the exposed orbit, and examine the parts beneath. The Levator palpebRj® is a long, thin, and triangular muscle, situated in the upper part of the orbit on the middle line; it arises from the upper margin of the optic foramen, and from the fibrous sheath of the optic nerve ; and is inserted into the upper border of the superior tarsal cartilage. Relations.—By its upper surface with the fourth nerve, supra- orbital nerve and artery, periosteum of the orbit, and, in front, inner face of the broad tarsal ligament. By its under surface it rests on the superior rectus, globe of the eye, and conjunctiva; it receives its nerve and artery by this aspect. Nerve Supply.—Superior division of the third nerve. The Rectus superior (attollens) arises from the upper margin of the optic foramen, and from the fibrous sheath of the optic nerve ; and is inserted into the upper surface of the globe of the eye at a point somewhat more than three lines from the margin of the cornea. Relaiions.—By its upper surface with the levator palpebrse muscle; by the under surface with the optic nerve, ophthalmic artery and nasal nerve, from which it is separated by the adipose tissue of the orbit, and, in front, with the globe of the eye, the tendon of the superior oblique muscle being interposed. Nerve Supply.—Superior division of the third nerve. The Rectus inferior (depressor) arises from the inferior margin of the optic foramen by a tendon (ligament of Zinn) which is com- mon to it and the internal and external rectus, and from the fibrous sheath of the optic nerve; it is inserted into the inferior surface of the globe of the eye, a little more than two lines from the margin of the cornea. Relations.—By its upper surface with the optic nerve, inferior oblique branch of the third nerve, adipose tissue of the orbit, and under surface of the globe of the eye. By its under surface with 184 MUSCLES OF THE FACE. the periosteum of the floor of the orbit, and inferior oblique muscle. Nerve Supply.—Inferior division of the third nerve. The Rectus internus (adductor); the thickest and shortest of the straight muscles, arises from the common tendon, and from the fibrous sheath of the optic nerve; and is inserted into the inner surface of the globe of the eye at two hues from the margin of the cornea. Relations.—By its internal surface with the optic nerve, adipose tissue of the orbit and eyeball. By its outer surface with the periosteum of the orbit; by its upper border with the anterior and posterior ethmoidal ves- sels, nasal and infra-trochlear nerve. Nerve Supply.—Inferior di- vision of the third nerve. The Rectus externus (ab- ductor) the longest of the straight muscles, arises by two heads, one with the origin of the superior rectus, from the margin of the optic foramen, the other partly from the com- mon tendon, and partly from the lower margin of the sphenoidal fissui’e; the nasal, third, and sixth nerve passing between them. It is inserted into the outer surface of the globe of the eye, a little more than two lines from the margin of the cornea. Relations.—By its internal surface with the third, nasal, sixth, and optic nerve, ciliary ganglion and nerves, ophthalmic artery and vein, adipose tissue of the orbit, inferior oblique muscle, and eye- ball. By its external surface with the periosteum of the orbit and lachrymal gland; by the upper border with the lachrymal vessels and nerve. Nerve Supply.—The sixth nerve. The recti muscles present several characters in common; thus, they are thin, have each the form of an isosceles triangle, bear the same relation to the globe of the eye, and are inserted in a similar manner into the sclerotic, at about two lines from the circum- ference of the cornea. The points of difference relate to thickness and length; the internal rectus is the thickest and shortest, the external the longest, and the superior the most thin. The insertion of the four recti into the globe of the eye forms a tendinous expan- sion, which is continued as far as the margin of the cornea, and is termed tunica albuginea. Fig. 142.* * Muscles of tlie eyeball; the view is taken from the outer side of the right orbit. 1. Levator palpebra?. 2. Superior oblique. 3. Superior rectus. 4. Cut outer end of the external rectus. 5. The two heads of origin of the external rectus. 6. Optic nerve. 7. Internal rectus. 8. Inferior rectus. 9. Inferior oblique. OCULAR GROUP. 185 The Obliquus superior (troclilearis) is a fusiform muscle arising from the margin of the optic foramen, and from the fibrous sheath of the optic nerve ; it passes forward to the pulley at the internal angular process of the frontal bone; its tendon is then reflected outwards beneath the superior rectus to the outer part of the globe of the eye, where it is inserted into the sclerotic coat, at about midway between the margin of the cornea and the optic nerve. The trochlea or pulley of the superior oblique muscle is a fibro- cartilaginous ring attached to the depression beneath the internal angular process of the frontal bone. The ring is fiat, about a line in width, and provided with a synovial membrane, which is con- tinued, together with a fibrous sheath, for a short distance, upon the tendon. (Sometimes the ring is supported, or in part formed, by a process of bone. Relations— By its superior surface with the fourth nerve, supra- trochlear nerve, and periosteum of the orbit. By the inferior surface with the adipose tissue of the orbit, upper border of the internal rectus, and the vessels and nerves crossing that border. Nerve Supply.—The fourth nerve. The Obliques inferior, a thin and narrow muscle, arises from the inner margin of the superior maxillary bone, immediately external to the lachrymal groove, and passes beneath the inferior rectus, to be inserted into the outer and posterior part of the eye- ball, at about two lines from the entrance of the optic nerve. Relations.—By its superior surface with the inferior rectus muscle and eyeball; by the inferior surface with the periosteum of the floor of the orbit, and external rectus. Nerve Supply.—Inferior division of the third nerve. The muscles of the orbit are separated from the globe of the eye- ball and structures immediately surrounding the optic nerve, by a fascia, which is continuous with the broad tarsal ligament and tarsal cartilages. This fascia is termed tunica vaginalis oculi, or capsule of Tenon. It is pierced anteriorly, for the passage of the six orbital muscles, by six openings, through which the tendons of the muscles play as through pulleys. The use assigned to it is to protect the eyeball from the pressure of its muscles during their action; by its means, also, the recti muscles are enabled to give a rotatory movement to the eyeball; and in brutes antagonize the retractor muscle. Actions.—The levator palpebras raises the upper eyelid. The four recti, acting singly, pull the eyeball in the four directions : upwards, downwards, inwards, and outwards. Acting by pairs, they carry the eyeball in the diagonal of these directions, viz., upwards and inwards, upwards and outwards, downwards and in- wards, downwards and outwards. Acting all together, they directly retract the globe within the orbit. The superior oblique muscle, acting alone, rolls the globe inwards and forwards, and carries the pupil outwards and downwards to the lower and outer angle of the orbit. The inferior oblique acting alone, rolls the globe outwards and backwards, and carries the pupil outwards and upwards to the 186 MUSCLES OF THE FACE. upper and outer angle of the eye. Both muscles acting together draw the eyeball forward, and give the' pupil that slight degree of eversion which enables it to admit the largest field of vision. 4. Nasal Group.— Pyramidalis nasi, Compressor naris, Dilatator naris, Depressor alee nasi. The Pyramidalis nasi is a small pyramidal slip of muscular fibres sent downwards on the bridge of the nose by the occipito- frontalis. It is inserted into the ten- dinous expansion of the compressor naris. Relations.—By its upper surface with the integument; by its under surface with the periosteum of the frontal and nasal bone. Its outer border corre- sponds with the edge of the orbicularis palpebrarum; its inner border with its fellow, from which it is separated by a narrow cellular space. Nerve Supply.—Infraorbital branch of facial. The Compressor naris (transversus nasi) is a thin and triangular muscle; it arises by its apex from the canine fossa of the superior maxillary bone, and spreads out upon the side of the nose into a thin tendinous expansion, which is continuous across the ridge with the muscle of the opposite side. It is connected at its origin with a muscular fasciculus which is attached to the nasal process of the superior maxillary bone immediately below the origin of the levator labii superioris absque nasi. This muscular slip was termed by Albinus, musculus anomalus, from its attachment to bone by both ends ; and by Santorinus, musculus rhomboideus. Relations.—By its superficial surface with the levator labii superioris proprius, levator labii superioris alasque nasi, and integu- ment ; by its deep surface with the superior maxillary and nasal bone, and with the alar and lateral cartilage of the nose. Fig. 143.* * Muscles of the nose ; after Arnold. 1. Pyramidal is nasi. 2. Upper part of the levator labii superioris alasque nasi turned aside. 3. Compressor naris. 4. Musculus anomalus. 5. Levator proprius alas nasi anterior. 6. Levator proprius aloe nasi posterior. 7. Part of the depressor aim nasi. 8. Upper seg- ment of the orbicularis oris. 9. Naso-labialis. 10. Fasciculi accessorii of the orbicularis. 11. A small muscle termed by Arnold, compressor narium minor; it extends between the end of the nose and the alar cartilage. Its existence is doubtful. SUPERIOR LABIAL GROUP. 187 Nerve Supply.—Infraorbital branch of facial. The Dilatator naris is a thin and indistinct muscular apparatus expanded on the ala of the nostril, and consisting of an anterior and posterior slip. The anterior slip (levator proprius abe nasi anterior) arises from the upper border and surface of the alar carti- lage, and is inserted into the integument of the border of the nos- tril. The posterior slip (levator proprius alse nasi posterior) arises from the nasal process of the superior maxillary bone, and sesamoid cartilages, and is inserted into the integument of the border of the nostril, its posterior half. These muscles are difficult of dissection, from the close adhesion of the integument with the nasal cartilages. Nerve Supply.—Infraorbital branch of facial. The Depressor al.-e nasi (myrtiformis) is brought into view by drawing upwards the upper lip and raising the mucous membrane. It arises from the superior maxillary bone in front of the roots of the second incisor and. canine tooth (myrtiform fossa), and passes upwards and inwards to be inserted into the posterior part of the columna and ala nasi. It is closely connected with the deep sur- face of the orbicularis. Relations.—By its superficial surface with the mucous mem- brane of the mouth, orbicularis oris and levator labii superioris alteque nasi; by its deep surface with the superior maxillary bone. Nerve Supply.—Infraorbital branch of facial. Actions.—The pyramidalis nasi, as a point of attachment of the occipito-frontalis, assists that muscle in its action: it also draws down the inner angle of the eyebrow, and by its insertion fixes the aponeurosis of the compressores narium, and tends to elevate the nose. The compressores narium appear to act in expanding rather than compressing the nares; hence probably the collapsed state of the nares from paralysis of these muscles in the last moments of life, or in compression of the brain. The dilatator naris is a dilator of the nostril, and the depressor alse nasi draws downwards both the ala and columna of the nose, the depression of the latter being assisted by the naso-labialis. 5. Superior Labial Group.— Orbicularis oris, Levator labii superioris alseque nasi, Levator labii superioris proprius, Levator anguli oris, Zygomaticus major, Zygomaticus minor. The Orbicularis oris is a sphincter muscle, completely sur- rounding the mouth, and possessing consequently neither origin nor insertion. It is composed of two thick semicircular planes of fibres, which embrace the rima of the mouth, and interlace at their extre- mities, where they are continuous with the fibres of the buccinator and the other muscles connected with the angle of the mouth. The upper segment is attached by means of a small muscular fasciculus (naso-labialis) to the columna of the nose: and other fasciculi con- nected with both segments, and attached to the maxillary bones, are termed “ accessorii.” Several anatomists consider the orbicularis 188 MUSCLES OF THE FACE. as composed of two portions, internal or marginal, in immediate contact with, the lips, and thick; and external, broad and thin; the separation between the two being indicated by the coronary arteries. Relations.—By its superficial surface with the integument of the lips, with which it is closely connected. By its deep surface wTith the mucous membrane of the mouth, the labial glands and coronary arteries being interposed. By its circumference with the numerous muscles which move the lips, and by the inner border with the mucous membrane of the rima of the mouth. Nerve Supply.—Infraorbital and buccal branches of the facial. The Levator labii superioris al.eque nasi (pyramidalis) is a thin triangular muscle; it arises from the upper part of the nasal process of the superior maxillary bone; and, becoming broader as it descends, is inserted by two portions, one into the ala of the nose, the other into the orbicularis oris and upper lip. Relations.—By its superficial surface with the orbicularis palpe- brarum, facial artery, and integument. By its deep surface with the superior maxillary bone, musculus anomalus, compressor naris, dilatator naris, and alar cartilage. Nerve Supply.—Infraorbital branch of facial. The Levator labii superioris proprius (incisorius) is a thin quadrilateral muscle; it arises from the lower border of the orbit, immediately above the infraorbital foramen, and passing obliquely downwards and inwards, is inserted into the integument of the upper lip, its deep fibres being blended with those of the orbicularis. Relations.—By its superficial surface with the lower segment of the orbicularis palpebrarum, facial artery, and integument. By its deep surface with the compressor naris, levator anguli oris, orbicu- laris oris, and infraorbital artery and nerve. Nerve Supply.—Infraorbital branch of facial. The Levator anguli oris (caninus) arises from the canine fossa of the superior maxillary bone, and passes obliquely outwards to be inserted into the angle of the mouth ; its fibres being continued into the inferior segment of the orbicularis, and depressor anguli oris. Relations.—By its superficial surface with the levator labii supe- rioris proprius, branches of the infraorbital artery and nerve, and interiorly with the integument. By its deep surface with the supe- rior maxillary bone and buccinator muscle. Nerve Supply.—Infraorbital branch of facial. The Zygomatic muscles are two slender fasciculi of fibres which arise from the malar bone, and are inserted into the upper lip. The zygomaticus major descends to the angle of the mouth, and is continuous with the inferior segment of the orbicularis, depressor auguli oris, and risorius Santorini. The zygomaticus minor, lying in front of the major, becomes connected with the outer border of the levator labii superioris proprius, and is attached to the integu- ment of the upper lip. This muscle is often wanting. Relations.—The zygomaticus mayor is iu relation by its super- INFERIOR LABIAL GROUP. 189 ficial surface with the lower segment of the orbicularis palpebrarum above, and with the fat of the cheek and integument for the rest of its extent. By its deep surface with the malar bone, masseter, buccinator, and facial vessels. The zygomaticus minor being in front of the major, has no relation with the masseter; interiorly it rests on the levator anguli oris. Nerve Supply.—Infraorbital branch of facial. Actions.—The orbicularis oris produces the direct closure of the lips by means of its continuity, at the angles of the mouth, with the fibres of the buccinator. When acting singly in the forcible closure of the mouth, the integument is thrown into wrinkles, in conse- quence of its firm connexion with the surface of the muscle; its naso-labial fasciculus draws downwards the columna nasi. The levator labii superioris alteque nasi lifts the upper lip with the ala of the nose, and expands the opening of the nares. The levator labii superioris proprius is the proper elevator of the upper lip: acting singly, it draws the lip a little to one side. The levator anguli oris lifts the angle of the mouth and draws it imvards, while the zygomatici pull it upwards and outwards, as in laughing, and produce the dimple in the cheek. In the movement of laughter the zygomatici are assisted by the risorius Santorini. 6. Inferior Labial Group.— Depressor labii inferioris, Depressor anguli oris, Risorius Santorini, Levator labii inferioris. Dissection.—To dissect the inferior labial region, continue the vertical section from the middle of the lower lip to the point of the chin. Then carry an incision along the margin of the lower jaw to its angle. Dissect off the integument and superficial fascia from this surface, and the muscles of the inferior labial region will be exposed. The Depressor labii ineerioris (quadratus menti) arises from the oblique line by the side of the symphysis of the lower jaw, and passing upwards and inwards, is inserted into the orbicularis muscle and integument of the lower lip. Its inner fibres interlace with those of the opposite muscle, the outer fibres reach nearly to the angle of the mouth. Relations.—By its superficial surface with the platysma myoides, part of the depressor anguli oris, and the integument of the chin with which it is closely connected. By the deep surface with the levator labii inferioris, labial glands, mucous membrane of the lower lip, and mental nerve and artery. Nerve Supply.—Supra-maxillary of facial. The Depressor arguli oris (triangularis) is a triangular plane of muscle arising by a broad base from the external oblique ridge of the lower jaw, and inserted by its apex into the angle of the mouth, where it is continuous with the levator anguli oris, zygomaticus major, and upper segment of the orbicularis. Near its insertion it is joined by the following muscle. 190 MUSCLES OF THE FACE. Relations.—By its superficial surface with the integument; by its deep surface with the depressor labii inferioris, buccinator and branches of the mental nerve and artery. Nerve Supply.—Supra-maxillary of facial. The Risorius Santorini is a thin and triangular muscle, con- sisting of a few scattered fasciculi of fibres which arise from the fascia covering the masseter muscle, and converge to the angle of the mouth, where they become connected with the outer border of the depressor anguli oris, and continuous with the zygomaticus major. This muscle is generally regarded as a part of the platysma myoides. Nerve Supply.—Supra-maxillary of facial. The Levator labii inferioris (levator menti) is a short but strong muscle arising from the incisive fossa of the lower jaw, and inserted into the integument of the chin. It is in relation with the mucous membrane of the mouth, with its fellow, and with the de- pressor labii inferioris. Nerve Supply.—Supra-maxillary of facial. Actions.—The depressor labii inferioris draws the lower lip directly downwards, and at the same time a little outwards. The depressor anguli oris, from the radiated direction of its fibres, will pull the angle of the mouth either downwards and forwards, or downwards and backwards, and be expressive of grief; or acting with the levator anguli oris, zygomaticus major, and risorius San- torini, will draw the angle of the mouth upwards and backwards or directly backwards. The levator labii inferioris raises and pro- trudes the integument of the chin. 7. Maxillary Group.— Masseter, Temporal, Buccinator, Pterygoideus externus, Pterygoideua internus. Dissection.—The masseter lias been already exposed by the pre- ceding dissection. The Masseter (gaao-dogai, to chew) is a short, thick, and some- what quadrilateral muscle, composed of two planes of fibres, super- ficial and deep. The superficial layer arises by a strong aponeurosis from the malar process of the superior maxillary bone, lower border of the malar bone and zygoma; and passes downwards and back- wards to be inserted into the ramus and angle of the inferior maxilla. The deep layer arises also from the zygomatic arch, but extends farther back upon the zygoma, and passes downwards and forwards, to be inserted into the upper half of the ramus. This muscle is tendinous and muscular in structure; and covered in by a fascia (fascia parotideo-masseterica) which is connected with the zygomatic arch above, and encloses the parotid gland behind. Relations.—By its external surface with the zygomaticus major, risorius Santorini and platysma myoides. parotid gland and Stenon's duct, transverse facial artery, pes anseriuus, and integument. By MAXILLARY GROUP. 191 its internal surface with the temporal muscle, buccinator, from which it is separated by a mass of fat, and ramus of the lower jaw. By its posterior border with the parotid gland; by the anterior border with the facial artery and vein. Nerve Supply.—Masseteric branch of the inferior maxillary of the fifth cerebral nerve. Dissection.—Make an incision along the upper border of the zygoma, for the purpose of separating the temporal fascia from its attachment. Then saw through the zygomatic process of the malar bone, and through the root of the zygoma near the meatus audito- rius. Draw down the zygoma, and with it the origin of the mas- seter, and dissect the latter muscle away from the ramus and angle of the inferior maxilla. ISTow remove the temporal fascia from the rest of its attachment, and the whole of the temporal muscle will be brought into view. The Temporal is a broad and radiating muscle, occupying a con- siderable extent of the side of the head, and filling the temporal fossa. It is covered in by a dense fascia (temporal fascia), which is attached along the temporal ridge on the side of the skull, extend- ing from the external angular process of the frontal bone to the mastoid portion of the temporal; and inferiorly to the upper border of the zygoma. The muscle arises by tendinous fibres from the whole length of the temporal ridge, and by muscular fibres from the temporal fascia and entire surface of the temporal fossa. Its fibres converge to a strong and narrow tendon, which is inserted into the apex and internal surface of the coronoid process of the lower jaw. Relations.—By its external surface with the temporal fascia (which separates it from the attollens and attrahens aurem muscle, and temporal vessels and nerves) and with the zygoma and mas- seter. By its internal surface with the bones forming the temporal fossa, the external pterygoid muscle, part of the buccinator, and the internal maxillary artery with its deep temporal branches. Nerve Supply.—Temporal branches of the inferior maxillary of the fifth cerebral nerve. By sawing through the coronoid process near its base, and pull- ing it upwards, together with the temporal muscle, which may be dissected from the fossa, we obtain a view of the entire extent of the buccinator and external pterygoid muscle. The Buccinator (buccina, a trumpet; alveolo-labialis), the trumpeter’s muscle, arises from the alveolar process of the superior maxillary bone, the external oblique line of the inferior maxillary as tar forward as the second bicuspid tooth, and the pterygo-maxil- lary ligament. This ligament is the raphe of union between the buccinator and superior constrictor muscle, and is attached by one extremity to the hamular process of the internal pterygoid plate, and by the other to the extremity of the molar ridge. The fibres of the muscle converge towards the angle of the mouth, where some are continuous with the levator and depressor anguli oris, and the 192 MUSCLES OF THE FACE. rest cross eaclr other, the superior being continuous with the inferior segment of the orbicularis oris, the inferior with the superior seg- ment. The muscle is invested externally by a thin fascia (buccal) which extends backwards to the pharynx. Relations.—By its external surface, posteriorly, with a large and rounded mass of fat, which separates the muscle from the ramus of the lower jaw, temporalis, and masseter : anteriorly with the risorius Santorini, zygomatici, levator anguli oris, and depressor anguli oris. It is also in relation with a part of Stenon’s duct, (which pierces it opposite the second molar tooth of the upper jaw,) with the trans- verse facial artery, branches of the facial and buccal nerve, and facial artery and vein. By its internal surface with the buccal glands and mucous membrane of the mouth. Nerve Supply.—Infraorbital branch of facial. The Pterygoideus externus is a short and thick muscle, broader at its origin than at its insertion. It arises by two heads, one from the under surface of the great ala of the sphenoid and pterygoid ridge; the other from the outer surface of the external pterygoid plate, tuberosity of the palate bone and tuberosity of the superior maxillary. The fibres pass backwards to be inserted into the neck of the lower jaw and into the interarticular fibrocartilage. The in- ternal maxillary artery passes between the two heads of this muscle. Relations.-—By its external surface with the ramus of the lower jaw, temporal muscle, and internal maxillary artery; by its internal surface with the internal pterygoid muscle, internal lateral ligament of the jaw, arteria meningea media, and inferior maxillary nerve; by its upper border with the muscular branches of the inferior maxillary nerve; the internal maxillary ar- tery passes between its two heads, and its lower head is pierced by the buccal nerve. Nerve Supply.—Pterygoid branch of inferior maxillary of fifth cere- bral nerve. The external pterygoid muscle must now be removed, the ramus of the lower jaw sawn through its lower third, and the head of the bone dislocated from its socket and withdrawn, for the purpose of seeing the pterygoideus in- ternus. The Pterygoidetjs internets is a thick quadrangular muscle. It arises from the pterygoid fossa and descends obliquely backwards, to be inserted into the ramus and angle of the lower jaw : it re- Fig. 144.* * The two pterygoid muscles. The zygomatic arch and the greater part of the ramus of the lower jaw have been removed in order to bring these muscles into view. 1. The sphenoid origin of the external pterygoid. 2. Its pterygoid origin. 3. The internal pterygoid. AURICULAR GROUP. 193 sembles the masseter in appearance and direction, and was named by Winslow, internal masseter. Relations.—By its external surface with the external pterygoid, inferior maxillary nerve and branches, internal maxillary artery and branches, internal lateral ligament, and ramus of the lower jaw. By its internal surface with the tensor palati, superior constrictor and fascia of the pharynx; by its posterior border with the parotid gland. Nerve Supply.—Pterygoid branch of inferior maxillary of fifth cerebral. Actions.—The maxillary muscles are the active agents in masti- cation, and form an apparatus admirably fitted for that office. The buccinator circumscribes the cavity of the mouth, and with the aid of the tongue keeps the food under the immediate pressure of the teeth. By means of its connexion with the superior constrictor, it shortens the cavity of the pharynx from before backwards, and be- comes an auxiliary in deglutition. The temporal, the masseter, and the internal pterygoid are the bruising muscles, drawing the lower jaw against the upper with great force. The two latter, from the obliquity of their direction, assist the external pterygoid in grinding the food, by carrying the lower jaw forward upon the upper; the jaw being brought back again by the deep portion of the masseter and posterior fibres of the temporal. The whole of these muscles, acting in succession, produce a rotatory movement of the teeth upon each other, which, with the direct action of the lower jaw against the upper, effects the mastication of the food. 8. Auricular Group.*— Attollens aurem, Attrahens aurem, Betrahens aurem. Dissection.—The three small muscles of the ear may be exposed by removing a square of integument from around the auricula. This operation must be performed with care, otherwise the muscles, which are extremely thin, will be raised with the superficial fascia. They are best dissected by commencing with their tendons, and thence proceeding in the course of their radiating fibres. The Attollens aurem (superior auriculae), the largest of the three, is a thin triangular plane of muscular fibres, arising from the lateral portion of the galea aponeurotica and aponeurosis of the occipito-frontalis, at about the middle of the temporal ridge, and inserted into the convexity of the fossa triangularis of the pinna. It is in relation by its external surface with the integument, and by the internal with the galea aponeurotica and temporal fascia. It receives its nerve supply from the auriculo-temporal nerve, with some filaments from the facial nerve. The Attrahens aurem (anterior auriculae), also triangular, arises from the lateral portion of the aponeurosis of the occipito- frontalis above the zygoma, and is inserted into the spine of the helix. * See Fig. 304. 194 MUSCLES OF THE NECK. It is in relation by its external surface with the integument; and by the internal with the galea aponeurotica, temporal fascia, and temporal artery and veins. It receives its nerve supply from the aurieulo-temporal nerve, with filaments from the facial. The Retrahens attrem (posterior auriculae) arises by two (some- times three) muscular slips from the root of the mastoid process. They are inserted into the posterior surface of the concha. It is in relation by its external surface with the integument, and by its internal surface with the mastoid portion of the temporal bone. It is supplied by the posterior auricular branch of the facial nerve. Actions.—The actions of the auricular muscles are expressed in their names ; they have but little power in man, hut are important muscles in brutes. MUSCLES OF THE NECK. The muscles of the neck may he arranged into eight groups, cor- responding with the natural divisions of the region; they are, 1. Superficial group. 2. Depressors of the os hyoides and larynx. 3. Elevators of the os hyoides and larynx. 4. Lingual group. 5. Pharyngeal group. 6. Palatine group. 7. Prsevertebral group. 8. Laryngeal group. The muscles in each group are as follow:— 1. Superficial group. Platysma myoides, Sterno-cleido-mastoideus. 2. Depressors of the os hyoides and larynx. Sterno-hyoideus, Sterno-thyroideus, Thyro-hyoideus, Omo-hyoideus. 3. Elevators of the os hyoides and larynx. Digastricus, Stylo-hyoideus, Mylo-liyoideus, Genio-hyoideus, Genio-hyo-glossus. 4. Muscles of the tongue. Genio-hyo-glossus, Hyo-glossus, Ling\ialis, Styloglossus, 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 pliaryngeus. 7. Prcevertehral group. Rectus anticus major, Rectus anticus minor, Scalenus anticus, Scalenus medius, MUSCLES OF THE NECK. 195 Scalenus posticus, Longus colli. 8. Muscles of the larynx. C rico-tliyroideu s, Crico-arytaenoideus posticus, Crico-arytasnoideus lateralis, Thy ro - ary taenoideus, Arytsenoideus. Dissection.—The dissection of the neck should be commenced by- making an incision along the middle line of its fore part from the chin to the sternum, and bounding it superiorly and inferiorly by two transverse incisions; the superior being carried along the margin of the lower jaw, and across the mastoid process to the tubercle on the occipital bone, the inferior along the clavicle to the acromion process. The square flap of integument thus included should be turned back from the entire side of the neck, which brings into view the superficial fascia, and on the removal of a thin layer of superficial fascia the platysma myoides will be exposed. The Platysma myoides (n\arvs jaOs el8os, broad muscle-like lamella; latissimus colli; subcutaneus colli; thoraco-facialis) is a thin plane of muscular fibres, situated beneath the integument on the side of the neck; it arises from the fascia of the pectoralis major and deltoid muscle, and passes obliquely upwards and inwards to be inserted into the side of the chin, oblique line of the lower jaw, angle of the mouth, and cellular tissue of the face. The ante- rior fibres are continuous beneath the chin, with the muscle of the opposite side; the next interlace with the depressor anguli oris and depressor labii inferioris; the posterior fibres are disposed in a transverse direction across the lower part of the face, arising from the fascia of the parotid gland and masseter muscle, and inserted into the angle of the month (risorius Santorini). The entire muscle is analogous to the cutaneous muscle of brutes, the panniculus carnosus. Relations.—By its external surface with the integument, with which it is closely adherent below, but loosely above. By its internal surface, below the clavicle, with the pectoralis major and deltoid; in the neck with the trapezius, sterno-mastoid, external jugular vein and deep cervical fascia ; on the face, with the parotid gland, masseter, facial artery and vein, buccinator, depressor anguli oris, and depressor labii inferioris. Nerve Supply.—Its upper part by the facial, its lower by the superficial cervical. On raising the platysma throughout its whole extent, the sterno- mastoid is brought into view. The Stekno-cleido-mastoideus is the large oblique muscle of the neck, and is situated between two layers of the deep cervical fascia. It arises, as implied by its name, from the sternum and clavicle (kA«$iW), and passes obliquely upwards and backwards, to be inserted into the mastoid process of the temporal, and superior curved line of the occipital bone. The sternal portion arises by a rounded tendon, increases in breadth as it ascends, and spreads out to a considerable extent at its insertion. The clavicular portion is 196 MUSCLES OF THE NECK. broad and flesby, separate from the sternal portion below, but blended with the posterior surface of the latter as it ascends. The two portions of this muscle are sometimes described as sepa- rate muscles under the names of sterno-mastoideus (nutator capitis internus, vel anticus) and cleido-mastoideus (nutator capitis ex- ternus, vel posticus). A sesamoid bone is sometimes found in the sternal tendon ; this is regarded as the sternal rudiment of a cervical rib; and these osseous formations have been described by Breschet under the name of ossa suprasternalia, vel episternalia. Fig. 145.* Relations.—By its superficial surface with, the integument, platysma myoides, external jugular vein, superficial branches of the cervical plexus of nerves, and anterior layer of the deep cervical fascia. By its deep surface with the deep layer of the cervical fascia, sterno-clavicular articulation, sterno-hyoid, sterno-thyroid, * Muscles of the anterior aspect of the neck; on the right side of the figure the superficial muscles are seen, on the left the deep. 1. Posterior belly of digastricus. 2. Its anterior belly. Aponeurotic pulley, through which its tendon is seen passing, attached to the body of the os hyoides 3. 4. Stylo- hyoideus muscle, transfixed by the posterior belly of the digastricus. 5. Mylo- hyoideus. 6. Genio-hyoideus. 7. The tongue. 8. Hyo-glossus. 9. Stylo-glossus. 10. Stylo-pliaryngeus. 11. Sterno-mastoid. 12. Its sternal origin. 13. Its clavicular origin. 14, Sterno-hyoid. 15. Sterno-thyroid of the right side. 16. Thyro-hyoid. 17. Hyoid portion of the omo-hyoid. 18, 18. Its scapular portion; on the left side, the tendon of the muscle is seen to be bound down by a portion of the deep cervical fascia. 19. Clavicular portion of the trape- zius. 20. Scalenus anticus, of the right side. 21. Scalenus posticus; the scalenus medius is seen between the two. REGIONAL ANATOMY OF THE NECK. 197 omo-hyoid, scaleni, levator anguli scapulae, splenii, and posterior belly of the digastricus muscle; phrenic nerve, transversa colli and suprascapular artery; deep lymphatic glands, sheath of the common carotid and internal jugular vein, descendens noni nerve, external carotid artery with its posterior branches, and commence- ment of the internal carotid artery; cervical plexus of nerves, pneumogastric, spinal accessory, hypoglossal, sympathetic, and facial nerve, and parotid, gland. It is pierced on this aspect by the spinal accessory nerve. Nerve Supply.—Spinal accessory nerve. Actions.—The platysma produces a muscular traction on the integument of the neck, which prevents it from falling so flaccid in old persons as it would if the extension of the skin were the mere result of elasticity. It draws also on the angle of the mouth, and is one of the depressors of the lower jaw. The transverse fibres draw the angle of the mouth outwards. The sterno-mastoid muscles (nutatores capitis) are the great anterior muscles of con- nexion between the thorax and the head. Both muscles acting together bow the head directly forwards. The clavicular portions, acting more forcibly than the sternal, give stability and steadiness to the head in supporting weights. Either muscle acting singly would draw the head towards the shoulder of the same side, and carry the face towards the opposite side. Regional Anatomy of the Neck.—The region of the neck is divided into two great triangles by the sterno-mastoid muscle. The posterior triangle is bounded by the posterior border of the muscle, by the clavicle, and by the anterior edge of the trapezius. The anterior triangle is bounded by the anterior border of the sterno- mastoid, by the lower border of the inferior maxilla, and by the mesial line. The posterior triangle is subdivided into two, by the scapular belly of the omo-hyoid muscle. The posterior superior triangle is bounded by the posterior border of the sterno-mastoid, the anterior edge of the trapezius, and the posterior belly of the omo-hyoid. It contains the superficial descending branches of the cervical plexus, the spinal accessory nerve, the superficialis colli artery, and the cervical absorbents and glands. The posterior inferior or subclavian triangle is bounded by the clavicle, the posterior belly of the omo-hyoid, and the posterior border of the sterno-mastoid. A deeper subclavian space is bounded by the two former sides, and the third is the outer edge of the scalenus anticus. This triangle contains the third part of the subclavian artery, above and behind which are the trunks of the brachial plexus, below, and in front of it, almost overlapped by the clavicle the subclavian vein, in close proximity to which behind the clavicle is the transversalis humeri artery, both of which vessels, although not strictly in the triangle are apt to invade it as soon as the fascia is divided in the operation for ligature of the sub- clavian. 198 MUSCLES OF THE NECK. The anterior triangle has been divided into three. The inferior carotid, the supex-ior carotid and the submaxillary. The inferior carotid triangle is bounded by the mesial line, the anterior border of the sterno-mastoid, and the anterior belly of the omo-hyoid. The superior carotid triangle (the place of selection for ligature of the carotid arteries) is bounded by the anterior border of the sterno-mastoid, the anterior belly of the omo-hyoid, and the posterior belly of the digastricus. The submaxillary triangle is bounded by the two bellies of the digastricus and the base of the lower jaw. Second Group.—Depressors of the Os Ilyoides and Larynx. Sterno-hyoideus, Sterno-thyroideus, Thyro-hyoideus, Omo-hyoideus. Dissection.—These muscles are brought into view by removing the deep fascia from off the front of the neck between the two sterno-mastoid muscles. The omo-hyoid to be seen in its whole extent requires that the sterno-mastoid muscle be divided from its origin and turned aside. The Sterno-hyoideus is a narrow, riband-like muscle, arising from the posterior surface of the first bone of the sternum and from the posterior sterno-clavicular ligament (sometimes from the inner extremity of the clavicle, and sometimes from the cartilage of the first rib). It is inserted into the lower border of the os hyoides. The sterno-hyoidei are separated by a considerable interval at the root of the neck, approach each other as they ascend, and are again separated on the thyroid cartilage; they are frequently traversed below by a tendinous intersection. Relations.—By its external surface with the deep cervical fascia, platysma myoides and sterno-mastoid muscle; by its internal sur- face with the sterno-thyroid and thyro-hyoid muscle, and superior thyroid artery. Nerve Supply.—Descendens noni, a branch of the hypoglossal. The Sterno-thyroideus, broader than the preceding beneath which it lies, arises from the posterior surface of the upper bone of the sternum, and from the cartilage of the first rib ; it is inserted into the oblique line on the great ala of the thyroid cartilage. The inner borders lie in contact along the middle line, and the muscles are marked by a tendinous intersection at their lower part. Some of the fibres of this muscle are continued directly into the thyro- hyoideus without intervening attachment; others are continuous with the inferior constrictor. Relations.—By its external surface with the sterno-hyoid, omo- hyoid, and sterno-mastoid muscle; by its internal surface, with the trachea, inferior-thyroid veins, thyroid gland, lower part of the larynx, sheath of the common carotid artery, and internal jugular vein, subclavian vein, vena innominata, and, on the right side, arteria innominata. The middle thyroid vein lies along its inner border, ELEVATORS OF THE OS HYOIDES. 199 Nerve Supply.—Descendens noni. The Tiiyro-hyoideus is the continuation upwards of the sterno- thyroid muscle. It arises from the oblique line on the thyroid car- tilage, and is inserted into the lower border of the body, and great cornu of the os hyoides for one-half its length. Relations.—By its external surface with the sterno-hyoid and omo-hyoid muscle; by its internal surface with the great ala of the thyroid cartilage, thyro-hyoidean membrane, and superior laryngeal artery and nerve. Nerve Supply.—A special branch of the hypoglossal. The Omo-hyoideus (Joyos, shoulder) is a double-bellied muscle passing obliquely across the neck from the scapula to the os hyoides ; it forms an obtuse angle behind the sterno-mastoid, and is retained in that position by a process of the deep cervical fascia which forms a sheath for its tendon and holds it in connexion with the sternum and first rib. It arises from the upper border of the scapula and transverse ligament of the suprascapular notch, and is inserted into the os hyoides at the junction of the body and great cornu. Relations.—By its superficial surface with the trapezius, sub- clavius, clavicle, deep cervical fascia, platysma myoides, sterno- mastoideus, and integument. By its deep surface with the brachial plexus, scaleni muscles, phrenic nerve, sheath of the common carotid artery and jugular vein, descendens noni nerve, sterno- thyroid and thyro-hyoid muscle, and the sterno-hyoid at its insertion. Nerve Supply.—Descendens noni. Actions.—The four muscles of this group are depressors of the os hyoides and larynx. The three former drawing these parts downwards in the middle line, and the two omo-hyoidei regulating their traction to the one or other side of the neck, according to the position of the head. The omo-hyoid muscles, by means of their connexion with the cervical fascia, are rendered tensors of that portion of the deep fascia which covers the lower part of the neck, between the two sterno-mastoid muscles. The thyro-hyoideus, by approximating the hyoid bone to the thyroid cartilage, relaxes the hyo-epiglottic ligament, and permits the epiglottis to fall down over the aperture of the larynx during deglutition. Third Group.—Elevators of the Os Hyoides. Digastricus, Stylo-hyoideus, Mylo-hyoideus, G-enio-hyoideus, Genio-hyo-glossus. Dissection.—These are best dissected by placing a high block beneath the neck, and throwing the head backwards. The integu- ment has been already dissected away, and the removal of some cellular tissue and fat brings them clearly into view. The Digasthicus (8is, twice, yaa-rrjp, belly, biventer) is a small muscle situated immediately beneath the side of the body of the 200 MUSCLES OF THE NECK. lower jaw ; fleshy at each extremity, and tendinous in the middle. It arises from the digastric fossa and anterior border of the mastoid process of the temporal bone; pierces by its posterior belly the stylo-hyoideus muscle, and is inserted into a depression on the inner side of the lower jaw, close to the symphysis. The middle tendon is held in connexion with the body of the os hyoides by an aponeurotic loop, through which it plays as through a pulley ; the loop being lubricated by a synovial membrane. A thin layer of aponeurosis is given off from the tendon of the digastricus at each side, which is connected with the body of the os hyoides, and forms a strong plane of fascia between the anterior portions of the two muscles. This fascia, the supra-hyoidean, is continuous with the deep cervical fascia. Relations.—By its superficial surface with the platysma myoides, sterno-mastoid, anterior fasciculus of the stylo-hyoid muscle, parotid gland, and submaxillary gland. By its deep surface with the styloid muscles, hyo-glossus, mylo-hyoideus, external carotid artery, lingual and facial artery, internal carotid artery, jugular vein, and hypoglossal nerve. Nerve Supply.—The anterior belly of the digastric muscle is sup- plied by the mylo-hyoid nerve, a branch of the inferior maxillary ; the posterior belly by a branch of the facial. The Stylo-hyoideus is a small and slender muscle situated in immediate relation with the posterior belly of the digastricus, by which it is pierced. It arises from the middle of the styloid process, its outer side, and is inserted in the body of the os hyoides near the middle line. Relations.—By its superficial surface with the posterior belly of the digastricus, parotid gland and submaxillary gland; its deep relations are similar to those of the posterior belly of the digas- tricus. Nerve Supply.—A branch of the facial. The digastricus and stylo-hyoideus must be removed from their connexion with the lower jaw and os hyoides, and turned aside in order to see the next muscle. The Mylo-hyoideus {pvkt), mola, i.e., attached to the molar ridge of the lower jaw) is a broad and triangular plane of muscular fibres, forming, with its fellow of the opposite side, the inferior wall or floor of the mouth. It arises fleshy from the molar ridge of the lower jaw as far back as the last molar tooth, and proceeds inwards and backwards to the middle line, where its fibres are con- tinuous with those of the opposite side, the posterior fibres being inserted into the lower border of the body of the os hyoides. At the middle line the union is tendinous on the upper surface in front, on the lower behind, the rest being fleshy. Relations.—By its superficial or inferior surface, with the pla- tysma myoides, digastricus, supra-hyoidean fascia, submaxillary gland, submental artery and mylo-hyoidean nerve and artery. By its deep or superior surface with the genio-hyoideus, genio-hyo- ELEVATORS OF THE OS HYOIDES. 201 glossus, hyo-glossus, stylo-glossus, gustatory nerve, hypoglossal nerve, Wharton’s duct, sublingual gland, and mucous membrane of the floor of the mouth. Nerve Supply.—The mylo-hyoid nerve, a branch of the inferior dental. After the mylo-hyoideus has been examined, it should be cut away from its origin and insertion, and completely removed. The view of the next muscles would also be improved by dividing the lower jaw a little to the side of the symphysis, and drawing it out- wards ; or removing it altogether if the ramus have been already cut across in dissecting the internal pterygoid muscle. The tongue may then be drawn out of the mouth by means of a hook. The Genio-hyoideus (yevuov, the chin) arises from a small tubercle on the inner side of the symphysis of the lower jaw, and is inserted into the body of the os hyoides. It is a short and slender muscle, closely con- nected with its fellow and with the border of the following. Relations.—By its super- ficial or inferior surface with the mylo-hyoideus; by the deep or superior surface with the lower border of the genio- hyo-glossus. Nerve Supply.—The hypo- glossal nerve. The Genio - hyo - GLOSSUS (yXaxraa, the tongue) is a tri- angular muscle, narrow and pointed at its origin from the lower jaw, broad and fan- shaped at its attachment to the tongue. It arises from a tubercle above that of the genio-hyoideus, and spreads out to be inserted into the whole length of the tongue, from base to apex, and into the os hyoides. Relations.—By its inner surface with its fellow of the opposite side. By its outer surface with the mylo-hyoideus, hyo-glossus, Fig. 146 * * Styloid muscles and muscles of the tongue. 1. Portion of the temporal bone of the left side, with the styloid and mastoid process, and meatus audi- torius extemus. 2, 2. The right side of the lower jaw, divided at its sym- physis ; the left side having been removed. 3. Tongue. 4. Genio-hyoideus. 5. Genio-hyo-glossus. 6. Hyo-glossus; its basio-glossus portion. 7. Its cerato-glossus portion. 8. Anterior fibres of the lingualis issuing from between the hyo-glossus and genio-hyo-glossus. 9. Stylo-glossus, with part of the stylo-maxillary ligament. 10. Stylo-hyoideus. 11. Stylo-pharyn- 202 MUSCLES OF THE NECK. stylo-glossus, lingualis, sublingual gland, lingual artery, and hypo- glossal nerve. By its upper border with mucous membrane of the floor of the mouth, in the situation of the frrnnum linguae; by its lower border with the genio-hyoideus. Nerve Supply.—The hypoglossal nerve. Actions.—The whole of this group of muscles acts on the os hyoides when the lower jaw is closed, and on the lower jaw when the os hyoides is drawn downwards and fixed by the depressors of the os hyoides and larynx. The genio-hyo-glossus, is moreover, a muscle of the tongue ; its action upon that organ will be considered with the next group. Genio-hyo-glossus, Hyo-glossus, Lingualis, Fourth Group.—Muscles of the Tongue. Stylo-glossus, Palato-glossus. These are already exposed by the preparation we have just made; there remains, therefore, only to dissect and examine them. The Genio-hyo-glossus, the first of these muscles, has been de- scribed with the last group. The Hyo-glossus is a square-shaped plane of muscle, arising from the whole length of the great cornu and from the body of the os hyoides; and inserted between the stylo-glossus and lingualis into the side of the tongue. The direction of the fibres of that portion of the muscle which arises from the body is obliquely backwards; that from the great cornu obliquely forwards; hence they are de- scribed by Albums as two muscles, under the names of basio-glossus and cerato-glossus, to which he added a third fasciculus, arising from the lesser cornu, and spreading along the side of the tongue, the chondro-glossus. The basio-glossus slightly overlaps the upper part of the cerato-glossus, and is separated from it by the trans- verse portion of the stylo-glossus. Relations.—By its external surface with the digastricus stylo- hyoideus, stylo-glossus, mylo-hyoideus, gustatory nerve, hypo- glossal nerve, Wharton’s duct, and sublingual gland. By its in- ternal surface with the middle constrictor of the pharynx, lingualis, genio-hyo-glossus, lingual artery, and glosso-pharygeal nei’ve. Nerve Supply.—The hypoglossal nerve. The Lingualis.—The fibres of this muscle (lingualis longitudi- nalis inferior) may be seen towards the apex of the tongue, issuing from the interval between the hyo-glossus and genio-hyo-glossus ; and is best examined by removing the preceding muscle. It consists of a small fasciculus of fibres running longitudinally from the geus. 12. Os hyoides. 13. Thyro-hyoidean membrane. 14. Thyroid cartilage. 15. Thyro-hyoideus muscle arising from the oblique line of the thyroid carti- lage. 16. Cricoid cartilage. 17. Crico-thyroidean membrane, through wh.ch the operation of laryngotomy is performed. 18. Trachea. 19. Commence- ment of the oesophagus. MUSCLES OF THE TONGUE. 203 base, where it is attached to the os hyoides, to the apex of the tongue. By the outer border its fibres reach the plane of longitu- dinal fasciculi of the stylo-glossus and lingualis superficialis; and by its under surface, it is in relation with the ranine artery. The other muscles entering into the structure of the tongue, are the lingualis longitudinalis superior vel superficialis; and the lin- gualis transversus. The lingualis superior forms a thin plane on the upper surface of the organ, lying immediately beneath the mucous membrane. This layer is thicker in front than behind, and is covered posteriorly by a thin stratum of transverse fibres derived from the hyo-glossus. The lingualis transversus constitutes the chief bulk of the tongue; it lies between the lingualis superior and inferior, its fibres being attached at the middle line to the fibro- cartilaginous septum of the tongue, and laterally to the mucous membrane; some of its fibres are continuous with those of the stylo-glossus and hyo-glossus, and others are connected with the lesser cornua of the os hyoides. Nerve Supply.—The several layers of muscular fibre which con- stitute the lingualis muscle are supplied by the hypoglossal nerve. The Stylo-glossus arises from the apex of the styloid process and from the stylo-maxillary ligament; it divides on the side of the tongue into two parts, one transverse, which passes transversely inwards between the two portions of the hyo-glossus, and is lost among the transverse fibres of the substance of the tongue—the other longitudinal, which spreads out upou the side of the tongue, and is prolonged forwards with the lingualis as far as its tip. Relations.—By its external surface with the internal pterygoid muscle, gustatory nerve, parotid gland, sublingual gland, and mucous membrane of the floor of the mouth. By its internal sur- face with the tonsil, superior constrictor of the pharynx, and hyo- glossus. Nerve Supply.—The hypoglossal nerve. The Palato-glossus passes between the soft palate and the side of the base of the tongue, forming a prominence of the mucous membrane, which is called the anterior pillar of the soft palate. Its fibres are spread out superiorly among the muscular fibres of the palato-pharyngeus, and interiorly among the fibres of the stylo- glossus upon the side of the tongue. This muscle with its fellow constitutes the constrictor istlvmi faucium. Nerve Supply.—This muscle is supplied by branches from Meckel’s ganglion and the pharyngeal plexus. Actions.—The genio-hyo-glossus muscle effects several movements of the tongue. When the tongue is steadied and pointed by the other muscles, the posterior fibres of the genio-hyo-glossus would dart it from the mouth, while its anterior fibres would restore it to its former position. The whole length of the muscle acting on the tongue, would render it concave along the middle line, and form a channel for the current of fluid towards the pharynx, as in sucking. The apex of the tongue is directed to the roof of the mouth, and 204 MUSCLES OF THE NECK. rendered convex from before backwards by the linguales. The hyo- glossi, by drawing down the sides of the tongue, render it convex along the middle line. It is drawn upwards at its base by the palato-glossi, and backwards or to either side by the stylo-glossi. Thus the whole of the complicated movements of the tongue may be explained, by reasoning on the direction of the fibres of the muscles, and their probable actions. The palato-glossi muscles, assisted by the uvula, have the power of closing the fauces completely, an action which takes place in deglutition. Fifth Group.—Muscles of the Pharynx. Constrictor inferior, Constrictor medius, Constrictor superior, Stylo-pharyngeus, Palato-pharyngeus. Dissection.—To dissect the pharynx, the trachea and oesophagus are to be cut through at the lower part of the neck, and drawn upwards by dividing the loose cellular tissue which connects the back of the pharynx with the vertebral column. The saw is then to be applied behind the styloid processes, and the base of the skull sawn through. The vessels and loose structures should be removed from the preparation, and the pharynx stuffed with tow or wool for the purpose of distending it, and rendering the muscles more easy of dissection. The pharynx is invested by a proper pharyngeal fascia. The constrictors of the pharynx are web-like sheets of muscle with fibres differently disposed, which form a muscular bag attached to the base of the skull. This bag communicates in front with the mouth. Each of the constrictors may be described as having one posterior attachment and three lateral. The superior is attached to the tendinous raphe which hangs from the pharyngeal tubercle of the basilar process of the occipital bone; its lateral attachments are the internal pterygoid plate—the pterygo-maxillary ligament, and the mylo-hyoid ridge of the lower jaw. The middle is in like manner attached to the tendinous raph(i and its lateral attachments are the greater and lesser cornua of the hyoid bone and the stylo-hyoid ligament. The inferior is attached to the tendinous raphe, its lateral attachments are the thyroid and cricoid cartilages and the upper ring of the trachea. Their more particular description is as follows:— The Constrictor inferior, the thickest of the three constrictor muscles, arises from the upper ring of the trachea, the cricoid car- tilage, and the oblique line of the thyroid. Its fibres spread out, and are inserted into the middle line of the pharynx, the inferior fibres being almost horizontal, the superior oblique and overlapping the middle constrictor. Relations.—By its external surface with the vertebral column, longus colli, sheath of the common carotid artery, sterno-thyroid muscle, thyroid gland, and some lymphatic glands. By its internal surface with the middle constrictor, stylo-pharyngeus, palato-pha- MUSCLES OF THE PHARYNX. 205 ryngeus and mucous membrane of the pharynx. By its lower border, near the cricoid cartilage, it is in relation with the recurrent nerve; and by the upper border with the superior laryngeal nerve. The fibres of origin of this muscle are blended with those of the sterno-thyroid, thyro-hyoid, and crico-thyroid, and it frequently forms a tendinous arch across the latter; interiorly it is blended with the circular fibres of the oesophagus. The muscle must be removed before the next can be examined. The Constrictor medius arises from the great cornu of the os hyoides, from the lesser cornu, and from the stylo-hyoid liga- ment. It radiates, from its origin, and spreads out upon the side of the pharynx, the lower fibres descending and being overlapped by the constrictor inferior; the upper fibres ascending, so as to cover in the constrictor superior. It is inserted into the raphe of the pharynx, and by a fibrous aponeurosis into the basilar process of the occipital bone. Relations.—By its external surface with the vertebral column, longus colli, rectus anticus major, carotid vessels, inferior constrictor, hyo-glossus, lingual artery, pharyngeal plexus of nerves, and some lymphatic glands. By its internal surface, with the superior con- strictor, stylo-pharyngeus, palato-pharyngeus, and mucous mem- brane of the pharynx. The upper portion of this muscle must be turned down, to bring the whole of the superior constrictor into view; in so doing, the stylo-pharyngeus muscle will be seen passing behind its upper border. The Constrictor superior is a thin and quadrilateral plane of muscular fibres arising from the side of the tongue, the extremity of the molar ridge of the lower jaw, the pterygo-maxillary ligament, and lower third of the internal pterygoid plate; and inserted into Fig. 147* * Side view of the muscles of the pharynx. 1. Trachea. 2. Cricoid carti- lage. 3. Crico-thyroid membrane. 4. Thyroid cartilage. 5. Thyro-hyoidean membrane. 6. Os hyoides. 7. Stylo-hyoidean ligament. 8. (Esophagus. 9. In- ferior constrictor. 10. Middle constrictor. 11. Superior constrictor. 12. Stylo- pharyngeus, passing down between the superior and middle constrictor. 13. Upper concave border of superior constrictor; at this point the muscular fibres of the pharynx are deficient. 14. Pterygo-maxillary ligament. 15. Buc- cinator. 16. Orbicularis oris. 17. Mylo-hyoideus. 206 MUSCLES OF THE NECK. the raplie of the pharynx and basilar process of the occipital bone. Its superior fibres are arched, leaving a concave interspace between its upper border and the basilar process; some of its lower fibres are continuous with those of the genio-hyo-glossus on the side of the tongue, and it is overlapped interiorly by the middle constrictor. Between the side of the pharynx and the ramus of the lower jaw is a triangular interval, the maxillo-pharyngeal space, which is bounded at the inner side by the superior constrictor muscle; at the outer side by the internal pterygoid muscle; and behind by the rectus anticus major and vertebral column. In this space are situated the internal carotid artery, internal jugular vein, glosso- pharyngeal, pneumogastric, spinal accessory, and hypoglossal nerve. Relations.—By its external surface with the vertebral column and muscles of the latter, behind; with the vessels and nerves con- tained in the maxillo-pharyngeal space laterally, and with the middle constrictor, stylo-pharyngeus, and tensor palati. By its internal surface with the levator palati, palato-pharyngeus, tonsil, and mucous membrane of the pharynx. Nerve Supply.—The constrictor muscles of the pharynx are supplied by a plexus of nerves derived from the superior laryngeal and pharyngeal branches of the pneumogastric, the glosso-pharyn- geal, and cervical plexus, mixed with some fibres from the sym pathetic. The Stylo-phakyngeus (levator sen dilatator pharyngis) is a long and slender muscle arising from the inner side of the base of the styloid process; it descends between the superior and middle con- strictor muscle, and spreads out beneath the mucous membrane of the pharynx; it is inserted partly into the posterior border of the thyroid cartilage and partly into the internal face of the inferior constrictor. Relations.—By its external surface with the stylo-glossns muscle, external carotid artery, parotid gland, and middle constrictor. By its internal surface with the internal carotid artery, internal jugular vein, superior constrictor, palato-pharyngeus, and mucous mem- brane. Along its lower border is seen the glosso-pharyngeal nerve, which crosses it opposite the root of the tongue, to pass between the superior and middle constrictor and behind the hyo-glossus. Nerve Supply.—This muscle is supplied by the glosso-pharyngeal nerve. Associated in function with the preceding is a small muscle, not always present, the salpingo*-pharyngeus (levator pharyngeus in- ternus), which arises from the lower border of the Eustachian tube near its aperture, and passes down upon the inner surface of the side of the pharynx, where it becomes united with the palato- pharyngeus. The palato-pharyngeus is described with the muscles of the soft * <7dA.7rt.yf, a tube. MUSCLES OF THE SOFT PALATE. 207 palate. It arises from the soft palate, and is inserted into the inner surface of the pharynx, and posterior border of the thyroid cartilage. Actions.—The three constrictor muscles are important agents in deglutition; they contract upon the morsel of food as soon as it is received by the pharynx, and convey it downwards into the oeso- phagus. The stylo-pharyngei draw the pharynx upwards, and widen it laterally. The palato-pharyngei also draw it upwards, and with the aid of the uvula close the opening of the fauces. The salpingo-pharyngei are elevators of the upper part of the pharynx. Sixth Group.—Muscles of the soft Palate. Levator palati, Tensor palati, Azygos uvulas, Palato-glossus, Palato-pharyngeus. Dissection.—To examine these muscles, the pharynx must be opened from behind, and the mucous membrane carefully removed from off the posterior surface of the soft palate. The Levator palati, a moderately thick muscle, arises from the extremity of the petrous bone and from the posterior and inferior aspect of the Eustachian tube, and passing down by the side of the posterior nares spreads out between the fasciculi of origin of the palato-pharyngeus; it is inserted into the middle line, where it is continuous with the muscle of the opposite side, and is overlaid by the azygos uvulae. Relations.—Externally with the tensor palati and superior con- strictor muscle ; internally and posteriorly with the mucous mem- brane of the pharynx and soft palate; interiorly it passes between the two fasciculi of origin of the palato-pharyngeus to reach its insertion. Nerve Supply.—Branches from Meckel’s and Wharton’s ganglia. This muscle must be turned down from its origin on one side, and removed, and the superior constrictor dissected away from its ptery- goid origin, to bring the next muscle into view. The Tensor palati (circumflexus) is a slender and flattened muscle; it arises from the scaphoid fossa at the base of the internal pterygoid plate, from the spinous process of the sphenoid bone, and from the anterior aspect of the Eustachian tube. It lies between the internal pterygoid muscle and internal pterygoid plate, and winding around the hamular process of the latter, expands into a tendinous aponeurosis, which is inserted into the transverse ridge on the horizontal portion of the palate bone, and at the middle line is continuous with the aponeurosis of the opposite muscle. Relations.—By its external surface with the internal pterygoid muscle; by its internal surface with the levator palati, internal pterygoid plate, and superior constrictor. In the soft palate, its tendinous expansion is placed in front of the other muscles, and in contact with the mucous membrane. 208 MUSCLES OF THE NECK. Nerve Supply.—From the otic ganglion. The Azygos uvulae is a pair of small muscles situated along the mid line of the soft palate. They arise from the spine of the palate bone, and are inserted into the uvula. By their anterior surface Fig. 148.* they are in relation with the levatores palati, palato-glossi and an- terior fasciculus of the palato-pharyngei; posteriorly they have the thin posterior fasciculus of the palato-pharyngei and the mucous membrane. Nerve Supply-—Probably from Meckel’s and Wharton’s ganglia. The two next muscles are brought into view by raising the mucous membrane from off the pillars of the soft palate at each side. The Palato-glosstjs (constrictor istlimi fancium) is a small fas- ciculus of fibres, which arises in the soft palate as a radiated ex- pansion continuous with its fellow of the opposite side; and descends to be inserted into the side of the tongue. It is the pro- minence of this small muscle, covered by mucous membrane, that * Muscles of the palate (drawn by J. T. Gray). 1. Septum narium. 2. Eustachian tube. 3. Pterygoideus extemus. 4. Pterygoideus internus. 5. Levator palati mollis. 6. Circumflexus palati. 7. Superior constrictor of pharynx. 8. Azygos uvulae. 9. Palato-pharyngeus. 10. Stylo-pharyngeus. 11. Middle constrictor of pharynx. 12. Palato-pharyngeus (cut). 13. Inferior constrictor of pharynx. 14. (Esophagus. P1EEVERTEBEAL MUSCLES. 209 constitutes the anterior pillar of the soft palate. It has been named constrictor isthmi faucium, from a function it performs in common with the palato-pharyngeus—viz., constricting the opening of the fauces. The Palato-pharyngeus (constrictor isthmi faucium posterior) forms the posterior pillar of the fauces ; it arises by two fasciculi from the raphe of the soft palate, where its fibres are continuous with those of the muscle of the opposite side; and is inserted into the inner surface of the pharynx and posterior border of the thyroid cartilage. This muscle is broad above where it forms the whole thickness of the lower half of the soft palate, narrow in the posterior pillar, and again broad and thin in the pharynx where it spreads out previously to its insertion. The levator palati passes to its insertion between the two fasciculi of origin of this muscle. Relations.—-In the soft palate it is in relation with the mucous membrane both by its anterior and posterior surface; above, with the levator palati, and beloiv with the mucous glands situated along the margin of the arch of the palate. In the posterior pillar, it is surrounded for two-thirds of its extent by mucous membrane. In the pharynx, it is in relation by its outer surface with the superior and middle constrictor muscle, by its inner surface with the mucous membrane. Nerve Supply.—The palato-glossus and palato-pharyngeus are supplied from Meckel’s ganglion and the pharyngeal plexus. Actions.—The azygos uvulae shortens the uvula. The levator palati raises the soft palate, while the tensor spreads it out laterally so as to form a septum between the pharynx and posterior nares. Taking its fixed point from below, the tensor palati will dilate the Eustachian tube. The levator palati, and probably the tensor, by dilating the Eustachian tube during deglutition, permits the air to pass up into the tympanum ; and this is the principle of Pollitzer’s method of opening these tubes in Eustachian deafness. The palato- glossus and palato-pharyngeus constrict the opening of the fauces, and drawing down the soft palate, serve to press the mass of food from the dorsum of the tongue into the pharynx. Rectus anticus major, Rectus anticus minor, Scalenus anticus, Seventh Group.—Prcevertebral Muscles. Scalenus medius, Scalenus posticus, Lougus colli. Dissection.—These muscles have already been exposed by the removal of the pharynx from the anterior aspect of the vertebral column ; all that is further needed is the removal of the fascia by which they are invested. The Rectus anticus major (trachelo-suboccipitalis), broad and thick above, narrow and pointed below, arises from the anterior tubercles of the transverse processes of the third, fourth, filth, and sixth cervical vertebrae ; and is inserted into the basilar process of the occipital bone. 210 MUSCLES OF THE NECK. Relations.—By its anterior surface with the pharynx, internal carotid artery, internal jngular vein, superior cervical ganglion and trunk of the sympathetic nerve, pneumogastric, and spinal acces- sory nerve. By its posterior surface with the rectus anticus minor, and superior cervical vertebras; internally with the longus colli, and externally with the scaleni. Nerve Supply.—Anterior branch of the first cervical nerve. The Bectus anticus minor arises from the anterior border of the lateral mass of the atlas, and is inserted into the basilar process; its fibres being directed obliquely upwards and inwards. Relations.—By its anterior surface with the rectus anticus major, and superior cervical ganglion of the sympathetic. By its posterior surface with the articulation of the condyle of the occipital bone with the atlas, and anterior occipito-atloid ligament. Nerve Supply.—Anterior branch of the first cervical. The Scalenus anticus (costo-trachelius) is a triangular muscle, as its name implies, situated at the root of the neck, and appear- ing like a continuation of the rectus anticus major; it arises, by a flat and narrow tendon, from the upper and inner border of the first rib ; and is inserted into the anterior tubercles of the trans- verse processes of the third, fourth, fifth, and sixth cervical vertebras. Relations. — By its anterior surface with the sterno-mastoid, omo-hyoid, supra-scapular and transversa colli artery, phrenic nerve, and subclavian vein, by which latter it is separated from the subclavius muscle and cla- vicle. By its posterior surface with the pleura, the nerves which form the brachial plexus, and below, the subclavian artery. By its inner side with the longus colli, being separated by the ver- tebral artery; by its outer side with the scalenus medius. Its relations with the subclavian Fig. 149* * Prasvertebral group of muscles of tlie neck. 1. Eectus anticus major. 2. Scalenus anticus. 3. Lower part of the longus colli of the right side; it is concealed superiorly by the rectus anticus major. 4. Eectus anticus minor. 5. Upper portion of the longus colli. 6. Its lower portion ; the figure rests on the' seventh cervical vertebra. 7. Scalenus medius; behind which is seen the scalenus posticus. 8. Eectus lateralis, left side, 9. One of the inter- transversales. SCALENI—LONGUS COLLI. 211 artery and vein are important, the vein being before, the artery behind the muscle. Nerve Supply.—Branches of the brachial plexus. The Scalenus medius, the largest of the three, arises from the first rib between the groove of the subclavian artery and the tube- rosity, and is inserted by separate tendons into the posterior tubercles of all the cervical vertebrae excepting the first. Relations.—By its ante- rior surface with the bra- chial plexus and subclavian artery; posteriorly with the scalenus posticus, levator anguli scapulae, and cervi- calis ascendens; internally with the pleura, inter-trans- verse muscles, and cervical vertebrae; externally with the stemo-mastoid, omo- hyoid, supra-scapular and transversa colli artery. Nerve Supply.—Branches of the brachial plexus. The Scalenus posticus, of small size, arises by a thin tendon from the second rib between its tubercle and angle, and divides superiorly into two or three tendons which are inserted into the posterior tubercles of the two or three lower cervical vertebrae. The scalenus posticus was formerly described with the scalenus medius as one muscle ; while Albinus and Soemmerring make five scaleni. Relations.—In front with the scalenus medius ; behind with the two upper levatores costarum, and cervicalis ascendens. Nerve Supply.—Branches from the brachial and cervical plexus. The Longus colli (prsedorso-atloideus) is a long and flat muscle, consisting of two portions. The upper arises from the anterior Fig. 150.* * Lateral view of the muscles of the prae vertebral region and side of the neck. 1. The mastoid process of the temporal bone. 2. The zygoma. 3. The occipital bone. 4. The spine of the scapula. 5. The acromion process. 6. The. clavicle. 7. The longus colli muscle. 8. Scalenus anticus. 9. Scalenus medius. 10. Scalenus posticus. 11. Levator anguli scapulae. 12. Splenius. 13. Complexus. 14. Cut edge of the trapezius. 15. Rhomboideus minor. 16. Serratus posticus superior. 17. Supra-spinatus. 18. Opening oeween the scalenus anticus and medius for the subclavian artery; the number is placed on the first rib; and the fibres below it are those of the first intercostal muscle. 19. (Esophagus and trachea. 20. Constrictor inferior pharyngis. 21. Constrictor medius. 22. Constrictor superior. 212 MUSCLES OF THE TRUNK. tubercle of the atlas, and is inserted into the transverse processes of the third, fourth, and fifth cervical vertebras. The lower portion arises from the bodies of the second, third, and fourth, and trans- verse processes of the fifth and sixth, and passes down the neck to be inserted into the bodies of the three lower cervical and three upper dorsal vertebrae. We may thus arrange these attachments in a tabular form :— Origin. Insertion. Upper portion. Atlas 3rd, 4th, and 5th transverse processes. Lower portion. 2nd, 3rd, and 4th bodies • 5th and 6th transverse processes .... 3 lower cervical vertebras, bodies, 3 upper dorsal, bodies. In general terms, the muscle is attached to the bodies and trans- verse processes of the six superior cervical vertebrae above, and to the bodies of the last three cervical and first three dorsal below. Relations.—By its anterior surface with the pharynx, oeso- phagus ; sheath of the common carotid, internal jugular vein and pneumogastric nerve; sympathetic nerve, inferior laryngeal nerve, and inferior thyroid artery. By its posterior surface it rests on the cervical and upper dorsal vertebra}. Nerve Supply.—Brachial plexus Actions.—The rectus anticus major and minor preserve the equi- librium of the head upon the atlas; and acting with the longus colli, flex and rotate the head and the cervical portion of the verte- bral column. The scaleni muscles are flexors of the vertebral column; and, acting from above, fix the first and second ribs for the inspiratory muscles. These muscles are described with the anatomy of the larynx, in Chapter XI. Eighth Group.—Muscles of the Larynx. MUSCLES OF THE TRUNK. The muscles of the trunk may be subdivided into four natural groups; viz.: 1. Muscles of the hack. 2. Muscles of the thorax. 3. Muscles of the abdomen. 4. Muscles of the perinaeum. 1. Muscles of the Bach.—The region of the bach, in consequence of its extent, is common to the neck, upper extremities, and abdo- men : and its muscles, which are numerous, may be arranged into six layers. First Layer. Second Layer. Trapezius, Latissimus dorsi. Levator anguli scapulae, Rhomboideus minor, Rhomboideus major. MUSCLES OF THE BACK. 213 Third Layer. Serratus posticus superior, Serratus posticus inferior, Splenius capitis, Splenius colli. Fourth Layer. (Dorsal Group.) Sacro-lumbalis, Longissimus dorsi, Spinalis dorsi. (Cervical Group.) Cervicalis ascendens, Transversalis cervicis, Trachelo-mastoideus, Complexus. Fifth Layer. (Dorsal Group.) Semi-spinalis dorsi, Semi-spinalis colli. (Cervical Group.) Rectus posticus major, Rectus posticus minor, Rectus lateralis, Obliquus inferior. Obliquus superior. Sixth Layer. Multifid us spinas, Inter-spinales, Inter-transversales, Levatores costarum. First Layer. Dissection.—The muscles of this layer are to be dissected by making an incision along the middle line of the back, from the tubercle on the occipital bone to the coccyx. From the upper point of this incision carry a second transversely outwards to the back of the ear; interiorly an incision must be made from the extremity of the sacrum, along the crest of the ilium, to about its middle. For convenience of dissection, a fourth may be carried from the middle of the spine to the acromion process. The integument and super- ficial fascia, together, are to be dissected off the muscles in the course of their fibres, over the whole of this region. The Trapezius muscle (trapezium, a quadrangle with unequal sides) arises from the inner third of the superior curved line of the occipital bone, from the ligamentum nuchas, and from the supra- spinous ligament and spinous processes of the last cervical and all the dorsal vertebrae. The fibres converge from these various points, and are inserted into the scapular third of the clavicle, acromion process, and upper border of the spine of the scapula, as far back as its tubercle. The inferior fibres become, tendinous, near the scapula, and glide over the triangular surface at the origin of the spine, upon some loose cellular tissue. When the trapezius is dis- sected on both sides, the two muscles resemble a trapezium, or diamond-shaped quadrangle, on the posterior part of the shoulders; hence the musde was formerly named cucullaris (cucullus, a monk’s cowl). The occipital portion of the muscle is extremely thin; and the origin of the cervical and upper part of the dorsal portion tendinous, forming, with the muscle of the opposite side, a tendinous trapezium. Delations.—By its superficial surface with the integument and superficial fascia, to which it is closely adherent by its cervical 214 MUSCLES OF THE BACK. Mg. 151.* * First, second, and part of the third layer of muscles of the back; the first layer occupies the right, the second, the left side. 1. Trapezius. 2. Tendinous portion, forming, with a corresponding part of the opposite muscle, the ten- dinous ellipse on the back of the neck. 3. Acromion process and spine of the scapula. 4. Latissimus dorsi. 5. Deltoid. 6. Muscles of the dorsum of the scapula: infra-spinatus, teres minor, and teres major. 7. Obliquus extemus. 8. Gluteus medius. 9. Glutei maximi. 10. Levator anguli scapulfe. 11. Rhom- boideus minor. 12. Rhomboideus major. 13. Splenius capitis; the muscle immediately above, and overlaid by the splenius, is the complexus. 14. Sple- nius colli, partially seen; the common origin of the splenius is seen attached to the spinous processes below the origin of the rhomboideus major. 15. Ver- tebral aponeurosis. 16. Serratus posticus inferior. 17. Supra-spinatus. 18. Infra-spinatus. 19. Teres minor. 20. Teres major. 21. Long head of triceps, passing between teres minor and major to the arm. 22. Serratus magnus proceeding forwards from its origin at the base of the scapula. 23. Obliquus intemus abdominis. LATISSIMUS DORSI. 215 portion, loosely by its dorsal portion. By its deep surface, from above downwards, with the complexus, splenius, levator ariguli scapulae, supra-spinatus, a small portion of the serratus posticus superior, rhomboideus minor, rhomboideus major, intervertebral aponeurosis which separates it from the erector spinae, and with the latissimus dorsi. The anterior border of the cervical portion forms the posterior boundary of the posterior triangle of the neck. Its clavicular insertion sometimes advances to the middle of the clavicle, or as far as the outer border of the sterno-mastoid, and occasionally it has been seen to overlap the latter. This is a point to.be borne in mind in the operation for ligature of the subclavian artery. The spinal accessory nerve passes beneath the anterior border, near the clavicle, previously to its distribution to the under surface of the muscle. Nerve Supply.—Spinal accessory, and third and fourth cervical. The ligamentum nuchce is a thin fibrous band extended from the tubercle and spine of the occipital bone, to the spinous process of the seventh cervical vertebra, where it is continuous with the supra- spinous ligament. It is connected with the spinous processes of all the cervical vertebrae, excepting the atlas, by means of a series of small fibrous slips; and is the analogue of an important elastic ligament in animals. The Latissimus dorsi muscle covers the whole of the lower part of the back and loins. It arises from the spinous processes of the four or six inferior dorsal, and all the lumbar vertebra, from the supra-spinous ligament, spinous tubercles of the sacrum, posterior third of the crest of the ilium, and four lower ribs; the latter origin taking place by muscular slips, which indigitate with the external oblique muscle of the abdomen. The fibres from this extensive origin converge as they ascend, and cross the inferior angle of the scapula; they then curve around the lower border of the teres major muscle, and terminate in a short quadrilateral tendon, which gets in front of the tendon of the teres, and is inserted into the bicipital groove. The tendinous origin of the muscle is united by its under surface with the posterior lamella of the fascia lumborum, and forms the posterior part of the sheath of the erector spinas; it is also connected with the posterior aponeurosis of the obliquus internus. A synovial bursa is interposed between its upper border and the lower angle of the scapula, and another between the upper half of its tendon and that of the teres major; the two tendons being united interiorly. The muscle frequently receives a small fasciculus from the scapula as it crosses its inferior angle; and sometimes by means of its tendon, a small muscular fasciculus from the pectoralis major; its tendon also gives off fibres to the deep fascia of the upper arm. Relations.—By its superficial surface with the integument and superficial fascia, the latter being dense and fibrous in the lumbar region, and with the trapezius. By its deep surface, from below upwards, with the erector spinae, serratus posticus inferior, posterior 216 MUSCLES OF THE BACK. aponeurosis of the obliquus internus, obliquus extemus, serratus magnus, intercostal muscles and ribs, rhomboideus major, inferior angle of the scapula, and teres major. The latissimus dorsi, with the teres major, forms the posterior border of the axilla. Nerve Supply.—By the long subscapular branch of the posterior cord of the brachial plexus, and by the posterior branches of the dorsal and lumbar nerves. Second Layer. Dissection.—This layer is brought into view by dividing the two preceding muscles near their insertion, and turning them aside. The Levator anguli scapulae (trachelo-seapularis) arises by tendinous slips, from the posterior tubercles of the transverse pro- cesses of the four upper cervical vertebrae; and is inserted into the upper angle and posterior border of the scapula, as far as the triangular smooth surface at the root of its spine. Being the prin- cipal elevator of the shoulder, the levator anguli scapulae has been termed musculus patientice. Relations.—By its superficial surface with the trapezius, sterno- mastoideus, and integument. By its deep surface with the splenius colli, transversalis cervicis, cervicalis ascendens, scalenus posticus, and serratus posticus superior. The tendons of origin are interposed between the attachments of the scalenus medius in front and the splenius colli and transversalis cervicis behind. Nerve Supply.—By the rhomboid branch of the brachial plexus, and branches from the second, third, and fourth cervical. The Rhomboideus minor (dorso-scapularis; rhombus, a paralle- logram with four equal sides) is a narrow slip of muscle, detached from the rhomboideus major by a slight cellular interspace. It arises from the spinous processes of the last cervical and first dorsal vertebras and ligamentum nuchse; and is inserted into the edge of the triangular surface, on the posterior border of the scapula. The Rhomboideus major arises from the spinous processes and inter-spinous ligaments of the four upper dorsal vertebrae; and is inserted into the posterior border of the scapula as far as its inferior angle. The upper and middle portion of the insertion is effected by means of a tendinous band, which is attached in a longitudinal direction to the posterior border of the scapula. Relations.—By their superficial surface the rhomboid muscles are in relation with the trapezius, and the rhomboideus major with the latissimus dorsi and integument; by their deep surface with the serratus posticus superior, elector spinse, intercostal muscles and ribs. Nerve Supply.—The rhomboid muscles are supplied by a branch of the brachial plexus called rhomboid; it is derived from the fifth cervical. Third Layer. Dissection.—The third layer consists of muscles which arise from the spinous processes of the vertebral column, and pass out- wards. Lt is brought into view by dividing the lev tor anguli SEEEATI—SPLENIUS. 217 scapulae near its insertion, and reflecting the two rhomboid muscles upwards from their insertion into the scapula. The latter muscles should now be removed. The Serratus rosTicus superior (dorso-costalis) is situated at the upper part of the thorax; it arises from the ligamentum nuchas, and spinous processes of the last cervical and two upper dorsal vertebrae. The muscle passes obliquely downwards and outwards, and is inserted by four serrations into the upper border of the second, third, fourth, and fifth rib, a little beyond then- angle. Relations.—By its superficial surface with the trapezius, rhom- boideus major and minor, and serratus magnus. By its deep surface with the splenius, erector spinae, intercostal muscles and ribs. The Serratus posticus inferior (lumbo-costalis) arises from the spinous processes and interspinous ligaments of the two lower dorsal and two or three upper lumbar vertebrae, and passing obliquely upwards, is inserted by four serrations into the lower border of the four inferior ribs. Both muscles consist of a thin aponeurosis for about half their extent. Relations.—By its superficial surface with the latissimus dorsi, its tendinous origin being inseparably connected with the aponeurosis of that muscle. By its deep surface with the erector spinae, inter- costal muscles and lower ribs. The upper border is continuous with a thin tendinous layer, the vertebral aponeurosis. Nerve Supply.—-The serrati muscles are supplied by the external branches of the posterior divisions of the dorsal nerves. The Vertebral aponeurosis (fascia lumbo-dorsalis) is a thin membranous expansion, composed of transverse and longitudinal fibres, extending from the upper border of the serratus posticus inferior upwards beneath the serratus posticus superior to the neck, where it is lost in the cervical fascia. It is attached along the middle line to the spinous processes of the dorsal vertebrae, externally to the angles of the ribs, and forms the posterior boundary of a triangular sheath, which contains the erector spinae and deep muscles of the back. The other two boundaries of the triangular sheath, are the ribs and vertebrae in front and the spinous processes of the vertebrae at the middle line. The serratus posticus superior must be removed from its origin and turned outwards, to bring into view the whole extent of the splenius muscle. The Splenius muscle is single at its origin, but divides soon after into two portions, which are destined to distinct insertions. It arises from the lower half of the ligamentum nuchae, the spinous process of the last cervical, and spinous processes and interspinous ligaments of the six upper dorsal vertebrae ; it divides as it ascends the neck into the splenius capitis and splenius colli. The splenius capitis (cervico-mastoideus) is inserted into the rough surface of the occipital bone between the two curved lines, and posterior border of the mastoid process of the temporal bone. The splenius colli (dorso-trachelius) is inserted into the posterior 218 MUSCLES OF THE BACK. tubercles of the transverse processes of the three upjier cervical vertebrae. Relations.—By its superficial surface with the trapezius, sterno- mastoideus, levator anguli scapulae, rhomboideus minor and major, and serratus posticus superior. By its deep surface with the spinalis dorsi, longissimus dorsi, semi-spinalis colli, complexus, trachelo-mastoideus, and transversalis cervicis. The tendons of insertion of the splenius colli are interposed between and united with the tendons of the levator anguli scapulae in front, and the transversalis cervicis behind. Nerve Supply.—The great occipital, and the external branches of the posterior divisions of the cervical and five upper dorsal nerves. The splenii of opposite sides of the neck leave between them a triangular interval, in which the complexus is seen. Fourth Layer, Dissection.—The two serrati and two splenii muscles must be removed by cutting them away from their origin and insertion, and the vertebral aponeurosis laid open, to bring the fourth layer into view. Three of these muscles: viz., sacro-lumbalis, longissimus dorsi, and spinalis dorsi, are associated under the name of erector spin.®. They occupy the lumbar and dorsal portion of the back. The remaining four are situated in the cervical region. The Sacro-lumbalis and longissimus dorsi arise by a common origin from the posterior third of the crest of the ilium, the oblique sacro-iliac ligament, articular and spinous tubercles of the sacrum, spinous processes of the lumbar vertebras, and, deeply, from the posterior transverse tubercles of the lumbar vertebras; the external portion being fleshy, the internal tendinous. The tendinous por- tion is broad and flat, and gives origin by its deep surface to a con- siderable part of the muscular fibres. In the lumbar region, the muscle proceeding from this extensive origin is a broad and thick museulo-tendinous mass, on the surface of which, opposite the last rib, a line of separation is apparent, the outer portion, about one- third, being the sacro-lumbalis, the inner two-thirds the longissimus dorsi. The sacro-lumbalis (ilio-costalis, Theile) ascends upon the chest internally to the angles of the ribs, and is inserted by separate slips, the four upper tendinous, the two lower fleshy, into the angles of the six lower ribs. If this muscle be turned a little outwards, a number of tendinous slips will be seen which take their origin from the upper border of the ribs near their angles, and terminate in muscular fasciculi, which prolong the sacro-lumbalis to the upper part of the chest. This is the musculus accessorius ad sacro-lumbalem; it arises from the six lower ribs ; and is inserted by separate tendons into the angles of the six upper ribs and transverse process of the seventh cervical vertebra. SACRO-LUMBALIS—SPINALIS DORSI. 219 The longissirmts dorsi is inserted by two series of tendons, in- ternal and external: the internal being implanted into the posterior transverse processes (processus ac- cessorii) of the lumbar, and trans- verse processes of all the dorsal ver- tebrae ; the external into the trans- verse processes (lumbar ribs) of the lumbar vertebrae, and all the ribs, ex- cepting the first, between their tu- bercles and angles. The Spinalis dorsi arises from the spinous processes of the two upper lumbar and two lower dorsal vertebrae, and is inserted into the spinous processes of the upper dorsal vertebrae from the second to the sixth or eighth. It also receives several fasciculi from the longissimus dorsi and semi-spinalis dorsi. The two muscles form an ellipse, which em- braces the spinous processes of the dorsal vertebrae.-)" Relations. — The erector spin® muscle is in relation by its super- ficial surface (in the lumbar region) with the serratus posticus inferior and latissimus dorsi; (in the dorsal region) with the vertebral aponeu- rosis, which separates it from the latissimus dorsi, trapezius, and ser- ratus posticus superior, and with the splenius. By its deep surface (lumbar region) with the multifidus spin®, transverse processes of the lumbar vertebrae, and middle layer of the lumbar fascia, which separates it from the quadratus lumborum; (dorsal region) with the multifidus spin®, semi-spinalis dorsi, levatores costarum, intercostal muscles, Fig. 152.* * Fourth and fifth, and part of the sixth layer of the muscles of the back. 1. Common origin of the erector spinse. 2. Sacro-lumbalis. 3. Longissimus dorsi. 4. Spinalis dorsi. 5. Cervicalis ascendens. 6. Transversalis cervicis. 7 Trachelo-mastoideus. 8. Complexus. 9. Transversalis cervicis, showing its origin. 10. Semi-spinalis dorsi. 11. Semi-spinalis colli. 12. Rectus posticus minor. 13. Rectus posticus major. 14. Obliquus superior. 15. Obliquus inferior. 16. Multifidus spin®. 17. Levatores costarum. 18. Inter-transver- sales. 19. Quadratus lumborum. t Many anatomists include under the name of erector spinat not only the sacro-lumbalis with its accessory portion, and the longissimus dorsi, but also the spinalis dorsi, cervicalis ascendens, transversalis cervicis and trachelo- mastoid. 220 MUSCLES OF THE BACK. and ribs as far as tbeir angles. Internally or mesially, with the multifidus spines, and semi-spinalis dorsi, which separates it from the spinous processes and arches of the vertebra. The fascia lumborum, with the spinal column, aponeurosis of the latissimus dorsi, and ribs, forms a complete osseo-aponeurotic sheath for the erector spinee. The Cervicalis ascenders vel descendens is the continuation of the sacro-lumbalis upwards into the neck. It arises from the angle of the third, fourth, fifth and sixth rib, and is inserted by slender tendons into the posterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae. The term descendens, applied to this muscle, can only be correct when it is described as arising in the neck and passing downwards to the ribs. Relations.—By its superficial surface with the levator anguli sca- pulae ; by its deep surface with the upper intercostal muscles, ribs, and intertransverse muscles ; externally with the scalenus posticus and medius; internally with the transversalis cervicis. The ten- dons of insertion are interposed between the attachments of the scalenus medius and posticus and transversalis cervicis, with which they are united. The Transversalis cervicis appears to be the continuation upwards into the neck of the longissimus dorsi; it arises from the transverse processes of the five or six upper dorsal vertebrae, and is inserted into the posterior tubercles of the transverse processes of the cervical vertebra, from the second to the sixth. It receives a fasciculus from the longissimus dorsi and several small slips from the trachelo-mastoideus. Relations.—By its superficial surface with the levator anguli scapulae, splenius, and longissimus dorsi. By its deep surface with the complexus, trachelo-mastoideus, and vertebrae; externally with the musculus accessorius ad sacro-lumbalem and cervicalis ascen- dens; internally with the trachelo-mastoideus and complexus. The tendons of insertion of this muscle are interposed between the tendons of insertion of the cervicalis ascendens on the outer side, and those of origin of the trachelo-mastoid on the inner side. The Trachelo-mastoideus (complexus parvus) is likewise a con- tinuation upwards from the longissimus dorsi. It is a slender and delicate muscle, arising from the transverse processes of the three upper dorsal and last cervical, and from the articular processes of the three next cervical vertebrae, its origin being similar to that of the complexus, with which and the origin of the transversalis cer- vicis it is closely connected. It receives a fasciculus from the lon- gissimus dorsi, and is inserted into the posterior border and summit of the mastoid process. Relations.—The same as the preceding muscle, excepting that it is interposed between the transversalis cervicis and complexus. Nerve Supply.—This and the preceding muscles are supplied by the external branches of the posterior divisions of the dorsal and cervical nerves. The Complexus (trachelo-occipitalis) is a large muscle, forming C OMPLEXU S.—SEMI-SPIN ALES. 221 with the splenius the great bulk of the back of the neck. It crosses the direction of the splenius, arising from the transverse processes of the three upper dorsal and last cervical, and from the articular processes of the three next lower cervical vertebrae ; and is inserted into the rough surface of the occipital bone between the two curved lines, as far as the occipital spine. The complexus is marked in the upper part of the neck by a transverse tendinous intersection. A large fasciculus of the complexus lying superficially to that muscle, and remarkable for consisting of two fleshy bellies with an intermediate tendon, is usually described under the name of biventer cervicis. Considered as a separate muscle, it arises by three or four slips from the transverse processes of the dorsal vertebras, from the fourth to the seventh ; and is inserted into the inner portion of the superior curved line of the occipital bone. Its tendons of origin lie internally to the insertions of the longissimus dorsi, and are connected with those of the semi-spinalis colli; and its lower belly receives a fasciculus from the longissimus. The outer border of the upper belly is united with the complexus; in the rest of its course it is free. Relations.—By its superficial surface with the trapezius, splenius, trachelo-mastoideus, transversalis cervicis, and longissimus dorsi. By its deep surface with the semi-spinalis dorsi and colli, recti and obliqui. It is separated from its fellow of the opposite side by the ligamentum nuchae, and from the semi-spinalis colli by the profunda cervicis artery, princeps cervicis branch of the occipital, and pos- terior cervical plexus of nerves. Nerve Supply.—The great occipital, and internal branches of posterior divisions of the six lower cervical and five upper dorsal nerves. Fifth Layer. Dissection.—The muscles of the preceding layer are to be removed by dividing them transversely through the middle, and turning one extremity upwards, the other downwards. In this way the whole of the muscles of the fourth layer may be dissected off, and the re- maining muscles of the spine brought into a state to be examined. The Semi-spinales muscles are connected with the transverse and spinous processes of the vertebrae, spanning one-half the vertebral column ; hence their name semi-spinales. The Semi-spinalis dorsi arises from the transverse processes of the dorsal vertebrae from the sixth to the tenth; and is inserted into the spinous processes of the four upper dorsal and two lower cervical vertebrae. It is united below with the spinalis dorsi, and above -with the semi-spinalis colli; it also sends several small slips to the longissimus dorsi. The Semi-spinalis colli, larger than the preceding, arises from the transverse processes of the five or six upper dorsal vertebrae; and is inserted into the spinous processes of the cervical vertebrae from the second to the fifth. 222 MUSCLES OF THE BACK. Relations.—By their superficial surface the semi-spinales are in relation from below upwards with the spinalis dorsi, longissimus dorsi, complexus, splenius, profunda cervicis and princeps cervicis artery, and posterior cervical plexus of nerves. By their deep sur- face with the multifidus spinas muscle. Nerve Supply.—The semi-spinales are supplied by the internal branches of the posterior divisions of the dorsal and cervical nerves. On the middle line in the cervical region is a small muscle, the analogue of the spinalis dorsi, termed the spinalis cervicis. It is extremely irregular; arising from the spinous processes of the two upper dorsal or two lower cervical vertebras; and inserted into the spinous process of the axis, and sometimes into the next one or two vertebras. Occipital (Lroup.—This group of small muscles is intended for the movements of the cranium on the atlas, and atlas on the axis. The Rectus posticus major (superficialis) arises from the spinous process of the axis : and is inserted into the inferior curved line of the occipital bone. The Rectus posticus minor (profundus) arises from the spinous tubercle of the atlas; and is inserted into the rough surface of the occipital bone, beneath the inferior curved line. The Rectus lateralis arises from the transverse process of the atlas, and is inserted into the rough surface of the occipital bone, externally to the condyle. The Obliquus inferior (major) arises from the spinous process of the axis, and passes obliquely outwards to be inserted into the extremity of the transverse process of the atlas. The Obliquus superior (minor) arises from the extremity of the transverse process of the atlas, and passes obliquely inwards to be inserted into the rough surface of the occipital bone, between the curved lines, and directly behind the mastoid process. Relations.—By their superficial surface the recti and obliqui are in relation with a strong aponeurosis which separates them from the complexus. By their deep surface with the atlas and axis. The rectus posticus major partly covers in the rectus minor. The rectus lateralis is in relation by its anterior surface with the in- ternal jugular vein, and by its posterior surface with the vertebral artery. Nerve Supply.—The recti and obliqui are supplied by the pos- terior divisions of the first and second cervical nerves. Sixth Layer. Dissection.—The semi-spinales muscles must be removed to ob- tain a good view of the multifidus spinas, which lies beneath them, and fills up the concavity between the spinous and transverse pro- cesses, the whole length of the vertebral column. The Multifidus spines, consisting of about twenty-two small muscular fasciculi, extends along the vertebral groove from the MULTIFIDUS SPINJE—INTEE-TEANSYEESALES. 223 sacrum to the axis. The muscle commences by tendinous fibres on the dorsum of the sacrum, proceeding from the lateral tubercles of the sacrum and even from the lateral cornu of the coccyx, and passing obliquely upwards and inwards to the spinous tubercles. The fasciculi arise interiorly from the sacrum, ilium, and tendon of the erector spinse; in the lumbar region from the articular and posterior transverse processes of the vertebrae; in the dorsal region from the transverse processes ; and in the cervical region from the articular processes of the four inferior vertebrae. They are inserted into the spinous processes and laminae of all the vertebrae from the sacrum to the axis. Of the twenty-two fasciculi, six are lumbar, twelve dorsal, and four cervical. Each fasciculus, separate below, spreads out as it ascends, and passing over the next vertebra, is inserted into the four or five immediately above it. The muscle is thick interiorly; and the uppermost fasciculus larger than those immediately below it. Relations.—By its superficial surface with the longissimus dorsi, semi-spinalis dorsi, and semi-spinalis colli. By its deep surface with the laminae and spinous processes of the vertebral column, and in the cervical region with the ligamentum nuchas. The Intekspinales are small muscular slips arranged in pairs and situated between the spinous processes of the vertebras. In the cervical region there are six pairs of these muscles, the first being placed between the axis and third vertebra, the sixth between the last cervical and first dorsal; they are attached to the apices of the spinous processes, and are separated by the interspinous ligaments. In the dorsal region, rudiments of these muscles are occasionally met with between the upper and lower vertebrae, but are absent in the rest. In the lumbar region there are six pairs of interspinales, the first pair occupying the interspinous space between the last dorsal and first lumbar vertebra, the last, the space between the fifth lumbar and sacrum. They are thin, broad, and imperfectly developed. Rudimentary interspinales are occasionally met with between the sacrum and coccyx; these are the analogues of the caudal muscles of brutes; in man they are named collectively the extensor coccygis (sacro-coccygeus posticus). The Inter-transversales (inter-transversarii) are small quadri- lateral muscles situated between the transverse processes of the vertebrae. In the cervical region they are arranged in pairs cor- responding with the double conformation of the transverse processes, the vertebral artery and anterior division of a cervical nerve lying between them. The rectus anticus minor and rectus lateralis represent the inter-transversales between the atlas and cranium. In the dorsal region the anterior inter-transversales are represented by the intercostal muscles, while the posterior are mere tendinous bands, muscular only between the first and last vertebrae. In the lumbar region, the anterior inter-transversales are thin, and occupy only part of the space between the transverse processes. Analogues of posterior inter-transversales exist in the form of small muscular 224 MUSCLES OF THE BACK. fasciculi (interobliqui, inter-accessorii) extended between the rudi- mentary posterior transverse processes of the lumbar vertebra;. The Levatores costarum (supra-costales) are divided into long and short. The short (breves), twelve in number at each side, arise from the apex and lower border of the transverse process of the last cervical and eleven upper dorsal vertebrae; and pass downwards and outwards, radiating in their descent, to be inserted into the upper border of all the ribs, between the tuberosity and angle. The uppermost muscle is the smallest, and their breadth increases from above downwards. The levatores costarum longi, four in number at each side, arise from the transverse processes of the dorsal vertebrae, the seventh to the tenth, and are inserted into the four lower ribs; each muscle passing over a rib in its descent, and being attached to the rib below as far as its angle. The levatores longi lie superficially to the levatores breves and increase in size from above downwards. Relations.—By their superficial surf axe with the sacro-lumbalis, longissimus dorsi and transversalis cervicis. By their deep surface with the ribs and intercostal spaces ; the levatores breves close the intercostal spaces, and are united by their external border with the intercostales externi. Nerve Supply.—The multifidus spinas, interspinales, inter-transver- sales, and levatores costarum are supplied by branches from the pos- terior divisions of the spinal nerves, from the atlas to the sacrum. With regard to the origin and insertion of the muscles of the back, the student should be informed that no exact regularity attends their attachments. At the best, a knowledge of their pre- cise connexions, even were it possible to retain it, would be but a barren information, if not absolutely injurious, as tending to exclude more valuable learning. We have therefore arranged a plan, by which they may be more easily recollected, placing them iu a tabu- lar form (pp. 226, 227), that the student may see at a glance, the origin and insertion of each, and compare the natural grouping and similarity of attachment of the vai-ious layers. In this man- ner their actions also will be better comprehended, and learnt with greater facility. In examining the table, the student will observe the constant recurrence of the number four in the origin and insertion of the muscles. Sometimes the four occurs at the top or bottom of a region of the spine, and frequently includes part of two regions, taking two from each, as in the case of the serrati. Again, he will perceive that the muscles of the upper half of the table take their origin from spinous processes, and pass outwards to trans- verse, whereas the lower half arise mostly from transverse processes. To the student we commit these reflections, and leave it to the peculiar tenor of his own mind to make such arrangements as will be best retained in his memory. Actions.—The upper fibres of the trapezius draw the shoulder upwards and backwards; the middle fibres, directly backwards; ACTIONS OF THE MUSCLES OF BACK. 225 the lower, downwards and backwards. The lower fibres also act in producing rotation of the scapula on the chest. If the shoulder be fixed, the upper fibres will flex the spine towards the correspond- ing side. The latissimus dorsi is a muscle of the arm, drawing it backwards and downwards, and at the same time rotating it in- wards ; if the arm be fixed, the latissimus dorsi will draw the spine to that side, and, raising the lower ribs, be an inspiratory muscle; and if both arms be fixed, the two muscles will draw the whole trunk forwards, as in climbing or walking on crutches. The leva- tor anguli scapulas lifts the upper angle of the scapula, and with it the entire shoulder; the rhomboidei carry the scapula and shoulder upwards and backwards. The serrati are respiratory muscles acting in opposition to each other, the serratus posticus superior drawing the ribs upwards, and thereby expanding the chest; the inferior drawing the lower ribs downwards, and diminishing the cavity of the chest. The former is an inspiratory, the latter an expiratory muscle. The splenii muscles of one side draw the vertebral column backwards and to one side, and rotate the head towards the corresponding shoulder. The muscles of opposite sides acting together, draw the head directly backwards. They are direct antagonists of the sterno-mastoid muscles. The sacro-lumbalis with its accessory muscle, the longissimus dorsi and spinalis dorsi, are known by the general term of erector spince, which sufficiently expresses their action. They keep the spine supported in the vertical position by their broad origin from below, and. by their insertion, by distinct tendons, into the ribs and spinous processes. Being made up of a number of distinct fasci- culi, which act alternately, the spine is kept erect without fatigue, even when the muscles have to counterbalance a corpulent abdo- men. The continuations upwards of these muscles into the neck preserve the steadiness and uprightness of that region. When the muscles of one side act alone, the neck is rotated on its axis. The complexus, being attached to the occipital bone, draws the head backwards, and counteracts the muscles of the anterior part of the neck. It assists also in the rotation of the head. The semi-spinalis and multifidus spince muscles act directly on the vertebrae, and contribute to the general action of supporting the vertebral column erect. The four little muscles situated between the occiput and the first two vertebrae, effect the various movements between these bones; the recti producing the antero-posterior actions: the obliqui the rotatory motions of the atlas on the axis. The actions of the remaining muscles of the spine, the inter - spinales and inter-transversales, are expressed in their names. They approximate their attachments, and assist the more powerful muscles in preserving the erect position of the body. The levatores costarum raise the posterior parts of the ribs, and are probably more serviceable in preserving the articulation of the ribs from displacement, than in raising them in inspiration. 226 TABLE OF ORIGIN AND INSERTION ORIGIN. Layers. Spinous Processes. Transverse Processes. Ribs. Additional. 1st Layer. Trapezius . . £ last cervical, f occipital bone andj 12 dorsal s • • • *1 ligamentum nuchas J Latissimus dorsi . £ 4 or 6 lower dor- sal, 5 lumbar . j. . . 4 lower sacrum and ilium . i 2nd Layer. Levator anguli scapulas . . j ( 4uppercervi-h < cal posterior > (.tubercles . ) . . Rhomboideus minor | lig. nuchas and last cervical . }• ■ • RhombOideus major 4 upper dorsal . 3rd Layer. Serratus posticus j lig. nuchas, 1 . . . 2 upper dorsal J Serratus posticus f 2 lower dorsal, X inferior . . \ 2 upper lumbar S’ Splenius capitis . f Splenius colli. . 1 lig. nuchas, last, cervical 6 upper dorsal }. . . 4th Layer. Sacro-lumbalis ilium Accessorius ad 7 angles, 7 sacro-lumbalem j . . . . £ 6 lower \ . . . . Longissimus dorsi. . f ' t sacrum and lumbar \ vertebra; . . / Spinalis dorsi. . £ 2 lower dorsal, 2 upper lumbar }• ■ • angles, 3rd, 4th, Cervicalis ascendens . . . .( }. . . . 1 5 or 6 upper 5th, 6th ) Tranversalis cervicis . . .{ }• * • • . • TracbelO'.mastoideus . . . ( 3 upper dorsal, ] f articular processes > l 1 lower cervical ) ’ ’l 4tli, 5th, 6th cerv. ) Complexus ■ ■ •{ 3 upper dorsal, 1 lower cervical }• •{ articular processes! 4th, 5th, 6th cerv. > Biventer cervicis . . dorsal 4th to 7th 5th Layer. Semi-spinalis dorsi. • 6th to 10th dorsal Semi-spinalis colli . Rectus posticus major • • •{ axis 5 or 6 upper dorsal }• ■ Rectus posticus minor Rectus lateralis atlas atlas Obliquus inferior . Obliquus superior . axis atlas 6th Layer. Multifidus spinas . Inter-spinales • ■ •{ from sacrum to 4th cervical J- •( sacrum, ilium, ten-'i don of erector spi- > nas, articular proc.) cervical & lumbar ' -T cervical & lumbar last cervical and Inter-transversales Levatores costarum • l 11 upper dorsal r • OF THE MUSCLES OF THE BACK. 227 INSERTION. Spinous Processes. Transverse Processes. Ribs. Additional. . . . . . . . • • • •{ • • • •{ clavicle, acromion, and spine of scapula, bicipital groove of humerus. superior angle and base of scapula. base of scapula, base of scapula. 2nd, 3rd, 4th, and 5th. 3 upper cervical 4 lower. • • ' •{ occipital and temporal bone, and mastoid process. / dorsal, 2nd to 6th \ or 8th. • • • •{ • • • ■{ last cervical all the lumbar and dorsal. 3rd, 4th, 5th, 6th cervical. 2nd to 6th cer- vical. angles of 6 lower, angles of 6 upper. 11 lower, between tu- bercles and angles. • • • •{ . . . .{ mastoid process. occipital bone between the curved lines, occipital bone, supe- rior curved line. f 4 upper dorsal, t 2 lower cervical. 2nd to 6th cervical atlas. . . . . occipital bone, occipital bone, occipital bone. occipital bone. all except atlas . , • ■ • •{ all the laminse, except atlas. cervical and lumbar. cervical & lumbar • •{ all, between tubercles and angles. 228 MUSCLES OF THE THORAX. The principal muscles situated on the front and sides of the thorax belong in their actions to the upper extremity, with which they will be described. They are the pectoralis major and minor, subclavius and serratus magnus. The true thoracic muscles, which appertain exclusively to the actions of the ribs, are, the Intercostales externi, Intercostales interni, Subcostales, Triangularis sterni. The intercostal muscles are two planes of muscular and tendinous fibres directed obliquely between adjacent ribs and closing the inter- costal spaces. They are seen partially on the reflection of the pec- toral muscles, or on the inner surface of the chest. The triangularis sterni is within the chest, and requires the removal of the anterior part of the thorax to bring it into view. The I x ter cost ales externi, eleven on each side, commence pos- teriorly at the tubercles of the ribs, and advance forwards to the costal cartilages, where they terminate in a thin aponeurosis which is continued onwards to the sternum. Their fibres are directed obliquely downwards and inwards, pursuing the same line with those of the external oblique muscle of the abdomen. They are thicker than the internal intercostals, and more tendinous in structure. The Intercostales interni, also eleven on each side, commence anteriorly at the sternum, and extend backwards as far as the angle of the ribs, whence they are prolonged to the vertebral column by a thin aponeurosis. Their fibres are directed obliquely downwards and backwards, corresponding with those of the internal oblique muscle of the abdomen, and crossing those of the external intercostals. In structure the intercostal muscles consist of an admixture of muscular and tendinous fibres. They arise from the two lips of the lower border of the rib, the external from the outer lip, the internal from the inner; and are inserted into the upper border of the rib below, encroaching somewhat on its surfaces. Nerve Supply.—The intercostal nerves. The Subcostales (infracostales; intracostales) are nine or ten small muscles situated within the thorax at its posterior part, and lying upon the ribs. They increase in size from above downwards, and the direction of their fibres corresponds with that of the inter- costales interni. Each muscle arises from the front of a rib, and is inserted into the front of the rib but one below; the first sub- costalis is often absent. Relations.—The external intercostals, by their external surface, with the muscles which immediately invest the chest, viz., pecto- ralis major and minor, serratus magnus, serratus posticus superior TRIANGULARIS STERNI. 229 and inferior, scalenus posticus, sacro-lumbalis and longissimus dorsi with their continuations, cervicalis ascendens and transversalis cer- vicis, levatores costarum, and obliquus externus abdominis. By their internal surface with the internal intercostals, intercostal vessels and nerves, and posteriorly with the pleura, a thin aponeu- rosis being interposed. The internal intercostals, by their external surface with the external intercostals, and intercostal vessels and nerves; by their internal surface with the pleura costalis, trian- gularis sterni, subcostales, and. diaphragm. The Triangularis sterni (sterno-costalis), situated upon the inner wall of the front of the chest, arises by a thin aponeurosis from the side of the sternum, ensiform cartilage, and sternal ex- tremities of the costal cartilages from the third to the sixth or seventh; it is inserted by fleshy digitations into the second, third, fourth, and fifth costal cartilages and corresponding ribs. Relations.—By its external surface with the sternum, ensiform cartilage, costal cartilages, internal intercostal muscles, and internal mammary vessels. By its internal surface with the pleura cos-, tails, cellular tissue of the anterior mediastinum, and diaphragm. The lower fibres of the triangularis sterni are continuous with those of the transversalis abdominis. Nerve Supply.—The intercostal nerves. Actions of the Respiratory Muscles.—Respiration is produced by the alternate enlargement and diminution of the capacity of the thorax. The diaphragm by its descent enlarges the perpendicular measurement and produces abdominal inspiration. Abdominal expiration is the result of the recoil of the abdominal walls—at- mospheric pressure on them, and when forced the contraction of the abdominal muscles. Thoracic inspiration is an active move- ment produced by the elevation of the ribs which enlarges the capacity of the chest antero-posteriorly, and also laterally. It is accomplished by the powerful muscles of the chest, the serratus magnus, and pectorales major and minor, and others attached from above to the ribs. But during tranquil thoracic respiration, the elevation of the ribs is produced by the intercostales externi, and the opposite movement of expiration is owing to the elastic recoil of the costal cartilages, aided by the intercostales interni. Those fibres of the intercostales interni which are situated between the costal cartilages act like the externi in elevating the chest in in- spiration, their fibres having the same relation to the costo-sternal joint which the externi have to the costo-vertebral. Tranquil re- spiration is a vital effort produced by muscular contraction—tran- quil expiration a mechanical recoil. The account of the actions of the intercostal muscles here given, is in accordance with Mr. Hut- chison’s views, but many writers dispute the accuracy of his state- ments, especially with reference to the anterior fibres of the inter- costales interni. Many also believe that both sets of intercostals are elevators only. 230 MUSCLES OF THE ABDOMEN. The muscles of respiration may be enumerated as follows:— Intercostales externi, Levatores costarum, Dilating, or inspiratory muscles. Subcostales, Diaphragma, assisted occasionally by the Sterno-cleido-mastoidei, Scaleni, Serrati postici superiores, Pectorales minores, Subclavii, Pectorales majores, Latissimi dorsi, Cervicales ascendentes, Accessorii ad sacro-lumbales. SeiTati magni, Contracting, or expiratory muscles. Intercostales interni, Triangulares sterni, Obliqui externi, Obliqui interni, Transversales abdominis, Recti abdominis, Pyramidales, assisted occasionally by the Serrati postici inferiores, Longissimi dorsi, Sacro-lumbales, Quadrati lumborum, Serrati magni. To which may be added, as expiratory powers, the costal car- tilages ; acting by virtue of their elasticity. The muscles of the abdominal region are, the— MUSCLES OF THE ABDOMEN. Obliquus externus (descendens), Obliquus interims (ascendens), Cremaster, Transversalis, Rectus, Pyramidalis, Quadratus lumborum, Psoas parvus, Diaphragma. Dissection.—The dissection of the abdominal muscles is to be commenced by making three incisions :—The first, vertical, in the middle line, from over the lower part of the sternum to the pubes; the second, transverse, from the top of the first incision across the chest, as far back as the knife can be carried; the third, oblique, from the umbilicus, downwards and outwards, to the anterior superior spine of the ilium. The three flaps included by these incisions should then be dissected back in the direction of the fibres of the external oblique muscle, beginning at the angle of each. The in- tegument and superficial fascia should be dissected off separately, so as to enable the student to examine the relation of the vessels to the parts connected with hernia. When the external oblique muscle is dissected on both sides, a white tendinous line will be seen along the middle of the abdomen, extending from the ensiform cartilage to the pubes ; this is the linea alba. A little external to it, on each side, two curved lines will MUSCLES OF THE ABDOMEN. 231 Fg 153.* * Muscles of the anterior aspect of the trunk; on the left side the super- ficial layer is seen, on the right the deeper layer. 1. Pectoralis major. 2. Del- toid;. the interval between these muscles lodges the cephalic vein. 3. Ante- rior border of the latissimus dorsi. 4. Serratusmagnus. 5. Subclavius, right side. 6. Pectoralis minor. 7. Coraco-brachialis. 8. Upper part of the biceps, showing its two heads. 9. Coracoid process of the scapula. 10. Serratus magnus, right side. 11. External intercostal muscle of the fifth intercostal space. 12. External oblique. 13. Its aponeurosis; the median line to the right of this number is the linea alba: the curved line to its left, the linea semilu- naris ; the transverse lines above and below the cipher, the lineas transverse}. 14. Poupart’s ligament. 15. External abdominal ring ; the margin above the ring is the superior or internal pillar; the margin below the ring, the inferior or external pillar; the curved intercolumnar fibres are seen proceeding up- wards from Poupart’s ligament to strengthen the ring. The numbers 14 and 15 are placed on the fascia lata of the thigh ; the opening immediately to the left of 15 is the saphenous opening. 16. Rectus muscle of the right side brought into view by the removal of the anterior segment of its sheath ; * pos- terior segment of its sheath with the divided edge of the anterior seg- 232 MUSCLES OF THE ABDOMEN. be observed extending from tbe eighth rib to the spine of the pubes, and bounding the recti muscles; these are the linece semilunares. Some transverse lines, linece transversce, three in number, connect the lineae semilunares with the linea alba at and above the umbilicus. The External oblique muscle (obliquus externus abdominis, descendens: costo-abdominalis) is the external flat muscle of the abdomen. Its name is derived from the obliquity of its direction, and the descending course of its fibres. It arises by fleshy digita- tions from the external surface of the eight inferior ribs; the five upper digitations being received between corresponding processes of the serratus magnus, the three lower, of the latissimus dorsi. The fleshy fasciculi proceeding from this extensive origin terminate on the front of the abdomen in a broad aponeurosis, and posteriorly are inserted into the outer lip of the crest of the ilium, for two-thirds its length, and into the anterior superior spinous process. The aponeurosis is united, in front, by its under surface, with that of the obliquus internus, forming the anterior wall of the sheath of the rectus, and is inserted into the linea alba, front of the pubes, spine of the pubes and pectineal line. The lower border of the aponeurosis, which is stretched between the anterior superior spinous process of the ilium and the spine of the pubes, is round from being folded inwards, and forms Poupart's ligament; the insertion into the pectineal line is Gimbernat's ligament. Just above the crest of the pubes is the external abdominal ring, a triangular opening formed by the separation of the fibres of the aponeurosis of the external oblique. It is oblique in direction and corresponds with the course of the fibres of the aponeurosis. It is bounded below by the crest of the pubes; on either side by the borders of the aponeurosis, which are termed pillars; and above by some curved fibres (intercolumnar) which originate from Poupart’s ligament, and cross the upper angle of the ring, to give it strength. The external pillar, which is at the same time inferior from the obliquity of the opening, is inserted into the spine of the pubes; the internal or superior pillar forms an interlacement with its fellow of the opposite side over the front of the symphysis pubis. The external abdominal ring gives passage to the spermatic cord in the male, and the round ligament in the female : they are both invested in their passage through it by a prolongation of the fascia of the external oblique muscle, the intercolumnar fascia, or fascia spermatica. The pouch of inguinal hernia, in passing through this opening, receives the intercolumnar fascia as one of its coverings.* ment. 17. Pyramidalis muscle. 18. Internal oblique. 19. Conjoined tendon of the internal oblique and transversalis descending behind Poupart’e ligament to the pectineal line. 20. The arch formed between the lower curved border of the internal oblique muscle and Poupart’s ligament; it is beneath this arch that the spermatic cord and oblique inguinal hernia pass. * In connexion with this and the two following muscles the student should refer to the description of hernia at page 303. INTERNAL OBLIQUE MUSCLE. 233 Relations.—By its external surface witli the superficial fascia, integument, cutaneous vessels and nerves, particularly the super- ficial epigastric and superficial circuinflexa ilii vessels, and latissi- mus dorsi, by which it is overlapped posteriorly. By its internal surface with the internal oblique, lower part of the eight inferior ribs and intercostal muscles, cremaster, spermatic cord in the male, and round ligament in the female. The upper border of the ex- ternal oblique is continuous with the pectoralis major. Nerve Supply.—Anterior branches of the lower intercostals. The external oblique is now to be removed by making an incision from the anterior superior spine of the ilium towards the umbilicus as far as the aponeurosis can be separated from the subjacent muscle. From this latter point an incision is to be made to the crest of the pubis, and the aponeurosis included in these incisions to be turned down to Poupart’s ligament. The remainder of the muscle may be removed by carrying a pei’pendicular incision from the end of the first up to the chest, and dissecting off the aponeu- rosis and muscle. The Internal oblique muscle (obliquus internus abdominis, ascendens; ilio-abdominalis) is the middle fiat muscle of the abdo- men. It arises from the outer half of Poupart’s ligament, from the middle of the crest of the ilium for two-thirds its length, and from the fascia lumborum. Its fibres diverge from their origin, those from Poupart’s ligament curving downwards, those from the ante- rior part of the crest of the ilium passing transversely, and the rest ascending obliquely. The muscle is inserted into the pectineal line and crest of the pubes, linea alba, and lower border of the four in- ferior ribs. At its origin from the fascia lumborum it becomes the bond of union between the aponeurosis of the transversalis and that of the latissimus dorsi. Along the upper three-fourths of the linea semilunaris, the aponeurosis of the internal oblique separates into two lamellae, which pass one in front, the other behind the rectus muscle to the linea alba, where they are inserted; along the lower fourth, the aponeurosis passes in front of the rectus without separation. The two layers, which thus enclose the rectus, consequently form for it a sheath, which is incomplete at its posterior and inferior part. The lowest fibres of the internal oblique are inserted into the pectineal line of the pnbes in common with those of the trans- versalis muscle. Hence the tendon of this insertion is called the conjoined tendon of the internal oblique and transversalis. This tendon is situated directly behind the external abdominal ring, and serves to strengthen what would otherwise be a weak point in the abdomen. Sometimes the tendon is insufficient to resist the inter- nal pressure and is forced through the external ring; it then forms the distinctive covering of direct inguinal hernia. The spermatic cord passes beneath the arched border of the internal oblique muscle, between it and Poupart’s ligament. The interval between this lower border and Poupart’s ligament is there- 234 MUSCLES OF THE ABDOMEN. fore called the spermatic or inguinal canal. During its passage some fibres are given off from the lower border of the muscle, which accompany the cord downwards to the testicle, and form loops around it; this is the cremaster muscle. In the descent of oblique inguinal hernia, which travels the same course as the spermatic cord, the cremaster muscle forms one of its coverings. The Cremaster, considered as a distinct muscle, arises from the middle of Poupart’s ligament, and forms a series of loops upon the spermatic cord. A few of its fibres are inserted into the tunica vaginalis, the rest (crus internum) ascend along the inner side of the cord, to be inserted, with the conjoined tendon, into the pecti- neal line of the os pubis. Relations.—The internal oblique is in relation by its external surface with the external oblique, latissimus dorsi, spermatic cord, and external abdominal ring. By its internal surface with the transversalis muscle, fascia transversalis, internal abdominal ring, and spermatic cord. By its lower and arched border with the spermatic cord; forming the upper boundary of the spermatic canal. The cremaster is in relation by its external surface with the aponeurosis of the external oblique, and intercolumnar fascia ; by its internal surface with the fascia propria of the spermatic cord. The internal oblique muscle is to be removed by separating it from its attachment, to the ribs above, the crest of the ilium and Poupart’s ligament below. It should be divided behind by a verti- cal incision extending from the last rib to the crest of the ilium, as its lumbar attachment cannot at present be examined. The muscle is then to be turned forwards. Some degree of care will be required in performing this dissection, from the difficulty of distinguishing between this muscle and the one beneath. A thin layer of cellular tissue is all that separates them for the greater part of their extent. Near the crest of the ilium the circumflexa ilii artery ascends be- tween the two muscles, and forms a guide to their separation ; but just above Poupart’s ligament they are so closely united, that sepa- ration is impossible. Nerve Supply.—Ilio-inguinal and ilio-irppogastric of first lumbar, and anterior branches of lower intercostals. The Transversalis (lumbo-abdominalis) is the internal flat muscle of the abdomen; and is transverse in the direction of its fibres, as implied in its name. It arises from Poupart's ligament, somewhat less than the outer half, from the anterior two-thirds of the internal lip of the crest of the ilium ; from the transverse processes of the lumbar vertebrae through the medium of the posterior aponeurosis, and from the inner surface of the six inferior costal cartilages. The superior fibres, proceeding from the cartilage of the seventh rib, are inserted into the ensiform cartilage; the inferior fibres, proceeding from Poupart’s ligament, curve down- wards to be inserted by means of a tendinous expansion common to it, and the internal oblique, the conjoined tendon of the internal TRANSVERSALIS. 235 oblique and transversalis, into the pectineal line of the pubes; while the fibres intermediate between these points terminate near the outer border of the rectus in an aponeurosis, which is continued onwards to the litiea alba. The upper portion of the aponeurosis, closely united with the posterior lamella of the aponeurosis of the internal oblique, assists in form- ing the posterior wall of the sheath of the rectus, while the inferior portion, commencing at a point midway between the umbilicus and pubes, is continued with the undivided aponeurosis of the in- ternal oblique in front of the rectus. The posterior aponeurosis of the transversalis divides into three lamellae, anterior, middle, and pos- terior, which constitute the fascia lumborum. The anterior lamella, thin and membranous, is at- tached to the base of the trans- verse processes of the lumbar vertebrae; the middle lamella, of considerable thickness, to their apices; the posterior layer re- ceives the attachment of the pos- terior aponeurosis of the internal oblique, and farther back, near the border of the erector spinas, becomes united with the aponeu- rosis of the latissimus dorsi. Be- tween the anterior and middle lamella is lodged the quadratus lumborum ; and between the middle and posterior layer, the erector spinae and multifidus spinas, which are thus furnished with aponeu- Fig, 154.* * Lateral view of the trunk, showing its muscles, particularly the trans- versalis abdominis. 1. Costal origin of the latissimus dorsi. 2. Serratus inagnus. 3. Upper part of the external oblique, divided in the direction best calculated to show the muscles beneath without interfering with its indigita- tions with the serratus magnus. 4. Two of the external intercostal muscles. 5. Two of the internal intercostals. 6. Transversalis. 7. Its posterior apo- neurosis. 8. Its anterior aponeurosis forming the posterior layer of the sheath of the rectus. 9. Lower part of the left rectus with the aponeurosis of the transversalis passing in front. 10. Eight rectus muscle. 11. Arched opening left between the lower border of the transversalis muscle and Poupart’s liga- ment, through which the spermatic cord and oblique inguinal hernia pass. 12. Tensor vagina) femoris, gluteus medius and maximus invested by fascia lata. 236 MUSCLES OF THE ABDOMEN. Relations.—By its external surface with the internal oblique, the internal surface of the six lower ribs, and internal intercostal muscles. By its internal surface with the transversalis fascia, which separates it from the peritoneum, with the psoas magnus, the lower part of the rectus, and pyramidalis. The spermatic cord and oblique inguinal hernia pass beneath the lower border, but have no direct relation with it. The upper border is continuous with the diaphragm and triangularis sterni. Nerve Supply.—Anterior branches of lower intercostals. To dissect the rectus muscle, its sheath should be opened by a vertical incision extending from over the cartilages of the lower ribs to the front of the os pubis. The sheath may then be dissected off and turned aside ; this is easily done excepting at the line® trans- vers®, where a close adhesion subsists4between the muscle and the external wall of the sheath. The sheath contains the rectus and pyramidalis muscle. The Rectus (sterno-pubis) arises by a double tendon from the front and crest of the os pubis, and is inserted by three broad digi- tations into the cartilages of the fifth, sixth, and. seventh ribs. It is traversed by several tendinous intersections, called line® trans- vers® (inscriptiones tendine®). One of these is situated at the umbilicus, one over the ensiform cartilage, and one midway between these points; when a fourth exists, it occurs below the umbilicus. The line® transvers® are vestiges of the abdominal ribs of reptiles, and rarely extend completely through the muscle. Relations.—By its external surface with the anterior lamella of the aponeurosis of the internal oblique, below with the aponeurosis of the transversalis, and with the pyramidalis. By its internal surface with the ensiform cartilage, cartilages of the ribs from the fifth to the ninth, posterior lamella of the internal oblique, perito- neum, and epigastric artery and veins. Nerve Supply.—The ilio-hypogastric and anterior branches of intercostal nerves. The Pyramidalis (pubio-subumbilicalis) arises from the crest of the os pubis in front of the rectus, and is inserted into the linea alba at about midway between the umbilicus and pubes. It is enclosed in the sheath with the rectus, and rests against the lower part of that muscle ; it is sometimes absent. Nerve Supply.—The ilio-hypogastric nerve. The rectus may now be divided across the middle, and the two ends drawn aside for the purpose of examining the mode of con- struction of its sheath. The sheath of the rectus is formed, in front, for the upper three- fourths of its extent, by the aponeurosis of the external oblique and anterior lamella of the internal oblique; behind by the posterior lamella of the internal oblique and aponeurosis of the transversalis. Midway between the umbilicus and the pubes, the posterior wall of the sheath terminates in a thin curved margin (plica semilunaris, Douglassii) the aponeurosis of the three muscles passing, below this point, altogether in front of the rectus. QUADRATUS LUMBORUM—DIAPHRAGM. 237 The next two muscles can be examined only when the viscera of the abdomen are removed. To see the quadratus lumborum, it is also necessary to divide and draw aside the psoas muscle and the anterior lamella of the posterior aponeurosis of the transversalis. The Quadratus Lumborum (ilio-costalis) is concealed from view by the anterior lamella of the posterior aponeurosis of the trans- versalis muscle, which is inserted into the bases of the transverse processes of the lumbar vertebra}. When this lamella is divided, the muscle will be seen to consist of two portions :—one, the external, arising from the ilio-lumbar ligament and outer lip of the crest of the ilium for two inches in extent, and inserted into the apices of the transverse processes of the four upper lumbar vertebrae (sometimes also last dorsal) and last rib; the other, the internal and anterior portion, arises by tendinous slips from the transverse processes of the three or four lower lumbar vertebrae, and passes upwards to be inserted into the lower border of the last rib. If the muscle be cut across or removed, the middle lamella of the aponeurosis of the transversalis will be seen, attached to the apices of the transverse processes ; the quadratus being enclosed between the two lamella} as in a sheath. Relations.—Enclosed in the sheath formed by the aponeurosis of the transversalis muscle, it is in relation, in front, with the kidney, colon, psoas magnus, and diaphragm. Behind, but also separated by its sheath, with the erector spiriee. Nerve Supply.—Posterior branches of the lumbar nerves. The Psoas parvus is a small and infrequent muscle which arises from the last dorsal and first lumbar vertebra and from the inter- vertebral substance between them, and terminates in a long slender tendon which expands interiorly and is inserted into the ilio-pecti- neal line and eminence. The tendon is continuous by its outer border with the iliac fascia. Relations.—It rests on the psoas magnus, and is covered in by the peritoneum; superiorly it passes beneath the ligamentum arcuatum internum of the diaphragm. Nerve Supply.—Branches of the lumbar plexus. Diaphragm.—To obtain a good view of this important inspi- ratory muscle, the peritoneum should be dissected from its under surface. It is a transverse muscular septum between the thorax and abdomen, and is composed of two portions, thoracic and lumbar, the former being named the greater, the latter the lesser muscle. The thoracic portion arises from the ensiform cartilage by a dis- tinct slip and from the internal surface of the six inferior ribs indi- gitating with the transversalis. The fibres converge to be inserted into the central tendon. A triangular interval exists between the sternal and costal portion of the muscle at each side, closed by a few irregular muscular fibres and by the serous membranes of the cavity of the chest and abdo- men. A protrusion of any portion of the contents of the abdomen through this opening constitutes phrenic or diaphragmatic hernia. The lumbar portion consists of a right and left lateral half (pil- 238 MUSCLES OF THE ABDOMEN. lars, crura); each of which is composed of three smaller pillars or crura, internal, middle, and external. The crura arise from the front and lateral aspect of the bodies of the first, second, and third lumbar vertebrae, from the inter- vertebral substance between the first, second, third, and fourth, from the transverse process of the first, ligamentum arcuatum internum and externum, and last rib. The left crus is shorter than Fig. 155.* the right by the breadth of a vertebra, and does not advance so far forward on the front of the vertebral column. The crura are inserted into the whole length of the posterior border of the central tendon. The origin of the crura takes place by a strong tendon, from which and from the other points of attachment muscular fibres proceed. The internal pillar of the crus is its anterior fasciculus, which proceeds from the third lumbar vertebra; the middle pillar, smaller than the others, proceeds from the second vertebra; the external pillar, the largest of the three, from the first lumbar ver- tebra, ligamenta arcuata and last rib. The internal pillars ap- proach each other as they ascend, the arched interval between them being the aortic opening; their internal fibres, consisting of several fasciculi, cross each other in front of the aortic opening and * The diaphragm viewed from the front, showing its upper or throracic surface. 1, 1. The lateral segments of the thoracic portion; arising from 2, 2. The cartilages of the ribs; and inserted into 3. The central tendon. The right segment is seen to be higher than the left. 4. The fasciculus which arises from the ensiform cartilage. 5, 5. Lateral leaflets of the central tendon. 6. Opening for the inferior vena cava. 7. The oesophagus. 8. The thoracic aorta. 9. The abdominal aorta. 10. The tendon of the right crus of the dia- phragm ; that of the left is seen immediately above on the lumbar vertebras. 11, 11. The psoas muscles. DIAPHRAGM. 239 form the lateral boundaries of another opening of elliptical shape (oesophageal), and are then lost in the central tendon. In the de- cussation between the aortic and oesophageal opening the fibres of the right internal pillar are generally the most superficial. Between Fig. 156.* the lumbar and costal portion of the diaphragm at each side is a triangular interval like that between the costal and sternal portion, closed only by cellular tissue and the serous membranes of the two cavities. * Under or abdominal side of tbe diaphragm. 1, 2, 3. The thoracic portion; figure 1 rests on the central leaflet of the tendinous centre; figure 2 on the left or smallest leaflet: figure 3 on the right leaflet. 4. Fasciculus from the ensiform cartilage ; a small triangular space, closed only by the serous mem- branes of the abdomen and chest, is left on either side of the fasciculus. 5. Ligamentum arcuatum externum of the left side. 6. Ligamentum arcua- tum internum. 7. A small arched opening occasionally found, through which the lesser splanchnic nerve passes. 8. Tendon of the right or larger crus; a muscular fasciculus from this tendon curves to the left side of the greater muscle between the oesophageal and aortic opening. 9. Fourth lumbar ver- tebra. 10. Tendon of the left or shorter crus. 11. Aortic opening occupied by the cylinder of the aorta. 12. Portion of the oesophagus issuing through the oesophageal opening; in this figure the oesophageal opening is tendinous at its anterior part, a state that is not uncommon. 13. Opening for the infe- rior vena cava, in the tendinous centre of the diaphragm. 14. Psoas magnus passing beneath the ligamentum arcuatum internum; it has been removed on the opposite side to show the arch more distinctly. 15. Quadratus lumborum passing beneath the ligamentum arcuatum externum; this muscle has also been removed on the left side. 240 MUSCLES OF THE ABDOMEN. The ligamentum arcuatum internum is a tendinous arch thrown across the upper part of the psoas muscle from the side of the body of the first lumbar vertebra to the apex of its transverse process, extending sometimes also to that of the second. Beneath this arch the psoas magnus emerges from the chest. The ligamentum arcuatum externum is a tendinous band extended from the apex of the transverse process of the first lumbar vertebra to the lower border of the last rib. It forms an arch across the quadratus lumborum and is continuous with the anterior wall of the sheath of that muscle derived from the posterior aponeurosis of the transversalis abdominis. The tendinous centre of the diaphragm is shaped like a trefoil leaf, of which the central leaflet points to the ensiform cartilage, and is the largest; the lateral leaflets, right and left, occupy the corresponding portions of the muscle; the right being the larger and rounded, the left smaller and lengthened in its form. The openings in the diaphragm are three: one, quadrilateral, in the tendinous centre, at the union of the right and middle leaflets, for the passage of the inferior vena cava; a muscular opening of an elliptical shape formed by the internal pillars of the crura, the oesophageal, for the transmission of the oesophagus and pneumo- gastric nerves; a third, the aortic, formed by a tendinous arch thrown from the tendon of one crus to that of the other, beneath which pass the aorta and thoracic duct. The great splanchnic nerve passes through the diaphragm between the internal and middle pillar of the crus ; the trunk of the sympathetic and vena azygos between the middle and external pillar. The lesser splanch- nic nerve escapes between those fibres of the external pillar which proceed from the ligamentum arcuatum internum. Relations.—By its superior surface with the pleurae, pericardium, heart, and lungs. By its inferior surface with the peritoneum ; on the left with the stomach and spleen; on the right with the convexity of the liver; behind with the kidneys, supra-renal capsules, duodenum, and solar plexus. By its circumference with the ensiform cartilage, ribs, intercostal muscles, and vertebral column. Nerve Supply.—The phrenic nerve, derived from the third, fourth, and fifth cervical. Actions.—The external oblique muscle, acting singly, would draw the thorax towards the pelvis, and twist the body to the opposite side. Both muscles, acting together, flex the thorax directly on the pelvis. The internal oblique of one side draws the chest down- wards and outwards; both together bend it directly forwards. Either transversalis muscle, acting singly, will diminish the size of the abdomen on its own side, and both together will constrict the entire cylinder of the cavity. The recti muscles, assisted by the pyramidales, flex the thorax towards the pelvis, and, through the medium of the linese transversse, are enabled to act when their sheath is curved inwards by the action of the transversales. The MUSCLES OF THE PERINEUM. 241 pyramidales are tensors of the linea alba. The abdominal are ex- piratory muscles, and chief agents in expulsion ; by their action, the foetus is expelled from the uterus, the urine from the bladder, faeces from the rectum, bile from the gall-bladder, ingesta from the stomach and bowels in vomiting, and mucus and irritating sub- stances from the bronchial tubes, trachea, and nasal passages during coughing and sneezing. To produce these effects, they all act together. Their violent and continued action produces hernia, and, acting spasmodically, they may occasion rupture of the viscera. The quadratus lumborum draws the last rib downwards, and is an ex- piratory muscle; it also serves to bend the vertebral column to one or the other side. The psoas parvus is a tensor of the iliac fascia, and, taking its fixed origin from below, may assist in flexing the vertebral column forwards. The diaphragm is an inspiratory muscle, and the sole agent in tranquil inspiration. When in action, the muscle is drawn downwards, its plane being rendered oblique from the level of the ensiform cartilage, to that of the upper lumbar vertebra. During relaxation it is convex, and encroaches conside- rably on the cavity of the chest, particularly at the sides, where it corresponds with the lungs. It assists the abdominal muscles powerfully in expulsion, every act of that kind being preceded or accompanied by inspiration. Spasmodic action of the diaphragm produces hiccough and sobbing, and its rapid alternation of con- traction and relaxation, combined with laryngeal and facial move- ments, laughing and crying. MUSCLES OF THE PEK1NEUM. The muscles of the perineum are situated in the outlet of the pelvis, and consist of two groups, one of which belongs especially to the organs of generation and urethra, the other to the termination of the alimentary canal. To these may be added the anterior muscles of the coccyx. The muscles of the perineal region in the male, are the Accelerator urinse, Erector penis, Transversus perinei, Compressor urethrae, Sphincter ani, Levator ani, Coccygeus, Sacro-coccygeus anticus. Dissection.—To dissect the perineum, the subject should be fixed in the position for lithotomy, that is, the hands should be bound to the soles of the feet, and the knees kept apart. An easier plan is the drawing of the feet upwards by means of a cord passed through a hook in the ceiling. Both of these means of preparation have for their object the full exposure of the perineum. And as this is a dissection which demands some degree of delicacy and nice manipu- lation, a strong light should be thrown upon the part. A large sound is to be introduced into the bladder, and a string, tied round the testicles, to be fixed to its handle. This will retain the sound in the bladder and put the perineum on the stretch. An incision is 242 MUSCLES OF THE PERINEUM. to be made through the skin round the verge of the anus, and four others radiating from it—one to the tip of the coccyx, another to the base of the scrotum, and one on each side to the tuberosities of the ischium. The four flaps are to be dissected back with great care, the integument alone being removed so as to expose the sub- cutaneous sphincter and the superficial fascia, the description of which will be found in the section relating to the fasciae. After the fascia has been carefully dissected off and the perineal vessels and nerves turned aside, the muscles are brought into view. The Acceleratores urinas (bulbo-cavernosi) arise from a ten- dinous point in the centre of the perineum and from the fibrous raphe of the two muscles. From this origin the fibres diverge like Fig. 157.* the barbs of a pen; the posterior to be inserted into the triangular ligament and ramus of the pubes; the middle, to encircle the cor- pus spongiosum and meet on its upper side; the anterior, to spiead out on the corpus cavernosum at each side, and he inserted partly into its fibrous structure, and partly into the fascia penis. The posterior and middle insertions of these muscles are best seen by carefully raising one muscle from the corpus spongiosum and tracing Relations.—By their superficial surface with the superficial * Muscles of tlie perineum. 1. Acceleratores urinro; the figure rests on the corpus spongiosum penis. 2. Corpus cavernosum of one side. 3. Erector penis of one side. 4. Transversus perinei of one side. 5. Triangular space, through which the triangular ligament is seen. 6. Sphincter am; its ante- rior extremity cut off. 7. Levator ani of the left side; the deep space between the tuberosity of the ischium (8) and the anus, is the ischio-rectal fossa ; the same fossa is seen on the opposite side. 9. Spine of the ischium. 10. Left coccygeus muscle. The boundaries of the perineum are well exhibited in this engraving. ERECTOR PENIS—COMPRESSOR URETHRiE. 243 perineal fascia, dartos, superficial vessels and nerves of the perineum, and, on each side, the erector penis. By their deep surface with the corpus spongiosum and bulb of the urethra. The Elector penis (ischio-cavernosus) arises from the tuberosity of the ischium and from the ramus of the pubes on each side of the crus, and curves around the root of the penis; to be inserted into the upper surface of the corpus cavernosum, where it is continuous with a strong fascia which covers the dorsum of the organ, the fascia penis. Relations.—By its superficial surface with the superficial perineal fascia, dartos, and superficial perineal vessels and nerves. By its deep surface with the corpus cavernosum penis. Nerve Supply.—The perineal branch of the pudic nerve supplies the accelerators urinae and the erector penis. The Transversus perinei arises from the ramus of the ischium at each side, and is inserted into the central tendinous point of the perineum; where it is connected with the accelerator urinae and sphincter ani. Occasionally the transversus perinei is of large size, and spreads out as it approaches the middle line so as to become fan-shaped. The posterior fibres are continuous with those of the muscle of the opposite side; but the anterior are prolonged forwards upon the bulb and corpus spongiosum of the urethra as far as the middle of the penis, forming a broad layer which usurps the place and office of the accelerator uringe. A small slip of muscle is sometimes found in front of the trans- versus perinei: this is the transversus perinei alter. By its inner end it is continuous with the accelerator. Relations.—By its superficial surface with the superficial perineal fascia, and superficial perineal vessels and nerves. By its deep sur- face with the triangular ligament and internal pudic artery and veins. By its posterior border it is in relation with that portion of the superficial perineal fascia which passes upwards to become con- tinuous with the triangular ligament. Nerve Supply.—The perineal branch of the pudic nerve. To dissect the compressor urethrae, the three preceding muscles should be removed, so as to render the glistening surface of the triangular ligament apparent. This ligament should then be care- fully dissected away, and the corpus spongiosum penis divided through its middle, separated from the corpus cavernosum, and drawn forwards in order to put on the stretch the membranous por- tion of the urethra, with which the compressor muscles are con- nected. The compressor urethrae is, however, better seen in a dissection made from within the pelvis, after having turned down the bladder from its attachment to the os pubis, and removed a plexus of veins together with the pelvic fascia. The Compressor urethrae (constrictor urethrae membranaceae, constrictor isthmi urethrae) directed transversely across the peri- neum above the triangular ligament arises from the ramus of the pubes and ischium, their point of union, and from the anterior 244 MUSCLES OF THE PERINEUM. ligament of the bladder and prostate gland. Proceeding inwards it divides into two fan-shaped fasciculi, superior and inferior, which embrace the membranous portion of the urethra, and are continuous with the muscle of the opposite side. The superior fasciculus is continued forwards to the junction of the crura penis, and backwards to the prostate gland; on the upper surface of which it is spread out. The inferior fasciculus is attached to the bulb of the urethra in front, and extends to the prostate gland, behind. A third fasciculus, closely united with the two pre- ceding, consists of circular fibres, which enclose and form a muscu- lar sheath for the membranous part of the urethra. Under the name of Wilson’s muscles, a fourth fasciculus has been described as descending vertically from the body of the pubes, near the symphysis, to unite with the superior fasciculus of the compressor urethrae. This fasciculus is inconstant and its exis- tence doubtful. Nerve Supply.—The perineal branch of the pudic. The Sphincter ani is a thin and elliptical plane of muscle closely adherent to the integument, and surrounding the opening of the anus. It arises posteriorly in the superficial fascia around the coccyx, and by a fibrous raphe from the apex of that bone; and is inserted anteriorly into the tendinous centre of the perineum, and into the raphe of the integument, nearly as far forward as the com- mencement of the scrotum. Relations.—By its superficial surface with the integument. By its deep surface witli the internal sphincter, levator ani, cellular tissue and fat of the ischio-rectal fossa, and in front -with the super- ficial perineal fascia. The Sphincter ani internes is a muscular band embracing the extremity of the intestine, and formed by an aggregation of the circular muscular fibres of the rectum. Nerve Supply.—The sphincters are supplied by the anterior branch of the fourth sacral, and inferior hmmorrhoidal branch of the internal pudic. Part of the levator ani may be seen during the dissection of the Fig. 158.* * Posterior view of the pubes, with part of bladder and urethra attached. 1. Body of pubes. 2. Banius. 3. Obturator intemus muscle. 5. Portion of the fundus and neck of the bladder laid open. 6. Prostate gland. 7. Trans- verse fibres of the compressor urethrae, passing above the urethra. 8. Similar fibres passing beneath that canal. LEVATOR ANI—FEMALE PERINEUM. 245 anal portion of the perineum by removing the fat which surrounds the termination of the rectum in the ischio-rectal fossa. But to study the entire muscle, a lateral section of the pelvis must be made by sawing through the pubes a little to one side of the sym- physis, separating the bones behind at the sacro-iliac symphysis, and turning down the bladder and rectum. The pelvic fascia is then to be carefully raised, beginning at the base of the bladder and proceeding upwards, until the whole extent of the muscle is exposed. The Levator ani is a thin plane of muscular fibres, situated at each side of the pelvis. The muscle arises from the inner surface of the os pubis near the pubic arch, from the base and upper border of the spine of the ischium, and between those points, from a ten- dinous arch which occupies the line of division of the pelvic fascia into obturator fascia and recto-vesical fascia. Its fibres descend to be inserted into its fellow of the opposite side beneath the prostate gland, into the rectum, and behind the rectum into its fellow of the opposite side and the side of the extremity of the coccyx. Its an- terior fibres are sometimes described separately, under the name of levator prostati. In the female this muscle has an additional insertion into the vagina. Relations.—By its external or perineal surface, with a thin layer of fascia, by which, and by the obturator fascia, it is separated from the obturator internus muscle; with the fat in the ischio-rectal fossa, triangular ligament, sphincter ani, and posteriorly, gluteus maximus. By its internal or pelvic surface with the pelvic fascia, which separates it from the viscera of the pelvis and peri- toneum. Nerve Supply.—The anterior branch of the fourth sacral. The Coccygeus muscle, thin and triangular, arises from the spine of the ischium and lesser sacro-ischiatic ligament, and spreads out to be inserted into the side of the coccyx and lower part of the sacrum. Relations.—By its internal or pelvic surface with the cavity of the pelvis; by its external surface with the lesser sacro-ischiatic ligament; and by its borders, with the pyriformis above, and levator ani below. The Sacro-coccygetts anttcus (curvator coccygis), the analogue of an important muscle in brutes, but rudimentary in man, and more tendinous than fleshy in structure, is a small muscle which arises from the side of the last piece of the sacrum and first of the coccyx; and is inserted into the front of the last piece of the coccyx in common with its fellow of the opposite side. Sometimes it gives lateral offsets to the outer side of the second and third piece of the coccyx. Nerve Supply.—These two last muscles are supplied by the fourth and fifth sacral and coccygeal nerves. Female Perineum.—The muscles of the perineum in the female 246 MUSCLES OF THE PEKINEUM. are the same as in the male, and have received analogous names. They are smaller in size, and are modified to suit the difference of form of the organs; they are Constrictor vaginae, Erector elitoridis, Transversus perinei, Compressor urethrae, Sphincter ani, Levator ani, Coccygeus, Sacro-coccygeus anticus. The Constrictor vagina is analogous to the accelerator urinae of the male; it arises from the tendinous centre of the perineum, where it is continuous with the sphincter ani and transversus perinei; and passes forwards on each side of the entrance of the vagina, to be in- serted into the corpus cavernosum clitoridis. The Erector clito- ridis arises from the ramus of the ischium, and is inserted on each side into the crus clito- ridis. It is in relation by its inner border with the. constrictor vaginas. The Transversus pe- rinei is a small muscle arising on each side from the ramus of the ischium, and inserted into the side of the constrictor vaginas. The Compressor urethra has the same origin and insertion, and exercises the same functions in the female as in the male. The Sphincter ani and Sphincter ani internus surround the lower extremity of the rectum, as in the male. The Levator ani is inserted into the side of the vagina and rectum. The Coccygeus and Sacro-coccygeus anticus are identical with the same muscles in the male. Fig. 159.* * Muscles of the female perineum. 1. Anterior commissure of the labia rnajora. 2. Clitoris. 3. Vestibulum; the small opening below the number being the meatus urethras. 4. The vagina, encircled by 5, 5. The constrictor vaginae. 6, 6. The sphincter ani, enclosing the anus, and interlacing in front with the constrictor vagina;, the point of interlacement being the perineum. 7, 7. The tuberosity of the ischium; from which is seen arising 8. The transversus perinei; and 9. The erector elitoridis. 10, 10. The crura clito- ridis. 11, 11. Levator ani. 12, 12. Gracilis. 13, 13. Adductor magnus. 14, 14. Gluteus maximus. FEMALE PERINEUM. 247 Nerve Supply.—These muscles are supplied by tbe same nerves as the corresponding muscles of the male perineum. Actions.—The acceleratores urinre being continuous at the middle line, and attached at each side to the triangular ligament, by means of their posterior fibres, support the bulbous portion of the urethra, and acting forcibly, propel the semen, or the last drops of urine from the canal. The posterior and middle fibres, according to Krause,* contribute to the erection of the corpus spongiosum, by compressing the venous structure of the bulb; and the anterior fibres, according to Tyrrell,f assist in the erection of the entire organ by compressing the vena dorsalis, by means of their insertion into the fascia penis. The erector penis becomes entitled to its name from spreading out on the dorsum of the organ into a mem- branous expansion (fascia penis), which, according to Krause, compresses the dorsal vein during the action of the muscle, and especially after the erection of the organ has commenced. The transverse muscles serve to steady the tendinous centre, that the muscles attached to it may obtain a firm point of support. Ac- cording to Cruveilhier, they draw the anus backwards during the expulsion of the fasces, and antagonise the levatores ani, which carry the anus forwards. The compressor urethrae, taking its fixed point from the ramus of the ischium at each side, can, says Guthrie, “ compress the urethra so as to close it; I conceive completely, after the manner of a sphincter.” The external sphincter, being a cutaneous muscle, contracts the integument around the anus, and by its attachment to the tendinous centre of the perineum and point of the coccyx, assists the levator ani in giving support to the opening during expulsive efforts. The internal sphincter contracts the extremity of the cylinder of the intestine. The use of the leva- tor ani is expressed in its name; it is the antagonist of the diaphragm and abdominal expulsory muscles, and serves to support the rectum and vagina during their expulsive efforts. The levator ani acts in unison with the diaphragm, and rises and falls like that muscle in forcible respiration. Yielding to the propulsive action of the abdominal muscles, it enables the outlet of the pelvis to bear a greater force than a resisting structure, and, on the remission of such action, restores the perineum to its original form. The coc- cygei and sacro-coccygei muscles restore the coccyx to its natural position, after it has been pressed backwards during defalcation or parturition. * Muller, Archiv fiir Anatomie, Physiologic, &c. 1837. f Lectures in the College of Surgeons. 1839. 248 MUSCLES OF THE UPPER EXTREMITY. The muscles of the upper extremity may be arranged into groups corresponding with the respective regions of the limb, as follows:— Anterior Thoracic Region. Pectoralis major, Pectoralis minor, Subclavius. Lateral Thoracic Region. Serratus magnus. Anterior Scapular Region. Subscapularis. Posterior Scapular Region. Supra-spinatus, Infra-spinatus, Teres minor, Teres major. Acromial Region. Deltoideus. Anterior Humeral Region. Coraco-brachialis, Biceps brachii, Brachialis anticus. Anterior Brachial Region, superficial layer. Pronator radii teres, Flexor carpi radialis, Palmaris longus, • Flexor sublimis digitorum, Flexor carpi ulnaris. deep layer. Flexor profundus digitorum, Flexor longus pollicis, Pronator quadratus. Posterior Humeral Region. Triceps bracbii. Posterior Brachial Region, superficial layer. Supinator longus, Extensor carpi radialis longior, Extensor carpi radialis brevior, Extensor communis digitorum, Extensor minimi digiti, Extensor carpi ulnaris, Anconeus. deep layer. Supinator brevis, Extensor ossis metacarpi pollicis, Extensor primi internodii pollicis, Extensor secundi internodii poll: Extensor indicis. Radial Region (Thenar). Abductor pollicis, Flexor ossis metacarpi (opponens), Flexor brevis pollicis, Adductor pollicis. HAND. Ulnar Region (Hypothenar). Palmaris brevis, Abductor minimi digiti, Flexor brevis minimi digiti, Flexor ossis metacarpi. Lumbricales, Interossei palmares, Interossei dorsales. Palmar Region. MUSCLES OF THE UPPER EXTREMITY. 249 Anterior Thoracic Region. Dissection.—Make an incision along the line of the clavicle, from the upper part of the sternum to the acromion process, and thence down the arm as far as the level of the lower border of the latis- simns dorsi; a second carried transversely ontwards from the base of the ensiform cartilage to the posterior border of the axilla; and connect the two by a third, carried longitudinally along the middle of the sternum. The integument and superficial fascia are to he dissected separately from off the fibres of the muscle, and always in the direction of their course. For this purpose the dissector, if he have the right arm, will commence with the lower angle of the flap; if the left, with the upper angle. He will thus expose the pectoralis major muscle in its whole extent. Pectoralis major, Pectoralis minor, Subclavius. The Pectoralis major (sterno-humeralis) arises from the sternal half of the clavicle, from half the sternum its whole length, from the cartilages of all the true ribs, excepting the first and last, and from the aponeurosis of the external oblique muscle of the abdomen. From this extensive origin the fibres converge to be inserted by a broad and folded tendon into the external bicipital ridge of the humerus. The pectoralis major admits of a division into three portions, cla- vicular, sternal, and costal; the two former are separated from each other by a well-marked cellular interspace; the latter is dis- tinguished not only by its origin, but also by forming a fold beneath the sternal portion, and lying behind it at its insertion. At the latter point the three portions are superimposed, the clavicular being in front, the sternal next, the costal behind; the clavicular portion being prolonged at its insertion to the lower extremity of the bicipital ridge, the costal portion to its upper end. Relations.—By its external surface with the fibres of origin of the platysma myoides, mammary gland, superficial fascia and in- tegument. By its internal surface, on the thorax, with the clavicle, sternum, costal cartilages, intercostal muscles, subclavius, pecto- ralis minor, and serratus magnus; in the axilla, with the axillary vessels and glands. By its external border with the deltoid, from which it is separated above by a cellular interspace lodging the cephalic vein and descending branch of the thoracico-acromialis artery. Its lower border forms the anterior boundary of the axil- lary space. Nerve Supply.—External and internal anterior thoracic branches of the brachial plexus. The pectoralis major is to be removed by dividing its fibres along the lower border of the clavicle, and then carrying the in- cision perpendicularly downwards, parallel to the sternum, and at about three inches from its border. Divide some loose cellular tissue, and several small branches of the thoracic arteries, and 250 MUSCLES OF THE UPPER EXTREMITY. reflect the muscle outwards. We thus bring into view a region of considerable interest, in the middle of which is situated the pec- toralis minor. The Pectoralis mix or (costo-coracoideus) arises by three digita- tions from the front and upper border of the third, fourth, and fifth rib near their cartilages; and is inserted by a broad tendon into the anterior border and apex of the coracoid process of the scapula. It is closely united at its insertion with the coraco-brachialis. Relations.—By its anterior surface with the pectoralis major and superior thoracic vessels and nerves. By its posterior surface with the ribs, intercostal muscles, serratus magnus, axillary space, and axillary vessels and nerves. Its upper border forms the lower boundary of a triangular space, bounded above by the costo-coracoid membrane, and internally by the ribs; in this space are found the axillary vessels and nerves. Nerve Supply.—Internal anterior thoracic from the inner cord of the brachial plexus. The Subclavius (costo-clavicularis) arises by a round tendon from the cartilage and adjacent osseous part of the first rib; it is inserted into the under surface of the clavicle as far as the coraco- clavicular ligament. This muscle is enclosed in a partial sheath by the costo-coracoid membrane, an extension of the deep cervical fascia. Relations.—By its upper surface with the clavicle. By the lower with the subclavian artery and vein and brachial plexus, which separate it from the first rib. In front with the pectoralis major, the costo-coracoid membrane being interposed. Nerve Supply.—A branch from the fifth and sixth cervical. Actions.—The pectoralis major draws the arm against the thorax, while its upper fibres assist the upper part of the trapezius in raising the shoulder, as in supporting weights. The lower fibres depress the shoulder with the aid of the latissimus dorsi. Taking its fixed point from the shoulder, the pectoralis major assists the pectoralis minor, subclavius, and serratus magnus, in drawing up and expanding the chest. The pectoralis minor, in addition to this action, draws upon the coracoid process, and assists in rotating the scapula upon the chest. The subclavius draws the clavicle downwards and forwards, and thereby assists in steadying the shoulder. All the muscles of this group are agents in forced respi- ration, but are incapable of acting in that capacity until the shoulders are fixed. Lateral Thoracic Region. Serratus magnus. The Serratus magnus (serratus, indented like the edge of a saw; costo-scapularis), broad, thin, and trapezoid in shape, arises by nine fleshy serrations from the eight upper ribs, two of the serrations being attached to the second rib, and extends backwards upon the side of the chest, to be inserted into the whole length of the base of SUBSCAPULARIS. 251 the scapula, its anterior aspect. In structure, the muscle is com- posed of three portions, superior, formed by the serrations of the first two ribs, and inserted into the inner surface of the superior angle of the scapula ; middle, composed of the serrations connected with the third and fourth ribs, and inserted into the greater part of the posterior border; inferior, consisting of the last five serrations, these latter indigitate with the obliquus externus and form a thick muscular fasiculus, which is inserted into the scapula near its in- ferior angle. Relations.—By its superficial surface with the pectoralis major and minor, subscapularis, latissimus dorsi, and axillary vessels and nerves. By its deep surface with the ribs and intercostal muscles, to which it is connected by loose cellular tissue. Nerve Siopply.—External respiratory (posterior thoracic) nerve, from the fifth and sixth cervical. Actions.—The serratus magnus is the great external inspiratory muscle, raising the ribs when the shoulders are fixed, and thereby increasing the cavity of the chest. Acting upon the scapula it draws the shoulder forwards, as in the case of diseased lungs, where the chest has become almost fixed from apprehension of the ex- panding action of the respiratory muscles. Anterior Scapular Region. The Subscapularis arises from the whole of the under surface of the scapula excepting the superior and inferior angle, and termi- nates by a broad and thick tendon, which is inserted into the lesser tuberosity of the humerus, and by muscular fibres into the surface of bone immediately below that process. In structure the subscapularis is composed of eight or ten fasciculi, four or five of which arise from one side of as many aponeurotic processes at- tached to the ridges of the venter of the scapula; and. four or five proceed from the other side of the aponeurotic processes and from the surface of bone intervening between them. Its tendon forms part of the capsule of the joint, glides over a large bursa which separates it from the base of the coracoid process, and is lined by a prolongation of the synovial membrane of the articulation. Relations.—By its anterior surface with the serratus magnus, coraco-brachialis, and axillary vessels and nerves. By its posterior surface with the scapula, and shoulder-joint. Nerve Supply.—The short and middle subscapular nerves, branches from the posterior cord of the brachial plexus. Action.—It rotates the head of the humerus inwards, and is a powerful defence to the joint. When the arm is raised, it draws the humerus downwards. Subscapularis. Supra-spinatus, Infra-spinatus, Posterior Scapular Region. Teres minor, Teres major. 252 MUSCLES OF THE UPPER EXTREMITY. The Supra-spinatus muscle {supra, above; spina, the spine) arises from the supra-spinous fossa, spine of the scapula, and. proper investing fascia; and is inserted into the uppermost depression on the greater tuberosity of the humerus; the tendon being united near its attachment with that of the infra-spinatus. The tendon cannot be seen until the acromion process is removed. Relations.—By its upper surface with the trapezius, clavicle, acromion, and coraco-acromial ligament. From the trapezius it is separated by a strong fascia. By its lower surface with the supra- spinous fossa, supra-scapular vessels and nerve, origin of the omo- hyoid muscle, and upper part of the shoulder-joint, forming part of the capsular ligament. Nerve Supply.—The supra-scapular nerve, a branch from the fifth and sixth cervical. The Inpra-spinatus {infra, beneath ; spina, the spine) is covered in by a layer of tendinous fascia, which must be removed before the fibres of the muscle can be seen, the deltoid muscle having been previously turned down from its scapular origin. It arises from the whole of the infra-spinous fossa, excepting a small portion near the neck of the bone, from the spine of the scapula, and from the investing fascia; it is inserted into the middle depression of the greater tuberosity of the humerus ; its tendon being blended with that of the supra-spinatus above and the teres minor below. Relations.—By its posterior surface with the deltoid, latissimus dorsi, trapezius and integument. By its anterior surface with the infra-spinous fossa, supra-scapular and dorsal scapular vessels, and shoulder-joint; its tendon being fined by a prolongation from the synovial membrane. By its upper border it is in relation with the spine of the scapula ; and by the lower with the teres major and minor, being closely united with the latter. Nerve Supply.—The supra-scapular nerve. The Teb.es minor {teres, round) arises from the posterior surface of the lower border of the scapula for about the middle third of its extent; it is connected with the lower border of the preceding muscle, and is inserted into the inferior depression of the greater tuberosity of the humerus. The tendons of the three preceding muscles, with that of the subscapularis, are in immediate contact with the shoulder-joint, and form part of its ligamentous capsule, tliereby preserving the solidity of the articulation. They are there- fore the structures most frequently ruptured in dislocation of the head of the humerus. Relations.—By its posterior surface with the deltoid, and integu- ment. By its anterior surface with the inferior border and part of the dorsum of the scapula, dorsalis scapulae vessels, scapular head of the triceps, and shoulder-joint. By its upper border with the infra-spinatus ; by the lower with the teres major, and long head of the triceps. Nerve_ Supply.—A branch of the circumflex nerve. This branch ACROMIAL REGION. 253 is distinguished by a ganglionic enlargement, just before it enters the muscle. The Teres major muscle arises from the dorsal surface of the inferior angle of the scapula, and from its inferior border; it is inserted into the internal bicipital ridge of the humerus, imme- diately behind the tendon of the latissimus dorsi. At its origin this muscle is covered by the latissimus dorsi, but the latter shortly afterwards curves around its lower border and becomes placed in front; the two tendons at their insertion, one lying behind the other, are separated by a bursa. Relations.—By its •posterior surface with the latissimus dorsi, scapular head of the triceps and integument. By its anterior surface with the subscapularis, latissimus dorsi, coraco-brachialis, short head of the biceps, axillary vessels, and nerves of the brachial plexus. By its upper border it is in relation with the teres minor, from which it is separated by the scapular head of the triceps; and, by the lower, forms, with the latissimus dorsi, the lower and posterior border of the axilla. Nerve Supply.—Middle and long subscapular branches derived from the posterior cord of the brachial plexus. A large triangular space exists between the two teres muscles, which is divided into two minor spaces by the long head of the triceps. Actions.—The supra-spinatus raises the arm from the side; but feebly, from the disadvantageous direction of its force. The infra- spinatus and teres minor are rotators of the head of the humerus outwards. The most important use of these three muscles is the protection of the joint, and defence against displacement of the head of the humerus, in which action they co-operate with the sub- scapularis. The teres major combines, with the latissimus dorsi, in rotating the arm inwards, and at the same time carrying it towards the side, and somewhat backwards. Acromial Region. Deltoideus. The Deltoideus (A, delta; el80s, resemblance; attollens humeri; sub-acromio-humeralis) is the large triangular muscle which forms the convexity of the shoulder; it arises from the outer third of the clavicle, from the acromion process, and from the whole length of the spine of the scapula. The fibres from this broad origin con- verge to the middle of the outer side of the humerus, where they are inserted into a rough triangular elevation. In structure the deltoideus is composed of seven fasiculi, four of which are fleshy above and tendinous below; and three tendinous above and fleshy below. To bring the muscles beneath it into view, the deltoid must be cut away from its origin, and turned down; in so doing, a large bursa will be seen between its under surface and the head of the humerus. 254 MUSCLES OF THE UPPEE EXTEEMITY. Relations.—By its superficial surface with the brachial fascia, a few fibres of the platysma myoides, the superficial fascia, and integument. By its deep surface with the shoulder-joint (from which it is separated by a thin tendinous fascia and a synovial bur«a), the coraco-acromial ligament, coracoid process, pectoralis minor, coraco-brachialis, both heads of the biceps, tendon of the pectoralis major, tendon of the supra-spinatus, infra-spinatus, teres minor, teres major, scapular and external head of the triceps, circumflex vessels anterior and posterior, and humerus. By its anterior border with the external border of the pectoralis major, from which it is separated by a cellular interspace, lodging the cephalic vein and descending branch of the thoracico-acromialis artery. Its posterior border is thin and tendinous above, where it is connected with the aponeurotic covering of the infra-spinatus muscle, and thick below. Nerve Supply.—The circumflex nerve, from the posterior cord of the brachial plexus. Actions.—The deltoid is the elevator muscle of the arm in a direct line, and, by means of its extensive origin, it can carry the arm forwards or backwards so as to range with the hand a con- siderable segment of a large circle. The arm, raised by the deltoid, is an illustration of a lever of the third power, so common in the animal machine, by which velocity is gained at the expense of power. In this lever, the weight (hand) is at one extremity, the fulcrum (glenoid cavity) at the opposite end, the power (insertion of the muscle) between the two, but nearer to the fulcrum than to the weight. Coraco-brachialis, Anterior Humeral Region. Biceps brachii, Brachialis anticus. Dissection.—These muscles are exposed, on the removal of the integument and fascia from the anterior half of the upper arm, and the clearing away of the cellular tissue. The Coraco-brachialis, a name suggestive of its points of origin and insertion, arises from the apex of the coracoid process in com- mon with the short head of the biceps; and is inserted into a rough line on the inner side of the middle of the humerus. Relations.—By its anterior surface with the deltoid and pectoralis major. By its posterior surface with the shoulder joint, humerus, subscapularis, teres major, latissimus dorsi, short head of the triceps, and anterior circumflex vessels. By its internal border with the axillary and brachial vessels and nerves, particularly with the median and musculo-cutaneous nerve, by the latter of which it is pierced. By the external border with the short head of the biceps and brachialis anticus. Nerve Supply.—The external cutaneous nerve which pierces it about its middie. The Biceps brachii (bis—K( Splenic, Superior mesenteric, Spermatic, The Phrenic arteries (phrenicee; diaphragmaticse) are given off (frequently by a common trunk) from the anterior part of the aorta as soon as that vessel has emerged through the aortic opening. Passing obliquely outwards on the under surface of the diaphragm, each artery divides into two branches, an internal branch, which runs forwards and inosculates with its fellow of the opposite side in front of the oesophageal opening; and an external branch, which proceeds outwards towards the great circumference of the muscle, and sends branches to the supra-renal capsules. The phrenic arteries inosculate with branches of the internal mammary, inter- costal, epigastric, oesophageal, gastric, hepatic, and supra-renal ar- teries. They are not unfrequently derived from the coeliac axis, or from one of its divisions, and sometimes they give origin to the supra-renal arteries. The Cceliac axis (coeliaca; Koikla, ventriculus) is the first single trunk given off by the abdominal aorta. It arises opposite the upper border of the first lumbar vertebra, is about half an inch in length, and divides into three large branches, gastric, hepatic, and splenic. Relations.—The trunk of the coeliac axis has in relation with it, in front, the lesser omentum; on the right side, the right semi- lunar ganglion and lobus Spigelii of the liver; on the left side, the left semilunar ganglion and cardiac portion of the stomach; and below, the upper border of the pancreas and lesser curve of the stomach. It is completely surrounded by the solar plexus. The Gastric artery (coronaria ventriculi), the smallest of the three branches of the coeliac axis, ascends between the two layers of the lesser omentum to the cardiac orifice of the stomach, then runs along the lesser curvature to the pylorus, and inosculates with the pyloric branch of the hepatic. It is distributed to the 364 HEPATIC ARTERY, lower extremity of the oesophagus and lesser curve of the stomach; and anastomoses with the oesophageal arteries, vasa brevia of the splenic artery, and pyloric branch of the hepatic artery. The Hepatic akteky (hepatica) curves forward, and ascends along the right border of the lesser omentum to the liver, where it divides into two branches (right and left), which enter the transverse fissure, and are distributed along the portal canals to the right and left lobes.f It is in relation, in the right bor- der of the lesser omen- tum, with the ductus communis choledochus and portal vein, and is surrounded by the hepa- tic plexus of nerves, and numerous lymphatics. There are sometimes two hepatic arteries, in which case one is derived from the superior mesenteric. The Branches of the hepatic artery are, the Pyloric, Gastro-duodenalis, Gastro-epiploica dex- tra, Pancreatico-duodena- lis superior. Cystic. The Pyloric branch, given off from the he- patic near the pylorus, is distributed to the commencement of the duodenum and to the Fig. 204.* * Abdominal aorta with its branches. 1. Phrenic arteries. 2. Cceliac axis. 3. Gastric artery. 4. Hepatic artery, dividing into right and left hepatic branches. 5. Splenic artery, passing outwards to the spleen. G. Supra-renal artery of the right side. 7. Eight renal artery, longer than the left, passing outwards to the right kidney. 8. Lumbar arteries. 9. Superior mesenteric artery. 10. The two spermatic arteries. 11. Inferior mesenteric artery. 12. Sacra media. 13. Common iliacs. 14. Internal iliac, right side. 15. Ex- ternal iliac. 16. Epigastric artery. 17. Circumflexa ilii. 18. Common femoral artery, dividing into femoralis superficialis and profunda. t For the mode of distribution of the hepatic artery within the liver, see the “ Structural Anatomy ” of that organ in the Chapter on the Viscera. GASTRO-EPIPLOICA DEXTRA. 365 lesser curve of tlie stomach, where it inosculates with the gastric artery. The Gastro-duodenalis artery is a short but large trunk, which descends behind the pylorus, and divides into two branches, the gastro-epiploica dextra, and pancreatico-duodenalis superior. Pre- viously to its division it gives off some inferior pyloric branches to the small end of the stomach. The Gastro-epiploica dextra runs along the great curve of the stomach lying between the two layers of the great omentum, and inosculates at about its middle with the gastro-epiploica sinistra, a branch of the splenic artery. It supplies the greater curve of the stomach and great omentum; hence its name. The Pancreatico-duodenalis superior curves along the fixed Fig. 205.* * Branches of the coeliac axis. 1. Liver. 2 Its transverse fissure. 3. Gall- bladder. 4. Stomach. 5. (Esophagus. 6. Pylorus. 7. Duodenum, descend- ing portion. 8. Transverse portion of the duodenum. 9. Pancreas. 10. Spleen. 11. Aorta. 12. Ceeliac axis. 13. Gastric artery. 14. Hepatic artery. 15. Its pyloric branch. 16. Gastro-duodenalis. 17. Gastro-epiploica dextra. 18. Pan- creatico-duodenalis, inosculating with the inferior pancreatico-duodenalis. 19. Division of the hepatic artery into right and left branches; the right giving off the cystic branch. 20. Splenic artery, traced by dotted lines behind the stomach to the spleen; the figure rests on the aorta. 21. Gastro-epiploica sinistra, inosculating along the great curvature of the stomach with the gastro-epiploica dextra. 22. Pancreatica magna. 23. Vasa brevia to the great end of the stomach, inosculating with the gastric artery. 24. Superior mesenteric artery, emerging from between the pancreas and transverse portion of the duodenum. 366 SPLENIC ARTERY. border of the duodenum, partly concealed by the attachment of the pancreas, and is distributed to the pancreas and duodenum. It inosculates interiorly with the inferior pancreatico-duodenalis and pancreatic branches of the superior mesenteric artery. The Cystic artery, generally a branch of the right hepatic, is of small size, and ramifies between the coats of the gall-bladder, pre- viously to its distribution to the mucous membrane. The Splenic artery (splenica; lienalis), the largest of the three branches of the coeliac axis, passes horizontally to the left along the upper border of the pancreas, and divides into five or six large branches (r. splenici), which enter the hilum of the spleen, and are distributed to its structure. In its course the vessel is tortuous and serpentine, frequently making a complete turn upon itself. It lies in a narrow groove in the upper border of the pancreas, and is accompanied by the splenic vein which lies beneath it, and by the splenic plexus of nerves. The Branches of the splenic artery are, the Pancreatic® parv®, Pancreatica magna, Vasa brevia, Gastro-epiploica sinistra. The Pancreaticce parvce are numerous small branches distributed to the pancreas, as the splenic artery runs along its upjier border. One of these, larger than the rest, follows the course of the pan- creatic duct, and is called pancreatica magna. The Vasa brevia (gastric® breves) are five or six branches of small size which pass from the extremity of the splenic artery and its terminal branches, between the layers of the gastro-splenic omentum, to the great end of the stomach, to which they are dis- tributed, inosculating with branches of the gastric artery and gastro-epiploica sinistra. The Gastro-epiploica sinistra appears to be the continuation of the splenic artery; it passes forwards from left to right, along the great curve of the stomach, lying between the layers of the great omentum, and inosculates with the gastro-epiploica dextra. It is distributed to the greater curve of the stomach and great omentum. The Superior mesenteric artery (mesenterica vel mesaraica superior), the second of the single trunks, and next in size to the coeliac axis, arises from the aorta immediately below that vessel, and behind the pancreas. It passes forwards between the pan- creas and transverse duodenum, and descends within the layers of the mesentery, to the right iliac fossa, where it terminates, much reduced in size. In its course it forms a curve, the convexity being to the left, the concavity to the right; is in relation near its com- mencement with the portal vein; and is accompanied by two veins, and the superior mesenteric plexus of nerves. The Branches of the superior mesenteric artery are— Pancreatico-duodenalis inferior, Yasa intestini tenuis, Ileo-colica, Colica dextra, Oolica media. SUPEEIOK MESENTEEIC AETEEY. 367 The Pancreatico-duodenalis inferior is a small branch which arises from the superior mesenteric while behind the pancreas, and curves upwards along the line of junction of the pancreas and duo- Fig. 206.* denum. It supplies both those organs, and inosculates with the pancreatico-duodenalis branch of the hepatic. The Vasa intestini tenuis arises from the convexity of the supe- rior mesenteric artery. They vary from fifteen to twenty in num- ber, and are distributed to the small intestine from the duodenum to the termination of the ileum. In their course between the layers of the mesentery, they form a series of arches by the inosculation * Course and distribution of the superior mesenteric artery. 1. Descending portion of the duodenum. 2. Transverse portion. 3. Pancreas. 4. Jejunum. 5. Ileum 6. Caecum and appendix vermiformis. 7. Ascending colon. 8. Trans- verse colon. 9. Descending colon. 10. Superior mesenteric artery. 11. Colica media. 12. The branch which inosculates with the colica sinistra. 13. Pan- creatico-duodenalis inferior. 14. Colica dextra. 15. Ileo-colica. 16, 16. Yasa intestini tenuis. 368 SPERMATIC ARTERIES. of their larger branches; from these are developed secondary arches, and from the latter a third series of arches, from which the branches arise which are distributed to the coats of the intestine. From the middle branches a fourth and sometimes even a fifth series of arches is produced. By means of these arches a direct communication is established between all the branches given off from the convexity of the superior mesenteric artery; the upper branch inosculates with the inferior pancreatico-duodenalis; the lower with the ileo-colica. The Ileo-colic artery is the last branch given off by the concavity of the superior mesenteric. It descends to the right iliac fossa, and divides into branches which communicate and form arches, from which branches are distributed to the termination of the ileum, caecum, and commencement of the colon. This artery inosculates on the one hand with the termination of the mesenteric trunk; on the other, with the colica dextra. The Colica dextra arises from about the middle of the concavity of the superior mesenteric, and passing outwards behind the peri- toneum, divides into branches which form arches, and are distri- buted to the ascending colon. Its descending branches inosculate with the ileo-colica, the ascending with the colica media. The Colica media arises from the upper part of the concavity of the superior mesenteric, and passes forward between the layers of the transverse mesocolon, where it forms arches, and is distributed to the transverse colon. It inosculates on the right with the colica dextra; on the left, with the colica sinistra, a branch of the inferior mesenteric artery. The Spermatic arteries (spermaticas internse) are two small vessels which arise from the front of the aorta below the superior mesenteric; from their origin each artery passes obliquely outwards, and accompanies the corresponding ureter along the front of the psoas muscle to the border of the pelvis, where it is in relation with the external iliac artery. It is then directed outwards to the in- ternal abdominal ring, and follows the course of the spermatic cord along the spermatic canal and through the scrotum to the testicle, to which it is distributed. The right spermatic artery lies in front of the vena cava, and both vessels are accompanied by veins and by the spermatic plexuses of nerves. The spermatic arteries in the female (ovarian) descend into the pelvis and pass between the two layers of the broad ligaments of the uterus, to be distributed to the broad ligaments, ovaries, Fal- lopian tubes, and round ligaments; along the latter they are con- tinued to the inguinal canal and labium at each side. They inos- culate with the uterine arteries. The Inferior mesenteric artery (mesenterica inferior), smaller than the superior, arises from the abdominal aorta, about two inches below the origin of the latter vessel, and descends between the layers of the left mesocolon, to the left iliac fossa, where it divides into three branches: INFERIOR MESENTERIC ARTERY. 369 Colica sinistra, Superior haemorrhoidal. Sigmoid, The Colica sinistra (superior) is distributed to the descending colon; it passes upwards and outwards behind the peritoneum, and Fig. 207.* divides into two branches, one of which (ramns anastomoticns) ascends to inosculate with the colica media, while the other descends * Branches of the inferior mesenteric artery. 1, 1. The superior mesen- teric, and small intestines turned over to the right side. 2. Caecum and appendix eseci. 3. Ascending colon. 4. Transverse colon raised upwards. 5. Descending colon. 6. Sigmoid flexure. 7. Bectum. 8. Aorta. 9. In- ferior mesenteric artery. 10. Colica sinistra, inosculating with, 11, colica media. 12, 12. Sigmoid branches. 13. Superior hfemorrhoidal arterv, 14. Pancreas. 15. Descending portion of the duodenum. 370 SUPRA-RENAL—SACRA MEDIA. to communicate with the sigmoid branch. The inosculation of the colica sinistra with the colica media is the largest arterial anasto- mosis in the body. The Sigmoid artery (colica sinistra inferior) passes obliquely outwards behind the peritoneum and divides into branches which form arches, and are distributed to the sigmoid flexure of the colon. The superior branch inosculates with the colica sinistra, the inferior with the superior hsemorrhoidal artery. The Superior licemorrhoidal artery is the continuation of the inferior mesenteric. It crosses the ureter and left common iliac artery, and descending between the two layers of the mesorectum, is distributed to the rectum as far as its middle, anastomosing with the middle and inferior hasmorrhoidal arteries. The Supra-renal (suprarenales; capsulares) are two small vessels which arise from the aorta immediately above the renal arteries, and are distributed to the supra-renal capsules. They are sometimes branches of the phrenic or of the renal arteries. The Renal arteries (renales; emulgentes) are two large trunks given off from the sides of the aorta immediately below the superior mesenteric artery; the right is longer than the left, on account of the position of the aorta, and passes behind the vena cava to the kidney of that side. The left is somewhat higher than the right. They divide into several large branches previously to entering the kidney, and ramify very minutely in its vascular portion. The renal arteries supply several small branches to the supra-renal capsules, and one to the ureter. The Lumbar arteries (lumbales) correspond with the inter- costals in the chest; they are four or five in number at each side, curve around the bodies of the lumbar vertebras beneath the psoas muscles, and divide into two branches; one, dorsal branch, passes backwards between the transverse processes, and is distributed to the vertebras and spinal cord and muscles of the back; the other, parietal branch, taking its course behind the quadratus lumborum, supplies the abdominal muscles, and inosculates with branches of the internal mammary and epigastric artery. The first lumbar artery runs along the lower border of the last rib; the last, along the crest of the ilium. In passing between the psoas muscle and the vertebras, they ai e protected by a sei-ies of tendinous arches, which defend them and the communicating branches of the sym- pathetic nerve from pressure, during the action of the muscle. The Sacra media arises from the posterior part of the aorta at its bifurcation, and descends along the middle of the anterior sur- face of the sacrum to the first piece of the coccyx, where it termi- nates by inosculating with the lateral sacral arteries. It distributes branches to the rectum and anterior sacral nerves, and inosculates at either side with the lateral sacral arteries. Varieties in the Branches of the Abdominal Aorta,—The phrenic arteries are very rarely both derived from the aorta. One or both may be branches of the coeliac axis; one may proceed from the COMMON ILIAC ARTERIES. 371 gastric artery, from the renal, or from the upper lumbar. There are occasionally three or more phrenic arteries. The coeliac axis is variable in length, and gives off its branches irregularly. There are sometimes two or even three hepatic arteries, one of which may be derived from the gastric or from the superior mesenteric. The colica media is sometimes derived from the hepatic artery. The spermatic arteries are variable both in origin and number. The right spermatic may be a branch of the renal; the left, of the inferior mesenteric. The supra-renal arteries may be derived from the phrenic or renal arteries. The renal arteries present several varieties in number; there may be three or even four on one side, and one only on the other. When there are several renal arteries on one side, one may arise from the common iliac artery, from the front of the aorta near its lower part, or from the internal iliac. COMMON ILIAC ARTERIES. The abdominal aorta divides opposite the fourth lumbar vertebra into the two common iliac arteries. Sometimes the bifurcation takes place as high as the third, and occasionally as low as the fifth. The common iliac arteries (iliacce communes vel primitives) are about two inches in length; they diverge from the termination of the aorta, and pass downwards and outwards at each side to the margin of the pelvis, opposite the sacro-iliac symphysis, where they divide into the internal and external iliac. In old persons the com- mon iliac arteries are more or less dilated and curved in their course. The rigid artery is somewhat longer than the left, and forms a more obtuse angle with the termination of the aorta; the angle of bifurcation is greater in the female than in the male. Relations.—The relations of the two arteries are different at the two sides of the body. The rigid common iliac is in relation in front with the peritoneum, and is crossed at its bifurcation by the ureter. It is in relation behind with the two common iliac veins, and externally with the psoas magnus. The left is in relation in front with the peritoneum, and is crossed by the rectum and superior hsemorrhoidal artery, and, at its bifurcation, by the ureter. It is in relation' behind with the left common iliac vein, and externally with the psoas magnus. The Internal iliac artery (iliaca interna; hypogastrica) is a short- trunk, varying in length from an inch to two inches. It descends obliquely forwards to a point opposite the upper margin of the great sacro-ischiatic foramen, where it divides into an anterior and a posterior trunk. In the foetus, the internal iliac artery, under the name of hypogastric or umbilical, is continued onwards by the side of the fundus of the bladder to near its apex, whence it ascends by the side of the linea alba and urachus to the umbilicus, where it becomes the true umbilical artery. After birth, this artery ceases to be pervious beyond the side of the bladder, and the obliterated portion is converted into a fibrous cord. The projection of the two 372 INTERNAL ILIAC ARTERY. cords on the inner wall of the abdomen causes the depression at each side, which goes by the name of per itoneal fossa. Relations.—This artery rests externally on the sacral plexus and Fig. 208.* origin of the pyriform is muscle; posteriorly it is in relation with the internal iliac vein, and anteriorly with the ureter. Branches.—The branches of the anterior trunk are, the Superior vesical, Inferior vesical, Middle hemorrhoidal, Uterine, V aginal, Obturator, Ischiatic, Internal pudic. The branches of the posterior trank are, the Ilio-lumbar, Lateral sacral, Gluteal. The Superior vesical arteries are three or four small branches, which proceed from the pervious portion of the umbilical artery. They are distributed to the upper and middle part of the bladder. From one of these there passes off a small artery, the deferential, which accompanies the vas deferens along the spermatic cord. * Iliac arteries. 1. Aorta. 2. Left common iliac artery. 3. External iliac. 4. Epigastric artery. 5. Oircumflexa ilii. 6. Internal iliac artery. 7. Its anterior trunk. 8. Its posterior trunk. 9. The pervious portion of the umbilical artery giving off (1U) the superior vesical artery. 11. Internal pudic artery passing behind the spine of the ischium (12) and lesser sacro- ischiatic ligament. 13. Middle haunorrhoidal artery. 14. Ischiatic artery, also passing behind the anterior sacro-ischiatic ligament to escape from the pelvis. 16. Ilio-lumbar ascending to inosculate with the circumflexa ilii artery (5) and form an arch along the crest of the ilium. 17. Obturator artery. 18. Lateral sacral. 19. Gluteal artery passing through the upper part of the great sacro-ischiatic foramen. 20. Sacra media. 21. Eight common iliac artery cut short. 22. Femoral artery. OBTURATOR ARTERY. 373 The Inferior vesical, somewhat larger than the preceding, passes down upon the side of the bladder to its base, and is distributed to that region, the vesiculae seminales, and prostate gland. The Middle licemorrlioidal artery, frequently a branch of the preceding, passes downwards to the rectum, to which it is distri- buted, inosculating with the superior and inferior hsemorrhoidal arteries. In the female it distributes branches to the vagina. The Uterine artery passes inwards between the layers of the broad ligament to the neck of the uterus, and ascends in a tortuous course along its lateral border. It gives branches to the vagina, lower part of the bladder, Fallopian tube (tubaria), ovary (ovaria), and round ligament, and inosculates with the spermatic or ovarian artery. According to Weber the ovarian branch of the uterine is the special artery of the ovary. The Vaginal artery corresponds in position with the inferior vesical, and is distributed to the vagina and neighbouring parts of the bladder and rectum. The Obturator artery (obturatoria; arising frequently from the posterior trunk of the internal iliac) passes forwards from the anterior trunk, a little below the brim of the pelvis, to the upper border of the obturator foramen. Escaping from the pelvis through a tendinous arch formed by the obturator membrane, it divides into two branches, internal and external. Its branches within the pelvis are: an iliac branch, which sup- plies the bone of the iliac fossa, and inosculates with the ilio-lumbar artery; and a pubic branch which is given off close to the obturator foramen, and inosculates with its fellow of the opposite side, behind the pubes, and with the pubic branch of the epigastric artery. The internal branch curves inwards around the bony margin of the obturator foramen, and distributes twigs to the obtu- rator and adductor muscles, inosculating with the internal circumflex artery of the fe- moral. The external branch winds around the outer margin of the obturator foramen to the space between the gemellus in- ferior and quadratus femoris, where it inosculates with the ischiatic artery. In its course it inosculates also with the in- ternal circumflex, and sends a small branch through the notch in the acetabulum (ramus acetabidi) to supply the ligamentum teres. Flg. 209.* * Irregular origin of obturator artery from epigastric. 2nd variety internal to crural ring (from Wood “ On Rupture ”). 374 INTERNAL TUDIC ARTERY. The obturator artery sometimes arises from the external iliac, hut more frequently from the epigastric branch of that artery, in which case it runs doAvn directly to the obturator foramen, either on the outer or inner side of the crural ring,—if to the inner side it is in contact with (limbernat’s ligament, and is in danger in the operation for femoral hernia; fortunately it is bnt rarely found in this dangerous position. The Ischiatic artery (ischiadica; glutasa inferior) is the larger of the two terminal branches of the anterior division of the internal iliac. It passes downwards in front of the pyi'iformis and sacral plexus of nerves, lying internally to the pudic artery, to the lower part of the great ischiatic foramen, where it escapes from the pelvis - between the inferior border of the pyriformis and coccygeus. It then descends in the space between the trochanter major and tube- rosity of the ischium in company with the ischiatic nerves, and divides into several branches, the principal of which are, coccygeal, comes nervi ischiatici, and muscular. The Coccygeal branch pierces the great sacro-ischiatic ligament, and is distributed to the coccygeus and levator ani, and to the in- tegument around the anus and coccyx. The Comes nervi ischiatici is a slender branch, which accom- panies the great ischiatic nerve extending as far as the lower part of the thigh. The Muscular branches supply the muscles of the posterior part of the hip and thigh, and inosculate with the internal and external circumflex arteries, obturator, and superior perforating; some branches are also sent to the hip-joint. The Internal pudic artery (pudenda interna) the other terminal branch of the anterior trunk of the internal iliac, descends exter- nally to the ischiatic artery to the lower part of the great ischiatic foramen. It emerges from the pelvis through the great sacro- ischiatic foramen between the lower border of the pyriformis and the coccygeus, crosses the spine of the ischium, and re-enters the pelvis through the lesser sacro-ischiatic foramen ; in the next place it passes forward on the internal obturator muscle to the ramus of the ischium, being situated at about an inch from the margin of the tuberosity, and bound down by the obturator fascia; it then ascends bv the side of the ramus of the ischium and pubes, and near the symphysis pubis pierces the triangular ligament of the perineum and divides into two terminal branches, arteria corporis cavernosi, and arteria dorsalis penis. Branches.—The branches of the internal pudic artery within the pelvis are several small ramuscules to the levator ani and sacral nerves; and occasionally a branch which takes the place of the inferior vesical or middle hsemorrhoidal artery. The branches given off externally to the pelvis are, the Inferior hasmorrhoidal, Superficial perineal, (Transverse perineal), Artery of the bulb, Artery of the corpus cavernosum, Artery of the dorsum of the penis. INTERNAL PUDIC ARTERY. 375 The Inferior licemorrhoidal arteries (extern®) are three or four small branches, given off by the internal pudic while behind the Fig. 210.* tuberosity of the ischium. They cross the ischio-rectal fossa, and are distributed to the anus and to the muscles and integument of the anal region of the perineum, anastomosing with the branches of the middle hasmorrhoidal. The Superficial perineal artery (perintea) is given off near the attachment of the crus penis; it pierces the connecting layer of the perineal fascia and triangular ligament, and runs forward across the transversus perinei muscle, and along the groove between the accelerator urinas and erector penis to the septum scroti, upon which it ramifies under the name of arteria septi. It distributes branches to the scrotum (scrotales posteriores) and perineum. One of the latter, larger than the rest, crosses the perineum, resting on the transversus perinei muscle, and is named the transversa perinei. There are often two superficial perineal arteries. * Arteries of the perineum; on the right side the superficial arteries are seen, on the left the deep. 1. The penis ; the crus penis of the left side is cut through. 2. Aeceleratores urirife muscles, enclosing the bulbous portion of the corpus spongiosum. 3. Erector penis, spread out upon the crus penis of the right side. 4. Anus, surrounded by the sphincter ani. o. Kamus of ischium and pubes. 6. Tuberosity of ischium. 7. Lesser sacro-ischiatic ligament, attached by its small extremity to the spine of the ischium. 8. Coccyx. 9. In- ternal pudic artery, crossing the spine of the ischium, and entering the peri- neum. 10. Inferior liaemorrhoidal branches. 11. Superfieialis perinei artery, giving off a small branch, transversa perinei, upon the transversus perinei muscle. 12. The same artery on the left side cut off. 13. Artery of the bulb. 14. The two terminal branches of the internal pudic artery ; one is seen enter- ing the divided extremity of the crus penis, the artery of the corpus caverno- sum; the other, the dorsalis penis, ascends to the dorsum of the organ. 376 GLUTEAL ARTERY. The Artery of the bulb (bulbo-urethralis) is given off from the pudic nearly opposite the opening for the transmission of the urethra; it passes almost transversely inwards behind the trian- gular ligament, and pierces that ligament to enter the corpus spon- giosum at its bulbous extremity. It is distributed in the corpus spongiosum. The Artery of the corpus cavernosum (profunda penis) pierces the crus penis, and runs forward in the interior of the corpus caver- nosum, by the side of the septum pectiniforme. It ramifies in the parenchyma of the venous structure of the corpus cavernosum. The Dorsal artery of the penis (dorsalis penis) ascends between the two crura and symphysis pubis to the dorsum penis, and runs forward through the suspensory ligament, in the groove of the corpus cavernosum, to the glans, distributing branches in its course to the body of the organ and integument. The Internal pudic artery in the female is smaller than in the male; its branches, with their distribution, are, in principle, the same. The superficial perineal artery supplies the analogue of the lateral half of the scrotum, namely, the greater labium. The artery of the bulb supplies the commencement of the vagina; the artery of the corpus cavernosum, the cavernous body of the clitoris; and the arteria dorsalis clitoridis, the dorsum of that organ. The Iliolumbar artery (ileo-lombalis) ascends beneath the ex- ternal iliac vessels and psoas muscle, to the posterior part of the crest of the ilium, where it divides into two branches, a lumbar branch which supplies the psoas and quadratus lumborum, and sends a ramuscule through the fifth intervertebral foramen to the spinal cord and its membranes; and an iliac branch (r. transver- salis) which crosses the iliac fossa to the crest of the ilium, and inosculates with the lumbar arteries and circumflexa ilii; in its course it distributes branches to the iliacus and abdominal muscles. The Lateral sacral arteries (sacrales laterales) are generally two in number on each side, superior and inferior. The superior passes inwards to the first sacral foramen, and is distributed to the contents of the spinal canal, from which it escapes by the posterior sacral foramen, and supplies the integument of the dorsum of the sacrum. The inferior passes down by the side of the anterior sacral foramina to the coccyx; it first pierces and then rests on the origin of the pyriformis, and sends twigs into the sacral canal to supply the sacral nerves. Both arteries inosculate with each other and with the sacra media. The Gluteal artery (glutsea superior) is the continuation of the posterior trunk of the internal iliac ; it passes backwards between the lumbo-sacral and first sacral nerve through the upper part of the great sacro-ischiatic foramen and above the pyriformis muscle, and divides into three branches, superficial, deep superior, and deep inferior; while within the pelvis it gives off some muscular twigs to Branches of the posterior trunk. EPIGASTRIC AETERY. 377 the iliacus and pyriformis, and at its escape from the pelvis, a nutritions artery to the ilium. The Superficial branch passes backwards between the gluteus maximus and medius, and is distributed to the gluteus maximus and to the integument of the gluteal and sacral region. The Deep superior branch passes forwards along the superior curved line of the ilium, between the gluteus medius and minimus to the anterior superior spinous process, where it inosculates with the superficial circumflexa ilii and external circumflex of the femoral. There are frequently two arteries occupying the place of this branch. The Deep inferior branches, two or three in number, cross the gluteus minimus obliquely to the trochanter major, where they in- osculate with branches of the external circumflex and ischiatic artery, and send branches through the gluteus minimus to supply the capsule of the hip-joint. Varieties in the branches of the internal iliac.—The most im- portant of the varieties occurring among these branches is the origin of the dorsal artery of the penis from the internal iliac or ischiatic. The artery in this case passes forwards by the side of the prostate gland, and through the upper part of the transverse ligament of the perineum. It would be endangered in the operation of lithotomy. The dorsal artery of the penis is sometimes derived from the ob- turator, and sometimes from one of the external pudic arteries. The artery of the bulb, in its normal course, passes almost trans- versely inwards to the corpus spongiosum. Occasionally, however, it is so oblique in direction as to render its division in lithotomy unavoidable. The External iliac artery (iliaca externa; cruralis iliaca), of each side, passes obliquely downwards along the inner border of the psoas muscle, from opposite the sacro-iliac symphysis to the femoral arch, where it becomes the femoral artery. Relations.—It is in relation in front with the spermatic vessels, peritoneum, and a thin layer of fascia, derived from the iliac fascia, which surrounds the artery and vein. At its commencement it is crossed by the ureter, and near its termination by the genital branch of the genito-crural nerve and the circumflexa ilii vein. Externally it lies against the psoas muscle, from which it is sepa- rated by the iliac fascia; and posteriorly it is in relation with the external iliac vein, which, at the femoral arch, becomes placed to its inner side. The artery is surrounded by lymphatic vessels and several glands Branches.—Besides several small twigs which supply the lym- phatic glands and psoas muscle, the external iliac gives off two branches, the Epigastric, Circumflexa ilii. The Epigastric artery (epigastrica) arises from the front of the external iliac near Poupart’s ligament; and passing inwards between 378 FEMORAL ARTERY. the peritoneum and transversalis fascia, ascends obliquely to the sheath of the rectus. It enters that sheath near its lower third, passes upwards behind the rectus muscle, to which it is distributed, and, in the substance of that muscle, inosculates, near the ensiform cartilage, with the termination (superior epigastric) of the internal mammary artery. It lies internally to the internal abdominal ring and immediately above the femoral ring, and is crossed near its origin by the vas deferens in the male, and the round ligament in the female. The branches of the epigastric artery are, A cremasteric branch (spermatica externa) which accompanies the spermatic cord, and after supplying the cremaster muscle inos- culates with the spermatic artery. A pubic branch which is distributed behind the pubes, and sends a small branch of communication downwards to the obturator artery. Muscular branches which pass outwards between the abdominal muscles, and inosculate with the circumflexa ilii, lumbar, and in- ferior intercostal arteries. Superficial branches which pierce the rectus muscle, and are dis- tributed to the integument of the abdomen. The epigastric artery forms a prominence of the peritoneum, which divides the inguinal fossa into an internal and external por- tion ; it is from the former that direct inguinal hernia issues, and from the latter, oblique inguinal hernia. The Circumflexa ilii arises from the outer side of the external iliac, a little below the epigastric artery. It ascends obliquely along Poupart’s ligament, and curving around the crest of the ilium, inosculates with the ilio-lumbar and inferior lumbar artery. In its course the artery pierces the crural sheath and then lies between the transversalis muscle and fascia; near its termination it pierces the transversalis muscle and becomes placed between it and the internal oblique. Opposite the anterior superior spinous process of the ilium, it gives off a large ascending branch, which passes upwards between the internal oblique and transversalis, and divides into numerous branches which supply the abdominal muscles, and inos- culate with the inferior intercostal and the lumbar arteries. Emerging from beneath Poupart’s ligament, the external iliac artery enters the thigh and becomes the common femoral. The common femoral artery (femoralis; cruralis) passes down the inner side of the thigh, from Poupart’s ligament, at a point midway be- tween the anterior superior spinous process of the ilium and the symphysis pubis, to the opening in the adductor magnus, at the junction of the middle with the inferior third of the thigh, where it becomes the popliteal artery. The femoral artery and vein are enclosed in a strong sheath, femoral slieatli, which is formed for the greater part of its extent FEMORAL ARTERY. FEMORAL ARTERY. 379 by fibrous and areolar tissue, and by a process of fascia sent inwards from the fascia lata, blear Poupart’s ligament this sheath is much larger (infundibuliform) than the vessels it contains, and is continuous with the transversalis and iliac fascia. If the sheath be opened at this point, the artery will be seen in contact with the outer wall of the sheath. The vein lies next the artery, being separated from it by a fibrous septum, and be- tween the vein and the inner wall of the sheath, and divided from the vein by another thin fibrous septum, is a triangular interval (femoral or crural canal), into which the sac is protruded in femoral hernia. This space is occu- pied in the normal state of the parts by loose cellular tissue, and by lym- phatic vessels which pierce the inner wall of the sheath to make their way to a gland, situated in the femoral or crural ring. Relations.—The upper third of the femoral artery is superficial, being covered only by the integument, in- guinal glands, and superficial and deep fascia. The lower two-thirds are covered by the sartorius muscle. To its outer side the artery is in relation with the psoas, and vastus internus. Behind, it rests on the inner border of the psoas; it is next separated from the pectineus by the femoral vein, pro- funda vein and artery, and then lies on the adductor longus to its termination; near the lower border of the adductor longus it is placed in an aponeurotic sheath or canal (called Hunter's canal), Fig. 211.* * Anterior and inner aspect of the thigh, with the femoral artery. 1. Lower part of the tendon of the external oblique muscle; its inferior margin is Pou- part’s ligament. 2. External abdominal ring. 3, 3. Upper and lower part of the sartorius muscle; its middle portion being removed. 4. Eectus. 5. Vastus intemus. 6. Patella. 7. Iliacus and psoas ; the latter being nearest the artery. 8. Pectineus. 9. Adductor longus. 10. Tendinous canal for the femoral artery formed by the adductor magnus, and vastus internus. 11. Ad- ductor magnus. 12. Gracilis. 13. Tendon of the semi-tendinosus. 14. Fe- moral artery. 15. Superficial circumflexa ilii artery, taking its course along the line of Poupart’s ligament to the crest of the ilium. 2. Superficial epi- gastric artery. 16. The two external pudic arteries, superior and inferior. 17. Profunda artery, giving off, 18, its external circumflex branch ; and lower 380 FEMOEAL AETEEY. formed by an arch of tendinous fibres, thrown from the border of the adductor longus and the border of the opening in the adductor magnus, to the side of the vastus internus. To its inner side it is in relation at its upper part with the femoral vein, and lower down with the pectineus, adductor longus, and sartorius. The immediate relations of the artery are, the femoral vein, long saphenous nerve, and muscular nerve to the vastus internus. The vein at Poupart’s ligament lies to the inner side of the artery; but lower down gets behind it, and inclines to its outer side. The muscular nerve lies to the outer side, and somewhat upon the sheath for the lower two-thirds of its extent; and the long saphenous nerve is situated within the sheath, and in front of the artery for the same extent. Plan of the Relations of the Femoral Artery. Front. Fascia lata, Long saphenous nerve, Sartorius, Aponeurotic canal. Inner Side. Femoral vein, Pectineus, Adductor longus, Sartorius. Femoral Artery. Outer Side. Psoas, Vastus interims. Behind. Psoas muscle, Femoral vein, Adductor longus. Superficial circumflexa ilii, Superficial epigastric, Superior external pudic, Inferior external pudic, Branches.—The branches of the Femoral Artery are, the ' External circumflex, Internal circumflex, .Three perforating. Profunda, Muscular, Anastomotica magna. The Superficial circumflexa ilii artery (circumflexa ilii externa) arises from the femoral immediately below Poupart’s ligament, and passes obliquely outwards towards the crest of the ilium, where it pierces the fascia lata. It supplies the integument of the groin, superficial fascia, and inguinal glands. The Superficial epigastric (epigastrica superficialis) arises from the femoral immediately below Poupart’s ligament, pierces the fascia lata, and ascends obliquely towards the umbilicus between the two layers of the superficial fascia. It distributes branches to down the three perforantes. A small bend of the internal circumflex artery (8) is seen behind the inner margin of the femoral, just below the inferior external pudic artery. 19. The anastomotica magna, descending to the knee, upon which it ramifies (G). PROFUNDA FEMORIS ARTERY. 381 the inguinal glands and integument, and inosculates with branches of the deep epigastric and internal mammary artery. The Superior external pudic (pudenda externa, superior) arises near the superficial epigastric artery; it pierces the fascia lata at the saphenous opening, and passes transversely inwards, crossing the spermatic cord, to be distributed to the integument of the penis and scrotum (rami scrotales anteriores) in the male, and to the labia (rami labiales anteriores) in the female. The Inferior external pudic (pudenda externa, inferior) arises from the femoral a little below, and sometimes in common with, the preceding; it crosses the femoral vein immediately below the termination of the internal saphenous vein, and resting on the pectineus muscle reaches the inner border of the thigh, where it pierces the fascia lata, and is distributed to the integument of the external organs of generation and perineum. Both external pudics inosculate with the internal pudic artery. The Profunda femoris (femoralis profunda) arises from the outer and posterior side of the femoral artery about one inch and a half below Poupart’s ligament; it passes downwards and backwards and a little outwards, behind the adductor longus muscle, pierces the adductor magnus, and is distributed to the flexor muscles on the posterior part of the thigh. It is so large that it may be con- sidered a division of the common femoral, in which case the con- tinuation of the main trunk may be called Superficial. Plan of the Relations of the Profunda Artery. In Front. Profunda vein, Adductor longus. Inner Side. Pectineus, Adductor brevis, Adductor magnus, Outer Side. Yastus internus, Femur. Profunda Artery. Behind. Pectineus, Iliacus, Adductor brevis, Adductor magnus. Relations.—In its course downwards it rests successively on the pectineus iliacus, adductor brevis, and adductor magnus. To its outer side the tendinous insertion of the vastus internus muscle intervenes between it and the femur; on its inner side it is in rela- tion with the pectineus, adductor brevis, and adductor magnus; and in front it is separated from the femoral artery, above by the pro- funda and femoral vein, and below by the adductor longus muscle. Branches.—The branches of the profunda artery are, the external circumflex, internal circumflex, and three perforating arteries. 382 PROFUNDA FEMORIS ARTERY. The External circumflex artery (circumflexa femoris externa) passes outwards beneath the sartorius and rectus and in front of the crureus muscle, crossing between the divisions of the crural nerve, and divides into three sets of branches; ascending, which pass upwards beneath the sartorius, rectus, and tensor vaginae femoris, and inosculate with the terminal branches of the gluteal artery; descending, which pass downwards beneath the rectus muscle to inosculate with the superior articular arteries of the popliteal; and middle, which continue the original course of the artery around the thigh, pierce the vastus externus, and anastomose with branches of the ischiatic, internal circumflex, and superior perforating artery. It supplies the muscles of the anterior and outer side of the thigh. The Internal circumflex artery (circumflexa femoris interna) winds around the inner side of the neck of the femur, passing be- tween the pectineus and psoas, and over the upper border of the adductor brevis to the tendon of the obturator externus, which it accompanies to the space between the quadratus femoris and upper border of the adductor magnus. While on the obturator externus it gives off a branch which is distributed to that muscle, the ad- ductor brevis, and gracilis, and anastomoses with the obturator artery. It next gives off an articular branch, which enters the hip-joint through the notch in the acetabulum; and terminates in several branches which inosculate with the ischiatic, external cir- cumflex, and superior perforating artery. The Superior perforating artery passes backwards near the lower border of the pectineus. pierces the adductor brevis and magnus near the femur, and is distributed to the posterior muscles of the thigh; inosculating with the circumflex, ischiatic, and middle per- forating artery. The Middle perforating artery pierces the tendons of the ad- ductor brevis and magnus, and is distributed like the superior; inosculating with the superior and inferior perforating. From this branch is given off the nutritious artery of the femur. The Inferior perforating artery is given off below the adductor brevis, and pierces the tendon of the adductor magnus, supplying it and the flexor muscles, and inosculating with the middle perfo- rating artery above, and the articular branches of the popliteal below. It is through the medium of the branches of the profunda which inosculate above with branches of the internal iliac, and below with those of the popliteal artery, that the collateral cir- culation is maintained in the limb after ligature of the femoral artery. The Muscular branches are given off by the femoral artery throughout the whole of its course. They supply the muscles in immediate proximity with the artery, particularly those of the an- terior aspect of the thigh. One of these branches, larger than the rest, arises from the femoral immediately below the origin of the POPLITEAL ARTERY. 383 profunda, and passing outwards between the sartorius and rectus, divides into branches, which are distributed to all the muscles of the anterior aspect of the thigh. This may be named the superior muscular artery. The Anastomotica mayna (articularis genu superficialis) arises from the femoral near its termination at the opening in the adduc- tor magnus, and divides into a superficial and deep branch. The superficial branch accompanies the internal saphenous nerve to the knee, and piercing the fascia lata is distributed to the integument. The deep branch passes onwards through the substance of the vastus internus muscle, resting on the tendon of the adductor magnus, to the knee ; where it inosculates with the internal arti- cular branches of the popliteal, and the recurrent of the anterior tibial. It also sends a branch through the vastus internus, which supplies the synovial membrane of the joint, and inosculates with the superior external articular artery and external circumflex. POPLITEAL SPACE. This is a space of a diamond shape, situated at the back of the knee joint. It is bounded below by the outer and inner heads of the Gastrocnemius, above by the outer and inner hamstrings, in front by the posterior ligament of the knee-joint, and is covered in behind by the fascia lata of the thigh. It contains the popliteal vessels and their branches, the divisions of the great sciatic nerve, termination of the external saphenous vein, branches of the obtu- rator and lesser sciatic nerves, lymphatic glands, and areolar tissue. The popliteal artery lies at the bottom of this space, immediately in contact with the ligamentum posticum Winslowii, the vein lying superficial to it, and the internal popliteal nerve superficial to both vein and artery; the external popliteal nerve (perineal) descends on the outer side of the space, in contact with the Biceps tendon, and the lymphatic glands (four or five in number) surround the artery. The popliteal artery (poplitea, Fig. 213) commences from the termination of the femoral at the opening in the adductor magnus muscle, and passes obliquely outwards through the middle of the popliteal space to the lower border of the popliteus muscle, where it divides into the anterior and posterior tibial artery. In structure the popliteal artery is remarkable for the thickness of its walls. POPLITEAL ARTERY. 384 ANTERIOR TIBIAL ARTERY. Plan of the Relations of the Popliteal Artery. Superficially. Semi-membranosus, Popliteal nerve, Popliteal vein, Gastrocnemius, Plantaris, Soleus. Inner Side. Semi-membranosus, Internal condyle, Gastrocnemius. Outer Side. Biceps, External condyle, Gastrocnemius, Plantaris, Soleus. Popliteal Artery. Deeply. Femur, Ligamentum posticum Winslowii, Popliteal fascia. Relations.—In its course downwards it rests on the femur, then on the posterior ligament of the knee-joint, then on the fascia cover- ing the popliteus muscle. Superficially it is in relation with the semi-membranosus muscle, next with a quantity of fat which sepa- rates it from the deep fascia, and, near its termination, with the gastrocnemius, plantaris, and soleus ; superficial and external to it is the popliteal vein, and still more superficial and external the in- ternal popliteal nerve. By its inner side it is in relation with the semi-membranosus, internal condyle of the femur, and inner head of the gastrocnemius; and by its outer side with the biceps, exter- nal condyle of the femur, outer head of the gastrocnemius, plantaris, and soleus. Branches.—The branches of the popliteal artery are, the Superior external articular, Superior internal articular, Azygos articular, Inferior external articular, Inferior internal articular, Sural. The Superior articular arteries (articulares genu superiores), external and internal, wind around the femur, immediately above the condyles, to the front of the knee-joint, anastomosing with each other, with the external circumflex, anastomotica magna, inferior articular, and recurrent of the anterior tibial. The external passes beneath the tendon of the biceps, and the internal through an arched opening beneath the tendon of the adductor magnus. They supply the knee-joint and lower part of the femur, and give branches to the vasti muscles. The Azygos articular artery (articulares genu media) pierces the posterior ligament of the joint, the ligamentum posticum Winslowii, and supplies the crucial ligaments and synovial membrane. There are, frequently, several posterior articular arteries. The Inferior articular arteries (articulares genu inferiores) wind ANTERIOR TIBIAL ARTERY. 385 around the head of the tibia immediately below the joint; and anastomose with each other, the superior articular arteries, and the recurrent of the anterior tibial. The external passes beneath the two external lateral ligaments of the joint, the internal beneath the internal lateral ligament. They supply the knee-joint and the heads of the tibia and fibula. The Sural arteries (surales; sura, the calf) are two muscular branches of large size, distributed to the two heads of the gastroc- nemius muscle. Other muscular branches are given off from the upper part of the popliteal artery to supply the hamstring muscles. ANTERIOR TIBIAL ARTERY. The anterior tibial artery (tibialis antica) passes forwards be- tween the two heads of the tibialis posticus muscle, and through the opening in the upper part of the interosseous membrane, to the anterior tibial region. It then runs down the anterior aspect of the leg to the ankle-joint, where it becomes the dorsalis pedis. Relations.—In its course it rests on the interosseous membrane (to which it is connected by a little tendinous arch which is thrown across it), the lower part of the tibia, and the anterior ligament of the joint. In its upper third it is situated between the tibialis anticus and extensor longus digitorum, lower down between the tibialis anticus and extensor proprius pollicis; and just before it reaches the ankle it is crossed by the tendon of the extensor proprius pollicis, and becomes placed between that tendon and the tendons of the extensor longus digitorum. Its immediate relations are the venae comites and anterior tibial nerve; the latter lies at first to its outer side, at about the middle of the leg it is placed superficially to the artery, and at the ankle is again at its outer side. Plan of the Relations of the Anterior Tibial Artery. Front. Deep fascia, Tibialis anticus, Extensor longus digitorum, Extensor proprius pollicis, Anterior tibial nerve. Outer Side. Anterior tibial nerve, Extensor longus digitorum, Extensor proprius pollicis, Tendons of extensor lon- gus digitorum. Inner Side. Tibialis anticus, Tendon of extensor pro- prius pollicis. Anterior Tibial Artery. Behind. Interosseous membrane, Tibia (lower fourth), Ankle-joint. Branches.—The branches of the Anterior Tibial Artery are, the Recurrent, Muscular, External malleolar, Internal malleolar. 386 DORSALIS PEDIS ARTERY. The Recurrent branch (tibialis recurrens) passes upwards beneath the origin of the tibialis anticus muscle to the front of the knee- joint, upon which it is distributed, anasto- mosing with the articular arteries. The Muscular branches are numerous, they supply the muscles of the anterior tibial region. The Malleolar arteries (malleolares an- teriores) are distributed to the ankle-joint; the external, passing beneath the tendons of the extensor longus digitorum and pe- roneus tertius, inosculates with the ante- rior peroneal artery and dorsalis pedis; the internal, beneath the tendons of the extensor proprius pollicis and tibialis an- ticus, inosculates with branches of the pos- terior tibial and internal plantar artery. They supply branches to the ankle-joint. The Dorsalis Pedis Artery is continued forward along the tibial side of the dorsum of the foot, from the ankle to the base of the metatarsal bone of the great toe, where it divides into two branches, one of which dips between the two heads of the first dorsal interosseous muscle into the sole of the foot, and becomes continuous with the deep plantar arch; the other, called dorsalis hallucis, runs forwards in the first inter- osseous space. Relations.—The dorsalis pedis is situated along the outer border of the tendon of the extensor proprius pollicis; at its fibular side is the innermost tendon of the ex- tensor longus digitorum, and near its ter- mination, it is crossed by the inner tendon of the extensor brevis digitorum. It is accompanied by venae comites, and has the continuation of the anterior tibial nerve to its outer side. Fig. 212* * Anterior aspect of the leg and foot, showing the anterior tibial and dorsalis pedis artery; the tibialis anticus has been removed. 1. Tendon of insertion of the quadriceps extensor muscle. 2. Insertion of the ligamentum patellaa into the lower border of the patella. 3. Tibia. 4. Extensor proprius pollicis muscle. 5. Extensor longus digitorum. 6. The peronei. 7. Inner belly of the gastrocnemius and soleus. 8. Annular ligament. 9. Anterior tibial artery. 10. Its recurrent branch inosculating with (2) inferior articular, and (1) superior articular arteries, branches of the popliteal. 11. Internal malleolar artery. 17. External malleolar inosculating with the anterior peroneal artery 12. 13. Dorsalis pedis artery. 14. Tarsea and metatarsea ; the tarsea is nearest the ankle, the metatarsea is seen giving off the interossese. 15. Dorsalis hallucis artery. 16. Continuation of the dorsalis pedis into the sole of the foot. DORSALIS PEDIS AKTERY. 387 Plan of the Relations of the Dorsalis Pedis Artery. In Front. Integument, Deep fascia, Inner tendon of extensor brevis digitorum. Inner Side. Tendon of extensor pro- prius pollicis. Dorsalis Pedis Artery. Outer Side. Tendon of extensor lon- gus digitorum, Border of extensor brevis digitorum, Anterior tibial nerve. Behind. Bones and ligaments of the tarsus. Branches.—The branches of this artery are, the Tarsal, Metatarsal, Dorsalis hallucis, Magna pollicis. The Tarsal (externa) arches transversely across the tarsus, beneath the extensor brevis digitorum muscle, and supplies the articulations of the tarsal bones and outer side of the foot: it anas- tomoses with the external malleolar, peroneal arteries, and external plantar. The Metatarsal forms an arch (arcus tarseus vel dorsalis pedis) across the base of the metatarsal bones, and supplies the outer side of the foot; anastomosing with the tarsal and external plantar artery. From its convex side the metatarsal gives off three branches, interosseous, which pass forward upon the dorsal inter- osseous muscles, and divide into branches (dorsal collateral) for the supply of the sides of the toes between which they are placed. At their commencement these interosseous branches receive the pos- terior perforating arteries from the plantar arch, and opposite the heads of the metatarsal bones are joined by the anterior perforating branches from the digital arteries. The interosseous artery of the fourth interosseous space, in addition to the two dorsal collateral branches into which it bifurcates, sends a third branch to the outer side of the little toe. The Dorsalis hallucis (interossea dorsalis prima) runs forward upon the first dorsal interosseous muscle, and at the base of the first phalanx divides into two branches, one of which passes inwards be- neath the tendon of the extensor proprius pollicis, and is distributed to the inner border of the great toe, while the other bifurcates into two dorsal collateral digital branches for the adjacent sides of the great and second toe. The Arteria magna pollicis arises from the dorsalis pedis, while in the metatarsal space and just before its inosculation with the external plantar artery. It sends a digital branch to the inner border of the great toe on its plantar aspect, and bifurcates to supply the plantar collateral digital branches of the great and second toe. 388 The posterior tibial artery (tibialis postica) passes obliquely downwards along the tibial side of the leg from the lower border of the popliteus muscle to the concavity of the os calcis, where it di- vides into the internal and external plantar artery. Relations.—In its course it lies first on the tibialis posticus, next on the flexor longus digitorum, then on the tibia; it is covered in by the intermuscular fascia which separates it above from the soleus, below from the deep fascia and integument. It is accom- panied by vente comites, and by the posterior tibial nerve, which lies to its inner side at first, and to its outer side for the rest of its course. POSTERIOR TIBIAL ARTERY. Plan of the Relations of the Posterior Tibial Artery. Superficially. Soleus, Deep fascia;, Intermuscular fascia. Inner Side. Posterior tibial nerve (upper thiru), Vein. Posterior Tibial Artery. Outer Side. Posterior tibial nerve (lower two-thirds), Vein. Deeply. Tibialis posticus, Plexor longus digitorum, Tibia. Branches.—The branches of the posterior tibial artery are, the Peroneal, Nutritious, Muscular, Internal calcanean, Internal plantar, External plantar. The Peroneal artery (peronma; fibularis) is given off from the posterior tibial at about two inches below the lower border of the popliteus muscle ; it is nearly as large as the anterior tibial artery, and passes obliquely outwards to the fibula. It then runs down- wards along the inner border of the fibula to its lower third, where it divides into the anterior and posterior peroneal. Relations.—The peroneal artery rests on the tibialis posticus muscle, and is covered in by the soleus, intermuscular fascia, and fiexor longus pollicis, having the fibula to its outer side. Branches.—The branches of the peroneal artery are, muscular to the soleus and neighbouring muscles: nutrient to the fibula; and two terminal branches anterior and posterior peroneal. The Anterior peroneal artery (perontea antica vel perforans) pierces the interosseous membrane at the lower third of the leg, PERONEAL ARTERY. 389 and is distributed on the front of the outer malleolus, anastomosing with the external malleolar and tarsal artery. The Posterior 'peroneal continues onwards along the posterior aspect of the outer malleo- lus to the side of the os calcis, to which and to the muscles arising from it, it distributes ex- ternal calcanean branches. It anastomoses with the anterior peroneal, tarsal, external plantar, and posterior tibial artery; with the latter by means of a small transverse branch (ramus anastomoticus transversus). The Nutritious artery (nutritia tibieo) of the tibia arises from the trunk of the poste- rior tibial, frequently above the origin of the peroneal, and proceeds to the nutritious canal, which it traverses obliquely from below up- wards. The Muscular branches of the posterior tibial artery are distributed to the soleus and deep muscles of the posterior aspect of the leg. One of these branches is deserving of notice, a recurrent branch, which arises from the posterior tibial above the origin of the peroneal artery, pierces the soleus, and is distributed on the inner side of the head of the tibia, anastomosing with the inferior in- ternal articular. The Internal calcanean branches, three or four in number, proceed from the posterior tibial artery immediately before its division; they are distributed to the integument, to the inner side of the os calcis, and to the muscles which arise from its inner tuberosity; and anas- tomose with the external calcanean branches of the posterior peroneal, and with all the neighbouring arteries, forming around the heel a network of inosculations, rete calcaneum. Fig. 213.* * Posterior view of the leg, showing the popliteal and posterior tibial artery. 1. Tendons of the inner hamstring. 2. Tendon of the biceps, forming the outer hamstring. 3. Popliteus muscle. 4. Flexor longus digitorum. 5. Tibialis posticus. 6. The fibula ; immediately below the figure is the origin of the flexor longus pollicis ; the muscle has been removed in order to expose the peroneal artery. 7. Peronei muscles, longus and brevis. 8. Lower part of the flexor longus pollicis muscle with its tendon. 9. Popliteal artery giving off articular and muscular branches ; the two superior articular are seen in the upper part of the popliteal space passing above the two heads of the gastrocnemius muscle, which are cut through near their origin. The two in- ferior are in relation with the popliteus muscle. 10. Anterior tibial artery passing through the angular interspace between the two heads of the tibialis posticus muscle. 11. Posterior tibial artery. 12. The relative position of the 390 PLANTAR ARTERIES. The Inter nal plantar artery (plantaris interna) proceeds from the bifurcation of the posterior tibial at the inner malleolus, and passes along the inner border of the foot beneath the abductor pollicis, supplying the inner border of the foot and great toe. The External plantar artery (plantaris ex- terna), much larger than the internal, passes obliquely outwards between the first and second layer of the plantar muscles to the fourth meta- tarsal space. It then turns transversely inwards between the second and third layer, to the first metatarsal space, where it inosculates with the dorsalis pedis. The transverse portion of the artery describes a slight curve, having the con- vexity forwards ; this is the plantar arch (arcus plantaris). Branches.—The branches of the external plantar artery are, the Muscular, Articular, -ry i ) collateral, 1”1 a ’ ( anterior perforating. Posterior perforating. The Muscular and Articular tranches are distributed to the muscles of the sole of the foot and to the articulations of the tarsus. The Digital branches (interossese plantares) are four in number: the first is distributed to the outer side of the little toe; the three others pass forward to the cleft between the toes, and divide into collateral branches, which supply the ad- jacent sides of the three external toes, and the outer side of the second. At the bifurcation of the toes, a small branch is sent up- wards from each digital artery, to inosculate with the interosseous branches of the metatarsal; these are the anterior perforating arteries. Fig. 214.* tendons and artery at the inner ankle from within outwards, previously to their passing beneath the internal annular ligament. 13. Peroneal artery, dividing, a little below the figure, into two branches; the anterior peroneal is seen piercing the interosseous membrane. 14. Posterior peroneal. * Arteries of the sole of the foot; the first and part of the second layer of muscles having been removed. 1. Under and posterior part of the os calcis; to which the origins of the first layer of muscles remain attached. 2. Muscu- lus accessorius. 3. Long flexor tendons. 4. Tendon of the peroneus longus. 5. Termination of the posterior tibial artery. 6. Internal plantar. 7. Ex- ternal plantar artery. 8. The plantar arch giving off four digital branches, which pass forwards on the interossei muscles. Three of these arteries are seen dividing, near the heads of the metatarsal bones, into collateral branches for adjoining toes. PULMONARY ARTERY. 391 The Posterior perforating are three small branches which pass upwards between the heads of the three external dorsal interossei muscles, to inosculate with the arch formed by the metatarsal artery. Varieties in the Arteries of the Lower Extremity.—The femoral artery occasionally divides at Poupart’s ligament into two branches, and sometimes into three ; the former is an instance of the high division of the profunda artery; and in the latter the branches are the profunda, superficial femoral, and internal circumflex. The point of origin of the profunda artery varies considerably in different subjects, being sometimes nearer to and sometimes farther from Poupart’s ligament, but more frequently the former. The branches of the popliteal artery are very liable to variety in size; and in all these cases the compensating principle, so constant in the vascular system, is manifested. When the anterior tibial is of small size, the peroneal is large ; and in place of dividing into two terminal branches at the lower third of the leg, descends to the lower part of the interosseous membrane, and emerges upon the front of the ankle, to supply the dorsum of the foot; or the posterior tibial and plantar arteries are large, and the external plantar is continued between the heads of the first dorsal inter- osseous muscle, to be distributed to the dorsal surface of the foot. Sometimes the posterior tibial artery is small and thread-like: and the peroneal, after descending to the ankle, curves inwards to the inner malleolus, and divides into the two plantar arteries. If, in this case, the posterior tibial be sufficiently large to reach the ankle, it inosculates with the peroneal previously to the division of the latter. The internal plantar artery sometimes takes the distribution of the external plantar, which is short and diminutive, and the latter not unfrequently replaces a deficient dorsalis pedis. The varieties of arteries are interesting in the practical applica- tion of a knowledge of their principal forms to sui-gical operations; in their transcendental anatomy, as illustrating the normal type of distribution in animals; or, in many cases, as diverticula per- mitted by Nature, to teach her observers two important prin- ciples :—first, in respect to herself, that, however in her means she may indulge in change, the end is never overlooked, and a limb is as surely supplied by a leash of arteries, various in their course, as by those which we are pleased to consider normal in distribution ; and secondly, with regard to us, that we should be keenly alive to whatever is passing beneath our observation, and ready in the most serious operation to deviate from our course, and avoid—or give eyes to our knife, that it may see—the concealed dangers which it is our pride to be able to contend with and vanquish. PULMONARY ARTERY. The pulmonary artery (arteria pulmonalis) arises from the left side of the base of the right ventricle in front of the origin of the aorta, and ascends obliquely for the space of two inches to the 392 PULMONARY ARTERY. under surface of the arch of the aorta, where it divides into the right and left pulmonary artery. In its course upwards and back- wards it inclines to the left side, crossing the commencement of the aorta, and is connected by its left branch to the under surface of the arch by a thick and impervious cord (ligamentum arte- riosum; chorda ductus arteriosi), the remains of the ductus arte- riosus of the foetus. Relations.—It is enclosed for nearly the whole of its extent by the pericardium, and receives the attachment of the fibrous portion of that membrane by its upper portion. Behind, it rests against the ascending portion of the arch of the aorta and left auricle, on either side is the appendix of the corresponding auricle with a coronary artery ; and above, the superficial cardiac plexus, and the cord of the ductus arteriosus. The Eight pulmonary artery, longer and somewhat larger than the left, passes transversely outwards behind the ascending aorta and superior vena cava to the root of the right lung, where it divides into three branches for the three lobes. In its course it lies parallel with and in front of the right bronchus. The Left pulmonary artery, shorter and smaller than the right, crosses the descending aorta and left bronchus to the root of the left lung, where it divides ints two branches for the two lobes. The pulmonary arteries divide and subdivide in the structure of the lungs, and terminate in capillary vessels which form a network around the air-passages and cells, and become continuous with the radicles of the pulmonary veins. Relations.—In the root of the right lung, examined from above downwards, the pulmonary artery is situated between the bronchus and pulmonary veins, the former being above, the latter below: in the root of the left lung the artery is highest, next the bronchus, and then the veins. On both sides from before backwards, the artery is situated between the veins and bronchi, the former being in front, the latter behind. 393 CHAPTER VII. OF THE VEINS. The veins are the vessels which return the blood to the auricles of the heart, after it has been circulated by the arteries through the various tissues of the body. They are much thinner in struc- ture than the arteries, so that when emptied of their blood they become flattened and collapsed. The veins of the systemic circula- tion convey the dark-coloured and impure or venous blood from the capillary system to the right auricle of the heart, and they are found after death to be more or less distended with that fluid. The veins of the pulmonary circulation resemble the arteries of the systemic circulation in containing during life the pure or arterial blood, which they transmit from the capillaries of the lungs to the left auricle. The veins commence by minute radicles in the capillaries which are everywhere distributed through the textures of the body, and converge to constitute larger and larger branches, till they termi- nate in the main trunks which convey the venous blood directly to the heart. In diameter they are larger than the arteries, and, like those vessels, their combined are® would constitute a hollow cone, whereof the apex is placed at the heart, and the base at the surface of the body. It follows from this arrangement, that the blood in returning to the heart is passing from a larger into a smaller channel, and therefore that it increases in rapidity during its course. Veins admit of a threefold division into superficial, deep, and sinuses. The Superficial veins return the blood from the integument and superficial structures, and take their course between the layers of the superficial fascia; they then pierce the deep fascia in the most convenient and protected situations, and terminate in the deep veins. They are unaccompanied by arteries, and are the vessels usually selected for venesection. The Deep veins are situated among the deeper structures of the body, and generally in relation with the arteries; in the limbs they are enclosed in the same sheath with those vessels, and they return the venous blood from the capillaries of the deep tissues. In com- pany with all the smaller, and also with the secondary arteries, as the brachial, radial, and ulnar in the upper, and the tibial and peroneal in the lower extremity, there are two veins, placed one at 394 ,STRUCTURE OF THE VEINS. each side of the artery, and named venae comites. The larger arte- ries, as the axillary, subclavian, carotid, popliteal, femoral, are accompanied by a single venous trunk; and certain veins, such as those of the cranium, spinal canal, liver, and larger veins of bones, run apart from arteries. Sinuses differ from veins in their struc- ture ; and also in their mode of distribution, being confined to especial organs and situated within their substance. The principal venous sinuses are those of the dura mater, diploe, cancellous structure of bones, and uterus. The communications between veins are more frequent than those of arteries, and they take place between the larger as well as the smaller vessels; the venae comites communicate with each other in their course by means of short transverse branches which pass across from one to the other. These communications are strikingly exhibited in the frequent inosculations of the spinal veins, and in the various venous plexuses, as the spermatic plexus, and vesical plexus. The office of these inosculations is very apparent, as tend- ing to obviate the obstructions to which veins are particularly liable from the thinness of their coats, and from their inability to over- come much impediment by the force of their current. Yeins, like arteries, are composed of three coats, external, middle, and internal. The External coat is the thickest of the three, increasing by degrees from the smallest to the largest; in the former gradually diminishing until it is lost altogether, and nothing remains but the one coat of the capillary; in the veins of medium size acquiring double the thickness of the middle coat, and in some of the large veins attaining four or five times its thickness. In structure it resembles the external coat of arteries, consisting of areolar tissue interwoven with a network of elastic fibres of the finer and coarser kind. In some of the larger veins, as the inferior vena cava, the trunks of the hepatic veins, and vena portae, there exists besides, a layer of longitudinal smooth muscular fibres, occupying the inner half or two-thirds of the external coat, and, where the middle coat is absent, lying in contact with the internal coat. This muscular stratum is met with in its highest stage of development in that portion of the inferior vena cava which is embedded in the liver, the muscular fibres being intermingled with a fine network of elastic fibres. The Middle or contractile coat is thin, but firmer than the external, and composed of areolar tissue, elastic tissue, and smooth muscular fibres; the two latter being less in quantity than in the corresponding coat of arteries, and the muscular fibres being more abundant in the medium-sized than in the larger veins. The especial character of the middle coat of veins is,'however, the pre- sence of longitudinal as well as transverse fibres ; the longitudinal fibres consisting of closely-reticulated elastic tissue, occurring in layers and alternating with the circular layers composed of smooth muscular fibres intermingled with areolar tissue and fine elastic STRUCTURE OF THE VEINS. 395 fibres. The number of layers constituting the middle coat varies, according to the size and thickness of the vessel, from five to ten ; and they are so disposed that the inner and outer layers are mus- cular, while the longitudinal elastic layers are more abundant towards the inner than the outer portion of the coat, and, although stratified, communicate with each other at different points so as to form one continuous whole. In the veins of the lower extremity the middle coat is thicker than elsewhere, and in certain of the veins of the lower limb, as the popliteal, profunda, and saphena;, there exists an additional layer on the inner aspect of the middle coat, a layer composed of areolar tissue intermingled with fine elastic fibres and having a longitudinal fibrillation; the longitudi- nal lamina of the middle coat. In tracing the veins downwards to those of the smallest size, the layers of areolar tissue mingled with fine elastic fibres are the first to disappear; then the muscular element is reduced to a single layer, while its cells are separated and scanty and finally cease; the elastic element consisting of a network of fine elastic fibres is continued further and becomes con- tinuous with the coat of the capillaries. In that portion of the in- ferior cava which is embedded in the liver and in the larger hepatic veins, the middle coat is wranting and the external and internal coat are in contact. The Internal coat, stronger than that of arteries, is composed of an epithelium and an elastic membrane, between which is situated a striated nuclear lamella. The epithelium consists of nucleated cells, which are elongated in veins of large and medium size; elliptic and almost round in the smallest veins, and cease altogether in the transitional veins. The elastic membrane is not homogeneous and fenestrated as in arteries, but composed of a closely areolated longitudinal network of coarse and fine elastic fibres. In the smallest veins this membrane is lost and its place supplied by a layer of homogeneous or sub-fibrous areolar tissue. The veins which open into the heart, have an external annular layer of muscular fibres similar to those of the heart and presenting the same anastomosing structure. They are met with on the superior and inferior vena cava and around the pulmonary veins. Smooth muscular fibres are found in the veins of the gravid uterus in great abundance and highly developed, in all the three coats; while in other veins the muscular element is altogether absent, as in the maternal portion of the placenta; the greater part of the veins of the cerebral substance and pia mater; the sinuses of the dura mater and of the bones; the veins of the corpora cavernosa; probably those of the spleen; and the veins of the retina. These veins are simply composed of condensed areolar tissue more or less completely developed and lined by epithelium ; the sinuses of the dura mater have besides some fine elastic fibres. The Valves of veins are composed of a thin stratum of areolar tissue mingled with fine elastic fibres, and coated on the two sur- faces with the epithelial lining of the vessel. The segments or flaps 396 VEINS OF THE HEAD AND NECK. of the valves of veins are semilunar in form, and arranged in pairs, one upon either side of the vessel; in some instances there is hut a single flap, which has a spiral direction, and occasionally there are three. The free border of the valvular flaps is concave, and directed forwards, so that while the current of blood is permitted to flow freely towards the heart, the valves are distended, and the current intercepted, if the stream be- come retrograde in its course. On the car- diac side of each valve the vein is expanded into two pouches (sinuses), corresponding with the flaps of the valves, which give to the distended or injected vein a knotted appearance. The valves are most nume- rous in the veins of the extremities, par- ticularly in the deeper veins, and they are generally absent in the very small veins, and in the veins of the viscera, as in the portal and cerebral veins ; they are also absent in the large trunks, as in the venas cavas, vena) azygos, innominate, and iliac veins. Sinuses are venous channels, excavated in the structure of an organ, and lined by the internal coat of the veins; of this structure are the sinuses of the dura mater, whose external covering is the fibrous tissue of the membrane. The external investment of the sinuses of the uterus is the tissue of that organ ; and that of the bones, the lining membrane of the cells and canals. Veins, like arteries, are supplied with nutritious vessels, the vasa vasorum; their nervous filaments, few in number and of small size, are derived from the sympathetic and spinal system; they have been found only on the larger veins; as, the venae cavae, iliacs, crural, jugular, vertebral, and sinuses of the dura mater. I shall describe the veins according to the primary division of the body; taking first, those of the head and neck ; next, those of the upper extremity; then, those of the lower extremity; and lastly, the veins of the trunk. Fig. 215.* VEINS OE THE HEAD AND NECK. The veins of the head and neck may be arranged into three groups, namely, veins of the exterior of the head, veins of the diploe and interior of the cranium, veins of the neck. The veins of the exterior of the head are, the Facial, Internal maxillary, Temporal, Temporo-maxillary, Posterior auricular, Occipital. * Shows the arrangement of the valves of veins. A. The vein cut open and two pairs of valves exposed. B. The valves closed; showing the pouching which takes place on the proximal side of the valves. VEINS OF THE HEAD AND NECK. 397 The Facial vein (facialis anterior) commences on the anterior part of the head in a venous plexus, formed by the communications of the branches of the temporal, and descends along the middle line of the forehead, under the name of frontal vein, to the root of the nose, where it is connected with its fellow of the opposite side by a communicating trunk, the nasal arch. There are usually two frontal veins, which communicate by a transverse inosculation; but sometimes the vein is single and bifurcates at the root of the nose, into the two angular veins. From the nasal arch the frontal is continued downwards by the side of the root of the nose, and near the angle of the eye, under the name of angular vein; it then passes beneath the zygomatic muscles, becomes the facial vein, and descends along the anterior border of the masseter muscle, crossing the body of the lower jaw by the side of the facial artery, to the submaxillary gland, and from thence to the internal jugular vein, in which it terminates. The branches which the facial vein receives in its course are, the supra.-orbital, which joins the frontal vein; the dorsal veins of the nose, which terminate in the nasal arch; the ophthalmic, which com- municates with the an- gular vein; the palpe- bral and nasal, which open into the angular vein; a considerable trunk, the deep facial (maxillaris interna an- terior), which returns the blood from the spheno-maxillary fossa, from the infraorbital, palatine, vidian, and spheno-palatine veins, and joins the facial be- neath the zygomatic process of the superior maxillary bone; and the veins corresponding with the branches of the facial artery. The Internal maxil- lary vein receives the veins from the zygomatic and pterygoid fossa, which correspond generally with the branches of the internal maxillary artery; they Fig. 216.* * Superficial veins of the head and neck. 1. Fascial. 2. Temporal. 3. Transverse facial. 4. Posterior auricular. 5. Internal maxillary. 6. Ex- ternal jugular. 7. Posterior external jugular. 8. Anterior jugular. 9. Pos- terior scapular. 10. Internal jugular. 11. Occipital. 12. Subclavian. 398 VEINS OF THE DIPLOE. are so numerous and communicate so freely as to constitute a pterygoid plexus. Passing backwards behind the neck of the lower jaw, the internal maxillary joins the temporal vein. The Temporal vein commences on the vertex of the head by a plexiform network, which is continuous with the frontal, opposite temporal, auricular, and occipital vein. The ramifications of' this plexus form an anterior and posterior branch which unite imme- diately above the zygoma; the trunk is here joined by another large vein, the middle temporal, which collects the blood from the tem- poral muscle and outer segment of the orbit, and pierces the temporal fascia near the root of the zygoma. The temporal vein then descends in the substance of the parotid gland to the angle of the lower jaw, where it divides into two trunks, one of which, mounting upon the sterno-mastoideus muscle, constitutes the ex- ternal jugular vein; while the other, uniting first of all with the internal maxillary and then with the facial vein, becomes the temporo-maxillary vein. The temporal vein receives the anterior auricular, masseteric, transverse facial, and parotid veins. The Temporo-maxillary vein, a short trunk formed by the union of the temporo-maxillary trunk and facial vein, sends a branch to the anterior jugular, and terminates in the internal jugular vein. It receives the lingual, laryngeal, and superior thyroid vein. The Posterior auricular vein communicates with the plexus of the vertex of the head, and descends behind the ear to join the external jugular vein near its origin. It receives in its course the veins of the external ear and the stylo-mastoid vein. The Occipital vein commencing posteriorly in the plexus of the vertex of the head, follows the direction of the occipital artery, and passing deeply beneath the muscles of the back part of the neck, terminates in the external or internal jugular vein. This vein communicates with the lateral sinus by means of a large branch which passes through the mastoid foramen, the mastoid vein. VEINS OP THE DIPLOE. The diploe of the bones of the head is furnished in the adult with irregular sinuses (venae, diploeticce), which are formed by a conti- nuation of the internal coat of the veins into the osseous canals in which they are lodged. At the middle period of life these sinuses are confined to separate bones; but in old age, after the ossification of the sutures, they may be traced from one bone to the next. They receive their blood from the capillaries supplying the cellular structure of the diploe, and terminate externally in the veins of the pericranium, internally, in the veins and sinuses of the dura mater; they are separated from the bony walls of the canals by a thin layer of medulla. describes four of these diploetic veins, namely, frontal, anterior temporal, posterior temporal, and occipital. The frontal, the smallest of the four, escapes from the frontal bone at the supra- orbital notch, and opens into the supraorbital vein. The anterior SINUSES OF THE DUKA MATEK. 399 temporal also collects the blood from the frontal bone, and termi- nates either in the deep temporal veins or in the cavernous sinus. The posterior temporal commences in the parietal bone, and opens into the lateral sinus, sometimes sending a branch outwards to the veins of the scalp. The occipital, the largest of the four, originates in the occipital bone, and terminates in the occipital sinus, or ex- ternally in the occipital vein. The cerebral veins are remarkable for the absence of valves, and for the extreme tenuity of their coats. They may be arranged into the superficial, and deep or ventricular veins. The Superficial cerebral veins are situated on the surface of the hemispheres lying in the grooves formed by the convexities of the convolutions. They are named from the position which they may chance to occupy on the surface of the brain, either superior or in- ferior, internal or external, anterior or posterior. The Superior cerebral veins, seven or eight in number at each side, pass obliquely forwards, and terminate in the superior longi- tudinal sinus, in the opposite direction to the course of the stream of blood in the sinus. In the infant the direction of these veins is nearly transverse. The Deep or Ventricular veins commence within the lateral ven- tricles by the veins of the corpora striata and those of the choroid plezius, which unite to form the two venae Galeni. The Venae, Galeni pass backwards in the structure of the velum interpositum; and escaping through the fissure of Bichat, termi- nate in the straight sinus. The Cerebellar veins are disposed, like those of the cerebrum, on the surface of the lobes of the cerebellum; they are situated, some on the superior, some on the inferior surface, while others occupy the borders of the organ. They terminate in the lateral and petrosal sinuses. CEREBRAL AND CEREBELLAR VEINS. The sinuses of the dura mater are irregular channels formed by the splitting of the layers of that membrane, and lined on their inner surface by a continuation of the internal coat of the veins. They may be divided into two groups—those situated at the upper and back part of the skull, and those of the base of the skull. The former are, the SINUSES OF THE DUKA MATEK. Superior longitudinal sinus, Inferior longitudinal sinus, Straight sinus, Occipital sinuses, Lateral sinuses. The Superior longitudinal sinus is situated in the attached margin of the falx cerebri, and extends along the middle line of the arch of the skull, from the foramen caecum in the frontal, to the inner tuberosity of the occipital bone, where it divides into the 400 SINUSES OF THE DURA MATER. two lateral sinuses. It is triangular in form, small in front, and increases gradually in size as it passes backwards; it receives the superior cerebral veins which open into it obliquely, numerous small veins from the diploe, and near the posterior extremity of Fig. 217.* the sagittal suture the parietal veins, from the pericranium and scalp. Examined in its interior, it presents numerous transverse fibrous bands (trabeculae) the chordae Willisii, which are stretched across its inferior angle; and some small white granular masses, the glandules Pacchioni; the oblique openings of the cerebral veins, with their valve-like margin, are also seen on the walls of the sinus. The termination of the superior longitudinal sinus in the two lateral sinuses forms a considerable dilatation, into which the straight sinus opens from the front, and the occipital sinuses from below. This dilatation is named the torcular Herophilif, and is the point of communication of six sinuses, the superior longitudinal, two lateral, two occipital, and the straight. The Inferior longitudinal sinus is situated in the free margin of * Sinuses of the upper and back part of the skull. 1. Superior longitudinal sinus. 2, 2. Cerebral veins opening into the sinus from behind forwards. 3. Falx cerebri. 4. Inferior longitudinal sinus. 5. Straight sinus. 6. Venae. Galeni. 7. Torcular Ilerophili. 8. The lateral sinuses, with the occipital sinuses between them. 9. The termination of the inferior petrosal sinus of one side. 10. Bulbs of the internal jugular veins, corresponding with the jugular fossae. 11. Internal jugular veins. t Torcular (a press), from a supposition entertained by the older anatomists that the columns of blood, coming in different directions, compressed each other at this point. SINUSES OF THE DUKA MATEK. 401 the falx cerebri; it is cylindrical in form, and extends from near the crista galli to the anterior border of the tentorium, where it termi- nates in the straight sinus. It receives in its course several veins from the falx and sometimes one or two from the internal surface of the hemispheres. The Straight sinus (sinus tentorii) is the sinus of the tentorium it is situated at the line of union of the falx with the tentorium; is prismoid in form, and extends across the tentorium, from the termination of the inferior longitudinal sinus to the torcular Herophili. It receives the venae G-aleni, the cerebral veins from the inferior part of the posterior lobes, and the superior cerebellar veins. The Occipital sinuses (occipitales posteriores) are two canals of small size, situated in the attached border of the falx cerebelli; they commence by several small veins around the foramen magnum, and terminate by separate openings in the torcular Herophili. Not unfrequently they communicate with the termination of the lateral sinuses. The Lateral sinuses (sinus transversi, vel laterales), com- mencing at the torcular Hero- phili, pass horizontally outwards, in the attached margin of the tentorium, and then curve down- wards and inwards along the base of the petrous portion of the temporal bone, at each side, to the foramina lacera posteriora, where they terminate in the internal jugular veins. Each sinus rests in its course on the transverse groove of the occipital bone, pos- terior inferior angle of the parie- tal, mastoid portion of the tem- poral, and again on the occipital bone. They receive the cerebral veins from the inferior surface of the posterior lobes, the inferior cerebellar veins, superior petrosal sinuses, mastoid and posterior condyloid vein. These sinuses are often unequal in size, the right being larger than the left. Fig. 218.* * Sinuses of the base of the skull. 1. Ophthalmic veins. 2. Cavernous sinus of one side. 3. Circular sinus; the figure occupies the position of the pituitary gland in the sella turcica. 4. Inferior petrosal sinus. 5. Trans- verse or anterior occipital sinus. 6. Superior petrosal sinus. 7. Internal jugular vein. 8. Foramen magnum. 9. Occipital sinuses. 10. Toroular Herophili. 11, 11. Lateral sinuses. 402 CAVERNOUS SINUSES. The sinuses of the base of the skull are, the Cavernous, Inferior petrosal, Circular, S uperior petrosal, Transverse. The Cavernous sinuses are named from presenting a structure similar to that of the corpus cavernosum penis. They are situated at each side of the sella turcica, receiving, anteriorly, the ophthalmic veins through the sphenoidal fissures, and terminating posteriorly in the inferior petrosal sinuses. In the cavernous sinus is the in- ternal carotid artery, several filaments of the carotid plexus, the third, fourth, ophthalmic, and sixth nerve. The third, fourth, and Fig. 219.* 3rd nerve 4th nerve 5th nerve 6th nerve Dura Mater Venous canal. Internal carotid. ophthalmic nerves lie in the outer wall of the sinus, just beneath the dura mater; the sixth in the inner wall, between the sinus and the internal carotid artery. As the nerves approach the sphenoidal fissure they change their position, so that at that opening the fourth nerve is highest, next, the frontal and lachrymal branches of Sphenoidal Fissure. Fig. 220.f Cavernous Sinus. 4th nerve Frontal of 5th 3rd. 4th. oth. 6th. Lachrymal of 5th Supr. div. of 3rd Nasal of 5th Infer, div. of 3rd 6th nerve Gfasserian Ganglion. * Diagram of left cavernous sinus seen in section from behind, t Diagram of the nerves passing through the cavernous sinus. VEINS OF THE NECK. 403 the ophthalmic, then the upper division of the third, the nasal branch of the ophthalmic, the lower division of the third, and the sixth nerves, in the order here given. The artery is separated from the blood flowing through the sinus, by the lining membrane of the latter. Besides the ophthalmic vein the cavernous sinus receives the cerebral veins of the under part of the anterior lobe, a vein from the posterior border of the orbit (sinus spheno-parietalis) and the vein of the middle fossa of the cranium. The cavernous sinuses communicate by means of the ophthalmic with the facial veins, by the circular sinus with each other, and by the superior petrosal with the lateral sinuses. The Inferior petrosal sinuses are the continuations of the caver- nous sinuses backwards along the lower border of the petrous portion of the temporal bone at each side of the base of the skull, to the foramina lacera posteriora, where they terminate with the lateral sinuses in the commencement of the internal jugular veins. The Circular sinus (sinus of Ridley; ellipticus) is situated in the sella turcica, surrounding the pituitary gland, and communicating on each side with the cavernous sinus. The posterior segment is larger than the anterior. The Superior petrosal sinuses pass obliquely backwards along the attached border of the tentorium, on the upper margin of the petrous portion of the temporal bone, and establish a communica- tion between the cavernous and lateral sinus at each side. They receive one or two cerebral veins from the inferior part of the middle lobes, and a cerebellar vein from the anterior border of the cere- bellum. Near the extremity of the petrous bone these sinuses cross the oval aperture which transmits the fifth nerve. The Transverse sinus (basilaris; occipitalis anterior) passes transversely across the basilar process of the occipital bone, forming a communication between the two inferior petrosal sinuses. Some- times there are two sinuses in this situation, or, more properly, a plexus. The veins of the neck which return the blood from the head are, VEINS OF THE NECK. External jugular, Anterior jugular, Internal jugular, Vertebral. The External jugular vein, the continuation of the superficial division of the temporo-maxillary, augmented by the junction of the posterior auricular, and sometimes of the occipital, commences at the lower border of the parotid gland, in front of the sterno-mastoid muscle. It descends the neck in the direction of a line drawn from the angle of the lower jaw to the middle of the clavicle, crosses the sterno-mastoid, and terminates near the posterior and inferior attachment of that muscle, in the subclavian vein. In its course downwards, it lies on the anterior lamella of the deep cervical fascia, which separates it from the sterno-mastoid muscle, and is 404 JUGULAR VEINS, covered in by the platysma myoides and superficial fascia; at the root of the neck it pierces the deep cervical fascia. It is accom- panied, for the upper half of its course, by the auricularis magnus nerve. The branches which it receives are the occipital cutaneous and posterior cervical cutaneous, and, near its termination, the supra-scapular and posterior scapular. The external jugular vein is variable in size, and occasionally replaced by two veins. The Anterior jugular vein commences on the os hyoides by several small veins and by a branch from the temporo-maxillary, and passes downwards along the midline of the neck to the sternum ; it then turns outwards behind the lower part of the sterno-mastoi- deus and opens into the subclavian vein, near the termination of the external jugular. The two veins communicate with each other, and with the external and internal jugular vein. The Internal jugular vein, formed by the convergence of the lateral and inferior petrosal sinus, commences at the foramen lace- rum posterius on each side of the base of the skull, by a dilatation (bulbus venae jugularis), and descends the side of the neck, lying, in the first instance, to the outer side of the internal carotid, then on the outer side of the common carotid artery to the root of the neck, where it unites with the subclavian, and constitutes the vena innominata. At its commencement, the internal jugular vein is posterior and external to the internal carotid artery and eighth pair of nerves, the hypoglossal nerve being behind it; lower down, the vein and artery are on the same plane, the glosso-pharyngeal and hypoglossal nerve passing forwards between them, the pneumo- gastnc being between and behind in the same sheath, and the nervus accessorius crossing obliquely behind or before the vein at its upper part. The branches which the internal jugular receives in its course are, pharyngeal, occipital, deep division of the temporo-maxillary, and middle thyroid. The Vertebral vein descends by the side of the vertebral artery, in the canal formed by the foramina in the transverse processes of the cervical vertebrae, and at the root of the neck opens into the subclavian vein close to its termination. In the lower part of the vertebral canal it frequently divides into two branches, one of which advances forwards, while the other passes through the foramen in the transverse process of the seventh cervical vertebra, before open- ing into the subclavian vein. The branches which it receives in its course are the posterior condyloid vein, muscular veins, cervical meningo-rachidian veins, and near its termination, the superficial and deep cervical veins. The Inferior thyroid veins, two, and frequently more in number, are situated one on each side of the trachea, and receive the venous blood from the thyroid gland. They communicate with each other, and with the middle and superior thyroid veins, and form a plexus on the front of the trachea. The right vein terminates in the right VEINS OF THE UPPER EXTREMITY. 405 vena innominata, just at its union with the superior cava; the left in the left vena innominata. VEINS OE THE UPPER EXTREMITY. The veins of the upper extremity are deep and superficial. The deep veins accompany the branches and trunks of the arteries, and constitute their vence comites. The vena; comites of the radial and ulnar artery are enclosed in the same sheath with those vessels, and terminate at the bend of the elbow in the brachial veins. The brachial venae comites are situated one at each side of the artery, and open into the axillary vein; the axillary becomes the subcla- vian, and the subclavian unites with the internal jugular to form the vena innominata. The Superficial veins of the arm are, the Anterior ulnar vein, Posterior ulnar vein, Basilic vein, Radial vein, Cephalic vein, Median vein, Median basilic, Median cephalic. The Anterior ulnar vein collects the venous blood from the inner and palmar border of the hand and ascends along the anterior as- pect of the inner side of the forearm to the bend of the elbow, where it receives the median basilic, and becomes the basilic vein. The Posterior ulnar vein commences on the dorsum of the hand by the ulnar termination of the venous arch which receives the digital veins from the fingers, and, after being joined by a large vein, the vena salvatella, from the little finger, ascends along the posterior aspect of the forearm to the bend of the elbow, where it turns forward and terminates in the anterior ulnar vein. The Basilic vein (Paa-iXinds, royal, or principal) ascends from the common ulnar vein formed by the two preceding, along the inner side of the upper arm, and near its middle pierces the fascia; it then passes upwards to the axilla, and becomes the axillary vein. The Radial vein commences on the dorsum of the hand, by the radial termination of the venous arch, which receives the veins of the fingers. This origin is increased by the junction of some small veins from the thumb. The radial vein ascends the dorsal side of the forearm to a little below its middle, then lies on its anterior aspect to the bend of the elbow, where it receives the median cephalic, and becomes the cephalic vein. The Cephalic vein ( the sterno-mastoid muscle. 24. Branches to the trapezius. 504 INFERIOR LARYNGEAL NERVE. Fig. 270.* in the groove between the trachea and oesophagus, and piercing the lower fibres of the inferior constrictor mus- cle enters the larynx close to the articulation of the infe- rior cornu of the thyroid with the cricoid cartilage. It is distributed to all the mus- cles of the larynx, with the exception of the crico-thyroid, and communicates on the arytenoideus muscle with the superior laryngeal nerve. As it curves around the sub- clavian artery and aorta it gives branches (cardiac) to the heart and root of the lungs ; and as it ascends the neck it distributes filaments to the oesophagus and tra- chea, and communicates with the external laryngeal nerve and sympathetic. The Anterior pulmonary branches, two or three in number, are distributed upon the anterior aspect of the root of the lungs, forming, * Diagram of the eighth, ninth, and sympathetic nerves (from Hirschfeld and Le\eilld). 1. Fa- cial nerve. 2. Gloso-pharyngeal nerve, with its petrous ganglion. 3. Pueumogastric lerve. 4. Spi- nal accessory nerve. 5. Hypo- glossal nerve. 6. Superior cer- vical ganglion of sympathetic. 7. Loop between frst and second cervical nerves. 8. iarotid branch of sympathetic. 9. Tympanic nerve (Jacobson). 10. Its branch to carotid plexus. 11. its branch to Eustachian tube. 12. Its branch to fenestra ovalis. 13. its branch to fenestra rotunda. 14. Its union with small superficial petrosal rerve. 15. Its union with large superficial petrosal nerve. 16. Otic ganglion. 17. Auricular nerve of pneumogastric. 18. Junction of pneumogas trie with spiral accessory. 19. Junction of ninth nerve and first cervical nerve. 20. Junctim of mastoid branch of spinal accessory and second cervical nerve. 21. Pharjngeal plexus. 22. Superior laryngeal nerve. 23. External laryngeal nerve. 2i Middle cer- vical ganglion of sympathetic. 25. Junction of digastric nerve (seventh) with glosso-pharyngeal. SPINAL ACCESSORY NERVE. 505 with branches from the cardiac plexuses, 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 lungs ; they are joined by filaments from the third and fourth thoracic ganglia of the sympathetic, and form the posterior pulmo- nary plexus. (Esophageal branches are given off by the pneumogastric nerves above the root of the lungs ; below that point, the trunks of the nerves divided into several cords, form a plexus around the oeso- phagus, the right and left nerves communicating with each other. This plexus accompanies the oesophagus to the stomach, and is the oesophageal plexus (plexus guise). The Gastric branches are the terminal filaments of the pneumo- gastric nerves; they are spread out upon the anterior and posterior surface of the stomach, and are likewise distributed to the omen- tum, spleen, pancreas, liver, and gall-bladder. The branches of the anterior aspect of the stomach proceed from the left nerve and communicate with the hepatic plexus in the lesser omentum; those of the posterior aspect are derived from the right nerve and com- municate with the solar plexus. Spinal accessory nerve; eleventh pair of Soemmering.—The spinal accessory, a nerve of motion, arises by several filaments from the .side of the spinal cord as low down as the fifth or sixth cervical nerve, and ascends behind the ligamentum dentatum, and between the anterior and posterior roots of the spin al nerves, to the foramen lacerum posterius. It communicates in its course with the posterior root of the first cervical nerve, and entering the foramen lacerum, becomes applied against the posterior aspect of the superior ganglion of the pneumogastric, being contained in the same sheath of dura mater. The nerve then passes outwards and downwards, behind and sometimes in front of the internal jugular vein, to the upper and under part of the sterno-mastoid, pierces that muscle obliquely, and descends across the posterior triangle of the neck to the under surface of the trapezius to which it is distributed its branches being continued downwards to near the lower border of de muscle. The Branches of communication of the spinal accessory are one or two small branches from the superior ganglion of the pneumo- gastric, and a large branch which joins the pneumogastric between the two ganglia. Its Branches of distribution are muscular branches to the sterno- mastoid and trapezius. In the substance of the sterno-mastoid it communicates with branches of the cervical plexus, and in the posterior triangular space with the third and fourth cervical nerve. The pneumogastric and spinal accessory nerve together (nervus vagus cum accessorio) resemble a spinal nerve, of which the former with its ganglion is the posterior and sensitive root, the latter the anterior and motor root. The deep origin of the spinal accessory 506 HYPOGLOSSAL NERVE. may be traced into the grey substance of the floor of the fourth ventricle. Ninth pair of Willis; twelfth PAiRof Soemmering. Hypoglossal nerve ; lingual. —The hypoglossal is a nerve of motion, distributed to all the muscles of the tongue, most of those attached to the os hyoides, and the sterno-thyroid. It arises from the groove between the cor- pus pyramidale and corpus olivare by ten or fifteen fila- ments, which are collected into two bundles, and escape from the cranium through the anterior condyloid fora- men. At its exit from the cranium, the nerve lies be- hind the internal carotid ar- tery and internal jugular vein, then passing forward between the artery and .vein it descends to a point parallel with the angle of the lower jaw. It next curves forward around the occipital artery, with which it forms a loop, and crossing the ex- ternal carotid and lower part of the hyo-glossus muscle to the genio-hyo-glossus, sends filaments onwards with the anterior fibres of that muscle as far as the tip of the tongue. While resting on Fig. 271.* * Anatomy of the side of the neck, showing the nerves of the tongue. 1. Fragment of the temporal bone containing the meatus auditorius externus, mastoid, and styloid process. 2. Stylo-hyoid muscle. 3. Stylo-glossus. 4. Stylo-pharyngeus. 5. Tongue. 6, 18. Hyo-glossus muscle: its two por- tions. 7. Genio-liyo-glossus. 8. Genio-byoideus; both arise from the inner surface of the symphysis of the lower jaw. 9. Sterno-hyoid muscle. 10. Sterno- thyroid. 11. Thyro-hyoid, upon which the thyro-hyoidean branch of the hypoglossal nerve is seen ramifying. 12. Omo-hyoid crossing the common carotid artery (13), and internal jugular vein (i4). 15. External carotid giving off its branches. 16. Internal carotid. 17. Gustatory nerve giving a branch to the submaxillary ganglion (18), and communicating a little farther on with the hypoglossal nerve. 19. Submaxillary, or Wharton’s duct, passing forwards to the sublingual gland. The submaxillary ganglion is the small round body between figures 18 and 19. 20. Glosso-pharyngeal nerve, passing in behind the hyo-glossus muscle. 21. Hypoglossal nerve curving around tlie occipital artery. 22. Descendens noni nerve, forming a loop with (23) the communicans noni, which is seen arising by filaments from the upper cervical nerves. 24. Pneumogastric nerve, emerging from between the internal jugular vein and common carotid artery, and entering the chest. 25. Facial nerve, emerging from the stylo-mastoid foramen and crossing the external carotid artery. SPINAL NERVES. 507 the hyo-glossus muscle it is flattened, and beneath the mjdo- hyoideus communicates with the gustatory nerve. At its origin, the hypoglossal nerve sometimes communicates with the posterior root of the first cervical nerve. Its deep origin may be traced to one of the nuclei of grey substance, in the floor of the fourth ventricle, where it decussates with its fellow of the opposite side. The branches of the hypoglossal nerve are, branches of communi- cation and branches of distribution. The Branches of communication of the hypoglossal nerve are, several to the pneumogastric, with which nerve it is closely united ; one or two with the superior cervical ganglion of the sympathetic; and one or two with the loop between the first and second cervical nerve. The Branches of distribution are— Descendens noni, Thyro-hyoidean, Muscular. The Descendens noni is a long and slender nerve, which quits the hypoglossal just as it is about to form its arch around the occipital artery, and descends on the sheath of the carotid vessels. Just below the middle of the neck it forms a loop with a long branch (communieans noni) derived from the second and third cervical nerve. From the convexity of this loop branches are sent to the sterno-hyoideus, sterno-thyroideus, and both bellies of the omo- hyoideus; sometimes also a twig is given off to the cardiac plexus, and occasionally one to the phrenic nerve. If the descendens noni be traced to its origin, it will be found to be composed of a branch from the hypoglossal, and one from the first and second cervical nerve; occasionally it receives also a filament from the pneumo- gastric. ' The Thyro-hyoidean nerve is a small branch, distributed to the thyro-hyoideus muscle. It is given off by the trunk of the hypo- glossal near the posterior border of the hyo-glossus, and descends obliquely over the great cornu of the os hyoides. The Muscular branches are given off where the nerve is covered in by the mylo-hyoideus muscle, and rests on the hyo-glossus; several large branches take their course across the fibres of the genio-hyo-glossus to reach the substance of the tongue. Moreover, on the hyo-glossus muscle, the branches of the hypoglossal neiwe communicate with those of the gustatory nerve. SPINAL NERVES. There are thirty-one pairs of spinal nerves, each arising by two roots, an anterior or motor root, and a posterior or sensitive root. The anterior roots proceed from the anterior lateral sulcus, which marks the division of the anterior from the posterior part of the antero-lateral column of the spinal cord, and gradually approach towards the anterior median fissure as they descend. 508 SPINAL NERVES. The posterior roots, more regular than the anterior, proceed from the posterior lateral sulcus; they are larger, and the filaments Fig. 272.* Fig. 273f. of origin more numerous than those of the anterior roots; and in the intervertebral foramina there is a ganglion on each of their roots. The first cervical nerve forms an exception to these cha- racters ; its posterior root is smaller than the anterior; it often joins, in whole or in part, the spinal accessory nerve, and sometimes the hypoglossal; it has frequently no ganglion, and when the ganglion exists, it is often situated within the dura mater, the latter being the usual position of the ganglia of the last two pairs of spinal nerves. After the formation of a ganglion, the two roots unite, and con- stitute a spinal nerve, which escapes through the intervertebral foramen, and separates into an anterior cord for the supply of the front aspect of the body, and a posterior cord for the posterior aspect. In the first cervical, last sacral, and coccygeal nerve this division takes place within the dura mater; and in the upper four sacral nerves, externally to that cavity, but within the sacral canal. The anterior cords, with the exception of the first two cervical nerves, are larger than the posterior; an arrangement which is * Part of the cervical portion of the spinal cord, viewed on its posterior aspect; showing its membranes and the posterior roots of the spinal nerves. 1, 1. Posterior median fissure. 2, 2. Posterior roots of the cervical nerves; on the opposite side the corresponding roots are cut through near their origin. 3, 3. Membrana dentata. 4. Nervus accessorius, ascending between the pos- terior roots and membrana dentata; on the opposite side this nerve has been removed. 5.5. Dura mater. 6,6. Openings in the dura mater for the passage of the roots of the nerve. 7,7. Ganglia on the posterior roots of the spinal nerves. 8. Anterior roots of the spinal nerves. The posterior roots have been cut away in order to show each anterior root proceeding to join the nerve beyond the ganglion. t Roots of the spinal nerves. 1. Anterior root. 2. Posterior root. CERVICAL NERVES. 509 proportioned to the larger extent of surface they are required to supply. The Spinal nerves are classed as follows:— Cervical 8 pairs Dorsal 12 „ Lumbar 5 „ Sacral 5 „ Coccygeal 1 „ The cervical nerves pass off transversely from the spinal cord; the dorsal are oblique in direction; the lumbar and sacral, vertical; the latter form the large assemblage of nerves, at the termination of the cord, called cauda equina. The cauda equina occupies the lower third of the spinal canal. CERVICAL NERVES. The cervical nerves increase in size from above downwards; the first (suboccipital) passes out of the spinal canal between the occipital bone and atlas; the second between the posterior ring of the atlas and the lamina of the axis; and the last between the last cervical and first dorsal vertebra. Each nerve, at its escape from the intervertebral foramen, divides into an anterior and a posterior cord. The anterior cords of the four upper cervical nerves form the cervical plexus; the posterior cords, the posterior cervical plexus. The anterior cords of the four inferior cervical together with the first dorsal form the brachial plexus. Anterior cervical nerves.—The anterior cord of the first cer- vical or suboccipital nerve escapes from the vertebral canal through the groove on the posterior arch of the atlas, which supports the vertebral artery, lying beneath that vessel. It descends in front of the transverse process of the atlas, sends twigs to the rectus lateralis and rectus anticus minor, and forms an anastomotic loop by communicating with an ascending branch of the second nerve. Branches from this loop communicate with the pneumogastric nerve, hypoglossal nerve, and first cervical ganglion of the sympathetic. The anterior cord of the second cervical nerve, at its exit from the intervertebral foramen between the atlas and axis, gives twigs to the rectus anticus major, scalenus medius, and levator anguli scapulae, and divides into three branches: ascending branch, which com- pletes the arch of communication with the first nerve; and two descending branches, which form loops with corresponding branches of the third nerve. The anterior cord of the third cervical nerve, double the size of the preceding, divides at its exit from the intervertebral foramen into several branches, some of which are distributed to the rectus major, longus colli, and scalenus medius, while others communicate and form loops and anastomoses with the second and fourth nerve. The anterior cord of the fourth cervical nerve, equal in size with 510 CERVICAL PLEXUS. the preceding, sends twigs to the rectus major, longus colli, and levator anguli scapula?, communicates by anastomosis with the third, and sends a small branch downwards to the fifth nerve. Its principal branches pass downwards and outwards across the pos- terior triangle of the neck, towards the clavicle and acromion. The anterior cords of the fifth, sixth, seventh, and eighth cervical nerves will be described with the brachial plexus, of which they form a part. Cervical plexus.—The cervical plexus is constituted by the loops of communication and anastomoses which take place between the anterior cords of the first four cervical nerves. The plexus rests on the levator anguli scapulas, posterior and middle scalenus, and splenius colli muscle, and is covered in by the sterno-mastoid and platysma. The Branches of the cervical plexus may be arranged into three groups, superficial ascending, superficial descending, and deep:— Ascending, ' Superficialis colli, Auricularis magnus, Occipitalis minor. Superficial Acromiales, Claviculares, Sternales. Descending, Deep . . r Communicating branches, I Communicans noni, Muscular, k Phrenic. The Superficialis colli is formed by communicating branches from the second and third cervical nerves; it curves around the posterior border of the stemo-mastoid and crosses obliquely behind the ex- ternal jugular vein to the anterior border of that muscle, where it pierces the deep cervical fascia and divides into an ascending and a descending branch. The ascending branch passes upwards to the submaxillary region, and divides into four or five filaments, some of which pierce the platysma myoides, and supply the integument as high as the chin and lower part of the face; while others form a plexus with the inframaxillary branches of the facial nerve beneath the platysma. One or two filaments from this branch accompany the external jugular vein. The descending branch pierces the platysma and is distributed to the integument of the front of the neck as far downwards as the sternum. The Auricularis magnus, the largest of the three ascending branches of the cervical plexus, also proceeds from the second and third cervical nerve; it curves around the posterior border of the sterno-mastoid, and ascends upon that muscle, lying parallel with the external jugular vein, to the parotid gland, where it divides into an anterior and a posterior branch. CEEVICAL PLEXUS. 511 The anterior branch is distributed to the integument over the parotid gland, and to the gland itself, communicating with the facial nerve. The posterior branch ascends behind the ear, where it divides into auricular branches, supplying the pinna; and a mastoid branch which communicates with the posterior auricular branch of the facial and is distributed to the integument behind the ear. The auricular branches communicate with the auricular offsets of the facial nerve, pneumogastric nerve, and occipitalis minor. The Occipitalis minor arises from the second cervical nerve; it curves around the posterior border of the sterno-mastoid above the preceding, and ascends upon that muscle, parallel with its posterior border, to the lateral and posterior aspect of the cranium. It is distributed to the integument, to the occipital portion of the occipito-frontalis and attollens aurem, and communicates with the occipitalis major, auricularis magnus, and posterior auricular branch of the facial. Superficial descending branches.—The Acromiales and Clavicu- lares are two or three large nerves which proceed from the fourth cervical nerve, and pass downwards in the posterior triangle of the neck; they pierce the deep fascia, and, crossing the clavicle, are distributed to the integument of the front of the chest from the sternum to the acromion: hence their designation, claviculares and acromiales. The most anterior of the branches is named sternal, from its destination, and the outermost branch passes over the clavicular attachment of the trapezius, to reach the shoulder. Beep Branches.—The communicating branches are filaments which arise from the loop between the first and second cervical nerve, and pass inwards to communicate with the sympathetic, pneumogastric, and hypoglossal nerve. The first three cervical nerves send branches to the first cervical ganglion; the fourth sends a branch to the trunk of the sympathetic, or to the middle cervical ganglion. From the second cervical nerve a large branch is given off, which joins the spinal accessory nerve. The Gommunicans noni is a long and slender branch of commu- nication between the cervical plexus and descendens noni; it is formed by filaments from the second and third cervical nerve; de- scends at the outer side of the internal jugular vein, and forms a loop with the descendens noni over the sheath of the carotid vessels. The Muscular branches of the cervical plexus are distributed to the muscles of the front of the vertebral column and side of the neck. From the loop, between the first and second nerve, branches are given to the anterior recti; from the second cervical nerve a branch proceeds to the sterno-mastoid ; from the third and fourth nerve branches are distributed to the trapezius, levator anguli scapulae, scalenus medius, and scalenus posticus. The branch to the trapezius communicates with the spinal accessory nerve. The Phrenic nerve (internal respiratory of Bell) is formed by the 512 POSTERIOR CERVICAL NERVES. union of filaments from the third, fourth, and fifth cervical nerve, and one from the sympathetic. It descends to the root of the neck, resting on the scalenus anticus muscle, crosses the first portion of the subclavian artery, and enters the chest between it and the sub- clavian vein. Within the chest it passes downwards through the middle mediastinum, lying between the pleura and pericardium, and in front of the root of the lung, to the diaphragm; near the diaphragm it divides into branches which pierce that muscle, and are distributed on its under surface. Some of its filaments reach the abdomen through the openings for the oesophagus and vena cava, and communicate with the phrenic and solar plexus, and on the right side with the hepatic plexus. The left phrenic nerve is longer than the right, from the inclination of the heart to the left side, and crosses the arch of the aorta. The right nerve is situated more deeply in the upper part of the chest than the left, and lies in contact with the right vena innominata and superior vena cava. Both nerves cross in front of the origin of the internal mammary artery at their entrance into the chest. Posterior cervical nerves.—The posterior cords of the cervical nerves issue from between the transverse processes; and divide into an internal and external branch. The internal branch is directed inwards towards the middle of the spine, and, becoming cutaneous near the spinous processes of the vertebra, is then reflected out- wards to supply the integument. The external branch, smaller than the internal, is distributed to the muscles of the outer portion of the vertebral groove. The posterior cord of the first cervical nerve (sub-occipital), larger than the anterior, escapes from the vertebral canal through the opening for the vertebral artery, lying posteriorly to that vessel, and emerges in the triangular space formed by the rectus posticus major, obliquus superior, and obliquus inferior. It is distributed to the recti, obliqui and complexus, and sends a branch down- wards to communicate with the second cervical nerve; it has no external branch. The posterior cord of the second cervical nerve is three or four times larger than its anterior cord, and exceeds in size the other posterior cervical nerves. Its internal branch is the occipitalis major nerve. The posterior cord of the third cervical nerve is smaller than the second, but larger than the fourth ; its internal branch gives off a cutaneous branch to the back of the cranium. The posterior cords of the remaining cervical nerves go on pro- gressively decreasing in size to the seventh. The internal branches of the second, third, fourth, and fifth nerve lie on the semispinalis colli muscle, and are closely connected with a fascia which separates that muscle from the complexus. The second and third, with a branch from the first, constitute the pos- terior cervical plexus; and all the branches in their course to the surface pierce the complexus and trapezius and some the splenius. BRACHIAL PLEXUS. 513 The internal tranches of the sixth, seventh, and eighth nerve pass beneath the semispinalis colli, and are lost in the muscles without reaching the integument. The Occipitalis major nerve, the internal branch of the posterior cord of the second cervical nerve, ascends obliquely inwards between the obliquus inferior and complexus, pierces the complexus and trapezius after passing for a short distance between them, and ascends the posterior aspect of the head in company with the occi- pital artery. Soon after its escape from the trapezius, it receives a branch from the third cervical, and divides into numerous branches, which are distributed to the occipitalis muscle and to the' integument as far as the summit of the head. It communicates with the occipitalis minor nerve, and sends an auricular branch to the back of the ear. The Brachial or axillary plexus of nerves is formed by commu- nications between the anterior cords of the four lower cervical nerves and first dorsal. These nerves are alike in size, and their mode of disposition in the formation of the plexus as follows: the fifth and sixth unite to form a common trunk ; the last cervical and first dorsal also unite to form a single trunk ; the seventh cervical nerve lies for some distance apart from the rest, and then divides into two branches, which join the other cords. At the point of junction the plexus consists of two cords, from which a third is given off, and the three become placed, one to the inner side of the axillary artery, one behind, and one to its outer side. Lower down, each of the lateral cords gives off a branch which unites with its fellow in front of the artery, and surrounds the vessel; the trunk formed by the union of the two branches being the median nerve. The plexus is broad in the neck, narrows as it descends into the axilla, and again enlarges at its lower part, where it divides into its terminal branches. The brachial plexus communicates with the cervical plexus by means of a branch from the fourth to the fifth nerve ; and receives branches from the two inferior cervical ganglia of the sympa- thetic. The plexus is in relation in the neck with the scaleni muscles; lower down it is placed between the clavicle and subclavius muscle above, and the first rib and first serration of the serratus magnus muscle below. In the axilla, it is situated at first to the outer side of and then behind the axillary artery, resting by its outer border against the tendon of the subscapularis muscle. Lower down it completely surrounds the artery. The tranches of the brachial plexus are: from the outer cord, one of the anterior thoracic nerves, the musculo-cutaneous nerve, and the outer head of the median; from the inner cord, the other anterior thoracic nerve, inner head of the median, internal cuta- neous, lesser internal cutaneous of Wrisberg, and ulnar; from the BRACHIAL PLEXUS. 514 BRACHIAL PLEXUS. posterior cord, the suhseapular nerves, circumflex, and musculo- spiral. Besides these, the brachial plexus, while in the neck, gives off Fig. 274.* several superior muscular branches; one to tlie subclavius muscle, one to the rhomboid muscles and levator anguli scapulae; one of * The nerves of the axilla (from Ilirschfeld and Leveilld). 1. Scalenus medius. 2. ScalenHs anticus. 3. Cord formed by fifth and sixth cervical nerves. 4. Seventh cervical nerve. 5. Suprascapular nerve. 6. Subclavian artery (cut). 7. Insertion of subclavius. 8. Cord formed by eighth cervical and first dorsal nerves. 9. Pectoralis major (reflected). 10. Internal anterior thoracic nerve. 11. External anterior thoracic nerve. 12. Origin of subclavius. 13. Pectoralis minor (reflected). 14. Internal cutaneous nerve. 15. Axillary artery (cut). 16. Posterior thoracic nerve (Bell). 17. Musculo-cutaneous nerve. 18. Origin of pectoralis minor. 19. Median nerve. 20. Nerve of Wrisberg. 21. Coraco-brachialis. 22. Intercosto-humeral nerve. 23. nerve. 24. Subscapularis. 25. Brachial artery. 26. Lateral cutaneous branch of third intercostal nerve. 27. Middle subscapular nerve. 28. Short sub- scapular nerve. 29. Long subscapular nerve. 30. Pectoralis major (cut). 31. Basilic vein. 32. Serratus magnus. 33. Latissimus dorsi. BRACHIAL PLEXUS. 515 large size, the suprascapular; and a long and slender nerve which passes down the thoracic wall of the axilla, the posterior thoracic, or external respiratory nerve of Bell. In reference to their distribution, the branches of the brachial plexus may be arranged in three groups, thoracic, scapular, and brachial, as follows :— Thoracic. Anterior thoracic, Posterior thoracic. Scapular. Superior muscular, Suprascapular, Subscapular. Brachial. Musculo-cutaneous, Internal cutaneous, Lesser internal cutaneous, Median, Ulnar, Musculo-spiral, Circumflex. The Anterior thoracic nerves, two in number, proceed, one from tbe external cord of the plexus, the other from the internal cord. The former, the external or superficial branch, crosses the axillary artery in the space above the pectoralis minor to the front of the chest, and is distributed to the pectoralis major muscle. The internal or deeper branch issues from between the axillary artery and vein, and after forming a loop of communication with the preceding, is distributed to the under surface of the pectoralis minor and major. The Posterior thoracic, or external respiratory of Bell, is formed by the j unction of two offsets, one from the fifth, the other from the sixth cervical nerve; it crosses behind the brachial plexus to reach the side of the chest, and descends on the serratus magnus to the lower part of that muscle, to which it is distributed. The Superior muscular nerves are small branches to the longus colli and scaleni; and branches to the rhomboidei and subclavius. The Rhomboid branch proceeds from the fifth cervical nerve, and passing backwards through the fibres of the scalenus medius, and beneath the levator anguli scapulae, is distributed to the under sur- face of the rhomboid muscles. In its course it sometimes gives a branch to the levator anguli scapulae. The Subclavian branch, proceeding from the cord formed by the fifth and sixth nerve, descends in front of the subclavian artery to the subclavius muscle. This nerve usually communicates with the phrenic at its entrance into the chest. The Suprascapular nerve arises from the fifth cervical nerve, and proceeds obliquely outwards to the suprascapular notch; it passes through the notch, crosses the supra-spinous fossa beneath the supra-spinatus muscle, and running in front of the concave margin of the spine of the scapula enters the infra-spinous fossa, to be dis- 516 INTERNAL CUTANEOUS NERVE. tributed to the supra-spinatus and infra-spinatus muscle, and send two or three filaments to the shoulder-joint. The Subscapular nerves are three in number: one arises from the brachial plexus above the clavicle, the others from the posterior cord of the plexus within the axilla. The first or smallest supplies the upper part of the subscapularis muscle ; the second and largest {long subscapular) follows the course of the subscapular artery, and is distributed to the latissimus dorsi; the third supplies the lower part of the subscapularis muscle and teres major. Brachial nerves.—The brachial branches of the plexus are arranged in the following order : musculo-cutaneous, and one head of the median to the outer side of the artery; the other head of the median, internal cutaneous, lesser internal cutaneous, and ulnar, to its inner side ; the circumflex and musculo-spiral behind. The Musculo-cutaneous nerve (external cutaneous, perforans Casserii) arises from the brachial plexus in common with the ex- ternal head of the median; pierces the coraco-brachialis muscle, and passes between the biceps and brachialis anticus to the outer side of the bend of the elbow, where it perforates the deep fascia, and divides into an anterior and posterior branch. These branches pass behind the median cephalic vein, the anterior, the larger of the two, taking the course of the radial vein and communicating with the radial nerve on the back of the hand; the posterior and smaller following the direction of the supinator longus, communi- cating with the internal cutaneous, and at the lower third of the forearm sending off an arterial twig, which accompanies the radial artery to the wrist, and distributes filaments to the synovial mem- branes of the joint. The musculo-cutaneous nerve supplies the coraco-brachialis, biceps, and brachialis anticus in the upper arm, and the integument of the outer side of the forearm as far as the wrist and hand. The Internal cutaneous nerve, one of the internal and smaller branches of the axillary plexus, arises from the plexus in common with the ulnar and internal head of the median, and passes down the inner side of the arm in company with the basilic vein, giving off several cutaneous filaments in its course. At about the middle of the upper arm it pierces the deep fascia by the side of the basilic vein and divides into two branches, external and internal. The external branch, the larger of the two, divides into several branches which pass in front of, and sometimes behind, the median basilic vein at the bend of the elbow, and descend in the course of the palmaris longus muscle to the wrist, distributing filaments to the integument in their course and communicating with the anterior branch of the musculo-cutaneous on the outer side, and its own internal branch on the inner side of the forearm. The internal branch sends off several twigs to the integument over the inner con- dyle and olecranon, passes behind the inner condyle, and descends the forearm in the course of the ulnar vein as far as the wrist, supplying the integument of the inner side of the forearm, and MEDIAN NERVE, 517 communicating with the external branch of the same nerve in front, and the dorsal branch of the ulnar nerve at the wrist. The Lesser internal cutaneous nerve or nerve of Wrisberg, the smallest of the brachial nerves, arises with the preceding from the inner cord of the plexus, and issuing from beneath the axillary vein de- scends the inner side of the arm, to the middle of its posterior aspect, where it pierces the fascia and is distributed to the integument of the lower third of the upper arm as far as the olecranon. While in the axilla, the nerve of Wrisberg communicates with the intercosto-humeral nerve, and sometimes its place is taken by the latter. The Median nerve, named from its me- dian position in the arm and forearm, arises by two heads which proceed from the outer and inner cord of the plexus and embrace the axillary artery. The nerve lies at first to the outer side of the brachial artery, but crosses it in the middle, some- times in front and sometimes behind, and getting to its inner side descends to the bend of the elbow. It next passes between the two heads of the pronator radii teres and beneath the flexor sublimis digitorum, and runs down the middle of the forearm, lying between the latter muscle and the Fig. 275.* * Brachial plexus of nerves with its branches and their distribution. 1. Brachial plexus. 2. An- terior thoracic nerves. 3. Posterior thoracic or external respiratory of Bell. 4. Phrenic nerve. 5. Supra-scapular nerve. 6. Subscapular nerves. 7. Musculo-cutaneous nerve. 8. The point at which it pierces the coraco- brachialis muscle. 9. Internal cutaneous nerve; the point at which it pierces the deep fascia. 10. Origin of the median nerve by two heads. 11. Bend of the elbow where the median passes between the two heads of the pro- nator radii teres, and flexor sublimis digitorum. 12. Its muscular branches. 13. Anterior interosseous branch. 14. The point at which the nerve passes beneath the annular ligament and divides into six terminal branches. The branch which crosses the annular ligament is the superficial palmar. 15. Ulnar nerve. 16. The point at which it passes between the two heads of the flexor carpi ulnaris. 17. Its dorsal branch. 18. Termination of the nerve, dividing into a superficial and deep palmar branch. 19. Musculo- spiral nerve. 20. Muscular branches to the triceps. 21. Cutaneous nerve. 22. Posterior interosseous nerve piercing the supinator brevis muscle. 23. .Ra- dial nerve. The last two nerves are the terminal branches of the musculo- spiral. 24. The point at which the radial nerve pierces the deep fascia. 25. Circumflex nerve. 518 MEDIAN NERVE. Fig. 276.* flexor profundus to the wrist. It then dips beneath the annular ligament and enters the palm of the hand. Just above the wrist it is superficial, lying by the outer border of the tendons of the flexor sublimis digitorum. The Branches of the median nerve are—■ Muscular, Anterior interosseous, Superficial palmar, Digital. The Muscular branches are given off by the nerves at the bend of the elbow; they are distributed to all the muscles of the anterior aspect of the forearm, with the exception of the flexor carpi ulnaris, and ulnar half of the flexor profundus. The branch to the pro- nator radii teres sends off reflected fila- ments to the elbow-joint. The Anterior interosseous is a large branch accompanying the anterior in- terosseous artery, and supplying the deep layer of muscles of the forearm ; being lost inferioi’ly in the pronator quadratus. The Superficial palmar branch arises from the median at about the lower fourth of the forearm; it crosses the * Deep dissection of the front of the fore- arm and hand (from Hirschfeld and Leveilld). 1. Supinator longus (cut). 2. Ulnar nerve. 3. Brachialis anticus. 4. Biceps. 5. Mus- culo-spiral nerve. 6. Median nerve. 7. Pos- terior interosseous nerve. 8. Pronator teres and flexor carpi radialis (cut). 9. Extensor carpi radialis longior (cut). 10. Brachial ar- tery. 11. Supinator brevis. 12. Flexor sub- limis digitorum (cut). 13, 13. Hadial nerve. 14, 14. Plexor carpi ulnaris. 15. Extensor carpi radialis brevior. l(i. Ulnar artery. 17. Ka- dial origin of flexor sublimis digitorum (cut). 18. Flexor profundus digitorum. 19. Tendon of pronator teres. 20, 20. Dorsal branch of ulnar nerve. 21, 21. Eadial artery. 22, 22. Deep branch of ulnar nerve. 23. Flexor longus pollicis. 24. Abductor minimi digiti. 25. Anterior interosseous nerve. 26. Digital branches of ulnar nerve. 27. Tendon of supinator longus. 28. One of the lumbricales muscles, 29. Pronator quadratus. 31. Tendon of flexor carpi radialis, 33. Digital branches of median nerve. 35. Adductor pollicis. ULNAR NERVE. 519 annular ligament, and is distributed to the integument of the palm of the hand, and ball of the thumb. The median nerve at its termination in the palm of the hand is spread out and flattened, and divides into six branches, one mus- cular and five digital. The muscular branch is distributed to the muscles of the ball of the thumb. The digital branches are arranged as follows : two pass outwards to the thumb and supply its borders; the third runs along the radial side of the index finger, sending a twig to the first lumbri- calis in its course; the fourth subdivides for the supply of the adjacent sides of the index and middle finger, and gives a twig to the second lumbricalis ; the fifth receives a filament of communica- tion from the ulnar nerve, and supplies the collateral branches of the middle and ring finger. Opposite the base of the first phalanx, each nerve gives off a dorsal branch which runs along the border of the dorsum of the finger. Near its extremity the nerve divides into a palmar and a dorsal branch; the former supplying the sentient extremity of the finger; the latter the structures around and beneath the nail. The digital nerves in their course along the fingers lie to the inner side of and superficially to the arteries ; and the nerve of one side of a finger has no communication with that of the opposite side. The Ulnar nerve is somewhat smaller than the median, behind which it lies, gradually diverging from it in its course. It arises from the inner cord of the brachial plexus in common with the internal head of the median and internal cutaneous nerve, and runs down the inner side of the arm, to the groove between the internal condyle and olecranon, resting on the internal head of the triceps, and accompanied by the inferior profunda artery. At the elbow it is superficial, and supported by the inner condyle, against which it may be compressed, giving rise to the thrilling sensation along the inner side of the forearm and little finger, popularly ascribed to striking the “funny bone.” It then passes between the two heads of the flexor carpi ulnaris, and descends along the inner side of the forearm, crosses the annular ligament, and divides into two branches, superficial and deep palmar. At the commencement of the middle third of the forearm it comes into relation with the artery, and lies to the ulnar side of that vessel, as far as the hand. The Branches of the ulnar nerve are— Articular, Muscular, Cutaneous, Dorsal branch, Superficial palmar, Deep palmar. The Articular branches are several filaments to the elbow-joint, given off from the nerve while lying in the groove between the inner condyle and olecranon. The Muscular branches are distributed to the flexor carpi ulnaris and ulnar half of the flexor profundus digitorum. 520 MUSCULO-SPIRAL NERVE. The Cutaneous branch proceeds from about the middle of the nerve, and descends upon the ulnar artery to the hand, giving twigs to the integument in its course. One branch from its upper part, sometimes a separate offset from the nerve and sometimes absent, pierces the fascia, and communicates with the internal cutaneous nerve. The Dorsal branch passes backwards beneath the tendon of the flexor carpi ulnaris, at the lower fourth of the forearm, and divides into branches which supply the integument and two fingers and a half on the posterior aspect of the hand, communicating with the radial nerve, with which it forms an arch. The Superficial palmar branch, after giving some twigs to the palmaris brevis and inner border of the hand, divides into three filaments, two of which are distributed, one to the ulnar side of the little finger, and one to the adjoining borders of the little and ring finger, while the third, a communicating branch, joins the median nerve. The Deep palmar branch passes between the abductor and flexor minimi digiti, to the deep palmar arch, supplying the muscles of the little finger, interossei, two ulnar lumbricales, adductor pollicis, and inner head of the flexor brevis pollicis. The Musculo-spiral nerve, the largest branch of the brachial plexus, arises from its posterior trunk in common with the circum- flex, and, descending behind the axillary and brachial artery, winds around the humerus between the triceps and the bone, and in com- pany with the superior profunda artery, to the space between the brachialis anticus and supinator longus, and thence onwards to the bend of the elbow, where it divides into two branches, radial and posterior interosseous. The Branches of the musculo-spiral nerve are— Muscular, Cutaneous, Radial, Posterior interosseous, The Muscular branches are distributed to the triceps, anconeus, brachialis anticus, supinator longus, and extensor carpi radialis longior. The Cutaneous branches are three in number, internal and two external. The internal branch arises from the nerve in the axilla, and piercing the deep fascia in the upper third of tlie arm on its posterior aspect, communicates with the intercosto-humeral nerve, and is distributed to the integument of the posterior aspect of the upper arm, as far as the olecranon. The external cutaneous branches pass through the substance of the external head of the triceps, and pierce the deep fascia; one, upper, near the insertion of the deltoid, the other, lower, at about the middle of the upper arm. The upper branch follows the course of the cephalic vein, supplying the integument of the outer and fore part of the upper arm as far as the bend of the elbow. The lower branch passes down the outer side of the forearm, reaches the MUSCULO-SPIKAL NERVE. 521 posterior aspect at about its middle, and is continued onwards to the wrist, where it communicates with the pos- terior branch of themusculo-cutaneous. The jRadial nerve runs along the radial side of the forearm to the com- mencement of its lower third; it there passes beneath the tendon of the supi- nator longus, and, at about two inches above the wrist-joint, pierces the deep fascia and divides into an external and internal branch. The external branch, the smaller of the two, is distributed to the outer border of the thumb, and communi- cates with the posterior branch of the musculo-cutaneous nerve. The in- ternal branch crosses the direction of the extensor tendons of the thumb, and divides into several filaments for the supply of the ulnar border of the thumb, radial border of the index finger, and adjacent borders of the index and middle finger. It communicates above the wrist with the posterior branch of the musculo-cutaneous nerve, and on the back of the hand forms an arch by joining with the dorsal branch of the ulnar nerve. On the backs of the fingers the digital branches communi- cate with those of the median nerve. In the upper third of the forearm the radial nerve lies beneath the bor- der of the supinator longus muscle; in the middle third it is in relation with the radial artery, lying to its outer Fig. 277.* * Dissection of the muscnlo-spiral nerve and its branches (from Hirschfeld and Le- veilld). 1. Triceps. 2. Brachialis anticus. 3. Supinator longus. 4. Biceps. 5. Mus- culo-spiral nerve. 6. Musculo - cutaneous nerve. 7. Origin of extensor carpi radialis longior. 8. Radial nerve. 9. Posterior in- terosseous nerve. 10. Pronator radii teres. 11. Origin of extensor carpi radialis brevior. 12. Flexor carpi radialis. 13. Anconeus. 14. Tendon of supinator longus. 15. Supinator brevis. 16, 16. Tendon of extensor carpi radialis longior. 17. Extensor communis digitorum. 18, 18. Tendon of extensor carpi radialis brevior. 19, 19. Ex- tensor secundi internodii pollicis. 20, 20. Extensor ossis metacarpi pollicis. 21, 21. Extensor primi internodii pollicis. 522 DORSAL NERVES. side; and in the lower third it quits the artery, and passes beneath the tendon of the supinator longus to reach the back of the hand. The Posterior interosseous nerve, somewhat larger than the radial, separates from the latter at the bend of the elbow, pierces the supinator brevis muscle, and emerges from its lower border on the posterior aspect of the forearm, where it divides into branches which supply all the muscles of the posterior aspect of the forearm, with the exception of the anconeus, supinator longus, and extensor carpi radialis longior. One branch, longer than the rest, descends upon the interosseous membrane to the posterior part of the wrist, and forms a gangliform swelling (a common character of nerves which supply joints), from which numerous filaments are distri- buted to the wrist-joint. The Circumflex neeve arises from the posterior cord of the brachial plexus in common with the musculo-spiral. It passes downwards over the border of the subscapularis muscle, winds around the neck of the humerus with the posterior circumflex artery, and splits into an upper and lower division; the upper division is continued onwards beneath the deltoid, and distributed to the ante- rior part of that muscle, some of its branches piercing the muscular fibres and becoming cutaneous. The lower division sends a branch (remarkable for a gangliform swelling) to the teres minor, several branches to the posterior part of the deltoid, and mounting upon the border of that muscle becomes cutaneous, supplying the integu- ment over its lower half by means of several filaments. Besides its muscular and cutaneous branches, the trunk of the nerve gives off an articular branch, which enters the shoulder-joint at its posterior and under part. DOESAL STEEVES. The dorsal nerves are twelve in number at each side; the first appearing between the first and second dorsal vertebra; the last between the twelfth dorsal and first lumbar. They are smaller than the lower cervical nerves; diminish gradually iu size from the first to the tenth, and then increase to the twelfth. Each nerve, as soon as it has escaped from the intervertebral foramen, separates into an anterior and posterior cord; the anterior cords being the intercostal nerves, the posterior the dorsal branches of the dorsal nerves. The Dorsal branches pass directly backwards between the trans- verse processes of the vertebrae, lying internally to the anterior costo-transverse ligament, and each nerve divides into an internal and external branch. The internal branches diminish in size from the first to the last. The six upper branches pass inwards between the semispinalis dorsi and multifidus spinas, and, piercing the rhomboid, trapezius and latissimus dorsi, become cutaneous close to the spinous processes, and are then reflected outwards to supply the integument. The six lower branches are lost in the muscles of the spine. INTERCOSTAL NERVES. 523 The external branches increase in size from above downwards, and make their appearance in the line of separation between the longis- simus dorsi and sacro-luinbalis. The six upper branches are dis- tributed to those muscles and the levatores costarum. The six lower, after supplying the same muscles, pierce the serratns posticus inferior and latissimus dorsi in a line with the angles of the ribs, and becoming cutaneous, are directed downwards and forwards over the side of the trunk. Intercostal nerves.—The anterior cords of the dorsal nerves, twelve in number at each side, are the intercostal nerves. Each intercostal nerve passes outwards in the intercostal space in com- pany with the intercostal vessels, below which it lies ; at the com- mencement of its course it rests on the external intercostal muscle, further outwards it is placed between the two planes of intercostal muscles ; beyond the middle of the rib it enters the substance of the internal intercostal and reaches its inner surface, being in contact with the pleura; finally, at the anterior extremity of the intercostal space, it crosses in front of the triangularis sterni and internal mammary vessels and piercing the internal intercostal muscle and pectoralis major, is distributed to the integument of the front of the chest and mammary gland, under the name of anterior cutaneous. The intercostal nerve, near its origin, sends one or two filaments to the neighbouring dorsal ganglion of the sympathetic, and midway between the vertebral column and sternum, while situated between the intercostal muscles, gives off a lateral cutaneous branch which pierces the external intercostal muscle and divides into an anterior and posterior twig for the supply of the integument of the side of the thorax. This description applies in full only to the six upper intercostal nerves ; the six lower, with the exception of the last, cross the car- tilages of the ribs where the thorax is deficient and take their course between the internal oblique and transversalis muscle to the sheath of the rectus, and, after supplying that muscle, to the linea alba, by the side of which they reach the integument constituting the an- terior cutaneous nerves of the abdomen. The first and the last intercostal nerve are exceptions to this general scheme of distribution. The first ascends over the first rib to join the brachial plexus, and gives off only a small branch, to take the usual course of the other intercostal nerves. The last or twelfth nerve lies below the last rib, and after crossing the quadratus lumborum takes its course between the internal oblique and trans- versalis muscle like the other inferior intercostals. Near its origin it sends a branch, the dor si-lumbar, downwards to join the first lumbar nerve. The branches of the intercostal nerves are, muscular, lateral cu- taneous, and anterior cutaneous. The muscular branches are small twigs distributed to the inter- costal and neighbouring muscles. The Lateral cutaneous nerves, given off from the intercostals at 524 INTERCOSTAL NERVES. about the middle of the lateral half of the thorax, pierce the ex- ternal intercostal mnscle and pass between the fibres of the serratus Fig. 278.* * The nerves of the abdominal wall (from Hirschfeld and Reveille'). 1. Pee- toralis major (cut). 2. Serratus magnus. 3. Latissimus dorsi. 4. Intercostal muscles. 5. Rectus abdominis. 6. Section of obliquus externus. 7. Ob- liquus intemus. 8. Transversalis abdominis. 9, 9. Ninth dorsal nerve. 10, 10. Tenth dorsal nerve. 11, 11. Eleventh dorsal nerve. 12, 12. Twelfth dorsal nerve. 13. Lateral cutaneous branch of first lumbar (ilio-hypogastric). 14. Anterior cutaneous branch of ilio-hypogastric. 15. Anterior cutaneous branch of ilio-inguinal. 16. Ilio-hypogastric and ilio-inguinal nerves. 17. Lateral cutaneous branch of second intercostal nerve. 18. Lateral cuta- neous branch of intercostal nerve. LUMBAR NERVES. 525 magnus above and the obliquus externus below to reach the surface. The lateral cutaneous nerve then divides into an anterior and pos- terior branch. The anterior branches are directed forwards to sup- ply the integument of the antero-lateral aspect of the trunk, some of the superior branches turning around the inferior border of the pectoralis major to the mammary gland. The 'posterior branches take their course backwards to supply the integument of the postero- lateral aspect of the trunk, some of the superior turning around the posterior border of the axilla to reach the integument over the lower part of the scapula and latissimus dorsi; and that from the third intercostal being distributed to the integument of the axilla and neighbouring part of the arm. The first intercostal gives off no lateral cutaneous nerve; the lateral cutaneous branch of the second intercostal nerve will be presently described, under the name of intercosto-humeral nerve. The lateral cutaneous branch of the last intercostal nerve pierces the internal and external oblique muscle, crosses the crest of the ilium just behind the tensor vagina? femoris, and is distributed to the integument of the anterior part of the gluteal region as low down as the trochanter major. The Anterior cutaneous nerves are divided according to their position into those of the thorax and those of the abdomen. Having reached the surface they are reflected outwards to supply the integument of the front of the trunk. The anterior cutaneous branches of the third and fourth intercostal nerve are distributed to the mammary gland. The Intercosto-humeral nerve is the lateral cutaneous branch of the second intercostal nerve; after piercing the external intercostal muscle, it passes downwards into the axilla and communicates with a branch of the lesser internal cutaneous nerve of Wrisberg. It then perforates the deep fascia, and is distributed to the integu- ment of the inner and back part of the arm to about the middle, and to the integument covering the lower part of the scapula. On the back of the arm it communicates with the internal cutaneous branch of the musculo-spiral nerve. This nerve sometimes takes the place of the nerve of Wrisberg. LTJMBAE, NERVES. There are five pairs of lumbar nerves, of which the first makes its appearance between the first and second lumbar vertebra; the last between the fifth lumbar and the base of the sacrum. The anterior cords increase in size from above downwards. They com- municate at their origin with the lumbar ganglia of the sympa- thetic, and pass obliquely outwards behind the psoas magnus, or between its fasciculi, sending twigs to that muscle and to the quad- ratus lumborum. In this situation each nerve divides into two branches, a superior branch which ascends to form a loop of com- munication with the nerve above; and an inferior branch which descends to join in like manner the nerve below. The communi- 526 LUMBAR NERVES. cations and anatomoses which are thus established constitute the lumbar plexus. The posterior cords diminish in size from above downwards; they pass backwards between the transverse processes of the corre- sponding vertebrae, and each nerve divides into an internal and ex- Fig. 279.* ternal branch. The internal branch, the smaller of the two, passes inwards to be distributed to the multifidus spin® and inter-spinales. The external branches communicate with each other by several loops, and, after supplying the deeper muscles, pierce the sacro- lumbalis to reach the integument to which they are distributed * Lumbar plexus (from Hirschfeld and Leveilld). 1. Eight gangliated cord of sympathetic. 2. Abdominal aorta. 3, 3. Last dorsal nerves. 4. Psoas parvus. 5. Quadratus lumborum. 6. Psoas magnus. 7, 7. Ilio-hypogastric nerves. 8. Iliacus intemus. 9, 9. Ilio-inguinal nerve. 10. Lumbo-sacral nerve. 11, 11. Genito-crural nerves. 12. Gluteal nerve. 13. Iliac branch of ilio-hypogastric nerve. 14. Sacral plexus. 15, 15, 15. External cutaneous nerves. 17. Transversalis abdominis. 19. Obliquus intemus. 21. Obliquus externus. 23, 23. Anterior crural nerves. 25, 25. Obturator nerves. 27, 27. Crural branch of genito-crural nerve. 29. Genital branch of genito- crural nerve. 31. External iliac artery. 33. External abdominal ring, GENITO-CEURAL NERVE. 527 The external branches of the three upper lumbar nerves descend over the posterior part of the crest of the ilium, and are distributed to the integument of the gluteal region. Lumbar plexus.—The Lumbar plexus is formed by the communi- cations and anastomoses which take place between the anterior divisions of the four upper lumbar nerves, and between the latter and the last dorsal. It is narrow above, increases in breadth in- teriorly, and is situated between the transverse processes of the lumbar vertebrae and quadratus lumborum behind, and the psoas magnus muscle in front. The Branches of the lumbar plexus are the— Ilio-hypogastric, Ilio-inguinal, Genito-crural, External cutaneous, Obturator, Anterior crural. The Iliohypogastric nerve (superior musculo-cutaneous) pro- ceeds from the first lumbar nerve, and passes obliquely outwards between the fibres of the psoas magnus and across the quadratus lumborum to about the middle of the crest of the ilium. It then pierces the transversalis muscle, and between it and the internal oblique divides into its two terminal branches, iliac and hypo- gastric. The iliac branch pierces the internal and external oblique mus- cles close to their attachment, and a little behind the middle of the crest of the ilium ; it is distributed to the integument of the outer part of the hip. The hypogastric branch continues its course onwards, piercing first the internal oblique, and just above the external abdominal ring the aponeurosis of the external oblique. It is distributed to the integument of the hypogastric region and mons pubis. The Ilio-inguinal nerve (inferior musculo-cutaneous), smaller than the preceding, also arises from the first lumbar nerve. It passes obliquely downwards and outwards below the ilio-hypo- gastric nerve, and crosses the quadratus lumborum and iliacus muscle to the anterior part of the crest of, the ilium; it then pierces the transversalis muscle, and between that muscle and the obliquus internus communicates with the hypogastric nerve. It next pierces the obliquus internus, and following the course of the sper- matic cord, escapes at the external abdominal ring to be distributed to the scrotum and to the integument of the upper part of the thigh, internally to the saphenous opening; and in the female to that of the pudendum. The Genito-crural nerve proceeds from the second lumbar and by a few filaments from the loop between it and the first. It tra- verses the psoas magnus from behind forwards, and runs down the anterior surface of that muscle, lying beneath its fascia, to near Poupart’s ligament, where it divides into a genital and a crural branch. The genital branch (n. spermaticus seu pudendus externus) 528 EXTERNAL CUTANEOUS NERVE. crosses the external iliac artery to the in- ternal abdominal ring, and descends along the spermatic canal, lying behind the cord, to the scrotum, where it distributes twigs to the spermatic cord and cremaster mus- cle. In the female it gives twigs to the round ligament and external labium. At the internal abdominal ring this nerve sends off a branch, which, after supplying the lower border of the internal oblique and transversalis, is lost in the integument of the groin. The crural branch (lumbo-inguinalis), the most external of the two, descends along the outer border of the external iliac artery, and, crossing the origin of the cir- cumflexa ilii, enters the sheath of the femoral vessels in front of the femoral artery. It pierces the sheath below Pou- part’s ligament, and is distributed to the integument of the anterior aspect of the thigh as far as its middle. This nerve communicates with the middle cutaneous branch of the crural nerve, and is often very small. The External cutaneous nerve (in- guino-cutaneus) proceeds from the second lumbar, and from the loop between it and the third. It pierces the posterior fibres of the psoas muscle; and crossing the iliacus on the iliac fascia, to the anterior superior spinous process of the ilium, * A diagram showing the lumbar and sacral plexuses, with the nerves of the lower extremity. 1. The first four lumbar nerve £; which, with a branch from the last dorsal, constitute the lumbar plexus. 2. The four upper sacral nerves ; which, with the last lumbar, form the sacral plexus. 3. The two musculo-cutaneous nerves, branches of the first lumbar nerve. 4. Genito-crural nerve. 5. External cutaneous nerve. 6. Anterior crural or femoral nerve. 7. Its muscular branches. 8. Middle cutaneous branches. 9, 10. Internal cutaneous branches. 11. The long or internal saphenous. 12. Obturator nerve. 13. Gluteal nerve; a branch of the lumbo-sacral. 14. Internal pudic nerve. 15. Lesser ischiatic nerve. 16. Greater ischiatic nerve. 17. Internal popliteal nerve. 18. External popliteal nerve. 19. Muscular branches. 20. Posterior tibial nerve; dividing at. 21, into the two plantar nerves. 22. External saphe- nous nerve. 23. Anterior tibial nerve. 24. Musculo-cutaneous nerve, piercing the deep fascia, and dividing into two cutaneous branches, for the supply of the dorsum of the foot. OBTURATOR NERVE. 529 passes into the thigh, beneath Poupart’s ligament, where it divides into two branches, anterior and posterior. The posterior branch crosses the tensor vaginas femoris muscle to the outer and posterior side of the thigh, and supplies the in- tegument in that region. The anterior nerve, after passing for three or four inches down the thigh in a sheath formed by the fascia lata, becomes superficial, and divides into two branches, which are distributed to the integu- ment of the outer border of the thigh, and to the articulation of the knee. The Obturator nerve is formed by a branch from the third, and another from the fourth lumbar nerve, and is distributed to the obturator externus and adductor muscles of the thigh, the hip and knee-joint, the femoral and popliteal artery, and sometimes to the integument of the upper and inner part of the leg. Prom its origin it takes its course among the fibres of the psoas muscle, through the angle of bifurcation of the common iliac vessels, and along the inner border of the brim of the pelvis, to the obturator foramen, where it joins the obturator artery. Having escaped from the pelvis, it divides into an anterior and posterior branch. The anterior branch passes downwards in front of the adductor brevis, supplies that muscle together with the pectineus, gracilis, and adductor longus, and at the lower border of the latter unites with the internal cutaneous and long saphenous nerve, to form a plexus. It then passes onwards to the femoral artery, to which it distributes filaments. In its course this nerve gives off an arti- cular branch to the hip-joint; and a cutaneous branch, which pierces the fascia lata at the knee, communicates with the long saphenous nerve, and is distributed to the integument of the inner side of the leg as far as its middle. The cutaneous branch is often wanting, its place being supplied by the internal cutaneous nerve, and sometimes by the accessory obturator. The posterior branch pierces the obturator externus muscle, to which and to the adductor magnus it distributes branches ; it also gives off an articular branch which pierces the adductor magnus muscle, and accompanies the popliteal artery to the knee-joint. The Accessory obturator nerve, small and inconstant, is a high division of the obturator, being sometimes derived from it near its origin, and sometimes by separate filaments from the third and fourth lumbar nerve. It passes down the inner border of the psoas muscle, crosses the os pubis, and dips beneath the pectineus, where it divides into branches. One of its branches is distributed to the pectineus, another supplies the hip-joint, while a third communi- cates with the anterior branch of the obturator nerve, and when of large size constitutes its cutaneous branch. As already stated, the existence of the accessory obturator nerve is uncertain. The Anterior crural or femoral nerve is the largest of the divisions of the lumbar plexus; it is formed by the union of branches from the second, third, and fourth lumbar nerve, and is 530 ANTERIOR CRURAL NERVE. Fig. 281.* distributed to the integument of the front and inner side of the thigh, leg, and foot, to all the muscles of the front of the thigh (excepting one), to the iliacus, pectineus, femoral artery, and knee-joint. Emerging from be- neath the psoas, the nerve passes downwards in the groove between that muscle and the iliacus, and beneath Poupart’s ligament into the thigh, where it spreads out and divides into numerous branches. At Poupart’s liga- ment it is separated from the femoral artery by the breadth of the psoas muscle, which at this point is scarcely more than half an inch in diameter, and by the iliac fascia, beneath which it lies. Branches.—Within the pelvis, the anterior crural nerve gives off three or four twigs to the ilia- cus muscle, and a branch to the femoral artery. The latter di- vides into filaments which entwine about the artery, and follow its course downwards in the thigh. Below Poupart’s ligament the crural nerve becomes flattened out, and divides into numerous branches, which may be arranged into two principal groups, super- * Nerves of the thigh (from Hirsch- feld and Leveill4). 1. Gangliated cord of sympathetic. 2. Third lumbar nerve. 3. Branches to iliacus inter- nus. 4. Fourth lumbar nerve. 5. An- terior crural nerve. 6. Lumbo-sacral nerve. 7. Branch to psoas. 8. Obtu- rator nerve. 9. External cutaneous nerve (cut). 10. Nerve to pectineus. 11. Superficial division of anterior crural nerve (cut). 12. Superficial division of obturator nerve. 13, 13. Sartorius muscle. 14, 14. Adductor longus. 15. Branch to rectus. 16. Deep division of obturator nerve. 17. Branches to vastus intern us and crureus. 18. Adductor brevis. 19. Branch to vastus internus. 20. Adductor magnus. 21. Vastus externus. 22,22. In- ternal saphenous nerve. 23. Rectus femoris. 24. Patellar branch of saphenous nerve. 25. Vastus internus. 26. Gracilis. INTERNAL SAPHENOUS NERVES. 531 ficial and deep. The separate branches of these groups are as follows: Superficial. Middle cutaneous, Internal cutaneous, Long or Internal saphenous. Deep. Muscular, Articular. The Middle cutaneous nerve pierces the fascia lata at about three inches below Poupart’s ligament, and divides into two branches, which pass down the inner and front part of the thigh, and are distributed to the integument as low as the knee-joint. At its upper part the external branch communicates with the crural branch of the genito-crural nerve; and below, the internal branch communicates with the internal cutaneous. One or both of these branches sometimes pierce the sartorius muscle. The Internal cutaneous nerve passes inwards in front of the sheath of the femoral artery, and divides into an anterior and an ■inner branch. Previously to its division it gives off three cuta- neous filaments, which pierce the fascia near the internal saphenous vein, and following the course of that vessel, are distributed to the integument of the inner side of the thigh as low down as the knee. The uppermost of these filaments passes through the saphenous opening, the middle becomes subcutaneous at about the middle of the thigh, and the lowest pierces the fascia at its lower third. The anterior branch passes down the inner side of the thigh, and pierces the fascia at its lower third, near the internal saphenous vein. It then divides into two twigs, one of which continues on- wards to the inner side of the knee ; while the other curves out- wards to its outer side, communicating in its course with a branch of the long saphenous nerve. The inner branch descends along the inner and posterior border of the sartorius muscle to the knee, where it pierces the fascia lata, and gives off several cutaneous twigs. It then sends a small branch of communication to the long saphenous nerve, and passes downwards along the inner side of the leg, to which it is dis- tributed. While beneath the fascia lata it aids in the formation of a plexus by uniting with branches of the long saphenous nerve and descending branch of the obturator. When the latter is large the inner branch of the internal cutaneous nerve is small, and may terminate in the plexus, or merely give off a few cutaneous filaments. The Long or internal saphenous nerve inclines inwards to the sheath of the femoral vessels, and passes downwards in front of the sheath and beneath the aponeurotic expansion which covers the sheath, to the opening in the adductor magnus. It then quits the femoral vessels, and continuing to descend, passes between the tendons of the sartorius and gracilis, and reaches the internal saphenous vein. By the side of the latter it passes down the inner 532 SACRAL NERVES. side of the leg, in front of the inner ankle, and along the inner side of the foot as far as the great toe; being distributed to the integu- ment in its course. The branches of the long saphenous nerve in the thigh are: one or two to join the plexus formed by the obturator and internal cutaneous nerve ; and a large branch, the cutaneus patellce, which pierces the sartorius and fascia lata at the inner side of the knee, and divides into many twigs, which are distributed to the integu- ment of the front of the knee. Above the patella this branch com- municates with the anterior branch of the internal cutaneous nerve, and with the terminal twigs of the middle, and external cutaneous. Below the patella it communicates with other branches of the long saphenous ; the whole of these communications constituting a kind of plexus (plexus patellae). The branches of the long saphenous nerve below the knee are distributed to the integument of the front and inner side of the leg. By one of these branches it communicates with the cutaneous branch of the obturator nerve. The Muscular branches of the anterior crural nerve supply all the muscles of the front of the thigh (with the exception of the tensor vaginae femoris, which obtains its nerve from the superior gluteal) and the pectineus. The branch to the pectineus passes behind the sheath of the femoral vessels; the branches to the sar- torius, three or four in number, arise with the cutaneous nerves, and sometimes are supplied by the latter. The branch to the rectus enters the deep surface of that muscle. The branch to the vastus externus follows the course of the descending branch of the external circumflex artery; the branch to the crnreus passes directly to that muscle ; and the branch to the vastus internus, remarkable for its length, descends by the side of the sheath of the femoral vessels. The Articular branches are distributed to the knee-joint; one enters the joint at its outer side, being derived from the nerve of the vastus externus ; the other, proceeding from the nerve of the vastus internus, descends with the anastomotica magna to a level with the joint, and then pierces the capsular ligament. The Lumbo-sacral nerve.—The anterior division of the fifth lumbar nerve, conjoined with a branch from the fourth, constitutes the lumbo-sacral nerve, which descends over the base of the sacrum into the pelvis, and assists in forming the sacral plexus. SACRAL NERVES. There are five pairs of sacral nerves ; the first four escape from the vertebral canal through the sacral foramina, the last between the sacrum and coccyx. The -posterior sacral nerves are small, and diminish in size from above downwards ; they communicate with each other by means of anastomosing loops immediately after their escape from the posterior sacral foramina, and divide like the other spinal nerves into external and internal branches. The external SACRAL NERVES. 533 branches pierce the gluteus maximus, to which they give filaments, and are distributed to the integument of the posterior part of the Fig. 282.* gluteal region. The internal branches supply the multifidus spin® muscle and the integument over the sacrum and coccyx. * Side view of the nerves of the pelvis, the viscera having been removed (from Hirschfeld and Leveille). 1. Abdominal aorta. 2. Gangliated cord of sympa- thetic (left side). 3. Genito-crural nerve. 4. Left common iliac artery. 5. Eight common iliac artery. 6. Left lumbo-sacral cord. 7. Psoas muscle. 8. Gangliated cord of sympathetic (right side). 9. Internal iliac artery (cut). 10. Gluteal artery (cut). 11. Eight external iliac artery. 12. Eight lumbo- sacral nerve. 13. Obturator nerve. 14. First sacral nerve. 15. Gluteal nerve. 16. Pyriformis of left side (cut). 17. Obturator artery. 18. Second sacral nerve. 19. Obturator internus. 20. Pyriformis of right side. 21. Nerve to levator ani. 22. Sacral plexus. 23. Levator ani (cut). 24. Third sacral nerve. 25. Bulb of urethra covered by accelerator urime. 26. Nerve to ob- turator internus. 27. Transversus periueei (cut). 28. Fourth sacral nerve. 29. Dorsal nerve of penis. 30. Visceral branches (cut). 31. Inferior pudendal nerve. 32. Fifth sacral nerve. 33. Small sciatic nerve. 34. Coccygeus muscle. 36. Sixth or coccygeal nerve. 38. Internal pudie nerve. 40. Inferior htemorrhoidal nerve. 42. Posterior superficial perineal nerve. 44. Anterior superficial perineal nerve. 46. Deep perineal nerves to bulb and muscles. 534 SUPERIOR GLUTEAL NERVE. The anterior sacral nerves diminish in size from above down- wards ; the first is large, and unites with the lumbo-sacral nerve ; the second, of equal size, unites with the first; and the third, scarcely one-fourth so large as the second, joins with the two pre- ceding nerves in the formation of the sacral plexus. The fourth sacral nerve divides into two branches, one of which assists in forming the sacral plexus, the other separates into three branches : a communicating branch to unite with the fifth sacral nerve ; a visceral branch, to join with the hypogastric plexus and supply the bladder and prostate gland, and in the female, the vagina; and a muscular branch which sends filaments to the levator ani and coccygeus and a hwmorrhoidal branch to the sphincter ani and integument behind the anus. The fifth sacral nerve, issuing from between the sacrum and coccyx, pierces the coccygeus muscle, and receives the communi- cating branch from the fourth; it then communicates with the coccygeal nerve, and piercing the coccygeus a second time, is distri- buted to the integument over the dorsal surface of the coccyx. The coccygeal nei've pierces the coccygeus muscle, and unites with the fifth sacral nerve, in which it is lost. Each of the anterior cords of the sacral nerves communicates with the sympathetic at its point of escape from the sacral canal. Sacral plexus.—The Sacral plexus is formed by the union of the lumbo-sacral and the anterior cords of the three upper sacral nerves and one-half the fourth. The plexus is triangular in form, its base corresponding with the whole length of the sacrum, and its apex with the lower part of the great ischiatic foramen. It is in relation behind with the pyriformis muscle ; and in front with the pelvic fascia, which separates it from the internal iliac vessels and the viscera of the pelvis. The Branches of the sacral plexus are, Visceral, Muscular, Superior gluteal, Pudic, Lesser ischiatic, Greater ischiatic. The Visceral nerves are three or four large branches derived from the fourth and fifth sacral nerves : they ascend by the side of the rectum and bladder; in the female by the side of the rectum, vagina, uterus, and bladder; and interlace with branches of the hypogastric plexus, sending in their course numerous filaments to the pelvic viscera. The Muscular branches are one or two twigs to the levator ani; an obturator branch, which curves around the spine of the ischium to reach the internal surface of the obturator interims muscle; two twigs to thepyriformis; a branch to the gemellus superior; and a branch of moderate size, which descends between the gemelli muscles and the ischium, and is distributed to the gemellus inferior, quadratus femoris, and capsule of the liip-joint. The Superior gluteal nerve arises from the lumbo-sacral near PUDIC NERVE. 535 its junction with the first sacral nerve ; it passes out of the pelvis with the gluteal artery, through the great sacro-ischiatic foramen, and divides into a superior and an inferior branch. The superior branch follows the direction of the superior curved line of the ilium, accompanying the deep superior branch of the gluteal artery, and sends filaments to the gluteus medius and minimus. The inferior branch passes obliquely downwards and forwards between the gluteus medius and minimus,distributing numerous fila- ments to both, and terminates in the tensor vaginae femoris muscle. The Pudic nerve arises from the lower part of the sacral plexus and passes out of the pelvis through the great sacro-ischiatic fora- men below the pyriformis muscle. It crosses the spine of the ischium, and re-entering the pelvis through the lesser sacro-ischiatic foramen, accompanies the internal pudic artery along the outer wall of the ischio-rectal fossa, lying inferiorly to the artery and enclosed in the same sheath. Near its origin it gives off the inferior hcemor- rhoidd nerve, and in the ischio-rectal fossa divides into a superior and inferior branch. The Inferior haemorrhoidal nerve, often a branch of the sacral plexus passes through the lesser sacro-ischiatic foramen, and de- scends to the termination of the rectum to be distributed to the sphincter ani and integument. The Dorsalis penis nerve, the superior division of the internal pudic, ascends along the posterior surface of the ramus of the ischiun, pierces the triangular ligament, and accompanies the arteria dorsalis penis to the glans, to which it is distributed. At the roo; of the penis the nerve gives off a cutaneous branch which runs aong the side of the organ, gives filaments to the corpus caverncsum, and with its fellow of the opposite side supplies the integunent of the upper two-thirds of the penis. The Perineal nerve, or inferior terminal branch, larger than the precedmg, pursues the course of the superficial perineal artery in the perineum and divides into cutaneous and muscular branches. The cutaneous branches (superficial perineal), two in number, posterior and anterior, enter the ischio-rectal fossa and pass forward with tie superficial perineal artery to be distributed to the integu- ment a the perineum, scrotum, and under part of the penis. The posterior superficial perineal nerve sends a few filaments to the in- tegummt of the anus and sphincter ani; while the anterior gives off one or two twigs to the levator ani. The muscular branches proceed from a single trunk, which passes inwards behind the transversus perinei muscle ; they are distributed to the transversus perinei, accelerator urinae, and erector penis. The perineal nerve also sends two or three filaments to the corpus spongiosum. Ln the female the pudic nerve is distributed to the parts analo- gous to those of the male. The superior branch snpplie) the clitoris ; the inferior the vulva and perineum. 536 LESSEE ISCHIATIC NERVE. Fig. 283.* The Lesser ischiatic nerve passes out of the pelvis through the great sacro-ischiatic foramen below the pyriformis muscle, and continues its course downwards through the thigh to the lower part of the popliteal region, where it pierces the fascia and becomes subcutaneous. It then accom- panies the external saphenous rein to the lower part of the leg, and communicates with the external saphenous nerve. The branches of the lesserischi- atic nerve are, muscular and cuta- neous. The muscular or inferior gluteal are several large branches distributed to the gluteus maxi- mus. The Cutaneous branches are divisible into external, internal, and middle. The external cuta- neous branches are several fila- ments which turn arouid the lower border of the glutetE maxi- mus, and are distributed to the integument over the hip aid outer side of the thigh. The 'nternal cutaneous branches are distributed to the integument of tin upper and inner part of the thigi. One of these larger than the i?st, in- ferior pudendal, curves aromd the tuberosity of the ischium,piei’ces * Dissection of the buttock and back of the thigh (from Hirscheld and Leveilld). 1. Glutens maxinus. 2. Gluteus medius. 3. Gluteal aitery and nerve. 4. Gluteus minimus. 5. Nerve to obturator internus. 6. Pjrifonnis. 7. Pudic nerve. 8. Small sciatc nerve. 9. Great sacro-sciatic ligament. 10. Ob- turator internus and gemelli. 11. In- ferior gluteal nerve from smal sciatic. 12. Tendon of obturator extemus. 13. Inferior pudendal nerve (Soemneiing). 14. Quadratus femoris. 15. Gracilis. 16. Great sciatic nerve.. 17. Aldictor magnus. 18. Insertion of gluteus maximus. 19. United origins of semi-'en- dinosus and biceps. 20. Short head of biceps. 21. Semi-membrano;us. 22. Tendon of biceps. 23. Tendon of semi-tendinosus. 24. External popliteal nerve. 25. Internal popliteal nerve. 26. Communicans permei nerve. 27. Poplite alartery. 29. Gastrocnemius. 31. Communicans popltei nerve. GREAT ISCHIATIC NERVE. 537 the fascia lata near the ramus of that bone, and, after communicating with one of the superficial perineal nerves, is distributed to the integument of the scrotum and penis. The middle cuta- neous branches, two or three in num- ber, are derived from the lesser ischia- tic in its course down the thigh, and are distributed to the integument. The Great ischiatxc nerve is the largest nervous cord in the body; it is formed by the sacral plexus, or rather is a prolongation of the plexus, and at its exit from the great sacro-ischiatic foramen beneath the pyriformis muscle measures three-quarters of an inch in breadth. It descends through the middle of the space between the tro- chanter major and tuberosity of the ischium, and along the posterior part of the thigh to its lower third, where it divides into two large terminal branches, internal and external popli- teal. This division sometimes takes place at the plexus, and the two nerves descend side by side; occasionally they are separated at their commencement by a part or by the whole of the pyri- formis muscle. The nerve in its course down the thigh rests on the gemellus superior, tendon of the obturator in- ternus, gemellus inferior, quadratus femoris, and adductor magnus, and is covered in by the gluteus maximus and biceps. The Branches of the great ischiatic nerve, previously to its division, are, muscular and articular. The Muscular branches are given off from the upper part of the nerve and supply both heads of the biceps, the semi-tendinosus, semi-membranosus, and adductor magnus. The Articular branch descends to the upper part of the external condyle of Fig. 284.* * Superficial nerves of the back of the leg (from Ilirschfeld and Reveille). 1. Internal popliteal nerve. 2. External popliteal nerve. 3. Internal saphe- nous vein. 4. Nervus communicans peronei. 5. Nervus communicans poplitei. 6. External saphena vein. 7. Internal saphenous nerve. 8. Ex- ternal saphenous nerve. 9. Posterior tibial nerve. 538 PLANTAR NERVES. the femur, and divides into filaments, which are distributed to the fibrous capsule and synovial membrane of the knee-joint. The Internal popliteal nerve passes through the middle of the popliteal space, from the division of the great ischiatic nerve to the lower border of the popliteus muscle, accompanies the artery beneath the arch of the soleus, and becomes the posterior tibial nerve. It is superficial in the whole of its course, and lies exter- nally to the vein and artery. The Branches of the internal popliteal nerve are, muscular or sural, articular, and a cutaneous branch, the external saphenous. The Muscular branches, of considerable size, and four or five in number, are distributed to the two heads of the gastrocnemius, to the soleus, plantaris, and popliteus. The Articular branches, two or three in number, supply the knee-joint, two of the twigs accompanying the internal articular arteries. The External or short saphenous nerve (communicans poplitei, vel tibialis) proceeds from the middle of the internal popliteal, and descends in the groove between the two bellies of the gastrocnemius muscle to the middle of the leg; it then pierces the fascia, and, after receiving the communicans peronei, conies into relation with the external saphenous vein, and follows the course of that vein to the outer ankle, to which, and to the integument of the heel and outer side of the foot (cutaneus dorsi pedis externus), it distributes branches. The Posterior tibial nerve is continued along the posterior aspect of the leg from the lower border of the popliteus muscle to the posterior part of the inner ankle, where it divides into the in- ternal and external plantar nerve. In the upper part of its course it lies to the inner side of the posterior tibial artery; it then be- comes placed superficially to that vessel, and at the ankle is si- tuated to its outer side; in the lower third of the leg it lies parallel wit h the inner border of the tendo- A chillis. The Branches of the posterior tibial nerve are, three or four muscular twigs to the deep muscles of the posterior aspect of the leg, the branch to the flexor longus pollicis accompanies the fibular artery; one or two filaments which entwine around the artery and then terminate in the integument;* and a plantar cutaneous branch which pierces the internal annular ligament and is distributed to the integument of the heel, and inner border of the sole of the foot. The Internal plantar nerve, larger than the external, crosses the posterior tibial vessels to enter the sole of the foot, and becomes placed between the abductor pollicis and flexor brevis digitorum; it then enters the sheath of the latter muscle, and divides opposite the base of the metatarsal bones into three digital branches; one * It is extremely interesting, in a physiological point of view, to observe the mode of distribution of these arterial filaments. They seem to be monitors to the artery of the presence or approach of danger. EXTERNAL POPLITEAL NERVE. 539 to supply the adjacent sides of the great and second toe; the second the adjacent sides of the second and third toe; the third the cor- responding sides of the third and fourth toe. This distribution is precisely similar to that of the digital branches of the median nerve m the hand. In its course the internal plantar nerve gives off cutaneous branches to the integument of the inner side and sole of the foot; muscular branches to the muscles forming the inner and middle group of the sole ; a digital branch to the inner border of the great toe ; and arti- cular branches to the articulations of the tarsal and metatarsal bones. The External plantar nerve, the smaller of the two, follows the course of the external plantar ar- tery to the outer border of the mus- culus accessorius, beneath which it sends several deep branches to supply the adductor pollicis, inter - ossei, transversus pedis, and the articulations of the tarsal and me- tatarsal bones. It then gives branches to the integument of the outer border and sole of the foot, and sends forward two digital branches to supply the little toe and half the next. The External popliteal nerve (n. peroneus) one-half smaller than the internal, passes downwards by the side of the tendon of the biceps, and crosses the inner head of the gastrocnemius and the head of the soleus, to the neck of the fibula, it then pierces the peroneus longus muscle, and divides into two branches, anterior tibial and musculo- cutaneous. The Branches of the external popliteal nerve are, communicans peronei, cutaneous, and articular. Fig. 285.* * Second stage of dissection of sole of foot (from Hirsclifeld and Leveilld). 1. Internal annular ligament. 2. Flexor brevis digitorum (cut). 3. External plantar nerve. 4. External plantar artery. 5. Internal plantar nerve. 6. Ab- ductor minimi digiti. 7. Internal plantar artery. 8. Accessorius muscle. 9. Abductor pollicis. 10. Flexor longus digitorum. 11. Flexor longus pol- licis. 12. Flexor brevis minimi digiti. 13. Digital branches of internal plantar nerve. 14. Digital branches of external plantar nerve. 15. Flexor brevis pollicis. 16. One of the lumbricales. 540 SYMPATHETIC NERVES. The Communicans peronei, proceeding from the external pop- liteal near the head of the fibula, crosses the external origin of the gastrocnemius muscle, and, piercing the deep fascia, decends to the middle of the leg, where it joins the external saphenous nerve. It gives off one or two cutaneous filaments in its course. The Cutaneous branch passes down the outer side of the leg, supplying the integument. The Articular branches follow the external articular arteries to the knee-joint. The Anterior tibial nerve (n. interosseus, vel peroneus profun- dus) commences at the bifurcation of the external popliteal on the neck of the fibula, and passes beneath the upper part of the exten- sor longus digitorum, to reach the outer side of the anterior tibial artery, just as that vessel has emerged through the opening in the interosseous membrane. It descends the leg with the artery; lying at first to its outer side, then in front of it, and near the ankle be- coming again placed to its outer side. Reaching the ankle it passes beneath the annular ligament; accompanies the dorsalis pedis artery, supplies the adjacent sides of the great and second toe, and communicates with the internal division of the musculo-cutaneous nerve. The Branches given off by the anterior tibial nerve are, muscular to the muscles in its course; and at the ankle a tarsal branch which may be considered as one of the terminal divisions of the nerve. This branch passes outwards upon the dorsum of the foot, becomes ganglionic like the posterior interosseous nerve at the wrist, and supplies the extensor brevis digitorum muscle and the articulations of the tarsus and metatarsus. The Musculo-cutaneous nerve (n. peroneus superficialis) passes downwards along the fibula, in the substance of the peroneus longus; it then gets between the peroneus longus and brevis, next between the peronei and extensor longus digitorum, and at the lower third of the leg pierces the deep fascia, and divides into the internal and external cutaneous nerves of the foot. In its course it gives off several branches to the peronei muscles. The internal branch, the smaller of the two, is distributed to the inner side of the foot and great toe, and communicates with the anterior tibial and internal saphenous. The external, or larger branch, supplies the adjacent sides of the second and third, third and fourth, and fourth and fifth toes, and communicates with the external saphenous. SYMPATHETIC NERVES. The Sympathetic consists of a vertebral and prevertebral portion; the vertebral portion is composed of a series of ganglia united by a longitudinal cord, it descends along each side of the vertebral column from the head to the coccyx, communicates with the cranial and spinal nerves, and distributes branches to the internal organs and viscera. The prevertebral portion is that part of the sympa- OPHTHALMIC GANGLION. 541 tbetic which appertains to the viscera, comprising the numerous ganglia and plexuses of the head, chest, abdomen, and pelvis. The sympathetic nerve communicates with the cerebro-spinal nerves immediately at their exit from the cranium and vertebral canal. With the fourth and sixth nerve, however, it unites in the cavernous sinus; with the olfactory in the nose; and with the audi- tory in the meatus auditorius interims. The branches of distribution accompany the arteries which supply the different organs, and form communications around them which are called -plexuses, and take the name of the artery with which they are associated; thus we have the mesenteric plexus, hepatic plexus, and splenic plexus. All the internal organs of the head, neck, and trunk are supplied with branches from the sympathetic, and some of them exclusively; hence it is denominated the nerve of organic life. It is called the ganglionic nerve from being constituted of a number of ganglia; and from the constant disposition which it evinces in its distribution, to communicate and form small knots or ganglia. There are four sympathetic ganglia in the head; namely, the ophthalmic or lenticular, the spheno-palatine or Meckel’s, the otic or Arnold’s, and the snbmaxillary; three in the neck, superior, middle, and inferior cervical; twelve in the dorsal region; four in the lumbar region ; and four or five in the sacral region. Each ganglion may be considered as a distinct centre, receiving and giving branches in four different directions, viz., superior or ascending to communicate with the ganglion above; inferior or descending, to communicate with the ganglion below; external, to communicate with the spinal nerves ; and internal, to communicate with the sympathetic filaments of the opposite side, and be distri- buted to the viscera. As regards the spinal nerves it receives as well as gives, the white fibres of the sympathetic being derived from the cerebro- spinal nerves. CRANIAL PORTION OP THE SYMPATHETIC NERVE. Cranial Ganglia. Ophthalmic, or lenticular ganglion, Spheno-palatine, or Meckel’s ganglion, Otic, or Arnold’s ganglion, Submaxillary ganglion. The Ophthalmic ganglion (ciliary; lenticular) is a small quad- rangular and flattened ganglion situated within the orbit, between the optic nerve and external rectus muscle ; it is in close relation with the optic nerve and generally with the ophthalmic artery; and is surrounded by adipose tissue, which renders its dissection some- what difficult. It is of a reddish-grey colour, like other sympa- thetic ganglia. 542 OPHTHALMIC GANGLION. Its branches of distribution are the short ciliary nerves, which arise from its anterior angles in two groups ; the upper group con- sisting of about four filaments; the lower, of five or six. They accompany the ciliary arteries in a waving course, and divide into filaments which pierce the sclerotic around the optic nerve, to sup- ply the tunics of the eyeball. Its branches of communication are three: one, the long root, pro- Fig. 286.* ceeds from the nasal branch of the ophthalmic nerve and joins its superior angle ; a short and thick branch, the short root, from the * Cranial ganglia of the sympathetic nerve. 1. Ganglion of Eibes. 2. Fila- ment by which it communicates with the carotid plexus (3). 4. Ophthalmic or lenticular ganglion, giving off ciliary branches. 5. Part of the inferior division of the third nerve communicating with the ganglion by means of a short thick branch (short root). 6. Part of the nasal nerve, connected with the ganglion by means of a longer branch (long root). 7. A slender filament (the sympathetic root) sent directly backwards from the ganglion to the ca- rotid plexus. 8. Part of the sixth nerve in the cavernous sinus, receiving two branches from the carotid plexus. 9. Meckel’s ganglion (spheno-palatine). 10. Spheno-palatine nerves. 11. Descending or palatine branches. 12. Its internal or nasal branches. 13. Naso-palatine branch, one of the nasal branches. 14. Posterior branch of the ganglion, the Vidian nerve. 15. Its carotid branch (n. petrosus profundus), communicating with the carotid plexus. 16. Its petrosal branch (n. petrosus superficialis major), joining the intumes- centia gangliformis of the facial nerve. 17. Facial nerve. 18. Chorda tympani nerve, descending to join the gustatory nerve. 19. Gustatory nerve. 20. Submaxillary ganglion, receiving the chorda tympani, and other filaments from the gustatox-y. 21. Superior cervical ganglion of the sympathetic. SPHENO-PALATINE GANGLION. 543 Inferior division of the third nerve to its inferior angle; and a slender filament, the sympathetic root, from the carotid plexus. Occasionally the ophthalmic ganglion receives also a filament of communication from the spheno-palatine ganglion; and sometimes from the abducens nerve. The Spheno-palatine ganglion (Meckel’s), the largest of the cra- nial ganglia of the sympathetic, is situated in the spheno-maxillary fossa, a little below the superior maxillary nerve. It is of small size, of a reddish-grey colour, and triangular in shape; and is placed on the posterior part of the spheno-palatine nerves which it only partially involves. Its branches are divisible into four groups; ascending, descending, internal, and posterior. The ascending branches are three or four small filaments which are distributed to the periosteum of the orbit. One of these branches sometimes joins the ophthalmic ganglion; one the sixth nerve; and two the optic nerve. The descending branches are the three palatine nerves, anterior, middle, and posterior. The anterior or large palatine nerve descends from the ganglion through the posterior palatine canal, and emerges at the posterior palatine foramen. It then passes forward in the substance of the hard palate to which it is distributed, and communicates with the naso-palatine nerve. While in the posterior palatine canal, this nerve gives off several branches (inferior nasal), which enter the nose through openings in the palate bone, and are distributed to the middle and inferior meatus, inferior spongy bone, and antrum. The middle or external palatine nerve descends externally to the preceding to the posterior palatine foramen, and distributes branches to the tonsil, soft palate, and uvula. The posterior or small palatine nerve, quits the other nerves to enter a distinct canal, from which it emerges by a separate opening behind the posterior palatine foramen. It is distributed to the hard palate and gums near the point of its emergence, and also to the tonsil, soft palate, and uvula. The internal branches are the superior nasal and naso-palatine. The superior nasal nerves, four or five in number, enter the nasal fossa through the spheno-palatine foramen, and are distributed to the mucous membrane of the superior meatus, and superior and middle spongy bone. The naso-palatine nerve (Scarpa) enters the nasal fossa through the spheno-palatine foramen, and crosses the roof of the nares to reach the septum, to which it gives filaments. It then curves down- wards and forwards along the vomer, to the naso-palatine canal, and passes through that canal to the palate, to which and to the papilla behind the incisor teeth it is distributed. This nerve was described by Cloquet as uniting with its fellow in the naso-palatine canal and constituting the naso-palatine ganglion. The existence of this ganglion is disputed. 544 SUBMAXILLARY GANGLION. The posterior branches are the Vidian or pterygoid nerve, and the pterygo-palatine. The Vidian nerve passes directly backwards from the spheno- palatine ganglion, through the pterygoid or Vidian canal to the foramen lacerum basis cranii, where it divides into two branches, carotid and petrosal. The carotid branch (n. petrosus profundus) crosses the foramen lacerum, surrounded by the cartilaginous sub- stance which closes that opening, and enters the carotid canal to join the carotid plexus. The 'petrosal branch (n. petrosus major) enters the cranium through the foramen lacerum basis cranii, piercing the cartilaginous substance, and passes backwards beneath the Gasserian ganglion and dura mater, embedded in a groove on the anterior surface of the petrous bone to the hiatus Fallopii. In the hiatus Fallopii it receives a branch from Jacob- son’s nerve, and terminates in the intumescentia gangliformis of the facial nerve. The Vidian nerve is that by which Meckel’s ganglion derives its motor power. The pterygo-palatine nerve is a small branch which passes back- wards through the pterygo-palatine canal with the pterygo-palatine artery, to be distributed to the mucous membrane of the Eustachian tube and neighbouring part of the pharynx. The Otic ganglion (Arnold’s) is a small oval-shaped and flat- tened ganglion, lying against the inner surface of the inferior maxil- lary nerve, close to the foramen ovale; it is in relation, externally, with the trunk of that nerve, just at the point of union of the motor root; internally it rests against the cartilage of the Eustachian tube and tensor palati muscle; and posteriorly is in contact with the arteria meningea media. It is closely adherent to the internal pterygoid nerve, and appears like a swelling on that nerve. The branches of the otic ganglion are six in number; two of dis- tribution, and four of communication. The branches of distribution are, a small filament to the tensor tympani muscle, and one or two to the tensor palati. The branches of communication are, one or two filaments from the inferior maxillary nerve (short root); one or two filaments from the auriculo-temporal nerve; filaments from the nervi molles of the arteria meningea media, and the nervus petrosus superficialis minor (long root). The latter nerve ascends from the ganglion to a small canal situated between the foramen ovale and foramen spinosum, and passes backwards on the petrous bone to the hiatus Fallopii, where it divides into two filaments. One of these filaments enters the hiatus and joins the intumescentia gangliformis of the facial; the other passes to a minute foramen nearer the base of the petrous bone, and enters the tympanum, where it communicates with a branch of Jacobson’s nerve. The Submaxillary ganglion is a small round or triangular ganglion situated on the submaxillary gland, in close relation with the gustatory nerve, and near the posterior border of the mylo- hyoideus muscle. CAEOTID PLEXUS. 545 Its branches of distribution, six or eight in number, divide into many filaments, which supply the side of the tongue, the sub- maxillary gland, sublingual gland, and Wharton’s duct. Its branches of communication are, two or three from and to the gustatory nerve; one from the chorda tympani; two or three which form a plexus with branches of the hypoglossal nerve; and one or two filaments which pass to the facial artery, and communicate with the nervi molles from the cervical portion of the sympathetic. Carotid plexus.—The ascending branch of the superior cervical ganglion enters the carotid canal with the internal carotid artery, and divides into two branches, which form several loops of com- munication with each other around the artery. These branches, together with those derived from the carotid branch of the Vidian, constitute the carotid plexus. They also form frequently a small gangliform swelling at the under part of the artery, which is called the carotid ganglion. The latter, however, is not constant. The continuation of the carotid plexus onwards with the artery by the side of the sella turcica, is the cavernous plexus. The carotid plexus is the centre of communication between all the cranial ganglia, and, being derived from the superior cervical ganglion, between the cranial ganglia and those of the trunk; it also communicates with the greater part of the cerebral nerves, and distributes filaments with each of the branches of the internal carotid, to accompany those branches to their ultimate ramifica- tions. The branches which accompany the anterior cerebral artery at each side, unite upon the anterior communicating artery, and according to Ribes form a small ganglion, the ganglion of llibcs. The existence of this ganglion is disputed. The ophthalmic ganglion communicates with the plexus by means of the long branch which reaches it from the cavernous plexus. The spheno-palatine joins the plexus by means of the carotid branch of the Vidian. The submaxillary ganglion is brought into con- nexion with it by means of the otic ganglion, and the otic ganglion by means of the tympanic nerve and Vidian. It communicates with the third nerve in the cavernous sinus, and through the ophthalmic ganglion; frequently with the fourth in the formation of the nerve of the tentorium; with the Gasserian ganglion; with the ophthalmic division of the fifth in the cavernous sinus, and by means of the ophthalmic ganglion; with the superior maxillary, through the spheno-palatine ganglion; and with the in- ferior maxillary, through the otic ganglion. It sends two branches directly to the sixth nerve, which unite with it as it crosses the cavernous sinus: it communicates with the facial and auditory nerve, through the medium of the petrosal branch of the Vidian; and with the glosso-pharyngeal by means of two filaments to the tympanic nerve. 546 The superior cervical ganglion is long and fusiform, of a reddish- grey colour, smooth, and of considerable thickness, extending from within an inch of the carotid foramen in the petrous bone to opposite the lower border of the third cervical vertebra. It is in relation, in front, with the sheath of the internal carotid artery and internal jugular vein; and, behind, with the rectus anticus major muscle. Its branches are divisible into superior, inferior, external, and internal; to which may be added, as proper to this ganglion, anterior. The superior (carotid nerve) is a single branch which ascends by the side of the internal carotid, and divides into two branches; one lying to the outer, the other to the inner side of that vessel. The two branches enter the carotid canal, and, by their communi- cations with each other and with the carotid branch of the Vidian, constitute the carotid plexus. The inferior or descending branch, sometimes two, is the cord of communication with the middle cervical ganglion. The external branches are numerous, and may be divided into two sets; those which communicate with the glosso-pharyngeal, pneu- mogastric, and hypoglossal nerve; and those which communicate with the first four cervical nerves The internal branches are three in number; pharyngeal, to assist in forming the pharyngeal plexus; laryngeal, to join the superior laryngeal nerve and its branches ; and, superior cardiac nerve, or nervus superficialis cordis. The anterior branches accompany the external carotid artery with its branches, around which they form plexuses, and here and there small ganglia; they are named, from the softness of their texture, nervi molles, and from their reddish hue, nervi subruji. The branches accompanying the facial artery are conducted by that vessel to the submaxillary ganglion, and those which accompany the internal maxillary artery reach the otic ganglion through the medium of the arteria meningea media. The Middle cervical ganglion (thyroid ganglion) is small, and sometimes wanting. It is situat d opposite the fifth cervical ver- tebra, and rests against the inferior thyroid artery. This relation is so constant, as to have induced Haller to name it the “ thyroid ganglion.” Its superior branch, or branches, ascend to communicate with the superior cervical ganglion. Its inferior branches descend to join the inferior cervical ganglion ; one of these frequently passes in front of the subclavian artery, the other behind it. Its external branches communicate with the fifth and sixth cervi- cal nerve. CERVICAL PORTION OF THE SYMPATHETIC NERVE. CARDIAC NERVES. 547 Its internal'branches are filaments which accompany the inferior thyroid artery, inferior tJnjroid plexus; and the middle cardiac nerve, nervns cardiacus magnns. The Inferior cervical ganglion (vertebral ganglion) is much larger than the preceding, and constant in its existence. It is of a semi- lunar form, and situated on the base of the transverse process of the seventh cervical vertebra, immediately behind the vertebral artery ; hence its designation “ vertebral ganglion.” Its superior branches communicate with the 'middle cervical ganglion. The inferior branches pass some before and some behind the subclavian artery, to join the first thoracic ganglion. The external branches consist of two sets ; one which communi- cates with the sixth, seventh, and eighth cervical, and first dorsal nerve, and one which accompanies the vertebral artery along the vertebral canal, forming the vertebral plexus. The plexus sends filaments to all the branches given off by that artery, and communi- cates in the cranium with the filaments of the carotid plexus accompanying the branches of the internal carotid artery. The internal branch is the inferior cardiac nerve, nervu3 car- diacus minor. Cardiac nerves.—Theuardiae nerves are three in number at each side—namely, superior, middle, and inferior. The Superior cardiac nerve (nervus superficialis cordis) proceeds from the lower part of the superior cervical ganglion ; it descends the neck behind the common carotid artery and parallel with the trachea, crosses the inferior thyroid artery, and running by the side of the recurrent laryngeal nerve, enters the chest. The nerve of the right side passes either in front of or behind the subclavian artery and along the posterior aspect of the arteria innominata to the deep cardiac plexus. The left superior cardiac nerve runs by the side of the left carotid artery, and crosses the arch of the aorta to the superficial cardiac plexus. In its course it receives branches from the pneumogastric nerve, and sends filaments to the thyroid gland and trachea. The Middle cardiac nerve (nervus cardiacus magnus) proceeds from the middle cervical ganglion, or, in its absence, from the cord of communication between the superior and inferior ganglion. It is the largest of the three nerves, and lies parallel with the re- current laryngeal. At the root of the neck it divides into several branches, which pass some before and some behind the subclavian artery, communicates with the superior and inferior cardiac, pneu- mogastric and recurrent nerve, and descends to the bifurcation of the trachea, to join the deep cardiac plexus. The Inferior cardiac nerve (nervus cardiacus minor) arises from the inferior cervical ganglion, communicates with the recurrent laryngeal and middle cardiac nerve, and descends to the front of the bifurcation of the trachea, to the deep cardiac plexus. The Superficial cardiac plexus is situated immediately beneath 548 DEEP CARDIAC PLEXUS. the arch of the aorta and in front of the right pulmonary artery. It receives the superior cardiac nerve of the left side and the in- ferior cardiac branch of the left pneumogastric nerve, both of which cross the arch of the aorta between the left phrenic and pneumo- gastric nerve. It receives besides several filaments from the deep cardiac plexus, and sometimes a cardiac branch from the right pneumogastric nerve. Connected with the plexus is a small gan- glion (sometimes wanting), the cardiac ganglion of Wrisberg, which lies close to the right side of the fibrous cord of the ductus arte- riosus. The superficial cardiac plexus gives off filaments which pass along the front of the left pulmonary artery to the root of the left lung, where they communicate with the anterior pulmonary plexus; while the principal part of the plexus descends in the groove be- tween the pulmonary artery and aorta to the anterior longitudinal sulcus of the heart, where it comes into relation with the anterior coronary artery, and becomes the anterior coronary plexus. At the base of the heart, the anterior coronary plexus receives several filaments from the deep cardiac plexus. Its branches are dis- tributed to the substance of the heart in the course of the left or anterior coronary artery. The Deep or Great cardiac plexus is situated on the bifurca- tion of the trachea, above the right pulmonary artery and behind the transverse portion of the arch of the aorta. It receives, on the right side, the three cardiac nerves of the sympathetic of the same side, and the cardiac branches of the right pneumogastric and right recurrent nerve. On the left side it receives the middle and inferior cardiac nerves of the sympathetic of the left side; the cardiac branches of the left pneumogastric (excepting the in- ferior), and several cardiac branches from the left recurrent nerve. In other words, it receives all the cardiac filaments of the sym- pathetic, pneumogastric, and recurrent nerves, with the exception of the left superior cardiac of the sympathetic (nervus super- ficialis cordis) and the inferior cervical cardiac of the left pneumo- gastric, these two nerves being destined to the superficial cardiac plexus. The branches of the deep cardiac plexus, proceeding from its right and left division, pass downwards to join the coronary arteries, and outwards to the pulmonary plexuses. From the right division of the plexus the branches proceed before and behind the right pulmonary artery. Those which pass in front descend upon the trunk of the pulmonary artery to the left coronary artery, and help to form the anterior coronary plexus; those which pass behind the right pulmonary artery are distributed to the right auricle; a third set of filaments, proceed- ing from the right division of the deep cardiac plexus, follow the course of the right pulmonary artery to the anterior pulmonary plexus. From the left division of the plexus branches proceed beneath the arch of the aorta immediately to the right of the ligament of THORACIC GANGLIA. 549 the ductus arteriosus to join the superficial cardiac plexus; others pass outwards with the pulmonary artery to the pulmonary plexus ; a few descend to the left auricle ; but the chief bulk pass on to the right coronary artery and form the posterior coronary plexus. The Anterior coronary plexus proceeds from the superficial car- diac plexus, and receives other filaments from the deep cardiac plexus. It is distributed with the branches of the coronary artery on the anterior aspect of the heart. The Posterior coronary plexus proceeds from the deep cardiac plexus and principally from its left division. It follows the course of the arteries distributed to the posterior aspect of the heart. The thoracic portion of the sympathetic nerve is the trunk of the sympathetic in its course through the cavity of the thorax. It lies by the side of the vertebral column on the heads of the ribs and in- tercostal spaces; but at its lowest part comes into relation with the sides of the bodies of the last two dorsal vertebrae. The Thoracic ganglia are twelve in number at each side. They are flattened and triangular, or irregular in form, and present the peculiar reddish-grey colour and pearly lustre of sympathetic ganglia in general; they rest against the heads of the ribs, and are covered by the pleura costalis. The first two ganglia and the last are usually the largest; the latter being situated on the side of the body of the last dorsal vertebra. Their branches are branches of communication and branches of distribution. Some ascending filaments from the first ganglion assist in the formation of the vertebral plexus. The external or communicating branches, usually two in number for each ganglion, communicate with the intercostal nerves. The internal or visceral branches proceeding from the five or six upper ganglia, are of small size, and distributed to the aorta, oeso- phagus, vertebral column, and lungs. The branches to the lungs proceed from the third and fourth ganglia, and go to join the pos- terior pulmonary plexus. The visceral branches of the six lower ganglia unite to form the three splanchnic nerves. The Great splanchnic nerve proceeds from the sixth dorsal gan- glion, and receiving the branches of the seventh, eighth, ninth, and tenth, passes downwards along the front of the vertebral column, and, piercing the crus of the diaphragm, terminates in the semi- lunar ganglion. The Lesser splanchnic nerve is formed by filaments which issue from the tenth and eleventh ganglia; it pierces the crus of the dia- phragm, and joins the solar plexus near the middle line. The Third or renal splanchnic nerve proceeds from the last thoracic ganglion, and, piercing the diaphragm, terminates in the renal plexus. When absent, the place of this nerve is supplied by the lesser splanchnic. THORACIC PORTION OF THE SYMPATHETIC NERVE. 550 ABDOMINAL PLEXUSES. The Semilunar ganglion is a large, irregular, gangliform body, pierced by numerous openings, and appearing like the aggregation of a number of smaller ganglia, having spaces between them. It is situated by the side of the coeliac axis and root of the superior mesenteric artery, and extends outwards to the supra-renal capsule. The ganglia communicate both above and below the coeliac axis and form a gangliform circle, from which branches pass off in all direc- tions, like rays from a centre. Hence the entire circle has been named the solar plexus. The Solar or epigastric plexus receives the great and lesser splanchnic nerves; 1 the termination of the right pneumogastric nerve; some filaments from the right phrenic nerve ; and sometimes one or two from the left. It sends forth numerous filaments which accompany, under the name of plexuses, all the branches given off by the abdominal aorta. Thus we have, derived from the solar plexus, the— Phrenic, or diaphragmatic plexuses, Gastric plexus, Hepatic plexus, Splenic plexus, Supra-renal plexuses, Renal plexuses, Superior mesenteric plexus, Aortic plexus, Spermatic plexuses, Inferior mesenteric plexus. In connexion with the phrenic plexus of the right side, there is described a small ganglion diaphragmaticum, which is situated near the supra-renal capsule. In this ganglion branches of the right phrenic nerve communicate with those of the sympathetic. The Supra-renal plexuses are remarkable for their large size, and for a ganglion, which has received the name of ganglion supra- renale. The Renal plexuses are large, and receive the third splanchnic nerve. The Superior mesenteric plexus has several small ganglia at the root of the artery; and its nerves, which are whiter than those of the other plexuses, form a kind of nervous sheath to the artery and its branches. The Aortic plexus is a continuation of the solar plexus down- wards on the aorta, for the supply of the inferior branches of that trunk ; it receives also branches from the renal plexuses and lumbar ganglia. It is the source of origin of the inferior mesenteric plexus and part of the spermatic plexus, and terminates below in the hypogastric plexus. It likewise distributes branches on the inferior vena cava. The Spermatic plexus is derived from the renal plexus, but receives filaments from the aortic plexus. The Inferior mesenteric plexus is derived chiefly from the aortic plexus. 551 The lumbar portion of the trunk of the sympathetic is situated on the vertebral column, close to the anterior border of the psoas magnus muscle. It is continuous above, under the edge of the diaphragm, with the thoracic portion of the nerve, and below it descends upon the sacrum, in front of the anterior sacral foramina, to the coccyx. It presents four small ganglia and an intermediate cord. The Lumbar ganglia, four in number at each side, of a pearly grey colour and fusiform shape, are situated on the anterior part of the bodies of the lumbar vertebrae. The branches of the lumbar ganglia are branches of communi- cation and branches of distribution. The external or communicating branches, two or three in number from each ganglion, and longer than in the other regions, communi- cate with the lumbar nerves. The internal or visceral branches consist of two sets; the upper pass inwards in front of the abdominal aorta, and join the aortic plexus; the lower cross the common iliac arteries, and unite over the promontory of the sacrum to form the hypogastric plexus. The Hypogastric plexus is formed by the termination of the aortic plexus, and by the union of branches from the lower lumbar ganglia. It is situated over the promontory of the sacrum, between the two common iliac arteries, and bifurcates interiorly into two lateral portions, inferior hypogastric plexuses, which communicate with branches from the third and fourth sacral nerves. It distri- butes branches to the viscera of the pelvis, and sends filaments which accompany the branches of the internal iliac artery. LUMBAE POETION OF THE SYMPATHETIC NEEVE. The Sacral ganglia are four or five in number at each side. They are situated on the sacrum, close to the anterior sacral foramina, and resemble the lumbar ganglia in form and mode of connexion, although much smaller in size. The external or communicating branches are two from each ganglion, which pass outwards to communicate with the anterior sacral nerves and with the coccygeal nerve. The internal or visceral branches communicate very freely with the inferior hypogastric plexuses, and are distributed to the pelvic viscera. The last pair of sacral ganglia give off branches which join a small ganglion, situated on the first bone of the coccyx, called the ganglion impar, or azygos. This ganglion serves to connect the extremities of the two sympathetic nerves. It gives off a few small branches to the coccyx and rectum and communicates with the coccygeal nerve. SACEAL POETION OF THE SYMPATHETIC NEEVE. 552 CHAPTEK X. ORGANS OF SENSE. The organs of sense, the instruments by which the animal frame is brought into relation with surrounding nature, are five in number. Four of these organs are situated within the head; viz., the apparatus of smell, sight, hearing, and taste; the remaining organ, that of touch, is resident in the skin, and distributed over the surface of the body. THE NOSE AND NASAL FOSS.E. The organ of smell consists essentially of two parts: one external, the nose; the other internal, the nasal fossae. The nose is the triangular pyramid which projects from the centre of the face, immediately above the upper lip. Superiorly it is connected with the forehead by means of a narrow bridge; in- teriorly, it presents two openings, the nostrils, which overhang the mouth, and are so constructed that the odour of all substances must be received by the nose before they can be introduced within the lips. The septum between the openings of the nostrils is called the columna. Their entrance is guarded by a number of stiff hairs (vibrissce) which project across the openings, and act as a filter in preventing the introduction of foreign substances, such as dust or insects, with the current of air intended for respiration. The anatomical elements of which the nose is composed, are, 1. Integument. 2. Muscles. 3. Bones. 4. Fibro-cartilages. 5. Mucous membrane. 6. Vessels and nerves. 1. The Integument forming the tip (lobulus) and wings (aloe) of the nose is extremely thick and dense, so as to be with difficulty separated from the fibro-cartilage. It is furnished with an abun- dance of sebaceous glands, which, by their oily secretion, protect the extremity of the nose under alternations of temperature. The sebaceous matter of these glands becomes of a dark colour near the surface, from altered secretion, and also from attraction of the car- bonaceous matter floating in the atmosphere; hence the spotted appearance which the tip of the nose presents in large cities. When the integument is firmly compressed, the inspissated sebaceous secretion is squeezed out, and taking the cylindrical form of the excretory ducts of the glands, has the appearance of small white maggots (grubs; comedones) with black heads. 2. The Muscles are brought into view by reflecting the in- tegument ; they are the pyramidalis nasi, compressor naris, FIBRO-CARTILAGES OF THE NOSE. 553 dilatator naris, levator labii superioris alasque nasi, and depressor alas nasi. They have been already described with the muscles of the face. 3. The Bones of the nose are, the nasal, and nasal processes of the superior maxillary. 4. The Fibro-cartilages give form and stability to the nose, pro- viding, at the same time, by their elasticity, against injuries. They are five in number, namely, the— Fibro-cartilage of the septum, Two lateral fibro-cartilages, Two alar fibro-cartilages. The Fibro-cartilage of the septum, somewhat triangular in form, divides the nose into its two nostrils. It is connected above with the nasal bones and lateral fibro-cartilages; behind, with the eth- moidal septum and vomer; and below, with the palate processes of the superior maxil- lary bones. The alar fibro-cartilages and columna move freely on the fibro-cartilage of the septum, being but loosely connected with it by perichondrium. The Lateral fibro-cartilages are also trian- gular; they are connected, in front, with the fibro-cartilage of the septum; above, with the nasal bones; behind, with the nasal processes of the superior maxillary bones ; and below, with the alar fibro-carti- lages. Alar fibro-cartilages (lower lateral carti- lages).—Each of these cartilages is curved so as to correspond with the walls of the nostril, to which it forms a kind of rim. The inner portion is loosely connected with the same part of the opposite cartilage, to form the columna,. It is expanded and thickened at the point of the nose, to constitute the lobe; and on the side makes a curve corresponding with that of the ala. This curve is prolonged back- wards and downwards in the direction of the posterior border of the ala by three or four small fibro-cartilaginous plates (sesamoid car- tilages, cartilagines minores), which are appendages of the alar fibro-cartilage. The whole of these fibro-cartilages are connected with each other, and to the bones, by perichondrium, which, from its membranous structure, permits of the freedom of motion existing between them. Fig. 287.« * The fibro-cartilages of the nose. 1. One of the nasal bones. 2. Cartilage of the septum. 3. Lateral cartilage. 4. Alar cartilage. 5. Central portions of the alar cartilages which constitute the columna. 6. Cartilagines minores or sesamoid cartilages. 7. The nostril. 554 NASAL FOSSA!. 5. The Mucous membrane lining the interior of the nose, is con- tinuous with the skin externally, and with the pituitary membrane of the nasal fossae within. Around the entrance of the nostrils it is provided with the vibrissce. 6. Vessels and nerves.—The Arteries of the nose are, the lateralis nasi from the facial, and the nasalis septi from the superior coronary. Its Nerves are, the facial, infra- orbital, and nasal branch of the oph- thalmic. NASAL FOSS.E. To obtain a good view of the nasal fossae, the face must be divided through the nose by a vertical incision, a little to one side of the middle line. The Nasal Fossae are two irregular, compressed cavities, extending back- wards from the nose to the pharynx. They are bounded superiorly by the lateral cartilages of the nose, and by the nasal bones,'ethmoid, and sphenoid ; inferiorly, by the hard palate; and, in the middle line, they are separated by a bony and fibro-cartilaginous septum. A plan of the boundaries of the nasal fossae will be found at page 77. On the outer wall of each fossa, in the dried skull, are three pro- jecting processes, termed spongy bones. The two superior belong to the ethmoid, the inferior is a separate bone. In the fresh fossae these are covered with mucous membrane, and serve to increase the surface of that membrane by their prominence and convoluted form. The space intervening between the superior and middle spongy bone is the superior meatus; the space between the middle and inferior the middle meatus; and that between the inferior and the floor of the fossa the inferior meatus. These meatuses are passages which extend from before backwards, and it is in circulating through and amongst them that the atmo- sphere deposits its odorant particles upon the mucous membrane. There are several openings into the nasal fossae; thus, in the superior meatus are the openings of the sphenoidal and posterior ethmoidal cells; in the middle, the anterior ethmoidal cells, frontal sinuses, and antrum maxillare; and, in the inferior meatus, the termination of the nasal duct, and of the Eustachian tube. In the dried bone there are two additional openings, the spheno-palatine Fig. 288.* * The fibro-cartilages and bones of the nose viewed from the side. 1. Nasal bone. 2. Nasal process of the superior maxillary bone. 3. Cartilage of the septum. 4. Lateral cartilage. 5, 5. Alar cartilage. 6. Inner portion of the alar cartilage. 7. Sesamoid cartilages. 8. Areolar tissue of the ala nasi. 9. Aperture of the nostril. NASAL FOSSAE. 555 and the anterior palatine foramen; the former being situated in the superior, the latter in the inferior meatus. The Mucous membrane of the nasal fossae is called pituitary, or Schneide- rian. The former name being derived from the nature of its secretion, the latter from Schneider, who was the first to show that the secretion of the nose proceeded from the mucous membrane, and not from the brain, as was pre- viously imagined. It is closely adherent to the periosteum, constituting what is called a fibro-mucous membrane, and is continuous with the general gastro- pulmonary mucous membrane. From the nasal fossae it may be traced through the openings in the meatuses, into the sphenoidal and ethmoidal cells; into the frontal sinuses ; into the antrum maxil- lare; through the nasal duct to the surface of the eye, where it is continuous with the conj nnctiva; along the Eustachian tubes into the tympanum and mastoid cells, to which it forms the lining mem- brane ; and through the posterior nares into the pharynx and mouth, and thence through the lungs and alimentary canal. The surface of the membrane is furnished with laminated squa- mous epithelium near the aperture of the nares, and with ciliated columnar epithelium in the respi- ratory tract; in the latter it is also furnished with mucous glands, which are especially numerous on the septum at its posterior part. The mucous membrane which covers the upper and middle tur- Fig. 289.* Fig. 290.f * A section of the mucous membrane in the olfactory region. 1. Coloured part of the epithelium. 2. Nucleus. 3. Deeper part, containing olfactory cells and filaments. 4. Connective tissue. 5,5. Mucous glands. 6. Nerve twigs giving off terminal branches. t Olfactory cells and nerve terminations. A. Olfactory cells from frog. B. From man. C. Filaments of olfactory nerve from dog. 1. Epithelial cells, extending deeply into ramified processes. 2. Olfactory cells. 3. The rod-like processes of olfactory cells. 4. Their ciliated extremities. 5. Their central filaments. 556 ORGAN OF VISION. binated bones and the upper part of the septum (the olfactory tract) is of a darker colour, softer and more pulpy, its epithelium is columnar and non-ciliated, and the epithelial processes are prolonged at their deep extremities into threads which appear to join the connective tissue corpuscles. It also contains numerous glands, but these are more simple than the glands of the respiratory tract. Mingled with the cells of the columnar epithelium are certain peculiar rod-like bodies, each of which is connected with, or grows out from a nucleated cell (olfactory cell), while from the deeper surface of the same cell proceeds a fine thread, which is supposed to be continuous with a filament of the olfactory nerve, although this has never been satisfactorily proved. They bear a striking resemblance to the retinal rods and cones. Vessels and Nerves.—The Arteries of the nasal fossae are the an- terior and posterior ethmoidal, from the ophthalmic; and spheno- palatine and pterygo-palatine from the internal maxillary. The Nerves are, olfactory, spheno-palatine and naso-palatine from Meckel’s ganglion, and nasal branch of the ophthalmic. The filaments of the olfactory nerves differ from those of the cerebral and spinal nerves generally, in being devoid of the white matter of Schwann, they form a fine anastomotic network, and probably terminate in the olfactory cells above described. In the frog the olfactory fibres have been observed breaking up into a whole bundle of fine, pale, varicose fibrils which perforate the mucous membrane, and each of these appears then to join an olfactory cell (Schultz and Ivolliker). ORGAN OF VISION. The organ of vision consists of the two eyes and their con- nexions with the brain. The eyes are situated in the orbital fossae, on each side of the upper part of the face; they are freely moveable in consequence of being surrounded by fat and contained in a smooth fibrous capsule (capsule of Tenon), and have numerous muscles to perform their movements. They are protected from external violence by being situated in cavities with osseous walls, and have in front both cleansing and protective apparatus against the intrusion of foreign bodies. The fossae in which the eyes are situated have their axes directed outwards, but the eyes themselves are directed much more forwards, varying, however, in their direction with the distance or nearness of the object looked at, their axes being parallel in looking at distant objects, but converging slightly when near objects are viewed. The optic nerves follow the direction of the orbits, and therefore enter the eyeballs on their nasal side. We shall in the first place give a short account of those struc- tures which, although not essential to vision, are provided for the protection of the anterior part of the eye. APPENDAGES OF THE EYE. 557 These appendages of the eye {tutamina oculij are, the eyebrows, eyelids, eyelashes, conjunctiva, caruncula lachrymalis, and lachrymal apparatus. The Eyebrows (supercilia) are two prominent arches of integu- ment which overlie the superciliary ridges of the frontal bone. They are covered with short, stiff hairs directed obliquely upwards and outwards, and are connected beneath with the orbicularis palpe- brarum, occipito-frontalis, and corrugator supercilii muscles, by which they are moved. They serve to shade the eyes from too vivid light, to protect them from the entrance of dust from above, and to carry the moisture from the forehead on to the temple and lateral parts of the face, and so prevent its entering the eyes. The Eyelids (palpebrce) are two moveable folds, which serve by their closure to protect the anterior part of the eye from injury, or to exclude the light, as during sleep. When open they have an elliptical fissure between them {r ima palpebrarum), and it is upon the size of this that the apparent size of the eye depends. The angles of junction of the two lids are called canthi. The outer canthus is acute, so that but a small space is left between the lids ; the inner canthus is prolonged for a short distance towards the nose, and a triangular space called lacus lachrymalis is left between the lids in this situation. At the commencement of this space, upon the edge of each of the lids, is a small angular projection, the lachrymal papilla; and at the apex of each papilla is a small orifice, punctum lachrymals, the commencement of the lachrymal canal. The eyelids have entering into their structure, integument, orbi- cularis palpebrarum muscle, tarsal cartilages, Meibomian glands, and conjunctiva. The areolar tissue of the skin of the eyelids is remarkable for its looseness, and the absence of adipose substance ; it is particularly liable to serous infiltration. The fibres of the orbicularis are for the most part thin and pale, but a thicker band of fibres has been found internal to the eye- lashes, constituting the ciliary muscle of Riolan. The Tarsal cartilages are two thin plates of fibro-cartilage, about an inch in length, which give form and support to the eyelids. The upper cartilage is of a semilunar form, thicker in the middle than at its extremities ; its lower border is broad and flat, its upper thin and gives attachment to the levator palpebrae muscle and the palpebral ligament. The lower cartilage, narrower than the upper, is situated in the substance of the lower lid. Its upper border is flat, and corresponds with flat edge of the upper cartilage ; the lower border is attached to the palpebral ligament. Near the inner canthus, the tarsal cartilages terminate, at the commencement of the lacus lachrymalis, and are attached to the margin of the orbit by the tendooculi. At their outer extremity APPENDAGES OE THE EYE. 558 MEIBOMIAN GLANDS. they terminate at a short distance from the canthus, and are retained in position by a fibrous band which is part of the pal- pebral ligament, and is called the external tarsal ligament. The Palpebrcd ligament (broad tarsal ligament) is a fibrous mem- brane which is firmly attached to the periosteum around the mar- gin of the orbit, and to the internal free edges of the tarsal cartilages. It is thick and dense for the outer half of the orbit, but becomes thin to its inner side. Its use is to re- tain the tarsal cartilages in their place, and give support to the lids. The Meibomian glands are im- bedded in grooves on the under sur- face of each tarsal cartilage, and are distinctly seen on examining the inner aspect of the lids. They have the appearance of parallel strings of pearls, about thirty in number in the upper cartilage, and somewhat fewer in the lower; they open by minute foramina on the edges of the lids. They correspond in length with the breadth of the cartilage, and are con- sequently longer in the upper than in the lower lid. Each gland consists of a single lengthened follicle or tube, into which a number of small clusters of glandular vesicles open; the latter are so nume- rous as almost to conceal the tube by which the secretion is poured out on the edges Fig. 291.* Fig. 292.t * Appendages of the eye. 1. Superior tarsal cartilage. 2. Lower border of the cartilage on which are seen the openings of the Meibomian glands. 3. Inferior tarsal cartilage; along the upper border of this cartilage the open- ings of the Meibomian glands are likewise seen. 4. Lachrymal gland; its superior or orbital portion, o. Inferior or palpebral portion. 6. Lachrymal ducts, 7. Plica semilunaris. 8. Caruncula lachrymalis. 9. Puncta lacliry- malia of the lachrymal canals. 10. Superior lachrymal canal. 11. Inferior lachrymal canal. 12, Lachrymal sac. 14. Dilatation of the nasal duct, where it opens into the inferior meatus of the nose. 15. Nasal duck t Meibomian glands, as seen upon the inner side of the eyelids. 1. Upper lid. 2, Lower lid. 3,3. Conjunctiva. 4, Apertures of the Meibomian glands, forming a row along the free border of each eyelid. 5, 5. Papillas lachrymales. 6, f>. Puncta lachrymalia, 7. Apertures of the efferent duct of the lachrymal gland. CONJUNCTIVA—CARUNCULA LACHRYMALIS. 559 of the Ms. Occasionally an arch is formed between two of the follicles, producing a graceful appearance. The edges of the eyelids are furnished with strong, short, curved hairs, called eyelashes (cilia), arranged in two or more rows; those of the upper lid curving upwards, and those of the lower down- wards, so as not to interlace with each other in the closure of the lids, and prove an impediment to the opening of the eyes. Their follicles are supplied with sebaceous glands like those of other hairs. The Conjunctiva is the mucous membrane of the eye. It covers the whole of its anterior surface, and is reflected on the lids so as to form their internal layer. It is continuous with the general gastro-pulmonary mucous membrane, and sympathizes in its affec- tions, as may be observed in various diseases. From the surface of the eye it may be traced through the lachrymal ducts into the lachrymal gland, along the edges of the lids it is continuous with the mucous lining of the Meibomian glands, and at the inner angle of the eye it may be followed through the lachrymal canals into the lachrymal sac, and thence downwards through the nasal duct into the inferior meatus of the nose. Where it covers the cornea the conjunctiva is thin, transparent, and inseparable from the corneal substance ; it appears to consist of epithelial cells alone. In the conjunctiva at the circumference of the cornea a plexus of vessels is found, but this never extends entirely across the latter. The conjunctiva over the sclerotic is also thin and transparent, but is loosely applied and glides freely over the surface of the eyeball; it is freely supplied with blood by an irregularly disposed plexus of vessels. These vessels are readily distinguished from those of the sub-conjunctival tissue, by the latter radiating in nearly straight lines from the circumference of the cornea, and by their not gliding over the surface of the sclerotic on pressure. The sclerotic con- junctiva consists of stratified epithelium with an elastic basement membrane. The palpebral conjunctiva is thick, opaque, and red; it presents numerous papillae on its surface, and very closely resembles ordinary mucous membrane in structure. It consists of several layers of nucleated epithelium, a basement membrane, and elastic submucous tissue ; in the latter, numerous simple follicles are found, and near the reflected portion, certain racemose glands, similar in structure to the lachrymal gland. Between the eyelids and ball of the eye the conjunctiva forms an upper and lower fold, which are called the superior and inferior palpebral folds (retro-tarsal folds); it is in these that minute foreign bodies frequently become lodged. The Caruncula lachrymalis is the small reddish body which occupies the lacus lachrymalis at the inner canthus of the eye. In health it presents a bright pink tint; in sickness it loses its colour and becomes pale. It is studded with fine hairs, and consists of a dozen racemose sebaceous glands, with some few fat cells inter- mingled. 560 LACHRYMAL APPARATUS. Immediately to the outer side of the caruncula is a slight dupli- cature of the conjunctiva, called plica semilunaris; it is simply a fold of conjunctiva, and is the rudiment of the third lid or mem- brana niditans of birds. Vessels and Nerves.—The eyelids and other appendages of the eye are supplied with blood by the nasal, palpebral, and lachrymal branches of the ophthalmic, and the angular branch of the facial artery. The nerves are derived from the facial and fifth nerves. The Lachrymal apparatus consists of the lachrymal gland with its excretory ducts ; the puncta lachrymalia and lachrymal canals ; the lachrymal sac and nasal duct. The Lachrymal gland is situated at the upper and outer part of the orbit, in a depression of the orbital plate of the frontal hone, with the periosteum of which bone it is connected by fibrous bands; by its under surface it is in relation with the globe of the eye, and the superior and external rectus muscles. It is oval in shape, about three-quarters of an inch long, convex on its upper and con- cave on its under surface. The anterior portion is frequently separated from the rest by a slight depression, and is then de- scribed as the palpebral portion; it is situated in the upper eyelid, and extends downwards to the superior margin of the tarsal carti- lage. The gland consists of a number of aggregated racemose glands, similar in structure to the salivary and mucous glands. The secretion is conveyed away by from eight to twelve small ducts which run for a short distance beneath the conjunctiva, and open on its surface by separate orifices, about a twentieth of an inch apart, the greater number in the fold above the outer canthus, and two of them in the fold below. The Lachrymal canals commence at the minute openings, puncta lachrymalia, seen on the lachrymal papillae of the lids at the outer extremity of the lacus lachrymalis, and proceed inwards to the lachrymal sac, where they terminate beneath a valvular semilunar fold of mucous membrane (valve of Husclihe). The superior duct is the narrower and longer of the two, it at first ascends and then suddenly turns inwards towards the sac, forming an abrupt angle. The inferior duct forms the same kind of angle, by descending at first and then turning abruptly inwards. Both canals are dilated where they are bent. A valve-like projection (valve of Foltz) has been described as projecting from the side into the interior of the vertical portion of each canaliculus; it seems to be sufficient to close the tube completely when it is flattened by the orbicularis and tensor tarsi muscles. It no doubt pi-events the tears being driven back when such pressure is applied, as in winking ; and as a con- sequence they are then driven forward into the lachrymal sac. The two fasciculi of the tensor tarsi muscle are inserted into the canali- culi, and serve to draw them inwards and compress them. The Lachrymal sac is the dilated upper extremity of the nasal LACHRYMAL APPARATUS. GLOBE OF THE EYE. 561 duct. It is lodged in the groove of the lachrymal hone, and is often distinguished internally from the nasal duct by a semilunar or cir- cular valve. The sac consists of mucous membrane, but is covered in and retained in place by a fibrous expansion, derived from the tendon of the orbicularis, which is inserted into the ridge on the lachrymal bone; it is also covered by the tensor tarsi muscle, which arises from the same ridge, and in its action on the lachrymal canal makes pressure on the lachrymal sac. The nasal duct is a short canal, about three-quarters of an inch in length, directed downwards, backwards, and a little outwards to the inferior meatus of the nose, into which it opens. It is fined by mucous membrane, which is continuous with the conjunctiva above, and with the pituitary membrane of the nose below; it frequently forms an imperfect valve (valve of Ilasner) at the lower opening of the duct. Vessels and Nerves.—The lachrymal gland is supplied with blood by the lachrymal branch of the ophthalmic artery, with nerves by the lachrymal branch of the ophthalmic, and the orbital branch of the superior maxillary. GLOBE OF THE EYE. The globe or ball of the eye is irregularly spheroidal in form, having the segment of a smaller sphere (the cornea) projecting from it anteriorly, and being slightly flattened be- hind. Its transverse diameter is an inch, its antero - posterior and vertical diameters being a little short of this (’96 in.). Around the eyeball is a layer of fascia which separates it from the fat of the orbit, and enables it to move smoothly; this is the so-called tunica va- ginalis oculi, or capsule Fig. 293* * General diagram of the eye. 1. Cornea. 1. Corneal conjunctiva. 4. bcle- rotic. 2'. Sheath of the optic nerve, which is seen to be continuous with the sclerotic. 3. Vascular layers of the choroid. 3'. Pigmentary layer. 4. Ra- diating portion of the ciliary muscle. V. Cut fibres of circular portion, or muscle, of MiiUer. 5, 5. Ciliary processes. 6. Posterior chamber of the aqueous humour. 7, 7. Iris. 8. Optic nerve. 8'. Optic cumulus. 8 . Yellow spot. 9. Ora serrata. 10. Canal of Petit. 11. Anterior chamber of the aqueous humour. 12. Crystalline lens. 13. Chamber of the vitreous humour, 14. Canal of Schlemm. r. Nervous layers of the retina, t . Bacillai} and molecular layers of the retina. 562 EXTERNAL TUNIC. of Tenon; it is pierced by the tendons of the straight and oblique muscles, and is connected with the sclerotic by means of delicate fibrous threads. The globe of the eye is composed of a strong external fibrous coat, called the sclerotic, with its clear anterior portion, the cornea; a middle vascular and pigmentary covering, the choroid, which is also continued forwards to form a partition, the iris; and an in- ternal nervous tunic, the retina. It encloses certain refracting media, for the purpose of bringing rays of light to a focus on the retina; these are the vitreous and aqueous humour, and the crystal- line lens. External tunic.—Sclerotic.—The sclerotic hard) forms the outer covering of the posterior four-fifths of the globe of the eye. It is continuous posteriorly with the sheath of the optic nerve derived from the dura mater, and is pierced by the ciliary nerves and arteries. Anteriorly its fibres are continuous with the trans- parent ones of the cornea. It is thickest behind, but is strengthened in front by an expansion of the recti tendons, forming the tunica albuginea; this is covered for the greater part of its extent by the conjunctiva, and by reason of its brilliant whiteness gives occasion to the common expression, “ the white of the eye.” In structure the sclerotic is found to consist of white fibrous tissue, with some few elastic fibres and a great number of stellar nucleated cells ; the fibres are arranged in bundles which run both longitudinally and transversely, the superficial layers being chiefly longitudinal. The inner surface of the sclerotic is in contact with the choroid, and is connected to it by means of numerous threads of fibrous tissue, and by small vessels, these being tinged with the pigmentary matter of the choroid have a brown appearance, and hence the term membrana fusca is applied. At the entrance of the optic nerve a thin cribriform lamella, lamina cribrosa * takes the place of the sclerotic; it is pierced by a number of minute openings for the passage of the nervous filaments, and in the centre by a larger opening called jporus opticus, for the entrance to the eyeball of the arteria centralis retinas. The Cornea (corneus, homy) is the transparent prominent layer which constitutes the anterior fifth of the globe of the eye. It is circular, concavo-convex, and resembles a watch-glass. When ex- amined from the exterior, its vertical diameter is seen to be about one-sixteenth shorter than its transverse, in consequence of the overlapping above and below of the margin of the sclerotic; on the interior its outline is circular. It is continuous with the sclerotic, and is connected with the iris, choroid, and ciliary pro- cesses. The thickness of the cornea is from to of an inch; * The lamina cribrosa is generally described as the continuation of the scle- rotic, but it seems more probable (as Dr. T. Eeid suggests) that it is continuous with the choroid ; indeed, in an inflamed eyeball the fibres of the lamina have been distinctly traced into the choroid. MIDDLE TUNIC. 563 it is generally the same throughout, except at the outer edge, where it becomes a little thinner. Structure.—The cornea is divisible into four layers; these are, 1. Conjunctival epithelium; 2. Anterior elastic lamina; 3. Cornea propria; and 4. Membrane of Descemet or Demours. The first of these has been already described. The anterior elastic lamina is a transparent and apparently structureless layer, having an average thickness of from awo T¥oo an is highly elastic, shreds of it curling up im- mediately when detached. It is connected with the next layer by fine threads which run into the substance of the latter. The cornea propria forms the bulk of the cornea. It consists of numerous layers of delicate transparent fibres, which are continuous externally with those of the opaque scle- rotic. Between the strata nucleated cells are found, which freely anastomose with each other, and appear to be stellate in sections made parallel to the surface of the cornea. The membrane of Descemet or De- mours forms the posterior layer of the cornea, and lines the chamber of the aqueous humour; it consists of an elastic and an epithelial layer. The elastic layer (posterior elastic lamina of Bowman) is about of an inch in thickness, and resembles in all respects the anterior elastic lamina above described. The epithelium consists of a single layer of irregularly shaped nucleated cells. At the edges, the membrane of Descemet breaks up into threads, some of which are continued on to the iris to form the ligamentum pectinatum, others termi- nate in the inner wall of the canal of Fontana, and some few are connected with the ciliary muscle. Middle tunic.—The second or middle tunic of the eyeball is formed by the choroid, ciliary muscle, and iris, the ciliary processes being appendages developed from its inner surface. The Choroid (yopiov e’ldos, like the choroid, that is to say, “ vas- cular,”) is of a rich chocolate-brown colour on its external surface, and deep black within. It is connected to the sclerotic by means of the tine areolar tissue called membrana fusca, by vessels and nerves. Internally, it is in simple contact with the retina. It is pierced posteriorly for the passage of the optic nerve, and is con- nected anteriorly with the iris, ciliary processes, and the line of junction of the cornea and sclerotic. The choroid is composed of three layers, two of which are vas- Fig. 294.* * A vertical section of the cornea of an adult, showing the layers of which it is composed. 564 MEMBRANA PIGMENTI. cular, and the third, pigmentary. The external, or venous layer, consists principally of veins, the smaller branches of which are Fig. 295.* arranged in whorls (vasa vorticosa) round the chief trunks four or five in number. Between the meshes of the veins are stellate pig- mentary cells, which are connected together so as to form a fine web. The middle or arterial layer of the choroid (tunica Ruys- chiana) is formed principally of the ramifications of minute arteries, which form a complete network with very fine meshes. It is reflected inwards so as to form the ciliary processes. The inner layer (membrana j)igmenti) consists of cells containing pigment; these are hexagonal in form and are arranged like the tiles of a tesselated pavement. Throughout the whole of the proper choroid these cells are arranged in a single layer, and their nucleus remains clear, but on the ciliary processes and back of the iris there are several layers, and the nu- clei of the cells become obscured by the abundance of pigmentary matter. A structureless transparent membrane (membrane of Bruch) has been described as lying between the tunica Ruyschiana and the pig- mentary layer. Fig. 296.f * Dissection of the eyeball, showing its second tunic, and the mode of dis- tribution of the venae vorticosae of the choroid. 1. Part of the sclerotic coat. 2. Optic nerve. 3, 3. Choroid coat. 4. Ciliary ligament. 5. Iris. 6, 6. Venae vorticosae. 7, 7. Trunks of the venae vorticosae at the point where they have pierced the sclerotica. 8, 8. Posterior ciliary veins, which enter the eyeball in company with the posterior ciliary arteries, by piercing the sclerotic at 9. 10. One of the long ciliary nerves, accompanied by a long ciliary vein. t Pigmentary layer of the choroid. 1. The cells as seen from the surface. 2. The same viewed edgeways. 3. The fine pigment which fills the cells. ' IRIS. 565 In some animals the pigmentnm nigrum of the posterior wall of the eyeball is replaced by a layer of considerable extent, and of metallic brilliance, called tapetum; it appears to consist chiefly of white fibrous tissue. At the junction of the sclerotic and cornea with the choroid and iris, a small venous canal is found, called the canal of Schlemm or Fontana (sinus circularis iridis); it communicates with the venous trunks of the choroid. This canal seems to be more con- stant in the lower animals than in man, and has been observed to be very large in the negro (Dr. Eeid); its place is frequently taken by several small veins. The Ciliary muscle (formerly described as the ciliary ligament) is situated internally to the canal of Schlemm. It forms a greyish- white ring round the anterior part of the choroid, and is found to consist of unstriped muscular tissue, the fibres of which are con- nected in front with the inner surface of the sclerotic, and the fibres of the membrane of Descemet; they pass inwards and back- wards, and are attached to the choroid opposite and beyond the ciliary processes. Besides these fibres there are others, situated more internally, at the base of the ciliary processes ; these are dis- posed circularly, and consti- tute the circular muscle of Muller (sphincter ciliaris). The Iris (iris, a rainbow) is so named from its variety of colours in different indivi- duals ; it consists of muscular and fibrous tissue with pig- mentary cells, the latter being interspersed throughout the tissues, as well as forming a distinct posterior layer. The colour of the iris depends on the quantity and arrangement of the pigment cells; when the cells are in small quan- tity they are chiefly confined to the posterior layers, and the iris as seen from the front has a blue colour; but when in greater quantity, they are also dispersed through the tissues, and a grey or brown colour is the result. By its outer edge the iris is connected with the choroid and sclerotic; by its inner it forms the boundary of a circular opening called the jpupil; its anterior sur- face looks towards the cornea and is free; its posterior, looking Fig. 297.* * Anterior segment of a transverse section of the globe of the eye, seen from within. 1. Divided edge of the three tunics; sclerotic, choroid (the dark layer), and retina. 2. Pupil. 3. Iris, the surface presented to view in this section being the uvea. 4. Ciliary processes. 5. The scalloped anterior border of the retina. 566 CILIARY PROCESSES. towards the ciliary processes and lens, is in contact with them throughout greater part of its extent. The muscular tissue of the iris is of the unstriped variety. It con- sists of two sets of fibres, one of which is disposed circularly round the aperture of the pupil, so as to form a sphincter, the con- traction of which will diminish the size of the opening; the other set is gathered into numerous bands which radiate from the pupil- lary margin to the circumference, and serve by their contraction to dilate the pupil. The pigmentary layer, situated on the posterior surface of the iris, is of a deep purple tint, and hence has received the name of uvea (like a grape); it is continuous with the inner layer of the choroid. On its anterior surface the fibres of the iris have mingled with them some elastic fibres continuous with those of the membrane of Descemet, and are so arranged as to produce a festooned appear- ance. These festoons are very distinct in the eye of the ox and sheep; they form the ligamentum pectinatum. In the foetus a delicate vascular membrane closes in the pupil (membrana papillaris); it disappears about the seventh or eighth month. The Ciliary processes may be seen in two ways, either by re- moving the iris from its attachment to the choroid, when a front view of the processes will be obtained, or by making a transverse section through the globe of the eye, when they may be examined from behind, as in fig. 297. They consist of about eighty triangular folds, about one-third of which are smaller than the rest, and are interspersed at regular intervals. They have the same structure as the cho- roid, being composed of a vas- cular network and an internal pigmentary layer. Their peri- phery is connected with the ciliary muscle; the central bor- der is free, and rests against the circumference of the lens; the anterior surface corresponds with the uvea: the posterior Fig. 298.* * Posterior segment of a transverse section of the globe of the eye, seen from within. 1. Divided edge of the three tunics. The membrane covering the whole internal surface is the retina. 2. The entrance of the optic nerve with the arteria centralis retinas piercing its centre. 3, 3. Ramifications of the arteria centralis. 4. Foramen of Soemmering, in the centre of the axis of the eye; the shade from the sides of the section obscures the limbus luteus which surrounds it. 5. A fold of the retina, which generally obscures the foramen of Soemmering after the eye has been opened. INTERNAL TUNIC. 567 surface receives the folds of the suspensory ligament of the lens. Each of the larger folds measures about fo of an inch in length, and Jy of an inch in depth. Internal tunic.—This consists of the retina, with its continua- tion forwards, called the pars ciliaris retinue. The Retina is the inner nervous tunic of the eye, and that on which the images of external objects are produced. It is in contact by its external surface with the pigmentary layer of the choroid, and by its internal surface with the hyaloid membrane of the vitreous humour. It is firmly attached to the back part of the eye by means of the retinal artery and fibres of the optic nerve which enter it,but is loosely applied to the inside of the choroid throughout the rest of its extent. It terminates anteriorly, a little behind the base of the ciliary processes, in a festooned edge, the ora serrata; but from this edge there are continued forwards, over the ciliary pro- cesses to the base of the iris, some peculiar, elongated, nucleated cells, constituting the pars ciliaris retinue. In the fresh eye the retina is of a pale pink colour, and is trans- lucent, but it soon becomes opaque and yellowish, especially when in contact with fluids. At the back part of the retina, nearly in the axis of the eye, is a spot of a golden-yellow colour—macula lutea (called by Soemmering limbus luteus); it is elliptical in form, with a long diameter of about -jL of an inch, and short diameter 3V of an inch. In the middle of this is a depression, fovea centralis, where, the re- tina being thinned, the pigmentary matter of the choroid is seen through, hence it has the appearance of being a foramen, and was so described by Soemmering. This is the most sensitive spot of the retina, and being placed near the axis of the eye, receives the image of that part of an object to which the eye is directed, and of which the most vivid impression is obtained. About T\f of an inch to the inner side of the macula, is the entrance of the optic nerve. Here there is a slight elevation Fig. 299.* Fig. 300.t * Cells of the pars ciliaris retince. t Vertical section of the coats of the eye, at the point of entrance of the optic nerve, d. Retina, e. Choroid: f. Sclerotic, g. Sheath of the optic nerve, h. Fibres of the optic nerve, i. Central artery of the retina, k. Its point of subdivision. 1. Lamina cribrosa. 568 RETINA. (colliculus nervi optici), with a cupped centre, perforated by the arteria centralis retinae; the artery upon entering immediately breaking up into branches. This is the only part of the retina from which the power of vision is absent. The retina is thickest pos- teriorly in the immediate vicinity of the optic nerve, where it has a thickness of of an inch, but it thins as it passes forwards, and near the ora serrata measures only g-|o of an inch. Structure.—The external layer of the re- tina (bacillary layer) was formerly called Jacob's membrane, from its having been de- scribed by Dr. Jacob; it consists of a number of peculiar rod-like bodies, with which are mingled others with bulbous inner ex- tremities, called cones. The rela- tive proportion of rods and cones differs in different parts of the retina—thus, in the yellow spot the rods are absent, and the cones are attenuated and crowded; in the neighbourhood of the ora ser- rata, on the other hand, the rods are the most numerous, and the cones are interspersed at con- siderable intervals (fig. 301). The middle layer consists of several strata of corpuscles and molecules, which, upon minute examination, are found to be divi- sible into—(1) an outer stratum, consisting of oval corpuscles of small size, many of which are nu- cleated (outer corpuscular layer); (2) next to this a very narrow band of fine molecules (outer molecular layer): and (3) internal to this a layer of larger cor- puscles, all of which seem to be nucleated (inner corpuscular layer). The inner layer of the retina consists in part of the expanded Fig. 301.* Fig. 302.t * Bacillary layer of the retina, seen from the outer surface. 1. In the yellow spot. 2. In the neighbourhood of the yellow spot. 3. Near the ora serrata. t Diagram of the structures composing the retina. A. The structures viewed in situ. B. Shows the supposed connexion between the components of the several layers. 1. Bacillary layer (rods and cones). 2. Outer corpuscular layer. 3. Outer molecular layer. 4. Inner corpuscular layer. 5. Inner RETINA. 569 fibres of the optic nerve, and in part of superadded molecules and nerve-cells. Immediately in contact with the inner corpuscular layer above described is a stratum of fine molecules (inner molecular layer), and next to this one or two rows of multipolar nerve-cells, while, most internally, the fibres of the optic nerve form a thin layer. These structures are supported by a network of connective tissue, which is condensed so as to form a limiting membrane on the inside of the nerve fibres, and externally at the base of the bacil- lary layer. Besides the structures above described, there are also in the retina some peculiar filaments called the rods of Muller. These appear to be connected externally with pyriform cells at the bases of the rods and cones; some few have been observed to join the cells of the corpuscular layers, and some have been traced into the internal limiting membrane; these latter, however, are most likely simple filaments of the connective stroma, and not true rods of Muller. It is supposed that these elements connect the rods and cones with the fibres of the optic nerve, being connected inter- mediately with the cells of the corpuscular layers and the multi- polar cells above described; hitherto, however, this complete chain has not been satisfactorily demonstrated. At the yellow spot the retina becomes very much thinned, and the layers of which it is composed are one by one suppressed, until in the centre of the spot only a crowded layer of attenuated cones, a few cells of the outer granular layer, and a few nerve-cells ar- ranged like pavement epithelium, remain. At the entrance of the optic nerve, on the other hand, the bacillary and granular layers are absent, and the layer of nerve cells exists only at the border of the colliculus; the nerve fibres are, however, numerous, and form a very thick layer. Vessels.—The arteries of the retina are chiefly derived from the arteria centralis retinae, which enters the eye in the centre of the optic nerve, and breaks up immediately into branches, which ramify for the most part in the inner or nervous layers of the retina. The veins have a similar distribution, and terminate in the ophthalmic vein. The refracting media of the eye are the aqueous and vitreous humours, and the lens; but in conj unction with these we shall also describe the suspensory ligament and capsule of the lens, as well as the canal of Fetit. The Aqueous humour fills up the space between the cornea and the capsule of the lens with its suspensory ligament; it is a weakly albuminous fluid, with an alkaline reaction, and a specific gravity very little greater than that of water. The anterior chamber is the molecular layer. 6. Layer of nerve cells. 7. Layer of nerve fibres, a. Pig- mentary layer of the choroid, b. External limiting membrane, c. Connecting trabeculae (rods of Muller), d. Internal limiting membrane. 570 CRYSTALLINE LENS. space intervening between the cornea in front, and the ins and pupil behind. The posterior chamber was formerly described as the space between the posterior surface of the iris and pupil in front, and the ciliary processes, suspensory ligament, and lens behind,— but it is now known that the iris at the edge of the pupil is in ab- solute contact with the capsule of the lens, so that the term must now be restricted to the triangular interval existing between the ciliary processes, suspensory ligament and iris, at the circumference of the latter. The Vitreous humour forms the principal bulk of the globe of the eye, and supports the delicate retina internally. It is a transparent and highly albuminous fluid, enclosed in a delicate homogeneous membrane, the hyaloid membrane. Hannover supposed that septa of the hyaloid membrane also formed cells for the con- tained fluid, but microscopic examination has shown that such is not the case in the adult, though there undoubtedly are fibres in the centre of the vitreous in the foetus. Anteriorly the hyaloid is connected with the posterior part of the capsule of the lens, and forms the back of the canal of Petit—while a thickened prolongation of it forms the suspensory ligament of the lens. The Crystalline lens is situated im- mediately behind the pupil, and sur- rounded by the ciliary processes, which slightly overlap its margin. It is more convex on its posterior than its anterior surface, and is embedded in the anterior part of the vitreous humour, from which it is separated by the hyaloid membrane. It is invested by a peculiar transparent and elastic membrane, the capsule of the lens, which is thicker in front than be- hind, in consequence of the suspensory ligament joining it in front. The capsule is connected with the lens in front by means of a single layer of “ granular and nucleated polygonal cells,” which, at its edge, appear to become continuous with the nucleated fibres of the lens itself (fig. 303). The lens is retained in its place by means of the suspensory ligament, to be presently described. Structure.—The lens consists of concentric layers, of which the external are soft, the next firmer, and the central form a hardened nucleus. They are best demonstrated by boiling or by immersion in alcohol, when they are easily separated from each other. Fig. 303.* * The crystalline lens. 1. The lamina) of which the lens is composed. 2. The cells contained between the capsule and front of the lens. 3. Capsule of the lens. 4. Nuclear zone. DEVELOPMENT OF THE EYE. 571 Another division of the lens takes place at the same time : it splits into three triangular segments, having the sharp edge directed towards the centre, and the base towards the circumference. The concentric laminae are composed of minute hexagonal fibres, united with each other by means of irregularly serrated edges, the serra- tions of which accurately fit into each other. Some of the super- ficial fibres possess nuclei, which are usually arranged in regular zones, and are continuous in series with the nuclei of the cells be- tween the capsule and lens anteriorly (Babuchin). The Suspensory ligament of the lens—Retzius (Zonule of Zinn, —Zonula ciliaris), is a firm, transparent membrane, which passes from the fore part of the circumference of the lens to join the hya- loid membrane nearly opposite the ora serrata. It is gathered up into numerous plaits which fit into the depressions between the ciliary processes, and when withdrawn carry with them some of the pigment which covers those processes. Structurally, it is found to consist of pale longitudinal parallel fibres, which seem to resemble those of elastic tissue. Immediately around the circumference of the lens is a triangular canal, the canal of Petit, about a line and a half in breadth. It is bounded in front by the suspensory ligament; behind by the hya- loid membrane; and within by the border of the lens. The vessels of the globe of the eye are the long, short, and ante- rior ciliary arteries, and the arteria centralis retince. The long ciliary arteries, two in number, pierce the posterior part of the sclerotic, and pass forwards on each side, between that mem- brane and the choroid, to the base of the ciliary processes, where each divides into two branches, which form an elaborate network in the substance of the ciliary processes and iris. The short ciliary arteries pierce the posterior part of the sclerotic coat, and are dis- tributed to the middle layer of the choroid membrane (tunica Ruyschiana). The anterior ciliary are branches of the muscular arteries; they enter the eye just behind the junction of the cornea and sclerotic, and join the anastomotic circle of the iris. It is the increased number of these latter arteries, in iritis, that gives rise to the pecu- liar red zone round the circumference of the cornea. The distribu- tion of the arteria centralis retince has been already described. The Nerves of the eyeball are, the optic, two ciliary nerves from the nasal branch of the ophthalmic, and the ciliary nerves from the ophthalmic ganglion. VESSELS AND NERVES OP THE GLOBE OF THE EYE. The important circumstance to note in connexion with the de- velopment of the eye is—that whereas the globe of the eye and the vitreous humour are formed from those small lobes given off from DEVELOPMENT OP THE EYE. 572 ORGAN OF HEARING. the anterior cerebral vesicle, and known as the optic lobes—the an- terior part of the eye, including the crystalline lens, cornea, and iris, is developed from the integumentary structures of the face. ORGAN OF HEARING. The apparatus of hearing is composed of three parts, external ear, middle ear or tympanum, and internal ear or labyrinth. The External ear consists of two portions, the pinna and meatus; the former representing a kind of funnel which collects the vibrations of the atmosphere producing sounds, and the latter a tube which conveys the vibrations to the tympanum. The Pinna presents a number of folds and hollows on its surface, which have different names assigned to them. Thus, the external folded margin is the helix (eAt£, a fold). The elevation parallel with and in front of the helix is the antihelix (am, opposite). The pointed process, projecting like a valve over the opening of the ear, from the face, is the tragus (epayos, a goat), probably from being sometimes covered with bristly hair like that of a goat; and, a tubercle opposite this, is the antitragus. The lower dependent and fleshy portion of the pinna is the lobulus. The space between the helix and antihelix is named the fossa of the helix (scaphoid or innominate fossa). Another depression at the upper extremity of the antihelix, produced by a bifurcation of that ridge, is the fossa of the antihelix (oval or triangular fossa); and the large central space, to which all the channels converge, the concha, which opens directly into the meatus. The pinna is composed of integument, fibro-cartilage, ligaments, and muscles. The Integument is thin, contains an abundance of sebaceous glands, and is closely connected with the fibro-cartilage. The Fibro-cartilage gives form to the pinna, and is folded so as to produce the various convexities and grooves which have been described on its surface. The helix begins in the concha, and par- tially divides that cavity into two parts; on its anterior border, where it commences its curve upwards, is a tubercle or spine, and a little above this a small vertical fissure, the fissure of the helix. The termination of the helix and antihelix forms a lengthened pro- cess, the processus caudatus, which is separated from the concha by an extensive fissure. On the anterior surface of the tragus is another fissure, the fissure of the tragus; and, in the lobulus, the fibro-cartilage is wanting. The fibro-cartilage of the meatus is divided from the concha by several fissures (fissures of Santorinus), and at the upper and anterior part of the cylinder is a considerable space, which is closed by muscular and ligamentous fibres; it is firmly attached at its termination to the processus auditorius. The Ligaments of the external ear are those which attach the pinna to the side of the head—viz., anterior, posterior, and ligament of the tragus; and those of the fibro-cartilage, which serve to pre- MUSCLES OF THE PINNA. 573 serve its folds and connect the opposite margins of the fissures. The latter are two in number, the ligament between the concha and processus caudatus, and the broad ligament which extends from the upper margin of the fibro-cartilage of the tragus to the helix, and completes the meatus. The proper Muscles of the pinna are, the— Major helicis, Minor helicis, Tragicus, Antitragicus, Transversus auriculae, Obliquus auris. Fig. 304.* The Major helicis is a narrow band of muscular fibres situated on the anterior border of the helix. It arises from the spine of the helix and is inserted into the anterior border of that fold. The Minor helicis is placed upon the anterior extremity (crus) of the helix, at its commencement in the fossa of the concha. The Tragicus is a thin quadrilateral layer of muscular fibres, situated on the tragus. The Antitraxjicus arises from the antitragus, and is inserted into the posterior surface of the processus caudatus of the helix. * The pinna and its muscles; after Arnold. 1, 1. Helix. 2. Crus helicis. 3. Spina helicis. 4. Processus caudatus helicis. 5. Antihelix. 6, 6. Crura antihelicis. 7. Fossa innominata or scaphoidea. 8. Fossa triangularis. 0. Concha. 10. Tragus. 11. Antitragus. 12. Inoisura intertragica. 13. At- trahens aurem. 14. Attollens aurem. 15. Retrahens aurem. 16. Major helicis muscle. 17. Minor helicis. 18. Tragicus. 19. Autitragicus. 574 MEATUS AUDITORIUS. The Transversus auriculae, partly tendinous and partly muscular, extends transversely from the convexity of the concha to that of the helix, on the posterior surface of the pinna. The Obliquus auris (Tod) is a small band of fibres passing be- tween the upper part of the convexity of the concha and the con- vexity immediately above it. The Meatus aujjitokius is a canal, partly cartilaginous and partly osseous, about an inch in length, which extends in- wards and a little for- wards from the concha to the tympanum. It is narrower in the middle than at each extremity, forms an oval cylinder, the long diameter being vertical, is directed a little forwards, and is slightly curved on itself, the con- cavity looking down- wards. In consequence of the obliquity of the mem- brana tympani, the floor of the canal is a little longer than its roof. The cartilaginous por- tion of the tube forms a little less than half the passage. The osseous portionhasbeen described in connexion with the temporal bone. The skin of the meatus is very thin, especially towards the bottom of the passage; after maceration in water, the epithelial lining frequently comes away as a complete and very delicate pouch. Some stiff short hairs are also found in its interior, which stretch across the tube, and prevent the ingress of insects and dust. In the substance of its lining membrane are a number of ceruminous glands, which secrete the wax of the ear. Vessels and Nerves.—The pinna is plentifully supplied with arteries; by the anterior auricular from the temporal, by the pos- terior auricular from the external carotid, and by a branch from the occipital artery. Fig. 305.* * The pinna and its muscles, as seen from behind; after Arnold. 1, 1. Border of the helix. 2. Spine of the helix. 3. Convexity corresponding with the fossa scaphoidea. 4, 4. Convexity of the concha: the fissure between the numbers corresponds with the crus helicis. 5. Ponticulus conchae. 6, 6. Cartilage of the meatus. 7. Aperture of the meatus. 8. Attrahens aurem. 9. Attollens aurem. 10. Betrahens aurem. 11. Transversus auri- culae. 12. Obliquus auriculae. MIDDLE EAR OR TYMPANUM. 575 Its Nerves are derived from the auriculo-temporal of the fifth, the posterior auricular of the facial, and the auricularis magnus of the cervical plexus. Middle ear or tympanum.—The tympanum is an irregular bony cavity, compressed from without inwards, and situated within the petrous bone. It is bounded externally by the meatus and mem- brana tympani; internally, by the base of the petrous bone; behind, by the mastoid cells; and, throughout the rest of its circumference, by the thin osseous layer which connects the petrous with the squamous portion of the temporal bone. The Membrana tym- pani is a thin and semi- transparent membrane of an oval shape, its long diameter being vertical. It is inserted into a groove situated around the circumference of the meatus, near its termina- tion, and is placed ob- liquely across the area of that tube, the direction of the obliquity being downwards and inwards. It is concave towards the meatus, convex towards the tympanum, and com- posed of three layers, ex- ternal, or epithelial, con- tinuous with the integu- ment of the meatus; mid- dle, fibrous, the fibres of which radiate from the handle of the malleus ; and, internal, mucous, derived from the mucous lining of the typanum. The tympanum contains three small bones, ossicula auditus—viz., the malleus, incus, and stapes. Fig. 306.* * Diagram of the ear. p. Pinna, t. Tympanum. 1. Labyrinth. 1. Upper part of the helix. 2. Antihelix. 3. Tragus. 4. Antitragus. 5. Lobulus. 6. Concha. 7. Upper part of the fossa scaphoidea. 8. Meatus. 9. Membrana tympani, divided by the section. 10. The three little bones, crossing the area of the tympanum, malleus, incus, and stapes ; the foot of the stapes blocks up the fenestra ovalis of the inner wall of the tympanum. 11. Promontory. 12. Fenestra rotunda; the dark opening above the ossicula leads into the mastoid cells. 13. Eustachian tube ; the little canal upon this tube contains the tensor tympani muscle in its passage to the tympanum. 14. Vestibule. 15. Three semicircular canals, horizontal, perpendicular, and oblique. 16. Am- pullae of the perpendicular and horizontal canal. 17. Cochlea. 18. Depres- sion between the two tubuli which communicate with the tympanum and vestibule; the one is the scala tympani, terminating at 12 ; the other the scala vestibuli. 576 OSSICLES OF THE EAE. The Malleus {hammer) consists of a head, neck, handle {manu- brium), and two processes, long {processus gracilis), and short {processus brevis). The manubrium is connected with the mem- brana tympani by its whole length, extending below the central point of that membrane. It lies beneath the mucous layer of the membrane, and serves as a point of attachment to which the radi- ating fibres of the fibrous layer converge. The long process de- scends to a groove near the fissure of Glasser, and gives attachment to the laxator tympani muscle. The short process is a conical elevation at the junction of the manubrium with the rest of the bone, into it is inserted the tendon of the tensor tympani.- The head of the bone articulates with the incus. The Incus {anvil) is named from an imagined resemblance to an anvil. It has also been likened to a bicuspid tooth, having one root longer than, and widely separated from, the other. It consists of two pro- cesses, united nearly at right angles, and at their junction forming a flattened body, which articulates with the head of the malleus. The short process is attached to the margin of the opening of the mastoid cells by means of a liga- ment ; the long process descends nearly parallel with the handle of the malleus, and curves inwards, near its termina- tion. At its extremity is a small glo- bular ' projection, the os orbiculare, which in the foetus is a separate piece, but becomes anchylosed to the long pro- cess of the incus in the adult; this process articulates with the head of the stapes. The Stapes is shaped like a stirrup, to which it bears a close resemblance. Its head articulates with the os orbiculare, and the two branches (crura) are connected by their extremities with a flat, oval-shaped plate, representing the foot of the stirrup. The foot of the stirrup is received into the fenestra ovalis, to the margin of which it is connected by means of a ligament; it is in contact, by its surface, with the membrana vestibuli, and is covered in by the mucous lining of the tympanum. The neck of the stapes gives attachment to the stapedius muscle. The ossicula auditus are retained in position and moved upon themselves by means of ligaments and muscles. ' The Ligaments are three in number; the suspensory ligament of the malleus, which is attached by one extremity to the upper wall of the tympanum, and by the other to the head of the malleus; the Fig. 307.* * Small bones of the tympanum. A. Incus, b. Malleus, c. The three bones articulated. I). Stapes. E. The foot of the stapes. 1. Processus gra- cilis of the malleus. 2. Processus brevis. 3. Os orbiculare. MUSCLES OF THE TYMPANUM. 577 posterior ligament of the incus, a short and thick band, which serves to attach the extremity of the short process of that bone to the margin of the opening of the mastoid cells; and the annular ligament which connects the margin of the foot of the stapes with the circumference of the fenestra ovalis. Between the head of the malleus and the incus, and between the incus and stapes, there are distinct joints: the bones being united by ligaments, the osseous surfaces coated with cartilage, and the joints lined by complete synovial membranes. The Muscles of the tympanum are four in number, the— Tensor tympani, Laxator tympani, Laxator tympani minor, Stapedius. The Tensor tympani (musculus internus mallei) arises from the spinous process of the sphenoid, the petrous portion of the tem- poral bone and the Eustachian tube, and passes forwards in a distinct canal, separated from the tube by the processus cochleari- formis, to be inserted into the processus brevis of the malleus. The Laxator tympani (musculus externus mallei) arises from the spinous process of the sphenoid bone, and passes through an opening in the fissure of Glasser, to be inserted into the neck of the malleus, just above the root of the processus gracilis. This is re- garded as a ligament (anterior ligament of the malleus) by some anatomists. The Laxator tympani minor (posterior ligament of the malleus) arises from the upper margin of the meatus, and is inserted into the handle and processus brevis of the malleus. This is regarded as a ligament by some anatomists. The Stapedius arises from the interior of the pyramid, and escapes from its summit to be inserted into the neck of the stapes. Actions.—The action of the tensor and laxator tympani muscles is sufficiently indicated by their names, but that of the stapedius is more difficult to understand. It seems, however, evident that by its contraction it will tend to pull the foot of the stapes out of the fenestra ovalis, and may thus prevent too forcible excitation of the delicate internal ear. The stapedius is supplied by a branch from the facial nerve, and it is noteworthy that in cases of intra-cranial paralysis of the facial, there is often intolerance of loud sounds. Foramina.—The openings in the tympanum are ten in number, five large and five small; they are— Large openings. Meatus auditorius, Fenestra ovalis, Fenestra rotunda, Mastoid cells, Eustachian tube. Small openings. Entrance of chorda tympani, Exit of chorda tympani, For the laxator tympani, For the tensor tympani, For the stapedius. The opening of the meatus auditorius has been already described. The Fenestra ovalis (fenestra vestibuli) is a reniform opening, 578 OPENINGS INTO THE TYMPANUM. situated at the bottom of a small oval fossa (pelvis ovalis), in the upper part of the inner wall of the tympanum, directly opposite the meatus. The long diameter of the fenestra is horizontal, and its convex borders directed upwards. It is the opening of com- munication between the tympanum and vestibule, and is closed by the foot of the stapes and by the lining membrane of both cavities. The Fenestra rotunda (fenestra cochleae) is somewhat triangular in form, and situated in the inner wall of the tympanum, below and rather posteriorly to the fenestra ovalis, from which it is separated by a bony elevation, called the promontory. It serves to establish a communication between the tympanum and cochlea. In the fresh subject it is closed by a proper membrane (m. tympani secundaria) as well as by the lining of both cavities. The Mastoid cells are numerous, and occupy the whole of the in- terior of the mastoid process and part of the petrous bone. They communicate by a large irregular opening with the upper and pos- terior circumference of the tympanum. The Eustachian tube is a short canal about an inch and three- quarters in length, extending obliquely between the pharynx and the anterior circumference of the tympanum. It is directed down- wards, forwards, and inwards, and opens anteriorly, behind the in- ferior meatus of the nose, into the pharynx. It consists of an osseous and a fibro-cartilaginous portion, the former of which has been already described in connexion with the temporal bone. The cartilage of the Eustachian tube is of a triangular form, having its inferior angles rolled up towards each other, but leaving between them a gap on the under side, which is filled up with fibrous tissue. The tube is narrow where it opens into the tympanum, but expands anteriorly, so as to become wide and trumpet-shaped. The Smaller openings serve for the transmission of the chorda tympani nerve, and three of the muscles of the tympanum. The opening by which the chorda tympani enters the tympanum is at about the middle of its posterior wall, and near the root of the pyramid. The opening of exit for the chorda tympani is at the inner end of the fissure of Glasser in the outer wall of the tympanum. The nerve is usually contained in a canal (called the canal of Hugier) distinct from the fissure of Glasser. The opening for the laxator tympani muscle is situated in the fissure of Glasser, in the older wall of the tympanam. The opening for the tensor tympani muscle is in the anterior wall, immediately above the opening of the Eustachian tube. The opening for the stapedius muscle is at the apex of a conical bony eminence, the pyramid, which is situated on the posterior wall of the tympanum, immediately behind the fenestra ovalis. Directly above the fenestra ovalis is a rounded ridge formed by the projection of the aquaiductus Fallopii. Beneath the fenestra ovalis and separating it from the fenestra rotunda is the pro- montory, a rounded prominence formed by the projection of the first turn of the cochlea. It is channelled on its surface by three WALLS OF THE TYMPANUM. 579 small grooves, which lodge the three tympanic branches of Jacob- son’s nerve. The Foramina and processes of the tympanum may be arranged according to their situation, into four groups. 1. In the External wall, from above downwards are the— Meatus auditorius, closed by the membrana tympani. Fissure of Glasser, Opening for laxator tympani, Apertura chordae (exit). 2. In the Inner wall, are the— Ridge of the aquasductus Fallopii, Fenestra ovalis, Promontory, with the grooves for Jacobson’s nerve, Fenestra rotunda. 3. In the Posterior wall are the— Opening of the mastoid cells, Pyramid, and opening for the stapedius, Opening for Jacobson’s nerve, Apertura chordae (entrance). 4. In the Anterior wall are the— Canal for tensor tympani muscle, Eustachian tube. The tympanum is lined by a vascular mucous membrane, which invests the ossicula and chorda tympani, and forms the internal layer of the membrana tympani. From the tympanum it is re- flected into the mastoid cells, which it lines throughout, and it passes through the Eustachian tube to become continuous with the mucous membrane of the pharynx. Both in the Eustachian tube and cavity of the tympanum its epithelium is furnished with vibratile cilia, except on the membrana tympani. Vessels and Nerves.—The Arteries of the tympanum are derived from the internal maxillary, internal carotid, and posterior auri- cular. Its Nerves are—1. Minute branches from the facial, distributed to the stapedius muscle. 2. The chorda tympani, which leaves the facial nerve near the stylo-mastoid foramen, and arches upwards to enter the tympanum at the root of the pyramid; it then passes forwards between the handle of the malleus and long process of the incus, to its proper opening near the fissure of Glasser. 3. The tympanic branches of Jacobson’s nerve are distributed to the mem- branes of the fenestra ovalis and fenestra rotunda, and to the Eustachian tube, and form a plexus by communicating with the carotid plexus, otic ganglion, and Vidian nerve. 4. A filament from the otic ganglion to the tensor tympani muscle. 580 INTERNAL EAR OR LABYRINTH. Internal ear.—The Internal ear is called the labyrinth, from its complexity; it consists of an osseons cavity and certain mem- branous structures contained therein, the latter constituting the membranous labyrinth. The osseous labyrinth presents a series of cavities, which are channelled in the substance of the petrous portion of the temporal bone, and is situated between the cavity of the tympanum and the meatus auditorius internus. It is divided into three unequal portions; these are the— Vestibule, Semicircular canal, Cochlea. The Vestibule is the central part of the osseous labyrinth, it is irregularly ovoid in shape, and a little flattened from without in- wards. In front it communicates with the cochlea, and behind with tbe semicircular canals ; its outer wall separates it from the cavity of the tympanum, and its inner wall corresponds to the bottom of the meatus auditorius internus. In the outer wall there is seen the reniform opening of the fenestra ovalis, the margin of which presents a prominent ring towards the vestibule; it is closed in the recent state by the foot of the stapes and its annular ligament, as well as by the lining membrane of the labyrinth and a special membrane (membrana secundaria). In the anterior part of the inner wall is a circular depression which corresponds to the posterior segment of the cul-de-sac of the internal meatus; it is called fovea hemispherica, and is pierced by a cluster of openings (macula cribrosa) through which pass filaments of the vestibular branch of the auditory nerve, and twigs of the auditory artery. Behind this is a small ridge (crista vestibuli), and the commencement of a small canal called the aquceductus vestibuli, containing a tubular membranous sheath and a small vein. In the roof is another depression of oval form called fovea hemi- elliptica; it is separated from the fovea hemispherica by a slight ridge. Posteriorly, the five openings of the three semicircular canals are observed, the oblique and perpendicular canals joining by one extremity and so entering by a common opening. In front the vestibule opens into the cochlea by means of a wide, funnel-shaped opening, called apertura scales vestibulce. The openings of the vestibule may be arranged like those of the tympanum, into large and small. The large openings are seven in number:— Fenestra ovalis, Apertura scalse vestibuli, Five openings of the semicircular canals. SEMICIRCULAR CANALS—COCHLEA. 581 The small openings are three :— Aqumductus vestibuli, Openings for small arteries, Openings for filaments of the auditory nerve. The Semicircular canals are three bony passages communicat- ing with the vestibule, into which they open by both their ex- tremities. Near one extremity of each of the canals is a dilatation of its cavity which is called an ampulla. 1. The superior or perpendicular canal is directed transversely across the petrous bone, and forms that prominence on its anterior surface which we have already described. It commences by means of an ampulla in the upper part of the vestibule, and terminates posteriorly by joining with the oblique canal, and forming a common canal which opens into the back part of the vestibule. 2. The posterior or oblique canal corresponds with the posterior part of the petrous bone; it commences by an ampullary dilatation in the posterior part of the vestibule, and curves nearly perpen- dicularly upwards to terminate in the common canal. In the ampulla of this canal are numerous openings for nervous filaments. 3. The external or horizontal canal is directed outwards, towards the base of the petrous bone, and is shorter than the two preceding. It commences by an ampullary dilatation above the fenestra ovalis, and terminates near to the common canal. The cochlea (so-called from its resemblance to a snail’s-shell) is the most anterior part of the labyrinth, corresponding by its apex with the anterior wall of the petrous bone, and by its base with the anterior depression at the bottom of the cul-de-sac of the meatus auditorius internus. Its apex is arched so as to form a sort of dome, which is called the cupola. It consists of a gradually tapering canal, about one inch and a half in length, which makes two turns and a half around a central axis called the modiolus. The first coil projects into the tympanum, forming that rounded elevation which has already been described as the promontory. The central axis or mo- diolus is large near its base, where it corresponds to the first turn of the cochlea, but diminishes as it proceeds towards the apex. Its external surface is composed of dense tissue, but its interior Ftg. 308.* * Vertical section of the cochlea of a calf, showing the modiolus and scala?. 582 MEMBRANOUS LABYRINTH. is spongy, and is pierced by numerous canals, which run spirally in its length, transmitting the filaments of the cochlear nerve. The central canal is usually larger than the others; it transmits the artery of the modiolus as well as a nerve, and is called tubulus centralis modioli. The interior of the canal of the cochlea is partially divided into two passages (scalce) by means of a thin and porous lamina of bone, the lamina spiralis ossea, which is wound spirally round the modiolus in the direction of the canal. It extends about two- thirds across the diameter of the canal, and consists of two thin lamellae, between which, aud through the perforations on their surfaces, the filaments of the cochlear nerve reach the membranous portion of the cochlea. At the apex of the cochlea the osseous lamina terminates by a hook-shaped process (hamulus laminae spiralis); and here also the seal® communicate by means of a small opening called the helico- trema. Interiorly, one of the two seal®, the scala vestibuli, termi- nates by an oval aperture in the anterior part of the vestibule, while the other, the scala tvmpani, becomes somewhat expanded, and opens into the tympanum through the fenestra rotunda. The internal surface of the osseous labyrinth is lined by a fibro- serous membrane, which is analogous to the dura mater in per- forming the office of a periosteum by its exterior, whilst it fulfils the purpose of a serous membrane by its internal layer, secreting a limpid fluid, the perilymph (liquor Cotunnii), and sending a reflec- tion inwards upon the nerves distributed to the membranous laby- rinth. In the cochlea the membrane of the labyrinth invests the two surfaces of the bony lamina spiralis. The fenestra ovalis and fenestra rotunda are closed by an extension of this membrane across them, assisted by the membrane of the cavity of the tympanum, and a proper intermediate layer (membrana secundaria). Besides lining the interior of the osseous cavity, the membrane sends two delicate processes along the aqueducts of the vestibule and cochlea, to the dura mater, with which they are continuous. These pro- cesses are the remains of a communication originally subsisting between the dura mater and the cavity of the labyrinth. Membranous labyrinth.—This consists of certain membranous bags contained within the osseous cavity of the vestibule and semi- circular canals, and of the structures which serve to complete the spiral lamina of the cochlea. The membranous labyrinth of the semicircular canals and vesti- bule has the same general shape as the osseous cavity in which it is contained; it floats in the perilymph, and is held in position by numerous nerve filaments derived chiefly from the vestibular wall. It contains in its interior a fluid similar to the perilymph, which is called endolympli, and is secreted by its lining membrane. In structure, this part of the membranous labyrinth consists of an outer vascular layer which is made up of the ramifications of minute arteries and veins, of an internal layer of epithelium which MEMBRANOUS VESTIBULE. 583 in some respects resembles that of serous membranes, and of a middle layer which is transparent, and consists of nucleated cells, in the midst of which the filaments of the vestibular nerve seem to break up. The membranous vestibule consists of two sacs, a greater and a lesser. The greater sac, called the utricle (sac- culus communis), rests in the depres- sion called fovea hemi-elliptica, in the upper and back part of the vestibule; it is oblong, and slightly flattened from within outwards. Its inner wall is thickened, where it receives nume- rous branches of the vestibular nerve. Firmly attached to the wall of the utricle, is a small aggregation of crys- tals of carbonate of lime ; these are irregular in shape, and are called otoliths (ear-stones), or otoconia (ear- dust). The cavity of the utricle is con- tinuous with that of the membranous semicircular canals, but is distinct from that of the saccule. The lesser sac, called the saccule (sacculus proprius), is spherical in shape, and is situated in the lower and anterior part of the vestibule, lying in the depression of the fovea hemispherica. It Fig. 309.* * Labyrinth of the left ear, showing its cavities and the membranous labyrinth ; after Breschet. 1. Cavity of the vestibule; the figure rests on the utricle. 2. Ampulla of the perpendicular semicircular canal, receiving a fasci- culus from the superior branch of the vestibular nerve, 3. 4. Perpendicular canal with its contained membranous canal. 5. Ampulla of the horizontal semicircular canal, receiving a fasciculus from the superior branch of the vesti- bular nerve. 6. Termination of the membranous canal of the horizontal semi- circular canal, in the utricle. 7. Ampulla of the oblique semicircular canal, receiving a fasciculus from the inferior branch of the vestibular nerve. 8. Ob- lique semicircular canal with its membranous canal. 9. The common canal, resulting from the union of the perpendicular with the oblique semicircular canal. 10. Membranous common canal terminating in the utricle. 11. The otolith of the utricle seen through the membranous parietes. A fasciculus from the inferior branch of the vestibular nerve distributed to the utricle near the otolith. 12. Sacculi; its otolith is seen through its membranous parietes, and a fasciculus derived from the middle branch of the vestibular nerve is distributed to it. The spaces around the membranous labyrinth are occupied by the perilymph. 13. First turn of the cochlea ; the figure points to the scala tympani. 14. Extremity of the scala tympani, the fenestra rotunda. 15. La- mina spiralis ; the figure is situated in the scala vestibuli. 16. Opening of the scala vestibuli into the vestibule. 17. Second turn of the cochlea; the figure is placed on the lamina spiralis, and therefore in the scala vestibuli, the scala tympani being beneath the lamina. 18. Remaining half turn of the cochlea ; the figure is placed in the scala tympani. 19. Lamina spiralis terminating in its falciform extremity. The dark space included within the falciform curve of the extremity of the lamina spiralis is the helicotrema. 20. Infundibulum. 584 SCALA MEDIA, receives nerves through, the lamina cribrosa, and contains otoliths similar to those of the utricle. It is connected by means of a mi- nute passage (canalis reuniens), with a small canal, which is con- tained within the membranous part of the cochlea, and is called scala media. The membranous semicircular canals are about one-third the size of the osseous canals which lodge them; they open into the utricle. They have dilatations which correspond to the ampullae, but the dilatation of the membranous canals is proportionally greater than that of the osseous ones, so that at these places they nearly fill the osseous cavities in which they lie. Here also the wall is much thickened, and on it branches of the vestibular nerve are thickly distributed. These canals contain endolymph, and have some few otoliths distributed over their epithelial lining. The membranous part of the cochlea* not only completes the lamina spiralis, but also encloses a tube called the canalis mem- branacea or scala media, within which is a very complicated struc- ture called the organ of Gorti. The description of the membranous cochlea, therefore, resolves itself into a description of this canal, its boundaries, and the parts contained in it. Scala Media.—This canal is triangular in cross section, and is bounded externally by the osseous wall of the labyrinth, lined by its proper membrane. Internally it is bounded by a thin sheet called the membrane of Reissner, which separates it from the scala vestibuli. Its floor is formed by a membrane, which is stretched across from the lower edge of the osseous lamina spiralis to the cochlear wall, and is called the membrana basilaris. The scala media accompanies the lamina spiralis throughout, and terminates superiorly in a cul-de-sac near the helico-trema; below, it also ends in a blind ex- tremity, but from its inner side a small canal (cana lis reuniens)pa,8sea off to join the utricle, as already mentioned. On the upper surface of the osseous lamina spiralis, near to its outer edge, there is a thick prominence, called lim- bus lamina spiralis, which is firmly con- Fig. 310.t * To understand the description of the membranous cochlea, it is necessary that the student should constantly refer to fig. 310. t Section through one of the coils of the Cochlea:—s T, scala tympani; S y, scala vestibuli; c C, canalis cochleae; k, membrane of Reissner; Us to VESSELS AND NERVES OF THE INTERNAL EAR. 585 nected with the periosteum of the lamina. Its surface is irregular, being marked by certain fungiform prominences ; these are not all of the same length, the internal ones being short, while the external are long, and hang over towards the basilar membrane, so as to form a groove beneath them, which is called the sulcus spiralis. Cover- ing in the limbus, and stretching across from its outer edge to the outer wall of the scala, is an elastic membrane called membrana tedoria (membrane of Corti). It is nearly parallel with the basilar membrane, and thus divides the scala media into two parts, the inferior of which is the smallest, and contains the organ of Corti. The basilar membrane is stretched acress from the free edge of the osseous lamina to the outer wall of the spiral canal; it is on th ■ same plane as the lamina itself, and is firmly attached at its outer extremity by means of a thick ligament (spiral ligament) to the cochlear wall. The membrane of Beissner arises from the base of the limbus (or on its inner side), and extends across to the upper and outer part of the cochlear wall. It is directed somewhat obliquely, and sepa- rates the scala vestibuli from the scala media. The organ of Corti consists of those structures which are con- tained between the membrana tectoria above and the basilar membrane below. Its central and most important part consists of rod-like bodies, which are fixed firmly below to the basilar mem- brane, but above, their enlarged ends meet together like the beams of a roof, so as to enclose a triangular space. The inner rods over- lap the outer, and the latter have a process bent back towards the outer side of the canal, from which a layer of squamous cells proceeds, forming the membrana reticularis. On each side of these central bodies are others which appear to recline on the larger ones just described; they consist of an inner and an outer set. The inner ones bear a close resemblance to the cells of columnar epithelium; they are very numerous and closely set, completely filling up the sulcus spiralis; they’are flattened and nucleated. The outer ones are smaller and less numerous; they are elongated, but do not reach as high as the membrana tectoria; the outer of these are sometimes called cells of Claudius. VESSELS AND NERVES OF THE INTERNAL EAR. Vessels.—The arteries of the labyrinth are derived from the internal auditory branch of the basilar artery, and from the stylo- mastoid branch of the posterior auricular. The auditory artery at the bottom of the meatus internus divides into cochlear and vesti- bular branches, which accompany the branches of the auditory nerve to the vestibule and cochlea. Isp, lamina spiralis membranacea; Us, limbus laminae spiralis; ss, sulcus spiralis; gs, ganglion spirale seated on nc, the nervus cochlearis indicated by the black line ; Iso, lamina spiralis ossea; l, membrana tectoria; b, membrana basilaris ; c o, organ of Corti; Isp, ligamentum spirale ; c c, cells of Claudius ; 1, rod of Corti of the first order ; 2, rod of Corti of second order. 586 NERVES. The veins of the vestibule unite with those of the cochlea, and empty themselves into the superior petrosal sinus. Nerves.—In order that the student may fully understand the dis- tribution of the nerves of the internal ear, it is necessary, in the first place, that he should know something of the anatomy of the interior of the meatus auditorius internus. The meatus pursues a course directly outwards; it is about one- third of an inch in length, and terminates in two deep depressions, separated by a sharp horizontal ridge. The superior depression, the smaller of the two, is divided by a vertical ridge, into an ante- rior portion, which is the commencement of the aqumductus Fal- lopii, and a posterior portion, which corresponds with the upper part of the inner wall of the vestibule, and is pierced by numerous small foramina. The inferior depression presents posteriorly an oval pit, pierced by numerous foramina, which open into the vestibule. Near its anterior extremity, the inferior depression is marked by a spiral groove, which is pierced by minute openings for the passage of filaments of the cochlear nerve; this is called tractus spiralis foraminulentus. In the centre of the small piece of bone which this groove isolates, is one foramen larger than the rest, which leads into the central canal of the modiolus, tubulus centralis modioli. Upon the posterior wall of the lower depression, and op- posite to the spiral groove, is a longitudinal groove leading to a fora- men, which transmits a considerable branch of the vestibular nerve. The auditory and facial nerves enter the meatus internus together, accompanied by the auditory branch of the basilar artery. At the bottom of the meatus the facial enters the aqueduct of Fallopius, and is conducted along it to the stylo-mastoid foramen, as already described. The auditory nerve divides into two branches at the bottom of the meatus, a vestibular nerve and a cochlear nerve, the latter lying anterior to the former, and a little below the facial nerve. The vestibular nerve separates into three branches, superior, middle, and inferior. The superior vestibular branch gives off a number of filaments, which pass through the foramina in the pos- terior part of the superior depression; they enter the vestibule beside the crista vestibuli, and are distributed to the utricle, and the ampulla of tbe superior and external semicircular canals. The middle vestibular branch sends off numerous filaments, which pass through the foramina in the lower depression, enter the vestibule through the fovea hemispherica, and are distributed to the saccule. The inferior and smallest branch passes along the groove and through the foramen at the back part of the meatus; it is dis- tributed to the ampulla of the posterior canal. The filaments which pass to the canals bifurcate at their extremities, and are applied against the flattened side of each membranous ampulla; they then pass into the membranous wall, and into the partial septum, which has been already described as projecting into the ampulla. ORGAN OF TASTE. 587 The cochlear nerve divides into numerous filaments, which enter the foramina of the tractus spiralis in the base of the cochlea, pass upwards in the canals of the modiolus, and, bending outwards at right angles, pass between the two layers of the osseous lamina spiralis. Here the nerve filaments form a network, in the midst of which numerous small ganglia have been observed. From this plexus branches are given off externally, which perforate the bottom of the sulcus spiralis, and, it is supposed, terminate by becoming attached to the rods of Corti, and the cells which adjoin them on each side. The central portion of the cochlear nerve passes through the tubulus centralis modioli, and supplies the apicial portion of the lamina spiralis, and the adjoining structures. ORGAN OF TASTE. The Tongue is composed of muscular fibres, which are distributed in layers arranged in various directions: thus, some are disposed longitudinally (lingualis superficialis); others transversely (lin- gualis transversus); others, again, obliquely and vertically. Be- tween the muscular fibres is a considerable quantity of adipose substance, and in the middle of the organ a vertical septum of fibrous tissue. The tongue is connected, posteriorly, with the os hyoides by muscular attachment; and to the epiglottis by mucous membrane, which forms the three glosso-epiglottic folds called frcena epiglot- tidis. At either side it is held in connexion with the lower jaw by mucous membrane; and in front, a fold of that membrane, which is named frcenum linguae, is formed beneath its under surface. The surface of the tongue is covered by a dense layer analogous to the corium of the skin, which gives support to papillae. A raphe marks the middle line of the organ, and divides it into symmetrical halves. The Papillce of the tongue are, the— Papillae circumvallatae, Papillae filiformes, or conicae, Papillae fungiformes. The Papillce circumvallatce (p. lenticulares) are of large size, and from fifteen to twenty in number. They are situated on the dorsum of the tongue, near its root, and form a row at each side, which meets its fellow at the middle line, like the two branches of the letter A. Each papilla resembles a cone, attached by its apex to the bottom of a cup-shaped depression; hence they are also named papillae calyciformes. This cup-shaped, cavity forms a kind of fossa around the papilla, whence their name circumvallatce. At the meeting of the two rows of these papillae upon the middle of the root of the tongue, is a deep mucous follicle called foramen caecum. The Papillce conicae or filiformes cover the whole surface of the tongue in front of the circumvallatae, but are most abundant 588 papilla: of the tongue. towards its anterior part. They are conical at their base, and have projecting from their apices filiform processes, which are found to be products of the epithelium. They are arranged in rows, which at the back part of the tongue are nearly parallel with the circumvallate papillae, but get more longitudinal in their direction as we proceed forwards, so that at the tip of the tongue they get to be nearly parallel with the median longitudinal furrow, which marks the centre of the upper surface of the tongue. The Papillae fungiformes (p. capitate) are irregularly dispersed over the dorsum of the tongue, and are easily recognised among the other papillae by their rounded heads, larger size, and red colour. A number of these papillae will generally be observed at the tip of the tongue. All these papillae have minute secondary papillae projecting from their surfaces, and these are coated with a very dense epithelial layer, which is generally flat over the circumvallate and fungiform papillae, but in the others, forms hair-like processes, which vary greatly in their size and shape. The circumvallate and fungiform papillae appear alone to possess the special sense of taste, the filiform being much too dense at their apices for the apprehension of delicate sensation, and hitherto no nerve filaments have been traced into the secondary papillae which surmount them. The filiform, however, are probably endowed with common sensation, and it is manifest that they perform important service in assisting mastication. Behind the papillae circumvallate, at the root of the tongue, are a number of mucous glands (lingual), which open on the surface. There is also a small cluster beneath the tip of the tongue. Vessels and Nerves.—The tongue is abundantly supplied with blood by the lingual arteries. The Nerves are three in number, and of large size; the gusta- tory or lingual branch of the inferior maxillary is distributed to the papilla) and mucous membrane generally of the fore part and sides of the tongue, it is the nerve of common sensation to those parts. With it are distributed filaments of the chorda tympani; these seem to go chiefly to the papillae, and experiments tend to show that the sense of taste in the front and sides of the tongue is due to these, and not to the gustatory filaments, as was formerly supposed. The glosso-pliaryngeal nerve is distributed to the back part of the tongue, and more especially to the circumvallate papillae; it endows those parts with the sense of taste. The hypoglossal nerve is the motor nerve distributed to the muscles of the tongue. The terminal filaments of the sensory nerves are supposed in some cases to become attached to the inner ends of some of the epithelial cells, the connexion bearing a close resemblance to that observed in the retina, the cochlea, and the nasal mucous membrane. The Mucous membrane which invests the tongue is continuous ORGAN OF TOUCH. 589 with the derma along the margin of the lips. On either side of the frrnnum linguae it may he traced through the sublingual ducts into the sublingual glands, and along Wharton’s ducts into the sub- maxillary glands; from the sides of the cheeks it passes through the opening of Stenon’s ducts to the parotid glands : in the fauces, it forms the assemblage of follicles called ton- sils, and may thence be traced down- wards into the larynx and pharynx, where it is continuous with the general gastro-pulmonary mucous membrane. Beneath the mucous membrane of the mouth are a number of small glands, which pour their secretion upon the surface. A considerable number of these bodies are situated within the lips, in the palate, and in the floor of the mouth. They are named according to their position, labial glands, palatal glands, and buccal glands. ORGAN OF TOUCH. The Shin is the exterior investment of the body, which it serves to cover and protect. It is continuous at the apertures of the internal cavities with the lining membrane of those cavities, the internal skin or mucous membrane, and is composed essentially of two layers, derma and epidermis. The derma, cutis vera or corium, is the deep layer of the skin; it is composed of areolar tissue, muscular tissue, and fat, together with numerous blood-vessels, lymphatics, and nerves, which ramify through it. For convenience of description it is divided into a reticidar and papillary layer, but it must be remembered that these are nowhere separable the one from the other. The Reticular or deep layer of the derma presents some variety in thickness in different parts of the body. Thus in the more exposed regions, as the back, the outer sides of the limbs, the palms, and the soles, it is remarkable for its thickness; while on protected parts Fig. 311*i * The tongue with its papillae. 1. The raphd, which sometimes bifurcates on the dorsum of the tongue, as in the figure. 2, 2. Lobes of the tongue; the rounded eminences on this part, and near its tip, are the papillae fungi- formes. The smaller papillae, among which the former are dispersed, are the papillae filiformes. 3. Tip of the tongue. 4, 4. Its sides, on which are seen the lamellated and fringed papillae. 5, 5. The A-shaped row of papillae circumvallatse. 6. Foramen caecum. 7. Mucous glands of the root of the tongue. 8. Epiglottis. 9, 9. Fraena epiglottidis. 10, 10. Greater cornua of the os hyoides. 590 DERMA. it is comparatively thin, and on the eyelids, penis, and scrotum is peculiarly delicate. It is connected by its under surface with the common superficial fascia of the body. It is composed chiefly of white fibrous tissue collected into bundles, which are small and closely packed in the upper strata, large and coarse in the deeper strata; in the latter they form large areolae, which contain adipose tissue, and in the midst of the fibrous bundles the hair-bulbs and the sudoriferous glands are imbedded. The super- ficial strata contain much yellow elastic tissue, the quantity of which varies in different parts of the body, being much increased in the neigh- bourhood of joints. The deep strata contain unstriped muscular fibres, which are either gathered into bun- dles or dispersed among the fibrous tissue. In some parts the muscular tissue is so thick as to form a distinct layer, as in the “tunica dartos” of the scrotum, in the nipple and its areola, the penis and the perineum. There are also distinct bands of muscle connected with the hair follicles; these will de described in speaking of the hairs. Throughout the whole of the reticular layer connective tissue corpuscles are fouud, they generally anastomose so as to form a network. The Papillary or superficial layer of the derma is raised in the form of conical prominences or papillae. On the general surface of the body the papillae are short and exceedingly minute; but in other situations, as the palmar surface of the hands and fingers, and the plantar surface of the feet and toes, they are long and of large size. They also differ in arrangement; for, on the general surface, they are distributed at unequal distances and without order; whereas, on the palms and soles, and on the corresponding surfaces of the fingers and toes, they are collected into little square clumps, con- taining from ten to twenty papillae; and these little clumps are disposed in parallel rows. It is this arrangement in rows that gives rise to the characteristic parallel ridges and furrows which are met with on the hands and feet. The papillae in these little square Fig. 312* * Vertical section of skin of finger:—A, Epidermis, the surface of which shows hollow depressions, a a, between the papillary eminences, 6, and the openings of the perspiratory ducts, s ; at m is seen the deeper layer of the epidermis, or stratum Malpighii;—b, Cutis vera, in which are embedded the perspiratory glands, d, with their ducts, e, and also aggregations of fat-cells, /; at g is seen an arterial twig supplying the vascular papillae, p ; and at t one of the tactile papillae with its nerve. EPIDERMIS OR CUTICLE. 591 clumps are for the most part uniform in size and length, but every here and there one papilla may be observed which is longer than the rest. The largest papillae of the derma are those which produce the nail; in the dermal follicle of the nail they are long and filiform, while beneath its concave surface they form longitudinal and parallel plications which extend for nearly the entire length of that organ. In structure the papilla is composed of homo- geneous, nucleated, and fibrillated areolar tissue, with a few transverse elastic fibres. The papillae are separated from the epi- dermis by an apparently homogeneous basement membrane, which becomes evident as a transparent line, when the tissue is treated with a solution of chloride of gold. The papillae are divisible into vascular and nervous, the former predominating; some of the nervous papillae are occupied by a peculiar form of nerve termination called the tactile corpuscle of Meissner or Wagner. The Epidermis or cuticle (scarfskin) covers the superficial surface of the derma, which it serves to envelope and defend. That surface of the epidermis which is exposed to the influence of the atmosphere and exterior sources of injury, is hard and horny in texture, while that which lies in contact with the papillary layer is soft and cellular. Hence the epidermis, like the derma, is divisible into two layers, external and internal, the latter being termed the rete mucosum. Moreover, the epidermis is laminated in structure, and the laminae present a progressively increasing tenuity and density as they advance from the inner to the outer surface. This difference of density is dependent on the mode of growth of the epidermis, for as the external surface is constantly subjected to destruction from attrition and chemical action, so the membrane is continually re- produced on its internal surface; new layers being successively formed on the derma to take the place of the old. Immediately in contact with the basement membrane covering the papillae is a layer of columnar cells, and it is believed that these are the active agents in the selection of nourishment from the corium for the epidermis, and in the production of the new’ cells of the rete mucosum. These cells, by drawing nourishment from the corium, increase rapidly in size, more especially in length; the Fig. 313.* * Portion of skin from the palm of the hand. 1. Papillary layer. 2. Longi- tudinal furrows, marking the arrangement of the papilla) into ridges. 3. Trans- verse furrows dividing the ridges into small quadrangular clumps. In the figure a few only of the papillae are shown. 4. Eete mucosum raised from the papillary layer; its under surface presents an exact impression of the papillary layer. 5, 5. Perspiratory ducts drawn out straight by the separation of the rete mucosum from the papillary layer; the point at which each per- spiratory duct issues from the papillary layer, and pierces the rete mucosum, is the middle of the transverse furrow between the quadrangular clumps. 592 DEVELOPMENT OF EPIDERMIS. ■upper part then becomes separated from the rest to form a new cell, while the lower part, remaining still attached to the basement membrane, again elongates by the im- bibition of new material; again it divides, and so ad infinitum. The cells thus formed become larger by draw- ing nourishment from the corium, and it is probable that they also divide to form other cells. As this process goes on, the newest formed cells push the older ones away from the corium, and as the latter ascend towards the surface of the skin they undergo certain changes. In consequence of the pressure which they sustain they become flattened; as they get beyond the range of nutrition they become altered in consistence; and, finally, they become subject to evaporation. Thus it happens that the cell which is at first spherical becomes elliptical, then becomes still more flattened, and at length desiccates into a thin membranous scale, in which the nucleus is scarcely apparent; in this last form it is thrown off. The under surface of the epidermis is accurately modelled on the papillary layer of the derma, each papilla having its appropriate sheath in the newly-formed epidermis or rete mucosum, and each irregularity of surface of the former having its representative in the soft tissue of the latter. On the external surface, this character is lost; the minute elevations corresponding with the papillae are, as it were, polished down, and the surface is rendered smooth and uniform. The palmar and plantar surface of the hands and feet are, however, an exception to this rule; for here, in consequence of the large size of the papillae and their peculiar arrangement in rows, ridges corresponding with the papillae are strongly marked on the superficial surface of the epidermis. The epidermis is remarkable for its thickness in situations where the papillae are large, as in the palms and soles. In other situations, it assumes a character which is also due to the nature of the surface of the derma; namely, that of being marked by a network of linear furrows, which trace out the surface into small polygonal and lozenge-shaped areae. These lines correspond with the folds of the derma produced by its move- ments, and are most numerous where those movements are greatest, as in the flexures and on the convexities of joints. The dark colour of the skin among the natives of the South is due to the coloration of the primitive granules of which the cell is Fig. 314*. * Diagram illustrative of the development of the epidermis and of epithelia in general. 1. A new cell. 2. The cell seen to be increased in size. 3. The spheroidal cell. 4. The oval cell. 5. The elliptical cell. 6. The flattened cell; which, by contact of its walls, is speedily converted into a scale in which the nucleus is lost. 7. A nucleated scale as seen on its flat surface. 8. A cluster of such scales. APPENDAGES OF THE SKIN. 593 composed, especially the nucleus. As the cells desiccate, the colour of the granules is lost; hence the deeper hue of the rete mucosum. The 'pores of the epidermis are the openings of the perspiratory ducts, hair follicles, and sebiparous glands. Vessels and Nerves.—The Arteries of the derma, which enter its structure through the areolae of the under surface of the corium, divide into innumerable intermediate vessels, which form a rich capillary plexus in the superficial strata of the skin and in its papillary layer. In the papillae of some parts of the derma, as in the longitudinal plications beneath the nail, the capillary vessels form simple loops, but in other papillae they are convoluted to a greater or less degree in proportion to the size and importance of the papillae. The Lymphatic vessels probably form, in the super- ficial strata of the derma, a plexus, the meshes of which are inter- woven with those of the capillary and nervous plexus. No lym- phatics have as yet been discovered in the papillae. The Nerves of the derma, after entering the areolae of the deeper part of the corium, divide into minute fasciculi, which form a terminal plexus in the upper strata of the corium. Prom this plexus the primitive fibres pass off to their distribution as loops, in the papillae. In the less sensitive parts of the skin the loops are simple and more or less acute in their bend, in conformity with the figure of the papillae. In the sensitive parts, and especially in the tactile papillae of the pulps of the fingers, there are two loops, which are, moreover, associated with a peculiar body embedded in the substance of the papilla, the corpusculum tactus of Wagner. The appendages of the skin are the nails, hairs, sebaceous glands, and perspiratory glands and ducts. The Nails are horny appendages of the skin, identical in forma- tion with the epidermis, of which they are a part. A nail is convex on its external surface, concave within, and implanted by means of a thin margin or root in a fold of the derma, which is nearly two lines in depth, and acts the part of a follicle to the nail. At the bottom of the groove of the follicle are a number of filiform papillae, which produce the margin of the root, and, by the successive forma- tion of new cells, push the nail onwards in its growth. The con- cave surface of the nail is in contact with the derma, and the latter is covered by papillae, which perform the double office of retaining the nail in its place, and giving it increased thickness by the addi- tion of newly-formed cells to its under surface. It is this constant change occurring in the under surface of the nail, co-operating with the continual formation taking place along the margin of the root, which ensures the growth of the nail in the proper direction. The nail derives a peculiarity of appearance from the disposition and form of the papillae on the ungual surface of the derma (matrix). Thus, beneath the root, and for a short distance onwards towards its middle, the derma is covered by papillae which are more minute, APPENDAGES OF THE SKIN. 594 APPENDAGES OF THE SKIN. and consequently less vascular than the papillae somewhat farther on. This patch of papillae is bounded by a semilunar line, and that part of the nail covering it being lighter in colour than the rest, has been termed lunula. Beyond the lunula the papillae are raised into longitudinal plaits, which are exceedingly vascular, and give a deeper tint of redness to the nail. These plait-like papillae of the derma are well calculated by their form to offer an extensive surface both for the adhesion and formation of the nail. The granules and cells are developed on every part of their surface, both in the grooves between the plaits and on their sides, and a horny lamina is formed between each pair of plaits. When the under surface of a nail is examined, these longitudinal lamina;, corresponding with the longi- tudinal papillae of the ungual portion of the derma, are distinctly apparent, and if the nail be forcibly detached, the laminae may be seen in the act of parting from the grooves of the papillae. It is this structure that gives rise to the ribbed appearance of the nail. The papillary substance of the derma which produces the nail is con- tinuous around the circumference of the attached part of that organ with the derma of the surrounding skin, and the horny structure of the nail is consequently continuous with that of the epidermis. Hairs are horny appendages of the skin, produced by the involu- tion and subsequent evolution of the epidermis ; the involution con- stituting the follicle in which the hair is enclosed, and the evolution the shaft of the hair. Hairs vary much in size and length in dif- ferent parts of the body; in some they are so short as not to appear beyond the follicle; in others, they grow to a great length, as on the scalp; while along the margins of the eyelids, and in the whiskers and beard, they are remarkable for their thickness. Hairs are generally more or less flattened in form, and when the extremity of a transverse section is examined, it is found to possess an elliptical or reniform outline. This examination also demon- strates that the centre of the hair is porous and loose in texture, while its periphery is dense ; thus affording ground for its division into a cortical and a medullary portion. The free extremity of a hair is generally pointed, and sometimes split into two or three filaments. Its attached extremity is implanted deeply in the inte- gument, extending through the derma into the subcutaneous areolar tissue, where it is surrounded by adipose cells. The central ex- tremity of a hair is larger than its shaft, and is called the root or bulb. It is rounded or conical in shape. The hair is contained in a depression which passes deeply into the reticular layer of the corium, and is called the hair follicle. It is wide in its deepest part where it contains the bulb, gets narrower at the entrance of the ducts of the sebaceous glands, and again widens as it nears the surface. Its wall consists of two distinct layers, called respectively the external and internal sheath of the follicle, the former being continuous with the corium, and the latter with the epidermis. Between these layers and the hair itself a de- licate structure is observed, called the root sheath; it is also de- SEBACEOUS GLANDS. 595 scribed as composed of an outer and an inner layer. The inner layer (Huxley's sheath) consists of flat cells which answer to the horny layer of the epidermis; the outer is composed of soft cells like those of the rete mucosum, some of them containing pigment (layer of Henle). Connected with the hair follicles there are some fine bands of un- striped muscular fibre. These arise from the superficial part of the corium, and are inserted into the outside of the lower part of the follicle, below the sebaceous gland. They are placed on the side towards which the hair slopes, and by their contraction erect the hair ; hence they have received the name of erectores pili. The colour of the hair, like that of the epidermis, is due to the coloration of the primitive granules of the cells. The Sebaceous glands are embedded in the substance of the derma, and present every degree of complexity, from the simplest follicle to the compound lobulated gland. In some situations their excretory ducts open independently on the surface of the epidermis; while in others, they terminate in the follicles of the hairs. The sebaceous glands associated with the hairs are racemiform and lobulated, consisting of glandular vesicles which open by short pedunculated tubuli into a common excretory duct, and the latter, after a short course, into the hair- follicle. In the scalp there are two of the glands to each hair- follicle. On the nose and face the glands are of large size, and constantly associated with small hair-follicles. In the meatus auditorius the ceruminous glands are also large ; in the eyelids the cilia are supplied like other hairs with sebaceous glands, but the Meibomian glands may also be regarded as belonging to this class. The excretory ducts of sebaceous glands offer some diversity in different parts of the body ; in many situations they are short and straight, in others, as in the palms of the hands and soles of the feet, where the epidermis is thick, they assume a spiral course. The sebaceous ducts are lined by an inversion of the epidermis, which forms a thick and funnel-shaped cone at its commencement, but soon becomes uniform and soft. Sebaceous glands are met with in all parts of the body, but are most abundant in the skin of the face, and in those situations which are naturally exposed to the influence of friction. The sebaceous substance when it collects in inordinate quantities Pig. 315.* * The hairs and their connexions. 1. Hair bulb. 2. Inner sheath of the follicle. 3. Sebaceous gland. 4. Erector pili. 596 SUDORIPAROUS GLANDS. within the excretory ducts becomes the habitat of a remarkable parasitic animal, the steatozoon folliculorum. The Sudoriparous glands are situated deeply in the corium and also in the subcutaneous areolar tissue, where they are surrounded by adipose cells. They are small round or oblong bodies, composed of one or more convoluted tubuli, which open into a common effe- rent duct. The latter ascends from the gland through the derma and epidermis, and terminates on the surface by a funnel-shaped and oblique aperture or pore. The efferent duct presents some variety in its course upwards ; within the derma it is straight, or curved and serpentine, and if the epidermis be thin, proceeds more or less directly to the excreting pore. Sometimes it is spirally curved within the derma, and having passed the latter, is regularly and beautifully spiral in its passage through the epidermis, the last forming an oblique and valvular opening on the surface. The spiral course of the duct is especially remarkable in the thick epi- dermis of the palm of the hand and sole of the foot. On those parts of the skin where the papillae are irregularly distributed, the efferent ducts of the sudoriparous glands open on the surface also irregularly, while on the palmar and plantar surfaces of the hands and feet, the pores are situated at regular distances along the ridges, at points corresponding with the intervals of the small, square-shaped clumps of papillae. Indeed, the apertures of the pores, seen on the surface of the epidermal ridges, give rise to the appearance of small transverse furrows, which intersect the ridges from point to point. The efferent duct and tubuli of the sudoriparous gland are lined by an inflection of the epidermis. This inflection is thick and infundibuliform in the upper stratum of the derma, but soon be- comes uniform and soft. The infundibuliform projection is drawn out from the duct when the epidermis is removed, and may be perceived on the under surface of the latter as a nipple-shaped cone. A good view of the sudoriferous ducts is obtained by gently separating the epidermis of a portion of decomposing skin; or they may be better seen by scalding a piece of skin, and then with- drawing the epidermis from the derma. In both cases it is the lining sheath of epidermis, in other words, the epithelium, which i& drawn out from the duct. 597 CHAPTER XI. OP THE YISCEEA. That part of the science of anatomy which treats of the viscera is named splanchnology, from the Greek words TTis, upon the tongue) is a fibro-cartilage of a yellowish colour, studded with a number of small mucous glands, which are lodged in shallow pits on its surface. It is * This derivation has reference to the appearance of both cartilages taken together and covered by mucous membrane. In animals, which were the principal subjects of dissection among the ancients, the opening of the larynx, with the arytenoid cartilages, bears a curious resemblance to the mouth of a pitcher with a large spout. 610 LIGAMENTS OF THE LARYNX. shaped like a cordate leaf, and placed immediately in front of the opening of the larynx, which it closes completely when the larynx is drawn up beneath the base of the tongue. It is attached by its point to the receding angle of the thyroid cartilage. Ligaments.—The ligaments of the larynx are numerous, and may be arranged into four groups : 1. Those which articulate the thyroid with the os hyoides. 2. Those which connect it with the cricoid. 3. Ligaments of the arytenoid cartilages. 4. Ligaments of the epiglottis. 1. The ligaments which connect the thyroid cartilage with the os hyoides are three in number. Two Thyro-hyoidean ligaments pass between the superior cor- nua of the thyroid and the extremities of the greater cornua of the os hyoides; a sesamoid bone or cartilage is found in each. The Thyro-liyoidean membrane is a broad membranous layer, occupying the entire space between the upper border of the thyroid cartilage and the upper and inner border of the os hyoides. It is pierced by the superior laryngeal nerve and artery. 2. The ligaments connecting the thyroid to the cricoid cartilage are also three in number:— Two Capsular ligaments, with their synovial membranes, which form the articulation between the inferior cornua of the thyroid and the sides of the cricoid; and the crico-thyroidean membrane. The Crico-thyroidean membrane is a fan-shaped layer of yellow elastic tissue, thick in front (middle crico-thyroidean ligament) and thinner at each side (lateral crico-thyroidean ligament). It is at- tached by its apex to the lower border and receding angle of the thyroid cartilage, and by its expanded margin to the upper border of the cricoid and base of the arytenoid cartilages. Superiorly it is continuous with the inferior margin of the chorda) vocales. The front of the crico-thyroidean membrane is crossed by a small artery, the inferior laryngeal, and is the spot selected fo; the operation of laryngotomy. Laterally it is covered in by the crico-thyroidei and crico-arytenoidei laterales muscles. 3. The ligaments of the arytenoid cartilages are eight in number:— Two Capsular ligaments, with synovial membranes, which arti- culate the arytenoid cartilages with the cricoid, strengthened behind by two posterior crico-arytenoid bands or ligaments; and the supe- rior and inferior thyro-arytenoid ligaments. The superior thyro-arytenoid ligaments are two thin bands of yellow elastic tissue attached in front to the receding angle of the thyroid cartilage, and behind to the anterior and inner border of each arytenoid cartilage. The lower border of this ligament con- stitutes the upper boundary of the ventricle of the larynx, and the fold of mucous membrane caused by its prominence has been called the superior or false chorda vocalis. The inferior thyro-arytenoid ligaments, or true chordae vocales, are thicker than the superior, and like them composed of yellow MUSCLES OF THE LARYNX. 611 elastic tissue. Each, ligament is attached in front to the receding angle of the thyroid cartilage, and behind to the anterior angle ot the base of the arytenoid. The inferior border of the chorda vocalis is continuous with the lateral expansion of the crico-thyroid ligament. The superior border forms the lower boun- dary of the ventricle of the larynx. The space between the two chordae voeales is the glottis or rima glottidis. 4. The ligaments of the epiglottis are five in number—namely, three glosso- epiglottic, hyo-epiglottic, and thyro- epiglottic. The glosso-epiglottic ligaments (fraena epiglottidis) are three folds of mucous membrane, which connect the anterior surface of the epiglottis with the root of the tongue. The middle of these con- tains elastic tissue. The hyo-epiglottic ligament is a band of yellow elastic tissue passing between the anterior aspect of the epiglottis near its apex, and the upper margin of the body of the os hyoides. The th/yro-epiglottic ligament is a long and slender fasciculus of yellow elastic tissue, which embraces the apex of the epiglottis, and is inserted into the receding angle of the thyroid cartilage immediately below the anterior fissure and above the attachment of the chordae voeales. Muscles.—The intrinsic muscles of the larynx are eight in num- ber ; the five larger are the muscles of the chordae voeales and rima glottidis; the three smaller are muscles of the epiglottis. The five muscles of the chordae voeales and rima glottidis are, Fig. 321.* C rico-thvroideus, Crico-arytenoideus posticus,. Crico-arytenoideus lateralis, Thy ro - ary tenoideus, Arytenoideus. * Vertical section of the larynx, showing its ligaments. 1. Body of os hyoides. 2. Its great cornu. 3. Lesser cornu. 4. Ala of the thyroid car- tilage. 5. Superior cornu. 6. Inferior cornu. T. Pomum Adami. 8, 8. Thyro- hyoidean membrane; the opening in the membrane immediately above the posterior figure is for the passage of the superior laryngeal nerve and artery. 9. Tliyro-hyoidean ligament; the figure is placed immediately above the sesamoid bone or cartilage, a. Epiglottis, b. Hyo-epiglottic ligament. c. Thyro-epiglottic ligament, d. Arytenoid cartilage ; inner surface, c. Outer angle of base of arytenoid cartilage. f. Corniculum laryngis. g. Cuneiform cartilage, h. Superior thyro-arytenoid ligament, i. Inferior thyro-arytenoid ligament, or chorda vocalis; the elliptical space between the two thyro- arytenoid ligaments is the ventricle of the larynx, k. Cricoid cartilage. 1. Lateral portion of the crico-thyroidean membrane, m. Central portion of the same membrane, n. Upper ring of trachea, o. Section of isthmus of thyroid gland, p, p. Levator glandul® thyroidese. 612 MUSCLES OF THE LARYNX. The Crico-thyroid muscle arises from the anterior surface of the cricoid cartilage, and passes obliquely outwards and backwards to be inserted into the lower and inner border of the ala of the thyroid from its tubercle as far back as the inferior cornu. The Crico-arytenoideus posticus arises from the depression on the posterior surface of the cricoid cartilage, and passes upwards and out- wards to be inserted into the outer angle of the base of the arytenoid. The Crico-arytenoideus lateralis arises from the upper border of the side of the cricoid, and passes upwards and backwards to be insen'ted into the outer angle of the base of the arytenoid car- tilage. The Tliyro-arytenoideus arises from the re- ceding angle of the thyroid cartilage, close to the outer side of the chorda vocalis, and passes backwards parallel with the cord, to be inserted into the base and outer surface of the arytenoid cartilage. The Arytenoideus muscle occupies the posterior concave surface of the arytenoid cartilages, between which it is stretched. It con- sists of three planes of transverse and oblique fibres ; hence it was formerly considered as several muscles, under the names of trans- versi and obliqui. The three muscles of the epiglottis are, Thyro-epiglottideus, Aryteno-epiglottideus superior, Aryteno-epiglottideus inferior. The Tliyro-epiglottideus appears to be formed by the upper fibres of the thyro-arytenoideus muscle; they spread out on the external surface of the sacculus laryngis, and in the aryteno-epiglottidean fold of mucous membrane, on which they are lost; a few of the an- terior fibres being continued onwards to the side of the epiglottis (depressor epiglottidis). The Aryteno-epiglottideus superior consists of a few scattered muscular fibres, which pass forward in the fold of mucous membrane forming the lateral boundary of the entrance into the larynx, from the apex of the arytenoid cartilage to the side of the epiglottis. The Aryteno-epiglottideus inferior, described by Hilton, and closely connected with the sacculus laryngis, may be seen by raising the mucous membrane immediately above the ventricle of the larynx. It arises by a narrow and fibrous origin from the arytenoid cartilage, just above the attachment of the chorda vocalis; and passing forwards and a little upwards, expands over the upper Fig. 322.* * Posterior view of the larynx. 1. Thyroid cartilage, right ala. 2. Ascend- ing cornu. 3. Descending cornu. 4, 7. Cricoid cartilage. 5, 5. Arytenoid cartilages. 6. Arytenoideus muscle, consisting of oblique and transverse fasci- culi. 7. Crico-arytenoidei postici muscles. 8. Epiglottis. MUCOUS MEMBRANE OF THE LARYNX. 613 half or two-thirds of the sacculus laryngis; it is inserted by a broad attachment into the side of the epiglottis. Actions.—The crico-arytenoidei postici open the glottis while all the rest close it. The arytenoideus approxi- mates the arytenoid cartilages posteriorly, and the crico-arytenoidei laterales and thyro-aryte- noidei anteriorly; the latter, moreover, close the glottis mesially. The crico-thyroidei are tensors of the chordae vocales, and these muscles, to- gether with the thyro-arytenoidei, regulate the tension, position, and vibrating length of the vocal cords. The crico-thyroid muscles effect the tension of the chordae vocales by rotating the inferior cornua of the thyroid on the cricoid; by this action the anterior portion of the thyroid is drawn downwards, and made to approximate the upper edge of the cricoid, thus separating it further from the arytenoid to which the vocal cords are fixed. The crico-arytenoidei postici separate the chordae vocales by drawing the outer angles of the arytenoid cartilages outwards and downwards. The crico-arytenoidei laterales, by drawing the outer angles of the arytenoid cartilages forwards, ap- proximate the anterior angles to which the chordae vocales are attached. The thyro-arytenoidei draw the arytenoid cartilages forwards, and, by their connexion with the chordae vocales, act upon the whole length of those cords relaxing them. The thyro-epiglottideus acts principally by compressing the glands of the sacculus laryngis and the sac itself: by its attach- ment to the epiglottis it would act feebly upon that valve. The aryteno-epiglottideus superior serves to keep the mucous membrane of the sides of the opening of the glottis tense, when the larynx is drawn upwards and the opening closed by the epiglottis. Of the aryteno-epiglottideus, the functions appear to be, to compress the subjacent glands which open into the pouch; to diminish the capa- city of that cavity, and change its form; and to approximate the epiglottis and the arytenoid cartilage. Mucous Membrane.—The aperture of the larynx is a triangular or cordiform opening, broad in front and narrow behind ; bounded anteriorly by the epiglottis, posteriorly by the arytenoideus muscle, and on either side by a fold of mucous membrane stretched between the side of the epiglottis and the apex of the arytenoid cartilage. On the margin of this aryteno-epiglottidean fold the cuneiform car- tilage forms a prominence more or less distinct. The cavity of the Fig. 323.* * Side view of larynx, one ala of the thyroid cartilage removed. 1. Left ala of thyroid cartilage. 2. Eight arytenoid cartilage. 3. Corniculum laryngis 4. Cricoid cartilage. 5. Crico-arytenoideus posticus muscle. 6. Crico-aryte- noideus lateralis. 7. Thyro-arytenoideus. 8. Crico-thyroidean membrane. 9. One half the epiglottis. 10. Upper part of trachea. 614 MUCOUS MEMBRANE OF THE LARYNX. larynx is divided into two parts by an oblong constriction produced by the prominence of the chordae vocales. That portion of the cavity which lies above the constriction is broad and triangular above, and narrow below; that which is below it, is narrow above and broad and cylindrical below, the circumference of the cylinder corresponding with the ring of the cricoid; while the space included by the constriction is a narrow, triangular fissure, the glottis or rima glottidis. The form of the glottis is that of an isosceles triangle, bounded on the sides by the chordae vocales and inner surface of the arytenoid cartilages, and behind by the arytenoideus muscle. Its length is greater in the male than in the female, and in the former measures somewhat less than an inch. Immediately above the prominence caused by the chorda vocalis, and extending nearly its entire length on each side of the cavity of the larynx, is an ellip- tical fossa, the ventricle of the larynx. This fossa is bounded below by the chorda vocalis, which it serves to isolate, and above by a border of mucous membrane folded upon the lower edge of the superior thyro-arytenoid ligament (superior or false chorda vocalis). The whole of the cavity of the larynx, with its prominences and depressions, is lined by mucous membrane, which is continuous superiorly with that of the mouth and pharynx, and interiorly is prolonged through the trachea and bronchial tubes into the lungs. In the ventricles of the larynx the mucous membrane forms a caecal pouch of variable size, termed the sacculus laryngis. The sacculus laryngis is directed upwards, sometimes extending as high as the upper border of the thyroid cartilage, and occasionally above that border. When dissected from the interior of the larynx it is found covered by the ai-yteno-epiglottideus muscle and a fibrous mem- brane, which latter is attached to the superior thyro-arytenoid ligament below; to the epiglottis in front; and to the upper border of the thyroid cartilage above. If examined from the exterior of the larynx, it will be seen to be covered by the thyro-epiglottideus muscle. On the surface of its mucous membrane are the openings of sixty or seventy small racemose glands, which are situated in the sub-mucous tissue, and give to its external surface a rough and ill- dissected appearance. The secretion from these glands is intended for the lubrication of the chordae vocales, and is directed upon them by two small valvular folds of mucous membrane, which are situated at the entrance of the sacculus. The mucous membrane is closely connected to the epiglottis and to the chordae vocales, on the latter being remarkable for its thinness. It is invested by a columnar ciliated epithelium as high up as the superior folds of the ventricle of the larynx and lower half of the epiglottis. Glands.—The mucous membrane of the larynx is furnished with an abundance of mucous glands: many of these are situated on the epiglottis, in the sacculus laryngis, and in the aryteno-epiglottidean folds, where they are termed arytenoid. The body known as the epi- glottic gland is merely a mass of areolar and adipose tissue, situated in the triangular space between the front surface of the apex of THE TEACHEA. 615 the epiglottis, the hyo-epiglottidean and the thyro-hyoidean liga- ment. Vessels and Nerves.—The Arteries of the larynx are derived from the superior and inferior thyroid. The nerves are the superior laryngeal and recurrent laryngeal; both branches of the pneumo- gastric. The two nerves communicate with each other; but the superior laryngeal is distributed principally to the mucous mem- brane at the entrance of the larynx; the recurrent, to the muscles. The Trachea or wind-pipe is cylindrical for about two-thirds of its circumference, and flattened on the posterior third, where it rests on the oesophagus ; it extends from opposite the fifth cervical vertebra to opposite the third dorsal, where it divides into the two bronchi. The length of the trachea is about four inches, and its diameter from side to side nearly an inch; it is somewhat larger in the male than in the female. The right bronchus, larger than the left, passes oft* nearly at right angles, to the upper part of the corresponding lung. The left descends obliquely, and passes be- neath the arch of the aorta, to reach the left lung. It is composed of cartilaginous rings, fibrous membrane, muscular fibres, elastic tissue, and is lined by mucous membrane. The Cartilaginous rings are from fifteen to twenty in number, and extend for two-thirds around its cylinder, being deficient at the posterior part. The first ring is received within the lower margin of the cricoid cartilage, and is broader than the rest; the last is broad at the middle in consequence of the prolongation of the lower border into a triangular process which curves backwards at the point of bifurcation. The posterior extremities of the rings are rounded, and occasionally one or two rings will be found to bifurcate. The Fibrous membrane connects the rings and forms a thin cover- ing to them on the outer surface. Internally it does not reach the surface, and the rings have in consequence an appearance of greater prominence. It also stretches across between the rings on the pos- terior part of the trachea. The Muscular fibres are disposed trans- versely across the space, between the extre- mities of the rings behind. They are placed internally to the fibrous membrane. The Elastic tissue is disposed in longitudinal bundles, within the rings; and internally to the muscular layer behind. The Mucous membrane, which is pale, forms the internal lining of the tube, and has opening upon its surface the excretory tubes of numerous mucous glands ; it is furnished with a ciliated columnar * Ciliated epithelium from the trachea; after Kolliker. 1. External layer of longitudinal elastic fibres. 2. Homogeneous surface layer of the mucous membrane. 3. Bound cells. 4. Oval and oblong cells. 5. Ciliated cells. THE TRACHEA. Fig. 324.* 616 THYROID GLAND. epithelium, which is continuous with that of the larynx above and the bronchial tubes below. The Mucous glands are small ovoid bodies situated internally to the fibrous membrane, between that membrane and the muscular layer behind, and in the substance of the fibrous membrane between the rings. Their ducts open upon the mucous membrane. THYROID GLAND. The thyroid gland or body is a blood-vascular gland; in other words, it secretes into the numerous cells of which it is composed, a peculiar fluid, which, originally separated from the blood, is again taken up by the veins or lymphatic vessels or both, and conveyed into the circulation, in this way performing some function in con- nexion with the formation or renovation of the blood. It is situated on the trachea, and may therefore be considered in this place, although bearing no part in the function of respiration. This gland consists of two lobes, which are placed one on each side of the trachea, and are connected with each other by means of an isthmus, which crosses its upper rings, usually the third and fourth ; but in this respect there is some variety, a point necessary to be remembered in operations on the trachea. The lobes are somewhat conical in shape, being larger below than above, and the smaller end is continued upwards to the side of the thyroid cartilage. The isthmus is connected with the lower third of the two lobes, and often gives origin to a process of variable length and size, called the pyramid or third lobe. The pyramid is generally situated on the left side of the isthmus and is sometimes derived from the left lobe. The left lobe is somewhat smaller than the right, the weight of the entire gland being about one ounce and a half. It is, however, larger in young persons and females than in adult males, and undergoes a slight increase during menstruation. Its permanent enlargement constitutes bronchocele, goitre, or the Derbyshire neck. The structure of the thyroid is of a brownish-red colour, and is composed of a dense aggregation of minute and independent mem- branous cavities or vesicles enclosed by a plexus of capillary vessels, and connected together by areolar tissue. The vesicles are composed of a membrana propria lined by a tesselated epithelium of nucleated cells, and contain a clear yellowish fluid, in which are found cvto- blasts and cells; the latter measuring of an inch in diameter. A muscle is occasionally found connected with its isthmus, or with the pyramid, and is attached, superiorly, to the body of the os hyoides, or to the thyroid cartilage. It was named by Soemmering, “ levator glandules thyroideoifig. 321. Vessels and Nerves— It is abundantly supplied with blood by the superior and inferior thyroid arteries. Sometimes an additional artery is derived from the arteria innominata, and ascends upon the front of the trachea to be distributed to the gland. The wounding of the latter vessel, in tracheotomy, might be fatal to the patient. THE LUNGS. 617 The nerves are derived from the superior laryngeal and from the middle and inferior cervical ganglia of the sympathetic. THE LUNGS. The lungs are two conical organs, situated one at each side of the chest, embracing the heart, and separated from each other by that organ and by a membranous partition, the mediastinum. On the external or thoracic side they are convex, and correspond with the form of the cavity of the chest; internally they are concave, to receive the convexity of the heart. Superiorly they terminate in a tapering cone, which extends above the level of the first rib into the root of the neck, and interiorly they are broad and concave, and rest on the concave surface of the diaphragm. Their posterior border is rounded, broad, and long; the anterior, sharp, short, and marked by one or two deep fissures; and the inferior border which surrounds the base is also sharp. The colour of the lungs is pinkish- grey, mottled, and variously marked with black. The surface is figured with irregularly polyhedral outlines, which represent the lobules of the organ, and the area of each of these polyhedral spaces is crossed by lighter lines representing smaller lobules. The weight of the lungs is about forty ounces, the right lung being two ounces heavier than the left. Each lung is divided into two lobes, by a long and deep fissure, which extends from the posterior surface of the upper part of the organ, downwards and forwards to near the anterior angle of its base. In the right lung the upper lobe is subdivided by a second fissure, which extends obliquely forward from the middle of the preceding to the anterior border of the organ, and marks off a small triangular lobe. The left lung presents a deep notch in its anterior border, at a point corresponding with the apex of the heart. The right lung is larger than the left, in consequence of the inclination of the heart to the left side. It is also shorter, from the great convexity of the liver, which presses the diaphragm upwards on the right side of the chest considerably above the level of the left; and it has three lobes. The left lung is smaller, has only two lobes, but is longer than the right. Each lung is retained in its place by its root, which is formed by the pulmonary artery, pulmonary veins, and bronchial tubes, together with the bronchial vessels and pulmonary plexuses of nerves. The groove on the surface of the lung where the vessels enter its sub- stance is the hilum pulmonis ; and the position of the large vessels in the root of the lung, as follows : from before, backwards, they are placed in a similar order on both sides—viz. Pulmonary veins, Pulmonary artery, Bronchus. From above, downwards, on the right side, this order is exactly reversed; but on the left side, the bronchus has to stoop beneath 618 THE LUNGS. the arch of the aorta, which alters its position to the vessels. They are thus disposed on the two sides :— Higlit, Bronchus, Artery, Veins. Left, Artery, Bronchus, Veins. The special relations of the roots of the lung are, for the right, the descending cava, which lies in front, and the vena azygos, Fig. 325.* which arches over it from behind to terminate in the superior vena cava. The root of the left lung has the descending aorta lying behind it. Structure.—The lungs are composed of the ramifications of the bronchial tubes (bronchia), which terminate in intercellular pas- sages and air-cells, of the ramifications of the pulmonary arteries * Heart and lungs. 1. Eight ventricle, the vessels to the left of the figure are the middle coronary artery and veins ; those to its right, the left coronary artery and veins. 2. Left ventricle. 3. Right auricle. 4. Left auricle. 5. Pulmonary artery. 6. Right pulmonary artery. 7. Left pulmonary artery. 8. Ligament of the ductus arteriosus. 9. Arch of the aorta. 10. Superior vena cava. 11. Arteria innominata, and in front of it the right vena innomi- nata. 12. Right subclavian vein, and, behind it, its corresponding artery. 13. Right common carotid artery and vein. 14. Left vena innominata. 15. Left carotid artery and vein. 16. Left subclavian vein and artery. 17. Trachea. 18. Right bronchus. 19. Left bronchus. 20, 20. Pulmonary veins ; 18, 20, form the root of the right lung; and 7, 19, 20, the root of the left. 21. Superior lobe of the right lung. 22. Middle lobe. 23. Inferior lobe. 24. Superior lobe of the left lung. 25. Inferior lobe. BRONCHIAL TUBES. 619 and veins, bronchial arteries and veins, lymphatics, and nerves; the whole of these structures, being held together by areolar tissue, constitute the parenchyma. The parenchyma of the lungs, when examined on the surface or by means of a section, is seen to consist of small polyhedral divisions, or lobules, which are connected to each other by an inter-lobular areolar tissue. These lobules again consist of smaller lobules, and the latter are formed by a cluster of air-cells, in the parietes of which the capillaries of the pulmonary artery and pulmonary veins are distributed. Each lobule, taken alone, is provided with its separate bronchial tube, pulmonary artery, and vein, and is isolated from surrounding lobules by a process of areolar membrane derived from the subserous tissue; the entire lung is an assemblage of these lobules, so separated and so connected, held together by the pleura. The serous investing membrane of the lungs or pleura is con- nected with the surface of the lobules by means of a subserous areolar tissue, which forms a distinct layer, and being prolonged between the lobules, is the bond of adhesion between them. This layer contains elastic tissue, and is a chief source of the elasticity of the lungs; its interstices are moistened by a serous secretion, and are unincumbered with fat. Bronchial Tubes.—The two bronchi proceed from the bifurcation of the trachea opposite the third dorsal vertebra to their cor- responding lungs. The right, about an inch long, takes its course nearly at right angles with the trachea, and enters the upper part of the right lung ; while the left, two inches in length, and smaller than the right, passes obliquely beneath the arch of the aorta, and enters the lung at about the middle of its root. Upon entering the lungs they divide into two branches, and each of these divides and subdivides dichotomously to their ultimate termination in the inter- cellular passages and air-cells. The bronchial tubes continue to diminish in size until they attain a diameter of -gV to of an inch, and arrive within £ of an inch of the surface of the lung. They then become changed in structure, and are continued onwards in the midst of air-cells, under the name of intercellular passages. Lastly, the intercellular passages, after several bifurcations, terminate each by a csecal extremity or air- cell. The intercellular passages are at first cylindrical, like the bronchial tubes, but soon become irregular in shape from the great number of air-cells which open into them on all sides. The air- cells in the adult lung measure between jim To an inch, they are irregular in shape, and, most frequently, four-sided cavities, separated by thin septa, and communicating freely with the inter- cellular passages, and sparingly with the bronchial tubes. In structure the bronchial tubes are composed of cartilages, fibrous membrane, muscular fibres, elastic fibres, and mucous mem- brane. The cartilages in the primary bronchi are six or eight in number in the right bronchus, and ten or twelve in the left. In the subsequent divisions of the bronchial tubes, which are cylin- 620 STRUCTURE OF THE LUNGS. drical in figure, the cartilages assume the form of thin plates of 11 regular shajie and size, adapted to each other by their edges, and completely surrounding the tubes. The plates are most strongly developed around the bifurcations of the tubes, and the point of division is furnished with a cartilage of a semi- lunar form. They are found entering into the structure of the bronchial tubes until the latter are reduced to a quarter of a line in diameter, and are then lost. The fibrous membrane, which enters largely into the formation of the trachea and bronchial tubes, is the principal coat of the smallest tubes, and is con- tinued to their terminations in the in- tercellular passages and air-cells. The muscular fibres belong to the class of non-striated, smooth, or organic muscle, they are arranged in rings around the tube, and form a muscular coat which is placed externally to the cartilaginous plates and is continued as far as the extremity of the tubes, being absent in the intercellular passages and air-cells. The elastic fibres, arranged in longitudinal fasciculi, form a thin stratum next the mucous lining; this elastic coat is prolonged to the ends of the tubes, and scattered fibres are found around the intercellular passages and air-cells. The mucous mem- brane, lining the bronchial tubes, is provided with a ciliated columnar epithelium as far as their termination; but in the in- tercellular passages and air-cells it is altered in its characters, is thin and transparent, and coated with a squamous epithelium. The capillaries of the lungs form plexuses which occupy the walls and septa of the air-cells and the walls of the intercellular passages, but are not continued into the bronchial tubes. The septa between the air-cells consist of a single layer of the capillary plexus enclosed in a fold of the mucous lining membrane. The air-cells of the central part of the lung are most vascular, and at the same time smallest, whilst those of the periphery are less vascular and larger. The pigmentary matter of the lungs is contained in the air-cells, as well as in the areolar tissue of the inter-lobular spaces and blood-vessels ; it is composed chiefly of carbon. The Pulmonary artery, conveying the dark and impure venous blood to the lungs, terminates in capillary vessels, which form a dense network in the parietes of the intercellular passages and air- cells, and then converge to form the pulmonary veins, by which the Fig. 326.* * A diagram showing the dilatation of the ultimate bronchial tubes into intercellular passages, and the enlargement of the latter near the surface of the lung, a, a. Bronchial tubes, b, b. Intercellular passages, on the walls of which are seen opening the air-cells, c, c. Air-cells near the surface of the lung. PLEURiE—MEDIASTINUM. 621 arterial blood, purified in its passage through the capillaries, is re- turned to the left auricle of the heart. The Bronchial arteries, branches of the thoracic aorta, ramify on the parietes of the bronchial tubes, and terminate partly in bronchial veins which convey the venous blood to the vena azygos on the right side, and the superior intercostal vein on the left; and partly in the pulmonary capillaries. The Lymphatics, commencing on the surface and in the substance of the lungs, terminate in the bronchial glands. These glands, very numerous and often of large size, are placed at the roots of the lungs, around the bronchi, and at the bifurcation of the trachea. In early life they resemble lymphatic glands in other situations; but in old age, and often in the adult, are black, and filled with carbonaceous matter, and occasionally with calcareous deposits. The Nerves are derived from the pneumogastric and sympathetic. They form two plexuses: anterior pulmonary plexus, situated upon the front of the root of the lungs, and composed chiefly of filaments from the deep cardiac plexus; and posterior pulmonary plexus, on the posterior aspect of the root of the lungs, composed principally of branches from the pneumogastric. The branches from these plexuses follow the course of the bronchial tubes, and are distributed to the intercellular passages and air-cells. Each lung is enclosed, and its structure maintained, by a serous membrane, the pleura, which invests it as far as the root, and is then reflected on the parietes of the chest. That portion of the membrane which is in relation with the lung is called pleura pul- monalis, and that in contact with the parietes, pleura costalis. The reflected portion, besides forming the internal lining to the ribs and intercostal muscles, also covers the diaphragm and thoracic surface of the vessels at the root of the neck, extending for somewhat more than an inch above the margin of the first rib. At the lower border of the root of the lung is a fold of the pleura, which extends down by the side' of the posterior mediastinum to the diaphragm, and serves to retain the lower part of the lung in position. This fold is the broad ligament of the lung, ligamentum latum pul- monis. On its external surface, where the pleura is connected with sur- rounding parts, it is rough; on its inner surface, smooth. At the right side, where the diaphragm is pressed upwards by the liver, the pleura is shorter than on the left, but it extends higher into the neck ; while the left pleura, in consequence of the encroachment of the heart on the left side of the chest, is narrower than the right. PLEUKJE. MEDIASTINUM'. The approximation of the two reflected pleurae in the middle line of the thorax forms a septum, which divides the chest into the two pulmonary cavities. This is the mediastinum. The two pleurae 622 ABDOMEN. are not, however, in contact with each other at the middle line in the formation of the mediastinum, but have a space between them which contains all the viscera of the chest with the exception of the lungs. The mediastinum is divided into an anterior, middle, and posterior portion. The Anterior mediastinum is a triangular space, bounded in front by the sternum, and at each side by the pleura. It contains a quantity of loose areolar tissue, in which are found some lymphatic vessels passing upwards from the liver, the remains of the thymus gland, the origin of the sterno-hyoid, sterno-thyroid, and left trian- gularis sterni muscle, and the left internal mammary vessels. The Middle mediastinum contains the heart enclosed in its peri- cardium ; the ascending aorta; superior vena cava; pulmonary arteries and veins; bifurcation of the trachea; and phrenic nerves. The Posterior mediastinum is bounded behind by the vertebral column, in front by the pericardium, and at each side by the pleura. It contains the aorta; the greater and lesser azygos vein, and superior intercostal veins; the thoracic duct; cesophagus and pneumogastric nerves ; and the great splanchnic nerves. ABDOMEN. The abdomen is the inferior cavity of the trunk of the body; it is bounded in front and at the sides by the lower ribs and abdominal muscles; behind, by the vertebral column and abdominal muscles ; above, by the diaphragm ; and below, by the pelvis; and contains, the alimentary canal, the organs subservient to digestion—viz., the liver, pancreas, and spleen; and the organs of excretion, the kidneys, with the supra-renal capsules. Regions.—For convenience of description of the viscera, and of reference to the morbid affections of this cavity, the abdomen is divided into certain districts or regions. Thus, if two transverse lines be carried around the body, the one parallel with the cartilages of the eighth ribs, the other with the highest point of the crests of the ilia, the abdomen will be divided into three zones. Again, if a perpendicular line be drawn, at each side, from the cartilage of the eighth rib to the middle of Poupart’s ligament, the three primary zones will each be subdivided into three compartments or regions, middle and two lateral. The middle region of the upper zone being immediately over the small end of the stomach, is called epigastric (eVt yaargp, over the stomach), The two lateral regions being under the cartilages of the ribs, are called hypochondriac {vno \6v8poi, under the cartilages). The middle region of the middle zone is the umbilical; the two lateral, the lumbar. The middle region of the inferior zone is the hypogastric (vno yaargp, below the stomach); and the two lateral, the iliac. In addition to these divisions, we employ the term inguinal region, in reference to the vicinity of Poupart’s ligament. Position of the Viscera.—In the upper zone will be seen the REGIONS OF THE ABDOMEN. 623 liver, extending across from the right to the left side; the stomach and spleen on the left, and the pancreas and duodenum behind. In the middle zone is the transverse portion of the colon, with the upper part of the ascending and descending colon, omentum, small Fig. 327.* intestines, mesentery, and, behind, the kidneys and supra-renal capsules. In the inferior zone is the lower part of the omentum and small intestines, the csecum, ascending colon, descending colon with the sigmoid flexure, and ureters. The smooth and polished surface, which the viscera and parietes of the abdomen present, is due to the peritoneum. * Viscera of the abdomen in situ. 1, 1. Flaps of the abdominal parietes turned aside. 2. Liver, its left lobe. 3. Eight lobe. 4, Fundus of the gall* bladder. 5. Round ligament of the liver, issuing from the cleft of the longi- tudinal fissure, and passing along the parietes of the abdomen to the umbilicus. 6. Part of the broad ligament of the liver. 7. Stomach. 8. Its pyloric end. 9. Commencement of the duodenum. a. Lower extremity of spleen. 6, b. Greater omentum, c, c. Small intestines, d. Csecum. e. Appendix cseci. /. Ascending colon, g, g. Transverse colon, h. Descending colon. i. Sigmoid flexure of colon, k. Appendices epiploic® connected with the sig- moid flexure. 1. Three ridges representing the cords of the urachus and hypogastric arteries ascending to the umbilicus, m. Diaphragm, 624 PERITONEUM. The Peritoneum (irepireivtiv, to extend around) is a serous mem- brane, and therefore, a shut sac: a single exception exists in the human subject to this character—viz., in the female, where the peritoneum is perforated by the open extremities of the Fallopian tubes, and is continuous with their mucous lining. The simplest idea that can be given of a serous membrane, which will apply equally to all, is, that it invests the viscus or viscera, and is then reflected on the parietes of the containing cavity. If the cavity contain only a single viscus, the consideration of the serous membrane is ex- tremely simple. But in the abdomen, where there are a number of viscera, the serous membrane passes from one to the other until it has in- vested the whole, before it is reflected on the pa- rietes. Hence its re- flexions are a little more complicated. In tracing the re- flexions of the perito- neum, in the middle line, we commence with the diaphragm, which is lined by two layers, one from the parietes Fig. 328.* * Reflexions of the peritoneum. D. Diaphragm. L. Liver. s. Stomach c. Transverse colon. D. Transverse duodenum, p. Pancreas. I. Small intestines. r. Rectum. B. Urinary bladder. 1. Anterior layer of peritoneum, lining the under surface of the diaphragm. 2. Posterior layer. 3. Coronary ligament, formed by the passage of these two layers to the posterior border of the liver. 4. Lesser omentum; the two layers passing from the under surface of the liver to the lesser curve of the stomach. 5. The two layers meeting at the greater curve, then passing downwards and returning upon themselves, forming (6) the greater omentum. 7. Transverse meso-colon. 8. Posterior layer traced upwards in front of d, transverse duodenum, and p. pancreas, to become continuous with the posterior layer (2). 9. Foramen of Winslow: the dotted line bounding this foramen inferiorly marks the course of the hepatic PEBITONEUM. 625 in front, anterior, and one from the parietes behind, posterior. These two layers of the same membrane, at the posterior part of the diaphragm, descend to the upper surface of the liver, forming the coronary and lateral ligaments of the liver. They then surround the liver, one going in front, the other behind that viscus, and meeting at its under surface, pass to the stomach, forming the lesser omentum. They then, in the same manner, sur- round the stomach, and meeting at its lower border, descend for some distance in front of the intestines, and return to the trans- verse colon, forming the great omentum; they then surround the transverse colon, and pass directly backwards to the vertebral column, forming the transverse meso-colon. Here the two layers separate; the posterior ascends in front of the pancreas and aorta, and returns to the posterior part of the diaphragm, where it be- comes the posterior layer with which we commenced. The anterior descends, invests all the small intestines, and returning to the ver- tebral column, forms the mesentery. It then descends into the pelvis in front of the rectum, which it holds in its place by means of a fold called meso-rectum, forms a pouch, the recto-vesical fold, between the rectum and the bladder, ascends upon the posterior surface of the bladder, forming its false ligaments, and returns upon the anterior parietes of the abdomen to the diaphragm, whence we first traced it. In the female, after descending into the pelvis in front of the rectum, it is reflected upon the posterior surface of the vagina and uterus. It then descends on the anterior surface of the uterus, and forms at either side the broad ligaments of that organ. From the uterus it ascends upon the posterior surface of the bladder, and an- terior parietes of the abdomen, and is continued, as in the male, to the diaphragm. In this way the continuity of the peritoneum, as a whole, is dis- tinctly shown, and it matters not where the examination commence or where it terminate, still the same continuity of surface will be discernible throughout. If we trace it from side to side of the abdomen, we may commence at the umbilicus ; we then follow it outwards, lining the inner side of the parietes to the ascending colon; it surrounds that intestine; it then surrounds the small intestine, and, returning on itself, forms the mesentery. It then invests the descending colon, and reaches the parietes on the opposite side of the abdomen, whence it may be traced to the exact point from which we started. The viscera, which are thus shown to be invested by the peri- toneum in its course from above downwards, are the— artery forwards, to enter between the layers of the lesser omentum. 10. Me- sentery encircling the small intestine. 11. Becto-vesical fold, formed by the descending anterior layer. 12. Anterior layer traced upwards on the inner surface of the abdominal parietes to the layer (1), with which the examination commenced. 626 PERITONEUM. Liver, Stomach, Transverse colon, Small intestines, Pelvic viscera. The folds formed between these and between the diaphragm and the liver, are— (Diaphragm.) Broad, coronary, and lateral ligaments. (Liver.) Lesser omentum. (Stomach.) Greater omentum. (Transverse colon.) Transverse meso-colon. Mesentery, Meso-rectum, Recto-vesical fold, False ligaments of the bladder. And in the female, the— Broad ligaments of the uterus. The ligaments of the liver will be described with that organ. The Lesser omentum (gastro-hepatic) is the duplicature which passes between the liver and the upper border of the stomach. It is extremely thin, excepting at its right border, where it is free, and contains between its layers the— Hepatic artery, Ductus communis choledochus, Portal vein, Lymphatics, These structures are enclosed in a loose areolar tissue, called Glisson's capsule. The relative position of the three vessels is, the artery to the left, the duct to the right, the vein between and behind. If the finger be introduced behind this right border of the lesser omentum, it will be situated in an opening called the foramen of Winslow. In front of the finger will lie the right border of the lesser omentum ; behind it, the diaphragm, covered by the ascend- ing or posterior layer of the peritoneum ; below, the hepatic artery, curving forward from the coeliac axis; and above, the lobus Spigelii. These, therefore, are the boundaries of the foramen of Winslow, which is nothing more than a constriction of the general cavity of the peritoneum at this point, arising out of the necessity for the Hepatic plexus of nerves. PERITONEUM. 627 hepatic and gastric arteries to pass forwards from the coeliac axis to reach their respective viscera. If air be blown through the foramen, of Winslow, it will descend behind the lesser omentum and stomach to the space between the descending and ascending pair of layers, forming the great omen- tum. This is sometimes called the lesser cavity of the peritoneum, and that external to the foramen the greater cavity; in which case the foramen is considered as the means of communication between the two. It may be objected to this division that it tends to lead the inexperienced to believe that there are two cavities, while, in reality, there is but one, the foramen of Winslow being merely a constriction of that one, to facilitate the communication between the nutrient arteries and the viscera of the upper part of the abdomen. The Great omentum (gastro-colic) consists of four layers of peri- toneum, the two which descend from the stomach, and the same two, returning upon themselves to the transverse colon. A quantity of adipose substance is deposited around the vessels which ramify through its structure. It would appear to perform a double function in the economy: namely, protecting the intestines from cold; and, facilitating the movement of the intestines on each other during their vermicular action. The Transverse meso-colon (pea-os, middle, being attached to the middle of the cylinder of the intestine) is the medium of con- nexion between the transverse colon and the posterior wall of the abdomen. It affords to the nutrient arteries a passage to reach the intestine, and encloses between its layers, at the posterior part, the transverse portion of the duodenum. It also forms a transverse septum across the abdominal cavity. The Mesentery (peaov evrepov, connected to the middle of the cylinder of the small intestine) is the medium of connexion between the small intestines and the posterior wall of the abdomen. It is oblique in direction, being attached to the posterior wall, from the left side of the second lumbar vertebra to the right iliac fossa; retains the small intestines in their place, and gives passage to the mesenteric arteries, veins, nerves, and lymphatics. The Meso-rectum, in like manner, retains the rectum in con- nexion with the front of the sacrum. Besides this, there are some minor folds in the pelvis, as the recto-vesical fold, the false ligaments of the bladder, and the broad ligaments of the uterus. The Appendices epiploicce are small irregular pouches of the peritoneum, filled with fat, and attached like fringes to the large intestine. Three other duplicatures of the peritoneum are situated in the sides of the abdomen; they are the gastro-phrenic ligament, the gastro-splenic omentum, the ascending and descending meso-colon. The gastro-phrenic ligament is a small duplicature of the peri- toneum, which descends from the diaphragm to the extremity of the oesophagus, and lesser curve of the stomach. The gastro-splenic 628 ALIMENTARY CANAL. omentum (ligamentum gastro-lienale) is the duplicature which con- nects the spleen to the stomach. The ascending meso-colon is the fold which connects the upper part of the ascending colon with the posterior wall of the abdomen; and the descending meso- colon, that which retains the sigmoid flexure in connexion with the abdominal wall. ALIMENTARY CANAL. The Alimentary canal is a musculo-membranous tube, extending from the mouth to the anus. It is variously named in the different parts of its course; and is divided into, the Mouth, Pharynx, (Esophagus, Stomach, Duodenum, Jejunum, Ileum, Caecum, Colon, , Rectum. Small intestine Large intestine The Mouth (cavitas oris) is the irregular cavity which contains the organ of taste and the principal instruments of mastication. It is bounded, in front, by the lips; on either side, by the internal surface of the cheeks; above, by the hard palate and teeth of the upper jaw; below, by the tongue, the mucous membrane stretched between the arch of the lower jaw and the under surface of the tongue, and by the teeth of the inferior maxilla; and, behind, by the soft palate and fauces. The space between the teeth and fleshy walls of the face is the vestihulum oris. The Lips (labium superius et inferius) are two fleshy folds formed externally by common integument and internally by mucous mem- brane, and containing between these two layers, muscles, a quantity of fat, and numerous small labial glands. They are attached to the surface of the upper and lower jaw, and each lip is connected to the gum in the middle line by a fold of mucous membrane, the frcenum labii superior is and frcenum labii infer ioris, the latter being very small. The Cheeks (buccm) are continuous with the lips, and form the sides of the face; they are composed of integument, a large quantity of fat, muscles, mucous membrane, and buccal glands. The mucous membrane lining the cheeks is reflected above and below on the sides of the jaws, and is attached posteriorly to the anterior margin of the ramus of the lower jaw. At about its middle, opposite the second molar tooth of the upper jaw, is a papilla, on which may be observed a small opening, the aperture of the duct of the parotid gland. The Hard palate (palatum durum, seu, osteum) is a deuse struc- ture, composed of mucous membrane, palatine glands, areolar tissue, vessels, and nerves, and firmly connected to the palate pro- cesses of the superior maxillary and palate bones. It is bounded in GUMS—SOFT PALATE. 629 front and at each side by the alveolar processes and gums, and is continuous behind with the soft palate. Along the middle line it is marked by an elevated raphe, and presents at each side of the raphe a number of transverse ridges and grooves. Near its anterior extremity, and immediately behind the middle incisor teeth, is a papilla which corresponds with the termination of the anterior palatine canal, and receives the naso-palatine nerves. The Gums (gingivae) are composed of a thick and dense mucous membrane, which is closely adherent to the periosteum of the alveolar processes, and embraces the necks of the teeth. They are remarkable for their hardness and insensibility; and for their close contact, without adhesion, to the surface of the tooth. From the neck of the tooth they are reflected into the alveolus, and become continuous with the periosteal (peridental) membrane of that cavity. The Tongue has been already described as an organ of sense; it is invested by mucous membrane, which is reflected from its under part upon the inner surface of the lower jaw, and constitutes with the muscles beneath, the floor of the mouth. On the under surface of the tongue, near its anterior part, the mucous membrane forms a considerable fold, which is called the frcenum linguae; and on each side of the frmnum is a large papilla, caruncula sublingualis, the termination of the duct (Wharton’s duct) of the submaxillary gland. Running back from this papilla is a ridge, occasioned by the prominence of the sublingual gland; and opening along the summit of this ridge, a number of small openings, the apertures of the excretory ducts of the gland. Posteriorly the tongue is con- nected with the os hyoides by muscle, and to the epiglottis by three folds of mucous membrane, thefrcena epiglottidis. The Soft palate (palatum molle; velum pendulum palati) is a fold of mucous membrane situated at the posterior part of the mouth. It is continuous, superiorly, with the hard palate, and is composed of mucous membrane, palatine glands, and muscles. Hanging from the middle of its inferior border is a small rounded process, the uvula; and passing outwards from the uvula at each side are two curved folds of the mucous jnembrane, the arches or pillars of the palate. The anterior pillar (arcus palatinus inferior; glosso-palatinus) is continued downwards to the side of the base of the tongue, and is formed by the prominence of the palato-glossus muscle. The posterior pillar (arcus palatinus superior; pharyngo- palatinus) is prolonged downwards and backwards into the pharynx, being formed by the convexity of the palato-pharyngeus muscle. These two pillars, closely united above, are separated below by a triangular interval or niche, in which the tonsil is lodged. The space included between the soft palate and the root of the tongue is the isthmus of the fauces. It is bounded above by the soft palate; on each side by the pillars of the soft palate and tonsil; and below by the root of the tongue. It is the opening between the mouth and pharynx. 630 MUCOUS GLANDS OF THE MOUTH. The Tonsils (amygdalae) are two glandular organs, about half an inch in length, shaped like almonds, and situated between the anterior and posterior pillar of the soft palate, at each side of the fauces. They are composed of an assemblage of mucous follicles, which open on the surface by twelve or fifteen apertures. Exter- nally, they are invested by the pharyngeal fascia, which separates them from the superior constrictor muscle and internal carotid artery, and prevents an abscess from opening in that direction. In relation to surrounding parts, each gland corresponds with the angle of the lower jaw. The Mucous glands of the mouth (orales) are racemose or lobu- lated glands; they are yellowish or whitish in colour, rounded or multangular in form, and situated in the submucous areolar tissue. The labial glands vary in size from half a line to one line and a half in diameter, and form an almost continuous layer around the mouth. The buccal glands are numerous, but smaller than the labial; a few of larger size being located near the aperture of Stenon’s duct. The molar glands are placed between the masseter and buccinator, and pierce the latter with their ducts opposite the molar teeth. The 'palatine glands are situated in the posterior half of the hard palate and in the soft palate; in the latter forming a layer several lines in breadth. They are also numerous but small on the posterior part of the soft palate. The lingual glands form a thick stratum in the sub-mucous tissue beneath the mucous follicles .at the root of the tongue; this layer extends completely across the tongue, and their ducts, several lines in length, open by infundi- buliform expansions, some into the mucous folli- cles, others into the foramen caecum, others into the fossae of the papillae circumvallatae, and others between the papillae. Mucous glands of the same kind are also dispersed on other parts of the tongue, but are smaller and few in number: a small group is found between the vertical folds on the sides of the tongue and a con- siderable group on its under surface near the tip and on either side of the fraenum linguae. In minute structure the glandular organs of the mucous membrane of the mouth are divisible into follicles or follicular glands ; and racemose or lobulated glands. The follicular glands are simple, as those of the root of the tongue; or compound, like the tonsil, which is merely an aggregation of simple follicular glands. The racemose or lobulated glands may be of the simples t construction, consisting of from four to Fig. 329.* * Follicular gland from the root of the tongue; after Kolliker. 1. Epithe- lium. 2. Papillae of the mucous membrane. 3. Cavity of the follicle. 4. In- vesting coat of the gland, composed of areolar tissue. 5. Fibro-vascular matrix, forming the parenchyma of the gland; and containing, 6, 6, the closed capsules. STRUCTURE OF MUCOUS GLANDS. 631 eight lobules, which open directly into an excretory duct like the smaller oral glands, or of an aggregation of smaller and larger lobules, forming primary and secondary lobes, and finally a gland of considerable size, as the salivary. The follicular gland, in external appearance, is a mere crypt or pouch of mucous membrane, but the wall of the pouch is thickened, and presents two layers, superficial and deep, with an inter- mediate fibro-vascular matrix, in which are lodged a number of closed vesicles or capsules. These capsules are round or oblong, and whitish, from to of an inch in diameter, and composed of an external coat of homo- geneous areolar tissue, containing a greyish- white pulpy substance, consisting of small nucleated cells (3 0 of an inch), free nuclei, and a small quantity of alkaline fluid. The follicular glands of the root of the tongue form a continuous layer, stretching from the papillae circumvallatas backwards to the epi- glottis, and from the tonsil on one side to that on the other side of the fauces. They are lenticular and globular in figure, from half a line to two lines in diameter, and placed superficially so as to form prominences on the surface of the membrane. Each gland is furnished with a central aperture which opens into its cavity; the cavity being lined with mucous membrane and epithelium, and containing a greyish mucus. The deep layer of the follicular gland is firmly adherent to the submucous tissue, and overlies the proper mucous glands, which form a stratum be- neath the follicular glands. The tonsil is a compound follicular gland, consisting of an aggregation of fifteen or twenty simple folli- cular glands, intimately united and held to- gether so as to constitute a single organ. They are enclosed in a thick investing capsule of areolar tissue, with a certain proportion of elastic tissue. The capillary vessels of the follicular glands form a fine and close network around their bases. The racemose, or lobulated gland, is composed of several lobes, the lobes being made up of a branch or branches of an excretory Fig. 330.* Fig. 331 f * One lobe of a racemose mucous gland from the floor of the mouth; after Kolliker. 1. Sheath of areolar tissue. 2. Excretory duct. 3. Glandular vesicles or acini. t Plan of the structure of a racemose gland; after Kolliker. 1. An excre- tory tube unravelled, to show the composition of the lobule, of diverticula, and caecal terminations of the duct. 2. Appearance of the glandular vesicles, when grouped together in their normal state. 3. The main excretory duct. 632 SALIVARY GLANDS. duct, and vesicular dilatations. The excretory ducts terminate in a common excretory duct, which opens on the surface of the mucous membrane, and the glandular vesicles or acini are diverticula and ccecal terminations of the smaller convoluted branches of the ex- cretory ducts. The glandular vesicles are globular or oval or pyri- form in shape, about of an inch in diameter, and composed of a proper structureless coat, or membrana propria, lined by an epi- thelial layer of spheroidal nucleolo-nucleated cells, somewhat less than °f an i,ich in breadth. The nucleated cells contain white or coloured granules, which give the proper colour to the glands. The excretory ducts are composed of areolar and elastic tissue, and lined by a layer of columnar epithelium. The smallest racemose gland consists of several lobules, and the lobules are held together by areolar tissue, and by an external in- vesting coat of the same tissue intermingled with elastic fibres. The capillary vessels of the glands form a close network around the glandular vesicles; and the secretion of the glands is a clear yel- lowish mucus, with an occasional and accidental admixture of gra- nules, nuclei, and remains of cells. SALIVARY GLANDS. Communicating with the mouth are the excretory ducts of three pairs of salivary glands {glandules salivales), the parotid, sub- maxillary, and sublingual. The parotid gland {napa, near, ovs, £>tos, the ear), the largest of the three, is situated immediately in front of the external ear, and extends superficially for a short distance over the masseter muscle, and deeply behind the ramus of the lower jaw. It reaches inferiorly to below the level of the angle of the jaw, and posteriorly to the mastoid process, slightly overlapping the insertion of the sterno- mastoid muscle. Embedded in its substance are, the external carotid artery, temporal vein, and facial nerve; emerging from its anterior border, the transverse facial artery and branches of the facial nerve, and above, the temporal artery and auriculo-temporal nerve. The duct of the parotid gland (Stenon’s duct), about two inches in length, and about the diameter of a crow’s-quill, issues from the anterior part of the gland, just below the zygoma, and crosses the masseter muscle; it then curves inwards over the anterior border of the muscle, and pierces the buccinator opposite the second molar tooth of the upper jaw; its opening in the mouth being indicated by a prominent papilla. The duct is dense in structure, and its walls of considerable thickness in proportion to the area of the tube, which is remarkably small. A small glandular appendage, the soda parotidis, is con- nected with the upper part of the duct on the masseter muscle; and opens into it by one or several small ducts. The submaxillary gland, rounded in its form, is situated in the posterior part of the submaxillary triangle of the neck. It rests on SALIVARY GLANDS. 633 the hyo-glossus, stylo-glossus, and mylo-hyoideus muscle, and is covered in by the body of the lower jaw and the deep cervical fascia. It is separated from the parotid gland by the stylo-maxillary liga- ment, and from the sublingual gland by the mylo-hyoideus muscle. Embedded among its lobules are the facial artery and submaxillary ganglion. Its excretory duct, Wharton’s duct, about two inches in length, issues from the middle of the gland, and passes between the mylo- hyoideus and hyo-glossus to the fraenum linguae, by the side of which it terminates at the apex of a papilla, caruncula sublingualis. A process of the gland is prolonged with the duct for a short distance behind the mylo-hyoideus. The subungual is a long and flattened gland, situated beneath the mucous membrane of the floor of the mouth, at each side of the fraenum linguae. It is in relation at the fraenum with its fellow of the opposite side, and in the rest of its course lies between the lower jaw and genio-hyo-glossus, being bounded below by the mylo- hyoideus. It is in relation also with the duct of the submaxillary gland and the hypoglossal nerve. Its secretion is poured into the mouth by from seven to twenty short ducts, ductus Biviniani, which open on the ridge made by the gland in the floor of the mouth; the larger openings being situated by the side of the fraenum linguae. One of the ducts longer than the rest, and opening close to Wharton’s duct, has been named ductus Bartholini. Structure.—The salivary glands are of the conglomerate kind, consisting of lobes, which are made up of polyhedral lobules ; and these of smaller lobules ; in minute structure they correspond with the racemose mucous glands. The smallest lobule is composed of glandular vesicles, acini, which are minute caecal pouches, formed by the convolution and dilatation of the extreme ramifications of the ducts. These minute ducts unite to form lobular ducts, and the lobular ducts constitute by their union a single excretory duct. The glandular vesicles are connected by areolar tissue, so as to form a minute lobule; and the lobules and larger lobes are held together by a more condensed, but lax areolar tissue. The submaxillary and sublingual glands are looser in structure and their lobules larger than those of the parotid gland. The glandular vesicles, about ~T) of an inch in diameter, consist of a proper external coat or membrana propria, lined by a single layer of spheroidal epithelial cells. The cells are nucleolo-nucleated and contain granules, some of which are fatty and others pig- mentary. The excretory ducts are thick and dense, composed of areolar and elastic tissue, and lined by a layer of columnar epithe- lium ; and Wharton’s duct is additionally provided with a longi- tudinal layer of smooth muscular fibre. The secretion of the salivary glands is a clear fluid, sometimes containing a small quan- tity of mucus and the detrita of epithelial cells. 634 PHARYNX. Vessels and Nerves.—The parotid gland is abundantly supplied with arteries by the external carotid; the submaxillary by the facial and lingual; and the sublingual by the sublingual and sub- mental branches of the lingual artery. The capillaries form net- works around and in contact with the glandular vesicles. The Nerves of the parotid gland are derived from the auriculo- temporal branch of the inferior maxillary, from the auricularis magnus, and from the nervi molles accompanying the external carotid artery. The submaxillary gland is supplied by the branches of the submaxillary ganglion, sympathetic, and filaments from the mylo-hyoidean nerve; and the sublingual by filaments from the submaxillary ganglion and gustatory nerve. The pharynx (v, skin or leather). One of the membranes of the embryo. Choroid (Gk. x°Pl0V, the chorion, and tlSog, like.) Term applied to the middle coat of the eye from its vascularity. Chylo-poietic (Gk. yiAoc, juice, that is to say, chyle, and noikto, I make). Chyle-producing. Clavicle (Lat. clavis, a key). The collar bone. Cleido—as in cleido-mastoid (Gk. kXuq, a key). Belonging to the clavicle. Clinoid (Gk. ka bed, and ddog, like). The processes which border the sella turcica are so called because they bear some resemblance to the posts of a bedstead. Clitoris (probably from Gk. kXuvw, I shut up). The homologue in the female of the penis of the male. Coccyx (Gk. kokkv$, a cuckoo). The last bone of the vertebral column in man. It is supposed to resemble a cuckoo’s beak. Cochlea (Gk. KoyXof, a shell-fish). A spiral cavity in the internal ear. Cceliac (Gk. Ko'iXia, the belly). Belonging to the belly. Colon (Gk. kujXov, the colon). The large intestine. Concha (Gk. kovxg, a shell). The central parts of the external ear. Condyle (Gk. kovSvXoq, a knuckle). Term applied to certain articular osseous processes. Conjunctiva (Lat. con, together, and jungo, I join). The mucous membrane of the front of the eye, which connects the lids with the eyeball. Conoid (Gk. kwvoq, a cone, and dSoc, like). A cone-shaped portion of the coraco-clavicular ligament is thus called. Coracoid (Gk. Kopa%, a raven, and dcog, like). A process of the scapula supposed to resemble a raven’s beak. Cornea (Lat. corneus, horny). The anterior, transparent part of the eye. Cornua (Lat. cornu, a horn). Processes which project like horns. Coronary (Lat. corona, a crown). Forming a circlet like a crown. Coronoid (Gk. Kopiovr/, a crow, and dSog, like). Term applied to curved processes of bone, supposed to resemble a crow’s beak. Costal (Lat. costa, a rib). Belonging to the ribs. Cotyloid (Gk. kotvXt), a cup, ancl dSoc, like). The cup-shaped cavity which receives the head of the femur. Corpus callosum (Lat. corpus, a body, and callosum from callus, hard). A commissure of the brain. Cranium (Gk. Kpaviov, the skull). The skull. Cremaster (Gk. Kptpdw, I suspend). The suspensory muscle of the testicle. Cricoid (Gk. icp'ucog, a ring, and dSog, like). One of the cartilages of the larynx. 718 GLOSSARY OF ANATOMICAL TERMS. Crista (Lat. crista, a crest). A crest or ridge of bone. Crus (Lat. crus, a leg). A process or peduncle of the brain. Crural— crureus. Belonging to the leg. Cuboid (Gk. Kvflog, a cube, and tlSog, like). A cube-shaped bone. Cuneiform (Lat. cuneus, a wedge, and forma, shape). Wedge-shaped. Cystic (Gk. kuotiq, a bag). Belonging to the urinary or gall-bladder. Dartos (Gk. SaproQ, flayed). The subcutaneous layer of the scrotum. Deltoid (Gk. A, and tlSoc, like). The muscle so uamed is shaped like the Greek letter D. Dentine (Lat. dens, a tooth). The structure which forms the bulk of a tooth. Derma (Gk. Sipfia, the skin). The true skin. Diaphragm (Gk. Siatppaypa, a partition wall). The muscle which separates the cavity of the abdomen from that of the thorax. Diarthrosis (Gk. Sic, twice, and dpOpov, a joint). A joint with a moderate degree of motion. Digastric (Gk. Sic, twice, and yaargp, belly). A two-bellied muscle. Diploe (Gk. SinXovc, double). The osseous tissue between the two tables of the skull. Dissect (Lat. disseco, I cut to pieces). Emulgent (Lat. emulgeo, I milk, or drain out). Term applied to the renal arteries. Enamel (Lat. enamel). The hard substance covering the crown of a Enarthrosis (Gk. tv, in, and dpOpov, a joint). A ball and socket joint, in which the rounded head of one bone is received mto the cup-shaped socket of another. Encephalon (Gk. tv, in, and KttpaXg, the head). The brain. Endocardium (Gk. ivSov, within, and napSia, the heart). The lining membrane of the heart. • Endosteum (Gk. ivSov, within, and oqtsov, a bone). Ihe membrane which lines the interior of long bones. Ensiform (Lat. ensis, a sword, and forma, shape). The terminal piece of the sternum. . , Ephippium (Gk. irpinmov, a saddle). The ridge forming the back of the sella turcica is called dorsum ephippii. _ Epidermis (Gk. ini, upon, and Sipua, the skin). The superficial layer of the skin. Epididymis (Gk. ini, upon, and SiSvpbc, the testicle). A small lobule connected with the testicle. Epigastric (Gk. ini, upon, yaarrip, a belly). Applied to the arteries of the abdominal wall, and to the upper region of the abdomen. Epiglottis (Gk. ini, upon, and yXorrig, the glottis). Ihe cartilage which closes the glottis in deglutition. Epiphysis (Gk. ini, upon, and tpvio, I grow). The portions of long bones which grow by centres distinct from that of the shaft. Epiploic (Gk. ini, upon, and nXtw, I sail). Belonging to the omentum, this being called epiploon. Epithelium (Gk. ini, upon, and OaXXw, I grow). So called because it generally forms the superficial layers of tissues. Ethmoid (Gk. gOpbc, a sieve, and elSoc, like). A bone so called from the perforations in its horizontal plate. GLOSSARY OF ANATOMICAL TERMS. 719 Falciform (Lat. falx, a scythe or sickle, and forma, shape). Having a crescentic form and sharp edge, like a sickle. Falx. Fascia (Lat. fascia, a bundle). A sheet composed of bundles of fibrous tissue. Femur (Lat. femur). The thigh-bone. Fenestra (Lat. fenestra, a window). Term applied to the openings between the internal and middle ear. Fibula (Lat. fibula, a buckle). The lesser bone of the leg. Fimbria: (Lat. fimbmce, fringes). The fringes of the Fallopian tube. Flocculus (Lat. diminutive of ftoccus, a lock of wool). The part of the cerebellum on which the pneumogastric nerve lies. Follicle (Lat. dim. of follis, a bag). Small cavities with open mouths. Fontanelles (Lat. fons, a fountain). The spaces between the cranial bones in the foetus. Foramen (Lat. foro, I pierce). A hole. Fornix (Lat. fornix, an arch or vault). An arched commissure of the brain. Fourchette (Fr. fourchetle, a fork). The thin fold which connects the labia majora posteriorly. Fovea (Lat. fovea, a pit). A shallow depression. Frana (Lat. frcenum, a bridle). Bands of mucous membrane. Fundus (Lat.). The bottom. Fungiform (Lat. fungus, and forma, shape). Shaped like a mushroom. Galactophorus (Gr. yaXa, milk, and tpepw, I carry). Term applied to the ducts of the mammary gland. Ganglion (Gk. yayyXiov, a tumour or enlargement). A nerve centre. Gastric (Gk. yaarrjp, the stomach). Belonging to the stomach. Gastrocnemius (Gk. yaarrip, the belly, and tan'igr/, the leg). The muscle which forms the bulk of the bellied part of the leg. Gemellus (Lat. dim. of geminus, double). Twin muscles. Genial (Gk. ykvuov, the chin). Belonging to the chin. Geniculate (Lat. geniculum, a little knee). A ganglionic swelling on a bend of the facial nerve is called geniculate. Genio-hyo-glossus (Gk. ykvtiov, the chin; yXxaaa, the tongue). A muscle thus called is attached to the chin, hyoid bone, and tongue. Genio-hyoid. A muscle attached to the chin and hyoid bone. Ginglymus (Gk. yivyXvpoQ, a hinge). A hinge-joint. Glans (Lat. plans, an acorn). The extremity of the penis or clitoris. Glenoid (Gk. yXgvg, a socket, and rfSog, like). The articular cavities of the temporal bone and scapula are so called. Globus (Lat. globus, a ball). Term applied to parts of the epididymis. Glomerulus (Lat. glomus, a ball of thread). Like a ball of thread. The term is applied to the vascular tufts of the kidney. Glosso as in glosso-pharyngeal, hypoglossal, &c. (Gk. yXwaaa, the tongue). Belonging to the tongue. Glottis (Gk. y\mtt’iq). The mouth of the wind-pipe. Glutaius (Gk. yXovroQ, the buttock). The name given to the chief muscles of the buttock. Gomphosis (Gk. yoptpoQ, a nail). A nail-like articulation, as that of the teeth with the jaws. Gracilis (Lat. gracilis, slender). A long, thin muscle of the thigh. 720 GLOSSARY OF ANATOMICAL TERMS. Gubernaculum (Lat. gubemo, I steer or guide). The term is applied to the cord which guides the testicle in its descent. Gustatory (Lat. gusto, I taste). Connected with taste. Gyrus (Gk. yvpoQ, a ring). A convolution. Haemal (Gk. alga, blood). Containing the blood vessels. JLemorrhoidal (Gk. alga, blood, and pkw, I flow). The term is ap- plied to those vessels which bleed in piles. Hamular (Lat. hamus, a hook). Hook-shaped. Harmonia (Gk. apelv, to adapt). An articulation in which the bones are joined together without serration of the edges, or the interven- tion of cartilage. Helico-trema (Gk. tAi£, a spiral, and rprjga, a hole). The hole between the two seals of the cochlea. Helix. Helicine (Gk. t\i%, a spiral). Having a spiral form. Hepatic (Gk. rgizap, the liver). Relating to the liver. Hiatus (Lat. Mo, I open). An irregular opening. Hippocampus (Gk. 'i-mroKagirog, a sea-horse). Convolutions of the brain supposed to resemble a sea-horse, are so called. Hyaline (Gk. va\og, glass). Transparent and apparently structureless. Hyoid (Gk. v, the letter upsilon, and tlSog like). The hyoid bone is so named from its shape. Hypogastric (Gk. vird, under, and yaargp, the stomach). Beneath the stomach. Hypoglossal (Gk. vtto, under, and yAwtro-a, the tongue). Beneath the tongue. Hypothenar (Gk. vtto, under, and Gsvap, the palm). Ileum (Gk. tlXtio, I roll). A part of the small intestine. Iliac (Lat. ilia, the flanks). Belonging to the ilia or flanks. Inguinal (Lat. inguen, the groin). Belonging to the groin. Iris (Gk. ipig, the rainbow). The iris of the eye is called so from its bright colours. Ischium (Gk. <’ov, an animal). The generative cells of the male. Spermatic. Sphenoid (Gk. a, I grow). “An articulation in which there is no manifest motion.”—Hoblyn. Synchondrosis (Gk. avr, together, and xdvcpog, cartilage). An articula- tion partly cartilaginous and partly fibrous. T.-enia (Gk. raivia, a band). The term is applied to certain bands of nerve matter in the brain. Tarsus (Gk. rapaog, the upper surface of the foot). The bones of the posterior part of the foot. Temporal (Lat. tempora, the temples; from tempus, time). Belonging to the temples. Tendon (Gk. rtivot, I stretch). The fibrous extremity of a muscle, by which it is attached to bone. Tentorium (Lat. tentorium, a tent). A process of the dura mater. Thalamus (Gk. QaXapog, a bed). The part of the brain against which the optic nerves rest at their commencement, is called thalamus opticus. Theca (Gk. 6 pry, a case). The sheaths of the tendons of the fingers are called theca. Thenar (Gk. 6trap, the palm of the hand). The mass of muscles forming the ball of the thumb is called the thenar prominence. Thorax (Gk. OmpaZ, a breastplate). The chest. Thymus (Lat. thymus, thyme). A gland found in the upper part of the chest of young animals. GLOSSARY OF ANATOMICAL TERMS. 725 Thyroid (Gk. Qvpeog, a shield, and elcog, like). Shield-shaped. Tibia (Lat. tibia, a pipe or flute). The large bone of the leg. To ecu bar Herophili (Lat. torcular, a wine press). The meeting of the sinuses of the brain on the occipital bone. Literally it means the “ wine-press of Herophilus.” Trachea (Gk. rpaxvg, rough). The wind-pipe. It was formerly called arteria trachea, the “ rough air-passage;” rough from its cartilages. Trachelo- (Gk. rpdxyXog, the neck). Connected with the neck. Tragus (Gk. rpayog, a goat). A process of the external ear. Trigone (Gk. rpelg, three, and yiovia, an angle). A triangle at the base of the bladder. Trochanter (Gk. rpoxaw, I roll or turn). Two prominences of the femur are so named. Trochlea (Gk. rpoxog, a wheel). A kind of pulley. Turbinated (Lat. turbo, a whirl). The term is applied to certain coiled bones in the nasal cavities. Tympanic (Lat. tympanum, the drum of the ear). Belonging to the cavity of the middle ear, or to the drum. Ulna (Gk. diXevrj, the elbow). One of the bones of the forearm. Umbilicus (Lat. umbilicus). The navel. Uncinate (Lat. uncus, a hook). Hooked. Ungual (Lat. unguis, a nail). Belonging to the nail. Urachus (Gk. ovpov, urine, and tyoj, I hold). A cord which forms one of the ligaments of the bladder. It is the remains of the umbilical vesicle of the embryo. Ureter (Gk. ovp'su), I pass water). The tube which conveys the urine from the kidney to the bladder. Urethra (Gk. ovpov, urine). The tube which conveys the urine from the bladder. Uvula (Lat. diminutive of uva, a grape). The small tongue which depends from the centre of the soft palate. Vagina (Lat. vagina, a sheath). The term is generally restricted to the vulvo-uterine canal. Vertebras (Lat. vertere, to turn). The segments of the spinal column. So called because they turn on each other. Villi (Lat. villus, shaggy hair). Small processes on the mucous mem- brane of the small intestine. Vitreous (Lat. vitrum, glass). The transparent mass which occupies the posterior part of the globe of the eye. Volar (Lat. vola, the palm of the hand). Belonging to the palm. Vomer (Lat. vomer, a ploughshare). The central bone of the nose. Xiphoid (Gk. Zi