irrTTT HnH muuME )y//);/;^/ >(>/>//' ; : .'//;. r 'i'^ H $$MH *> THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA PRESENTED BY PROF. CHARLES A. KOFOID AND MRS. PRUDENCE W. KOFOID THE DISSECTOR'S MANUAL OF PRACTICAL ANB SURGICAL ANATOMY. ly BY ERAS MTTS^WTL S N. F. R. S. AUTHOR OF "A SYSTEM OP HUMAN ANATOMY," ETC. THE THIRD AMERICAN FROM THE LAST REVISED LONDON EDITION. tottfj tu anfc jFiftj-four EDITED BY WILLIAM HUNT, M.D. PEMO.NttTRATOR OF ANATOMY IN THE UNIVERSITY OF PENNSYLVANIA. PHILADELPHIA: BLANCHARD AND LEA. 1856. Entered according to the Act of Congress, in the year 1856, by BLANCHARD AND LEA, in the Office of the Clerk of the District Court of the United States in and for the Eastern District of Pennsylvania. PHILADELPHIA : T. K. AND P. G. COLLINS, PRINTERS. TO JONES QUAIN, M. D., THIS THE AUTHOR'S FIRST WORK IN EVER GRATEFUL REMEMBRANCE. PREFACE BY THE AMERICAN EDITOR. THE first two American editions of Mr. Wilson's book were published under the supervision of Dr. Goddard, who altered the arrangement of the English work, so as to agree with the mode of dissection usually adopted in Ame- rica. "In the English school" (as Dr. Goddard observes), " the dissector generally commences with the extremities, while with us the muscles and viscera of the abdomen claim the student's first attention ;" hence it was thought best to arrange the work accordingly. The present edition besides being much enlarged is somewhat modified from the others. New cuts have been added, illustrating many important subjects, and the editor can only hope that this guide to a knowledge of Practical Anatomy will fully sustain the reputation of its predeces- sors. The additions are inclosed between brackets [ ]. PHILADELPHIA, May, 1856. 1* CONTENTS. CHAPTER I. PAOR DISSECTION . . . . . . . . . vKi , , A) 26 CHAPTER II. ABDOtfBX. Superficial anatomy . . ^i^. -, * ;yn . . .166 Fifth pair of nerves . . . . . .176 Internal carotid artery . . . . - . .185 Facial nerve ; deep portion . . ... . 187 Eighth pair of nerves . . . . . . . 189 Hypoglossal nerve . . . . . . .193 Sympathetic nerve . . . . ... .193 Prse vertebral region . i-* &-.'' . . H; K . 196 Pharynx . ,' . . , , . . , -rv . 198 Soft palate . . . . % V- . . . 201 (Esophagus , . . . . . . , . . 203 CHAPTER IV. BRAIN AND SPINAL CORD. Membranes of the brain . . . . . . 04 Vessels of the brain . 209 CONTENTS. ix PAGE Cerebrum . . .*" . '* I . . . 212 Cerebellum . . + . fj . . . . 224 Base of the brain . . . . . . . 226 Medulla obi ongata . . *" r v - . 230 Fibres of the brain . # .. . .. ." '. . 233 Cranial nerves .. . . .. '-' : . 235 Sinuses of the cranium . .- .. . . 242 Spinal cord . .. ?v-: ; V C : * . 246 CHAPTER V. ORGANS OF SENSE. Nose and nasal fossae . . . . * 252 Appendages of the eye . . . * ,^. ,. . . 258 Lachrymal apparatus . . . ., ( * . . 261 Eyeball . . .. . , v>t . . , .. . 262 Ear . . .. . . ... - .,'., , . 271 Mouth and tongue . . . . . ,.,,- . 284 Larynx . .. . . .^ : . . ^. i( . 288 Skin . . . . . . ".^ A . .297 Appendages of the skin . . . . . . 301 CHAPTER VI. THORAX. Boundaries of the thorax . . . . fc . 305 Pleurae ; mediastinum . . . r . v> . . 306 Phrenic nerves . . . ; . i -. , . 307 Lungs . . . . ,-:. . :-. 308 Heart ./ . . . . ', . . 313 Great vessels of the heart . . . . . . 324 Nerves of the thorax . . . . ^ A 328 Pneumogastric nerve . . . f ? '.,-, 328 Sympathetic nerve . . . . . ^ . 329 Intercostal nerves . . . .,*'. -, . 331 Trachea . . . . * y^ . . . . 332 (Esophagus . . . . . -^ ^ . 333 Thoracic aorta . m . . . . . .. , ^. . 334 Azygos veins . . . , f . 335 Thoracic duct , . 336 X CONTENTS. CHAPTER VII. UPPER EXTREMITY. PAGE General anatomy . . . . . ,.#:.>: . 338 Table of muscles . . . . . r - ' ,' 339 Anterior thoracic region . . . . . . 343 Mammary gland . . . . . . 344 Operations on the axillary artery ; upper part . . . 347 Anatomy of the axilla ...... 348 Operations on the axillary artery ; lower part . . . 350 Brachial plexus of nerves ...... 352 Anatomy of the walls of the thorax . .* . 355 Anatomy of the shoulder and scapula . . . . 357 Anterior brachial region .... V 'r^. 362 Veins of the bend of the elbow . . . i a , 362 Accidents from venesection . . . ''*'* . 364 Operations on the brachial artery . . . . . 369 Anatomy of the forearm . . . . . . 371 Operations on the radial artery . . . " . 376 Operations on the ulnar artery 379 Palm of the hand ....... 386 CHAPTER VIII. LOWER EXTREMITY. Surgical observations ...... 392 Anterior femoral region . . . . . . 395 Internal femoral region .... '".'. . 402 Vessels of the thigh . . . . . . 404 Operations on the femoral artery . . . . ' .* 405 Nerves of the thigh . . . . . .410 Femoral hernia .. . . . * ' : .' ':" ; 412 Gluteal region ,* . . ."-^ ';"-." ' . 416 Posterior femoral regien .- . . , t> " '." . 423 Popliteal region . . . . . '"- Y ' . 425 Operation on the popliteal artery . . . V Y ; . 426 Anatomy of the leg ... - . . . ^ 428 Anterior tibial region . . . . . . 430 Operations on the anterior tibial artery . . . . 433 Dorsal region of the foot . ' . * . - . . . 434 Operation on the dorsalis pedis artery . . . 435 Fibular region . . . . . . 436 CONTENTS. Xl PAQB Posterior tibial region ; : *"' 'V . 437 Operations on the posterior tibial artery . . . 442 Operations on the peroneal artery . . . . . 443 Sole of the foot . . . * . . *?;; . : ! "-< ' i' 445 Actions of muscles of the lower extremity v . v." ' : 451 CHAPTER IX. PELVIS AND ORGANS OF GENERATION. Viscera of the pelvis . . . '''1'' '**-**< '". 7 452 Pelvic fascia ....... 454 Muscles of the cavity of the pelvU i.'. U.' . . . 455 Rectum . . . ^...^ . . . .456 Urinary bladder . ... . . . .456 Prostate gland . . . . ' . ' . 460 Vesiculee seminales . . . '"'"' . 460 Vessels of the pelvis . . ; 'i , -' / . 461 Nerves of the pelvis . . . -. ' : ; . . 465 Male organs of generation ...... 468 Penis . . . . . .... 468 Urethra ........ 470 Testes ........ 472 Female pelvis ....... 476 Female organs of generation ..... 478 Uterus ........ 478 External organs . . . . . . . 483 CHAPTER X. REGION OP THE BACK. Table of muscles ....... 485 Cutaneous nerves of the back ..... 486 Nerves and vessels of the back . . . . 493 Table of origins and insertions of muscle* . . . 500 CHAPTER XL ANATOMY OF THE PERINEUM. General considerations ...... 503 Internal pudic artery ...... 511 Operation of lithotomy '. . . .616 Female perineum . . . . . 517 Xii CONTENTS. CHAPTER XII. ANATOMY OF THE FOSTUS. PAGE Exterior anatomy of the foetus . . . . '.519 Foetal circulation . . . . . 519 Foetal thymus gland ... . . . .523 Foetal heart . . , , fj!r , r ^ . . . 526 Viscera of the abdomen . . . . . .526 Viscera of the pelvis ...... 528 Foetal testes, their descent ...... 528 CHAPTER XIII. LIGAMENTS. General anatomy . . . .... .530 Ligaments of the trunk . . . . .?-,.. u. 533 Ligaments of the upper extremity . . . . 545 Ligaments of the lower extremity . . . ; 555 THE DISSECTOH. CHAPTER I. DISSECTION. THE human body is composed of certain principal structures, which occupy the same relative position to each other, where- soever they be examined. To obtain a good knowledge of these, is 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. Superficial fascia. Deep fascia. Muscles. ( Arteries. Vessels, < Veins. ( Lymphatics. Nerves. 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 vessels and nerves which lie between them ; and in following the latter to their ulti- mate 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 3 26 THE DISSECTOR. divided, and in precisely the same order. Thus the student will perceive that one principal object of dissection is the practice of his knife in. the division and separation of these parts, so as to enable him to accomplish 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 are so necessary to the successful surgeon. Now, let us inquire into the nature of the structures composing the preceding table. The INTEGUMENT (integere, to cover in) is the investing cover- ing of the entire body ; in common parlance, the skin : it consists of the epiderma and derma. The Epiderma (cuticle, scarfskin) is the thin, horny layer which forms the surface of the integument. It is produced by the derma, upon which it is exactly moulded; is dense and hard on the outer surface, but softer within ; hence it has been described as consisting of two layers, of which the inner and deeper layer is called rete mucosum (rete, because the depressions caused by the papillae of the derma give it the appearance of a net; mucosum, from its softness). In intimate structure, the epiderma is com- posed of nucleated cells, which are thick in the part called rete mucosum, but flattened into thin scales in the outer layer. These cells are the seat of the pigment of the skin; which has a deeper hue in the thick and newly-formed cells than in the scales of the horny layer, where it is pale and almost lost, from drying. The epiderma is very thick in the palms of the hands and soles of the feet, and, in a state of increased density, constitutes the nails. The Derma, or cutis, or true skin, also presents a superficial and a deep layer. The former, constituting the surface of the derma, and formed into numberless minute papilla, is termed the papillary layer. The latter, being the chief bulk of the derma, is the corium. The papillary layer contains the capilla- ries and ultimate nervous plexuses of the skin; the corium is composed of fibres and strands of fibrous tissue, which form meshes of extreme fineness in the superficial portion of the layer, and coarser meshes in its deeper part. The meshes of the corium are occupied by fat, and give passage to the vessels and nerves of the papillary layer. The SUPERFICIAL FASCIA (fascia, a bandage), placed immediately beneath the tegument over every part of the body, is the medium of connection between that layer and the deeper parts. It con- sists of fibro-cellular tissue, in which is deposited an abundance of adipose tissue. The fat being a bad conductor of caloric, serves to retain the warmth of the body ; while it forms at the DEEP FASCIA MUSCLES VESSELS. 2t same time a yielding medium, through which the minute vessels and nerves pass to the papillary layer of the skin, without incur- ring the risk of obstruction from injury or pressure. By dissec- tion, 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 lymphatic vessels, or the cutaneous nerves, and in one instance 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 carry- ing 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 (aponeurotic fascia) is a white fibrous membrane, formed by a close interlacement of glistening fibres, which cross each other in various directions. To the eye it presents a brilliant, nacreous lustre. It is strong and unyielding, inclosing 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 protected 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 clavi- cle, scapula, elbow, and wrist, in the upper extremity. Its ten- sion is regulated in some situations by muscular action, as by the tensor vagina3 femoris and gluteus maximus in the thigh, and by the biceps and palmaris longus in the arm. The deep fascia of the neck (cellulo-fibrous fascia) is thinner, and has none of the resplendency of that of the limbs, although composed, like the latter, of white fibrous tissue. The MUSCLES (musculus, from movere, to move) are the moving organs of the body : they are made up of fibres disposed parallel to each other in a framework of cellular tissue. Towards the extremities of the muscles the fibres cease, and the cellular frame- work 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 movable end the "insertion." The muscles which inclose cavities, as the abdominal, are broad arid extensive; and their tendon is flattened out into a thin expansion, which is called " aponeurosis" (a?to, longe ; **vpo/, nervus ; a nerve widely spread out). This deriva- tion demands some explanation. The ancients named all the white fibres of the body vrvpa, or nerves. The VESSELS ;ire of three kinds, arteries, veins, and lym- phatics. Arteries are cylindrical tubes, composed of three layers, 28 THE DISSECTOR. an external, formed of condensed cellular tissue, the cellulo-Jibrous coat ; a middle, of fibres analogous to those of organic muscle, the contractile coat ; and a lining membrane, the internal or serous coat. After death they are usually found empty, but preserve their cylindrical form by reason of the thickness of their coats ; hence their name (a^p typew, to contain air), from a supposition of the ancients that they were intended to confine the vital spirits. Their office is to convey the vital fluid to every part of the sys- tem ; 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-colored 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 evi- dently marked on the exterior of the tube, by the swellings on that part of the vessel which immediately precedes them. The lymphatics (lympha, water) are small, delicate vessels which accompany the veins, and present many points of resem- blance 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 (vfvpa, nerves) are white flattened cords, composed of fibres, which are connected by one extremity with the cerebro- spinal axis ; and, by the other, are distributed 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 tubular fibres, inclosed in a peculiar transparent sheath, called neuri- lemma ; which, when freshly exposed, presents a continuous zigzag line along its cylinder. The nerves are usually found accompanying the arteries, and, in the extremities, are placed nearer the integument than those vessels, as if to be ready to apprise the neighboring muscles of the first approach of injury, that they may withdraw 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 connection to the numerous muscles, and bestow BONES LIGAMENTS. 29 general form upon the body. In the limbs they are hollow cylinders, 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 pro- jections of considerable length that serve as levers ; and smooth surfaces 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 proportion of the joints of the body are constructed upon this simple principle. When more extensive movements are demanded, the ball and socket joint is provided, and to accommodate its circular form, the four liga- ments are, as it were, united into one, which completely surrounds the ends of the two bones. Hence 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 carpus, and tarsus, small slips of ligaments 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 dependen- cies, before he can hope to display and examine them in the body with advantage. [The attention of the dissector should also be directed to some general facts in regard to the position of certain structures and their relative importance in the economy. Thus he should re- member that the great bloodvessels are placed upon the line of flexion, and as near as possible towards the inner side, and that this line includes all of the anterior aspect of the body, with the exception of the legs. By this arrangement, these essential parts are most effectually protected from injury, an(l least ex- posed to disturbance frorn the movements of the body. Jle 3* 30 THE DISSECTOR. should also not lose sight of the ordinary laws of physics and mechanics in his study of the human frame, for, by an intelligent application of these, he will frequently be enabled to comprehend and give a purpose to a part (as of a muscle, for example) even before he has an exact idea of its position and relations. 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 dis- sector 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. When the subject is injected with chloride of zinc, a plan generally adopted in this country, care should be taken not to remove too much of the integument at once, as the parts, when exposed, will dry and become hardened very rapidly, and will require to be soaked in water, in order to be again fit for dis- section.] CHAPTER II. ABDOMEN. [The dissection of the abdomen is to he 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 umbi- licus so as to isolate it. A second incision starts from the upper end of the first, downwards 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 spiuous 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, com- mencing at the upper corner, the external oblique muscle will be fully uncovered, and great care should be taken not to get beneath its tendon, the white shining fibres of which will serve as a guide to its muscular parts upon the thorax, and the outer side of the abdominal parietes. 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, and after this has been studied it should be removed in the di- rection of the fibres of the muscle and of its aponeurosis. One side of ABDOMEN. 31 the abdomen should be dissected exclusively for the muscles, and on this side the skin and fascia may be taken up together ; the other should be reserved for studying the relations of hernia.] The superficial fascia of the abdomen, like that in other parts of the body, is composed of cellular and adipose tissue. The quantity of fat varies considerably in different subjects. Near the groin the fascia is separable into two layers, between which are situated the superficial vessels and some inguinal glands. The superficial layer, in which the fat is chiefly found, is con- tinuous over Poupart's ligament with the superficial fascia of the thigh. The deep layer is attached to Poupart's ligament, and is lost on the upper part of the fascia lata. It contains but little fat, and is cellulo-fibrous in structure. The superficial fascia, divested of its fat, forms a sheath for the spermatic cord, and is prolonged over the penis and scrotum into the perineum, where it is continuous with the superficial fascia of that region. The superficial arteries of the abdomen are the superior exter- nal pudic, superficial epigastric, and superficial circumflexa ilii, all situated in the groin and branches of the femoral artery ; and cutaneous branches which accompany the lateral cutaneous and anterior cutaneous nerves ; the latter being derived from the in- tercostals, deep epigastric, and internal mammary artery. The superior external pudic artery crosses the external abdo- minal ring and spermatic cord, and is distributed to the integu- ment of the pubes and external organs of generation. The superficial epigastric lies externally to the external abdo- minal ring, and ascends towards the umbilicus, supplying the in- tegument in its course, and inguinal glands. The superficial circurnflexa ilii sends one or two small branches to the integument near the iliac extremity of Poupart's ligament. The veins accompanying these arteries terminate in the inter- nal saphenous vein. The superficial nerves of the abdomen are the lateral cutane- ous, anterior cutaneous, ilio-hypogastric, and ilio-inguinal. The lateral cutaneous nerves, five or six in number, are derived from the intercostal nerves. They pierce the muscles in a line with the thoracic branches, and divide like them into an anterior and posterior branch. The anterior branch is continued for- wards as far as the linea semilunaris. The posterior branch, smaller than the anterior, turns backward over the latissimus dorsi muscle. The lateral cutaneous branch of the last dorsal nerve is an ex- ception to the rest. It does not divide after piercing the exter- nal oblique muscle, but is directed downwards over the crest of the ilium, and is distributed to the integument of the hip as low 32 THE DISSECTOR. down as the trochanter major. The nerve crosses the crest of the ilium just behind the origin of the tensor vaginae femoris. The anterior cutaneous nerves are the terminations of the in- tercostal nerves ; they pierce the sheath of the rectus near the linea alba, and are reflected outwards to be distributed to the in- tegument. Like the lateral cutaneous nerves, they are accom- panied by small arteries. The ilio-hypogastric nerve, derived from the first lumbar nerve, divides into an iliac and hypogastric branch. The iliac branch pierces the muscles just above the crest of the ilium and behind its middle point, and is distributed to the integument of the glu- teal region. The hypogastric branch pierces the aponeurosis of the external oblique above the external abdominal ring, and is distributed to the integument of the hypogastric region. The ilio-inguinal nerve, also derived from the first lumbar nerve, emerges at the external abdominal ring, and is distributed to the scrotum and upper part of the thigh, internally to the saphenous opening. The lymphatic glands, three or four in number, are situated between the two layers of the superficial fascia above Poupart's ligament. They receive the lymphatics from the abdomen, upper and outer part of the thigh, and genital organs ; and their efferent ducts descend to the saphenous opening to enter the stream of lymphatics of the lower limb. The MUSCLES of the abdomen are the External oblique, Rectus, Internal oblique, Pyramidal is, Transversalis, Quadratus lumborum. When the external oblique muscle is dissected on both sides, a white tendinous line will be seen along the middle of the abdo- men, extending from the ensiform cartilage to the pubes : this is the linea alba. A little external to it, on each side, two curved lines will be observed extending from the eighth rib to the spine of the pubes, and bounding the recti muscles: these are the linece semilunares. Some transverse lines, linece transverse, three in number, connect the lineae semilunares with the linea alba at and above the umbilicus. The linea semilunaris was the situation formerly chosen for the opera- tion of tapping the abdomen in dropsy, paracentesis 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 semilunaris 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 MUSCLES OP THE ABDOMEN. Fig. 1. 33 THE MUSCLES OF THE ANTERIOR ASPECT OF THE TRUNK; ON THE LEFT SIDE THE SUPERFICIAL LATER 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. 5. The subclavius muscle of the right side. 6. The pectoralis minor. 7. The coraco-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 num- ber 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 exter- nal 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 inter- col mnnar fibres are seen proceeding upwardsfrom 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 trans- versalis descending behind Poupart's ligament to the pectineal line. 20. The arch formed between the lower curved border of the internal oblique muscle and Poupart's ligament; it is ben earth this arch that the spermatic cord and hernia pass. 21. Fascia lata femoris. 22. Saphenous opening. 34 THE DISSECTOR. 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 abandoned. Ventral hernia may occur in the course of this line. The linea alba is now selected for the operation of paracentesis abdo- minis. Being in the middle line it cannot change its place by distension, and there is no risk of wounding an artery. The spot selected for the operation is usually midway between the umbilicus and pubes. It is performed by making a small incision with a bistoury through the inte- gument and superficial fascia, and then introducing the trocar. This line is also the seat of operation for puncturing the bladder above the pubes ; which is performed in the same manner as paracentesis abdo- minis. The high operation for lithotomy, # practice disused in this country, has also its seat in the linea alba. The Ccesarean section, for opening the uterus and removing the fetus, an operation which is now becoming frequent in consequence of success ; and the operation for the removal of a part or the whole of the cyst in ovarian dropsy, are also practised in the linea alba. Moreover, a weakening of the linea alba, from over-distension, or con- genital deficiency, gives rise to the protrusion of intestine at the umbili- cus, 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 membrane of the bladder is pro- truded through the integument. The EXTERNAL OBLIQUE MUSCLE (oHiquus externus abdominis descendens) is the external flat muscle of the abdomen. Its name is derived from the obliquity of its direction, and the descend- ing 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. Soon after its origin it spreads out into a broad aponeurosis, and is inserted into the outer lip of the crest of the ilium for one-half its length, the anterior superior spine of the ilium, spine of the os pubis, pectineal line, front of the os pubis, and linea alba. The superior border of the obliquus externus is continuous with the lower border of the pectoralis major, and its fibres of origin with those of the external intercostal muscles. Its poste- rior border is separated from the anterior border of the latissimus dorsi by a cellular interval, but is sometimes overlapped by that muscle. The lower border of the aponeurosis, which is stretched between the anterior superior spinous process of the ilium and the spine of the os pubis, is round from being folded inwards, and forms Pouparfs ligament. Poupart's ligament is round at its outer part, but flattened from above downwards nearer the pubes, forming a groove which supports the spermatic cord. It is curved EXTERNAL OBLIQUE MUSCLE. 35 in its course, from its attach- ment to the fascia lata ; and its insertion into the pecti- neal line is Gimbernafs liga- ment. The attachment of Gimbernat's ligament to the pectineal line is about three quarters of an inch in length, and from this insertion some tendinous fibres are directed upwards and inwards behind the rectus muscle to the linea alba, and have received the name of triangular liga- ment. Just above the crest of the os pubis is the external abdominal ring, a triangu- THE INNOMINATE BONE OP THE LEFT lar opening formed by the SIDB, with-i. Poupart's ligament ; 2. r ,. , , J f Orirabernat s ligament. separation of the fibres of the aponeurosis of the external oblique. It is oblique in its direction, and corresponds with the course of the fibres of the aponeurosis. It is bounded below by the crest of the os pubis ; on either side, by the borders of the aponeurosis, which are called pillars ; and above by some curved fibres (intercolum- nar) which originate from Poupart's ligament, and cross the upper angle of the ring, so as to give it strength. The exter- nal pillar, which is at the same time inferior from the obliquity of the opening, is inserted into the spine of the os pubis ; the in- ternal or superior pillar forms an interlacement with its fellow of the opposite side over the front of the symphysis pubis. The external abdominal ring gives passage to the spermatic cord in the male, and the round ligament in the female: they are both invested in their passage through it by a thin fascia derived from the edges of the ring, and called inter columnar fascia , or fascia spermatica. The pouch of inguinal hernia, in passing through this opening, receives the intercolumnar fascia as one of its coverings. 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 the crest of the ilium to the anterior superior spine, and thence trans- versely onwards to the linea alba. The muscle may then be turned for- wards to the linea alba, or removed altogether. The lower portion of the aponeurosis should now be turned downwards, and left for subsequent examination. The INTERNAL OBLIQUE MUSCLE (obliquus intermit abdominis ascendens) is the middle flat muscle of the abdomen. It arises 36 THE DISSECTOR. from the outer half of Poupart's ligament, from the middle of the crest of the ilium for two-thirds its length, and by a thin apo- neurosis from the spinous processes of the lumbar vertebrae. Its fibres diverge from their origin, so that those from Poupart'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 pectinea} line and crest of the os pubis, linea alba, and lower borders of the five inferior ribs. Along the upper three-fourths of the linea semilunaris, the apo- neurosis 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 sepa- ration. The two layers, which thus inclose the rectus, form for it a partial sheath. The lowest fibres of the internal oblique are inserted into the pectineal line of the os pubis in common with those of the trans- Fig. 3. THE INTERNAL OBLIQUE AND TRANSVERSALIS MUSCLE IN THE INGUINAL REGION, WITH THE BOUNDARIES OP 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 oblique. 1'. Lower part of same turned down, 2, Internal oblique muscle. 3. Spermatic cord. 4. Saphenous vein. CREMASTER MUSCLE. 3t vcrsalis muscle. Hence the tendon of this insertion is called the conjoined tendon of the internal oblique and transversals. This structure corresponds with the external abdominal ring, and forms a protection to what would otherwise be a weak point in the ab- domen. Sometimes the tendon is insufficient to resist the pres- sure from within, and becomes forced through the external ring ; it then forms the distinctive covering of direct inguinal hernia. The spermatic cord passes beneath the arched border of the internal oblique muscle, between it and Poupart's ligament. During its passage, some fibres are given off from the lower border of the muscle, which ac- company the cord downwards to the testicle, and form loops around it ; this is the cremaster muscle. In the descent of oblique inguinal hernia, which travels the same course as the spermatic cord, the cremaster mus- cle forms one of its coverings. The CREMASTER, considered as a distinct muscle, arises from the middle of Poupart's ligament, and forms a series of loops upon the spermatic cord. A few of its fibres are inserted into the tunica vaginalis ; the rest ascend along the inner side of the cord, to be inserted, with the conjoined tendon, into the pectineal line of the os pubis. The internal oblique muscle is to be removed by separating it from its attachments to the ribs above, and the crest of the ilium and Poupart's ligament below. It should be divided behind by a vertical incision ex- tending from the last rib to the crest of the ilium, as its lumbar attach- ment cannot at present be examined. The muscle is then to be turned forwards. Some degree of care will be required in performing this dissec- tion 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. There will also be found between them branches of the intercostal arteries and nerves, the ilio-inguinal and ilio- hypogastric nerves, and near the crest of the ilium the circumflexa ilii artery, which ascends between the two muscles, and forms a valuable guide to their separation. Just above Poupart's ligament they are so closely connected, that it is impossible to divide them. The TRANSVERSALIS is the internal flat muscle of the abdomen ; 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 spinous and transverse processes of the lumbar vertebrae, and from the inner surface 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 os 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 4 THE DISSECTOR. Fig. 4. lamellae ; anterior, which is attached to the bases of the transverse processes of the lumbar vertebra ; middle, to the apices of the transverse processes ; and posterior, to the apices of the spinous processes. The anterior and middle lamella inclose the quad- ratus lumborum muscle ; the middle and posterior, the erector spinaB. The union of the posterior lamella with the posterior aponeurosis of the internal oblique, serratus postlcus inferior, and latissimus dorsi, constitutes the lumbar fascia. To dissect the rectus muscle, its sheath should he opened by a ver- tical incision extending from over the cartilages of the lower ribs to the front of the os pubis. The sheath may then be dissected off and turned to either side ; this is easily done excepting at the linese transversse, where a close adhesion subsists between the muscle and the external boundary of the sheath. The sheath contains the rectus and pyramidalis muscle. The RECTUS MUSCLE arises by a double tendon from the front and crest of the os pubis, and is inserted into the cartilages of the fifth, sixth, and seventh ribs. It is traversed by several tendinous intersections, called linese transversae. One of these is situated at the umbilicus, one over the ensiform cartilage, and one midway between these points; when a fourth exists, it is situated below the umbili- cus. They are vestiges of the abdominal ribs of reptiles, and very rarely extend completely through the muscle. The PYRAMIDALIS MUSCLE A LATERAL VIEW OF THE TRUNK OF THE BODY, SHOWING ITS MUSCLES, AND PARTICULARLY THE TRANSVERSALis ABDOMiNis. 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 transversalis muscle. 7. Its posterior aponeurosis. 8. Its anterior aponeurosis, forming the most posterior layer of the sheath of the rec- tus. 9. The lower part of the left rectus with the aponeurosis of the transver- salis passing in front. 10. The right rectus muscle. 11. The arched opening left between the lower border of the transversalis muscle and Poupart's liga- ment, through which the spermatic cord and hernia pass. 12. The gluteus maximus, and medius, and tensor vaginae femoris muscles invested by fascia lata. RECTUS MUSCLE PYRAMIDALIS MUSCLE ACTIONS. 39 arises from the crest of the os pubis in front of the rectus, and is inserted into the linea alba about midway between the umbi- licus and os pubis. It is inclosed in the same sheath with the rectus, and rests against the lower part of that muscle. It is sometimes wanting. 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 wall of the sheath terminates in a thin curved mar- gin, the aponeuroses of the three muscles passing altogether in front of the rectus. 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 out- wards : both together bend it directly forwards. Either transversalis muscle, acting singly, will diminish the size of the abdomen on its own side, and both together will constrict the entire cylinder of the cavity. The recti muscles, assisted by the pyramidales, flex the thorax towards the pelvis, and through the medium of the lineae transversae, are enabled to act when their sheath is curved inwards by the action of the trans- versales. The pyramidales are tensors of the linea alba. The abdomi- nal are expiratory muscles, and the chief agents of expulsion ; by their action the foetus is expelled from the uterus, the urine from the bladder, faeces from the rectum, bile from the gall-bladder, ingesta from the sto- mach and bowels in vomiting, and mucus and irritating substances from the bronchial tubes, trachea, and nasal passages during coughing and sneezing. To produce these efforts, they all act together. Their violent and continued action produces hernia ; and, acting spasmodically, they may occasion rupture of the viscera. Vessels and Nerves. The VESSELS of the abdominal parietes are, the intercostal and lumbar arteries ; circumflexa ilii ; and, in the sheath of the rectus, the epigastric and internal mammary. The intercostal arteries continue their course from the lower intercostal spaces between the internal oblique and transversalis muscle ; they are distributed to the muscles, and inosculate with the lumbar arteries, internal mammary, and epigastric. The lumbar arteries, four in number on each side, are branches of the abdominal aorta. Their course and distribution are similar to that of the intercostals. Each artery, between the transverse processes of the vertebrae, divides into a dorsal and abdominal branch. The dorsal branch passes backwards for the supply of the spine and muscles of the vertebral column. The abdominal branch advances between the transversalis and internal oblique 40 THE DISSECTOR. muscle to supply the parietes of the abdomen. These branches inosculate with the intercostal arteries above, the ilio-lumbar and circumflexa ilii below, and the internal mammary and epigas- tric in front. The circurnflexa ilii artery arises from the external iliac artery close to Pou part's ligament, and passes outwards behind that ligament to the crest of the ilium, and along the crest to its pos- terior part, where it inosculates with the ilio-lumbar artery. In its course, the artery pierces the crural sheath, and then lies be- tween the transversalis muscle and fascia ; near its termination it pierces the transversalis, and becomes placed between it and the internal oblique. An ascending branch is given off near the an- terior superior spine of the ilium ; this branch ascends in the cel- lular interval between the internal oblique and transversalis, and inosculates with the other arteries of the parietes. The epigastric artery arises from the front of the external iliac artery a little above the circumflexa ilii ; it bends inwards, and then ascends obliquely between the transversalis fascia and peri- toneum to the lower margin of the sheath ? of the rectus. Pierc- ing the transversalis fascia, it enters the sheath and ascends be- hind the rectus muscle to its upper part, where (in the substance of the muscle) it inosculates with the internal mammary artery. In the first part of its course the artery lies internally to the in- ternal abdominal ring, below the spermatic cord, and above the femoral ring. When the abdominal parietes are examined from within, the epigastric artery will be seen to form a prominent ridge, which divides the iliac fossa into an internal and external portion. It is in the former that direct inguinal hernia occurs ; in the latter oblique inguinal hernia. The branches of the epigastric artery are : A cremasteric branch which accompanies the spermatic cord, and after supplying the cremaster muscle inosculates with the spermatic artery. A pubic branch, which is distributed behind the pubes, and sends a small branch of communication downwards to the obtu- rator artery. Muscular branches, which pass outwards between the abdomi- nal muscles, and inosculate with the circumflexa ilii, lumbar, and intercostal arteries. Superficial branches, which are distributed to the integument of the abdomen. The internal mammary artery, a branch of the subclavian, is situated in the sheath of the rectus. It supplies the upper part of that muscle, and inosculates with the epigastric, intercostals, and lumbar arteries. The VEINS accompanying the arteries of the abdominal parietes EPIGASTRIC ARTERY. 41 take the course of their respective arterial branches ; the inter- costal veins terminate in the venae azygos, the lumbar in the in- ferior vena cava, and the circumflexa ilii and epigastric in the external iliac. The NERVES of the abdominal parietes are, the six lower inter- Fig. 5. ANTERIOR WALL OF THE ABDOMEN ; INTERNAL ASPECT. a, a, Linea alba, b, b. Linea semilunaris. c, c. Lineaa transversae. The letters c, c are placed on the posterior surface of the sheath of the rectus. d. The lower bor- der of this sheath, under which T;he epigastric artery is seen passing, e, / The rectus muscle : e refers also to the superior epigastric artery, a branch of the internal mammary ; and/, /to the proper epigastric artery, g. The internal mammary artery, h. Its musculo-phrenic branch, t, i. Part of the dia- phragm, k. Section of the three abdominal muscles. /. Section of the exter- nal and internal oblique ; the transversalis having been removed, m. The ex- ternal iliac artery, n. The circumflexa ilii artery, seen in its whole course on the right side in consequence of the removal of the transversalis muscle ; the leading line crosses the iliacus muscle, u. The external iliac vein. p. The crural ring. g. Gimbernat's ligament, s, t, refer to the arch formed between the lower borders of the internal oblique and transversalis muscle and Poupart's ligament ; the arch is crossed by the epigastric artery : the space s above the artery corresponds with the internal abdominal ring, and gives passage to ob- lique inguinal hernia : in this space is seen a part of the internal oblique muscle, which extends lower on Poupart's ligament than the transversalis. Through the space t is seen the aponeurosis of the external oblique muscle, v. The con- joined tendon of the internal oblique and transrersalis. 4* 42 THE DISSECTOR. costals, and two branches of the first lumbar nerve, namely, the ilio-hypogastric, and ilio-inguinal. The intercostal nerves pass from the intercostal spaces, be- tween the internal oblique and transversalis muscle, to the front of the abdomen, where they enter the sheath of the rectus. Near the linea alba they terminate by piercing the sheath, and becom- ing the anterior cutaneous nerves (page 32). Midway between the vertebral column and linea alba, each in- tercostal nerve gives off its lateral cutaneous branch, which pier- ces the internal and external oblique muscles to reach the sur- face (page 31). The last intercostal, or rather, the last dorsal nerve, lies below the last rib ; its lateral cutaneous branch does not divide like the rest, but is continued over the crest of the ilium, to the integu- ment of the hip. The ilio-hypogastric nerve pierces the transversalis just above the crest of the ilium, and a little posterior to its mid-point, and divides into its two branches, iliac and hypogastric. The iliac branch pierces the internal and external oblique muscles, and descends over the crest of the ilium, to be distributed to the in- tegument of the gluteal region. The hypogastric branch continues its course forward, a little above the crest of the ilium ; and, near the anterior superior spine, communicates with the ilio-inguinal nerve. It then pierces the internal oblique muscle, and, near the linea alba, the aponeurosis of the external oblique, and is distributed to the integument of the hypogastric region. The ilio-inguinal nerve, smaller than the preceding, and infe- rior to it in position, pierces the transversalis muscle in front of the anterior superior spine of the ilium, and communicates with the hypogastric branch of the ilio-hypogastric nerve. It then pierces the internal oblique muscle, and, passing through the external abdominal ring with the spermatic cord, is distributed to the integument of the upper and itfner part of the thigh, and to the neighboring part of the scrotum or pudendum. The vessels and nerves of the abdominal parietes having been carefully studied, the dissector should examine the lower border of the transver- salis muscle, and its relations to the internal oblique muscle (which has been already turned aside, but may be replaced for this examination) and to the spermatic cord. The latter will be found issuing from beneath the lower border of the muscle, between it and Poupart's ligament. Following the curve formed by the lower border of the muscle, he will find it descend behind the spermatic cord and Poupart's ligament, to be inserted, in conjunction with the internal oblique muscle, into the pec- tineal line of thepubes behind Grimbernat's ligament. The membranous structure which occupies the interval between the lower border of the transversalis and Poupart's ligament is the transversalis fascia, which is next to be examined. For this purpose the transversalis should be sepa- FASCIA TRANSVERSALI8. 43 Fig. 6. rated from its attachment to Poupart's ligament, and the crest of the ilium, and turned upwards and forwards; the muscle should then be di- vided by an incision carried from the middle of the crest of the ilium to the last rib, and another bordering the lower margin of the thorax. The muscle may then be turned over entirely to the middle line, and the transversalis fascia will be exposed. The fascia transversalis (fascia Cooperi from its important rela- tion to inguinal hernia being first particularly described by Sir Ast- ley Cooper) is a thin fibrous mem- brane which lines the internal sur- face of the transversalis muscle, and is interposed between that muscle and the peritoneum. It is thickest at the lower part of the abdomen where the muscular structure is weak, and becomes thinner as it ascends, until it is lost in the subserous cellular tissue. It is attached inferiorly to the re- flected margin of Poupart's liga- ment, and to the crest of the ilium ; internally, to the pectineal line and border of the rectus muscle ; and, at the inner part of the femoral arch, is continued beneath Pou- part's ligament, and forms the an- terior segment of the crural canal, or sheath of the femoral vessels. THE TRANSVERSALIS FASCIA, THE ABDOMINAL MUSCLES BEING REMOVED. 1. Poupart's ligament. 2. The transversalis fascia. 3. The internal abdominal ring, an open- ing in the transversalis fascia. 4. The internal abdominal ring is The situation of the external ab- situated in this fascia, at about ^ n al &5^trSf2taS midway between the symphysis trie artery between the two rings. " pubis and the anterior superior spine of the ilium, and fralf an inch above Poupart's ligament ; it is oval in form, and bounded on its inner side by a well-marked falciform border, but is ill-defined around its outer margin. From the circumference of the ring is given off an infundibuliform process, which surrounds the testicle and spermatic cord, consti- tuting the fascia propria of the latter, and forms the first invest- ment to the sac of oblique inguinal hernia. When the fascia propria has been carefully examined, it should be laid open by a longitudinal incision ; this will bring into view a layer of subserous fat, of variable thickness. When the fat is pushed aside with the handle of the scalpel, the peritoneum will be found to bulge at this point, and at the most prominent part of the bulge may be detected the librous remains of the obliterated process of the peritoneum, which ori- 44 THE DISSECTOR. ginally surrounded the testis during its descent in the foetus. This fibrous structure may present every degree of degradation; sometimes it is scarcely discernible, at other times it is a fibrous band of 'some bulk ; in another series of cases it is sacculated, or the tube of peritoneum may still be pervious. SPERMATIC CORD. The spermatic cord, composed of the ves- sels, nerves, and excretory duct of the testicle, and inclosed by certain coverings, takes its course from the internal abdominal ring, between the layers constituting the parietes of the abdo- men, to the external abdominal ring. The space so occupied by the spermatic cord is denominated the spermatic canal, and is about one inch and a half in length. It is bounded in front by the aponeurosis of the external oblique muscle; behind, by the transversalis fascia, and the conjoined tendon of the internal oblique and transversalis ; above, by the arched borders of the internal oblique and transversalis; below, by the grooved border of Poupart's ligament: and at each extremity by one of the ab- dominal rings, the internal ring at the internal termination, the external ring at the outer extremity. The coverings of the spermatic cord, while situated in the spermatic canal, are the fascia propria, derived from the fascia transversalis; and the cremaster muscle, derived from the lower border of the internal oblique. On emerging at the external abdominal ring, it receives the intercolumnar fascia from the borders of the ring, and is then inclosed in a sheath of superficial fascia; lastly, it is covered by the integument. The fascia propria, derived from the fascia transversalis, is an infundibuliform sheath, loosely connected with the cord by cel- lular tissue, in which adipose matter is deposited. The fibres of the cremaster muscle, held together by cellular tissue, and thus forming a cellulo-muscular layer, has received the name of cremasteric fascia ; and the intercolumnar fascia is also known as the spermatic fascia. The coverings of the cord may now be divided longitudinally, and turned aside, in order to bring into view its other components, the ves- sels, nerves, and excretory duct. The ARTERIES of the spermatic cord are the cremasteric, sper- matic, and deferential. The cremasteric artery is a small branch of the epigastric, and is distributed to the cremasteric fascia. The spermatic artery, a branch of the aorta, enters the inter- nal abdominal ring, and accompanies the cord to the testicle, to which it is distributed. The deferential artery is a small branch of the superior vesical artery, which accompanies the vas deferens to the testicle. The VEINS of the cord, the spermatic veins, ascend from the posterior border of the testicle. They form & plexus which con- ANATOMY OP HERNIA. 45 stitutes the chief bulk of the cord, and unite in a single vein, which accompanies the spermatic artery to terminate on the right side in the inferior vena cava, and on the left in the left renal vein. The lymphatic vessels of the spermatic cord terminate in the lumbar glands. The NERVES of the spermatic cord are the scrota! branch of the ilio-inguinal ; the genital branch of the genito-crural, which enters the internal abdominal ring and accompanies the cremas- teric artery to be distributed to the cremasteric fascia; and the spermatic plexus. The spermatic plexus is derived from the aortic and renal plexus, and accompanies the spermatic artery. The VAS DEFERENS, the excretory duct of the testis, is situated along the posterior border of the cord, where it may be distin- guished by the hard and cordy sensation which it communicates to the fingers. On reaching the internal abdominal ring, it lies internally to the spermatic vessels, and turns inwards behind the epigastric artery to the side and base of the bladder, where it terminates in the urethra. It is accompanied by its proper artery. In the female, the place Fig. 7. of the spermatic cord is occupied by the round ligament of the uterus, which takes exactly the same course as the cord, has the same relations and coverings, with the exception of the cremas- ter, and, after passing through the external ab- dominal ring, terminates in the superficial fascia of the groin. ANATOMY OF HERNIA. The herniae occurring in the parietes of the ab- domen have been divided by Sir Astley Cooper into four species; namely, um- THE ANATOMY OF INGUINAL HEUNIA, THK LEFT 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 (Pouparfs ligament). 3. Transverse fibres of the aponeurosis. 4. Pectineal portion of the fascia lata. 5. The spermatic cord. 6. The long saphenous vein. 7. Fascia lata feuioris; its sartorial portion. 46 THE DISSECTOR. bilical, ventral, inguinal, and femoral: to which may be added, as occasionally taking place, phrenic, obturator, ischiatic, gluteal, perineal, and, in the female, vaginal. Umbilical hernia occurs at the umbilicus from weakening of the linea alba, either by over-distension, as in utero-gestation, or from congenital deficiency. Its coverings are, the integument, superficial fascia, distended aponeurosis, and 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. Fig. 8. AFTER THE REMOVAL OP THE LOWER PART OP THE EXTERNAL OBLIQUE (WITH THE EXCEPTION OP A SMALL SLIP INCLUDING POUPART ! S LlGAMENT), 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 OP THE BLOODVESSELS LAID OPEN. 1. External oblique muscle. 2. Internal oblique. 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 conjoined 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 pectineal 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. OBLIQUE INGUINAL HERNIA. 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 abdominal ring, carrying before it the conjoined tendon of the internal oblique and transversalis muscles. One side of the abdomen having been reserved for the study of hernia, an incision should be made through the aponeurosis of the external oblique from the anterior superior spine of the ilium to the linea alba, and another along the margin of Poupart's ligament to the external pil- lar of the external abdominal ring. The aponeurosis should then be drawn down, and the internal oblique muscle and transversalis dissected separately and turned aside in a similar manner. The transversalis fascia and peritoneum should next be divided in the direction of the transverse incision from the crest of the ilium to the linea alba. The student may now follow the description of inguinal hernia, and examine the layers concerned in its course. Fig. 9. A DIRECT INGUINAL HERNIA ON THE LEFT SIDE, COVERED BV THK CONJOINED TENDON OF THE INTERNAL OBLIQUE AND TRANSVERSE MUSCLES. 1. Aponeurosis of the external oblique. 2. Internal oblique turned up. 3. Transversalis muscle. 4. Fascia transversa- lis. 5. Spermatic cord. 6. The hernia. N. B. A small part of the epigastric artery is seen through an opening made in the transversalis fascia. In OBLIQUE INGUINAL HERNIA, the intestine escapes from the cavity of the abdomen into the spermatic canal, through the in- ternal abdominal ring, pressing before it a pouch of peritoneum, which constitutes the hernial sac, and distending the infundibuli- form process of the transversalis fascia. After emerging through the internal abdominal ring, it passes fast beneath the lower and arched border of the transversalis muscle; then beneath the lower border of the internal oblique muscle; and finally through the external abdominal ring in the aponeurosis of the external oblique. From the transversalis muscle it receives no investment; while 48 THE DISSECTOR. passing beneath the lower border of the internal oblique, it ob- tains the creraaster muscle; and, upon escaping at the external abdominal ring, receives the intercolumnar fascia. So that the coverings of an oblique inguinal hernia, after it has emerged Fig. 10. A SMALL OBLIQUE INGUINAL HERNIA, AND A DIRECT ONE ARE SEEN ON THE RIGHT SIDE. A LITTLE OP THE EPIGASTRIC AR- TERY HAS BEEN LAID BARE, BY DIVIDING THE FASCIA TRANSVER- SALIS 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 co- vered by an elongation from the fascia transversalis. through the external abdominal ring, are, from the surface to the intestine, the Integument, Superficial fascia, Intercolumnar fascia, Cremaster muscle, Transversalis, or infundibuliform fascia, Peritoneal sac. There are three 1 varieties of oblique inguinal hernia: common, congenital, and encysted. Common oblique hernia is that which has been described above. Congenital hernia results from the non-closure of the pouch of peritoneum carried downwards into the scrotum by the testicle during its descent in the foetus. In consequence of this defect,, the intestine at some period of life is forced into the peritoneal canal, and descends through it into the tunica vaginalis, where it lies in contact with the testicle ; so that congenital hernia has 1 Verpeau describes a fourth, in which the protrusion takes place be- tween the edge of the rectus and the umbilical ligament, and then takes the course of the spermatic canal. DIRECT INGUINAL HERNIA. 49 no proper sac, but is contained within the tunica vaginalis. The other coverings are the same as those of common inguinal hernia. Fig. 11. Fig. 12. COMMON OBLIQUE INGUINAL HER- NIA. THK INTKSTINK IN A DISTINCT SAC OF PERITONEUM AND SEPA- RATED FROM THE TESTICLE BY THE TUNICA VAGINALIS. 1. The sac of the hernia. 2. The tunica vaginalis inclosing the testicle. 3, 4. The spermatic cord. CONGENITAL HERNIA, THE INTES- TINE BEING IN CONTACT WITH THE TESTICLE ; THE TUNICA VAGINALIS OF THE TESTICLE FORMING THE SAC OF THE HERNIA. 1. The tunica va- ginalis testis, continuous superiorly with the peritoneum, of which it is a part. 2. The testicle. 3. The sper- matic cord. Encysted hernia 1 (hernia infantilis of Hey) is that form of protrusion in which the pouch of peritoneum forming the tunica vaginalis, being only partially closed, and remaining open exter- nally to the abdomen, admits of the hernia passing into the scro- tum, behind the tunica vaginalis. So that the surgeon, in ope- rating upon this variety, requires to divide three layers of serous membrane ; the first and second layers being those of the tunica vaginalis, and the third the true sac of the hernia. DIRECT INGUINAL HERNIA has received its name from passing directly through the external abdominal ring, and forcing before it the opposing parietes. This portion of the wall of the abdo- men is strengthened by the conjoined tendon of the internal oblique and transversalis muscle, which is pressed before the her- nia, and forms one of its investments. Its coverings are, the 1 A case of this kind occurred to Mr. Listen in 1855. The student will find a full acconnt of it in a Clinical Lecture in the 1st volume of the Lan- cet for 18345, page 883. 5 50 THE DISSECTOR. Fig. 13. Integument, Superficial fascia, Intercolumnar fascia, Conjoined tendon, Transversalis fascia, Peritoneal sac. Direct inguinal hernia differs from oblique, firstly, in never at- taining the same bulk, in conse- quence of the resisting nature of the conjoined tendon of the inter- nal oblique and transversalis, and of the transversalis fascia; secondly, in its direction, having a tendency to protrude from the middle line, rather than towards it ; thirdly, in making for itself a new passage through the abdominal parietes, instead *.of following a natural channel; and fourthly, in the re- lation of the neck of its sac to the epigastric artery, that vessel lying to the outer side of the opening of the sac of direct hernia, and to the inner side of that of oblique hernia. All the forms of inguinal hernia are designated scrotal, when they have descended into that cavity. 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 tumor : hence one of many reasons for extreme care and caution in operating for strangu- lated hernia. Direct inguinal hernia often carries the spermatic cord before it, so that the vessels of which it is composed be- come spread over the front of the hernial sac, or slip to one side. In operating upon inguinal hernia, the importance of knowing the layers which cover it, and which are to be cut through be- fore reaching the bowel, is obvious; the oblique and direct her- nia differ from each other in this respect only in the composition of the fourth layer, the cremaster occupying that place in oblique hernia, and the conjoined tendon in direct. If the oblique in- guinal hernia had reached no further than the spermatic canal, then the aponeurosis of the external oblique muscle would take the place of the intercolumnar fascia. This form of oblique in- guinal hernia is termed bubonocele. ENCYSTED HERNIA; THE HER- NIAL SAC CONTAINING THE INTES- TINE BEING BEHIND THE TUNICA VAGINALIS. 1. The hernial sac. 2. The cavity of the tunica vagi- nalis. 3. The testicle. 4. The spermatic cord. The arrow shows that three layers of serous mem- brane must be divided before the intestine can be reached. DIRECT INGUINAL HERNIA. 51 The seat of stricture is commonly the neck of the sac in all the varieties of inguinal hernia, and the direction of the incision for Fig. 14. A PORTION OP THE WALL OP THE ABDOMEN AND OF THE PELVIS is HERE SKKN ON THE POSTERIOR ASPECT, THE OS INNOMINATUM OP THE LEFT SlDE WITH THE SOFT PARTS CONNECTED WITH IT HAVING BEEN REMOVED PROM THE REST OF THE BODY. 1. Symphysis of pubes. 1'. 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. Rec- tus, 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 spermatic 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. its liberation should be directly upwards, by which means any danger to the epigastric artery is avoided. Sometimes the stric- ture of oblique inguinal hernia is occasioned by the lower border of the internal oblique muscle, and sometimes by the external abdominal ring. In old and large hernia, the internal ring is dragged down so as to become placed opposite the external, and the two together form the neck of the sac. In direct hernia, the fascia transversalis with the border of the conjoined tendon are the structures forming the neck of the sac. When the layers of the abdominal parietes concerned in inguinal her- nia have been examined, an incision should be made from the umbilicus 52 THE DISSECTOR. to the anterior superior spine of the ilium at each side, and the triangu- lar flap included by these incisions turned down. On the surface of this flap will be seen several prominences and depressions which require to be noted. In the middle line behind the linea alba is a prominence caused by a fibrous cord called urachus, which ascends from the apex of the bladder to the umbilicus ; on either side of the middle line, and converging from the sides of the bladder to the urachus in their course to the umbilicus, is another prominence caused by a fibrous cord (umbilical ligament), the remains of the hypogas- tric artery of the foetus. This cord, at its lower part, lies in the direction of the epigastric artery, and divides the lower part of the anterior wall of the abdomen into two fossae, which cor- respond with the seat of protrusion of the oblique and direct inguinal hernia; the former passing through the outer fossa, and the latter through the inner, between the epigastric artery and the edge of the rectus. CAVITY OP THE ABDOMEN. The cavity of the abdomen may now be laid open by means of an in- cision made parallel with, but a little to the left of, the linea alba from the ensiform cartilage to the umbilicus, and another on each side from the umbilicus to the last rib. The flaps included by these incisions should then be turned back. The cavity of the abdomen is bounded in front and at the sides by the lower ribs and abdominal muscles ; behind, by the verte- bral column and abdominal muscles ; above, by the diaphragm ; and below, by the pelvis ; and contains the alimentary canal, the organs subservient to digestion, viz : the liver, pancreas, and spleen ; and the organs of excretion, the kidneys, with the supra- renal capsules. Regions. For convenience of description of the viscera, and of reference to the morbid affections of this cavity, the abdomen is divided into certain districts or regions. Thus, if two trans- verse lines be carried around the body, the one parallel with the cartilage of the eighth rib, the other with the highest point of the crests of the ilia, the abdomen will be divided into three zones. Again, if a perpendicular line be drawn, at each side, from the cartilage of the eighth rib to the middle of Poupart's ligament, the three primary zones will each be subdivided into three compartments or regions, a middle and two lateral. The middle region of the upper zone being immediately over the small end of the stomach, is called epigastric (frti yaa-r^p, over the stomach). The two lateral regions, being under the carti- lages of the ribs, are called hypochondriac (vx6 %av8poi, under the cartilages). The middle region of the middle zone is the CAVITY OF THE ABDOMEN. 53 umbilical; the two lateral, the lumbar. The middle region of the inferior zone is the hypogastric (ynb yaa-eyp, below the sto- Fig. 15. 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 region. 7. Umbilical. 8, 8. The two lumbar. 9. Hypogastric. 10, 10. The right and left iliac regions. 11. Regio pubis. mach) ; and the two lateral, the iliac. In addition to these di- visions, we employ the term inguinal region in reference to the vicinity of Poupart's ligament. Position of the Viscera. In the upper zone will be seen the liver, extending across from the right to the left side ; the stomach and spleen on the left, and the pancreas and duodenum behind. In the middle zone is the transverse portion of the colon, with the upper part of the ascending and descending colon, omentum, small intestines, mesentery ; and behind, the kidneys and supra- renal capsules. In the inferior zone is the lower part of the 5* THE DISSECTOR. omentum and small intestines, the caecum, ascending and des- cending colon, with the sigmoid flexure, and ureters. Fig. 16. THE VISCERA OP THE ABDOMEN IN SITU. 1. 1. The flaps of the abdominal parietes turned aside. 2. The liver, its left lobe. 3. Its right lobe. 4. The fundus of the gall-bladder. 5. The round ligament of the liver, issuing from the cleft of the longitudinal fissure, and passing along the parietes of the abdo- men to the umbilicus. 6. Part of the broad ligament of the liver. 7. The stomach. 8. Its pyloric end. 9. The commencement of the duodenum, a. The lower extremity of the spleen, b, b. The greater omentum. c, c. The small intestines, d. The caecum, e. The appendix caeci. f. The ascending colon. g,g. The transverse colon, h. The descending colon. *'. The sigmoid flexure of the colon. lc. Appendices epiploicae connected with the sigmoid flexure. I. , Three ridges, representing the cords of the urachus and the umbilical arteries ascending to the umbilicus, m. Part of the under surface of the diaphragm. The smooth and polished surface which the viscera and of the abdomen present, is due to the peritoneum. PERITONEUM. The peritoneum (rtfprtsivuv, to extend around) is a serous membrane, and therefore a shut sac : a single excep- tion exists in the human subject to this character, namely, in the female, where the peritoneum is perforated by the open extremi- ties of the Fallopian tubes, and is continuous with their mucous lining. The simplest idea that can be given of a serous membrane PERITONEUM. 55 which may apply equally to all, is, that it invests the viscus or viscera, and is then reflected upon the parietes of the containing cavity. If the cavity contain only a single viscus, the considera- THE REFLECTIONS OP THE PE- RITONEUM. D. The diaphragm. S. The stomach. C. The trans- verse colon. D. The transverse duodenum. P. The pancreas. I. The small intestines. R. The rectum. B. The urinary blad- der. 1. The anterior layer of the peritoneum, lining the under surface of the diaphragm. 2. The posterior layer. 3. The two lay- ers passing to the posterior border of the liver, and forming the co- ronary ligament. 4. The lesser omentum ; the two layers passing from the under surface of the liver to the lesser curve of the stomach. 5. The two layers meeting at the greater curve, then passing downwards and re- turning upon themselves, form- ing (6) the greater omentum. 7. The transverse mesocolon. 8. The posterior layer traced up- wards in front of D, the transverse duodenum, and P, the pancreas, to become continuous with the posterior layer (2). 9. The fora- men of Winslow ; the dotted line bounding this foramen inferiorly, marks the course of the hepatic artery forwards, to enter between the layers of the lesser omentum. 10. The mesentery encircling the small intestine. 11. The recto- vesical fold, formed by the de- scending anterior layer. 12. The anterior layer traced up- wards upon the internal surface of the abdominal parietes to the layer (I) nienced. Fig. 17. rith which the examination com- tion of the serous membrane is extremely simple. But in the abdomen, where there are a number of viscera, the serous mem- brane passes from one to the other until it has invested the whole, before it is reflected on the parietes. Hence its reflections are a little more complicated. In tracing the reflections of the peritoneum in the middle line, we commence with the diaphragm, which is lined by two layers, one from the parietes in front, anterior, and one from the parietes behind, posterior. These two layers of the same membrane, at the posterior part of the diaphragm, descend to the upper surface 56 THE DISSECTOR. of the liver, forming the coronary and lateral ligaments of the liver. They then surround the liver, one going in front, the other behind that viscus, and, meeting at its under surface, pass to the stomach, forming the lesser omentum. They then, in the same manner, surround the stomach, and, meeting at its lower border, descend for some distance in front of the intestines, and return to the transverse colon, forming the great omentum ; they then sur- round the transverse colon, and pass directly backwards to the vertebral column, forming the transverse mesocolon. Here the two layers separate ; the posterior ascends in front of the pancreas and aorta, and returns to the posterior part of the diaphragm, where it becomes the posterior layer with which we commenced. The anterior descends, invests all the small intestines, and, return- ing to the vertebral column, forms the mesentery. It then de- scends into the pelvis in front of the rectum, which it holds in its place by means of a fold called mesorectum, forms a pouch, the recto-vesical fold, between the rectum and bladder, ascends upon the posterior surface of the bladder, forming its false ligaments, and returns upon the anterior parietes of the abdomen to the diaphragm, whence we first traced it. In the female, after descending into the pelvis in front of the rectum, it is reflected upon the posterior surface of the vagina and uterus. It then descends on the anterior surface of the uterus, and forms at either side the broad ligaments of that organ. From the uterus it ascends upon the posterior surface of the bladder and anterior parietes of the abdomen, and is continued, as in the male, to the diaphragm. In this way the continuity of the peritoneum, as a whole, is distinctly shown, and it matters not where the examination com- mences or where it terminates, still the same continuity of surface will be discernible throughout. If we trace it from side to side of the abdomen, we may commence at the umbilicus ; we then follow it outwards, lining the inner side of the parietes, to the ascending colon ; it surrounds that intestine : it then surrounds the small intestine, and, returning on itself, forms the mesentery. It then invests the descending colon, and reaches the parietes on the opposite side of the abdomen, whence it may be traced to the exact point from which we started. The viscera which are thus shown to be invested by the peri- toneum in its course downwards are the Liver, Small intestines, Stomach, Pelvic viscera. Transverse colon, The folds, formed between these and between the diaphragm and the liver, are PERITONEUM. 5f (Diaphragm.) Broad, coronary, and lateral ligaments. (Liver.) Lesser or gastro-hepatic omentum. (Stomach.) Greater or gastro-colic omentum. (Transverse colon.) Transverse mesocolon. Mesentery, Meso-rectum, Recto-vesical fold, False ligaments of the bladder. And in the female, the Broad ligaments of the uterus. The ligaments of the liver will be described with that organ. The lesser omentum (gastro-hepatic) is the duplicature which passes between the liver and the upper border of the stomach. It is extremely thin, excepting at its right border, where it is free, and contains between its layers the Hepatic artery, Ductus communis choledochus, Lymphatics, Portal vein, Hepatic plexus of nerves. These structures are inclosed in a loose cellular tissue, called Glisson's 1 capsule. The relative position of the three vessels is, the artery to the left, the duct to the right, and the vein between and behind. If the finger be introduced behind this right border of the lesser omentum, it will be situated in an opening called the foramen of Window* In front of the finger will lie the right border of the lesser omentum ; behind it the diaphragm, covered by the as- cending or posterior layer of the peritoneum ; belotc, the hepatic artery, curving forwards from the creliac axis ; and above, the lobus Spigelii. These, therefore, are the boundaries of the foramen of Winslow, which is nothing more than a constriction of the general cavity of the peritoneum at this point, arising out 1 Francis Glisson, Professor of Medicine in the University of Cam- bridge. His work, " De Anatomia Hepatis," was published in 1654. 2 Jacob Benignus Winslow. His " Exposition Anatomique de la Struc- ture du Corps Humain" was published in Paris in 1732. 58 THE DISSECTOR. of the necessity for the hepatic and gastric arteries to pass for- wards from the cceliac axis to reach their respective viscera. If air be blown through the foramen of Winslow, it will de- scend behind the lesser omentum and stomach to the space between the descending and ascending pair of layers, forming the great omentum. This is sometimes called the lesser cavity of the peritoneum, and that external to the foramen the greater cavity ; in which case the foramen is considered as the means of communication between the two. There is a great objection to this division, as it might lead the inexperienced to believe that there were really two cavities. There is but one only, the fora- men of Winslow being merely a constriction of that one, to facilitate the communication between the nutrient arteries and the viscera of the upper part of the abdomen. The great omentum (gastro-colic) consists of four layers of peritoneum, the two which descend from the stomach, and the same two, returning upon themselves to the transverse colon. A quantity of adipose substance is deposited around the vessels which ramify through its structure. It would appear to perform a double function in the economy : 1st. Protecting the intes- tines from cold ; and, 2dly. Facilitating the movement of the in- testines upon each other during their vermicular action. The transverse mesocolon (ftt'coj, middle, being attached to the middle of the cylinder of the intestine) is the medium of con- nection between the transverse colon and the posterior wall of the abdomen. It affords to the nutrient arteries a passage to reach the intestine, and incloses between its layers, at the pos- terior part, the transverse portion of the duodenum. It also forms a transverse septum across the abdominal cavity. The mesentery (piaov I*f pr vena cava. The left spermatic vein terminates in the left renal vein. The ovarian veins represent the spermatic veins of the male, and collect the venous blood from the ovaries, round ligaments, Fallopian tubes, and communicate with the uterine sinuses. They terminate as in the male. The renal or emulgent veins return the blood from the kidneys ; their branches are situated in front of the divisions of the renal arteries, and the left opens into the vena cava somewhat higher than the right. The left is longer than the right in consequence of the position of the vena cava, and crosses the aorta immedi- ately below the origin of the superior ^mesenteric artery. It receives the left spermatic vein, which terminates in it at right angles ; hence the more frequent occurrence of varicocele on the left than on the right side. The supra-renal veins terminate partly in the renal veins, and partly in the inferior vena cava. The phrenic veins return the blood from the ramifications of the phrenic arteries ; they open into the inferior cava. The EXTERNAL ILIAC VEIN lies to the inner side of the corre- sponding artery at the os pubis ; but gradually gets behind it as 9* 102 THE DISSECTOR. it passes upwards along the brim of the pelvis, and terminates opposite the sacro-iliac symphysis, by uniting with the internal iliac, to form the common iliac vein. Immediately above Pou- part's ligament it receives the epigastric and circumflexa ilii vein ; it has no valves. The INTERNAL ILIAC VEIN is formed by vessels which corre- spond with the branches of the internal iliac artery ; it lies to the inner side of the internal iliac artery, and terminates by uniting with the external iliac vein, to form the common iliac. The COMMON ILIAC VEINS are formed by the union of the external and internal iliac vein on each side of the pelvis. The right com- mon iliac, shorter than the left, ascends obliquely behind the cor- responding artery ; and upon the intervertebral substance of the fourth and fifth lumbar vertebra, unites with the vein of the opposite side, to form the inferior cava. The left common iliac, longer and more oblique than the right, ascends behind and a little internally to the corresponding artery, and passes beneath the right common iliac artery, near its origin, to unite with the right vein in the formation of the inferior vena cava. The right common iliac vein has no branch opening into it ; the left receives the vena sacra media. These veins have no valves. The SYMPATHETIC NERVE, within the abdomen, consists of a prevertebral portion which is distributed to the viscera, and a vertebral portion which is the proper continuation of the nerve on the vertebral column. The prevertebral portion consists of the epigastric or solar, and the hypogastric plexus, with the numerous secondary plex- uses to which the former gives origin. The epigastric, or solar plexus, is an intricate interlacement of nervous cords and branches, situated around the coeliac axis and origin of the superior mesenteric artery, and resting upon the aorta and crura of the diaphragm. Laterally it extends on each side to the supra-renal capsules, and is covered in by the stomach, and on the right side by the inferior vena cava. Besides the nerves, the epigastric plexus has entering into its structure several nervous ganglia, and especially two of large size, the semilunar ganglia. The semilunar ganglion is a large irregular gangliform body, pierced by numerous openings, and appearing like the aggrega- tion of a number of smaller ganglia, having spaces between them. It is situated by the side of the coeliac axis and root of the supe- rior mesenteric artery, and extends outwards to the supra-renal capsules. The ganglia communicate both above and below the coeliac axis, and constitute a gangliform circle from which branches pass off in all directions, like rays from a centre. Hence the ap- pellation solar plexus. HYPOGASTRIC PLEXUS. 103 The epigastric plexus receives the great splanchnic nerves ; part of the lesser splanchnic nerves ; the termination of the right pneu- mogastric nerve ; some branches from the right phrenic nerve ; and sometimes one or two filaments from the left. It sends forth numerous filaments which accompany, under the name of plexuses, all the branches given off by the abdominal aorta. Thus we have, derived from this plexus, the Phrenic, or diaphragmatic Supra-renal plexuses, _ plexuses, Renal plexuses, Gastric plexus, Superior mesenteric plexus, Hepatic plexus, Aortic plexus, Splenic plexus, Spermatic plexuses, Inferior mesenteric plexuses. In connection with the phrenic plexus of the right side there is described a small ganglion diaphragmaticum, which is situated near the supra-renal capsule. In this ganglion branches of the right phrenic nerve communicate with those of the sympathetic. The supra-renal plexuses are remarkable for their large size, and for a ganglion, which has received the name of ganglion supra-renale. The renal plexuses are also large, and receive the third splanchnic nerve. The superior mesenteric plexus has several small ganglia at the root of the artery and its nerves, which are whiter than those of the other plexuses, form a kind of nervous sheath to the artery and its branches. The aortic plexus is a continuation of the solar plexus down- wards on the aorta, for the supply of the inferior branches of that trunk ; it receives also branches from the renal plexuses and from the lumbar ganglia. It is the source or origin of the inferior mesenteric plexus, and part of the spermatic plexus, and it ter- minates below in the hypogastric plexus. It likewise distributes branches on the inferior vena cava. The spermatic plexus is derived from the renal plexus, but re- ceives filaments from the aortic plexus. The inferior mesenteric plexus is derived chiefly from the aortic plexus. The HYPOGASTRIC PLEXUS is formed by the termination of the aortic plexus, and by the union of branches from the lower lumbar ganglia. It is situated over the promontory of the sacrum, between the two common iliac arteries, and bifurcates inferiorly into two lateral portions, inferior hypogastric plexuses, which communicate with branches from the third and fourth sacral nerves. It dis- tributes branches to all the viscera of the pelvis, and sends fila- ments which accompany the branches of the internal iliac artery. 104 THE DISSECTOR. The VERTEBRAL portion, or trunk of the sympathetic, is situated on the vertebral column, close to the anterior border of the psoas magnus muscle. It is continuous above, under the edge of the diaphragm, with the thoracic portion of the nerve, and below it descends upon the sacrum, in front of the anterior sacral foramina, to the coccyx. It presents four small lumbar ganglia which are fusiform in shape and of a pearly gray color. The branches given off by the ganglia are branches of commu- nication and branches of distribution. The branches of communication are ascending and descending to the ganglion above and below. The branches of distribution are external and internal. The external branches, two or three in number, and longer than in the other regions, communicate with the lumbar nerves. The internal branches consist of two sets ; of which the upper pass inwards in front of the abdominal aorta, and join the aortic plexus ; the lower branches cross the common iliac arteries, and unite over the promontory of the sacrum, to form the hypogastric plexus. LYMPHATIC VESSELS AND GLANDS. The deep lymphatic glands of the abdomen are the lumbar glands; they are very numerous, and are seated around the common iliac vessels, the aorta and vena cava. The deep lymphatic glands of the pelvis are the external iliac, internal iliac, and sacral. The external iliac are placed around the external iliac vessels, being in continuation by one extremity with the femoral lymph- atics, and by the other with the lumbar glands. The internal iliac glands are situated in the course of the in- ternal iliac vessels, and the sacral glands are supported by the concave surface of the sacrum. The deep lymphatic vessels are continued upwards from the thigh, beneath Poupart's ligament, and along the external iliac vessels to the lumbar glands, receiving in their course the epi- gastric, circumflexa ilii, and ilio-lumbar lymphatic vessels. Those from the parietes of the pelvis, and from the gluteal, ischiatic, and obturator vessels follow the course of the internal iliac arteries, and unite with the lumbar lymphatics. And the lumbar lymph- atic vessels, after receiving all the lymphatics from the lower extremities, pelvis, and loins, terminate by several large trunks in the receptaculum chyli. To see the receptaculum chyli and commencement of the thoracic duct, the inferior vena cava which was divided on the removal of the liver, and drawn aside for the examination of the right semilunar ganglion, should now he further drawn aside or turned down to reach the vertebral column. Any cellular tissue and fat which may impede the view, should be removed. DIAPHRAGM. 105 The receptaculum cihyli is a triangular oblong sac, the reservoir of the lymphatics of the lower half of the body ; it is situated on the front of the body of the second lumbar vertebra, behind and between the aorta and inferior vena cava, and close to the tendon of the right crus of the diaphragm. It receives, by its lower part, four or live large lymphatic trunks, and above, where it becomes narrowed, in order to constitute the thoracic duct, it is joined by the trunks of the lacteals. The upper part of the receptaculum chyli contracts its dimensions to the size of a small quill, and be- comes the thoracic duct, which ascends through the aortic opening in the diaphragm, to terminate in the root of the neck at the junction of the left internal jugular with the left subclavian vein. In the aortic opening, and between the two crura of the diaphragm, it is situated between the aorta, which is to the left, and the vena azygos major, which is to the right. DEEP MUSCLES OF THE ABDOMEN. The deep muscles of the abdomen are, the- Diaphragm, Psoas parvus, Psoas magnus, Iliacus internus, Quadratus lumborum. The peritoneum should now be dissected carefully from the surface of the diaphragm, and any cellular tissue or fat removed which may in any way obscure it. Its border of attachment to the ribs, and particularly its posterior border and the lesser muscle, should also be carefully made out. The DIAPHRAGM 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 eusiform carti- lage ; from the inner surface of the six inferior ribs, indigitating with the transversalis ; and from the ligamentnm arcuatum ex- ternum and internum. From these points, which form the internal circumference of the trunk, the fibres converge and are inserted into the central tendon. The ligamentum arcuatum externum is the upper border of the anterior lamella of the aponeurosis of the transversalis ; it arches across the origin of the quadratus lumborum muscle, and is attached, by one extremity, to the base of the transverse process of the first lumbar vertebra, and by the other, to the apex and lower margin of the last rib. The ligamentum arcuatum intemum, OT proprium, is a tendinous arch thrown across the psoas magnus muscle as it emerges from the chest. It is attached by one extremity to the base of the transverse process of the first lumbar vertebra, and by the other is continuous with the tendon of the lesser muscle opposite the body of the second. 106 THE DISSECTOR. The tendinous centre of the diaphragm is shaped like a trefoil leaf, of which the central leaflet points to the ensiform cartilage, THE UNDER OR ABDOMINAL SIDE or 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 number 3 on the right leaflet. 4. The thin fasciculus which arises from the ensiform cartilage ; a small triangular space is left on either side of this fasciculus, 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 aortic openings. 9. The fourth lumbar vertebra. 10. The left or shorter tendon 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 ten- dinous centre of the diaphragm. 14. The psoas magnus muscle passing beneath the. ligamentum arcuatum internum ; it has been removed on the opposite 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. 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 cartilages of the adjoining ribs, is a small triangular space where the mus- cular fibres of the diaphragm are deficient. This space is closed only by peritoneum on the side of the abdomen, and by pleura THE DIAPHRAGM. lOt within the chest. It is therefore a weak point, and a portion of the contents of the abdomen might, by violent exertion, be forced through it, producing phrenic, or diaphragmatic 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 surface 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, pillars), 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 sur- round the resophagus, so as to present the appearance of a figure of eight. The anterior fasciculus of the decussation is formed by the right crus. The openings in the diaphragm are three : one, quadrilateral, in the tendinous centre, at the union of the right and middle leaflets, for the passage of the inferior vena cava ; a muscular opening of an elliptic shape formed by the two crura, for the transmission of the oesophagus and pneumogastric 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, beneath which pass the aorta, the right vena azygos, and the thoracic duct. The great splanchnic nerves pass through openings in the lesser muscle on each side ; and the lesser splanchnic nerves, between the fibres which arise from the ligamentum arcuatum internum. The diaphragm, being interposed between the viscera of the chest and abdomen, is important in its relations to the organs contained in the two cavities. Above it is in contact with the pleurae, pericardium, heart, and lungs. By its inferior surface, with the peritoneum ; on the left, with the stomach and spleen ; on the right, with the convexity of the liver ; and behind, with the kidneys, supra-renal capsules, duodenum, and solar plexus. By its circumference, with the ribs, intercostal muscles, and ver- tebral column. To see the next muscle, the psoas magnus, a thin fascia must be laid open and turned aside. This fascia is a prolongation upwards of the iliac fascia, much attenuated in substance. It is attached to the bodies of the vertebrae, leaving an arched space corresponding with the constricted por- tion of each vertebra, for the passage of the lumbar vessels and external branches of the sympathetic nerve. Externally it is connected with .the aponeurosis of the transversalis muscle ; and above, with the ligamentum arcuatum internum. Lower down it is attached to the brim of the pelvis. The removal of the fascia brings into view the psoas magnus and parvus, and a nerve which pierces the muscle at about its middle and lies upon its anterior surface, the genito-crural ; care must be taken not to injure this nerve in the dissection of the fascia. The PSOAS MAGNUS (^oa, lumbus), situated by the side of the vertebral column in the loin, is a long fusiform muscle. It arises from the sides of the bodies of the last dorsal and all the lumbar vertebrae, from their intervertebral substances, transverse pro- 108 THE DISSECTOR. cesses, and the tendinous arches which are thrown across the constricted portion of the vertebras, to protect the lumbar arte- ries and external branches of the sympathetic nerve from pres- sure in their passage beneath the muscle. From this extensive origin the muscle passes along the brim of the pelvis and beneath Poupart's ligament to its insertion into the trochanter minor of the femur. This muscle issues from beneath the ligamentum arcuatum internum above, and is in relation, by its anterior surface, with the psoas parvus, kidney, and genito-crural nerve which pierces it at about its middle and then lies on its anterior surface. By its inner border and surface it is in relation with the lumbar vessels, the sympathetic nerve with its external branches, and, lower down, with the iliac vessels. Its substance is tra- versed by the nerves constituting the lumbar plexus ; and in the iliac fossa it has, escaping from beneath it and then lying along its outer border, the anterior crural nerve. The PSOAS PARVUS is a small and infrequent muscle, which arises from the last dorsal and first lumbar vertebra, and from the intervertebral substance between them ; it passes beneath the ligamentum arcuatum internum, and terminates in a long slender tendon which expands inferiorly, and is inserted into the ilio-pec- tineal line and eminence. The tendon is continuous, by its outer border, with the iliac fascia. To see the abdominal or pelvic portion of the iliacus interims muscle, the iliac fascia must be removed, and care must be taken to avoid injury to a nerve which crosses the iliacus muscle, the external cutaneous, and the anterior crural nerve which lies in the groove between the psoas and iliacus. The iliac fascia is a thin aponeurosis which covers in the iliacus muscle, and is continued upwards upon the front of the psoas to the ligamentum arcuatum internum. It is attached to the inner lip of the crest of the ilium, and passing behind the iliac vessels, is connected with the brim of the pelvis, Inferiorly, at Poupart's ligament, it is connected with the fascia transver- salis, and at the inner third of that ligament forms the posterior part of the femoral sheath. The ILIACUS MUSCLE arises from the whole extent of the inner concave surface of the ilium ; and by a few fibres from the base of the sacrum. This muscle passes beneath Poupart's ligament, to be inserted with the psoas into the trochanter minor of the femur. The QUADRATUS LUMBORUM muscle is concealed from view by the anterior lamella of the aponeurosis of the transversalis muscle, which is inserted into the bases of the transverse processes of the lumbar vertebrae. When this lamella is divided, the muscle will be seen to consist of two portions: one, the external, arising from the ilio-lumbar ligament and crest of the ilium for two inches LUMBAR NERVES. 109 in extent, and inserted into the apices of the transverse processes of the four upper lumbar vertebrae (sometimes also the last dorsal), and last rib ; the other, the inner and anterior portion, arises by tendinous slips from the transverse processes of the three or four lower lumbar vertebrae, and passes upwards, to be inserted into the lower border of the last rib. If the muscle be cut across or removed, the middle lamella of the transversalis will be seen attached to the apices of the transverse processes ; the quadratus being inclosed between the two lamellae as in a sheath. ACTIONS. The diaphragm is an inspiratory muscle, the contraction of its fibres increasing the cavity of the chest. It acts also as a muscle of expulsion by pressing upon the abdominal viscera, as in the expulsion of the excretions, of the foetus, &c. The spasmodic action of the muscle pro- duces hiccup, sobbing, &c. The psoas and iliacus muscles flex the trunk upon the lower extremi- ties or the legs upon the pelvis, at the same time everting the foot. The quadratus lumborum is -an expiratory muscle, and assists in fixing the chest. The psoas magnus, if not previously removed for the examination of the quadratus lumborum, must now be carefully dissected from its origin, for the purpose of bringing into view the lumbar plexus of nerves, which is situated in the substance of the muscle. LUMBAR NERVES. There are five pairs of lumbar nerves, of which the first makes its appearance between the first and second lumbar vertebrae, and the last between the fifth lumbar and the base of the sacrum. The anterior branches increase in size from above downwards. At their exit from the intervertebral foramina they receive the external branch of the lumbar ganglia of the sympathetic, and pass obliquely outwards behind the psoas magnus, or through its substance, sending twigs to that muscle and to the quadratus lumborum. In this situation each nerve divides into two branches : a superior branch, which ascends, to form a loop of communication with the nerve above ; and an inferior branch, which descends, to join in like manner the nerve below. The communications and anastomoses which are thus established, con- stitute the lumbar plexus. The posterior branches diminish in size from above downwards ; they pass backwards between the transverse processes of the corresponding vertebrae, and each nerve divides into an internal and an external branch. The internal branch, the smaller of the two, passes inwards, to be distributed to the multifidus spinee and interspinales ; and becoming cutaneous, supplies the integu- ment of the lumbar region on the middle line. The external branches communicate with each other by several loops j and 10 110 THE DISSECTOR. after supplying: the deeper muscles, pierce the sacro-lumbalis, to reach the integument to which they are distributed. The exter- nal branches of the three lower lumbar nerves (nervi clunium superiores postici), descend over the posterior part of the crest of the ilium, and are distributed to the integument of the gluteal region. LUMBAR PLEXUS. The lumbar plexus is formed by the com- munications and anastomoses which take place between the an- terior branches of the four upper lumbar nerves, and between the latter and the last dorsal. It is narrow above, increases in breadth inferiorly, and is situated between the transverse pro- cesses of the lumbar ver- tebrae and quadratus lura- borum behind, and the psoas magnus muscle in front. The branches of the lum- bar plexus are, the Ilio-hypogastric, Ilio-ingumal, Genito-crural, External cutaneous, Obturator, Anterior crural. The ILIO-HYPOGASTRIC NERVE proceeds from the first lumbar nerve, and passes obliquely outwards between the fibres of the psoas magnus, and across the quadratus lumborum to about the middle of the crest of the ilium. It then pierces the transversalis muscle, and between it and the internal oblique divides into its two terminal branches, iliac and hypo- gastric; the former being THE LUMBAR PLEXUS AND ITS BRANCHES (slightly altered from Schmidt). a. Last rib. b. Quadratus lumborum muscle, c. Oblique and transverse mus- cles, cut near the crest of the ilium, d. Os pubis. e. Adductor brevis muscle. f. Pectineus. g. Adductor longus. 1. Ilio-hypogastric branch. 2. Ilio-in- guinal. 3. External cutaneous branch. 4. Anterior crural nerve. 5. Acces- sory obturator. 6. Obturator nerve. 7. Genito-crural nerve divided into two at its origin from the plexus. 8. Gangliated cord of the sympathetic nerve. ANTERIOR CRURAL NERVE. Ill distributed to the integument of the hip ; and the latter, to that of the hypogastric region and external organs of generation (page 32). The ILIO-INGUINAL NERVE, smaller than the preceding, also arises from the first lumbar nerve. It passes obliquely down- wards and outwards below the ilio-hypogastric nerve, and crosses the quadratus lumborum and iliacus muscle in its course to the anterior part of the crest of the ilium : it then pierces the trans- versalis muscle ; next, the internal oblique ; and escaping at the external abdominal ring with the spermatic cord, is distributed to the scrotum and inner part of the thigh ; in the female, to the pudendum (page 32). The GENITO-CRURAL NERVE proceeds from the second lumbar nerve, and by a few fibres from the loop between it and the first. It traverses the psoas magnus from behind forwards, and runs down the anterior surface of that muscle, lying beneath its fascia, to near Pou partis ligament, where it divides into a genital and a crural branch. The genital branch (n. spermaticus, seu pudendus externus) crosses the external iliac artery to the internal abdominal ring, and descends along the posterior aspect of the spermatic cord to the scrotum. It is distributed to the cord and cremaster muscle ; and, in the female, to the round ligament and labium pudendi (page 45). The crural branch (lumbo-inguinalis) descends along the outer side of the external iliac artery, and, crossing the origin of the circumflexa ilii artery, enters the femoral sheath in front of the femoral artery. It pierces the sheath below Poupart's ligament, and is distributed to the integument of the upper and inner part of the thigh. The EXTERNAL CUTANEOUS NERVE (inguino-cutaneous) pro- ceeds from the second lumbar, and from the loop between it and the third. It pierces the posterior fibres of the psoas muscle ; and crossing the iliacus lying upon the iliac fascia, to the anterior superior spinous process of the ilium, passes into the thigh be- neath Poupart's ligament. It is distributed to the integument of the outer aspect of the thigh as far as the knee. The ANTERIOR CRURAL NERVE is the largest of the divisions of the lumbar plexus : it is formed by the union of cords from the second, third, and fourth lumbar nerves. Emerging from be- neath the psoas muscle, it passes downwards in the groove be- tween the psoas and iliacus, and beneath Poupart's ligament, into the thigh. At Poupart's ligament it is separated from the femoral artery by the breadth of the psoas muscle, which at this point is scarcely more than half an inch in diameter, and by the iliac fascia beneath which it lies. 112 . THE DISSECTOR. Its branches within the pelvis are three or four twigs to the iliaous muscle, and a long filament to the femoral artery. The OBTURATOR NERVE is formed by a branch from the third, and another from the fourth lumbar nerve ; it takes its course among the fibres of the psoas muscle, through the angle of bifur- cation of the common iliac vessels, and along the inner border of the brim of the pelvis, to the obturator foramen, where it joins the obturator artery, and passes into the thigh. It is distributed to the muscles of the inner aspect of the thigh, and to the hip and knee-joint. A small nerve is sometimes met with in association with the obturator, termed the accessory obturator nerve. This nerve may be a high division of the obturator, or it may arise separately from the third and fourth lumbar nerves. It passes down the inner border of the psoas muscle, and crosses the os pubis, to enter the thigh. LUMBO-SACRAL NERVE. The anterior division of the fifth lumbar nerve, conjoined with a branch from the fourth, consti- tutes the lumbo-sacral nerve, which descends over the base of the sacrum into the pelvis, and assists in forming the sacral plexus. CHAPTER III. HEAD AND NECK. THE head may be considered as an expansion of the superior 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 connection be- tween the head and the rest of the body : communication, by means of the trachea and oasophagus, with the internal organs ; connection, 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 princi- pal organs of sense. The exterior of the cranium presents for examination its con- vex surface, and on its sides the external organs of hearing. The face is more varied, comprehending, the orbits for the organs of vision ; the nose or external organ of smell ; the mouth, con- MUSCLES OP THE HEAD AND FACE. 113 taining the organ of taste ; and the jaws or apparatus of masti- cation. We shall commence the dissection of the head and neck, by devoting one side to the examination of the muscles, reserving the other for the study of the vessels and nerves. Fig. 33. THE MUSCLES OF THE HEAD AND FACE. 1. The frontal portion of the occipito-frontalis. 2. Its occipital portion. 3. Its aponeurosis. 4. The orbicularis palpebrarum, which con- ceals the corrugator supercilii and tensor tarsi. 5. The pyrainidalis nasi. 6. The compressor nasi. 7. The orbicularis oris. 8. The levator labii superioris alaeque nasi. The figure is placed on the nasal portion. 9. The levator labii superioris pro- prius : the lower part of the levator anguli oris is seen between the mus- cles 10 and 11. 10. The zygomati- cus minor. 11. The zygomaticua major. 12. The depressor labii in- ferioris. 13. The depressor anguli oris. 14. The levator labii inferi- oris. 15. The superficial portion of the masseter. 16. Its deep portion. 17. The attrahene aurem. 18. The buccinator. 19. The attollens aurem. 20. The temporal fascia which covers in the temporal muscle. 21. The retrahens aurein. 22. The anterior belly of the digastricus muscle ; the tendon is seen passing through the aponeurotic pully. 23. The stylo-hyoid muscle pierced by the posterior belly of the digastricus. 24. The mylo-hyoideus muscle. 25. The upper part of the stern o-mastoid. 26. The upper part of the trapezius. The muscle between 25 and 26 is the splenius. into certain natural groups, which of the head and face above esta- The MUSCLES are associated correspond with the divisions blished : thus we find Cranial group, Auricular group, Orbital group, Nasal group, The muscles belonging to each of these groups may be thus arranged : 1 . Cranial group. Occipito-frontalis. Superior labial group, Inferior labial group, Maxillary group. 2. Auricular group. Attollens aurem, Attruhens aurem, Retrahens aurem. 3. Orbital group. Orbicularis palpebrarum, Corrugator supercilii, Tensor tarsi. 4. Nasal group. Pyramidalis nasi, 10* 114 THE DISSECTOR. Compressor nasi, 6. Inferior labial group. Dilatator naris, (Orbicularis oris),' Depressor ala nasi. Depressor labii inferioris, 5. Superior labial group. Depressor anguli oris, (Orbicularis oris), 1 Levator labii inferioris. Levator labi superioris ateque ^ jfaxOay group. Levator labi superioris pro- Masseter, prius, Buccinator, Levator anguli oris, Temporalis, Zygomaticus major, Pterygoideus externus, Zygomaticus minor. Pterygoideus internus. The surface of the cranium is to be dissected by making a longitudinal incision along the vertex of the head from the tubercle on the occipital bone to the root of the nose, and a second incision along the forehead and around the side of the head to join the two extremities of the pre- ceding. Dissect the integument and superficial fascia carefully upwards and outwards, beginning at the anterior angle of the flap, where the muscular fibres are thickest. Having dissected these to their termina- tions in the aponeurosis, it will now be best to proceed to the posterior angle made by the above incisions, and to dissect upwards, taking the posterior fleshy portion of the muscle as a guide ; the flap can then care- fully be raised from the tendon, and the muscle fully exposed. This dissection requires care, for the muscle is very thin, and without atten- 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. 1. Cranial Group. The OCCIPITO-FRONTALIS is a broad mus- culo-aponeurotic layer, which covers the whole of the side of the vertex of the skull, from the occiput to the eyebrow. It arises by tendinous fibres from the outer two-thirds of the superior curved line of the occipital, and from the mastoid portion of the temporal bone. Its insertion takes place by means of the blend- ing of the fibres of its anterior portion with those of the orbicu- laris palpebrarum, corrugator supercilii, levator labii superioris alseque nasi, and pyramidalis nasi. The muscle is fleshy in front over the frontal bone and behind over the occipital, the two por- tions being connected by a broad aponeurosis. The two muscles together with their aponeurosis cover the whole of the vertex of the skull, hence their designation galea capitis; they are loosely adherent to the pericranium, but very closely to the integument, particularly over the forehead. 1 The Orbicularis, from encircling the mouth, belongs necessarily to both the superior and inferior labial regions ; therefore, to prevent mis- conception, we have inclosed it in both within brackets. ATTOLLENS AUREM TEMPORAL MUSCLE. 115 The action of the occipito-frontalis is to raise the eyebrows, thereby throwing the integument of the forehead into transverse wrinkles. Some persons have the power of moving the entire scalp upon the peri- cranium by means of these muscles. 2. Auricular Group. Attollens aurem, Attrahens aurem, Retrahens aurem. The dissection of these three small and superficial muscles requires the careful removal of the integument from around the pinna ; their exact position is shown by drawing the pinna from the side of the head, and they may be conveniently dissected by taking the prominent lines which they thus form as a guide for the incision. The ATTOLLENS AUREM (superior auriculae), the largest of the three, is a thin triangular plane of muscular fibres arising from the edge of the aponeurosis of the occipito-frontalis, and inserted into the convexity of the fossa triangularis and scaphoidea. The ATTRAHENS AUREM (anterior auriculae), also triangular, arises from the edge of the aponeurosis of the occipito-frontalis in front of the preceding, and is inserted into the spine of the helix. The RETRAHENS AUREM (posterior auriculae) arises by two muscular slips from the root of the mastoid process. They are inserted into the posterior surface of the concha. The actions of the auricular muscles are expressed in their names ; they have but little power in man, but are important muscles in brutes. Beneath the attrahens and attollens muscles is a white glistening fascia which may now be examined. The TEMPORAL FASCIA is a strong aponeurotic membrane, which covers in the temporal muscle at each side of the head, and gives origin by its internal surface to some of its fibres. It is attached to the whole extent of the temporal ridge above, and to the zygo- matic arch below ; in the latter situation it is thick, and consists of two layers, the external being connected to the upper border of the arch, and the internal to its inner surface. Some fat is found between these two layers, and also the orbital branch of the temporal artery. Separate the temporal fascia from the temporal ridge, and turn it down- wards ; the temporal muscle will then be exposed in the greater part of its extent. Above, the muscle is rough, from the necessity of dividing its libres in the removal of the fascia ; below, some fat and cellular tissue require removal to make it clean. The TEMPORAL MUSCLE, broad and radiating, occupies the tem- poral fossa, and expands over the side of the head. It arises by tendinous fibres from the temporal ridge, and by muscular fibres from the surface of bone constituting the temporal fossa, and from the temporal fascia. Its fibres converge to a strong and narrow 116 THE DISSECTOR. tendon, which is inserted into the apex and internal surface of the coronoid process of the lower jaw. Having now examined the muscles of the cranium, with the view to a speedy opening of the skull for the examination of the brain, the student should next proceed to study the vessels and nerves distributed upon the exterior of the cranium, and which would be destroyed by the removal of the calvaria. For this purpose the integument covering one side of the head has been left undisturbed. This may now be dissected in the manner directed for the dissection of the muscles (page 114), the integu- ment alone being removed, and the superficial fascia in which the vessels and nerves are embedded exposed to view. Vessels and Nerves of the Cranium. The arteries of the cra- nium are the supra-orbital and frontal from the ophthalmic ; the temporal artery ; posterior auricular and occipital. The supra-orbital artery escapes from the orbit through the supra-orbital notch in company with the supra-orbital nerve, and divides into a superficial and deep branch, which are distributed to the integument and muscles of the forehead and to the peri- cranium. The frontal artery, one of the terminal branches of the ophthal- mic, emerges from the orbit at its inner angle and ascends the middle of the forehead, to which it is distributed, anastomosing with its fellow of the opposite side. The temporal artery, one of the terminal branches of the external carotid, ascends in front of the ear and divides into an anterior and a posterior branch. The anterior temporal 1 arches forwards upon the temple, and is distributed to the integument and muscles of the scalp, inosculating with the supra-orbital and frontal artery. The posterior temporal curves upwards and backwards over the ear, and inosculates with its fellow of the opposite side, and with the occipital and posterior auricular arteries. The posterior auricular artery ascends in front of the mastoid process, and divides into two branches, one of which supplies the pinna and anastomoses with the posterior temporal, while the other crosses the mastoid process to the posterior portion of the occipito-frontalis, and inosculates with the occipital artery. The occipital artery, emerging from between the splenius and complexus, and piercing the trapezius muscle, ascends upon the occipito-frontalis muscle, and divides into branches which supply that muscle, the pericranium, and integument, and inosculate with their fellows of the opposite side, the posterior temporal and the posterior auricular artery. The veins of the scalp are found by the side of the arteries. The frontal vein, descending the mid-line of the forehead to the inner angle of the orbit, receives the supra-orbital vein, and becomes 1 This is the vessel which is selected for the operation of arteriotomy. NERVES OF THE CRANIUM. 117 the facial vein. The temporal and posterior auricular veins ter- minate in the external jugular, and the occipital veins in the in- ternal jugular. The NERVES distributed to the cranium are the supra-orbital and supra-trochlear branches of the first division of the fifth pair; temporal branches from the second and third divisions of the fifth and from the facial nerve ; posterior auricular from the facial ; auricularis magnus and occipitalis minor, from the anterior cervi- cal plexus; and occipitalis major, from the posterior division of the second cervical nerve. The supra-orbital nerve, issuing from the orbit through the supra-orbital notch with the artery of the same name, gives fila- ments to the eyelids, the muscles of the forehead and pericranium, and divides into two cutaneous branches, internal and external. The internal branch pierces the occipito-f rental is, and is dis- tributed to the integument as far as the summit of the head. The external branch, of larger size, communicates with the facial nerve, and piercing the occipito-frontalis, is distributed to the integu- ment as far back as the occiput. The supra-trochlear nerve emerges from the orbit at its inner angle, and piercing the muscle, is distributed to the integument in the middle line of the forehead. The temporal branch of the second division of the fifth or superior maxillary nerve pierces the temporal fascia a little above the zygoma, and is distributed to the integumejit of the front of the temple. It communicates with the facial nerve. The temporal branches, anterior and posterior, of the auriculo- temporal nerve, a branch of the third division of the fifth or inferior maxillary nerve, ascend upon the temple in front of the ear. The anterior branch is distributed to the integument as far as the summit of the head. The posterior branch is directed back- wards over the external ear, and supplies the integument, after giving twigs to the attrahens aurem and to the pinna. The temporal branches of the facial nerve, two or three in number, pass in a radiated manner over the temple, and are dis- tributed to the attrahens aurem, occipito-frontalis, and orbicularis palpebrarum muscle. They communicate with the temporal branch of the superior maxillary, and with the supra-orbital nerve. The posterior auricular nerve is a branch of the facial; taking its origin at the stylo-mastoid foramen, it ascends in front of the mastoid process to the back of the ear, and divides into an anterior and a posterior branch. The anterior branch (auricular) is dis- tributed to the retrahens aurem and to the pinna. The posterior branch (occipital) communicates with the auricularis magnus nerve, and is distributed to the occipito-frontalis. 118 THE DISSECTOR. The auricularis magnus nerve, derived from the cervical plexus, divides below the ear into branches, which are distributed to the back of the pinna ; and a mastoid branch, which commu- nicates with the preceding nerve, and is distributed to the integu- ment over the mastoid process. The occipitalis minor nerve, also a branch of the cervical plexus, reaches the occiput at the posterior border of the sterno-mastoid muscle, and mounting the back of the head, sends branches to. the occipito-frontalis and attollens aurem (auricular branch), com- municates with the posterior auricular nerve, and with the occipi- talis major. The occipitalis major nerve, a branch of the posterior divi- sion of the second cervical, pierces the trapezius muscle close to the occipital artery, and lies by the side of that vessel. Soon after its emergence from the trapezius, it receives a branch from the third cervical, and divides into numerous branches, which are distributed to the occipito-frontalis and integument as far as the summit of the head. It communicates with the occipitalis minor nerve, and sends an auricular branch to the back of the ear. The student may now open the skull, and examine the contents of that cavity ; for this purpose the brain must be removed. He will find in- structions for conducting this operation in Chapter IV., which is devoted to the anatomy of the brain and spinal cord. After the brain and spinal cord have been studied, the dissector may return to the anatomy of the face. If he be studying the right side of the face, an incision should be made from the front of the ear along the ramus of the lower jaw to its angle, and thence onwards along the margin of the jaw to the chin. The integument should be raised with care, and towards the middle line. If the student have the left side of the face, he should carry an incision from the middle line of the forehead along the ridge of the nose, the upper and the lower lip, to the chin, and then backward along the lower jaw, dissecting the flap from the middle line to the ear. The muscles may then be made clear by the removal of the cellular tissue and fat ; in dissecting them they should be put gently on the stretch, and cleaned in the direction of their fibres. 3. Orbital Group. Orbicularis palpebrarum, Corrugator supercilii, Tensor tarsi. The ORBICULARIS PALPEBRARUM is a sphincter muscle, sur- rounding the orbit and eyelids. It arises from the internal angu- lar process of the frontal bone, from the nasal process of the superior maxillary, and from a short tendon (tendo oculi) which extends between the nasal process of the superior maxillary bone, and the inner extremities of the tarsal cartilages of the eyelids. The fibres encircle the orbit and eyelids, forming a broad and thin muscular plane, which is inserted into the lower border of the tendo oculi, and into the nasal process of the superior maMil- lary bone. That portion of the muscle which occupies the eye- TENSOR TARSI. 119 lids (ciliaris) is composed of fibres, which are thin and pale, 1 and possess an involuntary action. The tendo oculi, in addition to its insertion into the nasal process of the superior maxillary bone, sends a process inwards, which expands over the lachrymal sac, and is attached to the ridge of the lachrymal bone : this is the reflected aponeurosis of the tendo oculi. The CORRUGATOR SUPERCILII is a small, narrow, and pointed muscle, situated immediately above the orbit and beneath the upper segment of the orbicularis palpebrarum. It arises from the inner extremity of the superciliary ridge, and is inserted into the under surface of the orbicularis palpebrarum at a point cor- responding with the middle of the superciliary arch. The TENSOR TARSI (Homer's 9 muscle) is a thin plane of mus- cular fibres, about three lines in breadth and six in length. It is best dissected by separating the eyelids from the eye, and turning them over the nose without disturbing the tendo oculi ; then dissect away the small fold of mucous membrane called plica semilunaris, and some loose cellular tissue under which the muscle is concealed. It arises from the orbital surface of the lachrymal bone, and passing across the lachrymal sac, divides into two slips, which are continuous with the margin of the ciliaris along the edges of the lids, 3 some few of its fibres being attached to the lachrymal canals as far as the puncta. ACTIONS. The palpebral portion of the orbicularis [ciliaris] acts invol- untarily in closing the lids, and from the greater curve of the upper lid, upon that principally. The entire muscle acts as a sphincter, drawing at the same time, by means of its osseous attachment, the integument and lids inwards towards the nose. The corrugatores superciliorum draw the eyebrows downwards and inwards, and produce the vertical wrinkles of the forehead. The tensor tarsi, or lachrymal muscle, is an auxiliary to the orbicularis, and draws the extremities of the lachrymal canals in- wards, so as to place the puncta in the best position for receiving the tears. It serves also to keep the lids in relation with the surface of the eye, and compresses the lachrymal sac. Dr. Horner is acquainted with two persons who have the voluntary power of drawing the lids inwards by these muscles so as to bury the puncta in the angle of the eye. 4. Nasal Group. Pyramidal is nasi, Compressor nasi, Dilatator naris, Depressor ala3 nasi. 1 Mr. Haynes Walton has shown that the margin of the ciliaris is thick, and its fibres redder than the rest of the ciliary muscle ; further- more, that its thickness is augmented by the addition of the tensor tarsi muscle. This portion of the muscle he conceives to be the agent in the production of Entropium. Med. Times and Gazette, May, 1852. 2 W. E. Horner, M. D., Professor of Anatomy in the University of Penn- sylvania,, The notice of this muscle is contained in a work published in Philadelphia in 1827, entitled " Lessons in Practical Anatomy." * Mr. Hayiies Walton, loc. cit. 120 THE DISSECTOR. Fig. 34. The PYRAMID ALIS NASi is a small pyramidal slip of muscular fibres sent downwards upon the bridge of the nose by the occipito- frontalis. It is inserted into the tendinous expansion of the compres- sores nasi. The COMPRESSOR NASI is a thin and triangular muscle ; it arises by its apex from the canine fossa of the superior maxillary bone, and spreads out upon the side of the nose into a thin tendinous expansion, which is continuous across its ridge with the muscle of the opposite side. It is connected at its origin with a mus- cular fasciculus which is attached to the nasal process of the superior maxillary bone immediately below the origin of the levator labii supe- rioris alaeque nasi. This muscular slip was termed by Albinus mus- cuhis anomahis, from its attachment to the bone by both ends ; and by Santorini, musculus rhomboideus. The DILATATOR NARIS is a thin and indistinct muscular apparatus expanded upon the ala of the nos- tril, and consisting of an anterior and posterior slip. The anterior slip (levator proprius alae nasi anterior) arises from the upper border and surface of the alar cartilage, and is inserted into the integument of the border of the nostril. The posterior slip (levator ala3 nasi posterior) arises from the nasal process of the superior maxillary bone and from the sesamoid cartilages, and is inserted into the integument of the border of the nostril for the posterior half of its extent. The dilatator naris muscle is difficult of dissection, from the close adhesion of the integument to the nasal cartilages. The DEPRESSOR AL^E NASI (myrtiformis) is brought into view by drawing upwards the upper lip and raising the mucous membrane. It arises from the superior maxillary bone in front of the roots of the second incisor and canine teeth (myrtiform fossa), and passes upwards and inwards to be inserted into the posterior part of the columna and ala nasi. It is closely connected with the deep surface of the orbicularis. REPRESENTS THE MUSCLES OP THE NASAL REGION, WITH SOME OF THOSE OF THE LIP. 1. Pyra- midalis nasi. 2. Levator labii superioris alacque nasi. 3. Com- pressor naris. 4. Levator pro- prius alee nasi anterior. 5. Leva- tor proprius alas nasi posterior. 6. Depressor alae nasi. 7. Orbi- cularis. 7*. Naso-labialis. MUSCLES OF THE NOSE. 121 ACTIONS. The pyramidalis nasi, as a point of attachment of the occi- pito-frontalis, assists that muscle in its action : it also draws down the inner angle of the eyebrow, and by its insertion fixes the aponeurosis of the compressores nasi, and tends to elevate the nose. The compressores nasi appear to act in expanding rather than in compressing the nares ; hence probably the compressed state of the nares from paralysis of these muscles in the last moments of life, or in compression of the brain. The dilatator naris is a dilator of the nostril, and the depressor al nasi draws downwards both the ala and columna of the nose, the depression of the latter being assisted by the naso-labialis. 5. Superior Labial Group. Orbicularis oris, Levator labii superioris alaeque nasi, Levator labii superioris proprius, Levator anguli oris, Zygoraaticus major, Zygomaticus minor. The ORBICULARIS ORIS is a sphincter muscle, completely sur- rounding the mouth, and possessing consequently neither origin nor insertion. It is composed of two thick semicircular planes of fibres, which embrace the rima of the mouth, and interlace at their extremities, where they are continuous with the fibres of the buccinator, and of the other muscles connected with the angle of the mouth. The upper segment is attached by means of a small muscular fasciculus (naso-labialis) to the columna of the nose ; and other fasciculi connected with both segments, and attached to the maxillary bones, are termed "accessorii." The LEVATOR LABII SUPERIORIS ALAEQUE NASI is a thin triangu- lar muscle ; it arises from the upper part of the nasal process of the superior maxillary bone ; and, becoming broader as it de- scends, is inserted by two distinct portions into the ala of the nose and upper lip. The LEVATOR LABII SUPERIORIS PROPRIUS is a thin quadrilateral muscle ; it arises from the lower border of the orbit, and, passing obliquely downwards and inwards, is inserted into the integu- ment of the upper lip, its deep fibres being blended with those of the orbicularis. The LEVATOR ANGULI ORIS arises from the canine fossa of the superior maxillary bone, and passes outwards to be inserted into the angle of the mouth, intermingling its fibres with those of the orbicularis, zygomatici, and depressor anguli oris. The ZYGOMATIC muscles are two slender fasciculi of fibres which arise from the malar bone, and are inserted into the angle of the mouth, where they are continuous with the other muscles attached to this part. The zygomaticus minor is situated in front of the major, and is continuous at its insertion with the levator labii superioris proprius : it is not unfrequently wanting. 11 THE DISSECTOR. ACTIONS. The orbicularis oris produces the direct closure of the lips by means of its continuity, at the angles of the mouth, with the fibres of the buccinator. When acting singly in the forcible closure of the mouth, the integument is thrown into wrinkles, in consequence of its firm connection with the surface of the muscle ; its naso-labial fascicu- lus draws downwards the columna nasi. The levator labii superioris alseque nasi lifts the upper lip with the ala of the nose, and expands the opening of the nares. The levator labii superioris proprius is the proper elevator of the upper lip ; acting singly, it draws the lip a little to one side. The levator anguli oris lifts the angle of the mouth and draws it inwards, while the zygomatici pull it upwards and outwards, as in laughing. 6. Inferior Labial Group. Depressor labii inferioris, Depressor anguli oris, Levator labii inferioris. The DEPRESSOR LABII INFERIORIS (quadratus menti), arises from the oblique line by the side of the symphysis of the lower jaw, and passing upwards and inwards, is inserted into the orbicularis muscle and integument of the lower lip. The DEPRESSOR ANGULI ORIS (triangularis oris), is a triangular plane of muscle arising by a broad base from the external oblique ridge of the lower jaw, and inserted by its apex into the angle of the mouth, where it is continuous with the levator anguli oris and zygomaticus major, and with a subcutaneous muscle called risorius Santorini. The risorius Santorini arises by two or three fasciculi from the fascia covering the masseter muscle, and is in- serted \r\iQ the angle of the mouth. The LEVATOR LABII INFERIORIS (levator menti), is a small conical slip of muscle arising from the incisive fossa of the lower jaw, and inserted into the integument of the chin. It is in rela- tion with the mucous membrane of the mouth, with its fellow, and with the depressor labii inferioris. T. Maxillary Group. Masseter, Buccinator, Temporalis, Pterygoideus externus, Pterygoideus internus. Before proceeding to the dissection of the masseter muscle, the parotid gland, which overlaps and partly conceals the muscle and sends its ex- cretory duct across it, should be examined. The gland is bound down by a strong fascia, which may be removed. The PAROTID GLAND (?tapa, near, ov$, iT'oj, the ear), is the largest of three salivary glands situated on each side of the face in the neighborhood of the mouth. The parotid, as its name implies, is placed immediately in front of the external ear, ex- tends superficially for a short distance over the masseter muscle, and deeply behind the ramus of the lower jaw. It reaches in- MASSETER. 123 feriorly to below the level of the angle of the jaw, and poste- riorly to the mastoid process, slightly overlapping the insertion of the sterno-mastoid muscle. Embedded in its substance, are the external carotid artery, the temporo-inaxillary vein, and facial nerve ; emerging from its anterior border, the transverse facial artery and branches of the facial nerve ; and above, the temporal artery and auriculo-temporal nerve. The duct of the parotid gland (Stenon's duct), about two inches in length, and about the diameter of a crow's-quill, issues from the anterior part of the gland, just below the zygoma, and crosses the masseter muscle ; it then curves inwards over the an- terior border of the muscle, and pierces the buccinator opposite the second molar tooth of the upper jaw; its opening in the mouth being indicated by a prominent papilla. A small glan- dular appendage, the soda parotidis, is connected with the upper part of the duct on the masseter muscle. Structure. The salivary are conglomerate glands, consisting of lobes, which are made up of polyhedral lobules, and these of smaller lobules. The smallest lobule is apparently composed of granules, which are minute caeca! pouches, formed by the dilatation of the extreme ramifica- tions of the ducts. These minute ducts unite to form lobular ducts, and the lobular ducts constitute by their union a single excretory duct. The caecal pouches are connected by cellular tissue, so as to form a minute lobule; the lobules are held together by a more condensed cellular layer; and the larger lobes are enveloped by a dense fibrous capsule, which is firmly attached to the deep cervical fascia. The submaxillary and sub- lingual glands are looser in structure, and their lobules are larger than those of the parotid gland. The duct of the parotid gland may now be cut across, when the small size of its area, as compared with the thickness of its wall, will be observed. The gland may then be drawn back, or so much of it removed as shall interfere with the examination of the masseter muscle. The MASSETER (paarfdopai, to chew), is a short, thick, and some- what quadrilateral muscle, composed of two planes of fibres, su- perficial and deep. The superficial layer arises by a strong aponeurosis from the tuberosity of the superior maxillary bone, the lower border of the ma*lar bone, and the zygoma, and passes backwards to be inserted into the ramus and angle of the inferior maxilla. The deep layer arises from the posterior part of the zygoma, and passes forwards, to be inserted into tfte upper half of the ramus. This muscle is tendinous and muscular in its structure. The buccinator muscle is in a great measure concealed from view by a lobulated mass of fat, which fills up the hollow in front of the masseter. Through this mass of fat the duct of the parotid gland makes its way. The fat is now to be removed in order to bring the muscle into view ; and the operation is to be conducted with care; in order to avoid disturb- ing the facial artery and vein. The muscle is invested by a thin fascia. 124 THE DISSECTOR. The BUCCINATOR MUSCLE (bticcina, a trumpet), the trumpeter's muscle, arises from the alveolar process of the superior maxilla, from the external oblique line of the inferior maxilla as far for- ward as the second bicuspid tooth, and from the pterygo-maxil- lary ligament. This ligament is the raphe of union between the buccinator and superior constrictor muscle, and is attached by one extremity to the hamular process of the internal pterygoid plate, and by the other to the extremity of the molar ridge. The fibres of the muscle converge towards the angle of the mouth, where they cross each other, the superior being continuous with the inferior segment of the orbicularis oris, and the inferior with the superior segment. The next step in the dissection necessary to display the remaining muscles of this group requires the section of the zygoma at both extremi- ties, and its removal, turning it down with the masseter. This brings into view the lower part of the temporal muscle, which has been already described (page 115). The coronoid process may then be cut across with a saw, and drawn upwards with the tendon of the temporal muscle. In the next place, that portion of the ramus of the jaw bet ween its neck and the angle must be sawn through and removed, when the two pterygoid muscles will become visible, and may be dissected. This preparation will also display the origin of the buccinator muscle from the pterygo- maxillary ligament. Fig. 35. THE TWO PTERYGOID MUSCLES. THE ZYGOMATIC ARCH AND THE GREATER PART OP THE RAMUS OF THE LOWER JAW HAVE BEEN RE- MOVED IN ORDER TO BRING THESE MUSCLES INTO VIEW. 1. The sphe- noid origin of the external pterygoid muscle. 2. Its pterygoid origin. 3. The internal pterygoid muscle. The EXTERNAL PTERYGOID IS a short and thick muscle, broader at its origin than at its insertion. It arises by two heads, one from the pterygoid ridge on the greater ala of the sphenoid; the other from the external pterygoid plate and tuberosity of the palate bone. The fibres pass backwards to be inserted into the neck of the lower jaw and the interarticular fibro- cartilage. The internal maxillary artery frequently passes between the two heads of this muscle. The external pterygoid muscle must now be removed, and the head of the lower jaw dislocated from its socket and withdrawn, for the purpose of seeing the pterygoideus internus. The INTERNAL PTERYGOID is a thick quadrangular muscle. It arises from the pterygoid fossa and descends obliquely back- wards, to be inserted into the ramus and angle of the lower jaw : NEEVES OF THE FACE. 125 it resembles the masseter in appearance and direction, and was named by Winslow the internal masseter. ACTIONS. The maxillary muscles are the active agents in mastication, and form an apparatus beautifully fitted for that office. The buccinator circumscribes the cavity of the mouth, and with the aid of the tongue keeps the food under the immediate pressure of the teeth. By means of its connection with the superior constrictor, it shortens the cavity of the pharynx from before backwards, and becomes an important auxiliary in deglutition. The temporal, the masseter, and the internal pterygoid are the bruising muscles, drawing the lower jaw against the upper with great force. The two latter, from the obliquity of their direction, assist the external pterygoid in grinding the food, by carrying the lower jaw for- ward upon the upper ; the jaw being brought back again by the deep portion of the masseter and posterior fibres of the temporal. The whole of these muscles, acting in succession, produce a rotary movement of the teeth upon each other, which, with the direct action of the lower jaw against the upper, eflects the proper mastication of the food. Vessels and Nerves of the Face. The vessels and nerves may now be dissected on the opposite side of the face. The integument should be removed with care, in the manner already pointed out for the examination of the muscles (page 118), and the vessels and nerves sought for and followed through their course. As a preparatory step, the branches of the facial nerve should be found as they issue from beneath the anterior border of the parotid gland, and traced backwards through the gland to their trunk ; they may then be traced in their distribution over the face. The FACIAL NERVE (portio dura), the motor nerve of the face, issues from the cranium through the stylomastoid foramen, passes forward through the parotid gland to the ramus of the jaw, and divides into two trunks, tempora-facial and cervico-facial. These trunks divide into numerous branches which escape from the anterior border of the parotid gland and are distributed in a radiated manner over the side of the face, from the temple to below the lower jaw ; on the masseter muscle the branches com- municate and form loops, and the whole arrangement over the side of the face has been termed pes anserinus. The branches of the facial nerve, at its exit from the stylo- mastoid foramen, are three in number, namely, the posterior auri- cular, a stylo-hyoid branch for the muscle of that name, and a digastric branch for the digastricus. The posterior auricular branch ascends in front of the mastoid process to the back of the ear, and divides into an anterior or auricular, and a posterior or occipital branch. The auricular branch communicates with the auricular branch of the pueumo- gastric nerve, and is distributed to the retrahens aurem and pinna. The occipital branch communicates with the auricularis magnus and occipitalis minor, and is lost in the occipito-frontalis muspje (page 117). 11* 126 THE DISSECTOR. The stylo-hyoid branch supplies the stylo-hyoideus muscle, and communicates with the sympathetic plexus of the external carotid artery. The digastric branch enters the posterior belly of the digastri- cus muscle, and communicates with the glosso-pharyngeal and pneumogastric nerve. The temporo-facial division, while in the parotid gland, sends a branch of communication along the carotid artery to the auri- culo-temporal nerve, and divides into temporal, malar, and infra- orbital branches. The temporal branches, ascending over the temporal region, Fig. 36. THE DISTRIBUTION OP THE FACIAL NERVE AND THE BRANCHES OP THE CER- VICAL PLEXUS. 1. The facial nerve, escaping from the stylo-mastoid foramen, and crossing 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 (|1) pver the submaxillary gland. The distribution of the branches of the facial in a radiated direction over the side of the face constitutes the pes anserinus. 12. The auricularis magnus nerve, one of the ascending branches of the cervical plexus. 13. The occipitalis minor, ascending along the posterior border of the sterno-mastoid muscle. 14. The superficial and deep descending branches of the cervical plexus. $5. The spinal accessory nerve, giving off a branch to the external surface of the trnpezius muscle. 16. The occipitalis taajqr nerve, the posterior branch of the second cervical nerve. FACIAL ARTEEY. 12t supply the attrahens aurem, occipito-frontalis, and orbicularis palpebrarum ; and communicate with the supra-orbital nerve and the temporal branch of the superior maxillary (page 117). The malar branches cross the malar bone to the outer angle of the eye, and supply the orbicularis palpebrarum, corrugator supercilii, and eyelids. They communicate with the subcutaneous malse branch of the superior maxillary nerve, and with branches of the ophthalmic nerve in the eyelids. The infra-orbital branches cross the masse ter muscle, and are distributed to the buccinator, elevator muscles of the upper lip, and orbicularis oris. They communicate with the terminal branches of the infra-orbital nerve, the infra-trochlear and nasal nerve. Two or more of these branches are found by the side of Stenon's duct. The cervico-facial division, smaller than the temporo-facial, communicates in the parotid gland with the auricularis magnus nerve, and divides into branches which admit of arrangement into three sets : buccal, supra-maxillary, and infra-maxillary. The buccal branches pass forwards across the masseter muscle towards the mouth, and distribute branches to the orbicularis oris and buccinator. They communicate with the branches of the temporo-facial, and with the buccal branch of the inferior maxillary nerve. The supra-maxillary branches are destined to the muscles of the lower lip, and take their course along the body of the lower jaw. They have a plexiform communication with the inferior dental nerve beneath the depressor anguli oris. The infra-maxillary branches (subcutanei colli) take their course below the lower jaw, pierce the deep cervical fascia, and are distributed to the platysma and integument. They commu- nicate with the superficialis colli nerve. The facial nerve has been called the sympatheticus minor, on account of its numerous communications with other nerves. Thus, within the cranium it communicates with the auditory nerve, spheno-palatine gan- glion, and pneumogastric nerve ; at its exit, with the glosso-pharyngeal, sympathetic, and cervical nerves ; and on the face with the three divi- sions of the fifth nerve. The FACIAL ARTERY, a branch of the external carotid, enters upon the face by curving around the body of the lowr jaw at the anterior inferior angle of the masseter muscle. It then passes forwards in a more or less tortuous course to the angle of the mouth, and ascends by the side of the nose to the inner angle of the eye, where it is named the angular artery ; it terminates by inosculating with the nasal and frontal branches of the ophthal- mic artery. In its course over the jaw it is covered by the platysma myoides, and at the angle of the mouth by the depres- 128 THE DISSECTOR. sor anguli oris and zygomatie muscles. It rests on the buccina- tor and elevator muscles of the lip. The branches of the facial artery are, twigs to the masseter muscle (masseteric), inferior labial, inferior coronary, superior coronary, and lateral nasal. The inferior labial branch passes forwards beneath the depres- sor anguli oris muscle, and is distributed to the muscles of the lower lip, inosculating with the labial branch of the inferior dental, and with the inferior coronary. The inferior coronary branch is given off at the angle of the mouth, and passes inwards near the edge of the lower lip, lying between the orbicularis and the mucous membrane : it inoscu- lates with its fellow of the opposite side. The superior coronary branch, arising close to, or in common with, the preceding, takes its course in the same manner along the upper lip, inosculating with its fellow of the opposite side. At the middle of the lip it sends a small branch upwards to the septum of the nose (artery of the septum). The lateral nasal branch is given off near the ala nasi, and passes beneath the levator labii superioris alaeque nasi, to be dis- tributed to the nose. It inosculates with the nasal branch of the ophthalmic artery. The FACIAL VEIN commences at the inner angle of the eye, where, under the name of angular vein, it receives the frontal vein from the forehead ; the frontal veins of opposite sides being united across the bridge of the nose by a transverse branch. The facial vein passes outwards beneath the zygomatic muscles to the anterior border of the masseter muscle, along which it descends to the lower jaw, where it joins the facial artery. Passing over the jaw it pierces the deep cervical fascia, and terminates in the internal jugular vein. The TRANSVERSE FACIAL ARTERY, a branch of the temporal artery, emerges from beneath the anterior border of the parotid gland, and runs transversely across the face a little above Stenon's duct. It supplies the muscles in its course, and inosculates with the facial and infraorbital artery. ANATOMY OF THE ORBIT. To open the orbit (the calvaria and brain having been removed) 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. PERIOSTEUM MUSCLES. 129 The PERIOSTEUM is a moderately thick white membrane, only slightly connected with the surface of the bones of the orbit on account of their smoothness and density, but firmly at the different sutures, or at the points of transit of vessels and nerves. It is continuous through the optic foramen and sphenoidal fissure with the dura mater, and at the margins of the orbit with the pericra- nium and periosteum of the face. Remove the periosteum from the whole of the upper surface of the ex- posed 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 muscles which move the eye- ball, four recti, two obliqui, and the elevator muscle of the upper eyelid. 3d. The ophthalmic artery with its branches. 4th. The ophthalmic vein with its tributaries. 5th. The nerves, which consist of three branches of the ophthalmic frontal, lachrymal, and nasal ; the third, fourth, and sixth, to the muscles ; and the ciliary ganglion with its branches. 6th. The lachrymal gland. In the middle line is the levator palpebrse muscle, and resting 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 lachrymal artery and nerve, and in front the lachrymal gland. If the levator palpebrae muscle, and with it the frontal nerve and supra- orbital artery, be divided through the middle and turned aside, the su- perior 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 reetus 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 a branch of the third nerve maybe seen entering its under surface, and a third plane will be brought into view. This re- quires 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 unweari- edly, until he has removed every particle of this fat, which is not difficult to do from its being contained in areolae of loose cellular tissue. In the middle line he will now perceive the optic nerve, crossed from without inwards by the ophthalmic artery and nasal nerve, and having to its outer side the ascending branch of the third nerve, the ciliary gan- glion 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 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. The MUSCLES of the orbit are seven in number; namely Levator palpebrse, Rectus externus, Rectus superior, Obliquus superior, Rectus inferior, Obliquus inferior. Rectus internus, 130 THE DISSECTOR. The dissection of the muscles of the orbit may be facilitated by drawing the globe of the eye forwards ; or, if it be desired, the muscles may be made tense by injecting the globe of the eye with tallow or wax. For Fig. 37. THE MUSCLES OP THE EYE- BALL ; THE VIEW IS TAKEN FROM THE OUTER SIDE OP THE RIGHT ORBIT. 1. A small fragment of the sphenoid bone around the en- trance 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 cartilaginous pulley. 7. Its re- flected 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 intermediate 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. this purpose a probe should be pushed along the optic nerve, so as to break down the cribriform plate of the sclerotic coat, and an injecting pipe introduced into the neurilemma of the nerve. By similar means the globe of the eye may be distended with air. The LEVATOR PALPEBR^E is a long, thin, and triangular muscle, situated in the upper part of the orbit on the middle line; it arises from the upper margin of the optic foramen, and from the fibrous sheath of the optic nerve, and is inserted into the upper border of the superior tarsal cartilage. The RECTUS SUPERIOR (attollens) arises from the upper margin of the optic foramen, and from the fibrous sheath of the optic nerve, and is inserted into the upper surface of the globe of the eye at a point somewhat more than three lines from the margin of the cornea. The RECTUS INFERIOR (depressor) arises from the inferior mar- gin of the optic foramen by a tendon (ligament of Zinn) which is common to it, the internal and the external rectus, and from the fibrous sheath of the optic nerve; it is inserted into the inferior surface of the globe of the eye, a little more than two lines from the margin of the cornea. The RECTUS INTERNUS (adductor), the thickest and shortest of the straight muscles, arises from the common tendon and from the. fibrous sheath of the optic nerve, and is inserted into the inner surface of the globe of the eye at two lines from the margin of the cornea. The RECTUS EXTERNUS (abductor), the longest of the straight OBLIQUUS SUPERIOR OBLIQUUS INFERIOR. 131 muscles, arises by two distinct heads, one from the common tendon, the other, with the origin of the superior rectus, from the margin of the optic foramen ; the nasal third and sixth nerves passing between its heads. It is inserted into the outer surface of the globe of the eye, a little more than two lines from the margin of the cornea. The recti muscles present several characters which are common to all ; thus, they are thin, have each the form of an isosceles triangle, bear the same relation to the globe of the eye, and are inserted in a similar man- ner into the sclerotica at about two lines from the circumference of the cornea. The points of difference relate to thickness and length ; the internal rectus is the thickest and shortest, the external rectus the longest of the four, and the superior rectus the most thin. The insertion of the four recti muscles into the globe of the eye forms a tendinous expansion, which is continued as far as the margin of the cornea, and is called the tunica albugiuea. ... . The OBLIQUUS SUPERIOR (trochlearis) is a fusiform muscle arising from the margin of the optic foramen and from the fibrous sheath of the optic nerve ; it passes forwards to the pul- ley beneath the internal angular process of the frontal bone ; its tendon is then reflected beneath the superior rectus muscle, to the outer and posterior part of the globe of the eye, where it is inserted into the sclerotic coat near the entrance of the optic nerve. The trochlea or pulley of the superior oblique muscle is a fibro- cartilaginous ring attached to the depression beneath the internal angular process of the frontal bone. The ring is flat, about a line in width, and provided with a synovial membrane, which is continued together with a fibrous sheath, for a short distance, upon the tendon. Sometimes the ring is supported, or in part formed, by a process of bone. The OBLIQUUS INFERIOR, a thin and narrow muscle, arises from the inner margin of the superior maxillary bone, immediately external to the lachrymal groove, and passes beneath the inferior rectus, to be inserted into the outer and posterior part of the eye- ball at about two lines from the entrance of the optic nerve. ACTIONS. The levator palpebrae raises the upper eyelid. The four recti, acting singly, pull the eyeball in the four directions : upwards, down- wards, inwards, and outwards. Acting by pairs, they carry the eyeball in the diagonal of these directions, viz : upwards and inwards, upwards and outwards, downwards and inwards, or downwards and outwards. Acting all together, they directly retract the globe within the orbit. The superior oblique muscle, acting alone, rolls the globe inwards and for- wards, and carries the pupil outwards and downwards to the lower and outer angle of the orbit. The inferior oblique acting alone, rolls the globe outwards and backwards, and carries the pupil outwards and upwards to the upper and outer angle of the eye. Both muscles acting together, draw the eyeball forwards, and give the pupil that slight degree of ever- sion which enables it to admit the largest field of vision. 132 THE DISSECTOR. Nerves of the Orbit. The dissection of the nerves of the orbit may be prosecuted either on the same side as the muscles, if the parts have not been too much dis- turbed, or the opposite orbit may be taken expressly for the purpose. The outer wall of the orbit should be broken away with the chisel and bone-nippers, to bring the apex of the orbit well into view, and the ante- rior clinoid process should also be removed. Furthermore, a thin layer of the dura mater should be raised from the side of the sella turcica, in Fig. 38. THE ORIGIN, COURSE, AND DISTRIBUTION OP 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 communication with the ciliary ganglion. 4. The fourth nerve, arising from the valve of Yieussens, immediately below the corpora quadrigemina, 9. 5. The fifth nerve, arising by two roots. 10. The posterior root from the corpus restiforme. 11. The anterior root from the corpus pyramidale. 12. The Cas- serian ganglion. 13. Its ophthalmic division. 14. Its superior maxillary divi- sion. 15. Its inferior maxillary division. 16. The frontal branch of the ophthalmic nerve. 17. The lachrymal branch. 18. The nasal. 19. Its com- munication with the ciliary ganglion. 20. Its ciliary branches. 21. The infra-trochlear branch, given off just as the nerve enters the anterior ethmoidal foramen. 6.6. The sixth nerv, 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 they enter the cavernous sinus. The third is the highest, then the fourth, next the ophthal- mic division of the fifth, and then the sixth. The arrow at 6 marks the rela- tion 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 ; three inferior, nasal, third, and sixth, pass between the two heads of the external rectus. NERVES OF THE ORBIT. 133 order to bring into view the trunks of the nerves in their course to the orbit, and the parts situated in the cavernous sinus. The NERVES of the orbit are the third, fourth, first division of the fifth, sixth, and the ophthalmic or ciliary ganglion, with its branches. The THIRD NERVE (motores oculorum) pierces the dura mater immediately in front of the posterior clinoid process, and pass- ing obliquely forwards and downwards, divides into two branches, which enter the orbit through the sphenoidal fissure, and be- tween the two heads of the external rectus muscle. The superior branch ascends and supplies the superior rectus and levator palpebrae. Fig. 39. Fig. 40. THE NERVES IN THE ORBIT ABOVE THE MUSCLES, BROUGHT INTO VIEW BY REMOVING THE RoOP OF THE OR- BIT AND THE PERIOSTEUM. 1. Fifth 2. Ophthalmic branch of same 3. Third nerve. 4. Fourth 5. Optic nerve. 6. Sixth a. Internal carotid artery. nerve. nerve. nerve. nerve, THE BEEP NERVES OP THE ORBIT Mis I ROM ABOVE BY REMOVING THE BONE AND DIVIDING THE ELEVATOR OP THE UPPER EYELID AND THE UPPER RECTUS MUSCLE. a. Inter- nal pterygoid muscle, b. Temporal muscle. r. Cut surface of bone. d. Elevator of the eyeli^l and upper rectug muscle. e. Carotid artery. 1. Optic nerve. 2. Fifth nerve. 3. Ophthalmic nerve. 4. Third nerve. 5. Sixth nerve. The inferior branch sends a branch beneath the optic nerve to the internal rectus, another to the inferior rectus, and a long branch to the inferior oblique muscle. From the latter a short 12 134 THE DISSECTOR. thick branch is given to the ophthalmic ganglion, forming its inferior root. The FOURTH NERVE (patheticus, trochlearis), the smallest of the cerebral nerves, pierces the dura mater below the third nerve, and passes obliquely upwards to enter the orbit through the upper part of the sphenoidal fissure; it therefore crosses the third nerve. Entering the orbit, the nerve passes across the levator palpebrae near its origin, and is distributed to the supe- rior oblique or trochlearis muscle, spreading out, contrary to the mode of distribution of the other nerves, on the orbital surface of the muscle. The fourth nerve communicates in the cavernous sinus with the ophthalmic nerve and the carotid plexus of the sympathetic; it also sends off a recurrent filament, which, in conjunction with a similar offset of the ophthalmic, is distributed to the tentorium cerebelli. Sometimes the communication with the ophthalmic takes place in the orbit, in which case the lachrymal nerve has the appearance of arising by two roots. The OPHTHALMIC NERVE, the upper branch of the Casserian ganglion, passes along the outer wall of the cavernous sinus, below the fourth nerve, and divides into three branches, frontal, lachrymal, and nasal. The nerve communicates, while in the sinus, with the carotid plexus and fourth nerve, and sends off a recurrent branch to the tentorium cerebelli. The FRONTAL NERVE enters the orbit immediately to the outer side of the fourth nerve, and passing forwards for some distance upon the levator palpebrae muscle, divides into a supra-orbital and supra-trochlear branch. The supra-orbital branch, which is the proper continuation of the nerve, passes out of the orbit through the supra-orbital notch, and mounts upon the forehead, supplying the integument, mus- cles, and pericranium (p. lit). While in the notch it sends filaments to the upper eyelid. The supra-trochlear branch passes inwards to the angle of the orbit, above the pulley of the superior oblique muscle, and is dis- tributed to the inner angle of the eye, the root of the nose, and middle line of the forehead (p. 117). It communicates with the infra-trochlear branch of the nasal nerve. The LACHRYMAL NERVE, the smallest of the three branches of the ophthalmic, enters the orbit on the outer side of the frontal, but inclosed in a separate sheath of dura mater; and passes for- wards, above the upper border of the external rectus muscle, to the lachrymal gland, where it divides into two branches, superior and inferior. The superior branch passes over the gland which it supplies on the upper surface, and traversing a foramen in the NEEVES OP THE ORBIT. 135 malar bone, communicates with the subcutaneous mala? and facial nerve. The inferior branch supplies the under surface of the gland, and supplies the upper lid and outer angle of the eye. The lachrymal nerve sometimes receives the branch of the fourth nerve destined for the ophthalmic, and appears to arise by two roots. The NASAL NERVE (naso-ciliaris) enters the orbit between the two heads of the external rectus and between the two branches of the third nerve. It crosses the optic nerve in company with the ophthalmic artery, and passing over the internal rectus, enters the anterior ethmoidal foramen, by which it is conducted to the cribriform plate of the ethmoid bone. It then passes through the slit-like opening by the side of the crista galli, and descends into the nose, where it divides into an internal and an external branch. The internal branch is distributed to the mucous mem- brane ; and the external branch, passing outwards between the nasal bone and cartilage, supplies the integument of the exterior of the nose as far as its tip. The branches of the nasal nerve are the ganglionic, ciliary, and infra-trochlear. The ganglionic branch, about half an inch in length and of small size, enters the upper angle of the ophthalmic ganglion, and constitutes its superior or long root. The long ciliary branches are two or three filaments given off from the nerve as it crosses the optic nerve. They pierce the sclerotic coat near the short ciliary nerves, and passing through the globe of the eye between the sclerotic and choroid, are dis- tributed to the iris. The infra-trochlear branch is given off close to the anterior ethmoidal foramen. It passes forwards along the upper border of the internal rectus to the inner angle of the eye, where it com- municates with the supra-trochlear nerve, and is distributed to the lachrymal sac and inner angle of the orbit. The SIXTH NERVE (abducens oculi) pierces the dura mater on the body of the sphenoid bone, and passes along the inner wall of the cavernous sinus, below the other nerves, and resting against the internal carotid artery to the sphenoidal fissure. It enters the sphenoidal fissure above the ophthalmic vein, and passing between the two heads of the external rectus, is distributed to that muscle. In the cavernous sinus the sixth nerve receives several filaments from the carotid plexus. The four nerves just described are situated, previously to their entry into the orbit, in the cavernous sinus ; the first three, namely, third, fourth, and three branches of the fifth, in the outer wall of the sinus, each nerve being inclosed in a separate sheath of dura mater; the remaining nerve, the sixth, in the internal wall of the sinus, that is, between the sinus and 136 THE DISSECTOR. the internal carotid artery. Another relation of the nerves is that from above downwards ; at their entrance into the sinus they are placed in the order of their numbers, namely, third, fourth, fifth, sixth ; but at the ethmoidal fissure, the fourth, frontal, and lachrymal are the highest, these Fig. 4], A TRANSVERSE SECTION OP THE CAVERNOUS SINUS OF THE RIGHT SIDE. The dura mater, splitting to inclose 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 di- vision of the fifth nerve. three entering the orbit above the origin of the levator palpebrae ; the others lie in the following relative position upper branch of the third, nasal, lower branch of the third and sixth. The three latter all pass between the two heads of the external rectus. Below the sixth nerve, at the sphenoidal fissure, is the ophthalmic vein. The OPHTHALMIC GANGLION (ciliary ; lenticular) is a small quad- rangular and flattened body of a reddish color, situated between the optic nerve and external rectus. Fig. 42. A REPRESENTATION or SOME OF THE NERVES OF THE ORBIT, ESPECI- ALLY TO SHOW THE LEN- TICULAR GANGLION. 1. Ganglion of the fifth. 2. Ophthalmic nerve. 3. Upper maxillary. 4. Low- er maxillary. 5. Nasal branch, giving the long root to the lenticular gan- glion. 6. Third nerve. 7. Inferior oblique branch of the third connected with the ganglion by the short root. 8. Optic nerve. 9. Sixth nerve. 10. Sympa- thetic on the carotid artery. Its branches of communication are three in number : one, the long root, which proceeds from its superior angle and joins the nasal nerve ; a short and thick branch, the short root, which proceeds from its inferior angle and joins the inferior branch of the third nerve ; and a slender filament from the carotid plexus, the sympathetic root. Its branches of distribution are the short ciliary nerves ; they proceed from the anterior angles of the ganglion in two groups, VESSELS OF THE ORBIT. 137 the upper group consisting of about four filaments, and the lower of five or six. They accompany the ciliary arteries hi a waving course, and divide into a number of filaments which pierce the sclerotic around the optic nerve, and supply the tunics of the eyeball. Vessels of the Orbit. The vessels of the orbit are the ophthalmic artery and vein with their branches. The OPHTHALMIC ARTERY arises from the internal carotid, just as the latter vessel pierces the dura mater, and enters the orbit through the optic foramen lying externally to the optic nerve. It then crosses the optic nerve to the inner wall of the orbit, and at the inner angle of the eye divides into two terminal branches, frontal and nasal. The branches of the ophthalmic artery, ten in number, may be arranged in two groups, the first group including the vessels dis- tributed to the circumference of the orbit ; and the second, those which supply the eyeball and its muscles. First Group. Lachrymal, Palpebral, Supra-orbital, Frontal, Posterior ethmoidal, Nasal. Anterior ethmoidal, Second Group. Muscular anterior ciliary, Ciliary, short and long, Centralis retinae. The lachrymal is the first branch of the ophthalmic artery, and is usually given off immediately before that artery enters the optic foramen. It follows the course of the lachrymal nerve, above the upper border of the external rectus muscle, and is distributed to the lachrymal gland. The small branches which escape from the gland supply the conjunctiva and upper eyelid. The lachrymal artery gives off a malar branch, which passes through the malar bone into the temporal fossa, and inosculates with the deep temporal arteries, while some of its branches be- come subcutaneous on the cheek, and anastomose with the trans- verse facial. The supra-orbital artery follows the course of the frontal^ nerve, resting on the levator palpebrae muscle ; it passes through the supra-orbital foramen, and divides into a superficial and deep branch, which are distributed to the muscles and integument of the forehead, and to the pericranium. At the supra-orbital foramen it sends a branch inwards to the diploe. 12* 138 . THE DISSECTOR. The ethmoidal arteries, posterior and anterior, pass through the ethmoidal foramina, and are distributed to the falx cerebri and to the ethmoidal cells and nasal fossae. The latter accom- panies the nasal nerve, and sends a branch to the frontal sinus. The palpebral arteries, superior and inferior, are given off from the ophthalmic, near the inner angle of the orbit ; they encircle the eyelids, forming a superior and an inferior arch near the borders of the lids, between the orbicularis palpebrarum and tarsal cartilage. At the outer angle of the eyelids, the superior palpebral inosculates with the orbital branch of the temporal artery. The inferior palpebral sends a branch to the nasal duct. The frontal artery, one of the terminal branches of the ophthalmic, emerges from the orbit at its inner angle, and ascends along the middle of the forehead. It is distributed to the integument, muscles, and pericranium. The nasal artery, the other terminal branch of the ophthalmic, passes out of the orbit above the tendo-oculi, and divides into two branches ; one of which inosculates with the angular artery, while the other, the dorsalis nasi, runs along the ridge of the nose, and is distributed to the integument of that organ. The nasal artery sends a small branch to the lachrymal sac. 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 arte- ries, which pierce the sclerotic near its margin of connection with the cornea, and are distributed to the iris. It is the con- gestion of these vessels that gives rise to the vascular zone around the cornea in iritis. The ciliary arteries are divisible into three groups, short, long, and anterior. The short ciliary (posterior), from ten to fifteen in number, 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 on opposite sides of the globe of the eye, and pass forwards between it and the choroid to the iris. They form an arterial circle around the circumference of the iris by inosculating with each other, and from this circle branches are given off which ramify in the substance of the iris, and form a second circle around the pupil. The anterior ciliary are branches of the muscular arteries; they terminate in the great arterial circle of the iris. The centralis retinas artery pierces the optic nerve obliquely, and passes forwards in the centre of its cylinder to the retina, where it divides into branches, which ramify in the inner layer of that membrane. It supplies the retina, hyaloid membrane, and zonula ciliaris ; and, by means of a branch sent forwards through ANATOMY OF THE NECK. 139 the centre of the vitreous humor in a tubular sheath of the hya- loid membrane, the capsule of the lens. The OPHTHALMIC VEIN commences at the inner angle of the eye, where it communicates with the angular vein and takes the course of the ophthalmic artery, receiving the veins correspond- ing with its branches. It quits the orbit through the sphenoidal fissure, after passing between the two heads of the external rectus, and opens into the cavernous sinus. At the sphenoidal fissure it lies beneath the sixth nerve. LACHRYMAL GLAND. The lachrymal gland is situated at the upper and outer angle of the orbit, and consists of two portions, orbital and palpebral. The orbital portion, about three-quarters of an inch in length, is flattened and oval in shape, and occupies the lachrymal fossa in the orbital plate of the frontal bone. It is in contact superiorly with the periosteum, with which it is closely connected by its upper and convex surface; by its inferior or jconcave surface it is in relation with the globe of the eye, and the superior and external rectus ; and by its anterior border with the broad tarsal ligament. By the posterior border it receives its vessels and nerves. The palpebral portion, smaller than the preceding, is situated in the upper eyelid, extending downwards to the superior margin of the tarsal cartilage. It is continuous with the orbital portion above, and is inclosed in an investment of dense fibrous membrane. The secretion of the lachrymal gland is conveyed away by from eight to twelve small ducts which run for a short distance beneath the conjunctiva, and open upon its surface by a series of pores, about one-twentieth of an inch apart, situated in a curved line a little above the upper border of the tarsal cartilage. For the anatomy of the appendages of the eye, and the rest of the lachrymal apparatus, the student is referred to Chap. V. ANATOMY OP THE NECK. The neck, as before stated, is the medium of communication and connection, between the head and the trunk of the body. Connection is established by means of the integument and sterno-mastoid muscle, the muscles of the prevertebral region, vertebral column, and muscles of the back. Communication is effected by means of apparatuses connected with respiration and deglutition. Associated with respiration is the larynx,' and with deglutition the os hyoides, the tongue, the soft palate, and the pharynx. These may be considered as the elements of the neck, and form so many regions, by which the muscles may be grouped and arranged. 140 THE DISSECTOR. Thus we find the 1. Superficial group. 2. Depressors of the os hyoides and larynx. 3. Elevators of the os hyoides and larynx. 4. Lingual group. 5. Soft palate group. 6. Pharyngeal group. 7. Pre vertebral group. 8. Proper muscles of the larynx. These eight groups, therefore, will form so many distinct ideas, by which the composition of the neck and the arrangement of its muscles may be associated in the mind. To facilitate still more the learning of these muscles, the student is informed that, with the exception of the first two, each group consists of five muscles. This is better shown in the following table : 1. Superficial group. Platysma myoides, Sterno-cleido-mastoideus. 2. Depressors of the os hyoides and larynx. Sterno-hyoideus, Sterno-thyroideus, Thyro-hyoideus, Omo-hyoideus. 3. Elevators of the os hyoides and larynx. Digastricus, Stylo-hyoideus, Mylo-hyoideus, Genio-hyoideus, Genio-hyo-glossus. 4. Muscles of the tongue. Genio-hyo-glossus, Hyo-glossus, Lingualis, Stylo-glossus, Palato-glossus. 5. Muscles of the soft palate. Levator palati, Tensor palati, Azygos uvula?, Palato-glossus, Palato-pharyngeus. 6. Muscles of the pharynx. Constrictor inferior, Constrictor medius, Constrictor superior, Stylo-pharyngeus, Palato-pharyngeus. 7. Prevertebral group. Rectus anticus major, Kectus anticus minor, Scalenus anticus, Scalenus posticus, Longus colli. 8. Muscles of the larynx. Crico-thyroid, Crico-arytaenoid, posticus, Crico-aryta3noid, lateralis, Thyro-aryta3noid, Arytaenoid. After this arrangement of the muscles has been well considered, and, we may add, learnt by heart, the student should commence the dissection of one side of the neck with a view to see their connections and relations. With this object an incision should DEEP CERVICAL FASCIA. 141 be made along the middle line of the neck from the chin to the sternum, and bounded superiorly and inferiorly by two trans- verse incisions; the superior one carried along the margin of the lower jaw, and across the mastoid process to the tubercle on the occipital bone, the inferior one along the clavicle to the acromion process. The square flap of integument thus included should be turned back from the entire side of the neck, which brings into view the superficial fascia. The superficial fascia consists of two layers, between which is placed the platysma myoides muscle. The external layer must therefore be reflected from off its fibres, to the same extent with the flap of integument, observing to dissect always in the course of the fibres. The PLATYSMA MYOIDES (rfa.aT'vf, fiv<, fZSof, broad muscle-like lamella) is a thin plane of muscular fibres, situated between the two layers of the superficial cervical fascia; it arises from the superficial fascia over the pectoralis major and deltoid muscles, and passes obliquely upwards and inwards along the side of the neck to be inserted into the side of the chin, oblique line of the lower jaw, the angle of the mouth, and into the cellular tissue of the face. The most anterior fibres are continuous beneath the chin with the muscle of the opposite side; the next interlace with the depressor anguli oris and depressor labii inferioris ; and the most posterior fibres are disposed in a transverse direction across the side of the face, arising from the fibrous covering of the parotid gland, and inserted into the angle of the mouth, consti- tuting the risorius Santorini 1 (page 122). The entire muscle is analogous to the cutaneous muscle of brutes, the panniculus car- nosus. 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 my- oides, while it crosses the direction 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 cer- vical fascia, the reflections of which we have next to examine. The deep cervical fascia is a strong cellulo-fibrous membrane, which invests the neck, forming sheaths for the various muscles, and retaining and supporting the vessels and nerves. It is at- tached posteriorly along the middle line to the ligamentum nuchae, being overlapped by the trapezius muscle; passes for- wards to the posterior border of the sterno-mastoid, and divides 1 John Dominico Santorinus, Professor of Anatomy in Venice. His notice of this muscle is contained in his "Observations Anatomicse," published in 1724. 142 THE DISSECTOR. into two layers which embrace that muscle, and unite again at its anterior border. It is then directed onwards to the middle line, where it becomes continuous with the deep fascia of the opposite side of the neck. The anterior layer, that which is su- perficial to the sterno-mastoid, is prolonged upwards on the side of the jaw and parotid gland, to the zygoma, 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 jaw, forming the stylo-maxillary ligament. Inferiorly it forms a loop, which acts as a pulley to the omo-hyoid muscle, and is then continued downwards behind the clavicle, so as to inclose the subclavius muscle. The extremities of the latter portion are attached firmly to the cartilage of the first rib and coracoid process : hence it is named costo-coracoid membrane or ligament. In the middle line the deep fascia is connected with the sternum. 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, tumors form beneath it, as bronchocele, enlargements of the lymphatic glands, aneu- rism, &c., the pressure which it then exerts may be fatal to the patient, from compression of the trachea, larynx, and nerves, unless the tension be relieved by incision. If the deep fascia be divided in the direction of the sterno-mastoid muscle, and turned aside, that muscle will be brought into view, and the posterior part of its sheath examined. The STERNO-CLETDO-MASTOIDEUS is the large oblique muscle of the neck. It arises, as implied by its name, from the sternum and clavicle (xXsiStoi/), and passes obliquely upwards and back- wards to be inserted into the mastoid process of the temporal, and into the superior curved line of the occipital bone. The sternal portion arises by a rounded tendon, increases in breadth as it ascends, and spreads out to a considerable extent at its insertion. The clavicular portion is broad and fleshy, and sepa- rate from the sternal portion below, but becomes gradually blended with the posterior surface of the latter as it ascends. ACTIONS. The platysma produces a muscular traction on the integu- ment 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, and is one of the depressors of the lower jaw. The sterno-mastoid muscles are the great anterior muscles of connection between the thorax and the head. Both muscles acting together bow the head directly forwards. The clavicular portions, acting more forcibly than the sternal, give stability and steadiness to the head in supporting 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. POSTERIOR TRIANGLE. 143 The sterno-mastoid muscle, stretching obliquely across the side of the neck, divides the latter into two great triangles, an- terior and posterior; each of which is subdivided into smaller triangles. The great anterior triangle, having its base at the Fig. 43. THE MUSCLES OF THE ANTERIOR ASPECT OP 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 attached 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. 6. 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 scalenus anticus, of the right side. 21. The scalenus posticus. 22. The scalenus medius. lower jaw and apex at the sternum, is bounded in front by the mid-line of the neck, behind by the sterno-mastoid, and above by the body of the lower jaw. This triangular space contains the carotid arteries, internal jugular vein, and large nerves of the neck ; the anterior border of the sterno-mastoid being the guide for the incision in ligature of the common carotid artery. The posterior triangle', having its base at the clavicle and apex at the occiput, is bounded in front by the sterno-mastoid muscle; behind by the trapezius, and below by the clavicle ; it contains 144 THE DISSECTOR. in its lower part the subclavian artery and vein, with some of their branches, and the brachial plexus of nerves. Both trian- gular spaces are covered in by the deep cervical fascia and pla- tysraa myoides muscle ; and the external jugular vein, in its ver- tical course down the neck, passes from the anterior triangle across the sterno-mastoid muscle to the posterior triangle. Fig. 44. THE TRIANGLES OP THE NECK, WITH THE EXTERNAL JUGULAR VEIN AND ASCENDING BRANCHES OP 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 sub- clavian triangle. 2. 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 superficial 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. The sterno-mastoid may now be removed by dividing it through the middle and turning aside its ends. The upper end will be found to be perforated by a large nerve, the spinal accessory of the eighth pair, which, after supplying the sterno-mastoid, takes its course across the posterior triangle to the under part of the trapezius. The deep layer of fascia is then to be dissected from off the side of the larynx and trachea towards the mid-line, when the second group of muscles, the depressors of the os hyoides and larynx, will be brought into view. Second Group. Depressors of the os hyoides and larynx. Sterno-hyoid, Thyro-hyoid, Sterno-thyroid, Omo-hyoid. OMO-HYOIDEUS. 145 The STERNO-HYOIDEUS is a narrow, ribbon-like muscle, arising from the posterior surface of the first bone of the sternum, and from the posterior sterno-clavicular ligament (sometimes from the inner extremity of the clavicle, and sometimes from the cartilage of the first rib). It is inserted into the lower border of the os hyoides. The sterno-hyoidei are separated by a considerable interval at the root of the neck, but approach each other as they ascend ; they are frequently traversed below by a tendinous inter- section. The sterno-hyoideus may be divided through the middle, and its ends turned aside. The STERNO-THYROIDEUS, broader than the preceding, beneath which it lies, arises from the posterior surface of the upper bone of the sternum, and from the cartilage of the first rib ; it is inserted into the oblique line on the great ala of the thyroid cartilage. The inner borders lie in contact along the middle line, and the muscles are marked by a tendinous intersection at their lower part. 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 lower border of the body, and into the great cornu of the os hyoides for one-half its length. The OMO-HYOIDEUS (<>o$, shoulder) is a double-bellied muscle passing obliquely across the neck from the scapula to the os hy- oides ; it forms an obtuse angle behind the sterno-mastoid muscle, and is retained in that position by means of a process of the deep cervical fascia which is connected to the inner border of its ten- don. It arises from the upper border of the scapula, and from the transverse ligament of the supra-scapular notch, and is inserted into the os hyoides at the junction of the body and great cornu. ACTIONS. The four muscles of this group are depressors of the os hy- oides and larynx. The three former drawing these parts downwards in tin- 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 orno-hyoid muscles, by means of their connection with the cervical fascia, are rendered tensors of that portion of the deep cervical fascia which covers the lower part of the neck, between the two sterno-mastoid muscles. The omo-hyoid muscle, crossing the neck obliquely in a direc- tion opposite to that of the sterno-mastoid, and crossing also the anterior and posterior triangular spaces, subdivides the latter into smaller triangles. The inferior angle of the great anterior triangle, cut off by the upper belly of the omo-hyoideus, is the inferior carotid triangle, while the space above is the superior carotid triangle. The apicial portion of the great posterior tri- angular space is the occipital triangle; while the space between the omo-hyoid and the clavicle is the subclavian triangle. The latter contains the subclavian artery and vein, and brachial 13 146 THE DISSECTOR. plexus of nerves ; and is bounded in front by the sterno-mastoid, above by the orao-hyoid, and below by the clavicle. The exter- nal jugular vein enters this space to join the subclavian vein, and it is here that the operation of tying the subclavian artery is performed. If the sterno-hyoid and sterno-thyroid muscles be divided, and the ends turned aside, the thyroid gland will be brought into view, lying upon the trachea, the two lobes being connected by a transverse portion which crosses the air-tube. THYROID GLAND. The thyroid gland consists of two lobes, which are placed one on each side of the trachea, and are connected with each other by means of an isthmus, which crosses its upper rings, usually the third and fourth ; but in this respect there is some variety, a point necessary to be remembered in operations on the trachea. The lobes are somewhat conical in shape, being larger below than above, and the smaller end is continued upwards to the side of the thyroid cartilage. The isthmus is connected with the lower third of the two lobes, and often gives origin to a process of variable length and size, called the pyramid or third lobe. The pyramid is generally situated on the left side of the isthmus, and is sometimes derived from the left lobe. The left lobe is somewhat smaller than the right, the weight of the entire gland being about one ounce and a half. It is, however, larger in young persons and females than in adult males, and under- goes a slight increase during menstruation. Its permanent en- largement constitutes bronchocele, goitre, or the Derbyshire neck. The structure of the thyroid is of a brownish-red color, and is com- posed of a dense aggregation of minute and independent membranous cavities inclosed by a plexus of capillary vessels, and connected together by cellular tissue. The cavities are filled with a yellowish fluid, in which are found cytoblasts and cells ; the latter measuring y^g of an inch in diameter. In young animals the cytoblasts lie in contact with the internal wall of the cavities, and constitute a kind of tessellated epithelium. A muscle is occasionally found connected with its isthmus, or with the pyramid, and is attached, superiorly, to the body of the os hyoides, or to the thyroid cartilage. It was named by Soem- mering the " levator glandulce thyroidece." Vessels and Nerves. It is abundantly supplied with blood by the superior and inferior thyroid arteries. Sometimes an addi- tional artery is derived from the arteria innominata, and ascends upon the front of the trachea to be distributed to the gland. The wounding of the latter vessel, in tracheotomy, might be fatal to the patient. The nerves are derived from the superior laryn- geal, and from the middle and inferior cervical ganglia of the sympathetic. The TRACHEA may now be examined with reference to the ope- ration of tracheotomy. MUSCLES OF THE OS HYOIDES. 147 Operation. Next to bleeding, tracheotomy is one of the most important operations on the human body, from the emergency of the circumstances under which the surgeon is called upon to act, and from the liability of their occurrence to every practitioner and at any moment. The student should not omit to perform this operation while dissecting the neck, for, although trifling in itself, it might be the instant means of saving, if not of restoring life. If called unexpectedly to a patient laboring under symptoms of threatened suffocation, he would not hesitate to perform it with his penknife ; therefore he taust familiarize himself with its steps. An incision is to be made to the extent of an inch and a half along the middle line of the neck, just above the sternum. This may divide the integument and superficial fascia. The next incision takes him to the space between the two sterno-thyroid muscles ; these are to be separated, an opening made into the trachea, and a canula, or writing quill, in- serted into it. This is the only part of the operation that requires care ; for some large veins, the inferior thyroid, and occasionally an inferior thyroid artery from the innominata, lie immediately upon the trachea. The bleeding resulting from the wound of any of these vessels might be fatal from pouring into the trachea. In the case of the artery it would be necessary to tie the divided extremities. LARYNGOTOMY is practised a little higher in the neck, immediately below the thyroid cartilage. The structures are to be divided as in the previous operation, and the point of a bistoury introduced into the larynx through the crico-thyroid membrane, in the space left by the divergence of the two crico-thyroid muscles. A small branch of communication between the two superior thyroid arteries (inferior laryngeal) crosses this ligament, the division of which, as it might give rise to disagreeable hemorrhage, must be carefully avoided. Third Group. Elevators of the os hyoides. Digastricns, Stylo-hyoid, Mylo-hyoid. Genio-hyoid. Genio-hyo-glossus. To dissect these muscles the neck should be supported by a high block, and the head thrown backwards. The deep fascia should be carefully removed, together with any cellular tissue or fat which may impede the view. The DIGASTRICUS (8tj, twice, yavtw, belly) is a small muscle situated immediately beneath the side of the body of the lower jaw ; it is fleshy at each extremity, and tendinous in the middle. It arises from the digastric fossa and anterior border of the mastoid process of the temporal bone, and is inserted into a de- pression on the inner side of the lower jaw, close to the sym- physis. The middle tendon is held in connection with the body of the os hyoides by an aponeurotic loop, through which it plays as through a pulley; the loop being lubricated by a synovial membrane. A thin layer of aponeurosis is given off from the tendon of the digastricus at each side, which is connected with 148 THE DISSECTOR. the body of the os hyoides, and forms a strong plane of fascia between the anterior portions of the two muscles. This fascia is named the supra-hyoidean. The digastricus muscle incloses on two sides, the lower jaw being the third, a small triangular space which is named, from its situation, submaxillary triangle; while it constitutes the upper boundary of the superior carotid triangle, the other two sides of the latter being the omo-hyoid below, and the sterno-mastoid behind. The student has now before him the three subdivisions of the anterior triangular space of the neck, namely, submaxillary , superior carotid, and inferior carotid. In the submaxillary triangle he will find the submaxillary gland, facial artery, and submental artery, the floor of the trian- gular space being formed by the mylo-hyoideus muscle. In the superior carotid triangle is the common carotid artery, dividing into the external and internal carotid, the internal jugu- lar vein, the hypoglossal nerve, descendens noni, pneumogastric, and behind the sheath of the carotid vessels, the sympathetic nerve. In the inferior carotid triangle is the sheath of the common carotid artery, the internal jugular vein and pneumogastric nerve being inclosed in the sheath with the artery. SUBMAXILLARY GLAND. This salivary gland, situated in the submaxillary triangle, is of a rounded form. It rests on the mylo-hyoideus, hyo-glossus, and stylo-glossus muscles, and is separated from the parotid gland by the stylo-maxillary ligament. Its lateral boundaries are the lower jaw, against which it lies, and the digastricus muscle, and it is covered in by the deep cer- vical fascia and platysma. Its excretory duct (Wharton's), about two inches in length, issues from the middle of the gland and passes between the mylo-hyoideus and hyo-glossus to the fraanum linguaa, by the side of which it terminates at the apex of a papilla. A process of the gland is prolonged with the duct for a short distance behind the mylo-hyoideus. The structure of the submaxillary gland is similar to that of the parotid already described (page 122), but its lobes are larger and less firmly held together by cellular tissue. Its duct also is thinner, being composed only of a fibrous coat lined by mucous membrane. The submaxillary gland has lying in a groove upon its upper surface the facial artery. The STYLO-HYOIDEUS is a small and slender muscle, 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 near the middle line. SUBLINQUAL GLAND. 149 The digastricus must be divided at its insertion into the lower jaw, its attachment to the os hyoides with that of the stylo-hyoideus separated, and the muscles turned aside in order to bring the next muscle into view. The supra-hyoidean fascia, and any cellular tissue and fat which may disfigure the muscle, should also be dissected away. The MYLO-HYOIDEUS (/AVX^, mola, i. e. t attached to the molar ridge of the lower jaw) is a broad and triangular plane of mus- cular fibres, forming, with its fellow of the opposite side, the inferior wall or floor of the mouth. It arises from the molar ridge of the lower jaw, and proceeds obliquely inwards to be inserted into the raphe of the two muscles and body of the os hyoides ; the raphe is sometimes deficient at its anterior part. After the mylo-hyoides has been examined, it should be cut away from its origin and insertion, and completely removed. The view of the next muscles would also be 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 (ytvtt.ov, the chin) arises from a small tubercle on the inner side of the symphysis of the lower jaw, and is inserted into the body of the os hyoides. It is a short and slender muscle, very closely connected with its fellow and with the border of the following. The GENIO-HYO-GLOSSUS (yXwooa, the tongue) is a triangular muscle, narrow and pointed at its origin from the lower jaw, broad and fun-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 os hyoides. 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 removal of the mylo-hyoideus brings into view, besides the last two muscles, the duct of the submaxillary gland, and the third and smallest of the salivary glands, the sublingual. SUBLINGUAL GLAND. The sublingual is a long and flattened gland situated in the floor of the mouth by the side of the fra- num linguae and tongue, and covered on this aspect by the mu- cous membrane. At the fraenum it is in relation with its fellow of the opposite side, and in the rest of its course lies between the lower jaw and genio-hyo-glossus, being bounded below by the mylo-hyoideus. It is in relation also with tfce duct of the sub- maxillary gland and the hypoglossal nerve. The sublingual gland in essential structure is. similar to the other saliyary glands j but the lobules, are more loosejv connected, 150 THE DISSECTOR. and in some instances lie apart from each other. Its secretion is poured into the month by from seven to twenty short ducts (ductus Riviniani), which open upon the ridge made by the gland in the floor of the mouth ; the larger openings being situated by the side of the fraenum linguae. One of the ducts, longer than the rest, and opening close to Wharton's duct, has been named ductus Bartholini. Fig. 45. THE STYLOID MUSCLES AND THE MUSCLES OP THE TONGUE. 1. A portion of the temporal bone of the left side of the skull in- cluding the styloid and mastoid processes, and the meatus a'udi- torius 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-glos- sus portion. 7. Its cerato-glossus portion. 8. The anterior fibres of the lingualis issuing from be- tween 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-pha- ryngeus muscle. 12. The os hy- oides. 13. The thyro-hyoidean membrane. 14. The thyroid car- tilage. 15. The thyrc-hyoideus muscle arising from the oblique line on the thyroid cartilage. 16. The cricoid cartilage. 17. The crico-thy- roidean membrane, through which the operation of laryngotomy is performed. 18. The trachea. 19. The commencement of the oesophagus. Fourth Group. Muscles of the tongue. Genio-hyo-glossus, Hyo-glossus, Lingualis, Stylo-glossus, Palato-glossus. These muscles are already exposed by the preparation of the last group ; the student has therefore only to clean them, to bring them more clearly into view. The genio-hyo-glossus is repeated with this group, as belonging in action to the present set of muscles as well as the last. The IJYO-GLOSSUS is a square-shaped plane of muscle, arising from the whole length of the great cornu and from the body of the QS hyoides, and inserted between the stylo-glossus and lin- PALATO-GLOSSUS. 151 gualis into the side of the tongue. The direction of the fibres of that portion of the muscle which arises from the body is obliquely backwards, and that from the great cornu obliquely forwards ; hence they are described by Albinus as two distinct muscles, under the names of basio-glossus and cerato-glossus, to which he added a third fasciculus, arising from the lesser cornu, and spreading along the side of the tongue, the chondro-glossus. The basio-glossus slightly overlaps the cerato-glossus at its upper part, and is separated from it by the transverse portion of the stylo-glossus. The hyo-glossus muscle is crossed lay two large nerves, and the duct of the submaxillary gland. The gustatory nerve is the highest of the three, the hypoglossal nerve the lowest, Wharton's duct and the deep process of the submaxillary gland lying between them. The LINGUALIS The fibres of this muscle (lingualis inferior) may be seen towards the apex of the tongue, issuing from the interval between the hyo-glossus and genio-hyo-glossus ; it is best examined by removing the preceding muscle. It consists of a small fasciculus of fibres, running longitudinally from the base, where it is attached to the os hyoides, to the apex of the tongue. By the outer border its fibres reach the plane of longitudinal fas- ciculi of the stylo-glossus; and by its under surface it is in rela- tion with the ranine artery. The STYLO-GLOSSUS arises from the apex of the styloid process and from the stylo-maxillary ligament; it divides upon the side of the tongue into a transverse and longitudinal portion : the transverse portion dips into the substance of the tongue between the two parts of the hyo-glossus ; the longitudinal portion spreads out upon the side of the tongue, and is prolonged forward as far as its tip. The PALATO-GLOSSUS passes between the soft palate and the side of the base of the tongue, forming a projection of the mu- cous membrane, which is called the anterior pillar of the soft palate. Its fibres are lost superiorly among the muscular fibres of the palato-pharyngeus, and inferiorly among the fibres of the stylo-glossus upon the side of the tongue. This muscle, with its fellow, constitutes the constrictor isthmi faucium. ACTIONS. The genio-hyo-glossus muscle effects several movements of the tongue. When the tongue is steadied and pointed by the other muscles, the posterior fibres of the genio-hyo-glossus would dart it from the mouth, while its anterior fibres would restore it to its original posi- tion. The whole length of the muscle acting upon the tongue, would render it concave along the middle line, and form a channel for the cur- rent of fluid towards the pharynx, as in sucking. The apex of the tongue is directed to the roof of the mouth, and rendered convex from before Ku-kwards by the linguales. The hyo-glossi, by drawing down the sides of the tongue, render it convex along the middle line. It is drawn up- 152 THE DISSECTOR. wards 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. The palato-glossi mus- cles, assisted by the uvula, have the power of closing the fauces com- pletely, an action which takes place in deglutition. VESSELS AND NERVES OF THE NECK. Having thus far studied the muscles, the dissector should turn to the opposite side of the neck, with the view of examining the vessels and nerves. The integument and superficial fascia having been dissected back, the platysma is brought into view, and may be carefully raised. Beneath it, in the anterior triangle, will be found the inframaxillary branches of the cervico-facial division of the facial nerve (page 127), and the superficialis colli nerve ; lying upon the sheath of the sterno- mastoid muscle is the auricularis magnus nerve and external jugular vein, with one or two lymphatic glands ; and in the lower part of the posterior triangle will be seen the clavicular and acromial branches of the cervical plexus. The SUPERFICIALIS COLLI nerve, one of the three superficial ascending branches of the cervical plexus, arises from the second and third cervical nerves, and curving around the posterior bor- der of the sterno-mastoid at about its middle, crosses that muscle to its anterior border ; it then pierces the deep cervical fascia, and divides into an ascending and descending branch. There are sometimes two nerves in place of this division into two branches. The ascending branch divides into several filaments, one of which ascends by the side of the external jugular vein; others communicate with the inframaxillary branches of the facial nerve, forming a kind of plexus ; and a third set piercing the platysma are distributed to the integument of the anterior triangle as high as the lower jaw. These latter supply the platysma, and communicate with the branches of the facial through that muscle. The descending branch pierces the platysma, and is distributed to the integument of the front of the neck as far downwards as the sternum. The AURICULARIS MAGNUS, the largest of the three branches of the cervical plexus, proceeds from the second and third cervical nerves. It pierces the deep fascia at the posterior border of the sterno-mastoid, and ascends beneath the platysma and parallel with the external jugular vein to the parotid gland, where it divides into an anterior and posterior branch. The anterior branch distributes filaments to the integument of the face over the parotid gland, and communicates with the facial nerve. The posterior branch ascends to the back of the ear, and divides ANTERIOR JUGULAR VEIN. 153 into filaments which are distributed to the pinna ; and a mastoid branch which supplies the integument behind the ear, and com- municates with the posterior auricular branches of the pneumo- gastric and facial nerve, and with the occipitalis minor. The OCCIPITALIS MINOR nerve, arising from the second cervical nerve, ascends along the posterior border of the sterno-mastoid, pierces the deep fascia near the occiput, and is distributed to the occipito-frontalis and attollens aurem (auricular branch), and to the lateral and posterior part of the head, communicating with the occipitalis major and posterior auricular branch of the facial. The EXTERNAL JUGULAR VEIN, formed by the union of the posterior auricular and temporo-maxillary vein in the parotid gland, descends over the sterno-mastoid muscle, lying between the deep cervical fascia and the platysma, to the posterior border of the sterno-mastoid, at its lower part, where it pierces the deep fascia and terminates in the subclavian vein. It communicates with the internal jugular vein in the parotid gland, and in the lower part of the neck with the anterior jugular. It also com- municates occasionally with the cephalic vein, by a branch from the latter which crosses the clavicle. The external jugular vein receives several superficial veins from the back part of the head and neck. Operation. The external jugular vein is generally opened, where it lies on the sterno-mastoid muscle. The finger should be placed on the vessel, below the point selected for incision, with the double object of rendering the vein tense, and preventing the admission of air. The incision should be directed obliquely upwards and backwards (Fig. 44, No. 10), so as to (KISS the direction of the fibres of the platysma, otherwise the fibres, by drawing the edges of the wound together, might prevent the flow of blood. The parts cut through will be the integument, the platysma with the two layers of the superficial fascia, between which it is placed, and the coats of the vein. The ANTERIOR JUGULAR VEIN is formed by branches which commence in the fore part of the neck. It passes along the an- terior border of the sterno-mastoid, and turning outwards behind the tendon of that muscle, terminates in the subclavian vein near the external jugular. It communicates with the external and internal jugular vein, and with its fellow of the opposite side of the neck. Superficial Lymphatic Glands. The superficial lymphatic glands of the neck are two or three beneath the chin and in the submaxillary triangle, and three or four in the course of the ex- ternal jugular vein. The largest of the latter are situated at the lower part of the vein, at the posterior border of the sterno-mastoid muscle. 154 THE DISSECTOR. POSTERIOR TRIANGULAR SPACE. The sheath of the sterno-mastoid may now be laid open by means of a longitudinal incision, and dissected back to the posterior border of the muscle. In the next place, the deep fascia covering the posterior trian- gular space should be carefully removed, in order to bring into view the nerves and vessels which it contains. Turning around the posterior border of the sterno-mastoid from behind, are the three ascending branches of the cervical plexus already described, namely, superficialis colli, auri- cularis magnus, and occipitalis minor; crossing the space below these, is the spinal accessory nerve in its course from the sterno-mastoid to the trapezius ; lower down are the descending branches of the cervical plexus, claviculares, and acromiales ; beneath the latter is the posterior belly of the omo-hyoid muscle, which marks the lower boundary of the occipital triangle, and the upper boundary of the subclavian triangle. On a level with this muscle is the transversalis colli artery, and lower down, behind the clavicle, the suprascapular artery. Moreover, lying deeply in the subclavian triangle, is the subclavian artery and brachial plexus of nerves. The subclavian triangle varies in its extent in different subjects ; the posterior belly of the omo-hyoideus, usually an inch and a half above the clavicle, may descend nearer to that bone ; or the sterno-mastoid and trapezius, instead of having between them a space equal to one-third the length of the clavicle, may approach each other, or even meet. The floor of the posterior triangle is formed by the muscles of the back of the neck, and by the middle and posterior scalenus. After studying the relative position of the contents of the posterior tri- angle, the sterno-mastoid may be divided through the middle, and its ends turned upwards and downwards. The spinal accessory nerve may then be seen piercing the upper part of the muscle, and the cervical nerves and cervical plexus may be dissected. CERVICAL NERVES. The cervical nerves are eight in number, the first passing out of the vertebral canal above the atlas, and the last between the seventh cervical and first dorsal vertebra. Each nerve, at its issue from the vertebral canal, splits into an anterior and posterior division. The posterior divisions have been already described. The anterior division of the first cervical, or suboccipital nerve, proceeds from its trunk, while the latter is placed on the posterior arch of the atlas; and passing forwards, beneath the vertebral artery, curves downwards, in front of the transverse process of the atlas, to form a loop of communication with an ascending branch of the second cervical nerve. This nerve supplies the rectus lateralis and rectus anticus minor muscle, and its loop receives branches of communication from the pneumogastric, hypoglossal, and sympathetic nerve. The anterior division of the second cervical nerve quits its trunk of origin by passing over the lamina of the axis; it then passes forwards externally to the vertebral artery and intertrans- verse muscles, and divides into an ascending branch, which com- ANTERIOR CERVICAL NERVES. 155 pletes the loop with the first nerve, and two descending branches, which form loops with corresponding branches of the third. The third and fourth cervical nerves, immediately on their exit from between the intertransverse muscles, divide in a similar manner into branches which form loops with the nerve above and below. Cervical Plexus. The communications so established between the anterior divisions of the four upper cervical nerves, consti- tute the cervical plexus. The plexus is situated behind the sterno-mastoid muscle, and rests on the levator anguli scapulae, posterior and middle scalenus, and splenius colli muscle. The branches of the cervical plexus admit of a primary divi- sion into superficial and deep ; and the superficial set are further divisible into ascending and descending. The following table exhibits this arrangement : ( Superficial is colli, /- Ascending, -j Auricularis magnus, Superficial . . J ( Occipitalis minor. f Communicating branches, Communicans noni, Muscular, Phrenic. The ascending superficial branches proceed from the second and third cervical nerves, and pass forwards to the posterior border of the sterno-mastoid muscle (p. 152). The descending superficial branches, two or three in number, proceed from the fourth cervical nerve, and pass downwards in the triangular space ; they then pierce the deep fascia, and cross- ing the clavicle, are distributed to the integument of the front of the chest from the sternum to the acromion : hence their desig- nation, claviculares and acromiales. The most anterior of the branches is named sternal, from its destination, and the outer- most branch passes over the clavicular attachment of the trape- zius to reach the shoulder. Deep Branches. The communicating branches are filaments of communication passing between the loop of the first cervical nerve and the pneuinogastric, hypoglossal, and sympathetic nerve, and communications between the other nerves and the sympathetic. The communicans noni is a long and slender branch of com- munication between the cervical plexus and the descendens noni. It arises from the second and third cervical nerves, and passing 156 THE DISSECTOR. downwards, by the side of the internal jugular vein to the middle of the neck, reaches the front of the sheath of the carotid vessels, and forms a loop with the descendens noni of the hypoglossal nerve. The muscular branches of the cervical plexus are distributed to the muscles of the front of the vertebral column and side of the neck. From the loop, between the first and second nerve, branches are given to the anterior recti. From the second cer- vical nerve a branch is given to the sterno-mastoid. From the third and fourth nerves branches are given off to the trapezius, levator anguli scapulae, and scalenus posticus. The branch to the trapezius communicates with the spinal accessory nerve. The phrenic nerve (internal respiratory of Bell) is formed by the union of filaments from the third, fourth, and fifth cervical nerve. It passes downwards, resting on the scalenus anticus muscle, and at the root of the neck receives a filament from the sympathetic. The nerve next passes between the subclavian artery and vein, and crossing the origin of the internal mammary artery, enters the chest. It then descends through the chest, between the pleura and pericardium, and in front of the root of the lung, to the diaphragm (page 105). BRACHIAL PLEXUS. The anterior divisions of the four lower cervical nerves and the first dorsal constitute, by their commu- nications, the brachial plexus. The mode of formation of the plexus is as follows : The fifth and sixth nerves unite to form a common trunk. The last cervical and first dorsal also unite as soon as they meet to form a single trunk ; the seventh cervical nerve lies for some distance apart from the rest, and then divides into two branches, which join the other cords. At this point, the plexus consists of two cords, from which a third is given off ; and the three cords become placed, one to the inner side of the axillary artery, one behind, and one to its outer side. The brachial plexus communicates with the cervical plexus by means of a branch from the fourth to the fifth nerve, and receives branches from the two inferior cervical ganglia of the sympathetic. The branches of the brachial plexus in the neck are some small branches to the longus colli and scaleni ; branches to the rhom- boidei and subclavius muscle, the suprascapular and posterior thoracic. The rhomboid branch proceeds from the fifth cervical nerve, and, passing backwards through the fibres of the scalenus medius, and beneath the levator anguli scapula, is distributed to the under surface of the rhomboid muscles ; in its course, it some- times gives a branch to the levator anguli scapulae. The subclavian branch proceeds from the cord formed by the fifth and sixth nerves, and descends in front of the subclavian SUBCLAVIAN ARTERY. 157 artery to the subclavius muscle ; this nerve usually communicates with the phrenic at its entrance into the chest. The posterior thoracic nerve (long thoracic ; external respira- tory of Bell) arises by two roots from the fifth and sixth cervical nerves, and, passing between the fibres of the middle scalenus, descends behind the brachial plexus to the serratus magnus, along which it is distributed to the lower border of that muscle. The suprascapular nerve proceeds from the fifth cervical nerve, and descends beneath the trapezius to the suprascapular fossa. Before proceeding to the study of the subclavian artery and its branches, the dissector should define and examine a group of muscles forming a pyramidal mass at the root of the neck, the scaleni ; these muscles are connected with the transverse processes of the cervical vertebrae above, and the first and second ribs below. According to different authors, they are two, three, or more in number. The SCALENUS ANTICUS arises from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebra;, and is inserted into the tubercle upon the upper and inner border of the first rib ; it is a triangular muscle, and at its oriirin is continuous with the rectus anticus major. The SCALENUS POSTICUS (scalenus medius and posticus) arises from the posterior tubercles of all the cervical vertebrae excepting the first ; it is inserted by two fleshy fasciculi into the first and second ribs. The anterior of the two fasciculi (scalenus medius) is large, and occupies all the surface of the first rib between the Fig. 46. THE ARCH OP THE AORTA, WITH ITS BRANCHES, AND THE COURSE OF THE SUBCLAVIAN ARTERIES. 1. The ascend- ing norta. 2. Its arch. 3. The descend- ing aorta. 4. The arteria innominata. 5. The right subclavian, the first or obliquely ascending 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 pneu- mogastric 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. groove for the subclavian artery and the tuberosity. The poste- rior (scalenus posticus) is small, and is attached to the second rib between its tubercle and angle. SUBCLAVIAN ARTERY and its Branches. The subclavian artery 14 158 THE DISSECTOR. ^ differs in its origin on the two sides of the body, and consequently in that portion of its course which is in relation with the cavity of the thorax. Qn its escape from the chest, its course Is alike on both sides ; the course of the artery is divided into three parts. First Part. On the right side the subclavian artery com- mences at the bifurcation of the arteria innominata, opposite the sterno-clavicular articulation, and passes obliquely outwards to the inner border of the scalenus anticus, where the second por- tion of its course begins. On the left side the subclavian artery proceeds from the pos- terior part of the arch of the aorta, and therefore lies more deeply in the chest, and is longer in its course. It ascends per- pendicularly to the inner border of the scalenus anticus. From this point the arteries correspond on both sides. Second Part. The artery next passes horizontally outwards behind the scalenus anticus ; and (third part) then curves out- wards and downwards to become, opposite the lower border of the first rib, the axillary artery. Relations. The first part of the artery is crossed in front by the internal jugular vein, vertebral vein, pneumogastric nerve, phrenic nerve, and one or two branches of the sympathetic ; behind it has the sympathetic nerve, on the right side the recur- rent nerve, and on the left the thoracic duct ; below, on the right side is the pleura ; that membrane being to its outer side on the left. The second portion of the artery has the scalenus anticus in front;' the scalenus medius and two lower nerves of the bjachial plexus behind; the upper nerves of the plexus above, and the pleura below. The scalenus anticus separates it from the phrenic nerve and subclavian vein, which latter is rather below the level of the artery. The third portion of the artery is situated in the subclavian triangle, and is more superficial than the rest. In front it is covered by the integument, platysma, and deep fascia, and crossed by the supraclavicular nerves. Lower down it is crossed by the suprascapular artery and vein, and gets behind the sub- clavius muscle and clavicle. Behind, it has the scalenus medius ; above, the brachial plexus ; and below, the first rib and subcla- vian vein. Operation. Ligature of the subclavian artery is performed on that vessel in the third part of its course, just after its issue from between the scaleni muscles, and where it rests on the first rib. An incision is made along the upper border of the clavicle, from the sternal portion of the sterno-mastoid muscle to the edge of the trapezius. This should divide the integument, superficial fascia, platysma, and deep VERTEBRAL ARTERY. 159 fascia ; and more or less of the clavicular portion of the sterno-mastoid muscle, according to its breadth or the depth of the artery. Then lay aside the knife, introduce a finger into the wound behind the vein, and feel for the tubercle on the first rib : immediately behind it is the cylinder of the artery, which may be recognized by its roundness and elasticity, and by its pulsation beneath the finger. One of the chief difficulties in the performance of the operation is the position of the vein, in front of the artery ; and when of large size and distended with blood it may present an inconvenient obstacle. Occasionally another impedi- ment arises from the termination of the external jugular vein in the middle of the space. The operator has to gnard against wounding these veins, or placing his ligature around any of the nerves of the brachial ] ilex us. The parts cut through in the operation are the integument, snper- Jicial fascia, platysma, supraclavicular nerves, clavicular origin of the sterno-mastoid muscle, deep fascia, cellular tissue. Branches. The branches of the subclavian artery are four, and sometimes five, in number. Three are given off from the first portion of the artery ; one, the superior intercostal, from the second portion ; and when a fifth artery exists, it arises from the third portion, and is the suprascapular. In a tabular form the branches are as follows : Vertebral, Internal mammary, f Inferior thyroid, Thyroid axis < Suprascapular, [ Transversalis colli. Superior intercostal Profunda cervicis. The VERTEBRAL ARTERY, the first and largest of the branches of the subclavian artery, arises from the posterior aspect of that trunk ; it ascends through the foramina in the transverse processes THE SUBCLAVIAN ARTERY, WITH ITS Fig. 47. BRANCHES. 1. The arteria innominate, di- viding into, 2. The right common carotid ar- tery, 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 subcla- vian artery : 6. The vertebral. 7. The infe- rior thyroid. 8. The thyroid axis, giving off its four branches. 9, 10. The two cervical branches of the subclavian : 9. The cervi- calis superficialis. 10. The cervicalis profun- da. 11, 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. of all the cervical vertebrae, excepting the last ; then winds back- wards around the articulating process of the atlas ; and, piercing 160 THE DISSECTOR. the dura mater, enters the skull through the foramen magnum. The two arteries unite at the lower border of the pons Varolii, to form the basilar artery. In the foramina of the transverse processes of the vertebrae the artery lies in front of the cervical nerves, and on the left side the artery is crossed by the thoracic duct. The branches of the vertebral artery in the neck are lateral spinal branches, which enter the intervertebral foramina,' and are distributed to the vertebra and spinal cord. The INTERNAL MAMMARY ARTERY arises from the under side of the subclavian, and passes down behind the subclavian vein to the cartilage of the first rib. It then descends by the side of the sternum, resting on the cartilages of the ribs, to the sheath of the rectus, where, under the name of superior epigastric, it ter- minates by inosculating with the epigastric branch of the exter- nal iliac. As the artery enters the chest it is crossed by the phrenic nerve. The relations and branches of the internal mammary artery are described in Chapter VII. The THYROID AXIS is a short trunk which arises from the front of the subclavian, close to the inner border of the anterior scalenus, and divides almost immediately into three branches; inferior thy- roid, suprascapular, and trans versalis colli. The INFERIOR THYROID ARTERY ascends obliquely in a serpen- tine course behind the sheath of the carotid vessels, and in front of the longus colli, to the inferior and posterior part of the thy- roid gland, to which it is distributed. It is in relation with the middle cervical ganglion of the sympathetic, which lies in front of it ; and sends branches to the trachea, larynx, and O3so- phagus. Near its origin the inferior thyroid artery gives off a large branch, the cervicalis ascendens, which passes up the neck, rest- ing on the anterior tubercles of the transverse processes of the cervical vertebrae, and occupying the groove between the scale- nus anticus and rectus anticus major. It is distributed to the deep muscles and glands of the neck, and sends branches through the intervertebral foramina to supply the spinal cord and its membranes. The SUPRASCAPULAR ARTERY (transversalis humeri) passes ob- liquely outwards behind the clavicle, and over the ligament of the suprascapular notch, to the supraspinatus fossa. It crosses in its course the scalenus anticus muscle, phrenic nerve, and sub- clavian artery, is distributed to the muscles of the dorsum of the scapula, and inosculates with the posterior scapular, and beneath the acromion process with the dorsal branch of the subscapular artery. COMMON CAROTID ARTERY. 161 The TRANSVERSALTS coLLi ARTERY passes transversely across the subclavian triangle at the root of the neck to the anterior bor- der of the levator anguli scapulae, where it divides into two ter- minal branches, the superficialis cervicis and posterior scapular. In its course it lies above the suprascapular artery, and crosses the scaleni muscles and brachial plexus of nerves, often passing between the latter. At its bifurcation it is covered in by the edge of the trapezius. The superficialis cervicis artery, its ascending branch, passes upwards under cover of the anterior border of the trapezius, and is distributed to the superficial muscles of the neck and deep cervical glands. The posterior scapular artery, the proper continuation of the transversalis colli, passes backwards to the superior angle of the scapula, and then descends along the posterior border of that bone to its inferior angle, where it inosculates with the subsca- pular artery. The SUPERIOR INTERCOSTAL ARTERY arises from the upper and back part of the subclavian artery behind the scalenus anticus, and passes down behind the pleura to the neck of the first rib, whence it descends to supply the first two intercostal spaces. The profunda cervicis artery arises by a common trunk with the preceding, or, more properly, is a branch of the superior intercostal, corresponding with the posterior branch of the other intercostal arteries. It passes backwards between the transverse processes of the seventh cervical and first dorsal vertebra, and ascends among the muscles at the back of the neck, to which it is distributed, inosculating with the princeps cervicis, a branch of the occipital. The SUBCLAVIAN VEIN, the continuation upwards of the axil- lary vein, commences opposite the lower border of the first rib, and ascends in front of the rib and scalenus anticus and behind the clavicle and subclavius muscle to opposite the sterno-clavicu- lar articulation, where it joins with the internal jugular vein to form the vena innominata. The subclavian vein is placed in front of, but rather below, the level of the subclavian artery, and is separated from the artery by the scalenus anticus, and by the phrenic and pneumogastric nerve. The branches which open into the subclavian vein are the external and anterior jugular externally to the scalenus anticus, and the vertebral internally to that muscle. Carotid Artery and its Branches. The COMMON CAROTID ARTERY differs in its origin and length on two sides of the neck. On the right side it proceeds from the 14* 162 THE DISSECTOR. bifurcation of the arteria innominata opposite the sterno-clavicu- lar articulation ; on the left it arises from the arch of the aorta, Fig. 48. THE CAROTID AR- TERIES WITH THE BRANCHES OP THE EX- TERNAL CAROTID. 1. 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 ar- tery. 6. The lingual arte- ry. 7. The facial artery. 8. The mastoid artery. 9, The occipital. 10. The posterior auricular. 11. The transverse facial ar- tery. 12. The internal maxillary. 13. The tem- poral. 14. The ascend- ing pharyngeal artery. and ascending to a parallel position in the neck, takes a course similar to the right. The common carotid artery ascends the neck by the side of the trachea and larynx to a point corresponding with the upper border of the thyroid cartilage, where it divides into the external carotid and internal carotid. In its course it is inclosed in a fibrous sheath, which also con- tains the internal jugular vein, lying to the outer side of the artery ; and the pneumogastric nerve, which lies between and behind both. The sheath rests upon the vertebral column, having interposed the sympathetic nerve and the muscles of the anterior surface of the vertebral column, namely, the longus colli and rectus anticus major. In front of the sheath, at its middle, is the loop formed between the descendens noni nerve and the communicating branch of the cervical plexus, with the filaments given off by the loop. With regard to the surface of the neck, the sheath of the caro- tid is deeply seated in the lower two-thirds of its extent, and superficially in its upper third. It is covered in below by the COMMON CAROTID ARTERY. 163 sterno-mastoid, sterno-hyoid, and sterno-thyroid muscles, and crossed at about its middle by the omo-hyoid. Above, it has in front only the platysma and deep fascia. It is also crossed, both its superficial and deep part, by the thyroid veins. Lying internally to the sheath is the trachea and larynx, with the inferior thyroid artery and recurrent laryngeal nerve, the two latter reaching that situation after having passed behind the sheath. On the left side of the neck, there is in addition the oesophagus. Externally to the sheath is a chain of lymphatic vessels and glands, the concatenated glands of the neck. The special relations of the left common carotid while within the chest are described in Chapter VI. It is crpssed by the left vena innominata, and in its course to the side of the neck rests upon the trachea, oesophagus, and thoracic duct. The common carotid artery gives off no branch in its course. The sheath of the carotid artery may now be carefully opened, and the relative positions of the internal jugular vein and pneumogastric nerve examined. Operations. The common carotid artery may be secured either in the upper or the lower carotid triangle. In the former, the high operation, the artery is comparatively superficial, and the operation proportionately simple. The incision is to be made along the anterior border of the sterno-mastoid, commencing an inch below the angle of the jaw, and carrying it half way down the neck. It should divide the integument, superficial fascia, platysma, and deep fascia. We then expose the sheath of the vessels, upon which lies the descendens noni nerve. Leave this nerve undisturbed, and open the sheath to its inner side, immediately above the omo-hyoid muscle ; then turn the needle around the artery from without inwards, guarding against including the pneumogastric nerve by keeping the point of the instrument close to the cylinder of the artery. The parts to be cut through are the integument, superficial fascia, platysma, superficialis colli nerve, deep fascia, and sheath of the vessels. In the inferior carotid triangle, the low operation is practised. The sterno-mastoid is still the guide for the incision, and the layers to be cut through are precisely the same as in the high operation. The sterno-mastoid is to be drawn aside, and the sheath will be found con- cealed by the sterno-thyroid muscle. This muscle is to be divided, and the sheath opened as in the previous operation. The descendens noni, if it extend so low, lies to the inner side of the sheath. The anterior jugular vein is situated along the inner border of the sterno-mastoid muscle, and should be looked for and avoided. The parts to be cut through are the same as in the previous operation, with the addition of the sterno-thyroid muscle. The arteria innominata is also tied in the lower carotid triangle, on the right side. The incision, three inches in length, should be made ob- liquely across the space between the two sterno-mastoid muscles, imme- diately above the sternum. It should commence over the right sterno- clavicular articulation, and be carried obliquely upwards to the sterno- mastoid muscle of the opposite side, dividing the integument, superficial, and deep fascia. The operator then separates the two sterno-thyroid muscles, and, following the course of the trachea, reaches that artery as 164 THE DISSECTOR. it crosses that tube to the right side. In the injected subject the stu- dent will find this by no means a difficult operation : the artery is much more superficial than might be expected, and the practice of the opera- tion on the subject will not only familiarize him with the natural posi- tion of the artery, but also with the proximity of the arch of the aorta, and the possibility of aneurism of that vessel making its appearance above the sternum. The inferior thyroid veins are very much in the way of this operation, and care must be taken not to wound them. An inferior thyroid artery, from the innominata, is also occasionally met with. The layers to be cut through are simply the integument, and superficial and deep fascia. The INTERNAL JUGULAR VEIN, larger than the common carotid artery, is the great venous trunk by which the blood from the Fig. 49. ANATOMY OF THE NECK. a. The anterior bellies of the digastric muscles; their tendinous pulleys are seen to be attached to the os hyoides, b. c. The mylo-hyoideus muscle, on which is seen the submental branch of the facial artery, d. The hyo-glossus muscle ; the artery above the letter is the facial ; the nerve below it, the hypoglossal ; the dotted lines below the nerve indicate the course of the lingual artery behind the muscle, e. The stylo-glossus mus- cle, f. The styloid process and muscles proceeding therefrom ; the white band above /is the stylo-maxillary ligament. The artery in front of'/ is the external carotid ; that behind it is the posterior auricular ; the large nerve crossing INTERNAL JUGULAR VEIN. 165 these arteries is the facial, g. The bifurcation of the external carotid artery into the temporal and internal maxillary, h. The posterior auricular branch of the facial nerve, and posterior auricular artery, i rests on the middle con- strictor and stylo-pharyngeus muscle ; the latter is crossed by the glosso-pha- ryngeal nerve, which is seen just above i. The large artery in front of i is the external carotid ; the artery behind it the occipital, and the large nerve below it the hypoglossal. It. The mastoid branch of the external carotid. The small nerve seen in the space above this branch is the superior laryngeal ; and the smaller nerve descending behind it, upon the carotid artery, the descendens noni. /. The superior thyroid artery ; just below the letter, the common carotid bifurcates into the external and internal carotid, m. The thyro- hyoidean membrane, on which are seen the superior laryngeal nerve and artery below, and the hyoidean branch of the superior thyroid above the letter. n. The thyro-hyoid muscle, o, o. The sterno -thyroid, p. The thyroid gland. q, q. Omo-hyoid muscle, r, r. The sterno-hyoid muscles, s. The left sterno- mastoid muscle, t. The origin of the right sterno-mastoid muscle, v. The superior obliquus capitis muscle ; the artery meandering over this muscle is the occipital ; the nerve to its right is the spinal accessory, w. The complexus muscle ; the small artery crossing it from the occipital, is the princeps cervicis. x. The splenius capitis. y, y. The levator anguli scapulae muscle, z. The scalenus posticus. 1. The scalenus medius. 2. The scalenus anticus. The two arteries crossing this muscle are the suprascapular (the lower) and trans- viT.-.'ilis colli (the upper) ; the trunk from which they proceed is the thyroid axis, which is also seen giving off the inferior thyroid artery ; the latter, after crossing behind the common carotid artery, 3, enters the lower part of the thy- roid gland, p. 4, 4. The subclavian artery. The large artery between the thyroid axis and common carotid is the vertebral, and the nerves crossing the subclavian in this situation, the pneumogastric (the larger) and a branch of the sympathetic. The artery proceeding from the subclavian below the thyroid axis, is the internal mammary, and the nerve near it, and lying on the scalenus anticus (2), is the phrenic. 5. The brachial plexus of nerves. 6, 7. The in- ternal jugular vein. The portion 6 accompanies the internal carotid artery; the portion 7 the common carotid. The opening just below 6 is the divided trunk of the facial vein ; the slender nerve to the right of 6 is the descendens noni ; the slender nerve to the left, which descends to join the descendens noni, is the communicating branch. The short trunk to the left of 6 is the second cervical nerve; the third and fourth cervical nerves are seen lower down, and the cervical plexus resting on the levator anguli scapulae and scalenus posticus muscle, y, y, z. The little artery to the left of the internal jugular vein, 7, is the cervicalis ascendens branch of the inferior thyroid. 8. The inferior con- strictor muscle ; the figure is placed between the trunk of the superior thyroid artery, and its muscular branch. 9. The oesophagus; the artery immediately above the figure is the inferior thyroid. 10. The trapezius muscle. 11. The deltoid. 12. The clavicular portion of the pectoralis major. 13. Its sternal portion. 14. The subclavius muscle. 15. The axillary artery, giving off the thoracico-acromialis artery. sinuses of the cranium reaches the heart. It commences at the jugular foramen in the base of the skull, and, passing down the front of the vertebral column, becomes inclosed in the sheath of the common carotid artery lying to the outer side and parallel with that vessel. At the root of the neck, on the right side, the vein diverges from the artery, and a triangular space is formed between them, through which the pneumogastric nerve may be seen ; on the left side no such separation exists. The internal jugular vein unites with the subclavian vein to form the vena innominata. 166 THE DISSECTOR. The branches which the internal jugular vein receives, while situated in the carotid sheath, are the superior and middle thy- roid veins. Lymphatic Glands and Vessels. The deep lymphatic glands and vessels of the neck are situated along the course of the in- ternal jugular vein, chiefly on its outer side, while a few are found by the side of the pharynx, esophagus, and trachea. The lymphatic vessels terminate, on the right side, in the ductus lymphaticus dexter, and on the left in the thoracic duct. The ductus lymphaticus dexter is a short trunk formed by the union of the lymphatic vessels of the right side of the head, right upper extremity, and right side of the thorax. It is situated at the root of the neck on the right side, and terminates at the point of junction of the internal jugular with the subclavian vein, on the posterior aspect of the vessel. At its termination it is provided with a pair of semilunar valves. The thoracic duct ascends into the left side of the root of the neck, behind the first portion of the subclavian artery, as high as the last cervical vertebra. It then curves downwards and forwards in front of the scalenus anticus and phrenic nerve, and terminates by opening into the posterior aspect of the junc- tion of the internal jugular and subclavian vein. In the root of the neck it receives the lymphatics of the left side of the head and neck, left upper extremity, and left half of the thorax. At its opening into the vein, the thoracic duct is provided with a pair of semilunar valves. The student should now proceed to dissect the external carotid artery and its branches, taking care not to divide the nerves which cross it in its course. The EXTERNAL CAROTID ARTERY ascends nearly perpendicularly from a point opposite the upper border of the thyroid cartilage to the space between the neck of the lower jaw and meatus audi- torius, where it divides into two terminal branches, the temporal and internal maxillary. In the beginning of its course it is superficial, being covered in only by the platysma and deep fascia, and crossed by the hypoglossal nerve; a little higher it is crossed by the digas- tricus and stylo-hyoid muscle; and higher still it enters the sub- stance of the parotid gland, and has in front of it the facial nerve and temporo-maxillary vein. Crossing behind it, and separating it from the internal carotid, is the stylo-pharyngeus and stylo-glossus muscle, the glosso-pharyngeal nerve, and the deep part of the parotid gland. The internal carotid artery lies at first to the outer side of the external carotid, but soon gets behind it. The branches of the external carotid (ten in number) are divided LINGUAL ARTERY. 167 into three sets anterior, posterior, and ascending. They are as follows : Anterior. Posterior. Superior thyroid, Sterno-mastoid, Lingual, Occipital, Facial. Posterior auricular. Ascending. Ascending pharyngeal, Parotidean, Temporal, Internal maxillary. 1. The SUPERIOR THYROID ARTERY, the first of the branches of the external carotid, arises from that trunk just below the great cornu of the os hyoides, and curves downwards to the thyroid gland. It is distributed by several large branches to the anterior part of the gland, and anastomoses with its fellow of the opposite side, and with the inferior thyroid arteries. In its course it passes beneath the omo-hyoid, sterno-thyroid, and sterno-hyoid muscles. The branches of the superior thyroid artery are the Hyoid, Inferior laryngeal, Superior laryngeal, Muscular. The hyoid branch passes forwards beneath the thyro-hyoideus, and is distributed to the depressor muscles of the os hyoides near their insertion. The superior laryngeal pierces the thyro-hyoidean membrane, in company with the superior laryngeal nerve, and supplies the mucous membrane and muscles of the larynx, sending a branch upwards to the epiglottis. The inferior laryngeal (crico-thyroid) is a small branch which crosses the crico-thyroidean membrane near the lower border of the thyroid cartilage. It sends branches through that membrane to supply the mucous lining of the larynx, and inosculates with its fellow of the opposite side. The muscular branches are distributed to the depressor muscles of the os hyoides and larynx. One of these branches crosses the sheath of the common carotid to the under surface of the sterno- mastoid muscle. The LINGUAL ARTERY arises just above the superior thyroid, and, bending upwards over the gibt cornu of the os hyoides, runs forward nearly parallel with that bone ; it then ascends to the under surface of the tongue, and passes onwards, in a ser- pentine course, to the tip of the organ, under the name of ranine artery. The first portion of the artery is superficial, although crossed 168 THE DISSECTOR. by the digastricus and stylo-hyoid muscle, and by the hypoglossal nerve. In its horizontal and oblique course it lies beneath the Fig. 50. THE ANATOMY OF THE SIDE OF THE TONGUE, WITH THE RELATIONS OF THE VESSELS AND NEKVES. 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 symphy- sis. 4. The genio-hyo-glossus muscle. 5. The genio-hyoideus muscle. 6. The cut edge of the mylo-hyoideus. 7. The com- mon carotid artery, dividing into the external and internal carotid. 8. The trunk of the superior 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 is 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 ar- tery ; they are from below, upwards, the mastoid, occipital, and posterior auri- cular. 16. The trunk of the ascending pharyngeal artery. 17. The trunk of the transverse 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. hyo-glossus, being at first placed between that muscle and the middle constrictor, and then between it and the genio-hyo- glossus. In its course along the under surface of the tongue, it lies between the lingualis and mucous membrane. The hyo- glossus muscle separates it from the hypoglossal nerve. Operation. The lingual artery is tied in the upper angle of the supe- rior carotid triangle. The external incision should be made parallel with the lower border of the posterior belly of the digastricus muscle. It should cut through the integument, superficial fascia, platysma, and deep fascia. The hyo-glossus will then form the floor of the wound, upon which rests the lingual nerve ; this must be carefully avoided by making the incision through the musclebelow the nerve. The artery will then be exposed in the second part oyits course. The structures to be cut through are the integument, superficial fascia, platysma, superjicialis colli nerve, deep fascia, and hyo-glossus muscle. The branches of the lingual artery are the Hyoid, Dorsalis linguae, Sublingual. FACIAL ARTERY. 169 The hyoid branch runs along the upper border of the os hyoides, and is distributed to the elevator muscles of the os hyoides, near their origin, inosculating with its fellow of the op- posite side. The dorsalis linguae ascends along the posterior border of the hyo-glossus muscle, to the dorsum of the tongue, and is distri- buted to the tongue, the fauces, and epiglottis, anastomosing with its fellow of the opposite side. The sublingual branch runs forwards on the genio-hyo-glossus muscle, and is distributed to the sublingual gland and to the muscles of the tongue. It is situated between the mylo-hyoideus and genio-hyo-glossus, generally accompanies Wharton's duct for a part of its course, and sends a branch to the fraenum linguae. It is the latter branch which affords the considerable hemorrhage which sometimes follows the operation of snipping the fraenum in children. The ranine artery (the continuation of the lingual beyond the origin of the sublingual), terminates at the tip of the tongue by inosculating with its fellow of the opposite side. The FACIAL ARTERY arises immediately above the lingual and a little above the great cornu of the os hyoides, and passes for- wards to the submaxillary gland, in which it lies embedded. It then curves around the body of the lower jaw, close to the an- terior 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. In its course to the lower jaw it is crossed by the digastricus and stylo-hyoid muscle, and then becomes lodged in the submax- illary gland, wherein it makes a considerable bend. Its course and relations on the face have been already described (p. 127). Operation. The facial artery is usually tied while resting on the body of the lower jaw, close to the anterior inferior angle of the masseter muscle. It is here superficial, and may be felt and seen pulsating im- mediately beneath the integument. It is covered by the integument, superficial fascia, and platysma. If it were necessary to tie the artery below the jaw, the upper border of the posterior belly of the digastric muscle would be the guide to the vessel. The ligature might then be passed around it just before it entered the submaxillary gland, whilst resting against the stylo-maxillary ligament. The structures to be cut through are the integument, superficial fascia, platysma, cervical branches of the facial nerve, and deep fascia. The branches of the facial artery below the lower jaw are, the Inferior palatine, Submaxillary, Tonsillar, Submeutal. The inferior palatine branch ascends between the stylo-glossus and stylo-pharyng'eus muscle, to be distributed to the tonsil and 15 170 THE DISSECTOR. soft palate, and anastomoses with the posterior palatine branch of the internal maxillary artery. The tonsillar branch ascends upon the side of the pharynx, and pierces the superior constrictor muscle, to be distributed to the tonsil. The submaxillary (glandular) are four or five branches which supply the submaxillary gland. T he submental branch runs forward upon the mylo-hyoid muscle, under cover of the body of the lower jaw, and anastomoses with branches of the sublingual and inferior dental artery. The STERNO-MASTOID ARTERY turns downwards from its origin, to be distributed to the sterno-mastoid muscle and lymphatic glands of the neck. Sometimes there are two branches. The OCCIPITAL ARTERY, smaller than the anterior branches, passes backwards behind the parotid gland and beneath the pos- terior belly of the digastricus, trachelo-mastoid, and sterno-mas- toid muscle, to the occipital groove in the mastoid portion of the temporal bone. It then ascends between the splenius and cornplexus, pierces the trapezius, and is distributed to the back of the head (p. 116). Opposite the angle of the jaw, the hypo- glossal nerve curves forward around the artery. Besides muscular branches to the muscles near which it passes, the occipital artery gives off but one named artery in the front of the neck ; namely, the inferior meningeal, which ascends by the side of the internal jugular vein, and passes through the foramen lacerum posterius to be distributed to the dura mater. The POSTERIOR AURICULAR ARTERY arises from the external carotid, above the level of the digastric and stylo-hyoid muscles, and ascends by the side of the styloid process, and behind the parotid gland, to the back part of the concha. It is distributed by two branches to the external ear and side of the head, anasto- mosing with the occipital and temporal arteries ; some of its branches pass through fissures in the fibro-cartilage, to reach the anterior surface of the pinna. The anterior auricular arteries are branches of the temporal. The posterior auricular sends a branch to the digastricus mus- cle, and several to the parotid gland ; it then gives off the stylo- mastoid, which enters the stylo-mastoid foramen, to be distributed to the aquaeductus Fallopii, labyrinth, mastoid cells, and tympa- num. The ASCENDING PHARYNGEAL ARTERY, the smallest of the branches of the external carotid, arises from that trunk near its bifurcation, and ascends between the internal carotid and the side of the pharynx to the base of the skull, where it divides into two branches meningeal, which enters the foramen lacerum pos- TEMPORAL ARTERY. 171 terms, to be distributed to the dura mater, and pharyngeal. It supplies the pharynx, tonsils, soft palate, and Eustachian tube. The ' PAROTIDEAN ARTERIES are four or five large branches which are given off from the external carotid whilst that vessel is situated in the parotid gland. They are distributed to the structure of the gland, their terminal branches reaching the in- tegument of the side of the face. The TEMPORAL ARTERY is one of the two terminal branches of the external carotid. It ascends over the root of the zygoma, and, at about an inch and a half above the zygomatic arch, divides into an anterior and a posterior temporal branch. The anterior temporal is distributed over the front of the temple and arch of the skull, and anastomoses with the opposite anterior temporal and with the supraorbital and frontal artery. The posterior temporal curves upwards and backwards, and inoscu- lates with its fellow of the opposite side, with the posterior auricular and occipital artery. The trunk of the temporal artery is covered by the parotid gland and by the attrahens aureni muscle, and rests on the tem- poral fascia. The branches of the temporal artery are : some small offsets to the parotid gland, articulation of the lower jaw, external ear and orbit ; and two of larger size the transverse facial and middle temporal. The branches to the external ear (anterior auricular) are two in number, and are distributed to the anterior portion of the pinna. The branch to the orbit (orbitar) passes forward, immediately above the zygoma, between the two layers of the temporal fascia, and inosculates beneath the orbicularis with a branch of the lachrymal artery. The transversalis faciei arises from the temporal immediately below the zygoma, and runs transversely across the face, resting on the masseter muscle, and lying parallel with and a little above Stenon's duct. It anastomoses with the facial and infra-orbital artery. The middle temporal branch passes through an opening in the temporal fascia immediately above the zygoma, and supplies the temporal muscle, inosculating with the deep temporal arteries. The examination of the next artery, the internal maxillary, requires the preparation already described (page 124) for the study of the pterygoid muscles. The temporal fascia should be divided along the upper border of thf zygoma ; the zygoma cut through with the saw at both ends, and turned down with the masseter muscle ; noting in this part of the dis- section the masseteric artery and nerve, which cross the sigmoid notch of THE DISSECTOR. the lower jaw, to enter the under surface of that muscle. The coronoid process of the lower jaw should then be sawn through, and drawn upwards with the temporal muscle. Next the neck of the lower jaw should be cut across ; and then the ramus, down to the dental foramen. The fat and cellular tissue may then be cleared away, carefully preserving any branches of nerves, and the internal maxillary artery and such of its branches as are visible at this stage of the dissection may be followed in their course. The INTERNAL MAXILLARY ARTERY, one of the terminal branches of the external carotid, commences in the substance of the parotid gland opposite the meatus auditorius. It passes forwards behind the neck of the lower jaw, curves around the lower border of the external pterygoid muscle, and ascends obliquely forwards upon the outer aspect of that muscle to the space between its two heads. It then passes horizontally inwards between the two heads of the external pterygoid, and enters the spheno-maxillary fossa, where it divides into its terminal branches. The artery admits of a natural division into three parts ; first, that situated behind the neck of the lower jaw, maxillary portion ; second, that in relation with the external pterygoid muscle, pterygoid portion; third, that situated in the spheno-maxillary fossa, spheno-maxillary portion. The maxillary portion is situated between the neck of the jaw and the internal lateral ligament and inferior dental nerve, and lies parallel with the auriculo-temporal nerve. The pterygoid Fig. 51. THE INTERNAL MAXILLARY AR- TERY, 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 maxil- lary, 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 ptery go- maxilla ry portion. The branches of the maxillary portion are, 7. A tym- panic branch. 8. The arteria me- ningea media. 9. The arteria me- ningeaparva. 10. The inferior dental artery. The branches of the second portion are wholly muscular, the as- cending 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 superior 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 re- markable bend which the third portion of the artery makes as it turns inwards to enter the pterygo-maxillary fossa. INTERNAL MAXILLARY ARTERY. 173 portion lies between the external pterygoid and the masseter and temporal muscle, and is crossed by the masseteric nerve. Having thus far examined the internal maxillary artery and its rela- tions, the head of the lower jaw should be dislocated and drawn forwards with the external pterygoid muscle, in order to be able to dissect the branches of the artery which lie behind. Before disturbing the muscle, however, the student should observe the nerves and vessels which are in relation with it. At its upper border he will find the temporal nerve, the deep temporal arteries, and the masseteric nerve. Piercing the muscle at its anterior part is the buccal nerve. Lying against the su- perior maxillary bone, just in front of its attachment, is the superior dental nerve, accompanied by its artery. Issuing from below the muscle are two large nerves, the gustatory and inferior dental ; and, passing backwards behind its condyloid attachment, is the auriculo-temporal nerve. When the external pterygoid muscle is drawn forwards, these nerves may be traced to their origin from the inferior maxillary nerve ; they should be cleared of fat and cellular tissue, as well as the arterial branches of the internal maxillary. Numerous veins, part of a plexus, will be found between the two pterygoid muscles ; these must be removed. The auriculo- temporal nerve may then be followed in its course backward, and a small nerve observed, the chorda tympani, which joins the gustatory nerve at an acute angle on the internal pterygoid muscle. The branches of the internal maxillary artery, grouped into three sets in correspondence with the divisions of the trunk of the artery, are as follows : Maxillary portion. Pterygoid portion. Tympanic, Deep temporal, Inferior dental, Pterygoid, Arteria meningea media, Masseteric, Artcria meningea parva. Buccal. Pterygo-maxillary portion. Superior dental, Infra-orbital, Ptery go-palati ne, Spheno-palatine, Descending or posterior palatine, Vidian. The tympanic branch passes into the tympanum through the fissura Glaseri, and is distributed to the laxator tyrapaui and membrana tympani ; on the latter, it inosculates with the stylo- mast old artery. The inferior dental descends to the dental foramen, and enters the canal of the lower jaw in company with the dental nerve. Opposite the bicuspid teeth, it divides into two branches, one of which is continued onwards within the bone as far as the sym- physis to supply the incisor teeth, while the other escapes with 15* 174 THE DISSECTOR. the nerve at the mental foramen, and anastomoses with the infe- rior labial and submental branch of the facial. It supplies the teeth of the lower jaw, sending small branches along the canals in their roots ; at the inferior dental foramen, it gives off a mylo- hyoid branch, which accompanies the mylo-hyoidean nerve. The arteria meningea media ascends behind the temporo- maxillary articulation to the foramen spinosum in the spinous process of the sphenoid bone, and, entering the cranium, divides into an anterior and a posterior branch, which are distributed to the dura mater and bone. The meningea parva is a small branch which ascends to the foramen ovale, and passes into the skull, to be distributed to the Casserian ganglion and dura mater ; it gives off a twig to the nasal fossae and soft palate. The muscular branches are distributed, as their names imply, to the five muscles of the maxillary region. The temporal branches (ternporales profundae) are two in number ; they inosculate with branches of the superficial temporal. The pterygoid branches are distributed to both the muscles of that name. The masseteric artery passes outwards, behind the tendon of the temporal mus- cle, and over the sigmoid notch, to the masseteric muscle. The buccal branch, arising over the anterior part of the pterygoid muscle, passes downwards with the buccal nerve to the buccinator muscle ; it inosculates with the facial and transverse facial artery. The superior dental artery (alveolar, superior maxillary) is given off from the internal maxillary just as that vessel is about to make its turn inwards to reach the spheno-maxillary fossa ; it descends upon the tuberosity of the superior maxillary bone, and sends its branches through several small foramina to supply the posterior teeth of the upper jaw and the antrum. The termi- nal branches are continued forwards upon the alveolar process, to be distributed to the gums and sockets of the teeth. To see the remaining brandies of the internal maxillary artery, the outer wall of the orbit must be divided with the saw to the level of the cheek, and removed. The saw should then be carried through the great ala of the sphenoid bone, the dura mater having been stripped from its surface, to the fora- men rotundum ; another section must be made through the squamous portion of the temporal bone to the foramen spinosum, and the extremities of the sections connected by means of the chisel. The piece of bone included by these incisions is then to be broken outwards, and any pieces of bone remqved which may interfere with the view of the inferior and superior maxillary nerves, passing through their respective openings and spheno-maxillary fossa. For the present, the student must be satisfied with tracing the branches as far as the openings through which they pass, and not attempt to follow them in their course ; he should also disturb the neighboring parts as little as possible, in order to aypid injury to Meckel's ganglion and its branches. VEINS OP THE EXTERNAL CAROTID. 175 The infra-orbital artery would appear from its size to be the proper continuation of the internal maxillary. It runs along the infra-orbital canal with the superior maxillary nerve, sending branches upwards into the orbit; and downwards, through canals in the bone, to supply the mucous membrane of the antrum, and the teeth of the upper jaw, and emerging on the face at the infra- orbital foramen. A branch sent to the incisor teeth is the ante- rior dental; and on the face the infra-orbital inosculates with the facial and transverse facial artery. The ptery go-palatine is a small branch which passes backwards through the pterygo-palatine canal, and supplies the upper part of the pharynx, Eustachian tube, and sphenoidal cells. The spheno-palatine, or nasal, enters the superior meatus of the nose through the spheno-palatine foramen in company with the nasal branches of Meckel's ganglion, and divides into two or three branches. One branch (artery of the septum), is distributed to the mucous membrane of the septum, and inosculates in the anterior palatine canal with a terminal branch of the descending palatine. Another branch supplies the mucous membrane of the lateral wall of the nares, antrum, sphenoid and ethmoid cells. The superior or descending palatine artery (posterior palatine), descends along the posterior palatine canal, in company with the palatine branches of Meckel's ganglion, to the posterior pala- tine foramen. It then bends forward, lying in a groove upon the bone, and is distributed to the palate. While in the poste- rior palatine canal it sends a branch backwards, through the small posterior palatine foramen, to supply the soft palate, and anteriorly it distributes a branch to the anterior palatine canal, which reaches the nares and inosculates with the branches of the spheno-palatine artery. The Vidian branch passes backwards along the pterygoid canal, and is distributed to the sheath of the Vidian nerve, and to the Eustachian tube. VEINS OF THE EXTERNAL CAROTID. The veins of the branches of the external carotid artery follow the direction of their re- spective vessels. The internal maxillary vein commences by the union of veins returning the blood from the zygomatic and ptery- goid fossa, where they are so numerous and communicate so freely with each other as to constitute a pterygoid plexus. Be- hind the neck of the lower jaw the internal maxillary vein unites with the temporal vein, and the two together constitute the tem- poro-maxillary vein. The temporo-maxillary vein descends through the substance of the parotid gland, receiving in its course the transverse facial, anterior auricular, and parotid veins. At the lower part of the gland it is joined by the posterior auri- 116 THE DISSECTOR. cular vein, and becomes the external jugular. The external jugular vein communicates with the internal jugular in the pa- rotid gland, and after receiving a cutaneous branch from the occipital region takes its course down the neck, across the sterno- mastoid muscle, to the subclavian vein. The facial, the occipital, the lingual, and superior thyroid veins open into the internal jugular vein. Fifth Pair of Nerves. The preparation already made for the examination of the internal maxillary artery and its branches, is that which is best suited for the display of the two maxillary divisions of the fifth nerve, superior and inferior. Within the cranium, the dura mater should be stripped off the bones of the middle fossa, so as to expose the Casserian ganglion, and the ganglion may be carefully raised from its bed in order to see the an- terior root of the nerve, in its course beneath the ganglion to join the inferior maxillary nerve. In the present dissection it will be more con- venient to study the inferior maxillary nerve before the superior. The FIFTH NERVE (trifacial ; trigeminus), is the great sensitive nerve of the head and face, and the largest of the cranial nerves. It is a flattened cord, composed of a number of filaments held together by a sheath of the arachnoid membrane. It passes through an oval opening in the dura mater, near the extremity of the petrous portion of the temporal bone, resting in a groove upon that bone, and spreads out into a large flattened semilunar ganglion the Casserian. The Casserian ganglion occupies a con- siderable extent of space immediately in front of the extremity of the petrous bone, and upon the base of the great wing of the sphenoid, and divides into three branches ophthalmic, superior maxillary, and inferior maxillary. The ophthalmic nerve, the smallest of the three, is about three quarters of an inch in length ; it is situated in the outer wall of the cavernous sinus, externally to the other nerves in the sinus, and divides into three branches -frontal, lachrymal, and nasal, which enter the orbit through the sphenoidal fissure (page 134). The superior maxillary nerve passes forwards to the foramen rotundum, through which it escapes from the cranium. The INFERIOR MAXILLARY NERVE, the largest of the three, proceeds from the posterior angle of the Casserian ganglion, and passes out of the cranium through the foramen ovale. It then divides into two portions external and internal. The EXTERNAL DIVISION, into which nearly the whole of the motor root may be traced, separates into five or six branches for the supply of the muscles of the temporo-maxillary region. The masseteric branch, passing over the external pterygoid muscle and behind the tendon of the temporal, crosses the sig- EXTERNAL DIVISION. 177 moid notch with the masseteric artery, and is distributed to the masseter muscle. The deep temporal branches, two in number, anterior and Fig. 52. THE BRANCHES OP THE FIFTH NERVE. 1. The Casserian ganglion. 2. The ophthalmic nerve. 3. The frontal nerve. 4. Its supra-trochlear branch. 5. The IJM hrvinal nerve. 6. The nasal nerve. 7. Its branch of communication with the ciliary ganglion. 8. The passage of the nerve through the anterior ethmoi- dal foramen. 9. The infra-trochlear nerve. 10. The superior maxillary nerve. 11. Its orbital branch. 12. The branches of communication with Meckel's gan- glion. 13. The posterior dental branches. 14. Middle dental branches. 15. The anterior dental branches. 16. The infra-orbital branches. 17. The infe- rior maxillary nerve. 18. Its external or muscular division. 19. The internal division of the inferior maxillary nerve. The arrow marks the separation of these two divisions of the nerve by the external pterygoid muscle. 20. The gustatory nerve. 21. The branch of communication with the submaxillary ganglion. 22. The inferior dental nerve, arising by two roots. 23. Its mylb- hyoidean branch. 24. The auricular nerve. 25. Its branch of communication with the facial nerve. posterior, pass between the external pterygoid muscle and the side of the cranium, to be distributed to the temporal muscle. The buccal branch is of large size, and pierces the lower fibres of the external pterygoid muscle at its anterior part. It sends a branch to the external pterygoid muscle, and is then distributed to the buccinator, where it communicates with the facial nerve. The internal pterygoid branch is a long and slender nerve, which passes inwards to the internal pterygoid muscle, and gives filaments in its course to the tensor palati and tensor tympani. ITS THE DISSECTOR. This nerve is remarkable for its connection with the otic gan- glion, to which it is closely attached. The external pterygoid branch is commonly derived from the buccal nerve. The examination of some of the preceding nerves will have required the drawing aside of the external pterygoid, and even, as in the case of the buccal nerve, the division of some of its fibres. The muscle must now be entirely removed, in order to see the branches of the internal division of the inferior maxillary nerve, which lie behind it. The INTERNAL DIVISION splits into three branches auriculo- temporal, inferior dental, and gustatory. The AURICULO-TEMPORAL NERVE passes backwards behind the articulation of the lower jaw, and enters the parotid gland, where it divides into two temporal branches. It generally consists of two cords, between which the arteria meningea media takes its course to the foramen spinosum. Its branches are, a small branch to the temporo-maxillary articulation ; two or three small branches to the parotid gland ; two branches to the meatus auris, which enter the canal between the fibro-cartilage and the processus auditorius ; "two auricular branches to the pinna ; a communicating branch to the otic gan- glion ; two communicating branches to the facial nerve ; and the temporal branches. The auricular branches, superior and inferior, are distributed to the pinna above and below the meatus. The inferior branch communicates with the sympathetic. The branches which communicate with the facial nerve em- brace the external carotid artery in their course. The temporal branches are anterior and posterior. The ante- rior accompanies the temporal artery, and supplies the integu- ment of the temporal region, communicating with the branches of the facial and supraorbital nerve; the latter is distributed to the upper part of the pinna, the attrahens aurem muscle, and the integument of the posterior part of the temple. The INFERIOR DENTAL NERVE, the largest of the three branches of the internal division of the inferior maxillary, passes down- wards with the inferior dental artery, at first between the two pterygoid muscles, and then between the internal lateral liga- ment and the ramus of the lower jaw, to the dental foramen. It then runs along the canal in the inferior maxillary bone, distri- buting branches (inferior maxillary plexus) to the teeth arid gums, and divides into two terminal branches incisive and mental. The branches of the inferior dental nerve, besides those given to the teeth, are the mylo-hyoidean and the two terminal branches. GUSTATORY NERVE. 179 The mylo-hyoidean branch quits the nerve just as it is about to enter the dental foramen. This branch pierces the insertion of the internal lateral ligament, and descends along a groove in the bone to the inferior surface of the mylo-hyoid muscle, to which, and to the anterior belly of the digastricus, it is dis- tributed. The incisive branch is continued forwards to the symphysis of the jaw, to supply the incisor teeth. The mental or labial branch emerges from the jaw at the mental foramen, beneath the depressor anguli oris, and divides into branches which supply the muscles and integument of the lower lip and chin, and communicate with the facial nerve. The mylo-hyoidean nerve is seen in the dissection of the mylo-hyoideus muscle, when the submaxillary region is turned upwards. It is, how- ever, better seen when a section is made through the body of the lower jaw a little to the side of the symphysis, and the jaw is drawn aside, after the detachment of the mylo-hyoideus muscle and buccinator, together with the pterygo-maxillary ligament and that portion of the superior constrictor which is connected with the lower jaw. If this pre- paration is not made for the mylo-hyoidean nerve, it is necessary in tracing the course of the following nerve. The GUSTATORY NERVE descends between the two pterygoid muscles, and makes a gentle curve forwards to the side of the tongue, along which it takes its course to the tip. On the side of the tongue it is flattened, and gives off numerous branches, which are distributed to the mucous membrane and papillae. In the upper part of its course the gustatory nerve lies be- tween the external pterygoid muscle and the pharynx, next between the two pterygoid muscles, then between the internal pterygoid and ramus of the jaw, and between the stylo-glossus muscle and the submaxillary gland ; lastly, it runs along the side of the tongue, resting against the hyo-glossus muscle, and crossing the duct of the submaxillary gland, and is covered in by the mylo-hyoideus and mucous membrane. The gustatory nerve, while between the pterygoid muscles, often receives a communicating branch from the inferior dental ; lower down it is joined at an acute angle by the chorda tympani, a small nerve which, arising from the facial in the aqueductus Fallopii, crosses the tympanum, and escapes from that cavity through the fissura Glaseri. Having joined the gustatory nerve, the chorda tympani is continued downwards in its sheath to the submaxillary ganglion. One or two branches are given by the gustatory nerve to the submaxillary ganglion. On the hyo-glossus muscle several branches of communication join with branches of the hypoglossal nerve, and others are sent to the sublingual gland and Wharton's duct. 180 THE DISSECTOR. The SUBMAXILLARY GANGLION, of small size and reddish color, is situated on the submaxillary gland, in close relation with the gustatory nerve, and near the posterior border of the mylo- hyoideus muscle. Its branches of distribution, six or eight in number, divide into many filaments, which supply the side of the tongue, the submaxillary and sublingual glands, and Wharton's duct. Its branches of communication are two or three from and to the gustatory nerve; one from the chorda tympani ; two or three which form a plexus with branches of the hypoglossal nerve ; and one or two filaments which pass to the facial artery, and com- municate with the nervi molles from the cervical portion of the sympathetic. If the student cut across the inferior maxillary nerve at its origin from the Casserian ganglion, and after breaking away the bone at the outer side of the foramen ovale draw the nerve outwards, he may find lying against the nerve, close to its exit from the foramen ovale, a small oval- shaped body the otic ganglion. Another guide to this small ganglion is the internal pterygoid nerve, upon which the ganglion is placed. Unless the subject be fresh, the dissector may fail to discover the gan- glion, which, to make it out clearly with its branches, requires a fresh subject and a special dissection. If the latter can be obtained, the ganglion is best found by dissecting from within ; taking the Eustachian tube, against which it lies, and the internal pterygoid nerve, as guides to its position. The OTIC GANGLION (Arnold's) is a small oval-shaped and flat- tened ganglion, situated upon the internal pterygoid nerve, and appearing like a swelling of that nerve. It lies against the inner surface of the inferior maxillary nerve, close to the foraman ovale, and is in relation internally with the Eustachian tube and tensor palati muscle, and behind with the arteria meningea media. The branches of the otic ganglion are seven in number ; two of distribution, and five of communication. The branches of distribution are, a small filament to the tensor tympani muscle, and one or two to the tensor palati muscle. The branches of communication are, one or two filaments from the inferior maxillary nerve (short root) ; one or two filaments from the auriculo-temporal nerve ; filaments from the nervi molles of the arteria meningea media and the nervus petrosus superjicialis minor (long root). The latter nerve ascends from the ganglion to a small canal situated between the foramen ovale and foramen spinosum, and passes backwards on the petrous bone to the hiatus Fallopii, where it divides into two filaments. One of these fila- ments enters the hiatus and joins the intumescentia gangliformis of the facial ; the other passes to a minute foramen nearer the base of the petrous bone, and enters the tympanum, where it communi- cates with a branch of Jacobson's nerve. SUPERIOR MAXILLARY NERVE. 181 The SUPERIOR MAXILLARY NERVE, issuing from the middle of the Casserian ganglion, passes through the foramen rotundum, then crosses the spheno-maxillary fossa, and enters the canal in Fig. 53. THE OTIC GANGLION SEEN FROM THE INNER SIDE. a. Internal pterygoid muscle. b. Carotid artery with the sympathetic. c. Mastoid process, d. Membrane of tympanum. e. Bones of tympanum. 1. Casserian ganglion. 2. First division of fifth. 3. Second division. 4. Third division. 5. Branch to tensor palati. 6. Small superficial petrosal nerve. 7. Chorda tympani. The nerve of the internal ptery- goid muscle is seen on the muscle. the floor of the orbit, along which it runs to the infra-orbital foramen. Emerging on the face, beneath the levator labii supe- rioris muscle, it divides into a number of branches, which form a plexus with the facial nerve. The branches of the superior maxillary nerve are divisible into three groups: Those which are given off in the spheno- maxillary fossa ; those in the infra-orbital canal ; and those on the face. They may be thus arranged : ( Orbital, or temporo-malar, Spheno-maxillary fossa, < Spheno-palatine, ( Posterior dental. ? Middle dental, (Anterior dental. ( Muscular, (Cutaneous. The orbital or temporo-malar branch enters the orbit through the spheno-maxillary fissure, and divides into two branches temporal and malar : the temporal branch ascends along the outer wall of the orbit, and after receiving a branch from the lachrymal nerve, passes through a canal in the malar bone, and enters the temporal fossa ; it then pierces the temporal muscle and fascia, and is distributed to the integument of the temple and side of the forehead, communicating with the facial and anterior temporal nerve. In the temporal fossa it communicates 16 Infra-orbital canal, On the face, 182 THE DISSECTOR. with the deep temporal nerves. The malar, or inferior, branch (subcutaneous malse) takes its course along the lower angle of the outer wall of the orbit, and emerges upon the cheek through an opening in the malar bone, passing between the fibres of the orbicularis palpebrarum muscle. It communicates with branches of the infra-orbital ajnd facial nerve. The spheno-palatine branches, two in number, pass downwards to the spheno-palatine, or Meckel's ganglion. The posterior dental branches, two in number, pass down- wards upon the tuberosity of the superior maxillary bone, where one enters a canal in the bone and is distributed to the molar teeth and lining membrane of the antrum, and communicates with the anterior dental nerve; while the other, lying externally to the bone, is distributed to the gums and buccinator muscle. The middle and anterior dental branches descend to the corre- sponding teeth and gums; the former beneath the lining mem- brane of the antrum, the latter through distinct canals in the walls of the bone. Previously to their distribution, the dental nerves form a plexus (superior maxillary plexus) in the outer wall of the superior maxillary bone, immediately above the alveo- lus. From this plexus the filaments are given off which supply the pulps of the teeth, gums, mucous membrane of the floor of the nares and the palate. The muscular and cutaneous branches are the terminating fila- ments of the nerve ; they supply the muscles, integument, and mucous membrane of the lower eyelid, cheek, nose, arid lip, and form a plexus by their communications with the facial nerve. The student may now proceed to examine the small ganglion con- nected with the superior maxillary nerve, and situated in the spheno- maxillary fossa. To ascertain the precise position of the ganglion, and the direction of its branches, he should refer to the skull, and make such observations with regard to the removal of parts of the bones as will enable him to obtain a good view of the contents of the cavity. The branches proceeding downwards from the superior maxillary nerve are the proper guide to the ganglion ; the nasal branches, which pass into the nose through the spheno-palatine foramen, can only be followed on a section of the skull, and must be left for a later period of the dis- section : the same remark applies to the palatine nerves ; but the Vidian may be traced backwards through the pterygoid canal, by cut- ting away with care the root of the pterygoid process, and may then be followed to the petrous portion of the temporal bone, where it joins the facial nerve. The SPHENO-PALATINE, or MECKEL'S GANGLION is situated in the spheno-maxillary fossa, at a short distance below the supe- rior maxillary nerve, with which it is connected by the two spheno-palatine nerves. It is of small size, triangular in shape, of a reddish-gray color, and is placed on the posterior part of the spheno-palatine nerves, which it only partially involves. SPHENO-PALATINE GANGLION. 183 Its branches are divisible into four groups, ascending, descend- ing, internal, and posterior. The ascending branches are three or four small filaments which are distributed to the periosteum of the orbit. The descending branches are the three palatine nerves ante- rior, middle, and posterior. The anterior or large palatine nerve descends from the ganglion through the posterior palatine canal, and emerges at the poste- rior palatine foramen. It then passes forwards in the substance of the hard palate to which it is distributed, and communicates with the naso-palatine nerve. While in the posterior palatine canal, this nerve gives off several branches (inferior nasal), which enter the nose through openings in the palate bone, and are distributed to the middle and inferior meatus, the inferior spongy bone, and the antrum. The middle or external palatine nerve descends, externally to the preceding, to the posterior palatine foramen, and distributes branches to the tonsil, soft palate, and uvula. The posterior or small palatine nerve passes down through a separate canal, and emerges through a separate opening behind the posterior palatine foramen. It is distributed to the hard palate and gums, near its point of exit, as also to the tonsil, soft palate, and uvula. The internal branches are the superior nasal and the naso- palatine. The superior nasal, four or five in number, enter the nasal fossa through the spheno-palatine foramen, and are distributed to the mucous membrane of the superior meatus and superior and middle spongy bones. The naso-palatine nerve enters the nasal fossa with the nasal nerves, and crosses the roof of the nares to reach the septum, to which it gives filaments. It then curves downwards and for- wards to the naso-palatine canal, and passes through that canal to the palate, to which and to the papilla behind the incisor teeth it is distributed. This nerve was described by Cloquet as uniting with its fellow in the anterior palatine canal, and consti- tuting the naso-palatine ganglion. The existence of this gan- glion is disputed. The posterior branches are the Yidian or pterygoid nerve and the pharjngeal. The Vidian nerve passes directly backwards from the spheno- palatine ganglion, through the pterygoid or Yidian canal, to the foramen lacerum basis cranii, where it divides into two branches, the carotid and petrosal. The carotid branch (n. petrosus profundiis) crosses the foramen lacerum, surrounded by the cartilaginous substance which closes that opening, and enters 184 THE DISSECTOR. the carotid canal to join the carotid plexus. Thepetrosal branch (nervus petrosus superficialis major) enters the cranium through the foramen lacerum basis cranii, piercing the cartilaginous sub- Fig. 54. THE CRANIAL GAN- GLIA OF THE SYMPA- THETIC NERVE. 1. The ganglion of Ribes. 2. The filament by which it communicates with the carotid plexus (3) . 4. The ciliary or lenticular ganglion, giving off ciliary branches for the supply of the globe of the eye. 5. Part of the inferior division of the third nerve, receiving a short thick branch from the ganglion. 6. Part of the nasal nerve, receiv- ing a longer branch from the ganglion. 7. A slender filament sent directly backwards from the ganglion to the sympathetic branches in the cavernous sinus. 8. Part of the sixth nerve in the cavernous sinus, receiving two branches from the carotid plexus. 9. Meckel's ganglion (spheno-palatine) . 10. Its ascending branches, communicating with the supe- rior maxillary nerve. 11. Its descending branches, the posterior palatine. 12. Its anterior branches, spheno-palatine or nasal. 13. The naso-palatine branch, one of the nasal branches. * The point where Cloquet imagined the naso- palatine ganglion to be situated. 14. The posterior branch of the ganglion, the Vidian nerve. 15. Its carotid branch, communicating with the carotid plexus. 16. Its petrosal branch, joining the angular bend of the facial nerve. 17. The facial nerve. 18. The chorda tympani nerve, which descends to join the gus- tatory nerve. 19. The gustatory nerve. 20. The submaxillary ganglion, re- ceiving the chorda tympani nerve from the gustatory. 21. The superior cervi- cal ganglion of the sympathetic. stance, and passes backwards beneath the Casserian ganglion and dura mater, embedded in a groove on the anterior surface of the petrous bone, to the hiatus Fallopii. In the hiatus Fallopii it receives a branch from Jacobson's nerve, and terminates in the intumescentia gangliformis of the facial nerve. The pharyngeal nerve is a small branch which passes back- wards through the pterygo-palatine canal with the pterygo-pala- tine artery, to be distributed to the mucous membrane of the Eustachian tube and neighboring part of the pharynx. While examining the nerves proceeding from Meckel's gan- glion, the dissector will observe the branches of the internal maxillary artery by which they are accompanied : the spheno- palatine artery enters the nose with the superior nasal nerves ; INTERNAL CAROTID ARTERY. 185 the descending palatine artery passes down to the palate with the palatine nerves ; and the Yidian artery accompanies the Vidian nerve. INTERNAL CAROTID ARTERY. The student may now proceed to examine the internal carotid artery, with which view he may remove any structure that conceals the artery. The internal jugular vein lies to its outer side ; it is crossed in front by the stylo-glossus and stylo-pharyngeus muscle and stylo-hyoid ligament, and higher up it has the parotid gland ; to its inner side is the pharynx and ascending pharyngeal artery (p. 170), and behind it has the verte- bral column, the rectus anticus major muscle, and some important nerves. As the student may wish to remove the styloid process, he should observe the relative position of the parts connected with it. Passing forward from the apex of this process to the angle of the jaw is the stylo- maxillary ligament, a process of the deep cervical fascia which separates the submaxillary from the parotid gland. Proceeding also from the apex of the process and partly from this ligament, is the stylo-glossus, the highest of the three styloid muscles. Arising from the middle of the styloid process, and coming forwards to the body of the os hyoides, is the stylo-hyoideus muscle, middle in position to the others but the most superficial of the three. Next the stylo-pharyngeus may be seen arising from the inner side of the base of the styloid process, and passing down- wards almost vertically to the middle of the pharynx, the lowest and deepest of the three muscles. Lastly, there is the stylo-hyoid ligament, a fibrous cord extending from the apex of the styloid process to the lesser cornu of the os hyoides. This ligament is sometimes cartilaginous or even osseous, and may be jointed with the styloid process above and the lesser cornu of the os hyoides below. At its lower part it is behind the hyo-glossus muscle, and gives origin to part of the middle constrictor muscle. The INTERNAL CAROTID ARTERY curves slightly outwards at its origin from the common carotid, and ascends nearly perpendicu- larly by the side of the pharynx to the carotid foramen in the petrous portion of the temporal bone. It then passes inwards along the carotid canal ; forwards by the side of the sella tur- cica ; and upwards by the anterior clinoid process, where it pierces the dura mater, and divides into three terminal branches. The course of this artery is remarkable for the number of angular curves which it forms ; one or two of these flexures are sometimes seen in the cervical portion, near the base of the skull ; by the side of the sella turcica, it resembles the Italic let- ter S placed horizontally. The internal carotid, which at first lies on the same plane with the external carotid, soon gets behind the latter, and higher up is separated from it by the stylo-glossus, stylo-pharyngeus, stylo- hyoid ligament, and parotid gland ; and is crossed by the glosso- pharyngeal nerve. To its inner side is the pharynx, tonsil, and ascending pharyngeal artery ; to its outer side, the internal jugu- 16* 186 THE DISSECTOR. lar vein ; between the vein and artery near the base of the skull, the glosso-pharyngeal, pneumogastric, and hypoglossal nerve ; and externally to the vein, the loop between the first and second cervical nerves. Behind, the artery rests on the rectus anticus major, the superior cervical ganglion of the sympathetic, the pharyngeal and superior laryngeal nerves being interposed. To follow the internal carotid artery through the petrous portion of the temporal bone, it is necessary to make a section of the skull from the back part of the mastoid process to the carotid foramen, keeping close to the outside of the styloid-mastoid foramen. This piece of bone may then be broken away and preserved for the subsequent examination of the mem- brana tympani, ossicula auditus, and chorda tympani nerve. The anterior wall of the carotid canal is to be furthermore broken away by the chisel. The petrous portion of the artery is in close contact with the periosteal lining of the carotid canal derived from the dura mater, and is embraced by the nerves of the carotid plexus. At the extremity of the canal, the artery is in relation with the under surface of the Casserian ganglion. By the side of the sella turcica the internal carotid artery is situated in the inner wall of the cavernous sinus, and is in relation by its outer side with the lining membrane of the sinus, the sixth nerve, and the ascending branches of the carotid plexus. The third, fourth, and ophthalmic nerve are placed in the outer wall of the sinus, and are separated by the latter from the artery. The cerebral portion of the artery is invested by a sheath of the arachnoid, and is in close relation with the optic nerve. The branches of the internal carotid artery are derived from its cranial portion, and are as follows : Tympanic, Anterior cerebral, Anterior meningeal, Middle cerebral, Ophthalmic, Posterior communicating, Choroidean. The tympanic is a small branch given off in the carotid canal ; it enters the tympanum, and inosculates with the tympanic branch of the internal maxillary and with the stylo-mastoid artery. The anterior meningeal, arising from the artery after its escape from the carotid canal, is distributed to the Casserian ganglion and dura mater of the middle fossa of the cranium. The ophthalmic artery is given off close to the anterior clinoid process, and passes through the optic foramen lying to the outer side of the optic nerve. Its distribution within the orbit has been already described (page 137). The anterior and middle cerebral artery, and the posterior com- municating, the terminal branches of the internal carotid, will be described with the anatomy of the brain in the next chapter. INTERNAL JUGULAR YEIN. The vein corresponding with the FACIAL NERVE. 1ST internal carotid artery, and which, lower in the neck, accompanies the common carotid, is the internal jugular. It commences at the jugular fossa, in the foramen lacerum posterius basis cranii, where it receives the blood from the sinuses of the dura mater. At its origin, the internal jugular vein is posterior to the internal carotid artery, but soon gets to its outer side, and keeps that position in relation to the common carotid artery in its course through the neck. The eighth pair of nerves, at its exit from the cranium, lies in front and to the inner side of the vein ; the hypoglossal nerve being behind its inner border. The glosso- pharyngeal and hypoglossal nerves then pass forwards, between the inner side of the vein and the internal carotid artery ; the pneumogastric, and superior cervical ganglion of the sympathetic, are placed at its inner side ; and the spinal accessory nerve crosses behind, and sometimes in front of it, at its upper part. The internal jugular vein receives the facial, occipital, lingual, pharyugeal, and superior and middle thyroid veins. FACIAL NERVE. The section already prescribed (page 185) for the demonstration of the internal carotid may be made subservient to the examination of the facial nerve in its course through the petrous bone. With this object the saw should not be carried too far or too deeply, and used only to divide such parts as may not be conveniently broken away with the chisel and hammer. The outer boundary of the stylo-mastoid foramen being laid open, the wall of the aqueductus Fallopii may be broken away in its course along the internal boundary of the tympanum to the anterior sur- face of the petrous bone, and thence backwards to the meatus. The FACIAL NERVE (portio dura of the seventh pair) passes into the meatus auditorius internus, with the auditory nerve or portio mollis, lying at first to the inner side and then upon the latter. At the bottom of the meatus it enters the aqueductus Fallopii, and takes its course forwards to the hiatus Fallopii, in the anterior surface of the petrous bone ; it then curves backwards towards the tympanum, and descends in the inner wall of that cavity to the stylo-mastoid foramen, through which it emerges. While in the meatus auditorius, the facial nerve communicates with the auditory nerve by one or two filaments. At the angu- lar bend of the aqueductus Fallopii, where the nerve is close to the anterior surface of the petrous bone, it presents a gangliform swelling (intumescentiagangliformis: ganglion geniculare), which receives the petrosal branch of th'e Vidian nerve and that of the otic ganglion, and sends a filament back to the auditory nerve. Behind the tympanum it is joined by one or two twigs from the auricular branch of the pneumogastric ; and lower down it gives off a tympanic branch to the stapedius muscle, and the chorda tympani nerve. 188 THE DISSECTOR. The chorda tympani nerve may now be sought for on the removed section of the bone previously made, and may be traced across the tympanum. Fig. 55 THB DISTRIBUTION OF THE FACIAL NERVE AND THE BRANCHES OF THE CER- VICAL PLEXUS. 1. The facial nerve, escaping from the stylo-mastoid foramen, and crossing 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 constitutes the pes anserinus. 12. The auricularis magnus nerve, one of the ascending branches of the cervical plexus. 13. The occipitalis minor, ascending 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 chorda tympani nerve quits the facial just above the stylo- mastoid foramen, and ascends by a distinct canal to the upper part of the posterior wall of the tympanum, which it enters through an opening situated between the base of the pyramid and the attachment of the membrana tympani. It then crosses the tympanum, between the handle of the malleus and long pro- cess of the incus to the anterior inferior angle of the cavity, and GLOSSO-PHARYNGEAL NERVE. 189 escapes through a distinct opening Fig- 56. in the fissura Glaseri, to join the gustatory nerve at an acute angle between the two pterygoid muscles (page 179). In its course through the tympanum it is inclosed within a sheath of mucous membrane. EIGHTH PAIR OF NERVES. The eighth pair consists of three nerves glosso - pharyngeal, pneumogastric, and spinal accessory which escape from the cranium at the foramen lacerum posterius, internally and an- teriorly to the internal jugular vein. At their point of exit the glosso- pharyngeal is in front of the other two, and has a separate sheath of dura mater. The pueumogastric and spinal accessory are inclosed in the same sheath. The GLOSSO-PHARYNGEAL NERVE, the smallest of the three, advances forwards between the internal carotid artery and jugular vein, and crosses the artery to the lower border of the stylo-pharyngeus muscle; it then turns forwards across the stylo-pha- ryngeus, and, getting behind the hyo-glossus muscle, is distributed to the mucous membrane of the tongue, the pharynx, and the tonsil. While in the jugular fossa, the nerve presents two gangliform, swell- ings; one, superior, of small size, ORIGIN AND DISTRIBUTION OF THE EIGHTH PAIR OP NERVES OF THE LEFT SIDE. 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 pharyngeal 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 plexus. 14. Car- diac nerves. 15. The recurrent laryngeal nerve. 16. Cardiac branches from the recurrent. 17. (Esophageal plexus. 18. Branches to the stomach. 19. A branch which joins the solar plexus. 20. The origin of the spinal accessory nerve. 21. Its branches to the sterno-mastoid muscle. 22. Terminal branches to the trapezius. 23. The origin of the facial nerve, p. The branches forming the pulmonary plexuses. 190 THE DISSECTOR. and involving only the posterior fibres of the nerve the gan- glion jugulare (Muller) ; the other, inferior, of larger size, nearly half an inch below the superior, and occupying the whole diameter of the nerve, the ganglion petrosum, or ganglion of Andersch. 1 The branches of the glosso-pharyngeal nerve are, branches of communication and branches of distribution. The branches of communication proceed chiefly from the gan- glion of Andersch; they are, one to join the auricular branch of the pneumogastric ; one to the ganglion of the pneumogastric ; one to the superior cervical ganglion of the sympathetic, ; and one, which arises below the ganglion, and pierces the posterior belly of the digastricus muscle, to join the facial nerve. The branches of distribution are Tympanic, Pharyngeal, Carotid, Tonsillitic, Muscular, Lingual. The tympanic branch (Jacobson's nerve) proceeds from the ganglion of Andersch, or from the trunk of the nerve immediately above the ganglion ; it enters a small bony canal in the jugular fossa, and divides into six branches, which are distributed upon the inner wall of the tympanum, and establish a plexiform com- munication (tympanic plexus) with the sympathetic and fifth pair of nerves. The branches of distribution supply the fenestra rotunda, fenestra ovalis, and Eustachian tube: those of commu- nication join the carotid plexus in the carotid canal, the petrosal branch of the Yidian nerve, and the otic ganglion. The carotid branches are several filaments which follow the trunk of the internal carotid artery, and communicate with the nervi molles of the sympathetic. The muscular branch divides into filaments, which are distri- buted to the posterior belly of the digastricus, stylo-hyoideus, stylo-pharyngeus, and constrictor muscles. The pharyngeal branches are two or three filaments, which are distributed to the pharynx and unite with the pharyngeal branches of the pneumogastric and sympathetic nerve to form the pharyngeal plexus. The tonsiUitic branches proceed from the glosso-pharyngeal nerve near its termination ; they form a plexus (circulus tonsil- laris) around the base of the tonsil, from which numerous fila- ments are given off to the mucous membrane of the fauces and soft palate. These filaments communicate with the descending palatine branches of Meckel's ganglion. The lingual branches enter the substance of the tongue be- 1 Charles Samuel Andersch. Tractatus Anatomico-Physiologica de Nervis Corporus Human! Aliquibis, 1797. PNEUMOGA6TRIC OR VAGUS NERVE. 191 neath the hyo-glossus and stylo-glossus muscle, and are distri- buted to the mucous membrane of the side and base of the tongue, and to the epiglottis and fauces. The PNEUMOGASTRIC or VAGUS NERVE, the largest of the three divisions of the eighth pair, at its escape from the jugular fora- men, is inclosed in a sheath of dura mater, which is common to it and the spinal accessory. The nerve takes its course down the side of the neck, lying at first between the internal carotid artery and jugular vein, and then between and behind the com- mon carotid artery and jugular vein, inclosed in the same sheath, to the superior opening of the thorax, through which it passes to the lungs and stomach. In the jugular foramen the pneumogastric nerve presents a small round ganglion, the superior or jugular ganglion; and, immediately at its exit, a gangliform swelling nearly an inch in length, the inferior ganglion (plexus gangliformis). The branches of the pneumogastric nerve are, the branches of communication and the branches of distribution. The branches of communication proceed from the ganglia: from the superior ganglion one or two branches pass to the spinal accessory; one or two to the superior ganglion of the sympathetic; and one to the inferior ganglion of the glosso- pharyngeal. From the inferior ganglion there pass off branches to the hypoglossal ; branches to the superior cervical ganglion of the sympathetic; and branches to the loop between the first and second cervical nerves. The branches of distribution are Auricular, Superior laryngeal, Pharyngeal, Cardiac, Inferior laryngeal. The auricular nerve is given off from the lower part of the jugular ganglion, or from the trunk of the nerve immediately below it, and receives immediately after its origin a small branch of communication from the glosso-pharyngeal. It then passes outwards behind the jugular vein, and on the outer side of that vessel enters a small canal in the petrous portion of the temporal bone near the stylo-mastoid foramen. Guided by this canal it reaches the descending part of the aqueductus Fallopii and joins the facial nerve. In the aqueductus Fallopii the auricular nerve gives off two small filaments, one of which communicates with the posterior auricular branch of the facial, while the other is distributed to the pinna. The pharyngeal nerve arises from the upper part of the supe- rior ganglion, and crosses behind the internal carotid artery to the upper border of the middle constrictor, upon which it forms 192 THE DISSECTOR. the pharyngeal plexus, assisted by branches from the glosso- pharyngeal, superior laryngeal, and sympathetic. The pharyn- geal plexus is distributed to the muscles and mucous membrane of the pharynx. The superior laryngeal nerve arises from the inferior ganglion, and descends behind the internal carotid artery to the -opening in the thyro-hyoidean membrane, through which it passes with the superior laryngeal artery, and is distributed to the mucous membrane of the larynx and arytenoideus muscle. On the latter, and behind the cricoid cartilage, it communicates with the recurrent laryngeal nerve. Behind the internal carotid it gives off the external laryngeal branch, which sends a twig to the pharyngeal plexus, and then descends to supply the inferior constrictor and crico-thyroid muscle and thyroid gland. This branch communicates inferiorly with the recurrent laryngeal and sympathetic nerve. The cardiac branches, two or three in number, arise from the upper and lower part of the nerve. Those from above commu- nicate with cardiac branches of the sympathetic. One large branch is given off just before the nerve enters the chest; on the right side this nerve descends by the side of the arteria innomi- nata to the deep cardiac plexus ; and on the left it passes in front of the arch of the aorta to the superficial cardiac plexus. The inferior laryngeal, or recurrent laryngeal nerve, curves around the subclavian artery on the right, and the arch of the aorta on the left side. It ascends in the groove between the trachea and oesophagus, and piercing the lower fibres of the in- ferior constrictor muscle enters the larynx close to the articula- tion of the inferior cornu of the thyroid with the cricoid cartilage. It is distributed to all the muscles of the larynx, with the excep- tion of the crico-thyroid, and communicates on the arytenoideus muscle with the superior laryngeal nerve. As it curves around the subclavian artery and aorta it gives branches (cardiac), to the heart and root of the lungs ; and as it ascends the neck it distributes filaments to the oesophagus and trachea, and commu- nicates with the external laryngeal nerve and sympathetic. The SPINAL ACCESSORY SWERVE, in its passage through the jugu- lar foramen, is contained in the same sheath of dura mater as the pneumogastric nerve, and is applied against the posterior aspect of its superior ganglion. Quitting the opening the nerve passes outwards behind and sometimes in front of the jugular vein to the upper part of the sterno-mastoid muscle, whence it is con- tinued obliquely across the posterior triangular space of the neck to the trapezius. The branches of communication of the spinal accessory are one or two small branches from the superior ganglion of the pneumo- SYMPATHETIC NERVE. 193 gastric, and a large branch which joins the pneumogastric be- tween the two ganglia. Its branches of distribution are muscular branches to the sterno-mastoid and trapezius. The HYPOGLOSSAL NERVE [ninth] passes out of the cranium through the anterior condyloid foramen, where it is situated be- hind the internal carotid artery and internal jugular vein; it then advances forwards between the artery and vein, and opposite the angle of the lower jaw curves around the occipital artery, and crosses the external carotid artery to the hyo-glossus muscle. Resting on the hyo-glossus muscle at its lower part, it becomes flattened, and divides into a number of branches which are dis- tributed to the muscles of the tongue. The branches of communication of the hypoglossal nerve are, several to the pnoumogastric, with which nerve it is closely united ; one or two with the superior cervical ganglion of the sympathetic ; and one or two with the loop between the first and second cervi- cal nerves. Its branches of distribution are the descendens noni, thyro- hyoidean, and muscular. The descendens noni is a long and slender nerve, which quits the hypoglossal just as it is about to form its arch around the occipital artery, and descends upon the sheath of the carotid vessels. Just below the middle of the neck, it forms a loop with a long branch from the second and third cervical nerves. From the convexity of this loop branches are sent to the sterno-hyoideus, stiTiio-thyroideus, and both bellies of the omo-hyoideus ; some- times also a twig is given off to the cardiac plexus, and occasion- ally one to the phrenic nerve. The thyro hyoidean nerve is a small branch distributed to the thyro-hyoideus muscle. It is given off from the trunk of the hypoglossal near the posterior border of the hyo-glossus muscle, and descends obliquely over the great cornu of the os hyoides. The muscular branches are given off where the nerve is covered in by the mylo-hyoideus muscle, and rests on the hyo-glossus ; several large branches take their course across the fibres of the genio-hyo-glossus to reach the substance of the tongue. More- over, on the hyo-glossus muscle, the branches of the hypoglossal nerve communicate with those of the gustatory nerve. SYMPATHETIC NERVE. The sympathetic nerve is brought into view by dividing the internal carotid artery and internal jugnlar vein, and drawing them aside together with the pneumogastric nerve. The cervical portion of the sympathetic nerve consists of three ganglia with their connecting cords and branches. 17 194 THE DISSECTOR. Fig. 57. The SUPERIOR CERVICAL GANGLION is long and fusiform, of a reddish-gray color, smooth, and of considerable thickness, extend- ing from within an inch of the carotid foramen in the petrous bone to opposite the lower border of the third cervical vertebra. It rests on the rectus anticus major muscle, and lies behind and to the inner side of the internal carotid artery. Its branches, like those of all the sym- pathetic ganglia are divisible into supe- rior, inferior, external, and internal ; to which may be added, as proper to this ganglion, anterior. The superior (carotid nerve) is a single branch which ascends by the side of the internal carotid, and divides into two branches ; one lying to the outer, the other to the inner side of that vessel. The two branches enter the carotid canal, and by their communications with each other, and with the petrosal branch of the Yidian, constitute the carotid plexus. The continuation of the carotid plexus onwards with the artery by the side of the sella turcica is the cavernous plexus, and from the latter branches having a plexiform distribution are given off with each branch of the artery. The carotid plexus, moreover, is the means of communication of the greater number of the cranial nerves with the rest of the sympathetic. It sends branches to the third nerve, the ophthalmic, the Casserian ganglion ; two large branches join the sixth nerve in the cavernous sinus ; it sends a branch to the ophthal- THE SYMPATHETIC NEUVE, ITS ENTIRE LENGTH. 1. The superior cervical fanglion. 2. Its ascending or carotid branch, which divides into two branches. . Its descending branch. 4. Its external branches, communicating with the first, second, and third cervical nerves. 5. Internal branches to communicate with the facial eighth and ninth pairs, and with the pharyngeal plexus. 6. The superior cardiac nerve, superficialis cordis. 7. The middle or great cardiac nerve, arising from the second cervical ganglion. 8. The inferior cardiac nerve, from the inferior cervical ganglion. 9. The first dorsal ganglion. 10. The last dorsal ganglion. 11,11. Spinal nerves. 12. Great splanchnic nerve. 13. The two semilunar ganglia, which form by their communications the solar plexus. 14. The lesser splanchnic nerve, forming the renal plexus. 15. Branches from the lumbar ganglia. 16. The hypogastric plexus. 17. Sacral ganglia. 18. The last ganglion or the sympathetic, ganglion impar. SYMPATHETIC NERVE. 195 mic ganglion; it communicates with the superior maxillary, the fat-in 1, and auditory nerve by means of the Vidian ; with the in- ferior maxillary by a branch from the otic ganglion; and with the glosso-pharyugeal by means of two filaments to the tympanic nerve. The inferior or descending branch, sometimes two, is the cord of communication with the middle cervical ganglion. The external branches are numerous, and may be divided into two sets : those which communicate with the glosso-pharyngeal, pneumogastric, and hypoglossal nerve ; and those which com- municate with the first four cervical nerves. The internal branches are three in number : pharyngeal, to assist in forming the pharyngeal plexus ; laryngeal, to join the superior laryngeal nerve and its branches ; and the superior cnrili (ic nerve, or nervus superficialis cordis. The anterior branches accompany the external carotid artery with its branches, around which they form plexuses, and here and there small ganglia ; they are called, from the softness of their texture, nervi molles, and from their reddish hue, nervi snhr-uji. The branches accompanying the facial artery are con- ducted by that vessel to the submaxillary ganglion, and those which accompany the internal maxillary artery reach the otic ganglion through the medium of the arteria meningea media. The MIDDLE CERVICAL GANGLION (thyroid ganglion) is of small size, and sometimes altogether wanting. It is situated opposite the fifth cervical vertebra, and rests against the inferior thyroid artery. This relation is so constant as to have induced Haller to name it the "thyroid ganglion." Its superior branch, or branches, ascend to communicate with the superior cervical ganglion. Its inferior branches descend to join the inferior cervical gan- glion ; one of these frequently passes in front of the subclavian artery, the other behind it. Its external branches communicate with the fifth and sixth cervical nerves. Its internal branches are filaments which accompany the inferior thyroid artery, the inferior thyroid plexus ; and the middle cardiac nerve, nervus cardiacus magnus. The INFERIOR CERVICAL GANGLION (vertebral ganglion) is much larger than the preceding, and is constant in its existence. It is of a semilunar form, and is situated on the base of the transverse process of the seventh cervical vertebra immediately behind the vertebral artery; hence its designation "vertebral ganglion." Its superior branches communicate with the middle cervical ganglion. 196 THE DISSECTOR. The inferior branches pass, some before and some behind the subclavian artery, to join the first thoracic ganglion. The external branches consist of two sets ; one which commu- nicates witn the sixth, seventh, and eighth cervical and first dorsal nerve, and one which accompanies the vertebral artery along the vertebral canal, forming the vertebral plexus. This plexus sends filaments to all the branches given off by the artery, and com- municates in the cranium with the filaments of the carotid plexus accompanying the branches of the internal carotid artery. The internal branch is the inferior cardiac nerve, nervus car- diacus minor. CARDIAC NERVES. The cardiac nerves are three in number on each side of the neck ; namely, superior, middle, and inferior. The superior cardiac nerve (nervus superficial cordis) arises from the lower part of the superior cervical ganglion, and descends the neck behind the sheath of the common carotid artery to the chest ; crossing in its course the inferior thyroid artery and recur- rent laryngeal nerve. The nerve of the left side follows the course of the carotid artery, and crossing the arch of the aorta terminates in the superficial cardiac plexus. The nerve of the right side crosses the subclavian artery sometimes in front and sometimes behind, and follows the posterior border of the arteria innominata to the deep cardiac plexus. The superficial cardiac nerve receives filaments from the pneumogastric nerve, and distributes branches to the thyroid gland and trachea. The middle cardiac nerve (nervus cardiacus magnus) proceeds from the middle cervical ganglion, or, in its absence, from the cord of communication between the superior and inferior ganglion. It is the largest of the three nerves, and lies parallel with the re- current laryngeal. At the root of the neck it divides into several branches which pass, some before and some behind, the subclavian artery, communicates with the superior and inferior cardiac, the pneumogastric, and recurrent nerve, and descends to the deep cardiac plexus. The inferior cardiac nerve (nervus cardiacus minor) arises from the inferior cervical ganglion, communicates with the recurrent laryngeal and middle cardiac nerve, and descends to the deep cardiac plexus. PR^EVERTEBRAL REGION. The student should now cut through the trachea and oesophagus, with the vessels and nerves of the neck opposite the first rib, and draw them forwards ; he should divide with the scalpel the loose cellular tissue which connects the back part of the pharynx with the vertebral column, and continue the separation to the base of the skull. He should then make a section of the cranium on each side behind the mastoid process, direct- ing the saw towards the basilar process, and then break through the PR^EVERTEBRAL REGION. m basilar process with the chisel and hammer, be made with care, and the eighth pair of nerves at their exit from the cranium as much as possible pre- served. Having accomplished this section, he may proceed to examine the muscles lying on the front of the vertebral column in the cervical region. The muscles of the praeverte- bral region are, the rectus anti- cus major and minor, longus colli, and two muscles which have been already examined, the scaleni. The RECTUS ANTICUS MAJOR, broad and thick above, and narrow and pointed below, 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 process of the occipital bone. The RECTUS ANTICUS MINOR arises from the anterior border of the lateral mass of the atlas, and is inserted into the basilar This preparation should Fig. 58. THE PR^EVERTEBRAL GROUP OF MUSCLES OP THE NECK. 1. The rec- tus anticus major muscle. 2. The sca- lenus anticus. 3. The lower part of the longus colli of the right side ; it is con- muscle. 6. Its lower portion ; the figure rests upon the seventh cervical verte- bra. 7, 8. The scalenus posticus. 9. One of the inter-transversales muscles. 10. The rectus lateralis of the left side. process, its fibres being directed cea . led superiorly by the rectus anticus *Y. j j . , maior. 4. The rectus anticus minor. obliquely upwards and inwards. 6< J The upper portion O f the longus colli The LONGUS COLLI is a long and flat muscle, consisting of two portions. The upper arises from the anterior tubercle of the atlas, and is inserted 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 fifth and sixth, and passes down the neck, to be inserted into the bodies of the three lower cervical and three upper dorsal vertebrae. We should thus arrange these attachments in a tabular form : Origin. Insertion. Upper) ^ t j as f 3d, 4th, and 5th transverse portion j ( processes. Lower! ^' 3( *' an( * 4t ^ Bodies ( 3 lower cervical vertebrae, portion f 5lh and 6th trans- ^ bodies ) verse processes ( 3 upper dorsal, bodies. 17* 198 THE DISSECTOR. In general terms, the muscle is attached to the bodies and transverse processes of the six superior cervical vertebrae above, and to the bodies of the last three cervical and first three dorsal below. The student should also examine in this region the rectus late- ralis, which is presented by its anterior face, and in the dissection of the back was seen only from behind ; and the anterior inter- transversales. The anterior division of the cervical nerves will be found between the anterior and posterior inter-transversales. If the anterior inter-transversales be removed, the vertebral artery will be seen taking its course upwards through the foramina in the transverse processes of the vertebra?. It lies in front of the cervical nerves, and is accompanied by the vertebral vein and vertebral plexus of nerves. Opposite each inter-vertebral foramen , the vertebral artery sends a spinal branch into the vertebral canal to supply the spinal cord. ACTIONS. The rectus anticus major and mi nor preserve the equilibrium of the head upon the atlas ; and, acting conjointly with the longus colli, flex and rotate the head and the cervical portion of the vertebral column. ANATOMY OF THE PHARYNX. Turning now to the portion which has been removed from the front of the vertebral column, the student may proceed to its dissection. By the removal of the cellular tissue from the nerves, he will be enabled to see the communications which take place between the eighth and ninth nerves and sympathetic ; and make out the origin of the upper branches of the pneumogastric, and particularly the branches distributed to the pharynx and larynx. Preparatory to dissecting the muscles of the pharynx, its cavity should be distended with tow or wool. The students should then remove the cellular tissue from off the muscles on one side, reserving the other for the examination of the vessels and nerves. The PHARYNX is a musculo-membranous sac resting against the vertebral column, and extending from the base of the skull to opposite the cricoid cartilage and fifth cervical vertebra. It is composed of muscles, mucous membrane, and a strong aponeu- rosis, and communicates in front with the cavity of the nose, mouth, and larynx. Above it is attached partly by muscle, but chiefly by aponeurosis, to the basilar process of the occipital bone and petrous portion of the temporal, and below it is con- tinous with the oesophagus. The MUSCLES of the pharynx are the superior, middle, and inferior constrictor, the stylo-pharyngeus, and palato-pharyn- geus. The CONSTRICTOR INFERIOR, the thickest of the three muscles, arises from the cricoid cartilage and the oblique line of the thy- roid. Its fibres spread out and are inserted into the fibrous raphe MUSCLES OP THE PHARYNX. 199 of the middle of the pharynx, the inferior fibres being almost horizontal, and the superior oblique and overlapping the middle constrictor. The upper border of the muscle is in relation with the superior laryngeal nerve, and the lower border near its origin with the inferior laryngeal or recurrent. Detach the upper portion of the inferior constrictor from its attachment to the raphe, and turn it downwards to bring the lower part of the next muscle into view. The CONSTRICTOR MEDIUS arises from the great cornu of the os hyoides, from the lesser cornu, and from the stylo-hyoidean liga- ment. It radiates, from its origin, upon the side of the pharynx, the lower fibres descending and being overlapped by the con- strictor inferior ; and the upper fibres ascending, so as to cover in the constrictor superior. It is inserted into the raphe, and by a fibrous aponeurosis into the basilar process of the occipital bone. The lower border of the muscle is in relation with the superior laryngeal nerve, and its upper border is separated from the superior constrictor by the stylo-pharyngeus muscle and glosso-pharyngeal nerve. The upper portion of this muscle must be turned down, to bring the whole of the superior constrictor into view ; in so doing, the stylo-pha- ryngeus muscle will be seen passing behind its upper border. Fig. 59. A SIDE VIEW OP THE MUSCLES OF THK PHAKYXX. 1. The trachea. 2. The cricoid cartilage. 3. The erico-thyroid membrane. 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 con- strictor. 11. The superior constrictor. 12. The stylo-pharyngeus muscle passing down between the superior and middle constrictor. 13. The upper concave bor- der of the superior constrictor ; at this point the muscular fibres of the pharynx are deficient. 14. The pterygo-maxillary liuMiiH-nt. 15. The buccinator muscle. Hi. The orbicularis oris. 17. The mylo- hyoideus. The CONSTRICTOR SUPERIOR is a thin and quadrilateral plane of muscular fibres, arising from the extremity of the molar ridge of the lower jaw, from the pterygo-maxillary ligament, and from the lower third of the internal pterygoid plate, and inserted into 200 THE DISSECTOR. the rapM and basilar process of the occipital bone. Its superior fibres are arched, and leave a concave interspace between its upper border and the basilar process ; some of its lower fibres are continuous with those of the genio-hyo-glossus on the side of the tongue ; and it is overlapped inferiorly by the middle con- strictor. Between the side of the pharynx and the ramus of the lower jaw is a triangular interval, the maxillo-pharyngeal space, which is bounded on the inner side by the superior constrictor muscle ; on the outer side by the internal pterygoid muscle ; and behind by the rectus anticus major and vertebral column. In this space are situated the internal carotid artery, the internal jugular vein, and the glosso-pharyngeal, pneumogastric, spinal accessory, and hypoglossal nerve. The STYLO-PHARYNGEUS is a long and slender muscle, arising from the inner side of the base of the styloid process ; it descends between the superior and middle constrictor muscles, and spreads out beneath the mucous membrane of the pharynx ; it is inserted partly into the posterior border of the thyroid cartilage, and partly into the internal face of the inferior constrictor. Along its lower border is seen the glosso-pharyngeal nerve which crosses it, opposite the root of the tongue, to pass between the superior and middle constrictor and behind the hyo-glossus. When the muscles of the exterior of the pharynx have been studied, the sac should be opened along the middle line, and the sides drawn apart in order to examine its interior. The pharynx presents seven openings, two at its upper and front part, the posterior nares ; one on each side of the posterior nares, the aperture of the Eustachian tube ; below the posterior nares, the opening of the mouth, or isthmus faucium ; lower down, the opening of the larynx ; and inferiorly, the oesophagus. The posterior nares are oval in shape, and separated from each other by the vomer. The apertures of the Eustachian tubes are two slit-like open- ings, situated one at each side of the fauces, and in a line with the posterior extremity of the inferior spongy bone. The Eus- tachian tube is a fibro-cartilaginous and osseous canal, which extends obliquely outwards and upwards to the tympanum, and is the medium of communication between that cavity and the external air. If the mucous membrane be removed from around the aperture, the fibro-cartilage will be found to be about an inch in length, broad at the extremity, and narrower as it pro- ceeds outwards. It is lined by mucous membrane which is con- tinuous with that of the tympanum, and is provided around the aperture with numerous mucous glands. Between the posterior nares and the opening of the mouth is a rausculo-membranous fold, which forms a kind of curtain at the SOFT PALATE TONSILS. 201 Fig. 60. back of the mouth, the soft palate or velum pendulum palati. Hanging from the middle of its inferior border is a small rounded process, the uvula ; and passing outwards from the uvula on each side are two curved folds of the mucous membrane, the arches or pillars of the palate. The anterior pillar is continued downwards to the side of the base of the tongue, and is formed by the prominence of the palato-glossus muscle. The posterior pillar \& prolonged down- wards and backwards into the pharynx, and is formed by the convexity of the palato-pharyn- geus muscle. These two pillars, closely united above, are sepa- rated below by a triangular inter- val or niche, in which the tonsil is lodged. The TONSILS (amygdalae) are two glandular organs, shaped like almonds, and situated between the anterior and posterior pillar of the Soft palate, On each Side of 1. The basilar process of the occi the fauces. They are Composed Ptal bone. 2 2 The petrous portion of an assemblage of mucous foi- licles, wllk'll Open Upon the SUr- face of the gland by about twelve apertures. Externally, they are invested by the pharyngeal fascia, which separates them from the su- perior constrictor muscle and in- ternal carotid artery, and prevents an abscess from opening in that direction. In relation to surrounding parts, each gland corre- sponds with the angle of the lower jaw. The space included between the soft palate and the root of the tongue is the isthmus of the fauces. It is bounded above by the soft palate, on each side by the pillars of the soft palate and ton- sils, and below by the root of the tongue. It is the opening between the mouth and pharynx. The opening into the larynx is broad in front and narrow be- hind. It is bounded in front by the epiglottis, and on the sides by the fold of mucous membrane stretched between the sides of the epiglottis and the arytenoid cartilages. In front of the epi- glottis is the root of the tongue. THE OPENINGS INTO THE PHARYNX. 4,4. The openings of the Eustachian tubes. 5. 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 oesophagus. 11, 11. The sides of the pharynx drawn open. 12. The oesophagus. 202 THE DISSECTOR. The opening into the oesophagus corresponding with the lower border of the inferior constrictor and the commencement of the circular muscular fibres, has the appearance of the aperture of a sphincter, the mucous membrane, paler than that of the pharynx, being thrown into folds. The student may now proceed to the removal of the mucous membrane from the posterior surface and pillars of the palate, and for some little distance on the side of the pharynx. On the middle line he will find a pair of small muscles which descend into the uvula ; these are the azygos uvulae. On the side of the soft palate, and coming down from the base of the cranium, is the levator palati. The attachment of the superior constrictor to the internal pterygoid plate should now be defined and divided in order to bring into view a muscle which lies under cover of that plate, the tensor palati. In the posterior pillar of the soft palate is the palato-pharyngeus muscle, and in the anterior pillar the palato- glossus. The MUSCLES of the soft palate are Levator palati, Azygos uvulae, Tensor palati, Palato-glossus, Palato-pharyngeus. The AZYGOS UVULAE is a pair of small muscles situated along the midline 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 portion of the temporal bone, and from the posterior aspect of the Eustachian tube, and passing down by the side of the posterior naris, spreads out between the fasciculi of origin of the palato-pha- ryngeus and is inserted into the raphe, where it is overlaid bythe azygos uvulae. The TENSOR PALATI (circumflexus), arises from the scaphoid fossa at the base of the internal pterygoid plate, from the adjacent part of the sphenoid bone, and from the anterior aspect of the Eustachian tube. It lies between the internal pterygoid muscle and in- ternal pterygoid plate, and winding around the hamular process of the lat- THE PHARYNX HAVING BEEN LAID OPEN FROM BEHIND, THE CONSTRICTORS WERE TURNED OUTWARDS, AND THE MUCOUS MEMBRANE WAS REMOVED FROM THEM AND FROM THE SOFT PALATE. THE POSTERIOR NARES, THE TONGUE, AND THE OPENING INTO THE LARYNX ARE SEEN, TOGETHER WITH THE FOLLOW- ING MUSCLES, viz : 1. Levator palati mollis. 2. Circumflexus palati. 3. Azygos uvulae. 4. This number rests on the tongue,- it points to the palato- glossus. 5. Palato-pharyngeus. 6. Posterior naris of one side. Fig. 61, MUSCLES OF THE PALATE. 203 ter, expands into a tendinous aponeurosis which is inserted into the transverse ridge on the horizontal portion of the palate bone and into the raphe\ The PALATO-PHARYNGEUS forms the posterior pillar of the fauces ; it arises by two fasciculi from the raphe of the soft palate, where its fibres are continuous with those of the muscle of the opposite side ; and is inserted into the inner surface of the pharynx and posterior border of the thyroid cartilage. This muscle is broad above where it forms the whole thickness of the lower half of the soft palate, narrow in the posterior pillar, and again broad and thin in the pharynx, where it spreads out pre- viously to its insertion. The levator palati passes to its insertion between the two fasciculi of origin of the muscle. The PALATO-GLOSSUS (constrictor isthmi faucium), is a small fasciculus of fibres which arises in the soft palate, and descends to be inserted into the side of the tongue. It is the projection of this small muscle, covered by mucous membrane, that forms the anterior pillar of the soft palate. It has been named con- strictor isthmi faucium, from a function it performs in common with the palato-pharyngeus, viz : of constricting the opening of the fauces. ACTIONS. The azygos uvulae shortens the uvula. The levator palati raises the soft palate, while the tensor spreads it out laterally so as to form a septum between the pharynx and posterior nares. Taking its fixed point from below, the tensor palati will dilate the Eustachian tube. The palato-glossus and palato-pharyngeus constrict the opening of the fauces, and by drawing down the soft palate, they serve to press the mass of food from the dorsum of the tongue into the pharynx. The (ESOPHAGUS commences at the lower border of the cricoid cartilage, and in its course down the neck rests on the vertebral column, inclining to the left so as to project beyond the border of the trachea on that side. It is composed of three coats muscular, cellular, and mucous. The muscular coat consists of two layers of fibres, of which the external are longitudinal, and the internal circular. The longitudinal fibres commence by three fasciculi, anterior and two lateral: the anterior fasciculus is attached to the longitudinal ridge on the posterior surface of the cricoid cartilage; the lateral fasciculi are connected with the inferior constrictor of the pha- rynx. The internal layer of circular fibres is continuous with the inferior constrictor. The mucous coat is covered by a thick, whitish epithelium, and is thrown into longitudinal folds. The anatomy of the nose, mouth, and larynx are contained in a subsequent chapter (V.), in which they are associated with the organs of vision and hearing. 204 THE DISSECTOR. CHAPTER IT. BRAIN AND SPINAL CORD. THE brain is a collective term which signifies those parts of the nervous system, exclusive of the nerves themselves, which are contained within the cranium: they are the cerebrum, cerebellum, and medulla oblongata. These are invested and protected by the membranes of the brain, and the whole together constitute the encephalon (lv xf^a^, within the head). To examine the encephalon with its membranes, the upper part of the skull must he removed by sawing through the external table, and break- ing the internal table with the chisel and hammer. After the calvaria 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 par- ticularly 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 connection results from numerous 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 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 Pacchionian bodies. The MEMBRANES of the encephalon and spinal cord are the dura mater, arachnoid membrane, and pia mater. The DURA MATER' is the firm, whitish or grayish layer which is brought into view when the calvaria is removed. It is a strong fibrous membrane, somewhat laminated in texture, and composed of white fibrous tissue. Lining the interior of the cranium, it serves as the internal periosteum of that cavity; it is prolonged also into the spinal column, under the name of theca vertebralis, but is not adherent to the bones in that canal as in the cranium. From the internal surface of the dura mater, processes are directed inwards for the support and protection of parts of the brain; while from its exterior, other processes are prolonged outwards to form sheaths for the nerves as they quit the skull 1 So named from a supposition that it was the source of all the fibrous membranes of the body. GLANDULE PACCHIONI. 205 and spinal column. Its external surface is rough and fibrous, and corresponds with the internal table of the skull. The inter- nal 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 instances of fibro-serous membrane in the body, formed in the same way, namely, the pericardium and tunica albuginea of the testicle. On the external surface 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 su- ]>ry nerve ; externally to the letter is the fissure of Sylvius, g, g. The substan- tia perforata. 2. The second pair, or optic nerves; the figure rests on the optic com- missure, h. The tuber cine- reum, on the summit of which is seen the infundibulum cut across. ', *'. The corpora al- bicantia. k. The locus per- foratus. 3, 3. The third pair of nerves: the figures are placed on the crura cerebri. /. The pons Varolii. m, m. The crura cerebelli. 4, 4. The fourth pair of nerves. 5, 5. The fifth pair, issuing from the crura cerebelli. 6. The sixth pair. 7, 7. The seventh pair; the smaller nerve is the portio dura 11, n. The corpora pyramidalia of the medulla oblongata. o. The medulla spi- nalis ; just above the letter is seen the decussation of the fibres of the corpora liyrninidalia. p. One of the corpora olivaria; the other is concealed by the filaments of the ninth nerve, q. One of the corpora restiformia; the other is concealed by the filaments of the eighth nerve. 8. The eighth nerve ; consist- ing of r, the glosso-pharyngeal ; 5, the pneumogastric ; t , the spinal accessory. 9. The ninth, or hypoglossal nerve, v, v. The anterior roots of the two upper spinal nerves, w, w. The pneumogastric lobules of the cerebellum, x, x. The border of the lobus superior of the cerebellum, y, y. The border of the lobus inferior anterior. The fissure between x and y is the sulcus horizontal. brain, and making a sudden curve upon themselves previously to their ascent to the lateral ventricles, constitute the corpora albi- cantia. When divided by section, these bodies will be found to be composed of a capsule of white substance, containing gray 20 230 THE DISSECTOR. matter, the gray matter of the two corpora being connected by means of a commissure. The locus perforatus (posticus) is a layer of whitish-gray sub- stance, connected in front with the corpora albicantia, behind with the pons Yarolii, and on each side with the crura cerebri, between which it is situated. It is perforated by several thick tufts of arteries, which are distributed to the thalami optici and third ventricles, of which latter it. assists in forming the floor. It is also called the pons Tarini. The crura cerebri (peduncles of the cerebrum) are two thick white cords, which issue from the anterior border of the pons Yarolii, and diverge to each side to enter the thalami optici. By their outer side the crura cerebri are continuous with the corpora quadrigemina, and above, they constitute the lower boundary of the aqueduct of Sylvius. In their interior, they contain gray matter, which has a semilunar shape when the crus is divided transversely, and has been termed the locus niger. The third nerve will be observed to arise from the inner side of each crus, and the fourth nerves wind around their outer border from above. The pons Varolii 1 (protuberantia annularis, nodus encephali) is the broad transverse band of white fibres which arches like a bridge across the upper part of the medulla oblongata ; and, con- tracting on each side into a thick rounded cord, enters the sub- stance of the cerebellum under the name of crus cerebelli. There is a groove along its middle which lodges the basilar artery. The pons Yarolii is the commissure of the cerebellum, and associates the two lateral lobes in their common functions. Resting against the pons, near its posterior border, is the sixth pair of nerves. On the anterior border of the crus cerebelli, at each side, is the thick bundle of filaments belonging to the fifth nerve, and, lying against its posterior border, the seventh pair of nerves. The upper surface of the pons forms a part of the floor of the fourth ventricle. MEDULLA OBLONGATA. The medulla oblongata (bulbus rachidicus) is the upper en- larged portion of the spinal cord. It is somewhat conical in shape, and a little more than an inch in length, extending from the pons Yarolii to a point corresponding with the upper border of the atlas. On the middle line, in front and behind, the medulla 1 Constant Varolius, Professor of Anatomy in Bologna : lie died in 1578. He dissected the brain in the course of its fibres, beginning from the medulla oblongata ; a plan which has since been perfected by Vieussens, and by Gall and Spurzheim. The work, containing his mode of dissec- tion, "De Resolutione Corporis Humani," was published after his death, in 1591. MEDULLA OBLONGATA. 231 oblongata is marked by two vertical fissures, the anterior and posterior median fissures, which divide it superficially into two Fig. 69. AN ANTERIOR VIEW OP THE MEDULLA OBLONOATA. a, a. Anterior pyramids. b. Their decussation across the middle line, c, c. The olivary bodies. d, d. Restiform bodies, e. Arci- form fibres, f. Fibres shown by Solly to pass from the anterior column of the cord to the cere- bellum, g. Anterior column. h. Lateral column, p. Pona Varolii. i. Its upper fibres. 5, 5. Roots of fifth nerves. Fig. 70. r\ POSTERIOR VIEW OP THE MEDULLA. OBLONOATA, AND BACK OF THE PONS VAROLII. The peduncles of the cere- bellum are cut short, d, d. Restiform bodies (fasciculi cuneati), passing up to become inferior peduncles of cerebellum. p, p. Posterior pyramids, v, v. Posterior fissure, or calamus scriptorius, extending along the floor of the fourth ventricle. a, a. Testes. b, b. Nates. /,/. Superior peduncles of cerebellum, c. Eminence connected with hypoglossal nerve, e. With glosso-pharyngeal nerve, i. With vagus nerve, v. With spinal accessory nerve. 7, 7. Roots of auditory nerves. symmetrical lateral cords or columns ; whilst each lateral column is subdivided by minor grooves into three smaller cords, namely, the corpora pyramidalia, corpora olivaria, and corpora restiformia. The corpora pyramidalia are two narrow convex cords, tapering slightly from above downwards, and situated one on either side of the anterior median fissure. At about an inch below the pons the corpora pyramidalia communicate very freely across the fissure by a decussation of their fibres, and at their point of entrance into the pons they are constricted into round cords. The fissure is somewhat enlarged by this constriction, and the enlarged space 232 THE DISSECTOR. has received the name of foramen caecum (Yicq d'Azyr) of the medulla oblongata. The corpora olivaria (named from some resemblance to the shape of an olive) are two oblong, oval-shaped, convex bodies, of about the same breadth with the corpora pyramidalia, about half an inch in length, and somewhat larger above than below. The corpus olivare is situated immediately external to the corpus pyramidale, from which, and from the corpus restiforme, it is separated by a well-marked groove. In this groove some longi- tudinal fibres are seen which inclose the base of the corpus olivare, and have been named funiculi siliquce, those which lie to its inner side being the funiculus internus, and those to its outer side the funiculus externus. Besides these there are other fibres which cross the corpus olivare obliquely : these are ihejibrtE arciformes. When examined by section, the corpus olivare is found to be a ganglion deeply embedded in the medulla oblongata, and meeting its fellow at the middle line behind the corpus pyramidale. The ganglion of the corpus olivare (corpus dentatum, nucleus olivae), like that of the cerebellum, is a yellowish-gray dentated capsule, open behind, and containing medullary substance from which a fasciculus of fibres proceeds upwards to the corpora quadrigemina and thalami optici. The nervous filaments which spring from the groove on the anterior border of the corpus olivare, are those of the hypoglossal nerve ; and those on its posterior border are the glosso-pharyngeal and pneuraogastric. The corpora restiformia (restis, a rope) comprehend the whole of the posterior half of each lateral column of the medulla oblon- gata. They are separated from the corpora olivaria by the grooves already spoken of ; posteriorly, they are divided from each other by the posterior median fissure and the fourth ventri- cle, and superiorly they diverge and curve backwards to enter the cerebellum, and constitute its inferior peduncles. Along the posterior border of each corpus restiforme, and marked off from that body by a groove, is a narrow white cord, separated from its fellow by the posterior fissure. This pair of narrow cords are termed the posterior pyramids (fasciculi graciles). Each fasci- culus forms an enlargement (processus clavatus) at its upper end, and is then lost in the corresponding corpus restiforme. The processus clavati are the lateral boundaries of the nib of the calamus scriptorius. The corpus restiforme is crossed near its entrance into the cerebellum by the auditory nerve, the choroid plexus of the fourth ventricle, and the pneumogastric lobule. The remaining portion of the medulla oblongata visible from the exterior, are the two slightly convex columns which enter into the formation of the floor of the fourth ventricle. These columns are the fasciculi teretes (innominati). FIBRES OP THE BRAIN. 233 DIVERGING FIBRES. The fibres composing the columns of the medulla oblongata have a special arrangement on reaching the upper part of that body; those of the corpora pyramidalia and olivaria enter the pons Varolii, and are thence prolonged through the crura cerebri, thalami optici, and corpora striata to the cerebral hemispheres ; but those of the corpora restiformia are reflected backwards into the cerebellum, and form its inferior peduncles. From pursuing this course, and spreading out as they advance, these fibres have been termed by Gall the diverging fibres. While situated within the pons, the fibres of the corpus pyramidale and olivare separate and spread out, and have gray substance interposed between them ; and they quit the pons, much increased in number and bulk, so as to form the crus cerebri. The fibres of the crus cerebri again are separated in the thalamus opticus, and are intermingled with gray matter, and they also quit that body greatly increased in number and bulk. Precisely the same change takes place in the corpus striatum, and the fibres are now so extraordinarily multiplied as to be capable of forming a large proportion of the hemispheres. Observing this remarkable increase in the white fibres, apparently from the admixture of gray substance, Gall and Spurzheim considered the latter as the material increase of formative substance to the white fibres, and they are borne out in this conclusion by several collateral facts, among the most prominent of which is the great vascularity of the gray substance ; the larger proportion of the nutrient fluid circulating through it is fully capable of effecting the increased growth and nutrition of the structures by which it is surrounded. For a like reason, the bodies in which this gray substance occurs, are called by the same physiologists " ganglia of increase" and by other authors simply ganglia. Thus, the thalami optici and corpora striata are the ganglia of the cerebrum ; or, in other words, informative ganglia of the hemispheres. The fibres of the corpora pyramidalia are not all of them destined to the course above described ; several fasciculi curve outwards to reach the corpora restiformia, some passing in front and some behind the corpus olivare on each side. These are the ar cif or m fibres; they are distinguish- ed by Mr. Solly into the superficial and deep cerebellar fibres. In the pons Varolii the continued or cerebral fibres (Solly) of the corpus pyramidale are placed between the superficial and deep layers of transverse fibres, and, escaping from the pons, constitute the inferior and inner segment of the crus cerebri. From the crus cerebri they pass for the most part be- neath the thalami optici into the corpora striata. The fibres which inclose the corpus olivare, under the name of fasci- culi siliquae, are separated by that body into two bands ; the innermost of the two bands, fun ic ulus siliquce internus, accompanies the fibres of the corpus pyramidale into the crus cerebri. The funiculus siliquce externus unites with a fasciculus proceeding from the nucleus olivae, and the com- bined column ascending behind the crus cerebelli divides into a superior and an inferior band. The inferior band proceeds with a fasciculus presently to be described, the fasciculus innominatus, into the upper seg- ment of the crus cerebri. The superior band (laqueus) ascends by the side of the processus e cerebello ad testes, and, crossing the latter ob- liquely, enters the corpora quadrigemina, in which many of its fibres are distributed, while the rest are continued onwards into the thalamus opticus. The corpora restiformia derive their fibres from the anterior as well as from the posterior columns of the medulla oblongata ; they diverge as 20* 234 THE DISSECTOR. they approach the cerebellum, and leaving between them the cavity of the fourth ventricle, enter the substance of the cerebellum, under the form of two rounded cords. These cords envelop the corpora rhomboidea, or ganglia of increase, and then expand on all sides so as to constitute the cerebellum. Besides the fibres here described, there are, in the interior of the me- dulla oblongata, behind the corpora olivaria, and more or less apparent between these bodies and the corpora restiformia, two large bundles of fibres, fhe fasciculi innominati. These fasciculi ascend behind the deep transverse fibres of the pons Varolii, and become apparent in the floor of the fourth ventricle, under the name of fasciculi teretes. From this point they are prolonged upwards beneath the corpora quadrigemina into the crura cerebri, of which they form the upper and outer segment, and are thence continued through the thalami optici and corpora striata into the hemispheres. The locus niger of the cms cerebri is a septum of gray matter interposed between these fasciculi and those of the corpora pyramidalia. CONVERGING FIBRES. In addition to the diverging fibres which are thus shown to constitute both the cerebrum and cerebellum, by their increase and development, another set of fibres are found to exist, which have for their office the association of the symmetrical halves and distant parts of the same hemispheres. These are called from their direction converging fibres, and from their office commissures. The commissures of the cerebrum and cerebellum are, the Corpus callosum, Middle commissure, Fornix, Posterior commissure, Septum lucidum, Peduncles of pineal gland, Anterior commissure, Pons Varolii. The corpus callosum is the commissure of the hemispheres. It is there- fore of moderate thickness in the middle, where its fibres pass directly from one hemisphere to the other; thicker in front (genu), where the anterior lobes are connected ; and thickest behind (splenium), where the fibres from the posterior lobes are assembled. The fibres which curve backwards into the posterior lobes from the splenium of the corpus callo- sum have been termed forceps, those which pass directly outwards into the middle lobes from the same point, tapetum, and those which curve forwards and inwards from the genu to the anterior lobes, forceps anterior. The fornix is an antero-posterior commissure, and serves to connect a number of parts. Below, it is associated with the tenia semicircularis, thalami optici, and peduncles of the pineal gland ; on each side, by means of the corpora fimbriata, with the middle lobes of the brain ; and, above, with the corpus callosum, and consequently with the hemispheres. The septum lucidum is a perpendicular commissure between the fornix and corpus callosum. The anterior commissure traverses the corpus striatum, and connects the anterior and middle lobes of opposite hemispheres. The middle commis- sure is a layer of gray substance, uniting the thalami optici. The posterior commissure is a white rounded cord, connecting the thalami optici. The peduncles of the pineal gland must also be regarded as commis- sures, assisted in their function by the gray substance of the gland. The pons Varolii is the commissure to the two hemispheres of the cere- bellum. It consists of transverse fibres, which are split into two layers by the passage of the fasciculi of the corpora pyramidalia and corpora olivaria. These two layers, the superior and inferior, are collected to- gether on each side, in the formation of the crura cerebelli. CRANIAL NERVES. 235 CRANIAL NERVES. Having studied the parts consti- tuting the base of the brain, the dis- sector may now proceed to examine the origins of the cranial nerves, and, where necessary, trace them through the substance of the brain to their real source. There are nine pairs* of cranial nerves, which, taken in their order from before backwards, are as fol- lows : 1st. Olfactory. 2d. Optic. 3d. Motores ocnlorum. 4th. Pathetici (trochleares). 5th. Trifacial (trigemini). 6th. Abducentes. * , (Facial (portio dura). ' | Auditory (portio mollis). f Glosso-pharyngeal. Q.I J Pneumogastric (vagus, par th " 1 vagum). [ Spinal accessory. 9th. Hypoglossal (lingual). Functionally or physiologically the cranial nerves admit of divi- sion into three groups, namely, nerves of special sense, nerves of motion, and compound nerves, that is, nerves which contain fibres both of sensation and motion. The nerves belonging to these groups are the following : FRONT VIEW OF CRURA CEREBRI, PONS, MEDULLA OBLONGATA, AND PART OF THE SPINAL CORD. The origins of some of the cranial nerves are shown. 2. Optic nerve. 3. Motor oculi. 4. Pathetic nerve. 5. Fifth, or trifacial nerve. 6. Ab- ducent nerve. 7. Auditory and fa- cial nerves seventh pair. 8. Eighth pair, including glosso-pharyngeal, vagus, and spinal accessory nerves. 9. Hypoglossal nerve. 1. A spinal nerve. ' [The author in the classification of these nerves has adopted that of Willis, which is in general use ; but that of Soemmering is undoubtedly pivtWabl.', because it is the moat natural; it gives us twelve pairs of cranial nerves. Of these two are considered as entering the internal auditory in.-atus, and three pass out of the posterior foramen lacerum. Soemmering's classification is as follows : Th- first 6 the same as above. 1> Facia1 ' Auditory. Glosso-pharyngeal. Pneumogastric. Spinal accessory. 7th nf 7th of 9th 7th gth 9th 10th llth 12th Hypoglossal.] 236 THE DISSECTOR. 1st. Olfactory. Special sense, Motion Compound 2d. Optic. 7th. Auditory. 3d. Motores oculorum. 4th. Pathetici. 6th. Abdncentes. Tth. Facial. 9th. Hypoglossal. 5th. Trifacial. 8th. Glosso-pharyngeal. Pneumogastric. Spinal accessory. FIRST PAIR : OLFACTORY. The olfactory nerve arises by three roots ; an inner root from the inner and posterior part of the anterior lobe, close to the substantia perforata ; a middle root from a papilla of gray matter (caruncula mammillaris), embedded in the anterior lobe ; and an external root, which may be traced as a white streak along the fissure of Sylvius into the corpus striatum, where it is continuous with some of the fibres of the anterior commissure. The nervous cord formed by the union of these three roots is soft in texture, prisinoid in shape, and embed- ded in a sulcus between two convolutions on the under surface of each anterior lobe of the brain, lying between the pia mater and the arachnoid. As it passes forwards it increases in breadth, and swells at its extremity into an oblong mass of gray and white substance, the bulbus olfactorius, which rests upon the cribriform lamella of the ethmoid bone. From the under surface of the bulbus olfactorius are given off the nerves which pass through the cribriform foramina and supply the mucous membrane of the nares. SECOND PAIR : OPTIC. The optic nerve, a nerve of large size, arises from the corpora geniculata on the posterior and inferior aspect of the thalamus opticus, from the thalamus itself, and from the nates. Proceeding from this origin, it winds around the crus cerebri as a flattened band, under the name of tractus opticus, and joins with its fellow in front of the tuber cinereum to form the optic commissure (chiasma). The tractus opticus is united with the crus cerebri and tuber cinereum, and is covered in by the pia mater ; the commissure is also connected with the tuber cinereum, from which it receives fibres, and the nerve beyond the commissure diverges from its fellow, becomes rounded in form, and is inclosed in a sheath derived from the arachnoid. The commissure rests on the processns olivaris of the sphenoid bone, and is composed of the fibres of the two nerves ; the innermost fibres cross each other to pass to opposite eyes, while the outer ORIGIN OF OPTIC NERVES. 23t fibres continue their course uninterruptedly to the eye of the cor- responding side. The neurilemma of the commissure, as well as that of the nerves, is formed by the pia mater. THIRD PAIR : MOTORES OCULORUM. The motor oculi, a nerve of moderate size, arises from the inner side of the cms cerebri, close to the pons Yarolii, and passes forward between the poste- rior cerebral and superior cerebellar artery. The fibres of origin of this nerve may be traced into the gray substance of the crus cerebri, 1 into the motor tract, 8 and as far as Pig. 72. THE ORIGIN AND DISTRIBUTION OF THE OPTIC NERVES. 1, 1. The thalami optici, their upper surface. 2. The middle commissure of the third ventricle, connecting the two thalami. 3. The posterior commissure of the third ven- tricle. 4. The foramen commune posterius. 5. The corpus geniculatum inter- num. 6. The corpus genicnlatum externum. 7. The corpora quadrigemina : the anterior pair are the nates, the posterior the testes. 8. One root of the optic nerve, arising from the corpus geniculatum externum 9. The other root, arising from the nates. 10. The commissure. 11. The expansion of the optic nerve into the retina. 12. A section of the retina, showing its three layers : the external is Jacob's membrane, the next the nervous, and the internal the vas- cular, formed by the ramifications of the arteria centralis retinae, which is seen at 13, piercing the optic nerve, and running forwards in the centre of that nerve. Mayo. Solly. THE DISSECTOR. the corpora quadrigemina and valve of Yieussens. In the caver- nous sinus it receives one or two filaments from the carotid plexus, and one from the ophthalmic nerve. FOURTH PAIR : PATHETICT (trochlearis). The fourth is the smallest cerebral nerve; it arises from the valve of Yieussens close to the testis, and winds around the crus cerebri to the base of the brain. FIFTH PAIR : TRIFACIAL (trigeminus.) The fifth nerve, the great sensitive nerve of the head and face, and the largest cranial nerve, is analogous to the spinal nerves in its origin by two roots from the anterior and posterior columns of the spinal cord, and in the existence of a ganglion on the posterior root. It arises 1 from a tract of yellowish-white matter situated in front of the floor of the fourth ventricle and the origin of the auditory nerve, and behind the crus cerebelli. This tract divides infe- riorly into two fasciculi which may be traced downwards into the spinal cord, one being continuous with the fibres of the anterior column, the other with the posterior column. Proceeding from this origin, the two roots of the nerve pass forward, and issue from the brain upon the anterior part of the crus cerebelli, where they are separated by a slight interval. The anterior is much smaller than the posterior, and the two together constitute the fifth nerve, which, in this situation, consists of seventy to a hun- dred filaments held together by pia mater. SIXTH PAIR : ABDUCENTES. The abducens nerve, about half the size of the motor oculi, arises by several filaments from the upper constricted part of the corpus pyramidale, close to the pons Yarolii. Proceeding forwards from this origin, it lies parallel with the basilar artery. Mr. Mayo traced the origin of this nerve between the fasciculi of the corpora pyramidalia to the posterior part of the medulla oblongata; and Mr. Grainger pointed out its connection with the gray substance of the spinal cord. SEVENTH PAIR. The seventh pair consists of two nerves which lie side by side on the posterior border of the crus cere- belli. The smaller and most internal of these, and, at the same time, the most dense in texture, is the facial nerve, or portio dura. The external nerve, which is soft and pulpy, and often grooved by contact with the preceding, is the auditory nerve, or portio mollis of the seventh pair. FACIAL NERVE (portio dura). The facial nerve, the motor nerve of the face, arises from the upper part of the groove be- 1 I have adopted the origin of this nerve given by Dr. Alcock, of Dublin, in the Cyclopaedia of Anatomy and Physiology, as the result of his dissections. Mr. Mayo also traces the anterior root of the nerve to a similar origin. ORIGIN OP EIGHTH PAIR. 239 tween the corpus olivare and the corpus restiforme, close to the pons Varolii, from which point its fibres may be traced deeply into the corpus restiforme. The nerve then passes forwards, resting on the crus cerebelli, and comes into relation with the auditory nerve, with which it enters the meatus auditorius in- ternus. AUDITORY NERVE (portio mollis). The auditory nerve takes its origin in the lineae transversie (striae medullares) of the ante- Fig. 73. THK ORIGIN AND DISTRIBUTION OF THE AUDITORY NERVE. I. The corpora quadrigemina. 2, 2. The processus e cerebello ad testes, at each side. 3, 3. The corpora restiformia. 4. The space included between these four bodies, the fourth ventricle. 5. The opening of the canal of communication which leads from the third ventricle, the iter & tertio ad quartum ventriculum. 6. The calamus scriptorius. 7. The posterior median columns of the spinal cord, which form by their divergence the point of the calamus, which is also called the ventricle of Arantius. 8. The lineae transversae of the fourth ventricle, which are the lines of origin of the auditory nerve. 9. The anterior branch of the auditory nerve, distributed to the cochlea. 10. The posterior, or vestibu- lar branch. 11. The utriculus communis, which conceals the sacculus proprius from view. 12. The ampulla of the oblique semicircular canal. 13. The am- pullae of the perpendicular and horizontal semicircular canals. rior wall or floor of the fourth ventricle, and winds around the corpus restiforme, from which it receives fibres, to the posterior border of the crus cerebelli, where it comes into relation with the facial nerve. From the softness of texture of the nerve, it presents a groove on its superior surface for the reception of the portio dura. The auditory nerve is the eighth pair of Soem- mering. EIGHTH PAIR. The eighth pair consists of three nerves, the glosso-pharyngeal, pneumogastric, and spinal accessory : these are the ninth, tenth, and eleventh pairs of Soemmering. 240 THE DISSECTOR. GLOSSO-PHARYNGEAL NERVE. This nerve arises by five or six filaments from the groove between the corpus olivare and resti- forme, or rather from the anterior border of the latter. The filaments unite to form a nerve of moderate size. The fibres of origin may be traced through the fasciculi of the corpus resti- forme to the gray substance in the floor of the fourth ventricle. PNEUMOGASTRIC NERVE (vagus). The pneumogastric arises by ten or fifteen filaments from the groove between the corpus olivare and corpus restiforme, or rather from the anterior border of the latter, immediately below the glosso-pharyngeal. The fibres of origin may be traced, like those of the glosso-pharyn- geal, to the gray substance in the floor of the fourth ventricle. SPINAL ACCESSORY. The spinal accessory nerve arises by several filaments from the side of the spinal cord, as low down as the fifth or sixth cervical nerve, and ascends behind the ligamen- tum denticulatuin and between the anterior and posterior roots of the spinal nerves to the side of the medulla oblongata, where it comes into relation with the two preceding nerves. NINTH PAIR : HYPOGLOSSAL NERVE (lingual). The hypoglos- sal nerve arises from the groove between the corpus pyramidale and corpus olivare by ten or fifteen filaments, which are collected into two bundles. The bundles unite and form a nerve of con- siderable size. At its origin, the hypoglossal nerve sometimes communicates with the posterior root of the first cervical nerve. Its deep ori- gin may be traced to the gray substance in the floor of the fourth ventricle. The student may now return to the cranium to examine the nerves in their passage through the dura mater and the foramina in the base of the skull. The olfactory bulb sends its numerous small nerves through the cribriform foramina of the ethmoid bone, in the sulcus situated on either side of the attachment of the falx cerebri to the crista galli. The optic nerve passes through the optic foramen, and receives in its passage a sheath from the dura mater. The dura mater at this point divides into two layers, one being continuous with the periosteum of the orbit, the other being the sheath of the optic nerve. The ophthalmic artery enters the orbit through the optic foramen, with the optic nerve lying to its outer side. The third, or motor oculi nerve, passes through an opening in the dura mater situated immediately in front of the posterior clinoid process, and takes its course through the outer wall of the cavernous sinus to the sphenoidal fissure through which it enters the orbit. The fourth nerve passes through the dura mater a little further COURSE OF CRANIAL NERVES. 241 back, and externally to the third nerve. It also takes its course through the outer wall of the cavernous sinus to the sphenoidal fissure, by which it enters the orbit (pp. 133, 134). The ffth nerve passes through a large oval opening in the dura mater, immediately behind and to the outer side of the fourth nerve. This opening is situated in the anterior part of the ten- torium cerebelli at its insertion into the petrous bone, and the nerve lies in a groove on the border of that bone near its extre- mity. After passing through this opening, the nerve enters the Casserian ganglion ; and if the ganglion be gently raised, the anterior root of the fifth nerve will be seen passing beneath the ganglionic mass to join with the inferior maxillary nerve. The sixth nerve enters an opening in the dura mater behind and to the inner side of the opening for the fifth nerve, and ascends upon the body of the sphenoid bone to reach the cavern- ous sinus below the other nerves. It lies in the inner wall of the sinus, between the sinus and the internal carotid artery, and passes into the orbit through the sphenoidal fissure. The seventh pair of nerves, consisting of the facial and audi- tory, enter the meatus auditorius internus, which is lined by the dura mater. The facial nerve lies in front of the auditory ; and a small artery, the internal auditory, a branch of the superior cerebellar, enters with them to be distributed to the internal ear. At the bottom of the meatus auditorius internus the facial nerve enters its special canal, the aqueductus Fallopii, and the auditory nerve divides into a number of small branches which pass into the cochlea and vestibule. The eighth pair of nerves, the glosso-pharyngeal, pneumo- gastric, and spinal accessory, pass through the dura mater and jugular foramen, behind and to the inner side of the seventh pair. The glosso-pharyngeal pierces the dura mater separately, and in front of the other two, and receives a sheath from that membrane in its passage. The pneumogastric and the spinal accessory also receive a sheath, which is common to the two nerves. The ninth, or hypoglossal nerve, pierces the dura mater by two or three separate filaments to the inner side of the eighth pair, and near the foramen magnum. Having passed through the dura mater, the filaments unite into a single nerve at the anterior condyloid foramen ; and the nerve receives a sheath from the dura mater. Immediately behind, and to the inner side of the optic foramen, the internal carotid artery will be seen emerging from the dura mater. And just below the margin of the foramen magnum, on either side, is the trunk of the vertebral artery penetrating the dura mater. The pituitary gland will be seen occupying the sella turcica, 21 242 THE DISSECTOR. and surrounded by that portion of the dura mater which stretches between the clinoid processes. To dissect the gland, the dura mater surrounding it must be turned aside and the posterior clinoid processes broken off; but as this pre- paration would injure the parts contained in the cavernous sinuses, it may be omitted until the cavernous sinuses have been examined and are completed. The gland is composed of two lobes, and the remains of the infundibulum will be seen attached to its upper surface (page 228). Fig. 74. THE SINUSES OF THE UPPER AND BACK PART OP THE SKULL. 1. The superior longitudinal si- nus. 2, 2. The cerebral veins opening into the sinus from behind for- wards. 3. Thefalx cere- bri. 4. The inferior longi- tudinal 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 petrosal sinus of one side. 10. The dilatations corre- sponding with the jugular fossae. 11. The internal jugular veins. SINUSES OF THE CRANIUM. The sinuses of the dura mater are irregular channels, formed by the splitting of the layers of that membrane, and lined upon their inner surface by a continuation of the internal coat of the veins. They may be divided into two groups : 1. Those situ- ated at the upper and back part of the skull. 2. The sinuses at the base of the skull. The former are, the Superior longitudinal sinus, Occipital sinuses, Inferior longitudinal sinus, Lateral sinuses. Straight sinus, The only dissection required for the sinuses, with the exception of the cavernous sinus, is to lay them open with the scissors or scalpel. The cavernous requires to be isolated after the examination of the nerves which occupy its external wall. The superior longitudinal sinus is situated in the attached margin of the falx cerebri, and extends along the middle line of SINUSES OF THE CRANIUM. 243 the arch of the skull, from the foramen caecum in the frontal, to the inner tuberosity of the occipital bone, where it divides into the two lateral sinuses. It is triangular in form, is small in front, and increases gradually in size as it passes backwards ; it receives the superior cerebral veins which open into it obliquely, numerous small veins from the diploe, and near the posterior extremity of the sagittal suture, the parietal veins, from the pe- ricranium and scalp. Examined in its interior, it presents nu- merous transverse fibrous bands (trabecula?), the chords Wiliisii, which are stretched across its inferior angle ; and some small white granular masses, the glandulae Pacchioni ; the oblique open- ings of the cerebral veins, with their valve-like margin, are also seen on the walls of the sinus. The termination of the superior longitudinal sinus in the two lateral sinuses forms a considerable dilatation, into which the straight sinus opens from the front, and the occipital sinuses from below. This dilatation is named the torcular Herophili, 1 and is the point of communication of six sinuses, the superior longitudinal, two lateral, two occipital, and the straight. The inferior longitudinal sinus is situated in the free margin of the falx cerebri; it is cylindrical in form, and extends from near the crista galli to the anterior border of the tentorium, where it terminates in the straight sinus. " It receives in its course several veins from the falx. The straight, or fourth sinus, is the sinus of the tentorium: it is situated at the line of union of the falx with the tentorium ; is prismoid in form, and extends across the tentorium, from the termination of the inferior longitudinal sinus to the torcular Hero- phili. It receives the vena3 Galeni, a the cerebral veins from the inferior part of the posterior lobes, and the superior cerebellar veins. The occipital sinuses are two canals of small size, situated in the -attached border of the falx cerebelli ; they commence by several small veins around the foramen magnum, and terminate by separate openings in the torcular Herophili. They not unfre- quently communicate with the termination of the lateral sinuses. The lateral sinuses, commencing at the torcular Herophili, pass horizontally outwards, in the attached margin of the tento- rium, and then curve downwards and inwards along the base of 1 Torcular (a press), from a supposition entertained by the older ana toniists that the columns of blood, coming in different directions, com- pressed 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.. 2 Claudian Galen, chief of the Greek physicians after Hippocrates, was born about the year 130. 244 THE DISSECTOR. Pig. 75. the petrous portion of the temporal bone, at each side, to the foramina lacera posteriora, where they terminate in the internal jugular veins. Each sinus rests in its course on the transverse groove of the occipital bone, posterior inferior angle of the parie- tal, mastoid portion of the temporal, and again on the occipital bone. They receive the cerebral veins from the inferior surface of the posterior lobes, the inferior cerebellar veins, the superior petrosal sinuses, the mastoid and posterior condyloid veins, and, at their termination, the inferior petrosal sinuses. These sinuses are often unequal in size, the right being larger than the left. The sinuses of the base of the skull are, the Cavernous, Superior petrosal, Inferior petrosal, Transverse. Circular, The cavernous sinuses are named from presenting a structure similar to that of the corpus cavernosum penis. They are situ- ated on each side of the sella turcica, receiving, anteriorly, the ophthalmic veins through the sphenoidal fissures, and terminating posteriorly in the inferior petrosal sinuses. In the internal wall of each cavernous sinus is the in- ternal carotid artery, accompa- nied by several filaments of the carotid plexus, and crossed by the sixth nerve ; and, in its external wall, the third, fourth, and oph- thalmic nerves. These structures are separated from the blood flow- ing through the sinus, by the tubular lining membrane. The cerebral veins from the under sur- face of the anterior lobes open into the cavernous sinuses. They communicate by means of the oph- thalmic with the facial veins, by the circular sinus with each other, and by the superior petrosal with the lateral sinuses. The inferior petrosal sinuses are the continuations of the cavernous sinuses backwards along the lower border of the petrous portion of THE SINUSES OF THE BASE OF THE SKULL. 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 occi- pital sinuses. 10. The torcular Herophili. 11, 11. The lateral sinuses. SINUSES OP THE CRANIUM. 245 the temporal bone at each side of the base of the skull; to the foramina lacera posteriora, where they terminate with the lateral sinuses in the commencement of the internal jugular veins. The circular sinus (sinus of Ridley) is situated in the sell a turcica, surrounding the pituitary gland, and communicating on each side with the cavernous sinus. The posterior segment is larger than the anterior. The superior petrosal sinuses pass obliquely backwards along the attached border of tentorium on the upper margin of the petrous portion of the temporal bone, and establish a communi- cation between the cavernous and lateral sinus at each side. They receive one or two cerebral veins from the inferior part of the middle lobes, and a cerebellar vein from the anterior border of the cerebellum. Near the extremity of the petrous bone these sinuses cross the oval aperture which transmits the fifth nerve. The transverse sinus (basilar, anterior occipital) passes trans- versely across the basilar process of the occipital bone, forming a communication between the two inferior petrosal sinuses. Some- times there are two sinuses in this situation. The ARTERIES of the dura mater are the anterior meningeal, from the ethmoidal, ophthalmic, and internal carotid ; the middle and small meningeal^ from the internal maxillary ; the inferior iitt'xuigeal, from the ascending pharyngeal and occipital ; and the posterior meningeal, from the vertebral. If the dura mater be stripped up in the middle fossa of the cranium, the arteria meningea media will be seen issuing from the foramen spinosum and dividing into two branches. The anterior branch crosses the great ala of the sphenoid to the groove or canal in the anterior inferior angle of the parietal bone, and gives off branches which ramify upon the external surface of the duramater, and anastomose with corresponding branches from the opposite side. The posterior branch crosses the squamous portion of the temporal bone torthe posterior part of the dura mater and craniuum. The arteria meningea media gives branches to the Casserian gan- glion and a small branch which enters the hiatus Fallopii to supply the facial nerve. Its other branches are destined to the bones of the cranium and dura mater. The NERVES of the dura mater are derived from the sympathetic, and accompany the arteries. Some filaments are also given to it by the Casserian ganglion ; and a large recurrent branch arises from the ophthalmic, and sometimes from the fourth nerve, in the cavernous sinus, and takes its course between the layers of the tentorium to the lateral sinus. Purkinje describes a nervous plexus as being situated around the trunk of the vena Galeni, and distributing filaments to the tentorium. 21* 246 THE DISSECTOR. SPINAL CORD. The dissection of the spinal cord requires that the spinal column should be opened throughout its entire length by sawing through the laminae of the vertebrae, close to the roots of the transverse processes, and raising the arches with a chisel ; the muscles of the back having been removed as a preliminary step. The spinal column contains the spinal cord, or medulla spinalis ; the roots of the spinal nerves ; and the membranes of the cord, viz : the dura mater, arachnoid, pia mater, and membrana dentata. The dura mater spinalis (theca vertebralis) is a cylindrical sheath of fibrous membrane, identical in structure with the dura mater of the skull, and continuous with that membrane. At the margin of the occipital foramen it is closely adherent to the bone ; by its anterior surface it is attached to the posterior common ligament, and below, by means of its pointed extremity, to the coccyx. In the rest of its extent it is comparatively free, being connected, by a loose cellular tissue, to the walls of the spinal canal. In this cellular tissue there exists a quantity of reddish, oily, adipose substance, somewhat analogous to the marrow of long bones. On either side, and below, the dura mater forms a sheath for each of the spinal nerves, to which it is closely adherent. Upon its inner surface it is smooth, being lined by the arachnoid ; and on its sides may be seen double openings for the two roots of each of the spinal nerves. The arachnoid is a continuation of the serous membrane of the brain. It incloses the cord very loosely, being connected to it only by long slender filaments 1 of cellular tissue, and by a longi- tudinal lamella which is attached to the posterior aspect of the cord. The cellular tissue is most abundant in the cervical region, and diminishes in quantity from above downwards ; and the longitudinal lamella is complete only in the dorsal region. The arachnoid passes off from the cord on either side with the spinal nerves, to which it forms a sheath ; and is then reflected on the dura mater, to constitute its serous surface. A connection exists in several places 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. It is occupied by a serous fluid, sufficient in quantity to expand the arachnoid and fill completely the cavity of the theca vertebralis. The sub-arachnoidean or cerebro-spinal jluid keeps up a con- stant and gentle pressure on the entire surface of the brain and 1 According to Mr. Rainey, these filaments are nervous fasciculi, hav- ing their origin in the arachnoid, and passing to the arteries of the cord. See p. 208. SPINAL CORD. 247 spinal cord, and yields with the greatest facility to the various movements of the cord, giving to those delicate structures the advantage of the principles so usefully applied by Dr. Arnott in the hydrostatic bed. The pia mater 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 mem- brane ; but is dense and fibrous in structure, and contains but few vessels. It invests the cord closely, and sends a duplicature into the fissura longitudinalis anterior, and another, extremely delicate, into the fissura 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, is prolonged downwards as a slender ligament (filum terminale), which descends through the centre of the cauda equina, and is attached to the dura mater lining the canal of the coccyx. This attachment is a rudiment of the original extension of the spinal cord into the canal of the sacrum and coccyx. The pia mater has, distributed to it, a number of nervous plexuses derived from the sympathetic. The membrana dentata (ligamentum dentatum) is a thin pro- cess of pia mater sent off from each side of the cord throughout its entire length, and separating the anterior from the posterior roots of the spinal nerves. The number of serrations on each side is about twenty, the first being situated on a level with the occipital foramen, and having the vertebral artery and hypoglos- sal nerve passing in front, and the spinal accessory nerve behind it, and the last opposite the first or second lumbar vertebra. Below this point, the merabrana dentata is lost in the filum ter- minale of the pia mater. The use of this membrane is to main- tain the position of the spinal cord in the midst of the fluid by which it is surrounded. The spinal cord of the adult, somewhat less than eighteen inches in length, extends from the pons Yarolii to opposite the first or second lumbar vertebra, where it terminates in a rounded point; in the child, at birth, it reaches the middle of the third lumbar vertebra, and in the embryo is prolonged as far as the coccyx. It presents a difference of diameter in different parts of its extent, and exhibits three enlargements. The uppermost of these is the medulla oblongata ; the next corresponds with the origin of the nerves destined to the upper extremities (brachial) ; and the lower enlargement (lumbar) is situated near its termina- tion, and corresponds with the attachment of the nerves which are intended for the supply of the lower limb. The brachial enlargement is flattened from before backwards, and extends from the third cervical vertebra to the first dorsal ; the lumbar 248 THE DISSECTOR. enlargement is flattened from side to side, and is smaller than the brachial. The spinal cord gives off near its termination that assemblage of nerves which has received the name of cauda equina. In form, the spinal cord is a flattened cylinder, and presents on its anterior surface a fissure, which extends into the cord to the depth of one-third of its diameter. This is the anterior median fissure. If the sides of the fissure be gently separated, they will be seen to be connected at the bottom by a layer of medullary substance, the anterior white commissure. On the posterior surface another fissure exists, which is so narrow between the second cervical and second lumbar nerve, as to be hardly perceptible. This is the posterior median fissure. It extends more deeply into the cord than the anterior fissure, and terminates in the gray substance of the interior. 1 These two fissures divide the medulla spinalis into two lateral cords, which are connected to. each other by the white commissure which forms the bottom of the anterior fissure, and by a commissure of gray matter situated behind the former. On either side of the poste- rior median fissure is a slight line which bounds on each side the posterior median columns. These columns are most apparent at the uppert part of the cord, in the medulla oblongata, where they have received the name of posterior pyramids. 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 trace, marked only by the attachments of the filaments of the anterior roots. The posterior lateral sulcus is more evident, and is a narrow grayish line, derived from the grayish substance of the interior. Although these fissures and sulci indicate a division of the spinal cord into three pairs of columns, namely, anterior, lateral, and posterior, the posterior median columns being regarded as a part of the posterior columns, it is customary to consider each half of the spinal cord as consisting of two columns only, the antero-lateral and the posterior. The antero-lateral columns are the columns of motion, and comprehend all that part of the cord situated between the fissura longitudinalis anterior and the pos- terior lateral sulcus, the gray line of origin of the posterior roots of the spinal nerves. The posterior columns are the columns of sensation. If a transverse section of the spinal cord be made, its internal structure may be seen and examined. It will then appear to be 1 According to some anatomists, there exists a posterior white commis- sure at the bottom of the posterior median fissure. SPINAL CORD. 249 composed of two hollow cylinders of white matter, placed side by side, and connected by a narrow white commissure. Each cylinder is filled with gray substance, which is connected by a commissure of the same matter (gray commissure). The form of the gray substance, as obseryed in the section, is that of two irregularly curved or crescentic lines joined by a transverse band. Fig. 76. 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 :ir;trhnoid membrane. 3, 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-arach- noidean 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 com- missure, connecting the two lateral halves of the cord. 10. The gray commissure, connecting the two semilunar processes of gray substance. 11. The sulcus longi- tudinalis posterior. 12, 12. The two anterior or motor columns of the spinal cord. 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 posterior root. 19. The spinal nerve dividing into its two primary branches, anterior and posterior. The extremities of the curved lines correspond with the sulci of origin of the anterior and posterior roots of the nerves. The anterior extremities, larger than the posterior, do not quite reach this surface ; but the posterior appear upon the surface, and form a narrow gray line, the sulcus lateralis posterior. The white substance of the spinal cord is composed of parallel fibres, which are collected into longitudinal laminae and extend throughout the entire length of the cora. These laminae are various in breadth, and are arranged in a radiated manner ; one border being thick and corresponding with the surface of the cord, while the other is thin and lies in contact with the gray substance of the interior. According to Rolando, the white substance constitutes a simple nervous membrane, which is folded into 250 THE DISSECTOR. longitudinal plaits, having the' radiated disposition above described. The anterior commissure, according to his description, is merely the continu- ation of this nervous membrane from one lateral cord across the middle line to the other. Moreover, Rolando considers that a thin lamina of pia mater is received between each of the folds from the exterior, while a layer of the gray substance is prolonged between them from within. Cruveilhier is of opinion that each lamella is completely independent of its neighbors, and he believes this statement to be confirmed by patho- logy, which shows that a single lamella may be injured or atrophied, and at the same time be surrounded by others perfectly sound. SPINAL NERVES. The nerves proceeding from the spinal cord are thirty-one pairs. Each nerve arises by two roots, an anterior or motor root, and a posterior or sensitive root. The anterior roots proceed from a narrow white line, anterior lateral sulcus, on the antero-lateral column of the spinal cord, and gradually approach towards the anterior median fissure as they descend. The posterior roots, more regular than the anterior, proceed from the posterior lateral sulcus, a narrow gray stria formed by the internal gray substance of the cord. They are larger, and the filaments of origin more numerous than those of the anterior roots. In the intervertebral foramina there is a ganglion on each of the posterior roots. The first cervical nerve forms an exception to these characters ; its posterior root is smaller than the anterior ; it often joins in whole or in part with the spinal accessory nerve, and sometimes with the hypoglossal : there is frequently no gan- glion upon it, and when the ganglion exists, it is often situated within the dura mater, the latter being the usual position of the ganglia of the last two pairs of spinal nerves. After the formation of a ganglion, the two roots unite, and constitute a spinal nerve, which escapes through the interverte- bral foramen, and separates into an anterior division for the sup- ply of the front aspect of the body, and a posterior division for the posterior aspect. In the first cervical and last sacral and coccygeal nerve this separation takes place within the dura mater, and in the upper four sacral nerves externally to that cavity, but within the sacral canal. The anterior divisions, with the excep- tion of the first two cervical nerves, are larger than the poste- rior; an arrangement which is proportioned to the large extent of surface they are required to supply. The spinal nerves are classed as follows: Cervical . /. .. - V J*. - 8 pairs. Dorsal =^ ' './'.> , . 12 " Lumbar . &%'* > . 5 " Sacral . - . . -'.- : . 5 " Coccygeal . . . .1 pair. SPINAL NERVES. 251 The cervical nerves pass off transversely from the spinal cord ; the dorsal are oblique in their direction ; and the lumbar and sacral, vertical ; the latter form the large assemblage of nerves at the termination of the cord, called cauda equina. The cauda equina occupies the lower third of the spinal canal. The ARTERIES of the spinal cord are, the anterior, posterior, and lateral spinal, which 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 and spinal cord form a complex venous plexus within and around the vertebral canal, and are divisible into three sets : Dorsi-spinal, Meningo-rachidian, Medulli-spinal. The dorsi-spinal form a plexus around the spinous, transverse and articular processes and arches of the vertebrae They re- ceive the returning blood from the dorsal muscles and surround- ing structures, and transmit it, in part to the meningo-rachidian, and in part to the vertebral, intercostal, lumbar, and sacral 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 (longitudinal spinal sinuses), which extend the whole length of the column, one 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 receive the large basi-vertebral veins from the interior of each vertebra. The meningo-rachidian veins communicate superiorly through the anterior condyloid foramina with the internal jugu- lars ; in the neck they pour their blood into the vertebral veins ; in the thorax, into the intercostals; and in the loins and pelvis into the lumbar and sacral veins, the communications being esta- blished through the intervertebral foramina. The medutti-spinal veins are situated between the pia mater and arachnoid; they communicate freely with each other to form plexuses, and send branches through the intervertebral foramina with each of the spinal nerves, to join the veins of -the trunk. 252 THE DISSECTOR. CHAPTER V. ORGANS OF SENSE. The Nose and Nasal Fossce. THE organ of smell consists essentially of two parts: one ex- ternal, the nose; the other internal, the nasal fossce. The dissection of the nose and nasal fossae is to be made on that piece of the face which has been already used in the examination of the pharynx and soft palate (pp. 196, 198). If the cartilages of the nose be dry, they should be softened by steeping in water and brought into a state fit for dissection. Any integument which may have been left on the nose should then be removed, together with cellular tissue, fat, and the remains of muscles. The dissection will be facilitated by stuffing the nostrils with cotton wool. The NOSE is the triangular pyramid projecting from the centre of the face, immediately above the upper lip. Superiorly, it is connected with the forehead, by means of a narrow bridge; in- feriorly, it presents two openings, the nostrils, which overhang the mouth, and are so constructed that the odor of all substances must be received by the nose, before they can be introduced within the lips. The septum between the openings of the nos- trils is called the columna. Their entrance is guarded by a num- ber of stiff hairs (vibrissce), which project across the openings, and act as a filter in preventing the introduction of foreign sub- stances, such as dust, or insects, with the current of air intended for respiration. The anatomical elements of wliich 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 wings (alee], of the nose is extremely thick and dense, so as to be with diffi- culty separated from the fibro-cartilage. It is furnished with an abundance of sebaceous follicles, which, 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 color near the surface, from altered secretion and also from 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 com- THE NOSE. 253 pressed, the inspissated sebaceous secretion is squeezed out from the follicles, and, taking the cylindrical form of their excretory ducts, has the appearance of small white maggots with black heads. 2. The muscles are brought into view by reflecting the integu- ment ; they are the pyramidalis nasi, compressor nasi, dilator naris, levator labii superioris ala3que nasi, and depressor labii superioris alaeque nasi. They have been already described with the muscles of the face. 3. The bones of the nose are the nasal, and nasal processes of the superior maxillary. 4. The Jibro-cartilages give form and stability to the outwork of the nose, providing, at the same time, by their elasticity, against injuries. They are five in number, namely, the Fibro-cartilage of the septum, T\vo lateral fibro-cartilages, Two alar fibro-cartilages. The Jibro-cartikige of the septum, somewhat triangular in form, divides the nose into its two nostrils. It is connected above with the nasal bones and lateral fibro-cartilages ; behind, with the ethmoidal septum and vomer; and below, with the palate processes of the superior maxillary bones. The alar fibro-carti- lages and columna move freely upon the fibre-cartilage of the septum, being but loosely connected with it by perichondrium. The IiitiTfil Jibro-cartilages are also triangular ; they are con- nected, in front, with the fibro-cartilage of the septum ; above, with the nasal bones ; behind, with the nasal processes of the superior maxillary bones ; and below, with the alar fibro-carti- lages. Alar Jibro-cartilages. Each of these cartilages is curved in such a manner as to correspond with the walls of the nostril, to which it forms a kind of rim. The inner portion is loosely con- nected 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 on the side makes a curve corresponding with that of the ala. This curve is prolonged downwards and forwards in the direction of the posterior border of the ala by three or four small fibro-cartilaginous plates (sesa- moid cartilages, cartilagines minores), which are appendages of the alar fibro-cartilage. The whole of these fibro-cartilages are connected with each other and to the bones by perichondrinm, which, from its mem- branous structure, permits of the freedom of motion existing between them. 5. The mucous membrane, lining the interior of the nose, is 22 254 THE DISSECTOR. continuous with the skin externally, and with the pituitary mem- brane of the nasal fossae within. Around the entrance of the nostrils it is provided with the vibrissce. Fig. 77. VIEW or THE BONES AND CARTI- FRONT VIEW OP THE CARTI- LAGES OF THE OUTER NOSE, FROM LAGES OF THE NOSE. Above is THE RIGHT SIDE. a. Nasal bone. seen the outline of the nasal bones. b. Nasal process of upper maxillary a. Front edge of the septal car- bone. 1. Right upper lateral car- tilage. b, b. Lateral cartilages, c, c. tilage. 2. Lower lateral cartilage, Alar cartilages, with their append- its outer part. 2*. Innjer part of ages. the same. 3. Sesamoid cartilages. 6. Vessels and Nerves. The arteries of the nose are the late- ralis nasi from the facial, and nasalis septi from the superior coronary. Its nerves are the facial, infra-orbital, and nasal branch of the ophthalmic. NASAL FOSSAE. To obtain a view of the nasal fossce, the face must be divided through the nose by a vertical incision a little to one side of the middle line. This incision should be made with the scalpel through the nose, and with the saw through one nasal bone, the frontal bone, the cribriform plate of the ethmoidal, and body of the sphenoid above ; and through the palatal process of the superior maxillary and palate bone bdow. When the section is made, the turbinated bones, with the spaces between them, will be exposed on one side, and the septum narium on the other ; both are covered by mucous membrane. The nasal fossae are two irregular, compressed cavities, extend- ing backwards from the nose to the pharynx. They are bounded superiorly by the lateral cartilage of the nose, and by the nasal, sphenoid, and ethmoid bones ; inferiorly by the hard palate ; NASAL VOB8JE. 255 and, in the middle line, they are separated from each other by a bony and fibre-cartilaginous 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 mucous membrane, and serve to increase the surface of that membrane by their prominence and convoluted form. The space intervening between the supe- rior and middle spongy bone is the superior meatus ; the space between the middle and inferior, the middle meatus ; and that between the inferior and the floor of the fossa, the inferior mea- tus. These meatuses are passages which extend from before back- wards, and it is in circulating through and amongst these that the atmosphere deposits its odorant particles upon the mucous Fig. 79. THE OUTER WALL OP THE LEFT NASAL FOSSA COVERED WITH THE PITUI- TARY MEMBRANE. 1. Frontal bone. 2. Nasal bone. 3. Superior maxillary. 4. Sphenoid. 5. The upper spongy bone. 6. Middle spongy bone. 7. Lower spongy bone. The three meatuses of the nose are seen below the three last- named bones. 8. The opening of the Eustachian tube. 9 is beneath the open- ing of the nasal duct. 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 eth- moidal cells, the frontal sinuses, and the antrum maxillare ; and, 256 THE DISSECTOR. in the inferior raeatus, the termination of the nasal duct. In the dried bone there are two additional openings, the spheno-pala- tine 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 pituitary, or Schneiderian ; the former name being derived from the nature of its secretion, the latter from Schneider, who was the first to show that the secretion of the nose proceeded from the mucous mem- brane, and not from the brain, as was formerly imagined. It is closely adherent to the periosteum, constituting what is called a fibro-mucous membrane, and is continuous with the general gastro-pulmonary mucous membrane. From the nasal fossae it may be traced through the openings in the meatuses, into the sphenoidal and ethmoidal cells; into the frontal sinuses; into the antrum 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 posterior nares into the pharynx and mouth, and thence through the lungs and alimentary canal. The surface of the membrane is furnished with a laminated epithelium near the apertures of the nares, and in the rest of its extent with a columnar epithelium supporting innumerable vibra- tile cilia. The ARTERIES of the nasal fossae are the anterior and posterior ethmoidal and spheno-palatine. The ethmoidal arteries are branches of the ophthalmic, and enter the nasal fossae through the foramina in the cribriform plate. They supply the mucous membrane of the upper part of the fossae. The spheno-palatine artery is a branch of the internal maxillary. It enters the nasal fossae with the nasal nerves through the spheno- palatine foramen at the posterior part of the superior meatus, and divides into several branches which are distributed to the mucous membrane of the spongy bones, posterior ethmoidal cells, and antrum. One branch, the artery of the septum, crosses the roof of the fossa, and passes downwards and forwards beneath the mucous membrane of the septum to the anterior palatine canal, where it inosculates with branches of the descending pala- tine artery. The NERVES of the nose and nasal fossae are the olfactory, the nasal and naso-palatine from Meckel's ganglion, and the nasal branch of the ophthalmic. The olfactory nerve is distributed to the mucous membrane of the nasal fossae by means of a number of branches which pass through the foramina in the cribriform plate of the ethmoid bone. NERVES OF THE NOSE. 257 The branches are arranged in three groups, an inner group, red- dish in color and soft, spread out upon the upper part of the septum ; an outer group, whiter and more firm, which descend through bony canals in the outer wall of the nares, and are dis- tributed on the superior and middle spongy bones ; and a middle group, which supply the mucous membrane of the roof of the nasal fossae. The nasal branches of MeckePs ganglion enter the nasal fossaB through the spheno-palatine foramen, and are distributed to the mucous membrane of the superior and middle spongy bones, the posterior ethmoidal cells, and the upper part of the septum. The naso-palatine nerve, also a branch of Meckel's ganglion, enters the nasal fossae with the nasal nerves, and, crossing the roof of the fossae, descends upon the septum beneath the mucous membrane to the naso-palatine canal. Passing through the naso- palatine canal, it enters the anterior palatine canal, and is distri- buted to the papilla behind the incisor teeth, communicating with its fellow of the opposite side and with the anterior palatine nerves. In its course the naso-palatine nerve gives several branches to the raucous membrane of the septum ; and the naso- palatine canal of the left side is in front of that of the right. The naso-palatine nerve, and also the inner group of branches of the olfactory, are best seen by cutting away the osseous portion of the septum, and tearing it away from the mucous membrane. Before this is done, the extent and relations of the cartilage of the septum should be examined. The outer group of branches of the olfactory nerve are to be sought for on the outer wall of the nasal fossae, and the nasal branch of the ophthalmic on the anterior part of its roof beneath the nasal bone. The nasal branch of the ophthalmic nerve enters the nasal fossae by the most anterior of the openings in the cribriform plate of the ethmoid bone, and divides into an internal and external branch. The internal branch is distributed to the mucous membrane of the septum as far as the aperture of the nostril. The external branch continues its course onwards, in a groove, upon the under surface of the nasal bone, passes between the nasal bone and lateral car- tilage, and is distributed to the exterior of the nose, as far as the aperture of the nostril. In the nasal fossae this branch gives off several filaments to the internal surface of the outer wall of the nose. Practical Observations. The mucous membrane is rendered an organ of smell by contact of the odorant particles. 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 hemorrhage 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 sponge against the posterior nares. This is effected by introducing an instrument carrying 22* 258 THE DISSECTOR. a curved spring with an eye at its extremity 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 respiration, 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 recol- lected ; 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 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 necessary 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 appendages of the eye. consisting of the eyelids, conjunctiva, and lachrymal apparatus, are to be examined from the exterior ; and the dis- section necessary for the purpose may be made either during the progress of the dissection of the face or at a later period, for example, after the examination of the nose, one orbit being reserved for the purpose. To expose the tarsal cartilages, all that is necessary is to remove the orbicu- laris palpebrarum muscle. To reach the lachrymal gland, and study the lachrymal canals and nasal duct, the eyelids must be separated from their connections above and below, and turned inwards. The appendages of the eye (tutamina oculi) are, the eyebrows, eyelids, eyelashes, conjunctiva, caruncula lachrymalis, and the lachrymal apparatus. The EYEBROWS (supercilid) are two projecting arches of integ- ument, covered with short thick hairs, which form the upper boundary of the orbits. They are connected beneath with the orliicularis, occipito-frontales, and corrugatores superciliorum muscles ; their use is to shade the eyes from too vivid a light, or protect them from particles of dust and moisture floating over the forehead. The EYELIDS (palpelrce) are two valvular layers placed in front of the eye, serving to defend it from injury by their closure. When drawn open, they leave between them an elliptical space (fissura palpebrarum), the angles of which are called canthi. The outer canthus is formed by the meeting of the two lids at an acute angle. The inner canthus is prolonged for a short distance in- wards, towards the nose, and a triangular space is left between the lids in this situation, which is called the lac,us lachrymalis. EYELIDS. MEIBOMTAN GLANDS. 259 At the commencement of the lacus lachrymalis, upon each of the two lids, is a small angular projection, the lachrymal papilla or tubercle ; and at the apex of each papilla a small orifice (punctum lachrymale), the commencement of the lachrymal canal. The eyelids have, entering into their structure, integument, orbicularis muscle, tarsal cartilages, Meibomian glands, and con- junctiva. The tegumentary cellular tissue of the eyelids is remarkable for its looseness, and for the absence of adipose substance ; it is par- ticularly liable to serous infiltration. The fibres of the orbicu- laris muscle covering the eyelids are extremely thin and pale. The tarsal cartilages are two thin lamella of fibro-cartilage, about an inch in length, which give form and support to the eye- lids. The superior is of a semilunar form, about one-third of an inch in breadth at its middle, and tapering to each extremity. Its lower border is broad and flat ; its upper is thin, and gives jittachment to the levator palpebra3 and to the fibrous membrane of the lids. The inferior Jibro-cartilage is an elliptical band, narrower than the superior, and 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 membrane. Near the inner canthus the tarsal cartilages termi- nate, at the commencement of the lacus lachrymalis, and are attached to the margin of the orbit by the tendo oculi. At their outer extremity they terminate at a short distance from the angle of the canthus, and are retained in their position by means of a decussation of the fibrous structure of the broad tarsal ligament, called the external palpebral or tarsal ligament. The fibrous membrane of the lids is firmly attached to the periosteum, around the margin of the orbit, by its circumference, 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 cartilages in their place, and give support to the lids ; hence it has been named the broad The Meibomian glands are imbedded in the internal surface of the cartilages, and are very distinctly seen on examining the inner aspect of the lids. They have the appearance of parallel strings of penrls, about thirty in number in the upper cartilage, and somewhat fewer in the lower; and open by minute foramina on the edges of the lids. They correspond 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 clustered follicles open ; the latter are 260 THE DISSECTOR. so numerous as almost to conceal the tube by which the secretion is poured out upon the margin of the lids. Occasionally an arch is formed between two of them, 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 eyelashes (cilia), im- portant 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. The duplicatures formed between the globe of the eye and the lids, are called the superior and inferior palpebral sinuses, of which the former is much deeper than the inferior. Where it covers the cornea the conjunctiva is very thin, and closely adherent, and no vessels can be traced into it. Upon the sclerotica it is thicker, and less adherent; but upon the inner surface of the lids is very closely connected, and exceedingly vascular. It is continuous with the general gastro- pulmonary 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 followed through the lachrymal canals into the lachrymal sac, and thence downwards, through the nasal duct, into the inferior meatus of the nose. The caruncula lachrymalis is the small reddish body which occupies the lacus lachrymalis at the inner canthus of the eye. In health, it presents a bright pink tint ; in sickness, it loses its color, and becomes pale. It consists of an assemblage of fol- licles similar to the Meibomian glands, embedded in a fibro-car- tilaginous tissue, and is the source of the whitish secretion which so constantly forms at the inner angle of the eye. It is covered with minute hairs, which are sometimes so long as to be visible to the naked eye. Immediately to the outer side of the caruncula is a slight du- plicature of the conjunctiva, called plica semilunaris, which contains a minute plate of cartilage, and is the rudiment of the third lid of animals, the membrana nictitans of birds. Vessels and Nerves. The palpebrae are supplied internally 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. 261 LACHRYMAL APPARATUS. The lachrymal apparatus consists of the lachrymal gland, with its excretory ducts; the puncta lachrymalia and lachrymal canals; the lachrymal sac and nasal duct. The lachrymal gland is brought into view by detaching the broad tarsal ligament from its connection with the upper margin of the orbit, and removing some cellular tissue and fat. The gland has been already described with the dissection of the orbit (p. 139). At the present time the relations of the palpebral portion may be more accurately observed, together with the excretory ducts. The lachrymal gland consists of two portions, orbital and palpebral. The orbital portion, the larger of the two, is flattened in form, and lies against the periosteum of the orbit, its anterior border being in relation with the broad tarsal ligament. The palpebral portion is connected with the anterior border of the orbital portion, by means of the dense fibrous membrane, which invests both portions. It is oblong in shape, lies in contact with the broad tarsal ligament, and is in relation, by its lower border, with the tarsal cartilage of the upper lid. The excretory ducts of the lachrymal gland are eight to twelve in number. They open upon the conjunctiva, in the direction of a curved line, situated a little above the tarsal cartilage at the outer part of the upper lid. Lachrymal Canals. The lachrymal canals commence at the minute openings, puncta lachrymalia, seen upon the lachrymal papillae of the lids at the outer extremity of the lacus lachryma- lis, and proceed inwards to the lachrymal sac, where they termi- nate beneath a valvular semilunar fold of the lining membrane of the sac. The superior duct at first ascends, and then turns suddenly inwards towards the sac, forming an abrupt angle. The inferior duct forms the same kind of angle, by descending at first, and then turning abruptly inwards. 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 is the upper extremity of the nasal duct, and is scarcely moro dilated than the rest of the canal. It is lodged in the groove of the lachrymal bone, and is often dis- tinguished, internally, from the nasal duct, by a semilunar or cir- cular valve. The sac consists of mucous membrane, but is covered in, and retained in 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, which arises from the same ridge, and in its action 262 THE DISSECTOR. upon the lachrymal canals may serve to compress the lachrymal sac. The nasal duct is a short canal, about three-quarters of an inch in length, directed downwards, backwards, and a little outwards Fig. 80. THE LACHRYMAL AP- PARATUS AND TARSAL CARTILAGES OF THE EYE- LIDS. 1. The tarsal car- tilage of the upper lid. 2. The tarsal cartilage of the lower lid ; the openings along the edges of the lids are those of the Meibo- mian ducts. 3. The ca- runcula lachrymalis. 4. The lachrymal gland pour- ing 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 termination in the inferior naeatus of the nose. 10. The inferior turbinated bone. to the inferior meatus of the nose, where it terminates by an ex- panded orifice. 1 It is lined by mucous membrane, which is con- tinuous with the conjuctiva above, and with- the pituitary mem- brane of the nose below. Obstruction, from inflammation and suppuration of this duct, constitutes the disease called fistula lachrymalis. Vessels and Nerves. The lachrymal gland is supplied with blood by the lachrymal branch of the ophthalmic artery ; and with nerves, by the lachrymal branch of the ophthalmic nerve. THE EYEBALL. The form of the eyeball is that of a sphere, of about one inch in diameter, having the segment of a smaller sphere engrafted upon its anterior surface, which increases its antero-posterior diameter. The axes of the two eyeballs are parallel with each other, but 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. [This orifice is more slit-like than "expanded."] THE EYEBALL. 263 For the dissection of the eyeball, the student must procure some sheep's eyes from the butcher ; the eyes in his own subject will be too far advanced in decomposition to be made use of by the time he is able to give his attention to them. Should he be able to procure a fresh human eye, the difficulty will be removed ; but for all the purposes of dissection, the sheep's or bullock's eye is preferable. For external form, he must study the human eye. To examine the exterior of the eyeball, the muscles, fat, and cellular tissue which invest it must be carefully dissected away. The globe of the eye is composed of tunics, and of refracting media called humors. The tunics are three in number, the 1. Sclerotic and cornea. 2. Choroid, iris, and ciliary processes, 3. Retina and zonula ciliaris. The humors are also three Aqueous, Crystalline (lens), Yitreous. FIRST TUNIC. The sclerotic and cornea form the external tunic of the eyeball, and give it its peculiar form. Four-fifths of the globe are invested by the sclerotic, the remaining fifth by the cornea. The sclerotic (crx^poj, 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 is pierced by that nerve as well as by the ciliary nerves and arteries. Anteriorly it presents a bevelled edge, which re- ceives 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 albugitiea, derived from the ex- pansion 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 mu- cous membrane of the front of the eye, the conjunctiva ; and, by reason of the brilliancy of its whiteness, 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 (lamina cribrosa), which is pierced by a number of minute openings for the passage of the nervous fila- ments. 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 eyeball. The cornea (corneus, horny) is the transparent projecting layer that constitutes the anterior fifth of the globe of the eye. In its form it is circular, concavo-convex, and resembles a watch-glass. It is received by its edge, which is sharp and thin, within the bevelled border of the sclerotic, to which it is very firmly attached, and it is somewhat thicker than the anterior portion of that 264 THE DISSECTOR. tunic. When examined from the exterior, its vertical diameter is seen to be about one-sixteenth shorter than the transverse, in consequence of the overlapping above and below, of the margin Fig. 81. THE EXTERNAL TUNIC OF THE EYE. 1. The sclerotic coat. 2. The tunica albuginea, formed by the expansion of the tendons of the four recti muscles. 3. The inser- tion of the superior rectus. 4. The insertion of the inferior rectus. 5. The insertion of the external rectus. 6. Small open- ings in the sclerotic for the passage of the ciliary arte- ries and nerves. 7. The optic nerve, which be- comes constricted at its point of entrance into the globe of the eye. 8. The of the sclerotica; on the interior, however, its outline is perfectly circular. The cornea is composed of four layers : namely, of the conjunctiva, of the cornea proper (which consists of several thin lamellae connected together by an extremely fine cellular tissue), of the cornea elastica (a " fine, elastic, and exquisitely transparent membrane, exactly applied to the inner surface of the cornea proper"), and of the lining membrane of the anterior chamber of the eyeball. The cornea elastica is remarkable for its perfect transparency even when submitted for many days to the action of water or alcohol, while the cornea proper is rendered opaque by the same immersion. To expose this membrane, Dr. Jacob suggests that the eye should be placed in water for six or eight days, and then that all the opaque cornea should be removed layer after layer. Another cha- racter of the cornea elastica is its great elasticity, which causes it to roll up when divided or torn, in the same manner as the capsule of the lens. The use of this layer, according to Dr. Jacob, is " to preserve the requisite permanent correct curvature of the flaccid cornea proper." The opacity of the cornea, produced by pressure on the globe, results from infiltration of fluid into the cellular tissue connecting its layers. This appearance cannot be produced in a sound living eye, although a small quantity of serous fluid (liquor cornese) is said to occupy the areolfe of the cellular tissue. Dissection. The sclerotic and cornea are now to be dissected away from the second tunic. This, with care, may be easily performed, the only firm connections subsisting between them being at the circumfer- ence 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 CHOROID MEMBRANE. 265 bit. Then separate it from its attachment around the circumference of the iris by a gentle pressure with the edge of the knife. The dissection oi tli. eye must be conducted under water. In the course of this dissection the ciliary nerves and long ciliary arte- ?vYx will be seen passing forwards between the sclerotic and choroid, to be distributed to the iris. SECOND TUNIC. The second tunic of the eyeball is formed by the choroid, ciliary ligament, and iris, the ciliary processes being an appendage developed from its inner surface. The choroid 1 is a vascular membrane of a rich chocolate-brown color upon its external surface, and of a deep black color within. It is connected to the sclerotic, externally, by an extremely fine cellular tissue (membrana fusca), and by 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 with the line of junction of the cornea and sclerotic, by a dense white structure, the ciliary ligament, which surrounds the circumference of the iris like a ring. Fig. 82. THE SECOND TUNIC OF THE EYE. 1. The choroid membrane upon which arc seen the curved lines marking the arrangement of the venae vorticosse. 2, 2. Ciliary nerves. 3. A long ciliary artery and nerve. 4. The ciliary li- gament. 5. The iris: the two sets of fibres are very distinctly seen, the exter- nal, radiating towards the centre, and the internal, circular, surrounding the pupil (6). The choroid membrane is composed of three layers, an external or venous layer, which consists principally of veins arranged in a peculiar manner : hence they have been named vence vorticosce. The marking on 1 The word choroid has been very much abused in anatomical lan- guage. It was originally applied to the membrane of the foetus called chorion, from the Greek word xf+iw (domicilium), that membrane being, as it were, the abode or receptacle of the foetus. Xo>ov comes from x.uptot, to take or receive. Now it so happens that the chorion in the ovum is a vascular membrane of peculiar structure. Hence the term choroid (%& ?tn iftof, like the chorion) has been used indiscriminately to signify vascular structures, (as in the choroid membrane of the eye, the choroid plexus, &c.) ; and we find Cruveilhier (in his work on Anatomy, vol. iii. p. 463) saying, in a note, "Choroide eat synonyme de vasculeuse." 23 266 THE DISSECTOR. 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. The middle or arterial- layer (tunica Ruyschiana), is formed principally by the ramifications of minute arteries. It is reflected inwards at its junction with the ciliary ligament, so as to form the ciliary processes. The internal layer is a de- licate membrane (membrana pigmenti), composed of several laminse of nucleated hexagonal cells, which contain the granules of pigmenturn, and are arranged so as to resemble a tessellated pavement. In animals, the pigmentum nigrum, on the posterior wall of the eye- ball, is replaced by a layer of considerable extent and of metallic bril- liancy, called the tapetum. The ciliary ligament, or circle (annulus albidus), is the bond of union between the external and middle tunics of the eyeball, and serves to connect the cornea and sclerotic, at their line of junction, with the iris and external layer of the choroid. It is also the point to which the ciliary nerves and vessels proceed previously to their distribution, and it receives the anterior ciliary arteries through the anterior margin of the sclerotic. A minute vascular canal is situated within the ciliary ligament, called the ciliary canal, or the canal of Fontana, from its dis- coverer. The iris (iris, a rainbow), is so named from its variety of color in different individuals : it forms a septum between the anterior and posterior chambers of the eye, and is pierced somewhat to the nasal side of its centre by a circular opening, which is called the pupil. By its periphery it is connected with the ciliary liga- ment, and by its inner circumference forms the margin of the pupil ; its anterior surface looks towards the cornea, and the pos- terior towards the ciliary processes and lens. The iris is composed of two layers, anterior or muscular, consisting of radiating fibres, which converge from the circumference towards the centre, and have the power of dilating the pupil, and circular, which surround the pupil like a sphincter, and by their action produce con- traction of its area. The posterior layer is of a deep purple tint, and is thence named uvea, from its resemblance in color to a ripe grape. The -ciliary processes (corpus ciliare), 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. They consist of a number of triangular folds, formed apparently by the plaiting of the middle and internal layer of the choroid. According to Zinn, they are about sixty in number, and may be divided into large and small, the latter being situated in the spaces between the former. Their periphery is connected with the ciliary liga- ment, and is continuous with the middle and internal layer of the choroid. The central border is free, and rests against the cir- THE RETINA. 26t cumference of the lens. The anterior surface corresponds with the uvea; the posterior receives the folds of the zonula ciliaris between its processes, and thus establishes a connection between the choroid and the third tunic of the eye. The ciliary pro- cesses are covered with a thick layer of pigmentum nigrum, which is more abundant upon them, and upon the anterior part of the choroid, than upon the posterior part of the latter. When the pigment is washed off, the processes are of a whitish color. THIRD TUNIC. The third tunic of the eye is the retina, which is prolonged forwards to the lens by the zonula ciliaris. I>i. section. If, after the preceding dissection, the choroid membrane be carefully raised and removed, the eye being kept under water, the retina may be seen very distinctly. The retina is composed of three layers : External, or Jacob's membrane, Middle, Nervous membrane, Internal, Vascular membrane. Jacobs membrane is extremely thin, and is seen as a mere film when the freshly dissected eye is suspended in water. Examined by the microscope, it is found to be composed of cells having a tessellated arrangement. Dr. Jacob considers it to be a serous membrane. The nervous membrane is the expansion of the optic nerve, and forms a thin semi-transparent bluish-white layer, which en- velopes the vitreous humor, and extends forward to the com- mencement of the ciliary processes, where it ter- Fig. 83. minates by an abrupt scalloped margin. Ac- cording to Treviranus, this layer is composed of cylindrical fibres, which proceed from the optic nerve, and, near their termination, bend abruptly inwards, to form the internal papil- lary layer, which lies in contact with the hyaloid membrane : each fibre THE THIRD TtJNIC OF THE EYE. 1. The re- ** 4r- u * tina terminating anteriorly in a scalloped border. Constituting by Its extre- 2 . The foramen of Soemmering. 3. The zonula mity a distinct papilla. ciliaris. 4. The lens. The vascular mem- brane consists of the ramifications of a minute artery, the arteria 268 THE DISSECTOR. centralis retinae, and its accompanying vein : the artery pierces the optic nerve, and enters the globe of the eye through the poms 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 continued anteriorly into the zonula ciliaris. The vascular layer forms distinct sheaths for the nervous papilla?, which constitute the inner surface of the retina. In the centre of the posterior part of the globe of the eye the retina presents a circular spot, which is called the foramen of Soemmering ; it is surrounded by a yellow halo, the limbm luteus, and is frequently obscured by an elliptical fold of the retina, which has been regarded as a normal condition of the membrane. The term foramen is misapplied to this spot, for the vascular layer and the membrana Jacobi are continued across it ; the nervous substance alone appearing to be deficient. It exists only in ani- mals having the axes of the eyeballs parallel with each other, as man, quadrumana, and some saurian reptiles, and is said to give passage to a small lymphatic vessel. The zonula ciliaris (zonula of Zinn) is a thin vascular layer, which connects the anterior margin of the retina with the ante- rior surface of the lens near its circumference. It presents upon its surface a number of small folds corresponding with the ciliary processes, between which they are received. 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 derive their vessels from the vascular layer of the retina. The under surface of the zonula is in contact with the hyaloid membrane, and around the lens forms the anterior fluted wall of the canal of Petit. The connection between these folds and the ciliary processes may be demonstrated by dividing an eye transversely into two portions, then raising the anterior half and allowing the vitreous humor to fall out by its own weight. The folds of the zonula will then be seen to be drawn out from between the folds of the ciliary processes. HUMORS. The aqueous humor is situated in the anterior and posterior chambers of the eye ; it is a weakly albuminous fluid, with an alkaline reaction, and a specific gravity very little greater than that of distilled water. According to Petit, it scarcely exceeds four or five grains in weight. The anterior chamber is the space intervening between the cor- nea in front, and the iris and pupil behind. The posterior chamber is the narrow space, less than half a line in depth, 1 bounded by the posterior surface of the iris and pupil in front, 1 Winslow and Lieutaud thought the iris to be in contact with the lens. It frequently adheres to the capsule of the latter in iritis. The depth of the posterior chamber is greater in old than in young persons. HUMORS OP THE EYE. 269 and by the ciliary processes, zonula ciliaris, and lens behind. The two chambers are lined by a thin layer, the secreting membrane of the aqueous humor. The vitreous humor forms the principal bulk of the globe of the eye. It is an albuminous and highly transparent fluid, in- Fig. 84. A LONGITUDINAL SEC- TION OF THE GLOBE OF THE EVE. 1. The sclerotic, thicker behind than the front. 2. The lamina cri- brosa ; the thin layer of the sclerotic, which is pierced with holes for the ]i:i.^:i#e of the nervous sub- stance of the optic nerve. 3. The cornea, which is seen to be inserted into the border of the sclerotic coat 4. The choroid membrane (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 border of the retina of 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 inclosed in its capsule. 14. The posterior cavity of the globe, in which the vitreous humor is lodged. 15. A minute ar- tery, a branch of the anterior centralis retinae, which traverses the centre of the vitreous humor to reach the capsule of the lens. closed in a delicate membrane, the hyaloid. From the inner surface of this membrane, numerous thin lamellae are directed inwards, and form compartments in which the fluid is contained. According to Hanover, these lamellae have a radiated arrange- ment, like those on the transverse section of an orange, and are about 180 in number. In the centre of the vitreous humor is a tubular canal, through which a minute artery is conducted from the arteria centralis retinai to the capsule of the lens. This ves- sel is injected without difficulty in the foetus. The crystalline humor or lens is situated immediately behind the pupil, and is surrounded by the ciliary processes, which tiirhtly overlap its margin. It is more convex on the posterior than on the anterior surface, and is imbedded in the anterior part of the vitreous humor, from which it is separated by the hyaloid membrane. It is invested by a peculiarly transparent and elastic membrane, the capsule of the lens, which contains a small quan- tity of fluid, called liquor Morgayni, and is retained in its place 23* 270 THE DISSECTOR. by the attachment of the zonula ciliaris. Dr. Jacob is of opinion that the lens is connected to its capsule by means of cellular tissue, and that the liquor Morgagni is the result of a cadaveric change. The lens consists of concentric layers, of which the external are soft, the next firmer, and the central form a hardened nucleus. These layers are best demonstrated by boiling, or by immersion in alcohol, when they separate easily from each other. Another division of the lens takes place at the same time : it splits into three triangular segments, which have the sharp edge directed towards the centre, and the base towards the circumference. The concentric lamellae are composed of minute parallel fibres, which are united with each other by means of scalloped borders, the convexity on the one border fitting into the concave scallop upon the other. Immediately around the circumference of the lens is a triangu- lar canal, the canal of Petit, about a line and a half in breadth. It is bounded, in front by the flutings of zonula ciliaris ; behind, by the hyaloid membrane ; and within, by the border of the lens. 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 forward on each side, between 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 middle layer of the choroid membrane. The anterior ciliary are branches of the muscular arteries. They enter the eye through the anterior part of the sclerotic, and are distributed to the iris. It is the increased number of these latter arteries, in iritis, that gives rise to the peculiar red zone around the circumference of the cornea. The arteria centralis retina enters the optic nerve at about half an inch from the globe of the eye, and, passing through the porns opticus, is distributed upon the inner surface of the retina, forming its vascular layer; one branch pierces the centre of the vitreous humor and supplies the capsule of the lens. The nerves of the eyeball are the optic, two ciliary nerves from the nasal branch of the ophthalmic, and the ciliary nerves from the ophthalmic ganglion. 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 nutrition 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 THE ORGAN OF HEARING. 271 thin, and the rays of light pass through its substance, they are immediately absorbed by the uvea; and if that layer be insuffi- cient, they are taken up by the black pigment of the ciliary processes. In Albinoes, where there is an absence of pigmentuin nigrum, the rays of light traverse the iris, and even the sclerotic, and so overwhelm the eye with light, that sight is destroyed, except in the dimness of evening, or at night. In the manu- facture of optical instruments, care is taken to color their inte- rior black, with the same object, the absorption of scattered rays. The transparent lamellated cornea and the humors of the eye have for their office the refraction of the rays in such proportion as to direct the image in the most favorable manner upon the retina. Where the refracting medium is too great, as in over convexity of the cornea and lens, the image falls short of the retina (myopia, near-sightedness); and where it is too little, the image is thrown beyond the nervous membrane (presbyopia, far- sightedness). These conditions are rectified by the use of spectacles, which provide a differently refracting medium ex- ternally to the eye, and thereby correct the transmission of light. THE ORGAN OP HEARING. The apparatus of hearing is composed of three parts, the ex- ternal ear, middle ear or tympa- num, and internal ear or labyrinth. The EXTERNAL EAR consists of two portions, the pinna and mea- tits ; the former representing a kind of funnel which collects the vibrations of the atmosphere, pro- ducing 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 nuuies assigned to them. Thus, tlio external folded margin is called the helix (?*e|, a fold). The elevation parallel to and in front of the helix is called antihelix i, opposite). The pointed Fig. 85. A VIEW OF THE LEFT EAR IN ITS NATURAL STATE. 1, 2. The origin and termination of the helix. 3. The antihelix. 4. The antitragus. 5. The tra- gus. 6. The lobus of the external ear. 7. Points to the scapha, and is on the front and top of the pinna. 8. The concha. 9. The meatus auditorius ex- tern us. 2T2 THE DISSECTOR. process, projecting like a valve over the opening of the ear from the face, is called the tragus (rpayoj, a goat), probably from being sometimes covered with bristly hair like that of a goat ; and a tubercle opposite to this is the antitragus. The lower de- pendent and fleshy portion of the pinna is the lobulus. The space between the helix and antihelix is named the fossa innominata (scaphoidea). Another depression is observed at the upper ex- tremity of the antihelix, which bifurcates and leaves a triangular space between its branches, called the fossa triangularis (ovalis) ; and the large central space, to which all the channels converge, is the concha, which opens directly into the meatus. The pinna is composed of integument, fibro- cartilage, ligaments, and muscles. The integument is thin, contains an abundance of sebaceous glands, and is closely connected with the fibro- cartilage. The integument should be dissected off from the fibro-cartilage, a task of some difficulty, in consequence of the close adhesion which subsists between them, in order to bring into view the cartilage with its ligaments and muscles. Over the muscles the integument must be raised with care, as, from their paleness, they might otherwise be dissected away. The fibro-cartilage gives form to the pinna, and is folded so as to produce the various convexities and grooves which have been described upon its surface. The helix commences in the concha, and partially divides that cavity into two parts ; on its anterior border, where it commences its curve upwards, is a tubercle or spine, and a little above this a small vertical fissure, the fissure of the helix. The termination of the helix and antihelix forms a lengthened process, the processus caudatus, which is separated from the concha by an extensive fissure. Upon the anterior sur- face of the tragus is another fissure, thejissure of the tragus, and, in the lobulus, the fibro-cartilage is wholly deficient. The fibro- cartilage of the meatus is divided from the concha by several fis- sures (fissures of Santorinus), and at the upper arid anterior part of the cylinder there is a considerable space, which is closed by ligamentous fibres ; it is firmly attached at its termination to the processus auditorius. ; . - The ligaments of the external ear are those which attach the pinna to the side of the head, viz : the anterior, posterior, and ligament of the tragus ; and those of the fibro-cartilage, which serve to preserve its folds and connect the opposite margins of the fissures. The latter are two in number, the ligament between the concha and the processus caudatus, and the broad ligament which extends from the upper margin of the fibro-cartilage of the tragus to the helix, and completes the meatus. TYMPANUM. 273 The proper muscles of the pinna are the Major helicis, Antitragicus, Minor helicis, Transversus auriculae, Tragicus, Obliquus auris. The major helicis is a narrow band of muscular fibres situated upon the anterior border of the helix. It arises from the spine of the helix, and is inserted into the anterior border of that fold. The minor helicis is placed upon the anterior extremity (crus) of the helix, at its commencement in the fossa of the concha. The tragicus is a thin quadrilateral layer of muscular fibres, situated upon the tragus. The antitragicus arises from the antitragus, and is inserted into the posterior surface of the processus caudatus of the helix. The transversus auriculae, partly tendinous and partly muscu- lar, extends transversely from the convexity of the concha to that of the helix, on the posterior surface of the pinna. The obliquus auris (Tod) is a small band of fibres passing be- tween the upper part of the convexity of the concha and the con- vexity immediately above it. Mr. Tod 1 describes, besides, a contractor meatiis, or trago- helicus muscle. The MEATUS AUDITORIUS is a canal, partly cartilaginous and partly osseous, about an inch in length, which extends inwards and a little forwards from the concha to the tympanum. It is narrower in the middle than at each extremity, forms an oval cylinder, the long diameter being vertical, and is slightly curved upon itself, the concavity looking downwards. It is lined by an extremely thin pouch of epithelium, which, when withdrawn after maceration, preserves the form of the meatus. Some stiff short hairs are also found in its interior, which stretch across the tube, and prevent the ingress of insects and dust. In the substance of its lining membrane are a number of ceruminous glands, which secrete the wax of the ear. Vessels and Nerves. The pinna is plentifully supplied with arteries by the anterior auricular from the temporal ; by the posterior auricular from the external carotid ; and by a branch from the occipital artery. Its nerves are derived from the auriculo-temporal of the fifth, the posterior auricular of the facial, and the auricularis magnus of the cervical plexus. MIDDLE EAR OR TYMPANUM. The tympanum is an irregular bony cavity, compressed from without inwards, and situated within the petrous bone. It is 1 " The Anatomy and Physiology of the Organ of Hearing," by David Tod. 1832. 2T4 THE DISSECTOR. bounded, externally, by the meatus and membrana tympani ; inter- nally, by the base of the petrous bone ; behind, by the mastoid cells ; and, throughout the Fi S- 86 - rest of its circumference, by the thin osseous layer which connects the petrous with the squamous portion of the temporal bone. The membrana tympani is a thin and semi-trans- parent membrane of an oval shape, its long diame- ter being vertical. It is MEMBRANA TYMPANI FROM THE OUTER (A) in?prtpH into n o-rnnvA cif AND FROM THE INNER ( B ) SlDBB.-l. Mem- ] * mtO a grOOVC Slt- brana tympani. 2. Malleus. 3. Stapes. 4. ua ted around the Circum- incus. ference of the meatus, near its termination, and is placed obliquely across the area of that tube, the direction of the obliquity being downwards and inwards. It is concave towards the meatus, convex towards the tympanum, and composed of three layers, external, or epithelial ; middle, fibrous and muscu- lar ; and internal, mucous, derived from the mucous lining of the tympanum. The tympanum contains three small bones, ossicula auditus, viz : the malleus, incus, and stapes. The malleus (hammer) consists of a head, neck, handle (manu- brium), and two processes, long (processus gracilis) and short (processus brevis). The manubrium is connected with the mem- brana tympani by its whole length, extending below the central point of that membrane. It lies beneath the mucous layer of the membrane, and serves as a point of attachment to which the radiating fibres of the fibrous layer converge. The long process descends to a groove near the fissura Glaseri, and gives attach- ment 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 than, and widely separated from, the other. It consists of two processes, which unite nearly at right angles, and at their junction form a flattened body, which articulates with the head of the malleus. The short process is attached to the mar- gin of the opening of the mastoid cells by means of a ligament ; the long process descends nearly parallel with the handle of the malleus, and curves inwards, near its termination. At its extre- mity is a small globular projection, the os orbiculare, which in TYMPANUM. 275 the foetus is a distinct bone, but becomes anchylosed to the long process of the incus in the adult : this process articulates with the head of the stapes. The stapes is shaped like a stirrup, to which it bears a close resemblance. Its head articulates with the os orbiculare, and the two branches (crura) are connected by their extremities with a flat, oval-shaped plate, representing the foot of the stirrup. The foot of the stirrup is received into the fenestra ovalis, to the mar- gin of which it is connected by means of a ligament : it is in con- tact, by its surface, with the membrana vestibuli, and is covered in by the mucous lining of the tympanum. The neck of the stapes gives attachment to the stapedius muscle. The ossicula auditiis are retained in their position and moved upon themselves by means of ligaments and muscles. The ligaments are three in number, the suspensory ligament of the malleus, which is attached by one extremity to the upper wall of the tympanum, and by the other to the head of the malleus ; the posterior ligament of the incus, a short and thick band which serves to attach the extremity of the short process of that bone to the margin of the opening of the mastoid cells ; and the an- nular ligament which connects the margin of the foot of the stapes with the circumference of the fenestra ovalis. These ligaments have been described as muscles, by Mr. Tod, under the names of superior capitis mallei, obliquus incudis externus posterior, and musculus vel structura stapedii inferior. Arnold adds as a fourth a suspensory ligament of the incus. The muscles of the tympanum are four in number, the Tensor tympani, Laxator tympani, Laxator tympani minor, Stapedius. The tensor tympani (musculus internus mallei) arises from the spinous process of the sphenoid, from the petrous portion of the temporal bone, and from the Eustachian tube, and passes forwards in a distinct canal, separated from the tube by the processus cochleariformis, to be inserted into the handle of the malleus, im- mediately below the root of the processus gracilis. The laxator tympani (musculus externus mallei) arises from the spinous process of the sphenoid bone, and passes through an opening in the fissura Glaseri, to be inserted into the neck of the malleus, just above the root of the processus gracilis. This is regarded as a ligament (anterior ligament of the malleus) by some anatomists. The laxator tympani minor (posterior ligament of the malleus) arises from the upper margin of the meatus, and is inserted into 276 THE DISSECTOR. the handle of the malleus, and the processus brevis. This is re- garded as a ligament by some anatomists. The stapedius arises from the interior of the pyramid, and escapes from its summit to be inserted into the neck of the stapes. Foramina. The openings in the tympanum are ten in number, Jive large, frudjive small; they are Large Openings. Meatus auditorius, Fenestra ovalis, Fenestra rotunda, Mastoid cells, Eustachian tube. Small Openings. Entrance of chorda tympani, Exit of the chorda tympani, For the laxator tympani, For the tensor tympani, For the stapedius. The opening of the meatus auditorius has been already de- scribed The fenestra ovalis (fenestra vestibuli) is a reniform opening, situated at the bottom of a small oval fossa (the pelvis ovalis), in the upper part of the inner wall of the tympanum, directly oppo- site the meatus. The long diameter of the fenestra is directed horizontally, and its convex borders upwards. It is the opening of communication between the tympanum and vestibule, and is closed by the foot of the stapes and by the lining membrane of both cavities. The fenestra rotunda (fenestra cochlea?) is somewhat triangular in its form, and situated in the inner wall of the tympanum, below and rather posteriorly to the fenestra ovalis, from which it is Fig. 87. THE TYMPANUM OF THE LEFT EAR. 1. Its inner wall. 2. A convex ridge marking the situa- tion of the aqueductus Fallopii ; the star shows its termination on the face of the section, in its course downwards to the stylo - mastoid foramen. 3. The fe- nestra ovalis. 4. The promon- tory. 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. separated by a bony elevation, called the promontory. It serves to establish a communication between the tympanum and the TYMPANUM. 277 cochlea. In the fresh subject it is closed by a proper membrane (m. tympani secundaria), as well as by the lining of both cavities. The mastoid cells are numerous, and occupy the whole of the interior of the mastoid process and part of the petrous bone. They communicate by a large irregular opening with the upper and posterior circumference of the tympanum. The Eustachian tube is a short canal about an inch and three- quarters in length, extending obliquely between the pharynx and the anterior circumference of the tympanum. In structure it is partly fibro-cartilaginous and partly osseous, is broad and ex- panded at its pharyngeal extremity, and narrow and compressed at the tympanum. The smaller openings serve for the transmission of the chorda tympani nerve, and three of the muscles of the tympanum. The opening by which the chorda tympani enters the tympa- num is at about the middle of its posterior wall, and near the root of the pyramid. The opening of exit for the chorda tym- pani is at the fissura Glaseri in the anterior wall of the tympa- num. The opening for the laxator tympani muscle is also situated in the fissura Glaseri, in the anterior wall of the tympanum. The opening for the tensor tympani muscle is in the inner wall, im- mediately above the opening of the Eustachian tube. The open- ing for the stapedius muscle is at the apex of a conical bony eminence, called the pyramid, which is situated on the poste- rior wall of the tympanum, immediately behind the fenestra ovalis. Directly above the fenestra ovalis is a rounded ridge formed by the projection of the aquceductus Fallopii. Beneath the fenestra ovalis and separating it from the fenestra rotunda is the pro- montory, a rounded prominence formed by the projection of the first turn of the cochlea. It is channelled upon its surface by three small grooves, which lodge the three tympanic branches of Jacobson's nerve. The/orawma and processes of the tympanum may be arranged, according to their situation, into four groups. 1. In the external wall is the meatus auditorius, closed by the membrana tympani. 2. In the inner wall, from above downwards, are the Opening for the tensor tympani, Ridge of the aquaeductus Fallopii, Fenestra ovalis, Promontory, with the grooves for Jacobson's nerve, Fenestra rotunda. 24 278 THE DISSECTOR. 3. In the posterior wall are the Opening of the mastoid cells, Pyramid, and opening for the stapedius, Opening for Jacobson's nerve. Apertura chordae (entrance). 4. In the anterior wall are the Eustachian tube, Fissura Glaseri, Opening for laxator tyrapani, Apertura chordae (exit). The tympanum is lined by a vascular mucous membrane, which invests the ossicula and chorda tympani, and forms the internal layer of the membrana tympani. From the tympanum it is reflected into the mastoid cells, which it lines throughout, and it passes through the Eustachian to become continuous with the mucous membrane of the pharynx. In the Eustachian tube it is furnished with vibratile cilia. Vessels and Nerves. The arteries of the tympanum are de- rived from the internal maxillary, internal carotid, and posterior auricular. Its nerves are 1. Minute branches from the facial, which are distributed to the stapedius muscle. 2. The chorda tympani, which leaves the facial nerve near the stylo-mastoid foramen, and arches upwards to enter the tympanum at the root of the pyra- mid ; it then passes forwards between the handle of the malleus and long process of the incus, to its proper opening in the fissura Glaseri. 3. The tympanic branches of Jacobson's nerve, which 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, otic ganglion, and Vidian nerve. 4. A filament from the otic ganglion to the tensor tympani muscle. INTERNAL EAR. The internal ear is called labyrinth, from the complexity of its communications ; it consists of a membranous and an osseous portion. The osseous labyrinth presents a series of cavities, which are channelled through the substance of the petrous bone, and is situated between the cavity of the tympanum and the meatus auditorius internus. It is divisible into the Yestibule, Semicircular canals, Cochlea. The VESTIBULE is a small three-cornered cavity, compressed from without inwards, and situated immediately within the inner INTERNAL EAR. 279 wall of the tympanum. The three corners, which are named ventricles or cornua, are placed one anteriorly, one superiorly, and one posteriorly. The anterior ventricle receives the oval aperture of the scala vestibuli ; the superior, the ampullary openings of the superior and horizontal semicircular canals ; the posterior, the ampullary opening of the oblique semicircular canal, the common aperture of the oblique and perpendicular canals, the termination of the horizontal canal, and the aperture of the aqureductus vestibuli. Fig. 88. A VIEW OP THE LABYRINTH OF THE LEFT EAR OF A FOETUS OF EIGHT MONTHS, AS SEEN FROM ABOVE. MAGNIFIED FOUR DIAMETERS. 1, 2, 3. The COChlea. 1, 1. Its first turn. 2, 2. Its second turn. 3, 3. Its third or half turn, and apex or cupola. 4. The fenestra rotunda. 5. The fenestra ovalis. 6. The groove around it. 7, 7. The vestibule. 8, 9, 10. The posterior semicircular canal, with its ampulla at 8. 11, 11. The superior semicircular canal. 12. The external semicircular canal. In the anterior ventricle is a small depression, which corresponds with the posterior segment of the cul-de-sac of the meatus audi- torius internus; it is called i\\z fovea hemispherica, and is pierced by a cluster of small openings, the macula cribrosa. In the su- perior ventricle of the vestibule is another small depression, the fovea elliptica, which is separated from the fovea hemispherica by a projecting crest, the eminentia pyramidalis. The latter is pierced by numerous minute openings for the passage of nervous lihuuents. The posterior ventricle presents a third small depres- sion, the fovea sulciformis, which leads upwards to the ostium 280 THE DISSECTOR. aquseductus vestibuli. The internal wall of the vestibule corre- sponds with the bottom of the cul-de-sac of the meatus audito- rius interims, and is pierced by numerous small openings for the Fig. 89. THE LABYRINTH'OF THE LEFT EAR. 1. The vestibule. 2. The fenestra ovalis, in its natural position, looking from the meatus auditorius externus ; the entrance into the vestibule from the tympanum. 3. The perpendicular semicircu- lar canal. 4. Its ampulla. 5. Its union with the oblique canal. 6. The oblique semicircular canal. 7. Its ampulla. 8. The horizontal se- micircular canal. 9. Its ampulla. 10. The cochlea, internal to and rather in front of the vestibule. 11. The fenestra rotunda, the en- trance into the scala tympani of the cochlea. 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. transmission of nervous filaments. In the external or tympanic wall is the reniform opening of the fenestra ovalis (fenestra ves- tibuli), the margin of which presents a prominent rim towards the cavity of the vestibule. The openings of the vestibule 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 Aquaeductus vestibuli, Openings for small arteries, Openings for branches of the auditory nerve. The fenestra ovalis has already been described ; it is the open- ing from the tympanum. The opening of the scala vestibuli is the oval termination of the vestibular canal of the cochlea. The aquceductus vestibuli (canal of Cotunnius) 1 is the com- mencement of the small canal which opens under the osseous scale on the posterior surface of the petrous bone. It gives pas- sage to a process of membrane (which is continuous internally with the lining membrane of the vestibule, and externally with the dura mater), and to a small vein. 1 Dominico Cotunnius, an Italian physician; Ms dissertation, "De Aquseductibus Auris Humanae Internse," was published in Naples in 1761. COCHLEA. 281 The openings for 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 communi- cating with the vestibule, into which they open by both extremi- ties. Near one extremity of each of the canals is a dilatation of its cavity, which is called the ampulla (sinus ampullaceus). The superior, or perpendicular canal (canalis semicircularis verticalis superior), is directed transversely across the petrous bone, form- ing a projection on the anterior face of the latter. It commences, by means of an ampulla, in the superior ventricle of the vestibule, and terminates posteriorly by joining with the oblique and form- ing a common canal which opens into the upper part of the pos- terior ventricle. The middle or oblique canal (canalis semicircu- laris verticalis posterior) corresponds with the posterior part of the petrous portion of the temporal bone ; it commences by an ampullary dilatation in the posterior ventricle, and curves nearly perpendicularly upwards to terminate in the common canal. In the ampulla of this canal are numerous minute openings for nervous filaments. The inferior or horizontal canal (canalis semi- circularis horizontalis) is directed outwards towards the base of the petrous bone, and is shorter than the two preceding. It commences by an ampullary dilatation in the superior ventricle, and terminates in the posterior ventricle. The COCHLEA (snail-shell) forms the anterior portion of the labyrinth, corresponding by its apex with the anterior wall of the petrous bone, and by its base with the anterior depression at the bottom of the cul-de-sac of the *eatus auditorius internus. It consists of an osseous and gradually tapering canal, about one inch and a half in length, which makes two turns and a half spi- rally around a central axis, called the .modiolus. The central axis, or modiolus, is large near its base, where it corresponds with the first turn of the cochlea, and diminishes in diameter towards its extremity. At its base, it is pierced by numerous minute openings, which transmit the filaments of the cochlear nerve. These openings are disposed in a spiral manner : hence they have received, from Cotunnius, the name of tractus spiralis foraminulentus. The modiolus is everywhere traversed, in the direction of its length, by minute canals, which proceed from the tractus spiralis foraminulentus, and terminate upon the sides of the modiolus, by opening into the canal of the cochlea or upon the surface of its lamina spiralis. The central canal of the tractus spiralis foraminulentus is larger than the rest, and is named the tubulus centralis modioli ; it is continued onwards to the extremity of the modiolus, and transmits a nerve and small artery (arteria centralis modioli). 24* 282 THE DISSECTOR. The interior of the canal of the cochlea is partially divided into two passages (scalae) by means of a thin and porous lamina of bone (zonula ossea laminae spiralis), which is wound spirally around the modiolus, in the direction of the canal. The bony septum extends for about two-thirds across the diameter of the canal, and in the fresh subject is prolonged to the opposite wall by means of a membranous layer, so as to constitute a complete partition, the lamina spiralis. This osseous lamina spiralis con- sists of two thin Iamella3 of bone, between which, and through the perforations on their surfaces, the filaments of the cochlear nerve reach the membrane of the cochlea. At the apex of the cochlea, the lamina spiralis terminates by a pointed, hook-shaped process, the haniulus laminae s-piralis. The two scalae of the cochlea, which are completely separated throughout their length in the living ear, communicate superiorly, over the hamulus laminae spiralis, by means of an opening common to both, which has been termed by Breschet helico-trema (e'3ii|, tXi'crtfw, volvere fpr^a}. Inferiorly, one of the two scalae, the scala vestibuli, terminates by means of an oval aperture in the anterior ventricle of the ves- tibule ; whi4e the other, the scala tympani, becomes somewhat expanded, and opens into the tympanum through the fenestra rotunda (fenestra cochleae). Near the termination of the scala tympani is the small opening of the aquaeductus cochleae. The internal surface of the osseous labyrinth is lined by &fibro- serous membrane, which is analogous to the dura mater in per- forming the office of a periosteum by its exterior, whilst it fulfils the purpose of a serous membrane by its internal layer, secreting a limpid fluid, the aqua la^byrinthi (perilymph, liquor Cotunnii), and sending a reflection inwards upon the nerves distributed to the membranous labyrinth. In the cochlea, the membrane of the labyrinth invests the two surfaces of the bony lamina spiralis, and being continued from its border across the diameter of the canal to its outer wall, forms the membranous lamina spiralis, and com- pletes the separation between the scala tympani and scala vestibuli. The fenestra ovalis and fenestra rotunda are closed by an extension of this membrane across them, assisted by the membrane of the tympanum, and a proper intermediate layer. Besides lining the interior of the osseous cavity, the membrane of the labyrinth sends two delicate processes along the aqueducts of the vestibule and cochlea, to the internal surface of the dura mater, with which they are continuous. These processes are the remains of communica- tion originally subsisting between the dura mater and the cavity of the labyrinth. 1 1 Cotunnius regarded these processes as tubular canals, through which, the superabundant aqua labyrinth! might be expelled into the cavity of MEMBRANOUS LABYRINTH. 283 The MEMBRANOUS LABYRINTH is smaller in size, but a perfect counterpart, with respect to form, of the vestibule and semicircular canals. Its consists of a small elongated sac, sacculus communis (utriculus communis) ; of three semicircular membranous canals, which correspond with the osseous canals, and communicate with the sacculus communis ; and of a small round sac (sacculus pro- prius), which occupies the anterior ventricle of the vestibule, and lies in close contact with the external surface of the sacculus communis. The membranous semicircular canals are two-thirds smaller in diameter than the osseous canals. The membranous labyrinth is retained in position by means of the numerous nervous filaments which are distributed to it from the openings of the inner wall of the vestibule, and is separated from the lining membrane of the labyrinth, by the aqua labyrinthi. In structure it is composed of four layers ; an external or serous layer, derived from the lining membrane of the labyrinth ; a vascular layer, in which an abundance of minute vessels are dis- tributed ; a nervous layer, formed by the expansion of the fila- ments of the vestibular nerve ; and an internal and serous mem- brane, by which the limpid fluid which fills its interior is secreted. Some patches of pigment have been observed by Wharton Jones, in the tissue of the membranous labyrinth of man. Among ani- mals such spots are constant. The membranous labyrinth is filled with a limpid fluid, first well described by Scarpa, and thence named liquor Scarpae (endo- lymph, vitreous humor of the ear), and contains two small cal- careous masses called otoconites. The otoconites (ot>$, U.TOJ, xovij, the ear-dust) consist of an assemblage of minute, crystalline par- ticles of carbonate and phosphate of lime, held together by ani- mal substance, and probably retained in form by a reflection of the lining membrane of the membranous labyrinth. They are found suspended in the liquor Scarpae ; one in the sacculus com- munis, the other in the sacculus proprius, from that part of each sac with which the nerves are connected. The AUDITORY NERVE divides into two branches at the bottom of the cul-de-sac of the meatus auditorius interims ; a vestibular nerve, and a cochlear nerve. The vestibular nerve, the posterior of the two, divides into three branches, superior, middle, and in- ferior. The superior vestibular branch gives off a number of fila- the cranium. Wharton Jones, in the article " Organ of Hearing," in the Cyclopaedia of Anatomy and Physiology, also describes them as tubular canals which terminate beneath the dura mater of the petrous bone in a small dilated pouch. In the ear of a man deaf and dumb from birth, he found the termination of the aqueduct of the vestibule of unusually large size, in consequence of irregular development. 284 THE DISSECTOR. ments which pass through the minute openings of the eminentia pyramidalis and superior ventricle of the vestibule, and are dis- tributed to the sacculus communis and ampullse of the perpendi- cular and horizontal semicircular canals. The middle vestibular branch sends off numerous filaments, which pass through the openings of the macula cribrosa in the anterior ventricle of the vestibule, and are distributed to the sacculus proprius. The in- ferior and smallest branch takes its course backwards to the pos- terior wall of the vestibule, and gives off filaments, which pierce the wall of the ampullary dilatation of the oblique canal, to be distributed upon its ampulla. According to Stiefensand, there is, in the situation of the point of entrance of the nervous filaments into the ampulla, a deep depression upon the exterior of the mem- brane, and upon the interior a corresponding projection, which forms a kind of transverse septum, partially dividing the cavity of the ampulla into two chambers. In the substances of the sacculi and ampullae, the nervous filaments radiate in all direc- tions, anastomosing with each other, and forming interlacements and loops ; and they terminate upon the inner surface of the membrane in minute papillae, resembling those of the retina. The cochlear nerve divides into numerous filaments which enter the foramina of the tractus spiralis foraminulentus in the base of cochlea, and passing upwards in the canals of the modiolus, bend outwards at right angles, to be distributed in the tissue of the lamina spiralis. The central portion of the nerve passes through the tubulus centralis of the modiolus, and supplies the apicial portion of the lamina spiralis. In the lamina spiralis, the nervous filaments, lying side by side, on an even plane, form numerous anastomosing loops, and spread out into a nervous membrane. According to Treviranus and Gottsche, the ultimate termina- tions of the filaments assume the form of papillae. The arteries of the labyrinth are derived from the internal auditory branch of the superior cerebellar or basilar artery, and from the stylo-mastoid. MOUTH AND TONGUE. In the section of the nasal fossae the incision was carried through the roof of the mouth, and the division of the soft palate was completed by an incision made with a scalpel. Care was taken not to disturb the cavity of the mouth any more than was necessary. We have now to study that cavity, together with the tongue, for which purpose any fragments of the preceding dissection, which may obscure the view, should be removed ; and that side of the mouth selected for examination which has been least injured. The mouth is the irregular cavity which contains the organ of taste, and the principal instruments of mastication. It is LIPS CHEEKS PALATE. 285 bounded, in front, by the lips ; Fig. 90. on either side, by- the internal surface of the cheeks ; above, by the hard palate and teeth of the upper jaw ; below, by the tongue, by the mucous membrane stretched between the arch of the lower jaw and the under surface of the tongue, and by the teeth of the inferior maxilla ; and, behind, by the soft palate and fauces. * The lips are two fleshy folds formed externally by common in- tegument, and internally by mu- cous membrane, and containing between these two layers, muscles, a quantity of fat, and numerous small labial glands. They are attached to the surface of the upper and lower jaw ; and each lip is connected to the gum in the middle line by a fold of mucous membrane, the frcenum labii supe- THE i TONGUE WITH IT s PAPILLA . . . '- J 7 r / 1. The raphe\ which in some nons, andfranum labii infenons, tongues bifurcates on the dorsum of the former being the larger of the the organ, as in the figure. 2, 2. ^ wo The lobes of the tongue. The mu r 7 /u \ rounded eminences on this part of The cheeks (buccae) are con- the orgaD( and near its _ tip are the tinuous on either hand with the lips, and form the sides of the face ; they are composed of in- tegument, a large quantity of fat, tongue. 4, 4. Its sides, on which muscles, mucous membrane, and are 8een the lameiiated and fringed i / 7 j papillae. 5, 5. The V-shaped row of buccal glands. papillae circumvallate. 6. The fora- The muCOUS membrane lining men csecum. 7. The mucous glands the cheeks is reflected above and of the roots of the tongue. 8. The below upon the sides of the jaws, gg "?,', iV? grS ?oa and is attached posteriorly to the of the os hyoides. anterior margin of the ramus of the lower jaw. At about its middle, opposite the second molar tooth of the upper jaw, is a papilla, upon which may be observed a small opening, the aperture of the duct of the parotid gland. The hardpalate is a dense structure, composed of mucous mem- brane, palatal glands, fibrous tissue, vessels, and nerves, and firmly connected to the palate processes of the superior maxillary and palate bones. It is bounded in front and on each side by the alveolar processes and gums, and is continuous behind with the papillae fungiformes. The smaller papilla, among which the former are dispersed, are the papillae conicw and filiformes. 3. The tip of the 286 THE DISSECTOR. soft palate. Along the middle line it is marked by an elevated raphe, and presents, upon each side of the raphe, a number of transverse ridges and grooves. Near its anterior extremity, and Fig. 91. a' P a/ * ** VARIOUS FORMS OF THE CONICAL COMPOUND PAPILLAE, DEPRIVED OF THEIR EPITHELIUM : a, b, and especially c, are the best marked, and were provided with the stiffest and longest epithelium ; their simple papillae are more acumi- nated, d, approaches the fungiform variety : e, f, come near the simple papillae. Magnified 20 diameters. immediately behind the middle incisor teeth, is a papilla which corresponds with the termination of the anterior palatine canal, and receives the naso-palatine nerves. The vessels and nerves of the hard palate are the descending palatine artery (page 175), and nerves (page 183), which emerge at the posterior palatine foramina and pass forwards, and the naso-palatine nerve (page 183), and artery of the septum (page 115), in front. If the mucous membrane be torn away from the side of the nasal fossa, at its posterior part, so as to expose the ascending portion of the palate bone and spheno-palatine foramen, the descending palatine artery and accompanying nerves may be seen through the thin plate of bone. This plate should be removed, and the artery and nerve followed in their course downwards to the posterior palatine foramen, and from that point forwards in the substance of the palate. The artery and nerve lie deeply in the palate, and for a part of their course in a groove on the bone. At the same time the two other palatine nerves, middle and posterior (page 183), may be dissected and traced to their distribution, the middle to the tonsil and soft palate ; the posterior to the posterior part of the palate as well as to the soft palate and tonsil. The gums are composed of a thick and dense mucous mem- brane, which is closely adherent to the periosteum of the alveolar processes, and embraces the necks of the teeth. They are remarkable for their hardness and insensibility; and for their close contact, without adhesion, to the surface of the tooth. From the neck of the tooth they are reflected into the alveolus, and become continuous with the periosteal (peridental) mem- brane of that cavity. TONGUE. The tongue is invested by mucous membrane, which THE TONGUE. 287 is reflected from its under part upon the inner surface of the lower jaw, and constitutes, with the muscles beneath, the floor of the mouth. Upon the under surface of the tongue, near its anterior part, the mucous membrane forms a considerable fold, which is called the frcenum linguae; and on each side of the fraenum is a large papilla, the commencement of the duct of the submaxillary gland (Wharton's duct). Running back from this papilla is a ridge, occasioned by the prominence of the sublingual gland ; and opening upon the summit of this ridge, a number of small openings, the apertures of the excretory ducts of the gland. Posteriorly the tongue is connected with the os hyoides by muscle, and to the epiglottis by three folds of mucous membrane, called \hefrcena epiglottidis. The mucous membrane of the mouth is continuous with the derma along the margin of the lips. On either side of the fraenum linguae it may be traced through the sublingual ducts, and along Wharton's ducts into the submaxillary glands. From the sides of the cheeks it passes through the opening of Stenon's ducts to the parotid glands. In the fauces it forms the assemblage of follicles called tonsils, and may thence be traced downwards into the larynx and pharynx, where it is continuous with the general gastro-pulmonary mucous membrane. Beneath the mucous membrane are a number of small glandular granules, which pour their secretion upon the surface. A con- siderable number of these bodies are situated within the lips, in the palate, and in the floor of the mouth. They are named, ac- cording to their position, labial glands, palatial glands, and buccal glands. The surface of the tongue is covered by a dense layer, analogous to the corium of the skin, which gives support to papillae. A raphe marks the middle line of the organ, and divides it into symmetrical halves. The papilla of the tongue are the Papillae circumvallatae, Papilla) filiformes, Papillae conicae, Papillae fungiformes. The papilla circumvallatce (p. lenticulares) are of large size, and from fifteen to twenty in number. They are situated on the dorsum of the tongue, near its root, and form a row on each side, which meets its fellow at the middle line, like the two branches of the letter A. Each papilla resembles a cone, attached by its apex to the bottom of a cup-shaped depression : hence they are also named papillae calyciformes. This cup-shaped cavity forms a kind of fossa around the papilla, whence their name, circum- vallatce. 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 ccecum. The papillce conica and filiformes cover the whole surface of 288 THE DISSECTOR. the tongue in front of the circumvallatse, but are most abundant towards its anterior part. They are conical and filiform in shape, and many of them are pierced at the extremity by a minute aper- ture. Hence they may be regarded as follicles, rather than sentient organs ; the true sentient papill* being extremely minute, and occupying their surface as they do that of the other papilla of the tongue. The papillae fungiformes (p. capitatae) are irregularly dispersed over the dorsum of the tongue, and are easily recognized among the other papillae by their rounded heads, larger size, and red color. A number of these papillae will generally be observed at the tip of the tongue. Behind the papilla circumvallataa, at the root of the tongue, are a number of mucous glands (lingual), which open upon the surface. There is also a small cluster beneath the tip of the tongue. In structure the tongue is composed of muscular fibres, which are dis- tributed in layers arranged in various directions : thus, some are disposed longitudinally (lingualis superficialis) ; others transversely (lingualis trans versus) ; others, again, obliquely and vertically. Between the mus- cular fibres is a considerable quantity of adipose substance, and in the middle of the organ a vertical septum of fibrous tissue. Vessels and Nerves. The tongue is abundantly supplied with blood by the lingual arteries. The nerves are three in number, and of large size : the gustatory branch of the inferior maxillary, which is distributed to the pa- pillae, and is the nerve of common sensation and taste ; the glosso- pharyngeal, which is distributed to the mucous membrane, glands, and papillae circumvallatse ; and the hypoglossal, which is the motor nerve of the tongue, and is distributed to the muscles. THE LARYNX. The larynx is situated at the fore-part of the neck, between the trachea and the base of the tongue. It is a short tube, having an hour-glass form, and is composed of cartilages, ligaments, muscles, vessels, nerves, and mucous membrane. The cartilages are the Thyroid, Two cornicula laryngis, Crycoid, Two cuneiform, Two arytenoid, Epiglottis. The thyroid (^p6? doos, like a shield) is the largest cartilage of the larynx : it consists of two lateral portions, or alee, which meet at an angle in front, and form the projection which is known by the name of pomum Adami. In the male, after puberty, the angle of union of the two alae is acute ; in the female, and before THE LARYNX. 289 puberty in the male, it is obtuse. Where the pomum Adami is prominent, a bursa mucosa is often found between it and the skin. Each ala is quadrilateral in shape, and forms a rounded border posteri- Fig. 92. orly, which terminates above, in the superior cornu and below, in the in- ferior cornu. Upon the side of the ala is an oblique line, or ridge, directed downwards and forwards, and bounded at each extremity by a tubercle. Into this line the sterno-thyroid muscle is inserted ; and from it the thyro-hyoid and inferior constrictor take their ori- gin. In the receding angle, formed by the meeting of the two alae upon the inner side of the cartilage, and near its lower border, are attached the epi- glottis, the chordae vocales, the thyro- arytenoid, and thyro-epiglottidean muscles. The cricoid (xpt'xoj tlBos, 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 ^01^1^0 4*\h "? fine specimens of white fibrin are frequently found with the coa- gula ; occasionally they are yellow and gelatinous. This appearance deceived the older anatomists, who called these substances " polypus of tin- heart:" they are frequently found in the right ventricle, and some- tiiiu-s in the left cavities. The RIGHT AURICLE is larger than the left, and consists of a principal cavity or sinus, and an appendix auricula?. The inte- rior of the sinus presents for examination five openings ; two valves ; two relics of frctal structure ; and two peculiarities in the proper structure of the auricle. To facilitate remembrance, they may be thus arranged : Openings. Valves. Superior cava, Eustachian valve, Inferior cava, Coronary valve. Coronary vein ReKcU of F(tal Structure. Foramina Thebesn, .. Auriculo-ventricular opening. Annulus ovalis, Fossa ovalis. Structure of the Auricle. Tuberculum Loweri, Musculi pectinati. The superior cava returns the blood from the upper half of the body, and' opens into the upper and back part of the auricle. The inferior cava returns the blood from the lower half of the body, and opens through the lower and posterior wall, close to the; partition between the auricles (septum auricularum). The direction of these two vessels is such, that a stream forced through the superior cava would be directed towards the anriculo-ventri- cular opening. In like manner, a stream rushing upwards by the inferior cava would force its current against the septum auri- cularum ; this is the proper direction of the two currents during foetal life. The coronary vein returns the venous blood from the substance 316 THE DISSECTOR. of the heart ; it opens into the auricle between the inferior cava and the auriculo-ventricular opening, under cover of the coro- nary valve. The foramina Thebesii are minute pore-like openings of small veins which issue directly from the muscular structure of the heart without entering the general venous current. These open- ings are also found in the left auricle, and in the right and left ventricles, but are generally believed to be mere caecal depres- sions. The auriculo-ventricular opening is the large opening of com- munication between the auricle and ventricle. The Eustachian valve is a part of the apparatus of foetal circu- lation, 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 sometfmes it remains of large size. It'is formed by a fold of the lining mem- brane of the auricle, containing some muscular fibres, is situated between the aperture of the inferior cava and the auriculo-ventri- cular opening, and is generally connected with the coronary valve. The coronary valve is a semilunar fold of the lining membrane, stretching across the mouth of the coronary vein, and preventing the reflux of 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, which occupies the place of the foramen ovale of the foetus. The fossa ovalis is an oval depression corresponding with the foramen ovale of the foetus. This opening is closed at birth by a thin valvular layer, which is continuous with the left margin of the annulus, and is frequently imperfect at its upper part. The depression or fossa in the right auricle results from this arrange- ment. There is no fossa ovalis in the left auricle. The tuberculum Loweri is the portion of auricle intervening between the openings of the superior and inferior cava. Being thicker than the walls of the veins, it forms a projection, which was supposed by Lower to direct the blood from the superior cava into the auriculo-ventricular opening. The musculi pectinati are small muscular columns situated in the appendix auriculae. They are o numerous, and arranged pa- rallel with each other; hence their cognomen, " pectinati, " like the teeth of a comb. The RIGHT or ANTERIOR VENTRICLE is triangular and prismoid in form. Its anterior side is convex, and forms the larger por- tion of the front of the heart. The posterior side, which is also THE HEART. 317 inferior, is flat, and rests on the diaphragm ; the inirer side cor- responds with the partition between the two ventricles, septum THE CAVITIES OF THE HEART. Fig. 102. 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 hy its valve. 5. The Eustachian valve. 6. The fossa ovalis, surrounded by the annulus ovalis. 7. The tuberculumLoweri. 8. Themus- culi pectinati. 9. The auriculo- ventricular opening. 10. The right ventricle. 11. The tri- cuspid valve, attached by the chordao tendinese to the carneao columnae, 12. 13. The pulmo- nary artery, guarded at its com- mencement by three semilunar valves. 14. The right pulmo- nary 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 cavaD, it passes through the auriculo-ventri- cular 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-ventricular opening. 19. The left ventricle. 20. The mitral valve, attached by its chorda) tendineae to two large columnae carneoe, 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 iiuirkt'd 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. vriitricnlornm. Superiorly, where the pulmonary artery arises, there is a dilatation of the ventricle, termed the infundibulum, or conus arteriosus. The right ventricle is to be laid open by making an incision parallel with, and a little to the right of, the anterior longitudinal furrow, from the pulmonary artery in front to the apex of the heart, and thence by the side of the posterior longitudinal furrow behind to the auriculo-ventricu- lar opening. It contains, to be examined, two openings, the anriculo ven- tricular and that of the pulmonary artery ; two apparatus of valves, the tricuspid and semilunar ; and a muscular and tendi- 27* 318 THE DISSECTOR. nous apparatus belonging to the tricuspid valves. They may be thus arranged : Auriculo-ventricalar opening, Tricuspid valves, Opening of the pulmonary artery, Semilunar valves, Chorda3 tendineae, Column* earner. The auriculo-ventricular opening is surrounded by a fibrous ring, covered by the lining membrane (endocardium) of the heart. It is the opening of communication between the right auricle and ventricle. The opening of the pulmonary artery is situated at the summit of the conus arteriosus, close to the septum ventriculorum, on the left side of the right ventricle, and upon the anterior aspect of the heart. The tricuspid valves are three triangular folds of the lining membrane, strengthened by a thin layer of fibrous tissue. They are connected by their base around the auriculo-ventricular open- ing ; and by their sides and apices, which are thickened, they give attachment to a number of slender tendinous cords, called chordae tendinese. The chordae tendinece are the tendons of the thick muscular columns (columnce carnece) which stand out from, the walls of the ventricle, and serve as muscles to the valves. A number of these tendinous cords converge to a single muscular attachment. The tricuspid valves prevent the regurgitation of blood into the auricle during the contraction of the ventricle, and they are prevented from being themselves driven back by the chordae tendineaa and their muscular attachments. This connection 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 semi- lunar and coronary. The valves consist, according to Mr. King, 1 of curtains, cords, and columns. The anterior valve or curtain is the largest, and is so placed as to prevent the filling of the pulmonary artery during the distension of the ventricle. The right valve or curtain is of smaller size, and is situated on the right side of the auriculo- ventricular opening. The third valve, or "fixed curtain," is connected by its cords to the septum ventriculorum. The cords (chordae tendinea?) of the anterior curtain are attached, princi- pally, to a long column (columna carnea), which is connected with the " right or thin and yielding wall of the ventricle." From the lower part of this column a transverse muscular band, the 1 " Essay on the Safety-Valve Function in the Right Ventricle of the Human Heart," by T. W. King. Guy's Hospital Reports, vol. ii. THE HEART. 319 "long moderator band," is stretched to the septum ventriculorum, or " solid wall" of the ventricle. The right curtain is connected, by means of its cords, partly with the long column, and partly with its own proper column, the second column, which is also attached to the "yielding wall" of the ventricle. A third and smaller column is generally connected with the right curtain. The "fixed curtain" is so named from its attachment to the " solid wall" of the ventricle, by means of cords only, without fleshy columns. Prom this arrangement of the valves it follows, that if the right ventricle be over distended, the thin or "yielding wall" will give way, and carry with it the columns of the anterior and right valves. The cords connected with these columns will draw down the edges of the corresponding valves, and produce an opening between the curtains, through which the superabundant blood may escape into the auricle, and the ventricle be relieved from over-pressure. This mechanism is therefore adapted to fulfil the function of a safety valve. The columnce camece (fleshy columns) is a name expressive of the appearance of the internal walls of the ventricles, which, with the exception of the infundibulum, seem formed of muscular col- umns interlacing in almost every direction. They are divided, according to the manner of their connection, into three sets. 1. The greater number are attached by the whole of one side, and merely form, convexities into the cavity of the ventricle. 2. Others are connected by both extremities, being free in the middle. 3. A few (columnae papillares) are attached by one extremity to the walls of the heart, and by the other give insertion to the chordae tendineae. The semilunar valves, three in number, are situated around the commencement of the pulmonary artery, being formed by a folding of its lining membrane, strengthened by a thin layer of fibrous tissue. They are attached by their convex borders, and free by the concave, which are directed upwards in the course of the vessel, 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, nnd effectually close the entrance of the tube. The margins of the valves are thicker than the rest of their extent, and each valve presents in the centre of this margin a small fibro-cartilaginous tubercle or nodule, called corpus Arantii, which locks in with 'the other two Huring the closure of the valves, and secures the tri- angular space which would otherwise be left by the approximation of three semilunar folds. On either side of the nodule the edge of the valve is folded and thin, and to this part the term lunula 320 THE DISSECTOR. has been applied. When the valves are closed, the lunulse are brought in contact with each other by their surfaces. Between the semilunar valves and the cylinder of the artery are three pouches, called the pulmonary sinuses (sinuses of Yal- salva). Similar sinuses are situated behind the valves at the commencement of the aorta, and are larger and more capacious than those of the pulmonary artery. The pulmonary artery commences by a scalloped border, cor- responding with the three valves which are attached along its edge. It is connected to the ventricle by muscular fibres, and by the lining membrane of the heart. The LEFT OR POSTERIOR AURICLE is somewhat smaller, but thicker, than the right ; of a cuboid form, and situated more pos- teriorly. The appendix auriculae is constricted at its junction with the auricle, and has a foliated 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 hori- zontal 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 ; the fossa oval is, as previously ob- served, is not seen on the left side of the septum auricularum. The parts to be examined are Four pulmonary veins, Auriculo-ventricular opening, Musculi pectinati. The pulmonary veins, two from the right and two from the left lung, open into the corresponding sides of the auricle. The two left pulmonary veins terminate frequently by a common opening. The auricula-ventricular opening is the aperture of communi- cation between the auricle and ventricle. . The musculi pectinati are fewer in number than in the right auricle, and are situated only in the appendix auriculas. LEFT VENTRICLE. The left ventricle is to be opened by making an incision a little to the left of the septum ventriculorum, and continuing it around the apex of the heart to the auriculo-ven- tricular opening behind. The left ventricle 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 towards the base. Its walls are about seven lines in thickness, those of the right ventricle being about two lines and a half. THE HEART. 321 It presents for examination, in its interior, two openings, two valves, and the tendinous cords and muscular columns; they may be thus arranged : Auriculo-ventricular opening, Mitral valves, Aortic opening, Semilunar valves, Chordae tendinea3, Column carnese. The auricula-ventricular opening is a dense fibrous ring, covered by the endocardium, but smaller in size than that of the right side. Its fibrous structure is closely connected with that of the right auriculo-ventricular and aortic rings; and at the junction of the three there is afibro-cartilaginous mass, and, in some animals, a portion of bone. . . The mitral valves are attached around the auriculo-ventricular opening, as are the tricuspid in the right ventricle. They are thicker than the tricuspid, and consist of 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 in 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 were named. These valves, like the tricuspid, are furnished with an apparatus of tendinous cords, chordae tendinece, which are attached to two very large columnce carnea. The columnce carnece admit of the same arrangement, into three kinds, as on the right side. Those which are free by one extremity, the column papillares, are two in number, and larger than those on the opposite side ; one being placed on the left wall of the ventricle, and the other at the junction of the septum ventriculorum with the posterior wall. The semilunar valves are placed around the commencement of the aorta, like those of the pulmonary artery ; they are similar in structure, and are attached to the scalloped border by which the aorta is connected with the ventricle. The nodule in the centre of each fold is larger than those in the pulmonary valves, and it was these that Arantius particularly described ; but the term " corpora Arantii" is now applied indiscriminately to both. The fossas between the semilunar valves and the cylinder of the artery are larger than those of the pulmonary artery; they are called the " sinus aortici" (sinuses of Valsalva). Structure. The heart is composed of muscular fibres, which are inter- posed between two membranes the pericardium externally, and endo- cardium within and are attached to the fibrous rings which surround the four great openings in the root of the heart the auriculo-ventricular openings, and those of the pulmonary artery and aorta. The fibres of the ventricles, taking their origin from these rings, wind 322 THE DISSECTOR. spirally around each ventricle, to the apex of the heart, and then turn abruptly inwards so as to form an internal layer to the preceding. The greater part of these recurrent fibres proceed to the fibrous rings, into which they are inserted, while some constitute the columnse papillares. A superficial set of fibres forms a thin stratum, which winds around both ventricles and binds them together. The fibres of the auricles, like those of the ventricles, arise from the fibrous rings, and, after winding more or less obliquely and transversely around the auricles some passing the two to form the septum auricu- larum return to be inserted into the fibrous rings. Some of the fibres are disposed in circles around the openings of the large veins. The endocardium is the serous lining membrane of the heart. It is thin and transparent, but somewhat thicker and less transparent on the left side than on the right. It forms the folds which, thickened by fibrous tissue, constitute the valves of the heart, and is continuous, at the aper- tures, with the internal coat of the arteries and veins. VESSELS OF THE HEART. The vessels of the heart maybe examined either before or after the dissection of the organ, as may best suit the convenience of the student. This might be done on the subject ; but as there are many more important things to study, and decay is rapid in its march, the student would do well to obtain a heart specially for the dissection of the ves- sels, and prepare them for that purpose by injection with colored tallow. The CORONARY ARTERIES arise from the aortic sinuses at the commencement of the ascending aorta, immediately above the free margin of the semilunar valves. The left, or anterior coro- nary, passes forwards between the pulmonary artery and left appendix auriculae, and divides into two branches ; one of which winds around the base of the left ventricle in the auriculo-ventri- cnlar groove, and inosculates with the right coronary, forming an arterial circle around the base of the heart ; while the other passes along the line of union of the two ventricles, upon the anterior aspect of the heart, to its apex, where it anastomoses with the descending branch of the right coronary. It supplies the left auricle and the anterior surface of both ventricles. The right or posterior coronary passes forward between the root of the pulmonary artery and the right auricle, and winds along the auriculo-ventricular groove to the posterior longitu- dinal furrow, where 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 surface of both ventricles, and sends a large branch along the sharp margin of the right ventricle to the apex of the heart. Cardiac Veins. The veins returning the blood from the sub- stance of the heart are the Great cardiac vein, Anterior cardiac veins, Posterior cardiac veins, Yense Thebesii. NERVES OF THE HEART. 323 The great cardiac vein (coronary) commences at the apex of the heart, and ascends along the anterior longitudinal groove to the base of the ventricles ; it then curves around the left auriculo- ventricular groove to the posterior part of the heart, where it terminates in the right auricle. It receives in its course the left cardiac veins from the left auricle and ventricle, and the posterior cardiac veins from the posterior longitudinal groove. The posterior cardiac vein, frequently two in number, com- mences also at the apex of the heart, and ascends along the posterior longitudinal groove, to terminate in the great cardiac vein. It receives the veins from the posterior aspect of the two ventricles. The anterior cardiac veins collect the blood from the anterior surface of the right ventricle; one larger than the rest runs along the right border of the heart and joins the trunk formed by these veins, which curves around the right auriculo-ventricular groove, to terminate in the great cardiac vein near its entrance into the right auricle; others cross the groove, and open directly into the auricle. The vence TTiebesii (vena3 minima)), are numerous minute ve- nules which convey the venous blood directly from the substance of the heart into the right auricle. Their existence is denied by some anatomists. NERVES OF THE HEART. The heart is supplied with nerves by the superficial and deep cardiac plexuses. The superficial cardiac plexus is situated immediately beneath the arch of the aorta and in front of the right pulmonary artery. It receives the superficial cardiac nerve of the left side and the inferior cardiac branch of the left pneumogastric nerve, both of which cross the arch of the aorta between the left phrenic and pneumogastric nerve. It receives besides numerous filaments from the deep cardiac plexus, and sometimes a cardiac branch from the right pneumogastric nerve. Connected with the plexus is a small ganglion (sometimes wanting), the cardiac ganglion of Wrisberr, which lies close to the right side of the fibrous cord of the ductus arteriosus. The superficial cardiac plexus gives off fihmients which pass along the front of the left pulmonary artery to the root of the left lung, where they communicate with the anterior pulmonary plexus; while the principal part of the plexus descends in the groove between the pulmonary artery and the aorta to the anterior longitudinal sulcus of the heart, where it comes into relation with the anterior coronary artery, and be- comes the anterior coronary plexus. At the base of the heart the anterior coronary plexus receives several filaments from the deep cardiac plexus. Its branches are distributed to the sub- 324 THE DISSECTOR. stance of the heart in the course of the anterior coronary artery. The deep cardiac plexus (great cardiac plexus), is situated in a triangular space, bounded in front by the arch of the aorta, behind by the trachea, its point of bifurcation, and below by the right pulmonary artery. The dissection of this plexus requires the removal of the arch of the aorta, and, like the examination of the coronary arteries, had better be made on a heart procured specially for the purpose. The deep cardiac plexus receives all the cardiac branches of the sympathetic with the exception of the nervus superficialis cordis of the left side ; and all the cardiac branches of the pneu- mogastric excepting the left inferior branch. It gives off nu- merous filaments; some, proceeding from its right side, pass in front of the right pulmonary artery to reach the right anterior pulmonary plexus; others descend along the trunk of the pulmo- nary artery to join the anterior coronary plexus ; and a third set pass behind the pulmonary artery to the posterior coronary plexus and right auricle. The filaments proceeding from its left side are directed, some forwards beneath the arch of the aorta to join the superficial cardiac plexus, some outwards to the left an- terior pulmonary plexus, and some to the left auricle; while the great bulk are continued downwards to the posterior coronary artery, and become the posterior coronary plexus, which supplies the muscular structure of the posterior aspect of the heart. GREAT VESSELS OF THE HEART. The great vessels connected with the heart are the pulmonary artery, aorta, superior and inferior cava, and four pulmonary veins. PULMONARY ARTERY. The pulmonary artery is the most an- terior of the vessels at the root of the heart. It arises from the left side of the base of the right ventricle, that part termed the infundibulum; and ascends for the space of two inches to the under side of the arch of the aorta, where it divides into two branches of nearly equal size, the right and left pulmonary ar- teries ; the left branch, just at its point of division, being con- nected with the aorta by a fibrous cord, the remains of the ductus arteriosus of the foetus. At its origin the pulmonary artery is in relation on either side with an appendix auricula and one of the coronary arteries; and behind it has the commencement of the aorta and left auricle. It is inclosed by the pericardium for nearly the whole of its length, its trunk and that of the aorta being contained in the same sheath of serous membrane. The right pulmonary artery, longer and somewhat larger than the left, passes transversely outwards behind the ascending aorta AORTA 325 and superior vena cava to the root of the right lung, where it divides into three branches for the three lobes. In its course it lies parallel with and in front of the right bronchus. THE LARGE VESSELS Fig. 103. WHICH PROCEED FROM THE ROOT OP THE HEART, WITH THEIR RELATIONS ; THE HEART HAS BEEN REMOV- ED. 1. The ascending aor- ta. 2. The arch. 3. The thoracic portion of the de-r scending aorta. 4. The ar- teria innominata dividing into, 5, the right carotid, which again divides, at 6, into the external and in- ternal carotid ; and 7, the right subclavian artery. 8. The axillary artery ; its ex- tent is designated by a dotted line. 9. The bra- ehiul artery. 10. The right pneumogastric nerve run- ning by the side of the com- mon carotid, in front of the right subclavian artery, and behind the root of the right lung. 11. The left common carotid, having to its outer side the left pneu- mogastric 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 ar- tery 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 relative 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 are pericar- diac and oesophageal branches. The left pulmonary artery, shorter and smaller than the right, crosses the descending aorta and left bronchus to the root of the left lung, where it divides into two branches for the two lobes. AORTA. The aorta, the great arterial trunk of the body, arises from the left ventricle at the middle of the root of the heart. It ascends at first forwards and to the right, next curves backwards 28 326 THE DISSECTOR. and to the left, and then descends on the left side of the vertebral column to the fourth lumbar vertebra. The aorta within the thorax is therefore divided into the arch and thoracic aorta. At its commencement the vessel presents three dilatations, the sinus aortici, which correspond with the spaces occupied by the three semilunar valves. The arch of the aorta, commencing at a point corresponding with the articulation of the cartilage of the fourth rib with the sternum on the left side, crosses behind and near the sternum to a point corresponding with the upper border of the articulation of the second rib with the sternum on the right side. It then curves backwards and to the left, and descends to the left side of the body of the third dorsal vertebra, and at the lower border of the latter vertebra becomes the thoracic aorta. The first or ascending portion of the arch, a little more than two inches in length, is almost wholly contained within the peri- cardium. It is crossed in front by the pulmonary artery : on its left side it has the left auricle and pulmonary artery ; on its right the right auricle and superior vena cava ; and behind the right pulmonary artery and veins. The second or transverse portion of the arch is crossed in front by the left phrenic nerve, left nervus superficialis cordis, left in- ferior cardiac of the pneumogastric, and left pneumogastric nerve. Behind it is in relation with the trachea, oesophagus, thoracic duct, the nerves to the deep cardiac plexus, and the left recurrent nerve. Above it gives off the arteria innominata, left carotid and left subclavian artery, and supports the left vena innominata ; and below is in relation with the superficial cardiac plexus, the bi- furcation of the pulmonary artery, cord of the ductus arteriosus, left bronchus, and left recurrent nerve. The third or descending portion of the arch lies against the third dorsal vertebra, and is partially covered by the left pleura. The ARTERIA INNOMINATA, the first and largest branch given off by the arch of the aorta, is an inch and a half in length. It ascends obliquely to the right sterno-clavicular articulation, where it divides into the right carotid and right subolavian artery. It is in relation in front with the left innominata, the sternum, and origin of the sterno-hyoid and sterno-thyroid muscles. Be- hind it has at first the trachea, and then the right pneumogastric nerve. To the right it is in relation with the right vena innomi- nata and pleura ; and on the left with the left common carotid artery, and the remains of the thymus gland. The arteria innominata usually gives off no branch ; but some- times a small vessel proceeds from it which ascends upon the front of the trachea to the thyroid gland. This is the middle thyroid artery of Harrison, the thyroidea ima of Neubauer. VENE INNOMINATE. 327 The LEFT COMMON CAROTID ARTERY, the second branch from the arch of the aorta, ascends obliquely to the left sterno-clavicu- lar articulation, and thence passes onwards to the side of the neck. It is in relation in front with the left vena innominata, which crosses it near its origin ; the remains of the thymus gland, and the origins of the sterno-hyoid and sterno-thyroid muscles. Be- hind, it rests in succession on the trachea, oesophagus, and tho- racic duct. To its inner side is the arteria innominata ; and ex- ternally the left pneumogastric nerve and pleura. The LEFT SUBCLAVIAN ARTERY, the third branch given off by the arch of the aorta, ascends perpendicularly to the inner border of the first rib, where it turns outwards over the rib and behind the scalenus anticus muscle. In consequence of the antero-poste- rior direction of the arch of the aorta, the left subclavian artery rests on the vertebral column and longus colli muscle. In front it has the pleura, the pneumogastric and phrenic nerve ; and to its inner side the trachea, oesophagus, and thoracic duct. SUPERIOR VENA CAVA. This large vein, about three inches in length, is formed by the union of the two venae innominatae. It commences immediately to the right of the arch of the aorta ; at about its middle becomes inclosed in the pericardium; and terminates in the upper part of the right auricle. It is in relation in front with the pericardium ; behind with the right pulmonary artery; to its inner side with the ascending aorta ; and externally with the pleura and right phrenic nerve. In the upper half of its course the superior vena cava receives several small veins from the mediastinum, and just before its en- trance into the pericardium it is joined from behind by the great azy^os vein. The VENE INNOMINATE are formed by the union of the inter- nal jugular and subclavian vein at each side. The right vena innominata, about an inch and a quarter in length, descends almost vertically by the side of the arteria inno- minata to unite with its fellow of the opposite side in the forma- tion of the superior vena cava. It is in relation by its outer side with the pleura and right phrenic nerve. This vein receives at its origin the trunk of the ductus lymphaticus dexter, which opens into it from behind ; and in its course it is joined by the right vertebral, right inferior thyroid, and right internal mammary vein. The left vena innominata, considerably longer than the right, crosses obliquely the three great arteries arising from the arch of the aorta to its junction with the right vena innominata. It is in relation in front with the left sterno-clavicular articulation, and the remains of the thymus gland, which separate it from the sternum. BeJiind, it has the upper border of the arch of the 328 THE DISSECTOR. aorta, the large arteries arising from it, and the nerves which pass in front of the arch. The veins opening into the left vena innominata are the left vertebral, left inferior thyroid, left mammary, superior intercostal, and several small veins from the anterior mediastinum. At its origin it receives the thoracic duct, which opens into it from be- hind. INFERIOR YENA CAVA. The inferior vena cava, the large trunk from the lower half of the body, after passing through the tendinous portion of the diaphragm, opens immediately into the posterior part of the right auricle. It receives no branches within the thorax. PULMONARY VEINS. The pulmonary veins returning the pure blood from the lungs to the left auricle lie in front of the other vessels in the roots of the lungs. There are two on each side, those of the left lung being the veins of its two lobes; while on the right side the veins of the superior and middle lobe are united into a single trunk. The right pulmonary veins are longer than the left, and pass behind the right auricle. The left pulmonary veins pass in front of the descending aorta. NERVES OF THE THORAX. The nerves found in the thorax are the phrenic, pneumogastric, and sympathetic. The first of these merely pass through the thorax in their way to the diaphragm : they have been already described, page 307. The pneumogastric and sympathetic sup- ply the viscera of the thorax in their course through its cavity. The PNEUMOGASTRIC NERVE, the largest of the three nerves of the eighth pair, after descending the neck in the sheath of the carotid vessels, enters the chest, and, passing backwards and inwards behind the root of the lungs, reaches the oesophagus, along which it takes its course to the stomach. As the two nerves of opposite sides of the chest differ in their course, it becomes necessary to examine each separately. The right nerve enters the chest after passing between the subclavian artery and vein ; it then passes inwards and backwards by the side of the trachea to the posterior aspect of the root of the lungs, where it forms the posterior pulmonary plexus. From the root of the lungs it proceeds as a double cord to the oesopha- gus, and takes its course along the posterior aspect of the oesopha- gus to the corresponding aspect of the stomach, to which it is distributed. At the lower part of the oesophagus the two cords reunite. The left nerve enters the chest between the left common caro- tid and subclavian artery, and behind the left vena iniiominata. SYMPATHETIC NERVE. 329 It crosses the arch of the aorta, around which the recurrent takes its course, and passes backwards to the posterior aspect of the root of the lungs, where, like the right, it forms the posterior pulmonary plexus. From the root of the lung it passes by one or two cords to the anterior aspect of the oesophagus, along which it takes its course to the corresponding aspect of the stomach. The branches of the pneumogastric nerves within the thorax are the recurrent, or inferior laryngeal, cardiac, pulmonary ante- rior and posterior, and cesophageaL The recurrent laryngeal nerve curves around the subclavian artery on the right side and the arch of the aorta on the left, and ascends in the groove between the trachea and oesophagus to the larynx. As it curves around its respective artery, the nerve gives off one or two cardiac branches to the deep cardiac plexus. The cardiac branches are the inferior cardiac given off from the pneumogastric just as that nerve is about to enter the chest ; and some cardiac branches given off within the thorax. The inferior cardiac branch of the right side passes down by the side of the arteria innominata to the deep cardiac plexus, and joins one of the cardiac branches of the sympathetic. The left inferior cardiac branch has been already described (page 314) ; it takes its course in front of the arch of the aorta to the superfi- cial cardiac plexus. The cardiac branches, given off within the thorax, are several small nerves to the deep cardiac plexus. On the right side they proceed from the trunk of the nerve ; on the left, from the recur- rent laryngeal. The anterior pulmonary are two or three small branches which pass forwards to the anterior aspect of the root of the lungs, and form, by their communications with filaments from the cardiac plexuses, the anterior pulmonary plexus. The posterior pulmonary branches, larger and more numerous than the anterior, proceed from the nerve where it is flattened and split into several cords. These branches are joined by fila- ments from the third and fourth thoracic ganglia of the sympa- thetic, and form the posterior pulmonary plexus. (J'^ophageal branches are given off by the pneumogastric nerves above the root of the lungs : below that point, the trunks of the nerves, divided into several cords, form a plexus around the oesophagus, the right and left nerves communicating with each other. This plexus accompanies the oesophagus to the stomach, and is the oesophageal plexus (plexus guise). SYMPATHETIC NERVE. The sympathetic nerve within the tho- rax consists of two portions ; one, prevertebral, composed of nerves descending from the neck, and forming the superficial and 28* 330 . THE DISSECTOR. deep cardiac plexus ; the other, the vertebral portion, being the trunk of the gan'gliated cord, situated on the heads of the ribs by the side of the vertebral column. The superficial cardiac plexus, situated beneath the arch of the aorta, has been already examined (p. 323). To see the deep cardiac plexus, it is necessary to draw aside the arch of the aorta, behind which it lies. This may be best effected by dividing the aorta through each extremity of the transverse portion of the arch, cutting through the ligament of the ductus arteriosus, and drawing the several parts of the vessel, with its large branches, upwards. By the removal of some cellular tissue and lymphatic glands, the deep cardiac plexus and lower part of the trachea, with its bifurcation, will be brought into view. The deep or great cardiac plexus is situated on the bifurcation of the trachea above the right pulmonary artery, and behind the transverse portion of the arch of the aorta. It receives, on the right side, the three cardiac nerves of the sympathetic of the same side, and the cardiac branches of the right pneumogastric and right recurrent nerve. On the left side it receives the middle and inferior cardiac nerves of the sympathetic of the left side; the cardiac branches of the left pneumogastric (excepting the infe- rior), and several cardiac branches from the left recurrent nerve. In other words, it receives all the cardiac filaments of the sympa- thetic, pneumogastric, and recurrent nerves, with the exception of the left superior cardiac of the sympathetic (nervus superficialis cordis) and the inferior cervical cardiac of the left pneumogastric, these two nerves being destined to the superficial cardiac plexus. The cardiac nerves being situated on a plane posterior to that of the arteries, are found in that situation at their entrance into the chest. The nerves of the right side pass for the most part behind (but sometimes in front of) the subclavian artery ; those of the left side enter the chest between the carotid and subclavian artery. The nervus superficialis cordis of the right side runs by the side of the arteria innominata ; that of the left side takes the left common carotid for its guide ; while the other nerves, in their course to the deep plexus, pass inwards to the side of the trachea. The branches of the deep cardiac plexus, proceeding from its right and left division, pass downwards to join the coronary arteries, and outwards to the pulmonary plexuses. From the right division of the plexus the branches proceed before and behind the right pulmonary artery. Those which pass in front descend upon the trunk of the pulmonary to the left coronary artery, and constitute the anterior coronary plexus ; those which pass behind the right pulmonary artery are distributed to the right auricle ; a third set of filaments, proceeding from the right division of the deep cardiac plexus follow the course of the right pulmonary artery to the anterior pulmonary plexus. From the left division of the plexus branches proceed beneath INTERCOSTAL NERVES. 331 the arch of the aorta immediately to the right of the ligament of the ductus arteriosnsto join the superficial cardiac plexus; others pass outwards with the pulmonary artery to the pulmonary plexus ; a few descend to the left auricle ; but the chief bulk pass on to the right coronary artery and form the posterior coronary plexus. The vertebral portion of the sympathetic nerve is the trunk of the sympathetic in its course through the cavity of the thorax. It lies by the side of the vertebral column upon the heads of the ribs and intercostal spaces ; but at its lowest part comes into re- lation with the sides of the bodies of the last two dorsal vertebra. To see the nerve distinctly, the pleura should be stripped from the sides of the vertebral column, and any fat which may impede the view of the nerve and its branches removed. The thoracic portion of the great sympathetic nerve consists of twelve ganglia with their connecting cords. The ganglia are flat, of a pearly hue, and somewhat triangular shape ; and each ganglion overlies the head of the corresponding rib. The first two ganglia are larger than the rest. The branches of the thoracic ganglia are external, or commu- nicating, two or three in number, to communicate with each inter- costal nerve ; and internal or visceral. The visceral branches, arising from the five or six upper gan- glia, are of small size, and are distributed to the aorta, esophagus, vertebral column, and lungs. The branches to the lungs proceed from the third and fourth ganglia, and go to join the posterior pulmonary plexus. The visceral branches of the six lower ganglia unite to form the three splanchnic nerves. The great splanchnic nerve proceeds from the sixth dorsal ganglion, and receiving the branches of the seventh, eighth, ninth, and tenth, passes downwards upon the front of the vertebral col- umn, and piercing the crus of the diaphragm, terminates in the semilunar ganglion. The lesser splanchnic nerve is formed by filaments which issue from the tenth and eleventh ganglia ; it pierces the crus of the diaphragm, and joins the solar plexus near the middle line. The third or renal splanchnic nerve proceeds from the last thoracic ganglion, and, piercing the diaphragm, terminates in the renal plexus. When absent, the place of this nerve is sup- plied by the lesser splanchnic. The process by which the sympathetic nerve was brought into view namely, that of stripping off the pleura exposes also the intercostal spaces, with the intercostal nerves and vessels. The relation of these parts may now be examined, and one of the intercostal nerves traced through its course. The INTERCOSTAL NERVES are twelve in number on each side of the thorax ; the eleven superior nerves lie in the intercostal 332 THE DISSECTOR. spaces, the twelfth below the lower border of the last rib. Each nerve lies upon an external intercostal muscle, but soon gets under cover of the internal intercostal, and then passes between the two planes of muscle to the front part of the chest. Near its origin the nerve receives two or three filaments from the neighboring ganglion of the sympathetic ; in its course it gives twigs to the intercostal muscles, and at the middle of the arch of the rib sends off the lateral cutaneous branch. The first intercostal nerve ascends from the intercostal space, and crosses the neck of the first rib to join the brachial plexus. It sends off a small intercostal branch, which takes the course of the other nerves to the front of the chest; but the latter gives no lateral cutaneous branch. The second intercostal nerve is remarkable for the large size of its lateral cutaneous nerve, the intercosto-humeral. The six inferior intercostal nerves at the termination of the in- tercostal spaces continue their course to the middle line of the body between the abdominal muscles. CONTENTS OP THE POSTERIOR MEDIASTINUM. Returning now to the middle line, the student may examine and dissect the parts which are usually enumerated as being con- tained in the posterior mediastinum. They are the oesophagus, aorta, venae azygos, and thoracic duct. In front of them, at the upper part of the chest, and for the first time fully brought into view, is the trachea. TRACHEA. The trachea or windpipe extends from the larynx to the lungs ; it lies over the vertebral column, and is about four inches in length. Its commencement corresponds in position with the fifth cervical vertebra, and its termination, where it divides into the two bronchi with the third dorsal vertebra. It is cylindrical for three-fourths of its circumference, but flattened behind, where it is in relation with the oesophagus. The bronchi have the same shape as the trachea, but the bronchial tubes into which the bronchi divide are perfectly cylindrical. The right bronchus, about an inch in length, is horizontal in direction, occupies the upper part of the root of the lung ; and divides into three bronchial tubes for the three lobes of the lung. The left bronchus, two inches in length, is oblique in direction, smaller than the right, and descends to the middle of the root of the lung. It divides into two bronchial tubes for the two lobes of the lung. In structure the trachea and bronchi are composed of fibre-cartilaginous rings, connected by a fibrous membrane ; they have also entering into their composition, muscular fibres, a coat of elastic tissue, mucous mem- brane and mucous glands. (ESOPHAGUS. 333 The fibro-cartilaginous rings are from fifteen to twenty in number, and extend for two-thirds around the cylinder of the trachea. The lowest ring differs in shape from the rest, being prolonged to a V-shaped point between the bronchi at the bifurcation of the trachea. The fibrous membrane incloses the rings completely, and forms a dis- tinct layer over their outer surface. The muscular fibres form a thin stratum, extending transversely be- tween the cartilaginous rings behind. The elastic coat is composed of fibres of elastic tissue disposed longi- tudinally. Where they invest the cartilages they form a thin layer, but behind, in the flat part of the tube between the cartilages, the fibres are gathered into strong fasciculi. The mucous membrane is closely adherent to the elastic coat, and is continuous above with the lining of the larynx, and below with that of the bronchial tubes. The mucous glands are small ovoid bodies situated externally to the fibrous membrane, and between that membrane and the muscular layer behind, and in the substance of the fibrous membrane between the rings. Their ducts open upon the mucous membrane. (ESOPHAGUS. The oesophagus commences in the neck oppo- site the fifth cervical vertebra, and pursues a slightly flexuous course through the posterior mediastinum to the cesophageal opening of the diaphragm. Through the neck it inclines slightly to the left side ; having entered the thorax, it bends a little to the right, and reaches the midline of the vertebral column oppo- site the fifth dorsal vertebra ; it then turns again to the left, gets in front of the aorta, and passes through the cesophageal opening in front of that vessel. In the upper part of the thorax the oesophagus lies behind the trachea, projecting a little on its left side ; it then passes behind the arch of the aorta, the left bronchus, and the pericardium. Laterally, it is in relation with the pleura ; on the right with the great vena azygos, and on the left with the aorta. It rests in its course downwards on the longus colli muscles, the right inter- qostal arteries, thoracic duct, and lower down on the aorta. In structure the oesophagus is composed of three coats, muscular, cellu- lar, and mucous. The muscular coat consists of two layers of fibres, longitudinal and cir- cular. The longitudinal fibres are connected above with the cricoid car- tilage and muscular structure of the pharynx, and form a thick stratum around the tube ; inferiorly they expand upon the stomach. The circular fibres forming the internal layer are continuous above with the muscular structure of the pharynx, and are also attached to the cricoid cartilage ; inferiorly they enlarge and surround the stomach. The muscular fibres of the upper part of the oesophagus are of the striated kind, the muscle of animal life ; and those of the lower part the non-striated kind, the muscle of organic life. The cellular coat is a moderately thick layer of cellular tissue, which connects together the muscular and the mucous coat ; it is loosely adhe- rent to the former, but closely to the latter. The mucous coat is thick, and presents upon its surface a few minute 334 THE DISSECTOR. and scattered papillae. It is arranged in longitudinal plicce, and is covered by a thick whitish epithelium of the squamous or tessellated kind. It is but loosely connected with the muscular coat. The mucous glands of the oesophagus (oesophageal glands) are most abundant at the lower part of the tube ; they are small lobulated bodies, situated in the cellular coat, and opening on the surface of the mucous membrane by means of long excretory tubes. THORACIC AORTA. The thoracic aorta, commencing at the lower border and left side of the third dorsal vertebra, curves gently towards the right as it descends, and as it passes through the aortic opening of the diaphragm lies upon the middle line of the vertebral column. The branches of the thoracic aorta are, the pericardiac, bron- chial, oesophageal, posterior mediastinal, and intercostal. The bronchial arteries, generally three in number, one for the right lung and two for the left, vary both in size and origin ; the right often proceeding from a short trunk common to it and one of the left bronchial branches, or from the first aortic intercostal. They take their course to the back of the root of the lung, and accompany the ramifications of the bronchial tubes through its substance. They give twigs also to the bronchial glands, oeso- phagus, and pericardium. The cesophageal arteries, four or five in number, arise from the anterior part of the aorta, and are distributed to the oesophagus, establishing a chain of anastomoses along that tube : the supe- rior inosculate with the bronchial arteries, and with oesophageal branches of the inferior thyroid arteries ; and the inferior with similar branches of the phrenic and gastric arteries. The posterior mediastinal arteries are small twigs distributed to the lymphatic glands and cellular tissue of the posterior medi- astinum. The intercostal arteries, nine in number on each side, the two superior spaces being supplied by the superior intercostal artery, a branch of the subclavian, arise from the posterior part of the aorta. The right intercostals are longer than the left on account of the position of the aorta. They ascend somewhat obliquely from their origin, and cross the vertebral column behind the thoracic duct, vena azygos major, and sympathetic nerve to the intercostal spaces ; the left passing beneath the superior inter- costal vein, vena azygos minor, and sympathetic. In the intercostal space, the artery comes into relation with the vein and nerve, the former being above, and the latter imme- diately below it. It is covered in by a thin fascia, continued from the free edge of the internal intercostal muscle to the vertebra ; and rests upon the external intercostal muscle. On first entering the intercostal space, the intercostal artery gives off a dorsal branch f which passes back close to the vertebrae VENA AZYGOS. 335 and between their transverse processes, to be distributed to the muscles and integument of the back, and by means of a small spinal twig to the interior of the vertebral column. The artery next takes its course along the middle of the intercostal space, and gradually ascends to the lower border of the rib above, with which it comes into relation at about its angle ; the artery then follows the lower border of the rib, lying between the two planes of intercostal muscles to the front of the chest, where it inoscu- lates with the corresponding anterior intercostal branch of the internal mammary artery. Besides the dorsal branch, and several small muscular branches, the intercostal artery, at about the middle of its course, gives off a large branch, which runs along the upper border of the rib below, to the front part of the chest, and inosculates with an anterior intercostal branch of the internal mammary. The upper pair of aortic intercostal arteries inosculate with the superior intercostals of the subclavians ; the lower pair anasto- mose with the lumbar and epigastric arteries in the parietes of the abdomen. SUPERIOR INTERCOSTAL ARTERIES. Supplying the upper two intercostal spaces on each side is the superior intercostal artery. It arises from the subclavian artery, and descends over the necks of the first and second ribs externally to the sympathetic nerve, and inosculates with the first aortic intercostal. It sends off branches to the first and second intercostal spaces, and dorsal branches to the muscles and integument of the back. VEINS OF TUB POSTERIOR MEDIASTINUM. The venae azygos major and minor and left superior intercostal vein constitute a small prevertebral system of veins, interposed between the supe- rior and inferior vena cava, and communicating with both. The VENA AZYGOS MAJOR commences in the lumbar region by a communication with the right lumbar veins. It passes through the aortic opening of the diaphragm, ascends along the right side of the vertebral column, and opposite the third dorsal vertebra arches forward over the root of the right lung, to terminate in the superior vena cava at its entrance into the pericardium. In its course its lies superficially to the right intercostal arteries, having the thoracic duct on its left and the pleura on its right side. It receives all the intercostal veins of the right side (with the exception of those of the first and second spaces), the vena azygos minor, and the right bronchial vein. The VENA AZYGOS MINOR commences in the lumbar region by a communication with one of the left lumbar veins, or with the left renal : it enters the chest through the aortic opening, or, more frequently, through the crus of the diaphragm, and ascends the left side of the vertebral column to the fifth or sixth vertebra, 336 THE DISSECTOE. Fig. 104. L which it crosses to terminate in the vena azygos major. It re- ceives the six or seven lower intercostal veins of the left side. The azygos veins have no valves. The right superior intercostal vein receives the veins of the first and second intercostal spaces, and opens into the subclavian vein of the same side. The left superior intercostal vein receives the veins from all the intercostal spaces (five or six) of the left side above the vena azygos mi- nor and the left bronchial vein. It communicates below with the vena azygos minor, and crosses the arch of the aorta to terminate in the left vena innominata. THORACIC DUCT. The thoracic duct is the great trunk of the lymphatic and chylous system. It commences in the abdomen on the second lumbar verte- bra by an enlargement of considerable size termed receptaculum cliyli ; enters the chest through the aortic opening, ascends upon the vertebral column be- tween the aorta and vena azygos major, and terminates at the root of the neck on the left side by opening into the angle of junction between the internal jugular and subclavian vein. At the aortic opening the thoracic duct lies close to the right crus of the diaphragm, in the thorax it rests upon the right intercostal arteries, and opposite the fourth dorsal vertebra inclines to the left side. A little higher it passes be- hind the arch of the aorta and reaches the left side of the oesophagus along which it takes its course, lying behind the left subclavian artery, to the root THE VEINS OF THE TRUNK. 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 superior intercostal vein. 8. The great vena azygos, communicating in- feriorly with one of the lumhar veins. 9. The lesser vena azygos, communicating inferiorly with a lumbar and with the left renal vein. 10. The inferior vena cava. 11, 11. The two common iliac veins. 12. The left external iliac. 13. The internal iliac vein. 34. 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. LYMPHATIC GLANDS. 33T of the neck. It there makes a hook-like bend from behind for- wards, to its termination. The thoracic duct is about eighteen or twenty inches in length, and near its origin as large as a goose quill ; as it ascends it diminishes in size, and near its termination again becomes dilated. At about the middle of the thorax it frequently divides into two branches, which soon after reunite ; sometimes it forms a kind of plexus in this situation ; and occasionally divides into two branches near its termination. The thoracic duct within the thorax receives the lymphatics of the left side of the chest, and from the left side of its contained viscera. The lymphatics of the right side of the chest and right half of the thoracic viscera terminate in a short trunk, the ductus lymphaticus dexter, situated in the root of the neck of the right side, and terminating in the junction of the right internal jugular and right subclavian vein. The thoracic duct and ductus lymphaticus dexter are both provided with valves, and at their termination is a large valve which prevents the regurgitation of blood from the veins. LYMPHATIC GLANDS. The lymphatic glands of the thorax are the anterior mediastiual, intercostal, cesophageal, bronchial, and cardiac. The anterior mediastinal glands are situated along the course of the internal mammary arteries ; they are six or seven in number on each side, and receive the lymphatic vessels from the anterior wall of the chest, the mediastinum, thymus gland, and pericardium. The intercostal glands are situated near the intercostal arteries on each side of the vertebral column. They receive the lymphatics from the intercostal spaces and posterior wall of the thorax. The cesophageal glands, fifteen or twenty in number, are situ- ated in the course of the oesophagus, and receive the lymphatics of that tube. The bronchial glands, ten or twelve in number, are placed near the bifurcation of the trachea and the roots of the lungs. They receive the lymphatics of the lungs both superficial and deep. The cardiac glands are three or four in number, and placed near the arch of the aorta ; they receive the lymphatics of the heart. All the lymphatics of the chest terminate eventually in the thoracic duct or ductus lymphaticus dexter. Internal Parietes of the Thorax. The intercostal muscles, which are examined, upon the exterior of the chest, at page 354, may now be studied from within. The internal intercostal is seen to terminate by an abrupt border, from which a thin aponeu- rosis is continued onwards over the intercostal vessels and nerve to the side of the vertebral column. 338 THE DISSECTOR. Iii the dome of the chest maybe examined the relative position of the parts which pass to and from the chest ; and in its floor the unequally convex surface of the diaphragm, with the open- ings which give passage to parts passing to and from the ab- domen. In the superior opening of the thorax will be seen, from before backwards, the sterno-hyoid and sterno-thyroid muscles ; remains of the thymus gland ; vense innominatae ; phrenic and pneumo- gastric nerves ; arteriainnominata and left carotid artery ; cardiac nerves ; trachea ; left recurrent nerve ; oesophagus ; left subclavian artery ; thoracic duct ; longus colli muscles ; superior intercostal arteries ; first dorsal nerve ; and sympathetic. Besides these parts, which are in the state of transit, there is at each side the pouch of pleura for the reception of the summit of the corresponding lung. The apertures in the floor of the thorax, and the parts to which they give passage, are, the quadrilateral opening in the tendinous centre of the diaphragm for the inferior vena cava ; the elliptical opening in the muscular structure of the diaphragm for the oeso- phagus and pneumogastric nerves, and the musculo-fibrous arch behind the central part of the diaphragm, the aortic opening, for the aorta, thoracic duct, and right vena azygos. The left vena azygos, sympathetic, and splanchnic nerves, pass through irregu- lar intervals in the muscular structure of the crura of the dia- phragm. After completing the thorax, the student must turn his attention to the dissection of the back and its muscles. CHAPTER VII. 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 super- ficial 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 connection between the upper ex- tremity and the rest of the skeleton ; it is the fulcrum of action UPPER EXTREMITY MUSCLES. 339 of the entire limb, and is prominently characteristic of animals possessing great power in the arms, as man, the bat, the mole, birds, &c. The scapula is a flat bone, and affords by its con- struction peculiar advantages ; giving origin, by its extensive surface, to a number of muscles, and being itself movable on the convexity of the thorax. This is the bone which secures the connection of the arm with the trunk, and provides for all the diversity of movement so characteristic of the upper extre- mity, and which entitles it to the designation of an " universal joint." The next bones, the humerus, radius, and ulna, have for their office the extension of the limb, for the purpose of supply- ing to the beautiful apparatus of the hand 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 muscles. The carpus is an assemblage of small bones belonging to the class of short bones. They are all slightly movable 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 intended for their action; they give breadth and extent to the hand, and facility in all the movements which that important organ is destined to perform. The muscles are naturally divided into groups, which concur mutually in certain actions necessary to the effective movements of the limb. The distribution of these groups, with their corre- sponding duties, will be best seen in a tabular analysis, thus : Anterior Thoracic Group. Posterior Thoracic Group, Pectoralis major. Trapezius. Pectoralis minor. Levator anguli scapulae. Subclavius. Rhomboideus major. Serratus magnus. Rhomboideus minor, Humeral Group. Subscapularis. Latissimus dorsi, Supra-spinatus. Pectoralis major, Infra-spinatus. Deltoid. Teres minor. Coraco-brachialis. Teres major. Anterior Brachial Group. Posterior Brachial Group. Biceps. Triceps. Brachialis anticus. Anconeus. 340 THE DISSECTOR. FORE- ARM. Anterior Group. Posterior Group. Pronator radii teres. Snpinator 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 nlnaris. Flexor digitorum profundus. Extensor communis digitornm. Flexor pollicis longus. Extensor minimi digiti. Palmaris longus. Extensor pollicis ossis metacarpi. Extensor pollicis primi internodii. Extensor pollicis secundi internodii. Extensor indicis. HAND. Radial Group. Ulnar Group. Flexor ossis metacarpi. Palmaris brevis. Flexor brevis 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 sup- p'orting heavy weights and becoming the point of resistance 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 an universal joint, and so valuable in application to its extensive uses. The muscles of the anterior brachial group are the flexors of the elbow, the perfect flexion of the joint being procured by an advantageous attachment to both the radius and ulna. The posterior brachinl group is the antagonist to the former, and ex- tends the forearm. Now, it is fair to anticipate, that as the bones increase in number, and the limb is carried further from the centre, the movements will increase in proportionate ratio. The move- ments of the shoulder were those of totality : the 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 forearm, the pronators and supinators, the former throwing the wrist and UPPER EXTREMITY ARTERIES. 341 hand inwards, the latter outwards. Now this action could not be effectively produced without the exertion of muscular force upon the axis of support to the wrist ; and we therefore find that the radius alone articulates with the wrist, and administers to all its movements, 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 musctes, jlexores and extensores carpi. The fingers are simply supplied for all their numerous movements of flexion and extension, by three flexors situated in the forearm, 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 pro- vides by its strength and elasticity for a powerful resistance to shocks received upon the surface of the hand. The muscles of the hand are flexors, abductors, and adductors. The short flexors of the thumb and little finger are necessary to the strength of grip so characteristic of the human hand. All the remaining muscles are abductors and adductors, with the exception of the palmaris brevis, which contracts the integument on the side of the hand, and the lurnbricales, which are accessory in their actions to the deep flexor. The abductor and adductor of the thumb are known by those names; the analogous muscles of the index finger are the first dorsal and first palmar interosseous ; 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 and third palmar interosseous. These movements of abduction 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 com- mences 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 inter- venes 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 protected situations for their course. Thus they are constantly placed on the inner side of the limb, and avoid the convexities of joints, where they would be subjected to injury, both from external pressure and over extension. The brachial artery is therefore 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 accqmr 29* 342 THE DISSECTOR. modates itself to the augmented lateral breadth of the forearm, and its increased number of components, the radius, the ulna, and intermediate space, by dividing into three branches corre- sponding with these three parts, the two bones and the interos- seous space. Its branches, therefore, are radial, ulnar, and inter- osseous ; 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 forearm, 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 forearm, 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 re- markable magnitude, as the profunda arteries. Other named branches owe their names to peculiarity of structure, and are, therefore, easily remembered. But the joints which are exposed to pressure and are uncovered, except by integument, derive an abundant supply of branches from all the surrounding sources. For instance, the elbow joint is provided with eight nutrient branches, the superior profunda and its posterior articular branch, inferior profunda, anastomotica magna, radial recurrent, anterior and posterior ulnar recurrents, 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 interest with their ex- istence. The veins of the upper extremity are the superficial and the deep : the former are placed between the two layers of the super- ficial fascia, the latter are associated with the arteries. All the arteries of the limbs and trunk which are below the second mag- nitude are accompanied by two veins, named " Venae comites ;" thus the radial, ulnar, interosseous, and brachial arteries, with their branches, have each their corresponding venae comites. The axillary and subclavian have each a single vein. The lymphatic vessels are rarely seen in an ordinary dissection, excepting under very favorable circumstances, as in anasarca, when they are sometimes observed, as white opaque threads, traversipg t^e transparent jelly-like cellular substance, and enter- UPPER EXTREMITY NERVES. 343 ing the lymphatic glands at all points of their circumference. They follow in their course the direction of the veins to which they bear an analogy. The lymphatic glands are accumulated in the loose cellular tissue of the axilla, arid 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 which is formed by the last four cervical and first dorsal nerve. A plexus is the means by which nervous branches destined to a single apparatus are associated in their structure previously to distribution, so that the sensations of each filament may harmonize with all the rest, and produce the unity of im- pulse which is necessary to perfect action. For it is evident that if an impression were received by the terminal filament of any one nerve, and excited a reflex movement, without a simultaneous impression upon the other nerves of the same limb and conse- quent muscular movement, 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 neighboring part of the chest ; and 2d, those destined to the arm. The former are named thoracic and scapular : the latter consist 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 forearm and hand, musculo-spiral, ulnar, and median. Let us now proceed to the dissection of the upper extremity, beginning with the ANTERIOR THORACIC REGION. Dissection. Make an incision along the line of the clavicle, from its sternal extremity, for about two-thirds of its length ; carry a second in- cision longitudinally along the middle of the sternum to its lower extremity, and a third along the lower border of the pectoral is major muscle and anterior border of the axilla to the arm. Dissect back the integument from the area included within these incisions. Then, in order further to expose the side of the chest and the axilla, carry a fourth incision from the angle of the preceding at the lower end of the sternum horizontally outwards to the side of the chest, three or four inches' below the axilla, and reflect the integument as before. The dissector should next proceed to seek for the cutaneous nerves situated in the superficial fascia, and in the upper part of the region he will find a thin stratum of muscular fibres, a part of the cutaneous muscle of the side of the neck, platysma myoides. He may then study the mammary gland, and, after this has been completed, dissect off the deep fascia from the whole of 344 THE DISSECTOR. the region and examine the muscles. In removing the deep fascia, the student must be reminded of the necessity of dissecting in the course of the fibres of the muscles, and his progress will be facilitated by put- ting the muscles on the stretch. The cutaneous nerves of the anterior thoracic region are, seve- ral cutaneous branches from the cervical plexus, which pass down over the clavicle and are distributed to the integument covering the pectoralis major muscle ; anterior-cutaneous of the thorax, which pierce the pectoralis major muscle near the sternum, and are reflected outwards to the integument and mammary gland ; and lateral cutaneous nerves of the thorax, which issue from the intercostal spaces on the side of the chest, and proceed upwards and forwards around the lower border of the pectoralis major to the integument covering that muscle, and to the mammary gland. On the side of the chest in and below the axilla are several cuta- neous nerves, proceeding from the lateral cutaneous branches of the intercostal nerves : these are the posterior branches of the lateral cutaneous nerves. Some pass backwards over the poste- rior border of the axilla, and are distributed to the integument covering the latissimus dorsi muscle and lower part of the scapula ; and two, proceeding from the second and third inter- costal nerves, are distributed to the integument of the inner side of the arm under the name of inter costo-humeral nerves. Mammary Gland. The mamma may be best studied in the female, although it exists also in the male. It is situated in the pectoral region, being separated from the pectoralis major mus- cle by the deep fascia ; and occupies a circular space which extends longitudinally from the third to the sixth rib, and hori- zontally from near the sternum to the axilla. Its base is some- what elliptical, the long diameter corresponding with the direc- tion of the fibres of the pectoralis major muscle ; and the left mamma is generally a little larger than the right. Near the centre of the convexity of each mamma is a small prominence of the integument, called the nipple (mammilla), which is surrounded by an areola having a colored tint. In females of fair complexions, before impregnation, the color of the areola is a delicate pink ; after impregnation, it assumes a brownish hue, which deepens in color as pregnancy advances ; and after the birth of a child, the brownish tint continues through life. The areola is furnished with a considerable number of seba- ceous glands, which secrete a peculiar fatty substance for the pro- tection of the delicate integument around the nipple. During suckling these glands are increased in size, and have the appear- ance of small pimples, projecting from the skin. At this period, they serve by their increased secretion to defend the nipple and areola from the excoriating action of the mouth of the infant. MAMMARY GLAND. 345 In structure, the mamma is a conglomerate gland, and consists of lobes, which are held together by a dense and firm cellular tissue ; the lobes are composed of lobules, and the lobules of minute csecal vesicles, the ultimate terminations of the excretory ducts. The excretory ducts (tubuli lactiferi, galactophori), from fifteen SUPERFICIAL NERVES Fig. 105. AND MUSCLES OP THE TRUNK. a. The platys- ma myoides muscle, b, b. The sterno-mastoid. c, c. The trapezius. d. Part of the deltoid, e. The pectoralis major. /. The biceps, g. The co- raco-brachialis. h. The triceps. *. The teres ma- jor, k. The teres minor. /, /. Thelatissimusdorsi. 771, m. The serratusmag- nus. The upper m is situ- ated in the lower part of the cavity of the axilla. n. The external oblique muscle ; the letter is ]>l;ir' SHOWING THE 360 THE DISSECTOR. In studying the connections of this muscle, the student should direct his attention to a muscle attached to the posterior border of the scapula, the rhomboideus major, and above this the small band of muscle, rhom- boideus minor, which is attached to that portion of the border which cor- responds with the base of the triangular expansion of the spine of the scapula over which the trapezius glides. The next two muscles are con- nected with the lower or anterior border of the scapula. The TERES MINOR (teres, round) muscle arises from the poste- rior surface of the lower border of the scapula for about the middle third of its extent. It is closely connected with the lower border of the preceding muscle, and is inserted into the inferior depression of the greater tuberosity of the humerus. The tendons of the three preceding muncles, with that of the subscapularis, are in immediate contact with the joint, and form part of its ligamentous capsule, thereby preserving the solidity of the articulation. They are therefore the structures most fre- quently ruptured in dislocation of the shoulder-joint with violence. The TERES MAJOR muscle arises from the dorsal surface of the inferior angle of the scapula, and from its inferior border. It is inserted conjointly with the tendon of the latissimus dorsi into the posterior bicipital ridge of the humerus. At its origin this muscle is covered by the latissimus dorsi, but the latter shortly afterwards curves around its lower border, and becomes placed in front. The two tendons at their insertion, one lying behind the other, are separated by a bursa. The VESSELS and NERVES of the posterior scapular region are the supra-scapular artery and nerve, and the dorsalis scapulae branch of the subscapular artery. The supra-scapular artery, a branch of the thyroid axis of the subclavian, crosses the root of the neck to the superior border of the scapula ; it then passes over the transverse ligament of the supra-scapular notch, and enters the supra-spinous fossa, getting beneath the supra-spinatus muscle. After giving branches to that muscle and the shoulder-joint, the artery passes in front of the spine of the scapula into the infra-spinous fossa, where it inosculates with dorsalis scapulae and posterior scapular. The supra-scapular nerve, a branch of the brachial plexus, enters the supra-spinous fossa through the supra-scapular notch, and, after supplying the muscle and shoul'der-joint, passes with the artery into the infra-spinous fossa, and is distributed to the infra-spinatus muscle. The dorsales scapula artery, a branch of the subscapular, curves around the inferior border of the scapula through the triangular space bounded by the teres minor above, teres major below, and long head of the triceps in front, and passing beneath the teres minor enters the infra-spinous fossa, and is distributed to its muscle, inosculating with the termination of the supra-scapular ANTERIOE SCAPULAE REGION. 361 Fig. 110. artery. While in the triangular space it gives off a branch which runs between the teres minor and major to the angle of the sca- pula, and inosculates with the posterior scapular artery. The posterior circumflex artery and nerve which supply the teres muscles will be found in the quad- rangular space in front of the long head of the triceps ; and along the posterior border of the scapula may be seen the twigs of distribution of another scapular artery, the posterior scapular. The posterior scapular artery is a branch of the transversaliscolli of the subclavian ; it descends along the posterior border of the scapula under cover of the levator an- guli scapulae and rhomboid muscles to the inferior angle. In its course it gives branches to both surfaces of the scapula, and inosculates in the infra-spinous fossa with supra-scapular and dorsalis scapulae arteries, and at its termination with the subscapular artery. Anterior Scapular Region. The only muscle situated in the anterior scapular region is the subscapularis, which is bound down by a thin process of aponeurotic fascia. To this aspect, along the posterior border of the scapula, is attached the serratus magnus muscle. The vessels and nerves of the region are the subscapular ; the posterior sca- pular artery may be seen uncovered by muscle lying along its posterior border. The SUBSCAPULARIS muscle arises from the whole of the under surface of the scapula excepting the superior and inferior in s upwards to the scapular angles, and terminates by a broad and eoicL^roS^iigamJnt* thick tendon, which is inserted into the passing outwards to the lesser tuberosity of the humerus, and by acromion. 4. The subsca- muscular fibres into the surface of bone immediately below that process. The substance of the muscle is traversed by several intersecting membranous layers, from which muscular fibres arise, the in- tersections being attached to the ridges on the surface of the scapula. Its tendon forms part of the capsule of the joint, glides over a large bursa which separates it from the 31 THE MUSCLES OP THE ANTERIOR ASPECT OF THK UPPER ARM. 1. The co- racoid process of the scapu- la. 2. Thecoraco-clavicular ligament (trapezoid), pass- 5. The teres major. 6. The cora- co-brachialis. 7. The bi- 8. The upper end of internal head of the triceps. 362 THE DISSECTOR. base of the coracoid process, and is lined by a prolongation of the synovial membrane of the articulation. The SUBSCAPULAR ARTERY, lying along the lower border of the scapula, sends branches to the subscapularis muscle, and inoscu- lates with the posterior scapular. A branch (infra-scapular) from the dorsalis scapulae passes beneath the muscle, and on the surface of the bone, inosculates with the supra-scapular above, and the posterior scapular behind. The subscapular nerves have been already described ; page 353. Anterior Brachial Region. Having placed the arm in a convenient position for dissection, an in- cision 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 dis- sected carefully back, and the superficial fascia exposed. The superficial vessels and nerves are then to be sought for in the superficial fascia, and examined. Lying along the outer side of the convexity formed by the biceps is a large vein, the cephalic, which may be traced upwards to the interspace between the deltoid and pectoralis major, and downwards to the outer side of the elbow-joint; below the elbow- joint it is the radial vein. On the inner side of the convexity of the biceps is another large vein, basilic, which at the elbow is formed by the union of the anterior and posterior ulnar veins. In the middle line of the forearm, between the radial and ulnar veins, is the median vein, which just below the elbow divides into two brandies, one to join the cephalic vein, median cephalic, and one to the basilic vein, median basilic. Behind the cephalic vein, and commencing at the middle of the arm, are two cutaneous branches from the musculo-spiral nerve ; and in the groove to the outer side of the tendon of the biceps at the bend of the elbow the external cutaneous nerve pierces the deep fascia. On the inner side of the arm immediately below the axilla, may be found the intercosto-humeral nerve and a cuta- neous branch of the musculo-spiral ; at about the middle of the upper arm the internal cutaneous nerve pierces the fascia and runs down the arm by the side of the basilic vein ; and at the lower third of the upper arm, and behind the preceding, is the lesser internal cutaneous nerve, or nerve of Wrisberg. CUTANEOUS VEINS. The median vein is so named from its position in the middle of the forearm. It receives the returning blood from the front of the hand and forearm, and near the elbow forms a trunk of moderate size, which is increased by a communicating branch, 9, from the deep veins. Just below the bend of the elbow, the median divides into two branches the median basilic and median cephalic. ANTERIOR BRACHIAL REGION. 363 Fig. 111. The median basilic vein, the larger of the two, passes obliquely inwards along the border of the biceps, and unites with the com- mon trunk of the ulnar veins to form the basilic vein. It crosses the braci'ial artery, being separated from it by the deep fascia, which is here strengthened by an aponeurotic slip, given off by the edge of the tendon of the biceps. The vein has one or two filaments of the internal cutaneous nerve passing in front, and others passing behind it. The relations of this vein should be carefully studied, in reference to the operation of bleeding, this being the vein the best suited for the purpose. The median cephalic vein, longer and somewhat smaller than the preceding, inclines outwards in the groove between the biceps and the supinator longus, to unite with the radial vein, and form the cephalic vein. The branches of the ex- ternal cutaneous nerve pass behind it. From the depth of the groove in which this vein is placed, and its smaller size, it is not usually selected for the operation of bleeding. In the best performed operations on these veins, inconvenience sometimes arises from the wound or division of the cutaneous nerves. This accident is most likely to occur in opening the median basilic, because the internal cutaneous nerves pass in front of that vein ; the ex-, ternal cutaneous nerves being behind the median cephalic vein. The results of such an accident may be slight or serious, in proportion to the dexterity of the operator, or the condition of the lancet. A sharp blade and a clean wound can never do amiss. THE SUPERFICIAL ANATOMY OF THE BEND OF THE ELBOW. 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 median vein. 9. The communi^ cation between the deep veins of the forearm 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 artery. 13. The slip of fascia derived from the tendon of the biceps, which separates the median basilic vein from the bra- chial artery. 14. The external cutaneous nerve, piercing the fascia and dividing into two branches, which pass behind the median cephalic vein. 15. The inter- nal cutaneous nerve dividing into branches, which pnss in front of the medirn basilic vein. 16. The nerve of Wrisberg. 17. The spiral cutaneous nerve, branch of the m use ulo -spiral nerve. 364 THE DISSECTOR. Occasionally the median basilic is completely transfixed, and the process of fascia derived from the edge of the biceps tendon injured. Inflammation may supervene and be followed by con- traction of the fascia, causing great pain and deformity to the patient. But this is not all ; the brachial artery is sometimes wounded also. The lancet has transfixed the entire cylinder of the vein, the process of fascia, and the coats of the artery. The conse- quences of this accident cannot be too strongly impressed upon the student's recollection, they are as follows : 1. " False aneurism is the most common form of disease fol- lowing the accidental wound of the artery at the bend of the arm." 1 In this case the blood rushing from the wounded vessel forms for itself a sac by the condensation of the surrounding tissues. 2. Aneurismal varix is the accident next in frequency: "the coats of the vein and artery become firmly agglutinated," and "the arterial blood is poured into the vein at each contraction in a small and forcible stream, occasioning a peculiar shrill sound." 3. The third variety, " Varicose aneurism," is rare. It con- sists in the formation of a false aneurism between the artery and vein, and communicating with both. Thus it may be shown that this operation, so apparently simple and easy of execution, that is constantly intrusted to the hands of the tyro apprentice, often before he has ever opened a manual of anatomy, is attended with dangers, if caution be not used, equal to those of many of the greater operations of surgery. We therefore advise the dissector not to pass hastily over this region, but consider well its relations and appliances. If other reasons for his attention were needed, he should recollect that every man is a judge of so common a proceeding. The radial vein collects the venous blood from the thumb and outer aspect of the hand and forearm; it is often of small size. Its junction with the median cephalic constitutes the cephalic vein. The cephalic vein (xf^>a^r>, the head) ascends the outer side of the arm to the groove between the pectoralis major and deltoid, where it is in relation with the descending branch of the thoracica acromialis artery, and terminates beneath the clavicle in the axil- lary vein. A large communicating branch sometimes crosses the clavicle between the external jugular and this vein, which gives it the appearance of being derived directly from the head hence its appellation. 1 The passages between inverted commas are quotations from Liston's " Practical Surgery." CUTANEOUS NERVES. 365 The ulnar veins, anterior and posterior, unite near the bend of the elbow to form a common ulnar trunk, and the latter, after receiving the median basilic, becomes the basilic vein. The basilic vein (J3aerficialis volee. 15. The ulnar artery. 16. Its superfi- cial palmar arch giving off digital branches to three fingers and a half. 17. The magna pollicis and radialis indicis arteries. 18. The posterior ulnar recur- rent. 19. The anterior interosseous artery. 20. The posterior interosseous, as it is passing through the interoseeous membrane. ARTERIES OF THE FOREARM. 379 the venae comites, and is in relation with the nlnar nerve for the lower two-thirds of its extent ; the nerve lying to its ulnar side. / Operations. The ulnar artery is usually tied in three situations : 1st. At the commencement of the middle third of the forearm, where it emerges from beneath the flexor sublimis. 2d. In the lower third. 3d. As it crosses the annular ligament. In the first two operations the border of the flexor carpi ulnaris muscle and tendon is the guide for the incision, in the latter the pisiform bone. The high operation is the most difficult, on account of the depth of the artery and the danger of separating the wrong muscles. The lower operations are simple and easy, the artery lying quite superficially. The ulnar nerve lies immediately to the ulnar side of the artery from the commencement of the middle third to the wrist, and therefore is not endangered in the upper operation. The venae comites are one at each side. The structures to be cut through are the integument, superficial fascia, deep fascia, the sheath of the vessels, and, at the wrist, the palmaris brevis muscle and tendinous band. The length of incision for the upper operation is three inches, and for the lower two. In wounds of arteries, wherever they occur, both extremities of the vessel are to be tied ; and this is the rule of practice for wounds in the palm of the hand. The branches of the nlnar artery in the forearm are the Anterior ulnar recurrent, Anterior carpal, Posterior ulnar recurrent, Posterior carpal, Jnterosseous, Metacarpal. Muscular, The anterior ulnar recurrent arises immediately below the elbow, and ascending between the pronator radii teres and bra- chialis anticus gives branches to the muscles and inosculates with the inferior profunda and anastomotica magna. This artery fre- quently arises from a common trunk with the following : The posterior ulnar recurrent, larger than the preceding, passes beneath the flexor sublimis digitorum muscle to the notch between the inner condyle and the olecranon, where it is in relation with the ulnar nerve, and inosculates with the inferior profunda and anastomotica magna. The interosseous artery is a short trunk, which arises opposite the tuberosity of the biceps, and passes backwards to the interos- seous membrane, where it divides into the anterior and posterior interosseous. The anterior interosseous artery passes down the front of the interosseous membrane, between the flexor profundus digitorum and flexor longus pollicis, and behind the pronator quadratus ; it then passes through an opening in the interosseous membrane to the back of the wrist, where it inosculates with the posterior carpal branches of the radial and ulnar. The anterior iuteros- seous artery gives off several muscular branches; nutrient branches to the radius and ulna; a companion branch to the median nerve ; 380 THE DISSECTOR. and at the upper border of the pronator quadratus, a small branch, which descends behind that muscle to inosculate with the anterior carpal arteries. ^ The posterior interosseous artery passes backwards through an opening between the upper part of the interosseous membrane and the oblique ligament, and descends between the superficial and deep layer of muscles of the back of the forearm to the wrist, where it inosculates with the posterior carpal arteries, and with the termination of the anterior interosseous. The posterior inter- osseous artery gives off at its upper part a recurrent branch, which ascends between the supinator brevis and extensor carpi ulnaris, and enters the anconeus, where it inosculates with a branch of the superior profunda. The muscular branches of the ulnar artery are distributed to the muscles of the ulnar border of the forearm. The anterior carpal branch crosses in front of the wrist-joint, and inosculates with the anterior carpal branch of the radial artery, forming an anterior carpal arch. The posterior carpal branch, taking a similar course across the back of the wrist, forms, with a similar inosculation, a posterior carpal arch. The metacarpal branch, often a branch of the preceding, passes along the inner border of the metacarpal bone of the little finger, and forms the dorsal collateral branch of that finger. The NERVES of the forearm are the radial, ulnar, and median, which belong to its anterior aspect ; and the interosseous, the nerve of its posterior region. The RADIAL NERVE, one of the terminal branches of the mus- culo-spiral (page 371), passes downwards along the outer side of the radial artery, and overlapped by the supinator longus to the lower third of the forearm, where it turns beneath the tendon of that muscle, and piercing the deep fascia is distributed to the back of the hand, the thumb, and two fingers and a half (page 372). The MEDIAN NERVE (page 370), lying in the hollow of the bend of the elbow, passes between the two heads of the pronator radii teres. It next gets beneath the flexor sublimis digitorum, and descends the middle of the forearm, lying between that muscle and the flexor profundus to its lower fourth. There it becomes superficial, and running along the outer border of the tendons of the flexor sublimis, passes beneath the annular ligament, and enters the palm of the hand. The branches of the median nerve in the forearm are, muscular, anterior interosseous, and superficial palmar. The muscular branches are distributed to all the muscles of POSTERIOE REGION OP THE FOREARM. 381 the superficial layer, except the flexor carpi ulnaris, and to one of the deep layer, the flexor profundus digitorum, its radial half. Tke anterior interosseous nerve, of large size, accompanies the anterior interosseous artery, and supplies the deep layer of muscles of the front of the forearm. The superficial palmar branch leaves the median nerve at the lower part of the forearm, and piercing the deep fascia, crosses the annular ligament, and is distributed to the integument of the palm of the hand. The TJLNAR NERVE (page 3 tO), entering the forearm in the groove behind the internal condyle between the two heads of the flexor carpi ulnaris, comes into relation with the ulnar artery at the commencement of its middle third. It then descends along the inner side of the artery to the wrist, crosses with it the annu- lar ligament, and divides into two palmar branches. The branches of the ulnar nerve in the forearm are, articular, muscular, cutaneous, and dorsal cutaneous. The articular branches are given to the elbow-joint, while the nerve lies in the groove between the internal condyle and the olecranon. The muscular branches are distributed to the flexor carpi ulnaris, and inner half of the flexor profundus digitorum. The cutaneous branch proceeds from about the middle of the nerve, and descends upon the ulnar artery to the hand, giving twigs to the integument in its course. One branch from its upper part, sometimes a separate offset from the nerve, and sometimes absent, pierces the fascia, and communicates with the internal cutaneous nerve. The dorsal cutaneous branch passes backwards, beneath the tendon of the flexor carpi ulnaris, at the lower third of the fore- arm, and piercing the deep fascia, supplies the ulnar side of the back of the hand, and one finger and a half (page 373). The POSTERIOR INTEROSSEOUS, the other division of the musculo- spiral nerve a^ the bend of the elbow, pierces the supinator brevis muscle, and is distributed to the back of the forearm. Its further examination must therefore be reserved until the posterior aspect of the forearm is dissected. Posterior Region of the Forearm. The deep fascia may now be dissected from the posterior aspect of the forearm in a manner similar to that practised on the anterior aspect ; the longitudinal incision should be bounded by a transrerse incision made along the upper border of the posterior annular ligament, and the fascia turned to either side. The posterior annular ligament is attached externally to the radius, and internally to the pisiform bone, and forms separate sheaths for the passage of the tendons of muscles to the hand. 382 THE DISSECTOR. The MUSCLES of the posterior region of the forearm are a su- perficial and a deep group ; the superficial Fig. 115. group or layer consists of seven muscles, namely : Supinator longus, Extensor carpi radialis longior, carpi radialis brevior, communis digitorum, minimi digiti, carpi ulnaris, Anconeus. The SUPINATOR LONGUS muscle is placed along the radial border of the forearm. It arises from the external condyloid ridge of the humerus, nearly as high as the in- sertion of the deltoid, and from the inter- muscular septum ; and is inserted into the base of the styloid process of the radius. 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, and from the inter- muscular septum. Its tendon passes through a groove in the radius, imme- diately behind the styloid process, to be inserted into the base of the metacarpal bone of the index finger. The EXTENSOR CARPI RADIALIS BREVIOR is seen by drawing aside the former mus- THE SUPERFICIAL LAYER OF MUSCLES OF THE POSTERIOR ASPECT OF THE FOREARM. 1. The lower part of the biceps. 2. Part of the brachialis anticus. 3. The lower part of the triceps, inserted into the olecranon. **t. The supinator 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 extensor 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. cle. It arises from the external condyle of the humerus and intermuscular septa, and is inserted into the base of the metacarpal bone of the middle finger. Its tendon is lodged in the same groove on the radius with that of the extensor carpi radialis longior. POSTERIOR REGION OF THE FOREARM. 383 Fig. 116. The EXTENSOR COMMUNIS DiGiTORUM arises from the external condyle by a common tendon with the preceding and two follow- ing muscles, from the intermnscular septa and deep fascia ; and divides into four tendons, which are inserted into the second and third phalanges of the fingers. At the metacarpo-phalangeal articulation each tendon becomes narrow and thick, and sends a thin fasciculus upon each side of the joint. It then spreads out, and receiving the tendon of the lumbricales and some tendinous fasciculi from the interossei, forms a broad aponeurosis, which covers the whole of the posterior aspect of the finger. At the first phalangeal joint the aponeurosis divides into three slips. The middle slip 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. Little oblique tendinous slips connect the tendons of the ring with the middle and little finger 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 finger is intro- duced into the meatus of the ear, the muscle was called by the older writers " auricularis." The EXTENSOR CARPI ULNARIS arises from the external condyle by the common tendon, from the border of the ulna, and from the deep fascia. Its tendon passes through the pos- terior groove in the ulna, to be inserted into the base of the metacarpal bone of the little finger. The ANCONEUS is a small triangular muscle, having the appearance of being a continuation of the triceps ; it arises from the outer condyle, and is insertedinto theolecranon and triangular surface of the upper extremity of the ulna. THB ARRANGEMENT OP THE EXTENSOR TENDON UPON THE DORSAL SURFACE OF A FINGER. 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 in- terossei, showing their bifid origin, 6, 6, and inserted by an aponeurotic expan- sion into the sides of the extensor tendon. 7. The second lumbricalis muscle, also inserted into the side of the extensor tendon. 384 THE DISSECTOR. Fig. 117. When these muscles have been examined, the extensor communis digitorum, extensor minimi digiti, and extensor carpi ulnaris should be divided, and the ends drawn aside, to bring into view the deep layer, which consists of five muscles : 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 extensors of the carpus are di- vided from their origin. It arises from the external condyle, external lateral and orbicular ligament, and from the ulna ; it winds around the upper part of the radius to be inserted into the upper third of its oblique line. The posterior interosseous artery and nerve are seen perforating the lower border of this muscle. The EXTENSOR OSSIS METACARPI POL- LICIS is placed immediately below the supinator brevis. It arises from the ulna, interosseous membrane, and radius, and is inserted, as its name implies, into the base of the metacarpal bone of the thumb. Its tendon passes through the groove immediately in front of the styloid process of the radius. The EXTENSOR PRIMI INTERNODII POL- LICIS, the smallest of the muscles in this layer, arises from the interosseous mem- brane and radius, and passes through the same groove with the extensor 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 inter- osseous 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 DEEP LAYER OF MUSCLES ON THE POSTERIOR ASPECT OP THE FORE- ARM. 1. The lower part of the humerus. 2. The olecranon. 3. The ulna. 4. The anconeus muscle. 5. The supinator brevis muscle. 6. The extensor ossis metacarpi pollicis. 7. The extensor primi internodii pollicis. 8. The ex- tensor 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. POSTERIOR REGION OF THE FOREARM. 385 The EXTENSOR INDICIS arises from the ulna as high up as the extensor ossis metacarpi pollicis, and inferiorly 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 posterior region of the forearm pass to their destination upon the hand. In the subject, the posterior annular liga- ment 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 super- ficial sheath in the annular ligament for the extensor secundi internodii. Further 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. ACTIONS. The anconeus is associated in its action with the triceps ex- tensor cubiti ; it assists in extending the forearm upon the arm. The supinator longus and brevis effect the supination of the forearm, and antagonize the two pronators. The extensores carpi radialis, longior and brevior, and ulnaris extend the wrist in opposition to the two flexors of the carpus. The extensor communis digitorum restores the fingers to the straight position, after being flexed by the two flexors, sublimis and profuudus. The extensor ossis metacarpi, primi internodii, and secundi internodii pollicis, are the especial extensors 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. The VESSELS and NERVES of the posterior region of the forearm are, the posterior interosseous artery and nerve. The posterior interosseous artery may now be seen issuing from between the contiguous borders of the supinator brevis and ex- tensor ossis metacarpi pollicis, or piercing the fibres of the former. Its course and distribution will be found described at page 380. The posterior interosseous nerve, commencing at the bifurca- tion of the musculo-spiral, in front of the external condyle of the humerus (page 371), pierces the supinator brevis on its an- terior aspect, and passes through the substance of the muscle to its lower part. It then escapes from the muscle, and after giving off several muscular branches, dips between the extensor primi and secundi internodii, to reach the interosseous mem- brane upon which it descends to the wrist-joint, On the wrist it forms a gangliform enlargement, which distributes filaments to the numerous articulations of the carpus. The posterior interosseous nerve supplies all the muscles of the posterior region 33 386 THE DISSECTOR. of the forearm, with the exception of the supinator longus, ex- tensor carpi radialis longior, and anconeus. PALM OF THE HAND. To dissect the palm of the hand, make an incision from the wrist to the root of the middle finger, and bound it by a transverse incision carried across the roots of the fingers. Raise the integument by beginning at the angles, and in dissecting the ulnar flap be careful not to injure or remove the palmaris brevis muscle. Afterwards carry an incision along the middle of each finger, and turn the integument aside. The palmaris brevis muscle and the cutaneous branches of the median and ulnar nerve should now be examined. The PALMARIS BREVIS is a thin plane of muscular fibres, about an inch in width, which arises from the annular ligament and Fig. 118. 1. The annular ligament. 2, 2. The origin and insertion of the ab- ductor 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 lum- bricales muscles, arising from the deep flexor tendons, upon which the numbers are placed. The tendons of the flexor sublimis have been re- moved from the palm of the hand. 8. One of the tendons of the deep flexors passing between the two ter- minal 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 por- tions of the flexor brevis to the last phalanx. 10. The abductor minimi digiti. 11. The flexor brevis minimi digiti. The edge of the adductor 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. palmar fascia, and passes transversely inwards to be inserted into the integument of the inner border of the hand. The superficial branch of the median nerve, and the cutaneous palmar branch of the ulnar nerve, have been already described at page 381. The former, besides supplying the palm of the hand, sends a few filaments to the ball of the thumb. The palmar fascia, which is brought into view by the removal of the superficial fascia and fat, consists of three portions, central and two lateral. The lateral portions are thin, and inclose the PALM OP THE HAND. 387 muscles of the borders of the hand. The central portion occupies the middle of the palm, and is strong and tendinous : it is narrow at the wrist, where it is attached to the annular ligament and receives the insertion of the tendon of the palmaris longus, and broad over the heads of the raetacarpal bones, where it divides into four processes, each of which subdivides to embrace the root of the corresponding finger. These processes are attached upon the middle line to the sheath of the tendons, and at the side of each finger to the lateral and transverse ligaments. The fascia is strengthened at its point of division into slips by strong fasci- culi of transverse fibres, and the arched interval left between each pair of slips gives passage to the tendons of the flexor muscles. The arches between the fingers transmit the digital vessels and nerves, and lumbricales muscles. The palmar fascia may now be removed, in doing which, care should be taken to avoid dividing the superficial palmar arch or its branches, and these latter, with their accompanying branches of the median nerve, may be' cleared by the removal of the cellular tissue and fat. This dis- section brings into view the muscles of the palm. The MUSCLES of the palm of the hand are arranged in three groups : a radial or thenar group belonging to the thumb ; an ulnar or hypothenar group to the little finger ; and a palmar group situated in the middle of the palm. The muscles of the radial group are the Abductor pollicis, Flexor ossis metacarpi (opponens), Flexor brevis pollicis, Adductor pollicis. The ABDUCTOR POLLICIS is a small, thin muscle, which arises from the trapezium bone and annular ligament. It is inserted into the base of the first phalanx of the thumb. This muscle must be divided from its origin, and turned aside, in order to see the next. The FLEXOR ossis METACARPI (opponens pollicis) 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 which lies the tendon of the flexor longus pollicis. The external portion arises from the trapezium and annular ligament ; 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. 888 THE DISSECTOR. The next muscle is brought into view by drawing aside the flexor brevis pollicis on the one side, and the tendons of the long flexors on the other. It cannot be fully seen until the latter hav.e been removed at a subsequent part of the dissection. The ADDUCTOR POLLICIS is a triangular muscle; it arises by a broad origin from the metacarpal bone of the middle finger ; and the fibres converge to its insertion into the base of the first pha- lanx of the thumb conjointly with the inner head of the flexor brevis. The muscles of the ulnar group are the Abductor minimi digit!, Flexor brevis minimi digiti, Adductor ossis metacarpi (opponens). The ABDUCTOR MINIMI DIGITI is a small tapering muscle which arises from the pisiform bone, where it is continuous with the tendon of the flexor carpi ulnaris ; and it is inserted into the base of the first phalanx of the little finger, and the expansion of the extensor tendon. This muscle may be divided through the middle and its ends turned aside, which will bring into view the two next muscles. The FLEXOR BREVIS MINIMI DIGITI is a small muscle arising from the unciform bone and annular ligament, and inserted into the base of the first phalanx. It is sometimes wanting. The ADDUCTOR ossis METACARPI, or adductor minimi digiti (opponens), arises from the unciform bone and annular ligament, and is inserted into the whole length of the metacarpal bone of the little finger. The muscles of the middle palmar region are the Lumbricales, Interossei. To bring the lumbricales into view, the tendons of the flexor sublimis should be snipped across at the annular ligament, and drawn from under the superficial palmar arch towards the fingers ; the tendons of the deep flexor are then exposed, with which the lumbricales are connected. 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 aponeurotic expan- sion of the extensor tendons on the radial side of the fingers. These small muscles often present varieties of origin, such as arising by two heads, or being connected with other than the radial border of the tendons. The tendons of the deep flexor may now be cut through at the annular ligament, and drawn towards the fingers. In making this section, a loose synovial membrane which incloses the tendons of both flexors in their passage beneath the annular ligament, and extends for a short distance above and below that ligament, will be divided. When these tendons are PALM OF THE HAND. 389 removed, the palmar interossei will be brought into view. Before examin- ing them, however, it may be convenient to study the vessels and nerves. The PALMAR INTEROSSEI, three in number, are placed upon the metacarpal bones, rather than between them. They arise from the base of the raetacarpal 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 belongs to the index finger, the second to the ring finger, and the third to the little finger, the middle finger being omitted. The dorsal interossei are seen from the palmar side of the hand, occu- pying the spaces between the metacarpal bones; but they are best examined by turning to the dorsal side. The DORSAL INTEROSSEI, four in number, are situated in the four spaces between the metacarpal bones. They are bipenniform muscles, and arise by two heads, from adjoining sides of the bases of the metacarpal bones. They are inserted into the base of the first phalanges, and into the aponeurosis of the extensor tendons. The first is inserted into the index finger, and from its use is called abductor indicts; the second and third are inserted into the middle finger, compensating its exclusion from the palmar group ; the fourth 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 shown by means of a table, thus : r j f ne dorsal (abductor indicis), Index finger, Middle finger, two dorsal. . - (one dorsal, Ring finger, Little finger, remaining palmar. The radial artery passes into the palm of the hand between the two heads of the first dorsal interosseous muscle and the perfo- rating branches of the deep palmar arch, between the heads of the other dorsal interossei. ACTIONS. The actions of the muscles of the hand are expressed in their names. Those of the radial group belong to the thumb, and prpvide for three of its movements, abduction, adduction, and flexion, The ulnar group, in like manner, are subservient to the same motions of the little finger ; and the interossei are abductors and adductors of the several fingers. The lumbricales are accessory in their actions to the deep flexors: they were called by the earlier anatomists fidicinii, 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. 119), the four dorsal interossei are abductors, and the three palmar adductors. It will therefore be seen that each finger is provided with its prpper adductor and abduptor, two 33* 390 THE DISSECTOR. flexors, and (with the exception of the middle and ring fingers) two extensors. The thumb has moreover a flexor and extensor of the nieta- Fig. 119. A DIAGRAM, SHOWING THE ADBUCTOR 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 referable. 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 interosseous, the abductor of the index finger : all the dorsal interossei arise by two heads, as is seen in the diagram. 4. The first palmar interos- seous, the adductor of the index finger. 5, 5. The second and third dorsal in- terossei muscles, both abductors of tho middle finger. 6. The second palmar interosseous, adductor of the ring-finger. 7. The fourth dorsal interosseous, 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. carpal bone ; and the little finger a flexor of the metacarpal bone without an extensor. The VESSELS of the palm of the hand are the termination of the ulnar, forming the superficial palmar arch, and the termina- tion of the radial forming the deep palmar arch, with their com- panion veins (venae comites). The TJLNAR ARTERY crosses the annular ligament by the side of the pisiform bone, and curves across the middle of the palm to the ball of the thumb, where it terminates by inosculating with the superficialis voles, a branch of the radial. The branches of the ulnar artery are, a communicating branch and four digital arteries. The communicating or deep branch arises close to the annular ligament, and dips between the abductor minimi digiti and flexor brevis to inosculate with the termination of the deep palmar arch. It is accompanied by the deep palmar branch of the ulnar nerve. The digital branches, fouj? In number, are given off from the convexity of the superficial palmar arch. The first and smallest is distributed to the ulnar side of the little finger. The other three are short trunks, which divide between the heads of the metacarpal bones, and form the collateral branch pf the radial PALM OF THE HAND. 391 side of the little finger, the collateral branches of the ring and middle fingers, and the collateral branch of the ulnar side of the index finger. On the last phalanx, the collateral arteries com- municate and form an arch, from which numerous branches are given off to the tip of the finger. The RADIAL ARTERY enters the palm of the hand between the two heads of first dorsal interosseous muscle, and crossing the palmar interossei to the base of the metacarpal bone of the little finger, terminates by inosculating with the communicating branch of the ulnar. It thus constitutes the deep palmar arch which lies near the basis of the metacarpal bones, while the superficial arch lies over the distal third of those bones, the two arches being separated by the tendons of the superficial and deep flexors, the lumbricales, and the median nerve. The branches of the radial artery in the palm of the hand are the Princeps pollicis, Perforantes, Radialis indicia, Recurrentes. Interosseae, The princeps pollicis, the great artery of the thumb, passes along the metacarpal bone of the thumb, between the first dorsal interosseous (abductor indicis) and flexor brevis pollices to the base of the first phalanx ; and between the two heads of the lat- ter muscle, in the groove of the tendon of the flexor longus, it divides into two collateral branches for the palmar borders of the thumb. The radialis indicis, the digital branch of the radial side of the index finger, is directed inwards between the abductor indicis and the flexor brevis and adductor pollicis to the side of the finger, along which it is distributed, forming its radial collateral artery. Near its origin it gives off a small branch (more frequently a direct branch of the radial), which inosculates with the super- ficial palmar arch. The interossecB palmares, three or four in number, are branches of the deep palmar arch ; they pass forward upon the interossei muscles, and inosculate with the digital branches of the superfi- cial arch, opposite the heads of the metacarpal bones. The perforantes, three in number, pass directly backwards be- tween the heads of the dorsal interossei muscles, and inosculate with the dorsal interosseous arteries. The recurrent branches of the deep palmar arch pass upwards in front of the wrist-joint, and inosculate with the arterial arch formed by the anterior carpal arteries. The NERVES of the palm of the hand are the ulnar and median. The ULNAR NERVE, crossing the annular ligament with the 392 THE DISSECTOR. ulnar artery, immediately divides into a superficial and deep branch. The superficial palmar branch, after giving some filaments to the palmaris brevis and inner border of the hand, divides into three branches, which are distributed, one to the ulnar side of the little finger, one to the adjoining borders of the little and ring fingers, and a communicating branch to join the median nerve. The deep palmar branch passes between the abductor and flexor minimi digiti to the deep palmar arch, supplying the muscles of the little finger, the interossei palmar and dorsal, the two ulnar lumbricales, adductor pollicis, and inner head of the flexor brevis pollicis. The MEDIAN NERVE, after passing beneath the annular ligament, is spread out and flattened, and divides into a muscular and five digital branches. The muscular branch is distributed to the abductor pollicis, flexor ossis metacarpi, and external head of the flexor brevis. The five digital nerves are thus disposed : two pass outwards to the thumb and supply its borders ; the third passes along the radial side of the index finger, sending a twig to the first lumbri- calis in its course ; the fourth subdivides for the supply of the adjacent sides of the index and middle fingers, and gives a twig to the second lumbricalis ; the fifth receives a filament of com- munication from the ulnar nerve, and supplies the collateral branches of the middle and ring fingers. On the fingers, the digital nerves lie to the inner side of, and superficially to, the arteries, and terminate by dividing into nume- rous twigs for their sentient extremities, and the structures en- gaged in the production of the nails. Near the base of the first phalanx each nerve gives off a dorsal branch, which takes its course along the dorsal border of the finger. CHAPTER VIII. THE LOWER EXTREMITY. BEFORE commencing the dissection of the lower extremity, the student will carefully reflect upon the objects of his proposed dis- section, and particularly upon the practical application of the in- formation which he is seeking to acquire. The lower extremity comprises all that portion of the body which forms the lower limb, and is bounded above by the external surface of the pelvis. It consists of a thigh, leg, and foot j of the hip, knee, ankle, THE LOWER EXTREMITY. 393 tarsal, metatarsal, and digital joints ; of a complicated apparatus of muscles ; of the femoral, popliteal, tibial, pedal, and plantar arteries ; of veins, lymphatics, nerves, bones, and ligaments. Now all these structures are liable to injury ; and the surgeon, upon such an occurrence, is called upon to remedy the accident, to apply the knowledge that he shall have gained, through the aid of his eyes and hands, in the dissecting-room. Suppose the accident be one involving deep and important parts without 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 cir- cumstances may render this comparison unavailing ; and he is then obliged to recall the observations he may chance to have made during his anatomical studies. Depend upon it, that a sound knowledge of the relations of the different portions of the limbs will ever be found of the highest possible value to the man who is suddenly called to the aid of a wounded fellow-creature. Indeed, such a knowledge should b considered as the leading characteristic of the accomplished surgeon. Starting with reflections such as these, the student will per- ceive that other observations are necessary to him in addition 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 ten- dons, may be ruptured ; the arteries may be wounded or diseased, requiring that incisions of considerable extent or depth should be made in their course, and a ligature placed around them ; or nerves may be ganglionated, and demand removal ; lastly, the whole limb may be disorganized, and call for amputation. In each and every of these circumstances, relief is simply and effect- ually bestowed, if the operator be well acquainted with the situa- tion and dissection of the various structures implicated in the accident or disease ; and these are to be learnt only in the dis- secting-room by careful observation and manipulation. Having the lower extremity extended on the table before him, and the leg everted, let the student carry a line (Fig. 120, i) from the extreme point of the anterior superior spinous process of the ilium to the symphysis 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 394 THE DISSECTOR. 120. spinous process of the ilium, and crossing the former at the mid- dle of the thigh, will mark the direction of the upper margin of the sartorius muscle, and inclose a triangular space (Scarpa's), which is bounded above by Poupart's liga- ment. Within this triangle, which cor- responds with the axillary space in the upper limb, the position of the femoral artery may be distinguished by a groove, and may be laid bare and secured, in any part of the line 2, which marks its course ; the usual situation for ligature of the fe- moral artery (Scarpa's operation), in pop- liteal aneurism, being at the point where the upper margin of the sartorius crosses its course, the border of this muscle form- ing the natural guide for the direction of the incision. At the pubic angle of this triangular space, is situated the saphenous opening, 11, through which the sac of fe- moral hernia is protruded. In rare cases, the femoral artery is tied below the lower border of the sartorius muscle (Hunter's operation) ; under such circumstances, a space, varying from one inch to one inch and a half, and parallel to the oblique line, should be allowed for the breadth of the sartorius, and the incision commenced im- mediately below this border, 6, still fol- lowing the original line of its course. Besides these, there is another point of importance to the surgeon, in the con- THE THIGH TURNED UPON ITS OUTER SIDE AS IN DISSECTING IT. 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 condyle 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 3 ; this line marks the upper border of the sartorius 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 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 trochanter major to the spine of the ilium. 8. Another line drawn from the trochanter major to the crest of the ilium. 9. The internal saphenous vein. 10. The superficial epigastric and superficial cir- cumflexa ilii veins, converging to open into it previously to its entrance into the saphenous opening. 11. The saphenous opening in the fascia lata. 12. The ext- ^al cutaneous nerve. 13. The middle cutaneous nerves, branches of the Crural. ANTERIOR FEMORAL REGION. 395 sideration of the proper projections on the surface of the limb, viz: the apophysis named trochanter 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 little liable to variation from strength or muscularity of the limb ; but is necessarily more prominent and more sharply defined in an emaciated person. 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, Y, extended from the same point to the anterior superior spinous process, may be compared with the same admeasurements on the opposite limb. An important measurement of the thigh, for the detection 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, between 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 measurement, 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 before the student commences 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 knowledge 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 with the position of the patella in relation to the spines of the ilium and pubes. The lower extremity is divided anatomically into several dis- tinct 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 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 commenced by making an incision (Fig. 120, i), from the anterior superior spinous process 396 THE DISSECTOR. of the ilium along the line of Poupart's ligament to the spinous process of the pubis, then carrying 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. It may be convenient to make a fourth incision across the middle of the thigh so as to diminish the extent of surface opened at once, and enable the student to concen- trate his attention in the first instance upon the most important part of the front of the thigh, namely, the triangular hollow space which con- tains the femoral vessels and the saphenous opening. 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 flap upon the outer side of the limb. He then turns to the opposite side, and repeats the same proceeding. But the student who 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 attentively 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 motion. Let him apply this reasoning to his scalpel, it must be handled lightly, and drawn without pressure across the textures to be divided : if he uses force and pressure, the best edge would be useless in his hands. The art of dis- secting with neatness and operating with dexterity, owes much to the good understanding existing between 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 lobules of fat, surrounded by 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, corre- sponding with the fatty depositions in the superficial fascia. The SUPERFICIAL FASCIA is composed of two layers, between which are situated the cutaneous vessels and nerves. To examine these an incision should be made by the side of the saphenous vein, and the superficial layer dissected outwards and upwards towards Poupart's ligament, over which it may be traced into the subcutaneous covering of the abdomen. This dissection is com- paratively easy in the groin, from the number of superficial ves- sels; nerves, and lymphatics which are found in that region, but lower down the thigh, the separation of the layers is impracti- cable. The deep layer is interposed between the superficial ves- sels and the fascia lata, and closes the saphenous. opening; the perforation of the latter portion of the superficial fascia by nume- rous lymphatic vessels has gained for it the appellation of cribri- form fascia. The parts to be examined in the superficial fascia are, the inguinal glands, the three small arteries, superficial circumflexa ilii, superficial epigastric and superior external pudic, the internal CUTANEOUS NERVES OF THE THIGH. 397 saphenous vein and its tributaries, the crnral portions of the ilio- inguinal and genito-crural nerves, the external, middle, and inter- nal cutaneous nerves, and in the lower part of the thigh the superficial branch of the auastoraotica magna artery, the internal saphenous nerve, and the extensive nervous interlacement situated around the front of the knee, the plexus patellae. The inguinal glands are situated along the line of Poupart's ligament, and near the termination of the saphenous vein ; the former receive the lymphatic vessels from the abdomen and genital organs ; the latter, of larger size, receive the lymphatics of the lower limb. The three small arteries, the superficial circumflexa ilii, the superficial epigastric, and the superior 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, superficial fascia, and inguinal glands : 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. 120, 9), (so^^f, perspicuous, 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 its office, saphenous 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, therefore, must not be passed over without remark. The saphenous vein is accompanied by superficial lymphatic ves- sels throughout the whole of its course. The cutaneous nerves will be found : the ilio-inguinal to the inner side of the saphenous opening; the genito-crural just exter- nally to the saphenous opening ; the two branches of the middle cutaneous nerve in the middle of the front of the thigh ; the inter- nal cutaneous, its three branches, in the line of the internal saphe- nous vein ; and the external cutaneous along the outer border of the thigh. The crural portion of the ilio-inguinal nerve is the continua- tion of that nerve, after it has escaped with the spermatic cord from the external abdominal ring. It terminates in the integu- ment of the upper part of the thigh, internally to the saphenous opening, after having supplied the scrotum. The ilio-iuguiiial nerve proceeds from the first lumbar nerve. 34 398 THE DISSECTOR. The crural branch of the genito-crural nerve pierces the fascia lata a little below Poupart's ligament, and just externally to the femoral artery from the sheath of which it escapes. It is dis- tributed to the integument as far as the middle of thigh, and com- municates with the middle cutaneous nerve. The genito-crural nerve proceeds from the second lumbar nerve. The middle cutaneous nerve is a branch of the anterior crural ; it pierces the fascia lata about three inches below Poupart's liga- ment, and divides into two branches, which are distributed to the integument of the front of the thigh as far as the knee. One or both of these branches sometimes pierce the sartorius muscle. The internal cutaneous nerve, also a branch of the anterior crural, passes inwards in front of the sheath of the femoral artery, and after giving off three cutaneous filaments, which pierce the fascia lata and follow the course of the internal saphenous vein, divides into an anterior and an inner branch. The anterior branch pierces the fascia lata at the lower third of the thigh, near the internal saphenous vein, which it follows to the inner side of the knee and divides into two terminal twigs. The inner branch pierces the fascia lata on the inner side of the knee, and is distributed to the integument along the inner side of the leg. The external cutaneous nerve ( Fig. 120, 12), is derived from the second lumbar nerve, and pierces the fascia lata about two inches below the anterior superior spine of the ilium, where it divides into two branches, one of which (posterior) crosses the tensor vaginae femoris muscle to the outer and posterior side of the thigh, and is distributed to the integument in that region ; the anterior branch, after passing downwards for several inches in a sheath of the fascia lata, divides into two twigs, which are distributed to the integument of the outer border of the thigh, and to the knee- joint. The long saphenous nerve pierces the deep fascia and becomes superficial at the side of the knee ; it is accompanied by the super- ficial branch of the anastomotica magna artery. The cutaneus patellae, a branch of the long saphenous, becomes superficial a little higher than the parent trunk, and assists in the formation of the plexus patellae, by means of its communications with the other cutaneous nerves of 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. It is an extremely dense mem- brane, consisting of glistening tendinous fibres, disposed longitu- dinally and circularly around the limb ; is thickest on the outer side of the thigh, and thinner on its inner side. The fascia lata en- FASCIA LATA CRIBRIFORM FASCIA. 399 velops the whole of the muscle of the thigh, and sends processes inwards, which form distinct sheaths for each. It is attached above to the prominent points about the pelvis, viz : to the pubes, Poupart's ligament, crest of the ilium, sacrum, and ischium ; below, to the heads of the tibia and fibula ; 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 maxi- mus. It is perforated at several points for the passage of cuta- neous nerves, and near the pubes is the saphenous opening. The existence of this opening (Fig. 120, 1 1), causes the divi- sion of the upper part of the fascia lata into two portions, an iliac portion situated towards the ilium, and a pubic portion to- wards the pubes. The iliac portion is attached along Poupart's ligament, as far as the spine of the pubes; from this point it is reflected downwards, in a curved direction, forming a sharp edge, called the falciform process. The edge of the falciform process immediately overlays and is reflected upon the sheath of the fe- moral vessels ; and the lower extremity of the curve is continuous with the pubic portion. The pubic portion is also attached to the spine of the pubes, 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 fascial coverings surrounding the muscles on the outer side of the thigh. From this description, it will be obvious that the iliac portion, being attached to Poupart's ligament, must be on a plane consi- derably anterior to the pubic portion which is attached to the bone; and it is between the two that the femoral vessels are placed, inclosed in their sheath. It follows also from this dispo- sition that the saphenous opening is oblique in its direction with regard to these two layers of fascia. It is, moreover, closed by some dense bands of cellular tissue, which are perforated by a number of minute openings for the transmission of the superficial lymphatic vessels of the lower extremity, and are hence named cribriform fascia (cribrum, a sieve). This cribriform fascia would be altogether unworthy the notice of the dissector, were it not for the arbitrary importance attached to every fibre of mem- brane or process of fascia that may possess the slightest relation to the protrusion of intestine 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 position, must necessarily form one of the coverings of the femoral hernia. The student may now remove the fascia lata, by dissecting it from its loose cellular attachment to the muscles, following always the course of their fibres. If the student would dissect well, he 400 TIIE DISSECTOR. Fig. 121. 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 we 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 successful issue be desired. 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 ; and an internal group of seven, as follows : Anterior Group. Tensor vaginae femoris. Sartorius. Rectus. Yastus internus. Yastus externus. Crureus. Internal Group. Iliacus internus. Psoas magnus. Pectineus. Adductor longus. Adductor brevis. Adductor magnus. Gracilis. As soon as these two tables are got by heart, the student may commence the dissection of the muscles which they represent. 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 its anterior superior spinous process, and {^inserted between twolayers of thefascia lata at about one-fourth down the thigh. The SARTORIUS (tailor's muscle), is a long ribbon-like muscle, arising from the ante- THE MUSCLES OF THE ANTERIOR FEMORAL REGION. 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 in- ternus. 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. MUSCLES ANTERIOR FEMORAL REGION. 401 rior superior spinous process of the ilium and from the notch immediately below that process ; 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 expansion covers in the insertion of the tendons of the gracilis and semitendinosus muscles. The inner border of the sartorius muscle is the guide to the opera- tion for tying the femoral artery in the middle of its course ; and the outer boundary of Scarpa's triangular space. The RECTUS (straight) muscle is fusiform in its shape and bi- penniform 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 in- serted by a broad and strong tendon into the upper border of the patella. It is more correct to consider the patella as a sesarnoid bone, developed within the tendon of the rectus ; and the liga- mentum patellae as the continuation of the tendon to its insertion into the tubercle of the tibia. The rectus must now be divided through its middle, and the two ends turned aside, to bring clearly into view the next muscles. The next three muscles are generally considered collectively under the name of triceps extensor criiris. Adopting this view, the muscle surrounds the whole of the femur, except the rough line (linea aspera) upon its posterior aspect. Its division into three parts is not well defined ; the fleshy mass upon each side being distinguished by the names of vastus internus and exter- nus, the middle portion by that of crureus. The VASTUS EXTERNUS, narrow below and broad above, arises from the base of the trochanter major, the outer surface of the femur and outer lip of the linea aspera and from the intermuscu- lar fascia ; and passes down to be inserted into the outer border of the patella ; or rather, by means of the ligamentum patellae, into the tubercle of the tibia, conjointly with the rectus and two following muscles. The VASTUS INTERNUS, broad below and narrow above, arises from the anterior intertrochanteric line, inner surface of the fe- mur, inner lip of the linea aspera, and intermuscular fascia, and is inserted into the inner border of the patella. By its mesial border it is blended with the crureus. The CRUREUS (crus, the leg) arises from the anterior inter- trochanteric line and anterior surface of the femur to within two inches of the patella. It is continuous by its inner border with the vastus internus, and is inserted into the upper border of the patella ; its tendon occupying its cutaneous aspect. When the crureus is divided from its insertion, a small mus- 34* 402 THE DISSECTOR. cular fasciculus is often seen upon the lower part of the femur ; this fasciculus is inserted into the pouch of synovial membrane that extends upwards from the knee-joint behind the patella, and is named, from its situation, sub-crureus. It would seem to be intended to support the synovial membrane. ACTIONS. The tensor vaginae 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 carry- ing 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 fulcrum. 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 extremity. Internal Femoral Region. The origins of the iliacus and psoas muscles being situated within the abdomen, the entire muscles cannot be seen in this dissection ; but as a part of them quits that cavity to be inserted into the femur, that portion necessarily 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. A few fibres of this muscle proceed from the sacrum, and others from the capsular ligament of the hip-joint. The PSOAS MAGNUS (^oa, lumbus, a loin), situated by the side of the vertebral column in the loins, is a long fusiform muscle. It arises from the bodies and bases of the transverse processes of the last dorsal and all the lumbar vertebra. It also takes its origin from the intervertebral substances and from a series of tendinous arches attached to the vertebra, and intended for the protection of the lumbar vessels and branches of the sympathetic nerve, in their passage between the muscle and the bone. The tendon of the psoas magnns 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 with the last two muscles : the first, of considerable size, is situated between their under surface and the capsule of the hip-joint ; the other, much smaller, is interposed between the conjoined tendon and the an- terior part of the trochanter minor. The PECTINEUS is a flat and quadrangular muscle ; it arises from the pectineal line (pecten, a crest) of the os pubis, and from the surface of bone in front of that line ; and is inserted into the line MUSCLES INTERNAL FEMORAL REGION. 403 leading from the anterior intertrochanteric line to the linea aspera of the femur. The ADDUCTOR LONGUS (adducere, to draw to), the most super- ficial of the three adductors, arises by a round and thick tendon from the front surface of the os pubis, immediately below the angle of that bone ; and, assuming a flattened and expanded form as it descends, is inserted into the middle third of the linea aspera. The pectineus and adductor longus form the inner boundary of the triangular space of Scarpa, in which the femoral vessels and nerves are lodged. They must be divided, the pectineus 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 brevis. The ADDUCTOR BREVIS, placed behind the pectineus and adductor longus, is fleshy, and thicker than the adductor longus ; it arises from the body of the os pubis, and is inserted into the line leading from the trochanter minor to 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 entirely, after sepa- rating the anterior branch 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 obtu- rator externus. The OBTURATOR EXTERNUS muscle (obturare, to stop up) arises from the obturator membrane, and from the surface of bone im- mediately surrounding it anteriorly, viz: from the 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 tro- chanteric fossa of the femur. Although this muscle belongs properly to another group (glutseal region), it has been deemed consistent with 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 situation which it actually occupies. The ADDUCTOR MAGNUS is a broad triangular 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 of the os pubis and ischium and from the side of the tuber ischii ; and radiating in its passage outwards, is inserted into the whole length of the linea aspera, and inner con- dyle 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 404 THE DISSECTOR. body of the os pubis along the edge of the symphysis, and from the margin of the ramus of the pubes 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 likewise 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 ramifica- tions 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, ex- cepting the main trunks, had better be removed 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 : the latter are as follows : Superficial circumflexa ilii. epigastric. Superior external pudic. Inferior external pudic. ( External circumflex. Profunda -< Internal circumflex. (Three perforating. Muscular. Anastomotica magna. The femoral artery and vein are inclosed in a sheath, the femoral sheath, which is broad and funnel-shaped at Poupart's ligament, but narrows to the size of the vessels two inches below that point. The infundibular portion of the sheath is aponeu- rotic in structure, and is continuous with the transversalis and iliac fasciae ; but lower down, where it closely invests the vessels, it consists of condensed cellular tissue. In the infundibuliform portion of the sheath, the artery and vein lie side by side, sepa- rated by a septum ; and to the inner side of the vein, also sepa- rated by a septum, is a space occupied by a lymphatic gland and some loose cellular tissue the femoral or crural canal. Above, FEMORAL ARTERY. 405 the femoral canal opens into the abdomen by an aperture which is termed the femoral or crural ring ; below, it is lost in the con- traction of the sheath. Below the infundibular portion of the femoral sheath, two nerves, the long saphenous and muscular branch to the vastus in- ternus, both branches of the anterior crural, are found in relation with the vessels. Above, they lie to the outer side; but lower down, the long saphenous passes in front of the artery and enters the aponeurotic sheath which incloses the vessels. These nerves are to be borne in mind in the operation for tying the femoral artery in the upper third of the thigh (Scarpa's operation). In this operation the incision (about three inches in length), is made along the upper and inner edge of the sartorius muscle, and crosses obliquely the direction of the vessels. The integument is first divided, then the superficial fascia ; next the deep fascia, or fascia lata ; the edge of the sartorius muscle is then to be drawn aside and the sheath of the vessels exposed ; the operator opens the sheath with care, to avoid injuring the two nerves just referred to, and the needle is placed around the artery, taking care to separate it as little as possible from its connections. In making the first incision the saphenous vein must be remembered, lest it be divided, and the point of the artery selected for the application of the ligature should be between four and five inches below Poupart's liga- ment. The femoral vein is here altogether behind the artery. In the operation below the sartorius (Hunter's operation), the incision, three inches in length, is made along the lower and outer border of the sartorius, in the groove between that muscle and the vastus internus. The parts cut through are the same as in Scarpa's operation ; the sarto- rius must be drawn upwards and inwards ; and the artery secured where it lies under cover of the aponeurotic fascia stretched across it between the adductor longus and magnus on the one side, and the vastus internus on the other. The FEMORAL ARTERY runs down the inner side of the thigh, from Poupart's ligament, at a point exactly midway between the anterior superior spinous process of the ilium and symphysis pubis, to the hole in the adductor magnus, at the junction of the middle with the inferior third of the thigh, where it becomes the popliteal artery. The femoral vein is at first to the inner side, and upon the same plane with the artery, but lower down ; the vein becomes placed behind and rather to the outer side of the artery, and retains that relation throughout the rest of its course. delations. The upper third of the femoral artery is super- ficial, being covered only by the integument, superficial fascia, fascia lata, and some lymphatic glands. The lower two thirds are covered by the sartorius muscle. To its outer side the artery rests against the psoas and vastus internus, and is separated from the anterior crural nerve by the breadth of the former muscle. Behind, it has the psoas muscle which intervenes between it and the hip-joint ; it is next separated from the pectineus by the 406 THE DISSECTOR. femoral vein, profunda vein and artery, and then lies on the adductor longus to its termination. While beneath the sartorius muscle it is placed in an aponeurotic sheath, or canal formed by Fig. 122. A VIEW OP THE ANTERIOR AND IN- KER ASPECT OP THE THIGH, SHOWING THE COURSE AND BRANCHES OP THE FEMORAL ARTERY. 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 ar- tery. 8. The pectineus. 9. The ad- ductor longus. 10. The tendinous canal for the femoral artery formed by the adductor magnus, and vastus internus 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 epi- gastric 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 anastomotica magna, descending to the knee, upon which it ramifies (6). tendinous fibres extended like a bridge from the adductor longus and magnus to the vastus internus ; this is the aponeurotic sheath through which the long saphenous nerve takes its course. Branches. The superficial circumflexa ilii, superficial epigas- tric, superior external pudic, and inferior external pudic, are four small arteries given off from the femoral, immediately below Poupart's ligament. The superficial circumflexa ilii passes outwards beneath the fascia lata, and piercing that structure near the anterior superior spine of the ilium, becomes cutaneous and is distributed to the PEOFUNDA FEMORIS. 407 integument. In its course it sends off several twigs which pierce the fascia to reach the inguinal glands. The superficial epigastric, after piercing the fascia lata, ascends towards the umbilicus and inosculates with branches of the deep epigastric. The superior external pudic artery passes inwards across the spermatic cord, and is distributed to the penis and scrotum in the male, and labia in the female. It inosculates with the inter- nal pudic artery. The two latter arteries are important in their connection with hernial tumors occurring in this region : I have seen both of them crossing an inguinal, and the latter ramifying upon a femoral hernia. In tjie opera- tion they are liable to division ; but, from their small size, would cause very little inconvenience. The inferior external pudic is given off from the femoral a little below and sometimes in common with the superior exter- nal pudic ; it crosses the femoral vein immediately below the termination of the internal saphenous vein, and resting on the pectineus reaches the inner border of the thigh ; it then pierces the fascia lata and is distributed to the integument of the exter- nal organs of generation and perineum, communicating with branches of the internal pudic. The PROFUNDA FEMORIS artery is given off from the outer side of the femoral, about one inch and a half below Poupart's liga- ment. From its large size, it may be considered as a division of the femoral rather than a branch : and, in this view, the short trunk has been called the common femoral (femoralis communis), and its two divisions, femoralis superficialis and femoralis profunda ; the superficial femoral being intended for the supply of the knee and leg, while the profunda is distributed to the thigh. The pro- funda artery is best examined by drawing aside or 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 flexor muscles of the posterior part of the thigh. Relations. The profunda artery rests successively upon the pectineus, the conjoined tendon of the psoas and iliacus, 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. 408 THE DISSECTOR. The branches of the profunda artery are the external circum- flex, internal circumflex, and three perforating arteries. The external circumflex artery passes outwards beneath the sartorius and rectus, and in front of the crureus muscle, passing between the divisions of the crural nerve, and divides into three sets of branches ; ascending, which pass upwards beneath the sartorius, rectus, and tensor vaginae fernoris, and inosculate with the terminal branches of the gluteal artery ; descending, which pass downwards beneath the rectus muscle to inosculate with the superior articular arteries of the popliteal ; and middle, which continue the original course of the artery around the thigh, pierce the vastus externus, and anastomose with branches of the ischi- atic, internal circumflex, and superior perforating artery. It supplies the muscles on the anterior and outer side of the thigh. The internal circumflex artery winds around the inner side of the neck of the femur, passing between the pectineus and psoas, and over the upper border of the adductor brevis to the tendon of the obturator externug, which it accompanies to the space between the quadratus femoris and upper border of the adductor magnus. While on the obturator externus it gives off a branch which is distributed to that muscle, the adductor brevis and gra- cilis, and anastomoses with the obturator artery. It next gives off an articular branch which enters the hip-joint through the notch in the acetabulum ; and terminates in several branches which inosculate with the ischiatic, external circumflex, and supe- rior perforating arteries. The superior perforating artery passes backwards near the lower border of the pectineus, pierces the adductor brevis and magnus near the femur, and is distributed to the posterior muscles of the thigh ; inosculating freely with the circumflex and ischiatic arteries, and with the branches of the middle perforating artery. The middle perforating artery pierces the tendons of the adduc- tor brevis and magnus, and is distributed like the superior ; inos- culating with the superior and inferior perforantes. From this branch is given off the nutritious artery of the femur. The inferior perforatiny artery is given off below the adductor brevis, and pierces the tendon of the adductor magnus, supplying it and the flexor muscles, and inosculating with the middle per- forating artery above, and with the articular branches of the popliteal below. It is through the medium of the branches of the profunda, which inosculate above with branches of the internal iliac, and below with those of the popliteal artery, that the collateral circu- lation is maintained in the limb after ligature of the femoral artery. We now return to the superficial femoral. It gives off mus- VEINS OF FEMORAL REGION. 409 cular branches throughout the whole of its course, which supply the muscles in immediate proximity with the artery, particularly those of the anterior aspect of the thigh. One of these branches, larger than the rest, arises from the femoral immediately below the origin of the profunda, and passing outwards between the rectus and sartorius, divides into branches, which are distributed to all the muscles of the anterior aspect of the thigh. This may be named the superior muscular artery. The anastomotica magna arises from the femoral, near to its termination at the opening in the adductor magnus, and divides into a superficial and deep branch. The superficial branch accompanies the internal saphenous nerve to the knee, and piercing the fascia lata is distributed to the integument. The deep branch passes onwards through the substance of the vastus internus muscle, and resting on the tendon of the adductor magnus to the knee, where it inosculates with the internal articular branches of the popliteal, and the recurrent of the anterior tibial. It also sends a branch to the vastus internus, which supplies the syno- vial membrane of the joint, and inosculates with the superior external articular artery and external circumflex. 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, internal and external. The internal branch curves inwards around the bony margin of the obturator foramen, and distributes branches to the obturator and adductor muscles, inosculating with the internal circumflex artery of the femoral. The external branch winds around the outer margin of the obturator foramen to the space between the gemel- lus inferior and quadratus femoris, where it inosculates with the ischiatic artery. In its course it inosculates also with the internal circumflex artery, and sends a small branch through the notch in the acetabulum, to supply the ligamentum teres. The VEINS of the anterior femoral region are superficial and deep. The superficial, are the internal saphenous, and its tribu- taries. The deep, are the femoral and profunda, with their tri- butaries. The femoral vein commences at the hole in the adductor magnus, and ascends behind the artery to within two inches of Pou part'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 pro- funda vein, commencing with the ultimate ramifications of the profunda artery, ascends in front of that vessel to its origin from 35 410 THE DISSECTOR. the common femoral artery, where 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 vence comites. They communicate freely across the cylinder of the artery by short transverse trunks. Yeins are considerably larger than the arteries Fig. 123. which they accompany. Nerves of the Anterior Femoral Region. The student will now direct his attention to the nerves of this region. They are derived from the lumbar plexus : and are the External cutaneous, Genito-crural, (Middle cutaneous, Internal cutaneous, Long saphenous, Muscular, Obturator. The EXTERNAL CUTANEOUS NERVE, 4, IS de- scribed with the superficial fascia at page 398. The crural portion of the genito-crural nerve ; and the crural distribution of the ilio-inguinal nerve have also been described in the same place. The ANTERIOR 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 outer border of the psoas magnus muscle, and runs downwards in the groove between that muscle and the iliacus internus to Poupart's ligament. It is there separated from the femoral artery by the breadth of the psoas muscle, usually not more than half an inch wide ; and immediately below Poupart's ligament divides into superficial and deep branches : while within the pelvis it gives off several twigs to the iliacus muscle, and sends down a branch to supply the femoral artery. The superficial branches are the middle cu- THE LUMBAR PLEXUS WITH ITS BRANCHES. 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. OBTURATOR NERVE. 411 taneons, internal cutaneous, and internal saphenous ; the deep branches are the muscular and articular. The middle and internal cutaneous nerves have been already described ; page 398. The long saphenous or internal saphenous nerve inclines in- wards to the sheath of the femoral vessels, and passes downwards in front of the sheath and beneath the aponeurotic expansion which covers the sheath, to the opening in the adductor magnus. It then quits the femoral vessels, and, continuing to descend, passes between the tendons of the sartorius and gracilis, and reaches the internal saphenous vein. By the side of the latter it passes down the inner side of the leg, in front of the inner ankle and along the inner side of the foot as far as the great toe. The branches of the internal saphenous are, one or two in the thigh to communicate with the obturator nerve and internal cutaneous, the three together forming a plexus ; one, at the knee, the cu- taneous patella, which pierces the sartorius muscle and is distri- buted to the front of the knee, assisting, by its communications with other cutaneous nerves of the knee, to form the plexus patellce ; and several cutaneous twigs below the knee. Of the deep branches of the anterior crural nerve the muscular supply all the muscles of the anterior femoral region (excepting one) and the pectineus. The excepted muscle is the tensor vaginae femoris, which receives its nerves from the superior gluteal. The sartorius muscle receives three or four branches, which arise with the cutaneous nerves, and frequently are supplied by the latter. The branch to the vastus extemus accompanies the de- scending branch of the external circumflex artery. The branch to the vastus internus muscle (short saphenous, of some authors, from arising frequently in common with the long saphenous, and pursuing a parallel course in the upper part of the thigh) descends upon the sheath of the femoral vessels, and beneath the aponeurotic fascia of the sheath. It is of large size, and sends off several twigs to the vastus internus, and a long articular filament to the synovial membrane of the knee-joint. This latter accompanies the deep branch of the anastomotica magna. The OBTURATOR NERVE is formed by a branch from the third and another from the fourth lumbar nerve, and, passing down- wards through the psoas muscle and bifurcation of the common iliac vessels, 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 an anterior and a posterior branch. The anterior branch passes in front of the adductor brevis and supplies that muscle, the pectineus, gracilis, and adductor longus, and, at the lower border of the latter, unites with the internal 412 THE DISSECTOR. cutaneous nerve and internal saphenous to form a plexus. In its course this nerve gives off an articular twig to the hip-joint, a cutaneous branch which pierces the fascia lata at the knee ; and after communicating with the internal saphenous nerve is dis- tributed to the integument as far as the middle of the leg ; and a twig from its termination to the femoral artery. The posterior branch pierces the obturator externus muscle, and sends twigs for its supply as well as the adductor magnus muscle ; it also sends down an articular filament which accompa- nies the popliteal artery to the knee-joint. A portion of the obturator nerve is sometimes given off in an irregular manner, and proceeds in an irregular course. When it exists, it is either a high division of the obturator, or takes its origin by separate cords from the third and fourth lumbar nerves. It is called the accessory obturator nerve ; passes down along the inner border of the psoas muscle to the front of the pelvis, crosses the body of the os pubis, and gets beneath the pectineus. It gives branches to the pectineus muscle and hip-joint, and joins the anterior branch of the obturator, forming, when of large size, the cutaneous branch of that nerve. We advise the student to have made himself thoroughly master of this region and of each, before he ventures to direct his attention to another, and to proceed methodically, following with care every line of proceeding here pointed out, unless, indeed, he can himself suggest a better or one more familiar to his mode of study, for we are well convinced that the same plan will not be found advantageous to all. Let him question his knowledge upon each of the preceding sections, and remark the adage "Memoria augetur ex colendo." FEMORAL HERNIA. After proceeding, as we have here directed, with the common 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 vessels should have been left undis- turbed. The sheath may now be opened, and the parts contained within the sheath and adjacent parts examined. Stretching across from the anterior superior spinous process of the ilium to the spine of the pubes is Poupart's ligament, which forms an arch over the concave border of the pelvis, the crural or femoral arch. Beneath this arch will be seen to pass a number of important structures, which are disposed in the following order, from without inwards : external cutaneous nerve, 6 (Fig. 124); iliacus internus muscle, 7; anterior crural nerve, 8 ; psoas maguus muscle, 9 ; crural division of the genito-crural nerve, 10; femoral artery, 11; femoral vein, 12 ; FEMORAL HERNIA. 413 lymphatic vessels ; the four latter being inclosed in a common sheath. The sheath, 13, 14, of the femoral vessels is the fibrous covering which invests the artery and vein during their passage beneath Fig. 124. A SECTION OP 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 superior 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 the pubis, externally by the femoral vein, and internally by (16) Gimbernat's ligament. the femoral arch. It is formed by the internal lining of the abdo- men ; and as this has received various names, according to the situations it may occupy, as transversals 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 immediately 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 ligament is two inches, and in the female more; but at two inches below the ligament, the sheath has diminished to three-quarters of an inch, and merges into the common cellular covering of the vessels. 35* 414 THE DISSECTOR. Now it is obvious that the artery and vein, placed side by side, cannot occupy an area two inches in breadth, and therefore 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, we shall see a space, 14, to the inner side of the vein, which is only occupied by cellular tissue, lymphatic vessels, and a lymphatic gland. So that the inner wall of the sheath is separated by a considerable interval from the vein, while the outer wall, 13, is in close contact, and adherent to the artery : moreover, the sheath is divided by septa into three parts, one septum being placed between the artery and vein, and another between the vein and the space to its inner side ; this space being the crural or femoral canal. The lymphatic gland is placed immediately under Poupart's ligament, and may be easily pushed into the cavity of the abdo- men by using very slight pressure with the finger. The opening, 15 (Fig. 124), thus produced by the finger is the crural or femoral ring: it is bounded in front by Poupart's liga- ment, 1, behind by the body of the pubes, 2, to the outer side of the femoral vein, 12, and to the inner side by Gimbernat's liga- ment, 16. This ligament is one insertion of Poupart's ligament, which expands in a radiated manner to be attached along the sharp edge of the pectineal line. Fig. 125. A SECTION OF THE STRUC- TURES WHICH PASS BENEATH THE FEMORAL ARCH. 1. Pou- part'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, in- closed in the sheath of the psoas and iliacus. 11. Gim- bernat's ligament. 12. The femoral ring, within the femoral eheath. 13. The femoral vein. 14. The fe- moral artery : the two vessels and the ring are surrounded by the femoral sheath, and thin septa are sent between the anterior and posterior wall of the sheath, dividing the artery from the vein, and the vein from the femoral ring. FEMORAL HERNIA. 415 If the student, before passing his finger through the femoral from the sheath, should attempt to press it from within the abdomen, after tearing away the peritoneum, he will find an ob- stacle 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 crural canal, carrying with it the peritoneum and septum crurale. Secondly, it advances forwards 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 de- scribed (page 399), as forming the cribriform fascia. Thirdly , it turns upwards over Poupart's ligament. To return it again to the cavity of the abdomen, we must pur- sue the converse of the direction which is followed in its descent, . e., we must press it first downwards below Poupart's ligament, then backwards through the saphenous opening, then upwards through the femoral ring ; having previously flexed and rotated the thigh inwards, in order to relax the structures concerned in the hernia. But should the intestine be strangulated, that is, constricted in its passage, so as to arrest the progress of the aliment, and by dis- tension 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 in- testine. The surgeon must, therefore, know well what parts are likely to meet his knife in the living dissection. Two of these are common to the whole body, and must be divided in every operation ; the others are peculiar to the region : they are six in number, namely : integument ; superficial fascia ; cribriform fascia ; fascia propria (sheath of the vessels) ; septum crurale ; peritoneal sac. After opening the peritoneal sac, the surgeon examines the in- testine and feels for the stricture. This is generally the margin of tha femoral ring ; or it may be the upper curve of the saphe- nous opening ; if the former, Gimbernat's ligament is the proba- ble cause of the stricture, and should be divided horizontally ; if the latter, the incision necessary for the liberation of the intes- tine should be made upwards and inwards. This is the anatomical principle of practice in every case of femoral hernia ; and the incision required for the relief of the stricture is very slight. But if the operator be a bad dissector, and, by a necessary consequence, a bad operator, he may, instead 416 THE DISSECTOR. of loosening the ring, carry his incision altogether through Pou- part's ligament, or very likely still further, and cut across the spermatic or epigastric artery, and so complete the operation with the life of his patient. Such an operator should be forewarned that a variety in the distribution of the arteries sometimes occurs in the vicinity of the femoral ring ; and unless he be guarded, his reputation may be forever destroyed by an unfortunate complication of this kind. The variety consists in the origin of the obturator artery, from the epigastric immediately above the femoral ring. The artery arising in this situation, descends 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 near the margin of Gimber- nat'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. There- fore the safety of the patient demands that the surgeon should always conduct his operation as if his patient were the subject of this anomalous distribution, and he may then reflect upon his conduct even after an unsuccessful issue without self-reproach. 1 GLUTEAL REGION. The subject being turned on its face, and a block placed beneath the pubes to support the pelvis, the student commences 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 posterior fifth of the crest of the ilium, to the apex of the trochanter major: this marks the upper border of the gluteus niaximus ; and a third incision from the apex of the coccyx along the fleshy margin of the lower border of the gluteus maximus, to the outer side of the thigh, about four inches below the apex of the trochanter major. He then reflects the in- tegument, superficial fascia, and deep fascia, which latter is very thin over this muscle, from the gluteus maximus, following 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 which binds down the gluteus medius, the other portion of this region. The more advanced student may wish to dissect the cutaneous nerves in this region ; in which case he removes only the integument, and then proceeds to seek for the nerves and follow them in their course. 1 The author has met with five or six instances of this dangerous dis- tribution in about 300 bodies, which is a large average. In a prepara- tion now before him, a large branch of communication between the epi- gastric and obturator artery takes that remarkable course along the margin of Gimbernat's ligament, leaving the femoral ring to its outer side. GLUTEAL REGION. 417 Fig. 126. The CUTANEOUS NERVES distributed to this region are : 1. Branches of the external cutaneous, which turn back from a little below the anterior superior spine of the ilium. 2. The lateral cutaneous branch of the last dorsal nerve, which crosses the crest of the ilium just behind the origin of the tensor vagina? femoris muscle and supplies the integument as low as the trochanter major. 3. The iliac branch of the ilio-hypogastric nerve, which crosses the crest of the ilium a little beyond its middle, and is of small size. 4. Two or three branches, given off by the posterior division of the lumbar nerves ; these cross the crest of the ilium further back than the preceding. 5. Two or three branches frm the posterior sacral nerves. Besides these, the integument covering the lower border of the gluteus maximus receives a few cuta- neous branches from the lesser sciatic nerve. The MUSCLES of the gluteal region are Gluteus maximus, medius, minimus, Pyriformis, Gemellus superior, Obturator internus, Gemellus inferior, Obturator externus, Quadratus femoris. The GLUTEUS MAXIMUS (yXovfof, nates) is the thick, fleshy mass of muscle, of a quad- rangular shape, which forms the convexity of the nates. In structure, it is extremely coarse, being made up of large fibres, which are collected into fasciculi, 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 posterior surface of the sacrum and THE MUSCLES OF THE POSTERIOR FEMORAL AND GLUTEAL REGION. 1. The glutens medius. 2. The glutens maximus. 3. The vastus externus covered in by fascia lata. 4. The long head of the biceps. 5. Its short head. 6. The semi-tendinosus. 7. The semi-membranosug. 8. The gracilis. 9. A part of the inner border of the adductor magnus. 10. The edge of the sartorius. H. 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 eeini-merubranosus, the inner hamstring. 418 THE DISSECTOR. coccyx, and from the great sacro-ischiatic ligament. It passes obliquely outwards and downwards, to be inserted into the rough line leading from the trochanter major to the liriea aspera, and is continuous by means of its tendon with the fascia lata covering the outer side of the thigh. Several bursse are situated between this muscle and subjacent parts ; one upon the tuberosity of the ischium, one between its tendon and the trochanter major, and one between it and the tendon of the vastus externus. After this muscle lias been sufficiently studied, it must be turned down from its origin. Its dissection, however, from the parts beneath demands considerable care, as a number of arteries and nerves are situated immediately below it. The GLUTEUS MEDIUS is placed in front of rather than beneath the gluteus maximus, and is covered in by a process of the deep fascia, which 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 dorsum ilii, and from the dense fascia above mentioned. Its fibres converge to the outer 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 ; a bursa will be found between its tendon and the trochanter. The GLUTEUS MINIMUS (Fig. 128, i) is a radiated muscle, aris- ing from the surface of the dorsum ilii, between the superior and inferior curved lines : its fibres converge to the anterior border of the trochanter major, into which it is inserted by means of a rounded tendon. There is no distinct separation between the gluteus medius and minimus anteriorly. The gluteus minimus should be divided through its tendon and turned upwards in order to show that head of the rectus muscle which proceeds from the upper lip of the acetabulum. To understand the exact relations and origins of the next muscles, the student 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 excavated sweep immediately above this spine is called the great sacro-ischiatic notch, in contradis- tinction 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 radiate 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 further 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 posterior 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, SACRO-ISCHIATIC OPENINGS. 419 and more posterior : hence it is named the posterior or great sacro-ischia- tic ligament. These two ligaments convert the notches into foramina, which are thence called the superior or great sacro-ischiatic foramen, and the inferior or lessor sacro-ischiatic foramen. Let us now return to the muscles. The PYRIFORMIS muscle (Fig. 128, 3, pyrum, a pear, t. e. pear- shaped) arises from the anterior surface of the sacrum, by little slips interposed between the anterior sacral foramina from Fig. 127. the first to the fourth. It passes out of the pelvis, through the great sacro-ischiatic foramen, and is insertedby a rounded ten- don into the posterior border of the trochanter major. Immediately below the pyri- formis is a small slip of muscle, the GEMELLUS SUPERIOR (gemel- lus, double, twin) : it arises from the spine of the ischium, and is inserted into the upper border of the tendon of the obturator interims, and into the digital fossa of the trochan- ter major. The OBTURATOR INTERNUS arises from the inner surface of the anterior wall of the pelvis, being attached to the margin of bone around the obturator foramen, and to the obturator membrane. 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 pulley, is faced with cartilage, and provided with a synovial bursa to facilitate its movements. The tendon of the obturator is supported on each side by the 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. THE DEEP MUSCLES OP THE GLTT- TEAL REGION. 1. The external sur- face of the ilium. 2. The posterior surface of the sacrum. 3. The pos- terior sacro-iliac ligaments. 4. The tuberosity of the ischium. 5. The great or posterior sacro-ischiatic liga- ment. 6. The lessor or anterior sacro- ischiatic ligament. 7. The trochanter major. 8. The gluteus minimus. 9. The pyriformis. 10. The gemellus superior. 11. The obturator in tern us muscle, passing out of the lessor sacro- ischiatio foramen. 12. The gemellna inferior. 13. The quadratus femoris. 14. The upper part of the adductor magnns. 15. The vastus externus. 16. The biceps. 17. The gracilis. 18. The semi-tendinosus. 420 THE DISSECTOR. The GEMELLUS INFERIOR arises from the posterior point of the tuberosity of the ischium, and is inserted into the lower 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 quadra- tus femoris, may be seen the tendon of the obturator externus, becoming more superficial as it passes outwards to its "insertion into the digital fossa of the trochanter major : it arises from the external surface of the obturator ligament, and from the margin of bone immediately surrounding it. (Page 403.) The QUADRATUS FEMORIS (Fig. 128, 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 tro- chanter 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 standing 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 in- wards. The gluteus medius and maximus, from their insertion into the posterior aspect of the bone, rotate the limb outwards : the latter is, moreover, a tensor of the fascia of the thigh. The other muscles rotate the limb outwards, everting the knee and foot ; hence they are named external rotators. Vessels and Nerves of the Gluteal Region. Arteries. Nerves. f Superficial branch. . f Superior branch. Gluteal \ Deep superior branch. Gluteal ^ branch> (. Deep inferior branch. Ischi " ' ^ -' ischiatici. I internal. Great ischiatic. Internal pudic. Internal pudic. The gluteal artery and nerve (Fig. 128, 11) are found imme- diately above the pyriformis muscle ; the other vessels and nerves, 12, 14, immediately beneath that muscle. The GLUTEAL ARTERY is the continuation of the posterior trunk of the internal iliac ; it passes out of the pelvis through the great sacro-ischiatic foramen, above the pyriformis muscle, and divides into three branches ; superficial, deep superior, and deep inferior. The superficial branch passes backwards between the gluteus maximus and medius, and is distributed to the gluteus maximus and to the integument of the gluteal and sacral region. The deep superior branch passes forwards along the superior curved line of the ilium, between the gluteus medius and minimus to the anterior superior spinous process of the ilium where it inoscu- VESSELS OF GLUTEAL REGION. 421 Fig. 128. lates with the superficial circumflexa ilii and external circumflex. There are frequently two arteries occupying the place of this branch. The deep inferior branches, two or three in number, cross the gluteus minimus obliquely to the trochanter major, where they inosculate with branches of the external circumflex and ischiatic arteries, and send branches through the muscle for the supply of the hip-joint. The arteries in this region are all branches of the internal iliac within 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 ante- rior trunk of the internal iliac, escapes from the pelvis beneath the pyriformis muscle, and passing downwards with the ischiatic nerves, in the interval between the tuberosity of the ischium andthe trochanter major, divides into several branches, the prin- cipal of which are the coccygeal, comes nervi ischiatici and muscular. The coccygeal branch pierces the great sacro-ischiatic ligament, and is distributed to the coccygeus and leva- tor ani muscles, and to the integument of the anal and coccygeal region. The comes nervi ischiatici is a slender branch which accompanies the great ischiatic nerve, extending as far as the lower part of the thigh. The muscular branches supply the muscles of the posterior part of the hip and thigh, and send twigs to the hip- joint. They' inosculate with the inter- nal and external circumflex arteries, obturator, and superior perforating. A DEEP POSTERIOR VIEW OF THE ANATOMY OF THE HlP J SHOWING THE MuS- CLES, VESSELS, AND NERVES, WHICH ARE EXPOSED BY THE REMOVAL OF THB GLUTEUS MAXIMUS MUSCLE. 1. The gluteus minimus muscle. 2. The tro- chanter major of the femur. 3. The pyriformis muscle. 4. The tendon of the obturator internus muscle, bounded above by the gemellns superior, and below by the gemellus inferior. 5. The quadratus femoris muscle. 6. The adductor ni.i^nus. 7. The vastus externus muscle. 8. The long head of the biceps. 9. The serai-tendinosus. 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-ischiatic ligament. * The tuberosity of the ischium. 16. Tho posterior branches of the sacral nerves. 36 422 THE DISSECTOR. The INTERNAL PUBIC ARTERY, the other terminal branch of the anterior trunk of the internal iliac, also issues from the pelvis through the great ischiatic foramen below the pyriformis to dis- appear immediately beneath the great sacro-ischiatic ligament, and pursue its course within the pelvis. From the description usually given of this artery, the student might imagine that its course was extremely eccentric, going out of the pelvis and then going in. But if he refer 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 upon the projection inwards of the spine of the ischium, upon which the artery, with its veins and nerve, rests in this region. Upon entering the lesser ischiatic foramen, the internal pudic artery crosses the lower part of the obturator internus muscle to the ramus of the ischium, along which, and the ramus of the pubes, it ascends to the symphysis. Its branches are distributed to the perineum. The VEINS, as in all the secondary arteries of the body, are placed by the side of the arteries in pairs, which are called "vence comites." Nerves of the Gluteal Region. The GLUTEAL NERVE (superior gluteal; Fig. 128, n ; Fig. 132, 2) is a branch of the lumbo-sacral or fifth lumbar nerve. It passes out of the pelvis with the gluteal artery through the great sacro- ischiatic foramen, and divides into a superior and inferior branch. The superior branch follows the direction of the superior curved line of the ilium, accompanying the deep superior branch of the gluteal artery, and sends filaments to the gluteus medius and minimus. The inferior branch passes obliquely downwards and forwards between the gluteus medius and minimus to the tensor vaginae femoris, and is distributed to all the three muscles. The LESSER ISCHIATIC NERVE (Fig. 128, is; Fig. 132, G), one of the branches of the sacral plexus, passes out of the pelvis through the great sacro-ischiatic foramen below the pyriformis muscle, and continues its course downwards through the middle of the thigh to the lower part of the popliteal region, where it pierces the fascia and becomes subcutaneous. It then associates itself with the external saphenous vein, and descends to the lower part of the leg communicating with the external saphenons nerve. The branches of the lesser ischiatic nerve are muscular and cuta- neous. The muscular or inferior gluteal are several large branches distributed to the gluteus maximus. POSTERIOR FEMORAL REGION. 423 The cutaneous branches are divisible into external, internal, and middle. The external cutaneous branches are several filaments which turn around the lower border of the gluteus maximus, and are distributed to the integument over the hip and outer side of the thigh. The internal cutaneous branches are distributed to the integument of the upper and inner part of the thigh. One of these branches, larger than the rest, inferior pudendal, curves around the tuberosity of the ischium, pierces the fascia lata near the ramus of that bone, and, after communicating with the superficial perineal nerve, is distributed to the integument of the scrotum and penis. The middle cutaneous branches, two or three in number, are derived from the lesser ischiatic in its course down the thigh and are distributed to the integument. The GREAT ISCHIATIC NERVE (Fig. 128, 12; Fig. 132, ,7) is the largest nervous cord in the body ; it is formed by the sacral plexus, or rather is a prolongation of the plexus ; and at its exit from the great sacro-ischiatic foramen, beneath the pyriformis, measures three quarters of an inch in breadth. It descends through the middle of the space between the trochanter major and tuberosity of the ischium, and along the posterior part of the thigh to its lower third, where it divides into two large terminal branches, internal and external popliteal. This division some- times takes place at the plexus, and the two nerves descend side by side ; sometimes one passes out of the pelvis above the pyriformis, or even pierces that muscle. In its course downwards the nerve rests on the gemellus superior, tendon of the obturator internus, gemellus inferior, quadratus femoris, and then gets between the flexor muscles and abductor magnus; a few muscular twigs are given off by the nerve while in the gluteal region. The INTERNAL PUBIC NERVE (Fig. 128, i4j Fig. 132, 5) may be seen lying by the side of the internal pudic artery. It proceeds from the lower part of the sacral plexus, and passing out of the pelvis through the great sacro-ischiatic foramen below the pyri- formis muscle, enters it again through the lesser sacro-ischiatic foramen, and accompanies the internal pudic artery in its course. 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 integument to either side. In the su- perficial fascia will be seen the cutaneous branches of the lesser ischiatio nerve. 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- 424 THE DISSECTOR. Biceps. Semi-tendinosus. Semi-membranosus. The BICEPS FLEXOR CRURIS (bis, double xt^a^, head) arises by two heads, one by a common tendon with the semi-tendinosus from the upper and back part of the tuberosity of the ischium ; the other, muscular, and much shorter, from the lower two-thirds of the external border of the linea aspera. This muscle forms the outer hamstring, and is inserted by a strong tendon into the head of the fibula ; a portion of the tendon being continued into the fascia of the leg. The SEMI-TENDINOSUS, remarkable for its long tendon, arises in common with the long head of the biceps from the upper and back part of the tuberosity of the ischium. It is inserted into the inner tuberosity of the tibia; and sends an expansion to the fascia of the leg. 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 expan- sion upon its anterior and posterior surfaces, arises from the tube- rosity of the ischium, in front of the common origin of the two preceding muscles. It is inserted into the posterior part of the inner tuberosity 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 aponeurotic ex- pansion which binds down the popliteus muscle, the popliteal fascia ; and the third turns upwards and outwards to the ex- ternal condyle of the femur, forming the middle portion of the posterior ligament of the knee-joint (ligamentum posticum Winslowii). The tendons of the two last muscles, viz : the semi-tendinosus 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 radiated expanse of the ad- ductor magnus, upon which the great ischiatic nerve and 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 and Nerves of the Posterior Femoral Region. The ARTERIES of this region are the external and internal cir- cumflex, three perforating, the termination of the profunda ferno- ris and the popliteal. POPLITEAL REGION. 425 The middle branch of the external circumflex is seen piercing the upper part of the vastus externus, to inosculate with the in- ternal circumflex, ischiatic, and superior perforating artery. The internal circumflex makes its appearance between the upper border of the adductor magnus, and the lower border of the quadratus femoris. It inosculates with the external circumflex, ischiatic, and superior perforating artery. The three perforating arteries emerge on the posterior aspect of the thigh, by passing through tendinous arches between the adductor magnus and the linea aspera. They anastomose with each other, with the circumflex and ischiatic arteries above, and with the articular branches of the popliteal below. The pro- funda artery passes through the adductor magnus, close to the linea aspera, and is protected from pressure by a tendinous arch, thrown across the bone. It makes its appearance at about an inch above the commencement of the popliteal artery. The NERVES in this region are the greater and lesser ischiatic. The continuation of the lesser ischiatic is seen upon the semi- tendinosus muscle. The great ischiatic nerve (Fig. 132, 7) runs down the middle of the posterior femoral region, being situated between the flexor muscles and the adductor magnus. At the lower third of the thigh it divides into two nerves of nearly equal size, the internal popliteal, 9, and external popliteal, 8. Its branches are muscular and articular. The muscular branches are distributed to the biceps, semi-tendiriosus, semi-merabranosus and adductor magnus. The articular branch descends to the external condyle of the femur and is distributed to the knee-joint. POPLITEAL REGION. The lower part of the posterior femoral region is a surgical region of some importance, the popliteal (Fig. 129). It is a dia- mond-shaped space, bounded above on each side by the two ham- strings 1, 2 r and below by the two heads, 3, 3, of the great muscle of the calf, the gastrocnemius. On dissecting 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 converge, which must be divided in making an incision for the purpose of reaching the artery. If the superficial fascia be dissected away, the external saphenous vein will be seen passing through an oval foramen in the deep popliteal fascia, to termi- nate in the popliteal vein. Some cutaneous branches of nerves from the lesser ischiatic and internal cutaneous of the anterior crural may also be found in the superficial fascia. 36* 426 THE DISSECTOR. Fig. 129. The deep popliteal fascia is thin, and will be removed without being observed, unless the dissector proceed cautiously. It is a part of the common deep fascia (fascia lata) investing the entire limb. Beneath the deep fascia is a quantity of adipose substance which fills up the whole popliteal space, from the bone and joint to the surface, and protects and supports the popliteal vessels and nerves. It will be recollected, that at the upper part of this popliteal space the great ischiatic nerve divides into two branches of nearly equal size, the internal and external popliteal. The internal popliteal, 4, runs along the middle line of this space, from apex to apex of its diamond- shaped area. It is placed near 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 a large branch of the internal popliteal, the external saphenous nerve, and the external popliteal nerve, 6, lying along the tendon of the biceps muscle. To the inner side of the internal 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. If therefore it were necessary to place a ligature around the popliteal artery, we should make a longitudinal incision along the middle of the pop- liteal space, which should divide the integument, the superficial fascia, remembering the external saphenous vein, the deep fascia, then cautiously make our way through the adipose substance, a little to the inner side of the middle line, down to the artery, and hook around it the aneurismal needle. In the upper part of the popliteal space, the artery lies comparatively superficially; and is altogether to the inner side of the internal pop- liteal nerve. In the middle portion it is deepest : THE POPLITEAL REGION, AND THE SUPERFICIAL ANATOMY OF THE CALF OF THE LEG. 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 their relative position from within outwards ; the artery being the deepest, next the vein, and the nerve quite superficial. 5. The termination of the is- chiatic nerve dividing into the internal popliteal nerve, and 6, the peroneal or external popliteal. 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 harder of the soleus muscle. 10. The tendo Achillis. POPLITEAL ARTERY. 42f and between the heads of the gastrocnemius, it again becomes superficial, but is crossed by numerous muscular branches, both of the artery and nerve, which would interfere with the progress of an operation. 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. 129, 4) runs obliquely out- wards, through the middle of the popliteal space, from the opening in the abductor magnus, to the lower border of the pop- liteus muscle, where it divides into the anterior and posterior tibial artery. In this course it rests first on the femur, then on the posterior ligament of the knee-joint, then on the fascia covering the pop- liteal muscle : superficial and external to it is the popliteal vein, and still more superficial and external, the internal popliteal nerve. It has, also, in relation with it, four or five lymphatic glands which lie near its cylinder. The branches of the popliteal artery are, the Superior external articular, Superior internal articular, Azygos articular, Inferior external articular, Inferior internal articular, SuraJ. 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 external circumflex, the anastomotica magna, the inferior articular 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 adductor magnus. They sup- ply the knee-joint and lower part of the femur, and give branches to the vasti muscles. The azygos articular artery pierces the posterior ligament of the joint, the ligamentum posticum Winslowii, and supplies the crucial ligaments and synovial membrane. 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 inter- nal lateral ligament. The sural arteries (sura, the calf) are two muscular branches of large size, distributed to the two heads of the gastrocnemius muscle. Other muscular branches are given off from the upper part of the popliteal to supply the hamstring muscles. 428 THE DISSECTOR. The INTERNAL POPLITEAL NERVE (Fig. 129, 4 ; Fig. 132, 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 superficial in the whole of its course, and lies externally to the vein and artery. The branches of the internal popliteal nerve are, muscular or sural, articular, and a cutaneous branch the external saphenous nerve. The muscular branches, of considerable size, and four or five in number, are distributed to the gastrocnenrius, soleus, plantaris, and popliteus muscles. The articular branches, two or three in number, supply the knee-joint; two of the twigs accompanying the internal articular arteries. The external or short saphenous nerve (communicans poplitei, vel tibialis) proceeds from the middle of the internal popliteal, and descends in the groove between the two bellies of the gas- trocnemius muscle to the middle of the leg; it then pierces the fascia, and, after receiving the communicans peronei, comes into relation with the external saphenous vein, and follows the course of that vein to the outer ankle, to which and to the integument of the heel and foot it distributes branches. The EXTERNAL POPLITEAL NERVE (peroneal, Fig. 129, e ; Fig. 132, s), one-half smaller than the internal, passes downwards by the side of the tendon of the biceps, and crosses the internal head of the gastrocnemius and the head of the soleus to the neck of the fibula; it then pierces the peroneus longus muscle and divides into two branches, anterior tibial and musculo-cutaneous. The branches of the external popliteal nerve are the communi- cans peronei, cutaneous and articular. The communicans peronei, proceeding from the external pop- liteal near the head of the fibula, crosses the external origin of the gastrocnemius muscle, and, piercing the deep fascia, descends to the middle of the leg, where it joins the external saphenous nerve. It gives off one or two cutaneous filaments in its course. The cutaneous branch descends the outer side of the leg, sup- plying the integument. The articular branches take the course of the external articu- lar arteries to the knee-joint, to which they are distributed. Dissection of the Leg. The leg is naturally divided into three regions, anterior tibial, jibular, and posterior tibial. Each region is composed of its DISSECTION OF THE LEO. 429 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, Internal saphenous vein, Extensor longus digitorum, Internal saphenous nerve, Peroneus tertius, Musculo-cutaneous nerve, Extensor proprius pollicis, Anterior tibial artery, Anterior tibial nerve. 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 disarticulating at the hip-joint, as it gives him an opportu- nity, 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 between the tibia and the fibula, from the knee to the ankle, and bounding it inferiorly by a trans- verse incision, extending from one malleolus to the other. And to ex- pose 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 ter- minated 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, it 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. In dissecting the superficial fascia from the anterior tibial region, it is desirable to commence by finding the situation of the superficial vessels and nerves, and take them as a point of departure, and a guide to the direction in which the dissection should be pursued. Unless this be done, there is a danger of cutting away branches of vessels or filaments of nerves without perceiving them. Although this advice is suggested by the dissection of the present region, it is equally applicable to all the regions of the body. The young dissector must apply to one of his seniors or to the Demonstrator to have the precise spot pointed out to him, where superficial vessels or nerves are to be found. The following remarks will aid him in his search. On the inner side of the leg will be found the internal saphe- nous vein, and the numerous branches which empty themselves into it in its course. This vein commences on the inner side of the dorsum of the foot, where it receives the inner termination of a venous arch which lies across the metatarsal bones. It then runs in front of the inner malleolus and ascends the inner side of the leg; passes behind the inner condyle of the femur, and is con- tinued upwards along the inner side of the thigh to the saphenous opening. In company with the internal saphenous vein is the internal 430 THE DISSECTOR. saphenous nerve, a branch of the anterior crural. This nerve pierces the fascia lata at the knee, and gives off several cutaneous filaments in its course downwards. Below the ankle it is distri- buted to the inner side of the foot and great toe. In the neigh- borhood of the long saphenous nerve may be found the cutaneous branch of the obturator nerve, which unites with the internal saphe- nous, and supplies the integument of the inner side of the leg as far as its middle. Taking its course along the outer border of the anterior tibial region, is the cutaneous branch of the external popliteal nerve ; and, at the lower third of the leg and close to the fibula, the musculo-cutaneous nerve will be found piercing the deep fascia, and dividing into its two cutaneous branches. These branches pass downwards in front of the ankle to the dorsum of the foot and toes, to which they are distributed ; the external branch, the larger of the two supplying three toes and a half; the internal branch one toe and a half. 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, and forms separate canals for them in their passage forwards to the dorsum of the foot. The anterior annular ligament consists of two portions, upper and lower ; the upper portion is the broad band connected with the tibia and fibula, now described. The lower portion is placed on the dorsum of the foot, extending between the inner malleolus and the outer surface of the os calcis : the inner extremity has, besides, a second attachment to the plantar fascia, with which it is continuous. 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. ( Vide Chap. I.) The deep fascia is easily separated from the muscles in the lower part of the leg, but above it is closely connected to them, and cannot be removed without dividing some of their fibres. When removing the deep fascia, the anterior annular ligament should be left uninjured. Muscles of the Anterior Tibial Region. Tibialis anticus, Extensor longus digitorum, Peroneus tertius, Extensor proprius pollicis. TIBIALIS ANTICUS EXTENSORS. 431 Fig. 130. The TIBIALIS ANTICUS muscle (flexor tarsi tibialis) arises from the outer tuberosity and upper two-thirds of the tibia, from the interosseous membrane, intermuscular fascia, and deep fascia; its tendon passes through a distinct sheath in the annular ligament, and is inserted into the inner and under side of the internal cunei- form bone, and base of the metatarsal bone of the great toe. The EXTENSOR LONGUS DiGiTORUM arises from the outer tube- rosity of the tibia, from the head and upper three-fourths of the fibula, from the interosseous membrane, intermuscular fascia, and 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 ex- tensor tendons, both in the hand and in the foot is remarkable (Fig. 116) ; each tendon spreads into a broad aponeurosis, which is situated over the first phalanx, and receives on its borders the insertion of the lumbricales and interossei ; this aponeurosis divides into three slips ; the middle slip is inserted into the base of the second phalanx, and the two lateral slips are continued onwards to be inserted into the base of the third. The PERONEUS TERTIUS (flexor tarsi fibularis) arises from the lower fourth of the fibula, and intermuscular fascia ; it is inserted into the base of the metatarsal bone of th^ little toe. Although it ap- pears to be merely a part of the extensor longus digitorum, it may be looked upon as analogous to the flexor carpi ulnaris of the forearm. Sometimes it is alto- gether wanting. The EXTENSOR PROPRIUS POLLICIS lies between the tibialis anticus and extensor longus digitorum. It arises from the lower two-thirds of the fibula and inter- THE MUSCLES OF THE ANTERIOR TIBIAL REGION. 1. The extensor muscles inserted into the patella. 2. The subcutaneous surface of the tibia. 3. The til. i:ilis anticus. 4. The extensor communis digitorum. 5. The extensor pro- prius 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 ten- don in front of this number is that of the peroneus tertius ; and that behind it, the tendon of the peroneus brevis. 432 THE DISSECTOR. osseous membrane. Its tendon 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 ter- Fig. 131. tins are direct flexors of the tarsus upon the leg ; acting in conjunction with the tibialis posticus, and peroneus longus and brevis, they direct the foot either inwards or outwards, and preserve its flatness in progression. The extensor longus digi- torum, and extensor proprius pollicis, are direct extensors of the phalanges : but continuing their action, they assist the tibialis anticus and peroneus tertius, in flexing the entire foot upon the leg. Taking their origin from below, they increase the stability of the ankle. Vessels and Nerves of the Anterior Tibial Region. We have seen in a previous section that the popliteal artery divides into the anterior and posterior tibial. The ANTERIOR TIBIAL passes forwards be- tween the two heads of the tibialis posticus muscle, 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, where it becomes the dorsalis pedis. In its course it rests upon the inter- osseous membrane, the lower part of the tibia, and the anterior ligament of the joint. In the upper third of its course it is situated be- tween the tibialis anticus and extensor longus digitorum ; lower down between the tibialis anticus and extensor proprius pollicis ; and just before it reaches the ankle it is crossed by the tendon of the extensor proprius pol- THE ANTERIOR ASPECT OF THE LEG AND FOOT, SHOWING THE ANTERIOR TIBIAL AND DORSALIS PEDIS ARTERIES, WITH THEIR BRANCHES. 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 longus digitorum. 6. The peronei muscles. 7. The inner belly of the gastrocnemius 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 dorsalispedis artery. 14. The tarseaand 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. ANTERIOR TIBIAL ARTERY. 433 licis, and becomes placed between that tendon and the tendons of the extensor longus digitorum. Its immediate relations are, the venae comites, and the anterior tibial nerve : the latter lies at first to its outer side ; about the middle of the leg it becomes placed in front of the artery ; and at the ankle is again at its outer side. Operations. The anterior tibial artery may be tied in any part of its course (after it lias escaped through the opening in the interosseoua membrane), by making an incision in the direction of a line drawn from the midpoint, between the anterior borders of the tibia and fibula in the upper third of the leg, to the middle of the ankle. The operation in the upper third of the course of the artery is one of considerable difficulty. 1st. On account of the absence of any positive guide to the interspace between the tibialis anticus and extensor longus digitorum muscles ; 2d. On account of the great depth of the artery ; and 3dly. On account of the unyielding nature of the deep fascia, which con- stricts the external orifice of the wound. In consequence of these im- pediments, the artery is never operated upon in this situation, excepting for the purpose of securing both ends of the vessel in accidental wounds. The incision in the integument and deep fascia must be four inches in length. The artery has a vein to either side, vence comites ; the nerve lies to its outer side. In the middle third of the leg, the incision is to be made in the same direction, and about three inches in length. The structures to be divided are the integument, superficial fascia, and deep fascia. Then the interspace between the tibialis anticus and extensor proprius pollicis is to be found, and the two muscles separated. Lying at the bottom of the interval be- tween them, and supported by the interosseous membrane, will be seen the artery, accompanied by its venae comites, and having the anterior tibial nerve resting upon it. The nerve is to be drawn carefully aside, the sheath of the vessels opened, and the ligature conveyed, by means of the aneurism needle, around the artery. In the lower third of the leg, an incision in the same direction but two inches in length will suffice. The structures to be cut through are the same as in the former operation. The artery will be found resting on the bone, between the tendons of the tibialis anticus and extensor longus digitorum, or, nearer to the ankle, between the tendons of the extensor longus digitorum and extensor proprius pollicis. The relations to the veins are the same ; the nerve lies to its outer side. The branches of the anterior tibial artery are the Recurrent, External malleolar, Muscular, Internal malleolar. The recurrent branch passes upwards to the front of the knee- joint upon which it is distributed, anastomosing with the articular arteries. It pierces the origin of the tibialis anticus muscle. The muscular branches supply the muscles of the anterior tibial region. The malleolar arteries are distributed to the ankle-joint ; the external passing beneath the tendons of the extensor longus digitorum and peroneus tertius, and inosculating with the ante- 37 434 THE DISSECTOR. rior peroneal artery and dorsalis pedis ; the internal beneath the tendons of the extensor proprius pollicis and tibialis anticus, in- osculates with branches of the posterior tibial and internal plantar artery. The ANTERIOR TIBIAL NERVE (inter osseous , Fig. 132, 13), com- mences at the bifurcation of the external popliteal upon the neck of the fibula, and passes beneath the upper part of the extensor longus digitorum, to reach the outer side of the anterior tibial artery, just as that vessel has passed through the opening in the interosseous membrane. It descends with 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 on the foot accompanies the dorsalis pedis artery to the space between the great and second toe. 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 The EXTENSOR BREVIS DIGITORUM muscle arises from the outer side of the os calcis, crosses the foot obliquely, and terminates in four tendons, the innermost of which is inserted into the base of the first phalanx of the great toe, and 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 of 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 pha- lanx, and into the digital expansion of the tendons 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 (posterior 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 first metatarsal space, where it gives off a branch, the dorsalis pollicis, and then dips DORSALIS PEDIS ARTERY. 435 between the two heads of the first dorsal interosseous muscle into the sole of the foot, and becomes continuous with the deep plantar arch. In its course along the foot it gives off the tarsea and metatarsea, and is placed on the outer side of the tendon of the extensor proprius pollicis; on its fibular side it has the tendon of the extensor longus digitorum, and near its termi- nation is crossed by the inner tendon of the extensor brevis digitorum. Operation. The dorsalis pedis artery is to be exposed, by making an incision two inches in length along the external border of the tendon of the extensor proprius pollicis muscle, beginning at the ankle-joint. The artery, accompanied by its two veins and nerve, rests upon the bones of the tarsus, between the tendons of the extensor proprius pollicis and ex- tensor longus digitorum. Near the base of the metatarsal bones it is crossed by the innermost tendon of the extensor brevis digitorum. The tarsea crosses the dorsum of the foot in an arched direc- tion, beneath the extensor brevis digitorum muscle. It supplies the articulations of the tarsal bones, and inosculates at the outer border of the foot with the external malleolar, peroneal arteries, and external plantar. The metatarsea forms a similar arch across the bases of the metatarsal bones, and terminates on the outer side of the foot by inosculating with the tarsea, and external plantar artery. From its convex side the metatarsea gives off three branches, the in- terossece, which pass forwards on the interossei muscles and divide into branches (dorsal collateral), which supply the sides of the toes between which they are placed. Near their origin the interosseae receive the posterior perforating branches from the plantar arch; and at their bifurcation they are joined by the an- terior perforating branches from the digital arteries. The inter- osseous artery of the fourth interosseous space, in addition to the two dorsal collateral branches into which it bifurcates, sends a third to the outer side of the little toe. The dorsalis pollicis runs forward upon the first dorsal inter- osseous muscle, and at the base of the first phalanx divides into two branches, one of which passes beneath the tendon of the ex- tensor proprius pollicis, and is distributed to the inner border of the great toe ; the other bifurcates into two collateral branches, which supply the adjacent sides of the great and second toe. While in the metatarsal space the dorsalis pedis artery gives off another branch, magna pollicis, which sends a digital branch to the inner border of the great toe, and then bifurcates to sup- ply the collateral digital branches of the great and second toe. The VEINS of the dorsum of the foot are a venous arch which lies across the metatarsus, and the internal and external saphenons veins. The venous arch receives the digital veins by its convex side, and terminates in the saphenous veins. 436 THE DISSECTOR. The internal saphenous vein, taking its origin by the veins of the great toe and inner termination of the venous arch, passes upwards along the inner border of the foot, and in front of the inner ankle to the side of the leg, whence it is continued to the saphenous opening. The external saphenous vein commences in a similar manner on the outer side of the little toe and side of the foot ; it receives the outer termination of the venous arch, passes behind the outer ankle, and ascends along the back of the leg to the popliteal region, where it enters an opening in the deep fascia and joins the popliteal vein. The NERVES distributed upon the dorsum of the foot are five in number, namely, the internal and external branches of the musculo-cutaneous nerve ; the internal and external saphenous nerves, and the anterior tibial. The cutaneous branches of the musculo-cutaneous nerve divide into a leash of branches which spread out upon the dorsum of the foot in their course to the toes. The internal branch, the smaller of the two, is distributed to the inner side of the foot and great toe, and communicates with the anterior tibial and internal saphenous. The external, or larger branch, supplies the adja- cent sides of the second and third, third and fourth, and fourth and fifth toes, and communicates with the external saphenous. The internal or long saphenous nerve passes along the inner side of the foot as far as the base of the metatarsus, and com- municates with the internal cutaneous nerve. The short or external saphenous nerve advances along the outer border of the foot from behind the outer ankle. It is distributed to the outer side of the little toe, and sometimes its inner side and the adjacent side of the next. It communicates with the external cutaneous nerve. The anterior tibial nerve gives off a large branch to the ex- tensor brevis digitorum muscle, and becoming superficial on the first interosseous muscle, is distributed to the adjacent sides of the great and second toe ; while on the interosseous muscle it receives a branch of communication from the internal cutaneous nerve, and sometimes this branch is so large as to supersede the anterior tibial in its distribution. The branch to the extensor brevis digitorum, after supplying the muscle, becomes gangliform and distributes branches to the articulations of the tarsus. Fibular Region. If the leg be turned upon its inner side and the deep fascia removed from over the fibula, two muscles will be exposed which arise from that bone : these are the peroneus longus and brevis. They are separated from the muscles before and behind by intermuscular septa, from which POSTERIOR TIBIAL REGION. 437 they partly take their origin. At the outer ankle the deep fascia is thickened, and, extending from the external malleolus to the side of the os calcis, constitutes the external annular ligament. This ligamentous band forms a sheath for the peronei muscles in their passage behind the outer ankle ; the sheath is lined bjjr synovial membrane. The PERONEUS LONGUS (rtfpov*?, fibula, extensor tarsi fibularia longior) arises from the head and upper half of the fibula ; also from the deep fascia and intermuscular septa : its tendon passes behind the outer malleolus to a groove in the cuboid bone, through which it proceeds obliquely across the foot to be in- serted into the base of the metatarsal bone of the great toe. The tendon is thickened where it passes behind the external malleo- lus, and a sesamoid bone is developed in that part which is lodged in the groove of the cuboid bone. The PERONEUS BREVIS (extensor tarsi fibularis brevior) arises from the lower half of the fibula and from the intermuscular septa ; its tendon passes behind the external malleolus, with the tendon of the preceding muscle, and through a groove in the os calcis to be inserted into the base of the metatarsal bone of the little toe. ACTIONS. The peronei muscles are extensors of the foot conjointly with the tibialis posticus. They antagonize the tibialis anticus and peroneus tertius, which 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 muscle be carefully turned aside from its origin, the external popliteal or peroneal nerve will be seen to give off a small re- current branch, which takes the course of the recurrent tibial artery to the front of the knee ; and then divides into its two terminal branches, the anterior tibial nerve and musculo- cutaneous. The anterior tibial nerve may now be seen piercing the head of the extensor longus digitorum to reach the anterior tibial artery; its course has already been described, page 434. The musculo-cutaneous, the proper nerve of the region, passes downwards in the substance of the peroneus longus ; it then gets between the peroneus longus and brevis ; then between the pe- ronei and the extensor longus digitorum ; and at the lower third of the leg pierces the deep fascia and divides into the internal and external cutaneous nerves of the foot. In its course among the muscles the nerve gives several branches to the peronei. The cutaneous branches have been already described, page 436. Posterior Tibial Region. This region is best dissected by making an incision from the middle of the popliteal space, down the middle of the posterior part of the leg, to the tuberosity of the os calcis, bounding it inferiorly by a transverse in- 37* 438 THE DISSECTOR. Fig. 132. cision to each raalleolus. Turning aside the two flaps of integument, the superficial fascia is brought into view, and between its two layers will be found the superficial vessels and nerves. In the middle line is the external saphenous vein, accompanied above by the lesser ischiatic nerve, and below, by the ex- ternal saphenous nerve. On the inner side of the leg is the internal saphenous vein and nerve, with the termination of the internal cutaneous nerve. On the outer side are several cutaneous branches from the external popliteal, one of which is the communicans peronei. The external saphenous vein (Fig. 129, s) commences on the outer side of the little toe, and after receiving the external termi- nation of the venous arch, passes along the outer side of the foot, behind the external malleolus, and up the middle of the back of the leg to the popliteal region. In its course along the leg it lies in the groove between the two bellies of the gastrocne- mius muscle, and in the ham pierces the deep fascia to join the popliteal vein. The lesser ischiatic nerve pierces the popli- teal fascia and descends by the side of the external saphenous vein to the point of emergence of the external saphenous nerve, with which it joins, after giving off several cutaneous twigs. The short or external saphenous nerve (Fig. 129, 7 ; Fig. 132, i e) will be found lying by the side of the external saphenous vein ; in the lower part of the leg it pierces the deep fascia just below the gastrocnemic groove, and descends with the external saphenous vein ; passes behind the external malleolus and along the outer border of the foot. It is distributed to the outer part of the foot and little toe, and communicates with the external cutaneous nerve. A DIAGRAM SHOWING THE FORMATION AND BRANCHES or THE SACRAL PLEXUS. 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 por- tion. 15. Its cutaneous portion. 16. The external saphenous nerve, formed by the union of the communicans poplitei, and communicans peronei. GASTROCNEMIU8. 439 The internal saphenous vein and nerve have been described with the dissection of the anterior tibial region. The internal cutaneous branches of the anterior crural are distributed to the integument of the inner side of the calf behind the internal sa- phenous vein. The communicans peronei, a branch of the external popliteal nerve, pierces the deep fascia near the head of the fibula, and descends to the external saphenous nerve, which it joins ; in its course it gives off cutaneous filaments. Along the outer border of the leg are other cutaneous branches, de- rived from the external politeal nerve. Fig- 133. The DEEP FASCIA, in the upper part of this region, is thin : below it is thicker ; on the inner side it is connected with the tibia, and externally is continuous with the deep fascia of the front of the leg. If the deep fascia be turned aside, the three muscles forming the superficial group of the posterior tibial region will be brought into view ; they are Gastrocnemius, Plantaris, Soleus. The GASTROCNEMIUS (yaatpoxvypiov, the bellied part of the leg) arises by two heads from the two condyles of the femur, the inner head being the longest. They unite to form the beautiful muscle so characteristic of this region of the limb. It is inserted, by means of the tendo Achillis, into the lower part of the poster tuberosity of the os calcis, a syno- vial bursa being placed between the tendon and the upper part of the tuberosity. The gastrocnemius 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, situ- ated between the gastrocnemius and soleus, arises from the outer condyle of the femur, THE SUPERFICIAL MUSCLES OP THE POSTERIOR ASPECT OF THE LEO. 1. The biceps muscle forming the outer hamstring. 2. The tendons forming the inner hamstring. 3 The popliteal space. 4. The gastrocnemius muscle. 5, 5. The solens. 6. The tendo- Achillis. 7. The posterior tuberosity of the os calcis. 8. The tendons of the peroneus longus and brevis muscles passing be- hind the outer ankle. 9. The tendons of the deep layer passing into the foot behind the inner ankle. 440 THE DISSECTOR. and is inserted, by its long and delicately slender tendon, into the posterior tuberosity of the os calcis, by the side of the tendo Achillis. It crosses between the gastrocnemius and soleus in its descent. 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 middle third of the tibia. Its fibres converge to the tendo Achillis, by which it is inserted into the posterior tuberosity of the os calcis. Fig. 134. Between 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 exten- sive origin, and turned down. ACTIONS. The three muscles of the calf draw 1 1/ & r^?i powerfully on the os calcis, and lift the heel ; con- tinuing their action, they raise the entire body. This action is attained 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 per- form 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. An inter muscular fascia serves to separate the superficial from the deep group, and by its strong attachments to the bones at each side, binds down the muscles closely in their places. On removing this fascia, the muscles of the deep group are brought clearly into view ; they are Popliteus, Flexor longus pollicis, Flexor longus digitorum, Tibialis posticus. The POPLITEUS muscle (poples, the ham of the leg) forms the floor of the popliteal region THE DEEP LAYER OF MUSCLES OP THE POSTERIOR TIBIAL REGION. 1. The lower extremity of the femur. 2. The ligamentum posticum Winslowii. 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 liga- ment. 6. The popliteus muscle. 7. The flexor longus digitorum. 8. The tibialus posticus. 9. The flexor longus pollicis. 10. The peroneus longus mus- cle. 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. TIBIALIS POST1CU8. 441 at its lower part, and is bound tightly down by a strong fascia derived from the middle slip of the tendon of the semi-mem- branosus 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 and within the capsular ligament of the joint. 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 popliteal muscle, popliteal line. The next three muscles in their course into the sole of the foot pass under cover of an aponeurosis extended between the inner malleolus ^and the side of the os calcis, the internal annular ligament. 'This ligament is narrow at its attachment to the tibia and broad where it is connected with the os calcis ; above it is continuous with the deep fascia of the leg, and below gives origin to one of the muscles of the sole of the foot. Towards the bone it sends inwards partitions for the separation of the tendons and vessels. The FLEXOR LONGUS POLLicis is the most superficial of the three muscles. It arises from the lower two-thirds' of the fibula, passes through a groove in the astragalus and os calcis, which is converted by tendinous fibres into a distinct sheath lined by syno- vial membrane, into the sole of the foot, and is inserted into the base of the last phalanx of the great toe. 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 ; it then passes through a second sheath which is connected with a groove in the astragalus and os calcis, 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 ori- gin, and the flexor longus digitorum drawn aside, to bring into view a fascia which is attached on either side to the tibia and fibula, and which binds down the tibialis posticus. The two preceding muscles take part of their origin from this fascia. The TIBIALIS POSTICUS (extensor tarsi tibialis) lies upon the interosseojis membrane, between the two bones of the leg. It arises by two heads from the adjacent sides of the tibia and fibula their whole length, from the interosseous membrane, and from the aponeurosis which binds it in its place. Its tendon passes inwards beneath the tendon of the flexor longus digitorum, and runs in the same sheath ; it then passes through a proper sheath over 442 THE DISSECTOR. Fig. 135. the deltoid ligament and beneath the cal- caneo-scaphoid articulation to be inserted into the tuberosity of the scaphoid and inter- nal cuneiform bone ; a process of its tendon being prolonged outwards to the external cuneiform. The student will observe that the two latter muscles change their relative position to each other in their course. Thus, in the leg, the position of the three muscles from within outwards, is flexor longus digitorum, tibialis posticus, flexor longus pollicis. At the inner malleolus, the relation of the tendons is tibialis posticus, flexor longus digi- torum, both in the same sheath ; then a broad groove, which lodges the posterior tibial artery, venae comites, and nerve ; and lastly, the flexor longus pollicis. The ARTERIES of the posterior tibial region are the posterior tibial and its branches. The POSTERIOR TIBIAL ARTERY passes ob- liquely downwards along the tibial side of the leg from the lower border of the popliteus muscle to the concavity of the os calcis, where it divides into the internal and external plantar artery. In its course, it rests upon the tibialis posticus, flexor longus digitorum, and tibia, and is covered in by the intermus- cular fascia. It is accompanied by venae comites, and the posterior tibial nerve, which lies to its inner side above, and to the outer side in the rest of its course. Operation. One of the most difficult operations A POSTERIOR VIEW OP THE LEG, SHOWING THE POPLITEAL AND POSTERIOR TIBIAL ARTERIES. 1. The tendons forming the inner hamstring. 2. The tendon of the biceps forming the outer hamstring. 3. The popliteus muscle. 4. The flexor longus digitorum. 5. The tibialis posticus. 6. The fibula ; imme- diately below 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 mus- cular branches ; the two superior articular are seen in the upper part of the pop- liteal 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 pop- liteus muscle. 10. The anterior tibial artery passing through the angular inter- space 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 pos- terior peroneal. POSTERIOR TIBIAL ARTERY. 443 in the entire body is the ligature of the posterior tibial artery, in the upper third of its course. It is happily one rarely required, excepting in the case of accidental wound, where both extremities of the vessel must be secured. An incision, four or five inches in length, is made parallel with the inner border of the tibia, and about half an inch distant. This will divide the integument, superficial fascia, and deep fascia ; the border of the gastrocnemius is then to be held aside, and another incision of the same extent made through the soleus down to the intermuscular fascia. When the intermuscular fascia is clearly exposed, it may be slit up. The artery, with its venae comites and nerve, lie immediately beneath it, near the middle line of the leg, and resting upon the tibialis posticus muscle. The nerve lies upon the artery, or directly to its outer side. In the middle third of the course of the artery a longitudinal incision two inches and a half in length should be made parallel with the internal border of the tibia and tendo Achillis, and midway between them. The integument, superficial and deep fascia should be divided and the sheath of the vessels opened upon a director. The artery lies between the venae comites, and the nerve is to the outer side. At the ankle, an incision two inches in length is sufficient. It must be directed obliquely from the inner border of the tendo Achillis, to the point of the internal malleolus, or in the opposite direction, as may be most convenient. It will divide the integument, superficial fascia, and deep fascia. The next step, in the living subject, would be to feel for the pulsation of the artery ; but. in the dead, the student will find the sheath containing the vessels at about three-quarters of an inch from the edge of the malleolus. The nerve lies to the outer side of the artery. If the student open a sheath lying immediately under cover of the malleolus, he will find it to contain the tendons of the flexor longus digitorum and tibialis posticus muscles. And if he get too near the tendo Achillis, he will open the sheath of the tendon of the flexor longus pollicis. The branches of the posterior tibial artery are the Peroneal, Internal calcanean, Nutritious, Internal plantar, Muscular, External plantar. The peroneal artery is given off from the posterior tibial at about two inches below the lower border of the popliteus mus- cle; it is nearly as large as the anterior tibial artery, and passes obliquely outwards to the fibula. It then runs downwards along the inner border of the fibula to its lower third, where it divides into the anterior and posterior peroneal artery. At the upper part of its course it rests upon the tibialis posticus, but soon gets under cover of the flexor longus pollicis, having the fibula to its outer side. The peroneal artery, previously to its division, gives off muscular branches and a nutrient branch to the fibula. Operation. From the very deep position of the fibular artery beneath the flexor longus pollicis muscle, and behind the fibula, this is a very difficult operation. This may well be conceived, when it is recollected that it has been proposed to saw away a portion of the bone to reach the artery. Like the operation on the upper part of the tibial arteries, it is not likely to be required except in the case of accidental wound. The operation is performed in the middle third of the leg, previously to the 444 THE DISSECTOR. division of the artery into the anterior and posterior peroneal. An inci- sion, four inches in length, must be made parallel with and at about an inch distant from the fibula. The integument, superficial and deep fascia, being drawn aside, the soleus and intermuscular fascia must be divided to the same extent. The flexor longus pollicis is then to be separated from the fibula, and drawn outwards. Beneath this muscle, by the side of the fibula, will be found the artery. It has no accompany- ing nerve. 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 with the external malleolar and tarsal artery. The posterior peroneal continues onwards along the posterior aspect of the outer malleolus to the side of the os calcis, to which, and to the muscles arising from it, it distributes external calcanean branches. It anastomoses with the anterior peroneal, tarsal, external plantar, and posterior tibial artery with the latter by means of a small transverse branch. The nutritious artery of the tibia arises from the trunk of the tibial, frequently above the origin of the peroneal, and proceeds to the nutritious canal, which it traverses obliquely from below upwards. The muscular branches of the posterior tibial artery are distri- buted to the soleus and deep muscles on the posterior aspect of the leg. One branch is deserving of notice, a recurrent branch, which arises from the posterior tibial above the origin of the peroneal artery, pierces the soleus, and is distributed upon the inner side of the head of the tibia, anastomosing with the inferior internal articular. The internal calcanean branches, three or four in number, pro- ceed from the posterior tibial artery immediately before its divi- sion ; they are distributed to the inner side of the os calcis, to the integument, and to the muscles which arise from its inner tuberosity, and anastomose with the external calcanean branches of the posterior peroneal, and with all the neighboring arteries. The POSTERIOR TIBIAL VEINS receive the veins which accom- pany the numerous branches of the posterior tibial and peroneal arteries, and terminate in the popliteal vein. The POSTERIOR TIBIAL NERVE is continued along the posterior aspect of the leg from the lower border of the popliteus muscle to the posterior part of the inner ankle, where it divides into the internal and external plantar nerve. In the upper part of its course it lies to the inner side of the posterior tibial artery ; it then becomes placed to its outer side ; in the lower third of the leg it lies parallel with the inner border of the tendo Achillis. The branches of the posterior tibial nerve are muscular twigs to the deep muscles of the posterior aspect of the leg ; the branch SOLE OF THE FOOT. 445 to the flexor longns pollicis accompanies the fibular artery; one or two filaments which entwine around the artery and then termi- nate in the integument ; and a plantar cutaneous branch which is distributed to the integument of the heel, and inner border of the sole of the foot. SOLE OF THE FOOT. Dissection. The sole of the foot is to be dissected by carrying a longi- tudinal incision along the middle of the foot from the heel to the base of the toes, and crossing it in the latter situation by a transverse incision. The integument is next to be dissected off the superficial fascia, so as to fog. 136. Fig. 137. THE FIRST LAYER OP MUSCLES IN THE SOLE OF THE FOOT ; THIS LAYER IS EXPOSED BY THE REMOVAL OF THE PLANTAR FASCIA. 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 bifurcation of the tendons of the flexor brevis digitorum. 38 THE THIRD AND A PART OF THK SECOND LAYER OF MUSCLES OF THE SOLE OF THE FOOT. 1. The divided edge of the plantar fascia. 2. The musculus accessorius. 3. The tendon of the flexor longus digitorum, pre- viously 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 dorsal. 10. A convex ridge formed by the tendon of the peroneus longus muscle in its oblique course across the foot. 446 THE DISSECTOR. make an inner and an outer flap. Each of the toes is then to be treated in a similar manner, being laid open by a longitudinal incision. The SUPERFICIAL FASCIA is closely adherent to the integument, and must be raised in the same manner, turning the flaps to either side. In so doing, the cutaneous nerve of the sole of the foot is to be sought for near the heel ; and near the front of the foot, the digital arteries and nerves to the outer sides of the great and little toes. When turned up and examined on its under surface, the superficial fascia 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 strong aponenrotic structure stretched between the under surface of the tuberosities of the calcaneum and the heads of the metatarsal bones. It thus serves a double purpose, being mainly instrumental in preserving the convexity of the arch of the foot, while it protects from injurious 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 occupies the middle of the sole, and terminates towards the toes in five slips, which are held firmly together by transverse bands of fibres passing between and interlacing them. Each of the slips embraces the base of the corresponding toe, and is attached in the middle to the sheath of the flexor tendons, and at either side to the head of the meta- tarsal bone. Between the slips at their base, the transverse bands of fibres already described form a kind of arch of protection to the digital vessels and nerves. The lateral portions of the plantar fascia cover in the muscles of the borders of the foot ; the inner portion being continuous with the fascia of the dorsum of the foot, and the outer one attached to the os calcis and base of the metatarsal bone of the little toe. Between these latter points the fascia forms a thick band, which gives origin to a part of the abductor minimi digiti muscle. At the junction of the middle with the lateral portions of the fascia lata, two septa are sent inwards, which separate the three superficial muscles, and form a complete sheath for the middle muscle, the flexor brevis digitorum. 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 latter dissection cannot, however, be effected without dividing many of the muscular fibres of the flexor brevis digitorum, which arise from the surface of the fascia. When the fascia is removed the lateral septa may be seen, together with two digital nerves which perforate the septa, and the tendon of the flexor longus pollicis. SOLE OP THE FOOT. 447 The MUSCLES of the sole of the foot may be arranged in four layers: First Layer. Abductor poll ids, Flexor brevis digitorum. Abductor minimi digiti, Second Layer. Tendon of the flexor longus pollicis, Accessorins, Tendons of the flexor longus digitorum, Luinbricales. Third Layer. Flexor brevis pollicis, Flexor brevis minimi digiti, Adductor pollicis, 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 tuberosity of the os calcis, the other from the internal annular ligament and plantar fascia. Insertion, into the base of the first phalanx of the great toe, and internal sesamoid bone. The ABDUCTOR MINIMI DIGITI lies along the outer border of the sole of the foot. It arises from the outer tuberosity of the os calcis, and from the plantar fascia, as far forward as 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 (pcrforatus) is placed between the two preceding muscles. It arises from the under surface of the os calcis, plantar fascia, and intermuscular septa, 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 l> ^section. These muscles are to be divided posteriorly from their origin, 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. 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 under surface of the os calcis ; the inner slip being fleshy, the outer tendinous and blended with the ligamentum longum plantai. It is inserted into the outer side and upper surface of the tendon of the flexor longus digitorum. The LUMBRICALES (lumbricus, an earthworm) are four little muscles arising from the tendons of the flexor longus digitorum 448 THE DISSECTOR. at their point of bifurcation, and inserted into the expansion of the extensor tendons, and into the base of the first phalanx of the four lesser toes on their tibial side. The innermost lumbri- calis is connected with only one tendon. Dissection. To expose the third layer of muscle without disturbing the vessels, cut the tendons of the long flexors across through the inser- tion of the accessorius, draw that muscle with the tendons 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 in- ternal plantar nerve will run considerable risk, unless the student be careful. The FLEXOR BREVIS POLLICIS arises by a pointed tendinous process from the side of the cuboid, the external cuneiform bone, and the expanded tendon of the tibialisposticus; itisinsertedbj two heads into the base of the first phalanx of the great toe, the inner head being conjoined with the insertion of the adductor pollicis, the outer head with the adductor pollicis and transversus pedis. Two 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 peroneus longus, and from the base of the third and fourth metatarsal bones. It is inserted into the base of the first phalanx of the great toe, in conjunction with the outer head of the flexor brevis pollicis. The FLEXOR BREVIS MINIMI DIGITI arises from the base of the metatarsal bone of the little toe, and from the sheath of the ten- don of the peroneus longus. It is inserted into the base of the first phalanx of the little toe, on its outer side. The TRANSVERSUS PEDIS arises by fleshy slips from the heads of the metatarsal bones of the four lesser toes. Its tendon is in- serted into the base of the first phalanx of the great toe, being blended with that of the adductor pollicis. The plantar interossei muscles (page 450), must be left until the arte- ries 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 451). The ARTERIES of the sole of the foot are the internal and ex- ternal plantar, the terminal branches of the posterior tibial artery at the inner malleolus. Their distribution maybe thus expressed in a tabular form : internal plantar f milscular articular Posterior tibial externalplantar posterior perforating. NERVES OP SOLE OP FOOT. 449 Fig. 138. The INTERNAL PLANTAR ARTERY passes along the inner border of the foot beneath the abductor pollicis, and distributes branches to the inner border of the foot and great toe. The EXTERNAL PLANTAR ARTERY, much larger than the inter- nal, passes obliquely outwards between the first and second layers of the plantar muscles, to the fifth metatarsal space. It then turns horizontally inwards between the second and third layers, to the first metatarsal space, where it inosculates with the dorsalis pedis. The horizontal portion of the artery describes a slight curve, having the convexity forwards ; this is the plantar arch. The muscular and articular branches of the external plantar artery are distributed to the muscles in the sole of the foot and to the articulations of the tarsus. The digital branches are four in number ; the first is distri- buted to the outer side of the little toe ; the three others pass forwards to the cleft between the toes, and divide into collateral branches, which supply the adjacent sides of the three ex- ternal tos, and the outer side of the second. At the bifurcation of the toes, a small branch is sent upwards from each digital artery, to inosculate with the interosseous branches of the metatarsea ; these are the anterior perforating arteries. The posterior perforating are three small branches which pass upwards be- tween the heads of the three external dorsal interossei muscles, to inosculate with the arch formed by the metatarsea artery. The NERVES of the sole of the foot are, like the arteries, the internal and external plantar (Fig. 132, 12 ), terminal branches of the posterior tibiaf. The INTERNAL PLANTAR NERVE, larger than the external, crosses the posterior tibial vessels to enter the sole of the foot, and becomes placed between the THE ARTERIES OP THE SOLE OF THE FOOT ; THE FIRST AND A PART OF THE SECOND LAYER OF MUSCLES HAVING BEEN REMOVED. 1. The under and posterior part of the os calcis ; to which the origins of the first layer of muscles remain attached. 2. The rausculus accessorius. 3. The long flexor tendons. 4. The tendon of the peroneus longus. 5. The termination of the posterior tihial artery. 6. The internal plantar. 7. The external plantar artery. 8. The plantar arch giving off four digital branches, which pass forwards on the interossei muscles to divide into collateral branches. 38* 450 THE DISSECTOR. abductor pollicis and flexor brevis digitorum ; it then enters the sheath of the latter muscle, and divides opposite the bases of the metatarsal bones into three digital branches; one to supply the adjacent sides of the great and second toe ; the second the adjacent sides of the second and third toe ; and the third the corresponding sides of the third and fourth toe. This distribution is precisely similar to that of the digital branches of the median nerve. In its course the internal plantar nerve gives off cutaneous branches to the integument of the inner side and sole of the foot ; muscular branches ; a digital branch to the inner border of the great toe ; and articular branches to the articulations of the tarsal and metatarsal bones. The EXTERNAL PLANTAR NERVE, the smaller of the two, follows the course of the external plantar artery to the outer border of the musculus accessorius, beneath which it sends several deep branches to supply the adductor pollicis, interossei, transversus pedis and the articulations of the tarsal and metatarsal bones. It then gives branches to the integument of the outer border and sole of the foot, and sends forward two digital branches to supply the little toe and half the next. When the arteries and nerves have been examined, the transversus pedis and other muscles may be removed which impede the view of the plantar interossei. They are covered in by a thin aponeurotic fascia which is attached in front to a ligamentous band passing between the heads of the metatarsal bones, the transverse ligament. This ligament as well as the fascia must be divided in order to bring the full extent of the interossei into view. The PLANTAR INTEROSSEI muscles are three in number, and are placed upon rather than between the metatarsal bones. They arise from the base of the 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 adductors. When the anatomy of the muscles, vessels, and nerves of the sole of the foot is completed, and the student is preparing to study the ligaments, he should lay open the groove in the cuboid bone by dividing the liga- mentous sheath in which 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 ten- don which lies in contact with the cuboid, he will find a sesamoid bone. In some instances the deposit of bone has not taken place, and the thick- ening of the tendon is merely fibro-cartilaginous. The insertion of the tendon of the tibialis posticus may also be examined at the same time with advantage. MUSCLES OF THE LOWER EXTREMITY. 451 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 move- ments 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 compound organ made up of a number of parts, each part performing 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 two latter actions being very imperfect. The muscles performing these movements are the following : Flexion. Extension. Tibialis anticus, Tibialis posticus, Peroueus tertius. Peroneus longus, brevis, and where forcible action is required, as in walking, Gastrocnemius, Plantaris, Soleus. 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. 452 THE DISSECTOR. Adduction. Abduction. dorsal - 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 mus- cles 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 lumbricales, 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 transversely in the foot across the heads of the metatarsal bones, which has for its office the drawing together of the toes. CHAPTER IX. PELVIS AND ORGANS OF GENERATION. THE cavity of the pelvis is that portion of the great abdominal cavity which is included within the bones of the pelvis below the level of the linea ilio-pectinea and the promontory of the sacrum. It is bounded by the cavity of the abdomen above, and by the perineum below. Its internal parietes are formed in front, below, and at the sides, by the peritoneum, pelvic fascia, levatores ani and obturator muscles ; and behind by the coccygei muscles, sacro-ischiatic ligaments, pyriformis muscle, sacral plexus of nerves, sacrum, and coccyx. The VISCERA of the pelvis in the male, are the urinary bladder, vesiculae seminales, prostate gland, and rectum ; and in the female, the urinary bladder, uterus, vagina, and rectum. Yiewed from above, the urinary bladder will be seen to form a convexity, pointed in the male, more obtuse in the female, behind the ossa pubis ; the rectum, flexuous in its course, rests against the sacrum. In the male, the bladder and rectum are in contact ; THE PELVIS. 453 in the female, the uterus is interposed, and with its broad liga- ments stretching out on each side forms a transverse septum, which divides the cavity of the pelvis into an anterior and a posterior part. The peritoneum invests the pelvic viscera only partially ; thus Fig. 139. A SIDE VIEW OF THE VISCERA OF THE MALE PELVIS IN SITU. THE RIGHT SIDE OF THE PELVIS HAS BEEN REMOVED BY A VERTICAL SECTION MADE THHOUGH THE OS PUBIS, NEAR TO THE SYMPHYSIS .' 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 mem- branous 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 fascia, just aa it is making its bend backwards to constitute the third portion. 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. it forms a complete covering for the upper portion of the rectum, and connects it by a duplicature (mesorectum) to the surface of the sacrum ; lower down it covers only the anterior surface of the rectum, and is reflected from it upon the posterior surface 454 THE DISSECTOR. of the bladder. The fold or pouch, formed between the rectum and the bladder, is the recto-vesical. In the female, the pouch intervenes between the rectum and the vagina, and is the recto- vaginal; and a second pouch is formed between the uterus and bladder, the utero-vesical fold. From the sides of the bladder the peritoneum ascends upon the walls of the pelvis, and its re- flection from the sides of the organ to the pelvis have been named false ligaments of the bladder. The PELVIC FASCIA is an aponeurotic layer situated beneath the peritoneum, forming a covering to the walls of the pelvis, and reflected from its walls upon the viscera. The pelvic fascia is attached to the internal surface of the ossa pubis near the symphysis, to the body of the pubes above the origin of the ob- turator internus muscle, to the ilio-pectineal line of the brim of the pelvis as far back as the sacro-iliac articulation, and to the margin of the great sacro-ischiatic foramen. Having descended upon the wall of the pelvis as low as the pubic arch in front, and the spine of the ischium behind, it divides, in the direction of a line drawn between those points, into two layers, internal and external. The internal layer (recto-vesical), is continued downwards to the prostate gland, neck of the bladder (vagina), and rectum, to which it is closely attached; and is reflected for a short distance upwards and downwards on these viscera. This layer is in contact, by its external surface, with the levator ani muscle and coccygeus; and is prolonged backwards over the sacral nerves to the lower part of the sacrum and the coccyx, to which it is attached, meeting on the middle line the layer of the opposite side. The external layer is the obturator fascia, it covers in the obturator muscle, and is attached to the ramus of the pubes and ischium in front, and to the tuberosity of the ischium and falciform border of the great sacro-ischiatic liga- ment below. The levator ani arises from the line of division of the two preceding layers, and the obturator layer sends off a thin aponeurotic expansion which covers the external surface of that muscle. The obturator fascia, together with this aponeurotic expansion, constitute the ischio-rectal fascia, which lines the ischio-rectal fossa, and is attached in front to the triangular liga- ment of the perineum. The anterior part of the pelvic fascia is separated from its fellow of the opposite side by a narrow interval, and the fascia passing from the side of the symphysis to the upper part of the prostate gland and front of the neck of the bladder, constitutes the anterior true ligament of the bladder (pubio-vesical) ; a little further outwards, the fascia passing to the side of the neck of the bladder, constitutes its lateral true ligament; and reflected forwards from the neck of the bladder upon the prostate, MUSCLES OF THE PELVIS. 455 it forms a sheath for that gland which incloses the prostatic plexus of veins. Upon the rectum and vagina it also forms a sheath. 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 pubes with the saw on the left side, a little external to the symphysis. Then let him cut through the psoas muscle and iliac vessels opposite the sacro-iliac symphysis, and divide the ligaments of that articulation. Next cut away with the scalpel the structures adhering to the inner surface of the pubes and ilium of the same side ; taking care to separate the pelvio fascia from its connections and from the surface of the obturator muscle ; then snip across the spine of the ischium, so as to leave the attachments of the levator ani, coccygeus, and lesser sacro-ischiatic ligament ; and after cutting through the pyriformis muscle, remove the bone altogether. The MUSCLES brought into view by this dissection are the coc- cygeus and levator ani. The COCCYGEUS muscle is a thin triangular muscle. It arises from the spine of the ischium and lesser sacro-ischiatic ligament, and spreads out to be inserted into the side of the coccyx and lower part of the sacrum. The coccygeus rests upon the lesser sacro- ischiatic ligament, and is in relation, by its posterior border, with the pyriforrais ; and by the anterior, with the levator ani. The LEVATOR ANI is a thin muscle, situated between the two layers (recto-vesical and obturator) of the pelvic fascia, and forming, with its fellow of the opposite side, a movable boundary to the outlet of the pelvis. It arises from the inner surface of the os pubis, near the pubic arch, from the base and upper border of the spine of the ischium, and between these points from a tendinous arch, which occupies the line of division of the pelvic fascia. Its fibres descend, to be inserted into its fellow of the opposite side beneath the prostate gland, into the rectum, and behind the rec- tum, into its fellow of the opposite side and the side of the ex- tremity of the coccyx. The anterior and posterior borders of the levator ani are thicker than the rest of the muscle, from the larger extent of origin of the muscular fibres; the anterior border arising in part from the ramus of the pubes, and the posterior from the posterior border of the spine of the ischium. The anterior border of the two muscles is separated by a space which gives passage to the urethra, and in the female, to the vagina. This space is closed within the pelvis by the pelvic fascia and anterior ligaments of the bladder. The anterior portion of the muscle forms a loop beneath the prostate gland with the corresponding portion of the opposite side ; and this portion has been described under the names of levator or compressor prostate. 456 THE DISSECTOR. The ACTION of the coccygeus muscle is to flex the coccyx ; that of the levator ani, to lift the prostate gland, lower part of the anus and coccyx, and thus contract the space of the outlet of the pelvis. The levatores ani are antagonistic of the diaphragm and the rest of the expulsory mus- cles, and serve to support the rectum and vagina during their expulsive efforts. The levator ani acts in unison with the diaphragm, and rises and falls like that muscle in forcible respiration. Yielding to the pro- pulsive action of the abdominal muscles, it enables the outlet of the pelvis to bear a greater force than a resisting structure, and on the remission of such action it restores the perineum to its original form. When the coccygeus and levator ani muscle are removed, the recto- vesical layer of the pelvic fascia may be traced to its attachments to the neck of the bladder and rectum, and over the prostate gland, to which it forms a sheath. The recto-vesical fascia may now be turned down, and the cellular tissue and fat removed from the side of the bladder, recto-vesical pouch of the peritoneum and rectum. The dissection may be facilitated by blowing air into the bladder, and placing a little cotton wool in the recto- vesical pouch of the peritoneum, and also into the rectum ; but care should be taken to avoid over distension of these parts ; it would be better to leave them flaccid than to stretch their coats. In the progress of this dissec- tion the remains of the hypogastric artery should be followed forwards to the abdominal parietes, and the ureter to the side of the bladder ; the vas deferens should also be traced downwards behind the vesicula semi- nalis to the base of the prostate. The RECTUM. The rectum, between seven and eight inches in length, commences at the sacro-iliac symphysis on the left side, and terminates at the anus. It is divided anatomically into three portions, upper, middle, and lower. The upper portion, com- prising half its length, is completely surrounded by the perito- neum, which connects it to the wall of the pelvis by means of the mesorectum. It is in relation with the left internal iliac vessels, ureter, and sacral plexus of nerves. The middle portion, three inches in length, and extending from opposite the middle of the sacrum to the tip of the coccyx, is covered by peritoneum only in front and for two-thirds of its extent. It is in relation behind with the sacrum and coccyx, and in front with the vesiculse semi- nales, the triangular portion of the bladder situated between those organs, and the prostate gland. The lower portion, an inch and a half in length, curves backwards from the prostate gland oppo- site the tip of the coccyx, to the anus. This portion is more or less dilated, and is supported by the levatores ani. URINARY BLADDER. The urinary bladder is a hollow membranous viscus, triangular and flattened against the pubes when empty, ovoid when distended, situated behind the pubes and in front of and upon the rectum. It is larger in its vertical diameter than from side to side, and its long axis is directed from above obliquely downwards and back- wards. URINARY BLADDER. 457 The bladder is divided into body, fundus, base, and neck. The body comprehends the middle zone of the organ ; i\\z fundus (su- perior fundus), its upper segment ; the base (inferior fundus) the lower broad extremity which rests on the rectum ; and the neck, the narrow constricted portion which is applied against the pros- tate gland. It is retained in position by ligaments, which are divisible into true and false. The true ligaments are five in number, two an- terior, two lateral, and the cord of the urachus. The false liga- ments are folds of the peritoneum, and are also five in number, two posterior, two lateral, and one superior. The anterior liga- ments are formed by the recto-vesical fascia in its passage from the inner surface of the pubes on each side of the symphysis to the neck of the bladder and prostate gland. The lateral ligaments are also formed by the recto-vesical fascia in its passage from the levatores ani muscles to the sides of the prostate gland and neck of the bladder. The ligament of the urachus is a fibrous cord resulting from the obliteration of a tubular canal (urachus) existing in the embryo. Fig. 140. THE PELVIC VISCERA OP 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 glnnd, with a portion of the levator ani covering its fore part. 4. Urinary bladder. 5. Intestinum rectum. 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'. Vesiculn seminalis. 9. Ureter. The cut edge of the peritoneum is seen jagged over the bladder and the rectum. 39 458 THE DISSECTOR. It proceeds from the summit of the bladder, and ascends along the linea alba to the umbilicus. The posterior false ligaments are the fold of peritoneum formed on each side of the pelvis by the obliterated hypogastric artery ; this fold also contains the ureter and the vessels and nerves of the bladder. The lateral false ligaments are formed by the passage of the peritoneum, from the side of the pelvis to the side of the bladder. The obliterated hypogastric artery lies along the line of reflection of the membrane. The superior or suspensory false ligament is the fold of peri- toneum caused by the prominence of the cord of the urachus and the cords of the obliterated hypogastric arteries. The bladder is composed of four coats serous, muscular, cel- lular, and mucous. The serous coat is partial and derived from the peritoneum, which invests the posterior surface and sides of the bladder from about oppo- site the point of termination of the ureters to its summit, whence it is guided to the anterior wall of the abdomen by the hypogastric cords and urachus. The muscular coat consists of two layers : an external layer composed of longitudinal fibres, the detrusor urinae ; and an internal layer of ob- lique and circular fibres irregularly distributed. The longitudinal fibres arise from the anterior ligaments of the bladder (tendons of the detrusor urinse), the neck of that organ, and the base of the prostate gland, and spread out as they ascend to the fundus ; here a small fasciculus follows the course of the urachus, but the greater number converge upon the posterior surface of the organ and descend to its neck, where they are inserted into the isthmus of the prostate gland, and into a ring of mus- cular tissue, which surrounds the commencement of the prostatic portion of the urethra. In the female they are inserted into the vagina. The lateral fibres commence at the prostate gland and muscular ring of the urethra on one side, and spread out as they ascend upon the side of the bladder, to descend upon the opposite side, and be inserted into the pros- tate and opposite segment of the same ring. Two bands of oblique fibres are described by Sir Charles Bell, as originating at the termina- tions of the ureters, and converging to the neck of the bladder ; the ex- istence of these muscles is not well established. The fibres corresponding with the trigonum vesicae are transverse. Mr. Guthrie 1 observes that there are no fibres at the neck of the blad- der capable of forming a sphincter vesicae ; but Mr. Lane 2 has described a fasciculus of muscular fibres which surround the commencement of the urethra, and perform such an office. These fibres form a narrow bundle above the urethra, but spread out below, behind the prostate gland : they are brought into view by dissecting off the mucous membrane from around the orifice of the urethra. Sir Astley Cooper has described around the urethra, within the pros- 1 " On the Anatomy and Diseases of the Neck of the Bladder and of the Urethra." * Lancet, vol. i., 1842-3, p. 670. URINARY BLADDER. 459 tate gland, a ring of elastic tissue, or, rather, according to Mr. Lane, of muscular fibres, which has for its object the closure of the urethra against the involuntary passage of the urine. It is into this ring that the longi- tudinal fibres of the detrusor urinae are inserted, so that the muscle, taking a fixed point at the pubes, will not only compress the bladder, and thereby tend to force its contents along the urethra, but will at the same time, by means of its attachment to the ring, dilate the en- trance of the urethra, and afford a free egress to the contents of the bladder. The cellular, or submucous coat, is the thick layer of cellular tissue, which is interposed between the mucous and muscular coat, and forms the bond of union between them. The mucous coat is thin and smooth, of a pale rose color, and exactly moulded on the muscular coat, to which it is connected by the cellular coat ; its papillae are very minute, and there are a number of mucous follicles, especially near the neck of the organ. This mucous membrane is continuous, through the ureters, with the lining membrane of the uri- niferous ducts, and through the urethra, with that of the prostatic ducts, tubuli seminiferi, and Cowper's glands. The cells of the epithelium are of the spheroidal kind. Upon the internal surface of the base of the bladder is a tri- angular smooth plane, of a paler color than the rest of the mucous membrane, the trigonnm vesic, or trigone vesicate. This is the most sensitive part of the bladder, and the pressure of calculi upon it gives rise to great suffering. It is bounded on each side by the raised ridge, corresponding with the muscles of the ureters, at each posterior angle by the openings of the ureters, and in front by a slight elevation of the mucous membrane at the entrance of the urethra, called uvula vesicce. The external surface of the base of the bladder corresponding with the trigonura, is also triangular, and is separated from the rectum by a thin layer of fibrous membrane, derived from the recto-vesical fascia. It is bounded behind by the recto-vesical fold of peritoneum; and on each side by the vas deferens and vesicula seminalis, which converge almost to a point at the base of the prostate gland. It is through this space that the open- ing is made in the recto-vesical operation for puncture of the bladder. The arteries of the urinary bladder are the superior vesical, three or four small branches which proceed from the commencement of the hypo- gastric artery, previously to its complete obliteration ; and the inferior vesical, from the internal iliac. The latter is distributed to the base of the bladder, vesiculae seminales, and prostate gland. The veins are numerous and of large size, and form a plexus around the neck and at the base of the bladder; the plexus communicates with the prostatic plexus and with the hemorrhoidal veins. The nerves of the bladder are derived from the inferior hypogastric plexuses and their communications with the third and fourth sacral nerves. 460 THE DISSECTOR. PROSTATE GLAND. The prostate gland (rtpoietwt, pneponere) is situated in front of the neck of the bladder, behind the triangular ligament and pelvic fascia, and upon the rectum, through which latter it may be felt with the finger. It surrounds the commencement of the urethra for somewhat more than an inch of its extent, and resembles a Spanish chestnut both in size and form ; the base being directed backwards towards the neck of the bladder, the apex forwards, and the convex side towards the rectum. It is retained firmly in position by the anterior and lateral ligaments of the bladder, and by a process of the recto-vesical fascia, which forms a sheath around it. It consists of three lobes, two lateral and a middle lobe or isthmus ; the lateral lobes are distinguished by an indentation on the base of the gland, and a slight furrow on its upper and lower surface. The third lobe, or isthmus, is a small transverse band which passes between the two lateral lobes at the base of the organ. In structure, the prostate gland is composed of ramified ducts, termi- nating in lobules of follicular pouches, which are so closely compressed as to give to a thin section of the gland a cellular appearance. It is pale in color and hard in texture, splits easily in the course of its ducts, and is surrounded by a proper fibrous covering, and by a plexus of veins which are inclosed by the sheath derived from the recto-vesical fascia. Its secretion is poured into the prostatic portion of the urethra by fifteen or twenty excretory ducts. The ducts of the lateral lobes open into the urethra on each side of the veru montanum ; those of the third lobe open upon and behind the veru. The urethra, in passing through the prostate, lies one-third nearer its upper, than its lower surface. The arteries of the prostate gland are small, and derived from the infe- rior vesical and middle hemorrhoidal. The veins form a plexus around the gland, which receives from the front the veins of the penis, and termi- nates in the vesical plexus. VESICTIL^E SEMINALES. On the under surface of the base of the bladder, and converging towards the base of the prostate gland, are two tabulated and somewhat pyriform bodies, about two inches in length, the vesi- culse seminales. Their upper surface is in contact with the base of the bladder ; the under side rests on the rectum, separated only by a process derived from the recto-vesical fascia ; the larger extremities are directed backwards and outwards, and the smaller ends almost meet at the base of the prostate. They inclose between them a triangular space, which is bounded posteriorly by the recto-vesical fold of peritoneum, and corresponds with the trigonum vesicae on the interior of the bladder. Each vesicula is formed by the convolutions of a single tube, which gives off seve- ral irregular csecal branches. It is inclosed in a fibrous mem- INTERNAL ILIAC ARTERY. 461 brane, derived from the recto-vesical fascia, and is constricted beneath the isthmus of the prostate gland into a small excretory duct. The vas deferens, somewhat enlarged and sacculated, lies along the inner border of each vesicula, and is included in its fibrous investment. It communicates with the duct of the vesi- cula, beneath the isthmus of the prostate, and forms the ejacula- tory duct. The ejaculatory duct is about three-quarters of an inch in length, and running forwards, first between the base of the pros- tate and the isthmus, and then through the tissue of the veru montanum, opens on the mucous membrane of the urethra, by the side of, or within the aperture of the sinus pocularis. In structure, the vesiculae seminales are composed of three coats : exter- nal, which is cellular ; middle, fibrous and contractile ; and internal or mucous, a thin mucous membrane, presenting a delicate reticular mark- ing, like that of the gall-bladder, and invested by a squamous epithe- lium. The bladder and rectum may now be turned down, and the peritoneum removed from the right wall of the pelvis. This will bring into view the pelvic fascia and its recto-vesical layer, which may be examined from the inside. In the next place the internal iliac artery should be sought for in the posterior false ligament of the bladder, and the cellular tissue and fat which conceal it and its branches removed. The ARTERIES of the pelvis are the internal iliac and its branches ; the superior hemorrhoidal, from the inferior mesenteric ; and the arteria sacra media, from the aorta. The INTERNAL ILIAC ARTERY is a short trunk between one and two inches in length. It proceeds from the common iliac artery, opposite the sacro-iliac symphysis, and passes obliquely down- wards and forwards, to a level with the upper border of the sacro-ischiatic foramen, where it separates into an anterior and posterior division. From the extremity of the artery, a fibrous cord is continued onwards by the side of the bladder to near its summit, and thence onwards by the side of the linea alba to the umbilicus : this is the remains of the hypogastric artery of the foetus. In the foetus the internal iliac artery, under the name of hypo- gastric, takes the course just indicated, and becomes the umbilical artery. After birth, the artery ceases to be pervious beyond the side of the bladder, where it gives off the superior vesical arteries. The internal iliac artery is in relation in front with the ureter ; behind, with the internal iliac vein ; and towards the wall of the pelvis, with the sacral plexus and pyriformis. The branches of the internal iliac are, from the apterior trunk, the 462 THE DISSECTOR. Superior vesical, Yaginal, Inferior vesical, Obturator, Middle hemorrhoidal, Ischiatic, Uterine, Internal pudic ; from the posterior trunk, the Ilio-lumbar, Lateral sacral, Gluteal. The superior vesical arteries are three or four small branches, which proceed from the pervious portion of the hypogastric cord. They are distributed to the upper and middle part of the bladder. From one of these there passes off a small artery, the deferential, which accompanies the vas deferens along the spermatic cord. The inferior vesical, somewhat larger than the preceding, passes down upon the side of the bladder to its base, and is distributed to that region, the vesiculse seminales, and prostate gland. Fig. 141, LONGITUDINAL SECTION OF THE PELVIS, SHOWING ITS CAVITY AND THE INTERNAL ILIAC ARTERY. a. The iliacus interims muscle, crossed by the external cutaneous nerve, b. The psoas muscle, and genito-crural nerve, c. The in- ferior vena cava. d. The aorta. e. The right common iliac artery. /. The left common iliac artery and vein. g. The external iliac artery and vein. h. The circum- flexa ilii artery inosculating with i, the ilio-lumbar artery, k. The epigastric artery. I. The obtura- tor internus muscle, in. The le- vator ani. n. Part of the prostate gland supported by the levatorani. o. The membranous part of the urethra, p. The bulb. q. The corpus cavernosum penis, r, r. The sphincter ani. s. The lower extremity of the rectum, t. The coccygeus muscle. v, v. The pyriformis muscle, crossed by the sacral nerves. w. The arteria sacra media, x. The internal iliac artery, y. Its anterior trunk ; the artery above the letter is the un- obliterated portion of the hypo- gastric artery, which gives off the superior vesical arteries, and be* comes converted into a fibrous cord, z. The artery below y, is the obturator, and the nerve above it the obturator nerve. A little further on the nerve and artery are seen passing through the obturator foramen. 1. The inferior vesical artery, giving off the middle hemorrhoidal. 2. The anterior trunk, dividing into internal pudic and ischiatic. 3. The ilio-lumbar artery. 4. The lateral sacral artery, sending branches into the anterior sacral foramina. 5. The glu- teal artery. 6, 6. The sacrum. 7. The coccyx. 8. The symphysis pubis. 9, The suspensory ligament of the penia. INTERNAL PUDIC ARTERY. 463 The middle hemorrhoidal artery, frequently a branch of the preceding, passes downwards to the rectum, to which it is distri- buted, inosculating with the superior and inferior hemorrhoidal arteries. In the female, it distributes branches to the vagina. The uterine artery passes downwards between the layers of the broad ligament, to the neck of the uterus, and then ascends in a tortuous course along its lateral border, between the layers of the broad ligament. It gives off branches to the vagina, the lower part of the bladder, the Fallopian tube, and round ligament, and inosculates with the spermatic or ovarian artery. The vaginal artery corresponds in position with the inferior vesical, and is distributed to the vagina and neighboring parts of the bladder and rectum. The OBTURATOR ARTERY, sometimes a branch of the posterior division, passes forwards below the brim of the pelvis to the upper part of the obturator foramen, through which it escapes into the thigh. Its branches within the pelvis are : an iliac branch, which sup- plies the bone of the iliac fossa, and inosculates with the ilio- lumbar artery ; and a pubic branch which is given off close to the obturator foramen, and inosculates with its fellow of the opposite side, behind the pubes, and with the pubic branch of the epigas- tric artery. The ISCHIATIC ARTERY is the larger of the two terminal branches of the anterior division of the internal iliac. It passes down- wards in front of the pyriformis and sacral plexus of nerves, and internally to the pudic artery, to the lower part of the great ischiatic foramen, where it escapes from the pelvis between the lower border of the pyriformis and the coccygeus, to both of which it distributes branches. The INTERNAL PUDIC ARTERY, the other terminal branch of the anterior division of the internal iliac, descends externally to the ischiatic artery to the lower part of the great ischiatic foramen, and passes through the foramen between the lower border of the pyriformis and coccygeus. It then crosses the spine of the ischium, and re-enters the pelvis through the lesser ischiatic foramen. In the next place it passes forward upon the obturator fascia, and above the tuberosity of the ischium, to the perineum, to which it is distributed. The branches of the internal pndic artery within the pelvis are several small twigs to the levator ani and sacral nerves, and occa- sionally a branch which takes the place of the inferior vesical or middle hemorrhoidal artery. POSTERIOR DIVISION. The ILIO-LUMBAR ARTERY ascends be- neath the external iliac vessels and psoas muscle, to the posterior part of the crest of the ilium, where it divides into two branches: 464 THE DISSECTOR. a lumbar branch, which supplies the psoas and quadratns lumbo- rum muscles, and sends a ramuscule through the fifth interverte- 142. 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 artery. 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 inter- nal 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 anterior 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 lateral sacral. 19. The gluteal artery escaping from the pelvis through the upper part of the great sacro-ischiatic foramen. 20. The sacra- media. 21. The right common iliac artery cut short. 22. The femoral artery. bral foramen to the spinal cord and its membranes ; and an iliac branch, which passes across the iliac fossa to the crest of the ilium, where it inosculates with the lumbar and circumflexa ilii arteries. In its course it distributes branches to the iliacus and abdominal muscles. The LATERAL SACRAL ARTERIES are generally two in number on each side, superior and inferior. The superior passes inwards to the first sacral foramen, and is distributed to the contents of the spinal canal, from which it escapes by the posterior sacral foramen, and supplies the integument on the dorsum of the sacrum. The inferior passes down by the side of the anterior sacral foramina to the coccyx ; it first pierces and then rests upon the origin of the pyriformis, and sends branches into the sacral canal, to supply the sacral nerves. Both arteries inosculate with each other and with the sacra media. INTERNAL ILIAC VEIN. 465 The GLUTEAL ARTERY is the continuation of the posterior trunk of the internal iliac : it passes backwards between the lumbo- sacral and first sacral nerve through the upper part of the great sacro-ischiatic foramen and above the pyriformis muscle. While within the pelvis it gives off some muscular twigs to the iliacus and pyriformis muscle ; and at its escape from the pelvis, a nutri- tious artery to the ilium. The superior hemorrhoidal artery is the continuation of the inferior mesenteric artery into the pelvis ; it divides in the meso- rectum into two branches, which are distributed on each side of the rectum as far as its lower part, and inosculates with the middle and inferior hemorrhoidal arteries. The arteria sacra media descends along the middle of the sacrum from the bifurcation of the aorta. It gives off lateral b ranches, which inosculate with the lateral sacral arteries, and terminates on the coccyx. The VEINS of the pelvis unite to form the internal iliac vein. The INTERNAL ILIAC VEIN receives the returning blood by the gluteal, ischiatic, internal pudic, and obturator veins from the exterior of the pelvis, and by the vesical and uterine plexuses from within. It lies at first to the inner side and then behind the internal iliac artery, and terminates by uniting with the ex- ternal iliac vein, to form the common iliac vein. The vesical and prostatic plexus surrounds the neck and base of the bladder, the prostate gland, and membranous portion of the urethra. It receives the veins from the external organs of generation, the dorsal vein of the penis, after piercing the trian- gular ligament, dividing into two branches before joining it. The plexus is surrounded by the sheath of pelvic fascia which incloses the prostate gland, and spreads over the base of the bladder. The internal pudic vein, besides the branches which accompany the internal pudic artery, receives a hemorrhoidal vein from a plexus which surrounds the lower part of the rectum, the hemor- rlioiilal plexus. The uterine and vaginal plexus is situated around the vagina and upon the sides of the uterus ; above, it is in communication with the ovarian plexus. The ilio-lumbar and lateral sacral veins terminate in the com- mon iliac vein ; and the middle sacral vein, in the left common iliac vein. The LYMPHATIC VESSELS of the pelvis are those proceeding from the deeper structures of the external organs of generation, the walls and viscera of the pelvis. They terminate in a chain of alands, situated in the course of the iliac vessels^ and the efferent ducts of the latter unite with the lumbar glands. The NERVES of the pelvis are the five sacral and coccygeal nerve 466 THE DISSECTOR. derived from the spinal cord, the hypogastric plexus, and the trunk of the sympathetic. The SACRAL NERVES are five in number on each side ; the an- terior divisions of the four upper nerves issue from the sacrum through the anterior sacral foramina, the fifth escapes between the sacrum and coccyx, and pierces the coccygeus muscle. The two upper nerves are of large size ; the third is scarcely one-fourth as large as the second ; the fourth is much smaller than the third ; and the fifth than the fourth. The first three nerves, with a part of the fourth and the lumbo-sacral nerve, unite to form the sacral plexus. The fourth sacral nerve divides into two branches, one of which assists in forming the sacral plexus, the other separates into three branches : a communicating branch, to unite with the fifth sacral nerve ; a visceral branch, to join with the hypogastric plexus and supply the bladder and prostate gland, and in the female, the vagina ; and a muscular branch which sends filaments to the le- vator ani and coccygeus and an hemorrhoidal branch to the sphincter ani and integument behind the anus. The fifth sacral nerve, issuing from between the sacrum and coccyx, pierces the coccygeus muscle, and receives the communi- cating branch from the fourth ; it then communicates with the coccygeal nerve, and piercing the coccygeus a second time, is distributed to the integument over the dorsal surface of the coccyx. The coccygeal nerve pierces the coccygeus muscle, and unites with the fifth sacral nerve, in which it is lost. Each of the anterior divisions of the sacral nerves receives a filament from the sympathetic at its point of escape from the sacral canal. SACRAL PLEXUS. The sacral plexus is formed by the union of the lumbo-sacral, the three upper sacral nerves, and one half the fourth. It is triangular in form, its base corresponding with the whole length of the sacrum, and its apex with the lower part of the great sacro-ischiatic foramen. It rests on the pyriformis muscle, and is crossed by the branches of the internal iliac vessels. The branches of the sacral plexus are chiefly destined for the supply of the lower limb, and are given off externally to the pel- vis ; those which proceed from the plexus within the pelvis, are some muscular branches to the pyriformis, and obturator internus, the superior gluteal nerve, and pudic. The branches to the pyriformis muscle are commonly two in number ; the branch to the obturator internus passes out of the pelvis through the great sacro-ischiatic foramen, with the internal pudic vessels an$ nerve crosses the spine of the ischium, and re- enters the pelvis through the lesser sacro-ischiatic foramen, to be distributed to the muscle. HYPOGASTRIO PLEXUS. 46f The SUPERIOR GLUTEAL NERVE arises from the lumbo-sacral nerve, near its junction with the first sacral nerve, and passes out of the pelvis through the upper part of the great sacro-rschiatic foramen, above the pyriformis muscle. It is distributed to the gluteal muscles. The PUDIC NERVE arises from the lower part of the sacral plexus, and passes out of the pelvis through the great sacro- ischiatic foramen, below the pyriformis muscle. It crosses the spine of the ischium, and re-entering the pelvis through the lesser sacro-ischiatic foramen, accompanies the internal pudic artery along the outer wall of the ischio-rectal fossa to the perineum. In its course along the ischio-rectal fossa, it lies below the artery, and divides into two branches, perineal and dorsal artery of the penis. Near its origin the pudic nerve gives off the inferior hemor- rhoidal nerve, which passes through the lesser sacro-ischiatic foramen, and crosses the ischio-rectal fossa with one of the infe- rior hemorrhoidal arteries, to be distributed to the sphincter ani- and integument around the anus. This nerve sometimes proceeds directly from the sacral plexus. SYMPATHETIC NERVE. The sympathetic nerve within the pelvis consists of the trunk of the nerve, and the pre-vertebral portion. The trunk of the nerve presents four or five small fusiform ganglia, situated on the sacrum close to the anterior sacral fora- mina; the uppermost ganglion communicates with the last of the lumbar ganglia; the lowest ganglion of each side communicates with a small ganglion situated on the first bone of the coccyx, the ganglion impar, or azygos, which thus becomes the bond of union between the extremities of the two sympathetic nerves. The branches of the sacral ganglia are branches of communi- cation, and branches of distribution. The branches of communication are two from each ganglion, which pass outwards, to communicate with the anterior sacral nerves, and with the coccygeal nerve. The branches of distribution pass inwards upon the front of the sacrum, and follow the course of the branches of the arteria sacra media. Other branches, proceeding from the first and second ganglia, join the hypogastric plexus ; and a third set, issuing from the ganglion impar and its communicating cords, is distributed to the coccyx. HYPOGASTRIC PLEXUS. The pre-vertebral portion of the sympathetic system, within the pelvis, consists of the hypo- gastric plexus and its lateral divisions, the inferior hypogastric plexuses. The hypogastric plexus is the prolongation of the aortic plexus 468 THE DISSECTOR. into the pelvis. It is situated over the front of the sacrum at its upper part, and divides into two lateral portions, the inferior hyp ogastric plexuses, which descend to the sides of the base of the bladder, vagina, and rectum. Each inferior hypogastric plexus receives branches from the third and fourth sacral nerves, and gives off plexuses, which ac- company the branches of the internal iliac artery, and take the names of the respective arteries. The inferior hypogastric plexus supplies the bladder, prostate gland, vesiculse seminales, corpus cavernosum, penis, rectum; and, in the female, the vagina, uterus with its appendages, and ovaries. MALE ORGANS OF GENERATION. The organs of generation in the male are the penis and testes, with their appendages. PENIS. The penis is divisible into a body, root, and extremity. The body is surrounded by a thin integument, which is remark- able for the looseness of its cellular connection with the deeper parts of the organ, and for containing no adipose tissue. The root is broad, and firmly adherent to the rami of the pubes and ischium by means of two strong processes, the crura, and is con- nected to the symphysis pubis by a fibrous membrane, the liga- mentum suspensorium. The extremity, or glans penis, resembles an obtuse cone, some- what compressed from above downwards, and of a deeper red color than the surrounding skin. At its apex is a small vertical slit, the meatus urinarius, which is bounded by two, more or less protuberant labia ; and, extending backwards from the meatus, is a depressed raphe, to which is attached a loose fold of mucous membrane, the fraenum praputii. The base of the glans is marked by a projecting collar, the corona glandis, upon which are seen a number of small papillary elevations, the glandulae Tysoni (odoriferae). Behind the corona is a deep fossa (fossa glandis, cervix), bounded by a circular fold of integument, the pfceputium, which, in the quiescent state of the organ, may be drawn over the glans, but, in its distended state, is obliterated, and serves to facilitate its enlargement. The internal surface of the prepuce is lined by mucous membrane, covered by a thin epithelium ; this membrane is reflected over the glans penis, and, at the meatus urinarius, is continuous with the mucous lining of the urethra. In dissecting the penis, an incision should be made along the middle of the dorsuin of the organ, and the integument turned aside. Then the PENIS. 469 superficial fascia may be dissected back and the ligamentum suspenso- rium and dorsal vessels and nerves brought into view. The superficial fascia is thin, and its cellular structure free from fat ; it is continuous with the superficial fascia of the abdo- men above, and with the dartos and superficial fascia of the peri- neum below. The ligamentum suspensorium penis is a strong fibrous mem- brane of triangular form, attached by its apex to the symphysis pubis ; and by its base, to the body of the penis. Near its attach- ment it separates into two layers, between which the dorsal ves- sels and nerves take their course. The penis is composed of the corpus cavernosum and corpus spongiosum, and contains in its interior the longest portion of the urethra. The corpus cavernosum is distinguished into two lateral por- tions (corpora cavernosa) by an imperfect septum, and by a supe- rior and inferior groove, and is divided posteriorly into two crura. It is firmly adherent, by means of its crura, to the rami of the pubes and ischium ; and each crus, previously to its junction with its fellow, presents a slight enlargement, which has been named by Kobelt the bulb. The corpus cavernosum forms, ante- riorly, a single rounded extremity, which is received into a fossa in the base of the glans ; the superior groove lodges the dorsal vessels of the organ, and the inferior receives the corpus spon- giosum. Its fibrous tunic is thick, elastic, and extremely firm, and sends a number of fibrous bands and cords (trabecula?) in- wards from its inferior groove, which cross its interior in a radiat- ing direction, and are inserted into the inner walls of the tunic. These trabeculas are most abundant on the middle line, where they are ranged vertically, side by side, somewhat like the teeth of a comb, and constitute the imperfect partition of the corpus cavernosum, called septum pectiniforme. The septum is more complete at its posterior than towards its anterior part. The tunic of the corpus cavernosum consists of strong longi- tudinal fibrous fasciculi, closely interwoven with each other. Its internal structure is composed of erectile tissue. The corpus spongiosum is situated along the under surface of the corpus cavernosum, in its inferior groove. It commences by its posterior extremity between and beneath the crura penis, where it forms a considerable enlargement, the bulb, and termi- nates anteriorly by another expansion, the glans penis. Its middle portion, or body, is nearly cylindrical, and tapers gradually from its posterior towards its anterior extremity. The~bulb is adhe- rent to the iriangular ligament by means of a prolongation of that membrane ; in the rest of its extent the corpus spongiosum 40 470 THE DISSECTOR. is attached to the corpus cavernosum by cellular tissue, and by veins which wind around that body to reach the dorsal vein. It is composed of erectile tissue, inclosed by a dense fibrous layer, much thinner than that of the corpus cavernosum, and contains in its interior the spongy portion of the urethra, which lies nearer its upper than its lower wall. The bulb exhibits a tendency to division into two lobes, an appearance which is due to the existence of a thin longitudinal septum in its internal structure. Erectile tissue is a peculiar cellulo-vascular structure, entering in con- siderable proportion into tlie composition of the organs of generation. It consists essentially of a plexus of veins so closely convoluted and inter- woven with each other, as to give rise to a cellular appearance when examined by means of a section. The veins forming this plexus are smaller in the glans penis, corpus spongiosum, and circumference of the corpus cavernosum, than in the central part of the latter, where they are large and dilated. They have no other coat than the internal lining prolonged from the neighboring veins ; and the interstices of the plexus are occupied by a peculiar reddish fibrous tissue. They receive their blood from the capillaries of the arteries in the same manner as veins in general, and not by means of vessels having a peculiar form and distri- bution, as described by Miiller. The helicine arteries of that physiolo- gist have no existence. Vessels and Nerves. The arteries of the penis are derived from the internal pudic ; they are, the arteries of the bulb, arteries of the corpus cavernosum, and dorsales penis. Its veins are superficial and deep. The deep veins run by the side of the deep arteries, and terminate in the internal pudic veins. The superficial veins escape in considerable num- ber from the base of the glans, and converge on the dorsum penis, to form a large dorsal vein, which receives other veins from the corpus cavernosum and spongiosum in its course, and passes backwards between two layers of the ligamentum suspensorium, and through the triangular ligament, beneath the arch of the pubes, to terminate in the prostatic plexus. Previously to its termination it divides into two trunks. The lymphatics terminate in the inguinal glands. The nerves are derived from the pudic nerve, sacral plexus, and hypogastric plexus. URETHRA. The urethra is the membranous canal, extending from the neck of the bladder to the meatus urinarius. It is curved in its course, and composed of two layers, a mucous coat and an elastic fibrous coat. The mucous coat is thin and smooth; it is continuous, internally, with the mucous membrane of the bladder; externally, with the investing membrane of the glans ; and at certain points of its extent, with the lining membrane of the numerous ducts which open into the urethra, namely, those of Cowper's glands, the prostate gland, vasa deferentia, and vesiculae seminales. The elastic fibrous coat varies in thickness in different parts of the course of the urethra : it is thick in the prostate gland, forms a firm investment for the membranous portion of the canal, and is URETHRA. 4T1 thin in the spongy portion, where it serves as a bond of connec- tion between the mucons membrane and the corpus spongiosum. The urethra is about eight inches in length, and is divided into a prostatic, membranous, and spongy portion. The prostatic portion, a little more than an inch in length, is situated in the prostate gland, about one-third nearer its upper than its lower surface, and extending from its base to its apex. Upon its lower circumference or floor is a longitudinal ridge or crest, the veru montanum, or caput gallinaginis; and on each side of the veru, a depressed fossa, the prostatic sinus, in which are seen the numerous openings (fifteen to twenty) of the prostatic ducts. The veru montanum is most prominent in the centre ; and immediately in front of the prominent part, is the opening of a small caecal sac, the sinus pocularis, or utriculus prostaticus. This sac is the analogue of the uterus; it is nearly half an inch in length, and extends back beneath the third lobe of the prostate. It causes, by its approach to the surface, the prominence of the veru raontanum, and is composed of two coats, mucous and fibrous. The fibrous coat is thick, and contains on each side the ejaculatory duct. The mucous coat is provided with an abund- ance of muciparous glands. The ejaculatory ducts terminate on each side within the aperture of the sinus pocularis, by slit-like openings. When the sinus pocularis is of large size, it is capable of receiving the point of a small catheter, and by that means interfering with an import- ant operation. In case of such interruption, the point of the instrument must be carried along the upper wall of the urethra. The prostatic portion of the urethra, when distended, is the most dilated part of the canal ; but, excepting during the pas- sage of urine, is completely closed, by means of a ring of muscu- lar tissue, which encircles the urethra as far as the anterior extre- mity of the veru montanum. In the contracted state of the urethra, the veru montanum acts as a valve, being pressed upwards against the roof of the canal ; but during the action of the detrusor muscle of the bladder, the whole ring is expanded by the longitudinal muscular fibres which are inserted into it ; and the veru is especially drawn downwards by two delicate tendons, which were traced by Mr. Tyrrell from the posterior fibres of the detrusor into the tissue of this process. The membranous portion, the narrowest part of the canal, measures about three lines in diameter, and is somewhat less than an iqch in length. It extends from the apex of the prostate gland to the bulb of the corpus spongiosum, and passes through the triangular ligament. Its coats are the mucous membrane, elastic fibrous tissue, and compressor urethra? muscle. The sub- mucous tissue is richly supplied with vessels. 472 THE DISSECTOR. The spongy portion, about six inches in length, forms the rest of the extent of the canal, and is lodged in the corpus spongi- osum from its commencement at the triangular ligament to the meatus urinarius. It is narrowest in the body, and becomes dilated at each extremity, posteriorly in the bulb, where it is named the bulbous portion, and anteriorly in the glans penis, where it forms the fossa navicularis. The meatus urinarius is the most constricted part of the canal; so that a catheter, which will enter that opening, may be passed freely through the whole extent of a normal urethra. Opening into the bulbous portion are two small excretory ducts about an inch in length, which may be traced backwards, between the coats of the urethra and the bulb, to the under part of the membranous portion behind the triangular ligament, where they originate in two small lobulated and somewhat compressed glands of about the size of peas. These are Cowper's glands : they are situated immediately beneath the membranous portion of the urethra, and are inclosed by the lower segment of the compressor urethras muscle, so as to be subject to muscular com- pression. Upon the whole of the internal surface of the spongy portion of the urethra, and especially along its lower surface, are numerous small openings or lacunce, which are the apertures of mucous glands situated in the submucous cellular tissue. The openings of these lacuna? are directed forwards, and are liable occasionally to intercept the point of a small catheter in its passage into the bladder. At about an inch and a half from the opening of the meatus, in the upper wall of the urethra, one of these lacuna? is generally found much larger than the rest, and is named the lacuna magna. In a preparation of this lacuna, made by Sir Astley Cooper, the extremity of the canal presents several large primary ramifications. TESTES. The testes are two small glandular organs, suspended from the abdomen by the spermatic cords, and inclosed in an external tegumentary covering, the scrotum. The SCROTUM is distinguished into two lateral halves or hemi- spheres by a raphe, which is continued anteriorly along the under surface of the penis, and posteriorly along the middle line of the perineum to the anus. Of these two lateral portions the left is somewhat longer than the right, and corresponds with the greater length of the spermatic cord on the left side. The scrotum is composed of two layers, the integument and a proper covering, the dartos; the integument is extremely thin, transparent, and abundant, and beset by a number of hairs, which TESTE8. 473 issne obliquely from the skin, and have prominent roots. The dartos is a thin layer of contractile fibrous tissue, intermediate in properties between muscular fibre and elastic tissue ; it forms the proper tunic of the scrotum, and sends inwards a septum (septum scroti), which divides it into two cavities for the two testes. The dartos is continuous around the base of the scrotum with the common superficial fascia of the abdomen and perineum. The SPERMATIC CORD is the medium of communication between the testes and the interior of the abdomen : it is composed of arteries, veins, lymphatics, nerves, the excretory duct of the tes- ticle, and investing tunics. It commences at the internal abdomi- nal ring, where the vessels of which it is composed converge, and passes obliquely along the spermatic canal ; the cord then escapes at the external abdominal ring, and descends through the scrotum to the posterior border of the testicle. The left cord is somewhat longer than the right, and permits the left testicle to reach a lower level than its fellow. The TESTIS (testicle) is a small, oblong, and rounded gland, about an inch and a half in length, somewhat compressed on the sides and behind, and suspended in the cavity of the scrotum by the spermatic cord. Its position in the scrotum is oblique; so that the upper ex- tremity is directed upwards and forwards, and a little outwards; the lower, downwards and backwards, and a little inwards; the convex border looks forwards and downwards; and the flattened border, to which the cord is attached, backwards and upwards. Lying against its outer and posterior border is a flattened body, which follows the course of the testicle, and extends from its upper to its lower extremity; this body is named from its relation to the testis epididymis (ixi, upon, 8t'8v^o$, the testicle) ; it is divided into a central part or body, an upper extremity or globus major, and a lower extremity, globus minor (cauda) epididymis. The globus major is situated against the upper end of the testicle, to which it is closely adherent; the globus minor is placed at its lower end, is attached to the testis by cellular tissue, and curves upwards to become continuous with the vas deferens. The testis is invested by three tunics, tunica vaginalis, tunica albuginea, and tunica vasculosa; and is connected to the inner surface of the dartos by a large quantity of extremely loose cellu- lar tissue, in which fat is never deposited, but which is very sus- ceptible of serous infiltration. The tunica vaginalis is a pouch of serous membrane derived from the peritoneum in the descent of the testis, and afterwards obliterated, from the abdomen to within a short distance of the gland. Like other serous coverings, it is a shut sac, investing the organ, and thence reflected so as to form a bag around its 40* 4H THE DISSECTOR. circumference; hence it is divided into the tunica vaginalis pro- pria, and tunica vaginalis reflexa. The tunica vaginalis propria covers the surface of the tunica albuginea, and surrounds the epi- didymis, connecting it to the testis by means of a distinct dupli- cature. The tunica vaginalis reflexa is attached by its external surface, through the medium of a quantity of loose cellular tissue, to the inner surface of the dartos. Between the two layers is the smooth surface of the shut sac, moistened by its proper secretion. The tunica albuginea (dura mater testis) is a thick fibrous membrane of a bluish white color, and the proper tunic of the testicle. It is adherent externally to the tunica vaginalis propria, and, from the union of a serous with a fibrous membrane, is con- sidered to be a fibro-serous membrane, like the dura mater and pericardium. After surrounding the testicle, the tunica albuginea is reflected from its posterior into the interior of the gland, and forms a projecting longitudinal ridge, which is called the medias- tinum testis (corpus Highmorianum 1 ), from which numerous fibrous cords (trabeculas, septula) are given off to be inserted into the inner surface of the tunic. The mediastinum serves to con- tain the vessels and ducts of the testicle in their passage into the substance of the organ ; and the fibrous cords are admirably fitted, as has been shown by Sir Astley Cooper, to prevent compression of the gland. If a transverse section be made of the testis, and the surface of the mediastinum examined, it will be observed that the bloodvessels of the substance of the organ are situated near the posterior border of the mediastinum, while the divided ducts of the rete testis occupy a place nearer the free margin. The tunica vasculosa (pia mater testis) is the nutrient mem- brane of the testis. It is situated immediately within the tunica albuginea, and incloses the substance of the gland, sending pro- cesses inwards between the lobules, in the same manner that the pia mater is reflected between the convolutions of the brain. The substance of the testis consists of numerous conical flattened lobules (lobuli testis), the bases being directed towards the surface of the organ, and the apices towards the mediastinum. Krause found between four and five hundred of these lobules in a single testis. Each lobule is invested by a distinct sheath formed of two layers, one being derived from the tunica vasculosa, the other from the tunica albuginea. The lobule is composed of one or several minute tubuli, tubuli seminiferi, 2 exceedingly convoluted, anastomosing frequently with each other near their extremi- 1 Nathaniel Highmore, a physician of Oxford, in his " Corporis Human! Disquisitio Anatomica," published in 1651, considers the corpus Highmo- rianum as a duct formed by the convergence of the fibrous cords, which he mistakes for smaller ducts. 2 Lauth estimates the whole number of tubuli seminiferi in each testis at 840, and their average length at 2 feet 3 inches. According to this calculation, the whole length of the tubuli seminiferi would be 1890 feet. TESTE8. 475 ties, terminating in loops or in free caecal ends, and of the same diameter (ylfl of an inch, Lauth) throughout. The tubuli seminiferi are of a bright yellow color ; they become less convoluted in the apices of the lobules, and terminate by forming between twenty and thirty small straight ducts of about twice the diameter of the tubuli seminiferi, the vasa recta. The vasa recta enter the substance of the mediastinum, and terminate in from seven to thirteen ducts, smaller in diameter than the vasa recta. These ducts pursue a waving course from below upwards through the fibrous tissue of the mediastinum ; they communicate freely with each other, and constitute the rete testes. At the upper extremity of the mediastinum, the ducts of the rete testes terminate in from nine to thirty small ducts, the vasa efferentia, ' which form by their convolutions a series of conical masses, the coni vasculosi; from the bases of these cones tubes of larger size proceed, which constitute, by their complex convolutions, the body of the epidi- dymis. The tubes become gradually larger towards the lower end of the epididymis, and terminate in a single large and convoluted duct, the vas deferens. Fig. 142. THE ANATOMY OP THE TESTICLE. I. The tunica albuginea. 2. The mediastinum testis, or corpus High- raorianum. 3. A fibrous cord passing between two of the lobules from the mediastinum to the inner surface of the tunica albuginea. Similar cords are observed between the other lo- bules. 4. The tunica vasculosa or pia mater testis. 5. Two of the lo- bules of which the substance of the testicle is composed. They are seen to consist of the convolutions of mi- nute tubes, tubuli seminiferi. 6. The small straight tubes by which the tubuli seminiferi terminate, vasa rec- ta. 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 convolutions 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. I 1 . The body of the epididymis. 12. The globus minor of the epididyrais. 13. The vas deferens, ascending to the external abdominal ring. The arrows mark the course of the secre- tion along the tubes. The epididymis is formed by the convolutions of the excretory seminal ducts, externally to the testis, and previously to their termination in the 1 Each vas efferens with its cone measures, according to Lauth, about 8 inches. The entire length of the tubes composing the epididymis, ac- cording to the same authority, is about 21 feet. 476 THE DISSECTOR. vas deferens. The more numerous convolutions, and the aggregation of the coni vasculosi at the upper end of the organ, constitute the globus major ; the continuation of the convolutions downwards is the body, and the smaller number of convolutions of the single tube at the lower ex- tremity, the globus minor. The tubuli are connected together by a very delicate cellular tissue, and are inclosed by the tunica vaginalis. A small convoluted duct, of variable length, is generally connected with the duct of the epididymis immediately before the commencement of the vas deferens. This is the vasculum aberrans of Haller ; it is attached to the epididymis by the cellular tissue in which that body is enveloped. Sometimes it becomes dilated towards its extremity, but more frequently retains the same diameter throughout. The vas deferens may be traced upwards from the globus minor of the epididymis, along the posterior part of the spermatic cord, and along the spermatic canal to the internal abdominal ring. From the ring it is reflected inwards to the side of the fundus of the bladder, and descends along its posterior surface, crossing the direction of the ureter, to the inner border of the vesicula seminalis. In this situation it becomes somewhat larger in size, and sacculated, and terminates at the base of the prostate gland by uniting with the duct of the vesicula seminalis and constituting the ejaculatory duct. The ejaculatory duct, which is thus formed by the junction of the duct of the vesicula seminalis with the vas deferens, passes forwards in the outer wall of the sinus pocularis, and terminates by a slit-like opening, close to or just within the aperture of the sinus. FEMALE PELVIS. The boundaries of the pelvis in the female are the same as those of the male. The contents are the bladder, vagina, uterus with its appendages, and the rectum. Some portion of the small intestine also occupies the upper part of its cavity. The bladder is in relation with the ossa pubis in front, with the uterus behind (from which it is usually separated by a convo- lution of small intestine), and with the neck of the uterus and vagina beneath. The form of the female bladder corresponds with that of the pelvis, being broad from side to side, and often bulging more on one side than on the other. This is particu- larly evident after frequent parturition. The coats of the bladder are the same as those of the male. The urethra, about an inch and a half in length, is lodged in the upper and anterior wall of the vagina, in its course down- wards and forwards, beneath the arch of the pnbes, to the meatus urinarius. It is lined by mucous membrane disposed in longi- tudinal folds, and is continuous, internally with that of the blad- der, and externally with that of the vulva. The mucous mem- brane is surrounded by a proper coat of elastic tissue (to which FEMALE PELVIS. 47T the muscular fibres of the detrusor urinae are attached), by a plexus of bloodvessels, and by the fibres of the compressor urethras. It is to the elastic tissue that is due the remarkable Fig. 144. A SIDE VIEW OP THE VISCERA OP THE FEMALE PELVIS. 1. The sym- physis pubis ; to the upper part of which the tendon of the rectus muscle is attached. 2. The abdominal parietes. 3. The collection of x'at, 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 urinarius. 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 fund us uteri. The cavitaa uteri is seen along the centre of the organ. 19. The rectum, showing the disposition 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 peritoneum. 23. The utero vesical fold. 24. The reflection of the peritoneum, 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. dilatability of the female urethra, and its speedy return to its original diameter. The meatus is encircled by a ring of fibrous tissue, which prevents it from distending with the same facility as the rest of the canal ; hence it is sometimes advantageous, in 478 THE DISSECTOR. performing this operation, to divide the margin of the meatus with the knife. VAGINA. The vagina is a membranous eanal leading from the vulva to the uterus, and corresponding in direction with the axis of the outlet of the pelvis. It is constricted at its commencement, but near the uterus becomes dilated, and is closed by the contact of the anterior with the posterior wall. Its length is variable ; but it is always longer upon the posterior than upon the anterior wall, the former being usually about five or six inches in length, and the latter four or five. It is attached to the cervix of the uterus, which latter 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 contractile fibrous tissue, resem- bling the dartos of the scrotum. The upper fourth of the posterior wall of the vagina is covered, on its pelvic surface, by the peritoneum ; while in front the peritoneum is reflected from the upper part of the cervix of the uterus to the posterior surface of the bladder. On each side it gives attachment, superiorly, to the broad ligaments of the uterus ; and infe- riorly, to the pelvic fascia and levatores ani. The mucous membrane presents a number of transverse papillce or rugce, upon the upper and lower surface of the canal, the rugae extending out- wards on each side from a middle raphe. The transverse 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 thin cuticular epithelium, which is continued from the labia, and terminates by a fringed border at about the middle of the cervix uteri. The middle, or erectile layer, consists of erectile tissue inclosed be- tween two layers of fibrous membrane ; this layer is thickest near the commencement of the vagina, and becomes gradually thinner as it ap- proaches the uterus. The external, or dartoid layer of the vagina serves to connect it to sur- rounding 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 less closely united, and that intestine is therefore less frequently affected in prolapsus. UTERUS. The uterus is a flattened organ of a pyriform shape, having the base directed upwards and forwards, and the apex downwards and backwards in the line of axis of the inlet of the pelvis, and forming a considerable angle with the course of the vagina. It is convex on its posterior surface, and somewhat flattened on its anterior aspect. In the unimpregnated state it is about three inches in length, two in breadth across its broadest part, and one in thickness ; and is divisible into fundus, body, cervix, and os UTERUS. 479 uteri. At the period of puberty the uterus weighs about one ounce and a half; after parturition, from two to three ounces; and at the ninth month of utero-gestation, from two to four pounds. Fig. 145. THE FEMALE INTERNAL ORGANS OF GENERATION. I. 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 inclosed 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. The fundtis and body are inclosed in a duplicature of perito- neum, which is connected with the sides of the pelvis, and forms a transverse septum between the bladder and rectum. The folds formed by this duplicatnre of peritoneum on each side of the organ are the broad ligaments of the uterus. The cervix is the lower portion of the organ. It is distin- guished from the body by a well-marked constriction ; around its circumference is attached the upper end of the vagina ; and at its extremity is an opening which is nearly round in the virgin, and transverse after parturition, the os uteri (os tincae), bounded before and behind by two labia, the anterior labium being the most thick, and the posterior somewhat the longer. The opening of the os uteri is of considerable size, and is named the orificium uteri externum; the canal then becomes narrowed, and at the upper end of the cervix is constricted into a smaller opening, the orificinm internum. 1 At this point the canal of the cervix 1 The orifioium internum is not unfrequently obliterated in old persons. Indeed, this obliteration is so common, as to have induced Mayer to re- gard it as normal. 480 THE DISSECTOE. expands into the shallow triangular cavity of the uterus, the in- ferior angle corresponding with the orificium internum, and the two superior angles (which are funnel-shaped and represent the original bicornute condition of the organ), with the commence- ment of the Fallopian tubes. In the canal of the cervix uteri are two longitudinal folds, anterior and posterior to which nu- merous oblique folds converge so as to give the idea of branches from the stem of a tree ; hence this appearance has been deno- minated the arbor vitce uterina. Between these folds and around the os uteri are numerous mucous follicles. It is the closure of the mouth of one of these follicles, and the subsequent disten- sion of the follicle with its proper secretion, that occasions those vesicular appearances so often noticed within the mouth and cervix of the uterus, called the ovula of Naboth. Structure. The uterus is composed of three tunics : of an external or serous coat, derived from the peritoneum, which constitutes the duplica- tures on each side of the organ, called the broad ligaments ; of a middle or muscular coat, which gives thickness and bulk to the uterus ; and of an internal or mucous membrane, which lines its interior, and is continuous on the one hand with the mucous lining of the Fallopian tubes, and on the other with that of the vagina. In the unimpregnated state the muscular coat is exceedingly condensed in texture, offers resistance to section with the scalpel, and appears to be composed of whitish fibres inextricably interlaced and mingled with bloodvessels. In the impregnated uterus the fibres are of large size, distinct, and disposed in two layers superficial and deep. The superfi- cial layer consists of fibres which pursue a vertical direction, some being longitudinal, and others oblique. The longitudinal fibres are found principally on the middle line, forming a thin plane upon the anterior and posterior face and fundus of the organ. The oblique fibres occupy chiefly the sides and the fundus. At the angles of the uterus the fibres of the superficial layer are continued outwards upon the Fallopian tubes, and into the round ligaments and ligaments of the ovaries. The deep layer consists of two hollow cones of circular fibres, having their apex at the openings of the Fallopian tubes, and intermingling with each other by their bases on the body of the organ. These fibres are continuous with the deep muscular layer of the Fallopian tubes, and indicate the primitive formation of the uterus by the blending of these two canals. Around the cervix uteri the muscular fibres assume a circular form, in- terlacing with and crossing each other at acute angles. The mucous membrane presents on its surface numerous minute aper- tures corresponding with mucous glands, and is provided with a columnar ciliated epithelium, which extends from the middle of the cervix uteri to the extremities of the Fallopian tubes. Vessels and Nerves. The arteries of the uterus are the uterine from the internal iliac, and the ovarian from the aorta. The veins are large and remarkable ; in the impregnated uterus they are called sinuses, and consist of canals channelled through the substance of the organ, being merely lined by the internal membrane of the veins. They terminate on each side of the uterus in the uterine plexuses. The lymphatics ter- minate in the lumbar glands. The nerves of the uterus are derived from the hypogastric and sperma- FALLOPIAN TUBES. 481 tic plexuses, and from the sacral plexus. They have been made the subject of special investigation by Dr. Robert Lee, who has successfully repaired the omission made by Dr. William Hunter, in this part of the anatomy of the organ. In his numerous dissections of the uterus, both in the unimpregnated and gravid state, Dr. Lee has made the discovery of several large nervous ganglia and plexuses. The principal of these, situated on each side of the cervix uteri immediately behind the ureter, he terms the hypogastric ganglion ; it receives the greater number of the nerves from the hypogastric and sacral plexus, and distributes branches to the uterus, vagina, bladder, and rectum. Of the branches to the uterus, a large fasciculus proceeds upwards by the side of the organ towards its angle, where they communicate with branches of the sperma- tic plexus, and form another large ganglion, which he designates the spermatic ganglion, and which supplies the fundus uteri. Besides these, Dr. Lee describes vesical and vaginal ganglia, and anterior and posterior subperitoneal ganglia and plexuses, which communicate with the preceding, and constitute an extensive nervous network over the entire uterus. Dr. Lee concludes his observations by remarking : " These dissections prove that the human uterus possesses a great system of nerves, which en- larges with the coats, bloodvessels, and absorbents during pregnancy, and which returns after parturition to its original condition before con- ception takes place. It is chiefly by the influence of these nerves that the uterus performs the varied functions of menstruation, conception, and parturition, and it is solely by their means that the whole fabric of the nervous system sympathizes with the different morbid affections of the uterus. If these nerves of the uterus could not be demonstrated, its physiology and pathology would be completely inexplicable." 1 APPENDAGES OF THE UTERUS. The appendages of the uterus are inclosed by the lateral dupli- catures of peritoneum, called the broad ligaments. They are the Fallopian tubes and ovaries'. The FALLOPIAN TUBES or oviducts, the uterine trumpets of the French writers, are situated in the upper border of the broad ligaments, and are connected with the superior angles of the uterus. They are somewhat trumpet-shaped, being smaller at the uterine than at the free extremity, and narrower in the middle than at either end. Each tube is about four or five inches in length, and more or less flexous in its course. The canal of the Fallopian tube is exceedingly minute ; its inner extremity opens by means of the o'stium uterinum into the upper angle of the cavity of the uterus, and the opposite end into the cavity of the peritoneum. The free or expanded extremity of the Fallopian tube presents a double and sometimes a triple series of small processes or fringes, which surround the margin of the trumpet or funnel-shaped opening, the ostium abdominale. This fringe-like appendage to the end of the tube has gained for it the appella- tion of the fimbriated extremity ; and the remarkable manner in 1 Philosophical Transactions for 1842. 41 482 THE DISSECTOR. which this circular fringe applies itself to the surface of the ovary during sexual excitement, the additional title of morsus diaboli. A short ligamentous cord proceeds from the fimbriated extremity, to be attached to the distal end of the ovary, and serves to guide the tube in its seizure of that organ. The Fallopian tube is composed of three tunics : an external and loose investment derived from the peritoneum ; a middle or muscular coat, con- sisting of circular [internal] and longitudinal [external] fibres, continuous with those of the uterus ; and an internal or lining mucous membrane, which is continuous on the one hand with the mucous membrane of the uterus, and at the opposite extremity with the peritoneum. In the minute canal of the tube the mucous membrane is thrown into longitudinal folds or rugae, which indicate the adaptation of the tube for dilatation. The OVARIES (testes muliebres) are two oblong flattened and oval bodies of a whitish color, and uneven surface, situated in the posterior layer of peritoneum of the broad ligaments. They are connected to the upper angles of the uterus at each side by means of a rounded cord, consisting of fibrous tissue and a few muscular fibres derived from the uterus the ligament of the ovary. By the opposite extremity they are connected by another and a shorter ligament to the fimbriated aperture of the Fallo- pian tube. In structure the ovary is composed of a cellulo-nbrous parenchyma or stroma, traversed by bloodvessels, and inclosed in a capsule consisting of three layers : a vascular layer, which is situated most internally, and sends processes inwards to the interior of the organ ; a middle or fibrous layer (tunica albuginea) of considerable density ; and an external invest- ment of peritoneum. In the cells of the stroma of the ovary the small vesicles or ovisacs of the future ova, the Graafian vesicles, are developed. There are usually about fifteen fully formed Graafian vesicles in each ovary ; and Dr. Martin Barry has shown that countless numbers of microscopic ovisacs exist in the parenchyma of the organ, but that very few are perfected so as to produce ova. After conception, a yellow spot, the corpus luteum, is found in one or both ovaries. The corpus luteum is a globular mass of yellow spongy tissue, traversed by white areolar bands, and containing in its centre a small cavity, more or less obliterated, which was originally occupied by the ovum. The interior of the cavity is lined by a puckered membrane, the remains of the ovisac. In recent corpora lutea,the opening by which the ovum escaped from the ovisac through the capsule of the ovary is distinctly visible ; when closed, a small cicatrix may be seen on the surface of the ovary, in the situation of the opening. A similar appear- ance to the preceding, but of smaller size, and without a central cavity, is sometimes met with in the ovaries of the virgin ; this is & false corpus luteum. Vessels and Nerves. The arteries of the ovaries are the spermatic or ovarian ; the veins form an ovarian plexus, which terminates in the uterine plexus. The nerves are derived from the spermatic plexus. The ROUND LIGAMENTS are two muscular and fibrous cords between four and five inches long, situated within the layers of EXTERNAL ORGANS OF GENERATION. 483 the broad ligaments, and extending from the upper angles of the uterus, and along the spermatic canals, to the labia majora, in which they are lost. They are accompanied by a small artery, by several filaments of the spermatic plexus of nerves, by a plexus of veins, and by a process of the peritoneum, which represents the serous membrane investing the spermatic cord in the male. In the young subject, this process extends for a short distance along the spermatic canal, and is denominated the canal of NucJc; it is occasionally pervious in the adult. The plexus of veins oc- casionally becomes varicose, and forms a small tumor at the external abdominal ring, which has been mistaken for inguinal hernia. The round ligaments serve to retain the uterus in its proper position in the pelvis, and during utero-gestation, to draw the anterior surface of the organ against the abdominal parietes. EXTERNAL ORGANS OF GENERATION. The female organs of generation are divisible into the internal and external ; the internal are contained within the pelvis, and have been already described ; they are the vagina, uterus, ovaries, and Fallopian tubes. The external organs are the mons Veneris, labia majora, labia minora, clitoris, meatus urinarius, and the opening of the vagina. The mons Veneris is the eminence of integument, situated upon the front of the ossa pubis. Its cellular tissue is loaded with adipose substance, and the surface covered with hairs. The labia majora are two large longitudinal folds of integument, containing cellular tissue, fat, and a tissue resembling the dartos. They inclose an elliptical fissure, the common urino-sexual open- ing or vulva. The vulva receives the inferior opening of the urethra and vagina, and is bounded, anteriorly, by the commis- sura superior, and posteriorly, by the commissura inferior. Stretching across the posterior commissure is a small transverse fold, the frcennlum labiorum or fourchette, which is ruptured during parturition ; and immediately within this fold is a small cavity, the fossa navicularis. The length of ^ic perineum is measured from the posterior commissure to the margin of the anus, and is usually not more than an inch. The external surface of the labia is covered with hairs ; the inner surface is smooth, and lined by mucous membrane, which contains a number of se- baceous follicles, and is covered by a thin cuticular epithelium. The use of the labia majora is to favor the extension of the vulva during parturition ; for, in the passage of the head of the foetus, the labia are unfolded and completely effaced. The labia minora, or nympha, are two smaller folds, situated within the labia raajora. Superiorly, they are divided into two 484 THE DISSECTOR. processes, which surround the glans clitoridis, the superior fold forming the prseputium clitoridis, the inferior its fraenulura. In- feriorly, they diminish gradually in size, and are lost on the sides of the opening of the vagina. The nymphae consist of mucous membrane, covered by a thin cuticular epithelium. They are provided with a number of mucous follicles, and contain, in their interior, a plexus of bloodvessels. The clitoris is a small elongated organ, situated in front of the ossa pubis, and supported by a suspensory ligament. It is formed by a small body, which is analogous to the corpus caver- nosum of the penis, and like it arises from the ramus of the os pubis and ischium on each side, by two crura. At the extremity of the clitoris is a small accumulation of erectile tissue, which is highly sensitive, and is termed the glans. The corpus caverno- sum clitoridis, like that of the penis, is composed of erectile tissue, inclosed in a dense layer of fibrous membrane, and is susceptible of erection. Like the penis, also, it is provided with two small muscles, the erectores clitoridis. At about an inch behind the clitoris is the entrance of the vagina, an elliptical opening, marked by a prominent margin. The en- trance to the vagina is closed, in the virgin, by a membrane of a semilunarform, which is stretched across the opening; this is the hymen. 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 imperf orate hymen. The hymen must not be considered a necessary accompaniment of virginity, for its existence is very uncertain. When present, it assumes a varity of appearances : it may be a membranous fringe, with a round opening in the centre ; or a semilunar fold; leaving an opening in front ; or a transverse septum, having an opening both in front and behind ; or a vertical band with an opening at each side. The rupture of the hymen, or its rudimentary existence, gives rise to the appearance of a fringe of papillae around the opening of the vagina; these are the caruncula myrtiformes. The triangular smooth surface between the clitoris and the en- trance of the vagina, which is bounded on each side by the upper portions of the nymphaB, is the vestibule. At the posterior part of the vestibule, and near the margin of the vagina, is the opening of the urethra the meatus urinarius ; and around the meatus an elevation of the mucous membrane, formed by the aggregation of numerous mucous glands. This prominence serves as a guide to finding the meatus, in the opera- tion of introducing the female catheter. Beneath the vestibule on each side, and extending from the clitoris to the side of the vagina, are two oblong or pyriform REGION OP THE BACK. 485 bodies, consisting of erectile tissue inclosed in a thin layer of fibrous membrane. These bodies are narrow above (pars inter- media), broad and rounded below, aud are termed by Kobelt, who considers them analogous to the bulb of the male urethra, the bulbi vestibuli. Behind these bodies, and lying against the outer wall of the vagina, are two small glands analogous to Cowper's glands in the male subject ; these are the glands of Bartholine. Each gland opens, by means of a long duct, upon the inner side of the corre- sponding nympha. CHAPTER X. 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 pos- terior parts of the limbs. The student must therefore endeavor to accommodate his dissection to these rules. The most appro- priate time for making this dissection is when the examination of the front of the shoulder and contents of the thorax has been completed. 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. Fourth Layer. Trapezius, (Dorsal Group.) Latissimus dorsi, Sacro-lumbahs, Longissimus dorsi, Second Layer. Spinajis dorsi. Levator anguli scapulffi, (Cervical Group.) Rhomboideus minor, Cervicalis ascendens, Rhomboideus major. Transversalis colli, Trachelo-mastoideus, TJtird Layer. Complexus. Serratus posticus superior, Btyb Layer. Serratus posticus inferior, (Dorsal Group.) Splenius capitis, Semi spinalis dorsi, Splenius colli. Semi spinalis colli. 41* 486 THE DISSECTOR. (Cervical Group.) Sixth Layer. Rectus anticus major, Multifidus spin*, ' Rectus anticus minor, Inter-spinales, Rectus laterahs, Inter-transversales. Obhquus inferior, Levatores costarum. Ubhquus superior. For the dissection of the back, an incision should be made along the middle of the spine, from the tubercle on the occipital bone to the sacrum. From the upper extremity of this incision, carry a second transversely outwards to the back of the ear ; and from its lower end a third, along the crest of the ilium to about its middle. As the flap included by these incisions is too large to be conveniently manageable, a fourth incision should be made from the middle of the back, transversely outwards to the tip of the acromion. The two flaps should then be dissected care- fully oft from the whole of this surface, when the superficial fascia will be exposed. The student should now seek for the superficial cutaneous vessels and nerves of the back. The former are small, and, taking their course usually in company with the nerves, are useful as guides to the situa- tion of the latter. The superficial cutaneous nerves of the neck and upper half of the back pierce the trapezius close to the spine, and pass outwards in their distribution to the integument. Those of the lower half of the back issue from the latissimus dorsi, at a point corresponding with the angle of the ribs ; and those proceeding from the lumbar nerves reach the surface in the situation of the outer border of the sacro-lum- balis. The cutaneous nerves of the back are derived from the posterior divisions of the spinal nerves. Each posterior division of a spinal nerve divides into an internal and external branch. The internal branch is directed inwards towards the middle of the spine, and becoming cutaneous near the spinous processes of the vertebra, is then reflected outwards to supply the integument. The internal branch of the posterior division of i\\v first cervi- cal, or suboccipital nerve is distributed, when it exists, to the integument of the back of the head. The internal branch of the posterior division of the second cervical is the occipitalis major nerve, which pierces the origin of the trapezius muscle in its course to the back of the head to join the occipital artery. The internal branch of the third cervical nerve, when it arrives at the surface, gives off a small cutaneous branch to the integu- ment of the head, before it takes its reflected course on the back of the neck. The cutaneous branches in the cervical region are derived from the third, fourth, and fifth cervical nerves ; the internal branches of the three remaining nerves being intended for the supply of the muscles. The cutaneous nerves in the thoracic region are derived : the MUSCLES OF THE BACK. 48f st.r pper from the internal branches of the posterior division ; the six lower from the external branches of the posterior division. The former pierce the trapezius near the spinous processes, and are directed outwards. The latter pierce the latissimus dorsi over the angles of the ribs, and are directed downwards over the side of the trunk. The cutaneous nerves, in the lumbar region, are derived from the external branches of the posterior division of the three upper lumbar nerves ; they reach the surface in a line with the outer border of the sacro-lumbalis, and descend over the crest of the ilium to the integument of the gluteal region. The cutaneous nerves in the sacral region, derived from the external branches of the three upper sacral nerves, are distributed to the integument of the sacral and posterior part of the gluteal region ; and those of the last two sacral nerves to the integument over the coccyx. When, the cutaneous nerves have been studied, the superficial fascia should be removed from the muscles in the direction of their fibres, and the muscles of the superficial layer brought into view; they are the trapezius and latissimus dorsi. FIRST LAYER. The TRAPEZIUS muscle (trapezium, a quadrangle "with unequal sides) arises from the superior curved line of the occipital bone, ligamentum nucha3, and supraspinons ligament and spinous pro- cesses of the last cervical and all the dorsal vertebra. The fibres converge from these various points, and are inserted into the scapular third of the clavicle, acromion, and the whole length of the upper border of the spine of the scapula. The inferior fibres become tendinous near the scapula, and glide over the triangular surface at the posterior extremity of its spine, upon a bursa mu- cosa. When the trapezius is dissected on both sides, the two muscles resemble a trapezium, or diamond-shaped quadrangle, on the posterior part of the shoulders : hence the muscle was for- merly named cucularis (cucullus, a monk's oowl). The cervical 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 Jdnd of tendinous ellipse. The anterior border of the cervical portion of the trapezius forms the posterior boundary of the posterior triangle of the neck. The njnn.'il accessory nerve, which crosses this triangle, passes beneath the border of the trapezius, and is distributed to the under-sur- face of the muscle as far as its lower portion. There is also con- nected with the anterior border of the muscle in the neck a small artery, the superficialis cervicis, a branch of the transversalis colli. 488 THE DISSECTOR, Fig. 146. THE FIRST AND SECOND AND 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 por- tion which, with a corresponding portion in the opposite muscle, forms the ten- dinous 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 dorsum 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 rhom- boideus major. 13. The splenius capitis; the muscle immediately above, and overlaid by the splenius, is the complexus. 14. The splenius colli, only par- tially seen ; the common origin of the splenius is seen attached 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 serratus magnus, proceeding forwards from its origin at the base of the scapula. 23. The internal oblique muscle. MUSCLES OF THE BACK. 489 The trapezius muscle should be divided by a longitudinal incision directed along the middle of the back, and the two portions turned aside. By turning the muscle back from its cervical origin, the ligamentum nuchae will be brought into view ; and lower down, the removal of the muscle will enable the student to see the upper portion of the latissimus dorsi. The ligamentum nuchce is a thin fibrous band extended from the tubercle and spine of the occipital bone to the spinous pro- cess of the seventh cervical vertebra, where it is continuous with the supraspinous ligament. It is connected with the spinous pro- cesses of all the cervical vertebrae, excepting the atlas, by means of a series of small fibrous slips. It is the analogue of an im- portant elastic ligament in animals. The LATISSIMUS DORSI muscle covers the whole of the lower part of the back and loins. It arises from the spinous processes of the six inferior dorsal vertebras, from all the lumbar and sacral spinous processes, from the posterior third of the crest of the ilium, and from the three lower ribs ; the latter origin takes place by muscular slips, which indigitate with the external oblique muscle of the abdomen. The fibres from this extensive origin converge as they ascend, and cross the inferior angle of the scapula ; they then curve around the inferior border of the teres major muscle, and terminate in a short quadrilateral tendon which lies in front of the tendon of the teres and is inserted into the bicipital groove. A synovial bnrsa is interposed between the muscle and the lower angle of the scapula, and another between its tendon and that of the teres major. The muscle frequently receives a small fasciculus from the scapula as it crosses its inferior angle. The latissimus dorsi maybe divided by a longitudinal incision directed across the lower ribs to the posterior part of the crest of the ilium, and the two portions of the muscle turned aside. In making this dissection, care must be taken to avoid injuring a small muscle which lies beneath the serratus posticus inferior. SECOND LAYER. The second layer of muscles consists of the levator anguli sca- pulae, rhomboideus minor and rhomboideus major. The LEVATOR ANGULI SCAPULAE arises by tendinous slips, from the posterior tubercles of the transverse processes of the four upper cervical vertebras, 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 rhom- boideus major by a slight cellular interspace. It arises from the spinous process of the last cervical vertebra and ligamentum 490 THE DISSECTOR. 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 from the interspinous liga- ments ; it is inserted into the posterior border of the scapula as far as its inferior angle. The upper and middle portion of the insertion is effected by means of a tendinous band, which is at- tached in a longitudinal direction to the posterior border of the scapula. The transversdlis colli artery, a branch of the thyroid axis of the subclavian, will be seen, at this stage of the dissection, cross- ing the posterior triangle of the neck, a short distance above the clavicle, to the levator anguli scapulae, where it divides into two branches, the superficialis cervicis, which has been already ex- amined in connection with the anterior border of the trapezius, and the posterior scapular artery. The latter, which is the proper continuation of the transversalis colli, passes beneath the levator anguli scapulae ; it then turns down and runs along the base of the scapula, under cover of the rhomboid muscles, to its inferior angle, where it inosculates with the subscapular artery. When the rhomboid muscles are divided and turned aside, the artery will be seen accompanied by a nerve (the rhomboid) which dis- tributes branches to the levator anguli scapulae and rhomboidi muscles. THIRD LAYER. The third layer of muscles is brought into view when the rhomboidei and levator anguli scapulae are divided through the middle and turned aside. To make them more clear, the spinous attachment of the rhomboid muscles may be removed altogether. The third layer consists of the serratus posticus superior, serratus posticus inferior, and splenius. The SERRATUS POSTICUS SUPERIOR is situated at the upper part of the thorax ; it arises from the ligamentum nuchae, the spinous process of the last cervical and those of the two upper dorsal vertebrae. The muscle passes obliquely downwards and outwards, and is inserted by four serrations into the upper border of the second, third, fourth, and fifth ribs. The SERRATUS POSTICUS INFERIOR arises from the spinous pro- cesses and interspinous ligaments of the last two dorsal and two upper lumbar vertebrae, and passing obliquely upwards, is inserted by four serrations into the lower- border of the four lower ribs. Both muscles are constituted by a thin aponeurosis for about half their extent. The upper border of the serratus posticus inferior is continuous with a thin tendinous layer, the vertebral aponeurosis. This MUSCLES OF THE BACK. 491 aponeurosis is a thin membranous expansion composed of longi- tudinal and transverse fibres, and extending the whole length of the thoracic region. It is attached mesially to the spinous pro- cesses of the dorsal vertebras, and externally to the angles of the ribs ; superiorly it is continued upwards beneath the serratus posticus superior, with the lower border of which it is sometimes connected. It serves to bind down the erector spinae, and sepa- rate it from the superficial muscles. The serratus posticus superior must be removed from its origin and turned outwards, to bring into view the whole extent of the splenius muscle. The SPLENIUS MUSCLE is single at its origin, but divides soon after into two portions, which are destined to distinct insertions. It arises from the lower half of the ligamentum nucha3, the spinous process of the last cervical, and the spinous processes and inter- spinous ligaments of the six upper dorsal vertebrae ; it divides as it ascends the neck into the splenius capitis and colli. The splenius capitis is inserted into the rough surface of the occipital bone between the two curved lines, and into the raastoid portion of the temporal bone. The splenius colli is inserted into the pos- terior tubercles of the transverse processes of the three or four upper cervical vertebrae. Returning to the serratus posticus inferior, its thin tendon of origin will be found inseparably united with that of the latissi- mus dorsi, and both are connected by their under surface with another aponeurotic expansion, the fascia lumborum. The fascia lumborum is the posterior aponeurosis of the transversalis abdominis muscle, and occupies the space between the crest of the ilium and ' last rib ; it also gives attachment to the in- ternal oblique muscle of the abdomen, and binds down the lumbar portion of the large muscles of the next layer, the erector spinae. FOURTH LAYER. The fourth layer is to be brought into view by removing from its origin the splenius muscle, and dividing and turning aside the vertebral aponeurosis and fascia lumborum. This layer con- sists of the sacro-lumbalis, longissimus dorsi and spinalis dorsi in the lumbar and dorsal region, and the cervicalis ascendens, transversalis colli, trachelo-mastoideus and complexus 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 lumbar vertebrae : opposite the last rib a line of separation begins to be perceptible between the two muscles. The sacro-lumbalis is in- 492 THE DISSECTOR. Fig. 147. serted by separate tendons into the angles of the six lower ribs. On turning the muscle a little outwards, a number of tendinous slips will be seen taking their origin from the ribs, and termi- nating in a muscular fasciculus, by which the sacro-lumbalis is prolonged to the upper part of the thorax. This is the muscnlus accessorius ad sacro-lumbalem ; it arises from the angles of the six lower ribs, and is inserted by separate tendons into the angles of the six upper ribs. The longissimus dorsi is inserted into the transverse processes of all the lumbar and dorsal vertebrae, and into the six or eight lower ribs, be- tween their tubercles and angles. The SPINALIS DORSI arises from the spinous processes of the two upper lumbar and two lower dorsal vertebrae, and is inserted into the spinous processes of all the upper dorsal vertebras. The two muscles form an ellipse, which appears to inclose the spinous processes of all the dorsal vertebrae. The CERVICALIS ASCENDENS is the continuation of the sacro-lumbalis upwards into the neck. It arises from the angles of the four upper ribs, and is inserted by slender ten- dons into the posterior tubercles of the transverse processes of the four lower cervical vertebrae. The TRANSVERSALIS COLLI WOllld appear to be the continuation up- wards into the neck of the longis- simus dorsi ; it arises from the trans- verse processes of the third, fourth, fifth, and sixth dorsal vertebrae, and is inserted into the posterior tuber- cles of the transverse processes of the four or five inferior cervical vertebras. THE FOURTH AND FIFTH, AND PART OF THE SIXTH LAYER OF THE MUSCLES OF THE BACK. 1. The common origin of the erector spinae muscle. 2. The sacro-lumbalis. 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 obliquus inferior. 16. The multifidus spinae. 17. The levatores costarum. 18. Inter- transversales. 19. The quadratus lumborum. NEEVES OP THE BACK. 493 The TRACHELO-MASTOID is likewise a continuation upwards from the longissimus dorsi. It is a slender and delicate muscle, arising from the transverse processes of the four upper dorsal and four lower cervical vertebrae, and inserted into the mastoid process to the inner side of the digastric fossa. 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 processes of the four upper dorsal, and from the transverse and articular processes of the four lower cervical vertebrae, and is inserted into the rough surface on the occipital bone between the two curved lines, near the occipital spine. A large fasciculus of the complexus is so distinct from the principal mass of the muscle as to have led to its description as a separate muscle under the name of biventer cervicis. This appellation is not inappropriate, for the muscle consists of a central tendon, with two fleshy bellies. The com- plexus is marked in the upper part of the neck by a transverse tendinous intersection. The posterior divisions of the spinal nerves and some arteries are brought into view with this layer. These nerves and vessels are now to be examined ; for which purpose the complexus should be cut across its middle, and its ends turned aside ; or so much of the muscles removed as may be necessary to bring the next layer fully into view. CERVICAL NERVES. The posterior divisions of the cervical nerves issue from between the transverse processes, and divide into an internal and external branch. The internal branch is directed inwards to the spinous processes of the vertebrae, and after supplying the muscles of the inner portion of the vertebral groove becomes cutaneous, and is distributed to the infegument of the neck (page 486). The external branch is smaller than the internal, and is distributed to the muscles of the outer portion of the vertebral groove. There are certain exceptions to this general idea of the distri- bution of the posterior divisions of the cervical nerves which may now be mentioned. The first, or suboccipital nerve has no external branch ; it appears in the space between the recti and obliqui muscles, and is distributed to those muscles and the complexus. It also sends a branch downwards to communicate with the internal branch of the second cervical nerve. The internal branch of the second cervical nerve is the occipi- talis major nerve ; it pierces the complexus and trapezius, and is distributed to the integumeat of the scalp, taking the direction of the occipital artery. The internal branches of the second, third, fourth, and fifth nerves lie upon the semispinalis colli muscle, and are closely con- 42 494 THE DISSECTOR. Fig. 148. VESSELS AND NERVES OF THE BACK OF THE NECK AND THORAX. a. The complexus muscle, b, b. The splenius capitis. c. The splenius colli. d. The serratus posticus superior, e. The levator anguli scapulae. /. The spinalis dorsi. g. The longissimus dorsi. h. The sacro-lumbalis. i. The transversalis colli. k. The cervicalis ascendens. /. The trachelo-mastoideus. m. The rectus posticus minor, n. Rectus posticus major, o. The transverse process of the atlas, with the obliquus capitis superior and inferior muscles. p, p. The multifidus spinse muscle, q, q. The levatores costarum. r, r. The tendons of insertion of the longissimus dorsi muscles into the transverse processes of the dorsal vertebrae, s, s. Its tendons of insertion into the ribs, t, t. The two upper insertions of the sacro-lumbalis into the angles of the ribs, v, v. The insertions of the musculus accessorius ad sacro-lumbalem. iv, w. The external intercostal muscles, x. The spine of the scapula, y. The acromion process, z. The mastoid process. 1, 1. The occipital artery ; on the left side it is seen giving oflF its princeps cervicis branch, which descends near o to inos- culate with 2. The profunda cervicis artery. 3. The vertebral artery. 4. The transversalis colli artery. 5. Its superficial cervicis branch. 6. The pos- terior scapular artery. 7, 7, 8. The suprascapular artery ; the upper 7 is on the clavicle; the middle in the supraspinous fossa; the lower in the infraspinous fossa ; below the latter is the dorsalis scapulae branch of the subscapular artery. 9. The posterior auricular branch of the facial nerve. 10, 10. The occipitalis minor nerve. 11, 11. The occipitalis major. 12. The occipital branch of the third cervical nerve. 13. The posterior division of the first cervical nerve. 14, 14. The posterior divisions of the third, fourth, and fifth cervical nerves. 15, The posterior divisions of the sixth, seventh, and eighth cervical nerves. 16, 16. The posterior divisions of the dorsal nerves; each dividing into an in- VESSELS AND NERVES OP THE BACK. 495 nected with a fascia which separates that muscle from the corn- plexus. The second and third, with a branch from the first, constitute the posterior cervical plexus ; and all the branches in their course to the surface pierce the complexus and trapezius and some the splenius. The internal branches of the sixth, seventh, and eighth nerves pass beneath the semispinalis colli, and are lost in the muscles without reaching the integument. DORSAL NERVES. The posterior divisions of the twelve dorsal nerves appear between the transverse processes, and, like the cervical, divide into an internal and external branch. The in- ternal branches diminish in size from the first to the last. The six upper branches pass inwards beneath the semispinalis dorsi, between that muscle and the raultifidus spina3, and, piercing the rhomboid, trapezius, and latissimus dorsi muscles, become cuta- neous close to the spinous processes, and are reflected outwards to supply the integument (page 486). The six lower branches are lost in the muscles of the spine. The external branches increase in size from above downwards, and make their appearance in the line of separation between the longissimus dorsi and sacro-lumbalis. The six upper branches are distributed to those muscles and levatores costarum. The six lower, after supplying the same muscles, pierce the serratus posticus inferior and latissimus dorsi in a line with the angles of the vertebra3 and become cutaneous (page 487). LUMBAR NERVES. The posterior divisions of these nerves, five in number, also appear between the transverse processes 19 the muscular interspace between the longissimus dorsi and multi- fidus spinaB. Like the cervical and dorsal nerves, they divide into an internal and external branch. The internal branches are distributed to the muscles lying close to the spinous processes, and chiefly to the multifidus spinas. The external branches supply the muscles lying upon the trans- verse processes, and the three upper pierce the aponeurosis of the latissiraus dorsi, and become cutaneous (page 487). VESSELS OF THE BACK. The arteries brought into view by the dissection of the deep muscles of the back, are the princeps cervicis, a branch of the occipital; the vertebral artery; the pro- funda cervicis ; and the dorsal branches of the intercostal and lumbar arteries. ternal and external branch, and accompanied by corresponding arteries. 17,17. The posterior cutaneous branches of the six upper dorsal nerves. 18. The pos- terior cutaneous branch of the seventh dorsal nerve, piercing the longissimus dorsi muscle. 496 THE DISSECTOR. The OCCIPITAL ARTERY is seen issuing from beneath the sterno- mastoid and splenius muscle ; passing over the origin of the complexus, and then piercing the trapezius in its course to the back of the head. The princeps cervicis, a branch of the occipital, passes down- wards between the complexus and semispinalis colli muscle, sup- plies the muscles in its course, and inosculates with branches of the vertebral and with the profunda cervicis. The VERTEBRAL ARTERY is seen in the space bounded by the recti and obliqui muscles ; where it is making its curve behind the articular process of the atlas, previously to passing through the opening in the posterior occipito-atloid ligament. The sub- occipital nerve may also be seen issuing from beneath the artery. The vertebral artery gives off a few muscular twigs, which inos- culate with the princeps cervicis and profunda cervicis. The PROFUNDA CERVICIS artery is a branch of the superior in- tercostal of the subclavian : it appears on the back of the neck, between the transverse processes of the last cervical and first dorsal vertebra, and takes its course upwards between the com- plexus and semispinalis colli. It supplies the muscles in its way, and inosculates with the princeps cervicis and branches of the vertebral. The INTERCOSTAL ARTERIES, at the commencement of the inter- costal spaces, give off a dorsal branch, which passes backwards, between the transverse processes and between the body of the vertebra and the anterior costo-transverse ligament, to the pos- terior aspect of the trunk. Each dorsal branch accompanies the dorsal branch of the intercostal nerve, and, like it, divides into an internal and extenal branch, which take a similar course to the branches of the nerve. The internal branch is distributed to the muscles lying near the spinous processes, one twig be- coming cutaneous with the corresponding branch of the nerve. The external branch supplies the longissimus dorsi, sacro- lumbalis, and levatores costarum ; twigs of the lower dorsal branches becoming cutaneous with the nerves which they accom- pany. As the dorsal branch of the intercostal artery passes near the intervetebral foramen, it gives off a spinal branch, which is distributed to the membranes of the spinal cord and to the ver- tebraB. The dorsal branches of the lumbar arteries have a similar dis- tribution to those of the intercostals. The veins of the hack correspond with the arteries, and pass forwards, between the transverse processes of the vertebrae, to open into the vertebral veins in the neck, and the intercostal and lumbar veins in the rest of the trunk. In the cervical regions MUSCLES OP THE BACK. 497 the veins are large and communicate freely, constituting a kind of plexus. FIFTH LAYER. The fifth layer consists of the semispinales, situated in the cer- vical and dorsal regions, and the small group of recti and obliqui at the upper part of the cervical region. The recti and obliqui and semispinalis colli are already exposed by the removal of the muscles of the preceding layer ; the semispinalis dorsi is brought into view by the removal of the longissimus dorsi and spinalis dorsi. The SEMISPINALES muscles are connected with the transverse and spinous processes of the vertebrae, spanning one-half the vertebral column; hence their name semispinales. The semispinalis dorsi arises from the transverse processes of the dorsal vertebras from the sixth to the tenth ; and is inserted into the spinous processes of the four upper dorsal and two lower cervical vertebrae. The semispinalis colli arises from the transverse processes of the five or six upper dorsal vertebrae, and is inserted into the spinous processes of the cervical vertebrae from the second to the fifth. The RECTUS POSTICUS MAJOR arises from the spinous process of the axis, and is inserted into the inferior curved line of the occipital bone. The RECTUS 'POSTICUS MINOR arises from the spinous tubercle of the atlas, and is inserted into the rough surface on the occi- pital bone, beneath the inferior curved line. The RECTUS LATERALIS is extended between the transverse pro- cess of the atlas and the occipital bone ; it arises from the transverse process of the atlas, and is inserted into the rough sur- face of the occipital bone, externally to the condyle. The OIILIQUUS 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 trans- verse process of the atlas, and passes obliquely inwards, to be inserted into the rough surface of the occipital bone between the curved lines. SIXTH LAYER. The sixth layer of the muscles of the back includes a muscle lying beneath the semispinales, multifidus spinae, the small muscles passing between the spinous processes, others passing between the transverse processes, and some small muscles ex- 42* 498 THE DISSECTOR. tended between the transverse processes and the ribs, the levatores costarum. No other dissection is required for the demonstration of these muscles, than the removal of the semispinales and some cellular tissue. The MULTIFIDUS SPIN^E consists of a great number of fleshy fasciculi extending between the transverse and spinous processes 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 lowest fibres of origin proceed from the sacrum, and in the lumbar and cervi- cal regions from the articular processes. Some deep fasciculi of this muscle have been described by Theile under the name of rotatores spince. The INTERSPINALES are small muscular slips arranged in pairs, and situated between the spinous processes of the vertebrae. In the cervical region there are six pairs of these muscles, the first being placed between the axis and third vertebra, and the sixth between the last cervical and first dorsal. In the dorsal region, rudiments of these muscles are occasionally met with between the upper and lower vertebrae, but are absent in the rest. In the lumbar region there are six pairs of interspinales, the first pair occupying the interspinous space between the last dorsal and first lumbar vertebra, and the last the space between the fifth lumbar and sacrum. They are thin and imperfectly deve- loped. Rudimentary interspinales are occasionally met with be- tween the lower part of the sacrum and the coccyx; these are the analogues of the caudal muscles of brutes ; in man they have been named collectively, the extensor coccygus [sacro-coccygeus posticus]. The INTERTRANSVERSALES are small quadrilateral muscles situ- ated between the transverse processes of the vertebrae. In the cervical region they are arranged in pairs corresponding with the double conformation of the transverse processes, the vertebral artery and anterior division of the cervical nerves lying between them. The rectus anticus minor and rectus lateralis represent the intertransversales between the atlas and cranium. In the dorsal region the anterior intertransversales are represented by the intercostal muscles, while the posterior are mere tendinous bands, muscular only between the first and last vertebrae. In the lumbar region, the anterior intertransversales are thin, and occupy only part of the space between the transverse processes. Analogues of posterior intertransversales exist in the form of small muscular fasciculi (interobliqui) extended between the rudimentary posterior transverse processes of the lumbar ver- tebrae. MUSCLES OP THE BACK. 499 The LEVATORES COSTARUM, twelve in number on each side, arise from the tranverse processes of the dorsal vertebrae, and pass obliquely outwards and downwards to be inserted into the rough surface between the tubercle and angle of the rib below them. The first of these muscles arises from the transverse pro- cess of the last cervical vertebra, and the last from that of the eleventh dorsal. The levatores of the inferior ribs, besides the distribution here described, send a fasciculus downwards to the second rib below their origin, and consequently are inserted into two ribs: There are four of these levatores costarum longi, for the four inferior ribs. With regard to the origin and insertion of the muscles of the back, the student should be informed that no exact regularity attends their attachments. At the best, a knowledge of their precise connections, even were it possible to retain it, would be but a barren information, if not absolutely injurions, as tending to exclude more valuable learning. I have therefore endeavoured to arrange a plan, by which they may be more easily recollected, by placing them in a tabular form (p. 500), that the student may see, at a glance, the origin and insertion of each, and compare the natural grouping and similarity of attachments of the various layers. In this manner, also, their actions will be better com- prehended, and learned with greater facility. 500 THE DISSECTOR. ORIGIN. Layers. Spinous processes Transverse processes. Ribs. Additional. 1st Layer. Trapezius last cervical, 12 dorsal ;. ( occipital bone, } < and ligamen- > ( turn nuchae ) Latissimus dorsi < 6 lower dorsal, 5 ) lumbar $ .. 3 lower sacrum and ilium 2d Layer. Levator anguli sca- pulae 4 upper cervical .. .. Rhomboideus min. lig. nuchae, and last cervical .. .. Rhomboideus major 4 upper dorsal .. 3d Layer. Serratus posticus superior lig. nuchae, last cervical, 2 up- per dorsal ., Serratus posticus ^ 2 lower dorsal, 2 inferior \ upper lumbar * * Splenius capitis lig. iiuchae, last cervical, 6 up- k * * Splenius colli per dorsal .. > 4th Layer. Sacro lumbalis . . sacrum and ilium Sacro accessorius ad sacro-lumba- lem .. .. angles of 6 lower } Longissimus dorsi i. .. ' 1 sacrum and lum- ) bar vertebrae 5 Spinalis dorsi 2 lower dorsal, 2 upper lumbar .. .. .. Cervicalis ascendens .. .. angles of 4 upper Transversalis colli .. 3d, 4th, 5th, and 6th dorsal .. .. Trachelo-mastoideus .. 4 upper dorsal, 4 lower cervical .. .. Complexus .. 4 upper dorsal, 4 lower cervical .. 5th Layer. Semi-spinalis dorsi .. 6th to 10th dor- ) sal I Semi-spinalis colli .. 5 or 6 upper dor- f sal j Rectus posticus maj . axis .. .. Rectus posticus min. atlas Rectus lateralis atlas ' Obliquus inferior axis Obliquus superior .. axis .. 6th Layer. Multifldus spinse .. 5 from sacrum to ) 3d cervical j .. .. Interspinales < cervical and \ ( lumbar \ .. .. Intertransversalis .. cervical and \ lumbar j .. Levatores costarum .. last cervical and 1 11 dorsal j .. MUSCLES OF THE BACK. 501 I NSERTION. Spinous processes. Transverse processes. Ribs. Additional. . . . . . . . . . . .. f clavicle and spine of \ the scapula. ***' " !.' ' -V ; ? V. ->?*";' ' .. ; _ fbicipital groove of ( the humerus. -' .. ("angle and base of the \ scapula. '- .. ' : '.. ' : ' .;' base of the scapula. f" .. base of the scapula. y .. 2d, 3d, 4th, and 5th. I lower ribs. '-4tt?n"i<-. %.. 4 upper cervical. f occipital and tera- \ poral bone. . . .. angles of 6 lower. ".. " \. .. angles of 6 upper. .. ,'".. f all the lumbar I and dorsal ( 6 or 8 lower ribs be- < tween tubercles and ( angles. 8 upper dorsal. 4 lower cervical. .. 4 lower cervical. .. .. .. mastoid process. .. .. { occipital bone between the curved lines. !4 npper dorsal, 2 lower cervical. 2d to 5th cervi- cal. atlas.' occipital bone, occipital bone, occipital botie. occipital bone. {From last lumbar to axis, cervical and lum- bar. /cervical and \ lumbar. f all the ribs between the | tubercles and angles. 502 THE DISSECTOR. In examining the foregoing table, the student will observe the con- stant recurrence of the number four in the origin and insertion of the muscles. Sometimes the/owr occurs at the top or bottojn of a region of the spine, and frequently includes a part of two regions, and takes two from each, as in the case of the serrati. Again, he will perceive that the muscles of the upper half of the table take their origin from spinous processes, and pass outwards to transverse, whereas the lower half arise mostly from transverse processes. To the student we commit these reflections, and leave it to the peculiar tenor of his own mind to make such arrangements as will be best retained by his memory. ACTIONS. The upper fibres of the trapezius draw the shoulder up- wards and backwards : the middle fibres, directly backwards ; and the lower, downwards and backwards. The lower fibres also act by produc- ing rotation of the scapula upon the chest. If the shoulder be fixed, the upper fibres will flex the spine towards the corresponding side. The latissimus dorsi is a muscle of the arm, drawing it backwards and down- wards, and at the same time rotating it inwards ; if the arm be fixed, the latissimus dorsi will draw the spine to that side, and, raising the lower ribs, be an inspiratory muscle ; and if both arms be fixed, the two muscles will draw the whole trunk forwards, as in climbing or walking on crutches. The levator anguli scapulae lifts the upper angle of the scapula, and with it the entire shoulder, and the rhonaboidei carry the scapula and shoulder upwards and backwards. The serrati are respiratory muscles acting in opposition to each other, the serratus posticus superior drawing the ribs upwards, and thereby ex- panding 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 of one side draw the vertebral column backwards and to one side, and rotate the head towards the corresponding shoulder. The muscles of opposite sides, acting together, will draw the head directly backwards. They are the natural antagonists of the sterno-mastoid muscles. The sacro-lumbalis with its accessory muscle, the longissimus dorsi, and the spinalis dorsi, are known by the general term of erectores spince, which sufficiently expresses their action. They keep the spine supported in the vertical position by their broad origin from below, and by means of their insertion, by distinct tendons, into the ribs and spinous processes. Be- ing 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 development. The continuations upwards of these muscles into the neck preserve the steadiness and uprightness of that region. When the muscles of one side act alone, the neck is rotated upon its axis. The complexus, by being attached to the occipital bone, draws the head backwards, and counteracts the mus- cles on the anterior part of the neck. It assists also in the rotation of the head. The semi-spin ales and multifidus spince muscles act directly on the ver- tebras, and contribute to the general action of supporting the vertebral column erect. The four little muscles situated between the occiput and the first two vertebrae effect the various movements between these bones, the recti producing the antero-posterior actions, and the obliqui the rotatory mo- tions of the atlas on the axis. The actions of the remaining muscles of the spina the interspinales and intertransversales are expressed in their names. They approximate PERINEUM. 503 their attachments, and assist the more powerful muscles in preserving the erect position of the body. The levatores costarum raise the posterior parts of the ribs, and are pro- bably more serviceable in preserving the articulation of the ribs from dislocation than in raising them in inspiration. CHAPTER XL 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 urethra and the termination of the alimentary canal. These are parts of delicate and complicated structure, and largely supplied with ves- sels and nerves. They are also peculiarly liable, from the nature of their functions, to causes of irritation and disease. Indeed, disease is more frequent and various in this region than in any other of the body. Nearly the whole of the affections admit of relief or cure from operative procedure. Hence the perineum is the most important surgical region of the entire system, and incisions are made through it to a great depth and in various directions. A good knowledge of its component structures and relations is therefore highly necessary to the surgeon, for a mis- directed incision, 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, super- ficial fascia, muscles, vessels, and nerves. But to suit the pecu- liar functions of this region, they are somewhat differently distri- buted and arranged. To obtain a clear and precise idea of the nature of the perineum, 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 pubes, on each side the ramus and tuberosity of the ischiura and great sacro-ischiatic ligaments, and behind the coccyx. If he draw a line transversely across this outlet from the ante- rior 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 gene- 504 THE DISSECTOR. ration; the posterior, to the termination of the alimentary canal. Let us first examine the anterior or genital space. A thin aponeurosis is stretched across this anterior space, from the ramus of the pubes and ischium on one side, to the same part on the. opposite side. This is the triangular ligament. It is a septum of division between the interior and exterior of the pelvis, between the internal organs of generation and the external. Externally to the triangular ligament is the penis, whicn is composed of two lengthened bodies the corpus cavernosum above, and the corpus spongiosum below. The corpus cavern- 'osum is firmly attached to the ramus of the pubes 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 on its escape from the trian- gular ligament, 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 enlarged, and is called the bulb; at its opposite ex- tremity 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 bloodvessels and nerves from the internal pudic artery and nerve. The muscles, vessels, and nerves are in immediate relation with the commence- ment of the penis, and directly external to the triangular ligament. Then the whole of these parts are covered in and held firmly in their places by the superficial perineal fascia, which is con- tinuous with the triangular ligament posteriorly, and is firmly attached on each side to the ramus of the pubes and ischium, whilst, anteriorly, it is continuous with the cellular base of the common superficial fascia of the scrotum and abdomen. So that the genital portion of the perineum consists of two layers of aponeurosis, which are connected posteriorly and at the sides, and inclose a triangular space, in which are contained the root of the penis, with its muscles, vessels, and nerves. Exter- nally to the superficial perineal fascia, is the integument. The posterior or anal portion of the perineum, instead of a resist- ing membranous partition, like the triangular ligament, is divided from the cavity of the pelvis by a convex muscular septum the levator ani muscle, which arises from nearly the whole circum- ference of the interior of the pelvis, and is inserted around the extremity of the rectum. A broad band of muscular fibres em- braces the lower end of the intestine, forming the internal sphinc- ter ; and superficially to it is the flat ellipse of the external sphinc- ter, which is covered by the superficial fascia and integument. Externally to the sphincter, between it and the internal wall of PERINEUM. 505 the pelvis, is the ischio-rectal fossa, which contains a large collec- tion of fat. Dissection. To dissect the perineum, the subject should be fixed in the position for lithotomy, that is, the hands should be bound to the soles of the feet, and the knees kept apart. An easier plan is the drawing of the feet upwards, by means of a cord passed through a hook in the ceiling. Both of these means of preparation have for their object the full exposure of the peri- neum. And as this is a dissection which demands some degree of delicacy and nice manipulation, a strong light should be thrown 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 pubes 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 tuberosity and ramus of the ischium, and ramus of the pubes, to the opposite side of the scrotum, where the two extremities may be connected by a transverse incision. The in- cision will completely surround the perineum, following very nearly the outline of its boundaries. Now let the student dissect off the integument carefully from the whole of the included space, and he will expose the fatty cellular structure of the common superficial fascia. The superficial fascia of the perineum, like that of the_ groin, consists of two layers, of which the external is cellular, and contains adipose tissue in variable proportion ; and the internal is membranous and divested of fat. In the superficial layer is contained a cutaneous muscle the sphinc- ter ani, which has been already dissected, in the removal of the integu- ment. The SPHINCTER ANI is a thin and elliptical plane of muscle, closely adherent to the integument, and surrounding the opening of the anus. It arises, posteriorly, in the superficial fascia around the coccyx, and by a fibrous raphe from the apex of that bone ; and is inserted, anteriorly, into the tendinous centre of the perineum, and into the raphe of the istegument, nearly as far forward as the commencement of the scrotum. The sphincter ani may now be turned back from its anterior part : in raising it some small vessels and a nerve will be found joining it from the ischio-rectal fossa ; these are the inferior hemorrhoidal vessels and nerve. In the next place the student should dissect off the superficial layer of the superficial fascia from the deep layer, and pick out with care all the fat from the ischio-rectal fossa, taking care to avoid injuring the deep layer of the superficial fascia, and especially that portion of it which turns back to unite with the triangular ligament. 43 506 THE DISSECTOR. The deep or membranous layer of the superficial perineal fascia is a strong but thin fibrous layer, which binds down the root of the penis and muscles of the genital portion of the perineum. It is firmly attached at each side to the ramus of the pubes and ischium nearly as far back as the tuberosities of that bone. Across the middle of the perineum it turns backwards, to become continuous with the triangular ligament. In front, it is conti- nuous with the dartos of the scrotum, the superficial fascia of the penis, and the deep layer of the superficial fascia of the abdomen. Moreover, it is connected on the middle line with the raphe of the muscles of the spongy portion of the urethra and septum scroti, and thus divides the perineum into two lateral cavities, more or less complete. It follows, from this arrangement, that if urine had escaped from the urethra at the point where that tube had just traversed the triangular ligament, it would be unable to follow the laws of gravity, and pass backwards towards the anus, on account of the communication between the superficial perineal fascia and the ligament. It could not pass outwards into the thighs, on account of the connection of the superficial perineal fascia to the ramus of the pubes 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 account of the tension and resistance of the deep layer of the superficial perineal fascia; and, unless speedily opened by the surgeon, might give rise to consequences dangerous to life. Behind the posterior and folded border of the superficial fascia, is situated, at each side, the ischio-rectal fossa. This fossa in- terposed, as its name implies, between the lower part of the rectum, and the side of the ischium, is bounded, in front, by the folded border of the superficial perineal fascia and triangular ligament ; behind, by the border of the gluteus maximus and great sacro-ischiatic ligament; internally, by the levator ani and sphincter ani ; and externally, by the internal obturator muscle and obturator fascia. In this, the outer wall of the ischio-rectal fossa, at a little more than an inch from the surface, and inclosed in a special sheath of fascia, are the internal pudic vessels and nerve, and crossing the fossa to the anus, the inferior hemor- rhoidal vessels and nerve. The width of the ischio-rectal fossa is about an inch, and its depth two inches. The best manner of dissecting the superficial perineal fascia is to make an incision from the middle point of the upper incision PERINEUM. 507 to the tuberosity of the ischium on each side. We thus form a A shaped flap, which, on being turned downwards (Fig. 153, -4), displays very distinctly the continuity of this fascia with the triangular ligament. The two side flaps (5, 5), are then to be dissected outwards, and the firm connection between this fascia and the.ramus of pubes and ischium demonstrated. When the student has thus satisfied himself of the connections of the superficial perineal fascia, he must proceed to remove the fat and cellular tissue, which 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 com- mencement of the corpus cavernosum (crus 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 nerves on one side had better be dissected away with the fat and cellular tissue. Fig. 149. THE MUSCLES OP THE PERINEUM. 1. The accelerators urinae muscles, the figure rests upon the corpus spongiosum penis. 2. The corpus cavernoeum of one side. 3. The erector penis of one side. 4. The transversus 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 boun- daries of the perineum are well seen in this engraving. The MUSCLES of the genital portion of the perineum, are the Acceleratores urinse, Erectores penis, Transversus perinei. 508 THE DISSECTOR. The ACCELERATORES TIRING; (bulbo-cavernosi) arise from a 'tendinous point in the centre of the perineum, and from the fibrous raphe of the two muscles. From this origin the fibres diverge, like the plumes of a pen ; the posterior fibres, to be in- serted into the triangular ligament and ramus of the pubes ; the middle, to encircle the corpus spongiosum, and meet on its upper side; and the anterior, to spread out upon the corpus caver- nosum at each side, and be inserted, partly into its fibrous struc- ture, and partly into the fascia of the penis. The posterior and middle insertions of these muscles are best seen, by carefully raising one muscle from the corpus spongiosum and tracing its fibres. The ERECTOR PENIS (ischio-cavemosus) arises from the tube- rosity of the ischium and ramus of the pubes, and curves around the root of the penis, to be inserted into the upper surface of the corpus cavernosum, where it is continuous with a strong fascia which covers the dorsum of the organ the fascia penis. The TRANSVERSUS PERINEI arises from the ramus of the ischium on each side, and is inserted into the central tendinous point of the perineum. A small slip of muscle is sometimes found in front of the transversus perinei ; this is the transversus perinei alter. By its inner end it is con- tinuous with the accelerator. The three muscles above described form the boundaries of a triangular space, of which the floor is constituted, by the triangular ligament. The space is bounded, internally, by the accelerator urinse ; externally, by the erector penis ; and behind, by the transversus perinei. Through this space the incision is made in lithotomy, and the transversus perinei muscle and artery are cut across. The superficial perineal vessels, which occupy this space, are also liable to be divided. The muscles of the anal portion of the perineum, are the sphincter ani external and internal, and the levator ani. If the external sphincter ani be raised at the side as far as its attach- ment to the anus, the rounded border of the internal sphincter will be brought into view. The SPHINCTER ANI INTERNUS is a muscular band embracing the extremity of the intestine, and formed by an aggregation of the circular muscular fibres of the rectum. Part of the levator ani may now be seen, forming the floor and inner boundary of the ischio-rectal fossa. Its fibres may be traced to their insertion into the extremity of the rectum, and the muscle will be seen to be covered by a thin fascia. The examination of the muscle in its entire extent must be left until the pelvis is examined from within. It arises within the pelvis, and is inserted into the coccyx, the raphe be- tween the coccyx and rectum, the side of the rectum, the central tendi- nous point of the perineum, and into its fellow of the opposite side. Actions. The acceleratores urinae being continuous at the middle line, and attached on each side to the triangular ligament by means of PERINEUM. 509 their posterior fibres, will support the bulbous portion of the urethra, and acting suddenly, will propel the semen, or the last drops of urine from Fig. 150. ANATOMY OF THE PERINEUM. a, a. The testes, covered by cellular tissue, the scrotum being drawn up. b. The corpus spongiosum penis, e, c. The cor- pus cavernosum. d. The acceleratores urinae muscles, e. The tendinous cen- tre of the perineum. f,f. The slip of the accelerator urinae, which surrounds the corpus cavernosum. g, g. The erector penis ; the letter is placed on the ramus of the ischium. h, h. The transversus perinei muscle ; the letter is placed on the tuberosity of the ischium. *'. The sphincter ani. k, k. The le- vntorani. I. The coccyx, m^m. The gluteus maximus. n. The origin of the adductor lonpus. o. The gracilis. p. The adductor magnus. q. The con- joined head of the biceps and semitendinosus. r, r. The internal pudic artery, on the left side accompanied by the pudic nerve ; the letters rest on the tuber- osity of the ischium ; the inferior hemorrhoidal arteries are seen crossing the right ischio-rectal fossa (/-) to reach the surface. *. The internal pudio artery giving off the artery of the bulb : the small artery lying superficially to the pudic at this point, and then running along the penis to a, is the superficial perineal ; it is seen giving off a transversalis perinei branch, which crosses the transversus perinei muscle (h) ; on the left side the nerves of the perineum are principally shown, t. The hemorrhoidal branch of the fourth sacral nerve, v, v. The inferior pudendal nerve, a branch of the lesser sciatic, w. The inferior hemorrhoidal nerve proceeding from the pudic. x. The superficial perineal nerve, posterior branch ; the anterior branch is seen issuing from beneath the transversus perinei muscle, and running forwards by the side of the posterior branch, in the groove of the penis, to the scrotum at y. 43* 510 THE DISSECTOR. the canal. The posterior and middle fibres, according to Krause, 1 con- tribute towards the erection of the corpus spongiosum, by producing compression of the venous structure of the bulb ; and the anterior fibres, according to Tyrrell, 2 assist in the erection of the entire organ, by com- pressing the vena dorsalis by means of their insertion into the fascia penis. The erector penis becomes entitled to its name from spreading out upon the dorsum of the organ into a membranous expansion (fascia penis), which, according to Krause, compresses the dorsal vein during the action of the muscle, and especially after the erection of the organ has commenced. The transverse muscles serve to steady the tendinous centre, that the muscles attached to it may obtain a firm point of sup- port. According to Cruveilhier, they draw the anus backwards during the expulsion of the feces, and antagonize the levatores ani which carry the anus forwards. The external sphincter, being a cutaneous muscle, 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 intestine. Now that the muscles of the perineum have been examined, the stu- dent should remove at one side the accelerator urinse, transversus perinei and erector penis, and detach the crus penis from the bone ; he will then bring into view a smooth shining aponeurotic layer which forms, as it were, the floor of the genital portion of the perineum. This is the external surface of the triangular ligament. By means of the handle of the scalpel it may be traced to its attachment into the ramus of the pubes and ischium ; on the middle line it is continuous with the cover- ing of the penis behind the bulb, and below it is continuous with the folded border of the superficial perineal fascia. It is the internal boundary of the pouch of the genital portion of the perineum, which contains the root of the penis together with its muscles, vessels and nerves. The triangular ligament, or deep perineal fascia, is a thin layer of aponeurosis which is stretched across the anterior portion of the outlet of the pelvis; it is attached on each side to the pelvic border of the ramus of the pubes and ischium as far back as the origin of the erector penis muscle. Anteriorly, it is convex and closely connected with the subpubic ligament ; while, posteriorly, it is concave, and turns forwards around the posterior border of the transversus perinei muscle, to become continuous with the superficial perineal fascia. At its middle, it is about an inch and a half in depth ; at one inch below the pubic arch, it is pierced by the membranous portion of the urethra, and nearer the pubic arch, by the dorsal vein of tfye penis and internal pudic arteries. Directly behind the ligament are situated the deep transversus perinei and compressor urethra muscle, the arteries of the bulb, and Cowper's glands, and more deeply the pelvic fascia, which has been sometimes described as the posterior layer of the trian- gular ligament. 1 Miiller, Archiv fiir Anatomie, Physiplogie, c., 1837. 8 Lectures in the College of Surgeons. 1839. VESSELS OF THE PERINEUM. 511 VESSELS AND NERVES OF THE PERINEUM. The INTERNAL PUBIC ARTERY, one of the terminal branches of the internal iliac artery, in pursuing its course along the inner wall of the pelvis, crosses the spine of the ischium. Hence it is described as passing out of the pelvis through the great sacro- ischiatic foramen, and re-entering the pelvis through the lesser sacro-ischiatic foramen. It then passes forwards to the ramus of the ischium, resting against the obturator fascia and inclosed in a special sheath ; and ascends along the inner border of the Fig. 151. A DEEPER DISSECTION THAN THAT REPRESENTED IN FIGURE 149, THE I'KIMXKAL 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, f. Levator ani. g. Sphincter. h. Tuberosity of ischium. k. Glutneus 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. ramus of the ischiura and pubes to near .the arch of the pubes, where it perforates the triangular ligament and divides into two terminal branches the artery of the corpus cavernosum and dorsalis penis. While crossing the obturator muscle, the artery is situated in the outer wall of the ischio-rectal fossa, at some- what more than an inch from the surface of the tuberosity. 512 THE DISSECTOR. The branches of the internal pudic artery in the perineum are the Inferior heraorrhoidal, Arteria corporis bulbosi, Superficialis perinei, Arteria corporis cavernosi, Transversalis perinei, Arteria dorsalis penis. The inferior hemorrhoidal arteries (external) are three or four small branches, given off by the internal pudic while behind the 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 cms penis on the left side is cut through. 2. The acceleratores urinae muscles, inclosing the bulbous por- tion of the corpus spongiosum. 3. The erector penis, spreads out upon the crus penis of the right side. 4. The anus surrounded by the sphincter ani muscle. 5. The ram us of the ischium and os pubis. 6. The tuberosity of the ischium. 7. The lessor 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 hemorrhoidal 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 ter- minal 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. tuberosity of the ischium. They cross the ischio-rectal fossa, and are distributed to the anus, and to the muscles and integu- ment of the anal region of the perineum. The superficial perineal artery is given off near the attach- ment of the crus penis ; it pierces the connecting layer of the superficial fascia and triangular ligament, arid runs forward across the transversus perinei muscle, and along the groove between the NERVES OP THE PERINEUM. 513 accelerator urinae and erector penis to the septum scroti, upon which it ramifies under the name of arteria septi. It distributes branches to the scrotum and to the perineum in its course for- wards. One of the latter, larger than the rest, crosses the peri- neum, resting on the transversus perinei muscle, and is named the transversalis perinei. There are often two superficial peri- nea! arteries. The artery of the bulb is given off from the pudic, nearly opposite the opening for the transmission of the urethra ; it passes almost transversely inwards behind the triangular liga- ment, and pierces that ligament, to enter the corpus spongiosum at its bulbous extremity. It is distributed to the corpus spongio- sum. The artery of the corpus cavernosum, one of the terminal branches of the internal pudic, pierces the crus penis, and runs forward in the interior of the corpus cavernosum, by the side of the septum pectiniforme. It ramifies in the parenchyma of the venous structure of the corpus cavernosum. The dorsal artery of the penis ascends between the two crura and symphysis pubis to the dorsum penis, and runs forward, through the suspensory ligament, in the groove of the corpus cavernosum, to the glands, distributing branches in its course to the body of the organ and integument. The VEINS of the perineum, excepting the dorsal vein of the penis, unite to form the internal pudic vein, which follows the course of the artery, and terminates in the internal iliac vein. The dorsal vein of the penis, after piercing the triangular liga- ment just beneath the subpubic ligament, divides into two trunks, and terminates in the prostatic plexus. The NERVES of the perineum are, an hemorrhoidal branch from the fourth sacral nerve, the inferior pudeudal nerve a branch of the lesser ischiatic nerve, and the pudic. The hemorrhoidal branch of the fourth sacral nerve issues from between the coccygeus muscle and levator ani, and is distributed to the muscles and integument behind the anus. The inferior pudendal nerve pierces the fascia lata near the rainus, and just in front of the tuberosity of the ischium, and passes forward in the superficial fascia of the perineum to the scrotum, to which and to the root of the penis it is distributed. In its course it communicates with the posterior superficial pe- rineal nerve. The PUDIC NERVE arises from the lower part of the sacral plexus, and passes out of the pelvis through the great sacro-ischiatic fora- men below the pyriformis muscle. It then follows the course of the internal pudic artery along the wall of the ischio-rectal fossa, lying inferiorly to the artery and inclosed in the same sheath. 514 THE DISSECTOR. its origin it gives off the inferior hemorrhoidal nerve, and in the ischio-rectal fossa divides into a superior and an inferior branch. The inferior hemorrhoidal nerve, often a branch of the sacral plexus, passes through the lesser sacro-ischiatic foramen, and descends to the termination of the rectum, to be distributed to the sphincter ani and integument. The dorsalis penis nerve, the superior division of the internal pudic, ascends along the posterior surface of the ramus of the ischium, pierces the triangular ligament, and accompanies the arteria dorsalis penis to the glans, to which it is distributed. At the root of the penis the nerve gives off a cutaneous branch which runs along the side of the organ, gives filaments to the corpus cavernosum, and with its fellow of the opposite side supplies the integument of the upper two-thirds of the penis and prepuce. The perineal nerve, or inferior terminal branch, larger than the preceding, pursues the course of the superficial perineal artery in the perineum, and divides into cutaneous and muscular branches. The cutaneous branches (superficial perineal), two in number, posterior and anterior, enter the ischio-rectal fossa, and pass forwards with the superficial perineal artery, to be distri- buted to the integument of the perineum, scrotum, and under part of the penis. The posterior superficial perineal nerve also sends a few filaments to the integument of the anus and sphinc- ter ani ; while the anterior gives off one or two twigs to the levator ani. The muscular branches proceed from a single trunk which passes inwards behind the transversus perinei muscle ; they are distributed to the transversus perinei, accelerator urinso, and erector penis. The perineal nerve also sends two or three fila- ments to the corpus spongiosum. The student should now bring more completely into view the surface of the triangular ligament, for which purpose he should divide the cor- pus spongiosum at about an inch in front of the bulb, separate it from the corpus cavernosum, and turn it down. One crus of the corpus cav- ernosum has been already cut through, so that the penis may also be drawn aside. When the surface of the triangular ligament is fully ex- posed and cleaned, he should raise the triangular ligament carefully, and remove it, in order to bring into view the parts which lie behind. These are a pair of muscles, the deep transversus perinei and compressor urethrse, Cowper's glands, the membranous portion of the urethra, and the arteries of the bulb. The TRANSVERSUS PERINEI PROFUNDUS (perinaeus profundus) is a thin muscle which arises from the ramus of the pubes and ischium by tendinous fibres, and passes inwards to the anterior extremity of the membranous portion of the urethra, where it is COMPRESSOR URETHRA. 515 united, by means of a raph, with its fellow of the opposite side, and is also inserted into the posterior part of the bulb. The COMPRESSOR URETHRA (constrictor urethra membranaceae, constrictor isthrai urethrse) arises from the upper and lower sur- face of the anterior ligament of the bladder, and passing inwards towards the middle line, divides into two fasciculi, superior and inferior, which embrace the membranous portion of the urethra. The superior fasciculus is continued forwards to the junction of the crura penis, with which it is connected, and backwards to the prostate gland, upon the upper surface of which it is spread out. The inferior fasciculus is continued directly into its fellow of the opposite side, beneath the membranous portion of the urethra. A third fasciculus, closely united with the two preceding, con- sists of circular fibres, which inclose and form a muscular sheath for the membranous part of the urethra. Fig. 153. THE STRUCTURES CONTAINED BETWEEN THE TWO LAYERS OP THE DEEP PERINEAL FASCIA. 1. The symphysis pubis. 2, 2. The ramus of the puhis and ischium. 3, 3. The tuberosities of the ischia. 4. A triangular portion of the superficial fascia turned down, and shown to be continuous with the deep fascia (6). 5, 5. Two portions of the superficial perineal fascia, showing its connection to the minus 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 urethras muscle of one side. 9. The inferior fasciculus of the compressor urethra. The two fasciculi (8) and (9), constitute Guthrie's muscle of one side. 10. The pubic portions of the compressor 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 cavernosuin. 15. The arteria dorsalis penis. 516 THE DISSECTOR. Under the name of Wilson's muscles, a fourth fasciculus has been described as descending vertically from the body of the pubes, near the symphysis, to unite with the superior fasciculus of the compressor ure- thrae. This fasciculus is inconstant, and its existence is doubtful. Actions. The transversus perinei profundus draws the urethra and the bulb backwards ; according to Santorinus, it also assists the accele- rator urinae in its action of compressing the bulb. The compressor urethras, taking its fixed point from the ramus of the pubes and ischium at each side, can, says Mr. Gruthrie, "compress the urethra, so as to close it, I conceive completely, after the manner of a sphincter." COWPER'S GLANDS are two small bodies of the size and shape of peas somewhat compressed, situated beneath the membranous portion of the urethra, immediately behind the bulb and trian- gular ligament, and between the deep transversus perinei muscle and deep segment of the compressor urethras. The gland is lobulated in structure, and furnished with an excretory duct about an inch in length, which passes forwards by the side of the urethra, between it and the substance of the bulb, and ter- minates by opening, into the bulbous portion of the urethra. Each gland is furnished with a small arterial twig from the artery of the bulb. The OPERATION OF LITHOTOMY, which especially gives interest to the anatomy of the perineum, requires the division of the different struc- tures which enter into its composition. An incision has to be made through the perineum to the neck of the bladder. Another operation, the puncture of the bladder through the perineum, is also performed by incising in the same direction and through the same parts. In his second dissection, the student should practise the former operation, and afterwards examine the structures through which his incision has passed, and the liabilities that might ensue from proceeding igno- rantly. In lithotomy the patient is fixed by binding the palms of the hands against the soles of the feet, and holding apart the knees. The operator has thus the whole expanse of the perineum before his eyes ; he observes the elevated line (raphe), which runs along the middle of the perineum to the anus, and he feels for the tuberosity of the ischium ; he then commences an incision at the raphe, about an inch and a half, more or less, in front of the anus. The exact point for the commencement of the incision must always be left to the judgment of the operator, who will proportion the length of his incision to the size and age of his patient, his fatness, ot emaciation ; an inch and a half being about the average distance in an adult of ordinary condition. The incision is carried obliquely downwards and outwards, to a point one-third nearer to the tuberosity of the ischium than to the anus, and should terminate opposite the middle of the anus. The pro- portional distance between the tuberosity of the ischium and anus, is the Scylla and Charybdis of the operation ; for approaching nearer the former would endanger the internal pudic artery ; and the latter, the rectum ; particularly if the surgeon have neglected the precaution of emptying that bowel previously to the operation. The first step, then, of the operation is to make a steady incision from the raphe", an inch and a half in front of the anus, obliquely downwards OPERATION OF LITHOTOMY. 517 and outwards to a point one-third nearer the tuberosity of the ischium tli.-ui the anus, and opposite the middle of that opening. This incision should divide the integument, the superficial perineal fascia, the lower fibres of the accelerator urinse, the transversus perinei muscle and artery, and some branches of the inferior hemorrhoidal arteries and nerve. It may also divide the superficial perineal vessels and nerves. The operator now inserts his finger into the upper part of the incision, drawing aside the bulb of the urethra, and presses his nail into the groove of the staff, just at the point where the urethra escapes from the triangular ligament : he then conveys the point of a knife, guided by his finger nail, into the groove at the under part of the cylinder of the ure- thra, and carries it onwards, along the groove in the stalf, into the bladder. In withdrawing the knife he depresses the handle, so as to divide but slit/htli/ the neck of the bladder, prostate gland, and triangular ligament, and more extensively any of the other textures which may have re- mained undivided by the first incision. The form in the opening thus made must evidently be triangular, the lias.' being at the integument, the apex at the neck of the bladder. The insertion of the knife into the under part of the cylinder, of the urethra, is a precaution for avoiding the artery of the bulb, 1 which might other- wise be divided, and give rise to unpleasant hemorrhage. The third step of the operation consists in introducing the finger of the left hand through the wound into the bladder, dilating the neck of that viscus, and breaking the prostate gland in the direction of the inci- sion, for the purpose of securing space for the removal of the calculus. Then passing the forceps along the finger, the calculus is seized by its short diameter, and must be withdrawn in the axis of the pelvis. The structures cut through in this operation in their order of division, are the Integument, Superficial perineal fascia, Bulbous portion of the accelerator urinse muscle, Transversus perinei muscle, Transversalis perinei artery, Triangular ligament, Membranous portion of the urethra, Lower segment of the deep transversus perinei muscle, Lower segment of the compressor urethras, Some fibres of the levator ani, l'r< .state gland, Neck of the bladder. 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 distension to which this part is submitted in parturition. The entrance of the vagina is encircled by a sphincter, which is not unlike the accelerator urinoe of the male. The clitoris is the penis of the female, composed of its corpus cavernosum, and 1 The author has seen two or three instances of the early division of this artery, in which no precaution on the part of the surgeon could have availed, and the artery must have been inevitably divided. 44 518 THE DISSECTOR. therefore provided with erectores clitoridis, analogous to the erec- tores penis. The transversus perinei, sphincters, and levator ani, are precisely the same as in the male. The dissection of the female perineum should be the same as that already prescribed for the male. The integument having been turned aside, the superficial fascia and superficial vessels should be examined and removed. The labia majora, being composed of integument and cellular tissue, should also be removed, and the muscles brought into view, and carefully cleaned. The MUSCLES of the female perineum are the Constrictor vaginae, Transversus perinei, superficial and deep, Erector clitoridis, Compresser urethras, Sphincter ani. The CONSTRICTOR VAGINJE is analogous to the accelerator urinae of the male : it arises from the tendinous centre of the perineum, where it is continuous with the sphincter ani and transversus perinei ; and passes forwards on each side of the en- trance of the vagina, to be inserted into the corpus cavernosum 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 TRANSVERSUS PERINEI PROFUNDUS is situated above the triangular ligament : as in the male, it is inserted into the ure- thra. The ERECTOR CLITORIDIS arises from the ramus of the ischium, and is inserted on each side into the crus clitoridis. The COMPRESSOR URETHRA has the same origin and insertion, and exercises the same functions in the female as in the male. The SPHINCTER ANI surrounds the lower extremity of the rec- tum, as in the male. The LEVATOR ANI is inserted into the side of the vagina and rectum. The TRIANGULAR LIGAMENT is the same as in the male, but of less extent. The VESSELS and NERVES of the perineum are identical with those of the male, with the exception that the artery of the bulb is distributed to the vagina. The nerve of the bulb has a similar distribution. FCETAL CIRCULATION. 519 CHAPTER XII. ANATOMY OF THE Fwer jaw, though not with the joint, is the stylo-maxillary ligament, a process of the deep cervical fascia extended between the point of the styloid process and the angle of the jaw. It is attached to the jaw between the insertions of 540 THE DISSECTOR. the masseter and internal pterygoid muscle, and separates the parotid from the submaxillary gland. ACTIONS. The movements of the lower jaw are depression, by which the mouth is opened ; elevation, by which it is closed ; a forward and backward movement ; and a movement from side to side. In the movement of depression, the interarticular cartilage glides for- ward on the eminentia articularis, carrying with it the condyle. If this movement be carried too far, the superior synovial membrane is rup- tured, and dislocation of the fibro-cartilage with its condyle into the zy- gomatic fossa occurs. In elevation the fibrous cartilage and condyle are returned to their original position. The forward and backward move- ment is a gliding of the fibro-cartilage upon the glenoid articular surface, in the antero-posterior direction ; and the movement from side to side, in the lateral direction. Dislocations. The dislocations of the lower jaw are three : 1. Com- plete ; 2. Partial ; and 3. Subluxation. In Complete dislocation, both condyles are thrown forwards into the zygomatic fossae. In Partial dislocation, one condyle is thrown forwards into the zygo- matic fossa. In Subluxation, the condyle is displaced from its interarticular fibro- cartilage. 6. Articulation of the Ribs with the Vertebra. The ligaments of these articulations are so strong as to render dislocation im- possible ; the neck of the rib would break before displacement could occur : they are divisible into two groups : 1. Those connecting the head of the rib with the bodies of the vertebra ; and 2. Those connecting the neck and tubercle of the ribvfiih the transverse processes. They are 1st Group. 2d Group. Anterior costo-vertebral or Anterior costo-transverse, stellate, Middle costo-transverse, Capsular, Posterior costo-transverse. Interarticular ligament. Two synovial membranes. The anterior costo-vertebral or stellate ligament consists of three short bands of ligamentous fibres that radiate from the anterior part of the head of the rib. The superior band passes upwards, and is attached to the vertebra above ; the middle fasciculus is attached to the intervertebral substance ; and the inferior, to the vertebra below. In the first, eleventh, and twelfth ribs, the three fasciculi are attached to the body of the corresponding vertebra. The capsular ligament is a thin layer of ligamentous fibres, surrounding the joint in the interval left by the anterior liga- ment ; it is thickest above and below the articulation, and pro- tects the synovial membranes. ARTICULATIONS OF THE RIBS. 541 The inter articular ligament is a thin band which passes be- tween the sharp crest on the head of the rib and the interverte- bral substance. It divides the joint into two cavities, which are each furnished with a separate synovial membrane. The first, eleventh, and twelfth ribs have no interarticular ligament, and consequently but one synovial membrane. The anterior costo-transverse ligament is a broad band com- posed of two fasciculi, which ascend from the crest-like ridge on the neck of the rib, to the transverse process immediately above. This ligament separates the anterior from the dorsal branch of the intercostal nerve. The middle costo-transverse ligament is a very strong inter- osseous ligament, passing directly between the posterior surface of the neck of the rib, and the transverse process against which it rests. The posterior costo-transverse ligament is a small but strong fasciculus, passing obliquely from the tubercle of the rib to the apex of the transverse process. The articulation between the tubercle of the rib and the transverse process, is provided with a small synovial membrane. There is no anterior costo-transverse ligament to the first or last rib ; and only rudimentary posterior costo-transverse liga- ments to the eleventh and twelfth ribs. ACTIONS. The movements permitted by the articulations of the ribs are upwards and downwards, and slightly forwards a*nd backwards; the movement increasing in extent from the head to the extremity of the rib. The forward and backward movement is very trifling in the seven superior, but greater in the inferior ribs ; the eleventh and twelfth are very movable. 7. Articulation of the Ribs with the Sternum, and with each other. The ligaments of the costo-sternal articulations are Anterior costo-sternal, Superior costo-sternal, Posterior costo-sternal, Inferior costo-sternal, Synovial membranes. The anterior costo-sternal ligament is a thin band of ligament- ous fibres, passing in a radiated direction from the extremity of the costal cartilage to the anterior surface of the sternum, and intermingling its fibres with those of the ligament of the oppo- site side, and with the tendinous fibres of origin of the pectoralis major muscle. The posterior costo-sternal ligament is much smaller than the anterior ; and consists of a thin fasciculus of fibres, situated on the posterior surface of the articulation. The superior and inferior costo-sternal ligaments are narrow fasciculi, corresponding with the breadth of the cartilage, and 46 542 THE DISSECTOR. connecting its superior and inferior borders with the side of the sternum. The synovial membrane is absent in the articulation of the first rib, its cartilage being usually continuous with the sternum ; that of the second rib has an interarticular ligament, with two synovial membranes. The sixth and seventh ribs have several fasciculi of strong lig- amentous fibres, passing from the extremity of their cartilages to the anterior surface of the ensiform cartilage, which latter they are intended to support. They are named the costo-xyphoid ligaments. The sixth, seventh, and eighth, and sometimes the ffth and the ninth costal cartilages, have articulations with each other, and a perfect synovial membrane at each articulation. They are con- nected by ligamentous fibres which pass from one cartilage to the other, external and internal ligaments. The ninth and tenth are connected at their extremities by liga- mentous fibres, but have no synovial membranes. ACTIONS. The movements of the costo-sternal articulations are very trifling ; they are limited to a slight degree of sliding motion. The first rib is the least, and the second the most movable. 8. Articulations of the Sternum. The pieces of the sternum are connected by means of a thin plate of fibro-cartilage placed between each, and by an anterior and posterior ligament. The fibres of the anterior sternal ligament are longitudinal in direc- tion, but so blended with the anterior costo-sternal ligaments, and the tendinous fibres of origin of the pectoral muscles, as scarcely to be distinguished as a distinct ligament. The posterior sternal ligament is a broad smooth plane of longitudinal fibres, placed upon the posterior surface of the bone, and extending from the manubrium to the ensiform cartilage. These ligaments contribute very materially to the strength of the sternum, and to the elasticity of the front of the chest. 9. Articulation of the Vertebral Column with the Pelvis. The last lumbar vertebra is connected with the sacrum by the same ligaments with which the various vertebra are connected to each other ; viz : anterior and posterior common ligaments, interverte- bral substance, ligainenta subflava, capsular ligaments, and inter and supra-spinous ligaments. There are, however, two proper ligaments connecting the ver- tebral column with the pelvis ; these are, the Lumbo-sacral, Lumbo-iliac. The lumbo-sacral or sacro-vertehral ligament is a thick trian- gular fasciculus of ligamentous fibres, connected, above, with the transverse process of the last lumbar vertebra; and, below, with the posterior part of the upper border of the sacrum. ARTICULATIONS OF THE PELVIS. 543 The lumbo-iliac or ilio-lumbar ligament passes from the apex of the transverse process of the last lumbar vertebra, to that part of the crest of the ilium which surmounts the sacro-iliac articula- tion. It is triangular in form. 10. Articulations of the Pelvis. The ligaments belonging to the articulations of the pelvis are divisible into four groups : (1.) those connecting the sacrum and ilium ; (2.) those passing between the sacrum and ischium ; (3.) between the sacrum and coccyx; (4 ) between the two pubic bones. 1st. Between the sacrum and ilium: Sacro-iliac anterior, Sacro-iliac posterior. 2d. Between the sacrum and ischium : Sacro-ischiatic anterior (short), Sacro-ischiatic posterior (long). 3d. Between the sacrum and coccyx : Sacro-coccygean anterior, Sacro-coccygean posterior. 4th. Between the ossa pubis : Anterior pubic, Posterior pubic, Superior pubic, Subpubic, Interosseous fibro-cartilage. (1.) Between the Sacrum and Ilium. The anterior sacro-iliac liijnment consists of numerous short ligamentous fibres, which pass from bone to bone on the anterior surface of the joint. The posterior sacro-iliac or interosseous ligament is composed of numerous strong fasciculi of ligamentous fibres, which pass horizontally between the rough surfaces of the posterior half of the sacro-iliac articulation, and constitute the principal bond of connection between the sacrum and the ilium. One fasciculis of tliis ligament, longer and larger than the rest, is distinguished, from its direction, by the name of the oblique sacro-iliac ligament. It is attached by one extremity to the posterior superior spine of the ilium, and by the other to the third transverse tubercle on the posterior surface of the sacrum. The surfaces of the two bones forming the sacro-iliac articula- tion are partly covered with cartilage, and partly rough and con- nected by the interosseous ligament. The anterior or auricular half is coated with cartilage, which is thicker on the sacrum than on the ilium. The surface of the cartilage is irregular and provided with a very delicate synovial membrane, which cannot 544 THE DISSECTOR. be demonstrated in the adult, but is apparent in the young sub- ject, and in the female during pregnancy. (2.) Between the Sacrum and Ischium. The anterior or lesser sacro ischiatic ligament is thin, and triangular in form. It is attached by its apex to the spine of the ischium, and by its broad extremity to the side of the sacrum and coccyx, interlacing its fibres with the greater sacro-ischiatic ligament. The anterior sacro-ischiatic ligament is in relation, in front with the coccygeus muscle, and behind with the posterior liga- ment, with which its fibres are intermingled. By its upper border it forms part of the lower boundary of the great sacro- ischiatic foramen; and by the lower, part of the lesser sacro-ischi- atic foramen. The posterior or greater sacro-ischiatic ligament, considerably larger, thicker, and more posterior than the preceding, is nar- rower in the middle than at each extremity. It is attached, by its smaller end, to the inner margin of the tuberosity and ramus of the ischium, where it forms a falciform process, which pro- tects the internal pudic artery and is continuous with the obtura- tor fascia. By its larger extremity it is inserted into the side of the coccyx, sacrum, and posterior inferior spine of the ilium. The posterior sacro-ischiatic ligament is in relation, in front, with the anterior ligament, and behind with the gluteus maximus, to some of the fibres of which it gives origin. By its superior border it forms part of the boundary of the lesser ischiatic fora- men, and by its lower border a part of the boundary of the peri- neum. It is pierced by the coccygeal branch of the ischiatic artery. The two ligaments convert the sacro-ischiatic notches into foramina. (3.) Between the Sacrum and Coccyx. The anterior sacro- coccygean ligament is a thin fasciculus passing from the anterior surface of the sacrum to the front of the coccyx. The posterior sacro-coccygean ligament is a thick ligamentous layer, which completes the lower part of the sacral canal, and connects the sacrum with the coccyx posteriorly, extending as far as the apex of the latter bone. Between the two bones is a thin disk of soft fibrous cartilage. In females there is frequently a small synovia! membrane. This articulation admits of a certain degree of movement backwards during parturition. The ligaments connecting the different pieces of the coccyx consist of a few scattered anterior and posterior fibres and a thin disk of fibro-cartilage. They exist only in the young subject; in the adult the pieces become ossified. (4.) Between the Ossa Pubis. The anterior pubic ligament is composed of ligamentous fibres, which pass obliquely across ARTICULATIONS OP THE CLAVICLE. 545 the union of the two bones from side to side, and form an inter- lacement in front of the symphysis. The posterior pubic ligament consists of a few irregular fibres uniting the pubic bones posteriorly. The superior pubic ligament is a thick band of fibres connect- ing the angles of the pubic bones superiorly, and filling the in- equalities upon the surface of the bones. The subpubic ligament is a thick arch of fibres connecting the two bones inferiorly, and forming the upper boundary of the pubic arch. The interosseous jibro-cartilage unites the two surfaces of the pubic bones in the same manner as the intervertebral substance connects the bodies of the vertebrae. It resembles the interver- tebral substance also in being composed of oblique fibres disposed in concentric layers, which are more dense towards the surface than near the centre. It is thick in front, and thin behind. A synovial membrane is sometimes found in the posterior half of the articulation. This articulation becomes movable towards the latter term of pregnancy, and admits of a slight degree of separation of its surfaces. The obturator ligament or membrane is not a ligament of arti- culation, but simply a fibrous membrane stretched across the obturator foramen. It gives attachment by its surfaces to the two obturator muscles, and leaves a space in the upper part of the foramen, for the passage of the obturator vessels and nerve. The numerous vacuities in the walls of the pelvis, and their closure by ligamentous structures, as in the case of the sacro- ischiatic fissures and obturator foramina, serve to diminish very materially the pressure on the soft parts during the passage of the head of the foetus through the pelvis in parturition. LIGAMENTS OP THE UPPER EXTREMITY. The ligaments of the upper extremity may be arranged in the order of the articulations between the different bones. They are the 1. Sterno-clavicular articulation, 2. Scapulo-clavicular articulation, 3. Ligaments of the scapula, 4. Shoulder-joint, 5. Elbow-joint, 6. Radio-ulnar articulation, 7. Wrist-joint, 8. Articulation between the carpal bones, 9. Carpo-metacarpal articulation, 46* 546 THE DISSECTOR. 10. Metacarpo-phalangeal articulation, 11. Articulation of the phalanges. 1. Sterno-clavicular Articulation. The sterno-clavicular is an arthrodial articulation. Its ligaments are Anterior sterno-clavicular, Posterior sterno-clavicular, Interclavicular, Costo-clavicular (rhomboid), Interarticular fibro-cartilage, Two synovial membranes. The anterior sterno-clavicular ligament is a broad ligamentons layer extending obliquely downwards and inwards, covering the anterior aspect of the articulation. The ligament is in relation by its anterior surface with the integument and sternal origin of the sterno-mastoid muscle ; behind with the interarticular fibro- cartilage and synovial membranes. The posterior sterno-clavicular ligament is a broad fasciculus, covering the posterior surface of the articulation. It is in rela- tion by its anterior surface with the interarticular fibro-cartilage and synovial membranes, and behind with the sterno-hyoid and sterno-thyroid muscles. The two ligaments are continuous at the upper and lower part of the articulation, so as to form a complete capsule around the joint. The interclavicular ligament is a cord-like band which crosses from the extremity of one clavicle to that of the other, and is closely connected with the upper border of the sternum. It is separated by cellular tissue from the sterno-thyroid muscles. The costo-clavicular ligament (rhomboid), is a thick fasciculus of fibres, connecting the sternal extremity of the clavicle with the cartilage of the first rib. It is situated obliquely between the rib and the under surface of the clavicle, and is in relation in front with the tendon of origin of the subclavius muscle, and behind with the subclavian vein. It is the rupture of the rhomboid ligament in dislocation of the ster- nal end of the clavicle, that gives rise to the deformity peculiar to this accident. The interarticular Jibro-cartilage is nearly circular in form, and thicker at the edges than in the centre. It is attached, above to the clavicle, below to the cartilage of the first rib, and throughout the rest of its circumference to the anterior and pos- terior sterno-clavicular ligaments. It divides the joint into two cavities, which are lined by distinct synovial membranes. This cartilage is sometimes pierced through its centre, and not unfre- quently deficient, to a greater or less extent, at its lower part. ARTICULATIONS OF THE CLAVICLE. 54T ACTIONS. The movements of the sterno-clavicular articulation are, a gliding movement of the fibro-cartilage with the clavicle, upon the articu- lar surface of the sternum, in the direction, forwards, backwards, up- wards, and downwards ; and circumduction. This articulation is the centre of the movements of the shoulder. Dislocations. The dislocations of the sternal extremity are two, for- wards and backwards. The dislocation forwards may be partial. The Dislocation forwards, if complete, is accompanied by the rupture of all the ligaments of the joint. The Dislocation backivards is extremely rare. Sir Astley Cooper re- cords only a single case, which occurred in consequence of distortion of the spine. 2. Sea pulo- clavicular Articulation. The ligaments of the sca- pular end of the clavicle are the Superior acromio-clavicular, Inferior acromio-clavicular, Coraco-clavicular (trapezoid and conoid). Interarticular fibro-cartilage, Two synovial membranes. The superior acromio-clavicular ligament is a moderately thick plane of fibres passing between the extremity of the clavicle and acromion, on the upper surface of the joint. The inferior acromio- clavicular ligament is a thin plane situ- ated on the under surface. These two ligaments are continuous with each other in front and behind, and form a complete capsule around the joint. The coraco-clavicular ligament (trapezoid, conoid), is a thick fasciculus of ligamentous fibres, passing obliquely between the base of the coracoid process and the under surface of the clavi- cle, and holding the end of the clavicle in firm connection with the scapula. When seen from before, it has a quadrilateral form ; hence it is named trapezoid: and examined from behind, it has a triangular form, the base being upwards ; hence another name, conoid. The interarticular fibro-cartilage is often indistinct, from hav- ing partial connections with the fibro-cartilaginous surfaces of the two bones between which it is placed; and is not unfre- quently absent. When partial, it occupies the upper part of the articulation. The synovial membranes are very delicate. There is, of course, but one when the fibro-cartilage is incom- plete. ACTIONS. The acromio-clavicular articulation admits of two move- ments ; gliding of the surfaces upon each other, and rotation of the sca- pula upon the extremity of the clavicle. /ti.-iliH-ntions. The scapular end of the clavicle can be dislocated in one direction only, viz : upwards. If the dislocation be severe, the coraco- clavicular ligament is completely ruptured. It is a more frequent acci- dent than dislocation of the sternal end of the clavicle. 548 THE DISSECTOR. The proper ligaments of the scapula are the Coraco-acromial, Transverse. The coraco-acromial ligament is a broad and thick triangular band, which forms a protecting arch over the shoulder-joint. It is attached, by its apex, to the point of the acromion process ; and, by its base, to the external border of the coracoid process its whole length. This ligament is in relation, above, with the under surface of the deltoid muscle ; and below, with the tendon of the supra-spinatus muscle, a bursa mucosa being usually inter- posed. The transverse or coracoid ligament is a narrow but strong fasciculus, which crosses the notch in the upper border of the scapula from the base of the coracoid process, and converts it into a foramen. The supra-scapular nerve passes through this foramen ; the artery, over it. 4. Shoulder- Joint. The scapulo-humeral articulation is an enarthrosis, or ball-and-socket joint ; its ligaments are, the Capsular, Coraco-humeral, Glenoid. The capsular ligament completely encircles the articulating head of the scapula and head of the humerus, and is attached to the neck of each bone. It is thick above, where resistance is most required, and strengthened by the tendons of the supra- spinatus, infra-spinatus, teres minor, and subscapularis muscles ; below, it is thin and loose. The capsule is incomplete at the point of contact with the tendons, so that they obtain, upon their inner surface, a covering of synovial membrane. The coraco-humeral ligament is a broad band which descends obliquely outwards, from the border of the coracoid process to the greater tuberosity of the humerus, and serves to strengthen the superior and anterior part of the capsular ligament. The glenoid ligament is the prismoid band of fibro-cartilage, which is attached around the margin of the glenoid cavity, for the purposes of protecting its edges and deepening its cavity. It divides, superiorly, into two slips, which are continuous with the long tendon of the biceps ; hence the ligament is fre- quently described as being formed by the splitting of that tendon. The cavity of the articulation is traversed by the long tendon of the biceps, which is inclosed in a sheath of synovial membrane in its passage through the joint. The synovial membrane of the shoulder-joint is extensive ; it communicates, anteriorly, through an opening (foramen ovale) in the capsular ligament with a large bursal sac, which lines the under surface of the tendon of the subscapularis muscle. Supe- riorly, it frequently communicates through another opening in the capsular ligament, with a bursal sac belonging to the infra- ARTICULATION OP THE ELBOW. 549 spinatus muscle; and it, moreover, forms a sheath around that portion of the tendon of the biceps, which is included within the joint. ACTIONS. The shoulder joint is capable of every variety of motion, viz : of movement forwards and backwards, of abduction and adduction, of circumduction and rotation. invocations. The dislocations of the head of the humerus are/owr in number : 1. Downwards, and inwards, into the axilla. 2. Forwards, under the pectoral muscles. 3. Backwards, on the dorsum of the scapula. 4. Partial, when the anterior part of the capsular ligament is torn through, and the head of the bone rests against the coracoid process. The muscles immediately surrounding the shoulder-joint are, the sub- scapularis, supra-spinatus, infra-spinatus, teres minor, long head of the triceps, and deltoid ; the long tendon of the biceps is within the capsular ligament. 5. Elbow-Joint. The elbow is a ginglymoid articulation ; its ligaments &refour in number : Anterior, Internal lateral, Posterior, External lateral. The anterior ligament is a broad and thin membranous layer, descending from the anterior surface of the humerus, immediately above the joint, to the coronoid process of the ulna and orbicular ligament. On each side, it is connected with the lateral liga- ments. It is composed of fibres which pass in three different directions ; vertical, transverse, and oblique, the latter being ex- tended downwards and outwards to the orbicular ligament, into which they are attached inferiorly. This ligament is covered in by the brachialis anticus muscle. The posterior ligament is a broad and loose layer, passing between the posterior surface of the humerus and the anterior surface of the base of the olecranon, and connected at each side with the lateral ligaments. It is covered in by the tendon of the triceps. The internal lateral ligament is a thick triangular layer, at- tached above, by its apex, to the internal condyle of the humerus; and below, by its expanded border, to the margin of the greater sigmoid cavity of the ulna, extending from the coronoid process to the olecranon. At its insertion it is intermingled with some transverse fibres. The internal lateral ligament is in relation posteriorly with the ulnar nerve. The external lateral ligament is a strong and narrow band, which descends from the external condyle of the humerus, to be inserted into the orbicular ligament, and into the ridge on the ulna, with which the posterior part of the latter ligament is con- 550 THE DISSECTOE. nected. This ligament is closely united with the tendon of ori- gin of the supinator brevis muscle. The synovial membrane is extensive, and is reflected from the cartilaginous surfaces of the bones upon the inner surface of the ligaments. It surrounds, inferiorly, the head of the radius, and forms an articulating sac between it and the lesser sigmoid notch. ACTIONS. The movements of the elbow-joint are, flexion and extension, which are performed with remarkable precision. The extent to which these movements are capable of being effected, is limited, in front by the coronoid process, and behind by the olecranon. Dislocations. The dislocations occurring at this articulation are Jive in number : 1. Radius and ulna, backwards. 2. Radius and ulna, to either side. 3. Ulna, backwards. 4. Radius, forwards. 5. Radius, backwards. This is a very rare accident. In the two latter dislocations, the annular ligament of the head of the radius is ruptured. The muscles immediately surrounding, and in contact with the elbow- joint are, in front, the brachialis anticus ; to the inner side, the pronator radii teres, flexor sublimis digitorum, and flexor carpi ulnaris ; exter- nally, the extensor carpi radialis brevior, extensor communis digitorum, extensor carpi ulnaris, anconeus, and supinator brevis ; and behind, the triceps. 6. The Radio-ulnar Articulation. The radius and ulna are firmly held together by ligaments which are connected with both extremities of the bones, and with the shaft; they are, the Orbicular, Anterior inferior, Oblique, Posterior inferior, Interosseous, Interarticular fibro-cartilage. The orbicular ligament (annular, coronary), is a firm band several lines in breadth, which surrounds the head of the radius, and is attached by each end to an extremity of the lesser sigmoid cavity. It is strongest behind where it receives the external lateral ligament, and is lined on its inner surface by a reflection of the synovial membrane of the elbow-joint. The rupture of this ligament permits the dislocation of the bead of the radius. The oblique ligament (called also ligamentum teres, in contra- distinction to the interosseous ligament), is a narrow slip of liga- mentous fibres, descending obliquely from the base of the coronoid process of the ulna to the inner side of the radius, a little below its tuberosity. The interosseous ligament is a broad and thin plane of aponeu- rotic fibres passing obliquely downwards, from the sharp ridge ARTICULATION OP THE WRIST. 551 on the radius to that on the ulna. It is deficient superiorly, is broader in the middle than at each extremity, and is perforated at its lower part for the passage of the anterior interosseous ar- tery. The posterior interosseous artery passes backwards, be- tween the oblique ligament and the upper border of the interos- seous ligament. This ligament affords an extensive surface for the attachment of muscles. The interosseous ligament is in relation, in front, with the flexor profundus digitorum, flexor longus pollicis, pronator quadratus, and anterior interosseous artery and nerve ; behind, with the supinator l>rc vis, extensor ossis metacarpi pollicis, extensor primi iuternodii pol- licis, extensor secundi internodii pollicis, extensor indicis ; and near the wrist, with the anterior interosseous artery and posterior interosseous nerve. The anterior inferior ligament is a thin fasciculis of fibres, passing transversely between the radius and ulna. The posterior inferior ligament is also thin and loose, and has the same disposition on the posterior surface of the articula- tion. The interarticular, or triangular fibro-cartilage, acts the part of a ligament, between the lower extremities of the radius and ulna. It is attached, by its apex, to a depression on the inner surface of the styloid process of the ulna ; and by its base, to the edge of the radius. This fibro-cartilage is lined, upon its upper surface, by a synovial membrane, which forms a duplicature be- tween the radius and ulna, and is called the membrana saccifur- mis. By its lower surface it enters into the articulation of the wrist-joint. ACTIONS. The movements taking place between the radius and the ulna are, the rotation of the former upon the latter ; rotation forwards being termed pronation, and rotation backwards supination. In these movements the head of the radius turns upon its own axis within the orbicular ligament and lesser sigmoid notch of the ulna ; while, inferiorly, the radius presents a concavity which moves upon the rounded head of the ulna. The movements of the radius are chiefly limited by the an- terior and posterior inferior ligaments, hence these are not unfrequently ruptured in great muscular efforts. 1 Dislocations. The dislocation of these two bones from each other at the upper end, have been indicated in the dislocations occurring at the elbow-joint. They are, the displacement of the head of the radius for- wards and backwards, and are accompanied with rupture of the annular ligament. At the lower end of the two bones, the ulna may be separated from the radius by the rupture of the connections of the interarticular fibro-cartilaga. 7. Wrist-Joint. The wrist is a ginglymoid articulation ; the articular surfaces entering into its formation being the radius and under surface of the triangular fibro-cartilage above, and the rounded surfaces of the scaphoid, semilunar, and cuneiform bone below ; its ligaments are four in number : 552 THE DISSECTOR. Anterior, Internal lateral, Posterior, External lateral. The anterior ligament is a broad and membranous layer, consisting of three fasciculi, which pass between the lower part of the radius and the scaphoid, semilunar, and cuneiform bones. The posterior ligament, also thin and loose, passes between the posterior surface of the radius, and the posterior surface of the semilunar and cuneiform bones. The internal lateral ligament extends from the styloid process of the ulna to the cuneiform and pisiform bones. The external lateral ligament is attached, by one extremity, to the styloid process of the radius, and by the other, to the side of the scaphoid bone, some of its fibres being prolonged to the tra- pezium. The radial artery rests on this ligament, as it passes backwards to the first metacarpal space. The synovial membrane of the wrist-joint lines the under sur- face of the radius and interarticular cartilage above, and the first row of bones of the carpus below. The relations of the wrist-joint are, the flexor and extensor tendons by which it is surrounded, and the radial and ulnar artery. ACTIONS. The movements of the wrist-joint are flexion, extension, ^ad- duction, abduction, and circumduction. In these motions the articular surfaces glide upon each other. Dislocations. The dislocations at the wrist-joint are of three kinds : 1. Of both bones, backwards or forwards ; a rare accident. 2. Of the radius, for 10 ards. 3. Of the ulna, from its connection with the radius. 8. Articulations between the Carpal Bones. These are amphi- arthrodial joints, with the exception of the conjoined head of the os magnum and unciforme, which is received into a cup formed by the scaphoid, semilunar, and cuneiform bones, and constitutes an enarthrosis. The ligaments are Dorsal, Interosseous fibro-cartilages, Palmar, Anterior annular. The dorsal ligaments are ligamentous bands, that pass trans- versely and longitudinally from bone to bone, upon the dorsal surface of the carpus. The palmar ligaments are fasciculi of the same kind, but stronger than the dorsal, having the like disposition on the pal- mar surface. The interosseous ligaments are fibro-cartilaginous lamellae situ- ated between the adjoining bones in each range : in the upper range, they close the upper part of the spaces between the sca- phoid, semilunar, and cuneiform bones ; in the lower range, they are stronger than in the upper, and connect the os magnum on ARTICULATIONS OF THE WRIST. 553 the one side to the unciforme, on the other to the trapezoides, and leave intervals through which the synovial membrane is con- tinued to the bases of the metacarpal bones. * The anterior annular ligament is a firm ligamentous band, which connects the bones of the two sides of the carpus. It is attached, by one extremity, to the trapezium and scaphoid, and by the other, to the unciform process of the unciforme and base of the pisiform bone ; it forms an arch over the anterior sur- face of the carpus, beneath which the tendons of the long flexors and the median nerve pass into the palm of the hand. The articulation of the pisiform bone with the cuneiform is provided with a distinct synovial membrane, which is protected by fasciculi of ligamentous fibres, forming a kind of capsule around the joint ; they are inserted into the cuneiform, unci- form, and base of the metacarpal bones of the little finger. Synovial Membranes. There are five synovial membranes, entering into the composition of the articulations of the carpus : The first is situated between the lower end of the ulna and the interarticular fibro-cartilage ; it is called sacciform, from forming a sacculus between the lateral articulation of the ulna with the radius. The second is situated between the lower surface of the radius and interarticular fibro-cartilage above, and the first range of bones of the carpus below. The third is the most extensive of the synovial membranes of the wrist; it is situated between the two rows of carpal bones, and passes between the bones of the second range, to invest the carpal extremities of the four metacarpal bones of the fingers. The fourth is the synovial membrane of the articulation of the metacarpal bone of the thumb with* the trapezium. The fifth is situated between the pisiform and cuneiform bones. ACTIONS. Very little movement exists between the bones in each range, but more is permitted between the two ranges. The motions in tin- latter situation are those of flexion and extension. 1 > /.^locations. The dislocation of a carpal bone from violence is of very rare occurrence. The os magnum and cuneiform bones are sometimes par- tially dislocated from relaxation of their ligaments ; this is more frequent in the former than in the latter bone. 9. The Carpo-metacarpal Articulations. The second row of bones of the carpus articulates with the metacarpal bones of the four fingers, by dorsal and palmar ligaments-; and the me- tacarpal bone of the thumb with the trapezium, by a true cap- sul-ir I'njament. There is also in the carpo-metacarpal articula- tion a thin iuterosseous band, which passes from the ulnar edge 47 554 THE DISSECTOR. of the os magnum to the bases of the third and fourth metacar- pal bones at their point of connection. The dorsal ligaments are strong fasciculi which pass from the second range of carpal to the metacarpal bones ; with the ex- ception of the little finger, there are two fasciculi to each bone ; namely, to the index finger, one each from the trapezium and trapezoides ; to the middle finger, one each from the trapezoides and os magnum ; to the ring finger, one each from the os mag- num and unciform ; and to the little finger, one from the unci- form. The palmar ligaments are thin fasciculi, arranged upon the same plan on the palmar surface. The synovial membrane is a continuation of the great synovial membrane of the two rows of carpal bones. The capsular ligament of the thumb is one of the three true capsular ligaments of the skeleton ; the other two being the shoulder-joint and hip-joint. The articulation has a proper sy- novial membrane. The metacarpal bones of the four fingers are firmly connected at their bases by means of dorsal and palmar ligaments, which extend transversely from one bone to the other, and by interos- seous ligaments, which pass between their contiguous surfaces. Their lateral articular facets are lined by a reflection of the great synovial membrane of the two rows of carpal bones. ACTIONS. The movements of the metacarpal on the carpal bones are restricted to a slight degree of sliding motion, with the exception of the articulation of the metacarpal bone of the thumb with the trapezium. In the latter articulation the movements are: flexion, extension, adduction, abduction, and circu induction. Dislocations of these articulations only occur from great violence, as the bursting of a gun, or the crushing of the hand by a great weight. The kind of displacement depends therefore upon the nature of the in- jury, and not upon the peculiar conformation of the joint. The metacarpal bone of the thumb may be dislocated from the trape- zium, and thrown inwards, so as to rest between the trapezium and the base of the metacarpal bone of the index finger. 10. Metacarpo-phalangeal Articulation. The metaearpo-pha- langeal articulation is a ginglymoid joint; its ligaments are four in number : Anterior, Two lateral, Transverse. The anterior ligaments are thick and fibro-cartila^inous, and form part of the articulating surface of the joints. They are grooved, externally, for the lodgement of the flexor tendons, and by their internal aspect form part of the articular surface for the head of the metacarpal bone. They are continuous at each side with the lateral ligaments. ARTICULATIONS OF THE PHALANGES. 555 The lateral ligaments are strong narrow fasciculi, holding the bones together at each side. The transverse ligament is a strong ligamentons band, passing across the heads of the raetacarpal bones of the four fingers, and connected with the anterior ligaments. The expansion of the extensor tendon over the back of the fingers takes the place of a posterior ligament. ACTIONS. The articulation admits of movement in four different direc- tions, viz : of flexion extension, adduction, and abduction, the two latter being limited "to a small extent. It is also capable of cir conduction. Dislocations. The observations upon the dislocations of the bases of the metacarpal bones, relate also to their heads. The first phalanx of the thumb may be dislocated backwards, so as to rest with its base upon the metacarpal bone. This accident is frequently rendered compound by laceration of the integument. 11. Articulation of the Phalanges. These articulations are ginglymoid joints; they are formed by three ligaments. Anterior, Two lateral. The anterior ligament is firm and fibro-cartilaginous, and forms part of the articular surface for the head of the phalanges. Exter- nally, it is grooved for the reception of the flexor tendons. The lateral ligaments are very strong; they are the principal bond of connection between the bones. The extensor tendon takes the place and performs the office of a posterior ligament. ACTIONS. The movements of the phalangeal joints are flexion and ex- tension, these movements being more extensive between the first and second phalanges than between the second and third. J Dislocations. The second phalanges are but rarely dislocated from the first. The last phalanges are dislocated from the second backwards ; the base of the last phalanx resting upon the back of the second beneath the extensor tendon. The same dislocation occurs in the thumb. In connection with the phalanges it may be proper to examine certain fibrous bands termed thecce or vaginal ligaments, which serve to retain the tendons of the flexor muscles in their position u pon the flat surface of the bones. These fibrous bands are attached at each side to the lateral margins of the phalanges; they are thick in the interspaces of the joints, thin where the tendons lie upon the joints, and are lined upon their inner surface by synovial membrane. LIGAMENTS OF THE LOWER EXTREMITY. The ligaments of the lower extremity, like those of the upper, may be arranged in the order of the joints to which they belong; these are, the 1. Hip-joint. 2. Knee-joint. 556 THE DISSECTOR. 3. Articulation between the tibia and fibula. 4. Ankle-joint. 5. Articulation of the tarsal bones. 6. Tarso-metatarsal articulation. 7. Metatarso-phalangeal articulation. 8. Articulation of the phalanges. 1. Hip-Joint. The articulation of the head of the femur with the acetabulum constitutes an enarthrosis, or ball-and-socket joint. The articular surfaces are the cup-shaped cavity of the acetabulum and the rounded head of the femur; the ligaments are Jive in number, viz : Capsular, Teres, Ilio-fernoral, Cotyloid, Transverse. The capsular ligament is a strong ligamentous capsule, em- bracing the acetabulum superiorly, and inferiorly the neck of the femur, and connecting the two bones firmly together. It is much thicker upon the upper part of the joint, where more resistance is required, than upon the under part, and extends further upon the neck of the femur on the anterior and superior than on the posterior and inferior side, being attached to the inter-trochan- teric line in front, to the base of the great trochanter above, and to the middle of the neck of the femur behind. The ilio-femoral ligament is an accessory and radiating band, which descends obliquely from the anterior inferior spinous pro- cess of the ilium to the anterior inter-trochanteric line, and strengthens the anterior portion of the capsular ligament. The ligamentum teres, triangular in shape, is attached, by a round apex, to the depression just below the middle of the head of the femur, and by its base, which divides into two fasciculi, into the borders of the notch of the acetabulum. It is formed by a fasciculus of fibres, of variable size, surrounded by synovial membrane ; sometimes the synovial membrane alone exists, or the ligament is wholly absent. The cotyloid ligament is a prismoid cord of fibre-cartilage, attached around the margin of the acetabulum, and serving to deepen that cavity and protect its edges. It is much thicker upon the upper and posterior border of the acetabulum than in front, and consists of fibres which arise from the whole circum- ference of the brim, and interlace with each other at acute angles. It is directed inwards towards the acetabulum. The transverse ligament is a strong fasciculus of ligamentous fibres, continuous with the cotyloid ligament, and extended across the notch of the acetabulum. It converts the notch into a fora- ARTICULATION OP THE KNEE. 557 men, through which the articular branches of the internal cir- cumflex and obturator arteries enter the joint. The fossa at the bottom of the acetabulum is filled by a mass of fat covered by synovial membrane, which serves as an elastic cushion for the head of the bone during its movements. This was considered by Havers as the synovial gland. The synovial membrane is extensive; it invests the head of the femur, and is continued around the ligamentum teres into the acetabulum, whence it is reflected upon the inner surface of the capsular ligament back to the head of the bone. The muscles immediately surrounding and in contact with the hip- joint are, in front, the psoas and iliacus, which are separated from the ( apsular ligament by a large synovial bursa ; above; the short head of the rectus and the gluteus minimus; behind, the pyriformis, gemellus superior, obturator internus, gemellus inferior, and quadratus femoris ; and to the inner side, the obturator externus and pectineus. ACTIONS. The movements of the hip-joint are very extensive ; they are : flexion, extension, adduction, abduction, circumduction, and rotation. Dislocations. The dislocations of the hip-joint are four in number: 1. Upwards, upon the dorsum of the ilium. 2. Downwards, into the foramen ovale. 3. Backwards and upwards, into the ischiatic notch. 4. Forwards and upwards, upon the body of the pubes. 2. Knee-Joint. The knee is a ginglyinoid articulation of large size, and is provided with numerous ligaments; they are thirteen in number: Anterior or ligamentum patella, Posterior or ligamentum posticum Winslowii, Internal lateral, Two external lateral, Anterior or external crucial, Posterior or internal crucial, Transverse, Two coronary. Two semilunar fibro-cartilages, Synovial membrane. The first Jive are external to the articulation ; the next five are internal to the articulation; the remaining three are mere folds of synovial membrane, and have no title to the name of ligaments. In addition to the ligaments, there are two fibro- cartilages, and a synovial membrane. The anterior ligament, or ligamentum patella, is the prolonga- tion of the tendon of the extensor muscles of the thigh down- wards to the tubercle of the tibia. It is, therefore, no ligament ; and, as the patella is simply a sesamoid bone developed in the 47* 558 THE DISSECTOR. tendon of the extensor muscles for the defence of the front of the knee-joint, the ligamentum patellae lias no title to consider- ation, either as a ligament of the knee-joint or as a ligament of the patella. A small bursa mucosa is situated between the ligamentum patellae near its insertion and the front of the tibia, and another of large size is placed between the anterior surface of the patella ancUthe fascia lata. It is the latter which is inflamed in the "housemaid's knee." The posterior ligament, ligamentum posticum Winslowii, is a broad expansion of ligamentous fibres, which covers the whole of the posterior part of the joint. It is divisible into two lateral portions, which invest the condyles of the femur, and a central portion which is depressed, and is formed by the interlacement of fasciculi passing in different directions. The strongest of these fasciculi is that which is derived from the tendon of the semi- membranosus ; it passes obliquely upwards and outwards from the posterior part of the inner tuberosity of the tibia, to the ex- ternal condyle of the femur. Other accessory fasciculi are given off by the tendon of the popliteus and by the heads of the gas- trocnemius. The middle portion of the ligament supports the popliteal artery and vein, and is perforated by several openings for the passage of branches of the azygos articular artery and for the nerves of the joint. * '* The internal lateral ligament is a broad and trapezoid layer of ligamentous fibres, attached, above, to the tubercle on the inter- nal condyle of the femur; and below, to the inner tuberosity of the tibia. It is crossed, at its lower part, by the tendons of the inner hamstring from which it is separated by a synovial bursa, and it covers in the anterior slip of the semi-membranosus tendon and the inferior internal articular artery. External lateral Ligament. The long external lateral ligament is a strong rounded cord, which descends from the posterior part of the tubercle upon the external condyle of the femur, to the outer part of the head of the fibula. The short external lateral ligament is an irregular fasciculus situated behind the preceding, arising from the external condyle near the origin of the head of the gastrocnemius muscle, and inserted into the posterior part of the head of the fibula. It is firmly connected with the external sernilunar fibro-cartilage, and appears principally intended to connect that cartilage with the fibula. The long external lateral ligament is covered in by the tendon of the biceps, and has pass- ing beneath it the tendon of origin of the popliteus muscle, and the inferior external articular artery. The true ligaments within the Joint are, the crucial, transverse, and coronary. ARTICULATION OF THE KNEE. 559 The anterior, or external crucial ligament, arises from the de- pression upon the head of the tibia in front of the spinous pro- cess, and passes upwards and backwards, to be inserted into the inner surface of the- outer condyle of the femur, as far as its pos- terior border. It is smaller than the posterior. The posterior, or internal crucial ligament arises from the de- pression upon the head of the tibia, behind the spinous process, and passes upwards and forwards, to be inserted into the inner condyle of the femur. This ligament is less oblique and larger than the anterior. The transverse ligament is a small slip of fibres, which extends transversely from the external semilunar fibro-cartilage, near its anterior extremity, to the anterior convexity of the internal carti- lage. The coronary ligaments are the short fibres by which the con- vex borders of the semilunar cartilages are connected to the head of the tibia, and to the ligaments surrounding the joint. The semilunar Jtbro-cartilages are two falciform plates of fibro- cartilage, situated upon the margin of the head of the tibia, and serving to deepen the surface of articulation for the condyles of the femur. They are thick along their convex border, and thin and sharp along their concave edge. The internal semilunar fibro-cartilage forms an oval cup for the reception of the internal condyle of the femur; it is connected, by its convex border, to the head of the tibia and to the internal and posterior ligaments, by means of its coronary ligament ; and by its two extremities is firmly implanted into the depressions in front of and behind the spinous process. The external semilunar fibro- cartilage bounds a circular fossa for the external condyle; it is connected by its convex border with the head of the tibia, and to the external and posterior ligaments by means of its coronary ligament; by its two extremities it is inserted into the depression between the two projections which constitute the spinous process of the tibia. The two extremities of the external cartilage being inserted into the same fossa, form almost a complete circle, and the cartilage being somewhat broader than the internal, nearly covers the articular surface of the tibia. The external semilunar fibro-cartilage, besides giving off a fasciculus from its anterior border to constitute the transverse ligament, is continuous by some of its fibres with the extremity of the anterior crucial liga- ment; posteriorly, it divides into three slips; one, a strong cord, ascends obliquely forwards, and is inserted into the anterior part of the inner condyle of the femur in front of the posterior crucial ligament; another is the fasciculus of insertion into the fossa of the spinous process; and the third, of small size, is continuous with the posterior part of the anterior crucial ligament. 560 THE DISSECTOR. The ligamentum mucosum is a slender conical process of syno- vial membrane, inclosing a few ligamentous fibres which proceed from the transverse ligament. It is connected, by its apex, with the anterior part of the condyloid notch ; and by its base, is lost in the mass of fat which projects into the joint beneath the patella. The alar ligaments are two fringed folds of synovial membrane, extending from the liganientura mucosum, along the edges of the mass of fat, to the sides of the patella. The synovial membrane of the knee-joint is by far the most extensive in the skeleton. It invests the cartilaginous surface of the condyles of the femur, head of the tibia, and inner surface of the patella. It covers both surfaces of the semilunar fibro-carti- lages, and is reflected upon the crucial ligaments, and inner sur- face of the ligaments which form the circumference of the joint. On each side of the patella, it lines the tendinous aponeuroses of the vastus internus and vastus externus muscles, and forms a pouch of considerable size between the extensor tendon and the front of the femur. It also forms the folds in the interior of the joint, called "ligamentum mucosum," and "ligamenta alaria." The superior pouch of the synovial membrane is supported and raised during the movements of the limb by a small muscle, the subcrureus, which is inserted into it. Between the ligamentum patellae and the synovial membrane is a considerable mass of fat, which presses the membrane to- wards the interior of the joint, and occupies the fossa between the two condyles. Besides the proper ligaments of the articulation, the joint is protected, on its anterior part, by the fascia lata, which is thicker upon the outer than upon the inner side, by a tendinous expan- sion from the vastus internus, and by some scattered ligamentous fibres which are inserted into the sides of the patella. The ex- pansion has been termed the capsular ligament. ACTIONS. The knee-joint is one of the strongest of the articulations of the body, while at the same time it admits of the most perfect degree of movement in the directions of flexion and extension. During flexion, the articular surface of the tibia glides forward on the condyles of the femur ; the lateral ligaments, the posterior, and the crucial ligaments "are relaxed; while the ligamentum patellae, being put upon the stretch, serves to press the adipose mass into the vacuity formed in the front of the joint. In extension, all the ligaments are put upon the stretch, with the exception of the ligamentum patellae. When the knee is semi-flexed, a partial degree of rotation is permitted. Dislocations. The patella may be dislocated in three directions : 1. Outwards, which is the most frequent. 2. Inwards, less frequent ; in both these cases there will be rupture of the ligamentum patellae, unless there has been previous weakness of the oint. ARTICULATION OP THE TIBIA AND FIBULA. 561 3. Upwards, accompanied with rupture of the ligamentum patella. The dislocations of the knee-joint are/owr in number : 1. Tibia, forwards. 2. Tibia, 'backwards. 3. Tibia, to either side. The dislocations to either side are incomplete. The semilunar fibro-cartilages may become displaced from relaxation of the ligaments of the knee, and become fitted between the condyles of the femur and the tibia, so as to render the joint immovable. 3. Articulation between the Tibia and Fibula. The tibia and fibula are held firmly connected by means of seven ligaments, viz : Anterior, ") , Interosseons inferior, Posterior, j a Anterior, | , } Interosseous membrane, Posterior, j Transverse. The anterior superior ligament is a strong fasciculus of parallel fibres, passing obliquely downwards and outwards, from the outer tuberosity of the tibia to the anterior surface of the head of the fibula. The posterior superior ligament, thicker and stronger than the anterior, is disposed in a similar manner on the posterior surface of the joint. Within the articulation there is a distinct synovial membrane, which is sometimes continuous with that of the knee-joint. The interosseous membrane, or superior interosseous ligament, is a broad layer of aponeurotic fibres, which pass obliquely down- wards and outwards, from the sharp ridge on the tibia, to the iuner edge of the fibula, and are crossed at an acute angle by a few fibres passing in the opposite direction. The ligament is deficient above, leaving a considerable interval between the bones, through which the anterior tibial artery takes its course forward to the anterior aspect of the leg, and near its lower third there is an opening for the anterior peroneal artery and vein. The interosseous membrane is in relation, in front, with the tibialis anticus, extensor longus digitorum, extensor proprius pollicis, anterior tibial vessels and nerve, and anterior peroneal artery ; behind, with the tibialis posticus, flexor longus digitorum, and posterior peroneal artery. The inferior interosseous ligament consists of short and strong fibres, which hold the bones firmly together inferiorly, where they are nearly in contact. This articulation is so firm that the fibula is likely to be broken in the attempt to rupture the ligament. The anterior inferior ligament is a broad band, consisting of 562 THE DISSECTOR. two fasciculi of parallel fibres, which pass obliquely across the anterior aspect of the articulation of the two bones at their infe- rior extremity, from the tibia to the fibula. The posterior inferior ligament is a similar band, upon the posterior surface of the articulation. Both ligaments project somewhat below the margin of the bones, and serve to deepen the cavity of articulation with the astragalus. The transverse ligament is a narrow band of ligamentous fibres, continuous with the preceding, and passing transversely across the back of the ankle-joint between the two malleoli. The synovial membrane of the inferior tibio-fibular articulation, is a duplicature of the synovial membrane of the ankle-joint, re- flected upwards for a short distance between the two bones. ACTIONS. Between the tibia and fibula there exists an obscure degree of movement, which is principally calculated to enable the latter to re- sist injury by yielding for a trifling extent to the pressure exerted. 4. Ankle- Joint. The ankle is a ginglymoid articulation ; the surfaces entering into its formation are the under surface of the tibia with its malleolus and the malleolus of the fibula, above ; and the surface of the astragalus with its two lateral facets, below. The ligaments are three in number : Anterior, Internal lateral, External lateral. The anterior ligament is a thin membranous layer, passing from the margin of the tibia to the astragalus in front of the articular surface. It is in relation, in front, with the extensor tendons of the great and lesser toes, tendons of the tibialis anticus and peroneus tertius, and anterior tibial vessels and nerve. Pos- teriorly, it lies in contact with the extra-synovial adipose tissue and synovial membrane. The internal lateral, or deltoid ligament, is a triangular layer of fibres, attached, superiorly, by its apex to the internal mal- leolus, and, inferiorly, by an expanded base to the astragalus, os calcis, and scaphoid bone. Beneath the superficial layer of this ligament is a much stronger and thicker fasciculus, which con- nects the apex of the internal malleolus with the side of the astragalus. This internal lateral ligament is covered in, and partly concealed by the tendon of the tibialis posticus, and at its posterior part, is in relation with the tendons of the flexor longus digitorum, and flexor longus pollicis. The external lateral ligament consists of three strong fasciculi, which proceed from the inner side of the external malleolus, and diverge in three different directions. The anterior fasciculus passes forwards, and is attached to the astragalus; the posterior, backwards, and is connected with the astragalus posteriorly ; and ARTICULATIONS OF THE TARSUS. 563 the middle, longer than the other two, descends, to be inserted into the outer side of the os calcis. " It is the strong union of this bone," says Sir Astley Cooper, with the tarsal bones, by means of the external lateral ligaments, " which leads to its being more frequently fractured than dislo- cated." The transverse ligament of the tibia and fibula occupies the place of a posterior ligament. It is in relation, behind, with the posterior tibial vessels and nerve and tendon of the tibialis pos- ticus muscle ; in front, with the extra-synovial adipose tissue and synovial membrane. The synovial membrane invests the cartilaginous surfaces of the tibia and fibula (sending a duplicature upwards between their lower ends), and the upper surface and two sides of the astragalus. It is then reflected upon the anterior and lateral ligaments, and upon the transverse ligament posteriorly. ACTIONS. The movements of the ankle-joint are flexion and extension only, without lateral motion. Dislocations. The dislocations occurring at this joint, Are four in num- ber: 1. Tibia inwards, the foot being turned outwards. This is Pott's dis- location, and in this case the deltoid ligament is ruptured, and the fibula fractured, at about three inches from its lower extremity. In a more severe case, a portion of the fibular side of the tibia is split off, and the broken end of the fibula rests upon the cartilaginous surface of the astra- galus. 2. Tibia outwards, the foot being turned inwards. In this case, which is the most serious of the accidents occurring to the ankle-joint, the inner condyle of the tibia is fractured, the deltoid ligament remaining whole; the fibula is splintered, and the astragalus sometimes fractured. The external ligaments generally remain whole ; if the fibula be uninjured, they must be ruptured. 3. Tibia forwards. This is a partial dislocation ; the tibia is thrown forwards, so as to rest partly on the scaphoid bone ; and the fibula is fractured. 4. Both bones backwards. This is extremely rare ; there is not more than one or two cases on record. 5. Articulation of the Tarsal Bones. The ligaments which connect the seven bones of the tarsus to each other are of three kinds : Dorsal, Plantar, Interosseous. The dorsal ligaments are small fasciculi of parallel fibres, which pass from each bone to all the neighboring bones with which it articulates. The only dorsal ligaments deserving of particular mention are, the external and posterior calcaneo-astragaloid, which, with the interosseous ligament, complete the articulation of the astragalus with the os calcis ; the superior and internal, calcanco-cuboid ligaments ; and the superior astragalo-scaphoid 564 THE DISSECTOR. ligament. The internal calcaneo-cuboid, and the superior cal- caneo-scaphoid ligament, which are closely united posteriorly, in the deep groove which intervenes between the astragalus and os calcis, separate, anteriorly, to reach their respective bones ; they form the principal bond of connection between the first and se- cond range of bones of the foot. It is the division of this por- tion of these ligaments that demands the careful attention of the surgeon in performing Chopart's operation. The plantar ligaments have the same disposition on the plantar surface of the foot; three of them, however, are of large size, and have especial names, viz : the Calcaneo-scaphoid, Long calcaneo-cuboid, Short calcaneo-cuboid. The inferior calcaneo-scaphoid ligament is a broad fibro-carti- laginous band of ligament, which passes forward from the an- terior and inner border of the os calcis to the edge of the scaphoid bone. In addition to connecting the os calcis and scaphoid, it supports the astragalus, and forms part of the cavity in which the rounded head of the latter bone is received. It is lined upon its upper surface by the synovial membrane of the astragalo- scaphoid articulation. The firm connection of the os calcis with the scaphoid bone, and the feebleness of the astragalo-scaphoid articulation, are con- ditions favorable to the occasional dislocation of the head of the astragalus. The long calcaneo-cuboid, or ligamentum longum plantce, is a long band of ligamentous fibres, which proceeds from the under surface of the os calcis to the rough surface on the under part of the cuboid bone, its fibres being continued onwards to the bases of the third and fourth metatarsal bones. This ligament forms the inferior boundary of a canal in the cuboid bone, through which the tendon of the peroneus longus passes to its insertion into the base of the metatarsal bone of the great toe. The short calcaneo-cuboid or ligamentum breve plantce, is situ- ated nearer the bones than the long plantar ligament, from which latter it is separated by adipose tissue ; it is broad and extensive, and ties the under surface of the os calcis and cuboid bone firmly together.' The interosseous ligaments are five in number ; they are short and strong ligamentous fibres situated between adjoining bones, and firmly attach'ed to their rough surfaces. One of these, the calcaneo-astragaloid, is lodged in the groove between the upper surface of the os calcis and the lower of the astragalus. It is large and very strong, consists of vertical and oblique fibres, and ARTICULATIONS OF THE TARSUS. 565 serves to unite the os calcis and astragalus solidly together. The second interosseous ligament, also very strong, is situated be- tween the sides of the scaphoid and cuboid bone ; while the three remaining interosseous ligaments connect strongly together the three cuneiform bones and the cuboid. The synovial membranes of the tarsus are four in number : one, for the posterior calcaneo-astragaloid articulation ; a second, for the anterior calcaneo-astragaloid and astragalo-scaphoid ar- ticulation occasionally an additional small synovial membrane is found in the anterior calcaneo-astragaloid joint ; a third, for the calcaneo-cuboid articulation ; and a fourth, the large tarsal synovial membrane, for the articulations between the scaphoid and three cuneiform bones, the cuneiform bones with each other, the external cuneiform bone with the cuboid, and the two external cuneiform bones with the bases of the second and third meta- tarsal bones. The prolongation which reaches the metatarsal bones passes forwards between the internal and middle cuneiform bones. A small synovial membrane is sometimes met with, be- tween the contiguous surfaces of the scaphoid and cuboid bone. ACTIONS. The movements permitted by the articulation between the astragalus and os calcis, are a slight degree of gliding, in the directions forwards and backwards, and laterally, from side to side. The movements of the second range of tarsal bones are very trifling, being greater be- tween the scaphoid and three cuneiform bones than in the other articu- lations. The movements occurring between the first and second range are the most considerable : they are adduction and abduction, and in a minor degree flexion, which increases the arch of the foot, extension, which flattens the arch. 1 Dislocations. The dislocations of these bones recorded by Sir Astley Cooper, are : 1. Dislocation of the astragalus: in this case the calcaneo-astragaloid interosseous ligament must be ruptured. 1 2. Dislocation of the live anterior bones of the tarsus from the astra- galus and os calcis. 3. Dislocation of the internal cuneiform bone. 6. Tarso-metatarsal Articulation. The ligaments of this ar- ticulation are Dorsal, Plantar, Interosseous. The dorsal ligaments connect the metatarsal to the tarsal bones, and the raetatarsal bones with each other. The precise arrange- ment of these ligaments is of little importance ; but it may be remarked that the base of the second metatarsal bone, articulat- ing with the three cuneiform bones, receive* a ligamentous slip from each, while the rest, articulating with a single tarsal bone, receive only a single tarsal slip. The plantar ligaments have the same disposition on the plantar surface. 48 566 THE DISSECTOR. The interosseous ligaments are situated between the bases of the metatarsal bones of the four lesser toes, and also between the bases of the second and third metatarsal bones and the in- ternal and external cuneiform bones. The metatarsal bone of the second toe is implanted by its base between the internal and external cuneiform bones, and is the most strongly articulated of all the metatarsal bones. This disposition must be recollected in amputation at the tarso-meta- tarsal articulation. The synovial membranes of this articulation are three in num- ber : one for the metatarsal bone of the great toe, one for the second and third metatarsal bones (which is continuous with the great tarsal synovial membrane), and one for the fourth and fifth metatarsal bones. ACTIONS. The movements of the metarsal "bones upon the tarsal and upon each other, are very slight ; they are such only as contribute to the strength of the foot, by permitting a certain degree of yielding to opposing forces. Dislocations. These bones are not dislocated, except by extreme violence. 1. Metatarso-phalangeal Articulation. The ligaments of this articulation, like those of the articulation between the first pha- langes and metacarpal bones of the hand, are : Inferior or plantar, Two lateral, Transverse. The inferior or plantar ligaments are thick and fibro-carti- laginous, and form part of the articulating surface of the joint. The lateral ligaments are short and very strong, and situated one on each side of the joints. The transverse ligaments are strong bands, which pass trans- versely between the anterior ligaments. The expansion of the extensor tendon supplies the place of a dorsal ligament. ACTIONS. The movements of the first phalanges upon the rounded heads of the metatarsal bones, are : flexion, extension, adduction, and abduction. Dislocation of the first phalanges from the heads of the metacarpal bones is extremely rare. 8. Articulation of the Phalanges. The ligaments of the pha- langes are the same as those of the fingers, and have the same disposition. Their actions are also similar. They are Inferior or plantar, Two lateral. INDEX Abdomen, 30 superficial fascia of, .31 arteries of, .'il Abdominal regions, 52 Abdominal ring, 35 Abductor oculi, 130 Acervulus, 222 Acetabuluin, 556 Acini, 83 Adductor oculi, 130 Air-cells, 311 Albino, 271 Alimentary canal, 59 Allantois, 528 Amphi arthrosis, 530 Ampulla, 281, 346 Amygdala), 201, 223, 225 Andersch, ganglion of, 190 Aneurism, false, 364 varicose, 364 Aneurismal varix, 364 Annulus albidus, 266 (.v:ilis, 316, 522 Antihelix, 271 Antitragus, 272 Antrum pylori, 59 Anus, 64 Aorta, 96, 325 Aortic sinuses, 321, 326 Aponeurosis, 27 Apparatus ligamentosus oolli, 537 Appendices epiploicse, 58 Appendix auriculae, 315, 320 vermiformis, 62, 527 Aqua labyrinthi, 282 Aquaeductus cochleae, 282 vestibuli, 280 Aqueduct of Sylvius, 222 Aqueous humor, 268 Anschnoid membrane, 207, 246 Arbor vitae cerebelli, 226 uterina, 480 Arch, aortic, 326 femoral, 412 palmar, superficial, 376, 378, 390 Arciform fibres, 232, 233 Areola, 344 Arnold's ganglion, 180 ARTERIES : general anatomy, 28 alveolar, 174 anastomotica brachialis, 369 femoralis, 409 angular, 127, 169 aorta, 96, 325 articulares genu, 427 auricular anterior, 171, 273 posterior, 116, 170, 273 axillary, 349 azigos, 427 basilar, 210 brachial, 368 bronchial, 312, 334 buccal, 174 bulbosi, 513 calcanean, 444 capsular, 98 carotid, common, 161, 327 external, 166 internal. 185, 209 carpal radial, 377 ulnar, 380 cavernosi, 513 centralis modioli, 281 centralis retinae, 138, 267, 270 cerebellar, 211 cerebral, 209, 211 cervicalis ascendens, 160 choroidean, 210 ciliary, 138, 270 circumflex femoris, 408, 425 humeri, 351, 358, 361 ilii, 40 superficial, 31, 397, 406 coccygeal, 421 coeliac, 73, 97 colica dextra, 70 sinistra, 71 media, 70 comes nervi ischiatici, 421 phrenici, 308, 356 ccmmunicans cerebri, 209, 210 568 INDEX. ARTERIES continued. coronaria cordis, 322 labii, 128 ventriculi, 73 corporis bulbosi, 513 cavernosi, 513 cremasteric, 40, 44 crico-thyroid, 167 cystic, 75, 88 deferential, 44, 462 dental, 173, 174 digitales mantis, 390 pedis, 449 dorsales pollicis, 378 dorsalis carpi, 377, 380 hallucis, 435 indicis, 378 linguae, 169 nasi, 138 pedis, 434 penis, 513 pollicis, 434, 435 scapulae, 360 eraulgent, 98 epigastric, 40, 100 superficial, 31, 397, 407 ethmoidal, 138, 256 facial, 127 169 femoral, 404, 405 frontal, 116, 138 gastric, 73 gastro-duodenalis, 74 epiploica dextra, 75 sinistra, 75 gluteal, 420, 465 hemorrhoidal, superior, 72, 463, 465 external, 512 hepatic, 73, 81, 85 hyoid, 167, 169 hypogastric, 461, 521 ileo-colic, 70 iliac, common, 99 external, 99 internal, 461 ilio-lumbar, 463 infra-orbital, 175 innominata, 326 intercostal, 39, 334, 355, 496 anterior, 357 superior, 161, 335 interosseous, 379, 385 intestini tenuis, 70 ischiatic, 421, 463 labial, 128 lachrymal, 137, 262 laryngeal, 167 lateralis nasi, 128, 254 lingual, 167 lumbar, 39, 98 magna pollicis, 435 ARTERIES continued. malar, 137 malleolar, 433 mammary internal, 40, 160, 356 masseteric, 127, 174 mastoid, 170 maxillary, internal, 172 superior, 174 mediastinal, 334, 357 meningea, anterior, 186, 245 inferior, 170, 245 media, 174, 245 parva, 174, 245 posterior, 210, 245 mesenteric, superior, 69 inferior, 71 metacarpal, 377, 380 metatarsal, 435 musculo-phrenic, 357 mylo-hyoid, 174 nasal, 128, 138, 175, 254 obturator, 409, 463 occipital, 116, 170, 496 oesophageal, 334 ophthalmic, 137, 186 orbitar, 171 ovarian, 98 palatine, descending, 175 inferior, 169 posterior, 175 superior, 175 palpebral, 138, 260 pancreatica magna, 75 pancreaticae parvae, 75 pancreatico-duodenali?, 75 inferior, 70 parotidean, 171 perforantes, femoral, 408, 425 palmares, 391 plantares, 449 pericardiac, 334, 357 perinea! superficial, 512 peroneal, 443 pharyngea ascendens, 170 phrenic, 97 plantar, 449 popliteal, 427 princeps cervicis, 496 pollicis, 391 profunda cervicis, 16], 496 femoris, 407 humeri, 369 pterygoid, 174 pterygo-palatine, 175 pubic, 40, 463 pudic, external, 31, 397, 407 internal, 422, 463, 511 pulmonary, 312 pyloric, 75 radial, 376, 391 INDEX. 569 ART E RI E s continued. rudialis indicis, 391 rnnine, 167, 169 recurrens interossese, 380 rndinlis, 377 tibialis, 429, 433 ulnaris, 379 renal, 95, 98 sacra lateralis, 464 im-ilia, 99, 465 scapular posterior, 161, 361 septum, artery of, 256 sigmoid, 72 spermatic, 44, 98 spheno-palatine, 175, 256 spinal, 210, 251 splenic, 73, 75, 91 sterno-mastoid, 170 stylo-mastoid, 170 subclavian, 157, 327 sublingual, 169 submaxillary, 170 submental, 170 subscapular, 351, 362 superficialis cervicis, 161 volae, 377 supra-orbital, 116, 137 supra-renal, 92, 98 scapular, 160, 360 sural, 427 tarsea, 435 temporal, 116, 171 temporales profundaa, 174 thoracic, 334, 350 thyroidea inferior, 160 media, 326 superior, 167 tibialis antica, 432 postica, 442 tonsillar, 170 transversalis colli, 161 faciei, 128, 171 humeri, 160 perinei, 513 tympanic, 173, 186, 278 ulnur, 378, 390 umbilical, 519 uterine, 463 vagina], 463 vasa brevia, 75 intestini tenuis, 70 vertebral, 159, 210, 496 vesical, 459, 462 Vidian, 175 Arthrodia, 531 Articulations, 533 Arytenoid cartilages, 289 glands, 296 Auricles of the heart, 315, 320. 321 Auriculo-ventricular openings, 316, 320 Axilla, 348 Axis coeliac, 73, 97 thyroid, 160 Bartholine's duct, 150 glands, 485 Base of the brain, 226 Bauhini, valvula, 66 Bichat, fissure of, 213 Biliary ducts, 84, 86, 88 Bladder, 456, 476, 528 Bones, general anatomy, 28 Botal, foramen of, 526 Brain, 204 Brachium anterius, 222 posterius, 222 Bronchi, 311, 332 Bronchial cells, 311 tubes, 311, 332 Bronchocele, 146 Brunner's glands, 68 Bubonocele, 50 Bulb, corpus spongiosum, 469 Bulbi foruicis, 229 vestibuli, 485 Bulbous part of the urethra, 472 Bulbus olfactorius, 236, 240 rachidicus, 230 Caecum, 62 Calamus scriptorius, 223 Calices, 95 Camper's ligament, 510 Canal of Fontana, 266 Nuck, 483 Petit, 268, 270 Sylvius, 222 Cotunnius, 280 Canthi, 258 Capillaries, 28 Capitula laryngis, 289 Capsule of Glisson, 57, 76, 83 Capsules, supra-renal, 91, 527 Caput gallinaginis, 471 Cardiac orifice, 59 Carpus, 552 Cartilage, interarticular of clavicle, 546, 547 interarticular of jaw, 539 interarticular of wrist, 551 semilunar, 559 Caruncula lachrymalis, 260 mamillaris, 236 Carunculae myrtiformes, 484 Casserian ganglion, 176 Cauda equina, 248, 251 Cava, vena, 100, 327, 328 Cells, development of, 299 Cellular tissue, 25 Centrum ovale, 212, 213 48* 570 INDEX. Cerebellum, 224 Cerebro-spinal fluid, 208, 246 Cerebrum, 212 Ceruminous follicles, 273 glands, 303 Cervical ganglia, 194 Chambers of the eye, 268 Cheeks, 285 Chiasma nervorum opticorum, 236 Chordae longitudinales, 213 tendineaa, 318, 321 vocales, 292 Willisii, 243 Choroid membrane, 265 plexus, 215, 220, 224 Cilia, 256, 260 Ciliary canal, 266 ligament, 265. 266 processes, 266 Circle of Willis, 211 Circulation, adult, 315 foetal, 519 . Circulus tonsillaris, 190 venosus Halleri, 306 Clitoris, 484 Cochlea, 281 Coeliac axis, 73, 97 Colon, 62 Columna nasi, 252 Columnae carneaa, 319, 321 papil lares, 319 Columns of spinal cord, 248 Commissures, 221, 249 great, 213 Conarium, 222 Concha, 272 Congestion of the liver, 87 Coni renales, 94 vasculosi, 475 Conjoined tendon, 37 Conjunctiva, 260 Conus arteriosus, 317 Converging fibres, 234 Corium, 26, 66, 297 Cornea, 263 Cornicula laryngis, 289 Cornu Ammonis, 217 Cornua of the ventricles, 214, 216 Corona glandis, 468 Coronary valve, 316 Corpora albicantia, 229 Arantii, 319, 321 cavernosa, 469 geniculata, 221 Malpighiana, 94, 95 mammillaria, 229 olivaria, 232 pisiformia, 229 pyramidalia, 231 quadrigemina, 222 Corpora restiformia, 223, 232 striata, 215 Corpus callosum, 213 cavernosum, 4G9 cilia re, 266 dentatum, 226, 232 fimbriatum, 216, 217, 218 geniculatum, 221 Highmorianurn, 474 luteum, 482 psalloides, 219 rhomboideum, 226 spongiosum, 469 striatum. 215 Covered band of Reil, 213 Cowper's glands, 516 Cranial nerves, 235 Cribriform fascia, 396, 399, 415 lamella, 263 Cricoid cartilage, 289 Circo-thyroid membrane, 290 Crura cerebelli, 226 Crura cerebri, 230 Crura penis, 469 Crural canal, 404, 414 ring, 405, 414 Crystalline lens, 269 Cuneiform cartilages, 290 Cuticle, 26, 299 Cutis, 26, 297 Cutis anserina, 298 Cystic duct, 88 Cytoblast, 299 Dartos, 472 Derbyshire neck, 146 Derma, 26, 297 Detrusor urinae, 458 Diaphragm, 105 Diarthrosis, 531 Digital cavity, 216 DISLOCATIONS : ankle, 563 carpal bones, 553 carpo-metacarpal, 554 clavicle, 547 elbow, 550 hip, 557 jaw, 540 knee, 560 metacarpo-phalangeal, 555 metatarso-phalangeal, 566 phalanges, 555 radius and ulna, 551 shoulder, 549 tarsal bones, 665 wrist, 552 Diverging fibres, 233 Dorsi-spinal veins, 251 Ductus ad nasum, 262 INDEX. 571 Ductus arteriopu?, f>21, f>2f> communis choledochus, 76, 88 cysticus, 88 t j.-ii-uhitorius, 476 hepaticus, 84, 88 lymphaticus dexter, 166, 337 pancreaticus, 90 prostatic, 460 thoracicus, 166, 336 venosus, 520 Duodenum, 60 Dura mater, 204, 246 Ear, 271 Ejaculatory duct, 476 Eininentia collateral!*, 217 pyramidal!?, 279 Enarthrosis, 531 Encephalon, 204 Endocardium, 322 Endolymph, 283 Entozoon folliculorum, 303 Epiderma, 26, 299 Epidiilymis, 473 Epigastric region, 52 Epiglottic gland, 296 Epiglottis, 290 Epiglotto-hyoidean ligament, 292 Epithelium, 66 Erectile tissue, 470 Eustachian tube, 200, 277 valve, 316 Eye, 268- Eyebrows, 258 globe, 262 lashes, 260 lids, 258 Falciform process, 399 Fallopian tubes, 481 Falx cerebelli, 206 cerebri, 206 FASCIA : general anatomy of, 26 cervical, 141 cremasteric, 44 cribriform, 396, 399, 415 deep, -27 dentata, 218 ili.-u-a, 108 intercoluinnar, 35 lata, 398 lumbar, 491 obturator, 454 palmar, 386 pelvica, 454 perinea), 547, 505 plantar, 446 popliteal, 426 propria, 43, 44, 415 FASCIA continued. recto-vesical, 454 spermatic, 44 superficial, 26 temporal, 115 transversalis, 43 Fasciculi graciles, 232 innominati, 223, 232, 234 siliquae, 232, 234 teretes, 223, 232, 234 Fauces, 201 Femoral arch, 412 canal, 404, 414 hernia, 412 ring, 405, 414 Fenestra oval is, 276 rotunda, 276 Fibraa arciformes, 232, 233 Fibres of the brain, 233 heart, 321 Fibrous cartilage : interarticular of the f clavicle, 546, 547 jaw, 539 knee, 559 wrist, 551 Filum terminale, 247 Fimbriac, Fallopian, 481 Fissura palpebrarum, 258 Fissure of Bichat, 213 brain, 213,227 Sylvius, 212, 228 Fissures of the liver, 79 of external ear, 272 spinal cord, 248 Flocculus, 225 Foetal circulation, 519 Foetus, anatomy of, 519 Follicles of Lieberkiihn, 68 Foramen, Botal, of, 526 caecum, 232, 287 commune anterius, 215, 218, 221 postering, 322 Monro, of, 215, 218, 221 ovale, 519, 526 saphenum, 397 Soemmering, of, 268 Window, of, 57 Foramina Thebesii, 316 Forceps cerebri, 234 Fornix, 216, 218 Fossa innominata, 272 ischio-rectal, 505, 506 Fossa navicularis urethrir, 472 navicularis pudendi, 483 ovalis, 272, 316, 522 scaphoidea, 272 triangularis, 272 Fourchette, 483 Fovea hemispherica, 279 5T2 INDEX. Fovea elliptica, 279 sulciformis, 279 Frrena epiglottidis, 287, 292 Fraenulum labiorum, 483 Fraenum labii, 285 linguae, 287 praeputii, 468 Funiculi graciles, 232 siliquse, 232 Galea capitis, 114 Gall-bladder, 87 Ganglia, cervical, 194 increase of, 233 lumbar, 104 sacral, 467 semilunar, 102 thoracic, 331 Ganglion of Andersen, 190 Arnold's, 180 azygos, 467 cardiac, 323 Casserian, 176 ciliary, 136 Cloquet's, 183 diaphragmaticum, 103 geniculare, 187 impar, 467 jugular, 190, 191 lenticular, 136 Meckel's, 182 Muller's, 190 naso-palatine, 183 ophthalmic, 136 otic, 180 petrous, 190 semilunar, 102 spheno-palatine, 182 submaxillary, 180 thyroid, 195 vertebral, 195 Wrisberg's, 323 Genu corporis callosi, 213 Gimbernat's ligament, 35 Ginglymus, 531 Gland, epiglottic, 296 pineal, 222 pituitary, 228, 241 prostate, 460 thymus, 523 thyroid, 146, 523 Glands, aggregate, 68 arytenoid, 296 Bartholine's. 485 bronchial, 337 Brunner's, 68 buccal, 285 cardiac, 387 ceruminous, 273, 303 concatenate, 163 Glands, Cowpcr's, 516 duodenal, 68 gastric, 67 inguinal, 32, 397 intercostal, 337 labial, 285 lachrymal, 139, 261 Lieberkuhn's, 68 lingual, 288 lumbar, 104 lymphatic, 28 mammary, 344 mediastinal, 337 mesenteric, 71 Meibominn, 259 ossophageal, 337 Pacchionian, 205 parotid, 122 Peyer's, 68 salivary, 122, 148, 149 sebaceous, 303 solitary, 68 sublingual, 149 submaxillary, 148 sudoriferous, 303 tracheal, 297 Glandulae odoriferae, 468 Pacchioni, 205 Tysoni, 468 Glans clitoridis, 484 penis, 468 Glisson's capsule, 57, 76, 83 Globus major epididymis, 473 minor epididymis, 473 Glomeruli, 94 Glottis, 295 Goitre, 146 Gomphosis, 568 Graafian vesicles, 482 Gubernaculum testis, 528 Gums, 286 Guthrie's muscle, 515 Gyri cerebri, 212 operti, 228 Gyrus fornicatus, 217 Hair, 302 Hamulus lamina spiralis, 282 Harmonia, 530 Heart, 313, 526 Helicine arteries, 470 Helico-trema, 282 Helix, 271 Hepatic duct, 84, 88 Hernia, congenital, 48 diaphragmatic, 107 direct, 49 encysted, 49 femoral, 412 infantilis, 49 INDEX. 573 Hernia, inguinal, oblique, 47 scrotal, 50 umbilical, 46 ventral, 46 Hilton's muscle, 293 Jlilum lienis, 90 pulmonis, 309 renale, 93 Hippocampus major, 217 minor, 216 Horner's muscle, 118 , Horny band, 215 Humors of the eye, 2fi8 Hyaloid membrane, 269 Hymen, 484 Hypochondriac regions, 52 Hypogastric region, 53 Hypophysis cerebri, 228 Ileo-caecal valve, 66 Ileum, 61 Iliac regions, 53 Incus, 274 Infundibula, 95 Infundibulum cerebri, 228 cordis, 317 Inguinal region, 53 Integument, 26 Interarticular cartilages of the cla- vicle, 546, 547 jaw, 539 wrist, 551 Intercolumnar fascia, 35 fibres, 35 Intermuscular septa, 366 Intervertebral substance, 535 Intestinal canal, 60 Intumescentia gangliformis, 187 Iris, 266 Ischio-rectal fossa, 505, 506 Isthmus of the fauces, 201 Iter ad infundibulum, 221 & tertio ad quarturn ventriculum, 222 Jacob's membrane, 267 Jejunum, 61 Joint, ankle, 562 elbow. 549 hip, 556 lower jaw, 538 knee, 557 shoulder, 548 wrist, 551 formation of, 29 Kidneys, 93, 527 Labia majora, 483 minora, 483 Labyrinth, 278 Lachrymal canals, 261 gland, 139, 261 papilla, 259 puncta, 259, 261 sac, 261 tubercles, 259 Lacteals, 71 Lacunae, 472 Lacus lachrymalis, 258 Lamina cinerea, 227 cribrosa, 263 spiral!-. 282 Laqueus, 222 Large intestine, 62 Laryngotomy, 147 Larynx, 288 Lateral ventricles, 214 Lens, 269 Lenticular ganglion, 136 Levers, 368, 440 Lieberkuhn's follicles, 68 Lien succenturiatus, 91 Ligament, 29 LIGAMENTS, 530 acromio-clavicular, 547 alar, 537, 560 ankle, of the, 562 annular, of the ankle, 430 radius, 550 wrist anterior, 533 posterior, 373 arena tu in exit-run m. 105 internum, 105 atlo-axoid, 537 bladder, of the, 454, 457 breve pi an toe, 564 calcaneo-astragaloid, 564 cuboid, 564 scaphoid, 564 capsular of the hip, 556 jaw, 539 rib, 540 shoulder, 548 thumb, 554 larynx, 290 carpal, 552 carpo-metacarpal, 553 common anterior, 534 posterior, 534 conoid, 547 coracoid, 548 coraco-acromial, 548 clavicular, 547 humeral, fls coronary, 550 coronary of the knee, 559 coeto-clavicular, 546 coracoid, 142 sternal, 541 574 INDEX. LIGAMENTS continued. costo-transverse, 541 vertebral, 540 xyphoid, 542 cotyloid, 556 crico-arytenoid, 291 crico-thyroidean, 290 crucial, 559 cruciform, 538 deltoid, 562 dentatum, 247 elbow, of the, 549 glenoid, 548 glosso-epiglottic, 292 hip-joint, of the, 556 hyo-epiglottic, 292 ilio-femoral, 556 interarticular of ribs, 541 interclavicular, 546 interosseous : calcaneo-astragaloid, 564 peroneo-tibial, 561 radio-ulnar, 550 inter-spinous, 536 inter-transverse, 536 inter-vertebral, 535 jaw, of the, 538 knee, of the, 557 larynx, of the, 290 lateral, of the ankle, 562 elbow, 549 jaw, 538 knee, 558 phalanges, foot, 566 phalanges, hand, 555 wrist, 551 liver, of the, 78 longum plantae, 564 lumbo-iliac, 543 lumbo-sacral, 542 metacarpal, 554 metatarsal, 566 mucosum, 560 nuchse, 489, 536 oblique, 550 obturator, 545 occipito-atloid, 536 axoid, 537 odontoid, 537 orbicular, 550 ovary, of the, 482 palpebral, 259 patellae, 537 pelvis, of the, 543 peroneo-tibial, 561 phalanges, of the foot, 566 of the hand, 555 plantar, long, 564 plantar, short, 564 posticum Winslowii, 424, 558 LIGAMENTS continued. Poupart's, 34 pterygo-maxillary, 124 pubic, 544 pulmonis, 306 radio-ulnar, 550 rhomboid, 546 rotundum, hepatis, 78 round, 45, 482 sacro-coccygean, 544 sacro-iliac, 543 sacro-ischiatic, 544 sacro-vertebral, 542 scapulo-clavicular, 547 shoulder, of the, 548 stellate, 540 sternal, 542 sterno-clavicular, 546 stylo-maxillary, 142, 539 subflava, 535 subpubic, 545 supra-spinous, 536 suspensoriurn axis, 537 hepatis, 78 penis, 469 tarsal, 259, 563 tarso-metatarsal, 565 teres, 550, 556 thyro-arytenoid, 291 thyro-epiglottic, 292 thyro-hyoidean, 290 tibio-fibular, 561 transverse : of the acetabulum, 556 of the ankle, 563 of the atlas, 538 of the knee, 559 of the metacarpus, 555 of the metatarsus, 506 of the scapula, 548 of the semilunar cartilages, 559 trapezoid, 547 tympanum, of the, 275 uterus, broad, of the, 479 vaginal, 555 wrist, of the, 551 Zinn, of, 130 Ligamentum nuchae, 489 latum pulmonis, 306 Limbus luteus, 268 Linea alba, 32 Linece semilunares, 32 transversse, 32, 213 Linguetta laminosa, 223 Lips, 285 Liquor Cotunnii, 282 cornea, 264 Morgagni, 269 Scarpa, of, 283 Liver, 77, 527 INDEX. 575 Lobules of the liver, 80 Lobuli testis, 474 Lobulus auris, 272 centralis nasi, 252 pneumogastricus, 225 Lobus caudatus, 81 quadratus, 80 Spigelii, 81 Locus niger, 230 perforatus anticus, 228 posticus, 230 Lumbar fascia, 491 regions, 53 Lungs, 308, 526 Lunula, 302, 319 Lymphatic glands and vessels, 28 abdominal, 32, 104 axillary, 349 bronchial, 337 cardiac, 337 cervical, 153, 166 iliac, 104 inguinal, 32, 397 intestines, 71, 73 kidneys, 96 lacteals, 71 liver, 81 lungs, 312 mcdiastinal, 337 mesenteric, 71 pelvis, 465 spleen, 91 testicle, 473 Lyra, 219 Macula cribrosa, 279 Malleus, 274 Malpighian bodies, 94, 95 Mammilla, 344 Mammae, 344 Mammary gland, 344 Mastoid cells, 277 Matrix, 301 Maxillo-pharyngeal space, 200 Meatus auditorius, 273 urinarius, female, 484 male, 472 Meatuses of the nares, 255 Meckel's ganglion, 182 Meconium, 527 Mediastinum, 306 testis, 474 Medulla innominata, 228 oblongata, 230 Meibomian glands, 259 Membrana dentata, 247 fusca, 265 nictitans, 260 pigmenti, 266 pupillaris, 523 Membrana sacciform!?, 553 tympani, 274 Membrane, choroid, 265 hyaloid, 269 Jacob's, 267 of the ventricles, 224 Membranous urethra, 471 labyrinth, 283 Mesenteric glands, 71 Mesentery, 58 Mesocola, 58 Mesorectum, 58 Metacarpus, 553 Metatarsus, 565 Mitral valve, 321 Modiolus, 281 Mons Veneris, 483 Monticulus cerebelli, 225 Morsus diaboli, 482 Mouth, 284 Mucous membrane, structure, 66 MUSCLES :" general anatomy of, 27 abductor indicis, 389 minimi digiti, 388, 447 oculi, 130 pollicis, 387, 447 accelerator urinae, 508 accessorius, 447 adductor brevis, 402 longus, 402 magnus, 402 minimi digiti, 388 oculi, 130 pollicis, 388, 448 anconeus, 383 anomalus, 120 anterior auriculae, 115 antitragicus, 273 arytenoideus, 293 aryteno-epiglottideus, 293 attolens aurem, 115 oculum, 130 atrahens aurem, 115 auricularis, 383 azygos uvulae, 202 basio-glossus, 151 biceps flexor cruris, 424 cubiti, 366 biventer cervicis, 493 brachialis anticus, 367 buccinator, 124 bulbo-cavernosus, 508 cerato-glossns, 151 cervicalis ascendens, 492 i liar is. 119 circumflexus palati, 202 coccygeus, 455 complexus, 493 compressor nasi, 120 576 INDEX. MUSCLES continued. compressor prostatae, 455 urethrse, 515, 518 constrictor isthmi faucium, 203 pharyngis, 198, 199 urethras, 515 vaginae, 518 coraco-brachialis, 366 corrugator supercilii, 118 cremaster, 37, 528 crico-arytenoid lateralis, 292 posticus, 292 thyroideus, 292 crureus, 401 cucullaris, 487 deltoid, 358 depressor alae nasi, 120 anguli oris, 122 epiglottidis, 293 labii. 122 oculi, 130 detrusor urinae, 458 diaphragm, 105 digastricus, 147 dilatator naris, 120 erector clitoridis, 484, 518 penis, 508 spinae, 502 extensor carpi radialis, 382 carpi ulnaris, 382 coccygis, 498 digiti minimi, 383 digitorum brevis, 434 digitorum communis, 383 digitorum longus, 431 indicis, 385 extensor ossis metacarpi, 384 pollicis proprius, 431 internodii pollicis, 384 flexor accessorius, 447 brevis digiti min., 388, 448 carpi radialis, 374 ulnaris, 374 digitorum brevis, 447 profundus, 375 sublimis, 375 longus digitorum, ped., 441 longus pollicis, 376 ossis metacarpi, 387 pollicis brevis, 387, 448 longus, 441 gastrocnemius, 439 gemellus, 419, 420 genio-hyo-glossus, 149 hyoideus, 149 gluteus maximus, 417 medius, 418 minimus, 418 gracilis, 402 helicis major, 273 MUSCLES continued. helicis minor, 273 hyo-glossus, 150 iliacus, 108, 402 indicator, 385 infra-spin atus, 359 intercostales, 354 interobliqui, 498 interossei, 389, 434, 450 interspinales, 498 intertransversales, 408 ischio-cavernosus, 508 larynx, of the, 292 latissimus dorsi, 354, 489 laxator tympani, 275 levator anguli oris, ]21 scapulae, 489 ani, 455, 518 glandulae thyroidese, 146 labii, 121, 122 menti, 122 palati, 202 palpebrae, 130 prostatae, 455 levatores costarum, 499 lingualis, 151, 288 longissimus dorsi, 491 longus colli, 197 lumbricales, 388, 447 mallei externus, 275 internus, 275 masseter, 123 multifidus spinae, 498 mylo-hyoideus, 149 myrtiformis, 120 naso-labialis, 121 obliquus externus abdominis, 34 internus abdominis, 35 auris, 273 capitis, 497 oculi, 131 obturator externus, 402 internus, 419 occipito-frontalis, 114 omo-hyoideus, 145 opponens digiti minimi, 388 pollicis, 387 orbicularis oris, 121 palpebrarum, 118 palato-glossus, 151, 203 pha.ryngeus, 203 palmaris brevis, 386 longus, 374 pectineus, 402 pectoralis major, 346 minor, 347 perineus profundus, 514 peroneus brevis, 437 longus, 437 tertius, 431 INDEX. 571 MUSCLES eontinned. plantaris, 439 platysma myoides, 141 popliteus, 439 posterior auriculae, 115 pronator quadratus, 376 radii teres, 374 psoas magnus, 107, 402 parvus, 108 pterygoideus, 124 pyramidalis abdominis, 38 nasi, 120 pyriformis, 419 quadratus femoris, 420 lumborum, 108 menti, 122 quadriceps feraoris, 402 rectus abdominis, 38 capitis anticus major, 197 minor, 197 lateralis, 497 posticus, 497 femoris, 401 oculi externus, 130 inferior, 130 internus, 130 superior, 130 retrahens aurem, 115 rhomboideus, 489, 490 risorius Santorini, 122, 141 sacro-lumbalis, 491 sartorius, 400 scalenus anticus, 157 medius, 157 posticus, 157 semispinalis, 497 semi-membranosus, 424 semi-tendinosus, 424 serratus magnus, 354 posticus, 490 soleus, 440 sphincter ani, 505, 508, 518 vagina), 518 vesicae, 458 ppinalis dorsi, 492 splenius, 491 stapedius, 276 sterno-hyoideus, 145 sterno-cleido mastoideus, 142 thyroideus, 145 stylo-glossus, 151 hyoideus, 148 pharyngeus, 200 snbclavius, 348 subcrureus, 402 subscapularis, 361 superior auriculae, 115 supinator brevis, 384 longus, 382 supra-spinatus, 359 MUSCLES continued. temporal, 115 tensor-palati, 202 tensor tarsi, 118, 261 tympani, 275 vaginae iemoris, 400 teres major, 360 minor, 360 thyro-arytenoideus, 292 epiglottideus, 293 hyoideus, 145 tibialis anticus, 431 posticus, 441 trachelo-mastoideus, 493 tragicus, 273 transversalis abdominis, 37 colli, 492 transversus auriculae, 273 pedis, 448 perinei, 508, 518 perinei alter, 508 profundus, 514, 518 trapezius, 487 triangularis oris, 122 sterni, 355 triceps extensor cruris, 401 cubiti, 367 trochlearis, 131 ureters, of the, 458 vastus externus, 401 internus, 401 Wilson's, 516 zygomaticus, 121 Musculi pectinati, 316, 320 Myopia, 271 Naboth, ovula of, 480 Nails, 361 Nares, 252 Nasal duct, 262 fossse, 254 Nates cerebri, 222 NERVBS : general anatomy, 28 abducentes, 135, 238 accessorius, 192, 240 accessory obturator; 412 acromiales, 155, 357 auditory, 283, 241 auricularis anterior, 118 magnus, 118, 152 posterior, 117, 125 vagi, 191 auriculo-temporal, 178 brachial, 352 buccal, 177 cardiac. 192, 196, 323, 329 carotid, 183, 190, 194 cervical anterior, 154 posterior, 493 578 INDEX. NERVE s continued. cervico-facial, 125, 127 chorda tympani, 188, 278 ciliary, 135, 136 circumflex, 358, 370 claviculares, 155 coccygeal, 466 cochlear, 284 communicans noni, 155 peronei, 428, 439 poplitei, 428 tibialis, 428 cranial, 235 crural, 111, 410 cutaneus dorsi, 486 externus brachialis, 365, 370 externas femoralis, 111, 398 internus brachialis, 365, 370 femoralis, 398 medius femoralis, 398 patellae, 398, 411 spiralis, 365, 372 dental, 178, 182 descendens noni, 193 digastric, 125 digital, 392 dorsal, 495 dorsalis penis, 514 eighth pair, 189, 239, 241 facial, 125, 187, 238 femoral, 410 fifth pair, 176, 241 first pair, 236 fourth pair, 238, 134 frontal, 134 gastric, 76, 103 genito-crural, 111, 398 glosso-pharyngeal, 189, 240 gluteal, 422, 467 inferior, 422 gustatory, 179 hemorrhoidal, 467, 513 hypo-glossal. 193, 240 ilio-hypogastric, 32, 42, 110 ilio-inguinal, 32, 42, 110, 397 * incisive, 178, 179 inferior maxillary, 176 infra-trochlear, 135 inguino-cutaneous, 111, 397 intercostal, 42, 331, 355 intercosto-humeral, 344, 366 interosseous anterior, 381 posterior, 381, 385 ischiaticus major, 423, 425 minor, 422, 438 Jacobson's, 190, 278 labial, 179 lachrymal, 134 NERVE s continued. laryngeal inferior, 192, 329 recurrept, 192, 329 superior, 192, 195 lingual, 240 lumbar anterior, 109 posterior, 109, 495 lumbo-inguinal, 111 sacral, 112 malar, 126 masseteric, 176 maxillaris inferior, 176 superior, 176, 181 median, 370, 380 mental, 178 molles, 195 motores-oculorum, 133, 237 musculo-cutaneous arm, 370, 372 leg, 430, 437 musculo-spiral, 370, 372 mylo-hyoidean, 179 nasal, 135, 183, 257 naso-ciliaris, 135 naso-palatine, 183, 257 ninth pair, 193, 240, 241 obturator, 112, 411 occipitalis major, 118, 493 minor, 118, 153 oesophageal, 329 olfactory, 236, 256 ophthalmic, 134, 176 optic, 236, 267 orbital, 181 palatine, 183, 286 palmar, 381, 392 pathetici, 134, 238 perforans Casserii, 370 perineal, 514 peroneal, 428 petrosal, 180, 183 pharyngeal, 184, 190, 191, 195 phrenic, 156, 307 plantar, 449, 450 pneumogastric, 191, 240, 328 popliteal, 428 portio dura, 125, 187, 238 mollis, 239 pterygoid, internal, 177 external, 178, pudendalis inferior, 423, 513 pudendus externus, 111 pudic internal, 423, 467, 513 pulmonary, 329 radial, 372, 380 recurrent, 329 renal, 103 respiratory, external, 157, 353 sacral, 466 saphenous, external, 428, 436, 438 INDEX. 519 NERVES cnniinnrtL saphenous, long or internal, 398, 405, 1 1 I short, 411, 428, 438 sciatic, 422, 423, 438 second pair, 236 seventh pair, 238, 241 sixth pair, 238, 135, 241 spermatic, 45, 103, 111 spheno-palatine, 182 spinal, 250 spinal accessory, 192, 240 splanchnic, 331 stylo-hyoid, 125 subcutanei colli, 127 subcutaneous inalae, 182 suboccipital, 493 subrufi, 195 subscapnlar, 353 superficialis colli, 152 cordis, 195 superior maxillary, 170, 181 supra-orbital, 117, 134 scapular, 157, 353, 360 trochlear, 117, 134 sympatheticus major, 193, 329, 467 minor, 127 temporal, 117, 126, 177, 178 temporo -facial, 125 malar, 181 third pair, 133, 237 thoracic, 157, 328, 353 thyro-hyoidean, 193 tibialis, anterior, 434, 436 posterior, 444 tonsillitic, 190 trifacial, 176, 238 trigeminus, 176, 238 trochlearis, 134, 238 tympanic, 190 ulnar, 370, 381, 391 vagus, 191, 240 vestibular, 283 Vidian, 183 Wrisberg, of, 365, 370 Neurilemma, 28 Nidus hirundinis, 225 Nipple, 344 Nodulus, 223, 225 Nodus encephali, 230 Nose, 252 Nucleus olivae, 232 Nuck, canal of, 483 Nymphae, 483 (Esophagus, 203, 333 Omentum, gastro-hepatic, 57 gastro-splenic, 59 great, 58 lesser, 57 27 Opening in the diaphragm, 107 OPERATIONS : arteria innominata, 163 axillary artery, 347, 350 brachial artery, 369 Caesarian section, 34 carotid artery, 163 crural hernia, 415 dorsalis pedis artery, 435 facial artery, 169 femoral artery, 405 hernia, 415 fibular artery, 443 hernia, crural, 415 femoral, 415 inguinal, 50 Bcrotal, 50 Hunter's, 405. inguinal hernia, 50 laryngotomy, 147 lingual artery, 168 lithotomy, 516 peracentesis abdominis, 32 peroneal artery, 443 plugging nares, 257 polypi narium, 258 popliteal artery, 426 radial artery, 376 Scarpa's, 405 scrotal hernia, 50 subclavian artery, 158 tibial artery, anterior, 433 posterior, 442 tracheotomy, 147 ulnar artery, 379 venesection, 363 Optic commissure, 228, 236 thalami, 215, 220 Orbiculare, os, 274 Orbit, 128 Os tincse, 479 Ossicula auditus, 274 Ostium abdominale, 481 uterinum, 481 Otoconites, 283 Ovaries, 482, 528 Oviducts, 481 Ovisacs, 482 Ovula Graafiana, 482 Naboth, of, 480 Pacchionian glands, 205 Palate, hard, 285 soft, 201 Palmar arches, 376, 378, 390 Palpebrte, 258 Palpebral ligaments, 259 sinuses, 260 Pancreas, 89 580 INDEX, Papillae of the nail, 302 of the skin, 298 of the tongue, 287 calyciformes, 287 capitatse, 288 circumvallata3, 287 conicae, 287 filiformes, 287 fungiformes, 288 lenticulares, 287 Parotid gland, 122 Peduncles of the cerebellum, 226 of the cerebrum, 230 of the pineal gland, 222 Pelvis, viscera of, 452, 528 Penis, 468 Pericardium, 313 Perilymph, 282 Perineum, 503 Peritoneum, 54 Perspiratory ducts, 304 Pes accessorius, 217 anserinus, 125 hippocampi, 217 Peyer's glands, 68 Pharynx, 198 Pia mater, 208, 247 Pigmentum nigrum, 266 Pillars of the palate, 201 of the external abdominal ring, Pineal gland, 222 Pinna, 271 Pituitary gland, 228, 241 membrane, 256 Pleura, 306 Plexus, aortic, 103 axillary, 352 brachial, 156, 352 cardiac, 323, 324, 330 carotid, 194 cavernous, 194 cervical anterior, 155 posterior, 495 choroid, 215 circulus tonsillaris, 190 coeliac, 102 coronary, 323 epigastric, 102 gangliformis, 191 gastric, 103 hemorrhoidal, 465 hepatic, 82, 103 hypogastric, 103, 467 lumbar, 110 maxillary, 175, 180 mesenteric, 103 oasophageal, 329 patellar, 411 pharyngeal, 190, 192, 195 phrenic, 103 Plexus, prostatic, 460, 465 pterygoid, 175 pulmonary, 312, 329 renal, 103 sacral, 466 solar, 102 spermatic, 45, 103 splenic, 91, 103 submaxillary, 152 supra-renal, 103 tympanic, 278 uterine, 465 vaginal, 465 of Portal vein, 86 vertebral, 196 vesical, 460, 465 Plica semilunaris, 260 Plicae, longitudinales, 66 Pneuruogastric lobule, 225 Polypus of the heart, 315 Pomum Adami, 288 Pons Tarini, 230 Varolii, 230 Pores, 300 Portal vein, 76, 81, 84 Portio dura, 125, 187, 238 mollis, 239 Porus optic us, 263 Poupart's ligament, 34 Prepuce, 468 Presbyopia, 271 Processus e cerebello ad testes, 223, 226 brevis, 274 clavatus, 232 gracilis, 274 vermiformes, 224, 225 Promontory, 276, 277 Prostate gland, 460 Prostatic urethra, 471 Protuberantia annularis. 230 Pulmonary artery, 312, 324 plexuses, 312, 329 sinuses, 320 veins, 320, 328 Puncta lachrymalia, 259, 261 vasculosa, 213 Pupil, 266 Pylorus, 59 Pyramid, 225, 277 Pyramids, anterior, 231 Ferrein, of, 94 Malpighi, of, 94 posterior, 232 Raphe, corporis callosi, 213 Raphe of tongue, 287 Receptaculum chyli, 105, 336 Rectum, 63, 456 Regions, abdominal, 52 Reil, island of, 228 INDEX. 581 Rete mucosum, 26, 299 testes, 475 Retina, 267 Ridley, sinus of, 245 Rima glottidis, 295 Ring, abdominal external, 35 femoral, 405, 414 internal, 43 Rivinian's ducts, 150 Root of lung, 309 Rugae, 66 Sacculus communis, 283 laryngis, 295 proprius, 283 Salivary glands, 122, 148, 149 Saphenous opening, 397 veins, 397, 425, 429 Scala tympani, 282 vestibuli, 282 Scarf-skin, 26, 299 Scarpa's triangle, 394 Schindylesis, 530, 532 Schneiderian membrane, 256 Sclerotic coat, 263 Scrotum, 472 Sebaceous glands, 303 Semicircular canals, 281 Semilunar fibro-cartilages, 559 valves, 319, 321 Septum auricularum, 315 crurale, 415 lucidum, 218 pectiniforme, 469 scroti, 473 Sheath of the rectus, 39 Sigmoid flexure, 62 valves, 319, 321 Sinuses, structure, 242 Sinus arapullaceus, 281 aortic, 321 basilar, 245 cavernous, 244 circular, 245 fourth, 243 . lateral, 243 longitudinal inferior, 243 superior, 242 occipital, 243 palpebral, 260 petrosal inferior, 244 superior, 245 pocularis, 471 prostatic, 471 pulmonary, 320 rectus or straight, 243 renal is, 93 rhomboidalis, 223 spinal, 251 transverse, 245 Sinus Valsalva, of, 320, 321 Skin, 297 Small intestines, 60 Socia parotid is, 123 Soft palate, 201 Spermatic canal, 44 cord, 44, 473 Spheno-palatine ganglion, 182 Spinal cord, 246 nerves, 250 veins, 251 Spleen, 90 Splenium corporis callosi, 213 Spongy part of the urethra, 472 Stapes, 275 Stenon's duct, 123 Steatozoon folliculorum, 303 Stomach, 59, 527 Striae laterales, 213 medullares, 239 Structure of alimentary canal, 64 of bladder, 458 of cornea, 264 of heart, 322 of liver, 82 of lungs, 311 of oesophagus, 334 of ovary, 482 of parotid gland, 123 of prostate gland, 460 of testicle, 474 of tongue, 288 of trachea, 332 of uterus, 480 of vagina, 478 of vesiculae seminales, 461 Sub-arachnoidean fluid, 208, 246 space, 207, 246 tissue, 207 Sublingual gland, 149 Submaxillary gland, 148 Substantia perforate, 228 Sudoriferous ducts, 303 glands, 303 Sulci of the spinal cord, 248 Supercilia, 258 Superficial fascia, 26 Pupra-renal capsules, 91, 527 Suspensory ligament, liver, 78 penis, 469 Sutures, 530 Sympathetic system, 102, 193, 329 Symphysis, 531 Synarthrosis, 530 Syndesmology, 530 Synovia, 533 Synovial membrane, 533 Tapetum cerebri, 234 oculi, 266 582 INDEX, Tarin, horny band of, 215 Tarsal cartilages, 259 Tarsus, 563 Tela choroidea, 219 Tendinous centre of diaphragm, 106 Tendo Achillis, 439 oculi, 118 Tendon, 27 Tenia hippocampi, 216, 217 semicircular is, 215 Tarini, 215 Tentorium cerebelli, 206 Testes cerebri, 222 muliebres, 482 Testicles, 472 descent, 529 Thalami optici, 215, 220 Theca vertebralis, 246 Thecae, 555 Thoracic duct, 166, 336 Thorax, 305 Thymus gland, 523 Thyro-hyoid membrane, 290 Thyroid axis, 160 Thyroid cartilage, 288 gland, 146 Tomentum cerebri, 208 Tongue, 286 Tonsils, 201 cerebelli, 225 Torcular Herophili, 243 Trabs cerebri, 213 Trabeculae, 469 Trachea, 296, 332 Tracheotomy, 147 Tractus motorius, 237 opticus, 236 spiralis, 281 Tragus, 272 Triangles of the neck, 143, 145, 148 Triangular ligament, 506, 510, 518 Tricuspid valves, 318 Trigonum vesicae, 459 Trochlearis, 131, 134 Tuber cinereum, 228 Tubercula quadrigemina, 222 Tuberculum Loweri, 316 Tubuli galactophori, 345 lactiferi, 345 seminiferi, 474 uriniferi, 94 Tunica albuginea oculi, 26S testis, 474 nervei, 65 Ruyschiana, 266 vaginalis, 473 vasculosa testis, 474 Tutamina oculi, 258 Tympanum, 273 Tyson's glands, 468 Umbilical region, 53 Urachus, 52, 457. 528 Ureter, 95 , ', Urethra, female, 476 male, 470 Uterus, 478, 528 Utriculus comrnunis, 283 Uvea, 266 Uvula cerebelli, 223, 225 palati, 201 vesicae, 459 Vagina, 478 Vallecula, 225 Valsalva, sinuses of, 320, 321 Valve, arachnoid, 224 Bauhini, 66 coronary, 316 Eustachian, 316 ileo-caecal, 66 mitral, 321 pyloric, 66 rectum, of the. 66 semilunar, 319, 321 Tarin, of, 225 tricuspid, 318 Vieussens, of, 223, 225 Valvulae conniventes, 66 Vasa efferentia, 475 lactea, 71, 345 lymphatica, 28 recta, 475 Vasculum aberrans, 476 Vas deferens, 45, 476 VEINS : structure, 28 angular, 128 auricular, 117, 175 axillary, 352 azygos, 335 basilic, 365 cardiac, 322 cava inferior, 100, 328 superior, 327 cephalic, 304 cerebellar, 212 cerebral, 211 coronary, 315, 323 corporis striati, 215 dorsalis penis, 513 dorsi-spinal, 251 emulgent, 101 facial, 128, 176 femoral, 409 frontal, 116 Galeni, 212 gastric, 76 hepatic, 81, 85 iliac, 101, 465 innominatse, 327 INDEX. 583 VE I N s rontin urd. intercostal superior, 335 jugular, anterior, 153 external, 153, 178 internal, 164, 186 lumbar, 101 maxillary internal, 175 median, 362, 372 basilic, 363 cephalic, 363 medulli-spinal, 251 meningo-rachidian, 251 mesenteric, superior, 71 inferior, 73 occipital, 116 ophthalmic, 139 ovarian, 101 parietal, 243 phrenic, 101 popliteal, 426 portal, 76, 84 profunda femoris, 409 prostatic, 460, 465 pulmonary, 328 radial, 364, 371 renal, 96, 101 salvatella, 371 saphenous external, 425, 436, 438 internal, 397, 429, 436 spermatic, 44, 101 spinal, 251 splenic, 76 subclavian, 161 temporal, 117, 175 temporo-maxillary, 175 Thebesii, 323 thyroid, 166, 187 tibial, 444 ulnar, 365, 371, 372 VEIN s rontimifd. umbilical, 519 uterine, 465 vertebral, 251 vesical, 465 Velum interpositum, 208, 219 medullare, 223, 225 pendulum palati, 201 Venae comites, 342 Galeni, 215, 219 vorticosae, 265 Ventricles of the brain : fifth, 218 fourth, 223 lateral, 214 third, 221 of the corpus callosnm, 213 Ventricles of the heart, 316, 320 of the larynx, 295 Vermiform processes, 224, 225 Vermis, 225 Vertebral aponeurosis, 490 Veru montanum, 471 Vesiculae seminales, 460 Vestibule, 278 Vestibulum vaginae, 484 Vibrissae, 252, 254 Villi, 67 Vitreous humor, 269 Vulva, 483 Wharton's duct, 148, 287 Willis, circle of, 211 Wilson's muscles, 516 Wrisberg, nerve of, 349, 365, 370 Zonula ciliaris, 267 Zonula ossea lamina spiralis, 282 of Zinn, 268 THE END. 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