jiii ■;;,.•; :",a;',*.: ■.vJ^Kii"' ?\. f I THE DISSECTOR. THE DISSECTOR; OR, PMCTICAL AND SUEGICAL ANATOMY. BY ERASMUS WILSON, AUTHOR OP A "SYSTEM OF HUMAN ANATOMY," ETC. WITH ONE HUNDRED AND FIFTEEN ILLUSTRATIONS. EDITED BY PAUL B. GODDARD, M. D. A NEW AND IMPROVED EDITION. PHILADELPHIA: BLANCHARD AND LEA. 18 51. Entered, according to the Act of Congress, in the year 1843, by LEA * BLANCHARD, in the Clerk's Office of the District Court for the Eastern District of Pennsylvania. King & Baird, Printars. TO JONES QUAIN, M.D., THIS WORK IS INSCRIBED HIS SINCERE AND GRATEFUL FRIEND, THE AUTHOR. PKEFACE TO THE SECOND AMERICAN EDITION. The work of Mr. Wilson, which is here presented in a new guise, was calculated for the English school, where the dis- sector generally commences with the extremities, and when they are finished studies the viscera, if any remains of them can be found. They have probably got into this habit in consequence of the trunks of their subjects being generally much decomposed before they procure them. In the United States, however, subjects are generally fresh, and the muscles and viscera of the abdomen claim the student's first attention; and it was thought that a new arrangement of this most ex- cellent Dissector would prove a valuable aid to the student of practical anatomy. It has, therefore, been carefully modified in such a manner that the student, by following the order of parts as they are laid down, will obtain the utmost advantage which can be derived from a single subject. The reputation which the work has acquired in the United States, has shown the Editor that he was not mistaken in his estimate of its value. In preparing this new edition, there- 8 PREFACE. fore, he has endeavored to supply any deficiencies that the advance of scientific investigation may have created in the work, and trusts that it may be found, as heretofore, a com- plete and reliable guide to the student of Practical Anatomy. A number of new cuts have been added, illustrating the difficult and important anatomy of hernia and the perineum, which are accompanied with full descriptive explanations. Philadelphia, March 1851. CONTENTS. INTRODUCTION. CHAPTER I. General composition of the body Nature of dissection Nature of surgical operation Integument; cuticle—rete mucosum—cutis Superficial fascia Deep fascia .... Muscles. .... Vessels ;—Arteries—Veins . Lymphatics—Nerves—Bones Ligaments;—Joints . CHAPTER II. Muscles of the abdomen. Linea alba—surgery of the . Linea semilunaris—surgery of the External oblique muscle. Poupart's ligament . Gimbernat's ligament External abdominal ring Internal oblique muscle Transverse muscle . Rectus muscle Sheath of the rectus Anatomy of Hernia . Umbilical Hernia Ventral Hernia Inguinal Hernia Transversalis fascia . 10 CONTENTS. Internal abdominal ring Spermatic canal Oblique inguinal Hernia Direct inguinal Hernia Seat of Stricture Congenital Hernia . Encysted Hernia Vessels cf the abdominal parietes Nerves of the abdominal parietes Cavity of the abdomen Regions of the abdomen Position of the viscera Peritoneum . Lesser omentum Foramen of Winslow Great omentum Transverse meso-colon Mesentery . Meso-rectum Appendices epiploicse G astro-splenic omentum Viscera of the Abdomen . Stomach Small intestine Duodenum Jejunum Ileum . Large intestine Ccecum . Colon Rectum Mucous membrane of the alimentary canal Structure of the mucous membrane Epithelium . Papillary layer Villi . Sub-mucous fibrous layer Follicles Solitary Glands Aggregate Glands, Peyer's Duodenal glands, Brunner's Gastric follicles. Muscular coat of the alimentary canal Serous coat of the alimentary canal Vessels of the alimentary canal Nerves of the alimentary'canal Superior mesenteric artery Superior mesenteric vein Lacteals—Mesenteric glands Superior mesenteric plexus Inferior mesenteric artery Coeliac axis . Gastric artery Hepatic artery Splenic artery CONTENTS. 11 Ductus communis choledochus Liver Lobes . Fissures Ligaments Vessels . Vessels and nerves of the Liver Gail-Bladder Kiernan's Researches, upon the the Liver . Lobules Acini of Malpighi Glisson's capsule Portal vein Hepatic duct Hepatic artery . Hepatic veins . Nerves and Lymphatics Summary Physiological deductions Pathological deductions Spleen Pancreas Semilunar ganglia Solar plexus Sympathetic Abdominal Aorta Relations Branches Phrenic arteries Supra-renal arteries Renal arteries Spermatic arteries Lumbar ai'teries Sacra media. Inferior vena cava Relations Branches Right Spermatic vein Renal veins . Kidneys Ureters Diaphragm . Openings Posterior abdominal muscles Lumbar plexus of nerves Branches structure and minute anatomy of 12 CONTENTS. CHAPTER III. head and neck. Muscles of the head—arrangement Dura mater .... Glandulae Pacchioni Falx cerebri .... Tentorium cerebelli .... Falx cerebelli .... Sinuses of the dura mater . , Superior longitudinal sinus Inferior longitudinal sinus Straight sinus Occipital sinus Lateral sinuses Torcular Herophili Cavernous sinuses Inferior petrosal sinus . Circular sinus .... Superior petrosal sinus . . Transverse sinus Arteries of the dura mater . , Nerves of the dura mater . Arachnoid membrane Sub-arachnoidean cellular tissue Sub-arachnoidean fluid Pia mater . . Arteries of the brain Circle of Willis .... Development of the cerebro-spinal axis in animals Development of the cerebro-spinal axis in man Cerebrum . Medullary and corticle substance Centrum ovale majus . Corpus callosum Lateral ventricles Corpus striatum Tenia semicircularis Choroid plexus .... Corpus fimbriatum Middle cornu .... Hippocampus major Fascia dentata .... Fornix .... Velum interpositum Thalami optici .... Third ventricle .... Corpora quadrigemina . Pineal gland .... Fourth ventricle CONTENTS. 13 Valve of Vieussens Calamus scriptorius Lininj membrane of the ventricles Cerebellum Peduncles Base of the Brain . Tuber cinereum and infundibulum Corpora albicantia Crura cerebri . Pons Varolii Medulla Oblongata Corpora pyramidalia Corpora olivaria Corpora restiformia Diverging fibres of the brain Arciform fibres . Converging fibres Commissures Cerebral nerves . Olfactory . Optic Auditory Motor tract Motores oculorum Abducentes Lingual Respiratory nerves of Bell Pathetici Fascial nerve Glosso-pharyngeal nerve Pneumogastric nerve Spinal accessory nerve Trifacial nerve . Muscles of the neck Superficial fascia Platysma myoides . Deep cervical fascia . Sterno-cleido-mastoid muscle Muscles—groups Parotid gland Fascial nerve Branches Communications External jugular vein Superficialis colli nerve Auricularis magnus nerve Occipitalis minor nerve Triangles of the neck Great anterior triangle Great posterior triangle Submaxillary triangle . Superior carotid triangle Inferior carotid triangle Suboccipital triangle Subclavian triangle 14 CONTENTS. Common carotid artery Relations External carotid artery . Relations . Branches . Superior thyroid artery Lingual artery . Facial artery . . , Mastoid artery . Posterior auricular artery Occipital artery Transversalis faciei artery Temporal artery Internal maxillary artery Ascending pharyngeal artery Internal carotid artery Relations . Branches . Internal jugular vein Anterior jugular vein Subclavian artery Branches Vertebral artery Basilar artery . Thyroid axis Inferior thyroid artery Supra-scapular artery Posterior scapular artery Superficialis cervicis artery Profunda cervicis artery Superior intercostal artery Internal mammary artery Nerves of the neck Glosso-pharyngeal nerve Pneumogastric nerve Pharyngeal nerve . Superior laryngeal nerve Recurrent laryngeal nerve Spinal accessory nerve . Lingual nerve . Sympathetic nerve Superior cervical ganglion Middle cervical ganglion Inferior cervical ganglion Cervical nerves Anterior cervical plexus Phrenic nerve . Posterior cervical plexus Larynx Thyroid cartilage Cricoid cartilage Arytenoid cartilage , Epiglottis Ligaments of the larynx Chordae vocales CONTENTS. 15 Muscles of the larynx Mucous membrane of the larynx Glottis Ventricle of the larynx Sacculus laryngis Glands of the larynx . Vessels and nerves of the larynx Trachea .... Thyroid Gland Orbit .... Tabular arrangement of structures Muscles of the orbit Nerves—arrangement in cavernous sinus Ophthalmic nerve Fourth nerve Third nerve Sixth nerve . . Ciliary ganglion Ophthalmic artery Fifth pair of nerves Superior maxillary nerve Inferior maxillary nerve Gustatory nerve Inferior dental nerve Auricular nerve Cranial ganglia of the sympathetic Otic ganglion Spheno-palatine ganglion Submaxillary ganglion Naso-palatine ganglion Pharynx Muscles of the pharynx Openings into the pharynx Soft palate . Fauces Muscles of the soft palate Prevertebral region • Muscles CHAPTER IV. ORGANS OF SENSE. NOSE Eye Nasal fossae Boundaries Meatuses Pituitary membrane Vessels of the nose Nerves of the nose Practical observations 16 CONTENTS. Sclerotic coat . Cornea . Choroid coat Ciliary ligament Iris Ciliary processes Retina . Zonula ciliaris . Aqueous humour Chambers oi the eye Vitreous humour Crystalline lens Canal of Petit . Vessels of the eye-ball . Nerves of the eye-ball . Physiological observations Appendages of the Eye Eyebrows Eyelids. Meibomian glands Eyelashes . Conjunctiva Caruncula lachrymalis . Plica semilunaris Lachrymal apparatus Lachrymal gland Puncta lachrymalia Lachrymal sac Nasal duct Ear Pinna Muscles of the pinna Meatus auditorius Vessels and nerves of the pinna Tympanum Membrana tympani Ossicula auditus Muscles of the tympanum Openings in the tympanum Eustachian tube Vessels of the tympanum Nerves of the tympanum Labyrinth Vestibule Semicircular canals Cochlea Auditory nerve . Arteries of the labyrinth Tongue Papillae circumvallatse . Papillae conicae and filiformes Papillae fungiformes Vessels of the tongue . Nerves of the tongue . CONTENTS. 17 Skin Cutis . Corium Papillary layer Rete mucosum . Cuticle Nails . Hairs . Sebaceous follicles Perspiratory duct Pores CHAPTER V. ANATOMY OF THE PERINEUM. General idea Dissection Common superficial fascia . Superficial perineal fascia . Muscles of the perineum Internal pudic artery Branches Dorsalis penis vein . Compressor venae dorsalis muscle Internal pudic nerve Compressor urethrae muscle Cowper's glands Perineum in the female Muscles of the female perineum Arteries Nerves . . CHAPTER VI. PELVIS AND ORGANS OF GENERATION. Bladder Ligaments of the bladder Coats of the bladder . Trigone vesicale Uvula vesicae Muscles of the ureters Urethra Prostatic portion Membranous portion Spongy portion Cowper's glands Prostate gland Vesiculae seminales Vasa deferentia Ejaculatory duct 18 CONTENTS. Pelvic fascia Levator ani muscle Internal iliac artery Sacral plexus of nerves Penis Corpora cavernosa Corpus spongiosum Scrotum Testicle Tunica vaginalis Tunica albuginea Tunica vasculosa Epididymis Vas deferens Spermatic cord Surgery of the testicle and cord Female pelvis and organs of generation Bladder Female urethra Mons Veneris Labia majora Labia minora, or Nymphro Clitoris Hymen Meatus urinarius Vagina Uterus Fallopian tubes Ovaries CHAPTER VII. REGION OF THE BACK. Arrangement of the muscles Posterior thoracic region—First layer Second layer Third layer Fourth layer Fifth layer Sixth layer Table of origins . Table of insertions. Actions of the muscles of the back Spinal Cord Membranes of the spinal cord Sub-arachnoidean fluid Membrana dentata Motor columns Sensitive columns Spinal nerves—Origins Arrangement . CONTENTS. Dorsi-spinal veins Meningo-rachidian veins Medulli-spinal veins CHAPTER VIII. thorax. Thorax—Boundaries Muscles .... Thoracic fascia .... Lungs ..... Pleura ..... Anterior mediastinum Middle mediastinum Pericardium .... Heart ..... Circulation ..... Right auricle .... Right ventricle Left auricle .... Left ventricle . Structure of the heart Coronary arteries . Aorta—ascending—arch Pulmonary artery . Superior vena cava Pulmonary veins . Trachea—Bronchi . Posterior mediastinum Relations—Branches . Vena azygos major Vena azygos minor Superior intercostal vein Thoracic duct . GEsophagus . Pneumogastric nerves Sympathetic nerve . Splanchnic nerves . Cardiac ganglion and plexuses CHAPTER IX. UPPER EXTREMITY. General principles in the disposition of the Bones Muscles . Arteries • • Veins—Lymphatics Nerves Anterior thoracic region Muscles • 20 CONTENTS. Lateral thoracic regi-n Muscles Subscapular region Acromial region Bend of the elbow Nerves Veins Anterior brachial region Muscles . Posterior scapular region Muscles . Posterior brachial region Triceps muscle Axilla Axillary artery Branches Brachial artery Relations Branches Axillary plexus of nerves Fore-arm—anterior region Muscles—superficial group Deep group . Radial artery Branches Ulnar artery Relations Branches Median nerve Ulnar nerve Musculo-spiral nerve Fore-arm—posterior region Muscles—Superficial layer Deep layer . Palmar region Muscles—Radial group Ulnar group Palmar group CHAPTER X. LOWER EXTREMITY. Surgical observations Anterior femoral region Superficial fascia Superficial vessels and nerves Saphenous opening Deep fascia;—fascia lata . Cribriform fascia Muscles—Anterior group Internal group Femoral artery CONTENTS. 21 Operation—Relations Branches Profunda artery . Relations—Branches Obturator artery Veins Nerves Crural nerve Obturator nerve Femoral hernia Coverings—Operations Gluteal region Muscles Arteries Nerves Posterior femoral region Muscles Arteries Nerves Popliteal region Popliteal artery . Relations Popliteal nerve Anterior tibial region Superficial anatomy Muscles Anterior tibial artery Relations Branches Anterior tibial nerve Dorsal region of the foot Muscles Dorsalis pedis artery Branches Nerves Fibular region Muscles Nerves Posterior tibial region Superficial anatomy Muscles—Superficial group Deep group Posterior tibial artery Branches Peroneal artery Branches Sole of the foot Plantar fascia Muscles . Arteries . Nerves Plantar interossei muscles Analysis of the arrangement and action of the muscles ot the lower extremity . 406 22 CONTENTS. CHAPTER XL ON THE LIGAMENTS. Synarthrosis Harmonia Schindylesis Gomphosis Sutura Amphi-arthrosis Symphisis Diarthrosis Arthrodia Ginglymus Enarthrosis LAGAMENTS OF THE TRUNK Articulations of the vertebral column of the atlas with the occipital bone of the axis with the occipital bone of the atlas with the axis of the lower jaw . . Dislocations . . of the ribs with the vertebrae of the ribs with the sternum of the vertebral column with the pelvis of the pelvis Ligaments of the upper extremity Sterno-clavicular articulation Scapuloclavicular articulation Proper ligaments of the scapula Shoulder-joint Elbow-joint .... Radio-ulnar articulation Wrist-joint .... Articulation between the carpal bones Carpo-metacarpal articulation Metacarpo-phalangeal articulation Articulation of the phalanges Ligaments of the lower extremity Hip-joint .... Knee-joint .... Articulation between the tibia and fibula Ankle-joint .... Articulation of the tarsal bones Articulation of the tarsus with the metatarsus Metatarso-phalangeal articulation Articulation of the phalanges CONTENTS. 23 CHAPTER XII. sympathetic nerve. General description . Cranial Ganglia Ganglion of Ribes Ciliary ganglion . Naso-palatine ganglion Spheno-palatine ganglion Vidian nerve Submaxillary ganglion Otic ganglion Carotid plexus Cervical Ganglia Superior cervical ganglion Middle cervical ganglion Inferior cervical ganglion Vertebral plexus . Cardiac nerves Cardiac ganglion . Great cardiac plexus Anterior cardiac plexus Posterior cardiac plexus Anterior coronary plexus Posterior coronary plexus Thoracic Ganglia Great splanchnic nerve Lesser splanchnic nerve Semilunar ganglion Solar plexus Abdominal plexuses Lumbar Ganglia Aortic plexus Hypogastric plexus Sacral Ganglia Ganglion impar, or azygos THE DISSECTOR. CHAPTER I. DISSECTION. The human body is composed of certain principal struc- tures, which occupy the same relative position to each other, wheresoever they be examined. To obtain a good knowledge of these, is, therefore, the first duty of the dissector; the more particularly, that a just conception of their nature and position will greatly facilitate the future progress of his studies. These parts may be thus arranged, in the order of their superposition :— Integument, Arteries, Superficial fascia, Veins, Deep fascia, Lymphatics, Muscles, Nerves, Vessels, Bones and ligaments, and cellular tissue, the common connecting medium of the body, by which they are all held together. The business of dissection, therefore, consists in dividing and turning aside the integument, the superficial fascia, and the deep fascia ; in freeing the muscles from their enveloping cellular tissue ; in separating them, so as to display the ves- sels and nerves which lie between them ; and in following the latter to their ultimate ramifications. In the same manner the performance of an operation with the aid of the knife, as, for example, the tying of an artery, requires the division of the integument, superficial fascia, and deep fascia, the separation of the muscles, and the finding and securing of the vessel. So again in amputation, the same structures are to be divided, and in precisely the same order. Thus the student will perceive that one principal ob- ject of dissection, is the practice of his knife in the division 2 14 THE DISSECTOR. and separation of these parts, so as to enable him to accom- plish his end with ease and dexterity. All the operations of dissection should be conducted with the same delicacy that is observed in the treatment of the living subject. The result of such practice must be obvious — the attainment of that confidence and precision in surgical manipulations, which is so necessary to the intelligent surgeon. Now, let us inquire into the nature of the structures com- posing the preceding table. The integument (integere, to cover in,) is the investing covering of the entire body ; in common parlance, the skin : it consists, of Cuticle, p . (Papillary layer, Rete mucosum, \ Corium. The cuticle (epidermis, scarf-skin) is the thin horny layer that protects the surface of the integument. The rete muco- sum is the soft layer interposed between the cuticle and cutis, in which the colouring particles of the skin are de- posited. It is modelled upon the papillae of the cutis, sx> as to resemble a beautiful network when examined beneath the microscope. Hence its designation rete; and mucosum from having been seen only when softened by decomposition, or by the irritation of a blister when the cuticle is raised. It may, however, with care, be separated from the cutis in layers of considerable size. The cutis (oxvtos the skin, dermis) is formed of two layers —a superficial, the papillary, which presents a surface bris- tled with papillary elevations variously arranged, in which resides the sensibility to touch; and a deep layer, the corium (leather,) which is firm, elastic, and resisting, and is made up of fibres and bands closely interwoven into each other, so as to give strength and support to the tegumentary covering. The superficial fascia (fascia, a bandage,) placed imme- diately beneath the tegument over every part of the body, is the medium of connexion between that layer and the deeper parts. It consists of cellular tissue, in which is de- posited an abundance of adipose matter. The fat, being a bad conductor of caloric, serves to retain the warmth of the body; while it forms at the same time a yielding tissue through which the minute vessels and nerves may pass to the papillary layer of the skin, without incurring the risk of ob- struction from injury or pressure upon the surface. By THE DISSECTOR. 15 dissection, the superficial fascia may be separated into two layers, between which are found the superficial or cutaneous vessels and nerves; as the superficial epigastric artery, the saphenous veins, the radial and ulnar veins, the superficial lmyphatic vessels, or the cutaneous nerves, and in one in- stance a muscle, platysma myoides. The deep fascia is a dense and resisting layer, found chiefly in the extremities and in the neck, where large vessels are carrying onwards the circulating fluids in opposition to the laws of gravity, and where muscles are often acting with prodigious force. In other situations, as over the trunk of the body or upon the head, this layer cannot be said to exist. The deep fascia in the limbs is a tendino-fibrous membrane, formed by a close interlacement of tendinous fibres, which cross each other in various directions. To the eye it presents a brilliant, nacreous lustre. It is strong and unyielding, enclosing the entire limb, and is prolonged into its substance so as to form distinct sheaths to all the muscles. Upon the inner side of the limb it is thin; on the outer and less pro- tected side it is dense and thick. It is connected to the prominent points about the limb, as to the pelvis, knee, and ankle, in the lower extremity, and to the clavicle, scapula, elbow, and wrist, in the upper extremity. Its tension is regulated in some situations by muscular action, as by the tensor vaginae femoris and gluteus maximus in the thigh, and by the biceps and palmaris longus in the arm. The deep fascia of the neck is different in its structure from that in the limbs ; it is a cellulo-fibrous membrane, and consists of cellular tissue very much condensed. It has no tendinous fibres, and none of their resplendency. In its office, it acts precisely the same part with the tendino-fibrous fasciae. The muscles (musculus, from movere, to move) are the moving organs of the body : they are made up of fibres dis- posed parallel to each other in a framework of cellular tissue. Towards the extremities of the muscles the fibres cease, and the cellular framework is condensed into a rounded cord, called tendon (tendo, a sinew,) by which it is attached to the bones. The more fixed extremity of a muscle is called the "origin;" its more moveable end the "insertion." The muscles which enclose cavities, as the abdominal, are broad and extensive ; and their tendon is flattened out into a thin 16 THE DISSECTOR. expansion, which is called "aponeurosis" (a*o, long£ — vtvpov, nervus—a nerve widely spread out.) This derivation demands some explanation. The ancients named all the white fibres of the body «i<£a, or nerves. The vessels are of three kinds—arteries, veins, and lym- phatics. The former are cylindrical tubes, composed of three layers—an external, formed of condensed cellular tis- sue, the " cellular coat;" a middle, of fibres of elastic tissue, the "fibrous coat;" and a lining membrane, or "serous coat." After death they are usually found empty, but pre- serve their cylindrical form, by reason of the thickness of their coats ; hence their name (7p trjpnv, to contain air,) from a supposition of the ancients that they were intended to con- fine the vital spirits. Their office is to convey the vital fluid to every part of the system ; and their ultimate terminations are denominated, from their extreme minuteness, capillaries (capillus, hair). The veins are found in company with the arteries; with the exception of the superficial veins. They return the blood from the capillary vessels of the arteries to the right side of the heart, to be then circulated through the lungs. They are larger than the arteries, and after death are found filled with dark coloured blood. The coats are the same as those of the arteries, but much thinner ; and the internal coat is reflected inwards at various points, so as to form valves. The position of these valves is evidently marked on the exterior of the tube, by the swellings on that part of the vessel which imme- diately precedes them. The lymphatics (lympha, water,) are small, delicate ves- sels which accompany the veins, and present many points of resemblance with them. They return a limpid fluid to the venous circulation, and are provided with a number of valves placed at short distances, which, with the corresponding swellings, give them a knotted appearance. Their coats are the same as those of veins and arteries. Near the flexures of the joints they enter small red bodies, called glands, from which they emerge fewer in number, and larger in size. They are too minute to be seen in an ordinary dissection, unless the subject be anasarcous. The nerves (vtVpa, nerves) are white, flattened cords, com- posed of filaments, which are connected by one extremity with the cerebro-spinal axis ; and, by the other, are dis- THE DISSECTOR. 17 tributed to all the textures of the body, communicating to them sensibility and power of motion. The smallest nerve is made up of a number of filaments, enclosed in a peculiar transparent sheath, called neurilema; which, when freshly exposed, presents a contiguous zigzag line along its cylinder The nerves are usually found accompanying the arteries, and, in the extremities, are placed nearer to the integument than those vessels, as if to be ready to apprize the neighbouring muscles of the first approach of injury, that they may with- draw the more immediately important organs, the arteries, from its consequences. The bones are" the organs of support to the animal frame. They give firmness and strength to the entire fabric, afford points of connexion to the numerous muscles, and bestow ge- neral form upon the body. In the limbs they are hollow cylin- ders, calculated by their form and structure to support weight, and resist violence. In the trunk and head they are flattened and arched, to protect cavities and provide extensive surfaces of attachment. In many situations they present projections of considerable length that serve as levers; and smooth sur- faces that possess all the mechanical advantages of the pulley. While strength and solidity are the principal objects sought for in the shaft of the bone, the extremities are expanded into broad surfaces, that they may transmit the weight of the body with perfect security to the bones below. In the formation of a joint a new organ is introduced, "the ligament" (ligare, to bind). It consists of short strata of fibres passing from bone to bone, in order to connect them together. The different varieties of joint demand a different arrangement of these ligaments. Thus the hinge joint, as the elbow, wrist, knee, ankle, moving in one direction only, has necessarily a squareness of form, and is provided with a ligament to each of its four sides. These are named from their position, anterior, posterior, and lateral. A great pro- portion of the joints of the body are constructed upon this simple principle. When more extensive movements are de- manded, the ball and socket joint is provided, and to accom- modate its circular form, the four ligaments are, as it were, united into one; which completely surrounds the ends of the two bones. Hence in the capsular ligaments of the hip, the shoulder, and the thumb; and when repose and solidity are the great objects, as in the vertebral column, the pelvis, the 2* 18 THE DISSECTOR. carpus, and tarsus; small slips of ligament are seen passing from bone to bone in every direction in which these straight bands can be arranged, without inconvenience to the general plan. These then are the structures of which, with the exception of the viscera, the whole animal frame is composed; and it is incumbent upon the student of anatomy to possess a clear and distinct idea of all these parts, their uses, and natural depen- dencies, before he can hope to display and examine them in the body with advantage. [The dissector should furnish himself with an apron with sleeves, which will protect his clothes from the contact with the subject or table, and a case of dissecting instruments. This case must contain from three to six scalpels of different sizes, a tenaculum, a double hook, a pair of forceps, a couple of needles, a pair of scissors, and a cartilage knife. Every other requisite is usually furnished by the rooms in which the student dissects. A dissector in the country must provide himself in addition with several large sponges, a couple of blocks of different sizes, a saw, and a mallet, and chisel.] CHAPTER II. ABDOMEN. [The dissection of the abdomen is to be commenced by an incision from the lower part of the second piece of the sternum down the median line to the pubis, this incision must be carried on each side of the umbilicus so as to isolate it. A second incision starts from the upper end of the first, down- wards and outwards, forming an angle with the first of about forty-five degrees. A third is to be commenced at the pubis and carried to the anterior superior spinous process of the ilium, and from thence around the crista of the ilium as far back as possible When the skin and superficial fascia are raised from the central line outwards, commencing at the upper corner, the external oblique muscle will be fully un- covered. These latter incisions must be repeated on the opposite side of the subject.] The integument alone should be dissected at first, leaving the superficial fascia. Between THE DISSECTOR. 19 the two layers of the superficial fascia, at the lower part of the abdomen, is the superficial epigastric artery and vein; and, near the crest of the ilium, some branches of the super- ficial circumflex artery and vein. When these have been ex- amined, the superficial fascia may be removed from the muscle. In turning back the flap, several superficial nerves will be cut across;. these are cutaneous branches of the lower intercostal and lumber nerves. If the flap be in the way, it may be re- moved altogether. One side of the abdomen should be dis- sected exclusively for the muscles, and on this side the skin and fascia may be taken up together; the other should be re- served for studying the relations of hernia. Fig. 1. Surface of the abdomen, with lines (1, 2, 3, 4) drawn upon it, marking off its artificial subdivisions into regions. 5, 5. Right and left hypochondriac. 6. Epigastric regions. 7. Umbilical. 8, 8. The two lumbar. 9. Hypogastric. 10, 10." The right and left iliac regions. 11. Regio pubis. The Muscles of the Abdomen are the 20 THE DISSECTOR. External oblique, Rectus, Internal oblique, Pyramidalis. Transversalis, If the external oblique muscle be dissected on both sides, a white tendinous line will be seen along the middle of the abdomen, extending from the ensiform cartilage to the pubis, this is the linea alba. A little external to it, on each side, two curved lines will be observed extending from the sides of the chest to the pubis, and bounding the recti muscles; these are the linese semilunares. Some transverse lines, linese transversa, three or four in number, connect the lineae semilunares with the linea alba. The Linea semilunaris was the situation formerly chosen for the operation of tapping the abdomen in dropsy, para- centesis abdominis. But being merely the outer margin of a muscle, it is liable to alter its position with the expansion to which the whole of the abdominal muscles are subjected in that disease. The rectus may, in this way, be spread over the whole anterior half of the abdomen, and the linea semi- lunaris become so much displaced as hardly to be discerned by external examination. Again, the sheath of the rectus contains a large artery {epigastric); and with the increased breadth of the muscle, this also changes its course. In a few instances the artery has been wounded in consequence of this change of position, and the operation in the linea semilunaris is, therefore, altogether abandoned. Ventral hernia may occur in the course of this line. The Linea alba is now selected for the operation of para- centesis abdominis. Being in the middle line it cannot change its place by distention, and there is no risk of wounding an artery. The spot selected for the operation is usually mid- way between the umbilicus and pubis. It is performed by making a small incision with a bistoury through the integu- ment and superficial fascia, and then introducing the trochar. This line is also the seat of operation for puncturing the bladder above the pubis; which is performed in the same man- ner as paracentesis abdominis. The High operation for lithotomy, a practice wholly dis- used in this country, has also its seat in the linea alba. The Caesarian section for opening the uterus and removing the foetus, an operation which is now becoming frequent, in consequence of success, is also practised in the linea alba. THE DISSECTOR. 21 Moreover, a weakening of the linea alba, from over-disten- tion, or congenital deficiency, gives rise to the protrusion of intestine at the umbilicus, called umbilical hernia. Deficiencies of development also occur in this line, in which some of the abdominal viscera are exposed; the most frequent instance of this arrest is in the case where the mucous mem- brane of the bladder is protruded through the integument. (Exstrophy of the bladder.) The External oblique muscle (obliquus externus abdominis) is the external flat muscle of the abdomen. Its name is de- rived from the obliquity of its direction, and the descending course of its fibres. It arises by fleshy digitations from the external surface of the eight inferior ribs. The five upper digitations being received between corresponding processes of the, serratus magnus, and the three lower of the latissimus dorsi, it spreads out into a broad aponeurosis, which is inserted into the outer lip of the crest of the ilium for one-half its length, the anterior superior spinous process of the ilium, spine of the pubis, pectineal line, front of the pubis, and linea alba. The lower border of the aponeurosis, which is stretched between the anterior superior spinous process of the ilium (fig. 3. 2.,) and the spine of the pubis, is folded inwards, forming Pouparfs ligament, fig. 2. 1. The insertion into the pec- tineal line is Gfimbernafs ligament.* Just above the crest of the pubis is the External abdo- minal ring, (fig. 3. 1.,) a triangular opening formed by the separation of the fi- bres of the aponeurosis of the external oblique. It is oblique in its direction, and corresponds with the course of the fibres of the aponeu- rosis. It is bounded below by the crest of the pubis; on either side, by the borders of ' J . . . . Ihe innominate bone of the left side the aponeurosis, which are with, 1., Poupart's ligament; 2. Gim. called pillars ; and above, by bernat's ligament. * Antonio de Gimbernat, was surgeon to the King of Spain; he published 22 THE DISSECTOR. some curved fibres, which originate from Poupart's ligament, and cross the upper angle of the ring, so as to give it strength. The external pillar, fig. 3. 2. which is at the same time inferior, from the obliquity of the opening, as inserted into spine of the pubis; the internal or superior pillar, fig. 3. 1. forms an interlacement with its fellow of the opposite side, over the front of the symphisis pubis. Fig. 3. The anatomy of inguinal hernia, the right inguinal region. The aponeurosis of the external oblique muscle and the fascia lata.—1. The internal pillar of the abdominal ring. 2. The external pillar of same (Poupart's ligament). 3. Transverse fibres of the aponeurosis. 4. Pubio part of the fascia lata. 5. The spermatic cord. 6. The long saphenous vein. 7. Fascia latafemoris. The external abdominal ring gives passage to the spermatic cord in the male, and round ligament in the female; they are both invested jn their passage through it by a thin fascia derived from the edges of the ring, and called inter-columnar fascia, or fascia spermatica. an excellent essay on femoral hernia in 1793, in which he pointed out the relations of this portion of the tendon of the external oblique to the neck of the sac. His work is entitled "Nuevo Mitodo de Operar en la Hernia Crural." THE DISSECTOR. 23 The pouch of inguinal hernia, in passing through this opening, receives the inter-columnar fascia, as one of its coverings. The posterior border of the external oblique is in close relation with the anterior border of the latissimus dorsi, which sometimes overlaps it. The external oblique is now to be removed by making an incision across the ribs just below its origin to its posterior border, and another along Poupart's ligament and the crest of the ilium. Poupart's ligament should be left entire, as it gives attachment to the next muscles. The muscles may then be turned forwards towards the linea alba. Fig. 4. The muscles of the anterior aspect of the trunk; on the left Bide the superficial layer is seen, and on the right the deeper layer. 1. The pectoralis major muscle. 2. The deltoid; the interval between these muscles lodges the cephalic vein. 3. The anterior border of the latissimus dorsi. 4. The serrations of the serratus magnus. 2. The sub- clavius muscle of the right side. 6. The pectoralis minor. 7. The coraco- 24 THE DISSECTOR. brachialis muscle. 8. The upper part of the biceps muscle, showing its two heads. 9. The coracoid process of the scapula. 10. The serratus magnus of the right side. 11. The external intercostal muscle of the fifth intercostal space. 12. The external oblique muscle. 13. Its aponeurosis; the median line to the right of this number is the linea alba; the flexuous line to its left is the linea semilunaris; and the transverse lines above and below the number, the lineae transversae, of which there were only three in this subject. 14. Poupart's ligament. 15. The 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 upwards from Poupart's ligament to strengthen the ring. The numbers 14 and 15 are situated upon the fascia lata of the thigh; the opening immediately on the right of 15 is the saphenous opening. 16. The rectus muscle of the right side brought into view by the removal of the anterior segment of its sheath; * the posterior segment of its sheath with the divided edge of the anterior segment. 17. The pyramidalis muscle. 18. The internal oblique muscle. 19. The conjoined tendon of the internal oblique and transversalis descending behind Poupart's ligament to the pec- tineal 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 hernia pass. The Internal oblique muscle (obliquus internus abdominis) is the middle flat muscle of the abdomen. It arises from the outer half of Poupart's ligament, from the middle of the crest of the ilium for two-thirds of its length, and by a thin aponeu- rosis from the spinous processes of the lumbar vertebras. Its fibres diverge from their origin, so that those from Pou- part's ligament curve downwards, those from the anterior part of the crest of the ilium pass transversely, and the rest ascend obliquely. The muscle is inserted into the pectineal line, crest of the pubis, linea alba, and lower borders of the five inferior ribs. Along the upper three-fourths of the linea semilunaris, the aponeurosis of the internal oblique separates into two lamellae, which pass one in front and the other behind the rectus muscle to the linea alba, where they are inserted;_ along the lower fourth, the aponeurosis passes altogether in front of the rectus without separation. The two layers which thus enclose the rectus, form for it a partial sheath. The lowest fibres of the internal oblique are inserted into the pectineal line, in common with those of the transversalis muscle. Hence the tendon of this insertion is called the conjoined tendon of the internal oblique and transversalis (fig. 5. 6.) This structure corresponds with the external abdominal ring, and forms a protection to what would other- wise be a weak point in the abdomen. Sometimes it is THE DISSECTOR. 25 insufficient to resist the pressure from within and becomes forced through the external ring: it then forms the distinc- tive covering of direct inguinal hernia. The spermatic cord passes beneath the arched border of the internal oblique muscle, between it and Poupart's liga- ment. During its passage some fibres are given off from the lower border of the muscle, which accompany the cord down- wards 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 with the spermatic cord, the cremaster muscles form one of its coverings. Fig. 5. The internal oblique and transversalis muscle in the inguinal region, with the boundaries of the inguinal canal. The aponeurosis of the external oblique muscle having been divided and turned down, the internal oblique is brought into view with the spermatic cord escaping beneath its lower edge.—1. Aponeurosis of the external ob- lique. V. Lower part of same turned down. 2. Internal oblique muscle. 3. Spermatic cord. 4. Saphenous vein. The Cremaster, considered as a distinct muscle, arises from mn 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 ascending along the inner 26 THE DISSECTOR. abdominis. side of the cord, to be inserted, with the conjoined tendon, into the pectineal line of the pubis. A large nerve is seen piercing the lower fibres of the internal oblique muscle, and passing through the external abdominal ring with the spermatic cord, to which it is dis- tributed : this is the scrotal Fig. 6. A lateral view of the trunk branch of the ilio-scrotal nerve of the body showing its muscles, (superjor musculo-CUtaneoUs). and particularly the transversalis ^ £, . tit t • The internal oblique muscle is to be removed by separating it from its attachment to the ribs above, and to the crest of the ilium and Poupart's ligament below. It should be divided behind by a vertical incision extending from the last rib to the crest of the ilium, as its lumbar attachment cannot at present be examined. The mus- cle is then to be turned forwards. Some degree of care will be re- quired in performing this dis- section 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 circumflex ilii artery ascends between the two muscles, and forms a valuable guide to their 1. The costal origin of the latissimus dorsi muscle. 2. The serratus magnus. 3. The upper part of the external oblique muscle divided in the direction best calculated to show the muscles beneath without interfering with its indigitations with the serratus magnus. 4. Two of the external intercostal muscles. 5. Two of the internal intercostals. 6. The transver- salis muscle. 7. Its posterior aponeurosis. 8. Its anterior aponeurosis, forming the most posterior layer of the sheath of the rectus. 9. The lower part of the left rectus with the aponeurosis of the transversalis passing in front. 10. The right rectus muscle. 11. The arched opening left between the lower border of the transversalis muscle and Poupart's ligament, through which the spermatic cord and hernia pass. 12. The gluteus maximus and medius, and tensor vaginae femoris muscles invested by fascia lata. THE DISSECTOR. 27 separation. Near to Poupart's ligament they are so closely connected that it is impossible to divide them. The Transversalis is the internal flat muscle of the abdo- men ; it is transverse in the direction of its fibres, as is implied in its name. It arises from the outer third of Poupart's ligament, from the internal lip of the crest of the ilium, its anterior two-thirds; from the lumbar vertebrae, and from the inner surfaces of the six inferior ribs, indigitating with the diaphragm. Its lower fibres curve downwards, to be inserted, with the lower fibres of the internal oblique, into the pectineal line, and form the conjoined tendon. Throughout the rest of its extent it is inserted into the crest of the pubis and linea alba. The lower fourth of its aponeurosis passes in front of the rectus to the linea alba; the upper three-fourths, with the posterior lamella of the internal oblique, behind it. The Posterior aponeurosis of the transversalis divides into three lamellae:— 1. Anterior, which is attached to the bases of the trans- verse processes of the lumbar vertebrae. 2. Middle, to the apices of the transverse processes. 3. Posterior, to the apices of the spinous processes. The anterior and middle lamellae enclose the quadratus lumborum muscle; and the middle and posterior, the erector spinae. The union of the posterior lamella of the transversalis with the posterior aponeurosis of the internal oblique, serratus posticus inferior, and latissimus dorsi, constitutes the lumbar fascia. The spermatic cord and oblique inguinal hernia pass beneath the lower border of the transversalis muscle, but have no direct relation with it. Direct inguinal hernia forces the conjoined tendon before it, which forms one of its coverings. The muscular branch of the circumflex ilii artery will be seen near to the crest of the ilium, ramifying upon the transversalis. Some muscular and cutaneous branches of the lumbar nerves will soon be seen perforating its fibres. To dissect the rectus muscle, the sheath should be opened by a vertical incision extending from over the cartilages of the lower ribs to the front of the pubis. The sheath may then be dissected off and turned to either side: this is easily done excepting at the lineae transversae, where a close adhe- sion subsists between the muscle and the external boundary of the sheath. The sheath contains the rectus and pyrami- dalis muscles. 28 THE DISSECTOR. The Rectus muscle arises by a flattened tendon from the crest of the pubis, and is inserted into the cartilages of the fifth, sixth, and seventh ribs. It is traversed by several tendinous zig-zag lines, called lineae transversa. One of these is situated at the umbilicus, two above that point, and one below. They are vestiges of the abdominal ribs of reptiles, and very rarely extend completely through the muscle. The Pyramidalis muscle arises from the crest of the pubis in front of the tendon of the rectus, and is inserted into the linea alba at about midway between the umbilicus and the pubis. The rectus may now be divided across the middle, and the two ends drawn aside for the purpose of examining the mode of formation 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 the anterior lamella of the internal oblique, and behind by the posterior lamella of the internal oblique and the aponeurosis of the transversalis. At the commencement of the lower fourth, the posterior Avail of the sheath terminates in a thin curved margin, the aponeurosis of the three muscles passing altogether in front of the rectus. The quadratus lumborum must be left until the viscera of the abdomen have been examined. 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, would flex the thorax directly on the pelvis. The internal oblique of one side draws the chest downwards 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 upon the chest. The abdominal muscles are the chief agents of expulsion; by their action the foetus is expelled from the uterus, the urine from the bladder, the faeces from the rectum, the bile from the gall-bladder, and the ingesta from the stomach and bowels in vomiting. To produce these efforts they all act together. Their violent and continued action produces hernia; and, add- ing spasmodically, they may occasion rupture of the viscera. THE DISSECTOR. 29 Anatomy of Hernia. The herniae occurring in the parietes of the abdomen have been divided by Sir Astley Cooper into four species; namely, umbilical, ventral, inguinal, and femoral: to which may be added, as occasionally occurring, phrenic, obturator, ischiatic, gluteal, perineal, and, in the female, vaginal. Umbilical hernia occurs at the umbilicus from weakening Fig. 7. After the removal of the lower part of the external oblique (with the ex- ception of a small slip including Poupart's ligament), the lower portion of the internal oblique was raised, and thereby the transversalis muscle and fascia have been brought into view. The femoral artery and vein are seen to a small extent, the fascia lata having been turned aside and the sheath of the blood-vessels laid open.—1. External oblique muscle. 2. Internal ob- lique. 2/. Part of same turned up. 3. Transversalis muscle. Upon the last-named muscle is seen a branch of the circumflex iliac artery, with its companion veins; and some ascending tendinous fibres are seen over the con- joined tendon of the two last-named muscles. 4. Transversalis fascia. 5. Spermatic cord covered with the infundibuliform fascia from preceding. 6. Upper angle of the iliac part of fascia lata. 7. The sheath of the femoral vessels. 8. Femoral artery. 9. Femoral vein. 10. Saphenous vein. 11. A vein joining it. 30 THE DISSECTOR. of the linea alba, either by over-distention, as in utero-gesta- tion, or from congenital deficiency. Its coverings are the Integument, Distended aponeurosis, Superficial fascia, Peritoneum. Ventral hernia occurs chiefly in the linea semilunaris, and from the same causes: its coverings are the same; but it has usually three layers of aponeurosis. Inguinal hernia is of two kinds, oblique and direct: the former takes the course of the spermatic canal, descending by the side of the spermatic cord. The latter (direct) pushes directly through the external ab- dominal ring, carrying before it the conjoined tendon of the internal oblique and transversalis muscles. Dissection.—One side of the abdomen having been reserved „. _ ml .. „ for the study of hernia, the apo- Fiq. 8. The transversalis fas- . „ r, i vv cia, the abdominal muscles being neurosis of the external oblique removed. muscle should now be carefully dissected and turned down. The abdominal parietes, in the ingui- nal region, should in the next place be cut through, and the flap drawn forwards, so that the inter- nal surface of the region may be examined. When the peritoneum is removed from the surface, it will be found adherent at a part corresponding with the entrance of the spermatic cord into the spermatic canal. The vessels com- posing the cord will be seen con- verging to this point, the sperm- atic artery from over the psoas muscle, and the vas deferens from 1. Poupart's ligament. 2. The transversalis fascia. 3. The internal ab- dominal ring, an opening in the transversalis fascia. 4. The situation of the external abdominal ring. 5. A dotted line marking the course of the epigastric artery between the two rings. the side of the bladder. The epigastric artery will also be seen ascending obliquely to the sheath of the rectus. Beneath the peritoneum, and immediately investing the transversalis muscle, is the transversalis fascia (fig. 8. 2.,) a dense layer of cellular fibrous membrane, continuous with Poupart's ligament, 1., below, and on the inner side with the edge of the sheath of the rectus: above and upon the outer THE DISSECTOR. 31 side it is gradually lost in the subserous cellular tissue. In this fascia, which is an important defence to the occurrence of hernia in the inguinal region, is situated the opening for the transmission of the spermatic cord, the internal abdomi- nal ring, 3. Fig. 9. A portion of the wall of the abdomen and of the pelvis is here seen on the posterior aspect, the os innominatum of the left side with the soft parts connected with it having been removed from the rest of the body.—1. Sym- physis of pubes. V. Horizontal branch of same. 2. Irregular surface of the ilium which has been separated from the sacrum. 3. Spine of ischium. 4. Tuberosity of same. 5. Obturator internus. 6. Rectus, covered with an elongation from 7. Fascia transversalis. 8. Fascia iliaca covering iliacus muscle. 9. Psoas magnus cut. 10. Iliac artery. 11. Iliac vein. 12. Epigastric artery and its two accompanying veins. 13. Vessels of sper- matic cord, entering the abdominal wall at the internal ring. The ring was in this case of small size. 14. Two obturator veins. 15. The obliterated umbilical artery. This cord, it will be remembered, is not naturally in con- tact with the abdominal parietes in this situation. The internal abdominal ring^ (fig. 8. 3.,) is an oblique opening in the fascia transversalis, situated midway between the anterior superior spinous process of the ilium and the spine of the pubis, and about half an inch above Poupart's ligament. The border of the ring invests the spermatic cord with an infundibuliform sheath in its passage through it, and the hernial protrusion taking the same course obtains neces- sarily the same sheath or covering. 32 THE DISSECTOR. The Spermatic canal is the oblique space in the abdominal parietes, near to Poupart's ligament, which transmits the sper- matic cord. It is about an inch and a-half in length, is termi- nated at one extremity by the internal ring, and at the other by the external ring. It is bounded in front by the aponeu- rosis of the external oblique, and behind by the fascia trans- versalis and conjoined tendon above by the lower margins of the internal oblique and transversalis muscles, and below by the folded edges of Poupart's ligament. It is along this oblique canal that the hernial protrusion travels in its passage from the abdomen: hence it is named Oblique inguinal hernia. The intestine, pushing before it a sac of peritoneum, enters the internal ring, and receives from it the infundibuliform process of the transversalis fascia, which, in the absence of hernia, invests the spermatic cord alone. It then passes beneath the lower border of the trans- versalis muscle, but without any immediate relation. It next passes beneath the lower border of the internal oblique, and receives the cremaster muscle as a covering. Lastly, emerg- ing from the external abdominal ring, it obtains the inter- columnar fascia, and becomes placed beneath the superficial fascia and integument. The different layers which it thus obtains in its progress, and which the surgeon must cut through, were he called to operate on a strangulated hernia of this kind, the coverings of the hernia, as they are technically called, are, the Integument, Cremaster, Superficial fascia, Fascia transversalis, Inter-columnar fascia, Peritoneal sac. If the hernia be small and become strangulated while situated within the spermatic canal, the external wall of that canal must be laid open. The layers to be divided would then be, the Integument, Cremaster, Superficial fascia, Fascia transversalis, Aponeurosis of the external oblique, Peritoneal sac. Oblique inguinal hernia in its course through the spermatic canal lies above the spermatic cord. In rare cases the hernial protrusion may separate the components of the cord, so that some of them may lie in front of the tumour. Hence one of many reasons for extreme care and caution in operating for strangulated hernia. THE DISSECTOR. 33 Turning again to the inner wall of the abdomen, and ob- serving the position of the internal ring, the epigastric artery will be seen ascending to its inner side. And on the inner side of the artery is a smooth and rather depressed triangular surface, which is the seat of the protrusion of intestine in direct inguinal hernia. Direct inguinal hernia is named from passing directly through the external abdominal ring. It pushes before it a sac of peritoneum, the transversalis fascia, the conjoined ten- don, and as it escapes at the external ring receives an in- vestment from the inter-columnar fascia. Its coverings are therefore, the Integument, Conjoined tendon, Superficial fascia, Transversalis fascia, Inter-columnar fascia, Peritoneal sac. In escaping at the external ring it often carries the sper- matic cord before it, so that the vessels of which it is com- posed become spread over the front of the hernial sac, or slip to one side. The Seat of stricture in all the varieties • of ingui- nal hernia is always the neck of the sac. In recent oblique hernia the neck of the sac is formed by the internal ring. In old and large hernia, the internal ring is dragged down so as to become placed exactly opposite the external,.and the two together form its neck. In direct hernia, the fascia transversalis with the border of the conjoined tendon are the structures forming the neck of the sac. A direct injminal hernia on the leftside, covered by the conjoined ten- don of the internal oblique and transverse muscles.-l. Aponeurosis of The external oblique. 2. Internal oblique turned up. 3. Transversalis muscle. 4. Fascia transversalis. 5. Spermatic cord. 6. The hernia-NB A small part of the epigastric artery is seen through an opening made in the transversalis fascia. Fig. 10. 34 THE DISSECTOR. If oblique and direct her- nia existed together, it is obvious from the position of the epigastric artery, (fig. 9.12.) that that vessel would be placed between the necks of both; and if either ex- isted separately, the artery would be situated to the inner side of oblique, and to the outer side of direct her- nia. In the division of the stricture, therefore, the sur- geon would make his incision upwards and outwards in oblique and upwards and A small oblique inguinal hernia, and a direct one, are seen on the right side. A little of the epigastric artery has been laid bare, by dividing the fascia transversalis immediately over it.—1. Tendon of the external ob- lique. 2. Internal oblique turned up. 3. Transversalis. 4. Its tendon (the epigastric artery is shown below this number). 5. The spermatic cord (its vessels separated). 6. A bubonocele. 7. Direct hernia protruded be- neath the conjoined tendon of the two deeper muscles, and covered by an elongation from the fascia transversalis. Fig. 12. Common oblique inwards in direct hernia, to avoid wound- inguinal hernia. The in-ing this artery. But as the diagnosis of T^iZlT^^-^ ™t •»•»• °f th* hernia is always rated from the testicle by uncertain, and as the division of the epi- the tunica vaginalis. gastric artery would possibly be fatal, and as moreover obliquity in the direc- tion of the incision is quite unnecessary for the safety of the operation, experi- ence has established the rule, that the incision should be made directly upwards in every case of inguinal hernia; and if the history of femoral hernia be referred to, it will be seen that a general principle may be established, that in all cases of abdominal hernia, inguinal, femoral, um- bilical, or ventral, the incision is invari- ably to be made directly upwards. 1. The sac of the hernia. 2. The tunica vaginalis enclosing the testicle. 3, 4. The spermatic cord. THE DISSECTOR. 35 Fig. 13. Congenital her- nia, the intestine being in contact with the tes- ticle ; the tunica vagi- nalis of the testicle form- There are two varieties of oblique in- guinal hernia occasionally met with; these are congenital and encysted. Both result from protrusions, which take the course of the spermatic canal, and they ing the sac of the hernia differ from common oblique inguinal, and from each other, only in relation to the tunica vaginalis of the testicle. In the descent of the testicle from the abdomen into the scrotum in the foetus, a sac of peritoneum is carried with it. The form of this sac may be familiarly illustrated by the simile of a Florence flask. The neck of the pouch from the internal ring to near the testicle, be- comes gradually closed and obliterated, and that portion of it which remains and encloses the testicle is the tunica vagi- nalis. Fig. 13. 1. The tunica vaginalis testis, continu- ous superiorly with the peritoneum, of which it is a part. 2. The testicle. 3. The spermatic cord. ,-i 77. 7 • / /■ i n \ Fig. 14. Encysted hernia; Common oblique hernia, (fig. 12.,) OC- the hernial sac containing curring in this condition of the tunica the intestine being behind vaginalis, is placed altogether above it, the tunica vaginalis. and in a distinct sac or pouch of peri- toneum. Congenital hernia (fig. 13.) results from the nonclosure of the sac of the tunica vaginalis; the intestine, in its descent, passes along the open canal left by the transit of the testicle, and enters the tunica vaginalis, being in actual contact with the testicle. The sac of congenital hernia is, therefore, the tunica vaginalis itself. In other respects it exactly re- sembles common oblique hernia. Fig. 14. 1. The hernial sac. 2. The cavity of the tunica vaginalis. 3. The testicle. 4. The spermatic cord. The arrow shows that three lay- ers of serous membrane must be divided before the intestine can be reached. 36 THE DISSECTOR. In encysted hernia* (fig. 14.) (hernia infantilis of Hey) the neck of the pouch of the tunica vaginalis is closed only at the upper part, and the hernia carrying with it a peritoneal sac descends behind the tunica vaginalis, so that, in operating, the surgeon opens first the tunica vaginalis, and, finding no hernia, cuts through its other side until he reaches the hernial sac. He thus divides three layers of serous membrane, before arriving at the intestine. In other respects the hernia re- sembles common oblique inguinal. The Arteries of the Abdominal parietes are the superficial and deep epigastric, superficial and deep-circumflexed ilii, internal mammary, inferior intercostal, and lumbar. The Lymphatics accompany the veins, those from the lower part of the abdome^ passing into the inguinal glands, and those from the upper ascending to the mediastinal glands. The Nerves are the inferior intercostal and musculo-cuta- neous branches of the lumbar plexus. The student should now lay open the abdomen by means of a crucial incision, and study its divisions into regions, the position of the viscera, and the peritoneum. The Cavity of the abdomen 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 dia- phragm ; and, below, by the pelvis. Regions.—See Fig. 1. If two transverse lines be carried around the body, the one parallel with the convexities of the ribs, the other with the highest points 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 compart- ments or regions, a middle and two lateral. The middle region of the upper zone being immediately over the small end of the stomach, is called Epigastric ({*<,— yo3*w, over the stomach,) fig. 1. 6. The two lateral regions being under the cartilages of the ribs, are called Hypochon- driac (vftb—xovSpoi, under the cartilages,) 5. The middle region of the middle zone is the Umbilical, 7. The two lateral, the * A case of this kind occurred to Mr. Liston in 1835. The student will find a full account of it in a Clinical Lecture in the 1st volume of the Lan- cet for 1834-5, page 883*. THE DISSECTOR. 37 Lumbar, 8. The middle region of the inferior zone is the Hypogastric (i>*6—ya z- a a t ( Pancreatico-duodenahs. Cystic. The Pyloric branch is distributed to the pylorus and lesser curve of the stomach, and inosculates with the gastric. The G-astro-duodenalis descends behind the pylorus, and divides into two branches, the gastro-epiploica dextra and pancreatico-duodenalis. The gastro-epiploica dextra runs along the great curve of the stomach, and inosculates at about its middle with the gastro-epiploica sinistra, a branch of the splenic artery. It supplies the great curve of the stomach, and the great omentum, hence the derivation of its name. The pancreatico-duodenalis curves along the fixed border of the duodenum, and is distributed to it and to the head of the pancreas : it anastomoses with the first jejunal branch of the superior mesenteric artery. The Cystic is a small branch distributed between the coats of the gall bladder. The Splenic artery passes outwards along the upper border of the pancreas to the spleen, where it divides into five or six large branches, which are distributed to that organ, It usually makes several serpentine bends in its course, and sometimes a complete circular curve upon itself. Its branches are,— Pancreaticae parvae, Vasa brevia, Pancreatica magna, Gastro-epiploica sinistra. The Pancreaticce parvce are small nutrient branches dis- tributed to the pancreas, as the splenic artery runs along its upper border. One of these, larger than the rest, follows the course of the pancreatic duct, and is called pancreatica magna. The Vasa brevia are several small branches distributed to the great end of the stomach. 5* 54 THE DISSECTOR. The Gastro-epiploica sinistra runs forwards from left to right along the great curve of the stomach, and inosculates with the gastro-epiploica dextra. It is distributed to the greater curve of the stomach and great omentum. The Gastric and splenic veins terminate in the portal vein, and the hepatic veins in the vena cava. Each of the arteries is accompanied by a corresponding plexus of nerves derived from the solar plexus; they are the gastric, hepatic, and splenic plexuses. The relations of the vessels situated in the right border of the lesser omentum should now be examined more particularly. The hepatic artery will be found to the left, the ductus communis choledochus to the right, and the portal vein behind and between them. The student will also perceive very distinctly how the lower boundary of the foramen of Winslow is formed by the hepatic artery. The Ductus communis choledochus is formed by the junction of the hepatic with the cystic duct. It descends along the right margin of the lesser omentum, and behind the descending duodenum to its inner border. It terminates with the pancreatic duct, near the interior angle of the duodenum, after running for some distance obliquely between the muscular and mucous coats of the intestine. Just before its termination it is considerably constricted. Its entrance upon the inner surface of the intestine is marked by a small elevated papilla. The Liver may now be removed from the abdomen and examined separately. To effect this object it will be necessary to cut through the folds of peritoneum which are connected with its upper surface, and the hepatic artery, ductus com- munis choledochus, portal vein, and vena cava from below. The Liver is situated in the right hypochondriac region, and extends across the epigastrium into the left hypochon- drium. It presents a narrow thin border anteriorly, which corresponds with the margin of the thorax, and a rounded border posteriorly, which rests against the diaphragm. Superi- orly it is convex, and inferiorly concave. It is divided into five lobes, two principal, and three minor lobes; they are the Right lobe, Lobulus Spigelii, Left lobe, Lobulus caudatus. Lobulus quadratus, THE DISSECTOR. 55 The lobes are separated from each other by fissures, of which there are also five, viz., the Longitudinal fissure, Fissure for the gall bladder, Fissure for the ductus venosus, Fissure for the vena cava. Transverse fissure, The Right and Left lobes are separated by the longitudinal fissure, and in front by the notch which lodges the round ligament. The right is much larger than the left, and presents the subdivisions which give rise to the minor lobes. The Lobulus quadratus is bounded, in front by the free border of the liver, and, behind, by the transverse fissure; to the right by the gall bladder, and to the left by the longitudinal fissure. The Lobulus Spigelii* is a small triangular lobe, which is bounded in front by the transverse fissure, and on the sides by the fissures for the ductus venosus and vena cava. The Lobulus caudatus is a small tail-like appendage to the lobulus Spigelii, from which it runs outwards like a crest into the right lobe. In some livers it is extremely well marked, in others it is small and ill defined. The Longitudinal fissure runs from before backwards, commencing at a deep notch in the anterior border of the liver. At about half way between the anterior and posterior borders, it is joined by the transverse fissure which originates in the right lobe. The continuation of the longitudinal fissure backwards, from the extremity of the transverse fissure to the posterior border of the liver, is the fissure for the ductus venosus. The Fissure for the gall bladder is simply the depression in which that organ is lodged, and the fissure for the vena cava a deep notch, sometimes a short tunnel in the posterior rounded border of the liver through which the vessel passes. Upon the upper or convex surface of the liver are seen its ligaments: these are, the Two lateral, Coronary, Longitudinal, Round. The two Lateral ligaments are formed by the two layers of peritoneum, which pass from the under surface of the diaphragm * Adrian Spigel, a Belgian physician, professor at Padua after Casserius in 1616. He assigned considerable importance to this little lobe, but it was described by Sylvius full sixty years before him. 56 THE DISSECTOR. to the liver. They correspond with the two lobes; one being the right, the other the left lateral ligament. The Longitudinal ligament (broad, ligamentum suspenso- rium hepatis) is an anteroposterior fold of peritoneum, ex- tending from the notch on the anterior border of the liver to the junction of the lateral ligaments. At the union of the longitudinal ligament with the two lateral, a triangular space is left which is uncovered by peritoneum, and where the diaphragm is in contact with the substance of the liver. The peritoneum around this space forms a kind of corona, hence it is called coronary ligament. The Round ligament is a fibrous cord, situated between the two layers of peritoneum in the anterior border of the broad ligament. It may be traced from the umbilicus to the notch in the anterior border of the liver, and through the longitudinal fissure to the vena cava. It is the remains of the umbilical vein of the foetus. The vessels entering into the structure of the liver are also five in number: they are the Hepatic artery, Hepatic ducts, Portal vein, Lymphatics. Hepatic veins, The Hepatic artery and Portal vein enter the liver at the transverse fissure; from which point the branches of the portal vein spread out to every part of the liver, so that their direction is from below upwards. The Hepatic veins commence at the circumference of the liver, and proceed from before backwards, to open into the vena cava upon its posterior border. Hence the branches of the two veins cross each other in their course. The portal vein is accompanied to its ultimate divisions by a loose cellular tissue, the capsule of Glisson, which surrounds it in the right border of the lesser omentum. This capsule, by establishing only a loose connexion between the vessels and the substance of the liver, permits the veins to contract upon themselves, when emptied of their blood. The branches of the hepatic veins, on the contrary, are closely united by the circumference of their cylinders to the substance of the liver, hence they are unable to contract. The student will, there- fore, easily distinguish between the openings of the two veins in a section of the organ : the branches of the portal vein will be found collapsed, and those of the hepatic veins widely open. THE DISSECTOR. 57 Again, in company with the portal vein, he will observe the hepatic artery and ducts, while the hepatic veins are solitary. Vessels and nerves.—The liver is supplied with the hepatic artery for nutrition; the portal vein for secretion; and the hepatic veins to convey to the inferior cava the resi- dual blood. The smaller hepatic ducts unite to form a single duct for each of the two principal lobes, and these again form, by their union, the common hepatic duct. The Lymphatics are variously distributed: those of the convex surface proceed upwards through the anterior medi- astinum to the glands about the heart, and those from the concave surface pass backwards to the receptaculum chyli. The Nerves of the liver are the filaments of the hepatic plexus, derived from the solar plexus. The Gall-bladder is of a pyriform shape, and is lodged in a fissure on the under surface of the right lobe. The apex is directed upwards, and the fundus projects slightly beyond the narrow free border of the liver. It has three coats, an internal mucous, middle fibrous, and external, a partial investment of peritoneum. The Internal, or mucous coat, presents a beautifully reti- culated structure in the interior of the bladder, and at its neck forms a spiral valve. It is continuous through the hepatic duct with the mucous membrane lining all the ducts of the liver, and through the ductus communis choledochus, with the mucous membrane of the alimentary canal. The Fibrous membrane is a thin, but strong layer, formed by an interlacement of tendinous fibres. It is connected on the one side with the liver, and on the other with the peritoneum. The Peritoneal coat is a partial covering, investing only that side of the bladder which is unattached. It serves to bind down the gall-bladder, and keep it in its place. The excretory duct of the gall-bladder is the cystic, which unites with the hepatic to form the ductus communis choledo- chus. It is by the latter that the bile is conveyed into the duodenum. 58 THE DISSECTOR. Structure and Minute Anatomy of the Liver, according to Mr. Kiernan. The Liver is composed of lobules, of a connecting medium called Glisson's capsule, of the ramifications of the portal vein, hepatic ducts, hepatic artery, hepatic veins, lymphatics, and nerves, and is enclosed and retained in its proper situation by the peritoneum. We shall de- scribe each of these structures singly, following rigidly the discoveries of Mr. Kiernan. 1st. The Lobules are small granular bodies of an irregular form, and presenting a number of rounded projecting processes upon their surface. When divided longitudinally (Jig. 19. 2.) they have a foliated appearance, and transversely, (fig. 18. 1.) a polygonal outline with sharp or rounded angles, according to the smaller or greater quantity of Glis- son's capsule contained in the liver. The base, (fig. 19. 4.) of each lobule is flattened and rests upon an hepatic vein, which is thence named sub-lobular. The rest of the surface of the lobule is called cap- sular, and is enclosed in a cellular sheath derived from Glisson's capsule. This cellular sheath separates each lobule from those surrounding it, and the interval in which it is contained is called the interlobular fissure, (jig. 19. 6. fig. 18. 3.) At the angle formed by the apposition of several lobules, the interlobular fissure dilates into a small space of a triangular or quadrangular form : this is the interlobular space, (fig. 18. 13.) In the centre of each lobule is situated a small vein, (fig. 18. 19. fig. 1. 3.,) the intra-lobular, which runs in the logitudinal direction of the lobule, and passes through the centre of its base to terminate in the sub-lobular vein, and thus forms a principal bond of connexion between the lobule and the vein. The intra-lobular vein invariably corresponds with the form of the lobule: it is composed of a central vessel, and of from four to six or eight smaller vessels, which terminate in the central vessel. The central vessel represents the centre of the lobule, and the smaller vessels the number of processes which are developed upon its surface. There is a slight variety of form between the lobules of the centre and those of the surface; the former are more angular, from being compressed by the surrounding substance; the latter have the outline more rounded, and appear larger from being placed obliquely on the hepatic veins which pass nearly parallel with the upper and lower surfaces of the liver to terminate at its posterior border. " The form of the lobules bears no relation to the arrangement of the ducts, the form of each lobule being always correspondent to the branches of the intra- lobular hepatic vein occupying the centre of the lobule." " Each lobule is composed of a plexus of biliary ducts, of a venous plexus formed by branches of the portal vein, of a branch of an hepatic vein, and of minute arteries; nerves and absorbents, it is to be pre- sumed, also enter into their formation, but cannot be traced into them." " Examined with the microscope, a lobule is apparently composed of THE DISSECTOR. 59 numerous minute bodies of a yellowish colour, and of various forms, connected with each other by vessels These minute bodies are the acini of Malpighi." " If an uninjected lobule be examined and con- trasted with an injected lobule, it will be found that the acini of Mal- pighi in the former are identical with the injected lobular biliary plexus in the latter, and the blood-vessels in both will be easily dis- tinguished from the ducts." Glisson's capsule is the cellular tissue which envelopes the hepatic vessels in the right border of the lesser omentum, and accompanies them through the transverse fissure to their ultimate ramifications. It forms a distinct capsule for each of the lobules, and is continuous with the fibrous layer which invests the entire liver, its proper capsule. But " Glisson's capsule," observes Mr. Kiernan, " is not mere cellular tissue ; it is to the liver what the pia mater is to the brain; it is a cellulo-vascu- lar membrane in which the vessels divide and subdivide to an extreme degree of minuteness; which lines the portal canals, forming sheaths for the larger vessels contained in them, and a web in which the smaller vessels ramify ; which enters the interlobular fissures, and with the vessels forms the capsules of the lobules, and which finally enters the lobules, and with the blood-vessels expands itself over the secreting biliary ducts. Hence arises a natural division of the capsule into three portions, a vaginal, an interlobular, and a lobular portion. The Vaginal portion encloses the portal vein, hepatic duct, and artery in the canals through which they ramify. In the larger canals it sur- rounds the vessels completely, but in the smaller it is situated only to that side on which the ducts and artery are placed ; the opposite side of the portal vein being in close contact with the capsular surface of the lobules. The Interlobular portion forming the sheath of each of the lobules, and occupying the interlobular fissures, gives support to the ramifications of the portal vein, hepatic ducts, and artery, previously to their entrance into the lobules. The Lobular portion accompanies the vessels into the substance of the lobule. The Poktal vein ramifies through the liver in canals which commence at the transverse fissure, and spread from below upwards throughout the entire organ. These portal canals are formed by the capsular sur- faces of the lobules, and contain, besides the vein, a duct and an artery. The branches of the vein, according to the arrangement established by Mr. Kiernan, are divisible into those which are given off in the canals, vaginal; those which ramify into the interlobular fissures, interlobular : and the terminal branches which are distributed within the lobules, lobular. The trunks of the portal vein, hepatic duct, and artery, are completely surrounded by Glisson's capsule in the larger canals ; but in the smaller ones (fig. 18.) the capsule (9.) is situated only at that side on which the duct and artery are placed, the vein on the opposite side of its cylinder being in contact with capsular surfaces of the lobules. The portal vein being thus separated from the lobules, all around in the larger canals, and for one-third of its cylinder in the smaller, forms a plexus which ramifies in the capsule of Glisson, and has the effect of bringing the vein in relation with all the lobules foming the canal. The branches 60 THE DISSECTOR. of the vein forming this plexus which extends throughout the whole course of the canals, are the vaginal, and from the plexus are given oft the interlobular veins opposite each interlobular space. From tne side of the vein which is in contact with the lobules in the smaller canals, the interlobular veins are given off directly to the interlobular spaces, no vaginal branches or plexus being necessary If the smaller portal veins be laid open, the outline of the lobules bounded by the interlobular fissures will be seen through their coats, and the opening of a venous branch will be observed to correspond with each interlobular space. "The Interlobular branches (fig. 18. 5.5.) of the portal fein cover, with their ramifications, the whole external surface of the lobules, with the exception of their bases, and of those extremities of the superficial lobules which appear on the surfaces of the liver. The freest commu- nications take place between these ves- Fig. 18. Transverse section of seia . when successfully injected, which a small portal canal and its vessels can ke done with size only, the inter- ftom Mr. Kiernan's paper in the i0t,aiar fissures in which they are con- Philosophical Transactions for t&ine^t whether examined on the sur- 1833- faces of the liver or on the surface of a section, are coloured with the injection. Mercury thrown into a large branch of the portal vein returns by other large branches. This communication takes place through the medium of the inter- lobular branches; for though the vagi- nal branches in the same canal anasto- mose freely with each other, yet those of one canal communicate with those of another through the medium of the in- tervening interlobular branches alone. The interlobular veins also form com- munications between the lobular veins of a lobule and those of contiguous lo- bules. Hence it appears that the freest 1. Transverse sections of the lobules of the liver. 2. Intra-lobular hepatic veins in the centres of the lobules. 3. Interlobular fissures, in which ramify branches of the portal vein, hepatic artery, and hepatic ducts. 4. The portal vein, from which pass off on all sides interlobular veins (5. 5.) which ramify in the interlobular fissures. 6. The hepatic artery. 7. The hepatic duct. 8. A branch from each of the three vessels seen entering one of the interlobular fissures. 9. The cellular tissue, Glisson's capsule, by which they are all surrounded. It will be observed that the boundaries of the ca- nal in which the portal vein is lodged, are formed by the sides of the lobules and interlobular fissures, and not by the bases of the lobules, as are those of the sub-lobular veins. 10. A lobule in the state of "passive congestion," or "hepatic venous congestion." 11. A lobule in the state of portal ve- nous congestion. 12. The patches indicating the existence of "active con- gestion." anastomoses exist between all the branches of the portal vein, and that the interlobular branches form the medium of communication. " When the portal vein is imperfectly injected, and the venous circles, THE DISSECTOR. 61 formed by its interlobular branches around the lobules, are not brought into view, these branches are seen in the spaces, and three or four smaller branches are seen shooting into the fissures communicating with the spaces. These are the stellated vessels of anatomists. When the vessels are well injected, the stellae are all continuous with each other, and the venous circles are formed; the stellated appearance, therefore, arises from the incomplete injection of the vessels." The Lobular veins form a plexus within each lobule, and converge from the circumference to the centre to terminate in the hepatic vein. " This plexus interposed between the interlobular portal veins and the intra-lobular hepatic vein, constitutes the venous part of the lobule, and may be called the lobular venous plexus. The circular, ovoid, and oblong portions of the biliary plexus, seen," by means of a microscope of moderate power, " between the branches of the venous plexus, are the acini of Malpighi. The venous branches returning the blood from the coats of the ducts, and from the vasa vasorum of all the vessels in the liver, ter- minate in the portal vein." The Hepatic duct (fig- 18. 7.) enters the liver by the transverse fis- sure, and accompanies the portal vein and hepatic artery throughout all the ramifications of the portal canals, and through the interlobular fissures, to the substance of the lobules, wherein it terminates by forming the lobular biliary plexus. Hence the division which Mr. Kiernan has established for the portal vein, hepatic artery, and Glisson's capsule, is equally applicable to the duct, viz. vaginal, interlobular, and lobular. The Vaginal branches arise from the principal ducts, nearly at right angles, and passing transversely across the capsule, divides into numerous branches, which form the vaginal plexus. The branches of the plexus run in the direction of the fissures, so as to form a net-work of vessels corresponding in form to the fissures upon which they lie. From this net-work of ducts both lobular and inter-lobular branches arise; " the former enter the lobules on the parietes of the canals ; the latter leave the canals at the spaces, to ramify between the lobules." " The transverse branches, and those which arise immediately from them, do not anastomose with each other, but the smaller branches sometimes appear to do so ; I cannot, however, from dissection, affirm that they do, for those which appear to anastomose are _ exceedingly small vessels, and meet each other at the spaces, hence it is difficult to ascertain whether they really anastomose, or enter the spaces together without anastomosing." The Interlobular ducts ramify with branches of the portal vein and hepatic artery, upon the capsules of the lobules in the inter-lobular fissures. They communicate very freely with each other, so that injec- tion thrown into the hepatic duct of the left side will return by that of the right. The Lobular duels enter the substance of the lobules, and form a plexus, the lobular biliary, of which the lobule is principally composed. They terminate in coecal extremities, as do other glands, and form the true glandular portion of the globule. # _ " The coats of the ducts are highly vascular ; the rugae on their in- ternal surface, and those on the internal surface of the gall-bladder are formed by the ramifications of the larger blood vessels, arteries as well 6 62 THE DISSECTOR. as veins, covered by the mucous membrane. This membrane is studded with vascular papillae: and to the rupture of the delicate vessels forming these papillae is to be attributed the facility with which Soemmering and other anatomists injected the ducts from the arteries and veins, andnot to any direct communication between the vessels and the ducts." The venous blood is returned from the ducts into the portal vein. " From their extreme vascularity alone we might infer, that the ducts serve another purpose besides that of the conveyance of bile ; and all anatomists are acquainted with the muciparous follicles of the lining membrane of their larger branches ; in the smaller branches the existence of the follicles has been denied. In the former they are irregularly distributed over the surface ; in the latter they are closely arranged in two longitudinal lines, occupying opposite sides of the ducts; and arranged in this manner they will be found in the smallest duct that can be examined." The Hepatic artery enters the liver with the portal vein and hepatic duct, at the transverse fissure, and accompanies their ramifications to their ultimate terminations. Its branches, therefore, admit of the same division, with those of the portal vein and hepatic duct, into the vaginal, interlobular, and lobular. In the portal canals, "the hepatic artery (fig. 18. 6.) and duct, (7.,) running together on one side of the canal, or winding spirally within it, are in opposition with but a very Limited number of spaces ; the two vessels are, however, brought into opposition with all the spaces by means of plexuses, from which the interlobular branches arise." " The branches forming these plexuses are the first which arise from the artery, duct, and vein ; they form a vr scular sheath around these vessels, and may be called vaginal branches." The Vaginal branches anastomose very freely with each other, so much so, that " if the left artery be injected in the transverse fissure, the injection will return by the right artery ; this communication takes place by means of vaginal branches, which the left artery gives off in the fissure, and which anastomose with similar branches of the right artery." The Interlobular arteries are given off from the vaginal plexus, and enter the interlobular spaces and fissures, and are distributed upon the capsular surface of the lobules, but more particularly within the coats of the interlobular ducts, around which they form a very vascular net- work. " No anastomoses can be shown to exist between the interlobular arteries ;"—" but, as the vaginal arteries communicate freely with each other, and as the interlobular ducts also communicate with each other, and as the arteries ramify in the coats of the ducts, we may conclude that the interlobular arteries anastomose." " From the superficial interlobular fissures, small arteries emerge and ramify in the proper capsule, on the convex and concave surface of the liver, and in the ligaments. These are the capsular arteries." Where the capsule is well developed, " these vessels cover the surfaces of the liver with a beautiful plexus," and " anastomose with branches of the phrenic, internal mammary, and supra-renal arteries," and with the epigastric. " The Lobular arteries are exceedingly minute and few in number: THE DISSECTOR. 63 they are the nutrient vessels of the lobules, and, probably, terminate in the plexuses formed by the portal vein." "The Hepatic veins are contained in canals, which maybe called the hepatic venous canals ;" they Flg_ 19- The distribution of the he- commence in the interior of each patic veins, according to Mr. Kiernan. lobule, by the intra-lobular vein. erom Mr. Kiernan's paper in the Phi- The intra-lobular vein, (fig. 19. 3.) losophical Transactions for 18 previously to piercing the coats of the intes- tine. Their course between the coats of the duodenum is always very oblique. The pancreas and duodenum may now be removed, and the nerves and vessels dissected which lie on the lumbar vertebrae. Near to the coeliac axis on either side, and piercing the crust of the diaphragm, is a large nerve, the greater splanchnic which enters an irregular ganglion of a semilunar form, situated by the side of the coeliac axis. The Semilunar ganglia send numerous branches of com- munication from one to the other, so as to form an intricate plexus around the coeliac axis, which is called the solar plexus. From the solar plexus, as from a centre, smaller plexuses are given off, which accompany all the branches of the abdominal aorta, and the aorta itself; hence we have the gastric plexus, hepatic plexus, splenic plexus, superior mesenteric plexus, spermatic plexus, inferior mesenteric plexus, renal plexus, aortic plexus, &c. A little external to the greater splanchnic nerve, i sthe lesser splanchnic, which usually pierces the diaphragm over the li- gamentum arcuatum internum, and joins the renal plexus. The Sympathetic nerve, within the abdomen, "descends in front of the lumbar vertebrae at each side of the great vessels. 68 THE DISSECTOR. It presents four ganglia of a fusiform shape, from which branches are given off to communicate with the spinal nerves and other branches of large size, which pass inwards in front of the great vessels, and unite over the bifurcation of the aorta to form the hypogastric plexus. The branches of the hypogastric plexus are distributed to the viscera in the pelvis, and communicate very freely with those of the sacral plexus. The Abdominal aorta enters the abdomen through the aortic opening of the diaphragm, and descends, lying rather to the left side of the vertebral column, to the fourth lumbar vertebra, where it divides into the two common iliac arteries. Relations.—It is crossed, in front, by the left renal vein, pan- creas, transverse duodenum, and mesentery; and, behind, is in relation with the thoracic duct and receptaculum chyli. On its left side is the left semilunar ganglion and sympathetic nerve; and, on the right, the vena cava, right semilunar gan- glion, and commencement of the vena azygos. Branches.—The branches of the abdominal aorta, in their order of origin, are the Phrenic, ( Gastric, Coeliac axis < Hepatic, ( Splenic. Superior mesenteric, Spermatic, Supra-renal, Inferior mesenteric, Renal, Lumbar, Sacra-media. The Phrenic are two small arteries which are distributed upon the under surface of the diaphragm. The Coeliac axis is destined to the supply of the stomach and duodenum, liver, spleen, pancreas, and omentum. The Superior mesenteric artery is distributed to the jeju- num, ileum, coecum, ascending and transverse colon. The Supra-renal are two small vessels, sometimes branches, of the phrenic or renal arteries, distributed to the renal capsules. The Renal arteries are two large trunks given off on each side of the aorta to the kidneys; the right is longer than the left, from the position of the aorta, and crosses behind the vena cava to reach the kidney. The Spermatic arteries are two small vessels given off from the front -of the aorta ; they pass outwards to the ureters, which they accompany for a short distance, then leave them, THE DISSECTOR. 69 and cross the iliacus muscle on each side to the internal abdo- minal ring, through which they decsend along the spermatic canal to the testicle. They are each accompanied by two spermatic veins. Fig. 20. The abdominal aorta with its branches. 1. The phrenic arteries. 2. The coeliac axis. 3. The gastric artery. 4. The hepatic artery, dividing into the right and left hepatic branches. 5. The splenic artery, passing outwards to the spleen. 6. The supra-renal ar- tery of the right side. 7. The right renal artery, which is longer than the left, passing outwards to the right kidney. 8. The lumbar arteries. 9. The superior mesenteric artery. 10. The two spermatic arteries. 11. The inferior mesenteric artery. 12. The sacra media. 13. The common iliacs. 14 The internal iliac of the right side. 15. The external iliac artery. 16. The epigastric artery. 17. The circumflexa ilii artery. 18. The femoral artery. These arteries, in the female, are distributed to the ovaries. 70 THE DISSECTOR. The Inferior mesenteric artery supplies the descending colon, sigmoid flexure, and upper part of the rectum. The Lumbar arteries correspond with the intercostals in the chest; they are five in number on each side, and curve around the bodies of the lumbar vertebrae, beneath the psoas muscles, and divide into two branches; one of which passes backwards between the transverse processes, and is distributed to the muscles of the back, whilst the other supplies the abdo- minal muscles. In passing between the psoas muscles and the vertebrae, they are protected by a series of tendinous arches, which defend them and the communicating branches of the sympathetic from pressure during the action of the muscle. The Sacra media arises from the aorta at its bifurcation into the two iliacs; it descends along the front of the sacrum, giving branches on either side, which enter the anterior sacral foramina, and supply the sacral nerves. The Inferior vena cava (fig. 81. 10.) commences at the fourth lumbar vertebra, being formed by the union of the two common iliac veins, 18. 11. It ascends along the front of the vertebral column on the right side of the aorta, and reaches the posterior border of the liver. It then passes through a groove in that organ, and through the opening in the central tendon of the diaphragm, and terminates in the under part of the right auricle. Relations.—It is crossed in front by the pancreas, transverse duodenum and mesentery, and behind by the right renal and lumbar arteries. To its left is the aorta, and on the right the sympathetic nerve. Branches.—The branches which the inferior vena cava re- ceives in the abdomen, are the Vena-sacra media (fig. 81. 14.) Lumbar - - 15. Right spermatic - 16. Renal 17. 18. Hepatic. - - 19. _ The Vena sacra media (fig. 81. 14.) terminates at the junc- tion of the two common iliac veins. The Lumbar veins, 22. 15., return the venous blood from the muscles of the posterior part of the abdomen, and from the spinal veins. The upper lumbar branches communicate with the azygos veins. The Right spermatic vein (fig. 81. 16.) is formed by the THE DISSECTOR. 71 union of the veins of the right spermatic cord. It follows the course of the right spermatic artery, and terminates in the inferior cava. The Renal veins (fig. 81. 17. 18.) return the venous blood from the kidneys ; the left is longer than the right, on account of the position of the vena cava on the right side, and crosses the aorta to open into it. The spermatic vein of the left side terminates, at right angles, in the left renal vein: hence arises an impediment to the return of the blood, both on account of the greater length of the left than the right spermatic vein, and the direction of its entrance into the renal vein. As a consequence of this obstacle, varicocele occurs most frequently on the left side. The Hepatic veins are of very large size, and open into the cava while that vessel is situated within the liver. Kidneys. The Kidneys are situated in the lumbar regions, on each side of the vertebral column, and A section of the behind the peritoneum. liiey are kidney; surmounted by the usually enclosed in a quantity of fat, supra - renal capsule; the and rest upon the anterior lamella of swellings upon the surface , • p j_i v mark the original constitution the aponeurosis of the transversalis of the organ by distinct lobes. muscle, which separates them from the quadratus lumborum, upon the lower border of the diaphragm. They are surmounted by the renal cap- sules, two yellowish triangular and flattened bodies, which project in- wards towards the vertebral column, and are closely connected with the semilunar ganglia, from which they receive a number of filaments. The renal capsules belong to the economy of the faetus, in which they are as large as the kidneys themselves. In the adult they consist of two lobes, and have an internal cavity, which contains a dark coloured fluid. 1. The supra-renal capsule. 2. The vascular portion of the kidney, 3. 3. Its tubular portion, consisting of cones. 4, 4. Two of the papillae pro- iecting into thin corresponding calices. 5, 5, 5. The three infundibula; the middle 5 is situated in the mouth of a calyx. 6. The pelvis. 7. The ureter. 72 THE DISSECTOR. *V The right kidney is somewhat lower than the left, being pressed downward by the liver; it is in relation in front with the descending portion of the duodenum. The concavity of the kidney is directed towards the verte- bral column, and receives the vessels; the convexity looks outwards towards the parietes. Structure.—Each kidney is invested by its proper fibrous capsule. When divided by a perpendicular section, it presents two structures, an external, vascular (cortical,) which is of a red colour, and consists chiefly of the ramifications of vessels, and an internal, tubular (medullary,) of a light colour and smooth texture, formed by the aggregation of the minute excretory, tubuli. The tubuli are arranged into conical processes, called Cones. Each cone terminates in a Papilla, which is pierced by a number of minute openings, which are the terminations of the tubuli. The points of the papillae are invested with mucous membrane, which is continuous with the lining of the tubuli, and forms a small cup-like pouch, the Calyx, around the extremity of each papilla. There are from fifteen to twenty of these calices. Their union at each ex- tremity, and in the middle of the kidney, forms three larger cavities, the Infundibula, and the union of the three infundi- bula constitutes the Pelvis, from which the ureter passes downwards to the urinary bladder. The Ureters are dilatable tubes, of about the size of a goose quill, and eighteen inches in length. They descend along the posterior wall of the abdomen, and cross, in their course, the psoas muscle, common iliac artery, and vas defe- rens, and terminate in the posterior and lateral part of the base of the bladder, after passing for some distance obliquely between its coats. At the concave border of the kidney, the vessels observe the following relation to each other from before backwards, the veins are situated most superficially next the branches of the artery, and then the pelvis and ureter. The kidney is supplied with nerves by the renal plexus, which is _ derived from the solar plexus and from the lesser splanchnic nerve. The student must now examine the Muscles, which are situated on the posterior wall of the abdomen. These are the Diaphragm, Psoas parvus, Psoas magnus^ Quadratus lumborum, Iliaeus internus. THE DISSECTOR. 73 Diaphragm.—To obtain a good view of this important inspiratory muscle, the peritoneum should be dissected from its under surface. It is the muscular septum between the thorax and abdomen, and is composed of two portions, a greater and a lesser muscle. The greater muscle arises from the ensiform cartilage, from the inner surfaces of the six inferior ribs, indigitating with the transversalis, and from the ligamentum arcuatum externum, and internum. From these Fig. 22. The under or abdominal side of the diaphragm. 1, 2, 3. The greater muscle; the figure 1 rests upon the central leaflet of the tendinous centre; the number 2 on the left or smallest leaflet; and num- ber 3 on the right leaflet, 4. The thin fasciculus which arises from the en- siform cartilage; a small triangular space is left on either side of this fas- ciculus which is closed only by the serous membrane of the abdomen and chest. 5. The ligamentum arcuatum externum of the left side. 6. The ligamentum arcuatum internum. 7. A small arched opening occasionally found, through which the lesser splanchnic nerve passes. 8. The right or larger tendon of the lesser muscle; a muscular fasciculus from this tendon curves to the left side of the greater muscle between the oesophageal and aor- tic openings. 9. the fourth lumbar vertebra. 10. The left or shorter ten- don of the lesser muscle. 11. The aortic opening occupied by the aorta, which is cut short off. 12. A portion of the oesophagus issuing through the oesophageal opening. 13. The opening for the inferior vena cava, in the tendinous centre of the diaphragm. 14. The psoas magnus muscle passing be- neath the ligamentum arcuatum internum; it has been removed on the oppo- site side to show the arch more distinctly. 15. The quadratus lumborum passing beneath the ligamentum arcuatum externum; this muscle has also been removed on the left side. 71 THE DISSECTOR. points which form the internal circumference of the trunk, the fibres converge and are inserted into the central tendon. The Ligamentum arcuatum externum is a fibrous band, extending from the last rib to the transverse _ process of the first lumbar vertebra, it arches across the origin of the quad- ratus lumborum muscle, and gives attachment to the posterior fibres of the greater muscle of the diaphragm above, and to the anterior lamella of the transversalis below. The Ligamentum arcuatum internum, or proprius, is a tendinous arch thrown across the psoas magnus muscle as it emerges from the chest. It is attached by one extremity to the transverse process of the first lumbar vertebra, and by the other to the body of the second. The Tendinous centre of the diaphragm is shaped like a tre- foil leaf; of which the central leaflet points to the ensiform car- tilage, and is the largest; the lateral leaflets, right and left, occupy the corresponding portions of the muscle; the right being the larger and more rounded, and the left smaller and lengthened in its form. Between the sides of the ensiform cartilage and the carti- lages of the adjoining ribs, is a small triangular space where the muscular fibres of the diaphragm are deficient. This space is closed only by peritoneum on the side of the abdomen, and by pleura within the chest. It is therefore a weak point, and a portion of the contents of the abdomen might by vio- lent exertion, be forced through it, producing phrenic or dia- phragmatic hernia. The Lesser muscle of the diaphragm takes its origin from the bodies of the lumbar vertebrae by two tendons. The right, larger and longer than the left, arises from the anterior sur- face of the bodies of the second, third, and fourth vertebrae; and the left from the side of the second and third. The tendons form two large fleshy bellies (crura,) which ascend to be inserted into the central tendon. The inner fasciculi of the two crura cross each other in front of the aorta, and again diverge to surround the oesophagus, so as to present a figure-of-eight like appearance. The anterior fasciculus of the decussation is formed by the right crus. The Openings in the diaphragm are three: one, quadrilate- ral in the tendinous centre, at the union of the right and middle leaflets, for the passage of the inferior cava; a mus- cular opening of an elliptic shape, formed by the two crura THE DISSECTOR. 75 for the transmission of the oesophagus and pneumo-gastric nerves ; and a third, the aortic, which is formed by a tendinous arch thrown from the tendon of one crus to that of the other across the vertebral column, beneath which pass the aorta, the right vena azygos, and the thoracic duet. One of the splanchnic nerves sometimes passes through the aortic opening, but more frequently they both pierce the crura. The lesser splanchnic nerves pass between the muscular fibres, which proceed from the ligamentum arcuatum internum at each* side. The Psoas magnus muscle lies at each side of the vertebral column in the lumbar region. It arises from the interverte- bral substance of the last dorsal and four upper lumbar ver- tebrae, and from a tendinous arch thrown across the constricted portion of the bodies of the same bones. These arches are intended to protect the lumbar arteries, and communicating branches of the sympathetic nerve. It is inserted with the iliacus muscle by a common tendon into the lesser trochanter of the femur. The psoas muscle is traversed by the branches of the lum- bar plexus, and is pierced by the genito-crural nerve, which runs upon its anterior surface. The Psoas parvus arises from the tendinous arches and in- tervertebral substance of the last dorsal and first lumbar ver- tebrae, and soon terminates in a long slender tendon which is inserted into the pectineal line of the pubis. The psoas and iliacus muscles are covered in by the iliac fascia, which may now be examined. It will be found at- tached to the inner margin of the crest of the ilium, and to the folded border of Poupart's ligament; in both of which situations it is continuous with the transversalis fascia. It crosses the psoas muscle, and passes beneath the iliac vessels to be attached to the brim of the pelvis, where it is continuous with the pelvic fascia. Below it forms the posterior wall of the sheath of the femoral vessels: and above it is continued upon the psoas muscles to be attached to the sides of the lum- bar vertebrae and ligamentum arcuatum internum. The Iliacus interims muscle occupies the fossa on the inner surface of the ilium, from which it arises. It is crossed by the external cutaneous nerve and the crural nerve lies in the groove between it and the psoas magnus. It is inserted by a 76 THE DISSECTOR. tendon common to it and the psoas magnus, into the trochanter minor. The psoas magnus shonld be removed, in order to bring into view the quadratus lumborum muscle. The Quadratus lumborum muscle is concealed from view by the anterior lamella of the aponeurosis of the transversalis muscle, which is inserted hno the bases of the transverse processes of the lumbar vertebrae, and ligamentum arcuatum externum. When this lamella is divided the muscle will be seen arising from the last rib, and from the transverse pro- cesses of the four upper lumbar vertebrae. It is inserted into the posterior fourth of the crest of the ilium. If the muscle be cut across or removed, the middle lamella of the trans- versalis will be seen attached to the apices of the transverse processes; the quadratus being enclosed between the two lamellae as in a sheath. Actions.—The diaphragm is an inspiratory muscle, the con- traction of its fibres increasing the cavity of the chest. It acts also as a muscle of expulsion, by pressing upon the abdo- minal viscera, as in the expulsion of the excretions of the foetus, &c. The spasmodic action of the muscle produces hie- up, sobbing, &c. The psoas and iliacus muscles, flex the trunk upon the lower extremities or the legs upon the pelvis, at the same time everting the foot. The quadratus lumborum is an ex- piratory muscle, and assists in fixing the chest. The psoas magnus, if not previously removed, must now be carefully dissected from its origin for the purpose of bringing into view the lumbar plexus of nerves, which is situated be- hind it. The Lumbar plexus of nerves is formed by the anterior branches of the last dorsal and four upper lumbar nerves. The posterior branches passing backwards, to be distributed to the muscles and integument of the loins. The anterior branches increase in size from above downwards, and the pos- terior diminish in like proportion. The plexus is connected by communicating branches passing from one nerve to the other at their exit from the intervertebral foramina, besides which, each trunk receives one or two filaments from the lumbar ganglia of the sympathetic. The Branches of the lumbar plexus are the THE DISSECTOR. 77 Musculo-cutaneous, Crural, External cutaneous, Obturator. Genito-crural, The Musculo-cutaneous nerves (fig. 98. 3.,) two in number, proceed from the first lumbar nerve. They cross the quad- ratus lumborum muscle, and, piercing the transversalis, di- vide into, two branches; a cutaneous branch, which pierces the muscle, and is distributed to the integument over the hip and buttock; and a muscular branch, which winds along the crest of the ilium, and is distributed to the abdominal muscles, lying first between the transversalis and internal oblique, and then between the internal and the external oblique muscle. The superior nerve, after piercing the fibres of the internal oblique muscle, passes through the external ring with the spermatic cord, and is distributed to the scrotum; hence it is often called ilio-scrotal. The inferior nerve supplies the ab- dominal muscles. The External cutaneous nerve (fig. 98. 4.,) (inguino-cutan- eous) proceeds from the second lumbar nerve. It pierces the posterior fibres of the psoas muscle, and crossing the iliacus obliquely to the anterior superior spinous process of the ilium, passes into the thigh beneath Poupart's ligament, and distri- butes cutaneous branches to the integument of the groin and of the outer side of the thigh. The Genito-crural (fig. 98. 5.,) proceeds also from the se- cond lumbar nerve. It traverses the psoas magnus from behind forwards, and runs down on its anterior surface to near Poupart's ligament, where it divides into two branches; genital, which passes through the internal abdominal ring, and is distributed to the spermatic cord; and crural, which supplies the integument on the inner side of the thigh. The Crural nerve (fig. 98. 6.,) is formed by the union of branches from the second, third, and fourth lumbar nerves. It passes beneath the psoas magnus, and runs along its outer border to the thigh, where it is distributed. The Obturator nerve (fig, 98. 12.)is formed by the union of two branches, one from the third and the other from the fourth lumbar nerve. It runs along the inner border of the pelvis, resting upon the pelvic fascia to the obturator foramen, through which it emerges to supply the muscles on the inner side of the thigh. The last lumbar nerve, the lumbosacral (fig. 107. 1.) de- 7* 78 THE DISSECTOR. scends into the pelvis to join the four upper sacral nerves, and assists in forming the sacral plexus. CHAPTER III. HEAD AND NECK. The Head may be considered as an expansion of the supe- rior part of the vertebral column, for the reception of the brain and the principal organs of sense. The Neck is the medium of communication and connexion between the head and the rest of the body;—communication, by means of the trachea and oesophagus, with the internal organs: connexion, by means of the muscles and vertebral column, with the superficies and osseous fabric of the trunk. The head may be divided into the cranium and face, the former being the osseous recipient of the brain, and the latter the apparatus for the development and protection of the principal organs of sense. The exterior of the cranium presents but little for the study of the anatomist; the face is more varied, comprehending—1. The orbits for the organs of vision: 2. The nose or external organ of smell; 3. The mouth, containing the organ of taste; 4. The jaws or apparatus of mastication; and, immediately behind the jaws on the sides of the base of the skull, 5. The external organ of hearing. We shall commence the dissection of the head and neck, by devoting one side to the learning of the muscles, reserving the other for the study of the vessels and nerves. The Occipito frontalis is to be dissected by making a longi- tudinal 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, begin- ning 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 atten- THE DISSECTOR. 79 tion would be raised with the integument. There is no deep fascia on the face and 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 a distinct sheath. The attachments of the Occipito-frontalis are expressed in its name. It arises from the rough surface immediately above the superior curved line of the occipital bone, being separated from its fellow by a considerable interval, and arches over the head to be inserted into the orbicularis palpebrarum and the nasal tuberosity of the frontal bone. A narrow slip from each muscle is continued downwards upon the nasal bones to form the pyramidalis nasi muscle. The muscle is fleshy in front over the frontal bone, and behind over the occipital, the two portions being connected by a broad tendinous aponeurosis. The muscles of opposite sides cover the whole of the vertex of the skull, from the middle line to the temporal ridge. After examining the occipito-frontalis muscle, the student should remove the brain, as being the portion of the head most susceptible of decomposition. To examine the encephalon with its membranes, the upper part of the skull must be removed by sawing through the external table, and breaking the internal table with the chisel and hammer. After the calvarium has been loosened all round, it will require a considerable degree of force to tear the bone away from the dura mater. This adhesion is particularly firm at the sutures, where the dura mater is continuous with a membranous layer interposed between the edges of the bones : in other situations, the connexion results from nume- rous vessels which permeate the inner table of the skull. The adhesion subsisting between the dura mater and bone is greater in the young subject than in the adult. ^ Upon being torn away, the internal table will present the deeply grooved and ramified channels corresponding with the branches of the arteria meningea media. Along the middle line will be seen a groove corresponding with the superior longitudinal sinus, and on either side may be frequently observed some depressed fossae corresponding with the Pac- chionian bodies. 80 THE DISSECTOR. The membranes of the encephalon and spinal cord are the dura mater, arachnoid membrane, and pia mater. The Dura mater* is the firm, bluish, fibrous membrane which is exposed on the removal of the calvarium. It lines the interior of the skull and spinal column, and sends pro- cesses inwards for the support and protection of the different parts of the brain. It also sends processes externally, which form sheaths for the nerves as they quit the skull and spinal column. Its external surface is rough and fibrous, and cor- responds with the internal table of the skull. The internal surface is smooth, and lined by the thin varnish-like lamella of the arachnoid membrane. The latter is a serous membrane. Hence the dura mater becomes a fibro-serous membrane, being composed of its own proper fibrous structure, and the serous layer derived from the arachnoid. There are two other in- stances of fibro-serous membrane in the body, formed in the same way — the pericardium and tunica albuginea of the testicle. On either side of the dura mater, the branches of the middle meningeal artery may be seen ramifying; and in the middle line is a depressed groove, formed by the subsidence of the upper wall of the superior longitudinal sinus. If the sinus be opened along its course, it will be found to be a triangular channel, crossed at its lower angle by numerous white bands, called chordae Willisii ;f granular bodies are also occasionally seen in its interior: these are glandulae Pacchioni. The Glandular Pacchioni\ are small, round, whitish granu- lations, disposed in clusters. They are found in three situa- tions : 1. On the dura mater, to either side of the superior longitudinal sinus, where they often produce considerable indentations in the inner wall of the skull; 2. In the superior longitudinal sinus ; 3. On the under surface of the dura mater, by the side of the sinus, connecting that membrane to the arachnoid and pia mater. * So named from a supposition that it was the source of all the fibrous membranes of the body. f Willis lived in the seventeenth century: he was a great defender of the opinions of Harvey. % These bodies have no analogy whatsoever with glands. Their nature and use are but imperfectly known. They are not found in infancy. They were described as conglobate glands by Pacchioni, in an epistolary disserta- tion, "De Glandulis Conglobsitis Durae Meningis indeque ortis Lymphaticis ad Piam Matreni productis," published in Rome, in 1705. THE DISSECTOR. 81 If the student cut through one side of the dura mater, and turn it upwards towards the middle line, he will observe the smooth internal surface of the dura mater. He will perceive also the large cerebral veins filled with dark blood, passing from behind forwards to open into the superior longitudinal sinus, and the firm connexions by means of these veins and the Pacchionian bodies between the dura mater and the pia mater. If he separate these with his scalpel, he will see a vertical layer of dura mater descending between the hemi- spheres, and if he draw one side of the brain a little outwards, he will distinctly perceive its extent: this is the falx cerebri. The processes of dura mater which are sent inwards towards the interior of the skull, are the falx cerebri, tentorium cere- belli, and falx cerebelli. The Falx cerebri, (falx, a sickle,) so nsftned from its sickle- like appearance, narrow in front, broad behind, and forming a sharp curved edge below, is attached in front to the crista galli process of the ethmoid bone, and behind to the tentorium cerebelli. The Tentorium cerebelli (tentorium, a tent,) is a roof of dura mater, thrown across the cerebellum and attached to the margin of the petrous portion of the temporal bone at each side, to the transverse ridge of the occipital bone, which lodges the lateral sinuses behind, and to the clinoid processes in front. It supports the posterior lobes of the cerebrum, and prevents their pressure* on the cerebellum leaving only a small opening anteriorly, for the transmission of the crura cerebri. The Falx cerebelli is a small process attached to the vertical ridge of the occipital bone beneath the lateral sinus, and to the tentorium. It is received into the indentation between the two lobes of the cerebellum. The student cannot see the two latter processes until the brain is removed; but he should consider the attachments of the tentorium upon the dried skull, for he will have to divide it in the removal of the brain. He should now proceed to that operation, for which purpose the dura mater is to be in- cised all round, on a level with the section through the skull, and the scissors are to be carried deeply between the hemi- spheres of the brain in front, to cut through the anterior part * In leaping animals, as the feline and canine genera, the tentorium forms a bony tent. 82 THE DISSECTOR. of the falx ; then draw the dura mater backwards, and leave it hanging by its attachment to the tentorium. Raise the anterior lobes of the brain carefully with the hand, and lift the olfactory bulbs from the cribriform fossae with the handle of the scalpel. Then cut across the two optic nerves and internal carotid arteries. Next divide the infundibulum and third nerve, and carry the knife along the margin of the petrous bone at each side, so as to divide the tentorium near its attachment. Cut across the fourth, fifth, sixth, seventh, and eighth nerves in succession with a sharp knife, and pass the scalpel as far down as possible into the vertebral canal, .to sever the spinal cord, cutting first to one side and then to the other, in order to divide the vertebral arteries and first cervical nerves. Then let him press the cerebellum gently forwards with the fingers of the right hand, the hemispheres being supported with the left, and the brain will roll into his hand. We shall now complete the description of the dura mater to avoid perplexing the student by recurring to it in another place; but we would counsel him to commence the examina- tion and study of the brain, while it is firm and fresh. The layers of the dura mater separate in several situations, so as to form irregular channels which receive the venous blood. These are the sinuses of the dura mater: they are lined in their interior by a continuation of the lining mem- brane of the veins. The Superior longitudinal sinus is formed by the splitting of the layers of the dura mater along the line of attachment of the falx cerebri. It is triangular in form, is narrow ante- riorly, and increases in breadth as it proceeds backwards. It terminates at the middle of the occipital bone, by dividing into the two lateral sinuses. This sinus sometimes communi- cates in front with the nasal veins through the foramen coecum. In its interior are found the chordae Willisii above described, and some Pacchionian bodies. The cerebral veins opening into the superior longitudinal sinus present a very peculiar disposition: they enter from behind forwards directly oppo- site to the venous current in the sinus, and so obliquely that the inner wall of the vein is enabled to perform the ofiice of a valve, and prevent the reflux of the blood into the veins in an over-distended condition of the sinus. The Inferior longitudinal sinus is much smaller than the THE DISSECTOR. 83 superior. It is circular in its form, and contained within the free margin of the falx cerebri. It terminates posteriorly in the straight sinus at the anterior border of the tentorium. The Straight sinus, (fourth,) is the sinus of the tentorium. It receives the venae Galeni* from the velum interpositum, and runs backwards along the arch of the tentorium to the termi- nation of the superior longitudinal sinus. Fig. 23. The sinuses of the upper and back part of the skull. 1. The superior longitudinal sinus 2, 2. The cerebral veins opening into the sinus from behind forwards. 3. The falx cerebri. 4. The inferior lon- gitudinal sinus. 5. The straight or fourth sinus. 6. The venae Galeni. 7. The torcular Herophili. 8. The two lateral sinuses, with the occipital sinuses between them. 9. The termination of the inferior petrosafsinus of one side. 10. The dilatations corresponding with the jugular fossae. 11. The internal jugular veins. The Occipital sinus is a small venous channel, which col- lects its blood from around the foramen magnum, and ascends along the fixed border of the falx cerebelli, to terminate in the torcular Herophili. The Lateral sinuses, starting from the termination of the superior longitudinal, curve around the occipital bone in the fixed border of the tentorium, and descend on each side behind the base of the petrous bone to the foramen lacerum posterius, where they pour their current into the internal jugular vein. These sinuses rest successively on the occipital * Claudian Galen, chief of the Greek physicians after Hippocrates, was born about the year 130. 84 THE DISSECTOR. bone, posterior inferior angles of the parietal, temporal, and occipital bones. The point of termination of the superior longitudinal sinus is therefore the centre of convergence of the straight and occipital sinuses, and the starting point of the lateral sinuses. Hence it is named the conflux of the sinuses or torcular He- rophili.* The sinuses of the base of the skull are as follows:— The Cavernous sinuses are so named from presenting a cellular structure in their interior. They are placed on the side of the sella turcica, receiving the ophthalmic veins ante- riorly, and terminating posteri- Fig. 24. The sinuses of the base 0rlv in the inferior petrosal si- «f fiio ot„n J r nuses. In the outer wall of this sinus (fig. 48.) are situated the third, fourth, and ophthalmic nerves, and in the inner wall with the internal carotid artery, the sixth nerve, and branches of the carotid plexus. These parts are separated from the blood of the sinus only by its lining mem- brane. The Inferior petrosal sinuses are the continuations of the cav- ernous sinuses backwards along the lower border of the petrous bone to the foramen lacerum pos- terius, where they open with the lateral sinuses into the internal jugular veins. 1. The ophthalmic veins. 2. The cavernous sinus of one side. 3. The circular sinus; the figure occupies the position of the pituitary gland in the sella turcica. 4. The inferior petrosal sinus. 5. The transverse or anterior occipital sinus. 6. The superior petrosal sinus. 7. The internal jugular vein. 8. The foramen magnum. 9. The occipital sinuses. 10. The torcu- lar Herophilii. 11, 11. The lateral sinuses. *_Torcular, (a press,) from a supposition entertained by the older ana- tomists that the columns of blood, coming in different directions, compressed each other at this point. Herophilus was a great anatomist, and was well informed on many parts of the human structure; he lived about 500 years before Christ. THE DISSECTOR. 85 The remaining sinuses are communicating channels passing between the preceding; thus, The Circular sinus is situated in the sella turcica, sur- rounding the pituitary gland, and communicates on either side with the cavernous sinus. The Superior petrosal sinus runs along the attached border of the tentorium, on the upper margin of the petrous bone, and establishes a communication between the cavernous and the lateral sinus at each side. The Transverse simis (basilar, anterior occipital) passes transversely across the basilar process of the occipital bone, forming a communication between the two inferior petrosal sinuses. The sinuses of the dura mater communicate with the ex- terior of the skull by several large veins. On the summit of the skull a considerable vein opens into the superior longitu- dinal sinus, through the parietal foramen. Behind the ear a large vein opens into the lateral sinus, through the mastoid foramen; and at the base of the skull, another communicates with the lateral sinus, through the posterior condyloid fora- men. They communicate also very freely with the sinuses of the diploe. The Arteries of the dura mater are the Anterior meningeal from the internal carotid. Middle meningeall from the ^^ maxin Memngea parva J ^ Inferior meningeal from the ascending pharyngeal and occipital arteries. Posterior meningeal from the vertebral. The Nerves are derived from the nervi molles of the sym- pathetic, the Casserian ganglion, the ophthalmic nerve, and sometimes from the fourth; they are given off while these nerves are situated by the side of the sella turcica. The branches of the ophthalmic and fourth nerves are recurrent, and are distributed between the layers of the tentorium as far as the lateral sinus. Arachnoid Membrane. The Arachnoid (apo,*^—«&>?, like a spider's web,) so named from its extreme tenuity, is the serous membrane of the cere- bro-spinal centre, and, like other serous membranes, a shut 8 86 THE DISSECTOR. sac. It envelopes the brain and spinal cord, and is reflected upon the inner surface of the dura mater, giving to that mem- brane its serous investment. The arachnoid is thin and transparent on the upper surface of the brain, and may be demonstrated by inserting a blow- pipe and injecting beneath it a stream of air. In other situations, as at the base of the brain and between the cere- bellum and medulla oblongata, it is semitransparent and dense in its structure, and is rendered very evident by passing across from one convexity to another. In inflammation of the me- ninges, this membrane is often thickened and opaque. The arachnoid is attached to the surface of the pia mater by a loose cellular tissue ; the sub-arachnoidean. This tissue is filamentous at the base of the brain, between the hemi- spheres, and around the spinal cord, where the arachnoid is disposed very loosely. The Sub-arachnoidean cellular tissue is the seat of an abundant serous secretion, the sub-arachnoidean fluid, which fills all the vacuities existing between the arachnoid and pia mater, and distends the arachnoid of the spinal cord so com- pletely, as to enable it to occupy the whole of the space included in the sheath of the dura mater. The arachnoid also secretes a serous fluid from its inner surface, which is small in quantity compared with the sub- arachnoidean liquid. It does not enter into the ventricles of the brain, as imagined by Bichat, but is reflected inwards upon the venae Galeni for a short distance only, and returns upon those ves- sels to the- dura mater of the tentorium. It surrounds the nerves as they originate from the brain, and forms a sheath around them to their point of exit from the skull. It is then reflected back upon the inner surface of the dura mater. The cerebral nerves are retained in connection with the brain prin- cipally by this membrane, so that, in separating it from the brain, the nerves are also torn away. There are no vessels apparent in the arachnoid, and no nerves have been traced into it. Pia Mater. The Pia Mater is a vascular membrane composed of innu- merable vessels held together by a thin cellular layer. It invests the whole surface of the brain, dipping into its convo- THE DISSECTOR. 87 lutions, and forming a fold in its interior called velum inter- positum. It forms folds ('choroid plexuses,) also, in other situations, as in the fourth ventricle, and in the longitudinal grooves of the spinal cord. This membrane differs very strikingly in its structure in different parts of the cerebro-spinal axis. Thus, on the sur- face of the cerebrum, in contact with the soft gray matter of the brain, it is excessively vascular, forming remarkable loops of anastomoses between the convolutions, and distributing multitudes of minute straight vessels to the gray substance. In the substantia perforata, again, and locus perforatus, it gives off tufts of small arteries, which pierce the white matter to reach the gray substance in the interior. But upon the crura cerebri, pons Varolii, and spinal cord, its vascular cha- racter seems almost lost. It has become a dense fibrous mem- brane, difficult to tear off, and forming the proper sheath of the spinal cord. The pia mater is the nutrient membrane of the brain, and derives its blood from the internal carotid and vertebral arte- ries. Its Nerves are the minute filaments of the sympathetic, which accompany the branches of the arteries. The Arteries of the brain maintain a remarkable communi- cation at its base, which is called the Circle of Willis. If the arachnoid membrane be removed, and the connexions of the pia mater slightly separated, these vessels may be distinctly seen and examined. At the fissure of Sylvius the internal carotid artery will be seen to divide into three branches: Anterior cerebral, Middle cerebral, Posterior communicating. The Anterior cerebral artery passes forwards in the great longitudinal fissure between the two hemispheres of the brain; then curves backwards along the corpus callosum, and inoscu- lates with the posterior cerebral artery. It gives branches to the inner surface of the hemispheres. The two anterior cerebral arteries are connected soon after their origin by a short anastomosing trunk, the anterior communicating. The Middle cerebral artery passes outwards along the fissure of Sylvius, and divides into several large branches, which supply the anterior and middle lobes. Near its origin it gives off the numerous small branches which enter the substantia perforata. 88 THE DISSECTOR. The Posterior communicating artery, very variable in size, sometimes double, and sometimes altogether absent, passes backwards and inosculates with the posterior cerebral, a branch of the basilar. Commencing at the posterior extremity of the base of the brain, the two Vertebral arteries will be seen converging to the inferior border of the pons Varolii, where they form the Basilar. The vertebrals are often unequal in size, one being much larger than the other. Their branches within the skull are, Anterior spinal, Posterior spinal, Posterior meningeal, Inferior cerebellar. The Anterior spinal is a small artery which unites with its fellow of the opposite side, and forming a common trunk, de- scends on the anterior aspect of the spinal cord to the cauda equina, where it is distributed. The Posterior spinal winds around the medulla oblongata to the posterior aspect of the cord, and descends on either side nearly as far as the cauda equina, communicating very freely with the spinal branches of the intercostal arteries. The Posterior meningeal, often a branch of the inferior cerebellar, is distributed to the dura mater. The Inferior cerebellar arteries wind around the upper part of the medulla oblongata to the under surface of the cere- bellum, to which they are distributed. This artery gives off a small branch which accompanies the seventh pair of nerves into the meatus auditorius internus. The Basilar artery, so named from its position at the base of the skull, runs forwards to the upper border of the pons Varolii, where it divides into four ultimate branches, two to either side. While resting against the pons, it gives off seve- ral transverse branches to the crura cerebelli. Its branches are, Transverse, Superior cerebellar, Posterior cerebral. The Superior cerebellar supplies the upper surface of the cerebellum, and inosculates with the inferior cerebellar. The Posterior cerebral passes off on either side to the pos- terior lobes of the cerebrum, and communicates on the corpus callosum with the anterior cerebral arteries. It is separated from the superior cerebellar artery, by the third nerve, and is in close relation with the fourth, in its course around the crus cerebri. Anteriorly near its origin, it gives off a tuft of small vessels, which enter the locus perforatus, and it re- THE DISSECTOR. 89 ceives the posterior communicating arteries from the internal carotid. Fig. 25. The circle of Willis. The branches of the arteries have refe- rences only on one side, on account of their symmetrical distribution. 1. The vertebral arteries. 2. The two anterior spinal branches uniting to form a single vessel. 3. One of the posterior spinal arteries. 4. The posterior meningeal. 5. The inferior cerebellar. 6. The basilar artery giving off its transverse branches to either side. 7. The superior cerebellar artery 8. The posterior cerebral. 9. The posterior communicating branch of the internal carotid. 10. The internal carotid artery, showing the cur- vatures it makes within the skull. 11. The ophthalmic artery divided across. 12. The middle cerebral artery. 13. The anterior cerebral arteries con- nected by, 14. The anterior communicating artery. The communications established between the anterior cere- bral arteries in front, and the internal carotids and posterior cerebral arteries behind, by the communicating arteries, con- stitute the Circle of Willis. Were we called upon to answer how this circle was formed, we should say by the anterior communicating, anterior cerebral arteries, and internal caro- 90 THE DISSECTOR. tids; posterior communicating, posterior cerebrals, and basi- lar artery. The Circle of Willis includes within its area, several parts of the base of the brain, which should also be attended to. They may probably be more advantageously explained by the following plate. . The Cerebro-spinal axis or centre consists of the brain and spinal cord. The Encephalon (tv xt$, broad muscle-like THE DISSECTOR. 125 lamella,) is a thin plane of muscular fibres, arising betAveen the two layers of superficial fascia, over the pectoralis major muscle, and passing obliquely upAvards and inwards, along the side of the neck, to be inserted into the body of the lower jaw, the angle of the mouth, and side of the chin. The an- terior fibres are continuous below the chin with the^ muscle of the opposite side. That portion of the muscle which is con- tinued upwards to the angle of the mouth, was formerly called risorius Santorini* (the laughing muscle of Santorinus). The entire muscle is analogous to the cutaneous muscle of brutes, panniculus carnosus. Upon removing the platysma, and with it the deep layer of superficial fascia, we bring into view the external jugular vein, and ascending branches of the cervical plexus of nerves. The jugular vein is lying obliquely along the neck, parallel with the fibres of the platysma myoides, Avhile it crosses the direc- tion of the sterno-mastoid muscle. The sterno-mastoid is as yet concealed from view by a layer of fascia, which covers in the whole of the side of the neck. This is the deep cervical fascia, the reflections of which we have next to examine. The Deep cervical fascia differs in structure from the deep fascia of the limbs, in having no tendinous fibres, and being composed entirely of condensed cellular tissue. It is attached posteriorly along the middle line of the neck to the ligamen- tum nuchae, being overlapped by the trapezius muscle. It then passes forwards around the side of the neck to the posterior border of the sterno-mastoid, where it divides into two layers which embrace that muscle, and unite again at its anterior border. It is then directed onwards to the middle line, Avhere it becomes continuous with the deep fascia of the opposite side of the neck. The anterior layer, that which is superficial to the sterno-mastoid, is prolonged upwards on the side of the jaw and parotid gland, and downwards over the clavicle and pectoralis major muscle. The posterior layer, which can only be examined by removing or drawing aside the sterno-mastoid muscle, is attached superiorly to the styloid process of the temporal bone, and is thence reflected to the angle of the jaAv, * John Dominico Santorinus, Professor of Anatomy in Venice. His no- tice of this muscle is contained in his "Observations Anatomicre," published 126 THE DISSECTOR. forming the stylo-maxillary ligament. Inferiorly it forms a loop, which acts as a pulley to the omo-hyoid muscle, and is then continued doAvmvards behind the clavicle, so as to enclose the subclavius muscle. The extremities of the latter portion are attached firmly to the cartilage of the first rib and to the coracoid process: hence it is named costo-coracoid membrane or ligament. In the middle line the deep fascia is continuous with the thoracic fascia. This fascia is of great importance in a surgical point of view. In its normal condition, it binds down firmly all the structures of the neck, and preserves their natural position. When, however, tumours form beneath it, as bronchocele, en- largements of the lymphatic glands, aneurism, &c, the press- ure which is then exerted by this membrane may be fatal to the patient, from the compression of the trachea, larynx, and nerves, unless the tension be relieved by an incision. The Sterno-cleido mastoid muscle is to be exposed by open- ing the sheath formed around it by the deep fascia. It arises, as its name implies, from the sternum and claATicle, (*toioW,) and passes obliquely upwards and backwards to be inserted into the mastoid process and superior curved line of the occi- pital bone. The sternal portion arises by a rounded tendon, increases in breadth as it ascends, and spreads out to a con- siderable extent at its insertion. The clavicular portion is broad and fleshy, and separate from the sternal portion below, but becomes gradually blended with its posterior surface as it ascends. 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 upon the angle of the mouth. The sterno-mastoid muscles are the great anterior muscles of connexion between the thorax and the head. Both muscles acting together will bow the head directly forwards. The clavicular portions, acting more for- cibly than the sternal, give stability and steadiness to the head m supporting great weights. Either muscle acting singly would draw the head towards the shoulder of the same side, and carry the face towards the opposite side. The anterior border of the sterno-mastoid muscle is the guide for the incisions in ligature of the carotid artery. The sterno-mastoid may now be removed, by dividing it THE DISSECTOR. 127 through the middle, and turning aside its ends. The upper end will be seen to be pierced by a large nerve, the spinal accessory of the eighth pair. The deep layer of fascia is then to be dissected from off the side of the larynx and tra- chea, towards the middle line, in order to bring into vieAv the second group of muscles of the neck. The Sterno-hyoideus is a narrow ribband-like muscle, arising from the posterior surface of the first bone of the sternum and sterno-clavicular articulation, and from the cartilage of the first rib. It is inserted into the body of the os hyoides. The sterno hyoidei are separated by a considerable interval at the root of the neck, but approach each other as they ascend. The Sterno-thyroideus, broader than the preceding, arises from the posterior surface of the upper bone of the sternum, and is inserted into the oblique line on the ala of the thyroid cartilage. The Thyro-hyoideus is the continuation upwards of the sterno-thyroid muscle. It arises from the oblique line on the thyroid cartilage, and is inserted into the body and great cornu of the os hyoides. The Omo-hyoideus (uuo;, shoulder,) passes obliquely across the neck from the scapula to the os hyoides. It arises from the upper border of the scapula, and from the transverse liga- ment of the supra-scapular notch, and is inserted into the body of the os hyoides. It is a double-bellied muscle, its extremities being muscular, and the middle a rounded tendon. The tendon glides through a loop formed by the posterior layer of the deep fascia, which serves it as a pulley. Actions.—The four muscles of this group are the depress- ors 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 folloAving are best dissected by placing a high block beneath the neck, and throwing the head backwards, the in- tegument has been already dissected away, and the removal of the cellular tissue and fat brings them clearly into view. The Digastrius (&$, twice, yaur^p, belly) is fleshy at each extremity, and tendinous in the middle. It arises from the digastric fossa, immediately behind the mastoid process of the temporal bone, and is inserted into a depression on the inner 128 THE DISSECTOR. side of the lower jaw, close to the symphisis. 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. Fig. 35. The muscles of the anterior aspect of the neck; on the left side the superficial muscles are seen, and on the right the deep. 1. The posterior belly of the digastricus muscle. 2. Its anterior belly. The aponeurotic pulley, through which its tendon is seen passing, is at- tached to the body of the os hyoides, 3. 4. The stylo-hyoideus muscle, transfixed by the posterior belly of the digastricus. 5. The mylo-hyoideus. G. The genio-hyoideus. 7. The tongue. 8. The hyo-glossus. 9. The stylo- glossus. 10. The stylo-pharyngeus. 11. The sterno-mastoid muscle. 12. Its sternal origin. 13. Its clavicular origin. 14. The sterno-hyoid. 15. The sterno-thyroid of the right side. 16. The thyro-hyoid. 17. The 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. The clavicular portion of the trapezius. 20. The sca- lenus anticus, of the right side. 21. The scalenus posticus. The Stylo-hyoideus is situated in immediate relation with the posterior belly of the digastricus muscle, by which it is pierced. It arises from the middle of the styloid process, and is inserted into the body of the os hyoides. The digastricus and stylo-hyoideus must be removed from their connexion Avith the lower jaAv and os hyoides, and turned aside to see the next muscle. The Mylo-hyoideus (uu^, mola, i. e. attached to the molar THE DISSECTOR. 129 ridge of the lower jaw) is a broad triangular plane of muscu- lar fibres, forming, Avith its fellow of the opposite side, the inferior wall or floor of the mouth. It arises from the molar ridge on the loAver jaw, and proceeds obliquely inwards to be inserted into the raphe of the two muscles and body of the os hyoides. After the mylo-hyoideus has been examined, it should be cut away from its origin and insertion, and completely re- moved. The view of the next muscles would also be greatly improved by dividing the lower jaw a little to the side of the symphysis, and drawing it outwards 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 (ywuov, the chin) arises from a small tubercle upon the inner side of the symphisis of the lower jaAv, and is inserted into the body of the os hyoides. It is a short prettily formed muscle, very closely connected with the border of the following. The Genio-hyo-glossus (yncwoa, the tongue) is a triangular 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 immediately above that of the genio- hyoideus, and spreads out to be inserted into the whole length of the tongue, from its base to the apex, and into the body of the os hyoides. Actions.—The whole of this group of muscles acts upon the os hyoides, when the lower jaw is closed, and upon 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. The Hyo-glossus is a square-shaped plane of muscle, arising from the whole length of the great cornu of the os hyoides, and inserted into the side of the tongue. This muscle is remarkable from being crossed by two large nerves, the gustatory and lingual, and by the duct (Wharton's) of the submaxillary gland. See fig. 40. The lingual artery and glosso-pharyngeal nerve pass be- hind it. The Lingualis.—The fibres of this muscle may be seen to- wards the apex of the tongue, issuing from the space betAveen 130 THE DISSECTOR. Fig. 36. The styloid muscles and the the hyO-gloSSUS and genio- muscles of the tongue. hyO-gloSSUS. It is better examined, however, by re- moving the preceding mus- cle. It consists of a small fasciculus of fibres, running from the base longitudinal- ly, where it is attached to the os hyoides, to the apex of the tongue. The Stylo glossus arises from the apex of the sty- loid process, and from the s t y 1 o-maxillary ligament, and is inserted into the side of the tongue, nearly as far as the tip, intermingling its fibres with those of the hyo-glossus. 1. A portion of the temporal bone of the left side of the skull including the styloid and mastoid processes, and the meatus auditorius externus. 2. 2. The right side of the lower jaw, divided at its symphysis; the left side having been removed. 3. The tongue. 4. The genio-hyoideus muscle. 5. The genio-hyo-glossus. 6. The hyo-glossus muscle; its basio-glossus portion. 7. Its cerato-glossus portion. 8. The anterior fibres of the lin- gualis issuing from between the hyo-glossus and genio-hyo-glossus. 9. The stylo-glossus muscle, with a small portion of the stylo-maxillary ligament. 10. The stylo-hyoid. 11. The stylo-pharyngeus muscle. 12. The os hyoides. 13. The thyro-hyoidean membrane. 14. The thyroid cartilage. 15. The thyro-hyoideus muscle arising from the oblique line on the thyroid cartilage. 16. The cricoid cartilage. 17. The crico-thyroidean membrane, through which the operation of laryngotomy is performed. 18. The trachea. 19. The commencement of the oesophagus. The Palato glossus passes between the soft palate, and the side of the base of the tongue, forming a projection of the mucous membrane, which is called the anterior pillar of the soft palate. Actions.—The genio-hyo-glossus muscle effects several movements of the tongue, as might be expected from its ex- tent. 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 original position. The whole length of the muscle acting upon the tongue, would render it concave along the THE DISSECTOR. 131 middle line, and form a channel for the current of fluid to- wards the pharynx, as in sucking. The apex of the tongue is directed to the roof of the mouth, and 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 upon the direction of the fibres of the muscles, and their probable actions. We have now proceeded as far as this stage of the dissec- tion will permit us. The examination of the other muscles will require a preparation that would be injurious to the oppo- site side of the neck, which we have as yet kept untouched, for the purpose of studying the arteries and nerves. We post- pone, therefore, the consideration of the remaining layers until the progress of the dissection shall enable us to examine them. The student should now commence the dissection of the opposite side of the face and neck, with a view to study the vessels, nerves, and glands which are situated in those regions. For this purpose he should carry a vertical incision directly downwards in front of the external ear from the posterior part of the temple to the angle of the lower jaw; from this draw four transverse incisions, the uppermost along the middle of the forehead to the middle line, another to the angle of the eyelid, a third to the angle of the mouth, and a fourth along the border of the lower jaw to the chin. Then dissect each of these strips of integument carefully away, so as to expose the superficial fascia over the whole of the side of the face. Immediately in front of the external ear, betAveen it and the ramus of the loAver jaw, is the large salivary gland, the Parotid (rtapa, near; o«j, wfoj, the ear). This gland extends for some little distance over the side of the face, overlapping the masseter muscle. It reaches inferiorly to below the level of the angle of the lower jaw, and posteriorly to the mastoid process, slightly overlapping the insertion of the sterno-mas- toid muscle. At its upper extremity near the root of the zygoma, the temporal artery is seen issuing from beneath it; and in front, along its anterior border, the transversalis facci 132 THE DISSECTOR. artery, the excretory duct, and several branches of the facial nerve will be observed. Fig. 37. The distribution of the facial nerve and the branches of the cer- vical plexus. 1. The facial nerve, escaping from the stylo-mastoid foramen, and cross- ing the ramus of the lower jaw; the parotid gland has been removed in order to see the nerve more distinctly. 2. The posterior auricular branch; the digastric and stylo-mastoid filaments are seen near the origin of this branch. 3. Temporal branches, communicating with (4) the branches of the frontal nerve. 5. Facial branches, communicating with (6) the infra orbital nerve. 7. Facial branches, communicating with (8) the mental nerve. 9. Cervico- facial branches, communicating with (10) the superficialis colli nerve, and forming a plexus (11) over the submaxillary gland. The distribution of the branches of the facial in a radiated direction over the side of the face con- stitutes the pes anserinus. 12. The auricularis magnus nerve, one of the ascending branches of the cervical plexus. 13. The occipitalis minor, as- cending along the posterior border of the sterno-mastoid muscle. 14. The superficial and deep descending branches of the cervical plexus. 15. The spinal^accessory nerve, giving off a branch to the external surface of the trapezius muscle. 16. The occipitalis major nerve, the posterior branch of the second cervical nerve. The duct of the parotid gland (Stenon's duct) proceeds from the upper part of the gland, and crosses the masseter muscle transversely to its anterior border, where it pierces the buccinator muscle, and opens upon the mucous membrane of THE DISSECTOR. 133 the mouth, opposite the second molar tooth of the upper jaw. A second portion of gland is often developed from the duct, while on the masseter muscle, and is called socia parotidis. If the border of the parotid gland be raised, a plexus of large nerves, branches of the facial (portio dura,) will be seen beneath, and in its structure. This plexus is named from bearing some resemblance to the spreading foot of a palmi- pede, pes anserinus (goose's foot). By tracing the branches back through the gland, we reach the trunk of the nerve, and with a little care it may be exposed as far as the point where it issues from the stylo-mastoid foramen. We must then fol- low its branches forwards, in the opposite direction. These will be seen to radiate over the side of the temples, face, and upper part of the neck. The Facial nerve (portio dura) arises from the upper part of the respiratory tract in the medulla oblongata. It enters the meatus auditorius internus with the auditory nerve (portio mollis), and at the bottom of that cavity passes into the canal which is expressly intended for it, the aqueductus Fallopii. In this canal it directs its course at first forwards towards the hiatus Fallopii, where it forms a gangliform swelling, and re- ceives the petrosal branch of the Vidian nerve. It then curves backwards towards the tympanum, and descends along its inner wall to the stylo-mastoid foramen. Emerging at the stylo-mastoid foramen, it passes forwards within the parotid gland, and crossing the external carotid artery to the ramus of the jaAv. While situated within the gland, it is joined by a branch from the auricular nerve, and divides into two trunks, which, by their subdivision and communications, form the pes anserinus. The pes anserinus divides into the numerous branches which supply the muscles over the whole side of the face. The Branches of the Facial Nerve are, Within the aqueductus ( Tympanic, Fallopii. \ (Chorda tympani.*) ._,,, . j7 ("Communicating, After emerging at the \ posterior auri(fuiar5 stylo-mastoid fora- i Di tri men-_______________[Stylo-hyoid._______________ * The chorda tympani is not a branch of the facial, but being in close con- nexion with it, and being given off from it like a branch, we have inserted it here lest it should be overlooked. 12 134 THE DISSECTOR. ~ j7 . f Temporal-facial, On the face. j Cervicofacial. The Tympanic branches are two small filaments, which are distributed to the stapedius and tensor tympani muscles. The Chorda tympani quits the facial nerve just before it emerges from the stylo-mastoid foramen. Entering the tym- panum at its posterior and superior angle, it crosses its cavity between the handle of the malleus and long process of the incus, to its anterior inferior angle. It then escapes through the fissura Glaseri, and joins the gustatory nerve at an acute angle between the two pterygoid muscles. Enclosed in the neurilema* of the gustatory nerve, it descends to the sub- maxillary gland, where it unites with the submaxillary gan- glion. It is a branch of the fifth pair. The Communicating branches are filaments which it receives from the glosso-pharyngeal and pneumogastric nerves. The Posterior auricular nerve ascends behind the ear, and crosses the mastoid process to the occipito-frontalis muscle; it gives branches also to the attolens and retrahens muscles of the pinna. The Digastric branch supplies the posterior belly of the digastricus muscle. The Stylo-hyoid branch is distributed to the stylo-hyoid muscle. The facial nerve then enters the parotid gland, and divides into its two ultimate trunks—temporo-facial and cer- vico-facial. The Temporo facial gives off a number of branches which are distributed over the temple and upper half of the face, supplying the muscles of this region, and communicating AA'ith the branches of the supra-orbital nerve. The inferior bran- ches, which accompany Stenon's duct, form a plexus with the terminal branches of the infra-orbital nerve. The Cervico-facial divides into a number of branches that are distributed to muscles on the lower half of the face, and upper part of the neck. The cervical branches form a plexus (fig. 38. 11.) with the superficialis colli nerve over the sub- maxillary gland. The Facial nerve has been named sympathetica minor, on account of the number of communications Avhich it maintains * No proof of this independent relation of the chorda, tympani to the gus- tatory nerve has yet been afforded by anatomy; and recent physiological discoveries throw much doubt over the question. THE DISSECTOR. 135 On the face and neck with with other nenres. These will be best seen in a tabular ar- rangement :— r .1 , (Auditory nerve, In the petrous bone it ) -n . fi i *• v-j- r . , ,±1 < Petrosal branch ot Vidian, communicates with ) /-.,. n v (^ Otic Ganglion. At its exit from the ( n, i , ,7 /•! x • J Glosso-pharyngeal, stylo-mastoid fora-< -n r f -b ' ^ ..7 *^ ) Pneumogastric. mew, m£A (^ ° T .-, ..j 7 7 C Auricular of the inferior maxillary, In the parotid aland } A . •, . *7' ..-, l u < Auricularis magnus, ( Occipitalis minor. Supra-orbital, Infra-orbital, Temporo-malar of the superior maxillary, Buccal, Mental, ^Superficialis colli. From the supra-orbital, infra-orbital, and mental foramina, will be found issuing the terminal branches of the fifth nerve distributed to the face. They form plexuses of communica- tion with branches of the facial nerve. Ascending obliquely across the face from the anterior infe- rior angle of the masseter muscle to the angle of the eye, is the facial artery: and descending along the anterior border of the masseter to join the artery, as it crosses the border of the jaAV, is the facial vein. The Integument, which has already been partly removed from the neck, may now be dissected back altogether, bound- ing it by an incision made along the line of the clavicle. The superficial fascia is next to be removed, and with it the platysma myoides, noting the direction in which its fibres run. The deep fascia is thus brought into view, extending from the border of the trapezius to the middle line on the front of the neck. In relation with this fascia on the side of the neck, are certain parts which demand the student's especial at- tention : they are,—the external jugular vein, the ascend- ing branches of the cervical plexus, viz :—Superficialis colli, Auricularis magnus, Occipitalis minor, Sterno-mastoid muscles. The external jugular vein lies upon the deep fascia. 136 THE DISSECTOR. The nerves lie partly between the two layers of the deep fascia, and partly superficial to them. The muscle is between the tAvo layers, being the cause of their separation. The External jugular vein (fig. 38. 8.) is the superficial venous trunk of the neck; it receives the returning blood from the exterior of the side of the head, being formed by the Temporal vein, Internal maxillary, Posterior auricular, and near to the clavicle is joined by cutaneous veins from the back of the neck. Immediately beneath the parotid gland it communicates with the internal jugular vein. Course.—Emerging from the parotid gland in which it lies imbedded, it descends somewhat obliquely along the side of the neck, and behind the clavicle to the subclavian vein. Relations.—It lies upon the sheath of the sterno-mastoid muscle for nearly its whole course, being placed for a short space to its anterior border above, and upon its posterior border below. It is accompanied by the auricularis magnus nerve, and is covered by the platysma muscle, enclosed be- tAveen the two layers of superficial fascia. The next step in the dissection is to open the sheath of the sterno-mastoid muscle, and carefully trace the three ascending branches of the cervical plexus to their destination. The Superficialis colli (fig. 38. 11.) pierces the fascia at the anterior border of the muscle, and ascends obliquely towards the lower jaAv, beneath which it forms a plexus with the cervico-facial branches of the facial nerve. It is distri- buted to the integument on the front of the neck. The Auricularis magnus (fig. 38. 13.,) the largest of the three, pierces the fascia, and accompanies the external jugu- lar vein. It is distributed to the integument over the parotid gland, and to the external ear, and communicates with the facial nerve. The Occipitalis minor (fig. 38. 14.) ascends along the pos- terior border of the sterno-mastoid muscle, and is distributed to the integument of the occiput. Having learned the jugular vein and ascending nerves of the cervical plexus, attention must now be directed to the sterno-mastoid muscle, from which the fascia should be re- moved so as to expose its entire length. The fascia should also be dissected from the whole of the rest of the neck both THE DISSECTOR. 137 before and behind the sterno-mastoid, so as to enable us to examine the deep parts as an entire layer. Behind the sterno- mastoid some difficulty will arise in the dissection, from the number of branches given off by the cervical plexus. Fig. 38. Tne triangles of the neck, with the 'external jugular vein and ascending branches of the cervical plexus. 1. The sterno-mastoid muscle, which divides the side of the neck into two great triangles, the anterior and posterior, a. The submaxillary triangle. b. The superior carotid triangle, c. The inferior carotid triangle, d. The sub-occipital triangle, e. The subclavian triangle. '1. The border of the lower jaw. 3. 3. The digastric muscle. 4. The superior belly of the omo- hyoid muscle. 5. Its inferior belly. 6. The trapezius muscle. 7. The parotid gland. 8. The external jugular vein. 9. A dotted line, marking the direction of the fibres of the platysma myoides muscle. 10. A small arrow, showing the direction of the incision for opening the jugular vein. 11. The superficialis colli nerve, which forms a plexus with (12.) a branch from the facial nerve, over the submaxillary triangle. 13. The auricularis magnus nerve. 14. The occipitalis minor. 15. The descending superficial branches of the plexus. 16. The spinal accessory nerve. When this preparation has been entirely completed, the side of the neck will present a pretty regular square;— bounded aboA'e by the margin of the lower jaw and occiput, beloAV by the clavicle, in front by the middle line of the neck, and behind by the vertebral column. The sterno-mastoid muscle (fig. 38. 1.) extends diagonally across this space, from the anterior inferior to the posterior superior angle, and divides it into tAvo triangles of nearly equal size, the great anterior and the great posterior triangle. The Great anterior triangle (fig. 38, a, b, c.) is bounded 12* 138 THE DISSECTOR. above by the body of the lower jaw; in front, by the middle line of the neck j and, behind, by the sterno-mastoid muscle. It is subdivided into three minor triangles :—1. The submax- illary triangle, a, formed by the two bellies of the digastric muscle, 3, 3, and the border of the loAver jaAV, 2. 2. The superior carotid triangle, b, formed by the posterior belly of the digastric muscle, 3, the upper belly of the omo-hyoid, 4, and the sterno-mastoid. And 3. The inferior carotid triangle, c, which is bounded by the superior belly of the omo-hyoid muscle, the sterno-mastoid muscle, and the middle line of the neck. The Great posterior triangle (fig. 38. d, e.) is bounded, in front, by the sterno-mastoid; behind, by the border of the trapezius muscle; and, below, by the clavicle. It is subdi- vided into two minor triangles by the inferior belly, 5. of the omo-hyoid muscle. 1. The suboccipital triangle, d, situated above the omo-hyoid; and 2. The subclavian triangle, e, which is bounded in front by the sterno-mastoid muscle; be- hind, by the inferior belly of the omo-hyoid; and, below, by the claAricle. These triangles are thus particularly indicated, because they contain certain important parts; for instance, the Sub- maxillary triangle, a., contains in the posterior half of its area the submaxillary gland in which the facial artery lies embedded, while it conceals from view the commencement of Wharton's duct, the gustatory nerve, and the submaxillary ganglion. The anterior angle is occupied by the mylo-hyoideus muscle, the submental branch of the facial artery, and the mylo-hyoidean nerve. And in the inferior angle may be ob- served a small portion of the lingual nerve. The Submaxillary gland is situated in the posterior angle of the submaxillary triangle of the neck. It rests upon the hyo-glossus and mylo-hoideus muscles, and is covered in by the body of the loAver jaw and by the deep cervical fascia. It is separated from the parotid gland by the stylo-maxillary ligament, and from the sublingual by the mylo-hyoideus muscle. Embedded amongst its lobules is the facial artery and the submaxillary ganglion. The Excretory duct (Wharton's) of the submaxillary gland, passes obliquely forwards behind the mylo-hyoideus muscle, and resting upon the hyo-glossus to the papilla, situated at THE DISSECTOR. 139 each side of the fraenum linguae. It is in contact throughout its course with the mucous membrane of the floor of the mouth. The Sublingual gland is situated beneath the mucous mem- brane of the floor of the mouth, on each side of the fraenum linguae. It is in relation, above, with the mucous membrane; in front, with the depression on each side of the symphisis of the loAver jaw ; externally, Avith the mylo-hyoideus muscles, and internally, with the lingual nerve and genio-hyo-glossus muscle. It pours its secretion into the mouth by seven or eight small ducts, which open upon the mucous membrane on each side of the fraenum linguae. 2. The Superior carotid triangle, b., contains the upper portion of the common carotid artery, and its bifurcation into the external and internal carotids; the superior thyroid and the commencement of the lingual and facial arteries; the in- ternal jugular vein and a chain of lymphatic glands; the descendens noni nerve in front of the sheath of the carotid, the pneumogastric within, and the superior laryngeal and sympathetic behind. Crossing the upper angle is the lingual nerve. 3. In the Inferior carotid triangle, c, are found the lower part of the common carotid artery and jugular vein, descend- ens noni, pneumogastric and sympathetic nerves, and recur- rent laryngeal nerve. 4. The Suboccipital triangle, d., contains the suboccipital nerve at its upper angle, and the spinal accessory nerve and branches of the cervical plexus below. 5. The Subclavian triangle, e., contains the termination of the external jugular vein, the third part of the course of the subclavian artery, and the brachial plexus of nerves, and is crossed by the posterior scapular artery. We would not counsel the student to learn up the contents of these triangles by rote; the notice of their* contents is meant chiefly for the dissector, who, in reading each structure, should seek for it in its appropriate place. The names of the regions carry with them the best idea of their principal fea- tures, and these the least attentive learner cannot fail of recollecting. The use of a good knowledge of the triangular 140 THE DISSECTOR. space is its application to the operations for ligature of the arteries of the neck. Vessels of the Neck. Divide the sterno-mastoid muscle through its middle, and turn aside the ends; the upper extremity will be seen to be pierced by the spinal accessory nerve. Then dissect off the posterior layer of the deep fascia, and the sheath of the caro- tid vessels will be exposed throughout its entire extent. Lying upon the sheath, and forming a loop at about its mid- dle, is a long slender nenre, the descendens noni. Open the sheath, and it will be found to contain the carotid artery, jugular vein, and pneumogastric nerve. Behind it is the re- current laryngeal, and sympathetic nerve. Dissect the cel- lular tissue and lymphatic glands, which are numerous in the course of the jugular vein, from around the vessels, for the purpose of examining them and their relations more satisfac- torily. The Carotid artery (xapa, the head) of the right side (fig. 42. 8.) is shorter and larger than that on the left: the former being a branch of the innominata, commences opposite the right sterno-clavicular articulation, the latter from the arch of the aorta. From either point the carotid ascends the side of the neck to a level with the upper border of the thyroid car- tilage, where it divides (fig. 40. 7.) into the external carotid and internal carotid. Relations.—The Common carotid of the right side rests, first, upon the longus colli muscle, then upon the rectus anti- cus major, the sympathetic nerve being interposed. The in- ferior thyroid artery and recurrent laryngeal nerve pass behind it at its lower part. To its inner side is the trachea, recurrent laryngeal nerve, and larynx: to its outer side the jugular vein and pneumogastric nerve; and in front the sternothyroid, sterno-mastoid, omo-hyoid and platysma mus- cles, and the descendens noni nerve. The Left'carotid (fig. 42. 9.) is smaller than the right, and more deeply seated. In addition to the relations just enu- merated, which are common to both, it is crossed near its commencement by the left vena innominata; lies upon the trachea: then gets to its side, and is in relation with the oesophagus and thoracic duct. THE DISSECTOR 111 The External carotid artery (fig. 40.) asends perpen- dicularly from opposite the upper border of the thyroid car- tilage, to the space between the neck of the lower jaw and the meatus auditorius. Fig. 39. The carotid arteries with the branches of the external carotid. ■ i. The common carotid. 2. The external carotid. 3. The internal carotid. 4. The carotid foramen in the petrous portion of the temporal bone. 5. The superior thyroid artery. 6. The lingual artery. 7. The facial artery. 8. The mastoid artery. 9. The occipital. 10. The poste- rior auricular. 11. The transverse facial artery. 12. The internal maxil- lary. 13. The temporal. 14. The ascending pharyngeal artery. Relations.—In front it is crossed by the posterior belly of the digastricus and stylo-hyoideus and platysma myoides muscles ; by the lingual nerve (fig. 40. 21.) near its origin; and hio-her up, Avhere it is situated in the substance of the parotiof gland, by the facial nerve. Behind, it is separated from the internal carotid by the stylo-pharyngeus and stylo- glossus muscles, glosso-pharyngeal nerve, 20., and part of the parotid gland. The External carotid artery is intended for the supply ot 142 THE DISSECTOR. the organs in the neck and the external part of the head. If we reflect upon what these organs and parts should be, we shall find, that taking them in succession, from below upwards, thev arc, in front—1st. The thyroid gland and larynx. 2d." The tongue. 3d. The surface of the face. Behind— 4th. The mastoid muscle. 5th. The external ear. 6th. The occiput. And above—7th. The pharynx. 8th. The side of the face. 9th. The temple and side of the head; and 10th. The deep parts in the face. These are so many arterial regions on the exterior of the head, and upper part of the neck : They are ten in number, and a branch of the external carotid is destined to the supply of each. The branches, therefore, are— Anterior. Posterior. 1. Superior thyroid. 4. Mastoid. 2. Lingual. 5. Posterior auricular. 3. Facial. 6. Occipital. Superior. 7. Ascending pharyngeal. 9. Temporal. 8. Transverse facial. 10. Internal maxillary. The Anterior branches arise from the commencement of the external carotid, within a short distance of each other. The lingual and facial bifurcate, not unfrequently form a common trunk. I. The Superior thyroid artery (fig. 40. 8.) descends to the thyroid gland to Avhich it is distributed, anastomising with its fellow of the opposite side, and Avith the inferior thyroid arteries. Its branches are— (1.) Superior Thyroid.—Branches. Hyoid, Muscular. Laryngeal, The Hyoid branch is distributed to the insertion of the de- pressor muscles into the os hyoides. The Laryngeal pierces the thyro-hyoidean membrane, in company with the superior laryngeal nerve, and supplies the mucous membrane and muscles of the larynx. The Muscular branch is distributed to the depressor muscles of the os hyoides and larynx. THE DISSECTOR. 143 2. Lingual artery:—1st. Crosses obliquely (fig. 40. 9.) the great cornu of the os hyoides. 2d. It passes forwards parallel, 11., with the upper border of the os hyoides. 3d. Ascends, 12., to the under surface of the tongue; and 4th. Runs forward in a serpentine direction to its tip, under the name of ranine artery. 13. Its course is thus divided into four parts, and the relations of each are to be studied sepa- rately, with a view to operations on the artery in any part of its course. Fig. 40. The anatomy of the side of the tongue, with the relations of the vessels and nerves. 1. The hyo-glossus muscle, arising from the side of the os hyoides below, and inserted into the side of the tongue, where it mingles its fibres with those of the stylo-glossus muscle. 2. 3. A section of the lower jaw at the symphysis. 4. The genio-hyo-glossus muscle. 5. The genio-hyoideus mus- cle. 6. The cut edge of the mylo-hyoideus. 7. The common carotid artery, dividing into the external and internal carotid. 8. The trunk of the supe- rior thyroid artery. 9. The lingual artery; the first or oblique portion of its course, resting upon the great cornu of the os hyoides, and upon (10) the middle constrictor muscle. 11. The second, or horizontal portion of the lingual artery; its course beneath the hyo-glossus muscle it marked by dotted lines. 12. The third, or perpendicular portion of the lingual artery. 13. Its termination, the ranine artery. 14. The trunk of the facial artery. 15. The three posterior branches of the external carotid artery; they are from below, upwards, the mastoid, occipital, and posterior auricular. 16. The trunk of the ascending pharyngeal artery. 17. The trunk of the trans- verse facial artery. 18. The two terminal branches of the external carotid, the internal maxillary and temporal. 19. The gustatory branch of the fifth nerve. * Its communication with the lingual nerve. 20. The glosso-pha- ryngeal nerve. 21. The lingual, or hypoglossal nerve. 22. Wharton's duct. 23. The sublingual gland. Relations.—The first part of its course, 9., rests upon the 144 THE DISSECTOR. great cornu of the os hyoides, and the origin of the middle constrictor muscle, 10., of the pharynx; the second, 11, is situated between the middle constrictor and hyo-glossus mus- cles, the latter separating it from the lingual nerve, 21. In the third part of its course, 12., it lies between the hyo-glos- sus and genio-hyo-glossus, 4., and in the fourth, 13. (ranine,) rests upon the lingualis to the tip of the tongue. Its bran- ches are,— (2.) Lingual Artery.—Branches. Hyoid, Sublingual. Dorsalis linguae, The Hyoid branch is distributed to the origins of the ele- vator muscles of the os hyoides. The Dorsalis linguce ascends along the posterior border of the hyo-glossus muscle to the dorsum of the tongue, Avhere it is distributed, anastomosing with its fellow of the opposite side. The Sublingual branch runs along the anterior border of the hyo-glossus, and is distributed to the sublingual gland and muscles of the tongue. 3. Facial artery. (Fig. 40.14.)—The facial artery ascends obliquely to the submaxillary gland, in which it lies embedded. It then curves around the body of the lower jaAv, close to the anterior inferior angle of the masseter muscle, ascends to the angle of the mouth, and thence to the angle of the eye, where it is named the angular artery. Relations.—Below the jaw it passes beneath the digastri- cus and stylo-hyoid muscles, and at the angle of the mouth beneath the zygomatic muscles. Its branches are divided into those which are given off below the jaw and those on the face: they may be thus arranged,— (3.) Facial Artery.—Branches. Below the jaw. Inferior palatine, Sub-mental. Submaxillary, On the face. Masseteric, Superior coronary, Inferior labial, Lateralis nasi. Inferior coronary, THE DISSECTOR. 145 The inferior palatine branch ascends between the stylo- glossus and stylo-pharyngeus muscles, to be distributed to the tonsil and soft palate. The Submaxillary are the numerous small branches sup- plying the submaxillary gland. The Sub-mental branch runs forwards upon the mylo-hyoid muscle, under cover of the body of the lower jaw, and anas- tomoses with branches of the sublingual and inferior dental arteries. The Masseteric branch is distributed to the masseter and buccinator muscles. The Inferior labial branch is distributed to the muscles and integument of the lower lip. The Inferior coronary runs along the edge of the lower lip, close to the mucous membrane, and inosculates with the cor- responding artery of the opposite side. The Superior coronary follows the same course along the upper lip, inosculating with the opposite superior coronary artery. The Lateralis nasi is distributed to the ala and septum of the nose. The Inosculations of the facial artery are very numerous: thus it anastomoses with the sublingual branch of the lingual, with the inferior dental as it escapes from the mental foramen, infra-orbital at the infra-orbital foramen, transverse facial on the side of the face, and at the angle of the eye with the na- sal branch of the ophthalmic artery. The Posterior branches of the external carotid (fig. 40,15.,) viz., the mastoid, posterior auricular, and occipital, are next to be dissected and studied. 4. The Mastoid artery turns downwards to be distributed to the sterno-mastoid muscle; sometimes it is replaced by tAvo small branches. 5. The Posterior auricular artery ascends beneath the lower border of the parotid gland, and behind the concha, to be dis- tributed to the external ear and side of the head, anastomos- ing Avith the occipital and temporal arteries: some of its bran- ches pass through the fissures in the fibro-cartilage, to be distributed to the anterior surface of the pinna. The anterior auricular arteries are branches of the temporal. Branches.—The posterior auricular gives off but one named 13 146 the dissector. branch, the stylo-mastoid, which enters the stylo-mastoid fora- men to be distributed to the aqueductus Fallopii and tympa- num. 6. The Occipital artery passes backwards beneath the pos- terior belly of the digastricus, the trachelo-mastoid, and sterno-mastoid muscles, to the occipital groove in the mastoid portion of the temporal bone. It then ascends between the splenius and complexus muscles, and is distributed upon the occiput, anastomosing with the posterior auricular and tempo- ral arteries. Branches.—It gives off only two branches, inferior menin- geal and princeps cervicis. The Inferior meningeal ascends by the side of the internal jugular vein, and passes through the foramen lacerum poste- rius to be distributed to the dura mater. The Arteriaprinceps cervicis is a large but irregular branch. It descends the neck between the complexus and semi-spinalis colli, and inosculates with the profunda cervicis of the sub- clavian. This branch is the means of establishing a very important collateral circulation between the branches of the carotid and subclavian, in ligature of the common carotid artery. The Superior branches have now to be examined and traced throughout their course; we must commence with the two superficial arteries, the deeper ones requiring an especial dis- section. 7. The Transversalis faciei (fig. 40. 17.) arises from the external carotid Avhilst that trunk is lodged within the parotid gland; it crosses the masseter muscle in company with Stenon's duct, and is distributed to the muscles and integument on the side of the face. 8. The Temporal artery (fig. 40. 18.) is one of the two ter- minal branches of the external carotid. It ascends over the root of the zygoma, and divides into three branches:—1st. Anterior temporal, Avhich is-distributed on the front of the temple and arch of the skull, anastomosing Avith the supra- orbital branch of the ophthalmic artery. 2. Posterior tem- poral, which passes toAvards the back of the head, anastomos- ing with the posterior auricular and occipital arteries. And 3. Middle temporal, Avhich pierces the fascia, and supplies the temporal muscle. the dissector. 147 Branches.—While resting upon the zygoma, the temporal artery gives off several branches to the external ear, the an- terior auricular arteries. It is sometimes necessary to open the temporal artery for the purpose of producing a powerful effect upon the system; in this case, the more prominent of the tAvo superficial vessels should be chosen. The structures to be cut through are sim- ply the integument and superficial fascia; and the mode of arresting the flow of blood is to divide the cylinder of the artery completely across, so that the extremities of the ves- sels may be retracted within the superficial fascia. The middle coat of the artery becomes contracted by this proceeding, and is draAvn within the external one. The internal maxillary artery passes inAvards behind the neck of the lower jaw to the deep structures in the face; we require, therefore, to remove several parts for the purpose of seeing it completely. To obtain a good view of the vessel, the zygoma should be sawn across close to the external ear, and the malar bone near to the orbit. Turn down the zygo- matic arch with the masseter muscle. In doing this, a small artery and nerve will be seen crossing the sigmoid arch of the lower jaw, and entering the masseter muscle (the masseteric.) Cut away the tendon of the temporal muscle from its insertion into the coronoid process, and turn it upwards towards its origin: some vessels will be seen entering its under surface; these are the deep temporal. Then saw the ramus of the jaw across its middle, and dislocate it from its articulation with the temporal bone. Be careful in doing this to carry the blade of the knife close to the bone, lest any branches of nerves should be injured. Next remove this portion of bone, and with it the external pterygoid muscle. The artery, together with the deep branches of the inferior maxillary nerve, will be seen lying upon the internal pterygoid. These are to be carefully freed of fat and cellular tissue, and then examined. 10. The Internal maxillary artery (fig. 40. 18. fig. 41. 4.) is one of the two terminal branches of the external carotid. Commencing in the substance of the parotid gland, opposite the meatus auditorius externus, it first passes horizontally be- hind the neck of the lower jaw, next obliquely upAvards between the tAvo pterygoid muscles ; it then bends suddenly into the pterygo-maxillary fossa. Its course is thus resolved into three 118 THE DISSECTOR. portions—1. That situated behind the neck of the jaw, the maxillary portion, 4.; 2. That between the pterygoid mus- cles, muscular portion, 5.; and 3. Its bend into the pterygo- maxillary fossa, pterygo-maxillary portion, 6. Fig. 41. The internal maxillary artery, with its branches. 1. The external carotid artery. 2. The trunk of the transverse facial artery. 3. 4. The two terminal branches of the external carotid. 3. The temporal artery; and 4. The internal maxillary, the first or maxillary portion of its course: the limit of this portion is marked by an arrow. 5. The second, 'or muscular portion, of the artery; the limits are bounded by the arrows. 6. The third, or pterygo-maxillary portion. The branches of the maxillary portion are, 7. A tympanic branch. 8. The arteria meningea media. 9. The arteria meningea parva. 10. The inferior dental artery. The branches of the second portion are wholly muscular, the ascending ones being distributed to the temporal, and the descending to the four other muscles of the inter- maxillary region, viz. the two pterygoids, the masseter and buccinator. The branches of the pterygo-maxillary portion of the artery are, 11. The supe- rior dental artery. 12. The infra-orbital artery. 13. The posterior palatine. 14. The spheno-palatine, or nasal. 15. The pterygo-palatine. 16. The Vidian. * The remarkable bend which the third portion of the artery makes as it turns inwards to enter the pterygo-maxillary fossa. Relations.—The maxillary portion is situated between the ramus of the jaw and internal lateral ligament, lying parallel to the auricular nerve : the pterygoid portion betAveen the tAvo pterygoid muscles, crossing the gustatory and dental nerves. It then makes a remarkable bend (fig. 41.*) Avhich projects between the tAvo heads of the external pterygoid muscle, and passes directly inAvards to the pterygo-maxillary fossa, where it divides into its terminal branches. THE DISSECTOR. 149 Internal maxillary artery.—Branches. Maxillary portion (fig. 41. 4.) Tympanic, 7., Inferior dental, 10., Arteria meningea media, 8., Arteria meningea parva, 9. f Deep temporal branches, T./T 7 .. I External pterygoid, Muscular portion I T , , r, J & • -,' [^Buccal. r Superior dental, 11., r,. .„ Infra-orbital, 12., Ptery qo-maxillary -p., , ' . \ c ■t (tl 41 J "terygo-palatme, 15., ■% n ^^' "| Spheno-palatine, 14., *' | Posterior palatine, 13., [ Vidian, 16. Maxillary portion (fig. 41. 4.)—The Tympanic branch, 7. is very small, and not likely to be seen in an ordinary dis- section ; it passes into the tympanum through the fissura Glaseri. The Inferior dental, 10, descends to the dental foramen, and enters the canal of the lower jaw in company with the dental nerve. At the chin it escapes Avith the nerve from the mental foramen, and anastomoses with the inferior labial and submental branches of the facial. It supplies the teeth of the lower jaw, sending small branches along the canals in their roots. The Arteria meningea media, 8., is the great artery of the dura mater. It passes between the roots of the dental nerve, and through the foramen spinosum in the spinous process of the sphenoid, to the deep groove at the anterior inferior angle of the parietal bone. It divides into several branches, which ramify upon the external surface of the dura mater, and anastomose with corresponding branches from the oppo- site side. The Meningea parva, 9, is a small branch which ascends to the foramen ovale, and passes into the skull to be distri- buted to the dura mater. Muscular portion (fig. 44. 5.)—The distribution of the muscular branches is implied in their names, supplying the five muscles of the temporo-maxillary region. 13* , 150 THE DISSECTOR. Pterygo-maxillary portion (fig. 41. 6.)—The branches of this portion of the artery cannot be seen at the present stage of the preparation; they must be left until the dissec- tion has proceeded more deeply. The Superior dental branch, 11, is given off from the artery, just as it makes its remarkable bend* inwards. It passes down upon the posterior surface of the superior maxillary bone, and sends its branches through several small foramina to sup- ply the posterior teeth of the upper jaw. The Infra-orbital, 12, would appear, from its size, to be the proper continuation of the artery. It is, however, more convenient to consider it simply as a branch. It runs along the infra-orbital canal with the superior maxillary nerve, sending branches downwards through canals in the bone, to supply the mucous lining of the antrum and teeth of the upper jaw, and escapes from the infra-orbital foramen, inoscu- lating Avith the facial and transverse facial arteries. The Pterygo-palatine, 15., is a small branch which passes through the pterygo-palatine canal, and supplies the upper part of the pharynx. The Spheno-palatine, 14., or nasal, enters the spheno-pala- tine foramen with the nasal branches of Meckel's ganglion, and is distributed to the mucous membrane of the nares. The Posterior palatine branch, 13., descends along the posterior palatine canal, in company with the posterior pala- tine branches of Meckel's ganglion. It is distributed to the palate. The Vidian branch, 16., passes backwards along the ptery- goid canal, and is distributed to the sheath of the Vidian nerve. The external carotid artery should now be divided near its origin, and draAvn upwards, or removed altogether. The ramus of the jaw should also be saAvn across, and dissected aAvay from the insertion of the internal pterygoid muscle and pterygo-maxillary ligament, in order to bring into vieAV the side of the pharynx. The rest of the parotid gland may then be removed from its situation, and its deep relations attentively observed. We shall thus be enabled to trace the course of the remaining branch of the external carotid artery, and see the relations of the internal carotid. The Ascending pharyngeal artery (fig. 40. 16.) arises from the external carotid, near to its bifurcation, and as- THE DISSECTOR. 151 cends by the side of the pharynx to the base of the skull, Avhere it divides into branches which enter the foramina in that region, to be distributed to the dura mater. It supplies the pharynx. The Internal carotid artery ascends perpendicularly from its bifurcation, opposite the upper border of the thyroid cartilage, to the carotid foramen in the petrous bone. It then curves inwards along the carotid canal, passes forwards by the side of the sella turcica, and at the anterior clinoid process pierces the dura mater and divides into three branches. Its course is naturally divided into four portions :—1. Cervical, situated in the neck ; 2. Petrous, occupying the carotid canal; 3. Cavernous, lying by the side of the sella turcicaj 4. Cere- bral, after it has pierced the dura mater. Relations.—The cervical portion rests upon the rectus anticus major, and superior cervical ganglion of the sympa- thetic, and partly on the internal jugular vein, lingual and pneumogastric nerves. It is crossed behind by the pharyn- geal and superior laryngeal nerves. To its inner side it has the pharynx, tonsil, and ascending pharyngeal artery; to its outer side the jugular vein, commencement of the eighth pair, and lingual nerve. And it is crossed in front by the stylo- glossus and stylo-pharyngeus muscles, and glosso-pharyngeal nerve, being covered in by the parotid gland. The Petrous portion is in relation with the carotid plexus, and is covered by the Casserian ganglion. The Cavernous portion is placed to the inner side of the cavernous sinus, and is crossed by the nerves passing to the orbit, viz., third, fourth, ophthalmic branch of the fifth and sixth, and branches of the sympathetic. The Cerebral portion is lodged in the fissure of Sylvius. Branches.—There are no branches given off by the cer- vical portion of the internal carotid: from the other portions are derived the following:— Internal Carotid.—Branches. Petrous portion Tympanic. n ( Anterior meningeal, Cavernous portion | 0pllthalmic. {Anterior cerebral, Middle cerebral, Posterior communicating. 152 THE DISSECTOR. The Tympanic is a small branch which enters the tympanum through a minute foramen in the carotid canal. The Anterior meningeal is distributed to the dura mater and Casserian ganglion. The Ophthalmic artery enters the orbit through the fora- men opticum, to be distributed to the globe of the eye and surrounding structures. Its course and branches are de- scribed with the dissection of the orbit. The three remaining arteries are described with the mem- branes of the brain, Chapter VI. The Veins of the head and neck are the external and internal jugular. The former receives its blood from the temporal, internal maxillary, and auricular veins, and from the superficial parts of the neck, and descends obliquely backwards between the platysma myoides and sterno-mastoid muscle, to terminate in the subclavian vein behind the cla- vicle. The Internal jugular vein commences at the jugular fossa, in the foramen lacerum posterius, Avhere it receives the blood from the sinuses in the interior of the cranium. It descends the neck at first behind, and then to the outer side of the internal carotid artery, and continues its course within the sheath of the common carotid, and, lying to its outer side, to the inner border of the first rib, where it unites Avith the subclavian vein, and forms the vena innominata. On the left side the vein, at its termination, advances rather in front of the artery: on the right it diverges from the artery, leaving a triangular space between them. The internal jugu- lar receives the veins from the deep parts at the base of the skull and neck, and is joined in the submaxillary space by a communicating branch from the external jugular, the facial, and occipital veins. Along the anterior border of the sterno-mastoid muscle is a small vein, formed by branches from the superficial parts on the front of the neck. It is often of large size, and is named anterior jugular. The Subclavian artery, on the right side (fig. 42. 5.) arises from the arteria innominata, 4., opposite the sterno-clavicu- lar articulation, and on the left, 10., from the arch of the aorta, 2. The right is consequently shorter than the left, and situated on a plane superficial to it. THE DISSECTOR. 153 The course of the artery is divided into three portions, first, second, and third. The First portion on the right Fig. 42. The arch of the aorta, side, 5, passes obliquely outwards with its branches, and the course to the inner border of the scalenus of tke subclavian arteries- anticus. On the left side, 10., it ascends perpendicularly to the inner border of the scalenus anti- cus; the remainder of the course of the artery is the same on both sides. The Second portion, 6. 11., passes transversely outwards be- tween the two scaleni. The Third portion, 7. 12., downwards and outwards over the first rib. From the superficial and deep position of the tAvo arteries, the 1. The ascending aorta. 2. Its arch. 3. The descending aorta. 4. The arteria innominata. 5. The right subclavian, the first, or obliquely ascend- ing portion of its course. 6. The second, or transverse portion. 7. The third, or obliquely descending portion. 8. The right carotid artery. 9. The left carotid. 10. The left subclavian artery; the first, or perpendicular portion. 11. The second, or transverse. 12. The third, or oblique portion. 13. The right pneumogastric nerve, giving off the recurrent * around the subclavian artery. 14. The left pneumogastric, sending its recurrent branch * around the arch of the aorta. ** The two recurrent laryngeal nerves. right lies in front of the pleura which covers its posterior surface, whilst the left is situated near the vertebral column, behind the pleura. The innominata vein is in front of the artery on both sides, lying parallel to it on the right, and crossing it at the upper part on the left. In consequence of the oblique direction of the artery on the right side, it is crossed by the pneumogastric, 13., cardiac, and phrenic nerves, and the recurrent winds around it, whilst on the left side they all run parallel with it. The thoracic duct is placed immediately behind and parallel with the first portion of the artery on the left side. The Second portion of the artery is situated between the tAvo scaleni muscles, and is separated from the subclavian vein by the scalenus anticus. The Third portion has the brachial plexus almost in con- 154 THE DISSECTOR. tact Avith it above, the subclavian vein in front, and the first rib below. Branches.—The Branches of the subclavian artery (fig. 43.) are given off from its first portion; they are five in number. 3. Ascending. 2. Descending. T Vetebral, fig. 43. 6. f Inferior thyroid, 7. I™, ., . 0 Supra-scapular, 12. Thyroid axis, 8, j Posterior scapular, 11. Profunda cervicis, 10. [Superficialis cervicis, 9. J Superior intercostal, 14. \ Internal mammary, 13. Fig. 43. The subclavian ar- tery, with its branches. The Vetebral artery (fig. 43. 6.) ascends through the foramina in the transverse processes of all the cervical vertebrae, excepting the last, then winds backwards around the articulating process of the at- las, and piercing the dura mater, enters the skull through the fora- men magnum. The two arteries unite at the lower border of the pons Varolii to form the basilar artery, which runs forwards to its anterior border, and divides into four termi- nal branches. 1. The arteria innominata, dividing into, 2. The right common carotid artery, and 3. The right subclavian artery, the first part of its course, from which all the branches are given off. 4. The second part of its course. 5. The third part of its course. 6. 7. The two visceral branches of the subclavian artery, 6. The vertebral. 7. The inferior thyroid. 8. The thyroid axis, giving off its four branches. 9. 10. The two cervical branches of the subclavian;—9. The cervicalis superficialis, 10. The cervicalis pro- io ml H" 12' The two scaPular branches;—11. The posterior scapular. 12. The supra-scapular. 13. 14. The two thoracic branches;—13. The internal mammary artery, 14. The superior intercostal The branches of the Vertebral artery are— Branches. r Lateral spinal, , Anterior spinal, Vertebral J Posterior spinal, Posterior meningeal, (^Inferior cerebellar. THE DISSECTOR. 155 f Transverse, Basilar -l Superior cerebellar, [^Posterior cerebral. The Lateral spinal branches enter the intervertebral fora- mina, and are distributed to the dura mater of the spinal cord. The Anterior spinal is a small branch which unites with its fellow of the opposite side, on the front of the medulla oblongata. The artery formed by the union of these two vessels descends along the anterior aspect of the spinal cord, to which it distributes branches as far as the cauda equina. The Posterior spinal is a small branch running down the posterior surface of the spinal cord, parallel with its fellow of the opposite side, and distributing branches as far as the cauda equina. The Posterior meningeal is a small branch to the dura mater, lining the inferior occipital fossae. The Inferior cerebellar artery is distributed to the under surface of the cerebellum. Basilar Artery.—Branches. The Transverse branches of the basilar artery supply the pons Varolii, and adjacent parts of the brain. The Superior cerebellar and Posterior cerebral arteries are the terminal branches of the basilar. The superior cerebellar is distributed to the upper surface of the cerebellum, and the posterior cerebral to the posterior lobes of the cerebrum, in- osculating on the corpus callosum with the anterior cerebral arteries. They are separated from each other at their com- mencement by the third nerve. The Thyroid axis (fig. 43. 8.) is a short trunk which im- mediately divides into its four branches. The Interior thyroid artery (fig. 43. 7.) passes behind the sheath of the carotid vessels, to the inferior part of the thyroid gland, to which it is distributed. It also gives branches to the trachea, lower part of the larynx and oeso- phagus. It is in relation Avith the middle cervical ganglion of the sympathetic, which rests upon it. The Supra-scapular artery, 12., (transversalis humeri) passes obliquely backAvards behind the clavicle, and across the ligament of the notch, to the supra-spinatus fossa. It is dis- tributed to the muscles on the dorsum of the scapula, and 156 THE DISSECTOR. inosculates with the posterior scapular, and beneath the acro- mion process with the dorsal branch of the subscapular artery. The Posterior scapular artery, 11., (transversalis colli,) passes transversely across the subclavian triangle at the root of the neck, to the superior angle of the scapula. It then descends along the posterior border to its inferior angle, where it inosculates with the subscapular artery, a branch of the axillary. Relations.—It passes behind, and sometimes in front of the scalenus anticus, between the nerves forming the brachial plexus, and beneath the levator anguli scapulae rhomboideus minor and major muscles. Branches.—Some ascending branches are given off at the superior angle of the scapula, which inosculate with the pro- funda cervicis. The Superficialis cervicis artery, 9., is a small vessel, which ascends upon the anterior tubercles of the transverse processes of the cervical vertebrae, and distributes branches to the muscles on the anterior aspect of the vertebral column in the neck. The Profunda cervicis, 10., passes backwards between the transverse processes of the sixth and seventh cervical ver- tebrae, and then ascends the back part of the neck, between the complexus and semi-spinalis colli muscles. It inosculates above Avith the princeps cervicis of the occipital artery, and below with the posterior scapular. The Superior intercostal artery, 14., descends behind the pleura upon the necks of the first two ribs. Its branches supply the first two intercostal spaces. The Internal mammary artery, 13., descends by the side of the sternum, resting upon the costal cartilages, to the dia- phragm : it then pierces the anterior fibres of the diaphragm, and enters the sheath of the rectus, where it inosculates with the epigastric artery, a branch of the external iliac. The Branches of the internal mammary are,— Anterior intercostal—mammary, Comes nervi phrenici, Mediastinal, Pericardiac, Musculo-phrenic. The Anterior intercostals supply the intercostal spaces on THE DISSECTOR. 157 the front part of the chest, and inosculate with the aortic in- tercostal arteries. They give off several large branches to the mammary gland, which anastomose freely with the thora- cic branches of the axillary artery. The Comes nervi phrenici is a long and slender branch which accompanies the phrenic nerve. The Mediastinal and pericardiac branches are small vessels distributed to the anterior mediastinum and pericardium. The Musculo-phrenic artery winds along the attachment of the diaphragm to the ribs, supplying it with branches. If we now proceed to an analysis of the distribution of the branches of the subclavian artery, we shall find that two, Internal mammary (fig. 43.13.), Superior intercostal, 14., are distributed to the parieties of the thorax; two, Supra-scapular, 12., Posterior scapular, 11., are distributed to the shoulder; two others, Superficialis cervicis, 9., Profunda cervicis, 10., supply the neck; and of the remaining two, one is distributed to the thyroid gland, Inferior thyroid, 7., and the other to the spinal cord and brain, Vertebral, 6. The operation for ligature of the subclavian artery has been already described. This operation can only be performed in . the third part of its course. The first part lies too deeply, is surrounded with important relations, and is giving off the five branches; and the second lies behind the scalenus anticus muscle. The third part of the artery is, however, compara- tively superficial, and the operation may be performed upon it Avith perfect security. Nerves of the Neck. Having now considered all the vessels of the neck, we must next turn our attention to the nerves which occupy this region; they are the eighth and ninth pairs of cerebral, the sympa- thetic, and the eight cervical nerves. 14 158 THE DISSECTOR. Fig. 44. Origin and distri- The EIGHTH PAIR (fig. 44.) of Ce- bution of the eighth pair of rebrai nerves consists of the qlosso- nerves of the left side. , 7 n . . pharyngeal, 6., pneumogastric or va- gus, 10., and spinal accessory, 21. They arise from the respiratory tract of Bell, the two former, 5. 8., between the corpus olivare and restiforme; the latter, 20., from the spinal cord, op- posite the fourth cervical vertebra: hence its cognomen, spinal. The spinal accessory ascends from its ori- gin between the anterior and poste- rior roots of the spinal nerves, to join the other tAvo, and the three to- gether escape from the skull, through the foramen lacerum posterius, lying to the inner side, and rather in front of the jugular vein. The Glosso-pharyngeal nerve presents a gangliform SAvelling, the ganglion of Andersch,* fig. 44. 6. (ganglion petrosum,) upon that por- tion of its cylinder which is situated in the jugular fossa. It then passes forwards between the jugular vein and internal carotid artery, to the stylo-pharyngeus muscle, and de- scends along its inferior border to the hyo-glossus, beneath which it pas- ses to be distributed to the mucous membrane of the tongue, and to the mucous glands of the mouth and ton- sils. 1. The medulla oblongata. 2. The corpus pyramidale of the left side. 3. The corpus olivare. 4. The corpus restiforme. 5. The origin of the glosso-pharyngeal nerve. 6. The ganglion of the glosso-pharyngeal nerve, or of Andersch. 7. A branch from the glosso-pharyngeal nerve to the pha- ryngeal plexus. 8. The origin of the pneumogastric nerve. 9. The upper ganglion of the pneumogastric. 10. The lower or plexiform ganglion of the nerve. 11. The pharyngeal nerve, descending to form the pharyngeal plexus.* 12. The superior laryngeal nerve. 13. A branch to the pharyngeal * Charles Samuel Andersch. Tractatus Anatomico-Physiologica de Nervis Corporus Humani Aliquibis, 1797. THE DISSECTOR. 159 plexus. 14. Cardiac nerves. 15. The recurrent laryngeal nerve. 16. Car- diac branches from the recurrent. 17. CEsophageal plexus. 18. Branches to the stomach. 19. A branch which joins the yolar plexus. 20. The origin of the spinal accessory nerve. 21. Its branches to the sterno-mastoid mus- cle. 22. Terminal branches to the trapezius. 23. The origin of the facial nerve, p. The branches forming the pulmonary plexuses. Its Branches may be thus arranged: Communicating branches with the Facial, Tympanic, Pneumogastric, Muscular, Spinal accessory, Pharyngeal. Sympathetic, The Branches of communication are common to the facial, eighth pair, and sympathetic; they form a complicated plexus at the base of the skull. The Tympanic is a remarkable branch described by Jacob- son, and hence called Jacobson's nerve. It arises from the ganglion of Andersch, and passes through a small canal in the petrous bone to the internal wall of the tympanum, where it divides into six branches, which are thus distributed:— 1. To the fenestra rotunda, 2. To the fenestra ovalis, 3. To the Eustachian tube, 4. To the carotid plexus, 5. To the cranial branch of the Vidian, 6. To the otic ganglion. These filaments are extremely small, and cannot be seen in the adult tympanum, unless by a lucky section. They are best dissected in the ear of the foetus. In the cat they are very distinct and easily demonstrated. The Muscular branch divides into filaments, which are dis- tributed to the stylo-pharyngeus and to the posterior belly of the digastricus and stylo-hyoideus muscle. The Pharyngeal branches, 7., are two or three filaments sent to the side of the pharynx and pharyngeal plexus. The Pneumogastric nerve (vagus) forms a short rounded ganglion (fig. 50. 9.) as it passes through the foramen lacerum posterius. Having escaped at this opening, it presents a second gangliform swelling, 10., nearly an inch in length, and surrounded by an irregular plexus of white nerves, which communicate Avith each other, with the other divisions of the eighth pair, and with the trunk of the pneumogastric beloAV 160 THE DISSECTOR. the ganglion. This second, or plexiform ganglion, (ganglion of the superior laryngeal branch of Sir Astley Cooper,) is situated, at first, behind the internal carotid artery, and then between that vessel and the internal jugular vein. The pneu- mogastric nerve then descends the neck within the sheath of the carotid vessels, lying behind and between the artery and vein#to the root of the neck. Here the course of the nerve at opposite sides becomes different. The right passes between the subclavian artery and vein to the posterior mediastinum, then behind the root of the lung to the oesophagus, which it accompanies to the stomach, lying on its posterior aspect. The left enters the chest parallel with the left subclavian artery, crosses the arch of the aorta, and descends behind the root of the lung, and along the anterior surface of the oesophagus, to the stomach. The two nerves communicate freely with each other on the stomach, and with the solar plexus. The Branches of the pneumogastric nerve are the follow- ing :— Communicating branches Avith the Facial, Cardiac, Glosso-pharyngeal, Inferior or recurrent laryngeal, Spinal accessory, Pulmonary anterior, Lingual, Pulmonary posterior, Sympathetic, (Esophageal, Pharyngeal, Gastric. Superior laryngeal, The Branches of communication are the same, with the addition of the lingual, as those Ave before noticed in con- nexion with the glosso-pharyngeal. The Pharyngeal nerve (fig. 44. 11.) arises from the pneu- mogastric, close to the foramen lacerum posterius, and de- scends behind the internal carotid artery to the upper border of the middle constrictor, upon which it forms the pharyngeal plexus (fig. 44.,*) assisted by branches from the glosso-pha- ryngeal, superior laryngeal, and sympathetic. The Superior laryngeal nerve (fig. 44. 12.) arises from the inferior ganglion of the pneumogastric, of which it appears almost a continuation; hence the ganglion has been named by Sir Astley Cooper, " the ganglion of the superior laryn- geal branch." The nerve descends behind the internal carotid THE DISSECTOR. 161 artery to the opening in the thyro-hyoidean membrane, through which it passes with the superior laryngeal artery, and is dis- tributed to the mucous membrane of the larynx, communi- cating on the arytenoid muscle, and behind the cricoid cartilage, with the recurrent laryngeal nerve. Behind the internal carotid it gives off the external laryngeal branch, which sends a branch to the pharyngeal plexus, and then descends to supply the inferior constrictor and crico-thyroid muscles and thyroid gland, and communicates by two or three branches with the recurrent laryngeal, and sympathetic nerves. Mr. John Hilton, demonstrator of anatomy at Guy's Hos- pital, who has made some able dissections of the nerves of the larynx, for which Ave refer the student to a masterly description in the 2d vol. of the Guy's Hospital Reports, concludes that the superior laryngeal nerve is the nerve of sensation to the larynx, being distributed solely (with the exception of its external laryngeal branch) to the mucous membrane, cellular tissue, and glands. If this fact be taken in connexion with the observations of Sir Astley Cooper, and the dissections of the origin of the nerve by Mr. Edward Cock, we shall perceive that, both in the ganglionic origin of the nerve, and in its distribution, we have striking evidence of its sensitive function. The recurrent, or superior laryn- geal nerve, is the proper motor nerve, and is distributed to the muscles of the larynx. The Cardiac branches, 14., one or two in number, cross the lower part of the common carotid to communicate with the cardiac branches of the sympathetic, for the supply of the heart. The Recurrent laryngeal, or inferior laryngeal nerve (fig. 44. 15.,) curves around the subclavian artery on the right (fig. 42. 13. *) and the arch of the aorta on the left side (fig. 42. 14. *) It ascends in the groove between the trachea and oesophagus, and piercing the lower fibres of the inferior con- strictor muscle, enters the larynx close to the articulation of the inferior cornu of the thyroid with the cricoid cartilage. It is distributed to all the muscles of the larynx, with the exception of the crico-thyroid, and communicates with the superior laryngeal nerve. As it curves around the subclavian artery and aorta, it gives branches (fig. 44. 16.) to the heart and root of the lungs; and, as it ascends the neck, it gives "I A He 162 THE DISSECTOR. branches to the oesophagus and trachea, and communicates with the external laryngeal nerve and sympathetic. In function it is the proper motor nerve of the larynx. The remaining branches of the pneumogastric have been described •with the anatomy of the thorax. Fig. 45. The anatomy of the side of the neck, showing the nerves of the tongue. 1. A fragment of the temporal bone containing the meatus auditorius ex- ternus, mastoid, and styloid process. 2. The stylo-hyoid muscle. 3. The stylo-glossus. 4. The stylo-pharyngeus. 5. The tongue. 6. The hyo- glossus muscle ; its two portions. 7. The genio-hyo-glossus muscle. 8. The genio-hypideus; they both arise from the inner surface of the symphysis of the lower jaw. 9. The sterno-hyoid muscle. 10. The sterno-thyroid. 11. The thyro-hyoid, upon which the hyoid branch of the lingual nerve is seen rami- fying. 12. The omo-hyoid, crossing the common carotid artery (13,) and internal jugular vein (14.) 15. The external carotid giving off its branches. 16. The internal carotid. 17. The gustatory nerve giving off a branch to the submaxillary ganglion (18,) and communicating a little farther on with the hypoglossal nerve. 19. The submaxillary, or Wharton's duct, passing forwards to the sublingual gland. 20. The glosso-pharyngeal nerve. 21. The hypoglossal nerve curving around the occipital artery. i>2 The descendens noni nerve, forming a loop with (23) the communicans noni, which is seen to be arising by filaments from the upper cervical nerves. 24 The pneumo- gastric nerve, emerging from between the internal jugular vein and common carotid artery, and entering the chest. 25. The facial nerve, emerging from the stylo-mastoid foramen, and crossing the external carotid artery THE DISSECTOR. 163 The Spinal accessory nerve, on escaping from the fora- men lacerum posterius, passes backwards behind the internal jugular vein, and descends obliquely to the upper part of the sterno-mastoid muscle, which it pierces (fig. 44. 21.) It then passes obliquely across the side of the neck to the trapezius muscle, to which it is distributed, 22. It communicates, like the preceding nerves, with the other branches of the eighth pair, and with the sympathetic. Its branches supply the sterno-mastoid and trapezius muscles. The Lingual nerve (ninth, hypo-glossal,) the true motor nerve of the tongue, arises by several filaments from the side of the corpus pyramidale of the medulla oblongata, and escapes from the skull through the anterior condyloid fora- men. It then passes fonvards behind the internal jugular vein, and descends along its outer border to a point parallel with the angle of the loAver jaw. It next curves inwards around the occipital artery, with Avhich it forms a loop, and crosses the loAver part of the hyo-glossus muscle to the genio- hyo-glossus, in which it terminates. It is distributed to the muscles of the tongue, and principally to the genio-hyo- glossus. It is separated from the lingual artery by the hyo- glossus muscle, and, while resting on this muscle, presents a flattened appearance. The Branches of the lingual nerve are,— Communicating branches with the Pneumogastric, Sympathetic. Descendens noni, Hyoidean branch, Communicating filaments with the Gustatory nerve. The Communications between the lingual nerve, the eighth pair, and the sympathetic, are situated at the base of the skull, as we have before noted for the divisions of the eighth pair. The Descendens noni is a long slender nerve which quits the lingual just as it is about to form its arch around the occipital artery, and descends upon the sheath of the carotid vessels. Just below the middle of the neck, it forms a loop with a long branch (communicans noni) from the second and third cervical nerves. From the convexity of this loop, branches are sent to the depressor muscles of the larynx. If 164 THE DISSECTOR. the descendens noni be traced to its connexion with the lingual nerve, and examined with care, it will be found to be formed by two filaments, one from the lingual, the other, of larger size, from the first and second cervical nerves.* The Hyoidcan branch is a small branch distributed to the insertions of the depressor muscles of the larynx. The Communicating filaments, Avith the gustatory nerve, are two or three small branches which ascend upon the ante- rior part of the hyo-glossus muscle, and join corresponding branches sent downwards by the gustatory. The Sympathetic nerve, in the neck, descends from the carotid foramen in the temporal bone, behind the internal carotid artery and sheath of the common carotid and internal jugular vein, to the head of the first rib, where it forms the first dorsal ganglion, and becomes thoracic. In its course downwards it rests upon the rectus anticus major and longus colli muscles, and forms three ganglia,—superior, middle, and inferior. The Superior cervical ganglion is long and fusiform, extending from near the carotid foramen to opposite the bifurcation of the common carotid. All the ganglia and nerves of the sympathetic present a peculiar reddish-gray appearance and pearly lustre. Since the time of Bichat, the ganglia have been regarded as so many distinct centres, from which nerves are given off in all directions. These directions may, for the convenience of arrangement and description, be reduced to four, viz. superior, inferior, external, and internal. The superior branches com- municate with the ganglion above. The inferior, with the ganglion below. The external, with the spinal nerves at their exit from the intervertebral foramina. The internal branches, hoAvever, are distributed to the viscera. The Branches of the superior cervical ganglion are, there- fore, superior, inferior, external and internal: to which may be added, as proper to this ganglion, anterior. The Superior branch enters the carotid canal and divides into two branches, Avhich form frequent communications with each other (carotid plexus) and are ultimately distributed Avith the terminal branches of the internal carotid artery. * The connexion between the lingual and cervical nerves is subject to much irregularity. THE DISSECTOR. 165 They communicate also with the sixth nerve in the cavernous sinus. The carotid plexus, formed by the communicating filaments passing between these tAvo branches, is augmented by the re- ception of a branch from the Vidian, and another from the tympanic branch of the glosso-pharyngeal. The Inferior branch, often double, communicates with the middle cervical ganglion: it also sends filaments to the third and fourth cervical nerves. The External branches are the branches of communication Avith the facial, glosso-pharyngeal, pneumogastric, spinal ac- cessory, and lingual nerves; also with the first and second cervical nerves. The Internal branches are, pharyngeal, filaments commu- nicating with the pharyngeal plexus upon the middle con- strictor muscle; laryngeal, to communicate with the external laryngeal nerve; and a long branch, which descends to the thorax, and is distributed to the heart; the Superior cardiac nerve (n. superficialis cordis.) The Anterior branches are small soft filaments called nervi molles, which accompany the ramifications of the external carotid artery. The Middle cervical ganglion is of small size, and situated upon the inferior thyroid artery (hence, thyroid ganglion,) opposite the fifth or sixth vertebra: sometimes it is behind the artery, or altogether wanting. Branches.—Superior, communicating with the first cervical ganglion. Inferior, communicating Avith the third cervical ganglion. External, communicating with the third, fourth, and fifth cervical nerves. Internal, a large branch which descends to the heart; the Middle cardiac nerve (n. cardiacus magnus.) The Inferior cervical ganglion, of a semilunar form, is situated immediately behind the vertebral artery, supported by the transverse process of the seventh cervical vertebra. Branches.—Superior, to communicate Avith the second cervi- cal ganglion. Inferior, to communicate with the first dorsal ganglion. External, to communicate with the fifth, sixth, and seventh cervical nerves; and one or two small filaments which ascend along the vertebral artery. 166 THE DISSECTOR. Internal, several branches to communicate with the recur- rent nerve; and a branch to the heart, the Inferior cardiac nerve. The cardiac nerves are very irregular, both in origin and course: they cross the innominata artery on the right, and the left carotid on the left side, and pass in front of the tra- chea to the base of the heart. The Cervical nerves are eight in number, and increase in size from above downAvards. The first (sub-occipital) passes out of the spinal canal betAveen the occipital bone and the atlas; the last, between the last cervical and first dorsal ver- tebrae. Each nerve, at its escape from the intervertebral foramen, divides into an anterior and posterior branch. The anterior branches of the four upper cervical nerves form the cervical plexus; the posterior branches, the posterior cervical plexus. The anterior branches of the four inferior cervical and first dorsal from the brachial plexus. The Cervical plexus is formed by loops of communica- tion which pass from one nerve to another ; the communicat- ing branch between the first and secofid nerves is very small; the others have several communicating branches which are larger in size. The plexus rests upon the levator anguli scapulae and posterior scalenus muscles. Its Branches may be arranged into three groups, ascend- ing, descending superficial, and descending deep. f Superficialis colli, Ascending < Auricularis magnus, (^Occipitalis minor. "Superficial / A<™.™?les, 1 J \ Claviculares. Descending L j Communicans noni, Deep < Phrenic, (^ (^Muscular. The Superficialis colli (fig. 38. 11.) crosses the sterno- mastoid muscle obliquely, and divides into two branches ; one is distributed to the integument on the side of the neck, the other ascends to the submaxillary region, and forms a plexus with the cervical branches of the facial. The Auricularis magnus (fig. 38. 13.,) the largest of the three, curves around the posterior border of the sterno- mastoid, and ascends by the side of the jugular vein to the THE DISSECTOR. 167 external ear, supplying that organ and the integument over the parotid gland and side of the face. It communicates in the parotid gland with the facial nerve. The Occipitalis minor (fig. 38. 14.) ascends along the pos- terior border of the sterno-mastoid muscle, and is distributed to the integument on the posterior part of the head. The Claviculares (fig. 38. 15.) and acromiales are several large branches Avhich descend over the claAricle, and are dis- tributed to the integument of the chest and shoulder. The Communicans noni is a long branch formed by fila- ments from the second and third cervical nerve: it descends and forms a loop with the descendens noni over the sheath of the carotid vessels. The Phrenic nerve is formed by filaments from the third, fourth, and fifth cervical nerves, receiving also a branch from the sympathetic. It descends to the root of the neck, resting upon the scalenus anticus muscle, then crosses the first portion of the subclavian artery, and enters the chest between it and the subclaAdan vein. Within the chest it passes through the middle mediastinum, between the pleura and pericardium to the diaphragm to which it is distributed, and communicates in the abdomen with the phrenic and solar plexus, particularly on the left side. The left phrenic nerve is rather longer than the right, from the inclination of the heart to the left side. Posterior cervical plexus.—The posterior branches of the first, second, and third cervical nerves, send branches of communication between each other, which form a small plexus beneath the complexus muscle. All the branches of the posterior cervical plexus are distributed to the muscles on the back part of the neck, with the exception of a large ascending branch of the second cervical nerve, the occipitalis major. This nerve pierces the complexus, and ascends with the occipital artery, to be distributed to the integument on the posterior part of the head. It supplies no muscles. Organ of Voice. The Larnyx is situated at the forepart of the neck between the trachea and the base of the tongue. It is composed of cartilages, ligaments, muscles, vessels, and nerves, and mucous membrane. The Cartilages are, the 168 THE DISSECTOR. Thyroid, Two Arytenoid, Cricoid, Epiglottis. The Thyroid (flwpwj—«««*, like a shield) is the largest car- tilage of the larynx; it consists of two lateral portions or alee, which meet at an acute angle in front, and form the pro- jection which is known by the name of pomum Adami. Where the pomum Adami is prominent, a burso mucosa is often found between it and the skin. Each ala is quadrilateral, and forms a rounded border pos- teriorly, which terminates above, in the superior cornu, and below, in the inferior cornu. Upon the side of the ala is an oblique line, into which the sterno-thyroid muscle is inserted, and from which the thyro- hyoid takes its origin. Behind this is a vertical line which gives origin to the inferior constrictor muscle. In the receding angle formed by the meeting of the tAvo alae upon the inner side of the cartilage, and near to its lower border, are attached the epiglottis, the chordae vocales, the thyro-arytenoid, and the thyro-epiglottidean muscles. The Cricoid (xpixoj—«8oj, like a ring) is a ring of cartilage, narrow in front and broad behind, where it is surmounted by two rounded surfaces, which articulate with the arytenoid car- tilages. Upon .the middle of line, posteriorly, is a vertical ridge which gives attachment to the oesophagus. On each side of the ridge are the depressions which lodge the crico- arytenoidei postici muscles. On either side of the ring is a glenoid cavity, which articulates with the inferior cornu of the thyroid cartilage. The Arytenoid cartilages (apvtwa,* a pitcher) two in number, are triangular in form. They are broad below, where they articulate with the upper border of the cricoid, and give at- tachment to the crico-arytenoidei postici, crico-arytenoidei laterales, and thyro-arytenoidei muscles, and chordae vocales; and pointed above, where they articulate Avith two little curved cartilages, called cornieula laryngis (capitula laryngis). On the posterior surface they are concave, and lodge the aryte- noideus muscle. * 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 striking resemblance to the mouth of a pitcher having a large spout. THE DISSECTOR. 169 The Epiglottis (tft(,y%ufri(, upon the tongue) is a fibro-carti- lage of a yellowish colour; studded with a number of small mucous glands, which are lodged in shallow pits upon its sur- face. It is shaped like a cordate leaf, and is placed immedi- ately 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, between the two alae of the thyroid cartilage. Two small cartilaginous tubercles (cuneiform) are often found in the folds of the mucous membrane which bound the opening of the larynx laterally. Ligaments.—The ligaments of the larynx are numerous, and may be arranged into four groups: 1. Those which articu- late 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. The two Thyro-hyoidean ligaments pass between the supe- rior cornua of the thyroid and the extremities of the greater cornua of the os hyoides: a sesamoid bone is found in each. The Thyro-hyoidean membrane is a broad membranous layer, occupying the entire space between the thyroid cartilage and 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-thyroi- dean membrane, through which the operation of laryngotomy is performed. The latter is sometimes crossed by a small artery. 3. The ligaments of the arytenoid cartilages are four in number:— Tavo Capsular ligaments and synovial membranes, Avhich articulate the arytenoid cartilages with the cricoid; and the thyro-arytenoid ligaments, or chordae vocales, Avhich pass back- Avards from the receding angle of the thyroid cartilage, near to its loAver border, to be inserted into the bases of the aryte- noid cartilages. The space between these two ligaments is the glottis, or rima glottidis. 170 THE DISSECTOR. 4. The ligaments of the epiglottis are five in number:— 1. Three folds of mucous membrane, one at the middle, and one at each side, called fraena epiglottidis, which hold the epiglottis back to the tongue. 2. Epiglotto-hyoidean ligament, which connects the epiglottis to the posterior surface of the os hyoides. 3. The ligament which attaches the epiglottis to the receding angle of the thyroid cartilage. Fig. 46. A side view of the larynx: one A posterior view of the larynx. ala of the thyroid cartilage has been removed. 1. The thyroid cartilage. 2. One of its ascending cornua. 3. One of the descending cornua. 4. 7. The cricoid cartilage. 5. 5. The arytenoideus cartilages. 6. The arytenoideus muscle, consisting of oblique and transverse fasciculi. 7. The crico-arytenoid postici muscles. 8. The epiglottis. 1. The remaining ala of the thyroid cartilage. 2. One of the arytenoid cartilages. 3. One of the cornicula laryngis. 4. The cricoid cartilage. 5. The crico-arytenoideus posticus muscle. 6. The crico-arytenoideus late- ralis. 7. The thyro - arytenoideus. 8. The crico - thyroidean membrane. 9. One half of the epiglottis. 10. The upper part of the trachea. The Muscles of the larynx are eight in number; the five larger are the muscles of the chordae vocales and rima glotti- lis; the three smaller are muscles of the epiglottis. The five muscles of the chordae vocales and rima glottidis are the Crico-thyroid, Crico-arytenoideus posticus, Crico-arytenoideus lateralis, Thyro-arytenoideus, Arytenoideus. The Crico-thyroid muscle arises from the anterior surface THE DISSECTOR. 171 of the cricoid cartilage, and is inserted into the lower and inner border of the thyroid. The Crico-arytenoideus posticus arises from the depression on the posterior surface of the cricoid cartilage, and is in- serted into the base of the arytenoid. The Crico-arytenoideus lateralis arises from the upper bor- der of the side of the cricoid, and is inserted into the base of the arytenoid cartilage. The Thyro-arytenoideus arises from the receding angle of the thyroid cartilage, close to the outer side of the corda vo- calis, and passes backwards parallel with the chord, to be in- serted into the base of the arytenoid cartilage. The Arytenoideus muscle occupies the posterior concave sur- face of the arytenoid cartilages, between Avhich it is stretched. It consists of several planes of transverse and oblique fibres: hence it Avas formerly considered as several muscles, under the names of transversi and obliqui. The three muscles of the epiglottis are the Thyro-epiglottideus, Aryteno-epiglottideus superior, Aryteno-epiglottideus inferior (Hilton's muscle). The Thyro-epiglottideus appears to be formed by the upper fibres of the thyro-arytenoideus muscle: they spread out upon the external surface of the sacculus laryngis, on Avhich they are lost; a few of the anterior fibres being continued onwards to the side of the epiglottis. The Aryteno-epiglottideus superior consists of a few scat- tered fibres, AA'hich pass forwards in the fold of mucous mem- brane, 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.—This muscle was dis- covered by Mr. Hilton, and is very important in relation to the sacculus laryngis, vvith which it is closely connected. It may be found 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 at- tachment of the chorda vocalis; and passing forwards, and a little upAvards, expands over the upper half, or tAvo-thirds of the sacculus laryngis, and is inserted by a broad attachment into the side of the epiglottis. 172 THE DISSECTOR. Actions.—The crico-thyroid and arytenoid muscles are contractors of the rima glottidis: the crico-arytenoideus pos- ticus and lateralis, and the thyro-arytenoideus, are dilators. The crico-thyroid muscles elongate, and thereby bring to- gether the chordae vocales, by draAving the thyroid cartilage doAvn wards and forwards; their posterior attachment at the arytenoid cartilages being fixed. The arytenoid muscles ap- proximates the arytenoid cartilages, and consequently the chordae vocales, directly. The crico-thyroidei postici being attached to the outer side of the base of the arytenoid cartilages, draw them from each other, and stretch the chordae vocales. The crico-arytenoidei laterales draw the arytenoid cartilages from each other, but relax the chordae vocales; and the thyro-arytenoidei increase the width of the glottis, by directly relaxing the chordae vo- cales. The thyro-epiglottideus acts principally by compressing the glands of the sacculus laryngis and the sac itself: by its at- tachment to the epiglottis it would act feebly upon that valve. The aryteno-epiglottideus superior serve 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," writes Mr. Hilton, "to compress the subjacent glands which open into the pouch; to diminish the capacity of that cavity, and change its form; and to approximate the epiglottis and the arytenoid cartilage." Mucous membrane.—The larynx is lined by the mucous membrane, which is continued from the mouth and pharynx, and prolonged onwards through the trachea and bronchi to the bronchial cells. The chordae vocales form two horizontal projections of the mucous membrane, and constitute the late- ral boundaries of the glottis, or rima glottidis. Immediately above the horizontal projection of the chorda vocalis, at each side, is a depressed fossa, the ventricle of the larynx. The superior boundary of the ventricle is an arched border of mu- cous membrane, Avhich is very incorrectly termed the superior chorda vocalis. If the rounded extremity of a probe be in- troduced into the ventricle of the larynx, and then directed upAvards, it will enter a considerable pouch, which has been recently described by Mr. Hilton which great care, as the THE DISSECTOR. 173 sacculus laryngis.* From the ventricle of the larynx the sacculus is continued upwards, nearly as high as the upper border of the thyroid cartilage, and sometimes beyond it. When dissected from the interior of the larynx, it is found covered by the aryteno-epiglottideus muscle and a fibrous membrane, which is attached to the superior chorda vocalis 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-epi- glottideus muscle. On the surface of its mucous membrane are the openings of sixty or seventy small follicular glands, which are situated in the sub-mucous tissue, and give its ex- ternal surface a rough and ill-dissected appearance. This mucous secretion 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 Entrance of the larynx is formed by two folds of mu- cous membrane, stretched between the apices of the arytenoid cartilages and the sides of the epiglottis. The arytenoid glands and superior aryteno-epiglottidean muscles are situated within these folds. The Glands of the larynx are, 1. The epiglottic—most improperly named—for it consists merely of a mass of fat * This sac was discovered and described by Mr. Hilton before he was aware that it had already been pointed out by the older anatomists. We ourselves made a dissection, which we still possess, of the same sac in an enlarged state during the. month of August 1837, without any knowledge either of Mr. Hilton's labours, or Morgagni's account. The sac projected considerably above the upper border of the thyroid cartilage, and the extremity had been snipped off on one side in the removal of the muscles. The larynx was pre- sented to us by Dr. George Moor of Camberwell: he had obtained it from a child who died of bronchial disease; and he conceived that this peculiar dis- position of the mucous membrane might explain some of the symptoms by which the case was accompanied. Cruveilhier made the same discovery in equal ignorance of Morgagni's description, for we read in a note at page (577, vol. ii. of his Anatomie Descriptive,—" J'ai vupour la premiere fois cette ar- riere cavite" chez un individu affecte" de phthisie laryngee, oil elle 6tait tres- developpee. Je fis des recherches sur le larynx d'autres individus, et je trouvai que cette disposition etait constante. Je ne savais pas alors que Morgagni avait indique" et fait reprdsenter la meme disposition." Cruviel- hier compares its form very aptly to a "Phrygian casque," and Morgagni's. figure, Advers. 1. Epist. Anat. 8. plate 2. fig. 4., has the same appearance. But neither of these anatomists notice the follicular glands described by Mr. Hilton. 15* 174 ME DISSECTOR. situated between the convexity of the epiglottis and the thyro- hyoid membrane; 2. The arytenoid glands, some small gra- nules found in the folds of mucous membrane near the apex of the arytenoid cartilage. Vessels and Nerves.—The arteries of the larynx are de- rived from the superior and inferior thyroid. The nerves are the superior laryngeal and recurrent laryngeal; both bran- ches of the pneumogastric. The two nerves communicate with each other freely; but the superior laryngeal is distri- buted principally to the mucous membrane at the entrance of the larynx; the recurrent, to the muscles. In children, and in the female, the larynx is less developed than in the adult male; the thyroid cartilage forms a more obtuse angle, and is less firm: in the male the angle is acute, and the cartilage often converted into bone. The Trachea extends from opposite the fifth cervical ver- tebra to opposite the third dorsal, where it divides into two bronchi. The right bronchus, larger than the left, passes off nearly at right angles, to the upper part of the corresponding lung. The left descends obliquely, and passes beneath the arch of the aorta, to reach the left lung. The Trachea is composed of Fibro-cartilaginous rings, Muscular fibres, Fibrous membrane, Glands. Mucous membrane, The Fibro-cartilaginous rings are from fifteen to twenty in number, and extend for two-thirds around the cylinder of the trachea. They are deficient at the posterior part, where the tube is completed by fibrous membrane. The last ring has usually a triangular form in front. The rings are connected to each other by a membrane of yellow elastic fibrous tissue, which in the space between the extremities of the cartilages, posteriorly, forms a distinct layer. The Muscular fibres form a thin layer, extending trans- versely betAveen the extremities of the cartilages. On the posterior surface they are covered in by a cellulo-fibrous la- mella, in which are lodged the tracheal glands. These are small flattened ovoid bodies, situated in great number between «the fibrous and muscular layers of the membranous portion of the trachea, and also between the two layers of elastic fibrous tissue connecting the rings. They pour their secretion upon the mucous membrane. THE DISSECTOR. 175 Tliyroid Gland. The Thyroid gland consists of two lobes, which are situated one on each side of the trachea, and are connected with each other by means of an isthmus, which crosses its upper rings. There is considerable variety in the situation and breadth of this isthmus; which should be recollected in the performance of operations upon the trachea. The gland is larger in young subjects, and in females, than in the adult and males. It is the seat of an enlargement called bronchocele, goitre, or the Derbyshire neck. A muscle is occasionally found connected with its upper border or with its isthmus, and attached, superiorly, to the body of the os hyoides. It was named by Soemmering the " Levator glandulae thyroideae." 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 this vessel in tracheotomy, might be fatal to the patient. The Nerves are derived from the superior laryngeal and sympathetic. The Orbit. The student should now direct his attention to the anatomy of the orbit, and of the fifth pair of nerves. To open the orbit (the calvarium and brain having been re- moved) the frontal bone must be sawn through at the inner extremity of the orbital ridge; and externally, at its outer extremity. The roof of the orbit may then be comminuted with the hammer; a process easily performed, on account of the thinness of the orbital plate of the frontal bone and lesser wing of the sphenoid. The superciliary portion of the orbit may now be driven forwards by a smart blow, and the broken fragments of the roof of the orbit removed. The periosteum will then be exposed unbroken and undisturbed. Remove the periosteum from the Avhole of the upper sur- face of the exposed orbit, and the muscles, vessels, and nerves may then be examined. The contents of the orbit are, 1st. The globe of the eye appended to the extremity of the optic nerve. 2d. The six 176 THE DISSECTOR. muscles which move the eyeball, four recti and two obliqui, and the elevator muscle of the upper eyelid. 3d. The oph- thalmic artery, with its numerous branches. 4th. The oph- thalmic vein with its tributaries. 5th. The nerves, which consist of three branches of the ophthalmic—frontal, lachry- mal, and nasal; the third, fourth, and sixth, to the muscles and the ciliary ganglion with its branches". 6th. The lachry- mal gland. We shall pursue the plan of the examination of the orbit, that we have heretofore followed in the examination of the neck. Studying the muscles and the more prominent rela- tions of the various structures on the one side, and the vessels and nerves on the opposite. In the middle line is the levator palpebrae muscle, and rest- ing upon it the frontal nerve, with its accompanying artery, the supra-orbital. To the inner side is the obliquus superior, and running along its border the fourth nerve posteriorly, and the infra-trochlear branch in front. To the outer side is the upper border of the external rectus supporting the lachry- mal artery and nerve, and in front the lachrymal gland. If now the levator palpebrae muscle, and with it the frontal nerve and artery be divided through the middle and turned aside, the superior rectus will be seen occupying the middle place, and if the obliquus superior be also divided and its ends thrown aside, the upper margin of the internal rectus will occupy the inner side supporting the infra-trochlear nerve. Next divide the superior rectus through the middle, and draw its ends asunder, in doing which some branches of the third nerve may be seen entering its under surface, and a third plane will be brought into view. This requires to be freed of a large quantity of fat, before the structures situated in it can be fully seen. The student must work cautiously and unweariedly, until he has removed every particle of this fat, which however is not difficult to do from its being con- tained in areolae of loose cellular tissue. In the middle line he will now perceive the optic nerve, crossed from without inAvards by the ophthalmic artery and nasal neiwe, and having to its outer side the ascending branch of the third nerve, the ciliary ganglion with its branches, the ciliary arteries, and a little more externally, in contact with the external rectus muscle, the sixth nerve. Next divide the optic nerve through its middle, and draw THE DISSECTOR. 177 it forwards, when a layer will be observed, which is formed by the inferior rectus muscle supporting the long branch of the third nerve in the middle line; and in front, the inferior oblique muscle connected with the globe of the eye. A tabular arrangement of these structures will probably enable the student to learn their respective relations with more facility. The plan represents the right orbit. The student should now commence the examination of the muscles of the orbit; and, in order to render them tense and more easy of dissection, he should inject the globe of the eye Avith tallow or wax. This is easily done by pushing a probe through the optic nerve into the globe of the eye, in order to break down the cribriform plate of the sclerotic coat, and then inserting an injection pipe. The Muscles of the orbit are seven:— Levator palpebrae, Internal rectus, Superior rectus, Superior oblique, Inferior rectus, Inferior oblique. External rectus, The Levator palpebrae arises from the common tendon. This tendon is common to all the muscles of the orbit, with the exception of the inferior oblique, and is attached to the bones immediately around the optic foramen. The muscle is inserted into the tarsal cartilage of the upper eyelid. The Superior rectus arises from the common tendon, and is inserted into the upper surface of the globe of the eye. The Internal rectus arises from the common tendon, and is inserted into the outer surface of the globe of the eye. The External rectus arises by two heads, one from the common tendon, the other from the edge of the greater ala of the sphenoid bone. It is inserted into the outer surface of the globe of the eye. The Inferior rectus arrises from the common tendon, and is inserted into the under surface of the globe of the eye. The Obliquus superior arises from the common tendon, and runs forwards to the pulley beneath the internal angular pro- cess of the frontal bone. Its tendon is thence reflected to its insertion upon the posterior and external surface of the globe of the eye, beneath the superior rectus. The Inferior oblique arises from the nasal process of the superior maxillary bone, and passes outwards beneath the in- 178 THE DISSECTOR. ferior rectus and eyeball, to be inserted into its posterior and external surface beneath the external rectus. Actions.—The levator palpebrae raises the upper eyelid. The four recti, acting singly, pull the eyeball in the four di- rections of upwards, downwards, inwards, and outwards. Act- ing by pairs, they carry the eyeball in the diagonal of these directions, viz. upwards and inwards, upwards and outwards, downwards and inwards, or downwards and outwards. Acting all together, they retract the globe within the orbit, as occurs in cholera. The superior oblique muscle, acting alone, rotates the globe inwards and forwards, and carries the pupil out- wards and downwards to the lower and outer angle of the orbit. The inferior oblique, acting alone, rotates the globe outwards and upwards, and carries the pupil outwards and upwards to the upper and outer angle of the eye. Both mus- cles acting together, draw the eyeball forwards, and give the pupil that slight degree of eversion which enables it to receive the largest field of view. Fig. 47. The muscles of the eyeball; the view is taken from the outer side of the right orbit. 1. A small fragment of the sphenoid bone around the entrance of the optic nerve into the orbit. 2. The optic nerve. 3. The globe of the eye. 4. The levator palpebrae muscle. 5. The superior oblique muscle. 6. Its cartila- ginous pulley. 7. Its reflected tendon. 8. The inferior oblique muscle, the small square knob at its commencement is a piece of its bony origin broken off. 9. The superior rectus. 10. The internal rectus almost concealed by the optic nerve. 11. Part of the external rectus, showing its two heads of origin. 12. The extremity of the external rectus at its insertion; the inter- mediate portion of the muscle having been removed. 13. The inferior rectus. 14. The tunica albuginea, formed by the expansion of the tendons of the four recti. The opposite orbit should now be opened in the way already directed, with a view to study the distribution of the nerves and vessels. THE DISSECTOR. 179 Nerves of the Orbit. The student should remove with a chisel as much of the outer wall of the orbit as possible, and break away the ante- rior clinoid process. Then let him remove the thin layer of dura mater that forms the outer boundary of the cavernous sinus. He will thus expose the four nerves passing by the side of the "sella turcica" to enter the orbit through the sphenoidal fissure. These should be separately and carefully traced through their course: they are the Third or motor oculi (fig. 49. 3.,) Fourth or patheticus, 4., Ophthalmic or first division of the fifth, 13., Sixth or abducens, 6. They are placed in the above order from above downwards, at their entrance into the cavernous sinus; but the ophthalmic nerve soon divides into its three branches, frontal, lachrymal, and nasal, and the relative situation of the others is also changed with regard to each other. At the sphenoidal fissure, the six nerves are disposed in two sets, a superior consisting of Fourth (fig. 49. 4.,) Frontal, 16., Lachrymal, 17., which enter the orbit above the origin of the levator palpe- bral muscle; and an inferior set, the Nasal (fig. 49. 18.,) Third, 3., Sixth, 6., which enter the orbit between the two Fig. 48. A transverse sec- heads of the external rectus muscle. tion of the cavernous sinus of While passing by the side of thethe riSht side- sella turcica, the third, (fig. 48. 5.,) fourth, 6., and ophthalmic, 7., nerves, are situated in the outer wall of the sinus, 4.; the sixth, 3., and internal carotid artery, 2., being placed in the inner wall. 1. The dura mater, splitting to enclose the vessels and nerves. 2. The internal carotid artery. 3. The sixth nerve, receiving a branch from the sympathetic. 4. The cavernous sinus. 5. The third nerve. 6. The fourth nerve. 7. The ophthalmic division of the fifth nerve. The Ophthalmic nerve (fig. 49. Id. fig. 50. 2.) arises from 180 THE DISSECTOR. the Casserian ganglion, beneath the dura mater, and passes forwards through the outer wall of the cavernous sinus, lying externally to the other nerves, and divides into its three bran- ches. Previously to its division, it gives off a small recurrent nerve* that passes backwards between the two layers of ten- torium, as far as the lateral sinus. Fig. 49. The origin, course, and distribution of the nerves of the^ orbit. The pons Varolii, and medulla oblongata are in outline, and the horizontal portion of the carotid artery marks the situation of the cavernous sinus. 1. The pons Varolii. 2. The medulla oblongata. 3. The third nerve, arising from the crus cerebri. 7. Its ascending branch. 8. Its communi- cation with the ciliary ganglion. 4. The fourth nerve, arising from the valve of Vieussens, immediately below the corpora quadrigemina, 9. 5. The fifth nerve, arising by two roots. 10. The posterior root from the corpus resti- forme. 11. The anterior root from the corpus pyramidale. 12. The Cas- serian ganglion. 13. Its ophthalmic division. 14. Its superior maxillary division. 15. Its inferior maxillary division. 16. The frontal branch of the ophthalmic nerve. 17. The lachrymal branch. 18. The nasal. 19. Its communication with the ciliary ganglion. 20. Its ciliary branches. 21. The infra-trochlear branch, given off just as the nerve enters the anterior eth- moidal foramen. 6. 6. The sixth nerve, arising from the corpus pyramidale. 22. The ciliary ganglion, giving off ciliary nerves. 23. The outline of the optic nerve. 24. The internal carotid artery. 25. The corpus olivare. The arrow at 3. marks the relative situation of the four nerves of the orbit, as * This recurrent nerve to the dura mater is sometimes a branch of the fourth nerve, of which distribution the author has a preparation now before him. Arnold of Heidelberg, an authority of great weight, assigns it solely to the ophthalmic, and has displayed its distribution in a beautifully dissected preparation which the author has also attentively examined. It was from this preparation that his beautiful plate was drawn. THE DISSECTOR. 181 they enter the cavernous sinus. The third is the highest, then the fourth, next the ophthalmic division of the fifth, and then the sixth. The arrow at 6. marks the relation of the six nerves as they enter the sphenoidal fissure;— the three superior, fourth, frontal, and lachrymal enter the orbit above the origin of the levator palpebrae;—the three inferior, nasal, third, and sixth, pass between the two heads of the external rectus. The Branches of the ophthalmic nerve are, the Frontal, Lachrymal, Nasal. The Frontal nerve (fig. 49 16.) mounts above the levator palpebrae, and runs forwards, resting upon that muscle to the supra-orbital foramen, through which it escapes upon the fore- head, and supplies the integument of that region. It gives off one small branch, the supra-trochlear (fig. 50. 4.,) which passes inwards above the pulley of the superior ob- lique muscle, and is distributed to the integument at the inner angle of the eye and root of the nose. The Lachrymal nerve* (fig. 49. 17.) is the smallest of the three. It inclines slightly outwards to the upper border of the external rectus muscle, along which it runs to the lachry- mal gland and upper eyelid, to which it is distributed. A small branch pierces the malar bone, and communicates with the facial nerve. The Nasal nerve (fig. 49. 18.) passes forwards between the two heads of the external rectus muscle, crosses the optic nerve in company with the ophthalmic artery, and enters the anterior ethmoidal foramen (fig. 50. 8.) immediately above the internal rectus. It then traverses the upper part of the ethmoid bone to the cribriform plate, and passes downAvards through the most anterior of its foramina into the nose, where it divides into two branches, one supplying the mucous membrane, near the anterior openings of the nares; the other, passing out between the fibro-cartilages, is distributed on the integument at the extremity of the nose. Branches.—Within the orbit it gives off three branches. * Mr Swan in his dissections of the nerves, has found the lachrymal nerve to'be formed by a branch from the ophthalmic and one from the fourth nerve- and he describes this mode of formation as its normal origin. We have s'ometimes seen the lachrymal nerve arising in this manner, but more frequently proceeding directly from the ophthalmic, without any communi- cation with the fourth nerve. 16 182 THE DISSECTOR. A ganglionic branch {fig. 50. 7.) (given or received) from the superior angle of the ciliary ganglion. One or two ciliary filaments (fig. 49. 20.) which leave the nerve as it crosses the optic nerve. They pierce the sclerotic, and pass between that tunic and the choroid to the iris. The Infra trochlear (fig. 50. 9.) is given off just as the nerve is about to enter the anterior ethmoidal foramen. It passes along the superior border of the internal rectus to the inner angle of the eye, where it is distributed. # The Fourth nerve (fig. 49. 4.) (patheticus,) the smallest of the cerebral nerves, arises from the valve of Vieussens, and enters the cavernous sinus through a canal in the tentorium, close to the opening which transmits the fifth nerve. It is at first placed below the third nerve, but ascends above it as it passes forwards and crosses the levator palpebrae to be distri- buted on the orbital surface of the superior oblique muscle. The Third nerve (fig. 49. 3.) (motor oculi) arises from the crus cerebri, and enters the cavernous sinus by an opening in the dura mater, close to the posterior clinoid process. It then descends to the space between the two heads of the ex- ternal rectus, and, entering the orbit, divides into two branches, a superior and an inferior branch: it also commu- nicates with the ciliary ganglion by means of a short trunk. The Superior branch, 7., mounts above the optic nerve to supply the superior rectus, levator palpebrae, and internal rectus. The Inferior branch runs forwards upon the inferior rectus muscle, and is distributed to it and the inferior oblique. The Ganglionic branch, 8., short and thick, passes to the inferior angle of the ciliary ganglion. The Sixth mirve (fig. 49. 6.) (abducens) arises from the upper part of the corpus pyramidale. It pierces the dura mater on the basilar process of the sphenoid bone, and enters the cavernous sinus behind the ophthalmic nerve, by which it is concealed in its Avhole course. Passing betAveen the two heads of the external rectus muscle, it soon enters its sub- stance, and is distributed to that muscle. It is the only nerve situated in the inner wall of the cavernous sinus. Branches.—The two ascending branches of the carotid plexus pass upAyards by the side of the internal carotid artery, and communicate with this nerve in the cavernous sinus. See Dage 164. THE DISSECTOR. 183 The Ciliary ganglion (fig. 49. 22.) (lenticular) is a small square-shaped ganglion, situated close to the outer side of the optic nerve. It receives branches at its tAvo posterior angles, from the nasal branch of tho ophthalmic and inferior branch of the third nerve. Branches.—From its anterior border it gives off eight or nine filaments, which arrange themselves into two sets: a superior set pierce the sclerotic slightly above the entrance of the optic nerve, and an inferior set below it. A posterior fila- ment is described by Arnold as passing backwards from the ganglion to the cavernous sinus, and folloAving the course of the carotid artery to its plexus. Vessels of the Orbit. The Ophthalmic artery is a branch of the internal ca- rotid : it enters the orbit through the foramen opticum, imme- diately to the outer side of the optic nerve. It then crosses the optic nerve, and runs along the inner wall of the orbit to the inner angle of the eye, where it divides into two branches, the frontal and nasal: the latter inosculates very freely with the angular artery. Branches.—Its branches maybe arranged into three groups:— 1st, those distributed to the circumference of the orbit; 2d. Muscular branches ; 3d. Branches supplying the globe of tie eye. 1st. Lachrymal, Supra-orbital, Posterior ethmoidal, Anterior ethmoidal, Palpebral, Frontal, Nasal. 2d. Muscular—anterior ciliary. 3d. Ciliary, Centralis retinae. The Lachrymal is the first branch of the ophthalmic artery, and is usually given off before that artery enters the optic foramen. It follows the course of the lachrymal nerve, along the upper border of the external rectus muscle, and is dis- tributed to the lachrymal gland and upper eyelid. The Supra-orbital artery follows the course of the frontal 184 THE DISSECTOR. nerve, resting on the levator palpebrae muscle: it passes through the supra-orbital foramen, and is distributed to the muscles and integument of the forehead. The Ethmoidal arteries, posterior and anterior, pass through the ethmoidal foramina, and are distributed to the ethmoidal cells and nasal fossae. The Palpebral arteries, superior and inferior, encircle the eyelids to which they are distributed. The Frontal artery, one of the terminal branches of the ophthalmic, emerges from the orbit at its inner angle, and is distributed upon the middle of the forehead. The Nasal artery, the other terminal branch of the oph- thalmic, distributes a branch to the ridge of the nose, and inosculates with the angular artery. The Muscular branches, usually two in number, superior and inferior, supply the muscles of the orbit; and upon the anterior aspect of the globe of the eye give off the anterior ciliary arteries, which pierce the sclerotic near its margin of connexion with the cornea, and supply the iris. It is the congestion of these vessels that gives rise to the vascular zone around the cornea in iritis. The Ciliary arteries are divided, according to their ex- tent, into short, long, and anterior. The Short ciliary, very numerous, pierce the sclerotic around the entrance of the optic nerve, and supply the choroid coat and ciliary processes. The long ciliary, two in number, pierce the sclerotic upon opposite sides of the globe of the eye, and pass forwards between it and the choroid to the iris to which they are distributed. The anterior have been de- scribed. The Centralis retinae artery pierces the optic nerve, and passes forwards in the centre of its cylinder to the retina, where it divides into branches, AAThich form the inner layer of that membrane. It supplies the retinae, hyaloid membrane, and capsule of the lens, by means of a branch sent forwards through the centre of the vitreous humour. The Ophthalmic vein collects the venous blood from all parts of the orbit, and forms a large trunk, which crosses the optic nerve with the ophthalmic artery, and passes between the two heads of the external rectus, to open into the caver- nous sinus. THE DISSECTOR. 185 Fifth Pair of Nerves. The student should now proceed to the dissection of the fifth pair of nerves. For this purpose the contents of the orbit should be entirely removed, and its external wall sawn through nearly to a level with its floor. Then reflect the dura mater from the anterior surface of the petrous bone, so as to expose the Casserian* ganglion and its three divisions. The Fifth nerve (trigeminus, trifacial) arises by two roots, one from the corpus pyramidale (fig. 49. 11.;) the other, 10., from the corpus restiforme. The nerve pierces the dura mater at the insertion of the tentorium into the extremity of the petrous bone, and forms the large ganglion of a semilunar form called Casserian (fig. 49. 12., fig. 50. 1.) The ganglion immediately divides into the three large nerves, the ophthal- mic, superior maxillary, and inferior maxillary. The Ophthalmic has just been described with the contents of the orbit. We must now examine the maxillary nerves. The Superior maxillary nerve (fig. 50. 10.) passes for- wards to the foramen rotundum, crosses the spheno-maxillary fossa, and enters the canal in the floor of the orbit, along which it runs to the infra-orbital foramen. Emerging on the face, beneath the levator labii superioris muscle, it divides into a lash of branches, 16., which are distributed to the muscles and integument of the cheek, and form a plexus with the facial nerve. Branches:— In the spheno-maxillary fossa. Two from Meckel's ganglion, fig. 50. 12. Orbital - - 11. Posterior dental - 13. In the infra-orbital canal. Middle dental - 14. Anterior dental - 15. On the face. Muscular \ Cutaneous j 16. * Julius Casserius was appointed to fill the Anatomical Chair in Padua, iu 1609. He died in 1G27. 16* 186 THE DISSECTOR. The Two branches (fig. 50. 12.) from Meckel's ganglion ascend from that body to join the nerve, as it crosses the spheno-maxillary fossa. The Orbital branch (fig. 50. 11.) enters the orbit through the spheno-maxillary fissure, and divides into two branches; lachrymal, which ascends along the outer wall of the orbit to the lachrymal gland, and communicates with the lachrymal nerve; temporo-malar, Avhich passes forwards and divides into two branches, one piercing the malar bone, and distributed to the integument of the cheek; the other escaping through the outer wall of the orbit, to supply the temporal muscle. Fig. 50. The branches of the fifth nerve. 1. The Casserian ganglion. 2. The ophthalmic nerve. 3. The frontal nerve. 4. Its supra-trochlear branch. 5. The lachrymal nerve 6 The nasal nerve. 7. Its branch of communication with the ciliary 'ganglion. 8. The passage of the nerve through the anterior ethmoidal foramen 9 The infra-trochlear n*rve- 10- The superior maxillary nerve. 11. Its orbital branch. 12. The branches of communication with Meckel's sans-lion 13 The posterior dental branches. 14. Middle dental branches. 15 The anterior dental branches 16. The infra-orbital branches. 17. The inferior maxil- lary nerve. 18. Its external or muscular division. 19. The internal division of the inferior maxilhn-y nerve. The arrow marks the separation of these two divisions of the nerve by the external pterygoid muscle. 20. The gus- ^nSonerV'> T)'. "f ^ °f, C0I™ic^ ™th the submaxilLy ganglion. 22. The inferior dental nerve, arising by two roots 23 Its mylo-hyoidean branch. 24. The auricular nerve 25. iTs branch of com munication with the facial nerve. orancu oi com THE DISSECTOR. 187 The Posterior dental branches (fig. 50. 13.) pass through small foramina, in the posterior surface of the superior max- illary bone, and supply the posterior teeth. The Middle and Anterior dental branches (fig. 50. 14. 15.) descend to the teeth, the former beneath the lining mem- brane of the antrum, the latter through distinct canals in the walls of the bone. The Inferior maxillary nerve (fig. 50. 17.) is the largest of the three divisions of the Casserian ganglion, and is augmented in size by the anterior root of the fifth, Avhich passes behind the ganglion, and unites with the inferior max- illary, previously to its exit from the foramen ovale. By turning up the ganglion, this portion of the nerve may be easily seen, as a white rounded cord, altogether different in appearance and structure from the ganglion, against which it lies. Escaping at the foramen ovale the nerve divides into tAvo portions, an external, 18., into.which is traced the whole of the anterior root of the fifth, and an internal, 19.; the two portions being separated from each other by the external pterygoid muscle. The External division, 18., obtaining the whole of the motor function of the fifth, by means of its anterior root, im- mediately diA'ides into five branches, which are distributed to the muscles of the temporo-maxillary region: these are— Masseteric, which crosses the sigmoid notch with the mas- seteric artery to the masseter muscle. Temporal, two branches passing between the upper border of the external pterygoid muscle and the temporal bone to the temporal muscle. Buccal, a large branch which pierces the fibres of the ex- ternal pterygoid, to reach the buccinator muscle. External pterygoid, to the external pterygoid muscle. Internal pterygoid, to the internal pterygoid muscle. To see the branches of the internal division requires a little additional dissection. The external wall of the orbit having been already removed to trace the superior maxillary nerve, the student should make a section through the great ala of the sphenoid bone to near the foramen rotundum. Another in- cision should be carried parallel with the margin of the petrous bone to near the foramen ovale, and the intervening portion of bone broken away with the hammer. The chisel 188 THE DISSECTOR. and hammer will complete the removal of the remaining bone, if the nerve be not already exposed as it is passing through the foramen ovale. The external pterygoid muscle, which has hitherto protected the nerves from the- saw and hammer, is then to be removed, and the nerves, as they lie upon the in- ternal pterygoid, cleared of fat and cellular tissue. The Internal division (fig. 50. 19.) of the inferior maxil- lary nerve divides into three large branches :— Gustatory, Auricular. Inferior dental, The Gustatory nerve (fig. 50. 20.) descends between the two pterygoid muscles to the side of the tongue, where it be- comes flattened, and divides into numerous filaments, which are distributed to the papilae and mucous membrane. Relations.—It lies at first betAveen the two pterygoid muscles, next between the internal pterygoid and ramus of the jaw, then between the stylo-glossus muscle and submaxillary gland; lastly, it runs along the side of the tongue, resting upon the hyo-glossus muscle, and covered in by the mylo- hyoideus and mucous membrane. Branches.—While between the pterygoid muscles, it receives the chorda tympani, which joins it at an acute angle. At the submaxillary gland, the chorda tympani, 21., quits the nerve to enter the submaxillary ganglion. While resting on the hyo-glossus muscle, it sends filaments of communication (fig. 40. *) to the lingual nerve, Avhich is also situated upon this muscle. The Inferior dental nerve (fig. 50. 22.) arises from the inferior maxillary by two nervous cords, betAveen which passes the arterior meningea media. It descends to the den- tal foramen Avith the inferior dental artery, between the in- ternal lateral ligament and the ramus of the lower jaw. It then runs along the canal in the inferior maxillary bone, dis- tributing branches to the teeth, and emerges upon the chin at the mental foramen, Avhere it communicates Avith branches of the facial nerve, and is distributed to the integument. It gives off but one branch, the mylo-hyoidean, 23., Avhich leaves the nerve just as it is about to enter the dental fora- men. This branch pierces the insertion of the internal lateral ligament, and descends along a groove in the bone to the ex- ternal surface of the mylo-hyoid muscle, to Avhich it is distri- buted. THE DISSECTOR. 189 The Auricular nerve (fig. 50. 24.) passes directly back- wards behind the articulation of the loAver jaw, against Avhich it rests. In this situation it divides into two branches, which reunite, and form a kind of plexus. From the plexus two branches are given off—one, 25., to communicate with the facial nerve in the parotid gland. The other, or temporal branch, ascends upon the root of the zygoma in front of the external ear, and is distributed to the pinna, the meatus, and the integument of the temple. It is pressure upon this nerve, which produces the agony of pain in abscess in the meatus. Cranial Ganglia of the Sympathetic Six sympathetic ganglia are described as existing in the head : they are, the Ganglion of Ribes, Naso palatine, or Cloquet's, Ciliary ganglion, Otic, or Arnold's, Spheno-palatine, or Meckel's, Submaxillary ganglion. The Ganglion of Ribes is a small ganglion of communica- tion between the sympathetic filaments of the anterior cere- bral arteries. It is situated on the anterior communicating artery. The remaining five ganglia are situated in relation Avith the fifth nerve and its branches. Thus, The Ciliary ganglion communicates with the nasal branch of the ophthalmic nerve. The Spheno-palatine is the sympathetic ganglion of the superior maxillary nerve. The Naso-palatine ganglion (if it exist) is a dependence on the spheno-palatine. The Otic ganglion is situated on the internal pterygoid nerve, in relation with the motor root of the inferior maxil- lary nerve. The Submaxillary ganglion communicates with the gusta- tory nerAre. We shall describe them here,* in the order in which they are best dissected; the ganglion of Ribes belongs to the con- sideration of the brain; and the ciliary has been already noticed, page 183. * A more minute description of these ganglia, with an engraving, will be found in the Chapter " On the Sympathetic Nerve." 190 THE DISSECTOR. Otic Ganglion.—A small ganglion discovered by Arnold, of Heidelberg, is situated in contact with the internal surface of the inferior maxillary nerve, near to the foramen ovale. A good demonstration of this ganglion requires a fresh sub- ject and an especial dissection. In an ordinary dissection it will be best seen by dividing the inferior maxillary nerve at the foramen ovale, and drawing it outwards with hooks. The student should then dissect its inner surface carefully, under a strong light, and he will perceive a small ash-coloured body upon the course of the internal pterygoid nerve. Its fila- ments are too small to be seen in this dissection; they com- municate with the motor root of the inferior maxillary, the auricular, tympanic, facial, and sympathetic nerves, and two are distributed to the tAvo muscles, tensor tympani and tensor palati. The spheno-palatine ganglion should next be examined: for this purpose the root of the pterygoid process must be broken away with the chisel. A glance at the base of the skull will show the student how far this incision should be carried. The tAvo descending branches from the superior maxillary nerve are the proper guides to the ganglion. The Spheno-palatine ganglion (Meckel's) is the largest of the cranial ganglia, and is situated in the pterygo-maxil- lary fossa. It gives off branches in four different directions. Upwards, two branches to communicate Avith the superior maxillary nerve. Downwards, the posterior palatine nerves. Inwards, spheno-palatine or nasal branches. Backwards, the Vidian nerve. The Posterior palatine nerves, three in number, descend through the palatine canal to the posterior palatine foramina, distributing branches to the mucous membrane of the nose, Eustachian tube, and palate. The Nasal branches pass into the nose through the spheno- palatine foramen, supplying the mucous membrane, covering the turbinate bones and septum. One of the latter, longer than the rest, (naso-palatine branch,) descends by the side of the septum to the naso-palatine canal, where it communicates with the naso-palatine ganglion. The Vidian* nerve passes directly backAvards through the * Vidus Vidius, Professor of Anatomy in the College of France, in 1542, THE DISSECTOR. 191 pterygoid canal, and divides into two branches, carotid and petrosal. The Carotid branch enters the carotid canal, and commu- nicates with the carotid plexus. (Page 164.) The Petrosal branch enters the skull through the foramen lacerum basis cranii, and passes backwards beneath the Cas- serian ganglion to the hiatus Fallopii, on the anterior aspect of the petrous bone, where it unites with the facial just as that nerve is forming its angular bend. Near to the stylo- mastoid foramen, it is reflected backwards from the facial nerve, and crosses the tympanum in a curved direction be- tAveen the handle of the malleus and long process of the incus, and assumes the name of chorda tympani. Escaping from the tympanum through the fissura Glaseri, it descends to the gustatory nerve, which it joins at an acute angle ; and at the submaxillary gland it quits that nerve to enter the submaxil- lary ganglion. The Submaxillary ganglion is situated in the submaxil- lary gland, close to the gustatory nenre, to Avhich it is con- nected by the nerve above described, and by several smaller branches. It sends off a number of filaments, which are distributed upon the ducts of the submaxillary gland. The Naso-palatine ganglion (Cloquet's) is described by Cloquet as occupying the naso-palatine canal, giving branches, anterior palatine to the palate, and communicating Avith Meckel's ganglion by means of the naso-palatine nerve. Its existence is denied by Arnold, who has shown the naso- palatine passing as a distinct nervous filament through the naso-palatine canal to the papilla on the palate behind the incisor teeth. Cruveilhier, also, has been unable to find this ganglion. The sympathetic system will be found described as a Avhole in Chapter XL Pharynx. The student should now proceed to examine the remainder of the muscles of the neck, together with the anatomy of the pharynx and larynx. For this purpose the following prepara- tion must be made. The trachea and oesophagus are to be cut through at the loAver part of the neck, and drawn up- and in Pisa, in 1547. He was the predecessor of Sylvius, in the College of France. His "Anatomia Corporis Humani" was published, in 1611, at Venice, after his death. 192 THE DISSECTOR. wards by dividing the loose cellular tissue which connects the pharynx to the vertebral column. The saAv 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 a musculo-membranous sac, situated upon the vertebral column, and extending from the base of the skull to a point parallel with the cricoid cartilage, where it becomes constricted to form the oeso- Fig. 51. A side view of the muscles phagUS of the pharynx. ■ The 'Mmdes of the pharynx are, the Constrictor inferior, Constrictor medius, Constrictor superior, Stylo-pharyngeus, Pa- lato-pharyngeus. The Constrictor inferior arises from the two upper rings of the trachea, from the cricoid, and the side of the thyroid cartilage. It is inserted into the tendinous raphe overlapping the middle constrictor. This muscle must be removed before the next can be examined. In dissecting the surface of the next muscle, the pharyn- geal plexus will require to be removed. 1. The trachea. 2. The cricoid cartilage. 3. The crico-thyroid mem- brane. 4. The thyroid cartilage. 5. The thyro-hyoidean membrane. 6. The os hyoides. 7. The stylo-hyoidean ligament. 8. The oesophagus. 9. The inferior constrictor. 10. The middle constrictor. 11. The superior con- strictor. 12. The stylo-pharyngeus muscle passing down between the supe- rior and middle constrictor. 13. The upper concave border of the superior constrictor; at this point the muscular fibres of the pharynx are deficient. 14. The pterygo-maxillary ligament. 15. The buccinator muscle. 16. The orbicularis oris. 17. The mylo-hyoideus. The Constrictor medius arises from the great cornu of the os hyoides, from the lesser cornu, and from the stylo-hyoidean ligament. ^ It radiates from its orign upon the side of the pharynx, its loAver fibres descending and being overlapped by THE DISSECTOR 193 the constrictor inferior, its upper fibres ascending so as to cover in the constrictor superior. It is inserted into the raphe and basilar process of the occipital bone. The upper portion of this muscle must be turned down, to bring the Avhole of the superior constrictor into view; in so doing, the stylo-pharyngeus muscle will be seen passing be- neath its upper border. The Constrictor superior arises from the extremity of the molar ridge of the lower jaw, from the pterygo-maxillary liga- ment, and from the lower half of the internal pterygoid plate. Its fibres curve around the pharynx, to be inserted into the raphe and basilar process of the occipital bone. It is over- lapped by the middle constrictor. The upper part of the pharynx, on each side between the base of the skull and the upper curved border of the superior constrictor, is deficient of muscular fibres, being completed only by the mucous mem- brane. The Stylo-pharyngeus muscle arises from the inner side and base of the styloid process: it descends between, the su- perior and middle constrictor muscles, and is inserted into the posterior border of the thyroid cartilage. This muscle is the guide in dissection to the glosso-pharyngeal nerve, which runs along its lower border, and crosses it opposite the root of the tongue. Lower down it is in relation Avith the pharyngeal branch of the pneumogastric nerve, which passes to the middle constrictor to form the pharyngeal plexus. The Palato-pharyngeus is described with the muscles of the soft palate. It arises from the soft palate, and is inserted into the inner surface of the pharynx. Actions.—The three constrictor muscles contract upon the morsel of food as soon as it is received by the pharynx, and convey it gradually downwards into the oesophagus. The stylo-pharyngei draw the pharynx upwards and widen it late- rally. The palato-pharyngei also draw it upwards, and nar- row the opening of the fauces. Interior of the Pharynx. After examining the exterior of the pharynx with its muscles, it should be laid open in order to examine the inte- rior. For this purpose, an incision should be made along the middle line posteriorly, and the sides drawn out and pinned aside. 17 194 THE DISSECTOR. Fig. 52. The openings pharynx. There are seven openings in the pharynx:— Posterior nares, two, Larynx, Eustachian tubes, two, CEsophagus. Mouth, The Posterior nares (fig. 52. 3. 3.) are the two large openings at the upper and front part of the pharynx. On either side is the irregular depression in the mucous membrane, marking the entrance of the Eustachian tube, 4. Beneath the posterior nares is the large opening into the mouth, 7., and beneath it the opening of the larynx, 8._ The oesophageal opening, 10., is the lower con- stricted portion of the pharynx. The opening into the mouth is partly concealed by a moveable curtain, which is called soft pa- late, or velum pendulum palati: the opening itself is namedfauces. Soft palate (fig. 52. 5.)— Hanging from the middle of the soft palate, is a rounded process, the uvula. From the uArula, on each side, the soft palate forms an arch, which is continued into two projecting pillars or half arches that are continuous below with the sides of the base of the tongue and pharynx.' Between the projecting pillars is a niche lodging the tonsil. 1. The basilar process of the occipital bone. 2. 2. The petrous portion of the temporal bone. 3. 3. The posterior nares, separated by the vomer. 4. 4. The openings of the Eustachian tubes. 5. The soft palate. 6. 6. The posterior arches of the soft palate. 7. The opening from the mouth. 8. The epiglottis. 9. The opening into the larynx. 10. The opening into the oeso- phagus. 11. 11. The sides of the pharynx drawn open. 12. The oesophagus. Fauces.—The boundaries of the fauces are the soft palate above the tongue beloAv, and on either side these t\vo pillars of the soft palate, with the the intervening tonsil. The Muscles of the soft palate are, Azygos uArulae, Levator palati, Tensor palati, Palato-glossus, Palato-pharyngeus. If the mucous membrane be carefully raised from off the soft palate, these muscles will be brought distinctly into view. THE DISSECTOR. 195 The Azygos uvulae is not a single muscle, as might be in- ferred from its name, but a pair of small muscles, placed side by side in the middle line of the soft palate. They arise from the spine of the palate bone, and are inserted into the uvula. The Levator palati arises from the extremity of the petrous bone and Eustachian tube, and spreads out in the structure of the soft palate. This muscle must be turned down from its origin on one side, and removed, and the superior con- strictor dissected away from its pterygoid origin, to bring the next muscle into view. The Tensor palati (circumflexus) arises from the scaphoid fossa at the base of the internal pterygoid plate and from the Eustachian tube, and descends to the hamular process around which it turns, and expands into a tendinous aponeurosis, which is inserted into the transverse ridge on the palate plate of the palate bone, and into the raphe. The tensor palati is separated from the levator by the Eustachian tube and ptery- goid origin of the superior constrictor. These three muscles are placed in the reverse order of their description from before backwards; the tensor palati being the most anterior, next the levator palati, and then the azy- gos uvulae. 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-glossus (constrictor isthmi faucium) is a small fasciculus of fibres that arises in the soft palate, and descends to be inserted into the side of the tongue. It is the projection of this small muscle that forms 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. of constricting the opening of the fauces. The Palato-pharyngeus forms the posterior pillar (fig. 52. 6. 6.) of the fauces; it arises from the soft palate, and is inserted into the muscular structure of the pharynx. 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 betAveen the pharynx and posterior nares during deglutition. The palato-glossus and pharyngeus constrict the opening of the fauces, and press the food from the dorsum of the tongue into the pharynx. 196 THE DISSECTOR. The larynx is described in Chap. VII., on the organs of sense. Praevertebral Region. The remaining region of the neck is the praevertebral, which is provided with a group of five muscles. They have been already exposed by the removal of the pharynx; they are the Rectus anticus major, Rectus anticus minor, Scalenus anticus, Scalenus posticus, Longus colli. The Rectus anticus major arises from the anterior tuber- cles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and is inserted into the basilar pro- cess of the occipital bone. The Rectus anticus minor arises from the anterior border Fig. 53. The prevertebral group of Of tne atlas> an(1 is inserted into muscles of the neck. the basilar process. The Scalenus anticus appears like a continuation of the rectus anticus major; it arises from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and is inserted into the tubercle upon the first rib. The phrenic nerve and sub- clavian vein lie upon the scale- nus anticus and the subclavian artery behind it. The Scalenus posticus arises from the posterior tubercles of all the cervical vertebrae except- ing the first. It is inserted by two fleshy slips into the first and seeond ribs. 1. The rectus anticus major muscle. 2. The scalenus anticus. 3. The lower part of the longus colli of the right side; it is concealed superiorly by the rectus anticus major. 4. The rectus anticus minor. 5. The upper por- tion of the longus colli muscle. 6. Its lower portion ; the figure rests upon the seventh cervical vertebra. 7. The scalenus posticus. 8. The rectus lateralis of the left side. 9. One of the intertransversales muscles. The Longus colli consists of tAvo portions. The upper arises from the anterior tubercle of the atlas, and is inserted THE DISSECTOR. 197 into the transverse processes of the third, fourth, and fifth cervical vertebrae. The lower portion arises from the bodies of the second, third and fourth, and transverse processes of the fourth and fifth, and passes down the neck to be inserted into the bodies of the three lower cervical and three upper dorsal vertebrae. We should thus arrange these attachments in a tabular form :— Origin. Insertion. Upper \ A+i / 3d, 4th, and 5th transverse pro- portion. / a I cesses. T A 2d, 3d, and 4th bodies, f 3 lower cervical vertebrae, bodies. .. >- 4th and 5th transverse i 0 , •. . ,. „ portion. f ) 3 upper dorsal, bodies. r J processes. (^ rr In general terms, the muscle is attached to the bodies and transverse processes of the five superior cervical vertebrae above, and to the bodies of the last three cervical and first three dorsal below. Actions.—The rectus anticus major and minor preserve the equilibrium of the head upon the atlas. The longus colli flexes the anterior part of the vertebral column, and the scaleni are inspiratory muscles raising the first and second ribs. CHAPTER VIII. ORGANS OF SENSE. The Nose and Nasal Fossae. 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 projecting from the centre of the face, immediately above the upper lip. Superi- orly, it is connected with the forehead, by means of a narroAV brido-e; inferiorly, 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 (vibrissee,) which project across the openings, and act as a filter in pre- 17* 198 THE DISSECTOR. venting 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. The integument; 2. Muscles; 3. Bones; 4. Fibro- cartilages ; 5. Mucous membrane ; 6. Vessels and nerves. 1. The Integument forming the tip (lobulus) and Avings (alae) of the nose is extremely thick and dense, so as to be Avith difficulty separated from the fibro-cartilage. It is fur- nished with a number of sebaceous follicles, Avhich by their oily secretion, protect the extremity of the nose in excessive alternations of temperature. The sebaceous matter of these follicles becomes of a dark colour upon the surface, from the attraction of the carbonaceous matter floating in the atmo- sphere: 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 from the follicles, and retaining the form of their interior, has the appearance of small Avhite maggots with black heads. 2. The Muscles are brought into view by reflecting the integument: they are the pyramidalis nasi; compressor nasi; levator labii superioris alaeque nasi; and depressor labii su- perioris alaeque nasi. They have been already described with the muscles of the face. 3. The Bones of the nose, are the nasal, and nasal pro- cesses of the superior maxillary. 4. Tbe Fibro-cartilages give form and stability to the out- Avark of the nose, providing at the same time, by their elas- ticity, against injuries. They are five in number, the Cartilage of the septum, Two lateral cartilages, Two alar cartilages. The Cartilage of the septum, somewhat triangular in form, divides the nose into its tAvo nostrils. It is connected above with the nasal bones and lateral cartilages: behind Avith the ethmoidal septum and vomer; and beloAV with the palate pro- cesses of the superior maxillary bones. The alar cartilages and columna move freely upon the cartilage of the septum, being but loosely connected Avith it by perichondrium. The Lateral cartilages are also triangular; they are con- nected, along the middle line, with the cartilage of the sep- tum: above, with the nasal bones; behind, with the nasal THE DISSECTOR. 199 processes of the superior maxillary: and below, with the alar cartilages. Alar cartilages.—Each of these cartilages is curved in such a manner as to correspond with the opening of the nos- tril, to which it forms a kind of rim. The inner portion is loosely connected with the same part of the opposite cartilage, so as to form the columna. It is expanded and thickened at the point of the nose to constitute the lobe; and, upon the side, expands into the oval form of the ala. Besides these, there are some small irregular cartilaginous plates, which will be discovered in the course of the dissec- tion, but which are unworthy a separate description. The whole of these cartilages are connected with each other, and to the bones, by perichondrium, which, from its membranous structure, permits of the freedom of motion ex- isting between them. 5. The Mucous membrane, lining the interior of the nose, - is continuous with the skin externally, and Avith the pituitary membrane of the nasal fossae within. Around the entrance of the nostrils it is provided with the vibrissae. 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 ophthalmic. Nasal Fossje. To obtain a good vieAv of the nassal fossae, the face must be divided through the nose by a vertical incision, a little to one side of the middle line. The Nassal fossae are two irregular, compressed cavities, extending backwards from the nose to the pharynx. They are bounded, superiorly, by the sphenoid and ethmoid bones. Inferiorly, by the hard palate, and in the middle line they are separated from each other by a bony septum. Upon the outer wall of each fossa, in the dried skull, are three projecting 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 the mucous mem- brane, and serve to increase its surface by their projection and by their convoluted form. The space intervening between the tAvo superior spongy 200 THE DISSECTOR. bones is the superior meatus ; the space between the superior and middle bones is the middle meatus; and that between the inferior and floor of the fossa is the inferior meatus. These Meatuses are passages Avhich extend from before backwards, and it is in rushing through and amongst these, that the atmosphere deposites* 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 ethmoi- dal cells; the frontal sinuses, and the antrum maxillare; and, in the inferior meatus, the termination of the nasal duct. In the dried bone there are two additional openings, the spheno- palatine and the anterior palatine foramen, the former being situated in the superior, and the latter in the inferior meatus. The Mucous membrane of the nasal fossae is called pitu- m ary or Schneiderian. The former name being derived from its secretion, the latter from Schneider, who was the first to show that the secretion of the nose proceeded from the mu- cous membrane, and not from the brain, as was formerly im- agined. It is continuous with the general pulmono-digestive mucous membrane, and may be traced through the openings into the meatuses, into the sphenoidal and ethmoidal cells, into the antrum maxillare, through the nasal duct to the surface of the eye, where it is continuous with the conjunctiva, along the Eustachian tubes into the tympanum and mastoid cells, to which it forms the lining membrane, and through the pos- terior nares into the pharynx and mouth, and thence through the lungs and alimentary canal. Vessels and Nerves.—The arteries of the nasal fossae are the anterior and posterior ethmoidal, from the ophthalmic and spheno-palatine, and pterygo-palatine from the internal maxillary. The Nerves are, the olfactory, the spheno-palatine branches of Meckel's ganglion, and the nasal branch of the oph- thalmic. The Olfactory is the special nerve of smell. Its bulb gives off a considerable number of branches, which pass through the cribriform foramina, and spread upon the osseous surface of the mucous membrane, some passing to the septum, and others to the superior and middle spongy bones. The Spheno-palatine nerves are branches of Meckel's gan- THE DISSECTOR. 201 glion, which enter the fossae through the spheno-palatine foramen, and are distributed to the mucous membrane; one branch, larger than the rest, crosses to the septum, and de- scends by its side to the anterior palatine canal, where it com- municates with- the naso-palatine ganglion. These nerves associate the organ of smell with the organs of sense and of nutrition, by means of the sympathetic nerve. The Nasal nerve enters the nasal fossae through the most anterior of the openings in the cribriform lamella, and divides into two branches, one of which is distributed to the mucous membrane of the septum and around the nostril; the other passes between the cartilages of the nose, and is distributed to the integument on its exterior. Practical Observations.—The mucous membrane is ren- dered an organ of smell by the contact of the odorant par- ticles. If the secretion be deficient, the contact is not appreciable, and there is loss of smell. Or, if the membrane be swollen and thickened, there is likewise loss of smell; both of these conditions are consequences of common cold. When haemorrhage occurs from the mucous membrane, it may proceed to so great an extent as to endanger life. In such a case the nasal fossae must be stopped from behind, by drawing a piece of dry sponge against the posterior nares. This is effected by introducing an instrument, carrying a curved spring with an eye at the end of it, along the inferior meatus to the pharynx. The spring is then pressed onwards, and is directed by its curve into the posterior part of the mouth; the thread bearing the sponge is passed through the eye of the spring, and the instrument with the thread is withdrawn through the nose. The sponge is then carefully directed beneath the soft palate, and drawn gently against the posterior openings of the nose. Growths of various kinds (polypi) proceed from the mucous membrane, and increase to a great size, impeding nasal re- spiration, forcing the bones out of their places, and doing great mischief. They are generally attached by a narrow pedicle, and may be removed with the polypus forceps. In performing this operation, the direction of the meatuses must be recollected, otherwise there would be danger of entangling the instrument, and pulling away one of the spongy bones. When the tube of the stomach-pump cannot be passed through the mouth, it may be introduced into that viscus by 202 THE DISSECTOR. passing it along the inferior meatus of the nose. Patients, with extensive injury to the jaws, have been nourished for a long time solely by liquid food poured into the stomach in this way. In obstruction of the nasal duct, it is often of great con- sequence to introduce a probe into it from the inferior meatus. This operation should therefore be practised upon the subject. The Eye with its Appendages. The form of the eyeball is that of a sphere, having a seg- ment of a smaller sphere ingrafted upon its anterior surface, which increases its antero-posterior diameter. The axes of the two eyeballs are parallel with each other, and do not correspond with the axes of the orbits, which are directed outwards. The optic nerves follow the direction of the orbits, and therefore enter the eyeballs to their nasal side. The Globe of the eye is composed of tunics and humours. The tunics are three in number, the 1. Sclerotic and cornea, 2. Choroid, iris, and ciliary processes, 3. Retina and zonula ciliaris. The Humours are also three :— Aqueous, Crystalline (lens,) Vitreous. Fig. 54. The external tunic of the eye. 1 The sclerotic coat. 2. The tunica albuginea, formed by the expansion ot the tendons of the four recti muscles. 3. The insertion of the superior rectus. 4. The insertion of the inferior rectus. 5. The insertion of the external rectus. 6. Small openings in the sclerotic for the passage of the ciliary arteries and nerves. 7. The optic nerve, which becomes constricted at its point of entrance into the globe of the eye. 8. The cornea THE DISSECTOR. 203 1. The Sclerotic and cornea form the external tunic of the eyeball, and give to it its peculiar form. Four-fifths of the globe are invested by the sclerotic, the remaining fifth by the cornea. The Sclerotic (fig. 54. 1. fig. 57. 1.) (rx^poy, hard) is a dense fibrous membrane, thicker behind than in front. It is continuous, posteriorly, with the sheath of the optic nerve, which is derived from the dura mater, and it is pierced by that nerve as well as by the ciliary nerves and arteries. Anteriorly it presents a bevelled edge, which receives the cornea in the same way that a watch-glass is received by the groove in its case. Its anterior surface is covered by a thin tendinous layer, the tunica albuginea (fig. 54. 2.,) derived from the expansion of the tendons of the four recti muscles. By its posterior surface it gives attachment to the two oblique muscles. The tunica albuginea is covered, for a part of its extent, by the mucous membrane of the front of the eye, the conjunctiva. And, by reason of the brilliancy of its white- ness, gives occasion to the common expression, " The white of the eye." At the entrance of the optic nerve, the sclerotic forms a thin cribriform lamella (fig. 54. 2.) (lamina cribrosa,) which is pierced by a number of minute openings for the passage of the nervous filaments. One of these openings, larger than the rest, and situated in the centre of the lamella, is the porus opticus through which the arteria centralis retinae enters the eye. The Cornea (fig. 54. 8., fig. 57. 3) (corneus, horny) is the transparent projecting layer that forms the anterior fifth of the globe of the eye. In its form it resembles a watch-glass. In structure it consists of five or six thin lamellae, connected to each other by a delicate cellular tissue. It is covered by the conjunctiva in front, and lined by the membrane of the aqueous humour behind. By its edge, which is sharp and thin, it is received Avithin the bevelled border of the sclerotic, to which it is very firmly attached. It is thicker than the anterior portion of the sclerotic. The cornea is not perfectly circular, the transverse diameter being slightly greater than the vertical. This form is parti- cularly evident in animals. The opacity of the cornea, pro- duced by pressure on the globe, results from the infiltration 204 THE DISSECTOR. of fluid into the cellular tissue connecting its layers. This appearance cannot be produced in a sound living eye. The sclerotic and cornea are now to be dissected away from the second tunic; this, with care, may be easily performed, the only connexions subsisting between them being at the circumference of the iris, the entrance of the optic nerve, and the perforation of the ciliary nerves and arteries. Pinch up a fold of the sclerotic near its anterior circumference, and make a small opening into it, then raise the edge of the tunic, and with a pair of fine scissors, having a probe point, divide the entire circumference of the sclerotic, and cut it away bit by bit. Then separate it from its attachment around the cir- cumference of the iris by a gentle pressure with the edge ef the knife. The dissection of the eye must be conducted under water. In the course of this dissection the ciliary nerves and long ciliary arteries will be seen passing forwards between the sclerotic and choroid, to be distributed to the iris. 2. The Second tunic (fig. 55.) of the eye-ball is formed by the choroid and iris; the ciliary processes being an appendage developed from its inner surface. Fig. 55. The second tunic of the eye. 1. The choroid membrane upon which are seen the curved lines marking the arrangement of the venre vorticosae. 2. 2. Ciliary nerves. 3. A long ciliary artery and nerve. 4. The ciliary ligament, 5. The iris: the two sets of fibres are very distinctly seen, the external, radiating towards the centre, and the internal, circular, surrounding the pupil 6. The Choroid (fig. 55. 1., fig. 57. 4.) is a vascular mem- brane of a rich chocolate brown colour upon its external sur- * THE DISSECTOR. 205 face, and of a deep black colour within. It is connected to the sclerotic externally by an extremely fine cellular tissue, and by the passage of nerves and vessels. Internally it is in simple contact with the third tunic of the eye, the retina. It is pierced posteriorly for the passage of the optic nerve, and is connected anteriorly with the iris, ciliary processes, and junction of the cornea and sclerotic, by a dense Avhite structure, the ciliary ligament, which surrounds the circum- ference of the iris like a ring. The choroid membrane is composed of three layers,—1. an external venous, Avhich consists principally of veins arranged in a peculiar manner: hence they have been named venae vorticosae. The marking upon the surface of the membrane produced by these veins resembles so many centres, to which a number of curved lines converge. It is this layer which is connected with the ciliary ligament. 2. The middle, or arte- rial layer (tunica Ruyschiana) is formed principally of the ramifications of minute arteries, and secretes upon its surface the pigmentum nigrum. It is reflected inAvards at its junc- tion with the ciliary ligament, so as to form the ciliary pro- cesses. 3. The internal layer is a delicate membrane (mem- brana pigmenti) which retains the pigmentum nigrum in its place. This membrane presents a beautiful appearance be- neath the microscope, being composed of regular hexagonal plates, and resembling a tessellated pavement. In animals the pigmentum nigrum is replaced by a layer of metallic brilliancy, called the tapetum. The Ciliary ligament, or circle (fig. 55. 4., fig. 57. 5.,) is the bond of union between the external and middle tunics of the eye, and serves to connect the cornea and sclerotic with the iris and external layer of the choroid. It is also the point to which the ciliary nerves and vessels proceed pre- viously to their distribution, and it receives the anterior ciliary arteries through the anterior margin of the sclerotic. A miuute vascular canal is situated within the ciliary liga- ment, called the ciliary canal, or the canal of Fontana, from its discoverer. The Iris (fig. 55. 5., fig. 57. 6.) (iris, a rainbow) is so named from its variety Of colour in different individuals: it forms a septum betAveen the anterior and posterior chambers of the eye, and is pierced in its centre by a circular opening, which is called the pupil (fig. '55. 6., fig. 57.*) By its peri- 18 * 206 THE DISSECTOR. phery it is connected Avith the ciliary ligament, and by its inner circumference forms the margin of the pupil: its ante- rior surface looks towards the cornea, and the posterior towards the ciliary processes and lens. It is composed of two layers, an anterior or fibrous, con- sisting of radiating fibres Avhich converge from the circum- ference towards the centre, and have the power of dilating the pupil, and circular, Avhich surround the pupil like a sphincter, and by their action produce contraction of its area. The posterior layer is of a deep purple tint, and is thence named uvea, from its resemblance in colour to a ripe grape. The Ciliary processes may be seen in two ways, either by removing the iris from its attachment to the ciliary ligament, 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. The ciliary processes consist of a number of triangular folds, formed apparently by the plaiting of the internal layer of the choroid. They are, according to Zinn, about sixty in number, and may be divided into large and small, the latter being situated in the spaces between the former. The base of each triangle is situated towards the circumference of the eye, the apex towards the centre. The periphery is connected with the ciliary ligament, and is continuous with the internal layer of the choroid. The central border is free, and rests against the circumference of the lens. The anterior surface corresponds with the uvea; the posterior receives the folds of the zonula ciliaris between its processes, and thus estab- lishes a connexion between the choroid and hyaloid membrane. The ciliary processes are covered by a thick layer of pigmen- tum nigrum, which is more abundant upon them and upon the anterior part of the choroid than upon the posterior. When the pigment is washed off, the processes are of a whitish colour. 3. The Third tunic (fig. 56.) of the eye is the retina, which is prolonged forwards to the lens by the zonula ciliaris. Dissection.—If, after the preceding dissection, the choroid membrane be carefully raised and removed, the eye being kept under water, the retina will be seen very distinctly. The Retina (fig. 56. 1., fig. 57. 8.) is composed of three layers:— External, or Jacob's membrane, THE DISSECTOR. 207 Middle, Nervous membrane, Internal, Vascular membrane. Jacob's membrane is extremely thin, and is seen as a floccu- lent film when the eye is suspended in water. It is the sup- porting membrane to the nervous substance of the second layer. Dr. Jacob considers it a serous membrane. Fig. 56.—The third tunic of the eye. 1. The retina terminating anteriorly in a scolloped border. 2. The fora- men of Soemmering. 3. The zonula ciliaris. 4. The lens. The Nervous membrane is the expansion of the optic nerve, and forms a thin semi-transparent bluish white layer, Avhich envelopes the vitreous humour, and extends forwards to the commencement of the ciliary processes, Avhere it terminates in an abrupt scolloped margin. The Vascular membrane consists of the ramifications of a minute artery, the arteria centralis retinae, which pierces the optic nerve and enters the globe of the eye through the porus opticus, in the centre of the lamina cribrosa. This artery may be seen very distinctly by making a transverse section of the eyeball. Its branches are continuous anteri- orly with the zonula ciliaris. The retina is deficient posteriorly at a spot corresponding with the axis of the globe of the eye. This spot is called the foramen of Soemmering, (fig. 56. 2,) and is surrounded by a yellow halo, the limbus luteus. It exists only in ani- mals having the axis of the eyeballs parallel with each other, as man, quadrumana, and some reptiles. The Zonula ciliaris, (fig. 56. 6. fig. 57. 9., (Zonula of Zinn,) is a thin vascular layer which connects the anterior margin of the retina Avith the circumference of the lens. It 208 THE DISSECTOR. presents upon its surface a number of small folds correspond- ing with the ciliary processes, between which they are re- ceived. These processes are arranged in the form of rays around the lens, and the spaces between them are stained by the pigmentum nigrum of the ciliary processes. They appear to derive their vessels from the vascular layer of the retina. The under surface of the zonula is in contact with the hya- loid membrane, and around the lens forms the anterior fluted wall of the canal of Petit. Fig. 57. A longitudinal section of the globe of the eye. 1. The sclerotic, thicker behind than the front. 2. The lamina cribrosa; the thin layer of the sclerotic, which is pierced with holes for the passage of the nervous substance of the optic nerve. 3. The cornea, which is seen to be inserted into the border of the sclerotic coat. 4. The choroid mem- brane (the dark layer.) 5. The ciliary ligament. 6. The iris. * The pupil. 7. The ciliary processes. 8. The retina (the white layer.) 9. The dotted line represents the zonula ciliaris, which is continued from the anterior bor- der of the retina to the capsule of the lens. 10. The innermost line is the hyaloid membrane, which may be followed behind the lens. 11. The canal of Petit. 12. The anterior chamber of the eye. The narrow space between the iris and the ciliary processes and lens is the posterior chamber. 13. The lens enclosed in its capsule. 14. The posterior cavity of the globe, in which the vitreous humour is lodged. 15. A minute artery, a branch of the ante- rior centralis retinas, which traverses the centre of the vitreous humour to reach the capsule of the lens. The connection between these folds and the ciliary pro- cesses, may be very easily demonstrated by dividing an eye transversely into two portions, then raising the anterior half, and allowing the vitreous humours to separate from its attach- ment by its OAvn weight. The folds of the zonula will then be seen to be drawn out from between the folds of the ciliary processes. THE DISSECTOR. 209 The Humours of the eye are each provided with its proper membrane. The Aqueous humour is situated in the anterior and poste- rior chambers of the eye. The Anterior chamber (fig. 57. 12.) is the space inter- vening betAveen the cornea in front, and the iris and pupil behind. The Posterior chamber, smaller than the anterior, is the narroAV space bounded by the posterior surface of the iris and pupil in front, and by the ciliary process and lens be- hind. The tAvo chambers are lined by a thin layer, the secreting membrane of the aqueous humour. The Vitreous humour forms the principal bulk of the globe of the eye. It is enclosed in a delicate membrane, the hya- loid (fig. 57. 10.,) which sends processes into its interior, forming cells in which the humour is retained. A small artery, 15., may sometimes be traced through the centre of the vitreous humour to the capsule of the lens. It is surrounded by a sheath of the hyaloid membrane, which is reflected for- wards with it. This vessel is easily injected in the foetus. The Crystalline humour or lens (fig. 57. 13.) is situated immediately behind the pupil, and is surrounded by the ciliary processes, Avhich slightly overlap its margin. It is more convex on the posterior than on the 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 proper capsule, which contains a small quantity of fluid called liquor Morgagni, and is retained in its place by the attachment of the zonula ciliaris. The lens consists of concentric layers, of which the exter- nal are soft, the next firmer, and the central form a hardened nucleus. These layers are best demonstrated by boiling, when they separate easily from each other. Another divi- sion of the lens takes place at the same time: it splits into three triangular segments, which have the sharp edge directed toAvards the centre, and the base towards the circumference. Immediately around the circumference of the lens is a tri- angular canal, the canal of Petit, (fig. 57. 11.,) which is bounded in front by the flutings of the zonula ciliaris, behind by the hyaloid membrane, and within by the border of the lens. 18* 210 THE DISSECTOR. The Vessels of the globe of the eye are the long and short and anterior ciliary arteries, and the arteria centralis retinae. The long ciliary arteries, two in number, pierce the posterior part of the sclerotic, and pass fonvard on each side betAveen that membrane and the choroid, to the ciliary ligament, where they divide into two branches, which are distributed to the iris. The short ciliary arteries pierce the posterior part of the sclerotic coat, and are distributed to the internal layer of the choroid membrane. The anterior ciliary are branches of the muscular arteries. They enter the eye through the ante- rior part of the sclerotic, and are distributed to the iris. It is the increased number of these arteries in iritis that forms the peculiar red zone around the circumference of the cornea. The Arteria centralis retinae enters the optic nerve at about half an inch from the globe of the eye, and passing through the porus opticus is distributed upon the inner surface of the retina, forming its vascular layer; one branch pierces the centre of the vitreous humour, and supplies the capsule of the lens. The Nerves of the eyeball are the optic, two ciliary nerves from the nasal branch of the fifth, and the ciliary nerves from the lenticular ganglion. Observations.—The sclerotic is a tunic of protection, and the cornea a medium for the transmission of light. The choroid supports the vessels destined for the nourishment of the eye, and by its pigmentum nigrum absorbs all loose and scattered rays that might confuse the image impressed upon the retina. The iris, by means of its powers of expansion and contraction, regulates the quantity of light admitted through the pupil. If the iris be thin, and the rays of light pass through its substance, they are immediately absorbed by the uvea, and if that layer be insufficient, they are taken up by the black pigment of the ciliary processes. In Albinoes, where there is a deficiency of pigmentum nigrum, the rays of light traverse the iris and even the sclerotic, and so overAvhelm the eye with light, that sight is destroyed, except in the dimness of evening, or at night. In the manufacture of optical instruments, care is taken to colour their interior black, with the same object, the absorp- tion of scattered rays. ; The transparent lamellated cornea and the humours of the eye have for their office the refraction of the rays in such THE DISSECTOR. 211 proportion as to direct the image in the most favourable man- ner upon the retina. Where the refracting medium is too great, as in over convexity of the cornea and lens, the image is thrown beyond the retina (presbyopia, long-sightedness;) and where it is too little, the image falls short of the nervous membrane (myopia, short-sightedness.) These conditions are rectified by the use of spectacles, which provide a differently refracting medium external to the eye, and thereby correct the transmission of light. Appendages of the Eye. The Appendages of the eye (tutamina oculi) are the eye- brows, eyelids, eyelashes, conjunctiva, caruncula lachrymalis, and the lachrymal apparatus. The Eyebrows, (supercilia,) are two projecting arches of integument covered with short thick hairs, which form the upper boundary of the orbits. They are connected beneath with the orbicularis, occipito-frontalis, and corrugator super- cilii muscles; their use is to shade the eyes from a too vivid light, or protect them from particles of dust and moisture flowing over the forehead. The Eyelids (palpebrae) are two valvular layers placed in front of the eye, which defend it from injury by their closure. When they are drawn open they leave between them an elliptic space, the angles of which are called canthi. Near to the inner canthus two small projections, (fig. 58. 5.) are observed on both lids, upon which are seen the openings of the lachrymal ducts (puncta lachrymalia.) Hence they are named lachrymal tubercles. The eyelids have, entering into their structure, integument, orbicularis muscle, tarsal cartilages, Meibomian glands, and conjunctiva. The tegumentary cellular tissue of the eyelids is remark- able for its looseness and entire absence of adipose substance. It is particularly liable to serous infiltration. The fibres of the orbicularis muscle covering the eyelids, are extremely thin and pale. The Tarsal cartilages are two thin lamellae of fibro-carti- lage, which give form and support to the eyelids. The su- perior (fig. 58. 1.) is of a semilunar form, broad in the middle, and tapering to each extremity. Its lower border is 212 THE DISSECTOR. broad and flat, its upper is thin, and gives attachment to the levator palpebrae and to the fibrous membrane of the lids. The Inferior fibro-cartilage (fig. 58. 2.) is a narrow ellipti- cal band situated in the substance of the lower lid. Its upper border is flat, and corresponds with the flat edge of the upper cartilage. The lower is held in its place by the fibrous mem- brane. The cartilages do not extend quite so far as the angles of the lids. The Fibrous membrane of the lids is firmly attached to the periosteum, around the margin of the orbit, by its circum- ference, and to the tarsal cartilages by its central margin. It is thick and dense on the outer half of the orbit, but becomes thin to its inner side. Its use is to retain the tarsal carti- lages in their place, and give support to the lids; hence it has been named the broad tarsal ligament. The Meibomian glands are embedded in the internal sur- face of the cartilages, and are very distinctly seen on ex- amining the inner surface of the lids. They have the appearance of parallel strings of pearls, about tAventy or twenty-four upon each cartilage, and open by minute fora- mina (fig. 58. 1. 2.) upon the edges of the lids. They cor- respond in length with the breadth of the cartilage, and are consequently 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 rounded follicles open ; the latter are so numerous as almost to conceal the tube by which the secretion is poured out upon the margin of the lids. They are figured, after a very careful examination, in Dr. Quain's "Elements of Anatomy." Occasionally an arch is formed between two of them, as is seen in that figure, and produces a very graceful appearance. The edges of the eyelids are furnished with a triple row of long thick hairs, which curve upwards from the upper lid, and downwards from the lower, so that they may not interlace with each other in the closure of the eyelids, and prove an impediment to the opening of the eyes. These are the eye- lashes (cilia,) important organs of defence to the sensitive surface of so delicate an organ as the eye. The Conjunctiva is the mucous membrane of the eye. It covers the whole of its anterior surface, and is then reflected upon the lids so as to form their internal layer. It is very thin, and closely adherent Avhere it covers the cornea, and no THE DISSECTOR. 21«i vessels can be traced into it. Upon the sclerotica it is thicker and less adherent, and to the inner surface of the lids is con- nected by loose cellular tissue. It is continuous with the general pulmono-digestive mucous membrane, and sympathizes in its affections, 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 may be traced through the puncta lachrymalia into the lachrymal sac, and thence downwards through the nasal duct into the inferior meatus of the nose. Fig. 58. The lachrymal apparatus and tarsal cartilages of the eyelids. 1. The tarsal cartilage of the upper lid. 2. The tarsal cartilage of the lower lid;—the openings along the edges of the lids are those of the Mei- bomian ducts. 3. The caruncula lachrymalis. 4. The lachrymal gland pouring out its secretion by seven small ducts. 5. The lachrymal tubercles with the openings of the lachrymal ducts called puncta lachrymalia. 6. 6. The lachrymal ducts. 7. The lachrymal sac. 8. The nasal duct. 9. Its termi- nation in the inferior meatus of the nose. 10. The inferior turbinated bone. The Caruncula lachrymalis (fig. 58. 3.) is the small red- dish body which occupies the inner angle or canthus of the eye. In health it presents a bright pink tinge, in sickness it 214 THE DISSECTOR. loses its colour and becomes pale. It consists in an as- semblage of mucous follicles, and is the source of the whitish secretion which so constantly forms at the inner angle of the eye. It is frequently found studded with short hairs. Immediately to the outer side of the caruncula, is a slight duplicature of the conjunctiva, called plica semilunaris, which is the rudiment of the third lid of animals, the membrana nictitans of birds. Vessels and nerves.—The palpebrae are supplied intern- ally with arteries from the ophthalmic, and externally from the facial and transverse facial. Their nerves are branches of the fifth and of the facial. Lachrymal Apparatus. The Lachrymal apparatus consists of the lachrymal gland and excretory ducts, the puncta lachrymalia and lachrymal sac. The Lachrymal gland (fig. 58. 4.) is a small flattened body having two lobes, situated at the upper and outer angle of the eye, resting upon the eyeball by its under surface, and against the wall of the orbit by the upper. Its secretion is poured out upon the surface of the conjunctiva by seven small excretory ducts. Puncta lachrymalia.—Near to the inner canthus are two slight projections on the edges of the eyelids. These are the lachrymal tubercles (fig. 58. 5.,) and upon the point of each may be seen a small opening, the punctum lachrymale, the commencement of the corresponding lachrymal duct. From these points the lachrymal ducts, 6. 6., proceed to the lachry- mal sac. The superior duct first ascends, then turns suddenly inwards towards the sac, forming an abrupt angle. The in- ferior duct forms the same kind of angle, by descending at first, and then turning abruptly inwards. They are dense and elastic in structure, and remain constantly open, so that they act like capillary tubes in absorbing the tears from the surface of the eye. The two fasciculi of the tensor tarsi muscle are inserted into these ducts, and serve to draw them inwards. The Lachrymal sac (fig. 58. 7.) is the upper extremity of the nasal duct, and is not more dilated than any other por- tion of the canal. It is lodged in the groove of the lachrymal bone, and is often distinguished internally from the nasal THE DISSECTOR. 215 duct by a semilunar or circular valve. It consists of mucous membrane, but is covered in and retained in its 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, Avhich arises from the same ridge, and in its action upon the lachrymal ducts may serve to compress the lachrymal sac. The Nasal duct (fig. 58. 8.) is a short canal directed doAvn- wards and backwards and a little inwards to the inferior meatus of the nose, where it terminates. It is lined by the mucous membrane, which is continuous with the conjunctiva above and the pituitary membrane of the nose beloAV. Ob- struction to this duct gives origin to the disease called fistula lachrymalis. Vessels and nerves.—The lachrymal gland is supplied Avith blood by the lachrymal branch of the ophthalmic artery, and with nerves by the lachrymal branch of the ophthalmic and orbital branch of the superior maxillary. The Organ of Hearing. The Ear is composed of three parts,—1. external ear ; 2. middle ear, or tympanum; 3. internal ear, or labyrinth. The External ear consists of two portions, the pinna and meatus; the former representing a kind of funnel which col- lects the vibrations of the atmosphere, called sounds, and the latter a tube which conveys the vibrations to the tympanum. The Pinna presents a number of folds and hollows upon its surface, which have different names assigned to them. Thus the external folded margin is called the helix (tu%, a fold.) The elevation parallel to and in front of the helix is called antihelix (aivti, opposite.) The pointed process, pro- jecting like a valve over the opening of the ear from the face, is called the tragus (fpayoj, a goat,) probably from being some- times covered with bristly hair like that of a goat; and a tubercle opposite to it is the antitragus. The loAver depen- dent and fleshy portion of the pinna is the lobulus. The space between the helix and antihelix is named the fossa in- nominata. Another depression is observed on the upper ex- tremity of the antihelix, which bifurcates and leaves a triangular space between its branches called the scaphoid fossa ; and the large central space to which all the channels converge is the concha, which opens directly into the meatus. 216 THE DISSECTOR. The pinna is composed of integument, fibro-cartilage, and muscles. The Integument is thin, and closely connected Avith the fibro-cartilage. The Fibro-cartilage gives form to the pinna, and surrounds the commencement of the meatus. It is firmly attached to the external auditory process, and is deficient in the lobulus. The proper Muscles of the pinna are the Major helicis, Antitragicus, Minor helicis, Trans versus auriculae. Tragicus, The Major helicis is a narrow band of muscular fibres situated upon the anterior border of the helix, just above the tragus. The Minor helicis is placed upon the posterior extremity of the helix. The Tragicus is a thin layer of muscular fibres, situated upon the tragus. The Antitragicus arises from the antitragus, and is in- serted into the posterior part of the helix. The Transversus auriculae, partly tendinous and partly mus- cular, extends transversely faom the convexity of the concha to that of the helix, on the posterior surface of the pinna. These vessels are rudimentary in the human ear, and de- serve only the title of muscles in the ears of animals. Two other muscles are described by Mr. Tod,* the obliquus auris and contractor meatus, or trago-helicus. There are also a number of ligaments which connect the opposite borders of the fissures in the fibro-cartilage. The meatus auditorius is a canal partly cartilaginous and partly osseous, about an inch in length, which extends in- wards and a little forwards from the concha to the tympa- num. It is narroAver in the middle than at each extremity, and forms an oval cylinder, the long diameter being vertical; and is slightly curved upon itself, the concavity looking doAvn- wards. It is lined by an extremely thin pouch of cuticle, which, when withdrawn after maceration, preserves the form of the meatus. Some stiff short hairs are also found in its interior, * " The Anatomy and Physiology of the Organ of Hearing," by David Tod, 1832. THE DISSECTOR. 217 which stretch across the tube, and prevent the ingress of in- sects and dust. Beneath the cuticle are a number of small ceruminous follicles, which secrete the wax of the ear. Vessels and nerves.—The pinna is plentifully supplied with arteries; by the anterior auricular from the temporal, and by the posterior auricular from the external carotid. Its Nerves are derived from the auricular branch of the fifth, and the auricularis magnus of the cervical plexus. 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 membrana tympani; internally, by its inner wall; and in its circumference by the petrous bone and mastoid cells. The Membrana tympani is stretched obliquely from above downwards across the extremity of the meatus auditorius, and gives attachment by its centre and inner surface to the handle of the malleus. It is depressed toAvards the centre, and is concave towards the meatus, and convex toAvards the tympanum. It is composed of three layers, an external cuti- cular, middle fibrous and muscular, and internal mucous, derived from the mucous lining of the tympanum. The tympanum contains four small bones, ossicula auditus, viz. the Malleus, Orbiculare, Incus, Stapes. The Malleus (hammer) consists of a head, neck, handle, (manubrium,) and two processes, long (processus gricilis) and short (processus brevis.) It is attached by the manubrium to the membrana tympani, the extremity of the handle extend- ing to the centre of that membrane. Its connexion is effected by being inserted between the mucous lining and the fibrous and muscular layer. Its long process descends to the fissura Glaseri, and gives attachment to the laxator tympani muscle. Into the short process is inserted the tendon of the tensor tympani, and 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, and widely separated from the other. It consists of two processes, which join each other nearly at right angles, and at their junction form a flattened body, which articulates with the head of the malleus. The short process is free; the long process descends nearly parallel 218 THE DISSECTOR. with the handle of the malleus, and curves inwards, near to its termination, to articulate with the os orbiculare. The Os orbiculare is a small spherical bone, distinct in the foetus, but anchylosed to the long process of the incus in the adult, and appearing only as a process of that bone. It arti- culates with the head of the stapes. The Stapes is shaped like a stirrup, to which it bears a very close resemblance. Its head articulates with the os orbiculare, and the two branches are connected at its extre- mity by a flat oval-shaped plate, representing the foot of the stirrup, which fits accurately the opening from the typanum into the vestibule, the fenestra oralis. The neck of the stapes gives attachment to the stapedius muscle. The 3Iuscles of the tympanum are also four, the Tensor tympani, Laxator tympani minor, Laxator tympani, Stapedius. To these Mr. Tod has added five others, the posterior mal- lei, superior capitis mallei, obliquus incudis externus posterior, triangularis incudis, and musculus, or structura stapedius in- ferior; for the history of Avhich Ave must refer the lover of minute anatomy to the work previously quoted. The Tensor tympani arises from the petrous portion of the temporal bone, and from the Eustachian tube, and passes for- wards in a distinct canal separated from the tube by the pro- cessus cochleariformis, to be inserted into the short process of the malleus. The Laxator tympani arises from the spinous process of the sphenoid bone, and passes through an opening in the fissura Glaseri, to be inserted into the long process of the malleus. The Laxator tympani minor arises from the upper margin of the meatus, and is inserted into the handle of the malleus. The Stapedius arises from the interior of the pyramid, and escapes from its summit to be inserted into the neck of the stapes. The openings in the tympanum are ten in number, five large and^we small; they are the Large openings. Small openings. Meatus auditorius, Fenestra ovalis, Fenestra rotunda Mastoid cells, Eustachian tube. Entrance of the chorda tympani, Exit of the chorda tympani, For the laxator tympani, For the tensor tympani, For the stapedius. THE DISSECTOR. 219 The opening of the Meatus auditorius has been already. described. The Fenestra ovalis (fig. 59. 3.) is an oval opening, situated in the upper part of the inner wall of the tympanum, directly opposite the meatus; it is the opening of communication be- tween the tympanum and vestibule, and is closed by the foot of the stapes and by the lining membranes of both caArities. The Fenestra rotunda (fig. 59. 5.) is somewhat triangular in its form, and situated in the inner Avail of the tympanum, below and rather posteriorly to the fenestra ovalis, from Avhich it is separated by a bony elevation, called the promon- tory, 4. It serves to communicate the tympanum Avith the cochlea. In the fresh subject it is closed by a proper mem- brane, as well as by the mucous lining of both cavities. The Mastoid cells are very numerous, and occupy the whole of the interior of the mastoid process, and part of the petrous bone. They communicate by a large irregular opening (fig. 59. 12.) Avith the upper and posterior circumference of the tympanum. * Fig. 59. The tympanum of the left ear. 1. Its inner wall. 2. A convex ridge marking the situation of the aque- ductus Fallopii; the star shows its termination on the face of the section, in its course downwards to the stylo-mastoid foramen. 3. The fenestra ovalis. 4. The promontory. 5. The fenestra rotunda. Anteriorly (6.) is the entrance of the Eustachian tube. 7. The opening for the tensor tympani. 8. The opening for the laxator tympani; and (9.) the opening of exit for the chorda tympani nerve. Posteriorly (10.) is the opening of entrance for the chorda tympani; and (11.) the pyramid with the small opening at its apex which gives passage to the tendon of the stapedius muscle. Superiorly is a large opening (12.) leading backwards to the mastoid cells. The Eustachian tube (fig. 59. 6.) is a canal of communi- cation extending -obliquely between the pharynx and the an- 220 THE DISSECTOR. terior circumference of the tympanum. In structure it is partly fibro-cartilaginous and partly osseous, is broad and expanded at its pharyngeal extremity, and narrow and com- pressed at the tympanum. The Smaller openings serve for the transmission of the chorda tympani nerve, and three of the muscles of the tym- panum. The Opening (fig. 59. 10.) by which the chorda tympani enters the tympanum, is near the root of the pyramid, at about the middle of the posterior wall. The Opening of exit (fig. 59. 9.) of the chorda tympani, is at the fissura Glaseri in the anterior wall of the tympanum. The Opening for the laxator tympani muscle (fig. 59. 8.) is also situated in the fissura Glaseri, in the anterior wall of the tympanum. The Opening for the tensor tympani muscle (fig. 59. 7.) 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, called the pyramid (fig. 59. 11.) which is situated on the posterior wall of the tympanum, im- mediately behind the fenestra ovalis. Directly above the fenestra ovalis is a rounded ridge (fig. 59. 2.,) formed by the projection of the aqueductus Fallopii. Beneath the fenestra ovalis, and separating it from the fenestra rotunda, is the promontory (fig. 59. 4.,) a rounded projection channelled upon its surface by three small grooves, which lodge the three tympanic branches of Jacobson's nerve. The Foramina and processes of the tympanum may be arranged into four groups, according to their situation. 1. In the External wall is the meatus auditorius, closed by the membrana tympani. 2. In the Inner wall (fig. 59.,) from above downwards, are the Ridge of the aqueductus Fallopii, 2., Fenestra ovalis, 3., Promonotory, 4., Grooves for Jacobson's nerve, Fenestra rotunda, 5. 3. In the Posterior trail are the Opening of the mastoid cells, 12., Pyramid, 11., THE DISSECTOR. 221 Opening for the stapedius, Apertura chordae (entrance,) 10. 4. In the Anterior wall are the Eustachian tube, 6., Opening for the tensor tympani, 7., Opening for the laxator tympani, 8., Apertura chordae (exit,) 9. 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 tym- panum it is reflected into the mastoid cells, which it lines throughout, and passes through the Eustachian tube to be- come continuous with the mucous membrane of the pharynx. Vessels and nerves.—The Arteries of the tympanum are derived from the internal maxillary, internal carotid, and posterior auricular. Its Nerves are—1. Minute branches of the facial, which are distributed to the muscles. 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 the opening in the fissura Glaseri. 3. The tympanic branches of Jacobson's nerve, Avhich are distributed to the membranes of the fenestra ovalis and fenestra rotunda, and to the Eustachian tube, and form a plexus by communicating with the carotid plexus and otic ganglion. Internal Ear. The Internal ear is called labyrinth, from the complexity of its communications, and consists of a series of cavities which are channelled through the substance of the petrous bone. It is situated between the cavity of the tympanum and the meatus auditorius internus. The Labyrinth (fig. 60.) consists of the Vestibule, Cochlea. Semicircular canals, The Vestibule is a small oval cavity, situated immediately within the inner wall of the tympanum. It is named vesti- bule, from being, as it were, the hall of communication be- tween the other cavities of the ear, It therefore presents a number of openings corresponding with these different cavities. 222 THE DISSECTOR. They may be arranged, like those of the tympanum, into large and small. The Large openings are seven in number, viz. the Fenestra ovalis, Scala vestibuli, Five openings of the three semicircular canals. The Small openings are the Aqueductus vestibuli, Openings for small arteries, Three openings for branches of the auditory nerve. The Fenestra ovalis (fig. 59. 3. fig. 60. 2.) is closed by the lining membrane of the vestibule, and by the foot of the stapes. It is the opening into the tympanum. The opening of the Scala vestibuli is the communication between the vestibule and the cochlea. The Aqueductus vestibuli is the commencement of the small canal which opens upon the posterior surface of the petrous bone. It gives passage to a small vein, which termi- nates in the superior petrosal sinus. The Openings for the arteries and nerves are situated in the internal wall of the vestibule, and correspond with the termination of the meatus auditorius internus. The Semicircular canals are three bony passages which com- Fig. 60. The labyrinth of municate with the vestibule; oneis per- the left ear. pendicular (fig. 60. 3.) in its direction and corresponds with a tubercle upon the anterior surface of the petrous bone ; another is oblique, 6.; and the third is horizontal, 8. Each canal presents a dilatation at one extremity, which is called ampulla, 4. 9. 7. The \j two undilated extremities of the per- pendicular and oblique canals unite to form a single tube, 5.; all the others open singly into the vestibule, hence the five openings of the three canals. 1. The vestibule. 2. The fenestra ovalis, in its natural position, look- ing from the meatus auditorius externus; the entrance into the vestibule from the tympanum. 3. The perpendicular semicircular canal. 4. Its ampulla. 5. Its union with the oblique canal. 6. The oblique semicircular canal. 7. Its ampulla. 8. The horizontal semicircular canal. 9. Its am- pulla. 10. The cochlea, internal to and rather in front of the vestibule. 11. The fenestra rotunda, the entrance into the scala tympani of the cochlea. THE DISSECTOR. 223 12. The canal of the cochlea leading from the fenestra rotunda to make its first turn. 13. The extremity of the canal called the cupola. The vestibule contains two sacs formed by the expansion of the auditory nerve. The larger of these is the utriculus communis, the smaller the sacculus proprius. The semicir- cular canals contain tubes of nervous membrane, which com- municate with the utriculus communis, and form three dila- tations corresponding with the ampulae at the extremities of the canals. These sacs, together with the nervous tubes lodged in the canals, contain a limpid secretion, which is called liquor of cotunnius* The sacs likewise contain a calcareous deposite, which is analagous to the otolites or calcareous crystalline masses found in the vestibular sac of fishes. This deposite has been recently described by Breschet, and is called by him Otoconite (ouj, wro;, the ear—xon$,) dust. The sacs and membranous canals do not completely fill the cavities of the bone, but leave a space which is occupied by another fluid, the liquor of Scarpa or aqua labyrintjii. The vestibule and semicircular canals are lined by a thin mucous membrane which secretes the aqua labyrinthi. The Cochlea (fig. 60. 10.) (snail shell) is a spiral canal, which describes two turns and a half arouud a central pillar which is called modiolus. It is situated in the anterior part of the petrous bone, its base being directed backwards and inwards, and corresponding with the termination of the cul- de-sac of the meatus auditorius internus. The canal of the cochlea is divided into two equal parts by a thin bony lamina, lamina spiralis, which is wound spirally around the modiolus. The two half canals, thus formed, are called scala tympani and scala vestibuli. At the apex of the cochlea the two scalae communicate and form a dilated cavity, which is termed the cupola (fig. 60. 13.) The Lamina spiralis is not continued entirely across the canal of the cochlea, but is completed by the mucous membrane which lines its interior. Near to the termination of the scala tympani is the opening of a small canal aque- ductus cochleae, which passes backAvards to the jugular fossa. It transmits a small vein from the cochlea, which opens into the commencement of the internal jugular vein. * Dominico Cotunnius, an Italian physician ; his dissertation " De Aquae- ductibus Auris Humanae Interine," was published in Naples, in 1701. 224 THE DISSECTOR. The cavity of the cochlea is lined throughout by a thin mucous membrane, Avhich is continuous with that of the vestibule, but Avhich closes the fenestra rotunda. It is filled Avith the aqua labyrinthi. The Openings into the cochlea are, the fenestra rotunda from the tympanum, the opening into the vestibule, the aqueductus cochleae, and the openings for the branches of the auditory nerve. Auditory nerve.—When the auditory nerve reaches the extremity of the meatus auditorius internus, it divides into two branches, 1. The larger or anterior to the cochlea. 2. The smaller or posterior to the vestibule and semicircular canals. The Anterior branch divides into a number of minute fila- ments Avhich pierce the base of the cochlea, and expand in its mucous lining: others enter the modiolus, which is hollowed into canals, to receive them, and pass off through small open- ings in its circumference.to expand in the mucous membrane covering the lamina spiralis. The Posterior or vestibular portion of the nerve divides into three branches, which are distributed—1. The larger to form the utriculus communis, and the membranous tubes of the perpendicular and horizontal canals. 2. To form the sacculus proprius. 3. The smallest to form the membranous tube of the oblique canal. The Arteries of the labyrinth are derived principally from the auditory branch of the inferior cerebellar artery. Organ of Taste. The Tongue is composed of muscular fibres, which are dis- tributed in layers arranged in various directions : thus some are disposed longitudinally, others transversely, others again obliquely and vertically. BetAveen the muscular fibres is a considerable quantity of adipose substance. The tongue is connected posteriorly with the os hyoides by muscular attachment, and to the epiglottis by mucous mem- brane, forming the three folds which are called fraena epiglot- tidis. On either side it is held in connexion with the lower jaw by mucous membrane, and in front a fold of that mem- brane is formed beneath its under surface, which is named fraenum linguae. The surface of the tongue is covered by a dense layer THE DISSECTOR. 225 analogous to the corium of the skin, which gives support to the papillae. A raphe marks the middle line of the organ, and divides it into symmetrical halves. The Papilla of the tongue, are the Papillae circumvallatae, -------fungiformes, -------conicae, -------filiformes, The Papillae circumvallatae are of large size, and from fifteen to twenty in number. They are situated on the dor- sum of the tongue near its root, and form a row upon each side, which meets its fellow at the middle line, like the t\vo branches of the letter A. They resemble cones attached by the 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 papillae, hence their name circumvallatae. 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 coecum. The Papillae fungiformes are irregularly dispersed over the dorsum of the tongue, and are easily recognized amongst the other papillae by their rounded heads and larger size. The Papillae conicae and filiformes cover the whole surface of the tongue in front of the circumvallatae, but are most abundant upon its tip. They are conical and filiform in shape, and have their points directed backwards. Behind the papillae circumvallatae, at the root of the tongue, are a number of mucous glands, which open upon the* surface. They have been improperly described as papillae by some authors. The papillae are covered with cuticle, which forms minute sheaths around them. The cuticular sheaths become enor- mously enlarged and lengthened in some fevers. Dr. Henle, of Berlin, has recently shown the cuticular covering, or epithelium, to be formed of irregularly quadrilateral scales, having a nucleus in the centre of each. Vessels and nerves.—The tongue is abundantly supplied with blood by the lingual arteries. The Nerves are three in number, and of large size—1. The gustatory branch of the fifth, which is distributed to the papillae and is the nerve of common sensation. 2. The glosso-pharyn- 226 THE DISSECTOR. geal, which is distributed to the mucous membrane, follicles, and glands of the tongue, and has been shown by the ex- periments of Panizza to be the true nerve of taste. This nerve also associates the tongue with the pharynx and larynx. 3. The lingual, which is the motor nerve of the tongue, and is distributed to the muscles. The Mucous membrane, which invests the tongue, is con- tinuous with the cutis along the margins of the lips. On either side of the fraenum linguae, it may be traced through the sublingual ducts into the sublingual glands, and along Wharton's ducts into the submaxillary glands ; from the sides of the cheeks it passes through the openings of Stenon's ducts to the parotid gland; in the fauces, it forms the as- semblage of follicles called tonsils, and may be thence traced downwards into the larynx and pharynx, where it is con- tinuous with the general pulmono-digestive mucous membrane. Beneath the mucous membrane of the mouth are a number of small glandular granules, which pour their secretion upon the surface. A considerable number of them are situated within the lips, in the palate, and in the floor of the mouth. They are named from the position which they may chance to occupy, labial, palatine glands, &c. Organ of Touch. The Skin is composed of three layers : viz. the Cutis, Cuticle. Rete-mucosum, The Cutis (dermis) or true skin covers the entire surface of the body, and is continuous with the mucous membrane which lines its cavities. It consists of two layers, a deep one called corium, and a superficial or papillary layer. Fig. 61. A section of the skin. 1. The corium. 2. The papillary layer of the cutis. 3. The rete mu- cosum modelled upon the papillae. 4. The cuticle. 5. Spiral sweat ducts, opening at the pores upon the ridges of the cuticle. THE dissector. 227 The Corium (fig. 61. 1.) is the base of support to the skin, and owes its density of structure to an interlacement of fibrous bands which form a firm and elastic web. On its under sur- face it presents a number of areolae, in which are lodged cells of adipose tissue. It is connected by this surface with the general superficial fascia of the body. On the upper surface, the fibres are more closely aggre- gated, and form a smooth plane for the support of the papil- lary layer. The corium differs very much in thickness in different parts of the body; thus, on the lips, eyelids, and scrotum, it is ex- tremely thin. On the head, back, soles of the feet, and palms of the hands, it is very thick, and on the more exposed parts of the body it is much thicker than on those which are pro- tected. The Papillary layer (fig. 61. 2.) is soft, and formed by minute papillae which cover every part of its surface. On the body generally, the papillae are irregular in their form and distribution: they are best seen in the palm of the hand or sole of the foot, where they are distributed in linear ridges, as is indicated by the linear markings on the cuticle. In these situations each papdla resembles a molar tooth, having four tubercles, one of them being generally longer than the others. Between each of the papillae is the opening for the perspiratory duct. The papillae beneath the nail have a peculiar arrangement and structure. At the root of the nail the papillae are nume- rous, but small and very vascular ; opposite to the part of the nail called lunula, they are scarcely raised above the surface, and less vascular, but beyond this point they form lengthened vascular plicae, which afford a large surface for secretion. These lengthened papillae deposite the horny secretion in longitudinal lamellae, which give to the nail the ribbed ap- pearance it presents on its surface. Vessels and nerves.—The papillae are abundantly sup- plied with vessels and nerves, the former to enable them to perform the office of secretion in the production of the cuticle, the latter to give them the sensibility necessary to an organ of touch. The Rete mucosum (fig. 61. 3.) is a distinct layer, inter- posed between the cuticle and cutis, and is the seat of the colour in the negro and the darker tribes of mankind. The 228 the dissector. name rete mucosum given to it by Malpighi conveys a very inaccurate notion of its structure, for it is neither a network, nor is it mucous. It is thin upon the general surface of the body, but is thick in the palm of the hand and sole of the foot, where it may be easily separated as a distinct layer. Examined beneath the microscope, it is seen to be moulded accurately upon the papillae, being thick in the spaces between these, and thin over their convexities; hence arises the ap- pearance of a network. In the rete mucosum from the hand, these depressions are seen to be arranged in a linear series, as are the papillae ; in other situations they are more irre- gular, but correspond always with the distribution of the papillae. There is no rete mucosum beneath the nails. The colouring particles are situated in the rete mucosum, and are most abundant upon the ridges which correspond with the furrows between the papillae. Vessels and nerves.—The rete mucosum has been injected by Mr. Cruikshank, and in a case of small-pox by Sir Astley Cooper. No nerves have been traced into the substance of the rete. The Cuticle (fig. 61. 4.) (epidermis, scarf-skin) is the horny unorganized lamella secreted by the cutis, which covers and protects the entire surface of the more delicate layers of the skin. At the entrance to the cavities it is continuous with the epithelium or cuticular covering of the mucous membrane. In situations exposed to pressure, as the palm of the hand , and sole of the foot, it is very thick; on other parts it forms only a thin layer. The cuticle is marked on the surface by a net-work of lines : these are more numerous and larger near to joints, Avhere they form deep wrinkles on account of the inelastic nature of its structure. Their appearance differs in different regions of the body, but every where depends upon the same cause, the inelasticity of the cuticle. Upon the palms of the hands and soles of the feet the cu- ticle presents a number of linear elevations Avhich correspond with the rows of papillae in those parts. This is particularly evident upon the tips of the fingers, where there is a circular arrangement of papillae. Upon the inner surface of the cuticle a number of depres- sions and linear furrows are seen corresponding with the pro- jections of the papillae. A number of conical processes are also observed on this surface, Avhich correspond with the pass- THE dissector. 229 age of hairs through the cuticle, and with the openings of the perspiratory ducts. The openings in the cuticle are the pores or openings for the perspiratory ducts, the openings for the passage of the hairs, and those of the sebaceous follicles. The Appendages to the skin are the nails, hairs, sebaceous fol- licles, and perspiratory ducts. The Nails are parts of the cuticle secreted in the same manner, composed of the same material, but disposed in a peculiar way to serve an especial purpose—the protection of the tactile extremities of the fingers. The white semilunar mark at the base of the nail is called the lunula. The cuti- cle is closely connected Avith it all round, and in maceration the nail comes off with that layer. The Hairs have a very different structure and arrangement from that of the nails : they grow by roots Avhich are im- planted in the corium, and traverse the papillary layer, the rete mucosum, and the cuticle, to reach the surface. As they pass through the rete mucosum and cuticle, they receive a reflected covering from each, and the cuticle is closely adhe- rent around the cylinder of the hair before it emerges from the surface. The hair is homogeneous in structure, having no canal in its interior : it is supplied with the means of nutrition by the vessels at its root. The Sebaceous follicles are abundant in some parts of the skin, as in the armpits, the nose, &c. They are small per- pendicular pouches secreting a peculiar oily matter, and lined by a thin layer of cuticle. The Perspiratory ducts (fig- 61. 5.) are spiral tubes com- mencing apparently in the corium, and proceeding upwards between the papillae, to terminate by open pores upon the surface of the cuticle. They are easily seen by examining with the microscope a thin section of skin made perpendicu- larly to the surface. Their origin is not yet clearly made out. Breschet asserts that they proceed from distinct globu- lar glands. Analogy is opposed to his view, but we have not yet succeeded in ascertaining their origin satisfactorily. If a portion of skin be scalded with hot water, and the cuticle raised, the perspiratory ducts may be seen most distinctly extended in straight lines between the separating layers. The Pores are best observed during perspiration, when the 20 230 THE DISSECTOR. fluid is seen oozing through their minute openings. In the hand and sole of the foot they are easily seen by the naked eye without this assistance. They are disposed at regular distances along the ridges of the cuticle, and give rise to the appearance of lines cutting the ridges transversely. CHAPTER X. ANATOMY OF THE PERINEUM. The Perineum is the inferior part of the trunk of the body in which are situated the two great excretory outlets, the ure- thra and the termination of the alimentary canal. These are parts of delicate and complicated structure, and largely sup- plied with vessels and nerves. They are also peculiarly liable, from the nature of their functions, to causes of irrita- tion and disease. Indeed, disease is more frequent and va- rious in this region, than in any other of the body. Nearly the Avhole of the affections admit of relief or cure from opera- tive procedure. Hence the perineum is the most important surgical region of the entire system, and incisions are made through it to great depth and in various directions. A good knowledge of its component structures and relations is there- fore highly necessary to the surgeon, for a misdirected inci- sion, by wounding important parts, would involve the most serious consequences, and probably prove fatal to the patient. The anatomical composition of the perineum is the same as that of any other part of the body, consisting of integument, superficial fascia, deep fascia, muscles, vessels, and nerves. But to suit the peculiar functions of this region, they are somewhat differently distributed and arranged. To obtain a clear and precise idea of the nature of the pe- rineum, the student must take in his hand a pelvis in which the sacro-ischiatic ligaments have been left in their proper positions. Let him now turn to the outlet of the pelvis, and he will be enabled to trace the boundaries of the perineum. In front he will have the arch of the pubis, on each side the ramus and tuberosity of the ischium and great sacro-ischiatic ligaments and behind the coccyx. If he draw a line transversely across this outlet from the THE DISSECTOR. 231 anterior extremity of one tuberosity of the ischium to the same point on the other, he will divide the opening into two parts of nearly equal size. The anterior space belongs to the organs of generation, the posterior to the termination of the alimentary canal. Let us first examine the anterior or geni- tal space. A strong, fibrous membrane is stretched across this ante- rior space from the ramus of the pubis and ischium on one side to the same parts on the opposite side. This is called the "Deep perineal fascia." It is a septum of division be- tween the interior and the exterior of the pelvis, between the internal organs of generation and the external. The deep perineal fascia is not, however, a single membrane, but con- sists of two layers, between which are situated the membra- nous portion of the urethra, the compressor urethrae muscle, part of the internal pudic arteries, the arteries of the bulb, and Cowper's glands. Externally to the deep fascia is the penis, which is com- posed of three lengthened bodies, the two corpora cavernosa above, and the corpus spongiosum below. The corpora caver- nosa are firmly attached to the ramus of the pubis and ischium on each side, by two diverging processes, called crura penis. The corpus spongiosum is the medium of transmission for the urethra, which enters that body immediately that it escapes from the deep perineal fascia, and takes its course through its interior to its termination at the meatus urinarius. The extremity of the corpus spongiosum, which receives the urethra, is considerably enlarged, and is called the bulb; at its opposite extremity it is again enlarged, and forms the glans penis. The penis is moved by three pairs of muscles, which are the muscles of the perineum. It is supplied with blood-ves- sels and nerves from the internal pudic artery and nerve. The muscles, vessels, and nerves, are in immediate relation with the commencement of the penis, and directly external to the deep perineal fascia. Then the whole of these parts are covered in and held firmly in their places by the superficial perineal fascia, which is continuous with the deep perineal fascia posteriorly, and is firmly attached on each side to the ramus of the pubis and ischium, whilst anteriorly it is continuous with the cellular 232 THE DISSECTOR. base of the common superficial fascia of the scrotum and ab- domen. So that the genital portion of the perineum consists of two layers of fascia, which are connected posteriorly and at the sides, and enclose a triangular space, in which are contained the root of the penis, with its muscles, vessels, and nerves. Externally to the superficial perineal fascia, is the common superficial fascia of the body and the integument. The Posterior or anal portion of the perineum, instead of a resisting membranous partition, like the deep perineal fas- cia, is divided from the cavity of the pelvis by a convex mus- cular septum, the levator ani muscle, which arises from nearly the whole circumference of the interior of the pelvis, and is inserted around the extremity of the rectum. A broad band of muscular fibres embraces the lower end of the intestine, forming the internal sphincter ; and superficially to it is the flat ellipse of the external sphincter, which is covered by the common superficial fascia and integument. 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 draAving 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 Avhich demands some degree of delicacy and nice manipulation, a strong light should be throAvn upon the part. Having fixed the subject, and drawn the scrotum upwards by means of a string or hook, carry an incision from the base of the scrotum along the ramus of the pubis and ischium and tuberosity of the ischium, to a point parallel with the apex of the coccyx; then describe a curve over the coccyx to the same point on the opposite side, and continue the incision onwards along the opposite tube- rosity, and ramus of the ischium, and ramus of the pubis, to the opposite side of the scrotum, where the tAvo extremities may be connected by a transverse incision. This incision will completely surround the perineum, folloAving very nearly the outline of its boundaries. Now let the student dissect off the integument carefully from the Avhole of the included space, and he will expose the fatty cellular structure of the common superficial fascia, which exactly resembles the super- ficial fascia in every other situation. THE DISSECTOR. 233 Having exposed the Common superficial fascia, the student repeats the incision by Avhich he divided the integument, and dissects off the common superficial fascia in the same Avay as the preceding layer. This dissection displays the superficial perineal fascia, which is analagous to the deep fascia of other regions; but, from the circumstance of another layer in the perineum as- suming the title of deep, we must for the present submit to this apparent departure from the unity of plan which Ave have heretofore had ample evidence of in the pursuit of our dissec- tions. The Superficial perineal fascia is very tough and resisting in the genital region, thin and ill-defined in the anal region. The latter portion scarcely deserves our attention ; the former requires careful examination. It is firmly attached to the ramus of the pubis and ischium on each side, nearly as far back as the tuberosity, where it becomes continuous with the deep perineal fascia. In front it is continuous with the cover- ing of the scrotum, called dartos. It folloAvs from this arrangement, that if urine had escaped from the urethra at the point where that tube had just tra- versed the deep perineal fascia, it would be unable to follow the laAvs of gravity, and pass backwards towards the anus, on account of the communication between the superficial perineal fascia and the deep perineal fascia. It could not pass out- wards into the thighs, on account of the connexion of the superficial perineal fascia to the ramus of the pubis and ischium. It would, therefore, burrow among the muscles at the root of the penis, and be constrained to follow the direction of the penis forwards into the scrotum and thence upwards into the cellular tissue of the lower part of the abdomen. An abscess in this situation is excessively painful, on ac- count of the tension and resistance of the superficial perineal fascia; and, unless speedily opened by the surgeon, might give rise to consequences dangerous to life. The best manner of dissecting the superficial perineal fascia is to make an incision from the middle point of the upper in- cision to the tuberosity of the ischium on each side. We thus form a A shaped flap, which on being turned downwards (fig. 66. 4.,) displays very distinctly the continuity of this fascia Avith tho deep perineal fascia (6,) The two side flaps (5. 5.) 234 THE DISSECTOR. are then to be dissected outwards, and the firm connexion be- tween this fascia and the ramus of pubis and ischium demon- strated. When the student has thus satisfied himself of the connex- ions of the superficial perineal fascia, he must proceed to remove the fat and cellular tissue, Avhich conceal from view the muscles and superficial vessels of the perineum. In the middle line is the projection of the corpus spongiosum, and on each side the commencement of the corpora cavernosa (crura penis.) Upon these bodies are situated two pairs of muscles, and, between them, the superficial perineal vessels and nerves. To see the muscles clearly, the vessels and neiwes on one side had better be dissected away with the fat and cellular tissue. The Muscles of the genital region of the perineum, are the Accelerators urinae, Erectores penis, Transversi perinei. Fig. 62. The muscles of the perineum. 1. The accelerators urinae muscles; the figure rests upon the corpus spongiosum penis. 2. The corpus cavernosum of one side. 3. The erec- tor penis of one side. 4. The tranversus perinei of one side. 5. The triangular space through which the deep perineal fascia is seen. 6. The sphincter ani; its anterior extremity is cut off. 7. The 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 upon the opposite side. 9. The spine of the ischium. 10. The left coccygeus muscle. The boundaries of the perineum are well seen in this engraving. The Accelerators urinae arise from a tendinous point in the centre of the perineum and from the raphe'. From these origins the fibres diverge like the plumes of a pen; the in- THE DISSECTOR. 235 ferior fibres are inserted into the ramus of the pubis and ischium; the middle completely encircle the corpus spongio- sum, and meet upon its upper side; and the anterior spread out upon the corpus cavernosum on each side, into which they are inserted. The insertions of these muscles may be seen by carefully raising one muscle from the corpus spongiosum and tracing its fibres. The Erector penis arises from the ramus and tuberosity of the ischium and is inserted into the corpus cavernosum on each side. The Transversus perinei arises from the tuberosity of the ischium on each side, and is inserted into the central tendinous point of the perineum. The Anal portion of the perineum must now be examined. When the superficial fascia is dissected off, a thin layer of muscular fibres will be observed, surrounding the anus like an ellipse : this is the external sphincter ani. It is attached anteriorly to the tendinous point of the perineum, and pos- teriorly to the point of the coccyx. If this muscle be care- fully removed, the edge of a flat band of muscular fibres will be found embracing the lower extremity of the rectum; this is the sphincter ani internus. Surrounding the anus is a quantity of loose cellular tissue, containing adipose matter and some small arterial branches,— the external hemorrhoidal: this is the seat of the burrowing sinuses which often occur in this region. When the fat is dis- sected away, the fibres of the levator ani will be seen con- verging from the circumference of the pelvis, to be inserted into the lower extremity of the rectum. Actions.—The acceleratores urinae being continuous at the middle line, and attached on either side to the bone, will sup- port the spongy portion of the urethra, and acting suddenly, will propel the last drops of urine or the semen from the canal. The erector penis is rather a depressor than an erector muscle. The erection of this organ results from internal dis- tention. The muscle tends to draw it downwards while in this state, and probably serves the purpose of a stay, to direct its course in its appropriate function. The transverse muscles serve to steady the tendinous centre, that the muscles attached to it may obtain a firm point of support. 236 THE DISSECTOR. The External sphincter contracts the integument around the anus, and by its attachment to the tendinous centre, and to the 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 in- testine. The levator ani acts in unison Avith 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 actions, it restores the perineum to its original form. Arteries.—The perineal arteries are branches of the in- ternal pudic, one of the terminal divisions of the internal iliac. The Internal Pudic Artery leaves the pelvis through the great sacro-ischiatic foramen below the pyriformis muscle, crosses the spine of the ischium, and re-enters the pelvis through the lesser sacro-ischiatic foramen ; it then crosses 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 next ascends the ramus of the ischium, enters between the two layers of the deep perineal fascia, lying along the border of the ramus of the pubis, and at the symphisis pierces the anterior layer of the deep perineal fascia, very much diminished in size, and reaches the dorsum of the penis, along which it runs, supply- ing that organ under the name of dorsalis penis. Its branches are— Within the pelvis— Middle hemorrhoidal; In the perineum— External hemorrhoidal (3 or 4.) Superficialis perinei, Transversalis perinei, Arteria bulbosi, Arteria corporis cavernosi, Arteria dorsalis penis. The External hemorrhoidal arteries are three or four small branches given off by the internal pudic while behind the tuberosity of the ischium. They are distributed to the anus, and to the muscles and fascia in the anal region. THE DISSECTOR. 237 Fig. 63. The perineum and part of the thighs after the skin and a portion of the superficial fascia had been removed. a. Superficial fascia, b. Accelerator urina?. c. Erector penis, d. Trans- versa perinei. e. Upper point of sphincter ani. /. The edge of the glu- teus maximus.—1. Superficial perineal artery. 2. Superficial perineal nerve. The Superficial perineal artery is given off near the attach- ment of the crus penis: it pierces the connecting layer of the superficial and deep perineal fascia, and runs forwards in front of the transversus perinei muscle, and along the groove between the accelerator urinae and erector penis to the scro- tum, to which it is distributed. It gives nutrient branches to the perineum as it passes forwards. One of these, larger than the rest, crosses the perineum, resting on the trans- versus perinei muscle: and is therefore named transversalis perinei. The three remaining arteries are the proper vessels of the penis ; they are distributed to the corpus spongiosum, corpora cavernosa, and dorsum penis. The Artery of the bulb (fig. 66. 13) is given off from the pudic nearly opposite the opening for the transmission of the urethra : it passes obliquely inwards betAveen the two layers 238 THE DISSECTOR. of the deep perineal fascia, and pierces the anterior layer to enter the corpus spongiosum, to which it is distributed. Fig. 64. A deeper dissection than that represented in the last figure, the perineal muscles being removed, and also the fat in the ischio-rectal fossa. a. Superficial fascia, b. Accelerator urinae. c. Crus penis, d. The bulb. e. Triangular ligament of urethra. /. Levator ani. g. Sphincter, h. Tube- rosity of ischium, k. Glutasus maximus. * Cowper's gland of the left side. 1. Pudic artery. 2. Superficial perineal artery and nerve. The inferior hemorrhoidal arteries and the artery of the bulb are likewise shown. The Artery of the corpus cavernosum (fig. 66. 14.) pierces the crus penis, and runs forwards in its interior, supplying its cellular structure. The Dorsal artery of the penis (fig. 66. 15.) ascends be- tween the two crura and the symphisis pubis to the dorsum penis, and runs forwards by the side of the suspensory liga- ment in the groove between the corpora cavernosa to the glans, distributing branches in its course to the body of the organ and to the integument. The Veins of the perineum require no distinct notice: they maintain the same relation to the arteries that the smaller veins do in other parts. The principal vein of the penis, the great dorsal vein, is remarkable both for its mode of origin and for its size. It THE DISSECTOR. 239 commences by a number of veins, Avhich return the blood from the glans penis, and which converge to form a vessel of considerable bulk, which runs in the groove between the dorsal arteries, and receives veins from the corpora cavernosa in its course: it passes between the fibres of the suspensory liga- ment of the penis, and through a tendinous arch beneath the symphisis pubis, to the prostate gland, where it communicates with a remarkable plexus of veins, situated around the neck of the bladder. Fig. 65. The arteries of the perineum; on the right side the superficial arteries are seen, and on the left the deep. 1. The penis, consisting of corpus spongiosum and corpus cavernosum. The crus penis on the left side is cut through. 2. The acceleratores urinae muscles, enclosing the bulbous portion of the corpus spongiosum. 3. The erector penis, spread out upon the crus penis of the right side. 4. The anus, surrounded by the sphincter ani muscle. 5. The ramus of the ischium and os pubis. 6. The tuberosity of the ischium. 7. The lesser sacro-ischiatic ligament, attached by its small extremity to the spine of the ischium. 8. The coccyx. 9. The internal pudic artery, crossing the spine of the ischium, and entering the perineum. 10. External haemorrhoidal branches. 11. The superficialis perinei artery, giving off a small branch, transversalis perinei, upon the transversus perinei muscle. 12. The same artery on the left side cutoff. 13. The artery of the bulb. 14. The two terminal branches of the internal pudic artery ; one is seen entering the divided extremity of the crus penis, the artery of the corpus cavernosum; the other, the dorsalis penis, ascends upon the dorsum of the organ. The numerous veins Avhich converge from the glans to form the dorsal Arein have a peculiar arrangement, and form a kind of plexus upon the neck of the penis. In the dog, the dorsal vein is embraced by a muscle of 240 THE DISSECTOR. considerable size, while passing beneath the arch of the pubis, the compressor venae dorsalis. This muscle has been described by Mr. Houston, of Dublin, as existing in the human sub- ject. It arises from the ramus of the pubis on each side, and, arching upwards, unites by a thin tendon with its fellow of the opposite side, over the dorsal vein. The two muscles, when in action, would therefore draw down the tendon, and compress the vein against the root of the penis. The dorsal vein of the penis is so large, and its communi- cations with the pelvic veins so free, that we have frequently succeeded in injecting the right side of the heart and veins of the neck by placing the injecting-pipe in the dorsal vein of the penis. The Nerves of the perineum are branches of the internal pudic. The Internal pudic nerve is an offset of the sacral plexus : it passes out of the pelvis with the internal pudic artery, and lies by the side of that vessel throughout its course. Its branches correspond Avith the branches of the artery, and need no distinct description. The dissector may noAV remo\re the muscles and vessels of the perineum, that he may see more clearly the texture and position of the bulbous portion of the corpus spongiosum with the artery entering its posterior part; then let him cut across the corpus spongiosum at about its middle, and, turning it doAyn from the rest of the penis, remove it altogether by di- viding the urethra close to the deep perineal fascia. This proceeding displays the convergence of the crura penis, and the round opening in the deep perineal fascia, through which the urethra passes. The student must then carefully dissect off the anterior layer of the deep perineal fascia, which will bring into view the membranous part of the urethra, the compressor urethras muscle (fig. 66. 8. 9. 10.,) the artery of the bulb, (13.) the internal pudic artery (12.) at each side, and two small yellowish bodies (11.) about the size of lentils, placed immediately beneath the urethra, Cowper's glands. The Compressor urethras* muscle, fig. 66., [Wilson's and Guthrie's muscles,] consists of two portions: one of which is • f uj the ?PP°rt,mity of giving the description of this muscle, we are indebted to the liberality and courtesy of Mr. Guthrie, and also to Mr. Charles Guthrie, who removed the preparation from its bottle that we might examine it thoroughly. THE DISSECTOR. 241 transverse in its direction, and passes inwards to embrace the membranous urethra; the other is perpendicular, and de- scends from the pubis. The transverse portion, discovered by Mr. Guthrie, arises, by a narrow tendinous point, from the upper part of the ramus of the ischium, on each side, and di- vides into two fasciculi, 8. 9., Avhich pass inAvards and slightly upwards, and embrace the membranous portion of the urethra and Cowper's glands. As they pass towards the urethra, they spread out and become fan-shaped, and are inserted into a tendinous raphd upon the upper and loAver surfaces of the urethra, extending from the apex of the prostate gland, to which they are attached posteriorly, to the bulbous portion of the urethra, with which they are connected in front. When seen from above, these portions resemble two fans, connected by their expanded border along the middle line of the mem- branous urethra, from the prostate to the bulbous portion of the urethra. The same appearance is obtained by viewing them from below. Fig. 66. The structures contained between the two layers of the deep perineal fascia. 1. The symphisis pubis. 2. 2. The ramus of the pubis and ischium. 3. 3. The tuberosities of the ischia. 4. A triangular portion of the super- ficial fascia turned down, and shown to be continuous with the deep fascia (6.) 5. 5. Two portions of the superficial perineal fascia, showing its con- nexion to the ramus of the pubis and ischium. 6. 6. The posterior layer of the deep perineal fascia, the anterior layer having been removed. 7. The membranous portion of the urethra cut across. 8. The superior fasciculus of the compressor urethrae muscle of one side. 9. The inferior fasciculus of the compressor urethrae. The two fasciculi, (8.) and (9.,) constitute Guthrie's muscle of one side. 10. The pubic portions of the compressor 21 242 THE DISSECTOR. urethras, Wilson's muscles. 11. Cowper's glands, partly embraced by the lower fasciculus of the compressor urethrae muscle. 12. The internal pudic artery passing posteriorly to the crus of the compressor urethras. 13. The artery of the bulb. 14. The artery of the corpus cavernosum. 15. The arteria dorsalis penis. The Perpendicular portion (fig. 66.10.,) described by Mr. Wilson, arises by two tendinous points from the inner surface of the arch of the pubis, on each side of, and close to the symphysis. The tendinous origins soon become muscular, and descend perpendicularly to be inserted into the upper fasciculus of the transverse portion of the muscle ; so that it is not a distinct muscle surrounding the membranous portion of the urethra, and supporting it as in a sling, as was de- scribed by Mr. Wilson, but merely an upper origin of the more important muscle discovered by Mr. Guthrie. Fig. 67. Besides the superficial fascia and the perineal muscles, by the removal of which the spongy erectile tissue and the crura penis were uncovered, the anterior layer of the deep perineal fascia was cut away in the preparation for this sketch, and thus the pudic arteries, with their branches for the bulb. and Cowper's glands have been laid bare. The rectum, too, having been dissected from its connexions and drawn back, the prostate gland, the semi- nal vesicles, and part of the urinary bladder have been brought into view.— 1. Fascia lata covering the adductor muscles of the thigh. 2. Glutaeus maximus. 3. Rectum. 4. Crus penis of left side. 5. Corpus spongiosum urethraj. 6. Prostate. 7. Vesicula seminalis and vas deferens of left side. 8. A small part of urinary bladder. 9. Right dorsal artery, with the artery of the bulb and Cowper's gland resting against the inner layer of the deep perineal fascia. The last-named parts are at considerable depth, but the size within which it was necessary to restrict the drawing, did not admit of the appcaranco of depth being sufficiently preserved in this representation. THE DISSECTOR. 243 The compressor urethrae may be considered either as two symmetrical muscles meeting at the raphe', or as a single muscle : we have adopted the latter course in the above description, as appearing to us the more consistent with the general connexions of the muscle, and with its actions. The internal pudic artery (fig. 66. 12.) lies behind the transverse portion of the muscle at each side, near its attach- ment to the ischium. The artery of the bulb, 13., is given off from the pudic above the transverse portion, and passes in- wards in front of the muscle, to enter the posterior part of the bulb. Actions.—Taking its fixed point from the ramus of the ischium at each side, "it can," says Mr. Guthrie, "compress the urethra so as to close it; I conceive completely, after the manner of a sphincter." The transverse portion will also have a tendency to draw the urethra downwards, whilst the per- pendicular portion will draw it upwards towards the pubis. The inferior fasciculus of the transverse muscle, enclosing Cow- per's glands, will assist them in evacuating their secretion. Fig. 68. The pubic arch with the attachments of the perineal fascia. 1,1,1. The superficial perineal fascia divided by a a. shaped incision into three flaps ; the lateral flaps are turned over the ramus of the os pubis and ischium at each side, to which they are firmly attached; the posterior flap is continuous with the deep perineal fascia. 2. The deep perineal fascia. 3. The opening for the passage of the membranous portion of the urethra, previously to entering the bulb. 4. Two projections of the anterior layer of the deep perineal fascia, corresponding with Cowper's glands. 244 THE DISSECTOR. Cowper's glands (fig. 66. 11. fig. 69. 16.) are two small clusters of mucous follicles, which pour their secretion by two slender ducts into the bulbous portion of the urethral canal. They are enclosed by the fibres of the compressor urethrae muscle, by which they are assisted in the excretion of their proper fluid. The rest of the anatomy of this region belongs to the viscera of the pelvis. Perineum in the Female. The structures in the female perineum are the same as in the male, but somewhat modified to suit the difference of form in the organs of generation. The integument and superficial fascia are thrown into folds, called labia, to prepare for the enormous distention to which this part is submitted in parturi- tion. The entrance of the vagina is encircled by a sphincter, which is not unlike the accelerator urinae of the male. The clitoris is the penis of the female, composed of its two cor- pora cavernosa, and therefore provided with erectores clitori- dis analogous to the erectores penis. The transversus perinei, sphincters, and levator ani, are precisely the same as in the male. The Muscles of the female perineum are the Constrictor vaginae, Compressor urethrae, Transversus perinei, Sphincter ani. Erector clitoridis, The Constrictor vaginae 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 passes forwards on each side of the entrance of the vagina, to be inserted into the ramus of the pubis and corpus caver- nosum clitoridis. The Transversus perinei is a small muscle arising on each side from the ramus of the ischium, and inserted into the side of the constrictor vaginae. The Erector clitoridis arises from the ramus of the ischium, and is inserted on each side into the crus clitoridis. The Compressor urethrae has the same origins and inser- tions, and exercises the same functions in the female as in the male. The Sphincter ani surrounds the lower extremity of the rectum, as in the male. THE DISSECTOR. 245 The Levator ani is inserted into the side of the vagina and rectum. The Arteries of the perineum are branches of the internal pudic, and are distributed as in the male : they are the External hemorrhoidal, Superficialis perinei, Vaginal arteries, Artery of the corpus cavernosum, Artery of the dorsum clitoridis. The Nerves accompany each of the branches of the artery, and are also derived from the internal pudic and from the hypogastric plexus. CHAPTER XL PELVIS AND ORGANS OF GENERATION. The student must now turn his attention to the study of the viscera of the pelvis; therefore, after examining their relative position from above, he should proceed to separate the os innominatum of the left side ; so as to obtain a side view of these organs. For this purpose he must divide the pubis with the saw on the left side, a little external to the symphisis. Then let him cut through the psoas muscle and iliac vessels opposite the sacro-iliac symphisis, and divide the ligaments £of that articulation. Next cut away with the scalpel the structures adhering to the inner surface of the pubis and ischium of the same side, force the os innominatum outwards and remove it altogether. We shall first consider the contents of the male, and then of the female pelvis. The Viscera of the male pelvis are the Bladder, Vesiculae seminales, Prostate gland, Rectum. A careful dissection of the side of the pelvis, when the os innominatum has been removed, will bring these organs dis- tinctly into view. Bladder.—The Bladder is an oblong membranous viscus, situated behind the pubis and in front of the rectum. It is larger in its vertical axis than from side to side. It is divided into body, fundus, base, and neck. The body (fig. 69. 4.) 246 THE DISSECTOR. comprehends the middle zone of the organ; the fundus, its upper segment; the base, the lower broad extremity, which rests upon the rectum; and the neck the narrow con- stricted portion Avhich is applied against the prostate gland. The bladder is retained in its proper situation by ligaments. The walls of the pelvis, in addition to the bones by which they are formed, are lined internally by the peritoneum; the pelvic fascia, (fig. 69. 7.,) which is continued downwards from the iliac fascia, and is attached below to the sides of the bladder and rectum; the levator ani muscles, the obtu- rator fascia, and the internal obturator muscle. Fig. 69. The pelvic viscera of the male seen on the left side. 1. The body of the left pubes sawed through. 2. Corpus cavernosum penis. 2/. Corpus spongiosum. 3. Prostate gland, with a portion of the levator ani covering its fore part. 4. Urinary bladder. 5. Intestinum rec- tum. 6. Deep perineal fascia—its two layers. 7. Cut edge of the pelvic fascia, extending from the pubes to the back part of the prostate. 8. Vas deferens. 8'. Vesicula seminalis. 9. Ureter. The cut edge of the perito- neum is seen jagged over the bladder and the rectum. 510 The Ligaments of the bladder are the true and false ; the true ligaments are seven in number, two posterior, two ante- rior, two umbilical ligaments, and the urachus. The false ligaments are four in number, and are formed by the peri- toneum. The two Posterior ligaments are formed by the reflection of the pelvic fascia upon the sides of the base of the bladder. THE dissector. 247 The Anterior ligaments (fig. 69. 7.) are also formed by the pelvic fascia, which passes from the inner surface of the pubis, on each side of the symphisis, to the front of the bladder. The Umbilical ligaments are the fibrous cords which result from the obliteration of the umbilical arteries of the foetus; they pass fonvards on each side of the fundus of the bladder, and ascend beneath the peritoneum to the umbilicus. Fig. 70. A side view of the viscera of the male pelvis in stiu. The right side of the pelvis has been removed by a vertical section made through the os pubis, near to the symphisis: and another through the middle of the sacrum. 1. The divided surface of the os pubis. 2. The divided surface of the sacrum. 3. The body of the bladder. 4. Its fundus; from the apex is seen passing upwards the urachus. 5. The base of the bladder. 6. The ureter. 7. The neck of the bladder. 8. 8. The pelvic fascia; the fibres immediately above 7 are given off from the pelvic fascia and represent the anterior ligaments of the bladder. 9. The prostate gland. 10. The mem- branous portion of the urethra, between the two layers of the deep perineal fascia. 11. The deep perineal fascia formed of two layers. 12. One of Cowper's glands between the two layers of deep perineal fascia, and beneath the membranous portion of the urethra. 13. The bulb of the corpus spongiosum. 14. The body of the corpus spongiosum. 15. The right crus penis. 16. The upper part of the first portion of the rectum. 17. The recto-vesical fold of peritoneum. 18. The second portion of the rectum. 19. The right vesicula seminalis. 20. The vas deferens. 21. The rectum covered with the descending layer of the pelvic fWcia, just as it is making its bend backwards to constitute the third pfrtion. 22. A part of the levator ani muscle investing the lower part of the rectum. 23. The external sphincter ani. 24. The interval between the deep and superficial perineal fascia; they are seen to be continuous beneath the figure. 248 THE DISSECTOR. The Urachus is a fibrous cord formed by the obliteration of a tubular communication in the embryo; it is very strong and is attached to the apex of the bladder, and thence ascends to the umbilicus. The umbilical ligaments and urachus guide the ascent of the bladder in retention of urine. The False ligaments are folds of the peritoneum. The two Posterior correspond with the passage of the ureters from the pelvis to the base of the bladder; and the two lateral are formed by the vasa deferentia, as they pass inwards from the internal abdominal ring to the sides of the fundus of the bladder. The Ureters (fig. 69. 9.) terminate in the sides of the base of the bladder, and pass for some distance obliquely between its coats, before they open on the mucous membrane. Their openings into the bladder are constricted, and sur- rounded by the thick and dense submucous issue of the trigone vesicale, which prevents their free dilatation in an over dis- tended state of the bladder, or in the passage of a calculus. The obliquity of their entrance is preserved by the two mus- cles of the ureters, which are attached to their openings of entrance behind, and converge as they advance forwards to be inserted into the fibrous tissue of the uvula. The ureters are crossed in their course on the sides of the bladder by the vasa deferentia, Avhich descend internally to them to the necks of the vesiculae seminales at the base of the prostate gland. The Coats of the bladder are three—a partial external coat, derived from the peritoneum, a muscular coat, and an internal lining membrane, or mucous coat. The peritoneal coat covers the posterior surface and sides of the bladder, from about opposite the point of termination of the two ure- ters to its summit, whence it is guided to the anterior wall of the abdomen by the umbilical ligaments and urachus. The muscular coat consists of two layers of muscular fasciculi, which are disposed around the bladder in various directions, and cross each other in their course. Those of the external layer are longitudinal; they commence upon the upper surface of the prostate, where they are clustered together, and are firmly connected Avith the anterior ligaments of the bladder. Hence the lower fibres of these ligaments are sometimes called the tendons of the bladder. They then pass upwards THE DISSECTOR. 249 upon the anterior surface of the organ, turn around its fundus, and return upon the posterior surface to the base of the prostate gland, where they are inserted into the fibrous tissue of the neck of the bladder. The lateral fibres pass off obliquely upon the sides of the organ, and some form loops of support to the ureters at their entrance between the coats of the bladder. The internal layer is best dissected by re- moving the mucous membrane from the inner surface of the bladder : it may also be demonstrated by dissecting off the longitudinal layer. The internal layer consists of muscular fibres, which are disposed in an oblique, spiral, and trans- verse direction, and cross each other frequently. They cease almost entirely at the neck of the bladder, and very few transverse fibres can be detected in this situation, so that the term "sphincter vesicae" is very incorrect. This has been very clearly proved by the investigations of Mr. Guthrie. The aggregate of the muscular fibres of the bladder is called detrusor urinae. The mucous coat is thick and smooth, and in a contracted state is thrown into a number of rugae. It lines the interior of the bladder, is continuous, by means of the ureters, with the mucous lining of the kidney and uriniferous tubuli, and, through the urethra, with the prostatic coeca, seminiferous tubuli, and CoAvper's glands. It is but loosely connected with the muscular coat, and is sometimes, as in violent exer- tion, or in the continued efforts arising from the irritation of stone, or old stricture, forced between its fibres, and made to form a protrusion externally to the bladder. This is encysted bladder, and several of these cysts may exist in the same individual. Sometimes they contain calculi; and, when a stone has escaped into one of these sacs, it ceases to be a source of irritation to the patient. The Submucous tissue is moderately thick throughout the whole of the bladder ; but around the openings of the ureters, at the trigone vesicale, and around the neck of the bladder and urethra, it becomes still thicker, more dense, and "elastic, and is continuous with the elastic membrane of the urethra." Mr. Guthrie considers it as a " superadded structure," which by becoming thickened in chronic disease of the bladder, gives rise to the formation of a "bar or dam," quite inde- pendent of any enlargement of the prostate gland, and forms 250 THE DISSECTOR. a considerable, and even fatal obstruction to the passage of the urine. Upon the inner wall of the base of the bladder, is a tri- angular smooth surface called " trigone vesicale," which is the most sensitive part of the whole organ, so that when rough calculi become placed against it, they give rise to extreme pain. The apex of the angle is situated at the commence- ment of the urethra, and corresponds Avith the projection of mucous membrane called uvula vesicae; the posterior angles are formed by the openings of the ureters. The sides are bounded by two elevated ridges of mucous membrane, pro- duced by two muscular bands, which pass from the extremi- ties of the ureters to the commencement of the urethra; these are the muscles of the ureters ; they consist partly of muscular and partly of elastic tissue. The three sides of the trigone are about an inch and a quarter in length. The external surface of the trigone vesicale is also trian- gular, and is closely adherent to the rectum. It is bounded behind by the fold of peritoneum that passes from the rectum to the bladder; on each side by the vasa defe- rentia and vesiculae seminales, and the apex, by the third lobe of the prostate gland. It is through this triangle that the opening is made in the recto-vesical operation for punc- ture of the bladder. The operator must therefore be careful in selecting the centre of the space: if he push the trochar too near the prostate, he may wound that gland and not enter the bladder; if to either side, the vasa deferentia or vesiculae seminales may be transfixed; and if too far posteriorly he may wound the peritoneum, and anticipate all the dangers of peritoneal inflammation. The adhesion between the bladder and rectum might also be separated by an inexpert operator. The Urethra is the excretory canal of the bladder, it commences at the neck of that organ, and terminates at the meatus upon the glans penis. It is about nine inches long, and is divided into three portions; the prostatic, membranous, and spongy. The Prostatic urethra is the most dilated part of the canal, and is a little more than an inch in length. It is situated in the prostate gland, one-third nearer to the upper than to the lower surface of that body. Upon its inferior wall or floor is a lengthened fold of mucous membrane, called caput gallina- THE DISSECTOR. 251 ginis, (cockscomb) or veru montanum. At the commence- ment of this fold is a pouch of the mucous membrane, the sinus pocularis, and into this pouch open the two ejaculatory ducts from the vesiculae seminales. On either side of the veru montanum are a number of openings, the terminations of the prostatic ducts. The Membranous portion of the urethra is the narrowest part of the canal, is a little less than an inch in length, and is situated within the two layers of the deep perineal fascia. Its coverings are, the mucous lining; an elastic fibrous coat; a muscular covering from the compressor ure- thrae muscle; and a fibrous investment from the deep pe- rineal fascia. Immediately that it escapes from the deep perineal fascia, it is received into the upper part of the bulb of the urethra, and becomes the spongy portion. The Spongy portion of the urethra is named from being enclosed by the corpus spongiosum penis. The commence- ment of the corpus spongiosum forms the bulb, hence the in- cluded urethra is called the bulbous portion. Next to the prostatic portion, the bulbous is the most dilated part of the canal. In the body of the corpus spongiosum, the canal diminishes in size, but, within the glans penis, it forms a third dilatation called fossa navicularis, and, at the meatus con- tracts so much as to be smaller than at any other part of the tube. The bulbous portion has, opening into it, the two small excretory ducts of Cowper's glands. These small bodies, (fig. 66. 11.,) about the size of peas, are situated imme- diately beneath the membranous portion of the urethra, betAveen the tAvo layers of the deep perineal fascia, and are covered by the inferior fasciculus of the compressor urethrae muscle. They are composed of mucous follicles and their ducts, about three quarters of an inch in length, pass fonvards to open into the bulbous urethra. In the mucous membrane are a number of mucous follicles or lacunae. These are most numerous upon the upper wall of the canal, and have their openings directed forwards so as to catch the point of a catheter in its passage into the bladder, and give rise to a temporary impediment. In a case of this kind the instrument should be Avithdrawn a little, and then pushed gently on, with a slight depression of the point. One of these lacunae, larger than the rest, is called lacuna 252 THE DISSECTOR. magna ; it is situated at about an inch and a half from the meatus. It is said to be the seat of the secretion of the drop of matter which is squeezed from the urethra in old gonor- rhoea. Prostate gland.—The Prostate gland (fig. 69. 3.) sur- rounds the upper surface of the neck of the bladder, and is situated within the pelvis. It has the shape and size of a Spanish chestnut; the base being directed backwards towards the bladder, the apex forwards to the deep perineal fascia; the flat side upwards, and the convex side downwards. The latter lies in contact with the rectum, and may be distinctly felt through its coats. It is retained in its place by the two tendons of the blad- der, which are continuous with the anterior ligaments of the bladder, by the attachments of the pelvic fascia below, and by a process of the internal layer of the deep fascia, which forms a sheath around the membranous urethra, and is in- serted into the prostate. It consists of three lobes, two lateral and a middle lobe; the latter is a small transverse process connected with the base of the gland. It supports the elastic tissue which forms the projection of mucous membrane at the commencement of the urethra, called uvula vesicae, and when enlarged presses the uvula inAvards towards the interior of the bladder, and produces a great impediment to the Aoav of urine. The Ducts of the prostate, from twenty to twenty-five in number, open into the prostatic urethra on each side of the veru montanum. The urethra, in passing through the prostate, lies nearer to its upper than its loAver surface. Vesicul./e seminales.—At the base of the prostate gland are the vesiculae seminales (fig. 69. 8.) each formed by the convolutions of a single dilated tube, and enclosed in a dense fibrous membrane. Their larger extremities are directed backwards, and are separated from each other by a consider- able interval; the smaller converge to a point anteriorly, and almost meet at the base of the prostate gland. They form in this manner the lateral boundaries of a triangular space, Avhich corresponds Avith the triangle on the inner surface of the bladder, called trigone vesicale. Vasa deferentia.—The Vas deferens (fig. 69. 8.) from each testicle enters the abdomen at the internal abdominal THE DISSECTOR 253 ring, and passes inwards to the side of the fundus of the bladder ; it then descends along its posterior surface, and crosses the direction of the ureter to the base of the prostate gland. When it reaches the vesicula seminalis it becomes connected by cellular tissue to its inner border, and termi- nates by a small duct, which unites Avith a similar duct from the vesicula seminalis, to form the ductus ejaculatorius. The ejaculatory duct is about three quarters of an inch in length, and passes forwards between the prostate gland and the lining membrane of the urethra, to terminate near its fellow of the opposite side in the sinus pocularis. If the bladder and rectum be separated from their lateral connexions and turned down, the attachments of the pelvic fascia and the levator ani muscle may next be seen and ex- amined. The Pelvic fascia is continuous Avith the iliac fascia along the border of the pelvis, and is prolonged doAvnwards, so as to line the interior of its cavity. At its lower part it is re- flected from the sides of the pelvis upon the rectum, the base of the bladder, and prostate gland, forming the lateral true ligaments of the bladder. In front it forms its anterior true ligaments. If this fascia be carefully raised, a thin layer of muscular fibres will be seen beneath it, which should now be dissected. The Levator ani is a thin plane of muscular fibres situated on each side of the pelvis. It arises from the inner surface of the pubis, from the spine of the ischium, and between those points from the angle of union between the obturator and the pelvic fascia. Its fibres descend to be inserted into a raphe" in front of the coccyx, into the lower part of the rec- tum, base of the bladder, and prostate gland. Wilson's and Guthrie's muscles (the compressor urethrae) are situated between the two layers of the deep perineal fas- cia, and are described with the perineum. Actions.—The use of the levator ani is expressed in its name. It is the antagonist to the diaphragm and the rest of the expulsory muscles, and serves to support the rectum and vagina during their expulsive efforts. In the operation for lithotomy on children and emaciated persons, its action is often very remarkable, contracting spasmodically, and pro- ducing a fluttering which is very annoying to the operator. If the levator ani muscle be separated from its origin, and 254 THE DISSECTOR. turned downwards, the obturator fascia will be seen beneath, and the mode of origin of the middle fibres of the muscle may be examined. The obturator fascia binds down the internal obturator muscle, and covers in the internal pudic vessels and nerve. The Arteries and Nerves of the pelvis should now be dis- sected. This is easily done by taking the trunk of the in- ternal iliac as a guide to its branches. The Nerves forming the sacral plexus may be traced from the anterior sacral foramina. Fig. 71. The distribution and branches of the iliac arteries. 1. The aorta. 2. The left common iliac artery. 3. The external iliac. 4. The epigastric artery. 5. The circumflexa ilii. 6. The internal iliac ar- tery. 7. Its anterior trunk. 8. Its posterior trunk. 9. The umbilical artery giving off [10) the superior vesical artery. After the origin of this branch, the umbilical artery becomes converted into a fibrous cord—the umbilical ligament. 11. The internal pudic artery passing behind the spine of the ischium (12) and lesser sacro ischiatic ligament. 13. The middle hemorrhoidal artery. 14. The ischiatic artery, also passing behind the an- terior sacro ischiatic ligament to escape from the pelvis. 15. Its inferior vesical branch. 16. The ilio-lumbar, the first branch of the posterior trunk (8) ascending to inosculate with the circumflexa ilii artery (5) and form an arch along the crest of the ilium. 17. The obturator artery. 18. The late- ral sacral. 19. The gluteal artery escaping from the pelvis through the upper part of the great sacro-ischiatie foramen. 20. The sacra-media. 21. The right common iliac artery cut short. 22. The femoral artery. The Internal iliac artery, as soon as it enters the pel- vis, divides into two trunks, an anterior and posterior; the anterior division has connected Avith it the remains of the umbilical artery, and then divides into the ischiatic and inter- nal pudic arteries; the posterior division gives off the smaller THE DISSECTOR. 255 pelvic branches, and passing out of the pelvis becomes the gluteal artery. The branches may be thus arranged. Anterior Trunk. Posterior Trunk. Umbilical, Ilio-lumbar, Ischiatic, Obturator, Internal pudic, Lateral sacral, Gluteal. The Umbilical is the commencement of the fibrous cord, which passes forwards by the side of the fundus of the blad- der, and then ascends converging to the urachus, and its fel- low of the opposite side, as far as the umbilicus. It is pervious for a short distance only, and gives off several small branches, called superior vesical, Avhich are distributed to the fundus and side of the bladder, and extend as far as the prostate gland. The Ischiatic artery descends to the lower border of the great sacro-ischiatic foramen, and escapes from the pelvis be- low the pyriformis muscle. It gives off a few small branches within the pelvis to the rectum, fundus of the bladder, and vesiculae seminales. The Internal pudic artery also passes through the great sacro-ischiatic foramen, below the pyriformis muscle, but nearer to the sacrum than the ischiatic. It crosses the spine of the ischium, and re-enters the pelvis through the lesser sacro-ischiatic foramen; it then crosses the tuberosity of the ischium at about an inch from its lower border, resting upon the obturator muscle, and bound down by the obturator fascia. It next ascends along the edge of the ramus of the ischium and pubis, between the tAvo layers of the deep perineal fascia, giving off branches to the perineum and penis, and terminates in the dorsalis penis artery. Its branches within the pelvis are the middle hemorrhoidal. In the female it is distributed in the same manner to the perineum and external organs of generation. The Ilio-lumbar artery ascends beneath the psoas muscle to the posterior part of the crest of the ilium, along which it takes its course, supplying the adjoining muscles. It inoscu- lates Avith the lumbar arteries and with the circumflexa ilii. The Obturator artery passes forwards a little below the brim of the pelvis, to the upper border of the obturator fora- men. It enters the thigh through an opening in the obturator 256 THE DISSECTOR. ligament, and is distributed to the muscles of the upper and inner part of the thigh, and to the hip joint. The Lateral sacral is a small artery which runs by the side of the anterior sacral foramina, and sends branches into them for the supply of the sacral nerves. It anastomoses with the sacra-media. The Gluteal artery passes directly outwards through the upper part of the great sacro-ischiatic foramen, above the py- riformis muscle, and is distributed to the gluteal muscles. Sacral plexus of nerves.—The Sacral plexus is formed by the anterior branches of the last lumbar and four upper sacral nerves, and receives filaments from the sympathetic ganglia. The last lumbar nerve is called lumbosacral; it gives origin to the gluteal nerve. The Branches of the sacral plexus are, the visceral, which are distributed to the viscera of the pelvis, viz., the blad- der, prostate gland, uterus, rectum, &c, and communicate very freely with the termination of the hypogastric plexus; and the external, which are three in number. Internal pudic, Lesser ischiatic, Greater ischiatic. The Gluteal nerve passes out of the pelvis with the gluteal artery, through the great sacro-ischiatic foramen, above the pyrifomis muscle, and is distributed with the branches of that artery. The Internal pudic nerve passes out of the pelvis through the great sacro-ischiatic foramen, beloAV the pyriformis muscle, and follows the course and distribution of the internal pudic artery. The Lesser ischiatic nerve passes out of the pelvis through the great sacro-ischiatic foramen, in company with the great ischiatic nerve, and is distributed to the muscles of the ischi- atic region, and to the integument on the posterior aspect of the thigh. The Great ischiatic nerve is formed by the union of all the nerves which form the sacral plexus. It is a thick nervous band of considerable breadth. It leaves the pelvis through the great sacro-ischiatic foramen, below the loAver border of the pyriformis muscle, and is distributed to the lovver ex- tremity. The last two sacral, or rather, the Coccygeal nerves, are dis- THE DISSECTOR. 257 tributed to the lower extremity of the rectum, and perineum, and communicate with branches of the hypogastric plexus. The Sympathetic nerve within the pelvis is composed of four or five small ganglia on each side, which terminate on the coccyx in a single ganglion, called ganglion impar. The sacral ganglia give filaments to each of the sacral nerves and visceral filaments, which are distributed to the viscera of the pelvis, and communicate with the filaments of the hypogas- tric plexus. External Organs of Generation in the Male. Penis.—The Penis is composed of three lengthened bodies, closely united to each other, the two corpora cavernosa and the corpus spongiosum. The Corpora cavernosa (fig. 69. 22.) are firmly attached at their commencement to the ramus of the ischium and pubis, where they form the crura penis ; they then pass for- wards, and meeting in the middle line, become intimately united, and constitute the chief bulk of the body of the penis. They consist of cellular structure enclosed in a very dense fibrous investment, and are separated by an incomplete par- tition, which is named septum pectiniforme. They terminate anteriorly in a rounded extremity, which is received into a depression on the posterior part of the glans penis. The Corpus spongiosum (fig. 69. 19.) is situated in the groove upon the under surface of the two corpora cavernosa. It commences posteriorly, by a considerable enlargement, which is called the bulb, 21., and terminates, anteriorly, in a rounded extremity, named the glans penis, 20. The bulb is attached to the anterior layer of the deep perineal fascia, by a process which is sent forwards to enclose the membranous portion of the urethra. The corpus spongiosum is connected to the corpora cavernosa by means of cellular tissue, and the glans is applied against their extremity and attached to it by the same medium. The urethra enters the bulb as soon as it escapes from the deep perineal fascia, and runs forwards through the corpus spongiosum to the meatus. The corpus spongiosum is named from its spongy cellular structure, which resembles that of the interior of the corpus cavernosum. It is enclosed in a thin layer of fibrous mem- brane. The Glans penis (fig. 69. 20.) is covered by a very thin 22* 258 THE DISSECTOR. cuticle, and is surrounded by an elevated ridge, called corona glandis. A number of sebaceous glands, the glandulae odo- riferae, or Tyson's glands, are situated around the corona. The glans is protected by a duplicature of integument, called the prepuce, which is retained in connexion with the under surface of the glans, by a thin fold called the fraenum pre- putii. There is a deep fossa around the corona glandis, be- tween it and the attachment of the prepuce, in which syphili- tic sores occasionally occur; when this is the case, they are extremely troublesome, and often burrow beneath the corona to a considerable depth. The integument of the penis is remarkable for its loose- ness, and for the absence of adipose substance in its cellular tissue. The penis is supported by a ligament, Ligamentum suspen- sorium (fig. 56. 23.) which descends from the symphisis pubis, to be inserted by two portions into the corpora cavernosa. Vessels and nerves.—The Arteries of the penis are de- rived from the internal pudic; they are the arteries of the bulb, of the corpora cavernosa, and of the dorsum of the penis. The Veins return the blood by the sides of the arte- ries to a plexus situated around the neck of the bladder. The dorsal vein is of very large size, and runs from before back- Avards in the groove on the dorsum of the penis. It passes between the tAvo portions of the suspensory ligament, and beneath the pubic symphisis, to open into the vesical plexus. The Lymphatics pass outwards to the inguinal glands. The Nerves are branches of the internal pudic nerve and hypogastric plexus, and accompany each branch of the arte- ries. Scrotum.—The Scrotum (purse, leather bag) is the tegu- mentary fold Avhich contains the testicles. It consists of two layers, the integument and dartos. The Integument is extremely thin, and in very large quan- tity. It is covered Avith hairs issuing obliquely from the skin, and having prominent roots. Along the middle line it is marked by a raphe\ The Dartos is a contractile fibrous layer, situated immedi- ately beneath the integument, and forming a distinct covering. It also divides the cavity of the scrotum into two equal chambers by a septum (septum scroti) of the same structure. The Structure of the dartos is intermediate between muscle THE DISSECTOR. 259 and elastic fibrous tissue, and is called by some authors " dartoid tissue." Testicle.—The Testicles are lodged within the two cavities formed by the dartos, and are surrounded by an extremely loose and abundant cellular tissue, which contains no adipose substance. The Coverings of the spermatic cord and testicle are the Spermatic fascia, Fascia propria. Cremasteric, The Spermatic fascia is the intercolumnar fascia derived from the external abdominal ring, which is carried downwards Avith the testicle in its descent in the foetus. The Cremasteric covering (erythroid) is formed by the ex- pansion of the fibres of the cremaster muscle, which are also carried down in the descent of the testicle. The Fascia propria consists of the transversalis fascia, carried down by the testicle in its descent. The Proper coverings of the testicle are, the tunica vagina- lis, and tunica albuginea. The Tunica vaginalis is a porch of serous membrane derived from the peritoneum in the descent of the testicle, and after- wards obliterated from the abdomen to within a short distance of the testicle. Like other serous coverings, it is a shut sack investing the organ, and thence reflected so as to form a bag around its circumference; hence it is divided into the tunica vaginalis propria, and tunica vaginalis refiexa. The Tunica albuginea is a thick fibrous membrane of a white color, and is the proper tunic of the testicle. From the union of a serous membrane with a fibrous tunic, the tunica vaginalis is considered as a fibro-serous membrane, and is ranged with the dura mater and pericardium. If the tunica vaginalis reflexa be laid open, it will be found to contain, in its interior, the testicle and a flattened body lying to its outer side, the epididymis. The Testicle is an ovoid gland slightly flattened at its sides. If it be divided by a transverse section, it will be observed that the tunica albuginea, (fig- 72. 1.,) after investing it com- pletely, is reflected inwards along its posterior border, so as to form a projecting ridge in its interior, called mediastinam testis, 2., (corpus Highmorianum.) From the mediastinum, a number of fibrous cords, 3., pass off and radiate in all direc- tions towards the inner surface of the tunic to Avhich they are 260 THE DISSECTOR. firmly attached. For a knowledge of the use of this arrange- ment, as of many other very important structures in the body, anatomists are indebted to Sir Astley Cooper, who has shown that this simple disposition is beautifully adapted to the pur- pose of preventing the compression of the substance of the testicle: and, truly, we know of no structure in the animal economy that evinces more striking evidence of design than does this. In the section of the mediastinum testis, two groups of minute foramina will be observed, one near the external surface of the mediastinum, consisting of divided arteries and veins ; the other near to its inner edge,—of the divided tubes of the rete testis. Fig. 72. The anatomy of the testicle. 1. The tunica albuginea. 2. The mediastinum testis, or corpus Highmori- anum. 3. A fibrous cord passing between two of the lobules from the medi- astinum to the inner surface of the tunica albuginea. Similiar cords are observed between the other lobules. 4. The tunica vasculosa or pia mater testis. 5. Two of the lobules of which the substance of the testicle is com- posed. They are seen to consist of the convolutions of minute tubes, tubuli seminiferi. 6. The small straight tubes by which the tubuli seminiferi ter- The dissector. 261 minate, vasa recta. 7. The rete testis, an aggregation of tubuli situated in the anterior half of the mediastinum. The posterior half (8.) is occupied by the arteries and veins. 9. 9. The vasa efferentia. 10. The conical convo- lutions of tubuli called coni vasculosi. This portion of the organ being of large size, and situated externally to the testicle, is the globus major of the epididymis. 11. The body of the epididymis. 12. The globus minor of the epididymis. 13. The vas deferens, ascending to the external abdominal ring. The arrows mark the course of the secretion along the tubes. Upon the inner surface of the tunica albuginea, is the tunica vasculosa testis, (fig. 72. 4.,) the nutrient membrane of the testicle. It sends vascular processes inwards between the lobules. Sir Astley Cooper has compared the tunica albuginea to the dura mater, and the tunica vasculosa to the pia mater of the brain. The Substance of the testis is composed of minute tubes (tu- buli seminiferi) very much convoluted and arranged in lobules, (fig. 72. 5.,) (lobuli testis.) The apices of the lobules are directed towards the mediastinum, and terminate in small, straight ducts called vasa recta, 6. The vasa recta form a net-work of minute tubes, running from below upwards within the substance of the mediastinum, which is called the rete testis, 7. The ducts forming the rete, quit the testis at its upper and posterior part under the name of vasa efferentia, 9. 9., which are eight or ten in number, and the vasa effer- entia become convoluted into cones, called coni vasculosi, 10. The convolutions of the vasa efferentia, external to the testi- cle, constitute the epididymis. The upper end of the epididy- mis is of large size, from the great assemblage of convoluted tubes in the coni vasculosi; hence it is named globus major, 10. The middle portion or body of the epididymis, 11., is formed by the convolutions of a single tube, and the lower portion, or globus minor, 12., consists of the convolutions of the vas deferens, previously to commencing its ascending course. The convolutions of these tubes in the epididymis are secured by a fibrous membrane, which is covered by the tunica vaginalis. The Vas deferens (fig. 72. 13.) commences, therefore, in the globus minor epididymis at the lower part of the testicle, and ascends along the posterior part of the sper- matic cord to the external abdominal ring. It then passes along the spermatic canal, and through the internal abdominal ring, to the side of the fundus of the bladder. It next descends along the posterior wall of the bladder, crossing the 262 THE DISSECTOR. direction of the ureter, and terminates at the base of the prostate gland by uniting with the duct of the vesicula semi- nalis to form the ejaculatory duct. The Spermatic cord consists of the vessels and nerves pass- ing to and from the testicle, enclosed in several tunics or fasciae. The left cord is a little longer than the right: hence the left testicle is the lower of the two. The cord is placed behind the testicle, so that the convexity of the testis looks forwards and a little outwards. Vessels and nerves.—The arteries of the cord are the spermatic, from the aorta ; cremasteric, from the epigastric; and deferential, from the vesical artery. The Veins are numerous, and have valves at very short distances. They are sometimes called vasa pampiniformia, from the peculiar tendril-like arrangement of the smaller vessels. The Lym- phatics are beautifully shown in the injections made by Sir A. Cooper : they terminate in the lumbar glands. The Nerves are derived from the spermatic plexus, and from the genito-crural and ilio-scrotal branches of the lumbar plexus. The Coverings of the cord are the fascia spermatica, cre- master, and fascia propria. Surgery of the Testicle and Spermatic Cord. When the tunica vaginalis remains unclosed, the intestine being forced into it, lies in contact with the testicle: this is Congenital hernia (fig. 13. page 35.) Hydrocele, in infants and young children, often communi- cates Avith the cavity of the abdomen from the same deficiency of closure. When the tunica vaginalis is closed at the upper point only and the hernial sac descends behind it, we have a case of Encysted hernia (fig. 14. page 35.) If the hernial sac were to descend into the tunica vaginalis, instead of behind it, the serous membrane rising all around it, that also would be a form of encysted hernia. When the tunica vaginalis is closed from point to point only, fluid may collect in the unobliterated portions, and form one or more sacs. This is the Hydrocele of the cord. If the fluid collect in the tunica vaginalis itself, the case is common Hydrocele. If blood in place of serous fluid occupy the tunica vaginalis, the case is one of Hematocele. THE DISSECTOR. 263 If the veins of the cord be enlarged and tortuous, or vari- cose, the case is one of Varicocele, or spermatocele. Swelled testicle is often called Hernia, humoralis ; and in- guinal hernia, descending into the scrotum, forms Scrotal hernia. Female Pelvis and Organs of Generation. The contents of the female pelvis are the bladder, vagina, uterus, with its appendages, and rectum. Fig. 73. A side view of the viscera of the female pelvis. 1. The symphisis pubis; to the upper part of which the tendon of the rectus muscle is attached. 2. The abdominal parietes. 3. The collection of fat, forming the projection of the mons Veneris. 4. The urinary bladder. 5. The entrance of the left ureter. 6. The canal of the urethra, converted into a mere fissure by the contraction of its walls. 7. The meatus urina- rius. 8. The clitoris, with its praeputium, divided through the middle. 9. The left nympha. 10. The left labium majus. 11. The meatus of the vagina, narrowed by the contraction of its sphincter. 12. The canal of the vagina, upon which the transverse rugae are apparent. 13. The thick wall of separation between the base of the bladder and the vagina. 14. The wall of separation between the vagina and rectum. 15. The perineum. 16. The os uteri. 17. Its cervix. 18. The fundus uteri. The cavities uteri is seen along the centre of the organ. 19. The rectum, showing the disposi- tion of its mucous membrane. 20. The anus. 21. The upper part of the rectum, invested by the peritoneum. 22. The recto-uterine fold of the pe- ritoneum. 23. The uteros vesical fold. 24. The reflection of the perito- neum, from the apex of the bladder, upon the urachus to the internal sur- face of the abdominal parietes. 25. The last lumbar vertebra. 26. The sacrum. 27. The coccyx. 264 THE DISSECTOR. The Bladder is in relation with the pubis in front, and with the vagina beneath. Its form corresponds with that of the pelvis, being broad from side to side, and often bulging more on one side than the other. This is particularly evident after frequent parturition. The Coats of the bladder are the same as those of the male. The Muscular coat has its two layers, the external and the internal; the longitudinal fibres of the former are attached to a ring of thickened submucous tissue, which surrounds the commencement of the urethra, and is connected, like the pros- tate gland in the male, to the inner surface of the os pubis by means of the tendons of the bladder. This enlargement, Mr. Guthrie conceives to be analogous to the prostate in the male; and he describes it as the prostate gland of the female. An opposite opinion, viz. that there is no prostate gland in the female, is entertained by the greater number of anatomists. The Urethra is extremely short, not more than an inch and a half in length. It is enclosed in the upper wall of the vagina, and terminates at its anterior extremity. The Female organs of generation are divided into external and internal. The External organs are the Mons Veneris, labia maiora, labia minora or nymphae, clitoris, meatus urinarius, and the entrance to the vagina. The Internal organs are the vagina, uterus, ovaries, Fallo- pian tubes, and ligaments. External Organs of Generation. The Mons Veneris is an eminence of integument, situated upon the pubis. Its cellular tissue is loaded with adipose sub- stance, and the surface covered with hairs. The Labia majora are two large longitudinal folds of in- tegument, consisting of fat and loose cellular tissue. They enclose an elliptic opening called the vulva, and are united posteriorly by a thin commissure called the fourchette, which is always ruptured in parturition. Immediately within this commissure is a small cavity, the fossa navicularis. The breadth of the perineum is measured from the four- chette to the margin of the anus, and is usually not more than an inch across. The external surface of the labia is covered with hairs; THE DISSECTOR. 265 the inner surface is smooth, and lined by mucous membrane, which contains a number of sebaceous follicles, and is covered by a thin epithelium. The use of the labia majora is to favour the extension of the vulva during parturition; for, in the passage of the head of the child, the labia are completely unfolded and effaced. The Labia minora, or nymphae, are two smaller folds situ- ated within the labia majora. Superiorly they are divided into two processes, which surround the glans clitoridis and form its prepuce, preputium clitoridis. Inferiorly, they dimi- nish gradually in size, and are lost on the sides of the open- ing of the vagina. The nymphae consist of mucous membrane, covered in by a thin epithelium. They are provided with a number of se- baceous follicles, and contain, in their interior, a thin layer of erectile tissue. The Clitoris is a small elongated organ, situated in front of the pubis, and supported by a suspensory ligament. It is formed by the union of tAvo small bodies, Avhich are analogous to the corpus cavernosa of the penis, and, like them, arise from the ramus of the pubis and ischium on each side, by two crura. The extremity of the clitoris is called its glans. It is composed of erectile tissue, enclosed in a dense layer of fibrous membrane, and is susceptible of erection. Like the penis, it is provided with two small muscles, the erectores cli- toridis, which arise from the ramus of the ischium, and are inserted into the crura. At about an inch beneath the clitoris is the entrance of the vagina, an elliptic opening, marked by a projecting margin. The entrance to the vagina is closed in the virgin by a mem- brane called the Hymen, which is stretched across the open- ing. Sometimes the membrane forms a complete septum, and gives rise to great inconvenience by preventing the escape of the menstrual effusion. It is then called an imperforate hy- men. The hymen is not by any means a necessary accom- paniment to virginity, for it does not constantly exist. When present it assumes a variety of appearances: it may be a membranous fringe, with a round opening in the centre, or it is a semilunar fold, leaving an opening in front; or a transverse septum, having an opening both in front and be- hind. The rupture of the hymen or its rudimentary existence, 23 266 THE DISSECTOR. gives rise to the appearance of granulations around the opening of the vagina: these are called carunculae myrti- formes. The triangular smooth surface between the clitoris and the entrance of the vagina, which is bounded on each side by the upper portions of the nymphae, is the Vestibule. At the upper angle of the vagina is an elevation formed by the projection of the upper wall of the canal: and imme- diately in front of this tubercle, and surrounded by it, is the opening of the urethra, the Meatus urinarius. Internal Organs of Generation. Vagina.—The Vagina is a membranous canal, leading from the vulva to the uterus, and corresponding in direction Avith the axis of the outlet of the pelvis. At the commence- ment it is constricted, but near the uterus becomes consider- ably dilated. Its length is very variable; but it is always longer upon the posterior than upon the anterior Avail. The former is usually about five or six inches in length, and the latter four or five. It is inserted into the cervix of the uterus, which projects into the upper extremity of the canal. In Structure the vagina is composed of a mucous lining, a layer of erectile tissue, and an external tunic of a fibrous structure, resembling the dartos of the scrotum. The upper half of the posterior wall of the vagina is covered, on its pel- vic surface, by the peritoneum ; and, in front, the peritoneum is reflected from its upper part to the posterior surface of the bladder. The Mucous membrane presents a number of transverse papillae or rugae upon its upper and loAver surfaces, which ex- tend outwards on each side from a middle raphe. The trans- verse papillae and raphe' are more apparent upon the upper than upon the lower surface, and the two raphe" are called the columns of the vagina. The mucous membrane is covered by a thick epithelium, which is continued from the labia, and terminates by a fringed border at the inner margin of the os uteri. The External or dartoid layer of the vagina, serves to con- nect it to the surrounding viscera. Thus, it is very closely adherent to the under surface of the bladder, and drags that organ down with it in prolapsus uteri. To the rectum it is THE DISSECTOR. 267 more loosely connected, which is therefore less frequently af- fected in prolapsus. Fig. 74. The female internal organs of generation. 1. The upper part of the vagina. 2. The os uteri, projecting into the vagina; the posterior lip is seen to be longer and larger than the anterior. 3. The cervix uteri. 4. The body of the uterus. 5. Its fundus. 6. The broad ligament of the left side, having enclosed between its layers (7.) the Fallopian tube, and (8.) the round ligament. On the right side the broad ligament is removed, so as to bring more clearly into view the structures which it contains. 9. The Fallopian tube. 10. Its fimbriated extremity. 11. One of its fimbriae attached to the ovary. 12. The ovary attached by its ligament to the upper angle of the uterus. 13. The round ligament. Uterus.—The Uterus (fig. 74. 4.) is a flattened organ of a pyriform shape, having the base directed upwards. Its di- rection corresponds with the axis of the inlet of the pelvis; it therefore forms a considerable angle with the direction of the vagina. It is about three inches in length, tAvo in breadth across its broadest part, and one in thickness. It is divided into fundus, body, cervix, and os uteri. The Fundus (fig. 74. 5.) and Body, 4., are enclosed in a duplicature of peritoneum, which is connected with the tAvo sides of the pelvis, and forms a transverse septum between the bladder and rectum. The folds on either side of the uterus are the broad ligaments, 6. They contain several im- portant parts. The Cervix, 3., gives attachment to,the vagina, and the os uteri, 2., projects into the upper part of the vagina, and pre- sents a transverse opening. Within and around the os uteri are occasionally found some smallvesicles, which are called the ovula of Naboth. These are dilated mucous follicles, having the open- ings closed by adhesion. The posterior lip of the os uteri is thicker and more projecting than the anterior. 268 THE DISSECTOR. The Cavity of the uterus is triangular in its form, the upper angles corresponding Avith the commencement of the Fallo- pian tubes. In the cervix of the organ is an arborescent arrangement of folds, which is called arbor vitae uterina. Structure.—The uterus has three coats—an internal, or mu- cous, a fibrous or muscular, and a peritoneal coat. In the un- impregnated state the fibrous structure is dense and pale, and very indistinct; but in the impregnated uterus it is decidedly muscular, and may be clearly demonstrated. The fibres are then observed to be disposed in three layers—an external, consisting of longitudinal fibres, a middle of oblique fibres, some of which pass off upon the Fallopian tubes, and others upon the round ligaments ; and a third layer consists of con- centric circles of fibres, having their centre at the commence- ment of the Fallopian tubes. In the cervix uteri the fibres are circular. Vessels and nerves.—The Arteries of the uterus are the uterine from the internal iliac, and the spermatic from the aorta. The Veins are very large and remarkable; in the impregnated uterus they are called sinuses, and consist of canals channelled through the substance of the organ, and are merely lined by the internal membrane of the veins. The Nerves are derived from the hypogastric and sperm- atic plexuses, and from the sacral plexus. The Appendages of the uterus are enclosed by the lateral duplicatures of peritoneum, called the broad ligaments. They are the Fallopian tubes and ovaries. The Fallopian tubes (fig. 74. 7.) are two tubular prolon- gations which pass off on each side from the upper angles of the uterus. At their commencement (ostium uterinum) they are small, but they gradually increase as they pass outwards, and terminate by expanded fimbriated extremities, 10. (ostium abdominale.) One of these fringes, 11., longer than the rest, is attached to the ovary, and serves to guide the tube in its seizure of that organ. The tube is lined by mucous membrane, which is continu- ous with that of the uterus, and at the fimbriated extremity is in connexion Avith the peritoneum. This is the only instance in the human being of a natural opening existing in a serous membrane. The Ovaries (fig. 74. 12.) are two oblong flattened bodies of a yellowish colour, situated in the posterior folds of the THE DISSECTOR. 269 broad ligaments. They are connected to the upper angles of the uterus at each side by a rounded cord, the ligament of the ovary. The Structure of the ovary is a spongy vascular tissue, containing serous vesicles (Graafian,) and enclosed in a dense, fibrous tissue, covered by peritoneum. These vessels are simple cysts, containing a limpid fluid, of various size, and from ten to fifteen in number in each ovary. They are the ova in which the future embryo is developed. Bauer states, that the vesicles which are nearest the surface have a minute floating body in their interior, which is the rudiment of the germ. After conception, a yellow spot is often found in one or both ovaries, and has been named the corpus luteum. It is formed of yellow, condensed substance, deposited in the place of the ovum, which has escaped. This was formerly con- sidered a certain evidence of conception having taken place; but nothing can be more fallacious. It does not always exist in women who have borne children, and it has been found in virgins, and even in a child five years of age. Vessels and Nerves.—The Arteries of the ovaries are the spermatic. Its Nerves are derived from the spermatic plexus. The uterus is held in its place by two round ligaments, which are connected with the angles of the uterus, and pass forwards beneath the peritoneum to the internal abdominal ring: they then follow the course of the spermatic canal on each side to the labia majora. While in the spermatic canal they have the same relations as the spermatic cord, which they represent in the female. They are accompanied by a small artery, and several fila- ments of the spermatic plexus of nerves. 23* 270 THE DISSECTOR. CHAPTER VII. REGION OF THE BACK. It is customary in most dissecting rooms to turn the body upon its face after the lapse of a few days, that the student may have an opportunity of studying the muscles of the back and the posterior parts of the limbs. _ The student must, therefore, endeavour to accommodate his dissection to these rules. The region of the back is, from its extent, common to the neck, the upper extremities, and the abdomen. The muscles of which it is composed are numerous, and may be arranged into six layers. First Layer. Trapezius, Latissimus dorsi, Second Layer. Levator anguli scapulae, Rhomboideus minor, Rhomboideus major. Third Layer. Serratus posticus superior, Serratus posticus inferior, Splenius capitis, Splenius colli. Fourth Layer. (Dorsal Group.) Sacro lumbalis, Longissimus dorsi, Spinalis dorsi. (Cervical Group.) Cervicalis ascendens, Transversalis colli, 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. Multifidus spinae, Levatores costarum, Supra-spinales, Inter-spinales, Inter-transversales. Posterior Thoracic Region.—First Layer. Trapezius, Latissimus dorsi. THE DISSECTOR. 271 If the subject be turned upon its face, the posterior mus- cles of the shoulder and arm may be examined. Two of these form the superficial layer of muscles of the back, the trapezius and latissimus dorsi. Dissection.—They are to be dissected by making an incision along the middle line of the back, from the tubercle on the occipital bone to the sacrum. From the upper point of this incision carry a second along the side of the neck, to the middle of the clavicle. Inferiorly, an incision must be made from the extremity of the sacrum, along the crest of the ilium, to about its middle. For the convenience of dissection, a fourth may be carried from the middle of the spine to the acromion process. The integument and superficial fascia, to- gether, 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 un- equal sides) arises from the superior curved line on the occipi- tal bone, from the ligamentum nuchae, spinous processes of the last two cervical and all the dorsal vertebrae. The fibres converge from these various points, and are inserted into the scapular third of the clavicle, the acromion process, and the whole length of the upper border of the spine of the scapula. The inferior fibres become tendinous near to the scapula, and glide over the triangular surface of the posterior extremity of its spine, being separated from it by a bursa mucosa. When the trapezius is dissected on both sides, the two muscles re- semble a trapezium or a diamond-shaped quadrangle on the posterior part of the shoulders: hence the muscle was form- erly named cucullaris (cucullus, a monk's cowl.) The cervi- cal and upper part of the dorsal portion of the muscle is tendinous at its origin, and forms with the muscle of the opposite side a kind of tendinous ellipse. The Latissimus dorsi muscle covers the whole of the lower part of the back and loins. It arises from the spinous pro- cesses of the six inferior dorsal vertebrae, all the lumbar and sacral, from the posterior third of the crest of the ilium, and from the three lower ribs by muscular slips, which indigitate with the external oblique muscle of the abdomen. The fibres converge as the muscle passes upwards and crosses over the inferior angle of the scapula, to be inserted with the teres major into the posterior bicipital ridge of the humerus. A synovial bursa is interposed between the muscle and the lower 272 THE DISSECTOR. angle of the scapula: sometimes it has a muscular connexion with the scapula at this point. The latissimus dorsi is occasionally thrown off the inferior angle of the scapula, a painful and puzzling accident, and not easy of reduction. The bursa too is liable to become inflamed, when a tumour of very large size may be found in this situa- tion resulting from the distention of the synovial sac. The trapezius muscle may now be removed, by cutting it away from its insertion, and turning it to the opposite side; and the latissimus dorsi, by dividing it near to its tendon, and turning it down. Posterior Thoracic Region.—Second Layer. We thus bring into view a group of three muscles, forming the second layer of muscles of the back, which belong in their actions to the scapula:— Levator anguli scapulae, Rhomboideus minor, Rhomboideus major. The Levator anguli scapulae arises by distinct slips from the posterior tubercles of the transverse processes 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. The Rhomboideus minor (rhombus, a parallelogram 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 two cervical vertebrae and ligamentum nuchae, 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 of the four upper dorsal vertebrae and their supra-spinous liga- ments, and is inserted into the posterior border of the scapula as far as its inferior angle. Third Layer. The Third layer consists of muscles which arise from the spinous processes of the vertebral column, and pass outwards. It is brought into view by dividing the levator anguli scapulae near its insertion, and reflecting the two rhomboid muscles upwards from their insertion into the scapula, and removing them altogether. THE DISSECTOR. 278 Fig. 75. The first and second part of the third layer of muscles of the back; the first layer being shown upon the right, and the second on the left side. 1. The trapezius muscle. 2. The tendinous portion which, with a cor- responding portion in the opposite muscle, forms' the tendinous ellipse on the back of the neck. 3. The acromion process and spine of the scapula. 4. The latissimus dorsi muscle. 5. The deltoid. 6. The muscles of the dor- sum of the scapula, infra-spinatus, teres minor, and teres major. 7. The external oblique muscle. 8. The gluteus medius. 9. The glutei maximi. 10. The levator anguli scapulae. 11. The rhomboideus minor. 12. The rhomboideus major. 13. The splenius capitis; the muscle immediately above, and overlaid by the splenius, is the complexus. 14. The splenius colli, only partially seen ; the common origin of the splenius is seen at- tached to the spinous processes below the lower border of the rhomboideus major. 15. The vertebral aponeurosis. 16. The serratus posticus inferior. 17. The supra-spinatus muscle. 18. The infra-spinatus. 19. The teres minor muscle. 20. The teres major. 21. The long head of the triceps, passing between the teres minor and major to the upper arm. 22. The ser- ratus magnus, proceeding forwards from its origin at the base of the scapula. 23. The internal oblique muscle. 274 THE DISSECTOR. The Serratus posticus superior arises from the spinous pro- cesses of the last two cervical and upper dorsal vertebrae, and is inserted, by four serrations into the posterior surface of the second, third, fourth and fifth ribs. The Serratus posticus inferior arises from the spinous pro- cesses of the last two dorsal and tAvo upper lumbar vertebrae, and is inserted by four serrations into the four lower ribs. These two muscles are connected by a thin tendinous fascia, called the intervertebral aponeurosis. The serratus posticus superior must be removed from its origin and turned outwards, to bring into view the whole ex- tent of the splenius muscle. The Splenius muscle is single at its origin, but divides soon after into two portions, which are destined to distinct inser- tions. It arises from the spinous processes of ten vertebrae, the four lower cervical and six upper dorsal, and divides as it ascends the neck into the splenius capitis and colli. The Splenius capitis is inserted into the rough surface of the oc- cipital bone between the two curved lines, and into the mas- toid process. The Splenius colli is inserted into the transverse processes of the four upper cervical vertebrae. The two serrati and two splenii must be removed by cut- ting them away from their origins and insertions to bring the fourth layer into view. Fourth Layer. Three of these muscles, viz. sacro-lumbalis, longissimus dorsi, and spinalis dorsi, are associated under the name of erector spinas. 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 com- mon origin from the posterior third of the crest of the ilium, from the posterior surface of the sacrum, and from the lum- bar vertebrae: opposite the last rib a line of separation begins to be marked between the two muscles. The Sacro-lumbalis is inserted by separate tendons into the angles of the six lower ribs. On turning the muscle a little outwards, a num- ber of tendinous slips will be seen taking their origin from the ribs, and terminating in a muscular fasciculus, by which THE DISSECTOR. 275 the sacro-lumbalis is prolonged to the upper part of the thorax. This is the musculus accessorius ad saero-lumbakm: it arises from the J^t ^T^tyToi angles of the loAver ribs, and is in- the muscles of the back. serted by separate tendons into the angles of the six upper ribs. The Longissimus dorsi is in- serted into all the ribs, between their tubercles and angles. The Spinalis dorsi arises from the spinous processes of the two upper lumbar and tAvo lower dorsal vertebrae, and is inserted into the spinous processes of all the upper dorsal vertebrae, the tAvo muscles form an ellipse, which appears to enclose the spinous processes of all the dorsal vertebrae. Cervical group.—The Cervica- lis ascendens appears to be the continuation of the sacro-lumbalis upwards into the neck. It arises from the angles of the four upper ribs, and is inserted into the trans- verse processes of the four lower cervical vertebrae. The Transversalis colli would appear to be the continuation up- wards into the neck of the longis- simus dorsi, it arises from the transverse processes of- the four 1. The common origin of the erector spinse muscle. 2. The sacro-lum- balis. 3. The longissimus dorsi. 4. The spinalis dorsi. 5. The cervicalis ascendens. 6. The transversalis colli. 7. The trachelo-mastoideus. 8. The complexus. 9. The transversalis colli, showing its origin. 10. The semi- spinalis dorsi. 11. The semi-spinalis colli. 12. The rectus posticus minor. 13. The rectus posticus major. 14. The obliquus superior. 15. The obli- quus inferior. 16. The multifidus spinae. 17. The levatores costarum. 18. Intertransversales. 19. The quadratus lumborum. upper dorsal vertebrae, and is inserted into the transverse processes of the four middle cervical vertebrae. The Trachelo-mastoid is likeAvise a continuation upwards from the longissimus dorsi. It is a very slender and delicate 276 THE DISSECTOR. mnscle, arising from the transverse processes of the four up- per dorsal, and four lower cervical vertebrae, and inserted into the mastoid process. The Complexus is a large muscle, and with the splenius forms the great bulk of the back of the neck. It crosses the direction of the splenius, arising from the transverse pro- cesses of the four upper dorsal, and four lower cervical ver- tebrae, and inserted into the rough surface on the occipital bone, between the two curved lines near to the spinous pro- cess. A portion of the complexus muscle is named Biventer cervicis, from consisting of a central tendon, with two fleshy bellies. The muscles of this layer are best removed by dividing them transversely through the middle, and turning one ex- tremity upwards, the other downwards. In this way the whole of the muscles of the fourth layer may be got rid of, and the remaining muscles of the spine brought into a state to be examined. Fifth Layer. The Semi-spinales muscles are connected with the trans- verse and spinous processes of the vertebrae, hence their name semi-spinalis. The Semi-spinalis dorsi arises from the transverse pro- cesses of the six lower dorsal vertebrae, and is inserted into the spinous processes of the four upper dorsal, and two lower cervical vertebrae. The Semi-spinalis colli arises from the transverse processes of the four upper dorsal vertebrae, and is inserted into the spinous processes of four upper cervical vertebrae, commenc- ing with the axis. Occipital group.—This group of small muscles is intended for the varied movements of the cranium on the atlas, and the atlas on the axis. They are extremely pretty muscles in appearance. The Rectus posticus major arises from the spinous process of the axis, and is inserted into the inferior curved line, on the occipital bone. The Rectus posticus minor 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 is interposed between the transverse THE DISSECTOR. 277 process of the atlas and the occipital bone ; it arises from the transverse process of the atlas, and is inserted into the rough surface of the occipital bone, external to the condyle. The Obliquus inferior arises from the spinous process of the axis, and is inserted into the extremity of the transverse process of the atlas. The Obliquus superior arises from the extremity of the transverse process of the atlas, and is inserted into the rough surface of the occipital bone, between the curved lines. Sixth Layer. The semi-spinales muscles must both be removed to obtain a good view of the multifidus spinae which lies beneath them, and fills up the concavity between the spinous and transverse processes, the whole length of the vertebral column. The Multifidus spinae consists of a great number of fleshy fasciculi, extending between the transverse and spinous pro- cesses of the vertebrae, from the sacrum to the axis. Each fasciculus arises from a transverse process, and is inserted into the spinous process of the first or second vertebra above. The Levatores costarum arise from the transverse processes of the dorsal vertebrae, and are inserted into the rough surface between the tubercle and angle of the rib below them. The Supra-spinales are little fleshy bands lying on the spinous processes of the vertebrae in the cervical region. The Inter-spinales are a succession of little pairs of mus- cles, lying between the bifid tubercles of the spinous pro- cesses of the cervical vertebrae. The Inter-transversales are also arranged in pairs, and pass betAveen the bifid tubercles of the transverse processes of the cervical vertebrae. They are sometimes found in the lumbar region. With reo-ard to the origin and insertion of the muscles of the back, the student should be informed that no regularity attends their attachments. At the best a knowledge of their exact connexions, even were it possible to_ retain, would be but a barren information, if not absolutely injurious, as tend- ing to exclude more valuable learning. We have, therefore, ^ endeavoured to arrange a plan, by which they may be more easily recollected, by placing them in a tabular form, that the student may see, at a single glance, the origin and insertion 24 278 THE DISSECTOR. 1st Layer. Trapezius..... Latissimus dorsi 2d Layer. Levator anguli scapulas SPINOUS PROCESSES. last cervical, 12 dorsal • • • 6 lower dorsal, 5 lumbar ■ • • • ORIGIN. TRANSVERSE PROCESSES. Rhomboideus min. 1 Rhomboideus major- 3d Layer. Serratus posticus 1 superior........J Serratus posticus \ inferior.........J Splenius capitis •• -1 Splenius colli.....J 4th Layer. Sacro-lumbalis ..... ----accessorius ad ) sacro-lumbalem J Longissimus dorsi- ■ • Spinalis dorsi.....-J Cervicalis ascendens • Transversalis colli- • • Trachelo-mastoideus. lig. nuchae, 2 lower cervical 4 upper dorsal • • 2 lower cervical 2 upper dorsal 2 lower dorsal 2 upper lumbar 4 lower cervical, 6 upper dorsal Complexus........ 6th Layer. Semi-spinalis dorsi • Semi-spinalis colli- ■ Rectus posticus maj Rectus posticus min Rectus lateralis Obliquus inferior- •• Obliquus superior- ■ 6th Layer. Multifidus spinae • • • 2 lower dorsal, 2 upper lumbar 4 upper cervical occipital bone, and) lig. nuchae......J sacrum and ilium • • • 4 upper dorsal • • 4 upper dorsal ■ • 4 lower cervical 4 upper dorsal • • 4 lower cervical 6 lower dorsal • • 4 upper dorsal • • Levatores costarum Supra-spinales..... Inter spinales...... Inter-transversales • axis ' atlas ' cervical cervical atlas axis from sacrum to 3d cervical, all the dorsal ■ angles of 6 lower angles of 4 upper sacrum and ilium - } lumbar ■ }:::: THE DISSECTOR. 279 INSERTION. SPINOUS PROCESSES. TRANSVERSE PROCESSES. RIBS. ADDITIONAL. :: :::: | clavicle and spine of the scapula. posterior bicipital ridge of the humerus. ........ :::: :::: * angle and base of the sca-pula. base of the scapula. base of the scapula. 2d, 3d, 4th, and 5th. 4 lower ribs. :::: :::: { 4 upper cervical. ........ { angles of 6 lower. angles of 6 upper. occipital bone between the curved lines. 8 upper dorsal ...... { 4 lower cervical. 4 middle do. all the ribs between the tubercles and angles. mastoid process. ........ { occipital bone between the curved lines. J 4 upper dorsal, ( 2 lower cervical. J 4 upper cervical, \ except atlas. occipital bone. occipital bone. occipital bone. atlas. occipital bone. ("from last lumbar \ to axis. ...... { all the ribs between the tubercles and angles. cervical. cervical. cervical. 280 THE DISSECTOR. of each, and compare the natural grouping and similarity of attachments of the various layers. In this manner, also, their actions will be better comprehended, and learnt with greater facility. See table, pp. 278, 279. In examining this table, the student will observe the con- stant recurrence of the number four in the origin and inser- tion of the muscles. Sometimes the four occurs at the top or bottom of a region of the spine, and frequently includes a part of two regions, and takes tAvo from each, as in the case of the serrata. Again, he will perceive that the muscles of the upper half of the table take their origin from spinous processes, and pass outwards to transverse, whereas the lower half arises mostly from transverse processes. To the student, then, we commit these reflections, and leave it to the peculiar tenour of his own mind to make such arrangements as will be best retained by his memory. Actions.—The first two layers are muscles of the shoulder and arm, to move which their efforts are directed. Their ac- tions have been described, with those of the shoulder. The two serrati are respiratory muscles acting in opposi- tion to each other—the serratus posticus superior, drawing the ribs upwards, and thereby expanding the chest; and 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 draw the head backwards and to one side, so as to direct the face toAvards the shoulder. Both muscles, acting together, will draw the head directly back- wards. They are the natural antagonists of the sterno-mas- toid muscles. The Sacro-lumbalis, with its accessory muscle, the longissi- mus dorsi and spinalis dorsi, are known by the general term of erector spinae, which sufficiently expresses their actions. They keep the spine supported in the vertical position by their broad origin from beloAV, and through their insertion by distinct tendons into the ribs and spinous processes. Being made up of a number of distinct fasciculi, which alternate in their actions, the spine is kept erect without fatigue, even when they have to counterbalance a corpulent abdominal de- velopment. The continuations upwards of these muscles into the neck preserve the steadiness and uprightness of that re- gion. When the muscles of one side act alone, the neck is THE DISSECTOR. 281 rotated upon its axis. The complexus, by being attached to the occipital bone, draws the head backwards, and counter- acts the muscles on the anterior part of the neck. It assists also in the rotation of the head. The Semi-spinales and multifidus spinae muscles act directly on the vertebrae, and contribute to the general action of sup- porting 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 ac- tions, and the obliqui the rotatory motions of the atlas on the axis. The actions of the remaining muscles of the spine, the supra and interspinals and intertransversales, are expressed in their names. They approximate their attachments, and assist the more powerful muscles in preserving the erect po- sition of the body. The Levatores costarum raise the posterior parts of the ribs, and are probably more serviceable in preserving the articulation of the rib from dislocation, than in raising them in inspiration. Spinal Cord. The dissection of the spinal cord requires that the spinal column should be opened throughout its entire length by saw- ing through the laminae of the vertebrae, close to the roots of the transverse processes, and raising the arches with a chisel, after the muscles of the back have been removed. The Spinal column contains the spinal cord, or medulla spinalis ; the roots of the spinal nerves ; and the membranes of the cord, viz. dura mater, arachnoid, pia mater, and mem- brana dentata. The Dura mater (fig. 77. 1.) (theca vertebralis) is conti- nuous with the dura mater of the skull: it is closely attached around the border of the occipital foramen, particularly in front, to the posterior common ligament. In the vertebral canal it is connected only by loose cellular tissue, containing an oily fluid, somewhat analogous to the marroAV of long bones. On either side, and below, it forms a sheath, 2. 2., for each of the spinal nerves, to which it is closely adherent. Upon its inner surface it is smooth, being lined by the 24* 282 THE DISSECTOR. arachnoid ; and on either side may be seen the double open- ing for the two roots of each of the spinal nerves. The Arachnoid (fig. 77.) is a continuation of the serous membrane of the brain. It encloses the cord very loosely, being connected to it only by long slender cellular filaments; passes off on either side with the spinal nerves, to which it forms a sheath ; and is then reflected upon the dura mater, to constitute its serous surface. A connexion exists in several situations between the arachnoid of the cord and that of the dura mater. The space between the arachnoid and the spinal cord is identical with that already described as existing between the same parts in the brain, the Sub-arachnoidean space (fig. 77. 4.) It is filled in both with a serous fluid, sufficient in quantity to expand the arachnoid, and fill completely the cavity of the theca vertebralis. The Sub-arachnoidean fluid keeps up a constant and gentle pressure upon the entire sur- face of the brain and spinal cord, and yields with the greatest facility to the Ararious movements of the cord, giving to those delicate structures the advantage of the principles so usefully applied by Dr. Arnott in the hydrostatic bed. Fig. 77. Section of the spinal cord with its membranes. 1. The dura mater. 2. 2. The dura mater, forming a sheath for each of the roots of a spinal nerve, and afterwards a sheath for the nerve itself. The dotted line represents the arachnoid membrane. 8. 3. A sheath formed by the arachnoid around each of the roots of the spinal nerve during its passage through that membrane. 4. The space between the two layers of the arachnoid ; an arrow at each side shows that this space is continuous all around the spinal cord, and that the disposition of the membrane at 3. 3. is a mere sheath. 5. The space between the arachnoid and pia mater, the sub-arachnoidean space, in which is lodged the sub-arachnoidean fluid. 6. One of the dentations of the ligamentum denticulatum. 7. 7. The pia mater of the cord. 8. The sulcus longitudinalis. 9. The white commissure, connecting the two lateral halves of the cord. 10. The gray commissure, connecting the two semilunar processes of gray. 11. The sulcus longitudi- nalis posterior. 12.12. The two anterior or motor columns of the spinal cord. THE DISSECTOR. 283 13. 13. The two lateral columns. 14. 14. The two posterior or sensitive columns. 15. 15. The posterior median columns, bounded by two shallow fissures. 16. The origin of the anterior or motor root of a spinal nerve. 17 The origin of its posterior or sensitive root. 18. The ganglion on the pos- terior root. 19. The spinal nerve dividing into its two primary branches, anterior and posterior. The Pia mater (fig. 77. 7. 7.) is the immediate investment of the cord, and, like the other membranes, is continuous with that of the brain. It is not, however, like the pia mater cerebri, a vascular membrane, but is dense and fibrous in its structure, and contains very few vessels. It invests the cord closely, and sends a duplicature into the sulcus longitudinalis anterior, and another, extremely delicate, into the sulcus longitudinalis posterior. It forms a sheath for each of the filaments of the nerves, and for the nerves themselves ; and, inferiorly, at the conical termination of the cord, it is pro- longed downwards, and forms a slender ligament, which de- scends through the centre of the cauda equina, and is attached to the dura mater lining the canal of the sacrum. The Membrana dentata (fig. 77. 6.) is a process of the pia mater sent off from either side of the cord throughout its entire length, and separating the anterior from the posterior roots of the spinal nerves. Between each of the nerves it forms a serration, which is attached to the dura mater, and unites the tAvo layers of the arachnoid membrane at that point. The processes are about twenty in number at each side. Their use is to maintain the position of the spinal cord in the midst of the fluid by which it is surrounded. The Spinal cord extends from the pons Varolii to opposite the second lumbar vertebra, where it terminates in a rounded point; it is not of the same thickness throughout, but pre- sents three enlargements. The uppermost of these is the medulla oblongata, the next corresponds Avith the origin of the nerves destined to the upper extremities; and the lower enlargement is situated near to its termination, and corres- ponds with the attachment of the nerves which are intended for the supply of the lower limb. In form, the spinal cord is a flattened cylinder, and pre- sents on its anterior surface a groove (fig. 77, 8.,) which ex- tends into the cord to the depth of one-third of its diameter. This is the sulcus longitudinalis anterior. If the sides of the groove be gently separated, they will be seen to be connected at the bottom by a layer of medullary substance, 9. 284 THE DISSECTOR. On the posterior surface another fissure (fig. 77.11.) exists, which is so narrow as to be hardly perceptible without careful examination. This is the sulcus longitudinalis posterior. It extends much more deeply into the cord than the anterior sulcus, and terminates in the gray substance of the interior. These two fissures divide the medulla spinalis into two lateral cords, which are connected to each other only by the white layer, 9., which forms the bottom of the anterior longitudinal sulcus. On either side of the sulcus longitudinalis posterior is a slight line, which bounds on either side the posterior median columns (fig. 77.15.) These are most apparent at the upper part of the cord, near to the fourth ventricle, where they are separated by the point of the calamus scriptorias. Two other lines are observed on the medulla, the anterior and posterior lateral sulci, corresponding with the attachment of the anterior and posterior roots of the spinal nerves. The Anterior lateral sulcus is a mere line, marked only by the attachment of the filaments of the anterior roots. The Posterior lateral sulcus is more evident; and is formed by a narrow grayish fasciculus derived from the gray sub- stance of the interior. These sulci divide the medulla into four fasciculi or cords, viz.— Anterior columns, Posterior columns, Lateral columns, Median columns. The Anterior (fig. 77. 12.12.) are the motor columns, and give origin to the motor roots of the spinal nerves. They are continued upwards into the medulla oblongata, under the name of corpora pyramidalia. The Lateral columns (fig. 77. 13. 13.) are divided in their function betAveen motion and sensation; and contain the fasciculus described by Sir Charles Bell as the respiratory tract. Some anatomists consider the anterior and lateral column on each side as a single column, under the name of anterolateral. ^ The Posterior (fig. 77. 14. 14.) are the columns of sensa- tion, and give origin to the sensitive roots of the spinal nerves. Their superior terminations are named corpora restiforma. The Median posterior columns (fig. 77. 15. 15.) have no function at present assigned to them. If a transverse section (fig. 77.) of the spinal cord be mader THE DISSECTOR. 285 its internal structure may be seen and examined. It would then appear to be composed of two hollow cylinders of white matter, placed side by side, and connected by a narrow white commissure, 9. Each cylinder is filled with gray substance, which is connected by a commissure of the same matter. The form of the gray substance, as observed in the section, is that of two half moons placed back to back, and joined by a trans- verse band, 10. The horns of the moons correspond to the sulci of origin of the anterior and posterior roots of the nerves. The anterior horns do not quite reach this surface, but the posterior appear upon the surface, and form a narrow gray line. Spinal nerves.—There are thirty-one pairs of spinal nerves, each arising by two roots, an interior or motor root, and a posterior or sensitive root. The Anterior roots (fig. 77.16.) arise from a narrow white line, and approach nearer to the middle line as they descend. The Posterior roots (fig. 77. 17.,) more regular than the anterior, arise from a narrow gray band formed by the inter- nal gray substance of the cord. These roots are larger, and the filaments of origin more numerous, than these of the an- terior roots. A ganglion, 18., is formed upon each of the posterior roots in the intervertebral foramina. The first cervical nerve forms an exception to these characters ; its anterior root is larger than the posterior, and there is frequently no ganglion on its posterior root. After the formation of the ganglion, the two roots unite, and constitute a spinal nerve (fig. 77. 19.,) which escapes through the intervertebral foramen, and divides into an an- terior branch, for the supply of the front half of the body, and a posterior branch, for the posterior half. The Spinal nerves are divided into Cervical - 8 pairs Dorsal - - - 12 Lumbar 5 Sacral - 6 31 The Cervical nerves pass off transversely from the spinal cord; the dorsal are oblique in their direction ; and the lum- bar vertical; and form the large assemblage of nerves at the termination of the cord called cauda equina. 286 THE DISSECTOR. The Arteries of the spinal cord are, the anterior, posterior, and lateral spinal, Avhich are derived from the vertebral; and branches from the intercostal and lumbar arteries, which enter the canal through the intervertebral foramina. The Veins of the vertebral column are divided into three sets:— Dorsi-spinal, Meningo-rachidian, Medulli-spinal. The Dorsi-spinal form a plexus around the spinous, trans- verse and articular processes and arches of the vertebrae. They receive the returning blood from the dorsal muscles and surrounding parts, and convey it into the meningo-rachidian veins. The Meningo-rachidian veins are situated between the theca vertebralis and the vertebrae. They communicate freely with each other by means of a complicated plexus. In front they form two longitudinal trunks which extend the whole length of the column on each side of the posterior common ligament, and are joined on the body of each vertebra by transverse trunks, which pass beneath the ligament, and re- ceive the large vertebral veins from the interior of each ver- tebra. They pour their blood into the vertebral veins in the neck, into the intercostal and azygos veins in the thorax, and into the lumbar and sacral veins in the loins and pelvis, by means of communicating trunks, which escape at the inter- vertebral foramina. The Medulli-spinal veins are situated between the pia mater and arachnoid; they communicate freely with each other, and form plexuses, and send branches through the in- tervertebral foramina with each of the spinal nerves, to join the veins of the trunk. THE DISSECTOR. 287 CHAPTER VIII. THORAX. The Thorax is the conical cavity situated at the upper part of the trunk which contains the chief organs of respiration and circulation. Dissection.—Its dissection consists of dividing the ribs on each side from the second to the fifth, and removing the an- terior wall of the chest by separating its muscular connexions, and sawing across the sternum. The Boundaries of the chest are the ribs, intercostal mus- cles, vertebral column, and sternum, which form its circum- ference. The first rib, and thoracic fascia above, and the diaphragm below. It is much deeper on the posterior than on the anterior wall, in consequence of the obliquity of the diaphragm. The Muscles of the chest are the intercostals and triangu- laris sterni. The intercostals consist of muscular and tendinous fibres, which are directed obliquely between the ribs. They are dis- posed in two planes, the external and internal, and cross each other in the direction of their fibres. The External intercostals, eleven on each side, commence posteriorly at the vertebral column, and advance forwards to within a few inches of the sternum, becoming gradually thin and aponeurotic. Their fibres are directed obliquely down- wards and inwards, pursuing the same line with those of the external oblique muscle of the abdomen. The Internal intercostals, eleven on each side, commence anteriorly at the sternum, and extend backwards to within a short distance of the vertebral column. Their fibres are di- rected obliquely doAvnwards and backwards, and correspond in direction with those of the internal oblique muscle of the abdomen. The intercostal vessels and nerves pursue their course be- tween the two planes of muscles. The Triangularis sterni, situated upon the inner Avail of the chest, arises by a thin aponeurosis from the side of the 288 THE dissector. sternum and sternal extremities of the costal cartilages, and is inserted by fleshy digitations into the cartilages of the third, fourth, fifth, and sixth ribs, and often into that of the second. Actions.—The intercostal muscles raise the ribs when they act from above, and depress them when they take their fixed point from below. They are, therefore, both inspiratory and expiratory muscles. The triangularis sterni draws down the costal cartilages. The Thoracic fascia is a dense layer of cellulo-fibrous mem- brane stretched horizontally across the superior opening of the thorax. It is firmly attached to the concave margin of the first rib, and to the inner surface of the sternum. In front it leaves ah opening for the connexion of the cervical with the thoracic portion of the thymus gland; and behind it forms an arch across the vertebral column, to give passage to the oeso- phagus. At the point where the great vessels and trachea pass through the thoracic fascia it divides into an ascending and descending layer. The ascending layer is attached to the trachea, and becomes continuous with the sheath of the caro- tid vessels and with the deep cervical fascia; and the descend- ing layer descends upon the trachea to its bifurcation, sur- rounds the large vessels arising from the arch of the aorta and the upper part of the arch itself, and is continuous with the fibrous layer of the pericardium. It is connected also Avith the venae innominatae and superior cava, and is attached to the cellular capsule of the thymus gland. "The thoracic fascia," writes Sir Astley Cooper, "performs three important offices:— 1st. It forms the upper boundary of the chest, as the dia- phragm does the lower. 2d. It steadily preserves the relative situation of the parts which enter and quit the thoracic opening. 3d. It attaches and supports the heart in its situation through the medium of its connexion with the aorta and large vessels which are placed at its curvature." Vessels and Nerves. The Arteries of the parietes of the chest are the aortic intercostals; superior intercostals, from the subclavian; anterior intercostals, from the internal mam- mary ; and the thoracic branches from the axillary. The Nerves are the intercostal and thoracic branches. THE DISSECTOR. 289 Viscera of the Thorax. The contents of the chest are the lungs and heart, Avith their investing membranes, and the great vessels. The Lungs occupy the sides of the chest. In the healthy state they are of a pinkish gray colour mottled Avith black. The Right lung (fig. 78. 1.) is larger than the left, in con- sequence of the inclination of the heart to the left side : it is also shorter, from the encroachment of the liver upon the right side, which presses the diaphragm upwards considerably above the level of the left. The right lung has three lobes, of which the middle is the smallest, and is placed anteriorly. The left lung has only two. Each lung is retained in its place by its root (fig. 78. 3. 3.) which is formed by the pulmonary artery and veins and bron- chial tubes, together with the bronchial vessels and pulmonary plexuses of nerves. The large vessels of the root of the lung are arranged in the same order from before, backwards on both sides, viz.— Pulmonary veins, Pulmonary artery, Bronchus. From above, doAvmvards, on the right side, this order is exactly reversed. On the left side the bronchus has to stoop beneath the arch of the aorta, which alters its position to the vessels. They are thus disposed on the two sides:— Right. Left. Bronchus, Artery, Artery, Bronchus, Veins. Veins. Structure.—The lungs are composed of the ramifications of the bronchial tubes, which terminate in bronchial cells (air cells,) of the ramifications of the pulmonary artery and veins, bronchial artery and veins, lymphatics and nerves. The whole of these structures being held together by cellular tis- sue, Avhich forms their parenchyma. Bronchial tubes.—The fibro-cartilaginous rings which are observed in the trachea become incomplete and irregular in the bronchi, and in the bronchial tubes are lost altogether. At the termination of these tubes the fibrous coat ceases, and 25 290 THE DISSECTOR. the cell is formed solely by the lining mucous membrane. The ramification of the bronchial tubes is effected by a binary sub- division. Vessels and Nerves.—The nutrition of the lungs is per- formed by the bronchial arteries. The lymphatics terminate at their roots in the bronchial glands. These glands are very numerous at the bifurcation of the trachea, and around the bronchi. In early life they resemble lymphatic glands in other situations; but in the adult, and in old age, they are quite black, and filled with carbonaceous matter, and often with calcareous deposites. The Nerves are derived from the pneumogastric and sym- pathetic. They form two plexuses ; 1. anterior pulmonary plexus, situated upon the front of the root of the lungs; 2. posterior pulmonary plexus, on the posterior aspect of the root of the lungs. The branches from these plexuses follow the course of the bronchial tubes, and are distributed to the bronchial cells. Pleura.—Each lung is enclosed in a serous membrane (fig. 78. 5. 4. 4.,) which invests it as far as the root, and is then reflected upon the parietes of the chest. That portion of the membrane which is in relation with the lung is called pleura pulmonalis, 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 the thoracic surface of the vessels at the root of the neck. The pleura must be dissected from off the root of the lung to see the vessels of Avhich it is formed and the pulmonary plexuses. 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 are not, however, in con- tact Avith each other at the middle line in the formation of the mediastinum, but leave a space between them which con- tains all the viscera of the chest excepting the lungs. The mediastinum is divided into the anterior, middle, and posterior. The Anterior mediastinum (fig. 78. 6.) is a triangular space bounded in front by the sternum, and on either side by the pleura. It contains a quantity of loose cellular tissue, in THE DISSECTOR. 291 which are found some lymphatic glands and vessels passing upwards from the liver; the remains of the thymus gland, the origins of the sterno-hyoid and sterno-thyroid muscles, and the internal mammary vetsels. The Middle mediastinum (fig. 78. 7.) contains the heart enclosed in its pericardium, 8. 8.; the ascending aorta; the bifurcation of the trachea; the superior vena cava ; and the phrenic nerves, 9. 9. Fig 78. A diagram representing a transverse section of the chest, and the relative position of the viscera. 1. The right lung. 2. The left lung. 3. The root of the lungs, with the order of vessels from before backwards, shown, v. The pulmonary vein. a. The pulmonary artery, b. The bronchus. 4.4. The point of reflection of the pleura, from the root of the lung upon the parietes. 5. The cavity of the pleura: that which is in contact with the lung is the pleura pulmo- nalis, and that with the wall of the chest, pleura costalis. 6. The anterior mediastinum, bounded by the sternum in front, and by the pleura at each side. 7. The heart, in the middle mediastinum. 8. The cavity of the peri- cardium. 9. 9. The phrenic nerves lying between the pleura and pericar- dium, in front of the root of the lungs. 10. The descending aorta. 11. The vena azygos. 12. The thoracic duct. 13. The oesophagus, accompa- nied by the two pneumogastric nerves. These parts, from No. 10. to 13., are all within the posterior mediastinum, which is bounded on each side by the pleura, and behind by the vertebral column. 14. 14. The sympathetic nerve at each side. The Posterior mediastinum is bounded behind by the ver- tebral column, in front by the pericardium, and on each side by the pleura. It contains the descending aorta (fig. 78. 10.;) the greater, 11., and lesser azygos veins, and superior 292 THE DISSECTOR. intercostal vein ; the thoracic duct, 12.; the oesophagus and pneumogastric nerves, 13.; and the great splanchnic nerves. Previously to opening the pericardium, if the sides of the middle mediastinum be examined, the phrenic nerves, 9. 9., will be seen shining through the pleura in front of the roots of the lungs. The left phrenic nerve is a little longer than the right, in consequence of having to curve around the con- vexity of the heart, and from the greater depth of the diaphragm on the left, than on the right side. The phrenic nerves arise from the third, fourth, and fifth cervical nerves, and are distributed to the diaphragm, Avhere they commu- nicate, particularly the left, with filaments from the solar plexus. Pericardium, (fig. 78. 8.) The pericardium is a fibro- serous membrane, like the dura mater, and resembles that membrane, also, in deriving its serous layer from the reflected serous membrane of the viscus which it encloses. It consists, therefore, of two layers, an external fibrous and an internal serous. The fibrous layer is attached, above, to the great vessels at the root of the heart, being continuous with the thoracic fascia, and beloAV to the tendinous portion of the diaphragm. The serous membrane invests the heart, and is then reflected upon the inner surface of the fibrous layer. If the pericardium be laid open, the heart is brought into view. The Heart (fig. 78. 7., fig. 79.) is situated obliquely in the chest, the base being directed upwards and backwards towards the right shoulder; the apex forwards, and to the left, points to the space betAveen the fifth and sixth ribs, at about two or three inches from the sternum. Its under side is flattened, and rests upon the tendinous portion of the diaphragm; its upper side is rounded and convex, and formed principally by the right ventricle, and partly by the left. Surmounting the ventricles are the corresponding auricles, whose auricular ap- pendages are directed fonvards, and slightly overlap the root of the pulmonary artery. The pulmonary artery is the large anterior vessel at the root of the heart: it crosses obliquely the commencement of the aorta. The heart consists of two auricles and tAvo ventricles, which are respectively named, from their position, right and left. The right is the venous side of the heart; it receives into its auricle the venous blood from every part of the body, by the superior and inferior THE DISSECTOR. 293 cavae and coronary vein. From the auricle the blood passes into the ventricle, and from the ventricle through the pulmo- nary artery, to the capillaries of the lungs. From these it is returned as arterial blood to the left auricle; from the left auricle it passes into the left ventricle; and from the left ventricle is carried through the aorta, to be distributed to every part of the body, and again returned to the heart by the veins. This constitutes the course of the adult circula- tion. The heart is best studied in situ. If, however, it be re- moved from the body, it should be placed in the position indi- cated in the above description of its situation. A transverse incision should then be made along the ventricular margin of the right auricle, from the appendix to its right border, and crossed by a perpendicular incision, carried from the superior to the inferior cava. The coagulated blood should be with- drawn. Sometimes some fine specimens of white fibrine are found with the coagulum, at other times it is yellow and ge- latinous. This appearance deceived the older anatomists, who called these substances "polypus of the heart;" they are also frequently found in the right ventricle, and sometimes in the left cavities. The Right auricle (fig. 79.1.) is larger than the left, and is diArided into a principal cavity, and an appendix auriculae, 8. The interior of this auricle presents for examination five openings; two valves; two relicts of foetal structure; and two peculiarities in the proper structure of the auricle. They may be thus arranged. ' Superior cava, Inferior cava, Openings ----■/ Coronary vein, Foramina Thebesii, ^Auriculo-ventricular opening. Tr , j Eustachian valve, [ alves.....1 Coronary valve. t» 7 - , j} j> j. 7 j. ) Annulus ovalis, Relicts of foetal structure j Fogga ovalis# r, , j. ,, . 7 f Tuberculum Loweri, Structure of the auricle^ Mugculi pectinati> The Superior cava (fig. 79. 2.) returns the blood from the upper half of the body, and opens into the upper and front part of the auricle. 25* 294 THE DISSECTOR. Fig. 79. The cavities of the heart. 1. The right auricle. 2. The entrance of the superior cava. 3. The entrance of the inferior cava. 4. The opening of the coronary vein, half closed by its valve. 5. The Eustachian valve. 6. The fossa ovalis, sur- rounded by the annulus ovalis. 7. The tuberculum Loweri. 8. The mus- culi pectinati. 9. The auriculo-ventricular opening. 10. The right ventricle. 11. The tricuspid valve, attached by the chordse tendinae to the carnse co- lumna?, 12. 13. The pulmonary artery, guarded at its commencement by three semilunar valves. 14. The right pulmonary artery, passing beneath the arch and behind the ascending aorta. 15. The left pulmonary artery, crossing in front of the descending aorta. * The remains of the ductus arteriosus, acting as a ligament between the pulmonary artery and arch of the aorta. The arrows mark the course of the venous blood through the right side of the heart. Entering the auricle by the superior and inferior cavae, it passes through the auriculo-ventricular opening into the ventricle, and thence through the pulmonary artery to the lungs. 16. The left auricle. 17. The openings of the four pulmonary veins. 18. The auriculo-ventricu- lar opening. 19. The left ventricle. 20. The mitral valve, attached by its chorda? tendinoe to two large columnte carnese, which project from the walls of the ventricle. 21. The commencement and course of the ascending aorta behind the pulmonary artery, marked by an arrow. The entrance of the vessel is guarded by three semilunar valves. 22. The arch of the aorta. The comparative thickness of the two ventricles is shown in the diagram. The course of the pure blood through the left side of the heart is marked by arrows. The blood is brought from the lungs by the four pulmonary veins into the left auricle, and passes through the auriculo-ventricular opening into the left ventricle, from whence it is conveyed by the aorta to every part of the body. The Inferior cava, 3., returns the blood from the lower half of the body, and opens into the lower and posterior wall, close to the partition between the auricles (septum auricula- THE DISSECTOR. 295 rum.) The direction of these two vessels is such that a stream forced through the superior cava would be directed towards the auriculo-ventricular opening. In like manner, a stream rushing upwards by the inferior cava would force its current against the septum auricularum ; this is the proper direction of the two currents during foetal life. The Coronary vein (fig. 79. 4.) returns the venous blood from the substance of the heart; it opens into the auricle be- tween the inferior cava and the auriculo-ventricular opening, under cover of the coronary valve. The Foramina Thebesii* are minute pore-like openings, by which the venous blood exhales directly from the muscular structure of the heart into the auricle, without entering the venous current. These openings are also found in the left auricle, and in the right and left ventricles. The Auriculo-ventricular opening (fig. 79. 9.) is the large opening of communication between the auricle and ventricle. Valves.—The Eustachian valve (fig. 79. 5.) is a part of the apparatus of foetal circulation, and serves to direct the placental blood from the inferior cava, through the foramen ovale into the left auricle. In the adult it is a mere vestige and imperfect, though sometimes it remains of large size. It is formed by a fold of the lining membrane of the auricle, and is situated between the opening of the inferior cava and the auriculo-ventricular opening. It is generally connected with the Coronary valve, 4., which is a semilunar fold of the lining membrane, stretching across the mouth of the coronary vein, and preventing the reflux of the blood in the vein during the contraction of the auricle. The Annulus ovalis is situated on the septum auricularum, opposite the termination of the inferior cava. It is the rounded margin of the septum, 6., which occupies the place of the foramen ovale in the foetus. The Fossa ovalis (fig. 79. 6.) is an oval depression corres- ponding with the foramen ovale in the foetus. This opening is closed at birth by a thin valvular layer, which is continu- ous with the left margin of the annulus. The depression or fossa in the right auricle results from this arrangement. There is no fossa ovalis in the left auricle. * Adam Christian Thebesius. His discovery of the openings now known by his name is contained in his "Dissertatio Medica de Circulo Sanguinis in Corde," 1708. 296 THE DISSECTOR. The Tuberculum Loweri (fig. 79. 7.) is the portion of auricle intervening betAveen the openings of the superior and inferior cavae. Being thicker than the walls of the veins, it forms a projection, Avhich was supposed, by Lower, to direct the blood from the superior cava into the auriculo-ventricular opening. The Musculi pectinati, 8. are small muscular columns situ- ated in the appendix auriculae. They are very numerous, and are arranged parallel with each other; hence their cognomen, "pectinati," like the teeth of a comb. The Right Ventricle, 10., is triangular and three-sided in its form. Its anterior side is convex, and forms the larger proportion of the front of the heart. The inferior side is flat, and rests upon the diaphragm; and the inner side corresponds with the partition between the two ventricles, septum ventri- culorum. The right ventricle is to be laid open by making an incision parallel Avith, and a little to the right of, the middle line, from the pulmonary artery in front, to the apex of the heart, and thence by the side of the middle line behind, to the auriculo- ventricular opening. It contains, to be examined, two openings, the auriculo- ventricular and that of the pulmonary artery; two appa- ratuses of valves, the tricuspid and semilunar; and a muscular and tendinous apparatus belonging to the tricuspid valves. They may be thus arranged:— Auriculo-ventricular opening, Opening of the pulmonary artery, Tricuspid valves, Semilunar valves, Chordae tendineae, Columnae carneae. The Auriculo-ventricular (fig. 79. 9.) is surrounded by a fibrous ring, covered by the lining membrane of the heart. It is the opening of communication betAveen the right auricle and ventricle. The Opening of the pulmonary artery, 13., is situated close to the septum ventriculorum, on the left side of the right ven- tricle, and upon the anterior aspect of the heart. The Tricuspid valves (fig. 79. 11.) are three triangular folds of the lining membrane, strengthened by a thin layer of THE DISSECTOR. 297 tendinous fibres. They are connected around the auriculo- ventricular opening by their base. Their sides and apex are thickened, and give attachment to a number of slender ten- dinous cords ; called chordae tendineae. The chordae tendineae are the tendons of the thick muscular columns (columnse cameee,) 12., which stand out from the walls of the ventricle, and serve as muscles to the valves. A number of these ten- dinous cords converge to a single muscular attachment. The tricuspid valves prevent the regurgitation of the blood into the auricle during the contraction of the ventricle, and they are prevented from being themselves driven back by the chordae tendineae and their muscular attachments. This connexion of the muscular columns of the heart to the valves, has caused their division into active and passive. The Active valves are the tricuspid and mitral; the Passive the mere folds of lining membrane, viz. the semilunar, Eusta- chian, and coronary. The Columnae carneae (fleshy columns) is a name expressive of the appearance of the internal walls of the ventricles, which seem formed of muscular columns interlacing in almost every direction. They are divided into three sets, according to the manner of their connexion. 1. The greater number are attached by the whole of one side, and merely form con- vexities into the cavity of the ventricle. 2. Others are con- nected by both extremities, being free in the middle. 3. And a few are attached by one extremity only to the Avails of the heart, the other giving insertion to the chordae tendineae. The Semilunar valves (fig. 79. 13.) are three folds of the lining membrane, situated around the commencement of the pulmonary artery. They are attached by their convexities, and free by the concavities, which are directed upwards in the course of the vessels, so that, during the current of the blood along the artery, they are pressed against the sides of the cylinder, but if any attempt at regurgitation ensue, they are immediately expanded, and effectually close the entrance of the tube. In the centre of the free margin of each of the valves, is a small fibro-cartilaginous tubercle, called corpus Arantii, Avhich locks in with the tAvo others during the closure of the valves, and secures the triangular space that would otherwise be left by the approximation of three semilunar folds. Between the semilunar valves and the cylinder of the 298 THE DISSECTOR. artery are three pouches, called the pulmonary sinuses. Similar sinuses are situated beneath the valves at the com- mencement of the aorta, and are much larger and more ca- pacious than those of the pulmonary artery. The Pulmonary artery commences by a scolloped border, corresponding Avith the three valves, which are attached along its edge. It is connected to the ventricle by fibrous tissue, and by the lining membrane of the heart. The Left Auricle (fig. 79. 16.) is somewhat smaller than the right; of a cuboid form, and situated more posteriorly. The appendix auriculae is constricted at its junction with the auricle, and has an arborescent appearance. It is directed forwards towards the root of the pulmonary artery, to which the auriculae of both sides appear to converge. The left auricle is to be laid open by a i shaped incision, the horizontal section being made along the border which is attached to the base of the ventricle. It presents for examination five openings, and the muscular structure of the appendix are these: Four pulmonary veins, Auriculo-ventricular opening, Musculi pectinati. The Pulmonary veins (fig. 79. 17.,) two from the right lung, and two from the left, open into the corresponding sides of the auricle. The two left pulmonary veins terminate fre- quently by a common opening. The Auriculo-ventricular opening, 18., is the aperture of communication between the ventricle and auricle. The Musculi pectinati are feAver in number than in the right auricle, and are situated only in the appendix auriculae. Left Ventricle.—The left ventricle is to be opened, by making an incision a little to the left of the septum ventricu- lorum, and continuing it around the apex of the heart, to the auriculo-ventricular opening behind. The left ventricle (fig. 79. 19.) is conical, both in external figure, and in the form of its internal cavity. It forms the apex of the heart, by projecting beyond the right ventricle, while the latter has the advantage in length toAvards the base. Its walls are about seven lines in thickness, those of the right ventricle being about 2^ lines. It presents for examination, in its interior tAvo opening?, THE DISSECTOR. 299 two valves, and the tendinous cords and muscular columns; they may be thus arranged. Auriculo-ventricular opening, Aortic opening, Mitral valves, Semilunar valves, Chordae tendineae, Columnae carneae. The Auriculo-ventricular opening, 18., is a dense fibrous ring, covered by the lining membrane of the heart, but smaller in size than that of the right side. The Mitral valves, 20., are attached around the auriculo- ventricular opening, as are the tricuspid in the right ventricle. They are thicker than the tricuspid, and consist of only two segments, of which the larger is placed between the auriculo- ventricular opening and the commencement of the aorta, and acts the part of a valve to that foramen, during the filling of the ventricle. The difference of size of the two valves, both being triangular, and the space between them, has given rise to the idea of a "bishop's mitre," after which they are named. These valves, like the tricuspid, are furnished with an appa- ratus of tendinous cords, chordae tendineae, which are attached to tAvo very large columnae carneae. The Columnae carneae admit of the same arrangement into three kinds, as on the right side. Those Avhich are free by one extremity are only two in number, and much larger than those on the opposite side. The Semilunar valves, 21., are placed around the com- mencement of the aorta, like those of the pulmonary artery, and, like them, are attached to the scolloped border, by which the aorta is connected with the ventricle. The tubercle in the centre of each fold is larger than those in the pulmonary valves, and it Avas these that Arantius particularly described; but the term " corpora Arantii," is noAV applied indiscrimi- nately to both. The fossae between the semilunar valves and the cylinder of the artery are much larger than those of the pulmonary artery; they are called the "sinus aortici." Structure of the heart.—The muscular fibres of the heart are divided into proper and common. The proper fibres of the auricles form a thin muscular layer over its surface, 300 THE DISSECTOR. their extremities being attached to the fibrous rings of the auriculo-ventricular openings. The common fibres are wound transversely around both auricles, and serve to bind them together. The proper fibres of the ventricles are oblique, in their direction, and are wound spirally round and round, so as to form two irregular conical cylinders, open at both extremities. The common fibres take their origin from the fibrous rings of the auriculo-ventricular openings, and descend obliquely from the right towards the left, in front, and from the left to4 the right behind, to the apex of the heart. Here they are reflected inwards, through the opening in the inferior ex- tremity of the cylinder of the proper fibres, and form the inner muscular stratum of the ventricles. They terminate by being inserted, as they arose, into the fibrous rings of the auriculo-ventricular openings. Thus it is, that the common fibres hold both the auricles and ventricles together, the common point of insertion being the zones of the auriculo-ventricular openings. They form, therefore, the superficial layer of the heart, passing from one ventricle across to the other, and by a peculiar turn upon themselves at the apex are reflected imvards through the inferior openings of the conical cylinders, so as to form the internal or deep layer of the ventricles, enclosing between their two layers the cylinders of the proper fibres. Vessels.—The Arteries of the heart are the right and left coronary. The Left or anterior coronary passes forwards, between the pulmonary artery and left appendix auriculae, and runs along the line of union of the two ventricles to the apex of the heart, Avhere it inosculates Avith the right coronary. It supplies the left auricle and the adjoining sides of both ventricles. The Right or posterior coronary passes forwards, between the root of the pulmonary artery and the right auricle, and Avinds along the auriculo-ventricular groove, to the posterior median furrow, Avhere it descends upon the posterior aspect of the heart to its apex, and inosculates with the left coronary. It is distributed to the right auricle and to the posterior sur- face of both ventricles. Both coronary arteries arise from the root of the aorta in the sinus aortici, behind the semilunar valves. THE DISSECTOR. 301 The Veins accompany the arteries, and empty themselves by the common coronary vein into the right auricle. The Lymphatics terminate in the glands about the root of the heart. . Nerves.—The Nerves of the heart are derived from the car- diac plexuses, which are formed by communicating filaments from the sympathetic and pneumogastric. Great Vessels of the Heart. The vessels at the root of the heart may be thus arranged:— Superior and inferior cava, Four pulmonary veins, Pulmonary artery, Aorta. As all these vessels bear a certain relation to the aorta, we shall therefore commence by describing that trunk. The Aorta (fig. 69. 21. 22.) arises from the left ventricle, at the middle of the root of the heart. It ascends at first to the right, then curves backwards and to the left, and descends on the left side of the vertebral column to the fourth lumbar vertebra. Hence it is diAdded into the ascending arch, and descending aorta. Relations.—The Ascending aorta has in relation with it, in front, the trunk of the pulmonary artery, thoracic fascia, and pericardium; behind, the right pulmonary veins and ar- tery ; to the right side, the right auricle and superior cava; and to the left, the left auricle and trunk of the pulmonary artery. Arch.—The upper border of the arch is parallel with the second dorsal vertebra, and it terminates opposite the lower border of the third. The anterior surface of the arch is crossed by the left pneu- mogastric nerve, and the cardiac branches of that nerve, and of the sympathetic. _ The posterior surface of the arch is in relation with the bifurcation of the trachea, and great cardiac plexus, the car- diac and left recurrent nerves, and the thoracic duct. The superior border gives off the three great arteries, viz. the innominata, left carotid, and left subclavian. The inferior border or concavity of the arch is in relation with the remains of the ductus arteriosus, the cardiac ganglion and left recurrent nerve, and has passing beneath it the right pulmonary artery and left bronchus. The Descending aorta is situated in the posterior mediasti- 26 302 THE dissector. num, and rests upon the vertebral column. Its relations will be described Avith that space. Fig. 80. The large vessels which proceed from the root of the heart, with their relations; the heart has been removed. 1. The ascending aorta. 2. The arch. 3. The thoracic portion of the descending aorta. 4. The arteria innominata dividing into, 5, the right carotid, which again divides at 6, into the external and internal carotid; and 7, the right subclavian artery. 8. The axillary artery; its extent is desig- nated by a dotted line. 9. The brachial artery. 10. The right pneumogas- tric nerve running by the side of the common carotid, in front of the right subclavian artery, and behind the root of the right lung. 11. The left com- mon carotid, having to its outer side the left pneumogastric nerve, which crosses the arch of the aorta, and as it reaches its lower border is seen to give off the left recurrent nerve. 12. The left subclavian artery becoming axillary, and brachial in its course, like the artery of the opposite side. 13. The trunk of the pulmonary artery connected to the concavity of the arch of the aorta by a fibrous cord, the remains of the ductus arteriosus. 14. The left pulmonary artery. 15. The right pulmonary artery. 16. The trachea. 17. The right bronchus. 18. The left bronchus. 19. 19. The pulmonary veins. 17. 15. and 19; on the right side, and 14, 18, and 19, on the left, constitute the roots of the corresponding lungs, and the rela- tive position of these vessels is carefully preserved. 20. Bronchial arteries. 21. 21. Intercostal arteries, the branches from the front of the aorta above and below the number 3 uie pericardiac and oesophageal branches. THE DISSECTOR. 303 The Pulmonary artery (fig. 79. 13.) arises from the upper part of the left side of the right ventricle, in front of the origin of the aorta. It crosses the root of the aorta some- what obliquely to the under surface of the arch, to which it is connected by a ligamentous cord (fig. 79.*,) the remains of the ductus arteriosus. It then divides into two branches, the right and left pulmonary arteries. The Right pulmonary artery, 14., passes beneath the arch and behind the ascending aorta, to the root of the right lung, where it divides into branches which are distributed to its three lobes. The Left pulmonary artery, 15., rather larger than the right, passes in front of the descending aorta to the root of the left lung. The Superior vena cava (fig. 79. 2. fig. 81. 1.) is a short trunk situated to the right, and rather in front of the ascend- ing aorta. It is formed by the junction of the two venae in- nominatae. The Venae innominatae (fig. 81. 2, 3.,) are formed by the junction of the internal jugular, 4., and subclavian veins, 5., at each side. The right vena innominati is short, and de- scends almost vertically to the superior cava. The left is long, and crosses obliquely the branches arising from the arch of the aorta. The Inferior cava (fig. 79. 3.) passes through a quadrilate- ral opening in the tendinous centre of the diaphragm, and immediately enters the right auricle, so that its extent within the chest is not more than half or three quarters of an inch. Pulmonary veins.—The Right pulmonary veins, anterior to the other vessels in the root of the lung, pass behind the right auricle to open into the right side of the left auricle. The Left pulmonary veins, also anterior to the other ves- sels in the root of the lung, pass in front of the descending aorta to open into the left side of the corresponding auricle. Trachea and Bronchi.—Behind the arch of the aorta, the trachea divides into the two bronchi. The right bronchus passes off at right angles, and enters the upper part of the right lung. It crosses behind the superior cava, and has the vena azygos curving around it to terminate in that vein. The left bronchus is oblique in its direction, having to stoop be- neath the arch of the aorta to reach the root of the lung. It enters the lung, therefore, at the middle, and not at the up- 304 the dissector. per part, as does the right. Hence the difference of relation of the two bronchi in the roots of the lungs. Posterior mediastinum.—If the lungs be removed near to their roots, or thrown to one side, the posterior mediasti- num may be dissected and examined. The contents of the posterior mediastinum, are the Descending aorta, • Thoracic duct, Vena azygos major, Oesophagus, Vena azygos minor, Pneumogastric nerves, Superior intercostal vein, Great splanchnic nerves. The Descending or Thoracic aorta (fig. 78. 10.) is situated to the left side of the vertebral column, but approaches the middle line as it descends, and at the aortic opening of the diaphragm is altogether in front of the column. After enter- ing the abdomen, it again falls back to the left side. Relations.—It is in relation, behind, with the vertebral column and lesser vena azygos ; in front, with the oesophagus and right pneumogastric nerve; to the left side, with the pleura; and to the right, with the thoracic duct, Branches.—Its branches are pericardiac, bronchial, oeso- phageal, and intercostal arteries. The Pericardiac are a few tAvigs to the posterior part of the pericardium. The Bronchial, two superior and two inferior, arise from the upper part of the artery, and pass to the roots of the lungs, to be distributed with the bronchial tubes. They are the nutritious arteries of the lungs. The (Esophageal are several small branches given off from the front part of the aorta to the oesophagus. The Intercostal, or posterior intercostal branches are ten in number on each side, the two superior spaces being sup- plied by the superior intercostal artery, a branch of the sub- clavian. The right intercostals are longer than the left, on account of the position of the aorta. They cross the verte- bral column behind the thoracic duct, vena azygos major, and •sympathetic nerve, to the intercostal spaces, the left passing beneath the lesser vena azygos and sympathetic. In the in- tercostal spaces, or rather upon the external intercostal mus- cles, each artery gives off a dorsal branch for the supply of the muscles of the back. It then comes into relation with its vein and nerve, the former being above, and the latter beloAV, and divides into two branches, which run along the borders of the contiguous ribs between the two planes of intercostal the dissector. 305 muscles, and anastomose with the anterior intercostal arteries, branches of the internal mammary. The branch corresponding with the Fi9- 81. The veins of the lower border of the rib is the larger of the tAvo. They are protected from pressure during the action of the in- tercostal muscles, by little tendinous arches thrown across and attached by each extremity to the bone. The venae azygos and superior in- tercostal vein, form a kind of system of themselves for returning the ve- nous blood from the parietes of the chest and vertebral column, in the vacant interval left by the two cavae, as they advance forwards to be con- nected Avith the heart. They like- wise establish a communication be- tween those two trunks. The Vena azygos major (fig. 81. 8. fig. 78. 11.) arises in the lumbar re- gion by a communication with the lumbar veins ; sometimes it is joined by a branch directly from the infe- rior vena cava, or by one from the renal vein. It passes through the aortic opening in the diaphragm, and ascends upon the right side of the vertebral column to the third dorsal vertebra, where it arches forwards over the right bronchus, and termi- nates in the superior cava. It re- ceives all the intercostal veins of the right side, together with the bronchial and vena azygos minor. 1. The superior vena cava. 2. The right vena innominata. 3. The left vena innominata. 4. The internal jugular vein of the left side. 5. The subclavian vein of the left side. 6. The external jugular vein. 7. The su- perior intercostal vein. 8. The great vena azygos, communicating inferi- orly with one of the lumbar veins. 9. The lesser vena azygos, communi- cating inferiorly with a lumbar and with the left renal vein. 10. The inferior vena cava. 11. 11. The two common iliac veins. 12. The right external iliac. 13. The internal iliac vein. 14. The vena sacra media. 15. 15. The lumbar veins. 16. The.right spermatic vein. 17. The left renal vein, into which is seen opening from below the left spermatic vein. 18. The right renal vein. 19. The hepatic veins. 26* 306 the dissector. The Vena azygos minor (fig. 81. 9.) commences in the lumbar region, on the left side, by a communication Avith the lumbar or renal veins. It passes beneath the border of the diaphragm, and ascending upon the left side of the vertebral column, crosses the fifth or sixth dorsal vertebra to open into the vena azygos major. It receives the six or seven lower intercostal veins of the left side. The azygos veins are said to have no valves. The Superior intercostal vein (fig. 81. 7.) is the trunk formed by the union of the five or six upper intercostal veins of the left side. It communicates below with the vena azygos minor and ascends to terminate in the left vena innominata. The Thoracic duct (fig. 78. 12.) arises in the abdomen from the receptaculum chyli, Avhich is situated on the second lumbar vertebra. It enters the thorax through the aortic opening in the diaphragm, behind and between the aorta and vena azygos. Then ascends perpendicularly between the aorta and vena azygos, passes behind the arch of the aorta, and along the course of the left subclavian artery into the neck, where it makes a sudden turn downwards, and termi- nates at the junction of the left jugular with the left subcla- vian vein. In the thorax it often divides into two or three branches, which afterwards reunite. It is provided with valves like the rest of the lymphatic system. The thoracic duct is the common lymphatic trunk of the whole of the lower half of the body, the left side of the tho- rax, the left upper extremity, and the left side of the head and neck. The lymphatic vessels of the right side of the thorax, right upper extremity, and right side of the head and neck, unite to form the ductus lymphaticus dexter, which opens into the junction of the right jugular and subclavian veins. The (Esophagus (fig. 78; 13.) commences on a level with the lower border of the cricoid cartilage, opposite to the fifth cervical vertebra. It descends upon the vertebral column, a little to the left of the trachea, and passing down behind the arch of the aorta, becomes placed immediately in front of the descending aorta upon which it lies. Near to the lower part of the chest it advances forwards, and passes through a mus- cular opening in the diaphragm to terminate in the stomach. It is accompanied by the pneumogastric nerves. THE DISSECTOR. 307 Pneumogastric nerves.—The Right pneumogastric nerve, after its entrance into the chest, between the right subclavian artery and vein, descends obliquely behind the superior cava and behind the root of the lungs, to the posterior surface of the oesophagus, along which it runs to the stomach. The Left pneumogastric nerve runs parallel with the left subclavian artery at its entrance into the chest, crosses the arch of the aorta, then passes behind the root of the left lung to the anterior surface of the oesophagus, along which it pro- ceeds to the stomach. , Branches.—At their entrance into the chest they both give off cardiac branches (fig. 44. 14.) to the cardiac plexuses. The left (fig. 42. 14.) while crossing the arch of the aorta, gives off the left recurrent nerve which winds around the arch close to the cord of the ductus arteriosus, and ascends by the side of* the trachea to be distributed to the larynx. At the roots of the lungs some branches are distributed upon their anterior aspect, forming the anterior pulmonary plexuses, and a larger number behind, constituting by their communications the posterior pulmonary plexuses. (Fig. 44. p.) The pulmonary plexuses, particularly the anterior, are augmented by branches from the great cardiac plexus. The branches of these plexuses are distributed with the bronchial tubes to the bronchial cells. On the oesophagus the nerves divide into a number of branches, which communicate with each other and constitute the oesophageal plexus. (Fig. 44. 17.) Near to the pylorus they collect into two principal trunks, which form a kind of nervous collar around the lower end of the oesophagus, from which branches are distributed to the stomach. The left pneumogastric supplies chiefly the anterior surface of the stomach. The right supplies the posterior surface, and ter- minates in the solar plexus. The great splanchnic nerves are derived from the dorsal portion of the sympathetic, with which they are described. All these parts contained in the posterior mediastinum are held together by a loose cellular tissue, in which are contained a number of lymphatic glands. The Sympathetic nerve (fig. 78. 14. fig. 115.) in the chest consists of a chain of ganglia, extending along each side of the vertebral column. The ganglia, twelve in number, rest 308 THE DISSECTOR. upon the heads of the ribs, and are covered by the pleura costalis. Each ganglion, considered as a centre, gives off four sets of branches—1. to join the ganglion above: 2. to join the ganglion below: 3. to each of the intercostal nerves: 4. to the viscera of the thorax and abdomen. The latter consist of branches to the cardiac and pulmonary plexuses and pos- terior mediastinum, and of two named branches, the greater and lesser splanchnic nerves. The Greater splanchnic nerve (fig. 115. 12.) is formed by the union of filaments from the sixth, seventh, eighth, ninth, and tenth ganglia. It passes inwards to the posterior medi- astinum, resting upon the side of the vertebral column, and pierces the crus of the diaphragm to join the semilunar gan- glion in the abdomen. The Lesser splanchnic nerve, 14., is formed by the union of filaments from the tenth and eleventh ganglia. It pierces the diaphragm and joins the renal plexus. The Intercostal nerves, tAvelve in number, issue from the intervertebral foramina, and divide into two branches:—1. A posterior branch which passes backwards between the ribs, and is distributed to the muscles of the back ; 2. An anterior branch (intercostal) which follows the course of the intercostal artery betAveen the two intercostal muscles. It gives off nu- merous branches in its course, and near to the sternum pierces the external intercostal muscle, to be distributed to the pec- toralis major and integument. At the great convexity of the chest it gives off a cutaneous branch, which pierces the mus- cles, and is distributed to the integument on the side of the trunk. Cardiac ganglion and plexuses.—Beneath the arch of the aorta to the right of the ligament of the ductus arteriosus is a large sympathetic ganglion, the cardiac ganglion. It re- ceives the superior cardiac nerve (superficialis cordis) from each side, and branches from the pneumogastric and recur- rent nerves, and gives off a number of filaments, which form a plexus by their communications — the anterior cardiac plexus. The branches of this plexus pass dowmvards on the right side of the pulmonary artery to the left coronary artery, where they receive the name of anterior coronary plexus, and are distributed to the anterior aspect of the heart. THE DISSECTOR. 309 The inferior and middle cardiac nerves converge to the great cardiac plexus, which is situated upon the bifurcation of the trachea, behind the arch of the aorta, and above the right pulmonary artery. From this plexus proceed two sets of branches—1. Anterior, which pass forwards between the aorta and pulmonary artery, and are distributed principally to the right auricle, communicating with the anterior coro- nary plexus; 2. Posterior, more numerous, which follow the Course of the right coronary artery, and form the posterior coronary plexus. The branches of this plexus are distributed to the left auricle and posterior surface of the ventricle. Besides those to the heart, numerous branches are sent from the cardiac plexuses to the pulmonary plexuses, particu- larly to the anterior. When these nerves have been examined, the student should apply himself to observe the relations of the large vessels and tubes at the upper part of the thorax. He will find the left vena innominata the most superficial, lying obliquely across the three branches of the arch of the aorta, as it de- scends to form the superior cava with the vena innominata of the right side. It receives the superior intercostal and infe- rior thyroid veins. CHAPTER IX. THE UPPER EXTREMITY. The upper extremity is the member developed from the upper part of the thoracic arch, as the lower extremity is the member developed from the pelvic arch. It consists of an apparatus of bones, joints, muscles, vessels, and nerves, and is covered by the common investments of the entire body, viz. the deep and superficial fascia, and the integument. The bones of the upper extremity are the clavicle, scapula, humerus, radius and ulna, carpal, metacarpal, and phalanges. The clavicle is the medium of connexion between the upper extremity and the rest of the skeleton; it is the fulcrum of action of the entire limb, and is prominently characteristic of animals possessing great power in their arms, as man, the bat, the mole, birds, &c. The scapula is a flat bone, and 310 THE DISSECTOR. affords by its construction peculiar advantages ; giving origin by its extensive surface, to a number of muscles, and being itself moveable on the convexity of the thorax. This is the bone which secures the connexion of the arm to the trunk, and provides for all that diversity of movement so character- istic of the upper extremity, and which entitles it to the designation of a "universal joint." The next bones, the hu- merus, radius, and ulna, have for their ofiice the extension of the limb, for the purpose of supplying to the beautiful apparatus of the hand all the advantages which are to be obtained by a voluntary approximation or extension from the body. They are, therefore, denominated long bones, and like all bones of this class are divisible into a shaft, an upper and a lower extremity. The shaft is more or less cylindrical and smooth, whilst the extremities are projected into processes which serve as levers for the attachment and action of mus- cles. The carpus is an assemblage of small bones belonging to the class of short bones. They are all slightly moveable upon each other, and bestow pliancy and strength by means of the mutual yielding which exists between them. The metacarpal bones and phalanges are long bones, of a length proportionate to the arm and to the moving powers which are intended for their action; they give breadth and extent to the hand, and facility in all the movements which that impor- tant organ is destined to perform. The Muscles are naturally divided into groups, which con- cur mutually in certain actions that are obviously necessary to the effective movements of the limb. The distribution of these groups, with their corresponding duties, will be best seen in a tabular analysis, thus:— Anterior Thoracic Group. Posterior TJwracic Group. Pectoralis major. Trapezius. Pectoralis minor. Levator anguli scapulae. Subclavius. Rhomboideus major. Serratus magnus. Rhomboideus minor. Humeral Group. Subscapulars. Latissimus dorsi. Supra-spinatus. Pectoralis major. Infra-spinatus. Deltoid. Teres minor. Coraco-brachialis. Teres major. THE DISSECTOR. 311 Anterior Brachial Group. Posterior Brachial Group. Biceps. Triceps. Brachialis anticus. Anconeus. Fore-arm. Anterior Group Posterior Group. Pronator radii teres. Supinator radii longus. Pronator radii quadratus. Supinator radii brevis. Flexor carpi radialis. Extensor carpi radialis longior. Flexor carpi ulnaris. Extensor carpi radialis brevior. Flexor digitorum sublimis. Extensor carpi ulnaris. Flexor digitorum profundus. Extensor communis digitorum. Flexor pollicis longus. Extensor minimi digiti. Palmaris longus. Extensor ossis metacarpi pollicis. Extensor primi internodii pollicis. Extensor secundi internodii pollicis Extensor indicis. Hand. Radial Group. Ulnar Group. Flexor ossis metacarpi. Palmaris brevis. Flexor breA'is pollicis. Flexor ossis metacarpi. Abductor pollicis. Flexor brevis minimi digiti. Adductor pollicis. Abductor minimi digiti. Palmar Group. Lumbricales. Interossei palmares. Interossei dorsales. The Anterior and posterior thoracic groups preserve the fixity and steadiness of the shoulder, and render it capable of supporting heavy weights and becoming the point of resist- ance to the actions of the humeral muscles. They also move the scapula freely on the chest, and afford all the advantages of the strongest articulation by bone. The humeral group carries the arm throughout all that circle of motion which is so necessary to a universal joint, and so valuable in applica- tion to its extensive uses. The muscles of the anterior brachial group are the flexors of the elbow, the perfect flex- ion of the joint being procured by an advantageous attach- 312 THE DISSECTOR. ment to both the radius and ulna. The posterior brachial group is the antagonist to the former, and extends the fore- arm. Now, it is fair to anticipate, that as the bones increase in number, and the limb is carried farther from the centre, the movements will increase in proportionate ratio. The move- ments of the shoulder were those of totality : motions of the scapulo humeral joint were of the most simple kind, such as would result from the application of a round ball against a shallow socket; those of the elbow were in one direction only, flexion and extension; but the wrist requires an apparatus for the action of the powerful twist which is so remarkable in that joint. And this is provided for by two pairs of the muscles of the fore-arm, the pronators and supinators, the former throwing the wrist and hand inwards, the latter out- wards. Now this action could not be effectively produced without the exertion of muscular force upon the axis of sup- port to the wrist; and we therefore find that the radius alone articulates with the wrist, and administers to all its move- ments, while the ulna is reserved as the especial agent in the motions of the elbow. Besides pronation and supination, the wrist possesses powerful flexion and extension, and to this office are assigned the next muscles, flexores and extensores carpi. The fingers are simply supplied for all their nume- rous movements of flexion and extension, by three flexors situated in the fore-arm, and six extensors; one flexor and three extensors being intended for the especial use of the thumb. The remaining muscle, the palmaris longus, is an extensor of the palmar fascia, which provides by its strength and elasticity for a powerful resistance to shocks received upon the surface of the hand. The muscles of the hand are, flex- ors, abductors, and adductors. The short flexors of the thumb and little finger are necessary to the strength of grip so cha- racteristic of the human hand. All the remaining muscles are abductors and adductors (see fig. 94.,) with the exception of the palmaris brevis, which contracts the integument on the side of the hand, and the lumbricales, which are acces- sory in their actions to the deep flexor. The abductor and adductor of the thumb are known by those names; the analo- gous muscle of the index finger are the first dorsal and first palmar interossei; of the middle finger the two next dorsal interossei; of the ring finger the fourth dorsal and second palmar; and of the little finger the abductor minimi digiti THE DISSECTOR. 313 and third palmar interosseus. These movements of abduc- tion and adduction are highly valuable in the grasp of large or irregular bodies, or in the contraction of the bulk of the hand in various important surgical manipulations. The main artery for the supply of the upper extremity commences within the thorax, and, arching over its brim, passes beneath the clavicle; hence it is named subclavian. On quitting the side of the chest, it is received into the space which intervenes between the scapula and ribs, and acquires the name of that space, axillary. It then runs along the arm to the bend of the elbow, under the name of brachial. Now it is an established principle in the distribution of arteries, that they always select the most projected situations for their course. Thus they are constantly placed on the inner side of the limb, and studiously avoid the convexities of joints, where they would be subjected to injury, both from external pressure and over extension. The brachial artery is there- fore placed along the inner side of the arm, as is the femoral in the thigh; the brachial dips deeply into the space of the elbow, as does the popliteal into the space of the ham. Arrived at the bend of the elbow, the brachial artery ac- commodates itself to the augmented lateral breadth of the fore-arm, and its increased number of components, the radius, the ulna, and the intermediate space, by dividing into three branches corresponding with these three parts, the two bones and the interosseous. Its branches, therefore, are radial, ulna, and interosseus; as in the leg we find the posterior tibial and fibular corresponding with the two bones, and the anterior tibial with the interosseous space. The Radial artery supplies all the parts placed upon the radial side of the fore-arm, and passing between the two heads of the first dorsal interosseous muscle, is distributed to the thumb and deep structures in the hand, under the name of the deep palmar arch. The Ulnar supplies all the parts placed upon the ulnar side of the fore-arm, and in the hand forms the superficial palmar arch, from which the branches pass off, which are distributed to the fingers. In the supply of branches, the muscles necessarily come in for a large share, which receive no names unless they assume a remarkable magnitude, as the profunda arteries. Other named branches owe their names to peculiarity of structure, 27 314 THE DISSECTOR. and are, therefore, easily remembered. But the joints which are exposed to pressure and are uncovered, except by integu- ment, derive an abundant supply of branches from all the surrounding sources. For instance, the elbow joint is pro- vided with eight nutrient branches, the superior profunda, and its posterior articular branch, inferior profunda, anastomotica magna, radial recurrent, anterior and posterior ulna recur- rents, and interosseous recurrent. The knee has seven named branches, the wrist three, and the ankle four. Thus it may be shown that the principle of arrangement of the arteries, as of the muscles and the rest of the systems, is the same throughout the entire body; the exceptions are individualities that associate objects of importance and in- terest with their existence. The Veins of the upper extremity are the superficial and the deep: the former are placed between the two layers of the superficial fascia, the latter are associated Avith the arte- ries. All the arteries of the limbs and trunk which are be- low the second magnitude are accompanied by two veins, " Venae comites;" thus the radial, ulnar, interosseous, and brachial arteries, with their branches, have each their corre- sponding venae comites. The axillary and subclavian have each a single vein. The Lymphatic vessels are rarely seen in an ordinary dis- section, excepting under very favourable circumstances, as in anasarca, when they are sometimes observed, as Avhite opaque threads, traversing the transparent jelly like cellular sub- stance, and entering the lymphatic glands at all points of their circumference. They folloAv in their course the direction of the veins to which they bear a remarkable analogy. The lymphatic glands are accumulated in the loose cellular tissue of the axilla, and two or three may be met with in the course of the basilic vein. The Nerves of the upper extremity are derived from the brachial plexus Avhich is formed by the last four cervical and the first dorsal nerves. A plexus is the means by Avhich nervous branches destined to a single apparatus are associated in their structure previously to distribution, so that the sen- sations of each filament may harmonize with all the rest, and produce the unity of impulse Avhich is necessary to perfect action. For it is evident that if an impression were received THE DISSECTOR. 315 by the terminal filament of any one nerve, and excited a re- flex movement, without a simultaneous impression upon the other nerves of the same limb and consequent muscular move- ment, that an opposition of action would result; which is inconsistent with natural and healthy function. We are, therefore, interested in the complex interlacements and union of a number of nerves in the formation of a plexus, when we reflect upon the important benefits which such a disposition confers. The branches which are given off by the brachial or axillary plexus are, 1st., those distributed to the shoulder and neigh- bouring part of the chest; and 2d, those destined to the arm. The former are named thoracic and scapular; the latter con- sist of six nerves ;—one, which supplies the muscles about the shoulder joint, the circumflex; two, going to the integument of the arm, external and internal cutaneous; and three, like the three arteries, supplying the fore-arm and hand, musculo- spiral, ulnar, and median. Let us now proceed to the dissection of the upper extremity. Dissection.—Make an incision along the line of the clavicle, from the upper part of the sternum to the acromion process; a second along the lower border of the great pectoral muscle, from the lower end of the sternum to the insertion of its ten- don into the humerus; and connect the two by a third, car- ried longitudinally along the middle of the sternum. The integument and superficial fascia are to be dissected off the fibres of the muscle together, 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. Muscles of the Shoulder and upper Arm. Anterior Thoracic Region. Pectoralis major. Pectoralis minor. Subclavius. The Pectoralis major muscle arises from the sternal two- thirds of the clavicle, half of the sternum its whole length, and from the cartilages of all the true ribs, excepting the 316 THE dissector. first. It is inserted by a broad tendon into the anterior bi- cipital ridge of the humerus. That portion of the muscle which arises from the clavicle, is separated from that connected with the sternum by a dis- tinct cellular interspace ; hence we speak of the clavicular portion and sternal portion of the pectoralis major. The fibres from this very extensive origin converge towards a nar- row insertion, giving the muscle a radiated appearance. But there is a peculiarity about the formation of its tendon which must be carefully noted. The whole of the lower border is folded inwards upon the upper portion, so that the tendon is doubled upon itself. Another peculiarity results from this arrangement; the fibres of the upper portion of the muscle are inserted into the lower part of the ridge, and those of the lower portion into the upper part. Fig. 82. The vessels and nerves of the deep pectoral region. 1. The deltoid muscle. 2. The clavicle. 3. The subclavius muscle, covered in by the costo-coracoid membrane. 4. The pectoralis minor muscle. 5. The triangular space, in which the subclavian artery is tied below the clavicle; and which contains, 6. The subclavian vein. 7. The subclavian artery. 8. The brachial plexus of nerves. 9. The superior thoracic artery and nerve. 10. The thoracic branch of the thoracico- acromialis, artery. 11. The descending branch of the thoracico-acromialis, descending by the side of the cephalic vein. 12. The acromial branch of the thoracico-acromialis. 13. The inferior thoracic artery and nerve. THE DISSECTOR. 317 14. The thoracico-alaris branch of the axillary artery. 15. The internal cutaneous and ulnar nerves resting on the axillary vein. 16. The median nerve embracing the axillary artery, with its two heads. 17. The external cutaneous nerve, piercing the coraco brachialis muscle. 18. The coraco- brachialis. 19. The biceps muscle. The pectoralis major muscle is separated from the deltoid by a deep cellular interspace, in which are seen the cephalic vein and the descending branch of the thoracico-acromialis artery. (Fig. 82. 11.) Dissection.—The pectoralis major is now to be removed by dividing its fibres along the lower border of the clavicle, and then carrying the incision perpendicularly doAvnwards, paral- lel 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 reflect the muscle outwards. We thus bring into view a region of considerable interest, from which the fat and cellular tissue must be carefully removed. In the middle of this region is the pectoralis minor muscle (fig. 82. 4.,) and above it a triangular space bounded superi- orly by the costo-coracoid membrane, 3., which covers in the subclavius muscle, and by the second rib and two adjoining interspaces internally. In this triangular space, 5., are found, the subclavian vein, 6., the subclavian artery, 7., and the bra- chial plexus of nerves, 8., all resting on the first rib; the acromial thoracic, 10., and superior thoracic arteries, 9., with their veins and nerves, and the cephalic vein, 11. Below the pectoralis minor, the axillary artery is seen embraced by the two heads of the median nerve 16., having to its inner side the axillary vein, and in front the inferior thoracic, 13., and axillary thoracic, 14., branches. The Pectoralis minor arises by three digitations from the third, fourth, and fifth ribs, and is inset ted into the coracoid process of the scapula. The Subclavius muscle arises by a round tendon from the cartilage of the first rib, and is inserted into the under surface of the clavicle. This muscle is concealed by the costo-cora- coid membrane, an extension of the deep cervical fascia, by Avhich it is invested. 27* 318 THE DISSECTOR. Lateral Thoracic Region. Serratus Magnus. The Serratus magnus (serratus, indented like the edge of a saw,) arises by fleshy serrations from the nine upper ribs excepting the first, and extends backwards upon the side of the chest, to be inserted into the whole length of the base of the scapula. It indigitates by means of its five lower serra- tions with the obliquus externus abdominis. Subscapular Region. Subscapularis. The Subscapularis muscle arises from the whole of the un- der surface of the scapula, excepting the superior angle, and terminates by a broad and thick tendon, which is inserted into the lesser tuberosity of the humerus. The tendon of this muscle forms a part of the capsule of the joint, and is lined by its synovial membrane. Acromial Region. Deltoid. The convexity of the shoulder is formed by a large triangu- lar muscle, the Deltoid (a, delta; «5o$, resemblance,) which 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 converge to the middle of the outer side of the humerus, where they are inserted into a rough triangular elevation. This muscle is remarkable for its coarse texture, and the combination of tendinous and mus- cular fibres. The deltoid muscle may now be cut away from its origin, and turned down for the purpose of bringing into view the muscles and tendons placed immediately around the shoulder joint. In so doing, a large bursa will be seen be- tween the under surface of the muscle and the head of the humerus. Bend of the Elbow. Before, however, proceeding any farther with the dissection of the shoulder, it would be advisable to study the super- THE dissector. 319 ficial anatomy of the bend of the elbow. With this view an incision should be made through the integument, along the middle of the biceps muscle, to about three inches below the elbow, and bounded at its extremity by a transverse incision. The integument is next to be dissected carefully back, and a second incision carried in the same direction to divide the ex- ternal layer of the superficial fascia. This operation must be conducted with care, for a number of superficial nerves and veins occupy this region of the arm; they may be thus ar- ranged :— Internal cutaneous nerve. Intercosto-humeral, or nerve of Wrisberg. External cutaneous nerve. Spiral cutaneous nerve. Posterior ulnar vein. Anterior ulnar vein. Basilic vein. Radial vein. Cephalic vein. Median vein. Median cephalic vein. Median basilic vein. The Internal cutaneous nerve, (fig. 83. 15.) is one of the internal and smallest of the branches of the axillary plexus: it pierces the fascia immediately below the axilla, and runs down the inner side of the upper arm, to the bend of the elbow, where it divides into several branches, which pass in front of the median basilic vein, and are distributed to the in- tegument on the inner side of the fore-arm as far as the hand, communicating in their course with the external cutaneous. The Intercosto-humeral cutaneous nerves are the external branches of the first, second, and third intercostal nerves: they pierce the external intercostal muscle, and supply the parts in the axilla and the integument on the inner side of the arm. That from the second intercostal nerve is the longest of the three, and extends as far as the elbow; it is sometimes called the nerve of Wrisberg, 16. m The External cutaneous nerve, 14., pierces the deep fascia just above the bend of the elbow, where it emerges from be- 320 THE DISSECTOR. neath the tendon of the biceps. It passes behind the median Fig. 83. The superficial cephalic vein, and divides into several anatomy of the bend of branches, which supply the integument the elbow. on i\lQ outer side of the fore-arm as far as the hand, communicating with the internal cutaneous. The Spiral cutaneous nerve, 17., is a branch of the musculo-spiral: it pierces the deep fascia immediately below the insertion of the deltoid muscle, and runs down the outer side of the fore- arm to the integument of which it is distributed. Two veins return the blood from the inner side of the hand and fore-arm, the anterior, 3., and posterior ulnar, 4., veins; the latter commences by the vein of the little finger, vena salvatella. They ascend the ulnar border of the fore-arm, one on the anterior surface, the other on the posterior, and near to the elbow unite to form a common ul- nar vein, 5. At the bend of the elbow, the common ulnar vein is joined by the median basilic, and the common trunk is called the basilic vein. 1. The radial vein. 2. The cephalic vein. 3. The anterior ulnar vein. 4. The posterior ulnar vein. 5. The common ulnar vein. 6. The basilic vein. 7. The point at which the basilic vein pierces the fascia. 8. The me- dian vein. 9. The communication between the deep veins of the fore-arm and the median. 10. The median cephalic vein. 11. The median basilic vein. 12. A slight convexity of the deep fascia, formed by the brachial ar- tery. 13. The slip of fascia derived from the tendon of the biceps, which sepa- rates the median basilic vein from the brachial artery. 14. The external cutaneous nerve, piercing the fascia and dividing into two branches, which pass behind the median cephalic vein. 15. The internal cutaneous nerve dividing into branches, which pass in front of the median basilic vein. 16. The nerve of Wrisburg. 17. The spiral cutaneous nerve, branch of the musculo-spiral nerve. The Basilic vein, 6. ($a,a%tu, three heads,) arises by three heads. Considered in relation to their length, these heads have been named long, short, and middle, and, in reference to their position, internal, external, and middle; the term 324 THE DISSECTOR. middle, in the former case, referring to the external head, and in the latter case to the long head. This has given rise to much confusion and misunderstanding. We shall, there- fore, confine ourselves to the designations derived from their relations. The external head arises from the humerus im- mediately below the insertion of the teres minor. The internal head (short) arises from the humerus immediately below the insertion of the teres major. The scapular head (long) lies between the two others, and arises from the upper third of the inferior border of the scapula. The three heads unite to form a broad aponeurotic tendon, which is inserted into the olecranon process of the ulna. The scapular head of the triceps passes between the teres minor and major, and divides the triangular space between those two muscles into two smaller spaces, one of which is tri- angular, the other quadrangular. The triangular space is bounded by the teres minor, teres major, and scapular head of the triceps ; it gives passage to the dorsalis scapulae artery and veins. The quadrangular space is bounded on three sides by the three preceding muscles, and on the fourth by the humerus. Through this space pass the posterior cir- cumflex arteries and veins and circumflex nerve. Having thus examined all the muscles of the shoulder and upper arm, let us now inquire into their functions. 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 draAving 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 dowmvards and forwards, and thereby assists in steadying the shoulder. 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 we see to be the case in diseased lungs, Avhere the chest has become almost fixed from apprehension of the expanding action of the respiratory muscles. The trapezius muscle carries the entire shoulder THE DISSECTOR. 325 upwards and backwards, and is assisted in this action by the levator anguli scapulae, rhomboideus minor, and rhomboideus major. Acting in the opposite direction, they flex the ver- tebral column toAvards the shoulder. The lower fibres of the trapezius unite with the latissimus dorsi, in drawing the shoulder and arm doAvmvarcls and backwards. When the arms are fixed, as by crutches, or seizing the branch of a tree, the latissimi dorsi muscles lift the entire trunk and carry it forwards. The supra-spinatus, infra-spinatus, teres minor, and sub- scapularis, are the circumductur muscles of the arm; they regulate the movements of the head of the humerus against the glenoid cavity. The deltoid is the elevator muscle of the arm in a direct line; and, by means of its extensive origin, can carry the arm forwards or backAvards so as to range with the hand a considerable segment of a large circle. The arm, raised by the deltoid, is a good illustration of a lever of the third power, so common in the animal machine, by which velocity is gained at the expense of poAver. In this lever the Aveight (hand) is at one extremity, the fulcrum (the glenoid cavity) at the opposite end, and the power (the insertion of the muscle) between the tAvo, but nearer to the fulcrum than the weight. The muscles of the anterior brachial region are flexors; the coraco-brachialis flexing the humerus on the scapula, and carrying it inwards. The biceps and brachialis anticus flex the fore-arm upon the arm. The former possesses also the additional action of supinating the fore-arm, by means of the obliquity of its insertion into the tuberosity of the radius. The triceps is an extensor of the fore-arm; hence its title, triceps extensor cubiti. AXILLA. The Axilla (arm-pit) is the space between the side of the chest and shoulder. In form it resembles a triangular cone, the apex being above at the clavicle, the base beloAV at the lower borders of the pectoralis major and latissimus dorsi. It is bounded in front by the tAvo pectoral muscles; behind, by the subscapularis, teres major, and latissimus dorsi; and, '28 326 THE DISSECTOR. internally, by the serratus magnus and side of the chest. The axillary space contains the Axillary artery Avith its seven branches, Axillary vein, Axillary plexus of nerves, Long thoracic or external respiratory nerve, Three intercosto-humeral nerves, Lymphatic glands imbedded in cellular tissue. Axillary Artery. The Axillary artery forms a gentle curve through the ax- illary space from the lower border of the first rib to the loAver border of the latissimus dorsi. The artery is separated from its anterior relations by cel- lular tissue above, and below by the tAvo heads of the median nerve. The axillary vein lies at first to its inner side, and then gets in front of the artery. A slight inspection of this artery and its numerous rela- tions, will serve to show that its ligature would be an ex- tremely injudicious and dangerous operation, warranted only by the pressure of extreme circumstances. But the student may be called upon to give the steps of the operation; he must, therefore, reflect upon the position, depth, and relations of the artery. A superficial vessel requires only a short in- cision, the length increasing with the depth of the artery. Branches.—The branches of the Axillary artery are seven in number:— Thoracico-acromialis, Subscapular, Superior thoracic, Circumflex anterior, Inferior thoracic, Circumflex posterior. Thoracico-axillaris, The thoracico-acromialis and superior thoracic, are found in the triangular space above the pectoralis minor. The inferior thoracic and thoracico-axillaris, below the pec- toralis minor. And the three remaining branches below the lower border of the subscapularis. The Thoracico-acromialis (fig. 82.) is a short trunk that ascends to the space above the pectoralis minor muscle, and divides into three branches,—thoracic, 10., which is distributed to the pectoral muscles and mammary gland ; acromial, 12., passing outwards to the acromion; descending, 11., to the THE DISSECTOR. 327 space between the deltoid and pectoralis major that lodges the cephalic vein. The Superior thoracic, 9. (short) runs along the upper border of the pectoralis minor, and is distributed to the pec- toral muscles and mammary gland. The Inferior thoracic, 13. (long) runs along the lower border of the pectoralis minor, and is distributed to the pec- toral and serratus muscles, and mammary gland. The Thoracico-axillaris, 14., is a small branch distributed to the plexus of nerves and glands in the axilla. The Subscapular artery, the largest of the branches of the axillary, runs along the loAver border of the subscapularis muscle, to the inferior angle of the scapula, where it inoscu- lates with the posterior scapular, a branch of the subclavian. It supplies the muscles on the under surface, and inferior border of the scapula, and side of the chest. At about an inch and a half from the axillary, it gives off a large branch, the dorsalis scapulae, which passes backwards through the triangular space bounded by the teres minor, teres major, and scapular head of the triceps, and beneath the infra- spinatus to the dorsum of the scapula, where it is distributed, inosculating with the supra-scapular and posterior scapular arteries. The Circumflex arteries wind around the neck of the hu- merus. The anterior, very small, passes beneath the coraco- brachialis and short head of the biceps, and sends a branch upwards along the bicipital groove to supply the shoulder- joint. The Posterior circumflex, of larger size, passes backwards through the quadrangular space bounded by the teres minor and major, the scapular head of the triceps and the humerus, and is distributed to the deltoid muscle and joint: sometimes this artery is a branch of the superior profunda of the bra- chial. It then ascends behind the tendon of the teres major, and is distributed to the deltoid without passing through the quadrangular space. Brachial Artery. The Brachial Artery runs down the inner side of the arm, from the loAver border of the latissimus dorsi to the bend of the elbow. 328 THE DISSECTOR. Relations.—In its course downwards, it rests upon the coraco-brachialis muscle, internal head of the triceps, and brachialis anticus. To its outer side are the coraco-brachialis and biceps muscles, and in front it has the basilic vein, and is crossed by the median nerve. Its relations, within its sheath, are the venae comites. Fig. 86. The axillary and brachial artery, with their branches. Brachial Artery—Branches: Superior profunda—Posterior articular, Inferior profunda, Anastomotica magna. The Superior profunda winds around the humerus, between the triceps and the bone, to the space between the brachi- alis anticus and supinator lon- gus, where it inosculates with the radial recurrent branch. It accompanies the musculo- spiral nerve. In its course it supplies the triceps muscle, and gives off one remarkable branch (posterior articular) which de- scends to the joint, and inos- culates with the posterior in- terosseous recurrent branch. The Inferior profunda de- scends to the space between the inner condyle and olecra- non in company with the ulnar nerve, and inosculates with the posterior ulnar recurrent. The Anastomotica magna is given off at right angles from the brachial, at about two inches above the joint. It pass- es directly inwards, and divides into two branches which in- osculate with the anterior ul- nar recurrent, and inferior pro- funda. THE DISSECTOR. 329 1. The deltoid muscle. 2. The biceps. 3. The tendinous process given off from the tendon of the biceps, to the deep fascia of the fore-arm. It is this process which separates the median basilic vein from the brachial artery. 4. The outer border of the brachialis anticus muscle. 5. The supinator longus. 6. The coraco-brachialis. 7. The middle portion of the triceps muscle. 8. Its inner head. 9. The axillary artery. 10. The brachial artery;—a dark line marks the limit between these two vessels. 11. The thoracica acromialis artery dividing into its three branches; the number rests upon the coracoid process. 12. The superior and inferior thoracic arteries. 13. The serratus magnus muscle. 14. The subscapular artery. The posterior circumflex and thoracica axillaris branches are seen in the figure between the inferior thoracic and subscapular. The anterior circum- flex is observed, between the two heads of the biceps, crossing the neck of the humerus. 15. The superior profunda artery. 16. The inferior profunda. 17. The anastomotica magna inosculating inferiorly with the anterior ulnar recurrent. 18. The termination of the superior profunda, inosculating with the radial recurrent in the interspace between the brachialis anticus and supinator longus. Axillary Plexus. The Axillary plexus of nerves is formed by the commmu- nications of the anterior branches of the last four cervical and first dorsal nerves. The plexus is broad in the neck, but narrows as it approaches the axillary artery, lying at first external to that vessel, then getting behind it, and at about the middle of the axilla completely surrounding it. At this point it divides into six ultimate branches. The branches given off from the plexus, previously to its division, are tho- racic and scapular. The Short thoracic nerves (fig. 82. 9. 13.,) two or three in number, are distributed to the muscles and integument at the upper part of the thorax accompanying the superior and in- ferior thoracic arteries. The Long thoracic (external respiratory of Bell) is a long branch arising from the fourth and fifth cervical nerves, im- mediately after their escape from the intervertebral foramina. It passes down behind the plexus and upon the side of the chest, resting on the serratus magnus muscle, to which it is distributed. The Supra-scapular nerve passes backwards to the notch in the superior border of the scapula, through which it emerges into the supra-spinous fossa, supplying the supra-spinatus and neighboring muscles. 28* 330 THE DISSECTOR. The Subscapular nerves are three in number; they pass inAvards, and supply the subscapularis muscle. One of them, larger than the others, accompanies the subscapular artery, and distributes branches to the adjoining muscles. The terminal branches of the plexus are arranged in the folloAving order—the external cutaneous, and one head of the median to the outer side of the artery ; the other head of the median, internal cutaneous, and ulnar, upon its inner side ; and the circumflex and musculo-spiral behind. The External cutaneous nerve (fig. 82. 17., fig. 83. 14.) (musculo-cutaneous, perforans Casserii) pierces the coraco- brachialis muscle, then passes between the biceps and bra- chialis anticus, to the outer side of the bend of the elbow, where it perforates the fascia, and divides into branches, which run behind the median cephalic vein, and supply the integu- ment on the outer side of the fore-arm as far as the hand. It communicates on the fore-arm with branches of the internal cutaneous. The Median nerve (fig. 82. 16.) is so called, because it runs along the middle of the arm to the palm of the hand, and is, therefore, intermediate in position, between the radial and ulnar nerves. It commences by two heads, which embrace the axillary artery; lies at first to the outer side of the bra- chial artery, which it crosses at its middle, and descends on its inner side to the bend of the elbow. It then passes betAveen the two heads of the pronator radii teres and flexor sublimis digitorum muscles, and runs doAvn the fore-arm, between the flexor sublimis and profundus, and beneath the annular ligament, to the palm of the hand. The Internal cutaneous nerve (fig. 83. 15.) is intended for the supply of the integument, on the inner side of the fore-arm as far as the hand: it has already been described in the superficial anatomy of the bend of the elbow. (See page 321.) The Ulnar nerve runs down the inner side of the arm, to the groove betAveen the internal condyle and olecranon, resting upon 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 is easily compressed, giving rise to the thrilling sensation along the inner side of the fore-arm and little finger, ascribed to striking THE DISSECTOR. 331 the " funny bone." At this point the nerve passes between the two heads of the flexor carpi ulnaris muscle. If these nerves, together with the brachial artery, be draAvn aside, the tAvo posterior branches of the plexus, circumflex and musculo-spiral, are brought into view. The Circumflex nerve passes over the border of the sub- scapularis muscle, and winds around the neck of the humerus, with the posterior circumflex artery, supplying the deltoid muscle and shoulder-joint. The Musculo-spiral nerve is the largest branch of the plexus : it winds around the humerus in the spiral groove, accompanied by the superior profunda artery, to the space between the brachialis anticus and supinator longus mus- cles, and thence onwards to the bend of the elbow, where it divides into two branches, the posterior interosseous and radial nerve. Its branches in the upper arm are, 1. Muscular to the triceps, hence its designation "musculo;" "spiral" being applied to its course. 2. Spiral cutaneous nerve, (fig. 83. 17.,) Avhich pierces the deep fascia, between the deltoid and external head of the triceps muscle, and supplies the integu- ment on the outer side of the fore-arm, as far as the wrist. It is described at page 313. The course of the median, ulnar, and radial nerves in the fore-arm will be described in the next section. Fore-arm. Dissection.—The dissection of the fore-arm has been par- tially commenced in the examination of the bend of the elbow. It must now be continued by carrying the incision along the middle of the fore-arm and over the wrist to the root of the middle finger, where it may be terminated by a transverse incision made across the heads of the metacarpal bones. The integument is then to be turned to either side. In performing this operation on the ulnar side of the' hand, care must be taken to avoid raising the thin layer of muscular fibres which forms the palmaris brevis muscle. An incision is to be carried along the middle of the palmar surface of each of the fingers, and the integument turned aside from these to sIioav the flexor 332 THE DISSECTOR. tendons, and the artery and nerve at either border of the finger. The superficial fascia is next to be dissected off, and the cutaneous nerves traced dowmvards between its layers to the hand. The superficial veins may also be cleared of the sur- rounding fat and cellular tissue. The Deep fascia of the fore-arm is dense and thick, and very different from the thin layer of the upper arm. Towards the inner condyle, it has a muscular connexion, and is strengthened by the band of fascia (fig. 83. 13.,) derived from the tendon of the biceps. It presents all the general characters of deep fascia ; surrounding all the muscles of the fore-arm, being attached to the prominent points of bones, forming sheaths for the numerous muscles, and by its inner surface giving origin to muscular fibres. At the wrist it be- comes much thickened, and is attached to the projecting points of the scaphoid and trapezium bones on one side, and to the pisiform and unciform bones on the other, forming the anterior annular ligament; posteriorly it forms another band less thick than the anterior. It is attached to the bones by each extremity of the posterior annular ligament, and binds down the extensor tendons as they pass forAvards to the hand. In the palm of the hand is a dense tendinous fascia, the palmar, which is analogous to the dense layer Avhich we pre- viously examined in the sole of the foot, the plantar fascia. The Palmar fascia is narrow towards the wrist, and attached to the annular ligament. Approaching the base of the fingers it becomes broad, and divides into four slips, each of which is subdivided into two smaller slips, which are inserted into the sides of the bases of the first phalanges, giving passage to the flexor tendons. The point of division of these slips is strengthened by a strong interlacement of transverse fibres. THE DISSECTOR. 333 Muscles of the Fore-arm. The deep fascia of the fore-arm may now be divided and turned aside, and the superficial layer of muscles of the fore- arm examined. There are eight muscles , . , o ^i P „n Fig. 8/. Superficial on the anterior aspect of the tore-arm, all laye* of muscles of thc flexors and pronators, five in the superfi- fore-arm. cial layer, and three in the deep. The superficial muscles in their order, from radius to ulna, are Anterior Aspect.—Superficial Group. Pronator radii teres, Flexor carpi radialis, Palmaris longus, Flexor sublimis digito- rum, Flexor carpi ulnaris. The Pronator radii teres arises by two heads, one from the inner condyle of the humerus and fascia of the fore-arm, the other from the coronoid process of the ulna ; the median nerve passing betAveen them. Its tendon is inserted into the mid- dle third of the oblique ridge of the radius. The two heads of this muscle are best seen, by cutting away that which arises from the inner condyle, and turning it aside. The second head will then be seen Avith the median nerve lying across it. The Flexor carpi radialis arises from the inner condyle and the sheath of fascia which surrounds it. Its tendon passes through a groove in the scaphoid bone, to be inserted into the base of the metacar- pal bone of the index finger. 1. The lower part of the biceps, with its tendon. 2. A part of the bra- chialis anticus, seen beneath the biceps. 3. A part of the triceps. 4. The pronator radii teres. 5. The flexor carpi radialis. 6. The palmaris longus. 7. One of the fasciculi of the flexor sublimis digitorum; the rest of the muscle is seen beneath the tendons of the palmaris longus and flexor carpi radialis. 8. The flexor carpi ulnaris. 9. The palmar fascia. 10. The palmaris brevis muscle. 11. The abductor pollicis muscle. 12. One portion of the flexor brevis pollicis; the leading line crosses a part of the abductor pollicis. 13. The supinator longus muscle. 14. The extensor ossis metacarpi, and extensor primi internodii pollicis, curving around the lower border of the fore-arm. 334 THE DISSECTOR. of muscles of the fore- The Palmaris longus muscle arises from the innner con- dyle, and from the sheath of fascia which surrounds it. It is inserted into the palmar fascia. Cut the flexor carpi radialis and palmaris longus from their origins, in order to obtain a good vieAV of the whole extent of origin of the flexor sublimis digitorum. The Flexor sublimis digitorum (perforatus) arises from the inner condyle, coronoid process of the ulna, and oblique line of the radius. The median nerve and ulnar artery pass be- tween its origins. It divides into four f'miiBfiifia nf thl el™, tendons, which are inserted into the base of the second phalanges of the fingers, splitting at their terminations to give passage to the tendons of the deep flexors; thence its design Sitioji perforatus. The Flexor carpi ulnaris arises by two heads, one from the inner condyle, the other from the olecranon and two thirds of the inner border of the ulna. The ulnar nerve passes between its two heads. Its tendon is inset-ted into the pisiform bone. RemoAre the flexor sublimis, and draw the pronator teres upwards Avith hooks, the deep layer Avill then be exposed: it consists of the Deep Group.—Flexor profundus digi- torum, flexor longus pollicis, pronator quadratus. The Flexor profundus digitorum (per- forans) arises from the upper two-thirds of the ulnar and part of the interosseous membrane, and terminates in four ten- dons, Avhich pass beneath the annular ligament, and between the tAvo slips of the flexor sublimis, (hence its designation perforans,) to be inserted into the base of the last phalanges. Four little muscular fasciculi, 1. The internal lateral ligament of the elbow-joint. 2. The ligament. 3. The orbicular ligament of the head of the radius. flexor profundus digitorum muscle. 5. The flexor longus pollicis. pronator quadratus. 7. The abductor pollicis muscle. 8. The dorsal in- called anterior 4. The 6. The THE DISSECTOR. 335 terosseous muscle of the middle finger, and palmar interosseous of the ring- finger. 9. The dorsal interosseous muscle of the ring-finger, and palmar interosseous of the little finger. lumbricales, are connected with the tendons of this muscle in the hand, They will be described with the muscles of the hand. The Flexor longus pollicis arises from the upper two-thirds of the radius, and part of the interosseous membrane. Its tendon passes beneath the annular ligament to be inserted into the base of the last phalanx of the thumb. If the tendons of the last two muscles be drawn aside or divided, the third muscle of this group will be brought into view, lying across the lower part of the two bones. The Pronator quadratus arises from the ulna, and is inserted into the lower fourth of the oblique line on the outer side of the radius. This muscle occupies about the lower fourth of the two bones, is broad at its origin, and narrower at its insertion. Actions.—The pronator radii teres and pronator quadratus muscles rotate the radius upon the ulnar, and render the hand prone. The remaining muscles are flexors:—two flexors of the wrist, flexor carpi radialis and ulnaris: two of the fingers, flexor sublimis and profundus, the former flexing the second phalanx, the latter the last; one flexor of the last phalanx of the thumb, flexor longus pollicis. The palmaris longus is a # tensor of the palmar fascia. Arteries of the Fore-arm. The Arteries on the anterior aspect of the fore-arm are the radial, ulnar, and interosseous. The brachial artery at the bend of the elbow divides into two branches, the radial and ulnar. Radial Artery. The Radial artery runs along the radial side of the fore- arm, from the bend of the elbow to the wrist; it there turns around the base of the thumb, beneath its extensor tendons, and passes between the two heads of the first dorsal interos- seous muscle, into the palm of the hand. It then crosses the metacarpal bones to the ulna side of the hand, forming the deep palmar arch, and terminates by inosculating with the superficial palmar arch. 336 THE DISSECTOR. In the upper half of its course, the radial artery is situated betAveen the supinator longus muscle, and pronator radii tore in the lower half between the tendons of the supinator longus, and flexor carpi radialis. It rests in its course downwards, upon the insertions of the supinator brevis, and pronator radii teres, radial origin of the flexor sublimis, flexor longus pollicis, and pronator quadratus, and is covered in by the in- tegument and fasciae. The Branches of the Radial artery may be arranged into four groups :— Elbow - - Recurrent radial. Fore-arm - Muscular branches. ^Superficialis volae. Carpalis anterior. Wrist -^ Carpalis posterior. ! Metacarpals. Dorsales pollicis. Princeps pollicis. Radialis indicis. Interosseae. Perforantes. The Recurrent branch turns upward in the space between the supinator longus and brachialis anticus to supply the structures about the joint. It inosculates with the superior profunda artery The Muscular branches, as in every other part of the body, supply the muscles adjacent to the artery. The Superficialis volae is given off from the radial artery while at the Avrist. It passes betAveen the fibres of the ab- ductor pollicis muscle, and inosculates with the termination of the ulnar artery, completing the superficial palmar arch. The Carpal branches are intended for the supply of the Avrist, the anterior carpal in front, and the posterior, the larger of the t\vo, behind. The Metacarpal branch runs fonvards on the second dor- sal interosseous muscle, and is distributed to the adjoining sides of the index and middle fingers. Sometimes it is of very large size. The Dorsales pollicis are tAvo small branches, running along the sides of the dorsal aspect of the thumb. The Princeps pollicis descends along the border of the THE DISSECTOR. 337 metacarpal bone, between the abductor indicis and abductor pollicis to the base of the first phalanx, Avhere it divides into two branches, which are distributed to the tAvo sides of the palmar aspect of the thumb. The Radialis indicis is also situated between the abductor indicis and abductor pollicis, and runs along the radial side of the index finger, forming its collateral artery. The interosseae and perforantes are branches of the deep palmar arch, the former supplying the interosseous muscles, the latter passing between the two heads of the dorsal interos- sei, to inosculate with the carpal and metacarpal branches. 1. The lower part of the biceps muscle. 2. The inner condyle of the humerus with the humeral origin of the pronator radii teres and flexor carpii radialis divided across. 3. The deep portion of the pronator radii teres. 4. The supinator longus muscle. 5. The flexor longus pollicis. 6. The prona- tor quadratus. 7. The flexor profundus digitorum. 8. The flexor carpi ulnaris. 9. The annular ligament with the tendons passing beneath it into the palm of the hand; the figure is placed on the tendon of the palmaris longus muscle divided close to its insertion. 10. The brachial artery. 11. The anastomotica magna inosculating superiorly with the inferior profunda, and inferiorly with the anterior ulnar recurrent. 12. The radial artery. 13. The radial recurrent artery inosculating with the termination of the superior profunda. 14. The superfici- alis volae. 15. The ulnar artery. 16. Its superficial palmar arch giving off digital branches to three fingers and a half. 17. The magna pollicis and radialis indicis arteries. 18. The posterior ulnar recurrent. 19. The anterior interosseous artery. 20. The pos- terior interosseous, as it is passing through the interosseous membrane. Ulnar Artery. The Uln ar artery crosses the arm obliquely to the commencement of its middle third, it then runs down the ulnar side of the fore-arm to the wrist, crosses the annular ligament, and forms the superficial palmar 29 Fig. 79. The arteries of the fore-arm. 338 THE DISSECTOR. arch, which terminates by inosculating with the superficialis volae. Relations.—In the upper or oblique portion of its course, it lies between the superficial and deep layers of muscles of the fore-arm. In the second part of its course, it is placed between the flexor carpi ulnaris, and flexor sublimis digitorum. While crossing the annular ligament, it is protected from in- jury by a strong tendinous arch, thrown over it from the pisiform bone; and in the palm it rests upon the tendons of the flexor sublimis, being covered in by the palmar fascia. The Branches of the Ulnar artery may be arranged into four groups:— t™ j Anterior ulnar recurrent. [ Posterior ulnar recurrent. {T , f Ant. inteross. Interosseous^ -r> . • . . { Post, inteross.—recurrent. Muscular Wrist f Carpalis anterior. \ Carpalis posterior. Hand Digitales, four. The Anterior ulnar recurrent returns upon the elbow, be- tween the pronator teres and brachialis anticus and inoscu- lates with the anastomotica magna. The Posterior ulnar recurrent returns upon the elbow, by passing beneath the origins of the superficial layer of mus- cles, and then betAveen the two heads of the flexor carpi ulnaris. It inosculates with the inferior profunda and anastomotica magna. The Common interosseous is a short trunk, which divides into the anterior and posterior interosseous arteries. The Anterior interosseous runs down the fore-arm upon the interosseous membrane, and at the upper border of the pronator quadratus pierces that membrane, and descends to the back of the wrist, where it inosculates with the posterior carpal branches of the radial and ulnar. The Posterior interosseous artery passes back through an opening between the upper part of the interosseous membrane and the oblique ligament, and is distributed to the muscles on the posterior aspect of the fore-arm. It gives off a recurrent branch, Ayhich returns upon the elbow beneath the anconeous THE DISSECTOR. 339 muscle, and anastomoses with the posterior articular branch of the superior profunda. The Muscular branches supply the muscles situated on the ulnar border of the fore-arm. The Carpal branches, anterior and posterior, are distributed to the anterior and posterior aspects of the wrist joint. The posterior is the largest. The Digital branches supply the collateral branches to the little, ring, and middle fingers, and the ulnar side of the in- dex finger. The Superficial palmar arch receives the termination of the deep arch, near to the carpal extremity of the little finger, and terminates in the superficialis volae, upon the ball of the thumb. Nerves of the Fore-arm. The Nerves of the fore-arm are the cutaneous, the median, ulnar, radial, and posterior interosseous. The cutaneous nerves, derived from the external cutaneous, internal cutane- ous and spiral cutaneous, have been already described. (See pages 319, 320.) Median Nerve. The Median nerve runs down the anterior aspect of the fore-arm, from the bend of the elboAv to the hand, where it divides into its five terminal branches. Relations.—At the bend of the elbow, it passes between the two heads of the pronator radii teres and flexor sublimis digitorum muscles. In the fore-arm, it lies between the flexor sublimis and pro- fundus, and at the wrist it passes with the tendons of these two muscles beneath the annular ligament into the palm of the hand. Branches.—The branches of the median nerve may be arranged in two groups, there being none given off in the upper arm. t* f Muscular. lore-arm < A ... ( Anterior interosseous. tt j j Superficial palmar. \ Five digital. 340 THE DISSECTOR. The Muscular branches are distributed to the muscles on the anterior aspect of the fore-arm. The Anterior interosseous is a large branch, accompanying the anterior interosseous artery, and supplying the deep layer of muscles in the fore-arm. It passes beneath the pronator quadratus muscle, and pierces the interosseous membrane near to the wrist. On reaching the posterior aspect of the wrist, it joins a large and remarkable ganglion, which gives off a number of branches for the supply of the joint. The Superficial palmar branch arises from the median nerve immediately above the annular ligament, and is distri- buted to the integument in the palm of the hand. The Digital branches are five in number ; two pass out- wards to the thumb; one to the radial side of the index finger; one subdivides for the supply of the adjoining sides of the index and middle fingers ; and the remaining one, for the supply of the adjoining sides of the middle and ring fingers. Ulnar Nerve. The Ulnar nerve runs along the ulnar side of the fore-arm to the wrist, crosses the annular ligament Avith the ulnar artery, and divides into two branches, superficial and deep palmar. Relations.—At the elbow the nerve lies in the groove between the inner condyle of the humerus and olecranon, and between the two heads of the flexor carpi ulnaris muscle. At the commencement of the middle third of the fore-arm, it becomes applied against the artery, and lies to its ulnar side, as far as the hand. Branches.—The branches of the ulnar nerve may be ar- ranged into four groups :— Upper arm - To the triceps muscle. Fore-arm - Muscular. Dorsum of hand Dorsal branch. Palm of hand i Superficial palmar. [ Deep palmar. A feAV filaments are given to the short head of the triceps. the dissector. 341 The Muscular branches supply the muscles on the ulnar side of the fore-arm. The Dorsal branch passes beneath the tendon of the flexor carpi ulnaris, at the lower third of the fore-arm, and divides into branches which supply two fingers and a half on the posterior aspect of the hand, and communicate with the radial nerve. The Superficial palmar branch divides into four filaments, which are distributed to the ulnar border of the hand, to the ulnar side of the little finger, to the adjoining borders of the little and ring fingers, and a communicating branch is sent to join the median nerve. The Deep palmar branch passes between the abductor and flexor minimi digiti, to the deep palmar arch, supplying all the deep parts in the palm of the hand. Musculo-spiral Nerve. The Musculo-spiral nerve, at the bend of the elbow, divides into two branches of nearly equal size, the radial and poste- rior interosseous. The Radial runs along the radial side of the fore-arm to the commencement of its lower third; it then passes beneath the tendon of the supinator longus to the back of the wrist and hand, where it supplies two fingers and a half, and com- municates with the dorsal branch of the ulnar nerve. It gives off a few branches to the muscles on the radial side of the fore-arm. Relations.—In the upper third of the fore-arm it lies beneath the border of the supinator longus muscle. In the middle third it is in relation Avith the radial artery, lying to its outer side. It then quits the artery, and passes beneath the tendon of the supinator longus, to reach the back of the hand. The Posterior interosseous nerve separates from the radial at the bend of the elbow, pierces the supinator brevis muscle, and emerges from its lower border on the posterior aspect of the fore-arm, where it divides into branches which supply the whole of the muscles on the posterior aspect of the fore-arm. One branch, longer than the rest, descends to the posterior part of the wrist-joint, where it forms a large gangliform swelling (the common character of nerves which supply joints,) 342 the dissector. from which numerous branches are distributed to the wrist joint. The branches of the Musculo-spiral nerve may be thus arranged:— TT (Muscular, Upper-arm j gpiral cutaneous< t-t J Radial, lore-arm j Posterior interosseous. If we make an analysis of the supply of nerves to the muscles of the upper extremity, from the various sources above described, Ave shall find them disposed according to the following, arrangement:— Deltoid muscle—Circumflex nerve. j j {front—External cutaneous. PP ' \ back—Musculo-spiral. ■r, f front—Median, ulnar, and radial. 1 back—Radial and posterior interosseous. TT /I (front—Median and ulnar. \ back—Radial and ulnar. Posterior Region of the Fore-arm. No new dissection is required for this region: the integu- ment already thrown back from the anterior region is now to be removed altogether, and Avith it the superficial fascia: in this proceeding the posterior ulnar vein may be seen through- out its course, taking its origin inferiorly from the vein of the little finger, " vena salvatella." On the radial side, the radial vein may be observed commencing by the veins on the back of the hand, and Avinding around the radial border of the fore-arm to the bend of the elbow. The posterior branches of the internal cutaneous nerve are distributed along the course of the posterior ulnar vein, and the external cutaneous and spiral cutaneous, on the radial border of the fore-arm. At the lower third of the fore-arm, the radial nerve is seen piercing the fascia, to reach the back part of the hand; and, just above the wrist, the dorsal branch of the ulnar emerges from the fascia to the same destination. On removing the deep fascia, the superficial layer of muscles is brought into vieAV. TnE DISSECTOR. 313 The Supinator longus muscle is placed along the radial border of the fore-arm. It arises from the external condyloid ridge of the hu- Fig.W. The superficial merus, nearly as high as the insertion p^Jeriop ^ecf of the of the deltoid, and is inserted into the fore-arm. base of the styloid process of the ra- dius. This muscle must be divided through the middle, and the two ends turned to either side to expose the next muscle. The Extensor carpi radialis longior arises from the external condyloid ridge below the preceding. Its tendon passes through a groove in the radius, imme- diately behind the styloid process, to be inserted into the base of the metacar- pal bone of the index finger. The Extensor carpi radialis brevior is seen by drawing aside the former muscle. It arises from the external condyle of the humerus, and is inserted into the base of the metacarpal bone of the middle finger. Its tendon is lodged in the same groove of the radius with the extensor carpi radialis longior. 1. The lower part of the biceps. 2. Part of the brachialis anticus. 3. The lower part of the triceps, inserted into the olecranon. 4. The su- pinator longus. 5. The extensor carpi radialis longior. 6. The extensor carpi radialis brevior. 7. The tendons of insertion of these two muscles. 8. The extensor communis digitorum. 9. The eqtensor minimi digiti. 10. The extensor carpi ulnaris. 11. The anconeus. 12. Part of the flexor carpi ulnaris. 13. The extensor ossis metacarpi and extensor primi internodii muscle, lying together. 14. The extensor secundi internodii; its tendon is seen crossing the two tendons of the extensor carpi radialis longior and brevior. 15. The posterior annular ligament. The tendons of the common extensor are seen upon the back of the hand, and their mode of distribution on the dorsum of the fingers. Posterior Aspect.—Superficial Layer: Supinator longus, Extensor carpi radialis longior, ---------carpi radialis brevior, 344 THE dissector. Extensor communis digitorum, ---------minimi digiti, ---------carpi ulnaris, Anconeus, The Extensor communis digitorum arises from the external condyle, and divides into four tendons, which are inserted into the second and third phalanges of the ranlement rf * the finSers- The same peculiarities exist in the extensor tendon up- arrangement of these tendons as was before on the dorsal sur- noticed in the extensor tendons of the foot. face of a finger. Opposite the first phalanx, the tendon (fig. 91. 2.) spreads out so as to form a broad aponeurosis, which covers the whole of the posterior aspect of the finger. At the first joint the aponeurosis divides into three slips. The middle slip, 3., is inserted into the base of the second phalanx, and the two lateral portions are continued onwards on each side of the joint, to be inserted into the last phalanx, 4. Little oblique tendinous slips connect the tendons of this muscle as they cross the back of the hand. The Extensor minimi digiti (auricularis) is an off-set from the extensor communis. It assists in forming the tendinous expansion on the back of the little finger, and is inserted into the last two phalanges. It is to this muscle that the little finger owes its power of separate extension, and from being called into action when the point of the little finger is introduced into the meatus of the ear for the purpose of removing unpleasant sensa- tions, or producing titillation : the muscle was called by the older writers "auricuaris." 1. The metacarpal bone of the middle finger. 2. The extensor tendon expanding into a broad aponeurosis, which divides into three slips. 3. The middle slip, inserted into the base of the second phalanx. 4. The two lateral slips, inserted into the base of the third phalanx. 5. 5. Two dorsal interossei, showing their bifid origin, 6. 6., and inserted by an aponeurotic expansion into the sides of the extensor tendon. 7. The second lumbricalis muscle, also inserted into the side of the extensor tendon. The Extensor carpi ulnaris arises from the external con- the dissector. 345 dyle and the upper two-thirds of the border of the ulna. Its tendon passes through the posterior g2 ^ groove m the ulna, to be inserted intoof mUSCies 0n the posterior the base of the metacarpal bone of the aspect of the fore-arm. little finger. The Anconeus arises from the outer condyle, and is inserted into the olecra- non and triangular surface on the upper extremity of the ulna. When these muscles have been ex- amined, the extensor communis digito- rum and extensor minimi digiti should be removed, and the extensor carpi ul- naris drawn aside, to bring into view the deep layer, which consists of five muscles. Deep Layer. Supinator brevis, Extensor ossis metacarpi pollicis, ---------primi internodii pollicis, ---------secundi internodii pollicis, ---------indicis. The Supinator brevis cannot be seen in its entire extent, until the radial ex- tensors of the carpus are divided from their origin. It arises from the external condyle and external lateral ligament, and winds around the upper part of the radius to be inserted into the upper third of its oblique line. The posterior 1. The lower part of the humerus. 2. The olecranon. 3. The ulna, 4. The anconeus muscle. 5. The supinator brevis muscle. 6. The ex- tensor ossis metacarpi pollicis. 7. The extensor primi internodii pollicis. 8. The extensor secundi internodii pollicis. 9. The extensor indicis. 10. The first dorsal interosseous muscle. The other three dorsal interossei are seen between the metacarpal bones of their respective fingers. interosseous artery and nerve are seen perforating the lower border of this muscle. The Extensor ossis metacarpi pollicis is placed immediately below the supinator brevis. It arises from the ulna, interosse- ous membrane, and radius, and is inserted, as its name implies, 346 the dissector. into the base of the metacarpal bone of the thumb. Its ten- don passes through the groove immediately in front of the styloid process of the radius. The Extensor primi internodii pollicis, the smallest of the muscles in this layer, arises from the interosseous membrane and radius, and passes through the same groove with the ex- tensor ossis metacarpi, to be inserted into the base of the first phalanx of the thumb. The Extensor secundi internodii pollicis arises from the ulna and interosseous membrane. Its tendon passes through a distinct groove in the radius, and is inserted into the base of the last phalanx of the thumb. The Extensor indicis arises from the ulna as high up as the extensor ossis metacarpi pollicis, and from the interos- seous membrane. Its tendon is inserted into the aponeurosis formed by the common extensor tendon of the index finger. When the posterior surface of the lower extremities of the radius and ulna is examined, a number of grooves will be seen, through which the tendons of the muscles of the pos- terior region of the fore-arm pass to their destination upon the hand. In the subject, the posterior annular ligament forms for them a number of distinct sheaths. Their relative position from radius to ulna must be attentively studied. Into the base of the styloid process of the radius is inserted the tendon of the supinator longus. Immediately in front of the styloid process, is a groove which lodges the tendons of the extensor ossis metacarpi and primi internodii; immediately behind it another, broad and shallow, for the tendons of the extensor carpi radialis longior and brevior, which are crossed obliquely by a superficial sheath in the annular ligament for the extensor secundi internodii. Farther inwards is a small groove for the tendon of the extensor indicis, and a large one for the extensor communis. Upon the ulna is a groove for the extensor minimi digiti and extensor carpi ulnaris. They may be thus arranged in a tabular form :— f Extensor ossis metacarpi, \-------- primi internodii. Styloid process, the insertion of the tendon of the supinator longus. ( Extensor secundi internodii, J--------carpi radialis longior, t-------- carpi radialis brevior. the dissector. 347 Extensor indicis. {Extensor communis digitorum, -------- minimi digiti, -------- carpi ulnaris. Actions.—The anconeus is associated in its action with the triceps extensor cubiti: it assists in extending the fore-arm upon the arm. The supinator longus and brevis effect the su- pination of the fore-arm, and antagonize the two pronators. The extensores carpi radialis, longior, and brevior, and ul- naris, extend the wrist in opposition to the two flexors or the carpus. The extensor communis digitorum restores the fingers to the straight position, after being flexed by the two flexors, sublimis and profundus. The extensor ossis metacarpi, primi internodii, and secundi internodii pollicis, are the especial ex- tensors of the thumb, and serve to balance the actions of the flexor ossis metacarpi, flexor brevis, and flexor longus pollicis. The extensor indicis gives the character of extension to the index finger, and is hence named indicator, and the extensor minimi digiti supplies that finger with the power of exercising a distinct extension. Palmar Region. The Muscles of the hand are arranged in three groups : a radial group belonging to the thumb; an ulnar group to the little finger; and a palmar group situated in the middle of the palm of the hand. The muscles of the Radial group are the Abductor pollicis, Flexor ossis metacarpi (opponens,) Flexor brevis pollicis, Abductor pollicis. The Abductor pollicis arises from the scaphoid bone and annular ligament. It is inserted into the base of the first phalanx. Cut this muscle from its origin, and turn it upwards; you will then see The Flexor ossis metacarpi (opponens ;) it arises from the trapezium and annular ligament, and is inserted into the whole length of the metacarpal bone. The flexor ossis metacarpi may now be divided from its origin and turned aside, in order to show the next muscle. The Flexor brevis pollicis consists of two portions, between 348 THE DISSECTOR. AA'hich lies the tendon of the flexor longus pollicis. The ex- ternal portion arises from the trapezium and annular liga- ment ; the internal portion from the trapezoides and os magnum. They are both inserted into the base of the first phalanx of the thumb, having a sesamoid bone in each of their tendons to protect the joint. Fig. 93. 1. The annular ligament. 2. 2. The origin and insertion of the abductor pollicis muscle; the middle portion has been removed. 3. The flexor ossis metacarpi, or opponens pollicis. 4. One portion of the flexor brevis pollicis. 5. The deep portion of the flexor brevis pollicis. 6. The adductor pollicis. 7. 7. The lumbricales muscles, arising from the deep flexor tendons, upon which the numbers are placed. The tendons of the flexor sublimis have been removed from the palm of the hand. 8. One of the tendons of the deep flexors passing between the two terminal slips of the tendon of the flexor sublimis to reach the last phalanx. 9. The tendon of the flexor longus pollicis, passing between the two portions of the flexor brevis to the last phalanx. 10. The abductor minimi digiti. 11. The flexor brevis minimi digiti. The edge of the flexor ossis metacarpi, or adductor minimi digiti, is seen projecting beyond the inner border of the flexor brevis. 12. The prominence of the pisiform bone. 13. The first dorsal interosseous muscle. The Adductor pollicis is a triangular muscle; it arises from the os magnum and metacarpal bone of the middle finger; the fibres converge to its insertion into the base of the first phalanx. Ulnar group. The muscles of the little finger are the Abductor minimi digiti, THE DISSECTOR 349 Flexor brevis minimi digiti, Flexor ossis metacarpi (adductor). On removing the integument from the ball of the little finger, a thin layer of muscular fibres is found between the two layers of superficial fascia. This is the Palmaris brevis. Its fibres arise from the palmar fascia, and pass transversely inwards to be inserted into the integument on the inner bor- der of the hand. When the superficial and deep fascia is removed, the Ab- ductor minimi digiti will be seen arising from the pisiform bone. It is inserted into the base of the first phalanx of the little finger. The Flexor brevis minimi digiti arises from the unciform bone and annular ligament, and is inserted into the base of the first phalanx. The Flexor ossis metacarpi (adductor,) arises from the un- ciform bone and annular ligament, and is inserted into the Avhole length of the metacarpal bone of the little finger. Middle palmar region.—The muscles in this region are the Lumbricales, t , . f palmar 3. Inter0SSeii dorsal 4. The Lumbricales, four in number, are accessories to the deep flexor muscles. They arise from the radial side of the tendons of the deep flexor, and are inserted into the aponeu- rotic expansion of the extensor tendons (fig. 91. 7.) on the radial side of the fingers. The Palmar interossei, three in number, are placed upon the metacarpal bones, rather than between them. They arise from the base of the metacarpal bone of one finger, and are inserted into the base of the first phalanx and aponeurotic expansion of the extensor tendon of the same finger. The first (fig. 94. 4.) belongs to the index finger; the second, 6., to the ring finger; and the third, 8, to the little finger. The middle finger being excluded. On turning to the dorsum of the hand, the four dorsal in- terossei are seen in the four spaces between the metacarpal bones. They are bipenniform muscles, (fig. 91. 5. 5.,) and arise by two heads, 6. 6., from the adjoining sides of the base of the metacarpal bones. They are inserted into the base of the first phalanges, and aponeurosis of the extensor tendons. The first (fig. 94. 3.) is inserted into the index finger, and 30 350 THE DISSECTOR. from its use is called abductor indicis; the second and third (fig. 91. 5. 5., fig. 94. 5. 5.,) are inserted into the middle finger, compensating its exclusion from the palmar group; the fourth, (fig. 94. 7.) is attached to the ring finger; so that each finger is provided with two interossei, with the exception of the little finger, as may be shoAvn by a table. T j j. ( one dorsal, (abductor indicis,) fiq. 94. 3. index finger < , kj: c\a a J a \ one palmar, fig. 94. 4. Middle finger, two dorsal, fig. 94. 5. 5. -n ■ jj f one dorsal, fig. 94. 6. 9 J " y one palmar, fig. 94. 7. Little finger, remaining palmar, fig. 94. 9. Fig. 94. A diagram showing the abductor and adductor muscles of the hand, and the attachments and actions of the interossei. The middle finger is made longer than the rest, in order to mark the central axis of the hand, to which the movements of abduction and adduction are referrible. The dotted lines represent the six abductor muscles, and the plain lines the four adductors. 1. The abductor pollicis, arising from the scaphoid bone. 2. The adductor pollicis, arising from the whole length of the middle metacarpal bone. 3. The first dorsal interosseus, the abductor of the index finger: all the dorsal interossei arise by two heads, as is seen in the diagram. 4. The first palmar interosseous, the adductor of the index finger. 5. 5. The second and third dorsal interossei muscles, both abductors of the middle finger. 6. The second palmar interosseous, adductor of the ring-finger. 7. The fourth dorsal in- terosseus, abductor of the ring-finger. 8. The third palmar interosseous, adductor of the little finger. 9. The abductor of the little finger, arising from the pisiform bone. The radial artery passes into the palm of the hand between the two heads of the first dorsal interosseous muscle and the THE DISSECTOR. 351 perforating branches of the deep palmar arch, between the heads of the other dorsal interossei. Actions.—The actions of the muscles of the hand are ex- pressed in their names. Those of the radial group belong to the thumb, and provide for three of its movements, abduction, adduction wa(\ flexion. The ulnar group, in like manner, are subservient to the same motions of the little fingers, and the interossei are abductors and adductors of the second finger. The lumbricales are accessory in their actions to the deep flexors: they were called by the earlier anatomists, fiducinae, i. e., fiddlers' muscles, from an idea that they might effect the fractional movements by which the performer is enabled to produce the various notes on that instrument. In relation to the axis of the hand, (fig. 94.,) the four dor- sal interossei are abductors, and the three palmar, adductors. It will, therefore, be seen that each finger is provided with its proper adductor and abductor, two flexors, and (with the ex- ception of the middle and ring fingers) tAvo extensors. The thumb has moreover a flexor and extensor of the metacarpal bone; and the little finger a flexor of the metacarpal bone without an extensor. CHAPTER X. THE LOWER EXTREMITY. Before commencing the dissection of the lower extremity, the student will carefully reflect upon the objects of his pro- posed dissection, and particularly upon the practical applica- tion of the information Avhich he is seeking to acquire. The lower extremity comprises all that portion of the body which forms the loAver limb, and is bounded above by the external surface of the pelvis. It consists of a thigh, leg, and foot— of the hip, knee, ankle, tarsal, metatarsal, and digital joints —of a complicated apparatus of muscles—of the femoral, popliteal, tibial, pedal, and plantar arteries—of veins, lymph- atics, nerves, bones, and ligaments. Now all these structures are liable to injury; and the sur- geon, upon such an occurrence, is called upon to remedy the accident—to apply the knowledge that he shall have gained, 352 THE DISSECTOR. Fig.95. The thigh turned upon its outer side as in through the aid of his eyes and hands, in the dissecting room. Suppose the accident be one involving deep and im- portant parts Avithout affecting the surface, or exposing to the eyes the structure which may be injured : in such a case the surgeon has recourse to the comparative form and position of the adjoining limb ; but circumstances may render this comparison unavailing; and he is then obliged to recall the ob- ,9.-1 dissecting it servations he may chance to nave made during his anatomical studies. Depend upon it, that a sound knowledge of the relations of the different portions of the limb Avill ever be found of the highest possible value to the practitioner who is suddenly called to the aid of a wounded fellow-creature. Indeed, such a knoAV- ledge should be considered as the leading characteristic of the accomplished sur- geon. Starting with reflections such as these, the student will perceive that other ob- servations are necessary to him in addi- tion to those which arise out of the mere dissection of the component parts of the limb which he is about to study. The thigh may be dislocated at the hip, or at the knee ; the muscles, or their tendons, may be ruptured; the arteries may be wounded or diseased, requiring that in- cisions of considerable extent or depth should be made in their course, and a ligature placed around them; or nerves may be ganglionated, and demand re- moval; lastly, the whole limb may be disorganized, and call for amputation. 1. A line drawn from the anterior superior spine of the ilium to the spine of the pubis ; these two points are represented by crosses. 2. A second line extended from the middle of the preceding to the tubercle on the inner con- dyle of the femur. This line marks the direction of the femoral artery. 3. A third line, drawn from the spine of the pubis to the tubercle on the inner condyle of the femur. 4. A fourth line drawn from the spine of the ilium to the middle of line three; this line marks the upper border of the sarto- rius muscle, and is the direction for the incision in securing the artery in the upper third of its course. 5. The outline of the sartorius muscle. 6. THE DISSECTOR. 353 The direction of the incision in operating upon the femoral artery, below the sartorius muscle, shown by a dotted line. 7. A line drawn from the trochan- ter major to the spine of the ilium. 8. Another line drawn from the tro- chanter major to the crest of the ilium. 9. The interni'l saphenous vein. 10. The superficial epigastric and superficial circumflexa ilii veins, convei g- ing to open into it previously to its entrance into the saphenous opening. 11. The saphenous opening in the fascia lata. 12. The external cutaneous nerve. 13. The middle cutaneous nerves, branches of the interior crural. In each and every of these circumstances, relief is simply and effectually bestowed, if the operator be Avell acquainted with the situation and dissection of the various structures which may be implicated in the accident or disease; and these are to be learnt only in the dissecting room by careful ob- servation and manipulation. Having the loAver extremity extended on the table before him, and the leg everted, let the student carry a line (fig. 95. 1.) from the extreme point of the anterior superior spinous process of the ilium to the symphisis pubis, and then another, 2. from the middle of the preceding to that projection upon the inner condyle of the femur, which gives attachment to the internal lateral ligament of the knee-joint; this will mark the course of the femoral artery. If the leg be perfectly straight, without inversion or eversion, the line must be carried to the apex of the patella. Again, if a line, 3., be drawn from the spinous process of the pubis along the inner border of the •thigh to the projection on the internal condyle, a second line, 4., drawn from the anterior superior spinous process of the ilium, and crossing the former at the middle of the thigh, will mark the direction of the upper margin of the sartorius mus- cle, and enclose a triangular space, which is bounded above by Poupart's ligament. Within this triangle, the femoral artery may be laid bare and secured, in any part of the line 2. Avhich marks its course; the usual situation for ligature of the femoral artery, in popliteal aneurism, being at the point where the upper margin of the sartorius crosses its course, the border of this muscle forming the natural guide for the direction of the incision. At the pubic angle of this trian- gular space, is situated the saphenous opening, 11., through Avhich the sac of femoral hernia is protruded. In rare cases, the femoral artery is tied below the lower border of the sar- torius muscle; under such circumstances, a space, varying from one inch to one inch and a half, and parallel to the ob- lique line, should be allowed for the breadth of the sartorius, 354 THE DISSECTOR. and the incision commenced immediately below this border, 6., still following the original line of its course. Besides these, there is another point of equal importance to the surgeon, in the consideration of the proper projections on the surface of the limb, viz., the apophysis named trochan- ter major. For it is this prominence that marks the altered position of the limb in dislocations or diseases of the hip- joint, or fractures about the neck of the femur. It is a point liable to variation from strength or muscularity of the limb; but is necessarily more prominent and more sharply defined in an emaciated individual. A line, 8. drawn from the upper point of the trochanter major, to the most convex part of the crest of the ilium, and another, 7., extended from the same point to the anterior superior spinous process, may be com- pared with the same admeasurements on the opposite limb. An important measurement of the thigh, for the detec- tion of dislocation, is obtained by extending a line from the anterior superior spinous process of the ilium to the apex of the patella, and comparing its length with that on the opposite limb. If shortening be found to exist, whilst the distance, 8., betAveen the trochanter major and the crest of the ilium is the same on both sides of the body, then the cause of the diminution of length must exist in the bone, and be the result of fracture. This may be determined by another admeasurement, made between the apex of the trochanter major and the lower point of the patella. Let it not be said that these directions are too obvious to deserve attention ; they must be followed carefully; and be- fore the student commence his dissection, he should have himself made and repeated the observations here advised; have impressed well upon his memory the relative position of each landmark; and have cut down upon the artery at various points. By such means he will gain confidence in his know- ledge and precision in the performance of surgical operations. Again, in displacement of the ends of the bone from fracture of the femur, it is of the greatest importance to their proper adjustment, that he be -well acquainted Avith the position of the patella in relation to the spines of the ilium and pubis. The lower extremity is divided anatomically into several distinct compartments or regions, the separate and relative study of which serves materially to facilitate the student's apprehension of the whole. The regions of the thigh are, THE DISSECTOR. 355 the anterior femoral, internal femoral, gluteal, posterior femoral, and popliteal; of the leg, the anterior tibial, fibular, sural, or superficial posterior tibial, and deep posterior tibial; of the foot, the dorsal and plantar regions. Anterior Femoral Region. The dissection of the anterior femoral region is best com- menced by making an incision (fig. 95. 1.) from the anterior superior spinous process of the ilium along the line of Pou- part's ligament to the spinous process of the pubis, then carry- ing a second, 2. along the course of the femoral artery to the inner condyle of the femur, and bounding it inferiorly by a third, carried transversely across the head of the tibia. The student then nips up the integument with his forceps at the upper angle, and dissects back that layer so as to expose the superficial fascia, beneath, and form a broad flap upon the outer side of the limb. He then turns to the opposite side, and repeats the same proceeding. But the student Avho handles a scalpel for the first time, will not find its application so easy as this description would lead him to infer. If he examine the edge of his blade at- tentively with a lens, he will perceive that it is actually a microscopic saw. Now a saw divides by being drawn across the material to be. cut; and no direct force applied to the 'saw, would carry it through the substance without this mo- tion. Let him apply this reasoning to his scalpel, it must be handled lightly, and drawn without pressure across the tex- tures to be divided: if he use force and pressure, the best edge Avould be useless in his hands. The art of dissecting with neatness and operating Avith dexterity, owes much to the good understanding existing betAveen the knife and the hand; and the best operators have ever been the best dissectors. If the student have reflected the integument well, he will have exposed the superficial fascia, which may be known by its soft yellow surface, studded with vesicles of fat, sur- rounded with the white areolae of cellular tissue in which they are contained. The under surface of the integument, the corium of the skin, will appear quite white, and present a number of depressions, corresponding with the fatty deposi- tions in the superficial fascia. The superficial fascia is composed of two layers, between which are situated the cutaneous vessels and nerves. To ex- 356 THE DISSECTOR. amine these, incisions may be made through its superficial layer in the same direction with those previously described, and this structure dissected back. The parts to be examined in the superficial fascia are Inguinal glands, Superficial circumflexa ilii artery, ---------epigastric artery, --------- external pudic artery, Internal saphenous vein, and its tributaries, External, middle, and internal cutaneous nerves. The inguinal glands are situated in clusters along the line .of Poupart's ligament, and near the termination of the saphenous vein. They receive the cutaneous lymphatic vessels from the loAver extremity, lower part of the abdomen, and genital organs. The three small arteries, the superficial circumflexa ilii, the superficial epigastric, and the superficial external pudic, are the first branches of the femoral artery. They pierce the deep fascia immediately beneath Poupart's ligament, and are distributed to the skin and superficial fascia ; the circumflexa ilii taking its course along Poupart's ligament towards the crest of the ilium ; the epigastric ascending upon the abdomen towards the umbilicus; and the pudic passing inwards to the scrotum, or labia pudendi. The internal saphenous vein, fig. 95. 9.; (aa^M^, perspicu- ous, obvious) of considerable size, sometimes consisting of two parallel trunks, receives its current of blood from the superficial veins of the inner side of the foot, leg and thigh, along which it runs, and terminates in the femoral vein near the pubic extremity of Poupart's ligament, by passing through an aperture in the deep fascia, named from this office, saphe- nous opening, 11. Just as the vein curves inwards to enter this opening, it receives a number of small veins, 10., which converge from the abdomen, hip, and genital organs. These vessels play a conspicuous part in femoral hernia, and, there- fore, must not be passed over without remark. The saphenous vein is accompanied by superficial lymphatic vessels through- out the whole of its course. The external cutaneous nerve, fig. 95. 12. (cutis, the skin) is derived from the second lumbar nerve, and pierces the fascia lata at .about tAvo inches beloAV the anterior superior spine of the ilium, where it divides into two sets of branches, THE DISSECTOR. 357 one of which crosses the tensor vaginae femoris muscle to the outer and posterior side of the thigh; the other, consisting of tAvo or three nerves, is distributed along the external and anterior border of the thigh, as far as the knee. The middle cutaneous nerves, 13, two or three in. number, are branches of the anterior crural nerve: they pierce the deep fascia, at variable distances, below Poupart's ligament, to be distributed to the superficial fascia and integument on the front of the thigh as low down as the knee. The internal cutaneous nerve is the crural division of the genito-crural nerve; it pierces the* deep fascia at about four inches below Poupart's ligament, and runs doAvn the inner side of the thigh towards the knee. When these structures have been well examined, the deep layer of superficial fascia may be removed, in order to bring into view the deep fascia. The deep fascia of the thigh, from being the most extensive in the body, is named fascia lata (latus, broad). It is an ex- tremely dense membrane, consisting of glistening tendinous fibres, disposed longitudinally and circularly around the limb; is thickest upon the outer side of the thigh, and thinner upon its inner side. The fascia lata envelopes the whole of the muscles of the thigh, and sends processes inwards, which form distinct sheaths for. each. It is attached above to the promi- nent points about the pelvis, viz., to the pubis, Poupart's liga- ment, crest of the ilium, sacrum, and ischium; below, to the condyles of the femur and patella; and behind, to the linea aspera. Besides these, it has two muscular attachments, one by means of the tensor vaginae femoris ; the other through the gluteus maximus. It is perforated at several points for the passage of the cutaneous nerves, and near to the pubis is the saphenous opening. The existence of this opening, fig. 95. 11., causes the di- vision of the upper part of the fascia lata into two portions, an iliac portion situated toAvards the ilium, and a pubic por- tion towards the pubis. The iliac portion is attached along Poupart's ligament, as far as the spine of the pubis ; from this point it is reflected downwards, in a curved direction, forming a sharp edge, called the falciform process (falx, a sickle). The edge of the falciform process immediately overlays and is re- flected upon the sheath of the femoral vessels; and the loAver extremity of the curve is continuous Avith the pubic portion. 358 THE DISSECTOR. The pubic portion is also attached to the spine of the pubis, and along the pectineal line, as far as the inner border of the psoas muscle ; here it divides into two layers, which embrace that muscle and the iliacus, and are then lost in the facial coverings surrounding the different muscles on the outer side of the thigh. From this description it will be obvious that the iliac por- tion, being attached to Poupart's ligament, must be on a plane considerably anterior to the pubic portion, which is attached to the bone; and it is between the two that the femoral vessels are placed, enclosed in their sheath. It follows also from this disposition that the saphenous opening is oblique in its direction with regard to these two layers of fascia. It is, moreover, closed by some dense cellular tissue, which is per- forated by a number of minute openings for the transmission of the superficial lymphatic vessels of the lower extremity. and is hence named cribriform fascia (cribrum, a sieve). This cribriform fascia would be altogether unAvorthy the notice of the dissector, were it not for the arbitrary importance at- tached to every fibre of membrane or process of fascia that may possess the slightest relation to the protrusion of intes- tine from the cavity of the abdomen. For this reason it is that the saphenous opening is so urgently recommended to the student's attention ; and the cribriform fascia, from its posi- tion, must necessarily form one of the coverings of the femo- ral hernia. The student may now remove the fascia lata, by dissecting it from its loose cellular attachment to the muscles, following ahvays the course of their fibres. If the student would dissect well, he must treasure this rule as a golden maxim,—" muscles must always be dissected in the course of their fibres." And, let us remind him again (for Ave cannot too strenuously insist upon the application of the principles of dissection to the operations of surgery) that, in the living body, the same rule must be rigidly adhered to, if a success- ful issue be desired. THE DISSECTOR. 359 Muscles of the Anterior Femoral Region. The muscles of the anterior femoral region are arranged in two groups, an anterior group, consisting of six muscles— Tensor vaginae femoris, Vastus internus, Sartorius, Vastus externus, Rectus, Crureus. And an internal group of seven, viz :— Iliacus internus, Adductor brevis, Psoas magnus Adductor magnus, Pectineus, Gracilis. Adductor longus, As soon as these two tables are got by heart, the student may commence the dissection of the muscles which they re- present. Anterior group.—The Tensor vaginae femoris (stretcher of the sheath of the thigh) is a short flat muscle, situated on the outer side of the hip. It arises from the crest of the ilium, near to its anterior superior spinous process, and is in- serted between two layers of the fascia lata at about one-third down the thigh. The Sartorius (tailor's muscle) is a long riband-like muscle, arising from the curved notch, between the anterior superior, and anterior inferior spinous processes of the ilium : it crosses obliquely the upper third of the thigh, descends behind the inner condyle of the femur, and is inserted by an aponeurotic expansion into the inner tuberosity of the tibia. This expan- sion covers in the insertion of the tendons of the gracilis and semitendinosus muscles. The upper border of the sartorius muscle is the guide to the operation for tying the femoral artery in the middle of its course. The Rectus (straight) muscle is fusiform in its shape and bipenniform in the disposition of its fibres: it arises by two round tendons—one from the anterior inferior spinous process of the ilium, the other from the upper lip of the acetabulum. It is inserted by a broad and strong tendon into the upper 360 THE DISSECTOR. region. border of the patella. It is more correct to consider the pa- tella as a sesamoid bone, developed within ofSaLSrmotl^ tendon of the rectus; and the liga- mentum patellae as the continuation of the tendon to its insertion into the spine of the tibia. The rectus must now be divided through its middle, and the two ends turned aside, to bring clearly into vieAV the next muscles. The three next muscles are generally considered collectively under the name of triceps extensor cruris. Adopting this view, the muscle surrounds the whole of the femur, except the rough line (linea as- pera) upon its posterior aspect. Its divi- sion into three parts is not well defined; the fleshy mass upon each side being dis- tinguished by the names of vastus inter- nus and externus, the middle portion by that of crureus. The Vastus externus, narrow below and broad above, arises from the outer border of the patella, and is inserted into the femur and outer side of the linea as- pera, as high as the base of the trochanter major. The Vastus internus, broad below and narrow above, arises from the inner border of the patella, and is inserted into the fe- mur and inner side of the linea aspera as high up as the trochanter minor. 1. The crest of the ilium. 2. Its anterior superior spinous process. 3. The gluteus medius. 4. The tensor vaginae femoris; its insertion into the fascia lata is shown inferiorly. 5. The sartorius. 6. The rectus. 7. The vastus externus. 8. The vastus internus. 9. The patella. 10. The iliacus internus. 11. The psoas magnus. 12. The pectineus. 13. The adductor longus. 14. Part of the adductor magnus. 15. The gracilis. The Crureus (crus, the leg,) arises from the upper border of the patella, and is inserted into the front aspect of the femur, as high as the anterior inter-trochanteric line. When the crureus is divided from its insertion, a small mus- cular fasciculus is often seen upon the lower part of the femur, THE DISSECTOR. 361 which is inserted into the pouch of synovial membrane, that extends upwards from the knee-joint, behind the patella. This is named, from its situation, subcrureus, and would seem to be intended to support the synovial membrane. Actions.—The tensor vagina femoris renders the fascia lata tense, and slightly inverts the limb. The sartorius flexes the leg upon the thigh, and continuing to act, the thigh upon the pelvis, at the same time carrying the leg across that of the opposite side, into the position in which tailors sit; hence its name. Taking its fixed point from below, it assists the extensor muscles in steadying the leg for the support of the trunk. The other four muscles have been collectively named quadriceps extensor, from their similarity of action. They extend the leg upon the thigh, and obtain a great increase of power by their attachment to the patella, which acts as a ful- crum. Taking their fixed point from the tibia, they steady the femur upon the leg, and the rectus, by being attached to the pelvis, serves to balance the trunk upon the lower ex- tremity. Internal group.—The origins of the iliacus and psoas muscle being situated within the abdomen, the entire muscles cannot be seen in this dissection; but as a part of them quit that cavity to be inserted into the femur, that portion neces- sarily belongs to the anatomy of the thigh. The Iliacus internus is a flat, radiated muscle : it arises from the inner concave surface of the ilium, and, after joining with the tendon of the psoas, is inserted into the trochanter minor of the femur. The Psoas magnus (4-00, lumbus, a loin,) situated by the side of the vertebral column in the loins, is a long fusiform muscle. It arises from the intervertebral substances, part of the bodies and bases of the transverse processes, and from a series of tendinous arches thrown across the constricted por- tion of the last dorsal and four upper lumbar vertebrae. These arches are intended to protect the lumbar arteries and sym- pathetic filaments of nerves from pressure, in their passage beneath the muscle. The tendon of the psoas magnus unites with that of the iliacus, and the conjoined tendon is inserted into the posterior part of the trochanter minor. Two synovial bursae are found in relation Avith the last two muscles : the first of considerable size is situated between their under surface and the border of the pelvis; the other much 31 362 THE DISSECTOR. smaller is interposed between the conjoined tendon and the anterior part of the trochanter minor. The Pectineus is the flat quadrangular muscle which arises from the pectineal line (pecten, a crest) of the os pubis, and is inserted into the line leading from the trochanter minor to the linea aspera. The Adductor longus (adducere, to draw to,) the most su- perficial of the three adductors, arises by a round tendon from the angle of the os pubis, and, assuming a flattened form, is inserted into the middle third of the linea aspera. The pectineus must be divided near its origin and turned outwards, and the adductor longus through its middle, turning its ends to either side to bring into view the adductor breAris. The Adductor brevis, placed beneath the pectineus and ad- ductor longus, is fleshy, and thicker than the adductor longus: it arises from the body and ramus of the os pubis, and is in- serted into the upper third of the linea aspera. It is pierced by the middle perforating artery, and supports the anterior branch of the obturator nerve and artery. The adductor brevis may now be divided from its origin and turned outwards, or its inner two-thirds may be cut away en- tirely, after separating the anterior branches of the obturator artery and nerve from its surface. This exposes the entire extent of the adductor magnus, and a fleshy mass of muscle which covers in the obturator foramen,—the obturator ex- ternus. The Obturator externus muscle (obturare, to stop up,) arises from the obturator membrane, and from the surface of bone immediately surrounding it, viz., from the body and ramus of the os pubis and ischium: its tendon passes behind the neck of the femur, to be inserted with the external rotator muscles, into the digital fossa of the trochanter major. Although this muscle belongs properly to another group (glutaeal region,) it has been deemed consistent Avith the object of this work to describe every organ which may come beneath the observation of the student in the progress of his dissection, in the precise situation which it actually occupies. The Adductor magnus is a broad and extensive muscle, forming a septum of division between the muscles situated on the anterior, and those on the posterior aspect of the thigh. It arises by fleshy fibres from the ramus and side of the tube- rosity of the ischium, and radiating in its passage outwards, THE DISSECTOR. 363 is inserted into the whole length of the linea aspera, and inner condyle of the femur. The adductor magnus is pierced by five openings : the three superior, for the three perforating arteries, and the fourth for the termination of the profunda. The fifth is the large, oval opening in the tendinous portion of the muscle, that gives passage to the femoral vessels. The Gracilis (slender) is situated along the inner border of the thigh: it arises by a broad, but very thin, tendon, from the edge of the ramus of the pubis and ischium, and is inserted by a rounded tendon into the inner tuberosity of the tibia, beneath the expansion of the sartorius. Actions. — The iliacus, psoas, pectineus, and adductor longus muscles bend the thigh upon the pelvis, and, at the same time, from the obliquity of their insertion into the lesser trochanter and linea aspera, rotate the entire limb outwards: the pectineus and adductors adduct the thigh powerfully; and, from the manner of their insertion into the linea aspera, they assist in rotating the limb outwards: the gracilis is like- wise an adductor of the thigh, but contributes also to the flexion of the leg, by its attachment to the inner tuberosity of the tibia. Vessels of the Thigh. The arteries of the anterior aspect of the thigh are next to be examined : they are best dissected by following the branches through their ramifications from the main trunk. The scalpel may be carried along the side of their cylinder without danger of dividing their coats; but if it be turned in the opposite direction, they must inevitably be cut across. They are easily separated from the cellular tissue and adipose substance, and from the smaller veins which surround them. All the veins, excepting the main trunks, had better be re- moved at once, otherwise their intricacy and bleeding will greatly interfere with the student's progress, and confuse his dissection. Femoral Artery. The arteries situated on the anterior aspect of the thigh are the femoral and its branches: they may be thus ar- ranged :— Femoral artery. Branches. Superficial circumflex ilii. 364 THE DISSECTOR. Superficial epigastric. --------- external pudic. Deep external pudic. ( External circumflex. Profunda. < Internal circumflex. ( Three or four perforating. Muscular. Anastomotica magna. The femoral artery and vein are enclosed in a sheath of con- „ „„ . . x. densed cellular substance. The sheath Fig. 97. A view of the ., , ,„ ,, j r i, anterior and inner aspect is broad andfunnel-shaped above, but of the thigh, showing the narrows considerably in its descent, and course and branches of the Decomes more closely applied about the femoral artery. vessels. At the upper third of the thigh, two nerves become placed upon the sheath: these are the long and short saphenous branches of the ante- rior crural nerve. The larger of the two pierces the sheath and accompanies the femoral vessels within its interior. The smaller lies upon the sheath till \ti arrives opposite the vastus internus muscle, to which it is distributed. Operation.—These nerves are found to observe the above relation to the femoral artery, in the operation for tying that vessel. The integument is first divided, then the superficial fascia, next the deep fascia; then the edge of the sartorius muscle is drawn aside, and the sheath of the vessels exposed, upon which lie these two saphenous nerves, and the operator is careful in opening the sheath to avoid injuring them. The Femoral artery runs down the inner side of the thigh, from Pou- part's ligament, at a point exactly mid- way betAveen the anterior superior spi- nous process of the ilium and symphisis pubis, to the hole in the adductor mag- THE DISSECTOR. 365 1. The lower part of the aponeurosis of the external oblique muscle ; its inferior margin is Poupart's ligament. 2. The external abdominal ring. 3, 3. The upper and lower part of the sartorius muscle ; its middle portion having been removed. 4. The rectus. 5. The vastus internus. 6. The patella. 7. The iliacus and psoas ; the latter being nearest the artery. 8. The pectineus. 9. The adductor longus. 10. The tendinous canal for the femoral artery formed by the adductor magnus, and vastus interims muscles. 11. The adductor magnus. 12. The gracilis. 13. The tendon of the semi- tendinosus. 14. The femoral artery. 15. The superficial circumflexa ilii artery taking its course along the line of Poupart's ligament, to the crest of the ilium. 2. The superficial epigastric artery. 16. The two external pudic arteries, superficial and deep. 17. The profunda artery giving off 18, its external circumflex branch; and lower 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 deep external pudic artery. 19. The anasto- motica magna, descending to the knee, upon which it ramifies (6.) nus, at the junction of the middle with the inferior third of the thigh. The femoral vein is at first to the inner side, and upon the same plane with the artery, but loAver down ; the vein becomes placed behind the artery, and retains that rela- tion throughout the rest of its course. Relations.—The upper third of the femoral artery is su- perficial, being covered only by the integument and superfi- cial and deep fasciae. The lower two-thirds are covered by the sartorius muscle. To its outer side the artery rests first against the psoas, next against the rectus, then against the vastus internus. Behind it has, first, the body of the pubis, then the tendon of the psoas and iliacus; it is next separated from the pectineus by the femoral vein, profunda vein and artery, and then lies on the adductor longus to its termina- tion : near the lower border of the adductor longus, it is placed in an aponeurotic canal, formed by an arch of tendi- nous 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. Branches.—The superficial circumflexa ilii, superficial epi- gastric, superficial and deep external pudics, are four small arteries given off from the femoral, immediately below Pou- part's ligament. The distribution of the first three has been described at page 355. The superficial epigastric and super- ficial pudic are important, from their connexion with hernial tumours occurring in this region: we have seen both of them crossing an inguinal, and the latter ramifying upon a femoral hernia. In the operation they are liable to division; but, from their small size, would cause very little inconvenience. 31* 366 THE DISSECTOR. The deep external pudic is so named from being placed be- neath the fascia lata : it is given off from the femoral about an inch beloAV the superficial pudic, and, at the inner border of the thigh, pierces the fascia, to be distributed to the inte- guments of the scrotum and labium pudendi. The Profunda femoris artery is given off from the femoral, at two inches below Poupart's ligament. From its large size, it may be considered as a division of the femoral rather than a branch: and, in this vieAV, the short trunk has been called the common femoral, (femoralis communis,) and its two divi- sions, femoralis superficialis and femoralis profunda; the su- perficial femoral being intended for the supply of the knee and leg, while the profunda is distributed to the thigh. The profunda artery is best examined by removing the superficial femoral, and dissecting away the femoral and profunda veins, that conceal the artery from view. The adductor longus would also be dissected from its insertion with advantage. The Course of the profunda artery is downwards and back- wards, and a little outwards, behind the adductor longus muscle: it then pierces the adductor magnus, and is distributed to the ham-string muscles. Relations.—It rests successively upon the conjoined tendon of the psoas and iliacus, the pectineus, adductor brevis, and adductor magnus muscles. To its outer side, the tendinous insertion of the vastus internus muscle intervenes between it and the femur, and in front it is separated from the femoral artery above by the profunda vein and femoral vein; and below by the adductor longus muscle. The branches of the profunda artery are the external cir- cumflex, internal circumflex, and three perforating arteries. The External circumflex artery passes outwards between the divisions of the crural nerve, then between the rectus and crureus muscles, and divides into three branches ; ascending, which inosculates Avith the terminal branches of the gluteal artery ; descending, which inosculates with the superior ex- ternal articular artery; and middle, which continues the ori- ginal course of the artery around the thigh, and anastomoses with branches of the ischiatic, internal circumflex, and supe- rior perforating arteries. It supplies the muscles on the an- terior and outer side of the thigh. r * The Internal circumflex artery winds around the inner side of the neck of the femur, passing between the pectineus and THE DISSECTOR. 367 psoas, and along the border of the external obturator muscle, to the space between the quadratus femoris and upper border of the adductor magnus, Avhere it anastomoses with the ischi- atic, external circumflex, and superior perforating arteries. It supplies the muscles on the upper and inner side of the thigh, anastomosing with the obturator artery, and sends a small branch through the notch in the acetabulum into the hip-joint. The Superior perforating artery passes backwards between the pectineus and adductor brevis, pierces the adductor mag- nus, and is distributed to the posterior muscles of the thigh ; inosculating freely with the circumflex and ischiatic arteries, and with the branches of the middle perforating artery. The Middle perforating artery pierces the adductor brevis and magnus, and is distributed like the superior; inosculating with the superior and inferior perforantes. It gives off the nutritious artery of the femur. The Inferior perforating artery is given off below the ad- ductor brevis, and pierces the adductor magnus, supplying it and the flexor muscles, and inosculating with the middle per- forating artery above, and the articular branches of the po- pliteal below. It is through the medium of these branches, that the collateral circulation is maintained in the limb after ligature of the femoral artery. We now return to the superficial femoral: its muscular branches are distributed on either side to the adjacent muscles. The Anastomotica magna arises from the femoral, while in the tendinous canal formed by the adductors and vastus in- ternus. It runs along the tendon of the adductor magnus to the inner condyle, and inosculates with the superior internal articular artery: some of its branches are distributed to the vastus internus muscle, and the crureus, and terminate by anastomosing with the descending branches of the external circumflex and superior external articular artery. When the pectineus muscle is divided through its origin and turned down, a small artery will be seen issuing from the opening in the upper part of the obturator membrane; this is the obturator artery, a branch of the internal iliac. The Obturator artery, after passing through the obturator foramen, divides into two branches ; anterior, which rests upon the adductor brevis, supplying that muscle, together with the pectineus and adductor longus : and posterior, which 368 THE DISSECTOR. folloAvs the direction of the obturator externus muscle to the space betAveen the gemellus inferior and quadratus femoris, Avhere it inosculates with the ischiatic artery. It sends a branch through the notch in the acetabulum to the hip-joint. The Veins in this region, as in every other of the body, are superficial and deep. The superficial, are the internal saphenous, and its tributaries. The deep, are the femoral and profunda, Avith their tributaries. The femoral vein commences at the hole in the adductor magnus, and ascends behind the artery to within two inches of Poupart's ligament, where it receives the profunda vein; it then becomes placed to the inner side of the artery, and continues in that position to Poupart's ligament. After passing beneath the ligament, it receives the name of external iliac vein. The profunda vein, commencing with the ultimate ramifications of the profunda artery, ascends in front of that vessel to its origin from the common femoral artery, when it joins the femoral vein. The tributary veins are those accompanying the branches of the main arteries. They are usually two to each branch, one on either side ; hence they are called venae comites. They com- municate freely across the cylinder of the artery by short transverse trunks. Veins are considerably larger than the arteries which they accompany. Nerves of the Anterior Femoral Region. The student will noAv direct his attention to the nerves of this region, fig. 98. They are all derived from the lumbar plexus: and are the External cutaneous, Genito-crural, ( Cutaneous branches, Crural. < Muscular, ( Saphenous. Obturator. The External cutaneous nerve, 4., is described with the superficial layer at page 357. The crural portion of the genito-crural nerve, 5., forming the internal cutaneous nerve of the thigh, has also been described (page 357.) The Crural or femoral nerve, 6., is the largest of the branches from the lumbar plexus. It is formed by the union of the second, third, and fourth lumbar nerves, passes beneath THE DISSECTOR. 369 the outer border of psoas magnus muscle, and runs downwards in the groove between that muscle and the iliacus internus to Poupart's ligament. It is there separated Fi 98 xheium- from the femoral artery by the breadth of the bar plexus with its psoas muscle, usually not more than half an branches. inch wide; and immediately below Poupart's ligament divides into three sets of branches :— Cutaneous—fig. 95. 13. fig. 98. 8.; three or four in number which pierce the deep fascia to supply the integument, forming the middle cutaneous nerves on the forepart of the thigh. One or two of these will be seen to pass through the sartorious muscle. Muscular— fig. 98. 7., distributed to the muscles on the forepart of the outer side of the thigh; 'and Saphenous—fig. 98. 9. Two long branches larger than the others, which incline inwards to the sheath of the vessels, upon which they rest for some distance. The smaller of the two is the short saphenous nerve, 10.; it leaves the sheath at the lower third of the thigh, and is distributed to the vastus internus muscle. The larger is the long or internal saphenous nerve, 11.; it usually enters the sheath and accompanies the artery, until that vessel is about to pass through the opening in the ad- ductor magnus. The nerve then pierces the aponeurotic canal of the artery, passes be- tween the tendons of the sartorious and gra- cilis ; and gets into relation with the internal saphenous vein, by the side of which it de- scends along the inner side of the leg, in front of the inner ankle, and along the inner border of the foot and side of the great toe, supplying it and the integuments in its course. 1. The dorsal lumbar nerve. 2. The four upper lumbar nerves. 3. The two musculo cutaneous nerves, branches of the first lumbar nerve. 4. The external cutaneous nerve. 5. The genito crural nerve. 6. The crural or femoral nerve. 7. Its muscular branches. 8. Its cutaneous branches, middle cutaneous. 9. Its descending or saphenous branches. 10. The short saphenous nerve. 11. The long or internal saphenous. 12. The obturator nerve. The Obturator nerve, 12., is formed by a branch from the 370 THE DISSECTOR. third, and another from the fourth lumbar nerve. The nerve runs 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 two branches —anterior, which passes in front of the adductor brevis, sup- plying that muscle, tfie pectineus, and adductor longus, and sending a branch downwards to join the long saphenous nerve; and a posterior branch which passes downwards be- hind the adductor brevis, supplying it, the obturator externus, and the adductor magnus. Femoral Hernia. After proceeding, as we have here directed, with the com- mon anatomy of the anterior femoral region, the student may now turn his attention to the special anatomy of that portion of the region through which the intestine finds its way in femoral hernia. With this object the sheath of the vessel should have been left undisturbed. Fig. 99. A section of the structures which leave the pelvis through the femoral arch;—the vessels and their sheath only, being left. 1. Poupart's ligament, the upper boundary of the femoral arch. 2. Its lower boundary, the border of the pubis and ilium. 3. The anterior su- perior spine of the ilium. 4. The spine of the pubis. 5. The pectineal line of the pubis. 6. The external cutaneous nerve. 7. The iliacus muscle. 8. The crural nerve. 9. The psoas magnus muscle. 10. The crural branch of the genito-crural nerve. 11. The femoral artery. 12. The femoral vein, receiving the internal saphenous vein, which pierces the sheath to open into it. 13. The external portion of the sheath of the femoral vessels, lying in contact with the artery. 14. The large funnel-shaped cavity in the sheath, to the inner side of the vein, which receives the sac of femoral hernia 15. The femoral ring, bounded in front by Poupart's ligament, behind by th pubis, externally by the femoral vein, and internally by (16.) Gimbernat's ligament. THE DISSECTOR. 371 If now the scalpel be carried along the line of Poupart's ligament, cutting through the intervening structures down to the bone, and leaving only the common femoral artery and vein enclosed in their sheath (fig. 99.,) it will be seen that Poupart's ligament, which is extended from the anterior superior spine of the ilium to the spine of the pubis, forms a considerable arch over the concave border of the pelvis. This is the femoral arch, and beneath it will be seen to pass a number of important structures. They are disposed in the following order from without, inwards :— The external cutaneous nerve, 6. Iliacus internus muscle, 7. Anterior crural nerve, 8. Psoas magnus muscle, 9. Crural division of the genito-crural nerve, 10. Femoral artery, 11. ^ Femoral vein, 12. V enclosed in a common sheath. Lymphatic vessels, J The sheath, 13. 14., of the femoral vessels is the fibrous covering which invests the artery and vein during their pas- sage beneath the femoral arch. It is formed by the internal lining of the abdomen ; and as this has received various names, according to the situations it may occcupy, as trans- versalis fascia, iliac fascia, pelvic fascia, although actually but one and the same membrane, so the sheath is said to be formed in front by the transversalis fascia to the outer side, by the iliac fascia, and to the inner side by the pelvic fascia; for Poupart's ligament is the line of union of these three regions of the internal abdominal fascia; and in escaping immedi- ately beneath Poupart's ligament the vessels necessarily carry with them a part of each. The breadth of the sheath of the vessels at Poupart's liga- ment is two inches, and in the female more; but at four inches, below the ligament, the sheath has diminished to three quar- ters of an inch. Now it is obvious that the artery and vein, placed side by side, cannot occupy an area two inches in breadth, and there- fore that there must be either some other structure situated within the sheath, or an imperfectly filled space. The latter is the fact; for, if we open the sheath, Ave shall see a space, 14, to the inner side of the vein, which is only occupied by 372 THE DISSECTOR. loose cellular tissue, lymphatic vessels, and a lymphatic gland. So that the inner wall of the sheath is separated by a con- siderable interval from the vein, while the outer wall, 13, is in close contact, and adherent to the artery. Fig. 100. A section of the structures which pass beneath the femoral arch. 1. Poupart's ligament. 2. 2. The iliac portion of the fascia lata, attached along the margin of the crest of the ilium, and along Poupart's ligament, as far as the spine of the os pubis (3.) 4. The pubic portion of the fascia lata, continuous at 3 with the iliac portion, and passing outwards behind the sheath of the femoral vessels to its outer border at 5, where it divides into two layers; one is continuous with the sheath of the psoas (6) and iliacus (7 ;) the other (8) is lost upon the capsule of the hip-joint (9.) 10. The femoral nerve, enclosed in the sheath of the psoas and iliacus. ll. Gimber- nat's ligament. 12. The femoral ring, within the femoral sheath. 13. The femoral vein. 14. The femoral artery: the two vessels and the ring are surrounded by the femoral sheath, and thin septa are sent between the an- terior and posterior wall of the sheath, dividing the artery from the vein, and the vein from the femoral ring. The lymphatic gland is placed immediately under Poupart's ligament, and may be easily pushed into the cavity of the ab- domen by using very slight pressure Avith the finger. The opening, 15., thus produced by the finger is the femo- ral ring: it is bounded in front by Poupart's ligament, 1., behind by the body of the pubis, 2., to the outer side by the femoral vein, 12, and to the inner side by Gimbernat's liga- ment, 16. This ligament is one insertion of Poupart's liga- ment, which expands in a radiated form to be attached along the sharp edge of the pectineal line. THE DISSECTOR. 373 If the student, before passing his finger through the femo- ral ring from the sheath, should attempt to press it from with- in the abdomen, after tearing away the peritoneum, he will find an obstacle in a thin cellular membrane which is spread across the opening at its entrance: this is the septum crurale. Now the course which the intestine follows in femoral hernia may be thus described. It first descends through the femoral ring into the sheath of the vessels, carrying with it the perito- neum and septum crurale. Secondly, it advances fonvards through the saphenous opening in the fascia lata, this being the weakest side of the sheath of the vessels. In this part of its course it gains two additional coverings, viz. the sheath of the vessels called "fascia propria," and the perforated cellular tissue before described (page 358.) as forming the cribriform fascia. Thirdly, coming in contact with the nu- merous small veins Avhich open at this point into the saphenous vein, and spread before the descending hernia like a net, it is prevented from farther descent, and is pressed upwards over Poupart's ligament. To return it again to the cavity of the abdomen we must pursue the converse of the direction Avhich is followed in its descent, i. e., we must press it first downwards below Pou- part's ligament, then backwards through the saphenous open- ing, then upwards through the femoral ring. But should the intestine be strangulated, that is, nipped in its passage, so as to arrest the progress of the aliment, and by distention and pressure cause obstruction to the circulation of the blood, and endanger the life of the patient, we must have recourse to an operation for its relief. This operation consists in dividing carefully all the structures covering the hernia, down to the intestine. The surgeon must, therefore, knoAV well Avhat parts are likely to meet his knife in the living dissection. Tavo of these are common to the Avhole body, and must be divided in every operation; the others are peculiar to the region; they are The integument, Superficial fascia, Cribriform fascia, Fascia propria (sheath of the vessels,) Septum crurale, Peritoneal sac. After opening the peritoneal sac, the surgeon examines the 374 THE DISSECTOR. intestine and feels for the stricture. This is generally at the margin of the femoral ring; and, introducing his finger nail beneath this margin, he divides it slightly with a blunt-pointed bistoury, and returns the intestine into the abdomen, after having satisfied himself of its uninjured condition. Now the student might ask, What structure produces the stricture? or what band, being thus slightly divided, so im- mediately liberates it ? Let him make this experiment on the dead body. Cut through Poupart's ligament while the finger is forced through the femoral ring: the constriction is not re- moved. Cut Gimbernat's ligament, the inner boundary of the ring, the constriction still remains ; but cut a thin fibrous band which crosses the vessels beneath Poupart's ligament, and the ring falls instantly flaccid. This is the margin of the unopened sheath of the vessels, and therefore must be the seat of the stricture. This is the anatomical principle of practice in every case of femoral hernia; and pursued in this way no danger is in- curred to the patient. But if the operator be a bad dissector, and, by a necessary consequence, a bad operator, he may, instead of loosening the ring by the slight manoeuvre here described, carry his incision altogether through Poupart's ligament, or very likely still farther, and cut across the sper- matic or epigastric artery, and so complete the operation Avith the life of his patient. Such an operator should be forewarned that a variety in the distribution of the arteries sometimes occurs in the vici- nity of the femoral ring; and unless he be guarded, his reputation may be for ever destroyed by an unfortunate complication of this kind. This variety consists in the origin of the obturator artery, from the epigastric immediately above the femoral ring. The artery arising in this situation, de- scends most frequently in contact with the external iliac vein, and would therefore be placed to the outer side of the hernial sac, and be comparatively safe. But sometimes the obturator encircles the ring in its course to the obturator foramen, winding along on the margin of Gimbernat's ligament, and would necessarily occupy a very dangerous position in the operation, actually encircling the neck of the hernial sac, and might be wounded by the most skilful operator. Therefore the safety of the patient demands that the surgeon should always conduct his operation as if his patient were the sub- THE DISSECTOR. 375 ject of this anomalous distribution, and he may then reflect upon his conduct even after an unsuccessful issue Avith confi- dence and satisfaction.* Gluteal Region. The subject being turned on its face, and a block placed beneath the pubis to support the pelvis, the student com- mences the dissection of this region, by carrying an incision from the apex of the coccyx along the crest of the ilium to its anterior superior spinous process, or vice versa, if he be on the left side. He then makes an incision from the poste- rior fifth of the crest of the ilium, to the apex of the tro- chanter major; this marks the upper border of the gluteus maximus; and a third incision from the apex of the coccyx along the fleshy margin of the loAver border of the gluteus maximus, to the outer side of the thigh, about four inches be- low the apex of the trochanter major. He then reflects the integument, superficial fascia, and deep fascia, which latter is very thin over this muscle, from the gluteus maximus, fol- lowing rigidly the course of its fibres; and having exposed the muscle in its entire extent, he dissects the integument and superficial fascia from off the deep fascia Avhich binds down the gluteus medius, the other portion of this region. The muscles of the gluteal region are, Gluteus maximus, Obturator internus, ------- medius, Gemellus inferior, -------minimus, Obturator externus, Pyriformis, Quadratus femoris. Gemellus superior, The Gluteus maximus (y-hovtos, nates,) is the thick, fleshy mass of muscle, of a quadrangular shape, which forms the convexity of the nates. In structure, it is extremely coarse, being made up of large fibres, which are collected into fas- ciculi, and these again into distinct muscular masses, separated by deep cellular furrows. It arises from the posterior fifth of the crest of the ilium, from the border of the sacrum and coccyx, and from the great sacro-ischiatic ligament. It passes * The author has met with five or six instances of this dangerous distri- bution in about 300 bodies, which is a large average. In a preparation now before him, a large branch of communication between the epigastric and obturator arteries takes that remarkable course along the margin of Gim- bernat's ligament, leaving the femoral ring to its outer side. 376 THE DISSECTOR. Fig. 101. The mus- cles of the posterior femoral and gluteal region. obliquely outwards and downwards to be inserted into the rough line leading from the trochanter major to the linea aspera, and is continuous by means of its tendon. Avith the fascia lata, covering the outer side of the thigh. After this muscle has been sufficiently studied, it must be turned doAvn from its origin. Its dissec- tion, however, from the parts beneath de- mands considerable care, as a number of arteries and nerves are situated immedi- ately below it. The Gluteus medius is placed in front rather than beneath the gluteus maximus, and is covered in by a process of the deep fascia, Avhich is very thick and dense. It arises from the outer lip of the crest of the ilium for four-fifths of its length from the surface of bone between that border, and the superior curved line on the dor- sum ilii, and from the dense fascia above- mentioned. Its fibres converge to the up- per part of the trochanter major into which its tendon is inserted. This muscle should now be removed from its origin and turned down, so as to expose the next which is situated beneath it. The Gluteus minimus (fig. 103. 1.) is a pretty, radiated muscle, arising from the surface of the dorsum ilii, between the su- perior and inferior curved lines : its fibres converge to the anterior border of the tro- chanter major, into which it is inserted by means of a rounded tendon. To understand the exact relations and origins of the next muscles, the student 1. The gluteus medius. 2. The gluteus maximus. 3. The vastus exter- nus covered in by fascia lata. 4. The long head of the biceps. 5. Its short head. 6. The semi-tendinosus. 7. The semi-membranosus. 8. The gra- cilis. 9. A part of the inner border of the adductor magnus. 10. The edge of the sartorius. 11. The popliteal space. 12. The gastrocnemius muscle; its two heads. The tendon of the biceps forms the outer hamstring; and the sartorius with the tendons of the gracilis, semi-tendinosus, and semi- membranosus, the inner hamstring. THE DISSECTOR. 377 should consult his skeleton. Upon the posterior and lateral aspect of the pelvis, he will find a considerable vacuity. This is broken in upon by a sharp spinous process projected from the border of the ischium, the spine of the ischium : the ex- cavated sweep immediately above this spine is called the great sacro-ischiatic notch, in contra-distincton to another sweep beneath the spine, named the lesser sacro-ischiatic notch ; and the lesser sacro-ischiatic notch is bounded inferiorly by a thick tubercle, the tuberosity of the ischium. In the subject, the narrow extremity of a radiated ligament is attached to the spine of the ischium, while its expanded end is connected to the side of the sacrum and coccyx: hence it is named sacro- ischiatic, and is known by the cognomina, lesser and anterior, which serve to distinguish it from another ligament, radiated at each extremity, attached by the broader end to the poste- rior spinous process of the ilium, the side of the sacrum and coccyx, and by its smaller end to the inner border of the tuberosity of the ischium. This ligament is necessarily longer than the former, and more posterior: hence it is named the posterior or great sacro-ischiatic ligament. These two ligaments convert the notches into foramina, which are thence called the superior or great sacro-ischiatic foramen, and the inferior or lesser sacro-ischiatic foramen. Let us now pro- ceed to the muscles, fig. 103. The Pyriformis muscle, 3., (pyrum, a pear, i. e. pear- shaped) arises from the anterior surface of the sacrum, by little slips that are interposed between the anterior sacral foramina. It passes out of the pelvis, through the great sacro- ischiatic foramen, and is inserted by a rounded tendon into the digital fossa of the trochanter major. Immediately below the pyriformis is a small slip of muscle, the Gemellus superior (gemellus, double, twin:) it arises from the spine of the ischium, and is inserted into the upper bor- der of the tendon of the obturator internus, and into the digi- tal fossa of the trochanter major. The Obturator internus arises from the inner surface of the anterior Avail of the pelvis, being attached to the margin of bone around the obturator foramen, and to the obturator mem- brane. It passes out of the pelvis through the lesser sacro- ischiatic foramen, and is inserted by a flattened tendon into the digital fossa of the trochanter major. The lesser sacro- ischiatic notch, over which this muscle plays as through a 378 THE DISSECTOR. pulley, is faced with cartilage, and provided with a synovial bursa to facilitate its movements. The tendon of the obtu- rator is supported on each side by the two gemelli muscles (hence their names,) which are inserted into the sides of the tendon, and appear to be auxiliaries or superadded portions of the obturator internus. Fig. 102. The deep muscles of the gluteal region. 1. The external surface of the ilium. 2. The posterior surface of the sacrum. 3. The posterior sacro-iliac ligaments. 4. The tuberosity of the ischium. 5. The great or posterior sacro-ischiatic ligament. 6. The lesser or anterior sacro-ischiatic ligament. 7. The trochanter major. 8. The gluteus minimus. 9. The pyriformis. 10. The gemellus superior. 11. The obturator internus muscle, passing out of the lesser sacro-ischiatic foramen. 12. The gemellus inferior. 13. The quadratus femoris. 14. The upper part of the adductor magnus, 15. The vastus externus. 16. The biceps. 17. The gracilis. 18. The semi-tendinous. The Gemellus inferior arises from the posterior point of the tuberosity of the ischium, and is inserted into the loAver border of the tendon of the obturator internus, and into the digital fossa of the trochanter major. Placed deeply between the gemellus inferior and the quad- ratus femoris, may be seen the tendon of the obturator exter- nus, becoming more superficial as it passes outwards to its insertion into the digital fossa of the trochanter major: it THE DISSECTOR. 379 arises from the external surface of the obturator ligament, and from the margin of bone immediately surrounding it. (Page 362.) The Quadratus femoris, 5. (square-shaped) arises from the external border of the tuberosity of the ischium, and is inserted into a rough line on the posterior border of the trochanter major, which is thence named linea quadrati. Actions.—The glutei muscles are abductors of the thigh, when they take their fixed point from the pelvis. Taking their fixed point from the thigh, they steady the pelvis on the head of the femur : this action is peculiarly obvious in stand- ing on one leg: they assist also in carrying the leg forward, in progression. The gluteus minimus being attached to the anterior border of the trochanter major, rotates the limb slightly inwards. The gluteus medius and maximus, from their insertion Fi9- 103. A deep posterior into the posterior aspect of the bone, ™ i^tTi^ rotate the limb outwards : the latter vessels, and nerves, which are is, moreover, a tensor of the fascia of exposed by the removal of the the thigh. The other muscles rotate &luteus maximus muscle- the limb outwards, everting the knee and foot; hence they are named ex- ternal rotators. The gluteal artery and nerve (fig. 103. 11.) are found immediately above the pyriformis muscle; the other ves- sels and nerves, 12. 14., immediately beneath that muscle. The Gluteal artery is a branch of the internal iliac ; it passes out of the pelvis through the great sacro-ischiatic foramen, above the pyriformis mus- cle, and immediately divides into three branches. 1st. A superficial branch directed backAvards, and dis- tributed to the gluteus maximus. 2. A deep superior branch, which passes along the superior curved line of the dorsum of the ilium, between the 1. The gluteus minimus muscle. 2. The trochanter major of the femur, 3. The pyriformis muscle. 4. The tendon of the obturator internus muscle, bounded above by the gemellus superior, and below by the gemellus inferior. 380 THE DISSECTOR. 5. The quadratus femoris muscle. 6. The adductor magnus. 7. The vns- tus externus muscle. 8. The long head of the biceps. 9. The semi-tendi- nosus. 10. The gracilis. 11. The gluteal artery and nerve, escaping from the pelvis above the pyriformis muscle. 12. The great ischiatic nerve. 13. The lesser ischiatic nerve, and between the two the ischiatic artery. 14. The pudic artery and nerve. All these vessels and nerves pass out from the pelvis below the pyriformis muscle. 15. The great or posterior sacro-ischi- atic ligament. The tuberosity of the ischium. 16. The posterior branches of the sacral nerves. gluteus medius and minimus, to the anterior superior spinous process, where it terminates by anastomosing with the super- ficial circumflexa ilii and external circumflex arteries. It is distributed to the gluteus medius and minimus muscles. 3. A deep inferior branch, which descends obliquely upon the glu- teus minimus muscle to the trochanter major, and inosculates with the external circumflex artery. The arteries in this region, are all branches of the internal iliac Avithin the pelvis, and the nerves are derived from the sacral plexus; hence, a part of their course cannot, at present be seen. They all quit the pelvis through the great sacro- ischiatic foramen. The Ischiatic artery, one of the terminal branches of the internal iliac, escapes from the pelvis beneath the pyriformis muscle, and passes doAvnwards Avith the ischiatic nerves, in the interval betAveen the tuberosity of the ischium and tro- chanter major. It gives off three branches. 1st. Coccygeal, which pierces the sacro-ischiatic ligament, and is distributed to the coccygeus and levator ani muscles, and to the integu- ment about the coccyx. 2. Inferior gluteal,—several muscu- lar branches supplying the loAver part of the gluteus maximus. 3. Comes nervi ischiatici (companion to the ischiatic nerve,) a small but long and regular branch, Avhich accompanies the great ischiatic nerve.—Besides these, branches are distributed to the neighbouring muscles, the external rotators. The ischiatic artery inosculates with all the surrounding arteries, viz. with the gluteal, internal pudic, obturator, the external and internal circumflex, and superior perforating of the profunda. The Internal pudic artery, 14., the other terminal branch of the internal iliac, also issues from the pelvis, through the great ischiatic foramen below the pyriformis, to disappear immediately beneath the great sacro-ischiatic ligament, and pursue its course Avithin the pelvis. THE DISSECTOR. 381 From the description usually given of this artery, the stu- dent might imagine that its course Avas extremely eccentric, going out of the pelvis and then going in. But if he refer again to his skeleton and to the subject, he will see that the artery forms the most gentle curve imaginable in this part of its course ; and that its various relation to the pelvis depends entirely upon the projection inAvards of the spine of the ischium, upon Avhich the artery, with its vein and nerve, rest in this region. Upon entering, then, the lesser ischiatic foramen, the in- ternal pudic artery crosses the lower part of the obturator internus muscle to the ramus of the ischium, along Avhich, and the ramus of the pubis, it ascends to the symphisis. Its branches are distributed to the perineum. The Veins, as in all the secondary arteries of the body, are placed by the sides of the arteries in pairs, which are called "venae comites." Nerves of the Gluteal Region. The Gluteal nerve (fig. 103. 11., fig. 107. 2.) is a branch of the lumbo-sacral (5th lumbar:) it leaves the pelvis with the gluteal artery, and distributes filaments with each arterial branch. The Lesser ischiatic nerve (fig. 103. 13., fig. 107. 6.) is a branch of the sacral plexus; it passes out of the pelvis through the great sacro-ischiatic foramen beneath the pyriformis mus- cle, and divides into four sets of branches. 1st. Inferior gluteal, supplying the lower part of the gluteus maximus. 2. Internal posterior cutaneous, a branch that winds around the tuberosity of the ischium, and supplies the integument of the perineum and of the inner and posterior side of the thigh. 3. Middle posterior cutaneous, one or two branches of which pierce the fascia, and run down the middle of the posterior aspect of the thigh, supplying the integument. 4. The pro- per continuation of the nerve upon the flexor muscles as far as the popliteal region. The Great ischiatic nerve (fig. 103. 12., fig. 107. 7.) is the largest in the body; it is formed by the sacral plexus, or rather it is a prolongation of the plexus. At its exit from the great sacro-ischiatic foramen beneath the pyriformis, it mea- sures three quarters of an inch in breadth. It descends through the middle of the space between the trochanter 382 THE DISSECTOR. major and tuberosity of the ischium into the thigh. In its course it rests on the gemellus superior tendon of the obtura- tor internus, gemellus inferior, and quadratus femoris muscles, and in the thigh upon the adductor magnus muscle; it is covered in by the three flexor muscles of the leg. While in the gluteal region, it gives off merely a few muscular branches. This nerve is sometimes formed of tAvo portions, one oi which pierces the pyriformis muscle. At other times, the tAvo portions remain separate all the way down the thigh. The Internal pudic nerve (fig. 103. 14., fig. 107. 5.,) also a branch of the sacral plexus, folloAvs the course and distri- bution of the internal pudic artery, giving off filaments Avith each of its branches. Posterior Femoral Region. Carry an incision along the middle of the posterior aspect of the thigh, as far as the bend of the knee. Bound it in this situation by a transverse incision, and reflect the integu- ment to either side. In the superficial fascia will be seen the two cutaneous branches of the lesser ischiatic nerve, and two or three cutaneous branches from the great ischiatic. Upon removing the superficial fascia, the deep fascia will be found to be extremely thin; and, on turning it aside, we bring into view the three muscles of this region, the flexors of the leg— Biceps. Semi-tendinosus. Semi-membranosus. The Biceps flexor cruris (bi, double—caput head) arises by two heads, one by a common tendon with the semi-tendinosus; the other muscular, and much shorter, from the lower two- thirds of the external border of the linea aspera. This muscle forms the outer ham-string, and is inserted by a strong tendon into the head of the fibula. The Semi-tendinosus, remarkable for its long tendon, arises in common Avith the long head of the biceps from the tube- rosity of the ischium. It is inserted into the inner tuberosity of the tibia. These two muscles must be dissected from the tuberosity of the ischium to bring into view the origin of the next. The Semi-membranosus, remarkable for the tendinous ex- pansion upon its anterior and posterior surfaces, arises from THE DISSECTOR. 383 the tuberosity of the ischium, in front of the common origin of the tAvo preceding muscles. It is inserted into the posterior part of the head of the tibia; at its insertion, the tendon splits into three portions, one of which is inserted in a groove on the inner side of the head of the tibia, beneath the internal lateral ligament. The second is continuous, with an aponeu- rotic expansion that binds down the popliteus muscle; the popliteal fascia; and the third turns upwards and outwards to the external condyle of the femur, forming the posterior liga- ment of the knee-joint (ligamentum posticum Winslowii.) The tendons of the last two muscles, viz., the semi-tendi- nosus and semi-membranosus, with those of the gracilis and sartorius, form the inner hamstring. If the semi-membranosus muscle be turned down from its origin, the student will bring into view the broad and radi- ated expanse of the adductor magnus, upon Avhich the three flexor muscles above described rest. Actions.—These three hamstring muscles are the direct flexors of the leg upon the thigh; and, by taking their origin from below, they balance the pelvis on the lower extremities. Arteries of the Posterior Femoral Region. The Arteries of this region are the terminal branches of the external and internal circumflex, the three perforating, the termination of the profunda femoris, and the popliteal. The branches of the external circumflex are seen piercing the upper part of the A^astus externus, to inosculate Avith the internal circumflex, ischiatic, and superior perforating arte- ries. The internal circumflex makes its appearance betAveen the upper border of the adductor magnus, and the lower border of the quadratus femoris. It inosculates Avith the external circumflex, ischiatic, and superior perforating arteries. The three perforating arteries emerge on the posterior aspect of the thigh, by passing through tendinous arches be- tween the adductor magnus and the linea aspera. They anas- tomose with each other, Avith the circumflex and ischiatic arteries above, and with the articular branches of the popli- teal below. The profunda escapes through the adductor magnus, close to the linea aspera, and is protected from pres- sure by a tendinous arch which is thrown across the bone. It makes its appearance at about an inch above the commence- ment of the politeal artery. 384 THE DISSECTOR. The Nerves in this region are the greater and lesser ischi- atic. The continuation of the lesser ischiatic is seen upon the semi-tendinosus muscle. The Great ischiatic nerve (fig. 107. 7.,) runs down the middle of the posterior femoral region, being situated between the flexor muscles and the adductor magnus. At the loAver third of the thigh it divides into two nerves of nearly equal size, the popliteal, 9., and peroneal, 8. Its branches are simply muscular and cutaneous. Popliteal Region. The lower part of the posterior femoral region is a surgical region of some importance, the popliteal. Fig. 104. The po- We shall, therefore, describe it separately. pliteal region, and the The popliteal region tfig% 104.) is a dia- superficial anatomy of t -i i -i 1 -i the calf of the leg. mond-shaped space, bounded above on each side by the two hamstrings 1. 2., and below by the two heads, 3. 3., of the great muscle of the calf, the gastrocnemius. On dissect- ing back the integument, a large vein, 8., which runs up the middle of the posterior part of the leg, the external saphenous, is seen between the layers of the superficial fascia. To this several cutaneous veins con- verge, which must be divided in making an incision for the purpose of reaching the artery. If the superficial fascia be dissect- ed away, the external saphenous vein will be seen passing through an oval foramen in the deep popliteal fascia, to terminate in the popliteal vein. The deep popliteal fascia is thin, and Avill be removed Avithout being observed, unless the dissector proceed cautiously. It is a part of the common deep fascia investing the en- tire limb. Beneath the deep fascia is a quan- tity of adipose substance which fills up the Avhole popliteal space, from the bone and joint to the surface, and protects and sup- ports the popliteal vessels and nerves. 1. The inner hamstring. 2. The outer hamstring. 3, 3. The two heads of the gastrocnemius muscle. 4. The popliteal artery, vein, and nerve, in THE DISSECTOR. 385 their relative position from within outwards ; the artery being the deepest, next the vein, and the nerve quite superficial. 5. The termination of the ischiatic nerve dividing into the popliteal nerve, and 6. the peroneal. 7. The external saphenous nerve, formed by the union of the communicans peronei, from the peroneal, and communicans poplitei from the popliteal nerve. 8. The external saphenous vein. 9. The outer border of the soleus muscle. 10. The tendo Achillis. It will be recollected, that at the upper part of this popli- teal space the great ischiatic nerve divides into two branches of nearly equal size—the popliteal and peroneal. The popli- teal, 4., runs along the middle line of this space, from apex to apex of its diamond-shaped area. It is placed near to the surface, and is easily found on slightly separating the adipose tissue. This nerve divides the region into two equal halves: in the external one will be found two small nerves, branches of the popliteal and peroneal, called communicans poplitei and communicans peronei, and the peroneal nerve itself, 6., lying along the tendon of the biceps muscle. To the inner side of the popliteal nerve, at a variable depth, is the popliteal vein, to which the external saphenous vein will serve as a guide, and to the inner side of the vein, and still deeper, resting on the femur, is the popliteal artery. The floor of the popliteal space is formed by the expanded inferior extremity of the femur, by the knee-joint, and by the popliteal muscle immediately below the joint. The Popliteal artery (fig. 103. 5.) runs obliquely outwards, through the middle of the popliteal space, from the tendinous opening in the adductor magnus, to the lower border of the po- pliteus muscle, where it divides into the anterior and poste- rior tibial arteries. Relations.—It rests first on the femur, then on the pos- terior ligament of the knee-joint, then on the fascia covering the popliteus muscle: superficial and external to it is the po- pliteal vein, and still more superficial and external, the popli- teal nerve. The Superior articular arteries, external and internal, wind around the femur immediately above the condyles, to the front of the knee-joint, anastomosing with each other, with the ex- ternal circumflex, the anastomotica magna, the inferior articu- lar and the 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 abductor magnus. The Azygos articular artery pierces the posterior ligament 386 THE DISSECTOR. of the joint, ligamentum posticum Winslowii, and supplies the synovial membrane, in its interior. The Inferior articular arteries wind 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, and the internal beneath the internal lateral ligament. The Sural arteries (sura, the calf) are muscular branches of large size and variable number, distributed to the gastroc- nemius and soleus muscles. Popliteal nerve (fig. 104. 4., fig. 107. 9.) runs through the middle of the popliteal space, from the division of the great ischiatic nerve to the lower border of the popliteus muscle, where it passes with the artery beneath the arch of the soleus, and becomes the posterior tibial nerve. It is super- ficial in the whole of its course, and lies externally to the vein and artery. Its branches are muscular or sural (fig. 107. 10.,) Avhich are distributed to the muscles of the calf; and the communi- cans poplitei, which unites with a similar branch, communicans peronei, from the peroneal nerve, to form the external saphe- nous nerve, (fig. 104. 7., fig. 107. 16.) The Peroneal nerve (fig. 104. 6., fig. 107, 8.) descends by the side of the tendon of the biceps to the head of the fibula, pierces the origin of the peroneus longus muscle, and divides into two branches, the anterior tibial, (fig. 107. 13.) and musculo-cutaneous, 14. It gives off but one branch in its course, the communicans peronei which unites with the com- municans poplitei. Dissection of the Leg. The leg is naturally divided into three regions, anterior tibial, fibular, and posterior tibial. Each region is composed of its appropriate muscles, vessels, and nerves. Those of the anterior tibial region may be thus arranged : Superficial to the fascia. Beneath the fascia. Tibial recurrent artery, Tibialis anticus, Peroneal cutaneous nerve, Extensor longus digitorum, Internal saphenous vein, Peroneus tertius, Internal saphenous nerve, Extensor proprius pollicis, Anterior tibial artery, Anterior tibial nerve. THE DISSECTOR. 387 The student will find it convenient, before commencing the dissection of the leg, to separate the limb from the rest of the body, by dividing the muscles, and sawing across the femur at about its middle. This step is better than disarticu- lating at the hip-joint, as it gives him an opportunity, at an after period, of studying the ligaments of the hip. The dis- section of the anterior tibial region is to be commenced by carrying an incision along the middle of the leg, midway be- tween the tibia and the fibula, from the knee to the ankle, and bounding it inferiorly by a transverse incision, extending from one malleolus to the other. And to expose the tendons on the dorsum of the foot, the longitudinal incision may be carried onwards to the outer side of the base of the great toe, and be terminated by another incision directed across the heads of the metatarsal bones. When the integument of these two regions has been turned aside, a small artery must be sought for near the head of the tibia, which pierces the deep fascia, and turns upwards upon the knee-joint, to inosculate with the articular arteries. This is the recurrent branch of the anterior tibial artery. The superficial fascia may now be dissected from off the deep fascia. At the lower third of the leg, this separation must be conducted with care, for two nerves of considerable size will be found piercing the deep fascia near to the fibula, and running downwards in the superficial fascia to the dorsum of the foot. These are the peroneal cutaneous nerves, (fig. 107. 15.,) the cutaneous division of the musculo-cutaneous branch of the peroneal. These branches must be traced with care, following each filament, and separating it from the ad- hering cellular tissue. They are distributed to all the toes. The external, the larger of the two, will be found supplying three toes and a half; the internal, the great toe, and one- half the second. If the inner flap of the integument in the leg be dissected farther back, so as to expose the inner condyle of the femur and the superficial fascia behind the tibia and internal malleo- lus, the course of a vein of considerable size will be exposed in its entire length. Below, it will be seen resting on the in- ternal malleolus, and collecting its blood by numerous small branches from the inner side of the dorsum of the foot. This is the commencement of the internal saphenous vein. It next runs upwards along the inner side of the leg, behind the inner 388 THE DISSECTOR. condyle of the femur, and may be traced along the inner side of the thigh (fig. 95. 9.) to the saphenous opening. Immediately beneath the inner condyle of the femur, the internal saphenous nerve (fig. 98. 11.,) a branch of the ante- rior crural, will be seen piercing the deep fascia, after having passed between the tendons of the sartorius and gracilis mus- cles. The nerve descends by the side of the vein, giving off cutaneous branches in its course, crosses the inner malleolus, and is distributed to the inner side of the foot and great toe, and communicates with the internal cutaneous branch of the fibular cutaneous. The deep fascia is strong and tendinous, and firmly attached to the tibia and fibula. By its internal surface it gives origin to the muscles of this region, and between the two malleoli it forms a dense band, called anterior annular ligament, which binds down the tendons of the extensor muscles in their pass- age forwards to the dorsum of the foot. An incision may now be made through the deep fascia, in the course of a line drawn from the midpoint between the head of the fibula and spine of the tibia, to midway between the inner and outer malleolus. This will mark the course of the anterior tibial artery: and an incision made in any part of this line will expose that vessel in its course between the muscles. The structures to be divided, are the same as in any other part of the body. The deep fascia is easily separated from the muscles in the loAver part of the leg, but above it is closely connected to them, and cannot be removed without dividing some of their fibres. Muscles of the anterior tibial region: Tibialis anticus, Extensor communis.digitorum, Peroneus tertius, Extensor proprius pollicis. The Tibialis anticus muscle (flexor tarsi tibialis) arises from the upper two-thirds of the tibia, from the interosseous membrane, and from the deep fascia; its tendon passes through a distinct sheath in the annular ligament, and is inserted into the inner side of the internal cuneiform bone, and base of the metatarsal bone of the great toe. THE DISSECTOR. 389 The Extensor longus digitorum arises -%• l°5- The muscles of from the head of the tibia, from thethe anterior tibial reSion- upper three-fourths of the fibula, from the interosseous membrane, and from the deep fascia. Below it divides into four tendons, which pass beneath the annular ligament, to be inserted into the second and third phalanges of the four lesser toes. The mode of insertion of the extensor tendons, both in the hand and in the foot, is remarkable (fig. 81.;) each tendon spreads into a broad apo- neurosis over the first phalanx; this aponeurosis divides into three slips, the middle one is inserted into the base of the second phalanx, and the two lateral slips are continued onwards to be in- serted into the base of the third. The Peroneus tertius (flexor tarsi fibularis) arises from the lower fourth of the fibula, and is inserted into the base of the metatarsal bone of the little toe. Although it appears to be merely a part of the extensor longus digitorum, it may be looked upon as analogous to the flex- or carpi ulnaris of the fore-arm. Some- times it is altogether wanting. 1. The extensor muscles inserted into the patella. 2. The subcutaneous surface of the tibia. 3. The tibialis anticus. 4. The extensor communis digitorum. 5. The extensor proprius pollicis. 6. The peroneus tertius. 7. The peroneus longus. 8. The peroneus brevis. 9. 9. The borders of the soleus muscle. 10. A part of the inner belly of the gastrocnemius. 11. The extensor brevis digitorum; the tendon in front of this number is that of the peroneus tertius; and that behind it, the tendon of the peroneus brevis. The Extensor proprius pollicis lies between the tibialis an- ticus and extensor longus digitorum. It arises from the lower two-thirds of the fibula and interosseous membrane. Its ten- don passes through a distinct sheath in the annular ligament, and is inserted into the base of the last phalanx of the great toe. Actions —The tibialis anticus and peroneus tertius are 33* 390 THE DISSECTOR. Fig. 106. The an- direct flexors of the tarsus upon the leg, terior aspect of the acting in conjunction with the tibialis posti- !TlSf'3<™> and peroneus longus and brevis; they and dorsalis pedis direct the foot either inwards or outwards, arteries, with their and preserve its flatness in progression. The extensor longus digitorum, and extensor proprius pollicis, are direct extensors of the phalanges: but continuing their action, they assist the tibialis anticus and peroneus ter- tius, in flexing the entire foot upon the leg. Taking their origin from below, they increase the stability of the ankle. Anterior tibial artery.—We have seen in a previous section, that the popliteal artery divides into the anterior and posterior tibial. The anterior tibial passes forwards between the two heads of the tibialis posticus mus- cle, then through the opening in the upper part of the interosseous membrane, to the anterior tibial region. From this point it runs down the anterior aspect of the leg to the ankle joint. Relations.—It rests upon the interosse- ous membrane, the lower part of the tibia, and the anterior ligament of the joint. In the upper third of its course it is situated between the tibialis anticus and extensor communis digitorum, lower doAvn 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 be- tween that tendon and the tendons of the extensor longus digitorum. 1. The tendon of insertion of the quadriceps, extensor muscle. 2. The insertion of the ligamentum patellae into the lower border of the patella. 3. The tibia. 4. The extensor proprius pollicis muscle. 5. The extensor lon- gus digitorum. 6. The peronei muscles. 7. The inner belly of the gastroc- nemius and the soleus. 8. The annular ligament beneath which the extensor tendons and the anterior tibial artery pass into the dorsum of the foot. 9. The anterior tibial artery. 10. Its recurrent branch inosculating with (2) the inferior articular, and (1) the super articular artery, branches of the popliteal. 11. The internal malleolar artery. 17. The external malleolar inosculating with the anterior peroneal artery, 12. 13. The dorsalis pedis THE DISSECTOR. 391 artery. 14. The tarsea and metatarsea arteries; the tarsea is nearest the ankle, the metatarsea is seen giving off the interosseae. 15. The dorsalis hallucis artery. 16. The communicating branch. The Branches of the anterior tibial artery are the follow- ing :— {Recurrent, in x U 1 ' 11 1 External malleolar, Internal malleolar. The Recurrent branch passes upwards to the front of the knee-joint upon Avhich it is distributed, anastomosing with the articular arteries. It pierces the origin of the tibialis anticus muscle. The Muscular branches supply the muscles of this region. The Malleolar arteries are distributed to the ankle joint; the external passing beneath the tendons of the extensor lon- gus digitorum and peroneus tertius, and inosculating with the anterior peroneal artery; the internal beneath the tendons of the extensor proprius pollicis and tibialis anticus, inosculates with branches of the posterior tibial artery. The Anterior tibial nerve (fig. 97. 13.) commences at the bifurcation of the peroneal upon the head of the fibula, and passes beneath the upper part of the extensor longus digito- rum, to reach the outer side of the anterior tibial artery, just as that vessel has passed through the opening in the interos- seous membrane. It descends Avith the artery, lying at first to its outer side, and then in front of it, and near the ankle becomes again placed to its outer side. It supplies the mus- cles of the anterior tibial region, and terminates in the dor- salis pedis nerve. Dorsal Region of the Foot. The deep fascia in this region is extremely thin, and can hardly be said to exist; the muscles on the dorsum of the foot are, Extensor brevis digitorum, 4 Dorsal interossei { bicipital j \ £ctoS. The Extensor brevis digitorum muscle arises from a tuber- cle on the outer side of the os calcis, crosses the foot obliquely, and terminates in four tendons, the innermost of which is in- serted into the base of the first phalanx of the great toe, and 392 THE DISSECTOR. the other three into the sides of the long extensor tendons of the second, third, and fourth toes. The Dorsal interossei muscles are placed between the meta- tarsal bones; they resemble the analogous muscles in the hand in arising by two heads from the adjacent sides of the metatarsal bones; their tendons are inserted into the base of the first phalanx, and into the digital expansion of the ten- dons of the long extensor. The First dorsal interosseous is inserted into the inner side of the second toe, and is therefore an adductor; the other three are inserted into the outer side of the second, third, and fourth toes, and are therefore abductors. Communicating arteries (perforantes,) between the dorsum and sole of the foot, pass between the bifid origins of these muscles. The Artery of the dorsum of the foot, Dorsalis pedis, is the continuation of the anterior tibial: it runs along the dorsum of the foot, from the ankle to the base of the metatarsal bone of the great toe : here it divides into two branches, the com- municating, which passes between the two heads of the first dorsal interosseous, and inosculates with the termination of the external plantar artery and the dorsalis hallucis, which runs forwards upon the first dorsal interosseous muscle, and at the base of the first phalanx divides into two branches, which supply the adjacent sides of the great and second toes. Relations.—The dorsalis pedis is situated along the outer border of the tendon of the extensor proprius pollicis ; on its fibular side is the tendon of the extensor longus digitorum, and near to its termination it is crossed by the inner tendon of the extensor brevis digitorum. Branches: Dorsalis pedis, Tarsea, Metatarsea,—interosseae, Communicating, Dorsalis hallucis,—collateral digital. The Tarsea arches transversely across the tarsus, supplying the articulations of the tarsal bones and the outer side of the foot; it anastomoses with the external malleolar and posterior peroneal arteries. The Metatarsea forms an arch across the base of the meta- tarsal bones, and supplies the outer side of the foot; it sends branches (interossei) to the dorsal interossei muscles, and re- THE DISSECTOR. 393 ceives communicating branches (perforates) from the plantar arch. The Nerves supplying the dorsum of the foot are five in number: Internal peroneal cutaneous, External peroneal cutaneous, Anterior tibial, External saphenous, Internal saphenous. The Peroneal cutaneous nerves have been described at page 375.: they communicate with the three other nerves. The Anterior tibial nerve accompanies the dorsalis pedis artery, supplying the extensor brevis digitorum and the great toe, and communicates with the internal peroneal cutaneous. The External saphenous nerve passes from the posterior part of the leg behind the outer malleolus, and is distributed to the outer border of the foot, accompanying the branches of the external saphenous vein. This nerve usually commu- nicates with the external peroneal cutaneous by means of a large branch. The Internal saphenous nerve crosses the inner ankle by the side of the internal saphenous vein, and is distributed to the inner border of the foot and great toe. It sends, or re- ceives a communicating branch from the internal peroneal cutaneous. Fibular Region. If the leg be turned upon its inner side, and the deep fascia be removed from over the fibula, two muscles will be exposed which arise from that bone; these are the peroneus longus and brevis. The Peroneus longus.(rfspow?, fibula, extensor tarsi fibularis longior) arises from the upper third of the fibula: its tendon passes behind the outer malleolus to a groove in the cuboid bone, through which it proceeds obliquely across the foot to be inserted into the base of the metatarsal bone of the great toe. A sesamoid bone is developed in that part of the tendon which is lodged in the groove of the cuboid bone. The Peroneus brevis (extensor tarsi fibularis brevior) arises from the lower two-thirds of the fibula, passes behind the external malleolus, with the tendon of the preceding muscle, and is inserted into the base of the metatarsal bone of the little toe. 394 THE DISSECTOR. and branches of the sa- cral plexus. Actions.—The peronei muscles are extensors of the foot conjointly with the tibialis posticus. They antagonize the tibialis anticus and peroneus tertius, Avhich are flexors of the foot. The whole of these muscles acting together tend to maintain the flatness of the foot, so necessary to security in walking. There is no artery in this region; but if the peroneus longus be carefully turned down from its origin, Fig. 107. A diagram the peroneal nerve and its branches will showing the formation be e oge(L and branches ot the sa- m, t» -i / /• i ak n \ i The Peroneal nerve (fig. 107. 8.) de- scends from the division of the great ischi- atic nerve, along the tendon of the biceps, to the head of the fibula, where it pierces the origin of the peroneus longus muscle. At this point it divides into two branches, anterior tibial, 13., and musculo-cutane- ous, 14. The Anterior tibial nerve, 13. passes through the upper part of the extensor longus digitorum muscle, and accompanies the anterior tibial artery, lying at first to the outer side and then resting upon that vessel. Upon the dorsum of the foot it lies by the side of the dorsalis pedis artery, and is distributed to the adjoining sides of the great and second toes, after having supplied the muscles on the dorsum of the foot. The Musculo-cutaneous nerve, 14.,passes for a short distance between the peroneus longus and extensor longus digitorum, both of which muscles it supplies; hence its title "musculo." At the lower third of the leg it pierces the deep fascia, and di- vides into the tAvo peroneal cutaneous nerves of the foot; hence " cutaneous." The Peroneal cutaneous nerves, 15., are distributed to the integument on the dor- sum of the foot, and to all the toes; the internal supplying one and a half, and the external three and a half. THE DISSECTOR. 395 1. The lumbo sacral nerve, descending to join the sacral plexus, and giving off a large branch. 2. The gluteal nerve. 3. The anterior branches of the four upper sacral nerves. 4. The sacral plexus. 5. The internal pudic nerve. 6. The lesser ischiatic nerve. 7. The great ischiatic nerve. 8. The peroneal nerve. 9. The popliteal nerve. 10. Its sural branches. 11. The posterior tibial nerve dividing inferiorly into the two plantar nerves, 12. 13. The anterior tibial nerve. 14. The musculo-cutaneous nerve, its muscular portion. 15. Its cutaneous portion. 16. The external saphenous nerve, formed by the union of the communicans poplitei, and communicans peronei. Posterior Tibial Region. This region is best dissected by making an incision from the middle of the popliteal space, down the middle of the poste- rior part of the leg, to the tuberosity of the os calcis, bounding it inferiorly by a transverse incision to each malleolus. Turn- ing aside the two flaps of integument, the superficial fascia is brought into view, and betAveen its two layers in the middle line of the calf, the external saphenous vein and nerve. The External saphenous vein (fig. 104. 8.) commences by small branches on the outer border of the foot, ascends behind the external malleolus towards the groove between the two bellies of the gastrocnemius, and terminates by piercing the deep fascia in the middle of the popliteal space, and opening into the popliteal vein. The External saphenous nerve (fig. 104. 7., fig. 107.16.) will be found lying by the side of this vein. It is formed by the union of two branches, communicans poplitei and communi- cans peronei, from the two divisions of the great ischiatic nerve. The nerve thus formed pierces the deep fascia below the fleshy part of the gastrocnemius muscle, and descends by the side of the external saphenous vein, supplying the integu- ment in its course to the outer border of the foot to which its branches are distributed, communicating with the external peroneal cutaneous nerve. The Deep fascia, in the upper part of this region, is thin: below it becomes thicker. It is connected on each side with the tibia and fibula, and at the ankle forms the internal and external annular ligaments. If the deep fascia be turned aside, the three muscles forming the superficial group of this region will be brought into view. Gastrocnemius, Plantaris, Soleus. The Gastrocnemius (yaotpoxvyfuov, the bellied part of the leg) arises by two heads from the two condyles of the femur, the 396 THE DISSECTOR. :/ inner head being the longest. They unite to form the beauti- ful muscle so characteristic of this region of the limb. It is inserted, by means of the tendo Achillis, into the lower part of the tuberosity of the os calcis, a synovial bursa being placed between the tendon and the upper part of the tube- rosity. The grastrocnemius must be removed from its origin, and turned down, in order to expose the next muscle. The Plantaris (planta, the sole of the foot), an extremely diminutive muscle, situated between the Fig. 108. The super- gastrocnemius and soleus, arises from the 521*?^*^ & r*?r Td?ie °/ih? fem,ur> ri»imerted leg. by its long and delicately slender tendon, into the tuberosity of the os calcis, by the side of the tendo Achillis. BetAveen the fibular and tibial origins of this muscle is a tendinous arch, beneath which the popliteal vessels and nerve pass into the leg. The soleus muscle must now be divided along its extensive origin, and turned down. The Soleus (solea, a sole) is the broad muscle upon which the plantaris rests. It arises from the head and upper third of the fibula, from the oblique line, and mid- dle third of the tibia. Its fibres converge to the tendo Achillis, by which it is in- serted into the tuberosity of the os calcis. Actions.—The three muscles of the calf draAV powerfully on the os calcis, and lift the heel; continuing their action, they raise the entire body. This action is at- tained by means of a lever of the second power, the fulcrum (the toes) being at one end, the weight (the body supported on the tibia) in the middle, and the power (these muscles) at the other extremity. They are therefore the walking muscles, and perform all movements that require the support of the whole body from the ground, as dancing, leaping, &c. Taking their fixed point from below, they steady the leg upon the foot. 1. The biceps muscle forming the outer hamstring. 2. The tendons forming the inner hamstring. 3. The popliteal space. 4. The gastrocne- THE DISSECTOR. 397 region. mius muscle. 5. 5. The soleus. 6. The tendo Achillis. 7. The posterior tuberosity of the os calcis. 8. The tendons of the peroneus longus and brevis muscles passing behind the outer ankle. 9. The tendons of the deep layer passing into the foot behind the inner ankle. Deep Group. An Imtermuscular fascia serves to separate the superficial from the deep group, and by its strong at- ^ 109. The deep tachments to the bones at each side, binds layer of muscles of down the muscles closely in their places. On the. posterior tibial removing this fascia, the muscles are brought clearly into view— Poplitens, Flexor longus digitorum, Flexor longus pollicis, Tibialis posticus. The Popliteus muscle (poples, the ham of the leg) forms the floor of the popliteal region at its lower part, and is bound tightly down by a strong fascia derived from the middle slip (page 384.) of the tendon of the semi- membranosus muscle. It arises by a rounded tendon from a deep groove on the outer side of the external condyle of the femur, beneath the external lateral ligament. It spreads obliquely over the head of the tibia, and is inserted into the surface of bone above its oblique line. This line is often called, from being the limit of insertion of the popliteus muscle, popliteal line. The Flexor longus pollicis is the most superficial of the three next muscles. It arises from the lower two-thirds of the fibula, passes through a distinct tendinous canal into the sole of the foot, and is inserted into the base of the last phalanx of the great toe. 1. The lower extremity of the femur. 2. The ligamentum posticum Wins- lowii. 3. The tendon of the semi-membranosus muscle dividing into its three slips. 4. The internal lateral ligament of the knee-joint. 5. The external lateral ligament. 6. The popliteus muscle. 7. The flexor longus digitorum. 8. The tibialis posticus. 9. The flexor longus pollicis. 10. The peroneus longus muscle.' 11. The peroneus brevis. 12. The tendo Achillis divided at its insertion into the os calcis. 13. The tendons of the tibialis posticus and flexor longus digitorum muscles, just as they are about to pass beneath the internal annular ligament of the ankle; the interval between the latter tendon and the tendon of the- flexor longus pollicis is occupied by the posterior tibial vessels and nerve. 34 398 THE DISSECTOR. The Flexor longus digitorum (perforans) arises from the surface of the tibia, immediately below the popliteal line. Its tendon passes through a sheath common to it and the tibialis posticus behind the inner malleolus into the sole of the foot, where it divides into four tendons, which are inserted into the base of the last phalanx of the four lesser toes, perforating the tendons of the flexor brevis digitorum. The flexor longus pollicis must now be removed from its origin, and the flexor longus digitorum drawn aside, to bring into view the entire extent of the tibialis posticus. The Tibialis posticus (extensor tarsi tibialis) lies upon the interosseous membrane, between the two Fig. 110. A pos- bones of the leg. It arises by two heads leri°r shoTinf the fr0m the adJacent sides of tne tibia and fibula popliteal and pos- their whole length, and from the interosseous terior tibial artery, membrane. Its tendon passes inwards be- neath the tendon of the flexor longus digi" torum, and runs in the same sheath, but internal to it, into the sole of the foot, to be inserted into the tuberosity of the scaphoid and internal cuneiform bone. The student will observe that the two lat- ter muscles change their relative position to each other in their course. Thus, in the leg, the position of the three muscles from with- in outwards, is flexor longus digitorum, tibi- alis posticus, flexor longus pollicis. At the inner malleolus, the relation of the tendons is tibialis posticus, flexor longus digitorum, both in the same sheath; then a broad groove, which lodges the posterior tibial artery, vense comites, and nerve; and lastly, the flexor longus pollicis. The arteries of the posterior tibial region are,— {1 ( anterior peroneal, " l \ posterior peroneal. muscular. The Posterior tibial artery runs down the tibial side of the leg, from the lower border of the popliteus muscle to the inner ankle. THE DISSECTOR. 399 1. The tendons forming the inner hamstring. 2. The tendon of the biceps forming the outer hamstring. 3. The popliteus muscle. 4. The flexor lon- gus digitorum. 5. The tibialis posticus. 6. The fibula; immediately be- low the figure is the origin of the flexor longus pollicis; the muscle has been removed in order to expose the peroneal artery. 7. The peronei muscles, longus and brevis. 8. The lower part of the flexor longus pollicis muscle with its tendon. 9. The popliteal artery giving off its articular and muscu- lar 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 to their origin. The two inferior are in relation with the popliteus muscle. 10. The anterior tibial artery passing through the angular interspace between the two heads of the tibialis posticus muscle. 11. The posterior tibial artery. 12. The relative position of the tendons and artery at the inner ankle from within outwards, previously to their passing beneath the internal annular ligament. 13. The peroneal artery, dividing into two branches; the anterior peroneal is seen piercing the interosseous membrane. 14. The posterior peroneal. Relations.—It rests, 1st, upon the tibialis posticus; 2dly, upon the flexor longus digitorum; 3dly, upon the tibia, and is covered in by the intermuscular fascia. Branches.—The Peroneal artery is given off from the pos- terior tibial, at about tAvo inches below the loAver border of the popliteus muscle; it inclines outwards, and runs along the inner border of the fibula to its lower third, where it divides into its two branches, anterior and posterior peroneal. Relations.—It rests upon the tibialis posticus, and is covered in by the flexor longus pollicis, having the fibula to its outer side. The Anterior peroneal artery, at the lower third of the leg, pierces the interosseous membrane, and is distributed on the front of the outer malleolus, anastomosing Avith the external malleolar and tarsal arteries. The Posterior peroneal continues onwards to the posterior aspect of the outer malleolus, anastomosing with the anterior peroneal, tarsal, external plantar, and posterior tibial arteries. The Muscular branches are distributed to the muscles in the course of the posterior tibial artery. The Posterior tibial nerve, which is the only nerve in this region, is a continuation of the popliteal: it lies at first to the outer side of the artery, rests upon it in the middle of its course, and then gets to its outer side again, in which situa- tion it enters the sole of the foot. 400 THE DISSECTOR. Sole of the Foot. Dissection.—The sole of the foot is best dissected by carry- ing an incision around the heel, and along the inner and outer borders of the foot, to the great and little toes. This incision should divide the integument and superficial fascia, and both together should be dissected from the deep fascia, as far for- ward as the base of the phalanges, where they may be re- moved from the foot altogether. The Superficial fascia is closely adherent to the integu- ment; and, Avhen thus turned up, has the appearance of a dense cushion of fat held down at numerous points by strong cellular tissue. The Deep, or plantar fascia, is a beautiful structure stretched between the under surface of the tuberosity of the calcaneum and the bases of the first phalanges of the toes. It thus serves a double purpose, being mainly instrumental in preserving the convexity of the arch of the foot, while it protects from inju- rious pressure the soft parts between it and the bones. This fascia is divided into three portions, a middle and two lateral. The middle portion is very dense, and is made up of strong tendinous fibres, closely interlaced with each other. It occu- pies the middle of the sole, and terminates towards the toes in five slips. Each of these slips is subdivided into two smaller slips, which are inserted into the sides of the base of the first phalanx of each toe, and give passage to the flexor tendons. The lateral portions are comparatively thin. They cover the muscles on the sides, and are continuous with the deep fascia on the dorsum of the foot. At the junction of the middle with the lateral portions, two septa are sent inwards, and are attached to the under surface of the tarsal bones. These two partitions divide the muscles into three groups, a middle and two lateral. The lateral portions of the plantar fascia are easily removed from the muscles. The middle portion must be divided through its middle, and each extremity raised separately; the anterior towards the toes, from which it may be divided; the posterior towards the os calcis: this, however, cannot be effected with- out dividing many of the muscular fibres of the flexor brcAris digitorum, Avhich arise from the surface of the fascia. The muscles of the sole of the foot may be arranged in four layers:— THE DISSECTOR. 401 First Layer. Abductor pollicis, Abductor minimi digiti, Flexor brevis digitorum. Second Layer. Tendon of the flexor longus pollicis, Tendons of the flexor longus digitorum, Accessorius, Lumbricales (4.) Third Layer. Flexor brevis pollicis, Adductor pollicis. Flexor brevis minimi digiti, Transversus pedis. Fourth Layer. Three plantar interossei (all adductors). The Abductor pollicis lies along the inner border of the foot; it arises by two heads, between which the tendons of the long flexors, arteries, veins, and nerves enter the sole of the foot. One head arises from the inner side of the tuberosity of the calcis, the other from the internal ligament and tuber- osity of the scaphoid bone. Insertion, into the base of the first phalanx of the great toe. The Abductor minimi digiti lies along the outer border of the sole of the foot. It arises from the outer side of the os calcis, and from the base of the metatarsal bone of the little toe, and is inserted into the base of the first phalanx of the little toe. The Flexor brevis digitorum (perforatus) is placed between the two preceding muscles. It arises from the under surface of the os calcis and plantar fascia, and is inserted by four tendons into the base of the second phalanx of the four lesser toes. Each tendon divides, previously to its insertion, to give passage to the tendon of the long flexor: hence its cognomen perforatus. These muscles are to be divided posteriorly from their ori- gin, and anteriorly through their tendons, and removed. This will bring into view the second layer, and the external plantar artery and nerve, which lie obliquely across it. 34* 402 THE DISSECTOR. At the point where the tendons of the long flexors cross each other, a communicating slip is sent between them which associates their action. The Musculus accessorius arises by two slips from either side of the tuberosity of the os calcis; the inner slip being fleshy, the outer tendinous. It is inserted into the outer side of the tendon of the flexor longus digitorum. Fig. 111. The first layer of muscles in the sole of the foot; this layer is exposed by the removal of the plantar fascia. Fig. 112. The third and a part of the second layer of muscles of the sole of the foot. Fig. 111. 1. The os calcis. 2. The posterior part of the plantar fascia divided transversely. 3. The abductor pollicis. 4. The abductor minimi digiti. 5. The flexor brevis digitorum. 6. The tendon of the flexor longus pollicis muscle. 7. 7. The lumbricales. On the second and third toes, the tendons of the flexor longus digitorum are seen passing through the bifur- cation of the tendons of the flexor brevis digitorum. Fig. 112. 1. The divided edge of the plantar fascia. 2. The musculus accessorius. 3. The tendon of the flexor longus digitorum, previously to its division. 4. The tendon of the flexor longus pollicis. 5. The flexor brevis pollicis. 6. The adductor pollicis. 7. The flexor brevis minimi digiti. 8. The transversus pedis. 9. Interossei muscles, plantar and dor- sal. 10. A convex ridge formed by the tendon of the peroneus longus mus- cle in its oblique course across the foot. THE DISSECTOR. 403 The Lumbricales (lumbricus, an earthworm) are four little muscles arising from the tibial side of the tendons of the flexor longus digitorum, and inserted into the expansion of the extensor tendons, and into the base of the first phalanx of the four lesser toes. Dissection.—To expose the third layer of muscles without disturbing the vessels; cut the tendons of the long flexors across through the insertion of the accessorius, and draw that muscle Avith the tendon backwards, by means of hooks, and snip off the digital extremities of the tendons. A little cleaning of fat and cellular tissue will then bring clearly into view the third layer of muscles. In this dissection the branches of the internal plantar nerve will run considerable risk, unless the student be careful, The Flexor brevis pollicis arises by a pointed tendinous pro- cess from the side of the cuboid, and from the external and middle cuneiform bones, and is inserted by two heads into the base of the first phalanx of the great toe. Tavo sesamoid bones are developed in the tendons of insertion of these two heads, and the tendon of the flexor longus pollicis lies in the groove between them. The Adductor pollicis arises from the cuboid bone, from the sheath of the tendon of the peroneous longus, and from the base of the third and fourth metatarsal bones. It is in- serted into the base of the first phalanx of the great toe. The Flexor brevis minimi digiti arises from the base of the metatarsal bone of the little toe, and from the sheath of the tendon of the peroneus longus. It is inserted into the base of the first phalanx of the little toe. The Transversus pedis arises by fleshy slips from the heads of the metatarsal bones of the four lesser toes. Its tendon is inserted into the base of the first phalanx of the great toe. The plantar interossei muscles (page 405.) must be left un- til the arteries and nerves have been dissected and studied. Actions.—The actions of the muscles in the sole of the foot are implied in their names. See analysis (page 406.) Arteries of the Sole of the Foot. The Arteries of the sole of the foot are the internal and external plantar, the terminal branches of the posterior tibial artery. Their distribution may be thus expressed in a tabu- lar form:— 404 THE DISSECTOR. Posterior tibial. - internal plantar. external plantar. (muscular. .. ... f anterior perforating. dlgltal {collateral posterior perforating. The posterior tibial artery immediately behind the inner maleolus divides into its two terminal branches. The Internal plantar, the smaller of the two, runs along the innner border of the foot between the abductor pollicis and flexor brevis digitorum muscles, and supplies the inner border of the foot and great toe. The External plantar artery passes obliquely outwards between the first and second layer of Fig. 113. The arte- plantar muscles to the fifth metatarsal ries of the sole of the space. It then turns horizontally in- TiTHllrtTi ™rds between the second and third lay- muscles having been re- ers to the first metatarsal space, where moved. it inosculates with the communicating branch from the dorsalis pedis. The horizontal portion of the artery de- scribes a slight curve, having the con- vexity forwards. This is the plantar arch. Branches.—1st. Muscular, to the muscles in the sole of the foot. 2d. The digital, four in number, pass forwards to the cleft between the toes, and divide into collateral branches, which supply the sides of the three external toes, and the outer side of the second. At the bifur- cation of the toes, a small branch is sent upwards from each digital artery to inos- culate with the interosseous branches of the metatarsea; these are the anterior perforating arteries. 3d. The Posterior perforating are three small branches which pass upwards be- tAveen the heads of the three external dor- sal interossei muscles, to inosculate with the arch formed by the metatarsea artery. 1. The under and posterior part of the os calcis ; to which the origins of the first layer of muscles remain attached. 2. The musculus accessorius. 3. The long flexor tendons. 4. The tendon of the peroneous longus. 5. The termination of the posterior tibial artery. 6. The internal plantar. 7. The THE DISSECTOR. 405 external plantar artery. 8. The plantar arch giving off four digital branches, which pass forwards on the interossei muscles to divide into collateral branches. Nerves of the Sole of the Foot. The Nerves of the sole of the foot are, like the arteries, the internal and external plantar (fig. 107. 12.) terminal branches of the posterior tibial. [internal plantar { three toes and a nalf" Posterior tibial < I . , . „ I external plantar J one toe and a half. { { sole of the foot. There is a difference in the distribution of the nerves in this region, as contrasted with the arteries, which it is difficult to explain. However, as far as the student is concerned, it may be possibly as easy to recollect by a mnemonic of oppo- sition as of resemblance. Thus the external plantar artery supplies three toes and a half, and the nerve one and a half. The internal plantar artery supplies half a toe, and the nerve three and a half. The Internal plantar nerve, larger than the external, lies in the fissure between the abductor pollicis and flexor brevis digitorum, and divides into four branches, which pass forwards between the first and second layers of muscles to be dis- tributed to the three inner toes and one side of the fourth. The External plantar nerve, the smaller of the tAvo, follows the course of the external plantar artery, to the outer border of the musculus accessorius, beneath which it sends several large muscular branches to supply the sole of the foot. It then gives branches to the outer border of the foot, and sends forwards two digital branches to supply the little toe and one half the next. When the arteries and nerves have been examined, the muscles may be removed Avhich impede the view of the plantar interossei. The plantar interossei muscles are three in number, and are placed upon rather than betAveen the metatarsal bones. They arise from the base of metatarsal bones of the three outer toes, and are inserted into the inner side of the extensor tendon and base of the first phalanx of the same toes. In their action they are all abductors. When the anatomy of the muscles, vessels, and nerves of the sole of the foot is completed, and the student is pre- 406 THE DISSECTOR. paring to study the ligaments, he should lay open the groove in the cuboid bone by dividing the ligamentous sheath in Avhich it is contained, and expose the tendon of the peroneus longus in its passage across the foot, to its insertion into the base of the metatarsal bone of the great toe. In that portion of the tendon which lies in contact with the cuboid, he will find a sesamoid bone. In some instances the deposite of bone has not taken place and the thickening in that portion of the tendon is merely fibro-cartilaginous. Analysis of the Arrangement and Actions of the Muscles of the Lower Extremity. The lower extremity is composed of, 1st. the femur; 2d. the tibia and fibula ; 3d. the tarsus; 4th the toes. The trunk is the fixed point from which arise the muscles that move the thigh. The articulation of the hip is a universal joint; hence the movements are very numerous, but they may all be referred to the four primary directions, forwards, backwards, inwards, outwards, to which is added rotation on its axis. The articulation of the femur with the tibia is a hinge joint, and is therefore applicable only to flexion and extension: the muscles performing these actions, arise from the pelvis and femur. But as we descend, we find the length of the bones diminishing while their numbers increase. The foot is a com- pound organ made up of a number of parts, each part per- forming distinct movements. We are therefore prepared to find a number of muscles destined to supply these demands. But numerous as they really are, they may, by a careful analysis, be arranged and grouped under a few simple actions. The movements of the tarsus may be referred to four heads, flexion, extension, adduction, abduction, the latter two actions being very imperfect. The muscles performing these move- ments are the following:— Flexion. Extension. Tibialis anticus, Tibialis posticus, Peroneus tertius. Peroneus longus, --------- brevis, and where forcible action is required as in Avalking, Gastrocnemius, Plantaris. Soleus. THE DISSECTOR. 407 Adduction. Abduction. Tibialis anticus, Peroneus longus, -------posticus. --------brevis. The movements of the toes may in the same manner be reduced to precisely the same simplicity of action thus:— Flexion. Extension. Flexor longus digitorum, Extensor longus digitorum. -------brevis digitorum, ---------brevis digitorum. -------accessorius, -------minimi digiti. Adduction. Abduction. Interossei / * dorsa1, Interossei, 3 dorsal. ' \ 3 plantar. Abductor minimi digiti. The great toe, like the thumb in the hand, enjoys an inde- pendence of action, and is therefore provided with distinct muscles to perform its movements. But even here the direction of the actions is nothing more than is possessed by each of the other toes, and may be referred to the same plan, thus:— Flexion. Extension. Flexor longus pollicis, Extensor proprius pollicis, -------brevis pollicis. ---------brevis digitorum. Adduction. Abduction. Adductor pollicis. Abductor pollicis. The only muscles excluded from this table are the lum- bricales, four small muscles, which, from their attachments to the tendons of the long flexor, appear to be assistants to their action ; and the transversus pedis, a small muscle placed trans- versely in the foot across the heads of the metatarsal bones, which has for its office the drawing together of the toes. 408 THE DISSECTOR. CHAPTER XL ON THE LIGAMENTS. The mechanism by which the different bones of the skeleton are connected with each other is called a "joint." Every bone in the body articulates with one or more bones, and as each differs from the other in its form and in its use, we are prepared to expect a great variety in the forms of joints. They may all, however, be reduced to three classes—1. Synarthrosis ; 2. Amphi-arthrosis ; and 3. Diarthrosis. Synarthrosis (aw, together ; apepioai;, articulation,) is that form of joint in which the bones are intimately and immoveably connected Avith each other. There are four kinds of synar- throsis. 1. Harmonia (ap«, to adapt,) in which the bones merely lie in opposition with each other; as in the palate processes of the superior maxillary and palate bones Avith those of the opposite side, and with each other; the basilar process of the occipital bone Avith that of the sphenoid ; the nasal bones with each other, and with the superior maxillary bones. 2. Schindylesis (axivfotyns, a fissure,) in which a projection of one bone is inserted into a groove or fissure in another; as in the articulations of the vomer with the rostrum of the sphenoid, and Avith the central lamella of the ethmoid bone. 3. Gomphosis (yop$os, a nail,) a mode of articulation, of which the insertion of the teeth into the alveolar processes is the only example ; their roots being fixed into the alveoli, like nails into a board. 4. Sutura (sutura, a seam,) is the most solid of the four forms of synarthrosis: it is that which is employed for the articulation of the flat bones of the skull with each other. It presents two varieties sutura serrata, which is illustrated in the serrated union of the frontal Avith the parietal bones, the parietal bones Avith each other, or with the occipital; and sutura squamosa, the scale-like connexion of the temporal bone with the parietal. Amphi-arthrosis (<*/i^, both, ap0py...J. -.......•..-